Ten-Minute Synthesis of a New Redox-Active Aqueous Binder for Flame-Retardant Li-S Batteries

As a critical role in battery systems,polymer binders have been shown to efficiently suppress the lithium polysulfide shuttling and accommodate volume changes in recent years.However,preparation processes and safety,as the key criterions for Li-S batteries'practical applications,still attract less attention.Herein,an aqueous multifunction binder(named PEI-TIC)is prepared via an easy and fast epoxy-amine ring-opening reaction(10 min),which can not only give the sulfur cathode a stable mechanical property,a strong chemical adsorption and catalytic conversion ability,but also a fire safety improvement.The Li-S batteries based on the PEI-TIC binder display a high discharge capacity(1297.8 mAh g^(-1)),superior rate performance(823.0 mAh g^(-1)at 2 C),and an ultralow capacity decay rate of 0.035%over more than 800 cycles.Even under 7.1 mg cm^(-2)S-loaded,the PEI-TIC electrode can also achieve a high areal capacity of 7.2 mA h g^(-1)and excellent cycling stability,confirming its application potential.Moreover,it is also noted that TG-FTIR test is performed for the first time to explore the flame-retardant mechanism of polymer binders.This work provides an economically and environmentally friendly binder for the practical application and inspires the exploration of the flame-retardant mechanism of all electrode components.

Dual-single-atoms of Pt-Co boost sulfur redox kinetics for ultrafast Li-S batteries

Applications of lithium-sulfur(Li-S)batteries are still limited by the sluggish conversion kinetics from polysulfide to Li_(2)S.Although various single-atom catalysts are available for improving the conversion kinetics,the sulfur redox kinetics for Li-S batteries is still not ultrafast.Herein,in this work,a catalyst with dual-single-atom Pt-Co embedded in N-doped carbon nanotubes(Pt&Co@NCNT)was proposed by the atomic layer deposition method to suppress the shuttle effect and synergistically improve the interconversion kinetics from polysulfides to Li_(2)S.The X-ray absorption near edge curves indicated the reversible conversion of Li_(2)Sx on the S/Pt&Co@NCNT electrode.Meanwhile,density functional theory demonstrated that the Pt&Co@NCNT promoted the free energy of the phase transition of sulfur species and reduced the oxidative decomposition energy of Li_(2)S.As a result,the batteries assembled with S/Pt&Co@NCNT electrodes exhibited a high capacity retention of 80%at 100 cycles at a current density of 1.3 mA cm^(−2)(S loading:2.5 mg cm^(−2)).More importantly,an excellent rate performance was achieved with a high capacity of 822.1 mAh g^(−1) at a high current density of 12.7 mA cm^(−2).This work opens a new direction to boost the sulfur redox kinetics for ultrafast Li-S batteries.

Configuring single-layer MXene nanosheet onto natural wood fiber via C-Ti-C covalent bonds for high-stability Li-S batteries

Lithium-sulfur batteries(LSBs)are considered promising candidates for next-generation battery technologies owing to their outstanding theoretical energy density and cost-effectiveness.However,the low conductivity and polysulfide shuttling effect of S cathodes severely hamper the practical performance of LSBs.Herein,in situ-generated single layer MXene nanosheet/hierarchical porous carbonized wood fiber(MX/PCWF)composites are prepared via a nonhazardous eutectic activation strategy coupled with pyrolysis-induced gas diffusion.The unique architecture,wherein single layer MXene nanosheets are constructed on carbonized wood fiber walls,ensures rapid polysulfide conversion and continuous electron transfer for redox reactions.The C-Ti-C bonds formed between MXene and PCWF can considerably expedite the conversion of polysulfides,effectively suppressing the shuttle effect.An impressive capacity of 1301.1 m A h g^(-1)at 0.5 C accompanied by remarkable stability is attained with the MX/PCWF host,as evidenced by the capacity maintenance of 722.6 m A h g^(-1)after 500 cycles.Notably,the MX/PCWF/S cathode can still deliver a high capacity of 886.8 m A h g^(-1)at a high S loading of 5.6 mg cm^(-2).The construction of two-dimensional MXenes on natural wood fiber walls offers a competitive edge over S-based cathode materials and demonstrates a novel strategy for developing high-performance batteries.

