阅读说明：本技术 一种硫化物包覆的正极材料及其制备方法和锂离子电池 (Sulfide-coated positive electrode material, preparation method thereof and lithium ion battery ) 是由 贾孝波 严武渭 杨顺毅 黄友元 于 2019-08-28 设计创作，主要内容包括：本发明提供了一种硫化物包覆的正极材料及其制备方法和锂离子电池。所述硫化物包覆的正极材料包括含锂正极材料以及包覆在含锂正极材料表面的硫化物包覆层,所述含锂正极材料包括三元材料。所述制备方法包括：1)将含锂正极材料与溶剂混合并与硫源进行反应,得到表面带有硫化锂的正极材料；2)将表面带有硫化锂的正极材料与其他原料混合,进行热处理,得到所述硫化物包覆的正极材料。本发明提供的硫化物包覆的正极材料解决了三元正极材料表面残碱的问题以及表面结构不稳定的问题,其表面结构稳定性好、离子电导率高、界面阻抗低,具有低残碱和循环稳定性优异的特性。(The invention provides a sulfide-coated positive electrode material, a preparation method thereof and a lithium ion battery. The sulfide-coated positive electrode material comprises a lithium-containing positive electrode material and a sulfide coating layer coated on the surface of the lithium-containing positive electrode material, and the lithium-containing positive electrode material comprises a ternary material. The preparation method comprises the following steps: 1) mixing a lithium-containing anode material with a solvent and reacting with a sulfur source to obtain an anode material with lithium sulfide on the surface; 2) and mixing the cathode material with the lithium sulfide on the surface with other raw materials, and carrying out heat treatment to obtain the sulfide-coated cathode material. The sulfide-coated cathode material provided by the invention solves the problems of surface residual alkali and unstable surface structure of a ternary cathode material, and has the characteristics of good surface structure stability, high ionic conductivity, low interface impedance, low residual alkali and excellent cycling stability.)

1. The sulfide-coated positive electrode material is characterized by comprising a lithium-containing positive electrode material and a sulfide coating layer coated on the surface of the lithium-containing positive electrode material, wherein the lithium-containing positive electrode material comprises a ternary material.

2. The sulfide-coated positive electrode material according to claim 1, wherein the ternary material has a layered structure;

preferably, the ternary material is a single crystal material;

preferably, the ternary material has a molecular formula of Li_aNi_xCo_yM_1-x-yO₂Wherein a is more than or equal to 0.9 and less than or equal to 1.1, x is more than or equal to 0.5 and less than or equal to 1.0, y is more than 0 and less than or equal to 0.3, and M is Mn and/or Al;

preferably, the lithium-containing positive electrode material has an average particle diameter of 3.5 to 17.0 μm.

3. The sulfide-coated positive electrode material according to claim 1 or 2, wherein the sulfide coating layer is a sulfide solid state electrolyte coating layer;

preferably, the sulfide solid electrolyte coating layer is mainly prepared from lithium sulfide, an auxiliary component and a stabilizer as raw materials;

preferably, the auxiliary component comprises phosphorus pentasulfide;

preferably, the auxiliary component has an average particle size of 1 to 100 nm;

preferably, the stabilizer comprises any one of zirconium dioxide, ferrous sulfide or copper oxide or a combination of at least two of the same;

preferably, the average particle size of the stabilizer is 30-60 nm;

preferably, in the sulfide coating layer, the mole percentage of lithium sulfide, auxiliary components and stabilizing agent as raw materials is (70-80): [ (20-a) - (30-a) ]: a, wherein, a is more than 0 and less than or equal to 10;

preferably, the thickness of the sulfide coating layer is 5-100 nm.

4. A method for producing the sulfide-coated positive electrode material according to any one of claims 1 to 3, comprising the steps of:

(1) mixing a lithium-containing anode material with a solvent and reacting with a sulfur source to obtain an anode material with lithium sulfide on the surface;

(2) and (2) mixing the cathode material with the lithium sulfide on the surface in the step (1) with other raw materials, and carrying out heat treatment to obtain the sulfide-coated cathode material.

5. The method according to claim 3 or 4, wherein the solvent of step (1) comprises any one or a combination of at least two of anhydrous ethanol, diethyl ether or hexane;

preferably, the mixing method in the step (1) is stirring;

preferably, the sulfur source of step (1) comprises hydrogen sulfide;

preferably, the method for reacting with a sulfur source in step (1) comprises: introducing sulfur source gas into a reaction system;

preferably, the introduction rate of the sulfur source gas is 1-5L/min;

preferably, the reaction of step (1) is carried out for 1-2 h;

preferably, the reaction of step (1) is carried out with stirring;

preferably, the reaction with the sulfur source of step (1) is carried out in an inerting reactor;

preferably, step (1) further comprises: after the reaction, the reaction product was subjected to solid-liquid separation and dried.

