Conveying Advanced Li‐ion Battery Materials into Practice The Impact of Electrode Slurry Preparation Skills

Li‐ion batteries (LIB's) are of the greatest practical utility for portable electronics and electric vehicles (EV's). LIB energy, power and cycle life performances depend on cathode and anode compositions and morphology, electrolyte composition and the overall cell design. Electrode morphology is influenced by the shape and size of the active material (AM), conductive additive (CA) particles, the polymeric binder properties, and also on the AM/CA/binder mass ratio. At the same time, it also substantially depends on the electrode preparation process. This process is usually comprised of mixing a solvent, a binder, AM and CA powders, and casting the resulting slurry onto a current collector foil followed by a drying process. Whereas the problems of electrode morphology and their influence on the LIB‐electrode performance always receive a proper attention, the influence of slurry properties and slurry preparation techniques on the electrode morphology is often overlooked or at least underrated. The present work summarizes the current state‐of‐the‐art in the field of LIB‐electrode precursor slurries preparation, characterized by multicomponent compounds and large variations in sizes and shapes of the solid components. Approaches to LIB‐electrode slurry preparation are outlined and discussed in the context of the ultimate LIB‐electrode morphology and performance.     

Ultrahigh‐Capacity and Fire‐Resistant LiFePO4‐Based Composite Cathodes for Advanced Lithium‐Ion Batteries

The growing demand for advanced energy storage devices with high energy density and high safety has continuously driven the technical upgrades of cell architectures as well as electroactive materials. Designing thick electrodes with more electroactive materials is a promising strategy to improve the energy density of lithium‐ion batteries (LIBs) without alternating the underlying chemistry. However, the progress toward thick, high areal capacity electrodes is severely limited by the sluggish electronic/ionic transport and easy deformability of conventional electrodes. A self‐supported ultrahigh‐capacity and fire‐resistant LiFePO₄ (UCFR‐LFP)‐based nanocomposite cathode is demonstrated here. Benefiting from the structural and chemical uniqueness, the UCFR‐LFP electrodes demonstrate exceptional improvements in electrochemical performance and mass loading of active materials, and thermal stability. Notably, an ultrathick UCFR‐LFP electrode (1.35 mm) with remarkably high mass loading of active materials (108 mg cm^?2) and areal capacity (16.4 mAh cm^?2) is successfully achieved. Moreover, the 1D inorganic binder‐like ultralong hydroxyapatite nanowires (HAP NWs) enable the UCFR‐LFP electrode with excellent thermal stability (structural integrity up to 1000 °C and electrochemical activity up to 750 °C), fire‐resistance, and wide‐temperature operability. Such a unique UCFR‐LFP electrode offers a promising solution for next‐generation LIBs with high energy density, high safety, and wide operating‐temperature window.     

3D Hierarchical Porous α‐Fe2O3 Nanosheets for High‐Performance Lithium‐Ion Batteries

To develop a long cycle life and good rate capability electrode, 3D hierarchical porous α‐Fe₂O₃ nanosheets are fabricated on copper foil and directly used as binder‐free anode for lithium‐ion batteries. This electrode exhibits a high reversible capacity and excellent rate capability. A reversible capacity up to 877.7 mAh g^?1 is maintained at 2 C (2.01 A g^?1) after 1000 cycles, and even when the current is increased to 20 C (20.1 A g^?1), a capacity of 433 mA h g^?1 is retained. The unique porous 3D hierarchical nanostructure improves electronic–ionic transport, mitigates the internal mechanical stress induced by the volume variations of the electrode upon cycling, and forms a 3D conductive network during cycling. No addition of any electrochemically inactive conductive agents or polymer binders is required. Therefore, binder‐free electrodes further avoid the uneven distribution of conductive carbon on the current collector due to physical mixing and the addition of an insulator (binder), which has benefits leading to outstanding electrochemical performance.     