Electrochemical Realization of 3D Interconnected MoS_(3)/PPy Nanowire Frameworks as Sulfur-Equivalent Cathode Materials for Li-S Batteries

The development of freestanding and binder-free electrode is an effective approach to perform the inherent capacity of active materials and promote the mechanism study by minimizing the interference from additives.Herein,we construct a freestanding cathode composed of MoS_(3)/PPy nanowires(NWs)deposited on porous nickel foam(NF)(MoS_(3)/PPy/NF)through electrochemical methods,which can work efficiently as sulfur-equivalent cathode material for Li-S batteries.The structural stability of the MoS_(3)/PPy/NF cathode is greatly enhanced due to its significant tolerance to the volume expansion of MoS_(3)during the lithiation process,which we ascribe to the flexible 3D framework of PPy NWs,leading to superior cycling performance compared to the bulk-MoS_(3)/NF reference.Eliminating the interference of binder and carbon additives,the evolution of the chemical and electronic structure of Mo and S species during the discharge/charge was studied by X-ray absorption near-edge spectroscopy(XANES).The formation of lithium polysulfides was excluded as the driving cathode reaction mechanism,suggesting the great potential of MoS_(3)as a promising sulfur-equivalent cathode material to evade the shuttle effect for Li-S batteries.The present study successfully demonstrates the importance of structural design of freestanding electrode enhancing the cycling performances and revealing the corresponding mechanisms.

Mechanochemical strategy assisted morphology recombination of COFs for promoted kinetics and LiPS transformation in Li-S batteries

A covalent organic frameworks(COFs)material with regular pores and stable structure can be used as the host of lithium-sulfur batteries to improve battery kinetics and polysulfides conversion.Herein,we designed and synthesized two kinds of rod-liked bulk COFs by adjusting different pore sizes(COF-BTD and COF-TFB),unfortunately,the active sites masking and sluggish kinetics have not met our expectations.Generally,the available layered COFs prepared from mechanochemical can expose abundant active sites and favorable kinetics than bulk COFs.Thus,simple mechanical ball milling is applied to activate the above COFs(M-COFs group).It is worth noting that layered R-COF-BTD is directly synthesized from rod-liked precursors by simple morphological reconstruction.A series of characterization methods are used to systematically explore the advantages of the group of M-COFs@S electrodes in the cycling process,including the effects of specific morphology on the kinetics and transformation of polysulfides.Our research provides a feasible plan for the development and selection of the host material of lithium-sulfur batteries.

Conversion of LiPSs Accelerated by Pt-Doped Biomass-Derived Hyphae Carbon Nanobelts as Self-Supporting Hosts for Long-Lifespan Li-S Batteries

Rechargeable Li-S batteries(LSBs)are emerging as an important alternative to lithium-ion batteries(LIBs),owing to their high energy densities and low cost;yet sluggish redox kinetics of LiPSs results in inferior cycle life.Herein,we prepared multifunctional self-supporting hyphae carbon nanobelt(HCNB)as hosts by carbonization of hyphae balls of Rhizopus,which could increase the S loading of the cathode without sacrificing reaction kinetics.Trace platinum(Pt)nanoparticles were introduced into HCNBs(PtHCNBs)by ion-beam sputtering deposition.Based on the X-ray photoelectron spectroscopy analyses,the introduced trace Pt regulated the local electronic states of heteroatoms in HCNBs.Electrochemical kinetics investigation combined with operando Raman measurements revealed the accelerated reaction mechanics of sulfur species.Benefiting from the synergistic catalytic effect and the unique structures,the as-prepared PtHCNB/MWNCT/S cathodes delivered a stable capacity retention of 77%for 400 cycles at 0.5 C with a sulfur loading of 4.6 mg cm^(-2).More importantly,remarkable cycling performance was achieved with an high areal S loading of 7.6 mg cm^(-2).This finding offers a new strategy to prolong the cycle life of LSBs.

In Situ-Constructed Li_(x)MoS_(2)with Highly Exposed Interface Boosting High-Loading and Long-Life Cathode for All-Solid-State Li-S Batteries

