A positive electrode binder, a method for preparing the same, a positive electrode sheet, and a battery

Abstract

The application provides a positive electrode binder and a preparation method thereof, a positive electrode sheet and a battery, the positive electrode binder comprising a conductive polymer, a binding polymer and a conductive nano filler, the conductive polymer forming a core, the binding polymer being formed on the surface of the core to form a shell, and the shell having a gap region exposing the core, the gap region on the surface of the core forming a conductive site, and the conductive nano filler being overlapped with the conductive site to form a conductive network; the application breaks through the technical bottleneck of the traditional positive electrode binder that the conductive performance and the binding performance are restricted by each other by innovatively designing the core-shell structure of the 'conductive polymer core-binding polymer shell', and forming the conductive network by accurately overlapping the conductive site and the conductive nano filler, and simultaneously ensuring the formability and the binding firmness of the positive electrode sheet, and significantly improving the conductive performance, the cycle stability and the rate performance of the positive electrode.

Description

Technical Field

[0001] This invention relates to the field of battery technology, specifically to a positive electrode binder and its preparation method, a positive electrode sheet, and a battery. Background Technology

[0002] Energy density is one of the core performance indicators of lithium-ion batteries, directly determining the battery's range and applicability to various applications. Increasing the proportion of active materials in the positive electrode is one of the key methods to improve the energy density of lithium-ion batteries. In the preparation process of the positive electrode of lithium-ion batteries, the binder, as a core auxiliary component, mainly plays a role in firmly bonding the positive electrode active material, conductive agent, and current collector, ensuring the structural integrity and mechanical stability of the positive electrode. Its performance and ratio directly affect the overall performance of the battery. Currently, the binder widely used in the cathode of traditional lithium-ion batteries is polyvinylidene fluoride (PVDF). Although this type of binder has a certain bonding strength, it does not possess electrical conductivity and cannot participate in electron transport. To construct an effective electron transport channel, a large amount of conductive agents, such as conductive carbon black and carbon nanotubes, need to be added to the cathode system. This results in the proportion of the cathode main material (cathode active material) typically being limited to 92%~98%, making it difficult to increase further and failing to meet the application requirements of high-energy-density batteries (such as power batteries and high-end energy storage batteries). Meanwhile, the addition of excessive conductive agent can also bring a series of derivative problems: on the one hand, excessive conductive agent will significantly increase the porosity of the electrode, resulting in uneven electrolyte wetting, which in turn affects the lithium-ion transport efficiency and increases battery polarization; on the other hand, excessive porosity will weaken the mechanical strength of the positive electrode, and during the battery charge and discharge cycle, active material shedding, electrode powder shedding, delamination and other phenomena are likely to occur, which seriously degrades the cycle stability and service life of the battery. To address the non-conductive nature of traditional binders, existing technologies have attempted to improve their conductivity. The most common method involves simple blending of conductive polymers with binders, aiming to leverage the intrinsic conductivity of the polymers to enhance the binder's conductivity, thereby reducing the amount of conductive agent needed and increasing the proportion of active material. However, this method suffers from significant technical drawbacks: the compatibility between conductive polymers and traditional binders is poor, leading to phase separation during blending and preventing the formation of a uniform and stable composite system. Furthermore, simple blending cannot construct a continuous and complete conductive network. During battery cycling, the conductive network is prone to breakage and failure due to the volume expansion and contraction of the active material. Therefore, it fails to fundamentally solve the problem of synergistic improvement in conductivity and bonding performance, making it difficult to meet the requirements for high-energy-density, high-cycle-stability lithium-ion batteries. Therefore, overcoming these technical problems and drawbacks is a key issue that needs to be addressed. Summary of the Invention

[0003] To address the problems of limited positive electrode active material ratio, excessive conductive agent dosage, easy breakage of conductive network, and difficulty in synergistically improving the conductivity and bonding performance of binder in existing technologies, this invention provides a positive electrode binder and its preparation method, a positive electrode sheet, and a battery.

[0004] The technical solution adopted by the present invention to solve the above-mentioned technical problems is as follows: The first aspect of the present invention provides a positive electrode binder comprising a conductive polymer, a bonding polymer, and a conductive nanofiller, wherein the conductive polymer forms a core, the bonding polymer is formed on the surface of the core to form a shell, and the shell has a gap region exposing the core, the gap region on the surface of the core forms conductive sites, and the conductive nanofiller overlaps with the conductive sites to form a conductive network.

[0005] Optionally, the conductive polymer includes one or more of polyaniline, polypyrrole, or poly3,4-ethylenedioxythiophene.

[0006] Optionally, the adhesive polymer includes one or more of polyacrylic acid, sodium carboxymethyl cellulose, or modified starch.

[0007] Optionally, the conductive nanofiller includes one or more of conductive carbon black, carbon nanotubes, or graphene nanosheets.

[0008] Optionally, the system further includes a coupling agent, through which the conductive polymer and the bonding polymer are chemically bonded; the coupling agent includes one or more of silane coupling agents, titanate coupling agents, and aluminate coupling agents.

[0009] Optionally, the mass ratio of the conductive polymer, the binding polymer, the conductive nanofiller and the coupling agent is (10~20):(60~75):(5~15):(1~3).

[0010] Optionally, it also includes a dispersant, which includes one or more of sodium dodecylbenzenesulfonate, polyethylene glycol, polyvinylpyrrolidone, and sodium citrate; the mass ratio of the conductive nanofiller to the dispersant is (5~15):(0.5~2).

[0011] A second aspect of the present invention provides a method for preparing a positive electrode binder, comprising the following steps: S1. Dissolve the conductive polymer and the binder polymer in a solvent, and the binder polymer is coated on the core surface with gaps to obtain a core-shell polymer dispersion; S2. The conductive nanofiller is added to the core-shell polymer dispersion to form a mixed solution, which is then subjected to high-speed shear dispersion and ultrasonic treatment to obtain the positive electrode binder.

[0012] Optionally, in step S1, "dissolving the conductive polymer and the bonding polymer in a solvent" further includes dissolving a coupling agent in a solvent to achieve chemical bonding between the conductive polymer and the bonding polymer; the reaction temperature is 50~60℃, and the reaction time is 2~3h.

[0013] Optionally, in step S2, "adding conductive nanofillers to the core-shell polymer dispersion" further includes dissolving the dispersant in the core-shell polymer dispersion.

[0014] Optionally, the mass ratio of conductive nanofiller to dispersant is (5~15):(0.5~2).

[0015] Optionally, in step S2, the high-speed shear dispersion time is 30-40 min, and the ultrasonic treatment time is 10-15 min.

[0016] Optionally, in step S2, the solid content of the mixed solution is 20% to 30%.

[0017] A third aspect of the present invention provides a positive electrode sheet, comprising a positive current collector and a positive active material layer disposed on both sides of the positive current collector, wherein the positive active material layer comprises a positive active material and a positive binder, and the positive binder is the positive binder described above, or a positive binder prepared by the method of preparing the positive binder described above.

