Secondary batteries and electronic devices

Abstract

The present invention provides a secondary battery and an electronic device. The secondary battery includes a positive electrode piece, the positive electrode piece includes a positive electrode current collector and a positive electrode film layer, the positive electrode film layer is provided on at least one side of the positive electrode current collector, the positive electrode film layer includes a positive electrode active material and organic particles provided on the surface of the positive electrode active material, the organic particles generate a thermal polymerization reaction under heat treatment conditions to form an insulating layer that covers at least a part of the surface of the positive electrode active material. When the adhesion between the positive electrode film layer and the positive electrode current collector before and after the heat treatment and the resistance of the positive electrode piece before and after the heat treatment satisfy a suitable relationship, the secondary battery can have better safety characteristics and cycle characteristics.

Description

[Technical Field]

[0001] Cross-Reference to Related Applications This application claims the priority of the Chinese patent application with application number 202310258701.4 filed on March 17, 2023, entitled "Secondary Battery and Electronic Device", the entire content of which is incorporated herein by reference.

[0002] Technical Field The present invention relates to the technical field of batteries, in particular to a secondary battery and an electronic device. [Background Art]

[0003] With the development of battery technology, the performance of batteries can gradually meet the general application requirements of various devices, so that batteries are widely applied in devices such as household appliances, power devices and energy storage devices. Here, safety performance and cycle performance are two fundamental performances when batteries are applied in various devices. However, during thermal runaway, the safety performance and cycle performance of batteries degrade, which may affect the normal operation of various devices. [Summary of Invention]

[0004] The present invention provides a secondary battery and an electronic device, wherein the secondary battery has better safety performance and cycle performance.

[0005] In a first aspect, the present invention provides a secondary battery. The secondary battery includes a positive electrode piece, the positive electrode piece includes a positive electrode current collector and a positive electrode film layer, the positive electrode film layer is provided on at least one side of the positive electrode current collector, the positive electrode film layer includes a positive electrode active material and organic particles provided on the surface of the positive electrode active material, the organic particles undergo a thermal polymerization reaction under heat treatment conditions to form an insulating layer that covers at least a portion of the surface of the positive electrode active material, when the adhesive force between the positive electrode current collector and the positive electrode film layer before heat treatment of the positive electrode piece is F1 N / m, and the adhesive force between the positive electrode current collector and the positive electrode film layer after heat treatment of the positive electrode piece is F2 N / m, then F1 and F2 satisfy 1 ≤ F2 / F1 ≤ 2, and the resistance of the positive electrode piece before heat treatment is R 前 When R 前 The resistance is 1Ω to 3Ω, and the resistance of the positive electrode piece after heat treatment is R. 後 When R 前 and R 後 R 後 -R 前 The resistance of the positive electrode piece satisfies ≥1Ω, and the measurement area is 153.94mm². 2 This is obtained by measurement under room temperature conditions where the pressing force is 3.5t and the holding time is 50s.

[0006] In the secondary battery provided by the present invention, the organic particles can undergo a thermal polymerization reaction under heat treatment conditions to form an insulating layer covering at least a part of the surface of the positive electrode active material. On one hand, the insulating layer formed by the thermal polymerization reaction can enhance the structural stability of the positive electrode active material and make it less prone to phase transition at high temperatures. Furthermore, the insulating layer increases the resistance of the positive electrode sheet, reduces the contact current when a short circuit occurs between the positive electrode sheet and the negative electrode sheet in the secondary battery, and can reduce heat generation. On the other hand, after undergoing the thermal polymerization reaction, the organic particles can contribute to improving the adhesive force between the positive electrode film layer and the positive electrode current collector. When F1 and F2 satisfy the above relationship, the risk of the positive electrode film layer falling off from the positive electrode current collector at high temperatures can be reduced. Therefore, enabling the organic particles to undergo a thermal polymerization reaction under heat treatment conditions can improve the safety performance of the secondary battery. In addition, since the probability that the organic particles undergo a thermal polymerization reaction in a normal temperature atmosphere is low, the influence on the electrochemical performance of the secondary battery can be reduced. At high temperatures, the insulating layer formed by the thermal polymerization reaction of the organic particles that covers at least a part of the surface of the positive electrode active material can reduce the probability of the positive electrode active material coming into contact with the electrolyte at high temperatures. And, the resistance R of the positive electrode sheet before heat treatment 前 is 1 Ω to 3 Ω, and the resistance R after heat treatment 後 and R 前 satisfy R 後 -R 前 ≧1 Ω. Thereby, when the secondary battery is at high temperature, not only the risk of thermal runaway of the secondary battery is reduced, but the secondary battery also has good cycle performance at high temperature. Therefore, the secondary battery provided by the present invention has good safety performance and cycle performance.

[0007] According to any one of the above embodiments of the first aspect of the present invention, F1 and F2 satisfy 1.2≦F2 / F1≦1.6. When F2 / F1 is within the above range, the risk of the positive electrode film layer falling off from the positive electrode current collector can be further reduced, and the safety performance of the secondary battery can be further improved.

[0008] According to any one of the above embodiments of the first aspect of the present invention, F1 is 10 to 30.

[0009] According to any of the above embodiments of the first aspect of the present invention, R 後 R is ≥2.1Ω. 後 When the above range is maintained, the occurrence of thermal runaway in secondary batteries can be further reduced, and safety characteristics can be further improved.

[0010] According to any of the above embodiments of the first aspect of the present invention, the organic particles comprise at least one monomer from formulas I, II, and III, and / or It comprises an oligomer formed from at least one monomer from formulas I, II, and III, The structures of Equations I, II, and III are as follows: [ka] R1 includes one or more of the following: hydrogen, methyl group, ethyl group, amino group, hydroxyl group, and metal ions. R2 is Imino base and Hosfinidene Includes one or more of the elements, R3 is C5-C6 cycloalkyl Ren C5-C6 cycloalkyl groups containing and / or substituted with one or more of fluorine, chlorine, bromine, nitrogen, and phosphorus. Ren Includes the base.

[0011] In the above embodiment, the organic particles containing the monomer and / or oligomer formed from the monomer readily undergo thermal polymerization at high temperatures to form an insulating layer that covers the surface of the positive electrode active material. This rapidly increases the resistance of the secondary battery at high temperatures, reduces the current when a short circuit occurs, and contributes to improving the safety characteristics of the secondary battery.

