阅读说明：本技术 一种纳米铆钉核壳结构正极材料及制备方法 (Nano rivet core-shell structure cathode material and preparation method thereof ) 是由 刘孟 任重民 刘健 张胜其 林欢 王德宇 于 2018-06-27 设计创作，主要内容包括：本发明公开了一种纳米铆钉核壳结构正极材料,包括由外壳包裹内核所构成的颗粒单元,所述颗粒单元的内核是由含锂多元过渡金属氧化物一次颗粒组成的二次球形颗粒；所述含锂多元过渡金属氧化物一次颗粒之间通过填隙在它们间隙中的纳米含锂氧化物结合；本发明能有效地抑制锂离子电池正极材料二次颗粒沿一次颗粒之间的界面粉化,使得锂离子电池能具有高的比容量、优良的循环性能和安全性能,且能形成均匀的具备电化学活性包覆层的纳米铆钉核壳结构正极材料。(The invention discloses a nano rivet core-shell structure cathode material, which comprises a particle unit formed by wrapping a core by a shell, wherein the core of the particle unit is a secondary spherical particle formed by lithium-containing multi-transition metal oxide primary particles; the primary particles of the lithium-containing multi-transition metal oxide are combined through the nano lithium-containing oxide which is filled in the gaps of the primary particles; the invention can effectively inhibit the interface pulverization of the secondary particles of the lithium ion battery anode material along the primary particles, so that the lithium ion battery has high specific capacity, excellent cycle performance and safety performance, and can form a uniform nano rivet core-shell structure anode material with an electrochemical active coating layer.)

1. The nanometer rivet core-shell structure cathode material comprises a particle unit formed by wrapping an inner core by a shell, and is characterized in that:

the inner core of the particle unit is a secondary spherical particle consisting of lithium-containing multi-element transition metal oxide primary particles; the primary particles of the lithium-containing multi-transition metal oxide are combined through the nano lithium-containing oxide which is filled in the gaps of the primary particles;

the lithium-containing multi-transition metal oxide primary particle has a chemical composition of Li_1+aNi_bCo_cA_dM_1-b-c-dO₂Wherein a is more than or equal to 0.1 and less than or equal to 0.2, b is more than 0 and less than or equal to 1, c is more than 0 and less than or equal to 0.5, and d is more than 0 and less than or equal to 0.5; a is Mn or Al; the M is one or more of Cr, Mg, Ga, Ti, Fe, Cu, Sb, Sr, Ca, K, Na, Sn, Zn, V and Sc;

the chemical composition of the nano lithium-containing oxide is Li_eR_fO_gOne or more of; wherein, e + f × (valence of R) =2 g; r is selected from one or more of Nb, La, Ag, In, Te, Hf, Pb, Ce, Pr, Nd, Sm, Eu, Gd, Ho, Er, Tm and Yb;

the shell of the particle unit comprises at least one shell layer consisting of crystalline phase materials and/or amorphous phase materials;

the crystalline phase material is selected from at least one of compounds of chemical formulas shown in formulas (I), (II), (III) and (IV):

Li_1+hNi_iCo_jMn_1-h-iO₂ （I）

wherein h is more than or equal to-0.1 and less than or equal to 0.2, i is more than or equal to 0 and less than or equal to 1, and j is more than or equal to 0 and less than or equal to 0.5;

Li_1+mMn₂O_4+n （II）

wherein m is more than or equal to-0.1 and less than or equal to 0.2, n is more than or equal to-0.14 and less than or equal to 0.5;

Li_1+pNi_0.5Mn_1.5O_4+q （III）

wherein p is more than or equal to-0.1 and less than or equal to-0.2, and q is more than or equal to-0.14 and less than or equal to 0.5;

Li_1+tFe_1-sMn_sPO₄ （IV）

wherein t is more than or equal to-0.1 and less than or equal to 0.2, and s is more than or equal to 0 and less than or equal to 1;

the amorphous phase material is selected from at least one of compounds of chemical formulas shown in formulas (V) and (VI):

Li_uQ_vO_w （V）

wherein u + v × (valence of Q) =2 w;

Q_xO_y （VI）

wherein, x (valence of Q) =2 y;

q is selected from one or more of Zr, Ta, Y, Sb, Mo, Pb, Bi, W, Sn, Ga, Cd, Sc, Ba, V, Cr, Ti and Zn.

