A Novel Strategy for the Selection of Polysulfide Adsorbents Toward High‐Performance Lithium‐Sulfur Batteries

Abstract

shuttle effect still attenuates the capacity during cycles. And the preparation processes of the carbon materials used are usually complex and time-consuming. 2) Metal oxides have been widely studied as electrode materials [11][12][13] and strong chemical interaction of the metal oxides with polysulfides has been utilized to limit the shuttle effect during cycles. [14][15][16][17][18][19][20][21] It was found that the metal oxides can form strong chemical adsorption affinity with polysulfides, which significantly inhibits the shuttle effect and improves the cycle performance of LSBs. Nevertheless, most of the metal oxides cannot provide capacity due to their discrepant discharge-charge voltage with sulfur, adding them into the active materials will decrease the specific capacity of the cathodes. Therefore, if we choose a polar cathode material whose discharge-charge voltage coincides with sulfur, it can not only control the undesirable shuttle of LiPS but also contribute part of capacity to LSBs. [22] TiO 2 has been intensively studied as both anode and cathode materials for lithium-ion batteries because of its dischargecharge voltage around ≈1.7 V. [23][24][25][26] Using TiO 2 as an adsorbent for polysulfides has been extensively studied in recent years. [27][28][29][30] However, its contribution to the capacity of the cathode was often neglected due to the low discharge-charge platform. In this work, we used TiO 2 as an example to investigate the contributes of the TiO 2 additive to the adsorption for polysulfides and the total capacity of sulfur cathode. The cathode with a sandwich structure shown in Figure 1 was prepared by a simple coating method. In such a cathode, the 3D interwoven structure of CNTs can facilitate the transportation of electrons and ions and limit the shuttle of polysulfides by physical adsorption to some extent. The TiO 2 nanoparticles act not only as an absorbent to immobilize polysulfides but also as an active material in cathode to react with lithium ions during discharge process and thus contribute extra cathode capacity to batteries. As a result, the sandwich cathode with a reasonable composition ratio of CNTs to TiO 2 nanoparticles and a higher sulfur loading delivers a reversible capacity of 816 mAh g −1 after 200 cycles at 0.5 C and a capacity as high as 517 mAh g −1 after 500 cycles at 1.0 C. X-ray diffraction (XRD) patterns of the sandwich cathode were in situ measured to analyze the phase change during discharge-charge processes, and the interactions between the polysulfides and the TiO 2 additive were investigated based on density functional theory (DFT). The experimental data prove that our hypothesis can be realized and the work provides a new idea for the selection of the polysulfide adsorbents.Selection of polysulfide adsorbents for most lithium-sulfur batteries (LSBs) has only one purpose, which is to suppress the shuttle effect. However, addition of the polysulfides adsorbents inevitably reduces the energy density of LSBs. In this article, a new idea to select a polar ca...

Improving Electrochemical Performance and Safety of Lithium–Sulfur Batteries by a “Bulletproof Vest”

“…By observing the edge of the ultrathin film, it is found that ANFs have excellent film-forming properties because even if the thickness of the film is only a few tens of nanometers, a complete film can be formed (Figure d). In addition, the film can be clearly curved, indicating that it has excellent flexibility and is not easily broken during the volume change of sulfur, which is more advantageous than the freestanding interlayers prepared by other groups. , EDS elemental mapping analysis shows that elements C, N, O, and Ni are evenly scattered in the NAFN interlayer (Figure S6). One interesting finding is that the active material under the NAFN film also has morphological changes.…”

“…In addition, the film can be clearly curved, indicating that it has excellent flexibility and is not easily broken during the volume change of sulfur, which is more advantageous than the freestanding interlayers prepared by other groups. 27,28 EDS elemental mapping analysis shows that elements C, N, O, and Ni are evenly scattered in the NAFN interlayer (Figure S6). One interesting finding is that the active material under the NAFN film also has morphological changes.…”

Electrochemical Behavior Promotion of Polysulfides by Cobalt Selenide/Carbon Cloth Interlayer in Lithium−Sulfur Batteries

“…To enhance the chemisorption of the interlayer and increase the kinetics of redox reaction, transition metal compounds are greatly studied. [10] For example, transition metal oxides, [11] carbides, [12] sulfides, [13] phosphates, [14] etc. have strong bonding and interaction, which can effectively adsorb with LiPSs.…”

The Application of Indium Oxide@CPM-5-C-600 Composite Material Derived from MOF in Cathode Material of Lithium Sulfur Batteries

“…However, although sulfur has many advantages, such as low cost, abundant natural resources and low toxicity, several issues need to be solved for sulfur as a cathode for practical application of Li-S battery. First, during the process of charging and discharging, Li-S batteries have a large volume expansion, and it is easy to cause damage to the structure of the negative electrode material during the cycle; Second, the poor electronic conductivity of element S (5 × 10 −30 cm −1 at 25 • C) can affect the conductivity of materials and the rate performance of batteries; Third, During the cycle, the production of Li 2 S and Li 2 S 2 will coat the surface of the active material, thereby preventing Li + from entering the electrode; Fourth, the intermediate products (polysulfides) of the reaction easily dissolve in the electrolyte, which will cause severe capacity decay, resulting in a serious "shuttle effect" [11][12][13][14].…”