Framework material for preparing electrolyte membrane, preparation method of framework material, electrolyte membrane as well as preparation method and application of electrolyte membrane

Abstract

The invention discloses a framework material for preparing an electrolyte membrane, a preparation method of the framework material, the electrolyte membrane and a preparation method and application of the electrolyte membrane, and the framework material for preparing the electrolyte membrane comprises multistage branched fibers and inorganic filler uniformly dispersed on the multistage branched fibers. Due to the high specific surface area and abundant sites of the multi-stage branched fibers, the multi-stage branched fibers can easily perform interfacial interaction with the inorganic filler, and the inorganic filler can be uniformly dispersed on a multi-stage branched fiber skeleton structure by utilizing a nano micro-area effect, so that an abundant and continuous Li < + > transmission network can be formed to enhance Li < + > conduction. Besides, the framework material compounded by the multistage branched fibers and the inorganic filler is used as an inner core framework of the all-solid-state electrolyte membrane or the semi-solid-state electrolyte membrane, so that the overall mechanical property can be enhanced, and the purpose of inhibiting the growth of lithium dendrites on the physical level can be achieved.

Description

Technical Field

[0001] This invention relates to the field of battery materials technology, and more specifically, to framework materials for preparing electrolyte membranes, methods for preparing the same, electrolyte membranes, methods for preparing the same, and their applications. Background Technology

[0002] Solid-state electrolytes (SSEs) are core materials for achieving high safety and high energy density in solid-state batteries (SSBs). Their thermal stability, ionic conductivity, chemical stability, and interfacial properties directly affect the safety performance, battery capacity, and cycle performance of SSBs. Based on material properties, all-solid-state electrolytes can be divided into three types: inorganic solid-state electrolytes (ISEs), solid polymer electrolytes (SPEs), and organic-inorganic composite solid-state electrolytes (CSEs). However, both ISEs and SPEs have inherent limitations. Therefore, adding inorganic fillers to SPEs to form organic-inorganic composite solid-state electrolytes (CSEs) simultaneously improves mechanical properties, conductivity, and ion transference number, overcoming the shortcomings of single-type solid-state electrolytes. This is currently the most promising research direction for achieving a performance balance in SSBs.

[0003] However, due to the influence of too many factors, such as the morphology, structure, size, and chemical properties of inorganic fillers, the composite method of inorganic fillers and polymers, and polymer modification, CSE still cannot meet the comprehensive performance requirements of solid-state batteries. Summary of the Invention

[0004] The purpose of this invention is to overcome the above-mentioned deficiencies of the prior art and to provide a framework material for preparing electrolyte membranes, a method for preparing the same, an electrolyte membrane, a method for preparing the same, and its applications.

[0005] The technical problem solved by this invention is achieved by the following technical solution.

[0006] The present invention provides a framework material for preparing electrolyte membranes, comprising multi-level branched fibers and inorganic fillers uniformly dispersed on the multi-level branched fibers.

[0007] The present invention also provides a method for preparing the above-mentioned skeleton material for preparing electrolyte membranes, which includes: preparing multi-level branched fibers using organic polymers, and dispersing and attaching inorganic fillers to the surface of the multi-level branched fibers.

[0008] The present invention also provides an electrolyte membrane, wherein the electrolyte membrane uses a thin film made of the above-mentioned skeleton material as the core layer, and the electrolyte membrane can be a semi-solid electrolyte membrane or an all-solid electrolyte membrane.

[0009] Preferably, the all-solid electrolyte membrane comprises: a PEO layer / core layer / PEO layer, wherein the PEO layer contains PEO and lithium salt;

[0010] Preferably, the semi-solid electrolyte membrane comprises: a core layer and a liquid electrolyte coated on the core layer.

[0011] The present invention also provides a method for preparing the above-mentioned electrolyte membrane, comprising the following steps: preparing multi-branched fibers using an organic polymer, and dispersing and attaching inorganic fillers to the surface of the multi-branched fibers; using a thin film formed by the composite of multi-branched fibers and inorganic fillers as a core layer; then casting a solution containing PEO and lithium salt onto the core layer to form PEO layers on both sides of the core layer, and drying to obtain an all-solid electrolyte membrane; or immersing the core layer in a liquid electrolyte or dripping a liquid electrolyte onto the core layer, and drying to obtain a semi-solid electrolyte membrane.

