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Comparison of safety of various types of lithium batteries

From:CTECHI GROUP Limited     Release time:2020-01-02

Overview:From the current mainstream technology of lithium-ion batteries, there are several types of lithium cobaltate, lithium manganate, lithium iron phosphate, and polymers. Their different materials and structural characteristics will affect the battery preparation technology and use. The resulting security is also different.

Comparison of safety of various types of lithium batteries

From the current mainstream technology of lithium-ion batteries, there are several types of lithium cobaltate, lithium manganate, lithium iron phosphate, and polymers. Their different materials and structural characteristics will affect the battery preparation technology and use. The resulting security is also different.

(1) Lithium cobaltate battery: The biggest feature in preparation is that after being fully charged, a large amount of lithium ions remain on the positive electrode. In other words, the negative electrode cannot accommodate more lithium ions attached to the positive electrode, but in the overcharged state, the excess lithium ions on the positive electrode will still swim toward the negative electrode, and metal cannot be formed on the negative electrode because it cannot be fully contained. Lithium, because this metal lithium is a dendritic crystal, so it is called dendrite. Once the dendrite is formed, it will provide the opportunity to pierce the diaphragm. A diaphragm pierce will create an internal short circuit. Because the main component of the electrolyte is carbonate, the lightning and boiling point are low, so it will burn or even explode at higher temperatures. Controlling the formation of lithium dendrites is relatively easy on small-capacity lithium batteries. Therefore, lithium cobaltate batteries are currently limited to small-capacity batteries such as portable electronic devices, and cannot be used for power batteries.

Polymer lithium batteries: The theoretical specific energy available has been greatly improved. Compared with lithium cobaltate batteries, they can better play high-capacity functions. However, polymer batteries also use cobalt acid. Lithium and organic electrolytes do not fundamentally address safety issues. From the perspective of use, if the battery is short-circuited, it will generate excessive current. The electrolyte of polymer lithium batteries is a colloid, which is not easy to leak, which eliminates the possibility of leakage. However, more violent combustion will occur. Therefore, spontaneous combustion is the biggest hidden danger of polymer lithium batteries.

3. Lithium manganate battery: The material of the lithium manganate battery has certain advantages. It can ensure that the lithium ion of the positive electrode can be completely embedded in the carbon pores of the negative electrode when it is fully charged, instead of being in the positive electrode like lithium cobaltate. There is a certain residue, which basically avoids the generation of dendrites. This is the theoretical understanding. In fact, if a lithium manganate battery encounters a strong external force or cuts corners during the preparation process, it may cause the battery to rapidly form lithium ions during the charge and discharge cycle. A dendrite is formed when the negative electrode does not have time to fully receive lithium ions. Avoiding this consequence is guaranteed by testing at the factory. In short, a qualified lithium manganate battery will generally not cause a safety accident. Because of the stable structure of lithium manganate, its oxidation performance is much lower than that of lithium cobaltate. Even if an external short circuit (rather than an internal short circuit), the precipitation of metallic lithium can basically be avoided to cause combustion and explosion.

Lithium iron phosphate battery: This is an ideal power battery, which can be used in power tools and power cars. The theoretical capacity of lithium iron phosphate is 170mAh / g, and the actual reachable capacity of the material is 160mAh / g.

In terms of safety, lithium iron phosphate has high thermal stability and low electrolyte oxidation ability, so it has high safety; however, its disadvantage is low conductivity, which requires modification technology to improve. As a result, the volume is too large and the amount of electrolyte is large. Moreover, due to its large capacity and poor battery consistency, lithium iron phosphate technology is currently under study.


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