A Flexible 3D Multifunctional MgO‐Decorated Carbon Foam@CNTs Hybrid as Self‐Supported Cathode for High‐Performance Lithium‐Sulfur Batteries

One of the critical challenges to develop advanced lithium‐sulfur (Li‐S) batteries lies in exploring a high efficient stable sulfur cathode with robust conductive framework and high sulfur loading. Herein, a 3D flexible multifunctional hybrid is rationally constructed consisting of nitrogen‐doped carbon foam@CNTs decorated with ultrafine MgO nanoparticles for the use as advanced current collector. The dense carbon nanotubes uniformly wrapped on the carbon foam skeletons enhance the flexibility and build an interconnected conductive network for rapid ionic/electronic transport. In particular, a synergistic action of MgO nanoparticles and in situ N‐doping significantly suppresses the shuttling effect via enhanced chemisorption of lithium polysulfides. Owing to these merits, the as‐built electrode with an ultrahigh sulfur loading of 14.4 mg cm^?2 manifests a high initial areal capacity of 10.4 mAh cm^?2, still retains 8.8 mAh cm^?2 (612 mAh g^?1 in gravimetric capacity) over 50 cycles. The best cycling performance is achieved upon 800 cycles with an extremely low decay rate of 0.06% at 2 C. Furthermore, a flexible soft‐packaged Li‐S battery is readily assembled, which highlights stable electrochemical characteristics under bending and even folding. This cathode structural design may open up a potential avenue for practical application of high‐sulfur‐loading Li‐S batteries toward flexible energy‐storage devices.     

Bifunctional Separator with a Light‐Weight Carbon‐Coating for Dynamically and Statically Stable Lithium‐Sulfur Batteries

Sulfur is appealing as a high‐capacity cathode for rechargeable lithium batteries as it offers a high theoretical capacity of 1672 mA h g^?1 and is abundant. However, the commercialization of Li‐S batteries is hampered by fast capacity fade during both dynamic cell cycling and static cell resting. The poor electrochemical stability is due to polysulfide diffusion, leading to a short cycle life and severe self‐discharge. Here, we present the design of a bifunctional separator with a light‐weight carbon‐coating that integrates the two necessary components already inside the cell: the conductive carbon and the separator. With no extra additives, this bifunctional carbon‐coated separator allows the use of pure sulfur cathodes involving no complex composite synthesis process, provides a high initial discharge capacity of 1389 mA h g^?1 with excellent dynamic stability, and facilitates a high reversible capacity of 828 mA h g^?1 after 200 cycles. In addition, the static stability is evidenced by low self‐discharge and excellent capacity retention after a 3 month rest period.     

A Free‐Standing and Ultralong‐Life Lithium‐Selenium Battery Cathode Enabled by 3D Mesoporous Carbon/Graphene Hierarchical Architecture

High capacity cathode materials for long‐life rechargeable lithium batteries are urgently needed. Selenium cathode has recently attracted great research attention due to its comparable volumetric capacity to but much better electrical conductivity than widely studied sulfur cathode. However, selenium cathode faces similar issues as sulfur (i.e., shuttling of polyselenides, volumetric expansion) and high performance lithium‐selenium batteries (Li–Se) have not yet been demonstrated at selenium loading >60% in the electrode. In this work, a 3D mesoporous carbon nanoparticles and graphene hierarchical architecture to storage selenium as binder‐free cathode material (Se/MCN‐RGO) for high energy and long life Li–Se batteries is presented. Such architecture not only provides the electrode with excellent electrical and ionic conductivity, but also efficiently suppresses polyselenides shuttling and accommodates volume change during charge/discharge. At selenium content of 62% in the entire cathode, the free‐standing Se/MCN‐RGO exhibits high discharge capacity of 655 mAh g^?1 at 0.1 C (97% of theoretical capacity) and long cycling stability with a very small capacity decay of 0.008% per cycle over 1300 cycles at 1 C. The present report demonstrates significant progress in the development of high capacity cathode materials for long‐life Li batteries and flexible energy storage device.     

