MXene-Derived Defect-Rich TiO2@rGO as High-Rate Anodes for Full Na Ion Batteries and Capacitors

Abstract Sodium ion batteries and capacitors have demonstrated their potential applications for next-generation low-cost energy storage devices. These devices's rate ability is determined by the fast sodium ion storage behavior in electrode materials. Herein, a defective TiO 2 @reduced graphene oxide (M-TiO 2 @rGO) self-supporting foam electrode is constructed via a facile MXene decomposition and graphene oxide self-assembling process. The employment of the MXene parent phase exhibits distinctive advantages, enabling defect engineering, nanoengineering, and fluorine-doped metal oxides. As a result, the M-TiO 2 @rGO electrode shows a pseudocapacitance-dominated hybrid sodium storage mechanism. The pseudocapacitance-dominated process leads to high capacity, remarkable rate ability, and superior cycling performance. Significantly, an M-TiO 2 @rGO//Na 3 V 2 (PO 4 ) 3 sodium full cell and an M-TiO 2 @rGO//HPAC sodium ion capacitor are fabricated to demonstrate the promising application of M-TiO 2 @rGO. The sodium ion battery presents a capacity of 177.1 mAh g −1 at 500 mA g −1 and capacity retention of 74% after 200 cycles. The sodium ion capacitor delivers a maximum energy density of 101.2 Wh kg −1 and a maximum power density of 10,103.7 W kg −1 . At 1.0 A g −1 , it displays an energy retention of 84.7% after 10,000 cycles.