Amorphous Manganese Oxides: An Approach for Reversible Aqueous Zinc-Ion Batteries

Abstract

Crystalline manganese oxides have attracted the most attention in aqueous zinc-ion batteries due to their diverse nanostructures and low cost. However, extensive studies on amorphous manganese oxides are lacking. Herein, we report a mesoporous amorphous manganese oxide (UCT-1-250) as a cathode material with high capacity (222 mAh g–1), good cyclability (57% capacity retention after 200 cycles), and an acceptable discharge plateau (between 1.2 and 1.4 V). An approach to mechanistic studies was performed by comparison of UCT-1-250 and other crystalline manganese oxides through electrochemical, elemental, and structural analyses. An in situ conversion to ZnMn2O4 spinel phase after initial cycling contributes to the high performance. The irreversible capacity fading is due to the formation of the woodruffite phase.

Recent Development of Mn‐based Oxides as Zinc‐Ion Battery Cathode

“…This increasing attention in the development of ZIB has been greatly propelled by the use of environmental benign aqueous‐based electrolyte, high theoretical capacity of Zn, and the high amount of global Zn reserve [4,12,15] . As a consequence of this renewed interest in ZIB, numerous reports have been focused heavily on the development of suitable cathode materials that can exhibit reversible Zn 2+ storage [12,19,20] . This is because the cathode, being one of the main components in ZIB, can influence the achievable electrochemical performance significantly [12,21] .…”

Vibrant Color Palettes of Electrochromic Manganese Oxide Electrodes for Colorful Zn‐Ion Battery

“…[ 26 ] The XPS spectrum of O 1s presented in Figure S2c, Supporting Information, verifies the formation of manganese oxide layer, which exhibits three peaks at 529.8, 531.4, and 532.6 eV corresponding to different oxygen species in the MnO bond (lattice oxygen), MnOH bond (surface hydroxyls or defect oxide), and HOH bond (surface‐adsorbed water), respectively. [ 27–29 ] As indicated by the results above, a bilayer structure comprising Ti and Mn 2 O 3 layers is formed on the electrode.…”

“…The initial cathodic scan shows an intense peak at 1.08 V due to the activation process (Mn 3+ to Mn 2+ ). [28,30] In the following cycles, the reduction peak is divided into two peaks at 1.2 and 1.35 V, whereas the oxidation peaks at around 1.78 V are almost overlapped. The two reduction peaks at 1.35 and 1.2 V are attributable to the progressive insertion of H + and Zn 2+ into the lattice of the manganese oxide electrode, accompanied by the reduction of Mn 4+ to lower oxidation state Mn 3+ / Mn 2+ , [31] where a further activation of the cathodic material may exist in the cycles following the initial one, as supported by the appearance of increasing peak current at 1.35 V. On the contrary, the broad oxidation peak appearing at 1.78 V during the anodic sweep is ascribed to the Zn 2+ /H + extraction and reinstatement of Mn(IV) state.…”

The synergistically enhanced activity and stability of layered manganese oxide via the engineering of defects and K+ ions for oxygen electrocatalysis

“…13 Impressively, the electroactivity of crystalline materials can be improved based on amorphous architecture upon structural evolution. 13 To our knowledge, various published approaches are available for introducing disordered structures, including interfacial engineering, 14,15 hetero-atomic/ionic coupling, 16,17 and self-doping. 18 For example, with ultrasonic assistance, the Huang group partially converted NiFe 2 O 4 into NiFe(OH) x and reduced the OER overpotential at 10 mA cm −2 from 388 to 276 mV (vs. RHE).…”