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.     

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.     

Effect of the Anion Activity on the Stability of Li Metal Anodes in Lithium‐Sulfur Batteries

With the significant progress made in the development of cathodes in lithium‐sulfur (Li‐S) batteries, the stability of Li metal anodes becomes a more urgent challenge in these batteries. Here the systematic investigation of the stability of the anode/electrolyte interface in Li‐S batteries with concentrated electrolytes containing various lithium salts is reported. It is found that Li‐S batteries using LiTFSI‐based electrolytes are more stable than those using LiFSI‐based electrolytes. The decreased stability is because the N–S bond in the FSI^? anion is fairly weak and the scission of this bond leads to the formation of lithium sulfate (LiSO_x) in the presence of polysulfide species. In contrast, in the LiTFSI‐based electrolyte, the lithium metal anode tends to react with polysulfide to form lithium sulfide (LiS_x), which is more reversible than LiSO_x formed in the LiFSI‐based electrolyte. This fundamental difference in the bond strength of the salt anions in the presence of polysulfide species leads to a large difference in the stability of the anode‐electrolyte interface and performance of the Li‐S batteries with electrolytes composed of these salts. Therefore, anion selection is one of the key parameters in the search for new electrolytes for stable operation of Li‐S batteries.     

Stabilizing Solid Electrolyte Interphases on Both Anode and Cathode for High Areal Capacity,High‐Voltage Lithium Metal Batteries with High Li Utilization and Lean Electrolyte

High‐energy‐density lithium metal batteries are considered the most promising candidates for the next‐generation energy storage systems. However, conventional electrolytes used in lithium‐ion batteries can hardly meet the demand of the lithium metal batteries due to their intrinsic instability for Li metal anodes and high‐voltage cathodes. Herein, an ester‐based electrolyte with tris(trimethylsilyl)phosphate additive that can form stable solid electrolyte interphases on the anode and cathode is reported. The additive decomposes before the ester solvent and enables the formation of P‐ and Si‐rich interphases on both electrodes that are ion conductive and robust. Thus, lithium metal batteries with a high‐specific‐energy of 373 Wh kg^?1 can exhibit a long lifespan of over 80 cycles under practical conditions, including a low negative/positive capacity ratio of 2.3, high areal capacity of 4.5 mAh cm^?2 for cathode, high‐voltage of 4.5 V, and lean electrolyte of 2.8 µL mAh^?1. A 4.5 V pouch cell is further assembled to demonstrate the practical application of the tris(trimethylsilyl)phosphate additive with an areal capacity of 10.2 and 9.4 mAh cm^?2 for the anode and cathode, respectively. This work is expected to provide an effective electrolyte optimizing strategy compatible with current lithium ion battery manufacturing systems and pave the way for the next‐generation Li metal batteries with high specific energy and energy density.     

Flexible Electrocatalytic Nanofiber Membrane Reactor for Lithium/Sulfur Conversion Chemistry

Severe lithium polysulfide (LiPS) shuttle effects and sluggish electrochemical conversion kinetics constitute bottlenecks in developing fast‐rechargeable, high‐energy, and high‐power Li/S batteries. Here, a flexible and conductive TiN–Ti₄O₇ core‐shell nanofiber (TiNOC) membrane reactor is designed to electrocatalytically mediate Li/S conversion chemistry. The Ti, N, and O atoms in the nanofiber function as electrocatalysts and chemical confinement active sites to initiate long‐chain LiPS conversion and phase change, as well as to suppress soluble LiPS shuttling. With a sulfur cathode‐membrane reactor module configuration, Li/S cells possess a high sulfur utilization of 91.20%, good rate capability of 869.10 mA h g^?1, and high capacity retention of 92.49%, with a coulomb efficiency of 99.57% after 200 cycles at 5 C. Density functional theory (DFT) calculations revealed that the optimized chemisorption configurations facilitate the elongation of Li? S and S? S bonds, as well as charge transfer along Ti? S and Li? N bonds, which favors bond breakage, bond formation, and the activation of solid‐state S₈, Li₂S₂, and Li₂S. Layer‐by‐layer module stacking provides Li/S batteries with a high areal sulfur loading of 12.00 mg cm^?2 to deliver a high areal capacity of 14.40 mA h cm^?2 at 2.26 mA. Two batteries in series can power real‐world applications such as light emitting diode (LED) bulbs with a high energy output of 69.00 mW h.     

