Additive and preparation method thereof, positive electrode slurry, positive electrode plate, secondary battery and electric device

Abstract

The invention provides an additive and a preparation method thereof, a positive electrode slurry, a positive electrode plate, a secondary battery and an electric device, the additive is a polymer, the main chain of the polymer is a polyether structure, the polymer comprises a phenyl-containing group, and the phenyl-containing group is located on the main chain of the polymer and / or on the branch chain of the polymer.

Description

Technical Field

[0001] The present disclosure relates to the field of batteries, and in particular, to additives and preparation methods thereof, positive electrode slurry, positive electrode sheets, secondary batteries, and electrical devices. Background Art

[0002] In recent years, with the advancement of lithium-ion secondary battery technology, lithium-ion secondary batteries have been widely used in energy storage systems such as hydropower, thermal power, wind power, and solar power plants. They are also widely used in power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace, and other fields. With the rapid development of lithium-ion secondary batteries, higher requirements have been placed on their energy density, cycle performance, and safety performance. However, many problems still exist in the preparation of slurry and electrode sheets, which require further improvement. Summary of the Invention

[0003] In one aspect, the present application provides a battery additive comprising a polymer having a polyether backbone and containing phenyl groups located on the backbone and / or on side chains of the polymer. Thus, the additive can improve the stability, solids content, and dispersion uniformity of a positive electrode slurry.

[0004] According to an embodiment of the present application, the phenyl-containing group is located on the side chain of the polymer, thereby improving the dispersion effect of the additive.

[0005] According to an embodiment of the present application, the terminal group of the polymer includes the phenyl-containing group, thereby improving the dispersion effect of the additive.

[0006] According to an embodiment of the present application, the polymer further includes nitrogen-containing groups, and the nitrogen-containing groups are located on the side chains of the polymer, thereby improving the dispersion effect of the additive.

[0007] According to an embodiment of the present application, the structure of the polymer is as shown in formula (1),

[0008] Where R is C1-C 10 wherein the alkyl group or phenyl group is an alkyl group or a phenyl group, a is the number of the first repeating unit in the polymer, b is the number of the second repeating unit in the polymer, c is the number of the third repeating unit in the polymer, and d is the number of the fourth repeating unit in the polymer. Thus, the flexibility of the additive can be improved.

[0009] According to an embodiment of the present application, the structure of the polymer is as shown in Formula (2) or Formula 3,

[0010]

[0011] Wherein, e is the number of the fifth repeating unit in the polymer, and f is the number of the sixth repeating unit in the polymer. Thus, the flexibility, plasticizing effect and dispersing effect of the additive can be improved.

[0012] According to an embodiment of the present application, a and c are independently 1-400.

[0013] According to an embodiment of the present application, b and d are independently 1-2000.

[0014] According to an embodiment of the present application, the e is 1-400, and / or the f is 1-2000.

[0015] In another aspect of the present application, a method for preparing the aforementioned additive is provided, comprising: providing a monomer containing an epoxy group; and polymerizing the monomer to form a polymer having a polyether backbone, wherein the polymer includes phenyl groups located on the backbone and / or on side chains of the polymer. Thus, the aforementioned additive having both excellent dispersing and plasticizing effects can be prepared in a relatively simple manner.

[0016] According to an embodiment of the present application, the monomer includes an epoxy compound, and the polymerization reaction of the monomer includes: adding an initiator to a solution of the epoxy compound to obtain a first solution through a first heating reaction, wherein the first solution contains a polymer having a first repeating unit structure and a second repeating unit structure; adding a chlorinating agent to the first solution to obtain a second solution, wherein the second solution contains the polymer having the first repeating unit structure and the second repeating unit structure substituted with terminal chlorine; adding a substituted bishydroxyalkane to the second solution to obtain a third solution, wherein the substituent of the substituted bishydroxyalkane includes a nitrogen-containing group or a phenyl-containing group; adding an epoxy compound to the third solution to obtain a fourth solution through a second heating reaction, wherein the fourth solution contains a polymer having a first repeating unit structure, a second repeating unit structure, a third repeating unit structure, and a fourth repeating unit structure. In this way, a polymer having phenyl groups and / or nitrogen-containing groups on the side chains can be obtained.

[0017] According to an embodiment of the present application, the method further comprises: adding a chlorinating agent to the fourth solution to obtain a fifth solution, wherein the fifth solution contains the polymer having the first repeating unit structure, the second repeating unit structure, the third repeating unit structure, and the fourth repeating unit structure, which is substituted with terminal chlorine; adding a substituted bishydroxyalkane to the fifth solution to obtain a sixth solution, wherein the substituent of the substituted bishydroxyalkane includes a nitrogen-containing group or a phenyl-containing group; adding an epoxy compound to the sixth solution, and obtaining an eleventh solution through a third heating reaction, wherein the eleventh solution contains the polymer having the first repeating unit structure, the second repeating unit structure, the third repeating unit structure, the fourth repeating unit structure, the fifth repeating unit structure, and the sixth repeating unit structure. In this way, a polymer having multiple phenyl groups and / or nitrogen-containing groups on the side chains can be obtained.

[0018] According to an embodiment of the present application, the epoxy compound includes ethylene oxide and propylene oxide, which is conducive to the occurrence of ring-opening polymerization reaction.

[0019] According to an embodiment of the present application, the initiator includes a hydroxyl compound. Thus, various non-polar groups can be introduced through the initiator.

[0020] According to an embodiment of the present application, the chlorinating agent includes thionyl chloride, which is beneficial to increasing the chlorination of hydroxyl groups.

[0021] According to an embodiment of the present application, the reaction temperatures of the first heating reaction, the second heating reaction, and the third heating reaction are independently 90° C. to 140° C. This is conducive to sufficient progress of the reaction.

[0022] According to an embodiment of the present application, the main chain carbon number of the substituted bishydroxyalkane is 1 to 20. This facilitates the introduction of phenyl groups and / or nitrogen-containing groups into the polymer.

[0023] In another aspect, the present application provides a positive electrode slurry comprising: a positive electrode active material; and an additive, wherein the additive comprises the aforementioned additive or an additive prepared using the aforementioned method. This provides a positive electrode slurry that has a good dispersion of the positive electrode active material and is less prone to cracking after coating.

[0024] According to an embodiment of the present application, the sum of the mass fraction of the positive electrode active material and the mass fraction of the additive in the positive electrode slurry is 92 wt % to 96 wt %, thereby increasing the solid content of the positive electrode slurry.

[0025] In another aspect of the present application, a positive electrode sheet is provided, comprising a positive electrode current collector and a positive electrode active material layer, wherein the positive electrode active material layer is formed by solidifying the aforementioned positive electrode slurry, or the positive electrode active material layer includes the aforementioned additive, or the positive electrode active material layer includes the additive prepared by the aforementioned method. Thus, the positive electrode sheet has all the features and advantages of the aforementioned positive electrode slurry, the aforementioned additive, and the aforementioned preparation method, and will not be further described here.

[0026] According to an embodiment of the present application, the thickness of a single layer of the positive electrode active material layer is 30 μm to 500 μm, thereby increasing the energy density of the positive electrode sheet.

[0027] According to an embodiment of the present application, the positive electrode active material layer includes a positive electrode active material, wherein the positive electrode active material includes a core and a carbon coating layer, wherein the carbon coating layer at least partially covers the surface of the core. This helps to improve the dispersibility of the positive electrode active material in the positive electrode active material layer.

[0028] According to an embodiment of the present application, the positive electrode active material layer includes conductive carbon, which helps to improve the dispersibility of the conductive carbon in the positive electrode active material layer.