6. The production method according to any one of claims 4 to 5, wherein in the step (2), the other raw materials include an auxiliary component and a stabilizer;

preferably, the auxiliary component comprises phosphorus pentasulfide;

preferably, the auxiliary component has an average particle size of 1 to 100 nm;

preferably, the stabilizer comprises any one of zirconium dioxide, ferrous sulfide or copper oxide or a combination of at least two of the same;

preferably, the average particle size of the stabilizer is 30-60 nm;

preferably, the mol percentage of the lithium sulfide, the auxiliary component and the stabilizer is (70-80): [ (20-a) - (30-a) ]: a, wherein a is more than 0 and less than or equal to 10.

7. The method according to any one of claims 4 to 6, wherein the mixing of step (2) is carried out under a protective atmosphere;

preferably, the protective atmosphere comprises nitrogen and/or argon;

preferably, the mixing of step (2) is carried out in a coating machine;

preferably, the rotating speed of the coating machine is 141-910 rpm;

preferably, the mixing time of step (2) is 0.5-1 h.

8. The production method according to any one of claims 4 to 7, wherein the heat treatment of step (2) is performed under a protective atmosphere;

preferably, the protective atmosphere comprises nitrogen and/or argon;

preferably, the temperature of the heat treatment in the step (2) is 500-650 ℃;

preferably, the heating rate of the heat treatment in the step (2) is 1.5-5 ℃/min;

preferably, the time of the heat treatment in the step (2) is 5-9 h;

preferably, the heat treatment method of step (2) comprises: and placing the mixed product into a closed quartz tube, placing the quartz tube into a tube furnace, and carrying out heat treatment under a protective atmosphere.

9. The method for preparing according to any one of claims 4 to 8, characterized in that it comprises the following steps:

(1) stirring and mixing the lithium-containing anode material and absolute ethyl alcohol, introducing hydrogen sulfide gas at the introduction rate of 1-5L/min, reacting for 1-2h under the stirring condition, and then carrying out solid-liquid separation and drying to obtain the anode material with lithium sulfide on the surface;

(2) mixing the positive electrode material with the lithium sulfide on the surface in the step (1), the auxiliary component and the stabilizer in a coating machine for 0.5-1h under a protective atmosphere, wherein the rotating speed of the coating machine is 141-650 rpm, then placing the mixed product in a closed quartz tube, then placing the quartz tube in a tube furnace, heating at the heating rate of 1.5-5 ℃/min under the protective atmosphere, and carrying out heat treatment at the temperature of 500-650 ℃ for 5-9h to obtain the sulfide coated positive electrode material;

the mol percentage of the lithium sulfide, the auxiliary component and the stabilizer is (70-80): [ (20-a) - (30-a) ]: a, wherein a is more than 0 and less than or equal to 10.

10. A lithium ion battery comprising the sulfide-coated positive electrode material according to any one of claims 1 to 3.

Technical Field

The invention belongs to the technical field of battery materials, and relates to a positive electrode material, a preparation method thereof and a lithium ion battery, in particular to a sulfide-coated positive electrode material, a preparation method thereof and a lithium ion battery.

Background

Rechargeable lithium ion batteries have taken a significant position in the development of clean energy with their advantages of low cost, high reliability, and long life, and have enjoyed great success in the fields of consumer electronics, portable devices, and electric vehicles. In addition, as government policies have increased the demand for energy density, the development of high energy density lithium ion batteries is urgently in need of a cathode material having a high specific capacity, a long cycle and a wide operating voltage.

Wherein the nickel is rich (nickel content)>60%) of a layered oxide positive electrode material (LiNi)_xCo_yMn_1-x-yO₂Or LiNi_xCo_yAl_1-x-yO₂) The cost is low, the discharge capacity is high, and the lithium ion battery is a positive electrode material with great potential in current commercialization. But it also presents certain problems in itself: 1) the surface structure is unstable: the lithium removal of the electrode material is started from the surface layer, the phenomenon of excessive lithium removal occurs in the surface layer structure along with the charging, meanwhile, the layered structure of the high-nickel ternary material is converted into a spinel structure and an inert rock salt structure, a thicker inert layer (the main component is NiO) is formed on the surface layer of the material along with the increase of the charging times, and in addition, serious side reaction occurs between high-valence transition metal ions with strong oxidizing property in the surface layer and electrolyte, so that the polarization increase, the impedance increase and the capacity rapid attenuation of the battery are caused; 2) residual alkali problem on the surface of the material: the nickel element in the ternary material is alkaline, has high affinity with air moisture and carbon dioxide, and reacts with the surface of the material to generate LiOH and Li₂CO₃I.e., "residual alkali", the presence of residual alkali not only affects the electrochemical properties and storage properties of the materials, but also hinders the preparation of electrodes, preventing their practical use.

The electrochemical performance of the cathode material can be improved by modifying the surface of the cathode material by synthesizing a solid electrolyte through a conventional solid phase method, for example, CN108682819A mixes a carbon material into the solid electrolyte to coat and modify the cathode material, so that the electron conductivity of the cathode material is improved, and the rate characteristic and the cycle characteristic of the cathode material are greatly improved. But the improvement degree is limited, and the problem of residual alkali on the surface of the material is not solved.

