C: Taras Makarenko / PEXELS

Will solid-state batteries bail out electric vehicles?

Recently, the US National Highway Traffic Safety Administration issued a recall for electric-vehicle batteries made by LG Energy Solution of South Korea. Fires have been caused by some of these batteries, which are used in Mercedes, Hyundai, and General Motors products, among others.

The problem is that rare manufacturing defects can cause overheating and fires. An Associated Press article describing the recall notes that recalls made voluntarily by individual manufacturers for these batteries date back to February of 2020. In November of that year, GM began recalling over 140,000 Chevrolet Bolt EVs to replace possibly defective LG batteries, and LG paid GM $2 billion in compensation.

The insurance industry obviously has a stake in this matter, and a small survey conducted by its Highway Loss Data Institute showed that the rate of fires for electric cars is about the same as it is for gasoline-burners:  0.2 per 1,000 insured vehicle years.

If the best you can say about electric car fires is that they’re no worse than fires in gas-powered ones, that’s faint praise.

Combustible

The underlying problem in electric-car battery fires is the technology. You may not be aware that the liquid or gel electrolyte in the type of lithium battery used in electric vehicles cannot be exposed to air without catching fire. This is one reason that manufacturing such a battery is so tricky.

Back when photographic film was the only way to take pictures, manufacturers figured out how to make hundreds of square yards of sensitive film every day in total darkness. But it wasn’t easy, and the fact that film never got as cheap as, say, toilet paper, had an incalculable effect on the entire industry.

Unless the electric-car business manages to break free of liquid-electrolyte batteries, it may find itself stuck in a similar rut. Except for the battery, an electric car is markedly cheaper to make than a fossil-fuel one. The electronics and the motors are much simpler than the corresponding parts of a gas-powered car.

But right now, the cheapest electrics on the market are many thousands of dollars more costly than an average gas model because of the darned battery, and so the vision of replacing most of our gas-guzzlers with electrics remains just that: a vision.

Potential alternative

On the technological horizon is a development that could change all that:  the solid-state battery. Michael Faraday himself (1791-1867) discovered that solid materials such as silver sulfide could act as electrolytes, which means that ions can move about through them under the influence of electric fields. But up to now, truly solid electrolytes (as opposed to the liquid or gel-like products used in most batteries today) have resisted commercialization for a number of reasons.

A significant milestone in the development of solid-state batteries happened when John Goodenough, who was one of the original developers of current lithium-battery technology, announced in 2017 that he had made a solid-state battery with a glass electrolyte. According to some sources, solid-state batteries could have up to 2.5 times the energy density of current lithium batteries, although it is not clear whether this is a volume or mass energy density.  Either way, it would mean that for the same size or weight battery, a car using a solid-state battery might have a longer driving range than a gasoline car with a typical gas tank.

No one knows yet how to make solid-state batteries cheaply. Thin-film technologies such as vacuum deposition are sometimes used, and while there is concern that such technologies may be difficult to scale, vacuum deposition in other manufacturing areas has been applied to rolls of plastic and other large-scale manufactured goods.  So it’s more a question of investment and effort than fundamental technological obstacles, I suspect.

Tall order

Several automakers, notably Volkswagen and Toyota, are investing heavily in solid-state battery technology. But they have the obstacle shared by all automakers that any product engineered for automotive use has to be a lot more durable and reliable than anything used in the military or even aerospace fields.

Do you think military tank drivers go ten thousand miles without needing any service, or astronauts think they’ll be able to ride their rockets for ten thousand launches without having any problems? Yet we start a car several times a day for years and expect nothing to go wrong.

It’s that kind of standard that every electric-vehicle battery is expected to meet, and the wonder is that they have come this far.  Pardon an old technologist for making a statement that is more intuitive than fact-based, but when I look at a typical EV battery that consists of several thousand individually-manufactured, hermetically sealed, and electrically insulated cells, I see a technology that is fundamentally immature.

Digital computers remained the expensive province of a few wealthy institutions until manufacturers learned to take the many thousands of largely similar components and integrate them onto a chip.

Pricey

I suspect that electric cars will also remain in the realm of the wealthy until solid-state batteries bring the core cost down to the point that people will want to buy them, not because they’re afraid of global warming or want something to match their Patek Phillipe watch, but because they’re cheaper and easier to run than gas-powered ones.

In the meantime, we’re going to have to put up with recalls like the ones for the LG batteries that catch fire on rare occasions, because it seems to be the nature of liquid-electrolyte lithium cells to do that once in a while.

The best manufacturers can do is to watch their processes and inspections rigorously and hope that a better technology will come along that will let them make batteries more like people make computer chips these days, rather than like photographic film was once made, under difficult and unique conditions that are hard to maintain for long.

This article has been republished from Engineering Ethics with permission.

 


Karl D. Stephan

Karl D. Stephan received the B. S. in Engineering from the California Institute of Technology in 1976. 
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