Interface Engineering of Biomass-Derived Carbon used as Ultrahigh-Energy-Density and Practical Mass-Loading Supercapacitor Electrodes

The development of flexible electrodes with high mass loading and efficient electron/ion transport is of great significance but still remains the challenge of innovating suitable electrode structures for high energy density application. Herein, for the first time, lignosulfonate-derived N/S-co-doped graphene-like carbon is in situ formed within an interface engineered cellulose textile through a sacrificial template method. Both experimental and theoretical calculations disclose that the formed pomegranate-like structure with continuous conductive pathways and porous characteristics allows sufficient ion/electron transport throughout the entire structures. As a result, the obtained flexible electrode delivers a remarkable integrated capacitance of 6534 mF cm⁻² (335.1 F g⁻¹) and a superior stability at an industrially applicable mass loading of 19.5 mg cm⁻². A pseudocapacitive cathode with ultrahigh capacitance of 7000 mF cm⁻² can also be obtained based on the same electrode structure engineering. The as-assembled asymmetric supercapacitor achieves a high areal capacitance of 3625 mF cm⁻², and a maximum energy density of 1.06 mWh cm⁻², outperforms most of other reported high-loading supercapacitors. This synthesis method and structural engineering strategy can provide materials design concepts and a wide range of applications in the fields of energy storage beyond supercapacitors.     

Hierarchical Integrated Hybrid Structural Electrodes Based on Co-N/C and Mo-doped NiCo-LDH@Co-N/C Anchored on MX/CF for High Energy Density Fiber-Shaped Supercapacitor

The judicious design of highly electrochemically active materials on 1D fiber substrate to form a hierarchical integrated hybrid structure is an efficient technique to improve the limited cylindrical space and volumetric energy density of fiber-shaped supercapacitors (FSCs). Herein, a 3D negative electrode, consisting of vertically aligned interconnected mesoporous Co-N/C leaf-like structure on 1D MXene-carbon fiber (Co-N/C@MX/CF) is prepared by controlling the composition and morphology. At the same time, a 3D positive electrode is also prepared by introducing Mo in NiCo-LDH anchored on Co-N/C@MX/CF (Mo-NiCo-LDH@Co-N/C@MX/CF) by electrodeposition method. Benefitting from the systematic hierarchical structures with highly accessible surface area, adequate pore size and easy permeation of electrolyte, both positive and negative electrodes demonstrate highly improved electrochemical performance with areal capacity/capacitance of 0.96 mAh cm⁻²/4.55 mF cm⁻² at a current density of 3.86 mA cm⁻², respectively. Furthermore, the fiber-shaped solid-state hybrid supercapacitor (FSHSC) based on Mo_1.5NiCo-LDH@Co-N/C@MX/CF(+)//Co-N/C_0.5@MX/CF(−) is fabricated, exhibiting compelling energy density of 86.72 mWh cm⁻³ at a power density of 480.30 mW cm⁻³ with an outstanding capacitance retention of 80.2% after 20000 galvanostatic-charge-discharge cycles. This study puts forward a new perspective on the development of highly efficient FSCs for practical application.     

Flexible Carbon Dots-Intercalated MXene Film Electrode with Outstanding Volumetric Performance for Supercapacitors

2D MXenes have emerged as promising supercapacitor electrode materials due to their metallic conductivity, pseudo-capacitive mechanism, and high density. However, layer-restacking is a bottleneck that restrains their ionic kinetics and active site exposure. Herein, a carbon dots-intercalated strategy is proposed to fabricate flexible MXene film electrodes with both large ion-accessible active surfaces and high density through gelation of calcium alginate (CA) within the MXene nanosheets followed by carbonization. The formation of CA hydrogel within the MXene nanosheets accompanied by evaporative drying endow the MXene/CA film with high density. In the carbonization process, the CA-derived carbon dots can intercalate into the MXene nanosheets, increasing the interlayer spacing and promoting the electrolytic diffusion inside the MXene film. Consequently, the carbon dots-intercalated MXene films exhibit high volumetric capacitance (1244.6 F cm⁻³ at 1 A g⁻¹), superior rate capability (662.5 F cm⁻³ at 1000 A g⁻¹), and excellent cycling stability (93.5% capacitance retention after 30 000 cycles) in 3 m H₂SO₄. Additionally, an all-solid-state symmetric supercapacitor based on the carbon dots-intercalated MXene film achieves a high volumetric energy density of 27.2 Wh L⁻¹. This study provides a simple yet efficient strategy to construct high-volumetric performance MXene film electrodes for advanced supercapacitors.     

