Pole piece, battery containing the pole piece, battery preparation method and electronic device

Abstract

The application relates to the technical field of batteries, in particular to a pole piece, a battery containing the pole piece, a battery preparation method and electronic equipment. The pole piece comprises a current collector and an electrode active material layer arranged on at least one surface of the current collector, the electrode active material layer has a porous structure, the electrode active material layer comprises an electrode active material, a binder and an interface modifier, the interface modifier comprises a fluorine-containing chain segment and an anchoring group used for anchoring on the surface of the electrode active material. The pole piece can improve electrode-electrolyte interface wettability and reduce interface impedance.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and in particular to an electrode, a battery containing the electrode, a battery preparation method, and an electronic device. Background Technology

[0002] Polymer electrolyte batteries, as an important branch of semi-solid-state batteries, have attracted much attention due to their high safety. However, existing polymer batteries suffer from problems such as insufficient wetting at the electrode-electrolyte interface and high interfacial impedance.

[0003] Existing technologies generally improve the poor electrode-electrolyte interface wettability of polymer electrolyte batteries by modifying the polymer electrolyte. For example, patent CN118943508A improves the electrolyte's wetting effect on the electrode by adding stabilizers to slow down the increase in polymer electrolyte viscosity; patent CN120413786A improves the interfacial performance between the polymer electrolyte and electrode materials by developing a three-dimensional network structure polymer electrolyte containing fluorocarbonate compounds. These solutions improve the electrolyte-electrode interface performance by modifying the electrolyte, but do not modify the electrode itself. Summary of the Invention

[0004] The present invention provides an electrode sheet that can improve the wettability of the electrode-electrolyte interface and reduce the interfacial impedance.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: An electrode includes a current collector and an electrode active material layer disposed on at least one surface of the current collector, the electrode active material layer having a porous structure; the electrode active material layer includes an electrode active material, a binder, and an interface modifier, the interface modifier including fluorine-containing segments and anchoring groups for anchoring to the surface of the electrode active material.

[0006] In some embodiments, the interface modifier is a compound having the following general structural formula: F-(CF2)nRX; Where n is an integer from 4 to 12; R is selected from single bonds, C1-C6 alkylene groups, ether groups or ester groups; X is an anchoring group, selected from hydroxyl, carboxyl, phosphate, acrylate or methacrylate groups.

[0007] In some embodiments, the number-average molecular weight of the interface modifier is 200-800.

[0008] In some embodiments, the electrode active material layer includes uniformly distributed primary pores and secondary pores, wherein the pore size of the primary pores is 0.1-1 μm and the pore size of the secondary pores is 1.0-5 μm.

[0009] In some embodiments, the electrode active material layer is formed by coating the current collector surface with an electrode slurry and curing it. The electrode slurry comprises the following components in parts by weight: 94.5-97.5 parts of electrode active material, 0.5-1.5 parts of conductive agent, 1.0-2.5 parts of binder, 0.2-2.5 parts of interface modifier, and 0.2-3.0 parts of pore-forming agent.

[0010] In some embodiments, the pore-forming agent is at least one of ammonium salt, thermally expandable polymer microspheres, and azo foaming agent modified with an activator, wherein the gas production of the ammonium salt is greater than or equal to 100 mL / g.

[0011] In some embodiments, the ammonium salt is at least one selected from ammonium carbonate, ammonium bicarbonate, and ammonium formate.

[0012] The present invention also provides a battery comprising a positive electrode, a negative electrode, a separator, and a polymer electrolyte, wherein the separator is located between the positive electrode and the negative electrode, and the positive electrode and / or the negative electrode are the aforementioned electrode plates.

[0013] The present invention also provides a method for preparing the above-mentioned battery, characterized by comprising the following preparation steps: Step 1: Assemble the positive electrode, negative electrode, and separator into a battery cell; Step 2: Inject the polymer electrolyte precursor into the cell under vacuum conditions, then polymerize it at 60-80℃ for 1-24 hours, followed by polymerization at 80-90℃ for 2-24 hours, so that the polymer electrolyte precursor is polymerized into polymer electrolyte, thus obtaining a polymer battery.

[0014] The present invention also provides an electronic device comprising the battery described above.

[0015] The beneficial effects of this invention are: By introducing interface modifiers with specific structures into the electrode active material layer, the originally hydrophobic or low surface energy polymer electrolyte can more easily spread on the electrode surface and penetrate into the porous electrode structure, thereby achieving more complete interfacial contact and significantly improving the wettability of the electrode-polymer electrolyte interface. Improved interfacial wettability reduces voids and poor contact areas at the interface, promoting efficient metal ion transport at the interface, thus significantly reducing the electrode-electrolyte interfacial resistance and improving battery rate performance and cycle stability. The interface modifier is firmly anchored to the electrode active material surface through anchoring groups, preventing migration or loss during subsequent liquid injection or hot pressing. Simultaneously, its fluorinated segments can regulate the local microenvironment, optimizing the interaction with the polymer electrolyte. Detailed Implementation

[0016] To make the objectives, technical solutions, and technical effects of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are described clearly and completely. The embodiments described below are some embodiments of the present invention, but not all embodiments. All other embodiments obtained by those skilled in the art in conjunction with the embodiments of the present invention without creative effort are within the scope of protection of the present invention. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall be followed; where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0017] In the description of this invention, the term "and / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0018] In the description of this invention, "at least one" means one or more, and "more than one" means two or more. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or multiple items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can both mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can each be single or multiple.

