Si/CrSi₂ Alloy Anodes Synthesized by a High-Energy Ball-Milling Method for Lithium-Ion Batteries: Microstructure, Electrochemistry, and Carbon Coating

Abstract

This work successfully introduced the different ratios of metallic Cr into micrometer Si bulk via a high-energy ball-milling method to synthesize nanostructured Si/CrSi2 alloy anodes with enhanced electrochemical performance in lithium-ion batteries (LIBs). This study demonstrated that the in situ-formed CrSi2 could effectively suppress the generation of crystalline Li3.75Si in the lithiation process, dilute Si’s volume expansion, and improve electronic conductivity. Concretely, Si85Cr15 displayed an outstanding reversible volumetric capacity of ∼1400 A h·L–1 and 100-cycle capacity retention at 0.2 C of 90.1% with an average Coulombic efficiency of 99.46%. Moreover, another advantage of Si85Cr15 is good compatibility with the carbon-coating treatment at 800 °C by virtue of the reinforced thermal stability derived from a high melting point of CrSi2. The homogeneous distribution of Si and metal silicide crystallites was better maintained in Si85Cr15@c-PDA compared to our previously annealed Si–Cu3Si–NiSi2 alloys at the same temperature. Correspondingly, the cycle stability and rate capability of Si85Cr15@c-PDA were further improved with a capacity retention of 93.1/90.6% at 0.2/0.5 C (100/200 cycles) and 40% at 2 C, respectively. The excellent electrochemical performance indicates that Si/CrSi2 alloys may be prospective candidates as compositions in the carbon-coated anode materials for industrialized LIBs.