Polytrisulfide used as lithium-sulfur electrolyte additive, and preparation method and application thereof
Polytrisulfides were precisely synthesized by copolymerizing elemental sulfur with lipoic acid derivatives through a catalytic system design, which solved the problems of low purity and efficiency in the synthesis of polytrisulfides in the existing technology and improved the performance of lithium-sulfur batteries.
Patent Information
- Application Number
- CN202511453531.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-10-13
- Publication Date
- 2026-01-09
AI Technical Summary
Existing technologies make it difficult to efficiently synthesize pure polytrisulfides, which limits their application in the lithium battery field. Furthermore, the synthesis methods are complex and costly, and they lack industrialization potential.
A catalytic system is designed to control the cracking of elemental sulfur through the copolymerization reaction of elemental sulfur and lipoic acid derivatives, and to accurately synthesize polytrisulfides as additives for lithium-sulfur electrolytes. Bulk or solution polymerization is carried out using a catalytic system composed of organic bases, organic ammonium salts and chain initiators.
Polytrisulfide with excellent electrochemical properties was prepared to improve the specific capacity and cycle stability of lithium-sulfur batteries and reduce the specific capacity decay rate.
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Figure CN121293499A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of polymer materials, specifically relating to a polytrisulfide used as an additive in lithium-sulfur electrolytes, its preparation method, and its application. Background Technology
[0002] Elemental sulfur, a major byproduct of industrial desulfurization, remains in large surplus beyond its direct use in the production of sulfuric acid, sulfur-containing pharmaceuticals, and vulcanized rubber. The storage and transportation of elemental sulfur incurs significant costs, and improper storage can cause serious environmental problems. Therefore, utilizing elemental sulfur to produce high-value-added products is one effective way to achieve the resource utilization of elemental sulfur, which is of great significance to human production and life. One important form of sulfur utilization is its introduction into the polymer backbone. The introduction of sulfur atoms often endows materials with excellent optical, electrochemical, mechanical, self-healing, and heavy metal adsorption capabilities.
[0003] The introduction of dynamic covalent SS bonds brings many attractive properties to polymers, making them promising for a wide range of applications. Among them, trisulfide bonds, as a typical sulfur-rich group (containing two SS bonds), exhibit higher reactivity than disulfide bonds due to their greater number of reaction sites (Sci. Adv. 2020, 6, eabc1725). This high reactivity makes the incorporation of trisulfide bonds into polymers a promising area for applications in biomedicine, organic synthesis, and materials science. In the field of lithium-ion batteries, the application of trisulfide compounds is particularly prominent. For example, adding organic trisulfide compounds to the electrolyte can effectively improve battery capacity (Angew. Chem. Int. Ed. 2016, 55, 10027; ACS Energy Lett. 2016, 1, 1221). The high reactivity of trisulfide bonds helps form a more stable solid-state electrolyte interfacial film at the electrode interface, thereby improving the battery's cycle performance and coulombic efficiency.
[0004] However, the synthesis of trisulfide compounds still faces certain challenges. Although various methods exist for constructing trisulfide bonds, the synthesized products often contain impurities such as disulfide bonds, which can lead to a decline in battery performance (Angew. Chem. Int. Ed. 2019, 58, 13513). Despite the significant potential of trisulfide compounds in improving lithium-ion battery performance, further optimization of their synthesis and purification techniques remains crucial for their large-scale application.
[0005] In 2022, our research group developed a copolymerization reaction of elemental sulfur with cyclic thioalkanes to prepare corresponding disulfides or polysulfides. However, it was unable to accurately prepare polytrisulfides (Angew. Chem. Int. Ed. 2022, 61, e202115950). In 2023, Coote et al. used electrochemically initiated ring-opening polymerization of pre-synthesized cyclic trisulfide compounds to prepare polytrisulfides (J. Am. Chem. Soc. 2023, 145, 11798-11810). The drawback is that the types of monomers suitable for this method are extremely limited, and the synthesis process is complex and costly, currently lacking the potential for industrial application. In 2024, Qu Dahui et al. achieved the copolymerization of elemental sulfur with lipoic acid derivatives (such as thioctic esters) via free radical polymerization (Nat. Commun. 2024, 15, 3855). They determined the polymer structure to be a homopolymer of lipoic acid derivatives and polysulfides (such as disulfide, trisulfide, and tetrasulfide) formed by copolymerization with elemental sulfur using Raman spectroscopy and other methods. However, due to the lack of effective control over the decomposition of elemental sulfur during the reaction, the resulting polymer is a mixture containing multiple polymer chain segments, severely hindering its application in lithium-sulfur batteries. Therefore, developing a method for efficiently constructing trisulfide bonds using inexpensive monomers has significant theoretical and practical value.
[0006] To address the above issues, this invention proposes to design a catalytic system to achieve the controllable pyrolysis of elemental sulfur in the copolymerization reaction of lipoic acid derivatives and elemental sulfur, thereby accurately synthesizing lipoic acid-based polytrisulfides and providing a material basis for their application in the field of lithium-sulfur battery electrolyte additives. Summary of the Invention
[0007] To address the above problems, this invention provides a method for synthesizing polytrisulfides by copolymerizing lipoic acid derivatives with elemental sulfur. The resulting polymer exhibits excellent electrochemical performance and can be used as an additive in lithium-sulfur electrolytes. Its specific capacity is 884.98~1112.07 mAh / g, and its specific capacity decay rate is 0.041%~0.055%.
[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows.
