A soft package battery and structural battery with all carbon fibers as positive and negative electrodes

Abstract

The application belongs to the technical field of structural electrochemical energy devices, and particularly relates to a soft package battery and a structural battery with all-carbon fibers as positive and negative electrodes. The soft package battery with all-carbon fibers as positive and negative electrodes comprises a positive electrode, a negative electrode, an electrolyte, a diaphragm and an external packaging structure. Carbon fiber fabrics are sequentially subjected to yarn spreading and low-temperature plasma treatment to obtain treated carbon fibers. The positive electrode is obtained by depositing an Al plating layer on both sides of the treated carbon fibers, and then coating a positive electrode active material on the Al plating layer. The negative electrode is obtained by depositing a Cu plating layer on both sides of the treated carbon fibers, and then coating a negative electrode active material on the Cu plating layer. The application solves the problems of insufficient conductivity and excessive interface resistance in the prior art by means of plating metal on the surface of the fibers, and realizes the dual performance of mechanical bearing and high-efficiency energy storage by utilizing the flexibility of the fibers and the mutual laminated structure of the positive and negative electrodes.

Description

Technical Field

[0001] This invention belongs to the field of structural electrochemical energy device technology, specifically involving the cross-application of lightweight composite materials and energy storage technology, and particularly involving a soft-pack battery and structural battery with all carbon fiber as positive and negative electrodes. The structural battery with all carbon fiber as positive and negative electrodes is a structural battery that replaces the traditional metal current collector with all carbon fiber materials. Background Technology

[0002] In currently widely used lithium-ion battery structures, aluminum foil is typically used as the positive electrode current collector, while copper foil is used as the negative electrode current collector. Although metal foils have good conductivity, they have high density, poor flexibility, and insufficient interfacial compatibility with composite material structures, failing to meet the comprehensive requirements of aerospace and electric transportation devices for lightweighting, load-bearing capacity, and safety.

[0003] Carbon fiber, as a material with high specific strength and high specific modulus, possesses excellent electrical conductivity and corrosion resistance. By coupling its load-bearing capacity with its electrochemical properties, it can achieve functional-structural integration, making it a promising direction for next-generation structural batteries. However, existing carbon fiber-based composite material structural batteries generally suffer from insufficient current collector conductivity, excessive interfacial resistance, and difficulties in electrode integration. Summary of the Invention

[0004] To address the problems of insufficient current collector conductivity, excessive interfacial resistance, and difficulty in electrode integration in existing fiber composite material structure batteries, this invention provides a structural battery with all carbon fiber as positive and negative electrodes and its preparation method. In this structural battery with all carbon fiber as positive and negative electrodes, the core components are the positive and negative electrodes. The positive electrode consists of unrolled carbon fibers, an Al coating, and a positive electrode active material. The negative electrode consists of unrolled carbon fibers, a Cu coating, and a negative electrode active material. By plating metal onto the fiber surface, the problems of insufficient conductivity and excessive interfacial resistance in existing technologies are solved. This invention proposes a lightweight structural battery with carbon fiber composite conductive current collectors for both positive and negative electrodes. By utilizing the flexibility of the fibers and the stacked structure of the positive and negative electrodes, it achieves both mechanical load-bearing capacity and high-efficiency energy storage performance.

[0005] Based on the above technical objectives, the present invention adopts the following technical solution: This invention protects a pouch battery with all carbon fiber as positive and negative electrodes, including a positive electrode, a negative electrode, an electrolyte, a separator, and an external encapsulation structure. A solid electrolyte film or separator material is used to complete the electrochemical system isolation and ion transport, realizing the stacked encapsulation of pouch battery cells. The positive electrode, separator, and negative electrode are stacked and encapsulated by an external encapsulation structure. The electrolyte is located between each two adjacent layers. After encapsulation, a pouch battery with all carbon fiber as positive and negative electrodes is obtained. In this invention, the positive and negative electrodes of the pouch battery with all carbon fiber as positive and negative electrodes both use carbon fiber fabric as the current collector substrate.