[0019] It should be understood that the weights of the relevant components mentioned in the embodiments of this invention can refer not only to the specific content of each component, but also to the proportional relationship between the weights of the components. Therefore, any scaling up or down of the content of the relevant components according to the embodiments of this invention is within the scope of this invention. Specifically, the weights mentioned in the embodiments of this invention can be well-known units of mass in the chemical industry, such as μg, mg, g, and kg.

[0020] Furthermore, unless the context explicitly uses it otherwise, the singular form of a word should be understood as including the plural form of that word. The terms "comprising" or "having" are intended to specify the presence of a feature, quantity, step, operation, element, part, or combination thereof, but are not intended to exclude the presence or possible addition of one or more other features, quantities, steps, operations, elements, parts, or combinations thereof.

[0021] An embodiment of the present invention provides an electrode sheet comprising a current collector and an electrode active material layer disposed on at least one surface of the current collector, the electrode active material layer having a porous structure; the electrode active material layer comprises an electrode active material, a binder, and an interface modifier, the interface modifier comprising fluorine-containing segments and anchoring groups for anchoring to the surface of the electrode active material.

[0022] This invention adds an interface modifier to the electrode active material layer. The interface modifier includes fluorinated segments and anchoring groups for anchoring to the surface of the electrode active material. The anchoring groups can form strong chemical adsorption or covalent bonds with the metal oxides or functional groups on the electrode active material surface, ensuring the stable presence of the interface modifier on the electrode surface. The fluorinated segments (such as perfluorinated segments) have low surface energy characteristics, which can effectively regulate the wetting behavior of the electrode surface. After the interface modifier is "anchored" to the electrode surface by the anchoring groups, its fluorinated segments will arrange themselves outwards in an orderly manner, spreading evenly on the electrode surface, transforming the originally high surface energy electrode surface into an ultra-low surface energy (≤25 mN / m) surface. This better matches the surface tension of the polymer precursor, resulting in a significantly reduced contact angle and easier wetting process. By in-situ and uniformly introducing modifiers during the electrode manufacturing process in conjunction with the slurry process, the interface modifiers can completely cover the surface of all active material particles of the electrode to form a low surface energy interface, including the pores between particles. This ensures that the polymer electrolyte and the electrode form a maximum and uniform physical contact area, significantly improving the wettability of the electrode-polymer electrolyte interface.

[0023] Interfacial impedance is mainly composed of contact impedance and charge transfer impedance. Sufficient and uniform wetting ensures close microscopic contact between the electrode and electrolyte, eliminating the significant impedance caused by poor contact. Simultaneously, the modifier synergistically with subsequent polymer polymerization forms a "gradual interface structure," a region of continuously changing composition and structure. This provides a continuous transport channel for metal ions (such as lithium and sodium ions) without sharp interfaces, eliminating the need for ions to cross abrupt high-energy-barrier interfaces. The dense, chemically inert fluorine molecular layer formed by fluorine-containing segments on the electrode surface effectively blocks direct contact between the polymer electrolyte / solvent and the highly active electrode surface (especially the positive electrode). This effectively suppresses side reactions such as electrolyte oxidation and decomposition during the early stages of battery cycling (formation stage), preventing the formation of an excessively thick, non-uniform, and high-impedance solid electrolyte interface film. This chemically stable interface facilitates more efficient solvation / desolvation of metal ions, i.e., reducing charge transfer impedance.

[0024] In summary, by introducing interface modifiers with specific structures into the electrode active material layer, the originally hydrophobic or low surface energy polymer electrolyte can more easily spread on the electrode surface and penetrate into the porous electrode structure, thereby achieving more sufficient interfacial contact and significantly improving the wettability of the electrode-polymer electrolyte interface. Improved interfacial wettability reduces voids and poor contact areas at the interface, promoting efficient transport of metal ions (such as lithium ions and sodium ions) at the interface, thus significantly reducing the electrode-electrolyte interfacial resistance and improving battery rate performance and cycle stability. The interface modifiers are firmly anchored to the electrode active material surface through anchoring groups, preventing migration or loss during subsequent liquid injection or hot pressing. Simultaneously, their fluorinated segments can regulate the local microenvironment, optimizing the interaction with the polymer electrolyte.

