One‐Step In Situ Formation of N‐doped Carbon Nanosheet 3D Porous Networks/TiO2 Hybrids with Ultrafast Sodium Storage

In spite of the satisfactory advancement in preparing TiO₂‐based hybrid structures, most methods rely on additional template‐based multistep reactions for engineering the given structure. Herein, a unique self‐template and in situ recrystallization strategy is explored to synthesize uniform flowerlike multicompositional structures of nitrogen‐doped porous carbon nanosheet networks immobilizing TiO₂ nanoparticles (TiO₂∩NPCSs) via a self‐prepared single precursor and subsequent thermal treatment. Depending on the unique coordination ability of 2,4‐dihydroxybenzoic acid with metal ions under alkaline conditions to form a flowerlike network, a self‐produced single precursor can be achieved. Careful investigations of the self‐prepared precursor reveal a high practicability of the present synthetic scheme. Because of the novel structural and compositional features, these TiO₂∩NCSN flowers indicate superior sodium storage properties when evaluated as anodes for sodium‐ion batteries. Impressively, the TiO₂∩NCSN flowers deliver high reversible capacities of 152 mAh g^?1 at 2C for 3000 cycles and 114 mAh g^?1 at 10C for 10000 cycles, as well as an ultrahigh rate capability up to 50C with a capacity of 101 mAh g^?1. The facile method could stimulate further capability in precise construction of complex architectures with complicated compositions for different device applications.     

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.     

Extraordinary Performance of Carbon‐Coated Anatase TiO2 as Sodium‐Ion Anode

The synthesis of in situ polymer‐functionalized anatase TiO₂ particles using an anchoring block copolymer with hydroxamate as coordinating species is reported, which yields nanoparticles (≈11 nm) in multigram scale. Thermal annealing converts the polymer brushes into a uniform and homogeneous carbon coating as proven by high resolution transmission electron microscopy and Raman spectroscopy. The strong impact of particle size as well as carbon coating on the electrochemical performance of anatase TiO₂ is demonstrated. Downsizing the particles leads to higher reversible uptake/release of sodium cations per formula unit TiO₂ (e.g., 0.72 eq. Na⁺ (11 nm) vs only 0.56 eq. Na⁺ (40 nm)) while the carbon coating improves rate performance. The combination of small particle size and homogeneous carbon coating allows for the excellent electrochemical performance of anatase TiO₂ at high (134 mAh g^?1 at 10 C (3.35 A g^?1)) and low (≈227 mAh g^?1 at 0.1 C) current rates, high cycling stability (full capacity retention between 2nd and 300th cycle at 1 C) and improved coulombic efficiency (≈99.8%).     

Sulfur‐Impregnated,Sandwich‐Type,Hybrid Carbon Nanosheets with Hierarchical Porous Structure for High‐Performance Lithium‐Sulfur Batteries

Sandwich‐type hybrid carbon nanosheets (SCNMM) consisting of graphene and micro/mesoporous carbon layer are fabricated via a double template method using graphene oxide as the shape‐directing agent and SiO₂ nanoparticles as the mesoporous guide. The polypyrrole synthesized in situ on the graphene oxide sheets is used as a carbon precursor. The micro/mesoporous strcutures of the SCNMM are created by a carbonization process followed by HF solution etching and KOH treatment. Sulfur is impregnated into the hybrid carbon nanosheets to generate S@SCNMM composites for the cathode materials in Li‐S secondary batteries. The microstructures and electrochemical performance of the as‐prepared samples are investigated in detail. The hybrid carbon nanosheets, which have a thickness of about 10–25 nm, high surface area of 1588 m² g^?1, and broad pore size distribution of 0.8–6.0 nm, are highly interconnected to form a 3D hierarchical structure. The S@SCNMM sample with the sulfur content of 74 wt% exhibits excellent electrochemical performance, including large reversible capacity, good cycling stability and coulombic efficiency, and good rate capability, which is believed to be due to the structure of hybrid carbon materials with hierarchical porous structure, which have large specific surface area and pore volume.     

