Helical Polyurethane-Initiated Unique Microphase Separation Architecture for Highly Efficient Lithium Transfer and Battery Performance of a Poly(ethylene oxide)-Based All-Solid-State Electrolyte

Abstract

Poly(ethylene oxide) (PEO) with excellent solvating capacity toward lithium salts and easy processable feature is considered as the promising polymer electrolyte matrix for energy storage devices. However, the poor capacity and cycling performances of PEO-based batteries resulted from weak mechanical strength and electrochemical properties greatly limit its development. Herein, chiral polyurethane (HPU) with a unique helical configuration is integrated into PEO, and a well-defined microphase separation architecture is induced in the resulted PEO@HPU hybrid. Besides the decreased crystallinity of PEO, the well-organized ordered and disordered microphase structure provides a “green channel” for Li+ transfer, contributing to a record lithium ion transference number of 0.43 for PEO-based dual-ion conductors. The mechanical strength and dimensional stability of PEO are significantly improved by the introduction of rigid helical segments and intermolecular hydrogen bondings. The electrochemical window and the ionic conductivity of the PEO@HPU hybrid are 5.0 V (vs Li+/Li) and 4.92 × 10–5 S cm–1 (60 °C), respectively. By synergism of the decreased crystallinity and microphase separation, the LiFePO4/Li cell assembled with the optimized PEO@HPU presents a high discharge capacity of 153 mA h g–1 at 0.1 C, and the capacity retention ratio is 83.6% after the 80th cycle with a Coulombic efficiency of approximately 99%. The growth of lithium dendrites is effectively inhibited, and the improved interfacial compatibility between PEO@HPU and the Li metal electrode also plays a crucial role. The introduction of a helical structure and the induced microphase separation may provide a new strategy for developing advanced solid-state polymer electrolytes for practical applications.

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