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

The recently explored FeNb 11 O 29 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 Cr 3+ doping is employed, and Cr x Fe 1- x Nb 11 O 29 ( x   =   0 and 0.2) materials were fabricated using a solid-state reaction. X-ray diffraction analyses combined with Rietveld refinements demonstrate that the Cr 3+ doping does not destroy the orthorhombic shear ReO 3 crystal structure ( Amma space group) of FeNb 11 O 29 or obviously change the unit cell volume. Scanning electron microscopy images combined with specific surface area tests reveal the similar particle size after the Cr 3+ doping. Due to the free 3 d electrons in the Cr 3+ ions, the electronic conductivity of Cr 0.2 Fe 0.8 Nb 11 O 29 is enhanced by three orders of magnitude comparing with FeNb 11 O 29 . Consequently, Cr 0.2 Fe 0.8 Nb 11 O 29 exhibits improved electrochemical properties. At 0.1C, it delivers a large reversible capacity of 254   mAh   g −1 . At 10C, it still provides a large capacity of 123   mAh   g −1 with large retention of 86.9% after 500 cycles. In contrast, FeNb 11 O 29 shows a small capacity of 57   mAh   g −1 and small retention of 41.6%. These results reveal that Cr 0.2 Fe 0.8 Nb 11 O 29 can be a promising anode material for high-performance lithium-ion batteries.