Advanced Lithium Sulfur Batteries Research Articles

An all-biomaterials-based aqueous binder based on adsorption redox-mediated synergism for advanced lithium–sulfur batteries

The complex multistep electrochemical reactions of lithium polysulfides and the solid–liquid–solid phase transformation involved in the S8 to Li2S reactions lead to slow redox kinetics in lithium–sulfur batteries (Li–S batteries). However, some targeted researches have proposed strategies requiring the introduction of significant additional inactive components, which can seriously affect the energy density. Whereas polymer binders, proven to be effective in suppressing shuttle effects and constraining electrode volume expansion, also have promising potential in enhancing Li–S batteries redox kinetics. Herein, a novel aqueous polymer binder is prepared by convenient amidation reaction of fully biomaterials, utilizing its inherent rich amide groups for chemisorption and redox mediating ability of thiol groups to achieve adsorption redox-mediated synergism for efficient conversion of polysulfides. Li–S batteries based on N-Acetyl-L-Cysteine-Chitosan (NACCTS) binder exhibit high initial discharge specific capacity (1260.1 ​mAh ​g−1 at 0.2 ​C) and excellent cycling performance over 400 cycles (capacity decay rate of 0.018% per cycle). In addition, the batteries exhibit great areal capacity and stable capacity retention of 83.6% over 80 cycles even under high sulfur loading of 8.4 ​mg ​cm−2. This work offers a novel perspective on the redox-mediated functional design and provides an environmentally friendly biomaterials-based aqueous binder for practical Li–S battery.

Heterostructures Regulating Lithium Polysulfides for Advanced Lithium-Sulfur Batteries.

Sluggish reaction kinetics and severe shuttling effect of lithium polysulfides seriously hinder the development of lithium-sulfur batteries. Heterostructures, due to unique properties, have congenital advantages that are difficult to be achieved by single-component materials in regulating lithium polysulfides by efficient catalysis and strong adsorption to solve the problems of poor reaction kinetics and serious shuttling effect of lithium-sulfur batteries. In this review, the principles of heterostructures expediting lithium polysulfides conversion and anchoring lithium polysulfides are detailedly analyzed, and the application of heterostructures as sulfur host, interlayer, and separator modifier to improve the performance of lithium-sulfur batteries is systematically reviewed. Finally, the problems that need to be solved in the future study and application of heterostructures in lithium-sulfur batteries are prospected. This review will provide a valuable reference for the development of heterostructures in advanced lithium-sulfur batteries.

Constructing Wide-Temperature Lithium-Sulfur Batteries by Using a Covalent Organic Nanosheet Wrapped Carbon Nanotube.

Lithium-sulfur (Li-S) batteries hold the superiority of eminent theoretical energy density (2600Wh kg-1 ). However, the ponderous sulfur reduction reaction and the issue of polysulfide shuttling pose significant obstacles to achieving the practical wide-temperature operation of Li-S batteries. Herein, a covalent organic nanosheet-wrapped carbon nanotubes (denoted CON/CNT) composite is synthesized as an electrocatalyst for wide-temperature Li-S batteries. The design incorporates the CON skeleton, which contains imide and triazine functional units capable of chemically adsorbing polysulfides, and the underlaid CNTs facilitate the conversion of captured polysulfides enabled by enhanced conductivity. The electrocatalytic behavior and chemical interplay between polysulfides and the CON/CNT interlayer are elucidated by in situ X-ray diffraction detections and theoretical calculations. Resultantly, the CON/CNT-modified cells demonstrate upgraded performances, including wide-temperature operation ranging from 0 to 65 °C, high-rate performance (625 mAh g-1 at 5.0 C), exceptional high-rate cyclability (1000 cycles at 5.0 C), and stable operation under high sulfur loading (4.0mg cm-2 ) and limited electrolyte (5µL mgs -1 ). These findings might guide the development of advanced Li-S batteries.

