In Situ Formation of Co9S8 Quantum Dots in MOF‐Derived Ternary Metal Layered Double Hydroxide Nanoarrays for High‐Performance Hybrid Supercapacitors

Layered double hydroxides (LDHs) are promising cathode materials for supercapacitors because of the enhanced flow efficiency of ions in the interlayers. However, the limited active sites and monotonous metal species further hinder the improvement of the capacity performance. Herein, cobalt sulfide quantum dots (Co₉S₈‐QDs) are effectively created and embedded within the interlayer of metal‐organic‐frameworks‐derived ternary metal LDH nanosheets based on in situ selective vulcanization of Co on carbon fibers. The hybrid CF@NiCoZn‐LDH/Co₉S₈‐QD retains the lamellar structure of the ternary metal LDH very well, inheriting low transfer impedance of interlayer ions. Significantly, the selectively generated Co₉S₈‐QDs expose more abundant active sites, effectively improving the electrochemical properties, such as capacitive performance, electronic conductivity, and cycling stability. Due to the synergistic relationship, the hybrid material delivers an ultrahigh electrochemical capacity of 350.6 mAh g^?1 (2504 F g^?1) at 1 A g^?1. Furthermore, hybrid supercapacitors fabricated with CF@NiCoZn‐LDH/Co₉S₈‐QD and carbon nanosheets modified by single‐walled carbon nanotubes display an outstanding energy density of 56.4 Wh kg^?1 at a power density of 875 W kg^?1, with an excellent capacity retention of 95.3% after 8000 charge–discharge cycles. Therefore, constructing hybrid electrode materials by in situ‐created QDs in multimetallic LDHs is promising.     

Nanostructured Ternary Electrodes for Energy‐Storage Applications

A three‐component, flexible electrode is developed for supercapacitors over graphitized carbon fabric, utilizing γ‐MnO₂ nanoflowers anchored onto carbon nanotubes (γ‐MnO₂/CNT) as spacers for graphene nanosheets (GNs). The three‐component, composite electrode doubles the specific capacitance with respect to GN‐only electrodes, giving the highest‐reported specific capacitance (308 F g^?1) for symmetric supercapacitors containing MnO₂ and GNs using a two‐electrode configuration, at a scan rate of 20 mV s^?1. A maximum energy density of 43 W h kg^?1 is obtained for our symmetric supercapacitors at a constant discharge‐current density of 2.5 A g^?1 using GN–(γ‐MnO₂/CNT)‐nanocomposite electrodes. The fabricated supercapacitor device exhibits an excellent cycle life by retaining ≈90% of the initial specific capacitance after 5000 cycles.     

Supported Ionic Liquid Gel Membrane Electrolytes for Flexible Supercapacitors

In this work, a novel and easy‐to‐use methodology is developed to prepare supported ionic liquid gel membranes (SILGMs) by incorporating ionogels into commercial porous supports, to use as both electrolytes and separators for supercapacitors. Macroscopic sol–gel transition temperature, Fourier transform infrared spectra, and thermal behaviors of the ionogels are systematically investigated. Ionic conductivities of the ionogels and SILGMs are measured from 25 to 100 °C. The ionic conductivities of the ionogels are lower by one order of magnitude once they are incorporated into the supports. Nonetheless, the ionic conductivity of the SILGMs has reached the practical application level required for energy storage and conversion devices. Furthermore, the stability and flexibility of SILGMs are investigated as flexible electrolytes for supercapacitor devices (see Video in the Supporting Information). Charge–discharge cycling of symmetric supercapacitors based on the SILGMs reveal specific capacitance as high as 153 F g⁻¹ at 0.1 A g⁻¹, and remain at 101 F g⁻¹ at 10 A g⁻¹. The capacitance retention after 10 000 charge–discharge cycles at 5.0 A g⁻¹ is as high as 97%, demonstrating excellent cycle stability of the device. The studies suggest that SILGMs are promising candidates for stable, high performance, and flexible energy storage and conversion devices that could be made by high volume roll‐to‐roll processing.     

