Titanium-Containing Metal–Organic Framework Modified Separator for Advanced Lithium–Sulfur Batteries

Abstract

The shuttling of polysulfide intermediates (Li2S n , 2 < n ≤ 8) and the dendrite growth on the Li-metal surface have blocked the practical applications of lithium–sulfur (Li–S) batteries. Functionalizing the separator provides a straightforward approach to address these issues. Herein, we demonstrate a multifunctional MIL-125­(Ti)-modified polypropylene/polyethylene separator for advanced Li–S batteries. The MIL-125­(Ti), a Ti-containing metal–organic framework (MOF), features an open-skeleton construction, a high intrinsic microporosity and a Lewis acid characteristic. Compared with pristine separator, that with MIL-125­(Ti) coating shows better electrolyte wettability and less resistance. The unique coating layer acts as an effective physical and chemical barrier region to capture polysulfide species without affecting the smooth transport of Li+. Meanwhile, the highly ordered micropores with a diameter of ∼1.5 nm in the MOFs guide in a homogeneous Li+ plating and thereby inhibit lithium dendrites. Consequently, the MOF-modified separator enables a significantly improved cycling stability and rate capability of the Li–S battery. The capacity retention of over 60% at 0.2 C (1 C = 1675 mA g–1) upon 200 cycles and a specific capacity of 612 mAh g–1 at 2 C is realized. The facile approach offers an effective pathway toward high-performance Li–S batteries.

Metal-organic frameworks enable broad strategies for lithium-sulfur batteries

“…Therefore, the conclusions obtained in the above two works must be taken into account when choosing the appropriate MOF for modifying the separator of an Li-S battery. In addition to the MOFs mentioned above, more recently, Ti-containing [ 54 ] and Zr-based [ 55 ] MOF practices have also been used to modify the Li-S battery separator.…”

Multifunctional MOF‐Based Separator Materials for Advanced Lithium–Sulfur Batteries

“…For this reason, Qi et al chose Ti-MOF, that is, MIL-125 (Ti) as the main material for separator modification. [91] Specifically, the metal salt and organic ligand were tetra-n-butyl titanate and terephthalic acid, respectively, and MIL-125(Ti) was synthesized by the solvothermal method. By the strategy, a modified membrane with a coating thickness of about 20 µm can be prepared via coating of the PP/PE commercial membrane with the slurry.…”

“…c) The long-term cyclability of the cells with MIL-125(Ti)-PP/PE and PP/PE separators at 0.2C. a-c) Reproduced with permission [91]. Copyright 2020, American Chemical Society.…”

Progress and Prospect of Organic Electrocatalysts in Lithium−Sulfur Batteries

“…The role of organic electrocatalysts in a Li−S battery includes: 1) chemically bind LiPSs through active sites to inhibit the shuttle effect (Li N. et al, 2021); 2) accelerate the redox reactions of LiPSs (Wang C. et al, 2020); 3) improve the utilization of active materials by regulating the nucleation and growth kinetics of Li 2 S (Yang X. et al, 2019). The introduction of organic electrocatalytic materials on the sulfur cathode is considered to be a feasible solution for addressing problems in Li−S batteries.…”

“…In this system, traditional PP separators cannot fully realize the advantages of Li−S batteries, causing decreased discharge capacity and Coulombic efficiency (Mathew et al, 2020). Similar to the regulation of interlayers, traditional separators can be reasonably functionalized and modified through controlling the pore structure, ion conductivity, adsorption, and catalysis of LiPSs (Qi et al, 2020). In recent few years, reports on the subject of separator modifications by organic electrocatalysts have proliferated.…”