A stretchable flexible lithium-ion battery and preparation method thereof

Abstract

The present invention discloses a stretchable flexible lithium-ion battery and a preparation method, belonging to the field of electrochemical energy storage technology. The present invention adds an elastic polymer to the positive and negative electrode slurries to replace the traditional polyvinylidene fluoride, thereby improving the stretchability of the battery. The positive and negative electrode slurries and the battery assembly method can ensure that the battery can be normally charged and discharged when stretched by 20%. Flexible batteries can be prepared for the design of wearable electronic devices.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrochemical energy storage, and in particular relates to a stretchable flexible lithium-ion battery and a preparation method thereof. Background Art

[0002] In recent years, with the trend toward smarter and more integrated wearable devices, flexible wearable electronic technology has become a hot research area. The rapid development of wearable devices has led to higher demands on energy supply devices. Supercapacitors or batteries are often used to power them. To withstand the tensile and deformation demands of wearable devices, requirements are placed on the stretchability of the battery and the adaptability of the power supply structure. However, traditional lithium-ion battery products are rigid, and the materials such as the battery's electrodes, current collectors, and substrates are rigid and lack the ability to withstand strain, making them difficult to use for powering wearable devices. In addition, some flexible batteries can only bend slightly and cannot be stretched. They also have disadvantages such as a complex production process and low energy density.

[0003] Chinese patent application CN118281371A discloses a method for preparing a leather-integrated, fully flexible zinc-ion battery. Using leather as a substrate, conductive polymers and zinc powder are composited on both sides of the leather. Different current-extraction materials and flexible outer packaging are selected to create a flexible zinc-ion battery. Chinese patent application CN118645704A discloses a flexible battery with freely designable shapes and a preparation method. The battery uses aluminum-coated aramid and copper-coated aramid as positive and negative current collectors, respectively. The surfaces are coated with positive and negative electrode materials, and the negative electrode is assembled with the positive electrode to form fibrous positive and negative electrodes. The fibrous positive and negative electrodes are then arranged according to the desired battery shape, the tabs are connected, a gel electrolyte is injected, and the battery is sealed to form a battery.

[0004] Although the above-mentioned related technologies can achieve the flexibility of the battery, they can usually only achieve a certain degree of bending or folding, and it is difficult to meet the stretching requirements in multiple directions. In common flexible battery designs, the electrodes and electrolyte materials are prone to rupture or delamination when subjected to stretching, resulting in a sharp decline in battery performance. In common stretchable battery designs, only the stretchability of a single electrolyte, the stretchability of the current collector material, etc., or the stretchability of the battery pack structure can be achieved, and the stretchable battery design of the entire battery cannot be completed. If the battery can be stretched and can be charged and discharged under stretching conditions, it will be very convenient for the application of wearable electronic devices, and can be designed according to the stretching requirements of different parts of the wearable electronic devices to cope with more complex human body environments. Therefore, it is necessary to provide a lithium-ion battery that can achieve battery flexibility and meet the needs of complex deformations such as stretching. Summary of the Invention

[0005] To address these technical issues, the present invention proposes a stretchable, flexible lithium-ion battery and its preparation method. This invention incorporates an elastic polymer into the positive and negative electrode slurries, replacing the traditional polyvinylidene fluoride (PVDF) to improve the battery's stretchability. The positive and negative electrode slurries and battery assembly ensure normal charging and discharging even when stretched by 20%.

[0006] To achieve the above-mentioned purpose, the present invention provides the following technical solutions: One of the technical solutions of the present invention:

[0007] The present invention provides a method for preparing a stretchable flexible lithium-ion battery, wherein at least one of polystyrene-polybutadiene-polystyrene (SBS), polystyrene-polyisoprene-polystyrene (SIS), and polystyrene-polyethylene-polybutylene-polystyrene (SEBS) is used as a binder for positive electrode slurry and negative electrode slurry; and one of n-hexane, cyclohexane, and ethyl acetate is used as a solvent for the positive electrode slurry and negative electrode slurry.

[0008] Furthermore, the method for preparing the stretchable flexible lithium-ion battery comprises the following steps:

[0009] Step 1: Mixing a PDMS (polydimethylsiloxane) prepolymer and a cross-linking agent, stirring them thoroughly to mix them evenly, removing bubbles, and obtaining a mixture, coating the mixture on a flexible substrate, and drying to obtain a PDMS film;

[0010] Step 2: Adding the binder to an organic solvent and heating to dissolve it to obtain a positive electrode precursor solution and a negative electrode precursor solution;

[0011] Step 3: mixing the positive electrode precursor solution, lithium iron phosphate, and conductive carbon black, and stirring evenly to form a positive electrode slurry;

[0012] Step 4: mixing the negative electrode precursor solution, graphene, and conductive carbon black, and stirring uniformly to form a negative electrode slurry;

[0013] Step 5: coating silver paste on the surface of the PDMS film as positive and negative current collectors respectively, and drying to obtain a combination of a positive electrode region current collector, a negative electrode region current collector and a substrate material;

[0014] Step 6: applying the positive electrode slurry to the positive electrode current collector area and drying to obtain a positive electrode sheet; applying the negative electrode slurry to the negative electrode current collector area and drying to obtain a negative electrode sheet;

[0015] Step 7: On the positive electrode current collector area on the positive electrode sheet, an aluminum tab is placed using silver paste as a binder, and the positive electrode is obtained after drying; on the negative electrode current collector area on the negative electrode sheet, a nickel tab is placed using silver paste as a binder, and the negative electrode is obtained after drying. The PDMS film is added at the connection between the positive and negative electrodes and the tabs as a fixing layer connecting the tabs and the battery;

[0016] Step 8: dripping an electrolyte solution between the positive and negative electrodes and on the surfaces of the positive and negative electrodes, covering the surfaces of the positive and negative electrodes with the PDMS film, and obtaining the stretchable flexible lithium-ion battery through sealing, standing, forming, and volume separation;

[0017] There is no order between step 3 and step 4; there is no order between step 5 and step 6.

