Biotopologically structured composite materials for low temperature energy storage

Abstract

Conventional compositing methods for energy storage materials produce disconnected ion/electron channels, leading to low energy and power densities at low temperatures. This study leverages the advantages of seaweed cell walls with topologically ordered ion transport channels and natural doping with heteroatoms, to develop an energy-saving fabriation strategy based on electrodeposition. A biotopologically structured configuration is constructed by depositing NiCo layered double hydroxides (NiCo-LDH) array on seaweed derived porous carbon (SAC). Microstructure investigation indicates that the composite electrode (SAC/NiCo-LDH) presents an ordered structure and good two-phase interface with highly connected ion/electron transport channels. The SAC/NiCo-LDH electrode shows excellent performance with a specific capacitance of 1985 F g-1 at a current density of 1 A g-1 (76% capacitance retention at 10 A g-1), and cycle stability (80.7% capacitance retention after 10000 cycles), more than double those prepared by conventional hydrothermal method. Furthermore, by utilizing SAC/NiCo-LDH and SAC as positive and negative electrodes, respectively, a supercapacitor device delivers an energy density of 92.4 Wh kg-1 (power density of 0.8 kW kg-1) at room temperature, one order of magnitude higher than those of porous carbon-based devices. When using an aqueous gel electrolyte, the device exhibits an energy density of 43.7 Wh kg-1 even at a low temperature of -30 °C, which is far superior to most low-temperature supercapacitors. This work may inspire the materials design for energy storage in extreme environments.