Binder, method for manufacturing the same, electrode sheet, lithium ion battery, and wearable device

Abstract

The embodiment of the present application provides a kind of binder, its manufacturing method, electrode sheet, lithium ion battery and wearable device.The binder includes supramolecule with beta-fold structure and linear molecule with linear structure, when binder is used in electrode sheet of lithium ion battery, supramolecule can still move freely along beta sheet, can effectively dissipate energy, reduce mechanical stress, so as to avoid the cracking and falling of electrode material doped with binder in electrode sheet after large deformation, and the beta-fold structure of supramolecule can promote supramolecule to restore to original state after external force is removed.Therefore, the binder provided in the embodiment can ensure that electrode material maintains stable shape and is closely covered on the surface of current collector, so as to ensure that electrode sheet maintains stable state in various severe deformations.

Description

Technical Field

[0001] This application relates to the field of lithium-ion battery technology, and more specifically, to an adhesive, a method for manufacturing the same, an electrode sheet, a lithium-ion battery, and a wearable device. Background Technology

[0002] With the increasing demand for wearable and portable electronic devices, flexible energy storage devices have been widely developed. Among various storage devices, lithium-ion batteries (LIBs) have high commercial value due to their high energy density and long cycle life.

[0003] However, due to the inherent rigidity of LIB electrode materials, their elasticity is limited. Meanwhile, traditional current collectors, such as aluminum (Al) and copper (Cu), have flat, smooth surfaces with weak adhesion, resulting in limited bonding between the current collector and the electrode material. After repeated dynamic deformations, LIBs are prone to loss of contact area between the negative and positive electrodes, and the electrode material is also susceptible to cracking and detachment from the metal current collector, further forming partially isolated particles. This leads to poor electron transport and ion dynamics due to uneven current distribution, ultimately resulting in loss of capacity and stability, and even safety issues.

[0004] Furthermore, increasing the loading of active materials leads to an increase in electrode thickness, and some problems are amplified under dynamic deformation, such as the inherent volume changes and structural collapse of the electrode material. Therefore, most reported flexible battery research has been conducted under low active material loading, exhibiting lower energy densities. Summary of the Invention

[0005] This application addresses the shortcomings of existing methods by proposing an adhesive, its manufacturing method, electrode sheets, a lithium-ion battery, and a wearable device to solve the technical problem of how to improve the load capacity of a flexible lithium-ion battery while ensuring its stability.

[0006] In a first aspect, embodiments of this application provide an adhesive, wherein the adhesive molecule comprises a supramolecular molecule and a linear molecule crosslinked with the supramolecular molecule; the supramolecular molecule comprises a plurality of crosslinked chain structures to form a β-sheet structure, the β-sheet structure comprising an array of reversible hydrogen bonds; the linear molecule is polyacrylic acid, the polyacrylic acid comprising a plurality of polar groups, at least a portion of the polar groups being covalently linked to the supramolecular molecule.

[0007] Optionally, each of the chain structures includes a soft segment, a hard segment, and a chain extender, wherein the soft segment, the hard segment, and the chain extender are connected by covalent bonds, and in the extension direction of the supramolecular, any two soft segments, any two hard segments, and any two chain extenders are not connected, and the chain extender is located at the end of the supramolecular.

[0008] Optionally, the ratio of the soft segment to the hard segment is 1:3 to 1:5; the ratio of the hard segment to the chain extender is 3:2 to 5:4.

[0009] Optionally, the soft segment comprises polyethylene glycol or polytetrahydrofuran, wherein the molecular weight of the polyethylene glycol is 1000-3000 and the molecular weight of the polytetrahydrofuran is 1000-3000; the hard segment comprises isophorone diisocyanate; and the chain extender comprises maleic dihydrazide or adipate dihydrazide.

[0010] Optionally, the carboxyl group of the polyacrylic acid forms an amide bond with the amino group of the maleic dihydrazide to serve as a covalent bond between the linear molecule and the supramolecular, or the carboxyl group of the polyacrylic acid forms an amide bond with the amino group of the adipic dihydrazide to serve as a covalent bond between the linear molecule and the supramolecular; the molecular weight of the polyacrylic acid is 500,000 to 1,000,000.

[0011] Secondly, embodiments of this application provide an electrode sheet, which includes:

[0012] current collector;

[0013] A coating layer covers the surface of the current collector, the material of which includes the electrode material and the aforementioned binder.

[0014] Thirdly, embodiments of this application provide a lithium-ion battery, which includes the electrode sheets described above.

[0015] Fourthly, embodiments of this application provide a wearable device that includes the aforementioned lithium-ion battery.

[0016] Fifthly, embodiments of this application provide a method for manufacturing an adhesive, comprising:

[0017] Prepare supramolecular structures comprising multiple cross-linked chain structures to form β-sheet structures, wherein the β-sheet structures include reversible hydrogen bond arrays;

[0018] A linear molecule, wherein the linear molecule is polyacrylic acid comprising a plurality of polar groups, is provided, and the polyacrylic acid is reacted with the supramolecular so that at least a portion of the polar groups are covalently linked to the supramolecular.

[0019] Optionally, a supramolecular structure comprising multiple cross-linked chain structures to form a β-sheet structure is prepared, including:

[0020] Isophorone diisocyanate and polyethylene glycol are dissolved in a first solvent and a first catalyst is added. The reaction is carried out at 60℃~100℃ under argon protection for 1h~5h. The ratio of polyethylene glycol to isophorone diisocyanate is 1:3~1:5.

[0021] Maleic dihydrazide or adipic dihydrazide is added as a chain extender, and the reaction is carried out at 30℃~50℃ under argon protection for 10h~20h to obtain the supramolecular, wherein the ratio of isophorone diisocyanate to the chain extender is 3:2~5:4.

[0022] In this configuration, polyethylene glycol serves as a soft segment, and isophorone diisocyanate serves as a hard segment. In the extension direction of the supramolecular, no two soft segments, no two hard segments, and no two chain extenders are connected, and the chain extender is located at the end of the supramolecular.

[0023] Optionally, the polyacrylic acid is reacted with the supramolecular to covalently link at least a portion of the polar groups to the supramolecular, including:

[0024] The polyacrylic acid, as a linear molecule, was dissolved in a second solvent and a second catalyst was added. The reaction was carried out under argon protection at 40°C to 60°C for 10 to 15 hours.

