Novel Core–Shell-Type Design of Na0.5[Li0.5(Ni0.8Co0.1Mn0.1)1−x(Ni0.5 Co0.1Mn0.4)x]O2 Cathode Material for Sodium-Ion Batteries

Abstract

High-nickel cathode materials possess several disadvantages such as poor cycle performance and thermal instability resulting from the side reaction with the electrolyte that occurs during cycling. In order to improve the cycle performance and thermal stability of the Na0.5[Li0.5(Ni0.8Co0.1Mn0.1)]O₂ (core), we synthesized the core-shell structure of Na0.5[Li0.5(Ni0.8Co0.1Mn0.1)1-x(Ni0.5Co0.1Mn0.4)x]O₂. The results of energy-dispersive X-ray spectroscopy (EDS) line analysis showed that the core of the high-nickel NCM precursor and the shell of the low-nickel NCM precursor were successfully synthesized as two phases. The core-shell cathode material shows a small capacity loss after 30 cycles (capacity retention=60.78%) compared with the core cathode material (capacity retention = 48.57%). The results of differential scanning calorimetry (DSC) show that the 4.6 V charged core-shell cathode material has a large exothermic peak at 297.4 °C, and the low reaction releases 246.1 J·g-1 of heat. The core-shell cathode material shows improved electrochemical performance and is a thermally stable material for use as a cathode material for sodium-ion batteries.