Effective Polysulfide Rejection by Dipole‐Aligned BaTiO3 Coated Separator in Lithium–Sulfur Batteries

Although the exceptional theoretical specific capacity (1672 mAh g^?1) of elemental sulfur makes lithium–sulfur (Li–S) batteries attractive for upcoming rechargeable battery applications (e.g., electrical vehicles, drones, unmanned aerial vehicles, etc.), insufficient cycle lives of Li–S cells leave a substantial gap before their wide penetration into commercial markets. Among the key features that affect the cyclability, the shuttling process involving polysulfides (PS) dissolution is most fatal. In an effort to suppress this chronic PS shuttling, herein, a separator coated with poled BaTiO₃ or BTO particles is introduced. Permanent dipoles that are formed in the BTO particles upon the application of an electric field can effectively reject PS from passing through the separator via electrostatic repulsion, resulting in significantly improved cyclability, even when a simple mixture of elemental sulfur and conductive carbon is used as a sulfur cathode. The coating of BTO particles also considerably suppresses thermal shrinkage of the poly(ethylene) separator at high temperatures and thus enhances the safety of the cell adopting the given separator. The incorporation of poled particles can be universally applied to a wide range of rechargeable batteries (i.e., metal‐air batteries) that suffer from cross‐contamination of charged species between both electrodes.     

Yolk–Shell Structured Assembly of Bamboo‐Like Nitrogen‐Doped Carbon Nanotubes Embedded with Co Nanocrystals and Their Application as Cathode Material for Li–S Batteries

Despite their high theoretical specific capacity (1675 mA h g^?1), the practical application of Li–S batteries remains limited because the capacity rapidly degrades through severe dissolution of lithium polysulfide and the rate capability is low because of the low electronic conductivity of sulfur. This paper describes novel hierarchical yolk–shell microspheres comprising 1D bamboo‐like N‐doped carbon nanotubes (CNTs) encapsulating Co nanoparticles (Co@BNCNTs YS microspheres) as efficient cathode hosts for Li–S batteries. The microspheres are produced via a two‐step process that involves generation of the microsphere followed by N‐doped CNTs growth. The hierarchical yolk–shell structure enables efficient sulfur loading and mitigates the dissolution of lithium polysulfides, and metallic Co and N doping improves the chemical affinity of the microspheres with sulfur species. Accordingly, a Co@BNCNTs YS microsphere‐based cathode containing 64 wt% sulfur exhibits a high discharge capacity of 700.2 mA h g^?1 after 400 cycles at a current density of 1 C (based on the mass of sulfur); this corresponds to a good capacity retention of 76% and capacity fading rate of 0.06% per cycle with an excellent rate performance (752 mA h g^?1 at 2.0 C) when applied as cathode hosts for Li–S batteries.     

Nitrogen‐Doped Mesoporous Carbon Promoted Chemical Adsorption of Sulfur and Fabrication of High‐Areal‐Capacity Sulfur Cathode with Exceptional Cycling Stability for Lithium‐Sulfur Batteries

As one important component of sulfur cathodes, the carbon host plays a key role in the electrochemical performance of lithium‐sulfur (Li‐S) batteries. In this paper, a mesoporous nitrogen‐doped carbon (MPNC)‐sulfur nanocomposite is reported as a novel cathode for advanced Li‐S batteries. The nitrogen doping in the MPNC material can effectively promote chemical adsorption between sulfur atoms and oxygen functional groups on the carbon, as verified by X‐ray absorption near edge structure spectroscopy, and the mechanism by which nitrogen enables the behavior is further revealed by density functional theory calculations. Based on the advantages of the porous structure and nitrogen doping, the MPNC‐sulfur cathodes show excellent cycling stability (95% retention within 100 cycles) at a high current density of 0.7 mAh cm^‐2 with a high sulfur loading (4.2 mg S cm^‐2) and a sulfur content (70 wt%). A high areal capacity (≈3.3 mAh cm^‐2) is demonstrated by using the novel cathode, which is crucial for the practical application of Li‐S batteries. It is believed that the important role of nitrogen doping promoted chemical adsorption can be extended for development of other high performance carbon‐sulfur composite cathodes for Li‐S batteries.     

