Exploration of Cr0.2Fe0.8Nb11O29 as an advanced anode material for lithium-ion batteries of electric vehicles

Abstract

The recently explored FeNb11O29 is an advanced anode material for lithium-ion batteries due to its large specific capacity and high safety. However, its poor electronic conductivity significantly limits its rate capability. To tackle this issue, a Cr3+ doping is employed, and CrxFe1-xNb11O29 (x=0 and 0.2) materials were fabricated using a solid-state reaction. X-ray diffraction analyses combined with Rietveld refinements demonstrate that the Cr3+ doping does not destroy the orthorhombic shear ReO3 crystal structure (Amma space group) of FeNb11O29 or obviously change the unit cell volume. Scanning electron microscopy images combined with specific surface area tests reveal the similar particle size after the Cr3+ doping. Due to the free 3d electrons in the Cr3+ ions, the electronic conductivity of Cr0.2Fe0.8Nb11O29 is enhanced by three orders of magnitude comparing with FeNb11O29. Consequently, Cr0.2Fe0.8Nb11O29 exhibits improved electrochemical properties. At 0.1C, it delivers a large reversible capacity of 254mAhg−1. At 10C, it still provides a large capacity of 123mAhg−1 with large retention of 86.9% after 500 cycles. In contrast, FeNb11O29 shows a small capacity of 57mAhg−1 and small retention of 41.6%. These results reveal that Cr0.2Fe0.8Nb11O29 can be a promising anode material for high-performance lithium-ion batteries.