[0009] A polytrisulfide used as an additive in lithium-sulfur electrolytes, wherein the main chain repeating unit of the polytrisulfide is a type of sulfur-containing polymer material with trisulfide bonds as the main chain functional group; the main chain repeating unit does not contain polysulfide, polydisulfide, or polysulfide segments, wherein the polysulfide segments are segments with more than 3 consecutive sulfur atoms; the general structural formula of the polytrisulfide is as follows:
[0010]
[0011] Where n takes values from 5 to 2000; FG represents methoxy, ethoxy, n-butoxy, isopropoxy, benzyloxy, phenoxy, ethylamino, diethylamino, n-butamino, isopropamino, benzylamino, and phenylamino.
[0012] Furthermore, the number-average molecular weight of the polytrisulfide is 2000~500000 g / mol, and the molecular weight distribution is 1.5~2.2.
[0013] A method for preparing polytrisulfides as additives in lithium-sulfur electrolytes, wherein the polytrisulfides are prepared from elemental sulfur and lipoic acid derivatives using a catalytic system composed of an organic base, an organic ammonium salt, and a chain initiator, and are obtained by bulk polymerization or solution polymerization to yield polytrisulfides with well-defined structures; the general formula of the polymerization reaction is as follows:
[0014]
[0015] Furthermore, the organic base used in the catalytic system is triethylamine, tri-n-butylamine, diisopropylethylamine (DIPEA), phosphazene base P1, phosphazene base P2, phosphazene base P4, 4-dimethylaminopyridine (DMAP), 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD), or 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene (MTBD).
[0016] Furthermore, the organic ammonium salt in the catalytic system is one of the following: tetramethylammonium chloride, tetramethylammonium bromide, tetraethylammonium chloride, tetraethylammonium bromide, tetraethylammonium iodide, tetrabutylammonium chloride, tetrabutylammonium bromide, tetrabutylammonium iodide, tetrabutylammonium acetate, tetrabutylammonium tribromide, tetrabutylammonium nitrate, tetrabutylammonium hydrogen sulfate, tetrabutylammonium fluoride, benzyltriethylammonium chloride, benzyltripropylammonium chloride, benzyltributylammonium chloride, benzyltributylammonium bromide, hexadecyltrimethylammonium chloride, dodecyltrimethylammonium chloride, bis(triphenyl)phosphine ammonium chloride, methyltriphenylphosphonium bromide, and allyltriphenylphosphonium bromide.
[0017] Furthermore, the chain initiator is ethanethiol, propanethiol, n-butanethiol, benzylthiol, ethylenedithiol, thiophene, 1,2-propanedithiol, 1,3-propanedithiol, p-dibenzylthiol, p-dibenzylthiol, cyclohexanedithiol, 2-hydroxyethanethiol, 2-hydroxy-1-propanethiol, 3-hydroxy-1-propanethiol, dimercaptoethyl sulfide, 2,3-dithio(2-mercapto)-1-propanethiol, or pentaerythritol tetra-3-mercaptopropionate.
[0018] Furthermore, the molar ratio of the chain initiator to the organic base is 1:2 to 3:1, preferably 1:1; the molar ratio of the organic base to the organic ammonium salt is 1:2 to 3:1, preferably 1:1.
[0019] Furthermore, the thioctic acid derivative used is one of the following: methyl thiocate, ethyl thiocate, isopropyl thiocate, isobutyl thiocate, benzyl thiocate, phenyl thiocate, acetamide thiocate, diacetamide thiocate, n-butyramide thiocate, isopropyl thiocate, benzamide thiocate, and benzamide thiocate.
[0020] Furthermore, the ratio of the lipoic acid derivative to elemental sulfur is 2:1 to 16:1; the molar ratio of the lipoic acid derivative to the organic base is 100:1 to 8000:1.
[0021] Furthermore, the polymerization reaction is carried out at 0~80°C. o Perform at C for 0.1–24 h.
[0022] Furthermore, if the polymerization reaction is carried out in solution, the solvent used is selected from any one of toluene, xylene, trichlorobenzene, tetrahydrofuran, 1,4-dioxane, ethylene glycol dimethyl ether, and diethylene glycol dimethyl ether.
[0023] An application of a polytrisulfide as an additive in lithium-sulfur electrolytes, wherein the polytrisulfide is used to improve the performance of lithium-sulfur batteries. The lithium-sulfur batteries with added polytrisulfide have a specific capacity of 600~1200 mAh / g and a specific capacity decay rate of 0.04%~0.08%.
[0024] Compared with existing technologies, the present invention has the following significant advantages:
[0025] 1. The polytrisulfide obtained by the present invention is obtained by polymerization of elemental sulfur and lipoic acid derivatives. Lipoic acid derivatives are widely available, so polytrisulfides with rich structures can be prepared.
[0026] 2. The method for preparing polytrisulfides from elemental sulfur and lipoic acid derivatives proposed in this invention has not been reported before;
[0027] 3. The reaction conditions are mild, the catalyst activity is high, and the polymer selectivity is high;
[0028] 4. The resulting polytrisulfide contains no polyether or polydisulfide segments;
[0029] 5. As an additive for lithium-sulfur electrolytes, polytrisulfide small molecule trisulfides have a more significant effect on improving the electrochemical performance of lithium-sulfur batteries. Attached Figure Description
[0030] Figure 1 The polymer product obtained in Example 11 H NMR spectrum.
[0031] Figure 2 The image shows the Raman spectrum of the polymer obtained in Example 1.
[0032] Figure 3 This is a differential scanning calorimeter of the polymer product obtained in Example 1.
[0033] Figure 4 The thermogravimetric analysis curve of the polymer obtained in Example 1 is shown.
[0034] Figure 5 The polymer product obtained in Example 1 is used as an additive for lithium-sulfur electrolyte, and the blank electrolyte is compared with the product obtained in Example 1 at a discharge rate of 0.5 C.
[0035] Figure 6 The polymer product obtained in Example 1 is used as an additive for lithium-sulfur electrolyte, and its discharge rate is compared with that of a blank electrolyte at 2 C.
