High Pseudocapacitance Boosts Ultrafast, High-Capacity Sodium Storage of 3D Graphene Foam-Encapsulated TiO2 Architecture

Anatase TiO2 is an attractive anode for Li-ion batteries and Na-ion batteries because of its structural stability. However, the electrochemical capability of anatase TiO2 is unsatisfactory due to its intrinsically low electrical conductivity and poor ion diffusivity at the electrode/electrolyte interface. We prepared 3D lightweight graphene aerogel-encapsulated anatase TiO2, which exhibits a high reversible capacity (390 mA h g(-1) at 50 mA g(-1)), a superior rate performance (164.9 mA h g(-1) at 5 A g(-1)), and a long-term cycling capability (capacity retention of 86.8% after 7800 cycles). The major energy-storage mechanism is surface capacitance dominated, which favors a high capacity and fast Na+ uptake. The inherent features of 3D porous aerogels provide additional active reaction sites and facilitate fast charge diffusion and easy ion access. This will enable the development of 3D interconnected, graphene-based, high-capacity active materials for the development of next-generation energy-storage applications.