Alternative-Ultrathin Assembling of Exfoliated Manganese Dioxide and Nitrogen-Doped Carbon Layers for High-Mass-Loading Supercapacitors with Outstanding Capacitance and Impressive Rate Capability

Manganese dioxide (MnO₂) materials have received much attention as promising pseudocapacitive materials owing to their high theoretical capacitance and natural abundance. Unfortunately, the charge storage performance of MnO₂ is usually limited to commercially available mass loading electrodes because of the significantly lower electron and ion migration kinetics in thick electrodes. Here, an alternatively assembled 2D layered material consisting of exfoliated MnO₂ nanosheets and nitrogen-doped carbon layers for ultrahigh-mass-loading supercapacitors without sacrificing energy storage performance is reported. Layered birnessite-type MnO₂ is efficiently exfoliated and intercalated by a carbon precursor of dopamine using a fluid dynamic-induced process, resulting in MnO₂/nitrogen-doped carbon (MnO₂/C) materials after self-polymerization and carbonization. The alternatively stacked and interlayer-expanded structure of MnO₂/C enables fast and efficient electron and ion transfer in a thick electrode. The resulting MnO₂/C electrode shows outstanding electrochemical performance at an ultrahigh mass loading of 19.7 mg cm⁻², high gravimetric and areal capacitances of 480.3 F g⁻¹ and 9.4 F cm⁻² at 0.5 mA cm⁻², and rapid charge/discharge capability of 70% capacitance retention at 40 mA cm⁻². Furthermore, asymmetric supercapacitor based on high-mass-loading MnO₂/C can deliver an extremely high energy of 64.2 Wh kg⁻¹ at a power density of 18.8 W kg⁻¹ in an aqueous electrolyte.     

Tandem Carbon Hollow Spheres with Tailored Inner Structure as Sulfur Immobilization for Superior Lithium–Sulfur Batteries

The construction of lithium–sulfur battery cathode materials while simultaneously achieving high areal sulfur-loading, adequate sulfur utilization, efficient polysulfides inhibition, rapid ion diffusion, etc. remains a major challenge. Herein, an internal regulatory strategy to fabricate the unique walnut-like yolk–shell carbon flower@carbon nanospheres is presented (WSYCS) as sulfur hosts. The internal carbon flower, suitable cavity, and external carbon layer effectively disperse the insulate sulfur, accommodate volumetric expansion, and confine polysulfides, thus improving the performance of lithium–sulfur batteries. The finite element simulation method also deduces the enhanced Li⁺ diffusion and lithium–sulfur reaction kinetics. More importantly, WSYCS2 is grafted onto carbon fiber (CF) by electro-spinning method to form a tandem WSYCS2@CF 3D film as a sulfur host for the free-standing electrode. The corresponding battery exhibits an extremely high areal capacity of 15.5 mAh cm⁻² with a sulfur loading of 13.4 mg cm⁻². Particularly, the flexible lithium–sulfur pouch cell delivers a high capacity of 8.1 mAh cm⁻² and excellent capacity retention of 65% over 800 cycles at a relatively high rate of 1C, corresponding to a calculated energy density of 539 Wh kg⁻¹ and 591 Wh L⁻¹. This work not only provides guidance for tailoring thick carbon/sulfur electrodes but also boosts the development of practical lithium–sulfur batteries.     

