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Why Use Lithium Ion Batteries With Caution?

Nov. 09, 2019

At present, there are more and more opportunities to use lithium batteries, and the performance of lithium batteries is becoming more and more satisfactory. Lithium batteries must be used with care, especially when charging them. Wrong operation may result in: heat, bloating, cracking, smoking, fire, explosion, etc. So what are the problems caused by incorrect operation of a lithium-ion battery? The Rack Mount Li-Ion Battery System supplier will come to tell you.

The so-called wrong operation is not charging in a regular way. For example, the picture is simple and easy to operate, and the DC power supply is used for charging, so that it cannot be fully self-stopped, causing over-charging, which may eventually lead to serious consequences. The use of liquid lithium-ion batteries requires special care, because this type of battery is a steel-shell sealing structure. Excessive charging and discharging of the electrode can cause internal pressure to become large, heat, and eventually a strong explosion! The polymer lithium battery should be slightly safer, because this is the plastic-sealed outer casing of the aluminum-plastic composite film, so theoretically no explosion will occur, but abnormal operation will also cause serious problems such as failure, smoke, and fire.

Rack Mount Li-Ion Battery System

Rack Mount Li-Ion Battery System

Why is there a safety problem with lithium batteries?

1. How is the internal short circuit formed: The biggest hidden danger of the Lithium-Ion Battery Energy Storage System is that the lithium ion battery using lithium cobaltate is overcharged (even during normal charge and discharge), and lithium ions are deposited on the negative electrode to form dendrites. Pierce the diaphragm and form an internal short circuit. (Electric bicycle batteries are generally used lithium manganese oxide, safety performance is higher than lithium cobalt oxide)

2. Generate large current: external short circuit, internal short circuit will generate excessive current of several hundred amperes.

(1) When an external short circuit occurs, the battery is discharged at a large current due to an excessively low external load. It consumes a lot of energy on the internal resistance and generates a huge amount of heat.

(2) Internal short circuit, the main reason is that the diaphragm is penetrated, a large current is formed inside, and the temperature rise causes the diaphragm to melt, and the short-circuit area is enlarged, thereby forming a vicious circle.

(3) Where is the gas coming from: Lithium-ion battery to achieve a high operating voltage of 3-4.2V for a single cell (the working voltage of nickel-metal hydride and nickel-niobium battery is 1.2V, and the working voltage of lead-acid battery is 2V), must be taken The organic electrolyte is decomposed with a voltage greater than 2V, and the organic electrolyte is electrolyzed under high current and high temperature conditions, and the gas is generated by electrolysis, which causes the internal pressure to rise and severely breaks through the casing.

(4) How does the combustion occur: the heat is derived from a large current, and at the high voltage (above 5V), the oxide of the positive electrode also undergoes an oxidation reaction to precipitate metallic lithium, in the case where the gas causes the casing to rupture. Direct contact with the air causes combustion, and at the same time ignites the electrolyte, a strong flame occurs, and the gas rapidly expands and explodes.

(5) Whether the polymer battery has safety problems: The difference between the polymer battery and the lithium ion battery is that the electrolyte is gelatinous or semi-solid, and the lithium ion battery electrolyte is in a liquid state. At the same time, the polymer battery uses the flexible packaging of the aluminum-plastic composite film, when the gas is generated inside, the shell can be broken earlier to avoid excessive gas accumulation and severe cracking. However, polymer batteries do not fundamentally solve the safety problem. Similarly, using positive electrode materials such as lithium cobaltate and lithium manganate and organic electrolytes, smoke or even more violent combustion occurs, and combustion is the most safety of polymer batteries. 

The above is a description of the High C-Rate LFP Battery System manufacturer's precautions regarding the operation of lithium batteries, hoping to help everyone.

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