One of the biggest concerns about EVs is that the batteries will need replacing after a few years, at great expense. After all, your smartphone battery is likely to have seen better days within as little as three years. But a Tesla researcher is getting ready to kick this idea into touch once and for all, after demonstrating batteries that could potentially outlive most human beings.
Tesla enthusiasts are likely to have heard of Jeff Dahn already. He’s a professor at Dalhousie University and has been a research partner with Tesla since 2016. His focus has been to increase the energy density and lifetime of lithium-ion batteries, as well as reducing their cost. Dahn appears to have hit the motherload along with colleagues on his research team. In a paper published in the Journal of the Electrochemical Society, the group claims to have created a battery design that could last 100 years under the right conditions.
Fancy an EV that will last 100 years and 4 million miles? A Tesla researcher may have just what you … [+] need.
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Dahn’s paper contrasts cells based on Li[Ni0.5Mn0.3Co0.2]O2 chemistry (“NMC 532”) to LiFePO4. The latter is the “Lithium Iron Phosphate” (aka LFP) chemistry that Tesla is currently using in Chinese-built standard Model 3 cars imported into Europe. The LFP chemistry has lower energy density than more widespread Lithium-Ion alternatives, but is cheaper, more durable, and allegedly safer, too. LFP can last up to 12,000 charge-discharge cycles, so beating it in this regard is no mean feat. Dahn’s NMC 532 cells showed no capacity loss after nearly 2,000 cycles. The paper extrapolates this out to imply a 100-year lifespan (they obviously haven’t been testing the battery that long).
Dahn also presented a keynote in March at the international battery seminar in Orlando, Florida, where he talked about a “4-million-mile battery”. This included some of the findings in the paper, prior to its release this month. Dahn had previously promised the “million-mile battery”, and has been testing cells based on his adjusted chemistry since October 2017. Apparently, they have been going strong and after 4.5 years of continuous cycling at room temperature, they have only seen 5% degradation. This would mean they could power an EV for 4 million miles before needing to be replaced.
Part of the reasons for the longevity is the switch from polycrystalline to single-crystal cathodes, which don’t break down so rapidly during the charge-discharge cycle. The NMC 532 chemistry Dahn is using contrasts with the NMC 811 chemistry currently employed by LG Chem, which has eight parts nickel in its cathodes for each part of manganese and cobalt. Last year the Tesla Model Y switched from NMC 811 to LG Chem’s NCMA chemistry cells, aka “high nickel”. These are expensive compared to either LFP or NMC 811 but offer the highest density for longest range. NCMA chemistry uses nickel, cobalt, manganese, and aluminum for its cathodes, but the majority is nickel (89%).
The orange diamonds in graph a) show that the NMC 532 chemistry showed no reduction in capacity … [+] after nearly 2,000 cycles.
Jeff Dahn
The NMC 532 chemistry Dahn has been testing promises another leap forward in battery technology. However, cars don’t need to last 100 years, and they don’t need to go 4 million miles either. Considering that the average vehicle age in the USA is 12 years doing 14,000 miles per year, the mean lifetime distance driven by an American car is 168,000 miles, and in Europe it’s a lot less. So, in reality, batteries with 4-million-mile durability will enable applications such as vehicle-to-grid, which will increase the rate of charge-discharge cycling. But they are more likely to be most useful for static energy storage in houses and for grid buffering capacity from an intermittent renewable supply.
Hydrogen enthusiasts often argue that batteries are just a stopgap until Fuel Cell Electric Vehicles and hydrogen storage systems hit the mainstream. But with all the development taking place in battery technology, hydrogen is likely to be too little, too late when it does arrive in volume for transportation. Technologies like those Dahn is working on, alongside lithium sulfur developments such as from Theion and ultra-rapid charging technology such as StoreDot’s, will mean that in just a few years’ time batteries have solved all the problems posed against them.
