Ether-Induced Phase Transition toward Stabilized Layered Structure of MoS2 with Extraordinary Sodium Storage Performance

Ether-based electrolytes have long been proven to be advantageous over ether-based electrolytes in sodium ion batteries (SIBs), but the understanding of their effect on the phase transition of electrode materials during electrochemical cycling is very limited. In this work, we study the phase transition and electrochemical performance of 2H-MoS2 in ether- and ester-based electrolytes. Interestingly, we find that the MoS2 anode develops MoS2/diglyme-Na+ superlattices induced by cointercalation of Na+ and an ether solvent in an ether-based electrolyte, rather than the conversion reaction observed in ester-based electrolytes. The superlattices consist of mixed semiconductive 2H and metallic 1T phases, and are structurally stable and kinetically favorable for the repeated sodiation, which greatly enhances the capacity, cycling, and rate performance of MoS2. Specifically, the three-dimensional MoS2 nanoflowers deliver an ultrahigh capacity of 446.5 mAh g(-1) at 5 A g(-1) with no capacity fading after more than 3700 cycles in an ether-based electrolyte.