The diaphragm is one of the key inner layer components. The performance of the separator determines the interface structure and internal resistance of the lithium-ion battery, which directly affects the capacity, cycle and safety performance of the battery. Separators with excellent performance are important for improving the overall performance of batteries.
The function of the separator in lithium-ion batteries is mainly reflected in two aspects:
One is to provide security for lithium-ion batteries. The diaphragm material must first have good insulation to prevent short circuit between the positive and negative electrodes or punctured by burrs, particles and dendrites. Therefore, the diaphragm must have a certain tensile and puncture strength, and it is not easy to tear. And it basically maintains dimensional stability under sudden high temperature conditions, and will not cause large-area short circuit and thermal runaway of the battery due to shrinkage.
The second is to supply microporous channels for charging and discharging functions and rate performance to lithium-ion batteries. Therefore, the separator must be a film with high porosity and uniform distribution of micropores. The characteristics of the material itself and the pore characteristics after film formation restrict the migration of lithium ions in the battery, which is reflected in the performance parameter of ionic conductivity.
1. The insulating layer can effectively prevent the positive and negative electrodes from contacting and causing internal short circuit.
2. The semi-permeable layer, which is mainly present in liquid batteries such as lithium-ion batteries, can organize the passage of relatively large molecules and only allow the passage of small-volume charged ions, which can increase the concentration difference near the positive and negative electrodes, which is beneficial to diffusion of ions, thereby improving the storage efficiency of the battery.
The ion conductivity of lithium-ion battery separator is directly related to the overall performance of the battery. The micropore self-closing protection is used for safety protection of battery users and equipment.
