Polymer solid electrolyte, preparation method and application thereof

Abstract

The application discloses a kind of polymer solid electrolyte and its preparation method and application, the preparation method of polymer solid electrolyte includes precursor solution in 1~20T strong magnetic field in situ polymerization obtains the polymer solid electrolyte, the precursor solution includes polymer matrix, electrolyte salt and solvent, and does not contain magnetic material;The direction of the magnetic field is perpendicular to precursor solution surface.The application utilizes strong magnetic field to reduce polymer crystallinity, induces polymer molecular chain ordered arrangement, simultaneously locks this structure by in-situ polymerization.The technology constructs high-efficiency ion transmission network in polymer under the premise of not introducing magnetic filler, significantly improves ion conductivity (room temperature ion conductivity>1 mS / cm), assembles into all-solid-state battery, obtains good ion transference number, oxidation voltage window, first discharge capacity and first coulomb efficiency.

Description

Technical Field

[0001] This invention relates to the field of solid-state battery technology, specifically to an in-situ polymer solid electrolyte based on direct control of polymer chain orientation by a strong magnetic field, its preparation method, and its application. Background Technology

[0002] With the rapid development of new energy vehicles and large-scale energy storage technologies, the demand for high-energy-density and high-safety rechargeable batteries is becoming increasingly urgent. Traditional liquid lithium-ion batteries pose serious safety hazards due to the use of flammable organic electrolytes, such as leakage, combustion, and even explosion. Replacing liquid electrolytes with solid electrolytes is a key approach to solving these problems.

[0003] Polymer solid electrolytes are considered a key direction for the commercialization of all-solid-state batteries due to their advantages such as light weight, good flexibility, excellent processing performance, and good contact with the electrode interface. However, in polymer electrolytes prepared by conventional solution casting or hot pressing methods, the polymer crystallinity is high, the chain segment arrangement is disordered, the ion transport channels are not fully optimized, and the room temperature ionic conductivity is still difficult to exceed 10. -4 The S / cm level is significantly lower than the threshold for commercial application (>1 mS / cm).

[0004] In recent years, magnetic field-assisted technology has shown great potential in the preparation of polymer composite electrolytes (comprising polymers and active fillers). For example, Chinese patent application CN111403804A describes the use of magnetic field-induced magnetic composite fibers (Fe3O4 / lithium lanthanum titanate) vertically aligned on a polymer matrix, which increases the polymer's ionic conductivity to 1.7 × 10⁻⁶. -4S / cm. Chinese patent application CN118800949A uses a magnetic field (0.1-5 T) combined with gamma-ray irradiation for in-situ curing to achieve directional alignment of SiO2@Fe3O4 nanoparticles and reduce interfacial impedance. Chinese patent application CN117438645A uses a vertical magnetic field (1.1-1.4 T) to guide the orientation of Fe3O4@SiO2 hollow nanorods, followed by UV curing to form vertical lithium-ion channels. Chinese patent application CN106654369A uses a 0.5 T magnetic field to regulate the vertical alignment of Fe3O4 nanorods in a PVDF-HFP matrix, improving the ionic conductivity of the gel electrolyte. Chinese patent application CN111725566A uses a magnetic field (0.5-1.4 T) to induce the orientation of organically modified sepiolite@Fe3O8 nanofibers, enhancing the mechanical properties of PEO-based electrolytes. Chinese patent application CN115483432A describes the directional alignment of LAGP@Fe3O4 core-shell nanowires using a magnetic field (0.2-0.5T) to form a continuous ion-permeable layer. Chinese patent application CN120767407A uses a 0.1-0.5T magnetic field to drive the enrichment of organometallic acid salt ions on the membrane surface, forming a fast ion-conducting interface. Chinese patent application CN112421122A uses a 0.8T magnetic field to achieve a two-dimensional ordered arrangement of Fe3O4 nanoparticles within a block polymer, thereby improving conductivity.

[0005] The above analysis shows that existing magnetically controlled polymer battery materials generally employ an indirect control strategy. This involves adding magnetic nanoparticles (such as Fe3O4 or SiO2@Fe3O4) to the polymer matrix and using an external magnetic field (0.1-5 T) to induce these particles to align and form ion transport channels. Although this method can effectively improve ionic conductivity, it has the following fundamental limitations: 1) Loss of flexibility: Rigid magnetic fillers destroy the intrinsic flexibility of the polymer, leading to poor contact between the electrolyte membrane and the electrode interface; 2) Secondary interface problems: The incompatibility between magnetic particles and the polymer matrix introduces new interface defects (such as Fe3O4 agglomeration), hindering ion transport; 3) Process complexity: It requires multi-step control of the magnetic field and curing conditions (such as ultraviolet / irradiation), and it is difficult to ensure uniform distribution of the filler.

