Flexible foldable lithium ion battery pack and preparation method thereof

Abstract

The invention relates to the technical field of lithium ion batteries, in particular to a flexible foldable lithium ion battery pack and a preparation method thereof.The flexible foldable lithium ion battery pack comprises a flexible substrate and a plurality of soft package single batteries arranged on the two sides of the flexible substrate at intervals; the spacing distance between two adjacent soft package single batteries is greater than the sum of the thickness of a single soft package single battery and the thickness of the flexible substrate, and the plurality of soft package single batteries are connected in series or in parallel; the positive electrode and the negative electrode of the soft package single battery are multi-section electrodes prepared in an intermittent coating mode, and the flexible foldable lithium ion battery pack can be wound in the longitudinal direction and can be folded in the transverse direction. A certain blank area is formed between adjacent coating areas of the multi-section electrode, the bending degree of the soft package battery can be adjusted by adjusting the length of the blank area, and 180-degree folding of a single battery can be achieved at most. The number of the positive and negative plates in the battery is adjustable, and the capacity of the formed flexible foldable lithium ion battery pack is relatively high and adjustable.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium ion batteries, and in particular to a flexible and foldable lithium ion battery pack and a preparation method thereof. Background Art

[0002] In recent years, with the sharp increase in demand for outdoor electricity, coupled with the energy crisis, "electricity anxiety" has led to the explosion of a sub-segment of the energy storage industry - the portable mobile energy storage track. Portable energy storage power supply, referred to as "outdoor power supply", is a small energy storage device with a built-in lithium-ion battery that replaces traditional small fuel generators. It has the characteristics of large capacity, high power, safety and portability. At present, portable energy storage products are generally box-shaped and equipped with handles for easy lifting and moving. However, for single-person outdoor work, this box-shaped product takes up a lot of space and is not convenient to carry. At present, most flexible and portable energy storage products are fiber-like products, or flexible products made by screen printing. These products have disadvantages such as low capacity and short battery life. Therefore, it is of great significance to develop an energy storage battery device that has both capacity and flexible portability.

[0003] The information disclosed in this background technology section is only intended to deepen the understanding of the overall background technology of the present invention, and should not be regarded as acknowledging or suggesting in any form that the information constitutes the prior art known to those skilled in the art. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a flexible and foldable lithium-ion battery pack and a method for preparing the flexible and foldable lithium-ion battery pack, and to achieve the technology that the lithium-ion battery can be rolled longitudinally and folded transversely through process optimization of the preparation method.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is:

[0006] A flexible foldable lithium-ion battery pack comprises a flexible substrate and a plurality of soft-packed single cells which are spaced apart on both sides of the flexible substrate, wherein the spacing between two adjacent soft-packed single cells is greater than the sum of the thickness of a single soft-packed single cell and the thickness of the flexible substrate, and the spacing between two adjacent soft-packed single cells is less than the sum of the thickness of the two soft-packed single cells, and the plurality of soft-packed single cells are connected in series or in parallel; the foldable structure is arranged as a surface-type structure, and the battery and the flexible substrate are bonded by strong glue.

[0007] The positive electrode and negative electrode of the soft-pack single cell are multi-segment electrodes made by intermittent coating. The spacing between each segment and the number of coated segments can be adjusted according to actual winding needs. The flexible foldable lithium-ion battery pack can be rolled longitudinally and folded transversely.

[0008] When the battery is wound longitudinally, since the positive and negative electrode materials are coated in multiple sections, the spacing area between each electrode coating section is composed only of a flexible substrate and a current collector, which acts like a hinge, allowing the electrode sheet to be folded or bent more freely. These spacing areas reduce the stress concentration between the coating materials, thereby reducing the damage to the electrode material caused by winding. The gap between each coating section allows the entire battery to be wound into an axis longitudinally without significantly affecting the integrity of the electrode.

[0009] When the battery is folded horizontally, since the spacing between two adjacent soft-packed cells on both sides of the flexible substrate is greater than the sum of the thickness of a single soft-packed cell and the thickness of the flexible substrate, these areas have high flexibility. During the folding process, these spacing parts can bend and stretch naturally, thereby providing additional buffer space for the cells. The flexible substrate further enhances the flexibility of the entire structure, allowing the battery pack to withstand greater deformation when folded.

