Methods to improve overcharge safety of lithium batteries.

Methods to improve overcharge safety of lithium batteries.

Lithium ion batteries are a new type of energy with high capacity and long cycle life, and they have a wide range of applications. However, lithium-ion batteries have safety hazards such as explosion and combustion during overcharging. At the same time, the surface of the carbon negative electrode in an overcharged state can also be reduced in safety due to the deposition of metallic lithium [1], and even ultimately lead to battery explosion. Therefore, how to improve the overcharge safety of lithium-ion batteries has always been a research focus. Shenzhen Puxun Battery analyzes the methods to improve the overcharge safety of various parts inside lithium-ion batteries.

1. Electrode
Developing positive and negative electrodes that are resistant to overcharging is an important aspect of improving safety for lithium-ion batteries. Qiu Weihua et al. synthesized a series of LiCoxNii using solid-phase method and found that when the Ni/Co ratio was 8:2, it had good overcharge resistance. Wan Xinhua et al. found that the overcharge resistance of AA type lithium-ion batteries assembled with lithium cobalt oxide embedded nickel oxide is much higher than that of lithium cobalt oxide.

Another overcharge protection method for electrodes is to apply a layer of PTC coating between the current collector and the active material. When the internal temperature of the battery is too high, the PTC layer will dissociate due to heat, and the active material will detach from the chip to prevent further overcharge of the battery.

2. Overcharge protection mechanism of electroactive polymer film

The overcharge protection mechanism of electroactive polymers is achieved by utilizing the significant changes in conductivity during the re doping and de doping processes of certain polymers. It can provide overcharge protection for a battery that is in an overcharge state without affecting the normal operation of other batteries; And when the battery is working normally as a whole, the protected battery can resume normal operation. Karen E. Thomas Alyea's research shows that electroactive polymer films made from poly (3-butylthiophene) P3BT can provide reversible overcharge protection for lithium-ion batteries at around 4.2V without affecting battery performance.

3. Overcharge protection for electrolyte
Adding an appropriate amount of additives in lithium-ion battery electrolysis can provide overcharge protection for lithium-ion batteries. At present, there are more studies on oxidation-reduction electrochemical additives and electro polymer additives. Ferrocene and its derivatives, Dihydrophenazine derivatives, imidazolium sodium, and dimethyl bromobenzene all belong to redox pairs. Biphenyl, cyclohexene, thiophene, furan, dichloroanisole, and trifluoromethoxybenzene can all polymerize at a certain voltage to provide protection for lithium-ion batteries.