Pore-forming method for diaphragms of lithium ion batteries

Abstract

The invention belongs to the technical field of lithium ion batteries, and particularly relates to a pore-forming method for diaphragms of lithium ion batteries. The method comprises the following steps: fully dissolving a pore-forming agent into a solvent so as to prepare a pore-forming agent solution; uniformly coating the pore-forming agent solution on the surface of a to-be-cold-pressed diaphragm, and carrying out baking on the diaphragm at a temperature lower than the sublimation or decomposition temperature of the pore-forming agent, so that a solvent of the pore-forming agent solution is volatilized, and the pore-forming agent is recrystallized in the diaphragm; and carrying out cold pressing on the diaphragm, and then carrying out baking on the diaphragm at a temperature higher than the sublimation or decomposition temperature of the pore-forming agent, so that the pore-forming agent recrystallized in the diaphragm is sublimated or decomposed, thereby obtaining a porous diaphragm. According to the invention, through regulating the viscosity of the pore-forming agent solution, a diaphragm with adjustably-distributed pores can be obtained, and the regulating method is simple and flexible, and wide in applicable range; and particularly, according to the invention, an efficient gradient pore distribution structure that more pores are distributed on the surface layer of the diaphragm and less pores are distributed on the inner layer of the diaphragm can be realized just through selecting an appropriate viscosity of the pore-forming agent solution..

Description

technical field [0001] The invention belongs to the technical field of lithium-ion batteries, and in particular relates to a pore-forming method for a lithium-ion battery diaphragm. Background technique [0002] Since the large-scale commercialization of lithium-ion batteries, they have been widely used in portable electrical appliances such as laptops, cameras, and mobile communications due to their advantages of high energy density and high power density. However, with the continuous updating of the design of consumer electronic products and the widening of application requirements, the requirements for battery performance (such as fast charging and discharging performance, good low temperature performance) are also increasing. [0003] As known in the industry, the improvement of battery performance depends on the rapid conduction of two channels in the battery system: ion channels and electron channels. For the rapid conduction of ion channels, the key lies in the porou...

AI Technical Summary

Problems solved by technology

Because the former needs to add pore-forming agent to the slurry, which is a very sensitive metastable system, it will have a certain impact on the selection of slurry formulation and the pulping process; and if you want to make a highly efficient porous material with more pores on the surface and fewer pores in the inner layer. structure, this method requires the preparation of slurries with different concentrations of pore-forming agents and multi-layer coating to achieve, which is a very complicated process

The diaphragm punching method is mainly to create a specific hole structure in the diaphragm through mechanical / physical methods. During the implementation of this method, it will cause mechanical / physical damage to the active material in the diaphragm, resulting in a decrease in the energy density of the cell. reduce; and this method is difficult to achieve large-scale, efficient mass production in a short period of time, in addition, the diaphragm punching method also requires the use of expensive precision instruments and equipment