[0012] According to any of the above embodiments of the first aspect of the present invention, the monomer comprises one or more of maleimide, bismaleimide, pyrrole, and 2,5-dimethylpyrrole.

[0013] According to any of the above embodiments of the first aspect of the present invention, the number average molecular weight of the oligomer is 2000 or less than 2000.

[0014] According to any of the above embodiments of the first aspect of the present invention, the oligomer includes one or more of maleimide oligomers and bismaleimide oligomers.

[0015] According to any of the above embodiments of the first aspect of the present invention, the mass percentage m of the organic particles in the positive electrode membrane layer is 0.3% to 2%. When the mass percentage m of the organic particles in the positive electrode membrane layer falls within the above range, the resistance of the positive electrode sheet after heat treatment can be further increased, thereby improving the safety performance of the secondary battery at high temperatures.

[0016] According to any of the above embodiments of the first aspect of the present invention, the thickness D of the positive electrode membrane layer and the mass percentage m of the organic particles in the positive electrode membrane layer satisfy at least one of the following features. I) When the thickness D of the positive electrode membrane layer satisfies 30 μm ≤ D ≤ 100 μm, the mass percentage m of the organic particles in the positive electrode membrane layer satisfies 1% ≤ m ≤ 2%. II) When the thickness D of the positive electrode membrane layer satisfies 100 μm < D ≤ 200 μm, the mass percentage m of the organic particles in the positive electrode membrane layer satisfies 0.3% ≤ m ≤ 1%.

[0017] According to any of the above embodiments of the first aspect of the present invention, the heat treatment is placing the positive electrode sheet in an atmosphere at a temperature of 120°C to 140°C for 60 minutes. When the heat treatment temperature falls within the above range, the safety performance of the secondary battery at high temperatures is improved, and the secondary battery can operate normally under high temperature conditions.

[0018] In a second aspect, the present invention provides an electronic device including the secondary battery according to any one of the embodiments of the first aspect of the present invention.

[0019] The above description is merely an outline of the proposed technical solution of the present invention. In order to more clearly understand the technical solution of the present invention and to implement it in accordance with the specifications, and in order to more clearly understand the above and other objectives, features and advantages of the present invention, specific embodiments of the present invention will be described below. [Brief explanation of the drawing]

[0020] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings that need to be used in the embodiments of the present invention are briefly introduced below. Obviously, the drawings described below represent only a few embodiments of the present invention, and those skilled in the art can obtain other drawings based on these without any creative effort. [Figure 1] Figure 1 is a schematic diagram showing the cross-sectional structure of a positive electrode piece according to several embodiments of the present invention. [Explanation of Symbols]

[0021] 10-positive electrode piece, 11-positive electrode current collector, 12-positive electrode membrane layer, 121-positive electrode active material, 122-organic particles. [Modes for carrying out the invention]

[0022] The following examples are provided solely to illustrate the technical concept of the present invention and are therefore illustrative only, and do not limit the scope of protection of the present invention.

[0023] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which the present invention pertains. The terms used herein are for illustrative purposes only and are not intended to limit the present invention. The terms “including” and “having” in the specification and claims of the present invention, and any variations thereof, are intended to include non-exclusive inclusion.

[0024] In this specification, “Examples” means that certain features, structures, or properties described in relation to the Examples may be included in at least one example of the Invention. The phrase “Examples” appearing in various parts of the Specification does not necessarily refer to the same Example, nor does it refer to separate or alternative Examples that are mutually exclusive with each other. Those skilled in the art will understand, both explicitly and implicitly, that the Examples described herein may be combined with other Examples.

[0025] In describing embodiments of the present invention, the term "and / or" simply describes the relationship between related objects, indicating that three relationships are possible. For example, "A and / or B" can represent three situations: A existing alone, A and B existing simultaneously, and B existing alone. In this specification, the letter " / " usually indicates an "or" relationship between the preceding and following related objects.

[0026] In the description of embodiments of the present invention, unless otherwise specified, "greater than or equal to" and "less than or equal to" include a reference quantity, and "multiple types" and "multiple" in "one or more types" and "one or more" mean two or more types (pieces).

[0027] The grouping of alternative elements or embodiments disclosed herein should not be construed as limiting. Each group member may be adopted and claimed independently, or adopted and claimed in any combination with other members of the group or other elements found herein. One or more members of a group may be included in or removed from a group for convenience and / or patentability reasons. In any event of such inclusion or removal, this specification shall be deemed to include the modified group and thus satisfy the written description of all Markush groups used in the claims.

[0028] It will be apparent to those skilled in the art that various modifications and changes can be made to the present invention without departing from the scope of protection. Therefore, the present invention is intended to cover modifications and changes to the present invention that fall within the corresponding claims (the scope of protection claimed) and their equivalent scope. Furthermore, embodiments relating to the examples of the present invention can be combined with each other, insofar as they do not contradict each other.

[0029] Before describing the scope of protection according to embodiments of the present invention, we will first specifically describe the problems that exist in the related technologies of the present invention in order to make the embodiments easier to understand. When a secondary battery is used or exposed to a high-temperature environment, its internal temperature rises. Upon reaching a certain temperature, the CEI film on the positive electrode undergoes decomposition and an irreversible phase transition, simultaneously releasing heat and oxygen gas. The generated oxygen gas is highly reactive and decomposes the electrolyte it comes into contact with, affecting the cycle characteristics of the secondary battery. This decomposition of the electrolyte further increases heat generation and gas production, causing the internal temperature of the secondary battery to rise further. As a result, the separator contracts, the positive electrode active material expands, the adhesion between the positive electrode film layer and the current collector decreases, detachment occurs, thermal runaway occurs, and the secondary battery faces safety risks such as combustion and even explosion.

[0030] Therefore, the present invention provides a secondary battery and an electronic device, the secondary battery having good safety characteristics and cycle characteristics.

[0031] In the present invention, the secondary battery may include a lithium secondary battery. Exemplarily, the lithium secondary battery may include, but is not limited to, a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery, or a lithium ion polymer secondary battery.