CN108807926A discloses a Co/B Co-coated nickel-cobalt-manganese-lithium ion positive electrode material and a preparation method thereof. The method comprises the following steps: step S1, weighing a nickel-cobalt-manganese composite precursor; s2, weighing a certain amount of F and W-containing compound and a certain amount of lithium source compound according to the metal content of nickel, cobalt and manganese in the nickel-cobalt-manganese precursor according to an expected proportion; step S3, adding the compound containing F and W, a nickel-cobalt-manganese precursor and a lithium source compound into a high-speed mixer together for full mixing, and then calcining to obtain a doped base material; step S4, adding the doped base material into deionized water, uniformly stirring, then dropwise adding cobalt salt, and continuously stirring to obtain cobalt hydroxide coated anode material slurry; step S5, filtering, washing and drying the positive electrode material slurry to obtain positive electrode material powder coated by cobalt hydroxide; step S6, mixing the cobalt hydroxide-coated positive electrode material powder with lithium salt and carrying out secondary sintering to obtain a cobalt-coated positive electrode material; and step S7, adding the compound containing the B source and the positive electrode material coated with the cobalt into a high-speed mixer for fully mixing, and then calcining to obtain the Co/B Co-coated nickel-cobalt-manganese-lithium positive electrode material. The method has extremely complicated steps, and although the method has a certain effect of reducing the surface residual alkali, the preparation cost and the raw material cost make the method have poor industrial application prospect.

CN109148878A discloses a method for treating residual alkali on the surface of a lithium-containing cathode material, a cathode material and a lithium ion battery. The method comprises the following steps: lithium carbonate on the surface of the lithium-containing cathode material is reacted with a reducing agent under an inert atmosphere, so that the lithium carbonate is reduced into a gaseous product and an oxide of lithium. Although the method is simple to operate, the effect is poor, and the residual alkali treatment is not thorough.

Disclosure of Invention

Aiming at the defects in the prior art, the invention aims to provide a sulfide-coated cathode material, a preparation method thereof and a lithium ion battery. The cathode material provided by the invention has low residual alkali and excellent cycling stability.

In order to achieve the purpose, the invention adopts the following technical scheme:

in a first aspect, the present invention provides a sulfide-coated positive electrode material, where the sulfide-coated positive electrode material includes a lithium-containing positive electrode material and a sulfide coating layer coated on a surface of the lithium-containing positive electrode material, and the lithium-containing positive electrode material includes a ternary material.

The sulfide-coated cathode material provided by the invention solves the problems of residual alkali on the surface of a ternary cathode material and unstable surface structure. The positive electrode material provided by the invention has the advantages of good surface structure stability, high ionic conductivity and low interface impedance.

In the sulfide-coated positive electrode material provided by the invention, the sulfide coating layer can completely coat the surface of the lithium-containing positive electrode material and can also partially coat the surface of the lithium-containing positive electrode material. The sulfide coating layer can remove residual alkali on the surface of the lithium-containing anode material on one hand, and also plays a role in improving the stability of the surface structure of the anode material in the charging and discharging process on the other hand, thereby improving the electrochemical performance of the material.

The following is a preferred technical solution of the present invention, but not a limitation to the technical solution provided by the present invention, and the technical objects and advantageous effects of the present invention can be better achieved and achieved by the following preferred technical solution.

As a preferable technical scheme of the invention, the ternary material is of a layered structure.

Preferably, the ternary material is a single crystal material.

Preferably, the ternary material has a molecular formula of Li_aNi_xCo_yM_1-x-yO₂Where 0.9. ltoreq. a.ltoreq.1.1, for example a is 0.9, 0.95, 1, 1.05 or 1.1 etc., 0.5. ltoreq. x < 1.0, for example x is 0.5, 0.6, 0.7, 0.8 or 0.9 etc., 0 < y. ltoreq.0.3, for example y is 0.1, 0.15, 0.2, 0.25 or 0.3 etc., M is Mn and/or Al.

Preferably, the lithium-containing positive electrode material has an average particle size of 3.5 to 17.0. mu.m, for example, 3.5. mu.m, 5.2. mu.m, 7.5. mu.m, 9.0. mu.m, 10.0. mu.m, 12.5. mu.m, 15.0. mu.m, or 17.0. mu.m, but is not limited to the values listed, and other values not listed in the numerical range are also applicable.

In a preferred embodiment of the present invention, the sulfide coating layer is a sulfide solid electrolyte coating layer. The sulfide solid electrolyte coating layer is adopted, so that the stability of the surface structure of the anode material in the charging and discharging process can be obviously improved, and the electrochemical performance of the material is further improved.

Preferably, the sulfide solid electrolyte coating layer is mainly prepared from lithium sulfide, an auxiliary component and a stabilizer as raw materials. The lithium in the lithium sulfide is provided by residual alkali on the surface of the lithium-containing cathode material, the auxiliary component is used for reacting with the lithium sulfide to form the solid electrolyte, and a small amount of stabilizer can react with the lithium sulfide and the auxiliary component to form the solid electrolyte, and can also improve the stability and prevent the sulfide solid electrolyte from releasing hydrogen sulfide gas.

Preferably, the auxiliary component comprises phosphorus pentasulfide.

