Over‐stoichiometric metastabilization of cation‐disordered rock salts

Cation‐disordered rock salts (DRXs) are well known for their potential to realize the goal of achieving scalable Ni‐ and Co‐free high‐energy‐density Li‐ion batteries. Unlike in most cathode materials, the disordered cation distribution may lead to more factors that control the electrochemistry of DRXs. An important variable that is not emphasized by research community is regarding whether a DRX exists in a more thermodynamically stable form or a more metastable form. Moreover, within the scope of metastable DRXs, over‐stoichiometric DRXs, which allow relaxation of the site balance constraint of a rock salt structure, are particularly underexplored. In this work, these findings are reported in locating a generally applicable approach to “metastabilize” thermodynamically stable Mn‐based DRXs to metastable ones by introducing Li over‐stoichiometry. The over‐stoichiometric metastabilization greatly stimulates more redox activities, enables better reversibility of Li deintercalation/intercalation, and changes the energy storage mechanism. The metastabilized DRXs can be transformed back to the thermodynamically stable form, which also reverts the electrochemical properties, further contrasting the two categories of DRXs. This work enriches the structural and compositional space of DRX families and adds new pathways for rationally tuning the properties of DRX cathodes. © 1999-2024 John Wiley & Sons, Inc or related companies.

Description

This work was financially supported by University of New Mexico new faculty startup award, research allocation committee award, and Oak Ridge Associated Universities Ralph E. Powe Junior Faculty Enhancement Award. Use of the Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory is supported by the Office of Science, Office of Basic Energy Sciences of the U.S. Department of Energy under Contract No. DE-AC02-76SF00515. Acquisition of the quantum cascade laser used for s-SNOM IR imaging in this work was supported by NSF award 2154617. S.Z. was supported by faculty startup award at South Dakota School of Mines and Technology. The ICP-MS instrument was supported in part by NIH P20GM130422 and P30ES032755. The authors greatly appreciate the neutron beamtime granted from ECHIDNA in ANSTO.

Keywords

Salts, Metastable states, Nickel, Lithium ion batteries, Cathodes, Thermodynamics, Stoichiometry, Energy storage, Electrochemistry

Citation

Wang, Y., Outka, A., Takele, W. M., Avdeev, M., Sainio, S., Liu, R., Kee, V., Choe, W., Raji-Adefila, B., Nordlund, D., Zhou, S., Kan, W. H., Habteyes, T. G., & Chen, D. (2023). Over-stoichiometric metastabilization of cation-disordered rock salts. Advanced Materials, 35(51), 2306396. doi:10.1002/adma.202306396