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Lithium-ion batteries catch fire much easier when charging compared to lead acid batteries. This is because that the electrolyte types they use are quite different. Lead acid batteries use aqueous solution as electrolyte while lithium-ion batteries use organic solvent as electrolyte instead. Organic solvent is a kind of flammable materials like gasoline, alcohol and more. Once the positive and negative electrodes come into direct contact and it will cause a short circuit, which leads to rapid discharging and overheated quickly within seconds.
Lithium-ion batteries use multiple single Lithium-ion battery cells to form batteries group in parallel or/and in series. Once one of single Lithium-ion battery cells overheats, it will trigger a chain reaction and the rest will be overheated easily. This will make the battery catch fire or explode easily.
Why can lead acid batteries use aqueous solution while lithium-ion batteries have to use dangerous organic solvent as electrolyte then? This is because that the highest ionized voltage of aqueous solution is only 2V, which is far from enough for lithium-ion batteries. In order to raise energy density, lithium-ion batteries must use organic solvent as electrolyte. When organic electrolyte is sealed into a small limited space, it will bring high risk of catching fire and explosion.
When the SEI membrane on the surface of the negative electrode is damaged due to various kinds of reasons, the carbon and lithium compounds produced during charging will not be able to react normally. There will be huge heat generated inside the batteries. When temperature is rising, the positive electrode will release oxygen automatically. The possibility of catching fire and explosion will be raised dramatically once the 3 conditions of combustion, heat released when temperature rising, flammable materials and oxygen, are all ready.
The materials of positive electrode are transitional metal oxide while the negative electrode is made of carbon and graphite. As the positive electrode will release oxygen automatically when the temperature is rising, we will not be able to extinguish fire by isolating oxygen. That is to say, it will make no sense to use dry powder fire extinguisher to fight fire for electric vehicles. Thus, it is very dangerous once lithium-ion batteries catch fire.
How can we solve the safety issue of lithium-ion battery then? This is a complicated systematic project which requires a full series of perfect measures to execute from battery design, isolated plate manufacturing and battery charging process. Thus, once users have purchased lithium-ion battery electric bicycles, users must read user manual carefully and thoroughly before using electric bicycles, follow all instructions described in the user manual correctly and properly to ensure safe operation when charging and keep the lithium ion battery in good working status always. To avoid catching fire and explosion, it is required to perform safety inspection and evaluation to lithium ion battery at least once a year. If you find out that the batteries are not chargeable any more, please stop charging them immediately. And, do not try to repair them by yourself. Please send or bring them to our authorized electric bicycle stores or repair service centers near you and ask them for help instead.