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Dendrite growth and side reactions of the Zn metal anode limit the cycle life of aqueous Zn batteries. Herein, we propose a sodium dichloroisocyanurate electrolyte additive with a low concentration of 0.1 M to modify the Zn interface environment and construct a stable organic–inorganic solid–electrolyte interface on the Zn electrode. It suppresses corrosion reactions and directs uniform Zn deposition. The cycle life of the Zn electrode in symmetric cells extends to 1100 h at 2 mA cm−2 and 2 mA h cm−2, and the Zn plating/stripping coulombic efficiency reaches 99.5% for more than 450 cycles. [ABSTRACT FROM AUTHOR]

Transition metal layered double hydroxides (LDHs) are widely used as high‐performance cathode materials for aqueous alkaline zinc (Zn) batteries. Yet, the strongly alkaline electrolytes may lead to undesirable rechargeability of the alkaline devices and environmental issues. Herein, as a research prototype, CoNi LDH material is designed with abundant H vacancies using electrochemical methods (denoted as CoNi LDH(v)). As a Zn‐ion battery cathode, CoNi LDH(v) exhibits promising electrochemical performances in mild ZnSO4 electrolyte, such as a good specific capacity of 185 mAh g−1 at the current density of 1.2 A g−1, a high average discharge potential of 1.6 V versus Zn2+/Zn, and a large energy density of 296.2 Wh kg−1 at the power density of 1894 W kg−1, outperforming most of the cathode materials for aqueous Zn‐ion batteries. Experimental and computational results indicate that the introduced H vacancies in the double hydroxide matrix induce the improved electronic conductivity and cation adsorption thermodynamics, endowing the double hydroxides with good electrochemical activity for reversible cation insertion. Structural and spectroscopy studies identify that CoNi LDH(v) experiences reversible H+/Zn2+ co‐intercalation mechanism in an aqueous ZnSO4 electrolyte. As far as it is known, it is the first report on transition‐metal‐based double hydroxides used for mild aqueous Zn‐ion batteries. [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]

VOPO4⋅x H2O has been proposed as a cathode for rechargeable aqueous zinc batteries. However, it undergoes significant voltage decay in conventional Zn(OTf)2 electrolyte. Investigations show the decomposition of VOPO4⋅x H2O into VOx in the electrolyte and voltage drops after losing the inductive effect from polyanions.PO43− was thus added to shift the decomposition equilibrium. A high concentration of cheap, highly soluble ZnCl2 salt in the electrolyte further prevents VOPO4⋅x H2O dissolution. The cathode shows stable capacity and voltage retentions in 13 m ZnCl2/0.8 m H3PO4 aqueous electrolyte, in direct contrast to that in Zn(OTf)2 where the decomposition product VOx provides most electrochemical activity over cycling. Sequential H+ and Zn2+ intercalations into the structure are revealed, delivering a high capacity (170 mAh g−1). This work shows the potential issue with polyanion cathodes in zinc batteries and proposes an effective solution using fundamental chemical principles. [ABSTRACT FROM AUTHOR]

[Display omitted] • A high donor number electrolyte additive of N -methylpyrrolidone is demonstrated for aqueous Zn batteries. • It preferential adsorbs on both electrode surface and generates stable electrode-electrolyte interface. • Side reactions are inhibited and uniform Zn deposition is realized at Zn electrode. • Stable Zn plating-stripping is achieved for 1100 h, and coulombic efficiency reaches 99.5 %. • Vanadium dissolution is prevented for the V 6 O 13 ·H 2 O cathode, which enhances cycling stability. Aqueous Zn batteries provide high safety and low cost. However, the Zn metal anode experiences various side reactions and dendritic growth in aqueous electrolytes. Herein, we regulate the interfaces at both Zn anode and vanadium oxide cathode in aqueous batteries with a high donor number electrolyte additive. The N -methylpyrrolidone (NMP) molecule with the donor number of 27.3 is introduced to the ZnSO 4 electrolyte at the low concentration of 5 %. It preferentially adsorbs on both electrode surface and induces electrode–electrolyte interfaces composed of mixed organic and inorganic species. Thanks to the effective protection of solid-electrolyte interface (SEI) on Zn anode, the corrosions from electrolytes are inhibited, and 99.5 % coulombic efficiency of plating-stripping is realized. The Zn deposition behavior is also modified, which ensures uniform Zn growth and stable Zn plating-stripping for 1100 h. Meanwhile, the cathode-electrolyte interface (CEI) at the V 6 O 13 ·H 2 O cathode effectively suppresses vanadium dissolution, and the capacity retention over cycling is enhanced. Our work presents an effective strategy to simultaneously promote the electrochemical performance of both electrodes in aqueous Zn batteries. [ABSTRACT FROM AUTHOR]

