1. Introduction to lithium iron phosphate battery
Lithium iron phosphate (lithium iron phosphate, LiFePO4, abbreviated as LFP) is a positive electrode material for lithium-ion batteries, which has the ability to insert and extract lithium ions in lithium-ion batteries. Its theoretical specific capacity is 170mAh/g, and the actual specific capacity of mass-produced materials is about 140-145mAh/g (1C, full battery, 2.5-3.65V).
When LFP materials are used in lithium-ion batteries, they have the following characteristics:
1. Good theoretical security:
Because of its small volume change during the process of inserting and inserting lithium ions, it is called a "zero phase change material" together with lithium titanate. This also determines the theoretically excellent cycle performance of lithium iron phosphate materials.
2. Good theoretical security:
The decomposition temperature of lithium iron phosphate is about 750℃, which is much higher than 200-300℃ of ternary materials, and there is no oxygen precipitation during decomposition, which makes it have better theoretical safety. It is called together with lithium manganate materials. The two safest cathode materials.
3. Low energy density
Compared with NCM ternary materials, the energy density of LFP is relatively low, which is mainly determined by three factors:
1) The capacity of LFP material is 140mAh/g, which is lower than that of ternary material (the current capacity of NCM523 is 155-180mAh/g);
2) The compaction density of LFP material is relatively low. The compaction density of the currently used LFP material is basically 2.2-2.6g/cm3, while the compaction density of the commonly used NCM523 material is 3.4-3.6 g/cm3; this parameter determines Under the same coating weight, NCM material can roll the pole piece thinner;
3) The rated voltage of the LFP battery is generally 3.2V, while the rated voltage of the NCM ternary battery is generally 3.6-3.7V.
4. Poor conductivity/power/low-temperature performance
Because the resistance of LFP materials to release lithium ions is relatively large (lattice binding force, which can be called impedance), and the electronic conductivity is poor, it is generally considered that the power performance and low-temperature performance of LFP materials are poor. However, the current mass-produced LFP materials have basically avoided this problem through particle parameterization, carbon coating technology, and carbon-coated aluminum foil technology.
In view of the above characteristics, lithium iron phosphate batteries are generally used in pure electric buses/energy storage and other fields that require low energy density and high cycle life and safety requirements.
However, it should be noted that good safety and good cycle performance are just the theoretical characteristics of LFP materials. The cycle performance, safety performance, and reliability of the battery are not only determined by the positive electrode material but other matching materials (negative electrodes, electrolytes, separators, etc.) ) Has a greater comprehensive impact, and the battery processing process has a significant impact on cycle performance and reliability. After being processed into a battery system, the design and processing of the battery pack also have a decisive influence. Therefore, we cannot simply say that the safety and cycle performance of LFP batteries are good. This is the wrong guide of some technical media.
Manly 3.2V LiFePo4 Battery cell
MANLY Battery Company, a professional manufacturer of lithium iron phosphate batteries, provides customized services for multi-series parallel lithium iron phosphate batteries/lithium iron phosphate power batteries. The products are widely used in electric bicycles, golf carts, electric wheelchairs, electric tools, electric toys, Solar batteries, emergency lights, solar street lights, UPS backup power supplies, and various instruments.
