Secondary battery and electronic device

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 priority to a Chinese patent application bearing application number 202310258701.4, filed on March 17, 2023, and entitled "Secondary Battery and Electronic Device," the entire contents of which are incorporated herein by reference.

[0002] Technical Field The present invention relates to the field of battery technology, and more particularly to secondary batteries and electronic devices. [Background technology]

[0003] With the development of battery technology, its performance can gradually meet the general application requirements of various devices, so that it is widely used in devices such as household appliances, power devices, energy storage devices, etc. Here, safety characteristics and cycle characteristics are two basic performances in the application of batteries to various devices. However, when thermal abuse occurs, the safety characteristics and cycle characteristics of the battery may deteriorate, which may affect the normal operation of various devices. Summary of the Invention

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

[0005] In a first aspect, the present invention provides a secondary battery, the secondary battery including a positive electrode piece, the positive electrode piece including a positive electrode current collector and a positive electrode film layer, the positive electrode film layer being provided on at least one side of the positive electrode current collector, the positive electrode film layer including a positive electrode active material and organic particles provided on a surface of the positive electrode active material, the organic particles forming an insulating layer that causes a thermal polymerization reaction under heat treatment conditions to cover at least a part of the surface of the positive electrode active material, the adhesive strength between the positive electrode current collector and the positive electrode film layer before the heat treatment of the positive electrode piece being F1 N / m, and the adhesive strength between the positive electrode current collector and the positive electrode film layer after the heat treatment of the positive electrode piece being F2 N / m, F1 and F2 satisfy 1≦F2 / F1≦2, and the resistance of the positive electrode piece before the heat treatment is R 前 Then, R 前 The resistance of the positive electrode piece after heat treatment is 1Ω to 3Ω. 後 Then, R 前 and R 後 is R 後 -R 前 ≥ 1Ω, and the resistance of the positive piece is 153.94mm 2 The measurement was performed under room temperature conditions with a pushing force of 3.5t and a holding time of 50s.

[0006] In the secondary battery provided by the present invention, the organic particles can generate 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 the one hand, the insulating layer formed by the thermal polymerization reaction can strengthen the structural stability of the positive electrode active material and make it difficult for it to undergo phase transition at high temperatures. The insulating layer can also increase the resistance of the positive electrode piece, reduce the contact current when the positive electrode piece and the negative electrode piece in the secondary battery are short-circuited, and reduce heat generation. On the other hand, the organic particles can contribute to improving the adhesion between the positive electrode film layer and the positive electrode current collector after generating a thermal polymerization reaction. When F1 and F2 satisfy the above relationship, the risk of the positive electrode film layer falling off the positive electrode current collector at high temperatures can be reduced. Therefore, the fact that the organic particles can generate a thermal polymerization reaction under heat treatment conditions can improve the safety characteristics of the secondary battery. In addition, the probability that the organic particles will generate a thermal polymerization reaction in the secondary battery under normal temperature atmosphere is low, so that the impact on the electrochemical characteristics of the secondary battery can be reduced. The insulating layer formed by the thermal polymerization reaction of the organic particles at high temperature and covering at least a part of the surface of the positive electrode active material can reduce the probability that the positive electrode active material comes into contact with the electrolyte at high temperature. 前 is 1Ω to 3Ω, and the resistance R after heat treatment 後 and R 前 is R 後 -R 前 ≧1Ω. This not only reduces the risk of thermal runaway of the secondary battery when it is exposed to high temperatures, but also ensures that the secondary battery has good cycle characteristics at high temperatures. Therefore, the secondary battery provided by the present invention has good safety characteristics and cycle characteristics.

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

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

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

[0010] According to any of the above embodiments of the first aspect of the invention, the organic particles comprise at least one monomer of formula I, formula II and formula III, and / or An oligomer formed of at least one monomer of formula I, formula II, and formula III, The structures of Formula I, Formula II and Formula III are as follows: [ka] R1 includes one or more of hydrogen, a methyl group, an ethyl group, an amino group, a hydroxyl group, and a metal ion; R2 comprises one or more of an amino group and a phosphino group; R3 comprises a C5-C6 cycloalkyl group and / or a C5-C6 cycloalkyl group substituted with one or more of fluorine, chlorine, bromine, nitrogen and phosphorus.

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

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

[0013] According to any of the 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 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 embodiments of the first aspect of the present invention, the mass ratio m of the organic particles in the positive electrode film layer is 0.3% to 2%. When the mass ratio m of the organic particles in the positive electrode film layer is within the above range, the resistance of the positive electrode sheet after heat treatment can be further increased, thereby improving the safety characteristics of the secondary battery at high temperatures.