[0025] Specifically, the "gradient interface structure" refers to an integrated interface region where the composition, structure, and properties transition continuously without clear boundaries. Under the action of the interface modifier, the polymer precursor and electrode particle surface are fully wetted, forming a structure where the chemical composition transitions continuously and gradually from the interior of the electrode active material to the surface modifier molecular layer, and then to the polymer electrolyte network, without drastic abrupt changes. The electrode active material layer of this invention has a porous structure. These porous structures can be primary pores formed between the electrode active materials or secondary pores formed through certain processes, constituting a three-dimensional pore network. After the polymer precursor enters these networks, it solidifies to form a three-dimensional interpenetrating network that intertwines and permeates with the electrode skeleton, forming a gradient interface structure. The current collector-porous electrode active material layer-polymer electrolyte form a smoothly transitioning mechanical modulus structure (i.e., a gradient interface structure), which effectively buffers the stress generated by the volume expansion / contraction of the active material during charging and discharging, prevents interface delamination, and greatly improves cycle life. The electrode region, which is dominated by electronic conductivity, transitions to a mixed electronic / ionic conductivity region, and then to a polymer region, which is dominated by ionic conductivity. This provides an optimal path for charge exchange and significantly reduces charge transfer impedance.

[0026] The number-average molecular weight of the interface modifier is between 200 and 5000.

[0027] In some embodiments, the interface modifier is a compound having the following general structural formula: F-(CF2) n -RX; Where n is an integer from 4 to 12; R is selected from single bonds, C1-C6 alkylene groups, ether groups or ester groups; X is an anchoring group, selected from hydroxyl, carboxyl, phosphate, acrylate or methacrylate groups.

[0028] The perfluoroalkylene chain segments are limited to n=4-12 to ensure that the fluorinated chains have sufficient length to form a stable low surface energy layer (≤ 25 mN / m). This avoids excessively long chains that would lead to excessive molecular rigidity, difficulty in orderly arrangement on the electrode surface, or interference with ion transport. A suitable chain length balances hydrophobicity / low surface energy characteristics with molecular flexibility / spreading ability, enabling the modifier to form a dense and continuous fluorinated interface layer on the inner wall of the porous electrode. The core role of the R group is to balance molecular flexibility and chemical stability, ensuring effective connection between the perfluoro chain segments and the anchoring group X, while remaining inert under the battery's operating voltage. The X group is crucial in determining whether the modifier can be firmly and stably bonded to the electrode surface; it exhibits strong adsorption and weak reactivity.

[0029] Ether groups have similar polarity to ether oxygen bonds and carbonate solvents in polymer electrolytes, exhibiting good compatibility and enhancing molecular chain flexibility, which facilitates dense arrangement at the electrode interface. C1-C6 alkylene groups possess extremely high chemical inertness; saturated alkanes are extremely stable throughout the battery voltage window (0-4.5V), making them difficult to oxidize or reduce. Alkylene chains provide steric buffers, preventing excessive crowding of fluorinated segments and promoting their extension on the electrode surface. Ester groups (-CH2-C(O)O-CH2-) can act as additional hydrogen bond acceptors, forming stronger interactions with electrode binders (such as polyacrylic acid) or the surface of active materials, enhancing the immobilization ability of modifiers. Single-bond connections enable shortest path anchoring, suitable for thickness-sensitive ultrathin electrode systems.

[0030] X is limited to -OH, -COOH, -PO3H2, acrylate (-OC(O)CH=CH2) or methacrylate (-OC(O)C(CH3)=CH2). These groups can all undergo strong chemisorption or coordination with electrode active materials (such as -OH on the surface of transition metal oxides or metal sites). In particular, acrylate / methacrylate end groups can not only be physically adsorbed, but also participate in free radical copolymerization reactions during the subsequent thermal polymerization of polymer electrolyte precursors, chemically bonding the interface modifier to the polymer electrolyte network, forming a three-in-one covalently linked interface of "electrode-modifier-electrolyte", which greatly improves the interfacial bonding strength and long-term cycling stability.

[0031] The interface modifier of the present invention has a linear molecular structure. Compared with branched or star-shaped structures, linear molecular configuration is easier to disperse uniformly in electrode slurry and is less prone to phase separation or aggregation during coating and drying process. This ensures that the modifier is uniformly covered on the surface of electrode active material particles and the inner wall of pores, avoiding ion transport obstruction caused by local high concentration.

[0032] In summary, this invention limits the interface modifier to F-(CF2). n-RX type linear fluorinated compounds, with precise control over their chain length (n), linker (R), and functional end groups (X), not only ensure that the fluorinated segments effectively construct ultra-low surface energy interfaces to promote polymer electrolyte wetting, but also achieve strong anchoring, good dispersibility, and potential chemical coupling with the electrolyte network through tunable R groups and multifunctional X end groups, thereby further enhancing interface stability, reducing interface impedance, and improving the overall electrochemical performance of the battery.