Solid‐State Plastic Crystal Electrolytes: Effective Protection Interlayers for Sulfide‐Based All‐Solid‐State Lithium Metal Batteries

All‐solid‐state lithium metal batteries (ASSLMBs) have attracted significant attention due to their superior safety and high energy density. However, little success has been made in adopting Li metal anodes in sulfide electrolyte (SE)‐based ASSLMBs. The main challenges are the remarkable interfacial reactions and Li dendrite formation between Li metal and SEs. In this work, a solid‐state plastic crystal electrolyte (PCE) is engineered as an interlayer in SE‐based ASSLMBs. It is demonstrated that the PCE interlayer can prevent the interfacial reactions and lithium dendrite formation between SEs and Li metal. As a result, ASSLMBs with LiFePO₄ exhibit a high initial capacity of 148 mAh g^?1 at 0.1 C and 131 mAh g^?1 at 0.5 C (1 C = 170 mA g^?1), which remains at 122 mAh g^?1 after 120 cycles at 0.5 C. All‐solid‐state Li‐S batteries based on the polyacrylonitrile‐sulfur composite are also demonstrated, showing an initial capacity of 1682 mAh g^?1. The second discharge capacity of 890 mAh g^?1 keeps at 775 mAh g^?1 after 100 cycles. This work provides a new avenue to address the interfacial challenges between Li metal and SEs, enabling the successful adoption of Li metal in SE‐based ASSLMBs with high energy density.     

Designing a High‐Performance Lithium–Sulfur Batteries Based on Layered Double Hydroxides–Carbon Nanotubes Composite Cathode and a Dual‐Functional Graphene–Polypropylene–Al2O3 Separator

Designing an optimum cell configuration that can deliver high capacity, fast charge–discharge capability, and good cycle retention is imperative for developing a high‐performance lithium–sulfur battery. Herein, a novel lithium–sulfur cell design is proposed, which consists of sulfur and magnesium–aluminum‐layered double hydroxides (MgAl‐LDH)–carbon nanotubes (CNTs) composite cathode with a modified polymer separator produced by dual side coating approaches (one side: graphene and the other side: aluminum oxides). The composite cathode functions as a combined electrocatalyst and polysulfide scavenger, greatly improving the reaction kinetics and stabilizing the Coulombic efficiency upon cycling. The modified separator enhances further Li⁺‐ion or electron transport and prevents undesirable contact between the cathode and dendritic lithium on the anode. The proposed lithium–sulfur cell fabricated with the as‐prepared composite cathode and modified separator exhibits a high initial discharge capacity of 1375 mA h g^?1 at 0.1 C rate, excellent cycling stability during 200 cycles at 1 C rate, and superior rate capability up to 5 C rate, even with high sulfur loading of 4.0 mg cm^?2. In addition, the findings that found in postmortem chracterization of cathode, separator, and Li metal anode from cycled cell help in identifying the reason for its subsequent degradation upon cycling in Li–S cells.     

A Lithium‐Sulfur Battery with a High Areal Energy Density

The battery community has recently witnessed a considerable progress in the cycle lives of lithium‐sulfur (Li‐S) batteries, mostly by developing the electrode structures that mitigate fatal dissolution of lithium polysulfides. Nonetheless, most of the previous successful demonstrations have been based on limited areal capacities. For realistic battery applications, however, the chronic issues from both the anode (lithium dendrite growth) and the cathode (lithium polysulfide dissolution) need to be readdressed under much higher loading of sulfur active material. To this end, the current study integrates the following three approaches in a systematic manner: 1) the sulfur electrode material with diminished lithium polysulfide dissolution by the covalently bonded sulfur‐carbon microstructure, 2) mussel‐inspired polydopamine coating onto the separator that suppresses lithium dendrite growth by wet‐adhesion between the separator and Li metal, and 3) addition of cesium ions (Cs⁺) to the electrolyte to repel incoming Li ions and thus prevent Li dendrite growth. This combined strategy resolves the long‐standing problems from both electrodes even under the very large sulfur‐carbon composite loading of 17 mg cm^?2 in the sulfur electrode, enabling the highest areal capacity (9 mAh cm^?2) to date while preserving stable cycling performance.     

