High-volumetric pseudocapacitive sodium storage in densely packed mesoporous titanium dioxide-carbon composite

Transition metal oxides with small grain sizes are promising candidates for capacitive charge storage. However, the overall performance of such oxide materials is still limited by low tap density and finite conductivity. Here, we present a type of densely packed titanium dioxide (TiO2) composite that comprises three-dimensional aligned mesoporous TiO2 microspheres and coated ultrathin mesoporous carbon shells. The fabricated mesoporous meso-TiO2@meso-C complex possesses a highly accessible surface area (134 m2 g−1), dual mesopore channels (11.8 and 21.6 nm), and a much higher tap density (1.52 g cm−3). As expected, this designed mesoporous composite achieves superior electrochemical performance, including both a maximized specific capacity of 255 mAh g−1 and a volumetric capacity of 390 mAh cm−3 at 0.025 A g−1. Our mesoscopic composite electrode that enables fast redox reaction reveals the importance of incorporating conductive and dense mesostructures as an alternative pathway for high-volumetric pseudocapacitive materials.