Batteries that power our electronic devices contain heavy metals and other materials that are toxic to the environment. A new battery technology inspired by biology, bio-batteries, overcomes many of these problems. The technology may one day lead to biodegradable batteries that store energy more efficiently than today's heavy duty lithium-ion batteries.
Most electronic devices we use today like cell phones and computers use lithium-ion batteries for their power. These batteries can store a lot of energy, leading to longer use times before recharging than other battery types. But the metals and chemicals used in lithium ion batteries can be dangerous, says Shelley Minteer.
"Interestingly enough, if something makes a very high energy density battery, it often times has a very energetic material and can have sort of safety issues associated with that," explains Menteer, a professor of chemistry and materials science and engineering at the University of Utah. "And we see that with lithium ion. So you've seen the reports of people's laptops catching on fire, you know issues with cars, etc."
To keep these batteries safe means they have to be packaged very carefully and other safety mechanisms such as a temperature sensor have to be included so they don't overheat.
"Because lithium is sort of dangerous chemistry, the protective container takes up a certain amount of space. We are basically hitting the limit taking into account that we have to have the protective cases," says Minteer.
As electronics continue to advance, they need higher battery capacities. Safety concerns and other technological considerations mean that it may not be long before lithium ion batteries can no longer keep up. This has lead to an explosion of research into the development of whole new types of batteries.
"It used to be that we were ok with a cell phone that we used sporadically and now we need our cell phone to take videos, to take pictures, to have a color screen and all of these things require energy," says Minteer. "We have had to sort of change how we think about designing batteries to be able to design them for the applications that people want to use them for today."
Minteer is on the forefront of battery technology. Her lab is developing biodegradable batteries that contain no toxic metals or chemicals.
"We are making batteries that are for all intents and purpose edible. Not that we eat them, but they are edible."
She says her batteries are inspired by biology since every day we consume food, and cells in our bodies convert that food into energy.
"The power house of the living cell, or the energy conversion component of the living cell happens in the mitochondria," says Minteer. "So we either remove the mitochondria intact [from yeast, spinach, or potatoes] and put it on an electrode surface. Or we remove the part of the mitochondria, the actual enzymes or catalysts in the mitochondria that do energy conversion from the cell and put them on the electrode surface," she explains.
The fuel for this type of battery is not a dangerous chemical, but instead can be the same kinds of things that we ingest, like sugar or alcohol. The mitochondria or enzymes convert the fuel into electrical energy.
"We have technology that we know is extremely efficient in the living cell, and if we can get that kind of efficiency we would have energy densities that are over an order of magnitude or roughly 20 times as energy dense as lithium ion batteries," says Minteer. "But we haven't yet got that complete efficiency you that see in the living cell, so we are working on how we can improve that."
Currently, bio-batteries are able to generate high enough current densities to power many portable electronic devices.
"You're typically talking about lifetimes that are on the days to weeks range for mitochondria, so relatively short," says Minteer. "On the other hand with enzymes it really depends on what we do to protect the enzymes. If we protect the enzymes from degradation we can get months to years worth of life out of the enzyme, similar lifetimes to what you would get out of a lot of your traditional battery technologies."
The benefits of bio-batteries are obvious in terms of disposal. It's estimated that Americans throw away 358 million pounds of batteries ever year, dispersing toxic materials into our air, water, and soil. But there are also specific applications that could be more suitable for a bio-battery. Imagine a pacemaker that runs on a battery that uses the sugar in a person's blood stream. Or since the batteries can be made flexible, they could be used in wearable electronics.
Minteer says some applications will take longer to develop than others, but expects to see simple applications come out within a couple of years.
"Some applications, like using biodegradable batteries in a greeting card, doesn't require a lot of engineering," says Minteer. "If instead you look at the battery that is in your cell phone, the battery in your cell phone is a smart device. Any type of smart battery that requires a great deal of power management is longer down the engineering scale than something that can just use the energy as it comes directly out of the battery."
So the next time you open a greeting card, it's just possible that you might be using a bio-battery.