The cost of lithium iron phosphate battery is lower than that of ternary battery, and it has good safety and long service life. With the advancement of technology, the actual energy density of lithium iron phosphate batteries is also infinitely close to the theoretical energy density. Therefore, its market share is also steadily increasing, and has exceeded the installed capacity of ternary lithium batteries. However, the shortcomings of lithium iron phosphate (LiFePO4, LFP) are also obvious: poor low temperature performance, low tap density, poor conductivity, etc. , How to improve the low-temperature performance of lithium iron phosphate battery? Today Grepow technicians will take you to discuss how to improve the low-temperature performance of lithium iron phosphate battery.
How to improve the low temperature performance of lithium iron phosphate battery?
- Surface coating reduces the surface resistance of LFP particles
Lithium battery at low temperature, the impedance at the electrode material interface will increase, and the ion diffusion rate will also decrease. Coating a conductive layer on the surface of LFP will effectively reduce the contact resistance between electrode materials, thereby increasing the diffusion rate of ions into and out of LFP.
Generally, the cladding material is carbon material. For example, using amorphous carbon or carbon nanotubes or graphene for coating, these materials can reduce the interfacial impedance of the LFP electrode material. Another is the use of metal or metal oxide coatings. Studies have shown that CeO2 particles can be evenly distributed on the surface of LFP. At low temperature, the desorption/intercalation ability and electrode kinetics of LFP are significantly improved after CeO2 improvement.see more:72v 100ah lithium battery pack
- Bulk phase doping reduces the resistance of LFP electrodes
Ion doping can form vacancies in the LFP lattice structure, thereby promoting the diffusion of lithium ions in the electrode material.
Studies have shown that LFe0.92Mg0.08(PO4)0.99F0.03 obtained by Mg and F co-doping has better electrochemical performance at low temperature. The doping of the two ions did not change the particle size and structure of the material, but also increased the ion conduction rate and electron transfer rate.
- Optimization of electrolyte
This point may not only be applicable to LFP systems, but lithium batteries of ternary or other organic electrolyte systems can be applied.
At low temperatures, the transport of lithium ions at the electrode/electrolyte interface is the controlling step for their performance. To improve low-temperature performance, one of the most important points is to increase the electrochemical reaction rate at the interface. Therefore, the optimization of the SEI film is very important, and the properties of the SEI film are determined by the electrolyte and the surface properties of the electrode. Therefore, optimization of the electrolyte can also improve the low-temperature performance of lithium batteries.
Studies have shown that introducing co-solvents with longer molecular chains or higher molecular weight esters into the electrolyte can increase the stability of the SEI film, enable the stable insertion of lithium ions, and reduce the polarization of the battery.
In addition, the choice of lithium salt in the electrolyte will also affect the lithium ion conductivity and the stability of the SEI film.
- Optimization of charging strategy
Pulse current is used to rapidly heat up the battery temperature at low temperature.
During the charging process of lithium batteries, the movement and polarization of ions in the electrolyte will promote the internal heat generation of lithium batteries. This heat generation mechanism can be effectively used to improve its performance at low temperatures.Also read:lifepo4 battery 48v 400ah
lithium battery
Studies have shown that experimental tests using commercial lithium batteries can verify the difference in heat generation between continuous charging and pulse charging. As can be seen from the figure above, the microsecond pulse time can promote more heat generation in the lithium battery.
- Adopt new battery structure
The improvement of LFP's low-temperature performance can not only start from the material aspect, but also the improvement of the battery structure is very helpful.