An asymmetric gel electrolyte, an in-situ polymerization preparation method thereof and application thereof in lithium-sulfur batteries

Abstract

The application relates to an asymmetric gel electrolyte and an in-situ polymerization preparation method thereof and application of the asymmetric gel electrolyte in a lithium-sulfur battery. N-(2-aminoethyl)-3-aminopropyl trimethoxysilane is mixed with polyethylene glycol and dimethyl sulfoxide and polymerized to obtain a light yellow polymer matrix; lithium carbonate, lanthanum oxide and zirconium dioxide are mixed and sintered to prepare LLZO; the polymer matrix and the LLZO are mixed with 1,3-dioxolane, ethylene glycol dimethyl ether, lithium bistrifluoromethanesulfonimide and lithium hexafluorophosphate to form two kinds of gel electrolyte precursor solutions which are respectively drop-coated on the positive electrode side and the negative electrode side of a diaphragm; the asymmetric structure realizes the functional decoupling of the electrolyte in space, the positive electrode side can effectively inhibit the shuttle of polysulfides, promote the dissociation of lithium salt and the transmission of lithium ions, so that the ionic conductivity is improved; the negative electrode side provides a continuous lithium ion conduction path and helps to form a dense and stable mixed SEI layer, promotes the uniform deposition of lithium ions and effectively alleviates the generation of lithium dendrites.

Description

Technical Field

[0001] This invention belongs to the field of lithium-sulfur battery electrolyte preparation technology, specifically relating to an asymmetric gel electrolyte, its in-situ polymerization preparation method, and its application in lithium-sulfur batteries. Background Technology

[0002] Lithium-sulfur batteries, with their high theoretical energy density of approximately 2600 Wh / kg and advantages such as abundant sulfur resources and low cost, are considered an important candidate system for next-generation energy storage technology. However, lithium-sulfur batteries still face serious technical bottlenecks in practical applications, mainly manifested in the shuttle effect of lithium polysulfides and the continuous formation of lithium dendrites, which lead to the loss of active materials, reduced battery coulombic efficiency, shortened cycle life, and are accompanied by higher safety risks.

[0003] Traditional liquid electrolytes, widely used in general, readily dissolve lithium polysulfides, exacerbating their shuttle movement between the positive and negative electrodes. Furthermore, they are flammable and have poor interfacial compatibility with lithium metal, easily leading to safety issues such as interfacial instability and dendrite puncture of the separator. While solid-state electrolytes offer advantages in intrinsic safety and mechanical strength, they often suffer from poor interfacial contact with the electrodes, high interfacial impedance, and severe electrochemical polarization, limiting the battery's rate performance and cycle stability.

[0004] Therefore, gel polymer electrolytes (GPEs) combine the mechanical integrity of solid electrolytes with the high ionic conductivity of liquid electrolytes, and are considered a promising solution for mitigating polysulfide diffusion and suppressing lithium dendrite growth. However, existing gel electrolytes still suffer from problems such as a narrow electrochemical stability window, insufficient lithium polysulfide immobilization capacity, and limited suppression of lithium dendrite growth, making it difficult to simultaneously meet the different interface requirements of the positive and negative electrode sides. In summary, constructing a gel electrolyte that can be formed in situ and introducing an asymmetric structure for differentiated regulation of the positive and negative electrode sides, to achieve a synergistic design of effective polysulfide regulation and lithium dendrite suppression, is a key technological direction for obtaining high-performance lithium-sulfur batteries. Summary of the Invention

[0005] Technical problem solved: This invention provides an asymmetric gel electrolyte and its in-situ polymerization preparation method and its application in lithium-sulfur batteries, which solves the core technical problems of existing lithium-sulfur batteries, such as loss of active material due to lithium polysulfide shuttle, rapid capacity decay, insufficient rate performance, increased battery polarization and impedance caused by shuttle effect, and uncontrolled growth of lithium dendrites that seriously shortens battery life.

[0006] Objective of the invention: By constructing an asymmetric gel electrolyte structure that spatially decouples the functions of the positive and negative electrode interfaces, the electrolyte can be optimized differently for the interface requirements of the positive and negative electrodes respectively. This allows for effective fixation of lithium polysulfides and suppression of the shuttle effect on the positive electrode side, promoting lithium salt dissociation and improving lithium ion transport and overall ionic conductivity. On the negative electrode side, it creates an ion conduction environment conducive to the formation of a dense and stable mixed SEI layer, promoting uniform lithium ion deposition and effectively mitigating the formation and growth of lithium dendrites, thereby improving the cycle stability and safety of lithium-sulfur batteries.