Strategic Pore Architecture for Accommodating Volume Change from High Si Content in Lithium‐Ion Battery Anodes

To be a thinner and more lightweight lithium‐ion battery with high energy density, the next‐generation anode with high gravimetric and volumetric capacity is a prerequisite. In this regard, utilizing high silicon (3579 mAh g^?1) content in the electrode for the anode has been highlighted as a practically relevant approach. However, there still remains a crucial issue related to intrinsic volume expansion (>300%) of silicon upon lithiation, which can directly affect severe electrode swelling as well as accelerate its capacity fading by triggering structural degradation and electrical contact loss between particles. Herein, macropore‐exploited design, which can accommodate the volume change of high silicon content within the extended pore of graphite upon repeated cycling, is introduced. Such unique macropore‐exploited design leads to much less electrode swelling, by preserving its morphological integrity and contact between particles, than that of the comparative group with different sized pore and silicon distribution. As a result, this anode (914 mAh g^?1) demonstrates notable gravimetric (220 Wh kg^?1 at 6000 W kg^?1) and volumetric energy density (623 Wh L^?1 upon full lithiation after 100 cycles), exceeding that of a nano‐silicon blended graphite anode (127 Wh kg^?1 and 229 Wh L^?1) in the full‐cell system.     

Silicon Anode with High Initial Coulombic Efficiency by Modulated Trifunctional Binder for High‐Areal‐Capacity Lithium‐Ion Batteries

High‐capacity electrode materials play a vital role for high‐energy‐density lithium‐ion batteries. Silicon (Si) has been regarded as a promising anode material because of its outstanding theoretical capacity, but it suffers from an inherent volume expansion problem. Binders have demonstrated improvements in the electrochemical performance of Si anodes. Achieving ultrahigh‐areal‐capacity Si anodes with rational binder strategies remains a significant challenge. Herein, a binder‐lithiated strategy is proposed for ultrahigh‐areal‐capacity Si anodes. A hard/soft modulated trifunctional network binder (N‐P‐LiPN) is constructed by the partially lithiated hard polyacrylic acid as a framework and partially lithiated soft Nafion as a buffer via the hydrogen binding effect. N‐P‐LiPN has strong adhesion and mechanical properties to accommodate huge volume change of the Si anode. In addition, lithium‐ions are transferred via the lithiated groups of N‐P‐LiPN, which significantly enhances the ionic conductivity of the Si anode. Hence, the Si@N‐P‐LiPN electrodes achieve the highest initial Coulombic efficiency of 93.18% and a stable cycling performance for 500 cycles at 0.2 C. Specially, Si@N‐P‐LiPN electrodes demonstrate an ultrahigh‐areal‐capacity of 49.59 mAh cm^?2. This work offers a new approach for inspiring the battery community to explore novel binders for next‐generation high‐energy‐density storage devices.     

Nanosilicon‐Based Thick Negative Composite Electrodes for Lithium Batteries with Graphene as Conductive Additive

Reduced graphene oxide (rGO) is used as a conductive additive for nanosilicon‐based lithium battery anodes with the high active‐mass loading typically required for industrial applications. In contrast to conventional Si electrodes that use acetylene black (AcB) as an additive, the rGO system shows pronounced improvement of electrochemical performance, irrespective of the cycling conditions. With capacity limitation, the rGO system results in improved coulombic efficiency (99.9%) and longer cycle life than conventional electrodes. Upon cycling without capacity limitation, much higher discharge capacity is maintained (2000 mAh g^?1 after 100 cycles for 2.5 mg of Si cm^?2). Used in conjunction with the bridging carboxymethyl cellulose binder, the crumpled and resilient rGO allows highly reversible functioning of the electrode in which the Si particles repeatedly inflate and deflate upon alloying and dealloying with lithium.     

