Enhancing Rate Capability, Capacity, and Durability of Co-Doped Germanium Phosphide Anodes for Li-Ion Batteries

While germanium-based anodes for Li-ion batteries (LIBs) have potential to offer high energy density, their commercialization is impeded by low ionic and electronic conductivity and poor tolerance to volume change during cycling. Here a new quaternary CuGeSiP₃ anode is reported to simultaneously overcome these limitations. Synthesized via ball milling process, CuGeSiP₃ displays high ionic and electronic conductivity and excellent flexibility to accommodate volume change, attributed to increased structural entropy and reversible formation of favorable intermediates of both electronic and Li ion conductors, as confirmed by experimental measurements and theoretical calculations. When used as an LIB anode, CuGeSiP₃ demonstrates large reversible capacity, high Coulombic efficiency, robust cycling stability, and high-rate capability because it undergoes a reversible lithiation process that involves intercalation and conversion reaction. When composited with layered graphite, the electrode demonstrates exceptional cycling stability (1 261 mA h g⁻¹ after 600 cycles at 400 mA g⁻¹ and 861 mA h g⁻¹ after 1 450 cycles at 20 00 mA g⁻¹) and ultrahigh rate capability (448 mA h g⁻¹ at 20 000 mA g⁻¹). Further, the quaternary, pentanary, and hexanary cation-disordered phosphides are also synthesized, all having similar Li-storage superiority, implying the multiple co-doping strategy is applicable to other material systems.