Enhancing Charge Storage of Anatase Nanoparticles through Pseudocapacitance in Amorphous–Crystalline–Amorphous Architectures

The diverse electrochemical properties of amorphous titanium oxide and the limited understanding of the structure–property relationship pose challenges for its broader application. This study unravels the impact of crystalline disorder in anatase on its electrochemical behavior. A systematic two-step wet chemical synthesis followed by calcination was employed to prepare a series of anatase electrodes, ranging from low (Ant-T80) to fully crystalline (Ant-T550). Structural analyses, including XRD and FTIR, reveal the amorphous-to-crystalline transition between 235 and 450 °C, with increased crystallinity and crystallite size and decreased Ti–OH vibration band intensity at higher calcination temperatures. Electrodes with very low (Ant-T80) or high (Ant-T550) crystallinity exhibit suboptimal performance. The charge storage mechanism evolves with increasing crystallinity, transitioning from capacitive dominance to pseudocapacitance to intercalation. Notably, Ant-T250 and Ant-T400 showcase an amorphous–crystalline–amorphous architecture, which offers an open framework, accessible short ion-diffusion channels, faster lithiation kinetics, and likely enhanced electronic conductivity. This results in improved electrochemical performance through intercalation pseudocapacitance. Ant-T250 excels at providing a high capacity at low rates, while Ant-T400 exhibits a remarkable reversible discharge capacity at various rates, emphasizing excellent structural stability and capacity retention.