Dual Strategies of Na+ Electrolyte Additives and Dendrites Protective Ti3C2TX-MXene/Zn Anode with 2D MXene Nanosheet Encased Niobium Pyrophosphate (NbP2O7) Composite Binder-Free Cathode for Stable Zinc-Ion Storage

Abstract

Zinc-ion capacitors (ZICs) are promising next-generation energy storage systems (ESS) owing to high safety, material abundance, environmental friendliness, and low cost; however, the energy density of ZICs must be improved to compete with lithium-ion batteries (LIBs). Here, the study implements three strategies to enhance the electrochemical performance and manage dendritic growth on Zn anodes, including crafting a highly efficient redox electroactive niobium pyrophosphate (NbP2O7)/Ti3C2TX-MXene binder-free cathode, incorporating a NaClO4 additive electrolyte, and applying a protective Ti3C2TX-MXene layer on Zn anode. The cathode facilitates rapid Zn2+ ion diffusion and a stable host structure. An electrostatic protection layer formed in additive electrolyte and MXene layers regulates the uniform distribution of the electric fields and supports the equalization of nucleation sites. These results are supported by density functional theory (DFT) calculations. The ZICs display an excellent specific capacitance (113.3 F g−1 at 1.5 A g−1) in aqueous additive electrolytes. The flexible solid-state ZICs exhibits a volumetric capacitance of 865.05 mF cm−3, and an energy density of 0.347 mWh cm−3 at 2.29 mW cm−3 along with capacitance retention of >100% over 38 000 charge-discharge cycles.