Boosting the Energy Density of Aqueous Batteries via Facile Grotthuss Proton Transport

Abstract

The recent developments in rechargeable aqueous batteries have witnessed a burgeoning interest in the mechanism of proton transport in the cathode materials. Herein, for the first time, we report the Grotthuss proton transport mechanism in α‐MnO2 which features wide [2×2] tunnels. Exemplified by the substitution doping of Ni (≈5 at.%) in α‐MnO2 that increases the energy density of the electrode by ≈25 %, we reveal a close link between the tetragonal‐orthorhombic (TO) distortion of the lattice and the diffusion kinetics of protons in the tunnels. Experimental and theoretical results verify that Ni dopants can exacerbate the TO distortion during discharge, thereby facilitating the hydrogen bond formation in bulk α‐MnO2. The isolated direct hopping mode of proton transport is switched to a facile concerted mode, which involves the formation and concomitant cleavage of O−H bonds in a proton array, namely via Grotthuss proton transport mechanism. Our study provides important insight towards the understanding of proton transport in MnO2 and can serve as a model for the compositional design of cathode materials for rechargeable aqueous batteries.

Structure and Properties of Prussian Blue Analogues in Energy Storage and Conversion Applications

“…Revealing the electrochemical reaction mechanisms during charge/discharge process is of great importance to develop advanced electrode materials, [ 58–60 ] and the crystal and electronic structures of electrodes can be detected by many methods, including in situ/ex situ X‐ray diffractions (XRD), [ 61,62 ] transmission electron microscopy (TEM), [ 63,64 ] soft X‐ray spectroscopy (SXS), [ 65 ] etc. For PBA materials, the open frameworks provide numerous 3D tunnels for intercalating various carrier ions.…”

Non‐Metal Ion Co‐Insertion Chemistry in Aqueous Zn/MnO2 Batteries

“…Owing to the bond competition between MnÀO and OÀH bonds, the electron density of oxygen atoms in MnÀO bonds is increased (Figure 1 c). [12] As a result, the hydrogen bonds between MnO 2 and NH 4…”

Superior cycling stability of H0.642V2O5·0.143H2O in rechargeable aqueous zinc batteries

“…To increase the cycle life of the Zn anode, researchers have recently developed certain optimization strategies such as tuning electrolytes with additives [13], applying "water in salt" electrolytes [14], organic/inorganic coating [15,16], and utilizing 3D current collectors [17,18]. Furthermore, the electrochemical performance of cathode materials has been improved using optimization methods such as metal substitution [19], coating with conductive layers [20,21], applying pre-intercalation strategy [22,23], and defect engineering [24,25]. Pre-intercalation engineering provides a basic and effective insight for optimizing the structure and correlated electrode performance of Mn-and Vbased host materials.…”