# A Review of Lithium-Sulfur Batteries Based on Metal-Organic Frameworks: Progress and Prospects
## 3 Alternative Strategies for Metal-Organic Frameworks to Improve the Performance of LSBs
### Intermediate Layer Modified by Metal-Organic Framework Material  
In LSBs, the shuttle effect of soluble intermediate lithium polysulfides (LiPSs) within sulfur cathodes results in the irreversible loss of active material and degradation of the lithium anode, ultimately leading to decreased specific capacity and impaired cycling stability [74]. The insertion of a functional interlayer between the sulfur cathode and separator serves as an effective strategy to inhibit the shuttling of LiPSs, offering advantages such as ease of handling, a broad selection of materials, and multifunctional integration [75]. Non-carbon materials, including layered double hydroxides (LDHs), metal-organic frameworks (MOFs), and metal oxides/sulfides/carbides [76], typically exhibit stronger interactions with LiPSs, rendering them increasingly appealing as interlayer materials for LSBs due to their potential to mitigate the shuttle effect. [PERSON] et al. [77] successfully synthesized heterostructure LDH-MOF (Figure 10a) via a simple solvothermal reaction between NiCo-LDH and 1,4-benzenedicarboxylic acid (BDC). Hybridization of MOFs and LDHs can combine their advantages and is suitable for use as interlayer materials for LSBs. In investigating the electrochemical performance of lithium sulfur batteries (LSBs) utilizing various separators, as illustrated in Figure 10b,c, the Tafel slopes associated with peaks b and c in the cell employing NiCo-MOF/LDH@PE are 28 mV dec\({}^{-1}\) and 69.1 mV dec\({}^{-1}\), respectively. These values are significantly smaller than those observed in cells using pure PE, NiCo-LDH@PE, and NiCo-MOF@PE separators. This comparison highlights the remarkable electrocatalytic activity of NiCo-MOF/LDH in enhancing the conversion reactions within lithium-ion batteries. Additionally, [PERSON] et al. [78] synthesized Mg-MOF-74 directly on free-standing carbon paper (MOF/C-paper). By subjecting Mg-MOF-74 to pyrolysis, it was converted into a highly porous carbon material (MgO@C/C-paper) with uniformly dispersed magnesium oxide nanoparticles. This composite was then utilized as an interlayer in an LSBs, as depicted in Figure 10d. Three types of LSB coin cells were assembled, each with a cathode sulfur content of 1.7 mg cm\({}^{-2}\). These included a standard cell without any interlayer, a cell with a C-paper interlayer positioned between the cathode and the separator, and a cell with an MgO@C/C-paper interlayer sandwiched between the cathode and the separator. The cyclic tests shown in Figure 10e were performed at a current density of 0.2 C with cut-off voltages of 1.7 and 2.8 V. The cyclic tests were performed at a current density of 0.2 C with a cut-off voltage of 1.7 and 2.8 V. In addition, the Coulomb efficiencies after 200 cycles were 98.3%, 98.7% and 99.0% for standard, C and MgO@C/C papers, respectively. The high electrical conductivity and large surface of the interlayer provide many reaction sites for polysulfides and improve polysulfide utilization. However, the formation of Li\({}_{2}\)S\({}_{2}\) and Li\({}_{2}\)S is expected to eventually passivate the surface of the C paper, while the MgO@C layer prevents passivation. Figure 10: (**a**) Schematic representation of the transition from layered NiCo-LDH to NiCo-MOF/LDH nanorods and the subsequent preparation of NiCo-MOF/LDH@PE. (**b**,**c**) Tafel plots of peaks b (**b**) and c (**c**) (reprinted/adapted with permission from [77]; copyright 2023, _Materials Today Physics_). (**d**) Schematic representation of the redox reaction of polysulfides on C and MgO@C/C papers; MgO nanoparticles anchor the dissolved polysulfides and diffuse onto the carbon composites for reduction. (**e**) Reduction of polysulfides without an interlayer (labelled ‘standard’), C paper, and MgO@C/C paper at 0.2 \({}^{\circ}\)C sulfide, and diffuses onto the carbon composite for reduction.