[0025] The supramolecular material is added, and the mixture is reacted at 50℃~100℃ for 24h~48h, followed by sedimentation and purification to obtain the binder.

[0026] The beneficial technical effects of the technical solutions provided in this application include:

[0027] The binder, its manufacturing method, electrode sheet, lithium-ion battery, and wearable device provided in this application embodiment include a supramolecular structure with a β-sheet structure and a linear molecule with a linear structure. Based on the structure of the supramolecular and linear molecules, when the binder is used in the electrode sheet of the lithium-ion battery, the supramoleculars can still move freely along the β-sheet. Therefore, when the electrode sheet deforms, the free movement of the supramoleculars along the β-sheet can effectively dissipate energy and reduce mechanical stress, thereby preventing cracking and detachment of the electrode material doped with binder in the electrode sheet after large deformation. Furthermore, the β-sheet structure of the supramoleculars can cause the supramoleculars to return to their original state after the external force is removed. Therefore, the binder provided in this embodiment can ensure that the electrode material maintains a stable shape and ensures that the electrode material tightly covers the surface of the current collector, thereby ensuring that the electrode sheet remains stable under various severe deformations. The stable state of the electrode sheet is beneficial to ensuring that the lithium-ion battery provides higher energy density.

[0028] Additional aspects and advantages of this application will be set forth in part in the description which follows, and will become apparent from the description or may be learned by practice of this application. Attached Figure Description

[0029] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the following description of the embodiments taken in conjunction with the accompanying drawings, wherein:

[0030] Figure 1 This is a structural formula of an adhesive molecule provided in the embodiments of this application;

[0031] Figure 2 is a schematic diagram showing the changes of the electrode sheet provided in the embodiment of this application during the deformation process, wherein... Figure 2a This is a schematic diagram of the electrode sheet before it deforms under stress. Figure 2b This is a schematic diagram of the electrode sheet undergoing deformation under stress. Figure 2c This is a schematic diagram of the electrode sheet after deformation under stress.

[0032] Figure 3 is a partially enlarged schematic diagram of region Q of the electrode sheet shown in Figure 2, in which... Figure 3a This is a magnified schematic diagram of region Q of the electrode sheet before deformation under stress. Figure 3b This is a magnified schematic diagram of region Q of the electrode sheet during the deformation process under stress. Figure 3c This is a magnified schematic diagram of region Q of the electrode sheet after deformation under stress.

[0033] Figure 4 A schematic flowchart illustrating the method for preparing the adhesive provided in this application embodiment;

[0034] Figure 5 for Figure 4 A flowchart illustrating step S1 in the method for preparing the adhesive shown.

[0035] Figure 6 for Figure 4 A flowchart illustrating step S2 in the method for preparing the adhesive shown.

[0036] Figure 7 The mechanical property test diagrams of the adhesive provided in the embodiments of this application are as follows: a is the stress-strain curve, b is the cyclic stress-strain curve, c is the stress relaxation curve, d is the optical image of the adhesive film stretching and recovery, and e is the mechanical durability test.

[0037] Figure 8The following are adhesion test diagrams of the adhesive provided in the embodiments of this application: a is the peel test curve of test sample 1 and control sample 1; b is the peel test curve of test sample 2 and control samples 2-3; c is a schematic diagram of the bending test process; d is a photograph of test samples 1-2 and control samples 1-3 after bending; e is a SEM image of test samples 1-2 and control sample 1 after bending test.

[0038] Figure 9 Cycle performance diagrams of binder-assembled batteries under different deformations provided in embodiments of this application;

[0039] Figure 10 Voltage curves of the binder-assembled battery under different deformations provided in the embodiments of this application;

[0040] Figure 11 Cyclic performance diagram of a binder-assembled battery provided in an embodiment of this application under dynamic bending deformation;

[0041] Figure 12 Voltage curves of binder-assembled batteries under dynamic bending deformation provided in embodiments of this application;

[0042] Figure 13 Cyclic performance diagram of a binder-assembled battery under dynamic torsional deformation, provided in an embodiment of this application;

[0043] Figure 14 Voltage curves of binder-assembled batteries under dynamic torsional deformation provided in embodiments of this application;

[0044] Figure 15 Cycle performance diagram of a binder-assembled battery under dynamic winding deformation, provided in an embodiment of this application;

[0045] Figure 16 Voltage curves of the binder-assembled battery provided in the embodiments of this application under dynamic winding.

[0046] Figure Labels

[0047] 10-Linear molecule; 20-Supramolecular; 210-Soft segment; 220-Chain extender; 230-Hard segment;

[0048] 100 - Current collector; 200 - Coating layer; 2001 - Binder; 2002 - Electrode material. Detailed Implementation

[0049] The embodiments of this application are described below with reference to the accompanying drawings. It should be understood that the embodiments described below with reference to the accompanying drawings are exemplary descriptions for explaining the technical solutions of the embodiments of this application, and do not constitute a limitation on the technical solutions of the embodiments of this application.

[0050] Those skilled in the art will understand that, unless specifically stated otherwise, the singular forms “a,” “an,” “the,” and “the” used herein may also include the plural forms. It should be further understood that the word “comprising” as used in this application’s specification means the presence of the stated features, integers, steps, operations, and / or components, but does not exclude implementation as supported by this art, other features, information, data, steps, operations, components, and / or combinations thereof. The term “and / or” as used herein refers to at least one of the items defined by the term; for example, “A and / or B” can be implemented as “A,” or as “B,” or as “A and B.”

[0051] To make the objectives, technical solutions, and advantages of this application clearer, the embodiments of this application will be described in further detail below with reference to the accompanying drawings.

[0052] First, let's introduce and explain several terms used in this application:

[0053] Supramolecular (SP): Generally refers to a complex, organized aggregate composed of two or more molecules bound together by intermolecular interactions, maintaining a certain integrity to give it a definite microscopic structure and macroscopic properties.