Reinforced Lewis covalent bond by twinborn nitride heterostructure for lithium-sulfur batteries

The practical application of lithium-sulfur (Li-S) batteries, as promising next-generation batteries, is hindered by their shuttle effect and the slow redox kinetics. Herein, a tungsten and molybdenum nitride heterostructure functionalized with hollow metal-organic framework-derived carbon (W2N/Mo2N) was proposed as the sulfur host. The hollow spherical structure provides storage space for sulfur, enhances electrical conductivity, and inhibits volume expansion. The metal atoms in the nitrides bonded with lithium polysulfides (LiPSs) through Lewis covalent bonds, enhancing the high catalytic activity of the nitrides and effectively reducing the energy barrier of LiPSs redox conversion. Moreover, the high intrinsic conductivity of nitrides and the ability of the heterostructure interface to accelerate electron/ion transport improved the Li+ transmission. By leveraging the combined properties of strong adsorption and high catalytic activity, the sulfur host effectively inhibited the shuttle effect and accelerated the redox kinetics of LiPSs. High-efficiency Li+ transmission, strong adsorption, and the efficient catalytic conversion activities of LiPSs in the heterostructure were experimentally and theoretically verified. The results indicate that the W2N/Mo2N cathode provides stable, and long-term cycling (over 2000 cycles) at 3 C with a low attenuation rate of 0.0196% per cycle. The design strategy of a twinborn nitride heterostructure thus provides a functionalized solution for advanced Li-S batteries.

Phosphorus-doped few-layer graphite wrapped metallic cobalt as interlayer for advanced lithium–sulfur batteries

The shuttle effect and sluggish redox kinetics of sulfur cathode are the main barriers to commercializing lithium-sulfur (Li–S) batteries. Fabricating functional interlayers is considered as one of the efficient approaches to suppress the shuttle effect while accelerating the conversion kinetics of polysulfides. Herein, the nanofiber-type interlayer composed of cobalt wrapped with few-layer phosphorus-doped graphite (CoPG) is elaborately designed, which is expected to chemically adsorb the polysulfides while accelerating the redox conversion of polysulfides anchored on phosphorus-doped graphite. Electrochemical measurements sufficiently verify that the usage of the designed CoPG interlayer significantly prolongs the longevity of Li–S batteries, reaching 694 mAh/g with a capacity decay rate of 0.11% at the current density of 2.0C. Remarkably, Li–S battery sustains for 125 cycles and maintains ultrahigh capacity retention of 92% at the current density of 0.2C even with a sulfur loading of 5.8 mg/cm2. The theoretical computation further confirms the intensive interactions between CoPG and polysulfides, consistent with the experimental outcomes. Encapsulating the electrocatalyst with a few-layer polarized graphite enables the interlayer with adsorption and catalysis functions, which provides a promising strategy for advanced Li–S batteries.

A coral-like composite of CoP-modified polyaniline-derived carbon chain skeleton as an efficient sulfur host for lithium-sulfur batteries

Lithium-sulfur batteries (LSBs) have attracted wide attention in the field of rechargeable batteries due to their high theoretical energy density. However, the severe “shuttle effect” of lithium polysulfides (LiPSs) and the slow conversion kinetics are key factors restricting the commercial application of LSBs. To address these issues, we designed and prepared a coral-like composite of CoP-modified polyaniline-derived carbon chain skeleton (CoP/C) as the sulfur host for LSBs. The carbon chains can provide multidirectional channels for the transport of Li+ and electron; and the uniformly scattered CoP can adsorb the LiPSs through chemical adsorption and simultaneously promote their conversion, thus the “shuttle effect” can be effectively alleviated. Meanwhile, the effect of the amount of aniline monomer on the electrochemical performance of sulfur cathode were studied. After sulfur loading, the CoP/C-300/S (with aniline monomer addition of 300 μL) exhibits the best electrochemical performance. At 1 C, after 500 cycles, it still maintains a reversible specific capacity of 478 mA h g−1, with a decay rate of 0.074% per cycle, indicating its excellent cycling stability. This work provides a new approach for the application of CoP material in advanced LSBs.

Scavenging of “Dead Sulfur” and “Dead Lithium” Revealed by Integrated–Heterogeneous Catalysis for Advanced Lithium–Sulfur Batteries

AbstractThe simultaneous engineering of sulfur cathode and Li anode is critical for electrolyte‐starved high energy density Li–S batteries, in which slow electrochemical conversions and side chemical reactions of dead sulfur are found to be the determining factors in limiting the sulfur utilization, corresponding to the poor reversible capacity of Li–S batteries. Herein, this work challenges the conventional wisdom of heterogeneous and homogeneous catalyses in Li–S batteries and proposes the concept of integrated–heterogeneous catalysis to simultaneously scavenge the dead sulfur and dead lithium to compensate the active materials sulfur and lithium loss simply through adding a small amount of ZnI2 into conventional electrolyte of Li–S cells. Regulated by integrated–heterogeneous catalysis, over 1300 h of cycling is realized in Li||Li symmetric cells, revealing superb compatibility of the ZnI2‐incorporated electrolyte with lithium metal. Meanwhile, the ZnI2 shows good prospects in promoting the reutilization of dead sulfur in both theoretical calculation and experimental tests. Practically, a high initial capacity of 1170 mAh g−1 with decent cycling stability is achieved in electrolyte‐starved and high‐loading pouch cells (5.0 µL mg−1 and 5.2 mg cm−2).