[0018] Aiming at the problem that the existing technology cannot complete the design of batteries of arbitrary shapes, and only part of the structure is stretchable or a stretchable battery array is used, and the individual batteries cannot be stretched. The present invention introduces elastic polymers (such as polystyrene-polybutadiene-polystyrene, polystyrene-polyisoprene-polystyrene, polystyrene-polyethylene-polybutylene-polystyrene) in the positive and negative electrode slurries for the first time, replacing traditional polyvinylidene fluoride as a binder. This type of elastic polymer has both high elasticity and excellent mechanical properties, and can maintain the integrity of the internal structure and avoid cracking when subjected to tensile deformation. At the same time, its excellent electrochemical stability ensures that the battery performance is not affected during the charge and discharge process. Compared with traditional rigid binder materials, the high strain recovery ability of elastic polymers greatly improves the stretchability of the battery, so that the battery still maintains excellent conductivity and cycle life under multiple deformation conditions. Through systematic optimization, the present invention adopts flexible PDMS (polydimethylsiloxane) as the base material, and combines stretchable conductive silver paste as positive and negative current collectors to ensure the integrity of the overall battery structure under stretching conditions. The flexibility and elasticity of the PDMS substrate effectively mitigates damage to the electrode material caused by external forces, while the ductility and conductivity of the silver paste remain stable after multiple deformations. The high degree of matching between the flexible current collector and the electrode material achieves the overall stretchability of the battery.

[0019] In step 1, the mass ratio of the PDMS prepolymer to the cross-linking agent is 10:1; and / or

[0020] The bubbles are removed by placing the uniformly mixed PDMS prepolymer and cross-linking agent into a vacuum drying oven for drying; and / or

[0021] The density of the mixture on the flexible substrate is 100-200 mg / m 2 , i.e. 100-200 mg of the mixture is uniformly coated per square meter of the flexible substrate; and / or

[0022] The drying temperature is 60-100°C.

[0023] Illustratively, in step 1, the flexible substrate is a high molecular polymer substrate such as polyvinyl chloride (PVC) and polyethylene terephthalate (PET).

[0024] In the step 2, the mass ratio of the binder to the solvent is (1-3): (40-60); and / or

[0025] The heating temperature is 40-60° C., and the heating and dissolving is carried out under stirring conditions. Preferably, the heating method is water bath heating. Preferably, the heating and dissolving is carried out in a water bath pot with a rotor, and the stirring speed of the rotor is 1000-1500 rpm.

[0026] In the step 3, the mass ratio of the positive electrode precursor solution to lithium iron phosphate and conductive carbon black is (80-160):(12-20):(1-3).

[0027] In step 3, lithium iron phosphate is used as the positive electrode active material, and conductive carbon black is used as the conductive additive.

[0028] In the step 4, the mass ratio of the negative electrode precursor solution, graphene and conductive carbon black is (80-160):(12-20):(1-3).

[0029] In step 4, graphene is used as the negative electrode active material, and conductive carbon black is used as the conductive additive.

[0030] In step 5, the coating thickness of the silver paste is 0.05-0.1 mm; the coating speed is 10-20 mm / s; and / or

[0031] The drying temperature is 100-140° C. and the drying time is 30-50 minutes.

[0032] Exemplarily, in step 5, the silver paste has a viscosity of 15-25 Pa.s and a solid content of 57-67%.

[0033] In step 6, the coating thickness of the positive electrode slurry is 0.05 mm to 0.1 mm, and the coating speed is 10 to 20 mm / s; and / or

[0034] The coating thickness of the negative electrode slurry is 0.05 mm to 0.1 mm, and the coating speed is 10 to 20 mm / s.

[0035] Exemplarily, in step 6, the drying temperature is 45-60°C.

[0036] In step 7, the width of the aluminum tab is 3-6 mm and the thickness is 0.05-0.15 mm; and / or

[0037] The nickel tab has a width of 3-6 mm and a thickness of 0.05-0.15 mm.

[0038] Exemplarily, in step 7, the drying temperature is 45-60°C.

[0039] In step 8, the density of the electrolyte solution is 1.2-1.3 g / cc, the lithium salt of the electrolyte solution is LiPF6, the mass fraction of the lithium salt in the electrolyte solution is 10-15 wt.%, and the solvent of the electrolyte solution is a mixture of ethylene carbonate, ethyl methyl carbonate and dimethyl carbonate in a mass ratio of 1:1:1.

[0040] The second technical solution of the present invention:

[0041] The present invention also provides a stretchable flexible lithium-ion battery prepared according to the above method.

[0042] The stretchable flexible lithium-ion battery of the present invention can also be charged and discharged when stretched, and can be used to design wearable electronic devices according to the stretching requirements of different parts to cope with more complex human body environments.

[0043] Compared with the prior art, the present invention has the following advantages and technical effects:

[0044] The present invention prepares an electrode precursor solution by adding at least one of polystyrene-polybutadiene-polystyrene (SBS), polystyrene-polyisoprene-polystyrene (SIS), and polystyrene-polyethylene-polybutylene-polystyrene (SEBS) as a binder, and one of n-hexane, cyclohexane, and ethyl acetate as a binder solvent. Conductive carbon black is used as a conductive material, lithium iron phosphate is used as a positive electrode, and graphene is used as a negative electrode to prepare stretchable positive and negative electrodes respectively. Compared with the existing method of using polyvinylidene fluoride as a binder, N-methylpyrrolidone as a binder solvent, conductive carbon black as a conductive material, lithium iron phosphate as a positive electrode, and graphene as a negative electrode, the stretchability of the positive and negative electrodes is improved while ensuring that the specific capacity is similar to that of the prior art. The present invention uses stretchable conductive silver paste as a current collector, replacing traditional aluminum foil as a positive current collector and copper foil as a negative current collector, thereby improving the stretchability of the current collector. The present invention uses stretchable PDMS substrate, current collector, positive and negative electrodes to provide a design scheme for stretchable full-battery materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] The accompanying drawings, which constitute part of the present invention, are provided to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are provided to explain the present invention and do not constitute an undue limitation of the present invention. In the accompanying drawings:

[0046] Figure 1 Schematic diagram of the structure of a stretchable flexible lithium-ion battery prepared in an embodiment of the present invention, wherein: 1-polyvinyl chloride substrate, 2-PDMS film substrate, 3-PDMS film cover layer, 4-aluminum sheet positive electrode tab, 5-nickel sheet negative electrode tab, 6-silver paste layer, 7-positive electrode, 8-negative electrode, 9-electrolyte;

[0047] Figure 2 This is a photograph of the combination of the positive electrode region current collector, the negative electrode region current collector, and the substrate material prepared in Example 1;

[0048] Figure 3 The following are photos of the positive electrode coated with the positive electrode slurry and the negative electrode coated with the negative electrode slurry prepared in Example 1;

[0049] Figure 4 This is a front view of the encapsulated stretchable flexible lithium-ion battery in Example 1;

