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Lithium-sulfur batteries (LSBs) have attracted widespread attention because of their advantages such as high discharge capacity and high energy density. Although LSBs have good development potential, there are still many obstacles, such as poor conductivity, volume expansion etc., especially shuttle effect which seriously limit the application of LSBs. To restrain the shuttle effect, we proposed a novel Co 3 O 4 /ZnO dodecahedral heterojunction as a separator blocking layer which was derived form ZIF-67/ZIF-8 bimetallic MOF. Since the bimetallic oxide heterojunction contains more abundant oxygen vacancies, it has better adsorption and catalytic performances than monometallic oxides. Co 3 O 4 /ZnO coated on the PE separator can effectively block the lithium polysulfides (LiPSs) shuttle due to its good adsorption ability, furthermore, the catalytic effect will accelerate the reaction of LiPSs and improve the electrochemical performances. Consequently, the initial discharge specific capacity of the Co 3 O 4 /ZnO modified separator battery at 0.5 C rate reaches up to 875.5 mAh g−1 when the cathode sulfur areal density is 3 mg cm−2, and still keep 500.9 mAh g−1 after 400 long cycles. Even when the cathode sulfur areal density is 5 mg cm−2, it still shows good cycle stability. • Co 3 O 4 /ZnO dodecahedral heterojunction is derived from ZIF-67/ZIF-8 bimetallic MOF. • Co 3 O 4 /ZnO heterojunction is used as a separator coating material for Li-S battery. • Co 3 O 4 /ZnO heterojunction show excellent absorption and catalytic effect for polysulfides. [ABSTRACT FROM AUTHOR]

• CeO2@Co-N-C is derived from ZIF 67@Ce-MOF precursor. • CeO2@Co-N-C is applied to the separator modification layer of Li-S battery. • CeO2@Co-N-C show excellent adsorption and catalytic effect on polysufides. High energy density Lithium-sulfur batteries (LSBs) have become one of the future energy storage devices. However, the shuttle effect induced by the diffusion of polysulfides between the positive and negative electrodes makes the application prospects of LSBs very challenging. So as to overcome this difficult challenge, a special Co-N-C@CeO 2 -C composite which displays the Co-N-C nanoparticle coated on CeO 2 -C nanorods structure was obtained using ZIF-67@Ce-MOF precursor, and applied as the separator modification material for LSBs. This Co-N-C@CeO 2 -C composite has a higher specific surface area and more micro/ meso porous structures than the simple Ce-MOF derived CeO 2 -C nanorod. The presence of Co-N-C nanoparticles can induce the charge imbalance, resulting in more oxygen vacancy defects and plenty of active sites. By virtue of its excellent physical and chemical adsorption ability, the long chain polysulfide can be quickly bound to the surface of the material, furthermore the metal active centers are used to accelerate the transformation of polysulfides, effectively inhibiting its shuttle effect. Moreover, the combination of Co-N-C enhanced the conductivity of CeO 2 -C nanorod and the mobility of lithium ions. Therefore, when the sulfur content is 2.8 mg cm−1, the specific capacity of 915.9 mAh g−1 is released under 0.5 C, and there is still 46.63 % capacity retained after 700 cycles. Even under a high sulfur area density of 5 mg cm−1, an initial discharge capacity of 933.9 mAh g−1 can be achieved, furthermore it can maintain 72.75 % of the initial capacity at the 120th cycle, demonstrating its application value. The precursor ZIF-67@Ce-MOF was made by mixing ZIF-67 with Ce-MOF, and the dodecahedral-coated nanorod structure CeO2@Co-N-C was calcined at high temperature under N 2. Applied to lithium-sulfur battery separator coating to enhance battery performance. MOF has a large specific surface area and abundant metal active sites on the rod-like structure. The shuttle effect can be suppressed by strong adsorption of polysulfides physically and chemically and more effective catalytic loading of polysulfides into Li 2 S 2 /Li 2 S. And Co-N-C nanoparticles can also enhance lithium ion transport capacity and improve electrochemical performance. [Display omitted] [ABSTRACT FROM AUTHOR]