[0006] Chinese patent application CN120767407A discloses a polymer electrolyte membrane, its preparation method, and its application. Comparative Example 2 discloses the following: A polymer, plasticizer, and lithium salt are dissolved in an organic solvent to obtain a polymer electrolyte slurry; wherein the polymer has a mass of 1 g, the plasticizer has a mass of 0.2 g, and the lithium salt has a mass of 362 mg; wherein the polymer is polyethylene oxide, the plasticizer is succinate, and the lithium salt is lithium bis(trifluoromethanesulfonyl)imide; the organic solvent is anhydrous acetonitrile, and the amount used is 25 ml. The polymer electrolyte slurry is coated onto a template, subjected to static treatment under an external magnetic field, and then vacuum dried to obtain a polymer electrolyte membrane; wherein the direction of the external magnetic field is perpendicular to the template, the template material is polytetrafluoroethylene, the thickness of the polymer electrolyte membrane is 20 μm, the magnitude of the external magnetic field is 0.3 T, the static treatment time is 12 h, and the vacuum drying temperature is 60 °C for 12 h. They disclosed a method of directly treating the electrolyte membrane using a magnetic field, but the ionic conductivity of the solid electrolyte membrane they prepared was 0.85 mS / cm, which could not meet the requirements for commercial application (>1 mS / cm). Summary of the Invention

[0007] The technical problem to be solved by this invention is how to improve the room temperature ionic conductivity of polymer solid electrolyte to above 1 mS / cm without adding any magnetic filler, so as to meet the requirements of commercial application.

[0008] To achieve the above objectives, the present invention employs the following technical means:

[0009] A polymer solid electrolyte is prepared by means of in-situ polymerization of a precursor solution under a strong magnetic field of 1-20T to obtain the polymer solid electrolyte; the precursor solution includes a polymer matrix, an electrolyte salt and a solvent, and does not contain magnetic materials; the direction of the magnetic field is perpendicular to the surface of the precursor solution.

[0010] Beneficial effects: The precursor solution of this invention does not contain magnetic materials. The strong magnetic field acts directly on the polymer molecular chains, inducing them to form an ordered arrangement structure. This orientation structure is locked through in-situ polymerization, constructing a highly efficient ion transport channel. Simultaneously, the addition of a magnetic field during in-situ polymerization effectively reduces the crystallinity of the polymer, further optimizing ion transport.

[0011] Preferably, the magnetic material is one or a mixture of two of inorganic magnetic materials and organic magnetic materials.

[0012] Preferably, the precursor solution is composed of a polymer matrix, an electrolyte salt, and a solvent; or, the precursor solution is composed of a polymer matrix, an electrolyte salt, a solvent, an initiator, and / or a crosslinking agent.

[0013] Preferably, the polymer matrix is ​​selected from one or more of polyvinylidene fluoride polymers, polyether polymers, polycarbonate polymers, polyacrylonitrile polymers, polymethyl methacrylate polymers, polysiloxane polymers, and single-ion conductor polymers.

[0014] Preferably, the polymer matrix is ​​one or a mixture of PEO, PMMA, and PVDF.

[0015] Preferably, the electrolyte salt is a lithium salt and / or a sodium salt.

[0016] Preferably, the electrolyte salt includes one of lithium metal ion salt and sodium metal ion salt, corresponding to the polymer solid electrolyte of lithium-ion all-solid-state battery and the polymer solid electrolyte of sodium-ion all-solid-state battery, respectively.

[0017] Preferably, the lithium salt is selected from one or more of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium perchlorate (LiClO4), lithium hexafluorophosphate (LiPF6), and lithium difluorooxalate borate (LiDFOB).

[0018] Preferably, the sodium salt is selected from one or more of sodium bis(trifluoromethanesulfonyl)imide (NaTFSI), sodium perchlorate (NaClO4), and sodium hexafluorophosphate (NaPF6).

[0019] Preferably, the precursor solution further includes a crosslinking agent and / or an initiator.

[0020] Preferably, the initiator is one or both of thermal initiators and photoinitiators; the crosslinking agent is selected from one or more of polyethylene glycol diacrylate (PEGDA), polyethylene glycol dimethyl ether (PEGDME), trimethylolpropane triacrylate (TMPTA), and trimethylolpropane trimethacrylate (TMPTMA).

[0021] Preferably, the thermal initiator is one or a mixture of two of azobisisobutyronitrile and benzoyl peroxide; the photoinitiator is one or a mixture of two of 2,2-dimethoxy-2-phenylacetophenone and 2-hydroxy-2-methyl-1-phenyl-1-propanone (HMPP).

[0022] Preferably, the solvent is one or a mixture of N,N-dimethylformamide, acetonitrile, and succinic anion.

[0023] Preferably, the crosslinking agent has a mass of 5-60% of the polymer matrix mass, more preferably 5-20%; or a volume of 3-8 vol% of the precursor solution volume, preferably one of 3 vol%, 4 vol%, 5 vol%, 6 vol%, 7 vol%, and 8 vol%.

[0024] Preferably, the mass of the crosslinking agent is one of 5%, 8%, 10%, 15%, 20%, 25%, 35%, 40%, 45%, 50%, and 60% of the polymer matrix mass.

[0025] Preferably, the initiator accounts for 0.5-2.5% of the polymer matrix mass, and more preferably one of 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.5%, 2%, and 2.5%.

[0026] Preferably, the polymer solid electrolyte has a room temperature ionic conductivity of 1.02-5.51 mS / cm, an ion transference number of 0.56-0.86, an oxidation voltage window of 4.3-4.95 V, an initial discharge capacity of 115.5-233.5 mAh / g, and an initial coulombic efficiency of 90.3-96.8%.