[0010] In the present invention, the lithium-ion battery pack uses a flexible substrate and a multi-segment coated electrode arranged at intervals, so that the battery has extremely high flexibility, so that the battery pack can be rolled into a cylindrical shape in the longitudinal direction, and can meet the needs of various special-shaped devices and complex installation spaces. On this basis, through the coating method of the multi-segment electrode and the combination of the flexible substrate, sufficient bending space is provided, which effectively ensures that the internal structure of the battery will not be damaged when it is folded horizontally. This feature enables the battery to be used in various foldable devices while maintaining good electrical performance and mechanical strength.

[0011] The present invention distributes the positive electrode and the negative electrode in multiple stages by discontinuous coating, so that a certain interval is retained between the electrodes, providing sufficient buffer space when the battery is longitudinally wound or transversely folded, thereby avoiding peeling or bending damage of the electrode layer.

[0012] Preferably, the flexible substrate is an insulating flexible material, including one or more of glass fiber woven blanket, non-woven fabric, high-strength carbon fiber paper, and polyurethane film, which effectively enhances the flexibility and durability of the overall battery pack, and can be rolled into a cylindrical shape and easily folded in the horizontal direction.

[0013] Preferably, the positive electrode of the soft-pack single cell includes a positive composite current collector and a positive electrode material coating layer. The positive electrode material coating layer can be arranged on one side or both sides of the positive composite current collector, and the positive electrode material coating layer is multi-stage coated on the surface of the positive composite current collector. The positive composite current collector is a sandwich structure with a polyimide film as the middle substrate and aluminum films on both sides. The thickness of the substrate is 4.5-6.0μm, and the thickness of the aluminum film is 0.8-1.5μm. The composite current collector itself has a certain flexibility. At the same time, the interval of the multi-stage coating provides space for the bending and winding of the battery, and can effectively avoid the electrode material falling off and battery failure caused by the bending of the battery. The positive electrode material coating layer is made by multi-stage coating of a slurry made of nano-lithium iron phosphate, a conductive agent and a binder, and the interval between each slurry is 2-50mm. This spacing design provides a key buffer space for the flexibility of the battery.

[0014] Preferably, the negative electrode of the soft-pack single cell includes a negative electrode composite current collector and a negative electrode material coating layer. The negative electrode material coating layer can be arranged on one side or both sides of the negative electrode composite current collector, and the negative electrode material coating layer is multi-stage coated on the surface of the negative electrode composite current collector. The negative electrode composite current collector is a sandwich structure with a polyimide film as the middle substrate and copper films on both sides. The thickness of the substrate is 3.0-4.5μm, and the thickness of the copper film is 0.8-1.5μm. The negative electrode material coating layer is made by multi-stage coating of a slurry made of a uniform mixture of graphite, a conductive agent and a binder, and the interval between each slurry is 5-50mm.

[0015] In the present invention, the current collectors of the positive electrode and the negative electrode both adopt a sandwich structure, that is, a polyimide film (with flexibility) in the middle and aluminum or copper films on both sides. This design not only maintains the overall conductivity of the electrode sheet, but also improves their mechanical flexibility. Multi-stage coating is performed on this current collector. When winding and folding, the polyimide substrate can play a good role in flexibility support, while the aluminum or copper film part can maintain the stability of the electrical connection of the electrode material.

[0016] Preferably, the soft-pack single cell battery further comprises a diaphragm and an electrolyte, the diaphragm is a polypropylene diaphragm, the electrolyte is a commercial electrolyte, and the single soft-pack single cell battery can be formed into a cylindrical shape.

[0017] The technical solution adopted by the method for preparing the flexible foldable lithium-ion battery pack provided by the present invention is:

[0018] A method for preparing a flexible foldable lithium-ion battery pack comprises the following steps:

[0019] S1. Evenly mix nano lithium iron phosphate, conductive agent and binder to form positive electrode slurry, and use transfer coating to coat the positive electrode slurry on the positive electrode composite current collector at intervals, with each section of slurry spaced 2-50mm apart; the coating interval allows the electrode sheet to have a more flexible deformation space when being bent or wound, avoiding the electrode material from falling off or breaking due to stress concentration, thereby improving the flexibility and mechanical durability of the battery.