New Binder‐Free Metal Phosphide–Carbon Felt Composite Anodes for Sodium‐Ion Battery

Metal phosphides are promising anode candidates for sodium‐ion batteries (SIBs) due to their high specific capacity and low operating potential but suffer from poor cycling stability caused by huge volume expansion and poor solid‐state ion transfer rate. Herein, a new strategy to grow a new class of mesoporous metal phosphide nanoarrays on carbon felt (CF) as binder‐free anodes for SIBs is reported. The resultant integrated electrodes demonstrate excellent cycling life up to 1000 times (>90% retention rate) and high rate capability of 535 mAh g^?1 at a current density of 4 A g^?1. Detailed characterization reveals that the synergistic effect of unique mesoporous structure for accommodating huge volume expansion during sodiation/desodiation process, ultrasmall primary particle size (≈10 nm) for providing larger electrode/electrolyte contact area and shorter ion diffusion distance, and 3D conductive networks for facilitating the electrochemical reaction, leads to the extraordinary battery performance. Remarkably, a full SIB using the new CoP₄/CF anode and a Na₃V₂(PO₄)₂F₃ cathode delivers an average operating voltage of ≈3.0 V, a reversible capacity of 553 mAh g^?1, and very high energy density of ≈280 Wh kg^?1 for SIBs. A flexible SIB with outstanding mechanical strength based on this binder‐free new anode is also demonstrated.     

Multidimensional Ordered Bifunctional Air Electrode Enables Flash Reactants Shuttling for High‐Energy Flexible Zn‐Air Batteries

Direct growth of electrocatalysts on conductive substrates is an emerging strategy to prepare air electrodes for flexible Zn‐air batteries (FZABs). However, electrocatalysts grown on conductive substrates usually suffer from disorder and are densely packed with “prohibited zones”, in which internal blockages shut off the active sites from catalyzing the oxygen reaction. Herein, to minimize the “prohibited zones”, an ordered multidimensional array assembled by 1D carbon nanotubes and 2D carbon nanoridges decorated with 0D cobalt nanoparticles (referred as MPZ‐CC@CNT) is constructed on nickel foam. When the MPZ‐CC@CNT is directly applied as a self‐supported electrode for FZAB, it delivers a marginal voltage fading rate of 0.006 mV cycle^?1 over 1800 cycles (600 h) at a current density of 50 mA cm^?2 and an impressive energy density of 946 Wh kg^?1. Electrochemical impedance spectroscopy reveals that minimal internal resistance and electrochemical polarization, which is beneficial for the flash reactant shuttling among the triphase (i.e., oxygen, electrolyte, and catalyst) are offered by the open and ordered architecture. This advanced electrode design provides great potential to boost the electrochemical performance of other rechargeable battery systems.     

SiO2‐Enhanced Structural Stability and Strong Adhesion with a New Binder of Konjac Glucomannan Enables Stable Cycling of Silicon Anodes for Lithium‐Ion Batteries

Silicon‐based anodes with high theoretical capacity have intriguing potential applications for next‐generation high‐energy lithium‐ion batteries, but suffer from huge volumetric change that causes pulverization of electrodes. Rational design and construction of effective electrode structures combined with versatile binders remain a significant challenge. Here, a unique natural binder of konjac glucomannan (KGM) is developed and an amorphous protective layer of SiO₂ is fabricated on the surface of Si nanoparticles (Si@SiO₂) to enhance the adhesion. Benefiting from a plethora of hydroxyl groups, the KGM binder with inherently high adhesion and superior mechanical properties provides abundant contact sites to active materials. Molecular mechanics simulations and experimental results demonstrate that the enhanced adhesion between KGM and Si@SiO₂ can bond the particles tightly to form a robust electrode. In addition to bridging KGM molecules, the SiO₂‐functionalized surface may serve as a buffer layer to alleviate the stresses of Si nanoparticles resulting from the volume change. The as‐fabricated KGM/Si@SiO₂ electrode exhibits outstanding structural stability upon long‐term cycles. A highly reversible capacity of 1278 mAh g^?1 can be achieved over 1000 cycles at a current density of 2 A g^?1, and the capacity decay is as small as 0.056% per cycle.     

