Negative plate, preparation method and battery

Abstract

The invention provides a negative plate, a preparation method and a battery. The negative plate comprises a negative current collector; the active material layer is arranged on the surface of the negative electrode current collector, the active material layer comprises a negative electrode active material, a conductive agent, a binder and a conductive polymer layer, the conductive polymer layer is formed on the surfaces of the negative electrode active material and the conductive agent and forms a continuous surface, and the conductive polymer layer comprises 3, 4-ethylenedioxythiophene and pyrrole; the conductive polymer layer is obtained through polymerization by a constant current method; the conductive polymer layer can effectively stabilize the interface between the negative electrode and the electrolyte, inhibit side reaction and prolong the cycle life of the battery; the conductive polymer layer formed by copolymerization of EDOT and pyrrole has good electronic conductivity and certain ion transmission capability, so that the interface impedance is reduced, and the rate capability and the charge-discharge efficiency of the battery are improved; the conductive polymer layer is formed through a constant current method, so that uniform, compact and firm coating can be realized, the active material layer is effectively prevented from falling off, and the structural integrity of the electrode is enhanced.

Description

Technical Field

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

[0002] In the field of lithium-ion batteries, especially for applications requiring high energy density (such as electric vehicles and consumer electronics), silicon-containing materials are considered important candidates for next-generation anodes due to their high theoretical specific capacity (e.g., pure silicon can reach approximately 4200 mAh / g). However, silicon-containing materials experience severe volume expansion (up to 300% or more) during charge and discharge, leading to particle pulverization, electrode structure collapse, and repeated rupture and regeneration of the solid electrolyte interphase (SEI) film, resulting in rapid capacity decay and shortened cycle life.

[0003] To alleviate the above problems, existing technologies generally use silicon-carbon composite materials as the negative electrode active material, and directly mix conductive additives (such as carbon black, conductive graphite, carbon nanotubes (CNTs) or graphene) into the slurry to improve the overall conductivity of the electrode. A typical process includes: mixing silicon-containing materials, conductive agents, and binders in a certain proportion to form a slurry, then coating it onto a copper foil current collector, and finally drying and rolling it to form a negative electrode sheet.

[0004] However, this traditional approach has the following significant drawbacks: uneven dispersion of the conductive agent, forming local "dead zones"; the conductive agent (especially nanomaterials such as CNTs) is prone to agglomeration, making it difficult to achieve uniform dispersion in the slurry, resulting in some active particles not being effectively connected, forming "blind zones" for electron transport, and reducing material utilization.

[0005] Even with ideal conductive agent distribution, the contact between the conductive agent and the active particles is still mainly "point-to-point," resulting in a small contact area and high interfacial resistance. Under high current or long-cycle conditions, contact failure is likely to occur. Therefore, overcoming the aforementioned technical problems and defects has become a key issue that needs to be addressed. Summary of the Invention

[0006] To address the problem that the active particles of the negative electrode are not effectively connected in existing silicon negative electrode sheets, this invention provides a negative electrode sheet, its preparation method, and a battery.

[0007] 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 negative electrode sheet, comprising: Negative electrode current collector; An active material layer is disposed on the surface of the negative electrode current collector; the active material layer includes a negative electrode active material, a conductive agent, a binder, and a conductive polymer layer; the negative electrode active material includes a silicon-containing material; the negative electrode active material and the conductive agent are mixed together and bonded together by the binder; the conductive polymer layer is formed on the surfaces of adjacent negative electrode active materials and the conductive agent to form a continuous surface; the monomers of the conductive polymer layer include 3,4-ethylenedioxythiophene and pyrrole; the conductive polymer layer is obtained by constant current polymerization.

[0008] Optionally, the thickness of the conductive polymer layer is 0.5-2 μm.

[0009] Optionally, the molar ratio of the 3,4-ethylenedioxythiophene to the pyrrole is (0.01-0.1):(0.01-0.1).

[0010] Optionally, the molar ratio of the 3,4-ethylenedioxythiophene to the pyrrole is (1-5):(1-5).

[0011] Optionally, the total mass of the negative electrode active material, the binder, and the conductive agent is taken as 100%, wherein the mass percentage of the negative electrode active material is 90.5%-93.5%; the mass percentage of the binder is 6%-9%; and the mass percentage of the conductive agent is 0.3%-0.5%.

[0012] Optionally, the silicon-containing material includes one or more of silicon particles, silicon suboxide, and silicon-carbon materials.

[0013] Optionally, the silicon-containing particles are selected from silicon-carbon materials, wherein the silicon content in the silicon-carbon materials is 40%-60% by mass.

[0014] A second aspect of the present invention provides a method for preparing a negative electrode sheet, comprising the following steps: The negative electrode active material, conductive agent, and binder are mixed into a slurry and coated onto the surface of the negative electrode current collector. The polymer electrolyte forms a conductive polymer layer on the surfaces of the adjacent negative electrode active material and the conductive agent by a constant current method. The polymer electrolyte includes 3,4-ethylenedioxythiophene and pyrrole.

[0015] Optionally, in the polymerization electrolyte, the concentration of 3,4-ethylenedioxythiophene is 0.01-0.1 mol / L; And / or, in the polymerization electrolyte, the concentration of the pyrrole is 0.01-0.1 mol / L.

[0016] Optionally, the polymerization electrolyte further includes potassium chloride, wherein the concentration of potassium chloride in the polymerization electrolyte is 0.05-0.5 mol / L.

[0017] Optionally, the polymeric electrolyte further includes a pH adjuster, which includes one or more of perchloric acid, sulfuric acid, hydrochloric acid, p-toluenesulfonic acid, and trifluoromethanesulfonic acid.

[0018] Optionally, the pH value of the polymer electrolyte is 0.1-2.

[0019] Optionally, an Ag / AgCl electrode is used as a reference electrode in the constant current method; and / or, a Pt electrode is used as a counter electrode in the constant current method.

[0020] Optionally, during the constant current method, the current is 0.2-10 mA / cm. 2 ; and / or, the reaction time is 10-600s.

[0021] A third aspect of the present invention provides a battery comprising a positive electrode, a negative electrode, and a separator, wherein the negative electrode is the negative electrode described above, or a negative electrode prepared by the method described above.

