Electrochemical Properties of Layered NaxNix/2Mn1−x/2O2 (0.5 ≤ x ≤ 1.1) with P3 Structure as Cathode for Sodium‐Ion Batteries. Issue 4 (26th February 2022)

• Record Type: Journal Article
• Authors: Yang, Liangtao; Sun, Yanan; Adelhelm, Philipp
• Is Part Of: Energy technology. Volume 10:Issue 4(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-02-26
• Subjects: cathode materials -- energy storage -- layered oxides -- sodium-ion batteries; Energy development -- Periodicals; Power resources -- Periodicals; 333.79
• DOI: 10.1002/ente.202101121
• Languages: English
• ISSNs: 2194-4288

Abstract

Abstract : The Na properties of Ni and Mn containing layered oxides of the type Na x Ni x /2 Mn1− x /2 O2 are explored between Na contents of 0.5≤ x ≤1.1. Charge balance is maintained by adjusting the Ni/Mn ratio. X‐ray diffraction and scanning electron microscopy are used to characterize the structure and morphology. The primary phase for all as‐synthesized materials is P3, especially at Na contents below x ≤ 0.8. Samples with a Na content of x ≥ 0.9 lead to the formation of Na and Ni secondary phases. The Na storage properties are studied in half cells with two different voltage windows between 1.5–4.0 V and 2.2–4.5 V (vs Na + /Na). Ni and Mn redox are active between 1.5 and 4.0 V accompanying three voltage plateaus at 3.7, 3.0, and 2.1 V, respectively. An additional high‐voltage plateau (>4.0 V) is observed when increasing the cutoff voltage to 4.5 V. The initial Na content has a strong influence on the discharge capacity which ranges from 90 mAh g −1 ( x = 1.1) to 210 mAh g −1 ( x = 0.6). C‐rate tests up to 2C and cycle life over 150 cycles are discussed. Overall, the composition Na0.6 Ni0.3 Mn0.7 O2 shows the most favorable properties with respect to capacity retention, rate capability, and initial Coulomb efficiency. Abstract : Layered transition metal oxides are the most promising cathode materials for sodium‐ion batteries as their composition can be varied over a wide range. In this study, the properties of P3‐Na x Ni x /2 Mn1− x /2 O2 with 0.5≤ x ≤1.1 is studied. While capacity fade is observed for all materials, the most favorable composition is Na0.6 Ni0.3 Mn0.7 O2 providing an initial capacity of 209 mAh g −1 .