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.     

3D Printing Quasi‐Solid‐State Asymmetric Micro‐Supercapacitors with Ultrahigh Areal Energy Density

A 3D printing approach is first developed to fabricate quasi‐solid‐state asymmetric micro‐supercapacitors to simultaneously realize the efficient patterning and ultrahigh areal energy density. Typically, cathode, anode, and electrolyte inks with high viscosities and shear‐thinning rheological behaviors are first prepared and 3D printed individually on the substrates. The 3D printed asymmetric micro‐supercapacitor with interdigitated electrodes exhibits excellent structural integrity, a large areal mass loading of 3.1 mg cm^?2, and a wide electrochemical potential window of 1.6 V. Consequently, this 3D printed asymmetric micro‐supercapacitor displays an ultrahigh areal capacitance of 207.9 mF cm^?2. More importantly, an areal energy density of 73.9 µWh cm^?2 is obtained, superior to most reported interdigitated micro‐supercapacitors. It is believed that the efficient 3D printing strategy can be used to construct various asymmetric micro‐supercapacitors to promote the integration in on‐chip energy storage systems.     

Thick Binder‐Free Electrodes for Li–Ion Battery Fabricated Using Templating Approach and Spark Plasma Sintering Reveals High Areal Capacity

The templating approach is a powerful method for preparing porous electrodes with interconnected well‐controlled pore sizes and morphologies. The optimization of the pore architecture design facilitates electrolyte penetration and provides a rapid diffusion path for lithium ions, which becomes even more crucial for thick porous electrodes. Here, NaCl microsize particles are used as a templating agent for the fabrication of 1 mm thick porous LiFePO₄ and Li₄Ti₅O₁₂ composite electrodes using spark plasma sintering technique. These sintered binder‐free electrodes are self‐supported and present a large porosity (40%) with relatively uniform pores. The electrochemical performances of half and full batteries reveal a remarkable specific areal capacity (20 mA h cm^?2), which is 4 times higher than those of 100 µm thick electrodes present in conventional tape‐casted Li–ion batteries (5 mA h cm^?2). The 3D morphological study is carried out using full field transmission X‐ray microscopy in microcomputed tomography mode to obtain tortuosity values and pore size distributions leading to a strong correlation with their electrochemical properties. These results also demonstrate that the coupling between the salt templating method and the spark plasma sintering technique turns out to be a promising way to fabricate thick electrodes with high energy density.     

Versatile N‐Doped MXene Ink for Printed Electrochemical Energy Storage Application

Printing is regarded as a revolutionary and feasible technique to guide the fabrication of versatile functional systems with designed architectures. 2D MXenes are nowadays attractive in printed energy storage devices. However, owing to the van der Waals interaction between the MXene layers, the restacking issues within the printed electrodes can significantly impede the ion/electrolyte transport and hence handicap the electrochemical performances. Herein, a melamine formaldehyde templating method is demonstrated to develop crumpled nitrogen‐doped MXene (MXene‐N) nanosheets. The nitrogen doping boosts the electrochemical performances of MXene via enhanced conductivity and redox activity. Accordingly, two types of MXene‐N inks are prepared throughout the optimization of the ink viscosity to fit the 2D screen printing and 3D extrusion printing, respectively. As a result, the screen printed MXene‐N microsupercapacitor delivers an areal capacitance of 70.1 mF cm^?2 and outstanding mechanical robustness. Furthermore, the 3D‐printed MXene‐N based supercapacitor manifests an areal capacitance of 8.2 F cm^?2 for a three‐layered electrode and readily stores a high areal energy density of 0.42 mWh cm^?2. The approach to harnessing such versatile MXene‐N inks offers distinctive insights into the printed energy storage systems with high areal energy density and large scalability.     

