Balanced Interfacial Ion Concentration and Migration Steric Hindrance Promoting High‐Efficiency Deposition/Dissolution Battery Chemistry

Abstract

The solid–liquid transition reaction lays the foundation of electrochemical energy storage systems with high capacity, but realizing high efficiency remains a challenge. Herein, in terms of thermodynamics and dynamics, this work demonstrates the significant role of both interfacial H+ concentration and Mn2+ migration steric hindrance for the high‐efficiency deposition/dissolution chemistry of zinc–manganese batteries. Specially, the introduction of formate anions can buffer the generated interfacial H+ to stabilize interfacial potential according to the Nernst equation, which stimulates high capacity. Compared with acetate and propionate anions, the formate anion also provides high adsorption density on the cathode surface to shield the electrostatic repulsion due to the small spatial hindrance. Particularly for the solvated Mn2+, the formate‐anion‐induced lower energy barrier of the rate‐determining step during the step‐by‐step desolvation process results in lower polarization and higher electrochemical reversibility. In situ tests and theoretical calculations verify that the electrolyte with formate anions achieve a good balance between ion concentration and ion‐migration steric hindrance. It exhibits both the high energy density of 531.26 W h kg‐1 and long cycle life of more than 300 cycles without obvious decay.

MOF-Derived Mn3O4@C Hierarchical Nanospheres as Cathodes for Aqueous Zinc-Ion Batteries

“…This result also suggests the pH evolution of the electrolyte, causing Zn 2+ , SO 4 2– , and the remaining OH – to combine to form ZHS subsequently . ZHS could also consume a large amount of H + produced by the manganese deposition reaction to stabilize the interfacial pH value during the charge process . In the 100th fully discharge state, the XRD pattern of Mn 3 O 4 @ is shown in Figure c; during charging/discharging, the characteristic diffraction peak of Mn 3 O 4 became inconspicuous due to the interference of the matrix, which is consistent with the literature report .…”

“…63 ZHS could also consume a large amount of H + produced by the manganese deposition reaction to stabilize the interfacial pH value during the charge process. 62 In the 100th fully discharge state, the XRD pattern of Mn 3 O 4 @ is shown in Figure 7c; during charging/discharging, the characteristic diffraction peak of Mn 3 O 4 became inconspicuous due to the interference of the matrix, which is consistent with the literature report. 64 At the same time, it is easy to find the characteristic peak belonging to ZHS, which is extremely consistent with the result of ex situ XRD patterns.…”

“…The characteristic peaks of Zn 4 (OH) 6 SO 4 ·5H 2 O (ZHS) gradually appeared in the discharge process, which may be due to hydrogen ion intercalation during discharge . According to the above results, it can also be further supported that the activated reaction of manganese-based cathodes is related to the formation of ZHS on the surface of the electrode in an aqueous electrolyte . This result also suggests the pH evolution of the electrolyte, causing Zn 2+ , SO 4 2– , and the remaining OH – to combine to form ZHS subsequently .…”

“…61 According to the above results, it can also be further supported that the activated reaction of manganese-based cathodes is related to the formation of ZHS on the surface of the electrode in an aqueous electrolyte. 62 This result also suggests the pH evolution of the electrolyte, causing Zn 2+ , SO 4…”

Modulating Cation Migration and Deposition with Xylitol Additive and Oriented Reconstruction of Hydrogen Bonds for Stable Zinc Anodes

“…The calculated E a2 value of the xylitol-infused ZnSO 4 electrolyte (16.14 kJ mol À 1 ) is lower than that of the pure ZnSO 4 electrolyte (18.76 kJ mol À 1 ), implying the newly formed hydrogen bond system is beneficial to the desolvation processes (Figure S15d, Supporting Information). [26] Since the dendrite growth and related side reactions directly occur at the electrode-electrolyte interface, the adsorption of xylitol molecules on the surface of the Zn anode is crucial for the subsequent deposition of Zn 2 + ions and the stability of ZIBs. Herein, density functional theory (DFT) computations were primarily utilized to analyze the possible adsorption mechanism, where the (002) plane of the Zn slab was selected as a preferred crystal plane for the plating process.…”