Preparation method of solid-state composite electrolyte

Abstract

The invention relates to the technical field of solid-state composite electrolytes, in particular to a preparation method of a solid-state composite electrolyte, which comprises the following steps: S1, providing a eutectic mixture which comprises a lithium salt and a hydrogen bond donor, and the lithium salt comprises a hydrogen bond acceptor; s2, providing a polymer material, wherein the polymer material comprises a polymer; s3, mixing and heating the eutectic mixture and the polymer material to form an electrolyte precursor; and S4, cooling the electrolyte precursor to obtain the solid-state composite electrolyte. The solid-state composite electrolyte is manufactured by using the eutectic mixture and the polymer material, so that the use of traditional organic solvents such as EC and PC for the lithium ion battery can be avoided, and the raw material cost can be reduced. The co-melting mixture and the polymer material are blended, so that the process temperature and energy consumption can be reduced, the manufacturing cost of the solid composite electrolyte can be reduced, and the manufacturing cost of a battery containing the solid composite electrolyte can be further reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of solid composite electrolytes, and more particularly to a method for preparing a solid composite electrolyte. Background Art

[0002] The popularity of various portable electronic products has also driven the development of various rechargeable batteries. Among these rechargeable batteries, lithium-ion batteries are widely used due to their high energy density and lack of memory effect.

[0003] Traditional lithium-ion batteries consist of a negative electrode, a positive electrode, and an electrolyte for transmitting lithium ions. The electrolyte is a liquid organic solvent, which is prone to problems such as leakage and explosion. The organic solvent in discarded lithium-ion batteries will also pollute the environment.

[0004] In view of the shortcomings of traditional lithium-ion batteries, some industry players have developed lithium-ion polymer batteries, which use colloidal or solid polymer electrolytes to replace electrolytes. However, when preparing polymer electrolytes, organic solvents such as ethylene carbonate (EC) or propylene carbonate (PC) are usually used to dissolve lithium salts and polymers under high temperature conditions to form a viscous liquid, which is then cooled to obtain the polymer electrolyte. However, EC and PC are expensive.

[0005] Furthermore, the high temperature condition is usually greater than 100° C., which results in energy consumption and is not conducive to reducing the manufacturing cost of the lithium-ion polymer battery.

[0006] Therefore, we proposed a solid composite electrolyte preparation method to solve the above problems. Summary of the Invention

[0007] In order to overcome the above-mentioned defects of the prior art, an embodiment of the present invention provides a method for preparing a solid composite electrolyte to solve the problems raised in the above-mentioned background technology.

[0008] To achieve the above object, the present invention provides the following technical solution: a method for preparing a solid composite electrolyte, comprising the following steps:

[0009] Step S1: providing a eutectic mixture, wherein the eutectic mixture comprises a lithium salt and a hydrogen bond donor, wherein the lithium salt comprises a hydrogen bond acceptor;

[0010] Step S2: providing a polymer material, wherein the polymer material comprises a polymer;

[0011] Step S3: mixing and heating the eutectic mixture and the polymer material to form an electrolyte precursor;

[0012] Step S4: Cooling the electrolyte precursor to obtain a solid composite electrolyte.

[0013] In a preferred embodiment, the lithium salt is selected from lithium bisimide or lithium bisimide.

[0014] In a preferred embodiment, the hydrogen bond acceptor is an amide compound selected from N-methylacetamide, acetamide, trifluoroacetamide or urea.

[0015] In a preferred embodiment, the molar ratio of the lithium salt to the hydrogen bond donor is 5:1 to 1:5.

[0016] In a preferred embodiment, the polymer is selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP), polyethylene glycol (PEO), polyacrylate, polyvinyl acetate (PVAc), polyvinyl alcohol (PVA), poly N-vinyl formamide (PNVF) or a combination thereof.

[0017] In a preferred embodiment, the weight ratio of polymer to eutectic mixture is 10:90 to 50:50;

[0018] The concentration of the polymer in the polymer material may be 1 wt% to 10 wt%;

[0019] The polymer material includes a solvent, and the polymer material is formed by mixing a polymer and the solvent. The forming step includes removing the solvent from the electrolyte precursor and then cooling the electrolyte precursor.

