Copper and Oxygen Redox in P2- and P3-Structured Copper-Based Cathodes for Sodium-Ion Batteries

Abstract

Lithium-ion batteries currently power our world, but as the demand is being ramped up in electric vehicles (EV) and the electric grid, the reliance on scarce resources like lithium and cobalt has become an increasingly serious issue. One proposed solution is sodium-ion batteries, which benefit greatly from the natural abundance of sodium and the unique ability to utilize iron or copper redox at the cathode. However, deeper understanding of the redox mechanism and consequent electrochemical performance in Na-ion cathodes is needed, especially regarding the possibility of oxygen redox and voltage fade during cycling. Here we focus on P2- and P3-structured (Na2/3X1/3Mn2/3O2) cathodes where X can be Cu or derivatives with partial lithium substitution, to elucidate how structure and lithium substitution influence the copper redox both in initial cycle and the following cycles. Synchrotron-based x-ray spectroscopy, microscopy, and scattering techniques provide insights into the redox mechanism, chemical species distribution, and phase transitions during the cycling.Acknowledgment: The work at Brookhaven National Laboratory was supported by the Assistant Secretary for Energy Efficiency and Renewable Energy, Vehicle Technology Office of the U.S. Department of Energy through the Advanced Battery Materials Research (BMR) Program under contract DE-SC0012704. This research used resources of the National Synchrotron Light Source II, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Brookhaven National Laboratory under Contract No. DE-SC0012704. Partial support for A. Ronne was provided by an NSF NRT Award in Quantitative Analysis of Dynamic Structures (DGE 1922639) as a fellowship.