[Display omitted] • Reversible MnO 2 /Mn2+ transformation is realized in mild aqueous electrolytes. • The Zn-Mn hybrid battery exhibit high discharge capacity and long cycle life. • The disproportionation of Mn3+ triggers the Mn2+ dissolution. • H+/Zn2+ insertion and the disproportionation occur sequentially upon discharging. The disproportionation of the Jahn-Teller (J-T) active manganese oxides (Mn3+) often leads to uncontrollable Mn2+ dissolution, which has been identified as one of the major causes of the performance degradation in conventional Zn-MnO 2 batteries. Herein, we use the "unwanted" disproportionation of the Mn3+ cations to realize effective MnO 2 /Mn2+ transformation, achieving high specific capacity (550 mAh g−1) and good cycling stability (5000 cycles without capacity decay) in a Zn-MnO 2 hybrid battery with mild aqueous electrolytes. Mechanism study shows that MnO 2 is deposited on the cathode during charging, H+/Zn2+ insertion and disproportionation occur sequentially during discharging, leading to Mn2+ dissolution. The generated high-valence manganese oxides via disproportionation further experience reduction-disproportionation-dissolution, which proceeds repeatedly in the expanded discharge potential to 0 V vs. Zn2+/Zn, resulting in the complete dissolution of the cathodic materials. Our results provide the fundamental understanding on the controversial mechanisms of Zn-MnO 2 batteries with mild aqueous electrolytes and highlight the effect of disproportionation in pushing the electrochemical performance of the promising Zn-MnO 2 hybrid batteries. [ABSTRACT FROM AUTHOR]

[Display omitted] • The electrodeposited vanadium oxide exhibits a high capacity of 402 mAh g−1. • The VO x cathode experiences an interactive dual-ion storage mechanism. • The H+ and Zn2+ insertion reactions exhibit different charge transfer/ion diffusion kinetics. Vanadium oxide (VO x) materials have gained considerable interest for rechargeable aqueous zinc ion batteries because of their structural and electrochemical diversities. However, the charge storage mechanism of the VO x cathode remains a topic of discussion. Herein we demonstrate a high-performance Zn/VO x cell where the binder-free VO x cathode with a layered structure is electrodeposited on a graphite substrate. This cathode with a high mass loading of 6 mg cm−2 exhibits high specific capacity of 402 mAh g−1 at the current density of 0.26 A g−1 in 6 M ZnCl 2 aqueous electrolyte. Good cycling stability of ~89% capacity retention can be achieved for 10,000 cycles at the fast discharge rate of 7.8 A g−1. Electrochemical and spectroscopy analysis indicates that the VO x cathode experiences an interactive dual-ion storage mechanism, including sequential H+ and Zn2+ insertion, as well as H+/Zn2+ co-insertion processes during discharging. The H+ and Zn2+ insertion kinetics is also studied. Results identify that excessive H+ storage in the initial discharge region will block the subsequent Zn2+ insertion and thus decrease the discharge capacity. The interfacial charge transfer and the ion diffusion processes of the dual-ion storage in VO x are crucial to achieving good electrochemical performance. [ABSTRACT FROM AUTHOR]

• Fe 3 O 4 /FeOOH heterostructure is constructed during electrochemical activation. • A built-in electric field is formed near the Fe 3 O 4 /FeOOH interface. • The activated electrode shows an enhanced capacity of 634 mAh g−1. • The assembled Ni-Fe cell shows a high energy density of 161.3 Wh kg−1 at 5.7 kW kg−1. Aqueous Ni-Fe batteries show promise for grid level energy storage due to their high safety and low cost. However, high capacities of Fe-based anodes can only be achieved under slow discharging rates. Moreover, an activation process is often required, the mechanism of which has not been fully understood. Herein, we present a facile and controllable method to uniformly deposit Fe 3 O 4 nanoparticles on a 3D graphite substrate. Post-mortem analysis demonstrates the partial conversion of Fe 3 O 4 to FeOOH during the subsequent in-situ electrochemical activation process, forming a Fe 3 O 4 /FeOOH heterostructure. Density functional theory calculations suggest that a built-in electric field is formed near the Fe 3 O 4 /FeOOH interface, which facilitates the charge transfers and lowers the adsorption energy of OH−. The above modification on the active material significantly improves its electrochemical activity. The activated electrode delivers a high capacity of 509 mAh g−1 at the ultra-high current density of 100 A g−1. A Ni-Fe cell assembled with activated Fe 3 O 4 /FeOOH anode and Ni-Co double hydroxide cathode provides a high energy density of 161.3 Wh kg−1 and a maximum power density of 43 kW kg−1, making it a good candidate for high safety, low cost, and environmental friendliness energy storage systems. [ABSTRACT FROM AUTHOR]