LiBF_4/LiODFB混合盐电解液的低温性能
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摘要
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%。
The low temperature-20 ℃ performance of electrolyte based on blend salts lithium tetrafluoroborate( LiBF_4) and lithium difluoro( oxalato) borate( Li ODFB) for lithium iron phosphate( LiFePO_4) Li-ion battery was studied. The relation between electric conductivity and electrolyte composition,temperature was discussed. Through the tests of cyclic voltammetry,charge-discharge,rate capability and electrochemical impedance spectroscopy( EIS),the specific discharge capacity and cycle stability of LiFePO_4 cathode in different electrolyte systems were compared at 25 ℃ and-20 ℃. The blend salts LiBF_4/Li ODFB based electrolyte had better electrochemical performance at 25 ℃ and-20 ℃. The battery with blend salts-based electrolyte was charged-discharged with 1. 0 C at25 ℃ and 0. 1 C at-20 ℃. The initial discharge capacity was 140 m Ah/g,which was higher than 130. 5 m Ah/g of lithium hexafluorophosphate( Li PF6)-based electrolyte at 25 ℃. The initial discharge capacity was 101. 7 m Ah/g and capacity retention was86. 62% after 100 cycles at-20 ℃,which was better than that of Li PF6 based electrolyte 97. 4 m Ah/g and 60. 57%.
The low temperature-20 ℃ performance of electrolyte based on blend salts lithium tetrafluoroborate( LiBF_4) and lithium difluoro( oxalato) borate( Li ODFB) for lithium iron phosphate( LiFePO_4) Li-ion battery was studied. The relation between electric conductivity and electrolyte composition,temperature was discussed. Through the tests of cyclic voltammetry,charge-discharge,rate capability and electrochemical impedance spectroscopy( EIS),the specific discharge capacity and cycle stability of LiFePO_4 cathode in different electrolyte systems were compared at 25 ℃ and-20 ℃. The blend salts LiBF_4/Li ODFB based electrolyte had better electrochemical performance at 25 ℃ and-20 ℃. The battery with blend salts-based electrolyte was charged-discharged with 1. 0 C at25 ℃ and 0. 1 C at-20 ℃. The initial discharge capacity was 140 m Ah/g,which was higher than 130. 5 m Ah/g of lithium hexafluorophosphate( Li PF6)-based electrolyte at 25 ℃. The initial discharge capacity was 101. 7 m Ah/g and capacity retention was86. 62% after 100 cycles at-20 ℃,which was better than that of Li PF6 based electrolyte 97. 4 m Ah/g and 60. 57%.
引文
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