ON A list of cutting-edge materials for high-tech applications, you might not expect to see wood near the top. But an experiment by Teng Li and Liangbing Hu of the University of Maryland may soon put it there. For Dr Li and Dr Hu, writing in Nano Letters, have just described how wood might be used to make one class of batteries cheaper by permitting the lithium now employed in them to be replaced with sodium.

As any high-school chemist knows, lithium and sodium are chemically similar. Sodium ions (sodium atoms with an electron missing, which makes them positively charged) are, however, five times the size of lithium ions. That matters because a battery works by shuttling ions between its anode and its cathode. The bigger the ion, the more damage this shuttling causes—and the shorter, in consequence, is the battery’s life. Hitherto, that has ruled sodium out as a plausible ingredient of batteries. But engineers would still like to devise a commercially viable sodium battery, because sodium is much more abundant than lithium.

Dr Li and Dr Hu wondered if the problem of electrode damage might be ameliorated by using a more pliant material for the frames on which the electrodes are suspended. These frames, which also transmit current to and from the electrodes, are normally made of metal, and are therefore rigid. But the two researchers reckoned that suitably treated wood could do the job of conduction equally well while providing more yielding support for an electrode that was continually expanding and contracting as ions moved in and out of it.

To test this idea, they used slivers of wood from yellow pines. First, they coated these with carbon nanotubes, to improve their conductivity. Then they applied a film of tin to each sliver. (Tin is the preferred material for the anode in a lithium or sodium battery.) This done, they immersed the slivers in an electrolyte containing sodium ions and put the resulting battery through 400 cycles of discharging and recharging. As a control, they built similar batteries using slivers of copper.

The wooden battery was not perfect. Its initial capacity was 339 milliamp hours per gram (mAH/g), but that fell to 145 mAH/g over the course of the 400 cycles. This, however, was not bad for a prototype, and far better than the copper-framed batteries managed. They had an initial capacity of 50 mAH/g. That fell to 22 mAH/g after just 100 cycles. Wood, then, seems a plausible candidate for battery frames.

Obviously you are not going to see wooden-framed batteries in your phone or laptop anytime soon. But that was never the plan for Dr Li and Dr Hu. What their work might lead to is giant sodium-ion batteries for the overnight storage of electricity from solar power stations. Cheap storage is the missing part of the solar-energy jigsaw—for solar cells themselves are now cheap enough to compete with fossil fuels, in sunny climes at least.

The search for solutions to the solar-energy problem has concentrated on making man-made materials more and more sophisticated. It would be a delicious irony if the jigsaw was completed not by one of these snazzy new substances but by one of the oldest materials around.