Flexible electrodes, their preparation, and batteries

Abstract

The present application discloses a flexible electrode, its preparation and battery. The flexible electrode of the present application includes a conductive fiber electrode matrix, the conductive fiber electrode matrix has a three-dimensional porous structure, an electrode active material is distributed at least in the conductive fiber electrode matrix, and a number of creases are distributed on the surface of the flexible electrode. The flexible electrode of the present application maintains a good structure during the bending process, and the stable electron conduction path ensures the stability of the electrochemical performance, strong bending resistance, high flexibility and capacity. The preparation method can ensure the stability of the performance and quality of the prepared flexible electrode, and high efficiency. The battery contains the flexible electrode of the present application, which has stable electrochemical performance, high safety and long life during the charge and discharge cycle.

Description

Technical Field

[0001] The present application belongs to the field of battery technology, and specifically relates to a flexible electrode, its preparation, and a battery. Background Art

[0002] As awareness of environmental protection and the energy crisis grows, lithium-ion batteries are becoming increasingly popular as a green and environmentally friendly energy storage technology. In smart devices such as wearables and flexible displays, lithium-ion batteries require not only excellent electrochemical performance but also the flexibility to match these devices. This demand for flexible lithium-ion batteries has arisen in response to these applications. Traditional lithium-ion batteries use mostly granular active materials that require a binder or other aid to evenly coat a conductive foil current collector. Metal foil (aluminum, copper foil) can fatigue and fracture under repeated flexibility testing, degrading battery performance. This is one of the reasons why conventional lithium-ion batteries lack flexibility. To address this issue, researchers have developed various flexible current collectors, such as the disclosed three-dimensional vanadium pentoxide nanoarray / carbon cloth flexible cathode material and its preparation method, which features warp-and-weft woven carbon fiber cloth with excellent flexibility. Alternatively, in another disclosed flexible lithium-ion anode and flexible lithium-ion battery, ultrathin electrodes are obtained using a filtration method, imparting excellent flexibility to the ultrathin electrodes. Alternatively, in another disclosed flexible lithium-ion electrode, active materials are distributed in an array on a foil current collector to impart flexibility to the electrode.

[0003] However, the existing flexible electrodes often have the following shortcomings:

[0004] 1) Conventional flexible carbon cloth current collectors are mostly woven from warp and weft fiber bundles, which have a large unit mass and are thick, which is not conducive to improving the battery energy volume or mass density;

[0005] 2) The load capacity is often low. Although the flexibility of the electrode can be improved to a certain extent, the inability to apply high load directly leads to the low energy density of the flexible electrode surface.

[0006] 3) The method of distributing active materials in an array has very low space utilization of electrodes / batteries, which is not conducive to improving battery energy density and has limited improvement in flexibility.

[0007] 4) Existing flexible electrodes are all designed to improve the bending resistance of the electrodes. Currently, the absence of creases on the surface after bending is basically used as one of the important inspection indicators for qualified quality. Specifically, the absence of creases on the surface of the electrode after bending is considered to have high flexibility quality. Summary of the Invention

[0008] The purpose of this application is to overcome the above-mentioned deficiencies in the prior art and to provide a flexible electrode and a preparation method thereof, so as to solve the technical problem that the flexibility and surface energy density of the existing flexible electrodes cannot be taken into account at the same time.

[0009] To achieve the above-mentioned application objectives, the first aspect of the present application provides a flexible electrode. The flexible electrode of the present application includes a conductive fiber electrode substrate having a three-dimensional porous structure, an electrode active material distributed at least within the conductive fiber electrode substrate, and a plurality of creases distributed on the surface of the flexible electrode.

[0010] Furthermore, adjacent folds are at least one of parallel, approximately parallel, partially touching, and intersecting.

[0011] Furthermore, in the flexible electrode, the content of the electrode active material contained in the crease is lower than the content of the electrode active material contained in the non-crease area.

[0012] Furthermore, the width of the fold is 1 μm to 50 μm.

[0013] Furthermore, the distance between adjacent folds is 0.1 mm to 50 mm.

[0014] Furthermore, the folds are distributed along the width direction of the conductive fiber electrode substrate.

[0015] Furthermore, the porosity of the conductive fiber electrode matrix is ​​greater than 50%.

[0016] Furthermore, the density of the conductive fiber electrode matrix is ​​0.1 mg / cm 2 ~6mg / cm 2 .

[0017] Furthermore, the thickness of the conductive fiber electrode substrate is 5 to 500 μm.

[0018] Furthermore, the loading amount of the electrode active material on the conductive fiber electrode substrate is 1 to 100 mg / cm 2 .

[0019] Furthermore, the thickness of the flexible electrode is 5 μm to 500 μm.

[0020] Furthermore, the material of the conductive fiber electrode matrix includes at least one of conductive carbon fiber felt, metal-plated carbon fiber felt, and metal-plated polymer fiber felt.

[0021] Furthermore, the electrode active material is a positive electrode active material, and the flexible electrode is a positive electrode.

[0022] Or further, the electrode active material is a negative electrode active material, and the flexible electrode is a negative electrode.

[0023] In a second aspect of the present application, a method for preparing a flexible electrode is provided. The method for preparing a flexible electrode of the present application comprises the following steps:

[0024] Providing a conductive fiber electrode matrix with a three-dimensional porous structure;

[0025] Filling the electrode active material slurry into at least the three-dimensional porous structure of the conductive fiber electrode matrix and then drying it to obtain a fiber-based electrode;

[0026] The fiber-based electrode is bent so that a number of creases are distributed on the surface of the flexible electrode, thereby obtaining a flexible electrode.

[0027] Furthermore, the method for bending the fiber electrode includes the following steps:

[0028] The fiber-based electrode is bent and pulled through a roller, so that creases distributed along the width direction are formed on the surface of the fiber-based electrode.

[0029] Furthermore, there are at least two rotating rollers, which are distributed on both sides of the fiber-based electrode pulling route, and the two surfaces of the fiber-based electrode are bent and pulled simultaneously.

[0030] In a third aspect, the present application provides a battery comprising a positive electrode, a negative electrode, and a separator stacked between the positive electrode and the negative electrode, wherein the negative electrode and / or the positive electrode are the flexible electrodes of the present application or flexible electrodes prepared by the flexible electrode preparation method of the present application.

