As we all know, the high temperature performance of lithium battery packs is very good, the peak heat can reach 350 to 500℃, and it can still release 100% capacity at high temperature (60℃). But in the low temperature, its performance is a bit worse than that of other battery systems, so how to improve its low temperature performance?

Ⅰ. Factors affecting the low temperature performance of lithium iron phosphate battery packs

1. Production environment: Lithium iron phosphate battery pack is a high-tech product with many chemical raw materials and complicated processes. Its production environment has high requirements on temperature, humidity, dust, etc. If it is not controlled well, there will be fluctuation in the battery quality.

2. Poor conductivity and slow diffusion of lithium ion battery. During charging and discharging at a high rate, the actual specific capacity is low. This problem is a difficulty that restricts the development of the lithium iron phosphate industry, which is central to the situation that lithium iron phosphate has not been widely used.

3. The influence of materials. The positive electrode of lithium iron phosphate battery has relatively poor electronic conductivity, and it is more prone to polarization, which reduces the performance of capacity; the negative electrode is mainly charged at low temperature because it will give rise to safety issues; In terms of electrolyte, the viscosity may increase at low temperatures, and the migration resistance of lithium ion battery will increase; the fourth is the binder, which has a relatively large impact on the low temperature performance of the battery.

Ⅱ. How to improve the low temperature performance of lithium iron phosphate battery packs

1. The positive electrode is now nanoscaled. Its particle size, electrical resistance, and the axis length of the AB plane will affect the low temperature characteristics of the entire battery. Different technologies have different effects on the positive electrode. The low temperature discharge characteristics of batteries made of lithium iron phosphate with a particle size of 100 to 200 nanometers are better, and 94% can be released at -20°C. That is, the nanometerization of the particle size shortens the migration path and also improves the performance of low temperature discharge, because the discharge of lithium iron phosphate battery is mainly related to the positive electrode.

2. Considering the charging characteristics of the negative electrode, the low temperature charging of lithium ion battery is mainly affected by the negative electrode, including the particle size and the change in the spacing of the negative electrode. Three different artificial graphites are selected as the negative electrode to study the effect of different interlayer spacing and particle size on low temperature characteristics. From the perspective of the three materials, granular graphite with a large interlayer spacing has a smaller bulk resistance and ion migration resistance in terms of impedance.

3. In terms of charging, the lithium-ion battery cells for sale have a little problem with discharging at low temperatures in winter, but mainly have the problem of low temperature charging. Because in terms of the cross-current ratio, the cross-current ratio of 1°C or 0.5°C is very critical, it takes a very long time to reach a constant voltage. By improving the comparison of three different graphites, it is found that one of them has a greater improvement in the charging cross-current ratio at -20°C , from 40% to more than 70%, accompanied by increase in the layer spacing, and decrease in the particle size.

In the future, Tianneng will continue to provide consumers with diversified and high-performance products through a series of innovations, laying a solid foundation for the full opening of the new travel era!