锂电池用全固态聚合物电解质的研究进展

All-solid-state lithium-ion batteries based on polymer electrolytes:State of the art, challenges and future trends

目前大规模商业化的锂二次电池普遍采用有机碳酸酯类的液态电解质,易泄露、易燃烧、易爆炸等安全问题限制了该类电解质的进一步应用。全固态聚合物电解质(all-solid-state polymer electrolytes,ASPEs)电池具有安全性能好、能量密度高、工作温度区间广、循环寿命长等优点,是锂离子电池领域的研究热点之一。ASPEs通常还具有优异的力学性能,可以很好地抑制锂金属电极在充放电过程中的枝晶生长,所以在锂金属电池领域也具有十分重要的应用前景。作者综述了研究较多的几种ASPEs体系,包括聚氧化乙烯(PEO)基体系、聚碳酸酯基体系、聚硅氧烷基体系、聚合物锂单离子导体体系。PEO基ASPEs是研究最早且研究最多的一类ASPEs材料,但其高结晶性造成室温Li+迁移困难、离子电导率低等问题,所以研究人员研发了一系列降低PEO结晶度、提升体系离子电导率的改性手段。聚碳酸酯基ASPEs主链结构中含有强极性碳酸酯基团而且室温无定形态,使得锂盐更容易解离,且室温离子电导率一般较PEO基要高,是比较有潜力的PEO基ASPEs替代材料。除了碳链聚合物,玻璃化转变温度较低的聚硅氧烷基ASPEs体系也因为其较高的离子电导率受到研究人员关注。在锂电池充放电过程中,Li+才是有效载荷子,电解质中阴离子的迁移会增加电解质体系的浓差极化,所以阴离子不发生迁移、Li+迁移数接近于1的聚合物锂单离子导体也是一类具有研究价值的ASPEs材料。最后,本综述讨论了全固态聚合物电解质的应用前景及未来发展方向,指出了PEO基体系的研究重点在于发展有机-无机复合体系、聚碳酸酯基体系的研究重点在于发展与其它聚合物的共混体系、聚硅氧烷基体系的研究重点在于增强体系力学性能、聚合物锂单离子导体体系的研究重点在于设计离子电导率更高的新型聚阴离子锂盐。

The traditional rechargeable lithium batteries commonly used a large amount of non-aqueous liquid electrolytes leading to inherent hazards of leakages and fire. All-solid-state polymer electrolytes （ASPEs） attract intensive interests due to their unique properties, such as high safety characteristics, wide operating temperature range and long cycle life. They are expected to be the next generation of commercialized electrolytes in the field of lithium-ion battery. The dendritic growth of lithium metal electrode can also be well suppressed in the process of charging and discharging by ASPEs, because ASPEs usually have excellent mechanical properties. This review presents a brief overview of recent progress in ASPEs based on polyethylene oxide（PEO）, polycarbonate, polysiloxane and single lithium-ion conductor. PEO is the first class of ASPEs that are researched extensively, whose high crystallinity give rise to the difficult migration of Li~ and low ion conductivity. Aimed at the issue of crystallinity, researchers have exploited plenty of modifications to lower polymer chains＇ crystallinity and improve the conductivity of PEO. Lithium salts are easily dissolved in polycarbonates and resulted polymer electrolyte has higher ion conductivity than PEO because of its strongly polar carbonate groupand amorphous state at room temperature, which may be alternative materials of PEO potentially. Besides the carbon-chain polymers, polysiloxane with low glass transition temperature attracts widespread concerns from researchers because of its high conductivity. In addition, migration of anions will only exacerbate concentration polarization of electrolytes in the charge-discharge process, so single lithium-ion conductors without anions＇ migration are also worth to exploiting. Finally, the challenges and future trends towards high energy and all-solid-state polymer electrolytes batteries are also commented. PEO should be developed with the organic-inorganic composite system, polycarbonate should be developed with the blend system, polysiloxane should be enhanced with strong mechanical properties, single lithium-ion conductor should be designed with the new polyanion lithium salt that has higher conductivity.