电解液类型对双离子电池阴阳离子储存行为的影响

Effect of electrolyte types on the storage behaviors of anions and cations for dual-ion batteries

双离子电池是一种阴阳离子同时参与能量储存过程的新型电池,具有工作电压高、成本低、环境友好等优点。但正极高电压特性会引起电解液氧化分解。通过调节电解液浓度和溶剂组成系统地考察了电解液类型对PF-6嵌入行为的影响规律以及溶剂组成与负极稳定性之间的相容性关系。链状碳酸甲乙酯(EMC)溶剂促进PF-6在正极的嵌入过程,环状碳酸乙烯酯(EC)溶剂有利于负极稳定性。具有链状EMC和环状EC混合溶剂的1 mol·L^(-1)LiPF6-EC/EMC(3∶7,体积比)电解液更适用于双离子电池,以此作为电解液组装的石墨//软炭-双离子电池在580 W·kg^(-1)的功率密度下可提供98 W·h·kg^(-1)的能量密度,且在1 A·g-1电流密度下经1000圈循环后容量保持率为86.9%。

Dual-ion batteries(DIBs)have attracted extensive attention due to the virtues of high working voltage,low cost and environmental friendliness.However,the high voltage characteristics of the positive electrode will cause the electrolyte to oxidize and decompose.Since the electrolyte acts as the only source of active charge carriers,the electrochemical performance is limited by long-term decomposition and gas production of the electrolyte.We herein systematically investigate the effects of electrolyte concentration and types on the PF-6 intercalation behaviors and the compatibility between solvent composition and anodes by adjusting electrolyte concentration and solvent composition.The linear ethyl methyl carbonate(EMC)solvent is more favorable for the PF-6 to insert into the graphene layers than cyclic ethylene carbonate(EC)solvent.Moreover,EC solvent is the key component for the stability of anode.The mixed electrolyte of 1 mol·L^(-1)LiPF6-EC/EMC(3∶7,volume ratio)with the combination of linear EMC and cyclic EC is more applicable for DIBs,and the graphite//soft carbon DIB configuration assembled by the above electrolyte can provide an energy density of 98 W·h·kg^(-1)at a power density of 580 W·kg^(-1)with a capacity retention rate of 86.9%after 1000 cycles at 1 A·g^(-1).