Scientists from the Argonne National Laboratory, U.S. Department of Energy, have uncovered a critical hydrogenation mechanism that accelerates the degradation of lithium-ion batteries in electric vehicles (EVs).
Extending the lifespan of such batteries is crucial for the broader adoption of EV technologies, according to a press release published by the National Laboratory.
The research used the Advanced Photon Source (APS), a high-energy X-ray facility, to observe molecular-level changes in the battery components, shedding light on a process called self-discharge.
“Self-discharge is a phenomenon experienced by all rechargeable electrochemical devices,” Argonne senior chemist Zonghai Chen said.
“The process slowly consumes precious functional battery materials and deposits undesired side products on the surface of the battery components. This leads to continuous degradation of battery performance.”
Rot behind the battery degradation
The breakthrough discovery of a hydrogen-centered mechanism that explains the degradation in lithium-ion batteries is at the heart of the research.
The team demonstrated how self-discharge is caused by photons and electrons moving from the electrolyte into the cathode’s layered oxides.
The collaborative research involving Argonne, many U.S. academic institutions, and other recognized national labs validated the mechanism through experiments and computational studies.
“It is the ideal pairing of the X-ray studies and electrochemistry that enables our discoveries on how cathode hydrogenation occurs in lithium-ion batteries and impacts self-discharge,” said study lead Gang Wan, a physical science research scientist at Stanford University.
The findings close a long-standing information gap about cathode breakdown and electrolyte decomposition.
Michael F. Toney, a study co-author and professor at the University of Colorado Boulder, said that the “right chemistry for these cathode materials is necessary to improve the battery’s chemical stability and reduce the rate of self-discharge.”
“Degradation of the cathode reduces the battery’s lifetime,” he added.
According to the prevailing wisdom, the two primary explanations for cathode deterioration are oxygen release from cathodes and lithium loss.
However, other studies have concluded that “electrolytes tend to decompose on cathode surfaces,” creating a massive knowledge gap between the decomposition and degradation of the cathode and electrolyte within lithium batteries.
Advancing battery technology for EV revolution
The study opens new avenues for enhancing battery performance in EVs. Scientists aim to create batteries that are smaller, lighter and have a lower cost by addressing the self-discharge issue.
“By mitigating self-discharge, we can design a smaller, lighter and cheaper battery without sacrificing end-of-life battery performance,” stated Argonne’s senior chemist Zonghai Chen.
The APS is expected to play a crucial role in accelerating these advances by allowing scientists to perform even more precise atomic-level investigations of EV batteries , noted the press release published on Friday.
Meanwhile, the demand for EV batteries increased to over 750 GWh in 2023 from 2022, despite a minor slowdown in the 2021-2022 yearly growth, according to the International Energy Agency (IEA) last year report .
The U.S. and Europe experienced “fastest growth among major EV markets, reaching more than 40% year-on-year, closely followed by China at about 35%.”
However, the U.S. “remains the smallest market of the three, with around 100 GWh in 2023, compared to 185 GWh in Europe and 415 GWh in China.”
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