A method for preparing a quasi-solid lithium-sulfur battery containing a small molecule phosphorus-containing additive

Abstract

The present application belongs to the technical field of quasi-solid lithium-sulfur battery, and particularly relates to a preparation method of a quasi-solid lithium-sulfur battery containing a small-molecule phosphorus-containing additive. The present application uses DOL as a polymer skeleton main body, introduces a small-molecule additive containing a phosphorus element into a high polymer skeleton from molecular design, the hydroxyl in the small-molecule additive can exist hydrogen bond interaction with oxygen-containing functional groups in the polymer matrix, can effectively destroy the crystalline region, realizes the fast conduction of Li + , and the segmented movement of the polymer chain further promotes the transmission of Li + , improves the ionic conductivity of the GPE. Therefore, the prepared gel polymer electrolyte can effectively accelerate the conversion process of polysulfides, so as to improve the overall discharge capacity and significantly improve the energy density of the lithium-sulfur battery.

Description

Technical Field

[0001] The present invention belongs to the technical field of quasi-solid-state lithium-sulfur batteries, and in particular relates to a method for preparing a quasi-solid-state lithium-sulfur battery containing a small molecule phosphorus-containing additive. Background Art

[0002] With the continuous progress of social economy and science and technology, energy demand and consumption continue to rise worldwide. However, traditional fossil energy such as coal, natural gas and oil have been over-exploited and used, and resource supply is becoming increasingly serious. New electrochemical energy storage systems are a hot topic in the research field, among which lithium-ion batteries (LIB) are one of the more typical secondary batteries. It has many advantages such as high operating voltage, large specific capacity, long cycle life and no memory effect, so it has attracted much attention and research. However, due to its low theoretical specific capacity (<250Wh kg -1 ), so the actual energy density of the assembled battery generally cannot meet the urgent demand for high-capacity batteries in today's society.

[0003] Lithium-sulfur (Li-S) battery is a new type of electrochemical energy storage system. Its positive electrode uses elemental sulfur or sulfur-containing compounds, and the negative electrode uses metallic lithium. Energy storage and release are achieved through a multi-step electron transfer process and the process of gaining and losing electrons by metallic lithium. Compared with the traditional lithium cobalt oxide-graphite battery system, the Li-S battery with elemental sulfur as the positive electrode active material has a higher theoretical specific capacity (1675mAh g -1 ) and theoretical specific energy (2600Wh kg -1 ), boasting a capacity and energy output more than five times that of today's commercial lithium-ion batteries. Furthermore, the widespread and inexpensive availability of sulfur resources makes Li-S batteries promising and economically viable. Consequently, lithium-sulfur batteries have garnered significant attention from both academia and industry.

[0004] Although lithium-sulfur batteries have the advantages of high theoretical energy density, widespread positive electrode material resources, and long battery life, their charging and discharging processes are accompanied by multi-step chemical reactions and multi-phase transition processes, which lead to problems such as positive electrode volume expansion, lithium dendrites, and polysulfide shuttling during the reaction process, further affecting the safety and engineering process of lithium-sulfur batteries.

[0005] In recent years, quasi-solid electrolytes (GPEs) have attracted the attention of scientists. This electrolyte has good wettability for the separator, and at the same time, the precursor solution is in situ polymerized inside the battery through various means such as free radical, cationic or anionic polymerization, thereby constructing a safer quasi-solid electrolyte. In the electrolyte system of lithium-sulfur batteries, 1,3-dioxolane (DOL) plays a key role. Its characteristic is that it has the potential for ring-opening polymerization. Specifically, 1,3-dioxolane (DOL) can undergo cationic ring-opening polymerization under the induction of catalysts such as Lewis acid, and further participate in the process of constructing a high-quality solid electrolyte interface (SEI) film on the surface of the lithium negative electrode. In addition, the gel electrolyte evolved from the standard electrolyte of lithium-sulfur batteries has shown a positive promoting effect on improving battery performance due to its high compatibility with the lithium-sulfur battery system.

[0006] However, the ionic conductivity of the gel polymer electrolyte (pDOL-GPE) prepared by in-situ curing of conventional 1,3-dioxolane (DOL) is often low. This is because a large number of crystalline regions are generated in the conventional solvation structure, which leads to limited segmental motion of the polymer skeleton and hinders the Li + further migration.