[0016] According to any of the embodiments of the first aspect of the present invention, the thickness D of the positive electrode film layer and the mass ratio m of the organic particles in the positive electrode film layer satisfy at least one of the following characteristics. I) When the thickness D of the positive electrode film layer satisfies 30 μm ≤ D ≤ 100 μm, the mass ratio m of 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 mass ratio m of the organic particles in the positive electrode film layer satisfies 0.3% ≤ m ≤ 1%.

[0017] According to any of the embodiments of the first aspect of the present invention, the heat treatment is to place the positive electrode sheet 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.

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

[0019] The above description is only an outline of the technical solution of the present invention. In order to more clearly understand the technical solutions of the present invention and to implement them in accordance with the content of the specification, and to more clearly understand the above and other objectives, features and advantages of the present invention, specific embodiments of the present invention are described below. [Brief description of the drawings]

[0020] In order to more clearly describe 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 are only some embodiments of the present invention, and those skilled in the art can obtain other drawings based on these drawings without creative efforts. [Figure 1] FIG. 1 is a schematic diagram showing the cross-sectional structure of a positive electrode piece according to some 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. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] The following examples are only used to more clearly illustrate the technical solutions of the present invention, and are therefore merely illustrative, not intended to limit the protection scope of the present invention.

[0023] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present invention belongs. The terms used herein are for the purpose of describing specific examples only and are not intended to limit the present invention. The terms "comprise" and "have" and any variations thereof in the present specification and claims are intended to include non-exclusive inclusions.

[0024] In this specification, an "embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment may be included in at least one embodiment of the present invention. The appearance of this phrase in various places in the specification does not necessarily refer to all the same embodiment, nor does it refer to separate or alternative embodiments that are mutually exclusive with other embodiments. Those skilled in the art will understand, explicitly and implicitly, that the embodiments described herein may be combined with other embodiments.

[0025] In the description of the embodiments of the present invention, the term "and / or" simply describes a relation between related objects and indicates that three relations can exist, for example, "A and / or B" can indicate three situations: A exists alone, A and B exist simultaneously, and B exists alone. Note that the character " / " in this specification generally indicates that the related objects before and after it have an "or" relationship.

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

[0027] Groupings of alternative elements or embodiments disclosed herein should not be construed as limitations. Each group member may be taken alone and claimed alone, or taken and claimed in any combination with other members of the group or other elements found herein. It is contemplated that one or more members of a group may be included in or deleted from a group for reasons of convenience and / or patentability. When any such inclusion or deletion occurs, the specification is deemed to contain the modified group and thus fulfills the written description of all Markush groups used in the claims.

[0028] It will be obvious to those skilled in the art that various modifications and changes can be made in the present invention without departing from the scope of protection of the present invention. Therefore, the present invention is intended to cover the modifications and changes of the present invention that fall within the scope of the corresponding claims (scope of protection) and their equivalents. In addition, the embodiments of the present invention can be combined with each other unless they are inconsistent.

[0029] Before describing the scope of protection according to the embodiments of the present invention, problems existing in the related art of the present invention will be specifically described first in order to facilitate understanding of the embodiments of the present invention. When a secondary battery is used or exposed to a high temperature environment, its internal temperature will rise, and when it reaches a certain temperature, the CEI film of the positive electrode piece will decompose and undergo irreversible phase transition, releasing heat and oxygen gas at the same time. The oxygen gas generated is highly reactive and will decompose the electrolyte in contact with it, affecting the cycle characteristics of the secondary battery. The decomposition of the electrolyte will further increase the heat generation and gas generation, and the internal temperature of the secondary battery will further rise, causing the separator to shrink and the positive electrode active material to expand, which will reduce the adhesion between the positive electrode film layer and the current collector, causing them to fall off and cause thermal runaway, leading to the safety risk of secondary battery combustion and even explosion.

[0030] Therefore, the present invention provides a secondary battery and an electronic device, and the secondary battery has 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 FIG. 1, the present invention provides a secondary battery, the secondary battery includes a positive electrode piece 10, the positive electrode piece 10 includes a positive electrode current collector 11 and a positive electrode film layer 12, the positive electrode film layer 12 is provided on at least one side of the positive electrode current collector 11, the positive electrode film layer 12 includes 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 generate 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 121, when the adhesive strength between the positive electrode current collector 11 and the positive electrode film layer 12 before the heat treatment of the positive electrode piece 10 is F1 N / m, and the adhesive strength between the positive electrode current collector 11 and the positive electrode film layer 12 after the heat treatment of the positive electrode piece 10 is F2 N / m, F1 and F2 satisfy 1≦F2 / F1≦2, and the resistance of the positive electrode piece 10 before the heat treatment is R 前 Then, R 前 is 1Ω to 3Ω, and the resistance of the positive electrode piece 10 after heat treatment is R 後 Then, R 前 and R 後 is R 後 -R 前 ≧1Ω, and the resistance of the positive electrode piece 10 is 153.94 mm 2 The measurement was performed under room temperature conditions with a pushing force of 3.5t and a holding time of 50s.