2. The nano rivet core-shell structure cathode material according to claim 1, characterized in that: concentration C of Ni in the shell layer_Ni ^ShellLess than the concentration C of Ni in the core_Ni ^Core(ii) a Wherein, C_Ni ^Shell= (the sum of the number of moles of Ni in the shell layer/the number of moles of Ni and other metal elements in the shell layer) × 100%, C_Ni ^Core= (the sum of moles of Ni in the core/moles of Ni and other metal elements in the core) × 100%.

3. The nano rivet core-shell structure cathode material according to claim 1, characterized in that: the particle size of the lithium-containing multi-transition metal oxide primary particles is 50-1000nm, and the particle size of the secondary spherical particles is 0.5-50 mu m.

4. The nano rivet core-shell structure cathode material according to claim 1, characterized in that: the thickness of the shell of the particle unit is 1-500nm, and the particle unit is composed of 1-50 shell layers.

5. The nano rivet core-shell structure cathode material according to claim 1, characterized in that: the outer surface of the shell of the particle unit also comprises at least one surface protection layer, and the material composition of the surface protection layer is Al₂O₃、MgO、ZrO₂、ZnO、Y₂O₃、Ta₂O₅、Cr₂O₃、Nb₂O₅、Mo₂O₃、V₂O₅、TiO₂、Ga₂O₃、SrO、BaO、WO₂、Sb₂O₅、SnO、CdO、Bi₂O₃And PbO.

6. A preparation method of the nano rivet core-shell structure cathode material as claimed in any one of claims 1 to 4 is characterized in that: the method comprises the following steps:

1) stirring and mixing the precursor of the multi-element transition metal with the R element source, or settling or adsorbing the R element source on the surface of the precursor of the multi-element transition metal to obtain a precursor P1;

2) stirring and mixing the precursor P1 with a Q element source or settling or adsorbing the Q element source on the surface of the precursor P1 to obtain a precursor P2 coated with 1 layer of Q element source; or mixing and sintering the precursor P1 and a lithium source, and then stirring and mixing the precursor P1 and a Q element source, or settling or adsorbing the Q element source on the surface of the sintered material to obtain a precursor P2 coated with 1 layer of Q element source;

if a plurality of layers need to be coated, stirring and mixing the precursor P2 with a Q element source, or settling or adsorbing the Q element source on the surface of the precursor P2 to obtain a precursor P3 coated with 2 layers of Q element sources; repeating the coating to prepare a precursor P (n + 1) for coating n layers of Q element sources, wherein n is more than or equal to 2;

3) mixing the precursor P (n + 1) with the T element source to obtain a precursor P (n + 2);

4) and uniformly mixing the precursor P (n + 2) with a lithium source, and sintering to obtain the nano rivet core-shell structure cathode material.

7. The preparation method of the nano rivet core-shell structure cathode material according to claim 6, characterized in that: the multi-transition metal precursor is composed of a plurality of transition metal compounds; the transition metal compound is one or more of transition metal oxide, hydroxide, oxyhydroxide and carbonate.

8. The preparation method of the nano rivet core-shell structure cathode material according to claim 6, characterized in that: the R element source is an oxide, carbonate or hydroxide of an element R, and the R is selected from one or more of Nb, La, Ag, In, Te, Hf, Pb, Ce, Pr, Nd, Sm, Eu, Gd, Ho, Er, Tm and Yb; the Q element source is an oxide, carbonate or hydroxide of an element Q, and the Q is selected from one or more of Zr, Ta, Y, Sb, Mo, Pb, Bi, W, Sn, Ga, Cd, Sc, Ba, V, Cr, Ti and Zn; the source of the T element is oxide, carbonate or hydroxide of the element T, and the T is selected from one or more of Ni, Co, Mn and Fe.