Lithiophilic CuO Nanoflowers on Ti‐Mesh Inducing Lithium Lateral Plating Enabling Stable Lithium‐Metal Anodes with Ultrahigh Rates and Ultralong Cycle Life

Lithium (Li) metal anodes are promising candidates for high‐energy‐density batteries. However, uncontrollable dendritic plating behavior and infinite volume expansion are hindering their practical applications. Herein, a novel CuO@Ti‐mesh (CTM) is prepared by microwave‐assisted reactions, followed by pressing on Li wafers, leading to Li/CuO@Ti‐mesh (LCTM) composite anodes. The lithiophilic CuO nanoflowers on Ti‐mesh provides evenly distributed nucleation sites, inducing uniform Li‐ion lateral plating, which can effectively inhibit the growth of Li dendrites and volume expansion during cycling. The as‐prepared LCTM composite anode exhibits high Coulombic efficiency (CE) of 94.2% at 10 mA cm^‐2 over 90 cycles. Meanwhile, the LCTM anode shows a low overpotential of 50 mV at 10 mA cm^‐2 over 16 000 cycles and a low overpotential of 90 and 250 mV even at ultrahigh current densities of 20 and 40 mA cm^‐2. When paired with Li₄Ti₅O₁₂ (LTO), it enhances the capacity retention of LTO/Li wafer full cells by about two times from 36.6% to 73.0% and 42.0% to 80.0% at 5C and 10C with long‐term cycling. It is hoped that this LCTM anode with ultrahigh rates and ultralong cycle life may put Li‐metal anode forward to practical applications, such as in Li–S, Li‐air batteries, etc.     

High Capacity All‐Solid‐State Lithium Batteries Enabled by Pyrite‐Sulfur Composites

As the theoretical limit of intercalation material‐based lithium‐ion batteries is approached, alternative chemistries based on conversion reactions are presently considered. The conversion of sulfur is particularly appealing as it is associated with a theoretical gravimetric energy density up to 2510 Wh kg^?1. In this paper, three different carbon‐iron disulfide‐sulfur (C‐FeS₂‐S) composites are proposed as alternative positive electrode materials for all‐solid‐state lithium‐sulfur batteries. These are synthesized through a facile, low‐cost, single‐step ball‐milling procedure. It is found that the crystalline structure (evaluated by X‐ray diffraction) and the morphology of the composites (evaluated by scanning electron microscopy) are greatly influenced by the FeS₂:S ratio. Li/LiI‐Li₃PS₄/C‐FeS₂‐S solid‐state cells are tested under galvanostatic conditions, while differential capacity plots are used to discuss the peculiar electrochemical features of these novel materials. These cells deliver capacities as high as 1200 mAh g_(FeS2+S)^?1 at the intermediate loading of 1 mg cm^?2 (1.2 mAh cm^?2), and up to 3.55 mAh cm^?2 for active material loadings as high as 5 mg cm^?2 at 20 °C. Such an excellent performance, rarely reported for (sulfur/metal sulfide)‐based, all solid‐state cells, makes these composites highly promising for real application where high positive electrode loadings are required.     

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.     

Covalent Encapsulation of Sulfur in a MOF‐Derived S,N‐Doped Porous Carbon Host Realized via the Vapor‐Infiltration Method Results in Enhanced Sodium–Sulfur Battery Performance

Practical applications of room temperature sodium–sulfur batteries are still inhibited by the poor conductivity and slow reaction kinetics of sulfur, and dissolution of intermediate polysulfides in the commonly used electrolytes. To address these issues, starting from a novel 3D Zn‐based metal–organic framework with 2,5‐thiophenedicarboxylic acid and 1,4‐bis(pyrid‐4‐yl) benzene as ligands, a S, N‐doped porous carbon host with 3D tubular holes for sulfur storage is fabricated. In contrast to the commonly used melt‐diffusion method to confine sulfur physically, a vapor‐infiltration method is utilized to achieve sulfur/carbon composite with covalent bonds, which can join electrochemical reaction without low voltage activation. A polydopamine derived N‐doped carbon layer is further coated on the composite to confine the high‐temperature‐induced gas‐phase sulfur inside the host. S and N dopants increase the polarity of the carbon host to restrict diffusion of sulfur, and its 3D porous structure provides a large storage area for sulfur. As a result, the obtained composite shows outstanding electrochemical performance with 467 mAh g^?1 (1262 mAh g^?1_(sulfur)) at 0.1 A g^?1, 270 mAh g^?1 (730 mAh g^?1_(sulfur)) after 1000 cycles at 1 A g^?1 and 201 mAh g^?1 (543 mAh g^?1_(sulfur)) at 5.0 A g^?1.     