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

[0035] In the present invention, the heat treatment means that the surface or internal structure of the positive electrode film layer 12 is changed by subjecting the manufactured positive electrode piece 10 to heating, heat-retention, and cooling treatments.

[0036] In the present invention, the adhesive strength between the positive electrode current collector 11 and the positive electrode film layer 12 can be measured using a method or device well known in the art. For example, a high-speed tensile tester is used to measure the adhesive strength between the positive electrode current collector 11 and the positive electrode film layer 12 by the 90° method. The measurement method is as follows.

[0037] A part of the pole pieces coated with the positive electrode film layer 12 of the secondary battery is manufactured in a strip shape, and a part of the pole pieces is attached to a steel plate with double-sided tape from one end of the pole pieces along the length direction. Then, the steel plate is fixed at the corresponding position of a high-speed tensile tester, the pole pieces not attached to the steel plate are pulled up, and the pole pieces are clamped by connectors or directly into the clamp head. When the tension at the clamp mouth is greater than 0 kgf and less than 0.02 kgf, the test can be started with the high-speed tensile tester. The average value of the finally measured tensions is the adhesion strength 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 by using a method or device well known in the art, and for example, a BER1200 type sheet resistance meter is used to measure the resistance of the positive electrode piece 10. Specifically, the method includes the following steps:

[0039] Resistance measurement of positive electrode piece 10 before heat treatment: 1) Charge the secondary battery at a constant current of 0.5C up to the full charge voltage, then charge it at a constant voltage until the current reaches 0.025C (cutoff current) at the full charge voltage, bringing the secondary battery to a fully charged state. 2) The secondary battery is disassembled to obtain the positive electrode piece 10. 3) The positive electrode piece 10 is placed in an atmosphere with a humidity of 5% to 15% and allowed to stand for 30 minutes, then sealed and transferred for measurement. 4) Using a BER1200 type sheet resistance measuring instrument, the resistance of the positive electrode piece 10 at 25°C is measured, the interval between adjacent measurement points is 2 mm to 3 mm, at least 15 different points are measured, the resistance of all the measurement points is recorded, the average value of these measurement points is calculated, and the average value is the resistance R of the positive electrode piece 10 before the heat treatment. 前 The measurement parameters are indenter area of ​​153.94 mm 2 The pushing 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 constant current of 0.5C up to the full charge voltage, then charge it at a constant voltage until the current reaches 0.025C (cutoff current) at the full charge voltage, bringing the secondary battery to a fully charged state. 2) The secondary battery is disassembled to obtain the positive electrode piece 10. 3) The positive electrode piece 10 is placed in an oven at 140° C. and left for 60 minutes, cooled to 25° C., sealed, and then transferred for measurement. 4) Using a BER1200 type sheet resistance measuring instrument, the resistance of the positive electrode piece 10 at 25°C is measured, the interval between adjacent measurement points is 2 mm to 3 mm, at least 15 different points are measured, the resistance of all the measurement points is recorded, the average value of these measurement points is calculated, and the average value is the resistance R of the positive electrode piece 10 before the heat treatment. 後 The measurement parameters are indenter area of ​​153.94 mm 2 The pushing 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 generate 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 121. On the one hand, the insulating layer formed by the thermal polymerization reaction can strengthen the structural stability of the positive electrode active material 121 and make it difficult for the phase transition to occur at high temperatures. The insulating layer can also increase the resistance of the positive electrode piece 10, reduce the contact current when the positive electrode piece and the negative electrode piece in the secondary battery are short-circuited, and reduce 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 generating a thermal polymerization reaction. When F1 and F2 satisfy the above relationship, the risk of the positive electrode film layer 12 falling off from the positive electrode current collector 11 under high temperatures can be reduced. Therefore, the fact that the organic particles 122 can generate a thermal polymerization reaction under heat treatment conditions can improve the safety characteristics of the secondary battery. In addition, the probability that the organic particles 122 generate a thermal polymerization reaction in the secondary battery under normal temperature atmosphere is low, so that the impact on the electrochemical characteristics of the secondary battery can be reduced. The insulating layer that covers at least a part of the surface of the positive electrode active material 121 formed by the thermal polymerization reaction of the organic particles 122 can reduce the probability that the positive electrode active material 121 comes into contact with the electrolyte at high temperatures. 前 is 1Ω to 3Ω, and the resistance R after heat treatment 後 and R 前 is R 後 -R 前 ≧1Ω. This not only reduces the risk of thermal runaway of the secondary battery when it is exposed to high temperatures, but also allows the secondary battery to have better cycle characteristics at high temperatures. Therefore, the secondary battery provided by the present invention has good safety characteristics and cycle characteristics.