[0007] To achieve the above objectives, this application provides the following technical solution: A method for in-situ polymerization preparation of asymmetric gel electrolytes, specifically including the following steps: The first step involves mixing amino materials, polyethylene glycol, and dimethyl sulfoxide in a mass ratio of 7:30:11, heating and stirring in an oil bath under sealed conditions for 48 hours, followed by further heating at 100°C in air for 72 hours, and cooling to obtain a light yellow polymer material, denoted as Ami-cross. Step 2: Lithium carbonate, lanthanum oxide, and zirconium dioxide were mixed in a molar ratio of 7:3:2. Ethanol was added, and the mixture was manually ground for 30 minutes and then dried. The resulting mixture was placed in a crucible, compacted, and covered. It was sintered at 1150℃ for 8 hours. After cooling, the blocky sintered product was ball-milled at 200 r / min for 2 hours to obtain Li7La3Zr2O. 12 Powder, denoted as LLZO; Step 3: Prepare the electrolyte in the glove box. Mix 1,3-dioxapentane, ethylene glycol dimethyl ether and lithium bis(trifluoromethanesulfonyl)imide and stir for 30 minutes to obtain a mixed solution. Then add the initiator lithium hexafluorophosphate to form a uniform and transparent mixed solution of 1,3-dioxapentane, ethylene glycol dimethyl ether and lithium bis(trifluoromethanesulfonyl)imide, which is the precursor solution, denoted as PDOL. Step 4: In the glove box, add 3 parts of the light yellow polymer material obtained in Step 1 as an additive to 9 parts of the mixed solution of 1,3-dioxapentane, ethylene glycol dimethyl ether and lithium bis(trifluoromethanesulfonyl)imide obtained in Step 3. Stir for 30 minutes and then add 1 part of lithium hexafluorophosphate to obtain a uniform light yellow precursor solution, denoted as PDOL-Ami-cross. Step 5: Place the Li7La3Zr2O obtained in step 2 into the glove box. 12 One part was added as an additive to nine parts of the mixed solution of 1,3-dioxapentane, ethylene glycol dimethyl ether and lithium bis(trifluoromethanesulfonyl)imide obtained in step three. After stirring for 30 minutes, one part of lithium hexafluorophosphate was added to obtain a uniform milky white precursor solution, denoted as PDOL-LLZO.

[0008] Furthermore, the amino material in the first step is N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, the oil bath temperature is 100°C or 200°C, and the sealing method is sealing in an argon atmosphere or sealing in an oxygen atmosphere.

[0009] Furthermore, in the third step, the volume ratio of 1,3-dioxapentane to ethylene glycol dimethyl ether is 1:1, and the concentrations of lithium bis(trifluoromethanesulfonylimide) and lithium hexafluorophosphate are both 1 mol / L.

[0010] Furthermore, in the fourth step, the volume ratio of 1,3-dioxapentane to ethylene glycol dimethyl ether is 1:1, and the concentrations of lithium bis(trifluoromethanesulfonylimide) and lithium hexafluorophosphate are both 1 mol / L.

[0011] Furthermore, in the fifth step, the volume ratio of 1,3-dioxapentane to ethylene glycol dimethyl ether is 1:1, and the concentrations of lithium bis(trifluoromethanesulfonylimide) and lithium hexafluorophosphate are both 1 mol / L.

[0012] An asymmetric gel electrolyte prepared by any of the above-mentioned in-situ polymerization methods.

