Excess lithium enhances battery performance

Conventional battery materials have reached their theoretical performance limits. To increase the energy densities of rechargeable lithium-ion batteries, which will help promote renewable energy resources, researchers must investigate alternative materials.

Campéon and Yabuuchi present recent innovations in nickel- and cobalt-free battery materials, which exhibit a higher energy density than conventional battery materials based on nickel/cobalt ions.

Whereas lithium-ion batteries made from conventional materials rely on charge compensation from cation species, these nickel-/cobalt-free materials contain excessive lithium, meaning they rely on charge compensation from both a cation and an anion. Lithium-excess materials accumulate electric charges at a higher density than conventional materials.

“This innovative material synthesis guideline holds great promises toward the realization of a carbon-free society,” Naoaki Yabuuchi said. “Researchers should read this review to comprehend the current challenges facing next-generation lithium-ion batteries and to understand how to break through this wall and develop higher energy density battery material by focusing on the development of lithium-excess materials with cationic/anionic redox.”

The authors hope researchers use this review to guide their study of lithium-excess batteries, ultimately accelerating industrial development of nickel-/cobalt-free materials.

Low cyclability, the number of times a battery can be recharged before it breaks down, is currently a major roadblock to the development of lithium-excess batteries. They encourage future research efforts seek to understand how the anionic redox reaction destabilizes the material.

Lithium-excess batteries will likely play a role in the development of negative electrode-free systems, a new strategy to increase the energy density of batteries. The energy density of these systems depends only on positive electrode materials.

Source: “Fundamentals of metal oxide/oxyfluoride electrodes for Li-/Na-ion batteries,” by Benoît Denis Louis Campéon and Naoaki Yabuuchi, Chemical Physics Reviews (2021). The article can be accessed at https://aip.scitation.org/doi/full/10.1063/5.0052741 .