A Self‐Standing Flexible Gel Polymer Electrolyte for Dendrite‐Free Lithium‐Metal Batteries

Abstract

We discuss here a self-standing and flexible homogeneous amorphous gel polymer electrolyte (abbreviated as LiGPE) as an alternative electrolyte for lithium-metal batteries. The LiGPE, comprises of a large volume of liquid lithium bis(trifluoromethanesulfonyl) imide (LiTFSI) salt in tetra ethylene glycol dimethyl ether (TEGDME) electrolyte confined inside in situ synthesized network of acrylonitrile and acrylate, which is poly(ethylene glycol) methyl ether methacrylate or PEGMEMA. The glyme-based liquid electrolyte in the LiGPE discussed here, which is completely devoid of ionic liquids, essentially plays the role of a plasticizer. The LiGPE exhibits high room temperature ionic conductivity (2.3 mS cm−1), high lithium-transference number of approximately 0.6, good thermal stability (155 °C) and excellent electrochemical properties. At varying current densities, it facilitates a dendrite free plating and de-plating of lithium across its interface for long periods of time. The high oxidative stability against lithium (Li) up to 5.3 V strongly suggests that it will provide a safer operating Li-metal battery compared to conventional liquid electrolytes. The LiGPE, when assembled in Li-metal cell comprising of Li-metal anode and Li-ion insertion cathode material (LiFePO4, LFP), demonstrated excellent stability and delivered 90 % of theoretical capacity when cycled over 100 cycles. We discuss here a self-standing and flexible homogeneous amorphous gel polymer electrolyte (abbreviated as LiGPE) as an alternative electrolyte for lithium-metal batteries. The gel shows superior interfacial properties with lithium (Li) metal, supressing dendritic growth and enhancing Li-ion transference number (0.64). The high oxidative stability against Li up to 5.3 V strongly suggests that it will provide a safer operating Li-metal battery. The LiGPE, comprises of a large volume of liquid lithium bis(trifluoromethanesulfonyl) imide (LiTFSI) salt in tetra ethylene glycol dimethyl ether (TEGDME) electrolyte confined inside in-situ synthesized network of acrylonitrile and acrylate, which is poly(ethylene glycol) methyl ether methacrylate or PEGMEMA. The glyme-based liquid electrolyte in the LiGPE discussed here, which is completely devoid of ionic liquids, essentially plays the role of a plasticizer, enhancing the ionic conductivity (2.3 mS cm−1) without compromising with the mechanical stability or thermal stability (155 °C) of GPE.