Enthalpy-Driven Molecular Engineering Enables High-Performance Quasi-Solid-State Electrolytes for Stable Lithium Metal Batteries

The development of safe, high-performance lithium metal batteries represents the next frontier in energy storage technology, promising unprecedented theoretical energy density. However, the realization of this potential is hampered by significant safety risks and performance limitations associated with current liquid electrolytes, necessitating the exploration of alternative systems. Poly-1,3-dioxolane (poly-DOL) quasi-solid-state electrolytes (QSSEs) have emerged as a promising approach, yet challenges in achieving satisfactory Coulombic efficiency and long-term stability have impeded their practical implementation. While lithium nitrate can potentially address these efficiency issues, its incorporation typically results in prohibitively slow polymerization. To overcome these limitations, we present an innovative enthalpy-driven molecular engineering strategy. By harnessing the high polymerization enthalpy of 1,1,1-trifluoro-2,3-epoxypropane (TFEP) as a co-polymerization promoter with DOL, we successfully incorporate lithium nitrate into poly-DOL-based QSSEs. The resulting QSSE exhibits remarkable properties, including high ionic conductivity (2.23 mS cm^-1 at 25 °C) and superior oxidative stability (4.6 V vs. Li⁺/Li). Lithium symmetric cells employing this electrolyte demonstrate stable cycling for over 1300 hours at practical current densities. Notably, our co-polymerization strategy effectively mitigates poly-DOL crystallization, enabling unprecedented long-term stability in Li|LiFePO₄ cells, which exceed 2000 cycles at 1 C. We further validate the scalability of this approach in a ~1 Ah Li|NCM811 pouch cell, achieving an impressive 94.37% capacity retention after 60 cycles. This molecular engineering strategy, based on leveraging polymerization enthalpy, represents a significant advancement towards the realization of high-performance, in situ polymerized quasi-solid-state batteries for next-generation energy storage applications.