Si-Cr alloy anodes for Lithium-ion batteries Synthesized by a High-energy Ball-milling method: Microstructure, Carbon Coating, and Electrochemistry

A two-step modification for the electrochemical performance of Si-based anodes for LIBs is achieved in this study. Firstly, the Cr element is chosen as the doped media into Si bulk via a HEBM method and the fabricated Si-Cr precursors consist of nanocrystalline Si, CrSi2, and amorphous Si. The electrochemical analysis reveals that all ball-milled samples have a similar lithiation/delithiation mechanism with raw Si but the generation of cr-Li3.75Si can be effectively suppressed in the initial stage. The introduction of Cr can enhance cycle stability, volumetric capacity, coulombic efficiency, and electrical conductivity for Si-Cr alloys. The abnormal performance degradation phenomenon in previous Si-CuO system cannot be found here and the suggested Cr ratio is at least 15%. Furthermore, the selected Si85Cr15 precursor is conducted a carbon-coating treatment at 800 ℃, where it shows a 100- and 250-cycle capacity retention of ~93% at 0.2C and ~80% at 0.5C, respectively. The excellent cycle performance is considered related to the limited microstructure change of Si85Cr15@c-PDA due to a certain high-temperature tolerance of CrSi2 at 800 ℃. Meanwhile, it is also attributed to the synergistic effect of CrSi2 and c-PDA, with which Si85Cr15@c-PDA electrode possesses a stable structure and impedance change during the cycles.