[0042] In some embodiments of the present invention, the positive electrode membrane layer 12 further includes 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] Exemplarily, the adhesive may include one or more of polyvinyl alcohol, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene butadiene rubber, acrylic acid (ester)-modified styrene butadiene rubber, epoxy resin, and nylon.

[0044] In the above embodiment, when the secondary battery is subjected to high temperatures, the organic particles 122 undergo a thermal polymerization reaction and can form hydrogen bonds with the polymer material of the adhesive, thereby improving the adhesive strength between the positive electrode film layer 12 and the positive electrode current collector 11 at high temperatures and reducing the risk that the positive electrode film layer 12 will fall off 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 in the above range, the risk of the positive electrode film layer 12 falling off 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 10-30.

[0047] In some embodiments of the present invention, R 後 ≧2.1Ω. 後 When the temperature is within the above range, the occurrence of thermal runaway in the secondary battery can be further reduced, and the 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 a porous plate of a metal such as aluminum, copper, nickel, titanium, iron, etc., or an alloy thereof. In some specific embodiments of the present invention, the positive electrode current collector 11 is an aluminum foil.

[0049] In the above embodiment, the appropriate 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 at least one of, but is not limited to, an olivine structure material such as lithium manganese iron phosphate, lithium iron phosphate, lithium manganese phosphate, etc., a ternary structure material such as NCM811, NCM622, NCM523, NCM333, etc., a lithium cobalt oxide material, a lithium manganate material, other metal oxides capable of releasing lithium, etc.

[0051] In some embodiments of the present invention, organic particles 122 include at least one monomer of Formula I, Formula II, and Formula III, and / or an oligomer formed with at least one monomer of Formula I, Formula II, and Formula III, the structures of which are as follows: [ka] R1 comprises one or more of hydrogen, methyl, ethyl, amino, hydroxyl and metal ions; R2 comprises one or more of amino and phosphino groups; and R3 comprises a C5-C6 cycloalkyl group and / or a C5-C6 cycloalkyl group substituted with one or more of fluorine, chlorine, bromine, nitrogen and phosphorus.

[0052] In the above embodiment, the organic particles 122 containing the thermally polymerizable monomer and / or the oligomer formed from the monomer easily undergo a thermal polymerization reaction at high temperatures to form an insulating layer covering the surface of the positive electrode active material 121, which rapidly increases the resistance of the secondary battery at high temperatures and reduces the current when a short circuit occurs, thereby contributing 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 invention, the monomer comprises one or more of maleimide, bismaleimide, pyrrole, and 2,5-dimethylpyrrole.

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

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

[0057] In the above embodiment, since the mass proportion of the 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, so that the secondary battery has good safety characteristics under high temperatures.

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

[0059] In the present invention, the mass ratio m of the organic particles 122 in the positive electrode membrane layer 12 can be measured using a method or device well known in the art. For example, the organic particles 122 can be separated using a centrifuge. The specific method is as follows.

[0060] In a dry atmosphere at about 25°C with a humidity less than 2%, the positive electrode sheet 10 is taken out from the secondary battery, the positive electrode sheet 10 is immersed in a solvent to remove the film, and the film layer is uniformly dispersed in an NMP solvent using a disperser to obtain a slurry with a solid content of 30%. Next, the slurry is put into a centrifuge for centrifugation to obtain the organic particles 122 in the film layer. Finally, the organic particles 122 are dried at 85°C, weighed, and the mass ratio is calculated.

[0061] Exemplarily, the mass ratio of the 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 ratio of the organic particles 122 in the positive electrode film layer 12 may be 0.4% - 1.9%, 0.5% - 1.8%, 0.6% - 1.7%, 0.7% - 1.6%, 0.8% - 1.5%, 0.9% - 1.4%, but is not limited thereto.

[0062] Also, when the mass ratio m of the 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 the improvement of the safety characteristics of the secondary battery and can 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 ratio m of the 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 ratio m of the organic particles 122 in the positive electrode film layer 12 satisfies 0.3% ≤ m ≤ 1%.

[0065] In the present invention, the thickness of the positive electrode film layer 12 has a meaning known in the art and can be measured using a method or device known in the art. 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] In an atmosphere of about 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 a 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 interval between adjacent measurement points is 2mm to 3mm, at least 15 different points are measured, the thicknesses of all the measurement points are recorded, and the average value of these measurement points is calculated, and the average value is the thickness D of the positive electrode film layer 12.

