Regulating the Nanosize Effect of LiCoO2 for High-Performance Battery-Supercapacitor Hybrid Devices

The nanosize effect in nanostructured electrode materials is significant for boosting rate performance; however, it brings about low capacity, low Coulombic efficiency, and poor stability. In this work, 2D atomically thin (001)-oriented single-crystalline LCO (SC-LCO) nanosheets with longer Li+ intercalation distance and a surface dominated with (001) planes are constructed to regulate the nanosize effect. The SC-LCO not only owns large plateau region capacity even at high rate (194 mAh g(-1) at 1C and 111 mAh g(-1) at 50C) but also realizes remarkable improvement in the initial Coulombic efficiency (92% at 1C) and cycling stability (83% capacity retention for 500 cycles). The battery-supercapacitor hybrid devices (BSHDs) assembled with kinetics and capacity doubly matched SC-LCO and mesoporous TiNb2O7 nanosheets offer high energy density (244 Wh kg(-1) @ 693 W kg(-1)) and power density (15 kW kg(-1) @ 151 Wh kg(-1)). Further, pouch-type full cells are assembled, demonstrating the enormous applicability of this strategy.