Mechanical impact-resistant lithium-ion batteries based on SiO2-doped composite polymer separator

Lithium-ion batteries are used extensively in civil, military, and aerospace applications because of their high energy and power density. However, in practical applications, these batteries may encounter extreme cases characterized by transient high impacts, which impose stringent requirements on their safety and reliability. In recent years, the failure mechanism associated with the short-circuiting of lithium-ion-battery separators under high dynamic impacts has been investigated thoroughly. Based on the separator impact failure mechanism, we prepared a porous polymer polyvinylidene fluoride (PVDF) separator by doping gas-phase SiO2 (fumed silica) additive. The gas-phase SiO2 has a unique three-dimensional cluster structure, which is impact resistant. The impact resistance of the battery separator was tested using a high-dynamic-impact system. The voltage drop of the battery with 3% SiO2 content was 33.04% of that of the original PVDF battery. Material characterization of the separator was further explored by scanning electron microscope, static compression, and pore-size adsorption tests. The SiO2 with a special cluster structure was distributed uniformly on the surface of the separator and embedded in the inner walls of the pores. Under static compression, the current of the SiO2-PVDF separator with 3% content rose at a lower rate than that of the PVDF separator, with a minimum current of 1.04 mA. After adding SiO2, the separator pore size increased from 5 to 20 nm. Also, we used COMSOL to conduct impact simulations of different separators. The calculation results showed that the deformation (9.98%) and internal electrode current (0.018 A) of the SiO2-PVDF lithium-ion battery were lower than the deformation (23.09%) and internal electrode current (0.049 A) of the PVDF lithium-ion battery. The SiO2-doped composite polymer separator with a special cluster structure plays a crucial role in enhancing the impact resistance of lithium-ion batteries.