How to improve the low temperature performance of lithium battery?

We improve the low-temperature performance of lithium iron phosphate battery packs from four components: positive electrode, negative electrode, electro-hydraulic, and binder.

In terms of the positive electrode, it is now nano-sized. Its particle size, electrical resistance, and the length of the AB plane axis will affect the low temperature characteristics of the entire battery. Different processes also have different effects on the positive electrode. Batteries made of 100 to 200 nanometer particle size lithium iron phosphate have better low-temperature discharge characteristics, and can release 94% at -20 degrees, that is, the nanometerization of particle size shortens the migration path. It also improves the performance of low-temperature discharge, because lithium iron phosphate discharge is mainly related to the positive electrode.

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

In terms of charging, lithium-ion battery packs have little problem in low temperature discharge in winter, mainly low temperature charging. Because in terms of cross-current ratio, the cross-current ratio of 1C or 0.5C is very critical, and it takes a very long time to reach constant voltage. By improving the comparison of three different graphites, it is found that one of them has a relatively large charging constant current ratio at -20 degrees. The improvement was increased from 40% to more than 70%, the interlayer spacing was increased, and the particle size was decreased.

For the electrolyte, the electrolyte freezes at -20 degrees and -30 degrees, the viscosity increases, and the formation performance deteriorates. Electrolyte from three aspects: solvent, lithium salt, additives. The influence of solvent on low temperature of lithium iron phosphate battery pack ranges from more than 70% to more than 90%. On the basis of fixing the solvent system and lithium salt, low-temperature additives can increase the discharge capacity from 85% to 90%. That is to say, in the whole electrolyte system, the solvent, lithium salt and additives all affect the low-temperature characteristics of our power battery. There are certain effects, including other material systems as applicable. “

In terms of binder, under the condition of 20 degrees of charge and discharge, after the two kinds of dots have done more than 70 to 80 cycles, the entire pole piece has the status of binder failure, and the linear binder will not exist. this problem. In the whole system, after the improvement of the positive electrode, negative electrode, electrolyte and binder, the lithium iron phosphate battery has a better effect. One is the charging characteristics, -20, -30, -40 degrees The constant current ratio of charging at 0.5C at a temperature can reach 62.9%, and the discharge at a temperature of -20 degrees can release 94%, which are some characteristics of rate and cycle.

Post time: Nov-17-2022

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