[0050] Figure 5 This is a comparison diagram of the stretchable flexible lithium-ion battery in Example 2 after longitudinal stretching by 20%, with the left diagram showing before stretching and the right diagram showing after stretching;

[0051] Figure 6 This is a comparison diagram of the stretchable flexible lithium-ion battery after transverse stretching in Example 2, with the left diagram showing before stretching and the right diagram showing after stretching;

[0052] Figure 7 This is a diagram of the U-shaped current collector mold used in Example 4;

[0053] Figure 8 This is a diagram of the U-shaped positive electrode mold used in Example 4;

[0054] Figure 9 Schematic diagram of the structure of the stretchable flexible lithium-ion battery in Example 4, wherein: 1-polyvinyl chloride substrate, 2-PDMS film substrate, 3-PDMS film cover layer, 4-aluminum sheet positive electrode tab, 5-nickel sheet negative electrode tab, 6-silver paste layer, 7-positive electrode, 8-negative electrode, 9-electrolyte;

[0055] Figure 10 The left picture is before stretching, and the right picture is after stretching.

[0056] Figure 11 Schematic diagram of the structure of a spiral stretchable flexible lithium-ion battery, where: 1-polyvinyl chloride substrate, 2-PDMS film substrate, 3-PDMS film covering layer, 4-aluminum sheet positive electrode tab, 5-nickel sheet negative electrode tab, 6-silver paste layer, 7-positive electrode, 8-negative electrode, 9-electrolyte. DETAILED DESCRIPTION

[0057] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0058] It should be understood that the terms described herein are intended only to describe particular embodiments and are not intended to limit the present invention. In addition, for numerical ranges herein, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Each smaller range between any intermediate value within a stated value or stated range and any other stated value or intermediate value within the stated range is also encompassed by the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded within the scope.

[0059] Unless otherwise indicated, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of any conflict with any incorporated document, the contents of this specification shall prevail.

[0060] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments described herein without departing from the scope or spirit of the invention. Other embodiments will be apparent to those skilled in the art from the description of the invention. The description and examples are intended to be illustrative only.

[0061] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0062] In some embodiments of the present invention, a method for preparing a stretchable flexible lithium-ion battery is provided, comprising the following steps:

[0063] Step 1: Mix the PDMS prepolymer and the crosslinking agent, stir them thoroughly to mix them evenly, place them in a vacuum drying oven to remove bubbles, and obtain a mixture. The mixture is coated on a polyvinyl chloride substrate and dried to obtain a PDMS film. The mass ratio of the PDMS prepolymer to the crosslinking agent is 10:1, and the density of the mixture on the polyvinyl chloride substrate is 100-200 mg / m 2 , that is, 100-200 mg of the mixture is evenly coated on each square meter of polyvinyl chloride board, and the drying temperature is 60-100 ° C;

[0064] Step 2: adding a binder to an organic solvent and heating and dissolving the binder to obtain a positive electrode precursor solution and a negative electrode precursor solution, wherein the binder includes at least one of polystyrene-polybutadiene-polystyrene (SBS), polystyrene-polyisoprene-polystyrene (SIS), and polystyrene-polyethylene-polybutylene-polystyrene (SEBS); the solvent includes one of n-hexane, cyclohexane, and ethyl acetate; the mass ratio of the binder to the solvent is (1-3): (40-60); the heating temperature is 40-60° C., and the heating and dissolution are carried out under stirring conditions, preferably the heating method is water bath heating, and preferably the heating and dissolution is carried out in a water bath with a rotor, and the stirring speed of the rotor is 1000-1500 rpm; the flexible substrate is a polymer substrate such as polyvinyl chloride (PVC) and polyethylene terephthalate (PET);

[0065] Step 3: mixing the positive electrode precursor solution, lithium iron phosphate, and conductive carbon black, and stirring uniformly to form a positive electrode slurry, wherein the mass ratio of the positive electrode precursor solution to lithium iron phosphate and conductive carbon black is (80-160): (12-20): (1-3);

[0066] Step 4: mixing the negative electrode precursor solution, graphene, and conductive carbon black, and stirring uniformly to form a negative electrode slurry, wherein the mass ratio of the negative electrode precursor solution to the graphene and the conductive carbon black is (80-160): (12-20): (1-3);

[0067] Step 5: coating silver paste on the surface of the PDMS film (i.e., the PDMS film substrate) as positive and negative current collectors respectively, and drying to obtain a combination of a positive electrode region current collector, a negative electrode region current collector, and a substrate material, wherein graphene is used as the negative electrode active material and conductive carbon black is used as a conductive additive; the coating thickness of the silver paste is 0.05-0.1 mm; the coating speed is 10-20 mm / s; the drying temperature is 100-140° C., and the drying time is 30-50 min; the viscosity of the silver paste is 15-25 Pa.s, and the solid content is 57-67%;

[0068] Step 6: coating the positive electrode slurry on the positive electrode current collector area and drying to obtain a positive electrode sheet; coating the negative electrode slurry on the negative electrode current collector area and drying to obtain a negative electrode sheet, wherein the coating thickness of the positive electrode slurry is 0.05 mm-0.1 mm and the coating speed is 10-20 mm / s; the coating thickness of the negative electrode slurry is 0.05 mm-0.1 mm and the coating speed is 10-20 mm / s; and the drying temperature is 45-60°C;

[0069] Step 7: On the positive electrode current collector area on the positive electrode sheet, an aluminum sheet tab is placed using silver paste as a binder, and the positive electrode is obtained after drying; on the negative electrode current collector area on the negative electrode sheet, a nickel sheet tab is placed using silver paste as a binder, and the negative electrode is obtained after drying, and the PDMS film is added at the connection between the positive and negative electrodes and the tabs as a fixing layer connecting the tabs and the battery, wherein the width of the aluminum sheet tab is 3-6 mm and the thickness is 0.05-0.15 mm; the width of the nickel sheet tab is 3-6 mm and the thickness is 0.05-0.15 mm, and the drying temperature is 45-60°C;

[0070] Step 8: dripping an electrolyte solution between the positive and negative electrodes and on the surfaces of the positive and negative electrodes, covering the surfaces of the positive and negative electrodes with the PDMS film (i.e., the PDMS film covering layer), and obtaining a stretchable flexible lithium-ion battery by sealing, standing, forming, and volume separation, wherein the density of the electrolyte solution is 1.2-1.3 g / cc, the lithium salt of the electrolyte solution is LiPF6, the mass fraction of the lithium salt in the electrolyte solution is 10-15 wt%, and the solvent of the electrolyte solution is a mixture of ethylene carbonate, ethyl methyl carbonate, and dimethyl carbonate in a mass ratio of 1:1:1;

[0071] There is no order between step 3 and step 4; there is no order between step 5 and step 6.

