阅读说明：本技术 尖晶石结构的锂锰基正极活性材料和包含所述正极活性材料的正极和锂二次电池 (Spinel-structured lithium manganese-based positive electrode active material, and positive electrode and lithium secondary battery comprising same ) 是由 白韶螺 郑王谟 姜玟锡 李尚昱 卢恩帅 王文秀 于 2018-11-06 设计创作，主要内容包括：本发明涉及尖晶石结构的锂锰正极活性材料,以及包含所述正极活性材料的正极和锂二次电池,所述锂锰正极活性材料包含：下式1表示的锂锰氧化物,和设置在所述锂锰氧化物表面上的涂覆层,所述涂覆层包含选自由铝、钛、钨、硼、氟、磷、镁、镍、钴、铁、铬、钒、铜、钙、锌、锆、铌、钼、锶、锑、铋、硅和硫组成的组至少一种涂覆元素,从而显示出优异的高温储存特性：[式1]Li<Sub>1+</Sub><Sub>a</Sub>Mn<Sub>2-b</Sub>M<Sup>1</Sup><Sub>b</Sub>O<Sub>4-c</Sub>A<Sub>c</Sub>(在式1中,M<Sup>1</Sup>是包含锂(Li)的至少一种金属元素,A是选自由氟、氯、溴、碘、砹和硫组成的组的至少一种元素,0≤a≤0.2,0<b≤0.5,且0≤c≤0.1)。(the present invention relates to a spinel-structured lithium manganese positive electrode active material, and a positive electrode and a lithium secondary battery comprising the sameComprises the following steps: a lithium manganese oxide represented by the following formula 1, and a coating layer disposed on a surface of the lithium manganese oxide, the coating layer comprising at least one coating element selected from the group consisting of aluminum, titanium, tungsten, boron, fluorine, phosphorus, magnesium, nickel, cobalt, iron, chromium, vanadium, copper, calcium, zinc, zirconium, niobium, molybdenum, strontium, antimony, bismuth, silicon, and sulfur, thereby exhibiting excellent high-temperature storage characteristics: [ formula 1]Li 1+ a Mn 2‑b M 1 b O 4‑c A c (in formula 1, M 1 Is at least one metal element containing lithium (Li), A is at least one element selected from the group consisting of fluorine, chlorine, bromine, iodine, astatine and sulfur, 0. ltoreq. a.ltoreq.0.2, 0<b is less than or equal to 0.5, and c is less than or equal to 0 and less than or equal to 0.1).)

1. A spinel-structured lithium manganese-based positive electrode active material comprising:

A lithium manganese oxide represented by formula 1; and

A coating layer disposed on a surface of the lithium manganese oxide, the coating layer including at least one coating element selected from the group consisting of aluminum (Al), titanium (Ti), tungsten (W), boron (B), fluorine (F), phosphorus (P), magnesium (Mg), nickel (Ni), cobalt (Co), iron (Fe), chromium (Cr), vanadium (V), copper (Cu), calcium (Ca), zinc (Zn), zirconium (Zr), niobium (Nb), molybdenum (Mo), strontium (Sr), antimony (Sb), bismuth (Bi), silicon (Si), and sulfur (S),

[ formula 1]

Li_1+aMn_2-bM¹ _bO_4-cA_c

Wherein, in the formula 1,

M¹Is At least one metal element containing lithium (Li), A is At least one element selected from the group consisting of fluorine (F), chlorine (Cl), bromine (Br), iodine (I), astatine (At) and sulfur (S), 0. ltoreq. a.ltoreq.0.2, 0. ltoreq.a.ltoreq.0.2, 0<b is less than or equal to 0.5, and c is less than or equal to 0.1.

2. The spinel-structured lithium manganese-based positive electrode active material according to claim 1, wherein the doping element M¹Further contains at least one metal element selected from the group consisting of Al, Mg, Zn, B, W, Ni, Co, Fe, Cr, V, ruthenium (Ru), Cu, cadmium (Cd), silver (Ag), yttrium (Y), scandium (Sc), gallium (Ga), indium (In), arsenic (As), Sb, platinum (Pt), gold (Au) and Si.

3. The spinel-structured lithium manganese-based positive electrode active material according to claim 1, wherein the doping element M¹Further comprising a metal selected from the group consisting of Al and MgAt least one metal element of (a).

4. The spinel-structured lithium manganese-based positive electrode active material according to claim 1, wherein the lithium manganese oxide is represented by formula 1:

[ formula 1]

Li_1+aMn_2-bLi_b1M^a _b2O_4-cA_c

Wherein, in formula 1, M^aIs at least one metal element selected from the group consisting of Al and Mg, 0. ltoreq. a.ltoreq.0.2, 0<b1+ b2 is less than or equal to 0.5, c is less than or equal to 0 and less than or equal to 0.1, and b1/b2 is less than or equal to 0 and less than or equal to 1.3.

5. The spinel-structured lithium manganese-based positive electrode active material according to claim 1, wherein the coating layer contains at least one selected from the group consisting of Mg, Ti, B and W.

6. The spinel-structured lithium manganese-based positive electrode active material according to claim 1, wherein the coating layer has a thickness of 1nm to 1,000 nm.

7. The spinel-structured lithium manganese-based positive electrode active material according to claim 1, wherein the average particle diameter (D) of the lithium manganese-based positive electrode active material₅₀) Is 1 μm to 20 μm.

8. The spinel-structured lithium manganese-based positive electrode active material according to claim 1, wherein the specific surface area of the lithium manganese-based positive electrode active material is 0.1m²G to 1.5m²/g。

9. The spinel-structured lithium manganese-based positive electrode active material according to claim 1, wherein the lithium manganese-based positive electrode active material is in the form of primary particles or secondary particles formed by agglomeration of a plurality of primary particles.

10. The spinel-structured lithium manganese-based positive electrode active material according to claim 9, wherein the secondary particles are formed by agglomeration of 2 to 50 primary particles.

11. The spinel-structured lithium manganese-based positive electrode active material according to claim 2, further comprising a lithium boron composite oxide and a lithium tungsten composite oxide.

12. A positive electrode, comprising: a positive electrode current collector, and a positive electrode active material layer formed on the positive electrode current collector,

Wherein the positive electrode active material layer includes the spinel-structured lithium manganese-based positive electrode active material according to any one of claims 1 to 11.

13. The positive electrode of claim 12, wherein the positive electrode active material layer further comprises a lithium nickel cobalt manganese-based positive electrode active material represented by formula 2:

[ formula 2]

Li_1+x[Ni_yCo_zMn_wM² _v]O_2-pB_p

Wherein, in formula 2, M²Is At least one element selected from the group consisting of tungsten (W), copper (Cu), iron (Fe), vanadium (V), chromium (Cr), titanium (Ti), zirconium (Zr), zinc (Zn), aluminum (Al), indium (In), tantalum (Ta), yttrium (Y), lanthanum (La), strontium (Sr), gallium (Ga), scandium (Sc), gadolinium (Gd), samarium (Sm), calcium (Ca), cerium (Ce), niobium (Nb), magnesium (Mg), boron (B) and molybdenum (Mo), B is At least one element selected from the group consisting of fluorine (F), chlorine (Cl), bromine (Br), iodine (I), astatine (At) and sulfur (S), x is 0. ltoreq. x.ltoreq.0.3, Y is 0.50. ltoreq. Y<1，0<z<0.35，0<w<0.35, 0 is more than or equal to v is less than or equal to 0.1, and 0 is more than or equal to p is less than or equal to 0.1.

14. A lithium secondary battery comprising the positive electrode according to claim 12.

Technical Field

The present invention relates to a positive electrode active material for a lithium secondary battery, and a positive electrode and a lithium secondary battery comprising the same. In particular, the present invention relates to a spinel-structured lithium manganese-based cathode active material in which high-temperature storage characteristics and high-temperature life characteristics are excellent by improving the dissolution of Mn, and a cathode and a lithium secondary battery including the same.

Background

As technology develops and the demand for mobile devices increases, the demand for secondary batteries as an energy source has significantly increased. Among these secondary batteries, lithium secondary batteries having high energy density, high voltage, long cycle life and low self-discharge rate have been commercialized and widely used.

