δ-MnO2 nanoflower/graphite cathode for rechargeable aqueous zinc ion batteries

Abstract

Manganese oxide (MnO 2 ) is one of the most promising intercalation cathode materials for zinc ion batteries (ZIBs). Specifically, a layered type delta manganese dioxide (δ-MnO 2 ) allows reversible insertion/extraction of Zn 2+ ions and exhibits high storage capacity of Zn 2+ ions. However, a poor conductivity of δ-MnO 2 , as well as other crystallographic forms, limits its potential applications. This study focuses on δ-MnO 2 with nanoflower structure supported on graphite flake, namely MNG, for use as an intercalation host material of rechargeable aqueous ZIBs. Pristine δ-MnO 2 nanoflowers and MNG were synthesized and examined using X-ray diffraction, electron spectroscopy, and electrochemical techniques. Also, performances of the batteries with the pristine δ-MnO 2 nanoflowers and MNG cathodes were studied in CR2032 coin cells. MNG exhibits a fast insertion/extraction of Zn 2+ ions with diffusion scheme and pseudocapacitive behavior. The battery using MNG cathode exhibited a high initial discharge capacity of 235 mAh/g at 200 mA/g specific current density compared to 130 mAh/g which is displayed by the pristine δ-MnO 2 cathode at the same specific current density. MNG demonstrated superior electrical conductivity compared to the pristine δ-MnO 2 . The results obtained pave the way for improving the electrical conductivity of MnO 2 by using graphite flake support. The graphite flake support significantly improved performances of ZIBs and made them attractive for use in a wide variety of energy applications.

Layered Ca0.28MnO2·0.5H2O as a High Performance Cathode for Aqueous Zinc‐Ion Battery

“…However, Kheawhom et al suggest that only Zn 2+ ions insert into δ‐MnO 2 and transform into δ‐ZnMnO 2 in 0.5 m ZnSO 4 electrolyte. [ 15 ] Additionally, Kang et al study the mechanism of Zn 2+ ions intercalation in α‐MnO 2 , the formation of ZnMn 2 O 4 clearly confirms the insertion of Zn 2+ into α‐MnO 2 in 0.5 m Zn(NO 3 ) 2 electrolyte. [ 16 ] There is no doubt that the Zn 2+ ions can be reversibly inserted/extracted in MnO 2 .…”

Defect Engineering in Manganese‐Based Oxides for Aqueous Rechargeable Zinc‐Ion Batteries: A Review

“…[ 46–52 ] The reaction mechanisms for these manganese‐based oxides are summarized in Figure 3 . Three main mechanisms are reported for manganese‐based oxide, namely 1) Zn 2+ insertion/extraction, [ 53–55 ] 2) chemical conversion reaction, [ 38 ] and 3) H + /Zn 2+ insertion/extraction. [ 56–58 ]…”

Electrodeposited Manganese Oxide on Carbon Paper for Zinc‐Ion Battery Cathodes

“…have shown that the incorporation of K into the cathode can also help suppress Mn dissolution . Reducing particle size and increasing surface area of the active material has also been employed to address the poor conductivity of Mn oxides . Furthermore, the reaction mechanism surrounding Mn 3 O 4 materials, and Mn oxide compounds in general, is still not completely understood.…”

“…[1,4,5] Presently, several different categories of materials have been explored for use as cathodes, with the most popular ones being V oxide compounds, [4][5][6][7][8][9][10][11][12][13][14] Prussian blue analogues (PBA), [4,5,[15][16][17][18] and Mn oxide compounds. [4,5,[19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35] To a lesser extent, sustainable quinone analogs, metal sulfides, Chevrel phase compounds, and polyanion based compounds have also been explored. [4,5,36] Of the different materials explored for ZIB cathodes, the most commonly studied material is Mn oxide.…”

“…[39] Reducing particle size and increasing surface area of the active material has also been employed to address the poor conductivity of Mn oxides. [33] Furthermore, the reaction mechanism surrounding Mn 3 O 4 materials, and Mn oxide compounds in general, is still not completely understood. In the literature, many groups have argued that Mn oxide materials undergo Zn intercalation during battery cycling, with both discharge plateaus corresponding to Zn insertion into different sites within the cathode structure.…”