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 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.     

Disordered,Large Interlayer Spacing,and Oxygen‐Rich Carbon Nanosheets for Potassium Ion Hybrid Capacitor

Potassium ion storage technology as a promising substitute for the well‐developed lithium ion storage technology is still at the infancy stage of development, and exploring suitable electrode materials is critical for its practical application. Here, the great feasibility of disordered, large interlayer spacing, and oxygen‐rich carbon nanosheets (CNSs) prepared by chemical vapor deposition for potassium ion storage applications is demonstrated. As an anode material, the CNSs exhibit outstanding rate capability as well as excellent cyclic stability. Taking advantage of this, a potassium ion hybrid capacitor (PIHC) is constructed by employing such CNSs as the battery‐type anode and activated carbon as the capacitor‐type cathode. The resulting device displays a high energy density of 149 Wh kg^?1, an ultrahigh power output of 21 kW kg^?1, as well as a long cycling life (80% capacity retention after 5000 cycles), which are all close to the state‐of‐the‐art values for PIHCs. This work promotes the development of high‐performance anode material for potassium ion storage devices, and the designed PIHC pushes the energy density and power density to a higher level.     

Nature‐Inspired Tri‐Pathway Design Enabling High‐Performance Flexible Li–O2 Batteries

Trees have an abundant network of channels for the multiphase transport of water, ions, and nutrients. Recent studies have revealed that multiphase transport of ions, oxygen (O₂) gas, and electrons also plays a fundamental role in lithium–oxygen (Li–O₂) batteries. The similarity in transport behavior of both systems is the inspiration for the development of Li–O₂ batteries from natural wood featuring noncompetitive and continuous individual pathways for ions, O₂, and electrons. Using a delignification treatment and a subsequent carbon nanotube/Ru nanoparticle coating process, one is able to convert a rigid and electrically insulating wood membrane into a flexible and electrically conductive material. The resulting cell walls are comprised of cellulose nanofibers with abundant nanopores, which are ideal for Li⁺ ion transport, whereas the unperturbed wood lumina act as a pathway for O₂ gas transport. The noncompetitive triple pathway design endows the wood‐based cathode with a low overpotential of 0.85 V at 100 mA g^?1, a record‐high areal capacity of 67.2 mAh cm^?2, a long cycling life of 220 cycles, and superior electrochemical and mechanical stability. The integration of such excellent electrochemical performance, outstanding mechanical flexibility, and renewable yet cost‐effective starting materials via a nature‐inspired design opens new opportunities for developing portable energy storage devices.     

Structural Engineering of Hierarchical Micro‐nanostructured Ge–C Framework by Controlling the Nucleation for Ultralong‐Life Li Storage

The rational design of a proper electrode structure with high energy and power densities, long cycling lifespan, and low cost still remains a significant challenge for developing advanced energy storage systems. Germanium is a highly promising anode material for high‐performance lithium ion batteries due to its large specific capacity and remarkable rate capability. Nevertheless, poor cycling stability and high price significantly limit its practical application. Herein, a facile and scalable structural engineering strategy is proposed by controlling the nucleation to fabricate a unique hierarchical micro‐nanostructured Ge–C framework, featuring high tap density, reduced Ge content, superb structural stability, and a 3D conductive network. The constructed architecture has demonstrated outstanding reversible capacity of 1541.1 mA h g^?1 after 3000 cycles at 1000 mA g^?1 (with 99.6% capacity retention), markedly exceeding all the reported Ge–C electrodes regarding long cycling stability. Notably, the assembled full cell exhibits superior performance as well. The work paves the way to constructing novel metal–carbon materials with high performance and low cost for energy‐related applications.     

Very High Surface Capacity Observed Using Si Negative Electrodes Embedded in Copper Foam as 3D Current Collectors

Cu foam is evaluated as a replacement for metal foil current collectors to create 3D composite electrodes with the objective to produce Si‐based anodes with high loadings. The electrodes are prepared by casting the slurry into the porosity of the foam. With such a design, the loading and the surface capacity can reach values as high as 10 mg cm^?2 and 10 mAh cm^?2. Compared to the common 2D design, the 3D copper framework shows a great advantage in the cycle life (more than 400 cycles at a Si loading of 10 mg cm^?2 with commercial micrometric particles) and power performance. The thinness of the composite coating on the foam walls favors a better preservation of the electronic wiring upon cycling and fast lithium ion diffusion. A higher coulombic efficiency in half cells with lithium metal as the counter electrode is achieved by using carbon nanofibers (CNF) rather than carbon black (CB). The possibility to reach, in practice, higher surface capacity could allow a significant increase in both the volumetric and gravimetric energy densities by 23% and 19%, respectively, for the Cu foam‐silicon//LiFePO₄ stack compared to the graphite/LiFePO₄ stack of traditional design.     

