Manganese-based flow battery based on the MnCl2 electrolyte for energy storage

A perspective on manganese-based flow batteries

“…In table 2, the main performance characteristics of MnO 2 /Mn 2+ flow batteries are succinctly outlined. Notably, at a current density of 20 mA cm −2 , a long cycling life over 1000 cycles was obtained in a Zn-Mn flow battery [27]. In other cases, the operating current density was low and cycling life was short.…”

“…In order to enhance the energy density of a MnO 2 /Mn 2+ flow battery, the utilization of highly soluble MnCl 2 (6.42 M) as the active species, which also exhibits reduced sensitivity to temperature variations, has shown promise. Consequently, a Zn-Mn flow battery utilizing MnCl 2 as the catholyte is suggested [27]. However, challenges arise due to the Mn 3+ disproportionation and chlorine evolution reaction (Cl 2 /Cl − 1.36 V vs SHE, similar to MnO 2 /Mn 2+ , Mn 3+ /Mn 2+ ), which hinder the battery's performance.…”

“…The redox reactions involving Mn 3+ /Mn 2+ typically occur in highly acidic environments (pH < 1), exhibiting a high potential (1.51 V vs SHE) and high solubility, which are advantageous for the development of MFBs with elevated energy density. Nevertheless, Mn 3+ is susceptible to instability in aqueous solutions, leading to spontaneous disproportionation reactions that yield Mn 2+ and MnO 2 , ultimately resulting in diminished low coulombic efficiency (CE) of the battery [27]. Concurrently, the presence of residual non-conductive MnO 2 leads to passivation of the electrode surface, obstruction of flow paths, elevation of battery polarization, and deterioration of capacity.…”

Energy storage mechanism, advancement, challenges, and perspectives on vivid manganese redox couples

“…35–37 Furthermore, to achieve effective Mn 2+ /MnO 2 conversion, additives are introduced such as inorganic compounds, and redox mediators. 38–41…”

Promoting the reversibility of electrolytic MnO2-Zn battery with high areal capacity by VOSO4 mediator

“…The twoelectron transfer reaction involves the deposition and dissolution of MnO 2 , resulting in an impressive theoretical capacity of 616 mAh g -1 [12][13][14][15][16][17][18] . Notably, the MnO 2 -Zn battery benefits from the high reduction potential of Mn 2+ /MnO 2 (1.228 V), enabling it to achieve a high voltage output of 1.991 V [19][20][21][22][23][24][25][26][27][28] .…”