Written by IEEE | April 21, 2019
Batteries already play a major role in how we use electronics. But as we move toward renewable energy sources, more technologies (like automotive) are beginning to rely entirely on electricity stored in batteries, and lots of it.
To handle these increased demands, engineers and technologists have been working to improve two main types of rechargeable batteries: the lithium-ion batteries we commonly see in electronics, and the lead-acid batteries used in more industrial applications.
Currently, battery anodes (the electrode at the end of the battery through which the current enters) are made out of carbon. One idea explored on IEEE Spectrum is to use silicon instead, since lithium ions combine with silicon, which “means a smaller amount of anode material can store a lot more lithium. Silicon anodes could thus provide much larger capacities.”
Many of the efficiency issues that lithium-ion batteries face “can be traced largely to dendrites, tiny threadlike structures that form on the surface of an electrode over repeated cycles of charging and discharging,” according to researchers at Dartmouth and Stanford. They tend to grow when the battery is overcharged, according to the article.
They also create cracks that expose lithium to the electrolyte, and the resulting chemical reaction depletes the amount of lithium available, making the battery less efficient. Additionally, since dendrites are fragile, they “often break off from the anode, generating ‘dead lithium’ that cannot be reused,” further lowering the efficiency of the cell, according to the researchers. Ultimately, to compensate for this loss, “today’s batteries must include excess lithium, which adds substantially to their weight and cost.”
By adding lithium polysulfide and lithium nitrate to the electrolyte, the researchers were able to limit dendrite growth and increase the battery’s stability.
Another method to prevent dendrite growth is being pioneered by a company in Massachusetts. Instead of changing the liquid components, they’re coating the anode with a polymer-ceramic electrolyte. They say these semi-solid batteries can store twice as much energy as a comparably-sized conventional lithium-ion battery.
What about the lead batteries we still use widely for things like cars? While you might not expect it, a battery industry workshop recap on IEEE Spectrum says “In terms of dollars per kilowatt-hour of energy, lead batteries are already the most cost-effective energy storage system available. And unlike alternative types of storage, lead batteries are fully recyclable, allowing for minimal waste from their usage.” Participants in the workshop are focused on extending the cycle life of lead batteries and improving their charging process.
Progress in battery technology is particularly exciting from an environmental sustainability perspective. As solar panels become significantly more powerful, storing the power they generate is essential to improving our current grid without needing to make massive changes to the power distribution system itself.
In an interview with IEEE Spectrum, Silicon Valley visionary and Sun Microsystems co-founder Bill Joy talks about the implications advanced solid-state batteries could have on the grid: “Really cheap storage causes you to not have a power grid but an energy grid. And an energy grid is just not the same as a power grid. It’s totally amazing. Because you can buy and sell energy and use it later.”
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