Nanoparticles Encapsulated in Porous Carbon Matrix Coated on Carbon Fibers: An Ultrastable Cathode for Li‐Ion Batteries

Nanostructured V₂O₅ is emerging as a new cathode material for lithium ion batteries for its distinctly high theoretic capacity over the current commercial cathodes. The main challenges associated with nanostructured V₂O₅ cathodes are structural degradation, instability of the solid‐electrolyte interface layer, and poor electron conductance, which lead to low capacity and rapid decay of cyclic stability. Here, a novel composite structure of V₂O₅ nanoparticles encapsulated in 3D networked porous carbon matrix coated on carbon fibers (V₂O₅/3DC‐CFs) is reported that effectively addresses the mentioned problems. Remarkably, the V₂O₅/3DC‐CF electrode exhibits excellent overall lithium‐storage performance, including high Coulombic efficiency, excellent specific capacity, outstanding cycling stability and rate property. A reversible capacity of ≈183 mA h g^?1 is obtained at a high current density of 10 C, and the battery retains 185 mA h g^?1 after 5000 cycles, which shows the best cycling stability reported to date among all reported cathodes of lithium ion batteries as per the knowledge. The outstanding overall properties of the V₂O₅/3DC‐CF composite make it a promising cathode material of lithium ion batteries for the power‐intensive energy storage applications.     

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.     

Hierarchical Microcables Constructed by CoP@C⊂Carbon Framework Intertwined with Carbon Nanotubes for Efficient Lithium Storage

Transition‐metal phosphides (TMPs)‐based electrode materials with high capacity have attracted considerable interest as a promising anode material for lithium?ion batteries (LIBs). Herein, a hierarchical cable‐like structure composed of CoP@C core?shell nanoparticles (NPs) encapsulated in one‐dimensional (1D) porous carbon framework intertwined with N‐doped carbon nanotubes (CoP@C?PCF/NCNTs) is synthesized by a self‐templating, self‐catalytic, and subsequent vapor‐phase phosphorization strategy. The unique nanoarchitecture regime provides multiple advantages. The 1D carbon framework allows for quick ion and electron access, maintaining the integrity and accommodating the volume change of the structure during repeated discharging/charging. The internal carbon shell can prevent the direct aggregation of CoP NPs on cycling. The external NCNTs on the surface supply a staggered conductive network to promote electrolyte penetration and charge transportation. Impressively, the as‐fabricated hybrid nanocables deliver a reversible capacity of 712 mAh g^?1 at 0.5 A g^?1 for over 700 cycles with excellent rate capability as an anode material for LIBs. The significantly improved lithium storage properties of CoP@C?PCF/NCNTs reveal the importance of reasonable design and engineering of novel hierarchical structures with higher complexity.     

High Performance,Flexible, Solid‐State Supercapacitors Based on a Renewable and Biodegradable Mesoporous Cellulose Membrane

A flexible, transparent, and renewable mesoporous cellulose membrane (mCel‐membrane) featuring uniform mesopores of ≈24.7 nm and high porosity of 71.78% is prepared via a facile and scalable solution‐phase inversion process. KOH‐saturated mCel‐membrane as a polymer electrolyte demonstrates a high electrolyte retention of 451.2 wt%, a high ionic conductivity of 0.325 S cm^?1, and excellent mechanical flexibility and robustness. A solid‐state electric double layer capacitor (EDLC) using activated carbon as electrodes, the KOH‐saturated mCel‐membrane as a polymer electrolyte exhibits a high capacitance of 110 F g^?1 at 1.0 A g^?1, and long cycling life of 10 000 cycles with 84.7% capacitance retention. Moreover, a highly integrated planar‐type micro‐supercapacitor (MSC) can be facilely fabricated by directly depositing the electrode materials on the mCel‐membrane‐based polymer electrolyte without using complicated devices. The resulting MSC exhibits a high areal capacitance of 153.34 mF cm^?2 and volumetric capacitance of 191.66 F cm^?3 at 10 mV s^?1, representing one of the highest values among all carbon‐based MSC devices. These findings suggest that the developed renewable, flexible, mesoporous cellulose membrane holds great promise in the practical applications of flexible, solid‐state, portable energy storage devices that are not limited to supercapacitors.     