[0007] Therefore, under the premise of ensuring the construction of a safe and stable gel polymer electrolyte, it is urgent to significantly reduce the crystalline area in the polymer skeleton and improve the movement of polymer skeleton chain segments, so as to increase the overall energy density of lithium-sulfur batteries and further promote the engineering process of lithium-sulfur batteries. Summary of the Invention

[0008] The main purpose of this invention is to overcome the problem of a large number of crystalline regions that slow down the Li+ migration rate in the gel polymer electrolyte prepared after in-situ curing of traditional 1,3-dioxolane (DOL), which in turn leads to slow kinetics of lithium-sulfur batteries. A preparation method for high-performance quasi-solid-state lithium-sulfur batteries containing small molecule phosphorus additives is designed. The small molecule phosphorus additive trihydroxypropylphosphine (THPP) is used to regulate the crystal morphology in the polymer skeleton. The hydroxyl groups in THPP can interact with the oxygen-containing functional groups in the gel polymer electrolyte through hydrogen bonds, which can effectively destroy the crystallization region and achieve Li + The rapid conduction of Li+ is achieved through the segmented motion of the polymer chains, further promoting Li+ transport and improving the ionic conductivity of the gel polymer electrolyte. Furthermore, the unique phosphine-containing structure in THPP effectively accelerates the catalytic conversion of polysulfides, thereby alleviating the sluggish kinetics of quasi-solid-state lithium-sulfur batteries and enhancing their rate capability. The small molecule phosphorus-containing additive employed in this invention is readily available and offers excellent battery performance, thereby enhancing the electrochemical performance of quasi-solid-state lithium-sulfur batteries and providing new insights into the engineering of lithium-sulfur batteries.

[0009] The above-mentioned object of the present invention is achieved through the following technical solutions:

[0010] A method for preparing a quasi-solid-state lithium-sulfur battery containing a small molecule phosphorus-containing additive, comprising the following steps:

[0011] (1) Under magnetic stirring, the lithium-sulfur battery electrolyte is added to the initiator, and then vigorously stirred until the initiator is completely dissolved to obtain solution A;

[0012] (2) adding a small molecule phosphorus-containing additive to solution A and continuing to stir to ensure that the small molecule phosphorus-containing additive is completely dissolved to obtain a uniform and transparent precursor solution B;

[0013] (3) Assembling a lithium-sulfur battery using precursor solution B as the electrolyte;

[0014] (4) After the lithium-sulfur battery assembled in step (3) is left to stand at room temperature, the precursor solution B spontaneously transforms into a gel polymer electrolyte to form the final quasi-solid-state lithium-sulfur battery.

[0015] All the above steps were carried out in a glove box (O2<0.01ppm, H2O<0.01ppm).

[0016] Preferably, the lithium-sulfur battery electrolyte in step (1) comprises an ether solvent and a lithium salt.

[0017] Preferably, the ether solvent in step (1) is a mixture of 1,3-dioxolane (DOL) and ethylene glycol dimethyl ether (DME), and the volume ratio of the two is 1:1.

[0018] Preferably, the lithium salt in step (1) is one or a mixture of two or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bis(nonafluorobutylsulfonyl)imide, lithium perchlorate, lithium trifluoromethanesulfonate, lithium perfluorobutylsulfonate, lithium bis(trifluoromethanesulfonylimide), lithium bis(fluorosulfonylimide), lithium aluminate, lithium chloroaluminate, lithium fluorosulfonylimide, lithium chloride and lithium iodide; preferably, the lithium salt is one or a mixture of two of lithium bis(trifluoromethanesulfonylimide) and lithium bis(fluorosulfonylimide). The concentration of the lithium salt in the lithium-sulfur battery electrolyte is 1.0 to 2.0 mol / L.

[0019] Preferably, the initiator in step (1) is one or a mixture of two or more of aluminum trifluoromethanesulfonate (Al(OTf)3), scandium trifluoromethanesulfonate (Sc(OTf)3), lithium hexafluorophosphate (LiPF6), and lithium difluorooxalatoborate (LiDFOB); the concentration of the initiator in solution A is 1 mmol / L to 3 mmol / L, preferably 1 mmol / L.