[0020] Specifically, the binder includes polyvinylidene fluoride (PVDF) and N-methylpyrrolidone (NMP). PVDF and NMP have good compatibility. NMP can make PVDF dissolve evenly, ensuring that the prepared slurry is uniform and consistent, thereby improving the quality of electrode sheet coating. The conductive agent is carbon black, which can effectively improve the overall conductivity of the positive electrode. The particle size of nano lithium iron carbonate is 50 to 200nm, which increases the contact area between the electrode and the electrolyte, accelerates the insertion and deinsertion rate of lithium ions in the electrode material, and ultimately improves the charge and discharge performance and power density of the battery. The mass ratio of the binder, the conductive agent, and the positive electrode active material is 4:3:93, ensuring that the proportion of active materials is high enough, so that the battery has a higher energy density; the 50% solid content makes the slurry have good fluidity and is convenient for coating, while also ensuring that there are enough active materials in the coating layer, ensuring that the coated electrode sheet has a higher active material load, so that the battery has a higher capacity and energy density.

[0021] S2. Graphite, conductive agent and binder are uniformly mixed to form negative electrode slurry, and the negative electrode slurry is coated on the negative electrode composite current collector in intervals by transfer coating, with each section of slurry spaced 5-50 mm apart; so that a large interval is retained between each section of the coating layer. This spacing design can effectively avoid stress concentration on a certain coating section when the negative electrode sheet is bent or folded, increase the flexibility of the negative electrode sheet, and make the battery pack show higher mechanical adaptability when bent or folded.

[0022] Specifically, the graphite is one or more of natural graphite and artificial graphite, with a particle size of 5-20μm; it can provide a good specific surface area and a suitable lithium insertion path, which helps to achieve a faster lithium ion transmission rate during the charge and discharge process, while ensuring the structural stability and energy density of the material. The binder is sodium alginate and deionized water, the conductive agent is carbon black, and the mass ratio of the binder, conductive agent, and negative electrode active material is 3:2:95, which increases the conductivity while ensuring the bonding force, so that the negative electrode slurry has both good adhesion and conductivity. The solid content is 52%, which makes the slurry have good fluidity and is convenient for coating.

[0023] Preferably, in steps S1 and S2, the length of each slurry coating is 1-5 cm. The positive electrode slurry is coated on one side or both sides of the positive electrode composite current collector; the negative electrode slurry is coated on one side or both sides of the negative electrode composite current collector.

[0024] S3. Cut the multi-segment coated electrodes prepared in S1 and S2 into positive electrode sheets and negative electrode sheets, and prepare soft-pack monomer batteries using polypropylene separators and electrolytes;

[0025] Preferably, in step S3, the number of coating sections on the positive electrode sheet and the negative electrode sheet is 2-8, and the number of positive electrodes and negative electrodes in the battery is 1-20. Since the electrode coating layer is distributed in multiple sections on the electrode sheet, when the electrode sheet is subjected to mechanical stress (such as bending or folding), the spacing between the coating layers of each section can effectively disperse the stress, avoiding cracking or material shedding caused by stress concentration on a single coating layer, thereby improving the mechanical durability and service life of the electrode.

[0026] S4. The prepared soft-packed single cells are fixed on the flexible substrate by strong adhesive bonding. Two adjacent soft-packed single cells are placed on the upper and lower sides of the flexible substrate, and the spacing is greater than the sum of the thickness of the soft-packed single cells and the thickness of the flexible substrate. This alternating arrangement effectively balances the overall weight distribution and stress of the battery pack. When the battery pack is wound or folded, the arrangement of the batteries on the upper and lower sides of the substrate can disperse the stress and reduce the stress concentration in a single direction, thereby improving the overall flexibility and durability of the battery pack.

