期刊
ACS APPLIED ENERGY MATERIALS
卷 3, 期 1, 页码 715-722出版社
AMER CHEMICAL SOC
DOI: 10.1021/acsaem.9b01909
关键词
lithium ion battery; Li3V2(PO4)(3); Li+ mobility; Ti4+ doping; lithium vacancy; SSNMR
资金
- National Natural Science Foundation of China (NSFC) [21673065, 21611130177, 21403045]
The electrochemical properties of Li3V2(PO4)(3) (LVP) cathode of lithium ion batteries are often improved by ion doping. Nevertheless, the mechanism of ion doping has not been fully understood. Here, Ti4+ has been chosen as a typical dopant with similar atomic radius to the sixcoordinated V3+. A series of Li3TixV(2-x)(PO4)(3)/C samples are successfully synthesized by a sol-gel route. The Li-7 MAS NMR spectra of the LTxVP/C demonstrate that the doping of Ti4+ can enhance the mobility of Li ions. The results of electrochemical properties tests show that moderate Ti4+ doping is able to improve the high rate capability of the materials by increasing the electronic conductivity and Li-ion diffusion coefficient. The optimal sample (LT0.08VP/C) exhibits the best cycling behavior and rate capability, which can deliver 110.85 mAh/g and capacity retention of 99.36% at 10 C after 100 cycles. Electrochemical impedance spectroscopy results indicate that LT0.08VP/C possesses the minimum charge transfer resistance. The calculation results of cyclic voltammetry illustrate that the Li-ion diffusion coefficient of LT0.08VP/C has been improved. By combining the information extracted from a series of electrochemical characterizations and NMR tests, a structural model of Li+ vacancy is proposed to explain the improving of Li+ mobility.
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