• Sn-MOF derived a novel layer structure SnO 2. • Sn-MOF/CNTs derived a novel wool ball-like structure SnO 2 /CNTs composite. • SnO 2 and SnO 2 /CNTs are used as separator coatings for lithium-sulfur batteries. • SnO 2 and SnO 2 /CNTs show good adsorption and catalytic effect on polysulfides. Lithium-sulfur batteries (LSBs) are novel energy storage devices based on their high energy density. However, the application of LSBs faces many difficulties because of several obstacles, especially the shuttle effect of lithium polysulfides (LPs). In order to reduce the influence of the shuttle effect, we conducted the preparation of Sn-MOF which was successfully derived to SnO 2 and SnO 2 /CNTs and applied them as the separator coating layer. SnO 2 can effectively catalyze and adsorb polysulfides based on its unique lamellar structure, and the combination of CNT and SnO 2 further enhances the electrical conductance of the material which accelerates the Li ion migration, and thus improves the electrochemical performances. Experiments showed that the SnO 2 /CNTs coated separator LSB has a discharge capacity of 886.4 mAhg−1 in the first cycle under the sulfur areal density of 2.8 mgcm−2, and after 500 cycles, it still remains 509.6 mAhg−1. Furthermore, under the high sulfur areal density of 5 mgcm−2, the SnO 2 /CNTs modified separator battery still show stable cycle performance which demonstrate its application potential. [ABSTRACT FROM AUTHOR]

Lithium-sulfur batteries (LSBs) have been recognized as one of the most hopeful new energy storage devices. However, the shuttle effect of polysulfides seriously affects the commercial use of LSBs. In order to alleviate the shuttle effect, in this paper, A novel MoC/N-C composite was firstly prepared by calcining Mo doped ZIF-8 precursor in a nitrogen environment, and then the as prepared MoC/N-C composite was coated on the surface of the commercial polypropylene separator to act as a block layer of lithium polysulfides. The N-C derived from ZIF-8 under high-temperature carbonization can provide good electrical conductivity and block the diffusion of polysulfides by physical adsorption. At the same time, MoC will provide abundant chemisorption sites to effectively hinder the shuttle of polysulfides and promote their redox reactions. Because of the adsorption and catalytic function of MoC/N-C composite, the LSB battery show excellent electrochemical properties even at a high sulfur loading. [Display omitted] [ABSTRACT FROM AUTHOR]

Because of its high theoretical specific capacity, lithium-sulfur batteries are regarded as one of the most promising secondary batteries. However, there are still a series of problems, which seriously affect the commercial application of lithium-sulfur batteries. Therefore, a magnetic porous carbon material was developed in this work for the modification of lithium-sulfur battery separators, which may reduce the shuttle effect of polysulfides and increase its electrochemical performances. The solvothermal preparation of Ni-Zn bimetallic MOF precursors was followed by a high-temperature carbonization in nitrogen environment to sublimate Zn ions and produce porous structures, achieving Ni@C(Zn) composite. In order to improve the electrochemical performances of lithium-sulfur batteries, the Ni@C(Zn) composite was coated on one side of the polyethylene (PE) separator. Ni@C(Zn) composite displays good physisorption and chemisorption properties, and it can also operate as a secondary current collector to promote the usage of active materials as well as inhibiting shuttle effect of polysulfides. By using Ni@C(Zn) coated PE separator, the initial discharge specific capacity of lithium sulfur battery is as high as 1278.6 mAh g−1 at a current density of 0.05 C when the S cathode is loaded with 3 mg cm−2 active materials. Furthermore, the discharge specific capacity in the first cycle at 0.5 C is 749.4 mAh g−1, which remains at 461 mAh g−1 after 500 long cycles, and the capacity retention rate is as high as 61.5%. Even when the S loading is as high as 5 mg cm−2, it can still experience a stable cycle of 100 cycles at 0.2 C. • Ni@C(Zn) composite was derived by bimetallic Ni-Zn MOFs. • Ni@C(Zn) composite was used as separator modification layer of lithium sulfur battery. • larger specific surface area and higher porosity can better block the shuttle of polysulfides. • Ni@C(Zn) composites have good catalytic effect which can promote the redox conversion of polysulfides. [ABSTRACT FROM AUTHOR]

Because of its high theoretical specific capacity, lithium-sulfur batteries are regarded as one of the most promising secondary batteries. However, there are still a series of problems, which seriously affect the commercial application of lithium-sulfur batteries. Therefore, a magnetic porous carbon material was developed in this work for the modification of lithium-sulfur battery separators, which may reduce the shuttle effect of polysulfides and increase its electrochemical performances. The solvothermal preparation of Ni-Zn bimetallic MOF precursors was followed by a high-temperature carbonization in nitrogen environment to sublimate Zn ions and produce porous structures, achieving Ni@C(Zn) composite. In order to improve the electrochemical performances of lithium-sulfur batteries, the Ni@C(Zn) composite was coated on one side of the polyethylene (PE) separator. Ni@C(Zn) composite displays good physisorption and chemisorption properties, and it can also operate as a secondary current collector to promote the usage of active materials as well as inhibiting shuttle effect of polysulfides. By using Ni@C(Zn) coated PE separator, the initial discharge specific capacity of lithium sulfur battery is as high as 1278.6 mAh g−1 at a current density of 0.05 C when the S cathode is loaded with 3 mg cm−2 active materials. Furthermore, the discharge specific capacity in the first cycle at 0.5 C is 749.4 mAh g−1, which remains at 461 mAh g−1 after 500 long cycles, and the capacity retention rate is as high as 61.5%. Even when the S loading is as high as 5 mg cm−2, it can still experience a stable cycle of 100 cycles at 0.2 C. • Ni@C(Zn) composite was derived by bimetallic Ni-Zn MOFs. • Ni@C(Zn) composite was used as separator modification layer of lithium sulfur battery. • larger specific surface area and higher porosity can better block the shuttle of polysulfides. • Ni@C(Zn) composites have good catalytic effect which can promote the redox conversion of polysulfides. [ABSTRACT FROM AUTHOR]

