Aug 04, 2023

This dual


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A team of researchers at the East China University of Science and Technology (ECUST) has figured out a way to make Li-ion batteries cheaper and better. They have developed a unique strategy that allows them to increase the stability of nickel-rich cathode in Li-ion batteries.

Li-ion batteries are made up of four primary components; cathode, electrolyte, separator, and anode. The cathode and anode in the battery are coated with special materials to enhance their stability, conductivity, and energy density. It is believed that coating the cathode with a nickel-rich layer could give rise to more advanced high-energy Li-ion batteries.

The researchers suggest that such batteries will have better electrochemical performance and they will cost lesser than the currently used Li-ion batteries. However, nickel-coated cathodes are highly unstable and lead to a significant decrease in battery capacity in the long run.

"At this point in time, the use of lithium-ion batteries is mainly constrained by the limited specific capacity of their cathode material. Nickel-rich layered cathodes always suffer from rapid capacity fading because of the structural and interfacial instability that occurs with the long-term operation," the researchers note.

The newly proposed strategy can fix this problem.

The current study is not the first attempt to make nickel-rich cathodes work. Since high-performance Li-ion batteries are in great demand due to the fast-growing electric vehicle market, scientists have been trying to overcome the stability issues for some time. However, most such efforts have been focused on either surface coating or element doping.

The study authors believe that such unidirectional methods are not enough to overcome the "structural and interfacial instability" of nickel-rich cathodes. Moreover, these solutions often decrease the battery capacity instead of solving the problem. For instance, single-element doping mostly fails to stop the reaction between the cathode and electrolyte.

It causes electrolyte decomposition that eventually leads to a significant decrease in the life and performance of a Li-ion battery's life. Therefore, the researchers proposed a dual-modification strategy that promises to make nickel-rich cathodes stable and feasible in the long run.

Their battery cathode comes doped with titanium and coated with a nickel layer containing lithium yttrium dioxide (Li YO2). This dual modification is achieved through a sintering method that applies heat and pressure and turns everything (coating, doped material, and cathode) into a solid mass.

The researchers tested this cathode using X-ray diffraction and electron microscopy. These tests revealed that the modified cathode was both structurally stable and has better battery capacity retention than a regular cathode. After 100 and 500 charge cycles, the dual-modified cathode had capacity retention of 96.3 percent and 86.8 percent, respectively.

If you have still not been able to fully understand this single-step dual modification process, here is a simple explanation—-The strong titanium-oxygen bonds that result from doping actually improve the stability of the cathode. Whereas the LiYO2 nickel-rich coating successfully prevents electrolyte degradation and other detrimental side reactions that are usually responsible for the dissipating capacity of Li-ion batteries.

The researchers are now planning to test their dual-modified cathode's performance in challenging environments. "The stability under extremely harsh conditions will be studied to ensure the safety of the material and facilitate its commercial application," Hao Jiang, one of the study authors and a professor at ECUST, said in a press release.

Professor Jiang and their team also aim to make this process scalable so that batteries with the dual-modified cathode could soon become commercially available.

The study is published in the journal Particuology.