[0020] Removing the solvent from the electrolyte precursor at a temperature of 25° C. to 70° C. for 1 hour to 48 hours;

[0021] Removing the solvent from the electrolyte precursor is performed under vacuum conditions;

[0022] The solvent may be acetone, dimethylacetamide (DMA), dimethylformamide (DMF), dimethyl sulfoxide (DMSO), N-methylpyrrolidone (NMP), or acetonitrile;

[0023] The polymer material can be formed by mixing a polymer and a solvent at a temperature of 40°C-100°C.

[0024] In a preferred embodiment, the mixing temperature in step S3 is 25°C to 100°C.

[0025] In a preferred embodiment, a solid composite electrolyte comprises a eutectic mixture dispersed in a network structure formed by a polymer.

[0026] In a preferred embodiment, a solid-state battery comprises:

[0027] positive electrode;

[0028] negative electrode;

[0029] The electrolyte is disposed between the positive electrode and the negative electrode.

[0030] Technical effects and advantages of the present invention:

[0031] This innovation uses eutectic mixtures and polymer materials to manufacture solid composite electrolytes, which can avoid the use of organic solvents such as EC and PC traditionally used in lithium-ion batteries, and is conducive to reducing raw material costs.

[0032] This innovation helps reduce process temperature and energy consumption by blending the eutectic mixture with polymer materials, thereby reducing the manufacturing cost of the solid composite electrolyte and further reducing the manufacturing cost of batteries containing the solid composite electrolyte.

[0033] Furthermore, the finished product of this innovative solid composite electrolyte does not contain organic solvents, which can prevent leakage and environmental pollution, thereby improving safety and promoting environmental protection. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 is a flow chart of the steps of the method for manufacturing the composite electrolyte of the present invention;

[0035] Figure 2 This is a scanning electron microscope (SEM) photograph of the composite electrolyte of the present invention after removing the eutectic mixture;

[0036] Figure 3 is a schematic diagram of a battery in the present invention;

[0037] Figure 4 This is a graph showing the results of charge and discharge tests on the composite electrolyte of Example 1 of the present invention;

[0038] Figure 5 1 is a graph showing the results of charge and discharge tests on the composite electrolyte of Example 2 of the present invention;

[0039] Figure 6 3 is a graph showing the results of charge and discharge tests on the composite electrolyte of Example 3 of the present invention;

[0040] Figure 7 4 is a graph showing the results of charge and discharge tests on the composite electrolyte of Example 4 of the present invention;

[0041] Figure 8 1 is a graph showing the results of charge and discharge tests of the composite electrolyte of Example 5 of the present invention;

[0042] Figure 91 is a graph showing the results of charge and discharge tests of the composite electrolyte of Example 6 of the present invention;

[0043] Figure 10 This is a graph showing the results of ion conductivity testing of the composite electrolytes of Examples 7 to 9 of the present invention;

[0044] Figure 11 Graphs showing the results of ion conductivity tests on the composite electrolytes of Examples 10 to 12 of the present invention. DETAILED DESCRIPTION

[0045] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0046] Reference Figure 1-11 :

[0047] Please refer to Figure 1 , the manufacturing method of the solid composite electrolyte comprises the following steps:

[0048] Step S1 is to provide a eutectic mixture, wherein the eutectic mixture comprises a lithium salt and a hydrogen bond donor, and the lithium salt comprises a hydrogen bond acceptor.

[0049] Specifically, a lithium salt comprises lithium ions and anions, wherein the anions contain hydrogen bond acceptors. The hydrogen bond acceptors can be highly electronegative atoms in the anions with lone electron pairs. For example, the lithium salt can be LiTFSI or LIBETI, wherein the groups CF3SO2 and C2FsSO2 in the anions can contain hydrogen bond acceptors. The hydrogen bond donor can be an amide compound, which refers to a compound with an amide bond in its structure, such as N-methylacetamide, acetamide, trifluoroacetamide, or urea.

[0050] The mixing of lithium salt and hydrogen-bonding donor creates hydrogen bonds, which lowers the melting point of the eutectic mixture below the individual melting points of the lithium salt and hydrogen-bonding donor. This helps lower process temperatures, improves stability, and enhances the freedom of lithium ion migration. The molar ratio of lithium salt to hydrogen-bonding donor can be between 5:1 and 1:5.