[0018] Optionally, the total mass of the positive electrode active material layer is taken as 100%; the positive electrode active material accounts for 97%-99% of the mass of the positive electrode active material layer; and the positive electrode binder accounts for 1%-3% of the mass of the positive electrode active material layer.

[0019] A fourth aspect of the present invention provides a battery comprising a positive electrode as described above.

[0020] According to the positive electrode binder provided by this invention, the invention utilizes a unique core-shell structure design to allow the binder polymer to form a shell in a "gap-filled" manner, creating numerous exposed conductive sites on the surface of the conductive polymer core. This provides ample contact for the overlapping of conductive nanofillers. The conductive nanofillers precisely overlap with these exposed conductive sites, rapidly constructing a three-dimensional continuous conductive network spanning the entire electrode. Furthermore, the precise overlap between the conductive nanofillers and the conductive sites of the conductive polymer core, rather than simple physical mixing, relies on the fixing effect of the conductive sites. This effectively prevents the conductive nanofillers from detaching or agglomerating during battery charge-discharge cycles due to volume expansion and contraction, thus ensuring the continuity and stability of the conductive network. Attached Figure Description

[0021] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments of the present invention will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a schematic diagram of the structure of a positive electrode binder provided in an embodiment of the present invention; The reference numerals in the accompanying drawings are as follows: 1-Conductive polymer; 2-Binder polymer; 3-Conductive nanofiller; Detailed Implementation To make the technical problems solved, technical solutions, and beneficial effects of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without inventive effort are within the scope of protection of this invention.

[0023] Unless otherwise specified, the experimental methods used in the following examples are conventional methods; the materials and reagents used are commercially available unless otherwise specified.

[0024] like Figure 1 As shown, in one embodiment, the first aspect of the present invention provides a positive electrode binder, which includes a conductive polymer 1, a bonding polymer 2 and a conductive nanofiller 3. The conductive polymer 1 forms a core, the bonding polymer 2 is formed on the surface of the core to form a shell, and the shell has a gap region exposing the core. The gap region on the surface of the core forms conductive sites, and the conductive nanofiller 3 overlaps with the conductive sites to form a conductive network.

[0025] This invention employs a unique core-shell structure design, allowing the bonding polymer 2 to form an outer shell through a "gap-filled" encapsulation. This creates numerous exposed conductive sites on the surface of the conductive polymer 1 core, providing ample contact for the overlapping of the conductive nanofiller 3. The conductive nanofiller 3 precisely overlaps with these exposed conductive sites, rapidly constructing a three-dimensional continuous conductive network spanning the entire electrode. Furthermore, the precise overlap between the conductive nanofiller 3 and the conductive sites in the conductive polymer 1 core, rather than a simple physical mixing, relies on the fixing effect of the conductive sites. This effectively prevents the conductive nanofiller 3 from detaching or agglomerating during battery charge-discharge cycles due to volume expansion and contraction, thus ensuring the continuity and stability of the conductive network.

[0026] In summary, this invention, through the innovative design of a core-shell structure of "conductive polymer 1 core - bonding polymer 2 shell", and relying on the precise overlap of conductive sites and conductive nanofillers 3 to form a conductive network, breaks through the technical bottleneck of "mutual constraint between conductivity and bonding performance" between traditional positive electrode binders and conductive agents. While ensuring the formability and bonding strength of the positive electrode sheet, it significantly improves the conductivity, cycle stability and rate performance of the positive electrode.

[0027] In one embodiment, the conductive polymer 1 includes one or more of polyaniline, polypyrrole, or poly3,4-ethylenedioxythiophene.

[0028] In a preferred embodiment, the conductive polymer 1 is selected from poly3,4-ethylenedioxythiophene.

[0029] The conjugated structure of this type of conductive polymer 1 enables rapid electron migration and has excellent compatibility with conductive nanofiller 3, forming a highly efficient synergistic conductive effect with conductive nanofiller 3, further enhancing the conductivity of the conductive network.

[0030] In one embodiment, the adhesive polymer 2 comprises one or more of polyacrylic acid, sodium carboxymethyl cellulose, or modified starch.

[0031] The aforementioned materials possess excellent adhesion, film-forming properties, and compatibility with aqueous systems. They can tightly adhere to the conductive polymer core 1, conductive nanofiller 3, and positive electrode active material, firmly bonding the three together. Simultaneously, they form a tight interfacial bond with the current collector, effectively improving the peel strength and tensile strength of the positive electrode sheet. This prevents problems such as powder shedding, cracking, and delamination during the preparation, winding, and assembly of the electrode sheet, ensuring the integrity and mechanical stability of the electrode sheet. Furthermore, this type of bonding polymer 2 has good hydrophilicity and can form a stable interfacial bond with the core conductive polymer 1, preventing the coating layer from peeling off.

[0032] In a preferred embodiment, the bonding polymer 2 is selected from polyacrylic acid and sodium carboxymethyl cellulose; the mass ratio of polyacrylic acid to sodium carboxymethyl cellulose is 2:1. The composite bonding polymer 2 with this ratio combines the high bonding strength and excellent film-forming properties of polyacrylic acid with the good water solubility and steric hindrance dispersion of sodium carboxymethyl cellulose. It can closely adhere to the core of conductive polymer 1, conductive nanofiller 3 and positive electrode active material, firmly bonding the three together. At the same time, it forms a tight interfacial bond with the current collector, effectively improving the peel strength and tensile strength of the positive electrode sheet, avoiding problems such as powder shedding, cracking and delamination during the preparation, winding and assembly of the electrode sheet, and ensuring the molding integrity and mechanical stability of the electrode sheet. Moreover, the composite bonding polymer 2 with this ratio achieves an optimal balance between hydrophilicity and interfacial bonding, and can form a stable interfacial bond with the core conductive polymer 1, avoiding the peeling of the coating layer. At the same time, it is compatible with the aqueous preparation system and forms good compatibility with the conductive nanofiller 3, further improving the bonding strength of the three.

[0033] In one embodiment, the conductive nanofiller 3 includes one or more of conductive carbon black, carbon nanotubes, or graphene nanosheets.

[0034] Specifically, carbon nanotubes can build long-range conductive channels, graphene nanosheets can construct planar conductive networks, and conductive carbon black can fill interstitial conductive dead zones. These three components, together with conductive polymer 1, form a highly efficient synergistic conductive effect, further enhancing the conductivity of the conductive network.

[0035] This type of filler has a high specific surface area, excellent electrical conductivity and good dispersibility, and can form good compatibility with the core of the bonding polymer 2 and the conductive polymer 1, further improving the bonding strength of the three.