Interfacial Charge Field in Hierarchical Yolk–Shell Nanocapsule Enables Efficient Immobilization and Catalysis of Polysulfides Conversion

Inhibiting the shuttle effect of lithium polysulfides and accelerating their conversion kinetics are crucial for the development of high‐performance lithium–sulfur (Li–S) batteries. Herein, a modified template method is proposed to synthesize the robust yolk–shell sulfur host that is constructed by enveloping dispersive Fe₂O₃ nanoparticles within Mn₃O₄ nanosheet‐grafted hollow N‐doped porous carbon capsules (Fe₂O₃@N‐PC/Mn₃O₄‐S). When applied as a cathode for Li–S batteries, the as‐prepared Fe₂O₃@N‐PC/Mn₃O₄‐S can deliver capacities as high as 1122 mAh g^?1 after 200 cycles at 0.5 C and 639 mAh g^?1 after 1500 cycles at 10 C, respectively. Remarkably, even as the areal sulfur loading is increased to 5.1 mg cm^?2, the cathode can still maintain a high areal specific capacity of 5.08 mAh cm^?2 with a fading rate of only 0.076% per cycle over 100 cycles at 0.1 C. By a further combination analysis of electron holography and electron energy loss spectroscopy, the outstanding performance is revealed to be mainly traced to the oxygen‐vacancy‐induced interfacial charge field, which immobilizes and catalyzes the conversion of lithium polysulfides, assuring low polarization, fleet redox reaction kinetics, and sufficient utilization of sulfur. These new findings may shed light on the dependence of electrochemical performance on the heterostructure of sulfur hosts.     

A New P2‐Type Layered Oxide Cathode with Extremely High Energy Density for Sodium‐Ion Batteries

Herein, a new P2‐type layered oxide is proposed as an outstanding intercalation cathode material for high energy density sodium‐ion batteries (SIBs). On the basis of the stoichiometry of sodium and transition metals, the P2‐type Na_0.55[Ni_0.1Fe_0.1Mn_0.8]O₂ cathode is synthesized without impurities phase by partially substituting Ni and Fe into the Mn sites. The partial substitution results in a smoothing of the electrochemical charge/discharge profiles and thus greatly improves the battery performance. The P2‐type Na_0.55[Ni_0.1Fe_0.1Mn_0.8]O₂ cathode delivers an extremely high discharge capacity of 221.5 mAh g^?1 with a high average potential of ≈2.9 V (vs Na/Na⁺) for SIBs. In addition, the fast Na‐ion transport in the P2‐type Na_0.55[Ni_0.1Fe_0.1Mn_0.8]O₂ cathode structure enables good power capability with an extremely high current density of 2400 mA g^?1 (full charge/discharge in 12 min) and long‐term cycling stability with ≈80% capacity retention after 500 cycles at 600 mA g^?1. A combination of electrochemical profiles, in operando synchrotron X‐ray diffraction analysis, and first‐principles calculations are used to understand the overall Na storage mechanism of P2‐type Na_0.55[Ni_0.1Fe_0.1Mn_0.8]O₂.     

Partial Nitridation‐Induced Electrochemistry Enhancement of Ternary Oxide Nanosheets for Fiber Energy Storage Device

Fiber‐based power sources are receiving interest in terms of application in wearable electronic devices. Herein, fiber‐shaped all‐solid‐state asymmetric energy storage devices are fabricated based on a partially nitridized NiCo₂O₄ hybrid nanostructures on graphite fibers (GFs). The surface nitridation leads to a 3D “pearled‐veil” network structure, in which Ni–Co–N nanospheres are mounted on NiCo₂O₄ nanosheets' electrode. It is demonstrated that the hybrid materials are more potent than the pure NiCo₂O₄ in energy storage applications due to a cooperative effect between the constituents. The Ni–Co–N segments augment the pristine oxide nanosheets by enhancing both capacity and rate performance (a specific capacity of 384.75 mAh g⁻¹ at 4 A g⁻¹, and a capacity retention of 86.5% as the current is increased to 20 A g⁻¹). The whole material system has a metallic conductivity that renders high‐rate charge and discharge, and an extremely soft feature, so that it can wrap around arbitrary‐shaped holders. All‐solid‐state asymmetric device is fabricated using Ni–Co–N/NiCo₂O₄/GFs and carbon nanotubes/GFs as the electrodes. The flexible device delivers outstanding performance compared to most oxide‐based full devices. These structured hybrid materials may find applications in miniaturized foldable energy devices.     

