Pan‐Milling: Instituting an All‐Solid‐State Technique for Mechanical Metastable Oxides as High‐Performance Lithium‐Ion Battery Anodes

Abstract All‐solid‐state mechanochemistry is experiencing an exciting period of renaissance, thanks in part to the recent discovery of its ability to realize chemical synthesis that is inaccessible to solution‐based methods. Among them, high‐energy ball‐milling is widely used in large‐scale preparation of metal oxide composites for lithium‐ion batteries (LIBs). However, ball‐milling‐induced high‐energy mechanical activation may destroy crystalline structure, and thus the electrochemical activity of many metastable oxides such as anatase titanium dioxide (TiO₂). Herein, the mechanism that anatase TiO₂ undergoes the crystalline‐amorphous phase transformation subject to ball‐milling is reported and a new pan‐milling mechanochemical technique for preparation of stable anatase TiO₂/graphene (TiO₂/GNS) composites is demonstrated. The pan‐milling technique not only preserves the original crystal structure of TiO₂ but also realizes a good dispersion of TiO₂ nanoparticles on graphene nanosheets through its unique 3D shear force. When used as anode for LIBs, the pan‐milled TiO₂/GNS demonstrates high reversible specific capacity, excellent rate capability, and long cycle stability, in comparison to the ball‐milled TiO₂/GNS that shows no capacity. By tapping into the huge potential of pan‐milling mechanochemistry, this work opens the door to large‐scale all‐solid‐state preparation of mechanical metastable oxides with desired electrochemical performance for energy storage.