Regulated Cu/Co Elemental Composition To Build High-Performance Cathode Materials of Sodium-Ion Batteries

The precise design of a high-entropy cathode material can achieve excellent performance. Many scholars have conducted extensive research on element design, but studies on the roles of each element are relatively scarce in high-entropy systems. In this project, we adjusted the composition of Cu/Co elements and developed three materials, NaNi0.25Fe0.15Mn0.3Ti0.1Ce0.02Co0.09Li0.1O2 (HEO-Co), NaNi0.25Fe0.15Mn0.3Ti0.1Ce0.02Cu0.06Co0.05Li0.1O2 (HEO-CC), and NaNi0.25Fe0.15Mn0.3Ti0.1Ce0.02Cu0.13Li0.11O2 (HEO-Cu). The physical properties and electrochemical performances are analyzed. The appropriate introduction of the Cu element can reduce the voltage difference between the redox potential and the electrochemical polarization. Moreover, it possesses outstanding air and structural stability. The appropriate proportion of the Co element can expand the interlayer spacing of the Na layer, increase the diffusion coefficient of Na+, and achieve excellent rate performance. The appropriate ratio of Cu and Co combines the advantages of both elements, endowing cathode materials with a stable structure, excellent air stability, and electrochemical performance. This work thoroughly explores the specific roles of Cu and Co elements, providing valuable insights for the design of high-entropy cathode materials and a practical pathway toward industrial-scale applications.