Lithium transition metal composite oxides have been used as positive electrode active materials for lithium secondary batteries, and among these oxides, lithium cobalt composite metal oxides having high operating voltage and excellent capacity characteristics, such as LiCoO, are mainly used₂. However, LiCoO₂Has very poor thermal properties due to instability of a crystal structure caused by delithiation and is expensive, and thus a large amount of LiCoO is used₂There is a limitation as a power source for applications such as electric vehicles.

Lithium manganese-based oxides (LiMnO) have been developed₂Or LiMn₂O₄) Lithium iron phosphate compound (LiFePO)₄Etc.) or lithium nickel composite metal oxide (LiNiO)₂Etc.) as an alternative to LiCoO₂The material of (1). Among these materials, the lithium manganese-based oxide has advantages in that it is excellent in thermal stability and output characteristics and low in price, but has a limitation in that the generation of Mn from the lithium manganese-based oxide occurs during charge and discharge³⁺Structural deformation caused (Jahn-Teller deformation), and dissolution of manganese (Mn) occurs due to HF formed by reaction with an electrolyte solution at high temperature, thereby rapidly deteriorating the performance.

Therefore, it is required to develop a cathode active material in which a secondary battery having excellent high-temperature characteristics can be prepared at low cost by suppressing the Mn dissolution of the lithium manganese-based oxide.

Disclosure of Invention

[ problem ] to

An aspect of the present invention provides a spinel-structured lithium manganese-based cathode active material in which high-temperature storage characteristics and high-temperature lifespan characteristics are excellent by suppressing dissolution of manganese (Mn).

Another aspect of the present invention provides a positive electrode for a lithium secondary battery, which can realize excellent high-temperature storage characteristics and high-temperature lifespan characteristics by including the positive electrode active material.

Another aspect of the present invention provides a lithium secondary battery in which high-temperature storage characteristics and high-temperature life characteristics are excellent by including the positive electrode of the present invention.

[ solution ]

According to an aspect of the present invention, there is provided a spinel-structured lithium manganese-based positive electrode active material comprising: a lithium manganese oxide represented by formula 1; and a coating layer disposed on a surface of the lithium manganese oxide, the coating layer including at least one coating element selected from the group consisting of aluminum (Al), titanium (Ti), tungsten (W), boron (B), fluorine (F), phosphorus (P), magnesium (Mg), nickel (Ni), cobalt (Co), iron (Fe), chromium (Cr), vanadium (V), copper (Cu), calcium (Ca), zinc (Zn), zirconium (Zr), niobium (Nb), molybdenum (Mo), strontium (Sr), antimony (Sb), bismuth (Bi), silicon (Si), and sulfur (S).

[ formula 1]

Li_1+aMn_2-bM¹ _bO_4-cA_c

(in formula 1, M¹Is At least one metal element containing lithium (Li), A is At least one element selected from the group consisting of F, chlorine (Cl), bromine (Br), iodine (I), astatine (At) and S, and 0. ltoreq. a.ltoreq.0.2, 0<b is less than or equal to 0.5, and c is less than or equal to 0.1).

According to another aspect of the present invention, there is provided a positive electrode including: and a positive electrode active material layer formed on the positive electrode current collector, wherein the positive electrode active material layer includes the spinel-structured lithium manganese-based positive electrode active material of the present invention.

According to another aspect of the present invention, there is provided a lithium secondary battery comprising the positive electrode of the present invention.

[ advantageous effects ]

According to the present invention, the structural stability can be improved by doping the spinel-structured lithium manganese-based positive electrode active material with a doping element.

In addition, since the coating layer formed on the surface of the spinel-structured lithium manganese-based cathode active material minimizes contact between the cathode active material and an electrolyte solution, manganese dissolution at high temperature is suppressed, with the result that the spinel-structured lithium manganese-based cathode active material has better high-temperature storage characteristics and high-temperature lifespan characteristics than conventional cathode active materials.

Drawings

Fig. 1 is a graph showing capacity and resistance characteristics at high temperature (45 ℃) versus cycle number of secondary batteries prepared in examples 1 to 5 of the present invention and comparative examples 1 to 3; and

Fig. 2 is a graph showing capacity and resistance characteristics of the secondary batteries prepared in examples 1 to 5 of the present invention and comparative examples 1 to 3 during storage at high temperature (60 ℃).

Detailed Description

Hereinafter, the present invention will be described in more detail.

It should be understood that the words or terms used in the specification and claims should not be construed as meanings defined in a general dictionary, and it should be further understood that the words or terms should be construed as having meanings consistent with their meanings in the context of the related art and the technical idea of the present invention on the basis of the principle that the inventor can appropriately define the meanings of the words or terms to best explain the present invention.

In the present specification, the average particle diameter (D)₅₀) Can be defined as the particle diameter at 50% in the cumulative particle diameter distribution and can be measured using a laser diffraction method. Specifically, the average particle diameter (D)₅₀) After the target particles are dispersed in the dispersion medium, the dispersion medium is introduced into a commercial laser diffraction particle size meter (e.g., Microtrac MT 3000) and irradiated with ultrasonic waves having a frequency of about 28kHz and an output of 60W, and then the average particle diameter (D) at 50% in the cumulative particle volume distribution of the meter can be calculated₅₀)。

In this specification, Inductively Coupled Plasma (ICP) analysis was performed using an inductively coupled plasma-optical emission spectrometer (ICP-OES) (OPTIMA7300DV, PerkinElmer Inc.).

In the present specification, the "specific surface area" is measured by the Brunauer-Emmett-Teller (BET) method, wherein specifically, the specific surface area can be calculated from the nitrogen adsorption amount at a liquid nitrogen temperature (77K) using BELSORP-mini II of Bell Japan Inc.

In addition, in the present specification, unless otherwise specified, the expression "%" means wt%.

Positive electrode active material

First, the spinel-structured lithium manganese-based positive electrode active material of the present invention will be described.

The lithium manganese-based positive electrode active material of the present invention is a spinel-structured positive electrode active material comprising: a lithium manganese oxide represented by the following formula 1, and a coating layer disposed on a surface of the lithium manganese oxide.

[ formula 1]

Li_1+aMn_2-bM¹ _bO_4-cA_c

In formula 1, M¹Is a doping element substituted at a manganese site in the lithium manganese oxide, and may be at least one metal element including lithium (Li). A is an element substituted At an oxygen site in the lithium manganese oxide, and may be At least one element selected from the group consisting of fluorine (F), chlorine (Cl), bromine (Br), iodine (I), astatine (At), and sulfur (S).

1+ a represents a molar ratio of lithium in the lithium manganese oxide, and a may satisfy 0. ltoreq. a.ltoreq.0.2, for example, 0. ltoreq. a.ltoreq.0.1.

b represents doping element M in lithium manganese oxide¹And b may satisfy 0<b.ltoreq.0.5, for example 0.03. ltoreq. b.ltoreq.0.25. At M¹In the case where the molar ratio b of (a) satisfies the above range, a structurally stable positive electrode active material can be obtained while minimizing the extent of capacity reduction.

c represents a molar ratio of the element A in the lithium manganese oxide, and c may satisfy 0. ltoreq. c.ltoreq.0.1, for example, 0.01. ltoreq. c.ltoreq.0.05.

The lithium manganese oxide represented by formula 1 is doped with a doping element M having an oxidation number lower than that of manganese (Mn)¹。

Since the lithium manganese oxide is doped with a dopant having an oxidation number lower than that of MnHetero element M¹The average oxidation number of Mn ions is increased, thereby reducing the disproportionation reaction of Mn ions on the electrode surface during charge and discharge (2 Mn)³⁺＝Mn²⁺+Mn⁴⁺) Mn formed²⁺Therefore, it is possible to suppress the dissolution of Mn by suppressing the reaction with HF formed in the electrolyte solution.

In the present invention, when the lithium manganese oxide is doped with an element having an oxidation number greater than or equal to Mn, the average oxidation number of Mn ions decreases, and Mn generated by disproportionation reaction of Mn ions is produced²⁺The amount of (c) increases. Mn formed in this case²⁺After dissolution in the electrolyte, Mn²⁺Is reduced during charge and discharge to deposit on the surface of the negative electrode, and therefore, it may affect cell properties such as capacity deterioration.