Mesoporous Carbon Nanocube Architecture for High‐Performance Lithium–Oxygen Batteries

One of the major challenges to develop high‐performance lithium–oxygen (Li–O₂) battery is to find effective cathode catalysts and design porous architecture for the promotion of both oxygen reduction reactions and oxygen evolution reactions. Herein, the synthesis of mesoporous carbon nanocubes as a new cathode nanoarchitecture for Li–O₂ batteries is reported. The oxygen electrodes made of mesoporous carbon nanocubes contain numerously hierarchical mesopores and macropores, which can facilitate oxygen diffusion and electrolyte impregnation throughout the electrode, and provide sufficient spaces to accommodate insoluble discharge products. When they are applied as cathode catalysts, the Li–O₂ cells deliver discharge capacities of 26 100 mA h g^?1 at 200 mA g^?1, which is much higher than that of commercial carbon black catalysts. Furthermore, the mesoporous nanocube architecture can also serve as a conductive host structure for other highly efficient catalysts. For instance, the Ru functionalized mesoporous carbon nanocubes show excellent catalytic activities toward oxygen evolution reactions. Li–O₂ batteries with Ru functionalized mesoporous carbon nanocube catalysts demonstrate a high charge/discharge electrical energy efficiency of 86.2% at 200 mA g^?1 under voltage limitation and a good cycling performance up to 120 cycles at 400 mA g^?1 with the curtaining capacity of 1000 mA h g^?1.     

All‐Purpose Electrode Design of Flexible Conductive Scaffold toward High‐Performance Li–S Batteries

The main obstacles that hinder the development of efficient lithium sulfur (Li–S) batteries are the polysulfide shuttling effect in sulfur cathode and the uncontrollable growth of dendritic Li in the anode. An all‐purpose flexible electrode that can be used both in sulfur cathode and Li metal anode is reported, and its application in wearable and portable storage electronic devices is demonstrated. The flexible electrode consists of a bimetallic CoNi nanoparticle‐embedded porous conductive scaffold with multiple Co/Ni‐N active sites (CoNi@PNCFs). Both experimental and theoretical analysis show that, when used as the cathode, the CoNi and Co/Ni‐N active sites implanted on the porous CoNi@PNCFs significantly promote chemical immobilization toward soluble lithium polysulfides and their rapid conversion into insoluble Li₂S, and therefore effectively mitigates the polysulfide shuttling effect. Additionally, a 3D matrix constructed with porous carbonous skeleton and multiple active centers successfully induces homogenous Li growth, realizing a dendrite‐free Li metal anode. A Li–S battery assembled with S/CoNi@PNCFs cathode and Li/CoNi@PNCFs anode exhibits a high reversible specific capacity of 785 mAh g^?1 and long cycle performance at 5 C (capacity fading rate of 0.016% over 1500 cycles).     

