High‐Voltage All‐Solid‐State Lithium Metal Batteries Mediated by the YF3 Strengthened Polycaprolactone Electrolytes

Why It Matters

It provides a scalable electrolyte that mitigates interfacial degradation at >4.5 V, unlocking higher energy density and safety for solid‑state batteries essential to electric‑vehicle and grid‑storage markets.

Key Takeaways

• YF3 weakens Li‑polymer bonds, boosting conductivity.
• Oxidative stability reaches 5.1 V, enabling high‑voltage cathodes.
• Ni‑rich cells retain ~70% after 500 cycles.
• Li‑rich cells sustain 200 cycles at 4.8 V.
• Dual interface design stabilizes both cathode and anode.

Pulse Analysis

Solid‑state lithium metal batteries promise superior safety and energy density, yet their commercial rollout stalls at high voltages because conventional polymer electrolytes decompose and form unstable interphases. Polycaprolactone (PCL) offers mechanical robustness and thermal stability, but its carbonyl groups strongly coordinate lithium ions, limiting ionic transport and oxidative endurance. Researchers have therefore sought additive strategies that decouple lithium conduction from polymer coordination while simultaneously protecting the electrolyte from high‑potential oxidation.

In the reported YF3‑strengthened PCL electrolyte, the Lewis‑acidic YF3 particles accept electron density from the carbonyl groups, effectively weakening Li⁺‑polymer interactions. This subtle electronic shift accelerates lithium hopping, raising ionic conductivity without sacrificing mechanical integrity. Concurrently, YF3’s oxidative resistance extends the electrolyte’s voltage window to 5.1 V, allowing direct pairing with nickel‑rich (4.5 V) and lithium‑rich (4.8 V) cathodes. Performance data show Ni‑rich NCM9055 cells retaining nearly 70% capacity after 500 cycles, while Li‑rich cells maintain stable operation for 200 cycles—benchmarks previously unattainable with plain PCL SPEs.

The dual‑interface stabilization concept has broader implications for the battery industry. By addressing both cathodic and anodic interfacial degradation in a single material platform, manufacturers can simplify cell architecture, reduce reliance on costly ceramic layers, and accelerate the transition to high‑energy solid‑state systems. As automotive OEMs and grid‑scale storage providers target voltages above 4.5 V to meet range and efficiency goals, electrolytes like YF3‑PCL could become a cornerstone technology, driving next‑generation battery commercialization.