Strong Anionic Repulsion for Fast Na Kinetics in P2‐Type Layered Oxides

Abstract

An intriguing mechanism for enabling fast Na kinetics during oxygen redox (OR) is proposed to produce high‐power‐density cathodes for sodium‐ion batteries (SIBs) based on the P2‐type oxide models, Na2/3[Mn6/9Ni3/9]O2 (NMNO) and Na2/3[Ti1/9Mn5/9Ni3/9]O2 (NTMNO) using the “potential pillar” effect. The critical structural parameter of NTMNO lowers the Na migration barrier in the desodiated state because the electrostatic repulsion of O(2p)O(2p) that occurs between transition metal layers is combined with the chemically stiff Ti4+(3d)O(2p) bond to locally retain the strong repulsion effect. The NTMNO interlayer distance moderately decreases upon charging with oxygen oxidation, whereas that of NMNO decreases at a much faster rate, which can be explained by the dependence of OR activity on the coordination environment. Fundamental electrochemical experiments clearly indicate that the Ti doping of the bare material significantly improves its rate capability during OR, and detailed electrochemical and structural analyses show much faster Na kinetics for NTMNO than for NMNO. A systematic comparison of the two cathode oxides based on experiments and first‐principles calculations establishes the “potential pillar” concept of not only improving the sluggish Na kinetics upon OR reaction but also harnessing the full potential of the anionic redox for high‐power‐density SIBs.

Boosting the Ultrastable High-Na-Content P2-type Layered Cathode Materials with Zero-Strain Cation Storage via a Lithium Dual-Site Substitution Approach

“…The corresponding charge–discharge voltage curves at different rates exhibit only minor changes, again highlighting the excellent rate capability (Figure c). As illustrated in Figure d, N 0.9 L 0.1 NMO exhibits superior rate performance, with capacity retentions of 98%, 95%, 92%, and 86% at 1, 3, 5, and 10 C, respectively, in comparison to 0.1 C. This result exceeds those of other P2-type or composite cathode materials. ,,− Electrochemical impedance spectroscopy (EIS) , was conducted on N 0.7 NMO, N 0.9 NMO, and N 0.9 L 0.1 NMO at various temperatures to investigate the interfacial Na-ions transport kinetics . The Nyquist plots of the three samples at various temperatures, along with an equivalent circuit, are presented in Figure S10.…”

A Feasible Dual Modification Strategy of Internal Anion Redox Chemistry and Surface Engineering on P2 Layer-Structured Cathodes in Sodium-Ion Batteries

“…An X-ray diffraction (XRD) test was conducted on the synthesized samples to perform crystal structure characterization. As shown in Figure b, the XRD patterns of the prepared samples ML-1, ML-2, MLM, MLZ, and MLC demonstrate typical P2 layered structure peak patterns with a space group of P 6 3 mmc corresponding to a PDF card of 27–0751 . No obvious impurity peaks were detected in the modified samples MLM, MLZ, and MLC.…”

Suppressing the Shuttle Effect via Polypyrrole-Coated Te Nanotubes for Advanced Na–Te Batteries

“…While lithium-ion batteries have been widely used in energy storage systems, the increasing price of lithium metal and its uneven distribution within the Earth’s crust have prompted research efforts to find alternatives. − Among these alternatives, sodium-ion batteries have been considered promising candidates due to the natural abundance and affordability of sodium. Consequently, the demand for high-performance sodium-ion batteries has spurred the development of advanced cathode materials. − …”