[0036] In a preferred embodiment, the conductive nanofiller 3 is selected from carbon nanotubes and graphene nanosheets, with a mass ratio of 3:1. Under this ratio, the high aspect ratio of carbon nanotubes enables cross-regional conductive connections, and the sheet structure of graphene nanosheets can form a planar conductive substrate. The two complement each other and can form a stable interface with the active functional groups on the surface of the conductive polymer 1, further enhancing the bonding strength. This bonding method relies on the fixing effect of conductive sites, which can effectively prevent the conductive nanofiller 3 from falling off and agglomerating due to volume expansion and contraction during battery charge and discharge cycles, thereby ensuring the continuity and stability of the conductive network.

[0037] In one embodiment, a coupling agent is also included, through which the conductive polymer 1 and the bonding polymer 2 are chemically bonded; the coupling agent includes one or more of silane coupling agents, titanate coupling agents, and aluminate coupling agents.

[0038] Specifically, silane coupling agents are bifunctional compounds containing siloxane groups and organic functional groups. One end of the siloxy group (-Si(OR)3) hydrolyzes to generate silanol groups (-Si-OH), which can undergo dehydration condensation with the hydroxyl / carboxyl groups on the surface of conductive nanofiller 3 (carbon material, metal oxide) and conductive polymer 1 to form covalent bonds. The other end of the organic functional group can undergo covalent bonding / physical entanglement with the organic groups of the shell bonding polymer 2 and the core conductive polymer 1. It is the core coupling agent for core-shell structure construction and filler anchoring. The silane coupling agent is selected from one or more of aminosilane coupling agents, epoxysilane coupling agents, and methacryloxysilane coupling agents.

[0039] Specifically, the titanate coupling agent uses titanate groups as inorganic ends, which can coordinate and bond with hydroxyl groups on the surface of metal and metal oxide conductive fillers (such as nano silver powder, nano nickel powder, TiO2); the organic long chain is the organic end, which can physically entangle / van der Waals bond with the molecular chains of the shell bonding polymer 2, and the core is used for anchoring the metal-based conductive nanofiller 3. The silane coupling agent is selected from one or more of monoalkoxy fatty acid titanates, monoalkoxy phosphate titanates, and chelated titanates.

[0040] The inorganic end of the aluminate coupling agent is an aluminate group, which has a slightly weaker bonding ability with the oxide filler. However, the long-chain fatty acid group at the organic end has better compatibility with the binder polymer 2 and can help improve the adhesion of the shell binder polymer 2. The aluminate coupling agent is selected from one or more of monoalkoxy aluminates and chelated aluminates.

[0041] In one embodiment, the mass ratio of conductive polymer 1, binder polymer 2, conductive nanofiller 3 and coupling agent is (10~20):(60~75):(5~15):(1~3).

[0042] Specifically, the mass ratio of conductive polymer 1, binding polymer 2, conductive nanofiller 3, and coupling agent is any one of the following ratios or a range of any two ratios: 10:60:5:1, 10:75:15:3, 15:65:8:1.5, 15:70:10:2, 20:70:12:2.5, or 20:75:15:3; in a preferred embodiment, the mass ratio of conductive polymer 1, binding polymer 2, conductive nanofiller 3, and coupling agent is 15:70:10:2.

[0043] When the mass ratio of conductive polymer 1, binder polymer 2, conductive nanofiller 3, and coupling agent is (10~20):(60~75):(5~15):(1~3), the components achieve synergistic proportions and functional complementarity. The proportion of conductive polymer 1 is sufficient to form a continuous conductive core framework, providing ample conductive sites for the conductive network, without crowding out the coating space of binder polymer 2 due to an excessively high proportion. As the main component, binder polymer 2's proportion ensures the formation of a coating shell with precise gaps, achieving strong adhesion and formability of the electrode while not obscuring the conductive sites. The proportion of conductive nanofiller 3 can fully complement the conductive sites. The electrode is constructed by overlapping layers to form a cross-scale conductive network, and the excessive amount of filler will not cause a decrease in electrode adhesion or agglomeration. The trace proportion of coupling agent can achieve strong bonding at the core-shell interface and interfacial anchoring between conductive nanofiller 3 and conductive polymer 1, giving full play to the bridging effect. There is no excessive coupling agent agglomeration that blocks the conductive channels. Ultimately, the positive electrode binder achieves the optimal balance of conductivity, adhesion, interfacial stability and conductive network integrity within this ratio range, ensuring low contact resistance, high mechanical stability, excellent cycle stability and rate performance of the electrode. The functions of each component are maximized, which is suitable for the preparation requirements of lithium-ion battery positive electrodes.When the mass ratio of conductive polymer 1, binder polymer 2, conductive nanofiller 3, and coupling agent is less than 10:75:15:3, the proportion of each component is insufficient. The low proportion of conductive polymer 1 prevents the formation of a continuous conductive core framework, resulting in a lack of conductive sites and hindering the construction of the conductive network. Insufficient binder polymer 2 prevents the formation of a complete outer shell, significantly reducing electrode bonding strength and formability, and leading to powder shedding and cracking. A low proportion of conductive nanofiller 3 prevents sufficient overlap with the limited number of conductive sites, resulting in numerous dead zones in the conductive network, poor electrode conductivity, and high internal resistance. A low proportion of coupling agent prevents effective bonding at the core-shell interface and interfacial anchoring between the filler and conductive polymer 1, leading to easy peeling of the core-shell structure and filler detachment, significantly reducing the stability of the conductive network. Ultimately, this results in the positive electrode binder failing to balance conductivity and bonding performance, significantly degrading battery rate performance and cycle stability. When the mass ratio of conductive polymer 1, binder polymer 2, conductive nanofiller 3, and coupling agent is greater than 20:60:5:1, the proportion of each component... Excessive proportions of each component lead to several problems. An excessively high proportion of conductive polymer 1 encroaches on the coating space of binder polymer 2, preventing it from forming a complete outer shell and reducing electrode adhesion. Furthermore, excessive conductive polymer 1 tends to agglomerate, increasing the electrode's internal resistance. An excessively high proportion of binder polymer 2 results in an overly thick coating layer, obscuring the conductive sites of the conductive polymer 1 core, hindering the overlap of conductive nanofiller 3, disrupting the continuity of the conductive network, and significantly reducing electrode conductivity. An excessively high proportion of conductive nanofiller 3 is prone to agglomeration, failing to build an effective conductive network and reducing electrode adhesion, leading to powder shedding during electrode processing. An excessively high proportion of coupling agent also causes agglomeration, blocking conductive and lithium-ion transport channels, increasing electrode contact resistance. Excessive coupling agent forms ineffective coatings at the interface, weakening the stability of the core-shell structure and filler overlap. Ultimately, this results in dual damage to the conductivity and adhesion performance of the positive electrode binder, exacerbating battery polarization, significantly reducing rate performance, making the electrode structure prone to failure during cycling, and significantly accelerating capacity decay.

