Due to the favorable interfacial stability with electrodes, excellent processability, and reasonable material cost, organic–inorganic composite solid-state electrolytes have attracted broad interests in the field of solid-state batteries. In this study, we have developed a solid-state composite electrolyte with polyurethane (PU) as polymer matrix and TiO_2−x as nanofiller (denoted as PUL-TiO_2−x). The block copolymer PU features alternating soft and hard segments, which offers distinct advantages due to its unique structural arrangement. The soft segment of the block copolymer facilitates the dissociation of lithium salt, enabling the conduction of Li⁺, while the rich hydrogen bond network formed by the hard segment ensures the mechanical strength of the electrolyte. The profusion of Lewis acid sites on the TiO_2−x surface facilitates interactions with ether oxygen groups and bistrifluoromethanesulfonimide (TFSI⁻) anions, thereby enhancing ionic conductivity (σ) and expanding the electrochemical stability window of the electrolyte. Notably, the PUL-TiO_2−x electrolyte exhibits an impressive σ of 2.19 × 10⁻⁴ S·cm⁻¹ at 40 °C, a Li⁺ transference number of 0.47, and an electrochemical stability window of 4.98 V. The resulting LiNi_0.8Co_0.1Mn_0.1O₂ (NCM811)||Li battery demonstrates a specific capacity of 171 mAh·g⁻¹ and exhibits excellent cycling stability, maintaining its performance over 270 cycles at 40 °C. These findings underscore the immense potential of the PUL-TiO_2−x in advancing the development of high-performance all-solid-state lithium 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.