In Simple Terms
Researchers have found a way to make a battery’s liquid ingredients turn into a firm gel at room temperature, instead of heating them intensely. That gentler process may help protect the battery’s parts during manufacturing, and a large test cell delivered promising results. But getting the battery to work well in cold conditions remains a challenge.
Conventional lithium-ion batteries are nearing the practical limits of how much energy they can store, while the liquid inside them raises concerns about leaks and fire. Lithium-metal batteries with semi-solid electrolytes offer an appealing route to higher energy and better safety. But making them presents a tricky problem: how can a liquid mixture turn into a uniform gel inside the battery without the heat needed to trigger the reaction damaging the electrodes?
Why the Battery Needs a Gentler Recipe
Lithium-metal batteries are attractive in part because lithium metal has a theoretical anode capacity of 3860 milliamp-hours per gram. They can also use lithium- and manganese-rich cathodes with capacities above 250 milliamp-hours per gram. Combining these advantages in one cell could make it possible to store more energy than conventional lithium technology, whose practical energy density is approaching 300 watt-hours per kilogram.
Those numbers alone do not guarantee a successful battery. The contact between lithium metal and the electrolyte—the medium that carries ions between the electrodes—needs to form stable, uniform interfaces. If these layers develop unevenly, the electrodes may be damaged or the cell may lose its ability to operate through repeated cycles. Researchers are therefore trying to make the electrolyte inside the cell itself, triggering a chemical reaction that turns a liquid mixture into a semi-solid gel in contact with the cell’s internal surfaces.
One existing method heats the ingredients to temperatures above 60 degrees Celsius and uses a chemical initiator called azobisisobutyronitrile, or AIBN. Heating helps the reaction get going quickly, but it can also make the material harden suddenly, increasing heat and gas buildup. It may produce uneven layers on the anode and cathode and degrade electrode materials. The challenge is to use enough heat to start the reaction without damaging the structure the electrolyte is meant to protect.
Starting the Reaction Without an Oven
In a study published online in eScience on July 20, 2026, a team from Nankai University and the Haihe Laboratory of Sustainable Chemical Transformations in Tianjin, China, proposed a way to start radical polymerization at room temperature. The idea is not to replace every component of the battery. Instead, the researchers make it easier for monomer molecules to begin reacting, so the gel can form in place without relying on high temperatures.
The team chose an acrylic compound called pentaerythritol tetraacrylate, or PETEA, as the monomer that links up to form a polymer network. They used AIBN to initiate polymerization and added an activator called tris(pentafluorophenyl)borane, abbreviated TPFPB. The activator has a high maximum electrostatic potential, or ESPmax—a property that describes how charge is distributed across a molecule’s surface and can help explain how it interacts with other molecules.
According to the team’s chemical explanation, TPFPB binds to the carbonyl group in PETEA. This interaction changes the distribution of electrons within the monomer and makes the double bond between its carbon atoms more likely to take part in the reaction. Put simply, the activator primes the reaction site, so starting the polymer chains does not require a large burst of heat. The goal is not merely to make a gel in a container, but to form it within the pores and tiny spaces between battery components.
Several kinds of measurements supported this explanation. In a boron-11 nuclear magnetic resonance analysis, the boron signal shifted from minus 0.07 to plus 0.66 parts per million after the components reacted. Density functional theory calculations also showed that the reaction’s initiation barrier fell from 0.46 electron volts to 0.11 electron volts. The researchers wanted this change to make polymerization possible at room temperature, and they tested the process both in containers and in small coin cells.
What Changed Inside the Cell?
One of the most important places to examine is the boundary between the electrolyte and each electrode. These interfaces are more than simple borders between different materials: thin layers form there, affecting ion movement and the stability of reactions. Cells made with the electrolyte prepared at room temperature, designated RT-QSE, developed more uniform interfacial layers rich in lithium fluoride. These included the solid electrolyte interphase on lithium, known as the SEI, and the cathode-electrolyte interphase, known as the CEI.
This matters because more uniform layers may help spread lithium movement across the surface rather than concentrating it in a few spots. In a repeated lithium-plating and stripping test, the cell remained stable for more than 1200 hours at a current density of 0.5 milliamp-hours per square centimeter and an areal capacity of 1.0 milliamp-hours per square centimeter. The result applies to this specific test and its conditions; on its own, it does not establish how long a battery would last in every use. It does, however, offer an indication that the interface could withstand extended cycling in this experiment.