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.     

A Flexible and Ultrahigh Energy Density Capacitor via Enhancing Surface/Interface of Carbon Cloth Supported Colloids

Pseudocapacitors are now reaching the energy density limits set by the surface redox reaction of their electrode materials, requiring new cation paradigms for a fast cation Faradaic reaction with high capacitance. In this work, a flexible and ultrahigh energy density capacitor is reported via enhancing surface/interface of active colloids and supported carbon cloth. A flexible asymmetrical capacitor assembled with Ni²⁺ colloidal cathode and Fe³⁺ colloidal anode displays a high energy density of 353 W h kg^?1 at the power density of 2250 W kg^?1, outperforming recent reported pseudocapacitors, and shows superior cycling stability after 10 000 charge–discharge cycles at current density of 30 A g^?1. This work demonstrates that the optimized surface/interface of carbon cloth and colloids can lead to the enhancement of both stability and activity of colloidal electrode.     

A High‐Energy Density Asymmetric Supercapacitor Based on Fe2O3 Nanoneedle Arrays and NiCo2O4/Ni(OH)2 Hybrid Nanosheet Arrays Grown on SiC Nanowire Networks as Free‐Standing Advanced Electrodes

In this paper, a novel freestanding core‐branch negative and positive electrode material through integrating trim aligned Fe₂O₃ nanoneedle arrays (Fe₂O₃ NNAs) is first proposed with typical mesoporous structures and NiCo₂O₄/Ni(OH)₂ hybrid nanosheet arrays (NiCo₂O₄/Ni(OH)₂ HNAs) on SiC nanowire (SiC NW) skeletons with outstanding resistance to oxidation and corrosion, good conductivity, and large‐specific surface area. The original built SiC NWs@Fe₂O₃ NNAs is validated to be a highly capacitive negative electrode (721 F g^?1 at 2 A g^?1, i.e., 1 F cm^?2 at 2.8 mA cm^?2), matching well with the similarly constructed SiC NWs@NiCo₂O₄/Ni(OH)₂ HNAs positive electrode (2580 F g^?1 at 4 A g^?1, i.e., 3.12 F cm^?2 at 4.8 mA cm^?2). Contributed by the uniquely engineered electrodes, a high‐performance asymmetric supercapacitor (ASC) is developed, which can exhibit a maximum energy density of 103 W h kg^?1 at a power density of 3.5 kW kg^?1, even when charging the device within 6.5 s, the energy density can still maintain as high as 45 W h kg^?1 at 26.1 kW kg^?1, and the ASC manifests long cycling lifespan with 86.6% capacitance retention even after 5000 cycles. This pioneering work not only offers an attractive strategy for rational construction of high‐performance SiC NW‐based nanostructured electrodes materials, but also provides a fresh route for manufacturing next‐generation high‐energy storage and conversion systems.     

Spatial Charge Storage within Honeycomb‐Carbon Frameworks for Ultrafast Supercapacitors with High Energy and Power Densities

Carbon‐based supercapacitors store charge through the adsorption of electrolyte ions onto the carbon surface. Therefore, it would be more attractive for the enhanced charge storage if the locations for storing charge can be extended from carbon surface to space. Here, a novel spatial charge storage mechanism based on counterion effect from Fe(CN)₆^3? ions bridged by oxygen groups and confined into honeycomb‐carbon frameworks is presented, which can provide additionally spatial charge storage for electrical double‐layer capacitances in a negative potential region and pseudocapacitances from Fe(CN)₆^3?/Fe(CN)₆^4? in a positive potential region. More importantly, an ultrafast supercapacitor based on this novelty carbon can be charged/discharged within 0.7 s to deliver both high specific energy of 15 W h kg^?1 and ultrahigh specific power of 79.1 kW kg^?1 in 1 m Na₂SO₄ electrolyte, much higher than those of previously reported asymmetric supercapacitors in aqueous electrolytes, as well as excellent cycling stability. These features suggest a new generation of ultrafast asymmetric supercapacitors as novel high‐performance energy storage devices.     