Simultaneously tuning the defect and morphology to design urchin-like Fe-Co3O4-x as integrated trapping-catalyzing modified separator for superior lithium-sulfur batteries

The lithium-sulfur (Li-S) battery is a promising candidate for next-generation energy storage devices because of its high energy density and cost-effectiveness. However, its commercial application is still hampered by the severe lithium polysulfides (LiPSs) shuttling and the sluggish polysulfide redox kinetics. Herein, the defect-rich Fe-Co3O4-x with a unique 3D urchin-like architecture has been rationally designed using a microwave-assisted hydrothermal method followed by calcination. The morphology and surface defect of Fe-Co3O4-x are simultaneously regulated by altering the Fe doping content. The resulting Fe-Co3O4-x materials are confirmed with abundant oxygen defects and exhibit strong chemical entrapment towards LiPSs, as evidenced by both the experimental results and the DFT calculations. Under dual regulation, the nanorod-assembled urchin-like architecture could accelerate the electron/ion transport and significantly strengthen the LiPSs redox reaction kinetics. As expected, the assembled Li-S cell with Fe-Co3O4-x modified separator exhibits an ultralow capacity decay of 0.04% per cycle at 1 C after 800 cycles and excellent rate capability as high as 528 mAh g−1 at 5 C. Furthermore, the modification of Fe-Co3O4-x on the separator also improves the reversibility of the lithium anode deposition/stripping. This work provides new insights into effective strategies for designing 3D nanostructural oxygen defect-rich electrocatalysts to achieve advanced Li-S batteries.

Conductive Metal Organic Framework as Trapping Cathode Additive for High Performance Lithium-Sulfur Batteries

Lithium-Sulfur (Li-S) batteries with high capacity and energy density have arisen as one of the most promising secondary batteries. However, higher order lithium polysulfide (LiPSs) shuttling and insulating nature of sulfur cathode results in capacity degradation and premature failure of the cell [1]. Here for the first time, we have implemented conductive Cu metal-based Metal organic framework (Cu-MOF) as a Li-S battery cathode material. Cu-MOF cathode catalyst not only reduce the LiPSs shuttle effect but also increase the conductivity of Li-S battery cathode [2].Here, Cu-MOF pore morphology will trap the polysulfides and further prevent LiPSs shuttling. In addition, the well-defined architecture of organic ligands of Cu-MOF also participate to explicate the involved surface-binding mechanisms of S and polysulfide products. Furthermore, Cu-MOF improve the diffusion rate of Li ions, shackling LiPSs, upsurging conduction of electrons/ions, and regulating the deposition of Li2S2/Li2S towards cathode side [3]. Furthermore, sulfur active material is well percolated inside the pores of conductive Cu-MOF which shows the long-cycling performance as shown in Figure 1.Benefiting from the unique fibrous, porous, interwoven structure, the conductive MOF@S-composite cathode demonstrates a high initial capacity of 1671 mAh g–1 at 0.05 C rate with a good coulombic efficiency of >95% and the outstanding capacity of 849 mAh g-1 cycles even after 200 cycles at the 0.5 C-rate with coulombic efficiency of 98.3%. It is believed that, the experimental findings and mechanistic understanding of Cu-MOF cathode in this work will open a new avenue for the further development of other conductive MOFs in the Li-S batteries. Figure 1: Cycling performance of S@Cu-MOF composite at 0.5 C-rate. References Mingyue Wang, Zhongchao Bai, Ting Yang, Chuanhao Nie, Xun Xu, Yunxiao Wang, Jian Yang, Shixue Dou, and Nana Wan."Advances in High Sulfur Loading Cathodes for Practical Lithium-Sulfur Batteries." Energy Mater, no.12 (2022): 2201585.Dan Luo, Chaojie Li, Yongguang Zhang, Qianyi Ma, Chuyin Ma, Yihang Nie, Matthew Li, Xuefei Weng, Rong Huang, Yan Zhao, Lingling Shui, Xin Wang, Zhongwei Chen. "Design of Quasi-MOF Nanospheres as a Dynamic Electrocatalyst toward Accelerated Sulfur Reduction Reaction for High-Performance Lithium–Sulfur Batteries." Mater, no.34 (2022): 210554. Jun Zhang, Ye Shi, Yu Ding, Lele Peng, Wenkui Zhang, Guihua Yu. "A Conductive Molecular Framework Derived Li2S/N,P-Codoped Carbon Cathode for Advanced Lithium–Sulfur Batteries." Energy Mater, no.7 (2017): 1602876. Figure 1