[0027] Preferably, the mass ratio of polymer matrix to electrolyte salt is 1:0.1-0.55, more preferably one of 1:0.1, 1:0.25, 1:0.33, 1:0.35, 1:0.425, 1:0.48, and 1:0.55; or the molar ratio of polymer matrix to electrolyte salt is 1:0.1-0.2; more preferably 1:0.15.

[0028] Preferably, the polymer matrix accounts for 10-35% of the total mass of the polymer matrix and solvent; more preferably, it is one of 10%, 12%, 15%, 20%, 25.3%, 30%, and 35%.

[0029] The polymer solid electrolyte of the present invention has a high room temperature ionic conductivity (greater than 1 mS / cm). Specifically, the present invention reduces the crystallinity of the polymer and enhances the chain segment mobility through the synergistic effect of strong magnetic field induction and in-situ polymerization technology. At the same time, it enables the polymer crystalline molecular chains to be arranged in an orderly manner, constructing an efficient ion transport network at the atomic and molecular level. Without introducing any filler, the room temperature ionic conductivity of the polymer electrolyte is significantly improved.

[0030] This invention also proposes a method for preparing a polymer solid electrolyte, comprising the following steps: S1. Mix all raw materials evenly to obtain a precursor solution; S2. Cast or coat the obtained precursor solution onto the substrate; S3. Place the system obtained in S2 in a magnetic field generating device and apply a steady-state strong magnetic field with a strength of 1T~20T. In the magnetic field environment, carry out an in-situ polymerization reaction to solidify the precursor solution into a polymer solid electrolyte.

[0031] Preferably, in S1, the mass of the polymer matrix is ​​10% to 95% of the total solid content of the precursor solution; and the mass of the electrolyte salt is 5% to 80% of the total solid content of the precursor solution.

[0032] Preferably, in S1, the mass of the polymer matrix is ​​one of the following: 10%, 13%, 15%, 20%, 21.5%, 25%, 27%, 30%, 35%, 38.5%, 40%, 45%, 50%, 55%, 58%, 60%, 62%, 65%, 67.6%, 70%, 71.4%, 72.2%, 73.8%, 75%, 80%, 85%, 90%, 95% of the total solid content of the precursor solution. The mass of the electrolyte salt is one of the following percentages of the total solid content of the precursor solution: 5%, 7%, 8%, 9%, 10%, 15%, 17%, 18.5%, 20%, 23.8%, 25%, 27%, 30%, 32.4%, 35%, 40%, 44%, 45%, 48%, 50%, 51%, 55%, 57%, 59%, 60%, 62%, 65%, 70%, 75%, 77%, and 80%.

[0033] Preferably, in S1, the mixture is homogeneous under stirring conditions, the stirring temperature is 20℃~80℃, the stirring time is 0.5~24 hours, and the stirring speed is 100~1000 rpm.

[0034] Preferably, the thickness of the polymer solid electrolyte is 80-100 μm.

[0035] Preferably, in S3, the in-situ polymerization reaction is initiated by one or more of the following methods: thermal initiation, ultraviolet light initiation, electro-initiation, or electron beam irradiation initiation; the direction of the strong magnetic field is perpendicular to the electrolyte membrane plane or parallel to the ion transport direction.

[0036] Preferably, the temperature for thermally initiated polymerization is 40-80℃, and the time is 2-6 hours.

[0037] The substrate carrying the precursor solution is placed in the working area of ​​a strong magnetic field generator; the output parameters of the magnetic field generator are set, and a steady-state strong magnetic field with a strength of 1T~20T is applied; under the condition of maintaining the steady-state magnetic field environment, the precursor solution is triggered to undergo an in-situ polymerization reaction; by controlling the triggering conditions, the precursor solution is completely solidified under the action of the magnetic field to form a polymer solid electrolyte with low crystallinity and molecular chain orientation structure.

[0038] Preferably, for electrolytes prepared using a solvent system, they are peeled off from the substrate and placed in a vacuum drying device for drying to remove residual organic solvents; the drying temperature is 30℃~80℃, the vacuum degree is -0.1 MPa~-0.01 MPa, and the drying time is 6~48 hours.

[0039] The present invention also proposes a battery comprising the polymer solid electrolyte or the polymer solid electrolyte prepared by the preparation method described above.

[0040] Preferably, the battery is one of an all-solid-state lithium-ion battery or an all-solid-state sodium-ion battery.

[0041] Compared with the prior art, the present invention has the following beneficial effects: (1) Breakthrough room temperature ionic conductivity: The precursor solution of this invention contains no magnetic filler except for the polymer matrix, alkali metal salt, initiator and / or crosslinking agent. The magnetic field acts directly on the polymer. Through the synergistic effect of strong magnetic field induction and in-situ polymerization, the polymer molecular chains are arranged in an orderly manner along the magnetic field direction to form a continuous and efficient ion transport channel. This enables the room temperature ionic conductivity of the electrolyte to reach more than 1 mS / cm, which meets the requirements for commercial application and solves the long-standing problem of low room temperature conductivity of polymer electrolytes.

[0042] (2) No magnetic filler required, simplifying the process: This invention does not require the introduction of magnetic materials, avoiding problems such as filler agglomeration and increased interfacial impedance. The process is simpler, the cost is lower, and it is conducive to achieving the lightweighting of electrolytes.

