A spontaneous spatial network structural metal-organic framework composite polymer electrolytes with excellent lithium transport performance for dendrite-suppressing lithium metal batteries

Abstract

The solid-state polymer electrolytes (SPEs) for use in all solid-state lithium-metal batteries (ASSLMBs) are promising due to the high energy density and total safety. However, the scarcity of ion transport channels and the inefficient lithium-ion migration of SPEs have limited the growth of SPEs in practical applications. Herein, metal–organic frameworks (MOFs) structured nanoparticles (MOF-NP) were incorporated with PEO-based SPEs to obtain the composite polymer electrolytes (CPEs). Specifically, the MOF-NP are composed of MIL-101(Cr) covalently linked polymeric poly(ethylene glycol) diglycidyl ether (PEGDE) chains via the amino group. The amino groups in the MOF-NP formed the hydrogen bonds with PEO chains that reduce the crystallinity of the polymer matrix. In combination with the spontaneous spatial network created from the PEGDE chains, an additional continuous transport channel for Li⁺ was provided. Therefore, the prepared CPEs (CPEs-MNP) show a high Li⁺ transport capacity. It is confirmed that CPEs-MNP possesses 4 times higher ionic conductivity (1.2 × 10^-3 S·cm⁻¹ at 60 °C) and a much higher Li⁺ transfer number of 0.66. Furthermore, the assembled cell of Li|CPEs-MNP|Li cycling stable for 1200 h at 0.1 mA·cm⁻² and 60 °C with a small initial polarization voltage of 30.7 mV. Meanwhile, the LiFePO₄|CPEs-MNP|Li cell exhibits outstanding cycling stability and the discharge capacity reaches 133.2 mAh·g⁻¹ at 2C and 60 °C. It is believed that the as-developed CPEs have a greater vitality in the practical application of high-performance ASSLMBs.