Hierarchical Free‐Standing Carbon‐Nanotube Paper Electrodes with Ultrahigh Sulfur‐Loading for Lithium–Sulfur Batteries

The rational combination of conductive nanocarbon with sulfur leads to the formation of composite cathodes that can take full advantage of each building block; this is an effective way to construct cathode materials for lithium–sulfur (Li–S) batteries with high energy density. Generally, the areal sulfur‐loading amount is less than 2.0 mg cm^?2, resulting in a low areal capacity far below the acceptable value for practical applications. In this contribution, a hierarchical free‐standing carbon nanotube (CNT)‐S paper electrode with an ultrahigh sulfur‐loading of 6.3 mg cm^?2 is fabricated using a facile bottom–up strategy. In the CNT–S paper electrode, short multi‐walled CNTs are employed as the short‐range electrical conductive framework for sulfur accommodation, while the super‐long CNTs serve as both the long‐range conductive network and the intercrossed mechanical scaffold. An initial discharge capacity of 6.2 mA·h cm^?2 (995 mA·h g^?1), a 60% utilization of sulfur, and a slow cyclic fading rate of 0.20%/cycle within the initial 150 cycles at a low current density of 0.05 C are achieved. The areal capacity can be further increased to 15.1 mA·h cm^?2 by stacking three CNT–S paper electrodes—resulting in an areal sulfur‐loading of 17.3 mg cm^?2—for the cathode of a Li–S cell. The as‐obtained free‐standing paper electrode are of low cost and provide high energy density, making them promising for flexible electronic devices based on Li–S batteries.     

In Situ Formation of Copper‐Based Hosts Embedded within 3D N‐Doped Hierarchically Porous Carbon Networks for Ultralong Cycle Lithium–Sulfur Batteries

Lithium–sulfur (Li–S) batteries are promising energy storage systems due to their large theoretical energy density of 2600 Wh kg^?1 and cost effectiveness. However, the severe shuttle effect of soluble lithium polysulfide intermediates (LiPSs) and sluggish redox kinetics during the cycling process cause low sulfur utilization, rapid capacity fading, and a low coulombic efficiency. Here, a 3D copper, nitrogen co‐doped hierarchically porous graphitic carbon network developed through a freeze‐drying method (denoted as 3D Cu@NC‐F) is prepared, and it possesses strong chemical absorption and electrocatalytic conversion activity for LiPSs as highly efficient sulfur host materials in Li–S batteries. The porous carbon network consisting of 2D cross‐linked ultrathin carbon nanosheets provides void space to accommodate volumetric expansion upon lithiation, while the Cu, N‐doping effect plays a critical role for the confinement of polysulfides through chemical bonding. In addition, after sulfuration of Cu@NC‐F network, the in situ grown copper sulfide (Cu_xS) embedded within Cu_xS@NC/S‐F composite catalyzes LiPSs conversion during reversible cycling, resulting in low polarization and fast redox reaction kinetics. At a current density of 0.1 C, the Cu_xS@NC/S‐F composites' electrode exhibits an initial capacity of 1432 mAh g^?1 and maintains 1169 mAh g^?1 after 120 cycles, with a coulombic efficiency of nearly 100%.     

Freestanding Bilayer Carbon–Sulfur Cathode with Function of Entrapping Polysulfide for High Performance Li–S Batteries

Li–S batteries benefit from numerous advantages such as high theoretical capacity, high energy density, and availability of an abundance of sulfur. However, commercialization of Li–S batteries has been impeded because of low loading amount of active materials and poor cycle performance. Herein, a freestanding bilayer carbon–sulfur (FBCS) cathode is reported with superior electrochemical performance at a high sulfur loading level (3 mg cm^?2). The top component of the FBCS cathode is composed of interlacing multiwalled carbon nanotubes (MWCNT) and the bottom component is made up of a mixed layer of sulfur imbedded in MWCNT and N‐doped porous carbon (NPC). The MWCNT layer (top part of FBCS cathode) blocks polysulfide migration from the cathode to the anode, and NPC in the bottom part of the FBCS cathode not only provides spacious active sites but also absorbs polysulfide by the nitrogen functional group. The designed novel FBCS cathode delivered a high initial discharge capacity of 964 and 900 mAh g^?1 at 0.5 and 1 C, respectively. It also displayed an excellent capacity retention of 83.1% at 0.5 C and 83.4% at 1 C after 300 cycles.     

