研究四氟硼酸锂(LiBF_4)和二氟草酸硼酸锂(LiODFB)混合锂盐电解液用于磷酸铁锂(LiFePO4)锂离子电池时的低温-20℃性能。探讨电导率与电解液组成、温度的关系;通过循环伏安、充放电、倍率性能及电化学阻抗谱(EIS)测试,比较不同电解液体系...研究四氟硼酸锂(LiBF_4)和二氟草酸硼酸锂(LiODFB)混合锂盐电解液用于磷酸铁锂(LiFePO4)锂离子电池时的低温-20℃性能。探讨电导率与电解液组成、温度的关系;通过循环伏安、充放电、倍率性能及电化学阻抗谱(EIS)测试,比较不同电解液体系中LiFePO_4正极在25℃和-20℃的放电比容量、循环稳定性等。在25℃和-20℃下于2.5~4.2 V充放电,LiFePO_4电极在LiBF_4/Li ODFB基电解液体系中的电化学性能较好:在25℃时以1.0 C倍率充放电,混合盐基电解液电池的首次放电比容量为140 m Ah/g,优于六氟磷酸锂(Li PF6)基电解液的130.5 m Ah/g;-20℃时0.1 C倍率下,首次放电比容量为101.7 m Ah/g,100次循环的容量保持率为86.62%,优于Li PF6基电解液的97.4 m Ah/g和60.57%。展开更多
Sulfurized polyacrylonitrile(SPAN)is proposed as a promising cathode material for lithium sulfur batteries.However,the continuous side reactions at the electrolyte-electrode interfaces as well as the slow redox kineti...Sulfurized polyacrylonitrile(SPAN)is proposed as a promising cathode material for lithium sulfur batteries.However,the continuous side reactions at the electrolyte-electrode interfaces as well as the slow redox kinetics of SPAN cathode deteriorate the electrochemical performance.In this study,an electrolyte with dual-additives comprising 2-fluoropyridine(2-FP)and lithium difluorobis(oxalato)phosphate(LiDFBOP)was used to improve the performance of Li||SPAN cells.2-FP has a lower lowest occupied molecular orbital energy than that of the solvents in the electrolyte,leading to its prior reduction.A LiF-rich film can be formed on the electrode,effectively improving the stability of the electrolyte-electrode interfaces and prolonging the life.Simultaneously,LiDFBOP could form an electrolyte-electrode interface film containing a large amount of Li_(x)PO_(y)F_(z) species,compensating for the kinetic deterioration caused by the lower ionic conductive of LiF formed at the electrolyte-electrode interface.Hence,an electrode-interface film with good chemical stability and high Li^(+) transport was established by LiF and Li_(x)PO_(y)F_(z)-rich species.The Li||SPAN cell with the electrolyte containing dual-additives demonstrates an excellent capacity retention of 97.5%after 200 cycles at 1.0 C,25℃,comparing to 56.2%capacity retention without additives.Moreover,the rate capacities of cells with dual-additives can reach 1128.1 mAh/g at 5 C,comparing to only 813.5 mAh/g using electrolyte without additives.Our results shown that the dual-additives in electrolyte provide a promising strategy for practical application of lithium sulfur batteries with SPAN cathodes.展开更多
文摘研究四氟硼酸锂(LiBF_4)和二氟草酸硼酸锂(LiODFB)混合锂盐电解液用于磷酸铁锂(LiFePO4)锂离子电池时的低温-20℃性能。探讨电导率与电解液组成、温度的关系;通过循环伏安、充放电、倍率性能及电化学阻抗谱(EIS)测试,比较不同电解液体系中LiFePO_4正极在25℃和-20℃的放电比容量、循环稳定性等。在25℃和-20℃下于2.5~4.2 V充放电,LiFePO_4电极在LiBF_4/Li ODFB基电解液体系中的电化学性能较好:在25℃时以1.0 C倍率充放电,混合盐基电解液电池的首次放电比容量为140 m Ah/g,优于六氟磷酸锂(Li PF6)基电解液的130.5 m Ah/g;-20℃时0.1 C倍率下,首次放电比容量为101.7 m Ah/g,100次循环的容量保持率为86.62%,优于Li PF6基电解液的97.4 m Ah/g和60.57%。
基金financial support from the National Natural Science Foundation of China(Nos.52072378,22209189)the National Key R&D Program of China(No.2022YFB3803400)+1 种基金the Strategic Priority Research Program of the Chinese Academy of Sciences(Nos.XDA22010602 and 2022YFB3803400)Shenyang Science and Technology Program(No.22-322-3-19)。
文摘Sulfurized polyacrylonitrile(SPAN)is proposed as a promising cathode material for lithium sulfur batteries.However,the continuous side reactions at the electrolyte-electrode interfaces as well as the slow redox kinetics of SPAN cathode deteriorate the electrochemical performance.In this study,an electrolyte with dual-additives comprising 2-fluoropyridine(2-FP)and lithium difluorobis(oxalato)phosphate(LiDFBOP)was used to improve the performance of Li||SPAN cells.2-FP has a lower lowest occupied molecular orbital energy than that of the solvents in the electrolyte,leading to its prior reduction.A LiF-rich film can be formed on the electrode,effectively improving the stability of the electrolyte-electrode interfaces and prolonging the life.Simultaneously,LiDFBOP could form an electrolyte-electrode interface film containing a large amount of Li_(x)PO_(y)F_(z) species,compensating for the kinetic deterioration caused by the lower ionic conductive of LiF formed at the electrolyte-electrode interface.Hence,an electrode-interface film with good chemical stability and high Li^(+) transport was established by LiF and Li_(x)PO_(y)F_(z)-rich species.The Li||SPAN cell with the electrolyte containing dual-additives demonstrates an excellent capacity retention of 97.5%after 200 cycles at 1.0 C,25℃,comparing to 56.2%capacity retention without additives.Moreover,the rate capacities of cells with dual-additives can reach 1128.1 mAh/g at 5 C,comparing to only 813.5 mAh/g using electrolyte without additives.Our results shown that the dual-additives in electrolyte provide a promising strategy for practical application of lithium sulfur batteries with SPAN cathodes.