[0054] β-sheets, also known as β-pleated sheets or β-structures, are common secondary structures in proteins, composed of extended polypeptide chains. The conformation of a β-sheet is maintained by hydrogen bonds formed between the carbonyl oxygen of a peptide bond and another amide hydrogen atom located on the same or adjacent polypeptide chain. These hydrogen bonds are almost always perpendicular to the extended polypeptide chains, which can be either parallel (oriented from N to C) or antiparallel (with the polypeptide chains aligned in opposite directions).

[0055] Linear molecule: A chemical molecule in which all atoms in the molecular structure are located in a straight line. For example, polyacrylic acid (PAA) used in this application is a linear molecule.

[0056] Given the characteristics of wearable electronic devices, flexible energy storage devices are required as power sources. Lithium-ion batteries (LIBs) are commonly used power sources for electronic devices. However, due to the inherent rigidity of LIB electrode materials, their elasticity is limited. Furthermore, traditional current collectors, such as aluminum (Al) and copper (Cu), have flat, smooth surfaces and weak adhesion, resulting in limited bonding between the current collector and the electrode material. After repeated dynamic deformations, LIBs are prone to loss of contact area between the negative and positive electrodes, and the electrode material is also susceptible to cracking and detachment from the metal current collector, further forming partially isolated particles. Uneven current distribution leads to poor electron transport and ion dynamics, ultimately resulting in loss of capacity and stability, and even safety issues.

[0057] Furthermore, increasing the loading of active materials leads to an increase in electrode thickness, and some problems are amplified under dynamic deformation, such as the inherent volume changes and structural collapse of the electrode material. Therefore, most reported flexible battery research has been conducted under low active material loading, exhibiting lower energy densities.

[0058] To address these issues, the following methods are commonly used in existing technologies:

[0059] (i) Explore current collectors with good conductivity and high mechanical durability, including carbon nanotubes (CNTs), carbon cloth, graphite-based films, 3D carbon materials, etc.

[0060] (ii) Design new battery structures to reduce stress concentration and increase resistance to harsh deformations, such as linear, wavy, spine-like and human joint structures.

[0061] (iii) Enhance the adhesion between the active material and the current collector by electrode patterning.

[0062] However, the aforementioned methods still have some problems, such as high cost, low energy density, complex manufacturing processes, and difficulty in large-scale application. In summary, existing flexible lithium-ion batteries struggle to achieve both high energy density and high stability.

[0063] The inventors of this application have noticed the above-mentioned problems and have not solved them from the perspective of traditional electrode design, current collector design or battery structure. Instead, they have proposed a completely new way to solve the problems from the perspective of binder and put forward the technical solution of this application.

[0064] The technical solution of this application and how it solves the above-mentioned technical problems are described in detail below with specific embodiments. It should be noted that the following embodiments can be referenced, borrowed, or combined with each other, and the same terms, similar features, and similar implementation steps in different embodiments will not be described again.

[0065] This application provides an adhesive, please refer to the embodiments provided. Figure 1 The binder molecule includes a supramolecular and a linear molecule crosslinked with the supramolecular; the supramolecular 20 includes a plurality of crosslinked chain structures to form a β-sheet structure, the β-sheet structure including an array of reversible hydrogen bonds; the linear molecule 10 is polyacrylic acid, the polyacrylic acid includes a plurality of polar groups, at least some of which are covalently linked to the supramolecular 20.

[0066] Specifically, reversible hydrogen bond arrays are based on the dynamic reversibility of hydrogen bonds. Therefore, the aggregated hydrogen bond arrays can respond to stimuli from the external environment. For example, under the action of an external force, some hydrogen bonds in the array break and re-bond after the force is removed. Multiple reversible hydrogen bond arrays can be included within the same supramolecular structure 20, and these arrays can be of the same or different sizes. In this application, the reversible hydrogen bond arrays can be two-dimensional or three-dimensional arrays, that is, a two-dimensional or three-dimensional network formed by a large number of aggregated hydrogen bonds.

[0067] Please refer to Figure 1 In the adhesive molecule provided in this embodiment, each chain structure includes a soft segment 210, a hard segment 230, and a chain extender 220. The soft segment 210, hard segment 230, and chain extender 220 are connected by covalent bonds. In the extension direction of the supramolecular, any two soft segments 210, any two hard segments 230, and any two chain extenders 220 are not connected, and the chain extender 220 is located at the end of the supramolecular.

[0068] Specifically, the ratio of soft segment 210 to hard segment 230 is 1:3 to 1:5; the ratio of hard segment 230 to chain extender 220 is 3:2 to 5:4.

[0069] Specifically, the soft segment 210 includes polyethylene glycol or polytetrahydrofuran, wherein the molecular weight of polyethylene glycol is 1000-3000 and the molecular weight of polytetrahydrofuran is 1000-3000; the hard segment 230 includes isophorone diisocyanate; and the chain extender 220 includes maleic dihydrazide or adipate dihydrazide.

[0070] Please refer to Figure 1 In linear polyacrylic acid (PAA), the carboxyl group forms an amide bond with the amino group in maleic diacid hydrazide, serving as a covalent bond between the linear molecule and the supramolecular group; alternatively, the carboxyl group of PAA forms an amide bond with the amino group in adipic diacid hydrazide, also serving as a covalent bond between the linear molecule and the supramolecular group. The energy required to break a covalent bond is much greater than the energy required to break a hydrogen bond. Therefore, when the binder molecule is subjected to external force, the hydrogen bonds in the reversible hydrogen bond array break, while the covalent bonds between PAA and the supramolecular group remain intact.

[0071] In practice, the molecular weight of polyacrylic acid is between 500,000 and 1,000,000.

[0072] The binder provided in this embodiment includes supramolecular molecules with β-sheet structures and linear molecules with linear structures. Based on the structures of the supramolecular and linear molecules, when the binder is used in the electrode sheet of a lithium-ion battery, the supramolecular molecules can still move freely along the β-sheet. Therefore, when the electrode sheet deforms, the free movement of the supramolecular molecules along the β-sheet can dissipate some energy and reduce mechanical stress, thereby preventing cracking and detachment of the electrode material after large deformation. Furthermore, the β-sheet structure of the supramolecular molecules can cause them to return to their original state after the external force is removed, and the breaking and recombination of the reversible hydrogen bond array can serve as sacrificial bonds for energy dissipation, giving the binder high strength and high toughness. Therefore, the binder provided in this embodiment can ensure that the electrode material maintains a stable shape and that the electrode material tightly covers the surface of the current collector, thereby ensuring that the electrode sheet remains stable under various severe deformations. A stable electrode sheet is beneficial for ensuring that the lithium-ion battery provides higher energy density.

