Dispersant composition, pole piece and battery

Abstract

The invention discloses a dispersant composition, a pole piece and a battery. The dispersant composition comprises a polymer viscosity reducer, a small molecule viscosity reducer and a resin softening agent, and the mass content of the polymer viscosity reducer and / or the small molecule viscosity reducer is higher than that of the resin softening agent. The dispersant composition can achieve an anchoring effect and a steric hindrance synergistic effect on particles including an electrode active material, a conductive agent and the like in the electrode slurry, can effectively improve the dispersibility, the stability and the solid content of the electrode slurry, and reduces the viscosity of the electrode slurry; therefore, the distribution uniformity of each component in the active material layer contained in the pole piece, the film layer quality and the capacity density can be improved, the local pulverization phenomenon of the active material layer is relieved, and the capacity exertion and cycle performance and the capacity density of the pole piece are improved. An active material layer in at least one of a positive plate and a negative plate in the battery contains the dispersant composition.

Description

Technical Field

[0001] The present application belongs to the field of batteries, and specifically relates to a dispersant composition, a pole piece and a battery. Background Art

[0002] With the rapid development of mobile electronic devices, electric vehicles and renewable energy, batteries such as lithium-ion batteries, as key energy storage devices, have increasingly higher performance requirements. Among them, high energy density and long life are important performance indicators of batteries, and increasing the solid content of electrode slurry and the thickness of the active material layer of the electrode sheet is an effective way to improve energy density.

[0003] However, in actual operation, due to the high surface energy of electrode active materials such as positive electrode materials, agglomeration is easy to occur during the slurry making process, resulting in problems such as uneven slurry and high viscosity, which in turn leads to adverse consequences such as poor film quality, easy pulverization and low peeling strength of the active material layer of the electrode, which in turn leads to unsatisfactory energy density and cycle performance of the battery.

[0004] In view of the above problems, the commonly used solution is to add dispersants to the slurry to reduce the agglomeration of the electrode active materials, thereby improving the dispersibility of the electrode active materials and the uniformity of the slurry, thereby improving the quality of the pole piece. However, although the existing dispersants can improve the dispersibility of the electrode slurry to a certain extent, as the market has higher and higher requirements for battery energy density and cycle performance, the existing dispersants cannot meet the needs of current applications, and cannot improve the mechanical properties of the pole piece, such as structural stability. Summary of the invention

[0005] The purpose of this application is to overcome the above-mentioned deficiencies of the prior art and to provide a dispersant composition, an electrode and a battery to solve the technical problems that the existing dispersants are difficult to meet the requirements of the current electrode slurry and cannot simultaneously improve the mechanical properties of the electrode, resulting in unsatisfactory battery capacity density and cycle performance.

[0006] In order to achieve the above application purpose, in the first aspect, the present application provides a dispersant composition. The dispersant composition of the present application comprises a polymer viscosity reducer, a small molecule viscosity reducer and a resin flexibilizer, and the mass content of the polymer viscosity reducer and / or the small molecule viscosity reducer is higher than the mass content of the resin flexibilizer.

[0007] The dispersant composition of the embodiment of the present application can play an anchoring role and a steric hindrance synergistic role in the electrode slurry through the compounding of the polymer viscosity reducer, small molecule viscosity reducer and resin flexibilizer contained therein, can effectively improve the dispersibility and stability of the electrode slurry, and can reduce the viscosity of the electrode slurry, increase the solid content, thereby improving the uniformity of the distribution of the electrode active material in the active material layer contained in the pole piece, the film quality and the capacity density, alleviate the local pulverization phenomenon of the active material layer, and improve the capacity of the pole piece. Cyclic performance and capacity density. At the same time, it can also improve the flexibility of the active material layer and the bonding strength between the active material layer and the current collector, thereby improving the cycle performance of the pole piece.

[0008] In a second aspect of the present application, a pole piece is provided. The pole piece of the present application comprises an electrode active material and the dispersant composition of the present application.

[0009] The components contained in the pole piece of the embodiment of the present application, such as the electrode active material, the conductive agent and other components, can be evenly distributed, the film layer quality and surface density are high, the active material layer structure is stable, and the bonding strength with the current collector is high, so that the pole piece structure has good stability, good flexibility, and high peel strength, which effectively alleviates the undesirable phenomena such as pulverization of the active material layer and effectively improves the capacity density and cycle performance of the pole piece.

[0010] In a third aspect of the present application, a battery is provided. The battery of the present application comprises a positive electrode sheet and a negative electrode sheet, wherein the positive electrode sheet is the electrode sheet of the present application, and the electrode active material contained in the electrode sheet comprises a positive electrode active material;

[0011] and / or

[0012] The negative electrode sheet is the electrode sheet described in the present application, and the electrode active material contained in the electrode sheet includes a negative electrode active material.

[0013] Since at least one of the positive electrode sheet and the negative electrode sheet in the battery of the embodiment of the present application contains the dispersant combination of the embodiment of the present application, the electrode active material contained in the electrode sheet in the battery of the embodiment of the present application is evenly distributed in the active material layer and has a high solid content. Moreover, the electrode sheet has high structural stability, capacity density and cycle performance, thereby giving the battery high energy density and cycle performance. DETAILED DESCRIPTION

[0014] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present application more clearly understood, the present application is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0015] In this application, the term "and / or" describes the association relationship of associated objects, indicating that there may be three relationships. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone. A and B can be singular or plural. The character " / " generally indicates that the associated objects are in an "or" relationship.

