Rechargeable zinc-ion batteries (RZIBs) utilizing aqueous electrolytes can offer high safety, low cost, and fast charge/discharge ratings for large-scale energy storage. The use of water as electrolyte solvent facilitates low cost, facile processing, reduced safety concerns, and fast ion kinetics. However, free water molecules also instigate many simultaneously occurring undesired reactions in the RZIB system, leading to capacity fade and limited operational lifetime. Here, our review traces each undesired reaction and its cascade of detrimental ramifications on RZIB cycling. We discuss balancing merits, reported strategies, and future perspectives to mitigate these undesired reactions and further improve the RZIBs’ operational lifetimes.

www.advsustainsys.comion-based chemistries exclusively. Though few reviews document electrode materials and their performances for rechargeable aqueous Zn-and Al-ion batteries, [23,[25][26][27] a comprehensive understanding of ion storage mechanisms remains poorly enunciated. We believe the key to successful implementation of MV-ion batteries requires a simultaneous understanding of various elemental chemistries, in context with each other. Here, we summarize reported electrochemical reactions for Zn-ion and Al-ion electrodes. We compare activation mechanisms for ion transport and the role of water in various crystal lattices, and analyze specific challenges for electrode materials such as limited cation mobility, spontaneous dissolution, poor cycling, O 2 interaction, untoward proton/hydronium coinsertion, ineffective electrode-electrolyte interface formation, and current-collector corrosion. We illustrate how these challenges are dependent on some of the battery design parameters, with an aim to find optimized solutions or alternative strategies to increase the viability of Zn-ion aqueous batteries (ZIABs) and Al-ion aqueous batteries (AIABs) in BESS. Aqueous Rechargeable Electrodes for Zn-Ion StorageIn this review, we discuss rechargeable electrodes which can insert Zn 2+ ions. Since, electrodes for zinc-nickel batteries, [28,29] alkaline Zn-MnO 2 batteries, [30,31] or the hybrid zinc aqueous batteries, [32] store other ions (and not Zn 2+ ), we do not discuss these systems here. Majority of the literature for ZIAB electrodes spans various polymorphs of manganese dioxide, [33][34][35][36][37][38][39][40][41][42][43][44][45][46][47][48] vanadium compounds, [49][50][51][52][53][54][55][56][57][58][59][60][61] and hexacyanoferrates, [62][63][64][65] and we discuss few Zn 2+ storage mechanisms for these electrodes. Additionally, we also highlight key similarities, missing links in the reaction mechanism, and the role of water, if any. 2.

Rechargeable zinc-ion batteries (RZIB) present an interesting alternative to rechargeable Li-ion batteries. Among the active materials, layered vanadium-based oxides show a poor cell voltage but modifying this structure by attaching a phosphate group to the vanadium redox center can drastically enhance the cathode voltage. With this layered VOPO4 material, we demonstrate that preintercalating polypyrrole between crystallographic layers and using electrolyte with controlled water amounts are two absolutely essential conditions for easy and reversible Zn2+ (de)­intercalation, thus vastly improving battery outputs and long-term capacity retention. We establish that the rational design of open-layered structures hinges imperatively on factors like host structural integrity and electrode–electrolyte compatibility in delivering the performance of multivalent-ion batteries.

Electrocatalysts are one of the most important parts for oxygen evolution reaction (OER) to overcome the sluggish kinetics. Herein, amorphous Fe-Ni-P-B-O (FNPBO) nanocages as efficient OER catalysts are synthesized by a simple low-cost and scalable method at room temperature. The samples are chemically stable, in clear contrast to reported unstable or even pyrophoric boride samples. The Fe/Ni ratio of the FNPBO nanocages can be continuously adjusted to optimize the OER catalytic performance. The FNPBO nanocages composed of multicomponent elements can weaken the metal-metal bonds thus rearranging the electron density around the catalytic metal atom centers and reducing the energy barrier for intermediate formation. Hence the optimized FNPBO (Fe6.4Ni16.1P12.9B4.3O60.2) catalyst shows superior intrinsic electrocatalytic activity for OER. The low overpotential to afford the current density of 10 mA cm -2 (236 mV), the small Tafel slope (39 mV dec -1 ), and the high specific current density (26.44 mA cm -2 ) at a given overpotential of 300 mV make a sharp contrast to state-of-the-art RuO2 (327 mV, 136 mV dec -1 , and 0.028 mA cm -2 , respectively). Clean energy is highly desired for clean and sustainable future. [1][2][3] Hydrogen has been considered as an ideal alternative fuel to replace gasoline, which is environmental friendly with a

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