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The EV battery has gone through an epic transformation since the mid-1990s, when General Motors re-introduced zero emission battery power to the mobility market with the short lived EV1 sedan sporting a rack of lead-acid batteries under the hood. Still, further improvement is required if gasmobiles are to be sent to the dustbin of automotive history sooner rather than later, and researchers have hit upon a new type of material called lithium-rich layered oxide to do the trick.
A Better EV Battery, With Lithium-Rich Layered Oxide
Researchers around the world have been zeroing in on lithium-rich layered oxide due to its potential to produce next-level improvements in EV battery technology while shaving down expense. The idea is to replace part of the nickel on the EV battery cathode along with part of the cobalt, providing more space for lithium and manganese.
The result is an increase of up to 20% in energy density compared to conventional nickel-based cathodes. To gild the green lily, the layered oxide approach also reduces costs and supply chain headaches related to cathode materials.
“Lithium-rich layered oxide is one of the most promising candidates for the next-generation cathode materials of high-energy-density lithium ion batteries because of its high discharge capacity,” reads one representative comment, leading off the introduction of a study published in 2022.
There being no such thing as a free lunch, though, the lithium-rich layered oxide EV battery of the future is still a work in progress. “However, it has the disadvantages of uneven composition, voltage decay, and poor rate capacity, which are closely related to the preparation method,” the authors of the same study noted.
Better EV Batteries & The Oxygen Angle
Much water has passed under the EV battery research bridge over the past two years. In the latest development, researchers at POSTECH, the Pohang University of Science and Technology in Korea, reported a durability breakthrough in the lithium-rich layered oxide field, in which they tweaked the electrolyte to maximize cathode durability.
The new electrolyte out-performed a baseline formula by a long shot. “The research team’s enhanced electrolyte maintained an impressive energy retention rate of 84.3% even after 700 charge-discharge cycles, a significant improvement over conventional electrolytes, which only achieved an average of 37.1% energy retention after 300 cycles,” POSTECH explained in a press statement last week.
The journal Energy & Environmental Science has all the details under the title, “Decoupling capacity fade and voltage decay of Li-rich Mn-rich cathodes by tailoring surface reconstruction pathways.”
“Removing polar ethylene carbonate from the electrolyte significantly suppresses irreversible oxygen loss at the cathode–electrolyte interface, preferentially promoting the in situ layered-to-spinel phase transition while avoiding typical rocksalt phase formation,” the authors explain.
The shorter version is that previous research nailed oxygen loss during charging cycles as a main instigator of instability. The new electrolyte provides for a more stable environment at the interface with the cathode, minimizing oxygen loss.
All That Hard Work Is Beginning To Pay Off
Over here in the US, the Department of Energy has been hammering away at the task of stabilizing lithium-rich oxides for EV batteries and other applications, with Argonne National Laboratory among those taking the lead.
“Low-cobalt lithium metal oxide electrodes having higher voltage, increased stability, and contain less expensive manganese (Mn) for use in rechargeable lithium cells and batteries,” the lab notes. “Manganese is less expensive to use and more chemically benign than cobalt or nickel.”
“Either low-cost elements and/or other elements may be doped into the structure to provide better performance, at a lower cost, as needed,” they emphasize.
The Argonne team has been collaborating with other Energy Department facilities in the effort to engineer more stability into NMC cathodes that use less cobalt and less nickel, too. Last summer they published a study in the journal Nature Energy under the title, “Ultrastable cathodes enabled by compositional and structural dual-gradient design,” in which they describe a cathode that can “overcome voltage ceilings imposed by existing cathodes.”
“This design enables simultaneous high-capacity and high-voltage operation at 4.5 V without capacity fading, and up to 4.7 V with negligible capacity decay,” they note. The team deployed high tech imaging systems to determine that the cathode surface is “electrochemically and structurally indestructible, preventing surface parasitic reactions and phase transitions.”
More Than One Path To The Low-Cost EV Battery Of The Future
Speaking of General Motors, the company is among several EV battery stakeholders pursuing other ways to reduce the cost of NMC batteries. One strategy simply involves reducing the size of the EV battery. That doesn’t necessarily mean losing out on performance. The smaller NMC battery would be reserved for driving modes that require higher energy density. The car would also be equipped with less costly LFP (lithium iron phosphate) batteries to perform less demanding chores.
Industry observers have pointed out that the dual-chemistry approach is much more complicated than it may seem, partly due to differences in the charging cycles.
Though the charging differential poses a significant obstacle, it could provide a new opportunity for stakeholders in the EV battery swapping industry. Battery swapping is one of those ideas that seemed far-fetched just a few years ago, the idea being that you can drive into a station and swap out your whole battery for new one in less than five minutes, instead of waiting around to recharge it. More recently, the battery swapping industry has begun proving itself in the marketplace, with commercial fleets among the targets for adoption.
If recharging a dual-chemistry EV battery is too finicky for drivers to handle in person, the task could be taken up by swapping stations outfitted with the necessary systems. Drivers could roll away with a fresh charge on both chemistries each time, regardless of where they left off.
If the overall idea is to lower the cost of EV ownership and kick gasmobiles out of the picture sooner rather than later, battery swapping also lends itself to a lease model that reduces the up-front cost of owning an EV.
Some EV battery stakeholders are not waiting around for the swapping solution. The Novi, Michigan, startup ONE (Our Next Energy) is working on a dual-chemistry EV battery that deploys an LFP cell for everyday driving with a range of 150 miles, after which drivers can squeeze an extra 450 miles out of an anode-free companion cells.
ONE ran into some speed bumps this year, but the company reportedly expects to ramp up production of its long range batteries by the end of 2025.
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Photo (cropped): The state of EV battery technology has come a long way since 1996, when GM deployed lead-acid chemistry in a short-lived attempt to bring electric cars back from a decades-long hiatus (EV1 courtesy of GM via Smithsonian Institution).
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