超浓度水系电解液

   近日，University of Maryland的王春生课题组与U.S. Army Research Laboratory的许康课题组以及Huazhong University of Science and Technology的Miao Ling课题组合作在超浓度水系电解液方面取得新进展，相关成果以“Flexible Aqueous Li-Ion Battery with High Energy and Power Densities”发表在Advanced Materials上。水系锂离子电池具有高离子电导率、高安全性、价格低廉等优点，但其狭窄的电化学窗口却限制了其能量密度的高能化。超浓度电解液的出现使其能量密度从1.23V拓展到超过3.0V，为其高能密度的发展提供了可能。前期工作中用21mol/kgLiTFSI超浓度电解液（WiS）拓宽了电化学窗口到3.0V并使LiMn2O4/Mo6S8全电池的能量密度达到84Wh/kg；而以Tavorite型材料LiVPO4F作为正负极，WiS凝胶聚合物作为电解质(GPE)构建了柔性对称的FARLBs；该对称的LiVPO4F全电池还具有特别好的力学性能，且与GPE配合使用可获得非常优异的电化学性能；GPE中水与盐的强结合阻止了水分的蒸发，确保了全电池的正常工作，从材料水平上实现了真正柔性和安全的锂离子电池。

a) GITT characterization of LiVPO4F versus Ag/AgCl reference on both anode and cathode sides at 2 C. The potential has been converted to Li/Li+ reference. The specific capacities were evaluated by active material mass. b) Charge and discharge voltage profiles of LiVPO4F full cell at variousrates (right to left: discharging at 2, 20, 40, and 60 C). c) Capacity retentions and coulombic efficiency of LiVPO4F full cell at 20 C charge/discharge for 4000 cycles. The specific capacities were evaluated by total electrode mass. d) Ragone plot of LiVPO4F full cell (red stars) in comparison with representativereported aqueous Li-ion batteries and supercapacitors (cycles). All the gravimetric capacities and energy densities are based on the total weight of positive and negative electrodes including the active materials, carbon additives, and binders (electrolyte and cell packaging were not considered).

（林双双）