A flexible structure battery and its preparation method

Abstract

The present invention discloses a flexible structure battery and a preparation method thereof. The battery includes an integrated positive electrode layer, a gel electrolyte separator layer, and a multifunctional negative electrode layer; the integrated positive electrode layer includes a positive electrode substrate and a positive electrode active material layer; one side edge of the positive electrode substrate protrudes outward to form a positive electrode tab; the positive electrode active material layer is disposed on the portion of the positive electrode substrate surface except the positive electrode tab; the multifunctional negative electrode layer is a porous negative electrode substrate, and one side edge protrudes outward to form a negative electrode tab; the gel electrolyte separator layer is disposed between the integrated positive electrode layer and the multifunctional negative electrode layer. The flexible structure battery provided by the present invention is a lightweight composite material integrating structural load-bearing, mechanical flexibility, and electrical energy storage, which is both energy-saving and emission-reducing. It can be folded, bent, stretched, and twisted, and the porous electrodes also improve its electrochemical performance. It can be widely applied to many fields such as portable electronic devices, wearable electronic devices, automobiles, and aerospace.

Description

Technical Field

[0001] The present invention belongs to the technical field of the design and preparation of flexible electronic devices and structure - energy storage integrated composites, and particularly relates to a flexible structure battery and a preparation method thereof. Background Art

[0002] With the continuous growth of the global population and the rapid development of the economy, the demand for energy use in various countries is increasing day by day. So far, the types of energy used in various countries are still mainly natural energy such as oil and natural gas, which has also led to a significant reduction in the global reserves of natural resources and may face serious energy depletion problems. Moreover, its main emission, carbon dioxide, has caused serious pollution to the environment and hindered the realization of the "dual carbon" goal. In view of this, the new energy field has begun to thrive. It has the advantages of high energy storage efficiency, environmental friendliness, etc., effectively solving the problems of insufficient supply caused by the consumption of traditional energy and the increasingly severe environmental problems. In recent years, scholars at home and abroad have been committed to the development of new energy and the research of multifunctional energy storage composites, continuously improving the energy storage efficiency of new energy and integrating the multifunctional properties of materials. Therefore, vigorously developing new energy and new multifunctional energy storage composites has become a long - term development strategy and an inevitable trend for various countries in the fields of aerospace, transportation, etc.

[0003] The so - called multifunctional energy storage composites, the most representative one is the structure - energy storage integrated composites, and its core lies in the multifunctionalization of materials and the lightweight of structural components. Among them, the most representative one is the lightweight composite material that integrates structural load - bearing and electrical energy storage, that is: structural battery. When the structural battery works, the electrochemical reaction occurring inside is similar to that of a traditional lithium battery. The difference is that the electrodes and electrolytes of the structural battery use carbon fiber and polymer electrolyte with better mechanical load - bearing performance, which enables it to be used as a structural component and store electrical energy, achieving lightweight, higher safety and energy conservation and emission reduction. In addition to structural batteries, flexible batteries are also a type of battery that integrates excellent mechanical and electrochemical properties. With the continuous development of flexible electronic devices, flexible batteries have also become a frontier topic in the battery field. It has high flexibility, can be repeatedly folded, and can withstand deformations such as bending, stretching and twisting, so it can be widely used in wearable electronic devices, flexible display devices and intelligent biological devices. At present, there are many preparation processes for flexible batteries, but the most effective one is to start from the basic components of the battery (current collector, electrolyte and electrode material), and realize the flexibility of the entire battery structure through selecting flexible materials or preparing integrated electrodes with the help of flexible matrices. Consistent with the advantages of structural batteries, flexible batteries are also batteries with excellent mechanical properties, but the performance manifestation forms of the two are different. The latter is mainly manifested in its excellent mechanical flexibility.

