混合盐电解液对锂离子电容器性能的影响

Influence of blend salt electrolyte on the performance of Li-ion capacitors

优化电解液配方可提高锂离子电容器的性能。以六氟磷酸锂(LiPF_(6))和离子导电性好、热稳定性高的双(三氟甲基磺酰)亚胺锂(LiTFSI)为溶质,碳酸乙烯酯(EC)/碳酸二甲酯(DMC)/碳酸甲乙酯(EMC)(体积比1∶1∶1)为溶剂,配制锂离子电容器电解液。调控LiTFSI的添加量,研究LiPF_(6)和LiTFSI混合盐电解液对镍钴锰酸锂(LiNi_(0.5)Co_(0.3)Mn_(0.2)O_(2))+活性炭(AC)/硬碳(HC)锂离子电容器性能的影响。通过循环伏安、线性伏安、交流阻抗和充放电等测试,比较各电解液体系中锂离子电容器的比容量、循环稳定性等性能。与LiPF_(6)电解液相比,LiTFSI的加入可提高电解液的导电性和电压窗口,改善器件的容量发挥和循环稳定性。当LiTFSI添加量为0.2 mol/L时,锂离子电容器的比能量和比功率最高,以5.0 C倍率在2.5~4.0 V循环5000次后,容量保持率达91.3%。

The performance of Li-ion capacitors could be enhanced by optimizing the electrolyte formula.The electrolyte of Li-ion capacitors was prepared with lithium hexafluorophosphate(LiPF_(6))and lithium bis(trifluoroethane sulfonylimide)(LiTFSI)with good ionic conductivity and high thermal stability as solutes and ethylene carbonate(EC)/dimethyl carbonate(DMC)/methyl ethyl carbonate(EMC)(volume ratio 1∶1∶1)as solvent.By adjusting the addition of LiTFSI,the influence of electrolyte based on blend salts of the LiPF_(6)and LiTFSI for lithium nickel cobalt manganese oxide(LiNi_(0.5)Co_(0.3)Mn_(0.2)O_(2))+activated carbon(AC)/hard carbon(HC)Li-ion capacitors was studied.Through the tests of cyclic voltammetry,linear voltammetry,AC impedance and charge-discharge,the specific capacity and cycle stability of Li-ion capacitors in different electrolyte systems were compared.The addition of LiTFSI could increase the conductivity and voltage window of the electrolyte,the capacity utilization and cycle stability of device were improved compared with LiPF_(6)electrolyte.When the addition of LiTFSI was 0.2 mol/L,the specific energy and specific power of the Li-ion capacitor was the highest.After 5000 cycles in 2.5-4.0 V at 5.0 C rate,the capacity retention rate was 91.3%.