Benefits of Copper and Magnesium Cosubstitution in Na_0.5Mn_0.6Ni_0.4O₂ as a Superior Cathode for Sodium Ion Batteries

Abstract

Transition metal oxides are considered to be one kind of the most promising cathode materials for sodium ion batteries. Here, P2-type Na0.5Mn0.6­Ni0.2Cu0.1­Mg0.1O2 cathode material was designed and synthesized by a sol–gel method for the first time. The cosubstitution of copper and magnesium in Na0.5Mn0.6­Ni0.2Cu0.1­Mg0.1O2 inhibits the P2–O2 phase transition and enhances lattice spacing to reduce the resistance of sodium ion deintercalation and intercalation, which is beneficial to the improvement of electrochemical properties. A Na0.5Mn0.6­Ni0.2Cu0.1­Mg0.1O2 electrode delivers an initial specific capacity of 126.1 mAh g–1 with a high average voltage of 3.6 V (2–4.6 V) and 96.7% capacity retention after 100 cycles at 0.1C. More importantly, the full cells using this cathode material and hard carbon as anode exhibit initial reversible specific capacity of 70.8 mAh g–1 with energy density of 226.56 Wh kg–1 and high capacity retention of 90.1% after 200 cycles at 0.5C. Therefore, Na0.5Mn0.6­Ni0.2Cu0.1­Mg0.1O2 is able to be a cathode material with high operation voltage, good stability, high energy density, and excellent rate performance for sodium ion battery applications.

Single-phase P2-type layered oxide with Cu-substitution for sodium ion batteries

“…There are four groups of redox peaks that can be clearly observed in both curves and the introduction of copper does not increase the number of peaks. The reversible oxidation/reduction peaks at 3.39/3.29 V and 3.61/3.52 V were induced by the redox reactions of Ni 2 + /Ni 3 + and Ni 3 + /Ni 4 + , respectively, which ensure a high average operating voltage [26,27] . The peaks at 3.63/3.74 V correspond to the redox couples of Co 3 + /Co 4 + .…”

Oxide cathodes for sodium‐ion batteries: Designs, challenges, and perspectives

“…After the introduction of magnesium, obvious improvement in electrochemical performance and less CO 2 evolution were observed. P2‐type Na 0.5 Mn 0.6 Ni 0.2 Cu 0.1 Mg 0.1 O 2 has also been proven to be a promising cathode with excellent stability, high operation voltage, and high energy density for SIBs 168 . Cu and Mg cosubstitution suppresses the P2−O2 phase transition and extends cell parameters to facilitate Na + deintercalation and intercalation.…”

“…Compact particles effectively avoid unwanted side effects by reducing the volume of voids that can penetrate the promising cathode with excellent stability, high operation voltage, and high energy density for SIBs. 168 Cu and Mg cosubstitution suppresses the P2−O2 phase transition and extends cell parameters to facilitate Na + deintercalation and intercalation. The P2-Na 0.5 Mn 0.6 Ni 0.2 Cu 0.1 Mg 0.1 O 2 cathode shows a reversible specific capacity of 126.1 mAh g −1 at 0.1 C with 96.7% capacity retention after 100 cycles and 3.6 V high average discharge voltage.…”

High Power Energy Storage via Electrochemically Expanded and Hydrated Manganese-Rich Oxides

“…However, all peak intensities decrease after ∼0.5 V during the second cathodic sweep, as the change in particle volume during electrochemical expansion causes the electrode to delaminate from the current collector. Figure S3 shows similar behavior in a P2 oxide with a different composition, NaNMCu, where the inclusion of nickel led to Na + deintercalation and the subsequent formation of the birnessitelike phase at a lower potential (Kang et al, 2015;Wang L. et al, 2017;Chen et al, 2018). Overall, the operando results show that when these P2 oxides are cycled in an aqueous electrolyte, water incorporation occurs during Na + deintercalation, likely to offset the increasing electrostatic repulsion between the transition metal and oxygen layers.…”