Interfacial nitrogen engineering of robust silicon/MXene anode toward high energy solid-state lithium-ion batteries

Abstract

Replacing the conventional carbonate electrolyte by solid-state electrolyte (SSE) will offer improved safety for lithium-ion batteries. To further improve the energy density, Silicon (Si) is attractive for next generation solid-state battery (SSB) because of its high specific capacity and low cost. High energy density and safe Si-based SSB, however, is plagued by large volume change that leads to poor mechanical stability and slow lithium ions transportation at the multiple interfaces between Si and SSE. Herein, we designed a self-integrated and monolithic Si/two dimensional layered T3C2Tx (MXene, Tx stands for terminal functional groups) electrode architecture with interfacial nitrogen engineering. During a heat treatment process, the polyacrylonitrile not only converts into amorphous carbon (a-C) that shells Si but also forms robust interfacial nitrogen chemical bonds that anchors Si and MXene. During repeated lithiation and delithiation processes, the robust interfacial engineered Si/MXene configuration enhances the mechanical adhesion between Si and MXene that improves the structure stability but also contributes to form stable solid-electrolyte interphase (SEI). In addition, the N-MXene provides fast lithium ions transportation pathways. Consequently, the Si/MXene with interfacial nitrogen engineering (denoted as Si-N-MXene) deliveres high-rate performance with a specific capacity of 1498 mAh g−1 at a high current of 6.4 A g−1. A Si-N-MXene/NMC full cell exhibited a capacity retention of 80.5% after 200 cycles. The Si-N-MXene electrode is also applied to SSB and shows a relative stable cycling over 100 cycles, demonstrating the versatility of this concept.