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.     

A Molecular‐Cage Strategy Enabling Efficient Chemisorption–Electrocatalytic Interface in Nanostructured Li2S Cathode for Li Metal‐Free Rechargeable Cells with High Energy

Using high‐capacity and metallic Li‐free lithium sulfide (Li₂S) cathodes offers an alternative solution to address serious safety risks and performance decay caused by uncontrolled dendrite hazards of Li metal anodes in next‐generation Li metal batteries. Practical applications of such a cathode, however, still suffer from low redox activity, unaffordable cost, and poor processability of infusible and moisture‐sensitive Li₂S. Herein, these difficulties are addressed by developing a molecular cage–engaged strategy that enables low‐cost production and interfacial engineering of Li₂S cathodes for rechargeable Li₂S//Si cells. An efficient chemisorption–electrocatalytic interface is built in extremely nanostructured Li₂S cathodes by harnessing the confinement/separation effect of metal–organic molecular cages on ionic clusters of air‐stable, soluble, and low‐cost Li salt and their chemical transformation. It effectively boosts the redox activity toward Li₂S activation/dissociation and polysulfide chemisorption–conversion in Li‐S batteries, leading to low activation voltage barrier, stable cycle life of 1000 cycles, ultrafast current rate up to 8 C, and high areal capacities of Li₂S cathodes with high mass loading. Encouragingly, this highly active Li₂S cathode can be applied for constructing truly workable Li₂S//Si cells with a high specific energy of 673 Wh kg^?1 and stable performance for 200 cycles at high rates against hollow nanostructured Si anode.     

Ultrathin MnO2/Graphene Oxide/Carbon Nanotube Interlayer as Efficient Polysulfide‐Trapping Shield for High‐Performance Li–S Batteries

Ultrathin MnO₂/graphene oxide/carbon nanotube (G/M@CNT) interlayers are developed as efficient polysulfide‐trapping shields for high‐performance Li–S batteries. A simple layer‐by‐layer procedure is used to construct a sandwiched vein–membrane interlayer of thickness 2 µm and areal density 0.104 mg cm^?2 by loading MnO₂ nanoparticles and graphene oxide (GO) sheets on superaligned carbon nanotube films. The G/M@CNT interlayer provides a physical shield against both polysulfide shuttling and chemical adsorption of polysulfides by MnO₂ nanoparticles and GO sheets. The synergetic effect of the G/M@CNT interlayer enables the production of Li–S cells with high sulfur loadings (60–80 wt%), a low capacity decay rate (?0.029% per cycle over 2500 cycles at 1 C), high rate performance (747 mA h g^?1 at a charge rate of 10 C), and a low self‐discharge rate with high capacity retention (93.0% after 20 d rest). Electrochemical impedance spectroscopy, cyclic voltammetry, and scanning electron microscopy observations of the Li anodes after cycling confirm the polysulfide‐trapping ability of the G/M@CNT interlayer and show its potential in developing high‐performance Li–S batteries.     

