Lithium-selenium sulfide batteries with long cycle life and high energy density via solvent washing treatment

Abstract

SeS2 is a promising cathode material that has both advantages of S and Se. In a carbonate-based electrolyte, Li-SeS2 batteries show good cycle performance but work at low discharge voltage due to slow Li-ion diffusion. Here, we report a simple solvent treatment method for synthesizing cathode composite materials to overcome the disadvantage of carbonate-based electrolytes. The solvent washing treatment can effectively remove excess SeS2 that blocks carbon pores, which act as an electrolyte pathway. Additionally, the SeS2/OMC composite (w-SeS2/OMC) maintains the SeS2 configuration, thus leading to both the advantages of S and Se. As a result, enhanced Li-ion diffusion helps to reduce polarization and elevate the discharge voltage to ~2 V. In addition, it shows excellent capacity retention (360 mAh g−1) for 2,000 cycles at a 1C rate.