[0004] However, a series of problems have also emerged in the research and use of new batteries. Although conventional structural batteries have strong structural load-bearing capacity, the presence of their metal current collectors and rigid active materials results in poor flexibility. When applied to some structural components that need to be repeatedly folded, stress concentration may occur, leading to failure. Secondly, in order to pursue breakthroughs in mechanical properties during the design of conventional structural batteries, some of their electrochemical properties are often sacrificed. For traditional flexible lithium batteries, although they have high flexibility, they often exhibit various complex failure and safety problems due to the inability of the electrode layer to withstand some harsh mechanical environments (such as extrusion, impact, etc.). On the other hand, flexible lithium batteries are generally implanted and belong to parasitic structures, and cannot be directly used as structural components, which also causes unnecessary energy consumption.

[0005] Traditional structural batteries and flexible lithium batteries exhibit different mechanical property advantages. How to complement their advantages and disadvantages is of utmost importance. In the field of structure-energy storage integrated materials, how to optimize electrochemical and mechanical properties poses a huge challenge to designers. Summary of the Invention

[0006] In order to solve the above problems, the purpose of the present invention is to provide a flexible structural battery and its preparation method.

[0007] To achieve the above object, the flexible structural battery provided by the present invention includes: an integrated positive electrode layer, a gel electrolyte separator layer, and a multi-functional negative electrode layer; the integrated positive electrode layer includes: a positive electrode substrate and a positive electrode active material layer; a positive electrode tab protrudes outward from one side edge of the positive electrode substrate for external connection with other load circuits or devices; the positive electrode active material layer is disposed on the part of the positive electrode substrate surface except the positive electrode tab; the multi-functional negative electrode layer is a porous negative electrode substrate, and a negative electrode tab protrudes outward from one side edge, which serves as both the negative electrode of the battery and the negative electrode current collector; the gel electrolyte separator layer is disposed between the integrated positive electrode layer and the multi-functional negative electrode layer.

[0008] The positive electrode substrate is made of degummed carbon fiber cloth with a thickness of 110 - 330 μm; the degumming treatment is to soak the carbon fiber cloth in an acetone and ethanol solvent with a volume ratio of 1:2 for 20 h, then ultrasonically clean it with deionized water and dry it at a constant temperature of 80 °C for 10 h.

[0009] The positive electrode active material layer is formed by coating a positive electrode slurry, which is prepared by mixing a positive electrode active material, a conductive additive, and a binder in proportion with a solvent, on the surface of the positive electrode substrate except for the positive electrode tab, and then drying and curing it. The thickness is 1 - 2000 μm. The positive electrode active material is selected from any one of the lithium battery positive electrode materials including ternary positive electrode material NCM811, lithium manganate, lithium titanate, lithium cobaltate, and lithium iron phosphate. The conductive additive is selected from any one of graphene, conductive carbon black, and carbon nanotubes (CNTs). The binder is a polyvinylidene fluoride (PVDF) solution with a mass concentration of 4 - 6%. The solvent is N-methylpyrrolidone (NMP). The mass ratio of the positive electrode active material, the conductive additive, and the binder is 7:1.5:1.5.

[0010] The gel electrolyte separator layer is formed by curing a gel electrolyte composed of a polymer substance, a low molecular weight electrolyte solvent, and a lithium salt. The thickness is 15 - 25 μm.

[0011] The gel electrolyte is prepared by mixing a polymer substance, a low molecular weight electrolyte solvent, and a lithium salt in proportion and heating it to 55°C for 15 h to dissolve. Among them, the polymer substance is selected from at least one of polyvinylidene fluoride (PVDF), polyethylene oxide (PEO), poly(vinylidene fluoride - co - hexafluoropropylene) (PVDF - co - HFP), polyacrylonitrile (PAN), and polymethyl methacrylate (PMMA). The concentration of poly(vinylidene fluoride - co - hexafluoropropylene) (PVDF - co - HFP) is 0.1 - 0.3 g / ml. The low molecular weight electrolyte solvent is selected from at least one of ethylene carbonate, propylene carbonate, diethyl carbonate, dimethyl carbonate, and a mixture of ethylene carbonate (EC) and diethyl carbonate (DEC). The mass ratio of ethylene carbonate (EC) to diethyl carbonate (DEC) is 2 - 4:6 - 8. The lithium salt is selected from one of lithium hexafluorophosphate (LiPF6), lithium perchlorate (LiClO4), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), and lithium tetrafluoroborate (LIBF4). The dosage ratio of the polymer substance, the low molecular weight electrolyte solvent, and the lithium salt is 1 - 3 g:10 - 30 ml:1 - 2 g.

