Aquatic Environment Breaks the Size Confinement of the TiO ₂ Anodes in Aqueous Batteries

Abstract The particle size of TiO 2 anodes is commonly believed to have a negative impact on their mechanical properties. As submicron‐sized TiO 2 exhibits low surface energy, which reduces yield strength and leads to mechanical fracture during the two‐phase lithium storage mechanism, it is excluded from traditional nonaqueous lithium‐ion batteries. In this study, we discovered that TiO 2 demonstrates an independent size effect in an aqueous environment, mitigating the mechanical fracture associated with submicron‐sized TiO 2 . Our studies reveal that water molecules strongly interact with submicron TiO 2 materials, increasing the surface energy in aqueous electrolytes in a unique manner. This enhancement makes submicron TiO 2 more resilient during the lithiation and de‐lithiation reactions. Additionally, the transition from nano to submicron TiO 2 facilitates the inhibition of hydrogen evolution reactions (HER) in aqueous batteries and enhances the performance of electrode coatings. Consequently, submicron TiO 2 exhibits superior electrochemical performance in aqueous batteries, with an Ah‐level pouch battery achieving an energy density of 66 Wh kg −1 (217 Wh L −1 ) and demonstrating excellent cycling stability of over 1200 cycles. Our work has successfully addressed the size limitations of the TiO 2 anodes, offering an innovative perspective on micro‐sized electrode materials previously considered unsuitable for battery use.