[0029] According to an embodiment of the present application, the positive electrode active material layer includes a solvent, and the solvent includes N-methylpyrrolidone, thereby helping to improve the dispersion uniformity of various components in the positive electrode active material layer.

[0030] According to an embodiment of the present application, the folded positive electrode sheet can withstand rolling pressure 3 to 10 times, thereby improving the workability of the positive electrode sheet.

[0031] According to an embodiment of the present application, the resistivity of the positive electrode sheet is 1 Ω·cm-100 Ω·cm, thereby improving the conductivity of the positive electrode sheet.

[0032] According to an embodiment of the present application, the mass fraction of the additive in the positive electrode active material layer is 0.01 wt % to 2 wt %. Thus, the dispersibility of the carbonaceous material in the positive electrode active material layer can be improved with less additive.

[0033] According to an embodiment of the present application, the diameter of the carbon agglomerates in the positive electrode active material layer is no greater than 10 μm, thereby reducing the agglomeration of the carbonaceous material.

[0034] In another aspect of the present application, a battery is provided, comprising: a positive electrode sheet, wherein the positive electrode sheet is the aforementioned positive electrode sheet. Thus, the battery has all the features and advantages of the aforementioned positive electrode sheet, which will not be described in detail here.

[0035] In another aspect of the present application, an electrical device is provided, comprising the aforementioned battery. Thus, the electrical device has all the features and advantages of the aforementioned battery, which will not be described in detail here. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The above and / or additional aspects and advantages of the present application will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0037] Figure 1 Shows a schematic structural diagram of a positive electrode sheet according to one embodiment of the present application;

[0038] Figure 2 is a schematic diagram of a secondary battery according to one embodiment of the present application;

[0039] Figure 3 yes Figure 2 An exploded view of a secondary battery according to an embodiment of the present application is shown;

[0040] Figure 4 is a schematic diagram of a battery module according to one embodiment of the present application;

[0041] Figure 5 is a schematic diagram of a battery pack according to one embodiment of the present application;

[0042] Figure 6 yes Figure 5 An exploded view of a battery pack according to an embodiment of the present application is shown;

[0043] Figure 7 FIG. 1 is a schematic diagram of an electrical device using a secondary battery according to an embodiment of the present application as a power source.

[0044] Description of reference numerals:

[0045] 1: Battery pack; 2: Upper case; 3: Lower case; 4: Battery module; 5: Secondary battery; 10: Positive electrode sheet; 11: Positive current collector; 12: Positive active material layer; 51: Shell; 52: Electrode assembly; 53: Top cover assembly. DETAILED DESCRIPTION

[0046] The following embodiments of the present disclosure are described in detail. The following embodiments are illustrative and are intended only to explain the present disclosure and are not to be construed as limiting the present disclosure. Where specific techniques or conditions are not specified in the embodiments, the techniques or conditions described in the literature in the art or in the product specifications shall be followed.

[0047] During the coating process of the positive electrode slurry, as the solvent evaporates during the drying process, the binder forms bonds with each other and with the main material particles. Simultaneously, the binder molecules shrink, generating stress. Excessive stress can lead to cracking in the coating. Furthermore, the dispersion uniformity of the positive electrode slurry directly affects the difficulty of the coating process, the processability of the electrode sheet, and the performance of the electrical performance. Specifically, the functional groups on the surface of the positive electrode active material easily form hydrogen bonds with the binder, which in turn causes the positive electrode slurry to form a jelly-like gel. This significantly reduces fluidity, hindering the subsequent coating process and seriously affecting production efficiency.

[0048] While adding conventional plasticizers to the cathode slurry can alleviate coating cracking to a certain extent, this does not improve the dispersion uniformity of the cathode slurry. Furthermore, the addition of additional dispersants reduces the proportion of active material in the cathode active material layer, thereby reducing the energy density of the cathode sheet. Furthermore, in actual production, materials are typically fed through a pipeline system, and the more material types required, the higher the pipeline costs.

[0049] In the present application, taking the material with oxygen-containing functional groups on the surface as an example, when the binder is mixed with the material with oxygen-containing functional groups on the surface during the preparation of the positive electrode slurry, the oxygen-containing functional groups on the surface of the material, such as carboxyl, hydroxyl and carbonyl functional groups, are easily combined with the functional groups on the binder to form hydrogen bonds, thereby causing the positive electrode slurry to gel. In addition, when the material particles are mixed with the binder, coordination bonds (such as between iron and nitrogen), van der Waals forces, and positive and negative charge attraction will also be generated between the material particles and the binder. Interaction forces. Further, due to the interaction force generated between the material particles and the binder, during the coating and drying process of the positive electrode slurry, as the solvent in the positive electrode slurry evaporates, adhesion will occur between the binders and between the binders and the material particles. At the same time, the binder molecules shrink and generate stress. When the binder molecules shrink, stress will be generated. When the stress is too large, it will cause coating cracking.

[0050] Taking a positive electrode active material with a carbon coating as an example, when the carbon coating is formed on the core of the positive electrode active material, specifically, for example, a coating precursor is first formed on the core surface by a hydrothermal / solvothermal method, and then the carbon coating is formed on the core surface by high-temperature treatment, during the high-temperature treatment, some functional groups carried by the coating precursor cannot be completely removed by the high-temperature treatment. When the positive electrode active material is mixed with a binder during the preparation of the positive electrode slurry, the oxygen-containing functional groups remaining on the carbon coating, such as carboxyl, hydroxyl, and carbonyl functional groups, easily combine with the functional groups on the binder to form hydrogen bonds, thereby causing the positive electrode slurry to gel and significantly reducing the stability of the positive electrode slurry. When the positive electrode active material is mixed with the binder, interaction forces such as van der Waals forces and positive and negative charge attraction will also be generated between the positive electrode active material and the binder. Furthermore, due to the interaction force formed between the positive electrode active material particles and the binder, during the coating process of the positive electrode slurry, as the solvent in the positive electrode slurry evaporates, adhesion will occur between the binders and between the binder and the positive electrode active material particles. At the same time, the binder molecules will shrink, thereby generating stress. When the stress is too large, it will cause the coating to crack.

[0051] There are residual functional groups on the surface of the conductive carbon material, such as carboxyl, hydroxyl and carbonyl groups. When the conductive carbon material is mixed with the binder in the positive electrode slurry, it is easy to combine with the functional groups on the binder to form an interaction force, which in turn causes the positive electrode slurry to gel. The stability of the positive electrode slurry is significantly reduced, and coating cracking is prone to occur during the coating process of the positive electrode slurry. On the other hand, since the conductive carbon materials, such as conductive carbon black (Super P) and carbon nanotubes, have a small particle size and a large specific surface area, the conductive carbon materials themselves are very easy to agglomerate, which in turn causes the positive electrode slurry to gel, further reducing the stability of the positive electrode slurry. During the coating process of the positive electrode slurry, as the solvent in the positive electrode slurry evaporates, adhesion will occur between the binders and between the binders and the conductive carbon materials. At the same time, the binder molecules will shrink, which will generate stress. When the stress is too large, it will cause coating cracking. The polyether structure has good solubility in the positive electrode slurry solvent, and the polyether structure easily forms long chains. When the polyether structure material is adsorbed on the surface of the particle, it can effectively isolate the particle from the outside, thereby effectively providing the dispersion of the positive electrode slurry. The polyether structure can also form a lubricating layer between the polymer binder and between the polymer binder and the material particles, thereby reducing the stress generated on the electrode when the positive electrode slurry is coated and dried by utilizing the plasticizing effect of the polyether structure, thereby improving the coating cracking; further, phenyl groups are provided on the polyether structure, and the phenyl groups are easy to combine with the material particles having a carbon layer and are also easy to combine with the graphite sheet structure, thereby allowing the additive to form an additive coating layer on the surface of the material particles. The additive coating layer can hinder the agglomeration between the material particles having the carbon layer, thereby effectively improving the problem of easy generation of gel during the homogenization process of the positive electrode slurry. Materials with a carbon layer include conductive carbon and materials with carbon on the surface, such as positive electrode active materials with a carbon coating layer on the surface. For positive electrode slurries with poor dispersibility, agglomerates will exist in the positive electrode slurry, and the agglomerates will cover the solvent. The solvent covered by the agglomerates has no fluidity, which in turn leads to a reduction in the amount of free solvent that can flow, and a significant increase in the viscosity of the positive electrode slurry. By adding the additives in this application, the number of agglomerates in the positive electrode slurry is effectively reduced, the amount of solvent that is covered is reduced, and the amount of free solvent that can flow is increased, thereby reducing the viscosity of the slurry.

