Positive electrode sheet slurry, method for preparing the same, lithium ion battery, and vehicle

Abstract

The application provides a positive electrode sheet slurry, a preparation method thereof, a lithium ion battery and a vehicle, and the positive electrode sheet slurry comprises a positive electrode active material, a first binder, a second binder, a conductive agent and a first solvent; wherein the first binder comprises a polyacrylic binder, the second binder comprises a polyacrylate binder, and the first solvent comprises deionized water; and the mass ratio between the first binder and the second binder and the positive electrode active material is 2-5:90-96. By adding two different binders in the positive electrode sheet slurry, the two binders can play a synergistic effect, so that the binders have good adhesion strength and flexibility at the same time. The adhesion performance can be maintained, and the amount of the binder can be reduced. The positive electrode sheet slurry can be closely attached to the surface of the positive electrode sheet, the prepared positive electrode sheet has good flexibility, the gram capacity of the lithium ion battery can be improved to a certain extent, and the performance of the lithium ion battery is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of lithium ion batteries, in particular to a positive electrode sheet slurry of a lithium ion battery, a preparation method of the positive electrode sheet slurry of the lithium ion battery, a lithium ion battery, and a vehicle. BACKGROUND

[0002] In the prior art, the positive electrode sheet of a lithium ion battery can generally use metal as a base material, and the positive electrode active material is attached to the surface of the metal through a binder to obtain the positive electrode sheet. At present, for the positive electrode sheet, polyvinylidene fluoride (PVDF) can be generally used as the binder, and oily N-methyl pyrrolidone (NMP) can be used as the solvent to dissolve the binder and the positive electrode active material to obtain the positive electrode sheet slurry.

[0003] However, in the case of using polyvinylidene fluoride as the binder, the preparation process of the positive electrode sheet is generally required to be relatively strict, and the baking temperature is relatively high, which can easily lead to an increase in energy consumption and an increase in production cost. Meanwhile, under high temperature, polyvinylidene fluoride can easily react exothermically with metallic lithium or lithium-intercalated graphite to generate LiF and unsaturated bonds, which can cause thermal runaway risk and safety hazards.

[0004] Therefore, in the prior art, attempts have also been made to use a water-based binder and deionized water as a solvent to produce the positive electrode sheet slurry. However, the commonly used water-based binder such as butadiene styrene rubber has poor oxidation resistance due to the presence of unsaturated double bonds, and thus can easily lead to structural damage due to oxidation and loss of bonding strength when used in the positive electrode sheet. Therefore, it is difficult to apply the water-based slurry to the positive electrode sheet. SUMMARY

[0005] The technical problem to be solved by the present application is to provide a positive electrode sheet slurry of a lithium ion battery, a preparation method of the positive electrode sheet slurry of the lithium ion battery, a lithium ion battery, and a vehicle, so as to realize the use of the water-based slurry in the positive electrode sheet of the lithium ion battery and maintain good performance.

[0006] To solve the above problems, the present application discloses a positive electrode sheet slurry of a lithium ion battery, which comprises a positive electrode active material, a first binder, a second binder, a conductive agent, and a first solvent.

[0007] The first binder comprises a polyacrylic acid binder, the second binder comprises a polyacrylate binder, and the first solvent comprises deionized water. The mass ratio of the first binder and the second binder to the positive electrode active material is 2-5:90-96.

[0008] In an embodiment of the present application, the polyacrylic binder comprises at least one of polyacrylonitrile multi-copolymer, and / or copolymer of acrylic acid and acrylonitrile; and the polyacrylate binder comprises at least one of methoxy polyethylene glycol acrylate, polyethylene glycol diacrylate, and polybutyl acrylate.

[0009] In an embodiment of the present application, the conductive agent comprises a first conductive agent, a second conductive agent, and a third conductive agent.

[0010] In an embodiment of the present application, the first conductive agent comprises at least one of nanometer carbon fiber, carbon nanotube, and metal fiber; the second conductive agent comprises acetylene black and / or conductive graphite; and the third conductive agent comprises graphene; and the mass ratio between the first conductive agent, the second conductive agent, and the third conductive agent and the positive electrode active material is 1-3:90-96.

[0011] In an embodiment of the present application, a second solvent is further included, and the second solvent comprises an alcohol solvent; and the alcohol solvent comprises ethanol and / or isopropyl alcohol.

[0012] In an embodiment of the present application, the positive electrode active material comprises at least one of lithium cobaltate, lithium manganate, lithium iron phosphate, lithium vanadium phosphate, lithium manganese phosphate, lithium nickel cobalt manganese oxide, and lithium nickel cobalt aluminum oxide.

[0013] The present application also provides a preparation method of a positive electrode plate slurry of a lithium ion battery, which comprises:

[0014] Mixing the first binder with the second binder to obtain a composite binder;

[0015] Dissolving the conductive agent in the first solvent to obtain a first mixed solution;

[0016] Dissolving the composite binder in the first mixed solution to obtain a second mixed solution;

[0017] Adding the positive electrode active material into the second mixed solution, and uniformly dispersing at a high speed to obtain a positive electrode plate slurry.

[0018] In an embodiment of the present application, the step of dissolving the conductive agent in the first solvent to obtain a first mixed solution comprises:

[0019] After mixing the first solvent and the first conductive agent, adding the second solvent to obtain the first mixed solution.