All‐Printed,Stretchable Zn‐Ag2O Rechargeable Battery via Hyperelastic Binder for Self‐Powering Wearable Electronics

While several stretchable batteries utilizing either deterministic or random composite architectures have been described, none have been fabricated using inexpensive printing technologies. In this study, the authors printed a highly stretchable, zinc‐silver oxide (Zn‐Ag₂O) battery by incorporating polystyrene‐block ‐polyisoprene‐block ‐polystyrene (SIS) as a hyperelastic binder for custom‐made printable inks. The remarkable mechanical properties of the SIS binder lead to an all‐printed, stretchable Zn‐Ag₂O rechargeable battery with a ≈2.5 mA h cm^?2 reversible capacity density even after multiple iterations of 100% stretching. This battery offers the highest reversible capacity and discharge current density for intrinsically stretchable batteries reported to date. The electrochemical and mechanical properties are characterized under different strain conditions. The new stress‐enduring printable inks pave ways for further developing stretchable electronics for the wide range of wearable applications.     

Fabrication of Low‐Tortuosity Ultrahigh‐Area‐Capacity Battery Electrodes through Magnetic Alignment of Emulsion‐Based Slurries

High energy‐density, low‐cost batteries are critically important to a variety of applications ranging from portable electronics to electric vehicles (EVs) and grid‐scale storage. While tremendous research effort has been focused on new materials or chemistries with high energy‐density potential, design innovations such as low‐tortuosity thick electrodes are another promising path toward higher energy density and lower cost. Growing demand for fast‐charging batteries has also highlighted the need for negative electrodes that can accept high rate charging without metal deposition; low tortuosity can be a benefit in this regard. However, a general and scalable fabrication method for low‐tortuosity electrodes is currently lacking. Here an emulsion‐based, magnetic‐alignment approach to producing thick electrodes (>400 µm thickness) with ultrahigh areal capacity (up to ≈14 mAh cm^?2 vs 2–4 mAh cm^?2 for conventional lithium ion) is reported. The process is demonstrated for LiCoO₂ and meso‐carbon microbead graphite. The LiCoO₂ cathodes are confirmed to have low tortuosity via DC‐depolarization experiments and deliver high areal capacity (>10 mAh cm^?2) in galvanostatic discharge tests at practical C‐rates and model EV drive‐cycle tests. This simple fabrication method can potentially be applied to many other active materials to enable thick, low‐tortuosity electrodes.     

Conductive Metal–Organic Frameworks Selectively Grown on Laser‐Scribed Graphene for Electrochemical Microsupercapacitors

Conductive 2D metal–organic frameworks (MOFs) have merits beyond traditional MOFs for electrochemical applications, but reports on using MOFs as electrodes for electrochemical microsupercapacitors (MSCs) are practically non‐existent. In this work, a Ni‐catecholate‐based MOF (Ni‐CAT MOF) having good conductivity and exhibiting redox chemistry in the positive and negative voltage windows is developed. A novel process is developed to selectively grow the conductive Ni‐CAT MOF on 3D laser scribed graphene (LSG). The LSG with its superior wettability serves as a functional matrix‐current collector for the hybridization of conductive Ni‐CAT MOF nanocrystals. Impressively, MSCs fabricated using the hybrid LSG/Ni‐CAT MOF show significant improvement compared with MOF‐free LSG electrodes. Specifically, the LSG/Ni‐CAT MOF electrodes can deliver MSCs with a wide operating voltage (1.4 V), high areal capacitance (15.2 mF cm^?2), energy density (4.1 µWh cm^?2), power density (7 mW cm^?2), good rate performance, and decent cycling stability. This work opens up an avenue for developing electrochemical microsupercapacitors using conductive MOF electrodes.     

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.     

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.     

Densification by Compaction as an Effective Low‐Cost Method to Attain a High Areal Lithium Storage Capacity in a CNT@Co3O4 Sponge

Achieving a high areal capacity is essential for the transfer of outstanding laboratory electrode results to commercial applications and also to ensure there exists a capacity matched cathode and anode for a properly tuned battery. Despite intensive efforts, most electrode materials exhibit areal capacities lower than that of the graphite anodes (4 mA h cm^?2). An effective and low‐cost approach is reported to attain a high areal capacity via an intense densification by compacting a porous carbon nanotube sponge grafted with Co₃O₄ nanoparticles. The hybrid sponge can be compacted to a large degree (up to a tenfold densification) while still keeping its structural integrity and the 3D porous network. This method allows achieving a mass loading of up ?to 14.3 mg cm^?2 and an areal capacity of 12 mA h cm^?2 (at a current density of 200 mA g^?1) together with a gravimetric capacity of >800 mA h g^?1. This densification by compaction approach offers an effective and low‐cost strategy to develop high mass loading and areal capacity electrodes for practical energy storage systems.     

