Carbon fiber structure energy storage integrated composite material and preparation method thereof

Abstract

The invention provides a carbon fiber structure energy storage integrated composite material and a preparation method thereof, and belongs to the technical field of composite materials and electrochemical energy storage. The composite material is of a layered sandwich structure and sequentially comprises at least one carbon fiber negative electrode layer, a solid electrolyte diaphragm layer and at least one positive electrode layer from top to bottom, the carbon fiber negative electrode layer is composed of carbon fibers and a conductive polymer coating; a conductive polymer in the conductive polymer coating comprises one or more of poly (3, 4-ethylenedioxythiophene)-polystyrene sulfonate, polyaniline and polypyrrole. Through interface modification of the conductive polymer and introduction of the high-ionic-conductivity electrolyte, consideration of mechanical properties and electrochemical properties of the carbon fiber composite material is achieved, and the carbon fiber composite material has excellent thermal stability and safety and can be used for structural components needing light bearing and energy storage function integration, such as spacecrafts, unmanned aerial vehicles and electric carriers.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of composite materials and electrochemical energy storage technology, and in particular to a carbon fiber structure energy storage integrated composite material and a preparation method thereof. BACKGROUND

[0002] With the increasing demand for lightweight and efficient energy utilization, the concept of "structural energy storage" that combines structural materials with energy storage functions has attracted widespread attention. Structural energy storage composites can achieve electrical energy storage functions without increasing system mass by allowing load-bearing structures to also serve as batteries or capacitors, enabling multifunctional integration of structural components. Carbon fiber reinforced composites have excellent specific strength and specific modulus, and are commonly used as lightweight load-bearing materials in aerospace and vehicle structures. At the same time, carbon fibers also have good electrical conductivity and certain lithium ion intercalation capacity, and can be used as electrodes for electrochemical batteries. Therefore, designing carbon fiber composites as structural batteries or structural supercapacitors with both mechanical load-bearing and electrochemical energy storage functions has become a research hotspot.

[0003] Some existing technologies and patents have explored the feasibility of carbon fiber structural energy storage composites. For example, US patent US11769879B2 discloses a technical solution for a carbon fiber structural battery, in which carbon fibers serve as both the reinforcement of the composite material and the electrode of the battery, combined with specific solid-state electrolytes and positive electrode materials, achieving an integrated design of structure and energy storage. However, the existing technology still has some deficiencies in material selection and structural design: (1) Lack of conductive polymer interface: existing solutions often use traditional carbon-based conductive additives or inorganic coatings to improve electrode conductivity, and do not fully utilize new conductive polymers for surface functionalization of carbon fibers, resulting in the need to improve the conductivity and interfacial bonding performance of the fiber / resin interface; (2) Limited electrolyte system: many structural batteries use solid-state electrolytes with low ionic conductivity, which sacrifices certain electrochemical performance while improving the modulus of the composite material. In addition, such electrolytes have poor wetting and adhesion performance on the surface of carbon fibers, resulting in high interfacial contact resistance; (3) Single structural level design: current structural energy storage composites are mostly simple laminated structures or uniformly distributed fiber structures, lacking optimization design at the micro-fiber interface, meso-laminated structure, and macro-component level, making it difficult to simultaneously consider mechanical properties and energy storage performance; (4) Complex process and reliability: the existing preparation process is relatively complex, often requiring special coating or assembly processes, and interface defects are difficult to avoid during the preparation process, resulting in the need to further improve the reliability indicators such as cycle stability and thermal stability.

[0004] Therefore, it is of great significance to provide a carbon fiber structural energy storage integrated composite material with good interfacial conductivity and ion conduction performance. SUMMARY

[0005] The application aims to provide a carbon fiber structure energy storage integrated composite material and a preparation method thereof, so as to solve the technical problems of insufficient interface conductivity and limited ion conduction of the composite material in the prior art.

[0006] In order to achieve the above-mentioned application purposes, the application provides the following technical solutions.

[0007] The application provides a carbon fiber structure energy storage integrated composite material, which is a layered sandwich structure and sequentially comprises at least one carbon fiber negative electrode layer, a solid electrolyte separator layer and at least one positive electrode layer from top to bottom.

[0008] The carbon fiber negative electrode layer is composed of carbon fibers and a conductive polymer coating.