[0020] In an embodiment of the present application, the step of adding the positive electrode active material into the second mixed solution, and uniformly dispersing at a high speed to obtain a positive electrode plate slurry comprises:

[0021] After the positive electrode active material, the second conductive agent, and the third conductive agent are uniformly mixed, the second mixed solution is added, and after being uniformly dispersed at a high speed, the positive electrode tab slurry is obtained.

[0022] The embodiment of the present application also provides a lithium ion battery, which comprises a positive electrode tab coated with the positive electrode tab slurry according to the embodiment of the present application or comprises a positive electrode tab coated with the positive electrode tab slurry prepared by the preparation method according to the embodiment of the present application.

[0023] The embodiment of the present application also provides a vehicle, which comprises the lithium ion battery according to the embodiment of the present application.

[0024] Compared with the prior art, the present application has the following advantages:

[0025] The positive electrode tab slurry of the lithium ion battery according to the embodiment of the present application comprises two different binders, which can play a synergistic effect, so that the binders have good adhesion strength and flexibility at the same time. Thus, the adhesion performance can be maintained, and the amount of the binder can be reduced. The positive electrode tab slurry can be closely attached to the surface of the positive electrode tab, and the prepared positive electrode tab has good flexibility. Since the amount of the binder is reduced and the amount of the positive electrode active material is increased, the gram capacity of the lithium ion battery can be improved to some extent, and thus the performance of the lithium ion battery is improved. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 is a flowchart of the preparation method of the positive electrode tab slurry according to the embodiment of the present application;

[0027] Figure 2 is a schematic diagram of the solid content change of the positive electrode tab slurry according to the embodiment of the present application;

[0028] Figure 3 is a schematic diagram of the positive electrode tab according to the embodiment of the present application;

[0029] Figure 4 is a schematic diagram of the cycle performance test of the battery according to the embodiment of the present application. DETAILED DESCRIPTION

[0030] In order to make the above objectives, characteristics and advantages of the present application more apparent and comprehensible, the present application will be further described in detail below with reference to the drawings and specific embodiments.

[0031] The embodiment of the present application provides a positive electrode tab slurry of a lithium ion battery, which comprises a positive electrode active material, a first binder, a second binder, a conductive agent, and a first solvent.

[0032] The first binder includes a polyacrylic binder, the second binder includes a polyacrylate binder, and the first solvent includes deionized water; and the mass ratio of the first binder and the second binder to the positive active material is 2-5:90-96.

[0033] Specifically, the positive electrode tab slurry can be an aqueous slurry using deionized water as a solvent. It can include two different binders. Among them, the polyacrylic binder has a flexible chain molecular structure and a low glass transition temperature, and the acrylate binder has a rigid chain molecular structure. By adding two different binders to the positive electrode tab slurry, the two can work synergistically, so that the binder has good adhesion strength and flexibility at the same time. Thus, while maintaining good adhesion performance, the amount of binder is reduced. The positive electrode tab slurry can be tightly attached to the surface of the metal substrate of the positive electrode tab, and the "powder falling" phenomenon of the positive active material falling off is less likely to occur. At the same time, due to the good flexibility and less amount of the binder obtained by compounding the first binder and the second binder, the prepared positive electrode tab can have good flexibility.

[0034] In order to improve the conductivity of the conductive agent, a conductive agent can also be added to the positive electrode tab slurry, which can effectively improve the migration rate of lithium ions in the electrode material, thereby improving the charge and discharge efficiency of the electrode.

[0035] At the same time, with the reduction of the amount of the binder, the amount of the positive active material can be correspondingly increased. Thus, the conductivity, mass, and processing performance of the positive electrode tab can be improved to some extent, while the resistance of the positive electrode tab is reduced, which is conducive to improving the specific capacity of the lithium ion battery and improving the energy density of the lithium ion battery.

[0036] The mass ratio of the first binder and the second binder to the positive active material can be 2-5:90-96, for example, 2:96, 5:90, 3:95, 4:95, 4:92, etc., which is not limited in the present application.

[0037] In an embodiment of the present application, the polyacrylic binder includes a polyacrylonitrile multi-copolymer and / or a copolymer of acrylic acid and acrylonitrile; and the acrylate binder includes at least one of methoxy polyethylene glycol acrylate, polyethylene glycol diacrylate, and polybutyl acrylate.

[0038] Specifically, the polyacrylic binder can include a polyacrylonitrile multi-copolymer and / or a copolymer of acrylic acid and acrylonitrile, so that it can have ionic conductivity and strong polarity of cyano group, and the intermolecular force is large, which can effectively increase the adhesion.

[0039] The acrylate-based adhesive can include at least one of methoxypolyethylene glycol acrylate, polyethylene glycol diacrylate, and polybutyl acrylate, which can have a flexible chain structure, a low glass transition temperature, good softness itself, and a certain degree of viscosity, so that it can be used in combination, so that the adhesive has good bonding strength and flexibility. Thus, while maintaining good bonding performance, the amount of adhesive is reduced.

[0040] Preferably, the polyacrylic adhesive can be polyacrylonitrile multi-copolymer (LA133), and the acrylate-based adhesive can be polybutyl acrylate.

