Enabling stable and nonflammable all-solid-state lithium metal batteries via a silica nanoparticle/dimethyl methylphosphonate dual-additive strategy

초록

Poly(ethylene oxide) (PEO)-based solid polymer electrolytes (SPEs) are considered ideal for next-generation lithium metal batteries due to their safety over flammable liquid electrolytes. However, practical deployment remains severely hindered by insufficient ambient ionic conductivity, limited electrochemical stability, and susceptibility to lithium dendrite growth. Herein, a synergistic dual-additive strategy is reported by incorporating dimethyl methylphosphonate (DMMP) and silica nanoparticles (SiO2) into a PEO matrix. DMMP serves as a plasticizer to disrupt PEO crystallinity, accelerating lithium-ion mobility while imparting flame-retardancy. Simultaneously, SiO2 facilitates salt dissociation through Lewis acid-base interactions and provides a physical barrier against dendrites. Consequently, the optimized SPE (PEO/DMMP/SiO2-2) delivers an outstanding ionic conductivity of 1.10 × 10−5 S cm−1 at room temperature (7.0 × 10−4 S cm−1 at 60 °C), with a high lithium transference number of 0.40. The system exhibits a wide electrochemical stability window exceeding 5.5 V. Li/Li symmetric cells achieve stable, lithium plating/stripping cycling for over 700 h. Furthermore, LiFePO4/Li full cells demonstrate exceptional stability, delivering a high discharge capacity of 149.3 mAh g−1 with 80.6% capacity retention after 400 cycles at a 1C rate and 60 °C. This dual-additive approach offers a scalable pathway toward high energy density and intrinsic safety in all-solid-state batteries.

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