[0022] According to the negative electrode sheet provided by the present invention, a conductive polymer layer is formed on the surface of the negative electrode active material and the conductive agent to form a continuous surface. The conductive polymer layer is formed by copolymerization of 3,4-ethylenedioxythiophene (EDOT) and pyrrole, which can effectively stabilize the interface between the negative electrode and the electrolyte, suppress side reactions, and improve the cycle life of the battery. Moreover, the conductive polymer layer formed by copolymerization of EDOT and pyrrole has both good electronic conductivity and certain ion transport capability, which helps to reduce interface impedance and improve the rate performance and charge-discharge efficiency of the battery. In addition, the conductive polymer layer has certain mechanical strength and uniform ion flux regulation capability, which can suppress the formation of lithium dendrites to a certain extent and improve battery safety. Furthermore, the conductive polymer layer is formed by in-situ polymerization on the surface of the negative electrode active material and the conductive agent using a constant current method, which can achieve uniform, dense and firm coating, effectively prevent the active material layer from falling off and enhance the integrity of the electrode structure. The active material layer provides basic electrochemical activity, while the conductive polymer layer plays a dual role of protection and conductivity. The synergistic effect of the two significantly improves the overall capacity retention and cycle stability of the negative electrode. Attached Figure Description

[0023] 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.

[0024] Figure 1 This is a schematic diagram of the conductive network of the negative electrode sheet provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of the conductive network of the negative electrode sheet provided by the prior art of this invention; The reference numerals in the accompanying drawings are as follows: 100-Negative current collector; 2-Silicon-containing material; 21-Silicon particles; 22-Porous carbon skeleton; 23-Surface carbon coating; 31-Effective conductive agent; 32-Ineffective conductive agent; 33-Conductive polymer layer. Detailed Implementation

[0025] To make the technical problems solved, the technical solutions, and the beneficial effects of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0026] In the description of this invention, it should be understood that the terms "longitudinal," "radial," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientation or positional relationships, are based on the orientation or positional relationships shown in the accompanying drawings and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0027] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0028] In one embodiment, the first aspect of the present invention provides a negative electrode sheet, comprising: Negative electrode current collector 100; An active material layer is disposed on the surface of the negative electrode current collector 100. The active material layer includes a negative electrode active material, a conductive agent, a binder, and a conductive polymer layer 33. The negative electrode active material includes a silicon-containing material. The negative electrode active material and the conductive agent are mixed together and bonded together by the binder. The conductive polymer layer 33 is formed on the surfaces of adjacent negative electrode active materials and conductive agents to form a continuous surface. The polymer monomers of the conductive polymer layer 33 include 3,4-ethylenedioxythiophene and pyrrole. The conductive polymer layer 33 is obtained by constant current polymerization.

[0029] like Figure 2 As shown, a negative electrode active material layer is formed on both sides of a conventional negative electrode sheet. The negative electrode active material layer includes a negative electrode active material, a conductive agent, and a binder. The negative electrode active material includes a silicon-containing material 2. Some conductive agent particles adsorbed at the connection points of the silicon-containing material 2 are effective conductive agents 31; some conductive agent particles cannot be effectively adsorbed at the connection points of the silicon-containing material 2, forming ineffective conductive agents 32. The ineffective conductive agents 32 cannot play an effective electrical connection role between silicon-containing materials 2, forming many ineffective conductive networks. During cycling, the expansion of the silicon-containing material 2 will also cause some conductive networks to break and lose conductivity.

[0030] like Figure 1 As shown, this invention provides a conductive polymer layer 33 on the surfaces of adjacent negative electrode active materials and conductive agents. The conductive polymer layer 33 is formed by copolymerization of 3,4-ethylenedioxythiophene (EDOT) and pyrrole, which effectively stabilizes the interface between the negative electrode and the electrolyte, suppresses side reactions, and improves battery cycle life. Furthermore, the conductive polymer layer 33 formed by the copolymerization of EDOT and pyrrole possesses both good electronic conductivity and a certain ion transport capability, which helps reduce interfacial impedance and improve battery rate performance and charge / discharge efficiency. In addition, the conductive polymer layer 33 has a certain organic... The mechanical strength and uniform ion flux control capability can suppress the formation of lithium dendrites to a certain extent and improve battery safety. Furthermore, by using the constant current method to form a conductive polymer layer 33 on the surface of adjacent negative electrode active materials and conductive agents in situ, a uniform, dense and firm coating can be achieved, effectively preventing the negative electrode active materials, conductive agents or binders from falling off and enhancing the integrity of the electrode structure. The active material layer provides basic electrochemical activity, while the conductive polymer layer 33 plays a dual role of protection and conductivity. The synergistic effect of the two significantly improves the overall capacity retention and cycle stability of the negative electrode.

[0031] In summary, this technology, through its innovative dual-layer structure design, achieves efficient construction of the conductive network and long-term stability of the electrode structure, demonstrating significant technological advancement and promising prospects for industrial application.

[0032] In one embodiment, the thickness of the conductive polymer layer 33 is 0.5-2 μm.

[0033] Specifically, the thickness of the conductive polymer layer 33 is any one value or a range of any two values ​​among 0.5μm, 1μm, 1.5μm or 2μm; in a preferred embodiment, the thickness of the conductive polymer layer 33 is 1-1.5μm.

[0034] When the thickness of the conductive polymer layer 33 is 0.5-2μm, it can form a continuous, dense and flexible conductive network on the surface of adjacent negative electrode active materials and conductive agents. This not only effectively improves the electronic conductivity, but also fully buffers the mechanical stress caused by the volume expansion of silicon during charging and discharging, preventing particle pulverization and electrode structure collapse. At the same time, it allows lithium ions to migrate rapidly, thereby significantly improving the cycle stability, coulombic efficiency and rate performance of the negative electrode. When the thickness of the conductive polymer layer 33 is less than 0.5 μm, the film is too thin and it is difficult to completely cover the negative electrode active material. The exposed negative electrode active material in some areas is prone to uncontrollable side reactions in the electrolyte, which leads to repeated rupture and regeneration of the solid electrolyte interphase (SEI) film, resulting in continuous consumption of active lithium, increased internal resistance, and ultimately rapid capacity decay and shortened cycle life. When the thickness of the conductive polymer layer 33 is greater than 2 μm, the excessive thickness of the film will significantly increase the lithium ion diffusion path, increase the interfacial transport impedance, inhibit electrode reaction kinetics, and lead to a decrease in rate performance. At the same time, the excessively thick conductive polymer layer 33 is prone to microcracks, wrinkles, or even peeling due to the accumulation of internal stress during silicon volume change, losing its protective effect on the silicon-containing material 2 and accelerating electrode failure instead.

