An asymmetric capacitor of internal parallel hybrid electrodes with amphoteric lithium vanadium phosphate

作者：Liao Ying Chen; Tsai Dah Shyang; Huang Yu Sheng; Lu Tai Yu

来源：Journal of Solid State Electrochemistry, 2017, 21(3): 839-847.

DOI：10.1007/s10008-016-3435-9

• Asymmetric capacitor
• Lithium vanadium phosphate
• Internal parallel hybridization
• Prelithiation
• Mass balancing
• Activated carbon

Given that the amphoteric Li3V2(PO4)(3) (LVP) crystal exhibits different capacities in the high and low potential regions, we study its asymmetric capacitor and the mass balancing. Both the positive and the negative electrodes are prepared with 50 wt.% LVP balanced by activated carbon which provide battery and double-layer storage mechanisms; respectively. To retain the capacitor power feature with a sizable capacity, a proper internal hybridization is required to keep the battery mechanism functioning at high-rate cycling. The involvement of battery storage is assured if a high-voltage bulge is observed on the galvanostatic discharge curve. To preserve such a feature, the capacitor analysis indicates three factors are vital. A voltage window is wide enough, 4.0 V, such that the plateau of LVP around 3.6 V (vs. Li/Li+) may operate in discharging the positive electrode. The negative electrode is prelithiated to pin down the negative potential and allow the cell to utilize the permissible potential A proper mass ratio 2(+):1(-) provides sufficient but not too much battery storage in the positive electrode. Among the five mass ratios being studied, the 2(+):1(-) capacitor shows a respectable combination of specific energy 43 W h kg(-1) and power 520 W kg(-1) at 0.2 A g(-1), with over 80 % capacity retention in 200 cycles.

• 出版日期2017-3