Nanoporous carbon leading to the high performance of a Na3V2O2(PO4)2F@carbon/graphene cathode in a sodium ion battery

The Na3V2O2(PO4)(2)F/graphene sandwich cathode has attracted great attention as a potential candidate for sodium-ion batteries in view of its high capacity and good cycling ability. However, a big issue for Na3V2O2(PO4) 2F/graphene is its extremely poor electronic conductivity due to the multilayer structure in which Na3V2O2(PO4)(2)F particles are located between the graphene layers. We introduced carbon in the Na3V2O2(PO4)(2)F/graphene sandwich to form a 3D architecture - Na3V2O2(PO4)(2)F@carbon/graphene (NVPF@C/G). A battery with the NVPF@C/G cathode presents good electrochemical properties, a high capacity, 135.8 mAh g(-1) at 0.1C, with a capacity retention of 96.8% at 2C for fifty cycles. NVPF@C/G showed obvious advantage in the rate performance and cycle stability compared with the NVPF/G sandwich, which indicated that the nanoporous carbon integrated in the 3D structure plays a crucial role in improving the electrochemical performance. It is anticipated that such a new method of introducing nanoporous carbon for battery performance enhancement can be extended to other graphene-based sandwich structure electrodes.