[0073] Based on the same inventive concept, this application also provides an electrode sheet for a lithium-ion battery. Please refer to Figures 2 and 3. The electrode sheet includes a current collector and a coating layer covering the current collector. The material of the coating layer includes electrode material 2002 and the binder 2001 in the above embodiments.

[0074] Specifically, the electrode sheet is a positive electrode, the current collector material includes aluminum foil, the electrode material 2002 includes lithium cobalt oxide, a conductive agent, and a binder 2001.

[0075] Specifically, the electrode sheet is a negative electrode, the current collector material includes copper foil, the electrode material 2002 includes graphite, a conductive agent, and a binder 2001.

[0076] Specifically, the adhesive 2001 is randomly distributed in the coating layer, and the content of adhesive 2001 in the coating layer is 5% to 10%.

[0077] The binder 2001 molecules are randomly distributed in the electrode material 2002, and their working principle during the deformation process of the electrode sheet under external force is shown in Figures 2 and 3. The following is combined with... Figure 1 The diagram shows the adhesive 2001 molecules and provides a detailed explanation of its working principle. Please refer to [link / reference]. Figure 1 The chemical structure of the adhesive 2001 molecule shown is described. In this structure, the linear molecule is polyacrylic acid (PAA), and the supramolecular molecule is abbreviated as SP. Therefore, for ease of explanation, in the following embodiments, the adhesive 2001 provided in this application will be referred to as ASP adhesive 2001.

[0078] Specifically, Figure 1 In the adhesive 2001 molecule shown, the soft segment 210 of SP is polyethylene glycol (PEG), and the chemical structural formula of PEG is as follows: The hard segment 230 of SP is isophorone diisocyanate (IPDI), and the chemical structural formula of IPDI is as follows: SP's chain extender 220 is maleic dihydrazide (MD), and the chemical structural formula of MD is... .

[0079] Please refer to Figure 2a and Figure 3a Before being subjected to any external force, the coating layer of the electrode sheet is considered to be intact, and the binder 2001 molecules are randomly distributed in the electrode material 2002. At this time, no cracks are visible to the naked eye in the area Q of the coating layer.

[0080] Please refer to Figure 2b and Figure 3b An external force is applied to the electrode plate; for example, the direction of the applied force is... Figure 2b and Figure 3b The direction indicated by the middle arrow. Under external force, the electrode material 2002, which has poor toughness, is prone to cracking. However, because the electrode material 2002 is doped with binder 2001 molecules, it can prevent the electrode material 2002 from falling off the current collector surface and maintain the integrity of the electrode material 2002.

[0081] by Figure 1 The ASP molecule shown is used as an example for illustration; please refer to [reference needed]. Figure 2b and Figure 3b After deformation, the PAA chains first cause radial deformation of the network in soft segment 210 (PEG) and straightening of the chains between the connection points in SP. Then, the reversible hydrogen bond array in SP changes (e.g., redirection, rotation, deformation). The synergistic mechanism between these dynamic, rigid, high-density hydrogen bonds and the soft PEG can dissipate energy, reduce mechanical stress, prevent slippage of electrode material 2002 after large deformation, and slow down crack initiation. When the electrode sheet cracks under extreme deformation and high load conditions, the strong adhesion of the reversible hydrogen bond array and PAA ensures contact between the particles of electrode material 2002. This allows the coating layer to maintain a relatively intact morphology of electrode material 2002 even when cracks occur, thus ensuring relatively stable conductivity of the electrode sheet.

[0082] Please refer to Figure 2c and Figure 3c After the external force is removed, the reversible hydrogen bond array of ASP molecules recombines and the chain shrinks, which allows the cracks between the electrode materials 2002 to be healed. Even if the particles of electrode material 2002 at the crack are not restored to a single unit, they can still maintain contact to ensure the conductivity of the electrode sheet.

[0083] Based on the beneficial effects of the adhesive 2001 in the above embodiments, the electrode sheet provided in this embodiment can meet the flexibility requirements while significantly improving the electrical performance of the electrode sheet.

[0084] Based on the same inventive concept, this application also provides a lithium-ion battery, which includes the electrode sheet in the above embodiments and has the beneficial effects of the electrode sheet in the above embodiments, which will not be repeated here.

[0085] Specifically, the lithium-ion battery provided in this embodiment is a flexible lithium-ion battery. This flexible lithium-ion battery uses electrode sheets with binder 2001 as described in the above embodiment, which significantly improves electrical performance and greatly increases storage capacity.

[0086] Based on the same inventive concept, this application also provides a wearable device, which includes the flexible lithium-ion battery in the above embodiments and has the beneficial effects of the flexible lithium-ion battery in the above embodiments, which will not be repeated here.

[0087] Specifically, the wearable devices mentioned in this embodiment include not only smartwatches, smart bracelets, and smart glasses, but also wearable medical devices.

[0088] Based on the same inventive concept, a method for manufacturing an electrode sheet adhesive 2001 for a lithium-ion battery, such as... Figure 4 As shown, the manufacturing method includes:

[0089] S1: Prepare supramolecular structures comprising multiple cross-linked chain structures to form β-sheet structures, the β-sheet structures including reversible hydrogen bond arrays.

[0090] Specifically, such as Figure 5 As shown, in the manufacturing method provided in this embodiment, step S1 includes:

[0091] S101: Dissolve isophorone diisocyanate and polyethylene glycol in a first solvent and add a first catalyst. React at 60℃~100℃ under argon protection for 1h~5h. The molar ratio of polyethylene glycol to isophorone diisocyanate is 1:3~1:5. In this step, the first solvent is N,N-dimethylformamide, and the first catalyst is dibutyltin dilaurate. In this step, isophorone diisocyanate and polyethylene glycol can be added to the reaction flask first, followed by dibutyltin dilaurate and N,N-dimethylformamide. A water bath can be used for heating, for example, heating to 80℃, for a reaction time of 3h.

