Dispersing agent as well as preparation method and application thereof

Abstract

The invention relates to a dispersing agent as well as a preparation method and application thereof. The dispersant includes a first structural unit, a second structural unit, and a third structural unit. According to the dispersing agent provided by the invention, through the synergistic effect of the first structural unit, the second structural unit and the third structural unit, a long-chain solvated chain segment in the first structural unit has lipophilicity and proper steric hindrance, and the second structural unit is used as an anchoring functional group to anchor and adsorb active particles; an olefine acid group in the third structural unit is used as an anti-cracking functional group, one end of a dispersing agent anchors and adsorbs solid particles through the positioning effect of the anchoring functional group, the other end of the dispersing agent forms a protective layer on the outer surfaces of the solid particles, and when the particles collide to generate condensation or precipitation, the particles cannot be contacted due to the protective layer; further, the slurry keeps uniform dispersing performance, the slurry preparation and coating difficulty is reduced, the cracking degree of a pole piece is reduced, the resistance of an electrode is reduced, and the electrochemical performance of the battery is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and in particular to a dispersant and a preparation method and application thereof. Background Art

[0002] With the increasing demand for clean energy and the rapid development of new energy, secondary batteries as energy sources are widely used in energy storage power systems such as hydropower, thermal power, wind power and solar power stations, as well as power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace and other fields. The dispersibility of the electrode material in the positive electrode slurry directly affects the difficulty of the electrode coating process, and indirectly affects the electrochemical performance of the battery.

[0003] At present, positive electrode active materials are developing towards nano-scale and micron-scale particles. Active materials with small particle sizes can shorten the transmission path of lithium ions and improve the ionic conductivity and electrochemical stability of the electrode.

[0004] However, when the particle size of the positive electrode material is too small, its surface energy is high, and it is easy to agglomerate and precipitate during the slurry production process, which increases the difficulty of slurry preparation and coating. In addition, the dispersion uniformity of the slurry is reduced, which easily leads to cracking of the pole piece, increases the resistance of the electrode, and thus affects the electrochemical performance of the battery. Summary of the invention

[0005] Based on this, it is necessary to provide a dispersant and its preparation method and application to improve the dispersion uniformity of the positive electrode material in the slurry, reduce the difficulty of slurry preparation and coating, reduce the degree of cracking of the electrode, reduce the resistance of the electrode, and improve the electrochemical performance of the battery.

[0006] The first aspect of the present application provides a dispersant, which includes a first structural unit, a second structural unit and a third structural unit; the structural formula of the first structural unit is: ; The structural formula of the second structural unit is: ; The structural formula of the third structural unit is: ; where n is 1~50, R 1 Selected from C 3 -C 20 Alkyl or , m is 6~12; R 2 Selected from C 2 -C 10 alkyl.

[0007] In some embodiments, the dispersant has the general structural formula shown in formula (I):

[0008]

[0009] Formula (I);

[0010] In formula (I), a, b, and c are the polymerization degrees of the first structural unit, the second structural unit, and the third structural unit, respectively, and a:b:c is (5-25):(5-20):(1-10).

[0011] In some embodiments, the weight average molecular weight M of the dispersant is w It is 1000~10000.

[0012] The second aspect of the present application provides a method for preparing a dispersant, the method comprising the following steps: adding a first monomer, a second monomer and a third monomer to a solvent, and carrying out a polymerization reaction under the condition of an initiator to obtain a dispersant; wherein the structural formula of the first monomer is: , n is 1~50, R 1 Selected from C 3 -C 20 Alkyl or , m is 6 to 12; the second monomer is N,N-diethylacrylamide; the structural formula of the third monomer is , R 2 Selected from C 2 -C 10 alkyl.

[0013] In some embodiments, the initiator is selected from at least one of azobisisobutyronitrile (AIBN), azobisisoheptanenitrile, dimethyl azobisisobutyrate, dibenzoyl peroxide (BPO), lauroyl peroxide, and tert-butyl hydroperoxide.

[0014] In some embodiments, the solvent is selected from at least one of N-methylpyrrolidone and dimethyl sulfoxide.

[0015] In some embodiments, the polymerization reaction temperature is 60° C. to 90° C., and the reaction time is 3 h to 7 h.

[0016] The third aspect of the present application provides a positive electrode slurry, which includes the dispersant provided by the first aspect or the dispersant prepared by the preparation method provided by the second aspect.

[0017] In some embodiments, the mass percentage of the dispersant is 0.05% to 2%, based on the total mass of the solid matter in the positive electrode slurry.

[0018] The fourth aspect of the present application provides a positive electrode plate, which includes: a positive electrode collector; and a positive electrode active material layer, which is arranged on at least a portion of the surface of the positive electrode collector, and the positive electrode active material layer is prepared from the positive electrode slurry provided by the third aspect above.

[0019] A fifth aspect of the present application provides a secondary battery, which includes the positive electrode plate provided by the fourth aspect.

