water (1.23 V) limits both the operating voltage and energy density of aqueous batteries. Although adjusting the pH can effectively suppress hydrogen evolution at the anode, owing to the inherent voltage limit, another electrode compromise would occur. Fortunately, the solid-electrolyte interphase (SEI) acts to kinetically stabilize the electrolyte at potentials beyond their thermodynamic stability limits. Early research on SEI focused on the electrodes, and the findings have since been applied extensively to carbonate-based nonaqueous electrolytes, with successful outcomes. [9-13] However, SEI has many restrictive requirements in the standard aqueous battery. In traditional aqueous electrolytes, the decomposition products are H 2 and O 2 , which fail to deposit as solids on the surface of the electrodes. A superconcentrated (Li + (H 2 O) 2) n polymerlike chain aqueous electrolyte based on LiNO 3 salt was reported, achieving a 2.55 V stability window without forming a protective SEI. [14] But a high cathodic potential (2.35 V vs Li) to satisfy the demands of commercial anode materials such as Li 4 Ti 5 O 12 (1.55 V vs Li) remain challenging. Furthermore, the absence of SEI leads to a low energy density and limited cycle life in aqueous batteries. [15,16] More recently, some pioneering works offered new directions by developing high concentration aqueous electrolytes: 21 m (m = molality, mol kg −1) "water-in-salt" electrolyte, [17] 28 m "water-in-bisalt" electrolyte, [18] "water-in-ionomer" electrolyte, [19] hybrid aqueous-nonaqueous electrolyte, [20] molecular crowding electrolytes, [21] hydrate melt electrolytes, [22] and 63 m "water-in-hybrid-salt" electrolyte. [23] These approaches help to broaden the limited electrochemical stability window of aqueous electrolytes. Some of these modified electrolytes exhibited impressive energy density, compatibility with electrodes, and exceptional stable cycle performance. Although these efforts on aqueous electrolytes have introduced a new prospect for electrode protection by reducing water activity, the in situ SEI formation is still infancy. There is a need for in-depth research of SEI to reach the desired cycle stability and energy density. For instance, the thermodynamics and kinetics of expanding voltage windows in the SEI formation mechanism need to be investigated. In addition, no electrolyte has been identified to address the challenges of cycle stability and discharge capacity, nor has and study evaluated the correlation between SEIs' unique structures and their electrochemical Aqueous batteries are promising devices for electrochemical energy storage because of their high ionic conductivity, safety, low cost, and environmental friendliness. However, their voltage output and energy density are limited by the failure to form a solid-electrolyte interphase (SEI) that can expand the inherently narrow electrochemical window of water (1.23 V) imposed by hydrogen and oxygen evolution. Here, a novel (Li 4 (TEGDME)(H 2 O) 7) is proposed as a solvation electrolyte with sta...

Flexible solid-state zinc−air batteries are promising energy technologies with low cost, superior performance and safety. However, flexible electrolytes are severely limited by their poor mechanical properties. Here, we introduce flexible bacterial cellulose (BC)/poly(vinyl alcohol) (PVA) composite hydrogel electrolytes (BPCE) based on bacterial cellulose (BC) microfibers and poly(vinyl alcohol) (PVA) by an in situ synthesis. Originating from the hydrogen bonds among BC microfibers and PVA matrix, these composites form loadbearing percolating dual network and their mechanical strength is increased 9 times (from 0.102 MPa of pristine PVA to 0.951 MPa of 6-BPCE). 6-BPCE shows extremely high ionic conductivities (80.8 mS cm −1 ). In addition, the solidstate zinc−air batteries can stably cycle over 440 h without large discharge and charge polarizations equipped with zinc anode and Co 3 O 4 @Ni cathode. Moreover, flexible solid-state zinc−air batteries can cycle well at any bending angle. As flexible electrolytes, they open up a new opportunity for the development of superior-performance, flexible, rechargeable, zinc−air batteries.

Aqueous batteries have attracted extensive attention for their safety, low cost, and non-toxicity properties. However, the narrow electrochemical stability window and freeze of water at the low temperature limit energy...

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High-energy-density Li-metal batteries are of great significance in the energy storage field. However, the safety hazards caused by Li dendrite growth and flammable organic electrolytes significantly hinder the widespread application of Li-metal batteries. In this work, we report a highly safe electrolyte composed of 4 M lithium bis­(fluorosulfonyl)­imide (LiFSI) dissolved in the single solvent trimethyl phosphate (TMP). By regulating the solvation structure of the electrolyte, a combination of nonflammability and Li dendrite growth suppression was successfully realized. Both Raman spectroscopy and molecular dynamics simulations revealed improved dendrite-free Li anode originating from the unique solvation structure of the electrolyte. Symmetric Li/Li cells fabricated using this nonflammable electrolyte had a long cycle life of up to 1000 h at a current density of 0.5 mA cm–2. Furthermore, the Li4Ti5O12/TMP-4/Li full cells also exhibited excellent cycling performance with a high initial discharge capacity of 170.5 mAh g–1 and a capacity retention of 92.7% after 200 cycles at 0.2 C. This work provides an effective approach for the design of safe electrolytes with favorable solvation structure toward the large-scale application of Li-metal batteries.