[0032] secondary battery

[0033] Referring to Figure 1, the present invention provides a secondary battery, the secondary battery comprising a positive electrode piece 10, the positive electrode piece 10 comprising a positive electrode current collector 11 and a positive electrode film layer 12, the positive electrode film layer 12 provided on at least one side of the positive electrode current collector 11, the positive electrode film layer 12 comprising a positive electrode active material 121 and organic particles 122 provided on the surface of the positive electrode active material 121, the organic particles 122 forming an insulating layer that covers at least a portion of the surface of the positive electrode active material 121 by undergoing a thermal polymerization reaction under heat treatment conditions, when the adhesive force between the positive electrode current collector 11 and the positive electrode film layer 12 of the positive electrode piece 10 before heat treatment is F1 N / m, and the adhesive force between the positive electrode current collector 11 and the positive electrode film layer 12 of the positive electrode piece 10 after heat treatment is F2 N / m, then F1 and F2 satisfy 1 ≤ F2 / F1 ≤ 2, and the resistance of the positive electrode piece 10 before heat treatment is R 前 When R 前 The resistance is 1Ω to 3Ω, and the resistance of the positive electrode piece 10 after heat treatment is R. 後 When R 前 and R 後 R 後 -R 前 The resistance of the positive electrode piece 10 satisfies ≥1Ω, and the measurement area is 153.94mm². 2 This is obtained by measurement under room temperature conditions where the pressing force is 3.5t and the holding time is 50s.

[0034] In the present invention, the positive electrode piece 10 has two opposing sides, and therefore, the positive electrode film layer 12 may be provided on one of the two sides of the positive electrode current collector 11, or on each of the two sides of the positive electrode current collector 11, and the embodiments of the present invention are not particularly limited thereto.

[0035] Furthermore, in the present invention, heat treatment means changing the surface or internal structure of the positive electrode film layer 12 by performing heating, heat retention, and cooling treatment on the manufactured positive electrode piece 10.

[0036] In the present invention, the adhesive force between the positive electrode current collector 11 and the positive electrode film layer 12 can be measured using methods or equipment well known in the industry. For example, the adhesive force between the positive electrode current collector 11 and the positive electrode film layer 12 is measured using a high-speed tensile testing machine by the 90° method. The measurement method is as follows.

[0037] A portion of the electrode piece coated with the positive electrode film layer 12 of the secondary battery is manufactured in a strip shape, and a portion of the electrode piece is attached to a steel plate from one end along its length using double-sided tape. Next, the steel plate is fixed to the corresponding position on a high-speed tensile testing machine, the electrode piece not attached to the steel plate is pulled up, and the electrode piece is clamped by a connector or directly into the clamp head. When the tension at the clamp opening is greater than 0 kgf and less than 0.02 kgf, the test can be started on the high-speed tensile testing machine, and the average value of the final measured tension is taken as the adhesive force between the positive electrode film layer 12 and the positive electrode current collector 11.

[0038] In the present invention, the resistance of the positive electrode piece 10 can be measured using methods or equipment well known in the art, and exemplary, the resistance of the positive electrode piece 10 is measured using a BER1200 type sheet resistance meter. Specifically, this includes the following steps.

[0039] Resistance measurement of positive electrode piece 10 before heat treatment: 1) Charge the secondary battery at a rate of 0.5C with a constant current until it reaches full charge voltage, then charge it at a constant voltage until the current reaches 0.025C (cutoff current) at full charge voltage, bringing the secondary battery to a fully charged state. 2) Disassemble the above secondary battery to obtain the positive electrode piece 10. 3) Place the positive electrode piece 10 in an atmosphere with a humidity of 5% to 15% and leave it standing for 30 minutes, then seal it and transfer it for measurement. 4) Using a BER1200 type sheet resistance meter, measure the resistance of the positive electrode piece 10 at 25°C, with the distance between adjacent measurement points being 2mm to 3mm, measure at least 15 different points, record the resistance of all measurement points, calculate the average value of these measurement points, and use this average value to determine the resistance R of the positive electrode piece 10 before heat treatment. 前 The measurement parameters were an indenter area of ​​153.94 mm². 2 The pressing force is 3.5t, and the holding time is 50s.

[0040] Resistance measurement of positive electrode piece 10 after heat treatment: 1) Charge the secondary battery at a rate of 0.5C with a constant current until it reaches full charge voltage, then charge it at a constant voltage until the current reaches 0.025C (cutoff current) at full charge voltage, bringing the secondary battery to a fully charged state. 2) Disassemble the above secondary battery to obtain the positive electrode piece 10. 3) Place the positive electrode piece 10 in an oven at 140°C and leave it for 60 minutes to cool to 25°C. After that, seal it and transfer it to the oven for measurement. 4) Using a BER1200 type sheet resistance meter, measure the resistance of the positive electrode piece 10 at 25°C, with the distance between adjacent measurement points being 2mm to 3mm, measure at least 15 different points, record the resistance of all measurement points, calculate the average value of these measurement points, and use this average value to determine the resistance R of the positive electrode piece 10 before heat treatment. 後 The measurement parameters were an indenter area of ​​153.94 mm². 2 The pressing force is 3.5t, and the holding time is 50s.

[0041] In the secondary battery provided by the present invention, the organic particles 122 can undergo a thermal polymerization reaction under heat treatment conditions to form an insulating layer that covers at least a portion of the surface of the positive electrode active material 121. On the one hand, the insulating layer formed by the thermal polymerization reaction not only enhances the structural stability of the positive electrode active material 121 and makes it less susceptible to phase transitions at high temperatures, but also increases the resistance of the positive electrode piece 10, reduces the contact current when the positive electrode piece and negative electrode piece are short-circuited in the secondary battery, and reduces heat generation. On the other hand, the organic particles 122 can contribute to improving the adhesion between the positive electrode film layer 12 and the positive electrode current collector 11 after undergoing the thermal polymerization reaction, and if F1 and F2 satisfy the above relationship, the risk of the positive electrode film layer 12 detaching from the positive electrode current collector 11 at high temperatures can be reduced. Therefore, the ability of the organic particles 122 to undergo a thermal polymerization reaction under heat treatment conditions can improve the safety characteristics of the secondary battery. Furthermore, since the probability of the organic particles 122 undergoing a thermal polymerization reaction in a room temperature atmosphere is small, the impact on the electrochemical properties of the secondary battery can be reduced. The insulating layer covering at least a portion of the surface of the positive electrode active material 121, which is formed by the thermal polymerization reaction of organic particles 122, can reduce the probability of the positive electrode active material 121 coming into contact with the electrolyte at high temperatures. Furthermore, the resistance R of the positive electrode piece 10 before heat treatment 前 The resistance is 1Ω to 3Ω, and the resistance R after heat treatment is 後 and R 前 R 後 -R 前 The resistance is ≥1Ω. This not only reduces the risk of thermal runaway of the secondary battery when it is under high temperature conditions, but also allows the secondary battery to have better cycle characteristics at high temperatures. Therefore, the secondary battery provided by this invention has good safety and cycle characteristics.