[0031] Compared with the existing technology, this application has the following technical effects:

[0032] The conductive fiber electrode matrix contained in the flexible electrode provided in the first aspect of the present application gives the flexible electrode of the present application excellent electronic conduction characteristics and excellent flexibility. Its three-dimensional porous structure gives the flexible electrode of the present application a high loading amount of electrode active material, giving the flexible electrode of the present application a high surface capacity, and enhancing the stability of the loading of the electrode active material in the conductive fiber electrode matrix. In addition, the several folds distributed on the electrode can effectively release the stress of the flexible electrode during the bending process, so that the flexible electrode of the present application maintains good structural stability and stable electrochemical performance in subsequent bending applications or bending tests, greatly improving the bending resistance of the flexible electrode of the present application.

[0033] The flexible electrode preparation method provided in the second aspect of the present application bends a fiber-based electrode containing an electrode active material to form a plurality of creases on the surface. This allows the prepared flexible electrode to have high structural and electrochemical stability during the bending process and excellent bending resistance. In addition, the preparation method has easily controllable process conditions, can ensure the stability of the performance and quality of the prepared flexible electrode, and is highly efficient.

[0034] The batteries provided in the third aspect of the present application all contain the flexible electrodes of the present application. Therefore, the batteries of the present application have strong bending resistance, stable electrochemical performance during the charge and discharge cycle, high capacity and safety, and long life. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the specific implementation methods of the present application or the technical solutions in the prior art, the following is a brief introduction to the drawings required for use in the specific implementation methods or the description of the prior art. Obviously, the drawings described below are some implementation methods of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0036] Figure 1 This is a schematic diagram of the crease structure on the surface of the flexible electrode in an embodiment of the present application;

[0037] Figure 2 Schematic diagrams of the cross-section of a flexible electrode according to an embodiment of the present application; FIG. a is a schematic diagram of a flexible electrode according to an embodiment of the present application having a crease structure provided on one surface, and FIG. b is a schematic diagram of a flexible electrode according to an embodiment of the present application having a crease structure provided on both surfaces;

[0038] Figure 3 Schematic diagrams of fold structures of different morphologies on the surface of the flexible electrode according to an embodiment of the present application; Figure a is a schematic diagram of a structure in which the fold structures are perpendicular to each other, and Figure b is a schematic diagram of a structure in which the fold structures are not perpendicular to each other;

[0039] Figure 4 This is a schematic diagram of the process for preparing a flexible electrode according to an embodiment of the present application;

[0040] Figure 5 This is a schematic diagram of a fiber-based electrode being bent and pulled by a roller in a method for preparing a flexible electrode according to an embodiment of the present application;

[0041] Figure 6 This is a schematic diagram of a fiber-based electrode in a method for preparing a flexible electrode according to an embodiment of the present application, wherein the fiber-based electrode is subjected to a bending and pulling process by rollers provided on both sides;

[0042] Figure 7 This is a physical picture of the flexible fiber-based LCO positive electrode with a creased structure in Example A1 of the present application;

[0043] Figure 8 A resistance curve diagram of the flexible electrodes provided in Example A2, Comparative Example A1, and Comparative Example A2 of the present application in a bending resistance test;

[0044] Figure 9The figures are the physical pictures of the flexible fiber-based LCO positive electrode before and after the bending test in Comparative Example A1; Figure A is the physical picture of the flexible fiber-based LCO positive electrode in Comparative Example A1 after the bending test; Figure B is the physical picture of the flexible fiber-based LCO positive electrode in Comparative Example A1 after the bending test;

[0045] Figure 10 This is a photo of the crease-free flexible fiber-based LCO positive electrode after the bending test in Comparative Example A2;

[0046] Figure 11 1 is a cyclic charge and discharge curve diagram of the soft-pack battery in Example B1 and Comparative Example B1.

[0047] Description of the component numbers in the accompanying drawings:

[0048] 01-flexible electrode, 11-surface of the flexible electrode, 12-several creases distributed on the surface of the flexible electrode. DETAILED DESCRIPTION

[0049] In order to make the purpose, technical scheme and technical effect of the embodiments of the present application clearer, the technical scheme in the embodiments of the present application is clearly and completely described. The embodiments described below are part of the embodiments of the present application, rather than all of the embodiments. In conjunction with the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application. If the specific conditions are not specified in the embodiments, they are carried out according to conventional conditions or the conditions recommended by the manufacturer; if the manufacturer of the reagents or instruments is not specified, they are all conventional products that can be purchased commercially.

[0050] In this application, the term "and / or" describes the relationship between associated objects, indicating that three possible relationships exist. For example, "A and / or B" can mean: A exists alone, A and B exist simultaneously, and B exists alone. A and B can be singular or plural. The character " / " generally indicates that the associated objects are in an "or" relationship.

[0051] In the description of this application, "at least one" means one or more, and "plurality" means two or more. "At least one of the following" or similar expressions refers to any combination of these items, including any combination of single items or plural items. For example, "at least one of a, b, or c", or "at least one of a, b, and c" can all mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple.

[0052] It should be understood that the weights of the relevant components mentioned in the examples of this application may not only refer to the specific content of each component, but also represent the proportional relationship between the weights of the components. Therefore, as long as the content of the relevant components in the examples of this application is proportionally enlarged or reduced, it is within the scope disclosed in this application. Specifically, the weights in the examples of this application may be mass units known in the chemical industry, such as μg, mg, g, and kg.

[0053] In addition, unless the context clearly requires otherwise, expressions in the singular form of a word should be understood to include the plural form of the word. The terms "include" or "have" are intended to specify the presence of a feature, number, step, operation, element, part, or combination thereof, but are not used to exclude the presence or possibility of adding one or more other features, numbers, steps, operations, elements, parts, or combinations thereof.

[0054] In existing flexible electrodes, a flexible substrate is generally provided, and an electrode active layer is formed by coating the substrate. Traditional thinking holds that creases (cracks) on electrodes, including flexible electrodes, represent weak bonding between the active material and the current collector, and will affect the electronic conductivity of the electrode, thereby affecting the electrochemical properties of the electrode. Moreover, in flexible applications, (non-customized) creases such as those generated during bending are random and uncontrollable, and further development will lead to fractures and damage. Therefore, in the existing electrode quality evaluation system, the electrode is generally bent and then the surface of the electrode is tested to determine whether creases appear. If no creases appear, the electrode is judged to have high quality, strong bending resistance, and stable electrochemical properties. If creases appear, the electrode is judged to have unstable structure, poor bending resistance, and unstable electrochemical properties.

