Formation of a Surficial Bifunctional Nanolayer on Nb2 O5 for Ultrastable Electrodes for Lithium-Ion Battery

Abstract

Safe and long cycle life electrode materials for lithium-ion batteries are significantly important to meet the increasing demands of rechargeable batteries. Niobium pentoxide (Nb₂ O₅ ) is one of the highly promising candidates for stable electrodes due to its safety and minimal volume expansion. Nevertheless, pulverization and low conductivity of Nb₂ O₅ have remained as inherent challenges for its practical use as viable electrodes. A highly facile method is proposed to improve the overall cycle retention of Nb₂ O₅ microparticles by ammonia (NH₃ ) gas-driven nitridation. After nitridation, an ultrathin surficial layer (2 nm) is formed on the Nb₂ O₅ , acting as a bifunctional nanolayer that allows facile lithium (Li)-ion transport (10-100 times higher Li diffusivity compared with pristine Nb₂ O₅ microparticles) and further prevents the pulverization of Nb₂ O₅ . With the subsequent decoration of silver (Ag) nanoparticles (NPs), the low electric conductivity of nitridated Nb₂ O₅ is also significantly improved. Cycle retention is greatly improved for nitridated Nb₂ O₅ (96.7%) compared with Nb₂ O₅ (64.7%) for 500 cycles. Ag-decorated, nitridated Nb₂ O₅ microparticles and nitridated Nb₂ O₅ microparticles exhibit ultrastable cycling for 3000 cycles at high current density (3000 mA g^-1 ), which highlights the importance of the surficial nanolayer in improving overall electrochemical performances, in addition to conductive NPs.

Keywords: Nb2O5; electrodes; lithium; nitridation; surficial bifunctional nanolayers.