Achieving Ultrahigh-Rate and High-Safety Li⁺ Storage Based on Interconnected Tunnel Structure in Micro-Size Niobium Tungsten Oxides.

Abstract

Developing advanced high-rate electrode materials has been a crucial aspect for next-generation lithium ion batteries (LIBs). A conventional nanoarchitecturing strategy is suggested to improve the rate performance of materials but inevitably brings about compromise in volumetric energy density, cost, safety, and so on. Here, micro-size Nb₁₄ W₃ O₄₄ is synthesized as a durable high-rate anode material based on a facile and scalable solution combustion method. Aberration-corrected scanning transmission electron microscopy reveals the existence of open and interconnected tunnels in the highly crystalline Nb₁₄ W₃ O₄₄ , which ensures facile Li⁺ diffusion even within micro-size particles. In situ high-energy synchrotron XRD and XANES combined with Raman spectroscopy and computational simulations clearly reveal a single-phase solid-solution reaction with reversible cationic redox process occurring in the NWO framework due to the low-barrier Li⁺ intercalation. Therefore, the micro-size Nb₁₄ W₃ O₄₄ exhibits durable and ultrahigh rate capability, i.e., ≈130 mAh g^-1 at 10 C, after 4000 cycles. Most importantly, the micro-size Nb₁₄ W₃ O₄₄ anode proves its highest practical applicability by the fabrication of a full cell incorporating with a high-safety LiFePO₄ cathode. Such a battery shows a long calendar life of over 1000 cycles and an enhanced thermal stability, which is superior than the current commercial anodes such as Li₄ Ti₅ O₁₂ .