[0016] In this application, "at least one" means one or more, and "plurality" means two or more. "At least one of the following" or similar expressions refers to any combination of these items, including any combination of single items or plural items. For example, "at least one of a, b, or c", or "at least one of a, b, and c" can all mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, c can be single or multiple, respectively.

[0017] It should be understood that in the various embodiments of the present application, the size of the serial numbers of the above-mentioned processes does not mean the order of execution, some or all of the steps can be executed in parallel or sequentially, and the execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0018] The terms used in the embodiments of the present application are only for the purpose of describing specific embodiments, and are not intended to limit the present application. The singular forms "a", "said" and "the" used in the embodiments of the present application and the appended claims are also intended to include plural forms, unless the context clearly indicates other meanings.

[0019] The weight of the relevant components mentioned in the embodiment description of the present application can not only refer to the specific content of each component, but also represent the proportional relationship between the weights of the components. Therefore, as long as the content of the relevant components is proportionally enlarged or reduced according to the embodiment description of the present application, it is within the scope disclosed in the embodiment description of the present application. Specifically, the mass described in the embodiment description of the present application can be a mass unit known in the chemical industry such as μg, mg, g, kg, etc.

[0020] The terms "first" and "second" are used only for descriptive purposes to distinguish objects such as substances from each other, and should not be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features. For example, without departing from the scope of the embodiments of the present application, the first XX may also be referred to as the second XX, and similarly, the second XX may also be referred to as the first XX. Thus, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features.

[0021] As the market places higher and higher demands on battery performance such as energy density and service life, electrodes are one of the important components of batteries. Therefore, the performance of electrodes such as structural stability, capacity density and cyclability have an important impact on the battery's energy density and cycle life.

[0022] However, electrode active materials such as positive electrode active materials have characteristics such as easy agglomeration, which makes it difficult to further increase the solid content of the electrode slurry due to the agglomeration of the electrode active materials, resulting in uneven electrode slurry, high viscosity, and difficulty in further increasing the solid content, which makes it difficult to further increase the capacity density of the formed active material layer, and the film layer uniformity is not ideal. It is also easy to cause the active material layer to crack and fall off during the charge and discharge process. This makes the pole piece structure stability, capacity density and cycle performance unsatisfactory and difficult to further improve. These deficiencies of the electrode will directly affect the energy density, cycle performance and other properties of the battery, thereby restricting the battery from further meeting the needs of current applications.

[0023] In order to effectively improve the stability of the pole piece structure, capacity density and cycle performance, so as to improve the energy density, cycle performance and safety of the battery, the following technical solutions are proposed in the embodiments of the present application.

[0024] [Dispersant composition]

[0025] In a first aspect, the present invention provides a dispersant composition. The dispersant composition of the present invention comprises a polymer viscosity reducer, a small molecule viscosity reducer and a resin flexibilizer, and the mass content of the polymer viscosity reducer and / or the small molecule viscosity reducer is higher than the mass content of the resin flexibilizer.

[0026] In the dispersant composition of the embodiment of the present application, the viscosity reducer refers to a chemical auxiliary agent that has the function of regulating or reducing the viscosity of the slurry. A polymer viscosity reducer refers to a polymer viscosity reducer, that is, a high molecular viscosity reducer. The small molecule in the small molecule viscosity reducer refers to a non-polymer with a molecular weight less than 1000Da (Dalton), therefore, the small molecule viscosity reducer refers to a non-polymer viscosity reducer with a molecular weight less than 1000Da (Dalton). A resin flexibilizer refers to a type of resin that can improve the flexibility and impact strength of the electrode active material layer to a certain extent.

[0027] The polymer viscosity reducer and small molecule viscosity reducer contained in the dispersant composition of the embodiment of the present application can wet the surface of the electrode active material, conductive agent and other particles in the electrode slurry through the groups contained therein, and bind to the surface of these particles, hindering the contact between these particles and agglomeration; on the other hand, the molecules of the polymer viscosity reducer and small molecule viscosity reducer can also play a steric hindrance role, and can also hinder the contact between these particles and agglomeration, thereby improving the dispersibility of these particles. Moreover, the groups contained in each component of the polymer viscosity reducer, small molecule viscosity reducer and resin-based flexibilizer can interact with each other, so that the three can form a specific steric hindrance effect, so that the particles of the electrode active material, conductive agent and the like in the electrode slurry can play a steric hindrance synergistic role, hindering the contact between these particles and agglomeration. Therefore, the dispersant composition of the embodiment of the present application can play an anchoring role and a steric hindrance enhancement role in the electrode slurry through the compounding of the components it contains, and can effectively improve the dispersibility and stability of the electrode slurry, thereby improving the uniformity of the distribution of the electrode active material in the active material layer contained in the electrode and the film quality, alleviating the local pulverization of the active material layer, and improving the capacity and cycle performance of the electrode; it can also reduce the viscosity of the slurry, thereby increasing the solid content of the electrode slurry, thereby increasing the capacity density of the electrode.

