Precisely Tunable Synthesis of Binder-Free Cobalt Oxide-Based Li-Ion Battery Anode Using Scalable Electrothermal Waves.

Binder-free transition metal oxide-based anodes for lithium-ion batteries (LIBs), having high capacity and abundance, have received considerable attention. However, their low conductivity and unstable charge-discharge cycles must be addressed, and scalable fabrication routes for binder-free design with optimal phase tuning are necessary. Herein, we report a precisely tunable synthesis of binder-free cobalt oxide-based LIB anodes using scalable electrothermal waves. Needle-like nanoarrays of cobalt hydroxide on nickel foams are prepared as precursors, and Joule-heating-driven electrothermal waves passing through the metal foams cause transition to cobalt oxides with preserved structures and adjustable phase tuning of grains and oxygen vacancies. The rapid heating-cooling environment using electrothermal waves causes extreme input thermal energy over the activation energy of phase transitions and metastable phase trapping. This programmable route completes the selective grain characteristics and vacancy concentrations. The electrothermally tuned binder-free LIB anodes employing the CoO/Co 3 O 4 @Ni foam-based electrodes exhibit a high-rate capacity (3.7 mAh cm -2 ) at 2.4 mA cm -2 for 70 charge-discharge cycles. Accumulated electrothermal waves from multiple cycles broaden the tunable ranges of the morphological and chemical transitions causing rapid screening of the optimal phases for LIB anodes. This phase-tuning strategy will inspire precise yet efficient synthesis routes for diverse binder-free electrodes and catalysts.