Yolk-shell structured CuSi2P3@Graphene nanocomposite anode for long-life and high-rate lithium-ion batteries

Highlights: • Ternary CuSi₂P₃ has high electronic conductivity. • CuSi₂P₃ has a low Li-ion diffusion energy barrier. • CuSi₂P₃ shows better Li-storage properties than related binary and single-component electrodes studied. • A dual-carbon protection architecture is created by a two-step ball milling process. • A full battery based on CuSi₂P₃/C anode also shows long-term cycling stability. Silicon-based anode materials enable the development of commercial lithium-ion batteries (LIBs) with higher gravimetric energy densities than are currently available. However, the inherently low electronic and ionic conductivity as well as large volume expansion upon lithiation of Si hinder their use in practical applications. Here we report a cation-disordered CuSi₂P₃ material, synthesized using high-energy ball milling, that shows improved stability, larger capacity, and higher ionic and electronic conductivity than pure Si. When used as an anode for LIBs, CuSi₂P₃ demonstrates a high reversible capacity of 2069 mA h g⁻¹ with an initial Coulombic efficiency of 91% and a suitable working potential of 0.5 V (vs. Li⁺/Li). Further, after a two-step ball milling of CuSi₂P₃ with graphite, a yolk-shell structured carbon-coated CuSi₂P₃@graphene nanocomposite is formed that shows enhanced long-term cycling stability (1394 mA h g⁻¹ after 1500 cycles at 2 A g⁻¹; 1804 mA h g⁻¹ after 500 cycles at 200 mA g⁻¹) and rate capability (530 mA h g⁻¹ at 50 A g⁻¹), surpassing those for other Cu-Si, Cu-P, and Si-P compounds or single-component Si- and P-based composites. When coupled with a LiNi_0.5Co_0.2Mn_0.3O₂ (NCM) cathode in a full cell, the NCM//CuSi₂P₃ @graphene battery exhibits a high capacity of 140 mA h g⁻¹ after 200 cycles, demonstrating the potential of CuSi₂P₃ anodes for the next-generation high-performance LIBs.