[0028] In addition, the resin-based softener contained in the dispersant composition of the embodiment of the present application can improve the structural stability, flexibility of the active material layer and the bonding strength between the active material layer and the current collector, thereby improving the structural stability and peeling strength of the electrode, thereby improving the cycle performance of the electrode.

[0029] In some embodiments, the mass ratio of the polymer viscosity reducer, the small molecule viscosity reducer and the resin softener can be (10-30): (10-25): (0.1-0.5). In the exemplary embodiments, the mass ratios are 10:10:0.1, 10:15:0.1, 10:20:0.1, 10:25:0.1, 10:10:0.3, 20:10:0.3, 30:10:0.3, 20:20:0.3, 20:20:0.5, 30:20:0.3, 30:20:0.5 and other typical but non-limiting mass ratios or the range between any two mass ratios. The mass ratio of the three within this range can further enhance the anchoring effect and steric hindrance synergistic effect of the three on particles in the electrode slurry, including electrode active materials and conductive agents, thereby further improving the dispersibility and stability of the electrode slurry, reducing the viscosity of the slurry and increasing the solid content of the slurry and other properties, thereby further improving the uniformity of distribution of each component in the active material layer, improving the quality of the film layer, and at the same time improving the structural stability of the active material layer, thereby improving the mechanical properties such as the peeling strength of the electrode and the electrochemical properties such as the energy density and cycle performance.

[0030] Polymer viscosity reducer:

[0031] In the dispersant composition of the present application, as described above, the polymer viscosity reducer can use its functional groups with viscosity reducing effect to wet the particles of electrode active materials and conductive agents in the electrode slurry, and enhance the binding of the polymer viscosity reducer, small molecule viscosity reducer and resin components with the surface of these particles; at the same time, the molecules of the polymer viscosity reducer themselves also have steric hindrance. Therefore, the polymer viscosity reducer can prevent the particles from contacting each other to alleviate the agglomeration phenomenon between the particles.

[0032] In some embodiments, the polymer viscosity reducer includes at least one functional group selected from the group consisting of an amine group, an ester group, a hydroxyl group, an amide group, and a pyrrolidone ring. That is, the polymer viscosity reducer contains at least one functional group selected from the group consisting of an amine group, an ester group, a hydroxyl group, an amide group, and a pyrrolidone ring. These functional groups can give full play to related effects such as wetting and steric hindrance. For example, these groups exhibit certain polarity, and they can be combined on the surface of particles such as electrode active materials and conductive agents, and effectively alleviate the contact between particles in addition to enhancing the mutual repulsion between these particles; more importantly, these groups can interact with small molecule viscosity reducers and resins, so that the three can construct a steric hindrance system, which has a steric hindrance effect on particles such as electrode active materials and conductive agents, thereby preventing these particles from contacting each other to alleviate the agglomeration of these particles. Among them, the amides in these functional groups can interact with these particles such as conductive carbon conductive agents, thereby increasing the wetting and anchoring effects on these particles; the amides can also interact with components such as small molecule viscosity reducers and resins to form steric hindrance, thereby hindering the agglomeration of these particles; the pyrrolidone ring is solvent-philic and can enhance the solubility of the polymer viscosity reducer in the electrode slurry.

[0033] In some embodiments, the polymer viscosity reducer may include a class of polymers containing solvated segments, such as at least one of nonionic polymers and aldehyde resins. These types of polymer viscosity reducers contain rich functional groups, such as at least one of the above-mentioned amino groups, ester groups, hydroxyl groups, amides, and pyrrolidone rings, so that they can effectively play related roles such as wetting and steric hindrance on particles such as electrode active materials and conductive agents. In addition, they also contain solvated segments, which can effectively improve the solubility and dispersibility of the polymer viscosity reducer in solvents, such as electrode slurries.

[0034] In an embodiment, when the polymer viscosity reducer includes a nonionic polymer, the nonionic polymer includes at least one of pyrrole polymer, polyvinyl alcohol, and polyethylene glycol. In an exemplary embodiment, the pyrrole polymer includes at least one of polyvinyl pyrrolidone, polypyrrole, and vinyl pyrrolidone-vinyl acetate copolymer.

[0035] In the embodiment, when the polymer viscosity reducer includes aldehyde resin, in an exemplary embodiment, the aldehyde resin includes at least one of polyvinyl formal, polyvinyl carboxyacetaldehyde, and polyvinyl carboxybutyraldehyde.

[0036] These types of non-ionic polymers and aldehyde resins contain corresponding functional groups, such as pyrrolidone rings, which can effectively play related roles such as wetting and steric hindrance on particles such as electrode active materials and conductive agents, and contain solvated chain segments, and have good solubility and dispersibility in electrode slurries.

[0037] Small molecule viscosity reducer:

[0038] In the dispersant composition of the embodiment of the present application, as described above, the small molecule viscosity reducer can also wet the particles of the electrode active material and the conductive agent in the electrode slurry, and play a steric hindrance synergistic role with the components such as the polymer viscosity reducer and the resin, which can hinder the contact between the particles of the electrode active material and the conductive agent to alleviate the agglomeration phenomenon between these particles.

