Dan Sun,Rongting Guo,Yiju Lv,Wei Li,Mingjun Lu,Qiumei Wei,Zheng Liu,Guo-Cheng Han
Na 2 MnPO 4 F and Ti 3 C 2 ‑carbon quantum dots (CQDs) nanocomposites were prepared by wet mixing method combined with spray drying method, and the two materials were further compounded by heat treatment to get different ratios of Na 2 MnPO 4 F/Ti 3 C 2 -CQDs cathode material (NTC), the effects of Ti 3 C 2 -CQDs on the structure and electrochemical performance of the composite of Na 2 MnPO 4 F as a lithium-ion battery cathode material were investigated. The results showed that Na 2 MnPO 4 F was uniformly attached to the surface and between layers of Ti 3 C 2 -CQDs. The initial specific discharge capacity of NTC-2 at 0.1C was 67.8 mAh·g −1 , and the reversible capacity after 100 cycles was 60.7 mAh·g −1 , the capacity retention rate was as high as 90%, which all showed that Ti 3 C 2 -CQDs can enhance the cycle performance, rate performance and capacity retention rate of Na 2 MnPO 4 F. It also showed good rate performance under high current density . After the high current test, the current returned to 0.1C, and the capacity can be restored to the original value, which showed that the material has good structural stability. Therefore, Ti 3 C 2 -CQDs doped Na 2 MnPO 4 F is an important way to improve the electrochemical performance of polyanionic compounds.
Li Wei,Ai Huiting,Liu Zheng,Wei Chuchu,Han Guo-Cheng,Zhan Ling
In order to improve the electrochemical properties of Na 2 MnPO 4 F (NMPF), low-cost biomass cane bagasse was used as a carbon source for coating, Na 3 V 2 (PO 4 ) 2 F 3 (NVPF) was used as a doped phase to prepare different ratios of xNa 3 V 2 (PO 4 ) 2 F 3 ·(1-x)Na 2 MnPO 4 F@C (NVPF/NMPF@C) composite materials via a sol–gel method. The results including analysis of XRD, SEM, EDS, and XPS methods showed that NVPF/NMPF@C (x = 0.2) composite material had good crystallinity, and NVPF can be uniformly doped in NMPF@C. The rate performance of NVPF/NMPF@C composite was tested at 0.1, 0.2, 0.5, 1, and 2 C. The first discharge specific capacity of NVPF/NMPF@C composite electrode material reached 193 mAh/g and increased by approximately 20 times when compared to only 9 mAh/g of NMPF@C. The coulombic efficiency of NVPF/NMPF@C material remained 95% after 35 cycles at 0.1 C. The introduction of NVPF can improve charge transfer and Li + diffusion, and enhance the electrochemical behavior of the lithium-ion battery cathodes.
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