[0027] Preferably, in step S4, the number of soft-pack single cells is 2-20, and two adjacent soft-pack single cells are placed on the upper and lower sides of the flexible substrate, respectively, and the spacing distance between the two is 5-50 mm.

[0028] S5. The positive and negative electrodes of the batteries are connected respectively by metal braided belts to connect the batteries in series or in parallel.

[0029] Preferably, in step S5, the metal braided belt connecting the batteries in series or in parallel is one or more of a copper braided belt, a nickel braided belt, and a tinned copper braided belt.

[0030] The beneficial effects of the present invention are:

[0031] 1. The present invention proposes a method for preparing a flexible foldable lithium-ion battery pack, in which soft-pack batteries are placed on the upper and lower sides of a flexible substrate in an interval arrangement, and the interval between batteries is greater than the sum of the thickness of a single battery and the thickness of the flexible substrate; at the same time, the batteries are connected in series or in parallel using metal braids, which are flexible, bendable, and foldable. This allows the lithium-ion battery device to be folded and placed, and can be folded continuously, greatly reducing the space occupied and making it easy to carry.

[0032] 2. The electrode sheet in the present invention is a multi-segment coated electrode sheet, with a certain blank area between adjacent coated areas, which makes the prepared soft-pack battery bendable. By adjusting the length of the blank area, the curvature of the soft-pack battery can be adjusted, and a single battery can be folded 180 degrees at most. In addition, by increasing the number of coated sections in a single electrode sheet, multi-segment bending and folding of the soft-pack battery can be achieved. The lithium-ion battery device obtained by placing a multi-segment soft pack on a flexible substrate can achieve the purpose of radial winding.

[0033] 3. The lithium-ion battery in the present invention is a structural optimization of the current conventional battery, and the battery capacity is relatively high; secondly, the number of positive and negative electrodes in the battery is adjustable, so the capacity of the prepared bendable battery is adjustable, and the capacity of the formed flexible foldable lithium-ion battery pack is relatively high and adjustable. The use of fire-extinguishing materials such as glass fiber woven blankets as flexible substrates makes lithium-ion batteries have the advantages of being difficult to ignite and being able to be extinguished in time. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0035] Figure 1 is a schematic diagram of a single multi-segment electrode in Example 1;

[0036] Figure 2 The multi-segment flexible soft-pack battery in Example 1;

[0037] Figure 3 Schematic diagram of a lithium-ion battery placed on a flexible substrate;

[0038] Figure 4 Schematic diagram of bending of flexible foldable lithium-ion battery pack; DETAILED DESCRIPTION

[0039] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0040] It should be noted that when an element is referred to as being "fixed to" another element, it may be directly on the other element or there may be a central element. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be a central element at the same time. The terms "vertical", "horizontal", "left", "right" and similar expressions used herein are for illustrative purposes only and do not represent the only implementation method.

[0041] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0042] Components Commercial sources Polyvinylidene fluoride Maclean N-Methylpyrrolidone Maclean Carbon Black Shenzhen Kejing Lithium Iron Phosphate Shenzhen Kejing Sodium alginate Shenzhen Kejing graphite Shenzhen Kejing Polypropylene diaphragm Shenzhen Kejing Electrolyte Shenzhen Kejing Fiberglass Woven Blanket Suzhou Weidun

[0043] like Figures 1 to 4 A flexible foldable lithium-ion battery pack is shown, comprising a flexible substrate 10 and a plurality of soft-packed single cells 20 spaced apart on both sides of the flexible substrate 10, wherein the spacing between two adjacent soft-packed single cells 20 is greater than the sum of the thickness of a single soft-packed single cell 20 and the thickness of the flexible substrate 10, and the plurality of soft-packed single cells 20 are connected in series or in parallel; the foldable structure is arranged as a surface-type structure, and the soft-packed single cells 20 are bonded to the flexible substrate 10 by strong glue.

