3D Assembly of CoAl₂O₄ Spinel Nanosheets for Energy Storage

Two-dimensional (2D) materials have attracted attention for electrochemical energy storage applications because of their unique physical and chemical properties. However, the facile synthesis of thin 2D sheets remains a challenge. Herein, we demonstrate the formation of 3D assembly of thin Co–Al spinel sheets and carbon composite through a facile two steps process: hydrothermal synthesis of CoAl Layered double hydroxide (LDH) followed by heating of this LDH at high temperature to form CoAl2O4/C. This composite with a high specific surface area (SSA) of 102.7 m2 g–1 showed enhanced energy storage application. The CoAl2O4/C is capable of delivering specific capacitance of 1394 F g–1 under 1 A g–1 current density with 87% capacitance retention after 5000 cycles. For asymmetric supercapacitor (ASC), the CoAl2O4/C and activated carbon (AC) were used as cathode and anode, respectively. The device CoAl2O4/C//AC exhibits a high energy density of 76.34 W h kg–1 at a power density of 750.045 W kg–1 with good cyclic durability of 79% after 10 000 cycles. The improved electrochemical activity may be due to the 3D assembly of thin 2D Co–Al spinel nanosheets that allows easy electron and mass transport, high surface area, synergistic interaction among different components, etc. for which Co–Al spinel/C composite will find application in energy storage.