[0035] In one embodiment, the molar ratio of 3,4-ethylenedioxythiophene to pyrrole is (0.01-0.1):(0.01-0.1).

[0036] Specifically, the molar ratio of 3,4-ethylenedioxythiophene to pyrrole is any one value or a range of any two values ​​among 0.01:0.01, 0.01:0.05, 0.01:0.1, 0.05:0.01, 0.05:0.1, 0.1:0.01, or 0.1:0.05; in a preferred embodiment, the molar ratio of 3,4-ethylenedioxythiophene to pyrrole is (0.01-0.05):(0.01-0.05).

[0037] When the molar ratio of 3,4-ethylenedioxythiophene to pyrrole is (0.01-0.1):(0.01-0.1), effective copolymerization of EDOT and pyrrole can be achieved during the constant current polymerization process, forming a conductive copolymer coating with controllable structure and uniform composition. Within this ratio range, the advantages of the two monomers complement each other: EDOT provides high conductivity, good environmental stability and flexibility, while pyrrole enhances hydrophilicity, ion exchange capacity and interfacial wettability. The resulting copolymer has both excellent electronic / ionic dual conductivity and mechanical adhesion, which can significantly improve the interfacial stability, cycle life and rate performance of the negative electrode. By adjusting the molar ratio, the redox potential, band gap and surface energy of the polymer can also be finely controlled to adapt to different electrolyte systems or negative electrode materials.

[0038] In a preferred embodiment, the molar ratio of 3,4-ethylenedioxythiophene to pyrrole in the polymerization electrolyte is 1:5-5:1.

[0039] Specifically, the molar ratio of 3,4-ethylenedioxythiophene to pyrrole is any one value or a range of any two values ​​from 1:5, 1:4, 1:3, 1:2, 1:1, 2:5, 2:3, 2:1, 3:5, 3:4, 3:2, 3:1, 4:5, 4:3, 4:1, 5:4, 5:3, 5:2 or 5:1; in a preferred embodiment, the molar ratio of 3,4-ethylenedioxythiophene to pyrrole is (1-3):(3-1).

[0040] When the molar ratio of 3,4-ethylenedioxythiophene to pyrrole is 1:5-5:1, effective copolymerization of EDOT and pyrrole can be achieved during the constant current polymerization process, forming a conductive copolymer coating with controllable structure and uniform composition. Within this ratio range, the advantages of the two monomers are complementary: EDOT provides high conductivity, good environmental stability, and flexibility, while pyrrole enhances hydrophilicity, ion exchange capacity, and interfacial wettability. The resulting copolymer has both excellent electronic / ionic dual conductivity and mechanical adhesion, which can significantly improve the interfacial stability, cycle life, and rate performance of the negative electrode. By adjusting the molar ratio, the redox potential, band gap, and surface energy of the polymer can be finely controlled to adapt to different electrolyte systems or negative electrode materials. When the molar ratio of 3,4-ethylenedioxythiophene to pyrrole is less than 1:5, the content of EDOT units in the copolymer is insufficient, making it difficult to form a continuous conjugated main chain structure, resulting in a decrease in overall conductivity. Increased polymerization tendency leads to the formation of a brittle and unstable polypyrrole (PPy)-dominant phase, which is prone to volume expansion, cracking, or detachment during cycling; decreased environmental stability of the conductive polymer layer 33 (polypyrrole is easily oxidized and degraded in air), resulting in accelerated long-term electrochemical performance degradation; increased interfacial impedance, hindered lithium-ion transport, and reduced battery capacity retention and rate performance; when the molar ratio of 3,4-ethylenedioxythiophene to pyrrole is greater than 5:1, the pyrrole content is insufficient to effectively participate in copolymerization, the copolymer approaches a pure PEDOT structure, and hydrophilicity and interfacial wettability are significantly reduced; the compatibility of the coating with aqueous or polar electrolytes deteriorates, leading to insufficient electrolyte wetting and deterioration of interfacial ion transport kinetics; the lack of active sites provided by pyrrole weakens the ability to inhibit side reactions, and the stability of the SEI film may be affected; although the conductivity is high, the single function and insufficient interfacial adaptability make it difficult to fully exert the synergistic modification effect.

[0041] In one embodiment, the total mass of the negative electrode active material, binder, and conductive agent is taken as 100%, the mass percentage of the negative electrode active material is 90.5%-93.5%, the mass percentage of the binder is 6%-9%, and the mass percentage of the conductive agent is 0.3%-0.5%.

[0042] Specifically, the mass percentage of silicon-containing material 2 is any one value or a range of any two values ​​selected from 90.5%, 91%, 91.5%, 92%, 92.5%, 93%, or 93.5%; in a preferred embodiment, the mass percentage of silicon-containing material 2 is 91.5%-92.5%.

[0043] Specifically, the mass percentage of the adhesive is any one value or a range of any two values ​​selected from 6%, 7%, 8% or 9%; in a preferred embodiment, the mass percentage of the adhesive is 7%-8%.

[0044] Specifically, the mass percentage content of the conductive agent is any one value or a range of any two values ​​selected from 0.3%, 0.4%, or 0.5%; in a preferred embodiment, the mass percentage content of the conductive agent is 0.4%-0.5%.

[0045] When the mass percentage of the negative electrode active material is 90.5%-93.5%, the mass percentage of the binder is 6%-9%, and the mass percentage of the conductive agent is 0.3%-0.5%, it has the effect of balancing energy density and electrode thickness expansion. When the negative electrode active material, binder, and conductive agent do not meet the above ranges, it will lead to problems such as low energy density, excessive thickness expansion, excessive internal resistance, and poor rate performance.

[0046] In one embodiment, the silicon-containing material 2 includes one or more of silicon particles, silicon suboxide, and silicon-carbon materials; the selection of the above-mentioned silicon-containing material 2 takes into account both high specific capacity and cycle stability.

[0047] In one embodiment, the silicon-containing particles are selected from silicon-carbon materials, wherein the silicon content in the silicon-carbon materials is 40%-60% by mass.