[0009] The conductive polymer in the conductive polymer coating comprises one or more of poly(3,4-ethylenedioxythiophene)-polystyrene sulfonate, polyaniline and polypyrrole.

[0010] Further, the carbon fiber negative electrode layer is formed by in-situ chemical oxidation polymerization of carbon fibers immersed in a conductive polymer solution and addition of an oxidizing agent at 0-10 DEG C.

[0011] The concentration of the conductive polymer solution is 1-2%.

[0012] The oxidizing agent is a persulfate and / or a metal salt.

[0013] Further, the thickness of the conductive polymer coating is 0.1-10 microns.

[0014] The volume fraction of the carbon fibers in the composite material is 20-60%.

[0015] Further, the positive electrode layer is composed of a positive electrode active material, a conductive matrix and carbon fibers.

[0016] Further, the positive electrode active material comprises one or more of lithium iron phosphate, lithium nickel cobalt manganese oxide, lithium cobaltate and lithium manganate.

[0017] The conductive matrix is a combination of a binder and a conductive agent or a conductive polymer.

[0018] The binder comprises polyvinylidene fluoride.

[0019] The conductive agent comprises conductive carbon black.

[0020] The volume fraction of the carbon fibers is 10-40% of the positive electrode layer.

[0021] Further, the solid electrolyte separator layer comprises a thermosetting resin prepolymer and a lithium salt.

[0022] The thermosetting resin prepolymer comprises an epoxy resin and / or an epoxy acrylate prepolymer containing a polyether chain segment;

[0023] The lithium salt comprises LiPF6 and / or LiTFSI, and the concentration of the lithium salt is 0.5-2 mol / L;

[0024] The thickness of the solid electrolyte separator layer is 50-200 mu m.

[0025] Further, the solid electrolyte separator layer further comprises an ionic liquid;

[0026] The ionic liquid is an ionic liquid composed of 1-alkyl-3-methyl imidazole cation and BF4 - , PF6 - or TFSI - anion.

[0027] The application also provides a preparation method of the carbon fiber structure energy storage integrated composite material, comprising the following steps:

[0028] 1) The carbon fiber is immersed in a conductive polymer solution, an oxidizing agent is added, and in-situ chemical oxidation polymerization is formed at 0-10 DEG C to obtain a carbon fiber negative electrode layer;

[0029] 2) The positive electrode active material, the conductive agent and the binder are dissolved in a solvent and mixed to obtain a positive electrode slurry, and the positive electrode slurry is coated on the surface of another layer of pretreated carbon fiber to form a positive electrode layer;

[0030] 3) The carbon fiber negative electrode layer, the solid electrolyte separator layer and the positive electrode layer are sequentially stacked and then cured to obtain the carbon fiber structure energy storage integrated composite material.

[0031] Further, the specific steps of the carbon fiber pretreatment are that the carbon fiber sequentially passes through 300 DEG C baking and acetone cleaning, and then the carbon fiber is obtained.

[0032] The mass ratio of the positive electrode active material, the conductive agent and the binder is 85-95:2.5-7.5:2.5-7.5;

[0033] The coating amount of the positive electrode slurry is 5-15 mg / cm 2 .

[0034] Further, the curing adopts a vacuum hot pressing process, the curing temperature is 60-120 DEG C, the curing time is 2-10 h, and the curing pressure is 0.1-1 MPa.

[0035] The application has the following beneficial effects:

[0036] 1) The present application constructs a functionally graded interface of electronic / ion mixed conduction by introducing a conductive polymer coating on the surface of carbon fiber, significantly reduces the fiber-resin interface contact resistance, and improves the interface shear strength; the PEDOT: PSS coating used in the composite material of the present application not only has high conductivity, but also has flexibility; compared with the uncoated interface, the contact resistance is reduced by an order of magnitude, and the interface adhesion is increased by more than 20%, thereby significantly improving the conductivity and bonding strength of the interface;

[0037] 2) The composite solid electrolyte system in the present application ensures the mechanical properties while providing ion conductivity close to that of liquid electrolyte, with a room temperature ion conductivity of 10 -4 S / cm or more. Therefore, the rate performance and low temperature performance of the battery are greatly improved; at 1C rate, the battery can still output nearly 90% of the capacity, and also exhibits good discharge performance at-20℃ environment. This is due to the polyether modified solid electrolyte and ionic liquid gel materials, which improve the ion transport efficiency;

