【introduction】

Supramolecular materials are ordered structures assembled from organic building blocks by non-covalent interactions and have attracted a great deal of attention due to their abundant functional groups, regulatable spatial structure and environmentally friendly properties. Driven by a variety of intermolecular and intramolecular interactions, supramolecular materials assembly not only has important implications in organic chemistry, but also in a host of cutting-edge applications for future sustainable development such as selective adsorption and smart energy storage Design plays a crucial role. For energy storage applications, supramolecular materials can be used not only as a device but also as electrode materials. Because of its superior chemical regulatability, diversity of morphology and dynamic adaptability, supramolecular materials have unique advantages in the regulation of complex transport phenomena and reaction mechanism.

【Introduction】

Recently, Professor Zhang Qiang (Corresponding Author) at Tsinghua University introduced the reversible storage / release process of cucurbituril (CB) as a supramolecular capsule for dissolving polysulphides in lithium-sulfur (Li-S) batteries to control polysulphides Molecularly dissolved and published a research paper entitled "A Supramolecular Capsule for Reversible Polysulfide Storage / Delivery in Lithium-Sulfur Batteries" at Angew. Chem. Int. Ed. Li-S batteries coated with supramolecular capsule membrane exhibited higher coulombic efficiency with a significant increase in capacity from 300 mAh · g-1 to 900 mAh · g-1 at a sulfur loading of 4.2 mg · cm-2 . The application of supramolecular capsules provides a new perspective for understanding the complex multi-electron conversion reaction and is an efficient strategy for enhancing the performance of Li-S batteries and similar application systems.

【Introduction】

Figure 1 Schematic of the supramolecular capsule

a) Schematic of Li-S cell with G @ CB intercalation;

b) reversible storage / release of polysulfides in suitable CB channels;

c) Comparison of different materials on the atomic ratio of adsorbed atoms.

Figure 2 polysulfide in cucurbituril adsorption / desorption phenomena

a) Raman spectra of CB-Li2S6, pristine CB and Li2S6 dissolved in DME;

b) XRD patterns of CB with original CB, DME swollen CB, and Li2S4 adsorbed / desorbed;

c) Polysulfide "breath" schematic.

Figure 3 Morphology of G @ CB intercalation

a, b) SEM images of G @ CB;

c) TEM images of G @ CB;

d) nitrogen distribution of G @ CB;

e) XRD spectra of CB and G @ CB.

Figure 4 Comparison of electrochemical properties of materials

a) Cycle current at 0.5 C current density, capacity on the graph, coulomb efficiency on the graph below;

b) Capacity of Li-S battery (sulfur loading: 1.0 mg · cm-2);

c) Li-S battery cycle performance (sulfur loading: 4.2 mg · cm-2) at 0.1 C current density.

【summary】

The study prepared a supramolecular capsule using a supramolecular capsule for polysulfide storage / release, which was used in Li-S cells. Supramolecular cucurbiturils have abundant sites for exposure and adsorption, and have strong adsorption capacity for polysulfides. At the same time, the cucurbituril nanocapsules with a radius of about 15 nm were deposited on the surface of graphene to improve the kinetic properties. Therefore, the dissolution and diffusion of polysulfides in Li-S batteries are limited, and the performance, cycle stability and coulombic efficiency are high even at high sulfur loading rates or high rates. The study is a novel attempt at functional supramolecular materials and provides new insight and ideas for material selection and structural design of advanced Li-S batteries and similar applications.