Micro-phase separation type single-ion solid electrolyte as well as preparation method and application thereof

Abstract

The invention discloses a preparation method and application of a microphase separation type single-ion solid-state electrolyte, and belongs to the field of solid-state batteries. The single-ion solid electrolyte with a good microphase separation structure is obtained by modifying commercial polymers (such as polysulfone, polyether sulfone and the like) and grafting bisulfonyl imide lithium salt. A polymer continuous phase provides flexibility, an ion continuous phase forms an efficient lithium ion channel, and collaborative optimization of mechanical performance and ionic conductivity is achieved. When the electrolyte is used for the lithium metal battery, dendrite growth can be inhibited, and the cycling stability and safety of the battery are improved. According to the invention, the problem that the conductivity and mechanical property of the traditional single-ion electrolyte are difficult to balance is solved, and a key material is provided for a high-specific-energy and high-safety lithium metal battery.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of solid-state batteries, and particularly relates to a preparation method and application of a micro-phase separation type single-ion solid-state electrolyte. Through the design of the difference between the rigidity and flexibility of the main / side chain molecular structure, good nanoscale micro-phase separation of the single-ion solid-state electrolyte is generated, a polymer continuous phase with high mechanical strength and an ion cluster continuous phase with fast transmission rate are formed, and thus the preparation method and application of the single-ion solid-state electrolyte which takes into account the mechanical properties and ion transmission capacity. BACKGROUND

[0002] Secondary batteries using metal lithium as the negative electrode have extremely high energy density and wide application prospects in the future energy storage field. However, in the charging and discharging process of the traditional lithium metal secondary battery using liquid electrolyte, the uneven deposition of lithium ions causes dendrite growth, which seriously affects the cycle life of the battery and brings great safety risks. In addition, the flammability and volatility of the traditional liquid electrolyte further increase the safety risks of the lithium metal secondary battery. The industry and academia are working on technical breakthroughs in solid-state electrolyte design, the introduction of flame-retardant additives, the preparation of flame-retardant separators, the development of new electrolytes, and other aspects to develop high-safety, long-life lithium metal secondary batteries.

[0003] Among the reported strategies, single-ion solid-state electrolytes in which anions are fixed and charge transport is almost entirely borne by lithium ions are of great interest due to their advantages of inorganic solid electrolytes with lithium ion transference number close to 1 and polymer electrolytes with good flexibility. Studies have shown that single-ion solid-state electrolytes can suppress the formation of a "space charge layer" on the negative electrode surface by their lithium ion transference number close to 1, enhancing the uniformity of lithium ion deposition on the negative electrode surface and thus suppressing dendrite growth. In addition, single-ion solid-state electrolytes have low flammability and non-volatility, which have attracted much attention from researchers. However, single-ion solid-state electrolytes have always had the problem of low ionic conductivity in practical applications. To improve the ionic conductivity of single-ion solid-state electrolytes, researchers have proposed various strategies, mainly including compounding inorganic nanoparticles, reducing the negative charge of the anion on the polymer, introducing organic solvents as plasticizers, and reducing the thickness of the single-ion solid-state electrolyte. However, these strategies will affect the mechanical properties of single-ion solid-state electrolytes, which also restricts their practical application. Therefore, there is a contradiction between high ionic conductivity and good mechanical properties in the design of single-ion solid-state electrolytes.

[0004] The main reason is that the microphase separation structure of the single-ion solid electrolyte is not concerned in the molecular design process, so that the microphase separation cannot be realized, the polymer phase hinders the lithium ion transmission, and the ionic phase affects the film-forming property of the polymer phase. This is not conducive to the construction of long-life and high-safety lithium metal secondary batteries. Therefore, designing and synthesizing a single-ion solid electrolyte with a suitable microphase separation structure is the key to synchronously improving the ionic conductivity and mechanical properties, and has practical significance for promoting the application and development of lithium metal secondary batteries. SUMMARY

[0005] In view of the deficiencies of the prior art, the purpose of the present application is to provide a preparation method of a single-ion solid electrolyte with a suitable microphase separation structure, so as to synchronously improve its ionic conductivity and mechanical properties, and use it in a lithium metal solid-state battery to improve its electrochemical performance and safety performance.