[0072] In some embodiments of the present invention, the positive and negative electrodes are prepared by mold printing. Both the positive electrode mold and the negative electrode mold are SMT laser templates with a thickness of 80μm-200μm. The shape of the positive electrode mold and the negative electrode mold can be one of a line segment shape, a U shape, a cross finger shape and a spiral shape. The hollow area in the positive electrode mold is the effective area for coating the positive electrode slurry, and the coating area is greater than or equal to the negative electrode effective area. The area of ​​a single electrode in the positive electrode mold and the negative electrode mold is independently 30μm 2 -3cm 2 , the preferred range is 3mm 2 -1cm 2 ; The width of the electrode is 2mm-4mm.

[0073] In a typical embodiment of the present invention, the density of the electrolyte solution is 1.3 g / cc, the lithium salt of the electrolyte solution is LiPF6, the mass fraction of the lithium salt in the electrolyte solution is 15 wt%, and the solvent of the electrolyte solution is a mixture of ethylene carbonate, ethyl methyl carbonate and dimethyl carbonate in a mass ratio of 1:1:1.

[0074] This invention uses stretchable conductive silver paste as the current collector, replacing traditional carbon cloth, improving the current collector's stretchability. Using a stretchable PDMS substrate, current collector, and positive and negative electrodes, the invention provides a fully stretchable battery material design that ensures normal charging and discharging even when stretched by 20%.

[0075] Unless otherwise specified, the normal temperature in the examples and comparative examples of the present invention is 25±2°C.

[0076] All raw materials used in the examples and comparative examples of the present invention were purchased from commercial sources.

[0077] Dow Corning SYLGARD 184 silicone rubber is a two-component kit consisting of 1 kg of base material and 100 g of curing agent. Mix thoroughly in a 10:1 weight ratio, resulting in a medium-viscosity mixture with a consistency similar to SAE 40 motor oil (Model 184, Brand: Dow Corning, Origin: USA, Composition: PDMS and curing agent, Mixing ratio: 10:1 by weight). Regardless of thickness, the mixture cures into a tough, transparent elastomer suitable for electronic / electrical packaging and potting applications. Dow Corning SYLGARD 184 silicone rubber cures within a temperature range of 25°C to 150°C without exotherm, requiring no post-cure. After the cure process is complete, it can be used immediately within a temperature range of -55°C to 200°C. As an example, the PDMS prepolymer in the embodiments and comparative examples of the present invention is the basic component of Dow Corning SYLGARD-184 silicone rubber; the cross-linking agent used is the curing agent in Dow Corning SYLGARD-184 silicone rubber; polystyrene-polyisoprene-polystyrene, polystyrene-polybutadiene-polystyrene and polystyrene-polyethylene-polybutylene-polystyrene are all purchased from Aladdin; the silver paste is the EL-8622 series stretchable conductive silver paste purchased from Xin Shuangbang Technology Co., Ltd., with a silver paste viscosity of 20 Pa.s and a solid content of 62%; lithium iron phosphate is purchased from Aladdin, with a particle size of <5 μm and a purity of >97%.

[0078] In the embodiments of the present invention, "first efficiency" refers to the first efficiency of the battery, which describes the ratio of the capacity released by the lithium-ion battery during discharge after the first charge to the capacity charged during the first charge. This ratio is usually less than 1 because some lithium ions will be irreversibly lost during the first charge, mainly due to the formation of a stable solid electrolyte interface film (SEI film) on the surface of the negative electrode. The first efficiency is an important parameter to measure the actual degree of lithium insertion and the actual released capacity of the battery material. The higher the first efficiency, the less irreversible lithium loss and consumption during the positive electrode film formation process, which means the recoverable capacity is high.

[0079] The structural diagram of the stretchable flexible lithium-ion battery in Examples 1 to 3 of the present invention is shown in FIG. Figure 1 , wherein: 1-polyvinyl chloride substrate, 2-PDMS film substrate, 3-PDMS film covering layer, 4-aluminum sheet positive electrode tab, 5-nickel sheet negative electrode tab, 6-silver paste layer, 7-positive electrode, 8-negative electrode, 9-electrolyte.

[0080] It should be pointed out that the matters not described in detail in the present invention are conventional operating means in this field and are not the focus of the present invention. For example, specific methods such as sealing, standing, forming, and volume separation are all completed using conventional methods.

[0081] The technical solution of the present invention is further illustrated by the following examples.

[0082] Example 1

[0083] This embodiment provides a stretchable flexible lithium-ion battery and a preparation method:

[0084] Step 1: Mix 7g of PDMS prepolymer with 0.7g of cross-linking agent, stir thoroughly to mix them evenly, put them into a vacuum drying oven at room temperature to remove bubbles (the vacuum degree of the vacuum drying oven is 5kPa), and obtain a mixture. Apply the mixture on a polyvinyl chloride substrate (the density of the mixture is 100mg / m 2 , i.e., 100 mg of the mixture was evenly coated on each square meter of polyvinyl chloride substrate), and the mixture was placed in an oven (oven temperature was 60°C) and dried for 4 h to obtain a PDMS film;

[0085] Step 2: Add 0.1 g of polystyrene-polyisoprene-polystyrene (styrene mass ratio is 22%) to 2.6 g of n-hexane, heat and dissolve in a water bath at 50°C (water bath heating is carried out in a water bath with a rotor, the same below), and stir the rotor at a speed of 1000 rpm to obtain a positive electrode precursor solution; add 0.1 g of polystyrene-polyisoprene-polystyrene (styrene 22 wt.%) to 2.6 g of n-hexane, heat and dissolve in a water bath at 50°C, and stir the rotor at a speed of 1000 rpm to obtain a negative electrode precursor solution;

[0086] Step 3: 2.7 g of the positive electrode precursor solution, lithium iron phosphate, and conductive carbon black were mixed in a mass ratio of 2.7:0.4:0.05 and stirred to form a positive electrode slurry;

[0087] Step 4: 2.7 g of negative electrode precursor solution, graphene, and conductive carbon black were mixed in a mass ratio of 2.7:0.4:0.05 and stirred to form a negative electrode slurry;

[0088] Step 5: Coat two pieces of silver paste with a thickness of 80 μm, a length of 30 mm, and a width of 3 mm on the surface of the PDMS film obtained in step 1 as positive and negative current collectors, respectively, and bake them in an oven for 40 minutes at a temperature of 150°C to obtain a combination of the positive electrode region current collector, the negative electrode region current collector, and the substrate material;

[0089] Step 6: Apply the positive electrode slurry to the positive electrode current collector area using an 80μm four-sided coating machine. The coated positive electrode slurry has a thickness of 80μm, a length of 25mm, a width of 3mm, and a coating speed of 10mm / s. After drying in an oven at a temperature of 50°C, a positive electrode sheet is obtained. Apply the negative electrode slurry to the negative electrode current collector area using an 80μm four-sided coating machine. The coated negative electrode slurry has a thickness of 80μm, a length of 25mm, a width of 3mm, and a coating speed of 10mm / s. After drying in an oven at a temperature of 50°C, a negative electrode sheet is obtained.

