Oxygen‐Vacancy and Surface Modulation of Ultrathin Nickel Cobaltite Nanosheets as a High‐Energy Cathode for Advanced Zn‐Ion Batteries

Abstract

The development of high-capacity, Earth-abundant, and stable cathode materials for robust aqueous Zn-ion batteries is an ongoing challenge. Herein, ultrathin nickel cobaltite (NiCo O ) nanosheets with enriched oxygen vacancies and surface phosphate ions (P-NiCo O ) are reported as a new high-energy-density cathode material for rechargeable Zn-ion batteries. The oxygen-vacancy and surface phosphate-ion modulation are achieved by annealing the pristine NiCo O nanosheets using a simple phosphating process. Benefiting from the merits of substantially improved electrical conductivity and increased concentration of active sites, the optimized P-NiCo O nanosheet electrode delivers remarkable capacity (309.2 mAh g at 6.0 A g ) and extraordinary rate performance (64% capacity retention at 60.4 A g ). Moreover, based on the P-NiCo O cathode, our fabricated P-NiCo O //Zn battery presents an impressive specific capacity of 361.3 mAh g at the high current density of 3.0 A g in an alkaline electrolyte. Furthermore, extremely high energy density (616.5 Wh kg ) and power density (30.2 kW kg ) are also achieved, which outperforms most of the previously reported aqueous Zn-ion batteries. This ultrafast and high-energy aqueous Zn-ion battery is promising for widespread application to electric vehicles and intelligent devices.

Defect Promoted Capacity and Durability of N‐MnO2–x Branch Arrays via Low‐Temperature NH3 Treatment for Advanced Aqueous Zinc Ion Batteries

“…In the meantime, the peak intensity of OH bond (532.8 eV) of N‐MnO 2– x @TiC/C sample is higher than that of MnO 2 @TiC/C owing to the increased surface‐absorbed water. This indicates that the surface of N‐MnO 2– x @TiC/C sample becomes more active and accessible to soak electrolyte to participate in reactions . Further evidence is provided by the EPR spectra measured at room temperature.…”

Defect Engineering on Electrode Materials for Rechargeable Batteries

“…It found that oxygen vacancy could act as a shallow donor to improve electrical conductivity of metal oxide, and serve as active sites for electrode reactions. Therefore, the optimized P‐NiCo 2 O 4− x nanosheets electrode has the advantages of the improved conductivity and enhanced concentration of active site, thus significantly improving the capacity and rate performance of the material …”

Two‐Dimensional Transition Metal Carbides and Nitrides (MXenes): Synthesis, Properties, and Electrochemical Energy Storage Applications

“…Nowadays, energy storage devices (ESDs) are playing a crucial role in smart electronics and wearable textiles. Rechargeable batteries (including Li, Na, K, Zn‐ions) as well as supercapacitors are being considered as promising energy storage devices for sustainable development of smart electronics . While batteries are known for their high energy density, the cycle life and charging/discharging rate are unfavorable in most cases .…”