[0043] (3) High versatility and can be extended to sodium battery system: The method of the present invention is not only applicable to lithium salt system, but can also be directly extended to sodium salt system, providing a high-performance electrolyte solution for the development of sodium solid-state battery. Attached Figure Description

[0044] Figure 1 Schematic diagram of ion migration channels under no magnetic field / weak magnetic field and strong magnetic field; Figure 2 This data represents the variation of PEO crystallinity with magnetic field strength. Figure 3 This is a schematic diagram comparing the crystallinity under no magnetic field / weak magnetic field and strong magnetic field conditions. Detailed Implementation

[0045] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0046] Unless otherwise specified, all test materials and reagents used in the following examples are commercially available.

[0047] Unless otherwise specified in the embodiments, the techniques or conditions described in the literature in this field or in accordance with the product manual may be followed.

[0048] The PEO described below was purchased from Dongguan Kelude New Energy Technology Co., Ltd. The PMMA was purchased from Shanghai Maclean Biochemical Technology Co., Ltd. The PVDF was purchased from Dongguan Kelude New Energy Technology Co., Ltd.

[0049] Example 1 A method for preparing a polymer solid electrolyte with high ionic conductivity induced by a strong magnetic field specifically includes the following steps: Step 1: Weigh out PEO (Mw=1×10⁻⁶) 6 The precursor solution was dissolved in N,N-dimethylformamide (DMF) with a solid content of 15 wt%. Lithium salt LiTFSI (33 wt% of the total mass of polymer PEO), crosslinking agent PEGDA (5 wt% of the total mass of polymer PEO), and thermal initiator azobisisobutyronitrile (AIBN, 0.5 wt% of the total mass of PEO) were added. The mixture was stirred at 50 °C and 100 rpm for 4 h until completely dissolved, yielding a homogeneous and transparent precursor solution.

[0050] Step 2: The precursor solution is cast into a polytetrafluoroethylene mold, transferred to a magnetic field generator, and a magnetic field with a strength of 10T is applied. The mixture is then polymerized at 50°C for 6 hours to solidify the precursor solution into a film. The applied magnetic field is perpendicular to the film plane. Step 3: Post-processing: The obtained electrolyte membrane was transferred to a -0.1 MPa vacuum drying oven and dried at 60°C for 12 h to remove residual solvent, resulting in a 100 μm thick PEO solid electrolyte.

[0051] The solid electrolytes prepared above were subjected to ionic conductivity, ion transport number, and electrochemical window tests. Ionic conductivity was tested using AC impedance spectroscopy; ion transport number was tested using steady-state current spectroscopy after assembling a Li / polymer solid electrolyte / Li symmetric cell; and the electrochemical window of the solid electrolyte was tested using linear sweep voltammetry (LSV), with the test structure being Li / solid electrolyte / stainless steel sheet, the test potential range being from open circuit potential to 6V, and the scan rate being 0.5 mV / s. Li / polymer solid electrolyte / LiNi was also assembled. 0.8 Co 0.1 Mn 0.1 Cyclic specific capacity tests were conducted on O2 (NCM811) coin cells. The room temperature ionic conductivity of the solid electrolyte structure was measured to be 3.51 mS / cm, the ion transference number was 0.83, the oxidation voltage window was 4.55 V, the initial discharge capacity was 233.5 mAh / g, and the initial coulombic efficiency was 95.8%.

[0052] Example 2 A method for preparing a polymer solid electrolyte with high ionic conductivity induced by a strong magnetic field specifically includes the following steps: Step 1: Weigh PEO (weight-average molecular weight M) W =6×10 5 The precursor solution was dissolved in acetonitrile, with a solid content of 10 wt%. Lithium salt LiClO4 (53 wt% of the total mass of polymer PEO), crosslinking agent polyethylene glycol diacrylate (PEGDA, 8 wt% of the mass of PEO), and thermal initiator benzoyl peroxide (BPO, 0.6 wt% of the total mass of PEO) were added. The mixture was stirred at 30°C and 1000 rpm for 12 h until completely dissolved, yielding a homogeneous and transparent precursor solution.

[0053] Step 2: Cast the precursor solution into a polytetrafluoroethylene mold, transfer it to a magnetic field generator, apply a magnetic field with a strength of 5 T, and polymerize at 50°C for 6 h to solidify the precursor solution into a film; the applied magnetic field is perpendicular to the film plane. Step 3: Post-processing: The obtained electrolyte membrane was transferred to a -0.1 MPa vacuum drying oven and dried at 60°C for 12 h to remove residual solvent, resulting in a 100 μm thick PEO solid electrolyte.

[0054] The performance was tested using the same method as in Example 1. The room temperature ionic conductivity of the solid electrolyte with this structure was measured to be 1.51 mS / cm, the ion transference number to be 0.81, the oxidation voltage window to be 4.45 V, the initial discharge capacity to be 225.5 mAh / g, and the initial coulombic efficiency to be 96.8%.

[0055] Example 3 A method for preparing a polymer solid electrolyte with high ionic conductivity induced by a strong magnetic field specifically includes the following steps: Step 1: Preparation of precursor solution: Weigh PEO (Mw=1×10⁻³) at a mass ratio of 7:3. 6 ) and PMMA (Mw=5×10 5 The precursor solution was dissolved in acetonitrile, with a solid content of 12 wt%. Lithium salt LiPF6 (25 wt% of the total mass of polymers PEO and PMMA), crosslinking agent polyethylene glycol dimethyl ether (PEGDME, 10 wt% of the total mass of polymers PEO and PMMA), and thermal initiator AIBN (0.5 wt% of the total mass of polymers PEO and PMMA) were added. The mixture was stirred at 45°C and 1000 rpm for 4 h until completely dissolved, yielding a homogeneous and transparent precursor solution.

