CN116404361A

CN116404361A - Coating composition, composite isolating film, battery monomer, battery and electric equipment

Info

Publication number: CN116404361A
Application number: CN202310618322.1A
Authority: CN
Inventors: 李雷; 郑义; 康海杨; 孙成栋; 陈美煌; 赖润豪
Original assignee: Contemporary Amperex Technology Co Ltd
Current assignee: Contemporary Amperex Technology Co Ltd
Priority date: 2023-05-29
Filing date: 2023-05-29
Publication date: 2023-07-07
Anticipated expiration: 2043-05-29
Also published as: CN116404361B

Abstract

The application provides a coating composition, composite barrier film, battery monomer, battery and consumer, this coating composition includes: a benzoxazine resin particle and a binder, wherein the mass ratio of the binder to the benzoxazine resin particle is 1:1 to 1:20; the benzoxazine resin particles have a Dv50 particle size of 0.1 μm to 5 μm. According to the application, the coating composition can be used for preparing a coating on the surface of the base film to obtain the composite isolating film, and the composite isolating film has good heat resistance, so that the thermal failure temperature of the battery cell can be increased, and the battery cell has good thermal safety performance. In addition, the benzoxazine resin particles have excellent dielectric properties, so that polarization can be reduced, and the obtained composite isolating film has higher ionic conductivity, so that the battery monomer has better electrical properties.

Description

Coating composition, composite isolating film, battery monomer, battery and electric equipment

Technical Field

The application relates to the technical field of batteries, in particular to a coating composition, a composite isolating film, a battery monomer, a battery and electric equipment.

Background

The battery monomer has the advantages of reliable working performance, no pollution, no memory effect and the like, and is widely applied. For example, as environmental protection issues become more and more important, new energy automobiles become more and more popular, and the demand for power type battery cells will be on the rise.

As the battery application range becomes wider, the requirement for battery safety becomes higher. However, the heat resistance of the separator is poor in the battery cells, which results in deterioration of safety, and improvement of the heat resistance of the separator is required.

Disclosure of Invention

The application provides a coating composition, a composite isolating film, a battery monomer, a battery and electric equipment, and the heat resistance of the isolating film can be improved.

In a first aspect, the present application provides a coating composition comprising: comprising the following steps: a benzoxazine resin particle and a binder, wherein the mass ratio of the binder to the benzoxazine resin particle is 1:1 to 1:20; the benzoxazine resin particles have a Dv50 particle size of 0.1 μm to 5 μm.

According to the application, the coating composition can be used for preparing a coating on the surface of the base film to obtain the composite isolating film, the coating mainly takes benzoxazine resin particles as a framework, the coating has good thermal stability, the thermal shrinkage rate of the base film can be effectively reduced, meanwhile, the benzoxazine resin particles also have good insulating property and film forming property, and even if the base film is melted at a higher temperature, the base film can play a role in isolating the positive electrode from the negative electrode, so that the composite isolating film with good heat resistance can be obtained, and therefore, the composite isolating film can be used in a battery to prevent short circuits caused by contact between the positive electrode and the negative electrode due to shrinkage of the isolating film under a high temperature condition, the thermal failure temperature of a battery monomer can be improved, and the battery monomer has good thermal safety performance. In addition, the benzoxazine resin particles have excellent dielectric properties, so that polarization can be reduced, and the obtained composite isolating film has higher ionic conductivity, so that the battery monomer has better electrical properties.

In some embodiments, the binder includes at least one of polyacrylic acid, polyacrylate, polyvinylidene fluoride, styrene butadiene rubber, sodium carboxymethyl cellulose. The binder can be adopted to ensure that benzoxazine resin particles are stably combined on the surface of the base film, so that the stability of the composite isolating film is improved, and the heat resistance of the composite isolating film can be further improved.

In some embodiments, the benzoxazine resin particles have a Dv50 particle size of 0.5 μm to 3 μm. At this time, light and thin coating of the coating can be realized, and the energy density of the battery monomer is improved while the heat resistance and the ion transmission performance of the composite isolating film are ensured.

In some embodiments, the benzoxazine resin particles are cured and crushed from benzoxazine monomers; the benzoxazine monomer is obtained by reacting an amine compound, a phenol compound and an aldehyde compound in a solvent. The preparation method of the benzoxazine resin particles is simple, the cost is low, and the benzoxazine resin particles with different performances can be obtained by selecting different amine compounds, phenol compounds and aldehyde compounds, so that the benzoxazine resin particles have high designability, and therefore, the proper benzoxazine resin particles can be obtained according to actual needs.

In some embodiments, the amine groups in the amine compound, the phenolic hydroxyl groups in the phenolic compound, and the aldehyde groups in the aldehyde compound are in a molar ratio of 1 (1 to 1.5): 2 to 2.5. At the moment, the benzoxazine monomer can be better obtained, the waste of raw materials is reduced, the residual of small molecules in the benzoxazine resin particles is reduced, and the stability of the property of the benzoxazine resin particles is improved.

In some embodiments, the amine compound comprises a diamine compound and the phenolic compound comprises a monophenol compound. Benzoxazine resin particles obtained by using diamine compounds, monophenol compounds and aldehyde compounds have better thermal stability and dielectric properties, and can obtain composite isolating films with better heat resistance and ion transmission properties.

In some embodiments, the diamine compound comprises at least one of 1, 6-hexamethylenediamine, diaminodiphenylmethane, and diaminodiphenyl sulfone; the monophenol compound comprises at least one of phenol, p-methoxyphenol, cardanol and o-allylphenol; the aldehyde compound comprises formaldehyde and/or paraformaldehyde; the solvent comprises at least one of dioxane, chloroform and xylene. The raw materials for preparing the benzoxazine resin particles are cheap and easy to obtain, are more in variety, can be selected according to actual needs, and are suitable for industrial production.

In a second aspect, the present application provides a composite barrier film comprising: a base film, and

a coating layer formed from the coating composition according to any of the embodiments of the first aspect disposed on at least one surface of the base film.

According to the present application, the composite release film comprises a coating layer formed from the coating composition according to any of the embodiments of the first aspect, and it is therefore understood that the composite release film has the advantages of the first aspect.

In some embodiments, the coating has an areal density of 0.1g/m ² To 5g/m ² . At the moment, the heat resistance and the ion transmission performance of the composite isolating film are better, so that the battery monomer has better safety and electrical performance.

In a third aspect, the present application provides a battery cell comprising the composite separator of any one of the embodiments of the second aspect.

In a fourth aspect, the present application provides a battery comprising a battery cell according to any one of the embodiments of the third aspect.

In a fifth aspect, the present application provides an electrical device, including at least one of a battery cell according to any one of the embodiments of the third aspect or a battery according to any one of the embodiments of the fourth aspect.

The application provides a coating composition, which can prepare a coating on the surface of a base film to obtain a composite isolating film, wherein the composite isolating film has good heat resistance and ion transmission performance, and thus, a battery cell with good thermal safety performance and electrical performance can be obtained.

Drawings

Fig. 1 is a DSC (differential scanning calorimetry) diagram of benzoxazine resin particles in an embodiment of the present application.

Fig. 2 is a schematic view of a battery cell according to an embodiment of the present application.

Fig. 3 is an exploded view of the battery cell according to an embodiment of the present application shown in fig. 2.

Fig. 4 is a schematic view of a battery module according to an embodiment of the present application.

Fig. 5 is a schematic view of a battery according to an embodiment of the present application.

Fig. 6 is an exploded view of the battery of the embodiment of the present application shown in fig. 5.

