Research On Lithium-ion Battery Safety And High Temperature Self-protection Coating Technology

Lithium-ion batteries are regarded as one of the most important energy storage technologies.As the energy density of batteries increases,the battery is more prone to safety accidents if the energy is released unintentionally.Accidents related to fires and explosions of Lithium-ion batteries occur frequently worldwide.All of which are just reminding that improving the safety of lithium-ion batteries is imminent.Therefore,it is particularly important to test whether the battery can cause thermal runaway under abuse and to study battery safety protection technology under thermal runaway.The main research contents and results of this paper are as follows:Safety testing in case of lithium ion battery abuse.Tests are made to the battery cell under squeez,external short circuit,needle stick,overcharge and abuse During the extrusion process,the battery temperature reached 400 ℃ in only 23 seconds.In the case of external short circuit and overcharge,the battery temperature also rises above 100 ℃,reaching a more dangerous temperature range.The temperature changes during the acupuncture process are small,which may be because the energy of the battery cell is too low to quickly release heat when there’s a short circuit inside the battery.An ethylene-vinyl acetate(EVA)thermosensitive microsphere coating was prepared by solvent evaporation method.The effect of process conditions such as surfactant and stirring speed on the particle size of EVA thermosensitive microspheres was studied.The results showed that when sodium dodecyl sulfate(SDS)was selected as the surfactant,the rotation speed was 2000 rpm,and the volume ratio of SDS and chloroform was 2:1,EVA thermosensitive microspheres with a particle size of about 2 μm were prepared.Differential scanning calorimetry(DSC)test show that the melting point of EVA thermosensitive microspheres is 86 ℃.Thermogravimetric tests show that EVA thermosensitive microspheres have good thermal stability.Therefore,EVA thermosensitive microspheres can be used as a suitable thermosensitive material for battery thermal shutdown.Modify it on the separator and electrode for electrochemical test.The research results show that the battery can be successfully thermally shut down at a high temperature of 86 ℃.At room temperature,the electrode modification has higher charge and discharge capacity,cycle stability and rate performance than the battery with the modified coating of the separator.A polybutylene succinate(PBS)thermosensitive microsphere coating was prepared by solvent evaporation method.Optimal process parameters of EVA were used to prepare PBS thermosensitive microspheres with a particle size of about 2 μm.DSC test show that the melting point of PBS thermosensitive microspheres is 110 ℃.Thermogravimetric tests show that PBS thermosensitive microspheres have good thermal stability.It can be used as a more suitable material for battery thermal shutdown.Modify it on the separator and electrode for electrochemical test.The research results show that the battery can be successfully thermally shut down at a high temperature of 110 ℃.The battery rate performance and long cycle stability of the microsphere modified electrode are good,and the capacity retention rate after 100 cycles of long cycle is more than 80 %.The microsphere modified separator has excellent battery long-cycle performance,and the capacity retention rate is more than 90 % after 100 cycles of long cycle.However,the high-rate performance is poor,and the specific capacity of the battery modified by the microsphere coating at 5 C is only 52% of that of the conventional electrode.