[0052] In actual production, the viscosity of the positive electrode material slurry is directly proportional to the solid content. In order to meet the coating requirements, it is necessary to control the solid content of the positive electrode slurry so that it is not too high. In this application, the problem of excessive viscosity of the positive electrode slurry is alleviated to a certain extent by the addition of additives, that is, the reduction of the viscosity of the positive electrode slurry is achieved, so that the solid content of the positive electrode slurry can be further increased while meeting the coating requirements while meeting the viscosity requirements of the positive electrode slurry. The additives in this application have both dispersing and plasticizing functions, which can not only increase the solid content of the positive electrode slurry, improve the dispersion of the positive electrode slurry, but also improve the coating cracking during slurry coating.

[0053] In one aspect of the present application, a battery additive is provided. The additive is a polymer having a polyether backbone structure, and the polymer includes phenyl groups located on the backbone and / or on side chains of the polymer. The polymer of the present application has good dispersing and plasticizing effects, effectively reducing stress generated on the positive electrode sheet during coating and drying, thereby improving coating cracking. At the same time, it effectively improves the dispersibility of the positive electrode active material in the positive electrode slurry, maintaining a uniform and stable positive electrode slurry. By adding the aforementioned additive to the positive electrode slurry, the solid content of the positive electrode slurry can be increased and cracking of the positive electrode slurry can be prevented.

[0054] According to some embodiments of the present application, the position of the nitrogen-containing group is not particularly limited. For example, the monomer of the polymer may have a nitrogen-containing group substituent, that is, the nitrogen-containing group may be located on the side chain of the polymer. Further, the nitrogen-containing group may include at least one of amino, nitro, nitroso, oxime, cyano, cyanate, isocyanate, cyanate, isocyanate, thiocyanate, isothiocyanate, thiocyanate, isothiocyanate, carbodiimide, diazo, pyrrolyl, pyridyl, pyrimidinyl, isothiazolyl, thiazolyl, imidazole and acyl.

[0055] In some embodiments, the nitrogen-containing group can be an acyl group, and the nitrogen-containing group can be attracted to carbon materials, such as conductive carbon materials, and surface carbon-containing materials, such as positive electrode active material particles with a carbon coating layer on the surface, so that the additive is adsorbed on the surface of the particles, hindering the agglomeration between the particles, thereby achieving the effect of dispersing the particles.

[0056] According to some embodiments of the present application, by arranging a phenyl group on a polyether structure, the phenyl group and the carbon material, for example, the positive electrode active material particles containing a surface carbon layer, the conductive carbon, etc. can be strongly adsorbed on the surface of the positive electrode active material particles through interactions such as ionic bonds, covalent bonds or hydrogen bonds, etc., which can effectively suppress the strong interaction between the aqueous adhesive and the positive electrode active material, thereby effectively improving the problem of easy gelation during the homogenization process of the positive electrode slurry. The position of the phenyl group is not particularly limited. For example, the monomer of the polymer can have a phenyl substituent, or the phenyl group can be the end group of the polymer. Specifically, the phenyl group can be connected to the polyether structure by using an initiator containing a phenyl group during the preparation of the additive. The phenyl group can be attracted to the carbon material, such as a conductive carbon material, and the surface carbon-containing material, such as the positive electrode active material particles with a carbon coating layer on the surface, so that the additive is adsorbed on the surface of the particles, hindering the agglomeration between the particles, thereby achieving the effect of dispersing the particles.

[0057] According to some embodiments of the present application, the phenyl-containing group can be located on the side chain of the polymer, for example, see Formula (1)-Formula (3). The phenyl-containing group can attract carbon materials, such as conductive carbon materials, and surface carbon materials, such as positive electrode active material particles with a carbon coating layer, so that the additive is adsorbed on the surface of the particles, hindering the agglomeration of the particles, thereby achieving the effect of dispersing the particles.

[0058] It should be noted that the phenyl-containing group includes a phenyl group and a phenyl group substituted with other functional groups.

[0059] According to some embodiments of the present application, the structure of the polymer is as shown in formula (1),

[0060] Where R is C1-C 10 wherein the alkyl group or phenyl group is an alkyl group or a phenyl group, a is the number of the first repeating unit in the polymer, b is the number of the second repeating unit in the polymer, c is the number of the third repeating unit in the polymer, d is the number of the fourth repeating unit in the polymer, and Ph is a phenyl group. Thus, the flexibility of the additive can be improved.

[0061] According to some embodiments of the present application, the structure of the polymer is as shown in Formula (2) or Formula 3,

[0062]

[0063] Wherein, e is the number of the fifth repeating unit in the polymer, and f is the number of the sixth repeating unit in the polymer. Thus, the flexibility, plasticizing effect and dispersing effect of the additive can be improved.

[0064] According to some embodiments of the present application, a and c are independently 1-400.

[0065] According to some embodiments of the present application, b and d are independently 1-2000.

[0066] According to some embodiments of the present application, the e is 1-400, and / or the f is 1-2000.

[0067] In this application, all numerical values ​​disclosed herein are approximate, regardless of whether the word "about" or "approximately" is used. The numerical value of each number may vary by less than 10% or by a reasonable difference considered by a person skilled in the art, such as 1%, 2%, 3%, 4% or 5%.

[0068] In another aspect of the present application, a method for preparing the aforementioned additive is provided, comprising providing a monomer containing an epoxy group; polymerizing the monomer to form a polymer having a polyether backbone structure, wherein the polymer includes phenyl groups located on the backbone and / or on side chains of the polymer. This method allows for the preparation of the additive having the aforementioned excellent dispersing effect in a relatively simple manner.

[0069] Specifically, the following steps may be included:

[0070] According to some embodiments of the present application, the monomer includes an epoxy compound, and causing the monomer to undergo a polymerization reaction includes:

[0071] S10: Add an initiator to the epoxy compound solution to obtain a first solution through a first heating reaction

[0072] In some embodiments, referring to reaction formula (1), an epoxy compound is dissolved in a solvent to form an epoxy compound solution. When R is a benzene ring, the initiator is phenol, and potassium hydroxide is a catalyst. The aforementioned initiator and catalyst are added to the epoxy compound solution at 90° C. under vacuum stirring conditions to allow the epoxy compound to undergo ring-opening addition. The reaction temperature is raised to 140° C. and maintained for 1 h to 5 h to obtain a polymer having a first repeating unit structure and a second repeating unit structure.