[0033] Specifically, the structural formula of the ether group is -(CH2). a -O-(CH2) b - where a takes the value 1, 2, or 3, and b takes the value 1, 2, or 3. By controlling the chain length, we can avoid excessively long chains (total number of carbon atoms > 6) that would make the molecules too hydrophilic and weaken their interfacial stability.

[0034] In some embodiments, the number-average molecular weight of the interface modifier is 200-800. If the molecular weight is too small, it cannot form a dense, complete monolayer, resulting in incomplete interface coverage and high local impedance. Furthermore, compounds with excessively low molecular weight have low boiling points, poor gas and thermal stability, and are easily volatile, leading to easy loss during electrode drying or high-temperature battery operation, thus easily causing the interface modification effect to fail. On the other hand, small molecules have strong diffusion capabilities and easily migrate from the electrode interior to the bulk electrolyte, making it difficult to stably position at the electrode interface, resulting in a short-lasting effect. When the molecular weight is too large, the large molecules face high migration resistance in the nanoscale pores of the electrode slurry, making it difficult to effectively reach the target interface, leading to uneven modification. Moreover, excessively large molecules may form an excessively thick interface layer, significantly hindering lithium-ion transport and increasing charge transfer impedance. Excessive molecular weight also leads to excessively high electrode slurry viscosity, affecting rheological properties, causing uneven coating, and severely impacting battery manufacturing yield. It can also cause excessive residue, triggering side reactions and reducing energy density.

[0035] In some embodiments, the interface modifier is at least one selected from 2-(perfluorobutyl)ethyl acrylate, 2-(perfluorohexyl)ethyl acrylate, 2-(perfluorobutyl)ethyl methacrylate, 2-(perfluorohexyl)ethyl methacrylate, 1H,1H,7H-dodecylheptyl methacrylate, 1H,1H,2H,2H-perfluorooctanephosphonic acid, 1H,1H-perfluoro-1-heptanol, perfluoropentyl ethyl acrylate, fluoroethylene carbonate derivatives, perfluoropolyether alcohols, perfluorobutyl phosphate, and perfluorohexyl methacrylate.

[0036] The structural formulas and CAS numbers of the above-mentioned interface modifiers are as follows: 2-(Perfluorobutyl)ethyl acrylate: F-(CF2)4-CH2CH2-OC(O)-CH=CH2, CAS: 52591-27-2; 2-(Perfluorohexyl)ethyl acrylate: F-(CF2)6-CH2CH2-OC(O)-CH=CH2, CAS: 17527-29-6; 2-(Perfluorobutyl)ethyl methacrylate: F-(CF2)4-CH2CH2-OC(O)-C(CH3)=CH2, CAS: 1799-84-4; 2-(perfluorohexyl)ethyl methacrylate: F-(CF2)6-CH2CH2-OC(O)-C(CH3)=CH2, CAS: 2144-53-8; 1H,1H,7H-Dodecylfluoroheptylmethacrylate: F-(CF2)7-CH2-OC(O)-C(CH3)=CH2, CAS: 2261-99-6; 1H,1H,2H,2H-Perfluorooctanephosphonic acid: F-(CF2)6-CH2CH2-P(O)(OH)2, CAS: 252237-40-4; 1H,1H-perfluoro-1-heptanol: F-(CF2)6-CH2-OH, CAS: 375-82-6; Perfluoropentyl ethyl acrylate: C5F 11 C2H4OC(O)CH=CH2; Fluoroethylene carbonate derivatives: F-(CF2)4-OC(O)-O-CH=CH2; Perfluoropolyether alcohol: F-(CF2)6-CH2-O-CH2-OH; Perfluorobutyl phosphate: F-(CF2)4-CH2-PO3H2; Perfluorohexyl methacrylate: F-(CF2)6-CH2-OC(O)C(CH3)=CH2.

[0037] In some embodiments, the electrode active material layer includes uniformly distributed primary pores and secondary pores, wherein the pore size of the primary pores is 0.1-1 μm and the pore size of the secondary pores is 1.0-5 μm.

[0038] Primary and secondary pores form a pore network, which, combined with the action of interface modifiers, achieves deep and uniform wetting of the polymer electrolyte precursor. After curing, a gradient interface structure is formed, thereby reducing the interfacial impedance to ≤25Ω·cm. 2 the following.

[0039] Primary porosity is an "inherent property" of the electrode, namely the pores between slurry particles, which ensures basic reactivity. Secondary porosity is formed by the thermal decomposition of a pore-forming agent introduced in this invention, providing efficient transport kinetics.

[0040] In some embodiments, the electrode active material layer is formed by coating the current collector surface with an electrode slurry and curing it. The electrode slurry comprises the following components in parts by weight: 94.5-97.5 parts of electrode active material, 0.5-1.5 parts of conductive agent, 1.0-2.5 parts of binder, 0.2-2.5 parts of interface modifier, and 0.2-3.0 parts of pore-forming agent.