Hierarchical Carbon Decorated Li3V2(PO4)3 as a Bicontinuous Cathode with High‐Rate Capability and Broad Temperature Adaptability

Developing rechargeable lithium ion batteries with fast charge/discharge rate, high capacity and power, long lifespan, and broad temperature adaptability is still a significant challenge. In order to realize the fast and efficient transport of ions and electrons during the charging/discharging process, a 3D hierarchical carbon‐decorated Li₃V₂(PO₄)₃ is designed and synthesized with a nanoscale amorphous carbon coating and a microscale carbon network. The Brunauer–Emmett–Teller (BET) surface area is 65.4 m² g^?1 and the porosity allows for easy access of the electrolyte to the active material. A specific capacity of 121 mAh g^?1 (91% of the theoretical capacity) can be obtained at a rate up to 30 C. When cycled at a rate of 20 C, the capacity retention is 77% after 4000 cycles, corresponding to a capacity fading of 0.0065% per cycle. More importantly, the composite cathode shows excellent temperature adaptability. The specific discharge capacities can reach 130 mAh g^?1 at 20 C and 60 °C, and 106 mAh g^?1 at 5 C and –20 °C. The rate performance and broad temperature adaptability demonstrate that this hierarchical carbon‐decorated Li₃V₂(PO₄)₃ is one of the most attractive cathodes for practical applications.     

Ultrafine Copper Nanopalm Tree‐Like Framework Decorated with Iron Oxide for Li‐Ion Battery Anodes with Exceptional Rate Capability and Cycling Stability

Ultrafine copper nanopalm tree‐like frameworks conformally decorated with iron oxide (Cu NPF@Fe₂O₃) are prepared by a facile electrodeposition method utilizing bromine ions as unique anisotropic growth catalysts. The formation mechanism and control over Cu growth are comprehensively investigated under various conditions to provide a guideline for fabricating a Cu nanoarchitecture via electrochemical methods. The optimized Cu NPFs exhibit ultrathin (<90 nm) and elongated (2–50 µm) branches with well‐interconnected and entangled features, which result in highly desirable attributes such as a large specific surface area (≈6.97 m² g^?1), free transfer pathway for Li⁺, and high electrical conductivity. The structural advantages of Cu NPF@Fe₂O₃ enhance the electrochemical kinetics, providing large reactivity, fast Li⁺/electron transfer, and structural stability during cycling, that lead to superior electrochemical Li storage performance. The resulting Cu NPF@Fe₂O₃ demonstrates a high specific capacity (919.5 mAh g^–1 at 0.1 C), long‐term stability (801.1 mAh g^–1 at 2 C, ≈120% retention after 500 cycles), and outstanding rate capability (630 mAh g^–1 at 10 C).     

3D Hyperbranched Hollow Carbon Nanorod Architectures for High‐Performance Lithium‐Sulfur Batteries

Lithium‐sulfur batteries have been plagued for a long time by low Coulombic efficiency, fast capacity loss, and poor high rate performance. Here, the synthesis of 3D hyperbranched hollow carbon nanorod encapsulated sulfur nanocomposites as cathode materials for lithium‐sulfur batteries is reported. The sulfur nanocomposite cathodes deliver a high specific capacity of 1378 mAh g^‐1 at a 0.1C current rate and exhibit stable cycling performance. The as‐prepared sulfur nanocomposites also achieve excellent high rate capacities and cyclability, such as 990 mAh g^‐1 at 1C, 861 mAh g^‐1 at 5C, and 663 mAh g^‐1 at 10C, extending to more than 500 cycles. The superior electrochemical performance are ascribed to the unique 3D hyperbranched hollow carbon nanorod architectures and high length/radius aspect ratio of the carbon nanorods, which can effectively prevent the dissolution of polysulfides, decrease self‐discharge, and confine the volume expansion on cycling. High capacity, excellent high‐rate performance, and long cycle life render the as‐developed sulfur/carbon nanorod nanocomposites a promising cathode material for lithium‐sulfur batteries.     

