Future Environments: The Future of Energy with Nancy Sottos

Nancy Sottos, a professor of materials science and engineering, discusses green energy and the need for energy storage. Sottos’ collaborators include Jeff Moore, a professor of chemistry, and the late Scott White, a professor of aerospace engineering, in Beckman’s Autonomous Materials Systems Group.

How much of our energy needs currently rely on batteries? What is the proposed usage?

Energy needs don’t really rely on batteries, since batteries are for energy storage and must be charged with another form of energy (e.g. electricity). Batteries are used in a wide range of devices from personal electronics, home tools and equipment, and now automobiles. Additionally, there is support to use batteries to store energy generated by renewable sources. Wind and solar energy are generated intermittently—for example, when the sun is shining—so large batteries are needed to store this energy when the source is on and then deliver it at a more constant rate.

How do we store and discharge energy on a large scale?

Large-scale grid storage for renewable, grid-scale batteries do exist, but they need to be improved significantly.

Why are Lithium-ion batteries so popular in electronics and electric cars today? What are the drawbacks?

Batteries store large amount of energy in a relatively small package that can be delivered on demand. If there was no battery for your mobile phone, it would not be mobile and would be tethered by a power cord. For cars, batteries are replacing the combustion of gasoline as the energy source. Electric cars have no emissions. Although we still have to plug in electric cars to charge them, the electricity comes from a variety of sources including renewables and natural gas.

Why do rechargeable batteries eventually become unusable or unstable?

As batteries charge and discharge, a number of chemical and mechanical changes take place. Chemical changes include breakdown of the electrolyte, formation of reaction products, and undesirable dissolution of ions from the electrodes. These chemical changes can in turn cause mechanical problems like large expansion and contraction, cracking and delamination from the current collector. In a commercial battery, these changes take place slowly but eventually lead to a reduction of capacity (no longer holds charge). Another factor is if we try to operate a battery under conditions it was not designed for, it will become unstable. For example, if we try to charge or discharge it too rapidly, if the battery is expanding too much for its housing (e.g. a Samsung phone), or if the battery is damaged (e.g. due to a car accident).

What technologies are you working on to make batteries safer and more reliable?

Our group is working on self-healing strategies to mitigate damage due to expansion and contraction of the active materials. We also are working on the smart release of additives to extend the life of the battery and to prevent thermal runaway.

Which experimental battery technologies seem the most promising for the future?

I’m not really sure. I think solid state batteries (no liquid electrolyte) are promising because they are inherently safer, but there are still many technical challenges to solve.

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