Stretchable Lithium‐Ion Batteries Enabled by Device‐Scaled Wavy Structure and Elastic‐Sticky Separator

Fast developments and substantial achievements have been shaping the field of wearable electronic devices, resulting in the persistent requirement for stretchable lithium‐ion batteries (LIBs). Despite recent progress in stretchable electrodes, stretching full batteries, including electrodes, separator, and sealing material, remains a great challenge. Here, a simple design concept for stretchable LIBs via a wavy structure at the full battery device scale is reported. All components including the package are capable of being reversibly stretched by folding the entire pouch cell into a wavy shape with polydimethylsiloxane filled in each valley region. In addition, the stretchable, sticky, and porous polyurethane/poly(vinylidene fluoride) membrane is adopted as a separator for the first time, which can maintain intimate contact between electrodes and separator to continuously secure ion pathway under dynamic state. Commercial cathode, anode, and package can be utilized in this rationally designed wavy battery to enable stretchability. The results indicate good electrochemical performances and long‐term stability at repeatable release–stretch cycles. A high areal capacity of 3.6 mA h cm^?2 and energy density of up to 172 W h L^?1 can be achieved for the wavy battery. The promising results of the cost‐effective wavy battery with high stretchability shed light on the development of stretchable energy storages.     

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).     

Flexible Asymmetric Micro‐Supercapacitors Based on Bi2O3 and MnO2 Nanoflowers: Larger Areal Mass Promises Higher Energy Density

A flexible asymmetric supercapacitor (ASC) with high energy density is designed and fabricated using flower‐like Bi₂O₃ and MnO₂ grown on carbon nanofiber (CNF) paper as the negative and positive electrodes, respectively. The lightweight (1.6 mg cm^?2), porous, conductive, and flexible features make the CNF paper an ideal support for guest active materials, which permit a large areal mass of 9 mg cm^?2 for Bi₂O₃ (≈85 wt% of the entire electrode). Thus, the optimal device with an operation voltage of 1.8 V can deliver a high energy density of 43.4 μWh cm^?2 (11.3 W h kg^?1, based on the total electrodes) and a maximum power density of 12.9 mW cm^?2 (3370 W kg^?1). This work provides an example of large areal mass and flexible electrode for ASCs with high areal capacitance and high energy density, holding great promise for future flexible electronic devices.     

Integrated Conductive Hybrid Architecture of Metal–Organic Framework Nanowire Array on Polypyrrole Membrane for All‐Solid‐State Flexible Supercapacitors

Metal–organic frameworks (MOFs) with intrinsically porous structures are promising candidates for energy storage, however, their low electrical conductivity limits their electrochemical energy storage applications. Herein, the hybrid architecture of intrinsically conductive Cu‐MOF nanowire arrays on self‐supported polypyrrole (PPy) membrane is reported for integrated flexible supercapacitor (SC) electrodes without any inactive additives, binders, or substrates involved. The conductive Cu‐MOFs nanowire arrays afford high conductivity and a sufficiently active surface area for the accessibility of electrolyte, whereas the PPy membrane provides decent mechanical flexibility, efficient charge transfer skeleton, and extra capacitance. The all‐solid‐state flexible SC using integrated hybrid electrode demonstrates an exceptional areal capacitance of 252.1 mF cm^?2, an energy density of 22.4 µWh cm^?2, and a power density of 1.1 mW cm^?2, accompanied by an excellent cycle capability and mechanical flexibility over a wide range of working temperatures. This work not only presents a robust and flexible electrode for wide temperature range operating SC but also offers valuable concepts with regards to designing MOF‐based hybrid materials for energy storage and conversion systems.     