Cobalt‐Doped SnS2 with Dual Active Centers of Synergistic Absorption‐Catalysis Effect for High‐S Loading Li‐S Batteries

The application of Li‐S batteries is hindered by low sulfur utilization and rapid capacity decay originating from slow electrochemical kinetics of polysulfide transformation to Li₂S at the second discharge plateau around 2.1 V and harsh shuttling effects for high‐S‐loading cathodes. Herein, a cobalt‐doped SnS₂ anchored on N‐doped carbon nanotube (NCNT@Co‐SnS₂) substrate is rationally designed as both a polysulfide shield to mitigate the shuttling effects and an electrocatalyst to improve the interconversion kinetics from polysulfides to Li₂S. As a result, high‐S‐loading cathodes are demonstrated to achieve good cycling stability with high sulfur utilization. It is shown that Co‐doping plays an important role in realizing high initial capacity and good capacity retention for Li‐S batteries. The S/NCNT@Co‐SnS₂ cell (3 mg cm^?2 sulfur loading) delivers a high initial specific capacity of 1337.1 mA h g^?1 (excluding the Co‐SnS₂ capacity contribution) and 1004.3 mA h g^?1 after 100 cycles at a current density of 1.3 mA cm^?2, while the counterpart cell (S/NCNT@SnS₂) only shows an initial capacity of 1074.7 and 843 mA h g^?1 at the 100th cycle. The synergy effect of polysulfide confinement and catalyzed polysulfide conversion provides an effective strategy in improving the electrochemical performance for high‐sulfur‐loading Li‐S batteries.     

Shaping the Contact between Li Metal Anode and Solid‐State Electrolytes

Scientific and technological interest in solid‐state Li metal batteries (SSLMBs) arises from their excellent safety and promising high energy density. However, the practical application of SSLMBs is hindered by poor contact between the Li metal anode (LMA) and solid‐state electrolytes (SSEs). To circumvent this limitation, a pattern‐guided approach that shapes the LMA/SSE contact is disclosed to offer fast Li ion conduction in the interface. A thermally‐treated copper foam is used as the lithophilic pattern to confine and guide Li for forming a tight contact with garnet‐type SSE. The contact can be easily manipulated according to the shape of lithiophilic pattern, facilitating cell assembly. The resulting Li|patterned garnet|Li symmetric cell exhibits an interfacial resistance of 9.8 Ω cm², which is dramatically lower than that of 998 Ω cm² for Li|pristine garnet|Li symmetric cell. Being used in Li–sulfur batteries, the patterned garnet effectively eliminates the polysulfide shuttle and enables stable cycling performance, showing a low capacity decay of 0.035% per cycle over 1000 cycles. The fundamental contact process of metallic anodes/SSEs is carefully investigated. This contact strategy provides a new design concept to improve the interface wettability via a lithiophilic pattern for a variety of SSEs that cannot wet with metallic anodes.     

Rational Design of Multifunctional Integrated Host Configuration with Lithiophilicity-Sulfiphilicity toward High-Performance Li–S Full Batteries

High-energy-density Li–S batteries are considered one of the next-generation energy storage systems, but the uncontrolled Li-dendrite growth in Li metal anodes and the shuttling of polysulfides in S cathode severely impede the commercial development of Li–S batteries. Herein, a conductive composite architecture that is made up of bio-derived N-doped porous carbon fiber bundles (N-PCFs) with co-imbedded cobalt and niobium carbide nanoparticles is employed as a multifunctional integrated host for simultaneously addressing the challenges in both Li anodes and S cathodes. The implantation of Co and NbC nanoparticles bestows the N-PCFs matrix with synergistically enhanced degree of graphitization, electrical conductivity, hierarchical porosity, and surface polarization. Theoretical calculations and experimental results show that NbC with specific lithiophilic and sulfiphilic features can synchronously regulate the Li and S electrochemistry by realizing homogeneous lithium deposition with suppressed Li-dendrite growth and exerting catalytic effects for promoting the polysulfide conversion together with fast Li₂S nucleation. Hence, the assembled Li–S full batteries exhibit a superb rate capability (704 mAh g⁻¹ at 5 C) and cycling life (≈82.3% capacity retention after 500 cycles) at a sulfur loading over 3.0 mg cm⁻², as well as high reversible areal capacity (>6.0 mAh cm⁻²) even at a higher sulfur loading of 6.7 mg cm⁻².     