[0048] Specifically, the silicon content in the silicon-carbon material is any one value or a range of any two values ​​from 40%, 42%, 44%, 46%, 48%, 50%, 52%, 54%, 56%, 58%, or 60%; in a preferred embodiment, the silicon content in the silicon-carbon material is 45%-55%.

[0049] When the silicon content in silicon-carbon materials is 40%-60% by mass, the energy density and the cyclic expansion of silicon-carbon particles can be relatively balanced. When the silicon content in silicon-carbon materials is less than 40% by mass, the energy density of silicon-carbon materials will be too low. When the silicon content in silicon-carbon materials is greater than 60% by mass, the silicon-carbon particles will expand too much, affecting the cyclic thickness expansion rate and capacity retention rate.

[0050] like Figure 1-2 As shown, preferably, the structure of the silicon-carbon material of this application includes a porous carbon skeleton 22, silicon particles 21 and a carbon coating layer 23, with the silicon particles 21 embedded inside the porous carbon skeleton 22 and the porous carbon skeleton 22 covered with a carbon coating layer 23.

[0051] Using silicon-carbon materials can improve electronic conductivity: compensate for the low intrinsic conductivity of silicon; inhibit particle agglomeration and pulverization, and maintain structural integrity during cycling; stabilize the SEI film, reduce direct exposure of silicon to the electrolyte, and suppress excessive side reactions; and reserve expansion space (especially in porous or flexible carbon structures) to accommodate changes in silicon volume.

[0052] In one embodiment, the binder includes one or more of sodium carboxymethyl cellulose (CMC), styrene-butadiene rubber (SBR), polyvinylidene fluoride (PVDF), sodium alginate, polyacrylic acid (PAA), polyimide (PI), or combinations thereof.

[0053] In one embodiment, the conductive agent includes one or more of carbon black (such as SuperP), acetylene black, Ketjen black, graphene, carbon nanotubes (CNTs), carbon fibers, expanded graphite, or combinations thereof.

[0054] In one embodiment, a second aspect of the present invention provides a method for preparing a negative electrode sheet, comprising the following steps: The negative electrode active material, conductive agent, and binder are mixed into a slurry and coated onto the surface of the negative electrode current collector. The polymer electrolyte forms a conductive polymer layer 33 on the surface of adjacent negative electrode active material and conductive agent by a constant current method. The polymer electrolyte includes 3,4-ethylenedioxythiophene and pyrrole.

[0055] This invention forms a conductive polymer layer 33 on the surface of adjacent negative electrode active materials and conductive agents. The conductive polymer layer 33 is formed by copolymerization of 3,4-ethylenedioxythiophene (EDOT) and pyrrole, which can effectively stabilize the interface between the negative electrode and the electrolyte, suppress side reactions, and improve battery cycle life. Moreover, the conductive polymer layer 33 formed by the copolymerization of EDOT and pyrrole has both good electronic conductivity and certain ion transport capabilities, which helps to reduce interfacial impedance and improve battery rate performance and charge / discharge efficiency. In addition, the conductive polymer layer 33 has certain mechanical strength and uniform ion flux regulation capability, which can suppress the formation of lithium dendrites to a certain extent and improve battery safety. Furthermore, the conductive polymer layer 33 is formed by in-situ polymerization on the surface of the active material layer using a constant current method, which can achieve uniform, dense, and firm coating, effectively preventing the active material layer from falling off and enhancing the integrity of the electrode structure. The active material layer provides basic electrochemical activity, while the conductive polymer layer 33 plays a dual role of protection and conductivity. The synergistic effect of the two significantly improves the overall capacity retention and cycle stability of the negative electrode.

[0056] In one embodiment, the concentration of 3,4-ethylenedioxythiophene in the polymerization electrolyte is 0.01-0.1 mol / L.

[0057] Specifically, the concentration of 3,4-ethylenedioxythiophene is any one value or a range of any two values ​​selected from 0.01 mol / L, 0.015 mol / L, 0.02 mol / L, 0.025 mol / L, 0.03 mol / L, 0.035 mol / L, 0.04 mol / L, 0.045 mol / L, 0.05 mol / L, 0.055 mol / L, 0.06 mol / L, 0.065 mol / L, 0.07 mol / L, 0.075 mol / L, 0.08 mol / L, 0.085 mol / L, 0.09 mol / L, 0.095 mol / L, or 0.1 mol / L; in a preferred embodiment, the concentration of 3,4-ethylenedioxythiophene is 0.01-0.08 mol / L.

[0058] When the concentration of 3,4-ethylenedioxythiophene is 0.01-0.1 mol / L, it can polymerize on the negative electrode surface using a constant current method to form a uniform, dense layer with good conductivity. Synergistic copolymerization with pyrrole effectively regulates the electronic structure and ion transport properties of the polymer, improving interfacial stability and electrochemical reversibility. Within this concentration range, the polymerization rate is moderate, which is beneficial for obtaining a functional layer with controllable thickness, strong adhesion, and good mechanical flexibility, thereby significantly improving the cycle performance and rate capability of the battery. When the concentration of 3,4-ethylenedioxythiophene is less than 0.01 mol / L, the monomer concentration becomes too low, the polymerization reaction rate becomes too slow, or it is difficult to form a film effectively. If the polymer layer is too thin or even discontinuous, it cannot effectively cover the surface of the active material layer, resulting in insufficient interfacial protection. This leads to increased electrode / electrolyte interfacial impedance, inhibits ion / electron transport, and reduces the overall battery performance. When the concentration of 3,4-ethylenedioxythiophene is greater than 0.1 mol / L, it will lead to excessively high monomer concentration, triggering violent or non-uniform polymerization, which easily produces a rough, porous, or even powdery polymer layer. Excessive cross-linking or side reactions may accompany the polymerization process, reducing the flexibility of the film and its adhesion to the substrate. A thick and loose coating will hinder lithium-ion diffusion, increase interfacial resistance, and may peel off or break during cycling, thereby impairing electrode stability and cycle life.

[0059] In one embodiment, the concentration of pyrrole in the polymerization electrolyte is 0.01-0.1 mol / L.