[0012] The present invention also provides the above-mentioned skeleton material for preparing electrolyte membrane or the application of electrolyte membrane in lithium-ion battery.

[0013] The present invention has the following beneficial effects:

[0014] This invention provides a framework material for preparing electrolyte membranes, a method for preparing the same, an electrolyte membrane, the method for preparing the same, and its applications. The framework material for preparing electrolyte membranes provided by this invention includes multi-level branched fibers and inorganic fillers attached to the multi-level branched fibers. The multi-level branched fiber framework facilitates the uniform dispersion of the inorganic fillers on the multi-level branched fibers, avoids agglomeration, and improves the compatibility of the organic-inorganic interface through localized ion coordination, thereby forming abundant and continuous Li₂. + Transport network. Furthermore, using the aforementioned framework material as the core framework of the electrolyte membrane can enhance the overall mechanical properties and physically suppress lithium dendrite growth. The electrolyte membrane provided by this invention can be a semi-solid electrolyte membrane or an all-solid electrolyte membrane, further improving the overall mechanical strength and ion transport performance of the composite electrolyte membrane, and significantly enhancing the comprehensive performance of solid-state and semi-solid-state batteries. Attached Figure Description

[0015] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 This is a flowchart illustrating the preparation process of the framework material used to prepare electrolyte membranes.

[0017] Figure 2 This is a schematic diagram of the assembly of a high-safety, long-life all-solid-state battery.

[0018] Figure 3 Bar charts showing lithium ion transport number and ionic conductivity for different solid electrolyte membrane samples (50℃);

[0019] Figure 4 Multirate cycling performance of an all-solid-state battery assembled from Li / all-solid-state electrolyte membrane / LiFePO4;

[0020] Figure 5 Cyclic test results (50°C) of an all-solid-state symmetric battery assembled from Li / all-solid-state electrolyte membrane / Li.

[0021] Figure 6 Multirate cycling performance of an all-solid-state battery assembled from Li / all-solid-state electrolyte membrane / LiFePO4;

[0022] Figure 7 This is a comparison chart of the multi-rate cycle performance of the assembled semi-solid-state battery and the all-solid-state battery. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0024] The following is a detailed description of a framework material for preparing an electrolyte membrane, its preparation method, the electrolyte membrane itself, its preparation method, and its applications, provided by embodiments of the present invention.

[0025] In a first aspect, embodiments of the present invention provide a framework material for preparing an electrolyte membrane, comprising multi-level branched fibers and inorganic fillers uniformly dispersed on the multi-level branched fibers.

[0026] The molecular structure of dendritic hierarchical branched fibers endows dendritic hierarchical branched polymers with low chain entanglement and high free volume, providing a high specific surface area and abundant sites, making them easy to interact with inorganic fillers at the interface, thus enhancing compatibility and dispersibility. The skeleton material for preparing electrolyte membranes provided by this invention uses dendritic / hierarchical branched fibers as a matrix. Utilizing the nanoscale micro-region effect, inorganic fillers can be uniformly dispersed on the fibers, thereby ensuring uniform dispersion of inorganic fillers within the fibers and preventing agglomeration. Furthermore, the localized ion coordination enhances the compatibility of the organic-inorganic interface, which is beneficial for the formation of abundant and continuous Li₂. +Transport network. Furthermore, polymer solid electrolytes have poor cycle stability and the ability to suppress lithium dendrite growth. This invention utilizes the aforementioned framework material as the core framework of the electrolyte membrane to enhance overall mechanical properties, thereby achieving the goal of physically suppressing lithium dendrite growth.

[0027] In some alternative embodiments, the multi-branched fiber includes at least one of multi-branched polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), polymethyl methacrylate (PMMA), polyamide (PA), and polyimide (PI).

[0028] In some alternative embodiments, the inorganic filler includes at least one of layered double hydroxide (LDH), layered double oxide (LDO), tantalum-doped lithium lanthanum zirconium oxide (LLZTO), and lithium aluminum titanium phosphate (LATP), with a particle size of 300 nm to 700 nm.