[0067] In some embodiments of the present invention, the positive electrode membrane layer 12 further comprises a conductive agent, which comprises one or more of a carbon-based material, a metal-based material, a conductive polymer, and mixtures thereof.

[0068] Exemplarily, the carbon-based material includes one or more of carbon black, acetylene black, ketjen black, carbon fiber, and carbon nanotube. The metal-based material includes one or more of metal powder, metal fiber, copper, nickel, aluminum, and silver. The conductive polymer includes polyphenylene derivatives.

[0069] In some embodiments of the present invention, the heat treatment is performed by placing the positive electrode piece 10 in an atmosphere having 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 the positive electrode current collector 11, and after drying, cold pressing, cutting, slitting, and redrying, the positive electrode sheet 10 is obtained.

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

[0071] As can be understood, the negative electrode film layer may be provided on one surface of the negative electrode current collector, or may be provided on both surfaces of the negative electrode current collector. The embodiments of the present invention are not particularly limited thereto.

[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 a copper foil.

[0073] In some embodiments of the present invention, the negative electrode film layer contains a negative electrode active material, and the negative electrode active material may include one or more of silicon, silicon oxygen compound (SiOx, 0 < x ≤ 2), silicon alloy, silicon-carbon composite, graphite, mesocarbon microbeads (MCMB), hard carbon, soft carbon, Li-Sn alloy, Li-Sn-O alloy, Sn, SnO, SnO 2 Lithium titanate with a spinel structure Li 4 Ti 5 O 12 4, Li-Al alloy, and metallic lithium. By selecting the materials within the above range, it contributes to the improvement of the energy density of the secondary battery.

[0074] In some embodiments of the present invention, the negative electrode membrane layer further comprises an adhesive, which may include one or more of 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 membrane layer further comprises a conductive agent, which may include one or more of 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 membrane layer may further include other auxiliary agents, such as a thickening agent (eg, sodium carboxymethylcellulose (CMCNa)).

[0077] Furthermore, the materials in the negative electrode pieces are not limited to the above-mentioned materials, and other known materials used as negative electrode active materials, conductive agents, adhesives, and thickeners may be used.

[0078] The negative electrode piece in the present invention can be prepared according to the general method in the art, for example, by dispersing the negative electrode active material, conductive agent, adhesive and thickener in a solvent, which can be N-methylpyrrolidone (NMP) or deionized water, to form a uniform negative electrode slurry, and then coating the negative electrode slurry on a negative electrode current collector, drying and cold pressing to obtain a negative electrode piece.

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

[0080] In some embodiments of the present invention, the separator is a monolayer separator or a multilayer separator.

[0081] In the embodiment 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 that can be used for a secondary battery that is known in the art.

[0082] In addition, the secondary battery usually further contains an electrolyte, which is a carrier for transporting ions and can play a role in conducting ions between the positive electrode piece 10 and the negative electrode piece, thereby 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 any electrolyte known in the art. Exemplarily, the electrolyte solution includes an organic solvent and an electrolyte salt, and the organic solvent may include one or more of 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 is lithium hexafluorophosphate (LiPF 6 ), lithium tetrafluoroborate (LiBF 4 ), lithium perchlorate (LiClO 4 ), lithium hexafluoroarsenate (LiAsF 6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluoro(oxalato)borate (LiDFOB), lithium bis(oxalato)borate (LiBOB), lithium difluorophosphate (LiPO 2 F 2 ), lithium difluorobis(oxalato)phosphate (LiDFOP), and lithium tetrafluoro(oxalato)phosphate (LiTFOP).

[0085] The electrolyte solution can be prepared according to a method generally used in the art. For example, an organic solvent, an electrolyte salt, and any additives can be mixed uniformly to obtain an electrolyte solution. The order of addition of each material is not particularly limited.

[0086] The positive electrode piece 10, the separator and the negative electrode piece are stacked in order, and 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 placed in a case, and then an electrolyte is injected. After vacuum sealing, standing, formation, degassing, molding and other processes, a secondary battery can be obtained.

[0087] In some embodiments of the present invention, the case may include a hard case or a flexible case. Exemplarily, the material of the hard case may include a metal. The material of the flexible case may include a metal plastic film, such as an aluminum plastic film, a steel plastic film, etc.

[0088] electronic equipment The second aspect of the present invention provides an electronic device. The electronic device includes the secondary battery provided by 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 device according to the embodiment of the present invention is not particularly limited, and may be any known electronic device used in the art. In some embodiments of the present invention, the electronic device may include, but is not limited to, a notebook computer, a pen-input computer, a mobile computer, an electronic book player, a mobile phone, a portable facsimile, a portable copy machine, a portable printer, a stereo headset, a video recorder, a liquid crystal television, a portable cleaner, a portable CD player, a mini disc, a transceiver, an electronic notebook, a calculator, a memory card, a portable tape recorder, a radio, a backup power source, a motor, an automobile, a motorcycle, an assisted bicycle, a bicycle, a lighting device, a toy, a game machine, a clock, an electric tool, a flashlight, a camera, a large household battery, or a lithium ion capacitor.

