Emerging energy chemistry in lithium–sulfur pouch cells

正On pursuing high-energy-density energy storage systems beyond the current lithium-ion battery technique, lithium–sulfur(Li–S) batteries have attracted worldwide attention due to their ultrahigh theoretical energy density up to 500 Wh kg~(-1)[1]. The unique Li–S chemistry based on the conversion reactions between solid sulfur, dissolved lithium polysulfides, and solid lithium sulfide affords thermodynamic advantages including high cathode specific capacity and low anode potential [2]. However,     

Interpretable hybrid machine learning demystifies the degradation of practical lithium-sulfur batteries

<正>The ever-increasing future demands of electrification and grid storage have spurred continued research to develop rechargeable battery chemistries for reliable energy storage [1]. Beyond current lithium-ion batteries, lithium–sulfur battery represents a promising system due to its high energy density(2600 Wh kg^-1) and low material cost [2]. Despite the immense potential, lithium–sulfur batteries, as well as other upcoming battery technologies,     

Recent progress on confinement of polysulfides through physical and chemical methods

With high theoretical energy density and the natural abundance of S, lithium-sulfur(Li–S) batteries are considered to be the promising next generation high-energy rechargeable energy storage devices. However, issues including electronical insulation of S, the lithium polysulfides(Li PSs) dissolution and the short cycle lifespan have prevented Li–S batteries from being practical applied. Feasible settlements of confining Li PSs to reduce the loss of active substances and improve the cycle stability include wrapping sulfur with compact layers, designing matrix with porous or hollow structures, adding adsorbents owning strong interaction with sulfur and inserting polysulfide barriers between cathodes and separators. This review categorizes them into physical and chemical confinements according to the influencing mechanism. With further discussion of their merits and flaws, synergy of the physical and chemical confinement is believed to be the feasible avenue that can guide Li–S batteries to the practical application.     

MoS2 nanorods with inner caves through synchronous encapsulation of sulfur for high performance Li–S cathodes

Lithium–sulfur(Li–S)batteries have become one of the most promising candidates for next-generation batteries owing to their high specific capacity,low cost,and environment-friendliness.Many efforts have been made to mitigate the"shuttle effect"through physical adsorption and chemical bonding.MoS2 has been proposed as a cathode material to provide effective anchoring sites for lithium polysulfides(Li PSs),but is still limited by its layer structure.Herein,we designed novel MoS2 nanorods with inner caves based on our previous work,and performed synchronous encapsulation of sulfur during the synthesis process.The outer MoS2 tubular shells physically inhibit the outward diffusion of polysulfide species while the inner particles chemically anchor the polysulfides to prevent shuttling.As the cathode matrix in Li–S batteries,the electrochemical results deliver a high initial discharge capacity of 1213 mAhg^-1 for sulfur at 0.1 C.After cycling at 1 C for 300 cycles,the cells exhibit a capacity decay of only 0.076%per cycle and high average coulombic efficiency over 95%.The tubular MoS2 structure is an innovative and appealing design,which could be regarded as a prospective substrate for the improved performance of Li–S batteries.     

Edge sulfurized graphene nanoplatelets via vacuum mechano-chemical reaction for lithium–sulfur batteries

Lithium–sulfur batteries have great potential for high energy applications due to their high capacities,low cost and eco-friendliness. However, the particularly rapid capacity decay owing to the dissolution and diffusion of polysulfide intermediate into the electrolyte still hamper their practical applications.And the reported preparation procedures to sulfur based cathode materials are often complex, and hence are rather difficult to produce at large scale. Here, we report a simple mechano-chemical sulfurization methodology in vacuum environment applying ball-milling method combined both the chemical and physical interaction for the one-pot synthesis of edge-sulfurized grapheme nanoplatelets with 3D porous foam structure as cathode materials. The optimal sample of 70%S–Gn Ps-48 h(ball-milled 48 h) obtains 13.2 wt% sulfur that chemically bonded onto the edge of Gn Ps. And the assembled batteries exhibit high initial discharge capacities of 1089 mAh/g at 0.1 C and 950 mAh/g at 0.5 C, and retain a stable discharge capacity of 776 mAh/g after 250 cycles at 0.5 C with a high Coulombic efficiency of over 98%. The excellent performance is mainly attributed to the mechano-chemical interaction between sulfur and grapheme nanoplatelets. This definitely triggers the currently extensive research in lithium–sulfur battery area.     

Bimetallic Ni–Co MOF@PAN modified electrospun separator enhances high-performance lithium-sulfur batteries

Lithium–sulfur(Li–S) batteries with high energy density are considered promising energy storage devices for the next generation. Nevertheless, the shuttle effect and the passive layer between the separator and the electrodes still seriously affect the cycle stability and life. Herein, a bimetallic Ni–Co metal–organic framework(MOF) with adsorption and catalytic synergism for polysulfides was successfully synthesized as an electrospinning separator sandwich for Li–S batteries. Introducing porous ...     