[0012] The multifunctional negative electrode layer uses a porous carbon fiber cloth that has been degummed, chemically activated with a KOH solution, and impregnated with a gel electrolyte. The thickness is 110 - 330 μm. The degumming treatment involves soaking the porous carbon fiber cloth in an acetone and ethanol solvent with a volume ratio of 1:2 for 20 h, then ultrasonically cleaning with deionized water and drying at a constant temperature of 80 °C for 10 h. The chemical activation with the KOH solution involves impregnating the parts of the degummed porous carbon fiber cloth except for the negative electrode tab in the KOH solution, then placing it in a rotary evaporator to evaporate the solution, and then drying at 120 °C for 12 hours to obtain a porous carbon fiber cloth impregnated with KOH. Then, activation is carried out. The porous carbon fiber cloth impregnated with KOH is placed in a tubular furnace with a nitrogen flow, heated at a rate of 5 °C / min until the activation temperature of 850 °C is reached in the furnace, and kept at a constant temperature and statically activated for 1.5 h - 2 h. After terminating the activation, the porous carbon fiber cloth is repeatedly washed with distilled water until there is no OH- in the leaching solution, and then dried at 105 °C for 10 hours to obtain the activated porous carbon fiber cloth. Finally, the parts of the activated porous carbon fiber cloth except for the negative electrode tab are impregnated in the gel electrolyte for 10 min, then taken out and dried by ventilation for 30 min, and this process is repeated 2 - 4 times to solidify the gel electrolyte and obtain the multifunctional negative electrode layer.

[0013] The preparation method of the flexible structure battery is as follows: A layer of gel electrolyte is uniformly coated on the parts of the surface of the integrated positive electrode layer except for the positive electrode tab and on the parts of the surface of the multifunctional negative electrode layer except for the negative electrode tab. Then, it is dried in an oven until the gel electrolyte becomes semi-solid. The bottom surface of the integrated positive electrode layer and the top surface of the multifunctional negative electrode layer are stacked together. After the gel electrolyte solidifies, a gel electrolyte separator layer is formed between the integrated positive electrode layer and the multifunctional negative electrode layer. Then, the whole is roll-pressed and dried at a constant temperature of 60 °C. Finally, the edges are heat-sealed to obtain the flexible structure battery.

[0014] The thickness of the flexible structure battery is 1 mm.

[0015] Compared with the prior art, the flexible structure battery and its preparation method provided by the present invention have the following beneficial effects:

[0016] The flexible structure battery provided by the present invention is a lightweight composite material that integrates structural load-bearing, mechanical flexibility, and electrical energy storage, getting rid of the "parasitic attributes" of traditional batteries in terms of mass and volume, saving energy and reducing emissions. The preparation process is simple, and the shape can be customized. It can be folded, bent, stretched, and twisted, and the porous electrodes also improve its electrochemical performance. In the future, it can be widely applied in many fields such as portable electronic devices, wearable electronic devices, automobiles, and aerospace. Description of the Drawings

[0017] Figure 1 It is a three-dimensional structure diagram of the flexible structure battery provided by the present invention;

[0018] Figure 2 Schematic diagram of the integrated positive electrode layer and the coated electrolyte in the flexible structure battery provided by the present invention;

[0019] Figure 3 Schematic diagram of the multi-functional negative electrode layer and the gel electrolyte separator layer in the flexible structure battery provided by the present invention;

[0020] Figure 4 Schematic diagram of the bending state when the flexible structure battery provided by the present invention is in use; Detailed implementation manners

[0021] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0022] All materials used in the following embodiments of the present invention are commercially available products and are easy to obtain.