Fig. 7 is a schematic view of an electric device in which a battery cell according to an embodiment of the present application is used as a power source.

Reference numerals illustrate:

1, a battery; 2, upper box body; 3, lower box body; 4, a battery module; 5, a battery cell; 51 a housing; 52 electrode assembly; 53 top cap assembly.

Detailed Description

Embodiments of a coating composition, battery cell, battery and powered device of the present application are specifically disclosed below in detail, with appropriate reference to the accompanying drawings. However, unnecessary detailed description may be omitted. For example, detailed descriptions of well-known matters and repeated descriptions of the actual same structure may be omitted. This is to avoid that the following description becomes unnecessarily lengthy, facilitating the understanding of those skilled in the art. Furthermore, the drawings and the following description are provided for a full understanding of the present application by those skilled in the art, and are not intended to limit the subject matter recited in the claims.

The "range" disclosed herein is defined in terms of lower and upper limits, with a given range being defined by the selection of a lower and an upper limit, the selected lower and upper limits defining the boundaries of the particular range. Ranges that are defined in this way can be inclusive or exclusive of the endpoints, and any combination can be made, i.e., any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a particular parameter, it is understood that ranges of 60-110 and 80-120 are also contemplated. Furthermore, if the

minimum range values

1 and 2 are listed, and if the

maximum range values

3,4 and 5 are listed, the following ranges are all contemplated: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In this application, unless otherwise indicated, the numerical range "a-b" represents a shorthand representation of any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" have been listed throughout, and "0-5" is simply a shorthand representation of a combination of these values. When a certain parameter is expressed as an integer of 2 or more, it is disclosed that the parameter is, for example, an integer of 2, 3,4, 5, 6, 7, 8, 9, 10, 11, 12 or the like.

All embodiments and alternative embodiments of the present application may be combined with each other to form new solutions, unless specifically stated otherwise.

All technical features and optional technical features of the present application may be combined with each other to form new technical solutions, unless specified otherwise.

All steps of the present application may be performed sequentially or randomly, preferably sequentially, unless otherwise indicated. For example, the method comprises steps (a) and (b), meaning that the method may comprise steps (a) and (b) performed sequentially, or may comprise steps (b) and (a) performed sequentially. For example, the method may further include step (c), which means that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), may include steps (a), (c) and (b), may include steps (c), (a) and (b), and the like.

Reference herein to "comprising" and "including" means open ended, as well as closed ended, unless otherwise noted. For example, the terms "comprising" and "comprises" may mean that other components not listed may be included or included, or that only listed components may be included or included.

The term "or" is inclusive in this application, unless otherwise specified. For example, the phrase "a or B" means "a, B, or both a and B. More specifically, either of the following conditions satisfies the condition "a or B": a is true (or present) and B is false (or absent); a is false (or absent) and B is true (or present); or both A and B are true (or present).

As described in the background art above, although the application range of the battery is wider and wider, the requirement for the safety of the battery is higher and higher. The battery cell generally comprises a positive pole piece, a negative pole piece and an isolating film, wherein the isolating film is positioned between the positive pole piece and the negative pole piece and plays a role in conducting ions and isolating electrons.

However, the conventional separator generally uses a polyolefin film, such as a polyethylene film and a polypropylene film, and has the problems that the polyolefin film has poor heat resistance, and the polyethylene film and the polypropylene film are heated at 130 ℃ and 150 ℃ respectively to generate serious shrinkage, so that direct contact between positive and negative plates can be caused, further short circuit occurs, thermal runaway is caused seriously, and potential safety hazard is caused.

In view of the above problems, a ceramic coating is often prepared on a polyolefin film in the related art to reduce the thermal shrinkage of a separator, thereby preventing a short circuit caused by direct contact of positive and negative electrode sheets, and thus improving the safety of a battery cell. However, the problem is that the isolating film has ion conduction function in the battery monomer, and the traditional ceramic materials such as boehmite, alumina, silica and the like are mainly used as the heat-resistant coating at present, so that the dielectric property is poor, the ion transmission property is possibly poor due to polarization in the charge and discharge processes of the battery, the ion conductivity of the isolating film is reduced, and the electrical property of the battery is reduced; on the other hand, the ceramic material has poor film forming property, although the ceramic material can be bonded on the base film by using an adhesive, when the base film is melted at a higher temperature, the conventional ceramic coating cannot form a film stably, and at the moment, the isolating film cannot prevent short circuit caused by direct contact of the positive pole piece and the negative pole piece, so that the thermal failure temperature is lower, and the thermal safety performance at a high temperature is poor; in addition, the conventional ceramic material may also cause a decrease in the energy density of the battery cell due to its high density.

In view of the above technical problems, the embodiments of the present application provide a coating composition from the standpoint of improving coating properties, where the coating composition can prepare a heat-resistant coating on a base film to obtain a composite isolation film, and the coating composition contains benzoxazine resin particles, and has good thermal stability, insulation property and dielectric properties, and the obtained composite isolation film has good heat resistance and ion transmission properties, so that the thermal safety performance and electrical properties of a battery cell are improved. It is also worth noting that the benzoxazine resin particles have a lower density than the ceramic materials in the related art, and therefore the energy density of the battery cells is not significantly affected.

Coating composition

In a first aspect, embodiments herein provide a coating composition comprising: comprising the following steps: a benzoxazine resin particle and a binder, wherein the mass ratio of the binder to the benzoxazine resin particle is 1:1 to 1:20; the benzoxazine resin particles have a Dv50 particle size of 0.1 μm to 5 μm.

According to the application, the coating composition comprises benzoxazine resin particles and a binder, after the coating composition is used for forming a coating on a base film to obtain a composite isolating film, wherein the benzoxazine resin particles are used as a framework of the coating, the benzoxazine resin is obtained by ring-opening crosslinking and curing of benzoxazine monomers under a heating condition, the benzoxazine monomers are a kind of intermediate containing heterocyclic structures synthesized by taking amine compounds, phenolic compounds and aldehyde compounds as raw materials, and therefore the benzoxazine resin has a crosslinked network structure similar to that of phenolic resin, and more aromatic groups can be introduced into the main chain or side chains of the benzoxazine monomers by using different amine compounds and phenolic compounds, namely, the number of rigid groups in the benzoxazine monomers is increased, so that the obtained benzoxazine resin has better heat stability and strength compared with the phenolic resin, and has lower heat shrinkage rate (namely, the benzoxazine resin is not easy to shrink at a higher temperature). A DSC (differential scanning calorimetry) diagram of the benzoxazine resin particles according to an embodiment of the present application is shown in fig. 1, from which it is known that the benzoxazine resin particles have no exothermic and endothermic peaks at-70 ℃ to 400 ℃, indicating good thermal stability.

It can be understood that when the composite isolating film is heated, the base film is shrunk to drive the benzoxazine resin particles to be in quick contact and extrusion, and the benzoxazine resin particles have good thermal stability and high strength and are not easy to deform in the extrusion process, so that an acting force opposite to the shrinkage direction can be applied to the base film, the thermal shrinkage rate of the base film can be obviously reduced, and the heat resistance of the base film is improved; in addition, since the benzoxazine resin particles have very low heat shrinkage, namely, the stability of shape and structure can be ensured at high temperature, the benzoxazine resin particles in the coating can be ensured to be in quick contact and extrusion at higher temperature, so that the heat shrinkage of the base film is better reduced; furthermore, the benzoxazine resin particles have good film forming property and good heat stability in cooperation with the benzoxazine resin particles, so that even if the base film is melted at a higher temperature, the structure of the coating is not easy to damage, and the direct contact of the positive electrode plate and the negative electrode plate in the battery monomer can be prevented from generating short circuit, thereby improving the heat failure temperature of the battery monomer. In conclusion, in the battery cell using the composite isolating film, the composite isolating film has lower heat shrinkage rate at higher temperature, so that the probability of short circuit caused by direct contact of the positive electrode plate and the negative electrode plate in the battery cell is reduced, and the battery cell has higher heat failure temperature, so that the battery cell has good heat safety performance.

