Lithium ion battery explosion of technical analysis

Common explosion type analysis

The explosion of the battery core class form can be reduced to external short circuit, internal short circuit, and overcharge 3 kinds. Here the external refers to the external core, contains the internal battery insulation design caused by poor short circuit.

When core external short circuit, electronic components and failed to cut off the circuit, internal core can produce high fever, caused part electrolyte vaporizing cells it shell. When the battery is high inner temperature to 135 degrees Celsius, the good quality of diaphragm paper, will fine hole shut, electrochemical reaction to terminate or almost terminated, current plunged and the temperature also slowly drops, and avoid the explosion. But, pores close rate was so bad, or fine hole not shut down the diaphragm paper, will let the battery temperature continues to rise, more electrolytic liquid vaporization and will last a battery shell can be broken, even the batteries to make materials combustion temperature increase and explosion.

Internal short circuit mainly because of the aluminum foil and copper foil burr wear out the diaphragm, or lithium atomic dentrites crystallization wear out diaphragmatic membrane creates. These small needle metal, can cause micro short circuit. Because, the needle is very fine has certain resistance, therefore, is not necessarily going to a current. Copper aluminum foil burr department in the production process is caused, observable phenomenon is battery leakage too fast, most can be core factory or assembly plant screening out. Also, since the burr tiny, sometimes burned off, make the battery normal again. Therefore, for burr micro short circuit triggered the explosion of probability is not high.
This idea, can from the core enterprise internal are very soon after charging, low voltage is bad battery, but seldom bombings, get statistics support. Therefore, short-circuited the cause of the explosion, largely because of the overcharge cause. Because, after filling a piece is filled with lithium metal needle crystal, Pierce point is everywhere, in happen everywhere micro short circuit. Therefore, the battery temperature will be gradually raised, the last high temperature will electrolyte gas. This kind of situation, whether to high temperature burning explosion materials, or before the shell can be broken to make the air with lithium metal in the most violent oxidation, all is the explosion end.

But the overcharge internal cause short-circuit the explosion, must not happen in charge at that time. May the battery temperature is not high to make materials combustion, produced gas is not enough to hold the battery shell, consumers would cease charging, carry a cell phone to go out. Then many of the micro short circuit the heat produced in the slowly, and will improve battery temperature, after a period of time, to explode. The description of the common consumers are picked up the
http://www.topbatterycharger.co.uk phone found that mobile phone is very hot, throw away after the explosion.

The explosion of the comprehensive above type, we will focus on explosion-proof overcharge prevent, external short circuit, and to prevent ascension, core
All three aspects of sex. Among them the overcharge prevent and external short circuit prevent belong to electronic protection, and the battery system design and a larger battery relationship. Core security of ascension for chemical and mechanical key protection, and battery core factory have larger relationship.

Prevent explosion protection measures

The lithium battery core overcharge to the voltage higher than 4.2 V, will begin to have side effects. The higher the charging pressure, the higher the risk also follow. Lithium core voltages above 4.2 V, in the rest of the lithium battery anode materials atomic number less than half, this time the storage case often break down, let the battery capacity produce permanent decline. If continue to charge, because of the negative case has been filled with the lithium storage atoms, and subsequent lithium metal adds up to surface anode materials. These lithium atoms by negative surface will go to the direction of lithium ion to grow dentrites crystallization. These lithium metal crystalline diaphragm will pass through

Paper, make the anode and short circuit. Sometimes in short circuit happened before the battery first explosion, this is because in the overcharge process, such as electrolyte material will cracking produce gas, make the battery shell or pressure valves GuZhang rupture, let go in and accumulation in the negative oxygen atoms of surface lithium reaction, then explosion.

Therefore, the lithium battery, must set voltage limit, can also give dual attention to the battery life, capacity, and safety. The most ideal recharging voltage limit for 4.2 V.

Lithium core discharge should also have the lower voltage. When core voltage is lower than 2.4 V, part of the materials will begin to be destroyed. And because the battery will self-discharge, put the longer the lower voltage, therefore, discharge when had better not in 2.4 V didn't stop. Lithium battery from 3.0 V to 2.4 V discharge
FUJIFILM NP-140 Battery during this time, the release of energy accounts for only of the battery capacity of about 3%. Therefore, 3.0 V is an ideal discharge by voltage.

Charge and discharge, besides voltage limit, the current restrictions also has its necessary. Too much electricity, lithium ion too late into the storage space, will gather in the material surface. These lithium ion get electronic, will produce lithium in material surface atomic crystals and overcharge, can cause the risk. One thousand battery shell burst, would explode.

Therefore, the lithium ion battery protection, at least to include: charge voltage limit, discharge the lower voltage and current, three upper limit. General lithium battery inside, in addition to the lithium battery core outside, will have a protection board, this piece of protection board is mainly provide this three protection. But, protective plate this three protect it is not enough, the global lithium battery explosion or a mineshaft. To ensure the safety of the battery systems, to the battery must be the causes of the explosion, more careful analysis.

The article source:
http://www.mybatteriesshop.com

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