[0029] In some alternative embodiments, the mass ratio of multi-branched fibers to inorganic fillers is 7:3 to 2:3. If the amount of inorganic filler is small, the Li-conducting process still relies on polymer molecular chain segments. + With the primary component being inorganic, it's difficult to significantly improve ionic conductivity. Excessive inorganic filler leads to agglomeration or difficulty in dispersion, and the conduction pathways are random and difficult to control. Therefore, controlling the appropriate ratio of these two components is beneficial for forming abundant and continuous Li. + The transport network will improve the performance of CSE.

[0030] In a second aspect, embodiments of the present invention provide a method for preparing the above-mentioned skeleton material for preparing electrolyte membranes, comprising: preparing multi-level branched fibers using organic polymers, and dispersing and attaching inorganic fillers to the surface of the multi-level branched fibers.

[0031] CSE mainly consists of three parts: polymer matrix, inorganic filler, and lithium salt. However, how to control the dispersion degree and form of inorganic filler in polymer electrolyte to obtain more Li + Improving the conduction pathways and thus enhancing the performance of ion transport pathways is a major challenge in current CSE research. In recent years, researchers have primarily focused on improving the performance of CSEs by combining inorganic fillers with polymer electrolytes, such as granular, linear, and sheet-like three-dimensional fillers. This has been achieved through the use of inorganic fillers with different morphologies or chemical properties. However, research on the influence of polymer matrix morphology on the dispersion of inorganic fillers and the formation of ion transport pathways is scarce.

[0032] This invention is the first to employ a turbulent shearing method to prepare the framework material, which uses dendritic, multi-level branched fibers as the main framework of the all-solid or semi-solid electrolyte membrane. For example... Figure 1As shown, the process includes the following steps: (a) injecting a solution formed by mixing a polymer with a good solvent into a poor solvent; (b) during phase separation, the precipitate is stretched by turbulent shear stress; and (c) the precipitate forms polymer particles with a multi-level branched network structure. It can be seen that this invention utilizes the principle of phase transformation of an organic polymer solution in a non-solvent, applying ultra-high-speed turbulence during the phase transformation process (unlike simple mechanical stirring, a stirring head with relative internal and external motion is used), thereby preparing multi-level branched fibers with a multi-level branched fiber structure. These fibers are then combined with inorganic fillers through a nanoscale micro-area effect (i.e., short-range van der Waals forces are formed between the multi-level branched fibers and the nano-inorganic fillers, promoting the dispersion and attachment of the nano-inorganic fillers to the multi-level branched fibers). Finally, through filtration, a framework material for preparing an electrolyte membrane is obtained. This framework material is rich in continuous Li... + The transport network can effectively improve the overall ion transport performance of solid electrolytes.

[0033] In some alternative embodiments, the steps include: utilizing the phase transition process of the organic polymer from liquid to solid phase in a turbulent shear stress field to transform the organic polymer into multi-branched fibers, and dispersing and attaching the inorganic filler onto the multi-branched fibers.

[0034] Preferably, in the solvent system for the phase transition process of the organic polymer from the liquid phase to the solid phase, the solvent includes at least one of DMF, NMP, formic acid, and acetic acid, and the non-solvent includes at least one of isopropanol, water, and ethanol, with a stirring speed of 14,000-18,000 rpm and a stirring time of 10-20 minutes.

[0035] Preferably, the mass ratio of multi-branched fibers to inorganic fillers is 7:3 to 2:3;

[0036] Preferably, the concentration of the organic polymer dissolved in the solvent is 5-10%.

[0037] This invention utilizes the principle of phase transformation of organic polymer solutions in non-solvent environments. During the phase transformation process, ultra-high-speed stirring is employed, and turbulent shearing is used to form a multi-level branched fiber framework. Due to the nanoscale micro-region effect, the adsorbed inorganic filler can be uniformly dispersed on the framework structure, thereby forming abundant and continuous Li₂. + Transmission network. When the added inorganic filler is Li-Al-LDO, the rigid layered structure of Li-Al-LDO can also suppress lithium dendrite growth and prevent battery short circuits.

[0038] Thirdly, embodiments of the present invention provide an electrolyte membrane, wherein the electrolyte membrane uses a thin film made of the above-mentioned skeleton material as the core layer, and the electrolyte membrane can be a semi-solid electrolyte membrane or an all-solid electrolyte membrane.