[0036] Figure 7 The comparison of the performance of the polymer product obtained in Example 1 as an additive for lithium-sulfur electrolyte with that of the blank electrolyte at a discharge rate of 0.5 C is shown.
[0037] Figure 8 The performance of the polymer product obtained in Example 1 as an additive for lithium-sulfur electrolyte is compared with that of the blank electrolyte at a 2 C rate discharge cycle. Detailed Implementation
[0038] To provide a detailed description of the present invention, the technical solution of the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.
[0039] In this invention, the thioctic acid derivatives and catalysts used are numbered as shown in the following formulas.
[0040]
[0041]
[0042] Example 1
[0043] 10 mL Schlenk bar bottles with magnetic ingots at 130 oDry at C for more than 12 hours, then vacuum-evacuate and allow to cool to room temperature before purging with nitrogen for use. Under nitrogen protection, weigh a certain amount of organic base 2a at room temperature and add it to the mixture. The molar ratio of organic base 2a to benzyl mercaptan is 1 / 1, and the molar ratio of organic base 2a to the organic ammonium salt bis(triphenyl)phosphine ammonium chloride is 1 / 2. Then add elemental sulfur and thioclate 1a, with a molar ratio of thioclate 1a to elemental sulfur and organic base 2a of 400 / 50 / 1. Seal the strip bottle and place it in an oil bath preheated to 25°C, then start stirring. React for 2 hours, then stop stirring. Take out a very small amount of the reaction mixture for further processing. 1 ¹H NMR and GPC tests were performed to purify the remaining reactive polymer. Polymer purification: The crude product was first dissolved in a small amount of dichloromethane, then a large amount of methanol was added, and the mixture was stirred vigorously to precipitate the polymer. This process was repeated until a pale yellow polymer was obtained, which was then vacuum dried for later use. The polydisulfide prepared in this example... 1 The H NMR spectra are as follows: Figure 1 As shown in the figure, the polymer chain contains no polysulfide or polydisulfide segments, indicating a completely alternating structure. GPC testing results show that the polymer has a molecular weight of 17400 g / mol and a molecular weight distribution of 1.88. The differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) curves of this polymer are shown below. Figure 3 and Figure 4 As shown in the figure, the polymer has a glass transition temperature of -43.0 °C and a thermal decomposition temperature of 195.3 °C after a 5% weight loss. The discharge performance of this polymer as a lithium-sulfur electrolyte at 0.5 C and 2 C rates is as follows: Figure 5 and Figure 6 As shown, their specific capacities are 1112.07 mAh / g and 884.98 mAh / g, respectively. The cycling performance of this polymer as a lithium-sulfur electrolyte at 0.5 C and 2 C rates is as follows... Figure 7 and Figure 8 As shown, their specific capacity decay rates are 0.055% and 0.041%, respectively.
[0044] Example 2
[0045] 10 mL Schlenk bar bottles with magnetic ingots at 130 oDry at C for more than 12 hours, then vacuum-evacuate and allow to cool to room temperature before purging with nitrogen for use. Under nitrogen protection, weigh a certain amount of organic base 2a at room temperature and add it to the mixture. The molar ratio of organic base 2a to p-diphenylthiophenol is 1 / 1, and the molar ratio of organic base 2a to the organic ammonium salt bis(triphenyl)phosphine ammonium chloride is 1 / 1. Then add elemental sulfur and thioclate 1a, with a molar ratio of thioclate 1a to elemental sulfur and organic base 2a of 400 / 50 / 1. Seal the strip bottle and place it in an oil bath preheated to 25°C, then start stirring. React for 2 hours, then stop stirring. Take out a very small amount of the reaction mixture for further processing. 1 The remaining reactant polymer was purified by ¹H NMR and GPC analysis. GPC results showed a molecular weight of 2130 g / mol and a molecular weight distribution of 1.52. Polymer purification involved dissolving the crude product in a small amount of dichloromethane, then adding a large amount of methanol and stirring vigorously to precipitate the polymer. This process was repeated until a pale yellow polymer was obtained, which was then vacuum dried for later use. When this polymer was added to a lithium-sulfur battery, the specific capacity of the lithium-sulfur electrolyte at 0.5 C and 2 C rates was 1200 mAh / g and 900 mAh / g, respectively. The capacity decay rates of this polymer as a lithium-sulfur electrolyte at 0.5 C and 2 C rates were 0.06% and 0.04%, respectively.
[0046] Example 3
[0047] 10 mL Schlenk bar bottles with magnetic ingots at 130 o Dry at C for more than 12 hours, then vacuum-evacuate and allow to cool to room temperature before purging with nitrogen for use. Under nitrogen protection, weigh a certain amount of organic base 2a at room temperature and add it to the mixture. The molar ratio of organic base 2a to ethanethiol is 1 / 2, and the molar ratio of organic base 2a to the organic ammonium salt bis(triphenyl)phosphine ammonium chloride is 1 / 1. Then add elemental sulfur and thioclate 1a, with a molar ratio of thioclate 1a to elemental sulfur and organic base 2a of 8000 / 1000 / 1. Seal the strip bottle and place it in an oil bath preheated to 25°C, then start stirring. React for 8 hours, then stop stirring. Take out a very small amount of the reaction mixture for further processing. 1The remaining reactant polymer was purified by ¹H NMR and GPC analysis. GPC results showed a molecular weight of 507200 g / mol and a molecular weight distribution of 2.25. Polymer purification involved dissolving the crude product in a small amount of dichloromethane, then adding a large amount of methanol and stirring vigorously to precipitate the polymer. This process was repeated until a pale yellow polymer was obtained, which was then vacuum dried for later use. When this polymer was added to a lithium-sulfur battery, the specific capacity of the lithium-sulfur electrolyte at 0.5 C and 2 C rates was 1100 mAh / g and 800 mAh / g, respectively. The specific capacity decay rates of this polymer as a lithium-sulfur electrolyte at 0.5 C and 2 C rates were 0.07% and 0.05%, respectively.