[0092] S102: Add maleic dihydrazide or adipic dihydrazide as chain extender 220, and react under argon protection at 30℃~50℃ for 10h~20h to obtain supramolecular compounds. The molar ratio of isophorone diisocyanate to chain extender 220 is 3:2~5:4. In this step, the specific reaction temperature can be 40℃ and the reaction time can be 15h.

[0093] In the supramolecular obtained in step S1, polyethylene glycol serves as the soft segment 210 and isophorone diisocyanate serves as the hard segment 230. In the extension direction of the supramolecular, any two soft segments 210, any two hard segments 230, and any two chain extenders 220 are not connected, and the chain extender 220 is located at the end of the supramolecular.

[0094] S2: Provides a linear molecule, which is polyacrylic acid, comprising multiple polar groups, and reacts the polyacrylic acid with a supramolecular polymer so that at least some of the polar groups are covalently linked to the supramolecular polymer.

[0095] Specifically, such as Figure 6 As shown, the manufacturing method provided in this embodiment includes step S6:

[0096] S201: Polyacrylic acid, as a linear molecule, is dissolved in a second solvent and a second catalyst is added. The reaction is carried out at 40℃~60℃ under argon protection for 10h~15h. In this step, the second solvent is dimethyl sulfoxide, the second catalyst is 1,1'-carbonyldiimidazole, the specific reaction temperature can be 50℃, and the specific reaction time can be 12h.

[0097] S202: Add supramolecular molecules and react at 60℃~80℃ for 24h~48h, followed by sedimentation purification to obtain binder 2001. In this step, the specific reaction temperature can be 70℃, and the specific reaction time can be 36h; and sedimentation purification is carried out in diethyl ether.

[0098] As can be seen from the above steps, the steps and reaction conditions of the adhesive 2001 preparation method provided in this embodiment are relatively simple and easy to control, and the requirements for reaction equipment are low, so the production cost is low.

[0099] In order to investigate the performance of the adhesive provided in this application, the applicant used... Figure 1 Taking the binder 2001 molecule shown as an example, several experiments were designed to improve the mechanical properties of binder 2001, the adhesion of electrode material 2002 to the current collector, and the performance of lithium-ion batteries. The specific experimental items and results are as follows.

[0100] I. Mechanical Performance Testing

[0101] The applicant, as Figure 1The ASP adhesive 2001 shown was used to make a film, and the mechanical properties of the ASP film were tested. The specific test conditions and test results are described in detail below.

[0102] 1. Stress-strain testing of ASP thin films

[0103] A 0.5 mm thick ASP film was clamped in a stress-strain testing device, and the strain was gradually increased from 0. Figure 7 As shown in Figure a, the ASP film exhibits a combination of r-shaped and J-shaped curve characteristics. In the r-shaped region, the PAA chains rearrange along the stress direction, accompanied by the dissociation of some hydrogen bonds and a small movement of the SP portion, resulting in relatively small deformation of the ASP film. Upon increasing strain, due to the high-density reversible hydrogen bond array in the SP and the alignment of the soft segment 210 portion along the tensile direction, the breaking and rearrangement of the unique high-density hydrogen bond array in the ASP molecule can act as sacrificial bonds for significant energy dissipation, thus simultaneously generating high strength and high toughness. Furthermore, due to... Figure 7 It can be observed that the tensile strain of the ASP film can reach 1900%, indicating that the ASP film has good mechanical properties.

[0104] 2. Cyclic loading / unloading tests of ASP films under different maximum tensile strains

[0105] An ASP film with a thickness of 0.5 mm was subjected to cyclic loading / unloading tests at strains of 25%, 50%, and 100% to investigate its energy dissipation and elastic recovery capabilities. Figure 7 As shown in b, the hysteresis curve increases with increasing strain, indicating that friction between the entangled chains and the breaking of hydrogen bonds lead to significant energy dissipation. Importantly, the curve gradually recovers and approaches the original state after loading and unloading, with negligible residual strain, demonstrating that the ASP film exhibits good shape recoverability under different strains.

[0106] 3. Stress relaxation test of ASP film

[0107] A 0.5 mm thick ASP film was subjected to stress relaxation tests with a tensile strain of 30%. The obtained stress relaxation curves are shown below. Figure 7 As shown in Figure c, when the ASP film is maintained at a tensile strain of 30%, the required stress gradually decreases over time, and the time required for the required stress to decrease to 60% of the initial stress is approximately 60 minutes. This demonstrates that the ASP film has a long stress relaxation time, good elasticity retention, and can adapt to various deformations.

[0108] 4. Deformation recovery capability test of ASP film

[0109] This test used a 0.2mm thick ASP film, which was stretched to four times its initial length. After remaining stationary for 30 seconds, the ASP film returned to its initial size. Specifically, as shown below... Figure 7 As shown in d, the ASP film exhibits excellent deformation recovery capability.

[0110] 5. Cyclic durability test of ASP film at 30% strain

[0111] Cyclic stress ranging from 0 to 30% strain was applied to a 0.5 mm thick ASP film, with a cycle period of 1 minute. Cyclic tests were performed under these conditions, and the results are as follows: Figure 7 As shown in Figure e, a curve is plotted with time (800 min, i.e., 800 cycles) on the x-axis and strain on the y-axis. To better illustrate the effect of increasing cycle time on the curve for each cycle, the strain-time curves for the 200th, 400th, 600th, and 800th cycles are magnified for display. Figure 7 As can be seen from the results, after 800 cycles of testing, the residual strain of the ASP film remains very small, less than 1%, and after repeated verification, it is typically within the range of 0.5% to 1%. This demonstrates that the ASP film exhibits excellent durability and excellent shape recovery.

[0112] Through the above mechanical property tests, it can be seen that the ASP film has high strength, high toughness, good deformation recovery ability, good durability, and strong elasticity retention. These properties are crucial to ensuring close contact between the electrode material 2002 and the current collector, especially under large deformation and large active material load.

[0113] II. Adhesion Test

[0114] For flexible lithium-ion batteries, in addition to its good mechanical properties, the adhesion ability of the electrode binder 2001 to the positive electrode, negative electrode and current collector also has an important impact on the electrochemical performance of the lithium-ion battery.