[0013] This application also discloses the application of an asymmetric gel electrolyte prepared by any of the above-mentioned in-situ polymerization methods in lithium-sulfur batteries, the steps of which are as follows: S1: Carbon nanotubes and sulfur powder are mixed at a mass ratio of 1:3, manually ground for 30 min, heated at 155-180℃ for 10-14 h under an argon atmosphere, and cooled to room temperature to obtain a C / S mixed material; the C / S mixed material, Ketjen black and PVDF binder are ground at a weight ratio of 7:2:1 to form a slurry, the slurry is uniformly coated on aluminum foil by a scraping method, and dried at 60℃ for 10-12 h to obtain a positive electrode sheet, which is then punched into C / S circular electrode sheets; S2: Assemble the battery in the glove box, using C / S circular electrode as the positive electrode, Celgard 2500 as the separator, and commercial lithium metal sheet as the negative electrode. Place PDOL-Ami-cross and PDOL-LLZO on both sides of the separator as electrolytes. Complete the assembly of the asymmetric lithium-sulfur battery under argon protection. S3: The assembled battery is placed in a glove box to allow the electrolyte to polymerize in situ, forming a quasi-solid-state asymmetric lithium-sulfur battery.

[0014] Furthermore, in S1, the aluminum foil has a thickness of 30 μm, the coating thickness of the scraping method is 120 μm, and the diameter of the C / S circular electrode is 16 mm.

[0015] Furthermore, in S2, PDOL-Ami-cross is used as the electrolyte between the positive electrode and the separator, and PDOL-LLZO is used as the electrolyte between the negative electrode and the separator.

[0016] Furthermore, the settling time in S3 is 12-24 hours, the environment is argon atmosphere, and H2O < 0.1 ppm and O2 < 0.1 ppm.

[0017] This application provides an asymmetric gel electrolyte, its in-situ polymerization preparation method, and its application in lithium-sulfur batteries. Compared with the prior art, it has the following advantages: 1. Stable interface, capable of meeting the requirements of positive and negative electrode interfaces respectively: By introducing an asymmetric structure with spatial functional decoupling into the electrolyte, different functional gel electrolyte components are configured on the positive and negative electrode sides respectively, thereby specifically meeting the different requirements of the two electrode interfaces; the gel electrolyte has both good interfacial wettability and certain mechanical strength, which significantly improves the electrolyte / electrode interface contact and compatibility, which is beneficial to reduce polarization and improve the overall electrochemical performance of the battery; 2. Effectively suppresses lithium polysulfide shuttle effect and improves ionic conductivity: The PDOL-Ami-cross gel electrolyte on the positive electrode side can effectively adsorb and fix lithium polysulfides, significantly suppressing their shuttle migration between the positive and negative electrodes, reducing the loss of active materials and interfacial side reactions; the Si-O framework structure and amino functional groups in Ami-cross are conducive to lithium salt dissociation and lithium ion transport, thereby improving the ionic conductivity of the electrolyte and the positive electrode reaction kinetics; 3. Suppressing lithium dendrite growth and constructing a stable SEI to further improve ion conduction performance: The PDOL-LLZO gel electrolyte on the negative electrode side provides a continuous and stable conduction channel for lithium ions. At the same time, the LLZO filler and gel matrix work together to help construct a dense and stable mixed SEI layer in situ on the lithium metal surface, promote the uniform deposition of lithium ions on the negative electrode surface, effectively alleviate the nucleation and growth of lithium dendrites, further reduce interfacial impedance and improve ion conduction performance and cycle life. 4. Excellent process adjustability and performance controllability: By reasonably controlling parameters such as oil bath temperature and sealing atmosphere during the preparation of Ami-cross, its cross-linking degree, polar environment and compatibility with PDOL system can be finely adjusted, so that the obtained asymmetric gel electrolyte can achieve a designable balance in terms of mechanical strength, ion conduction and interfacial affinity, thereby giving the system high process controllability and performance adjustability, which is convenient for optimization for different battery design requirements; 5. Simple process flow, suitable for large-scale preparation: This application adopts in-situ polymerization to directly construct asymmetric gel electrolyte during battery assembly, without the need for complex equipment and cumbersome steps such as multiple impregnation and coating. The overall process route is simple, the operating conditions are mild, the raw materials are readily available and the cost is low, and it has good prospects for scale-up and industrial application. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the asymmetric lithium-sulfur battery prepared in Example 1 of this application; Figure 2 This is a 0.1C-2C rate curve from Example 1 of this application; Figure 3 This is a graph showing the 0.2C cycle performance of Embodiment 1 of this application after 100 cycles. Figure 4 This is a graph showing the 1C cycle performance of Embodiment 1 of this application after 400 cycles. Detailed Implementation

[0019] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and equivalent alterations or modifications also fall within the scope defined by the claims of this application.