[0073]

[0074] S20: Add a chlorinating agent to the first solution to obtain a second solution

[0075] In some embodiments, referring to reaction formula (2), in this step, the product obtained by reaction formula (1) is mixed with a chlorinating agent to react so as to replace the terminal hydroxyl group in the product obtained by reaction formula (1) with chlorine. Specifically, the product obtained by reaction formula (1) and thionyl chloride (SOCl2) can be reacted at room temperature for 4h-10h using dichloromethane (DCM) as a solvent to obtain the polymer having the first repeating unit structure and the second repeating unit structure with terminal chlorine substituted.

[0076]

[0077] S30: Adding a substituted bishydroxyalkane to the second solution to obtain a third solution

[0078] In some embodiments, referring to reaction formula (3), in this step, the product of reaction formula (2) is reacted with a substituted bishydroxyalkane at room temperature under the action of a catalyst (e.g., Et3N, i.e., triethylamine), followed by washing with dilute hydrochloric acid, extraction with ethyl acetate, and drying, filtration, and oven drying to obtain a reaction product, wherein the substituent of the substituted bishydroxyalkane includes a nitrogen-containing group or a phenyl-containing group, thereby introducing a nitrogen-containing group or a phenyl-containing group into the side chain of the polyether structure.

[0079]

[0080] S40: Adding an epoxy compound to the third solution to obtain a fourth solution through a second heating reaction

[0081] In some embodiments, referring to reaction formula (4), similar to the reaction in step S10, in this step, the terminal hydroxyl group of the product of reaction formula (3) is used as the initiating group, and after the epoxy compound is added, the epoxy compound can undergo ring-opening addition, and finally obtain a polymer having a first repeating unit structure, a second repeating unit structure, a third repeating unit structure, and a fourth repeating unit structure. In this way, a polymer having phenyl groups and / or nitrogen-containing groups on the side chains can be obtained.

[0082]

[0083] The reaction temperature and time in step S40 may refer to the conditions in step S10 and will not be described in detail here.

[0084] According to some embodiments of the present application, the method for synthesizing the additive further comprises:

[0085] S50: Add a chlorinating agent to the fourth solution to obtain a fifth solution

[0086] In some embodiments, referring to reaction formula (5), similar to the reaction in step S2, in this step, the product obtained by reaction formula (4) is mixed with a chlorinating agent to react so as to replace the terminal hydroxyl group in the product obtained by reaction formula (4) with chlorine. Specifically, the product obtained by reaction formula (4) and thionyl chloride (SOCl2) can be reacted at room temperature for 4h-10h using dichloromethane (DCM) as a solvent to obtain the polymer having the first repeating unit structure, the second repeating unit structure, the third repeating unit structure and the fourth repeating unit structure with terminal chlorine substituted.

[0087]

[0088] S60: Adding a substituted bishydroxyalkane to the fifth solution to obtain a sixth solution

[0089] In some embodiments, referring to reaction formula (6), similar to the reaction in step S30, in this step, the product of reaction formula (5) is reacted with a substituted bishydroxyalkane at room temperature under the action of a catalyst (e.g., Et3N, i.e., triethylamine), followed by washing with dilute hydrochloric acid, extraction with ethyl acetate, and drying, filtering, and oven drying to obtain a reaction product, wherein the substituent of the substituted bishydroxyalkane includes a nitrogen-containing group or a phenyl-containing group, thereby introducing multiple nitrogen-containing groups or phenyl-containing groups into the side chains of the polyether structure.

[0090]

[0091] S70: Adding an epoxy compound to the sixth solution to obtain an eleventh solution through a third heating reaction

[0092] In some embodiments, referring to reaction formula (7) and reaction formula (8), similar to the reaction in step S10, in this step, the terminal hydroxyl group of the product of reaction formula (6) is used as the initiating group, and after the epoxy compound is added, the epoxy compound can be subjected to ring-opening addition, and finally a polymer having a first repeating unit structure, a second repeating unit structure, a third repeating unit structure, a fourth repeating unit structure, a fifth repeating unit structure, and a sixth repeating unit structure is obtained. In this way, a polymer having multiple phenyl groups and / or nitrogen-containing groups on the side chain can be obtained.

[0093]

[0094] In some embodiments, the synthesis method of the substituted bishydroxyalkanes can refer to reaction formula (9) and reaction formula (10). Specifically, potassium permanganate can be used as an oxidant and water can be used as a solvent. The reaction can be carried out at 0°C under alkaline conditions for 1 hour. The mixture can then be acid-washed, extracted, dried, filtered, and separated by thin-layer chromatography to obtain bishydroxy-added ethane products of different substitutions. Among them, the bishydroxyalkanes obtained by reaction formula (9) are phenyl-substituted bishydroxyalkanes, and the bishydroxyalkanes obtained by reaction formula (10) are amide-substituted bishydroxyalkanes.

[0095]

[0096] According to some embodiments of the present application, the epoxy compound includes ethylene oxide and propylene oxide, which is conducive to the occurrence of ring-opening polymerization reaction.

[0097] According to some embodiments of the present application, the initiator includes a hydroxyl compound. Thus, a variety of non-polar groups can be introduced through the initiator.

[0098] According to some embodiments of the present application, the chlorinating agent includes thionyl chloride, which is beneficial to increasing the chlorination of hydroxyl groups.

[0099] According to some embodiments of the present application, the reaction temperatures of the first heating reaction, the second heating reaction, and the third heating reaction are independently 90° C. to 140° C. This is conducive to sufficient progress of the reaction.

[0100] According to some embodiments of the present application, the main chain carbon number of the substituted bishydroxyalkane is 1-20. This facilitates the introduction of phenyl groups and / or nitrogen-containing groups into the polymer. As an example, the substituted bishydroxyalkane can be substituted bishydroxyethane.

[0101] In another aspect of the present application, a positive electrode slurry is proposed, comprising: a positive electrode active material; an additive, wherein the additive comprises the aforementioned additive or an additive prepared by the aforementioned method. The positive electrode slurry additive in the present application can form a lubricating layer between the polymer binder and between the polymer binder and the positive electrode active material particles, thereby reducing the stress generated on the electrode when the positive electrode slurry is coated and dried by utilizing the plasticizing effect of the polyether structure; the additive coating layer can also be formed on the surface of the positive electrode active material particles. The additive coating layer can not only hinder the agglomeration between the particles, but also effectively suppress the strong interaction between the aqueous binder and the positive electrode active material particles, thereby effectively improving the problem of gelation during the homogenization process of the positive electrode slurry. In summary, the additive in the present application can not only increase the solid content of the positive electrode slurry, improve the dispersion of the positive electrode slurry, but also improve the coating cracking during the slurry coating. The additive in the present application has the functions of both a dispersant and a plasticizer and is applicable to a variety of positive electrode slurry systems. Regardless of whether the surface of the positive electrode active material used has a carbon coating layer, the additives in this application can be used to achieve plasticization and dispersion effects when preparing the corresponding positive electrode slurry. Those skilled in the art can make choices based on actual conditions.

[0102] According to some embodiments of the present application, the type of positive electrode active material is not particularly limited. For example, the positive electrode active material may include at least one of lithium cobalt oxide, lithium manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium manganese phosphate, lithium iron phosphate, lithium manganese iron phosphate, and a lithium-rich manganese-based solid solution. Furthermore, the positive electrode active material may include a core; and a carbon coating layer, the carbon coating layer at least partially coating the surface of the core. The core may be of the type described above for the positive electrode active material. Forming the carbon coating layer on the core surface can further improve the conductivity of the positive electrode active material. The polyether structure of the additive in the present application can form a lubricating layer between the polymer binder and between the polymer binder and the positive electrode active material particles, thereby reducing the stress generated on the electrode when the positive electrode slurry is coated and dried by utilizing the plasticizing effect of the polyether structure, thereby improving the coating cracking; further, by arranging nitrogen-containing groups on the polyether structure, utilizing the characteristics that the nitrogen-containing groups and the carbon layer on the surface of the positive electrode active material particles can be strongly adsorbed on the surface of the positive electrode active material particles through interactions such as ionic bonds, covalent bonds or hydrogen bonds, the additive can form an additive coating layer on the surface of the positive electrode active material particles. The additive coating layer can not only hinder the agglomeration between the particles, but also effectively inhibit the strong interaction between the aqueous binder and the conductive carbon material, thereby effectively improving the problem of easy generation of gel during the positive electrode slurry homogenization process.

