Quasi-solid polymer-in-ceramic membrane for Li-ion batteries

•Novel composite polymer-in-ceramic membrane.•Conformal coating of electrode surface.•Improved electrochemical performance.

The method of electrophoretic deposition (EPD) was used to fabricate ion-conducting polymer-in-ceramic membranes. TGA, DSC, XRD, TOFSIMS, ESEM and AC-impedance tests were used for the characterization of the films. We found that the relative content of polyethylene oxide and LiAlO2 in the membrane depends on the type of solvent and composition of the suspension. Films deposited at 50 V are smoother, conformal and more uniform than those prepared at 100, 150 and 200 V. TOFSIMS positive-ion-species images showed that with increase in concentration of ceramic powder in the suspension, the deposition of PEO occurs predominantly between the LiAlO2 particles. The ionic conductivity of a composite membrane, with impregnated 0.3 M LiTFSI–PYR14TFSI ionic-liquid electrolyte is 1–3 mS/cm at 30–60 °C and comparable to that of commercial battery separators. The conductivity of quasi-solid plasticized PEO-in-LiAlO2 electrolyte is 0.2 mS/cm at room temperature and does not change up to 100 °C. When deposited on a Si anode the membrane conformally follows the contours of the rough electrode surface and provides strong mechanical integrity to the anode, enabling improved capacity of the Li/Si cell. This study paves the way for the application of a new simple EPD approach to the preparation of wide-temperature-range quasi-solid lithium-ion conducting electrolytes.