阅读说明：本技术 一种锂离子电池复合正极材料及其制备方法 (Composite positive electrode material of lithium ion battery and preparation method thereof ) 是由 张建 夏保佳 谢晓华 于 2020-06-30 设计创作，主要内容包括：本发明涉及一种锂离子电池复合正极材料及其制备方法,所述复合电极材料包括基体材料、依次包覆与基体材料表面的第一包覆层和第二包覆层。本发明提供的锂离子电池复合正极材料及其制备方法,工艺简单,易于工业化生产,残碱低、循环和安全性能优异。(The invention relates to a composite anode material of a lithium ion battery and a preparation method thereof. The lithium ion battery composite anode material and the preparation method thereof provided by the invention have the advantages of simple process, easiness in industrial production, low residual alkali and excellent cycle and safety performance.)

1. A composite electrode material, characterized in that it is a composite electrodeThe electrode material comprises a base material, a first coating layer and a second coating layer, wherein the first coating layer and the second coating layer are sequentially coated on the surface of the base material, the base material is a nickel-rich layered positive electrode material, and the chemical formula of the nickel-rich layered positive electrode material is LiNi_xCo_yM_zO₂Wherein M is one or two of Mn and Al, x + y + z is 1, and x is more than or equal to 0.5; the first coating layer is nano metal oxide or nano metal metaphosphate; the second coating layer is nano lithium manganese iron phosphate.

2. The material of claim 1, wherein the nickel-rich layered positive electrode material is a lithium nickel cobalt manganese oxide material, wherein the molar ratio of Ni to Co to Mn is in the range of 5:2:3, 6:2:2, 7:1.5:1.5, 8:1:1, or 9.2:0.5: 0.3; or the nickel-rich layered positive electrode material is a nickel cobalt lithium aluminate material, wherein the molar ratio of Ni to Co to Al is 7:2:1, 8:1.5:0.5, 8.8:0.9:0.3 or 9.5:0.3: 0.2; or the nickel-rich layered positive electrode material is a nickel-cobalt-manganese-lithium aluminate material, wherein the molar ratio of Ni to Co to Mn to Al is 7:1:1:1, 8.3:0.7:0.5:0.5 or 9.8:0.1:0.05: 0.05.

3. The material according to claim 1, wherein the nano metal oxide is one or more of alumina, zirconia, titania, molybdenum oxide and tungsten oxide, the particle size is 5-100nm, and the mass ratio of the metal oxide to the base material is 0.1-5%.

4. The material as claimed in claim 1, wherein the nano metal metaphosphate is one or more of aluminum metaphosphate, lanthanum metaphosphate, yttrium metaphosphate and lithium metaphosphate, the particle size is 5-100nm, and the mass ratio of the metal metaphosphate to the base material is 0.1-5%.

5. The material according to claim 1, wherein the nano lithium manganese iron phosphate has a particle size of 20-200nm, and the mass ratio of the nano lithium manganese iron phosphate to the matrix material is 1-30%.

6. A method of preparing a composite electrode material, comprising:

(1) mechanically fusing nano metal oxide or nano metal metaphosphate with a base material, and annealing to obtain a first coating electrode material;

(2) and mechanically fusing the first coating electrode material and the nano lithium manganese iron phosphate to obtain the composite electrode material.

7. The method according to claim 1, wherein the base material in the step (1) is: mixing Ni_xCo_yM_z(OH)₂Or Ni_xCo_yM_zCO₃Uniformly mixing the precursor and a lithium source to obtain mixed powder, and sintering at high temperature to obtain the lithium-ion battery; wherein the high-temperature sintering temperature is 720-950 ℃ in an oxygen-containing atmosphere and is kept for 6-20 h.

8. The preparation method according to claim 6, wherein the annealing treatment in the step (1) is: keeping the temperature at 300-900 ℃ for 0.1-10 h in an oxygen-containing atmosphere.

9. A composite electrode material prepared by the method of claim 6.

10. A lithium ion battery, characterized in that a positive electrode material of the lithium ion battery contains the composite electrode material according to claim 1.

Technical Field

The invention belongs to the field of electrode materials for batteries and preparation thereof, and particularly relates to a composite anode material for a lithium ion battery and a preparation method thereof.

Background

With the increasing demand of the market on the energy density of lithium ion batteries, especially the higher demand of electric automobiles on the endurance mileage, the ternary cathode material LiNi_xCo_yM_1-x-yO₂(M ═ Mn, Al) has become the mainstream material of power lithium ion batteries, and the Ni content is being continuously increased, i.e., the capacity is being increased. Although the increase of the Ni content can improve the capacity of the cathode material and reduce the unit watt-hour cost, the reduction of the cycling stability and the safety performance of the material can be caused, and the problems of high residual alkali content of the material and gas generation in the battery cycling process are caused.

