Composite polymer solid electrolyte membrane and preparation method and application thereof

Abstract

The invention discloses a composite polymer solid electrolyte membrane and a preparation method and application thereof. The composite polymer solid electrolyte membrane is composed of MOF uniformly dispersed in a polymer matrix and lithium salt filled in an MOF channel. The obtained composite solid electrolyte membrane has excellent room-temperature ionic conductivity, remarkably improved lithium ion transference number and wide electrochemical window. The assembled lithium-lithium symmetrical battery shows super-strong cycle capacity exceeding 1500 hours, and the lithium iron phosphate-lithium battery shows high rate performance and excellent cycle stability. The feasibility of the developed electrolyte is verified by assembling various soft package batteries (including LiFePO4, LiNi0. 5Co0. 2Mn0. 3O2 and LiMn2O4 positive electrodes).

Description

Technical Field

[0001] The present invention belongs to the technical field of new energy materials, and specifically relates to a composite polymer solid electrolyte membrane and a preparation method and application thereof. Background Art

[0002] With the widespread use of lithium-ion batteries in electric vehicles, portable electronic devices, and energy storage systems, the safety risks of traditional liquid electrolytes (such as leakage and flammability) have become a key issue restricting their development. Solid-state batteries have attracted widespread attention from researchers due to their significant advantages in high energy density and high safety. The key to realizing the application of solid-state batteries lies in the development of high-performance solid-state electrolytes.

[0003] Currently, solid-state electrolytes fall into two main categories: inorganic solid-state electrolytes and polymer solid-state electrolytes. Inorganic solid-state electrolytes can be primarily categorized as oxides, sulfides, and halides. Their primary advantages lie in high ionic conductivity and excellent mechanical strength, but they suffer from issues such as high interfacial impedance, difficult processing, and, in the case of sulfide-based materials, instability in air. Polymer electrolytes, primarily composed of a polymer matrix (such as PEO and PVDF) and a lithium salt (such as LiTFSI), offer advantages such as low cost and ease of processing. However, they face challenges such as low room-temperature ionic conductivity, low ion transference numbers, and safety.

[0004] In contrast, composite polymer solid electrolytes, composed of polymers and functional fillers, are expected to combine the advantages of both, achieving a balance between high ion transport and good mechanical properties. However, commonly used inorganic fillers tend to agglomerate in polymers and have poor interfacial compatibility. Furthermore, limited lithium salt dissociation and uneven lithium ion transport pathways severely restrict the performance of composite solid electrolytes. Inadequate flame retardancy and high-voltage stability also limit their application in high-voltage battery systems.

[0005] For example, the invention application with publication number CN119315091A discloses a nitro-functionalized Zn-Mo bimetallic organic framework solid electrolyte and its preparation method. First, Zn-Mo bimetallic organic framework MOFs with nitro functional groups are synthesized by the reflux method, and then blended with lithium salt and polymer to obtain a viscous slurry, which is poured onto a glass plate to solidify. After standing, the slurry is vacuum dried at 60°C to obtain a nitro-functionalized Zn-Mo bimetallic organic framework solid electrolyte.

[0006] For example, the invention application with publication number CN117199516A discloses a composite solid electrolyte and its preparation method and application. The composite solid electrolyte includes a MOF array and a conductive filler, and the conductive filler fills the MOF array; the MOF array includes a nanotube structure that grows in the same direction and is arranged in an array, and the conductive filler includes a polymer electrolyte and a lithium salt.

[0007] In addition, existing composite electrolyte preparation processes such as electrospinning and hot pressing require multi-step processing, are costly and difficult to scale up, and the mechanical strength is difficult to meet the requirements of ultra-thinness (film thickness <20μm). Summary of the Invention

[0008] The present invention addresses the aforementioned technical issues in the prior art by providing a composite polymer solid electrolyte membrane, its preparation method, and its application. By leveraging the MOF pore confinement effect, lithium salts are preloaded into the multidimensional pores of the MOF, forming continuous ion transport channels. This significantly promotes lithium salt dissociation, significantly improving the lithium ion transference number and room-temperature ionic conductivity, while also exhibiting a wide electrochemical window, excellent mechanical properties, and good flame retardancy.

