A low cost shutdown sandwich-like composite membrane with superior thermo-stability for lithium-ion battery

A separator plays the key role in solving the safety issues of lithium-ion batteries. The currently used polyolefin separators are seriously limited by their low thermal stability. In this paper, a sandwich-like composite membrane with super-high thermal stability was designed and fabricated. In the design, a porous polybenzimidazole (PBI) layer was introduced on both sides of a PE separator by a typical phase inversion method. The porous PBI layer on both sides of the PE ensured high ion conductivity, high thermal stability and the nonflammable property. Meanwhile, this PE separator also acted as a shut-down layer at an elevated temperature. As a result, the PBI/PE/PBI (referred to as PBIE) sandwich-like composite membrane exhibited no dimensional shrinkage up to 200 °C. In addition, the prepared PBIE membrane could easily shut the battery down at about 140 °C. Combing these features of shut-down function and high thermal stability, the PBIE membrane is expected to internally solve the safety issues, which have been extremely troublesome so far for lithium-ion batteries.