[0090] The following examples will more fully describe the disclosed subject matter of the present invention, and these examples are for illustrative purposes only, since it will be apparent to those skilled in the art that various modifications and variations within the scope of the present invention may be made. 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 treatment, and the equipment used in the examples is commercially available.

[0091] In the following embodiments, for convenience of explanation, the secondary battery and the manufacturing method thereof will be described in detail using a lithium ion secondary battery as an example.

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

[0093] The positive electrode slurry was applied to an aluminum foil, and after drying, cold pressing, cutting and slitting, a positive electrode piece was obtained, where the thickness of the positive electrode film layer was about 100 μm.

[0094] Preparation of negative electrode pieces Graphite, carbon black as a conductive agent, SBR, and CMC as a thickener 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 applied to a copper foil, dried, and cold pressed to obtain a negative electrode piece.

[0095] Preparation of the separator The separator used was a polyethylene separator.

[0096] Preparation of electrolyte In a dry argon gas atmosphere, DMC and EMC were mixed in a mass ratio of 7:3 to form LiPF with a concentration of 1.3 mol / L. 6 The ingredients were added and mixed uniformly to obtain an electrolyte solution.

[0097] Preparation of lithium-ion secondary batteries The positive electrode pieces, separator, and negative electrode pieces are stacked in this order, and the separator is positioned between the positive electrode pieces and the negative electrode pieces to serve as an insulator. The stack is then wound to form an electrode assembly, and the electrode assembly is placed in a case. The above-prepared electrolyte is then 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 to 5 Resistance of the positive pole piece R 前 , R 後 Except for the different adhesive forces F1 and F22 between the positive electrode film layer and the positive electrode current collector, the preparation method was similar to that of Example 1. See Table 1 for details.

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

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

[0101] Examples 15 to 21 Except for the difference in the mass ratio m of the organic particles in the positive electrode film layer, the preparation method was similar to that of Example 2. See Table 3 for details.

[0102] Examples 22 to 27 Except for the thickness D of the positive electrode film layer and the mass ratio m of the organic particles in the positive electrode film layer, the preparation method was similar to that of Example 1. See Table 4 for details.

[0103] Measuring part (1) Measuring the resistance of the positive electrode Resistance measurement of positive electrode piece before heat treatment: 1) The secondary battery was charged at a constant current of 0.5C up to the full charge voltage, and then charged at a constant voltage until the current reached 0.025C (cutoff current) at the full charge voltage, bringing the secondary battery to a fully charged state. 2) The secondary battery was disassembled to obtain a 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 moved to another location for measurement. 4) Using a BER1200 type sheet resistance meter, measure the resistance of the positive electrode piece at 25°C, measure at least 15 different points with an interval of 2 mm to 3 mm between adjacent measurement points, record the resistance of all measurement points, calculate the average value of these measurement points, and use the average value as the resistance R of the positive electrode piece before heat treatment. 前 The measurement parameters are indenter area of ​​153.94 mm 2 The pushing force was 3.5t and the holding time was 50s.

[0104] Resistance measurement of the positive electrode piece after heat treatment: 1) The secondary battery was charged at a constant current of 0.5C up to the full charge voltage, and then charged at a constant voltage until the current reached 0.025C (cutoff current) at the full charge voltage, bringing the secondary battery to a fully charged state. 2) The secondary battery was disassembled to obtain a positive electrode piece. 3) The positive electrode piece was placed in a 140°C oven for 60 minutes, cooled to 25°C, sealed, and transferred for measurement. 4) Using a BER1200 type sheet resistance meter, measure the resistance of the positive electrode piece at 25°C, measure at least 15 different points with an interval of 2 mm to 3 mm between adjacent measurement points, record the resistance of all measurement points, calculate the average value of these measurement points, and use the average value as the resistance R of the positive electrode piece before heat treatment. 後 The measurement parameters are indenter area of ​​153.94 mm 2 The pushing 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 of 0.5C up to the full charge voltage, and then charged until the current reached 0.025C (cut-off current) at the full charge voltage, bringing the lithium-ion secondary battery to a fully charged state. The appearance of the lithium-ion battery before measurement was recorded.