[0103] According to some embodiments of the present application, the mass fractions of the components in the positive electrode slurry are not particularly limited. For example, the sum of the mass fraction of the positive electrode active material and the mass fraction of the additives in the positive electrode slurry can be 92 wt% to 96 wt%. When the mass fractions of the positive electrode active material and the additives in the positive electrode slurry are within the above range, the solid content in the positive electrode slurry is high, the stirring time required for slurry preparation is short, the solvent consumption is low, the coating drying efficiency is high, and the slurry preparation time is effectively saved.

[0104] According to some embodiments of the present application, the mass fraction of the positive electrode active material in the positive electrode slurry is not particularly limited. For example, when the sum of the mass fraction of the positive electrode active material and the mass fraction of the additive in the positive electrode slurry is 92wt%-96wt%, the mass fraction of the positive electrode active material in the positive electrode slurry can be 87-95.99wt%. When the mass fraction of the positive electrode active material in the positive electrode slurry is within the above range, the content of the positive electrode active material in the slurry is high, and the coated electrode sheet has a high energy density.

[0105] According to some embodiments of the present application, the mass fraction of the additive in the positive electrode slurry is not particularly limited. For example, when the sum of the mass fraction of the positive electrode active material and the mass fraction of the additive in the positive electrode slurry is 92 wt%-96 wt%, the mass fraction of the additive in the positive electrode slurry can be 0.01 wt%-2 wt%. When the mass fraction of the additive in the positive electrode slurry is within the above range, by adding a small amount of additive to the positive electrode slurry, the plasticity of the positive electrode slurry and the dispersion effect of the positive electrode active material can be effectively improved, thereby effectively increasing the solid content of the positive electrode slurry and improving coating cracking.

[0106] According to some embodiments of the present application, the mass fraction of each component in the positive electrode slurry is not particularly limited. For example, the positive electrode slurry may further include a conductive agent, and the sum of the mass fractions of the conductive agent and the binder in the positive electrode slurry may be 4-8wt%, wherein the mass fraction of the conductive agent may be greater than the mass fraction of the binder. For example, the mass fraction of the conductive agent may be twice the mass fraction of the binder.

[0107] According to some embodiments of the present application, the type of conductive agent in the positive electrode slurry is not particularly limited. For example, the conductive agent can include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. The polyether structure of the additive in the present application can form a lubricating layer between the polymer binder and between the polymer binder and the conductive agent particles, thereby reducing the stress generated on the electrode when the positive electrode slurry is coated and dried by utilizing the plasticizing effect of the polyether structure, thereby improving coating cracking; further, by providing nitrogen-containing groups on the polyether structure, the nitrogen-containing groups and the carbon layer on the surface of the conductive agent particles can be strongly adsorbed on the surface of the conductive agent particles through interactions such as ionic bonds, covalent bonds, or hydrogen bonds. This allows the additive to form an additive coating layer on the surface of the conductive agent particles. This additive coating layer can not only hinder the agglomeration between the particles, but also effectively inhibit the strong interaction between the aqueous binder and the conductive carbon material, thereby effectively improving the problem of gelation during the homogenization process of the positive electrode slurry.

[0108] According to some embodiments of the present application, the binder is a high molecular polymer, and its main functions are to bond and maintain the positive electrode active material, enhance the contact between the positive electrode active material and the conductive agent, and between the positive electrode active material and the current collector, and also stabilize the structure of the electrode. The type of binder is not particularly limited. For example, the binder in the positive electrode slurry may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyacrylonitrile, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer and fluorine-containing acrylate resin.

[0109] In another aspect of this application, reference is made to Figure 1This application provides a positive electrode sheet 10, comprising a positive electrode current collector 11 and a positive electrode active material layer 12. The positive electrode active material layer 12 is located on one side of the positive electrode current collector 11. The positive electrode active material layer 12 is formed by solidifying the aforementioned positive electrode slurry, or includes the aforementioned additives, or is prepared using the aforementioned method. As an example, the positive electrode current collector 11 has two opposing surfaces in its thickness direction. The positive electrode active material layer 12 can be disposed on either or both of the two opposing surfaces of the positive electrode current collector 11.

[0110] According to some embodiments of the present application, by adding an additive having both a plasticizing effect and a dispersing effect to the positive electrode slurry, the coating cracking of the positive electrode active material layer is effectively improved, and the production efficiency of the positive electrode sheet is improved. Specifically, the thickness of the positive electrode active material layer on the positive electrode sheet is not particularly limited. For example, the single layer thickness of the positive electrode active material layer can be 30μm-500μm. When the single layer thickness of the positive electrode active material layer is within the above range, the adhesion between the positive electrode active material layer and the current collector is strong, the positive electrode sheet has a higher energy density, and a thicker positive electrode active material layer can be obtained by a single coating, which effectively increases production capacity, reduces manufacturing costs, and facilitates large-scale production.

[0111] According to some embodiments of the present application, the positive electrode active material layer includes a positive electrode active material, and the positive electrode active material may include a core and a carbon coating layer, and the carbon coating layer at least partially covers the surface of the core. The additive in the present application is conducive to the dispersion of the carbon-containing material, thereby helping to improve the dispersibility of the positive electrode active material containing the carbon coating layer in the positive electrode active material layer.

[0112] According to some embodiments of the present application, the positive electrode active material layer includes conductive carbon. The additive in the present application facilitates the dispersion of the carbonaceous material, thereby helping to improve the dispersibility of the conductive carbon in the positive electrode active material layer.

[0113] According to some embodiments of the present application, the positive electrode active material layer includes a solvent. In some embodiments, the solvent in the positive electrode active material layer includes N-methylpyrrolidone, thereby helping to improve the dispersion uniformity of various components in the positive electrode active material layer.

[0114] According to some embodiments of the present application, the number of times the positive electrode sheet in the present application can withstand rolling pressure at the crease after being folded can be 3 to 10 times. As a result, the positive electrode sheet has better flexibility, which can improve the processability of the positive electrode sheet. The flexibility of the sheet can be tested according to the following method: fold the sheet in half, use a 2kg roller to roll over the crease at a speed of 2m / s, and observe whether the crease is light-transmitting. If not, fold the sheet in reverse, use 2kg to roll over the crease at a speed of 2m / s, and observe whether the crease is light-transmitting. Repeat the above steps until the crease is light-transmitting, and record the number of times the roller presses the sheet, which is the number of times the crease can withstand rolling pressure after the sheet is folded. The higher the number, the better the flexibility of the sheet.

[0115] According to some embodiments of the present application, the film resistivity of the positive electrode sheet in the present application can be 1Ω·cm-100Ω·cm. Because the additives in the present application can improve the dispersion uniformity of the carbon-containing material, the conductivity of the positive electrode sheet can be improved. The film resistivity of the electrode sheet can be characterized by directly measuring the film resistivity using a four-probe tester, such as the Lattice Electronics ST2263 dual-electrical digital four-probe tester.