[0006] The positive electrode is prepared according to the following steps: carbon fiber fabric is sequentially stretched and treated with low-temperature plasma to obtain treated carbon fiber. Then, an Al coating is deposited on both sides of the treated carbon fiber to form a positive electrode composite current collector. A positive electrode active material is then coated onto the Al coating to obtain the positive electrode. The negative electrode is prepared according to the following steps: carbon fiber fabric is sequentially stretched and treated with low-temperature plasma to obtain treated carbon fiber. Then, a Cu coating is deposited on both sides of the treated carbon fiber to form a negative electrode composite current collector. A negative electrode active material is then coated onto the Cu coating to obtain the negative electrode. Both the Al and Cu coatings are metallic coatings. Metallic coatings significantly improve the conductivity and mechanical strength of the fiber fabric, further improve the electron transport path, and reduce interfacial contact resistance. The positive and negative electrode composite current collectors serve as battery electrodes while simultaneously bearing external loads, achieving synergy between load-bearing and energy storage functions. The positive and negative electrode active materials are respectively loaded onto the metallized carbon fiber substrate surface to form the electrode structure of the composite current collector.

[0007] Preferably, the carbon fiber fabric has a thickness of 0.05mm to 0.1mm after unwinding, which shortens the electron transmission path, thereby reducing internal resistance and increasing specific surface area.

[0008] Preferably, the carbon fiber fabric is a plain weave or twill weave carbon fiber fabric with an areal density of 7 g / m³. 2 ~10g / m 2 The selected carbon fiber fabric has the potential for lightweight battery development.

[0009] Preferably, the Cu coating is formed by ion sputtering or electrochemical deposition, and the thickness of the Cu coating is 0.5 μm to 5 μm. If the Cu coating thickness is too low, the surface resistance will be too high; if the Cu coating thickness is too high, the overall thickness of the negative electrode will be increased too much, making it impossible to fabricate an ultra-thin and lightweight battery structure.

[0010] Preferably, the Al coating is formed by ion sputtering or electrochemical deposition, and the thickness of the Al coating is 0.5 μm to 5 μm. If the Al coating thickness is too low, the surface resistance will be too high; if the Al coating thickness is too high, the overall thickness of the positive electrode will be increased too much, making it impossible to fabricate an ultra-thin and lightweight battery structure.

[0011] Preferably, the positive electrode active material is a lithium iron phosphate-carbon nanotube composite material, which is prepared according to the following steps: lithium iron phosphate, carbon nanotubes and binder are mixed together in a solvent, and the mass ratio of lithium iron phosphate, carbon nanotubes and binder is 80~90:5~10:5~10. Further, the mass ratio of lithium iron phosphate, carbon nanotubes and binder is 90:5:5. The solvent is separated by vacuum drying and then solidified.

[0012] Preferably, the negative electrode active material is a graphite-carbon nanotube composite material, which is prepared according to the following steps: graphite, carbon nanotubes and binder are mixed together in a solvent, the mass ratio of graphite, carbon nanotubes and binder is 80~90:5~10:5~10, further, the mass ratio of graphite, carbon nanotubes and binder is 90:5:5, the solvent is separated by vacuum drying and solidified.

[0013] Preferably, a positive electrode tab is connected to the positive electrode, and the positive electrode tab is connected to the positive electrode through graphene conductive adhesive; a negative electrode tab is connected to the negative electrode, and the negative electrode tab is connected to the negative electrode through graphene conductive adhesive.

[0014] Preferably, the electrolyte is a commercial lithium-ion electrolyte, and more specifically, a lithium iron phosphate liquid electrolyte.

[0015] This invention also protects a structural battery, which is made using the above-mentioned all-carbon fiber as the positive and negative electrodes in a pouch cell, comprising: The battery body is composed of a pouch cell with all-carbon fiber as the positive and negative electrodes and a fiber prepreg. The pouch cell with all-carbon fiber as the positive and negative electrodes is sandwiched between the fiber prepreg and vacuum-cured to obtain the battery body. This battery body integrates mechanical load-bearing capacity and electrochemical energy storage. The electrodes are relatively thin, and the battery body also achieves the goals of ultra-thinness and lightweight design. Its tensile strength is ≥18MPa. Figure 8 As shown, it is suitable for fields with extremely high requirements for lightweighting and safety, such as aerospace and new energy vehicles.

[0016] The outer packaging components include vacuum valves, glass substrate, vacuum bag, breathable felt, separator, and release cloth. Two vacuum valves are symmetrically arranged on the glass substrate, and the battery body is located between the two vacuum valves. The breathable felt, separator, and release cloth are stacked in sequence, with the release cloth covering the battery body. Finally, a vacuum bag is used to cover the breathable felt and is detachably connected to the glass substrate.