[0056] Step 2: In-situ polymerization under a magnetic field: The precursor solution is cast into a polytetrafluoroethylene mold, transferred to a magnetic field generator, and a magnetic field with a strength of 17 T is applied. Polymerization is carried out at 65℃ for 5 h to solidify the precursor solution into a film; the applied magnetic field is perpendicular to the film plane. Step 3: Post-processing: The obtained electrolyte membrane was transferred to a -0.1 MPa vacuum drying oven and dried at 60°C for 12 h to remove residual solvent, resulting in a 90 μm thick PEO / PMMA composite solid electrolyte.

[0057] The performance was tested using the same method as in Example 1. The room temperature ionic conductivity of the solid electrolyte with this structure was measured to be 5.51 mS / cm, the ion transference number to be 0.81, the oxidation voltage window to be 4.55 V, the initial discharge capacity to be 228.3 mAh / g, and the initial coulombic efficiency to be 93.8%.

[0058] Example 4 A method for preparing a polymer solid electrolyte with high ionic conductivity induced by a strong magnetic field specifically includes the following steps: Step 1: Weigh out PVDF with a mass ratio of 3:2 (weight-average molecular weight Mw = 5 × 10⁻⁶). 5 ) and PEO (Mw=1×10 6 The precursor solution was dissolved in N,N-dimethylformamide (DMF) with a solid content of 15 wt%. Sodium salt NaTFSI (35 wt% of the total mass of polymers PVDF and PEO) and crosslinking agent PEGDA (5 wt% of the total mass of polymers PVDF and PEO) were added. The mixture was stirred at 50°C and 1000 rpm for 4 h until completely dissolved, yielding a homogeneous and transparent precursor solution.

[0059] Step 2: The precursor solution is cast into a polytetrafluoroethylene mold, transferred to a magnetic field generator, and a magnetic field with a strength of 15 T is applied. The mixture is then polymerized at 40°C for 6 hours to solidify the precursor solution into a film. The applied magnetic field is perpendicular to the film plane. Step 3: Post-processing: The obtained electrolyte membrane was transferred to a -0.1 MPa vacuum drying oven and dried at 60°C for 12 h to remove residual solvent, resulting in an 80 μm thick PVDF / PEO solid electrolyte.

[0060] The solid electrolyte prepared above was subjected to ionic conductivity, ion transport number, and electrochemical window tests. Ionic conductivity was tested using AC impedance spectroscopy. A Na / polymer solid electrolyte / Na symmetric cell was assembled, and ion transport number was tested using steady-state current spectroscopy. The electrochemical window of the solid electrolyte was tested using linear sweep voltammetry (LSV), with the test structure being Na / solid electrolyte / stainless steel sheet. The test potential range was from open circuit potential to 6V, and the scan rate was 0.5 mV / s. Cyclic specific capacity tests were conducted on a Na / polymer solid electrolyte / sodium nickel iron manganese oxide electrode NT0203 coin cell. The room temperature ionic conductivity of this composite solid electrolyte structure reached 3.58 mS / cm, the ion transport number reached 0.86, the oxidation voltage window was 4.55 V, the initial discharge capacity was 115.5 mAh / g, and the initial coulombic efficiency was 95.4%.

[0061] Example 5 A method for preparing a polymer solid electrolyte with high ionic conductivity induced by a strong magnetic field specifically includes the following steps: Step 1: Weigh out PVDF with a mass ratio of 3:2 (weight-average molecular weight Mw = 5 × 10⁻⁶). 5 ) and PEO (Mw=1×10 6 The precursor was dissolved in N,N-dimethylformamide (DMF) with a solid content of 15 wt%. Sodium salt NaClO4 (48 wt% of the total mass of polymers PVDF and PEO) was added, and the mixture was stirred at 50°C and 800 rpm for 4 h until completely dissolved, yielding a homogeneous and transparent precursor solution.

[0062] Step 2: Cast the precursor solution into a polytetrafluoroethylene mold, transfer it to a magnetic field generator, apply a magnetic field with a strength of 20 T, and polymerize at 80°C for 2 h to solidify the precursor solution into a film; the applied magnetic field is perpendicular to the film plane. Step 3: Transfer the obtained electrolyte membrane to a -0.1 MPa vacuum drying oven and dry at 60°C for 12 h to remove residual solvent, thereby obtaining a 100 μm thick PVDF-PEO solid electrolyte.

[0063] The solid electrolyte prepared above was subjected to ionic conductivity, ion transport number, and electrochemical window tests. Ionic conductivity was tested using AC impedance spectroscopy. A Na / polymer solid electrolyte / Na symmetric cell was assembled, and ion transport number was tested using steady-state current spectroscopy. The electrochemical window of the solid electrolyte was tested using linear sweep voltammetry (LSV), with the test structure being Na / solid electrolyte / stainless steel sheet. The test potential range was from open circuit potential to 6V, and the scan rate was 0.5 mV / s. Cyclic specific capacity tests were conducted on a Na / polymer solid electrolyte / sodium iron pyrophosphate (NFPP-S05) coin cell. The room temperature ionic conductivity of this solid electrolyte structure reached 2.58 mS / cm, the ion transport number reached 0.66, the oxidation voltage window was 4.95 V, the initial discharge capacity was 130.5 mAh / g, and the initial coulombic efficiency was 94.8%.