[0041] In an embodiment of the present application, the conductive agent can include a first conductive agent, a second conductive agent, and a third conductive agent.

[0042] The first conductive agent includes at least one of nanocarbon fiber, carbon nanotube, and metal fiber, the second conductive agent includes acetylene black and / or conductive graphite, and the third conductive agent includes graphene. The mass ratio between the mass of the first, second, and third conductive agents and the positive electrode active material is 1-3:90-96.

[0043] The conductive graphite can be various types of superconducting carbon black on the market, such as KS-6, ECP, ECP-600JD, etc.

[0044] Specifically, to further improve the conductivity of the positive electrode slurry, three different conductive agents can be added at the same time. The three different conductive agents can have different morphologies and particle sizes. By using different morphologies and particle sizes of conductive agents, an effective three-dimensional conductive network can be constructed by increasing the point-to-point, point-to-line, and point-to-surface combination between the conductive agent and the metal substrate, which can significantly reduce the use amount of the conductive agent while ensuring good electronic conductivity of the electrode sheet.

[0045] The mass ratio between the mass of the first, second, and third conductive agents and the positive electrode active material can be 1-3:90-96, for example, 1:96, 3:96, 1:90, 3:90, 2:93, 2:96, 2:90, etc. The present application does not limit this.

[0046] In an embodiment of the present application, a second solvent is further included, and the second solvent includes an alcohol solvent. The alcohol solvent includes ethanol and / or isopropyl alcohol.

[0047] Specifically, in the case of using deionized water as the solvent, since the deionized water has a relatively high surface tension, the adhesion effect of the positive electrode tab slurry on the surface of the positive electrode tab substrate can be affected. Therefore, the positive electrode tab slurry can further include a second solvent, which can include an alcohol solvent, specifically, ethanol and / or isopropyl alcohol. Ethanol and / or isopropyl alcohol are easy to obtain and have less environmental pollution compared to N-methyl pyrrolidone. They are easily soluble in deionized water, can effectively reduce the surface tension of deionized water, alleviate the internal residual stress problem of the positive electrode tab slurry when it is attached to the positive electrode tab, and will not have a negative impact on the bonding performance of the first binder or the second binder. Therefore, during the preparation of the positive electrode tab slurry, the positive electrode tab slurry can be defoamed, and the positive electrode tab slurry can be easily spread into a film on the surface of the metal substrate. At the same time, it can also be uniformly coated on the surface of the binder, the conductive agent, and the positive electrode active material, thereby reducing the agglomeration between the particles and facilitating the dispersion and stability of the slurry.

[0048] Therefore, the positive electrode tab slurry can be better attached to the surface of the positive electrode tab substrate, improving the coating effect of the positive electrode tab slurry, making the prepared positive electrode tab surface crack-free and flexible, and being able to meet different stacking modes and having excellent processability. At the same time, the binder, the positive electrode active material, the conductive agent, and the like in the positive electrode tab slurry can have better dispersion effect in the first solvent and the second solvent, thereby improving the stability of the positive electrode tab slurry.

[0049] In an embodiment of the present application, the positive electrode active material includes at least one of lithium cobaltate, lithium manganate, lithium iron phosphate, lithium vanadium phosphate, lithium manganese phosphate, lithium nickel cobalt manganese oxide, and lithium nickel cobalt aluminum oxide.

[0050] Lithium cobaltate, lithium manganate, lithium iron phosphate, lithium vanadium phosphate, lithium manganese phosphate, lithium nickel cobalt manganese oxide, and lithium nickel cobalt aluminum oxide can be relatively stably dispersed in the positive electrode tab slurry in an environment where deionized water is used as the solvent, and can better provide lithium ion insertion and extraction channels.

[0051] The positive electrode tab slurry of the lithium ion battery according to the embodiment of the present application can add two different binders to the positive electrode tab slurry, so that the two binders can work synergistically to make the binder have good bonding strength and flexibility. Therefore, the bonding performance can be maintained while reducing the amount of the binder. The positive electrode tab slurry can be closely attached to the surface of the positive electrode tab, and the prepared positive electrode tab can have good flexibility. At the same time, due to the reduction of the amount of the binder and the increase of the amount of the positive electrode active material, the specific capacity of the lithium ion battery can be improved to some extent, thereby improving the performance of the lithium ion battery.

[0052] The embodiment of the present application also provides a preparation method of a positive electrode sheet slurry of a lithium ion battery, which comprises the following steps:

[0053] In step 101, the first binder is mixed with the second binder to obtain a composite binder.

[0054] Specifically, in order to achieve the synergistic effect of the full mixing of the binders, the first binder is mixed with the second binder to obtain a composite binder before the binders are dissolved in the solution.

[0055] In step 102, the conductive agent is dissolved in the first solvent to obtain a first mixed solution.

[0056] Specifically, in order to improve the dispersion effect of the conductive agent in the positive electrode sheet slurry, the conductive agent is dissolved in the first solvent to obtain a first mixed solution before the conductive agent is added to the positive electrode sheet slurry.

[0057] In step 103, the composite binder is dissolved in the first mixed solution to obtain a second mixed solution.

[0058] After the mixing of the first binder and the second binder is completed, the composite binder is dissolved in the first mixed solution to obtain a second mixed solution, so that the mixed first binder and the second binder are well dispersed in the solution to obtain the second mixed solution.