[0106] The lithium ion secondary batteries were placed in an oven at 25°C, and the oven was heated to 150°C at a rate of 5°C / min, and kept at constant temperature for 60 minutes. Then, the measurement was stopped when the temperature dropped to 50°C, and 10 lithium ion batteries were grouped into one group. The state of the lithium ion secondary batteries during the measurement process was observed, and the criteria for determining whether the lithium ion secondary batteries passed was whether they did not burn or explode, that is, the thermal abuse passing rate = (the number of batteries that did not burn or explode) / 10 x 100%.

[0107] (3) Measurement of the mass ratio m of organic particles in the positive electrode film layer At about 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 membrane, and the membrane layer was uniformly dispersed in NMP solvent using a disperser to obtain a slurry with a solid content of 30%, and then the slurry was placed in a centrifuge and centrifuged to obtain the organic particles in the membrane layer. 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 In an atmosphere of about 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 interval between adjacent measurement points was 2mm to 3mm, 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, and the average value was taken as the thickness D of the positive electrode film layer.

[0109] (5) Measurement of adhesive strength F1 and F2 between the positive electrode current collector and the positive electrode film layer F1 Measurements: A part of the pole pieces coated with the positive electrode film layer is manufactured into a strip shape, and a part of the pole pieces is attached to a steel plate from one end of the pole pieces along the length direction with double-sided tape.Then, the steel plate is fixed at the corresponding position of the high-speed tensile tester, the pole pieces not attached to the steel plate are pulled up, and the pole pieces are clamped by connectors or directly into the clamp head, and when the tension of the clamp mouth is greater than 0kgf and less than 0.02kgf, the test can be started with the high-speed tensile tester, and the average value of the finally measured tensions is the adhesion force F1 between the positive electrode film layer and the positive electrode current collector.

[0110] Measurement of F2: The positive electrode pieces were placed in an oven at 140°C for 60 minutes and cooled to 25°C, after which some of the positive electrode film layers were produced in strips, and a portion of the positive electrode film layers was attached to a steel plate from one end of the positive electrode film layers along the length direction with double-sided tape. The steel plate was then fixed to the corresponding position of the high-speed tensile tester, and the pole pieces not attached to the steel plate were pulled up, and the pole pieces were clamped by connectors or directly into the clamp head. When the tension of the clamp mouth was greater than 0kgf and less than 0.02kgf, the test could be started with the high-speed tensile tester, and the average value of the final measured tension was taken as the adhesive strength F2 between the positive electrode film layer and the positive electrode current collector.

[0111] (6) Capacity retention measurement Under an atmosphere of (25±3)°C, the batteries were charged at a current of 0.5C until the voltage reached 4.5V, then charged at a constant voltage of 4.5V until the current reached 0.025C, and then fully discharged at currents of 0.2C and 2C, respectively, to obtain discharge capacities of 0.2C and 2C, respectively, and a discharge rate of 2C at discharge capacity / 0.2C discharge capacity.

[0112] Table 1 shows the resistance R of the positive electrode piece in Examples 1 to 5 and Comparative Examples 1 and 2. 前 , R 後 4 shows the adhesive forces F1 and F2 between the positive electrode film layer and the positive electrode current collector, and the measurement results.

[0113] [Table 1]

[0114] As can be seen from Table 1 by comparing the measurement results of Examples 1 to 5 and Comparative Examples 1-2, in the secondary battery provided by the present invention, the positive electrode film layer contains organic particles that generate a thermal polymerization reaction under heat treatment conditions, so that the structural stability of the positive electrode active material can be improved and the phase transition at high temperatures can be made difficult, and the resistance of the positive electrode piece at high temperatures can be increased. In addition, the organic particles can contribute to improving the adhesive force between the positive electrode film layer and the positive electrode current collector after the thermal polymerization reaction is generated, and when F1 and F2 satisfy the above relationship, the risk of the positive electrode film layer falling off the positive electrode current collector at high temperatures can be reduced. Therefore, when the positive electrode film layer contains organic particles that generate a thermal polymerization reaction under heat treatment conditions, the safety characteristics of the secondary battery can be improved. In addition, the resistance R of the positive electrode piece before heat treatment can be improved. 前 is 1Ω~3Ω, and the resistance R after the organic particles are heat-treated 後 and R 前 is R 後 -R 前 ≧1Ω, therefore, when the secondary battery is subjected to high temperatures, not only is the risk of thermal runaway of the secondary battery reduced, but also the secondary battery has good cycle characteristics at high temperatures.

[0115] Table 2 shows the materials of the organic particles in the positive electrode film layer and the measurement results for each of Examples 6 to 14.

[0116] [Table 2]

[0117] As can be seen from Table 2, the organic particles contain the thermally polymerizable monomer, so that the resistance R 前 is in the range of 1Ω to 3Ω, and the resistance R after heat treatment 後 and R 前 R 後 -R 前 ≧1Ω, which can improve the safety characteristics of the secondary battery and provide the secondary battery with excellent cycle characteristics.