On the other hand, since the benzoxazine resin is obtained by ring-opening polymerization and curing of the benzoxazine monomer, and compared with the common phenolic resin, strong acid is not required to be added as a catalyst, small molecules (such as unpolymerized monomers or catalysts) are hardly released in the benzoxazine resin. In the battery monomer using the composite isolating film, small molecules of benzoxazine resin particles in the coating hardly dissolve in electrolyte, so that side reactions can be prevented from affecting the electrical performance of the battery monomer; meanwhile, the benzoxazine resin has better dielectric property, polarization is not easy to occur in the charge and discharge process of the battery monomer, and in addition, a large number of aromatic groups on the benzoxazine resin are worth mentioning, so that the transmission of ions is facilitated, the composite isolation film has good ion transmission property, and the electric property of the battery monomer is improved.

In addition, it is worth mentioning that the benzoxazine resin particles have a lower density, so that the weight of the composite isolating film can be reduced, and the energy density of the battery cell can be improved.

The binder in the coating composition is mainly used for stable adhesion between the benzoxazine resin particles and the base film and between the benzoxazine resin particles, and it is understood that according to the description of the reduction of the thermal shrinkage rate of the base film by the benzoxazine resin particles, namely, by applying a force opposite to the shrinkage direction to the base film, the stable adhesion of the benzoxazine resin particles and the base film has a great influence on the effect of the benzoxazine resin particles, if no binder is added, the thermal shrinkage rate of the base film is difficult to reduce only by the friction force between the particles and the base film, whereas by adding the binder, the adhesion force between the particles and the base film is much higher than the friction force between the particles and the base film, so that the coating can reduce the thermal shrinkage rate of the base film better. In addition, the coating on the surface of the composite isolating film can be prevented from falling off easily due to the strong binding force, and after the base film is melted, the coating can still ensure the complete structure of the composite isolating film, the effect of the isolating film is exerted, the direct contact of the positive pole piece and the negative pole piece is prevented, so that the composite isolating film has better stability, and the safety of a battery monomer is improved.

In the embodiment of the application, the mass ratio of the binder to the benzoxazine resin particles is further defined to be 1:1 to 1:20, and it can be understood that if the content of the binder is too high, the coating applied to the base film is reduced due to the fact that the thermal stability and strength of the binder are poorer than those of the benzoxazine resin, so that the thermal shrinkage rate of the base film cannot be effectively reduced, and in addition, the coating difficulty is increased and the production cost is increased due to the fact that the binder is too high; if the content of the binder is too low, the binder cannot effectively play the role of the binder, namely the cohesiveness between the particles and the base film is poor, the acting force of the coating applied to the base film opposite to the shrinkage direction is reduced, meanwhile, the coating is unstable and easy to fall off powder, and after the base film is melted, the structure of the coating is damaged, so that the heat resistance and the stability of the composite isolating film are affected. Accordingly, it is desirable to control the mass ratio of the binder to the benzoxazine resin particles to be in the range of 1:1 to 1:20, for example, the mass ratio of the binder to the benzoxazine resin particles may be 1:1,1:2,1:3,1:4,1:5,1:6,1:7,1:8,1:9,1:10,1:11,1:12,1:13,1:14,1:15,1:16,1:17,1:18,1:19,1:20, or any of the values described above. Preferably, the mass ratio of the binder to the benzoxazine resin particles may be 1:4 to 1:18.

In the embodiment of the present application, the Dv50 particle diameter of the benzoxazine resin particles is further defined, and it is understood that, in general, the smaller the particle diameter of the benzoxazine resin particles is, the larger the number of particles per unit area of the base film is, and therefore, the larger the acting force of the particles on the base film opposite to the shrinkage direction is, the better the heat resistance of the obtained composite isolating film is; in addition, when the particle size is smaller, the coating is lighter and thinner on the premise of ensuring the heat resistance of the composite isolating film, and the energy density of the battery monomer is improved. Therefore, the Dv50 particle size of the benzoxazine resin particles can be reduced as much as possible, so that the composite isolating film with better heat resistance can be obtained. However, if the Dv50 particle size of the benzoxazine resin particles is too small, the influence on the air permeability of the composite isolating membrane is increased, it is understood that the smaller the particle size is, the larger the stacking density of the coating is, the smaller the porosity of the coating is, and even part of the benzoxazine resin particles can enter the inside of the aperture of the base membrane, so that the phenomenon of blocking holes is caused, and the ion transmission performance of the composite isolating membrane is reduced; on the other hand, the smaller the particle diameter, the worse the thermal stability of the particles, and the heat resistance of the composite separator may be deteriorated. In addition, benzoxazine resin particles with too small particle size can cause increased processing difficulty and increase production cost.

In summary, due to the good thermal stability, insulation and dielectric properties of the benzoxazine resin particles in the embodiments of the present application, compared with the ceramic materials used in the heat-resistant coatings in the prior art, the Dv50 particle size of the poly benzoxazine resin particles can be smaller, so as to improve the energy density of the battery monomer under the premise of ensuring the heat resistance and ion transmission properties of the composite isolation film. The Dv50 particle diameter of the benzoxazine resin particles may thus be controlled within a range of 0.1 μm to 5 μm, for example, the Dv50 particle diameter of the benzoxazine resin particles may be 0.1 μm,0.2 μm,0.3 μm,0.4 μm,0.5 μm,0.6 μm,0.7 μm,0.8 μm,0.9 μm,1.0 μm,1.5 μm,2.0 μm,2.5 μm,3.0 μm,3.5 μm,4.0 μm,4.5 μm,5.0 μm, or a range consisting of any of the above.

The Dv50 particle diameter of the porous phenolic resin microspheres in the present application has a meaning known in the art, and the Dv50 particle diameter is a particle size distribution on a volume basis, and 50% of the particles have a particle diameter smaller than this, and the Dv50 can be measured by methods and instruments known in the art. For example, reference may be made to GB/T19077-2016 particle size distribution laser diffraction, using a laser particle size analyzer (e.g.Mastersizer 2000E, UK).

In some embodiments, the binder includes at least one of polyacrylic acid, polyacrylate, polyvinylidene fluoride, styrene butadiene rubber, sodium carboxymethyl cellulose.

In the above embodiments, specific binders are listed, and one or more of them may be selected according to the implementation requirements by those skilled in the art. The above adhesives have better bonding effect, can ensure that the porous phenolic resin microspheres are stably combined on the surface of the base film, and improve the stability of the composite isolating film; in addition, the above-mentioned adhesives have good heat resistance and still have strong adhesion at a high temperature, so that the heat resistance of the composite separator can be further improved.

It should be noted that the binder includes, but is not limited to, several materials listed above, and any binder known in the art may be selected by those skilled in the art according to actual needs.

In some embodiments, the benzoxazine resin particles may have a Dv50 particle size of 0.5 μm to 3 μm. The inventor finds through a large number of experiments that when the Dv50 particle size of the benzoxazine resin particles is in the range of 0.5 mu m to 3 mu m, the benzoxazine resin particles still have good thermal stability, meanwhile, the obtained composition has good film forming property, the obtained composite isolating film has lower thermal shrinkage rate, the obtained battery monomer has higher thermal failure temperature, and the ionic conductivity of the composite isolating film can still meet the requirement; on the other hand, the coating can realize lighter and thinner coating, is more beneficial to reducing the weight of the composite isolating film and improving the energy density of the battery.