[0064] Example 6 A method for preparing a polymer solid electrolyte with high ionic conductivity induced by a strong magnetic field specifically includes the following steps: Step 1: Weigh out PVDF with a mass ratio of 5:3 (weight-average molecular weight Mw = 5 × 10⁻⁶). 5 ) and PEO (Mw=1×10 6 The precursor was dissolved in N,N-dimethylformamide (DMF) with a solid content of 12 wt%. Sodium salt NaPF6 was added, with a molar ratio of sodium salt to polymer monomers (PVDF and PEO) of 0.15:1. The mixture was stirred at 25°C and 1000 rpm for 13 h until completely dissolved, yielding a homogeneous and transparent precursor solution.

[0065] Step 2: The precursor solution is cast into a polytetrafluoroethylene mold, transferred to a magnetic field generator, and a magnetic field with a strength of 10 T is applied. The mixture is then polymerized at 40°C for 6 hours to solidify the precursor solution into a film. The applied magnetic field is perpendicular to the film plane. Step 3: Transfer the obtained electrolyte membrane to a -0.1 MPa vacuum drying oven and dry at 60°C for 12 h to remove residual solvent, thus obtaining a 100 μm thick PVDF / PEO solid electrolyte.

[0066] The solid electrolyte prepared above was subjected to ionic conductivity, ion transport number, and electrochemical window tests. Ionic conductivity was tested using AC impedance spectroscopy. A Na / polymer solid electrolyte / Na symmetric cell was assembled, and ion transport number was tested using steady-state current spectroscopy. The electrochemical window of the solid electrolyte was tested using linear sweep voltammetry (LSV), with the test structure being Na / solid electrolyte / stainless steel sheet. The test potential range was from open circuit potential to 6V, and the scan rate was 0.5mV / s. Cyclic specific capacity tests were conducted on a Na / polymer solid electrolyte / sodium iron pyrophosphate (NFPP-SO5) coin cell. The room temperature ionic conductivity of this solid electrolyte structure reached 1.58 mS / cm, the ion transport number reached 0.56, the oxidation voltage window was 4.85V, the initial discharge capacity was 120.5 mAh / g, and the initial coulombic efficiency was 95.8%.

[0067] Example 7 A method for preparing a polymer solid electrolyte with high ionic conductivity induced by a strong magnetic field specifically includes the following steps: Step 1: Weigh 59.0 wt% butadienenitrile (SN) and heat to 60°C, then add 20.0 wt% polyethylene oxide (PEO, Mw=1×10⁻⁶) sequentially. 6 The precursor solution was prepared by mixing 12.0 wt.% trimethylolpropane trimethacrylate (TMPTMA), 8.5 wt.% lithium hexafluorophosphate (LiPF6), and 0.5 wt.% photoinitiator 2,2-dimethoxy-2-phenylacetophenone (DMPA) at 1000 rpm for 2 hours.

[0068] Step 2: Cast the precursor solution into a polytetrafluoroethylene mold, transfer it to a magnetic field generator, apply a magnetic field with a strength of 5 T, and photocur it for 10 minutes under the conditions of emission wavelength of 365 nm and irradiation distance of 1 cm between the ultraviolet light and the precursor solution; the applied magnetic field is perpendicular to the film plane. Step 3: Transfer the obtained electrolyte membrane to a -0.1 MPa vacuum drying oven and dry at 60°C for 12 h to obtain a 100 μm thick SN / PEO solid electrolyte.

[0069] The solid electrolytes prepared above were subjected to ionic conductivity, ion transport number, and electrochemical window tests. Ionic conductivity was tested using AC impedance spectroscopy; ion transport number was tested using steady-state current spectroscopy after assembling a Li / polymer solid electrolyte / Li symmetric cell; and the electrochemical window of the solid electrolyte was tested using linear sweep voltammetry (LSV), with the test structure being Li / solid electrolyte / stainless steel sheet, the test potential range being from open circuit potential to 6V, and the scan rate being 0.5 mV / s. Li / polymer solid electrolyte / LiNi was also assembled. 0.8 Co 0.1 Mn 0.1 Cyclic specific capacity tests were conducted on O2 (NCM811) coin cells. The room temperature ionic conductivity of the solid electrolyte structure was measured to be 1.51 mS / cm, the ion transference number was 0.68, the oxidation voltage window was 4.65 V, the initial discharge capacity was 233.5 mAh / g, and the initial coulombic efficiency was 95.6%.

[0070] Example 8 A method for preparing a polymer solid electrolyte with high ionic conductivity induced by a strong magnetic field specifically includes the following steps: Step 1: Weigh out PEO (Mw=1×10⁻⁶) 6 The precursor solution was dissolved in N,N-dimethylformamide (DMF) with a solid content of 15 wt%. Lithium salt LiTFSI (33 wt% of polymer PEO) and crosslinking agent PEGDA (5 vol% of solution volume) were added. The mixture was magnetically stirred for 30 min (800 rpm) until completely dissolved to obtain the precursor solution. Step 2: The precursor solution is cast into a polytetrafluoroethylene mold, transferred to a magnetic field generator, and a magnetic field with a strength of 3 T is applied. The whole is subjected to electron beam irradiation to induce in-situ curing (59 kGy). After the homogeneous solution is completely cured into a film, the magnet is removed. The applied magnetic field is perpendicular to the film plane. The cured electrolyte is then demolded. Step 3: Transfer the obtained electrolyte membrane to a -0.1MPa vacuum drying oven and dry at 60℃ for 12 h to remove residual solvent, and obtain an 80μm thick PEO solid electrolyte.