[0009] The present invention first provides a method for preparing a composite polymer solid electrolyte membrane, comprising the following steps:

[0010] (1) dissolving a lithium salt in a first organic solvent to obtain a lithium salt solution a;

[0011] dissolving the polymer in a second organic solvent to obtain a mixed solution b;

[0012] (2) immersing the MOF material in a lithium salt solution a so that the pores of the MOF material adsorb lithium salts to obtain a pre-lithiated MOF material;

[0013] (3) dissolving the pre-lithiated MOF material obtained in step (2) in a third organic solvent to obtain a mixed solution c;

[0014] (4) uniformly mixing the mixed solution b and the mixed solution c to obtain a mixed solution d;

[0015] (5) forming a film of the mixed solution d obtained in step (4) to obtain a MOF-based composite membrane;

[0016] (6) Immersing the MOF-based composite membrane obtained in step (5) in a lithium salt solution a for activation to obtain a composite polymer solid electrolyte membrane.

[0017] Preferably, the lithium salt is at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium perchlorate, lithium trifluoromethanesulfonate, lithium bistrifluoromethanesulfonyl imide, and lithium bisoxalatoborate;

[0018] The polymer is at least one of polyethylene oxide, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polymethyl methacrylate, and polyacrylonitrile;

[0019] The MOF material is a porous structure material formed by the coordination of at least one metal ion or metal ion cluster and an organic ligand;

[0020] The metal ion is Mg2+ 、Al 3+ , Ca 2+ 、Ti 4+ 、V 4+ 、V 3+ 、V 2+ Cr 3+ 、Mn 3+ 、Mn 2+ 、Fe 3+ 、Fe 2+ 、Co 3+ 、Co 2+ 、Ni 2+ 、Ni + 、Cu 2+ 、Cu + 、Zn 2+ 、Ga 3+ 、Ge 4+ 、Ge 2+ 、As 5+ 、As 3+ 、As + 、Y 3+ 、Zr 4+ 、Mo 3+ 、pd 2+ 、Pd + ,pt 2+ , Pt + 、Ag + 、Cd 2+ 、In 3+ 、La 3+ 、Ce 4+ 、Ce 3+ , Hf 4+ At least one of;

[0021] The organic ligands are terephthalic acid, 2-methylimidazole, benzene-1,2,4,5-tetracarboxylic acid, 5-nitroisophthalic acid, isophthalic acid, nicotinic acid, 3-nitrophthalic acid, imidazole, 5-aminoisophthalic acid, isonicotinic acid, 1,3,5-tricarboxylic acid benzene, 2,3-pyridinedicarboxylic acid, 2,2'-bipyridine, 1,4-cyclohexanedicarboxylic acid, thiophene-2,5-dicarboxylic acid, pyrazine, butynedioic acid, [1,1'-biphenyl]-4-carboxylic acid, trans-1,4-cyclohexanedicarboxylic acid, cis-1,2-cyclohexanedicarboxylic acid, 2,3,5,6-tetrafluoroterephthalic acid, 2-nitroisophthalic acid ... terephthalic acid, pyrazine-2,3-dicarboxylic acid, 4,4'-biphenyldicarboxylic acid, fumaric acid, 3,4-pyridinedicarboxylic acid, 2,4-pyridinedicarboxylic acid, 4-aminobiphenyldicarboxylic acid, salicylic acid azine, 1H-imidazole-4,5-dicarboxylic acid, 1H-pyrazole-3,5-dicarboxylic acid hydrate, 4,4'-bipyridine, 3,6-di-2-pyridyl-1,2,4,5-tetrazine, 2,5-dibromoterephthalic acid, 2,5-dichloro-p-dibenzoic acid, trans-1,2-cyclohexanedicarboxylic acid, 3,5-pyrazoledicarboxylic acid, (1R,2R)-1,2-cyclohexanedicarboxylic acid, 2,2 1 -biphenyl dicarboxylic acid, 3,5-pyridine dicarboxylic acid, trimellitic acid, naphthalene-1,4-dicarboxylic acid, 4-hydroxyphthalic acid, 2,5-dihydroxyterephthalic acid, 5-hydroxyisophthalic acid, 1,4-phenylenedicarboxylic acid, 4-carboxyphenylacetic acid, 2-aminoterephthalic acid, cyclohexane-1,3-dicarboxylic acid, cis-1,4-cyclohexanedicarboxylic acid, 2,6-naphthalene dicarboxylic acid, cyclohexane-1,2,4,5-tetracarboxylic acid, 2-bromo at least one of 1,4-dibromo-2,5-diiodobenzene, 4,4′-dimethoxy-1,1′-biphenyl, 1-ethyl-2-methylquinolin-1-ium iodide, 1-ethyl-3-vinylimidazolium bromide, 1,3-bis(2,6-diisopropylphenyl)imidazolium chloride, iron phthalocyanine, 1,3-dibromo-5-(tert-butyl)benzene, tetrafluorophthalic acid, and tetrachlorophthalic acid hemihydrate.