[0039] In some embodiments, the small molecule viscosity reducer contains at least one functional group of a conjugated ring and a carboxyl group, that is, the small molecule viscosity reducer can include a small molecule viscosity reducer having at least one functional group of a conjugated ring and a carboxyl group. When the conjugated ring functional group is included, the small molecule viscosity reducer of these functional groups and the particles of the electrode active material and the conductive agent, especially the particles of the conductive agent, can interact with each other and play a steric hindrance, such as generating steric hindrance through ππ stacking with the conductive carbon, hindering the aggregation of the conductive carbon particles and causing agglomeration; in addition, the functional groups of the conjugated ring group can show a certain polarity under the influence of other groups contained in the small molecule viscosity reducer, so that the particles of the electrode active material and the conductive agent can be further anchored and repelled by charge. When the carboxyl functional group is included, these functional groups can be combined with the surface of the particles of the electrode active material and the conductive agent, play an anchoring effect and a charge repulsion effect on the particles of the electrode active material and the conductive agent, and can also reduce the agglomeration phenomenon between these particles and improve the dispersibility of these particles in the electrode slurry. Therefore, in the embodiments, the above-mentioned small molecule viscosity reducer contains both a conjugated ring and a carboxyl group.

[0040] In the embodiment, when the small molecule viscosity reducer contains a conjugated ring, the conjugated ring includes at least one of a benzene ring and a conjugated heterocyclic ring. When the conjugated ring contains a conjugated heterocyclic functional group, the conjugated heterocyclic functional group includes at least one functional group of furan and indole. In the exemplary embodiment, the small molecule viscosity reducer containing a furan functional group may include furan carboxylic acid; the small molecule viscosity reducer containing an indole functional group may include at least one of indole lactic acid and indole propionic acid. When the conjugated ring contains a benzene ring functional group, the small molecule viscosity reducer containing a benzene ring functional group may include but is not limited to a benzoic acid small molecule viscosity reducer. Of course, the small molecule viscosity reducer containing a carboxyl functional group or simultaneously containing at least one of a conjugated heterocyclic ring, a conjugated ring and a carboxyl functional group may also be at least one of the above-mentioned furan carboxylic acid, indole lactic acid, benzoic acid, etc.

[0041] The small molecule viscosity reducers with these functional groups can interact with particles such as electrode active materials and conductive agents, play a steric hindrance role or further play an anchoring role, hindering the aggregation and agglomeration of conductive carbon particles. At the same time, these small molecule viscosity reducers containing conjugated ring functional groups also contain carboxyl groups, which are polar and can effectively bind to the surface of particles including electrode active materials and conductive agents, enhance the charge repulsion and anchoring effect between particles, and improve the dispersibility of particles in electrode slurry.

[0042] Resin softener:

[0043] In some embodiments, the resin-based softener may include a resin capable of self-condensation reaction, wherein the resin capable of self-condensation reaction refers to a compound capable of self-condensation reaction, and generates a self-condensation product after self-condensation reaction.

[0044] In the dispersant composition of the embodiment of the present application, the resin-type softener including the resin that can self-condense can, under the action of the small molecule viscosity reducer, play a steric hindrance synergistic role with the small molecule viscosity reducer, the polymer viscosity reducer and other components. Moreover, the resin-type softener component can undergo a self-condensation reaction during the heat treatment process of the electrode processing, and generate a self-condensation compound in the active material layer of the electrode. The self-condensation product itself and further with the polymer viscosity reducer, the binder and other components can form a three-dimensional bonding network structure in the active material layer of the electrode, which plays a softening and bonding synergistic role, can improve the flexibility of the active material layer, enhance the structural stability of the active material layer and the bonding strength with the current collector, thereby improving the structural stability and peeling strength of the electrode, thereby improving the cycle performance of the electrode.

[0045] In some embodiments, the resin softener may include at least one functional group selected from the group consisting of an amine group and an amide group. In an embodiment, when the resin softener includes an amine group, the resin softener may be an amine resin; the resin softener containing an amine group, that is, the amine resin may include at least one of a urea-formaldehyde resin and a cyanamide resin. In an exemplary embodiment, the cyanamide resin may include at least one of a melamine formaldehyde resin and a benzoguanamine resin. When the resin softener includes an amide group, the resin softener may include an amide resin; the resin softener containing an amide group, that is, the amide resin may include polyamide polyamine epichlorohydrin.

[0046] On the one hand, these resin-based softeners can play a steric hindrance synergistic role with small molecule viscosity reducers, polymer viscosity reducers and other components in the electrode slurry. In particular, when the above-mentioned small molecule viscosity reducers include carboxyl-containing small molecule viscosity reducers, the amino groups contained in these resin-based softeners can play a synergistic viscosity reduction role with the carboxyl groups contained in the small molecule viscosity reducers to quickly wet the particles of electrode active materials and conductive agents, thereby playing a dispersing and synergistic role in the electrode slurry, improving the dispersibility and stability of the electrode slurry and the solid content and other properties; on the other hand, these resin-based softeners can undergo self-condensation reactions during the heat treatment process of the electrode processing or under the catalytic action of weak acids, and self-condensation reactions occur in the active material layer of the electrode to form a cross-linked network structure in the active material layer; at the same time, the lone pair of electrons on the nitrogen atoms contained in these resin-based softeners can form local large π bonds with binders such as PVDF in the active material layer. Therefore, these resin-based softeners can improve the elasticity and flexibility of the electrode, and improve the mechanical properties such as the structural stability and peel strength of the electrode.