[0055] Moreover, in existing flexible electrodes, it is generally achieved by providing a flexible current collector, and by the flexibility of the current collector itself to give the flexible electrode flexibility and bending properties. Therefore, generally people will choose a flexible substrate such as conductive fiber, and load the active material on the flexible substrate. In this way, the flexibility of the substrate determines the flexibility of the final electrode. However, as the load of active material loaded on the flexible substrate increases, the flexibility of the flexible electrode becomes worse (mainly because high-load active material will become rigid). This directly leads to an opposition between the active material loading amount of the flexible electrode and the flexibility of the flexible electrode. For example, in order to improve the flexibility of the flexible electrode, it is necessary to sacrifice the amount of active material loaded, resulting in low capacity and low surface energy of the flexible electrode. Or in order to increase the surface energy of the flexible electrode, it is necessary to increase the amount of active material loaded, resulting in low bending resistance of the flexible electrode and reduced flexibility. That is, in existing flexible electrodes, there is an antagonistic relationship between flexibility and surface energy.

[0056] In order to solve the conflicting relationship between the flexibility and surface energy of existing flexible electrodes, this application proposes a flexible electrode with excellent bending resistance, flexibility and high surface energy, and a preparation method thereof.

[0057] In the first aspect, the present invention provides a flexible electrode. Figures 1 to 2 As shown, the flexible electrode 01 includes a conductive fiber electrode matrix ( Figure 1 、 Figure 2 Not shown), the conductive fiber electrode matrix has a three-dimensional porous structure ( Figure 1 、 Figure 2 Not shown) and at least an electrode active material ( Figure 1 、 Figure 2 Not shown), and a plurality of folds 12 are distributed on the surface 11 of the flexible electrode 01.

[0058] Among them, the conductive fiber electrode matrix contained in the flexible electrode 01 of the embodiment of the present application constitutes the flexible current collector of the flexible electrode 01 of the embodiment of the present application, which is one of the factors that make the flexible electrode 01 of the embodiment of the present application have flexibility, and also serves as a carrier for loading the electrode active material. Specifically, the conductive fiber electrode matrix gives the flexible electrode 01 of the embodiment of the present application excellent bendability, and its conductivity gives the flexible electrode of the embodiment of the present application excellent electronic conduction characteristics. Its three-dimensional porous structure gives a high loading amount of electrode active material, giving the flexible electrode 01 of the embodiment of the present application a high surface capacity, and enhancing the stability of the electrode active material loaded in the conductive fiber electrode matrix.

[0059] In the embodiment, the porosity of the conductive fiber electrode matrix is ​​greater than 50%, and further greater than 80%. The high-porosity conductive fiber electrode matrix has excellent electronic conductivity and contains a rich three-dimensional porous structure, which has the characteristics and conditions for high loading of electrode active materials.

[0060] In the embodiment, the surface density of the conductive fiber electrode matrix is ​​0.1 mg / cm 2 ~6mg / cm 2 , further 0.5-2mg / cm 2 , specifically 0.1 mg / cm 2 , 0.5mg / cm 2 , 1mg / cm 2 , 2mg / cm 2 , 3mg / cm 2 , 4mg / cm 2 , 5mg / cm 2 , 6mg / cm 2Typical but non-limiting areal densities include . This is understood to refer to the areal density of the conductive fiber electrode matrix without electrode active material. Conductive fiber electrode matrices within this areal density range have a rich three-dimensional porous structure, which can increase the content of electrode active material, improve the areal energy of the flexible electrode 01, and reduce its weight. Furthermore, they exhibit excellent flexibility.

[0061] In addition, the thickness of the conductive fiber electrode matrix can be flexibly adjusted according to the application needs of the flexible electrode 01, and of course the size of the conductive fiber electrode matrix can be flexibly controlled. For example, in the embodiment, the thickness of the conductive fiber electrode matrix is ​​5 to 500 μm, further 10 to 300 μm, and further 50 to 200 μm, and specifically can be 5 μm, 10 μm, 30 μm, 50 μm, 70 μm, 100 μm, 130 μm, 150 μm, 180 μm, 230 μm, 260 μm, 300 μm, 400 μm, 500 μm, etc. Typical but non-limiting thicknesses. The conductive fiber electrode of this thickness not only has good flexibility and mechanical properties, but also increases the loading amount of the electrode active material, thereby increasing the capacity of the flexible electrode 01.

[0062] In a specific embodiment, the conductive fiber electrode substrate comprises at least one of conductive carbon fiber felt, metal-coated carbon fiber felt, and metal-coated polymer fiber felt. This material exhibits excellent flexibility, good electronic conductivity, and toughness, and can form a rich three-dimensional porous structure, thereby improving the mechanical properties and capacity of the flexible electrode 01.

[0063] The electrode active material contained in the flexible electrode 01 of the embodiment of the present application is the electrode active material contained in the electrode active layer contained in the conventional electrode, such as components including electrode materials, binders and conductive agents. Moreover, the ratio range of the electrode material, binder and conductive agent contained in the electrode active material can be the ratio contained in the conventional electrode, or it can be the ratio optimized based on improving the electrochemical performance of the electrode. Among them, the electrode material contained in the electrode active material can be selected according to the type of the flexible electrode 01 of the embodiment of the present application. For example, when the flexible electrode 01 of the embodiment of the present application is a positive electrode, the electrode material is a positive electrode material; when the flexible electrode 01 of the embodiment of the present application is a negative electrode, the electrode material is a negative electrode material. The binder and conductive agent contained in the electrode active material can be selected as needed.