9. The preparation method of the nano rivet core-shell structure cathode material according to claim 6, characterized in that: further comprising a step 5), specifically: sintering and coating at least one of the following surface protection layer materials on the surface of the nano rivet core-shell structure cathode material in the step 4) to prepare the nano rivet core-shell structure cathode material containing the protection layer: al (Al)₂O₃、MgO、ZrO₂、ZnO、Y₂O₃、Ta₂O₅、Cr₂O₃、Nb₂O₅、Mo₂O₃、V₂O₅、TiO₂、Ga₂O₃、SrO、BaO、WO₂、Sb₂O₅、SnO、CdO、Bi₂O₃、PbO。

10. The preparation method of the nano rivet core-shell structure cathode material according to claim 6, characterized in that: the lithium source is one or more of lithium carbonate, lithium hydroxide, lithium chloride, lithium nitrate and lithium acetate.

Technical Field

The invention relates to the technical field of lithium battery materials, in particular to a nano rivet core-shell structure anode material and a preparation method thereof.

Background

The gradual exhaustion of traditional energy sources makes the development and utilization of new energy sources get more and more attention. The lithium ion battery as a green novel energy source has the outstanding advantages of high energy density, long cycle life, low self-discharge efficiency, no memory effect, good safety and the like, and is widely applied to the fields of electronic products, power automobile batteries and the like. At present, lithium-containing multi-transition metal oxide materials are mainly spherical secondary particles in which primary particles are grown in an aggregated manner due to the limitation of synthesis techniques. After long-term electrochemical cycling, the secondary spherical material can be pulverized along the interface between the primary particles, so that the electrical contact between electrode materials is poor, the internal resistance is high, and the capacity of the battery is attenuated early. In addition, the high-nickel ternary material has the problems of high surface activity, instability in wet air and the like.

In order to solve the problem of material electrochemical performance attenuation caused by cracking of ternary material particles, the patents JP11329504A and EP2571083 respectively coat acetylene black and carbon fibers on the surface of primary particles of the positive electrode material, so that cracks can be filled when secondary particles are cracked, the conductivity of the positive electrode material is continuously maintained, and the cycle performance of the positive electrode material is maintained. However, acetylene black or carbon fibers coated on the surface of the primary particles are only filled between the primary particles, and the force between the carbon fibers and the primary particles is small, so that the contact internal resistance can be reduced only after the pulverization of the secondary particles, and the pulverization of the secondary particles cannot be well suppressed.

In order to solve the problem of unstable surface of ternary material, the conventional improvement method is to coat a layer of inert substance, such as MgO, TiO₂、Al₂O₃ (Ultrathin Al₂O₃ Coatings for Improved Cycling Performance and Thermal Stability of LiNi_0.5Co_0.2Mn_0.3O₂Cathe, Material electric Acta 203 (2016) 154-: CN102332577A), SiO₂(High-performance lithium ion batteries using SiO₂-coated LiNi_0.5Co_0.2Mn_0.3O₂ microspheres as cathodes, Journal of Alloys and Compounds 709 (2017) 708-. Most of coating methods are to treat sintered materials, and because the coating process usually needs to treat the sintered ternary materials in water or an organic solvent, secondary calcination is needed, and a local spinel phase is inevitably generated in the calcination process, the capacity of the materials is reduced, the cycle is deteriorated, gas is generated, and the potential safety hazard of the battery is increased. In addition, the current coating method has a small coating amount, cannot form a uniform coating layer, and the coating layer material has no electrochemical activity and cannot have lithium ion deintercalation capability, thereby affecting the electrochemical performance of the cathode material.

Disclosure of Invention

The technical problem to be solved by the invention is to overcome the defects of the prior art: the method can effectively inhibit the interface pulverization of the secondary particles of the lithium ion battery anode material along the primary particles, so that the lithium ion battery has high specific capacity, excellent cycle performance and safety performance, and can form a uniform nano rivet core-shell structure anode material with an electrochemical active coating layer, and the preparation method thereof.

The technical solution of the invention is as follows: a nanometer rivet core-shell structure anode material comprises a particle unit formed by wrapping a core by a shell, wherein the core of the particle unit is a secondary spherical particle formed by lithium-containing multi-transition metal oxide primary particles; the primary particles of the lithium-containing multi-transition metal oxide are combined through the nano lithium-containing oxide which is filled in the gaps of the primary particles;

the lithium-containing multi-transition metal oxide primary particle has a chemical composition of Li_1+aNi_bCo_cA_dM_1-b-c-dO₂One or more ofWherein a is more than or equal to 0.1 and less than or equal to 0.2, b is more than 0 and less than or equal to 1, c is more than 0 and less than or equal to 0.5, and d is more than 0 and less than or equal to 0.5; a is Mn or Al; the M is one or more of Cr, Mg, Ga, Ti, Fe, Cu, Sb, Sr, Ca, K, Na, Sn, Zn, V and Sc;