[0044] Specific as Figure 1 As shown, the positive electrode and the negative electrode of the soft-packed single battery 20 are multi-segment electrodes prepared by intermittent coating. The multi-segment coated electrode includes a tab 30 and an electrode sheet. When the multi-segment coated electrode is a positive electrode, the positive electrode includes a positive composite current collector 31 and a positive electrode material coating layer 32. The positive electrode material coating layer 32 is coated in multiple sections on the surface of the positive composite current collector 31. When the multi-segment coated electrode is a negative electrode, the negative electrode includes a negative composite current collector 33 and a negative electrode material coating layer 34. The negative electrode material coating layer 34 is coated in multiple sections on the surface of the negative composite current collector 33. The spacing distance between each section and the number of coated sections can be adjusted according to the actual winding needs. The flexible and foldable lithium-ion battery pack can be wound longitudinally and folded transversely.

[0045] In the present invention, the lithium-ion battery pack uses a flexible substrate 10 and a multi-segment coated electrode arranged at intervals, so that the battery has extremely high flexibility, so that the battery pack can be rolled into a cylindrical shape in the longitudinal direction, and can meet the needs of various special-shaped devices and complex installation spaces. On this basis, through the coating method of the multi-segment electrode and the combination of the flexible substrate 10, sufficient bending space is provided, which effectively ensures that the internal structure of the battery will not be damaged when it is folded horizontally. This feature enables the battery to be used in various foldable devices while maintaining good electrical performance and mechanical strength.

[0046] Preferably, the flexible substrate 10 is an insulating flexible material, including one or more of glass fiber woven blanket, non-woven fabric, high-strength carbon fiber paper, and polyurethane film, which effectively enhances the flexibility and durability of the overall battery pack, and can be rolled into a cylindrical shape and easily folded in the horizontal direction.

[0047] The positive electrode material coating layer 32 can be arranged on one or both sides of the positive electrode composite current collector 31. The positive electrode composite current collector 31 is a sandwich structure with a polyimide film as the middle substrate and aluminum films on both sides. The thickness of the substrate is 4.5-6.0μm, and the thickness of the aluminum film is 0.8-1.5μm. The composite current collector itself has a certain flexibility. At the same time, the interval of the multi-stage coating provides space for the bending and winding of the battery, and can effectively avoid the electrode material falling off and battery failure caused by the bending of the battery. The positive electrode material coating layer 32 is made by multi-stage coating of a slurry made of nano-lithium iron phosphate, a conductive agent and a binder, and the interval between each slurry is 2-50mm; this spacing design provides a key buffer space for the flexibility of the battery.

[0048] The negative electrode material coating layer 34 can be arranged on one side or both sides of the negative electrode composite current collector 33. The negative electrode composite current collector 33 is a sandwich structure with a polyimide film as the middle substrate and copper films on both sides. The thickness of the substrate is 3.0-4.5 μm, and the thickness of the copper film is 0.8-1.5 μm. The negative electrode material coating layer 34 is made of a slurry made of a uniform mixture of graphite, a conductive agent and a binder by multi-stage coating, and the interval between each slurry is 5-50 mm.

[0049] In the present invention, the current collectors of the positive electrode and the negative electrode both adopt a sandwich structure, that is, a polyimide film (with flexibility) in the middle and aluminum or copper films on both sides. This design not only maintains the overall conductivity of the electrode sheet, but also improves their mechanical flexibility. Multi-stage coating is performed on this current collector. When winding and folding, the polyimide substrate can play a good role in flexibility support, while the aluminum or copper film part can maintain the stability of the electrical connection of the electrode material.

[0050] Preferably, the soft-pack single battery 20 further includes a diaphragm and an electrolyte. The diaphragm is a polypropylene diaphragm, and the electrolyte is a commercial electrolyte. The single soft-pack single battery 20 can be formed into a cylindrical shape.

[0051] The technical solution adopted by the method for preparing the flexible foldable lithium-ion battery pack provided by the present invention is:

[0052] A method for preparing a flexible foldable lithium-ion battery pack comprises the following steps:

[0053] S1. Evenly mix nano lithium iron phosphate, conductive agent and binder to form positive electrode slurry, and use transfer coating to coat the positive electrode slurry on the positive electrode composite current collector at intervals, with each section of slurry spaced 2-50mm apart; the coating interval allows the electrode sheet to have a more flexible deformation space when being bent or wound, avoiding the electrode material from falling off or breaking due to stress concentration, thereby improving the flexibility and mechanical durability of the battery.