An Effective Polysulfide Trapping Strategy for the Development of a Scalable, High Energy Density Lithium-Sulfur Battery

Rechargeable lithium-sulfur (Li-S) batteries represent an attractive, “beyond Li-ion”, battery technology because they offer a high specific energy of 2,500 Wh/kg at the material level1 and 550 Wh/kg at the cell level.2 However, Li-S batteries face substantial technical challenges that have thus far prevented the realization of the battery’s tremendous performance potentials.3 One of the major technical challenges is low practical specific capacity and fast performance degradation due to the formation, migration, and shuttling of intermediate lithium polysulfides (PSs). Several strategies have been used to trap the PS species either chemically or physically; however, they either incur increased cost due to the use of expensive catalysts4 or suffer from the reduced battery specific energy due to added inactive weights from the cell design.5,6 We will present a novel strategy to address the PS-shuttle issue using a nanolayer polymer modified high surface area carbon (NPC) as a new type of PS-trapping material.7 When thin films of NPC were coated on sulfur electrodes (NPC-S), we found that our NPC-S based Li-S battery demonstrated a high discharge specific capacity (~1,600 mAh/g) that is nearing sulfur’s theoretical specific capacity. Our molecular dynamics simulation suggests such an excellent performance is attributed to NPC’s strong PS trapping capability via dipole-dipole interactions. We will show that, using a sustainable starting material, our approach is low-cost and economically scalable for the advanced Li-S battery technology. References Zhang, S. S., Journal of Power Sources 2013, 231, 153-162.Manthiram, A.; Fu, Y.; Su, Y.-S., Accounts of Chemical Research 2013, 46 (5), 1125-1134.Chen, Z. X.; Zhao, M.; Hou, L. P.; Zhang, X. Q.; Li, B. Q.; Huang, J. Q., Advanced Materials 2022, 2201555.Hamal, D.; Awadallah, O.; El-Zahab, B., Catalysis in Lithium-Sulfur Cathodes for Improved Performance and Stability. In 242nd The Electrochemical Society Meeting, Atlanta, GA, USA, 2022.Chung, S.-H.; Han, P.; Singhal, R.; Kalra, V.; Manthiram, A., Advanced Energy Materials 2015, 5 (18).Singhal, R.; Chung, S.-H.; Manthiram, A.; Kalra, V., Journal of Materials Chemistry A 2015, 3 (8), 4530-4538.Hasan, W.; Hyynh, K.; Razzaq, A.; Smdani, G.; Shende, R.; Paudel, T.; Xing, W., "Scalable, High Energy Density Lithium-Sulfur Batteries". In NASA Battery Workshop, November 15-17, 2022 , Huntsville, AL, USA, 2022. Acknowledgment This work was supported by the Larry and Linda Pearson Endowed Chair at the Department of Mechanical Engineering, South Dakoda School of Mines and Technology and by the South Dakota Governor’s Research Center for Electrochemical Energy Storage. Figure 1

Honeycomb-like porous carbon embedded ferrous sulfide nanoparticles as bifunctional separator modifier by forming sulfur bonds with polysulfides in advanced lithium-sulfur batteries