[0020] Preferably, the small molecule phosphorus-containing additive in step (2) is trihydroxypropylphosphine (THPP); the concentration of the small molecule phosphorus-containing additive in solution A is 0.2 mmol / L to 1.0 mmol / L, preferably 0.5 mmol / L.

[0021] Preferably, the stirring time in step (2) is 10 to 30 minutes.

[0022] Preferably, the positive electrode material of the lithium-sulfur battery is a sulfur loading material with a sulfur loading of 0.8 to 1.2 mg / cm 2 carbon-sulfur composite materials.

[0023] Preferably, the precursor solution B described in step (3) is added dropwise on the positive electrode sheet in an amount of 15 μL / mg to 40 μL / mg in terms of liquid-sulfur ratio (volume of precursor solution B to mass ratio of sulfur loaded on the positive electrode material).

[0024] Preferably, the separator of the lithium-sulfur battery is Celgard-2500; and the negative electrode material of the lithium-sulfur battery is a metallic lithium sheet.

[0025] Preferably, the standing time in step (5) is 12 hours to 36 hours.

[0026] Beneficial effects of the present invention:

[0027] The present invention uses 1,3-dioxolane (DOL) in situ ring-opening polymerization as the polymer skeleton of the quasi-solid-state lithium-sulfur battery. On this basis, a small molecule phosphorus-containing additive is innovatively introduced to create a quasi-solid electrolyte that accelerates ion conduction and electrochemical catalysis, thereby improving the ion / electron transfer kinetics of the quasi-solid-state electrolyte and realizing high-performance quasi-solid-state lithium-sulfur batteries. Specifically, there is a hydrogen bond interaction between the hydroxyl groups in the small molecule phosphorus-containing additive with a special structure and the oxygen-containing functional groups in the polymer skeleton, which can effectively destroy the crystallization area and achieve Li + The rapid conduction of Li + The additive's unique structure can effectively accelerate the catalytic conversion of polysulfides, thereby improving the sluggish kinetics of quasi-solid-state lithium-sulfur batteries and enhancing their rate performance. These advantages provide a new approach to the engineering application of high-performance quasi-solid-state lithium-sulfur batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 and Figure 2 They are respectively the electrochemical rate performance test curve and the cycle performance test curve of the quasi-solid electrolyte of Example 1 of the present invention. DETAILED DESCRIPTION

[0029] The following further illustrates the specific implementation of the present invention through the accompanying drawings and technical solutions.

[0030] Example 1

[0031] (1) 2.37 mg of aluminum trifluoromethanesulfonate (Al(OTf)3) and 0.76 mg of lithium hexafluorophosphate were added to a 10 ml transparent sample bottle as an initiator, and then 1.44 g of lithium bis(trifluoromethanesulfonyl imide) and 0.935 g of lithium bis(fluorosulfonyl imide) were weighed and mixed as lithium salts, and placed in a transparent sample bottle. Then, 2.5 mL of 1,3-dioxolane (DOL) and 2.5 mL of ethylene glycol dimethyl ether (DME) were added to the sample bottle in sequence and stirred vigorously until the above substances were completely dissolved to ensure that the initiator and lithium salt were completely dissolved;

[0032] (2) After the lithium salt and initiator are completely dissolved in the electrolyte, 0.52 mg of trihydroxypropylphosphine (THPP) is added to the sample bottle and stirred for 10 minutes to obtain a uniform and transparent precursor solution;

[0033] (3) Carbon-sulfur powder (70% sulfur content) was mixed with commercial binder PVDF and commercial conductive agent SuperP in a small amount of anhydrous NMP solvent in a mass ratio of 7:2:1, and the obtained slurry was evenly coated on carbon-coated aluminum foil and dried in a vacuum oven at 60°C overnight. After the electrode was completely cooled and dried, it was cut into pieces to obtain a circular lithium-sulfur battery positive electrode sheet with a diameter of 11 mm;

[0034] (4) Lithium-sulfur Battery Assembly: Coin-type CR2032 batteries were used for assembly in a glove box. Coin-type batteries were assembled and tested using a lithium metal sheet as the negative electrode, a single layer of polypropylene (PP, Celgard 2500) as the separator, the precursor solution obtained in step (2) above as the electrolyte, and the prepared organosulfur polymer as the positive electrode.