[0054] S2. Graphite, conductive agent and binder are uniformly mixed to form negative electrode slurry, and the negative electrode slurry is coated on the negative electrode composite current collector in intervals by transfer coating, with each section of slurry spaced 5-50 mm apart; so that a large interval is retained between each section of the coating layer. This spacing design can effectively avoid stress concentration on a certain coating section when the negative electrode sheet is bent or folded, increase the flexibility of the negative electrode sheet, and make the battery pack show higher mechanical adaptability when bent or folded.

[0055] Furthermore, in steps S1 and S2, the length of each slurry coating is 1-5 cm. The positive electrode slurry is coated on one side or on both sides of the positive electrode composite current collector; the negative electrode slurry is coated on one side or on both sides of the negative electrode composite current collector.

[0056] S3. Cut the multi-segment coated electrodes prepared in S1 and S2 into positive electrode sheets and negative electrode sheets, and prepare soft-pack monomer batteries using polypropylene separators and electrolytes;

[0057] Preferably, in step S3, the number of coating sections on the positive electrode sheet and the negative electrode sheet is 2-8, and the number of positive electrodes and negative electrodes in the battery is 1-20.

[0058] S4. The prepared soft-packed single battery is fixed on the flexible substrate by strong adhesive bonding, and two adjacent soft-packed single batteries are respectively placed on the upper and lower sides of the flexible substrate, and the spacing distance is greater than the sum of the thickness of the soft-packed single battery and the thickness of the flexible substrate; preferably, the number of soft-packed single batteries is 2-20, and two adjacent soft-packed single batteries are respectively placed on the upper and lower sides of the flexible substrate, and the spacing distance between the two is 5-50 mm;

[0059] S5. The positive and negative electrodes of the batteries are connected respectively by metal braids, and the batteries are connected in series or in parallel. The metal braids used to connect the batteries in series or in parallel are one or more of copper braids, nickel braids, and tinned copper braids.

[0060] Example 1

[0061] The flexible foldable lithium-ion battery is prepared by the preparation method of the present invention, and the specific operation steps are as follows:

[0062] S1. Use the binder polyvinylidene fluoride and N-methylpyrrolidone to prepare the glue solution, add the conductive carbon black and the lithium iron phosphate positive electrode material with a particle size of 200 nanometers to prepare the positive electrode slurry after complete dissolution, the mass ratio of the binder, the conductive agent and the positive electrode active material is 4:3:93, and the solid content is 50%;

[0063] S2. The slurry is coated on both sides of the composite conductive aluminum foil by transfer coating. The coating length of each section is 3 cm, and the interval between two adjacent sections is 6 mm. After coating, the coating is dried for standby use.

[0064] S3. A glue solution was prepared using a binder of sodium alginate and deionized water. After complete dissolution, conductive carbon black and artificial graphite negative electrode material with a particle size of 10 μm were added to prepare a negative electrode slurry. The mass ratio of the binder, the conductive agent, and the negative electrode active material was 3:2:95, and the solid content was 52%;

[0065] S4. The slurry is coated on both sides of the composite conductive copper foil by transfer coating. The coating length of each section is 3 cm, and the interval between two adjacent sections is 6 mm. After coating, the coating is dried for standby use;

[0066] S5. Cut the positive and negative electrode sheets into electrode sheets of the same size, with an electrode length of 13.8 cm and 4 coating sections;

[0067] S6. Using polypropylene as a separator and commercial electrolyte to prepare a soft-pack battery, wherein the number of positive electrodes is 6 and the number of negative electrodes is 5, and a single soft-pack battery can be bent into a cylindrical shape;

[0068] S7. Take 6 soft-pack batteries and place them in sequence on the upper and lower sides of the glass fiber woven blanket to form a row, with three batteries placed on each side. Use strong glue to bond the soft-pack batteries to the glass fiber woven blanket.