Single-atom catalysts for metal-sulfur batteries:Current progress and future perspectives

Metal-sulfur batteries are recognized as a promising candidate for next generation electrochemical energy storage systems owing to their high theoretical energy density,low cost and environmental friendliness.However,sluggish redox kinetics of sulfur species and the shuttle effect lead to large polarization and severe capacity decay.Numerous approaches from physical barrier,chemical adsorption strategies to electrocatalysts have been tried to solve these issues and pushed the rate and cycle performance of sulfur electrodes to higher levels.Most recently,single-atom catalysts(SACs)with high catalytic efficiency have been introduced into metal-sulfur systems to achieve fast redox kinetics of sulfur conversion.In this review,we systematically summarize the current progress on SACs for sulfur electrodes from aspects of synthesis,characterization and electrochemical performance.Challenges and potential solutions for designing SACs for high-performance sulfur electrodes are discussed.     

Grafting polymeric sulfur onto carbon nanotubes as highly-active cathode for lithium–sulfur batteries

Lithium–sulfur(Li–S)batteries are being explored as promising advanced energy storage systems due to their ultra-high energy density.However,fast capacity fading and low coulombic efficiency,resulting from the dissolution of polysulfides,remain a serious challenge.Compared to weak physical adsorptions or barriers,chemical confinement based on strong chemical interaction is a more effective approach to address the shuttle issue.Herein,we devise a novel polymeric sulfur/carbon nanotube composite for Li–S battery,for which 2,5-dithiobiurea is chosen as the stabilizer of long-chain sulfur.This offers chemical bonds which bridge the polymeric sulfur and carbon nanotubes.The obtained composite can deliver an ultra-high reversible capacity of 1076.2 m Ah g~(-1)(based on the entire composite)at the rate of 0.1 C with an exceptional initial Coulombic efficiency of 96.2%,as well as remarkable cycle performance.This performance is mainly attributed to the reaction reversibility of the obtained polymeric sulfur-based composite during the discharge/charge process.This was confirmed by density functional theory calculations for the first time.     

Synthesis of 3D Porous and Interconnected Hollow Carbon Nanospheres Array and Its Applications in Lithium-sulfur Batteries

Lithium-sulfur(Li–S) batteries are receiving much attention due to their high theoretical lithium storage capacity and energy density. However, the commercialization of Li–S batteries is mainly impeded by the inherent poor electrical conductivity of sulfur, the side shuttle behavior of polysulfides, and the volumetric change of sulfur during cycles. To solve these problems, here we report a unique 3D porous and interconnected hollow carbon nanospheres array(3D-HCNA) as sulfur host for lithium-sulfur batteries. This 3D-HCNA was synthesized through a nanocasting approach with sucrose as carbon precursors and mesoporous silica nanospheres as hard-templates. The silica nanospheres with special nanostructure were obtained by a biphase stratification approach. Owing to its unique architecture, as-prepared 3D-HCNA/S cathode with a high sulfur loading of 76 wt% exhibited excellent electrochemical performance. It showed highinitial capacity of 1318 m Ah/g at 0.05 C and good rate capability of 760 m Ah/g at 1 C. Moreover, excellent cycling performance was also observed with a capacity of 757 m Ah/g maintained after 200 cycles at 0.5 C.     

One stone two birds:Dual-effect kinetic regulation strategy for practical lithium–sulfur batteries

Lithium–sulfur(Li–S)batteries are deemed as one of the most promising energy storage systems due to their ultrahigh theoretical energy density of 2600 Wh kg^-1 far beyond the current lithium-ion battery technique[1].     

Rational design of Co nano-dots embedded three-dimensional graphene gel as multifunctional sulfur cathode for fast sulfur conversion kinetics

Lithium-sulfur(Li-S)batteries hold great promises to serve as next-generation energy storage devices because of their high theoretical energy density and environmental benignity.However,the shuttle effect of the soluble lithium polysulfides(LiPS)and intrinsic insulating nature of sulfur lead to low sulfur utilization and coulombic efficiency,leading to poor cycling performance.The impeded charge transportation and retard LiPS catalytic conversion also endows the Li-S batteries with sluggish redox reaction,leading to unsatisfied rate capability.In this study,Co-based MOF material ZIF-67 is used as the precursor to prepare Co nano-dots decorated three-dimensional graphene aerogel as sulfur immobilizer.This porous architecture establishes a highly conductive interconnected framework for fast charge/mass transportation.The exposed Co nano-dots serve as active sites to strongly trap LiPS,which endows CoNDs@G with low decomposition energy barrier for fast LiPS conversion reaction and promote the completely Li2 S catalytic transformation.Li-S cells based on the Co-NDs@G cathode exhibits excellent cyclability and a high capacity retention rate of 91.1%in 100 cycles.This strategy offers a new direction to design sulfur immobilizer for accelerated LiPS conversion kinetics of Li-S batteries.     