[0059] In a specific implementation, the composite binder can be slowly added to the first mixed solution under stirring, so that the composite binder can be uniformly dispersed in the first mixed solution containing the first solvent.

[0060] In step 104, the positive electrode active material is added to the second mixed solution, and after high-speed dispersion, a positive electrode sheet slurry is obtained.

[0061] After the mixing and dispersion of the first binder and the second binder are completed, the positive electrode active material is added to the second mixed solution, and then the mixed solution with the added positive electrode active material can be subjected to high-speed dispersion, so that the first binder, the second binder, the conductive agent and the positive electrode active material can be uniformly dispersed in the solvent, thereby obtaining the positive electrode sheet slurry.

[0062] In a specific implementation, after high-speed dispersion and uniformity, the positive electrode sheet slurry can have a high viscosity. Meanwhile, due to the high viscosity, the bubbles generated in the high-speed dispersion process can not be well eliminated. In this case, a proper first solvent and / or second solvent can be added to the positive electrode sheet slurry according to actual needs. In the case of high viscosity, a small amount of first solvent and / or N-methyl pyrrolidone can also be added to the positive electrode sheet slurry according to actual needs to reduce the viscosity, facilitate the elimination of bubbles, and facilitate the subsequent application of the positive electrode sheet slurry. After the viscosity adjustment is completed, the bubbles in the positive electrode sheet slurry can be further eliminated by vacuum defoaming.

[0063] In a specific implementation, in order to remove the large-particle block that can be generated in the preparation process of the positive electrode sheet slurry, so that the positive electrode sheet slurry can be more uniformly coated on the surface of the metal substrate, after the positive electrode sheet is defoamed, the positive electrode sheet slurry can be further passed through a 150-mesh screen to ensure that the positive electrode sheet slurry can have a good fineness.

[0064] In an embodiment of the present application, the step of dissolving the conductive agent in the first solvent to obtain a first mixed solution comprises:

[0065] S11, after mixing the first solvent and the first conductive agent, the second solvent is added to obtain a first mixed solution;

[0066] Specifically, in order to further improve the conductivity of the positive electrode sheet slurry, a conductive agent is added to the positive electrode sheet slurry. Meanwhile, in order to make the conductive agent, the binder, and the positive electrode active material of the positive electrode sheet slurry better dispersed in the solvent. The first conductive agent which is relatively difficult to disperse can be first dissolved in the first solvent and initially mixed, so that the first conductive agent can be better dispersed in the first solvent. Thereafter, the second solvent can be further added to make the first conductive agent better dispersed to obtain a second mixed solution.

[0067] In an embodiment of the present application, the step of adding the positive electrode active material to the second mixed solution and uniformly high-speed dispersing to obtain a positive electrode sheet slurry comprises:

[0068] S21, after mixing the positive electrode active material, the second conductive agent, and the third conductive agent uniformly, the second mixed solution is added, and after high-speed dispersion and uniformity, the positive electrode sheet slurry is obtained.

[0069] Specifically, a second conductive agent and a third conductive agent can be further added in the cathode tab slurry, the three different conductive agents can have different morphologies and particle sizes, by using the conductive agents with different morphologies and particle sizes, the combination of point-to-point, point-to-line, and point-to-plane between the conductive agent and the metal substrate can be increased, and an effective three-dimensional conductive network can be constructed, which can ensure good electronic conductivity of the tab while significantly reducing the use amount of the conductive agent.

[0070] Since the second conductive agent and the third conductive agent can be more easily dispersed in the solvent relative to the first conductive agent, at the same time, a plurality of powder materials are directly added to the second mixed solution, and the powder materials can be more difficult to be well dispersed in the slurry. Therefore, the powder-shaped cathode active material, the second conductive agent, and the third conductive agent can be first mixed, the powder materials are uniformly mixed, and then the powder-shaped mixture is added to the second mixed solution to obtain the cathode tab slurry.

[0071] As a specific example of the present application, Figure 1 A schematic diagram of a preparation method of a cathode tab slurry of a lithium ion battery according to an embodiment of the present application.

[0072] The preparation method of the cathode tab slurry of the lithium ion battery can include the following steps:

[0073] Step 201, the first conductive agent is mixed with the first solvent, and after being uniformly mixed, the second solvent is added, and after being fully mixed, the first mixed solution is obtained;

[0074] Step 202, the first binder and the second binder are mixed, and after being uniformly mixed, the composite binder is obtained;

[0075] Step 203, the composite binder is added to the first mixed solution, and after being uniformly dispersed, the second mixed solution is obtained;

[0076] Step 205, the powder-shaped cathode active material, the second conductive agent, and the third conductive agent are dry-mixed to obtain a powder-shaped mixture;

[0077] Step 206, the powder-shaped mixture is added to the second mixed solution, and is uniformly dispersed at high speed, then according to actual needs, the first solvent and / or N-methyl pyrrolidone are added to adjust the viscosity, and vacuum defoaming is used to eliminate the bubbles therein, and the cathode tab slurry is obtained.