[0048] Example 4
[0049] 10 mL Schlenk bar bottles with magnetic ingots at 130 o Dry at C for more than 12 hours, then vacuum-evacuate and allow to cool to room temperature before purging with nitrogen for use. Under nitrogen protection, weigh a certain amount of organic base 2a at room temperature and add it to the mixture. The molar ratio of organic base 2a to propanethiol is 1 / 1, and the molar ratio of organic base 2a to the organic ammonium salt bis(triphenyl)phosphine ammonium chloride is 1 / 2. Then add elemental sulfur and thioclate 1b, with a molar ratio of thioclate 1b to elemental sulfur and organic base 2a of 400 / 50 / 1. Seal the strip bottle and place it in an oil bath preheated to 25°C, then start stirring. React for 10 hours, then stop stirring. Take out a very small amount of the reaction mixture for further processing. 1 The remaining reactant polymer was purified by ¹H NMR and GPC analysis. GPC results showed a molecular weight of 18500 g / mol and a molecular weight distribution of 1.90. Polymer purification involved dissolving the crude product in a small amount of dichloromethane, then adding a large amount of methanol and stirring vigorously to precipitate the polymer. This process was repeated until a pale yellow polymer was obtained, which was then vacuum dried for later use. When this polymer was added to a lithium-sulfur battery, the specific capacity of the lithium-sulfur electrolyte at 0.5 C and 2 C rates was 1100 mAh / g and 700 mAh / g, respectively. The specific capacity decay rates of this polymer as a lithium-sulfur electrolyte at 0.5 C and 2 C rates were 0.08% and 0.06%, respectively.
[0050] Example 5
[0051] 10 mL Schlenk bar bottles with magnetic ingots at 130 oDry at C for more than 12 hours, then vacuum-evacuate and allow to cool to room temperature before purging with nitrogen for use. Under nitrogen protection, weigh a certain amount of organic base 2a at room temperature and add it to the mixture. The molar ratio of organic base 2a to n-butanethiol is 1 / 1, and the molar ratio of organic base 2a to the organic ammonium salt bis(triphenyl)phosphine ammonium chloride is 3 / 1. Then add elemental sulfur and thioclate 1c, with a molar ratio of thioclate 1c to elemental sulfur and organic base 2a of 400 / 50 / 1. Seal the strip bottle and place it in an oil bath preheated to 25°C, then start stirring. React for 2 hours, then stop stirring. Take out a very small amount of the reaction mixture for further processing. 1 ¹H NMR and GPC analyses were performed to purify the remaining reactant polymer. GPC results showed a polymer molecular weight of 21200 g / mol and a molecular weight distribution of 1.96. Polymer purification involved dissolving the crude product in a small amount of dichloromethane, then adding a large amount of methanol and stirring vigorously to precipitate the polymer. This process was repeated until a pale yellow polymer was obtained, which was then vacuum dried for later use. When this polymer was added to a lithium-sulfur battery, the specific capacity of the lithium-sulfur electrolyte at 0.5 C and 2 C rates was 1000 mAh / g and 600 mAh / g, respectively. The specific capacity decay rates of this polymer as a lithium-sulfur electrolyte at 0.5 C and 2 C rates were 0.06% and 0.04%, respectively.
[0052] Example 6
[0053] 10 mL Schlenk bar bottles with magnetic ingots at 130 o Dry at C for more than 12 hours, then vacuum-evacuate and allow to cool to room temperature before purging with nitrogen for use. Under nitrogen protection, weigh a certain amount of organic base 2a at room temperature and add it to the mixture. The molar ratio of organic base 2a to ethylenedithiol is 2 / 1, and the molar ratio of organic base 2a to the organic ammonium salt bis(triphenyl)phosphine ammonium chloride is 1 / 2. Then add elemental sulfur and thioclate 1d, with a molar ratio of thioclate 1d to elemental sulfur and organic base 2a of 400 / 50 / 1. After sealing the strip bottle, place it in an oil bath preheated to 25°C and start stirring. React for 2 hours, then stop stirring. Take out a very small amount of the reaction mixture for further processing. 1The remaining reactant polymer was purified by ¹H NMR and GPC analysis. GPC results showed a molecular weight of 18300 g / mol and a molecular weight distribution of 1.89. Polymer purification involved dissolving the crude product in a small amount of dichloromethane, then adding a large amount of methanol and stirring vigorously to precipitate the polymer. This process was repeated until a pale yellow polymer was obtained, which was then vacuum dried for later use. When this polymer was added to a lithium-sulfur battery, the specific capacity of the lithium-sulfur electrolyte at 0.5 C and 2 C rates was 980 mAh / g and 680 mAh / g, respectively. The specific capacity decay rates of this polymer as a lithium-sulfur electrolyte at 0.5 C and 2 C rates were 0.055% and 0.048%, respectively.