High‐Performance Flexible Solid‐State Ni/Fe Battery Consisting of Metal Oxides Coated Carbon Cloth/Carbon Nanofiber Electrodes

Aqueous Ni/Fe batteries have great potential as flexible energy storage devices, owing to their low cost, low toxicity, high safety, and high energy density. However, the poor cycling stability has limited the widely expected application of Ni/Fe batteries, while the use of heavy metal substrates cannot meet the basic requirement for flexible devices. In this work, a flexible type of solid‐state Ni/Fe batteries with high energy and power densities is rationally developed using needle‐like Fe₃O₄ and flake‐like NiO directly grown on carbon cloth/carbon nanofiber (CC–CF) matrix as the anode and cathode, respectively. The hierarchical CC–CF substrate with high electric conductivity and good flexibility serves as an ideal support for guest active materials of nanocrystalline Fe₃O₄ and NiO, which can effectively buffer the volume change giving rise to good cycling ability. By utilizing a gel electrolyte, a robust and mechanically flexible quasi‐solid‐state Ni/Fe full cell can be assembled. It demonstrates optimal electrochemical performance, such as high energy density (5.2 mWh cm^?3 and 94.5 Wh Kg^?1), high power density (0.64 W cm^?3 and 11.8 KW Kg^?1), together with excellent cycling ability. This work provides an example of solid‐state alkaline battery with high electrochemical performance and mechanical flexibility, holding great potential for future flexible electronic devices.     

Molten‐NaNH2 Densified Graphene with In‐Plane Nanopores and N‐Doping for Compact Capacitive Energy Storage

Capacitive carbons are attractive for energy storage on account of their superior rate and cycling performance over traditional battery materials, but they usually suffer from a far lower volumetric energy density. Starting with expanded graphene, a simple, multifunctional molten sodium amide treatment for the preparation of high‐density graphene with high capacitive performance in both aqueous and lithium battery electrolytes is reported. The molten sodium amide can condense the expanded graphene, lead to nitrogen doping and, what is more important, create moderate in‐plane nanopores on graphene to serve as ion access shortcuts in dense graphene stacks. The resulting high‐density graphene electrode can deliver a volumetric capacitance of 522 F cm^?3 in a potassium hydroxide electrolyte; and in a lithium‐ion battery electrolyte, it exhibits a gravimetric and volumetric energy density of 618 W h kg^?1 and 740 W h L^?1, respectively, and even outperforms commercial LiFePO₄.     

KTi2(PO4)3 with Large Ion Diffusion Channel for High‐Efficiency Sodium Storage

To accommodate the decreasing lithium resource and ensure continuous development of energy storage industry, sodium‐based batteries are widely studied to inherit the next generation of energy storage devices. In this work, a novel Na super ionic conductor type KTi₂(PO₄)₃/carbon nanocomposite is designed and fabricated as sodium storage electrode materials, which exhibits considerable reversible capacity (104 mAh g^?1 under the rate of 1 C with flat voltage plateaus at ≈2.1 V), high‐rate cycling stability (74.2% capacity retention after 5000 cycles at 20 C), and ultrahigh rate capability (76 mAh g^?1 at 100 C) in sodium ion batteries. Besides, the maximum ability for sodium storage is deeply excavated by further investigations about different voltage windows in half and full sodium ion cells. Meanwhile, as cathode material in sodium‐magnesium hybrid batteries, the KTi₂(PO₄)₃/carbon nanocomposite also displays good electrochemical performances (63 mAh g^?1 at the 230th cycle under the voltage window of 1.0–1.9 V). The results demonstrate that the KTi₂(PO₄)₃/carbon nanocomposite is a promising electrode material for sodium ion storage, and lay theoretical foundations for the development of new type of batteries.     

