Amino-modified UiO-66-NH₂ reinforced polyurethane based polymer electrolytes for high-voltage solid-state lithium metal batteries

Solid-state polymer electrolytes (SPEs) are candidate schemes for meeting the safety and energy density needs of advanced lithium-based battery because of their improved mechanical and electrochemical stability compared to traditional liquid electrolytes. However, low ionic conductivity and side reactions occurring in traditional high-voltage lithium metal batteries (LMBs) hinder their practical applications. Here, amino-modified metal-organic frameworks (UiO-66-NH₂) with abundant defects as multifunctional fillers in the polyurethane based SPEs achieve the collaborative promotion of the mechanical strength and room temperature ionic conductivity. The surface modified amino groups serve as anchoring points for oxygen atoms of polymer chains, forming a firmly hydrogen-bond interface with polycarbonate-based polyurethane frameworks. The rich interfaces between UiO-66-NH₂ and polymers dramatically decrease the crystallization of polymer chains and reduce ion transport impedance, which markedly boosted the ionic conductivity to 2.1 × 10⁻⁴ S·cm⁻¹ with a high Li⁺ transference numbers of 0.71. As a result, LiFePO₄|SPEs|Li cells exhibit prominent cyclability for 700 cycles under 0.5 C with 96.5% capacity retention. The LiNi_0.6Co_0.2Mn_0.2O₂ (NCM622)|SPEs|Li cells deliver excellent long-term lifespan for 260 cycles with a high capacity retention of 91.9% and high average Coulombic efficiency (98.5%) under ambient conditions. This simple and effective hybrid SPE design strategy sheds a milestone significance light for high-voltage Li-metal batteries.