[0044] In one embodiment, a dispersant is also included, which includes one or more of sodium dodecylbenzenesulfonate, polyethylene glycol, polyvinylpyrrolidone, and sodium citrate; the mass ratio of conductive nanofiller 3 to dispersant is (5~15):(0.5~2).

[0045] Dispersants can enhance the contact compatibility between conductive nanofillers 3 and the conductive sites on the surface of core-shell polymers, helping them to accurately bond together and ensuring the continuity and integrity of the three-dimensional conductive network. In addition, this type of dispersant has good compatibility with the components in the system (bonding polymer 2, coupling agent, etc.), with no adverse interactions, and will not introduce impurities that affect the electrochemical performance and bonding effect of the binder. It can also be adapted to the dual dispersion process of high-speed shearing + ultrasound, further improving dispersion efficiency and reducing dispersion energy consumption.

[0046] Specifically, the mass ratio of conductive nanofiller 3 to dispersant is any one value or a range of any two values ​​from 5:0.5, 5:2, 8:1, 10:1, 12:1.5 or 15:2; in a preferred embodiment, the mass ratio of conductive nanofiller 3 to dispersant is 10:1.

[0047] When the mass ratio of conductive nanofiller 3 to dispersant is (5~15):(0.5~2), the two achieve the optimal synergistic dispersion effect. The dispersant can be fully adsorbed on the surface of conductive nanofiller 3, exerting a steric hindrance effect and efficiently breaking up filler agglomerates. The conductive nanofiller 3 can achieve nanoscale uniform dispersion under the action of dispersant, fully contacting conductive sites and efficiently constructing a continuous three-dimensional conductive network. The synergistic ratio of the two ensures dispersion stability and the integrity of the conductive network. When the mass ratio of conductive nanofiller 3 to dispersant is less than 5:2, the proportion of dispersant is too high. Excessive dispersant will adsorb on the conductive sites on the surface of the core-shell polymer, obscuring the conductive sites and hindering the precise overlap between conductive nanofiller 3 and conductive sites, resulting in discontinuous conductive network and decreased conductivity. At the same time, excessive dispersant will have adverse interactions with the bonding polymer 2 in the system, weakening the electrode bonding strength. It may also introduce impurities due to dispersant residue, affecting the electrochemical stability of the binder. When the mass ratio of conductive nanofiller 3 to dispersant is greater than 15:0.5, the proportion of dispersant is insufficient and cannot fully cover the surface of conductive nanofiller 3, making it difficult to play an effective dispersing role. Conductive nanofiller 3 is prone to agglomeration and secondary agglomeration, which cannot achieve uniform dispersion. This results in a large number of dead corners in the conductive network, high internal resistance of the electrode, and the agglomerated filler will weaken the adhesion of the electrode, easily causing powder shedding, and ultimately deteriorating the overall performance of the binder.

[0048] In one embodiment, a second aspect of the present invention provides a method for preparing a positive electrode binder, comprising the following steps: S1. Dissolve conductive polymer 1 and binder polymer 2 in a solvent. The binder polymer 2 is coated on the core surface with gaps to obtain a core-shell polymer dispersion. S2. The conductive nanofiller 3 is added to the core-shell polymer dispersion to form a mixed solution. After high-speed shear dispersion and ultrasonic treatment, the positive electrode binder is obtained.

[0049] Specifically, dissolving conductive polymer 1 and binder polymer 2 in a solvent also includes the following steps: The conductive monomer, initiator, and dopant were dissolved in deionized water and stirred and polymerized at 25-35°C for 4-6 hours to obtain a dispersion of core-layer conductive polymer 1. Add binder polymer 2 to the dispersion of core layer conductive polymer 1; The conductive monomers include one or more of aniline, pyrrole, and 3,4-ethylenedioxythiophene. These conductive monomers have good water solubility and can be fully miscible with initiators and dopants in deionized water systems. They can be efficiently polymerized under mild conditions of 25~35℃ to form a core-layer conductive polymer 1 with a conjugated conductive structure. The polymer products have excellent dispersibility and readily form active functional groups on the surface, providing a stable structural basis for the subsequent interstitial coating of the bonding polymer 2 and the reservation of conductive sites.

[0050] This preparation method completes the core formation of conductive polymer 1 and the gap coating of bonding polymer 2 in one step. The coating gap can be precisely controlled to ensure that the conductive sites are fully exposed. The core-shell polymer dispersion is uniformly dispersed without agglomeration, and the system has excellent stability. Through a dual dispersion process of high-speed shearing and ultrasonic treatment, the conductive nanofiller 3 is uniformly dispersed at the nanometer scale and fully and precisely overlaps with the conductive sites, efficiently constructing a continuous and complete three-dimensional conductive network and improving conductivity. Moreover, the entire process is a physical dispersion and interfacial adsorption process, with no by-products generated and no impurities introduced, ensuring the electrochemical performance and safety of the binder. The product has good performance consistency and small batch-to-batch differences. The process has few steps and low equipment requirements, and can be adapted to existing industrial production lines. The process parameters are easy to control, resulting in high production efficiency, low energy consumption and low cost, and high feasibility for large-scale production. The two-step process of this invention integrates the construction of the core-shell structure and the formation of the conductive network. The resulting binder has a complete core-shell structure and good continuity of the conductive network, with excellent conductivity and bonding properties. It can fully exert dual core functions and is suitable for the preparation requirements of lithium-ion battery cathode sheets.

[0051] In one embodiment, in step S1, "dissolving the conductive polymer 1 and the bonding polymer 2 in a solvent" further includes dissolving a coupling agent in a solvent to achieve chemical bonding between the conductive polymer 1 and the bonding polymer 2; the reaction temperature is 50~60℃, and the reaction time is 2~3h.

[0052] The conductive core polymer 1, binder polymer 2, and coupling agent are simultaneously dissolved in a solvent system, ensuring uniform dispersion and full interfacial contact. The coupling agent effectively bridges the gaps, achieving stable chemical bonding between the conductive polymer 1 and binder polymer 2, strengthening the core-shell interfacial bond, and preventing coating peeling during subsequent use. The reaction temperature of 50-60℃ is suitable for the bonding reactivity of the coupling agent, efficiently triggering chemical bonding while ensuring gentle coating of binder polymer 2 without high-temperature degradation. Simultaneously, precise control of the coating gaps ensures full exposure of conductive sites on the core surface of conductive polymer 1. The reaction time of 2-3 hours allows for sufficient chemical bonding and gap coating reactions, resulting in a complete core-shell structure, a stable dispersion system, and no unreacted components. This provides a uniform core-shell polymer substrate for the subsequent dispersion and bonding of conductive nanofillers 3 and the construction of the conductive network. The entire process is compatible with aqueous systems, with mild and easily controllable process conditions, requiring no demanding equipment. It exhibits excellent compatibility with preceding and subsequent preparation steps, allowing seamless integration with subsequent processes and improving overall preparation efficiency.