Walnut‐Like Multicore–Shell MnO Encapsulated Nitrogen‐Rich Carbon Nanocapsules as Anode Material for Long‐Cycling and Soft‐Packed Lithium‐Ion Batteries

Metal oxide‐based nanomaterials are widely studied because of their high‐energy densities as anode materials in lithium‐ion batteries. However, the fast capacity degradation resulting from the large volume expansion upon lithiation hinders their practical application. In this work, the preparation of walnut‐like multicore–shell MnO encapsulated nitrogen‐rich carbon nanocapsules (MnO@NC) is reported via a facile and eco‐friendly process for long‐cycling Li‐ion batteries. In this hybrid structure, MnO nanoparticles are uniformly dispersed inside carbon nanoshells, which can simultaneously act as a conductive framework and also a protective buffer layer to restrain the volume variation. The MnO@NC nanocapsules show remarkable electrochemical performances for lithium‐ion batteries, exhibiting high reversible capability (762 mAh g^?1 at 100 mA g^?1) and stable cycling life (624 mAh g^?1 after 1000 cycles at 1000 mA g^?1). In addition, the soft‐packed full batteries based on MnO@NC nanocapsules anodes and commercial LiFePO₄ cathodes present good flexibility and cycling stability.     

Bifunctional MOF‐Derived Carbon Photonic Crystal Architectures for Advanced Zn–Air and Li–S Batteries: Highly Exposed Graphitic Nitrogen Matters

Nitrogen‐rich porous carbons (NPCs) are the leading cathode materials for next‐generation Zn–air and Li–S batteries. However, most existing NPC suffers from insufficient exposure and harnessing of nitrogen‐dopants (NDs), constraining the electrochemical performance. Herein, by combining silica templating with in situ texturing of metal–organic frameworks, a new bifunctional 3D nitrogen‐rich carbon photonic crystal architecture of simultaneously record‐high total pore volume (13.42 cm³ g^?1), ultralarge surface area (2546 m² g^?1), and permeable hierarchical macro‐meso‐microporosity is designed, enabling sufficient exposure and accessibility of NDs. Thus, when used as cathode catalysts, the Zn–air battery delivers a fantastic capacity of 770 mAh g_Zn^?1 at an unprecedentedly high rate of 120 mA cm^?2, with an ultrahigh power density of 197 mW cm^?2. When hosting 78 wt% sulfur, the Li–S battery affords a high‐rate capacity of 967 mAh g^?1 at 2 C, with superb stability over 1000 cycles at 0.5 C (0.054% decay rate per cycle), comparable to the best literature value. The results prove the dominant role of highly exposed graphitic‐N in boosting both cathode performances.     

Carbonized‐MOF as a Sulfur Host for Aluminum–Sulfur Batteries with Enhanced Capacity and Cycling Life

The rechargeable aluminum–sulfur (Al–S) battery is a promising next generation electrochemical energy storage system owing to its high theoretical capacity of 1672 mAh g^?1 and in combining low‐cost and naturally abundant elements, Al and S. However, to date, its poor reversibility and low lifespan have limited its practical application. In this paper, a composite cathode is reported for Al–S batteries based on S anchored on a carbonized HKUST‐1 matrix (S@HKUST‐1‐C). The S@HKUST‐1‐C composite maintains a reversible capacity of 600 mAh g^?1 at the 75th cycle and a reversible capacity of 460 mAh g^?1 at the 500th cycle under a current density of 1 A g^?1, with a Coulombic efficiency of around 95%. X‐ray diffraction and Auger spectrum results reveal that the Cu in HKUST‐1 forms S–Cu ionic clusters. This serves to facilitate the electrochemical reaction and improve the reversibility of S during charge/discharge. Additionally, Cu increases the electron conductivity at the carbon matrix/S interface to significantly decrease the kinetic barrier for the conversion of sulfur species during battery operation.     