Preferably, the auxiliary component has an average particle size of 1 to 100nm, for example 1nm, 10nm, 20nm, 30nm, 40nm, 50nm, 60nm, 70nm, 80nm, 90nm or 100nm, but not limited to the values listed, and other values not listed within this range are equally applicable, preferably 40 to 100 nm.

Preferably, the stabilizer comprises any one of zirconium dioxide, ferrous sulfide or copper oxide or a combination of at least two thereof.

Preferably, the stabilizer has an average particle size of 30 to 60nm, such as 30nm, 35nm, 40nm, 45nm, 50nm, 55nm, 60nm, and the like, but is not limited to the recited values, and other values not recited within the range of values are equally applicable, preferably 10 to 50 nm.

Preferably, in the sulfide coating layer, the mole percentage of the lithium sulfide, the auxiliary component and the stabilizer as raw materials is (70-80) < 20-a to (30-a) < a (mol%), for example, 70 (20-a): a, 72 (30-a): a, 75 (28-a): a, 78 (25-a): a or 80 (30-a): a, and the like, wherein 0 < a ≦ 10, for example, a is 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10, and the like. In the invention, if the auxiliary components are excessive, other impurities can be generated, so that the conductivity of the material is influenced; if the amount of the auxiliary component is too small, it may be difficult to form a desired sulfide solid electrolyte. In the invention, if the stabilizer is excessive, impurities are formed, and the impedance of the material is increased; if the amount of the stabilizer is too small, the sulfide solid electrolyte may be unstable to produce hydrogen sulfide gas.

Preferably, the sulfide coating has a thickness of 5 to 100nm, such as 5nm, 10nm, 25nm, 50nm, 75nm, or 100nm, but not limited to the recited values, and other values not recited within the range of values are equally applicable. In the invention, if the thickness of the sulfide coating layer is too thin, the coating effect is poor, and the improvement of the cycle performance of the material cannot be achieved; if the thickness of the sulfide coating layer is too thick, the transmission path of lithium ions is increased, and the impedance of the material is increased.

In a second aspect, the present invention provides a method for producing a sulfide-coated positive electrode material as described in the first aspect, the method comprising the steps of:

(1) mixing a lithium-containing anode material with a solvent and reacting with a sulfur source to obtain an anode material with lithium sulfide on the surface;

(2) and (2) mixing the cathode material with the lithium sulfide on the surface in the step (1) with other raw materials, and carrying out heat treatment to obtain the sulfide-coated cathode material.

In the preparation method provided by the invention, the sulfur source reacts with residual alkali on the surface of the lithium-containing anode material, so that lithium sulfide is generated on the surface of the lithium-containing anode material while the residual alkali is eliminated. And then synthesizing the sulfide electrolyte coated on the surface of the anode material by using lithium sulfide and other raw materials through a high-temperature solid-phase sintering method, so that the stability of the surface structure of the anode material in the charging and discharging processes can be obviously improved, and the electrochemical performance of the material is further improved.

The preparation method provided by the invention not only reduces the residual alkali amount on the surface of the material, but also takes the lithium sulfide generated by the reaction as the raw material to prepare the sulfide solid electrolyte coating, and the lithium sulfide is uniformly distributed on the surface of the material after the reaction, so that the prepared coating layer is uniform and compact, the processing performance of the material is favorably improved, the stability of the surface structure of the material in the charging and discharging process is greatly improved, and the high lithium ion conductivity of the sulfide solid electrolyte can also effectively reduce the interface impedance of the material, thereby obviously improving the electrochemical performance of the material.

As a preferred technical scheme of the invention, the solvent in the step (1) comprises absolute ethyl alcohol.

Preferably, the mixing method in step (1) is stirring.

Preferably, the sulfur source of step (1) comprises hydrogen sulfide. The hydrogen sulfide can easily react with residual alkali on the surface of the lithium-containing anode material to generate lithium sulfide, and the lithium sulfide is used as a principle of subsequent reaction and solves the problem of residual alkali on the surface of the anode material.

Preferably, the method for reacting with a sulfur source in step (1) comprises: and introducing sulfur source gas into the reaction system.

Preferably, the sulfur source gas is introduced at a rate of 1 to 5L/min, such as 1L/min, 2L/min, 3L/min, 4L/min, or 5L/min, but not limited to the recited values, and other values not recited within the range of values are also applicable. If the introduction rate of the sulfur source gas is too high, lithium sulfide formed on the surfaces of the particles is aggregated, so that the next solid-phase reaction is not facilitated; if the introduction rate of the sulfur source gas is too slow, the residual alkali on the surface is left.

Preferably, the reaction of step (1) is carried out for 1-2 h.

Preferably, the reaction of step (1) is carried out with stirring.

Preferably, the reaction with the sulfur source described in step (1) is carried out in an inerting reactor. By inerting the reactor is meant that the vessel is inert and does not react with the contents. The reactor can provide a sealed environment, and prevent water and carbon dioxide in the air from interfering the reaction and preventing the introduced gas from leaking. The inerting reactor is preferably an inerting reactor with a gas inlet (submerged tube) and a gas outlet (scrubber).

Preferably, step (1) further comprises: after the reaction, the reaction product was subjected to solid-liquid separation and dried.