[0022] Preferably, the first organic solvent is at least one of ethylene carbonate, diethyl carbonate, dimethyl carbonate, and ethyl methyl carbonate;

[0023] The second organic solvent is at least one of N,N-dimethylformamide, dimethylacetamide, N-methylpyrrolidone, chloroform, dichloromethane, acetonitrile, and acetone;

[0024] The third organic solvent is at least one of N,N-dimethylformamide, dimethylacetamide, N-methylpyrrolidone, chloroform, dichloromethane, acetonitrile, and acetone.

[0025] Preferably, the mass ratio of the MOF material to the polymer is 1:1 to 10. More preferably, the mass ratio of the MOF material to the polymer is 1:4 to 10. More preferably, the mass ratio of the MOF material to the polymer is 1:1 to 4.

[0026] Preferably, the lithium salt concentration in the lithium salt solution a is 1 to 6 mol L -1 .

[0027] Preferably, the polymer concentration in the mixed solution b is 5 wt% to 25 wt%. More preferably, the polymer concentration in the mixed solution b is 5 wt% to 18 wt%. More preferably, the polymer concentration in the mixed solution b is 18 wt% to 25 wt%.

[0028] Preferably, the concentration of the pre-lithiated MOF material in the mixed solution c is 5 wt % to 15 wt %. More preferably, the concentration of the pre-lithiated MOF material in the mixed solution c is 5 wt % to 10 wt %. More preferably, the concentration of the pre-lithiated MOF material in the mixed solution c is 10 wt % to 15 wt %.

[0029] Preferably, in step (5), the mixed solution d is cast on the substrate to form a film using a casting method or a solution casting method.

[0030] More preferably, the mixed solution d is cast on the substrate to a thickness of 200 to 400 μm; after drying, the thickness of the MOF-based composite membrane obtained does not exceed 20 μm. More preferably, after drying, the thickness of the MOF-based composite membrane obtained is 14 to 20 μm.

[0031] Preferably, in step (2), the MOF material is immersed in the lithium salt solution a for 48 to 72 hours. More preferably, in step (2), the MOF material is immersed in the lithium salt solution a for 72 hours.

[0032] Preferably, in step (6), the MOF-based composite membrane is immersed in the lithium salt solution a for activation for 2 to 12 hours. More preferably, in step (6), the MOF-based composite membrane is immersed in the lithium salt solution a for activation for 6 hours.

[0033] The present invention also provides a composite polymer solid electrolyte membrane prepared by the preparation method.

[0034] The present invention also provides application of the composite polymer solid electrolyte membrane in preparing an electrochemical device.

[0035] The present invention also provides an electrochemical device comprising a positive electrode sheet, a negative electrode sheet and the composite polymer solid electrolyte membrane.

[0036] The present invention has the following beneficial effects:

[0037] The present invention utilizes MOF uniformly dispersed in a polymer matrix and lithium salt filled in MOF channels to form a multifunctional ultra-thin composite polymer electrolyte membrane, thereby obtaining an ultra-thin, high-strength electrolyte membrane that takes into account both ion conduction and mechanical support. In addition, the process used is simplified and can be formed in one step by a tape casting method, which is suitable for industrial production. The thickness of the prepared electrolyte film is no more than 20 μm, the tensile strength is greater than 8 MPa, and the elongation at break is greater than 200%. Among them, the polymer provides a flexible skeleton and film-forming properties, the MOF porous structure is pre-loaded with lithium salt, and the MOF nanochannels greatly promote the dissociation of lithium salt and provide Li + The rapid transmission of Li creates a continuous channel, which + The flux is uniform, ensuring good interfacial compatibility.

[0038] Therefore, the obtained composite polymer electrolyte membrane has excellent ionic conductivity (about 3×10 -4 Scm -1 ), significantly improved Li + The transfer number (up to 0.9) and wide electrochemical window (4.9V) are achieved. The lithium / / lithium symmetric battery fabricated in this way has a low and stable overpotential and a service life of more than 1500 hours. The composite electrolyte membrane solid-state battery based on the design has high rate performance and stable cycle stability. In addition, various soft-pack batteries have been assembled, including LiFePO4, LiNi 0.5 Co 0.2 Mn 0.3 O2 and LiMn2O4 cathodes to verify the feasibility of the developed electrolyte. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 Thickness test diagram of a composite solid electrolyte membrane provided in Example 1 of the present invention ( Figure 1 (a)), SEM top view ( Figure 1 (b)) and SEM cross-sectional view ( Figure 1 (c)).

[0040] Figure 2 Graphs showing combustion experiments of the composite solid electrolyte membranes of Examples 1 and 2 of the present invention.

[0041] Figure 3 Graphs showing stress-strain curves of the composite solid electrolyte membranes of Examples 1 and 2 of the present invention.

