Regulating the local coordination model of homologous and heterogeneous niobium tungsten oxides toward ultrafast lithium storage

Abstract

Intercalation-type niobium tungsten oxide anodes show potential for use in high-power-density lithium-ion batteries (LIBs). Lithium activation barriers are vital factors determining the rate performance of niobium tungsten oxides. Lithium activation barriers located in the crystallographic shear plane are the highest in the entire block structure, as the rate-limiting factor for Li+ diffusion in the Wadsley–Roth crystallographic shear structure of niobium tungsten oxides. Nb(W)O6 octahedrons are distorted by introducing Nb18W8O69 (Nb18) into Nb16W5O55 (Nb16) to form heterogeneous composite structures. This distortion induces metal–oxygen bond lengthening in Nb16/Nb18, increasing the interspace between the edge-sharing octahedrons and thereby reducing the highest lithium activation barriers in the Nb16/Nb18 crystallographic shear plane and mitigating volume expansion. Nb16/Nb18 has an extraordinary rate capacity of 85 mA h g−1 at 100 C and structural stability with 86.3% capacity retention of its highest value at 100 C after 1000 cycles, with a high volumetric energy density of 647 W h L−1 at 134930 W L−1. Nb16/Nb18//LiCoO2 have a high energy density of 158 W h kg−1 at 12480 W kg−1. Thus, a new approach is proposed to improve the rate performance of niobium-based oxides with Wadsley–Roth crystallographic shear structure by employing homologous and heterogeneous composites.