Li intercalation in an MoSe2 electrocatalyst: In situ observation and modulation of its precisely controllable phase engineering for a high‐performance flexible Li‐S battery

Abstract Sophisticated efficient electrocatalysts are essential to rectifying the shuttle effect and realizing the high performance of flexible lithium‐sulfur batteries (LSBs). Phase transformation of MoSe 2 from the 2H phase to the 1T phase has been proven to be a significant method to improve the catalytic activity. However, precisely controllable phase engineering of MoSe 2 has rarely been reported. Herein, by in situ Li ions intercalation in MoSe 2 , a precisely controllable phase evolution from 2H‐MoSe 2 to 1T‐MoSe 2 was realized. More importantly, the definite functional relationship between cut‐off voltage and phase structure was first identified for phase engineering through in situ observation and modulation methods. The sulfur host (CNFs/1T‐MoSe 2 ) presents high charge density, strong polysulfides adsorption, and catalytic kinetics. Moreover, Li‐S cells based on it display capacity retention of 875.3 mAh g −1 after 500 cycles at 1 C and an areal capacity of 8.71 mAh cm −2 even at a high sulfur loading of 8.47 mg cm −2 . Furthermore, the flexible pouch cell exhibiting decent performance will endow a promising potential in the wearable energy storage field. This study proposes an effective strategy to precisely control the phase structure of MoSe 2 , which may provide the reference to fabricate the highly efficient electrocatalysts for LSBs and other energy systems.