Design of a niobium tungsten oxide/C micro-structured electrode for fast charging lithium-ion batteries

Abstract

Maximum energy storage in minimum charging time is increasingly important to evaluate the performance of lithium ion batteries (LIBs). High rate electrode materials require high ion and electron transport ability. Niobium tungsten oxides as emerging materials are employed as anodes for LIBs and show desirable rate performance owing to their high Li⁺ diffusion coefficients. However, most studies focus on the preparation and performance of niobium tungsten oxides at the nanoscale while electrode materials in micro grade result in high tap density and smaller electrode thickness with a shorter electron pathway under the same mass loading. Herein, Nb₁₈W₁₆O₉₃/C spheres in micro grade with a carbon layer coating on Nb₁₈W₁₆O₉₃ nanograins are synthesized via a facile solvothermal method. Owing to the enhanced electronic conductivity and protection of structural integrity by the carbon layer, the Nb₁₈W₁₆O₉₃/C anode exhibits excellent rate performance with 182.8 mA h g⁻¹ at a high rate of 5C with a capacity retention of 81% (based on 225.7 mA h g⁻¹ at 0.2C). In addition, superior cycling stability is shown with a capacity retention of 85.6% at 1C after 100 cycles and 68% at 5C after 300 cycles. This stable anode material with advanced rate capability shows huge competitiveness as a candidate for fast charging materials of LIBs.