3D Printing of Tunable Energy Storage Devices with Both High Areal and Volumetric Energy Densities

Developing advanced supercapacitors with both high areal and volumetric energy densities remains challenging. In this work, self‐supported, compact carbon composite electrodes are designed with tunable thickness using 3D printing technology for high‐energy‐density supercapacitors. The 3D carbon composite electrodes are composed of the closely stacked and aligned active carbon/carbon nanotube/reduced graphene oxide (AC/CNT/rGO) composite filaments. The AC microparticles are uniformly embedded in the wrinkled CNT/rGO conductive networks without using polymer binders, which contributes to the formation of abundant open and hierarchical pores. The 3D‐printed ultrathick AC/CNT/rGO composite electrode (ten layers) features high areal and volumetric mass loadings of 56.9 mg cm^?2 and 256.3 mg cm^?3, respectively. The symmetric cell assembled with the 3D‐printed thin GO separator and ultrathick AC/CNT/rGO electrodes can possess both high areal and volumetric capacitances of 4.56 F cm^?2 and 10.28 F cm^?3, respectively. Correspondingly, the assembled ultrathick and compact symmetric cell achieves high areal and volumetric energy densities of 0.63 mWh cm^?2 and 1.43 mWh cm^?3, respectively. The all‐component extrusion‐based 3D printing offers a promising strategy for the fabrication of multiscale and multidimensional structures of various high‐energy‐density electrochemical energy storage devices.     

Minimizing the Electrolyte Volume in Li–S Batteries: A Step Forward to High Gravimetric Energy Density

Sulfur electrodes confined in an inert carbon matrix show practical limitations and concerns related to low cathode density. As a result, these electrodes require a large amount of electrolyte, normally three times more than the volume used in commercial Li‐ion batteries. Herein, a high‐energy and high‐performance lithium–sulfur battery concept, designed to achieve high practical capacity with minimum volume of electrolyte is proposed. It is based on deposition of polysulfide species on a self‐standing and highly conductive carbon nanofiber network, thus eliminating the need for a binder and current collector, resulting in high active material loading. The fiber network has a functionalized surface with the presence of polar oxygen groups, with the aim to prevent polysulfide migration to the lithium anode during the electrochemical process, by the formation of S–O species. Owing to the high sulfur loading (6 mg cm^?2) and a reduced free volume of the sulfide/fiber electrode, the Li–S cell is designed to work with as little as 10 µL cm^?2 of electrolyte. With this design the cell has a high energy density of 450 Wh kg^?1, a lifetime of more than 400 cycles, and the possibility of low cost, by use of abundant and eco‐friendly materials.     

One‐to‐One Comparison of Graphite‐Blended Negative Electrodes Using Silicon Nanolayer‐Embedded Graphite versus Commercial Benchmarking Materials for High‐Energy Lithium‐Ion Batteries

While existing carbonaceous anodes for lithium–ion batteries (LIBs) are approaching a practical capacitive limit, Si has been extensively examined as a potential alternative because it shows exceptional gravimetric capacity (3579 mA h g^?1) and abundance. However, the actual implementation of Si anodes is impeded by difficulties in electrode calendering processes and requirements for excessive binding and conductive agents, arising from the brittleness, large volume expansion (>300%), and low electrical conductivity (1.56 × 10^?3 S m^?1) of Si. In one rational approach to using Si in high‐energy LIBs, mixing Si‐based materials with graphite has attracted attention as a feasible alternative for next‐generation anodes. In this study, graphite‐blended electrodes with Si nanolayer‐embedded graphite/carbon (G/SGC) are demonstrated and detailed one‐to‐one comparisons of these electrodes with industrially developed benchmarking samples are performed under the industrial electrode density (>1.6 g cc^?1), areal capacity (>3 mA h cm^?2), and a small amount of binder (3 wt%) in a slurry. Because of the favorable compatibility between SGC and conventional graphite, and the well‐established structural features of SGC, great potential is envisioned. Since this feasible study utilizes realistic test methods and criteria, the rigorous benchmarking comparison presents a comprehensive understanding for developing and characterizing Si‐based anodes for practicable high‐energy LIBs.     

