US scientists crack high-energy EV battery code to address range anxiety, safety
Each cathode has a critical state of charge that defines its safe operating limit.
Researchers are aiming to use nickel-based cathodes, one of the two electrodes that facilitate energy storage in batteries, for safer, high-energy electric vehicle (EV) batteries.
Nickel is less stable than other materials in terms of cycle life and thermal stability.
Now, researchers from the University of Texas at Austin and Argonne National Laboratory have made efforts to change that as they conducted more than 500 measurements on 15 high-nickel cathode materials.
The team discovered that each cathode has a critical state of charge that defines its safe operating limit. Researchers revealed that the strength of metal-oxygen bonds and surface reactivity influence this crucial state.
High-nickel cathodes to revolutionize the EV market
They also underlined that once the material exceeds this limit, instability creeps in. That can trigger the catastrophic condition of thermal runaway, when increased temperature releases energy that further heats the battery, substantially increasing the risk of failure and/or fires.
Arumugam Manthiram, a professor at the Walker Department of Mechanical Engineering and Texas Materials Institute and one of the leaders of the study published in the journal Nature Energy.
High-nickel cathodes have the potential to revolutionize the EV market by providing longer driving ranges,
“Our study provides a comprehensive analysis of their thermal stability, which is crucial for developing safer batteries.”
High-nickel oxide cathodes preferred in automotive lithium batteries
Researchers underlined that high-nickel oxide cathodes (LiNixM1−xO2) are preferred in lithium EV batteries, but they face thermal instability challenges.
They developed a thermal stability index, quantifying how the material reacts during thermal runaway. Factors influencing cathode thermal stability include cathode composition, surface chemistry, nickel content, and crystal size.
Researchers, said:
We present here a statistical thermal analysis based on the differential scanning calorimetry measurements of 15 representative cathode materials with different compositions, morphologies and states of charge,
The findings published in Nature revealed that each cathode has a critical state of charge that defines its safe operating limit, which is affected by the metal–oxygen bond strength and surface reactivity.
Making better EV batteries
Researchers in the study, said:
The thermal runaway temperature is dictated by the layered Li1−xNiO2 to LiNi2O4 spinel-like phase transition, which is thermodynamically determined by the metal–oxygen bond covalency and kinetically influenced by the cation mixing and particle size,
They used Raman spectroscopy to predict the thermal runaway temperature on the basis of the linear relationship between them.
Researchers, added:
Finally, we propose a thermal stability index to quantify cathode thermal stability as a guide for developing safer high-nickel cathodes,
The study is claimed to have far-reaching implications, offering a path to safer, more efficient EV batteries that can support the growing demand for transport. These advancements are said to be crucial for making EVs more viable and attractive for consumers.
Zehao Cui, a research associate in Manthiram’s group, said:
Our work provides a roadmap for the industry to follow, ensuring that the high energy density of these cathodes does not come at the cost of safety,
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US scientists crack high-energy EV battery code to address range anxiety, safety, source