[0035] In step (4), the lithium metal negative electrode used in the battery has a diameter of 15.5 mm, the diameter of the single-layer polypropylene separator is 19 mm, and the sulfur surface loading in each circular positive electrode is maintained at 1.0-1.5 mg / cm 2 The ratio of electrolyte addition to active material is controlled at 15-40 μL / mg.

[0036] The test showed that the gel conversion time was 24 hours, the gel formation temperature was room temperature, and the battery test results were shown in Table 1.

[0037] Example 2

[0038] (1) 0.76 g of lithium hexafluorophosphate and 359.43 mg of lithium difluorooxalatoborate were added to a 10 ml transparent sample bottle as an initiator, and then 1.44 g of lithium bis(trifluoromethanesulfonyl)imide and 1.47 g of lithium bis(nonafluorobutylsulfonyl)imide) were weighed and mixed as lithium salts, and placed in a transparent sample bottle. Then, 2.5 mL of 1,3-dioxolane (DOL) and 2.5 mL of ethylene glycol dimethyl ether (DME) were added to the sample bottle in sequence and stirred vigorously until the above substances were completely dissolved to ensure that the initiator and lithium salt were completely dissolved;

[0039] (2) After the lithium salt and initiator are completely dissolved in the electrolyte, 0.52 mg of trihydroxypropylphosphine (THPP) is added to the sample bottle and stirred for 30 minutes to obtain a uniform and transparent precursor solution;

[0040] (3) Carbon-sulfur powder (70% sulfur content) was mixed with commercial binder PVDF and commercial conductive agent SuperP in a small amount of anhydrous NMP solvent in a mass ratio of 7:2:1, and the obtained slurry was evenly coated on carbon-coated aluminum foil and dried in a vacuum oven at 60°C overnight. After the electrode was completely cooled and dried, it was cut into pieces to obtain a circular lithium-sulfur battery positive electrode sheet with a diameter of 11 mm;

[0041] (4) Lithium-sulfur Battery Assembly: Coin-type CR2032 batteries were used for assembly in a glove box. Coin-type batteries were assembled and tested using a lithium metal sheet as the negative electrode, a single layer of polypropylene (PP, Celgard 2500) as the separator, the precursor solution obtained in step (2) above as the electrolyte, and the prepared organosulfur polymer as the positive electrode.

[0042] In step (4), the lithium metal negative electrode used in the battery has a diameter of 15.5 mm, the single-layer polypropylene separator has a diameter of 19 mm, the sulfur surface loading in each circular positive electrode plate is maintained at 1.0 to 1.5 mg / cm2, and the ratio of the electrolyte addition amount to the active material is controlled at 15 to 40 μL / mg.

[0043] The test showed that the gel conversion time was 10 h, the gel formation temperature was room temperature, and the battery test results were shown in Table 1.

[0044] Example 3

[0045] (1) 359.43 mg of lithium difluorooxalatoborate and 2.3 mg of aluminum trifluoromethanesulfonate were added to a 10 ml transparent sample bottle as an initiator, and then 1.87 g of lithium bis(fluorosulfonyl)imide was weighed and placed in a transparent sample bottle as a lithium salt. Then, 2.5 mL of 1,3-dioxolane (DOL) and 2.5 mL of ethylene glycol dimethyl ether (DME) were added to the sample bottle in sequence and stirred vigorously until the above substances were completely dissolved to ensure that the initiator and the lithium salt were completely dissolved;

[0046] (2) After the lithium salt and initiator are completely dissolved in the electrolyte, 0.52 mg of trihydroxypropylphosphine (THPP) is added to the sample bottle and stirred for 20 min to obtain a uniform and transparent precursor solution;

[0047] (3) Carbon-sulfur powder (70% sulfur content) was mixed with commercial binder PVDF and commercial conductive agent SuperP in a small amount of anhydrous NMP solvent in a mass ratio of 7:2:1, and the obtained slurry was evenly coated on carbon-coated aluminum foil and dried in a vacuum oven at 60°C overnight. After the electrode was completely cooled and dried, it was cut into pieces to obtain a circular lithium-sulfur battery positive electrode sheet with a diameter of 11 mm;

[0048] (4) Lithium-sulfur Battery Assembly: Coin-type CR2032 batteries were used for assembly in a glove box. Coin-type batteries were assembled and tested using a lithium metal sheet as the negative electrode, a single layer of polypropylene (PP, Celgard 2500) as the separator, the precursor solution obtained in step (2) above as the electrolyte, and the prepared organosulfur polymer as the positive electrode.