[0023] Embodiment 1

[0024] Please refer to Figures 1-4 , and the preparation method of the flexible structure battery provided in this embodiment is described as follows:

[0025] 1. Prepare the integrated positive electrode layer 1

[0026] First, degrease the carbon fiber cloth. The method is to soak the carbon fiber cloth in an acetone and ethanol solvent with a volume ratio of 1:2 for 20 h, then ultrasonically clean it with deionized water and dry it at a constant temperature of 80 °C for 10 h; then cut the degreased carbon fiber cloth according to the customized shape, leaving a positive electrode tab 11-1 on one side edge during cutting to obtain a positive electrode substrate 11 with a thickness of 167 μm; then add lithium iron phosphate, carbon nanotubes and polyvinylidene fluoride with a mass concentration of 5% in a mass ratio of 7:1.5:1.5 to N-methylpyrrolidone and mix evenly to obtain a positive electrode slurry; then evenly coat the positive electrode slurry on the part of the surface of the positive electrode substrate 11 except the positive electrode tab 11-1 and dry and cure it to obtain a positive electrode active material layer 12 with a thickness of 500 μm; the integrated positive electrode layer 1 with a thickness of 667 μm is composed of the positive electrode substrate 11 and the positive electrode active material layer 12.

[0027] 2. Prepare the gel electrolyte

[0028] Mix 0.2 g / ml of poly(vinylidene fluoride - co - hexafluoropropylene) (PVDF - co - HFP), ethylene carbonate (EC) and diethyl carbonate (DEC) with a mass ratio of 3:7 and lithium hexafluorophosphate (LiPF6) according to the dosage ratio of 2 g:20 ml:1.5 g and heat to 55 °C for 15 h to dissolve, obtaining a gel electrolyte.

[0029] 3. Prepare the multifunctional negative electrode layer 3

[0030] First, degrease the porous carbon fiber cloth. The method is to soak the porous carbon fiber cloth in an acetone and ethanol solvent with a volume ratio of 1:2 for 20 h, then ultrasonically clean with deionized water and dry at a constant temperature of 80 °C for 10 h; then cut the degreased porous carbon fiber cloth according to the customized shape, leaving a negative electrode tab 3 - 1 at one side edge during cutting; then immerse the part of the degreased porous carbon fiber cloth except the negative electrode tab 3 - 1 in KOH solution, place it in a rotary evaporator to evaporate the solution, then dry at 120 °C for 12 h, and then place the porous carbon fiber cloth impregnated with KOH in a tube furnace with nitrogen flowing, heat at a rate of 5 °C / min until the activation temperature in the furnace reaches 850 °C, keep it at a constant temperature and stand for activation for 2 h. After terminating the activation, wash the porous carbon fiber cloth repeatedly with distilled water until the leaching solution is neutral and then dry at 105 °C for 10 h to obtain a porous carbon fiber cloth chemically activated by KOH solution; then immerse the part of the porous carbon fiber cloth chemically activated by KOH solution except the negative electrode tab 3 - 1 in the gel electrolyte for 10 min, then take it out and place it in a fume hood to cure for 30 min, and repeat this impregnation process 2 - 4 times to obtain a multifunctional negative electrode layer 3 with a thickness of about 294 μm.

[0031] 4. Prepare the flexible structure battery

[0032] Obtain the integrated positive electrode layer 1 in the above step

[0033] Uniformly coat a layer of gel electrolyte on the part of the surface of the integrated positive electrode layer 1 except the positive electrode tab 11 - 1 and the part of the surface of the multifunctional negative electrode layer 3 except the negative electrode tab 3 - 1. Then, when drying in an oven until the gel electrolyte becomes semi - solid, stack the bottom surface of the integrated positive electrode layer 1 and the top surface of the multifunctional negative electrode layer 3 together. After the gel electrolyte cures, a gel electrolyte separator layer 2 is formed between the integrated positive electrode layer 1 and the multifunctional negative electrode layer 3; then roll - press the whole and dry at a constant temperature of 60 °C; finally, heat - seal the edges to obtain a flexible structure battery with a thickness of about 1 mm.