Metallic Layered Polyester Fabric Enabled Nickel Selenide Nanostructures as Highly Conductive and Binderless Electrode with Superior Energy Storage Performance

Highly flexible and conductive fabric (CF)‐supported cauliflower‐like nickel selenide nanostructures (Ni₃Se₂ NSs) are facilely synthesized by a single‐step chronoamperometry voltage‐assisted electrochemical deposition (ECD) method and used as a positive electrode in supercapacitors (SCs). The CF substrate composed of multi‐layered metallic films on the surface of polyester fibers enables to provide high electrical conductivity as a working electrode in ECD process. Owing to good electrical conductivity, high porosity and intertwined fibrous framework of CF, cauliflower‐like Ni₃Se₂ NSs are densely integrated onto the entire surface of CF (Ni₃Se₂ NSs@CF) substrate with reliable adhesion by applying a chronoamperometry voltage of ?1.0 V for 240 s. The electrochemical performance of the synthesized cauliflower‐like Ni₃Se₂ NSs@CF electrode exhibits a maximum specific capacity (C _SC) of 119.6 mA h g^?1 at a discharge current density of 2 A g^?1 in aqueous 1 m KOH electrolyte solution. Remarkably, the specific capacity of the same electrode is greatly enhanced by introducing a small quantity of redox‐additive electrolyte into the aqueous KOH solution, indicating the C _SC≈251.82 mA h g^?1 at 2 A g^?1 with good capacity retention. Furthermore, the assembled textile‐based asymmetric SCs achieve remarkable electrochemical performance such as higher energy and power densities, which are able to light up different colored light‐emitting diodes.     

Lignin Laser Lithography: A Direct‐Write Method for Fabricating 3D Graphene Electrodes for Microsupercapacitors

In this work, a simple lignin‐based laser lithography technique is developed and used to fabricate on‐chip microsupercapacitors (MSCs) using 3D graphene electrodes. Specifically, lignin films are transformed directly into 3D laser‐scribed graphene (LSG) electrodes by a simple one‐step CO₂ laser irradiation. This step is followed by a water lift‐off process to remove unexposed lignin, resulting in 3D graphene with the designed electrode patterns. The resulting LSG electrodes are hierarchically porous, electrically conductive (conductivity is up to 66.2 S cm^?1), and have a high specific surface area (338.3 m² g^?1). These characteristics mean that such electrodes can be used directly as MSC electrodes without the need for binders and current collectors. The MSCs fabricated using lignin laser lithography exhibit good electrochemical performances, namely, high areal capacitance (25.1 mF cm^?2), high volumetric energy density (≈1 mWh cm^?3), and high volumetric power density (≈2 W cm^?3). The versatility of lignin laser lithography opens up the opportunity in applications such as on‐chip microsupercapacitors, sensors, and flexible electronics at large‐scale production.     

Free‐Standing 3D Nanoporous Duct‐Like and Hierarchical Nanoporous Graphene Films for Micron‐Level Flexible Solid‐State Asymmetric Supercapacitors

High energy density and power density within a limited volume of flexible solid‐state supercapacitors are highly desirable for practical applications. Here, free‐standing high‐quality 3D nanoporous duct‐like graphene (3D‐DG) films are fabricated with high flexibility and robustness as the backbones to deposit flower‐like MnO₂ nanosheets (3D‐DG@MnO₂). The 3D‐DG is the ideal support for the deposition of large amount of active materials because of its large surface area, appropriate pore structure, and negligible volume compared with other kinds of carbon backbones. Moreover, the 3D‐DG preserve the distinctive 2D coherent electronic properties of graphene, in which charge carriers move rapidly with a small resistance through the high‐quality and continuous chemical vapor deposition‐grown graphene building blocks, which results in a high rate performance. Marvelously, ultrathin (≈50 μm) flexible solid‐state asymmetric supercapacitors (ASCs) using 3D‐DG@MnO₂ as the positive electrode and 3D hierarchical nanoporous graphene films as the negative electrode display ultrahigh volumetric energy density (28.2 mW h cm^?3) and power density (55.7 W cm^?3) at 2.0 V. Furthermore, as‐prepared ASCs show high cycle stability clearly demonstrating their broad applications as power supplies in wearable electronic devices.     