[0053] In one embodiment, in step S2, "adding the conductive nanofiller 3 to the core-shell polymer dispersion" further includes dissolving the dispersant in the core-shell polymer dispersion.

[0054] Dissolving the dispersant in the core-shell polymer dispersion can further break up the agglomerates of the conductive nanofiller 3, improve its dispersion uniformity and stability in the core-shell polymer dispersion, and avoid secondary agglomeration of the filler leading to the breakage of the conductive network. At the same time, it can enhance the contact compatibility between the conductive nanofiller 3 and the conductive sites on the surface of the core-shell polymer, helping the two to accurately overlap and ensuring the continuity and integrity of the three-dimensional conductive network. In addition, this type of dispersant has good compatibility with the components in the system (binding polymer 2, coupling agent, etc.), with no adverse interactions, and will not introduce impurities that affect the electrochemical performance and bonding effect of the binder. It can also be adapted to the dual dispersion process of high-speed shearing + ultrasound, further improving dispersion efficiency and reducing dispersion energy consumption.

[0055] In one embodiment, in step S2, the high-speed shear dispersion time is 30-40 min, and the ultrasonic treatment time is 10-15 min.

[0056] Specifically, high-speed shear dispersion for 30-40 minutes can efficiently achieve primary deagglomeration of conductive nanofiller 3. Shear force breaks down large-sized agglomerates of filler, allowing the filler to be initially and uniformly dispersed in the core-shell polymer dispersion. At the same time, it allows the dispersant to be fully adsorbed on the filler surface, laying the foundation for subsequent ultrasonic treatment. This duration avoids insufficient deagglomeration due to excessively short shearing time, as well as energy waste and damage to the core-shell structure due to excessively long shearing time. Ultrasonic treatment for 10-15 minutes can further eliminate soft agglomerates of filler. Ultrasonic vibration disperses the filler to the nanoscale, ensuring that each filler particle can accurately contact and tightly overlap with the conductive sites on the surface of the core-shell polymer. At the same time, it avoids dispersant desorption and secondary agglomeration of filler due to excessively long ultrasonic time, and also avoids damage to the molecular chains of the binding polymer 2, which would affect the bonding performance.

[0057] In one embodiment, in step S2, the solid content of the mixed solution is 20% to 30%.

[0058] Specifically, the solid content of the mixed solution is any one value or a range of any two values ​​from 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, or 30%; in a preferred embodiment, the solid content of the mixed solution is 23%-27%.

[0059] When the solid content of the mixed solution is 20%~30%, an optimal balance between system fluidity and component dispersion stability can be achieved. This ensures uniform dispersion of components such as the core-shell polymer, conductive nanofiller 3, and dispersant. This solid content range allows for sufficient contact between the components, ensuring the continuity of the conductive network and the stability of the core-shell structure. When the solid content of the mixed solution is less than 20%, the solvent content in the system is too high, the dispersion of each component is too sparse, and the distance between the conductive nanofillers 3 is too large, making it difficult to fully overlap with the conductive sites on the surface of the core-shell polymer. This prevents the construction of a continuous and complete three-dimensional conductive network, resulting in a significant decrease in the conductivity of the binder. When the solid content of the mixed solution is greater than 30%, the viscosity of the system is too high, making it difficult for the conductive nanofillers 3 to achieve uniform dispersion and causing agglomeration. At the same time, the core-shell polymers tend to entangle with each other, obscuring the conductive sites and destroying the integrity of the conductive network.

[0060] In one embodiment, a third aspect of the present invention provides a positive electrode sheet, including a positive current collector and positive active material layers disposed on both sides of the positive current collector. The positive active material layers include a positive active material and a positive binder. The positive binder is the positive binder described above, or a positive binder prepared by the method described above.

[0061] The positive electrode active materials include one or more of lithium iron phosphate, ternary materials (lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide), lithium cobalt oxide, and lithium manganese oxide, which are suitable for the performance requirements of various lithium-ion battery positive electrodes.

[0062] The positive electrode binder exhibits excellent compatibility with the positive electrode active material. Its binder polymer 2 can firmly bond the positive electrode active material, conductive network, and positive electrode current collector, significantly improving the peel strength and mechanical stability of the positive electrode active material layer. This prevents problems such as active material detachment, powder shedding, and delamination during charge-discharge cycles and processing assembly, ensuring the structural integrity of the positive electrode sheet. Moreover, the three-dimensional continuous conductive network constructed by the positive electrode binder can penetrate the entire positive electrode active material layer, shortening the electron and lithium ion transport path, reducing the contact resistance between the active material and the current collector, and between the active material and conductive components. This fully utilizes the electrochemical activity of the positive electrode active material, improving the conductivity and rate performance of the positive electrode sheet. Simultaneously, the interstitial coating structure and flexible molecular chains of the binder can buffer the volume expansion and contraction of the positive electrode active material during charge-discharge cycles (lithium ion insertion / extraction), reducing the breakage and detachment of active material particles, extending the cycle life of the positive electrode sheet, and ensuring that the positive electrode sheet maintains good conductivity and bonding performance even after long-term cycling. Furthermore, the synergistic effect of coupling agents and dispersants further strengthens the interfacial bonding of various components in the active material layer, improving the overall stability and consistency of the positive electrode sheet.

[0063] In one embodiment, the total mass of the positive electrode active material layer is 100%; the positive electrode active material accounts for 97%-99% of the mass of the positive electrode active material layer; and the positive electrode binder accounts for 1%-3% of the mass of the positive electrode active material layer.

[0064] This formulation achieves optimal synergy between the electrochemical performance of the positive electrode active material and the bonding and conductivity functions of the binder. It ensures a high proportion of positive electrode active material, fully leveraging its electrochemical activity and improving the energy density of the positive electrode sheet. At the same time, it precisely achieves a strong bond between the active material, the conductive network, and the current collector through 1%-3% positive electrode binder. Furthermore, it relies on the three-dimensional conductive network constructed by the binder to ensure conductivity efficiency, avoiding problems such as excessive binder proportion encroaching on the space of the active material or insufficient bonding performance and electrode powder shedding due to insufficient binder proportion.

[0065] In one embodiment, a fourth aspect of the present invention provides a battery comprising a positive electrode as described above.