[0042] Figure 4 This is an AC impedance test diagram of the composite solid electrolyte membrane of Example 1, Example 2 and the comparative example of the present invention at room temperature.

[0043] Figure 5 This is a test chart of the ion migration number applied to a lithium-lithium battery according to Example 1 of the present invention.

[0044] Figure 6 This is a test chart of the ion migration number applied to a lithium-lithium battery according to Example 2 of the present invention.

[0045] Figure 7 This is a test chart of the ion migration number of a comparative example of the present invention applied to a lithium-lithium battery.

[0046] Figure 8 This is an electrochemical window test diagram of the composite solid electrolyte membrane applied to stainless steel-lithium batteries in Example 1, Example 2 and the comparative example of the present invention.

[0047] Figure 9 This is a test chart of the cycle performance of the composite solid electrolyte membranes of Example 1, Example 2 and the comparative example of the present invention applied to lithium-lithium batteries under one condition.

[0048] Figure 10 This is a rate performance test chart of Example 1, Example 2 and the comparative example of the present invention when the composite solid electrolyte membrane is applied to a lithium iron phosphate-lithium battery at room temperature.

[0049] Figure 11 This is a test chart of the cycle performance of composite solid electrolyte membranes of Example 1, Example 2 and the comparative example of the present invention applied to lithium iron phosphate-lithium batteries at room temperature.

[0050] Figure 12 This is a test diagram of the cycle performance of the composite solid electrolyte membranes of Examples 1 and 2 of the present invention applied to lithium iron phosphate-graphite soft-pack batteries; wherein, Figure 12 (a) is a soft pack battery assembled using the solid electrolyte membrane obtained in Example 1. Figure 12 (b) is a soft-pack battery assembled using the solid electrolyte membrane obtained in Example 2.

[0051] Figure 13 These are actual pictures of a light-emitting diode device lighting up in different states using a lithium iron phosphate-graphite soft-pack battery using the solid electrolyte membrane obtained in Example 1.

[0052] Figure 14 This is a cycle performance diagram of a lithium iron phosphate positive electrode laminate soft-pack battery using the solid electrolyte membrane obtained in Example 2.

[0053] Figure 15 This is a graph showing the cycling performance of different soft-pack batteries using the composite solid electrolyte membrane of Example 1 of the present invention. Figure 15 Middle (a) is a high nickel ternary positive electrode soft pack battery, Figure 15 (b) is a lithium manganese oxide positive electrode soft pack battery. DETAILED DESCRIPTION

[0054] The following examples further illustrate the present invention but should not be construed as limiting the present invention. All other aspects of the present invention obtained by making equivalent improvements and simple modifications without departing from the spirit and substance of the present invention are intended to fall within the scope of the present invention. Unless otherwise specified, the techniques used in the examples are conventional techniques well known to those skilled in the art.

[0055] Example 1

[0056] A method for preparing a composite polymer solid electrolyte membrane based on MOF material comprises the following steps:

[0057] (1) In an argon glove box, 2.8 g of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI, 1 mol L -1 ) was dissolved in 10 mL of ethyl methyl carbonate (EMC) and stirred for 12 h to obtain a lithium salt solution.

[0058] (2) 0.1 g of UIO-66(Zr) (MOF material) was immersed in 5 mL of the lithium salt solution obtained in step (1) for 72 h, then centrifuged and washed three times with ethyl methyl carbonate (EMC), and dried in vacuo at 80 °C for 12 h to obtain pre-lithiated UIO-66, referred to as U6-Li. + .

[0059] (3) 0.4 g of polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP, molecular weight 400,000) was dissolved in 1.8 g of N,N-dimethylformamide (DMF) at a mass concentration of 18 wt % and stirred for 12 hours.

[0060] (4) 0.1 g U6-Li obtained in step (2) + The solution was dissolved in 0.9 g of DMF at a mass concentration of 10 wt%, and stirred for 12 hours.

[0061] (5) The solutions obtained in step (3) and step (4) were mixed and stirred for 12 hours to form a uniform solution slurry.

[0062] (6) The slurry obtained in step (5) was cast on a glass substrate, scraped evenly using a 200 μm film-making scraper, and placed in a high vacuum oven at 60° C. and dried for 48 hours to evaporate the solvent to obtain a MOF-based composite film.

[0063] (7) The MOF-based composite film obtained in step (6) is immersed in the lithium salt solution in step (1) for activation for 6 hours. After being fished out and the residual liquid on the surface is wiped off, a composite solid electrolyte membrane is obtained, referred to as PH-U6-Li + .