[0060] Specifically, the concentration of pyrrole is any one value or a range of any two values ​​selected from 0.01 mol / L, 0.015 mol / L, 0.02 mol / L, 0.025 mol / L, 0.03 mol / L, 0.035 mol / L, 0.04 mol / L, 0.045 mol / L, 0.05 mol / L, 0.055 mol / L, 0.06 mol / L, 0.065 mol / L, 0.07 mol / L, 0.075 mol / L, 0.08 mol / L, 0.085 mol / L, 0.09 mol / L, 0.095 mol / L, or 0.1 mol / L; in a preferred embodiment, the concentration of pyrrole is 0.01-0.08 mol / L.

[0061] When the concentration of pyrrole is 0.01-0.1 mol / L, it can effectively copolymerize with 3,4-ethylenedioxythiophene (EDOT) to form a copolymer coating with uniform structure, high conductivity, and certain hydrophilicity. The introduction of pyrrole can enhance the redox activity and ion exchange capacity of the polymer, which helps to improve the lithium-ion transport kinetics at the negative electrode interface. Within this concentration range, the copolymerization reaction rate is moderate, which is conducive to obtaining a dense, flexible, and strongly adherent functional layer, thereby synergistically enhancing the cycle stability and rate performance of the electrode. When the concentration of pyrrole is less than 0.01 mol / L, the pyrrole monomer content will be too low, making it difficult to effectively participate in the copolymerization reaction, and the proportion of pyrrole units in the copolymer will be insufficient. The resulting polymer layer is mainly dominated by PEDOT and lacks the hydrophilicity and interfacial wettability advantages brought by pyrrole, which may reduce the electrolyte wetting effect. The overall film layer has a single function and limited inhibition of interfacial side reactions, and cannot fully exert the synergistic effect of the EDOT / Py copolymer. When the concentration of pyrrole is greater than 0.1 mol / L, it will cause pyrrole to be easily oxidized and polymerized. Excessive concentration will cause rapid homopolymerization or local overpolymerization, resulting in a rough coating, high brittleness, easy cracking or peeling. High concentration of pyrrole may inhibit the effective incorporation of EDOT, destroy the regularity of the copolymer structure, and reduce the electronic conductivity and long-term stability of the film. An excessively thick or non-uniform polymer layer will hinder the lithium-ion diffusion path, increase the interfacial impedance, and thus deteriorate the cycle performance and rate capability of the battery.

[0062] In one embodiment, the polymerization electrolyte further includes potassium chloride, and the concentration of potassium chloride in the polymerization electrolyte is 0.05-0.5 mol / L.

[0063] Specifically, the concentration of potassium chloride is any one value or a range of any two values ​​selected from 0.05 mol / L, 0.1 mol / L, 0.15 mol / L, 0.2 mol / L, 0.25 mol / L, 0.3 mol / L, 0.35 mol / L, 0.4 mol / L, 0.45 mol / L, or 0.5 mol / L; in a preferred embodiment, the concentration of potassium chloride is 0.1-0.4 mol / L.

[0064] When the potassium chloride concentration is 0.05-0.5 mol / L, the electrolyte has suitable ionic strength and conductivity, which can effectively reduce solution resistance and promote the uniform electrochemical oxidation polymerization of EDOT and pyrrole monomers on the silicon-based anode surface, thereby forming a dense, continuous, and highly conductive PEDOT / PPy composite film, significantly improving the cycle stability and rate performance of the anode. When the potassium chloride concentration is less than 0.05 mol / L, the electrolyte ionic strength is too low, leading to a significant increase in solution resistance, uneven current distribution, and local overpotential elevation, resulting in inconsistent polymerization reaction rates and a conductive polymer film formed. The presence of pores, incomplete coverage, or uneven thickness cannot effectively buffer the volume expansion of silicon-containing material 2, thereby reducing the cycle life and coulombic efficiency of the electrode. When the concentration of potassium chloride is greater than 0.5 mol / L, the excessively high ionic strength may cause double-layer compression, inhibiting the diffusion of monomers to the electrode surface. At the same time, a large number of Cl⁻ ions may undergo oxidation side reactions (such as the precipitation of chlorine gas) at high potentials, interfering with the main polymerization process and potentially causing the Ag / AgCl reference electrode potential to drift, affecting process stability. In addition, high salt concentrations may also cause crystallization during subsequent drying, damaging the integrity of the conductive polymer layer 33.

[0065] In one embodiment, the polymerization electrolyte further includes a pH adjuster, which includes one or more of perchloric acid, sulfuric acid, hydrochloric acid, p-toluenesulfonic acid, and trifluoromethanesulfonic acid. The use of the above-mentioned pH adjuster can promote the formation of cationic free radicals of EDOT and pyrrole (Py) monomers, which is beneficial to oxidative polymerization; provide a high concentration of H⁺ to enhance the conductivity of the solution; and inhibit side reactions (such as monomer hydrolysis and peroxidation).

[0066] In one embodiment, the pH of the polymer electrolyte is 0.1-2.

[0067] Specifically, the pH value of the polymerization electrolyte is any one value or a range of any two values ​​from 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9 or 2; in a preferred embodiment, the pH value of the polymerization electrolyte is 0.5-1.5.

[0068] When the pH of the polymerization electrolyte is 0.1-2, it favors the efficient cationic radical oxidative polymerization of 3,4-ethylenedioxythiophene (EDOT) and pyrrole (Py) monomers; simultaneously, high concentrations of H2O... + It can effectively inhibit side reactions (such as monomer hydrolysis or peroxidation degradation) and promote anion (such as ClO4) reactions. - TsO - Doping with substances such as PEDOT and PPy into the polymer chain forms a dense, highly conductive, and strongly adherent PEDOT / PPy composite film, significantly improving the interfacial stability and cycle performance of the silicon-based anode. However, when the pH of the polymer electrolyte is less than 0.1, it can lead to excessive H+. + Strong acid anions may corrode current collectors (such as copper foil) or damage the surface structure of silicon-containing materials 2. At the same time, extreme acidic environments can easily lead to excessively fast polymerization rates, triggering violent local nucleation and causing the conductive polymer layer 33 to become rough, porous, or even peel off. In addition, high concentrations of strong acids (such as HClO4) pose safety risks at low pH levels (such as thermal instability or increased oxidizing power), which is detrimental to process controllability and large-scale production. When the pH of the polymerization electrolyte is greater than 2, the system is not acidic enough, making it difficult to effectively protonate monomers and stabilize cationic free radical intermediates, resulting in a positive shift in polymerization initiation potential and a significant reduction in reaction rate. Meanwhile, pyrrole is prone to non-selective oxidation or the formation of insulating byproducts under weak acid or neutral conditions. The resulting conductive polymer layer 33 has poor conductivity and discontinuous coverage, making it impossible to effectively construct an electron transport network and buffer the volume expansion of the silicon anode, ultimately leading to increased electrode impedance and deterioration of cycle stability.