[0020] A sixth aspect of the present application provides an electrical device, which includes the secondary battery provided in the fifth aspect.

[0021] Compared with the traditional technology, this application has at least the following beneficial effects:

[0022] The dispersant provided in the present application has the synergistic effect of the first structural unit, the second structural unit and the third structural unit. The long-chain solvated segment in the first structural unit has lipophilicity and suitable steric hindrance, the tertiary amine group in the second structural unit acts as an anchoring functional group to anchor and adsorb the active particles, and the olefinic ester group in the third structural unit acts as an anti-cracking functional group to have excellent flexibility: when the dispersant is added to the slurry, one end of the dispersant anchors and adsorbs the solid particles through the positioning effect of the anchoring functional group, and the other end of the dispersant is suspended on the surface of the solid particles to form a protective layer, and the structure The long-chain solvated chain segments and appropriate steric hindrance of the first structural unit make the dispersant molecules have excellent wetting properties, while the polymer molecular segments form a stable three-dimensional barrier, thereby having stronger barrier properties. Combined with the flexibility of the third structural unit, it prevents the electrode from cracking after the slurry is coated. When particles collide to produce coagulation or precipitation, they will not be able to contact due to the presence of the protective layer, thereby maintaining uniform dispersion of the slurry, reducing the difficulty of slurry preparation and coating, reducing the degree of cracking of the electrode, reducing the resistance of the electrode, and improving the electrochemical performance of the battery.

[0023] In addition, the parts of the first structural unit, the second structural unit and the third structural unit close to the polymer chain segment all have C=O bonds, which can provide additional polar effects, improve the affinity of the dispersant to the solvent, and at the same time form a regular segment distribution, give play to the synergistic effect of the first structural unit, the second structural unit and the third structural unit, and enhance the dispersibility and structural stability of the dispersant. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 Schematic diagram of the dispersion principle of the dispersant provided in one embodiment of the present application. DETAILED DESCRIPTION

[0025] References to embodiments of the present application will now be provided in detail, one or more examples of which are described below. Each example is provided as an explanation rather than a limitation of the present application. In fact, it will be apparent to those skilled in the art that various modifications and variations may be made to the present application without departing from the scope or spirit of the present application. For example, a feature described or described as part of one embodiment may be used in another embodiment to produce a further embodiment.

[0026] Therefore, it is intended that the present application covers such modifications and variations that fall within the scope of the appended claims and their equivalents. Other objects, features and aspects of the present application are disclosed in or are apparent from the following detailed description. It will be appreciated by those of ordinary skill in the art that this discussion is merely a description of exemplary embodiments and is not intended to limit the broader aspects of the present application.

[0027] In the present application, the technical features described in an open manner include closed technical solutions composed of the listed features, and also include open technical solutions containing the listed features.

[0028] In this application, when it comes to numerical ranges, unless otherwise specified, the above numerical ranges are deemed to be continuous and include the minimum and maximum values ​​of the range, as well as each value between such minimum and maximum values. Further, when a range refers to an integer, each integer between the minimum and maximum values ​​of the range is included. In addition, when multiple ranges are provided to describe features or characteristics, the ranges can be merged. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges included therein.

[0029] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0030] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0031] If there is no special explanation, all steps of the present application can be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, it is mentioned that the method may also include step (c), which means that step (c) can be added to the method in any order. For example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0032] If there is no special explanation, the "include" and "comprising" mentioned in this application are open-ended or closed-ended. For example, the "include" and "comprising" may mean that other components not listed may also be included or only the listed components may be included or only the listed components may be included.

[0033] If not specifically stated, in this application, the term "or" is inclusive. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, any of the following conditions satisfies the condition "A or B": A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0034] Unless otherwise specified or incompatible herewith, the terms and phrases used herein shall have the following meanings:

[0035] The term "alkyl" refers to a saturated hydrocarbon containing primary (normal) carbon atoms, or secondary carbon atoms, or tertiary carbon atoms, or quaternary carbon atoms, or a combination thereof. Phrases containing this term, such as "C 1 ~C 9 "Alkyl" refers to an alkyl group containing 1 to 9 carbon atoms, each occurrence of which can be independently C 1 Alkyl, C 2 Alkyl, C 3 Alkyl, C 4 Alkyl, C 5 Alkyl, C 6 Alkyl, C 7 Alkyl, C 8 Alkyl or C 9 Suitable examples include, but are not limited to, methyl (Me, -CH 3 ), ethyl (Et, -CH 2 CH 3 ), 1-propyl (n-Pr, n-propyl, -CH 2 CH 2 CH 3 ), 2-propyl (i-Pr, i-propyl, -CH (CH 3 ) 2 ), 1-butyl (n-Bu, n-butyl, -CH 2 CH 2 CH 2 CH 3 ), 2-methyl-1-propyl (i-Bu, i-butyl, -CH 2 CH(CH 3 ) 2 ), 2-butyl (s-Bu, s-butyl, -CH (CH 3 )CH 2 CH 3 ), 2-methyl-2-propyl (t-Bu, t-butyl, -C(CH 3 ) 3 ), 1-pentyl (n-pentyl, -CH 2 CH 2 CH 2 CH2 CH 3 ), 2-pentyl (-CH(CH3)CH2CH2CH3), 3-pentyl (-CH(CH 2 CH 3 ) 2 ), 2-methyl-2-butyl (-C(CH 3 ) 2 CH 2 CH 3 ), 3-methyl-2-butyl (-CH(CH 3 )CH(CH 3 ) 2 ), 3-methyl-1-butyl (-CH 2 CH 2 CH(CH 3 ) 2 ), 2-methyl-1-butyl (-CH 2 CH(CH 3 )CH 2 CH 3 )、1-hexyl (-CH 2 CH 2 CH 2 CH 2 CH 2 CH 3 ), 2-hexyl (-CH(CH 3 )CH 2 CH 2 CH 2 CH 3 ), 3-hexyl (-CH(CH 2 CH 3 )(CH 2 CH 2 CH 3 ))、2-methyl-2-pentyl (-C(CH 3 ) 2 CH 2 CH 2 CH 3 ), 3-methyl-2-pentyl (-CH(CH 3 )CH(CH 3 )CH 2 CH 3 ), 4-methyl-2-pentyl (-CH(CH 3 )CH 2 CH(CH 3 ) 2 ), 3-methyl-3-pentyl (-C(CH 3 )(CH 2 CH 3 ) 2), 2-methyl-3-pentyl (-CH(CH 2 CH 3 )CH(CH 3 ) 2 )、2,3-dimethyl-2-butyl (-C(CH 3 ) 2 CH(CH 3 ) 2 )、3,3-dimethyl-2-butyl (-CH(CH 3 )C(CH 3 ) 3 and octyl (-(CH 2 ) 7 CH 3 ).

[0036] Herein, "anchoring functional group" refers to a functional group that can be adsorbed on the surface of nanoparticles to prevent further aggregation of the particles.

[0037] Herein, the "anti-cracking functional group" refers to a functional group having excellent flexibility and capable of improving the anti-cracking ability of the coating.

[0038] A first aspect of the present application provides a dispersant, which includes a first structural unit, a second structural unit and a third structural unit.

[0039] The structural formula of the first structural unit is: .

[0040] The structural formula of the second structural unit is: .

[0041] The structural formula of the third structural unit is: .

[0042] Where n is 1~50, R 1 Selected from C 3 -C 20 Alkyl or , m is 6~12; R 2 Selected from C 2 -C 10 alkyl.

[0043] The dispersant provided in the present application has the synergistic effect of the first structural unit, the second structural unit and the third structural unit. The long-chain solvated segment in the first structural unit has lipophilicity and suitable steric hindrance, the tertiary amine group in the second structural unit acts as an anchoring functional group to anchor and adsorb the active particles, and the olefinic ester group in the third structural unit acts as an anti-cracking functional group and has excellent flexibility: Figure 1As shown, when the dispersant is added to the slurry, one end of the dispersant anchors and adsorbs the solid particles through the positioning effect of the anchoring functional group, and the other end of the dispersant is suspended on the surface of the solid particles to form a protective layer. Combined with the long-chain solvation chain segment of the first structural unit and the appropriate spatial steric hindrance, the dispersant molecules have excellent wetting properties, while the polymer molecular segments form a stable three-dimensional barrier, thereby having stronger barrier properties. Combined with the flexibility of the third structural unit, the cracking of the electrode after the slurry is coated is prevented; when the particles collide to produce coagulation or precipitation, they will not be able to contact due to the presence of the protective layer, thereby maintaining a uniform dispersion of the slurry, reducing the difficulty of slurry preparation and coating, reducing the degree of cracking of the electrode, reducing the resistance of the electrode, and improving the electrochemical performance of the battery.

[0044] In addition, the parts of the first structural unit, the second structural unit and the third structural unit close to the polymer chain segment all have C=O bonds, which can provide additional polar effects, improve the affinity of the dispersant to the solvent, and at the same time form a regular segment distribution, give play to the synergistic effect of the first structural unit, the second structural unit and the third structural unit, and enhance the dispersibility and structural stability of the dispersant.

[0045] The polyether repeating unit and the long-chain alkyl or long-chain aryl group in the first structural unit can serve as solvation segments, and have appropriate steric hindrance, so that the entire polymer molecular chain can form a more stable steric barrier, which can prevent the aggregation and sedimentation of small solid particles, reduce the viscosity of the slurry, and stably disperse the solid particles. In addition, the long-chain alkyl or long-chain aryl group is lipophilic, and in the oily slurry, the segment can stretch freely, thereby better adapting to the solvent of the slurry and dispersing and dissolving the slurry.