[0090] Step 7: In the positive electrode current collector area, silver paste is used as a binder to place an aluminum tab with a width of 3 mm and a thickness of 0.1 mm; in the negative electrode current collector area, silver paste is used as a binder to place a nickel tab with a width of 3 mm and a thickness of 0.1 mm, and placed in an oven for drying (oven temperature is 45°C). After drying, a PDMS film is added at the connection between the positive and negative electrodes and the tabs (the preparation method of the PDMS film is the same as step 1) as a fixing layer connecting the tabs and the battery;

[0091] Step 8: drip an electrolyte solution between the positive and negative electrodes and on the surfaces of the positive and negative electrodes. The density of the electrolyte solution is 1.3 g / cc, the lithium salt of the electrolyte solution is LiPF6, the mass fraction of the lithium salt in the electrolyte solution is 15 wt%, and the solvent of the electrolyte solution is a mixture of ethylene carbonate, ethyl methyl carbonate and dimethyl carbonate in a mass ratio of 1:1:1; after dripping the electrolyte solution, ensure that the surface of the positive and negative electrodes is infiltrated; cover the surface with a PDMS film (the preparation method of the PDMS film is the same as step 1), and obtain a stretchable flexible lithium-ion battery through sealing, standing, chemical formation, and volume separation.

[0092] The photo of the combination of the positive electrode region current collector, the negative electrode region current collector and the substrate material prepared in Example 1 is shown in FIG. Figure 2 The photo of the positive electrode coated with the positive electrode slurry and the photo of the negative electrode coated with the negative electrode slurry prepared in Example 1 are shown in FIG. Figure 3 The main view of the stretchable flexible lithium-ion battery after packaging in Example 1 is shown in FIG. Figure 4 The battery surface is smooth and the paste adheres well to the substrate, with no visible cracks or delamination. This indicates that the combination of the flexible silver paste and the elastic polymer gives the coating good adhesion and flexibility.

[0093] Example 2

[0094] This embodiment provides a stretchable flexible lithium-ion battery and a preparation method:

[0095] Step 1: Mix 7g of PDMS prepolymer with 0.7g of cross-linking agent, stir thoroughly to mix them evenly, place them in a vacuum drying oven at room temperature to remove bubbles (vacuum degree of the vacuum drying oven is 5kPa), and obtain a mixture, which is then coated on a polyvinyl chloride substrate (density of the mixture is 200mg / m 2 ), put it into an oven (oven temperature is 60 ° C) and dry it for 4 h to obtain a PDMS film;

[0096] Step 2: Add 0.2 g of polystyrene-polyisoprene-polystyrene (17 wt.% styrene) to 3 g of cyclohexane, heat and dissolve in a 50°C water bath with a rotor stirring speed of 1500 rpm to obtain a positive electrode precursor solution; add 0.2 g of polystyrene-polyisoprene-polystyrene (17 wt.% styrene) to 3 g of n-hexane, heat and dissolve in a 50°C water bath with a rotor stirring speed of 1000 rpm to obtain a negative electrode precursor solution;

[0097] Step 3: 3.2 g of the positive electrode precursor solution, lithium iron phosphate, and conductive carbon black were mixed in a mass ratio of 3.2:0.35:0.05 and stirred to form a positive electrode slurry;

[0098] Step 4: 3.2 g of the negative electrode precursor solution, graphene, and conductive carbon black were mixed in a mass ratio of 3.2:0.35:0.05 and stirred to form a negative electrode slurry;

[0099] Step 5: Coat two pieces of silver paste with a thickness of 80 μm, a length of 30 mm, and a width of 3 mm on the surface of the PDMS film obtained in step 1 as positive and negative current collectors, respectively, and bake them in an oven for 40 minutes at a temperature of 150°C to obtain a combination of the positive electrode region current collector, the negative electrode region current collector, and the substrate material;

[0100] Step 6: Apply the positive electrode slurry to the positive electrode current collector area using an 80μm four-sided coating machine. The coated positive electrode slurry has a thickness of 80μm, a length of 25mm, a width of 3mm, and a coating speed of 10mm / s. After drying in an oven at a temperature of 50°C, a positive electrode sheet is obtained. Apply the negative electrode slurry to the negative electrode current collector area using an 80μm four-sided coating machine. The coated negative electrode slurry has a thickness of 80μm, a length of 25mm, a width of 3mm, and a coating speed of 10mm / s. After drying in an oven at a temperature of 50°C, a negative electrode sheet is obtained.

[0101] Step 7: Place aluminum tabs with a width of 4mm and a thickness of 0.1mm on the positive current collector area using silver paste as a binder; place nickel tabs with a width of 4mm and a thickness of 0.1mm on the negative current collector area using silver paste as a binder, and place in an oven to dry. After drying, add a PDMS film (the preparation method of the PDMS film is the same as step 1) at the connection between the positive and negative electrodes and the tabs as a fixing layer connecting the tabs and the battery;

[0102] Step 8: drip an electrolyte solution between the positive and negative electrodes and on the surfaces of the positive and negative electrodes. The density of the electrolyte solution is 1.3 g / cc, the lithium salt of the electrolyte solution is LiPF6, the mass fraction of the lithium salt in the electrolyte solution is 15 wt%, and the solvent of the electrolyte solution is a mixture of ethylene carbonate, ethyl methyl carbonate and dimethyl carbonate in a mass ratio of 1:1:1. After dripping the electrolyte solution, ensure that the surface of the positive and negative electrodes is wetted; cover the surface with a PDMS film (the preparation method of the PDMS film is the same as step 1), and obtain a stretchable flexible lithium-ion battery through sealing, standing, chemical formation, and volume separation.

