VPO4@C/graphene microsphere as a potential anode material for lithium-ion batteries

Abstract Three-dimensional PO 4 -based polyanionic structures composed of interconnected MO 6 octahedra and PO 4 tetrahedra, such as VPO 4 , are potential anode materials for Li-ion batteries given their excellent cyclic stability. However, the application of VPO 4 as an anode material has been limited by its low conductivity and drastic volume expansion. Herein, VPO 4 @C/graphene microspheres are designed and synthesised. P covalently bridges VPO 4 and graphene through P–C bonding and acts as a buffer layer to maintain structural stability during continuous charge–discharge cycling. Graphene and C improve the electrical conductivity of VPO 4 and reduce volume expansion during charge–discharge cycling. When applied as a Li-ion battery anode, the VPO 4 @C/graphene microspheres can achieve a specific capacity of 432.8 mA h g −1 after 100 cycles under the current densities of 100 mA g −1 . This performance is superior to that of commercial graphite. The VPO 4 @C/graphene microspheres provide a good rate performance with a capacity of 562.1, 494, 424.2 and 356 mAh g −1 under 200, 400, 1000 and 2, 000 mA g −1 , respectively. Furthermore, the VPO 4 @C/graphene microspheres achieve high tap density of > 1.2 g cm − 3 , which is higher than that of other nanomaterials ( −3 ) and is compatible with commercially available anode materials. Thus, VPO 4 @C/graphene microspheres are a promising anode material for Li-ion batteries.