Mn‐Rich P′2‐Na0.67[Ni0.1Fe0.1Mn0.8]O2 as High‐Energy‐Density and Long‐Life Cathode Material for Sodium‐Ion Batteries

Herein, P′2‐type Na_0.67[Ni_0.1Fe_0.1Mn_0.8]O₂ is introduced as a promising new cathode material for sodium‐ion batteries (SIBs) that exhibits remarkable structural stability during repetitive Na⁺ de/intercalation. The O? Ni? O? Mn? O? Fe? O bond in the octahedra of transition‐metal layers is used to suppress the elongation of the Mn? O bond and to improve the electrochemical activity, leading to the highly reversible Na storage mechanism. A high discharge capacity of ≈220 mAh g^?1 (≈605 Wh kg^?1) is delivered at 0.05 C (13 mAg^?1) with a high reversible capacity of ≈140 mAh g^?1 at 3 C and excellent capacity retention of 80% over 200 cycles. This performance is associated with the reversible P′2–OP4 phase transition and small volume change upon charge and discharge (≈3%). The nature of the sodium storage mechanism in a full cell paired with a hard carbon anode reveals an unexpectedly high energy density of ≈542 Wh kg^?1 at 0.2 C and good capacity retention of ≈81% for 500 cycles at 1 C (260 mAg^?1).     

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.     

Nature of FeSe2/N‐C Anode for High Performance Potassium Ion Hybrid Capacitor

Potassium ion hybrid capacitors have great potential for large‐scale energy devices, because of the high power density and low cost. However, their practical applications are hindered by their low energy density, as well as electrolyte decomposition and collector corrosion at high potential in potassium bis(fluoro‐sulfonyl)imide‐based electrolyte. Therefore, anode materials with high capacity, a suitable voltage platform, and stability become a key factor. Here, N‐doping carbon‐coated FeSe₂ clusters are demonstrated as the anode material for a hybrid capacitor, delivering a reversible capacity of 295 mAh g^?1 at 100 mA g^?1 over 100 cycles and a high rate capability of 158 mAh g^?1 at 2000 mA g^?1 over 2000 cycles. Meanwhile, through density functional theory calculations, in situ X‐ray diffraction, and ex situ transmission electron microscopy, the evolution of FeSe₂ to Fe₃Se₄ for the electrochemical reaction mechanism is successfully revealed. The battery‐supercapacitor hybrid using commercial activated carbon as the cathode and FeSe₂/N‐C as the anode is obtained. It delivers a high energy density of 230 Wh kg^?1 and a power density of 920 W kg^?1 (the energy density and power density are calculated based on the total mass of active materials in the anode and cathode).     

Heteroatom‐Doped Mesoporous Hollow Carbon Spheres for Fast Sodium Storage with an Ultralong Cycle Life

Carbon materials have attracted significant attention as anode materials for sodium ion batteries (SIBs). Developing a carbon anode with long‐term cycling stability under ultrahigh rate is essential for practical application of SIBs in energy storage systems. Herein, sulfur and nitrogen codoped mesoporous hollow carbon spheres are developed, exhibiting high rate performance of 144 mA h g^?1 at 20 A g^?1, and excellent cycling durability under ultrahigh current density. Interestingly, during 7000 cycles at a current density of 20 A g^?1, the capacity of the electrode gradually increases to 180 mA h g^?1. The mechanisms for the superior electrochemical performance and capacity improvement of the cells are studied by electrochemical tests, ex situ transmission electron microscopy, X‐ray diffraction, X‐ray photoelectron spectroscopy, and Raman analysis of fresh and cycled electrodes. The unique and robust structure of the material can enhance transport kinetics of electrons and sodium ions, and maintain fast sodium storage from the capacitive process under high rate. The self‐rearrangement of the carbon structure, induced by continuous discharge and charge, lead to the capacity improvement with cycles. These results demonstrate a new avenue to design advanced anode materials for SIBs.     