[0039] Preferably, the all-solid electrolyte membrane comprises: a PEO layer / core layer / PEO layer, wherein the PEO layer contains PEO and lithium salt;

[0040] Preferably, the semi-solid electrolyte membrane comprises: a core layer and a liquid electrolyte coated on the core layer.

[0041] To improve the mechanical strength of the electrolyte membrane, this invention employs a "sandwich structure" design. A flexible, easily processable polyethylene oxide (PEO) + lithium salt, with good compatibility with lithium metal, serves as the "outer shell" of the all-solid-state electrolyte membrane, avoiding point-to-point contact with the electrodes. Simultaneously, a chemically inert, mechanically robust, thermally stable, and easily processable multi-branched fiber and inorganic filler skeleton material is used as the inner core skeleton to enhance the overall mechanical strength and ion transport performance of the composite electrolyte membrane.

[0042] In some alternative embodiments, the core layer has a thickness of 30-50 μm, and the mass ratio of multi-branched fibers to inorganic fillers in the core layer is between 7:3 and 2:3.

[0043] In some alternative embodiments, the thickness of the PEO layer is 10-20 μm, and the mass ratio of EO in the PEO layer to Li in the lithium salt is 16:1-12:1.

[0044] Fourthly, embodiments of the present invention provide a method for preparing the above-mentioned electrolyte membrane, comprising the following steps: preparing multi-level branched fibers using an organic polymer, and dispersing and attaching inorganic fillers to the surface of the multi-level branched fibers, using a thin film formed by the composite of the multi-level branched fibers and inorganic fillers as a core layer; then casting a solution containing PEO and lithium salt onto the core layer to form PEO layers on both sides of the core layer, and obtaining a fully solid electrolyte membrane after drying; or immersing the core layer in a liquid electrolyte or dripping the liquid electrolyte onto the core layer, and obtaining a semi-solid electrolyte membrane after drying.

[0045] In some optional embodiments, the following steps are included: utilizing the phase transition process of organic polymers from liquid to solid phase in a turbulent shear stress field, the organic polymers are used to form multi-level branched fibers and composited with inorganic fillers, and then a core layer is formed by filtration; a solution containing PEO and lithium salt is poured onto the core layer to form PEO layers on both sides of the core layer, and after drying, an all-solid electrolyte membrane is obtained; or the core layer is immersed in a liquid electrolyte or a liquid electrolyte is dropped onto the core layer, and after drying, a semi-solid electrolyte membrane is obtained.

[0046] Preferably, the solution containing PEO and lithium salt is prepared by dispersing PEO and lithium salt in acetonitrile or aqueous solution under an inert gas environment and stirring to obtain a homogeneous mixed solution.

[0047] Fifthly, embodiments of the present invention provide an application of the above-mentioned framework material for preparing an electrolyte membrane or an electrolyte membrane in a lithium-ion battery.

[0048] The present invention will be further described below with reference to embodiments.

[0049] Example 1

[0050] (1) Preparation of the framework material: 1.2 g of PVDF and 1.2 g of Li-Al-LDO were weighed and dissolved in 14 mL of DMF solution, and the solution was magnetically stirred at room temperature for 24 h. Utilizing the principle of PVDF phase inversion, a phase inversion occurred in turbulent flow at 14000 rpm through the exchange of solvent (DMF) and non-solvent (isopropanol), causing PVDF to be stretched into multi-level branched fibers and Li-Al-LDO to be uniformly dispersed on the multi-level branched fiber framework (see [reference]). Figure 1 Finally, a film is formed by vacuum filtration and used as the core layer.

[0051] (2) Preparation of LDO / PVDF-PEO composite solid electrolyte membrane: First, a solution containing PEO and lithium salt was prepared. A certain amount of PEO and LiTFSI (the mass ratio of EO to Li was 16:1) were weighed in an argon atmosphere. Acetonitrile solution was added and the mixture was stirred with magnetic force to make it uniform. In an argon atmosphere, the core layer was cast to form PEO layers on both sides of the core layer. The sample after acetonitrile volatilization and drying was cut into an all-solid electrolyte membrane with a diameter of 18 mm and named LDO / PVDF-PEO.

[0052] (3) Battery assembly: Prepare the positive electrode material by mixing LiFePO4, Super P, and PVDF binder in a ratio of 8:1:1, and use lithium sheet as the negative electrode to assemble a Li / all-solid-state electrolyte membrane / LiFePO4 coin cell (see...). Figure 2 The device was tested for charge and discharge at 50°C within a voltage range of 2.1-4.2V.