[0006] The present application first chloromethylates a solvent-averse organic rigid skeleton polymer to make it graftable, and prepares a functionalized bis-sulfonimide salt by Hinsberg reaction of functionalized sulfuryl chloride and sulfonamide; then covalently grafts it to the above-mentioned polymer skeleton through nucleophilic substitution reaction, and obtains a single-ion solid electrolyte with good microphase separation structure by solution casting method. The network structure formed by the polymer continuous phase ensures that the electrolyte has good flexibility, and the ionic cluster continuous phase of the residual trace solvent forms a long-range ordered efficient ion channel. The microphase separation type single-ion solid electrolyte is used in a solid-state lithium metal battery, which can inhibit the dendrite growth of the negative electrode and enhance the safety of the battery. Such single-ion conduction type solid-state lithium metal battery will have good electrochemical performance and safety performance.

[0007] The purpose of the present application is achieved by the following technical solutions: The preparation method of the microphase separation type single-ion solid electrolyte comprises the following preparation steps: Step one: dissolve a high-strength, solvent-averse organic rigid skeleton polymer in anhydrous solvent, add Lewis acid catalyst and chloromethylation reagent under a protective atmosphere, and reflux for 4-12 h; after the reaction is completed, slowly pour the solution into the precipitation solvent to precipitate the product, then dissolve the product again in the solvent used in the reaction, and precipitate it again in the precipitation solvent, repeat this process 3-5 times to obtain pure chloromethylated polymer.

[0008]

[0009] The high-strength, solvent-repellent organic rigid skeleton polymer is one of polysulfone, polyether sulfone, polyether ether ketone, polybenzimidazole and derivatives thereof; the anhydrous solvent for chloromethylation reaction is one or more arbitrary proportion mixed solvents of trichloromethane, dichloromethane, 1,2-dichloroethane, tetrachloroethane, nitromethane, DMF, DMSO, etc., and the solvent dosage is 5-20 times the mass of the polymer; the Lewis acid catalyst is one of AlCl3, FeCl3, ZnCl2 and BF3·Et2O; R-OCH2Cl is a chloromethylation reagent, wherein R is methyl or ethyl; and the product precipitation solvent is water, methanol, ethanol and any proportion mixed solution thereof, and the solvent dosage is 1-5 times the volume of the reaction liquid.

[0010] Step two: dissolve the dried R-SO2-NH2 (R = CF3 / CF2H / CFH2 / F) in a solvent, add excess lithium carbonate or lithium hydroxide, stir at room temperature under a protective atmosphere for 6-12 h to obtain R-SO2-NHLi; dissolve 1-Br / Cl-(CH2)n-SO2-Cl (n = 3-8) in the same solvent, and add the solution dropwise to the R-SO2-NHLi solution, stir at 30-80°C for 12-48 h; filter and collect the filtrate, and obtain a solid powder after distillation under reduced pressure, and recrystallize the solid powder in an ether solvent to obtain 1-Br / Cl-(CH2)n-SO2-NLi-SO2-R (side-end functionalized bis-sulfonimidate lithium salt).

[0011] The solvent used for the reaction is one or any proportion of multiple mixed solvents of acetonitrile, dichloromethane, chloroform, DMF and DMSO; the molar ratio of R-SO2-NHLi and 1-Br / Cl-(CH2)n-SO2-Cl is 1:1-1.5; and the ether solvent used for recrystallization is one of diethyl ether, tetrahydrofuran, 1,3-dioxolane and 1,4-dioxane.

[0012] Step three: dissolve the double-end functionalized linear small molecule and the like in an ultradry high-boiling aprotic polar solvent, and add excess lithium hydride, stir at room temperature for 0.5-2 h to obtain a double-end lithiumated linear small molecule, dissolve the side-end functionalized bis-sulfonimidate lithium salt and the chloromethylated polymer in the same high-boiling aprotic polar solvent, add them into the reaction system through a constant-pressure dropping funnel in sequence, increase the temperature to 60-120°C, and continuously react for 8-24 h, and the product is precipitated in a precipitation solvent to obtain a main / side chain type mono-ion polymer lithium salt.

[0013] The molecular structure of the double-end functionalized small molecule is X-((CH2)2-Y-(CH2)2) nX, wherein X is OH, SH, NH2, Cl, Br, etc., Y is one of CH2, S, O, and n = 1-5; the high-boiling aprotic polar solvent is one or more of NMP, DMF, DMSO, etc. in any proportion; and the precipitating solvent is water, methanol, ethanol, or any proportion of a mixture thereof.

[0014] Step four: dissolve the main / side chain type single-ion polymer lithium salt in a polar solvent, with a lithium salt to solvent mass ratio of 1:30-60, stirring at 40-100°C for 2-8 hours to obtain a homogeneous transparent casting solution, which is then poured into a smooth-surfaced vessel, and dried at 60-120°C with continuous air blowing until the solvent is completely volatilized, to obtain a solid-state single-ion polyelectrolyte film with a bicontinuous phase.