the chemical composition of the nano lithium-containing oxide is Li_eR_fO_gOne or more of; wherein, e + f × (valence of R) =2 g; r is selected from one or more of Nb, La, Ag, In, Te, Hf, Pb, Ce, Pr, Nd, Sm, Eu, Gd, Ho, Er, Tm and Yb;

the shell of the particle unit comprises at least one shell layer consisting of crystalline phase materials and/or amorphous phase materials;

the crystalline phase material is selected from at least one of compounds of chemical formulas shown in formulas (I), (II), (III) and (IV):

Li_1+hNi_iCo_jMn_1-h-iO₂ （I）

wherein h is more than or equal to-0.1 and less than or equal to 0.2, i is more than or equal to 0 and less than or equal to 1, and j is more than or equal to 0 and less than or equal to 0.5;

Li_1+mMn₂O_4+n （II）

wherein m is more than or equal to-0.1 and less than or equal to 0.2, n is more than or equal to-0.14 and less than or equal to 0.5;

Li_1+pNi_0.5Mn_1.5O_4+q （III）

wherein p is more than or equal to-0.1 and less than or equal to-0.2, and q is more than or equal to-0.14 and less than or equal to 0.5;

Li_1+tFe_1-sMn_sPO₄ （IV）

wherein t is more than or equal to-0.1 and less than or equal to 0.2, and s is more than or equal to 0 and less than or equal to 1;

the amorphous phase material is selected from at least one of compounds of chemical formulas shown in formulas (V) and (VI):

Li_uQ_vO_w （V）

wherein u + v × (valence of Q) =2 w;

Q_xO_y （VI）

wherein, x (valence of Q) =2 y;

q is selected from one or more of Zr, Ta, Y, Sb, Mo, Pb, Bi, W, Sn, Ga, Cd, Sc, Ba, V, Cr, Ti and Zn.

Concentration C of Ni in the shell layer_Ni ^ShellLess than the concentration C of Ni in the core_Ni ^Core(ii) a Wherein, C_Ni ^Shell= (the sum of the number of moles of Ni in the shell layer/the number of moles of Ni and other metal elements in the shell layer) × 100%, C_Ni ^Core= (the sum of moles of Ni in the core/moles of Ni and other metal elements in the core) × 100%.

The particle size of the lithium-containing multi-transition metal oxide primary particles is 50-1000nm, and the particle size of the secondary spherical particles is 0.5-50 mu m.

The thickness of the shell of the particle unit is 1-500nm, and the particle unit is composed of 1-50 shell layers.

The outer surface of the shell of the particle unit also comprises at least one surface protection layer, and the material composition of the surface protection layer is Al₂O₃、MgO、ZrO₂、ZnO、Y₂O₃、Ta₂O₅、Cr₂O₃、Nb₂O₅、Mo₂O₃、V₂O₅、TiO₂、Ga₂O₃、SrO、BaO、WO₂、Sb₂O₅、SnO、CdO、Bi₂O₃And PbO.

The preparation method of the nano rivet core-shell structure cathode material comprises the following steps:

1) stirring and mixing the precursor of the multi-element transition metal with the R element source, or settling or adsorbing the R element source on the surface of the precursor of the multi-element transition metal to obtain a precursor P1;

2) stirring and mixing the precursor P1 with a Q element source or settling or adsorbing the Q element source on the surface of the precursor P1 to obtain a precursor P2 coated with 1 layer of Q element source; or mixing and sintering the precursor P1 and a lithium source, and then stirring and mixing the precursor P1 and a Q element source, or settling or adsorbing the Q element source on the surface of the sintered material to obtain a precursor P2 coated with 1 layer of Q element source;

if a plurality of layers need to be coated, stirring and mixing the precursor P2 with a Q element source, or settling or adsorbing the Q element source on the surface of the precursor P2 to obtain a precursor P3 coated with 2 layers of Q element sources; repeating the coating to prepare a precursor P (n + 1) for coating n layers of Q element sources, wherein n is more than or equal to 2;

3) mixing the precursor P (n + 1) with the T element source to obtain a precursor P (n + 2);

4) and uniformly mixing the precursor P (n + 2) with a lithium source, and sintering to obtain the nano rivet core-shell structure cathode material.

