A two-electron transfer mechanism of the Zn-doped δ-MnO₂ cathode toward aqueous Zn-ion batteries with ultrahigh capacity

Abstract

Neutral aqueous Zinc-ion batteries (ZIBs) have attracted considerable attention due to their safe and green features. As one typical cathode, birnessite MnO2 (δ-MnO2) suffers from low conductivity and structural instability,...

Ni‐MnO2/Graphene as Cathode Material for Super‐Capacity Aqueous Rechargeable Zn‐Ion Battery

“…After compositing with rGO, the contribution of inserted H þ and Zn 2þ to the capacity increases greatly at the same time. This may be related to oxygen vacancies, [10,27] two-electron reactions, [15,28] or interfaces. [29,30] It is also reported that this super-capacity phenomenon has also been found in vanadiumbased composite materials, [30] and the detailed mechanism still needs to be further studied.…”

Electron transmission matrix and anion regulation strategy-derived oxygen-deficient δ-MnO2 for a high-rate and long-life aqueous zinc-ion battery

“…The introduction of heteroatoms, especially cations, has been proved to be an effective way to boost reaction kinetics and suppresses the irreversible lattice distortion of MnO 2 . 9,40,41 The modification of cations (La 3+ , 36 K + , 37 Zn 2+ , 42 etc .) is often accompanied by the formation of oxygen vacancies, which is important for modifying the ion migration properties of MnO 2 .…”

Facile Construction of Zn‐Doped Mn3O4−MnO2 Vertical Nanosheets for Aqueous Zinc‐Ion Battery Cathodes

“…[25][26] Among various metal ions, the low valence cation of Zn 2 + has been demonstrated to effectively enhance intrinsic conductivity and boost electrolyte ion diffusion kinetics by the construction of oxygen vacancies as compared with other metal ions when intercalating into the manganese oxide materials, which can finally enhance the corresponding electrochemical performances. [27][28] However, only a very few reports relating to the usage in AZIB applications have been published, such as Zn doped δ-MnO 2 with an ultrahigh reversible capacity of 455 mAh g À 1 at 25 mA g À 1 and Zn 2 + stabilized layered-type MnO 2 structure with high rate capability of 124 mAh g À 1 at 3.0 A g À 1 . [27,29] In addition, specific capacitance depends not only on the electrical conductivity and ion transport properties but also on the effective contact area between the electrode materials and electrolytes.…”

“…[27][28] However, only a very few reports relating to the usage in AZIB applications have been published, such as Zn doped δ-MnO 2 with an ultrahigh reversible capacity of 455 mAh g À 1 at 25 mA g À 1 and Zn 2 + stabilized layered-type MnO 2 structure with high rate capability of 124 mAh g À 1 at 3.0 A g À 1 . [27,29] In addition, specific capacitance depends not only on the electrical conductivity and ion transport properties but also on the effective contact area between the electrode materials and electrolytes. For that, in terms of the improved specific capacity, MnO x with the three-dimensional (3D) framework has an advantage over the present MnO 2 with other morphologies due to its enhanced electrolyte-accessible surface area, which facilitates easy access of electrolytic ions into the interior of the electrodes.…”

“…Recent research has shown that the doping of metal ions can effectively improve the electrical conductivity of the metal oxides, because of their ability to offer high hole‐concentration as they replace high valance metal‐ions [25–26] . Among various metal ions, the low valence cation of Zn 2+ has been demonstrated to effectively enhance intrinsic conductivity and boost electrolyte ion diffusion kinetics by the construction of oxygen vacancies as compared with other metal ions when intercalating into the manganese oxide materials, which can finally enhance the corresponding electrochemical performances [27–28] . However, only a very few reports relating to the usage in AZIB applications have been published, such as Zn doped δ‐MnO 2 with an ultrahigh reversible capacity of 455 mAh g −1 at 25 mA g −1 and Zn 2+ stabilized layered‐type MnO 2 structure with high rate capability of 124 mAh g −1 at 3.0 A g −1 [27,29] .…”