[0015] wherein the medium-polarity solvent is one or more of acetonitrile, tetrahydrofuran, NMP, DMF, DMSO, etc. in any proportion.

[0016] Preferably, the reaction protection gas in step one and step two is one or a mixture of any proportion of N2 / Ar / He.

[0017] Preferably, the amount of Lewis acid catalyst used in step one is 1%-20% of the mass of the polymer, and the amount of chloromethylation reagent used is 1-5 times the mass of the polymer.

[0018] Preferably, the amount of solvent used in step two is 10-50 times the mass of the sulfonamide / sulfonyl chloride, and the amount of recrystallization solvent used in step two is 20-50 times the mass of the solid powder.

[0019] Preferably, the amount of solvent used in step three is 10-50 times the mass of the solute (double-end functionalized linear small molecule / side-end functionalized double sulfonamide lithium salt / chloromethylated polymer).

[0020] Preferably, the molar ratio of double-end functionalized linear small molecule:side-end functionalized double sulfonamide lithium salt:chloromethylated polymer in step three is 1:0.5-0.75:0.5-0.75.

[0021] Preferably, the volume of precipitating solvent used in step three is 1-5 times the volume of the reaction solution.

[0022] Preferably, the mass ratio of lithium salt to solvent used in step four is 1:30-60.

[0023] Another object of the present application is to provide a single-ion solid-state electrolyte with good microphase separation structure prepared by the above method.

[0024] Another object of the present application is to provide the application of the above-mentioned micro-phase separation type single-ion solid electrolyte in solid-state lithium metal / ion battery.

[0025] Compared with the prior art, the micro-phase separation type single-ion polyelectrolyte prepared by the technology provided by the present application has the following advantages and beneficial effects: (1) The micro-phase separation type single-ion polyelectrolyte prepared by the present application has high ion conductivity and transference number and excellent mechanical properties.

[0026] (2) The micro-phase separation type single-ion polyelectrolyte prepared by the present application can be applied to a solid-state battery, can effectively inhibit lithium dendrite growth in cooperation with lithium ion deposition uniformity and mechanical barrier of a separator, and greatly improves the cycle life of the solid-state battery.

[0027] (3) The method of the present application can avoid the crosstalk problem between the polymer phase and the ion phase in the traditional single-ion polyelectrolyte, realize the synchronous improvement of ion transmission capacity and mechanical properties, and promote the application and development of lithium metal batteries. BRIEF DESCRIPTION OF DRAWINGS

[0028] In order to more clearly illustrate the embodiments of the present application, the drawings involved in the embodiments will be briefly introduced below.

[0029] Figure 1 . TEM image of the micro-phase separation type single-ion solid electrolyte prepared in Example 1.

[0030] Figure 2 . SEM image of the micro-phase separation type single-ion solid electrolyte prepared in Example 1. (a) plane; (b) cross section.

[0031] Figure 3 . Tensile property test of the micro-phase separation type single-ion solid electrolyte prepared in Example 1.

[0032] Figure 4 . Electrochemical window test of the micro-phase separation type single-ion solid electrolyte prepared in Example 1.

[0033] Figure 5 . Ion conductivity test of the micro-phase separation type single-ion solid electrolyte prepared in Example 1.

[0034] Figure 6 . Li|Li symmetric battery performance test of the micro-phase separation type single-ion solid electrolyte prepared in Example 1.

[0035] Figure 7 . Li|LiFePO4 battery performance test of the micro-phase separation type single-ion solid electrolyte prepared in Example 1. DETAILED DESCRIPTION

[0036] The present invention will be further described in detail below with reference to the embodiments and accompanying drawings, but the embodiments of the present invention are not limited thereto. Example

[0037] Step 1: Dissolve polyethersulfone in ultra-dry chloroform (the mass of chloroform is 10 times the mass of polyethersulfone). Under argon protection, add zinc chloride powder (1 wt% of the mass of polyethersulfone) and chloromethyl methyl ether (equal mass of polyethersulfone). Reflux for 6 h. After the reaction is complete, slowly pour the solution into an equal volume of methanol-water solution (methanol to water volume ratio of 1:1) to precipitate the product. Dissolve the product again in chloroform and precipitate in the methanol-water solution. Repeat this process 3 times to obtain pure chloromethylated polyethersulfone.