In addition, doping element M¹At least one metal element selected from the group consisting of aluminum (Al), magnesium (Mg), zinc (Zn), boron (B), tungsten (W), nickel (Ni), cobalt (Co), iron (Fe), chromium (Cr), vanadium (V), ruthenium (Ru), copper (Cu), cadmium (Cd), silver (Ag), yttrium (Y), scandium (Sc), gallium (Ga), indium (In), arsenic (As), antimony (Sb), platinum (Pt), gold (Au), and silicon (Si) may be further included. Preferably, M is¹Li may be contained, and at least one metal element selected from the group consisting of Al and Mg may be further included.

Preferably, the lithium manganese oxide may be represented by formula 1 below.

[ formula 1]

Li_1+aMn_2-bLi_b1M^a _b2O_4-cA_c

In formula 1, M^aIs at least one metal element selected from the group consisting of Al and Mg, 0. ltoreq. a.ltoreq.0.2, 0<b1+ b2 is less than or equal to 0.5, c is less than or equal to 0 and less than or equal to 0.1, and b1/b2 is less than or equal to 0 and less than or equal to 1.3.

In formula 1, doping element M¹May preferably contain Li and consist of M^aThe metal elements shown. In this case, b1 represents a molar ratio of Li as a doping element in the lithium manganese oxide, and b2 represents a molar ratio of a metal element that may be further doped in addition to Li in the lithium manganese oxide. b1+ b2 represents the doping in lithium manganese oxideHetero element M¹And b1+ b2 may satisfy 0<b1+ b 2. ltoreq.0.5, for example 0.03. ltoreq.b 1+ b 2. ltoreq.0.25. In addition, the b1/b2 molar ratio may satisfy 0. ltoreq. b1/b 2. ltoreq.1.3, for example 0.5. ltoreq. b1/b 2. ltoreq.1.2. In the presence of Li and M^aDoping element M of¹In the case where the molar ratios b1 and b2 satisfy the above ranges, a structurally stable positive electrode active material can be obtained while minimizing the extent of capacity reduction.

Next, the coating layer serves to prevent manganese (Mn) from being dissolved at high temperature and to suppress gas generation during charge and discharge by preventing contact between the lithium manganese oxide and the electrolyte solution. The coating layer is disposed on a surface of the lithium manganese oxide, and includes at least one element (hereinafter, referred to as "coating element") selected from the group consisting of aluminum, titanium (Ti), W, boron (B), F, phosphorus (P), Mg, Ni, Co, Fe, Cr, V, Cu, calcium (Ca), Zn, zirconium (Zr), niobium (Nb), molybdenum (Mo), strontium (Sr), Sb, bismuth (Bi), Si, and S. The coating layer may preferably include at least one element selected from the group consisting of W, Mg, B and Ti, and may more preferably include at least one element selected from the group consisting of W and B.

According to one embodiment, in the lithium manganese-based positive electrode active material of the present invention, an element M is doped¹May be at least one metal element of Li, Al and Mg, and the coating layer may contain WO₃。

According to another embodiment, in the lithium manganese-based positive electrode active material of the present invention, the element M is doped¹May be at least one metal element of Li, Al and Mg, and the coating layer may contain B₂O₃。

According to another embodiment, in the lithium manganese-based positive electrode active material of the present invention, the element M is doped¹May be at least one metal element of Li, Al and Mg, and the coating layer may include TiO₂。

According to another embodiment, in the lithium manganese-based positive electrode active material of the present invention, the element M is doped¹May be at least one metal element of Li, Al and Mg, and the coating layer may include MgO₂。

The spinel-structured lithium manganese-based cathode active material of the present invention may include a lithium boron composite oxide and a lithium tungsten composite oxide.

For example, in a spinel-structured lithium manganese-based cathode active material, a lithium boron composite oxide and a lithium tungsten composite oxide may be present on the surface of the lithium manganese-based cathode active material. The lithium manganese-based positive electrode active material may preferably have secondary particles, and more preferably, a lithium boron composite oxide and a lithium tungsten composite oxide may be present in the secondary particles and on the surfaces of the secondary particles.

The lithium boron composite oxide may preferably be lithium borate, more preferably lithium borate, lithium tetraborate, lithium pentaborate, and most preferably Li₂B₄O₇。

the lithium tungsten composite oxide may preferably be lithium tungstate, and most preferably Li₂WO₄。

For example, in the preparation of a lithium manganese-based positive electrode active material, a lithium boron composite oxide and a lithium tungsten composite oxide may be formed on the lithium manganese-based positive electrode active material by mixing and sintering a boron raw material with a raw material including a lithium raw material, a manganese raw material, and a tungsten raw material. Since the lithium boron composite oxide and the lithium tungsten composite oxide are formed on the lithium manganese-based positive electrode active material, the battery resistance can be reduced and the dissolution of manganese during high-temperature storage can be suppressed.

The coating layer may be continuously or discontinuously formed on the surface of the lithium manganese oxide represented by formula 1.

For example, the coating layer may be formed in the form of islands in which particles containing the coating element are discontinuously attached to the surface of the lithium manganese oxide. In this case, the particles containing the coating element may be, for example, oxide particles, such as WO₃、B₂O₃、ZnO、Al₂O₃、TiO₂、MgO、CaO、NbO₂、SrO、CrO、Mo₂O₅、Bi₂O₃And SiO. In the case where the above-described oxide particles are present on the surface of the lithium manganese oxide, since the oxide particles capture and decompose HF formed by the reaction with the electrolyte solution shown in the following reaction formula 1, it is possible to suppress the generation of HFThe Mn of (3) is dissolved.

[ reaction formula 1]

ZnO+2HF→ZnF₂+H₂O

Al₂O₃+6HF→2AlF₃+3H₂O

In addition, the coating layer may be formed on the surface of the lithium manganese oxide in the form of a film including the coating element. In the case where the coating layer is formed in the form of a film, the effect of preventing contact between the electrolyte solution and the lithium manganese oxide is better, and the effect of inhibiting manganese dissolution is better. Preferably, the film comprises at least one element selected from the group consisting of W, Mg, B and Ti. In the case where the above-described film is formed on the surface of the lithium manganese oxide particles, by blocking contact with the electrolyte solution with the film, side reactions with the electrolyte solution and gas generation can be suppressed.

The coating layer may be formed in a region corresponding to 50% to 100%, preferably 80% to 100%, more preferably 90% to 100% of the total surface area of the lithium manganese oxide. In the case where the coating layer forming region satisfies the above range, the contact between the electrolyte solution and the lithium manganese oxide can be effectively blocked.

Further, the thickness of the coating layer may be 1nm to 1,000nm, for example 1nm to 100nm, or 10nm to 1,000 nm. In the case where the coating layer is formed in the form of a film, the thickness may be 1nm to 100 nm; in the case where the coating layer is formed in the form of oxide particles, the thickness may be 10nm to 1,000 nm. When the thickness of the coating layer satisfies the above range, the dissolution of manganese and the occurrence of side reactions with the electrolyte solution can be effectively suppressed while minimizing the deterioration of electrical properties.

The lithium manganese-based positive electrode active material of the present invention includes a doping element M with respect to the total weight of the lithium manganese-based positive electrode active material¹May be in the range of 500ppm to 40,000ppm, preferably 2,500ppm to 40,000ppm, and more preferably 3,000ppm to 40,000 ppm. When doping element M¹When the amount of (b) satisfies the above range, manganese dissolution at high temperatures is effectively suppressed, and thus a lithium secondary battery having excellent high-temperature storage properties can be realized.

According to one embodiment, the lithium manganese-based cathode active material may include Li, or Li and Al and Mg, or a combination thereof, as a doping element, wherein the content of Al may be 2,500ppm to 40,000ppm, for example 7,000ppm to 20,000ppm, based on the total weight of the lithium manganese-based cathode active material; and, the content of Li may be 500ppm to 12,000ppm, for example, 1,000ppm to 3,000ppm, based on the total weight of the lithium manganese-based positive electrode active material. In addition, the content of Mg may be 1,000ppm to 20,000ppm, for example, 3,000ppm to 10,000ppm, based on the total weight of the lithium manganese-based positive electrode active material.

Average particle diameter (D) of lithium manganese-based positive electrode active material of the present invention₅₀) Can be 1 μm to 20 μm, for example 1 μm to 8 μm, 7 μm to 20 μm, 8 μm to 20 μm, or 10 μm to 20 μm.

