Compositionally graded high-voltage P2-type cathode with superior structural stability and redox kinetics for advanced Na-ion batteries

• Published in: Nano research Vol. 17; no. 4; pp. 2755 - 2762
• Main Authors: Hou, Peiyu, Dong, Mohan, Sun, Zhenbo, Li, Feng
• Format: Journal Article
• Language: English
• Published: Beijing Tsinghua University Press 01.04.2024
• Subjects: Atomic/Molecular Structure and Spectra; Batteries; Biomedicine; Biotechnology; Cathodes; Chemical composition; Chemistry and Materials Science; Cobalt; Condensed Matter Physics; Electrochemistry; High voltage; High voltages; Kinetics; Manganese; Materials Science; Nanotechnology; Nickel; Nickel compounds; Phase transitions; Rechargeable batteries; Research Article; Sodium; Sodium channels (voltage-gated); Sodium-ion batteries; Solid solutions; Structural stability; Superstructures; Synergistic effect; P2-type cathode; phase transition; Na-ion battery; composition regulation; redox stability
• ISSN: 1998-0124; 1998-0000
• DOI: 10.1007/s12274-023-6181-1

Layered P2-type cathodes with high voltage, large capacity, and easy synthesis show great potential for developing sodium (Na)-ion batteries (NIBs). However, the P2–O2 phase transition makes their structural degradation and the Na + /vacancy ordering lowers their redox kinetics. Here, we rationally propose a compositionally graded P2-type cathode, where nickel (Ni) and manganese (Mn) fractions decrease gradually, and cobalt (Co) content increases contiguously from the inside to the outside of a secondary particle. Inside these particles, the Ni/Mn-based compound delivers high capacity and high voltage. On the surface of particles, the Co/Mn-based solid solution offers a stable buffer matrix. Benefiting from these synergistic effects, this graded P2-type cathode shows the elimination of P2–O2 transformation even when charged to 4.4 V, which enables good structural stability, maintaining capacity retention reaching ∼ 80% within 300 cycles. Moreover, the Na + /vacancy ordering superstructure is further suppressed, and the Na + diffusion kinetics is significantly improved. The proposed graded structure with optimized chemical composition offers a new perspective for eliminating the unwanted phase transition and thus enhancing the electrochemistry of high-voltage layered cathodes for advanced NIBs.