[0054] Example 7
[0055] 10 mL Schlenk bar bottles with magnetic ingots at 130 o Dry at C for more than 12 hours, evacuate and allow to cool to room temperature, then purge with nitrogen for use. Under nitrogen protection, weigh a certain amount of organic base 2b at room temperature and add it to the mixture. The molar ratio of organic base 2b to thiophenol is 2 / 1, and the molar ratio of organic base 2b to the organic ammonium salt tetrabutylammonium chloride is 1 / 1. Then add elemental sulfur and thioclate 1e, with a molar ratio of thioclate 1e to elemental sulfur and organic base of 400 / 50 / 1. Add toluene as a solvent, with a solvent-to-thioclate derivative volume ratio of 1:1. Seal the strip bottle and place it in an oil bath preheated to 25°C, and start stirring. React for 2 hours, then stop stirring. Take out a very small amount of the reaction mixture for further processing. 1 The remaining reactant polymer was purified by ¹H NMR and GPC analysis. GPC results showed a molecular weight of 23500 g / mol and a molecular weight distribution of 1.91. Polymer purification involved dissolving the crude product in a small amount of dichloromethane, then adding a large amount of methanol and stirring vigorously to precipitate the polymer. This process was repeated until a pale yellow polymer was obtained, which was then vacuum dried for later use. When this polymer was added to a lithium-sulfur battery, the specific capacity of the lithium-sulfur electrolyte at 0.5 C and 2 C rates was 1000 mAh / g and 700 mAh / g, respectively. The specific capacity decay rates of this polymer as a lithium-sulfur electrolyte at 0.5 C and 2 C rates were 0.075% and 0.050%, respectively.
[0056] Example 8
[0057] 10 mL Schlenk bar bottles with magnetic ingots at 130 oDry at C for more than 12 h, evacuate and allow to cool to room temperature, then purge with nitrogen for use. Under nitrogen protection, weigh a certain amount of organic base 2c at room temperature and add it to the mixture. The molar ratio of organic base 2c to 1,2-propanedithiol is 2 / 1, and the molar ratio of organic base 2c to the organic ammonium salt tetrabutylammonium bromide is 1 / 2. Then add elemental sulfur and thiocate ester 1f, with a molar ratio of thiocate ester to elemental sulfur and organic base 2c of 400 / 50 / 1. Add xylene as a solvent, with a volume ratio of solvent to thiocate derivative of 1:1. Seal the strip bottle and place it in an oil bath pre-cooled to 0°C, then start stirring. React for 24 h, then stop stirring. Take out a very small amount of the reaction mixture for further processing. 1 The remaining reactant polymer was purified by ¹H NMR and GPC analysis. GPC results showed a molecular weight of 24600 g / mol and a molecular weight distribution of 1.98. Polymer purification involved dissolving the crude product in a small amount of dichloromethane, then adding a large amount of methanol and stirring vigorously to precipitate the polymer. This process was repeated until a pale yellow polymer was obtained, which was then vacuum dried for later use. When this polymer was added to a lithium-sulfur battery, the specific capacity of the lithium-sulfur electrolyte at 0.5 C and 2 C rates was 700 mAh / g and 600 mAh / g, respectively. The specific capacity decay rates of this polymer as a lithium-sulfur electrolyte at 0.5 C and 2 C rates were 0.08% and 0.04%, respectively.
[0058] Example 9
[0059] 10 mL Schlenk bar bottles with magnetic ingots at 130 o Dry at C for more than 12 hours, evacuate and allow to cool to room temperature, then purge with nitrogen for use. Under nitrogen protection, weigh a certain amount of organic base 2d at room temperature and add it to the mixture. The molar ratio of organic base 2d to 1,3-propanedithiol is 1 / 1, and the molar ratio of organic base 2d to the organic ammonium salt tetrabutylammonium bromide is 1 / 1. Then add 1g of elemental sulfur and lipoic acid amide, with a molar ratio of lipoic acid amide to elemental sulfur and organic base 2d of 400 / 50 / 1. Add trichlorobenzene as a solvent, with a solvent-to-lipoic acid derivative volume ratio of 1:1. Seal the strip bottle and place it in an oil bath preheated to 40°C, and start stirring. React for 6 hours, then stop stirring. Take out a very small amount of the reaction mixture for further processing. 1¹H NMR and GPC analyses were performed to purify the remaining reactant polymer. GPC results showed a polymer molecular weight of 12800 g / mol and a molecular weight distribution of 1.83. Polymer purification involved dissolving the crude product in a small amount of dichloromethane, then adding a large amount of methanol and stirring vigorously to precipitate the polymer. This process was repeated until a pale yellow polymer was obtained, which was then vacuum dried for later use. When this polymer was added to a lithium-sulfur battery, the specific capacities of the lithium-sulfur electrolyte at 0.5 C and 2 C rates were 1200 mAh / g and 800 mAh / g, respectively. The specific capacity decay rates of this polymer as a lithium-sulfur electrolyte at 0.5 C and 2 C rates were 0.065% and 0.047%, respectively.
[0060] Example 10
[0061] 10 mL Schlenk bar bottles with magnetic ingots at 130 o Dry at C for more than 12 hours, evacuate and allow to cool to room temperature, then purge with nitrogen for use. Under nitrogen protection, weigh a certain amount of organic base 2e at room temperature and add it to the mixture. The molar ratio of organic base 2e to 2-hydroxy-1-propanethiol is 1 / 2, and the molar ratio of organic base 2e to the organic ammonium salt tetrabutylammonium bromide is 1 / 1. Then add elemental sulfur and lipoic acid amide for 1 hour. The molar ratio of lipoic acid amide to elemental sulfur and organic base 2e is 1000 / 125 / 1. Add tetrahydrofuran as a solvent, with a solvent-to-lipoic acid derivative volume ratio of 1:1. Seal the strip bottle and place it in an oil bath preheated to 60°C, then start stirring. React for 1 hour, then stop stirring. Take out a very small amount of the reaction mixture for further processing. 1 The remaining reactant polymer was purified by ¹H NMR and GPC analysis. GPC results showed a molecular weight of 37300 g / mol and a molecular weight distribution of 1.95. Polymer purification involved dissolving the crude product in a small amount of dichloromethane, then adding a large amount of methanol and stirring vigorously to precipitate the polymer. This process was repeated until a pale yellow polymer was obtained, which was then vacuum dried for later use. When this polymer was added to a lithium-sulfur battery, the specific capacity of the lithium-sulfur electrolyte at 0.5 C and 2 C rates was 1200 mAh / g and 900 mAh / g, respectively. The capacity decay rates of this polymer as a lithium-sulfur electrolyte at 0.5 C and 2 C rates were 0.065% and 0.042%, respectively.