According to one embodiment, the average particle diameter (D) of the lithium manganese-based positive electrode active material of the present invention₅₀) May be 1 μm to 8 μm. For particles having a small average particle diameter (D)₅₀) The small-particle size lithium manganese-based cathode active material of (a) can prepare a lithium manganese-based cathode active material having excellent structural stability and less side reaction with an electrolyte solution, compared to particles having a large average particle size, since the specific surface area thereof can be reduced by relatively increasing the amounts of doping elements and coating elements and controlling sintering conditions.

According to another embodiment, the average particle diameter (D) of the lithium manganese-based positive electrode active material of the present invention₅₀) May be 8 μm to 20 μm. For particles having a large average particle diameter (D)₅₀) The large-particle size lithium manganese-based positive electrode active material of (a), advantageously, the dissolution of manganese is relatively smaller compared to particles having a small average particle size.

in addition, the specific surface area of the lithium manganese-based active material may be 0.1m²G to 1.5m²(ii) in terms of/g. The specific surface area may be adjusted according to the particle diameter of the lithium manganese-based active material, wherein, for example, in the case where the lithium manganese-based active material is used in the form of small-sized particles in the cathode material to be described below, the specific surface area may be 0.5m²G to 1.5m²Per g, or 0.7m²G to 1.1m²and in the case where the lithium manganese-based active material is used in the form of large-sized particles, the specific surface area may beSo as to be 0.1m²G to 1m²Per g, or 0.25m²G to 0.7m²/g。

In addition, the lithium manganese-based positive electrode active material may be in the form of primary particles or secondary particles formed by agglomeration of a plurality of primary particles. The secondary particles may be formed by agglomeration of 2 to 100 or 2 to 50 primary particles, for example.

The lithium manganese-based positive electrode active material may contain impurities that are unintentionally introduced during the preparation process. The impurities may include, for example, Fe, Ni, sodium (Na), Cu, Zn, Cr, Ca, potassium (K), S, Mg, Co, Si, B, or combinations thereof. In the case where the amount of impurities is large, dendrite on the negative electrode may be caused, thereby reducing the battery life, and a low voltage failure caused by an internal short circuit may occur. In addition, among these impurities, impurities such as S have a limitation of corroding the Al current collector. Therefore, it is desirable to control the impurities to a predetermined amount or less.

For example, the content of the S impurity of the lithium manganese-based cathode active material of the present invention may be 20,000ppm or less, preferably 15,000ppm or less, and more preferably 1,000ppm or less, and the content of other impurities may be 400ppm or less, preferably 10ppm or less.

In addition, it is desirable that the lithium manganese-based positive electrode active material of the present invention may contain magnetic impurities, such as Fe, Cr, Ni, and Zn among the above impurities, in a total amount of 800ppb or less, for example, 25ppb or less. In the case where the amount of the magnetic impurities exceeds the above range, dendrite on the negative electrode may be caused, thereby reducing the battery life, or low voltage failure due to internal short circuit may occur.

Method for preparing positive electrode active material

Next, a method of preparing the lithium manganese-based positive electrode active material of the present invention will be described.

The lithium manganese-based cathode active material of the present invention may be prepared by the steps of: form M represented by formula 1¹Doped lithium manganese oxide, and mixing the lithium manganese oxide represented by formula 1 with a coating raw material and performing a heat treatment to form a coating layer. Hereinafter, each step of the production method of the present invention will be described in detail.

(1)M¹Formation of doped lithium manganese oxide

M represented by formula 1¹The doped lithium manganese oxide may be prepared by the following method: method (i): mixed manganese raw material containing M¹And a lithium raw material, and sintering the mixture; or method (ii): mixing manganese raw material with M¹Reacting the doping raw materials to form M¹Doped manganese precursor of M¹The doped manganese precursor is mixed with a lithium raw material, and the mixture is sintered. That is, in the present invention, the element M is doped¹May be added at the time of forming the manganese precursor, or may be added at the time of sintering the manganese raw material and the lithium raw material.

In this case, the manganese raw material may be an oxide, hydroxide, oxyhydroxide, carbonate, sulfate, halide, sulfide, acetate, or carboxylate containing manganese element, or a combination thereof, and may be specifically MnO₂、MnCl₂、MnCO₃、Mn₃O₄、MnSO₄、Mn₂O₃Or Mn (NO)₃)₂However, the manganese raw material is not limited thereto.

Containing M¹The doping raw material of (A) may be M-containing¹And can be, for example, Li (oh), Li (Li), hydroxide, oxyhydroxide, sulfate, carbonate, halide, sulfide, acetate, or carboxylate, or combinations thereof₂CO₃、Li₂O、Al₂(SO₄)₃、AlCl₃Al isopropoxide, AlNO₃、MgO、Mg(OH)₂、MgSO₄Or Mg (NO)₃)₂But containing M¹The doping raw material of (2) is not limited thereto.

The lithium raw material may be a lithium-containing carbonate (e.g., lithium carbonate) or a hydrate (e.g., lithium hydroxide monohydrate (LiOH. H)₂O), hydroxides (e.g., lithium hydroxide), nitrates (e.g., lithium nitrate (LiNO), etc.)₃) Etc.) or a chloride (e.g., lithium chloride (LiCl), etc.), but the lithium raw material is not limited thereto.

According to one embodiment, the lithium manganese oxide represented by formula 1 may be prepared by mixing a manganese raw material, containing M¹Mixing the doping raw material and the lithium raw material and thenSintering the mixture (method (i)).

Manganese raw material containing M¹The doping material and the lithium material may satisfy Mn and M in formula 1¹And the amount of the molar ratio of Li.

In addition, the mixing may be performed by solid-phase mixing or liquid-phase mixing. In the case where the components are mixed by solid-phase mixing, the sintering process may be performed without a separate drying process; in the case where the components are mixed by liquid phase mixing, the sintering process is performed after the mixed components are spray-dried. When the solid phase mixing method is used, the average particle diameter (D) having a low specific surface area can be obtained₅₀) The lithium manganese oxide has a small particle size of less than 8 μm, for example, 6 μm or less. In contrast, in the case of using the wet mixing method, the average particle diameter (D) is generally obtained₅₀) The particle size of the lithium manganese oxide is more than 8 μm.

Sintering may be carried out at 600 ℃ to 900 ℃, e.g., 700 ℃ to 800 ℃, for 5 hours to 24 hours, e.g., 10 hours to 15 hours.

For example, sintering may be carried out at 750 ℃ to 850 ℃, e.g., 780 ℃ to 830 ℃, for 5 hours to 24 hours, e.g., 10 hours to 15 hours. In the case where the above temperature and sintering time are satisfied, the over-sintering occurs to increase the size of the primary particles, and thus, the average particle diameter (D) of the primary particles can be obtained₅₀) Lithium manganese oxide of 1 μm or more, for example, 2 μm to 3 μm.

According to another embodiment, the lithium manganese oxide represented by formula 1 may be prepared by: mixing manganese raw material with M¹By reaction of the doping raw materials of (a) to form M¹Doped manganese precursor, the M¹The doped manganese precursor is mixed with the lithium raw material, and the mixture is sintered (method (ii)).

In particular, M¹The doped manganese precursor may be formed, for example, by reacting a manganese source with a manganese-containing compound¹By coprecipitation reaction of the doping raw materials. Manganese raw material and manganese-containing compound¹The doping raw material of (a) is the same as described above.

The coprecipitation reaction may be performed by a coprecipitation method well known in the art, and for example, the coprecipitation reaction may be performed in the following manner: a manganese raw material and a doping raw material are introduced into a coprecipitation reactor in an appropriate ratio and reacted while introducing an aqueous ammonia solution as a complexing agent and an alkaline aqueous solution as a pH adjuster.

when M is formed by the above-mentioned coprecipitation reaction¹When doping a manganese precursor, M¹The doped manganese precursor and the lithium raw material are mixed and then sintered to form a lithium manganese oxide.

M¹The doped manganese precursor and the lithium raw material may satisfy Mn, M in formula 1¹And the amount of Li in a molar ratio.

The mixing and sintering may be performed by the same method as that described in the method (i).