Hierarchical Zn–Co–S Nanowires as Advanced Electrodes for All Solid State Asymmetric Supercapacitors

A facile two‐step strategy is developed to design the large‐scale synthesis of hierarchical, unique porous architecture of ternary metal hydroxide nanowires grown on porous 3D Ni foam and subsequent effective sulfurization. The hierarchical Zn–Co–S nanowires (NWs) arrays are directly employed as an electrode for supercapacitors application. The as‐synthesized Zn–Co–S NWs deliver an ultrahigh areal capacity of 0.9 mA h cm^?2 (specific capacity of 366.7 mA h g^?1) at a current density of 3 mA cm^?2, with an exceptional rate capability (≈227.6 mA h g^?1 at a very high current density of 40 mA cm^?2) and outstanding cycling stability (≈93.2% of capacity retention after 10 000 cycles). Most significantly, the assembled Zn–Co–S NWs//Fe₂O₃@reduced graphene oxide asymmetric supercapacitors with a wide operating potential window of ≈1.6 V yield an ultrahigh volumetric capacity of ≈1.98 mA h cm^?3 at a current density of 3 mA cm^?2, excellent energy density of ≈81.6 W h kg^?1 at a power density of ≈559.2 W kg^?1, and exceptional cycling performance (≈92.1% of capacity retention after 10 000 cycles). This general strategy provides an alternative to design the other ternary metal sulfides, making it facile, free‐standing, binder‐free, and cost‐effective ternary metal sulfide‐based electrodes for large‐scale applications in modern electronics.     

Thermally Durable Lithium‐Ion Capacitors with High Energy Density from All Hydroxyapatite Nanowire‐Enabled Fire‐Resistant Electrodes and Separators

The reliability and durability of lithium‐ion capacitors (LICs) are severely hindered by the kinetic imbalance between capacitive and Faradaic electrodes. Efficient charge storage in LICs is still a huge challenge, particularly for thick electrodes with high mass loading, fast charge delivery, and harsh working conditions. Here, a unique thermally durable, stable LIC with high energy density from all‐inorganic hydroxyapatite nanowire (HAP NW)‐enabled electrodes and separators is reported. Namely, the LIC device is designed and constructed with the electron/ion dual highly conductive and fire‐resistant composite Li₄Ti₅O₁₂‐based anode and activated carbon‐based cathode, together with a thermal‐tolerant HAP NW separator. Despite the thick‐electrode configuration, the as‐fabricated all HAP NW‐enabled LIC exhibits much enhanced electrochemical kinetics and performance, especially at high current rates and temperatures. Long cycling lifetime and state‐of‐the‐art areal energy density (1.58 mWh cm^?2) at a high mass loading of 30 mg cm^?2 are achieved. Benefiting from the excellent fire resistance of HAP NWs, such an unusual LIC exhibits high thermal durability and can work over a wide range of temperatures from room temperature to 150 °C. Taking full advantage of synergistic configuration design, this work sets the stage for designing advanced LICs beyond the research of active materials.     

All‐Printed MnHCF‐MnOx‐Based High‐Performance Flexible Supercapacitors

Here, a simple active materials synthesis method is presented that boosts electrode performance and utilizes a facile screen‐printing technique to prepare scalable patterned flexible supercapacitors based on manganese hexacyanoferrate‐manganese oxide and electrochemically reduced graphene oxide electrode materials (MnHCF‐MnO_x/ErGO). A very simple in situ self‐reaction method is developed to introduce MnO_x pseudocapacitor material into the MnHCF system by using NH₄F. This MnHCF‐MnO_x electrode materials can deliver excellent capacitance of 467 F g^?1 at a current density of 1 A g^?1, which is a 2.4 times capacitance increase compared to MnHCF. In addition a printed, patterned, flexible MnHCF‐MnO_x/ErGO supercapacitor is fabricated, showing a remarkable areal capacitance of 16.8 mF cm^?2 and considerable energy and power density of 0.5 mWh cm^?2 and 0.0023 mW cm^?2, respectively. Furthermore, the printed patterned flexible supercapacitors also exhibit exceptional flexibility, and the capacitance remains stable, even while bending to various angles (60°, 90°, and 180°) and for 100 cycles. The flexible supercapacitor arrays integrated by multiple prepared single supercapacitors can power various LEDs even in the bent states. This approach offers promising opportunities for the development of printable energy storage materials and devices with high energy density, large scalability, and excellent flexibility.     