[0116] According to some embodiments of the present application, the mass fraction of the additive in the positive electrode active material layer is not particularly limited and can be determined by the dosage ratio during the feeding process. For example, the mass fraction of the additive in the positive electrode active material layer can be 0.01wt%-2wt%. In some embodiments, the mass fraction of the additive in the positive electrode active material layer can be 0.05wt%-0.8wt%. Thus, with a smaller amount of additive, the dispersion of the carbonaceous material in the positive electrode active material layer can be improved, thereby reducing the occurrence of coating cracking.

[0117] According to some embodiments of the present application, the agglomeration of particles can be divided into two types: soft agglomeration and hard agglomeration. Soft agglomeration is mainly caused by electrostatic forces and van der Waals forces between particles. Since the forces are weak, they can be eliminated by some chemical reactions or the application of mechanical energy. In addition to electrostatic forces and van der Waals forces, hard agglomerates are also formed due to chemical bonds, so hard agglomerates are not easy to destroy. In the present application, by adding the aforementioned additives that have both plasticizing and dispersing effects, the dispersibility of the carbon-containing material in the positive electrode slurry is effectively improved, the agglomeration between the particles in the positive electrode slurry is hindered, and the agglomeration of the carbon-containing material in the positive electrode active material layer is effectively reduced. Specifically, the diameter of the carbon agglomerates in the positive electrode active material layer in the present application may be no more than 10 μm. In some embodiments, the diameter of the carbon agglomerates in the positive electrode active material layer may be no more than 5 μm. The diameter of the carbon agglomerates in the positive electrode active material layer can be tested by referring to the following method: use an electron ion polisher to cut the electrode piece, and then use an EDS spectrometer to view the element distribution. The area containing only C elements is the carbon-containing material distribution area. The diameter of the carbon agglomerate can be obtained by counting the diameters of the carbon-containing material distribution area.

[0118] In another aspect of the present application, the present application proposes a secondary battery, comprising: a positive electrode sheet, the positive electrode sheet being the aforementioned positive electrode sheet. Typically, a secondary battery comprises a positive electrode sheet, a negative electrode sheet, an electrolyte, and a separator. During the battery charge and discharge process, active ions are embedded and extracted back and forth between the positive electrode sheet and the negative electrode sheet. The electrolyte plays the role of conducting ions between the positive electrode sheet and the negative electrode sheet. The separator is arranged between the positive electrode sheet and the negative electrode sheet, mainly to prevent the positive and negative electrodes from short-circuiting, while allowing ions to pass through.

[0119] According to some embodiments of the present application, the present application has no particular limitation on the shape of the secondary battery, which may be cylindrical, square, or any other shape. For example, Figure 2 The secondary battery 5 is a square structure as an example. Figure 3 The outer packaging may include a shell 51 and a cover plate 53. The shell 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 51 has an opening connected to the receiving cavity, and the cover plate 53 can be covered on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the isolation membrane can form an electrode assembly 52 through a winding process or a lamination process. The electrode assembly 52 is encapsulated in the receiving cavity. The electrolyte is impregnated in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the secondary battery 5 can be one or more, and those skilled in the art can select according to specific actual needs.

[0120] According to some embodiments of the present application, secondary batteries can be assembled into a battery module. The number of secondary batteries contained in the battery module can be one or more. The specific number can be selected by those skilled in the art according to the application and capacity of the battery module. Figure 4 4 is an example of a battery module. Figure 4 In the battery module 4, the multiple secondary batteries 5 can be arranged sequentially along the length of the battery module 4. Of course, they can also be arranged in any other manner. Furthermore, the multiple secondary batteries 5 can be secured using fasteners. The battery module 4 can also include a housing having a storage space, and the multiple secondary batteries 5 are accommodated in the storage space.

[0121] According to some embodiments of the present application, the above-mentioned battery modules can also be assembled into a battery pack. The number of battery modules contained in the battery pack can be one or more, and the specific number can be selected by those skilled in the art based on the application and capacity of the battery pack. Figure 5 and Figure 6 The battery pack 1 is used as an example. Figure 5 and Figure 6 The battery pack 1 may include a battery box and multiple battery modules 4 disposed in the battery box. The battery box includes an upper box body 2 and a lower box body 3. The upper box body 2 can cover the lower box body 3 and form an enclosed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner in the battery box.

[0122] In the description of this application, “plurality” means two or more.

[0123] For ease of understanding, the preparation method of the secondary battery in this application is briefly described below: the positive electrode active material, conductive agent, adhesive, and additive are added to the N-methylpyrrolidone solvent system, and the mixture is stirred and mixed to obtain the positive electrode slurry, and the positive electrode slurry is applied to the positive electrode collector, and the positive electrode sheet is obtained after drying and cold pressing. The negative electrode material, conductive agent, adhesive, and additive are added to the deionized water solvent system, and the mixture is stirred and mixed to obtain the negative electrode slurry, and the negative electrode slurry is applied to the negative electrode collector, and the negative electrode sheet is obtained after drying and cold pressing. A PE porous polymer film is used as an isolation membrane. The positive electrode sheet, isolation membrane, and negative electrode sheet are stacked in sequence, so that the isolation membrane is between the positive electrode and the negative electrode to play an isolation role, and then a bare cell is obtained by a winding process. The bare cell is placed in an outer package, injected with the prepared electrolyte and encapsulated to obtain the aforementioned secondary battery.

[0124] According to some embodiments of the present application, the positive electrode active material, conductive agent, binder, and additives can be added to an N-methylpyrrolidone solvent system at a weight ratio of (94-c):4:2:c, where c is 0.01-5%, and stirred and mixed thoroughly to obtain a positive electrode slurry. The negative electrode material, conductive agent, binder, and additives can be added to a deionized water solvent system at a weight ratio of 96:2:1:1, and stirred and mixed thoroughly to obtain a negative electrode slurry.

[0125] According to some embodiments of the present application, the positive electrode current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer material base and a metal layer formed on at least one surface of the polymer material base. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and 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.).

[0126] According to some embodiments of the present application, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and 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.).

[0127] According to some embodiments of the present application, the negative electrode material may adopt the negative electrode material for batteries known in the art. As an example, the negative electrode material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials and lithium titanate, etc. The silicon-based material can be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites and silicon alloys. The tin-based material can be selected from at least one of elemental tin, tin oxide compounds and tin alloys. However, the present application is not limited to these materials, and other traditional materials that can be used as battery negative electrode materials can also be used. These negative electrode materials can be used alone or in combination of two or more.

[0128] According to some embodiments of the present application, the binder in the negative electrode slurry may be selected from at least one 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).

[0129] According to some embodiments of the present application, the conductive agent in the negative electrode slurry may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0130] In another aspect of the present application, the present application proposes an electrical device, comprising: the aforementioned secondary battery. The secondary battery, battery module, or battery pack can be used as a power source for the electrical device, or as an energy storage unit for the electrical device. The electrical device may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric 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 are not limited thereto. The electrical device can select a secondary battery, battery module or battery pack according to its usage requirements.

[0131] According to some embodiments of the present application, Figure 7 This is an example of an electric device. This device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of the secondary battery, a battery pack or battery module can be used.

[0132] According to some embodiments of the present application, the power-consuming device may also be a mobile phone, a tablet computer, a laptop computer, etc. Such a device is usually required to be lightweight and thin, and may use a secondary battery as a power source.

[0133] The present invention will be described below by way of specific examples. It should be noted that the following examples are intended only to illustrate the present invention and are not intended to limit the scope of the present invention. Where specific techniques or conditions are not specified in the examples, they are determined according to the techniques or conditions described in the literature in this area or according to the product specifications. Reagents or instruments not specified by manufacturer are all commercially available conventional products.