[0069] S8. Use copper braided tape to connect 6 batteries to form a 2-in-parallel 3-in-series battery pack. The resulting lithium-ion battery device can be rolled into an axis along the bending direction of a single battery, and can be folded and placed in the lateral direction to form a square block, which reduces the space occupied and is easy to carry.

[0070] Comparative Example 1

[0071] S1. Use the binder polyvinylidene fluoride and N-methylpyrrolidone to prepare the glue solution, add the conductive carbon black and the lithium iron phosphate positive electrode material with a particle size of 200 nanometers to prepare the positive electrode slurry after complete dissolution, the mass ratio of the binder, the conductive agent and the positive electrode active material is 4:3:93, and the solid content is 50%;

[0072] S2. The slurry is coated on both sides of the composite conductive aluminum foil by transfer coating, and the coating is continuous without intervals. After the coating is completed, it is dried for standby use;

[0073] S3. A glue solution was prepared using a binder of sodium alginate and deionized water. After complete dissolution, conductive carbon black and artificial graphite negative electrode material with a particle size of 10 μm were added to prepare a negative electrode slurry. The mass ratio of the binder, the conductive agent, and the negative electrode active material was 3:2:95, and the solid content was 52%;

[0074] S4. Using transfer coating, the slurry is coated on both sides of the composite conductive copper foil, and the coating is continuous without intervals. After the coating is completed, it is dried for standby use;

[0075] S5. Cut the positive and negative electrode sheets into electrode sheets of the same size, with an electrode length of 13.8 cm;

[0076] S6. Using polypropylene as a separator and commercial electrolyte to prepare a soft-pack battery, wherein the number of positive electrodes is 6, the number of negative electrodes is 5, and a single soft-pack battery is in an inflexible block shape;

[0077] S7. Take 6 soft-pack batteries and place them in sequence on the upper and lower sides of the glass fiber woven blanket to form a row, with three batteries placed on each side. Use strong glue to bond the soft-pack batteries to the glass fiber woven blanket.

[0078] S8. Use copper braided tape to connect 6 batteries to form a 2-in-parallel 3-in-series battery pack. The resulting lithium-ion battery device can be folded and placed in the horizontal direction to form a square block, which reduces the space occupied and is easy to carry.

[0079] Comparative Example 2

[0080] S1. Use the binder polyvinylidene fluoride and N-methylpyrrolidone to prepare the glue solution, add the conductive carbon black and the lithium iron phosphate positive electrode material with a particle size of 200 nanometers to prepare the positive electrode slurry after complete dissolution, the mass ratio of the binder, the conductive agent and the positive electrode active material is 4:3:93, and the solid content is 50%;

[0081] S2. The slurry is coated on both sides of the composite conductive aluminum foil by transfer coating, and the coating is continuous without intervals. After the coating is completed, it is dried for standby use;

[0082] S3. A glue solution was prepared using a binder of sodium alginate and deionized water. After complete dissolution, conductive carbon black and artificial graphite negative electrode material with a particle size of 10 μm were added to prepare a negative electrode slurry. The mass ratio of the binder, the conductive agent, and the negative electrode active material was 3:2:95, and the solid content was 52%;

[0083] S4. Using transfer coating, the slurry is coated on both sides of the composite conductive copper foil, and the coating is continuous without intervals. After the coating is completed, it is dried for standby use;

[0084] S5. Cut the positive and negative electrode sheets into electrode sheets of the same size, with an electrode length of 13.8 cm and 4 coating sections;

[0085] S6. Using polypropylene as a separator and commercial electrolyte to prepare a soft-pack battery, wherein the number of positive electrodes is 6, the number of negative electrodes is 5, and a single soft-pack battery is in an inflexible block shape;

[0086] S7. Take 6 soft-pack batteries and fix them on one side of the glass fiber woven blanket using strong adhesive, arranging the batteries closely;

[0087] S8. Use copper tape to connect 6 batteries to form a 2-in-parallel 3-in-series battery pack. The resulting lithium-ion battery device cannot be bent or folded.

