Silicon nanoparticle loaded CaV4O9 microflowers for robust high capacity Li-ion Battery anodes

Abstract

Lithium-ion batteries are being constantly investigated so to enhance their properties like high energy density, rate performance and cycling stability. Calcium Vanadium Oxide (CVO) has been explored in this context since vanadium has the multi-electron transfer property which leads to higher stable capacity. Calcium oxide nanograins formed during a redox reaction buffers the volume change of electrodes. Silicon is another interesting option for anode material which provides higher capacity but within a few cycles, the capacity fades away, as it undergoes very high volume expansion and contraction in the discharge/charge cycles. The present study demonstrates that a physical mixture of CaV4O9 microflowers and Si nanoparticles (Si-NPs) synergistically acts to enhance the capacity as well as stability of the anode based upon such a mixture. The CaV4O9 microflowers were first synthesized by using the hydrothermal synthesis method. The prepared samples were characterized by scanning electron microscopy, powder X-ray diffraction and transmission electron microscopy. Anodes based upon CaV4O9, silicon nanoparticles (Si-NPs) and the CaV4O9/Si-NPs composites were then prepared and tested for their capacity and cycling stability. The Li-ion storage performance in pristine materials and the composites were analysed by Galvanostatic charge-discharge measurements, at a current density of 1 A g-1. The pristine CVO exhibits a stable specific capacity of 90 mAh g-1, the Si-NPs exhibit very high initial discharge capacity of 2398 mAh g-1, but it degrades after mere 50 cycles. The CVO-Si-NPs (80-20) composite shows a stable specific capacity of 450 mAh g-1, and the CVO-Si-NPs (50-50) composite shows very high and a stable specific capacity of 800 mAh g-1 up to 100 cycles, proving that the composite can be utilised as an efficient anode in Li ion battery.