Tellurium-impregnated P-doped porous carbon nanosheets as both cathode and anode for an ultrastable hybrid aqueous energy storage

Abstract

Constructing a battery–supercapacitor hybrid (BSH) aqueous system is a promising way to obtain safe energy storage devices with both high energy and power densities. It is of crucial importance to explore novel electrode materials for the development of BSH systems. Herein, P-doped porous carbon nanosheet confined Te nanocrystals (PCCT) is prepared as a highly stable electrode material for the BSH system. The specific structure enables the composite to show high performances when used as both cathode and anode. When the composite is applied as a cathode material, the reversible redox of Te/Te(IV) is realized and leads to a specific capacity of 153 mA h g⁻¹, based on the mass of the composite. As an anode material, the composite with P-doped porous structure (surface area is 531.4 m² g⁻¹) exhibits an excellent capacitance of 263 F g⁻¹. Although Te is unstable in alkaline solutions, the robust carbon confined effect enables the composite to be stably cycled for over 10 000 cycles in the KOH electrolyte, either as a cathode or anode. As a result, the BSH device assembled using PCCT as both cathode and anode delivers high energy/power densities (33.7 W h kg⁻¹ at 0.8 kW kg⁻¹ or 16.7 W h kg⁻¹ at 12.0 kW kg⁻¹) with ultra-stable cycling performance (10 000 cycles at 2 A g⁻¹ with a capacity retention of 94.8%). This work demonstrates the stable reversible redox reaction of Te/Te(IV) in alkaline condition, and provides durable electrode (both cathode and anode) materials for high performance BSH systems.