[0041] When the amount of interface modifier added is too small, the modifier molecules are insufficient to form a complete and continuous monomolecular coating on the electrode surface and the inner surface of the pores. A large number of unmodified "blank areas" exist on the electrode surface or in the pores. The polymer precursor tends to wet the modified low-energy areas and repel the unmodified high-energy areas, resulting in uneven interface wetting. Moreover, the unmodified "blank areas" are in direct contact with the electrolyte, which easily leads to side reactions and the formation of a thick and uneven passivation layer. At the same time, the discontinuous interface causes the ion transport path to be tortuous and unsmooth, which in turn leads to a decrease in battery energy efficiency, poor rate performance, increased battery internal resistance, and severe charge-discharge polarization. On the other hand, since the unmodified "blank areas" are in direct contact with the electrolyte, they are prone to side reactions, which lead to interface instability. The unstable interface causes continuous consumption of electrolyte and active lithium during cycling, which ultimately leads to rapid capacity decay, shortened lifespan, reduced coulombic efficiency, and a rapid decrease in battery reversible capacity. When the amount of interface modifier added is too large, the excess modifier may block the internal pore structure of the electrode, leading to obstruction of ion transport channels, decreased ionic conductivity, deterioration of electrode kinetic performance, and reduction of rate performance. Moreover, excessive low surface tension substances can easily interfere with the network formation of the binder, reduce adhesion, and lead to a decrease in electrode mechanical strength. During cycling, it is prone to powdering and peeling, causing the electrode active material layer to lose contact with the current collector, damaging the structural integrity of the electrode, and resulting in a decrease in battery life. Interface modifiers themselves are electrochemically inert, and excessive addition directly reduces the proportion of active material, resulting in a decrease in battery volume / mass energy density, a reduction in battery capacity per unit volume or weight, and an increase in raw material costs. In extreme cases, the agglomerates of some excessive modifiers may become active sites for electrochemical reactions, triggering unnecessary decomposition reactions, leading to increased gas production and reduced safety.

[0042] In this invention, by adding a pore-forming agent to the electrode slurry, the pore-forming agent decomposes under heat during the slurry curing process, forming large secondary pores inside the electrode. This provides a low-resistance, highly permeable main channel for the rapid injection of polymer precursors and the rapid migration of lithium ions, significantly improving the electrode-polymer electrolyte wetting efficiency and reducing the bulk ion transport impedance of the electrode. On the other hand, the capillary action of the pores ensures that the polymer precursor can penetrate deep into the electrode, up to the current collector interface, achieving complete activation of the electrode from the surface to the interior, maximizing the utilization rate of active materials, and avoiding performance degradation and safety risks caused by uneven wetting. The macroscopic pores created by the pore-forming agent provide space for the embedding of the polymer network, while the interface modifier ensures that the polymer can be perfectly spread and combined in these spaces and smaller primary pores, forming a stable three-dimensional interpenetrating and mechanically interlocked structure between the polymer electrolyte and the electrode. The secondary pores formed by the pore-forming agent provide a buffer space for the expansion and contraction of the active material during charging and discharging, thereby improving the cycle life of the battery. The secondary pores also act as ion "reservoirs" and "channels", reducing concentration polarization under high current and improving rate performance.

[0043] In some embodiments, the pore-forming agent is at least one of ammonium salt, thermally expandable polymer microspheres, and azo foaming agent modified with an activator, wherein the gas production of the ammonium salt is greater than or equal to 100 mL / g.

[0044] In some embodiments, the ammonium salt is at least one selected from ammonium carbonate, ammonium bicarbonate, and ammonium formate.

[0045] The thermally expandable polymer microspheres consist of a polymer shell encapsulating low-boiling-point hydrocarbon gases, and the polymer shell is at least one of PMMA and vinylidene chloride-acrylonitrile copolymer.

[0046] Preferably, the thermally expandable polymer microspheres are selected from the Expancell series and the acrylonitrile copolymer Matsumoto Microsphere series. Specifically, the Expancell series is 461DU20 or 820DU40; the acrylonitrile copolymer Matsumoto Microsphere series is F-50 and F-80.

[0047] This invention modifies azo-based foaming agents using an activator to match their decomposition characteristics with the electrode preparation process, ensuring that their decomposition products are harmless to the battery system. Specifically, the azo-based foaming agent of this invention is azodicarbonamide (AC), preferably ultrafine AC such as AC-150, AC-135, AC-03, and AC-05. The activator is at least one of zinc oxide, urea, PbO, MgO, zinc citrate, citric acid, adipic acid, and phthalic anhydride. The modification method can be a physical blending method, which is existing technology and will not be described in detail here.

[0048] The present invention also provides a battery comprising a positive electrode, a negative electrode, a separator, and a polymer electrolyte, wherein the separator is located between the positive electrode and the negative electrode, and the positive electrode and / or the negative electrode are the aforementioned electrode plates.