Hierarchical Multicomponent Electrode with Interlaced Ni(OH)2 Nanoflakes Wrapped Zinc Cobalt Sulfide Nanotube Arrays for Sustainable High‐Performance Supercapacitors

High energy density, fast recharging ability, and sustained cycle life are the primary requisite of supercapacitors (SCs); these necessities can be fulfilled by engineering a smart current collector with hierarchical combination of different active materials. This study reports a multicomponent design of hierarchical zinc cobalt sulfide (ZCS) hollow nanotube arrays wrapped with interlaced ultrathin Ni(OH)₂ nanoflakes for high‐performance electrodes. The ZCS exhibits a unique pentagonal cross‐section and a rough surface that facilitates the deposition of Ni(OH)₂ nanoflakes with a thickness of 7.5 nm. The ZCS/Ni(OH)₂ hierarchical electrode exhibits a high specific capacitance of 2156 F g^?1 and excellent cyclic stability with 94% retention over 3000 cycles. This is attributed to enhanced redox reactions, the direct growth of arrays on 3D porous foam acting as a “superhighway” for electron transport, and the increased availability of electrochemical active sites provided by the ultrathin Ni(OH)₂ flakes that also sustain the stability of the electrode by sacrificing themselves during long charge/discharge cycles. Symmetric SCs are assembled to achieve high energy density of 74.93 W h kg^?1 and exhibit superior cyclic stability of 78% retention with 81% coulombic efficiency over 10 000 cycles.     

Pseudocapacitive Charge Storage in Thick Composite MoS2 Nanocrystal‐Based Electrodes

A synthesis methodology is demonstrated to produce MoS₂ nanoparticles with an expanded atomic lamellar structure that are ideal for Faradaic‐based capacitive charge storage. While much of the work on MoS₂ focuses on the high capacity conversion reaction, that process is prone to poor reversibility. The pseudocapacitive intercalation‐based charge storage reaction of MoS₂ is investigated, which is extremely fast and highly reversible. A major challenge in the field of pseudocapacitive‐based energy storage is the development of thick electrodes from nanostructured materials that can sustain the fast inherent kinetics of the active nanocrystalline material. Here a composite electrode comprised of a poly(acrylic acid) binder, carbon fibers, and carbon black additives is utilized. These electrodes deliver a specific capacity of 90 mAh g^?1 in less than 20 s and can be cycled 3000 times while retaining over 80% of the original capacity. Quantitative kinetic analysis indicates that over 80% of the charge storage in these MoS₂ nanocrystals is pseudocapacitive. Asymmetric full cell devices utilizing a MoS₂ nanocrystal‐based electrode and an activated carbon electrode achieve a maximum power density of 5.3 kW kg^?1 (with 6 Wh kg^?1 energy density) and a maximum energy density of 37 Wh kg^?1 (with 74 W kg^?1power density).     

Molecular‐Level Design of Pyrrhotite Electrocatalyst Decorated Hierarchical Porous Carbon Spheres as Nanoreactors for Lithium–Sulfur Batteries

Lithium–sulfur batteries (LSBs) are a class of new‐generation rechargeable high‐energy‐density batteries. However, the persisting issue of lithium polysulfides (LiPs) dissolution and the shuttling effect that impedes the efficiency of LSBs are challenging to resolve. Herein a general synthesis of highly dispersed pyrrhotite Fe_1?xS nanoparticles embedded in hierarchically porous nitrogen‐doped carbon spheres (Fe_1?xS‐NC) is proposed. Fe_1?xS‐NC has a high specific surface area (627 m² g^?1), large pore volume (0.41 cm³ g^?1), and enhanced adsorption and electrocatalytic transition toward LiPs. Furthermore, in situ generated large mesoporous pores within carbon spheres can accommodate high sulfur loading of up to 75%, and sustain volume variations during charge/discharge cycles as well as improve ionic/mass transfer. The exceptional adsorption properties of Fe_1?xS‐NC for LiPs are predicted theoretically and confirmed experimentally. Subsequently, the electrocatalytic activity of Fe_1?xS‐NC is thoroughly verified. The results confirm Fe_1?xS‐NC is a highly efficient nanoreactor for sulfur loading. Consequently, the Fe_1?xS‐NC nanoreactor performs extremely well as a cathodic material for LSBs, exhibiting a high initial capacity of 1070 mAh g^?1 with nearly no capacity loss after 200 cycles at 0.5 C. Furthermore, the resulting LSBs display remarkably enhanced rate capability and cyclability even at a high sulfur loading of 8.14 mg cm^?2.     