To develop practical and outstanding lithium-sulfur (Li-S) batteries, it is advisable to adsorb soluble polysulfides and catalyze insoluble Li2S2/Li2S. Herein, a ferrous sulfide decorated honeycomb-like porous carbon (FeS/HMPC) was synthesized by sulfuration strategy to act as a separator modifier in Li-S batteries. Owing to the positive migration of the Fe d-band center, the binding of FeS to polysulfides is dominated by the S bond (Fe-SLiPSs), which makes FeS have strong adsorption capacity for various types of polysulfides. Moreover, FeS shows the minimum energy path for the migration of typical polysulfide Li2S. In other words, it has the smallest diffusion barrier. Hence, the FeS/HMPC-PP not only realizes the efficient suppression of the shuttle effect but also catalyzes the redox reaction of polysulfides. Benefiting from the above advantages, the FeS/HMPC-PP based cells exhibit a high initial capacity of 1673 mAh g−1 at 0.2 C and a reversible capacity of 686.7 mAh g−1 at 3 C after 500 cycles. Moreover, the cell with a high sulfur loading of 2.4mg cm−2 demonstrates an ultra-low-capacity decay of 0.007% per cycle at 0.2 C. This work provides novel insights and promising candidates to act as a functional separator for Li-S batteries with long life and high-rate electrochemical performance.

Preparation of CoO-CoP-CNT heterogeneous materials for advanced lithium-sulfur battery cathode electrode

A one-dimensional linear material (CoO-CoP-CNT) was successfully prepared and studied as a sulfur-loaded material for the cathode. This heterostructure material exhibits a high specific surface area (115.29 m2 g−1) and rich active sites, which effectively suppress the volume expansion of sulfur and enhance the catalysis and adsorption of LiPS. As a result, it mitigates the shuttle effect of LiPS and improves the electrochemical performance of the battery. The initial discharge capacity of the battery employing the sulfur carrier was measured at 979.9 mAh g−1 at 0.2 C, and it demonstrated a capacity of 367.9 mAh g−1 after 200 cycles of charging and discharging. At 2 C, the initial discharge capacity of S/CoO-CoP-CNT reached 743.7 mAh g−1, with a capacity retention rate of 42.0% after 500 cycles. These findings indicate that the battery with S/CoO-CoP-CNT positive electrode exhibits superior electrochemical performance.

Multi-functions of amino thiophenol additives for shielding lithium metal anode in advanced Li-S battery

Lithium-sulfur (Li-S) batteries have been considered as a promising candidate for the next generation of battery systems due to their high specific capacity and energy density. However, some barriers impede the application of Li-S batteries, such as the “shuttle effects” of lithium polysulfides (LPS), the poor electrical conductivity of sulfur, and lithium dendrite formation on lithium metal electrodes. Herein, we investigated a series of amino thiophenol as electrolyte additives: 2-amino thiophenol (2-ATP), 3-amino thiophenol (3-ATP), and 4-amino thiophenol (4-ATP); as well as p-phenylenediamine (PPD). These additives react with Li to form a stable and uniform solid electrolyte interphase (SEI) to protect the Li anode and minimize the interaction of Li with soluble LPS. Initial specific capacity at 0.1C and reversible specific capacity after 100 cycles are 1420 and 1043 mAh/g, 1429 and 982 mAh/g, 1148 and 871 mAh/g, 1317 and 791 mAh/g for 4-ATP, 3-ATP, 2-ATP, and PPD, respectively. Long-term cycling testing of Li-S cells was conducted at 0.2C and the cell with 4-ATP additives deliver an initial specific capacity of 1159 mAh/g and capacity retention of 77% after 300 cycles. The morphology and composition of the after-cycled SEI layers were examined by SEM and XPS. The findings suggest amino thiophenols (ATPs) form stable and smooth closed-packed SEI layers, that ameliorate lithium dendrite problems and LPS reactions with Li metal. 4-ATP is found to exhibit the best electrochemical performance followed by 3-ATP, 2-ATP, and PPD, which are in good agreement with the surface morphology. In addition, the amine group can assist the reaction between the thiol group and S8 on the cathode and modify the redox pathway of polysulfide.

Surface Engineering in Covalent Organic Polymers for High-Performance Li-S Batteries.

Lithium-sulfur (Li-S) batteries are promising energy storage technology due to their tempting high theoretical capacity and energy density. Nevertheless, the wastage of active materials that originates from the shuttling effect of polysulfides still hinders advancement of Li-S batteries. The effective design of cathode materials is extremely pivotal to solve this thorny problem. Herein, Surface engineering in covalent organic polymers (COPs) has been performed to investigate the influence of pore wall polarity on the performance of COP-based cathodes used for Li-S batteries. With the assistance of experimental investigation and theoretical calculations, performance improvement by increasing pore surface polarity and a synergy effect of the polarized functionalities, along with nano-confinement effect of the COPs, are disclosed, to which the improved performance of Li-S batteries including outstanding Coulombic efficiency (99.0%) and extremely low capacity decay (0.08% over 425 cycles at 1.0 C) is attributed. This work not only enlightens the designable synthesis and applications of covalent polymers as polar sulfur hosts with high utilization of active materials, but also provides a feasible guide for the design of effective cathode materials for future advanced Li-S batteries.