[0046] The second structural unit contains a tertiary amine functional group, which can provide more anchoring groups. These groups can be adsorbed on the surface of solid particles through hydrogen bonds, covalent bonds, and ions to prevent the particles from settling and agglomerating. In addition, the amide group in the second structural unit is substituted with an ethyl group, which has a suitable steric hindrance effect and is conducive to the formation of a protective layer on the particles.

[0047] Exemplarily, the dispersant has the general structural formula shown in formula (I):

[0048]

[0049] Formula (I);

[0050] In formula (I), n is 1 to 50, R 1 Selected from C 3 -C 20 Alkyl or , m is 6~12; R 2 Selected from C 2 -C 10Alkyl; a, b, c are the polymerization degrees of the first structural unit, the second structural unit, and the third structural unit, respectively.

[0051] In some embodiments, a:b:c is (5-25):(5-20):(1-10). Further, a:b:c is (5-15):(5-10):5. In this embodiment, by adjusting the proportion of different blocks in the block copolymer, the segment length of the block copolymer is adjustable, and the block structure of the polymer is optimized, thereby improving the dispersing ability and stabilizing ability of the dispersant; within the above-mentioned ratio range of the degree of polymerization, the dispersing performance of the material can be maximized.

[0052] In some embodiments, the weight average molecular weight M of the dispersant is w 1000-10000. For example, the molecular weight of the dispersant may be, but is not limited to, 1000, 2000, 3000, 4000, 5000, 6000, 7000, 8000, 9000, 10000. Within the above molecular weight range, the molecular chain length of the dispersant is moderate, which can provide good solubility and form a good block structure, thereby forming an effective steric barrier, forming a stable protective layer on the particle surface, and significantly improving the dispersion uniformity of the slurry.

[0053] The second aspect of the present application provides a method for preparing a dispersant, which comprises the following steps: adding a first monomer, a second monomer and a third monomer into a solvent, and performing a polymerization reaction under the condition of an initiator to obtain a dispersant.

[0054] Wherein, the structural formula of the first monomer is: , n is 1~50, R 1 Selected from C 3 -C 20 Alkyl or , m is 6~12.

[0055] The second monomer is N,N-diethylacrylamide.

[0056] The structural formula of the third monomer is , R 2 Selected from C 2 -C 10 alkyl.

[0057] In some embodiments, the polymerization reaction temperature is 60°C to 90°C, and the reaction time is 3h to 7h. Within the above temperature and time range, the initiator has a better initiation effect, can exert the best catalytic effect, has the fastest reaction rate, and has a higher product yield.

[0058] In some embodiments, the solvent is selected from at least one of N-methylpyrrolidone and dimethyl sulfoxide.

[0059] In some embodiments, the initiator is selected from one or more of azobisisobutyronitrile (AIBN), azobisisoheptanenitrile, dimethyl azobisisobutyrate, dibenzoyl peroxide (BPO), lauroyl peroxide and tert-butyl hydroperoxide.

[0060] In some embodiments, the polymerization reaction pressure is 0.05 MPa to 0.1 MPa. For example, the polymerization reaction pressure may be, but is not limited to, 0.05 MPa, 0.06 MPa, 0.07 MPa, 0.08 MPa, 0.09 MPa, or 0.1 MPa.

[0061] In some embodiments, the polymerization reaction is carried out under an inert atmosphere, which includes one of nitrogen, helium and argon.

[0062] The third aspect of the present application provides a positive electrode slurry, which includes the dispersant provided by the first aspect or the dispersant prepared by the preparation method provided by the second aspect.

[0063] Typically, the positive electrode slurry includes a positive electrode active material, a binder, a conductive agent, a dispersant and a solvent.

[0064] In some of the embodiments, the positive electrode slurry components are calculated by weight ratio and include 90-98 parts of positive electrode active material, 0.5-3 parts of conductive agent, 0.9-3 parts of binder and 50-100 parts of solvent.

[0065] In some embodiments, the mass percentage of the dispersant is 0.05% to 2%, based on the total mass of the solid matter in the positive electrode slurry. Exemplarily, the mass percentage of the dispersant can be, but is not limited to, 0.05%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2%. Further, the mass percentage of the dispersant is 0.3% to 1.5%.

[0066] In some embodiments, the positive electrode active material may include a positive electrode active material for a battery known in the art.

[0067] As an example, the positive electrode active material of a lithium-ion secondary battery may include at least one of the following materials: lithium-containing phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, the present application is not limited to these materials, and other traditional materials that can be used as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides may include, but are not limited to, lithium cobalt oxides (such as LiCoO 2 ), lithium nickel oxide (such as LiCoO 2 ), lithium manganese oxide (such as LiCoO 2 、LiMn 2 O 4 )), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O 2 (Also referred to as NCM 333 )、LiNi 0.5 Co 0.2 Mn 0.3 O 2 (Also referred to as NCM 523 )、LiNi 0.5 CO 0.25 Mn 0.25 O 2 (Also referred to as NCM 211 )、LiNi 0.6 Co 0.2 Mn 0.2 O 2 (Also referred to as NCM 622 )、LiNi 0.8 Co 0.1 Mn 0.1 O 2 (Also referred to as NCM 811 ), lithium nickel cobalt aluminum oxide (such as LiNi 0.8 Co 0.15 Al 0.05 O 2 ) and its modified compounds, etc. Examples of lithium phosphates containing olivine structures may include, but are not limited to, lithium iron phosphate (such as LiFePO 4 (also referred to as LFP), composite materials of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO 4 ), composite materials of lithium manganese phosphate and carbon, lithium iron manganese phosphate, lithium iron manganese phosphate (LiMn 0.6 Fe 0.4 PO 4The weight ratio of the positive electrode active material in the positive electrode active material layer is 80wt% to 100wt%, based on the total weight of the positive electrode active material layer.