[0115] Weak adhesion can lead to peeling and delamination of the electrode material 2002, resulting in poor contact and reduced capacity. To characterize adhesion, the applicant used an electrode sheet made with ASP adhesive 2001 from the above embodiments for 180° testing. Peeling tests were performed and compared with control samples. Detailed explanation follows.

[0116] First, the test samples and several control samples are introduced, as shown in Table 1.

[0117] Table 1. Material list of each structure in the sample

[0118]

[0119] Specifically, ASP refers to binder 2001 in the above embodiments of this application, PVDF refers to polyvinylidene fluoride, PAA refers to polyacrylic acid, and CMC refers to carboxymethyl cellulose. The positive electrode material is lithium cobalt oxide (LiCoO2), and the negative electrode material is graphite; the current collector of the positive electrode sheet is aluminum foil, and the current collector of the negative electrode sheet is copper foil.

[0120] 1. Peeling performance test

[0121] Peel performance tests were conducted on test samples 1-2 and control samples 1-3 in Table 1 using the same release tape. The following is a combination of... Figure 8 a and Figure 8 b. The structure of the peeling performance test is described.

[0122] The bonding test results of test sample 1 and control sample 1 are as follows: Figure 8 As shown in Figure a, compared to the positive electrode sheet using a traditional PVDF binder in control sample 1, the positive electrode sheet using ASP binder in test sample 1 showed a significant increase in both the maximum peak value and the average peel force. This means that when ASP binder is used as the binder for the positive electrode sheet, the adhesion between the electrode material LiCoO2 and the current collector aluminum foil is higher.

[0123] The bonding test results of test sample 2, control sample 2, and control sample 3 are as follows: Figure 8 As shown in b, the peak peel force in control samples 2 and 3 is approximately 1.4 N, meaning that the peak peel force in the negative electrode sheet using PAA and CMC adhesives is approximately 1.4 N, and the peel force is generally above 1.1 N. In contrast, the peak peel force in the negative electrode sheet using ASP adhesive is approximately 3.4 N, the peel curve is relatively stable with little fluctuation, and the peel force is generally above 2.5 N. It is evident that when ASP adhesive is applied to the negative electrode sheet, the adhesion is significantly improved compared to traditional PAA and CMC adhesives.

[0124] Furthermore, for the positive electrode, after the bonding test, the tape used for the bonding test of test sample 1 was clean, meaning no electrode material peeled off; while the tape used for control sample 1 had positive electrode material LiCoO2 adhered to it, exposing the current collector aluminum foil. For the negative electrode, after the bonding test, the tape used for the bonding test of test sample 2 had a small amount of negative electrode material graphite adhered to it, but the current collector copper foil was not exposed; while the tapes used for control samples 2 and 3 had a larger amount of negative electrode material graphite adhered to it, exposing the current collector copper foil. This also indicates that the ASP adhesive provided in this application is beneficial for improving the adhesion between the electrode material and the current collector.

[0125] II. Folding Test

[0126] The folding test process is as follows: Figure 8 As shown in c, with a bending radius of 0.5 mm, the adhesion to test samples 1-2 and control samples 1-3 in Table 1 was further evaluated through a folding test. The test results are as follows: Figure 8 d and Figure 8 As shown in e.

[0127] like Figure 8 As shown in d, after the folding test, the electrode sheets were observed by human eyes. Test sample 1 (positive electrode sheet) and test sample 2 (negative electrode sheet) showed no cracking or peeling. However, by human eye observation, control sample 2 and control sample 3 showed cracking and peeling, and control sample 3 showed large-area peeling. Figure 8 d does not show a photo of control sample 1. Please refer to the results of subsequent SEM observation of control sample 1.

[0128] To further demonstrate the folding test results, scanning electron microscopy (SEM) was used to observe the test samples 1-2 and control sample 1 after the folding test. The results are as follows: Figure 8 As shown in e.

[0129] Please refer to Figure 8 The first row of image e contains three SEM images, from right to left: an SEM image of the cross-section of the bend in test sample 1, an SEM image of the surface of the bend in control sample 1, and an SEM image of the cross-section of the bend in test sample 2. It can be seen that the coating (lithium cobalt oxide / ASP) in test sample 1 is tightly bonded to the aluminum foil, and there is no delamination of the lithium cobalt oxide / ASP; the coating (graphite / ASP) in test sample 2 is tightly bonded to the copper foil, and there is no delamination of the graphite / ASP; control sample 1 shows cracks and peeling.

[0130] To evaluate the superior performance of the ASP adhesive provided in this application, the applicant subjected test sample 1 and test sample 2 to extreme deformation through multiple folding operations. However, both test sample 1 and test sample 2 maintained the adhesion between the electrode material and the current collector, as well as the integrity of the coating layer.

[0131] III. Electrical Performance Testing of Flexible Lithium-ion Batteries

[0132] First, the battery to be evaluated is described. The positive electrode of the battery to be evaluated is test sample 1 from the above embodiments, and the negative electrode is test sample 2 from the above embodiments. The battery to be evaluated adopts a traditional pouch structure. For comparison, control sample 1 from the above embodiments is used as the positive electrode, and control samples 2 and 3 from the above embodiments are used as the negative electrodes, respectively, using a traditional pouch structure to construct control battery 1 and control battery 2. Details are shown in Table 2:

[0133] 1. Electrochemical performance testing of the battery under different static conformations

[0134] To evaluate the electrochemical performance under different stress conditions, the battery under evaluation was subjected to 1C (140 mAh g⁻¹). -1 The discharge capacity and cycle performance under certain conditions were evaluated. The static conformation of the battery under evaluation underwent different deformations, from flat to bending, twisting, winding, and folding. The test results were as follows: Figure 9 As shown in the image.

[0135] like Figure 9 As shown, the static conformation of the battery under evaluation is flat in the first 20 charge-discharge cycles; bent in the 21st to 30th charge-discharge cycles; twisted in the 31st to 40th charge-discharge cycles; wound in the 41st to 50th charge-discharge cycles; and folded in the 51st to 60th charge-discharge cycles.