Cathode Kinetics Evaluation in Lean-Electrolyte Lithium-Sulfur Batteries.

Lithium-sulfur (Li-S) batteries afford great promise on achieving practical high energy density beyond lithium-ion batteries. Lean-electrolyte conditions constitute the prerequisite for achieving high-energy-density Li-S batteries but inevitably deteriorates battery performances, especially the sulfur cathode kinetics. Herein, the polarizations of the sulfur cathode are systematically decoupled to identify the key kinetic limiting factor in lean-electrolyte Li-S batteries. Concretely, an electrochemical impedance spectroscopy combined galvanostatic intermittent titration technique method is developed to decouple the cathodic polarizations into activation, concentration, and ohmic parts. Therein, activation polarization during lithium sulfide nucleation emerges as the dominant polarization as the electrolyte-to-sulfur ratio (E/S ratio) decreases, and the sluggish interfacial charge transfer kinetics is identified as the main reason for degraded cell performances under lean-electrolyte conditions. Accordingly, a lithium bis(fluorosulfonyl)imide electrolyte is proposed to decrease activation polarization, and Li-S batteries adopting this electrolyte provide a discharge capacity of 985 mAh g-1 under a low E/S ratio of 4 μL mg-1 at 0.2 C. This work identifies the key kinetic limiting factor of lean-electrolyte Li-S batteries and provides guidance on designing rational promotion strategies to achieve advanced Li-S batteries.

Bidirectional Catalyst with Robust Lithiophilicity and Sulfiphilicity for Advanced Lithium–Sulfur Battery

AbstractThe application of lithium–sulfur batteries (LSBs) is immensely impeded by notorious shuttle effect, sluggish redox kinetics, and irregular Li2S deposition, which result in large polarization and rapid capacity decay. To obtain the LSBs with high energy density and fast reaction kinetics, herein, a heterostructure composed by nitrogen‐deficient graphitic carbon nitride (ND‐g‐C3N4) and MgNCN is fabricated via a magnesiothermic denitriding technology. Lithophilic C3N4 with abundant nitrogen‐deficient acts as a conductive framework, together with the sulfiphilic MgNCN, lithium‐polysulfides (LiPSs) can be effectively captured followed by a regulated Li2S nucleation. Furthermore, the oxidation conversion kinetics can be accelerated as well. As expected, the LSBs with catalytic MgNCN/ND‐g‐C3N4 as the interlayer exhibit remarkable electrochemical performance with a discharge capacity of 650 mAh g−1 at 4 C. Meanwhile, a low capacity decay of 0.008% per cycle can be reached at 1 C after 400 cycles. Even with a high areal sulfur loading of 5.1 mg cm−2, outstanding capacity retention can be achieved at 0.5 C (64.18%) and 1 C (90.46%). The presented strategy unlocks a new way for the LSBs design with highly efficient catalyst.

CoFe2O4@rGO as a Separator Coating for Advanced Lithium–Sulfur Batteries

Lithium–sulfur (Li–S) batteries are hindered by the undesired shuttle effect and sluggish electrochemical conversion kinetics. Herein, a well‐designed CoFe2O4@reduced graphene oxide (CFO@rGO) composite is used to modify the separator to develop a multifunctional polysulfide barrier. Density functional theory (DFT) calculations confirm that highly electronegative oxygen ions in CFO tend to bond with transition metal (TM) ions at octahedral (Oh) sites, which induces the formation of FeS and CoS bonds between CFO and polysulfides. This indicates that CFO can effectively anchor polysulfides. Furthermore, the low Li2S decomposition energy barrier and Li+ diffusion energy barrier reveal that CFO can accelerate the redox reaction kinetics of sulfur species. Electronic structure calculations speculate that the low‐energy barrier can be attributed to the electron‐hopping phenomenon between TM ions of different valence states at Oh sites. Benefiting from these advantages, a CFO@rGO/PP separator demonstrates satisfactory cycling performance (0.087% capacity decay rate at 2C with 500 cycles) and superb rate performance (686 mAh g−1 at 5C). This work provides a valuable reference for future research on spinel‐type materials as electrocatalysts for Li–S batteries.

