Chemically bonded MXene/SnSe2 composite with special structural transformation as a high-performance anode for lithium and potassium ions battery.

Sn-C bonding coupled MXene/SnSe 2 composites with SnSe 2 nanosheets vertically dispersed on the MXene surface undergo structural reconstruction and pulverization during cycling process. The large layer spacing of MXene provides enough interior space for SnSe 2 networks and nanoparticles. This structure possesses more and faster ions diffusion channels, demonstrating enhanced Li+ storage kinetics. [Display omitted] • MXene/SnSe 2 bonded by Sn-C displays SnSe 2 nanosheets vertically dispersed on MXene. • MXene/SnSe 2 composite shows excellent lithium and potassium ions storage properties. • MXene/SnSe 2 undergo structural reconstruction and pulverization during cycling process. Sn-C bonding coupled MXene/SnSe 2 composite with SnSe 2 nanosheets vertically coating on the MXene surface was prepared successfully by the solvothermal method, in which MXene matrix etched separately by HF and LiF/HCl was used to explore the improving effect on the electrochemical performance of SnSe 2. It is found that MXene etched by HF acid shows more obvious accordion-like structure with larger layer spacing, and its composite with SnSe 2 demonstrates better lithium and potassium storage properties. When employed as potassium-ion batteries (PIBs) anode, MXene/SnSe 2 electrode can deliver a reversible capacity of 222.8 mAh·g−1 till 300 cycles at the current density of 200 mA·g−1. As an anode for lithium-ion batteries (LIBs), MXene/SnSe 2 could provide high reversible capacity (515.6 mAh·g−1 after 300 cycles at 200 mA·g−1) and rate capacity (1015.1 mAh·g−1 at 500 mA·g−1 and 496.2 mAh·g−1 at 5000 mA·g−1). Even at 2000 mA·g−1, the capacity of MXene/SnSe 2 can be maintained at 322.6 mAh·g−1 after 500 cycles. Further analysis by ex-situ SEM finds that the MXene/SnSe 2 electrode undergoes structural reconstruction at the high current density of 2000 mA·g−1. In the first few cycles, SnSe 2 nanosheets are changed into a network structure and then in-situ pulverized into many small nanoparticles, all which immerged on MXene surface and between layers. Although MXene/SnSe 2 electrode experiences structural transformation, it retains apparent layered structure. This provides a fast channel for electrons and ions migration, resulting in higher Li+ diffusion rate and diffusion-controlled storage capacity. It is believed that the work could be acted as a reference for design composite with MXene and used for anode as well as other materials. [ABSTRACT FROM AUTHOR]