[0103] The comparison diagram of the stretchable flexible lithium-ion battery after longitudinal stretching by 20% in Example 2 is shown in FIG. Figure 5 The comparison diagram of the stretchable flexible lithium-ion battery after transverse stretching in Example 2 is shown in FIG. Figure 6 , it can be seen that under the conditions of 20% longitudinal and transverse stretching, there are no obvious cracks on the battery surface, and the current collector and electrode slurry still maintain good consistency. This shows that the positive and negative electrodes with PDMS substrate and elastic polymer as binder have excellent deformation adaptability under multi-axial stretching, and the delamination and peeling of the slurry during the stretching process are effectively suppressed.

[0104] Example 3

[0105] This embodiment provides a stretchable flexible lithium-ion battery and a preparation method:

[0106] Step 1: Mix 10g of PDMS prepolymer with 1g of cross-linking agent, stir thoroughly to mix them evenly, place them in a vacuum drying oven at room temperature for 1h to remove bubbles (oven temperature is 100℃), and then coat the mixture on a PET substrate (mixture density is 100mg / m 2 ), put it into an oven to obtain a PDMS film;

[0107] Step 2: Add 0.1 g of polystyrene-polyisoprene-polystyrene and 0.1 g of polystyrene-polyethylene-polybutylene-polystyrene to 2.5 g of ethyl acetate, and heat in a water bath at 50°C to dissolve to obtain a positive electrode precursor solution; add 0.1 g of polystyrene-polybutadiene-polystyrene (styrene 30 wt.%) and 0.1 g of polystyrene-polyethylene-polybutylene-polystyrene to 2.5 g of ethyl acetate, and heat in a water bath at 45°C to dissolve to obtain a negative electrode precursor solution;

[0108] Step 3: 2.7 g of the positive electrode precursor solution, lithium iron phosphate, and conductive carbon black were mixed in a mass ratio of 2.7:0.4:0.05 and stirred to form a positive electrode slurry;

[0109] Step 4: 2.7 g of negative electrode precursor solution, graphene, and conductive carbon black were mixed in a mass ratio of 2.7:0.4:0.05 and stirred to form a negative electrode slurry;

[0110] Step 5: Coat two pieces of 80 μm thick silver paste on the surface of the PDMS film prepared in step 1 as positive and negative current collectors, respectively, and bake them in an oven for 40 minutes at a temperature of 150°C to obtain a combination of the positive electrode region current collector, the negative electrode region current collector, and the substrate material;

[0111] Step 6: Coat the positive electrode slurry on the positive electrode current collector area using a four-sided coating machine with a length of 80 μm, a width of 30 mm, and a coating speed of 10 mm / s. After drying in an oven at 50°C, a positive electrode sheet was obtained.

[0112] The negative electrode slurry was coated on the negative electrode current collector area using an 80 μm four-sided coating machine. The coated negative electrode slurry had a thickness of 80 μm, a length of 25 mm, a width of 3 mm, and a coating speed of 10 mm / s. After drying in an oven at 45°C, a negative electrode sheet was obtained.

[0113] Step 7: Place aluminum tabs with a width of 3mm and a thickness of 0.1mm on the positive current collector area using silver paste as a binder; place nickel tabs with a width of 3mm and a thickness of 0.1mm on the negative current collector area using silver paste as a binder, and place them in an oven to dry. After drying, add a PDMS film (the preparation method of the PDMS film is the same as step 1) at the connection between the positive and negative electrodes and the tabs as a fixing layer connecting the tabs and the battery;

[0114] Step 8: drip an electrolyte solution between the positive and negative electrodes and on the surfaces of the positive and negative electrodes. The density of the electrolyte solution is 1.3 g / cc, the lithium salt of the electrolyte solution is LiPF6, the mass fraction of the lithium salt in the electrolyte solution is 15 wt%, and the solvent of the electrolyte solution is a mixture of ethylene carbonate, ethyl methyl carbonate and dimethyl carbonate in a mass ratio of 1:1:1; after dripping the electrolyte solution, ensure that the surface of the positive and negative electrodes is infiltrated; cover the surface with a PDMS film (the preparation method of the PDMS film is the same as step 1), and obtain a stretchable flexible lithium-ion battery through sealing, standing, chemical formation, and volume separation.

[0115] Example 4

[0116] This embodiment provides a stretchable flexible lithium-ion battery and a preparation method:

[0117] Step 1: Mix 7g of PDMS prepolymer with 0.7g of cross-linking agent, stir thoroughly to mix them evenly, put them into a vacuum drying oven at room temperature to remove bubbles (the vacuum degree of the vacuum drying oven is 5kPa), and obtain a mixture. Apply the mixture on a polyvinyl chloride substrate (the density of the mixture is 100mg / m 2 , i.e., 100 mg of the mixture was evenly coated on each square meter of polyvinyl chloride substrate), and the mixture was placed in an oven (oven temperature was 60°C) and dried for 4 h to obtain a PDMS film;

[0118] Step 2: Add 0.1 g of polystyrene-polyisoprene-polystyrene (22 wt.% styrene) to 2.6 g of n-hexane, heat and dissolve in a 50°C water bath (water bath heating is carried out in a water bath with a rotor, the same below), and stir the rotor at a speed of 1000 rpm to obtain a positive electrode precursor solution; add 0.1 g of polystyrene-polyisoprene-polystyrene (22 wt.% styrene) to 2.6 g of n-hexane, heat and dissolve in a 50°C water bath, and stir the rotor at a speed of 1000 rpm to obtain a negative electrode precursor solution;

[0119] Step 3: 2.7 g of the positive electrode precursor solution, lithium iron phosphate, and conductive carbon black were mixed in a mass ratio of 2.7:0.4:0.05 and stirred to form a positive electrode slurry;

[0120] Step 4: 2.7 g of negative electrode precursor solution, graphene, and conductive carbon black were mixed in a mass ratio of 2.7:0.4:0.05 and stirred to form a negative electrode slurry;

[0121] Step 5: Coat two U-shaped silver pastes on the surface of the PDMS film obtained in step 1 as positive and negative current collectors (see the U-shaped current collector mold used in the figure). Figure 7The length of the left side of the U-shaped area is 31.5mm, the length of the right side is 27mm, the width is 27mm, the width is 3mm, the interval between the two U-shaped areas is 1.5mm, and the total area is 436.5mm 2 ) Place in an oven and bake for 40 minutes at a temperature of 120° C. to obtain a combination of a positive electrode region current collector, a negative electrode region current collector, and a substrate material;

[0122] Step 6: Coat the positive electrode slurry on the positive electrode current collector area using an 80 μm four-sided preparation device. The coated positive electrode slurry has a thickness of 80 μm and a width of 3 mm. The coating area is U-shaped and the coating speed is 10 mm / s. After drying in an oven at 50 ° C, a positive electrode sheet is obtained (see the U-shaped positive electrode mold used). Figure 8 The negative electrode slurry was coated on the negative electrode current collector area using an 80 μm four-sided coating machine. The thickness of the coated negative electrode slurry was 80 μm and the width was 3 mm. The coating area was U-shaped and the coating speed was 10 mm / s. The negative electrode sheet was obtained by drying in an oven at a temperature of 50°C.