The lithium manganese iron phosphate is used as the material for upgrading the lithium iron phosphate, and has low cost and high discharge voltage (4.1V vs. Li/Li)⁺) High thermal stability and long cycle life, and can be mixed with the ternary cathode material for improving the cycle and safety performance of the ternary cathode material. For example, patent CN104300123A discloses that a nickel-cobalt-manganese ternary material and lithium manganese iron phosphate are physically mixed in a size mixing stage, and then a binder and a conductive agent are added in proportion to be mixed and made into a positive plate. However, the patent only carries out physical stirring and mixing on the ternary anode material of 8-12um and the lithium manganese iron phosphate of 6-12um, the two materials are only in point contact with each other, the binding force is poor, meanwhile, due to the difference of the material densities of the two materials, the two particles are difficult to uniformly disperse, and the used lithium manganese iron phosphate particles are large and difficult to achieveThe effect of the coating and therefore the improvement of the cycle and safety performance is limited.

Patents CN104733730A and CN107546379B disclose that nano lithium manganese iron phosphate is fixed on the surface of ternary positive electrode material particles by a mechanical fusion method, and although uniform coating of lithium manganese iron phosphate on the surface of ternary positive electrode material can be achieved, the binding force between the two is also enhanced. However, in the patent, a porous coating layer is formed on the surface of the ternary cathode material, so that the contact between the electrolyte and the ternary cathode material cannot be prevented, and the electrolyte and the ternary cathode material are in direct contact, so that the + 3-valent and + 4-valent transition metals in the ternary cathode material and the + 2-valent transition metal in the lithium manganese phosphate have the risk of reaction, and further the surface structures of the two are damaged, so that the interface impedance is increased, and the improvement effect is reduced.

Chinese patent application publication No. CN105406069A discloses a method for in situ synthesis of lithium manganese iron phosphate on the surface of a ternary cathode material by a wet process, in which the coated lithium manganese iron phosphate layer is uniform and the binding force is good, but high-temperature sintering is required in an argon inert atmosphere during the synthesis of lithium manganese iron phosphate, the ternary cathode material is likely to react with the lithium manganese iron phosphate at high temperature, and air or an oxygen-rich atmosphere is required during the synthesis of the ternary cathode material, and heat treatment in the inert atmosphere can destroy the structure of the ternary cathode material, thereby affecting the performance of the overall performance of the material.

Disclosure of Invention

The invention aims to solve the technical problem of providing a lithium ion battery composite anode material and a preparation method thereof, and overcomes the defects of poor cycle and safety performance in the prior art.

The composite electrode material comprises a base material, a first coating layer and a second coating layer, wherein the first coating layer and the second coating layer are sequentially coated on the surface of the base material, and the base material is a nickel-rich layerA positive electrode material of the chemical formula LiNi_xCo_yM_zO₂Wherein M is one or two of Mn and Al, x + y + z is 1, and x is more than or equal to 0.5; the first coating layer is nano metal oxide or nano metal metaphosphate; the second coating layer is nano lithium manganese iron phosphate.

The composite electrode material is obtained by mechanically fusing and coating raw materials comprising a base material, a first coating material and a second coating material, and carrying out one-time annealing treatment between two coatings.

Preferably, the nickel-rich layered cathode material is a lithium nickel cobalt manganese oxide material, wherein the range molar ratio of Ni to Co to Mn includes, but is not limited to, 5:2:3, 6:2:2, 7:1.5:1.5, 8:1:1, or 9.2:0.5: 0.3; or the nickel-rich layered cathode material is a nickel cobalt lithium aluminate material, wherein the range molar ratio of Ni to Co to Al includes, but is not limited to, 7:2:1, 8:1.5:0.5, 8.8:0.9:0.3, or 9.5:0.3: 0.2; or the nickel-rich layered positive electrode material is a nickel cobalt manganese lithium aluminate material, wherein the range molar ratio of Ni to Co to Mn to Al includes, but is not limited to, 7:1:1:1, 8.3:0.7:0.5:0.5, or 9.8:0.1:0.05: 0.05.

The nano metal oxide is one or more of aluminum oxide, zirconium oxide, titanium oxide, molybdenum oxide and tungsten oxide, the particle size is 5-100nm, and the mass ratio of the metal oxide to the base material is 0.1-5%.

The nano metal metaphosphate is one or more of aluminum metaphosphate, lanthanum metaphosphate, yttrium metaphosphate and lithium metaphosphate, the particle size is 5-100nm, and the mass ratio of the metal metaphosphate to the base material is 0.1-5%.