Constructing a High‐Strength Solid Electrolyte Layer by In Vivo Alloying with Aluminum for an Ultrahigh‐Rate Lithium Metal Anode

The serious safety issues caused by uncontrollable lithium (Li) dendrite growth, especially at high current densities, seriously hamper the rapid charging of Li metal‐based batteries. Here, the construction of Al–Li alloy/LiCl‐based Li anode (ALA/Li anode) is reported by displacement and alloying reaction between an AlCl₃‐ionic liquid and a Li foil. This layer not only has high ion‐conductivity and good electron resistivity but also much improved mechanical strength (776 MPa) as well as good flexibility compared to a common solid electrolyte interphase layer (585 MPa). The high mechanical strength of the Al–Li alloy interlayer effectively eliminates volume expansion and dendrite growth in Li metal batteries, so that the ALA/Li anode achieves superior cycling for 1600 h (2.0 mA cm^?2) and 1000 cycles at an ultrahigh current density (20 mA cm^?2) without dendrite formation in symmetric batteries. In lithium–sulfur batteries, the dense alloy layer prevents direct contact between polysulfides and Li metal, inhibiting the shuttle effect and electrolyte decomposition. Long cycling performance is achieved even at a high current density (4 C) and a low electrolyte/sulfur (6.0 µL mg^?1). This easy fabrication process provides a strategy to realize reliable safety during the rapid charging of Li‐metal batteries.     

3D Carbonaceous Current Collectors: The Origin of Enhanced Cycling Stability for High‐Sulfur‐Loading Lithium–Sulfur Batteries

The cycling stability of high‐sulfur‐loading lithium–sulfur (Li–S) batteries remains a great challenge owing to the exaggerated shuttle problem and interface instability. Despite enormous efforts on design of advanced electrodes and electrolytes, the stability issue raised from current collectors has been rarely concerned. This study demonstrates that rationally designing a 3D carbonaceous macroporous current collector is an efficient and effective “two‐in‐one” strategy to improve the cycling stability of high‐sulfur‐loading Li–S batteries, which is highly versatile to enable various composite cathodes with sulfur loading >3.7 mAh cm^?2. The best cycling performance can be achieved upon 950 cycles with a very low decay rate of 0.029%. Moreover, the origin of such a huge enhancement in cycling stability is ascribed to (1) the inhibition of electrochemical corrosion, which severely occurs on the typical Al foil and disables its long‐term sustainability for charge transfer, and (2) the passivation of cathode surface. The role of the chemical resistivity against corrosion and favorable macroscopic porous structure is highlighted for exploiting novel current collectors toward exceptional cycling stability of high‐sulfur‐loading Li–S batteries.     

Ultrafine Titanium Nitride Sheath Decorated Carbon Nanofiber Network Enabling Stable Lithium Metal Anodes

Nonuniform local electric field and few nucleation sites on the reactive interface tend to cause detrimental lithium (Li) dendrites, which incur severe safety hazards and hamper the practical application of Li metal anodes in batteries. Herein, a carbon nanofiber (CNF) mat decorated with ultrafine titanium nitride (TiN) nanoparticles (CNF‐TiN) as both current collector and host material is reported for Li metal anodes. Uniform Li deposition is achieved by a synergetic effect of lithiophilic TiN and 3D CNF configuration with a highly conductive network. Theoretical calculations reveal that Li prefers to be adsorbed onto the TiN sheath with a low diffusion energy barrier, leading to controllable nucleation sites and dendrite‐free Li deposits. Moreover, the pseudocapacitive behavior of TiN identified through kinetics analysis is favorable for ultrafast Li⁺ storage and the charge transfer process, especially under a high plating/stripping rate. The CNF‐TiN‐modified Li anodes deliver lower nucleation overpotential for Li plating and superior electrochemical performance under a large current density (200 cycles at 3 mA cm^?2) and high capacity (100 cycles with 6 mAh cm^?2), as well as a long‐running lifespan (>600 h). The CNF‐TiN‐based full cells using lithium iron phosphate and sulfur cathodes exhibit excellent cycling stability.     