[0038] 3) Since the composite material of the present application contains carbon fiber, it not only has high strength and high modulus, but also has high specific capacity and energy density of the energy storage unit. The tensile Young's modulus of the composite material of the present application can reach 60-80GPa, and the tensile strength is 800-1200MPa, close to the performance indicators of pure carbon fiber composite material; the specific capacity based on the mass of the positive electrode active material is about 150mAh / g, and the energy density of the whole composite material is about 30-50Wh / kg. Compared with the existing structural battery technology, the present application realizes higher energy storage performance without sacrificing mechanical properties;

[0039] 4) The present application uses carbon fiber as a supporting skeleton and combines solid electrolyte to ensure the stability of the electrode structure during charge and discharge cycles. The structural battery type composite material of the present application has a capacity retention rate of more than 90% after 500 cycles at 0.5C rate, and a coulombic efficiency of about 99%; the structural supercapacitor type composite material has a capacitance retention rate of about 95% after 10000 cycles. At the same time, after repeated thermal cycling and vibration impact in the temperature range of-40-80℃, the material does not appear delamination or performance degradation, showing excellent environmental adaptability and safety (no risk of liquid electrolyte leakage);

[0040] 5) The conductive polymer coating, lamination curing and other processes used in the present application are mature technologies, easy to realize large-scale production. The selected material system has good compatibility, and no special equipment is needed during the production process. In practical applications, components that are both structural parts and batteries / capacitors can be manufactured according to the traditional composite material forming process, providing a new solution for weight reduction of spacecraft, unmanned aerial vehicles and other devices. BRIEF DESCRIPTION OF DRAWINGS

[0041] Figure 1 Structure diagram of carbon fiber structure energy storage integrated composite material of the present application;

[0042] Figure 2 Stress-strain curve comparison chart of composite material of Example 1 and comparative example (without conductive polymer interface) in tensile test. DETAILED DESCRIPTION

[0043] The present application provides a carbon fiber structure energy storage integrated composite material, which is a layered sandwich structure, and sequentially comprises at least one carbon fiber negative electrode layer, a solid electrolyte separator layer and at least one positive electrode layer from top to bottom.

[0044] The carbon fiber negative electrode layer is composed of carbon fiber and a conductive polymer coating.

[0045] The conductive polymer in the conductive polymer coating comprises one or more of poly(3,4-ethylenedioxythiophene)-polystyrene sulfonate, polyaniline and polypyrrole.

[0046] In the present application, the carbon fiber is surface treated with a coupling agent before being coated with the conductive polymer, and the coupling agent is a silane coupling agent containing amino or epoxy groups, so as to enhance the bonding force between the conductive polymer coating and the carbon fiber.

[0047] In the present application, the carbon fiber negative electrode layer is formed by immersing carbon fiber in a conductive polymer solution, adding an oxidizing agent, and forming by in-situ chemical oxidation polymerization at 0-10℃.

[0048] The concentration of the conductive polymer solution is 1-2%, preferably 1.1-1.8%, and further preferably 1.3-1.5%.

[0049] The oxidizing agent is a persulfate salt and / or a metal salt, and is preferably a persulfate salt.

[0050] In the present application, the thickness of the conductive polymer coating is 0.1-10μm, preferably 0.2-9μm, and further preferably 0.5-8μm.

[0051] In the present application, if the thickness of the conductive polymer coating is <0.5μm, the fiber is easy to be exposed; and if the thickness of the conductive polymer coating is >5μm, the fiber is easy to be brittle.

[0052] In the present application, the volume fraction of the carbon fiber in the composite material is 20-60%, preferably 25-55%, and further preferably 30-50%.

[0053] In the present application, the purpose of uniformly covering the carbon fiber surface with the conductive polymer is to make the fiber / matrix interface have good electronic conduction and bonding performance.

[0054] In the present application, the positive electrode layer is composed of a positive electrode active material, a conductive matrix and carbon fibers.