[0051] Step S2 is to provide a polymer material, wherein the polymer material comprises a polymer.

[0052] Specifically, the polymer material may include only a polymer, or may be a polymer solution formed by mixing a polymer with a solvent. That is, the polymer material may be a polymer itself or a polymer solution.

[0053] The polymer may be PVDF·PTFE, PVDF-HFP·PEO, polyacrylate, PVAc, PVA, PNV, F, copolymers thereof, or combinations thereof. The aforementioned polyacrylate refers to polymers of acrylic acid and its derivatives. For example, the polyacrylate may be, but is not limited to, polymethyl methacrylate (PMMA), polyethyl methacrylate (poly(ethylmethacrylate), polymethyl acrylate (poly(methylacrylate)), polyethyl acrylate (poly(ethylacrylate)), and the like.

[0054] The term "poly- or copolymer-containing polymer" refers to a copolymer obtained by copolymerizing at least two of the aforementioned polymers in any proportion, and the term "poly- or combination-containing polymer" refers to a blended polymer (or mixed polymer) obtained by mixing at least two of the aforementioned polymers in any proportion.

[0055] The solvent is used to dissolve the polymer. A suitable solvent can be selected based on the properties of the polymer. The solvent can be, but is not limited to, acetone, DMA, DMF·DMSO·NMP, or acetonitrile. The concentration of the polymer in the polymer solution (polymer material) can be 1wt% to 10wt%. When the concentration of the polymer is too low, the time required for subsequent solvent removal may be increased. When the concentration is too high, the polymer may gel during the process.

[0056] The polymer solution (polymer material) can be formed by mixing the polymer and the solvent at a temperature of 40° C. to 100° C. By forming the polymer solution in advance, the uniformity of mixing the polymer material and the eutectic mixture can be improved;

[0057] However, the present invention is not limited thereto. When the eutectic mixture and the polymer material have high solubility, the solvent may be omitted. In addition, the concentration of the polymer and the preparation temperature may be flexibly adjusted depending on the type of polymer.

[0058] The order of step S1 and step S2 can be reversed or performed simultaneously.

[0059] Step S3 is a mixing step of mixing and heating the eutectic mixture and the polymer material to form an electrolyte precursor.

[0060] The temperature of the mixing step can be adjusted depending on the type of eutectic mixture and polymer materials. For example, the mixing step can be performed at a temperature of 25°C to 100°C. The weight ratio of the polymer to the eutectic mixture can be 10:90 to 50:50 (i.e., based on 100 parts by weight of the total weight of the polymer and the eutectic mixture, the weight of the polymer is 10-50 parts by weight, and the weight of the eutectic mixture is 50-90 parts by weight).

[0061] The weight ratio of the polymer to the eutectic mixture is preferably 15:85 to 30:70.

[0062] Step S4 is a forming step, which involves cooling the electrolyte precursor to obtain a composite electrolyte. Specifically, when the polymer material only comprises a polymer, cooling the electrolyte precursor to obtain a colloidal or solid composite electrolyte.

[0063] When the polymer material is a polymer-containing solution, the solvent in the electrolyte precursor can be removed first, and a colloidal or solid composite electrolyte can be obtained after the electrolyte precursor is cooled. The removal of the solvent in the electrolyte precursor can be carried out at a temperature of 25°C to 70°C for 1 hour to 48 hours, and can be carried out under vacuum conditions. The above-mentioned temperature and time can be adjusted according to the content and type of the solvent in the electrolyte precursor. More specifically, when performing the molding step, the electrolyte precursor can be injected into a mold, such as a polyethylene mold, and then placed at room temperature to cool (when the polymer material only contains a polymer), or, it can be placed in a vacuum oven to remove the solvent, and then placed at room temperature to cool (when the polymer material is a polymer solution).

[0064] As can be seen from the above-described composite electrolyte manufacturing method, the present invention does not require the use of organic solvents EC and PC used in lithium-ion batteries. The temperature of the mixing step of the present invention can be no higher than 100°C, and the finished composite electrolyte of the present invention does not contain organic solvents, thereby reducing costs and being environmentally friendly.

