Generating Oxygen Vacancies in MnO Hexagonal Sheets for Ultralong Life Lithium Storage with High Capacity

Abstract

The polar surface of (001) wurtzite-structured MnO possesses substantial electrostatic instabilities that facilitate a wurtzite to graphene-like sheet transformation during the lithiation/delithiation process when used in battery technologies. This transformation results in cycle instability and loss of cell efficiency. In this work, we synthesized MnO hexagonal sheets (HSs) possessing abundant oxygen vacancy defects (MnO-Vo HSs) by pyrolyzing and reducing MnCO3 HSs under an atmosphere of Ar/H2. The oxygen vacancies (Vos) were generated in the reduction process and have been characterized using a range of techniques: X-ray absorption fine structure, electron-spin resonance, X-ray absorption near edge structure, Artemis modeling, and R space Feff modeling. The data arising from these analyses inform us that the introduction of one Vo defect within each O atom layer can reduce the charge density by 3.2 × 10–19 C, balancing the internal nonzero dipole moment and rendering the wurtzite structure more stable, so inhibiting the change to a graphene-like structure. Density function theory calculations demonstrate that the incorporation of Vos sites significantly improves the charge accumulation around Li atoms and increases Li+ adsorption energies (−2.720 eV). When used as an anode material for lithium ion batteries, the MnO-Vo HSs exhibit high specific capacity (1228.3 mAh g–1 at 0.1 A g–1) and excellent cell cycling stabilities (∼88.1% capacity retention after 1000 continuous charge/discharge cycles at 1.0 A g–1).

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

“…Through comparison and analysis, notice that both N‐MnO 2– x and MnO 2 branches exhibit similar curves characteristic of standard MnO 2 phase, while the peak intensity of N‐MnO 2– x becomes relatively lower, indicating that the NH 3 treatment at 200 °C will not change its phase. Moreover, the relative intensity of FT peaks in N‐MnO 2– x is lower than that in MnO 2 , indicating a decrease of coordination number and/or an increase in the degree of disorder . In addition, phase transformation at 300 °C in NH 3 atmosphere is also confirmed by the synchrotron radiation technology.…”

“…On account of the dipole selection rule, this transition is forbidden in an octahedral symmetry. However, the transition is partially allowed owing to the mixing of 3d–4p orbital, which originates from the slightly distorted MnO 6 octahedral units . Simultaneously, the main peak B is ascribed to the dipole‐allowed transition from 1s electron to 4p orbital.…”

Defect Engineering on Electrode Materials for Rechargeable Batteries

“…Moreover, the introducing of oxygen vacancies can lead to greater interlayer spacing, which enhanced charge storage dynamics and maintain the integrity of the surface morphology of the electrode, so as to improve the performance of the material in the charging and discharging process. For example, Zou et al prepared MnO hexagonal nanosheets with enriched oxygen defects for lithium‐ion batteries by using heat treatment under reducing atmosphere ( Figure a) . The transmission electron microscopy (TEM) analysis combined with X‐ray near‐edge absorption structure analysis and R‐space Feff model fitting results indicated the existence of oxygen vacancy in hexagonal sheets.…”

“…a) Schematic diagram of defective MnO nanosheets. Reproduced with permission . Copyright 2019, American Chemical Society.…”

Natural Compounds Gallic Acid Derivatives for Long‐Life Li/Na Organic Batteries

“…Moreover, EA and TA are environmentally friendly, economical, and degradable compared to these synthetic aromatic compounds. The specific capacities of EA and TA LIBs can be comparable with those of metal oxide LIBs after cycling, and the cycling stabilities of EA and TA LIBs are better than those of metal oxide LIBs . The exceptional electrochemical performance of EA and TA indicates that they are promising anode materials for LIBs.…”