[0062] Example 11
[0063] 10 mL Schlenk bar bottles with magnetic ingots at 130 oDry at C for more than 12 hours, evacuate and allow to cool to room temperature, then purge with nitrogen for use. Under nitrogen protection, weigh a certain amount of organic base 2f at room temperature and add it to the mixture. The molar ratio of organic base 2f to cyclohexanedithiol is 1 / 1, and the molar ratio of organic base 2f to the organic ammonium salt tetrabutylammonium bromide is 1 / 1. Then add elemental sulfur and thiooctanoic acid amide 1i, with a molar ratio of thiooctanoic acid amide to elemental sulfur and organic base 2f of 4000 / 500 / 1. After sealing the strip bottle, place it in an oil bath preheated to 80°C and start stirring. React for 0.1 hours, then stop stirring. Take out a very small amount of the reaction mixture for further processing. 1 ¹H NMR and GPC analyses were performed to purify the remaining reactant polymer. GPC results showed a polymer molecular weight of 164,000 g / mol and a molecular weight distribution of 1.89. Polymer purification involved dissolving the crude product in a small amount of dichloromethane, then adding a large amount of methanol and stirring vigorously to precipitate the polymer. This process was repeated until a pale yellow polymer was obtained, which was then vacuum dried for later use. When this polymer was added to a lithium-sulfur battery, the specific capacity of the lithium-sulfur electrolyte at 0.5 C and 2 C rates was 1100 mAh / g and 810 mAh / g, respectively. The specific capacity decay rates of this polymer as a lithium-sulfur electrolyte at 0.5 C and 2 C rates were 0.075% and 0.064%, respectively.
[0064] Example 12
[0065] 10 mL Schlenk bar bottles with magnetic ingots at 130 o Dry at C for more than 12 hours, then vacuum-evacuate and allow to cool to room temperature before purging with nitrogen for use. Under nitrogen protection, weigh out 2g of an organic base at room temperature and add it to the mixture. The molar ratio of the organic base to 2-hydroxyethanethiol is 1 / 1, and the molar ratio of the organic base to the organic ammonium salt tetrabutylammonium bromide is 1 / 1. Then add elemental sulfur and 1g of lipoic acid amide, with a molar ratio of lipoic acid amide to elemental sulfur and 2g of organic base of 8000 / 1000 / 1. Seal the strip bottle and place it in an oil bath preheated to 25°C, then start stirring. React for 2 hours, then stop stirring. Take out a very small amount of the reaction mixture for further processing. 1¹H NMR and GPC analyses were performed to purify the remaining reactant polymer. GPC results showed a polymer molecular weight of 500,000 g / mol and a molecular weight distribution of 2.01. Polymer purification involved dissolving the crude product in a small amount of dichloromethane, then adding a large amount of methanol and stirring vigorously to precipitate the polymer. This process was repeated until a pale yellow polymer was obtained, which was then vacuum dried for later use. When this polymer was added to a lithium-sulfur battery, the specific capacity of the lithium-sulfur electrolyte at 0.5 C and 2 C rates was 990 mAh / g and 680 mAh / g, respectively. The specific capacity decay rates of this polymer as a lithium-sulfur electrolyte at 0.5 C and 2 C rates were 0.08% and 0.05%, respectively.
[0066] Example 13
[0067] 10 mL Schlenk bar bottles with magnetic ingots at 130 o Dry at C for more than 12 hours, then vacuum-evacuate and allow to cool to room temperature before purging with nitrogen for use. Under nitrogen protection, weigh out 2g of an organic base at room temperature and add it to the mixture. The molar ratio of the organic base to 3-hydroxy-1-propanethiol is 1 / 1, and the molar ratio of the organic base to the organic ammonium salt tetrabutylammonium bromide is 1 / 1. Then add elemental sulfur and 1k of thioctic amide, with a molar ratio of thioctic amide to elemental sulfur and 2g of organic base of 400 / 200 / 1. Seal the strip bottle and place it in an oil bath preheated to 25°C, then start stirring. React for 2 hours, then stop stirring. Take out a very small amount of the reaction mixture for further processing. 1 ¹H NMR and GPC analyses were performed to purify the remaining reactant polymer. GPC results showed a polymer molecular weight of 22500 g / mol and a molecular weight distribution of 2.13. Polymer purification involved dissolving the crude product in a small amount of dichloromethane, then adding a large amount of methanol and stirring vigorously to precipitate the polymer. This process was repeated until a pale yellow polymer was obtained, which was then vacuum dried for later use. When this polymer was added to a lithium-sulfur battery, the specific capacities of the lithium-sulfur electrolyte at 0.5 C and 2 C rates were 1180 mAh / g and 900 mAh / g, respectively. The specific capacity decay rates of this polymer as a lithium-sulfur electrolyte at 0.5 C and 2 C rates were 0.054% and 0.043%, respectively.
