New insights from Berkeley Lab may lead to increased battery capacity

Karin Goh/Staff

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Researchers from the Lawrence Berkeley National Laboratory published an article Thursday unveiling their insights into the previously unknown crystal structure of lithium- and manganese-enriched metal oxides found in batteries, the culmination of nearly four years of research.

Layered transition metal oxides are currently used in rechargeable batteries for electronic devices, such as cellphones. Increasing the lithium and manganese content in the cathode of these metal oxides — which forms half of the circuit that powers a battery — was discovered a decade ago to nearly double battery capacity. But the problems associated with the battery include voltage and capacity fade, which make the batteries less viable for reuse.

According to Gerbrand Ceder, campus professor in the department of materials sciences and engineering, the cathodes within a lithium ion battery are replaceable like different engines in a car.

Alpesh Shukla, one of the lead researchers in the study, said capacity and voltage fade cause the batteries to lose charge quickly with use. These problems occur due to structural changes that happen in the cathode of the battery. By studying the structure, researchers hope to find a way to make these batteries more viable for reuse while maintaining their capacity to hold greater amounts of lithium and manganese.

“It’s like an egg basket that gets smaller and smaller,” said Guoying Chen, principal investigator and staff scientist at the Berkeley Lab, referencing the decreasing battery capacity studied.

Previously, researchers had been separated into three schools of thought as to the structure of lithium- and manganese-enriched metal oxides. By examining a host of lithium- and manganese-enriched metal oxides from different directions under a microscope’s atomic resolution, researchers at the Berkeley Lab believe they have discovered these oxide structures.

Prior to this discovery, scientists considered options such as including little domains of inert material inside to hold the battery material together. The study, however, showed the structure was different than previously thought.

“Only if we understand the structure can we figure out why (cathodes) do what they do,” Ceder said. “The work is really very useful in that it lets us understand this new class of battery material that promises to have high capacity.”

Although the researchers now have a better understanding of the structure within these batteries, Chen said scientists’ next step is to examine structural changes that occur while the battery is in operation, so they can design new ways to account for voltage fade.

“(The researchers) didn’t themselves give a solution to the fade problem, but their works should really put us on the right track,” Ceder said.

Chen agreed, noting that this research is “not final,” and that scientists will likely explore the issue in future studies.

“This particular study was done on samples that we made in the lab with well-controlled particle methodology and composition, but these materials are very sensitive to composition,” Chen said, noting the scope of their experiment.

Contact Haruka Senju at [email protected].