[0038] Step 2: Dissolve dry CF3-SO2-NH2 in anhydrous acetonitrile (10 times the mass of CF3-SO2-NH2), add excess lithium carbonate, and stir for 12 h at room temperature under argon protection to obtain CF3-SO2-NHLi; dissolve 1-Cl-(CH2)3-SO2Cl in acetonitrile (10 times the mass of 1-Cl-(CH2)3-SO2Cl), an equimolar amount of CF3-SO2-NH2, in acetonitrile, and add this solution dropwise to the CF3-SO2-NHLi solution, stirring at 45°C for 48 h; filter and collect the filtrate, distill under reduced pressure to obtain a solid powder, recrystallize the solid powder in tetrahydrofuran (30 times the mass of the powder) to obtain 1-Cl-(CH2)3-SO2-NLi-SO2-CF3.

[0039] Step 3: Dissolve diethylene glycol in ultra-dry DMF (20 times the mass of diethylene glycol) and add excess lithium hydride. Stir at room temperature for 0.5 h to obtain LiO-CH2-CH2-O-CH2-CH2-OLi. Dissolve 0.5 molar amounts of 1-Cl-CH2-SO2-NLi-SO2-CF3 and 0.5 molar amounts of chloromethylated polyethersulfone in diethylene glycol in DMF (20 times the mass of the corresponding solutes). Then add them sequentially to the LiO-CH2-CH2-O-CH2-CH2-OLi solution through a constant pressure dropping funnel. Heat to 80°C and continue the reaction for 12 h. The product precipitates in an equal volume of methanol-water solution (methanol to water volume ratio of 1:1) to obtain a main / side chain type single-ion polymer lithium salt.

[0040] Step 4: Dissolve the above single-ion polymer lithium salt in ultra-dry DMF (lithium salt to solvent mass ratio of 1:30), stir at 60°C for 4 h to obtain a homogeneous transparent casting solution, then introduce it into a petri dish and continuously dry it at 80°C until the solvent evaporates completely to obtain a microphase-separated single-ion solid polyelectrolyte membrane with two continuous phases.

[0041] Figure 1 The image shows a high-resolution TEM characterization of the microphase-separated single-ion solid polyelectrolyte obtained in this embodiment. The image reveals that the electrolyte exhibits excellent nanoscale microphase separation, with the sizes of ionic and polymer clusters approximately 2-3 nm. This microphase-separated structure enables the decoupling of the ionic conductivity and mechanical properties of the single-ion solid electrolyte. Figure 2 The image shows a SEM image of the microphase-separated single-ion solid polyelectrolyte obtained in this embodiment. As can be seen from the image, the thickness of the microphase-separated single-ion solid electrolyte is about 20 μm, and its surface and cross-section are completely dense. Figure 3 The mechanical properties of the microphase-separated single-ion solid electrolyte obtained in this embodiment were tested. As can be seen from the figure, its tensile strength is about 14.2 MPa and its elongation at break is about 13.6%, showing good mechanical properties. Figure 4 The electrochemical window of the microphase-separated single-ion solid electrolyte obtained in this embodiment was tested. As can be seen from the figure, its electrochemical window reaches 4.65 V, which can basically meet the requirements of most commercial lithium-ion cathode materials, such as lithium iron phosphate (LFP) and lithium cobalt oxide (LCO). Figure 5 The ionic conductivity test results for the microphase-separated single-ion solid electrolyte obtained in this embodiment are as follows: at room temperature, its ionic conductivity is approximately 0.24 mS / cm. -1 Furthermore, the relationship between ionic conductivity and temperature conforms to Arrhenius's law. Figure 6 The lithium stripping / deposition performance of the lithium / lithium symmetric battery with microphase-separated single-ion solid polyelectrolyte obtained in this embodiment was tested. As shown in the figure, at 0.2 mA / cm²... 2 Under stable cycling conditions for 100 h, its polarization potential remained essentially unchanged, indicating that the single-ion solid electrolyte has good interfacial stability for the lithium metal anode.

[0042] The microphase-separated single-ion solid polyelectrolyte obtained in this embodiment was used as a solid electrolyte in Li|LiFePO4 for performance testing. The obtained microphase-separated single-ion solid polyelectrolyte membrane was cut into electrolyte membranes with a diameter of 19 mm, and a solid lithium metal secondary battery was assembled using lithium metal foil as the negative electrode and lithium iron phosphate as the positive electrode. Its electrochemical performance was then tested. Figure 7 ). Figure 7For the performance testing of the Li|LiFePO4 solid-state battery based on the microphase-separated single-ion solid polyelectrolyte obtained in this embodiment, its discharge specific capacity is about 158 ​​mAh / g at 0.2C, about 101 mAh / g when the rate is increased to 1C, and 57 mAh / g even when the rate is further increased to 4C. Furthermore, the capacity retention rate can reach 93.7% after 300 cycles at 1C.

