In situ hybrid crosslinking polymerization of 1,3-dioxolane on functionalized nanoparticles for ultrathin solid...

Poor interfacial contact poses a major limitation to the performance of solid-state batteries. In situ polymerization has emerged as an effective strategy to improve interfacial contact and facilitate ion transport. Among various monomers, 1,3-dioxolane (DOL) can be readily polymerized into poly(1,3-dioxolane) (PDOL), which exhibits high ionic conductivity and good chemical stability while maintaining intimate interfacial contact. However, the mechanical strength and electrochemical stability of pure PDOL electrolytes remain inadequate. Introducing inorganic fillers, especially high-ferroelectric nanoparticles, can enhance mechanical properties and homogenize the electric field distribution. Nevertheless, nanoparticle agglomeration during prolonged in situ polymerization poses a significant challenge. In this work, we develop a two-step approach to address these issues: first, modifying the surface of high-ferroelectric BaTiO₃ nanoparticles, and then constructing an in situ homogenized organic/inorganic crosslinked network. The resulting ultrathin (∼7 μm) solid polymer electrolyte demonstrates significantly improved performance, including a high Li⁺ transference number (0.68 vs. 0.44 for pure PDOL), a widened electrochemical window (4.9 V vs. 4.3 V for pure PDOL), and exceptional cycling stability. Li||Li symmetric cells stably cycle for over 2000 h at 0.5 mA cm^-2. LiFePO₄||Li full cells deliver a high specific capacity of 156 mAh g^-1 at 0.5C with 93.1 % capacity retention after 250 cycles, and 146 mAh g^-1 at 1C with a decay rate of only 0.04 % per cycle. The electrolyte also shows excellent compatibility with LiNi_0.8Co_0.1Mn_0.1O₂ cathodes, providing an initial capacity of 193 mAh g^-1 and retaining 158 mAh g^-1 after 150 cycles at 1C.