[0088] Those skilled in the art should understand that the present invention is not limited to the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, and these changes and improvements fall within the scope of the present invention to be protected. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A flexible foldable lithium-ion battery pack, characterized in that: It comprises a flexible substrate and a plurality of soft-packed single cells respectively arranged at intervals on both sides of the flexible substrate, wherein the interval between two adjacent soft-packed single cells is greater than the sum of the thickness of a single soft-packed single cell and the thickness of the flexible substrate, and the plurality of soft-packed single cells are connected in series or in parallel; The positive electrode and the negative electrode of the soft-pack single battery are multi-segment electrodes prepared by discontinuous coating, and the flexible foldable lithium-ion battery pack can be rolled longitudinally and folded transversely.

2. A flexible foldable lithium-ion battery pack according to claim 1, characterized in that: The flexible substrate is an insulating flexible material, including one or more of glass fiber woven blanket, non-woven fabric, high-strength carbon fiber paper, and polyurethane film.

3. A flexible foldable lithium-ion battery pack according to claim 1, characterized in that: The positive electrode of the soft-pack single cell comprises a positive composite current collector and a positive electrode material coating layer. The positive electrode material coating layer can be arranged on one side or both sides of the positive composite current collector. The positive electrode material coating layer is coated in multiple stages on the surface of the positive composite current collector.

4. A flexible foldable lithium-ion battery pack according to claim 3, characterized in that: The positive electrode composite current collector is a sandwich structure with a polyimide film as the middle substrate and aluminum films on both sides. The thickness of the substrate is 4.5-6.0 μm, and the thickness of the aluminum film is 0.8-1.5 μm.

5. A flexible foldable lithium-ion battery pack according to claim 3, characterized in that: The positive electrode material coating layer is prepared by multi-stage coating of a slurry made by uniformly mixing nano lithium iron phosphate, a conductive agent and a binder, and the interval between each slurry section is 2-50 mm.

6. A flexible foldable lithium-ion battery pack according to claim 1, characterized in that: The negative electrode of the soft-pack single cell comprises a negative electrode composite current collector and a negative electrode material coating layer. The negative electrode material coating layer can be arranged on one side or both sides of the negative electrode composite current collector. The negative electrode material coating layer is coated in multiple stages on the surface of the negative electrode composite current collector.

7. A flexible foldable lithium-ion battery pack according to claim 6, characterized in that: The negative electrode composite current collector is a sandwich structure with a polyimide film as the middle substrate and copper films on both sides. The thickness of the substrate is 3.0-4.5 μm, and the thickness of the copper film is 0.8-1.5 μm.

8. The flexible foldable lithium-ion battery pack according to claim 6, characterized in that: The negative electrode material coating layer is prepared by multi-stage coating of a slurry made by uniformly mixing graphite, a conductive agent and a binder, and the interval between each slurry section is 5-50 mm.

9. The method for preparing a flexible foldable lithium-ion battery pack according to any one of claims 1 to 8, characterized in that: The steps are as follows: S1. Prepare a positive electrode slurry, and coat the positive electrode slurry on the positive electrode composite current collector by transfer coating, with an interval of 2-50 mm between each section of slurry; S2. A negative electrode slurry is prepared, and the negative electrode slurry is coated on the negative electrode composite current collector by transfer coating, with each section of the slurry being spaced 5-50 mm apart; S3. Cut the multi-segment coated electrodes prepared in S1 and S2 into positive electrode sheets and negative electrode sheets, and prepare soft-pack monomer batteries using polypropylene separators and electrolytes; S4. The prepared soft-packed single cell is bonded and fixed on the flexible substrate, and two adjacent soft-packed single cells are placed on the upper and lower sides of the flexible substrate, respectively, with a spacing distance greater than the sum of the thickness of the soft-packed single cell and the thickness of the flexible substrate; S5. The positive and negative electrodes of the batteries are connected respectively by metal braided belts to connect the batteries in series or in parallel.

10. The method for preparing a flexible foldable lithium-ion battery pack according to claim 9, characterized in that: In step S4, the number of soft-pack single cells is 2-20, and two adjacent soft-pack single cells are placed on the upper and lower sides of the flexible substrate, respectively, and the spacing between the two is 5-50 mm.

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