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2017-08-03

Electric-car battery progress: incremental improvements, not revolutionary leaps




Lithium-ion cell and battery pack assembly for Nissan Leaf electric car in Sunderland, U.K., plant

The report that Toyota is planning an electric car with a solid-state battery for 2022 has led some fans and advocates to suggest huge new leaps in electric cars are imminent.
The 2011 Nissan Leaf had an EPA-rated range of 75 miles combined; the comparable figure for a 2017 Chevrolet Bolt EV is 238 miles.
That's remarkable progress, and clearly lithium-ion battery costs have come down faster over those seven years than anticipated a decade ago.
But don't be fooled into believing electric cars will improve incredibly, amazingly, unimaginably fast ... "because of Moore's Law."
As a recent article in the British Financial Times (subscription required) noted, "Batteries are not atom bombs, integrated circuits or penicillin."
That is, improvement in batteries is almost always incremental, coming a few percentage points at a time, with major leaps few and far between.
Consider how long it took, for example, to move from lead-acid battery cells (invented in 1859) to the nickel-metal-hydride chemistry that had twice its energy density.
The answer is 130 years: the first commercially available NiMH cell hit the market in 1989.
The movement from those two chemistries to lithium-ion cells that doubled energy density again was swift; the first commercial product using a lithium-ion battery, a Sony video camera, entered the market in 1991.
Toyota's solid-state news notwithstanding, industry analyst all expect the bulk of battery-electric and plug-in hybrid vehicles to use refined versions of today's lithium-ion batteries at least through 2025.
The energy density of automotive-scale lithium-ion cells will likely improve at a rate of about 7 percent a year, as it has done for small-format consumer cells over close to 30 years. (The Financial Times quotes one analyst suggesting 5 percent.)
Those improvements come from three sources: tweaks to anode, cathode, and electrolyte chemistries; improvements to fabrication processes; and economies of scale as innovations ramp up to tens of millions of cells a year.
That rate of improvement differs from the Manhattan Project to develop atomic weapons, the quest for a miracle antibiotic that led to penicillin, and the pace of integrated-circuit improvements laid out in Moore's Law, in which performance doubles every 18 months.
As the Financial Times noted, too many people "still have a childlike belief in the electric-battery industry" and miracle discoveries that will transform everything.
This ideology seems immune to fires in mobile phones, fading laptops, or collapsing prices for second-hand electric cars. “All these problems could be solved,” the after-dinner philosophers intone, “with some breakthroughs in battery technology.”
The reality is that an enormous amount of capital from investors and effort on the part of engineers produces "progress, not breakthroughs."
After 30 minutes on the phone with an executive at a solid-state battery technology startup, it's clear notable hurdles remain before it can be brought to market for vehicular use.
Improvement of 7 percent a year isn't necessarily slow, but it's not transformative in a single year. It requires, say, seven years to take out enough cost to change the vehicle significantly.
Luckily, automotive products tend to run in five- to seven-year cycles, so it's reasonable to expect notable improvements in battery capability with each new generation of electric car.
Holding your breath for the next battery breakthrough, however—or breathlessly circulating a paper on the promising outcome of a specific lab experiment—may produce more frustration than revelation.
Those solid-state cells? They likely won't power huge numbers of electric cars until 2025 or later, fully 15 years and two generations after EVs hit the market in December 2010. You have been warned