[0064] In the embodiment, based on the characteristics of the conductive fiber electrode matrix described above, the loading amount of the electrode active material on the conductive fiber electrode matrix is ​​1 to 100 mg / cm 2 , further can be 5 to 60 mg / cm 2Etc. Therefore, the electrode active material content in the flexible electrode 01 of the embodiment of the present application is high and has a high energy density. In addition, in addition to being filled in the three-dimensional porous structure of the conductive fiber electrode matrix, the electrode active material can also be combined on the surface of the conductive fiber electrode matrix. In the embodiment, the electrode active material can be simultaneously filled in the three-dimensional porous structure of the conductive fiber electrode matrix and combined on the surface of the conductive fiber electrode matrix to increase the capacity of the flexible electrode. In addition, whether the electrode active material is on the surface of the conductive fiber electrode matrix or whether there is an additional electrode active material can be selected and controlled according to the specific application needs and is not a necessary requirement.

[0065] In addition, based on the thickness of the conductive fiber electrode matrix and the loading amount of the electrode active material, in the embodiment, the thickness of the flexible electrode can be controlled in the range of 5 μm to 500 μm.

[0066] The several folds 12 distributed on the surface 11 of the flexible electrode 01 of the embodiment of the present application change the geometric structure of the surface 11 of the flexible electrode 01 and divide the surface 11 into several areas. By setting the folds 12 on the surface 11 of the flexible electrode 01 to change the spatial structure of the surface of the flexible electrode 01 or further change the distribution of the electrode active material in the conductive fiber electrode matrix, the stress of the flexible electrode 01 during the bending process can be effectively released, so that the flexible electrode 01 maintains good structural stability and electrochemical performance during the bending process, thereby improving the bending resistance of the flexible electrode 01. At the same time, the presence of the several folds 12 increases the bending performance of the flexible electrode 01, improves its flexibility and increases the content of the electrode active material, thereby achieving the flexible electrode 01 having both high flexibility and high surface energy characteristics. Among them, the several of the several folds 12 should be understood as more than two, and ideally the folds 12 are array folds formed by rich folds to be distributed on the surface of the flexible electrode 01. In addition, the folds 12 can be distributed on one surface or on two surfaces arranged oppositely.

[0067] In addition, the crease 12 is a geometric structure presented on the surface of the flexible electrode 01, and since the flexible electrode 01 also contains electrode active substances, the crease 12 is also related to the electrode active substances in certain cases. This is because when the crease 12 is formed, when the crease 12 reaches a certain depth, the electrode active substances will undergo a certain displacement. At this time, in an optional embodiment, in the flexible electrode, the content of the electrode active substances contained in the crease 12 is lower than the content of the electrode active substances contained in the non-crease area. Specifically, take two adjacent creases 12 as an example for further explanation: the content of the electrode active substances in the two adjacent creases 12 is lower than the content of the electrode active substances in the electrode area between the two adjacent creases 12. When the flexible electrode 01 of the embodiment of the present application is in this case, due to the flexibility and conductive properties of the conductive fiber electrode matrix, it has excellent bending resistance, and can maintain good structural stability and stable electrochemical performance in bending applications or bending tests. Moreover, due to the excellent conductivity and bending resistance of the conductive fiber electrode matrix, it can ensure the excellent electronic conduction characteristics of the flexible electrode 01 and the high surface capacity of the flexible electrode 01 when the content of the electrode active material contained in the crease 12 is lower than the content of the electrode active material contained in the non-crease.

[0068] In the embodiment, adjacent folds 12 are parallel, approximately parallel, partially parallel, partially in contact with each other, or intersecting. Figure 1 As shown. The fold 12 is a cross structure that can be but not limited to Figure 3 As shown in Figure a or Figure b. Of course, in addition to the folds of the above-mentioned morphology, folds of other morphologies can also be processed as needed. By adjusting and controlling the relationship between adjacent folds 12, the surface spatial structural characteristics of the flexible electrode 01 can be changed or the distribution of the electrode active material contained in the flexible electrode 01 can be further improved as described above at the fold 12, thereby improving the effective release of stress of the flexible electrode 01 during the bending process, and improving the structural stability and electrochemical performance of the flexible electrode 01 during the bending process. In addition, the direction of the fold 12 can be formulated as needed, that is,

[0069] In the embodiment, the distance between adjacent folds 12 is as follows: Figure 1 The L1 shown in FIG is 0.1 mm to 50 mm, further 1 to 50 mm, and specifically can be a typical but non-limiting spacing of 0.1 mm, 0.5 mm, 1 mm, 5 mm, 10 mm, 20 mm, 30 mm, 40 mm, 50 mm, etc. In another embodiment, the width of the fold 12 is as follows: Figure 1The L2 shown in is 1μm to 50μm, further 5-50μm, and can specifically be 1μm, 5μm, 10μm, 20μm, 30μm, 40μm, 50μm and other typical but non-limiting widths. Based on the spacing and width of the folds 12, in the embodiment, the spacing and width ratio of the folds 12 is defined as the spacing-to-width ratio. By controlling the spacing L1 between adjacent folds 12 and the width L2 of the folds 12 themselves, the surface spatial structural characteristics of the flexible electrode 01 are improved, and the stress release effect of the flexible electrode 01 during the bending process is further improved, and the structural stability and electrochemical performance of the flexible electrode 01 during the bending process are improved. Moreover, the content of the electrode active material can be increased while ensuring the flexibility and bending resistance of the flexible electrode 01, further improving the flexibility and high surface energy characteristics of the flexible electrode 01. In addition, the length L0 of the flexible electrode 01 in the longitudinal direction can be adjusted and controlled according to actual application needs.

[0070] In addition, the directions of adjacent creases 12 can be folded according to the needs of the application, and the creases 12 are distributed along the width direction of the conductive fiber electrode substrate. By controlling the distribution direction of the creases 12 to cope with the possibility of being folded in the direction during processing or application of the flexible electrode 01, the flexibility and bending resistance of the flexible electrode 01 during processing or application are improved, thereby improving the structural stability and electrochemical performance stability of the flexible electrode 01 during processing or application. In addition, when the surface of the conductive fiber electrode substrate of the flexible electrode 01 is combined with an electrode active material and forms an electrode active material layer, the crease 12 can also be expanded to be understood as a "crack" or "crack".