[0065] Solid composite electrolyte

[0066] The present invention provides a solid composite electrolyte, which is prepared using a composite electrolyte manufacturing method. The composite electrolyte of the present invention is in a solid or colloidal state.

[0067] The composite electrolyte of the present invention comprises a eutectic mixture and a polymer. The eutectic mixture is dispersed in the polymer, so that the composite electrolyte has the ability to conduct lithium ions and can be applied in the field of batteries.

[0068] Specifically, the polymers may form a network structure, and the eutectic mixture may be dispersed in the pores of the network structure.

[0069] Please refer to Figure 2, which is an SEM photograph of the composite electrolyte after removing the eutectic mixture according to one embodiment of the present invention. Due to the fear of contaminating the SEM, the eutectic mixture must be removed before using SEM observation. Specifically, the composite electrolyte can be cut open, washed several times with deionized water to remove the eutectic mixture on it, and then dried to remove water before using SEM observation.

[0070] As shown in Figure 2, the polymer has a network structure with many pores inside. The pores are the spaces originally occupied by the eutectic mixture.

[0071] solid-state batteries

[0072] Please refer to Figure 3 The present invention provides a solid-state battery comprising a positive electrode, a negative electrode and a solid composite electrolyte, wherein the solid composite electrolyte is disposed between the positive electrode and the negative electrode.

[0073] For details on solid composite electrolytes and their preparation methods, please refer to the above article. The positive electrode material can be lithium cobalt oxide (LiCoO2), lithium manganese oxide (LiMn2O4), lithium nickel oxide (LiNiO2), lithium iron phosphate (LiFePO4, LFP), lithium iron cobalt oxide (LiFeCoPO4), or lithium nickel cobalt manganese oxide (NCM or NMC). The negative electrode material can be graphite or lithium metal.

[0074] Example

[0075] Example 1: N-methylacetamide and LiTFSI were mixed in a molar ratio of 1:4 to provide a eutectic mixture. PVDF and acetone were prepared at 75°C to form a 5 wt% PV / DF solution to provide a polymer material. The eutectic mixture and the polymer material were mixed and stirred at room temperature to obtain an electrolyte precursor, wherein the weight ratio of PVDF to the eutectic mixture was 20:80 (i.e., the weight of the eutectic mixture was 4 times the weight of PVDF). The electrolyte precursor was poured into a 30 mm polyethylene circular mold and placed in a 40°C vacuum oven for one day to remove the acetone, thereby obtaining the composite electrolyte of Example 1.

[0076] Example 2-13: The types and / or proportions of the components such as the hydrogen bond donor, lithium salt, polymer, and solvent in Example 1 were changed as shown in the following table to produce the composite electrolyte of Example 2-12;

[0077]

[0078]

[0079] The composite electrolytes of Examples 1 to 6 were assembled into half-cells for charge and discharge tests. The half-cell structure used LFP as the positive electrode and lithium metal as the negative electrode.

[0080] The experimental results of Examples 1 to 6 are as follows: Figures 4 to 9 shown.

[0081] Depend on Figures 4 to 9 It can be seen that the composite electrolytes of Examples 1 to 6 have the ability to conduct lithium ions and can be applied in the battery field.

[0082] The composite electrolytes of Examples 7 to 12 were tested for ion conductivity, and the experimental results are shown in Figures 10 and 11.

[0083] Figure 10 In FIG11 , when PVDF is mixed with 1 wt% to 5 wt% of PMMA, its ion conductivity falls between 3.1x10 S / cm and 4.2x10+ S / cm. In FIG12 , when PVDF is mixed with 5 wt% to 16 wt% of PVAc, its ion conductivity falls between 4.8x105 S / cm and 3.7x10+ S / cm, indicating that the composite electrolyte of the present invention can select polymers of different components according to actual needs to obtain the required ion conductivity.

[0084] The composite electrolyte of Example 1 was assembled into the following structure: stainless steel / composite electrolyte / stainless steel. Linear sweep voltammetry (LSV) and cyclic voltammetry (CV) tests were performed, and it was found that the potential window of Example 1 could reach 5V.

