Combining ternary, ionic liquid-based, polymer electrolytes with a single-ion conducting polymer-based interlayer for lithium metal batteries

Abstract

Among the many approaches to improve the performance of lithium-metal batteries, ternary polyethylene oxide/ionic liquid/lithium salt electrolytes offer several advantages such as low flammability, high conductivity (vs. polyethylene oxide/lithium salt electrolytes) and, to a large extent, limiting the growth of dendrites at moderate currents. However, they suffer from relatively low mechanical strength for lithium metal confinement. Besides, the lithium transport numbers are very low, which is conducive to lithium depletion during plating at high current densities at the lithium/electrolyte interface. Thus, we show here that the combination of a ternary solid polymer electrolyte with a single-ion polymer-based conducting interlayer allows for a significant improvement of the cyclability of the lithium metal anode. This results in a strong improvement of the electrochemical performance of lithium-metal batteries using solid polymer electrolytes at 80 °C, with an 85% capacity retention after 350 cycles (vs. 60% after 62 cycles for the uncoated anode). This is attributed, via focused ion beam-scanning electron microscopy and X-ray photoelectron spectroscopy, to a denser lithium deposit, better contact with the electrolyte and a reduced reactivity of electrolyte species with the interlayer.