Why are lithium batteries dangerous?

Lithium is a metal that is particularly prone to reactions. Its appearance is silver-white, very soft, extensible, and flammable. Lithium metal is a substance that releases flammable gases when exposed to water.

The properties of lithium A metal:

1 In the event of water or moist air, flammable gas will be released;

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

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

4 Can cause serious Burns and corrosion.

Lithium or lithium batteries belong to Class 9 Dangerous Goods, the risk of which depends on the lithium contained.

1 Lithium battery is highly flammable;

Short circuit, overcharging, limit temperature, error operation or other error conditions can all catch fire;

Whether it is internal or external heating or physical impact, it can generate enough heat to cause the adjacent battery to heat out of control. The electrolytes released by the lithium metal battery are mixed with melted lithium metals and accompanied by a large pressure pulse. Flammable electrolytes and molten lithium metals can produce explosive mixtures;

4 Halon 1301(trifluoromethane bromomethane extinguishing agent) in Class C cargo holds can not effectively control the fire of lithium metal batteries.

Batteries are generally divided into primary batteries(non-rechargeable) and secondary batteries (rechargeable repeatedly). The lithium battery is a type of battery that uses a non-aqueous electrolyte from a lithium metal or lithium alloy as a negative electrode material. It is generally divided into two categories: a lithium metal battery and a lithium ion battery (including a lithium-ion polymer battery). The main difference lies in the lithium metal. The battery is a battery, contains metallic lithium, such as button batteries; The lithium ion battery is a secondary battery and does not contain metallic lithium.

Lithium-ion polymer batteries are widely used in portable electronic products such as mobile phones and tablets as representatives of secondary batteries. The reason for this is that the polymer series battery structure is used so that it requires only a small amount of liquid electrolytes. Therefore, this type of battery does not need a hard shell for protection. The shape is not limited, and its packaging volume can be greatly reduced. Based on these characteristics, lithium-ion polymer batteries have a tendency to replace traditional lithium-ion batteries.

When the lithium battery is in the charging process, the current sent by the charger exerts thrust on the lithium ion(Li +), passes from the positive electrode through the electrolyte to the negative electrode, and stores it in the form of electrochemical energy. When there is no more lithium ion flowing from the positive to the negative, the battery is full of electricity. In this process, the electrochemical driving force generated between the positive and negative poles of the battery is called the terminal voltage. As shown in Figure 3.

When the lithium battery is in the discharge process, the lithium ion attached to the negative electrode begins to migrate back to the positive electrode. During this process, the battery continues to discharge and the terminal voltage continues to drop. Once all lithium ions have been migrated from the positive pole and the battery is fully discharged, they need to be recharged and used.

Despite a series of precautionary measures, the possibility of spontaneous combustion of lithium-ion batteries still exists. If lithium battery spontaneous combustion occurs, the following steps are generally followed for emergency treatment:

First cut the power. In case of any anomaly, the power should be cut off at the first time.

When the battery appears to spontaneously ignite, the battery should be continuously cooled down immediately, and water saving is the ideal solution. If the fire is large, the ABC dry powder fire extinguisher or carbon dioxide fire extinguisher can be used to extinguish the open fire, and then use water to continuously cool the damaged battery, and check the battery that has spontaneously burned every 5 minutes. If it is still hot, continue to use water to cool the battery. Until the cooling is complete.

If possible, move the damaged battery to an open safe area and evacuate the surrounding population quickly.

Don't cool lithium batteries with ice. Because it will cause the internal heat to fail to emit, the continuous high temperature will further exacerbate the chemical reaction. At this time, the internal temperature will rise rapidly, and the electrolyte gas will accumulate in large quantities, which in turn will cause the battery explosion. Its power and destruction will be more terrible than the battery's "calm spontaneous combustion."

Even if there is an open fire, the use of foam fire extinguishers should be avoided, and the ejected foam adheres to the periphery of the battery to form a thermal insulator, thereby increasing chemical reactions and generating more heat.

Currently, lithium-ion battery manufacturers have developed a variety of methods to reduce fire risk and improve safety, such as setting protection circuits inside the battery, including overcharge protection, overcurrent/short circuit protection, and overdischarge protection.

The page contains the contents of the machine translation.