[0134] Synthesis of substituted bishydroxyalkanes

[0135] Referring to reaction formula (9), 0.5 mol potassium permanganate, 0.5 mol potassium hydroxide, and 0.5 mol styrene were dissolved in 100 mL of ethanol, stirred at 0°C for 1 h, and the first product was obtained after acid washing, extraction, drying, filtration, and separation.

[0136] Referring to reaction formula (10), 0.5 mol potassium permanganate, 0.5 mol potassium hydroxide, and 0.5 mol ethylene amide were hydrolyzed in 100 mL ethanol and stirred at 0°C for 1 h. The second product was obtained after acid washing, extraction, drying, filtration, and separation.

[0137] Example 1:

[0138] 1. Add 0.1 mol of phenol to 0.5 mol of potassium hydroxide, stir under vacuum at 90°C, then add 1 mol of ethylene oxide and 1 mol of propylene oxide, react at 140°C for 2 hours, then add 0.1 mol of thionyl chloride and 50 ml of dichloromethane and react at room temperature for 6 hours to obtain the third product.

[0139] 2. Add 0.5 mol of the first product and 0.5 mol of the third product to 1 mol of Et3N and react at room temperature for 24 hours. After acid washing, extraction and drying, the fourth product is obtained.

[0140] 3. Add 0.1 mol of the fourth product to 0.5 mol of potassium hydroxide, vacuum stir at 90°C, then add 1 mol of ethylene oxide and 1 mol of propylene oxide, react at 140°C for 2 hours, then add 0.1 mol of thionyl chloride and 50 ml of dichloromethane and react at room temperature for 6 hours. After precipitation, filtration and drying, the dry product is the additive.

[0141] Example 2:

[0142] 1. 0.1 mol of the fourth product in Example 21 was added to 0.5 mol of potassium hydroxide, and the mixture was stirred under vacuum at 90°C. Then, 1 mol of ethylene oxide and 1 mol of propylene oxide were added, and the mixture was reacted at 140°C for 2 h. Then, 0.1 mol of thionyl chloride and 50 ml of dichloromethane were added, and the mixture was reacted at room temperature for 6 h to obtain the fifth product.

[0143] 2. Add 0.5 mol of the first product and 0.5 mol of the fifth product to 1 mol of Et3N and react at room temperature for 24 hours. After acid washing, extraction and drying, the sixth product is obtained.

[0144] 3. Add 0.1 mol of the sixth product to 0.5 mol of potassium hydroxide, vacuum and stir at 90°C, then add 1 mol of ethylene oxide and 1 mol of propylene oxide, react at 140°C for 2 hours, then add 0.1 mol of thionyl chloride and 50 ml of dichloromethane and react at room temperature for 6 hours. After precipitation, filtration and drying, the dry product is the additive.

[0145] Example 3:

[0146] 1. 0.5 mol of the second product and 0.5 mol of the fifth product in Example 22 were added to 1 mol of Et3N and reacted at room temperature for 24 h. After acid washing, extraction, and drying, the seventh product was obtained.

[0147] 2. Add 0.1 mol of the seventh product to 0.5 mol of potassium hydroxide, vacuum and stir at 90°C, then add 1 mol of ethylene oxide and 1 mol of propylene oxide, react at 140°C for 2 hours, then add 0.1 mol of thionyl chloride and 50 ml of dichloromethane and react at room temperature for 6 hours. After precipitation, filtration and drying, the dry product is the additive.

[0148] Comparative Example 1

[0149] Comparative Example 1 is consistent with Example 1, except that no additive is added to the positive electrode slurry in Comparative Example 1.

[0150] Preparation of secondary batteries:

[0151] The preparation of the positive electrode sheet includes: S1: mixing a conductive agent (carbon black), the aforementioned additives, and a solvent (N-methylpyrrolidone) and stirring to obtain a first mixture; S2: adding a binder (polyvinylidene fluoride) to the first mixture and stirring and mixing to obtain a second mixture; S3: adding a positive electrode active material (lithium iron phosphate) to the second mixture and stirring and mixing to obtain a positive electrode slurry. The weight ratio of the positive electrode active material, conductive agent, binder, and additives in the positive electrode slurry is (94-c):4:2:c.

[0152] The positive electrode slurry is coated on the aluminum foil with a double-sided coating weight of 560g / m 2 The coating speed is 120m / min. After drying and cold pressing, the positive electrode sheet is obtained.

[0153] Preparation of negative electrode sheet: The negative electrode material (natural graphite), conductive agent (carbon black), binder (styrene-butadiene rubber), and additive (sodium carboxymethyl cellulose (CMC-Na)) are thoroughly stirred and mixed in a deionized water solvent system in a weight ratio of 96:2:1:1, and then coated on copper foil, dried, and cold pressed to obtain the negative electrode sheet.

[0154] PE porous polymer film is used as the isolation membrane.

[0155] The positive electrode sheet, separator, and negative electrode sheet are stacked in sequence, with the separator between the positive and negative electrodes, and wound to form a bare cell. The bare cell is placed in an outer packaging, injected with the prepared electrolyte, and encapsulated to form a secondary battery.

[0156] Table 1

[0157]

[0158] The positive electrode slurries and secondary batteries in the aforementioned examples and comparative examples were tested:

[0159] Positive electrode slurry solid content test method: The positive electrode slurry is coated on aluminum foil and dried to obtain a positive electrode sheet. The calculation formula of the positive electrode slurry solid content W is as follows:

[0160] W=(m1-m0) / (m2-m0)×100%

[0161] Among them, m0 is the mass of the aluminum foil, m1 is the mass of the positive electrode sheet after drying, and m2 is the mass of the wet positive electrode sheet obtained after the positive electrode slurry is coated on the aluminum foil.

[0162] Positive electrode diaphragm resistivity test method: Use a four-probe tester to directly test the diaphragm resistivity, for example: use the Lattice Electronics ST2263 dual-electric digital four-probe tester to directly test the diaphragm resistivity.

[0163] Battery capacity retention rate test method: Take lithium iron phosphate battery as an example, in an environment of 25℃, charge the secondary battery at a constant current of 0.33C to 3.65V, and then discharge it at a constant current of 0.33C to 2.5V. The measured discharge capacity is recorded as the initial capacity C0. Repeat the above steps for the same battery and record the discharge capacity C0 of the battery after n cycles. n , battery capacity retention rate P after n cycles n =100%×C n / C0. Here, the first cycle corresponds to n=1, the second cycle corresponds to n=2, and so on, the 100th cycle corresponds to n=100. The battery capacity retention rate after 1000 cycles was measured.

[0164] See Table 2 for test results.

[0165] Table 2

[0166]

[0167] An infrared spectroscopy test was performed on the additives in the positive electrode active material layer, specifically as follows: first, the positive electrode plate was soaked in N-methylpyrrolidone to soak the binder and additives in the positive electrode active material layer into the N-methylpyrrolidone, and then gel permeation chromatography (GPC) was used to remove the binder from the N-methylpyrrolidone containing the binder and additives. Finally, the additives were obtained by drying and subjected to an infrared spectroscopy test.

[0168] Test results show that the additives described in this application help improve the uniform distribution of conductive carbon in the positive electrode sheet, and by adding the additives to the positive electrode sheet, the sheet resistivity can be reduced. When the molecular weight of the additive is too high and / or the amount added to the positive electrode sheet is too high, the additives can act like a shield, causing the sheet resistance to increase.

[0169] The battery capacity retention rate is highly correlated with the electrode membrane resistivity. When the membrane resistivity is within a lower range, the battery capacity retention rate is higher. As the membrane resistivity exceeds a certain value, the battery capacity retention rate begins to decline significantly.