A highly flexible solid-state supercapacitor based on the carbon nanotube doped graphene oxide/polypyrrole composites with superior electrochemical performances

Flexible electrodes of ternary composites, in which highly conductive carbon nanotube films (CNFs) are coated with carbon nanotube-doped graphene oxide/polypyrrole (CNT-GO/PPy), have been fabricated via facile electrochemical synthesis. Long and short CNTs are separately doped into the composites (lCNT-GO/PPy and sCNT-GO/PPy) and their electrochemical performances are compared. Electrochemical measurements indicate that the doping of CNTs in the composites significantly improves the electrochemical behaviors of the GO/PPy electrodes. Notably, the lCNT-GO/PPy electrodes show superior electrochemical properties with respect to the sCNT-GO/PPy electrodes, which is related to the introduction of abundant CNTs in the former electrodes and their special microstructures. Two symmetric electrodes with the lCNT-GO/PPy composites coated on CNFs are assembled to fabricate a solid-state supercapacitor device, which features lightweight, ultrathinness, and high flexibility. The device achieves a high areal and volumetric specific capacitance of 70.0 mF cm⁻² at 10 mV s⁻¹ and 6.3 F cm⁻³ at 0.043 A cm⁻³, respectively. It also shows superior rate performance and cycle stability, with a capacitance retention rate of 87.7% for 10,000 cycles. The supercapacitor device fabricated is promising for the use in lightweight and flexible integrated electronics.     

Three-Dimensional Printed Mechanically Compliant Supercapacitor with Exceptional Areal Capacitance from a Self-Healable Ink

Known for its capability to architect tailored structures for the scaling of active materials in energy storage devices that cater for future electronics having stringent requirements on areal performance, 3D printing is receiving serious attention. However, lingering challenges originating from the notorious interfacial issue and weak component interaction restrain current devices from making a breakthrough in deliverable capacity and structural flexibility. In this work, the printed electrode delivers a record-breaking electrical double layer (EDL) areal capacitance of 27.1 F cm⁻² under an extremely large loading density of 134 mg cm⁻². This translates to a deliverable record-high EDL energy density of 1.26 mWh cm⁻² for device performance, which even rivals the highest value reported from highly loaded pseudocapacitors. The bespoke devices are enabled by a strategically formulated 3D printable ink that initiates efficient autonomous room-temperature self-healing and strong interplay between constituting ink components. These contribute to interlayer coalescing for eliminated interlayer resistance for a solid electrochemical performance and printed electrodes of great mechanical compliance. By tapping into the huge potential of 3D printing, this work lays a solid foundation on which flexible devices with customized geometry, functionality, and outstanding performance for a broad range of applications can be readily realized.     

Reassembly of MXene Hydrogels into Flexible Films towards Compact and Ultrafast Supercapacitors

The freestanding MXene films are promising for compact energy storage ascribing to their high pseudocapacitance and density, yet the sluggish ion transport caused by the most densely packed structure severely hinders their rate capability. Here, a reassembly strategy for constructing freestanding and flexible MXene-based film electrodes with a tunable porous structure is proposed, where the Ti₃C₂T_x microgels disassembled from 3D structured hydrogel are reassembled together with individual Ti₃C₂T_x nanosheets in different mass ratios to form a densely packed 3D network in microscale and a film morphology in macroscale. The space utilization of produced film can be maximized by a good balance of the density and porosity, resulting in a high volumetric capacitance of 736 F cm⁻³ at an ultrahigh scan rate of 2000 mV s⁻¹. The fabricated supercapacitor yields a superior energy density of 40 Wh L⁻¹ at a power density of 0.83 kW L⁻¹, and an energy density of 21 Wh L⁻¹ can be still maintained even when the power density reaches 41.5 kW L⁻¹, which are the highest values reported to date for symmetric supercapacitors in aqueous electrolytes. More promisingly, the reassembled films can be used as electrodes of flexible supercapacitors, showing excellent flexibility and integrability.     