[0136] like Figure 9 As shown, the battery under evaluation underwent 20 charge-discharge cycles with a flat conformation, and its capacity increased from 137.0 mAhg. -1 It slowly decreased to 134.7 mAhg. -1 The battery under evaluation was bent into an S-shape and subjected to 10 charge-discharge cycles in this S-shaped bending conformation. Calculations showed that the battery's capacity decayed by 0.052% per cycle in this S-shaped bending conformation. Subsequently, the battery was subjected to 10 charge-discharge cycles in a torsional conformation with a twist angle of 45°, maintaining a discharge capacity of 131.8 mAhg. -1 After cycling the battery under winding conditions for 10 cycles, its capacity remained almost unchanged. Finally, the battery underwent more stringent folding deformation, and no significant capacity decay was observed in 10 cycles (0.048% decay per cycle). This demonstrates that the battery exhibits good discharge capability and cycle performance under various deformation conditions.

[0137] Specifically, during the above-mentioned cycle, the average coulombic efficiency (CE) approached 100%, indicating that the ASP binder possesses strong adhesion and mechanical properties, giving the electrode sheet strong resistance to deformation. For example... Figure 10 As shown, in the charge-discharge curves of different conformations, the evaluated battery exhibited small overpotential changes, and the charge-discharge plateaus of the evaluated batteries in each conformation almost coincided with those of the battery in the planar conformation. Furthermore, the evaluated battery in the bent conformation showed excellent cycle performance, with a capacity closest to that of the battery in the planar conformation. The capacities of the evaluated batteries in the torsional, coiled, and folded conformations almost overlapped, although their capacity performance was not as good as that of the battery in the bent conformation, the difference from the battery in the planar conformation was not significant, less than 3%. This indicates that different conformations have a relatively small impact on the evaluated battery.

[0138] Since the most common conformation for flexible lithium-ion batteries used in wearable devices is bending when in operation (discharge state), the applicant tested the battery with the bending conformation under different charge and discharge efficiencies. For example, the discharge capacity reached 141.8 mAh g under 0.5C, 1C, 2C, and 3C conditions. -1 138.8mAhg -1 132.0mAhg -1 119.1mAhg -1 It can be seen that the battery under evaluation still has good electrical performance even at high current density.

[0139] 2. Energy density test of the battery to be evaluated

[0140] Considering the complexity of calculating the energy density of flexible batteries, the applicant used a water displacement method to measure the volume of the battery under evaluation to calculate its energy density, arriving at a calculated energy density of 420 Wh / L. -1 It has an energy density superior to most flexible lithium-ion batteries with complex structural designs.

[0141] 3. Electrochemical performance testing of the battery under different dynamic mechanical loads

[0142] The applicant also tested the stability of the battery to be evaluated, specifically by testing the electrochemical performance of the battery under three different dynamic mechanical loads: dynamic bending, dynamic torsion, and dynamic winding.

[0143] (1) Dynamic bending

[0144] The battery to be evaluated is dynamically bent with a bending radius of 20 mm. For example, the battery to be evaluated is bent 50,000 times in 35 charge-discharge cycles.

[0145] like Figure 11 and Figure 12 As shown, after 50,000 dynamic bending cycles and 35 charge-discharge cycles, the battery under evaluation still has 134.5 mAh g. -1 The discharge capacity decays by approximately 0.076% per cycle, and the coulombic efficiency (CE) is close to 100%. Throughout the bending process, the charge and discharge plateaus of the battery under evaluation almost overlap.

[0146] like Figure 12 As shown, under the same dynamic bending and charge-discharge cycle conditions as the battery under evaluation, the voltage curves of control battery 1 and control battery 2 showed large fluctuations during the dynamic bending process, while the voltage curve of the battery under evaluation did not show large fluctuations during the dynamic bending process, indicating that the ASP binder provided in this application has good adaptability to dynamic bending.

[0147] (2) Dynamic torsion

[0148] The battery under evaluation was subjected to dynamic torsion. During the process of torsion 100,000 times at a torsion angle of 45° at 1C, the battery under evaluation underwent 30 charge-discharge cycles.

[0149] like Figure 13 and Figure 14 As shown, the battery under evaluation performed well in 100,000 torsion cycles and 30 charge-discharge cycles, achieving a capacity retention rate of 96.6% and stable charging efficiency. The charge-discharge voltage curves of the battery under evaluation under different cycles largely overlapped, indicating that the battery under evaluation can maintain stable electrical performance under dynamic torsion, which means that the battery under evaluation has a stable internal structure. In contrast, control batteries 1 and 2 exhibited larger voltage fluctuations due to electrode material shedding or loose contact between the electrodes and the current collector.

[0150] (3) Dynamic winding

[0151] The battery to be evaluated was dynamically wound with a winding radius of 20 mm. Specifically, the battery to be evaluated was wound 600 times at 1C and then charged and discharged 20 times.

[0152] like Figure 15 and Figure 16As shown, the battery under evaluation retained 92.3% of its capacity after 600 dynamic winding cycles and 20 charge-discharge cycles, with a capacity decay of 0.38% per cycle and a coulombic efficiency (CE) close to 100%. This indicates that the electrode sheets in the battery under evaluation possess robust mechanical durability. Furthermore, the voltage curves of the battery under evaluation at different cycle numbers show small overpotential changes, further demonstrating that the battery under evaluation can maintain stable electrical performance under dynamic winding. In contrast, control batteries 1 and 2 exhibited larger and more random voltage fluctuations.

[0153] The above-mentioned experiments all demonstrate that the ASP binder provided in this application contributes to the enhancement of the stability, current density, and mechanical properties of flexible lithium-ion batteries. Furthermore, the batteries under evaluation exhibit stable impedance after different deformations, which also indicates that the ASP binder provided in this application helps improve the electrochemical stability of flexible lithium-ion batteries under dynamic mechanical loads.

[0154] By applying the embodiments of this application, at least the following beneficial effects can be achieved:

[0155] The adhesive, its manufacturing method, electrode sheet, lithium-ion battery, and wearable device provided in this application embodiment include a supramolecular structure with a β-sheet structure and a linear molecule with a linear structure. Based on the structure of the supramolecular and linear molecules, when the adhesive is used in the electrode sheet of the lithium-ion battery, the supramoleculars can still move freely along the β-sheet. Therefore, when the electrode sheet deforms, the free movement of the supramoleculars along the β-sheet can effectively dissipate energy and reduce mechanical stress, thereby avoiding cracking and detachment of the electrode material in the electrode sheet after large deformation. Furthermore, the β-sheet structure of the supramoleculars can promote the supramoleculars to return to their original state after the external force is removed. Therefore, the adhesive provided in this embodiment can ensure that the electrode material maintains a stable shape and ensures that the electrode material tightly covers the surface of the current collector, thereby ensuring that the electrode sheet remains stable under various severe deformations. The stable state of the electrode sheet is beneficial to ensuring that the lithium-ion battery provides higher energy density.