[0069] In one embodiment, an Ag / AgCl electrode is used as a reference electrode in the constant current method; and / or, a Pt electrode is used as a counter electrode in the constant current method.

[0070] Using Ag / AgCl electrodes in Cl-containing - The aqueous solution exhibits a highly reversible electrode reaction (AgCl + e⁻). - ⇌Ag+Cl - Its open-circuit potential is affected by temperature and Cl. - The concentration has minimal impact, providing a stable and reliable potential reference during long-term polymerization, which is beneficial for monitoring real-time potential changes of the working electrode (silicon anode) and ensuring process consistency. Furthermore, the polymerization electrolyte contains KCl (e.g., 0.05 mol / L) as a supporting electrolyte, providing the necessary Cl- for the Ag / AgCl electrode. - Environment, avoid Cl - Insufficient concentration can cause electrode potential drift or failure, thus ensuring the reliability of the reference performance.

[0071] Using a Pt electrode as the counter electrode, Pt has excellent electronic conductivity, which can efficiently conduct current, reduce ohmic losses, and facilitate precise control of constant current output.

[0072] In one embodiment, during the constant current method, the current is 0.2-10 mA / cm. 2 ; and / or, the reaction time is 10-600s.

[0073] Specifically, the current in the constant current method process is 0.2 mA / cm. 2 0.9mA / cm 2 1.6mA / cm 2 2.3mA / cm 2 3mA / cm 2 3.7mA / cm 2 4.4 mA / cm 2 5.1 mA / cm 2 5.8 mA / cm 2 6.5mA / cm 2 7.2mA / cm 2 7.9 mA / cm 2 8.6 mA / cm 2 9.3 mA / cm 2 or 10mA / cm 2 The value is any one point value or a range of any two point values; in a preferred embodiment, the current in the constant current method process is 1.6-2.3 mA / cm. 2 μm.

[0074] When the current in the constant current method is 0.2-10 mA / cm 2 EDOT and pyrrole undergo oxidative polymerization at a moderate rate on the surface of the active material layer, which is beneficial for forming a dense, uniform, strongly adhered, and highly conductive PEDOT / PPy composite conductive polymer layer 33. This film layer can effectively construct a continuous electron transport network and buffer the volume expansion of silicon during charging and discharging, thereby significantly improving the cycle stability and rate performance of the negative electrode. The current density during the constant current method is less than 0.2 mA / cm². 2 At low currents, the polymerization rate is too slow, leading to a significant increase in film formation time and low production efficiency. Simultaneously, the sparse nucleation sites at low currents easily form discontinuous, island-like, or ultrathin conductive polymer layers 33, which cannot completely cover the surface of the silicon-containing material 2, causing interruptions in the electron conduction path and making it difficult to effectively suppress silicon pulverization and repeated SEI film rupture. Ultimately, this results in increased electrode impedance and accelerated capacity decay. When the current density in the constant current method exceeds 10 mA / cm², further degradation occurs. 2At this time, the monomers rapidly oxidize on the electrode surface, triggering intense nucleation and rapid deposition, resulting in a loose, porous, and even cracked structure in the conductive polymer layer 33.

[0075] Specifically, the reaction time in the constant current method process is any one value or a range of any two values ​​from 10s, 50s, 100s, 150s, 200s, 250s, 300s, 350s, 400s, 450s, 500s, 550s, or 600s; in a preferred embodiment, the reaction time in the constant current method process is 50-300s.

[0076] When the reaction time in the galvanostatic process is 10-600 s, the PEDOT / PPy composite conductive polymer layer 33 can achieve sufficient and controllable in-situ deposition on the silicon-based anode surface, forming a uniform, continuous, and highly conductive coating film with a thickness of 0.5–2 μm. This film layer can effectively construct a fast electron transport channel and buffer the drastic volume expansion of silicon during lithiation / delithiation, significantly improving the cycle stability, coulombic efficiency, and rate performance of the anode. When the reaction time in the galvanostatic process is less than 10 s, the polymerization reaction time is too short, resulting in insufficient monomer oxidation. The formed conductive polymer layer 33 is incomplete and insufficient in thickness (usually <0.2 μm), failing to completely cover the surface. The surface of silicon-containing material 2; locally exposed silicon is prone to pulverization, repeated rupture of the SEI film, and continuous consumption of electrolyte during subsequent electrochemical cycles, resulting in rapid capacity decay and increased irreversible losses in the first cycle; when the reaction time in the constant current method is greater than 600s, it will lead to excessive growth of the conductive polymer layer 33, with a thickness exceeding 2μm, resulting in stress accumulation in the film layer, decreased structural density, and even cracking or peeling; at the same time, the excessively thick polymer layer will significantly increase the lithium ion diffusion path, increase the interface impedance, and inhibit the electrode reaction kinetics, resulting in deterioration of rate performance; in addition, long-term electrolysis may trigger side reactions (such as oxygen evolution of water and monomer peroxidation degradation), reducing the conductivity and electrochemical activity of the film.

[0077] In one embodiment, a third aspect of the present invention provides a battery comprising a positive electrode, a negative electrode, and a separator, wherein the negative electrode is the aforementioned negative electrode or a negative electrode prepared by the aforementioned method for preparing a negative electrode.

[0078] Specifically, the positive electrode sheet includes a positive current collector and positive active material layers disposed on both sides of the positive current collector. The positive active material layers include positive active material, which includes the aforementioned positive electrode material, or a positive electrode material prepared by the aforementioned method for preparing positive electrode material.

[0079] Specifically, the positive electrode current collector has two surfaces opposite each other in its own thickness direction, and the positive electrode active material layer can be disposed on either or both of the two opposite surfaces of the positive electrode current collector.

