Flexible thin-film battery based on solid-like ionic liquid-polymer electrolyte

• Solid-like gel polymer electrolyte was fabricated containing 60 wt% ionic liquid.
• The incorporation of nonvolatile ionic liquid offers enhanced safety and stability.
• A low-cost, scalable lamination method was employed to fabricate flexible LIBs.
• The flexible LIB could deliver a stable capacity in flat and bent configurations.

The development of high-performance flexible batteries is imperative for several contemporary applications including flexible electronics, wearable sensors and implantable medical devices. However, traditional organic liquid-based electrolytes are not ideal for flexible batteries due to their inherent safety and stability issues. In this study, a non-volatile, non-flammable and safe ionic liquid (IL)-based polymer electrolyte film with solid-like feature is fabricated and incorporated in a flexible lithium ion battery. The ionic liquid is 1-Ethyl-3-methylimidazolium dicyanamide (EMIMDCA) and the polymer is composed of poly(vinylidene fluoride-co-hexafluoropropene) (PVDF-HFP). The electrolyte exhibits good thermal stability (i.e. no weight loss up to 300 °C) and relatively high ionic conductivity (6 × 10−4 S cm−1). The flexible thin-film lithium ion battery based on solid-like electrolyte film is encapsulated using a thermal-lamination process and demonstrates excellent electrochemical performance, in both flat and bent configurations.

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