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Small molecule quinone compounds are attractive cathode materials for rechargeable aqueous zinc‐organic batteries (AZOBs) because of their structural diversity and low‐cost merits. Among them, nonpolar quinones are dominant given the relatively low solubilities in aqueous electrolytes. However, their poor electronic conductivity and accumulated Coulombic repulsion lead to underutilized active sites and sluggish redox kinetics. Here, polar 2,6‐dimethoxy‐1,4‐benzoquinone (m‐DMBQ) works as an advanced AZOB cathode with unexpectedly superior performance over the nonpolar isomer of 2,5‐dimethoxy‐1,4‐benzoquinone (p‐DMBQ). The asymmetric charge distribution of active centers in the p−π conjugated backbone of m‐DMBQ induces reduced bandgap with improved electronic conductivity and redox activity, thus achieving a high specific capacity of 312 mAh g−1 approaching the theoretical limit. Additionally, the lowest unoccupied molecular orbital energy level is lowered for an increased average discharge voltage of 0.88 V. Characterizations and computational studies revealed boosted competitiveness of H+ relative to Zn2+ for significantly enhanced charge transfer kinetics and reversibility. As a result, the as‐fabricated AZOB achieves a high energy density of 275 Wh kg−1 based on m‐DMBQ along with high‐rate capability and long‐term cycling stability. This work provides a new molecular engineering strategy through regulating charge distribution symmetry for boosting charge storage in organic cathodes. [ABSTRACT FROM AUTHOR]

The development of Mg‐ion batteries is hindered by the lack of cathode materials that allow facile and reversible Mg2+ intercalation at high potential. Herein, the authors present a polyanion cathode material of K2(VO)2(HPO4)2(C2O4)⋅4.5H2O (KVPCH) for Mg‐ion batteries. The inductive effect of polyanions ensures the high redox potential of the vanadium centers. In addition, the material contains structural water located between the layers. It helps with Mg2+ desolvation at the electrode–electrolyte interface and facilitates its diffusion in the structure, as confirmed by experimental analysis and theoretical calculations. Thanks to those factors, the KVPCH electrode presents excellent Mg storage capability at room temperature. It delivers 121 mAh g–1 capacity at 1C with a high average discharge potential of 0.16 V versus Ag/Ag+ (3.2 V vs Mg/Mg2+). A capacity retention of 87% is realized after 1500 cycles at 5C. A rocking‐chair Mg‐ion full cell is also demonstrated with the KVPCH cathode and a MoOx anode, which achieves 46 mAh g–1 capacity (based on the total active material mass of two electrodes). This work would bring effective paths for the design of cathode materials for Mg‐ion batteries. [ABSTRACT FROM AUTHOR]

The Mn2+ dissolution of MnO2 cathode materials causes rapid capacity decay in aqueous zinc batteries. We herein show that the dissolved Mn2+ can be deposited back to the cathode with the aid of a suitable conductive agent. The active material is thus retained for energy storage, and this MnO2/Mn2+ redox process also provides capacity. In the Mn2+ free ZnSO4 electrolyte, MnO2 delivers 325 mA h g−1 capacity at 0.1 A g−1, and 90.4% capacity retention is achieved after 3000 cycles at 5 A g−1. Our work demonstrates an effective strategy to realize stable cycling of MnO2 cathodes in aqueous zinc batteries without Mn2+ additives. [ABSTRACT FROM AUTHOR]

Mn‐based materials for aqueous energy storage are reaching the capacity ceiling due to the limited Mn4+/Mn3+ redox. The disproportionation of Mn3+ often occurs, forming soluble Mn2+ and thus leading to severer capacity decays. Here, an amorphous manganese phosphate material [AMP, Na1.8Mn4O1.4(PO4)3] is fabricated using an electrochemical method for the first time. Benefitting from the open framework and the insoluble nature of Mn2+ in AMP, the Mn3+/Mn2+ and Mn4+/Mn3+ redox couples can participate in the charge storage processes. The AMP electrode shows a high capacity of 253.4 mAh g−1 (912.4 F g−1 or 912.4 C g−1) at the current density 1 A g−1 and good rate capability. Experimental results indicate AMP experiences a mixed charge storage mechanism (i.e., cation intercalation and conversion reactions) in Na2SO4 electrolyte. Besides, electrolyte engineering can effectively prevent the decomposition of AMP during cycling test, achieving capacity retention of 97% in 5000 cycles. Importantly, AMP can accommodate different cations (e.g., Mg2+, Ca2+, etc.), exhibiting great potential for aqueous energy storage. [ABSTRACT FROM AUTHOR]

The energy storage behavior of the Li3V2(PO4)3 cathode in zinc batteries is evaluated. The dissolution or decomposition into vanadium oxide in aqueous electrolytes is revealed. Using the optimal combination of water and acetonitrile solvents in electrolyte, those processes are effectively prevented without sacrificing the Zn2+ de/insertion kinetics. Further investigation demonstrates a water induced phase transformation into a VOPO4 type structure, which is still a polyanion material and preserves the high voltage. It delivers 128 mA h g−1 capacity at 1C with 1.45 V discharge voltage, and 87 mA h g−1 capacity is retained at 10C. A stable cycling is obtained for 1000 cycles. [ABSTRACT FROM AUTHOR]

[Display omitted] • Quinone sites are introduced to PANI by a facile electrochemical method. • Polymer chains transform into expanded coil conformation at the same time. • Quinone provides extra redox sites, and expanded polymer enhances conductivity. • The electrode delivers 186 mAh g−1 capacity with quinone at 1.4 V and PANI at 1.1 V. • A stable capacity retention of 88.0% is achieved after 1500 cycles. Rechargeable aqueous batteries with zinc metal anodes are promising energy storage systems owing to their high safety and low lost. A suitable cathode material is in urgent demand. Organic materials offer adjustable electrochemical activity, and conducting polymers provide good electrical conductivity. Herein, we combine those advantages in one cathode material by the controlled introduction of quinone-type active sites onto polyaniline (PANI) nanorod-arrays through a facile electrochemical treatment. The process simultaneously transforms the polymer with a compact coil conformation into an expanded coil structure, resulting in facilitated electron transportations and charge transfer processes. In comparison to the original PANI, the electrochemically treated Q-PANI electrode exhibits extra electrochemical activity from quinone sites as well as enhanced capacity from PANI itself. Q-PANI delivers a high capacity of 186 mAh g−1 at 0.2 A g−1. Upon long-term cycling, 88.0% capacity retention is achieved after 1500 cycles at 2 A g−1. Detailed mechanism studies demonstrate the redox reaction on quinone sites at 1.4 V and nitrogen centers in PANI at 1.1 V. The work proposes a potential pathway towards high performance electrode materials for zinc batteries. [ABSTRACT FROM AUTHOR]