How do lithium batteries explode?

Category of causes of explosion: insufficient negative electrode capacity, excessive moisture content, internal short circuit, protection line aging failure, overcharge, overdischarge, external short circuit, external extrusion and violent collision.

Negative terminal capacity is insufficient

When the negative electrode opposite the positive part of the capacity is insufficient, or no capacity at all, part or all of the lithium generated during charging can not be inserted into the negative graphite interlayer structure, will be out on the surface of the negative electrode, forming a protrude "dendrite", and the next charge, this protrude part is more likely to cause lithium precipitation, after dozens to hundreds of times of cyclic charging and discharging, The dendrites grow and eventually puncture the diaphragm paper, creating a short circuit inside. The rapid discharge of the cell, produce a lot of heat, burn the diaphragm, and cause a larger short circuit phenomenon, high temperature will decompose the electrolyte into gas, negative carbon and diaphragm paper combustion, resulting in excessive internal pressure, when the shell of the cell can not bear the pressure, the cell will explode.

Excessive moisture content

Water can react with the electrolyte in the cell to produce gas. When charging, it can react with the generated lithium to produce lithium oxide, which causes the loss of the capacity of the cell and is easy to generate gas by overcharging the cell. The decomposition voltage of water is low, and it is easy to decompose and generate gas when charging. The cell will explode.

Internal short circuit

Due to the internal short-circuit phenomenon, the cell current discharge, produce a lot of heat, burn the diaphragm, and cause a larger short-circuit phenomenon, so that the cell will produce high temperature, the electrolyte decomposition into gas, resulting in excessive internal pressure, when the shell of the cell can not bear the pressure, the cell will explode.

overcharge

When the battery is overcharged, the structure of the positive electrode will change because of the excessive release of lithium in the positive electrode, and the release of too much lithium is easy to be inserted into the negative electrode, and it is easy to cause lithium analysis on the surface of the negative electrode. Moreover, when the voltage reaches more than 4.5V, the electrolyte will decompose and produce a lot of gas. Any of these could cause an explosion.

External short circuit

External short circuit may be caused by improper operation, or misuse, due to the external short circuit, the battery discharge current is very large, will make the cell heat, high temperature will make the diaphragm inside the cell shrink or completely bad, resulting in internal short circuit, and explosion.

A station with insufficient negative capacity

The negative electrode does not cover the positive electrode, the positive and negative electrode file matching error, the negative electrode pressure tablet crushing, negative particle, negative dew foil, negative concave point, negative scratch, negative dark mark, negative coating uneven, positive head and tail pile, positive coating uneven, positive dressing quantity is large, positive and negative mixing uneven, negative incoming capacity is low, positive incoming capacity is high, negative capacity is insufficient.