Liquid electrolytes currently used in lithium-ion batteries have critical drawbacks such as high flammability, high reactivity toward electrode materials, and solvent leakage. To overcome these issues, most recent research has focused on synthesis and characterization of highly conductive gel-type polymer electrolytes containing large numbers of organic solvents in the polymer matrix. There are still many hurdles to overcome, however, before they can be applied to commercial-level lithium-ion batteries. Since a large amount of organic solvent is required to achieve high ionic conductivity, battery safety is not significantly enhanced. In our study, we synthesized highly conductive quasi-solid-state electrolytes (QSEs) containing an ionically conductive oligomer (polycaprolactone triacrylate) and a small amount of organic solvent by employing click chemistry. In the QSE, polycaprolactone participates in dissociation of lithium salt and migration of lithium ions, resulting in high ionic conductivity. The Li/ LiNi 0.6 Co 0.2 Mn 0.2 O 2 cell that used this QSE exhibited good cycling performance and enhanced thermal stability, and durability; no organic solvent leakage was observed even under high pressure.

Lithium-ion batteries (LIBs) have been dominant power sources for various applications such as mobile electronic devices, electric vehicles and energy storage systems. However, liquid electrolyte currently used in LIBs has critical drawbacks such as high flammability and leakage problem. In this regard, various electrolyte systems have been studied to replace liquid electrolyte for enhancing the battery safety while maintaining the battery performance. Among them, the chemically cross-linked gel polymer electrolytes can enhance the thermal safety of LIBs by encapsulating organic solvent in the polymer matrix. However, they usually contain a large amount of organic solvents to achieve high ionic conductivity, and side reactions may occur during the cross-linking reaction. To overcome these problems, quasi-solid-state electrolytes are synthesized through thiol-ene click reaction, since the click reaction avoids side reactions and drives fast cross-linking under mild reaction conditions. The quasi-solid-state electrolyte was applied to the lithium-ion cell composed of graphite anode and LiNi0.6Co0.2Mn0.2O2 cathode. The cell employing quasi-solid-state electrolyte exhibited the enhanced safety compared with the liquid electrolyte-based cell and better cycling performance than all-solid-state lithium batteries at ambient temperature. Our result demonstrate that the quasi-solid-state polymer electrolytes are very promising electrolytes for achieving high performance and enhancing battery safety.

Lithium-ion batteries (LIBs) have been actively developed and are being used nowadays in various applications. However, liquid electrolyte currently used in LIBs has critical drawbacks such as flammability and leakage problem. To enhance the safety of LIBs, intensive efforts have been devoted to replace liquid electrolyte to safer electrolytes. Among the various promising electrolyte systems, solid polymer electrolytes have received great attention due to enhanced safety, absence of leakage and design flexibility. However, their low ionic conductivities preclude their practical applications at ambient temperatures. Accordingly, most relevant research has focused on the preparation and characterization of plasticized polymer electrolytes that contain small amount of organic solvent. In this work, we report the preparation and electrochemical characteristics of quasi-solid-state polymer electrolytes synthesized from ion-conductive poly(propylene carbonate) (PPC), which were in-situ cross-linked in the presence of small amount of plasticizing solvent by click chemistry. The polymer electrolyte was applied to the lithium polymer cell composed a lithium anode and a LiNi0.6Co0.2Mn0.2O2 cathode. Our result demonstrate that the quasi-solid-state polymer electrolytes are very promising electrolytes for achieving high performance and enhancing battery safety.