[0156] Those skilled in the art will understand that the steps, measures, and solutions in the various operations, methods, and processes discussed in this application can be alternated, modified, combined, or deleted. Furthermore, other steps, measures, and solutions in the various operations, methods, and processes discussed in this application can also be alternated, modified, rearranged, decomposed, combined, or deleted. Furthermore, steps, measures, and solutions in the prior art that are similar to those disclosed in this application can also be alternated, modified, rearranged, decomposed, combined, or deleted.

[0157] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, unless otherwise stated, "a plurality of" means two or more.

[0158] In the description of this specification, specific features, structures, materials, or characteristics may be combined in any suitable manner in one or more embodiments or examples.

[0159] It should be understood that although the steps in the flowcharts of the accompanying drawings are shown sequentially according to the arrows, the order in which these steps are implemented is not limited to the order indicated by the arrows. Unless explicitly stated herein, in some implementation scenarios of this application, the steps in each process can be executed in other orders as required. Moreover, some or all of the steps in each flowchart may include multiple sub-steps or multiple stages based on the actual implementation scenario. Some or all of these sub-steps or stages may be executed at the same time or at different times. In scenarios where the execution times are different, the execution order of these sub-steps or stages can be flexibly configured according to requirements, and this application does not limit this.

[0160] The above description is only a partial implementation of this application. It should be noted that for those skilled in the art, other similar implementation methods based on the technical concept of this application, without departing from the technical concept of this application, also fall within the protection scope of the embodiments of this application.

Claims

1. An adhesive, characterized in that, The binder molecules include supramolecular molecules and linear molecules crosslinked with the supramolecular molecules; The supramolecular structure comprises multiple cross-linked chain structures to form a β-sheet structure, the β-sheet structure comprising an array of reversible hydrogen bonds; each chain structure comprises a soft segment, a hard segment, and a chain extender, the soft segment, the hard segment, and the chain extender being covalently linked; the chain extender comprises maleic dihydrazide. The linear molecule is polyacrylic acid, which includes a plurality of polar groups, at least some of which are covalently linked to the supramolecular molecule; the carboxyl group of the polyacrylic acid forms an amide bond with the amino group of the maleic dihydrazide as a covalent bond between the linear molecule and the supramolecular molecule.

2. The adhesive according to claim 1, characterized in that, In the extension direction of the supramolecular segment, no two soft segments, no two hard segments, and no two chain extenders are connected, and the chain extenders are located at the ends of the supramolecular segment.

3. The adhesive according to claim 2, characterized in that, The ratio of the soft segment to the hard segment is 1:3 to 1:5; The ratio of the hard segment to the chain extender is 3:2 to 5:

4.

4. The adhesive according to claim 3, characterized in that, The soft segment includes polyethylene glycol or polytetrahydrofuran, wherein the molecular weight of polyethylene glycol is 1000-3000 and the molecular weight of polytetrahydrofuran is 1000-3000. The hard segment includes isophorone diisocyanate.

5. The adhesive according to claim 4, characterized in that, The molecular weight of the polyacrylic acid is 500,000 to 1,000,000.

6. An electrode sheet for a lithium-ion battery, characterized in that, include: current collector; A coating layer covering the surface of the current collector, the material of the coating layer comprising the electrode material and the binder according to any one of claims 1-5.

7. A flexible lithium-ion battery, characterized in that, Includes the electrode sheet as described in claim 6.

8. A wearable device, characterized in that, Including the flexible lithium-ion battery as described in claim 7.

9. A method for manufacturing an electrode sheet adhesive for a lithium-ion battery, characterized in that, include: A supramolecular structure comprising multiple cross-linked chain structures to form a β-sheet structure is prepared, the β-sheet structure comprising an array of reversible hydrogen bonds; each chain structure comprises a soft segment, a hard segment, and a chain extender, the soft segment, the hard segment, and the chain extender being covalently linked; the chain extender comprises maleic dihydrazide. A linear molecule is provided, the linear molecule being polyacrylic acid, the polyacrylic acid comprising a plurality of polar groups, the polyacrylic acid being reacted with the supramolecular so that at least a portion of the polar groups are covalently linked to the supramolecular; the carboxyl group of the polyacrylic acid is reacted with the amine group of the maleic dihydrazide to form an amide bond, which serves as the covalent bond between the linear molecule and the supramolecular.

10. The manufacturing method according to claim 9, characterized in that, Preparation of supramolecular structures comprising multiple cross-linked chain structures to form β-sheet structures, including: Isophorone diisocyanate and polyethylene glycol are dissolved in a first solvent and a first catalyst is added. The reaction is carried out at 60℃~100℃ under argon protection for 1h~5h. The ratio of polyethylene glycol to isophorone diisocyanate is 1:3~1:

5. Maleic dihydrazide or adipic dihydrazide is added as a chain extender, and the reaction is carried out at 30℃~50℃ under argon protection for 10h~20h to obtain the supramolecular, wherein the ratio of isophorone diisocyanate to the chain extender is 3:2~5:

4. In this configuration, polyethylene glycol serves as a soft segment, and isophorone diisocyanate serves as a hard segment. In the extension direction of the supramolecular, no two soft segments, no two hard segments, and no two chain extenders are connected, and the chain extender is located at the end of the supramolecular.

11. The manufacturing method according to claim 10, characterized in that, Reacting the polyacrylic acid with the supramolecular material to covalently link at least a portion of the polar groups to the supramolecular material includes: The polyacrylic acid, as a linear molecule, was dissolved in a second solvent and a second catalyst was added. The reaction was carried out under argon protection at 40°C to 60°C for 10 to 15 hours. The supramolecular material is added, and the mixture is reacted at 60℃~80℃ for 24h~48h, followed by sedimentation and purification to obtain the binder.

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