The multi-transition metal precursor is composed of a plurality of transition metal compounds; the transition metal compound is one or more of transition metal oxide, hydroxide, oxyhydroxide and carbonate;

the R element source is an oxide, carbonate or hydroxide of an element R, and the R is selected from one or more of Nb, La, Ag, In, Te, Hf, Pb, Ce, Pr, Nd, Sm, Eu, Gd, Ho, Er, Tm and Yb; the Q element source is an oxide, carbonate or hydroxide of an element Q, and the Q is selected from one or more of Zr, Ta, Y, Sb, Mo, Pb, Bi, W, Sn, Ga, Cd, Sc, Ba, V, Cr, Ti and Zn; the source of the T element is oxide, carbonate or hydroxide of the element T, and the T is selected from one or more of Ni, Co, Mn and Fe.

As optimization, the preparation method of the nano rivet core-shell structure cathode material further comprises a step 5), and specifically comprises the following steps: sintering and coating at least one of the following surface protection layer materials on the surface of the nano rivet core-shell structure cathode material in the step 4) to prepare the nano rivet core-shell structure cathode material containing the protection layer: al (Al)₂O₃、MgO、ZrO₂、ZnO、Y₂O₃、Ta₂O₅、Cr₂O₃、Nb₂O₅、Mo₂O₃、V₂O₅、TiO₂、Ga₂O₃、SrO、BaO、WO₂、Sb₂O₅、SnO、CdO、Bi₂O₃、PbO。

The lithium source is one or more of lithium carbonate, lithium hydroxide, lithium chloride, lithium nitrate and lithium acetate.

The sintering in the steps 2) and 4) is firstly sintering at the temperature of 450-700 ℃ for 2-24 hours and then sintering at the temperature of 700-1000 ℃ for 10-36 hours.

The invention has the beneficial effects that: the lithium ion battery anode material with the nano rivet structure is obtained by a simple and easy-to-implement synthesis method, and the nano lithium-containing oxide filling gaps among the primary particles can effectively generate lattice deformation or dislocation, so that the deformation stress of the lithium ion battery anode material is eliminated, the pulverization of secondary particles of the lithium ion battery anode material along the interface among the primary particles can be effectively inhibited, and the lithium ion battery can have high specific capacity, excellent cycle performance and safety performance. By adopting the method, the lithium ion battery anode material with the nano rivet structure can be obtained, secondary particles of the lithium ion battery anode material can be effectively inhibited from being pulverized along the interface between primary particles, the transmission distance of lithium ions between the primary particles is reduced, the lithium ion battery can have high specific capacity, excellent cycle performance and safety performance, meanwhile, the uniform core-shell structure with the electrochemical active coating layer is formed, the performance of the anode material is greatly improved, the surface composite coating layer shell has good lithium ion transmission capability, the surface side reaction is effectively inhibited, and the discharge capacity, the rate capability and the cycle performance of the anode material are obviously improved.

Drawings

Fig. 1 is a topographical view of precursor P1 prepared in comparative example 1.

FIG. 2 is a topographical view of precursor P4 prepared in example 2.

FIG. 3 is a topographical view of precursor P5 prepared in example 3.

FIG. 4 is preparation 3 of example 1^#Topography of the sample.

FIG. 5 is preparation 5 of example 3^#Topography of the sample.

FIG. 6 is a graph showing a comparative example 1Prepare 1^#And (4) a morphology graph of the sample after charge and discharge cycles.

FIG. 7 is preparation 5 of example 3^#And (4) a morphology graph of the sample after charge and discharge cycles.

FIG. 8 preparation 5 of example 3^#Transmission electron micrograph of sample.

FIG. 9 preparation 5 of example 3^#Transmission electron micrograph of sample.

FIG. 10 shows example 3 in which 5^#X-ray diffraction contrast plots of the samples.

FIG. 11 shows example 7 in which 9^#X-ray diffraction contrast plots of the samples.

Fig. 12 is an elemental distribution plot of a cross-section of a particle of precursor P5 prepared in example 3.

