2D molten salt strategy for preparing large-sized MoS2/C sheets with self-adaptive structural deformation for K-ion storage

Abstract

Due to the unique two-dimensional (2D) structure and large interlayer distance, MoS2 is considered as one potential anode material for fast-developed potassium ion energy storage. Differing to the intensive study on nano-sized MoS2, in this work our attention is focused on the probability of large-sized MoS2 sheets. Following this, a micrometer-scale crystalline MoS2 sheet with few-stacked layers and enlarged interlayer spacing anchored on carrageenan-derived carbon is fabricated by a novel 2D molten salt approach. Controlled by the 2D space-confined molten salt layers on the surface of KCl crystals, the oriented growth of MoS2 flakes creates the few layer-stacking MoS2 sheets in microscale. Meantime, the insertion of K+ in molten salts enlarges the interlayer distance and induces the production of 1 T phase. Besides, a novel self-adaptive structural deformation from MoS2/C sheets to bubble-wrap-like architecture has been discovered during electrochemical process, demonstrating the specific way of large-sized MoS2 sheets to alleviate volume expansion and exfoliation resulted from K-ion intercalation. Based on above synergistic effect, the optional samples exhibit a high capacity of 413 mAh g−1 at 0.1 A g−1, and an excellent cycling capability with a retention of 89.7% after 2000 cycles at 2 A g−1. The assembled potassium ion hybrid capacitor delivers a high energy of 130 Wh kg−1 and superior reversibility with 85.1% retention after 10,000 cycles.