Amorphous titanic acid electrode: its electrochemical storage of ammonium in a new water-in-salt electrolyte

Abstract

We report an amorphous titanic acid of TiO_1.85(OH)_0.30·0.28H₂O as a new electrode for aqueous ammonium-ion batteries, which operates in a new water-in-salt electrolyte—25 m NH₄CH₃COO. The titanic acid electrode exhibits a specific capacity nearly 8 times that from the crystalline TiO₂ electrode. In electrochemical reactions, the amorphous titanic acid provides abundant storage sites in its disordered structure and affords strong H-bonding toward the inserted NH₄⁺ ions.