(2) Coating layer formation step

When M represented by formula 1 is prepared by the above method¹When the lithium manganese oxide is doped, a coating layer containing at least one element (hereinafter, referred to as "coating element") selected from the group consisting of Al, Ti, W, B, F, P, Mg, Ni, Co, Fe, Cr, V, Cu, Ca, Zn, Zr, Nb, Mo, Sr, Sb, Bi, Si, and S is formed on the surface of the lithium manganese oxide of formula 1.

The coating layer may be formed by a method known in the art, and for example, a wet coating method, a dry coating method, a plasma coating method, or Atomic Layer Deposition (ALD) may be used.

The wet coating method can be performed, for example, in the following manner: an appropriate solvent (e.g., ethanol, water, methanol, or acetone) is added to the lithium manganese oxide and the coating material, and then mixed until the solvent disappears.

The dry coating method is a method of solid-phase mixing the lithium manganese oxide and the coating raw material without a solvent, and, for example, a mill mixing method or a mechanofusion method may be used.

The coating raw material may be an oxide, hydroxide, oxyhydroxide, carbonate, sulfate, halide, sulfide, acetate, or carboxylate, or a combination thereof, which includes at least one member selected from the group consisting of Al, Ti, W, B, F, P, Mg, Ni, Co, Fe, Cr, V, Cu, Ca, Zn, Zr, Nb, Mo, Sr, Sb, Bi, Si, and SThe element (hereinafter referred to as "coating element") may be, for example, ZnO, Al₂O₃、Al(OH)₃、Al₂(SO₄)₃、AlCl₃Al isopropoxide, Al (NO)₃)₃、TiO₂、WO₃、AlF₃、H₂BO₃、HBO₂、H₃BO₃、H₂B₄O₇、B₂O₃、C₆H₅B(OH)₂、(C₆H₅O)₃B、(CH₃(CH₂)₃O)₃B、C₃H₉B₃O₆、(C₃H₇O₃)B、Li₃WO₄、(NH₄)₁₀W₁₂O₄₁·5H₂O and NH₄H₂PO₄However, the coating material is not limited thereto.

After the coating raw material is attached to the surface of the lithium manganese oxide according to the above-described method, a coating layer may be formed by heat treatment. In this case, the heat treatment may be performed at 100 ℃ to 700 ℃, for example 300 ℃ to 450 ℃, for 1 hour to 15 hours, for example 3 hours to 8 hours.

Positive electrode

Next, the positive electrode for a lithium secondary battery of the present invention will be described.

The positive electrode of the present invention includes a positive electrode current collector and a positive electrode active material layer formed on the positive electrode current collector, wherein the positive electrode active material layer includes the spinel-structured lithium manganese-based positive electrode active material of the present invention, and, if necessary, further includes a conductive agent and/or a binder.

In this case, since the positive electrode active material is the same as described above, a detailed description thereof will be omitted, and only the remaining configuration will be described in detail below.

The positive electrode active material layer may further include a lithium nickel cobalt manganese-based positive electrode active material represented by the following formula 2.

[ formula 2]

Li_1+x[Ni_yCo_zMn_wM² _v]O_2-pB_p

In formula 2, M²Is a doping element substituted at a transition metal (Ni, Co, Mn) site, and may be at least one element selected from the group consisting of W, Cu, Fe, V, Cr, Ti, Zr, Zn, Al, In, Ta, Y, lanthanum (La), Sr, Ga, Sc, gadolinium (Gd), samarium (Sm), Ca, cerium (Ce), Nb, Mg, B, and Mo. Preferably, M is²May be at least one selected from the group consisting of Al, Zr, W, Ti, Nb and B.

B is an element substituted At an oxygen site in the lithium nickel cobalt manganese-based positive electrode active material, and may be At least one element selected from the group consisting of F, Cl, Br, I, At, and S.

1+ x represents a molar ratio of lithium in the lithium nickel cobalt manganese-based positive electrode active material, and x may satisfy 0. ltoreq. x.ltoreq.0.3, preferably 0. ltoreq. x.ltoreq.0.2, more preferably 0. ltoreq. x.ltoreq.0.1.

y represents a molar ratio of nickel in the lithium nickel cobalt manganese-based positive electrode active material, and y may satisfy 0.5 ≦ y <1, preferably 0.65 ≦ x <1, more preferably 0.7 ≦ y <1, for example 0.75 ≦ y < 1.

z represents a molar ratio of cobalt in the lithium nickel cobalt manganese-based positive electrode active material, and z may satisfy 0< z <0.35, preferably 0< z ≦ 0.3.

w represents a molar ratio of manganese in the lithium nickel cobalt manganese-based positive electrode active material, and w may satisfy 0< w <0.35, preferably 0< w ≦ 0.3.

When the molar ratios y, z, and w of the transition metals in the lithium nickel cobalt manganese-based oxide satisfy the above ranges, a cathode active material having excellent energy density can be obtained.

v represents doping element M in lithium nickel cobalt manganese based oxide²And v may satisfy 0. ltoreq. v.ltoreq.0.1, preferably 0.0005. ltoreq. v.ltoreq.0.08, more preferably 0.001. ltoreq. v.ltoreq.0.02, for example 0.002. ltoreq. v.ltoreq.0.01. When doping element M in lithium nickel cobalt manganese based oxide²When the molar ratio of (a) to (b) satisfies the above range, a positive electrode active material having excellent high-temperature stability can be obtained.

p represents the molar ratio of the element B in the lithium nickel cobalt manganese-based oxide, and p may satisfy 0. ltoreq. p.ltoreq.0.1, preferably 0. ltoreq. p.ltoreq.0.05.

In particular, the lithium nickel cobalt manganese-based oxide represented by formula 2 may be Li_1+x[Ni_yCo_zMn_w]O₂Or Li_1+x[Ni_yCo_zMn_wAl_v]O₂However, the lithium nickel cobalt manganese-based oxide represented by formula 2 is not limited thereto.

The lithium nickel cobalt manganese-based positive active material represented by formula 2 may further include a coating layer containing at least one coating element selected from the group consisting of Al, Ti, W, B, F, P, Mg, Ni, Co, Fe, Cr, V, Cu, Ca, Zn, Zr, Nb, Mo, Sr, Sb, Bi, Si, and S. For example, since the contact between the lithium nickel cobalt manganese-based positive electrode active material of formula 2 contained in the lithium secondary battery and the electrolyte solution is blocked by the coating layer to suppress the occurrence of side reactions, the life characteristics can be improved when used in the battery, and furthermore, the packing density of the positive electrode active material can be increased.

In the case of further including a coating element as described above, the amount of the coating element in the coating layer may be 100ppm to 10,000ppm, for example, 200ppm to 5,000ppm, based on the total weight of the lithium nickel cobalt manganese-based positive electrode active material represented by formula 2. For example, when the content of the coating element based on the total weight of the lithium nickel cobalt manganese-based positive electrode active material represented by formula 2 is within the above range, the occurrence of side reactions with the electrolyte solution can be more effectively suppressed, and the life characteristics can be further improved when used in a battery.

The coating layer may be formed on the entire surface of the lithium nickel cobalt manganese-based positive electrode active material represented by formula 2, or may be formed locally. In particular, in the case where the coating layer is locally formed on the surface of the lithium nickel cobalt manganese-based positive electrode active material represented by formula 2, the coating layer may be formed in a region corresponding to 5% or more and less than 100%, for example, 20% or more and less than 100% of the total surface area of the lithium nickel cobalt manganese-based positive electrode active material represented by formula 2.

Average particle diameter (D) of lithium nickel cobalt manganese-based positive electrode active material represented by formula 2₅₀) May be 1 μm to 20 μm, 2 μm to 10 μm, or 8 μm to 20 μm. When the average particle diameter (D) of the lithium nickel cobalt manganese-based positive electrode active material represented by formula 2₅₀) When the above range is satisfied, excellent electrode density and energy density can be achieved.

The lithium nickel cobalt manganese-based positive active material represented by formula 2 may have a grain size of 200nm to 500 nm. When the grain size of the lithium nickel cobalt manganese-based positive electrode active material represented by formula 2 satisfies the above range, excellent electrode density and energy density can be achieved.

