S-doped mesoporous graphene modified separator for high performance lithium-sulfur batteries

Due to their low cost,environmental friendliness and high energy density,the lithium-sulfur batteries(LSB)have been regarded as a promising alternative for the next generation of rechargeable battery systems.However,the practical application of LSB is seriously hampered by its short cycle life and high self-charge owing to the apparent shuttle effect of soluble lithium polysulfides.Using MgSO_(4)@MgO composite as both template and dopant,template-guided S-doped mesoporous graphene(SMG)is prepared via the fluidized-bed chemical vapor deposition method.As the polypropylene(PP)modifier,SMG with high specific surface area,abundant mesoporous structures and moderate S doping content offers a wealth of physical and chemical adsorptive sites and reduced interfacial contact resistance,thereby restraining the serious shuttle effects of lithium polysulfides.Consequently,the LSB configured with mesoporous graphene(MG)as S host material and SMG as a separator modifier exhibits an enhanced electrochemical performance with a high average capacity of 955.64 mA h g^(-1) at 1C and a small capacity decay rate of 0.109%per cycle.Additionally,the density functional theory(DFT)calculation models have been rationally constructed and demonstrated that the doped S atoms in SMG possess higher binding energy to lithium polysulfides than that in MG,indicating that the SMG/PP separator can effectively capture soluble lithium polysulfides via chemical binding forces.This work would provide valuable insight into developing a versatile carbon-based separator modifier for LSB.

Stabilizing zinc anode using zeolite imidazole framework functionalized separator for durable aqueous zinc-ion batteries

Aqueous zinc-ion batteries(AZIBs) hold great promise as a viable alternative to lithium-ion batteries owing to their high energy density and environmental friendliness.However,AZIBs are consistently plagued by the formation of zinc dendrites and concurrent side reactions,which significantly diminish their overall service life,In this study,the glass fiber separator(GF) is modified using zeolite imidazole salt framework-8(ZIF-8),enabling the development of efficient AZIBs.ZIF-8,which is abundant in nitrogen content,efficiently regulates the desolvation of [Zn(H_(2)O)_(6)]^(2+) to inhibit hydrogen production.Moreover,it possesses abundant nanochannels that facilitate the uniform deposition of Zn~(2+) via a localized action,thereby hindering the formation of dendrites.The insulating properties of ZIF-8 help prevent Zn^(2+) and water from trapping electron reduction at the layer surface,which reduces corrosion of the zinc anode.Consequently,ZIF-8-GF achieves the even transport of Zn^(2+) and regulates the homogeneous deposition along the Zn(002) crystal surface,thus significantly enhancing the electrochemical performance of the AZIBs,In particular,the Zn|Zn symmetric cell with the ZIF-8-GF separator delivers a stable cycle life at0.5 mA cm^(-2) of 2300 h.The Zn|ZIF-8-GF|MnO_(2) cell exhibits reduced voltage polarization while maintaining a capacity retention rate(93.4%) after 1200 cycles at 1.2 A g^(-1) The unique design of the modified diaphragm provides a new approach to realizing high-performance AZIBs.

Dendrite-free lithium anode achieved under lean-electrolyte condition through the modification of separators with F-functionalized Ti_(3)C_(2)nanosheets

An unstable solid electrolyte interphase(SEI)and chaotic lithium ion fux are key impediments to commercial high-energy-density lithium batteries because of the uncontrolled growth of rigid lithium dendrites,which would pierce through the conventional polypropylene(PP)separator,causing short circuit and safety issues.Herein,the homogenization of lithium ion fux and the generation of stable SEI layers on lithium anodes were achieved via coating a fuorine-functionalized Ti_(3)C_(2)(F-Ti_(3)C_(2))nanosheets on PP separator(F-Ti_(3)C_(2)@PP).F-Ti_(3)C_(2)nanosheets provide abundant ions pathways to homogeneously manipulate lithium ion fux and increase the Young’s modulus and electrolyte wettability of the separators.In addition,F species derived from the F-Ti_(3)C_(2)nanosheets would promote the formation of Li F-rich SEI film.The synergistic effect contribute to the uniform lithium deposition.Symmetric Li|Li,asymmetric Li|Cu and full Li|Li Fe PO4cells incorporated with the modified separators exhibit improved electrochemical performance even under lean electrolyte conditions.This work provides a feasible strategy to improve the performance of lithium batteries through both fuoridized SEI formation and lithium ion fux manipulation.