In the preferred technical scheme of the invention, in the step (2), the other raw materials comprise auxiliary components and stabilizing agents.

Preferably, the auxiliary component comprises phosphorus pentasulfide.

Preferably, the auxiliary component has an average particle size of 1 to 100nm, for example 1nm, 10nm, 20nm, 30nm, 40nm, 50nm, 60nm, 70nm, 80nm, 90nm or 100nm, but not limited to the values listed, and other values not listed within this range are equally applicable, preferably 40 to 100 nm.

Preferably, the stabilizer comprises any one of zirconium dioxide, ferrous sulfide or copper oxide or a combination of at least two thereof.

Preferably, the stabilizer has an average particle size of 30 to 60nm, such as 30nm, 35nm, 40nm, 45nm, 50nm, 55nm, 60nm, and the like, but is not limited to the recited values, and other values not recited within the range of values are equally applicable, preferably 10 to 50 nm.

Preferably, the molar percentage of the lithium sulfide, the auxiliary component and the stabilizer is (70-80) < 20-a) - (30-a > < a (mol%), for example 70 (20-a) < a, 72 (30-a) < a, 75 (28-a) < a, 78 (25-a) < a or 80 (30-a) < a, etc., wherein 0 < a < 10, for example, a is 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10, etc. In the actual preparation process, the method provided by the invention can sample and analyze the content of the lithium sulfide in the positive electrode material with the lithium sulfide on the surface before mixing, and further determine the addition amount of the auxiliary component and the stabilizer.

As a preferred embodiment of the present invention, the mixing in step (2) is carried out under a protective atmosphere.

Preferably, the protective atmosphere comprises nitrogen and/or argon;

preferably, the mixing of step (2) is carried out in a coating machine.

Preferably, the rotation speed of the coating machine is 141-910rpm, such as 141rpm, 150rpm, 200rpm, 300rpm, 400rpm, 500rpm, 600rpm, 700rpm, 800rpm or 910rpm, but is not limited to the enumerated values, and other unrecited values within the numerical range are also applicable.

Preferably, the mixing time in step (2) is 0.5 to 1 hour, such as 0.5 hour, 0.6 hour, 0.7 hour, 0.8 hour, 0.9 hour, 1 hour, etc., but not limited to the recited values, and other unrecited values within the range of values are also applicable.

In a preferred embodiment of the present invention, the heat treatment in step (2) is performed under a protective atmosphere.

Preferably, the protective atmosphere comprises nitrogen and/or argon.

Preferably, the temperature of the heat treatment in step (2) is 500-650 ℃, such as 500 ℃, 520 ℃, 550 ℃, 580 ℃, 600 ℃, 630 ℃ or 650 ℃, but not limited to the recited values, and other unrecited values within the range of values are equally applicable. In the present invention, if the heat treatment temperature is too high, the electrolyte may be caused to generate Li having poor ionic conductivity₃PS₄And Li₇PS₆A crystal; if the heat treatment temperature is too low, the resulting sulfide solid-phase electrolyte may have poor crystallinity.

Preferably, the heat treatment of step (2) has a temperature increase rate of 1.5-5 deg.C/min, such as 1.5 deg.C/min, 2 deg.C/min, 2.5 deg.C/min, 3 deg.C/min, 3.5 deg.C/min, 4 deg.C/min, 4.5 deg.C/min, or 5 deg.C/min, but is not limited to the recited values, and other values not recited in the range of values are also applicable.

Preferably, the heat treatment time in step (2) is 5-9h, such as 5h, 6h, 7h, 8h or 9h, but not limited to the recited values, and other values not recited in the range of values are also applicable.

Preferably, the heat treatment method of step (2) comprises: and placing the mixed product into a closed quartz tube, placing the quartz tube into a tube furnace, and carrying out heat treatment under a protective atmosphere.

As a further preferable technical scheme of the preparation method, the method comprises the following steps:

(1) stirring and mixing the lithium-containing anode material and absolute ethyl alcohol, introducing hydrogen sulfide gas at the introduction rate of 1-5L/min, reacting for 1-2h under the stirring condition, and then carrying out solid-liquid separation and drying to obtain the anode material with lithium sulfide on the surface;

(2) mixing the positive electrode material with the lithium sulfide on the surface in the step (1), the auxiliary component and the stabilizer in a coating machine for 0.5-1h under a protective atmosphere, wherein the rotating speed of the coating machine is 141-650 rpm, then placing the mixed product in a closed quartz tube, then placing the quartz tube in a tube furnace, heating at the heating rate of 1.5-5 ℃/min under the protective atmosphere, and carrying out heat treatment at the temperature of 500-650 ℃ for 5-9h to obtain the sulfide coated positive electrode material;

the mol percentage of the lithium sulfide, the auxiliary component and the stabilizer is (70-80): [ (20-a) - (30-a) ] and a (mol%), wherein a is more than 0 and less than or equal to 10.

According to the further optimized technical scheme, hydrogen sulfide serving as a raw material of the sulfide electrolyte can be prepared by fully utilizing the reaction of the hydrogen sulfide and residual alkali on the surface of the material, then other raw materials are added and uniformly mixed, and the sulfide electrolyte coated on the surface of the anode material is synthesized by adopting a high-temperature solid-phase sintering method, so that the stability of the surface structure of the anode material in the charging and discharging processes can be remarkably improved, and the electrochemical performance of the material is further improved.

