Solid‐Electrolyte Interphase for Ultra‐Stable Aqueous Dual‐Ion Storage

Abstract

non-flammable nature are of great potential for the grid-energy storage of renewable but intermittent energy sources. [1][2][3] The solid-electrolyte interphase (SEI) plays a crucial role in protecting electrodes in LIBs, endowing LIBs with long-term cycling for commercial applications. As an independent passivation phase deposit on electrode surfaces, the SEI blocks electron transport while enabling ionic conduction. It can passivate the anode and prevent the electrolyte from unfavorable degradation, extending the electrochemical stability window of the electrolyte. As expected, a robust aqueous SEI will hinder water molecules to access the surface of the electrode while allowing for Li + diffusion, thus suppressing the water splitting. Therefore, not only the voltage window of ALIBs would be extended, but also improve the cathodic stability of electrodes. Unfortunately, the SEI is hardly observed in typical ALIBs, owing to none of the dense solid states can be deposited from the water splitting. [4,5] Moreover, the high solubility of ionic compounds (derived from the electrolyte decomposition) in water than in organic electrolytes makes it difficult to maintain a stable SEI. [6] As the absent protection of aqueous SEI, a series of adverse reactions are participated at the interface of the electrode during long cycling, involving the structural collapse or dissolution of materials and/or redox mediators, proton co-intercalation, hydrogen evolution reaction (HER), or other irreversible degradations, thereby inducing to a critical issue for the long-term cycling. [7][8][9] Thanks to the sufficient population of solvation sheath with proper anions of water-in-salt electrolytes (WiSEs), the liquid structure and interfacial reactivity are naturally changed to form a dense SEI and deliver considerable cycling stability, compared favorably with that of the state-of-the-art LIBs. [10][11][12][13] It has been previously reported that the water reduction triggers the precipitation and degradation of bis(trifluoromethanesulfonyl)imide anion (TFSI − ) under negative polarization, followed by the SEI formation. The fate of water at the electrochemical interface is critical. [14][15][16] Nevertheless, the composition and formation mechanism of such dense and protective aqueous SEI are still under debate, which hinders the raising of the electrochemical stability of electrodes in ALIBs.In contrast to the well-explored inorganic anodes, tunable organic electrode materials (OEMs) with extremely high theoretical capacities have attracted great attention, owing to theirThe solid-electrolyte interphase (SEI) is the key component of the electrochemical electrode as a passivation layer, which enables a long calendar life for commercial applications. However, owing to the poor understanding of aqueous SEI in conventional aqueous electrolytes, the adoption of aqueous Li-ion batteries (ALIBs) has been drastically limited. Herein, the construction of a robust aqueous SEI is successfully demonstrated by introducing a ladderized heterocycl...

Advanced Characterization Techniques on Mechanism Understanding and Effect Evaluation in Zinc Anode Protection

“…[75,76] Among different strategies, the water-in-salt electrolyte (WiSE) with high salt-water ratio enables anion-rich solvation structure to suppress side reactions and construct stable AIL. [77][78][79] According to the results from in situ OM in Figure 4a, the uneven Zn plating in 1 m Zn(TFSI) 2 obviously is with lots of residual black spots during stripping, indicating the generation of "dead Zn" because of low CE for cycling. After three cycles, a vast accumulation of "dead Zn" led to terrible dendrite formation, causing serious security risks.…”