[0042] In some embodiments of the present invention, the positive electrode film layer 12 further comprises an adhesive, which improves the bonding between the positive electrode active materials 121 and also improves the bonding between the positive electrode active materials 121 and the positive electrode current collector 11.

[0043] Exemplary examples of adhesives may include one or more of the following: polyvinyl alcohol, hydroxypropyl cellulose, diacetylcellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylic (esterified) styrene-butadiene rubber, epoxy resin, and nylon.

[0044] In the above embodiment, when the secondary battery is under high temperature conditions, the organic particles 122 undergo a thermal polymerization reaction, which can form hydrogen bonds with the polymer material of the adhesive. This improves the adhesion between the positive electrode film layer 12 and the positive electrode current collector 11 at high temperatures, thereby reducing the risk of the positive electrode film layer 12 detaching from the positive electrode current collector 11 at high temperatures.

[0045] In some embodiments of the present invention, F1 and F2 satisfy 1.2 ≤ F2 / F1 ≤ 1.6. When F2 / F1 is within the above range, the risk of the positive electrode film layer 12 detaching from the positive electrode current collector 11 can be further reduced, and the safety characteristics of the secondary battery can be further improved.

[0046] In some embodiments of the present invention, F1 is 10 to 30.

[0047] In some embodiments of the present invention, R 後 R is ≥2.1Ω. 後 When the above range is maintained, the occurrence of thermal runaway in secondary batteries can be further reduced, and safety characteristics can be further improved.

[0048] In some embodiments of the present invention, the positive electrode current collector 11 may be a metal foil or a porous metal plate, for example, a foil or porous plate of a metal or an alloy thereof, such as aluminum, copper, nickel, titanium, or iron. In some specific embodiments of the present invention, the positive electrode current collector 11 is an aluminum foil.

[0049] In the above embodiment, a suitable positive electrode active material 121 can contribute to improving the electrochemical properties of the secondary battery, such as cycle characteristics and energy density.

[0050] In some embodiments of the present invention, the positive electrode active material 121 may include, but is not limited to, at least one of the following: olivine structural materials such as lithium iron manganese phosphate, lithium iron phosphate, lithium manganese phosphate; ternary structural materials such as NCM811, NCM622, NCM523, NCM333; lithium cobalt oxide materials; lithium manganese oxide materials; and other metal oxides capable of releasing lithium.

[0051] In some embodiments of the present invention, the organic particle 122 comprises at least one monomer from formulas I, II, and III, and / or comprises an oligomer formed from at least one monomer from formulas I, II, and III, the structures of formulas I, II, and III being as follows. [ka] R1 contains one or more of the following: hydrogen, methyl group, ethyl group, amino group, hydroxyl group, and metal ions, and R2 is, Imino base and Hosfinidene R3 contains one or more of the groups, and is a C5-C6 cycloalkyl group. Ren C5-C6 cycloalkyl groups containing and / or substituted with one or more of fluorine, chlorine, bromine, nitrogen, and phosphorus. Ren Includes the base.

[0052] In the above embodiment, the organic particles 122 containing the thermally polymerizable monomer and / or oligomer formed from the monomer readily undergo thermal polymerization at high temperatures to form an insulating layer that coats the surface of the positive electrode active material 121. This rapidly increases the resistance of the secondary battery at high temperatures, reduces the current when a short circuit occurs, and contributes to improving the safety characteristics of the secondary battery.

[0053] In some embodiments of the present invention, the metal ions in R1 may include one or more of sodium, potassium, and magnesium.

[0054] In some embodiments of the present invention, the monomer comprises one or more of maleimide, bismaleimide, pyrrole, and 2,5-dimethylpyrrole.

[0055] In some embodiments of the present invention, the number-average molecular weight of the oligomer is 2000 or less than 2000.

[0056] In some embodiments of the present invention, the oligomer comprises at least one of maleimide oligomers and bismaleimide oligomers.

[0057] In the above embodiment, by ensuring that the proportion of the mass occupied by organic particles 122 in the positive electrode film layer 12 is within an appropriate range, the resistance of the positive electrode piece 10 after heat treatment can be further increased, thereby enabling the secondary battery to have good safety characteristics at high temperatures.

[0058] In some embodiments of the present invention, the mass percentage m of organic particles 122 in the positive electrode film layer 12 is 0.3% to 2%. When the mass percentage m of organic particles 122 in the positive electrode film layer 12 is within the above range, the resistance of the positive electrode piece 10 after heat treatment can be further increased, improving the safety characteristics of the secondary battery at high temperatures.

[0059] In this invention, the percentage m of the mass occupied by organic particles 122 in the positive electrode film layer 12 can be measured using methods or equipment well known in the industry. For example, the organic particles 122 can be separated using a centrifuge. A specific method is as follows.

[0060] In a dry atmosphere at about 25°C with humidity less than 2%, take out the positive electrode sheet 10 from the secondary battery, immerse the positive electrode sheet 10 in a solvent to remove the film, uniformly disperse the film layer in an NMP solvent using a disperser to obtain a slurry with a solid content of 30%, then put the slurry into a centrifuge for centrifugation to obtain organic particles 122 in the film layer, finally dry the organic particles 122 at 85°C, weigh them and calculate the mass percentage.

[0061] For illustration, the mass percentage of organic particles 122 in the positive electrode film layer 12 may be 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%, or may be in a range consisting of any two of the above values, but is not limited thereto. For example, the range of the mass percentage of organic particles 122 in the positive electrode film layer 12 may be 0.4% to 1.9%, 0.5% to 1.8%, 0.6% to 1.7%, 0.7% to 1.6%, 0.8% to 1.5%, 0.9% to 1.4%, but is not limited thereto.

[0062] In addition, when the mass percentage m of organic particles 122 in the positive electrode film layer 12 and the thickness D of the positive electrode film layer 12 satisfy a predetermined relationship, it can contribute to improving the safety performance of the secondary battery and also contribute to the normal operation of the secondary battery at high temperatures.

[0063] In some embodiments of the present invention, when the thickness D of the positive electrode film layer 12 satisfies 30μm ≤ D ≤ 100μm, the mass percentage m of organic particles 122 in the positive electrode film layer 12 satisfies 1% ≤ m ≤ 2%.

