Binder-free fabricated transparent Nb4+ implanted Nb2O5-x ultra-thin negatrode with enhanced areal capacitance and exceptional cyclic stability in aqueous electrolyte

Direct coating and surface engineering of Nb2O5-based active storage materials are important techniques for improving their interfacial interactions with the current collector and electrolyte ions, which have been difficult to achieve in a facile and energy-efficient way. Herein, we report the binder-free coating of shear-structured Nb4+ implanted Nb2O5 (Nb2O5-x) sub-micron thin pseudocapacitive negatrode with wide negative operating voltage (−1.20 V vs Ag/AgCl), improved electronic and ionic conductivity, reduced charge transfer resistance and enhanced energy storage capacity. The Nb4+ implanted electrode exhibits 3.5 mF/cm2 c. a. At 5 mV/s and 100% capacity retention after 3000 constant charge-discharge cycles. The unique electrode was realized via mild de-oxidation of electrodeposited Nb2O5 in a vacuum-less, low-temperature surface engineering process. This simple strategy is suitable for improving current collector-Nb2O5-x-electrolyte interfacial interactions and for industrial-scale production of improved pseudocapacitive negatrodes. [Display omitted] •Binder-free coating of sub-micron thin Nb2O5-x pseudocapacitive electrode.•Implantation of Nb4+ into electrochemically deposited Nb2O5 with an oxygen scavenger.•Microstructural analysis of Nb2O5-x revealed a mixture of O–Nb12O29 and T-Nb2O5 phases.•Nb2O5-x showed improved charge storage capacity and remarkable cyclic stability which did not diminish over 3000 cycles.