Tribochemical Interface Engineering of TiS 4 –Argyrodite Composites for Metal Sulfide‐Based Solid‐State Batteries

Amorphous titanium tetrasulfide (TiS 4 ) is investigated as a high‐capacity cathode material for sulfide‐based solid‐state batteries using Li 6 PS 5 Cl argyrodite as solid electrolyte. A systematic comparison between low‐energy ball milling (LBM) and high‐energy ball milling (HBM) reveals that tribochemical processing intensity determines composite microstructure and electrochemical performance. HBM‐processed composites exhibit superior homogenization confirmed by quantitative FIB‐SEM analysis, achieving discharge capacities of 1110 mAh g S −1 at 0.05 C and 669 mAh g S −1 at 0.5 C. Despite lower bulk electronic conductivity, HBM composites demonstrate enhanced performance consistent with shortened solid‐state diffusion lengths and increased triple‐phase boundary density. SOC‐dependent electrochemical impedance spectroscopy reveals that HBM composites accumulate only 19% impedance growth at 100% SOC over 34 cycles compared to 41% for LBM counterparts, indicating superior interfacial stability. Time‐of‐flight secondary ion mass spectrometry provides spatial evidence for heterogeneous lithiation, with codetected TiS + and Li 3 S + species consistent with gradual structural reorganization along the conversion trajectory. Scalability is demonstrated through dry‐film electrode fabrication, and HBM‐processed cathodes achieve initial capacities of 1240 mAh g S −1 and retain 950 mAh g S −1 after 80 cycles. Absolute capacity values reflect the combined electrochemistry of TiS 4 and partially decomposed Li 6 PS 5 Cl. This work establishes tribochemical processing as a viable strategy for optimizing conversion‐type cathodes in solid‐state batteries.