Long Cycle Life All-Solid-State Sodium Ion Battery

All-solid-state sodium ion batteries (ASIBs) based on sulfide electrolytes are considered a promising candidate for large-scale energy storage. However, the limited cycle life of ASIBs largely restricts their practical application. Cycling-stable ASIBs can be achieved only if the designed cathode can simultaneously address challenges including insufficient interfacial contact, electrochemical and chemical instability between the electrode and electrolyte, and strain/stress during operation , rather than just addressing one or part of these challenges. Chevrel phase Mo₆S₈ has inherent high electronic conductivity and small volume change during sodiation/desodiation, and is chemically and electrochemically stable with the sulfide electrolyte, and therefore the only challenge of using Mo₆S₈ as the cathode for ASIBs is the insufficient contact between Mo₆S₈ and the solid electrolyte (SE). Herein, a thin layer of SE is coated on Mo₆S₈ using a solution method to achieve an intimate contact between Mo₆S₈ and the SE. Such a SE-coated Mo₆S₈ cathode enabled an ASIB with a high cycling performance (500 cycles), even much better than that of the liquid-electrolyte batteries with the Mo₆S₈ cathode. This work provides valuable insights for developing long-cycle life ASIBs.