In a third aspect, the present invention provides a lithium ion battery comprising a sulfide-coated positive electrode material as described in the first aspect.

Compared with the prior art, the invention has the following beneficial effects:

(1) the sulfide-coated cathode material provided by the invention solves the problems of surface residual alkali and unstable surface structure of a ternary cathode material, and has the characteristics of good surface structure stability, high ionic conductivity, low interface impedance, low residual alkali and excellent cycling stability. The conductivity of the anode material provided by the invention can reach 7.734 multiplied by 10^-4The capacity retention rate can reach 94.5 percent after the cycle is performed for 100 times under the conditions of S/m, 0.5C charge/1C discharge, the residual quantity of LiOH can be reduced to 0.219 weight percent, and Li₂CO₃The residual amount can be reduced to 0.174 wt%.

(2) The preparation method provided by the invention not only reduces the residual alkali on the surface of the lithium-containing anode material, but also takes the lithium sulfide generated by the reaction as the raw material to prepare the sulfide solid electrolyte coating layer, and the lithium sulfide is uniformly distributed on the surface of the material after the reaction, so that the prepared coating layer is uniform and compact, and the processing performance of the material is favorably improved; the stability of the surface structure of the material in the charging and discharging process is greatly improved by coating the sulfide solid electrolyte, and the high lithium ion conductivity of the sulfide solid electrolyte can also effectively reduce the interface impedance of the material, so that the electrochemical performance of the material is obviously improved.

Detailed Description

In order to better illustrate the present invention and facilitate the understanding of the technical solutions of the present invention, the present invention is further described in detail below. The following examples are merely illustrative of the present invention and do not represent or limit the scope of the claims, which are defined by the claims.

The following are typical but non-limiting examples of the invention:

example 1

This example provides a sulfide-coated positive electrode material including a lithium-containing positive electrode material LiNi_0.88Co_0.1Mn_0.02O₂And sulfide solid electrolyte coating Li coated on the surface of the lithium-containing cathode material₂S-P₂S₅-ZrO₂I.e. from Li₂S、P₂S₅And ZrO₂Prepared as a raw material, Li₂S、P₂S₅、ZrO₂In a molar ratio of 75:20: 5. P₂S₅Has an average particle diameter of 60nm, ZrO₂Has an average particle diameter of 40 nm. Positive electrode material LiNi_0.88Co_0.1Mn_0.02O₂Has an average particle diameter of 4.0 μm and a sulfide solid electrolyte coating layer thickness of 5 nm.

The embodiment also provides a preparation method of the sulfide-coated cathode material, which comprises the following specific steps:

(1) dispersing the anode material in absolute ethyl alcohol, continuously introducing hydrogen sulfide gas at the speed of 2L/min, and uniformly stirring for 1 h;

(2) filtering the product in the step (1),then the filter material is dried in a vacuum oven at 60 ℃ to obtain the raw material Li of the solid electrolyte₂A mixture of S and a positive electrode material;

(3) under the protection of argon atmosphere, according to Li₂S、P₂S₅、ZrO₂The molar percentage of the nano P is 75:20:5, and the dried mixture obtained in the step (2) and the nano P are respectively weighed₂S₅Powder and nano-ZrO₂Powder; they were mixed in a coating machine at 800rpm for 1 hour to obtain a mixed powder.

(4) And (4) transferring the product (mixed powder) obtained by mixing in the step (3) into a tubular furnace, and heating to 550 ℃ respectively at a heating rate of 3 ℃/min for heat treatment for 6h under the protection of argon atmosphere to obtain the sulfide-coated solid electrolyte modified cathode material.

The performance test results of the sulfide-coated cathode material provided in this example are shown in table 1.

Example 2

This example provides a sulfide-coated positive electrode material including a lithium-containing positive electrode material LiNi_0.88Co_0.1Mn_0.02O₂And sulfide solid electrolyte coating Li coated on the surface of the lithium-containing cathode material₂S-P₂S₅-ZrO₂I.e. from Li₂S、P₂S₅And ZrO₂Prepared as a raw material, Li₂S、P₂S₅、ZrO₂The molar percentage of (A) is 80:15: 5. P₂S₅Has an average particle diameter of 60nm, ZrO₂Has an average particle diameter of 60 nm. Positive electrode material LiNi_0.88Co_0.1Mn_0.02O₂Has an average particle diameter of 4.0 μm and a thickness of the sulfide solid electrolyte coating layer of 15 nm.

The embodiment also provides a preparation method of the sulfide-coated cathode material, which comprises the following specific steps:

(1) dispersing the anode material in absolute ethyl alcohol, continuously introducing hydrogen sulfide gas at the speed of 2L/min, and uniformly stirring for 1 h;

(2) in the step (1)Filtering the obtained product, and drying the filter material in a vacuum oven at 60 ℃ to obtain the raw material Li of the solid electrolyte₂A mixture of S and a positive electrode material;

(3) under the protection of argon atmosphere, according to Li₂S、P₂S₅、ZrO₂The mol percentage of the nano P is 80:15:5, and the mixture dried in the step (2) and the nano P are respectively weighed₂S₅Powder and nano-ZrO₂Powder; they were mixed in a coating machine at 800rpm for 1 hour to obtain a mixed powder.