Lithium‐Pretreated Hard Carbon as High‐Performance Sodium‐Ion Battery Anodes

Hard carbon (HC) is the state‐of‐the‐art anode material for sodium‐ion batteries (SIBs). However, its performance has been plagued by the limited initial Coulombic efficiency (ICE) and mediocre rate performance. Here, experimental and theoretical studies are combined to demonstrate the application of lithium‐pretreated HC (LPHC) as high‐performance anode materials for SIBs by manipulating the solid electrolyte interphase in tetraglyme (TEGDME)‐based electrolyte. The LPHC in TEGDME can 1) deliver > 92% ICE and ≈220 mAh g^?1 specific capacity, twice of the capacity (≈100 mAh g^?1) in carbonate electrolyte; 2) achieve > 85% capacity retention over 1000 cycles at 1000 mA g^?1 current density (4 C rate, 1 C = 250 mA g^?1) with a specific capacity of ≈150 mAh g^?1, ≈15 times of the capacity (10 mAh g^?1) in carbonate. The full cell of Na₃V₂(PO₄)₃‐LPHC in TEGDME demonstrated close to theoretical specific capacity of ≈98 mAh g^?1 based on Na₃V₂(PO₄)₃ cathode, ≈2.5 times of the value (≈40 mAh g^?1) with nontreated HC. This work provides new perception on the anode development for SIBs.     

High‐Performance Reversible Aqueous Zn‐Ion Battery Based on Porous MnOx Nanorods Coated by MOF‐Derived N‐Doped Carbon

Rechargeable aqueous zinc‐ion batteries (ZIBs) have been emerging as potential large‐scale energy storage devices due to their high energy density, low cost, high safety, and environmental friendliness. However, the commonly used cathode materials in ZIBs exhibit poor electrochemical performance, such as significant capacity fading during long‐term cycling and poor performance at high current rates, which significantly hinder the further development of ZIBs. Herein, a new and highly reversible Mn‐based cathode material with porous framework and N‐doping (MnO_x@N‐C) is prepared through a metal–organic framework template strategy. Benefiting from the unique porous structure, conductive carbon network, and the synergetic effect of Zn²⁺ and Mn²⁺ in electrolyte, the MnO_x@N‐C shows excellent cycling stability, good rate performance, and high reversibility for aqueous ZIBs. Specifically, it exhibits high capacity of 305 mAh g^?1 after 600 cycles at 500 mA g^?1 and maintains achievable capacity of 100 mAh g^?1 at a quite high rate of 2000 mA g^?1 with long‐term cycling of up to 1600 cycles, which are superior to most reported ZIB cathode materials. Furthermore, insight into the Zn‐storage mechanism in MnO_x@N‐C is systematically studied and discussed via multiple analytical methods. This study opens new opportunities for designing low‐cost and high‐performance rechargeable aqueous ZIBs.     

Frogspawn‐Coral‐Like Hollow Sodium Sulfide Nanostructured Cathode for High‐Rate Performance Sodium–Sulfur Batteries

Room‐temperature (RT) sodium–sulfur (Na–S) batteries are attractive cost‐effective platforms as the next‐generation energy storage systems by using all earth‐abundant resources as electrode materials. However, the slow kinetics of Na–S chemistry makes it hard to achieve high‐rate performance. Herein, a facile and scalable approach has been developed to synthesize hollow sodium sulfide (Na₂S) nanospheres embedded in a highly hierarchical and spongy conductive carbon matrix, forming an intriguing architecture similar to the morphology of frogspawn coral, which has shown great potential as a cathode for high‐rate performance RT Na–S batteries. The shortened Na‐ion diffusion pathway benefits from the hollow structures together with the fast electron transfer from the carbon matrix contributes to high electrochemical reactivity, leading to superior electrochemical performance at various current rates. At high current densities of 1.4 and 2.1 A g^?1, high initial discharge capacities of 980 and 790 mAh g^?1_sulfur can be achieved, respectively, with reversible capacities stabilized at 600 and 400 mAh g^?1_sulfur after 100 cycles. As a proof of concept, a Na‐metal‐free Na–S battery is demonstrated by pairing the hollow Na₂S cathode with tin‐based anode. This work provides guidance on rational materials design towards the success of RT high‐rate Na–S batteries.     