[0068] As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylic resin.

[0069] As an example, the conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0070] The fourth aspect of the present application provides a positive electrode plate, which includes a positive electrode current collector and a positive electrode active material layer. The positive electrode active material layer is disposed on at least a portion of the surface of the positive electrode current collector, and the positive electrode active material layer is prepared from the positive electrode slurry provided in the third aspect above.

[0071] In some of the embodiments, the positive electrode sheet can be prepared by the following method: coating the positive electrode slurry on the surface of the positive electrode collector and drying it to obtain the positive electrode sheet.

[0072] As an example, the positive electrode current collector has two surfaces facing each other in its thickness direction, and the positive electrode active material layer is disposed on any one or both of the two facing surfaces of the positive electrode current collector.

[0073] In some embodiments, 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 on a polymer material substrate. Among them, the metal material includes but is not limited to aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc. Polymer material substrate (such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0074] A fifth aspect of the present application provides a secondary battery, which includes the positive electrode plate provided by the fourth aspect.

[0075] Generally, a secondary battery includes a positive electrode sheet, a negative electrode sheet, an electrolyte and a separator. During the charge and discharge process of the battery, active ions are embedded and removed 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 set 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.

[0076] Negative electrode:

[0077] The negative electrode plate includes a negative electrode current collector and a negative electrode active material layer. The negative electrode active material layer is arranged on at least a part of the surface of the negative electrode current collector. The negative electrode active material layer includes a negative electrode active material.

[0078] As an example, the negative electrode current collector has two surfaces opposite to each other in its thickness direction, and the negative electrode film layer is disposed on any one or both of the two opposite surfaces of the negative electrode current collector.

[0079] In some embodiments, 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 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 on a polymer material substrate. Among them, the metal material includes but is not limited to copper, copper alloy, nickel, nickel alloy, lithium, lithium alloy, silver and silver alloy, etc. Polymer material substrate (such as substrates of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0080] In some of the embodiments, the negative electrode active material of the lithium ion secondary battery may adopt the negative electrode active material for the battery known in the art. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials and lithium titanate. The silicon-based material may 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 may be selected from at least one of elemental tin, tin oxide compounds and tin alloys. The weight ratio of the negative electrode active material in the negative electrode active material layer is 70wt%~100wt%, based on the total weight of the negative electrode active material layer.

[0081] In some embodiments, the negative electrode active material layer may further include a binder. The binder 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).

[0082] In some embodiments, the negative electrode active material layer may further include a conductive agent, which may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.

[0083] In some of the embodiments, the negative electrode sheet can be prepared by the following method: the above-mentioned components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder and any other components are dispersed in a solvent (such as deionized water) to form a negative electrode slurry; the obtained negative electrode slurry is coated on the negative electrode collector, and after a drying process, cold pressing such as rolling is performed to obtain the negative electrode sheet.

[0084] Electrolytes:

[0085] The electrolyte plays the role of conducting ions between the positive electrode and the negative electrode. The present application has no specific restrictions on the type of electrolyte, which can be selected according to needs. For example, the electrolyte can be liquid, gel or all-solid.

[0086] In some embodiments, the electrolyte is an electrolyte solution, which includes an electrolyte salt and a solvent.

[0087] In some embodiments, the electrolyte salt of the lithium ion secondary battery can be selected from lithium hexafluorophosphate (LiPF 6 ), lithium tetrafluoroborate (LiBF 4 ), lithium perchlorate (LiClO 4 ) lithium hexafluoroarsenate (LiAsF 6 ), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalatoborate (LiDFOB), lithium dioxalatoborate (LiBOB), lithium difluorophosphate (LiPO 2 F 2 ), one or more of lithium difluorooxalate phosphate (LiDFOP) and lithium tetrafluorooxalate phosphate (LiTFOP).

[0088] In some embodiments, the solvent can be selected from one or more of fluoroethylene carbonate (FEC), ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), cyclopentane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS) and diethyl sulfone (ESE).

[0089] In some embodiments, the electrolyte may further include additives, such as negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, additives that improve battery high or low temperature performance, etc.

[0090] Diaphragm:

[0091] In some embodiments, the secondary battery further comprises a separator. The present application has no particular limitation on the type of separator, and any known porous structure separator with good chemical stability and mechanical stability can be selected.

