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Why do lithium batteries explode

  • Author:James
  • Source:http://www.jaskeyworld.com/
  • Release Date:2016-09-20

Recently Note7 Samsung mobile phone battery explosion has become a hot thing, consumers more and more attention to the safety of the battery. Why lithium batteries will explode it, what are the reasons why the battery to explode it?

What is a lithium battery:

The so-called lithium-ion batteries were used two means can be reversibly inserting and extracting lithium ion secondary battery as a compound consisting of positive and negative. Such people will rely on lithium ion transport between positive and negative electrodes to complete a unique mechanism of battery charging and discharging of the lithium-ion battery work aptly called "rocking chair batteries", commonly known as "Lithium."

Lithium battery internal structure is very simple, is a positive electrode of lithium compound, in the middle of the electrolyte membrane and the anode carbon. When the battery is charged, lithium ions from the cathode de-embedded, embedded in the negative electrode, discharge the contrary. Generally use lithium transition metal oxide cathode do.

What is even explosion:

Substance quickly transition from one state to another state, and mechanical work instantaneously to release large amounts of energy in the form of work of the phenomenon known as explosion. Due to a sharp rise in pressure on the surrounding objects produce destructive explosion. Explosion is characterized by the sound of an explosion and destructive shock wave.

 

Cause of the explosion category analysis:

1. anode capacity shortage: lithium produced during charging can not be inserted between the negative electrode graphite layer structure but analysis of the negative electrode surface processes "dendrite" After several tens to hundreds of times charge-discharge cycles after "dendrite" grow, Finally, the paper will pierce the membrane so that the internal short circuit. Sharp discharge batteries produce a lot of heat, the electrolyte will be decomposed into gas, the carbon negative electrode and separator paper burning, causing internal pressure, when the batteries can not afford housing pressure will produce an explosion.

2. The moisture content is too high: the electrolyte can react with moisture and gases generated during charging of lithium oxide, so that the loss of capacity batteries could easily lead to overcharge produce gas, gas to generate a series of batteries internal pressure increases, when when the batteries housing can not withstand the pressure of the battery will explode.

3. Internal short circuit: the battery internal short-circuit high-current discharge batteries will generate a lot of heat to burn the diaphragm, resulting in greater short-circuit high temperature batteries, the electrolyte is decomposed into gas caused by excessive internal pressure, when the batteries can not shell it will explode when subjected to pressure.

4. overcharge: cathode material for lithium batteries when discharged excessive overcharging of the positive changes in the structure and emit too much lithium negative electrode can not be inserted easily cause analysis lithium negative electrode surface to form a "dendrite" piercing the diaphragm caused by internal short circuit, electrolyte will produce large amounts of gas caused an explosion when charging voltage reaches 4.5V or more.

5. External short circuit: leads to the battery discharge current is large so that heat batteries, high temperature batteries cause internal diaphragm shrinkage or complete destruction of an explosion caused by an internal short circuit.

 

Lithium battery design and production process, which will result in the case of an explosion:

1. The lithium battery production longevity poor quality production coating, winding process cleanliness and dryness is not enough, so that too much water and magazines into the battery, causing an explosion.

2. lithium battery electrolyte used substandard under certain conditions decomposition of water and cause an explosion.

3. binder failed to produce the powder out, resulting in the formation of burrs septum puncture, an internal short circuit, leading to an explosion of lithium batteries.

4. The spot welding nickel belt when the current is too large, the inside of the outer membrane damage or increased metal dust.

5. laser welding, heat transmitted through the housing positive ear, if not separated from the upper part of the positive electrode ear tape and separator, hot cathode ears will shrink the film or paper burn an explosion caused by an internal short circuit.

6. negative ear spot welding, heat to the ear on the negative, if not posted a good high temperature adhesive tape, a negative heat will burn the ears of the diaphragm cause an internal short circuit explosion.

7. bottom spot welding aluminum composite with nickel at the bottom of the shell wall will generate a lot of heat to the bottom of the pole core, if not completely cover the adhesive tape high temperature will burn membrane separator to produce an explosion caused by an internal short circuit.

8. The design of the positive excess, or coating unevenness, leading to vibration during transportation pole pieces dislocation, lithium dendrites occurs while charging.

9. aluminum or steel weld strength is not enough, the charging pressure is increased within the weld crack support, oxygen in the air and deposited on the surface of the lithium metal anode reaction, heat, combustion caused the explosion.