Lithium Sulfite Enhances Cycle Performance of All-Solid-State Batteries with Li2S-Based Positive Electrode Materials

Lithium-ion batteries are widely used owing to their advantageous performance characteristics. However, safety issues associated with liquid electrolytes have inspired the development of all-solid-state lithium–sulfur (Li/S) batteries as safe and high-energy-density candidates for next-generation batteries. Lithium sulfide (Li2S)-based positive electrode materials exhibit a high charge–discharge capacity and cycle performance. However, because of their insulating nature, ionic and electronic conduction pathways must be created for charge–discharge cycling. In this study, the incorporation of lithium sulfite (Li2SO3) to create nanoscale lithium ionic pathways in Li2S-based positive electrodes was investigated. Li2SO3 was synthesized and electrochemically characterized for the first time. Li2S–Li2SO3 samples were prepared via ball-milling, and the composite positive electrodes combined with conductive additives were utilized as positive electrodes in all-solid-state batteries. The cells with Li2SO3 exhibited a high reversible capacity, excellent rate performance (1C rate), and a long cycle life (1000 cycles). Li2SO3 will be useful not only for Li2S-based positive electrodes but also for the development of materials for all-solid-state batteries.