A Flexible and Safe Planar Zinc-Ion Micro-Battery with Ultrahigh Energy Density Enabled by Interfacial Engineering for Wearable Sensing Systems

Aqueous zinc-ion micro-batteries (ZIMBs) have attracted considerable attention owing to their reliable safety, low cost, and great potential for wearable devices. However, current ZIMBs still suffer from various critical issues, including short cycle life, poor mechanical stability, and inadequate energy density. Herein, the fabrication of flexible planar ZIMBs with ultrahigh energy density by interfacial engineering in the screen-printing process based on high-performance MnO₂-based cathode materials is reported. The Ce-doped MnO₂ (Ce-MnO₂) exhibits significantly enhanced capacity (389.3 mAh g⁻¹), considerable rate capability and admirable cycling stability than that of the pure MnO₂. Importantly, the fabrication of micro-electrodes with ultrahigh mass loading of Ce-MnO₂ (24.12 mg cm⁻²) and good mechanical stability is achieved through optimizing the interfacial bonding between different printed layers. The fabricated planar ZIMBs achieve a record high capacity (7.21 mAh cm⁻² or 497.31 mAh cm⁻³) and energy density (8.43 mWh cm⁻² or 573.45 mWh cm⁻³), as well as excellent flexibility. Besides, a wearable self-powered sensing system for environmental monitoring is further demonstrated by integrating the planar ZIMBs with flexible solar cells and a multifunctional sensor array. This work sheds light on the development of high-performance planar ZIMBs for future self-powered and eco-friendly smart wearable electronics.     

Biomass-Derived Inks with Tailored Pteridine Derivatives for Sustainable Printed Micro-Supercapacitors

Using biological redox compounds holds great potential in designing sustainable energy storage systems, but it is essential for structure optimization of biological redox centers and in-depth studies regarding their underlying energy storage mechanisms. Herein, a molecular simplification strategy is proposed to tailor the redox unit of pteridine derivatives, an essential component of ubiquitous electron transfer proteins in nature. The tailored pteridine derivatives can be combined with biomass holey graphene (BHG) to fabricate an ink with a micrometer-scale resolution for printing flexible electrodes for micro-supercapacitor (MSCs). The reversible tautomerism of pteridine derivatives from alloxazinic to isoalloxazinic structure is first unveiled in supercapacitors. Through molecular tailoring, printed MSC electrodes using pteridine derivatives/BHG ink demonstrate excellent charge storage, outstanding areal capacitance (95.3 mF cm⁻² at 0.1 mA cm⁻²), energy density (16.3 µWh cm⁻²), power density (208 µW cm⁻²), long-term cycling performance (90.5% retention after 10 000 cycles), easy integration, and exceptional flexibility (maintaining capacitance at various bending states). The non-covalent interaction of tailored pteridine molecules with redox centers and biomass porous graphene suggests a mature screen-printing technology for fabricating a sustainable energy storage system with a rational MSC configuration.     

Fast Kinetic Carbon Anode Inherited and Developed from Architectural Designed Porous Aromatic Framework for Flexible Lithium Ion Micro Capacitors

Lithium ion micro capacitors (LIMCs) demonstrate competitive advantages of simultaneously high energy/power densities and long cycle life over many other micro supercapacitors and micro batteries. However, these performances are significantly determined by the carbon anode with fast Li⁺ storage kinetics. Herein, a design strategy at the precursor side of a typical porous aromatic framework-5 (PAF-5) from the carbon bonding levels is proposed, and coupling with the post pyrolysis, the sp²/sp³ domains ratio, interlayer spacing, and pore structure of derived carbons can be synergistically balanced. The inherited sp² domains and porous structure from PAF-5 endow the derived carbon with high electron transport capability and fast Li⁺ adsorption capacity. Meanwhile, the developed sp³ domains and enlarged interlayer spacing also enable abundant and fast Li⁺ intercalation contribution, giving rise to a superior rate capability (141.9 mAh g⁻¹ at 4 A g⁻¹) that is 13 times better than a commercial graphite anode. A flexible LIMCs based on this carbon anode are fabricated, and simultaneously high energy/power densities (71.1 mWh cm⁻³/1.9 W cm⁻³), long cycle life (94.7% after 6,000 cycles), and flexibility are achieved, demonstrating a great feasibility of designed PAFs as the trimmed carbon anode precursors for high performance Li⁺ storage.     