[0066] As a core component of the battery, the positive electrode sheet's excellent conductivity, mechanical stability, and cycle stability directly contribute to the overall performance improvement of the battery. Utilizing the three-dimensional continuous conductive network built into the positive electrode sheet, it effectively reduces the overall internal resistance of the battery, minimizes polarization during charging and discharging, and enhances the battery's rate charge and discharge performance. This allows the battery to maintain a stable voltage platform and excellent capacity output even under high-rate operating conditions. The positive electrode sheet's good mechanical stability and cycle durability prevent problems such as internal short circuits and rapid capacity decay caused by positive electrode sheet powder shedding and delamination during long-term charge and discharge cycles, significantly extending the battery's cycle life and ensuring a high capacity retention rate even after 500 cycles. Simultaneously, the positive electrode sheet is prepared using an aqueous phase process, which is environmentally friendly and leaves no organic solvent residue, improving battery safety and reducing the risk of thermal runaway. The synergistic effect of the precise ratio of positive electrode active material and binder fully leverages the electrochemical potential of the positive electrode active material, increasing the battery's energy density and adapting to the application needs of different scenarios such as power batteries, energy storage batteries, and consumer electronics batteries. In addition, the cathode material has a simple manufacturing process and is suitable for large-scale industrial production, which can reduce the overall production cost of the battery. At the same time, the battery components are highly compatible with the cathode material, and no special modifications are required to other battery structures, which further enhances the feasibility of industrial production and the market promotion value of the battery.

[0067] In some embodiments, the battery further includes a negative electrode sheet, which comprises a negative current collector and a negative active material layer coated on the surface of the negative current collector. The negative active material layer comprises a negative active material, a negative binder, and a conductive agent. The negative active material is selected from one or more of graphite, hard carbon, soft carbon, silicon-based materials, and tin-based materials. The negative current collector is copper foil. The negative binder is selected from one or more of styrene-butadiene rubber and sodium carboxymethyl cellulose. The conductive agent is selected from one or more of conductive carbon black and carbon nanotubes. This negative electrode sheet has excellent compatibility with the aforementioned positive electrode sheet, and its electrochemical performance is precisely matched with that of the positive electrode sheet, effectively balancing the charge and discharge capacity of the battery and avoiding battery performance degradation caused by capacity mismatch between the positive and negative electrodes.

[0068] In some embodiments, the battery further includes a separator selected from one or more of polyethylene separators, polypropylene separators, polyimide separators, and polypropylene / polyethylene / polypropylene composite separators. The surface of the separator may be selectively coated with a ceramic coating (such as an alumina or zirconium oxide coating) to improve its high-temperature resistance and mechanical strength.

[0069] In some embodiments, the battery further includes an electrolyte, which is a commonly used electrolyte for lithium-ion batteries, comprising a solvent, a lithium salt, and optional additives, wherein the solvent is selected from one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate, the lithium salt is selected from one or more of lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, and lithium bis(trifluoromethyl)sulfonyl)imide, and the additives are selected from one or more of film-forming additives, flame retardant additives, and overcharge prevention additives (such as vinylene carbonate and fluoroethylene carbonate).

[0070] In some embodiments, the battery is prepared as follows: the positive electrode, separator, and negative electrode are wound or stacked in sequence to form an electrode assembly, which is then placed in, for example, an aluminum-plastic film, injected with electrolyte, formed, and packaged to produce a lithium-ion battery.

[0071] While the exemplary embodiments described above use lithium-ion batteries as examples, those skilled in the art will understand after reading this application that, without departing from the spirit of this application, specific examples of the battery can include all types of primary or secondary batteries. In particular, the battery is a lithium secondary battery, including lithium metal secondary batteries, lithium-ion secondary batteries, lithium polymer secondary batteries, or lithium-ion polymer secondary batteries.

[0072] The beneficial effects of the present invention will be further illustrated below with reference to the embodiments.

[0073] To make the inventive objectives, technical solutions, and beneficial effects of this invention clearer, the invention is further described in detail below with reference to embodiments. However, it should be understood that the embodiments of this invention are merely for illustrative purposes and not for limiting the invention, and the embodiments are not limited to those given in the specification. Materials not specified in the embodiments were prepared under conventional conditions or according to the conditions recommended by the material supplier.

[0074] Furthermore, it should be understood that the existence of other method steps before or after the combined steps, or the insertion of other method steps between these explicitly mentioned steps, does not preclude the existence of other method steps before or after the combined steps, or the insertion of other method steps between these explicitly mentioned steps, unless otherwise stated. It should also be understood that the combined connection relationship between one or more devices / apparatus mentioned in this invention does not preclude the existence of other devices / apparatus before or after the combined devices / apparatus, or the insertion of other devices / apparatus between these explicitly mentioned devices / apparatus, unless otherwise stated. Moreover, unless otherwise stated, the numbering of each method step is merely a convenient tool for identifying each method step, and not for limiting the order of the method steps or limiting the scope of the invention. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of the invention.

[0075] In the following embodiments, the reagents, materials and instruments used, unless otherwise specified, are commercially available or can be obtained through synthesis methods known in the art.

[0076] Table 1. Design of positive electrode binders for Examples 1-29 and Comparative Examples 1-9; Example 1 This embodiment illustrates the positive electrode binder, positive electrode sheet, and battery disclosed in this invention; it includes the following operational steps: Preparation of positive electrode binder: S1. The conductive monomer 3,4-ethylenedioxythiophene, the initiator ammonium persulfate (APS), and the dispersant sodium polystyrene sulfonate (PSS) are dissolved in deionized water at a mass ratio of 99.5:0.3:0.2. The mixture is stirred and polymerized at 25~35℃ for 4~6 h to obtain a core-layer conductive polymer dispersion. S2. Add shell-layer binding polymer (polyacrylic acid: sodium carboxymethyl cellulose = 2:1) and aminosilane coupling agent to the core-layer conductive polymer dispersion, heat to 50~60℃, and keep the reaction at this temperature for 2~3 h to allow the shell-layer binding polymer to coat the surface of the core-layer conductive polymer, thus obtaining a core-shell polymer dispersion; wherein, the mass ratio of conductive polymer, binding polymer and aminosilane coupling agent is 15:70:2; S3. Add conductive nanofiller (conductive carbon black: carbon nanotubes = 3:1) and dispersant sodium dodecylbenzenesulfonate to the core-shell polymer dispersion, disperse by high-speed shearing for 30-40 min, sonicate for 10-15 min, and adjust the solid content to 25% to obtain a highly conductive positive electrode binder; wherein the mass ratio of conductive nanofiller to dispersant is 10:1; Figure 1 As shown.

[0077] Preparation of positive electrode: The positive electrode active material and positive electrode binder are mixed in a ratio of 98:2 to prepare a positive electrode slurry. The positive electrode slurry is coated onto the surface of the positive electrode current collector on a coating machine. After drying, rolling, die cutting and other processes, a positive electrode sheet that meets the requirements is obtained.

[0078] Preparation of negative electrode: A negative electrode slurry was prepared by mixing graphite (a negative electrode active material), SBR (a negative electrode binder), and CMC (a dispersant) in a ratio of 98:1:1. The negative electrode slurry is coated onto the negative electrode current collector copper foil on a coating machine, and the negative electrode sheet is obtained after drying, rolling, die cutting and other processes.