[0053] (4) Performance testing: Li / all-solid-state electrolyte membrane / Li battery was assembled at 50℃. The initial and steady-state current of the battery were determined by the it curve. At the same time, the initial and steady-state resistance before and after the test it curve were measured, and the t-resistance of different samples of all-solid-state electrolyte membrane was calculated. Li + .

[0054] Example 2

[0055] The steps are similar to those in Example 1, except that the phase transition is carried out in turbulent flow at 16,000 rpm.

[0056] Example 3

[0057] The steps are similar to those in Example 1, except that the phase transition is carried out in turbulent flow at 18,000 rpm.

[0058] Example 4

[0059] The steps are similar to those in Example 1, except that the organic polymer is polyacrylonitrile (PAN).

[0060] Example 5

[0061] The steps are similar to those in Example 1, except that the organic polymer is polymethyl methacrylate (PMMA) and the inorganic filler is tantalum-doped lithium lanthanum zirconium oxide (LLZTO).

[0062] Example 6

[0063] Similar to the steps in Example 1, the only difference is that in step (3), when assembling the battery, 5 wt% of electrolyte LiPF6 (EC:DEC = 1:1 vol / vol) is dropped onto the core layer to obtain a semi-solid electrolyte membrane. The semi-solid electrolyte membrane is then used to assemble a semi-solid battery and to perform performance testing.

[0064] Example 7

[0065] Similar to the steps in Example 1, the only difference is that in step (3), when assembling the battery, 10wt% of electrolyte LiPF6 (EC:DEC = 1:1 vol / vol) is dropped onto the core layer to obtain a semi-solid electrolyte membrane. The semi-solid electrolyte membrane is then used to assemble a semi-solid battery and to perform performance tests.

[0066] Example 8

[0067] Similar to the steps in Example 1, the only difference is that after stretching PVDF into multi-branched fibers, 1.2g of Li-Al-LDO is added and magnetically stirred to uniformly disperse Li-Al-LDO on the multi-branched fiber skeleton. Finally, a film is formed by vacuum filtration and used as the core layer.

[0068] Comparative Example 1

[0069] Similar to the steps in Example 1, the only difference is that the solution containing PEO and lithium salt is cast into a film and used as an all-solid electrolyte membrane, named PEO.

[0070] Comparative Example 2

[0071] Similar to the steps in Example 1, the only difference is that: no LDO / PVDF multi-branched fiber skeleton was added. Instead, the solution of Li-Al-LDO was directly mixed with PEO and lithium salt, and then cast into a film, which was used as an all-solid electrolyte membrane and named LDO / PEO.

[0072] Comparative Example 3

[0073] Similar to the steps in Example 1, except that the mass ratio of PVDF to Li-Al-LDO is 8:3.

[0074] Comparative Example 4

[0075] Similar to the steps in Example 1, except that the mass ratio of PVDF to Li-Al-LDO is 1:3.

[0076] Test Results

[0077] 1. EIS test and lithium-ion transference number (t) of all-solid-state electrolyte membranes of different samples Li + )

[0078] Lithium-ion transference number refers to the number of lithium ions in a solid electrolyte. + The proportion of migration to the total number of ion migrations; a higher value indicates higher Li content. + The more efficient the transport in a solid electrolyte, the better. See also Figure 3 At 50℃, the t of LDO / PVDF-PEO Li + (0.41) is the highest, and the highest value is t. Li + This can improve battery charge / discharge rates, reduce concentration polarization, and promote uniform lithium deposition. For example... Figure 3 As shown, LDO is a porous layered material formed by calcining layered bimetallic hydroxide (LDH) to remove interlayer anions and water. It retains part of the LDH's layered structure, forming ordered interlayer channels and pores, providing transport paths for lithium ions. The abundant surface hydroxyl groups and defect sites can interact with lithium ions. In addition, the porous structure (mesoporous / microporous) generated by calcination provides a three-dimensional ion diffusion network. Functional groups (such as hydroxyl groups) on the inner surface of the pores promote lithium ion diffusion through adsorption-desorption mechanisms, and oxygen vacancies generated during calcination can serve as lithium ion trapping sites, promoting ion transitions through a local electric field.