[0064] In some embodiments of the present invention, when the thickness D of the positive electrode film layer 12 satisfies 100μm < D ≤ 200μm, the mass percentage m of organic particles 122 in the positive electrode film layer 12 satisfies 0.3% ≤ m ≤ 1%.

[0065] In this invention, the thickness of the positive electrode film layer 12 has an art-known meaning and can be measured using art-known methods or equipment. For example, the thickness of the positive electrode film layer 12 can be measured by a scanning electron microscope (SEM). The measurement method is as follows.

[0066] Under an atmosphere of approximately 25°C, the positive electrode piece 10 is removed from the secondary battery, and the electrolyte remaining on the surface of the positive electrode piece 10 is wiped off with dust-free paper. Next, the positive electrode piece 10 is placed under plasma and cut to obtain its cross-section. The cross-section of the positive electrode piece 10 is observed under SEM, and the thickness of the positive electrode film layer 12 on one side is measured. The distance between adjacent measurement points is 2 mm to 3 mm, and at least 15 different points are measured. The thickness of all measurement points is recorded, and the average value of these measurement points is calculated. This average value is defined as the thickness D of the positive electrode film layer 12.

[0067] In some embodiments of the present invention, the positive electrode film layer 12 further comprises a conductive agent, the conductive agent comprising one or more of carbon-based materials, metal-based materials, conductive polymers, and mixtures thereof.

[0068] Exemplary examples include carbon-based materials, which include one or more of the following: carbon black, acetylene black, Ketjen black, carbon fibers, and carbon nanotubes. Metal-based materials include one or more of the following: metal powders, metal fibers, copper, nickel, aluminum, and silver. Conductive polymers include polyphenylene derivatives.

[0069] In some embodiments of the present invention, the heat treatment involves placing the positive electrode piece 10 in an atmosphere at a temperature of 120°C to 140°C for 60 minutes. When the heat treatment temperature is within the above range, the safety characteristics of the secondary battery at high temperatures are improved, and the secondary battery can operate normally under high-temperature conditions. The positive electrode sheet 10 in the present invention can be prepared according to a general method in the art. For example, a positive electrode active material 121, organic particles 122, a conductive agent and an adhesive are dispersed and mixed in N-methylpyrrolidone (NMP) to form a uniform positive electrode slurry, the positive electrode slurry is coated on a positive electrode current collector 11, and after drying, cold pressing, cutting, slitting and re-drying, the positive electrode sheet 10 is obtained.

[0070] According to the secondary batteries known in the art, a secondary battery generally further comprises a negative electrode sheet and a separator, the negative electrode sheet comprises a negative electrode current collector and a negative electrode film layer provided on at least one side of the negative electrode current collector, and the separator is provided between the negative electrode sheet and the positive electrode sheet 10.

[0071] As can be understood, the negative electrode sheet may be provided with a negative electrode film layer on one surface of the negative electrode current collector, or may be provided with negative electrode film layers on both surfaces of the negative electrode current collector, and embodiments of the present invention do not particularly limit this.

[0072] In some embodiments of the present invention, the negative electrode current collector may be a metal foil or a porous metal plate, for example, a foil or a porous plate of a metal such as copper, nickel, titanium, iron or an alloy thereof. In some specific embodiments of the present invention, the negative electrode current collector is copper foil.

[0073] In some embodiments of the present invention, the negative electrode film layer comprises a negative electrode active material, and the negative electrode active material includes silicon, silicon oxygen compounds (SiOx, 0<x≦2), silicon alloys, silicon-carbon composites, graphite, mesocarbon microbeads (MCMB), hard carbon, soft carbon, Li-Sn alloys, Li-Sn-O alloys, Sn, SnO, SnO2, lithium titanate Li4Ti5O with a spinel structure 12 , one or more of Li-Al alloy and metallic lithium. Selecting materials within the above range contributes to improving the energy density of the secondary battery.

[0074] In some embodiments of the present invention, the negative electrode film layer further comprises an adhesive, which may include one or more of the following: styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0075] In some embodiments of the present invention, the negative electrode film layer further comprises a conductive agent, which may include one or more of the following: superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0076] In some embodiments of the present invention, the negative electrode film layer may further contain other auxiliary agents, such as a thickener (e.g., sodium carboxymethylcellulose (CMCNa)).

[0077] Furthermore, the material in the negative electrode piece is not limited to the materials described above, and other known materials used as negative electrode active materials, conductive agents, adhesives, and thickeners may be used.

[0078] The negative electrode pieces in this invention can be prepared according to common methods in the industry. For example, a negative electrode active material, a conductive agent, an adhesive, and a thickener are dispersed in a solvent, the solvent may be N-methylpyrrolidone (NMP) or deionized water, a uniform negative electrode slurry is formed, the negative electrode slurry is coated onto a negative electrode current collector, dried, and cold-pressed to obtain a negative electrode piece.

[0079] In some embodiments of the present invention, the separator may be polyethylene, polypropylene, polyvinylidene fluoride, or a multilayer composite film thereof.

[0080] In some embodiments of the present invention, the separator is a single-layer separator or a multi-layer separator.

[0081] In embodiments of the present invention, the shape and thickness of the separator are not particularly limited. The method for preparing the separator is a method for preparing a separator usable in secondary batteries that is known in the art.

[0082] Furthermore, secondary batteries typically contain an electrolyte, which acts as a carrier for transporting ions and can conduct ions between the positive electrode piece 10 and the negative electrode piece, thus ensuring advantages such as good cycle characteristics of the secondary battery.

[0083] In the present invention, the electrolyte is not particularly limited and may be an electrolyte known in the industry. For example, the electrolyte may include an organic solvent and an electrolyte salt, and the organic solvent may include one or more of the following: ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), ethyl methyl sulfone (EMS), and diethyl sulfone (ESE).

[0084] The electrolyte salt may contain one or more of the following: lithium hexafluoride phosphate (LiPF6), lithium tetraborate tetrafluoride (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoride arsenate (LiAsF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluoro(oxalato)borate (LiDFOB), lithium bis(oxalate)borate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorobis(oxalato)phosphate (LiDFOP), and lithium tetrafluoro(oxalato)phosphate (LiTFOP).

[0085] The electrolyte can be prepared according to common methods in the industry. For example, an electrolyte can be obtained by uniformly mixing an organic solvent, an electrolyte salt, and any additives. Here, the order in which each material is added is not particularly limited.