[0064] The physical picture and scanning electron microscope picture of the obtained solid electrolyte film are as follows: Figure 1 As shown, Figure 1 (a) is the thickness test using a film thickness meter. Figure 1 (b) is a top view of the scanning electron microscope. Figure 1 (c) is a cross-sectional view of the scanning electron microscope. Figure 1 It can be seen that the thickness of the prepared film is about 14 μm, the surface is flat, the thickness is uniform and the stacking is tight, and the UIO-66 nanoparticles are evenly distributed on the surface.

[0065] The flame retardancy test results of the obtained solid electrolyte film are as follows: Figure 2 It can be seen that the solid electrolyte film obtained by the present invention can be quickly self-extinguished after being ignited and has good flame retardancy.

[0066] The mechanical properties test results of the obtained solid electrolyte film are as follows: Figure 3 It can be seen that the solid electrolyte film obtained by the present invention has good flexibility and high mechanical strength (the maximum elongation can reach 242%, and the highest tensile strength is 8.1 MPa).

[0067] The solid electrolyte obtained above was assembled into a stainless steel symmetrical battery and subjected to AC impedance spectroscopy test, as shown in Figure 4 As shown in the figure, the room temperature ionic conductivity of the solid electrolyte is calculated to be 3.37×10 -4 Scm -1 .

[0068] Example 2

[0069] This embodiment provides a composite solid electrolyte membrane, and its preparation method is basically the same as that of Example 1, except that the MOF type used is ZIF-8. The rest of the operations are the same to obtain a composite solid electrolyte membrane, referred to as PH-Z8-Li + .

[0070] The flame retardancy test results of the solid electrolyte film are as follows: Figure 2 It can be seen that the solid electrolyte film obtained by the present invention can be quickly self-extinguished after being ignited and has good flame retardancy.

[0071] The mechanical properties test results of the obtained solid electrolyte film are as follows: Figure 3 It can be seen that the solid electrolyte film obtained by the present invention has good flexibility and high mechanical strength (the maximum elongation can reach 428%, and the highest tensile strength is 9.9 MPa).

[0072] The solid electrolyte obtained above was assembled into a stainless steel symmetrical battery and subjected to AC impedance spectroscopy test, as shown in Figure 4 As shown in the figure, the room temperature ionic conductivity of the solid electrolyte is calculated to be 2.26×10 -4 Scm-1 .

[0073] Comparative Example

[0074] This comparative example provides a composite solid electrolyte membrane, and its preparation method is basically the same as that of Example 1, except that UIO-66 is not added, and the rest of the operations are the same to obtain PH-Li + Composite solid electrolyte film.

[0075] The solid electrolyte obtained above was assembled into a stainless steel symmetrical battery and subjected to AC impedance spectroscopy test, as shown in Figure 4 As shown in the figure, the room temperature ionic conductivity of the solid electrolyte is calculated to be 4.94×10 -5 S cm -1 .

[0076] Test Example 1

[0077] The composite solid electrolyte membranes of Example 1, Example 2 and the comparative example were applied to a stainless steel / / stainless steel symmetrical battery, and the AC impedance spectrum was measured at room temperature using an electrochemical workstation. The test conditions were 10 mV amplitude and a frequency range of 1 MHz to 0.1 Hz. Figure 4 As shown. According to the formula:

[0078]

[0079] Calculation of ionic conductivity σ(S cm) of different electrolyte films -1 ), where L is the thickness of the solid electrolyte membrane (cm), R is the volume resistance value read in the AC impedance spectrum (R), and S is the contact area between the solid electrolyte membrane and the stainless steel electrode (cm- 2 ). According to the calculation results, PH-U6-Li + and PH-Z8-Li + The room temperature ionic conductivity of the composite solid electrolyte is 3.37×10 -4 Scm -1 and 2.26×10 -4 S cm -1 , higher than PH-Li + The ionic conductivity is 4.94×10 -5 S cm -1 .

[0080] Test Example 2

[0081] The composite solid electrolyte membranes of Example 1, Example 2 and the comparative example were applied to lithium / / lithium symmetrical batteries, and the chronoamperometric curves and AC impedance spectra were measured. According to the formula:

[0082]

[0083] Calculate the ion migration number (t Li+ ), where I0 and I SS are the initial current and steady-state current, ΔV is the applied polarization voltage (10 mV), R0 and R SS Represent the initial resistance and steady-state resistance respectively. Figure 5-Figure 7 PH-U6-Li can be obtained + PH-Z8-Li + and PH-Li + The ion transfer numbers are 0.90, 0.84 and 0.68, respectively, indicating that the introduction of MOF can improve the ion transfer number.