[0047] Based on the above schemes of polymer viscosity reducers, small molecule viscosity reducers, and resin softeners, in some embodiments, the above polymer viscosity reducers are selected from polymers containing at least one functional group selected from amine, ester, hydroxyl, amide, and pyrrolidone ring, while the small molecule viscosity reducers are selected from small molecule compounds containing conjugated ring functional groups containing carboxyl groups, and the resin softeners are selected from resin softeners containing at least one functional group selected from amine, amide, etc.

[0048] In this way, the polar groups contained in the polymer viscosity reducer can interact with the carboxyl groups contained in the small molecule viscosity reducer and the nitrogen atoms contained in the resin-type flexibilizer, such as bonding, so that the three can form a specific spatial stereo effect; and the carboxyl groups contained in the small molecule viscosity reducer and the amine groups, amide groups contained in the resin-type flexibilizer can quickly wet and act on the surface of the solid particles in the electrode slurry. Therefore, when the dispersant composition of the embodiment of the present application is used in the electrode slurry, it can quickly wet and combine with the surface of the solid particles in the electrode slurry, and play a steric hindrance and dispersion effect, which can significantly reduce the probability of solid particle contact and thus significantly reduce the agglomeration of solid particles, so that the solid particles are evenly dispersed, thereby significantly improving the dispersibility and stability of the electrode slurry, and can also increase the solid content.

[0049] At the same time, the resin-based softener containing at least one functional group such as amino group and amide group can undergo a self-condensation reaction to generate a self-shrinking compound during the heat treatment process of the electrode processing, and the self-shrinking compound forms a local large π bond and a three-dimensional cross-linked network structure together with the binder in the active material layer, thereby improving the structural stability of the active material layer and the bonding strength with the current collector, reducing the occurrence of adverse phenomena such as powdering of the active material layer, thereby improving the cycle performance of the electrode.

[0050] In some embodiments, based on the above embodiments, the dispersant composition of the embodiments of the present application may further include at least one component in a solvent.

[0051] In the embodiment, when the dispersant composition of the above application embodiment contains a solvent, the solvent acts as a solvent carrier, such as the above polymer viscosity reducer, small molecule viscosity reducer and resin softener are dissolved in the solvent, and the three are dissolved in the solvent so that the three are evenly dispersed in the solvent, thereby improving the steric hindrance synergistic effect of the three on particles including electrode active materials and conductive agents, thereby improving the dispersibility and stability of the electrode slurry as well as the solid content and other properties.

[0052] In the embodiment, when the dispersant composition of the embodiment of the present application contains a solvent, the mass ratio of the solvent to the polymer viscosity reducer is (60-85): (10-30). The content range of the solvent can make the components such as the polymer viscosity reducer, the small molecule viscosity reducer and the self-condensation precursor fully dissolved in the solvent, and give full play to the synergistic effect between the components.

[0053] In an embodiment, the solvent may be a solvent that can effectively dissolve the above polymer viscosity reducer, small molecule viscosity reducer and self-condensation precursor. For example, in an exemplary embodiment, the solvent may include at least one of N-methylpyrrolidone, N,N-dimethylformamide, etc. These types of solvents can effectively dissolve the above polymer viscosity reducer, small molecule viscosity reducer and resin flexibilizer and other components, and can improve the stability of each component.

[0054] In addition, the present application embodiment dispersant composition can be compounded according to the component type and content contained in the above dispersant composition, such as each component raw material can be physically mixed. When containing a solvent, the other components contained in the above dispersant composition can be added to the solvent for dissolution treatment, so that each component is evenly mixed to form a uniformly dispersed and stable mixed solution. When the present application embodiment dispersant composition contains a solvent, in order to improve the stability of components such as polymer viscosity reducers, small molecule viscosity reducers and self-condensation precursors dispersed in a solvent, the polymer viscosity reducer can be first dissolved in a solvent, and then a small molecule viscosity reducer is added to dissolve, and the first mixed solution is prepared; the resin-based flexibilizer is dissolved in a solvent alone, and the second mixed solution is prepared; finally, the first mixed solution and the second mixed solution are mixed in an environment such as room temperature or lower than room temperature, and the present application embodiment dispersant composition is prepared.

[0055] [Pole piece]

[0056] In a second aspect, the present application also provides a pole piece. The pole piece of the present application includes a current collector and an active material layer disposed on at least one surface of the current collector, wherein a dispersant is dispersed in the active material layer. The dispersant is the dispersant composition of the above-mentioned present application.

[0057] In this way, in the pole piece of the embodiment of the present application, various components such as electrode active materials, conductive agents and other components can be evenly distributed, the film layer quality and surface density are high, the active material layer structure is stable, and the bonding strength with the current collector is high, so that the pole piece structure has good stability, good flexibility, and high peel strength, which effectively alleviates the undesirable phenomena such as pulverization of the active material layer and effectively improves the capacity density and cycle performance of the pole piece.