[0068] Example 14
[0069] 10 mL Schlenk bar bottles with magnetic ingots at 130 oDry at C for more than 12 hours, then vacuum-fed and cooled to room temperature before purging with nitrogen. Under nitrogen protection, weigh out 2g of an organic base at room temperature and add it to the mixture. The molar ratio of the organic base to dithioethyl sulfide is 1 / 1, and the molar ratio of the organic base to the organic ammonium salt tetrabutylammonium bromide is 1 / 1. Then add 1L of elemental sulfur and thioctic acid amide, with a molar ratio of thioctic acid amide to elemental sulfur and 2g of organic base of 400 / 100 / 1. Seal the strip bottle and place it in an oil bath preheated to 25°C, then start stirring. React for 2 hours, then stop stirring. Take out a very small amount of the reaction mixture for further processing. 1 ¹H NMR and GPC analyses were performed to purify the remaining reactant polymer. GPC results showed a polymer molecular weight of 21600 g / mol and a molecular weight distribution of 1.92. Polymer purification involved dissolving the crude product in a small amount of dichloromethane, then adding a large amount of methanol and stirring vigorously to precipitate the polymer. This process was repeated until a pale yellow polymer was obtained, which was then vacuum dried for later use. When this polymer was added to a lithium-sulfur battery, the specific capacity of the lithium-sulfur electrolyte at 0.5 C and 2 C rates was 1134 mAh / g and 880 mAh / g, respectively. The specific capacity decay rates of this polymer as a lithium-sulfur electrolyte at 0.5 C and 2 C rates were 0.055% and 0.04%, respectively.
[0070] Example 15
[0071] 10 mL Schlenk bar bottles with magnetic ingots at 130 o Dry at C for more than 12 hours, evacuate and allow to cool to room temperature, then purge with nitrogen for use. Under nitrogen protection, weigh a certain amount of organic base 2h and add it to the mixture at room temperature. The molar ratio of organic base 2h to 2,3-dithio(2-mercapto)-1-propanethiol is 1 / 1, and the molar ratio of organic base 2h to the organic ammonium salt tetrabutylammonium bromide is 1 / 1. Then add elemental sulfur and lipoic acid amide 1h, with a molar ratio of lipoic acid amide to elemental sulfur and organic base 2h of 800 / 50 / 1. Add ethylene glycol dimethyl ether as a solvent, with a solvent-to-lipoic acid derivative volume ratio of 1:1. Seal the strip bottle and place it in an oil bath preheated to 25°C, and start stirring. React for 2 hours, then stop stirring. Take out a very small amount of the reaction mixture for further processing. 1The remaining reactant polymer was purified by ¹H NMR and GPC analysis. GPC results showed a polymer molecular weight of 8300 g / mol and a molecular weight distribution of 1.65. Polymer purification involved dissolving the crude product in a small amount of dichloromethane, then adding a large amount of methanol and stirring vigorously to precipitate the polymer. This process was repeated until a pale yellow polymer was obtained, which was then vacuum dried for later use. When this polymer was added to a lithium-sulfur battery, the specific capacity of the lithium-sulfur electrolyte at 0.5 C and 2 C rates was 1200 mAh / g and 950 mAh / g, respectively. The specific capacity decay rates of this polymer as a lithium-sulfur electrolyte at 0.5 C and 2 C rates were 0.045% and 0.041%, respectively.
[0072] Example 16
[0073] 10 mL Schlenk bar bottles with magnetic ingots at 130 o Dry at C for more than 12 hours, evacuate and allow to cool to room temperature, then purge with nitrogen for use. Under nitrogen protection, weigh a certain amount of organic base 2i at room temperature and add it to the mixture. The molar ratio of organic base 2i to pentaerythritol tetra-3-mercaptopropionate is 1 / 1, and the molar ratio of organic base 2i to the organic ammonium salt tetrabutylammonium bromide is 1 / 1. Then add elemental sulfur and lipoic acid amide 1j, with a molar ratio of lipoic acid amide to elemental sulfur and organic base 2i of 400 / 50 / 1. Add 1,4-dioxane as a solvent, with a solvent-to-lipoic acid derivative volume ratio of 1:1. Seal the strip bottle and place it in an oil bath preheated to 25°C, then start stirring. React for 2 hours, then stop stirring. Take out a very small amount of the reaction mixture for further processing. 1 ¹H NMR and GPC analyses were performed to purify the remaining reactant polymer. GPC results showed a polymer molecular weight of 7600 g / mol and a molecular weight distribution of 1.73. Polymer purification involved dissolving the crude product in a small amount of dichloromethane, then adding a large amount of methanol and stirring vigorously to precipitate the polymer. This process was repeated until a pale yellow polymer was obtained, which was then vacuum dried for later use. When this polymer was added to a lithium-sulfur battery, the specific capacities of the lithium-sulfur electrolyte at 0.5 C and 2 C rates were 1080 mAh / g and 840 mAh / g, respectively. The capacity decay rates of this polymer as a lithium-sulfur electrolyte at 0.5 C and 2 C rates were 0.065% and 0.042%, respectively.
[0074] Example 17
[0075] 10 mL Schlenk bar bottles with magnetic ingots at 130 oDry at C for more than 12 hours, evacuate and cool to room temperature, then purge with nitrogen for use. Under nitrogen protection, weigh a certain amount of organic base 2j at room temperature and add it to the mixture. The molar ratio of organic base 2j to benzyl thiol is 1 / 1, and the molar ratio of organic base 2j to the organic ammonium salt bis(triphenyl)phosphine ammonium chloride is 1 / 1. Then add elemental sulfur and thioclate 1a, with a molar ratio of thioclate 1a to elemental sulfur and organic base 2j of 400 / 50 / 1. Add diethylene glycol dimethyl ether as a solvent, with a volume ratio of solvent to thiocic acid derivative of 1:1. Seal the strip bottle and place it in an oil bath preheated to 25°C, and start stirring. React for 2 hours, then stop stirring. Take out a very small amount of the reaction mixture for further processing. 1 ¹H NMR and GPC analyses were performed to purify the remaining reactant polymer. GPC results showed a polymer molecular weight of 8300 g / mol and a molecular weight distribution of 1.81. Polymer purification involved dissolving the crude product in a small amount of dichloromethane, then adding a large amount of methanol and stirring vigorously to precipitate the polymer. This process was repeated until a pale yellow polymer was obtained, which was then vacuum dried for later use. When this polymer was added to a lithium-sulfur battery, the specific capacities of the lithium-sulfur electrolyte at 0.5 C and 2 C rates were 1150 mAh / g and 875 mAh / g, respectively. The specific capacity decay rates of this polymer as a lithium-sulfur electrolyte at 0.5 C and 2 C rates were 0.053% and 0.042%, respectively.
