Vascular System Inspired 3D Electrolyte Network for High Rate and High Mass Loading Graphene Supercapacitor

High charge rate and high mass loading ability are of practical importance for high power and high volumetric performance supercapacitors but are always challenged by tortuous and sluggish ion diffusion in thick electrodes. Here, inspired by the hepatic vascular system, hierarchical 3D electrolyte networks are proposed to facilitate ion diffusion across laminar graphene films, resulting in a 14-fold improved ion diffusion coefficient, better rate ability, and high mass loading ability for graphene supercapacitors. Such design enables graphene electrodes with high capacitance up to 236 F g-1, packing densities of 0.67-0.78 g cm-3 depending on structures; and core stack with 10 mg cm-2 mass loading exhibits a high energy density of 45.4 Wh L-1, which is among the state-of-the-art graphene supercapacitors. This study provides a comprehensive investigation of structure-related capacitive properties, guiding electrode design for high-rate and high-mass-loading graphene supercapacitors. Moreover, such design also benefits solid-state graphene supercapacitors by forming 3D gel electrolyte structures, which enable higher capacitance and better mechanical robustness, showing potential for flexible energy storage. Tortuous ion diffusion always restricts the high power and high mass loading ability of graphene supercapacitors, which are both critical to practical applications. Here, bioinspired 3D electrolyte networks are proposed to facilitate ion diffusion in laminar graphene while maintaining high packing densities. 14-fold improved ion diffusion coefficient and high capacitance of 236 F g-1 are achieved with this rational design. image