Patent Information丨Patents about Huawei's positive electrode composite materials

This article is an introduction to Huawei's latest patent CN116487541A, which involves positive electrode composite materials and their preparation methods, positive electrodes and batteries.

Huawei Patents	Patent content
Patent No	CN116487541A
Patent content	Cathode composite materials
Application date	2022/1/13
Public (announcement) date	2023/7/25

technical problem

There are currently three commonly used methods for high-temperature attenuation of positive electrode materials, mainly including doping, surface coating and charge and discharge system regulation. For the doping regulation method, although it will improve the cycle performance of the electrode, the increase in the doping amount often leads to capacity consumption. The second effective method is to coat the inorganic ceramic layer on the surface interface of the material through a sintering process, and achieve stable operation of the electrode material through the protective effect of the interface layer on the electrode. Since the coating material has a high density and high mass and cannot provide electrochemical activity, it will also lead to low material capacity. The third method is to use circuit regulation to set the charge and discharge system under different high and low temperature conditions to adjust the battery capacity. Since lithium ions are prone to over-emission at high temperatures, a system with a higher cut-off current or a lower charging voltage at higher temperatures can be used to reduce the high temperature coefficient of the battery. Although this method is efficient, it requires sensor implantation, occupies volume and sacrifices the energy density of the battery. At the same time, it is also very difficult to accurately monitor the internal temperature of the battery.

 

Technical means

A positive electrode composite material comprises: a plurality of positive electrode material particles; a coating layer, at least covering a portion of the outer surface of the plurality of positive electrode material particles, the coating layer comprising a thermoplastic polymer material and a conductive carbon material distributed in the polymer material, and the coating layer having a positive temperature coefficient.

A method for preparing a positive electrode composite material comprises: mixing and stirring a polymer material and a conductive carbon material in an organic solvent to obtain a slurry, wherein the polymer material is a thermoplastic polymer material; mixing and stirring the slurry and positive electrode material particles so that the slurry wraps the positive electrode material particles, and then drying and grinding, wherein the slurry forms a coating layer that wraps the positive electrode material particles, and the coating layer has a positive temperature coefficient.

The polymer material is selected from at least one of polyvinylidene fluoride, polyethylene, polyethylene oxide, polyacrylonitrile, polyvinyl alcohol, polystyrene sulfonate-poly (3,4-ethylenedioxythiophene), polyaniline, rubber, and nylon; the conductive carbon material is selected from at least one of conductive carbon black, carbon nanotubes, carbon fibers, and graphene; and the material of the positive electrode material particles is a positive electrode material containing alkali metal ions.

The mass of the conductive carbon material accounts for 30% to 80% of the total mass of the polymer material and the conductive carbon material.

The solid content of the slurry is 5wt% to 50wt%.

The positive electrode material particles account for 97% to 99.5% of the total mass of the polymer material, the conductive carbon material and the positive electrode material particles.

 

principle

The present application forms a coating layer on the surface of the positive electrode material particles, and the coating layer has a positive temperature coefficient. As the electrode operating temperature increases, the interface resistance increases, so the voltage generated in the coating layer will increase, thereby reducing the voltage on the positive electrode material. The voltage applied to the positive electrode material corresponds to the amount of alkali metal ions (such as lithium ions, sodium ions, and potassium ions) released, so this strategy can suppress/avoid excessive release of alkali metal ions in the positive electrode material as the temperature increases, reduce the high temperature coefficient, and thus greatly improve the battery cycle performance without sacrificing battery capacity.

 

Technical Effects

By using this special positive electrode material in the battery, the excessive release of alkali metal ions in the positive electrode material as the temperature rises can be effectively suppressed/avoided, thereby greatly improving the cycle performance of the battery without sacrificing the battery capacity.