As the persistent concerns regarding sluggish reaction kinetics and insufficient conductivities of sulfur cathodes in all-solid-state Li-S batteries(ASSLSBs),numerous carbon additives and solid-state electrolytes(SSEs)have been incorporated into the cathode to facilitate ion/electron pathways around sulfur.However,this has resulted in a reduced capacity and decomposition of SSEs.Therefore,it is worth exploring neotype sulfur hosts with electronic/ionic conductivity in the cathode.Herein,we present a hybrid cathode composed of few-layered S/MoS_(2)/C nanosheets(<5 layers)that exhibits high-loading and long-life performance without the need of additional carbon additives in advanced ASSLSBs.The multifunctional MoS_(2)/C host exposes the abundant surface for intimate contacting sites,in situ-formed LixMoS_(2)during discharging as mixed ion/electron conductive network improves the S/Li2S conversion,and contributes extra capacity for the part of active materials.With a high active material content(S+MoS_(2)/C)of 60 wt%in the S/MoS_(2)/C/Li_(6)PS_(5)Cl cathode composite(the carbon content is only~3.97 wt%),the S/MoS_(2)/C electrode delivers excellent electrochemical performance,with a high reversible discharge capacity of 980.3 mAh g^(-1)(588.2 mAh g^(-1)based on the whole cathode weight)after 100 cycles at 100 mA g^(-1).The stable cycling performance is observed over 3500 cycles with a Coulombic efficiency of 98.5%at 600 mA g^(-1),while a high areal capacity of 10.4 mAh cm^(-2)is achieved with active material loading of 12.8 mg cm^(-2).

Sandwiching Sulfur into the Dents Between N,O Co-Doped Graphene Layered Blocks with Strong Physicochemical Confinements for Stable and High-Rate Li-S Batteries

The development of lithium-sulfur batteries(LSBs)is restricted by their poor cycle stability and rate performance due to the low conductivity of sulfur and severe shuttle effect.Herein,an N,O co-doped graphene layered block(NOGB)with many dents on the graphene sheets is designed as effective sulfur host for high-performance LSB s.The sulfur platelets are physically confined into the dents and closely contacted with the graphene scaffold,ensuring structural stability and high conductivity.The highly doped N and O atoms can prevent the shuttle effect of sulfur species by strong chemical adsorption.Moreover,the micropores on the graphene sheets enable fast Li^+transport through the blocks.As a result,the obtained NOGB/S composite with 76 wt%sulfur content shows a high capacity of 1413 mAh g^-1 at 0.1 C,good rate performance of 433 mAh g^-1 at 10 C,and remarkable stability with 526 mAh g^-1 at after 1000 cycles at 1 C(average decay rate:0.038%per cycle).Our design provides a comprehensive route for simultaneously improving the conductivity,ion transport kinetics,and preventing the shuttle effect in LSBs.

CoB and BN composites enabling integrated adsorption/catalysis to polysulfides for inhibiting shuttle-effect in Li-S batteries

Lithium-sulfur(Li-S)batteries are hampered by the infamous shuttle effect and slow redox kinetics,resulting in rapid capacity decay.Herein,a bifunctional catalysis CoB/BN@rGO with integrated structure and synergy effect between adsorption and catalysis is proposed to solve the above problems.The integrated CoB and BN are simultaneously and uniformly introduced on the rGO substrate through a one-step calcination strategy,applied to modify the cathode side of PP separator.The transition metal borides can catalyze the conversion of lithium polysulfides(Li_(2)Sn,n≥4),whereas the bond of B-S is too weak to absorb LPS.Thus BN introduced can effectively restrict the diffusion of polysulfides via strong chemisorption with LiSnLi+…N,while the rGO substrate ensures smooth electron transfer for redox reaction.Therefore,through the integrated adsorption/catalysis,the shuttle effect is suppressed,the kinetics of redox reaction is enhanced,and the capacity decay is reduced.Using CoB/BN@rGO modified PP separator,the Li-S batteries with high initial capacity(1450 mAh g^(-1)at 0.35 mA cm^(-2))and long-cycle stability(700 cycles at 1.74 mA cm^(-2)with a decay rate of 0.032%per cycle)are achieved.This work provides a novel insight for the preparation of bifunctional catalysis with integrated structure for long-life Li-S batteries.

Direct insight into sulfiphilicity-lithiophilicity design of bifunctional heteroatom-doped graphene mediator toward durable Li-S batteries

The practical applications of lithium-sulfur(Li-S)battery have been greatly hindered by the severe polysulfide shuttle at the cathode and rampant lithium dendrite growth at the anode.One of the effective solutions deals with concurrent management of both electrodes.Nevertheless,this direction remains in a nascent stage due to a lack of material selection and mechanism exploration.Herein,we devise a temperature-mediated direct chemical vapor deposition strategy to realize the controllable synthesis of three-dimensional boron/nitrogen dual-doped graphene(BNG)particulated architectures,which is employed as a light-weighted and multi-functional mediator for both electrodes in Li-S batteries.Benefiting from the“sulfiphilic”and“lithiophilic”features,the BNG modified separator not only enables boosted kinetics of polysulfide transformation to mitigate the shuttle effect but also endows uniform lithium deposition to suppress the dendritic growth.Theoretical calculations in combination with electro-kinetic tests and operando Raman analysis further elucidate the favorable sulfur and lithium electrochemistry of BNG at a molecular level.This work offers direct insight into the mediator design via controllable synthesis of graphene materials to tackle the fundamental challenges of Li-S batteries.