In situ separator modification via CVD-derived N-doped carbon for highly reversible Zn metal anodes

Attention toward aqueous zinc-ion battery has soared recently due to its operation safety and environmental benignity.Nonetheless,dendrite formation and side reactions occurred at the anode side greatly hinder its practical application.Herein,we adopt direct plasma-enhanced chemical vapor deposition strategy to in situ grow N-doped carbon(NC)over commercial glass fiber separator targeting a highly stabilized Zn anode.The strong zincophilicity of such a new separator would reduce the nucleation overpotential of Zn and enhance the Zn-ion transference number,thereby alleviating side reactions.Symmetric cells equipped with NC-modified separator harvest a stable cycling for more than 1,100 h under 1 mA·cm^(−2)/1 mAh·cm^(−2).With the assistance of NC,the depth of discharge of Zn anode reaches as high as 42.7%.When assembled into full cells,the zinc-ion battery based on NC-modified separator could maintain 79%of its initial capacity(251 mAh·g^(−1))at 5 A·g^(−1) after 1,000 cycles.

Research status and prospect of separators for magnesium-sulfur batteries

Magnesium-sulfur(Mg-S)batteries have attracted wide research attention in recent years,and are considered as one of the major candidates to replace lithium-ion batteries due to the high theoretical energy density,low costs of active materials,and high safety.However,there are still significant challenges that need to be overcome before they can reach the large-scale practical applications.The key issue is the dissolution and shuttle effect of magnesium polysulfides(Mg-PSs),which leads to severe capacity degradation and shortens cycling life,greatly limiting the development of Mg-S batteries.In order to overcome these challenges,great efforts have been made in cathode materials,electrolytes,and separators.Herein,we review the investigations on suppressing the shuttle effect of Mg-PSs via the modification of separators,including schemes such as coating the functional materials that can hold Mg-PSs on the surface of polyolefin-based or glass fiber(GF)separators,forming gel polymer separators via cross-linking polymerization reactions,and developing gel polymer electrolytes coupled with GF separators.Furthermore,an outlook is proposed for the future design on separator exploitation to accelerate the development of Mg-S battery technology.

Balanced Polysulfide Containment and Lithium Ion Transport in Lithium-Sulfur Batteries via Nitrogen-doped Carbon Hollow Multi-shelled Structures on Modified Separators

Representing the next-generation technology in lithium-ion batteries,lithium-sulfur(Li-S)batteries offer increased specific energy without relying on scarce metals like nickel and cobalt,but suffer from a low practical specific energy due to poor conductivity and a short lifespan due to the shuttle effect of polysulfides.Balancing the confinement of polysulfides and the transport of lithium ions requires highly elaborate modifiers for separators.Hollow multi-shelled structures(HoMSs)show promise as hierarchical mesostructures for separators,offering multiple shell layers and internal cavities that effectively inhibit polysulfide shuttle.Thoughtful design of these structures is crucial to address these challenges effectively.In this study,nitrogen-doped carbon HoMS(NC HoMS)was created using polymer templates through a precisely controlled polymerization process.Batteries featuring NC HoMS-modified separators exhibit improved capacity and cycling stability in comparison to those utilizing commercial separators.Especially,triple-shelled NC HoMS strikes a balance in polysulfide containment and lithium ion transport.Featuring a sulfur loading of 6.34 mg/cm^(2),the Li-S battery can consistently complete 100 charge-discharge cycles,starting with a discharge capacity of 966.4 mA·h/g with a 75.8%capacity retention rate.NC HoMS holds potential as the separator modifier in addressing the polysulfide shuttle problem and facilitating the Li-ion transportation for advanced Li-S batteries.

Atomically Dispersed Iron Active Sites Promoting Reversible Redox Kinetics and Suppressing Shuttle Effect in Aluminum-Sulfur Batteries

Rechargeable aluminum-sulfur(Al-S)batteries have been considered as a highly potential energy storage system owing to the high theoretical capacity,good safety,abundant natural reserves,and low cost of Al and S.However,the research progress of Al-S batteries is limited by the slow kinetics and shuttle effect of soluble polysulfides intermediates.Herein,an interconnected free-standing interlayer of iron sin-gle atoms supported on porous nitrogen-doped carbon nanofibers(FeSAs-NCF)on the separator is developed and used as both catalyst and chemical barrier for Al-S batteries.The atomically dispersed iron active sites(Fe-N_(4))are clearly identified by aberration-corrected high-angle annular dark-field scanning transmission electron microscopy and X-ray absorption near-edge structure.The Al-S battery with the FeSAs-NCF shows an improved specific capacity of 780 mAh g^(−1)and enhanced cycle stability.As evidenced by experimental and theoretical results,the atomically dispersed iron active centers on the separator can chemically adsorb the polysulfides and accelerate reaction kinetics to inhibit the shuttle effect and promote the reversible conversion between aluminum polysulfides,thus improving the electrochemical performance of the Al-S battery.This work provides a new way that can not only promote the conversion of aluminum sulfides but also suppress the shuttle effect in Al-S batteries.

