Pusan National University Researchers Develop Game-Changing Method to Create Safer, Long-Lasting Lithium-Ion Batteries

A novel mathematical framework unlocks unlimited customization of full concentration gradient in high-nickel cathodes for improved safety and stability

SINGAPORE, July 16, 2025 /PRNewswire/ -- With the recent global push toward renewable energy and electric vehicles, the demand for lithium-ion batteries (LIBs) is rising rapidly. The performance and stability of LIBs largely depend on the cathode material, which can account for nearly 40–45% of the total battery cost. Among cutting-edge technologies, high-nickel cathodes stand out for their high energy density and cost efficiency. However, increasing the nickel content also intensifies side reactions, severely compromising interfacial robustness and mechanical integrity—factors that limit large-scale applications.

A promising solution is the use of full concentration gradient (FCG) or core–shell designs. In such structures, the nickel concentration gradually decreases from the core to the surface of each cathode particle, where it is replaced by more stable elements such as cobalt and manganese. This gradient enhances surface stability and mechanical strength. Unfortunately, the current fabrication methods offer limited tunability. Once the average composition is set, the slope and curvature of the gradient are also constrained, restricting the design flexibility of FCG cathodes.

In a new study, an international research team led by Associate Professor Hyun Deog Yoo from the Department of Chemistry and the Institute for Future Earth at Pusan National University, Korea, introduced a novel mathematical framework that enables fully flexible FCG design. "Unlike conventional methods, where adjusting one parameter affects the others, our approach allows independent and precise control over multiple descriptors, including average composition, slope, and curvature," explains Dr. Yoo. The team's findings were published on June 30, 2025, in the journal ACS Energy Letters.

Traditionally, FCG cathodes are synthesized via a coprecipitation method involving two tanks of metal precursor solutions. The first tank, rich in nickel (Ni), feeds directly into the reactor. The second tank, containing cobalt (Co) and manganese (Mn), is mixed into the first to reduce the Ni concentration over time. However, in conventional systems, the second tank's fixed flow rate limits each setup to just one specific gradient per average consumption.

The researchers overcame this limitation by expressing the flow rate of the second tank as a time-dependent mathematical function. This innovation allows independent tuning of the average composition, slope, and curvature—enabling the generation of a virtually unlimited range of concentration gradients using just two tanks. By integrating this approach with an automated reactor system, the team successfully synthesized five FCG Ni_0.8Co_0.1Mn_0.1(OH)₂ precursors with finely tuned gradients, verified through two- and three-dimensional elemental mapping.

The resulting high-nickel cathodes exhibited significantly improved mechanical and structural stability compared to conventional counterparts. They showed enhanced lithium-ion transport for better electrochemical performance and minimal particle cracking—an essential trait for long cycle life. Notably, the optimally designed FCG cathode retained 93.6% of its initial capacity after 300 cycles, the highest cycling stability reported for FCG cathodes of similar composition.

"Our approach has the potential to transform the safety and performance of LIB-based energy storage systems," says Dr. Yoo. "This could lead to safer consumer electronics and medical devices, more reliable electric vehicles, stable power grids, and broader adoption of renewable energy technologies."

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