[0085] The composite electrolyte of Example 1 was also tested for ion conductivity. The experimental results showed that the ion conductivity of Example 1 at room temperature was approximately 0.5 mS / cm.

[0086] The composite electrolyte of Example 1 was also tested for lithium ion transference number, and the lithium ion transference number of Example 1 was 0.45.

[0087] The composite electrolyte of Example 1 was subjected to a 0.2C battery life test. The experimental results showed that after 50 cycles of testing, nearly 99% of the original capacity was still retained.

[0088] The composite electrolyte of Example 1 was subjected to a Limiting Oxygen Index (LOI) test, and the LOI value thereof was found to be 22-23%, indicating that the composite electrolyte of Example 1 has flame retardancy and can improve the safety of the resulting battery.

[0089] In summary, the composite electrolyte of the present invention has the ability to conduct lithium ions and can be applied in the field of batteries.

[0090] Compared to previous technologies, this innovation utilizes a eutectic mixture and polymer materials to create a solid composite electrolyte, eliminating the need for organic solvents such as EC and PC, traditionally used in lithium-ion batteries. This reduces raw material costs. By blending the eutectic mixture with the polymer material, the present invention reduces process temperature and energy consumption, thereby lowering the manufacturing cost of the solid composite electrolyte and, consequently, the manufacturing cost of batteries containing the composite electrolyte. Furthermore, the finished solid composite electrolyte of the present invention does not contain organic solvents, preventing leakage and environmental contamination, improving safety and contributing to environmental protection.

[0091] Finally: The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a solid composite electrolyte, characterized in that: The following steps are involved: Step S1: providing a eutectic mixture, wherein the eutectic mixture comprises a lithium salt and a hydrogen bond donor, wherein the lithium salt comprises a hydrogen bond acceptor; Step S2: providing a polymer material, wherein the polymer material comprises a polymer; Step S3: mixing and heating the eutectic mixture and the polymer material to form an electrolyte precursor; Step S4: Cooling the electrolyte precursor to obtain a solid composite electrolyte.

2. The method for preparing a solid composite electrolyte according to claim 1, wherein: The lithium salt is selected from lithium bisimide or lithium bisimide.

3. The method for preparing a solid composite electrolyte according to claim 1, wherein: The hydrogen bond acceptor is an amide compound selected from N-methylacetamide, acetamide, trifluoroacetamide or urea.

4. The method for preparing a solid composite electrolyte according to claim 1, wherein: The molar ratio of the lithium salt to the hydrogen bond donor is 5:1 to 1:

5.

5. The method for preparing a solid composite electrolyte according to claim 1, wherein: The polymer is selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP), polyethylene glycol (PEO), polyacrylate, polyvinyl acetate (PVAc), polyvinyl alcohol (PVA), poly N-vinyl formamide (PNVF) or a combination thereof.

6. The method for preparing a solid composite electrolyte according to claim 1, wherein: The weight ratio of polymer to eutectic mixture is 10:90 to 50:50; The concentration of the polymer in the polymer material may be 1 wt% to 10 wt%; The polymer material includes a solvent, and the polymer material is formed by mixing a polymer and the solvent. The forming step includes removing the solvent from the electrolyte precursor and then cooling the electrolyte precursor. Removing the solvent from the electrolyte precursor at a temperature of 25° C. to 70° C. for 1 hour to 48 hours; Removing the solvent from the electrolyte precursor is performed under vacuum conditions; The solvent may be acetone, dimethylacetamide (DMA), dimethylformamide (DMF), dimethyl sulfoxide (DMSO), N-methylpyrrolidone (NMP), or acetonitrile; The polymer material can be formed by mixing a polymer and a solvent at a temperature of 40°C-100°C.

7. The method for preparing a solid composite electrolyte according to claim 1, wherein: The mixing temperature in step S3 is 25°C to 100°C.

8. A solid composite electrolyte according to any one of claims 1 to 7, characterized in that: The electrolyte comprises a eutectic mixture dispersed in a network structure formed by a polymer.

9. The solid-state battery according to claim 8, characterized in that: include: positive electrode; negative electrode; The electrolyte is disposed between the positive electrode and the negative electrode.

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