Amorphous Ge/LiAlGePO Composite Anodes with a Multistacking Structure Developed via Co‐Sputtering for High‐Capacity Li⁺‐Ion Batteries

Abstract To realize Ge anodes for next‐generation, high‐capacity, long‐life Li + ‐ion batteries, an amorphous LiAlGePO film is plasma‐sputtered as an oxide‐based Li solid electrolyte onto an active Li‐storage Ge material, where the LiAlGePO film suppresses capacity fading as a stable solid‐electrolyte interface layer. Multilayer anodes with LiAlGePO(top)/Ge(bottom) and LiAlGePO(top)/Ge‐LiAlGePO(bottom) structures show high discharge capacities of 799 and 810 mAh g −1 after 300 cycles at 0.16 A g −1 (0.1 C‐rate) and achieve high capacity retentions of 97.3% and 100%, respectively. A Ge‐LiAlGePO mixed anode also demonstrates a high discharge capacity of 1074 mAh g −1 after 300 cycles, with a capacity retention of 87.3%. The ionic conductivity of the amorphous LiAlGePO is improved by doping the film with N atoms; the Li 0.69 Al 0.91 Ge 1.52 P 3 O 10.5 N 0.22 film shows a 1.6 times higher ionic conductivity (1.42 × 10 −5 S cm −1 ) than the amorphous Li 1.28 Al 1.35 Ge 2.38 P 3 O 14.1 without N. Among the investigated anodes, the Li 0.69 Al 0.91 Ge 1.52 P 3 O 10.5 N 0.22 (top)/Ge(bottom) anode with the highest ion‐conductivity layer at the top exhibits the highest capacity retention of 95.2% after a total of 120 cycles even when operated at high current densities of 0.1–2 C‐rate.