[0049] In step (4), the lithium metal negative electrode used in the battery has a diameter of 15.5 mm, the single-layer polypropylene separator has a diameter of 19 mm, the sulfur surface loading in each circular positive electrode plate is maintained at 1.0 to 1.5 mg / cm2, and the ratio of the electrolyte addition amount to the active material is controlled at 15 to 40 μL / mg.

[0050] The test showed that the gel conversion time was 20 min, the gel formation temperature was room temperature, and the battery test results are shown in Table 1.

[0051] Example 4

[0052] (1) 1.23 mg of aluminum trifluoromethanesulfonate (Al(OTf)3) and 359.43 mg of lithium difluorooxalatoborate were added to a 10 ml transparent sample bottle as an initiator, and then 1.72 g of lithium bis(trifluoromethanesulfonyl imide) and 0.17 g of lithium chloroaluminate were weighed and mixed as lithium salts, and placed in a transparent sample bottle. Then, 2.5 mL of 1,3-dioxolane (DOL) and 2.5 mL of ethylene glycol dimethyl ether (DME) were added to the sample bottle in sequence and stirred vigorously until the above substances were completely dissolved to ensure that the Al(OTf)3 initiator and the lithium salt were completely dissolved;

[0053] (2) After the lithium salt and initiator are completely dissolved in the electrolyte, 0.21 mg of trihydroxypropylphosphine (THPP) is added to the sample bottle and stirred for 30 minutes to obtain a uniform and transparent precursor solution;

[0054] (3) Carbon-sulfur powder (70% sulfur content) was mixed with commercial binder PVDF and commercial conductive agent SuperP in a small amount of anhydrous NMP solvent in a mass ratio of 7:2:1, and the obtained slurry was evenly coated on carbon-coated aluminum foil and dried in a vacuum oven at 60°C overnight. After the electrode was completely cooled and dried, it was cut into pieces to obtain a circular lithium-sulfur battery positive electrode sheet with a diameter of 11 mm;

[0055] (4) Lithium-sulfur Battery Assembly: Coin-type CR2032 batteries were used for assembly in a glove box. Coin-type batteries were assembled and tested using a lithium metal sheet as the negative electrode, a single layer of polypropylene (PP, Celgard 2500) as the separator, the precursor solution obtained in step (2) above as the electrolyte, and the prepared organosulfur polymer as the positive electrode.

[0056] In step (4), the lithium metal negative electrode used in the battery has a diameter of 15.5 mm, the diameter of the single-layer polypropylene separator is 19 mm, and the sulfur surface loading in each circular positive electrode is maintained at 1.0-1.5 mg / cm 2 The ratio of electrolyte addition to active material is controlled at 15-40 μL / mg.

[0057] The test showed that the gel conversion time was 24 hours, the gel formation temperature was room temperature, and the battery test results were shown in Table 1.

[0058] Example 5

[0059] (1) 1.23 mg of scandium trifluoromethanesulfonate (Sc(OTf)3) and 2.3 mg of aluminum trifluoromethanesulfonate (Al(OTf)3) were added to a 10 ml transparent sample bottle as an initiator, and then 1.15 g of lithium bis(trifluoromethanesulfonyl imide) and 0.26 g of lithium perchlorate were weighed and mixed as lithium salts, and placed in a transparent sample bottle. Then, 2.5 mL of 1,3-dioxolane (DOL) and 2.5 mL of ethylene glycol dimethyl ether (DME) were added to the sample bottle in sequence and stirred vigorously until the above substances were completely dissolved to ensure that the Sc(OTf)3 initiator and the lithium salt were completely dissolved;

[0060] (2) After the lithium salt and initiator are completely dissolved in the electrolyte, add 1.04 mg of trihydroxypropylphosphine (THPP) into the sample bottle and continue stirring for 15 minutes to obtain a uniform and transparent precursor solution;

[0061] (3) Carbon-sulfur powder (70% sulfur content) was mixed with commercial binder PVDF and commercial conductive agent SuperP in a small amount of anhydrous NMP solvent in a mass ratio of 7:2:1, and the obtained slurry was evenly coated on carbon-coated aluminum foil and dried in a vacuum oven at 60°C overnight. After the electrode was completely cooled and dried, it was cut into pieces to obtain a circular lithium-sulfur battery positive electrode sheet with a diameter of 11 mm;

[0062] (4) Lithium-sulfur Battery Assembly: Coin-type CR2032 batteries were used for assembly in a glove box. Coin-type batteries were assembled and tested using a lithium metal sheet as the negative electrode, a single layer of polypropylene (PP, Celgard 2500) as the separator, the precursor solution obtained in step (2) above as the electrolyte, and the prepared organosulfur polymer as the positive electrode.