In some embodiments, the benzoxazine resin particles are cured from benzoxazine monomers and crushed; the benzoxazine monomer is obtained by reacting an amine compound, a phenol compound and an aldehyde compound in a solvent.

In the above embodiment, the preparation method of the benzoxazine resin particles is simple and low in cost, and the benzoxazine resin particles with different properties can be obtained by selecting different amine compounds, phenol compounds and aldehyde compounds, so that the benzoxazine resin particles have high designability, and therefore, suitable benzoxazine resin particles can be obtained according to actual needs.

For example, benzoxazine resin particles are obtained by curing and pulverizing benzoxazine monomers, and thus benzoxazine resin particles having different particle size distributions can be obtained by controlling the pulverizing conditions; the benzoxazine monomer is synthesized from three monomers of amine compound, phenol compound and aldehyde compound, and the specific types of the three monomers are not particularly limited, and the types of the monomers have significant influence on the properties (such as thermal stability, rigidity, dielectric property and the like) of the benzoxazine resin, so that the properties of the benzoxazine resin particles also have high designability, and the benzoxazine resin particles can be prepared and screened according to actual needs to obtain the benzoxazine resin particles which are more used in the coating composition.

In some embodiments, the molar ratio of amine groups in the amine compound, phenolic hydroxyl groups in the phenolic compound, and aldehyde groups in the aldehyde compound is 1 (1 to 1.5): 2 to 2.5.

In some of the above embodiments, the molar ratio of amine groups in the amine compound, phenolic hydroxyl groups in the phenolic compound, and aldehyde groups in the aldehyde compound is further defined. It can be understood that the reaction mechanism of synthesizing the benzoxazine monomer is that the molar ratio of the amino group in the amine compound to the phenolic hydroxyl group in the phenolic compound to the aldehyde group in the aldehyde compound is 1:1:2, so that the closer the molar ratio of the three groups is to 1:1:2, the less unreacted raw materials remain, the lower the raw material cost and the separation and purification cost of the benzoxazine monomer are, the less molecular residues in the benzoxazine resin particles can be effectively reduced, the stability of the benzoxazine resin particles is improved, the dissolution of the benzoxazine resin particles in the electrolyte of the battery monomer is prevented, the influence on the electrical performance of the battery monomer is reduced, and on the other hand, the improvement of the reaction rate and the yield is facilitated by the proper excessive raw materials, for example, the improvement of the reaction rate is facilitated while the complete reaction of the amino group is promoted. Therefore, the molar ratio of the amino group in the amine compound, the phenolic hydroxyl group in the phenolic compound and the aldehyde group in the aldehyde compound can be controlled to be 1 (1 to 1.5): 2 to 2.5, and the benzoxazine resin particles have better stability and higher yield. Further preferably, the molar ratio of the amine groups in the amine compound, the phenolic hydroxyl groups in the phenolic compound, and the aldehyde groups in the aldehyde compound may be 1 (1 to 1.1): 2 to 2.1.

As some examples, the method of preparing benzoxazine resin particles may include the steps of:

adding an amine compound, a phenol compound and an aldehyde compound into a solvent, and stirring and reacting for a first heating period at a first heating temperature to obtain a homogeneous solution;

washing the homogeneous phase solution with alkaline aqueous solution and water respectively, collecting organic phase, drying, filtering and concentrating to obtain benzoxazine monomer;

and curing the benzoxazine monomer at a second heating temperature for a second heating time to obtain benzoxazine resin, and then crushing and grinding to obtain benzoxazine resin particles.

It will be appreciated that different existing comminution and milling methods may be used to obtain benzoxazine resin particles having different particle size distributions, and those skilled in the art may choose from as desired.

As some examples, the amine groups in the amine compound may have a concentration of 0.1mol/L to 1mol/L of functional groups in the reaction system.

As some examples, the first heating temperature may be 80 ℃ to 120 ℃ and the first heating period may be 3 hours to 10 hours.

As some examples, the second heating temperature may be 150 ℃ to 220 ℃ and the second heating duration may be 2 hours to 6 hours.

It should be noted that, the heating temperature (including the first heating temperature and the second heating temperature) is not limited to a single temperature, and may also represent a temperature range, and the corresponding heating time period (including the first heating time period and the second heating time period) may also be the sum of the heating times at different heating temperatures, for example, after heating at 80 ℃ for 2 hours and then heating at 90 ℃ for 2 hours, and then heating at 80 ℃ to 90 ℃ for 4 hours.

It will be appreciated that the above methods are exemplary and that the benzoxazine resin particles may be prepared according to other methods known in the art.

In some of the above embodiments, it is further defined that the amine compound is a diamine compound and the phenol compound is a monophenol compound, that is, the obtained benzoxazine monomer is a diamine type bicyclo benzoxazine monomer. It can be understood that compared with the monocyclic benzoxazine monomer, the benzoxazine resin obtained by thermal polymerization of the bicyclic benzoxazine monomer has higher crosslinking degree, higher strength and better thermal stability, and the heat resistance of the obtained composite isolating film is better.

Further, the inventor has unexpectedly found in experiments that, when diamine-type compounds, monophenol-type compounds and aldehyde-type compounds are used for synthesizing diamine-type dicyclo-benzoxazine monomers, and curing and polymerizing to obtain benzoxazine resin particles, compared with when monoamine-type compounds, bisphenol-type compounds and aldehyde-type compounds are used for synthesizing bisphenol-type dicyclo-benzoxazine monomers, curing and polymerizing to obtain benzoxazine resin particles, the prepared composite isolating film has lower heat shrinkage rate and higher ionic conductivity, and the heat failure temperature of the obtained battery monomers is higher, so that the use of the diamine-type dicyclo-benzoxazine monomers for curing and polymerizing to obtain benzoxazine resin particles is more beneficial to improving the heat safety performance and the electrical performance of the battery monomers.

Without being bound by any theory, the reason for this may be that the thermal stability and dielectric properties of the benzoxazine resin particles are highly related to their molecular structures, and that the diamine-type bicyclo-benzoxazine monomer curing polymerized benzoxazine resin particles are more uniform and dense in crosslinking than bisphenol-type bicyclo-benzoxazine monomer curing polymerized benzoxazine resin particles, thereby making the thermal stability and dielectric properties of the benzoxazine resin particles more excellent and further improving the thermal safety and electrical properties of the battery cells.

In some embodiments, the diamine compound comprises at least one of 1, 6-hexamethylenediamine, diaminodiphenylmethane, and diaminodiphenylsulfone; the monophenol compound comprises at least one of phenol, p-methoxyphenol, cardanol and o-allylphenol; the aldehyde compound comprises formaldehyde and/or paraformaldehyde; the solvent comprises at least one of dioxane, chloroform and xylene.

In the above embodiment, specifically, raw materials usable for the production of the benzoxazine resin particles are listed, and the raw materials for the production of the benzoxazine resin particles are inexpensive and readily available, are of a large variety, can be selected according to actual needs, and are suitable for industrial production.

The diamine compound, the monophenol compound, the aldehyde compound, and the solvent are not limited to the above-mentioned ones, and those skilled in the art can select other types of diamine compounds, monophenol compounds, aldehyde compounds, and solvents according to actual needs.