Nitrogen doped hollow carbon nanospheres as efficient polysulfide restricted layer on commercial separators for high-performance lithium-sulfur batteries

The polysulfide shuttle limits the development of lithium-sulfur(Li-S) batteries with high energy density and long lifespan. Herein, nitrogen doped hollow carbon nanospheres(NHCS) derived from polymerization of dopamine on SiO_(2)nanospheres are employed to modify the commercial polypropylene/polyethylene/polypropylene tri-layer separators(PP/PE/PP@NHCS). The abundant nitrogen heteroatoms in NHCS exhibit strong chemical adsorption toward polysulfides, which can effectively suppress the lithium polysulfides shuttle and further enhance the utilization of active sulfur. Lithium-sulfur batteries employing the PP/PE/PP@NHCS deliver an initial discharge capacity of 1355 mAh/g and retain high capacity of 921 mAh/g after 100 cycles at 0.2 C. At a high rate of 2 C, the lithium-sulfur batteries exhibit capacity of 461 mAh/g after 1000 cycles with a capacity fading rate of 0.049% per cycle. This work demonstrates that the NHCS coated PP/PE/PP separator is promising for future commercial applications of lithium-sulfur batteries with improved electrochemical performances.

Robust In-Zr Metal-Organic Framework Nanosheets as Ultrathin Interlayer Toward High-Rate and Long-Cycle Lithium-Sulfur Batteries

Lithium-sulfur(Li-S)batteries have great potential as the next generation of high-energy-density storage systems.However,the practical viability of Li-S batteries is largely hampered by undesirable shuttling behavior and sluggish conversion kinetics of polysulfides.Herein,a multifunctional separatormodified layer(In/Zr-BTB nanosheets)with the merits of robust structures and efficient catalytic metal sites has been presented.In/Zr-BTB nanosheets inherit the stable structure from Zr-BTB and strengthen the catalytic performance due to the introduction of highly catalytic species indium via metal-ion exchange.The thickness and areal mass loading of the modified layer are only 260 nm and 0.011 mg/cm2,respectively.Nevertheless,the ultrathin modification layers with efficient catalytic species,compact structures,and uniform pore channels can realize fast Li+transport,effective polysulfide interception,and rapid catalytic conversion.Therefore,the In/Zr-BTB@PP cell with a high sulfur content of 80 wt%could maintain high capacity retention of 85.6%with a low capacity fading rate of 0.048%per cycle after 300 cycles even at a high current rate of 2 C.This work opens a new door toward the design of versatile metal-organic framework(MOF)nanosheets and multifunctional separators for high-energy-density Li-S batteries.

Advanced cellulose-based materials toward stabilizing zinc anodes

Rechargeable aqueous zinc metal batteries(RAZMBs) have received extensive attention for large-scale energy storage systems due to the merits of Zn anodes, including moderate volumetric and gravimetric energy density, low redox potential, abundant reserve, low cost and impressive intrinsic safety. However, Zn anodes suffer from a series of adverse reactions(dendrite growth,hydrogen evolution, and surface passivation) resulting in low Coulombic efficiency, large polarization, and unsatisfied cycling performance, which inevitably hinder the wide application of RAZMBs. To address the above issues, cellulose-based materials are widely used for Zn anode protection because of their unique physical and chemical properties and other advantages such as biocompatibility, non-toxicity, degradability and easy extraction. In order to better understand the current progress in cellulosebased materials for the Zn anode protection, we have classified and summarized the relevant literatures. In this review, we summarize and elaborate the causes of poor reversibility for Zn anodes, including dendrite formation, hydrogen evolution, and surface passivation. Subsequently, the effective strategies(anode interfacial engineering, gel electrolyte optimization, and separator modification) of cellulose-based materials toward stabilizing Zn anodes are overviewed. In the end, the existing challenges and prospects of cellulose-based materials in Zn anode protection are summarized to shed light on future work.