Sputtered Titanium Carbide Thick Film for High Areal Energy on Chip Carbon‐Based Micro‐Supercapacitors

The areal energy density of on‐chip micro‐supercapacitors should be improved in order to obtain autonomous smart miniaturized sensors. To reach this goal, high surface capacitance electrode (>100 mF cm^?2) has to be produced while keeping low the footprint area. For carbide‐derived carbon (CDC) micro‐supercapacitors, the properties of the metal carbide precursor have to be fine‐tuned to fabricate thick electrodes. The ad‐atoms diffusion process and atomic peening effect occurring during the titanium carbide sputtering process are shown to be the key parameters to produce low stress, highly conductive, and thick TiC films. The sputtered TiC at 10^?3 mbar exhibits a high stress level, limiting the thickness of the TiC‐CDC electrode to 1.5 µm with an areal capacitance that is less than 55 mF cm^?2 in aqueous electrolyte. The pressure increase up to 10^?2 mbar induces a clear reduction of the stress level while the layer thickness increases without any degradation of the TiC electronic conductivity. The volumetric capacitance of the TiC‐CDC electrodes is equal to 350 F cm^?3 regardless of the level of pressure. High values of areal capacitance (>100 mF cm^?2) are achieved, whereas the TiC layer is relatively thick, which paves the way toward high‐performance micro‐supercapacitors.     

Solid‐State Hybrid Fibrous Supercapacitors Produced by Dead‐End Tube Membrane Ultrafiltration

The development of flexible supercapacitors with high volumetric performance is critically important for portable electronics applications, which are severely volume limited. Here, dead‐end tube membrane (DETM) ultrafiltration is used to produce densely compacted carbon‐nanotube/graphene fibrous films as solid‐state supercapacitor electrodes. DETM is widely used in the water purification industry, but to date its use has not been explored for making supercapacitor electrode materials. Compared with vacuum‐assisted filtration, dead‐end filtration of the mixture through a porous membrane is carried out under much higher pressure, and thus the solvent can be gotten rid of much faster, with less energy consumption and in an environmentally friendly manner. More importantly, phase separation of the solid constituents in the mixture, due to concentration increase, can be suppressed in DETM. Therefore, highly uniform and densely compacted supercapacitor electrodes can be obtained with very high volumetric energy and power density. The volumetric energy density in this work (≈2.7 mWh cm^‐3) is at a higher level than all the all‐solid‐state fibrous supercapacitors reported to date. This can be attributed to the DETM process used, which produces a densely compacted network structure without compromising the availability of electrochemically active surface area.     

Anisotropic ZnS Nanoclusters/Ordered Macro-Microporous Carbon Superstructure for Fibrous Supercapacitor toward Commercial-Level Energy Density

Fibrous supercapacitor (FSC) is of great attention in wearable electronics, but is challenged by low energy density, owing to disordered diffusion pathway and sluggish redox kinetics. Herein, using micro-reaction strategy, an anisotropic superstructure is developed by in situ anchoring ultrafine zinc sulfine (ZnS) nanoclusters on conductively ordered macro-microporous carbon skeleton via interfacial C S Zn bonds (ZnS/SOM-C). The anisotropic superstructure affords 3D ordered macro-microporous pathways, large accessible surfaces, and highly dispersed active sites, which exhibit enhanced electrolyte mass diffusion, rapid interfacial charge transfer, and large faradaic ions storage (capacitance of 1158 F g⁻¹ in KOH aqueous solution). By microfluidic spinning, the ZnS/SOM-C is further assembled into fibrous electrode of FSC that delivers high capacitance (791 F g⁻¹), commercial-level energy density (172 mWh g⁻¹), and durable stability. As a result, the FSC can realize wearable self-powered applications (e.g., self-cleaning ventilatory mask, smartwatch, and display), exhibiting the superiority in new energy and wearable industry.     

