A separator coated with commercial LiFePO4 and conductive carbon for Li–S battery with good cycling performance

Abstract

Li–S batteries can meet the demand of market development in terms of high energy density, but the notorious ‘shuttle effect’ and lithium dendrites pose a great threat to their cycling and safety performance, and greatly hinder their commercialization process. Under high sulfur loadings and high current densities, unsatisfactory cycling performances are also headache issues. Here, modified separators (SPLFPPD) with LiFePO₄ (LFP) and Super P coating on the original separators (DKJ-14) are prepared to solve the above problems. The SPLFPPD has the advantages of a physical barrier to the polysulfides and promoting the catalytic conversion of polysulfides (S²⁻ and sulfides). Besides, the SPLFPPD can enable the uniform deposition of lithium ions, increase ionic conductivities, and fully utilize active S substances. The capacity attenuation of the assembled Li–S batteries with the SPLFPPD is 0.062% per cycle at 1C after 800 cycles, and 0.045% per cycle at 5C after 1000 cycles. The specific capacity can be stable up to about 500 mA h g⁻¹ after 400 cycles at 0.2C with a high S loading of 4.0 mg cm⁻². After 100 cycles, no signs of corrosion or lithium dendrites were observed. This work provides a feasible way to prepare commercial separators for high-performance Li–S batteries.