[0092] In some embodiments, the material of the diaphragm can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride. The diaphragm can be a single-layer film or a multi-layer composite film, without particular limitation. When the diaphragm is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0093] In some embodiments, the positive electrode sheet, the negative electrode sheet and the separator can be formed into an electrode assembly by a winding process or a lamination process.

[0094] A sixth aspect of the present application provides an electrical device, which includes the secondary battery provided in the fifth aspect.

[0095] Secondary batteries can be used as power sources for electrical devices or as energy storage units for electrical devices. Electrical devices may include, but are not limited to, mobile devices, electric vehicles, electric trains, ships and satellites, energy storage systems, etc. Among them, mobile devices may be, for example, mobile phones, laptops, etc.; electric vehicles may be, for example, pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc., but are not limited to these.

[0096] The present application will be further described below with reference to specific embodiments and comparative examples.

[0097] Example 1

[0098] Dispersants:

[0099] The first monomer tridecyl polyoxyethylene (10) ether acrylate, the second monomer N,N-diethylacrylamide, the third monomer butyl acrylate and the solvent N-methylpyrrolidone are mixed, and argon gas is introduced for protection. Under the conditions of a pressure of 0.08 MPa and a reaction temperature of 80°C, the mixture is stirred and dissolved at a speed of 100 rpm for 1 hour. Subsequently, 5 parts by mass of the initiator AIBN are added, the stirring speed is adjusted to 200 rpm, the reaction time is 5 hours, and the mixture is cooled to obtain a dispersant.

[0100] The molar ratio of the first monomer, the second monomer and the third monomer is 2:1:1; the polymerization degrees of the first structural unit, the second structural unit and the third structural unit in the dispersant prepared thereby are a, b and c respectively, a:b:c is 10:5:5, and the weight average molecular weight M of the dispersant is w is 8500.

[0101] Cathode slurry:

[0102] 97 parts by weight of positive electrode active material lithium iron phosphate, 1 part by weight of conductive agent conductive carbon black, 1 part by weight of binder polyvinylidene fluoride and the above dispersant were added to solvent N-methylpyrrolidone, stirred and dispersed to obtain positive electrode slurry.

[0103] The mass percentage of the dispersant is 0.5%, based on the total mass of the solid matter in the positive electrode slurry.

[0104] Positive electrode:

[0105] The positive electrode slurry was coated on a 13 μm thick positive electrode current collector aluminum foil, and the surface density was controlled to be 430 g / m 2 , and baked in an oven at 130°C to obtain a positive electrode sheet.

[0106] Example 2

[0107] The dispersant, positive electrode slurry and positive electrode sheet in this embodiment are basically the same as those in Embodiment 1, except that:

[0108] The molar ratio of the first monomer, the second monomer and the third monomer is 3:2:1; the polymerization degrees of the first structural unit, the second structural unit and the third structural unit in the dispersant prepared thereby are a, b and c respectively, a:b:c is 15:10:5, and the weight average molecular weight M of the dispersant is w is 12500.

[0109] Example 3

[0110] The dispersant, positive electrode slurry and positive electrode sheet in this embodiment are basically the same as those in Embodiment 1, except that:

[0111] The molar ratio of the first monomer, the second monomer and the third monomer is 5:3:2; the polymerization degrees of the first structural unit, the second structural unit and the third structural unit in the dispersant prepared thereby are a, b and c respectively, a:b:c is 25:15:10, and the weight average molecular weight M of the dispersant is w is 20000.

[0112] Example 4

[0113] The dispersant, positive electrode slurry and positive electrode sheet in this embodiment are basically the same as those in Embodiment 1, except that:

[0114] The molar ratio of the first monomer, the second monomer and the third monomer is 1:2:1; the polymerization degrees of the first structural unit, the second structural unit and the third structural unit in the dispersant prepared thereby are a, b and c respectively, a:b:c is 5:10:5, and the weight average molecular weight M of the dispersant is w is 5000.

[0115] Example 5

[0116] The dispersant, positive electrode slurry and positive electrode sheet in this embodiment are basically the same as those in Embodiment 1, except that:

[0117] The polymerization reaction was carried out at a reaction temperature of 60°C and a reaction time of 7 hours.

[0118] Example 6

[0119] The dispersant, positive electrode slurry and positive electrode sheet in this embodiment are basically the same as those in Embodiment 1, except that:

[0120] The polymerization reaction was carried out at a reaction temperature of 90°C and a reaction time of 3 h.

[0121] Example 7

[0122] The dispersant, positive electrode slurry and positive electrode sheet in this embodiment are basically the same as those in Embodiment 1, except that:

[0123] The mass percentage of the dispersant is 0.05%, based on the total mass of the solid matter in the positive electrode slurry.

[0124] Example 8

[0125] The dispersant, positive electrode slurry and positive electrode sheet in this embodiment are basically the same as those in Embodiment 1, except that:

[0126] The mass percentage of the dispersant is 2%, based on the total mass of the solid matter in the positive electrode slurry.