[0071] In the second aspect, based on the flexible electrode 01 described above, the present embodiment provides a method for preparing the flexible electrode 01 described above. The process flow of the method for preparing the flexible electrode 01 described in the present embodiment is as follows: Figure 4 As shown, the following steps are included:

[0072] S01: Providing a conductive fiber electrode substrate with a three-dimensional porous structure;

[0073] S02: filling the electrode active material slurry into at least the three-dimensional porous structure of the conductive fiber electrode matrix and then drying it to obtain a fiber-based electrode;

[0074] S03: Bending the fiber-based electrode so that a plurality of creases are distributed on the surface of the flexible electrode to obtain a flexible electrode.

[0075] The conductive fiber electrode substrate in step S01 is the conductive fiber electrode substrate contained in the flexible electrode 01 described above. The electrode active material slurry in step S02 is the slurry that forms the electrode active material contained in the flexible electrode 01 described above. The multiple creases formed by bending in step S03 are the multiple creases 12 contained in the surface 11 of the flexible electrode 01 described above. Therefore, in order to save space in the description of the embodiments of this application, the conductive fiber electrode substrate in step S01, the electrode active material slurry components in step S02, and the multiple creases formed by bending in step S03 will not be described in detail here.

[0076] In step S02, the electrode active material slurry is filled into at least the three-dimensional porous structure of the conductive fiber electrode matrix by various methods, such as spraying, doctor blade coating, and dipping. Furthermore, to increase the loading amount of the electrode active material and improve the compactness of the electrode active material in the conductive fiber electrode matrix, multiple coatings of the electrode active material slurry may be employed.

[0077] The drying process after coating the electrode active material slurry is to remove the solvent in the electrode active material slurry and solidify it. In addition, as needed, during or after the drying process, a processing step such as roller pressing can be performed according to a conventional electrode sheet preparation method.

[0078] The bending process in step S03 can be any method that can form the plurality of folds 12 on the surface 11 of the flexible electrode 01. Figure 5 The steps shown include the following:

[0079] The fiber-based electrode 01 ′ is bent and pulled through a roller 02 , so that creases 12 distributed along the width direction of the fiber-based electrode are formed on the surface of the fiber-based electrode 01 ′.

[0080] In a further embodiment, the rollers 02 include at least two or more rollers, which are distributed on both sides of the fiber-based electrode 01' pulling path. Figure 6 As shown, there are two rollers 02, which are distributed on both sides of the fiber-based electrode 01' pulling path. The two surfaces of the fiber-based electrode 01' are bent and pulled simultaneously to form folds 12 distributed along the width direction of the fiber-based electrode on the surface of the fiber-based electrode 01'.

[0081] Therefore, the above-mentioned flexible electrode preparation method directly bends the fiber-based electrode containing the electrode active material to form a number of creases on the surface, so that the prepared flexible electrode of the embodiment of the present application has the high bending resistance and high surface energy of the above-mentioned flexible electrode, and the stability of the structure and electrochemical performance during the bending process is high. In addition, the process conditions of the preparation method are easy to control, which can ensure the stability of the performance and quality of the prepared flexible electrode and high efficiency. Moreover, the bending resistance and surface energy of the flexible electrode can be improved by controlling the crease spacing, direction, etc.

[0082] On the third aspect, based on the flexible electrode and preparation method of the above-mentioned application embodiment, the embodiment of the present application also provides a battery. The battery includes a positive electrode, a negative electrode and a separator stacked between the positive electrode and the negative electrode, and of course also includes other necessary components of the battery, such as an electrolyte or electrolyte and a shell. Among them, the positive electrode and / or the negative electrode is the flexible electrode of the above-mentioned application embodiment. Since the battery contains the flexible electrode of the above-mentioned application embodiment, the battery not only has high capacity, but also has stable electrochemical performance, high safety and long life during the charge and discharge cycle, which expands the application field of the battery.

[0083] In addition, based on the structure of the above-mentioned battery, the battery can be a lithium battery, or of course a sodium battery. Among them, the lithium battery can be a lithium ion battery or a lithium metal battery.

[0084] The flexible electrode, preparation method thereof, battery, etc. of the embodiment of the present application are illustrated below through multiple specific embodiments.

[0085] 1. Flexible Electrode and Preparation Method Example

[0086] Example A1

[0087] This embodiment provides a flexible electrode and a method for preparing the same. The flexible electrode includes a carbon felt substrate and at least an LCO active material filled within the porous structure of the carbon felt substrate. The flexible electrode also has a plurality of creases distributed along its width. The LCO active material content and crease-related parameters are shown in Table 1 below.

[0088] The preparation method of the flexible electrode includes the following:

[0089] S1. Lithium cobalt oxide powder, carbon black, carbon nanotubes, and polyethylene oxide-nylon copolymer binder were mixed in a mass ratio of 85:5:5:5 and dispersed in an isopropyl alcohol / n-butanol mixed solvent to prepare a slurry. The slurry was then evenly doctor-coated on a 200 μm thick carbon felt. The LCO active material loading was controlled to 20 mg cm by multiple doctor-coatings. -2 ; Drying to obtain LCO fiber-based positive electrode sheet;

[0090] S2. The fiber-based electrode sheet is cut into 2 cm*4 cm pieces and then twisted and pressed on a roller with a diameter of 2 mm to obtain a flexible fiber-based LCO positive electrode with creases.

[0091] After testing, the actual flexible fiber-based LCO positive electrode of this embodiment is as follows Figure 7 As shown in the figure, it can be easily wound onto a thin round rod with a diameter of 1 mm, showing good flexibility.

[0092] Example A2

[0093] This embodiment provides a flexible electrode and a method for preparing the same. The flexible electrode comprises a nickel-plated carbon felt substrate and at least one LCO active material filled within the porous structure of the nickel-plated carbon felt substrate. The flexible electrode also has a plurality of creases distributed along its width. The LCO active material content and crease-related parameters are shown in Table 1 below.

[0094] The preparation method of the flexible electrode includes the following:

[0095] S1. Lithium cobalt oxide powder, carbon black, and polyvinylidene fluoride binder were mixed in a mass ratio of 90:5:5 and dispersed in nitrogen-methyl pyrrolidone solvent to prepare a slurry. The slurry was then evenly scraped onto a 200 μm thick nickel-plated carbon felt. The LCO active material loading was controlled to 25 mg / cm by multiple scrapings. 2 ; Drying to obtain LCO fiber-based positive electrode sheet;

[0096] S2. The fiber-based electrode sheet is cut into 2 cm*4 cm pieces and then twisted and pressed on a roller with a diameter of 1 mm to obtain a flexible fiber-based LCO positive electrode with creases.

