At present, the measures to improve the safety of lithium-ion batteries and prevent battery explosions mainly include improving the thermal stability of the battery, improving the overcharge protection ability and improving the ability to prevent the battery from short circuit. This article will provide an overview of methods to prevent overcharging of Li-ion batteries.
Methods to prevent overcharging of lithium-ion batteries:
1. Usually a dedicated charging circuit is used to control the charging and discharging process of the battery, or a safety valve is installed on a single battery to provide a greater degree of overcharge protection.
2. Secondly, a positive temperature coefficient resistor (PTC) is used, and its mechanism is that when the battery heats up due to overcharge, the internal resistance of the battery is increased, thereby limiting the overcharge current.
3. Special diaphragm can also be used. When the temperature of the separator is too high due to an abnormality in the battery, the pores of the separator shrink and block, preventing the migration of lithium ions and preventing the overcharge of the battery.
4. The internal protection of battery overcharge through additives is of great significance to simplify the battery manufacturing process and reduce production costs. Anti-overcharge additives include polymerized monomer additives and redox additives. The former is that when the charging voltage exceeds a certain value, the monomer polymerizes to form a conductive polymer film, which makes the battery self-discharge to a safe state; at the same time, the polymerization reaction generates gas, and the polymer product increases the internal resistance of the battery and enhances the combined device. sensitivity. Common polymerized monomers are aromatic compounds; the latter is that when the battery is overcharged, the additive undergoes an oxidation reaction at the positive electrode and then diffuses to the surface of the negative electrode to reduce to the original state until the end of charging. At present, there are more ferrocene and its derivatives, phenanthroline and bipyridine complexes of Fe, Ru, Ir and Ce, thiophene, anisole and bi-anisole, etc.
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