[0017] Preferably, vacuum packaging or hot pressing forming processes are used to enable the structural battery to have both compression load-bearing capacity.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention introduces a metallized carbon fiber composite current collector structure into both the positive and negative electrodes of a soft-pack battery and a structural battery using all carbon fiber as the positive and negative electrodes. By depositing Al and Cu coatings on both sides of the carbon fiber fabric after yarn spreading and plasma treatment, the carbon fiber maintains its lightweight, high strength and flexibility while significantly improving the uniformity of in-plane conductivity and electron transport efficiency, effectively solving the problems of insufficient conductivity and excessive interfacial contact resistance that are common in existing carbon fiber electrodes.

[0019] 2. By directly using the metallized carbon fiber composite current collector as the electrode load-bearing skeleton, this invention enables the electrode layer to bear structural loads while participating in energy storage, avoiding the problem in existing structural batteries where "battery cells are only used as functional fillers". This makes the battery cells truly become load-bearing components in the composite material structural system, thereby significantly improving the functional integration and material utilization efficiency of the structural battery.

[0020] 3. In view of the differences in electrochemical characteristics between the positive and negative electrodes, this invention uses Al coating and Cu coating respectively to match the corresponding active materials to construct a symmetrical composite current collector structure. This not only ensures the stable matching of the positive and negative electrodes in electrochemical performance, but also improves the structural integrity and long-term reliability of the electrodes during charge and discharge cycles. This technical solution is different from the existing structural battery design that only introduces carbon fiber in a single electrode or local area.

[0021] 4. The present invention adopts a composite design of unfolded carbon fiber fabric and ultra-thin metal coating, which makes the resulting electrode thin, light and flexible. It is not only conducive to the stacking and packaging of soft pack batteries, but also can be vacuum cured and molded together with fiber prepreg. It is suitable for applications with extremely high requirements for lightweighting and structural integrity, such as aerospace, new energy transportation. Attached Figure Description

[0022] The structural battery of this invention is particularly suitable for fields with strict requirements for lightweighting and structural strength, such as aerospace drones, advanced electric vehicle bodies, and flexible energy storage components. It can significantly improve equipment energy efficiency and structural integration, and has broad engineering application potential.

[0023] Figure 1 This is a schematic diagram of the structure of the battery body of the present invention.

[0024] Figure 2 This is a schematic cross-sectional view of the layered structure of a pouch cell with all carbon fiber as the positive and negative electrodes.

[0025] Figure 3 This is a diagram showing the unfolded shape of the carbon fiber fabric in Example 1.

[0026] Figure 4 The upper figure shows the physical image and microscopic SEM image of the positive electrode of Example 1, and the lower figure shows the schematic diagram of the positive electrode structure.

[0027] Figure 5 The upper figure shows the physical image and microscopic SEM image of the negative electrode of Example 1, and the lower figure shows the schematic diagram of the negative electrode structure.

[0028] Figure 6 This diagram illustrates the packaging steps for a pouch cell using all carbon fiber as both positive and negative electrodes.

[0029] Figure 7 This is a schematic diagram of the cycle performance test curve of the structure battery in Example 1.

[0030] Figure 8 The graphs show the mechanical performance load-bearing test curves of the structural battery in Example 1. The left graph shows the mechanical performance load-bearing test curves under three parallel measurements, and the right graph shows the mechanical performance load-bearing test curves under three parallel measurements on different surfaces.

[0031] Figure 9 This is a schematic diagram of the structure of the battery in Example 1.

[0032] Explanation of reference numerals in the attached figures: 1-Sealant, 2-Vacuum valve, 3-Glass substrate, 4-Vacuum bag, 5-Ventilation station, 6-Separating membrane, 7-Mold release cloth, 8-Fiber prepreg, 9-Soft pack battery with all carbon fiber as positive and negative electrodes, 901-Positive electrode, 902-Positive electrode tab, 903-Negative electrode, 904-Negative electrode tab, 905-Electrolyte, 906-Carbon fiber composite laminate, 907-Carbon fiber fabric, 908-Negative electrode active material, 909-Copper plating, 911-Positive electrode active material, 912-Metallic aluminum plating. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0034] In this invention, the core components of the all-carbon fiber structured battery, which uses carbon fiber as both positive and negative electrodes, are the positive and negative electrodes. The positive electrode 901 is prepared according to the following steps: carbon fiber fabric is sequentially unfurled and subjected to low-temperature plasma treatment to obtain treated carbon fiber 907. Then, an Al coating 912 is deposited on both sides of the treated carbon fiber 907 to form a positive electrode composite current collector. Finally, a positive electrode active material 911 is coated onto the Al coating 912 to obtain the positive electrode 901. The negative electrode 903 is prepared according to the following steps: carbon fiber fabric is sequentially unfurled and subjected to low-temperature plasma treatment to obtain… Carbon fiber 907 is processed, and then a Cu coating 909 is deposited on both sides of the processed carbon fiber 907 to form a negative electrode composite current collector. Then, a negative electrode active material 908 is coated on the Cu coating 909 to obtain a negative electrode 903. Compared with traditional metal foil current collector batteries, the all-carbon fiber composite current collector structure of the present invention effectively reduces the amount of metal used, avoids the risk of metal foil fatigue fracture and corrosion failure, and significantly improves the safety, durability and environmental adaptability of the structure battery while ensuring electrochemical performance, and has good engineering application prospects.