[0055] In the present application, the positive electrode active material comprises one or more of lithium iron phosphate, lithium nickel cobalt manganese oxide, lithium cobaltate and lithium manganate, preferably one or more of lithium iron phosphate, lithium cobaltate and lithium manganate, further preferably lithium iron phosphate and / or lithium cobaltate;

[0056] The conductive matrix is a combination of a binder and a conductive agent or a conductive polymer, preferably a combination of a binder and a conductive agent;

[0057] The binder is preferably polyvinylidene fluoride;

[0058] The conductive agent is preferably conductive carbon black;

[0059] The volume fraction of the carbon fibers is 10-40% of the positive electrode layer, preferably 12-38%, further preferably 15-35%.

[0060] In the present application, the purpose of the conductive matrix is to ensure that the positive electrode layer has sufficient electronic conductivity.

[0061] In the present application, the purpose of the carbon fibers in the positive electrode layer is to improve the mechanical strength and the continuity of the conductive network.

[0062] In the present application, the solid-state electrolyte separator layer comprises a thermosetting resin prepolymer and a lithium salt;

[0063] The thermosetting resin prepolymer comprises an epoxy resin containing polyether segments and / or an epoxy acrylate prepolymer, preferably an epoxy acrylate prepolymer;

[0064] The lithium salt comprises LiPF6 and / or LiTFSI, preferably LiPF6; the concentration of the lithium salt is 0.5-2 mol / L, preferably 0.6-1.8 mol / L, further preferably 0.8-1.5 mol / L;

[0065] The thickness of the solid-state electrolyte separator layer is 50-200 μm, preferably 60-180 μm, further preferably 70-150 μm.

[0066] In the present application, the solid-state electrolyte separator layer further comprises an ionic liquid;

[0067] The ionic liquid is an ionic liquid composed of a 1-alkyl-3-methylimidazolium cation and a BF4 - , PF6 - or TFSI - anion, preferably a BF4 - and / or PF6- , further preferably BF4 - .

[0068] The application also provides a preparation method of the carbon fiber structure energy storage integrated composite material, comprising the following steps:

[0069] 1) carbon fibers are immersed in a conductive polymer solution, an oxidizing agent is added, and in-situ chemical oxidation polymerization is carried out at 0-10℃ to obtain a carbon fiber negative electrode layer;

[0070] 2) a positive electrode active material, a conductive agent and a binder are dissolved in a solvent and mixed to obtain a positive electrode slurry, and the positive electrode slurry is coated on the surface of another layer of pretreated carbon fibers to form a positive electrode layer;

[0071] 3) the carbon fiber negative electrode layer, the solid electrolyte separator layer and the positive electrode layer are sequentially stacked and then cured to obtain the carbon fiber structure energy storage integrated composite material.

[0072] In the application, the specific steps of pretreating the carbon fibers are as follows: sequentially baking the carbon fibers at 300℃ and cleaning the carbon fibers with acetone.

[0073] In the application, the purpose of pretreating the carbon fibers is to remove the surface wetting agent and increase the polar groups to improve the adhesion of the coating.

[0074] In the application, the mass ratio of the positive electrode active material, the conductive agent and the binder is 85-95:2.5-7.5:2.5-7.5, preferably 87-94:3-5:3-5, and further preferably 90-93:4:4.

[0075] The coating amount of the positive electrode slurry is 5-15 mg / cm 2 , preferably 7-12 mg / cm 2 , and further preferably 8-10 mg / cm 2 .

[0076] In the application, the curing is performed by a vacuum hot pressing process, the curing temperature is 60-120℃, preferably 65-115℃, and further preferably 70-110℃, the curing time is 2-10h, preferably 3-9h, and further preferably 4-8h, and the curing pressure is 0.1-1MPa, preferably 0.2-0.9MPa, and further preferably 0.3-0.8MPa.

[0077] In the application, after the materials of the layers are assembled in a stacked manner, they are cured together to form an integrated composite material, and in the curing process, the conductive polymer coating on the surface of the carbon fibers and the solid electrolyte matrix occur interpenetration or copolymerization to form a firmly combined interface phase, thereby improving the structural integrity.

[0078] In the present application, after curing, drying, packaging and preliminary formation treatment are also included, and the specific steps are: applying sealing glue to the edge of the integrated composite material, waterproof packaging, and connecting the electrode lead-out end, which can be put into use after aging or initial cycle.

