A team of researchers have made a tiny, long-lasting, environmentally friendly battery made of wood coated with tin.This team used sodium instead of lithium, to make the battery environmentally benign.

Sodium doesn’t store energy as efficiently as lithium, so we won’t see this battery in our cell phone. Due to  its low cost and common materials, it can store huge amounts of energy at once, such as solar energy at a power plant.

Existing batteries are created on stiff bases, which are too brittle to withstand the swelling and shrinking. Liangbing Hu, Teng Li and their team found that wood fibers supply enough to let their sodium-ion battery last more than 400 charging cycles. 

Lead author Hongli Zhu and other team members noticed that after charging and discharging the battery hundreds of times, the wood ended up wrinkled and intact . Computer models are also showed that it  wrinkles effectively relax the stress during charging and recharging, so that the battery can survive many cycles.