Defect‐Concentration‐Mediated T‐Nb2O5 Anodes for Durable and Fast‐Charging Li‐Ion Batteries

Abstract

AbstractMetastable orthorhombic niobium pentoxide (T‐Nb2O5) is a promising anode to fulfill the requirements for high‐rate Li‐ion batteries (LIBs). Stoichiometric T‐Nb2O5 is plagued by low electric conductivity and particle pulverization after repeated charge/discharge processes. In this work, oxygen vacancies are implanted into T‐Nb2O5 particles via acid immersion of Nb2O5·nH2O with the formation of Lewis acid sites. The multiple characterizations and simulations reveal the lengthening of NbO bonds, and the transformation from NbO7 pentagonal bipyramids and NbO6 tetragonal bipyramids in T‐Nb2O5−x. The enrichment of oxygen vacancies endows T‐Nb2O5−x with higher electric conductivity, better electrochemical kinetics, larger pseudocapacitive contribution. O‐doped graphitic C3N4 is creatively proposed as a trace oxygen pump to repair excessive oxygen vacancies, and it also serves as a sacrifice template for Nb2O5−x growth to construct a porous and monolithic electrode network. Defect‐modulated Nb2O5−x displays extraordinary cycling stability (164 mAh g−1 at 5 C after 1100 cycles), high capacity retention (104 mAh g−1) at an ultrahigh rate (25 C), and large areal capacity (0.74 mAh cm−2) under high mass loading (4 mg cm−2). The practical prospect is proved by Nb2O5−x/LiNi0.8Co0.1Mn0.1O2 full cells with high average platform (2.12 V) and high specific capacity (229 mAh g−1). The oxygen‐defect modulation strategy on oxide anodes provides an alternative solution to fast‐charging and durable LIBs.