In the relentless quest for advanced electrochemical devices, electrolyte solvents have traditionally relied on oxygen- and nitrogen-based ligands. These conventional solvents have underpinned the development of lithium and sodium ion batteries, leveraging the strong dipole-ion interactions between ligands and alkali metal ions to facilitate ion dissociation and transport. However, while effective at ion conduction, these interactions often impose limitations on charge transfer kinetics at the electrolyte-electrode interface, ultimately impeding battery performance, especially under challenging conditions such as low temperature and high voltage.
Breaking the mold of traditional electrolyte chemistry, a groundbreaking study introduces hydrofluorocarbon (HFC) electrolytes that harness fluorine-based ligands, unveiling a new paradigm in electrolyte design. By synthetically tailoring alkanes with monofluorinated structures, researchers have crafted fluorine-containing solvents that combine designed steric hindrance with tailored Lewis basicity. This approach enables salt dissolution in concentrations exceeding 2 mol per liter, a remarkable benchmark that underscores the promise of these novel systems for next-generation battery applications.
Among the synthesized series of fluorinated solvents, 1,3-difluoro-propane (DFP) emerges as a standout candidate, delivering an exceptional combination of physicochemical properties. Notably, the DFP-based lithium-ion electrolyte exhibits strikingly low viscosity—measured at merely 0.95 centipoise (cP)—which is critical for facilitating ion transport, especially at subzero temperatures. Alongside this, the electrolyte showcases high oxidative stability, safely operating above 4.9 volts, thereby supporting high-voltage battery chemistries and extending operational windows previously restricted by less stable solvents.
Crucially, the innovative incorporation of fluorine atoms into the first solvation shell around lithium ions engenders a weak yet effective Li⁺–F coordination. This subtle interaction contrasts with the stronger Li⁺–O coordination found in classical ether or carbonate solvents and translates into improved lithium plating and stripping dynamics. Experimentally, this results in Coulombic efficiencies reaching up to 99.7%, a critical metric measuring the reversibility and efficiency of lithium cycling that is indispensable for long-lasting batteries.
Transport kinetics further highlight the advantage of fluorinated electrolytes. The exchange current density, a fundamental parameter reflecting charge transfer rate, is observed to be an order of magnitude greater for Li⁺ coordinated by fluorine ligands compared to those coordinated by oxygen at a chilling −50 °C. This enhancement implies more facile charge movement across the electrode-electrolyte interface, potentially overcoming key bottlenecks that have hampered battery performance in cold environments.
Performance metrics extend to practical battery configurations as well. Lithium-metal pouch cells utilizing these HFC-based electrolytes achieve unprecedented operation under ultralow electrolyte loading conditions—less than 0.5 grams of electrolyte per ampere-hour of capacity. Batteries constructed with these electrolytes deliver energy densities surpassing 700 watt-hours per kilogram at room temperature, an achievement that sets a new bar for energy storage devices. Even more impressively, at −50 °C, these systems maintain about 400 Wh/kg, highlighting their capability to function efficiently in harsh, cold environments where traditional electrolytes typically fail.
This breakthrough is more than an incremental improvement; it offers an alternative route beyond the limitations of conventional coordination chemistry. By cleverly manipulating the molecular design of electrolyte solvents to exploit the unique properties of fluorine, the research ushers in a new era for electrochemical energy storage. The implications for electric vehicles, grid storage, and portable electronics are profound, potentially enabling batteries to operate safely and efficiently across broader temperature ranges while delivering higher energy densities and extended lifespans.
The low viscosity of the fluorinated solvents directly mitigates ion transport resistance, a critical factor in battery performance, particularly at low temperatures where electrolyte viscosity commonly spikes. Combined with the elevated oxidative window, these electrolytes are also well-suited for pairing with high-voltage cathode materials, addressing one of the field’s longstanding challenges—achieving stable cycling at voltages above 4.5 V.
From a mechanistic perspective, the weak Li⁺–F interaction facilitates lithium-ion desolvation—a prerequisite step for effective charge transfer at the electrode surface. This reduced solvation strength lowers the energy barrier for lithium plating and stripping, minimizing the formation of dendrites and side reactions that plague lithium-metal batteries. The outcome is enhanced cycling stability and Coulombic efficiency, essential for commercial viability and safety.
This research also underscores the significance of steric effects combined with fluorination. The monofluorinated alkanes exhibit designed steric hindrance around the Li⁺ solvation sphere, suppressing strong ion pairing and aggregation phenomena that impede ionic conductivity. The net effect is an electrolyte medium that maximizes ion mobility without compromising electrochemical stability or safety.
The pioneering work detailed here opens new pathways for electrolyte innovation using hydrofluorocarbon chemistry. It not only challenges the dominance of oxygen and nitrogen-based solvents but also expands the toolbox for battery scientists aiming to push the boundaries of energy density, operational temperature, and longevity. Fluorine’s unique electronegativity and steric characteristics position it as a versatile element for future electrolyte formulations.
In conclusion, the development of hydrofluorocarbon electrolytes represents a paradigm shift poised to transform the landscape of lithium-ion and lithium-metal batteries. By integrating tailored fluorine chemistry at the molecular level, scientists have achieved a trifecta of features critical for advanced batteries: high salt solubility, exceptional low-temperature performance, and robust high-voltage stability. This innovation charts a promising course toward energy storage solutions that meet the ever-growing demands of modern technology and sustainability.
Subject of Research: Electrolyte solvents for lithium-ion and lithium-metal batteries focusing on hydrofluorocarbon-based systems.
Article Title: Hydrofluorocarbon electrolytes for energy-dense and low-temperature batteries.
Article References:
Wu, L., Zhang, J., Li, Y. et al. Hydrofluorocarbon electrolytes for energy-dense and low-temperature batteries. Nature (2026). https://doi.org/10.1038/s41586-026-10210-6
DOI: https://doi.org/10.1038/s41586-026-10210-6
