Why lithium batteries have security problems
1, how the internal short circuit is constituted: the biggest hidden danger of lithium-ion batteries is the use of lithium cobalt acid lithium-ion batteries in the case of overcharging (or even normal charging and discharging), lithium ions in the negative electrode pile up to form a dendrite, piercing the barrier, constituting an internal short circuit.
2, the occurrence of high current: external short circuit, internal short circuit will occur several hundred amperes of excessive current
i. When the external short circuit, because the external load is too low, the battery instantly discharge high current. A lot of energy is consumed in the internal resistance and huge heat occurs.
ii. internal short circuit, the main reason is that the barrier is penetrated, the internal constitutes a high current, the temperature rises leading to the melting of the barrier, the short circuit area expands, thus constituting a vicious circle
3, where the gas comes from: lithium-ion batteries to achieve a single cell 3 - 4.2V high operating voltage (nickel-hydrogen and nickel-chrome batteries operating voltage of 1.2V, lead-acid batteries operating voltage of 2V), must adopt the differentiation voltage greater than 2V organic electrolyte, and the use of organic electrolyte in high current, high temperature conditions will be electrolysis, electrolysis gas, resulting in The internal pressure will rise, which will break the shell seriously.
4, how the incineration occurs: heat from the high current, together with the high voltage (more than 5V), lithium cathode oxide will also occur oxidation reactions, precipitation of lithium metal, in the case of gas leading to the rupture of the shell, and air direct touch, resulting in incineration, together with the ignition of the electrolyte, a strong flame, rapid expansion of gas, bursting.
5, whether polymer batteries will have safety problems: the difference between polymer batteries and lithium-ion batteries is that the electrolyte is gel, semi-solid, and the lithium-ion battery electrolyte is liquid. Therefore, polymer batteries can be used in soft packaging, in the internal occurrence of gas, you can break the shell earlier to avoid excessive gas gathering and violent rise and crack. But the polymer battery does not fundamentally deal with the safety problem, the same use of lithium cobaltate and organic electrolyte, and the electrolyte is colloidal, not easy to leak, will occur more intense incineration, incineration is the biggest problem of polymer battery safety.
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