[0049] The present invention also provides a method for preparing the above-mentioned battery, characterized by comprising the following preparation steps: Step 1: Assemble the positive electrode, negative electrode, and separator into a battery cell; Step 2: Inject the polymer electrolyte precursor into the cell under vacuum conditions, then polymerize it at 60-80℃ for 1-24 hours, followed by polymerization at 80-90℃ for 2-24 hours, so that the polymer electrolyte precursor is polymerized into polymer electrolyte, thus obtaining a polymer battery.

[0050] The preparation method of this invention employs a gradient polymerization approach, first polymerizing at 60-80℃, and then polymerizing again at 80-90℃. This solves the fundamental problem of traditional one-step polymerization methods, namely, "curing begins before wetting is complete." The gradient polymerization of this invention, through precise control of the polymerization reaction kinetics, achieves "full wetting" and "complete curing" in stages, resulting in uniform wetting and curing, forming a stable integrated electrode-electrolyte structure with continuous transition characteristics.

[0051] The first stage (low-temperature stage, 60-80℃) is mainly the wetting stage. At lower temperatures, the polymerization reaction is slow to initiate, and the system viscosity increases slowly over time, providing ample time for wetting. The electrolyte enters the primary and secondary pores of the electrode through capillary forces, achieving uniform wetting. The second stage (high-temperature stage, 80-90℃) achieves complete solidification, with polymerization occurring rapidly and completely. Rapid heating can lead to localized preferential solidification, causing unevenness and microphase separation. Gradient polymerization can avoid this separation. Furthermore, existing processes involve high-temperature static setting after electrolyte injection to accelerate wetting, followed by high-temperature formation. Gradient polymerization is more compatible with existing polymer lithium-ion battery manufacturing processes.

[0052] The present invention also provides an electronic device comprising the aforementioned battery. Specifically, the electronic device may be an electric vehicle, an energy storage system, or a consumer electronics product.

[0053] To enable those skilled in the art to clearly understand the above-described implementation details and operations of the present invention, and to demonstrate the significant advancements in the performance of the embodiments of the present invention, the following examples illustrate the above technical solutions. Example 1

[0054] (1) Cathode preparation: Lithium iron phosphate, acetylene black, PVDF, interface modifier, and pore-forming agent were mixed at a mass ratio of 96:1:1.5:1:1.5. The interface modifier was... The pore-forming agent is ammonium carbonate, prepared into a slurry with a solid content of 65% using NMP as a solvent. This slurry is coated onto both surfaces of an aluminum foil current collector, and after vacuum drying at 120℃ and cold pressing, a positive electrode is obtained with a compaction density of 2.45 g / cm³. 3 The primary pores have a diameter of 0.5 μm, and the secondary pores have a diameter of 2.2 μm.

[0055] (2) Preparation of negative electrode: Graphite, conductive agent acetylene black (SP), binder styrene-butadiene rubber and thickener sodium carboxymethyl cellulose are mixed thoroughly in N-methylpyrrolidone solvent at a mass ratio of 98.1:0.5:0.7:0.7 to obtain negative electrode slurry. The slurry is coated on both sides of Cu foil under vacuum at 105°C. After rolling and slitting, the negative electrode is obtained.

[0056] (2) Assembly of polymer batteries: The positive electrode, separator (Celgard 2320), and negative electrode are assembled into a cell, and a PEGDA-based polymer electrolyte precursor containing 1.0M LiPF6 is injected. Then, gradient polymerization is carried out according to the following method: Phase 1: Maintain at 65℃ for 12 hours; Second stage: Maintain at 85℃ for 8 hours; The polymer electrolyte is cured to obtain a polymer battery. Example 2

[0057] The difference from Example 1 lies in the preparation of the positive electrode: The mass ratio of lithium iron phosphate, acetylene black, PVDF, interface modifier, and porogen was 95:1.2:2:0.8:2. The porogen was PMMA thermally expandable microspheres (Expancel 461DU20). The gradient polymerization conditions were: first stage polymerization at 65℃ for 18 h, and second stage polymerization at 85℃ for 10 h. The resulting positive electrode active material layer had a primary pore size of 0.5 μm and a secondary pore size of 3.1 μm. Example 3

[0058] The difference from Example 1 lies in the preparation of the positive electrode: The mass ratio of lithium iron phosphate, acetylene black, PVDF, interface modifier, and pore-forming agent was 94.8:0.8:2.2:1.5:2.5. The interface modifier had the structural formula F-(CF2)4-OC(O)-O-CH=CH2. The gradient polymerization conditions were: first stage polymerization at 75℃ for 8 hours, and second stage polymerization at 90℃ for 6 hours. The resulting positive electrode active material layer had a primary pore size of 0.6 μm and a secondary pore size of 3.7 μm. Example 4

[0059] The difference from Example 1 lies in the preparation of the positive electrode: lithium iron phosphate, acetylene black, PVDF, interface modifier, and pore-forming agent are prepared in a mass ratio of 96.8:1:1.5:0.2:1.5. Example 5