For the lithium nickel cobalt manganese-based positive electrode active material represented by formula 2, the amount of the transition metal in the active material particles may be a constant value regardless of the position, or the amount of the at least one metal element may vary depending on the position in the particles. For example, in the lithium nickel cobalt manganese-based positive electrode active material represented by formula 2, Ni, Mn, Co and M²May have a gradually changing concentration gradient, and the expression "gradually changing concentration gradient" means that the component has a concentration profile such that: the concentration of the component varies continuously and stepwise across the whole particle or in specific regions.

A commercially available lithium nickel cobalt manganese-based positive electrode active material may be purchased and used as the lithium nickel cobalt manganese-based positive electrode active material represented by formula 2, or the lithium nickel cobalt manganese-based positive electrode active material represented by formula 2 may be prepared by a preparation method of the lithium nickel cobalt manganese-based positive electrode active material known in the art.

For example, the lithium nickel cobalt manganese-based positive electrode active material represented by formula 2 may be prepared by the following method: the nickel-cobalt-manganese based precursor is mixed with a lithium source material and optionally a doping source material and then sintered.

The nickel-cobalt-manganese-based precursor may be a hydroxide, oxyhydroxide, carbonate or organic complex of nickel-manganese-cobalt, or may comprise a doping element M²A hydroxide, oxyhydroxide, carbonate or organic complex of nickel manganese cobalt. For example, the nickel cobalt manganese based precursor may be [ Ni ]_yCo_zMn_w](OH)₂、[Ni_yCo_zMn_wAl_v](OH)₂、[Ni_yCo_zMn_w]O, OH or [ Ni ]_yCo_zMn_wAl_v]O · OH, but the nickel cobalt manganese based precursor is not limited thereto.

Lithium raw materialthe compound may be a lithium-containing carbonate (e.g., lithium carbonate), a hydrate (e.g., lithium hydroxide monohydrate (LiOH. H)₂O), hydroxides (e.g., lithium hydroxide), nitrates (e.g., lithium nitrate (LiNO), etc.)₃) Etc.) or a chloride (e.g., lithium chloride (LiCl), etc.), but the lithium raw material is not limited thereto.

The doping raw material may be an oxide, hydroxide, sulfide, oxyhydroxide, or halide containing at least one element selected from the group consisting of W, Cu, Fe, V, Cr, Ti, Zr, Zn, Al, In, Ta, Y, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B, and Mo, or a mixture thereof.

Sintering may be performed at 600 ℃ to 1,000 ℃, e.g., 700 ℃ to 900 ℃, for 5 hours to 30 hours, e.g., 10 hours to 20 hours.

In the case where the lithium nickel cobalt manganese-based positive electrode active material represented by formula 2 includes a coating layer, the following process may be further performed: after sintering, the coating raw materials are added and mixed, and then heat-treated.

The coating raw material may be an oxide, hydroxide, oxyhydroxide, carbonate, sulfate, halide, sulfide, acetate, or carboxylate, or a combination thereof, which contains at least one element (hereinafter, referred to as "coating element") selected from the group consisting of Al, Ti, W, B, F, P, Mg, Ni, Co, Fe, Cr, V, Cu, Ca, Zn, Zr, Nb, Mo, Sr, Sb, Bi, Si, and S, for example, may be ZnO, Al, or a combination thereof₂O₃、Al(OH)₃、Al₂(SO₄)₃、AlCl₃Al isopropoxide, Al (NO)₃)₃、TiO₂、WO₃、AlF₃、H₂BO₃、HBO₂、H₃BO₃、H₂B₄O₇、B₂O₃、C₆H₅B(OH)₂、(C₆H₅O)₃B、(CH₃(CH₂)₃O)₃B、C₃H₉B₃O₆、(C₃H₇O₃)B、Li₃WO₄、(NH₄)₁₀W₁₂O₄₁·5H₂O and NH₄H₂PO₄However, the coating material is not limited thereto.

The coating layer may be formed by a method known in the art, and for example, a wet coating method, a dry coating method, a plasma coating method, or Atomic Layer Deposition (ALD) may be used.

The heat treatment may be carried out at 100 ℃ to 700 ℃, e.g., 300 ℃ to 450 ℃, for 1 hour to 15 hours, e.g., 3 hours to 8 hours.

The lithium nickel cobalt manganese-based positive electrode active material represented by formula 2 is a high nickel positive electrode active material having a nickel proportion of more than 50 mol%, and is excellent in energy density characteristics. Therefore, in the case where the lithium nickel cobalt manganese-based positive electrode active material represented by formula 2 is used in a mixture with the spinel-structured lithium manganese-based positive electrode active material of the present invention, the capacity problem that is a disadvantage of the lithium manganese-based positive electrode active material can be solved.

The positive electrode material including the lithium manganese-based positive electrode active material and the lithium nickel cobalt manganese-based positive electrode active material may have a bimodal particle size distribution including an average particle size (D)₅₀) Large-sized particles of 4 to 20 μm, and an average particle diameter (D)₅₀) Is the average particle diameter (D) of the large-size particles₅₀) From 10% to 75%, for example from 25% to 75% of small size particles. In the case where the positive electrode material having the bimodal particle size distribution is used as described above, a positive electrode having high electrode density and energy density can be formed.

Preferably, the average particle diameter (D) of the large-sized particles₅₀) Can be 8 μm to 20 μm, 8 μm to 15 μm, or 12 μm to 20 μm, and the small-sized particles have an average particle diameter (D)₅₀) May be 1 μm to 15 μm, 2 μm to 13 μm, 2 μm to 8 μm, or 4 μm to 13 μm.

According to one embodiment, the cathode material of the present invention may have a bimodal particle size distribution including large-sized particles having an average particle size of 8 to 15 μm and small-sized particles having an average particle size of 1 to 6 μm.

According to another embodiment, the cathode material of the present invention may have a bimodal particle size distribution including large-sized particles having an average particle size of 12 to 20 μm and small-sized particles having an average particle size of 4 to 13 μm.

The type of the active material constituting the small-sized particles and the large-sized particles is not particularly limited, but the active material may be a lithium manganese-based positive electrode active material and/or a lithium nickel cobalt manganese-based positive electrode active material.

According to one embodiment, in the cathode material of the present invention, the lithium manganese-based cathode active material may constitute large-sized particles, and the lithium nickel cobalt manganese-based cathode active material may constitute small-sized particles. In this case, the average particle diameter (D) of the lithium manganese-based positive electrode active material₅₀) May be 8 μm to 20 μm, for example, about 12 μm to 20 μm, and an average particle diameter (D) of the lithium nickel cobalt manganese-based positive electrode active material₅₀) Can be 1 μm to 15 μm, for example about 4 μm to 13 μm. When the lithium manganese-based positive electrode active material is used as large-sized particles satisfying the above range, the dissolution of manganese from the lithium manganese-based positive electrode active material can be more effectively suppressed, and as a result, the high-temperature stability of the battery can be further improved.

According to another embodiment, in the cathode material of the present invention, the lithium manganese-based cathode active material may constitute small-sized particles, and the lithium nickel cobalt manganese-based cathode active material may constitute large-sized particles. In this case, the average particle diameter (D) of the lithium manganese-based positive electrode active material₅₀) May be 1 μm to 15 μm, for example, about 1 μm to 8 μm, and an average particle diameter (D) of the lithium nickel cobalt manganese-based positive electrode active material₅₀) Can be 8 μm to 20 μm, for example about 8 μm to 15 μm. When the lithium manganese-based positive electrode active material is used as small-sized particles satisfying the above-described range, the amount of doping and/or coating of the lithium manganese-based positive electrode active material may be increased, and side reactions with the electrolyte solution may be minimized by allowing to have a low BET value.

According to another embodiment, the cathode material of the present invention may have a bimodal particle size distribution in which at least one of the lithium manganese-based cathode active material and the lithium nickel cobalt manganese-based cathode active material includes large-sized particles and small-sized particles.

The cathode material may include a lithium manganese-based cathode active material and a lithium nickel cobalt manganese-based cathode active material in a weight ratio of 10:90 to 90:10, such as 40:60 to 60: 40. When the mixing ratio of the lithium manganese-based positive electrode active material to the lithium nickel cobalt manganese-based positive electrode active material satisfies the above range, an electrode having excellent high-temperature storage properties and excellent capacity characteristics can be obtained.

The content of the cathode active material may be 80 parts by weight to 99 parts by weight, for example, 85 parts by weight to 98.5 parts by weight, based on 100 parts by weight of the total weight of the cathode active material layer. When the content of the positive electrode active material is within the above range, excellent capacity characteristics may be obtained.

