Stabilizing Solid‐Solution Reaction in TiNb ₂ O ₇ Anodes via Systematic Process Optimization for Fast‐Charging Kinetics

ABSTRACT TiNb ₂ O ₇ (TNO) with an open Wadsley‐Roth framework structure is a promising anode material for fast‐charging lithium‐ion batteries owing to its high safety and favorable Li ⁺ transport properties. However, its hydrothermal and calcination processes are characterized by multiple interacting factors. This complexity makes it difficult to optimize the material's morphology and phase purity using conventional single‐factor methods. Consequently, the fast‐charging potential of pure‐phase TNO remains largely unrealized. In this study, we employ an L ₁₆ (4 ⁴ ) orthogonal design method to systematically optimize this complex synthesis process. By locking in the optimal process window (hydrothermal treatment at 180°C for 12 h and calcination at 800°C for 5 h), we successfully created a low‐strain solid solution. This optimized TNO (denoted as O‐TNO) features low‐energy barriers for rapid Li ⁺ migration and enables a highly reversible solid‐solution transition mechanism. As a result, the O‐TNO anode delivers a reversible specific capacity of 175.5 mAh g ⁻¹ at a high rate of 10C, with a capacity retention of 73.6% after 500 cycles. This work fully unlocks the intrinsic fast‐charging potential of TNO through systematic process optimization, providing a reliable synthesis strategy and structural foundation for future material modifications based on this material.