[0071] The solid electrolytes prepared above were subjected to ionic conductivity, ion transport number, and electrochemical window tests. Ionic conductivity was tested using AC impedance spectroscopy; ion transport number was tested using steady-state current spectroscopy after assembling a Li / polymer solid electrolyte / Li symmetric cell; and the electrochemical window of the solid electrolyte was tested using linear sweep voltammetry (LSV), with the test structure being Li / solid electrolyte / stainless steel sheet, the test potential range being from open circuit potential to 6V, and the scan rate being 0.5 mV / s. Li / polymer solid electrolyte / LiNi was also assembled.0.8 Co 0.1 Mn 0.1 Cyclic specific capacity tests were conducted on O2 (NCM811) coin cells. The room temperature ionic conductivity of the solid electrolyte structure was measured to be 1.33 mS / cm, the ion transference number was 0.62, the oxidation voltage window was 4.55 V, the initial discharge capacity was 203.5 mAh / g, and the initial coulombic efficiency was 93.6%.

[0072] Example 9 The only difference from Example 1 is that the magnetic field strength is 1T.

[0073] The room temperature ionic conductivity of the solid electrolyte with this structure was measured to be 1.02 mS / cm, the ion transference number to be 0.57, the oxidation voltage window to be 4.3 V, the initial discharge capacity to be 210.3 mAh / g, and the initial coulombic efficiency to be 90.3%.

[0074] Table 1

[0075] Comparative Example 1 The preparation method of the polymer solid electrolyte in this comparative example is basically the same as that in Example 1. The difference is that in step 2, no magnetic field is added during the polymerization process, while the rest remains unchanged, and a polymer solid electrolyte is obtained. The ionic conductivity of the polymer solid electrolyte is 0.18 mS / cm, the ion transference number reaches 0.43, the oxidation voltage window is 4.23V, the initial discharge capacity is 185.5mAh / g, and the initial coulombic efficiency is 85.7% when measured at room temperature.

[0076] Comparative Example 2 The preparation method of the polymer solid electrolyte in this comparative example is basically the same as that in Example 1. The difference is that in step 2, the magnetic field strength is 0.3T, while the rest remains unchanged, and the polymer solid electrolyte is obtained. The ionic conductivity of the polymer solid electrolyte is 0.68 mS / cm, the ion transference number reaches 0.58, the oxidation voltage window is 4.35V, the initial discharge capacity is 195.3mAh / g, and the initial coulombic efficiency is 90.8% when measured at room temperature.

[0077] Comparative Example 3 The preparation method of the polymer solid electrolyte in this comparative example is basically the same as that in Example 1. The difference is that in step 2, a magnetic field of 0.95T is added during the polymerization process, while the rest remains unchanged, to obtain the polymer solid electrolyte. The ionic conductivity of the polymer solid electrolyte was measured to be 0.88 mS / cm, the ion transference number reached 0.63, the oxidation voltage window was 4.43V, the initial discharge capacity was 202.3 mAh / g, and the initial coulombic efficiency was 95.7% at room temperature.

[0078] Comparative Example 4 The preparation method of the polymer solid electrolyte in this comparative example is basically the same as that in Example 1. The difference is that in step 2, a 1T horizontal magnetic field (i.e., parallel to the surface of the precursor solution) is added during the polymerization process, while the rest remains unchanged, to obtain the polymer solid electrolyte. The ionic conductivity of the polymer solid electrolyte was measured to be 0.08 mS / cm, the ion transference number reached 0.41, the oxidation voltage window was 4.23V, the initial discharge capacity was 183.1 mAh / g, and the initial coulombic efficiency was 88.7% at room temperature.

[0079] Table 2

[0080] In Examples 1-9 of this invention, no magnetic filler was added, and a strong magnetic field was used for treatment. This directly utilizes the magnetic field to regulate the polymer chain structure, achieving precise control of the polymer's microstructure (such as crystal orientation) to form rapid ion channels. It also reduces the polymer's crystallinity, enhances chain segment mobility, strengthens material flexibility, and significantly improves the ionic conductivity and interfacial compatibility of the polymer electrolyte. The prepared electrolyte exhibits a room-temperature ionic conductivity of 1.02-5.51 mS / cm. In contrast, Comparative Examples 2-3 used weak magnetic fields of 0.3T and 0.95T. Due to the low diamagnetic coefficient of the polymer, these methods could not achieve the effect of precisely controlling the polymer's microstructure to form rapid ion channels. Furthermore, the magnetic energy was insufficient to reduce the polymer's crystallinity and enhance chain segment mobility. (See schematic diagram below.) Figure 1 and 3 As shown, the room temperature ionic conductivity of the obtained electrolyte membrane is only 0.68 mS / cm and 0.88 mS / cm, both less than 1 mS / cm, which cannot achieve the room temperature ionic conductivity of more than 1 mS / cm required by this invention to meet the requirements for commercial application. In contrast, in Comparative Example 4, a horizontal magnetic field was used, which made the orientation direction of the molecular chain perpendicular to the ion transport direction, thus hindering ion transport. Therefore, the ionic conductivity was only 0.08 mS / cm.