NiCo2O4 Nanofibers as Carbon‐Free Sulfur Immobilizer to Fabricate Sulfur‐Based Composite with High Volumetric Capacity for Lithium–Sulfur Battery

Both the energy density and cycle stability are still challenges for lithium–sulfur (Li–S) batteries in future practical applications. Usually, light‐weight and nonpolar carbon materials are used as the hosts of sulfur, however they struggle on the cycle stability and undermine the volumetric energy density of Li–S batteries. Here, heavy NiCo₂O₄ nanofibers as carbon‐free sulfur immobilizers are introduced to fabricate sulfur‐based composites. NiCo₂O₄ can accelerate the catalytic conversion kinetics of soluble intermediate polysulfides by strong chemical interaction, leading to a good cycle stability of sulfur cathodes. Specifically, the S/NiCo₂O₄ composite presents a high gravimetric capacity of 1125 mAh g^?1 at 0.1 C rate with the composite as active material, and a low fading rate of 0.039% per cycle over 1500 cycles at 1 C rate. In particular, the S/NiCo₂O₄ composite with the high tap density of 1.66 g cm^?3 delivers large volumetric capacity of 1867 mAh cm^?3, almost twice that of the conventional S/carbon composites.     

Superior Lithium Storage Capacity of α‐MnS Nanoparticles Embedded in S‐Doped Carbonaceous Mesoporous Frameworks

Herein, a Mn‐based metal–organic framework is used as a precursor to obtain well‐defined α‐MnS/S‐doped C microrod composites. Ultrasmall α‐MnS nanoparticles (3–5 nm) uniformly embedded in S‐doped carbonaceous mesoporous frameworks (α‐MnS/SCMFs) are obtained in a simple sulfidation reaction. As‐obtained α‐MnS/SCMFs shows outstanding lithium storage performance, with a specific capacity of 1383 mAh g^?1 in the 300th cycle or 1500 mAh g^?1 in the 120th cycle (at 200 mA g^?1) using copper or nickel foil as the current collector, respectively. The significant (pseudo)capacitive contribution and the stable composite structure of the electrodes result in impressive rate capabilities and outstanding long‐term cycling stability. Importantly, in situ X‐ray diffraction measurements studies on electrodes employing various metal foils/disks as current collector reveal the occurrence of the conversion reaction of CuS at (de)lithiation process when using copper foil as the current collector. This constitutes the first report of the reaction mechanism for α‐MnS, eventually forming metallic Mn and Li₂S. In situ dilatometry measurements demonstrate that the peculiar structure of α‐MnS/SCMFs effectively restrains the electrode volume variation upon repeated (dis)charge processes. Finally, α‐MnS/SCMFs electrodes present an impressive performance when coupled in a full cell with commercial LiMn_1/3Co_1/3Ni_1/3O₂ cathodes.     

Stabilization of Insoluble Discharge Products by Facile Aniline Modification for High Performance Li‐S Batteries

Continuous efforts have been made to attain high performance Li‐S batteries by preventing loss of soluble polysulfides, whereas issues related to insoluble discharge products, Li₂S₂ and Li₂S, have been underestimated. A facile and mild method, diazotization, that enables uniform functionalization on the surface of ordered mesoporous carbon (CMK‐3) with aniline functional groups while not deteriorating the original CMK‐3 microstructure is demonstrated. The aniline groups possess favorable interactions with insoluble discharge products. Thus, they homogeneously distribute the insoluble discharge products during cycling. The proposed materials exhibit outstanding electrochemical properties with regard to stability (920 mAh g^?1 at 0.2 C after 100 cycles) and rate capability (814 mAh g^?1 at 1 C) when evaluated as a cathode material for Li‐S batteries.     

