CN-122025609-A - Mixed positive electrode material, preparation method thereof, positive electrode plate and battery

CN122025609ACN 122025609 ACN122025609 ACN 122025609ACN-122025609-A

Abstract

The invention relates to the technical field of positive electrode materials, in particular to a blended positive electrode material, a preparation method thereof, a positive electrode plate and a battery. According to the invention, a grain size matching formula based on the unit cell volume change rate is introduced, a quantitative relation between the grain sizes of the ternary material and the phosphate material in the blended anode material and the unit cell volume change rate is established, dynamic matching of volume change of the two materials in a circulating process is realized, generation of an inter-grain electric isolation phenomenon can be better avoided, and further effective inhibition of an internal resistance increase rate and remarkable improvement of circulating stability are realized.

Inventors

DONG YAN
YIN CHONG
SUN WEILI

Assignees

宁波容百新能源科技股份有限公司

Dates

Publication Date: 20260512
Application Date: 20260330

Claims (10)

1. The mixed positive electrode material is characterized by comprising a first positive electrode active material and a second positive electrode active material, wherein the first positive electrode active material is a ternary positive electrode material, the second positive electrode active material is a phosphate positive electrode material, and the particle size D A of the first positive electrode active material and the particle size D B of the second positive electrode active material meet the following conditions ：D A = K·λ·D B ·（V B /V A ） 0.15 ,K=m B /m A ,V A =|V A Original, original -V A Filling material |÷V A Original, original ×100%,V B =|V B Original, original -V B Filling material |÷V B Original, original ×100%, Wherein, the particle diameter D A 、D B is the average particle diameter of the first positive electrode active material and the second positive electrode active material respectively; m A is the mixing mass of the first positive electrode active material; m B is the blending mass of the second positive electrode active material; V A is the rate of change of the unit cell volume of the first positive electrode active material before and after the charge-discharge process, V A Original, original 、V A Filling material is the unit cell volume at 0% soc before or after the charge-discharge of the first positive electrode active material and the unit cell volume at 100% soc after the charge-discharge, respectively; V B is the rate of change of the unit cell volume of the second positive electrode active material before and after the same charge-discharge procedure as the first positive electrode active material, V B Original, original 、V B Filling material is the unit cell volume at 0% soc before or after charge-discharge and at 100% soc after charge-discharge of the second positive electrode active material, respectively; lambda is an empirical coefficient and the value range is 1.0-2.0.
2. The blended cathode material according to claim 1, wherein the K value satisfies 0.42≤K≤19.
3. The blended cathode material according to claim 1 or 2, wherein the K value satisfies 1.5≤k≤9.
4. The blended cathode material according to claim 1 or 2, wherein the first cathode active material is at least one of single crystal particles, single crystal-like particles, polycrystalline particles, the single crystal particles or single crystal-like particles having an average particle diameter of 1 μm to 15 μm, and the polycrystalline particles having an average particle diameter of 2 μm to 20 μm; the second positive electrode active material is at least one of single crystal particles and single crystal-like particles, and the average particle diameter of the single crystal particles or the single crystal-like particles is 0.8 μm to 4.2 μm, preferably 1 μm to 2.5 μm.
5. The blended cathode material according to claim 4, wherein the first cathode active material is single crystal particles, single crystal-like particles, the single crystal particles, single crystal-like particles having an average particle diameter of 2.0 μm to 8.0 μm; or, the first positive electrode active material is polycrystalline particles, and the average particle diameter of the polycrystalline particles is 3.5-13 μm.
6. The blended cathode material according to claim 1 or 2, wherein the charge-discharge procedure refers to charging to 100% soc at 0.1C current or discharging to 0% soc at 0.1C current; and/or, D A 、D B is the average particle size at 0% soc before or after charging.
7. The blended cathode material according to claim 1 or2, wherein the first cathode active material has a chemical formula of Li [ Ni x Co y M z Mn w ]O 2-m R m , wherein 0< x≤ 0.99,0≤y≤0.2, 0≤z <0.1, 0≤w≤ 0.6,0≤m <0.1, and x+y+z+w=1, m including at least one of Mg, al, ti, sr, Y, zr, nb, mo, in, sb, ta, W, P, cr, la, zn, R including at least one of F, S, se, cl, B; The chemical formula of the second positive electrode active material is LiMn x Fe 1-x-y N y PO 4 , x is more than or equal to 0 and less than or equal to 1, y is more than or equal to 0 and less than or equal to 0.2, N comprises at least one of Ni, co, mg, al, ti, sr, Y, zr, nb, mo, in, sb, ta, W, P, cr, la, zn, and preferably, the second positive electrode active material also comprises a carbon material.
8. A method of preparing the blended cathode material of any of claims 1-7, comprising the steps of: obtaining a first positive electrode active material and a second positive electrode active material, and mixing the first positive electrode active material and the second positive electrode active material to ensure that the first positive electrode active material and the second positive electrode active material meet ：D A = K·λ·D B ·（V B /V A ） 0.15 ,K=m B /m A ,V A =|V A Original, original -V A Filling material |÷V A Original, original ×100%,V B =|V B Original, original -V B Filling material |÷V B Original, original ×100%, to obtain the blended positive electrode material; The first positive electrode active material is a ternary positive electrode material, and the second positive electrode active material is a phosphate positive electrode material, wherein the particle size D A 、D B is the average particle size of the first positive electrode active material and the second positive electrode active material respectively; m A is the mixing mass of the first positive electrode active material; m B is the blending mass of the second positive electrode active material; V A is the rate of change of the unit cell volume of the first positive electrode active material before and after the charge-discharge process, V A Original, original 、V A Filling material is the unit cell volume at 0% soc before or after the charge-discharge of the first positive electrode active material and the unit cell volume at 100% soc after the charge-discharge, respectively; V B is the rate of change of the unit cell volume of the second positive electrode active material before and after the same charge-discharge procedure as the first positive electrode active material, V B Original, original 、V B Filling material is the unit cell volume at 0% soc before or after charge-discharge and at 100% soc after charge-discharge of the second positive electrode active material, respectively; lambda is an empirical coefficient and the value range is 1.0-2.0.
9. A positive electrode sheet comprising a current collector and a positive electrode active layer on at least one surface of the current collector, wherein the positive electrode active layer comprises the blended positive electrode material according to any one of claims 1 to 7 or the blended positive electrode material prepared by the method of claim 8.
10. A battery comprising the positive electrode sheet according to claim 9.

