Researchers have developed a battery made from a sliver of wood coated with tin that shows promise for becoming a tiny, long-lasting, efficient and environmentally friendly energy source - 1,000 times thinner than a sheet of paper.

 Liangbing Hu, Teng Li and colleagues note that today’s batteries often use stiff, non-flexible substrates, which are too rigid to release the stress that occurs as ions flow through the battery. They knew that wood fibers from trees are supple and naturally designed to hold mineral-rich water, similar to the electrolyte in batteries. They decided to explore use of wood as the base of an experimental sodium-ion battery. Using sodium rather than lithium would make the device environmentally friendly.

Sodium-ion batteries offer an attractive option for low cost grid scale storage due to the abundance of Sodium. Tin is touted as a high capacity anode for sodium-ion batteries with a high theoretical capacity of 847 mAh/g, but it has limitations, like large volume expansion with cycling, slow kinetics and unstable solid electrolyte interphase (SEI) formation. The researchers created an anode consisting of a tin thin film deposited on a hierarchical wood fiber substrate that addresses the challenges of tin anodes. The softness of wood fibers relieves the mechanical stresses associated with the sodiation process, and the mesoporous structure functions as an electrolyte reservoir that allows for ion transport through the outer and inner surface of the fiber. 

Lead author Hongli Zhu and other team members describe lab experiments in which the device performed successfully through 400 charge-discharge cycles with an initial capacity of 339 mAh/g,  putting it among the longest-lasting of all sodium-ion nanobatteries. 

Batteries using the new technology would be best suited for large-scale energy storage applications, such as wind farms or solar energy installations, the report indicates.

Credit and link: DOI: 10.1021/nl400998t

Supported by the National Science Foundation and the University of Maryland NanoCenter.

Citation: Hongli Zhu, Zheng Jia, Yuchen Chen, Nicholas Weadock, Jiayu Wan, Oeyvind Vaaland, Xiaogang Han, Teng Li and Liangbing Hu, 'Tin Anode for Sodium-Ion Batteries Using Natural Wood Fiber as a Mechanical Buffer and Electrolyte Reservoir', Nano Letters 2013 13 (7), 3093-3100 DOI: 10.1021/nl400998t