The team also compared the mechanical properties of the SEI using atomic force microscopy and an analysis of the Derjaguin–Muller–Toporov modulus, known as DMT. The measured modulus was higher for the layer produced with the electrolyte prepared at room temperature than for the sample made using high-temperature processing. This describes the measured layer’s stiffness, a property that may affect how well it holds together as electrode volumes change during charging and discharging.
The difference extended to the lithium- and manganese-rich oxide cathode, or LRMO. Observations showed that its crystal structure remained more stable in cells with the electrolyte prepared at room temperature, without the gaps or vacancies seen in the comparison described by the researchers. By contrast, surfaces in the thermally polymerized sample appeared more disrupted, and its interfaces were less uniform. Ultrasonic imaging also showed better electrolyte penetration into the electrode—a particularly important feature for a thick cathode, where the electrolyte needs to reach beyond the outer surface.
From a Small Cell to an Amp-Hour-Scale Pouch
The tests went beyond coin cells. The researchers prepared an LRMO cathode with an areal capacity of 4 milliamp-hours per square centimeter; it retained 95.1% of its capacity after 100 cycles. This measurement shows how well the cell held up through repeated charging and discharging under the test conditions. It does not mean every commercial battery would automatically achieve the same result: performance depends on cell composition and dimensions, temperature, charging speed, and other factors.
The most notable scale-up step was a pouch cell with a capacity of 9.53 amp-hours. It contained a cathode with an areal capacity above 10 milliamp-hours per square centimeter, testing whether the electrolyte could reach into a dense electrode rather than simply work in thin layers. The cell recorded an energy density of 656.6 watt-hours per kilogram and an initial Coulombic efficiency of 94.4%. Initial Coulombic efficiency measures the charge recovered in the first cycle relative to the charge put in, offering an indication of early energy loss when operation begins.
These numbers are notable because they came from a pouch cell, not just a test of an isolated material, and because the cathode had a high areal capacity. Still, the energy-density figure should be understood as a result from an experimental cell made under the study’s conditions—not as a direct promise about the performance of batteries for cars, aircraft, or grid storage. Moving from a successful laboratory cell to a product requires repeatable manufacturing, thermal management, safety, long service life, and low cost, as well as testing under real-world conditions.
A Design Principle That Goes Beyond One Material
The researchers argue that the activator’s value may extend beyond speeding up the reaction of this particular PETEA formulation. The property the team focused on—high ESPmax—could help guide the selection of other compatible activators and monomers, opening the way to tailor the recipe to different electrodes or cell designs. This remains a design possibility that will need to be tested for each combination: success with specific materials does not automatically show that every acrylic monomer or activator will behave the same way.
Even so, the experiment offers a new way to approach a problem that has often been tackled by applying more heat. Instead of forcing a monomer to react through heating, researchers can adjust its behavior at the molecular level to make polymerization easier to start. If this process can be controlled consistently, it may help produce more uniform interfaces inside thick electrodes and reduce differences in how the material hardens across a cell. That could be especially important when scaling up to larger pouch cells, where it is difficult to ensure that heat or ingredients reach every part evenly.
Potential applications include electric-vehicle batteries, low-altitude aircraft, and grid-scale electricity storage—fields that could benefit from combining high energy with improved safety. But the research does not show that these uses are ready today. Thick electrodes still need to perform better at low temperatures, and the researchers pointed to possible changes to the cathode and plasticizer design as ways to address this limitation. That matters because a battery that works well in mild conditions may not maintain the same performance in the cold.
The Bottom Line
This work tackles one specific challenge for lithium-metal batteries: forming a gel electrolyte inside the cell without the intense heating that can harm electrodes and their interfaces. By adding TPFPB to a PETEA-and-AIBN system, the team triggered polymerization at room temperature and linked the process to a drop in the reaction’s initiation barrier from 0.46 to 0.11 electron volts, as well as more uniform interfaces in the tests described.
The results ranged from stability for more than 1200 hours in a lithium-plating and stripping test, to 95.1% capacity retention after 100 cycles for a cathode with an areal capacity of 4 milliamp-hours per square centimeter, and a 9.53 amp-hour pouch cell that recorded 656.6 watt-hours per kilogram and an initial Coulombic efficiency of 94.4%. These are promising signs that the approach can be scaled, not proof that a commercial battery is just around the corner. Better performance in the cold and evidence that the process can be manufactured reliably at scale will be essential before its prospects for everyday use can be judged.