[0170] The additives in this application can significantly improve the problem of coating cracking. When the content of the additive in the positive electrode slurry is too low, the additive cannot improve the coating cracking effect. When the content of the additive in the positive electrode slurry is too high, the improvement effect on coating cracking is no longer significantly improved, and negative effects such as demolding may occur.

[0171] In the description of this application, "A and / or B" may include the case of A alone, the case of B alone, or any of the cases of A and B, where A and B are only used for example, and may be any technical feature connected by "and / or" in this application.

[0172] Unless otherwise specified, all technical and scientific terms used in this application have the same meanings as commonly understood by those skilled in the art to which this application belongs. All patents and publications referred to in this application are incorporated herein by reference in their entirety. The terms "comprising" or "including" are open-ended expressions, meaning that they include the contents specified in this application but do not exclude contents elsewhere.

[0173] In the description of this specification, the description with reference to the terms "one embodiment", "another embodiment" and the like means that the specific features, structures, materials or characteristics described in conjunction with the embodiment are included in at least one embodiment of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in a suitable manner in any one or more embodiments or examples. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples, unless they are mutually inconsistent. In addition, it should be noted that in this specification, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated.

[0174] Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limitations on the present application. Ordinary technicians in this field can change, modify, replace and modify the above embodiments within the scope of the present application.

Claims

1. An additive for a battery, characterized in that: The additive is a polymer, the main chain of the polymer is a polyether structure, the polymer comprises a phenyl-containing group, and the phenyl-containing group is located on the main chain of the polymer and / or on the side chain of the polymer.

2. The additive according to claim 1, characterized in that The phenyl-containing groups are located on the side chains of the polymer.

3. The additive according to claim 1 or 2, characterized in that The end groups of the polymer include the phenyl-containing groups.

4. The additive according to any one of claims 1 to 3, characterized in that The polymer further includes nitrogen-containing groups, which are located on the side chains of the polymer.

5. The additive according to any one of claims 1 to 4, characterized in that The structure of the polymer is shown in formula (1), Where R is C1-C 10 wherein the alkyl group or the phenyl group is selected from the group consisting of: a, b, c, and d, wherein the alkyl group or the phenyl group is selected from the group consisting of: a, b, and c, and ...

6. The additive according to claim 5, characterized in that The structure of the polymer is shown in Formula (2) or Formula 3, Wherein, e is the number of the fifth repeating unit in the polymer, and f is the number of the sixth repeating unit in the polymer.

7. The additive according to claim 5 or 6, characterized in that The a and c are each independently 1-400.

8. The additive according to any one of claims 5 to 7, characterized in that The b and d are each independently 1-2000.

9. The additive according to claim 6, wherein the e is 1-400, and / or the f is 1-2000.

10. A method for preparing the additive according to any one of claims 1 to 9, characterized in that: include: providing a monomer, the monomer containing an epoxy group; The monomers are polymerized to form a polymer whose main chain is a polyether structure, wherein the polymer comprises phenyl groups, and the phenyl groups are located on the main chain of the polymer and / or on the side chains of the polymer.

11. The method according to claim 10, characterized in that The monomer includes an epoxy compound, and the step of causing the monomer to undergo a polymerization reaction includes: An initiator is added to a solution of an epoxy compound to undergo a first heating reaction to obtain a first solution, wherein the first solution contains a polymer having a first repeating unit structure and a second repeating unit structure; a chlorinating agent is added to the first solution to obtain a second solution, wherein the second solution contains the polymer having the first repeating unit structure and the second repeating unit structure with terminal chlorine substituted; adding a substituted bishydroxyalkane to the second solution to obtain a third solution, wherein the substituent of the substituted bishydroxyalkane comprises a nitrogen-containing group or a phenyl-containing group; An epoxy compound is added to the third solution, and a fourth solution is obtained through a second heating reaction, wherein the fourth solution contains a polymer having a first repeating unit structure, a second repeating unit structure, a third repeating unit structure, and a fourth repeating unit structure.

12. The method according to claim 11, characterized in that Further including: adding a chlorinating agent to the fourth solution to obtain a fifth solution, wherein the fifth solution contains the polymer having the first repeating unit structure, the second repeating unit structure, the third repeating unit structure, and the fourth repeating unit structure with terminal chlorine substituted; adding a substituted bishydroxyalkane to the fifth solution to obtain a sixth solution, wherein the substituent of the substituted bishydroxyalkane comprises a nitrogen-containing group or a phenyl-containing group; An epoxy compound is added to the sixth solution, and an eleventh solution is obtained through a third heating reaction, wherein the eleventh solution contains a polymer having a first repeating unit structure, a second repeating unit structure, a third repeating unit structure, a fourth repeating unit structure, a fifth repeating unit structure, and a sixth repeating unit structure.

13. The method according to claim 11 or 12, characterized in that The epoxy compounds include ethylene oxide and propylene oxide.

14. The method according to any one of claims 11 to 13, characterized in that: The initiator includes a hydroxy compound.

15. The method according to any one of claims 11 to 14, characterized in that: The chlorinating agent includes thionyl chloride.

16. The method according to claim 12, characterized in that The reaction temperatures of the first heating reaction, the second heating reaction, and the third heating reaction are independently 90° C.-140° C.

17. The method according to claim 11 or 12, characterized in that The main chain carbon number of the substituted bishydroxyalkane is 1-20.

18. A positive electrode slurry, characterized in that: include: positive electrode active material; An additive, wherein the additive comprises the additive according to any one of claims 1 to 9 or the additive prepared by the method according to any one of claims 10 to 17.

19. The positive electrode slurry according to claim 18, characterized in that The sum of the mass fraction of the positive electrode active material and the mass fraction of the additive in the positive electrode slurry is 92 wt % to 96 wt %.

20. A positive electrode plate, characterized in that: The positive electrode active material layer comprises a positive electrode current collector and a positive electrode active material layer, wherein the positive electrode active material layer is formed by solidifying the positive electrode slurry according to claim 18 or 19, or the positive electrode active material layer comprises the additive according to any one of claims 1 to 9, or the positive electrode active material layer comprises the additive prepared by the method according to any one of claims 10 to 17.

21. The positive electrode sheet according to claim 20, characterized in that: The thickness of a single layer of the positive electrode active material layer is 30 μm to 500 μm.

22. The positive electrode sheet according to claim 20 or 21, characterized in that: The positive electrode active material layer includes a positive electrode active material. The positive electrode active material includes a core and a carbon coating layer. The carbon coating layer at least partially covers a surface of the core.

23. The positive electrode sheet according to any one of claims 20 to 22, characterized in that: The positive electrode active material layer includes conductive carbon.

24. The positive electrode sheet according to any one of claims 20 to 23, characterized in that: The positive active material layer includes a solvent, and the solvent includes N-methylpyrrolidone.

25. The positive electrode sheet according to any one of claims 20 to 24, characterized in that: After the positive electrode sheet is folded, the fold can withstand rolling pressure 3-10 times.

26. The positive electrode sheet according to any one of claims 20 to 25, characterized in that: The film resistivity of the positive electrode plate is 1Ω·cm-100Ω·cm.

27. The positive electrode sheet according to any one of claims 20 to 26, characterized in that: The mass fraction of the additive in the positive electrode active material layer is 0.01 wt % to 2 wt %.

28. The positive electrode sheet according to any one of claims 20 to 27, characterized in that: The diameter of the carbon agglomerates in the positive electrode active material layer is no greater than 10 μm.

29. A battery, characterized in that: include: The positive electrode sheet is the positive electrode sheet according to any one of claims 20 to 28.

30. An electrical device, characterized in that: include: The battery according to claim 29.

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