[0097] After testing, the actual flexible fiber-based LCO positive electrode of this embodiment is Figure 7 Similar, but the crease spacing is smaller, and the electrode morphology remains essentially unchanged after repeated bending tests for more than 20,000 times in the bending resistance test. The resistance changes of the flexible electrode provided by Example A2 and the flexible electrodes provided by Comparative Examples A1 and A2 in the bending resistance test are further measured. The results are as follows: Figure 8 As shown in FIG, the flexible electrode provided by Example A2 has a stable resistance in the bending test of more than 20,000 times, indicating that its electronic conduction path is complete and stable. However, the flexible electrode provided by Comparative Example A2 has a completely broken electrode after more than 800 bending tests. Figure 10 The bending resistance of the flexible electrode provided by Comparative Example A1 is stronger than that of Comparative Example A1, but it is obviously worse than that of the flexible electrode of Example A2. After being bent for more than 4600 times, the electrode piece is completely broken. Figure 9 As shown in Figure B.

[0098] Example A3

[0099] This embodiment provides a flexible electrode and a method for preparing the same. The flexible electrode comprises a carbon felt substrate and at least an NCM811 active material filled within the porous structure of the carbon felt substrate. The flexible electrode also has a plurality of creases distributed along its width. The NCM811 active material content and crease-related parameters are shown in Table 1 below.

[0100] The preparation method of the flexible electrode includes the following:

[0101] S1. Nickel-cobalt-manganese ternary cathode powder (NCM811), carbon black, and polyvinylidene fluoride binder were mixed in a mass ratio of 92:4:4 and dispersed in nitrogen-methylpyrrolidone solvent to prepare a slurry. The slurry was then evenly spread on a 200 μm thick carbon felt. The NCM811 active material loading was controlled to 30 mg / cm by multiple spreads. 2 ; Drying to obtain NCM811 fiber-based positive electrode sheet;

[0102] S2. Cut the fiber-based electrode sheet into 2cm*4cm pieces and twist it around a metal rod with a diameter of 1mm to obtain a flexible fiber-based nickel-cobalt-manganese ternary positive electrode with creases.

[0103] The actual flexible fiber-based LCO positive electrode of this embodiment is Figure 7 Similar, but the crease spacing is smaller. After testing, the electrode morphology remained basically unchanged after being bent more than 20,000 times in the bending resistance test, the electronic conduction path was complete, and the electrode active material accounted for as high as 85%.

[0104] Example A4

[0105] This embodiment provides a flexible electrode and a method for preparing the same. The flexible electrode comprises a carbon felt substrate and at least an NCA active material filled within the porous structure of the carbon felt substrate. The flexible electrode also has a plurality of creases distributed along its width. The NCA active material content and crease-related parameters are shown in Table 1 below.

[0106] The preparation method of the flexible electrode includes the following:

[0107] S1. Nickel-cobalt-aluminum ternary cathode powder (NCA), carbon black, carbon nanotubes, and polyvinylidene fluoride binder were mixed in a mass ratio of 92:3:1:4 and dispersed in nitrogen-methylpyrrolidone solvent to prepare a slurry. The slurry was then evenly spread on a 300 μm thick carbon felt. The NCA active material loading was controlled to 45 mg / cm by multiple spreads. 2 ; Drying to obtain NCA fiber substrate;

[0108] S2. Cut the fiber-based electrode sheet into 2cm*4cm, and then twist it on a metal rod with a diameter of 3mm to obtain a flexible fiber-based nickel-cobalt-aluminum ternary positive electrode with creases.

[0109] Example A5

[0110] This embodiment provides a flexible electrode and a method for preparing the same. The flexible electrode comprises a carbon felt substrate and at least an LTO active material filled within the porous structure of the carbon felt substrate. The flexible electrode also has a plurality of creases distributed along its width. The LTO active material content and crease-related parameters are shown in Table 1 below.

[0111] The preparation method of the flexible electrode includes the following:

[0112] S1. Lithium titanate (LTO), carbon black, and polyvinylidene fluoride binder were mixed in a mass ratio of 92:4:4 and dispersed in nitrogen-methyl pyrrolidone solvent to prepare a slurry. The slurry was then evenly spread on a 200 μm thick carbon felt. The LTO active material loading was controlled to 20 mg / cm by multiple spreads. 2 ; Drying to obtain LTO fiber substrate;

[0113] S2. The fiber-based electrode sheet is cut into 2.2 cm*4.2 cm, and then twisted on a metal rod with a diameter of 1 mm to obtain a flexible fiber-based lithium titanate negative electrode with creases.

[0114] Example A6

[0115] This embodiment provides a flexible electrode and a method for preparing the same. The flexible electrode comprises a carbon felt substrate and at least an NCM811 active material filled within the porous structure of the carbon felt substrate. The flexible electrode also has a plurality of creases distributed along its width. The content of the LTO active material and the parameters associated with the creases are shown in Table 1 below.

[0116] The preparation method of the flexible electrode includes the following:

[0117] S1. Graphite (NCM811), carbon black, and polyacrylic acid binder were mixed in a mass ratio of 95:2:3 and dispersed in an aqueous solution to prepare a slurry. The slurry was then evenly doctor-bladed onto a 100 μm carbon felt. The NCM811 active material loading was controlled to 11 mg / cm by multiple doctor-blading techniques. 2 ; Drying to obtain a fiber-based graphite negative electrode;

[0118] S2. The fiber-based electrode sheet was cut into 2.2 cm*4.2 cm pieces, and then twisted on a metal rod with a diameter of 1 mm to obtain a creased flexible fiber-based graphite negative electrode.

[0119] Example A7

[0120] This embodiment provides a flexible electrode and a method for preparing the same. The flexible electrode includes a carbon felt substrate and at least an LCO active material filled within the porous structure of the carbon felt substrate. The flexible electrode also has a plurality of creases distributed along its width. The LCO active material content and crease-related parameters are shown in Table 1 below.