[0020] There are no particular restrictions on the source of any raw materials used in this invention; they can be purchased from the market or prepared using conventional methods known to those skilled in the art.

[0021] Example 1: This example provides a method for the in-situ polymerization preparation of asymmetric gel electrolytes, specifically including the following steps: Step 1: Mix amino material, polyethylene glycol and dimethyl sulfoxide in a mass ratio of 7:30:11, heat and stir in an oil bath at 100°C under argon atmosphere for 48 hours, then heat further at 100°C in air for 72 hours. After cooling, a light yellow polymer material is obtained, denoted as Ami-cross. Step 2: Lithium carbonate, lanthanum oxide, and zirconium dioxide were mixed in a molar ratio of 7:3:2 (to compensate for the loss of lithium due to volatility at high temperatures, 20% excess lithium carbonate was added). Ethanol was added, and the mixture was manually ground for 30 minutes, then dried. The resulting mixture was placed in a crucible, compacted, and covered. It was sintered at 1150℃ for 8 hours. After cooling, the blocky sintered product was ball-milled at 200 r / min for 2 hours to obtain the final product Li7La3Zr2O. 12 Powder, denoted as LLZO; Step 3: Prepare the electrolyte in the glove box. Mix 1,3-dioxapentane, ethylene glycol dimethyl ether and lithium bis(trifluoromethanesulfonyl)imide and stir for 30 minutes to obtain a mixed solution. Then add the initiator lithium hexafluorophosphate to form a uniform and transparent mixed solution of 1,3-dioxapentane, ethylene glycol dimethyl ether and lithium bis(trifluoromethanesulfonyl)imide, which is the precursor solution, denoted as PDOL. Step 4: In the glove box, add 3 parts of the light yellow polymer material obtained in Step 1 as an additive to 9 parts of the mixed solution of 1,3-dioxapentane, ethylene glycol dimethyl ether and lithium bis(trifluoromethanesulfonyl)imide obtained in Step 3. Stir for 30 minutes and then add 1 part of the initiator lithium hexafluorophosphate to obtain a uniform light yellow precursor solution, denoted as PDOL-Ami-cross. Step 5: Place the Li7La3Zr2O obtained in step 2 into the glove box. 12 One part was added as an additive to nine parts of the mixed solution of 1,3-dioxapentane, ethylene glycol dimethyl ether and lithium bis(trifluoromethanesulfonyl)imide obtained in step three. After stirring for 30 minutes, one part of lithium hexafluorophosphate initiator was added to obtain a uniform milky white precursor solution, denoted as PDOL-LLZO.

[0022] The application of the asymmetric gel electrolyte prepared by the in-situ polymerization method in lithium-sulfur batteries includes the following steps: S1: Carbon nanotubes and sulfur powder are mixed at a mass ratio of 1:3, manually ground for 30 min, heated at 155-180℃ for 10-14 h under an argon atmosphere, and cooled to room temperature to obtain a C / S mixed material; the C / S mixed material, Ketjen black and PVDF binder are ground at a weight ratio of 7:2:1 to form a slurry, and the slurry is uniformly coated on an aluminum foil with a thickness of 30 μm by a scraping method. The coating thickness of the scraping method is 120 μm, and it is dried at 60℃ for 10-12 h to obtain a positive electrode sheet, which is then punched into a C / S circular electrode sheet with a diameter of 16 mm; S2: Assemble the battery in a glove box, using C / S circular electrode sheets as the positive electrode, Celgard 2500 as the separator, and commercial lithium metal sheets as the negative electrode. Place PDOL-Ami-cross and PDOL-LLZO on both sides of the separator as electrolytes. PDOL-Ami-cross is used as the electrolyte between the positive electrode and the separator, and PDOL-LLZO is used as the electrolyte between the negative electrode and the separator. Complete the assembly of the asymmetric lithium-sulfur battery under argon protection. S3: Place the assembled battery in a glove box for 12-24 hours in an argon atmosphere with H2O < 0.1 ppm and O2 < 0.1 ppm to allow the electrolyte to polymerize in situ, forming a quasi-solid-state asymmetric lithium-sulfur battery.

