Aqueous Electrochemical Energy Storage with a Mediator‐Ion Solid Electrolyte

Abstract

soluble intermediate products during charge-discharge can result in a crossover between the two electrodes and consequent self-discharge, resulting in a reduction in cell efficiency. Furthermore, with the traditional porous-separator approach, any dendrite formed with metal-based anodes could penetrate through the separator into the cathode, causing short-circuit and safety hazards.From the electrochemical point of view, many liquid-phase or gas-phase materials exhibit both high electrochemical capacity and high operating voltages. They are promising to be used as electrodes for electrochemical energy storage systems. [3] However, as discussed above, the chemical crossover issue in batteries with the traditional porous separator strictly limits the use of liquid or gaseous electrode materials in a battery. Therefore, alternative reliable separator-strategies must be developed to make good use of liquid or gaseous electrode materials. Separating the liquid-phase or gas-phase electrodes with a solid electrolyte provides a promising strategy to not only avoid the liquid (or gaseous)-reactant crossover, but also completely circumvents the metal dendrite concerns. However, at present, cationic solid electrolytes at ambient temperatures are practically limited to alkali-metal ions (e.g., Li + and Na + ions). Although these solid electrolytes can be used with any catholyte or anolyte solutions, they have previously been used only for the development of nonaqueous (with organic anolytes or with molten electrodes) Li + -or Na +ion batteries. [4] This is because under the traditional battery operating principle, the transporting ion (Li + or Na + ion) in the solid electrolyte is directly involved in the anode reaction. Therefore, Li-based or Na-based anode has to be adopted in a battery, respectively, with a Li + -ion or a Na + -ion solid electrolyte, and neither Li nor Na can be used in aqueous environments. [5] Divalent-ion-based battery chemistries (e.g., Zn and Fe) can be used in aqueous solutions, but solid electrolytes capable of transporting divalent ions are practically unavailable due to the higher charge and heavier mass of the ions. [6] In view of the above considerations, it is, therefore, impossible or difficult to develop aqueous batteries with the currently available solidstate electrolytes (Li + -ion and Na + -ion solid electrolytes).Herein, we demonstrate a unique mediator-ion strategy for the development of aqueous batteries with a solid-electrolyte separator by properly managing the solid-state electrolyte (SSE), anolyte (the aqueous electrolyte at the anode), and catholyte This study presents a battery concept with a "mediator-ion" solid electrolyte for the development of next-generation electrochemical energy storage technologies. The active anode and cathode materials in a single cell can be in the solid, liquid, or gaseous form, which are separated by a sodium-ion solid-electrolyte separator. The uniqueness of this mediator-ion strategy is that the redox reactions at the anode and the cathode are...

Advanced Architectures and Relatives of Air Electrodes in Zn–Air Batteries

“…The separator should have a low electronic conductivity but a high ionic conductivity . The electrolyte should be appropriately active to Zn electrode, and have favorable conductivity as well as an excellent capability to sufficiently contact with air electrode . This review will focus on the air electrode, electrolyte, which is closely related to the air electrode, will also be briefly illustrated.…”

Electrochemistry: Retrospect and Prospects

“…The approach also allows fabrication of batteries with anodes of zinc, magnesium, iron and aluminium, solid ion conductors for which are practically unavailable. [45][46][47][48][49] The first battery with a mediator-ion solid electrolyte was unveiled by Chen et al in 2013: [45] an aqueous ZnÀ KMnO 4 cell with solid Zn as anode, a solution of KMnO 4 as cathode and an Li 1 + x + y Al x Ti 2-x Si y P 3-y O 12 ceramic as solid electrolyte. Other innovations have followed, notably those for ZnÀ air, [47] ZnÀ Br 2 [48] and FeÀ air.…”

“…[45][46][47][48][49] The first battery with a mediator-ion solid electrolyte was unveiled by Chen et al in 2013: [45] an aqueous ZnÀ KMnO 4 cell with solid Zn as anode, a solution of KMnO 4 as cathode and an Li 1 + x + y Al x Ti 2-x Si y P 3-y O 12 ceramic as solid electrolyte. Other innovations have followed, notably those for ZnÀ air, [47] ZnÀ Br 2 [48] and FeÀ air. [49] Going with the Flow Flow batteries, in particular, offer an opportunity to make renewable storage more affordable, and could accelerate prospects for utility-scale development of solar energy storage.…”

“…The physical decoupling of the anode and cathode avoids problems of undesirable chemical reactions due to crossover between the anode and cathode sides, internal gas diffusion and dendritic shorting. The approach also allows fabrication of batteries with anodes of zinc, magnesium, iron and aluminium, solid ion conductors for which are practically unavailable [45–49] . The first battery with a mediator‐ion solid electrolyte was unveiled by Chen et al .…”

“…in 2013: [45] an aqueous Zn−KMnO 4 cell with solid Zn as anode, a solution of KMnO 4 as cathode and an Li 1+ x + y Al x Ti 2– x Si y P 3– y O 12 ceramic as solid electrolyte. Other innovations have followed, notably those for Zn−air, [47] Zn−Br 2 [48] and Fe−air [49] …”