Recent advances in chemical adsorption and catalytic conversion materials for Li–S batteries

Owing to their low cost, high energy densities, and superior performance compared with that of Li-ion batteries, Li–S batteries have been recognized as very promising next-generation batteries. However, the commercialization of Li–S batteries has been hindered by the insulation of sulfur, significant volume expansion, shuttling of dissolved lithium polysulfides(Li PSs), and more importantly, sluggish conversion of polysulfide intermediates. To overcome these problems, a state-of-the-art strategy is to use sulfur host materials that feature chemical adsorption and electrocatalytic capabilities for Li PS species. In this review, we comprehensively illustrate the latest progress on the rational design and controllable fabrication of materials with chemical adsorbing and binding capabilities for Li PSs and electrocatalytic activities that allow them to accelerate the conversion of Li PSs for Li–S batteries. Moreover, the current essential challenges encountered when designing these materials are summarized, and possible solutions are proposed. We hope that this review could provide some strategies and theoretical guidance for developing novel chemical anchoring and electrocatalytic materials for high-performance Li–S batteries.     

Crosslinked polyacrylonitrile precursor for S@pPAN composite cathode materials for rechargeable lithium batteries

S@pPAN has become promising cathode materials in rechargeable batteries due to its high compressed density,low E/S ratio,no polysulfide dissolution,no self-discharge,and stable cycling.However,it is a big challenge to enhance its sulfur content which determines its practical specific capacity.Herein,we prepare crosslinked PAN as precursor,leading to effective enhancement of sulfur content up to 55 wt%and a reversible specific capacity of 838 mAh g _composites^-1 at 0.2C.Because of the microporous structure and high specific area,crosslinked PAN provides more space to accommodate sulfur molecule and improve the interfacial reaction of S@pPAN as well.This work provides a promising direction to design S@pPAN for lithium sulfur batteries with high energy density.     

Recent advances of metal phosphides for Li-S chemistry

Li-S batteries have been considered as one of advanced next-generation energy storage systems owing to their remarkable theoretical capacity(1672 m Ah g^-1)and high energy density(2600 Wh kg^-1).However,critical issues,mainly pertaining to lithium polysulfide shuttle and slow sulfur reaction kinetics,have posed a fatal threat to the electrochemical performances of Li-S batteries.The situation is even worse for high sulfur-loaded and flexible cathodes,which are the essential components for practical Li-S batteries.In response,the use of metal compounds as electrocatalysts in Li-S systems have been confirmed as an effective strategy to date.Particularly,recent years have witnessed many progresses in phosphidesoptimized Li-S chemistry.This has been motivated by the superior electron conductivity and high electrocatalytic activity of phosphides.In this tutorial review,we offer a systematic summary of active metal phosphides as promoters for Li-S chemistry,aiming at helping to understanding the working mechanism of phosphide electrocatalysts and guiding the construction of advanced Li-S batteries.     

Three-dimensionally interconnected Co9S8/MWCNTs composite cathode host for lithium–sulfur batteries

Several challenging issues,such as the poor conductivity of sulfur,shuttle effects,large volume change of cathode,and the dendritic lithium in anode,have led to the low utilization of sulfur and hampered the commercialization of lithium–sulfur batteries.In this study,a novel three-dimensionally interconnected network structure comprising Co9 S8 and multiwalled carbon nanotubes(MWCNTs)was synthesized by a solvothermal route and used as the sulfur host.The assembled batteries delivered a specific capacity of1154 m Ah g-1 at 0.1 C,and the retention was 64%after 400 cycles at 0.5 C.The polar and catalytic Co9 S8 nanoparticles have a strong adsorbent effect for polysulfide,which can effectively reduce the shuttling effect.Meanwhile,the three-dimensionally interconnected CNT networks improve the overall conductivity and increase the contact with the electrolyte,thus enhancing the transport of electrons and Li ions.Polysulfide adsorption is greatly increased with the synergistic effect of polar Co9 S8 and MWCNTs in the three-dimensionally interconnected composites,which contributes to their promising performance for the lithium–sulfur batteries.     

