Cellulose Nanofiber/Carbon Nanotube‐Based Bicontinuous Ion/Electron Conduction Networks for High‐Performance Aqueous Zn‐Ion Batteries

Abstract

Despite their potential as a next‐generation alternative to current state‐of‐the‐art lithium (Li)‐ion batteries, rechargeable aqueous zinc (Zn)‐ion batteries still lag in practical use due to their low energy density, sluggish redox kinetics, and limited cyclability. In sharp contrast to previous studies that have mostly focused on materials development, herein, a new electrode architecture strategy based on a 3D bicontinuous heterofibrous network scaffold (HNS) is presented. The HNS is an intermingled nanofibrous mixture composed of single‐walled carbon nanotubes (SWCNTs, for electron‐conduction channels) and hydrophilic cellulose nanofibers (CNFs, for electrolyte accessibility). As proof‐of‐concept for the HNS electrode, manganese dioxide (MnO2) particles, one of the representative Zn‐ion cathode active materials, are chosen. The HNS allows uniform dispersion of MnO2 particles and constructs bicontinuous electron/ion conduction pathways over the entire HNS electrode (containing no metallic foil current collectors), thereby facilitating the redox kinetics (in particular, the intercalation/deintercalation of Zn2+ ions) of MnO2 particles. Driven by these advantageous effects, the HNS electrode enables substantial improvements in the rate capability, cyclability (without structural disruption and aggregation of MnO2), and electrode sheet‐based energy (91 Wh kgelectrode−1)/power (1848 W kgelectrode−1) densities, which lie far beyond those achievable with conventional Zn‐ion battery technologies.

Hierarchical K‐Birnessite‐MnO2 Carbon Framework for High‐Energy‐Density and Durable Aqueous Zinc‐Ion Battery

“…The CNT@KMO@ GC displays the smallest bulk resistance (R bulk , the point that the high frequency region intersects the real axis) and charge transfer resistance (R ct , the diameter of the semicircle), verifying its highest electrical conductivity and electron-transfer kinetics. [32,33] This result further proves the highest electrical conductivity of CNT@KMO@GC among all the samples, indicating the best electrochemical performance.…”

“…The improvement of electrolyte wettability in CNT@KMO@GC facilitates the electrolyte into and out from the electrode, resulting in the enhanced electrochemical performance of CNT@KMO@GC. [32] The electrical conductivity of KMO, CNT@KMO, and CNT@KMO@GC was also studied. As shown in Figure 5b, the electrical conductivity of KMO, CNT@KMO, and CNT@KMO@GC is 0.06, 0.15, and 4.87 S cm −1 , respectively.…”

“…[5,10,[16][17][18] However, the low electronic/ionic conductivity and non-negligible manganese dissolution of MnO 2 result in the inferior rate performance and fast capacity decay of MnO 2 -based cathodes, hindering the commercialization of ZIBs. [19][20][21] Great endeavors have been dedicated to improve the reaction kinetics and structural stability of MnO 2 -based cathodes in strategies of polymorphs regulation, [16,22] preintercalation, [18,[23][24][25][26][27][28] heteroatom doping, [29,30] compositing with conductive materials, [18,[31][32][33][34][35] and Mn 2+ additives of electrolyte. [9,36] All these strategies have been proven to effectively improve the electrochemical performance of MnO 2 -based cathodes in ZIBs to some extent.…”

Ultrahigh‐Energy‐Density Flexible Lithium‐Metal Full Cells based on Conductive Fibrous Skeletons

“…This monotonous architecture often causes the inhomogenous distribution of cathode components, leading to sluggish electron/ion conduction in the through-thickness direction together with structural disruption upon exposure to mechanical deformation. [15][16][17][18][19] To date, a few studies have been reported on flexible LMBs, mainly focusing on the design of composite electrodes comprising porous carbon scaffolds, [20,21] carbon nanotubes, [13,22] and modified metal current collectors. [23,24] These works have shown improvements in electrochemical reversibility, redox Despite extensive studies on lithium-metal batteries (LMBs) that have garnered considerable attention as a promising high-energy-density system beyond current state-of-the-art lithium-ion batteries, their application to flexible power sources is staggering due to the difficulty in simultaneously achieving electrochemical sustainability and mechanical deformability.…”

Preparation and Comparative Study of Aerogels Based on Cellulose Nanocrystals and Nanofibers from Eucalyptus Pulp

“…Cellulose nanomaterials, such as cellulose nano bers (CNFs), cellulose nanocrystals (CNCs), 2,6,6tetramethylpiperidine-1-oxy-oxidized cellulose nano bers (TEMPO-CNFs), and other derivatives have received signi cant attention as a next-generation nanomaterial because of their abundancy, good biocompatibility, good chemical/physical properties, degradability, low-cost, large-scale production, and diverse use for composite materials (Dai et Kim et al 2020). Different treatment processes, which initiate degradation reactions, are used to break the glycosidic bonds in cellulose macromolecules to obtain cellulose nanoparticles with a onedimensional size ranging from 1-100 nm.…”