Boosting Sodium Storage in TiF3/Carbon Core/Sheath Nanofibers through an Efficient Mixed‐Conducting Network

Sodium‐ion batteries (SIBs) are considered to be promising energy storage devices for large‐scale grid storage application due to the vast earth‐abundance and low cost of sodium‐containing precursors. Designing and fabricating a highly efficient anode is one of the keys to improve the electrochemical performance of SIBs. Recently, fluoride‐based materials are found to show an exceptional anode function with high theoretical specific capacity, based on open‐framework structure enabling Na insertion and also exhibiting improved safety. However, fluoride‐based materials suffer from sluggish kinetics and poor capacity retention essentially due to low electric conductivity. Here, an efficient mixed‐conducting network offering fast pathways is proposed to address these issues. This network relies on titanium fluoride?carbon (TiF₃?C) core/sheath nanofibers that are prepared via electrospinning. Such highly interconnected electrodes exhibit an enhanced and faster sodium storage performance. Carbon sheath nanofibers are key to an efficient ion‐ and electron‐conducting network that enable Na⁺/e^? transfer to reach the nanosized TiF₃. In addition, in‐situ‐converted Ti and NaF particles embedded in the carbon matrix allow high reversible interfacial storage. As a result, the TiF₃?C core/sheath electrode exhibits a high capacity of 161 mAh g^?1 at a high current density of 1000 mA g^?1 over 2000 cycles.     

Sodium Sulfide Cathodes Superseding Hard Carbon Pre‐sodiation for the Production and Operation of Sodium–Sulfur Batteries at Room Temperature

This study demonstrates for the first time a room temperature sodium–sulfur (RT Na–S) full cell assembled based on a pristine hard carbon (HC) anode combined with a nanostructured Na₂S/C cathode. The development of cells without the demanding, time‐consuming and costly pre‐sodiation of the HC anode is essential for the realization of practically relevant RT Na–S prototype batteries. New approaches for Na₂S/C cathode fabrication employing carbothermal reduction of Na₂SO₄ at varying temperatures (660 to 1060 °C) are presented. Initial evaluation of the resulting cathodes in a dedicated cell setup reveals 36 stable cycles and a capacity of 740 mAh g_S^?1, which correlates to ≈85% of the maximum value known from literature on Na₂S‐based cells. The Na₂S/C cathode with the highest capacity utilization is implemented into a full cell concept applying a pristine HC anode. Various full cell electrolyte compositions with fluoroethylene carbonate (FEC) additive have been combined with a special charging procedure during the first cycle supporting in situ solid electrolyte interphase (SEI) formation on the HC anode to obtain increased cycling stability and cathode utilization. The best performing cell setup has delivered a total of 350 mAh g_S^?1, representing the first functional full cell based on a Na₂S/C cathode and a pristine HC anode today.     

A Novel Graphene Oxide Wrapped Na2Fe2(SO4)3/C Cathode Composite for Long Life and High Energy Density Sodium‐Ion Batteries

The cathode materials in the Na‐ion battery system are always the key issue obstructing wider application because of their relatively low specific capacity and low energy density. A graphene oxide (GO) wrapped composite, Na₂Fe₂(SO₄)₃@C@GO, is fabricated via a simple freeze‐drying method. The as‐prepared material can deliver a 3.8 V platform with discharge capacity of 107.9 mAh g^?1 at 0.1 C (1 C = 120 mA g^?1) as well as offering capacity retention above 90% at a discharge rate of 0.2 C after 300 cycles. The well‐constructed carbon network provides fast electron transfer rates, and thus, higher power density also can be achieved (75.1 mAh g^?1 at 10 C). The interface contribution of GO and Na₂Fe₂(SO₄)₃ is recognized and studied via density function theory calculation. The Na storage mechanism is also investigated through in situ synchrotron X‐ray diffraction, and pseudocapacitance contributions are also demonstrated. The diffusion coefficient of Na⁺ ions is around 10^?12–10^?10.8 cm² s^?1 during cycling. The higher working voltage of this composite is mainly ascribed to the larger electronegativity of the element S. The research indicates that this well‐constructed composite would be a competitive candidate as a cathode material for Na‐ion batteries.