Metal–Organic Framework‐Derived Anode and Polyaniline Chain Networked Cathode with Mesoporous and Conductive Pathways for High Energy Density, Ultrafast Rechargeable, and Long‐Life Hybrid Capacitors

Abstract

energy densities (100-160 Wh kg −1), they suffer from both slow charging rates attributed to their low power densities (<1000 W kg −1) and also short cycle stability. [3,4] As alternative energy storage systems (ESS), electrochemical capacitors (ECs) allow higher power densities and better cycle stability than LIBs, but typical ECs allow extremely small energy densities due to the surface-limited charge-discharge redox reactions. [5] Hence, the sole usage of a LIB or an EC does not give simultaneously high energy and power densities along with long cycle stability because of their complementary ion storage mechanisms. As a solution to this challenge, hybrid energy storages (HESs), where charges are asymmetrically stored by battery-type reactions in the anode and pseudocapacitive reactions in the cathode, are of great attraction as their charge and discharge processes can be controlled using different potential windows to increase energy density. [6-9] However, despite this promise, an anode structure is having both rich active sites for high capacity and also fast cation transport channels and electron conduction pathways, [10-13] and its compatible cathode structure is allowing both rapid anion movement and facile electron conduction and also rich ion adsorption and pseudocapacitive reactions are vital to realizing high energy density for prolonged operation in a single charge and high power density for fast chargeable capability in the HES full cell device. [14-16] In this work, we synthesize the mesoporous molybdenum dioxide structures derived from metal-organic frameworks (MOFs) coated with reduced graphene oxide (rGO) shells as high-capacity and high-rate anode structures (MoO 2 @rGO) and the in situ polymerized crosslinked polyaniline (PANI) chain-integrated rGO structures as high-capacity and high-rate cathode structures (PANI@rGO). MoO 2 has a high theoretical capacity (838 mAh g −1), efficient charge stability with the low electrical resistivity (≈8.8 × 10 −5 Ω cm −1 at 300 K), and excellent chemical stability. [17] However, to utilize MoO 2 as an anode material unit for high-capacity, its poor diffusivity and conductivity Hybrid lithium-ion energy storage devices are promising for future applications, but their anodes and cathodes still have structural limitations, for example, accommodating rich cationic/anionic reactions, rapid charge movement, and long cycle life. Herein, high-capacity/high-rate anode and cathode structures are developed to overcome these challenges. Molybdenum oxide (MoO 2)-implanted carbon frameworks making conductive carbon bonds with reduced graphene oxide (rGO) shells are developed as anode structures by forming mesoporous channels for fast lithium-ion transport, carbon-rGO pathways for facile electron conduction, and ultrafine MoO 2 units for high capacity. The operando X-ray diffraction and kinetics analyses reveal that lithium-ion insertion and extraction occur via capacitive and diffusioncontrolled reactions. Also, polyaniline (PANI) chains are elongated on rGO sheets throug...

Recent advances and future perspectives for aqueous zinc-ion capacitors

“…In particular, zinc-ion batteries have become the bellwether of aqueous rechargeable batteries [6,7], since they possess low redox potential, excellent electron conductivity and high safety [8]. Similarly, after a series of studies on lithium-ion capacitors [9][10][11], sodiumion capacitors [12,13], potassium-ion capacitors [14,15], and magnesium-ion capacitors [16], zinc-ion capacitors (ZIC) have gradually become the focus of ion hybrid capacitor research.…”

The Advance and Perspective on Electrode Materials for Metal–Ion Hybrid Capacitors

“…The former stores energy through reversible adsorption on the cathode surface, while the latter involves the diffusion of ions within the anode. [56][57][58][59][60] In comparison, battery-type electrode occurs metal-ion deposition/stripping reaction or metal-ion insertion/extraction process at the anode or cathode. Hybrid ion capacitor (HIC) delivers higher power density but lower capacity than metal-ion batteries due to the limitation of redox reaction at battery-type electrode.…”

Graphene-Based Cathode Materials for Lithium-Ion Capacitors: A Review

“…In addition, conductive polymers such as polyaniline (PANI) can also be applied as spacers to inhibit the restacking of graphene sheets considering their unique merits of high conductivity, excellent flexibility and high capacity derived from fast redox reaction. Ock et al proposed a high-capacity and high-rate PANI@rGO and used it as a capacitor-type electrode [ 128 ]. PANI@rGO was synthesized through depositing aniline on the surface of GO sheets and then forming a chain-integrated rGO-based composite after in situ polymerization and cross-linking of PANI ( Figure 11 a).…”