Two-Dimensional Silicon/Carbon from Commercial Alloy and CO₂ for Lithium Storage and Flexible Ti₃C₂T_<i>x</i> MXene-Based Lithium–Metal Batteries

Abstract

Silicon has been considered as the most promising anode candidate for next-generation lithium-ion batteries. However, the fast capacity decay caused by huge volume expansion and low electronic conductivity limit the electrochemical performance. Herein, atomic distributed, air-stable, layer-by-layer-assembled Si/C (L-Si/C) is designed and <i>in situ</i> constructed from commercial micron-sized layered CaSi₂ alloy with the greenhouse gas CO₂. The inner structure of Si as well as the content and graphitization of C can be regulated by simply adjusting the reaction conditions. The rationally designed layered structure can enhance electronic conductivity and mitigate volume change without disrupting the carbon layer or destroying the solid electrolyte interface. Moreover, the single-layer Si and C can enhance lithium-ion transport in active materials. With these advantages, L-Si/C anode delivers an 82.85% capacity retention even after 3200 cycles and superior rate performance. The battery-capacitance dual-model mechanism is certified <i>via</i> quantitative kinetics measurement. Besides, the self-standing architecture is designed <i>via</i> assembling L-Si/C and MXene. Lithiophilic L-Si/C can guide homogeneous Li deposition with alleviated volume change. With the MXene/L-Si/C host for lithium-metal batteries, an ultralong life span up to 500 h in a carbonate-based electrolyte is achieved. A full cell with a high-energy 5 V LiNi_0.5Mn_1.5O₄ cathode is constructed to verify the practicality of L-Si/C and MXene/L-Si/C. The rational design of a special layer structure may propose a strategy for other materials and energy storage systems.