[0079] Electrolyte preparation: Lithium hexafluorophosphate (LiPF6) was dissolved in a mixed solvent consisting of ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) in a mass ratio of 1:2:1 to obtain an electrolyte with a concentration of 1 mol / L.

[0080] Preparation of the diaphragm: PE porous polymer film is used as the membrane substrate; Battery manufacturing: The positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrodes to provide isolation. The electrodes are then stacked in this manner to form a battery cell. The battery cell is placed into a pre-formed battery casing, and the assembled battery cell is baked and dried. Then, the prepared electrolyte is injected, and the battery undergoes vacuum sealing, settling, and formation processes to obtain the battery.

[0081] Example 2-29 Examples 2-29 illustrate the positive electrode binder, positive electrode sheet, and battery disclosed in this invention, and include most of the operating steps in Example 1, except that: The parameters of the positive electrode binder shown in Table 1 are used.

[0082] Comparative Examples 1-10 Comparative Examples 1-9: These illustrate the positive electrode binder, positive electrode sheet, and battery disclosed in this invention, including most of the operational steps in Example 1, except that: The parameters of the positive electrode binder shown in Table 1 are used.

[0083] Comparative Example 10 is prior art, and its difference lies in: Preparation of positive electrode: A positive electrode slurry is prepared by mixing positive electrode active material, single-walled carbon nanotubes, conductive carbon black SP and binder PVDF in a ratio of 97.3:0.5:1.0:1.2. The positive electrode slurry is then coated onto the surface of the positive electrode current collector on a coating machine. After drying, rolling, die cutting and other processes, a positive electrode sheet that meets the requirements is obtained.

[0084] Performance testing The following performance tests were performed on the batteries prepared in Examples 1-29 and Comparative Examples 1-10: Adhesion strength test: The positive electrode adhesive is uniformly coated on the surface of the positive electrode current collector (coating thickness is 100±10μm), vacuum dried at 80℃ for 12h, and peel test is performed at 90℃ using a universal testing machine at a test rate of 5cm / min. The peel strength is recorded. A peel strength ≥15 N / cm is considered qualified, which verifies the bonding effect of the adhesive polymer and the rationality of the formulation.

[0085] Conductivity testing: Using a resistivity meter, the positive electrode sheet, after rolling, was cut into three segments with a length of 6–8 cm and a width of 5–7 cm from different positions using ceramic scissors. The resistivity meter was set to 25 MPa pressure and held for 25 s. The resistivity of the membrane was measured at 6 points on each positive electrode segment, for a total of 18 points on the three segments. The average value was taken to obtain the final membrane resistivity (unit: Ω·cm). Higher resistivity indicates poorer conductivity, verifying the construction effect of the three-dimensional conductive network and the synergy of the distribution ratios.

[0086] Rate performance test: At room temperature, a battery tester is used to fully charge the cell to 4.4V at 0.5C, and then discharge it at rates of 0.5C, 0.8C, 1.1C, 1.4C, 1.7C, and 2C. If the discharge capacity at 2C is greater than 85% of the discharge capacity at 0.5C, it is considered qualified, thus verifying the rate discharge performance of the cell.

[0087] Cyclic stability test: At room temperature, a battery tester is used to cycle the battery 500 times at a charge / discharge rate of 0.5C within a voltage range of 3~4.4V. The charge / discharge capacity and charge / discharge efficiency are recorded. The battery is considered qualified if the capacity retention rate is ≥80% and the average charge / discharge efficiency is ≥98% after 500 cycles, thus verifying the battery's comprehensive cycle performance.

[0088] Energy density test: Using the assembled soft-pack battery described above, complete one full charge and discharge cycle at room temperature (25±2℃) with a charge and discharge rate of 0.2C within a voltage range of 3~4.4V, and record the actual discharge capacity (mAh); measure the length, width and height of the cell (mm), and calculate the mass energy density of the battery according to the formula "energy density (Wh / L) = actual discharge capacity (mAh) × average battery operating voltage (V) ÷ battery volume (L) ÷ 1000".

[0089] The test results are shown in Table 2.

[0090] Table 2 Battery Electrochemical Performance Comparing Example 1 and Comparative Example 1, it can be seen that when the positive electrode binder includes a conductive polymer, the battery resistivity is significantly reduced, the rate performance and cycle stability are greatly improved, and the peel strength meets the requirements; when the positive electrode binder does not include a conductive polymer, the resistivity is significantly increased, the conductive network is missing, the rate performance and cycle performance are significantly reduced, and the overall performance does not meet the standards.

[0091] Comparing Example 1 and Comparative Example 2, it can be seen that when the positive electrode binder includes a bonding polymer, the peel strength is high, the electrode adhesion is good, and the electrochemical performance is stable; when the positive electrode binder does not include a bonding polymer, the peel strength is extremely low, the electrode is easy to fall off, and it cannot meet practical requirements.

[0092] Comparing Example 1 and Comparative Example 3, it can be seen that when the positive electrode binder includes conductive nanofillers, a three-dimensional conductive network can be constructed, resulting in low resistivity and excellent rate performance; when the positive electrode binder does not include conductive nanofillers, the conductive pathways are insufficient, the resistivity is too high, and the rate and cycle performance deteriorates.

[0093] Comparing Example 1 and Comparative Example 4, it can be seen that when the positive electrode binder includes a coupling agent, the interfacial bonding is better, the dispersion is more uniform, and the various performances are balanced and excellent; when the positive electrode binder does not include a coupling agent, the interfacial compatibility decreases, and the peel strength and cycle performance are slightly reduced.

[0094] Comparing Example 1 and Comparative Example 5, it can be seen that when the positive electrode binder includes a dispersant, the filler is evenly dispersed, the conductive network is complete, and the performance is stable and excellent; when the positive electrode binder does not include a dispersant, it is prone to agglomeration, conductivity and stability decrease, and the overall performance deteriorates.

[0095] Comparing Examples 1, 26-27 and 6-8, it can be seen that when the positive electrode binder uses poly(3,4-ethylenedioxythiophene), polyaniline or polypyrrole as the conductive polymer, the conductivity is good, the interface is stable, and the rate and cycle performance is excellent. When the positive electrode binder uses ethylenedioxythiophene, aniline or pyrrole conductive monomers, a stable conductive structure cannot be formed, the resistivity is high, the capacity retention rate is greatly reduced, and the performance is extremely poor.

[0096] Comparing Examples 1, 28 and 9, it can be seen that when polyacrylic acid, sodium carboxymethyl cellulose or modified starch is used as the bonding polymer in the positive electrode binder, the bonding strength is high, the stability is good, and the overall performance is excellent; when acrylic monomer is used as the positive electrode binder, the bonding effect is extremely poor, the electrode sheet is easy to fall off, and the electrochemical performance is greatly deteriorated.