[0084] Test Example 3

[0085] The composite solid electrolyte membranes of Example 1, Example 2, and the comparative example were applied to stainless steel / / lithium batteries for electrochemical window testing. Linear sweep voltammetry curves were recorded using an electrochemical workstation at a scan rate of 0.5 mV s -1 The voltage range is from open circuit voltage to 6V, and the electrochemical stability window of different solid electrolyte membranes is read according to the current rise. Figure 8 As shown, PH-U6-Li + PH-Z8-Li + The oxidation peaks on the voltammetric curves of the electrolyte all appear at about 4.9V, which is higher than that of PH-Li + 3.9V.

[0086] Test Example 4

[0087] The composite solid electrolyte membranes of Example 1, Example 2 and the comparative example were applied to lithium / / lithium symmetrical batteries and the cycle performance was tested. Figure 9 As shown, at room temperature 0.2mA cm- 2 The current density is 0.1 mAh cm- 2 When the battery is operated under the conditions of area capacity, both Example 1 and Example 2 can be stably cycled for more than 1500 hours, while the polarization of the comparative example increases sharply after about 300 hours of cycling.

[0088] Test Example 5

[0089] The obtained solid electrolyte composite membrane was applied to lithium iron phosphate (LFP) / / Li battery. The preparation method of the battery is as follows: commercial lithium iron phosphate, Ketjen black and PVDF were mixed with an appropriate amount of NMP in a mass ratio of 8:1:1 and then coated on aluminum foil to prepare the positive electrode sheet. The active material loading was 2 mg cm- 2In an argon-filled glove box, 2025-type button cells were assembled using the prepared cathode sheet as the positive electrode, the solid electrolyte membranes obtained in Example 1, Example 2, and the comparative example as the electrolyte, and a metal lithium sheet as the negative electrode. After standing for 12 hours, rate performance and cycle performance tests were conducted at room temperature (25°C).

[0090] like Figure 10 As shown in Figure 2, the rate performance of the assembled LFP / / Li battery was measured at different current densities of 0.1, 0.3, 0.5, 1, 2, 3, and 5 C. The batteries using the solid electrolytes of Example 1 and Example 2 showed excellent rate performance, with discharge capacities of 103 and 97 mAh g at 5 C, respectively. -1 , and when the current density is adjusted back from 5C to 0.1C, the capacity can be restored to the initial value. In contrast, the capacity of the battery using the comparative solid electrolyte at 5C is only 33mAh g -1 .

[0091] Figure 11 The cycling performance of various batteries is shown. For the comparative battery, the specific capacity decays rapidly, with a discharge capacity of 70 mAh g after only 80 cycles. -1 , low capacity retention (53.8%) and low coulombic efficiency. However, the batteries using the electrolytes of Example 1 and Example 2 can operate stably for more than 200 cycles. This shows that the MOF-based electrolyte has excellent Li + Transport properties and interface stability.

[0092] Test Example 6

[0093] In order to evaluate the practical application potential and safety performance of the prepared MOF-based composite solid electrolyte, Examples 1 and 2 were further applied to soft-pack batteries (cell size: ≈5×8 cm 2 , LFP mass loading is as high as 513 mg). Figure 12 As shown in (a) and (b), the initial discharge capacity of the soft pack batteries assembled using the electrolytes of Example 1 and Example 2 is 125 mAh g -1 and 124mAh g -1 After 100 cycles, the capacity remains at 101 mAh g -1 (capacity retention rate 81%) and 106mAh g -1 (Capacity retention rate 85%).

[0094] like Figure 13As shown in the figure, under several harsh conditions such as bending, folding and cutting, the soft-pack battery can still light up the connected light-emitting diode lamp. The puncture and shear tests prove that the battery does not catch fire or explode. Moreover, after a series of abuse tests, the obtained battery cell can still light up the LED lamp, which reflects that the prepared solid-state electrolyte has the characteristics of reliability and safety.

[0095] like Figure 14 As shown, when the battery is stacked to a capacity of 1Ah, the LFP soft-pack battery based on Example 2 has a high initial capacity (896mAh). After 200 cycles, it can provide a capacity of 702mAh, showing strong application prospects.

[0096] Test Example 7

[0097] Example 1 and LiNi 0.5 Co 0.2 Mn 0.3 O2 (NCM-523) and LiMn2O4 (LMO) positive electrodes were used to assemble soft pack batteries, and their charging voltages were 4.5V and 4.3V respectively. Figure 15 As shown, the NCM-523 and LMO soft-pack batteries driven by the electrolyte in Example 1 also exhibited high capacity, indicating their wide applicability.

