Factors affecting the low-temperature characteristics of lithium iron phosphate batteries
Although lithium iron phosphate batteries have significant advantages over other rechargeable batteries in terms of cycle life and charge capacity, their performance deteriorates slightly at low temperatures. Therefore, improving and enhancing the low-temperature performance of lithium iron phosphate batteries is a more reasonable way to improve their competitiveness.
First, the positive electrode material selected in lithium iron phosphate batteries has relatively weak electronic conductivity, making it very easy for polarization to occur, which in turn reduces the volume of the lithium-ion battery.
Second, the negative electrode of a lithium-ion battery is extremely harmful to low-temperature battery charging and other aspects, which will compromise the safety of the battery.
Third, the viscosity of the electrolyte in lithium iron phosphate batteries increases under low-temperature conditions, which in turn increases the characteristic impedance of lithium-ion battery transfer.
Methods to improve and enhance the low-temperature characteristics of lithium iron phosphate batteries
1. From the perspective of the positive electrode of lithium iron phosphate batteries, the three factors of particle size, resistance, and capacitance all affect the low-temperature performance of the battery. The low-temperature charge-discharge performance of lithium batteries can be improved through positive electrode manufacturing processes. Increasing the length of the planar axis can expand the transfer channels of lithium-ion batteries, which is beneficial to increasing the battery volume. Studies have found that the low-temperature charge-discharge characteristics of lithium iron phosphate batteries can release 914 particles at -20°C, with a particle size of 100-200 nm. The nanotechnology of particles can reduce the transfer path of particles, thereby improving their low-temperature charge-discharge performance.
2. For lithium iron phosphate batteries undergoing low-temperature charging, the negative electrode is the most critical component, primarily due to variations in particle size and spacing. Artificially synthesized high-purity graphite is a cathode material with varying layer spacing and particle size. High-purity graphite layers with larger layer spacing exhibit slightly lower intrinsic impedance and positive ion transfer impedance. Because the spacing of artificially synthesized high-purity graphite layers increases and the particle size decreases, low-temperature constant-current charging significantly improves the performance of lithium iron phosphate batteries.
3. When the temperature drops to -20°C or lower, lithium iron phosphate battery electrolytes are prone to freezing, increased viscosity, and deterioration of properties. Experiments show that the impact of organic solvents on low-temperature batteries varies from 70% to 90%, reaching several percentage points. In addition, different lithium salts also have a certain impact on battery charging characteristics. Experiments have found that simply changing the corrosion inhibitor, specifically the low-temperature corrosion inhibitor, can increase the charge-discharge capacity of the battery from 8% to 90%.
The above examples illustrate several aspects and key points for improving and enhancing the low-temperature performance of lithium iron phosphate batteries, primarily focusing on the internal material composition of the battery. In reality, to achieve rapid and efficient performance improvement at lower temperatures, it is necessary not only to improve the internal material composition of the battery but also to enhance its efficiency through various methods, such as intelligent battery management systems and integrated cycle systems.