(4) And (4) transferring the product (mixed powder) obtained by mixing in the step (3) into a tubular furnace, and heating to 550 ℃ respectively at a heating rate of 3 ℃/min for heat treatment for 6h under the protection of argon atmosphere to obtain the sulfide-coated solid electrolyte modified cathode material.

The performance test results of the sulfide-coated cathode material provided in this example are shown in table 1.

Example 3

This example provides a sulfide-coated positive electrode material including a lithium-containing positive electrode material Li_0.9Ni_0.8Co_0.15Al_0.05O₂And sulfide solid electrolyte coating Li coated on the surface of the lithium-containing cathode material₂S-P₂S₅-FeS₂I.e. from Li₂S、P₂S₅And FeS₂Prepared as a raw material, Li₂S、P₂S₅、FeS₂Is 70:25: 5. P₂S₅Has an average particle diameter of 100nm, FeS₂Has an average particle diameter of 30 nm. Cathode material Li_0.9Ni_0.8Co_0.15Al_0.05O₂Has an average particle diameter of 10.0 μm and a thickness of the sulfide solid electrolyte coating layer of 50 nm.

The embodiment also provides a preparation method of the sulfide-coated cathode material, which comprises the following specific steps:

(1) dispersing the anode material in ether in an inerting reactor, continuously introducing hydrogen sulfide gas at the speed of 1L/min, and uniformly stirring for 1.5 h;

(2) filtering the product obtained in the step (1), and then placing the filter material in a vacuum oven for drying at 60 ℃ to obtain a raw material Li of the solid electrolyte₂A mixture of S and a positive electrode material;

(3) under the protection of argon atmosphere, according to Li₂S、P₂S₅、FeS₂The mol percentage of the nano P is 70:25:5, and the dried mixture obtained in the step (2) and the nano P are respectively weighed₂S₅Powder and nano-FeS₂Powder; they were mixed in a coating machine at 141rpm for 0.8h to give a mixed powder.

(4) And (4) transferring the product (mixed powder) obtained by mixing in the step (3) into a tube furnace, and heating to 500 ℃ respectively at a heating rate of 1.5 ℃/min for heat treatment for 9h under the protection of argon atmosphere to obtain the sulfide-coated solid electrolyte modified cathode material.

The performance test results of the sulfide-coated cathode material provided in this example are shown in table 1.

Example 4

This example provides a sulfide-coated positive electrode material including a lithium-containing positive electrode material Li_1.1Ni_0.8Co_0.1Mn_0.1O₂And sulfide solid electrolyte coating Li coated on the surface of the lithium-containing cathode material₂S-P₂S₅CuO, i.e. made of Li₂S、P₂S₅And CuO as raw materials, Li₂S、P₂S₅And the molar percentage of CuO is 80:10: 10. P₂S₅Has an average particle diameter of 1nm and CuO has an average particle diameter of 40 nm. Cathode material Li_1.1Ni_0.8Co_0.1Mn_0.1O₂Has an average particle diameter of 16.8 μm and a thickness of the sulfide solid electrolyte coating layer of 100 nm.

The embodiment also provides a preparation method of the sulfide-coated cathode material, which comprises the following specific steps:

(1) dispersing the anode material in n-hexane in an inerting reactor, continuously introducing hydrogen sulfide gas at the speed of 5L/min, and uniformly stirring for 2 h;

(2) filtering the product obtained in the step (1), and then placing the filter material in a vacuum oven for drying at 60 ℃ to obtain a raw material Li of the solid electrolyte₂A mixture of S and a positive electrode material;

(3) under the protection of argon atmosphere, according to Li₂S、P₂S₅And (3) respectively weighing the dried mixture obtained in the step (2) and nano P, wherein the mol percentage of CuO is 80:10:10₂S₅Powder and nano-CuO powder; they were mixed in a coating machine at a rotation speed of 910rpm for 0.5h to obtain a mixed powder.

(4) And (4) transferring the product (mixed powder) obtained by mixing in the step (3) into a tubular furnace, and heating to 650 ℃ respectively at a heating rate of 5 ℃/min for 5 hours under the protection of argon atmosphere to obtain the sulfide-coated solid electrolyte modified cathode material.

The performance test results of the sulfide-coated cathode material provided in this example are shown in table 1.

Example 5

The sulfide-coated positive electrode material provided in this example was prepared using Li as a raw material for a sulfide solid electrolyte₂S、P₂S₅、ZrO₂Is 75:5:5, is otherwise the same as the sulfide-coated positive electrode material provided in example 1, and the preparation method is different from example 1 only in Li in step (3)₂S、P₂S₅、ZrO₂The molar percentages of (a) and (b) are proportioned according to the molar ratios of the present example.

The performance test results of the sulfide-coated cathode material provided in this example are shown in table 1.

