Next generation lithium-ion batteries could use lithium rich cathodes after a discovery at the Department of Energy’s Lawrence Berkeley National Laboratory.
The research group, led by Gerbrand Ceder of Berkeley Lab’s Materials Sciences Division, came to the conclusion after studying how and when oxygen is active in lithium-excessive cathodes.
The findings could enable the next generation of batteries to achieve around 50% higher energy density than current commercial lithium-ion batteries, claim the scientists.
Using a supercomputer, Ceder’s group developed a methodology of utilising quantum mechanical simulations to study electron charge transfer in cathode materials.
The finding were published online in Nature Chemistry under the title “The structural and chemical origin of the oxygen redox activity in layered and cation-disordered Li-excess cathode materials“.
Ceder said: “What we and others have been claiming recently is that you can take an electron off the oxygen and put it back, which is fairly radical. That’s the big idea for this cathode design.
“This paper specifically shows that it’s true and more importantly, shows under which conditions that it becomes true. “
The findings allow scientists to understand how the oxygen in a lithium-rich cathode was oxidized and how it competed with transition metals nickel, cobalt or manganese in oxidation.
Cathode materials in conventional lithium-ion batteries use lithium transition metal oxide, with the content of the lithium and the transition metal balanced.
During a battery’s cycle the transition metal in the cathode oxidizes and releases electrons which travel between the cathode and anode.
The finding showed the researchers how to manipulate those transition metals and oxygen oxidation to achieve higher energy density cathodes.
“This is a very exciting direction being pursued by battery scientists,” one of the paper’s lead authors Jinhyuk Lee said.
“It has been experimentally demonstrated many times that a lithium-excess cathode material can deliver higher energy density, about 50% higher than the current cathode materials in commercial lithium batteries.”
And with transition metals limited availability (45% of the world’s cobalt production now goes to lithium-ion batteries) the findings open the path to using 15 or 20 different transition metals, Ceder said.
“It’s not scalable. If we’re ever to all drive electric vehicles, there’s no way a cobalt-only technology can make it.
“We can use a much broader range of chemistry to look for cathodes, and we know exactly the kind of structures we want to engineer.”
The research started two years ago after Ceder’s group discovered that a so-called “disordered” cathode structure, previously dismissed by battery designers, could indeed be workable.
The paper’s lead authors included Dong-Hwa Seo, its other co-authors were Alexander Urban, Rahul Malik, and ShinYoung Kang.
Picture: (from left) Berkeley Lab researchers Dong-Hwa Seo, Alex Urban, Jinhyuk Lee, and Gerd Ceder