[0078] The preparation method of the positive electrode sheet slurry of the lithium ion battery of the embodiment of the present application adds two different binders in the preparation process, so that the two can play a synergistic effect, so that the binder has good bonding strength and flexibility at the same time. Thus, good bonding performance can be maintained while reducing the amount of binder. The positive electrode sheet slurry can be tightly attached to the surface of the positive electrode sheet, and the positive electrode sheet prepared at the same time can have good flexibility. At the same time, due to the reduction of the amount of binder, the amount of positive active material is increased, which can improve the gram capacity of the lithium ion battery to a certain extent, thereby improving the performance of the lithium ion battery.

[0079] The present application also provides a lithium ion battery comprising a positive electrode sheet coated with the positive electrode sheet slurry as described in the embodiments of the present application, or comprising a positive electrode sheet coated with the positive electrode sheet slurry prepared by the preparation method as described in the embodiments of the present application. The specific structural form and working principle of the positive electrode sheet slurry have been described in detail in the foregoing embodiments, and will not be repeated here.

[0080] The embodiment of the present application also provides a vehicle comprising the lithium ion battery as described in the embodiments of the present application. The specific structural form and working principle of the positive electrode sheet slurry used in the positive electrode sheet contained in the lithium ion battery have been described in detail in the foregoing embodiments, and will not be repeated here.

[0081] In order for those skilled in the art to better understand the present application, the preparation method of the positive electrode sheet slurry of the present application is described below through a plurality of specific embodiments.

[0082] Embodiment 1

[0083] The mass ratio of carbon nanotubes, superconducting carbon black and graphene: the mass ratio of LA133 binder and polybutyl acrylate: the mass ratio of lithium iron phosphate is 1.5:3:95.5. Among them, the mass ratio of carbon nanotubes, superconducting carbon black and graphene is 1:1:1; the mass ratio of the mass of LA133 binder and polybutyl acrylate is 1:1.

[0084] (1) Mix carbon nanotubes with deionized water, add ethanol after mixing uniformly, first stir at medium speed for 10 min, then stir at high speed for 50 min, to prepare a first mixed solution;

[0085] (2) Add LA133 binder and polybutyl acrylate to the stirring tank according to a certain proportion, set the stirring speed to 10 revolutions per minute and the dispersion speed to 600 revolutions per minute, stir for 20 min to prepare a composite binder;

[0086] (3) Add the composite binder to the first mixed solution, set the stirring speed to 30 revolutions per minute and the dispersion speed to 200 revolutions per minute, and stir for 40 min to obtain a second mixed solution;

[0087] (4) Dry mixing and dispersing the lithium iron phosphate in powder form, superconducting carbon black and graphene, the dry mixing and dispersing conditions are: revolution 15rmp, rotation 600rmp, time 60min, to obtain a mixture in powder form;

[0088] (5) Adding the mixture in powder form into the second mixed solution, adding into the stirring tank in multiple times, setting the stirring speed to 30 revolutions / minute, the dispersing speed to 800 revolutions / minute, and stirring for 30min; after all the main materials are added, setting the stirring speed to 10 revolutions / minute, the dispersing speed to 2500 revolutions / minute, and stirring for 120min;

[0089] (6) Adding deionized water and N-methyl pyrrolidone to adjust the viscosity, and eliminating the air bubbles in the mixture by vacuum defoaming, and obtaining the positive electrode sheet slurry after passing through a 150-mesh screen.

[0090] Example 2

[0091] The mass ratio of the carbon nanotube, acetylene black, KS-6, ECP, ECP-600JD and graphene: the mass ratio of the LA133 binder and the butyl acrylate: the mass ratio of the lithium iron phosphate is 1.5:3:95.5. Among them, the mass ratio of the carbon nanotube, acetylene black, KS-6, ECP, ECP-600JD and graphene is 1:1:1:1:1:1; the mass ratio of the LA133 binder and the butyl acrylate is 1:1.

[0092] (1) Mixing the carbon nanotube with deionized water, adding ethanol and isopropyl alcohol after mixing uniformly, stirring at medium speed for 10min, and stirring at high speed for 60min, to prepare a first mixed solution;

[0093] (2) Adding the LA133 binder and the butyl acrylate into a stirring tank, setting the stirring speed to 20 revolutions / minute, the dispersing speed to 100 revolutions / minute, and stirring for 30min, to prepare a composite binder;

[0094] (3) Adding the composite binder into the first mixed solution, setting the stirring speed to 10 revolutions / minute, the dispersing speed to 600 revolutions / minute, and stirring for 30min, to obtain a second mixed solution;

[0095] (4) Dry mixing and dispersing the lithium iron phosphate in powder form, acetylene black, KS-6, ECP, ECP-600JD and graphene, the dry mixing and dispersing conditions are: revolution 30rmp, rotation 1000rmp, time 30min, to obtain a mixture in powder form;

[0096] (5) the powder form mixture is added into the second mixed solution, added into the stirring tank in multiple times, the stirring speed is set to 10 r / min, the dispersion speed is set to 1500 r / min, and stirring is performed for 60 min; after all the main materials are added, the stirring speed is set to 30 r / min, the dispersion speed is set to 1500 r / min, and stirring is performed for 360 min;

[0097] (6) deionized water and N-methyl pyrrolidone are added to adjust the viscosity, and the air bubbles are eliminated by vacuum defoaming, and then the positive electrode sheet slurry is obtained after passing through a 150-mesh screen.

