Engineering solid-electrolyte interface from aqueous deep-eutectic solvent to enhance the capacity and lifetime of self-assembled heterostructures of 1T-MoS2/graphene

Formation of an inferior solid-electrolyte interface (SEI) over the electrode severely diminishes the specific capacity and cyclic stability of Li-ion batteries (LIB). Although this issue is tackled to some extent by the in-situ generation of SEI coatings via the use of electrolyte additives, the control over the optimum thickness and composition of SEI is still challenging. To address this issue, porous and flexible SEI coating is electrochemically deposited over the active electrode material from an aqueous deep-eutectic solvent. The uniform SEI film of 20 to 35 nm with the composition of C, N, F, O, and Li elements is preformed on the surface of a self-assembled composite of 1T-MoS2 and the positively charged reduced graphene oxide. With the aid of preformed SEI, the composite electrode significantly increases its specific capacity from 907 to 1350 mAh g−1 and rate capability from 28 to 75%. Even at a higher current density of 1 A g−1, specific capacity gradually rises from 960 to 1647 mAh g−1 after 2000 charge/ discharge cycles. Furthermore, the device shows indistinct electrolyte decomposition and negligible increase of charge transfer resistance during cycling. Our novel approach is extrapolated as a general protocol to improve the performance of LIBs.