[0079] The technical solutions provided by the present application will be described in detail below in conjunction with the embodiments, but they should not be understood as limiting the scope of protection of the present application.

[0080] Example 1

[0081] The Toray T700 carbon fiber plain fabric was sequentially subjected to 300℃ baking and acetone cleaning to obtain pretreated carbon fiber;

[0082] The pretreated carbon fiber was immersed in a poly(3,4-ethylenedioxythiophene)-polystyrene sulfonate solution with a concentration of 1.3% (the poly(3,4-ethylenedioxythiophene)-polystyrene sulfonate solution contains 5% dimethyl sulfoxide), ammonium persulfate was added, and after 20 min of immersion, the carbon fiber was vacuum dried at 80℃ for 4h to obtain a carbon fiber negative electrode layer with a carbon fiber content of 40%;

[0083] The carbon fiber negative electrode layer was immersed in an epoxy acrylate prepolymer solution with a lithium salt concentration of 1mol / L (the epoxy acrylate prepolymer solution includes LiTFSI lithium salt and epoxy acrylate prepolymer) to obtain a solid electrolyte separator layer;

[0084] Lithium iron phosphate, conductive carbon black and PVDF with a mass ratio of 92:4:4 and a particle size of 1μm were mixed in acetone to obtain a positive electrode slurry, and the positive electrode slurry was coated onto the solid electrolyte separator layer with a coating amount of 10mg / cm 2 Then another layer of pretreated carbon fiber surface was covered as a current collector to form a positive electrode layer;

[0085] Finally, the epoxy acrylate prepolymer solution was continuously poured, and the curing was carried out at 80℃ and 0.2MPa for 12h to form a 0.6mm sandwich structure composite material.

[0086] A 50mm diameter disc sample was used as a battery, and the initial discharge specific capacity was 142mAh / g (calculated based on LFP) at a rate of 0.2C, the capacity retention rate was 92% after 500 cycles at a rate of 0.5C, and the coulombic efficiency was maintained above 99%, showing good cycle stability. The overall energy density of the composite material was 32Wh / kg. It can be seen that the composite material of Example 1 maintains high mechanical properties while achieving stable lithium ion battery energy storage performance.

[0087] Example 2

[0088] The difference between Example 1 and Example 2 is that the conductive polymer in Example 2 is polyaniline. The pretreated carbon fiber is immersed in a hydrochloric acid-aniline monomer solution with a concentration of 0.5 mol / L, and the polyaniline coating is 0.2 μm;

[0089] The positive active material is changed to ternary material LiNi 0.3 Co 0.1 Mn 0.6 O2, and the coating amount of the positive electrode slurry is 8 mg / cm 2 .

[0090] The performance of the composite material of Example 2 is tested, and the test results are as follows: the Young's modulus of the obtained composite material is 68 GPa, and the strength is 950 MPa.

[0091] The initial specific discharge capacity at 0.2 C is 155 mAh / g (calculated based on NMC), the energy density is 45 Wh / kg, and the capacity retention rate after 300 cycles at 0.5 C is 88%. Compared with Example 1, the polyaniline coating improves the initial capacity and energy density, but the cycle stability decreases slightly. This shows that different conductive polymers have an impact on performance: the stability of PEDOT:PSS in long cycles is better than that of PANI.

[0092] Example 3

[0093] The difference between Example 1 and Example 3 is that an ionic liquid is additionally added to the solid electrolyte separator layer of Example 3. PVDF-HFP polymer (20 wt%) is dissolved in acetone, and 80 wt% of ionic liquid EMIM-BF4 and appropriate amount of LiTFSI (0.8 mol / L) are added.

[0094] The performance of the composite material of Example 3 is tested, and the test results are as follows: the fiber volume fraction of the obtained composite material is high, reaching 60%, the tensile modulus is 55 GPa, and the strength is 820 MPa. Due to the ionic liquid, the ionic migration rate is improved, and the room temperature ionic conductivity reaches 5 x 10 -4 S / cm. The specific capacity of the battery at 1 C rate can still reach more than 90% of that in Example 1 at 0.2 C; the discharge capacity at low temperature of -10°C is 70% of that at room temperature, which is significantly better than that of Example 1. The capacity retention rate after 200 cycles is about 95%. However, due to the softness of the PVDF-based gel, the dimensional stability of the composite material at high temperature (>100°C) is slightly low, and packaging and restraining measures need to be taken in the structural design, such as fiberglass tape winding + epoxy pouring. Example 3 shows that by changing the electrolyte system, the rate performance and low temperature performance of the composite material can be improved.