[0034] Example Two

[0035] 1. Prepare the integrated positive electrode layer 1

[0036] In this step, a ternary cathode material NCM811, carbon black, and polyvinylidene fluoride with a concentration of 4% are added to N-methylpyrrolidone in a mass ratio of 7:1.5:1.5 and mixed evenly to obtain a cathode slurry. The other steps are the same as those in Step 1 of Example 1, and an integrated cathode layer 1 is obtained.

[0037] 2. Preparation of gel electrolyte

[0038] In this step, poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-co-HFP) at 0.1 g / ml, ethylene carbonate (EC) and diethyl carbonate (DEC) in a mass ratio of 2:8, and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) are mixed in a dosage ratio of 1 g:10 ml:1 g and heated to 55 °C for 15 h to dissolve, obtaining a gel electrolyte.

[0039] 3. Preparation of multifunctional anode layer 3

[0040] This step is the same as Step 3 of Example 1.

[0041] 4. Preparation of flexible structure battery

[0042] This step is the same as Step 4 of Example 1.

[0043] Example 3

[0044] 1. Preparation of integrated cathode layer 1

[0045] In this step, lithium manganate, graphene, and polyvinylidene fluoride with a concentration of 6% are added to N-methylpyrrolidone in a mass ratio of 7:1.5:1.5 and mixed evenly to obtain a cathode slurry. The other steps are the same as those in Step 1 of Example 1, and an integrated cathode layer 1 is obtained.

[0046] 2. Preparation of gel electrolyte

[0047] In this step, poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-co-HFP) at 0.3 g / ml, ethylene carbonate (EC) and diethyl carbonate (DEC) in a mass ratio of 4:6, and lithium tetrafluoroborate (LiBF4) are mixed in a dosage ratio of 3 g:30 ml:2 g and heated to 55 °C for 15 h to dissolve, obtaining a gel electrolyte.

[0048] 3. Preparation of multifunctional anode layer 3

[0049] This step is the same as Step 3 of Example 1.

[0050] 4. Preparation of flexible structure battery

[0051] This step is the same as step 4 of the first embodiment. Although the embodiments of the present invention have been shown and described, those of ordinary skill in the art can understand that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and these all fall within the protection scope of the present invention.

Claims

1. A flexible structure battery, characterized in that: The flexible structure battery includes: an integrated positive electrode layer (1), a gel electrolyte separator layer (2), and a multi-functional negative electrode layer (3); the integrated positive electrode layer (1) includes: a positive electrode substrate (11) and a positive electrode active material layer (12); one side edge of the positive electrode substrate (11) protrudes outward to form a positive electrode tab (11-1) for facilitating external connection with other load circuits or devices; the positive electrode active material layer (12) is disposed at a position on the surface of the positive electrode substrate (11) except the positive electrode tab (11-1); the multi-functional negative electrode layer (3) is a porous negative electrode substrate, and one side edge protrudes outward to form a negative electrode tab (3-1), which serves as both the negative electrode of the battery and the negative electrode current collector; the gel electrolyte separator layer (2) is disposed between the integrated positive electrode layer (1) and the multi-functional negative electrode layer (3). The positive electrode substrate (11) is made of a degummed carbon fiber cloth with a thickness of 110 - 330 μm; the degumming treatment is to soak the carbon fiber cloth in an acetone and ethanol solvent with a volume ratio of 1:2 for 20 h, then ultrasonically clean it with deionized water and dry it at a constant temperature of 80 °C for 10 h. The multi-functional negative electrode layer (3) is made of a porous carbon fiber cloth that has been subjected to degumming, chemical activation with a KOH solution, and gel electrolyte impregnation treatment, with a thickness of 110 - 330 μm; the degumming treatment is to soak the porous carbon fiber cloth in an acetone and ethanol solvent with a volume ratio of 1:2 for 20 h, then ultrasonically clean it with deionized water and dry it at a constant temperature of 80 °C for 10 h; the chemical activation with a KOH solution is to immerse the part of the degummed porous carbon fiber cloth except the negative electrode tab (3-1) in a KOH solution, then place it in a rotary evaporator to evaporate the solution, and then dry it at 120 °C for 12 hours to obtain a porous carbon fiber cloth impregnated with KOH; then activation is carried out. The porous carbon fiber cloth impregnated with KOH is placed in a tubular furnace with a nitrogen flow, and the temperature is raised at a rate of 5 °C / min until the activation temperature of 850 °C in the furnace is reached, and it is kept at a constant temperature and statically activated for 1.5 h - 2 h. After the activation is terminated, the porous carbon fiber cloth is repeatedly washed with distilled water until there is no OH- in the leaching solution, and then dried at 105 °C for 10 hours to obtain the activated porous carbon fiber cloth; finally, the part of the activated porous carbon fiber cloth except the negative electrode tab (3-1) is immersed in the gel electrolyte for 10 min, then taken out and air-dried for 30 min, and this process is repeated 2 - 4 times to cure the gel electrolyte to obtain the multi-functional negative electrode layer (3).

