Zn²⁺ Pre‐Intercalation Stabilizes the Tunnel Structure of MnO₂ Nanowires and Enables Zinc‐Ion Hybrid Supercapacitor of Battery‐Level Energy Density

Abstract

Although there has been tremendous progress in exploring new configurations of zinc‐ion hybrid supercapacitors (Zn‐HSCs) recently, the much lower energy density, especially the much lower areal energy density compared with that of the rechargeable battery, is still the bottleneck, which is impeding their wide applications in wearable devices. Herein, the pre‐intercalation of Zn2+ which gives rise to a highly stable tunnel structure of ZnxMnO2 in nanowire form that are grown on flexible carbon cloth with a disruptively large mass loading of 12 mg cm−2 is reported. More interestingly, the ZnxMnO2 nanowires of tunnel structure enable an ultrahigh areal energy density and power density, when they are employed as the cathode in Zn‐HSCs. The achieved areal capacitance of up to 1745.8 mF cm−2 at 2 mA cm−2, and the remarkable areal energy density of 969.9 µWh cm−2 are comparable favorably with those of Zn‐ion batteries. When integrated into a quasi‐solid‐state device, they also endow outstanding mechanical flexibility. The truly battery‐level Zn‐HSCs are timely in filling up of the battery‐supercapacitor gap, and promise applications in the new generation flexible and wearable devices.

Fabrications of High‐Performance Planar Zinc‐Ion Microbatteries by Engraved Soft Templates

“…These reversible redox peaks belong to typical characteristics of Mn-based materials in neutral or weakly acidic aqueous zinc ion batteries, and the two reversible reduction peaks should be caused by insertion of Zn 2+ and H + into the cathode material. [26,33] These results are also in accordance with the recorded galvanostatic charge-discharge (GCD) curves ( Figure S5, Supporting Information). The CV curves overlap well after the first cycle, indicating a low polarization and high reversibility of the material.…”

A Highly Flexible and Lightweight MnO2/Graphene Membrane for Superior Zinc‐Ion Batteries

“…The gradual capacity augments during the initial 20 cycles may be ascribed to the electrode activation and some possible electrochemical oxidation of Mn 2+ into new active MnO 2 . [ 26,34 ] Note that high areal capacity is critical for practical applications, [ 46 ] we increase the mass loading of MnO 2 /rGO to 5.0 and 10 mg cm −2 . As displayed in Figure S8 (Supporting Information), the cells could deliver high areal capacity of 1.3 and 2.2 mAh cm −2 albeit with reduced specific capacities.…”

In Situ Electrochemical Synthesis of MXenes without Acid/Alkali Usage in/for an Aqueous Zinc Ion Battery

“…Over the past decade, MXenes have grown into the key versatile 2D materials that are widely applied to the liquid crystal, catalysis, sensors, nanogenerator, desalination, and microwave shielding fields. [1][2][3][4][5][6][7] Equipped with nanolaminate microstructure, superior conductivity, and sufficient surface chemistry, MXenes demonstrate the most promising potential for hosting both metal (Mg 2+ , Al 3+ , Na + , and Li + ) and nonmetal ions (NH 4 + , H + , and TMA + ). [8][9][10][11] At present, regarding fabrication of energy storage devices of MXenes, the conventional process consists of the initial MXenes synthesis and the subsequent devices assembly, which is multistep and complicated.…”