Capacitance-Enhanced Battery: Integrating High-Density Battery Capacity with Supercapacitive Swiftness in an Ultra-Large MXene Architecture.

The rapid advancement of electrochemical energy storage based on earth-abundant sodium (Na) ions necessitates the seamless integration of high energy density and fast charge-discharge kinetics. A persistent challenge in this domain is the sluggish ion migration kinetics associated with the large ionic radii of Na ions, which significantly impact high-energy output applications, such as acceleration and climbing. Herein, a concept of Capacitance-Enhanced Battery (CEB) is proposed that leverages an ultra-large MXene framework interfaced with a BiS@ZnS composite(hereafter abbreviated as BiZnS) to form a C@BiZnS@VC heterostructure for reaching a dynamic dual-mechanism response. At low current densities, the system operates predominantly in a battery mode, wherein sodium-ion alloying and conversion reactions within the BiZnS framework ensure high energy retention. At high current densities, the heterostructure facilitates a supercapacitive mode, where active sites at the MXene and BiZnS surfaces and interfaces engage in rapid ion adsorption-desorption, enabling instantaneous energy delivery. This dual functionality imparts exceptional electrochemical performance of the Na-ion batteries, with a remarkable specific capacity of 270.4 mAh g at an ultra-high current density of 100 A g and extraordinary durability, maintaining outstanding electrochemical stability over 10 000 cycles at 20 A g. These findings underscore the transformative potential of CEBs and establish dual-mechanism electrodes for next-generation energy storage systems.