In-situ polymerized siloxane cages for an interface-stable gel polymer electrolyte in lithium-metal batteries

The rising demand for high energy density and safe rechargeable batteries calls for alternatives beyond conventional lithium-ion systems. Lithium metal batteries (LMBs) offer ultrahigh theoretical capacity but face critical challenges, including interfacial instability, dendritic lithium growth. Herein, we design a gel polymer electrolyte (HPP), integrating a fluorinated polymer network with highly cross-linked polyhedral oligomeric silsesquioxane (POSS) cages. The three-dimensional network enhances mechanical strength and promotes uniform Li+ transport, effectively suppressing dendrite formation. Simultaneously, fluorinated components extend the electrochemical stability window and enable a robust lithium fluoride (LiF) rich interphase, stabilizing the cathode interface. Benefiting from this synergistic design, Li||Li symmetric cells exhibit stable cycling for over 3500 hours, while full cells retain 79% capacity after 500 cycles at 0.5 C and 87% after 200 cycles at 1 C. This work offers a rational strategy for electrolyte design to regulate interfacial chemistry and accelerate the development of high performance LMBs.