Positive electrode slurry and application thereof

Abstract

The invention relates to a positive electrode slurry and an application thereof, the positive electrode slurry comprises a high-nickel positive electrode material and an additive, and the additive comprises at least one of LiPF6, boric acid, oxalic acid, citric acid, tartaric acid, tetraethyl silicate, LiPO2F2 and HPF6; the additive can react with residual alkali on the surface of a high-nickel positive electrode material to reduce the alkalinity of positive electrode slurry and improve the stability and processability of the positive electrode slurry, so that the gas production of a battery prepared from the additive in the use process is reduced, the safety of the battery is improved, the application of the waterless high-nickel positive electrode material is facilitated, and the cost ofthe battery is reduced; meanwhile, the preparation process of the positive electrode slurry is simple to operate, and industrialization is easy to realize.

Description

technical field [0001] The invention belongs to the field of lithium batteries, and relates to a positive electrode slurry and an application thereof. Background technique [0002] Lithium nickel cobalt manganese (aluminum) oxide ternary material, LiNi x co x m z o 2 (x+y+z=1, M=Mn / Al), because of its high specific capacity, it is widely used in the field of electric vehicles. With the continuous improvement of the market's mileage demand for electric vehicles, ternary materials are gradually moving towards high nickel (x>0.6) direction. However, as the nickel content continues to increase, the synthesis temperature of ternary materials continues to decrease, resulting in higher residual alkali on the surface of the material, such as lithium carbonate and lithium hydroxide. It has the following disadvantages: on the one hand, due to the presence of lithium carbonate and lithium hydroxide, the ternary material is strongly alkaline, and during the preparation of the po...

AI Technical Summary

Problems solved by technology

It has the following disadvantages: on the one hand, due to the presence of lithium carbonate and lithium hydroxide, the ternary material is strongly alkaline, and during the preparation of the positive electrode slurry, the basic groups on the surface of the material will attack polyvinylidene fluoride ( The C-F and C-H bonds in PVDF) form a part of the carbon-carbon double bond, which leads to an increase in the viscosity of the slurry, and even forms a gel state, which affects the manufacture of the pole piece

On the other hand, lithium hydroxide will react with lithium salt (for example, LiPF6) in the electrolyte to generate HF gas, which will lead to corrosion of metal parts inside the battery, and will destroy the SEI film and consume the system. The active lithium in the battery accelerates the performance degradation of the battery; in addition, the reaction between lithium carbonate and HF releases CO2 gas, which affects the safety of the battery

[0003] CN106384816A discloses a high-nickel ternary lithium-ion battery positive electrode slurry, which includes the following components in parts by weight: high-nickel ternary positive electrode powder 90- 98 parts, 1-5 parts of conductive agent, 1-5 parts of binder; the molecular formula of the high-nickel ternary positive electrode powder is LiNixCoyMzO2, wherein x+y+z=1, 0.6≤x<1, M is a metal element; the binder is bonded by high bond strength A composite binder formed by mixing an alkaline-resistant binder and an alkali-resistant binder; this solution uses a specific binder to improve the processing performance of the positive electrode slurry, but it cannot improve the gas production of the resulting battery during use

[0004]At present, the washing process is mainly used in the industry to reduce the residual alkali on the surface of the ternary material. However, during the washing process, the Li in the surface layer of the ternary material will interact with water Proton exchange leads to deterioration of the capacity and cycle performance of the material; at the same time, water washing destroys the surface structure of the material and increases the specific surface area of ​​the material, resulting in an increase in side reactions with the electrolyte and accelerating the attenuation of the battery

At the same time, in order to reduce the negative impact of washing, it is usually necessary to heat-treat or coat the washed product to repair the surface structure of the material, but this measure will increase the difficulty of the process and increase the processing cost

[0005] CN111029550A discloses a method for surface modification of a high-nickel positive electrode material for a lithium-ion battery. First, the high-nickel positive electrode material is mixed with deionized water and stirred into a slurry; Then, under stirring conditions, add acidic solution and precipitant solution to the slurry at the same time, maintain the pH of the reaction system at 10.0-12.0 for reaction; then perform solid-liquid separation on the slurry obtained after the reaction, and dry the obtained solid After sieving, an unburned high-nickel cathode material with a coating layer on the surface is obtained; finally, the unfired high-nickel cathode material with a coating layer on the surface is heated to 300-700°C in an oxygen atmosphere and kept for 3-12 hours, and then cooled to room temperature to obtain a surface-modified high-nickel cathode material; although this solution can reduce the residual alkali on the surface of the high-nickel cathode material, the process is complicated and the cost is high

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