Optimization of Von Mises Stress Distribution in Mesoporous α‐Fe2O3/C Hollow Bowls Synergistically Boosts Gravimetric/Volumetric Capacity and High‐Rate Stability in Alkali‐Ion Batteries

Hollow structures are often used to relieve the intrinsic strain on metal oxide electrodes in alkali‐ion batteries. Nevertheless, one common drawback is that the large interior space leads to low volumetric energy density and inferior electric conductivity. Here, the von Mises stress distribution on a mesoporous hollow bowl (HB) is simulated via the finite element method, and the vital role of the porous HB structure on strain‐relaxation behavior is confirmed. Then, N‐doped‐C coated mesoporous α‐Fe₂O₃ HBs are designed and synthesized using a multistep soft/hard‐templating strategy. The material has several advantages: (i) there is space to accommodate strains without sacrificing volumetric energy density, unlike with hollow spheres; (ii) the mesoporous hollow structure shortens ion diffusion lengths and allows for high‐rate induced lithiation reactivation; and (iii) the N‐doped carbon nanolayer can enhance conductivity. As an anode in lithium‐ion batteries, the material exhibits a very high reversible capacity of 1452 mAh g^?1 at 0.1 A g^?1, excellent cycling stability of 1600 cycles (964 mAh g^?1 at 2 A g^?1), and outstanding rate performance (609 mAh g^?1 at 8 A g^?1). Notably, the volumetric specific capacity of composite electrode is 42% greater than that of hollow spheres. When used in potassium‐ion batteries, the material also shows high capacity and cycle stability.     

Catalytic Conversion of Polysulfides on Single Atom Zinc Implanted MXene toward High‐Rate Lithium–Sulfur Batteries

Although lithium–sulfur (Li–S) batteries are one of the most promising energy storage devices owing to their high energy densities, the sluggish reaction kinetics and severe shuttle effect of the sulfur cathodes hinder their practical applications. Here, single atom zinc implanted MXene is introduced into a sulfur cathode, which can not only catalyze the conversion reactions of polysulfides by decreasing the energy barriers from Li₂S₄ to Li₂S₂/Li₂S but also achieve strong interaction with polysulfides due to the high electronegativity of atomic zinc on MXene. Moreover, it is found that the homogenously dispersed zinc atoms can also accelerate the nucleation of Li₂S₂/Li₂S on MXene layers during the redox reactions. As a result, the sulfur cathode with single atom zinc implanted MXene exhibits a high reversible capacity of 1136 mAh g^?1. After electrode optimization, a high areal capacity of 5.3 mAh cm^?2, high rate capability of 640 mAh g^?1 at 6 C, and good cycle stability (80% capacity retention after 200 cycles at 4 C) can be achieved.     

Conductive CoOOH as Carbon‐Free Sulfur Immobilizer to Fabricate Sulfur‐Based Composite for Lithium–Sulfur Battery

Lithium–sulfur battery is recognized as one of the most promising energy storage devices, while the application and commercialization are severely hindered by both the practical gravimetric and volumetric energy densities due to the low sulfur content and tap density with lightweight and nonpolar porous carbon materials as sulfur host. Herein, for the first time, conductive CoOOH sheets are introduced as carbon‐free sulfur immobilizer to fabricate sulfur‐based composite as cathode for lithium–sulfur battery. CoOOH sheet is not only a good sulfur‐loading matrix with high electron conductivity, but also exhibits outstanding electrocatalytic activity for the conversion of soluble lithium polysulfide. With an ultrahigh sulfur content of 91.8 wt% and a tap density of 1.26 g cm^?3, the sulfur/CoOOH composite delivers high gravimetric capacity and volumetric capacity of 1199.4 mAh g^?1_‐composite and 1511.3 mAh cm^?3 at 0.1C rate, respectively. Meanwhile, the sulfur‐based composite presents satisfactory cycle stability with a slow capacity decay rate of 0.09% per cycle within 500 cycles at 1C rate, thanks to the strong interaction between CoOOH and soluble polysulfides. This work provides a new strategy to realize the combination of gravimetric energy density, volumetric energy density, and good electrochemical performance of lithium–sulfur battery.