FIG. 13 is 5 prepared in example 3^#Elemental profile of the cross section of the sample particle.

Fig. 14 is a discharge graph of the positive electrode materials prepared in comparative example 1, example 1 and example 3.

Fig. 15 is a graph of rate performance of the positive electrode materials prepared in comparative example 1, example 1 and example 3.

Fig. 16 is a graph showing cycle performance of the positive electrode materials prepared in comparative example 1, example 1 and example 3.

Detailed Description

The present invention will be described in further detail with reference to the following examples, but the present invention is not limited to the following examples.

The raw materials in the examples of the present application were all purchased commercially, unless otherwise specified.

The analysis method in the examples of the present application is as follows:

the morphological test analysis was performed using a scanning electron microscope S4800H manufactured by Hitachi, Japan and a transmission electron microscope Tecnai F20 manufactured by FEI, the Netherlands.

Electrochemical performance test analysis was performed using the LAND electrochemical test system CT2001A manufactured by Wuhanxinnuo electronics Co.

The performance test method of the anode material comprises the following steps:

uniformly mixing a positive electrode material, a conductive agent acetylene black and a binder polyvinylidene fluoride (PVdF) in a Nitrogen Methyl Pyrrolidone (NMP) solvent, wherein the mass ratio of the positive electrode material to the conductive agent to the binder is 85: 10: and 5, coating the uniformly mixed slurry on an aluminum foil, and performing vacuum drying at 120 ℃ for 12 hours to obtain the lithium ion battery anode.

The CR2032 type button lithium ion battery is assembled by using the pole piece as a positive electrode, using metal lithium as a negative electrode, adopting a solution of ethylene carbonate and dimethyl carbonate of 1mol/L lithium hexafluorophosphate as an electrolyte and adopting a polyethylene and polypropylene composite material with the thickness of 20 microns as a diaphragm. The assembled button cell is subjected to charge and discharge tests, and the voltage range is 2.8-4.3 volts.

Comparative example 1

According to the molar ratio of Ni, Co and Mn of 8: 1: 1 preparing a mixed solution, respectively weighing 232.63g, 29.10g and 25.10g of nickel nitrate hexahydrate, cobalt nitrate hexahydrate and manganese nitrate tetrahydrate, and adding 500mL of water for dissolving. 1000mL of a 5mol/L NaOH solution and 1000mL of a 2mol/L aqueous ammonia solution were prepared.

Adding 200mL of water into a reaction kettle protected by argon, simultaneously adding the mixed solution, a 5mol/L NaOH solution and a 2mol/L ammonia water solution into the reaction kettle, and controlling the final pH value of the solution to be 7-14. And after the sedimentation is finished, filtering and washing the precipitate, and drying at 80 ℃ to obtain a precursor P1.

The precursor P1100 g was weighed, and Li OH.H was weighed so that the molar ratio of the lithium source to the precursor P1 was 1.05₂O47.71 g and precursor P1 are mixed evenly, sintered for 4 hours at 550 ℃, and then sintered for 12 hours at 850 ℃ to obtain the cathode material LiNi_0.8Co_0.1Mn_0.1O₂Is marked as 1^#。

Comparative example 2

According to the molar ratio of Ni, Co and Mn of 5: 2: 3 preparing a mixed solution, weighing 131.42g of nickel sulfate hexahydrate, cobalt sulfate heptahydrate, and manganese sulfate monohydrate, 56.22g and 50.70g respectively, and adding 500mL of water for dissolving. 1000mL of a 4mol/L NaOH solution and 1000mL of a 2mol/L aqueous ammonia solution were prepared.

200mL of water is added into a reaction kettle protected by nitrogen, the mixed solution, a 4mol/L NaOH solution and a 2mol/L ammonia water solution are simultaneously added into the reaction kettle, and the final pH value of the solution is controlled to be 11.5. And after the sedimentation is finished, filtering and washing the precipitate, and drying at 80 ℃ to obtain a precursor P2.

The precursor P250 g was weighed, and the molar ratio of lithium source to precursor was 1.05: 1 weigh LiOH.H₂O23.94 g and precursor P2 are mixed evenly, sintered for 6 hours at 400 ℃ and then sintered for 12 hours at 850 ℃ to obtain LiNi_0.5Co_0.2Mn_0.3O₂Material, marked 2^#。