Simultaneous MgO coating and Mg doping of Na[Ni_0.5Mn_0.5]O₂ cathode: facile and customizable approach to high-voltage sodium-ion batteries

Abstract

Simultaneous surface MgO coating to bulk Mg doping of Na[Ni0.5Mn0.5]O2 cathode produces great synergy in sodium-ion battery performances.

Large-Scale Synthesis of the Stable Co-Free Layered Oxide Cathode by the Synergetic Contribution of Multielement Chemical Substitution for Practical Sodium-Ion Battery

“…Meanwhile, the detailed crystallographic parameters and atomic site occupations of the Rietveld refinement ( R wp 6.84% and R p 4.77%) are displayed in Table S1–S2 (Supporting Information), and the results show that copper, magnesium, and titanium elements localize at the octahedral 3b Wyckoff sites. Owing to the similar ionic radii and same valence (Ni 2+ = 0.69 Å, Cu 2+ = 0.73 Å, Mg 2+ = 0.72 Å, Mn 4+ = 0.53 Å, and Ti 4+ = 0.605 Å), the uniform incorporation of multielement chemical substitution into the TM layers could effectively modulate the crystal structure and alleviate the lattice strains driven by the large Ni ionic radius change during Na + intercalation/deintercalation, resulting in better structural stability [ 30 , 36 ]. Moreover, compared with the crystallographic parameter ( c = 16.0301 Å) of Cu and Ti cosubstituted NaNi 0.45 Cu 0.05 Mn 0.4 Ti 0.1 O 2 sample, the substitution of Mg 2+ in O3-NaNCMMT cathode material not only shows a pinning effect but also enlarges the interlayer spacing reasonably ( c = 16.0812 Å), which could improve the Na + diffusion coefficient and contribute to the high rate capability, as discussed later [ 37 ].…”

“…-P3′′ hex. , are inclined to result in rapid capacity decline and the sluggish kinetics as well as poor rate performance [ 30 ]. Therefore, improving the comprehensive performance of the Co-free NaNi 0.5 Mn 0.5 O 2 cathode materials through simultaneously enhancing the air stability, reducing or suppressing the irreversible phase transition, and alleviating the sluggish kinetics is of great importance to realize sodium-ion battery commercialization for market applications.…”

Impact of Mg and Ti doping in O3 type NaNi1/2Mn1/2O2 on reversibility and phase transition during electrochemical Na intercalation

“…7 However, the available capacity was limited to 120 mA h g À1 in the full cell 1 because of the narrower voltage range of approximately 2.0-3.8 V vs. Na + /Na to avoid the severe capacity decay by charging beyond 4.0 V. The capacity decay is known to be due to the signicant change in interslab spacing by extraction of almost all sodium ions from the structure 8 and surface deterioration. 9 To improve the cycle stability, coating with MgO was carried out by Hwang et al, and the performance is partly enhanced. 9 As we found in P2 type Na 2/3 Ni 1/3 Mn 2/3 O 2 , 10 Ti-substitution is effective to enhance the performance, but the obtained reversible capacity in the O3 type was limited to less than 150 mA h g À1 .…”

“…9 To improve the cycle stability, coating with MgO was carried out by Hwang et al, and the performance is partly enhanced. 9 As we found in P2 type Na 2/3 Ni 1/3 Mn 2/3 O 2 , 10 Ti-substitution is effective to enhance the performance, but the obtained reversible capacity in the O3 type was limited to less than 150 mA h g À1 . 11,12 Recently, Tarascon's group reported signicantly improved performance by the co-substitution of Ti and Cu in Na[Ni 1/2 Mn 1/2 ]O 2 as Na[Ni 1/2Àx Cu x Mn 1/2Ày Ti y ]O 2 (ref.…”

Approaches to synthesize MgO nanostructures for diverse applications

“…MgO coating on cathode materials is effective to enhance electrochemical performance of rechargeable batteries [ 118 , 119 , 120 ]. Similarly, it's coating on selected anode materials for various rechargeable batteries is found effective to improve the performance [ 121 , 122 ].…”