[0095] Example 4

[0096] Compared with Example 1, the difference is that the carbon fiber negative electrode of Example 4 is first treated with 3-aminopropyl triethoxysilane (KH550) as a coupling agent on the fiber surface before being coated with PEDOT:PSS to improve the adhesion of the fiber to the resin and coating, and 0.5wt% of multi-walled carbon nanotubes (MWCNT) is added to the positive electrode slurry to improve the electrical conductivity and toughness.

[0097] The performance of the composite material of Example 4 was tested, and the test results were as follows: the tensile strength of the composite material was increased to 1100 MPa, and the Young's modulus was 79 GPa, which was 10% higher than that of Example 1. The electrochemical performance was also improved: the capacity retention rate was 95% after 500 cycles at 0.5C, which was better than 92% of Example 1, which indicated that the surface coupling agent treatment and the synergistic effect of the nano-carbon filler effectively enhanced the interface adhesion and the internal conductive network, so that the composite material maintained more stable performance in long-term cycling.

[0098] Example 5

[0099] Compared with Example 1, the difference is that the positive electrode carbon fiber cloth is coated with PEDOT:PSS in Example 5 (the method is the same as that of Example 1), and the negative electrode carbon fiber cloth is coated with polyaniline (the method is the same as that of Example 2). The electrolyte is a gel formed by blending EMIM-BF4 ionic liquid with PVDF-HFP (without lithium salt). The fiberglass film impregnated with the gel is sandwiched between two pieces of electrodes and laminated and packaged to form a structural supercapacitor composite material at room temperature.

[0100] The performance of the composite material of Example 5 was tested, and the test results were as follows: the tensile modulus was 25 GPa, and the strength was 400 MPa (since there was no rigid resin matrix, the mechanical properties were mainly provided by the carbon fiber). In the voltage window of 0-3V, the surface capacitance was about 0.25 F / cm 2 After 10000 cycles of charge and discharge at a current of 1A / g, the capacitance retention rate was 94%, which showed extremely high cycle life and power characteristics. However, since a flexible gel electrolyte is used, its rigidity is low, and it is suitable for structural components that do not require high rigidity but require high power density. This example shows that by adjusting the composition and structure of the material, the composite material of the present application can also work in the form of a supercapacitor to meet different application requirements.

[0101] Comparative Example

[0102] Compared with Example 1, the difference is that there is no conductive polymer interface in the comparative example.

[0103] The composite materials of Example 1 and the comparative example were tested for tensile strength, and the test results are shown in Figure 2 Figure 2 ​It can be seen that the fiber direction tensile Young's modulus of the fiber of Example 1 is 72 GPa, the breaking strain is close to 1.4%, and the tensile strength is 1020 MPa; the fiber direction tensile Young's modulus of the fiber of the comparative example is 65 GPa, the breaking strain is 1.25%, and the tensile strength is 810 MPa.

[0104] From the above examples, the present application provides a carbon fiber structure energy storage integrated composite material and a preparation method thereof. The composite material is a layered sandwich structure, and from top to bottom, it is at least one carbon fiber negative electrode layer, a solid electrolyte separator layer and at least one positive electrode layer. The carbon fiber negative electrode layer is composed of carbon fiber and a conductive polymer coating. The conductive polymer in the conductive polymer coating includes one or more of poly(3,4-ethylenedioxythiophene)-polystyrene sulfonate, polyaniline and polypyrrole. The present application realizes the consideration of the mechanical properties and electrochemical properties of the carbon fiber composite material through the interface modification of the conductive polymer and the introduction of the high ionic conductivity electrolyte. The energy density of the composite material of the present application can reach 30-50 Wh / kg, the tensile Young's modulus is more than 60 GPa, the capacity retention rate after 500 cycles is more than 90%, and the composite material has excellent thermal stability and safety, and can be used for spacecraft, unmanned aerial vehicles, electric vehicles and other structural components that need to integrate light weight and energy storage functions.