Tuning dual-atom mediator toward high-rate bidirectional polysulfide conversion in Li-S batteries

An emerging practice in the realm of Li-S batteries lies in the employment of single-atom catalysts(SACs)as effective mediators to promote polysulfide conversion,but monometallic SACs affording isolated geometric dispersion and sole electronic configuration limit the catalytic benefits and curtail the cell performance.Here,we propose a class of dual-atom catalytic moieties comprising hetero-or homo-atomic pairs anchored on N-doped graphene(NG)to unlock the liquid–solid redox puzzle of sulfur,readily realizing Li-S full cell under high-rate-charging conditions.As for Fe-Ni-NG,in-depth experimental and theoretical analysis reveal that the hetero-atomic orbital coupling leads to altered energy levels,unique electronic structures,and varied Fe oxidation states in comparison with homo-atomic structures(FeFe-NG or Ni-Ni-NG).This would weaken the bonding energy of polysulfide intermediates and thus enable facile electrochemical kinetics to gain rapid liquid-solid Li_(2)S_(4)?Li_(2)S conversion.Encouragingly,a Li-S battery based on the S@Fe-Ni-NG cathode demonstrates unprecedented fast-charging capability,documenting impressive rate performance(542.7 mA h g^(-1)at 10.0 C)and favorable cyclic stability(a capacity decay of 0.016%per cycle over 3000 cycles at 10.0 C).This finding offers insights to the rational design and application of dual-atom mediators for Li-S batteries.

A semi-immobilized sulfur-rich copolymer backbone with conciliatory polymer skeleton and conductive substrates for high-performance Li-S batteries

Sulfur-rich polymers have gained a great deal of attention as the next-generation active materials in lithium-sulfur(Li-S)batteries due to their low cost,environmental compatibility,naturally sulfur uniform dispersion,and distinctive structure covalently bonding with sulfur atoms.However,the poor electrical conductivity and undesirable additional shuttle effect still hinder the commercial application of sulfur-rich polymers.Herein,we report a flexible semi-immobilization strategy to prepare allylterminated hyperbranched poly(ethyleneimine)-functionalized reduced graphene oxide(A-PEI-EGO)as sulfur-rich copolymer backbone.The semi-immobilization strategy can effectively reconcile the demand for polymer skeleton and conductive substrates through forming quaternary ammonium groups and reducing oxygen-containing functional groups,resulting in enhanced skeleton adsorption capacity and substrate electronic conductivity,respectively.Furthermore,the stable covalent bonding connection based on polymer molecules(A-PEI)not only completely prevents the additional shuttle effect of lithiation organic molecules and even sulfur-rich oligomers,but provides more inverse vulcanization active sites.As a result,the as-prepared A-PEI-EGO-S cathodes display an initial discharge capacity of1338 m A h g^(-1)at a rate of 0.1 C and an outstanding cycling stability of 0.046%capacity decay per cycle over 600 cycles.Even under 6.2 mg cm^(-2)S-loaded and sparing electrolyte of 6μL mg^(-1),the A-PEI-EGO-S cathode can also achieve a superior cycling performance of 98%capacity retention after 60 cycles,confirming its application potential.

Promoting reaction kinetics of lithium polysulfides by cobalt polyphthalocyanine derived ultrafine Co nanoparticles mono-dispersed on graphene flakes for Li-S batteries

Lithium-sulfur(Li-S)batteries have been considered as the next generation high energy storage devices.However,its commercialization has been hindered by several issues,especially the dissolution and shuttle of the soluble lithium polysulfides(LiPSs)as well as the slow reaction kinetics of LiPSs which may make shuttling effect even worse.Herein,we report a strategy to address this issue by in-situ transformation of Co−N_(x) coordinations in cobalt polyphthalocyanine(CoPPc)into Co nanoparticles(Co NPs)embedded in carbon matrix and mono-dispersed on graphene flakes.The Co NPs can provide rich binding and catalytic sites,while graphene flakes act as ideally LiPSs transportation and electron conducting platform.With a remarkable enhanced reaction kinetics of LiPSs via these merits,the sulfur host with a sulfur content up to 70 wt%shows a high initial capacity of 1048 mA∙h/g at 0.2C,good rate capability up to 399 mA·h/g at 2C.