NiCo2S4 Nanosheets Grown on Nitrogen‐Doped Carbon Foams as an Advanced Electrode for Supercapacitors

To push the energy density limit of supercapacitors, a new class of electrode materials with favorable architectures is strongly needed. Binary metal sulfides hold great promise as an electrode material for high‐performance energy storage devices because they offer higher electrochemical activity and higher capacity than mono‐metal sulfides. Here, the rational design and fabrication of NiCo₂S₄ nanosheets supported on nitrogen‐doped carbon foams (NCF) is presented as a novel flexible electrode for supercapacitors. A facile two‐step method is developed for growth of NiCo₂S₄ nanosheets on NCF with robust adhesion, involving the growth of Ni‐Co precursor and subsequent conversion into NiCo₂S₄ nanosheets through sulfidation process. Benefiting from the compositional features and 3D electrode architectures, the NiCo₂S₄/NCF electrode exhibits greatly improved electrochemical performance with ultrahigh capacitance (877 F g^?1 at 20 A g^?1) and excellent cycling stability. Moreover, a binder‐free asymmetric supercapacitor device is also fabricated by using NiCo₂S₄/NCF as the positive electrode and ordered mesoporous carbon (OMC)/NCF as the negative electrode; this demonstrates high energy density (≈45.5 Wh kg^?1 at 512 W kg^?1).     

Reversible Lithium‐Ion Uptake in Poly(methylmethacrylate) Thin‐Film via Lithiation/Delithiation at In Situ Formed Intramolecular Cyclopentanedione

Herein, it is proposed that poly(methylmethacrylate) (PMMA), a widely‐used thermoplastic in our daily life, can be used as an abundant, stable, and high‐performance anode material for rechargeable lithium‐ion batteries through a novel concept of lithium storage mechanism. The specially‐designed PMMA thin‐film electrode exhibits a high reversible capacity of 343 mA h g^?1 at C/25 and maintains a capacity retention of 82.6% of that obtained at C/25 when cycled at 1 C rate. Meanwhile, this pristine PMMA electrode without binder and conductive agents shows a high reversible capacity of 196.8 mA h g^?1 after 150 cycles at 0.2 C with a capacity retention of 73.5%. Additionally, PMMA‐based binder is found to enhance both the reversible capacity and rate capability of the graphite electrodes. Hence, this new type of organic electrode material may have a great opportunity to be utilized as the active material or rechargeable binder in flexible or transparent thin‐film batteries and all‐solid batteries. The present work also provides a new way of seeking more proper organic electrode materials which don't contain conjugated structures and atoms with lone pair electrons required in traditional organic electrode materials.     

Bifunctional Conducting Polymer Coated CoP Core–Shell Nanowires on Carbon Paper as a Free‐Standing Anode for Sodium Ion Batteries