[0079] 2. Full-cell performance of all-solid-state electrolyte membranes from different samples

[0080] The multi-rate cycling performance of different sample batteries at 0.1C, 0.2C, 0.5C, and 1C was tested at 50℃. For example... Figure 4As shown, Li / LDO / PVDF-PEO / LiFePO4 exhibits the highest discharge specific capacity at all discharge rates, with values ​​of 164 mAh·g⁻¹. -1 162mAh·g -1 169mAh·g -1 and 150mAh·g -1 It is worth noting that when recovering from a high rate of 1C to a low rate of 0.1C, Li / LDO / PVDF-PEO / LiFePO4 can still recover to 164 mAh·g. -1 This is because the multi-layered branched fiber skeleton of PVDF and the laminated structure of LDO provide more transport paths for lithium ions. At the same time, the strong Lewis acidity of LDO can adsorb anions and promote the dissociation of lithium salts, and lithium ions can form ion jumps on oxygen vacancies after LDO calcination. The combined effect of these two factors improves the lithium ion transport efficiency.

[0081] 3. Lithium plating / stripping experiment

[0082] Lithium dendrite growth is considered a major safety threat in all-solid-state lithium metal batteries, affecting the mechanical strength of the solid electrolyte and its thermal conductivity. Li + The interfacial stability between the lithium metal anode and the lithium metal electrode is considered a key factor affecting lithium dendrite growth. In a 50℃ environment, we conducted constant current charge-discharge experiments to perform lithium plating and stripping tests on Li / all-solid-state electrolyte membrane / Li symmetric batteries assembled with different samples of all-solid-state electrolyte membranes, to observe the ability of different solid-state electrolytes to suppress lithium dendrite growth. Figure 5 It can be observed that the addition of the PVDF fiber skeleton increases the mechanical strength of LDO / PVDF-PEO, thereby enhancing its ability to suppress lithium dendrites. In contrast, the PEO solid electrolyte exhibits a sudden drop in overpotential and the formation of a micro-short circuit at 280 h due to lithium dendrite penetration. LDO / PVDF-PEO shows the smallest overpotential (0.4 mV), which is attributed to the coordinated effect of LDO adsorbing anions through strong Lewis acidity, and the adsorption-desorption mechanism of the three-dimensional ion diffusion network generated by calcination, promoting lithium ion dissociation and diffusion, as well as more uniform deposition.

[0083] 4. The Influence of the Ratio of Organic Polymers to Inorganic Fillers in the Core Layer of All-Solid Electrolyte Membranes of Different Samples

[0084] like Figure 6As shown, if the proportion of inorganic filler in the skeleton material is too small (e.g., less than 30%), a continuous lithium-ion pathway cannot be formed, and lithium-ion transport will only be carried out through the coordination of PEO molecular chain segments with lithium ions; if the proportion of inorganic filler is too large (more than 60%), the inorganic filler will cause serious agglomeration, which will hinder lithium-ion transport and reduce lithium-ion transport efficiency.

[0085] 6. Full-cell performance of semi-solid electrolyte membranes

[0086] The batteries assembled from the electrolyte membranes prepared in Comparative Examples 1 and 2 were subjected to multi-rate cycling tests at 0.1C, 0.2C, 0.5C, and 1C (test temperature: 50°C). The semi-solid-state battery assembled from the electrolyte membrane prepared in Example 7 was subjected to multi-rate cycling tests at 0.1C, 0.2C, 0.5C, and 1C (test temperature: 25°C). Figure 7 As shown, the batteries assembled with the electrolyte membranes prepared in Comparative Examples 1 and 2 could not operate normally at 25°C, but the batteries assembled with the electrolyte membrane prepared in Example 7 could operate normally at 25°C and had a high discharge specific capacity at all rates, proving that the semi-solid-state batteries prepared using the scheme provided in the embodiments of the present invention also have good performance.

[0087] 7. Performance of electrolyte membranes prepared using different composite methods

[0088] Tests showed that the electrolyte membrane prepared using the framework material obtained in Example 1 has similar performance to the electrolyte membrane prepared using the framework material obtained in Example 8, and both can be used to prepare all-solid-state batteries or semi-solid-state batteries with good electrochemical performance.