Enhanced chemical trapping and catalytic conversion of polysulfides by diatomite/MXene hybrid interlayer for stable Li-S batteries

Lithium-Sulfur (Li-S) batteries with high theoretical energy density are promising energy storage systems in the next decades, while the lithium polysulfides (LiPSs) shuttling caused by the sluggish sulfur redox reaction severely lowers the practical performance. The use of interlayer between the cathode and separator has been widely investigated to physically or chemically block the LiPSs, while the introduction of catalytic materials is a more effective strategy to accelerate the conversion of LiPSs. MXene with rich surface chemistry has shown its potential for facilitating the catalytic conversion, however, the aggregation of MXene sheets usually leads to the loss of the catalytic active sites. Herein, we report a diatomite/MXene (DE/MX) hybrid material as the bifunctional interlayer for improving the adsorption/conversion of LiPSs in Li-S batteries. The diatomite with porous structure and rich silica-hydroxyl functional groups could trap LiPSs effectively, while prevent the aggregation of MXene. The DE/MX based interlayer showed bifunctions of enhancing the chemical adsorption and promoting the conversion of LiPSs. The Li-S batteries with the DE/MX interlayer delivered an improved cycling stability with a low capacity decay of 0.059% per cycle over 1000 cycles at 1.0 C. Moreover, stable 200 cycles can be realized with a high sulfur loading electrode up to 6.0 mg cm^(−2). This work provides an effective strategy to construct bifunctional interlayers for hindering the shuttling of LiPSs and boosting the practical application of Li-S batteries.

Low-temperature Li-S batteries enabled by all amorphous con version process of organosulfur cathode

The high degree of crystallinity of discharging in termediates of Li-S batteries(Li_(2)S_(2)/Li_(2)S)causes a severe capacity attenuation at low temperatures.Herein,a sulfur-rich polymer is fabricated,which enables all the discharging in termediates to exist in an amorphous state without long-range order,promoti ng the substantial conversion of discharging intermediates and enhancing Li-S batteries'performance at low temperatures greatly.This cathode material exhibits excellent performance both at room and low temperatures.Even under an extremely low temperature(-40℃),the discharge capacity can remain 67% of that at room temperature.Besides,in-situ UV/Vis spectroscopy and density functional theory calculations reveal that this organosulfur cathode undergoes a new mechanism during discharge.Li_(2)S_(6) and Li_(2)S_(3) are the primary discharging intermediates that are quite different from conventional Li-S batteries.These results provide a new directi on for a broader range of applications of Li-S batteries.

Anchoring polysulfide with artificial solid electrolyte interphase for dendrite-free and low N/P ratio Li-S batteries

Lithium sulfur batteries are regarded as a promising candidate for high-energy-density energy storage devices.However,the lithium metal anode in lithium-sulfur batteries encounters the problem of lithium dendrites and lithium metal consumption caused by polysulfide corrosion.Herein we design a dualfunction PMMA/PPC/LiNO3composite as an artificial solid electrolyte interphase(PMCN-SEI)to protect Li metal anode.This SEI offers multiple sites of C=O for polysulfide anchoring to constrain corrosion of Li metal anode.The lithiated polymer group and Li3N in PMCN-SEI can homogenize lithium-ion deposition behavior to achieve a dendrite-free anode.As a result,the PMCN-SEI protected Li metal anode enables the Li||Li symmetric batteries to maintain over 300 cycles(1300 h)at a capacity of 5 m Ah cm^(-2),corresponding to a cumulative capacity of 3.25 Ah cm^(-2).Moreover,Li-S batteries assembled with 20μm of Li metal anode(N/P=1.67)still deliver an initial capacity of 1166 m A h g-1at 0.5C.Hence,introducing polycarbonate polymer/inorganic composite SEI on Li provides a new solution for achieving the high energy density of Li-S batteries.