[0086] The positive electrode piece 10, the separator, and the negative electrode piece are stacked in order, the separator is positioned between the positive electrode piece 10 and the negative electrode piece, and then wound to obtain an electrode assembly. The electrode assembly is then placed in a case, the electrolyte is injected, and after going through processes such as vacuum sealing, standing, formation, degassing, and molding, a secondary battery can be obtained.

[0087] In some embodiments of the present invention, the case may include a rigid case or a flexible case. For example, the material of the rigid case may include metal. The material of the flexible case may include, for example, a metal-plastic film such as an aluminum-plastic film or a steel-plastic film.

[0088] electronic equipment A second aspect of the present invention provides an electronic device. This electronic device includes a secondary battery provided in the first aspect of the present invention. The secondary battery provided by the present invention has good safety characteristics and cycle characteristics, and therefore, the electronic device provided by the present invention also has good safety characteristics and cycle characteristics.

[0089] The electronic devices in embodiments of the present invention are not particularly limited, and known electronic devices used in the art may be used. In some embodiments of the present invention, the electronic devices may include, but are not limited to, notebook computers, pen-input computers, mobile computers, e-book players, mobile phones, portable facsimile machines, portable copiers, portable printers, stereo headsets, video recorders, LCD televisions, portable cleaners, portable CD players, MiniDiscs, transceivers, electronic notebooks, calculators, memory cards, portable tape recorders, radios, backup power supplies, motors, automobiles, motorcycles, electric assist bicycles, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, large household batteries, or lithium-ion capacitors.

[0090] The following examples illustrate the contents disclosed in the present invention in more detail, and are for illustrative purposes only, as it will be apparent to those skilled in the art that various modifications and changes can be made within the scope of the present invention. Unless otherwise specified, all parts, percentages, and ratios described in the following examples are by weight, all reagents used in the examples are commercially available or synthesized according to conventional methods and can be used directly without further processing, and the apparatus used in the examples is commercially available.

[0091] In the following embodiments, for the sake of explanation, we will use the case where the secondary battery is a lithium-ion secondary battery as an example and describe the secondary battery and its manufacturing method in detail.

[0092] Example 1 Preparation of positive electrode pieces Lithium cobalt oxide, a bismaleimide oligomer with a molecular weight of approximately 1000, conductive carbon, and PVDF were dispersed in N-methylpyrrolidone (NMP) in a mass ratio of 96:1:1:2 and mixed to form a homogeneous positive electrode slurry, in which case the solid content of the positive electrode slurry was 75%.

[0093] The positive electrode slurry was coated onto aluminum foil, and after drying, cold pressing, cutting, and slitting, a positive electrode piece was obtained, in which case the thickness of the positive electrode film layer was approximately 100 μm.

[0094] Preparation of negative electrode piece Graphite, carbon black (a conductive agent), SBR, and CMC (a thickening agent) were dispersed in deionized water in a mass ratio of 97:0.5:1.5:1 to form a uniform negative electrode slurry. The negative electrode slurry was coated onto copper foil, dried, and then cold-pressed to obtain a negative electrode piece.

[0095] Preparation of separators A polyethylene separator was used.

[0096] Preparation of electrolyte In a dry argon gas atmosphere, DMC and EMC were mixed in a mass ratio of 7:3, and 1.3 mol / L LiPF6 was added and mixed uniformly to obtain an electrolyte.

[0097] Preparation of lithium-ion secondary batteries The positive electrode piece, separator, and negative electrode piece are stacked in order, with the separator positioned between the positive and negative electrode pieces to act as a separator. After this, the assembly is wound to form an electrode assembly, which is then placed in a case. Next, the prepared electrolyte is injected into the case, and the lithium-ion secondary battery is prepared through processes such as vacuum sealing, standing, formation, and shaping.

[0098] Examples 2-5 Resistance R of the positive electrode piece 前 , R 後 The manufacturing method was similar to that of Example 1, except that the adhesive forces F1 and F22 between the positive electrode film layer and the positive electrode current collector were different. See Table 1 for details.

[0099] Comparative Examples 1-2 Resistance R of the positive electrode piece 前 , R 後The manufacturing method was similar to that of Example 1, except that the adhesive forces F1 and F22 between the positive electrode film layer and the positive electrode current collector were different. See Table 1 for details.

[0100] Examples 6-14 The preparation method was similar to that of Example 2, except that the material of the organic particles was different. See Table 2 for details.

[0101] Examples 15-21 The manufacturing method was similar to that of Example 2, except that the proportion of the mass m occupied by organic particles in the positive electrode film layer was different. See Table 3 for details.

[0102] Examples 22-27 The manufacturing method was similar to that of Example 1, except that the thickness D of the positive electrode film layer and the mass percentage m of organic particles in the positive electrode film layer were different. See Table 4 for details.

[0103] Measuring part (1) Measurement of the resistance of the positive electrode piece Resistance measurement of positive electrode piece before heat treatment: 1) The secondary battery was charged at a rate of 0.5C with a constant current until it reached full charge voltage, and then charged at a constant voltage until the current reached 0.025C (cutoff current) at full charge voltage, thereby bringing the secondary battery to a fully charged state. 2) The above secondary battery was disassembled to obtain the positive electrode piece. 3) The positive electrode piece was placed in an atmosphere with a humidity of 5% to 15% and left to stand for 30 minutes, then sealed and transferred for measurement. 4) Using a BER1200 type sheet resistance meter, measure the resistance of the positive electrode piece at 25°C, with the distance between adjacent measurement points being 2mm to 3mm, measure at least 15 different points, record the resistance of all measurement points, calculate the average value of these measurement points, and use this average value as the resistance R of the positive electrode piece before heat treatment. 前 The measurement parameters were an indenter area of ​​153.94 mm². 2 The pressing force was 3.5t, and the holding time was 50s.

[0104] Resistance measurement of positive electrode pieces after heat treatment: 1) The secondary battery was charged at a rate of 0.5C with a constant current until it reached full charge voltage, and then charged at a constant voltage until the current reached 0.025C (cutoff current) at full charge voltage, thereby bringing the secondary battery to a fully charged state. 2) The above secondary battery was disassembled to obtain the positive electrode piece. 3) The positive electrode piece was placed in an oven at 140°C for 60 minutes, cooled to 25°C, then sealed and transferred for measurement. 4) Using a BER1200 type sheet resistance meter, measure the resistance of the positive electrode piece at 25°C, with the distance between adjacent measurement points being 2mm to 3mm, measure at least 15 different points, record the resistance of all measurement points, calculate the average value of these measurement points, and use this average value as the resistance R of the positive electrode piece before heat treatment. 後 The measurement parameters were an indenter area of ​​153.94 mm². 2 The pressing force was 3.5t, and the holding time was 50s.