[0043] Examples 2-7 In Example 1, the polymer backbone in step one was replaced with polysulfone, polybenzimidazole, polyetheretherketone, polyarylsulfone, sulfonated polybenzimidazole, and polyphenylsulfone, respectively. The other preparation processes were the same as in Example 1, resulting in a single-ion solid electrolyte. A Li|LiFePO4 solid-state battery was then assembled and tested. The performance of the electrolytes obtained in Examples 2-7 and their assembled batteries is shown in Table 1.

[0044] Table 1 Performance of the single-ion solid electrolytes prepared in Examples 1-7 Example Polymer backbone class Ionic conductivity Tensile strength Elongation at break Discharge specific capacity (0.2 C) Discharge specific capacity (1 C) Capacity retention after 300 cycles at 1 C 1 Polyether sulfone 0.24 mS / cm -1 ]] 14.2 MPa 13.6% 158 mAh / g 101 mAh / g 93.7% 2 Polysulfone 0.22 mS / cm -1 ]] 13.5 MPa 12.8% 141 mAh / g 96 mAh / g 92.5% 3 Polybenzimidazole 0.23 mS / cm -1 ]] 12.9 MPa 10.9% 148 mAh / g 97 mAh / g 93.0% 4 Polyether ether ketone 0.20 mS / cm -1 ]] 13.0 MPa 11.1% 145 mAh / g 92 mAh / g 90.9% 5 Polyarylsulfone 0.24 mS / cm -1 ]] 15.5 MPa 11.5% 152 mAh / g 100 mAh / g 91.8% 6 Sulfonated polybenzimidazole 0.23 mS / cm -1 ]] 11.9 MPa 10.8% 149 mAh / g 97 mAh / g 92.6% 7 Polyphenylsulfone 0.22 mS / cm -1 ]] 15.1 MPa 12.7% 142 mAh / g 95 mAh / g 91.2% Example

[0045] Step 1: Dissolve polybenzimidazole in ultra-dry tetrachloroethane (tetrachloroethane mass is 15 times the mass of polybenzimidazole), add zinc chloride powder (2wt% of polybenzimidazole mass) and chloromethyl methyl ether (2 times the mass of polybenzimidazole mass) under helium protection, and reflux for 6 h; after the reaction is complete, slowly pour the solution into twice the volume of methanol aqueous solution (methanol to water volume ratio is 1:1) to precipitate the product, and then dissolve the product again in tetrachloroethane and precipitate in methanol aqueous solution. Repeat this process 5 times to obtain pure chloromethylated polybenzimidazole.

[0046] Step 2: Dissolve dry CF3-SO2-NH2 in anhydrous acetonitrile (50 times the mass of CF3-SO2-NH2), add excess lithium hydroxide, and stir for 12 h at room temperature under helium protection to obtain CF3-SO2-NHLi; dissolve 1-Cl-(CH2)3-SO2Cl in acetonitrile (50 times the mass of 1-Cl-(CH2)3-SO2Cl) in acetonitrile, and add this solution dropwise to the CF3-SO2-NHLi solution, stirring at 80°C for 12 h; filter and collect the filtrate, distill under reduced pressure to obtain a solid powder, recrystallize the solid powder in tetrahydrofuran (50 times the mass of the powder) to obtain 1-Cl-(CH2)3-SO2-NLi-SO2-CF3.

[0047] Step 3: Diethylene glycol was dissolved in ultra-dry NMP (20 times the mass of diethylene glycol), and excess lithium hydride was added. The mixture was stirred at room temperature for 0.5 h to obtain LiO-CH2-CH2-O-CH2-CH2-OLi. 0.55 molar amounts of 1-Cl-CH2-SO2-NLi-SO2-CF3 and 0.55 molar amounts of chloromethylated polybenzimidazole were also dissolved in NMP (20 times the mass of the corresponding solutes), and then added sequentially to the LiO-CH2-CH2-O-CH2-CH2-OLi solution through a constant pressure dropping funnel. The mixture was heated to 60°C and reacted for 24 h. The product precipitated in an equal volume of methanol-water solution (methanol to water volume ratio of 1:1) to obtain a main / side chain type single-ion polymer lithium salt.

[0048] Step 4: Dissolve the above single-ion polymer lithium salt in ultra-dry DMF (lithium salt to solvent mass ratio of 1:30), stir at 60°C for 4 h to obtain a homogeneous transparent casting solution, then introduce it into a petri dish and continuously dry it at 80°C until the solvent evaporates completely to obtain a microphase-separated single-ion solid polyelectrolyte membrane with two continuous phases.

