MoP nanoparticles dispersed on P, N co-doped graphite nanosheets as separator-modified material in high-loading lithium-sulfur batteries

Abstract

The cruising range of lithium batteries in new energy vehicles became main issue, so lithium-sulfur batteries (LSBs) with high theoretical energy density are becoming great expectations. However, the polysulfide-shuttle behavior and slow redox kinetics of the electrochemical processes result in a fast capacity and cycle life fade in LSBs, especially at high sulfur loads. In this paper, MoP nanoparticles were dispersed on P, N co-doped graphitic nanosheets (MoP/PNC) by one-step high-temperature phosphating method, which as a separator-modified material achieved an excellent electrochemical performance. The initial discharge specific capacity can reach 1470 mAh g−1 at a current density of 0.2C and the capacity attenuation per cycle in 600 cycles is only 0.074% (1C). Surprisingly, LSBs with MoP/PNC -modified separator can deliver a high area capacity of 9.30 mAh cm−2 with a sulfur loading up to 7.43 mg cm−2 on the positive electrode. The above-mentioned excellent electrochemical performances benefited from the synergistic effects of strong catalytic conversion ability of MoP and the physical/chemical adsorption and catalytic capability of PNC, which resulted in low polysulfide permeability and high sulfur utilization.