In some embodiments, the coating composition further includes a dispersant, which may include water, dimethylformamide (DMF), diethylformamide, dimethylacetamide (DMAc), N-methylpyrrolidone (NMP), methanol, ethanol, 1-propanol, 2-propanol (isopropanol), 1-butanol (N-butanol), 2-methyl-1-propanol (isobutanol), 2-butanol (sec-butanol), 1-methyl-2-propanol (tert-butanol), pentanol, hexanol, heptanol, or octanol; diols such as at least one of ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, 1, 3-propanediol, 1, 3-butanediol, 1, 5-pentanediol, hexanediol, glycerol, trimethylolpropane, pentaerythritol, sorbitol, ethylene glycol monomethyl ether, diethylene glycol monomethyl ether, triethylene glycol monomethyl ether, tetraethylene glycol monomethyl ether, ethylene glycol monoethyl ether, diethylene glycol monoethyl ether, triethylene glycol monoethyl ether, tetraethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monobutyl ether, triethylene glycol monobutyl ether, tetraethylene glycol monobutyl ether, acetone, methyl ethyl ketone, methyl propyl ketone, cyclopentanone, ethyl acetate, gamma-butyrolactone, and epsilon-propiolactone.

In some embodiments, the solids content in the coating composition may be 10% to 50%.

In some embodiments, other additives may also be included in the coating composition, such as defoamers, wetting agents, emulsifiers, anti-settling agents, and the like. Those skilled in the art can make optional additions as desired.

Method for preparing coating composition

The application also provides a preparation method of the coating composition, which comprises the following steps: the benzoxazine resin particles and the binder are dispersed in a dispersant to obtain a coating composition.

The specific types and amounts of the benzoxazine resin particles, the binder and the dispersant may be selected according to any of the embodiments of the first aspect.

Composite isolating film

a coating layer formed of the coating composition according to any of the embodiments of the first aspect disposed on at least one surface of a base film.

According to the present application, the composite release film comprises a coating layer formed from the coating composition of any of the embodiments of the first aspect, and it is therefore understood that the composite release film has the beneficial effects of the first aspect.

In any embodiment of the present application, the kind of the base film is not limited, and a separator film known in the art may be selected as the base film according to actual needs. For example, a single-layer polyolefin separator may be used as the base film, and the single-layer polyolefin separator may include at least one of a polyethylene separator and a polypropylene separator, or a multi-layer polyolefin separator may include at least one of a polypropylene-polyethylene-polypropylene separator and a polypropylene-polyethylene separator.

In some embodiments, the areal density of the coating is 0.1g/m ² To 5g/m ² 。

In the above embodiment, since the benzoxazine resin particles in the coating layer have good thermal stability, strength and film forming property and lower density, the coating layer can still enable the composite isolating film to have good heat resistance under the condition of lower surface density compared with the common ceramic coating layer, and in addition, the composite isolating film can have better ionic conductivity due to the lower surface density, so that the battery cell has good thermal safety performanceMeanwhile, the battery has better electrical performance, and meanwhile, the energy density of the battery monomer can be effectively improved. However, if the surface density of the coating is too low, the heat resistance of the composite isolating film cannot be ensured, and at the same time, when the base film is melted at a higher temperature, the coating cannot maintain a stable structure, and the thermal failure temperature of the battery monomer is reduced, so that the surface density of the coating can be controlled to be 0.1g/m ² To 5g/m ² Within a range of (1), for example, the areal density of the coating may be 0.1g/m ² ，0.2g/m ² ，0.3g/m ² ，0.4g/m ² ，0.5g/m ² ，0.6g/m ² ，0.7g/m ² ，0.8g/m ² ，0.9g/m ² ，1g/m ² ，1.2g/m ² ，1.4g/m ² ，1.6g/m ² ，1.8g/m ² ，2g/m ² ，2.2g/m ² ，2.4g/m ² ，2.6g/m ² ，2.8g/m ² ，3g/m ² ，3.5g/m ² ，4g/m ² ，4.5g/m ² ，5g/m ² Or any of the above values. Further preferably, the areal density of the coating may be 0.5g/m ² To 4g/m ² 。

Battery cell

According to the application, the battery cell comprises the composite isolating film of any embodiment of the second aspect, so it can be understood that the battery cell has the beneficial effects of the second aspect.

Typically, the battery cell also includes a positive electrode tab, a negative electrode tab, and an electrolyte. During the charge and discharge of the battery, active ions are inserted and extracted back and forth between the positive electrode plate and the negative electrode plate. The electrolyte plays a role in ion conduction between the positive electrode plate and the negative electrode plate.

[ Positive electrode sheet ]

The positive pole piece comprises a positive current collector and a positive film layer arranged on at least one surface of the positive current collector, wherein the positive film layer comprises the positive active material of the first aspect of the application.

As an example, the positive electrode current collector has two surfaces opposing in its own thickness direction, and the positive electrode film layer is provided on either one or both of the two surfaces opposing the positive electrode current collector.

In some embodiments, the positive current collector may employ a metal foil or a composite current collector. For example, as the metal foil, aluminum foil may be used. The composite current collector may include a polymeric material base layer and a metal layer formed on at least one surface of the polymeric material base layer. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel alloy, titanium alloy, silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

In some embodiments, the positive electrode active material may employ a positive electrode active material for a battery, which is well known in the art. As an example, the positive electrode active material may include at least one of the following materials: olivine structured lithium-containing phosphates, lithium transition metal oxides and their respective modified compounds. However, the present application is not limited to these materials, and other conventional materials that can be used as a battery positive electrode active material may be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides may include, but are not limited to, lithium cobalt oxide (e.g., liCoO) ₂ ) Lithium nickel oxide (e.g. LiNiO) ₂ ) Lithium manganese oxide (e.g. LiMnO ₂ 、LiMn ₂ O ₄ ) Lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (e.g., liNi) _1/3 Co _1/3 Mn _1/3 O ₂ (also referred to as NCM) ₃₃₃ ）、LiNi _0.5 Co _0.2 Mn _0.3 O ₂ (also referred to as NCM) ₅₂₃ ）、LiNi _0.5 Co _0.25 Mn _0.25 O ₂ (also referred to as NCM) ₂₁₁ ）、LiNi _0.6 Co _0.2 Mn _0.2 O ₂ (also referred to as NCM) ₆₂₂ ）、LiNi _0.8 Co _0.1 Mn _0.1 O ₂ (also referred to as NCM) ₈₁₁ ) Lithium nickel cobalt aluminum oxide (e.g. LiNi _0.85 Co _0.15 Al _0.05 O ₂ ) And at least one of its modified compounds and the like. Examples of olivine structured lithium-containing phosphates may include, but are not limited to, lithium iron phosphate (e.g., liFePO ₄ (also abbreviated as LFP)), composite material of lithium iron phosphate and carbon, and manganese lithium phosphate (such as LiMnPO) ₄ ) At least one of a composite material of lithium manganese phosphate and carbon, and a composite material of lithium manganese phosphate and carbon.

In some embodiments, the positive electrode film layer further optionally includes a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluoroacrylate resin.

In some embodiments, the positive electrode film layer further optionally includes a conductive agent. As an example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

In some embodiments, the positive electrode sheet may be prepared by: dispersing the above components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder and any other components, in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; and (3) coating the positive electrode slurry on a positive electrode current collector, and obtaining a positive electrode plate after the procedures of drying, cold pressing and the like.

[ negative electrode sheet ]

The negative electrode plate comprises a negative electrode current collector and a negative electrode film layer arranged on at least one surface of the negative electrode current collector, wherein the negative electrode film layer comprises a negative electrode active material.

