A Novel Quaternary Composite Solid State Electrolyte for Li Batteries

All-solid-state batteries continue to grow as an alternative to replace the traditional liquid-based ones not only because they provide increased safety but also higher power and energy density [1]. However, current solid-state electrolytes are either brittle (ceramics) or suffer low ionic conductivity at room temperature (polymers) [1]. Therefore, composite solid electrolytes are considered as a viable option. We have developed flexible and easy film-forming composite solid state electrolytes (CSEs). Our promising CSE is a quaternary composite that consists of the Solid polymer electrolyte (SPE) Poly(ethylene oxide)/ Lithium bis(trifluoromethanesulfonyl)imide (PEO/ LiTFSI), the fast conducting perovskite inorganic ceramic Li0.33La0.557TiO3 (LLTO) and the plasticizer Succinonitrile (SN). Over 40 samples with different (PEO/LiTFSI/LLTO/SN) compositions were prepared and characterized. The optimal mechanical and electrochemical properties was found for the sample 10S which has the following composition: 70%-PEO 12% LiTFSI 9%-LLTO 9%-SN. 10S had the ionic conductivity of ̴ 10-3 S/cm at 55 ̊ C and young’s modulus of around 105 MPa. The all-solid-state battery made by sandwiching 10S between a lithium metal anode and an NMC 532-based cathode achieved specific discharge capacities of 161 mAh/g at C/20. Pulsed-field gradient NMR was performed at different temperatures to measure the diffusion coefficient. The results have shown an Arrhenius-type dependence with a slope switch at around 55 ̊ C which is a similar behavior as the one observed in the Arrhenius plot obtained from conductivity measurements. Further investigation is underway to elucidate the conductivity mechanism in this new type of quaternary composite by advanced NMR and other techniques Reference [1] M. Keller, A. Varzi, S. Passerini, J. Power Sources 2018, 392, 206. Figure 1