Low-cost and flexible solid polymer electrolytes are promising in all-solid-state Li-metal batteries with high energy density and safety. However, both the low room-temperature ionic conductivities and the small Li⁺ transference number of these electrolytes significantly increase the internal resistance and overpotential of the battery. Here, we introduce Gd-doped CeO₂ nanowires with large surface area and rich surface oxygen vacancies to the polymer electrolyte to increase the interaction between Gd-doped CeO₂ nanowires and polymer electrolytes, which promotes the Li-salt dissociation and increases the concentration of mobile Li ions in the composite polymer electrolytes. The optimized composite polymer electrolyte has a high Li-ion conductivity of 5 × 10⁻⁴ S cm⁻¹ at 30 °C and a large Li⁺ transference number of 0.47. Moreover, the composite polymer electrolytes have excellent compatibility with the metallic lithium anode and high-voltage LiNi_0.8Mn_0.1Co_0.1O₂ (NMC) cathode, providing the stable cycling of all-solid-state batteries at high current densities.

Sulfide solid electrolytes (e.g., lithium thiophosphates) have the highest room-temperature ionic conductivity (~10⁻² S cm⁻¹) among solid Li-ion conductors so far, and thus have attracted ever-increasing attention for high energy-density and safety all-solid-state batteries (ASSBs). However, interfacial issues between sulfide electrolytes and electrodes have been the main challenges for their applications in ASSBs. The interfacial instabilities would occur due to side reactions of sulfides with electrodes, poor solid-solid contact, and lithium dendrites during charge/discharge cycling. In this review, we analyze the interfacial issues in ASSBs based on sulfide electrolytes, and in particular, discuss strategies for solving these interfacial issues and stabilize the electrode-electrolyte interfaces. Moreover, a perspective of the interfacial engineering for sulfide-based ASSBs is provided.

A self-standing, flexible and lithium dendrite growth-suppressing composite gel polymer electrolyte membrane was designed for the use of room-temperature lithium ion batteries. The multi-functional composite semi-interpenetrating polymer network (referred to as "Cs-IPN") electrolyte membrane was fabricated by combining a UV-cured ethoxylated trimethylolpropane triacrylate (ETPTA) macromer with alumina nanoparticles in the presence of liquid electrolyte and thermoplastic linear poly(ethylene oxide) (PEO). The polymer electrolyte membrane exhibits a semi-interpenetrating polymer network structure and a higher room temperature ionic conductivity, which impart the electrolyte with a significant cycling (120 mAh g⁻¹ after 200 cycles) and a remarkable rate (137 mAh g⁻¹ at 0.1 ℃, 130 mAh g⁻¹ at 0.5 ℃, 119 mAh g⁻¹ at 1 ℃ and 100 mAh g⁻¹ at 2 ℃) performance in Li/LiFePO₄ battery. More importantly, the polymer electrolyte possesses superior ability to inhibit the growth of lithium dendrites, which makes it promising for next generation lithium ion batteries.