May 20th 2026|6 min read
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LIKE ANY champion who spends too long at the top, the lithium-ion battery is stagnating. Over decades as the battery of choice in everything from smartphones to electric cars and drones, its design has been tweaked countless times to improve its energy density and performance. But, some scientists say, those improvements are approaching their theoretical limits. Even the best models are prone to dying out in the cold, rapidly losing capacity or—as is the case for those in household devices—spontaneously catching fire.
At the same time, demand for batteries has never been greater. 30% of cars sold in 2026 are expected to be electric vehicles (EVs) which rely on them for power. Last year American homes and businesses installed a record number of big batteries. According to Wood Mackenzie, a consultancy, by the end of the decade installations could rise by almost 40%. Worthy challengers are desperately needed.
Advances in materials science are at last bringing some within reach. Battery-builders are modifying existing materials and creating novel combinations to design batteries that store more energy while being safer and more stable than anything on the market today. The lithium-ion battery’s crown may be up for grabs.
Solid-state batteries are among the most exciting alternatives. When a conventional lithium-ion battery is charged, lithium ions migrate from the cathode to the anode; when it is discharged, they return. The medium the ions shuttle through is called the electrolyte, usually a flammable, organic solvent soaked into all of a battery’s components. In solid-state batteries, however, the anode, cathode and electrolyte are compressed together as slabs. This means more conductive materials can be packed into the same space, allowing for energy densities as high as 500 watt-hours per kilogram (Wh/kg), compared with about 300Wh/kg for liquid electrolytes. They are also less likely to combust.
Although solid-state batteries have been studied for decades, researchers have thus far been able to make only tiny versions for use in such devices as medical implants. The most significant barrier to scaling them up is brittleness. When cells are charged and discharged, the ions repeatedly embed themselves in the electrode material. That causes the battery to expand and contract, creating voids between the components that can lead to cracking and deformation. This slows down the ions and degrades the battery’s performance.
In January researchers at the Shenzhen Institutes of Advanced Technology, part of the Chinese Academy of Sciences, took a big step towards overcoming the brittleness problem. They created a high-performing electrolyte material by alternately stacking layers of ceramic 1-100nm thick with similarly thin sheets of polymer. The stack was then placed perpendicularly to the surface of the electrodes, like a layer cake sitting on its side. On its own, the ceramic is a good conductor but prone to cracking. The polymer, for its part, is flexible but a poor conductor. The combination allowed ions to flow as smoothly as the best existing solid-state electrolytes, but with a much lower tendency to crack.
There are other hurdles to overcome. As batteries charge and discharge, wiry crystals known as dendrites can grow on the electrodes’ surface, leading to cracking and, eventually, short circuits. Scientists have long believed that these form when excess lithium ions from the cathode accumulate on the surface of the anode (rather than being absorbed). Stronger electrode materials, which would resist the cracking, are an obvious solution. In a paper published in March, however, a team led by researchers at the Massachusetts Institute of Technology concluded this understanding was flawed. Instead, they said, dendrites grow when chemical reactions change the electrode’s properties, causing them to weaken. That suggests scientists should be looking for electrodes with greater chemical stability, not just strength.
Materials science can also make solid-state batteries faster. In conventional polymer electrolytes, ions can move only as fast as the surrounding polymer segments allow. A group at Oak Ridge National Laboratory in Tennessee, part of America’s Department of Energy, found a way of decoupling the two sets of movements. They achieved this by adding chemical compounds called zwitterions to polymer segments that would ordinarily be poor conductors. Although zwitterions are neutral molecules, they have charged regions that can give ions a boost. The team’s results showed that this configuration could make ions travel through the electrolyte as much as 10bn times faster. Future tests will show how it performs in a cell.
One noteworthy advantage of solid-state electrolytes is that they would open the door to materials other than lithium. Sodium-ion batteries, which replace the lithium in the cathode with sodium, are especially attractive. Sodium is not only cheaper and stabler than lithium, it is 1,000 times more abundant in Earth’s crust. Unfortunately sodium atoms are bigger and heavier than those of lithium, meaning they are unlikely to embed in conventional graphite electrodes. At present, the result is a heavier battery that can store less energy. Although better electrodes can improve matters—for example hard carbon, which is capable of absorbing sodium ions into its spongelike structure, outperforms graphite—no suitable liquid electrolytes have yet been found.
A solid electrolyte would be easier to work with. For one, the decreased risk of dendrite formation in solid-state batteries would allow anodes to be made out of highly reactive sodium metal. That would allow them to store more energy per kilogram than would be possible at present. Whereas a battery with a hard carbon anode has an energy density of around 175Wh/kg, sodium metal anodes could enable densities closer to 500Wh/kg.
To boost a solid-state sodium-ion battery’s capacity yet further, researchers are experimenting with removing the anode altogether. That would create space for a thicker cathode that can be packed with more sodium, in turn boosting how much energy a battery could store. Removing the anode need not be fatal to the battery’s operation. While it charges, the sodium ions would move from the cathode to another battery component known as the current collector, where they would accumulate until discharge occurs. In effect, an anode is created as the battery operates.
The heady pace of progress is the product of a truly global competition to produce the best solid-state design, says Shirley Meng, a materials scientist at the University of Chicago. The contest could also revolutionise the way batteries are manufactured. For now batteries with liquid electrolytes are built by submerging electrodes in vats of solvents and using enormous amounts of energy to dry them off. Solid-state batteries made in this way develop micropores on their surfaces, increasing the odds of malfunction. Thicker electrodes are also trickier to make because they dry unevenly.
So-called dry electrode manufacturing—in which dry powders are pressed together to form solid batteries—is, therefore, being taken increasingly seriously. Trials have shown that it cuts energy use by about half and manufacturing costs by about a fifth, while boosting the overall performance of the batteries. Many companies, including Tesla, a maker of batteries and EVs, and LG Energy Solution, a South Korean battery maker, are competing to be first to perfect it.
Distinguishing hype from reality is not easy. But recent developments mean that ambitious promises could be fulfilled. China’s Contemporary Amperex Technology, the world’s largest battery manufacturer, has said it will produce solid-state batteries by 2027 and plans to launch the first sodium-ion EV by the middle of this year. Samsung, a South Korean electronics company, has said it will mass produce solid-state batteries by 2027 while Toyota, a Japanese carmaker, has made a similar pledge. Ford Motors, an American car manufacturer, launched a battery-making unit this month, and plans to deliver large-scale batteries for data centres and industrial businesses by next year. In the battery-making business, these are electrifying times. ■
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This article appeared in the Science & technology section of the print edition under the headline “Charging ahead”
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