[0060] The difference from Example 1 lies in the preparation of the positive electrode: lithium iron phosphate, acetylene black, PVDF, interface modifier, and pore-forming agent are prepared in a mass ratio of 94.5:1:1.5:2.5:1.5. Example 6

[0061] (1) Preparation of the positive electrode: Lithium iron phosphate, acetylene black, PVDF, interface modifier, and pore-forming agent were mixed in a mass ratio of 96.2:0.9:1.4:0.5:1.0. The interface modifier was 2-(perfluorohexyl)ethyl methacrylate (CAS: 2144-53-8, structure: F-(CF2)6-CH2CH2-OC(O)-C(CH3)=CH2), and the pore-forming agent was ammonium bicarbonate (gas production ≥120mL / g). A slurry with a solid content of 65% was prepared using NMP as a solvent. After coating onto both sides of the aluminum foil current collector, the positive electrode was obtained by vacuum drying at 120℃ and cold pressing, with a compaction density of 2.42g / cm³. 3 The primary pore diameter is 0.4 μm, and the secondary pore diameter is 2.5 μm.

[0062] (2) Negative electrode preparation: completely consistent with Example 1.

[0063] (3) Assembly of polymer batteries: Consistent with Example 1, except that the gradient polymerization conditions are adjusted as follows: Phase 1: Maintain at 70℃ for 10 hours; Second stage: Maintain at 88℃ for 6 hours. Example 7

[0064] (1) Preparation of the positive electrode: NCM811 (ternary positive electrode active material), acetylene black, PVDF, interface modifier, and pore-forming agent were mixed at a mass ratio of 95.5:1.1:1.8:1.2:0.4. The interface modifier was 1H,1H,2H,2H-perfluorooctanephosphonic acid (CAS: 252237-40-4, structure: F-(CF2)6-CH2CH2-P(O)(OH)2), and the pore-forming agent was ammonium formate (gas production ≥110mL / g). A slurry with a solid content of 64% was prepared using NMP as solvent. After coating onto both sides of the aluminum foil current collector, the positive electrode was obtained by vacuum drying at 125℃ and cold pressing, with a compaction density of 2.50g / cm³. 3 The primary pore diameter is 0.6 μm, and the secondary pore diameter is 1.8 μm.

[0065] (2) Negative electrode preparation: completely consistent with Example 1.

[0066] (3) Assembly of polymer batteries: Consistent with Example 1, except that the gradient polymerization conditions are adjusted as follows: Phase 1: Maintain at 68℃ for 15 hours; Second stage: Maintain at 82℃ for 10 hours. Example 8

[0067] (1) Cathode preparation: Lithium iron phosphate, acetylene black, PVDF, and interface modifier were mixed at a mass ratio of 94.7:1.3:2.0:2.0. The interface modifier used was 1H,1H-perfluoro-1-heptanol (CAS: 375-82-6, structure: A slurry with a solid content of 66% was prepared using NMP as a solvent. This slurry was coated onto both sides of an aluminum foil current collector, vacuum dried at 115℃, and cold-pressed to obtain the positive electrode, with a compacted density of 2.48 g / cm³. 3 The primary pore size is 0.5μm, with no obvious secondary pores.

[0068] (2) Negative electrode preparation: completely consistent with Example 1.

[0069] (3) Assembly of polymer batteries: Consistent with Example 1, except that the gradient polymerization conditions are adjusted as follows: Phase 1: Maintain at 62℃ for 18 hours; Second stage: Maintain at 86℃ for 9 hours.

[0070] Comparative Example 1 The difference from Example 1 lies in the preparation of the positive electrode: Comparative Example 1: No interface modifiers or pore-forming agents were added. The mass ratio of lithium iron phosphate, acetylene black, and PVDF was 98:1:1. The polymerization process was a one-step polymerization at 85℃ for 20 hours.

[0071] Comparative Example 2 The difference from Example 1 lies in the preparation of the positive electrode: In Comparative Example 2, no porogen was added. Lithium iron phosphate, acetylene black, PVDF, and interface modifier were mixed in a mass ratio of 97.5:1:1.5:1. The interface modifier used was perfluorooctanoic acid (PFOA).

[0072] Comparative Example 3 The difference from Example 1 lies in the preparation of the positive electrode: Comparative Example 3 did not add any interface modifiers. The mass ratio of lithium iron phosphate, acetylene black, PVDF, and porogen was 97:1:1.5:1.5, and the porogen used was ammonium oxalate.

[0073] Comparative Example 4 The difference from Example 1 is as follows: No interface modifier was added to the positive electrode of Comparative Example 4. The positive electrode formulation was lithium iron phosphate, acetylene black, PVDF, and pore-forming agent in a mass ratio of 97:1:1.5:1.5. An interface modifier F-(CF2)6-CH2-O-CH2-OH, accounting for 1% of the total mass of the polymer electrolyte precursor, is added to the polymer electrolyte precursor.