[0121] The preparation method of the flexible electrode includes the following:

[0122] S1. Lithium cobalt oxide powder, carbon black, carbon nanotubes, and polyethylene oxide-nylon copolymer binder were mixed in a mass ratio of 85:5:5:5 and dispersed in an isopropyl alcohol / n-butanol mixed solvent to prepare a slurry. The slurry was then evenly doctor-coated on a 200 μm thick carbon felt. The LCO active material loading was controlled to 20 mg cm by multiple doctor-coatings. -2 ; Drying to obtain LCO fiber-based positive electrode sheet;

[0123] S2. The fiber-based electrode sheet is cut into 2 cm*4 cm pieces and then twisted and pressed on a roller with a diameter of 5 mm to obtain a flexible fiber-based LCO positive electrode with creases.

[0124] After testing, the actual flexible fiber-based LCO positive electrode of this embodiment is as follows Figure 7 As shown in the figure, it can be easily wound onto a thin round rod with a diameter of 1 mm, showing good flexibility.

[0125] Example A8

[0126] This embodiment provides a flexible electrode and a method for preparing the same. The flexible electrode comprises a carbon felt substrate and at least an NCA active material filled within the porous structure of the carbon felt substrate. The flexible electrode also has a plurality of creases distributed along its width. The NCA active material content and crease-related parameters are shown in Table 1 below.

[0127] The preparation method of the flexible electrode includes the following:

[0128] S1. Nickel-cobalt-aluminum ternary cathode powder (NCA), carbon black, carbon nanotubes, and polyvinylidene fluoride binder were mixed in a mass ratio of 92:3:1:4 and dispersed in nitrogen-methylpyrrolidone solvent to prepare a slurry. The slurry was then evenly spread on a 400 μm thick carbon felt. The NCA active material loading was controlled to 60 mg / cm by multiple spreads. 2 ; Drying to obtain NCA fiber substrate;

[0129] S2. Cut the fiber-based electrode sheet into 2cm*8cm, and then twist it on a metal rod with a diameter of 10mm to obtain a flexible fiber-based nickel-cobalt-aluminum ternary positive electrode with creases.

[0130] Example A9

[0131] This embodiment provides a flexible electrode and a method for preparing the same. The flexible electrode comprises a carbon felt substrate and at least an NCA active material filled within the porous structure of the carbon felt substrate. The flexible electrode also has a plurality of creases distributed along its width. The NCA active material content and crease-related parameters are shown in Table 1 below.

[0132] The preparation method of the flexible electrode includes the following:

[0133] S1. Nickel-cobalt-aluminum ternary cathode powder (NCA), carbon black, carbon nanotubes, and polyvinylidene fluoride binder were mixed in a mass ratio of 92:3:1:4 and dispersed in nitrogen-methylpyrrolidone solvent to prepare a slurry. The slurry was then evenly scraped onto a 500 μm thick carbon felt. The NCA active material loading was controlled to 90 mg / cm by multiple scrapings. 2 ; Drying to obtain NCA fiber substrate;

[0134] S2. The fiber-based electrode sheet is cut into 2cm*8cm pieces, and then twisted on a metal rod with a diameter of 40mm to obtain a flexible fiber-based nickel-cobalt-aluminum ternary positive electrode with creases.

[0135] Comparative Example A1

[0136] This embodiment provides a flexible electrode and a method for preparing the same. The flexible electrode includes a carbon felt substrate and at least an LCO active material filled in the porous structure of the carbon felt substrate. Compared to Example A2, the flexible electrode has no uniformly distributed creases on its surface.

[0137] The preparation method of the flexible electrode includes the following:

[0138] Lithium cobalt oxide powder, carbon black, and polyvinylidene fluoride binder were mixed in a mass ratio of 90:5:5 and dispersed in nitrogen methyl pyrrolidone solvent to prepare a slurry. The slurry was then evenly scraped onto nickel-plated carbon felt with a thickness of 200 μm. The LCO active material loading was controlled to 25 mg / cm by multiple scrapings. 2 ; Drying to obtain fiber-based LCO positive electrode.

[0139] Comparative Example A1 Figure 9 As shown in (A), after testing, it broke after more than 4600 bending tests in the bending resistance test. Figure 9 (B) shown.

[0140] Comparative Example A2

[0141] This embodiment provides a flexible electrode and a method for preparing the same. The flexible electrode includes an aluminum foil substrate and an LCO active material coated on the upper surface of the aluminum foil. Compared to Example A2, the surface of the flexible electrode is smooth and wrinkle-free.

[0142] The preparation method of the flexible electrode includes the following:

[0143] Lithium cobalt oxide powder, carbon black, and polyvinylidene fluoride binder were mixed in a mass ratio of 90:5:5 and dispersed in nitrogen methyl pyrrolidone solvent to prepare a slurry. The slurry was then evenly coated on a 20 μm aluminum foil, and the LCO loading was controlled to be 25 mg / cm 2 ; Dry to obtain a conventional LCO positive electrode.

[0144] After testing, the flexible electrode in comparative example A2 broke after being bent more than 800 times in the bending resistance test. Figure 10 shown.

[0145] The electrode active material content and crease-related dimensions of the flexible electrodes provided in Examples A1 to A9 and Comparative Examples A1 to A2 are measured and are shown in Table 1 below:

[0146] Table 1

[0147]

[0148] 2. Battery Example

[0149] Example B1

[0150] This embodiment provides a soft pack battery, whose positive electrode is the flexible LCO positive electrode provided in the above embodiment A2. The soft pack battery is specifically assembled as follows:

[0151] The 2.0cm*4.0cm LCO positive electrode sheet in Example 2 and the 2.2cm*4.2cm flexible metal lithium negative electrode sheet were attached to the tabs and encapsulated into a soft-pack battery with an aluminum-plastic film. A Celgard 2400 model separator and an ester electrolyte (the main component is 1M LiPF6 dissolved in a mixed electrolyte of EC, DMC and FEC, EC / DMC=3:7, and the FEC content is 10wt%) were used.

[0152] Example B2

[0153] This embodiment provides a soft pack battery, whose positive electrode is the flexible LCO positive electrode provided in the above embodiment A1, and the one provided in embodiment A6. The soft pack battery is specifically assembled as follows:

[0154] The 2.0cm*4.0cm LCO positive electrode sheet from Example A1 was matched with the 2.2cm*4.2cm flexible graphite negative electrode sheet from Example A6 by bonding, with an N / P ratio of 1.08. Tabs were attached and the battery was encapsulated with aluminum-plastic film to form a soft-pack battery. A Celgard 2400 separator was used, and the electrolyte was an ester electrolyte (primarily composed of 1M LiPF6 dissolved in a mixture of EC, DMC, and FEC, with an EC / DMC ratio of 3:7 and an FEC content of 10wt%).