Lamellar MXene Composite Aerogels with Sandwiched Carbon Nanotubes Enable Stable Lithium–Sulfur Batteries with a High Sulfur Loading

Realizing long cycling stability under a high sulfur loading is an essential requirement for the practical use of lithium–sulfur (Li–S) batteries. Here, a lamellar aerogel composed of Ti₃C₂T_x MXene/carbon nanotube (CNT) sandwiches is prepared by unidirectional freeze-drying to boost the cycling stability of high sulfur loading batteries. The produced materials are denoted parallel-aligned MXene/CNT (PA-MXene/CNT) due to the unique parallel-aligned structure. The lamellae of MXene/CNT/MXene sandwich form multiple physical barriers, coupled with chemical trapping and catalytic activity of MXenes, effectively suppressing lithium polysulfide (LiPS) shuttling under high sulfur loading, and more importantly, substantially improving the LiPS confinement ability of 3D hosts free of micro- and mesopores. The assembled Li–S battery delivers a high capacity of 712 mAh g⁻¹ with a sulfur loading of 7 mg cm⁻², and a superior cycling stability with 0.025% capacity decay per cycle over 800 cycles at 0.5 C. Even with sulfur loading of 10 mg cm⁻², a high areal capacity of above 6 mAh cm⁻² is obtained after 300 cycles. This work presents a typical example for the rational design of a high sulfur loading host, which is critical for the practical use of Li–S batteries     

High Lithium Ion Conductivity LiF/GO Solid Electrolyte Interphase Inhibiting the Shuttle of Lithium Polysulfides in Long‐Life Li–S Batteries

The “shuttle effect” that stems from the dissolution of polysulfides is the most fatal issue affecting the cycle life of lithium‐sulfur (Li–S) batteries. In order to suppress the “shuttle effect,” a new strategy of using a highly lithium ion conductive lithium fluoride/graphene oxide (LiF/GO) solid electrolyte interphase (SEI) to mechanically prevent the lithium dendrite breakthrough is reported. When utilized in Li–S batteries, the LiF/GO SEI coated separator demonstrates significant feature in mitigating the polysulfide shuttling as observed by in situ UV–vis spectroscopy. Moreover, the restrained “shuttle effect” can also be confirmed by analysis of electrochemical impedance spectroscopy and characterization of lithium dendrites, which indicates that no insulating layer of solid Li₂S₂/Li₂S is found on lithium anode surface. Furthermore, the LiF/GO SEI layer puts out good lithium ion conductivity as its lithium ion diffusion coefficient reaches a high value of 1.5 × 10^?7 cm² s^?1. These features enable a remarkable cyclic property of 0.043% of capacity decay per cycle during 400 cycles.     

Nanoflake Arrays of Lithiophilic Metal Oxides for the Ultra‐Stable Anodes of Lithium‐Metal Batteries

A molten lithium infusion strategy has been proposed to prepare stable Li‐metal anodes to overcome the serious issues associated with dendrite formation and infinite volume change during cycling of lithium‐metal batteries. Stable host materials with superior wettability of molten Li are the prerequisite. Here, it is demonstrated that a series of strong oxidizing metal oxides, including MnO₂, Co₃O₄, and SnO₂, show superior lithiophilicity due to their high chemical reactivity with Li. Composite lithium‐metal anodes fabricated via melt infusion of lithium into graphene foams decorated by these metal oxide nanoflake arrays successfully control the formation and growth of Li dendrites and alleviate volume change during cycling. A resulting Li‐Mn/graphene composite anode demonstrates a super‐long and stable lifetime for repeated Li plating/stripping of 800 cycles at 1 mA cm^?2 without voltage fluctuation, which is eight times longer than the normal lifespan of a bare Li foil under the same conditions. Furthermore, excellent rate capability and cyclability are realized in full‐cell batteries with Li‐Mn/graphene composite anodes and LiCoO₂ cathodes. These results show a major advancement in developing a stable Li anode for lithium‐metal batteries.     