A Low‐Cost,Self‐Standing NiCo2O4@CNT/CNT Multilayer Electrode for Flexible Asymmetric Solid‐State Supercapacitors

The demand for a new generation of flexible, portable, and high‐capacity power sources increases rapidly with the development of advanced wearable electronic devices. Here we report a simple process for large‐scale fabrication of self‐standing composite film electrodes composed of NiCo₂O₄@carbon nanotube (CNT) for supercapacitors. Among all composite electrodes prepared, the one fired in air displays the best electrochemical behavior, achieving a specific capacitance of 1,590 F g^?1 at 0.5 A g^?1 while maintaining excellent stability. The NiCo₂O₄@CNT/CNT film electrodes are fabricated via stacking NiCo₂O₄@CNT and CNT alternately through vacuum filtration. Lightweight, flexible, and self‐standing film electrodes (≈24.3 µm thick) exhibit high volumetric capacitance of 873 F cm^?3 (with an areal mass of 2.5 mg cm^?2) at 0.5 A g^?1. An all‐solid‐state asymmetric supercapacitor consists of a composite film electrode and a treated carbon cloth electrode has not only high energy density (≈27.6 Wh kg^?1) at 0.55 kW kg^?1 (including the weight of the two electrodes) but also excellent cycling stability (retaining ≈95% of the initial capacitance after 5000 cycles), demonstrating the potential for practical application in wearable devices.     

Sustainable 3D Structural Binder for High-Performance Supercapacitor by Biosynthesis Process

Flexible supercapacitors represent an attractive technology for the next generation of wearable consumer electronics as power sources but usually suffer from relatively low energy density. It is highly desired to construct high-performance electrodes for the practical applications of supercapacitors. Here, inspired by the natural structure of the spider web, an elaborate design of binder is reported through a biosynthesis process to construct flexible electrodes with both excellent mechanical properties and electrochemical performance. Through this strategy, a spider-web-inspired 3D structural binder enables large ion-accessible surface area and high packing density of active electrode material as well as efficient ion transport pathways. As a result, a high areal capacitance of 4.62 F cm^-2 and a high areal energy density of 0.18 mW h cm^-2 is achieved in the composite electrodes and symmetric supercapacitors, respectively, demonstrating a promising potential to construct flexible energy storage devices for diverse practical applications.     

Multifunctional Carbon Felt Electrode with N-Rich Defects Enables a Long-Cycle Zinc-Bromine Flow Battery with Ultrahigh Power Density

Zinc-bromine flow batteries (ZBFBs) are regarded as one of the most promising technologies for energy storage owing to high energy density and low cost. However, the sluggish reaction kinetics of Br₂/Br⁻ couples and zinc dendrite issue lead to low power density and poor cycle stability. Herein, a multifunctional carbon felt-based electrode (NTCF) with N-rich defects is fabricated for ZBFBs. The defects with abundant N-containing groups on carbon fibers of NTCF provide high catalytic activity on Br₂/Br⁻ reactions. Simultaneously, the lower energy barrier of N-rich defects to adsorb zinc atoms, and more deposition sites on NTCF induce more uniform zinc deposition. Thus, a ZBFB using NTCF as both the anode and cathode can stably operate at an unprecedentedly high current density of 180 mA cm⁻² with a coulombic efficiency of 97.25%. Moreover, a long cycle life of over 140 cycles with a coulombic efficiency of 98.93% for a Zn symmetric flow battery at 80 mA cm⁻² is achieved under a high areal capacity of 40 mAh cm⁻². This current density and areal capacity are by far the highest values ever reported for Zn symmetry flow batteries. Therefore, this work provides an available approach to improve the power density and cycle life of ZBFBs.     

