The impact of electrolytes and membranes on safety is mainly due to their properties.
Currently widely used commercial electrolytes are not ideally suited for safety due to their flammability and liquid state. Using solid-state electrolytes with a lithium-ion conductivity σLi+ > 104 Scm1 can prevent lithium atomization from piercing the separator and reaching the positive electrode, thus addressing safety concerns. It can also resolve stability issues arising from contact between the negative electrode and carbonate electrolytes, and between the positive electrode and aqueous electrolytes. Furthermore, safety can be effectively improved by using electrolytes with a wider electrochemical window (especially a higher LUMO), adding flame-retardant materials, and modifying mixed ionic liquid and organic liquid electrolytes into non-flammable electrolytes (without significantly reducing the ionic conductivity σLi).
The mechanical strength (tensile and puncture strength), porosity, and whether the diaphragm has a shut-off function are important factors in determining its safety.