[0098] Example 3

[0099] This embodiment provides a composite solid electrolyte membrane, and its preparation method is basically the same as that of Example 1, except that the mass of MOF used in step (2) is 0.04 g; in step (4), the pre-lithiated ZIF-8 material is dissolved in DMF according to 5 wt %; the remaining operations are the same to obtain a composite solid electrolyte membrane.

[0100] Table 1

[0101]

[0102]

[0103] The basic property parameters of the obtained solid electrolyte film are shown in Table 1, which also shows good physical and electrochemical properties.

[0104] Example 4

[0105] This embodiment provides a composite solid electrolyte membrane, and its preparation method is basically the same as that of Example 1, except that in step (1), the mass of LiTFSI is 16.8 g (6 mol L -1 ); the MOF type used in step (2) is MOF-801; the remaining operations are the same to obtain a composite solid electrolyte film.

[0106] The basic property parameters of the obtained solid electrolyte film are shown in Table 1, which also shows good physical and electrochemical properties.

[0107] Example 5

[0108] This embodiment provides a composite solid electrolyte membrane, and its preparation method is basically the same as that of Example 1, except that the MOF type used in step (2) is ZIF-8, with a mass of 0.4 g; the polymer used in step (3) is polyacrylonitrile (PAN, molecular weight of 150,000), the organic solvent is acetone, and the dissolution concentration is 25 wt%; in step (4), the pre-lithiated ZIF-8 material is dissolved in acetone at 5 wt%; step (6) is scraped evenly using a 400 μm film scraper; the remaining operations are the same to obtain a composite solid electrolyte film.

[0109] The basic property parameters of the obtained solid electrolyte film are shown in Table 1, which also shows good physical and electrochemical properties.

[0110] Example 6

[0111] This embodiment provides a composite solid electrolyte membrane, the preparation method of which is basically the same as that of Example 1, except that the MOF used in step (2) is ZIF-8, with a mass of 0.04 g; the polymer used in step (3) is polymethyl methacrylate (PMMA, molecular weight of 500,000), which is dissolved in acetonitrile at a mass concentration of 5 wt%; in step (4), the pre-lithiated ZIF-8 material is dissolved in acetonitrile at a mass concentration of 15 wt%; the remaining operations are the same to obtain a composite solid electrolyte membrane.

[0112] The basic property parameters of the obtained solid electrolyte film are shown in Table 1, which also shows good physical and electrochemical properties.

Claims

1. A method for preparing a composite polymer solid electrolyte membrane, characterized in that: The following steps are involved: (1) dissolving a lithium salt in a first organic solvent to obtain a lithium salt solution a; dissolving the polymer in a second organic solvent to obtain a mixed solution b; (2) immersing the MOF material in a lithium salt solution a so that the pores of the MOF material adsorb lithium salts to obtain a pre-lithiated MOF material; (3) dissolving the pre-lithiated MOF material obtained in step (2) in a third organic solvent to obtain a mixed solution c; (4) uniformly mixing the mixed solution b and the mixed solution c to obtain a mixed solution d; (5) forming a film of the mixed solution d obtained in step (4) to obtain a MOF-based composite membrane; (6) Immersing the MOF-based composite membrane obtained in step (5) in a lithium salt solution a for activation to obtain a composite polymer solid electrolyte membrane.