[0074] Comparative Example 5 The difference from Example 1 lies in the preparation of the positive electrode: the mass ratio of lithium iron phosphate, acetylene black, PVDF, interface modifier and pore-forming agent is 93:1:1.5:4:1.5.

[0075] Performance testing The batteries prepared in each embodiment and comparative example were subjected to the following performance tests, and the test results are recorded in Table 1.

[0076] (1) Interface impedance test: Electrochemical impedance spectroscopy was used for the test, with a test frequency range of 100kHz-10mHz, an amplitude of 10mV, and a test temperature of 25℃. (2) Cyclic performance test: At 25℃, charge and discharge cycle test is performed at a 1C rate within a voltage range of 2.5-3.65V; (3) Energy efficiency test: At 25℃, the ratio of discharge energy to charging energy is tested at a rate of 0.5C. (4) Gas production analysis: The amount of H2 and CO2 generated during the cycle was monitored by online differential electrochemical mass spectrometry.

[0077] Table 1 Examples 1-8 achieved a significant reduction in interfacial impedance (≤25Ω·cm) through the synergistic effect of interface modifiers and porogens combined with gradient polymerization. 2 It also has excellent cycle performance (capacity retention ≥85%).

[0078] Comparative Example 1 shows that in the absence of functional additives (interface modifiers and pore-forming agents), the interfacial impedance is high, the cycle performance is poor, and gas production is severe.

[0079] Comparative Example 2 shows that the use of an incompatible interface modifier (PFOA) leads to performance degradation and the highest gas production, demonstrating the importance of material selection in this invention.

[0080] Comparative Example 3 shows that although using an unsuitable pore-forming agent (ammonium oxalate) can improve some properties, the effect is limited and more gas is generated.

[0081] Comparative Example 4 demonstrates that adding the interface modifier to the electrolyte instead of the electrode cannot achieve the technical effect of this invention. Comparative Example 5 shows that although excessive addition of the interface modifier can maintain low gas production, the interface impedance increases, proving the necessity of precise dosage control.

[0082] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. An electrode sheet, characterized in that, The device includes a current collector and an electrode active material layer disposed on at least one surface of the current collector, the electrode active material layer having a porous structure; the electrode active material layer includes an electrode active material, a binder, and an interface modifier, the interface modifier including fluorinated segments and anchoring groups for anchoring to the surface of the electrode active material.

2. The electrode sheet according to claim 1, characterized in that, The interface modifier is a compound having the following general structural formula: F-(CF2) n -R-X; Where n is an integer from 4 to 12; R is selected from single bonds, C1-C6 alkylene groups, ether groups or ester groups; X is an anchoring group, selected from hydroxyl, carboxyl, phosphate, acrylate or methacrylate groups.

3. The electrode sheet according to claim 2, characterized in that, The number-average molecular weight of the interface modifier is 200-800.

4. The electrode sheet according to claim 1, characterized in that, The electrode active material layer includes uniformly distributed primary pores and secondary pores, wherein the pore size of the primary pores is 0.1-1 μm and the pore size of the secondary pores is 1.0-5 μm.

5. The electrode sheet according to claim 1, characterized in that, The electrode active material layer is formed by coating the current collector surface with electrode slurry and curing it. The electrode slurry comprises the following components in parts by mass: 94.5-97.5 parts of electrode active material, 0.5-1.5 parts of conductive agent, 1.0-2.5 parts of binder, 0.2-2.5 parts of interface modifier, and 0.2-3.0 parts of pore-forming agent.

6. The electrode sheet according to claim 5, characterized in that, The pore-forming agent is at least one of ammonium salt, thermally expandable polymer microspheres, and azo foaming agent modified with an activator, wherein the gas production of the ammonium salt is greater than or equal to 100 mL / g.

7. The electrode sheet according to claim 6, characterized in that, The ammonium salt is at least one of ammonium carbonate, ammonium bicarbonate, and ammonium formate.

8. A battery, characterized in that, It includes a positive electrode, a negative electrode, a separator, and a polymer electrolyte, wherein the separator is located between the positive electrode and the negative electrode, and the positive electrode and / or the negative electrode is the electrode sheet according to any one of claims 1-7.

9. The method for preparing a battery as described in claim 8, characterized in that, The preparation steps include the following: Step 1: Assemble the positive electrode, negative electrode, and separator into a battery cell; Step 2: Inject the polymer electrolyte precursor into the cell under vacuum conditions, then polymerize it at 60-80℃ for 1-24 hours, followed by polymerization at 80-90℃ for 2-24 hours, so that the polymer electrolyte precursor is polymerized into polymer electrolyte, thus obtaining a polymer battery.

10. An electronic device, characterized in that, This includes the battery as described in claim 8 or the battery prepared by the method of claim 9.

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