A novel air‐stable O3‐type layered oxide cathode material with low Ni content for sodium‐ion batteries

Abstract

A novel O3-NaMn 0.42 Fe 0.42 Ni 0.17 O 2 cathode material for sodium-ion batteries is synthesized, for the first time, by a co-precipitation method followed by solid-state reaction. The effect of Ni 2+ , Cu 2+ and Ca 2+ substitution for Mn 4+ and Fe 3+ on the structural stability, rate capability and cycling performance of the cathode material are examined. Chemical titration results and powder Xray diffraction patterns indicate that the substitution of Ni 2+ , Cu 2+ and Ca 2+ for Fe 3+ and Mn 4+ can inhibit the reaction of Na + ions in the structure of O3-NaMn 0.33 Fe 0.33 Ni 0.21 Cu 0.08 Ca 0.04 O 2 with air. The Ni 2+ , Cu 2+ and Ca 2+substituted O3-NaMn 0.33 Fe 0.33 Ni 0.21 Cu 0.08 Ca 0.04 O 2 cathode material show a higher capacity and better cycling stability than that of O3-NaMn 0.42 Fe 0.42 Ni 0.17 O 2, indicating that a small amount of Ni 2+ , Cu 2+ and Ca 2+ substitution can improve the structure/air stability and the electrochemical performance. When O3-NaMn 0.33 Fe 0.33 Ni 0.21 Cu 0.08 Ca 0.04 O 2 cathode material is combined with the hard carbon anode, a full cell gives 220 Wh kg À1 energy density and 100% capacity retention after 56 charge/discharge cycles at 0.5C. The O3-NaMn 0.33 Fe 0.33 Ni 0.21 Cu 0.08 Ca 0.04 O 2 can be thought of as a potential cathode active material to encourage progress toward sodium-ion battery commercialization due to the high industrial applicability of the synthesis process and good electrochemical performance. Prime Novelty StatementA novel O3-NaMn 0.42 Fe 0.42 Ni 0.17 O 2 cathode material for sod um on batter es is synthesized for the first time by a co-precipitation method with subsequent solid-state reaction. The substitution of Ni 2+ , Cu 2+ and Ca 2+ for Fe 3+ and Mn 4+ improves the air stability and electrochemical performance of O3-NaMn 0.33 Fe 0.33 Ni 0.21 Cu 0.08 Ca 0.04 O 2 cathode material. When O3-NaMn 0.33 Fe 0.33 Ni 0.21 Cu 0.08 Ca 0.04 O 2 cathode material couples with the hard carbon anode, a full cell gives an energy density of 220 Wh kg À1 and the capacity retention of 100% after 56 charge/discharge cycles.

Unravelling air/moisture stability of cathode materials in sodium ion batteries: characterization, rational design, and perspectives

“…Patat et al introduced a Cu/Ca co-doped NaMn 0.33 Fe 0.33 Ni 0.21 Cu 0.08 Ca 0.04 O 2 material that demonstrated reduced surface Na residues as analyzed by chemical titration. 137 The residual Na at% was only 2.2% compared to the 10.2% observed in the undoped NFM material. Yu et al investigated the effects of Ti doping on a series of O3 material compositions: Na 0.95 Ni 0.40 Fe 0.15 Mn 0.3 Ti 0.15 O 2 (NFMT), Na 0.95 Ni 0.4 Fe 0.15 Mn 0.45 O 2 (NFM), NaNi 0.5 Mn 0.35 Ti 0.15 O 2 (NMT), and NaNi 0.5 Mn 0.5 O 2 (NM).…”

“…To achieve accurate and dependable results, we recommend adopting the titration methods proposed in ref. 46, 136 and 137, as they effectively minimize the risk of additional NaOH formation associated with water washing.…”

Universal Design Strategy for Air‐Stable Layered Na‐Ion Cathodes toward Sustainable Energy Storage

“…We validate the effectiveness of d 2 OH /V by extending the reaction energy dataset to 20 doped O3 materials, as shown in Figure 2a, which shows a remarkable linear correlation with a high Pearson coefficient of 0.97. The air stability of each doped material is successfully ranked by the new descriptor d 2 OH /V, with elements, such as Al, [23] Li, [20,33,34] Cu, [17,18,12,[35][36][37] Fe, [38] and Mg, [39] which are generally known as effective dopants to improve the air stability, appear at the upper right corner of Figure 2a; while Mn-based materials are less stable and highvalence dopants, such as Nb and Zr, are even worse. Note that our model predicts Ca and Ti as less effective dopants which are seemingly contradictory to previous works, because here we only consider a uniform doping at transition metal sites in the bulk materials, rather than in Na sites.…”

Sodium layered oxide cathodes: properties, practicality and prospects

“…Li doping could also suppress the Mn redox activity, which is responsible for the J–T effect. 212,213 It was noted that the reversible capacity of Na x Cu–Fe–MnO 2 is lower than that of Na x Ni-Fe–MnO 2 , and thus the Na x Ni–Cu–Fe–MnO 2 (NCFM) cathode was rationally prepared, which exhibited a higher capacity, proper average voltage and good air stability. Consequently, O3-NaMn 0.33 Fe 0.33 Ni 0.21 Cu 0.08 Ca 0.04 O 2 delivered a higher discharge capacity of 119 mA h g −1 .…”