What are the main safety risks associated with lithium-ion batteries?

1. Safety risks of positive electrode materials

If the LiFePO4 Battery is used incorrectly, the internal temperature of the battery will rise, causing the positive electrode material to decompose and the electrolyte to oxidise. At the same time, these two reactions can generate a large amount of heat, further increasing the battery temperature.The influence of different delithium states on the lattice transformation, analysis temperature and thermal stability of the Lithium Battery is very different.

2. Safety risks of negative electrode materials

The negative electrode material used in the early days was lithium metal, and the assembled battery was prone to lithium dendrites piercing the diaphragm after multiple charges and discharges, resulting in short circuit, leakage and even explosion of the battery. Lithium-embedded compounds can effectively prevent the formation of lithium dendrites, greatly improving the safety of Li-ion batteries. When the temperature rises, the negative carbon electrode in the lithium embedding state first reacts exothermically with the electrolyte. Under the same charging and discharging conditions, the heat release rate of the reaction between the electrolyte and Li-embedded artificial graphite is much higher than that of Li-embedded mesophase carbon microspheres, carbon fibres and coke.

3, diaphragm and electrolyte safety risks

The electrolyte of Lithium Iron Phosphate Battery is a mixed solution of lithium salt and organic solvent, of which the commercial lithium salt is lithium hexafluorophosphate, which is prone to thermal analysis at high temperature and thermal chemical reactions with trace amounts of water and organic solvents, which reduces the thermal stability of the electrolyte. The organic solvent of the electrolyte is carbonate ester, which has a low boiling point and flash point, and is easily reacted with the lithium salt to release PF5 at high temperature, and is easily oxidised.

4, safety hazards in the manufacturing process

In the manufacturing process of lithium-ion batteries, electrode manufacturing, battery assembly and other processes will affect the safety of the battery. For example, the quality control of positive and negative electrode mixing, coating, rolling, cutting or stamping, assembly, electrolyte filling amount, sealing, forming and other processes will not affect the performance and safety of the battery. The average size of the slurry determines the average distribution of the active material on the electrode, which affects the safety of the battery. If the fineness of the slurry is too large, the expansion and contraction ratio of the negative electrode material will change greatly when the battery is charged and discharged, and precipitation of lithium metal may occur. If the size is too small, the internal resistance of the battery will be too high. If the heating temperature of the coating is too low or the drying time is too short, the solvent will remain, the binder will be partially dissolved and some of the active substances will be easily detached. The high temperature may cause carbonisation of the binder, and the active substance will fall off, resulting in internal short circuit of the battery.