[0155] Comparative Example B1

[0156] This comparative example provides a soft pack battery, whose positive electrode is the flexible LCO positive electrode provided in the comparative example A2. The soft pack battery is specifically assembled as follows:

[0157] The flexible LCO positive electrode sheet provided by Comparative Example A1 was attached to a flexible metal lithium negative electrode sheet of 2.2 cm*4.2 cm by attaching tabs and encapsulating them with aluminum-plastic film to form a soft-pack battery. A Celgard 2400 model separator and an ester electrolyte (the main component is 1M LiPF6 dissolved in a mixed electrolyte of EC, DMC and FEC, EC / DMC=3:7, and the FEC content is 10wt%) were used.

[0158] Performance testing of soft pack batteries

[0159] The soft-pack batteries in Examples B1 to B2 and Comparative Example B1 were assembled and the cycle performance tests were performed according to the following methods:

[0160] After standing for 24 hours and testing the voltage, 2 After 3 cycles of activation at a current density of 1 mA / cm 2 The charge and discharge cycles were carried out at a current density of .

[0161] The charge-discharge cycle curve of the soft pack battery of Example B1 is as follows: Figure 11 As shown. Figure 11 The full battery based on the creased cathode maintained good cycling stability after 60 cycles at a current density of 1 mA. Furthermore, 1000 bends were performed at 20 and 40 cycles, respectively, demonstrating that the flexible bending test had little effect on the battery capacity. These results demonstrate that batteries with flexible cathodes obtained through bending not only exhibit excellent electrochemical performance but also exhibit excellent reproducible bendability.

[0162] The flexible lithium-ion full cell with a creased positive electrode, as in Example B1, maintained good cycling stability after 100 cycles at a current density of 1 mA. Furthermore, the flexible flex test was performed 1,000 times every 20 cycles, for a total of 4,000 flex cycles. The flex test had little effect on the battery capacity, demonstrating that the battery, assembled with creased positive and negative electrodes, possesses excellent electrochemical and flexibility characteristics.

[0163] The cycle charge and discharge curve of the soft pack battery of comparative example B1 is as follows: Figure 11 As shown. Figure 11 It can be seen that after the full battery was cycled 20 times at a current density of 1 mA and performed the first 1000 bending test, the electrochemical performance of the electrode plummeted and decayed and failed. The main reason was that the mechanical damage of the electrode during bending caused the battery failure, indicating that the battery / electrode did not pass the flexibility evaluation.

[0164] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present application should be included in the scope of protection of the present application.

Claims

1. A flexible electrode comprising a conductive fiber electrode substrate, characterized in that: The conductive fiber electrode matrix has a three-dimensional porous structure, an electrode active material is distributed at least in the conductive fiber electrode matrix, and a plurality of folds are distributed on the surface of the flexible electrode; The content of the electrode active material in the fold is lower than that in the non-fold; The flexible electrode is prepared according to the following method: Providing a conductive fiber electrode matrix with a three-dimensional porous structure; Filling the electrode active material slurry into at least the three-dimensional porous structure of the conductive fiber electrode matrix and then drying it to obtain a fiber-based electrode; Bending the fiber-based electrode so that a plurality of creases are distributed on the surface of the flexible electrode to obtain a flexible electrode; The method for bending the fiber-based electrode comprises the following steps: The fiber-based electrode is subjected to a bending and pulling process by a roller, so that the crease is formed on the surface of the fiber-based electrode.

2. The flexible electrode according to claim 1, wherein: Adjacent folds are at least one of parallel, approximately parallel, partially touching, and intersecting; and / or The width of the fold is 1 μm to 50 μm; and / or The distance between adjacent folds is 0.1 mm to 50 mm.

3. The flexible electrode according to claim 2, wherein: The folds are distributed along the width direction of the conductive fiber electrode substrate.

4. The flexible electrode according to any one of claims 1 to 3, characterized in that: The porosity of the conductive fiber electrode matrix is ​​greater than 50%; and / or The surface density of the conductive fiber electrode matrix is ​​0.1 mg / cm 2 ~6 mg / cm 2 and / or The thickness of the conductive fiber electrode substrate is 5 to 500 μm; and / or The loading amount of the electrode active material on the conductive fiber electrode substrate is 1 to 100 mg / cm 2 and / or The thickness of the flexible electrode is 5 μm to 500 μm.

5. The flexible electrode according to any one of claims 1 to 3, characterized in that: The material of the conductive fiber electrode matrix includes at least one of conductive carbon fiber felt, metal-plated carbon fiber felt, and metal-plated polymer fiber felt.

6. The flexible electrode according to claim 4, characterized in that: The electrode active material is a positive electrode active material, and the flexible electrode is a positive electrode; or The electrode active material is a negative electrode active material, and the flexible electrode is a negative electrode.

7. The method for preparing a flexible electrode according to any one of claims 1 to 6, characterized in that: The steps include: Providing a conductive fiber electrode matrix with a three-dimensional porous structure; Filling the electrode active material slurry into at least the three-dimensional porous structure of the conductive fiber electrode matrix and then drying it to obtain a fiber-based electrode; Bending the fiber-based electrode so that a plurality of creases are distributed on the surface of the flexible electrode to obtain a flexible electrode; The method for bending the fiber-based electrode comprises the following steps: The fiber-based electrode is subjected to a bending and pulling process by a roller, so that the crease is formed on the surface of the fiber-based electrode.

8. The preparation method according to claim 7, characterized in that: The rollers include at least two and are distributed on both sides of the fiber-based electrode traction route to perform the bending and traction treatment on both surfaces of the fiber-based electrode simultaneously.

9. A battery comprising a positive electrode, a negative electrode, and a separator stacked between the positive electrode and the negative electrode, characterized in that: The negative electrode and / or the positive electrode is the flexible electrode according to any one of claims 1 to 6 or the flexible electrode prepared by the preparation method according to any one of claims 7 to 8.

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