The particle size of the nano lithium manganese iron phosphate is 20-200nm, and the mass ratio of the nano lithium manganese iron phosphate to the matrix material is 1-30%.

The preparation method of the composite electrode material comprises the following steps:

(1) mechanically fusing nano metal oxide or nano metal metaphosphate with a base material, and annealing to obtain a first coating electrode material;

(2) and mechanically fusing the first coating electrode material and the nano lithium manganese iron phosphate to obtain the composite electrode material.

The preferred mode of the above preparation method is as follows:

the base material in the step (1) is as follows: mixing Ni_xCo_yM_z(OH)₂Or Ni_xCo_yM_zCO₃Uniformly mixing the precursor and a lithium source to obtain mixed powder, and sintering at high temperature to obtain the lithium-ion battery; wherein the high-temperature sintering temperature is 720-950 ℃ in an oxygen-containing atmosphere and is kept for 6-20 h.

The lithium source is lithium carbonate or lithium hydroxide.

The molar ratio of Li (Ni + Co + M) in the mixed powder is (1.00-1.08): 1.

The annealing treatment in the step (1) comprises the following steps: keeping the temperature at 300-900 ℃ for 0.1-10 h in an oxygen-containing atmosphere.

And (2) in the step (1), the mechanical fusion is to coat the nano metal oxide or the nano metal metaphosphate on the surface of the matrix material particles in a mechanical fusion mode.

And (3) in the step (2), the mechanical fusion is to coat the nano lithium manganese iron phosphate on the surface of the first coating layer cathode material particles in a mechanical fusion mode.

The invention relates to a composite electrode material prepared by the method.

The invention provides a lithium ion battery, wherein the composite electrode material is a positive electrode material of the lithium ion battery.

Advantageous effects

(1) Coating nano metal oxide and metal metaphosphate on the surface of the nickel-rich layered positive electrode material, wherein the selected oxide and metaphosphate can react with lithium carbonate and lithium hydroxide remaining on the surface of the nickel-rich layered positive electrode material during annealing treatment to form a lithium ion conductor, so that the residual alkali content of the nickel-rich layered positive electrode material is reduced, the lithium ion conduction capability of the nickel-rich layered positive electrode material is improved, and the bonding force with the first coating layer is enhanced;

(2) the first coating layer can effectively isolate the nickel-rich layered positive electrode material from being in direct contact with the lithium manganese iron phosphate, so that spontaneous redox reaction between the nickel-rich layered positive electrode material and the lithium manganese iron phosphate is effectively prevented, the stability of an interface structure is improved, meanwhile, the sensitivity of the nickel-rich layered positive electrode material to environmental humidity is improved, and the storage and processing performances of the nickel-rich layered positive electrode material in the using process are improved;

(3) the first coating layer and the second coating layer are subjected to double coating design on the nickel-rich layered positive electrode material, so that the contact between the electrolyte and the nickel-rich layered positive electrode material can be more effectively reduced, the stability of the surface structure of the material is improved, and the exothermic reaction between the electrolyte and the nickel-rich layered positive electrode material under the abuse conditions of overcharge, short circuit, heating, needling and the like is more effectively inhibited, so that the cycle and safety performance of the material are more obviously improved;

(4) the coating is carried out by adopting a mechanical fusion mode, the nano material can be uniformly and tightly coated on the surface of the nickel-rich layered anode material particles, the process is simple, efficient and emission-free, and the method is suitable for industrial production.

Drawings

FIG. 1 is an SEM photograph of the matrix nickel-rich layered cathode material of comparative example 1;

FIG. 2 is an SEM photograph of a first clad nickel-rich layered cathode material of example 1;

FIG. 3 is an SEM photograph of a second clad nickel-rich layered cathode material of example 1;

fig. 4 is a charge and discharge curve before and after the nickel-rich layered positive electrode materials in example 1 and comparative example 1 are compounded;

fig. 5 is specific discharge capacity of the composite positive electrode materials of example 1 and comparative example 2 after being left for various periods of time;

fig. 6 is a 18650 cycle curve of a battery fabricated before and after the nickel-rich layered positive electrode materials of example 1, comparative example 1, and comparative example 2 were compounded;

fig. 7 is a 18650 thermal safety test curve of cells fabricated before and after the nickel-rich layered positive electrode materials of example 1 and comparative example 1 were compounded.

Detailed Description

The invention will be further illustrated with reference to the following specific examples. It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present invention. Further, it should be understood that various changes or modifications of the present invention may be made by those skilled in the art after reading the teaching of the present invention, and such equivalents may fall within the scope of the present invention as defined in the appended claims.