[0105] The above only describes the preferred embodiments of the present application, and it should be noted that for ordinary skilled persons in the art, several improvements and refinements can be made without departing from the principles of the present application, and these improvements and refinements should also be considered as the protection scope of the present application.

Claims

1. A carbon fiber structure energy storage integrated composite material, characterized in that: The composite material is a layered sandwich structure, which comprises, from top to bottom, at least one carbon fiber negative electrode layer, a solid electrolyte separator layer, and at least one positive electrode layer; The carbon fiber negative electrode layer is composed of carbon fiber and a conductive polymer coating; The conductive polymer in the conductive polymer coating comprises one or more of poly(3,4-ethylenedioxythiophene)-polystyrene sulfonate, polyaniline and polypyrrole.

2. The carbon fiber structure energy storage integrated composite material according to claim 1, characterized in that: The carbon fiber negative electrode layer is formed by immersing carbon fibers in a conductive polymer solution, adding an oxidant, and performing in-situ chemical oxidation polymerization at 0-10°C. The concentration of the conductive polymer solution is 1-2%; The oxidant is persulfate and / or metal salt.

3. The carbon fiber structure energy storage integrated composite material according to claim 2, characterized in that: The thickness of the conductive polymer coating is 0.1 to 10 μm; The volume fraction of the carbon fiber in the composite material is 20-60%.

4. The carbon fiber structure energy storage integrated composite material according to claim 2 or 3, characterized in that: The positive electrode layer is composed of positive electrode active material, a conductive matrix and carbon fibers.

5. The carbon fiber structure energy storage integrated composite material according to claim 4, characterized in that: The positive electrode active material includes one or more of lithium iron phosphate, lithium nickel cobalt manganese oxide, lithium cobalt oxide and lithium manganese oxide; The conductive matrix is ​​a combination of a binder and a conductive agent or a conductive polymer; The binder includes polyvinylidene fluoride; The conductive agent includes conductive carbon black; The volume fraction of the carbon fibers is 10 to 40% of the positive electrode layer.

6. The carbon fiber structure energy storage integrated composite material according to claim 1, 2 or 5, characterized in that: The solid electrolyte separator layer comprises a thermosetting resin prepolymer and a lithium salt; The thermosetting resin prepolymer includes epoxy resin and / or epoxy acrylate prepolymer containing polyether segments; The lithium salt includes LiPF6 and / or LiTFSI, and the concentration of the lithium salt is 0.5 to 2 mol / L; The thickness of the solid electrolyte separator layer is 50 to 200 μm.

7. The carbon fiber structure energy storage integrated composite material according to claim 6, characterized in that: The solid electrolyte separator layer also includes an ionic liquid; The ionic liquid is 1-alkyl-3-methylimidazolium cation and BF4 - PF6 - or TFSI - Ionic liquids composed of anions.

8. A method for preparing the carbon fiber structure energy storage integrated composite material according to any one of claims 1 to 7, characterized in that: The following steps are involved: 1) Immersing carbon fiber in a conductive polymer solution, adding an oxidant, and performing in-situ chemical oxidation polymerization at 0-10° C. to obtain a carbon fiber negative electrode layer; 2) dissolving the positive electrode active material, the conductive agent and the binder in a solvent and mixing them to obtain a positive electrode slurry, and coating the positive electrode slurry on the surface of another layer of pretreated carbon fibers to form a positive electrode layer; 3) The carbon fiber negative electrode layer, the solid electrolyte separator layer, and the positive electrode layer are stacked in sequence and then cured to obtain a carbon fiber structure energy storage integrated composite material.

9. The method for preparing the carbon fiber structure energy storage integrated composite material according to claim 8, characterized in that: The specific steps of carbon fiber pretreatment are: baking the carbon fiber at 300℃ and washing with acetone in sequence; The mass ratio of the positive electrode active material, the conductive agent and the binder is 85 to 95: 2.5～7.5：2.5～7.5； The coating amount of the positive electrode slurry is 5 to 15 mg / cm 2 .

10. The method for preparing the carbon fiber structure energy storage integrated composite material according to claim 8 or 9, characterized in that: The curing adopts a vacuum hot pressing process, the curing temperature is 60-120° C., the curing time is 2-10 hours, and the curing pressure is 0.1-1 MPa.

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