[0035] The technical solution of the present invention will be studied using the following embodiments. The specific research methods and results are shown below: Example 1 A method for fabricating a structural battery includes the following steps: S1. T700 grade plain weave carbon fiber fabric is selected as the electrode carrier substrate. The fiber bundle is evenly spread through the yarn spreading process, so that the thickness of the carbon fiber fabric is controlled at 0.07mm. Then, it is cleaned with acetone and then treated with low temperature plasma (power 200W) in nitrogen environment for 10min to increase its surface energy to 50mN / m, thus obtaining treated carbon fiber 907.

[0036] Al coating 912 was deposited on both sides of the treated carbon fiber 907 by ion sputtering. The thickness of Al coating 912 was 2 μm, and the thickness after sputtering reached 0.09 mm, with an area resistivity ≤3.4 Ω / □. Positive electrode active material 911 was then uniformly coated onto the Al coating 912. Positive electrode active material 911 is a lithium iron phosphate-carbon nanotube composite material, which is obtained by mixing lithium iron phosphate, carbon nanotubes, and a binder in a solvent. The mass ratio of lithium iron phosphate, carbon nanotubes, and binder was 90:5:5. Finally, the mixture was vacuum dried at 120°C for 12 h, forming a conductive layer to obtain positive electrode 901. After coating, the thickness of the positive electrode was only 0.15 mm.

[0037] Another treated carbon fiber 907 was used, and Cu coating 909 was deposited on both sides of the treated carbon fiber 907 by ion sputtering. The thickness of Cu coating 909 was 2 μm, and the thickness after sputtering reached 0.09 mm, with an area resistivity ≤3.4 Ω / □. Then, negative electrode active material 908 was uniformly coated on Cu coating 909. Negative electrode active material 908 is a graphite-carbon nanotube composite material, which is obtained by mixing graphite, carbon nanotubes and binder together in a solvent. The mass ratio of graphite, carbon nanotubes and binder is 90:5:5. Multi-level conductive network construction: carbon nanotubes and graphite were dispersed in N-methylpyrrolidone dissolved in polyvinylidene fluoride, coated on the surface of Cu coating 909, and finally vacuum dried at 120°C for 12 h. After drying, a conductive layer was formed, and negative electrode 903 was obtained. After coating, the thickness of negative electrode was only 0.17 mm.

[0038] S2. The positive electrode 901, separator, and negative electrode 903 are stacked and encapsulated using an external encapsulation structure. The external encapsulation structure is a symmetrically arranged carbon fiber composite laminate 906. After encapsulation, lithium iron phosphate liquid electrolyte 905 is injected into the external encapsulation structure so that the electrolyte 905 is located between each two adjacent layers, resulting in a soft-pack battery 9 with all carbon fiber as the positive and negative electrodes.

[0039] S3. The fiber prepreg 8 and the pouch cell 9 with all carbon fiber as positive and negative electrodes are cured together at room temperature to integrally cure the structure and the battery to obtain the battery body. The fiber prepreg 8 is made of epoxy resin and carbon fiber. The amount of carbon fiber in the fiber prepreg 8 will not affect the electrochemical performance of the pouch cell 9 with all carbon fiber as positive and negative electrodes.

[0040] S4. Two vacuum valves 2 are symmetrically mounted on the glass substrate 3. The battery body is placed between the two vacuum valves 2. The breathable felt 5, the separator 6, and the release cloth 7 are stacked and arranged so that the release cloth 7 covers the battery body. Finally, a vacuum bag 4 is used to cover the breathable felt 5, and the vacuum bag 4 is detachably connected to the glass substrate 3 using sealant 1. The battery with the desired structure is obtained by vacuum curing at room temperature.

