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.

Field‐assisted electrocatalysts spark sulfur redox kinetics: From fundamentals to applications

“…Correspondingly, the anti‐bonding state occupation, orbital energy level, and orientation of the hybrid orbitals determine the strength of hybridization. [ 120,178,211–219 ]…”

“…Correspondingly, the antibonding state occupation, orbital energy level, and orientation of the hybrid orbitals determine the strength of hybridization. [120,178,[211][212][213][214][215][216][217][218][219] When we are constantly looking at a bright future with field-assisted electrocatalysts, we cannot help but worry about whether the field effects can be used as a commercial boosting method or only as a supplementary means to experimentally elucidate the mechanisms behind enhanced sulfur redox kinetics in the conceptual stage. Admittedly, a highly interdisciplinary field-assisted electrochemistry, referring to a considerable amount of uncertainty constrained by multi-interferences in physical parameter variability, weakens the universality and inevitability of the corresponding conclusion.…”

Recent advances in molybdenum diselenide-based electrocatalysts: preparation and application in the hydrogen evolution reaction

“…38 Wang and coworkers reported that the phase evolution of MoSe 2 from 2H-MoSe 2 to 1T-MoSe 2 can be precisely controlled by in situ Li ions intercalation. 198 The corresponding 2H, 1T, and a mixed 1T/2H-MoSe 2 in HER have been widely investigated by S or P doping to adjust the phase structure. 102,103 By adjusting the ratio of Se to Mo, ultrathin 1T/2H MoSe 2 nanosheets obtained contained high percentage of 1T phase and a tunable layer thickness, which can provide abundant active sites and high conductivity and thereby promoted the HER performance.…”

Dynamic evolution of electrocatalytic materials for Li–S batteries

“…Furthermore, Wang et al explored the correlation between the degree of lithiation and phase evolution of MoSe 2 . 110 As shown in Fig. 4a, 2H-MoSe 2 was synthesized via in situ electrochemical intercalation of 1T-MoSe 2 , where the intercalation-induced phase transformation process is irreversible.…”

“…The binding energies of Li 2 S 6 on the surfaces of (e) 2H-MoSe 2 and (f) 1T-MoSe 2 , respectively. Reproduced with permission 110. Copyright 2022, John Wiley and Sons.…”