In this work, we developed simultaneously a new gel polymer electrolyte (GPE) material and a new battery design to reach both security (no leakage concern, no flammability, thermal stability) and application requirements (flexibility, thin system (<400µm)). We worked on a quaternary GPE based on a bi-components UV-curable polymer network giving the mechanical strength combined with a binary liquid phase composed of ionic liquid and Li salt. The GPE was optimized in terms of mechanical and electrochemical properties by varying the nature and the proportion of each components (polymer network, ionic liquid and Li salt) and the UV-curing parameters. The optimized GPE exhibits a good conductivity at room temperature (0.375mS.cm-1) and a Li+ transference number of 0.299 (NMR measurements) which is relatively high for this GPE type (Fig.a).
Our new battery design is composed of LiCoO2 cathode realized by standard coating processes. The liquid solution of GPE precursors is then deposited on the LiCoO2 cathode and directly polymerized by UV-curing (Fig.b). This step allows a good soaking of the electrolyte in the electrode pores. This system was then integrated in our thin battery design with Li metal foil as anode material (Fig.c). By optimizing each component dimension and sealing parameters (sealing conditions and adhesive type), we succeeded in producing a flexible, less than 400µm thick working battery (Fig.d) with interesting electrochemical performances (more than 2mAh.cm-2).
This work was done as part of the project EnSO. EnSO has been accepted for funding within the Electronic Components and Systems For European Leadership Joint Undertaking in collaboration with the European Union's H2020 Framework Programme (H2020/2014-2020) and National Authorities, under grant agreement n° 692482