[0089] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A skeleton material for preparing an electrolyte membrane, characterized by, include: Multi-level branched fibers and inorganic fillers uniformly dispersed on the multi-level branched fibers.

2. The framework material of claim 1, wherein, The mass ratio of the multi-branched fiber to the inorganic filler is 7:3 to 2:3; Preferably, the multi-branched fiber includes at least one of multi-branched polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), polymethyl methacrylate (PMMA), polyamide (PA), and polyimide (PI); Preferably, the inorganic filler comprises at least one of layered double hydroxide (LDH), layered double oxide (LDO), tantalum-doped lithium lanthanum zirconium oxide (LLZTO), and lithium aluminum titanium phosphate (LATP), with a particle size of 300 nm-700 nm.

3. A method for producing the framework material according to claim 1 or 2, characterized by, It includes: Multi-branched fibers are prepared using organic polymers, and the inorganic filler is dispersed and attached to the surface of the multi-branched fibers.

4. The production method according to claim 3, characterized by, Includes the following steps: By utilizing the phase transformation process of organic polymer from liquid to solid phase in a turbulent shear stress field, the organic polymer is transformed into the multi-level branched fiber, and the inorganic filler is dispersed and attached to the multi-level branched fiber. Preferably, in the solvent system of the phase transition process of the organic polymer from liquid to solid phase, the solvent includes at least one of DMF, NMP, formic acid, and acetic acid, and the non-solvent includes at least one of isopropanol, water, and ethanol, the stirring speed is 14000-18000 rpm, and the time is 10-20 minutes. Preferably, the mass ratio of the multi-branched fiber to the inorganic filler is 7:3 to 2:3; Preferably, the concentration of the organic polymer dissolved in the solvent is 5-10%.

5. An electrolyte membrane, characterized by, The electrolyte membrane uses a thin film made of the skeleton material as described in any one of claims 1-2 as the core layer, and the electrolyte membrane may be a semi-solid electrolyte membrane or a fully solid electrolyte membrane. Preferably, the all-solid electrolyte membrane comprises: a PEO layer / core layer / PEO layer, wherein the PEO layer contains PEO and lithium salt; Preferably, the semi-solid electrolyte membrane comprises: a core layer and a liquid electrolyte coated on the core layer.

6. The electrolyte film according to claim 5, characterized by The core layer has a thickness of 30-50 μm, and the mass ratio of the multi-branched fibers and the inorganic filler in the core layer is 7:3 to 2:

3.

7. The electrolyte film according to claim 5, characterized by The thickness of the PEO layer is 10-20 μm, and the mass ratio of EO in the PEO layer to Li in the lithium salt is 16:1-12:

1.

8. A method for preparing an electrolyte membrane according to any one of claims 5-7, characterized in that, The process includes the following steps: preparing multi-level branched fibers using organic polymers, dispersing and attaching the inorganic filler to the surface of the multi-level branched fibers, and using the film formed by the composite of the multi-level branched fibers and the inorganic filler as the core layer; then pouring a solution containing PEO and lithium salt onto the core layer to form PEO layers on both sides of the core layer, and drying to obtain an all-solid electrolyte membrane; or immersing the core layer in a liquid electrolyte or dripping the liquid electrolyte onto the core layer, and drying to obtain a semi-solid electrolyte membrane.

9. The preparation method according to claim 8, characterized in that, Includes the following steps: By utilizing the phase transition process of organic polymers from liquid to solid phase in a turbulent shear stress field, the organic polymers are formed into multi-level branched fibers and combined with the inorganic filler. Then, a core layer is formed by vacuum filtration. A solution containing PEO and lithium salt is then poured onto the core layer to form PEO layers on both sides of the core layer. After drying, an all-solid electrolyte membrane is obtained. Alternatively, the core layer can be immersed in a liquid electrolyte or a liquid electrolyte can be dropped onto the core layer. After drying, a semi-solid electrolyte membrane is obtained. Preferably, the solution containing PEO and lithium salt is prepared by the following method: under an inert gas environment, PEO and lithium salt are dispersed in acetonitrile or an aqueous solution and stirred to obtain a uniform mixed solution.

10. The application of the skeleton material according to any one of claims 1-2 or the electrolyte membrane according to any one of claims 5-7 in a lithium-ion battery.

Images