[0080] In some embodiments, the positive current collector can be a metal foil or a composite current collector. For example, aluminum foil can be used as the metal foil. The composite current collector may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector can be formed by forming a metal material such as aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy on the polymer material substrate. Exemplarily, the polymer material can be selected from polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc. In some embodiments, the positive electrode active material layer further includes a conductive agent; as an example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0081] In some embodiments, the positive electrode active material layer further includes a binder. As examples, the binder may include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, and tetrafluoroethylene-hexafluoropropylene copolymer.

[0082] In some embodiments, the positive electrode film may optionally include a conductive agent. As an example, the conductive agent may include at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0083] In some embodiments, the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive electrode active material, conductive agent, binder and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry onto the positive electrode current collector, and then obtaining the positive electrode sheet after drying, cold pressing and other processes.

[0084] Specifically, the separator can be any separator material suitable for lithium-ion batteries in the art, such as, but not limited to, one or more combinations of single-layer polypropylene, single-layer polyethylene, polyvinylidene fluoride, aramid, polyethylene terephthalate, polytetrafluoroethylene, polyacrylonitrile, polyimide, polyamide, polyester and natural fibers.

[0085] The battery in this application also includes an electrolyte, which may be one or more of a gel electrolyte, a solid electrolyte, and an electrolyte solution, including lithium salts and non-aqueous solvents.

[0086] 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.

[0087] The beneficial effects of the present invention will be further illustrated below with reference to the embodiments.

[0088] 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.

[0089] Furthermore, it should be understood that the one or more method steps mentioned in this invention do not preclude the existence of other method steps before or after the combination steps, or the insertion of other method steps between these explicitly mentioned steps, unless otherwise stated. It should also be understood that the combination 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 combination of 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.

[0090] 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.

[0091] Table 1 shows the design of negative electrode parameters for Examples 1-17 and Comparative Examples 1-3; Example 1 This embodiment illustrates the negative electrode sheet and battery disclosed in this invention; it includes the following operational steps: Preparation of negative electrode: The first negative electrode slurry was prepared by mixing silicon-containing porous carbon-supported silicon, binder, and conductive agent in a ratio of 92:7.5:0.5. The first negative electrode slurry is coated onto the negative electrode current collector copper foil on a coating machine, dried, and rolled to obtain a rolled electrode sheet; Preparation of polymerization electrolyte: Dissolve 0.05M KCl in aqueous solution, and after stirring and dissolving, add HClO4 to adjust the pH to 1. Add 0.01M EDOT (3,4-ethylenedioxythiophene) and 0.01M Py (pyrrole), and stir evenly to form polymerization electrolyte; The rolled electrode sheet was placed in the prepared polymerization electrolyte, with Ag / AgCl as the reference electrode, and polymerization was carried out using a constant current method at 2 mA / cm². 2 The current deposition time is seconds, forming a conductive polymer layer on the surface of adjacent negative electrode active material and conductive agent; The polymerized electrode sheets are washed with deionized water and dried to serve as negative electrode sheets. Preparation of positive electrode: Lithium cobalt oxide, single-walled carbon nanotubes, conductive carbon black SP, and binder PVDF are mixed in a ratio of 97.3:0.5:1.0:1.2 to prepare a positive electrode slurry. 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.

[0092] 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.

[0093] 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 the same manner to form a battery cell. The battery cell is placed into a pre-formed battery casing, and the electrolyte is injected into the baked and dried battery cell. After vacuum sealing, settling, and formation processes, the battery is obtained.

[0094] Example 2-17 Examples 2-17 illustrate the negative electrode and battery disclosed in this invention, including most of the operating steps in Example 1, with the following differences: The parameters of the negative electrode shown in Table 1 are used.

[0095] Comparative Examples 1-3 Comparative Examples 1-3 are used to illustrate the negative electrode sheet and battery disclosed in this invention, including most of the operating steps in Example 1, the difference being: The parameters of the negative electrode shown in Table 1 are used.

[0096] Performance testing The following performance tests were performed on the batteries prepared in Examples 1-17 and Comparative Examples 1-3: Internal resistance test: Test the 1KHz AC impedance of the positive and negative terminals of the battery cell.

[0097] Battery rate performance test: At 25℃, charge at 0.5C to 4.5V, cut off at 0.05C, and then discharge at 0.2C to 3.0V as the initial capacity; then charge at 0.5C to 4.5V, cut off at 0.05C, and then discharge at 2C to 3.0V as the rate discharge capacity; Capacity percentage = 2C discharge capacity / initial capacity.

[0098] Cyclic performance test: At 25℃, charge at 0.5C to 4.2V, cut off at 0.05C, and then discharge at 0.5C to 3.0V as the initial capacity. Repeat the cycle until the capacity retention rate decays to 80% of the initial capacity, and record the number of cycles.

[0099] The test results are shown in Table 2.

[0100] Table 2 Battery Electrochemical Performance Comparing Example 1 and Comparative Example 1, it can be seen that when only pyrrole is used as a monomer for polymerization, compared with composite polymers, the conductivity is reduced, and the overall cell conductivity, rate capability, and cycle performance are further slightly reduced.

[0101] Comparing Example 1 and Comparative Example 2, it can be seen that when only 3,4-ethylenedioxythiophene is used as a monomer for polymerization, the conductivity of the composite polymer is reduced, and the overall cell conductivity, rate capability, and cycle performance are slightly reduced. Comparing Example 1 and Comparative Example 3, it can be seen that without using 3,4-ethylenedioxythiophene and pyrrole polymer as a bridge, the battery's conductivity, rate performance, and cycle performance deteriorate significantly.

[0102] Comparing Examples 1-5, it can be seen that in the polymer electrolyte, when the concentration of 3,4-ethylenedioxythiophene is 0.01-0.1 mol / L, it exhibits lower internal resistance, higher rate performance, and better cycle performance. When the concentration of 3,4-ethylenedioxythiophene is less than 0.01 mol / L, the conductive polymer layer is thin, which leads to increased internal resistance, reduced rate performance, and reduced cycle performance. When the concentration of 3,4-ethylenedioxythiophene is greater than 0.1 mol / L, the conductive polymer layer is thicker, improving conductivity, but this results in reduced cycle performance and reduced rate performance.