The positive electrode collector is not particularly limited as long as it has conductivity without causing adverse chemical changes of the battery, and for example, stainless steel, aluminum, nickel, titanium, sintered carbon, or aluminum or stainless steel surface-treated with one of carbon, nickel, titanium, silver, or the like may be used. Also, the positive electrode current collector may generally have a thickness of 3 to 500 μm, and microscopic irregularities may be formed on the surface of the current collector to improve adhesion of the positive electrode active material. The positive electrode current collector may be used in various shapes, for example, in the shape of a film, a sheet, a foil, a mesh, a porous body, a foam, a nonwoven fabric, or the like.

The conductive agent is used to provide conductivity to the electrode, wherein any conductive agent may be used without particular limitation so long as it has suitable electronic conductivity and does not cause adverse chemical changes of the battery. Specific examples of the conductive agent may be: graphite, such as natural graphite or artificial graphite; carbon-based materials such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black, and carbon fiber; powders or fibers of metals such as copper, nickel, aluminum, and silver; conductive whiskers such as zinc oxide whiskers and potassium titanate whiskers; conductive metal oxides such as titanium oxide; or a conductive polymer such as a polyphenylene derivative, and any one thereof or a mixture of two or more thereof may be used. The content of the conductive agent may be generally 0.1 parts by weight to 15 parts by weight based on 100 parts by weight of the total weight of the positive electrode active material layer.

The binder improves adhesion between the positive electrode active material particles and adhesion between the positive electrode active material and the current collector. Specific examples of the binder may be polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer (EPDM), sulfonated EPDM, styrene-butadiene rubber (SBR), fluororubber, or various copolymers thereof, and any one thereof or a mixture of two or more thereof may be used. The content of the binder may be 0.1 to 15 parts by weight based on 100 parts by weight of the total weight of the positive electrode active material layer.

The positive electrode of the present invention may be prepared according to a common positive electrode preparation method, in addition to using the above spinel-structured lithium manganese-based positive electrode active material. In particular, a positive electrode material mixture prepared by dissolving or dispersing a positive electrode active material and optionally a binder and/or a conductive agent in a solvent is coated on a positive electrode current collector, and then the coated positive electrode current collector may be dried and rolled to prepare a positive electrode.

The solvent may be a solvent generally used in the art, for example, the solvent may include dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, or water, and any one thereof or a mixture of two or more thereof may be used. The amount of the solvent used may be sufficient if the cathode material mixture can be adjusted to have an appropriate viscosity in consideration of the coating thickness of the slurry and the manufacturing yield.

Further, as another method, the positive electrode may be prepared as follows: the positive electrode material mixture is cast on a separate support, and then the film peeled off from the support is laminated on a positive electrode current collector.

Lithium secondary battery

Next, the lithium secondary battery of the present invention will be described.

The lithium secondary battery of the present invention includes a positive electrode, a negative electrode, a separator provided between the positive electrode and the negative electrode, and an electrolyte, wherein the positive electrode is the same as the positive electrode of the present invention described above. Therefore, detailed description of the positive electrode will be omitted, and only the remaining configuration will be described below.

The negative electrode includes a negative electrode current collector and a negative electrode active material layer disposed on the negative electrode current collector.

The negative electrode collector is not particularly limited as long as it has high conductivity and does not cause adverse chemical changes of the battery, and for example, copper, stainless steel, aluminum, nickel, titanium, sintered carbon, copper or stainless steel surface-treated with one of carbon, nickel, titanium, silver, or the like, and aluminum-cadmium alloy may be used. In addition, the negative electrode current collector may generally have a thickness of 3 to 500 μm, and, similar to the positive electrode current collector, microscopic irregularities may be formed on the surface of the current collector to improve adhesion of the negative electrode active material. The negative electrode current collector may be used in various shapes, for example, in the shape of a film, a sheet, a foil, a mesh, a porous body, a foam, a nonwoven fabric body, or the like.

The anode active material layer selectively includes a binder and a conductive agent in addition to the anode active material.

Various anode active materials used in the art may be used as the anode active material, and the anode active material is not particularly limited. Specific examples of the anode active material may be: carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber, and amorphous carbon; a metal substance that can be alloyed with lithium, such as silicon (Si), aluminum (Al), tin (Sn), lead (Pb), zinc (Zn), bismuth (Bi), indium (In), magnesium (Mg), gallium (Ga), cadmium (Cd), a Si alloy, a Sn alloy, or an Al alloy; metal oxides which can be doped and dedoped with lithium, e.g. SiO_β(0<β<2)、SnO₂Vanadium oxide and lithium vanadium oxide; or a composite comprising a metal substance and a carbonaceous material, such as a Si-C composite or a Sn-C composite, and any one thereof or a mixture of two or more thereof may be used. In addition, a metallic lithium thin film may be used as a negative active material. In addition, both low-crystalline carbon and high-crystalline carbon can be used as the carbon material. Common examples of the low crystalline carbon may be soft carbon and hard carbon, and common examples of the high crystalline carbon may be irregular, planar, flaky, spherical or fibrous natural or artificial graphite, Kish graphite, pyrolytic carbon, mesophase pitch-based carbon fiber, mesocarbon microbeads, mesophase pitch and high-temperature sintered carbon, such asSuch as petroleum or coal tar pitch derived coke.

In the lithium secondary battery of the present invention, it is desirable to use a mixture of two or more carbon materials having a specific surface area as the negative electrode active material.

For example, the negative active material may include natural graphite and soft carbon, and may specifically include a specific surface area (BET) of 2.5m²G to 4.0m²Natural graphite/g and a specific surface area (BET) of 7m²G to 10m²Soft carbon per gram. When the positive electrode of the present invention and the negative electrode including the natural graphite satisfying the above specific surface area and the soft carbon are disposed in combination, the high-temperature durability of the secondary battery can be more improved. The negative active material layer may further include artificial graphite, if necessary, and in this case, the artificial graphite may have a specific surface area (BET) of 0.1m²G to 1.2m²/g。

In particular, the anode active material layer may include 70 to 95 wt% of natural graphite, 0 to 25 wt% of artificial graphite, and 5 to 30 wt% of soft carbon, based on the total weight of the anode active material.

In addition, the negative active material may include natural graphite and artificial graphite, and may specifically include a specific surface area (BET) of 2.5m²G to 4.0m²Natural graphite/g and a specific surface area (BET) of 0.1m²G to 1.2m²Per g of artificial graphite. If necessary, the anode active material layer may further include soft carbon, and in this case, the specific surface area (BET) of the soft carbon may be 7m²G to 10m²(ii) in terms of/g. In particular, the anode active material layer may include 10 to 50 wt% of natural graphite, 50 to 90 wt% of artificial graphite, and 0 to 20 wt% of soft carbon, based on the total weight of the anode active material. In this case, since the negative electrode rate capability is improved, a battery having excellent rapid cell charging characteristics and resistance characteristics can be realized.

The content of the anode active material may be 80 to 99 wt% based on the total weight of the anode active material layer.

The binder is a component contributing to adhesion between the conductive agent, the active material, and the current collector, wherein the binder is generally added in an amount of 0.1 to 10 wt% based on the total weight of the anode active material layer. Examples of the binder may be polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene copolymer (EPDM), sulfonated EPDM, styrene-butadiene rubber, fluororubber, and various copolymers thereof.

The conductive agent is a component for further improving the conductivity of the anode active material, wherein the conductive agent may be added in an amount of 10 wt% or less, for example, 5 wt% or less, based on the total weight of the anode active material layer. The conductive agent is not particularly limited as long as it has conductivity without causing adverse chemical changes in the battery, and for example, conductive materials that can be used are: graphite, such as natural graphite or artificial graphite; carbon black such as acetylene black, ketjen black, channel black, furnace black, lamp black and thermal black; conductive fibers such as carbon fibers and metal fibers; metal powders such as fluorocarbon powder, aluminum powder, and nickel powder; conductive whiskers such as zinc oxide whiskers and potassium titanate whiskers; conductive metal oxides such as titanium oxide; or a polyphenylene derivative.

