Lithium Storage in Microstructures of Amorphous Mixed‐Valence Vanadium Oxide as Anode Materials

Constructing three‐dimensional (3 D) nanostructures with excellent structural stability is an important approach for realizing high‐rate capability and a high capacity of the electrode materials in lithium‐ion batteries (LIBs). Herein, we report the synthesis of hydrangea‐like amorphous mixed‐valence VO x microspheres ( a ‐VO x MSs) through a facile solvothermal method followed by controlled calcination. The resultant hydrangea‐like a ‐VO x MSs are composed of intercrossed nanosheets and, thus, construct a 3 D network structure. Upon evaluation as an anode material for LIBs, the a ‐VO x MSs show excellent lithium‐storage performance in terms of high capacity, good rate capability, and long‐term stability upon extended cycling. Specifically, they exhibit very stable cycling behavior with a highly reversible capacity of 1050 mA h g −1 at a rate of 0.1 A g −1 after 140 cycles. They also show excellent rate capability, with a capacity of 390 mA h g −1 at a rate as high as 10 A g −1 . Detailed investigations on the morphological and structural changes of the a ‐VO x MSs upon cycling demonstrated that the a ‐VO x MSs went through modification of the local VO coordinations accompanied with the formation of a higher oxidation state of V, but still with an amorphous state throughout the whole discharge/charge process. Moreover, the a ‐VO x MSs can buffer huge volumetric changes during the insertion/extraction process, and at the same time they remain intact even after 200 cycles of the charge/discharge process. Thus, these microspheres may be a promising anode material for LIBs.