[0105] (2) Heat abuse passage rate measurement The lithium-ion secondary battery to be measured was charged at a constant current rate of 0.5C until it reached full charge voltage. Then, at full charge voltage, it was charged until the current reached 0.025C (cutoff current), bringing the lithium-ion secondary battery to a fully charged state. The appearance of the lithium-ion battery before measurement was then recorded.

[0106] Lithium-ion secondary batteries were placed in an oven at 25°C and heated to 150°C at a heating rate of 5°C / min, then kept at a constant temperature for 60 minutes. Next, after the temperature dropped to 50°C, the measurement was stopped. Ten lithium-ion batteries were grouped together, and the state of the lithium-ion secondary batteries during the measurement process was observed. The criterion for passing the test was that the lithium-ion secondary batteries did not burn or explode, i.e., the thermal disturbance pass rate = (number of batteries that did not burn or explode) / 10 × 100%.

[0107] (3) Measurement of the mass ratio m of organic particles in the positive electrode film layer At approximately 25°C in a dry atmosphere with a humidity of less than 2%, the positive electrode piece was removed from the secondary battery, the positive electrode piece was immersed in a solvent to remove the film, and the film layer was uniformly dispersed in NMP solvent using a disperser to obtain a slurry with a solid content of 30%. Next, the slurry was placed in a centrifuge and centrifuged to obtain organic particles from the film layer, and finally the organic particles were dried at 85°C, weighed, and the mass ratio was calculated.

[0108] (4) Measurement of the thickness D of the positive electrode film layer Under an atmosphere of approximately 25°C, the positive electrode piece was removed from the secondary battery, and the electrolyte remaining on the surface of the positive electrode piece was wiped off with dust-free paper. Next, the positive electrode piece was placed under plasma and cut to obtain its cross-section. The cross-section of the positive electrode piece was observed under SEM, and the thickness of the positive electrode film layer on one side was measured. The distance between adjacent measurement points was 2 mm to 3 mm, and at least 15 different points were measured. The thickness of all measurement points was recorded, and the average value of these measurement points was calculated. This average value was defined as the thickness D of the positive electrode film layer.

[0109] (5) Measurement of the adhesive strengths F1 and F2 between the positive electrode current collector and the positive electrode film layer F1 measurement: A portion of the electrode piece coated with a positive electrode film layer was manufactured in a strip shape, and a portion of the electrode piece was attached to a steel plate along its length using double-sided tape from one end of the electrode piece. Next, the steel plate was fixed to the corresponding position on a high-speed tensile testing machine, the electrode piece not attached to the steel plate was pulled up, and the electrode piece was clamped by a connector or directly into the clamp head. If the tension at the clamp opening was greater than 0 kgf and less than 0.02 kgf, the test on the high-speed tensile testing machine could be started, and the average value of the final measured tension was defined as the adhesion force F1 between the positive electrode film layer and the positive electrode current collector.

[0110] F2 measurement: The positive electrode pieces were placed in an oven at 140°C for 60 minutes and then cooled to 25°C. A portion of the electrode pieces coated with the positive electrode film layer was then manufactured into a strip shape, and a portion of the electrode piece was attached to a steel plate along its length using double-sided tape from one end. Next, the steel plate was fixed to the corresponding position on a high-speed tensile testing machine, and the electrode pieces not attached to the steel plate were pulled up. The electrode pieces were clamped by connecting them with a connector or directly into the clamp head. If the tension at the clamp opening was greater than 0 kgf and less than 0.02 kgf, the test on the high-speed tensile testing machine could be started, and the average value of the final measured tension was defined as the adhesion force F2 between the positive electrode film layer and the positive electrode current collector.

[0111] (6) Measurement of volume retention rate Under an atmosphere of (25±3)℃, the battery was charged with a current of 0.5C until the voltage reached 4.5V, then charged with a constant voltage of 4.5V until the current reached 0.025C, and then completely discharged with currents of 0.2C and 2C respectively, obtaining discharge capacities of 0.2C and 2C, and a discharge rate of 2C was obtained by dividing the discharge capacity of 2C by the discharge capacity of 0.2C.

[0112] Table 1 shows the resistance R of the positive electrode piece in Examples 1-5 and Comparative Examples 1-2. 前 , R 後 The adhesion forces F1 and F2 between the positive electrode film layer and the positive electrode current collector, as well as the measurement results, are shown, respectively.

[0113] [Table 1]

[0114] As can be seen from Table 1, comparing the measurement results of Examples 1-5 and Comparative Examples 1-2, in the secondary battery provided by the present invention, the positive electrode film layer contains organic particles that undergo a thermal polymerization reaction under heat treatment conditions. This improves the structural stability of the positive electrode active material, makes it less susceptible to phase transitions at high temperatures, and increases the resistance of the positive electrode piece at high temperatures. Furthermore, the organic particles can contribute to improving the adhesion between the positive electrode film layer and the positive electrode current collector after the thermal polymerization reaction has occurred. When F1 and F2 satisfy the above relationship, the risk of the positive electrode film layer detaching from the positive electrode current collector at high temperatures can be reduced. Therefore, when the positive electrode film layer contains organic particles that undergo a thermal polymerization reaction under heat treatment conditions, the safety characteristics of the secondary battery can be improved. Note that the resistance R of the positive electrode piece before heat treatment. 前 The resistance R is 1Ω to 3Ω, and the resistance R is present after the organic particles are heat-treated. 後 and R 前 is R 後 -R 前 The condition ≥1Ω is satisfied, and therefore, when the secondary battery is under high temperature conditions, not only is the risk of thermal runaway of the secondary battery reduced, but the secondary battery also exhibits good cycle characteristics at high temperatures.

[0115] Table 2 shows the materials and measurement results of the organic particles in the positive electrode film layers of Examples 6 to 14, respectively.

