## 1 Introduction  
Compared with the present cathode materials, sulfur has a higher specific capacity (1675 mAh/g), and the theoretical energy density of lithium-sulfur (Li-S) battery is as high as 2600 wh/kg, which is 3-5 times larger than other traditional lithium-ion batteries [1]. However, the Li-S battery also has several disadvantages, for example, the conductivity of sulfur at room temperature is low (\(5.0\times 10^{-30}\) S/cm) and the final products Li\({}_{2}\)S\({}_{2}\) and Li\({}_{2}\)S are nonconductive, which limits the rate performance of Li-S battery. Moreover, the intermediates of Li-S battery will dissolve in the organic electrolyte and diffuse across the membrane to the negative electrode, which results in the irreversible loss of the active substance and decay of battery cycle life, causing the \"shuttle effect\". In addition, parts of lithium sulfide are removed from the conductive framework and cannot be converted into S\({}_{8}\) or other high-order polysulfides in the charge-discharge process, which greatly affects the specific capacity [2]. Therefore, it has become important to construct a suitable cathode material system to solve these problems. The polymer cathode material with high sulfur content has a simple preparation process, low reaction temperature, and it has various molecular structures which are beneficial for material design. [PERSON] et al. [3] prepared the sulfur-containing composite based on linear polymer, in order to gather, fix, and connect the element sulfur with each other through a dynamic covalent bond [4]. During the charge-discharge process, the energy storage and release can be realized via the break and reconnection of sulfur-sulfur bond, which can reduce the generation of intermediates, and effectively protect the active substances from being dissolved in the electrolyte, and then improve the battery efficiency [5; 6]. However, above 159 \({}^{\circ}\)C, the octasulfur ring will be opened, and the end groups are linear polysulfide chains with sulfur radical, which will be polymerized into the homopolysulfide with higher molecular weight. This kind of homopolysulfide has poor solubility and fusibility. To solve this problem, the inverse vulcanization [7; 8; 9; 10] method was invented to prepare polymers with high sulfur content. In this process, molten sulfur was directly copolymerized with vinyl monomers, which not only increased the branching of sulfur chains, but also produced polysulfide rings. These changes effectively inhibited the depolymerization of homopolysulfides and enhanced the processability of the products [11; 12]. [PERSON] et al. [13] prepared a sulfur-based polymer via inverse vulcanization by using 1,3-diacetyrylbenzene (DEB) and sulfur. It was found that diyne or polydiyne in the polymer had crosslinked with sulfur, forming a semi-interpenetrating network structure. This special cage-like structure effectively inhibited the \"shuttle effect\" and enhanced battery performance. [PERSON] et al. [14] prepared a copolymer of sulfur-bismaleimide (BMI) via inverse vulcanization and used this copolymer as cathode material. The specific capacity of the battery after 50 cycles was about 400 mAh/g. [PERSON] et al. [15] synthesized copolymers of sulfur-divinylbenzene (DVB) via inverse vulcanization and utilized it as cathode material. The specific capacity of this product can match up with that of carbon/sulfur cathode material. [PERSON] et al. [16] prepared the phenol benzoxazine monomer-sulfur random copolymer at 185 \({}^{\circ}\)C and found that the curing temperature decreased from 242 to 185 \({}^{\circ}\)C. When this copolymer was used as cathode material, the specific capacity of the battery kept at 1006 mAh/g after 75 cycles. Though plenty of sulfur-based polymers have been prepared as cathode materials in Li-S battery, most reactants were aromatic hydrocarbons or compounds with relatively low polarity, which greatly limited the preparation and application of the Li-S battery.