Understanding intercalation chemistry for sustainable aqueous zinc–manganese dioxide batteries

Abstract

Amid the growing interest in rechargeable aqueous zinc-based batteries, tunnel-structured α-MnO2 has emerged as a promising cathode material owing to its low cost, high capacity and high safety.However, the precise charge storage mechanism, possibly involving proton and/or Zn ion insertion, has not been fully characterized especially at the atomistic level. Here, we report new insights through a combined investigation of atomic-scale electron microscopy, electrochemical analysis and ab initio simulations. We find that reversible Zn 2+ insertion into α-MnO2 framework is unlikely in the aqueous system, and that the charge storage process is dominated by H + insertion into the tunnel structures which are maintained upon discharging to HMnO2. Furthermore, we identify the local lattice positions for the hydroxyl (OH) groups in HxMnO2 as a function of H content. We reveal the consequent anisotropic structural change proceeding from the particle surface into the bulk, and thus account for the structural failure and capacity decay of the electrode upon cycling.Future work should consider optimizing proton insertion kinetics with enhanced host stability.

Reaction mechanism for the α-MnO2cathode in aqueous Zn ion batteries revisited: elucidating the irreversible transformation of α-MnO2into Zn–vernadite

“…A previous study has revealed that the H + intercalation leads to the lattice distortion of α-MnO 2 . 22 The reaction of H + intercalation into α-MnO 2 can thus be described:MnO 2 + x H + + x e − ⇌ H x MnO 2 …”

“…Recently, it has been proposed that Zn–vernadite (Zn x MnO 2 ) forms by the electrochemical reaction between ZHS and Mn 2+ in the electrolyte as given below: 22,33,44 2(ZnSO 4 ·3Zn(OH) 2 ·5H 2 O) + 3Mn 2+ → 3Zn x MnO 2 + 16H 2 O + (8 − 3 x )Zn 2+ + 2SO 4 2− + (6 − 6 x )e − …”

“…15,32–35 An alternative mechanism was proposed based on conversion reactions between zinc hydroxide sulfate and vernadite/birnessite. 21,22…”

Development of Proteins for High‐Performance Energy Storage Devices: Opportunities, Challenges, and Strategies

“…[11,12] Huge efforts have been devoted to developing new materials and battery chemistries to boost energy densities in the past ten years (Figure 1a). [13][14][15][16][17][18][19][20] However, the manufacture of current Li-ion batteries uses a large amount of toxic materials that need to be replaced with more environmentally friendly materials such as biomaterials. [21][22][23] The direct use of biomaterials as major components for battery manufacturing has attracted significant attention recently (Figure 1b).…”

From spent alkaline batteries to active Zn||ZnxMn2O4aqueous batteries: a mild process of cathode recycling and crystal engineering

“…12 Besides, the uniform dispersion of cathode particles with conductive carbon materials and the surface state of electrode materials (e.g., pH value and interface structure) would significantly affect electrolyte hydrolysis, large over-potential, and the overgrowth of a solid-state electrolyte interface (SEI). [13][14][15] On the other hand, hundreds of thousands of tons of Mn-based cathode waste are produced from tens of billions of spent alkaline batteries (ABs) every year, which could be a serious source of pollution or transformed into a considerable amount of renewable resources. For the spent ABs, there are several discharged cathode waste, such as Zn x Mn 2 O 4 , MnO(OH), Zn(OH) 2 and carbon.…”