2. The method for preparing a composite polymer solid electrolyte membrane according to claim 1, wherein: The lithium salt is at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium perchlorate, lithium trifluoromethanesulfonate, lithium bistrifluoromethanesulfonyl imide, and lithium bisoxalatoborate; The polymer is at least one of polyethylene oxide, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polymethyl methacrylate, and polyacrylonitrile; The MOF material is a porous structure material formed by the coordination of at least one metal ion or metal ion cluster and an organic ligand; The metal ion is Mg 2+ 、Al 3+ , Ca 2+ 、Ti 4+ 、V 4+ 、V 3+ 、V 2+ Cr 3+ 、Mn 3+ 、Mn 2+ 、Fe 3+ 、Fe 2+ 、Co 3+ 、Co 2+ 、Ni 2+ 、Ni + 、Cu 2+ 、Cu + 、Zn 2+ 、Ga 3+ 、Ge 4+ 、Ge 2+ 、As 5+ 、As 3+ 、As + 、Y 3+ 、Zr 4+ 、Mo 3+ 、Pd 2+ 、Pd + , Pt 2+ , Pt + 、Ag + 、Cd 2+ 、In 3+ 、La 3+ 、Ce 4+ 、Ce 3+ , Hf 4+ At least one of; The organic ligands are terephthalic acid, 2-methylimidazole, benzene-1,2,4,5-tetracarboxylic acid, 5-nitroisophthalic acid, isophthalic acid, nicotinic acid, 3-nitrophthalic acid, imidazole, 5-aminoisophthalic acid, isonicotinic acid, 1,3,5-tricarboxylic acid benzene, 2,3-pyridinedicarboxylic acid, 2,2'-bipyridine, 1,4-cyclohexanedicarboxylic acid, thiophene-2,5-dicarboxylic acid, pyrazine, butynedioic acid, [1,1'-biphenyl]-4-carboxylic acid, trans-1,4-cyclohexanedicarboxylic acid, cis-1,2 -cyclohexanedicarboxylic acid, 2,3,5,6-tetrafluoroterephthalic acid, 2-nitroterephthalic acid, pyrazine-2,3-dicarboxylic acid, 4,4'-biphenyldicarboxylic acid, fumaric acid, 3,4-pyridinedicarboxylic acid, 2,4-pyridinedicarboxylic acid, 4-aminobiphenyldicarboxylic acid, salicylic acid azine, 1H-imidazole-4,5-dicarboxylic acid, 1H-pyrazole-3,5-dicarboxylic acid hydrate, 4,4'-bipyridine, 3,6-di-2-pyridyl-1,2,4,5-tetrazine, 2,5-dibromoterephthalic acid, 2,5- Dichlorobenzoic acid, trans-1,2-cyclohexanedicarboxylic acid, 3,5-pyrazoledicarboxylic acid, (1R,2R)-1,2-cyclohexanedicarboxylic acid, 2,2'-biphenyldicarboxylic acid, 3,5-pyridinedicarboxylic acid, trimellitic acid, naphthalene-1,4-dicarboxylic acid, 4-hydroxyphthalic acid, 2,5-dihydroxyterephthalic acid, 5-hydroxyisophthalic acid, 1,4-phenylenedicarboxylic acid, 4-carboxyphenylacetic acid, 2-aminoterephthalic acid, cyclohexane-1,3-dicarboxylic acid, cis-1,4-cyclohexanedicarboxylic acid, 2 ,6-naphthalene dicarboxylic acid, cyclohexane-1,2,4,5-tetracarboxylic acid, 2-bromoterephthalic acid, 9-anthracenecarboxylic acid, 1,4-dibromo-2,5-diiodobenzene, 4,4'-dimethoxy-1,1'-biphenyl, 1-ethyl-2-methylquinolin-1-ium iodide, 1-ethyl-3-vinylimidazolium bromide, 1,3-bis(2,6-diisopropylphenyl)imidazolium chloride, iron phthalocyanine, 1,3-dibromo-5-(tert-butyl)benzene, tetrafluorophthalic acid, and tetrachlorophthalic acid hemihydrate.

3. The method for preparing a composite polymer solid electrolyte membrane according to claim 1, wherein: The first organic solvent is at least one of ethylene carbonate, diethyl carbonate, dimethyl carbonate, and ethyl methyl carbonate; The second organic solvent is at least one of N,N-dimethylformamide, dimethylacetamide, N-methylpyrrolidone, chloroform, dichloromethane, acetonitrile, and acetone; The third organic solvent is at least one of N,N-dimethylformamide, dimethylacetamide, N-methylpyrrolidone, chloroform, dichloromethane, acetonitrile, and acetone.

4. The method for preparing a composite polymer solid electrolyte membrane according to claim 1, wherein: The mass ratio of MOF material to polymer is 1:1 to 10; The lithium salt concentration in lithium salt solution a is 1 to 6 mol L -1 ; The polymer concentration in the mixed solution b is 5 wt% to 25 wt%; The concentration of the pre-lithiated MOF material in the mixed solution c is 5 wt % to 15 wt %.

5. The method for preparing a composite polymer solid electrolyte membrane according to claim 1, wherein: In step (5), the mixed solution d is poured on the substrate to form a film using a casting method or a solution casting method.

6. The method for preparing a composite polymer solid electrolyte membrane according to claim 5, characterized in that: The thickness of the mixed solution d cast on the substrate is 200 to 400 μm; after drying, the thickness of the obtained MOF-based composite film does not exceed 20 μm.

7. The method for preparing a composite polymer solid electrolyte membrane according to claim 1, wherein: In step (2), the MOF material is immersed in lithium salt solution a for 48 to 72 hours; In step (6), the MOF-based composite membrane is immersed in a lithium salt solution a for activation for 2 to 12 hours.

8. A composite polymer solid electrolyte membrane prepared by the preparation method according to any one of claims 1 to 7.

9. Use of the composite polymer solid electrolyte membrane according to claim 8 in the preparation of an electrochemical device.

10. An electrochemical device, characterized in that It comprises a positive electrode sheet, a negative electrode sheet and the composite polymer solid electrolyte membrane according to claim 8.

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