Exfoliated Triazine‐Based Covalent Organic Nanosheets with Multielectron Redox for High‐Performance Lithium Organic Batteries

The development of the next‐generation lithium ion battery requires environmental‐friendly electrode materials with long cycle life and high energy density. Organic compounds are a promising potential source of electrode materials for lithium ion batteries due to their advantages of chemical richness at the molecular level, cost benefit, and environmental friendliness, but they suffer from low capacity and dissatisfactory cycle life mainly due to hydrophobic dissolution in organic electrolytes and poor electronic conductivity. In this work, two types of triazine‐based covalent organic nanosheets (CONs) are exfoliated and composited with carbon nanotubes. The thin‐layered 2D structure for the exfoliated CONs can activate more functional groups for lithium storage and boost the utilization efficiency of redox sites compared to its bulk counterpart. Large reversible capacities of above 1000 mAh g^?1 can be achieved after 250 cycles, which is comparable to high‐capacity inorganic electrodes. Moreover, the lithium‐storage mechanism is determined to be an intriguing 11 and 16 electron redox reaction, associated with the organic groups (unusual triazine ring, piperazine ring, and benzene ring, and common C?N, ? NH? groups).     

Highly Reversible Na Storage in Na3V2(PO4)3 by Optimizing Nanostructure and Rational Surface Engineering

Sodium‐ion batteries (NIBs) have attracted more and more attention as economic alternatives for lithium‐ion batteries (LIBs). Sodium super ionic conductor (NASICON) structure materials, known for high conductivity and chemical diffusion coefficient of Na⁺ (≈10^?14 cm² s^?1), are promising electrode materials for NIBs. However, NASICON structure materials often suffer from low electrical conductivity (<10^?4 S cm^?1), which hinders their electrochemical performance. Here high performance sodium storage performance in Na₃V₂(PO₄)₃ (NVP) is realized by optimizing nanostructure and rational surface engineering. A N, B codoped carbon coated three‐dimensional (3D) flower‐like Na₃V₂(PO₄)₃ composite (NVP@C‐BN) is designed to enable fast ions/electrons transport, high‐surface controlled energy storage, long‐term structural integrity, and high‐rate cycling. The conductive 3D interconnected porous structure of NVP@C‐BN greatly releases mechanical stress from Na⁺ extraction/insertion. In addition, extrinsic defects and active sites introduced by the codoping heteroatoms (N, B) both enhance Na⁺ and e^? diffusion. The NVP@C‐BN displays excellent electrochemical performance as the cathode, delivering reversible capacity of 70% theoretical capacity at 100 C after 2000 cycles. When used as anode, the NVP@C‐BN also shows super long cycle life (38 mA h g^?1 at 20 C after 5000 cycles). The design provides a novel approach to open up possibilities for designing high‐power NIBs.     

Exploiting the Condensation Reactions of Acetophenone to Engineer Carbon‐Encapsulated Nb2O5 Nanocrystals for High‐Performance Li and Na Energy Storage Systems

Efficient synthetic methods to produce high‐performance electrode‐active materials are crucial for developing energy storage devices for large‐scale applications, such as hybrid supercapacitors (HSCs). Here, an effective approach to obtain controllable carbon‐encapsulated T‐Nb₂O₅ nanocrystals (NCs) is presented, based on the solvothermal treatment of NbCl₅ in acetophenone. Two separate condensation reactions of acetophenone generate an intimate and homogeneous mixture of Nb₂O₅ particles and 1,3,5‐triphenylbenzene (TPB), which acts as a unique carbon precursor. The electrochemical performance of the resulting composites as anode electrode materials can be tuned by varying the Nb₂O₅/TPB ratio. Remarkable performances are achieved for Li‐ion and Na‐ion energy storage systems at high charge–discharge rates (specific capacities of ≈90 mAh g^?1 at 100 C rate for lithium and ≈125 mAh g^?1 at 20 C for sodium). High energy and power densities are also achieved with Li‐ and Na‐ion HSC devices constructed by using the Nb₂O₅/C composites as anode and activated carbon (YPF‐50) as cathode, demonstrating the excellent electrochemical properties of the materials synthesized with this approach.     