Vanadium-based compounds and heterostructures as functional sulfur catalysts for lithium-sulfur battery cathodes

Lithium-sulfur(Li-S) batteries have attracted wide attention for their high theoretical energy density, low cost, and environmental friendliness. However, the shuttle effect of polysulfides and the insulation of active materials severely restrict the development of Li-S batteries. Constructing conductive sulfur scaffolds with catalytic conversion capability for cathodes is an efficient approach to solving above issues.Vanadium-based compounds and their heterostructures have recently emerged as f...     

Two-dimensional multimetallic sulfide nanosheets with multi-active sites to enhance polysulfide redox reactions in liquid Li_2S_6-based lithium-polysulfide batteries

The lithium-sulfur battery has attracted enormous attention as being one of the most significant energy storage technologies due to its high energy density and cost-effectiveness.However,the "shuttle effect" of polysulfide intermediates represents a formidable challenge towards its wide applications.Herein,we have designed and synthesized two-dimensional Cu,Zn and Sn-based multimetallic sulfide nanosheets to construct multi-active sites for the immobilization and entrapment of polysulfides with offering better performance in liquid Li2S6-based lithium-polysulfide batteries.Both experimental measurements and theoretical computations demonstrate that the interfacial multi-active sites of multimetallic sulfides not only accelerate the multi-chained redox reactions of highly diffusible polysulfides,but also strengthen affinities toward polysulfides.By adopting multimetallic sulfide nanosheets as the sulfur host,the liquid Li2 S6-based cell exhibits an impressive rate capability with 1200 mAh/g and retains 580 mAh/g at 0.5 mA/cm² after 1000 cycles.With high sulfur mass loading conditions,the cell with 2.0 mg/cm² sulfur loading delivers a cell capacity of 1068 mAh/g and maintains 480 mAh/g with 0.8 mA/cm² and 500 cycles.This study provides new insights into the multifunctional material design with multi-active sites for elevated lithium-polysulfide batteries.     

Recent progress in fluorinated electrolytes for improving the performance of Li–S batteries

Lithium–sulfur(Li–S) batteries represent a "beyond Li-ion" technology with low cost and high theoretical energy density and should fulfill the ever-growing requirements of electric vehicles and stationary energy storage systems. However, the sulfur-based conversion reaction in conventional liquid electrolytes results in issues like the so-called shuttle effect of polysulfides and lithium dendrite growth, which deteriorate the electrochemical performance and safety of Li–S batteries. Optimization of conventional organic solvents(including ether and carbonate) by fluorination to form fluorinated electrolytes is a promising strategy for the practical application of Li–S batteries. The fluorinated electrolytes, owing to the high electronegativity of fluorine, possesses attractive physicochemical properties, including low melting point,high flash point, and low solubility of lithium polysulfide, and can form a compact and stable solid electrolyte interphase(SEI) with the lithium metal anode. Herein, we review recent advancements in the development of fluorinated electrolytes for use in Li–S batteries. The effect of solvent molecular structure on the performance of Li–S batteries and the formation mechanism of SEI on the cathode and anode sides are analyzed and discussed in detail. The remaining challenges and future perspectives of fluorinated electrolytes for Li–S batteries are also presented.     

Ethylene sulfite based electrolyte for non-aqueous lithium oxygen batteries

Non-aqueous lithium–oxygen(Li–O_2) batteries have been considered as the superior energy storage system due to their high-energy density, however, some challenges limit the practical application of Li–O_2 batteries. One of them is the lack of stable electrolyte. In this communication, a novel electrolyte with ethylene sulfite(ES) used as solvent for Li–O_2 batteries was reported. ES solvent showed low volatility and high electrochemical stability. Without a catalyst in the air-electrode of Li–O_2 batteries, the batteries showed high specific capacity, good round-trip efficiency and cycling stability.     

Nanostructured energy materials for electrochemical energy conversion and storage: A review

Nanostructured materials have received tremendous interest due to their unique mechanical/electrical properties and overall behavior contributed by the complex synergy of bulk and interfacial properties for efficient and effective energy conversion and storage. The booming development of nanotechnology affords emerging but effective tools in designing advanced energy material. We reviewed the significant progress and dominated nanostructured energy materials in electrochemical energy conversion and storage devices, including lithium ion batteries, lithium–sulfur batteries, lithium–oxygen batteries, lithium metal batteries, and supercapacitors. The use of nanostructured electrocatalyst for effective electrocatalysis in oxygen reduction and oxygen evolution reactions for fuel cells and metal–air batteries was also included. The challenges in the undesirable side reactions between electrolytes and electrode due to high electrode/electrolyte contact area, low volumetric energy density of electrode owing to low tap density,and uniform production of complex energy materials in working devices should be overcome to fully demonstrate the advanced energy nanostructures for electrochemical energy conversion and storage. The energy chemistry at the interfaces of nanostructured electrode/electrolyte is highly expected to guide the rational design and full demonstration of energy materials in a working device.