[0116] [Table 2]

[0117] As can be seen from Table 2, the organic particles, by containing the aforementioned heat-polymerizable monomers, have a resistance R of the positive electrode piece before heat treatment. 前 The resistance R will be in the range of 1Ω to 3Ω after heat treatment. 後 and R 前 R 後 -R 前 This contributes to satisfying the ≥1Ω requirement, thereby improving the safety characteristics of the secondary battery and enabling it to have excellent cycle characteristics.

[0118] Table 3 shows the percentage of mass m occupied by organic particles in the positive electrode film layer of Examples 15 to 21, and the measurement results, respectively.

[0119] [Table 3]

[0120] As can be seen from comparing the measurement results of Examples 15 to 21 in Table 3, when the mass percentage m of organic particles in the positive electrode film layer is within the range of 0.3% to 2%, the safety characteristics of the secondary battery can be further improved, and the secondary battery can be given excellent cycle characteristics.

[0121] As can be seen from Table 3, comparing the measurement results of Examples 2, 3, 5 and Examples 15-21, R 前 The resistance is 1Ω to 3Ω, and R 前 and R 後 R 後 -R 前 In addition to satisfying ≥1Ω, if F1 and F2 satisfy 1.2 ≤ F2 / F1 ≤ 1.6, good cycle characteristics can be achieved, and the safety characteristics of the secondary battery can be further improved.

[0122] Table 4 shows the thickness D and m of the positive electrode film layer for Examples 22 to 27, as well as the measurement results, respectively.

[0123] [Table 4]

[0124] As can be seen by comparing the measurement results of Examples 22-27 in Table 4, when the thickness D of the positive electrode film layer satisfies 30 μm ≤ D ≤ 100 μm, and the percentage of the mass occupied by organic particles in the positive electrode film layer m satisfies 1% ≤ m ≤ 2%, R 後 and R 前 R 後 -R 前contributes to satisfying ≧1Ω, which can improve the safety characteristics of the secondary battery and allow the secondary battery to be provided with excellent cycle characteristics. When the thickness D of the positive electrode film layer satisfies 100 μm < D ≦ 200 μm, and the mass ratio m of organic particles in the positive electrode film layer satisfies 0.3% ≦ m ≦ 1%, R 後 and R 前 is R 後 -R 前 contributes to satisfying ≧1Ω, which can improve the safety characteristics of the secondary battery and allow the secondary battery to be provided with excellent cycle characteristics.

[0125] Finally, it should be noted that each of the above embodiments is used to explain the technical solution of the present invention, and is not intended to be limiting. Although the present invention has been described in detail with reference to each of the above embodiments, those skilled in the art can still modify the technical solutions described in the above embodiments, or equivalently replace some or all of the technical features thereof. The essence of the corresponding technical solutions resulting from such modifications or replacements does not depart from the spirit and scope of the technical solutions of the respective embodiments of the present invention, and all of these should be included within the scope of the claims and specification of the present invention. In particular, as long as there is no structural conflict, the technical features described in the respective embodiments can be combined in any manner. The present invention is not limited to the specific embodiments disclosed in the present specification, but includes all technical solutions falling within the scope of the claims.

Claims

1. It is a secondary battery, Including a positive electrode piece, The positive electrode piece includes a positive electrode current collector and a positive electrode film layer. The positive electrode film layer is provided on at least one side of the positive electrode current collector. The positive electrode film layer comprises a positive electrode active material and organic particles provided on the surface of the positive electrode active material. The organic particles undergo a thermal polymerization reaction under heat treatment conditions to form an insulating layer that covers at least a portion of the surface of the positive electrode active material. Let F1 be the adhesive force between the positive electrode current collector and the positive electrode film layer of the positive electrode piece before the heat treatment, and let F2 be the adhesive force between the positive electrode current collector and the positive electrode film layer of the positive electrode piece after the heat treatment, then F1 and F2 satisfy 1 ≤ F2 / F1 ≤ 2. The resistance of the positive electrode piece before heat treatment is R 前 When R 前 The resistance is 1Ω to 3Ω, and the resistance of the positive electrode piece after the heat treatment is R. 後 When R 前 and R 後 R 後 -R 前 Satisfying ≥ 1Ω, The resistance of the aforementioned positive electrode piece was measured over an area of ​​153.94 mm². ２ The measurement was taken under room temperature conditions where the pressing force was 3.5t and the holding time was 50s. In the positive electrode film layer, the proportion of the mass of the organic particles, m, is 0.3% to 2%. The thickness D of the positive electrode film layer is 30 μm to 200 μm. The thickness D of the positive electrode film layer and the ratio m of the mass occupied by the organic particles in the positive electrode film layer are: I) When the thickness D of the positive electrode film layer satisfies 30 μm ≤ D ≤ 100 μm, the proportion m of the mass occupied by the organic particles in the positive electrode film layer satisfies 1% ≤ m ≤ 2%. II) When the thickness D of the positive electrode film layer satisfies 100 μm < D ≤ 200 μm, the proportion m of the mass occupied by the organic particles in the positive electrode film layer satisfies 0.3% ≤ m ≤ 1%. A secondary battery that satisfies one of the following conditions.

2. The secondary battery according to claim 1, wherein F1 and F2 satisfy 1.2 ≤ F2 / F1 ≤ 1.

6.

3. The secondary battery according to claim 1, wherein F1 is 10 to 30.

4. R 後 is R 後 The secondary battery according to claim 1, which satisfies ≧2.1 Ω.

5. The organic particles include at least one monomer from formulas I, II, and III, and / or It comprises an oligomer formed from at least one monomer from formulas I, II, and III, The structures of the above formulas I, II, and III are as follows: 【Chemistry 1】 R1 contains one or more of the following: hydrogen, methyl group, ethyl group, amino group, hydroxyl group, and metal ions. R2 contains one or more of the imino group and phosfinidene group. The secondary battery according to claim 1, wherein R3 comprises a C5-C6 cycloalkylene group and / or a C5-C6 cycloalkylene group substituted with one or more of fluorine, chlorine, bromine, nitrogen, and phosphorus.

6. The monomer comprises one or more of maleimide, bismaleimide, pyrrole, and 2,5-dimethylpyrrole, and / or The number-average molecular weight of the oligomer is 2000, or less than 2000, and / or The secondary battery according to claim 5, wherein the oligomer comprises at least one of maleimide oligomer and bismaleimide oligomer.

7. The secondary battery according to claim 1, wherein the heat treatment involves placing the positive electrode piece in an atmosphere at a temperature of 120°C to 140°C for 60 min.

8. An electronic device comprising a secondary battery according to any one of claims 1 to 7.

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