Description

Mixed positive electrode material, preparation method thereof, positive electrode plate and battery Technical Field The invention relates to the technical field of positive electrode materials, in particular to a blended positive electrode material, a preparation method thereof, a positive electrode plate and a battery. Background The lithium ion battery is used as a high-energy-density energy storage device and is widely applied to the fields of electric automobiles, energy storage systems and consumer electronics. The positive electrode material is a core component for determining the energy density, the cycle life and the safety performance of the battery. Lithium iron phosphate (LFP) and lithium manganese iron phosphate (LMFP) are important materials in the field of power batteries because of their advantages of high safety, long cycle life, low cost, and the like. However, the energy density is low, and it is difficult to meet the higher requirements of the long-endurance vehicle type on the battery performance. To remedy this deficiency, attempts have been made in the prior art to blend high capacity ternary materials (e.g., NCM, NCA) with LFP/LMFP to increase overall energy density. In the practical application of a power battery, the circulation stability and interface contact performance of the positive electrode material directly determine the internal resistance change, the power output and the service life of the battery. The mismatch of voltage platform difference and volume change in the mixing system can easily cause the contact variation and even separation among particles to form an electric isolation phenomenon, thereby causing the problems of rapid rise of internal resistance, acceleration of capacity attenuation and the like. The problems are particularly remarkable under the high-temperature working condition, and the commercialized application of the blended cathode material is severely restricted. Therefore, developing a blended positive electrode material capable of effectively relieving the problem of electrical isolation in the cycling process is a key technical direction for improving the performance of the power battery. Disclosure of Invention Based on the above, the invention provides the blended positive electrode material, which can effectively alleviate the electrical isolation problem of the blended material in the circulation process, and further can realize effective inhibition of the internal resistance increase rate and remarkable improvement of the circulation stability. The preparation method of the blended anode material provided by the invention can be used for obtaining the blended material capable of relieving the problem of electrical isolation in the circulation process. The positive plate provided by the invention has the advantages of slower internal resistance increase and excellent cycling stability. The battery provided by the invention has excellent cycle performance. The invention provides a blended positive electrode material, which comprises a first positive electrode active material and a second positive electrode active material, wherein the first positive electrode active material is a ternary positive electrode material, the second positive electrode active material is a phosphate positive electrode material, and the particle size D A of the first positive electrode active material and the particle size D B of the second positive electrode active material meet the following conditions ：DA = K·λ·DB·（VB/VA）0.15,K=mB/mA,VA=|VA Original, original -VA Filling material |÷VA Original, original ×100%,VB=|VB Original, original -VB Filling material |÷VB Original, original ×100%, Wherein, the particle diameter D A、DB is the average particle diameter of the first positive electrode active material and the second positive electrode active material respectively; m A is the mixing mass of the first positive electrode active material; m B is the blending mass of the second positive electrode active material; V A is the rate of change of the unit cell volume of the first positive electrode active material before and after the charge-discharge process, V A Original, original 、VA Filling material is the unit cell volume at 0% soc before or after the charge-discharge of the first positive electrode active material and the unit cell volume at 100% soc after the charge-discharge, respectively; V B is the rate of change of the unit cell volume of the second positive electrode active material before and after the same charge-discharge procedure as the first positive electrode active material, V B Original, original 、VB Filling material is the unit cell volume at 0% soc before or after charge-discharge and at 100% soc after charge-discharge of the second positive electrode active material, respectively; lambda is an empirical coefficient and the value range is 1.0-2.0. The K value of the blended positive electrode material is more than or equal to 0.42 and less than or eq