[0098] Example 3

[0099] The mass ratio of the nanocarbon fiber, acetylene black and graphene, the mass ratio of the polyacrylonitrile multi-copolymer and methoxy polyethylene glycol acrylate, and the mass ratio of the lithium iron phosphate are 2:2:96. The mass ratio of the nanocarbon fiber, acetylene black and graphene is 2:1:1, and the mass ratio of the polyacrylonitrile multi-copolymer and methoxy polyethylene glycol acrylate is 2:1.

[0100] (1) the nanocarbon fiber is mixed with deionized water, and then ethanol is added, the stirring speed is first set to medium speed for 10 min, and then set to high speed for 30 min, to prepare a first mixed solution;

[0101] (2) the polyacrylonitrile multi-copolymer and methoxy polyethylene glycol acrylate are added into a stirring tank, the stirring speed is set to 15 r / min, the dispersion speed is set to 300 r / min, and stirring is performed for 20 min, to prepare a composite binder;

[0102] (3) the composite binder is added into the first mixed solution, the stirring speed is set to 15 r / min, the dispersion speed is set to 100 r / min, and stirring is performed for 60 min, to obtain a second mixed solution;

[0103] (4) the powder form lithium cobaltate, acetylene black and graphene are dry-mixed and dispersed, the dry-mixing and dispersion conditions are as follows: revolution speed 30 rmp, rotation speed 1000 rmp, and time 40 min, to obtain a powder form mixture;

[0104] (5) the powder form mixture is added into the second mixed solution, added into the stirring tank in multiple times, the stirring speed is set to 20 r / min, the dispersion speed is set to 1000 r / min, and stirring is performed for 60 min; after all the main materials are added, the stirring speed is set to 20 r / min, the dispersion speed is set to 2000 r / min, and stirring is performed for 180 min;

[0105] (6) deionized water, ethanol and isopropyl alcohol are added to adjust the viscosity, and the air bubbles are eliminated by vacuum defoaming, and then the positive electrode sheet slurry is obtained after passing through a 150-mesh screen.

[0106] Example 4

[0107] The mass ratio of metal fiber, acetylene black and graphene: copolymer of acrylic acid and acrylonitrile and polyethylene glycol diacrylate: lithium iron phosphate is 5:3:92. Among them, the mass ratio of metal fiber, acetylene black and graphene is 2:2:1; the mass ratio of copolymer of acrylic acid and acrylonitrile and polyethylene glycol diacrylate is 1:2.

[0108] (1) Mix the metal fiber with deionized water, add ethanol after uniform mixing, first stir at medium speed for 10 min, then stir at high speed for 40 min, to prepare a first mixed solution;

[0109] (2) Add copolymer of acrylic acid and acrylonitrile and polyethylene glycol diacrylate to the stirring tank, set the stirring speed to 20 rpm and the dispersion speed to 400 rpm, stir for 15 min, to prepare a composite binder;

[0110] (3) Add the composite binder to the first mixed solution, set the stirring speed to 20 rpm and the dispersion speed to 300 rpm, stir for 40 min, to obtain a second mixed solution;

[0111] (4) Dry-mix and disperse the lithium manganate, acetylene black and graphene in powder form, the dry-mixing and dispersing conditions are: revolution 20 rpm, rotation 800 rpm, time 40 min, to obtain a powder-form mixture;

[0112] (5) Add the powder-form mixture to the second mixed solution, add to the stirring tank in multiple times, set the stirring speed to 20 rpm and the dispersion speed to 1000 rpm, stir for 60 min; after all the main materials are added, set the stirring speed to 20 rpm and the dispersion speed to 2000 rpm, stir for 240 min;

[0113] (6) Add deionized water, ethanol and isopropyl alcohol to adjust the viscosity, and use vacuum defoaming method to eliminate the air bubbles, pass through a 150-mesh screen, to obtain a positive electrode slurry.

[0114] Example 5

[0115] The mass ratio of carbon nanotube, superconducting carbon black and graphene: LA133 binder and polybutyl acrylate: lithium vanadium phosphate is 1.5:3:95.5. Among them, the mass ratio of carbon nanotube, superconducting carbon black and graphene is 3:1:2; the mass ratio of LA133 binder and polybutyl acrylate is 1:1.

[0116] (1) The carbon nanotubes are mixed with deionized water, and after uniform mixing, ethanol is added. First, moderate stirring is performed for 10 minutes, and then high-speed stirring is performed for 40 minutes to prepare a first mixed solution;

[0117] (2) The LA133 binder and the polybutyl acrylate are added to a stirring tank in a certain proportion. The stirring speed is set to 15 revolutions per minute, the dispersion speed is set to 400 revolutions per minute, and stirring is performed for 20 minutes to prepare a composite binder;

[0118] (3) The composite binder is added to the first mixed solution. The stirring speed is set to 20 revolutions per minute, the dispersion speed is set to 300 revolutions per minute, and stirring is performed for 40 minutes to obtain a second mixed solution;

[0119] (4) The powder-shaped lithium vanadium phosphate, superconducting carbon black, and graphene are dry-mixed and dispersed. The dry-mixing and dispersion conditions are: revolution 25 rmp, rotation 800 rmp, and time 50 minutes to obtain a powder-shaped mixture;

[0120] (5) The powder-shaped mixture is added to the second mixed solution in multiple times. The stirring speed is set to 20 revolutions per minute, the dispersion speed is set to 1200 revolutions per minute, and stirring is performed for 60 minutes. After all the main materials are added, the stirring speed is set to 20 revolutions per minute, the dispersion speed is set to 2000 revolutions per minute, and stirring is performed for 240 minutes;

[0121] (6) Deionized water and N-methyl pyrrolidone are added to adjust the viscosity, and vacuum defoaming is performed to eliminate the air bubbles. After passing through a 150-mesh screen, a positive electrode slurry is obtained.