[0123] Step 7: In the positive electrode current collector area, silver paste is used as a binder to place an aluminum tab with a width of 3 mm and a thickness of 0.1 mm; in the negative electrode current collector area, silver paste is used as a binder to place a nickel tab with a width of 3 mm and a thickness of 0.1 mm, and placed in an oven for drying (oven temperature is 45°C). After drying, a PDMS film is added at the connection between the positive and negative electrodes and the tabs (the preparation method of the PDMS film is the same as step 1) as a fixing layer connecting the tabs and the battery;

[0124] Step 8: drip an electrolyte solution between the positive and negative electrodes and on the surfaces of the positive and negative electrodes. The density of the electrolyte solution is 1.2 g / cc, the lithium salt of the electrolyte solution is LiPF6, the mass fraction of the lithium salt in the electrolyte solution is 12 wt%, and the solvent of the electrolyte solution is a mixture of ethylene carbonate, ethyl methyl carbonate and dimethyl carbonate in a mass ratio of 1:1:1; after dripping the electrolyte solution, ensure that the surface of the positive and negative electrodes is infiltrated; cover the surface with a PDMS film (the preparation method of the PDMS film is the same as step 1), and obtain a stretchable flexible lithium-ion battery through sealing, standing, chemical formation, and volume separation.

[0125] The structural diagram of the stretchable flexible lithium-ion battery in this embodiment is shown in FIG. Figure 9 , wherein: 1-polyvinyl chloride substrate, 2-PDMS film substrate, 3-PDMS film covering layer, 4-aluminum sheet positive electrode tab, 5-nickel sheet negative electrode tab, 6-silver paste layer, 7-positive electrode, 8-negative electrode, 9-electrolyte.

[0126] The comparison diagram of the stretchable flexible lithium-ion battery after stretching in this embodiment is shown in FIG. Figure 10It can be seen that in the battery structure after stretching, there are no cracks in the U-shaped area, and the interface between the paste and the silver paste layer is stable, indicating that the multi-morphological design also has excellent deformation adaptability.

[0127] By using the same method as in Example 4 and replacing molds of different shapes, flexible batteries of different shapes can be obtained. Figure 11 .

[0128] Comparative Example 1

[0129] Step 1: Mix 7g of PDMS prepolymer with 0.7g of cross-linking agent, stir thoroughly to mix them evenly, place them in a vacuum drying oven at room temperature to remove bubbles (vacuum degree of the vacuum drying oven is 5kPa), and obtain a mixture, which is then coated on a polyvinyl chloride substrate (density of the mixture is 100mg / m 2 ), put it into an oven (oven temperature is 60 ° C) and dry it for 4 h to obtain a PDMS film;

[0130] Step 2: 0.8 g of lithium iron phosphate was mixed with conductive carbon black and polyvinylidene fluoride in a mass ratio of 8:1:1, and then 4 g of N-methylpyrrolidone was added and stirred to form a positive electrode slurry. The lithium iron phosphate was purchased from Aladdin, with a particle size of <5 μm and a purity greater than 97%;

[0131] Step 4: 0.8 g of graphene, conductive carbon black, and polyvinylidene fluoride were mixed in a mass ratio of 8:1:1, and then 4 g of N-methylpyrrolidone was added and stirred to form a negative electrode slurry;

[0132] Step 5: Coat two pieces of silver paste with a thickness of 80 μm, a length of 30 mm, and a width of 3 mm on the surface of the PDMS film prepared in step 1 as positive and negative current collectors, respectively, and bake and dry them in an oven for 40 minutes at a temperature of 150°C to obtain a combination of a positive electrode region current collector, a negative electrode region current collector, and a substrate material, wherein the silver paste is the EL-8622 series stretchable conductive silver paste purchased from Xin Shuangbang Technology Co., Ltd., with a silver paste viscosity of 20 Pa.s and a solid content of 62%;

[0133] Step 6: Coat the positive electrode slurry on the positive electrode current collector area using an 80μm four-sided preparation device. The coated positive electrode slurry has a thickness of 80μm, a length of 25mm, a width of 3mm, and a coating speed of 10mm / s. After drying in an oven at a temperature of 50°C, a positive electrode sheet is obtained. Coat the negative electrode slurry on the negative electrode current collector area using an 80μm four-sided preparation device. The coated negative electrode slurry has a thickness of 80μm, a length of 25mm, a width of 3mm, and a coating speed of 10mm / s. After drying in an oven at a temperature of 50°C, a negative electrode sheet is obtained.

[0134] Step 7: In the positive electrode current collector area, silver paste is used as a binder to place an aluminum tab with a width of 3 mm and a thickness of 0.1 mm; in the negative electrode current collector area, silver paste is used as a binder to place a nickel tab with a width of 3 mm and a thickness of 0.1 mm, and placed in an oven to dry at 45°C. After drying, a PDMS film is added at the connection between the positive and negative electrodes and the tabs (the preparation method of the PDMS film is the same as step 1) as a fixing layer connecting the tabs and the battery;

[0135] Step 8: drip an electrolyte solution between the positive and negative electrodes and on the surfaces of the positive and negative electrodes. The density of the electrolyte solution is 1.3 g / cc, the lithium salt of the electrolyte solution is LiPF6, the mass fraction of the lithium salt in the electrolyte solution is 15 wt%, and the solvent of the electrolyte solution is a mixture of ethylene carbonate, ethyl methyl carbonate and dimethyl carbonate in a mass ratio of 1:1:1; after dripping the electrolyte solution, ensure that the surfaces of the positive and negative electrodes are wetted; cover the surface with a PDMS film (the preparation method of the PDMS film is the same as step 1), and obtain a lithium-ion battery by sealing, standing, forming, and volume separation.