Elastic Carbon Nanotube Aerogel Meets Tellurium Nanowires: A Binder‐ and Collector‐Free Electrode for Li‐Te Batteries

Rechargeable Li batteries based on group VIA element cathodes, such as tellurium, are emerging due to their capability to provide equivalent theoretical volumetric capacity density to O and S, as well as an improved activity to react with Li. Herein, bifunctional and elastic carbon nanotube (CNT) aerogel is fabricated to combine with Te nanowires, yielding two types of binder/collector‐free Te cathodes to assemble Li‐Te batteries. The CNTs with high electronic conductivity and hollow porous structure enable stable electric contact and fast transportation of Li⁺, while trapping Te and Li₂Te in its network, triggering fast and stable Li‐Te electrochemistry. Both cathodes are also provided with fine compressibility, helping to buffer their volume changes during lithiation/delithiation and improving electrode integrity. Both cathodes deliver high specific capacity, fine cycling stability, and favorable high‐rate capability, proving their competence in building high‐energy rechargeable Li‐ion batteries.     

High‐Power Lithium Metal Batteries Enabled by High‐Concentration Acetonitrile‐Based Electrolytes with Vinylene Carbonate Additive

To enable next‐generation high‐power, high‐energy‐density lithium (Li) metal batteries (LMBs), an electrolyte possessing both high Li Coulombic efficiency (CE) at a high rate and good anodic stability on cathodes is critical. Acetonitrile (AN) is a well‐known organic solvent for high anodic stability and high ionic conductivity, yet its application in LMBs is limited due to its poor compatibility with Li metal anodes even at high salt concentration conditions. Here, a highly concentrated AN‐based electrolyte is developed with a vinylene carbonate (VC) additive to suppress Li⁺ depletion at high current densities. Addition of VC to the AN‐based electrolyte leads to the formation of a polycarbonate‐based solid electrolyte interphase, which minimizes Li corrosion and leads to a very high Li CE of up to 99.2% at a current density of 0.2 mA cm^‐2. Using such an electrolyte, fast charging of Li||NMC333 cells is realized at a high current density of 3.6 mA cm^‐2, and stable cycling of Li||NMC622 cells with a high cathode loading of 4 mAh cm^‐2 is also demonstrated.     

Hierarchical Defective Fe3‐xC@C Hollow Microsphere Enables Fast and Long‐Lasting Lithium–Sulfur Batteries

Lithium–sulfur (Li–S) batteries present one of the most promising energy storage systems owing to their high energy density and low cost. However, the commercialization of Li–S batteries is still hindered by several technical issues; the notorious polysulfide shuttling and sluggish sulfur conversion kinetics. In this work, unique hierarchical Fe_3‐xC@C hollow microspheres as an advanced sulfur immobilizer and promoter for enabling high‐efficiency Li–S batteries is developed. The porous hollow architecture not only accommodates the volume variation upon the lithiation–delithiation processes, but also exposes vast active interfaces for facilitated sulfur redox reactions. Meanwhile, the mesoporous carbon coating establishes a highly conductive network for fast electron transportation. More importantly, the defective Fe_3‐xC nanosized subunits impose strong LiPS adsorption and catalyzation, enabling fast and durable sulfur electrochemistry. Attributed to these structural superiorities, the obtained sulfur electrodes exhibit excellent electrochemical performance, i.e., high areal capacity of 5.6 mAh cm^?2, rate capability up to 5 C, and stable cycling over 1000 cycles with a low capacity fading rate of 0.04% per cycle at 1 C, demonstrating great promise in the development of practical Li–S batteries.