Lithium-sulfur batteries (LSBs) are of great interest to researchers due to their high theoretical specific capacity and high energy density. Unfortunately, because of sulfur's weak conductivity and the shuttle effect of polysulfides, the application prospects of LSBs are facing great challenges. To suppress the shuttle effect of polysulfides, nanorod-like CeO 2 and CeO 2 -C using Ce-MOF as the precursor was successfully prepared and applied to the separator of LSBs. Coating CeO 2 and CeO 2 -C obtained by calcination in different atmospheres on PE separators can effectively enhance the electrochemical properties of LSBs due to the excellent chemisorption and catalytic effect of CeO 2 on lithium polysulfides. In particular, CeO 2 -C which is obtained by calcination of Ce-MOF in N 2 atmosphere has abundant micro and meso porous structures, which can quickly adsorb polysulfide in the electrolyte and accelerate the redox kinetics at the same time. Moreover, the nano-rod structure of CeO 2 and CeO 2 -C also improves the conductivity of the separator. After a series of electrochemical tests, it was discovered that the discharge capacity of the CeO 2 -C coated separator battery on the first cycle was 1240 mA h g−1 when the cathode sulfur loading was approximately 2.5 mg cm−2, and that the discharge capacity remained 520 mA h g−1after 500 loops at 0.5 C. Even when the sulfur loading reaches 5.5 mg cm−2, it also has a good cyclic stability, demonstrating its application potential. Nanorod-like CeO 2 and CeO 2 -C were synthesized using Ce-MOF as precursor under different atmospheres, and successfully applied to the separator of LSBs. CeO 2 -C has excellent adsorption and catalytic ability due to its large specific surface area and dispersed active centers, and the conductivity of CeO 2 is improved after carbonization. Therefore, the modified LSBs have excellent electrochemical performance. [Display omitted] [ABSTRACT FROM AUTHOR]

Due to the increasing demand of new energy vehicles and large-scale power grids for high energy density devices, lithium-sulfur batteries (LSBs) have attracted more and more researchers' attention stemming from their advantages of high theoretical specific capacity, low cost of active substances and environmental friendliness. However, there are still some intractable problems hindering the commercialization of LSBs, among which the most serious problem is "shuttle effect" of polysulfides. For the purpose of solving this problem, this paper prepared hollow structure molybdenum sulfide/cobalt sulfide mixed with amorphous carbon (MoS 2 /Co 9 S 8 /C) (HMCC) nanoparticles using ZIF-67 as the precursor and coated on the side of ordinary PE separator facing the positive electrode by a simple scraper coating process. The combination of MoS 2 and Co 9 S 8 bimetallic sulfides can not only adsorb and catalyze the rapid transformation of intermediates, but also effectively conduct lithium ions mainly because of the exposure of many active sites of layered MoS 2 in the outermost layer. In addition, a small amount of carbon inside can enhance electrical conductivity of the coating, increasing the utilization of active substances, and the stable hollow structure can act as a "transfer station", greatly inhibiting the large amount of polysulfides to run off. The dual advantages of structure and composition make the modified separator have excellent performance in different current densities. Reversible specific capacities of 930.4 mAh g−1 and 690.7 mAh g−1 are released at 0.5 C and 1 C, and capacity retention of 72 % and 64 % after 500 and 600 cycles, respectively. In addition, due to the rapid conduction of lithium ions, the growth of lithium dendrites is greatly inhibited, which maintains the high safety of the battery. This provides a new research direction for the application of other new bimetallic sulfides in the separator modification of LSBs. • A hollow bimetallic sulfide composite MoS 2 /Co 9 S 8 /C is derived from ZIF-67. • MoS 2 /Co 9 S 8 /C is used as a separator coating layer for lithium polysulfides. • The hollow MoS 2 /Co 9 S 8 /C show both physical confinement and catalytic effect on lithium polysulfides. [ABSTRACT FROM AUTHOR]