Abstract

Despite appealing supercapacitive properties, the flexible asymmetric supercapacitor devices (FASCs) are still suffering from low mass loading and limited operating voltage, leading to unsatisfactory energy densities. Herein, we introduced a high-voltage anodic electro-deposition process (AED) which is a novel avenue enabling the synthesis of hierarchical MnO2 on activated carbon cloth (H-MnO2/ACC). Interestingly, the concomitant activation of carbon cloth substrate is found to be beneficial to improve the conductivity and hydrophilic nature of our novel electrode. A FASC based on H-MnO2/ACC-300 and reduced carbon cloth (RCC) was assembled using a mixed ionic liquid gel (ionogel) electrolyte. Benefiting from highly conductive paths derived from intimately attached fiber-MnO2 interfaces, hierarchically interpenetrated lamella MnO2 porosity and concentric MnO2 interlayer voids, as well as the merits of ionic liquid, the resultant FASC delivers an output voltage as high as 4 V and an impressive volumetric energy density of 3.82 mWh/cm3. Furthermore, the optimized H-MnO2/ACC-300 electrode with high mass loading can even retain 94.2% of initial capacitance upon 5000 cycles in 1 M Na2SO4. The unique H-MnO2/ACC can aid in the rational design towards flexible electronic devices with high mass loading and this synthetic strategy opens up enormous possibilities for the fabrication of electrodeposited materials.

Highlights

  • Flexible electronic devices are indispensable parts in modern life, applied widely in mobile electrical products, smart textile and artificial electronic skin, etc. [1,2,3,4,5,6,7] In this regard, electrochemical supercapacitors (SCs) have drawn considerable attention and emerged as a promising power source of flexible and lightweight electronic devices owing to their high-power density and long lifetimes [1,3,5]

  • The unique hierarchical MnO2 (H-MnO2)/ACC can aid in the rational design towards flexible electronic devices with high mass loading and this synthetic strategy opens up enormous possibilities for the fabrication of electrodeposited materials

  • Flexible supercapacitors were assembled with as-prepared H-MnO2/ ACC-300 as positive electrode and reduced carbon cloth (RCC) as the negative one, respectively

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Summary

Introduction

Flexible electronic devices are indispensable parts in modern life, applied widely in mobile electrical products, smart textile and artificial electronic skin, etc. [1,2,3,4,5,6,7] In this regard, electrochemical supercapacitors (SCs) have drawn considerable attention and emerged as a promising power source of flexible and lightweight electronic devices owing to their high-power density and long lifetimes [1,3,5]. With regard to reported active materials anchored on the surface of CC substrate, nanoscale layered manganese dioxide (MnO2) among transition-metal oxides (TMOs) with rich valence states, stands out as one of the most eye-catching choices for high-performance SC electrodes [1,17,24,25,26,27,28]. Based on Ostwald ripening, Song et al developed a two-step route to prepare a high mass loading MnO2 electrode with remarkable capacitance of 618 mF cm−2 at 200 mV s−1 [18]. All these methods involve multi-step processes which are costly, complicated and timeconsuming. The H-MnO2/ACC electrodes were systematically investigated in three-electrode cell, delivering superior electrochemical performance

Experimental section
Assembly of fiber-shaped asymmetric supercapacitor
Materials characterization
Results and discussions

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