Lithium-metal batteries have long promised a dramatic leap beyond today’s lithium-ion technology. By replacing the graphite anode with metallic lithium, researchers can theoretically store far more charge in a lighter package, opening a path toward electric vehicles with longer driving ranges, drones with greater endurance and compact electronics with substantially more energy. Yet one stubborn problem continues to undermine that promise: the battery can generate gas while it operates. A new study in Nature Chemistry examines why gas forms in lithium-metal batteries using ether-based electrolytes and explores strategies for suppressing it, addressing a failure mode that can quietly damage performance and complicate the design of next-generation cells.
Gas evolution is more than a cosmetic inconvenience. In a sealed battery, even a small amount of gas can increase internal pressure, deform electrodes, separate layers that must remain in close contact and alter the pathways through which ions move. The resulting mechanical changes can accelerate degradation, producing a feedback loop in which chemical instability causes physical damage, and physical damage exposes fresh surfaces to further chemical attack. In practical battery packs, pressure buildup also creates safety concerns and demands additional protective hardware, undermining the very improvements in weight and energy density that lithium-metal chemistry is intended to deliver.
The electrolyte—the liquid or gel that transports lithium ions between the electrodes—is central to this process. Ether-based solvents are widely investigated for lithium-metal batteries because they can support rapid ion transport and often form interfacial layers that help lithium deposit more evenly than in many conventional carbonate electrolytes. Their compatibility with lithium metal and their usefulness in high-rate operation have made them important candidates for advanced cells. But the same chemical environment that benefits lithium deposition can also create conditions in which the electrolyte is reduced or otherwise transformed at reactive electrode surfaces, generating volatile products.
The new work by Sung T. Hung, Y. Wang, Z. Cai and colleagues focuses on disentangling the origin of those gases. That task is more difficult than simply observing bubbles or measuring a pressure increase. A battery contains several possible sources of volatile compounds, including solvent breakdown, salt decomposition, reactions involving trace impurities and chemical transformations within the evolving interphase on the lithium surface. The interphase, often called the solid-electrolyte interphase, is a thin film produced when the electrolyte reacts during the first stages of battery operation. It can protect the electrode, but it is not necessarily static: it may continue to grow, crack, dissolve or regenerate as charging and discharging proceed.
Understanding which reactions produce gas—and under what conditions—allows scientists to distinguish symptoms from causes. If gas is generated primarily during lithium plating, for example, the critical chemistry may occur as lithium metal forms and creates highly reactive, freshly exposed surfaces. If it appears during stripping, the process may be linked to porous or electrically isolated lithium left behind after discharge. These deposits, sometimes described as “dead lithium,” can react with the electrolyte even after they are no longer participating effectively in the battery’s electrochemical cycle. The study’s central significance lies in connecting gas evolution with the chemical and structural changes that take place at these constantly changing interfaces.
The researchers investigate how electrolyte composition and electrode reactions interact, using chemical analysis and electrochemical measurements to identify gaseous products and trace their formation pathways. Such analysis is essential because different gases point to different degradation mechanisms. Hydrogen, for instance, can indicate reactions involving proton-containing impurities or solvent reduction, while hydrocarbons or other volatile organic compounds can reveal fragmentation of ether molecules. Gases containing components of the conducting salt may signal salt breakdown or reactions involving unstable intermediates. By comparing gas signatures with battery voltage, current, cycling history and electrode condition, researchers can build a more complete picture of when the electrolyte becomes vulnerable.
A key lesson from this chemistry is that “ether-based” does not describe a single, uniform behavior. The molecular structure of the solvent, the concentration of the lithium salt, the presence of additives, the amount of liquid electrolyte and the nature of the cathode can all change the reactions taking place inside a cell. Highly concentrated electrolytes, for example, alter the local arrangement of solvent molecules around lithium ions. This can reduce the number of free solvent molecules available to decompose at an electrode and can shift the composition of the interphase. Additives can have a similar effect by reacting preferentially and producing a protective film before more vulnerable electrolyte components are attacked. However, a formulation that suppresses one degradation pathway may introduce another, making a mechanistic understanding essential rather than relying on trial and error.
The study also highlights why lithium-metal batteries cannot be evaluated only by their initial capacity or short-term cycling performance. A cell may appear to function normally while accumulating gas and developing microscopic damage that becomes obvious only after many cycles. Gas generation can be influenced by pressure, temperature, current density and the amount of lithium being deposited, meaning that laboratory conditions can strongly affect the apparent stability of a formulation. In a commercial battery, the same chemistry must operate across a wide range of temperatures and power demands, while remaining compatible with manufacturing processes and safety requirements. Suppression strategies therefore need to reduce the underlying chemical reactions, not merely conceal their visible consequences.
Approaches emerging from this kind of research include optimizing salt concentration, selecting solvents with more favorable reduction pathways, introducing carefully chosen additives and engineering electrode surfaces or separators that limit direct contact between reactive lithium and the electrolyte. Another possibility is to control the morphology of lithium deposition so that the metal grows as a dense, uniform layer instead of a porous network with a large surface area. Because rough or filamentary lithium exposes more reactive area, improving deposition can reduce both electrolyte consumption and the opportunity for gas-forming reactions. Yet these solutions must be balanced against viscosity, conductivity, low-temperature performance, cost and compatibility with high-voltage cathodes.
The broader message is that gas evolution is not an isolated defect but a window into the hidden chemistry of lithium-metal batteries. Every bubble, pressure change or swelling event can reflect a chain of molecular reactions that begins at an electrode surface and spreads through the entire cell. By identifying the conditions that initiate those reactions and designing electrolytes that produce more stable interphases, the researchers point toward batteries that are not only more energy-dense but also more predictable and durable. The work arrives as the battery industry searches for technologies capable of storing more energy without increasing size, and it underscores a reality that viral headlines about “the next battery breakthrough” often overlook: commercial success will depend on controlling small, invisible reactions long before they become large, visible failures.
Subject of Research: Gas evolution and suppression in lithium-metal batteries using ether-based electrolytes
Article Title: Understanding and suppressing gas evolution in lithium metal batteries with ether-based electrolytes
Article References:
Hung, S.T., Wang, Y., Cai, Z. et al. Understanding and suppressing gas evolution in lithium metal batteries with ether-based electrolytes. Nat. Chem. (2026). https://doi.org/10.1038/s41557-026-02219-1
Image Credits: AI Generated
DOI: https://doi.org/10.1038/s41557-026-02219-1
Keywords: lithium-metal batteries, ether-based electrolytes, gas evolution, electrolyte decomposition, solid-electrolyte interphase, lithium deposition, battery safety, energy storage