[0023] Example 2, a method for in-situ polymerization preparation of asymmetric gel electrolytes, specifically includes the following steps: Step 1: Mix amino material, polyethylene glycol and dimethyl sulfoxide in a mass ratio of 7:30:11, heat and stir in an oil bath at 100°C under sealed O2 conditions for 48 hours, then heat further at 100°C in air for 72 hours. After cooling, a light yellow polymer material is obtained, denoted as Ami-cross. Step 2: Lithium carbonate, lanthanum oxide, and zirconium dioxide were mixed in a molar ratio of 7:3:2 (to compensate for the loss of lithium due to volatility at high temperatures, 20% excess lithium carbonate was added). Ethanol was added, and the mixture was manually ground for 30 minutes, then dried. The resulting mixture was placed in a crucible, compacted, and covered. It was sintered at 1150℃ for 8 hours. After cooling, the blocky sintered product was ball-milled at 200 r / min for 2 hours to obtain the final product Li7La3Zr2O. 12 Powder, denoted as LLZO; Step 3: Prepare the electrolyte in the glove box. Mix 1,3-dioxapentane, ethylene glycol dimethyl ether and lithium bis(trifluoromethanesulfonyl)imide and stir for 30 minutes to obtain a mixed solution. Then add the initiator lithium hexafluorophosphate to form a uniform and transparent mixed solution of 1,3-dioxapentane, ethylene glycol dimethyl ether and lithium bis(trifluoromethanesulfonyl)imide, which is the precursor solution, denoted as PDOL. Step 4: In the glove box, add 3 parts of the light yellow polymer material obtained in Step 1 as an additive to 9 parts of the mixed solution of 1,3-dioxapentane, ethylene glycol dimethyl ether and lithium bis(trifluoromethanesulfonyl)imide obtained in Step 3. Stir for 30 minutes and then add 1 part of the initiator lithium hexafluorophosphate to obtain a uniform light yellow precursor solution, denoted as PDOL-Ami-cross. Step 5: Place the Li7La3Zr2O obtained in step 2 into the glove box. 12 One part was added as an additive to nine parts of the mixed solution of 1,3-dioxapentane, ethylene glycol dimethyl ether and lithium bis(trifluoromethanesulfonyl)imide obtained in step three. After stirring for 30 minutes, one part of lithium hexafluorophosphate initiator was added to obtain a uniform milky white precursor solution, denoted as PDOL-LLZO.

[0024] The application of the asymmetric gel electrolyte prepared by the in-situ polymerization method in lithium-sulfur batteries includes the following steps: S1: Carbon nanotubes and sulfur powder are mixed at a mass ratio of 1:3, manually ground for 30 min, and then heated at 155-180℃ for 10-14 h under an argon atmosphere. After cooling to room temperature, a C / S mixed material is obtained. The C / S mixed material, Ketjen black and PVDF binder are ground at a weight ratio of 7:2:1 to form a slurry. The slurry is uniformly coated on an aluminum foil with a thickness of 30 μm by a scraping method. The coating thickness of the scraping method is 120 μm. The coating is dried at 60℃ for 10-12 h to obtain a positive electrode sheet, which is then punched into a C / S circular electrode sheet with a diameter of 16 mm. S2: Assemble the battery in a glove box, using C / S circular electrode sheets as the positive electrode, Celgard 2500 as the separator, and commercial lithium metal sheets as the negative electrode. Place PDOL-Ami-cross and PDOL-LLZO on both sides of the separator as electrolytes. PDOL-Ami-cross is used as the electrolyte between the positive electrode and the separator, and PDOL-LLZO is used as the electrolyte between the negative electrode and the separator. Complete the assembly of the asymmetric lithium-sulfur battery under argon protection. S3: Place the assembled battery in a glove box for 12-24 hours in an argon atmosphere with H2O < 0.1 ppm and O2 < 0.1 ppm to allow the electrolyte to polymerize in situ, forming a quasi-solid-state asymmetric lithium-sulfur battery.