[0058] In an embodiment, when the resin softener contained in the dispersant includes a resin that can undergo a self-condensation reaction, the self-condensation compound can undergo a self-polymerization reaction during the processing process of forming an active material layer on at least one surface of the current collector with an electrode slurry containing the dispersant composition of the embodiment of the present application, such as during a heat treatment process, to generate a self-condensation compound, and form a local large π bond with the binder, thereby forming a three-dimensional bonding network structure in the active material layer.

[0059] In the embodiment, in the pole piece of the embodiment of the present application, a polymer viscosity reducer is used as a marker, and the mass percentage of the polymer viscosity reducer in the active material layer can be 0.1% to 3%, and can be optionally 0.5% to 2.5%. In the exemplary embodiment, it can be 0.1%, 0.5%, 1%, 1.5%, 2.0%, 2.5%, 3.0% and other typical but non-limiting mass contents or the range between any two content values. According to the content of the polymer viscosity reducer in the active material layer, according to the mass content ratio relationship of each component in the dispersant composition of the embodiment of the text application above, the mass range of the dispersant composition of the embodiment of the present application in the active material layer can be indirectly reflected. This mass content range can improve the dispersion uniformity of components such as electrode active materials and conductive agents in the active material layer, improve the structural stability, capacity density and cycle performance of the pole piece, and has a high surface density.

[0060] In the embodiments, the active material layer of the electrode of the embodiments of the present application generally also includes components such as electrode active materials, binders, conductive agents, etc., or further includes components such as lithium supplements.

[0061] When the active material layer of the electrode of the embodiment of the present application includes components such as electrode active materials, binders, conductive agents, lithium supplements, etc., the electrode active materials, binders, conductive agents, lithium supplements, etc. components can be conventional contents, and their materials can be corresponding material types commonly used in the field of electrode.

[0062] In the embodiment, the electrode active material contained in the active material base layer of the electrode sheet of the embodiment of the present application can be a positive electrode active material or a negative electrode active material. Among them, when the electrode active material is a positive electrode active material, it can be a lithium battery positive electrode active material or a sodium battery positive electrode active material. At this time, the electrode sheet of the embodiment of the present application is a positive electrode sheet, and the active material layer provided on at least one surface of the positive electrode current collector is a positive electrode active material layer.

[0063] Similarly, when the electrode active material is a negative electrode active material, it can be a lithium battery negative electrode active material or a sodium battery negative electrode active material. In this case, the electrode sheet of the embodiment of the present application is a negative electrode sheet, and the active material layer disposed on at least one surface of the negative electrode current collector is a negative electrode active material layer.

[0064] [Battery]

[0065] On the third aspect, the embodiments of the present application also provide a battery. The battery of the embodiments of the present application includes necessary components such as a positive electrode sheet, a negative electrode sheet, a diaphragm or a solid electrolyte, and of course other necessary or auxiliary components. Among them, the diaphragm or solid electrolyte is arranged between the positive electrode sheet and the negative electrode sheet. The positive electrode sheet is the electrode sheet of the above-mentioned embodiment of the text application, that is, the positive electrode active material layer contained in the positive electrode sheet includes the dispersant composition of the above-mentioned embodiment of the text application. At this time, the electrode active material contained in the electrode sheet of the above-mentioned embodiment of the text application includes the positive electrode active material.

[0066] Alternatively, the negative electrode sheet is the electrode sheet of the above-mentioned application embodiment, that is, the negative electrode active material layer contained in the negative electrode sheet includes the dispersant composition of the above-mentioned application embodiment. In this case, the electrode active material contained in the electrode sheet of the above-mentioned application embodiment includes the negative electrode active material.

[0067] Alternatively, the positive electrode sheet is the electrode sheet of the embodiment of the above application, in which case the electrode active material contained in the electrode sheet of the embodiment of the above application includes the positive electrode active material. Meanwhile, the negative electrode sheet is the electrode sheet of the embodiment of the above application, in which case the electrode active material contained in the electrode sheet of the embodiment of the above application includes the negative electrode active material.

[0068] Since at least one of the positive electrode sheet and the negative electrode sheet in the battery of the embodiment of the present application is the electrode sheet of the embodiment of the present application, the electrode active material contained in the electrode sheet of the battery of the embodiment of the present application is evenly distributed in the active material layer and has a high solid content. Moreover, the electrode sheet has high structural stability, capacity density and cycle performance, thereby giving the battery high energy density and cycle performance.

[0069] The following uses a number of specific embodiments to illustrate the composite lithium-rich material of the present application, its preparation method, and application.

[0070] 1. Dispersant composition example:

[0071] Embodiment A1:

[0072] The present embodiment A1 to embodiment A6 and comparative examples A1 to comparative examples A3 provide a dispersant composition, respectively. Each dispersant composition contains the combination formula shown in each embodiment in Table 1.

[0073] Each dispersant composition is prepared by mixing the components according to the combination formula shown in each example in Table 1.

