Oxygen‐Deficient Birnessite‐MnO₂ for High‐Performing Rechargeable Aqueous Zinc‐Ion Batteries

Abstract

The development and commercialisation of Zinc‐Ion Batteries (ZIBs) faces a daunting challenge caused by the limited selection of cathode materials. Among all the available choices, Manganese‐Based Oxides show the most promising potential due to the various benefits such as, low costs, natural abundance of Manganese, environmental benignity and its multiple valence states. Most notably, Manganese Dioxide (MnO2) as a cathode material for ZIBs has always been a popular area of research as it can exist in various phases with tunnelled and layered structures for the (de‐)intercalation of Zn2+ ions. However, despite many works reported on enhancing the electrochemical performances of MnO2, most of the proposed methodologies of improving the performance is based on Zn2+ ion insertion kinetics and these methods has been pushed to saturation. Herein, we propose an alternative direction of creating oxygen deficiency via defect engineering to enhance the surface‐capacitive electrochemical performance of MnO2. In this work, the Zn//Oxygen‐deficient Birnessite‐MnO2 achieved a specific capacity of 378 mAh g−1 which is one of the highest among other existing Zn//Birnessite‐MnO2 battery systems. Thus, this work is expected to shine light on the potential of defect engineering as a strategy to enhance electrochemical performances of MnO2.

A Safe Flexible Self-Powered Wristband System by Integrating Defective MnO2–x Nanosheet-Based Zinc-Ion Batteries with Perovskite Solar Cells

“…For the core-level O 1s spectra, both samples show characteristic peaks at 529.6 and 531.2 eV, corresponding to the lattice oxygen (blue) and the oxygen-deficient (orange) sites, respectively (Figure 2b). 42 The significant enhancement of the peak intensity at 531.2 eV confirms the enrichment of oxygen defects for MnO 2−x @CC. 42 The Mn 2p 3/2 (641.8 eV) and Mn 2p 1/2 peaks (653.5 eV) can be further deconvoluted to peaks corresponding to Mn 4+ (blue and green) and Mn 3+ (orange and purple), as shown in Figure 2c.…”

“…42 The Mn 2p 3/2 (641.8 eV) and Mn 2p 1/2 peaks (653.5 eV) can be further deconvoluted to peaks corresponding to Mn 4+ (blue and green) and Mn 3+ (orange and purple), as shown in Figure 2c. 29,42 For the MnO 2−x @CC sample, the intensities of the Mn 4+ peaks weaken, while the intensities of the Mn 3+ peaks increase substantially, confirming the decreased valence state of part of Mn. Furthermore, the energy separation of Mn 3s peaks in the MnO 2−x @CC is 5.02 eV, wider than that (4.41 eV) of MnO 2 @ CC (Figure S4), suggesting a lower average valence of Mn in MnO 2−x @CC.…”

“…29,35 Second, it has been proven that the oxygen defects can enhance the structural stability of MnO 2 . 36,42 Third, oxygen defects are beneficial to promote the reversibility of Zn 2+ adsorption/desorption on MnO 2 , which may aid in improving the cycling stability. 34 In addition, we have explored the air stability of the H-MnO 2−x @CC electrode.…”

The charge density of intercalants inside layered birnessite manganese oxide nanosheets determining Zn-ion storage capability towards rechargeable Zn-ion batteries

“…This suggests that using the pre-intercalant with high charge density leads to the improvement of the redox activity of Zn 2+ ions. 32,33 In addition to the CV results, the GCD proles of d-MnO 2 with different intercalants were compared at a current density of 0.1 A g À1 , as presented in Fig. 2b.…”

Fundamental Understanding and Effect of Anionic Chemistry in Zinc Batteries

“…In short, it can be noted that the increased energy density is usually based on the activation of additional reactions, which requires the construction of thermodynamic metastable state of electrode bulk or electrode-electrolyte interface. These metastable reaction sites are not only conducive to high specific capacity and energy density, [68][69][70][71] but also can reduce the barrier during ion diffusion process. The improvement of reaction kinetics is significantly important to the rate performance and output power density, which will be discussed in the bulk anion defect regulation, mainly including anionic doping and vacancy.…”