[0063] In step (4), the lithium metal negative electrode used in the battery has a diameter of 15.5 mm, the diameter of the single-layer polypropylene separator is 19 mm, and the sulfur surface loading in each circular positive electrode is maintained at 1.0-1.5 mg / cm 2 The ratio of electrolyte addition to active material is controlled at 15-40 μL / mg.

[0064] The test showed that the gel conversion time was 24 hours, the gel formation temperature was room temperature, and the battery test results were shown in Table 1.

[0065] Comparative Example 1

[0066] A preparation process of a lithium-sulfur battery is as follows:

[0067] (1) 2.37 mg of aluminum trifluoromethanesulfonate (Al(OTf)3) and 0.76 g of lithium hexafluorophosphate were added to a 10 ml transparent sample bottle as an initiator, and then 0.21 g of lithium chloride and 1.40 g of lithium bis(fluorosulfonyl)imide were weighed and mixed as lithium salts, and placed in a transparent sample bottle. Then, 2.5 mL of 1,3-dioxolane (DOL) and 2.5 mL of ethylene glycol dimethyl ether (DME) were added to the sample bottle in sequence and stirred vigorously until the above substances were completely dissolved to ensure that the initiator and lithium salt were completely dissolved;

[0068] (2) Carbon-sulfur powder (70% sulfur content) was mixed with commercial binder PVDF and commercial conductive agent SuperP in a small amount of anhydrous NMP solvent in a mass ratio of 7:2:1, and the obtained slurry was evenly coated on carbon-coated aluminum foil and dried in a vacuum oven at 60°C overnight. After the electrode was completely cooled and dried, it was cut into pieces to obtain a circular lithium-sulfur battery positive electrode sheet with a diameter of 11 mm;

[0069] (3) Lithium-sulfur Battery Assembly: CR2032 button-type batteries were used for assembly in a glove box. Coin-type batteries were assembled using a lithium metal sheet as the negative electrode, a single layer of polypropylene (PP, Celgard 2500) as the separator, the precursor solution obtained in step (1) as the electrolyte, and the prepared organosulfur polymer as the positive electrode. The batteries were then tested.

[0070] In step (3), the lithium metal negative electrode used in the battery has a diameter of 15.5 mm, the diameter of the single-layer polypropylene separator is 19 mm, and the sulfur surface loading in each circular positive electrode is maintained at 1.0 to 1.5 mg / cm 2 The ratio of electrolyte addition to active material is controlled at 15-40 μL / mg.

[0071] The test showed that the gel conversion time was 24 hours, the gel formation temperature was room temperature, and the battery test results were shown in Table 1.

[0072] Table 1 Test results

[0073]

[0074] Test results demonstrate that the high-performance quasi-solid-state lithium-sulfur batteries prepared using the present invention, containing small molecule phosphorus-containing additives, exhibit superior rate performance and mass specific capacity compared to quasi-solid-state lithium-sulfur batteries without additives. Compared to Comparative Example 1, Examples 1, 2, 3, 4, and 5 exhibit significantly improved initial discharge capacity and rate performance.

[0075] Figure 1This is the rate performance curve of Example 1. As can be seen from the figure, the gel polymer electrolyte containing a small molecule phosphorus-containing additive still has a high discharge specific capacity at a 2C discharge rate, which accelerates the kinetic process of the gel polymer matrix to a certain extent. Figure 1 This is the cycle of Example 1. As can be seen from the figure, the gel polymer electrolyte containing small molecule phosphorus-containing additives is subjected to a 200-cycle long cycle test at a 0.5C discharge rate, and has excellent electrochemical performance. It slows down the "shuttle effect" of the lithium-sulfur battery to a certain extent and has good compatibility with the prepared gel polymer matrix.

