Why is lithium battery so dangerous?

The danger of lithium battery

Lithium is a metal that is particularly susceptible to reaction. It is silver-white in appearance, very soft, stretchable and flammable. Metallic lithium is a substance that releases flammable gases in contact with water.

A. metal lithium properties:

1 flammable gas is released when exposed to water or humid air;

2 When it is in a solid state, when the temperature exceeds its melting point of 180 ° C, it can burn itself;

3 when it is powder, it can be burned at room temperature;

4 can cause severe burns and corrosion.

B. lithium battery cells or lithium batteries are classified as Class 9 dangerous goods, and the hazard depends on the lithium contained.

1 lithium battery is highly flammable;

2 can be ignited under short circuit, overcharge, extreme temperature, wrong operation or other error conditions;

3 Whether it is due to internal reasons or external heating or physical impact, it can generate enough heat to cause thermal runaway of adjacent batteries. The electrolyte released by the lithium metal battery mixes the molten lithium metal with a large pressure pulse. A flammable electrolyte and molten lithium metal can produce an explosive mixture;

4 In the Class C cargo tank, the fire extinguishing agent Halon 1301 (trifluoro-bromomethane extinguishing agent) cannot effectively control the ignition of the lithium metal battery.

The battery is generally divided into a primary battery (not rechargeable) and a secondary battery (which can be repeatedly charged multiple times). Lithium battery is a kind of battery that uses lithium metal or lithium alloy as negative electrode material and uses non-aqueous electrolyte. It is generally divided into two categories: lithium metal battery and lithium ion battery (including lithium ion polymer battery), the main difference of lithium metal battery is a primary battery containing metal lithium, such as a button battery; and the lithium ion battery is a secondary battery, which does not contain metallic lithium, such as a mobile phone battery.

Among them, lithium ion polymer batteries are widely used in portable electronic products such as mobile phones and tablet computers as representatives of secondary batteries. The reason for this is that the polymer series battery structure is utilized so that only a small amount of liquid electrolyte is required, so that the battery does not require a hard outer casing for protection, the shape is not limited, and the packaging volume can be greatly reduced. Based on these characteristics, lithium ion polymer batteries have a tendency to replace traditional lithium ion batteries.

At present, the lithium battery is generally referred to as a lithium ion battery, and the positive and negative electrodes are composed of different lithium ion intercalation compounds, which is a device for realizing mutual conversion between chemical energy and electric energy. Its structure is mainly composed of the positive and negative electrodes of the battery.

The electrode material and electrolyte of the lithium battery are flammable, and the heat (internal or external) can cause a fire and decompose to generate gas, thereby increasing the possibility of battery explosion. Moreover, the strength of today's polymer separators is relatively low, which can easily damage the film in the event of collision or overheating, resulting in short circuit of the battery.

At the same time, the defects of the manufacturing process are also very likely to cause lithium battery safety problems. For example, the battery core is too long, causing a short circuit in contact with the pole piece or the housing; the tab is pressed against the core, causing a short circuit between the positive and negative poles; leaving metal powder, copper foil, aluminum foil fragments between the poles may lead to perforation of the diaphragm and thus cause a series of problems such as micro-short circuit.

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