[0136] The performance test of the flexible stretchable battery prepared in the above embodiment was carried out, and the test method involved was: using a Xinwei tester to measure the charge and discharge performance, with a charge rate of 0.1C, a discharge rate of 0.2C, and a cut-off voltage of 3.0-4.4V.

[0137] The performance test results of flexible stretchable batteries are shown in Table 1.

[0138] Table 1 Flexible stretchable battery performance test results

[0139]

[0140] The data in Table 1 demonstrate that the flexible, stretchable batteries of Examples 1-3 exhibit high specific capacity, coulombic efficiency, and charge-discharge performance. The appropriate coating process ensures the flexibility of the positive and negative electrodes and the stability of the coating layer, preventing cracking or shedding of the coating layer during use. In the unstretched state, the data from Examples 1-3 and Comparative Example 1 are similar, demonstrating that the specific capacity, coulombic efficiency, and charge-discharge performance of the flexible, stretchable batteries of the present invention are comparable to those of lithium-ion batteries prepared using existing methods.

[0141] The lithium ion batteries prepared in Example 1 and Comparative Example 1 were subjected to charge and discharge tests at stretching of 0%, 10%, and 20%, respectively (testing methods are the same as above). The results are shown in Table 2.

[0142] Table 2 Performance test results of flexible stretchable batteries after stretching

[0143]

[0144] It can be seen from the data in Table 2 that the lithium-ion battery of Example 1 can still be charged and discharged normally after stretching. The lithium-ion battery of Comparative Example 1 has a lower specific capacity and charge-discharge capacity than that of Example 1 when stretched by 10%, and cannot be charged normally when stretched by 20%. The elastic polymer added to the positive and negative electrode slurries of Example 1 replaces the polyvinylidene fluoride in Comparative Example 1, which improves the stretchability of the battery. The positive and negative electrode slurries and the battery assembly method can ensure that the battery can be charged and discharged normally when stretched by 20%. In summary, the preparation method of the present invention can be used to prepare flexible batteries with various shape requirements.

[0145] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A method for preparing a stretchable flexible lithium-ion battery, characterized in that: The following steps are involved: Step 1: Mixing a PDMS prepolymer and a cross-linking agent, stirring them thoroughly to make them uniform, removing bubbles, and obtaining a mixture, coating the mixture on a flexible substrate, and drying to obtain a PDMS film; Step 2: Adding the binder to an organic solvent and heating to dissolve it to obtain a positive electrode precursor solution and a negative electrode precursor solution; Step 3: mixing the positive electrode precursor solution, lithium iron phosphate, and conductive carbon black, and stirring evenly to form a positive electrode slurry; Step 4: mixing the negative electrode precursor solution, graphene, and conductive carbon black, and stirring uniformly to form a negative electrode slurry; Step 5: coating silver paste on the surface of the PDMS film as positive and negative current collectors respectively, and drying to obtain a combination of a positive electrode region current collector, a negative electrode region current collector and a substrate material; Step 6: applying the positive electrode slurry to the positive electrode current collector area and drying to obtain a positive electrode sheet; applying the negative electrode slurry to the negative electrode current collector area and drying to obtain a negative electrode sheet; Step 7: On the positive electrode current collector area on the positive electrode sheet, an aluminum tab is placed using silver paste as a binder, and the positive electrode is obtained after drying; on the negative electrode current collector area on the negative electrode sheet, a nickel tab is placed using silver paste as a binder, and the negative electrode is obtained after drying. The PDMS film is added at the connection between the positive and negative electrodes and the tabs as a fixing layer connecting the tabs and the battery; Step 8: dripping an electrolyte solution between the positive and negative electrodes and on the surfaces of the positive and negative electrodes, covering the surfaces of the positive and negative electrodes with the PDMS film, and obtaining the stretchable flexible lithium-ion battery through sealing, standing, forming, and volume separation; There is no order between step 3 and step 4; there is no order between step 5 and step 6; In step 3, the mass ratio of the positive electrode precursor solution to lithium iron phosphate and conductive carbon black is (80-160): (12-20): (1-3); In the step 4, the mass ratio of the negative electrode precursor solution, graphene, and conductive carbon black is (80-160): (12-20): (1-3); At least one of polystyrene-polybutadiene-polystyrene, polystyrene-polyisoprene-polystyrene, and polystyrene-polyethylene-polybutylene-polystyrene is used as a binder for the positive electrode slurry and the negative electrode slurry; and one of n-hexane, cyclohexane, and ethyl acetate is used as a solvent for the positive electrode slurry and the negative electrode slurry.

2. The method for preparing a stretchable flexible lithium-ion battery according to claim 1, wherein: In step 1, the mass ratio of the PDMS prepolymer to the cross-linking agent is 10:1; and / or The bubbles are removed by placing the uniformly mixed PDMS prepolymer and cross-linking agent into a vacuum drying oven for drying; and / or The density of the mixture on the flexible substrate is 100-200 mg / m 2 and / or The drying temperature is 60-100°C.

3. The method for preparing a stretchable flexible lithium-ion battery according to claim 1, wherein: In step 5, the coating thickness of the silver paste is 0.05-0.1 mm; the coating speed is 10-20 mm / s; and / or The drying temperature is 100-140° C. and the drying time is 30-50 minutes.

4. The method for preparing a stretchable flexible lithium-ion battery according to claim 1, wherein: In step 6, the coating thickness of the positive electrode slurry is 0.05 mm to 0.1 mm, and the coating speed is 10 to 20 mm / s; and / or The coating thickness of the negative electrode slurry is 0.05 mm to 0.1 mm, and the coating speed is 10 to 20 mm / s.

5. The method for preparing a stretchable flexible lithium-ion battery according to claim 1, wherein: In step 7, the width of the aluminum tab is 3-6 mm and the thickness is 0.05-0.15 mm; and / or The nickel tab has a width of 3-6 mm and a thickness of 0.05-0.15 mm.

6. The method for preparing a stretchable flexible lithium-ion battery according to claim 1, wherein: In step 8, the density of the electrolyte solution is 1.2-1.3 g / cc, the lithium salt of the electrolyte solution is LiPF6, the mass fraction of the lithium salt in the electrolyte solution is 10-15 wt.%, and the solvent of the electrolyte solution is a mixture of ethylene carbonate, ethyl methyl carbonate and dimethyl carbonate in a mass ratio of 1:1:

1.

7. A stretchable flexible lithium-ion battery, characterized in that: Prepared according to the method according to any one of claims 1 to 6.

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