Why does LFP (lithium iron phosphate, LiFePO4) battery perform better than other triple chemical battery during charging?

The key to the longer life of LFP battery is its working voltage, which is between 3.2 and 3.65 volts, lower than the voltage normally used by NCM battery. The lithium iron phosphate battery uses phosphate as the positive material and carbon graphite electrode as the negative electrode; They also have long service life, good thermal stability and good electromechanical performance.

3.2V

LFP battery operates at a nominal voltage of 3.2V, so when four batteries are connected, 12.8V battery can be obtained; 25.6V battery can be obtained when 8 batteries are connected. Therefore, LFP chemistry is the best choice to replace deep-cycle lead-acid batteries in various applications. So far, it is their low energy density that limits their use in large vehicles, because they are much cheaper and safer. This situation led to the adoption of this technology in the Chinese market, which is why 95% of lithium iron phosphate batteries are made in China.

12V battery

The battery with graphite anode and LFP cathode operates at a nominal voltage of 3.2 volts and a maximum voltage of 3.65 volts. With these voltages (also very low), 12000 life cycles can be achieved. However, batteries with graphite anode and NCM (nickel, cobalt and manganese oxide) or NCA (nickel, nickel and aluminum oxide) cathode can operate at a higher voltage, with a nominal voltage of 3.7 volts and a maximum voltage of 4.2 volts. Under these conditions, it is not expected to achieve more than 4000 charging and discharging cycles.

24V battery

If the working voltage is low, the liquid electrolyte between the two battery electrodes (through which lithium ions move) is chemically more stable. This part explains why the LTO battery operating at 2.3V and the LFP battery operating at 3.2V have better life than the NCM or NCA battery operating at 3.7V. When the battery has a higher charge and therefore a higher voltage, the liquid electrolyte will slowly start to corrode the battery electrode. Therefore, there is no battery using spinel at present. Spinel is a mineral formed by manganese and aluminum. Its cathode voltage is 5V, but new electrolyte and improved electrode coating are needed to prevent corrosion.

This is why it is necessary to keep the battery at the lowest possible SoC (state of charge or% charge), because it will work at a lower voltage and its life will be extended.


Post time: Feb-10-2023