[0118] Table 3 shows the mass ratio m of the organic particles in the positive electrode membrane layer and the measurement results for each of Examples 15 to 21.

[0119] [Table 3]

[0120] As can be seen from comparing the measurement results of Examples 15 to 21 in Table 3, when the mass ratio m of the 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 provided with excellent cycle characteristics.

[0121] As can be seen from Table 3, comparing the measurement results of Examples 2, 3, 5, and Examples 15 to 21, R 前 is 1Ω~3Ω, R 前 and R 後 R 後 -R 前 In addition to satisfying F1 / F2 / F1≦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 thicknesses D and m of the positive electrode film layer and the measurement results for Examples 22 to 27.

[0123] [Table 4]

[0124] As can be seen from Table 4 by comparing the measurement results of Examples 22 to 27, when the thickness D of the positive electrode film layer satisfies 30 μm≦D≦100 μm, and the mass ratio m of the organic particles in the positive electrode film layer satisfies 1%≦m≦2%, R 後 and R 前 R 後 -R 前Contributes to satisfying ≧1Ω, thereby improving the safety characteristics of the secondary battery and enabling the secondary battery to have excellent cycle characteristics. When the thickness D of the positive electrode film layer satisfies 100μm < D ≦ 200μm, when the mass ratio m of the organic particles in the positive electrode film layer satisfies 0.3% ≦ m ≦ 1%, R 後 and R 前 are R 後 -R 前 Contributes to satisfying ≧1Ω, thereby improving the safety characteristics of the secondary battery and enabling the secondary battery to have excellent cycle characteristics.

[0125] Finally, it should be noted that the above embodiments are used to illustrate the technical solutions of the present invention and are not restrictive. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art can still modify the technical solutions described in the above embodiments or perform equivalent substitutions on some or all of their technical features. However, these modifications and substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and all of these should be included in the scope of the claims and the specification of the present invention. In particular, as long as there is no structural contradiction, the technical features described in each embodiment can be combined in any way. The present invention is not limited to the specific embodiments disclosed in this specification, but includes all technical solutions included in the scope of the claims.

Claims

1. 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 includes a positive electrode active material and organic particles provided on a 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 a surface of the positive electrode active material; When the adhesive strength between the positive electrode current collector and the positive electrode film layer of the positive electrode piece before the heat treatment is F1 N / m, and the adhesive strength between the positive electrode current collector and the positive electrode film layer of the positive electrode piece after the heat treatment is F2 N / m, F1 and F2 satisfy 1≦F2 / F1≦2, The resistance of the positive electrode piece before the heat treatment is R 前 Then, R 前 is 1 Ω to 3 Ω, and the resistance of the positive electrode piece after the heat treatment is R 後 Then, R 前 and R 後 is R 後 -R 前 ≧1Ω is satisfied, The resistance of the positive electrode piece is measured over an area of ​​153.94 mm ２ The secondary battery is obtained by measuring under room temperature conditions where the pushing force is 3.5 t and the holding time is 50 s.

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

6.

3. 2. 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 , wherein the resistance satisfies ≧2.1Ω.

5. The organic particles comprise at least one monomer of formula I, formula II, and formula III, and / or An oligomer formed of at least one monomer of formula I, formula II, and formula III, The structures of Formula I, Formula II and Formula III are as follows: 【Chemistry 1】 R1 includes one or more of hydrogen, a methyl group, an ethyl group, an amino group, a hydroxyl group, and a metal ion; R2 comprises one or more of an amino group and a phosphino group; 2. The secondary battery of claim 1, wherein R3 comprises a C5-C6 cycloalkyl group and / or a C5-C6 cycloalkyl group substituted with one or more of fluorine, chlorine, bromine, nitrogen, and phosphorus.

6. The monomers include 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 includes at least one of a maleimide oligomer and a bismaleimide oligomer.

7. 2. The secondary battery according to claim 1, wherein the mass ratio m of the organic particles in the positive electrode film layer is 0.3% to 2%.

8. The thickness D of the positive electrode film layer and the mass ratio m of the organic particles in the positive electrode film layer are expressed as follows: I) when the thickness D of the positive electrode film layer satisfies 30 μm≦D≦100 μm, the mass ratio m of 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 mass ratio m of the organic particles in the positive electrode film layer satisfies 0.3%≦m≦1%; The secondary battery according to claim 1 , wherein at least one of the above conditions is satisfied.

9. The secondary battery according to any one of claims 1 to 8, wherein the heat treatment comprises placing the positive electrode piece in an atmosphere at a temperature of 120°C to 140°C for 60 minutes.

10. An electronic device comprising the secondary battery according to any one of claims 1 to 9.

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