Scalable plasticized polymer electrolytes reinforced with surface-modified sepiolite fillers – A feasibility study in lithium metal polymer batteries

• Polymers having high RT conductivity of the order of 10−4 S/cm.
• Electrochemical stability of 4.5 V at 70 °C with good mechanical stability.
• Remarkable lithium plating/stripping characteristics with dendrite suppression.
• Good cycling capabilities for LiFePO4 based Li metal polymer batteries.
• Easily upscalable Polymer electrolytes.

Electrochemical properties of (polyethylene oxide) (PEO)/lithium trifluoromethanesulfonate (LiTf)/ethylene carbonate (EC)/sepiolite extruded composite electrolytes were studied. Appreciable electrochemical stability of 4.5 V at 70 °C was observed for polymer composite membranes with d-α-tocopherol-polyethylene glycol 1000 succinate-coated sepiolite fillers. Lithium plating/stripping analysis indicated no evidence of dendrite formation with good interfacial properties which were further confirmed by postmortem analysis of the cells. Solid state NMR studies show the presence of two Li+ population in the membranes. The feasibility of these electrolytes has been shown with LiFePO4 cathode materials. Initial discharge capacity of 142 mAh/g was observed remaining at 110 mAh/g after 25 cycles with a coulombic efficiency of 96%. The upscaling of these polymers can be easily achieved by extrusion technique and the capacity can be improved by varying the cathode architecture.

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