[0074] Table 1

[0075]

[0076] 2. Lithium-ion battery example:

[0077] The present embodiments B1 to B6 and comparative examples B1 to B3 provide a lithium ion battery respectively. Each lithium ion battery is assembled into a lithium ion battery according to the following method:

[0078] 1) Positive electrode:

[0079] Under the same conditions, the positive electrode active material: Super P: PVDF: dispersant composition was mixed in a mass ratio of 96.5:1.3:2.2:0.193, and the positive electrode slurry was prepared in NMP solvent; the positive electrode slurry was subjected to coating-drying-cutting operations to prepare a positive electrode sheet, and the positive electrode sheet was baked in a vacuum oven at 100°C to remove trace water. Specifically, the positive electrode slurry in Example B1 contains the dispersant composition in Example A1, the positive electrode slurry in Example B2 contains the dispersant composition in Example A2, and so on, the positive electrode slurry in Comparative Example B3 contains the dispersant composition in Comparative Example A3.

[0080] 2) Negative electrode sheet: The negative electrode active material graphite, conductive agent Super P, thickener carboxymethyl cellulose (CMC), and binder styrene butadiene rubber (SBR) are mixed evenly in deionized water to form a negative electrode slurry, wherein the mass ratio of graphite: Super P: CMC: SBR is 95:2:0.5:2.5. The negative electrode slurry is coated on the current collector copper foil, and after drying-rolling-secondary drying process, the negative electrode sheet is made.

[0081] 3) Diaphragm: Use polyethylene (PE) diaphragm.

[0082] 4) Electrolyte: The electrolyte is a 1 mol / L LiPF6 solution, and the solvent is composed of EC (ethylene carbonate) and DEC (diethyl carbonate) in a volume ratio of 1:1.

[0083] 5) Assembly of secondary batteries:

[0084] The positive electrode sheet, negative electrode sheet, electrolyte and separator are assembled into a lithium-ion soft-pack battery according to the lithium-ion battery assembly requirements.

[0085] Related performance testing of lithium-ion batteries:

[0086] The lithium-ion batteries of the embodiments and comparative examples assembled in Section 5) were subjected to relevant performance tests as shown in Table 2 below, and the measured results are shown in Table 2 below.

[0087] Among them, the relevant performance test methods in Table 2 are as follows:

[0088] The test method for the solid content of the positive electrode slurry is as follows: the positive electrode slurry is placed in an oven at 120°C and dried to constant weight, and the ratio of the remaining weight of the slurry to the total weight of the slurry is measured.

[0089] Test methods for other performance indicators in Table 2 of the positive electrode slurry: After preparing the positive electrode slurry with a certain solid content, use a viscometer to test the viscosity of the positive electrode slurry at a speed of 30 rpm after standing for 0.5 h.

[0090] Battery monomer energy density test method: Battery charging: Place the battery in a charger, use a standardized charging mode, let it stand for 2 hours after it is fully charged, place it at room temperature and discharge it to 3.0V, and then let it stand for 2 hours before testing; Battery discharging: Install the charged battery in a standardized test instrument for a discharge test. During the test, the ambient temperature, humidity, atmospheric pressure and other conditions must be kept constant.

[0091] Battery cell capacity retention rate test method: The battery is first fully charged in a standard manner, then stored for 28 days under certain conditions, and discharged at a standard discharge rate to obtain a discharge capacity C1. The capacity retention rate = C1 / initial capacity.

[0092] Table 2

[0093]

[0094] Combined with Table 1 above, it can be seen from the test results in Table 2 that: Comparative Examples B1 to B6 show that, through the compounding of the components contained in the dispersant composition in Example A1, the viscosity reduction and viscosity stabilization performance of the positive electrode slurry in Example B1 is relatively good, and the positive electrode slurry is relatively balanced in all aspects. And the corresponding battery performance is also relatively excellent.

[0095] The macromolecular substance contained in the dispersant composition in Example A2 is replaced by polypyrrole with a vinyl pyrrolidone-vinyl acetate copolymer viscosity reducer, so that the viscosity reduction of the positive electrode slurry in the prepared Example B2 is relatively high, and the pole piece peeling strength is relatively reduced. It is speculated that the solvated chain content of the vinyl pyrrolidone-vinyl acetate copolymer viscosity reducer is relatively low, resulting in a decrease in the speed at which the solvent wets the positive electrode material. The copolymer belongs to an ester substance. Although it reduces the pole piece peeling strength, it is still better than the positive electrode slurry, pole piece and battery cell related performance in Comparative Examples B1 to B2.

[0096] The dispersant composition in Example A3 does not contain furan carboxylic acid, so the viscosity reduction of the positive electrode slurry in Example B3 is reduced. It is speculated that the furan ring can promote the dissolution and dispersion of PVDF, thereby promoting the dispersion of the positive electrode slurry. The corresponding battery cell related performance is close to that of Example B1.

[0097] The dispersant composition in Example A4 does not contain indole lactic acid, so that the viscosity reduction of the positive electrode slurry in Example B4 is also reduced. Indole is composed of a benzene ring connected to a thiophene ring, which may have a strong interaction with SP, and lactic acid is composed of hydroxyl and carboxyl groups, which are polar groups that can enhance hydrogen bonding and promote the dispersion of the positive electrode slurry. The corresponding battery cell related performance is close to that of Example B1.