[0122] Example 6

[0123] The mass ratio of the carbon nanotubes, acetylene black, KS-6, ECP, ECP-600JD, and graphene to the mass ratio of the LA133 binder to the polybutyl acrylate to the mass ratio of the lithium manganese phosphate is 1.5:3:95.5. Among them, the mass ratio of the carbon nanotubes, acetylene black, KS-6, ECP, ECP-600JD, and graphene is 1:1:1:1:1:1; the mass ratio between the LA133 binder and the polybutyl acrylate is 1:1.

[0124] (1) The carbon nanotubes are mixed with deionized water, and after uniform mixing, ethanol and isopropyl alcohol are added. First, moderate stirring is performed for 10 minutes, and then high-speed stirring is performed for 40 minutes to prepare a first mixed solution;

[0125] (2) The LA133 binder and the polybutyl acrylate are added to a stirring tank. The stirring speed is set to 15 revolutions per minute, the dispersion speed is set to 300 revolutions per minute, and stirring is performed for 10-30 minutes to prepare a composite binder;

[0126] (3) add the composite binder to the first mixed solution, set the stirring speed to 10-30 rpm, the dispersion speed to 300 rpm, and stir for 40 min to obtain a second mixed solution;

[0127] (4) dry-mix and disperse the lithium manganese phosphate in powder form, acetylene black, KS-6, ECP, ECP-600JD, and graphene, the dry-mixing and dispersion conditions are: revolution 20 rpm, rotation 700 rpm, and time 50 min, to obtain a mixture in powder form;

[0128] (5) add the mixture in powder form to the second mixed solution, add to the stirring tank in multiple times, set the stirring speed to 20 rpm, the dispersion speed to 1200 rpm, and stir for 50 min; after all the main materials are added, set the stirring speed to 20 rpm, the dispersion speed to 1000 rpm, and stir for 240 min;

[0129] (6) add deionized water and N-methyl pyrrolidone to adjust the viscosity, and eliminate the air bubbles in the mixture by vacuum defoaming, and then pass through a 150-mesh screen to obtain a positive electrode slurry.

[0130] Example 7

[0131] The mass ratio between the mass sum of the carbon nanotubes, acetylene black, KS-6, ECP, ECP-600JD, and graphene, the mass sum of the LA133 binder and the polybutyl acrylate, and the mass sum of the lithium nickel cobalt manganese oxide and the lithium nickel cobalt aluminum oxide is 1.5:3:95.5. The mass ratio between the carbon nanotubes, acetylene black, KS-6, ECP, ECP-600JD, and graphene is 1:1:1:1:1:1; the mass ratio between the lithium nickel cobalt manganese oxide and the lithium nickel cobalt aluminum oxide is 1:2.

[0132] (1) mix the carbon nanotubes with deionized water, uniformly mix, add ethanol and isopropyl alcohol, stir at medium speed for 10 min, and then stir at high speed for 50 min to obtain a first mixed solution;

[0133] (2) add the LA133 binder and the polybutyl acrylate to the stirring tank, set the stirring speed to 15 rpm, the dispersion speed to 400 rpm, and stir for 20 min to obtain a composite binder;

[0134] (3) add the composite binder to the first mixed solution, set the stirring speed to 10-30 rpm, the dispersion speed to 400 rpm, and stir for 50 min to obtain a second mixed solution;

[0135] (4) Dry-mixing and dispersing the nickel-cobalt-manganese lithium oxide and the nickel-cobalt-aluminum lithium oxide in powder form, acetylene black, KS-6, ECP, ECP-600JD, and graphene, the dry-mixing and dispersing conditions being: revolution 20 rmp, rotation 800 rmp, time 50 min, to obtain a mixture in powder form;

[0136] (5) Adding the mixture in powder form into the second mixed solution, adding into the stirring tank in multiple times, setting the stirring speed to be 25 revolutions / minute, the dispersing speed to be 1200 revolutions / minute, and stirring for 60 min; after all the main materials are added, setting the stirring speed to be 20 revolutions / minute, the dispersing speed to be 2000 revolutions / minute, and stirring for 360 min;

[0137] (6) Adding deionized water and N-methyl pyrrolidone to adjust the viscosity, and eliminating the air bubbles in the mixture by vacuum defoaming, and obtaining the positive electrode sheet slurry after passing through a 150-mesh screen.

[0138] Comparative Example 1

[0139] The mass ratio of the carbon nanotube, the superconducting carbon black, and the graphene: the mass sum of the carboxymethyl cellulose (CMC) and the styrene-butadiene rubber (SBR): the mass of the lithium vanadium phosphate is 1.5:3:95.5. Among them, the mass ratio of the carbon nanotube, the superconducting carbon black, and the graphene is 1:1:1; the mass ratio of the carboxymethyl cellulose (CMC) and the styrene-butadiene rubber (SBR) is 1:1.