[0127] Comparative Example 1

[0128] Cathode slurry:

[0129] 97 parts by weight of lithium iron phosphate as a positive electrode active material, 1 part by weight of conductive carbon black as a conductive agent, and 2 parts by weight of polyvinylidene fluoride as a binder were added to a solvent of N-methylpyrrolidone, and stirred and dispersed to obtain a positive electrode slurry.

[0130] Positive electrode:

[0131] The positive electrode slurry was coated on a 13 μm thick positive electrode current collector aluminum foil, and the surface density was controlled to be 430 g / m 2 , and baked in an oven at 130°C to obtain a positive electrode sheet.

[0132] Comparative Example 2

[0133] Dispersants:

[0134] The second monomer N,N-diethylacrylamide and the third monomer butyl acrylate were added to the solvent N-methylpyrrolidone and mixed, and argon gas was introduced for protection. Under the conditions of a pressure of 0.08 MPa and a reaction temperature of 80°C, the mixture was stirred and dissolved at a speed of 100 rpm for 1 hour; then, 5 parts by mass of initiator AIBN were added, the stirring speed was adjusted to 200 rpm, the polymerization reaction was carried out for 5 hours, and the mixture was cooled to obtain a dispersant.

[0135] The molar ratio of the second monomer to the third monomer is 1:1; the polymerization degrees of the second structural unit and the third structural unit in the dispersant prepared in this way are b and c, respectively, b:c is 5:5, and the weight average molecular weight of the dispersant is M w is 2000.

[0136] Cathode slurry:

[0137] 97 parts by weight of positive electrode active material lithium iron phosphate, 1 part by weight of conductive agent conductive carbon black, 2 parts by weight of binder polyvinylidene fluoride and the above dispersant were added to solvent N-methylpyrrolidone, stirred and dispersed to obtain positive electrode slurry.

[0138] The mass percentage of the dispersant in the positive electrode slurry is 0.5%, based on the total mass of the solid matter in the positive electrode slurry.

[0139] Positive electrode:

[0140] The positive electrode slurry was coated on a 13 μm thick positive electrode current collector aluminum foil, and the surface density was controlled to be 430 g / m 2 , and baked in an oven at 130°C to obtain a positive electrode sheet.

[0141] Comparative Example 3

[0142] Dispersants:

[0143] The first monomer tridecyl polyoxyethylene (10) ether acrylate and the third monomer butyl acrylate were added to the solvent N-methylpyrrolidone and mixed, and argon gas was introduced for protection. Under the conditions of a pressure of 0.08 MPa and a reaction temperature of 80°C, the mixture was stirred and dissolved at a speed of 100 rpm for 1 hour. Subsequently, 5 parts by mass of initiator AIBN were added, the stirring speed was adjusted to 200 rpm, the polymerization reaction was carried out for 5 hours, and the mixture was cooled to obtain a dispersant.

[0144] The molar ratio of the first monomer to the third monomer is 2:1; the polymerization degrees of the first structural unit and the third structural unit in the dispersant prepared thereby are a and c, respectively, a:c is 10:5, and the weight average molecular weight of the dispersant is M w is 7500.

[0145] Cathode slurry:

[0146] 97 parts by weight of positive electrode active material lithium iron phosphate, 1 part by weight of conductive agent conductive carbon black, 2 parts by weight of binder polyvinylidene fluoride and the above dispersant were added to solvent N-methylpyrrolidone, stirred and dispersed to obtain positive electrode slurry.

[0147] The mass percentage of the dispersant is 0.5%, based on the total mass of the solid matter in the positive electrode slurry.

[0148] Positive electrode:

[0149] The positive electrode slurry was coated on a 13 μm thick positive electrode current collector aluminum foil, and the surface density was controlled to be 430 g / m 2 , and baked in an oven at 130°C to obtain a positive electrode sheet.

[0150] Comparative Example 4

[0151] Dispersants:

[0152] The first monomer tridecyl polyoxyethylene (10) ether acrylate and the second monomer N,N-diethylacrylamide were added to the solvent N-methylpyrrolidone and mixed, and argon gas was introduced for protection. Under the conditions of a pressure of 0.08 MPa and a reaction temperature of 80°C, the mixture was stirred and dissolved at a speed of 100 rpm for 1 hour. Subsequently, 5 parts by mass of initiator AIBN were added, the stirring speed was adjusted to 200 rpm, the polymerization reaction was carried out for 5 hours, and the mixture was cooled to obtain a dispersant.

[0153] The molar ratio of the first monomer to the second monomer is 2:1; the polymerization degrees of the first structural unit and the second structural unit in the dispersant prepared in this way are a and b respectively, a:b is 10:5, and the weight average molecular weight M of the dispersant is w is 7500.

[0154] Cathode slurry:

[0155] 97 parts by weight of positive electrode active material lithium iron phosphate, 1 part by weight of conductive agent conductive carbon black, 2 parts by weight of binder polyvinylidene fluoride and the above dispersant were added to solvent N-methylpyrrolidone, stirred and dispersed to obtain positive electrode slurry.

