Enlarge / Ordered rock crystals, courtesy of a salt mine. (credit: Lech Darski )

Better batteries are a critical enabling technology for everything from your gadgets all the way up to the stability of an increasingly renewable grid. But most of the obvious ways of squeezing more capacity into a battery have been tried, and they all run straight into problems. While there may be ways to solve those problems, they're going to need a lot of work to overcome those hurdles.

Earlier this week, a paper covers a new electrode material that seems to avoid the problems that have plagued other approaches to expanding battery capacity. And it's a remarkably simple material: a variation on the same structure that's formed by crystals of table salt. While it's far from being ready to throw in a battery, the early data definitely indicate it's worth looking into further.

Lithium density

Lithium-ion batteries, as their name implies, involve shuffling lithium between the cathode and the anode of the battery. The consequence of this is that both of the electrodes will end up needing to store lithium atoms . So most ideas for next-generation batteries involve finding electrode materials that do so more effectively.

Sour beer has been around for centuries, and has become a favorite with craft brewers in recent years. But the brewing process can be unpredictable. To help brewers better understand how sour beers develop their distinctive complex flavors, chemists at the University of Redlands in California have been tracking various chemical compounds that contribute to those flavor profiles, monitoring how their concentrations change over time during the aging process. They presented their initial findings during the American Chemical Society's Fall 2020 Virtual Meeting & Expo last week.

Goses, lambics, and wild ales, oh my!

Brewers of standard beer carefully control the strains of yeast they use, taking care to ensure other microbes don't sneak into the mix, lest they alter the flavor during fermentation. Sour beer brewers use wild yeasts , letting them grow freely in the wort, sometimes adding fruit for a little extra acidity. Then the wort is transferred to wooden barrels and allowed to mature for months or sometimes years, as the microbes produce various metabolic products that contribute to sour beer's unique flavor. But the brewers don't always know exactly which compounds end up in the final product or how it will impact the overall flavor profile. "That is the quandary of the sour beer brewer," said co-author David Soulsby during a virtual press conference .

"Sour beer tastes very different from regular beer, but it's a very complex and rich flavor experience. These different flavors come from the complex processes that are occurring during aging," said co-author Teresa Longin, who also happens to be married to Soulsby. "These processes are hard to control and can be hard to reproduce. Our research focuses on understanding what these processes are, what's happening over time, so that the brewer can ultimately understand them and make better beer."

Monash University Associate Professor Matthew Hill, Dr. Mahdokht Shaibani, and Professor Mainak Majumder with the lithium-sulphur battery design. (credit: Monash University)

The name "lithium-ion battery" seems to imply that lithium is the essential ingredient that dictates the battery's performance characteristics. But that's less true than it appears. The electrodes that the lithium shuttles between are critical for dictating a battery's performance, which is why electrode materials played such a large role in the description of last year's Chemistry Nobel . Different electrode materials dictate the battery's performance in part based on dictating the energy difference between the charged and uncharged state. But they also determine how much lithium can be stored at an electrode, and through that the energy density of a battery.

There are a number of ideas floating around for new electrode materials that store lithium in fundamentally different ways: as solid lithium metal or as lithium oxide, which allows some of the electrode material to come from the air outside the battery. There are also chemicals that can store much more lithium per given area of volume. All of these options present serious issues (often more than one) that have kept them from being adopted so far. But a recent paper is promising a major breakthrough in something that's always been an attractive option for lithium storage: sulfur.

Alternate electrodes

"Holds lots of lithium" isn't a high bar to clear; if that was all we were looking for, some of these alternative electrode materials would be in use already. But there's a whole host of other characteristics: cheap and easy to work with, compatible with the chemistry of the rest of the battery components, holds up to repeated charge cycles, and so on.