As an example, the anode current collector has two surfaces opposing in its own thickness direction, and the anode film layer is provided on either one or both of the two surfaces opposing the anode current collector.

In some embodiments, the negative electrode current collector may employ a metal foil or a composite current collector. For example, as the metal foil, copper foil may be used. The composite current collector may include a polymeric material base layer and a metal layer formed on at least one surface of the polymeric material base material. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel alloy, titanium alloy, silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

In some embodiments, the anode active material may employ an anode active material for a battery, which is well known in the art. As an example, the anode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, and the like. The silicon-based material may be at least one selected from elemental silicon, silicon oxygen compounds, silicon carbon composites, silicon nitrogen composites, and silicon alloys. The tin-based material may be at least one selected from elemental tin, tin oxide, and tin alloys. However, the present application is not limited to these materials, and other conventional materials that can be used as a battery anode active material may be used. These negative electrode active materials may be used alone or in combination of two or more.

In some embodiments, the negative electrode film layer further optionally includes a binder. The binder may be at least one selected from 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).

In some embodiments, the negative electrode film layer further optionally includes a conductive agent. The conductive agent is at least one selected from superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.

In some embodiments, the negative electrode film layer may optionally further include other adjuvants, such as thickening agents (e.g., sodium carboxymethyl cellulose (CMC-Na)), and the like.

In some embodiments, the negative electrode sheet may be prepared by: dispersing the above components for preparing the negative electrode sheet, such as a negative electrode active material, a conductive agent, a binder and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; and coating the negative electrode slurry on a negative electrode current collector, and obtaining a negative electrode plate after the procedures of drying, cold pressing and the like.

[ electrolyte ]

The electrolyte plays a role in ion conduction between the positive electrode plate and the negative electrode plate. The type of electrolyte is not particularly limited in this application, and may be selected according to the need. For example, the electrolyte may be liquid, gel, or all solid.

In some embodiments, the electrolyte is an electrolyte. The electrolyte includes an electrolyte salt and a solvent.

In some embodiments, the electrolyte salt may be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis-fluorosulfonyl imide, lithium bis-trifluoromethanesulfonyl imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalato borate, lithium difluorodioxaato phosphate, and lithium tetrafluorooxalato phosphate.

In some embodiments, the solvent may be selected from at least one of ethylene carbonate, propylene carbonate, methylethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methylpropyl carbonate, ethylpropyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1, 4-butyrolactone, sulfolane, dimethyl sulfone, methyl sulfone, and diethyl sulfone.

In some embodiments, the electrolyte further optionally includes an additive. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives capable of improving certain properties of the battery, such as additives that improve the overcharge performance of the battery, additives that improve the high or low temperature performance of the battery, and the like.

In some embodiments, the positive electrode tab, the negative electrode tab, and the composite separator may be manufactured into an electrode assembly through a winding process or a lamination process.

In some embodiments, the battery cell may include an outer package. The outer package may be used to encapsulate the electrode assembly and electrolyte described above.

In some embodiments, the exterior packaging of the battery cell may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, or the like. The outer package of the battery cell may also be a pouch, such as a pouch-type pouch. The material of the flexible bag may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, and polybutylene succinate.

The shape of the battery cell is not particularly limited in this application, and may be cylindrical, square, or any other shape. For example, fig. 2 is a square-structured battery cell 5 as one example.

In some embodiments, referring to fig. 3, the outer package may include a housing 51 and a cover 53. The housing 51 may include a bottom plate and a side plate connected to the bottom plate, where the bottom plate and the side plate enclose a receiving chamber. The housing 51 has an opening communicating with the accommodation chamber, and the cover plate 53 can be provided to cover the opening to close the accommodation chamber. The positive electrode tab, the negative electrode tab, and the separator may be formed into the electrode assembly 52 through a winding process or a lamination process. The electrode assembly 52 is enclosed in the accommodating chamber. The electrolyte is impregnated in the electrode assembly 52. The number of the electrode assemblies 52 included in the battery cell 5 may be one or more, and those skilled in the art may select the number according to specific practical requirements.

Battery cell

In a fourth aspect, the present application provides a battery comprising the battery cell of any one of the embodiments of the third aspect.

According to the application, battery cell can assemble into the battery, and this application an embodiment still provides a battery, includes: the box body and the battery monomer; the battery cell is accommodated in the case.

The number of battery cells included in the above-described battery may be one or more, and the specific number may be selected by those skilled in the art according to the application and capacity of the battery.

Further, in the above battery, a plurality of battery cells exist in the form of assembled battery modules. Fig. 4 is a battery module 4 as an example. Referring to fig. 4, in the battery module 4, a plurality of battery cells 5 may be sequentially arranged in the longitudinal direction of the battery module 4. Of course, the arrangement may be performed in any other way. The plurality of battery cells 5 may be further fixed by fasteners.

Alternatively, the battery module 4 may further include a housing having an accommodating space in which the plurality of battery cells 5 are accommodated.

Fig. 5 and 6 are a battery 1 as an example. Referring to fig. 5 and 6, a battery case and a plurality of battery modules 4 disposed in the battery case may be included in the battery 1. The battery box includes an upper box body 2 and a lower box body 3, and the upper box body 2 can be covered on the lower box body 3 and forms a closed space for accommodating the battery module 4. The plurality of battery modules 4 may be arranged in the battery box in any manner.

The battery may be a secondary battery or a lithium battery.

Power utilization device

In a fifth aspect, the present application provides an electrical device comprising at least one of the battery cell of any of the embodiments of the third aspect or the battery of any of the embodiments of the fourth aspect.

The application also provides an electric device, which comprises the battery cell or the battery provided by the application. The battery cell or battery may be used as a power source for the power device and may also be used as an energy storage unit for the power device. The power utilization device may include mobile devices (e.g., cell phones, notebook computers, etc.), electric vehicles (e.g., electric-only vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but is not limited thereto.

As the electricity consumption device, the above-mentioned battery cell or battery may be selected according to the use requirement thereof.

Fig. 7 is an electrical device as an example. The electric device is a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle or the like.

As another example, the device may be a cell phone, tablet computer, notebook computer, or the like. The device is generally required to be light and thin, and a battery cell can be used as a power supply.

Examples

Hereinafter, embodiments of the present application are described. The embodiments described below are exemplary only for the purpose of illustrating the present application and are not to be construed as limiting the present application. The examples are not to be construed as limiting the specific techniques or conditions described in the literature in this field or as per the specifications of the product. The reagents or apparatus used were conventional products commercially available without the manufacturer's attention.

Example 1-1

(1) Preparation of benzoxazine resin particles

Diamine diphenyl methane (119 g,0.6mol, the mole number of amine groups is 1.2 mol), p-methoxyphenol (149 g,1.2mol, the mole number of phenolic hydroxyl groups is 1.2 mol) and paraformaldehyde (72 g, the mole number of aldehyde groups is 2.4 mol) are sequentially added into a 5L two-port bottle, 3L chloroform is used for dissolving, namely the mole number ratio of amine groups in amine compounds, phenolic hydroxyl groups in phenolic compounds and aldehyde groups in aldehyde compounds in the system is 1:1:2, the system is heated to 80 ℃ for 5 hours to obtain a homogeneous solution, the reaction is stopped, the temperature is reduced to room temperature, the reaction solution is respectively washed 3 times by 1mol/L sodium hydroxide solution and deionized water, and the organic phase is dried, filtered and concentrated by anhydrous sodium sulfate. Drying for 12 hours at 60 ℃ in a vacuum drying oven to obtain benzoxazine monomers;

the benzoxazine monomer is heated for 1h at the temperatures of 150, 180 and 220 ℃ respectively, and then crushed and ground to obtain benzoxazine resin particles with the Dv50 particle size of 0.1 mu m.