[0098] The dispersant compositions in Example A5 and Example A6 respectively adjusted the proportion of the resin softener. Since the amount of the resin softener added was very small, its effect on the positive electrode slurry was relatively smaller than that of the polymer viscosity reducer and the small molecule viscosity reducer. However, it was still able to play a synergistic role with these components to improve the viscosity of the positive electrode slurry; and the increase in the amount of the resin softener added could improve the peel strength of the positive electrode sheet.

[0099] The dispersant composition in Comparative Example A1 does not contain a polymer viscosity reducer relative to Examples A1 to A6, which significantly increases the viscosity of the positive electrode slurry in Comparative Example B1 and Examples B1 to B6, and the viscosity stability of the positive electrode slurry is poor, the pole piece peeling strength is also significantly reduced, and the corresponding battery performance is also significantly reduced, especially the capacity retention rate. It is speculated that the presence of the polymer viscosity reducer in the dispersant of the embodiment of the present application, with a large molecular weight, can stabilize the electrode slurry, increase the solid content of the electrode slurry, and the energy density is relatively large.

[0100] The dispersant composition in Comparative Example A2 does not contain a small molecule viscosity reducer relative to Examples A1 to A6, so that the solid content of the positive electrode slurry in Comparative Example B2 and Examples B1 to B6 is significantly reduced, while causing a significant increase in the viscosity of the positive electrode slurry, and the corresponding battery performance is also significantly reduced. It is speculated that the small molecule viscosity reducer in the dispersant of the present application example has an anchoring effect and can also increase the electrode peeling strength to a certain extent.

[0101] The dispersant composition in Comparative Example A3 does not contain a resin-based softener relative to Examples A1 to A6, so that the positive electrode sheet peeling strength in Comparative Example B3 and Examples B1 to B6 is significantly reduced, and the corresponding battery cell capacity retention rate is also significantly reduced. It is speculated that the resin-based softener in the dispersant of the embodiment of the present application can effectively form a three-dimensional network structure in the active material layer, and form a strong hydrogen bond with the PVDF in the positive electrode slurry, significantly improving the flexibility and peeling strength of the electrode sheet, and increasing the mechanical strength of the electrode sheet. At the same time, it can also play a certain steric hindrance synergistic role with the polymer viscosity reducer and small molecule viscosity reducer in the dispersant of the embodiment of the present application, improving the dispersibility and viscosity of the electrode slurry.

[0102] The above embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the present application. It should be pointed out that, for a person of ordinary skill in the art, several modifications and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the attached claims.

Claims

1. A dispersant composition comprising a polymer viscosity reducer, a small molecule viscosity reducer and a resin softener, wherein the mass content of the polymer viscosity reducer and / or the small molecule viscosity reducer is higher than the mass content of the resin softener.

2. The dispersant composition according to claim 1, characterized in that: The polymer viscosity reducer comprises at least one functional group selected from the group consisting of an amine group, an ester group, a hydroxyl group, an amide group, and a pyrrolidone ring; and / or The small molecule viscosity reducer contains at least one functional group selected from the group consisting of a conjugated ring and a carboxyl group; and / or The resin softener comprises at least one functional group selected from the group consisting of an amine group and an amide group; and / or The resin-based softener includes a resin capable of self-condensation reaction.

3. The dispersant composition according to claim 2, characterized in that: The polymer viscosity reducer further comprises a solvating segment; and / or The small molecule viscosity reducer contains both a conjugated ring and a carboxyl group; and / or The conjugated ring includes at least one of a benzene ring and a conjugated heterocyclic ring.

4. The dispersant composition according to claim 3, characterized in that: The small molecule viscosity reducer includes at least one of furanic acid, indole lactic acid and benzoic acid.

5. The dispersant composition according to any one of claims 2 to 4, characterized in that: The resin softener containing the amino group includes at least one of urea-formaldehyde resin and cyanamide resin; and / or The resin-based flexibilizer containing the amide group includes amide-based resin.

6. The dispersant composition according to claim 5, characterized in that: The cyanamide resin includes at least one of melamine formaldehyde resin and benzoguanamine resin; and / or The amide resin includes polyamide polyamine epichlorohydrin.

7. The dispersant composition according to any one of claims 1 to 4 and 6, characterized in that: The mass ratio of the polymer viscosity reducer, the small molecule viscosity reducer and the resin softener is (10-30): (10-25): (0.1-0.5); and / or The dispersant composition further comprises a solvent, in which the polymer viscosity reducer, the small molecule viscosity reducer and the resinous flexibilizer are dissolved.

8. The dispersant composition according to claim 7, characterized in that: The mass ratio of the polymer viscosity reducer to the solvent is (10-30): (60-85); and / or The solvent includes at least one of N-methylpyrrolidone and N,N-dimethylformamide.

9. A pole piece, characterized in that: The invention comprises an electrode active material and the dispersant composition according to any one of claims 1 to 7.

10. A battery comprising a positive electrode sheet and a negative electrode sheet, characterized in that: The positive electrode sheet is the electrode sheet according to claim 9, and the electrode active material contained in the electrode sheet includes a positive electrode active material; and / or The negative electrode sheet is the electrode sheet according to claim 9, and the electrode active material contained in the electrode sheet includes a negative electrode active material.

Images