A novel poly(phenazine-alt-pyromellitic anhydride) (PPPA) has been successfully designed and synthesized via a condensation polymerization strategy as promising cathode material in organic zinc-ion batteries. Electrochemical quartz crystal microbalance (EQCM), FTIR and XPS characterizations verify a reversible Zn2+-coordination mechanism in our PPPA cathode. Intriguingly, an ultrahigh Zn2+ diffusion coefficient of 1.2×10-7 cm2 s-1 was found in this large π-conjugated system, which is the highest one among all organic cathode materials for zinc-ion batteries. Theoretical calculations reveal the extended π-conjugated plane in our PPPA sample results in a significant reduction on energy gap, effectively accelerating intramolecular electron transfer during charge/discharge process. Our finding provides insights to achieve high zinc-ion transport kinetics by a design strategy on planar polymer system.

Organic Zinc-Ion Battery: Planar, π-Conjugated Quinone-Based Polymer Endows Ultrafast Ion Diffusion Kinetics.

Rechargeable aqueous Zn-ion batteries (ZIBs) are deemed as powerful candidates for large-scale energy-storage systems because of their intrinsic safety, inexpensive cost, and environment friendliness. However, the performance degeneration of ZIBs occurs by virtue of structural instability and uncompetitive conductivity of cathode materials. In this work, a vanadium oxide of Li0.21Mn1.44V8O20·0.55H2O (4-MLVO) cathode was successfully synthesized for the first time by optimizing the ratio of Mn/V. Intriguingly, the as-assembled traditional aqueous hybrid Li+/Zn2+ batteries based on the Li0.21Mn1.44V8O20·0.55H2O cathode, 1 M Li2SO4 + 2 M ZnSO4 electrolyte, and Super P@Zn anode possess superior performance of 350.0 mA h g–1 at the current density of 0.1 A g–1 and can accomplish 6000 cycles with 147.5 mA h g–1 at 10.0 A g–1. Moreover, the outstanding flexibility of sandwiched quasi-solid-state Zn//4-MLVO batteries with the CMC-Na+/PAM hydrogel electrolyte is demonstrated by multifarious deformation tests. The quasi-solid-state batteries at a bending state can achieve a high open voltage of 1.026 V and a specific capacity of 184.8 mA h g–1 at 0.1 A g–1. This work offers thoughts for the devisal of aqueous hybrid ZIB cathode materials and lays a foundation for advanced flexible energy devices. 

Vanadium Oxide with Elevated Interlayers for Durable Aqueous Hybrid Li+/Zn2+ Batteries

Enhancing the kinetics of vanadium oxides via conducting polymer and metal ions co-intercalation for high-performance aqueous zinc-ions batteries.

Spreading the full spectrum of layer-structured compounds for kinetics-enhanced aqueous multivalent metal-ion batteries

Vanadium oxides are considered one of the most promising cathode materials for aqueous zinc ion batteries. However, vanadium dissolution caused by undesirable side reactions greatly decreases the structure stability and capacity retention. In this work, an atomic layer-deposited ZnO layer is uniformly coated on a hydrated vanadium dioxide nanosheet array cathode, which effectively suppresses the vanadium dissolution and side reactions. The resultant cathode displays improved capacity retentions from 74 to 89% after 100 cycles at 0.5 A g–1 and from 29 to 71% after 990 cycles at 5 A g–1. Moreover, the structural evolution after electrochemical cycling of the cathode is thoroughly investigated to reveal the protection mechanism. The atomic layer deposition strategy may also be extended to the protection of other cathodes that suffer from the dissolution issue with wide choices of the protection layer materials. 

Atomic Layer-Deposited ZnO Layer on Hydrated Vanadium Dioxide Cathodes against Vanadium Dissolution for Stable Zinc Ion Batteries

Boosting the active sites and kinetics of VO2 by Mn pre-intercalated and PVP modified nanostructure to improve the cycle stability for aqueous zinc batteries

Zhenxin Hui

Papers

Boosting the active sites and kinetics of VO2 by Mn pre-intercalated and PVP modified nanostructure to improve the cycle stability for aqueous zinc batteries