[0041] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A soft-pack battery with all carbon fiber as positive and negative electrodes, comprising a positive electrode (901), a negative electrode (903), an electrolyte (905), a separator, and an external encapsulation structure, wherein the positive electrode (901), the separator, and the negative electrode (903) are stacked and encapsulated by the external encapsulation structure, and the electrolyte (905) is located between each adjacent two layers, and after encapsulation, the soft-pack battery (9) with all carbon fiber as positive and negative electrodes is obtained, characterized in that: The positive electrode (901) is prepared according to the following steps: carbon fiber fabric is sequentially spread and treated with low temperature plasma to obtain treated carbon fiber (907), and then Al coating (912) is deposited on both sides of the treated carbon fiber (907) to form a positive electrode composite current collector, and then positive electrode active material (911) is coated on the Al coating (912) to obtain the positive electrode (901). The negative electrode (903) is prepared according to the following steps: carbon fiber fabric is sequentially subjected to yarn spreading and low-temperature plasma treatment to obtain treated carbon fiber (907), and then Cu coating (909) is deposited on both sides of the treated carbon fiber (907) to form a negative electrode composite current collector, and then negative electrode active material (908) is coated on the Cu coating (909) to obtain the negative electrode (903).

2. The pouch cell with all-carbon fiber as positive and negative electrodes according to claim 1, characterized in that, After the carbon fiber fabric is unrolled, its thickness reaches 0.05mm to 0.1mm.

3. The pouch cell with all-carbon fiber as positive and negative electrodes according to claim 1, characterized in that, The carbon fiber fabric is selected from plain weave or twill weave carbon fiber fabric with an areal density of 7 g / m³. 2 ~10g / m 2 .

4. The pouch cell with all-carbon fiber as positive and negative electrodes according to claim 1, characterized in that, The Cu coating (909) is formed by ion sputtering or electrochemical deposition, and the thickness of the Cu coating (909) is 0.5 μm to 5 μm.

5. The pouch cell with all-carbon fiber as positive and negative electrodes according to claim 1, characterized in that, The Al coating (912) is formed by ion sputtering or electrochemical deposition, and the thickness of the Al coating (912) is 0.5 μm to 5 μm.

6. The pouch cell with all-carbon fiber as positive and negative electrodes according to claim 1, characterized in that, The positive electrode active material (911) is a lithium iron phosphate-carbon nanotube composite material. The lithium iron phosphate-carbon nanotube composite material is prepared according to the following steps: lithium iron phosphate, carbon nanotubes and binder are mixed together in a solvent, and the mass ratio of lithium iron phosphate, carbon nanotubes and binder is 80~90:5~10:5~10. The solvent is then dried and separated.

7. The pouch cell with all-carbon fiber as positive and negative electrodes according to claim 1, characterized in that, The negative electrode active material (908) is a graphite-carbon nanotube composite material. The graphite-carbon nanotube composite material is prepared according to the following steps: graphite, carbon nanotubes and binder are mixed together in a solvent, and the mass ratio of graphite, carbon nanotubes and binder is 80~90:5~10:5~10. The solvent is then dried and separated.

8. The pouch cell with all-carbon fiber as positive and negative electrodes according to claim 1, characterized in that, The positive electrode (901) is connected to a positive electrode tab (902), and the negative electrode (903) is connected to a negative electrode tab (904).

9. A structural battery, characterized in that, A pouch cell manufactured using all-carbon fiber as the positive and negative electrodes as described in any one of claims 1 to 8, comprising: The battery body is composed of a soft-pack battery (9) with the full carbon fiber as the positive and negative electrodes and a fiber prepreg (8). The soft-pack battery (9) with the full carbon fiber as the positive and negative electrodes is sandwiched between the fiber prepreg (8) and vacuum cured to obtain the battery body. The outer packaging components include a vacuum valve (2), a glass substrate (3), a vacuum bag (4), a breathable felt (5), a separator (6), and a release cloth (7). Two vacuum valves (2) are symmetrically arranged on the glass substrate (3), and the battery body is located between the two vacuum valves (2). The breathable felt (5), the separator (6), and the release cloth (7) are stacked in sequence, and the release cloth (7) covers the battery body. Finally, the vacuum bag (4) is used to cover the breathable felt (5) and is detachably connected to the glass substrate (3).

10. The structural battery according to claim 9, characterized in that, The structural batteries also employ vacuum encapsulation or hot-press forming processes.

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