2D hierarchical yolk-shell heterostructures as advanced host-interlayer integrated electrode for enhanced Li-S batteries

Lithium sulfur(Li-S)batteries hold great promising for high-energy-density batteries,but appear rapid capacity fading due to the lack of overall and elaborated design of both sulfur host and interlayer.Herein,we developed a novel two-dimensional(2D)hierarchical yolk-shell heterostructure,constructed by a graphene yolk,2D void and outer shell of vertically aligned carbon-mediated MoS2 nanosheets(G@void@MoS2/C),as advanced host-interlayer integrated electrode for Li-S batteries.Notably,the 2D void,with a typical thickness of^80 nm,provided suitable space for loading and confining nano sulfur,and vertically aligned ultrathin MoS2 nanosheets guaranteed enriched catalytically active sites to effectively promote the transition of soluble polysulfides.The conductive graphene yolk and carbon mediated shell sufficiently accelerated electron transport.Therefore,the integrated electrode of G@void@MoS2/C not only exceptionally confined the sulfur/polysulfides in 2D yolk-shell heterostructures,but also achieved catalytic transition of the residual polysulfides dissolved in electrolyte to solid Li2S2/Li2S,both of which synergistically achieved an extremely low capacity fading rate of 0.05%per cycle over 1000 times at 2C,outperforming most reported Mo based cathodes and interlayers for Li-S batteries.2D hierarchical yolkshell heterostructures developed here may shed new insight on elaborated design of integrated electrodes for Li-S batteries.

Trithiocyanuric acid derived g-C3N4 for anchoring the polysulfide in Li-S batteries application

Lithium-sulfur (Li-S) batteries have great potential as an electrochemical energy storage system because of the high theoretical energy density and acceptable cost of financial and environment.However,the shuttle effect leads to severe capacity fading and low coulombic efficiency.Here,graphitic carbon nitride(g-C3N4) is designed and prepared via a feasible and simple method from trithiocyanuric acid (TTCA) to anchor the polysulfides and suppress the shuttle effect.The obtained g-C3N4 exhibits strong chemical interaction with polysulfides due to its high N-doping of 56.87 at%,which is beneficial to improve the cycling stability of Li-S batteries.Moreover,the novel porous framework and high specific surface area of g-C3N4 also provide fast ion transport and broad reaction interface of sulfur cathode,facilitating high capacity output and superior rate performance of Li-S batteries.As a result,Li-S batteries assembled with g-C3N4 can achieve high discharge capacity of 1200 mAh/g at 0.2 C and over 800 mAh/g is remained after 100 cycles with a coulombic efficiency more than 99.5%.When the C-rate rises to 5 C,the reversible capacity of Li-S batteries can still maintain at 607mAh/g.

A Perspective on Energy Densities of Rechargeable Li-S Batteries and Alternative Sulfur-Based Cathode Materials

Lithium-ion battery has reached its capacity and energy density limits.In the past decade,significant efforts have been taken to explore new electrode materials that have the potential to enable high-energy-density battery systems.Among them,elemental sulfur is one of the high-capacity cathode candidates and has been studied intensively over the past decade.The formation of lithium polysulfides in ethereal liquid electrolyte upon cycling results in several challenges such as active material dissolution,shuttle effect,and limited cycle life.Although some approaches have been developed to overcome these issues,the attainable energy densities of lithium–sulfur(Li-S)batteries seem to be low.The main reason is largely due to the high electrolyte/sulfur(E/S)ratios used in the sulfur cathode.This perspective provides new insights on the energy density analysis of sulfur cathode.The“average mass density”of sulfur cathode is found to be a useful parameter for this purpose.Some emerging alternative sulfur-based cathode materials such as organopolysulfides and metal polysulfides which possess unique properties and performances are presented.They are promising to overcome the intrinsic issues associated with elemental sulfur cathode and enable truly high-energy-density Li-S battery systems.

New redox-mediating polymer binder for enhancing performance of Li-S batteries

Lithium-sulfur(Li-S)batteries are promising energy storage devices owing to their high energy density and the low cost of sulfur.However,they are still far from being applied commercially because of the detrimental capacity fade caused by the dissolution of lithium polysulfide(LPS)in liquid electrolyte.In this study,we introduced a new polymer binder having a redox-mediating function that assists in the reduction of soluble LPS to Li2S at the cathode to suppress the shuttle effect as well as enhance sulfur utilization.An amine group containing benzo(ghi)perylene imide(BPI)was synthesized and grafted onto poly(acrylic acid)to produce a redox-mediating polymer binder.An Li-S cell fabricated using the new redox-mediating polymer binder demonstrated a capacity decay retention of 0.036%per cycle up to 500 cycles at 0.5 C with a coulombic efficiency of 98%.