Advanced flexible batteries with high energy density and long cycle life are an important research target. Herein, the first paradigm of a high-performance and stable flexible rechargeable quasi-solid-state Zn-MnO battery is constructed by engineering MnO electrodes and gel electrolyte. Benefiting from a poly(3,4-ethylenedioxythiophene) (PEDOT) buffer layer and a Mn -based neutral electrolyte, the fabricated Zn-MnO @PEDOT battery presents a remarkable capacity of 366.6 mA h g and good cycling performance (83.7% after 300 cycles) in aqueous electrolyte. More importantly, when using PVA/ZnCl /MnSO gel as electrolyte, the as-fabricated quasi-solid-state Zn-MnO @PEDOT battery remains highly rechargeable, maintaining more than 77.7% of its initial capacity and nearly 100% Coulombic efficiency after 300 cycles. Moreover, this flexible quasi-solid-state Zn-MnO battery achieves an admirable energy density of 504.9 W h kg (33.95 mW h cm ), together with a peak power density of 8.6 kW kg , substantially higher than most recently reported flexible energy-storage devices. With the merits of impressive energy density and durability, this highly flexible rechargeable Zn-MnO battery opens new opportunities for powering portable and wearable electronics.

There is currently enormous and growing demand for flexible electronics for personalized mobile equipment, human–machine interface units, wearable medical‐healthcare systems, and bionic intelligent robots. Cellulose is a well‐known natural biopolymer that has multiple advantages including low cost, renewability, easy processability, and biodegradability, as well as appealing mechanical performance, dielectricity, piezoelectricity, and convertibility. Because of its multiple merits, cellulose is frequently used as a substrate, binder, dielectric layer, gel electrolyte, and derived carbon material for flexible electronic devices. Leveraging the advantages of cellulose to design advanced functional materials will have a significant impact on portable intelligent electronics. Herein, the unique molecular structure and nanostructures (nanocrystals, nanofibers, nanosheets, etc.) of cellulose are briefly introduced, the structure–property–application relationships of cellulosic materials summarized, and the processing technologies for fabricating cellulose‐based flexible electronics considered. The focus then turns to the recent advances of cellulose‐based functional materials toward emerging intelligent electronic devices including flexible sensors, optoelectronic devices, field‐effect transistors, nanogenerators, electrochemical energy storage devices, biomimetic electronic skins, and biological detection devices. Finally, an outlook of the potential challenges and future prospects for developing cellulose‐based wearable devices and bioelectronic systems is presented.

The present study aims to investigate the structure-morphology-rheology relationships for cellulose nanoparticles (CNPs), including cellulose nanofibers (CNFs), and cellulose nanocrystals (CNCs). CNCs were extracted from never dried CNFs using sulfuric acid with controlled hydrolysis time. The crystalline structure, surface charge, morphology and rheological behavior of the CNPs were measured and contrasted. The CNF suspensions exhibited rigid solid-like viscoelastic behavior even at a low concentration due to the formation of highly entangled network.Upon the acid hydrolysis, the network of rigid, long and highly entangled nanofibers was eliminated, resulting in a significant loss of viscoelastic properties. Both steady-state and dynamic rheological measurements showed that the rheological behavior of the CNC suspensions was strongly dependent on the concentration and acid hydrolysis time. The CNC suspensions exhibited elastic gel-like rheological behavior at high concentrations, but viscous liquid-like rheological behavior at low concentrations. Longer acid hydrolysis time produced CNCs with lower aspect ratio, leading to higher critical transition concentration for the formation of anisotropic phase. The aspect ratio of CNCs was predicted from the intrinsic viscosity using the Simha's equation. The theoretically predicted aspect ratio values corresponded well with the transmission electron microscopy results. Finally, the network of CNF and CNC suspensions were schematically proposed. and immobilized water molecules mainly existed. The differences in the physiochemical characteristics (e.g., aspect ratio, surface properties, flexibility) among CNPs resulted in distinctive network in the CNP suspensions.The mechanical disintegrated CNFs showed inactive surface characteristic (e.g., low zeta potential value and fewer hydroxyl groups), larger aspect ratio (> 80), and high flexibility, as observed previously. It is believed that the chemical interactions between CNFs, and the hydrogen bonds between CNF and water molecule were very weak, whereas the physical entanglements between CNFs were quite strong. Therefore, the network of CNF suspension mainly contained physical entanglements between CNFs ( Figure 8a). The physical entanglements between CNFs could be easily created due to the large aspect ratio and high flexibility of CNFs even at a very low concentration. This is the reason for the observed phenomenon that the CNF suspensions at any concentration level displayed solid-like viscoelastic properties (i.e., ′ ≈ 0 , ′ ≫ ′′ , and tan < 1). By contrast, the sulfuric acid-hydrolyzed CNCs carried negatively charged sulfate groups and a large number of hydroxyl groups on the surface. These highly active groups enabled the CNCs to greatly interact with each other as well as the adjacent water molecules. On the other hand, the needle-like CNCs with relatively low aspect ratio and high crystallinity had worse flexibility than CNFs, leading to the less possibility of formation of physically entangled network between CNCs...

Cellulose nanocrystals and cellulose nanofibers with I and II crystalline allomorphs (designated as CNC I, CNC II, CNF I, and CNF II) were isolated from bleached wood fibers by alkaline pretreatment and acid hydrolysis. The effects of concentration, particle size, surface charge, and crystal structure on the lyophilization-induced self-assembly of cellulose particles in aqueous suspensions were studied. Within the concentration range of 0.5 to 1.0 wt %, cellulose particles self-organized into lamellar structured foam composed of aligned membrane layers with widths between 0.5 and 3 μm. At 0.05 wt %, CNC I, CNF I, CNC II, and CNF II self-assembled into oriented ultrafine fibers with mean diameters of 0.57, 1.02, 1.50, and 1.00 μm, respectively. The size of self-assembled fibers became larger when more hydroxyl groups and fewer sulfates (weaker electrostatic repulsion) were on cellulose surfaces. Possible formation mechanism was inferred from ice growth and interaction between cellulose nanoparticles in liquid-crystalline suspensions.

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Exploring high‐efficiency, stable, and cost‐effective bifunctional electrocatalysts for overall water splitting is greatly desirable and challenging. Herein, a newly designed hybrid catalyst with Cr‐doped FeNi–P nanoparticles encapsulated into N‐doped carbon nanotubes (Cr‐doped FeNi–P/NCN) with unprecedented electrocatalytic activity is developed by a simple one‐step heating treatment. The as‐synthesized Cr‐doped FeNi–P/NCN with moderate Cr doping exhibits admirable oxygen evolution reaction and hydrogen evolution reaction activities with overpotentials of 240 and 190 mV to reach a current density of 10 mA cm−2 in 1 m KOH solution. When used in overall water splitting as a bifunctional catalyst, it needs only 1.50 V to give a current density of 10 mA cm−2, which is superior to its typically integrated Pt/C and RuO2 counterparts (1.54 V @ 10 mA cm−2). Density functional theory calculation confirms that Cr doping into a FeNi‐host can effectively alter the relative Gibbs adsorption energy and reduces the theoretical overpotential. Additionally, the synergetic effects between Cr‐doped FeNi–P nanoparticles and NCNs are regarded as significant contributors to accelerate charge transfer and promote electrocatalytic activity in hybrid catalysts.

Structural colored nanocomposites with photonic liquid crystal structures are desirable owing to their excellent optical performances, unique structural features and intelligent responsive behaviors.

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