Deciphering the Electrochemical Behaviors of the Electrode‐Electrolyte Coupling toward Advanced Electrochemical Energy Storage Device

Abstract

Aqueous electrochemical energy storage devices (AEESDs) exhibit tremendous potential for grid‐scale energy storage due to their high ionic conductivity, high safety, and environmental friendliness. Nevertheless, the improvement of energy density is always accompanied by the loss of power density due to the sluggish ion migration in the bulk of the electrode. Redox electrolytes are proposed as one of the most promising strategies to expand from electrode materials to the whole device to improve the energy density and power density of AEESDs simultaneously. It is thus vital to understand the electrochemical behaviors and mechanism of the coupling system between the electrode and redox electrolyte during the electrochemical charge‐discharge process. In this study, the electrochemical kinetic evolution model of the redox electrolyte in the electrode is established via quasi‐steady electrochemical measurement and in situ Raman study, revealing the redox reaction of electrolyte originates from charge transfer between ions in electric double layer (EDL). Accordingly, the electrochemical performances are optimized by adjusting the electrolyte concentration. The decline of coulombic efficiency is systematically analyzed, which can be attributed to ionic drifting during a redox reaction. This study may pioneer designing the advanced electrochemical energy storage device by integrating electrode materials and electrolytes.

Insight on the Energy Storage Mechanism and Kinetic Dynamic of Manganese Oxide‐Based Aqueous Zinc‐Ion Batteries

“…It is important to note that when each voltage step is long enough, the more favorable it is for probing the true reaction occurring at the electrodes. [156] For a conventional redox system, the i i obtained is large. As time progresses, the current decreases as the Reproduced with permission.…”

“…b) Schematic for MPSM (red curve: input potential, black curve: output current),and c) MPSM curves with different potential steps. Reproduced with permission [156]. Copyright 2021, Wiley-VCH GmbH.…”

Thermally responsive polymers for overcoming thermal runaway in high-safety electrochemical storage devices

“…5,6 Unfortunately, despite significant improvements in battery performance, ESDs have significant security flaws that limit their further application. [7][8][9] Super-fast charging or discharging and thermal abuse conditions such as short-circuiting and overcharging pose the risk of thermal runaway, which can have severe consequences. 10,11 For example, on October 15, 2022, South Korea's key data center lost power due to the combustion of LIBs, interrupting the services of the country's two Internet giants, Naver and Kakao.…”

Three-dimensional nano-folded transition-metal oxide electrode materials for high-performing electrochemical energy-storage devices

“…26 Sun et al performed studies on the electrochemical behavior between the electrode materials and electrolyte ions, and they found that a wrinkled electrode surface greatly benefits the adsorption of ions and the formation of electronic double layers, in which the excessive ions on the surface ensure effective electrode-material-related redox reactions, subsequently leading to an improvement in the capacity performance, where the confined electrolyte ions in the wrinkled regime reduce the self-charging effect caused by the ion drift. 27…”

“…26 Sun et al performed studies on the electrochemical behavior between the electrode materials and electrolyte ions, and they found that a wrinkled electrode surface greatly benefits the adsorption of ions and the formation of electronic double layers, in which the excessive ions on the surface ensure effective electrode-material-related redox reactions, subsequently leading to an improvement in the capacity performance, where the confined electrolyte ions in the wrinkled regime reduce the self-charging effect caused by the ion drift. 27 Here, we take the view that the transition-metal oxide electrode materials require an integral form with a welldefined local structure for effective electrochemical reactions during electrochemical charge/discharge processes, using the prototype of nickel oxide as the cathode of a supercapacitor device. In the experiments, we have developed the dynamic thermal oxidation route (i.e., electrical annealing) to fabricate three-dimensional (3D) nano-folded NiO, in which Ni was oxidized into NiO in an extremely rapid manner in air leading to the formation of the nano-folded structure in the products due to the uniaxial and biaxial shrinkage of the surface NiO.…”