Claims
1. A polytrisulfide used as an additive in lithium-sulfur electrolytes, characterized in that, The polytrisulfide described above is a type of sulfur-containing polymer material whose main chain repeating unit is a trisulfide bond as the main chain functional group; the main chain repeating unit does not contain polysulfide, polydisulfide, or polysulfide segments, wherein the polysulfide segments are segments with more than 3 consecutive sulfur atoms; the general structural formula of the polytrisulfide is as follows: ； Where n ranges from 5 to 2000; FG represents methoxy, ethoxy, n-butoxy, isopropoxy, benzyloxy, phenoxy, ethylamino, diethylamino, n-butamino, isopropamino, benzylamino, and phenylamino.
2. The polytrisulfide used as an additive in lithium-sulfur electrolyte according to claim 1 is characterized in that, The number-average molecular weight of the polytrisulfide is 2000~500000 g / mol, and the molecular weight distribution is 1.5~2.
2.
3. A method for preparing a polytrisulfide used as an additive in a lithium-sulfur electrolyte as described in claim 1 or 2, characterized in that, Polytrisulfides are produced from elemental sulfur and lipoic acid derivatives using a catalytic system composed of an organic base, an organic ammonium salt, and a chain initiator. The polymerization reaction follows a general formula: 。 4. The method for preparing polytrisulfide as an additive in lithium-sulfur electrolyte according to claim 3, characterized in that, The organic bases used in the catalytic system are triethylamine, tri-n-butylamine, diisopropylethylamine, phosphazene base P1, phosphazene base P2, phosphazene base P4, 4-dimethylaminopyridine, 1,8-diazabicyclo[5.4.0]undec-7-ene, 1,5,7-triazabicyclo[4.4.0]dec-5-ene or 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene; The organic ammonium salt used in the catalytic system is one of the following: tetramethylammonium chloride, tetramethylammonium bromide, tetraethylammonium chloride, tetraethylammonium bromide, tetraethylammonium iodide, tetrabutylammonium chloride, tetrabutylammonium bromide, tetrabutylammonium iodide, tetrabutylammonium acetate, tetrabutylammonium tribromide, tetrabutylammonium nitrate, tetrabutylammonium hydrogen sulfate, tetrabutylammonium fluoride, benzyltriethylammonium chloride, benzyltripropylammonium chloride, benzyltributylammonium chloride, benzyltributylammonium bromide, hexadecyltrimethylammonium chloride, dodecyltrimethylammonium chloride, bis(triphenyl)phosphine ammonium chloride, methyltriphenylphosphonium bromide, and allyltriphenylphosphonium bromide; The chain initiator is ethanethiol, propanethiol, n-butanethiol, benzylthiol, ethylenedithiol, thiophene, 1,2-propanedithiol, 1,3-propanedithiol, p-dibenzylthiol, p-dibenzylthiol, cyclohexanedithiol, 2-hydroxyethanethiol, 2-hydroxy-1-propanethiol, 3-hydroxy-1-propanethiol, dimercaptoethyl sulfide, 2,3-dithio(2-mercapto)-1-propanethiol, or pentaerythritol tetra-3-mercaptopropionate.
5. A method for preparing a polytrisulfide used as an additive in a lithium-sulfur electrolyte according to claim 3, characterized in that, The molar ratio of the chain initiator to the organic base is 1:2 to 3:1; the molar ratio of the organic base to the organic ammonium salt is 1:2 to 3:
1.
6. A method for preparing a polytrisulfide used as an additive in a lithium-sulfur electrolyte according to claim 3, characterized in that, The thioctic acid derivative used is one of the following: methyl thiocate, ethyl thiocate, isopropyl thiocate, isobutyl thiocate, benzyl thiocate, phenyl thiocate, acetamide thiocate, diacetamide thiocate, n-butyramide thiocate, isopropyl thiocate, benzamide thiocate, and benzamide thiocate.
7. The method for preparing a polytrisulfide used as an additive in a lithium-sulfur electrolyte according to claim 3, characterized in that, The ratio of the lipoic acid derivative to elemental sulfur is 2:1 to 16:1; the molar ratio of the lipoic acid derivative to the organic base is 100:1 to 8000:
1.
8. The method for preparing polytrisulfide as an additive in lithium-sulfur electrolyte according to claim 3, characterized in that, The polymerization reaction is carried out at 0~80°C. o Perform at C for 0.1–24 h.
9. A method for preparing a polytrisulfide used as an additive in a lithium-sulfur electrolyte according to claim 3, characterized in that, If the polymerization reaction is carried out in solution, the solvent used is selected from any one of toluene, xylene, trichlorobenzene, tetrahydrofuran, 1,4-dioxane, ethylene glycol dimethyl ether, and diethylene glycol dimethyl ether.
10. The application of a polytrisulfide as an additive for lithium-sulfur electrolytes according to any one of claims 1-2, or a polytrisulfide as an additive for lithium-sulfur electrolytes prepared by any one of claims 3-9, characterized in that, The polytrisulfide is used as an additive in lithium-sulfur electrolyte to improve the performance of lithium-sulfur batteries; the specific capacity of lithium-sulfur batteries with added polytrisulfide is 600~1200mAh / g, and the specific capacity decay rate is 0.04%~0.08%.