[0081] This invention involves magnetically induced in-situ polymerization and solidification of a mixed precursor solution containing a polymer matrix and an electrolyte salt (lithium salt and / or sodium salt) under a strong magnetic field of 1 T to 20 T. The strong magnetic field directly controls the polymer chain orientation, and post-processing yields a polymer solid electrolyte with high room temperature ionic conductivity (greater than 1 mS / cm). This method utilizes a strong magnetic field to reduce polymer crystallinity and induce ordered arrangement of polymer molecular chains. Combined with in-situ polymerization technology, it locks in the ordered structure, constructing a highly efficient ion transport network without introducing magnetic fillers, thus significantly improving ionic conductivity. The preparation process of this invention is simple and controllable. The one-step in-situ polymerization avoids the multi-step problems of filler dispersion and solidification in traditional magnetic control technology. The resulting electrolyte is suitable for all-solid-state lithium / sodium-ion batteries and lithium metal batteries.

[0082] Weigh out PEO (Mw=1×10) 6 The precursor solution was dissolved in N,N-dimethylformamide (DMF) with a solid content of 15 wt%. The solution was stirred at 50°C for 4 h until completely dissolved, yielding a homogeneous and transparent precursor solution. The precursor solution was cast into a polytetrafluoroethylene mold and transferred to a magnetic field generator. A magnetic field perpendicular to the surface of the precursor solution was applied, with a strength of 0T, 0.3T, 3T, 9T, 15T, or 20T. Polymerization was carried out at 50°C for 6 h to solidify the precursor solution into a film. The film was then dried at 60°C for 12 h in a -0.1 MPa vacuum drying oven to remove residual solvent, yielding a PEO sample. The crystallinity of the sample was tested, and the results are as follows: Figure 2 As shown, it can be seen that a magnetic field can reduce the crystallinity of PEO.

[0083] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A polymer solid electrolyte, characterized in that: The preparation method includes in-situ polymerization of the precursor solution under a strong magnetic field of 1~20T to obtain the polymer solid electrolyte; the precursor solution includes a polymer matrix, an electrolyte salt and a solvent, and does not contain magnetic materials; the direction of the magnetic field is perpendicular to the surface of the precursor solution.

2. The polymer solid electrolyte according to claim 1, characterized in that: The polymer matrix is ​​selected from one or more of the following: polyvinylidene fluoride polymers, polyether polymers, polycarbonate polymers, polyacrylonitrile polymers, polymethyl methacrylate polymers, polysiloxane polymers, and single-ion conductor polymers.

3. The polymer solid electrolyte according to claim 1, characterized in that: The electrolyte salt is a lithium salt and / or a sodium salt.

4. The polymer solid electrolyte according to claim 1, characterized in that: The precursor solution also includes a crosslinking agent and / or an initiator.

5. The polymer solid electrolyte according to claim 4, characterized in that: The initiator is one or both of thermal initiators and photoinitiators; the crosslinking agent is selected from one or more of polyethylene glycol diacrylate, polyethylene glycol dimethyl ether, trimethylolpropane triacrylate, and trimethylolpropane trimethacrylate.

6. The polymer solid electrolyte according to claim 5, characterized in that: The thermal initiator is one or a mixture of two of azobisisobutyronitrile and benzoyl peroxide; the photoinitiator is one or a mixture of two of 2,2-dimethoxy-2-phenylacetophenone and 2-hydroxy-2-methyl-1-phenyl-1-propanone (HMPP).

7. The polymer solid electrolyte according to any one of claims 1-6, characterized in that: Its room temperature ionic conductivity is 1.02-5.51 mS / cm; ion transference number is 0.56-0.86; oxidation voltage window is 4.3-4.95 V; initial discharge capacity is 115.5-233.5 mAh / g; and initial coulombic efficiency is 90.3-96.8%.

8. A method for preparing a polymer solid electrolyte as described in any one of claims 1-7, characterized in that: Includes the following steps: S1. Mix all raw materials evenly to obtain a precursor solution; S2. Cast or coat the obtained precursor solution onto the substrate; S3. Place the system obtained in S2 in a magnetic field generating device and apply a steady-state strong magnetic field with a strength of 1T~20T. In the magnetic field environment, carry out an in-situ polymerization reaction to solidify the precursor solution into a polymer solid electrolyte.

9. The method for preparing the polymer solid electrolyte according to claim 8, characterized in that, In S1, the mass of the polymer matrix is ​​10% to 95% of the total solid content of the precursor solution; the mass of the electrolyte salt is 5% to 80% of the total solid content of the precursor solution; in S3, the in-situ polymerization reaction is initiated by one or more of the following methods: thermal initiation, ultraviolet light initiation, electro-initiation, or electron beam irradiation initiation; the direction of the strong magnetic field is parallel to the ion transport direction.

10. A battery, characterized in that, It includes the polymer solid electrolyte as described in any one of claims 1-7 or the polymer solid electrolyte prepared by any one of the preparation methods described in claims 8-9.

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