(2) Preparation of composite isolation film

Using commercially available thicknesses ofA microporous film of PE polymer (from zebra electronic technologies company) with an average pore size of 80nm of 7 μm was used as substrate. And (3) adding 850g of deionized water into 150g of the polyacrylic acid binder and the benzoxazine resin particles according to the mass ratio of 1:10, and uniformly stirring and mixing to obtain the slurry. Coating the slurry on a substrate, drying the substrate by an oven, and coating the adhesive and the phenol benzoxazine resin on the substrate with the coating density of 1g/m ² And then rolling to obtain the composite isolating film.

(2) Preparation of positive electrode plate

Polyvinylidene fluoride (PVDF), lithium iron phosphate (LFP), conductive agent carbon black and N-methyl pyrrolidone (NMP) are fully stirred and uniformly mixed according to the mass ratio of 1.2:58.38:0.42:40, so that the anode slurry is prepared. The positive electrode slurry was prepared at a concentration of 200g/m ² The load capacity of the alloy is uniformly coated on an aluminum foil of the positive electrode current collector, and then the positive electrode plate is obtained through drying, cold pressing and cutting.

(3) Preparation of negative electrode plate

Artificial graphite, a conductive agent acetylene black, a binder Styrene Butadiene Rubber (SBR) and a thickener sodium carboxymethyl cellulose (CMC-Na) are added into deionized water according to the mass ratio of 96.2:1.0:1.6:1.2, and the negative electrode slurry (the solid content is 63%) is prepared after the materials are fully stirred and uniformly mixed. The negative electrode slurry was prepared at 98g/m ² The load capacity of the anode electrode is coated on the anode current collector copper foil, and then the anode electrode plate is obtained through drying, cold pressing and slitting.

(4) Preparation of electrolyte

Mixing Ethylene Carbonate (EC), ethylmethyl carbonate (EMC) and diethyl carbonate (DEC) at a volume ratio of 1:1:1 at 25deg.C to obtain a mixed solvent, and then mixing LiPF ₆ Dissolving in the mixed solvent to obtain electrolyte, wherein LiPF ₆ The concentration of (C) was 1mol/L.

(5) Preparation of secondary battery

Stacking, winding and cold-pressing the positive pole piece, the composite isolating film and the negative pole piece in sequence (bonding the diaphragm and the pole piece during the cold-pressing) to obtain an electric core; and placing the battery core into an outer package, adding the prepared electrolyte, and performing the procedures of packaging, standing, formation, aging and the like to obtain the secondary battery.

Examples 1-2 to 1-28, comparative examples 1-1 and comparative examples 1-2 are substantially the same as example 1-1, and the parameters for partial differences are shown in Table 1.

Comparative examples 1 to 3

Substantially the same as in example 1-1, except that a commercially available microporous PE polymer film having a thickness of 7 μm and an average pore diameter of 80nm was directly used as a separator for a secondary battery.

Comparative examples 1 to 4

The same as in example 1-1 except that, in the composite separator, alumina having a Dv50 particle diameter of 1 μm was used in place of benzoxazine resin particles to prepare a composite separator, the coating density was 2g/m ² Other conditions were the same, and the separator was used as a secondary battery.

Examples 2-1 to 2-10, comparative examples 2-1 and comparative examples 2-2 are substantially the same as examples 1-3, and the parameters for partial differences are shown in Table 2.

Test part

1. Thermal shrinkage test of barrier film

Sample preparation: the prepared isolating film is punched into samples with the width of 50mm and the length of 100mm by a punching machine, 5 parallel samples are taken and placed on A4 paper, and then the A4 paper with the samples is placed on corrugated paper with the thickness of 1mm to 5 mm.

Sample testing: setting the temperature of the blast type oven to 150 ℃, after the temperature reaches the set temperature and is stabilized for 30min, putting the A4 paper placed on the corrugated paper into the blast type oven, starting timing, measuring the length and the width of the isolating film after the set time (1 h in the application) is reached, and marking the values as a and b respectively.

And (5) calculating the thermal shrinkage rate: machine Direction (MD) heat shrinkage= [ (100-a)/100 ] ×100%, transverse Direction (TD) heat shrinkage= [ (50-b)/50 ] ×100%, and an average value of 5 parallel samples was taken as a test result.

2. Isolation film ion conductivity test

(1) 2025 button cell for testing was prepared: in a vacuum glove box, a lithium sheet is put into a battery cathode shell, and 150 mu L of upper part is added into the lithium sheetThe electrolyte was then put into the above-prepared separator (3.14 cm in area ² ) And (3) enabling the electrolyte to cling to the lithium sheet, adding 25 mu L of the electrolyte, placing the positive electrode sheet on the electrolyte, and packaging. The assembled button cell was removed from the vacuum glove box and left for 24 hours for further testing.

(2) And (3) testing: at an electrochemical workstation, at 10 ^-1 ~10 ⁶ The test was conducted in the frequency range of Hz to obtain the isolation film resistance Rb, and the ion conductivity sigma (unit: mS.cm) was calculated by the following formula ^-1 ）：

σ=L/(Rb×S)

Wherein: rb is equivalent resistance, and L and S are thickness and area of the isolating film to be tested respectively.

3. Hot box test of secondary battery

Charging the secondary battery to 4.2V at a constant current of 1C at 25 ℃, continuously charging at a constant voltage until the current is less than or equal to 0.05C, and standing for 5min; then each secondary battery was tested with a jig in a DHG-9070ADHG series high temperature oven, and was warmed from room temperature to 80±2 ℃ at a rate of 5 ℃/min, and held for 30min; and then heating at a heating rate of 5 ℃ per minute, and preserving heat for 30 minutes at each heating rate of 5 ℃ until the secondary battery fails. And monitoring the surface temperature change of the secondary battery in the temperature rising process, and obtaining the corresponding oven temperature when the temperature starts to rise sharply, namely the failure temperature of the hot box of the secondary battery. The higher the thermal case failure temperature of the secondary battery, the better the thermal safety performance of the secondary battery.

The test results are shown in tables 1 and 2.

TABLE 1

Note that: in table 1 "\" indicates that this parameter is not contained.

TABLE 2

From table 1, it is seen that the composite barrier film obtained in each example has better overall properties as compared with each comparative example. In comparative example 1-1, among them, the benzoxazine resin particles had too small particle size, resulting in poor ion conductivity of the separator. In comparative examples 1 to 2, the benzoxazine resin particles had too large particle size, resulting in higher heat shrinkage, lower heat box failure temperature of the secondary battery, and poorer thermal safety performance of the secondary battery. In comparative examples 1 to 3, the polyethylene-based film was directly used as the separator for the secondary battery, which had poor heat resistance, and thus had high heat shrinkage, low heat box failure temperature of the secondary battery, and poor thermal safety performance of the secondary battery. In comparative examples 1 to 4, the heat shrinkage rate was reduced as compared with comparative examples 1 to 3, but the reduction effect was not significant, probably because alumina was inferior in film forming property, although it had good heat resistance itself, but the improvement in heat resistance of the separator was not significant, and at the same time, when the base film was melted, the coating layer was difficult to maintain a stable structure, so that the increase in the heat box failure temperature of the secondary battery was small, and the thermal safety performance of the secondary battery was poor; in addition, as the dielectric property of the alumina is worse than that of benzoxazine resin, the ionic conductivity of the obtained composite isolating film is lower under the same condition, which is not beneficial to the electrical property of a secondary battery.