[0049] The obtained microphase-separated single-ion solid polyelectrolyte membrane was cut into an electrolyte membrane with a diameter of 19 mm. A Li|LiFePO4 solid battery was assembled using lithium metal foil as the negative electrode and a composite lithium iron phosphate electrode as the positive electrode. Its electrochemical performance and battery performance were then tested (see Table 2 for specific results).

[0050] Examples 9-11 In step two of Example 8, CF3-SO2-NH2 was replaced with CF2H-SO2-NH2, CFH2-SO2-NH2, and F-SO2-NH2, respectively. The other steps were the same as in Example 8. The key performance of the prepared single-ion solid electrolyte is shown in Table 2.

[0051] Table 2 Performance of the single-ion solid electrolytes prepared in Examples 8-11 Example [R-SO2-NH2] Ionic conductivity Tensile strength Elongation at break Discharge specific capacity (0.2 C) Discharge specific capacity (1 C) Capacity retention after 300 cycles at 1 C 8 CF3H-SO2-NH2 0.25 mS / cm -1 ]] 14.1 MPa 11.5% 161 mAh / g 110 mAh / g 94.1% 9 CF2H-SO2-NH2 0.24 mS / cm -1 ]] 13.1 MPa 13.4% 150 mAh / g 102 mAh / g 93.2% 10 CFH2-SO2-NH2 0.21 mS / cm -1 ]] 12.5 MPa 13.1% 146 mAh / g 93 mAh / g 92.5% 11 F-SO2-NH2 0.22 mS / cm -1 ]] 12.6 MPa 12.5% 147 mAh / g 95 mAh / g 90.6% Example

[0052] Step 1: Dissolve polysulfone in ultra-dry DMSO (DMSO mass is 5 times the mass of polysulfone), add aluminum chloride powder (5 wt% of polyethersulfone mass) and chloromethyl methyl ether (equal mass of polysulfone mass) under argon protection, and reflux for 4 h; after the reaction is complete, slowly pour the solution into twice the volume of ethanol aqueous solution (ethanol to water volume ratio is 1:1) to precipitate the product, and then dissolve the product again in DMSO and precipitate it in ethanol aqueous solution. Repeat this process 3 times to obtain pure chloromethylated polysulfone.

[0053] Step 2: Dissolve dry CF3-SO2-NH2 in anhydrous chloroform (20 times the mass of CF3-SO2-NH2), add excess lithium carbonate, and stir for 6 h at room temperature under argon protection to obtain CF3-SO2-NHLi; dissolve 1-Cl-(CH2)3-SO2Cl in chloroform (20 times the mass of 1-Cl-(CH2)3-SO2Cl) in chloroform, and add this solution dropwise to the CF3-SO2-NHLi solution, stirring at 50°C for 48 h; filter and collect the filtrate, distill under reduced pressure to obtain a solid powder, recrystallize the solid powder in tetrahydrofuran (20 times the mass of the powder) to obtain 1-Cl-(CH2)3-SO2-NLi-SO2-CF3.

[0054] Step 3: Dissolve diethylene glycol in a 1:1 volume ratio of ultra-dry DMF and NMP (10 times the mass of diethylene glycol), and add excess lithium hydride. Stir at room temperature for 1 h to obtain LiO-CH2-CH2-O-CH2-CH2-OLi. Dissolve 0.55 molar amounts of 1-Cl-CH2-SO2-NLi-SO2-CF3 and 0.75 molar amounts of chloromethylated polysulfone in diethylene glycol in a 10 times the mass of the corresponding solutes, respectively. Then add them sequentially to the LiO-CH2-CH2-O-CH2-CH2-OLi solution through a constant pressure dropping funnel, and heat to 80°C. Continue the reaction for 12 h. The product precipitates in an equal volume of methanol-water solution (1:1 volume ratio of methanol to water) to obtain a main / side chain type single-ion polymer lithium salt.

[0055] Step 4: Dissolve the above-mentioned single-ion polymer lithium salt in a mixed solution of ultra-dry DMF and NMP in a volume ratio of 1:1 (the mass ratio of lithium salt to solvent is 1:30), stir at 70°C for 4 h to obtain a homogeneous transparent casting solution, then introduce it into a petri dish and continuously dry it at 100°C until the solvent evaporates completely to obtain a microphase-separated single-ion solid polyelectrolyte membrane with two continuous phases.

[0056] The obtained microphase-separated single-ion solid polyelectrolyte membrane was cut into an electrolyte membrane with a diameter of 19 mm. A solid lithium metal secondary battery was assembled using lithium metal foil as the negative electrode and composite lithium iron phosphate electrode as the positive electrode. The electrolyte performance and battery performance were then tested.