Example 6

The sulfide-coated positive electrode material provided in this example was prepared using Li as a raw material for a sulfide solid electrolyte₂S、P₂S₅、ZrO₂Is 75:40:5, is otherwise the same as the sulfide-coated positive electrode material provided in example 1, and the preparation method is different from example 1 only in Li in step (3)₂S、P₂S₅、ZrO₂The mixture was prepared in the same manner as in the example.

The performance test results of the sulfide-coated cathode material provided in this example are shown in table 1.

Example 7

The sulfide-coated positive electrode material provided in this example was prepared using Li as a raw material for a sulfide solid electrolyte₂S、P₂S₅、ZrO₂Is other than 75:20:0 (i.e. no stabilizer ZrO is used)₂) Otherwise, the same as the sulfide-coated positive electrode material provided in example 1, and the difference between the preparation method and example 1 is only Li in step (3)₂S、P₂S₅、ZrO₂The mixture was prepared in the same manner as in the example.

The performance test results of the sulfide-coated cathode material provided in this example are shown in table 1.

Example 8

The sulfide-coated positive electrode material provided in this example was prepared using Li as a raw material for a sulfide solid electrolyte₂S、P₂S₅、ZrO₂Is 75:20:20, is otherwise the same as the sulfide-coated positive electrode material provided in example 1, and the preparation method is different from example 1 only in Li in step (3)₂S、P₂S₅、ZrO₂The mixture was prepared in the same manner as in the example.

The performance test results of the sulfide-coated cathode material provided in this example are shown in table 1.

Comparative example 1

The positive electrode material of this comparative example directly used the lithium-containing positive electrode material LiNi in example 1_0.88Co_0.1Mn_0.02O₂And the sulfide solid electrolyte coating layer is not coated.

The results of the performance test of the positive electrode material of this comparative example are shown in Table 1

Test method

Weighing a certain mass of sample, adding the sample into a certain amount of deionized water, performing ultrasonic treatment, filtering, performing constant volume, dividing a certain volume, using HCl with a certain concentration as a titrant, and performing titration on a Mettler-Tolyduo G20 automatic potentiometric titrator by adopting an equivalent point titration mode to obtain the surface residual alkali amount of the positive electrode material product provided by each embodiment and comparative example.

The positive electrode material products provided by the embodiments and the comparative examples are used as positive electrode active substances to prepare the lithium ion battery, and the preparation method comprises the steps of mixing the positive electrode active substances, the binding agent polyvinylidene fluoride and the conductive agent (SP conductive agent) in a ratio of 96:2:2 into NMP to form slurry, controlling the solid content to be 65%, coating the slurry on an aluminum foil to be used as a positive electrode, drying the slurry in a blast drying oven at 120 ℃ for 12h, punching the positive electrode sheet into a wafer with the diameter of 14mm, and drying the wafer in vacuum for 12 h; lithium sheet (phi 16mm thick 1mm) is used as a negative electrode, aluminum foil is used as a positive electrode, and electrolyte solute is 1M LiPF₆CR2016 button cells were prepared in an argon-filled glove box with EC and DMC (1: 2 volume ratio) as electrolyte solvents and Celgard2320 as separator (PP/PE/PP). Electrochemical tests were performed with this cell.

The capacity retention rate was tested with a blue cell test system (CT 2001A) over 100 charge-discharge cycles at a potential range of 3.0-4.3V, 0.5C charge/1C discharge (1C 210 mAh/g).

The powder was tested for conductivity with a powder conductivity meter under a load of 4 kN.

The results of the above tests are shown in the following table:

TABLE 1

It can be seen from the above examples and comparative examples that the sulfide-coated positive electrode materials provided in examples 1 to 4 of the present invention solve the problems of surface alkali residue and surface structure instability of the ternary positive electrode material, have the characteristics of low alkali residue and excellent cycling stability, and have high conductivity and low resistance.

Auxiliary ingredient (P) of example 5₂S₅) Too little, resulting in the formation of electrically coated materialThe conductivity is low and the cycle retention is low.

Auxiliary ingredient (P) of example 6₂S₅) Too much leads to the formation of other impurity phases in the solid electrolyte, and influences the conductivity and electrochemical performance of the material.

Stabilizer (ZrO) of example 7₂) Too little results in unstable structure of the solid electrolyte formed on the surface, easy decomposition and influence on the electrochemical performance of the material.

Stabilizer (ZrO) of example 8₂) Too much leads to impurities in the solid electrolyte formed on the surface, and influences the conductivity of the material, and further influences the electrochemical performance of the material.

Comparative example 1 does not coat a sulfide coating layer on the surface of the lithium-containing positive electrode material, resulting in a high residual alkali amount on the surface of the lithium-containing positive electrode material, poor cycle stability, and relatively low electrical conductivity.

The applicant states that the present invention is illustrated in detail by the above examples, but the present invention is not limited to the above detailed methods, i.e. it is not meant that the present invention must rely on the above detailed methods for its implementation. It should be understood by those skilled in the art that any modification of the present invention, equivalent substitutions of the raw materials of the product of the present invention, addition of auxiliary components, selection of specific modes, etc., are within the scope and disclosure of the present invention.