Synthesis of Nitrogen‐Doped KMn₈O₁₆ with Oxygen Vacancy for Stable Zinc‐Ion Batteries

Abstract

The development of MnO 2 as a cathode for aqueous zinc-ion batteries (AZIBs) is severely limited by the low intrinsic electrical conductivity and unstable crystal structure. Herein, a multifunctional modification strategy is proposed to construct N-doped KMn 8 O 16 with abundant oxygen vacancy and large specific surface area (named as N-KMO) through a facile one-step hydrothermal approach. The synergetic effects of N-doping, oxygen vacancy, and porous structure in N-KMO can effectively suppress the dissolution of manganese ions, and promote ion diffusion and electron conduction. As a result, the N-KMO cathode exhibits dramatically improved stability and reaction kinetics, superior to the pristine MnO 2 and MnO 2 with only oxygen vacancy. Remarkably, the N-KMO cathode delivers a high reversible capacity of 262 mAh g −1 after 2500 cycles at 1 A g −1 with a capacity retention of 91%. Simultaneously, the highest specific capacity can reach 298 mAh g −1 at 0.1 A g −1 . Theoretical calculations reveal that the oxygen vacancy and N-doping can improve the electrical conductivity of MnO 2 and thus account for the outstanding rate performance. Moreover, ex situ characterizations indicate that the energy storage mechanism of the N-KMO cathode is mainly a H + and Zn 2+ co-insertion/extraction process.

Electrocatalytic Reduction of CO2 to Ethanol at Close to Theoretical Potential via Engineering Abundant Electron‐Donating Cuδ+ Species

“…Moreover, Cu 2 S 1À x HN exhibits an obvious electron paramagnetic resonance (EPR) signal of sulfur vacancies at g = 2.005 compared to its counterpart of Cu 2 S HN (Figure 3f and Figure S8). [12] Then, Auger emission spectrum and X-ray absorption spectroscopy (XAS) was performed to analyze the electronic structure of Cu in Cu 2 S 1À x HN. The Cu in Cu 2 S 1À x HN shifts to higher binding energy compared to Cu 2 S HN, indicating its higher electronic density (Figure 3g).…”

Methods for Rational Design of Advanced Zn‐Based Batteries

“…Obviously, the P-NiCo 2 O 4-x cathode displayed higher specific capacities than the pristine NiCo 2 O 4 at the current densities from 6.0 to 60.4 A g −1 . Similarly, the oxygen vacancy strategies have also been used to enhance the electrochemical performance of the transition metal oxides, such as δ-MnO 2 , [48] ZnMn 2 O 4 , [49] β-MnO 2 [50] K 0.8 Mn 8 O 16 , [51,52] V 6 O 13 , [53] and so on. Among them, V 6 O 13 has the high theoretical capability (421 mAh g −1 ), but its strong electrostatic interaction with divalent Zn 2+ results in sluggish reaction kinetics and inhibition of reversible Zn 2+ storage.…”

Highly Flexible K‐Intercalated MnO2/Carbon Membrane for High‐Performance Aqueous Zinc‐Ion Battery Cathode

“…In Figure S16, Supporting Information, the Zn 2p spectra also confirm the KMO/CNFs are intercalated by Zn 2+ , in which there are two typical peaks of Zn 2p 1/2 and Zn 2p 3/2 , originating from Zn x MnO 2 and ZSH upon discharging to 0.8 V. [12a] After the cell is charged to 1.8 V, weak peaks corresponding to Zn-based compound are also observed, which may be due to the irreversible intercalation of Zn 2+ in the electrode. [23,44] The K + content decreases along with the increment of Zn 2+ during cycling, confirming the occurrence of ion exchange (Table S5, Supporting Information). [45] This process plays a vital role in stabilizing the interlayer structure of δ-MnO 2 .…”

“…[19] Furthermore, the inductively coupled plasma atomic emission spectrometer (ICP-AES) (Table S3, Supporting Information) suggests that the ratio of K:Mn is about 0.225:1 in KMO/CNFs, which indicates a large amount of K + was successfully inserted into the structure of MnO 2 , providing enough space for the further intercalation of Zn 2+ . [23] The analysis hereinbefore, together with ICP-AES and TGA results, reveals that the exact chemical formula of KMO is K 0.225 MnO 2 •0.76H 2 O. [24] The O 1s spectrum (Figure 2e) can be fitted into three peaks with MnOMn (530.1 eV), MnOH (531.5 eV), and HOH (532.5 eV), respectively.…”