[0025] Example 3: A method for in-situ polymerization preparation of asymmetric gel electrolytes, specifically including the following steps: Step 1: Mix amino material, polyethylene glycol and dimethyl sulfoxide in a mass ratio of 7:30:11, heat and stir in an oil bath at 200°C under argon atmosphere for 48 hours, then heat further at 100°C in air for 72 hours. After cooling, a light yellow polymer material is obtained, denoted as Ami-cross. Step 2: Lithium carbonate, lanthanum oxide, and zirconium dioxide were mixed in a molar ratio of 7:3:2 (to compensate for the loss of lithium due to volatility at high temperatures, 20% excess lithium carbonate was added). Ethanol was added, and the mixture was manually ground for 30 minutes, then dried. The resulting mixture was placed in a crucible, compacted, and covered. It was sintered at 1150℃ for 8 hours. After cooling, the blocky sintered product was ball-milled at 200 r / min for 2 hours to obtain the final product Li7La3Zr2O. 12 Powder, denoted as LLZO; Step 3: Prepare the electrolyte in the glove box. Mix 1,3-dioxapentane, ethylene glycol dimethyl ether and lithium bis(trifluoromethanesulfonyl)imide and stir for 30 minutes to obtain a mixed solution. Then add the initiator lithium hexafluorophosphate to form a uniform and transparent mixed solution of 1,3-dioxapentane, ethylene glycol dimethyl ether and lithium bis(trifluoromethanesulfonyl)imide, which is the precursor solution, denoted as PDOL. Step 4: In the glove box, add 3 parts of the light yellow polymer material obtained in Step 1 as an additive to 9 parts of the mixed solution of 1,3-dioxapentane, ethylene glycol dimethyl ether and lithium bis(trifluoromethanesulfonyl)imide obtained in Step 3. Stir for 30 minutes and then add 1 part of the initiator lithium hexafluorophosphate to obtain a uniform light yellow precursor solution, denoted as PDOL-Ami-cross. Step 5: Place the Li7La3Zr2O obtained in step 2 into the glove box. 12One part was added as an additive to nine parts of the mixed solution of 1,3-dioxapentane, ethylene glycol dimethyl ether and lithium bis(trifluoromethanesulfonyl)imide obtained in step three. After stirring for 30 minutes, one part of lithium hexafluorophosphate initiator was added to obtain a uniform milky white precursor solution, denoted as PDOL-LLZO.

[0026] The application of the asymmetric gel electrolyte prepared by the in-situ polymerization method in lithium-sulfur batteries includes the following steps: S1: Carbon nanotubes and sulfur powder are mixed at a mass ratio of 1:3, manually ground for 30 min, and then heated at 155-180℃ for 10-14 h under an argon atmosphere. After cooling to room temperature, a C / S mixed material is obtained. The C / S mixed material, Ketjen black and PVDF binder are ground at a weight ratio of 7:2:1 to form a slurry. The slurry is uniformly coated on an aluminum foil with a thickness of 30 μm by a scraping method. The coating thickness of the scraping method is 120 μm. The coating is dried at 60℃ for 10-12 h to obtain a positive electrode sheet, which is then punched into a C / S circular electrode sheet with a diameter of 16 mm. S2: Assemble the battery in a glove box, using C / S circular electrode sheets as the positive electrode, Celgard 2500 as the separator, and commercial lithium metal sheets as the negative electrode. Place PDOL-Ami-cross and PDOL-LLZO on both sides of the separator as electrolytes. PDOL-Ami-cross is used as the electrolyte between the positive electrode and the separator, and PDOL-LLZO is used as the electrolyte between the negative electrode and the separator. Complete the assembly of the asymmetric lithium-sulfur battery under argon protection. S3: Place the assembled battery in a glove box for 12-24 hours in an argon atmosphere with H2O < 0.1 ppm and O2 < 0.1 ppm to allow the electrolyte to polymerize in situ, forming a quasi-solid-state asymmetric lithium-sulfur battery.

[0027] Comparative Example 1 used PDOL-Ami-cross as the electrolyte between the positive electrode and the separator, and PDOL as the electrolyte between the negative electrode and the separator: the initial capacity was 798.5 mAh / g, and the capacity remained at 528.1 mAh / g after 400 cycles (66.1% retention). Compared with Example 1, the lack of ceramic powder LLZO as an additive resulted in a decrease in capacity, indicating that ceramic powder LLZO is crucial for suppressing lithium dendrite growth.

[0028] Comparative Example 2 used PDOL as the electrolyte between the positive electrode and the membrane, and PDOL-LLZO as the electrolyte between the negative electrode and the membrane: the initial capacity was 794.9 mAh / g, and the capacity remained at 563.0 mAh / g after 400 cycles (70.8% retention). Compared with Example 1, the synthesized organic polymer material Ami-cross was missing, and the capacity decreased, indicating that the synthesized organic polymer material Ami-cross is crucial for inhibiting polysulfide expansion.