Claims

1. A method for preparing a quasi-solid-state lithium-sulfur battery containing a small molecule phosphorus-containing additive, characterized in that: The specific steps are as follows: (1) Under magnetic stirring, the lithium-sulfur battery electrolyte is added to the initiator, and then vigorously stirred until the initiator is completely dissolved to obtain solution A; (2) Add a small molecule phosphorus-containing additive to solution A and continue stirring to ensure that the small molecule phosphorus-containing additive is completely dissolved to obtain a uniform and transparent precursor solution B; (3) Assembling a lithium-sulfur battery using precursor solution B as the electrolyte; (4) After the lithium-sulfur battery assembled in step (3) is left to stand at room temperature, the precursor solution B spontaneously transforms into a gel polymer electrolyte to form the final quasi-solid-state lithium-sulfur battery; The lithium-sulfur battery electrolyte in step (1) comprises an ether solvent and a lithium salt; wherein the ether solvent is a mixture of 1,3-dioxolane and ethylene glycol dimethyl ether; The small molecule phosphorus-containing additive described in step (2) is trihydroxypropylphosphine.

2. The method for preparing a quasi-solid-state lithium-sulfur battery containing a small molecule phosphorus-containing additive according to claim 1, characterized in that: The lithium salt in step (1) is one or a mixture of two or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bis(nonafluorobutylsulfonyl)imide, lithium perchlorate, lithium trifluoromethanesulfonate, lithium perfluorobutylsulfonate, lithium bis(trifluoromethanesulfonylimide), lithium bis(fluorosulfonylimide), lithium aluminate, lithium chloroaluminate, lithium fluorosulfonylimide, lithium chloride and lithium iodide; the concentration of the lithium salt in the lithium-sulfur battery electrolyte is 1.0~2.0mol / L.

3. The method for preparing a quasi-solid-state lithium-sulfur battery containing a small molecule phosphorus-containing additive according to claim 1 or 2, characterized in that: The initiator in step (1) is one or a mixture of two or more of aluminum trifluoromethanesulfonate, scandium trifluoromethanesulfonate, lithium hexafluorophosphate, and lithium difluorooxalatoborate; the concentration of the initiator in solution A is 1 mmol / L to 3 mmol / L.

4. The method for preparing a quasi-solid-state lithium-sulfur battery containing a small molecule phosphorus-containing additive according to claim 3, characterized in that: The concentration of the initiator in solution A is 1 mmol / L.

5. The method for preparing a quasi-solid-state lithium-sulfur battery containing a small molecule phosphorus-containing additive according to claim 1, 2 or 4, characterized in that: The concentration of the small molecule phosphorus-containing additive in solution A described in step (2) is 0.2 mmol / L ~1.0 mmol / L.

6. The method for preparing a quasi-solid-state lithium-sulfur battery containing a small molecule phosphorus-containing additive according to claim 5, characterized in that: The concentration of the small molecule phosphorus-containing additive in solution A described in step (2) is 0.5 mmol / L.

7. The method for preparing a quasi-solid-state lithium-sulfur battery containing a small molecule phosphorus-containing additive according to claim 1, 2, 4 or 6, characterized in that: The positive electrode material of the lithium-sulfur battery is a sulfur loading material with a sulfur loading of 0.8-1.2 mg / cm 2 The precursor solution B described in step (3) is added dropwise on the positive electrode sheet in an amount of 15µL / mg to 40µL / mg based on the volume of the precursor solution B and the mass ratio of the sulfur loaded on the positive electrode material.

8. The method for preparing a quasi-solid-state lithium-sulfur battery containing a small molecule phosphorus-containing additive according to claim 1, 2, 4 or 6, characterized in that: The separator of the lithium-sulfur battery is Celgard-2500; the negative electrode material of the lithium-sulfur battery is a metal lithium sheet.

9. The method for preparing a quasi-solid-state lithium-sulfur battery containing a small molecule phosphorus-containing additive according to claim 1, 2, 4 or 6, characterized in that: The stirring time in step (2) is 10 to 30 minutes; the standing time in step (4) is 12 hours to 36 hours.

10. The method for preparing a quasi-solid-state lithium-sulfur battery containing a small molecule phosphorus-containing additive according to claim 1, 2, 4 or 6, characterized in that: All steps were carried out in a glove box.

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