Accelerated Li2S conversion in sparingly-solvating electrolytes enabled with dipole-dipole interaction for wide-temperature Li-S batteries

Abstract

Utilizing sparingly-solvating electrolytes (SSEs), which suppress the dissolution of lithium polysulfides (Li2S4−8, LPSs), could reduce electrolyte consumption and thus retrieve the energy density competitiveness of lithium-sulfur batteries (LSBs). However, SSEs-based LSBs suffer from sluggish kinetics and rapid capacity degradation due to the accumulation of Li2S in the cathode. The catalytic approach, which is widely used to promote the sulfur conversion in ether-based LSBs, is rarely explored in SSEs-based LSBs due to the lack of a catalyst workable in the absence of dissolved LPSs. Here, by embedding CuS nanoparticles, which have high dipole-dipole interaction with Li2S, as polar sites into the carbon matrix of the sulfur cathode, we homogenize the Li2S deposition and accelerate the conversion kinetics. As a result, the cell with S/KB@CuS cathode realized a remarkable initial discharge capacity of 1469.5 mAh g−1 (87.7% of the theoretical value) with a reduced polarization potential (0.526V). Even at a low temperature of −15°C, the cell with S/KB@CuS cathode still delivered a capacity-retention of 799.0 mAh g−1 after 100 cycles. More importantly, the universality of the as-proposed dipole-dipole-interaction strategy is demonstrated with many other SSEs and polar additives.