[0103] Comparing Examples 1-2 and Examples 6-8, it can be seen that in the polymer electrolyte, when the concentration of pyrrole is 0.01-0.1 mol / L, it has lower internal resistance, higher rate performance, and better cycle performance. When the concentration of pyrrole is less than 0.01 mol / L, the conductive polymer layer is thin, which leads to increased internal resistance, reduced rate performance, and reduced cycle performance. When the concentration of pyrrole is greater than 0.1 mol / L, it has lower internal resistance, but the rate performance and cycle performance deteriorate significantly.

[0104] Comparing Examples 1, 3, 6-7, and 9, it can be seen that in the polymer electrolyte, when the molar ratio of 3,4-ethylenedioxythiophene to pyrrole is 0.2-5, it exhibits lower internal resistance, higher rate performance, and better cycle performance. When the molar ratio of 3,4-ethylenedioxythiophene to pyrrole is less than 0.2, the conductive polymer layer is thin, which leads to reduced conductivity, lower rate performance, and lower cycle performance. When the molar ratio of 3,4-ethylenedioxythiophene to pyrrole is greater than 5, the conductive polymer layer is thicker, improving conductivity, but excessive thickness leads to reduced cycle performance and lower rate performance.

[0105] Comparing Examples 1 and 10-13, it can be seen that when the concentration of potassium chloride is 0.05-0.5 mol / L, a conductive polymer film can be uniformly formed, resulting in a battery with lower internal resistance, higher rate performance, and better cycle performance. When the concentration of potassium chloride is less than 0.05 mol / L, the conductive polymer film is not fully formed, leading to deterioration in conductivity, rate performance, and cycle performance. When the concentration of potassium chloride is greater than 0.5 mol / L, the conductive polymer film is not densely formed, resulting in deterioration in conductivity, rate performance, and cycle performance.

[0106] Comparing Examples 1 and 14-17, it can be seen that when the pH value of the polymerization electrolyte is 0.1-2, it has lower internal resistance, higher rate performance, and better cycle performance. When the pH value of the polymerization electrolyte is less than 0.1, oligomers are easily formed, affecting the polymer properties, reducing conductivity, increasing internal resistance, reducing rate performance, and reducing cycle performance. When the pH value of the polymerization electrolyte is greater than 2, the pH value is too high, and nucleophilic OH⁻ will attack cationic free radicals, hindering polymerization, reducing conductivity, increasing internal resistance, reducing rate performance, and reducing cycle performance.

[0107] In summary, this technology, through its innovative dual-layer structure design, achieves efficient construction of the conductive network and long-term stability of the electrode structure, demonstrating significant technological advancement and promising prospects for industrial application.

[0108] 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 negative electrode sheet, characterized in that, include Negative electrode current collector; An active material layer is disposed on the surface of the negative electrode current collector. The active material layer includes a negative electrode active material, a conductive agent, a binder, and a conductive polymer layer. The negative electrode active material includes a silicon-containing material. The negative electrode active material and the conductive agent are mixed together and bonded together by the binder. The conductive polymer layer is formed on the surfaces of adjacent negative electrode active materials and the conductive agent to form a continuous surface. The monomers of the conductive polymer layer include 3,4-ethylenedioxythiophene and pyrrole. The conductive polymer layer is obtained by constant current polymerization.

2. The negative electrode sheet according to claim 1, characterized in that, The thickness of the conductive polymer layer is 0.5-2 μm.

3. The negative electrode sheet according to claim 1, characterized in that, The molar ratio of 3,4-ethylenedioxythiophene to pyrrole is (0.01-0.1):(0.01-0.1).

4. The negative electrode sheet according to claim 3, characterized in that, The molar ratio of 3,4-ethylenedioxythiophene to pyrrole is (1-5):(1-5).

5. The negative electrode sheet according to claim 1, characterized in that, The total mass of the negative electrode active material, the binder, and the conductive agent is taken as 100%. The mass percentage of the negative electrode active material is 90.5%-93.5%; the mass percentage of the binder is 6%-9%; and the mass percentage of the conductive agent is 0.3%-0.5%.

6. The negative electrode sheet according to claim 1, characterized in that, The silicon-containing material includes one or more of silicon particles, silicon suboxide, and silicon-carbon materials.

7. The negative electrode sheet according to claim 6, characterized in that, The silicon-containing particles are selected from silicon-carbon materials, and the silicon content in the silicon-carbon materials is 40%-60% by mass.

8. The method for preparing the negative electrode sheet according to any one of claims 1-7, characterized in that, Includes the following steps: The negative electrode active material, conductive agent, and binder are mixed into a slurry and coated onto the surface of the negative electrode current collector. The polymer electrolyte forms a conductive polymer layer on the surfaces of the adjacent negative electrode active material and the conductive agent by a constant current method. The polymer electrolyte includes 3,4-ethylenedioxythiophene and pyrrole.

9. The method for preparing the negative electrode sheet according to claim 8, characterized in that, In the polymerization electrolyte, the concentration of 3,4-ethylenedioxythiophene is 0.01-0.1 mol / L; And / or, in the polymerization electrolyte, the concentration of the pyrrole is 0.01-0.1 mol / L.

10. The method for preparing the negative electrode sheet according to claim 8, characterized in that, The polymerization electrolyte also includes potassium chloride, and the concentration of potassium chloride in the polymerization electrolyte is 0.05-0.5 mol / L.

11. The method for preparing the negative electrode sheet according to claim 8, characterized in that, The polymer electrolyte also includes a pH adjuster, which includes one or more of perchloric acid, sulfuric acid, hydrochloric acid, p-toluenesulfonic acid, and trifluoromethanesulfonic acid.

12. The method for preparing the negative electrode sheet according to claim 8, characterized in that, The pH value of the polymer electrolyte is 0.1-2.

13. The method for preparing the negative electrode sheet according to claim 8, characterized in that, The constant current method uses an Ag / AgCl electrode as a reference electrode; and / or, the constant current method uses a Pt electrode as a counter electrode.

14. The method for preparing the negative electrode sheet according to claim 8, characterized in that, During the constant current method, the current is 0.2-10 mA / cm. 2 ; and / or, the reaction time is 10-600s.

15. A battery, characterized in that, It includes a positive electrode, a negative electrode, and a separator, wherein the negative electrode is the negative electrode as described in any one of claims 1-7, or the negative electrode prepared by the method described in any one of claims 8-14.

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