Enhancing Sulfur Redox Conversion of Active Iron Sites by Modulation of Electronic Density for Advanced Lithium-Sulfur Battery.

Despite lithium-sulfur (Li-S) batteries possessing ultrahigh energy density as great promising energy storage devices, the suppressing shuttle effect and improving sulfur redox reaction (SROR) are vital for their practical application. Developing high-activity electrocatalysts for enhancing the SROR kinetics is a major challenge for the application of Li-S batteries. Herein, single-molecule iron phthalocyanine species are anchored on the N and P dual-doped porous carbon nanosheets (Fe-NPPC) via axial Fe-N coordination to optimize the electronic structure of active centers. The Fe-NPPC can promote the catalytic conversion of polysulfides by modulation of the electronic density in active moieties, endowing the Li-S battery with a high reversible capacity of 1023 mAh g-1 at 1 C as well as an ultralow capacity decay of 0.035% per cycle over 1500 cycles. Even with a high sulfur loading of 7.1mg cm-2 , the Li-S battery delivers a high areal capacity of 4.8 mAh cm-2 after 150 cycles at 0.2 C. With further increasing the sulfur loading to 9.2mg cm-2 , an excellent areal capacity of up to 9.3 mAh cm-2 is obtained at 0.1 C.

Rational construction of rich coordination-unsaturated Zr-BTB electrocatalyst towards advanced lithium-sulfur batteries

Lithium-sulfur (Li-S) batteries show great potential to achieve high-density energy storage, but their commercial application is severely hindered by the notorious shuttling effect of lithium polysulfides (LiPS) and their sluggish conversion kinetics. Herein, we develop a Quasi Zr-based metal–organic frameworks with the tritopic carboxylate ligand 1,3,5-tris(4-carboxyphenyl)benzene (BTB) microflowers with cross-linked CNTs (Q-Zr-BTB@CNTs). The deficiency of Zr-O coordination at the Zr6 node is realized via a control of the deligandation behavior, which subtly modulates the local environment and electronic structure towards enhanced chemical affinity to polysulfides. Meanwhile, the interweave of the ultrathin Q-Zr-BTB nanosheets and CNTs establishes a porous and conductive network for fast charge transfer as well as a vast exposure of active interfaces. As a result, such a combination of defect engineering and architecture construction imposes strong sulfur adsorption and catalyzation, endowing the S/Q-Zr-BTB@CNTs cathode with a high initial capacity (1130 mAh g−1 at 0.2 C) and an excellent cycling stability (500 cycles at 1 C with 0.05% decay per cycle), as well as a decent electrochemical performance even under a high sulfur loading up to 12.7 mg cm−2. This study provides a novel strategy of designing unsaturated coordination centers to boost sulfur catalysis for high-performance lithium sulfur batteries.

Nickel-embedded hierarchically-porous carbon microspheres as a multifunctional separator modifier for achieving advanced lithium-sulfur batteries

Lithium-sulfur batteries (LSBs), one of the most promising electrochemical energy storage systems, are in the spotlight due to their high theoretical energy density, alongside environmental friendliness and low cost of sulfur. Several unforgiving issues, however, hamper their commercial applications, such as the notorious shuttle effect of intermediary polysulfides and retarded redox kinetics, growth of dendritic Li, among other things. The crux of sorting out the problems above is designing a versatile material with good electrical conductivity, catalytic activity, together with abilities in suppression of polysulfide shuttling and Li dendrite growth. In this work, a composite of Ni nanoparticles embedded in the gradient-porous carbon microspheres (Ni/PCMS), acting like a miniature reactor, was fabricated as a separator modification material. Adequate electron conductivity can be guaranteed by the carbon substrate and the inlays of Ni nanoparticles. The physical/chemical adsorption and high Li+ transference number of Ni/PCMS assure suppressed shuttle effect and Li dendrite growth, respectively. Catalytic activity is fulfilled with the exposed Ni active sites. As a consequence, the batteries based on Ni/PCMS-modified separators achieve a high initial discharge capacity of 1426.7 mAh g−1 at 0.1 C and a low capacity fading rate of 0.078% per cycle over 800 cycles at 1 C. Even under a high sulfur mass loading of ∼ 3.0 mg cm−2, the battery still displays a superior rate performance of 555.6 mAh g−1 at 0.5 C. This work provides a thought for the rational design of a wide range of separator modifiers for high-performance Li-S batteries.