Four-million-mile battery is now a reality

Dahn, a world-renowned battery scientist and NSERC/Tesla Canada Chair, presented the exciting news during his keynote presentation (titled: More than a million miles and a century of life) at the international battery seminar (IBS) held 28 -31 March 2022 in Orlando, Florida.

The term “Million Mile” battery first came to life after Dahn’s 2019 open access publication in Journal of The Electrochemical Society (JES) stating “we conclude that cells of this type should be able to power an electric vehicle for over 1.6 million kilometers (1 million miles) and last at least two decades in grid storage”.

In an earlier interview with the Nickel Institute, Dahn said; “Our goal is to help lower the cost, increase the energy density and improve the lifetime of Li-ion cells”. Well, that goal has certainly been achieved! These single crystal LiNi_0.5Mn_0.3Co_0.2O₂ (NMC532)/graphite cells started testing in October 2017 and are still running at room temperature, amazingly realizing 4.5 years of continuous cycling with only ~ 5% degradation at 1C:1C. These incredible results can also be achieved at a higher temperature of 40 °C with 4.8 years of continuous cycling. The factors contributing to the cells' long lifetime include switching from polycrystalline NMC to single crystal NMC, the choice of quality artificial graphite (AG), and appropriate electrolyte additives.

Dahn and team also demonstrated the impact of upper cutoff voltage (UCV) in their 2022 JES publication concluding; “NMC811/graphite cells will benefit from an enormous lifetime boost when operated at a limited UCV of 4.06 V, where decades-long lifetimes can be achieved at 20 - 30 °C, if the best graphites are selected”.

Extremely long-life cells are significant for vehicle-to-grid application and utilizing storage capacity in electric vehicle batteries for solar and wind energy. “While 800 100% DoD[i] is enough for an electric vehicle battery, in vehicle-to-grid operation, vehicles will be charged and discharged when parked so more than 10,000 cycles will be required” Dahn said.

Later in his IBS presentation, Dahn showed results comparison between NMC811/AG - LiPF6 vs both LFP/AG – LiPF6 and LFP/LiFSI cells at 40 °C. The NMC811 cells greatly outperformed the Dalhousie LFP cells, which according to Dahn are equivalent to the best commercial LFP cells that they know of.

His keynote presentation was followed by a keynote panel discussion moderated by Vineet Mehta, Director of Battery Technology & Powertrain Architecture/Modeling at Tesla Motors.

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