[0057] Examples 13-17 In step 3 of Example 12, diethylene glycol (HO-(CH2)2-O(CH2)2-OH) was replaced with HO-((CH2)2-O(CH2)2)2-OH, HS-(CH2)2-S-(CH2)2-SH, Cl-(CH2)2-O(CH2)2-Cl, NH2-(CH2)6-NH2, and Cl-(CH2)6-Cl, respectively. The other steps were the same as in Example 8. The key performance of the prepared single-ion solid electrolyte is shown in Table 2.

[0058] Table 2 Performance of the single-ion solid electrolytes prepared in Examples 12-17 Example X-(CH2-Y-CH2) n -X]]> Ionic conductivity Tensile strength Elongation at break Discharge specific capacity (0.2 C) Discharge specific capacity (1 C) Capacity retention after 300 cycles at 1 C 12 HO-(CH2)2-O(CH2)2-OH 0.26 mS / cm -1 ]] 13.6 MPa 12.9% 155 mAh / g 100 mAh / g 95.4% 13 HO-((CH2)2-O(CH2)2)2-OH 0.24 mS / cm -1 ]] 13.1 MPa 14.2% 152 mAh / g 96 mAh / g 93.7% 14 HS-(CH2)2-S-(CH2)2-SH 0.19 mS / cm -1 ]] 12.9 MPa 13.1% 146 mAh / g 91 mAh / g 91.6% 15 Cl- (CH2)2-0 (CH2)2-Cl 0.25 mS / cm -1 ]] 11.3 MPa 12.5% 147 mAh / g 92 mAh / g 90.8% 16 [CAT] - [NH2-(CH2)6-NH2] 0.22 mS / cm -1 ]] 14.8 MPa 13.9% 141 mAh / g 88 mAh / g 90.3% 17 Cl- (CH2)6- Cl 0.21 mS / cm -1 ]] 15.1 MPa 15.4% 140 mAh / g 86 mAh / g 91.2% Comparative Example 1 Commercial lithium polystyrene sulfonate was directly used as a single-ion solid electrolyte in Li|LiFePO4. The specific capacity of the battery was measured to be 129 mAh / g at 0.2C, but the discharge specific capacity was only 64 mAh / g at 1C. After 30 cycles, the capacity had decayed to 33.6%.

[0059] Comparative Example 2 When polyvinylidene fluoride sulfonylimide lithium salt was used directly as a single-ion solid electrolyte in Li|LiFePO4, its specific capacity was measured to be 112 mAh / g at 0.2C, but the discharge specific capacity was only 38 mAh / g at 1C. After 30 cycles, the capacity had decayed to 28.9%.

[0060] Comparing the foregoing examples and comparative examples, the following conclusions can be drawn: the polymer electrolyte prepared using the technology of this invention has high ionic conductivity (0.19-0.26 mS / cm). -1 With its excellent mechanical properties, when assembled into a solid-state lithium battery, the optimal battery specific capacity can reach 161 mAh / g at 0.2C, and after 300 cycles at 1C, it still retains 90.3%-95.4% of its capacity, demonstrating excellent cycle stability. When commercial polymer lithium salts are used directly as solid electrolytes for lithium metal batteries, the specific capacity is lower (<130 mAh / g), and at high rates, polarization is severe, resulting in significant capacity decay (the specific capacity at 1C decreases to about 1 / 2-1 / 3 of the rated capacity), and poor cycle stability (the capacity decays to 28.9%-33.6% of the rated capacity after 30 cycles at 1C).

[0061] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution with reference to preferred embodiments of the present invention, and are not intended to limit it. The embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention should be considered as equivalent substitutions and are included within the protection scope of the present invention.