This study proposes a conformal surface coating of conducting polymer for protecting 1D nanostructured electrode material, thereby enabling a free‐standing electrode without binder for sodium ion batteries. Here, polypyrrole (PPy), which is one of the representative conducting polymers, encapsulated cobalt phosphide (CoP) nanowires (NWs) grown on carbon paper (CP), finally realizes 1D core–shell CoP@PPy NWs/CP. The CoP core is connected to the PPy shell via strong chemical bonding, which can maintain a Co–PPy framework during charge/discharge. It also possesses bifunctional features that enhances the charge transfer and buffers the volume expansion. Consequently, 1D core–shell CoP@PPy NWs/CP demonstrates superb electrochemical performance, delivering a high areal capacity of 0.521 mA h cm^?2 at 0.15 mA cm^?2 after 100 cycles, and 0.443 mA h cm^?2 at 1.5 mA cm^?2 even after 1000 cycles. Even at a high current density of 3 mA cm^?2, a significant areal discharge capacity reaching 0.285 mA h cm^?2 is still maintained. The outstanding performance of the CoP@PPy NWs/CP free‐standing anode provides not only a novel insight into the modulated volume expansion of anode materials but also one of the most effective strategies for binder‐free and free‐standing electrodes with decent mechanical endurance for future secondary batteries.     

Manganese Oxide/Carbon Aerogel Composite: an Outstanding Supercapacitor Electrode Material

Manganese oxide/carbon aerogel composite electrodes are prepared by a self‐limiting anodic‐electrochemical deposition of manganese oxide into a binder‐enriched carbon aerogel layer, drop‐cast on a graphite substrate, using 0.1 M Mn(CH₃COO)₂·4H₂O as the electrolyte. Manganese oxide grows in the form of thin nanofibers along the backbone of the carbon aerogel, leaving adequate working space for the electrolyte and enabling a fuller extent of the utilization of the manganese oxide to make the composite an outstanding supercapacitor electrode material. The manganese oxide is determined to be Mn₃O₄ with the Raman spectroscopy and high‐resolution transmission electron microscopy. The rectangularity of the cyclic‐voltammogram loops of the composite electrode is excellent and remains that way for scan rates up to a very‐high value of 500 mV s^?1, indicating extremely good redox reversibility and cycle efficiency. At a scan rate of 25 mV s^?1, the specific capacitance, as measured in 0.5 M Na₂SO₄ for a potential window of 0.1–0.9 V vs. Ag/AgCl, reaches a maximum value of 503 F g^?1 and experiences only a negligible decay of less than 1% at the 6000th cycle, implying an extraordinary cycling stability. The cycling efficiency is as high as 98% at a current density of 8 A g^?1 cm^?2, showing an almost‐ideal capacitive behavior. The power density reaches 48.5 kW kg^?1 and the energy density 21.6 W h kg^?1 at a scan rate of 500 mV s^?1, well above the specifications of current state‐of‐the‐art supercapacitors.     

Hydrous RuO2‐Decorated MXene Coordinating with Silver Nanowire Inks Enabling Fully Printed Micro‐Supercapacitors with Extraordinary Volumetric Performance

The fabrication of fully printable, flexible micro‐supercapacitors (MSCs) with high energy and power density remains a significant technological hurdle. To overcome this grand challenge, the 2D material MXene has garnered significant attention for its application, among others, as a printable electrode material for high performing electrochemical energy storage devices. Herein, a facile and in situ process is proposed to homogeneously anchor hydrous ruthenium oxide (RuO₂) nanoparticles on Ti₃C₂T_x MXene nanosheets. The resulting RuO₂@MXene nanosheets can associate with silver nanowires (AgNWs) to serve as a printable electrode with micrometer‐scale resolution for high performing, fully printed MSCs. In this printed nanocomposite electrode, the RuO₂ nanoparticles contribute high pseudocapacitance while preventing the MXene nanosheets from restacking, ensuring an effective ion highway for electrolyte ions. The AgNWs coordinate with the RuO₂@MXene to guarantee the rheological property of the electrode ink, and provide a highly conductive network architecture for rapid charge transport. As a result, MSCs printed from the nanocomposite inks demonstrate volumetric capacitances of 864.2 F cm^?3 at 1 mV s^?1, long‐term cycling performance (90% retention after 10 000 cycles), good rate capability (304.0 F cm^?3 at 2000 mV s^?1), outstanding flexibility, remarkable energy (13.5 mWh cm^?3) and power density (48.5 W cm^?3).