[0029] Comparative Example 3 used PDOL as the electrolyte, which was added dropwise between both the positive and negative electrodes and the membrane: the initial capacity was 756.9 mAh / g, and the capacity remained at 301.6 mAh / g after 400 cycles (retention rate of 39.8%). Compared with Example 1, the capacity decreased significantly when only PDOL was added as the electrolyte, indicating that PDOL alone has a limited inhibitory effect on polysulfides.

[0030] Table 1. Cycle performance of lithium-sulfur batteries prepared with Ami-cross material under different temperatures and sealed environments in the embodiments of this invention. .

[0031] Table 2. Cycle performance of lithium-sulfur batteries prepared with different electrolytes using asymmetric structures in the comparative examples of this invention after 400 cycles. .

[0032] Analysis of Examples 1-3 and Comparative Examples 1-3: As can be seen from Tables 1 and 2, in the examples, Example 1 (heated and stirred in an oil bath at 100℃ for 48 hours (sealed under argon atmosphere)) exhibited the best overall performance, with an initial capacity of 1062 mAh / g at 0.2C, a capacity of 934 mAh / g after 100 cycles, and a retention rate of 87.9%; Example 2 (heated and stirred in an oil bath at 100℃ for 48 hours (sealed under O2 atmosphere)) also exhibited the best overall performance, with an initial capacity of 911 mAh / g at 0.2C, a capacity of 709 mAh / g after 100 cycles, and a retention rate of 77.8%; Example 3 (heated and stirred in an oil bath at 200℃ for 48 hours (sealed under argon atmosphere)) also exhibited the best overall performance, with an initial capacity of 1010 mAh / g at 0.2C, a capacity of 817 mAh / g after 100 cycles, and a retention rate of 80.8%. This indicates that the Ami-cross material prepared "under argon atmosphere and at 100℃" has better performance when used in batteries, significantly improving battery capacity and retention rate. In the comparative examples, an asymmetric structure was adopted, and the battery was modified by injecting different electrolytes on both sides of the separator. Based on Comparative Example 3, the PDOL electrolyte on the negative electrode side was replaced with PDOL-LLZO electrolyte (Comparative Example 2), and the PDOL on the positive electrode side was replaced with Ami-cross (Comparative Example 1). Through the comparison of the three sets of comparative examples, it can be clearly seen that Example 1 is more helpful in suppressing the shuttle effect and dendrite growth of lithium polysulfides, and has better cycle performance.

[0033] The embodiments selected in the above materials are for ease of understanding and not for limiting the process method. Those skilled in the art can easily modify the process flow or transfer it to other cases without inventive change. If these modifications also fall under the category of similar claims or similar technology of this invention, then the intent of this invention also includes these modifications.

Claims

1. A method for in-situ polymerization preparation of an asymmetric gel electrolyte, characterized in that, Specifically, the following steps are included: Step 1: Mix amino material, polyethylene glycol and dimethyl sulfoxide in a mass ratio of 7:30:11, heat and stir in an oil bath under sealed conditions for 48 hours, then heat further at 100°C in air for 72 hours. After cooling, a light yellow polymer material is obtained, denoted as Ami-cross. Step 2: Lithium carbonate, lanthanum oxide, and zirconium dioxide were mixed in a molar ratio of 7:3:

2. Ethanol was added, and the mixture was manually ground for 30 minutes and then dried. The resulting mixture was placed in a crucible, compacted, and covered. It was sintered at 1150℃ for 8 hours. After cooling, the blocky sintered product was ball-milled at 200 r / min for 2 hours to obtain Li7La3Zr2O. 12 Powder, denoted as LLZO; Step 3: Prepare the electrolyte in the glove box. Mix 1,3-dioxapentane, ethylene glycol dimethyl ether and lithium bis(trifluoromethanesulfonyl)imide and stir for 30 minutes to obtain a mixed solution. Then add the initiator lithium hexafluorophosphate to form a uniform and transparent mixed solution of 1,3-dioxapentane, ethylene glycol dimethyl ether and lithium bis(trifluoromethanesulfonyl)imide, which is the precursor solution, denoted as PDOL. Step 4: In the glove box, add 3 parts of the light yellow polymer material obtained in Step 1 as an additive to 9 parts of the mixed solution of 1,3-dioxapentane, ethylene glycol dimethyl ether and lithium bis(trifluoromethanesulfonyl)imide obtained in Step 3. Stir for 30 minutes and then add 1 part of lithium hexafluorophosphate to obtain a uniform light yellow precursor solution, denoted as PDOL-Ami-cross. Step 5: Place the Li7La3Zr2O obtained in step 2 into the glove box. 12 One part was added as an additive to nine parts of the mixed solution of 1,3-dioxapentane, ethylene glycol dimethyl ether and lithium bis(trifluoromethanesulfonyl)imide obtained in step three. After stirring for 30 minutes, one part of lithium hexafluorophosphate was added to obtain a uniform milky white precursor solution, denoted as PDOL-LLZO.

2. The in-situ polymerization preparation method of the asymmetric gel electrolyte according to claim 1, characterized in that, The amino material in the first step is N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, the oil bath temperature is 100℃ or 200℃, and the sealing method is sealing in an argon atmosphere or sealing in an oxygen atmosphere.

3. The in-situ polymerization preparation method of the asymmetric gel electrolyte according to claim 1, characterized in that, In the third step, the volume ratio of 1,3-dioxapentane to ethylene glycol dimethyl ether is 1:1, and the concentrations of lithium bis(trifluoromethanesulfonylimide) and lithium hexafluorophosphate are both 1 mol / L.

4. The method for in-situ polymerization preparation of asymmetric gel electrolyte according to claim 1, characterized in that, In the fourth step, the volume ratio of 1,3-dioxapentane to ethylene glycol dimethyl ether is 1:1, and the concentrations of lithium bis(trifluoromethanesulfonylimide) and lithium hexafluorophosphate are both 1 mol / L.

5. The in-situ polymerization preparation method of the asymmetric gel electrolyte according to claim 1, characterized in that, In the fifth step, the volume ratio of 1,3-dioxapentane to ethylene glycol dimethyl ether is 1:1, and the concentrations of lithium bis(trifluoromethanesulfonylimide) and lithium hexafluorophosphate are both 1 mol / L.

6. An asymmetric gel electrolyte prepared by the in-situ polymerization method according to any one of claims 1-5.

7. The application of an asymmetric gel electrolyte prepared by the in-situ polymerization method according to any one of claims 1-5 in a lithium-sulfur battery, characterized in that: S1: Carbon nanotubes and sulfur powder are mixed at a mass ratio of 1:3, manually ground for 30 min, heated at 155-180℃ for 10-14 h under an argon atmosphere, and cooled to room temperature to obtain a C / S mixed material; the C / S mixed material, Ketjen black and PVDF binder are ground at a weight ratio of 7:2:1 to form a slurry, the slurry is uniformly coated on aluminum foil by a scraping method, and dried at 60℃ for 10-12 h to obtain a positive electrode sheet, which is then punched into C / S circular electrode sheets; S2: Assemble the battery in the glove box, using C / S circular electrode as the positive electrode, Celgard 2500 as the separator, and commercial lithium metal sheet as the negative electrode. Place PDOL-Ami-cross and PDOL-LLZO on both sides of the separator as electrolytes. Complete the assembly of the asymmetric lithium-sulfur battery under argon protection. S3: The assembled battery is placed in a glove box to allow the electrolyte to polymerize in situ, forming a quasi-solid-state asymmetric lithium-sulfur battery.

8. The method for in-situ polymerization preparation of asymmetric gel electrolyte according to claim 1, characterized in that, The aluminum foil in S1 has a thickness of 30 μm, the coating thickness of the scraping method is 120 μm, and the diameter of the C / S circular electrode is 16 mm.

9. The method for in-situ polymerization preparation of asymmetric gel electrolyte according to claim 1, characterized in that, In S2, PDOL-Ami-cross is used as the electrolyte between the positive electrode and the separator, and PDOL-LLZO is used as the electrolyte between the negative electrode and the separator.

10. The method for preparing asymmetric gel electrolyte by in-situ polymerization according to claim 1, characterized in that, The settling time in S3 is 12-24 hours, the environment is argon atmosphere, and H2O < 0.1 ppm and O2 < 0.1 ppm.

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