An Efficient Separator with Low Li‐Ion Diffusion Energy Barrier Resolving Feeble Conductivity for Practical Lithium–Sulfur Batteries

Due to unprecedented features including high‐energy density, low cost, and light weight, lithium–sulfur batteries have been proposed as a promising successor of lithium‐ion batteries. However, unresolved detrimental low Li‐ion transport rates in traditional carbon materials lead to large energy barrier in high sulfur loading batteries, which prevents the lithium–sulfur batteries from commercialization. In this report, to overcome the challenge of increasing both the cycling stability and areal capacity, a metallic oxide composite (NiCo₂O₄@rGO) is designed to enable a robust separator with low energy barrier for Li‐ion diffusion and simultaneously provide abundant active sites for the catalytic conversion of the polar polysulfides. With a high sulfur‐loading of 6 mg cm^?2 and low sulfur/electrolyte ratio of 10, the assembled batteries deliver an initial capacity of 5.04 mAh cm^?2 as well as capacity retention of 92% after 400 cycles. The metallic oxide composite NiCo₂O₄@rGO/PP separator with low Li‐ion diffusion energy barrier opens up the opportunity for lithium–sulfur batteries to achieve long‐cycle, cost‐effective operation toward wide applications in electric vehicles and electronic devices.     

A Layered‐Nanospace‐Confinement Strategy for the Synthesis of Two‐Dimensional Porous Carbon Nanosheets for High‐Rate Performance Supercapacitors

A general approach is developed for the synthesis of 2D porous carbon nanosheets (PCNS) from bio‐sources derived carbon precursors (gelatin) by an integrated procedure of intercalation, pyrolysis, and activation. Montmorillonite with layered nanospace is used as a nanotemplate or nanoreactor to confine and modulate the transformation of gelatin, further leading to the formation of 2D nanosheet‐shaped carbon materials. The as‐made 2D PCNS exhibits a significantly improved rate performance, with a high specific capacitance of 246 F g^?1 and capacitance retention of 82% at 100 A g^?1, being nearly twice that of microsized activated carbon particulates directly from gelatin (131 F g^?1, 44%). The shortened ion transport distance in the nanoscaled dimension and modulated porous structure is responsible for such an enhanced superior rate capability. More importantly, the present strategy can be extended to other bio‐sources to create 2D PCNS as electrode materials with high‐rate performance. This will also provide a potential strategy for configuring 2D nanostructured carbon electrode materials with a short ion transport distance for supercapacitors and other carbon‐related energy storage and conversion devices.     

A Lithium Oxythioborosilicate Solid Electrolyte Glass with Superionic Conductivity

As potential next‐generation energy storage devices, solid‐state lithium batteries require highly functional solid state electrolytes. Recent research is primarily focused on crystalline materials, while amorphous materials offer advantages by eliminating problematic grain boundaries that can limit ion transport and trigger dendritic growth at the Li anode. However, simultaneously achieving high conductivity and stability in glasses is a challenge. New quaternary superionic lithium oxythioborate glasses are reported that exhibit high ion conductivity up to 2 mS cm^?1 despite relatively high oxygen: sulfur ratios of more than 1:2, that exhibit greatly reduced H₂S evolution upon exposure to air compared to Li₇P₃S₁₁. These monolithic glasses are prepared from vitreous melts without ball‐milling and exhibit no discernable XRD pattern. Solid‐state NMR studies elucidate the structural entities that comprise the local glass structure which dictates fast ion conduction. Stripping/plating onto lithium metal results in very low polarization at a current density of 0.1 mA cm^?2 over repeated cycling. Evaluation of the optimal glass composition as an electrolyte in an all‐solid‐state battery shows it exhibits excellent cycling stability and maintains near theoretical capacity for over 130 cycles at room temperature with Coulombic efficiency close to 99.9%, opening up new avenues of exploration for these quaternary compositions.     

A Calcium‐Ion Hybrid Energy Storage Device with High Capacity and Long Cycling Life under Room Temperature

Ca‐ion based devices are promising candidates for next‐generation energy storage with high performance and low cost, thanks to its multielectrons, superior kinetics, as well as abundance (2500 times lithium). Because of the lack of an appropriate combination of suitable electrode materials and electrolytes, it is unsuccessful to attain a satisfactory performance on complete Ca‐ion energy storage devices. Here, the multiion reaction strategy is defined to construct a complete Ca‐ion energy storage device and a capacitor–battery hybrid mechanism is deliberately adopted. Profiting from the elaborate design, it exhibits a high reversible capacity of 92 mAh g^?1, unmatchable rate capability, and a high capacity retention of 84% over 1000 cycles under room temperature, which is the best performance of reported Ca‐based energy storage devices.