2. The flexible structural battery according to claim 1, wherein: The positive electrode active material layer (12) is formed by coating a positive electrode paste, which is prepared by mixing a positive electrode active material, a conductive additive, and a binder in proportion with a solvent, on the surface of the positive electrode substrate (11) except for the positive electrode tab (11-1), and then drying and curing it. The thickness is 1 - 2000 μm. Among them, the positive electrode active material is selected from any one of the positive electrode materials for lithium batteries, including ternary positive electrode material NCM811, lithium manganate, lithium titanate, lithium cobaltate, and lithium iron phosphate; the conductive additive is selected from any one of graphene, conductive carbon black, and carbon nanotubes; the binder is a polyvinylidene fluoride solution with a mass concentration of 4 - 6%; the solvent is N-methylpyrrolidone; the mass ratio of the positive electrode active material, the conductive additive, and the binder is 7:1.5:1.

5.

3. The flexible structural battery according to claim 1, wherein: The gel electrolyte separator layer (2) is formed by curing a gel electrolyte composed of a polymer substance, a low molecular weight electrolyte solvent, and a lithium salt. The thickness is 15 - 25 μm.

4. The flexible structural battery according to claim 3, wherein: The gel electrolyte is prepared by mixing a polymer substance, a low molecular weight electrolyte solvent, and a lithium salt in proportion and heating it to 55°C for 15 h to dissolve. Among them, the polymer substance is selected from at least one of polyvinylidene fluoride, polyethylene oxide, poly(vinylidene fluoride-co-hexafluoropropylene), polyacrylonitrile, and polymethyl methacrylate, and the concentration of poly(vinylidene fluoride-co-hexafluoropropylene) is 0.1 - 0.3 g / ml; the low molecular weight electrolyte solvent is selected from at least one of ethylene carbonate, propylene carbonate, diethyl carbonate, dimethyl carbonate, and a mixture of ethylene carbonate and diethyl carbonate, and the mass ratio of ethylene carbonate to diethyl carbonate is 2 - 4:6 - 8; the lithium salt is selected from one of lithium hexafluorophosphate, lithium perchlorate, lithium bis(trifluoromethanesulfonyl)imide, and lithium tetrafluoroborate; the dosage ratio of the polymer substance, the low molecular weight electrolyte solvent, and the lithium salt is 1 - 3 g:10 - 30 ml:1 - 2 g.

5. A method for preparing a flexible structure battery as described in claim 1, characterized in that: The preparation method of the flexible structure battery is as follows: A layer of gel electrolyte is uniformly coated on the surface of the integrated positive electrode layer (1) except for the positive electrode tab (11-1) and on the surface of the multi-functional negative electrode layer (3) except for the negative electrode tab (3-1). Then, when it is dried in an oven until the gel electrolyte becomes semi-solid, the bottom surface of the integrated positive electrode layer (1) and the top surface of the multi-functional negative electrode layer (3) are stacked together. After the gel electrolyte is cured, a gel electrolyte separator layer (2) is formed between the integrated positive electrode layer (1) and the multi-functional negative electrode layer (3). Then, the whole is roll-pressed and dried at a constant temperature of 60°C. Finally, the edges are heat-sealed to obtain the flexible structure battery.

6. The preparation method of the flexible structure battery according to claim 5, wherein: The thickness of the flexible structure battery is 1 mm.

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