Floating Catalyst Chemical Vapor Deposition Patterning Nitrogen-Doped Single-Walled Carbon Nanotubes for Shape Tailorable and Flexible Micro-Supercapacitors

Micro-supercapacitors (MSCs) as high-power density energy storage units are designed to meet the booming development of flexible electronics, requiring simple and fast fabrication technology. Herein, a fast and direct solvent-free patterning method is reported to fabricate shape-tailorable and flexible MSCs by floating catalyst chemical vapor deposition (FCCVD). The nitrogen-doped single-walled carbon nanotubes (N-SWCNTs) are directly deposited on a patterned filter by FCCVD with designable patterns and facilely dry-transferred on versatile substrates. The obtained MSCs deliver an excellent areal capacitance of 3.6 mF cm⁻² and volumetric capacitance of 98.6 F cm⁻³ at a scan rate of 5 mV s⁻¹ along with excellent long-term cycle stability over 125 000 circles. Furthermore, the MSCs show good performance uniformity, which can be readily integrated via connection in parallel or series to deliver a stable high voltage (4 V with five serially connected devices) and large capacitance (5.1 mF with five parallel devices) at a scan rate of 100 mV s⁻¹, enabling powering the light emitting displays. Therefore, this method blazes the trail of directly preparing flexible, shape-customizable, and high-performance MSCs.     

Robust Single-Walled Carbon Nanotube-Infiltrated Carbon Fiber Electrodes for Structural Supercapacitors: from Reductive Dissolution to High Performance Devices

Multifunctional electrodes for structural supercapacitors are prepared by vacuum infiltration of single-walled carbon nanotubes (SWCNTs) into woven carbon fibers (CFs); the use of reductive charging chemistry to form nanotubide solutions ensured a high degree of individualization. The route is highly versatile, as shown by comparing four different commercial nanotube feedstocks. In film form, the pure nanotubide networks (“buckypapers”) are highly conductive (up to 2000 S cm⁻¹) with high surface area (>1000 m² g⁻¹) and great electrochemical performance (capacitance of 101 F g⁻¹, energy density of 27.5 Wh kg⁻¹ and power density of 135 kW kg⁻¹). Uniformly integrating these SWCNT networks throughout the CF fabrics significantly increased electrical conductivity (up to 318 S cm⁻¹), surface area (up to 196 m² g⁻¹), and in-plane shear properties, all simultaneously. The CNT-infiltrated CFs electrodes exhibited intrinsically high specific energy (2.6–4.2 Wh kg⁻¹) and power (6.0–8.7 kW kg⁻¹) densities in pure 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMIM TFSI) electrolyte. Multifunctional structural supercapacitors based on CNT-coated CFs offer a substantial increase in capacitive performance while maintaining the tensile mechanical properties of the as-received CF-based composite. This non-damaging approach to modify CFs with highly graphitic, high surface area nanocarbons provides a new route to structural energy storage systems.     

Engineering 3D Ion Transport Channels for Flexible MXene Films with Superior Capacitive Performance

2D MXene materials are of considerable interest for future energy storage. A MXene film could be used as an effective flexible supercapacitor electrode due to its flexibility and, more importantly, its high specific capacitance. However, although it has excellent electronic conductivity, sluggish ionic kinetics within the MXene film becomes a fundamental limitation to the electrochemical performance. To compensate for the relative deficiency, MXene films are frequently reduced to several micrometer dimensions with low mass loading (<1 mg cm^?2), to the point of detriment of areal performance and commercial value. Herein, for the first time, the design of a 3D porous MXene/bacterial cellulose (BC) self‐supporting film is reported for ultrahigh capacitance performance (416 F g^?1, 2084 mF cm^?2) with outstanding mechanical properties and high flexibility, even when the MXene loading reaches 5 mg cm^?2. The highly interconnected MXene/BC network enables both excellent electron and ion transport channel. Additionally, a maximum energy density of 252 µWh cm^?2 is achieved in an asymmetric supercapacitor, higher than that of all ever‐reported MXene‐based supercapacitors. This work exploits a simple route for assembling 2D MXene materials into 3D porous films as state‐of‐the‐art electrodes for high performance energy storage devices.