[0156] The mass percentage of the dispersant is 0.5%, based on the total mass of the solid matter in the positive electrode slurry.

[0157] Positive electrode:

[0158] The positive electrode slurry was coated on a 13 μm thick positive electrode current collector aluminum foil, and the surface density was controlled to be 430 g / m 2 , and baked in an oven at 130°C to obtain a positive electrode sheet.

[0159] Test Case

[0160] The positive electrode sheets of the above embodiments and comparative examples were subjected to cracking performance test, membrane resistance test and flexibility test respectively. In addition, the positive electrode sheets of some embodiments and comparative examples were made into secondary batteries, and the electrical performance of the battery cells was verified.

[0161] The test results are shown in Table 1 below.

[0162] Cracking performance: The appearance of the pole piece is inspected under an electron microscope.

[0163] Diaphragm resistance test: using a diaphragm resistance meter, carried out under a pressure of 25kg.

[0164] Flexibility test: Cut a 10*20cm positive electrode sheet, fold it in half, and roll it on a 1kg roller for 3 times to observe the light transmittance of the electrode sheet. If the electrode sheet is not light-transmitting, continue to follow the above operation until the electrode sheet becomes light-transmitting and record the number of folding times.

[0165] Electrochemical performance: The positive electrode uses the electrode of some of the above cases, and the negative electrode uses a graphite system to prepare a soft-pack secondary battery. The prepared battery cell is subjected to a 25℃ 1C / 1C cycle test to compare the electrochemical performance. This experiment records the capacity retention rate of the battery cell after 200 cycles at 25℃.

[0166] Table 1

[0167]

[0168] As shown in Table 1, by comparing Examples 1 to 8 and Comparative Examples 1 to 4, it can be seen that the dispersant provided in the present application reduces the degree of cracking of the electrode, reduces the resistance of the electrode, and improves the flexibility of the electrode.

[0169] By comparing Example 1 and Comparative Examples 2 to 4, it can be seen that the first structural unit, the second structural unit and the third structural unit need to work together to effectively improve the performance of the dispersant. The pole piece prepared in this way has good appearance, low resistance and high flexibility, thereby improving the electrochemical performance of the battery.

[0170] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0171] The above-described 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 technical 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, characterized in that: comprising a first structural unit, a second structural unit and a third structural unit; The structural formula of the first structural unit is: ; The structural formula of the second structural unit is: ; The structural formula of the third structural unit is: ; Wherein n is 1 to 50, and R1 is selected from C3-C 20 Alkyl or , m is 6 to 12; R2 is selected from C2-C 10 alkyl.

2. The dispersant according to claim 1, characterized in that The dispersant has a general structural formula as shown in formula (I): Formula (I); In formula (I), a, b, and c are the polymerization degrees of the first structural unit, the second structural unit, and the third structural unit, respectively, and a:b:c is (5-25):(5-20):(1-10).

3. The dispersant according to claim 1 or 2, characterized in that The weight average molecular weight M of the dispersant w It is 1000~10000.

4. A method for preparing a dispersant, characterized in that: The following steps are involved: Adding the first monomer, the second monomer and the third monomer into a solvent, and carrying out a polymerization reaction under the condition of an initiator to obtain a dispersant; Wherein, the structural formula of the first monomer is: , n is 1 to 50, R1 is selected from C3-C 20 Alkyl or , m is 6~12; The second monomer is N,N-diethylacrylamide; The structural formula of the third monomer is , R2 is selected from C2-C 10 alkyl.

5. The method for preparing a dispersant according to claim 4, characterized in that: The initiator is at least one selected from azobisisobutyronitrile (AIBN), azobisisoheptanenitrile, dimethyl azobisisobutyrate, dibenzoyl peroxide (BPO), lauroyl peroxide and tert-butyl hydroperoxide; and / or, The solvent is selected from at least one of N-methylpyrrolidone and dimethyl sulfoxide; and / or, The reaction temperature of the polymerization reaction is 60° C. to 90° C., and the reaction time is 3 h to 7 h.

6. A positive electrode slurry, characterized in that: The invention comprises the dispersant according to any one of claims 1 to 3 or the dispersant prepared by the preparation method according to claim 4 or 5.

7. The positive electrode slurry according to claim 6, characterized in that: The mass percentage of the dispersant is 0.05% to 2%, based on the total mass of the solid matter in the positive electrode slurry.

8. A positive electrode sheet, characterized in that: include: Positive electrode current collector; as well as The positive electrode active material layer is arranged on at least a portion of the surface of the positive electrode current collector, and the positive electrode active material layer is prepared from the positive electrode slurry according to claim 6 or 7.

9. A secondary battery, characterized in that: Comprising the positive electrode sheet as described in claim 8.

10. An electrical device, characterized in that: Comprising the secondary battery as claimed in claim 9.

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