Comparing examples 1-1 to 1-8, it is understood that Dv50 particle size of the benzoxazine resin particles has a certain influence on heat resistance and ion conductivity of the composite separator, thereby affecting thermal safety performance and electrical performance of the secondary battery. When the Dv50 particle diameter of the benzoxazine resin particles is 0.5 μm to 3 μm, the obtained composite separator has better heat resistance and the secondary battery has better heat safety. It is understood that the larger the Dv50 particle size, the higher the porosity of the coating and the higher the ionic conductivity. When the Dv50 particle diameter of the benzoxazine resin particles is 0.1-5 mu m, the obtained composite isolating film has higher ion conductivity, can meet the use requirement of a secondary battery, and has better electrical property.

Comparing examples 1-9 to examples 1-16 and examples 1-3, it is clear that the raw materials for preparing the benzoxazine resin particles have a certain influence on the heat resistance and the ion conductivity of the composite isolating film, but have smaller influence, and have better heat resistance and ion transmission performance, and the thermal safety performance and the electrical performance of the secondary battery are better.

As is clear from the comparison of examples 1 to 9 to 1 to 20 and examples 1 to 3, the raw materials for preparing the benzoxazine resin particles have a certain influence on the heat resistance and the ion conductivity of the composite separator, but the kinds of the diamine compound and the monophenol compound have a smaller influence on the heat resistance and the ion conductivity of the composite separator (the comparison of examples 1 to 9 to 1 to 16 and examples 1 to 3), and the obtained composite separator has better heat resistance and ion transmission performance, and the secondary battery has better thermal safety performance and electrical performance.

The benzoxazine resin particles are obtained by curing bisphenol dicyclobenzoxazine monomers, the benzoxazine resin particles are obtained by curing diamine dicyclobenzoxazine monomers, the influence on heat resistance and ion conductivity of the composite isolating film is large, and when the benzoxazine resin particles are obtained by curing diamine dicyclobenzoxazine monomers, the obtained composite isolating film is better in heat resistance and ion transmission performance, and the secondary battery is better in thermal safety performance and electrical performance.

Comparing examples 1-21 to examples 1-28 and examples 1-3, it is understood that the higher the coating surface density, the better the heat resistance and poor ion transport properties of the composite separator, and at the same time, the lower the energy density of the secondary battery. When the coating surface density is 0.1g/m ² To 5g/m ² And the obtained composite isolating film has better heat resistance and ion transmission performance, and the secondary battery has better heat safety performance and electrical performance. Preferably, when the coating surface density is 0.5g/m ² To 4g/m ² In this case, the thermal safety performance and the electrical performance of the secondary battery can be better considered.

The possible reasons for the above results are described in the above summary and are not further described herein.

As can be seen from table 2, the thermal shrinkage rate of the composite separator obtained in each example was smaller, the thermal case failure temperature of the secondary battery was significantly increased, and the thermal case failure temperature of the secondary battery was significantly increased, as compared with each comparative example. In comparative example 2-1, the binder content was too high, and the heat resistance and dielectric properties of the binder were worse than those of the benzoxazine resin, so that the thermal shrinkage rate was higher, the ion conductivity was lower, and the thermal case failure temperature of the secondary battery was lower, and the thermal safety performance and electrical properties of the secondary battery were poor; in comparative example 2-2, the content of the binder was too low, which may cause that the benzoxazine resin particles could not be stably adhered to the surface of the base film, and thus the heat shrinkage rate of the base film could not be effectively reduced, and in addition, after the base film was melted, the coating was unstable, resulting in a lower heat box failure temperature of the secondary battery, and poor heat safety performance of the secondary battery; on the other hand, although the ionic conductivity is relatively high because the binder is relatively low and the porosity is relatively better, the electrical performance of the secondary battery is also adversely affected because the coating layer is unstable.

As is clear from comparison of examples 2-1, 2-2 and 1-3, the type of the common binder has less influence on the heat resistance and ion conductivity of the composite separator, and has better heat resistance and ion transport performance, and the secondary battery has better thermal safety performance and electrical performance.

Comparing examples 2-1, 2-3 to 2-9, it is understood that the mass ratio of the binder and the benzoxazine resin particles has a certain effect on the heat resistance and the ionic conductivity of the composite separator, thereby affecting the thermal safety performance and the electrical performance of the secondary battery. When the mass ratio of the binder to the benzoxazine resin particles is 1:1 to 1:20, the obtained composite isolating film has better heat resistance and the secondary battery has better heat safety. Preferably, when the mass ratio of the binder to the benzoxazine resin particles is 1:4 to 1:18, the obtained composite separator has better heat resistance and the secondary battery has better thermal safety. It will be appreciated that the lower the binder content, the higher the porosity of the coating, the higher the ionic conductivity, but the poorer the stability of the coating. When the mass ratio of the binder to the benzoxazine resin particles is 1:1 to 1:20, the obtained composite isolating film has higher ionic conductivity and better stability of the coating, can meet the use requirement of a secondary battery, and has better electrical property.

The present application is not limited to the above embodiment. The above embodiments are merely examples, and embodiments having substantially the same configuration and the same effects as those of the technical idea within the scope of the present application are included in the technical scope of the present application. Further, various modifications that can be made to the embodiments and other modes of combining some of the constituent elements in the embodiments, which are conceivable to those skilled in the art, are also included in the scope of the present application within the scope not departing from the gist of the present application.

Claims

1. A coating composition comprising: benzoxazine resin particles and a binder,

wherein the mass ratio of the binder to the benzoxazine resin particles is 1:1 to 1:20;

the benzoxazine resin particles have a Dv50 particle size of 0.1 μm to 5 μm.

2. The coating composition of claim 1, wherein the binder comprises at least one of polyacrylic acid, polyacrylate, polyvinylidene fluoride, styrene-butadiene rubber, sodium carboxymethyl cellulose.

3. The coating composition of claim 1, wherein the benzoxazine resin particles have a Dv50 particle size of 0.5 μιη to 3 μιη.

4. A coating composition according to any one of claims 1 to 3, wherein the benzoxazine resin particles are obtained by curing and pulverizing benzoxazine monomers;

the benzoxazine monomer is obtained by reacting an amine compound, a phenol compound and an aldehyde compound in a solvent.

5. The coating composition of claim 4, wherein the molar ratio of amine groups in the amine compound, phenolic hydroxyl groups in the phenolic compound, and aldehyde groups in the aldehyde compound is 1 (1 to 1.5): 2 to 2.5.

6. The coating composition of claim 4, wherein the amine compound comprises a diamine compound and the phenolic compound comprises a monophenol compound.

7. The coating composition of claim 6, wherein the diamine compound comprises at least one of 1, 6-hexamethylenediamine, diaminodiphenylmethane, and diaminodiphenyl sulfone;

the monophenol compound comprises at least one of phenol, p-methoxyphenol, cardanol and o-allylphenol;

the aldehyde compound comprises formaldehyde and/or paraformaldehyde;

the solvent comprises at least one of dioxane, chloroform and xylene.

8. A composite barrier film comprising: a base film, and

a coating layer formed from the coating composition according to any one of claims 1 to 7 disposed on at least one surface of the base film.

9. The composite barrier film of claim 8, wherein the coating has an areal density of 0.1g/m ² To 5g/m ² 。

10. A battery cell comprising the composite separator of claim 8 or 9.

11. A battery comprising the battery cell of claim 10.

12. An electrical device comprising at least one of the battery cell of claim 12 or the battery of claim 11.