Life + Outdoors » Field Notes

The Bane of Batteries



Right by the checkout counter of my local drugstore is a display of "heavy duty" zinc-carbon batteries. Nothing remarkable about that, you say. They were around when you were a kid, right? Actually, they were around when your grandparents were kids, having been patented in 1886 and manufactured commercially 12 years later by the forerunner of the Eveready company. Battery technology has improved since then, of course — but not by much.

The last real breakthrough, from the point of view of consumers, came with lithium-ion (Li-ion) rechargeable batteries, invented in the 1970s and first sold commercially in the 1990s. And truth be told, Li-ion batteries (a generic phrase referring to a whole class of cells using lithium or its compounds in their anodes) aren't that much better than zinc-carbon batteries. Plus, their safety record is spotty: Boeing experienced two Li-ion battery fires last year in its new 787 Dreamliner.

So why isn't battery technology following a version of Moore's Law for storage? Gordon Moore, co-founder of Intel Corporation, noted in 1965 that computing power, expressed as the number of transistors in an integrated circuit, had been doubling every two years, with no foreseeable limit to the trend. His prediction (not a law — gravity is a law!) has proved remarkably prescient, as evidenced by the processing speed and memory capacity of today's digital computers, cameras, smartphones and other electronic gadgets. So what's with batteries? If they'd been following their own Moore's Law since the invention of the transistor in 1947, lead-acid automobile batteries would be the size and weight of a dime by now.

The quick answer is electron size versus ion size. Ask a physicist, "How big is an electron?" and you're liable to hear something like, "We don't really talk much about that." Electrons have mass and charge — but they are infinitely small. That's why Moore's Law works: you're moving around electrons in an electric circuit, so chip performance is limited by lithography technology, not by the size of electrons.

The size (and thus weight) of a battery, on the other hand, is limited by the size of the ions (charged atoms or molecules) that transfer electric charge through a medium (the electrolyte) between the anode and cathode, all of which take up space. So while the capacity of electronics increases exponentially, doubling every couple of years, battery technology improves at glacial speed. The efficiency of lithium ion, the best battery technology available today, has barely doubled over the last 20 years.

Battery design is a compromise between many factors, including energy density (how much power can be stored in a given size and weight), cost, safety, rechargability (fast, and over thousands of times) and environmental friendliness. Incremental battery improvements are on the horizon — silicon anodes and lithium-air technology show promise — but we need a revolution or two more before electric cars become commonplace and solar and wind renewable power outpaces fossil fuels. It's going to take a huge effort to transform the science of energy storage, as those 128-year-old-technology D cells at the drugstore remind us.

Barry Evans' ( three electrifying Field Notes anthologies await you at Eureka Books, Northtown Books and Booklegger.

Add a comment