The low-temperature performance of lithium battery is one of the key factors that restrict the widespread use of lithium batteries. How to improve the low-temperature performance of lithium batteries is still a hot and difficult point of current research.

The battery system reaction process mainly includes four steps: Li+ transport in the electrolyte, crossing the electrolyte/electrode interface membrane, charge transfer, and Li+ diffusion in the active material body. At low temperatures, the rate of each step decreases, which causes the impedance of each step to increase, which leads to aggravation of electrode polarization, and causes problems such as a decrease in low- temperature discharge capacity and lithium precipitation in the negative electrode.

The poor low-temperature performance of lithium-ion batteries is mainly due to the following three factors:

At low temperatures, the viscosity of the electrolyte increases, and the conductivity decreases;

The electrolyte/electrode interface membrane impedance and charge transfer impedance increase;

The migration rate of lithium ions in the active material body is reduced. As a result, the electrode polarization is increased at low temperatures and the charge and discharge capacity is reduced.

The mainstream ways to improve the ion diffusion performance of cathode materials at low temperatures are as follows: 

Use materials with excellent conductivity to coat the active material body to improve the conductivity of the cathode material interface, reduce the interface impedance, and reduce the positive electrode material and the side reaction of the electrolyte stabilizes the material structure.

The second is to do bulk-doping of the material body with Mn, Al, Cr, Mg, F and other elements to increase the layer spacing of the material to increase the diffusion rate of Li+ in the body, reduce the diffusion resistance of Li+, and increase the low temperature of the battery. performance.

The third is to reduce the particle size of the material and shorten the Li+ migration path. It should be pointed out that this method will increase the specific surface area of the material and increase the side reaction with the electrolyte.