Scaling Printable Zn–Ag2O Batteries for Integrated Electronics

Printed batteries are an emerging solution for integrated energy storage using low‐cost, high accuracy fabrication techniques. While several printed batteries have been previously shown, few have designed a battery that can be incorporated into an integrated device. Specifically, a fully printed battery with a small active electrode area (<1 cm²) achieving high areal capacities (>10 mAh cm^?2) at high current densities (1–10 mA cm^?2) has not been demonstrated, which represents the minimum form‐factor and performance requirements for many low‐power device applications. This work addresses these challenges by investigating the scaling limits of a fully printed Zn–Ag₂O battery and determining the electrochemical limitations for a mm²‐scale battery. Processed entirely in air, Zn–Ag₂O batteries are well suited for integration in typical semiconductor packaging flows compared to lithium‐based chemistries. Printed cells with electrodes as small as 1 mm² maintain steady operating voltages above (>1.4 V) at high current densities (1–12 mA cm^?2) and achieve the highest reported areal capacity for a fully printed battery at 11 mAh cm^?2. The findings represent the first demonstration of a small, packaged, fully printed Zn–Ag₂O battery with high areal capacities at high current densities, a crucial step toward realizing chip‐scale energy storage for integrated electronic systems.     

Direct Growth of Flower‐Like δ‐MnO2 on Three‐Dimensional Graphene for High‐Performance Rechargeable Li‐O2 Batteries

A challenge still remains to develop high‐performance and cost‐effective air electrode for Li‐O₂ batteries with high capacity, enhanced rate capability and long cycle life (100 times or above) despite recent advances in this field. In this work, a new design of binder‐free air electrode composed of three‐dimensional (3D) graphene (G) and flower‐like δ‐MnO₂ (3D‐G‐MnO₂) has been proposed. In this design, graphene and δ‐MnO₂ grow directly on the skeleton of Ni foam that inherits the interconnected 3D scaffold of Ni foam. Li‐O₂ batteries with 3D‐G‐MnO₂ electrode can yield a high discharge capacity of 3660 mAh g^?1 at 0.083 mA cm^?2. The battery can sustain 132 cycles at a capacity of 492 mAh g^?1 (1000 mAh g_carbon ^?1) with low overpotentials under a high current density of 0.333 mA cm^?2. A high average energy density of 1350 Wh Kg^?1 is maintained over 110 cycles at this high current density. The excellent catalytic activity of 3D‐G‐MnO₂ makes it an attractive air electrode for high‐performance Li‐O₂ batteries.     

Hierarchically Porous,Ultrathick, “Breathable” Wood‐Derived Cathode for Lithium‐Oxygen Batteries

In this work, a hierarchically porous and ultrathick “breathable” wood‐based cathode for high‐performance Li‐O₂ batteries is developed. The 3D carbon matrix obtained from the carbonized and activated wood (denoted as CA‐wood) serves as a superconductive current collector and an ideal porous host for accommodating catalysts. The ruthenium (Ru) nanoparticles are uniformly anchored on the porous wall of the aligned microchannels (denoted as CA‐wood/Ru). The aligned open microchannels inside the carbon matrix contribute to unimpeded oxygen gas diffusion. Moreover, the hierarchical pores on the microchannel walls can be facilely impregnated by electrolyte, forming a continuous supply of electrolyte. As a result, numerous ideal triphase active sites are formed where electrolyte, oxygen, and catalyst accumulate on the porous walls of microchannels. Benefiting from the numerous well‐balanced triple‐phase active sites, the assembled Li‐O₂ battery with the CA‐wood/Ru cathode (thickness: ≈700 µm) shows a high specific area capacity of 8.58 mA h cm^?2 at 0.1 mA cm^?2. Moreover, the areal capacity can be further increased to 56.0 mA h cm^?2 by using an ultrathick CA‐wood/Ru cathode with a thickness of ≈3.4 mm. The facile ultrathick wood‐based cathodes can be applied to other cathodes to achieve a super high areal capacity without sacrificing the electrochemical performance.