Claims

1. A method for preparing a micro-phase separation type single-ion solid electrolyte, comprising the following preparation steps: Step one: dissolve high strength, solvent-averse, organic rigid skeleton polymer in anhydrous solvent, add Lewis acid catalyst and chloromethylation reagent under protective atmosphere, and reflux for 4-12 h; after the reaction is completed, slowly pour the solution into the precipitating solvent to precipitate the product, then dissolve the product again in the solvent used in the reaction, precipitate again in the precipitating solvent, and repeat this process 3-5 times to obtain pure chloromethylated polymer. Among them, The high-strength, solvent-repellent organic rigid skeleton polymer is one of polysulfone, polyethersulfone, polyether ether ketone, polybenzimidazole and derivatives thereof; the anhydrous solvent used in the chloromethylation reaction is one or more arbitrary proportion mixed solvents of trichloromethane, dichloromethane, 1,2-dichloroethane, tetrachloroethane, nitromethane, DMF, DMSO, etc., and the solvent dosage is 5-20 times the mass of the polymer; the Lewis acid catalyst is one of AlCl3, FeCl3, ZnCl2 and BF3·Et2O; R-OCH2Cl is the chloromethylation reagent, wherein R is methyl or ethyl; and the product precipitation solvent is water, methanol, ethanol and any arbitrary proportion mixed solution thereof, and the solvent dosage is 1-5 times the volume of the reaction solution; ； Step two: dry R-SO2-NH2 (R = CF3 / CF2H / CFH2 / F) is dissolved in a solvent, an excess of lithium carbonate or lithium hydroxide is added, and stirring is performed at room temperature under a protective atmosphere for 6-12 h to obtain R-SO2-NHLi; 1-Br / Cl-(CH2)n-SO2-Cl (n = 3-8) is dissolved in the same solvent, and the solution is added dropwise to the R-SO2-NHLi solution, and stirring is performed at 30-80°C for 12-48 h; the filtrate is filtered and collected, and a solid powder is obtained after distillation under reduced pressure, and the solid powder is recrystallized in an ether solvent to obtain 1-Br / Cl-(CH2)n-SO2-NLi-SO2-R (a side-end functionalized bis-sulfonimidate lithium salt). The solvent used in the reaction is one or an arbitrary proportion of a plurality of mixed solvents of acetonitrile, dichloromethane, chloroform, DMF and DMSO; the molar ratio of R-SO2-NHLi and 1-Br / Cl-(CH2)n-SO2-Cl is 1:1-1.5; and the ether solvent used for recrystallization is one of diethyl ether, tetrahydrofuran, 1,3-dioxolane and 1,4-dioxane; Step three: dissolve the double-end functionalized linear small molecule into the super-dry high-boiling aprotic polar solvent, and add excess lithium hydride, stir at room temperature for 0.5-2 h to obtain the double-end lithiumated linear small molecule, dissolve the side-end functionalized double-sulfonylimine lithium salt and chloromethylated polymer into the same high-boiling aprotic polar solvent, add into the reaction system through the constant pressure dropping funnel in turn, increase the temperature to 60-120°C, continue to react for 8-24 h, the product is precipitated in the precipitating solvent to obtain the main / side chain type single-ion polymer lithium salt. The molecular structure of the double-end functionalized small molecule is X-((CH2)2-Y-(CH2)2) n X, wherein X is OH, SH, NH2, Cl, Br, etc., Y is one of CH2, S, O, and n=1-5; the high-boiling aprotic polar solvent is one or more of NMP, DMF, DMSO, etc. in any proportion mixed solvent; the precipitating solvent is water, methanol, ethanol, and any proportion mixed solution thereof; Step four: the above main / side chain type single-ion polymer lithium salt is dissolved in a polar solvent, the mass ratio of lithium salt to solvent is 1:30-60, stirring is performed at 40-100°C for 2-8 h to obtain a homogeneous transparent casting solution, and then the casting solution is poured into a smooth-surfaced container, and continuous air blowing drying is performed at 60-120°C until the solvent is completely volatilized to obtain a solid-state single-ion polyelectrolyte membrane with a double-continuous phase. The polar solvent is one or more arbitrary proportion mixed solvents of acetonitrile, tetrahydrofuran, NMP, DMF and DMSO.

2. The reaction protection gas in steps one and two is one gas or an arbitrary proportion of a plurality of mixed gases of N2 / Ar / He.

3. The Lewis acid catalyst used in step one is 1%-20% of the mass of the polymer, and the dosage of the chloromethylation reagent is 1-5 times the mass of the polymer.

4. The solvent used in step two is 10-50 times the mass of the sulfonamide / sulfonyl chloride, and the recrystallization solvent used in step two is 20-50 times the mass of the solid powder.

5. The amount of solvent used in step three is 10-50 times the mass of the solute (doubly end-functionalized linear small molecule / sidely functionalized lithium bis-sulfonimide salt / chloromethylated polymer).

6. The molar ratio among the doubly end-functionalized linear small molecule, the sidely functionalized lithium bis-sulfonimide salt, and the chloromethylated polymer in step three is 1:0.5-0.75:0.5-0.

75.

7. The volume of the precipitated solvent in step three is 1-5 times the volume of the reaction solution.

8. The mass ratio of the lithium salt to the solvent in step four is 1:30-60.

9. A preparation method of the above-mentioned micro-phase separation structure single-ion solid-state electrolyte with good performance is provided.

10. The above-mentioned micro-phase separation structure single-ion solid-state electrolyte is applied to a solid-state lithium metal / ion battery.

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