[0097] Comparing Examples 1 and 29, it can be seen that when conductive carbon black, carbon nanotubes, or graphene nanosheets are used as conductive nanofillers in the positive electrode binder, conductivity can be effectively improved. Among them, the conductive carbon black + carbon nanotube composite system has the best overall performance.

[0098] Comparing Example 1 and Comparative Example 10, it can be seen that when the positive electrode sheet uses the positive electrode binder of the present invention, the energy density is higher, the cycle stability is better, and both bonding and conductivity are achieved; when the positive electrode sheet uses a mixture of general positive electrode binder and conductive agent, the energy density is lower and the synergy is not as good as that of the core-shell structure binder.

[0099] Comparing Examples 1-5, it can be seen that when the number of conductive polymer parts is 10-20, the balance between conductivity and adhesion is optimal, the resistivity is low, and the rate and cycle performance is excellent. When the number of conductive polymer parts is less than 10, the conductivity is insufficient, the resistivity increases, and the rate and cycle performance decreases. When the number of conductive polymer parts is greater than 20, the binder phase is relatively insufficient, the peel strength decreases, and the cycle stability deteriorates.

[0100] Comparing Examples 1 and 6-9, it can be seen that when the number of parts of the bonding polymer is 60-75, the peel strength is moderate, the conductivity is stable, and the overall performance is optimal; when the number of parts of the bonding polymer is less than 60, the bonding is insufficient, the peel strength is low, and the cycle stability decreases; when the number of parts of the bonding polymer is greater than 75, the proportion of conductive phase is too low, the resistivity increases, and the rate performance deteriorates.

[0101] Comparing Examples 1 and 10-13, it can be seen that when the number of conductive nanofillers is 5 to 15, the conductive network is complete, the resistivity is low, and the performance is stable; when the number of conductive nanofillers is less than 5, the conductive pathway is insufficient, the resistivity is high, and the rate of change decreases; when the number of conductive nanofillers is greater than 15, the dispersion difficulty increases, and it is easy to agglomerate, resulting in limited performance improvement and decreased stability.

[0102] Comparing Examples 1 and 14-17, it can be seen that when the number of coupling agents is 1 to 3, the interface modification effect is the best and the performance is balanced; when the number of coupling agents is less than 1, the interface binding is insufficient and the performance is slightly reduced; when the number of coupling agents is greater than 3, the excess coupling agent produces side effects, the resistivity increases and the performance deteriorates.

[0103] Comparing Examples 1 and 18-21, it can be seen that when the amount of dispersant is 0.5 to 2 parts, the dispersion effect is the best, the agglomeration is less, and the conductivity and stability are excellent; when the amount of dispersant is less than 0.5 parts, the dispersion is insufficient, agglomeration is easy, and the performance is significantly reduced; when the amount of dispersant is greater than 2 parts, the dispersant is excessive, the insulating phase increases, and the conductivity and cycle performance deteriorate.

[0104] Comparing Examples 1 and 22-25, it can be seen that when the solid content of the mixed solution is 20%~30%, the slurry has good fluidity and coating properties, uniform film formation, and optimal performance; when the solid content of the mixed solution is less than 20%, the coating is thinner, and the adhesion and conductivity are slightly reduced; when the solid content of the mixed solution is greater than 30%, the viscosity is too high, the dispersion is uneven, and the performance is significantly reduced.

[0105] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A positive electrode binder, characterized in that: The positive electrode binder includes a conductive polymer, a bonding polymer, and a conductive nanofiller. The conductive polymer forms a core, the bonding polymer is formed on the surface of the core to form a shell, and the shell has a gap region exposing the core. The gap region on the surface of the core forms conductive sites, and the conductive nanofiller overlaps with the conductive sites to form a conductive network.

2. The positive electrode binder according to claim 1, characterized in that: The conductive polymer includes one or more of polyaniline, polypyrrole, or poly3,4-ethylenedioxythiophene.

3. The positive electrode binder according to claim 1, characterized in that: The bonding polymer includes one or more of polyacrylic acid, sodium carboxymethyl cellulose, or modified starch.

4. The positive electrode binder according to claim 1, characterized in that: The conductive nanofiller includes one or more of conductive carbon black, carbon nanotubes, or graphene nanosheets.

5. The positive electrode binder according to claim 1, characterized in that: It also includes a coupling agent, through which the conductive polymer and the bonding polymer are chemically bonded; the coupling agent includes one or more of silane coupling agents, titanate coupling agents, and aluminate coupling agents.

6. The positive electrode binder according to claim 5, characterized in that: The mass ratio of the conductive polymer, the binding polymer, the conductive nanofiller and the coupling agent is (10~20):(60~75):(5~15):(1~3).

7. The positive electrode binder according to claim 1, characterized in that: It also includes a dispersant, which includes one or more of sodium dodecylbenzenesulfonate, polyethylene glycol, polyvinylpyrrolidone, and sodium citrate; the mass ratio of the conductive nanofiller to the dispersant is (5~15):(0.5~2).

8. The method for preparing the positive electrode binder according to any one of claims 1-7, characterized in that: Includes the following steps: S1. Dissolve the conductive polymer and the binder polymer in a solvent, and the binder polymer is coated on the core surface with gaps to obtain a core-shell polymer dispersion; S2. The conductive nanofiller is added to the core-shell polymer dispersion to form a mixed solution, which is then subjected to high-speed shear dispersion and ultrasonic treatment to obtain the positive electrode binder.

9. The method for preparing the positive electrode binder according to claim 8, characterized in that: In step S1, "dissolving the conductive polymer and the bonding polymer in a solvent" also includes dissolving a coupling agent in a solvent to achieve chemical bonding between the conductive polymer and the bonding polymer; the reaction temperature is 50~60℃, and the reaction time is 2~3h.

10. The method for preparing the positive electrode binder according to claim 8, characterized in that: In step S2, "adding conductive nanofillers to the core-shell polymer dispersion" further includes dissolving the dispersant in the core-shell polymer dispersion.

11. The method for preparing the positive electrode binder according to claim 8, characterized in that: In step S2, the high-speed shear dispersion time is 30-40 min, and the ultrasonic treatment time is 10-15 min.

12. The method for preparing the positive electrode binder according to claim 8, characterized in that: In step S2, the solid content of the mixed solution is 20% to 30%.

13. A positive electrode plate, characterized in that: It includes a positive current collector and a positive active material layer disposed on both sides of the positive current collector. The positive active material layer includes a positive active material and a positive binder. The positive binder is the positive binder according to any one of claims 1-7, or includes the positive binder prepared by the preparation method of the positive binder according to any one of claims 8-12.

14. The positive electrode sheet according to claim 13, characterized in that: The total mass of the positive electrode active material layer is taken as 100%; the positive electrode active material accounts for 97%-99% of the mass of the positive electrode active material layer; and the positive electrode binder accounts for 1%-3% of the mass of the positive electrode active material layer.

15. A battery, characterized in that: Including the positive electrode as described in claim 13 or 14.

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