A new biodegradable battery made of cellulose promises to offer thin, flexible, lightweight, inexpensive and environmentally-friendly batteries made without metal parts.
The battery is made from green algae known as Cladophora, found along freshwater beaches around the world.
The key to the battery's success is its large surface area. Made from algae-derived cellulose with 100 times the surface area of the cellulose found in sheets of notebook paper, the battery can manage far more conducting polymer than in previous incarnations.
That means better recharge, hold and discharge capabilities.
"We have long hoped to find some sort of constructive use for the material from algae blooms and have now been shown this to be possible," said researcher Maria Strømme, a nanotechnologist at Uppsala University in Sweden, in a statement. "This creates new possibilities for large-scale production of environmentally friendly, cost-effective, lightweight energy storage systems."
Lightweight, indeed. The new batteries consist of very thin layers of conducting polymer -- just 40 to 50 nanometers, or billionths of a meter, wide -- that coat algae cellulose fibers just 20 to 30 nanometers wide, collected into paper sheets.
The batteries are said to hold 50 to 200 percent more charge than similar conducting polymer batteries. With more optimization, the batteries could compete head-to-head with commercial lithium batteries, found in consumer electronics such as mobile phones and laptop computers, according to the researchers.
Better still, the batteries recharge faster than conventional rechargeable batteries. A regular battery takes at least an hour to recharge; the new batteries can recharge in eight minutes and as quickly as 11 seconds.
But what about lifespan? The new battery shows a 6 percent loss after 100 charging cycles, a vast improvement over comparable polymer batteries. (This is an important measurement. A common complaint about lithium ion batteries concerns their short shelf life, just a few hundred cycles before significant loss shows.)
"When you have thick polymer layers, it's hard to get all the material to recharge properly, and it turns into an insulator, so you lose capacity," said researcher Gustav Nyström, an electrochemist at Uppsala University, in a statement. "When you have thin layers, you can get it fully discharged and recharged."
The new batteries could be used in applications such as flexible electronics (e.g. e-book readers), clothing and packaging. The researchers said they were not intent on replacing conventional lithium ion batteries, but rather finding new uses for batteries, such as to power sensors in intelligent wallpaper or to power athletic clothing that monitors the body.
The researchers plan to test the batteries for charge loss over time as well as how well they can scale into larger formats.
Their findings were published last month in the journal Nano Letters.