The guest–host chemistry in polymer electrolytes plays a crucial role for all-solid-state Li metal batteries, where the stable operation of such batteries heavily relies on high ion conductivity, strong mechanical properties, and stable interfaces of the electrolyte. While traditional ceramic fillers can boost ion conductivity, they fail to improve interfacial stability. In this study, we introduce intermolecular hydrogen bonding into a polyethylene oxide (PEO)-based polymer electrolyte through the incorporation of metal organic framework (MOF) and lithium nitrate additives. The hydrogen on the PEO chain is found to be tightly interacted with the oxygen nodes of UiO-66 MOF and nitrate anions, creating a cross-linked framework that reduces the crystallinity of the PEO and enhances the integrity of composite. This interaction induces a beneficial Li₃N and LiF-rich solid electrolyte interphase, ensuring 2000 h of stable lithium metal operation without short-circuits. The strong polysulfide adsorption enables compatibility with high-capacity sulfur cathodes, resulting in solid-state Li-S batteries that can achieve a high capacity of 913.8 mAh·g⁻¹ and exhibit stable cycling performance. This work demonstrates the deep understanding of guest–host chemistry in polymer electrolytes and their potential in developing energy-dense solid-state Li metal batteries.

Compared with the planar two-dimensional (2D) all-solid-state thin film batteries (TFBs), three-dimensional (3D) all-solid-state TFBs with interdigitated contact between electrode and electrolyte possess great advantage in achieving both high energy and power densities. Herein, we report a facile fabrication of vertically aligned oxygen-deficient α-MoO_3-x nanoflake arrays (3D MO_x) using metal Mo target by direct current (DC) magnetron sputtering. By utilizing the 3D MO_x cathode, amorphous lithium phosphorus oxynitride solid electrolyte, and lithium thin film anode, 3D solid-state TFBs have been successfully fabricated, exhibiting high specific capacity (266 mAh g⁻¹ at 50 mA g⁻¹), good rate performance (110 mAh g⁻¹ at 1000 mA g⁻¹), and excellent cycle performance (92.7% capacity retention after 1000 cycles) in comparison with the 2D TFBs using the planar MO_x thin film as cathode. The superior electrochemical performance of the 3D TFBs can be attributed to the 3D architecture of the cathode, maximizing the cathode/electrolyte interface while retaining the short Li⁺ diffusion length. The charge/discharge measurements of the 3D MO_x cathode in liquid electrolyte, however, exhibit fast capacity fading, demonstrating the advantage of using transition metal oxide as cathode in solid-state batteries.