Coupling the Electronic Distribution and Oxygen Redox Potential via Cu Substitution of Layered Oxide Cathodes for Sodium-Ion Batteries

Abstract

Anionic redox chemistry is extensively studied by virtue of the promising strategy for appealing to the large capacity in sodium-ion batteries (SIBs). However, stimulating the lattice oxygen activity generally occurs at high voltage suffering from irreversible oxygen release, transition metal ion migration, and even structural distortion, which is a critical limitation for their further application. In this study, a series of Na y Li 0.1 Cu x Mn 0.9−x O 2 cathode materials are developed by introducing Cu 2+ into the transition metal layer. Theoretical calculations disclosed that the electron agglomeration around the O atom has been enhanced with the increase of Cu content, leading to a strong covalent bonding between Cu and O and contributing to a more stable structure. The local structure facilitates the loss of electrons, thus reducing the O redox potential along the charging process, which is further confirmed by an experimental study. Besides, the Cu substitution introduced a whole solid solution reaction during the charge−discharge process with small volume change, hence greatly improving the cycling performance of NLCMO systems. Our research provides unique insights into the activation mechanism of anionic redox reactions and provides critical guidance in further designing anionic redoxbased layered oxide systems.

Cation Configuration and Structural Degradation of Layered Transition Metal Oxides in Sodium-Ion Batteries

“…Achieving global carbon neutrality hinges on the continual advancement and widespread implementation of large-scale energy storage systems (ESSs). Lithium-ion batteries (LIBs), as one of the earliest commercialized ESSs, have already changed our life by their applications in electric vehicles and mobile electronics. − However, due to the shortage of lithium resources and the rising price of lithium salts, sodium-ion batteries (SIBs) present broad market prospects as the alternatives to complement LIBs in sustainable energy storage devices. − Besides, the physicochemical affinities between lithium and sodium afford the development of SIBs by drawing upon the extensive and successful research foundations established for LIBs. Given the cathode material’s significant influence on a battery’s cost and its electrochemical attributessuch as cycle stability, rate capability, and energy densitythe exploration of suitable cathode materials for SIBs becomes paramount. − The investigation of cathode materials for SIBs mainly includes primarily transition metal oxides, − polyanion compounds, , and Prussian blue analogues. , Statistics over the past five years reveal a consistent annual growth in papers related to these cathode materials as shown in Figure a, and the volume of articles on layered transition metal oxide (LTMO) cathode materials surpasses that of the other two cathode materials.…”