Lithium metal batteries promise dramatically higher energy density than today's lithium-ion technology, but their practical use has been limited by unstable interfaces and dangerous lithium dendrite growth. In this study, researchers developed a two-dimensional polymeric metal phthalocyanine layer that actively regulates anion movement and lithium-ion transport at the electrode–electrolyte interface. By guiding electrolyte anions toward the electrode surface and simultaneously accelerating lithium-ion conduction, the engineered layer promotes the formation of dense, lithium fluoride–rich interphases that stabilize lithium deposition. This molecularly designed interface significantly improves cycling stability, Coulombic efficiency, and safety under demanding operating conditions, offering a new strategy to unlock the long-term reliability of lithium metal and anode-free batteries.
Lithium metal is considered the ultimate anode material due to its extremely high theoretical capacity and low electrochemical potential, making it attractive for next-generation high-energy batteries. However, repeated lithium plating and stripping often lead to dendritic growth, unstable solid electrolyte interphases, and rapid electrolyte consumption, which severely limit battery lifetime and safety. While lithium fluoride–rich interphases are known to improve stability, existing approaches rely on passive decomposition processes that are difficult to control under realistic conditions. Moreover, few strategies simultaneously address interfacial chemistry and lithium-ion transport kinetics. Based on these challenges, there is a critical need to develop molecularly engineered interfacial layers that can actively regulate ion behavior and stabilize lithium metal electrodes.
Researchers from Sungkyunkwan University, Seoul National University, and collaborating institutions report a new molecular interfacial design that enables ultrastable lithium metal batteries. Published (DOI: 10.1016/j.esci.2025.100480) online on March 2026, in eScience , the study demonstrates that a two-dimensional polymeric cobalt phthalocyanine layer can simultaneously guide electrolyte anions and facilitate lithium-ion transport. This dual-function interface forms uniform, lithium fluoride–rich solid electrolyte interphases, enabling long-life lithium metal full cells and anode-free batteries to operate reliably under high current density, lean electrolyte, and high cathode loading conditions
The research team designed a multifunctional artificial layer based on polymeric metal phthalocyanines with precisely controlled metal centers and lithiophilic linkers. The two-dimensional structure allows conformal coating on carbon current collectors, creating a stable framework for lithium deposition. By selecting cobalt as the central metal, the material exhibits strong affinity for TFSI⁻ anions in the electrolyte. Spectroscopic analyses and cryogenic electron microscopy reveal that these anions are directionally attracted toward the electrode surface, where they preferentially decompose to form dense, uniform lithium fluoride–rich interphases.
At the same time, the incorporation of triethylene glycol linkers creates pseudo-crown ether–like pathways that accelerate lithium-ion transport across the interface. Electrochemical measurements show that this synergistic design dramatically reduces nucleation overpotential and suppresses dendritic lithium growth. Symmetric lithium cells maintained stable cycling for over 2,500 hours, while lithium metal full cells paired with high-loading cathodes operated for more than 600 cycles with minimal capacity loss. Even under stringent conditions—such as low N/P ratios and lean electrolyte usage—the engineered interface enabled anode-free full cells to cycle stably for over 500 cycles, highlighting its robustness and practical relevance.
"This work shows that controlling ion behavior at the molecular level can fundamentally change how lithium metal interfaces evolve," said the study's corresponding authors. "Instead of relying on passive interphase formation, we designed an artificial layer that actively directs anion flux while enhancing lithium-ion transport. The result is a stable, self-reinforcing interface that remains effective even under harsh operating conditions. This approach opens new opportunities for rational interfacial engineering in high-energy batteries."
The findings provide a versatile platform for advancing next-generation energy storage technologies. By enabling stable lithium metal and anode-free batteries under realistic conditions, the molecular interface design could significantly increase the energy density of electric vehicles, portable electronics, and grid-scale storage systems. The strategy is compatible with scalable coating processes and commercially relevant materials, making it attractive for industrial adoption. More broadly, the concept of ion-flux engineering offers a new design paradigm for battery interfaces, extending beyond lithium metal systems to other high-energy chemistries where interfacial instability remains a key bottleneck.
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eScience
Two-dimensional polymeric metal phthalocyanines with anion fluxing and Li-ion-conducting properties for lithium metal full batteries