Novel Cathode Materials for Na‐Ion Batteries Composed of Spoke‐Like Nanorods of Na[Ni_0.61Co_0.12Mn_0.27]O₂ Assembled in Spherical Secondary Particles

Abstract

The development of high‐energy and high‐power density sodium‐ion batteries is a great challenge for modern electrochemistry. The main hurdle to wide acceptance of sodium‐ion batteries lies in identifying and developing suitable new electrode materials. This study presents a composition‐graded cathode with average composition Na[Ni0.61Co0.12Mn0.27]O2, which exhibits excellent performance and stability. In addition to the concentration gradients of the transition metal ions, the cathode is composed of spoke‐like nanorods assembled into a spherical superstructure. Individual nanorod particles also possess strong crystallographic texture with respect to the center of the spherical particle. Such morphology allows the spoke‐like nanorods to assemble into a compact structure that minimizes its porosity and maximizes its mechanical strength while facilitating Na+‐ion transport into the particle interior. Microcompression tests have explicitly verified the mechanical robustness of the composition‐graded cathode and single particle electrochemical measurements have demonstrated the electrochemical stability during Na+‐ion insertion and extraction at high rates. These structural and morphological features contribute to the delivery of high discharge capacities of 160 mAh (g oxide)−1 at 15 mA g−1 (0.1 C rate) and 130 mAh g−1 at 1500 mA g−1 (10 C rate). The work is a pronounced step forward in the development of new Na ion insertion cathodes with a concentration gradient.

Improving the Performance of Layered Oxide Cathode Materials with Football‐Like Hierarchical Structure for Na‐Ion Batteries by Incorporating Mg2+ into Vacancies in Na‐Ion Layers

“…The diameter of an individual “football” is 2–4 μm, and the football is composed of plate‐like primitive particles of 500–600 nm. Such a unique morphology allows the electrolyte to penetrate into the inside of the football and facilitates Na‐ion transport, which is beneficial to the performance of the cathode materials …”

“…Such au nique morphology allows the electrolyte to penetrate into the inside of the football and facilitates Na-ion transport, which is beneficial to the performance of the cathode materials. [29] The oxidations tates of the TM elements were analyzed by using X-ray photoelectron spectroscopy (XPS), and the fitting results are shown in Figure4a-f. The binding energy (BE) values were calibratedf rom the C1sp eak (CÀC, BE = 284.5 eV).…”

“…[28,44] Such au nique morphologyo ft he football-like hierarchical structure is also significant for the structurals tability.S un and co-workers found an enhanced performance for SIBs caused by the improved mechanical strength of ah ierarchical structure with spherical secondary particles. [29] The capacity decay during cycles may be associated with Mn 3+ + dissolution. [45] In addition, inactive Mg ions can serve as pillars to stabilize the materials tructure upon the insertiona nd extraction of Na ions.…”

Excellent Comprehensive Performance of Na‐Based Layered Oxide Benefiting from the Synergetic Contributions of Multimetal Ions

“…[12] To tackle these issues, great efforts have been devoted to modulate mixed cation oxides with the aim of combining the respective advantages of various single cation oxides, such as NaNi 0.3 Fe 0.4 Mn 0.3 O 2 [13] and NaN i 1/3 Mn 1/3 Co 1/3 O 2 . [14,15] Another approach to improve the Na storage performance of layered oxides is to dope with electrochemically inactive elements in transition metal layers. [16][17][18] The inactive ions in material show a pinning effect to stabilize the structure, because inactive ions are irresponsible for the charge compensation on sodiation/desodiation and the distortion of MeO 6 centered by inactive ions is negligible.…”

Hierarchical Engineering of Porous P2‐Na2/3Ni1/3Mn2/3O2 Nanofibers Assembled by Nanoparticles Enables Superior Sodium‐Ion Storage Cathodes

“…[1][2][3][4] However, the pursuit of applicable Na-ion storage electrode materials seems harder than the exploration of their Li-ion counterparts due to the larger size and heavier mass of Na + versus Li + . [7,8] Among the currently proposed cathode candidates, such as transition metal oxides (TMOs), [9][10][11][12][13][14][15][16][17] polyanion-type compounds, [18][19][20][21][22][23] Prussian blue analogues, [24,25] and organic salts, [26,27] layered transition metal oxides are particularly intriguing because of their 2D frameworks offering free Na-diffusion channels. [7,8] Among the currently proposed cathode candidates, such as transition metal oxides (TMOs), [9][10][11][12][13][14][15][16][17] polyanion-type compounds, [18][19][20][21][22][23] Prussian blue analogues, [24,25] and organic salts, [26,…”