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Analysis of internal Micro - short Circuit of Lithium Battery

Author: Source: Datetime: 2016-10-06 10:30:58

In 2006, the lithium battery giant Sony's lithium batteries caused a number of Dell notebook computer explosion fire, causing the United States and Japan the official attention. Later, despite the use of a very safe A123 lithium iron phosphate battery, the US Toyota Prius hybrid vehicle modified by a third party after burning. There are new energy taxi and bus burnout in Hangzhou, Shanghai and Shenzhen in 2011.

internal Micro - short Circuit

Obviously, even the safest lithium iron phosphate system, LiFePo4 battery pack system, still can not avoid the occurrence of security incidents.

From the analysis of the chemical principle, the safety of lithium batteries worse than gasoline, but it is very light and convenient to take, so it is usually used in portable solar power generator. Gasoline is stored in tightly closed metal containers and is safe if both leaks (gasoline and air contact) and exposure to open flames (or Mars, initiation) are present. Lithium battery energy is stored in one (Positive electrode active material) and a reducing agent (negative electrode active material) on both sides of a thin membrane, a severe chemical reaction and an electrochemical reaction occur simultaneously in the case of occurrence of an internal short circuit (priming action) May fire, combustion, explosion, for organic solvent system lithium battery is easier to burn some.

Lithium battery failure mode, the single cell internal short circuit is undoubtedly the greatest harm, the most difficult to predict and analysis, there is no way to protect the external control circuit. Internal short circuit caused by high temperature, high resistance, is also likely to cause a chain reaction of the battery.

Currently widely believed that single-cell internal short circuit may be due to:

1) adsorbed on the diaphragm surface or the top of the single-cell battery shell, the bottom of the dust. Manufacturing environment, process control bad circumstances, will form a large number of positive / negative pole pieces of dust and welding caused by metal dust, and electrostatic adsorption on the surface of the diaphragm. Pole piece itself is not smooth, powder bonding strength is not enough, itself will cause this problem.

2) winding / laminating formed when the positive / negative pole piece dislocation.

3) metal solder joints, a very edge edge burr.

4) the formation of lithium dendrites on both sides of the diaphragm, due to non-uniform reaction caused by the local electrochemical reaction or over-charge and the formation of lithium dendrite.

5) uneven electrolyte distribution caused by positive / negative pole utilization is inconsistent.

6) The material itself. Material purity is not high, and the electrolyte compatibility is not good, the cathode metal material is not high voltage, the negative metal materials and lithium alloy, may form impurity deposition or lithium dendrites.

External factors. The external mechanical force causes the deformation of the single-cell shell and then cause the diaphragm displacement, damage, the external temperature is too high leading to excessive contraction of the diaphragm, damage, overcharge, forced discharge caused by the formation of lithium dendrite cell, may cause Internal short circuit.

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