A Novel High‐Energy Hybrid Supercapacitor with an Anatase TiO2–Reduced Graphene Oxide Anode and an Activated Carbon Cathode

A hybrid supercapacitor with high energy and power densities is reported. It comprises a composite anode of anatase TiO₂ and reduced graphene oxide and an activated carbon cathode in a non‐aqueous electrolyte. While intercalation compounds can provide high energy typically at the expense of power, the anatase TiO₂ nanoparticles are able to sustain both high energy and power in the hybrid supercapacitor. At a voltage range from 1.0 to 3.0 V, 42 W h kg^?1 of energy is achieved at 800 W kg^?1. Even at a 4‐s charge/discharge rate, an energy density as high as 8.9 W h kg^?1 can be retained. The high energy and power of this hybrid supercapacitor bridges the gap between conventional batteries with high energy and low power and supercapacitors with high power and low energy.     

Ultrafast All‐Solid‐State Coaxial Asymmetric Fiber Supercapacitors with a High Volumetric Energy Density

Fiber‐supercapacitors (FSCs) are promising energy storage devices that can complement or even replace microbatteries in miniaturized portable and wearable electronics. Currently, a major challenge for FSCs is achieving ultrahigh volumetric energy and power densities simultaneously, especially when the charge/discharge rates exceed 1 V s^?1. Herein, an Au‐nanoparticle‐doped‐MnO_x@CoNi‐alloy@carbon‐nanotube (Au–MnO_x@CoNi@CNT) core/shell nanocomposite fiber electrode is designed, aiming to boost its charge/discharge rate by taking advantage of the superconductive CoNi alloy network and the greatly enhanced conductivity of the Au doped MnO_x active materials. An all‐solid‐state coaxial asymmetric FSC (CAFSC) prototype device made by wrapping this fiber with a holey graphene paper (HGP) exhibits excellent performance at rates up to 10 V s^?1, which is the highest charge rate demonstrated so far for FSCs based on pseudocapacitive materials. Furthermore, our fully packaged CAFSC delivers a volumetric energy density of ≈15.1 mW h cm^?3, while simultaneously maintaining a high power density of 7.28 W cm^?3 as well as a long cycle life (90% retention after 10 000 cycles). This value is the highest among all reported FSCs, even better than that of a typical 4 V/500 µA h thin‐film lithium battery.     

High‐Energy Density Li‐Ion Capacitor with Layered SnS2/Reduced Graphene Oxide Anode and BCN Nanosheet Cathode

Lithium‐ion capacitors (LICs) with capacitor‐type cathodes and battery‐type anodes are considered a promising next‐generation advanced energy storages system that meet the requirements of high energy density and power density. However, the mismatch of charge‐storage capacity and electrode kinetics between positive and negative electrodes remains a challenge. Herein, layered SnS₂/reduced graphene oxide (RGO) nanocomposites are developed for negative electrodes and a 2D B/N codoped carbon (BCN) nanosheet is designed for the positive electrode. The SnS₂/RGO derived from SnS₂‐bonded RGO of high conductivity exhibits a capacity of 1198 mA h g^?1 at 100 mA g^?1. Boron and nitrogen atoms in BCN are found to promote adsorption of anions, which enhance the pseudocapacitive contribution as well as expanding the voltage of LICs. A quantitative kinetics analysis indicates that the SnS₂/RGO electrodes with a dominating capacitive mechanism and a diminished intercalation process, benefit the kinetic balance between the two electrodes. With this particular structure, the LIC is able to operate at the highest operating voltage for these devices recorded to date (4.5 V), exhibiting an energy density of 149.5 W h kg^?1, a power density of 35 kW kg^?1, and a capacity retention ratio of 90% after 10 000 cycles.