Preparation of LiFePO4/Li3V2(PO4)3/C composite cathode materials and their electrochemical performance analysis

In this study, 9LiFePO(4)center dot Li3V2(PO4)(3)/C (LFVP-91/C) composite cathode materials (molar ratio of LiFePO4:Li3V2(PO4)(3) = 9:1) were prepared using a sol-gel (SG) technique and spray drying (SP) technique, followed by a calcination process at 650-750 degrees C for 10 h. Oxalic acid and citric acid were used as chelating agents, L-ascorbic acid (AA) was used as a reducing agent, and sucrose (SUC) was used as a carbon source. For improving the electrochemical properties of LFVP-91/C, different conductive carbon materials were used as carbon additives, including graphene oxide (GO), graphene nanosheet (GNS), and carbon nanotube (CNT). The experimental results show that the best discharge capacities of as-prepared SG-LFVP-91/C are approximately 151.1 mAh/g at 0.1C/0.1C, 115.2 mAh/g at 0.2C/5C, and 98.2 mAh/g at 0.2C/10C. The capacity retention after 100 cycles at 1C/1C is 84.0%. After addition of GO, the best discharge capacity retention increases to 91.66% after 100 cycles at 1C/1C. Moreover, after addition of GNS + CNT, the discharge capacity of SP-LFVP-91/C/GNS + CNT composite material increases to 160.1 mAh/g at 0.1C/0.1C, 129.3 mAh/g at 0.2C/5C, and 117.8 mAh/g at 0.2C/10C. No capacity fading is observed after 30 cycles at 0.1C/0.1C. The capacity retentions after 100 cycles and 500 cycles at 1C/1C increase to 97.58% and 85.26%, respectively. This study demonstrates that the prepared SP-LFVP-91/C/GNS + CNT composite cathode materials are excellent candidates for use in lithium-ion power batteries for electric vehicles. (C) 2020 Elsevier B.V. All rights reserved.