Polysulfides adsorption and catalysis dual-sites on metal-doped molybdenum oxide nanoclusters for Li-S batteries with wide operating temperature

The development of electrocatalysts with high catalytic activity is conducive to enhancing polysulfides adsorption and reducing activation energy of polysulfides conversion, which can effectively reduce polysulfide shuttling in Li-S batteries. Herein, a novel catalyst NiCo-MoO x /rGO (rGO = reduced graphene oxides) with ultra-nanometer scale and high dispersity is derived from the Anderson-type polyoxometalate precursors, which are electrostatically assembled on the multilayer rGO. The catalyst material possesses dual active sites, in which Ni-doped MoO x exhibits strong polysulfide anchoring ability, while Co-doped MoO x facilitates the polysulfides conversion reaction kinetics, thus breaking the Sabatier effect in the conventional electrocatalytic process. In addition, the prepared NiCo-MoO x /rGO modified PP separator (NiCo-MoO x /rGO@PP) can serve as a physical barrier to further inhibit the polysulfide shuttling effect and realize the rapid Li+ migration. The results demonstrate that Li-S coin cell with NiCo-MoO x /rGO@PP separator shows excellent cycling performance with the discharge capacity of 680 mAh·g^(−1) after 600 cycles at 1 C and the capacity fading of 0.064% per cycle. The rate performance is also impressive with the remained capacity of 640 mAh·g^(−1) after 200 cycles even at 4 C. When the sulfur loading is 4.0 mg·cm^(−2) and electrolyte volume/sulfur mass ratio (E/S) ratio is 6.0 μL·mg^(−1), a specific capacity of 830 mAh·g^(−1) is achieved after 200 cycles with a capacity decay of 0.049% per cycle. More importantly, the cell with NiCo-MoO x /rGO@PP separator exhibits cycling performance under wide operating temperature with the reversible capacities of 518, 715, and 915 mAh·g^(−1) after 100 cycles at −20, 0, and 60 °C, respectively. This study provides a new design approach of highly efficient catalysts for sulfur conversion reaction in Li-S batteries.

Tri-functionalized polypropylene separator by rGO/MoO_(2) composite for high-performance lithium–sulfur batteries

The popularity of lithium–sulfur batteries has been increasing gradually due to their ultrahigh theoretical specific capacity and energy density. Nevertheless, they also have lots of drawbacks to be overcome, such as poor conductivity, severe volume expansion, and serious“shuttle effect”. In this work, reduced graphene oxide/molybdenum dioxide(rGO/MoO_(2)) composite is synthesized and applied to modify polypropylene separator. The modified polypropylene separator introduces synergistic tri-functions of physical adsorption, chemical interaction and catalytic effects, which can inhibit the“shuttle effect” and enhance the electrochemical performances of lithium-sulfur batteries. In the prepared r GO/MoO_(2) composite, the polar MoO_(2) chemically adsorbs the intermediate lithium polysulfide, while the rGO with good electrical conductivity not only acts as a physical barrier to prevent diffusion of polysulfide ions, but also improves the conversion efficiency of active material intercepted on the separator. As a consequence, the battery assembled with rGO/MoO_(2) modified polypropylene separator exhibits a reversible capacity of 757.5 mAh·g^(-1) after 200 cycles at0.2 C with a negligible capacity decay of 0.207% per cycle,which indicates a good long-period cycling stability. Furthermore, the rate performance and self-discharge suppression are also improved by introducing modified polypropylene separator. It shows that rGO/MoO_(2) composite is a promising material for separator modification in lithium-sulfur batteries.

Magnetic modification of diamagnetic agglomerate forming powder materials

A simple method for the magnetic modification of various types of powdered agglomerate forming dia- magnetic materials was developed. Magnetic iron oxide particles were prepared from ferrous sulfate by microwave assisted synthesis. A suspension of the magnetic particles in water soluble organic solvent （methanol, ethanol, propanol, isopropyl alcohol, or acetone） was mixed with the material to be modified and then completely dried at elevated temperature. The magnetically modified materials were found to be stable in water suspension at least for 2 months.

Bimetal-organic frameworks derived Co/N-doped carbons for lithium-sulfur batteries

Lithium-sulfur(Li-S) batteries have received extensive attention due to their high theoretical specific energy density.However,the utilization of sulfur is seriously reduced by the shuttle effect of lithium polysulfides and the low conductivity of sulfur and lithium sulfide(Li2S).Herein,we introduced bimetalorganic frameworks(Co/Zn-ZIF) derived cobalt and nitrogen-doped carbons(Co/N-C) into Li-S batteries through host design and sepa rator modification.The Co/N-C in Li-S batteries effectively limits the shuttle effect through simultaneously serving as polysulfide traps and chemical catalyst.As a result,the Li-S batteries deliver a high reversible capacity of 1614.5 mAh/g and superior long-term cycling stability with a negligible capacity decay of only 0.04% per cycle after 1000 cycles.Furthermore,they have a high area capacity of 5.5 mAh/cm2.