The anode active material layer may be prepared, for example, by the following process: dissolving or dispersing a negative electrode active material and optionally a binder and a conductive agent in a solvent to form a composition for negative electrode formation, coating the composition on a negative electrode current collector and drying the coated negative electrode current collector; or may be prepared by the following process: the composition for forming a negative electrode is cast on a separate support, and then the film separated from the support is laminated on a negative electrode current collector.

The anode active material layer may have a single-layer structure, or may have a multilayer structure in which two or more layers are stacked. For example, the negative electrode may include: the negative electrode current collector, the first negative electrode active material layer formed on the negative electrode current collector, and the second negative electrode active material layer formed on the first negative electrode active material layer, wherein the first negative electrode active material layer and the second negative electrode active material layer may have different compositions from each other.

For example, the first anode active material layer may include natural graphite, the natural graphite accounting for 5 to 100 wt%, for example, 80 to 100 wt%, of the total anode active material included in the first anode active material layer, and the second anode active material layer may include soft carbon, the soft carbon accounting for 15 to 95 wt%, for example, 15 to 65 wt%, of the total anode active material included in the second anode active material layer. When the anode having the above-described structure is used, the processability can be improved by improving the electrode adhesion, and a battery having excellent high-temperature storage characteristics as well as excellent quick-charge performance and electric resistance performance can be prepared.

The loading amount of the negative electrode may be 300mg/25cm²To 500mg/25cm²E.g. 300mg/25cm²To 400mg/25cm². When the loading amount of the negative electrode satisfies the above range, processing can be facilitated by ensuring sufficient electrode adhesion, a battery having excellent rapid charging performance and resistance performance can be realized, and energy density can be maximized.

In the lithium secondary battery, a separator separates a negative electrode and a positive electrode and provides a moving path of lithium ions, wherein any separator may be used as the separator without particular limitation as long as it is generally used in the lithium secondary battery, and particularly, a separator having high moisturizing ability to an electrolytic solution and low resistance to the transport of electrolyte ions may be used. Specifically, a porous polymer film, for example, a porous polymer film made of a polyolefin-based polymer (e.g., an ethylene homopolymer, a propylene homopolymer, an ethylene/butene copolymer, an ethylene/hexene copolymer, and an ethylene/methacrylate copolymer), or a laminated structure having two or more layers of the above-described polymers may be used. Also, a common porous nonwoven fabric, for example, a nonwoven fabric formed of high-melting glass fibers or polyethylene terephthalate fibers, may be used. In addition, a coated separator including a ceramic component or a polymer material may be used to ensure heat resistance or mechanical strength, and a separator having a single-layer or multi-layer structure may be selectively used.

Further, as the electrolyte used in the present invention, an organic liquid electrolyte, an inorganic liquid electrolyte, a solid polymer electrolyte, a gel-type polymer electrolyte, a solid inorganic electrolyte, or a melt-type inorganic electrolyte that can be used in a lithium secondary battery may be used, and the electrolyte is not particularly limited.

Specifically, the electrolyte may include an organic solvent and a lithium salt.

Any organic solvent may be used as the organic solvent without particular limitation so long as it can serve as a medium through which ions participating in the electrochemical reaction of the battery can move. Specifically, as the organic solvent, there can be used: ester solvents such as methyl acetate, ethyl acetate, γ -butyrolactone and ∈ -caprolactone; ether solvents such as dibutyl ether or tetrahydrofuran; ketone solvents such as cyclohexanone; aromatic hydrocarbon solvents such as benzene and fluorobenzene; or carbonate-based solvents such as dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (MEC), Ethyl Methyl Carbonate (EMC), Ethylene Carbonate (EC), and Propylene Carbonate (PC); alcohol solvents such as ethanol and isopropanol; nitriles such as Ra-CN (where Ra is a linear, branched or cyclic C2 to C20 hydrocarbyl group and may include double bond aromatic rings or ether linkages); amides, such as dimethylformamide; dioxolanes, such as 1, 3-dioxolane; or sulfolanes. Among these solvents, a carbonate-based solvent may be used, for example, a mixture of a cyclic carbonate (e.g., ethylene carbonate or propylene carbonate) having a high ion conductivity type and a high dielectric constant, and a low-viscosity linear carbonate-based compound (e.g., ethylene carbonate, dimethyl carbonate, or diethyl carbonate), which may improve the charge/discharge performance of a battery, may be used. In this case, when the cyclic carbonate and the chain carbonate are mixed in a volume ratio of about 1:1 to about 1:9, the performance of the electrolyte solution may be excellent.

Any lithium salt commonly used in an electrolyte solution for a lithium secondary battery may be used as the above-mentioned lithium salt without limitation, and for example, the lithium salt may include Li as a cation⁺And may include as an anion a compound selected from the group consisting of F^-、Cl^-、Br^-、I^-、NO₃ ^-、N(CN)₂ ^-、BF₄ ^-、ClO₄ ^-、AlO₄ ^-、AlCl₄ ^-、PF₆ ^-、SbF₆ ^-、AsF₆ ^-、BF₂C₂O₄ ^-、BC₄O₈ ^-、PF₄C₂O₄ ^-、PF₂C₄O₈ ^-、(CF₃)₂PF₄ ^-、(CF₃)₃PF₃ ^-、(CF₃)₄PF₂ ^-、(CF₃)₅PF^-、(CF₃)₆P^-、CF₃SO₃ ^-、C₄F₉SO₃ ^-、CF₃CF₂SO₃ ^-、(CF₃SO₂)₂N^-、(FSO₂)₂N^-、CF₃CF₂(CF₃)₂CO^-、(CF₃SO₂)₂CH^-、(SF₅)₃C^-、(CF₃SO₂)₃C^-、CF₃(CF₂)₇SO₃ ^-、CF₃CO₂ ^-、CH₃CO₂ ^-、SCN^-And (CF)₃CF₂SO₂)₂N^-At least one of the group consisting of. Specifically, the lithium salt may include one or more compounds selected from the group consisting of LiCl, LiBr, LiI, and LiClO₄、LiBF₄、LiB₁₀Cl₁₀、LiPF₆、LiCF₃SO₃、LiCH₃CO₂、LiCF₃CO₂、LiAsF₆、LiSbF₆、LiAlCl₄、LiAlO₄And LiCH₃SO₃A single material of the group, or a mixture of two or more thereof。

The lithium salt may be appropriately changed within a commonly used range, but the concentration in the electrolyte solution may be specifically 0.8M to 3M, for example, 0.1M to 2.5M.

In order to improve the life characteristics of the battery, suppress the decrease in the battery capacity, and increase the discharge capacity of the battery, various additives may be further added to the electrolyte in addition to the electrolyte components.

In addition, if necessary, an additive may be further included in the electrolyte. As the additive, for example, a halogenated alkylene carbonate-based compound (e.g., difluoroethylene carbonate), pyridine, triethyl phosphite, triethanolamine, cyclic ether, ethylenediamine, N-glyme, hexaphosphoric triamide, a nitrobenzene derivative, sulfur, a quinonimine dye, N-substituted oxazolidinone, N-substituted imidazolidine, ethylene glycol dialkyl ether, an ammonium salt, pyrrole, 2-methoxyethanol, or aluminum trichloride may be included, and these additives may be used alone or as a mixture. In this case, the additive may be contained in an amount of 0.1 to 5 wt% based on the total weight of the electrolyte.

The above-described lithium secondary battery of the present invention may be suitably used for portable devices such as mobile phones, notebook computers, and digital cameras, as well as electric vehicles such as Hybrid Electric Vehicles (HEVs).

Therefore, according to another embodiment of the present invention, there are provided a battery module (battery module) including the lithium secondary battery as a cell unit and a battery pack (battery pack) including the battery module.

The battery module or the battery pack may be used as a power source for at least one of the following middle-and large-sized devices: an electric tool; electric vehicles, including Electric Vehicles (EVs), hybrid electric vehicles, and plug-in hybrid electric vehicles (PHEVs); or an electrical power storage system.

The shape of the lithium secondary battery of the present invention is not particularly limited, and a cylindrical shape, a prismatic shape, a pouch shape, or a coin shape using a can may be used.

The lithium secondary battery of the present invention may be used not only in a battery cell used as a power source for a small-sized device, but also as a unit cell in a middle or large-sized battery module including a plurality of battery cells.

Hereinafter, the present invention will be described in detail according to specific examples. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these example embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.