Electrochemical Study of Polymorphic MnO2 in Rechargeable Aqueous Zinc Batteries

Abstract

Manganese dioxide is regarded as a promising energy functional material due to its open tunnel structure with enormous applications in energy storage and catalysis. In this paper, α-MnO2 with a 2 × 2 tunnel structure and β-MnO2 with a 1 × 1 tunnel structure were hydrothermally synthesized, which possess characteristic tunnel structures formed by the interconnected unit structure of [MnO6] octahedrons. With regards to their different tunnel dimensions, the specific mechanism of ion intercalation in these two phases and the effect on their performance as aqueous Zn-MnO2 battery cathodes are explored and compared. Comprehensive analyses illustrate that both α-MnO2 and β-MnO2 provide decent capacity in the aqueous battery system, but their intrinsic stability is poor due to the structural instability upon cycling. At the same time, experiments show that α-MnO2 has a better rate performance than β-MnO2 under larger currents, thus implying that the former has a broader application in this aqueous battery system.

Nanostructure Design of MnO2/Partially Oxidized Graphene Nanocomposite Cathode via One-Step Pulse Potential Strategy: Toward Ultralong-Life Zinc-Ion Batteries

“…According to Figure d, for α-MnO 2 , a cathodic peak at 1.18 V and a corresponding anodic peak at around 1.58 V can be recognized during the first cycle. On further cycling, the observed cathodic peak disappeared, and two distinct peaks emerged at 1.37 and 1.26 V. In addition, the initial anodic peak split into two peaks at 1.57 and 1.62 V. The difference observed in the CV curves can be attributed to the activation step and the large overpotential required for activation during the first cycle. − It is worth noting that the current density of the redox peaks at 1.37 and 1.62 V increases with continuous cycling, whereas the current density of the redox peaks at 1.26 and 1.57 V decreases. This behavior implies a possible competition between different states. ,, As shown in Figure e, the CV curves for MnO 2 /POG-4 exhibited consistent behavior over consecutive scans, indicating that the incorporation of POG did not influence the mechanism of the electrochemical process.…”

Structure–Property Interplay Within Microporous Manganese Dioxide Tunnels For Sustainable Energy Storage

“…Interestingly, although constructed by the same [MnO 6 ] units, the polymorphic OMS exhibit distinct ion transport properties. [67,68] For example, while α-MnO 2 (2×2 tunnels) transports Li + following an anisotropic pattern, such kinetic features are not seen in β-MnO 2 (1×1 tunnels), [69] or t-MnO 2 (3×3/3×4 tunnels). [46] Instead, β-MnO 2 shows partially reversible lattice evolution upon (de)lithiation, during which phase separation occurs and accounts for the partial irreversibility.…”

Structure–Property Interplay Within Microporous Manganese Dioxide Tunnels For Sustainable Energy Storage

“…Besides α‐MnO 2 , other OMS phases were also investigated in terms of their ion diffusion kinetics. Interestingly, although constructed by the same [MnO 6 ] units, the polymorphic OMS exhibit distinct ion transport properties [67,68] . For example, while α‐MnO 2 (2×2 tunnels) transports Li + following an anisotropic pattern, such kinetic features are not seen in β‐MnO 2 (1×1 tunnels), [69] or t‐MnO 2 (3×3/3×4 tunnels) [46] .…”

“…Interestingly, although constructed by the same [MnO 6 ] units, the polymorphic OMS exhibit distinct ion transport properties. [67,68] For example, while α-MnO 2 (2×2 tunnels) transports Li + following an anisotropic pattern, such kinetic features are not seen in β-MnO 2 (1×1 tunnels), [69] or t-MnO 2 (3×3/3×4 tunnels). [46] Instead, β-MnO 2 shows partially reversible lattice evolution upon (de)lithiation, during which phase separation occurs and accounts for the partial irreversibility.…”