[0140] (1) Mixing the carbon nanotube with deionized water, first stirring at medium speed for 10 min, and then stirring at high speed for 50 min, to prepare a first mixed solution;

[0141] (2) Adding the mass sum of the carboxymethyl cellulose (CMC) and the styrene-butadiene rubber (SBR) into a stirring tank according to a certain proportion, setting the stirring speed to be 10 revolutions / minute, the dispersing speed to be 600 revolutions / minute, and stirring for 20 min, to prepare a composite binder;

[0142] (3) Adding the composite binder into the first mixed solution, setting the stirring speed to be 10 revolutions / minute, the dispersing speed to be 200 revolutions / minute, and stirring for 40 min, to obtain a second mixed solution;

[0143] (4) Dry-mixing and dispersing the lithium vanadium phosphate, the superconducting carbon black, and the graphene in powder form, the dry-mixing and dispersing conditions being: revolution 15 rmp, rotation 600 rmp, time 60 min, to obtain a mixture in powder form;

[0144] (5) The mixture in powder form is added into the second mixed solution, and is added into the stirring tank in multiple times, the stirring speed is set to 30 rpm, the dispersion speed is set to 800 rpm, and stirring is performed for 30 min; after all the main materials are added, the stirring speed is set to 10 rpm, the dispersion speed is set to 2500 rpm, and stirring is performed for 120 min;

[0145] (6) Deionized water and N-methyl pyrrolidone are added to adjust the viscosity, and the air bubbles are removed by vacuum defoaming, and then the positive electrode sheet slurry is obtained after passing through a 150-mesh screen.

[0146] The following will illustrate some advantages of the embodiments of the present application compared with the prior art by specific experimental data.

[0147] The positive electrode sheet slurries prepared by using the preparation of Example 1, Example 2 and Comparative Example 1 are coated on 15 μm thick aluminum foils by a coating machine, and then dried and rolled to prepare the positive electrode sheets corresponding to Example 1, Example 2 and Comparative Example 1.

[0148] Slurry fineness test: The particle size of the slurry is tested by using a doctor blade fineness tester.

[0149] Slurry stability test: The positive electrode sheet slurries prepared by Example 2 and Comparative Example 1 are placed, and the liquid on the upper part of the positive electrode sheet is collected at different time periods, and the solid content is tested.

[0150] Positive electrode sheet surface cracking test: The coating method and drying method in the preparation process of the positive electrode sheet are controlled under the same conditions, and after the preparation of the positive electrode sheet is completed, the cracking of the positive electrode sheet is observed.

[0151] Positive electrode sheet flexibility test: The prepared positive electrode sheet is folded the same number of times, and then rolled back and forth three times using the same roller, and the cracking of the positive electrode sheet is recorded.

[0152] Battery performance test: lithium ion batteries containing the positive electrode sheets corresponding to Example 1, Example 2 and Comparative Example 1 are prepared, and then the lithium ion batteries are subjected to charge and discharge test, and the test conditions are: room temperature, 1C charging, 1C discharging, and voltage range 2.5-3.65V.

[0153] The test results are as follows:

[0154] Slurry fineness test:

[0155] The particle size of the positive electrode sheet slurry prepared by Example 1 is 8 μm. The particle size of the positive electrode sheet slurry prepared by Example 2 is 7 μm. The particle size of the positive electrode sheet slurry prepared by Comparative Example 1 is 16 μm.

[0156] It can be seen that the particle size of the positive electrode plate slurry prepared in Examples 1 and 2 is significantly smaller than that of Comparative Example 1, and both reach a particle size of less than or equal to 15 μm. Under this condition, the positive electrode plate slurry can have better slurry dispersion effect.

[0157] Slurry stability test:

[0158] As shown in the positive electrode plate slurry solid content change schematic diagram of Figure 2 With the increase of standing time, the upper layer solid content of Example 2 basically does not change, while the upper layer solid content of Comparative Example 1 gradually decreases.

[0159] It can be seen that the positive electrode plate slurry prepared in Example 2 has better stability and is more easily prepared into a good positive electrode plate.

[0160] Positive electrode plate surface cracking test:

[0161] Through visual observation, the positive electrode plate prepared from the positive electrode plate slurry prepared in Example 1 has a smooth surface without cracks. The positive electrode plate prepared from the positive electrode plate slurry prepared in Example 2 has a smooth surface without cracks. The positive electrode plate prepared from the positive electrode plate slurry prepared in Comparative Example 1 has a surface with a certain degree of cracks.

[0162] It can be seen that the positive electrode plate slurry prepared in Examples 1 and 2 can have better film forming effect and can better adhere to the surface of the metal substrate.

[0163] Positive electrode plate flexibility test:

[0164] As shown in the positive electrode plate schematic diagram of Figure 3 The positive electrode plate 302 prepared from the positive electrode plate slurry prepared in Example 1 has no cracks at the indentation. The positive electrode plate 303 prepared from the positive electrode plate slurry prepared in Example 2 has no cracks at the indentation. The positive electrode plate 301 prepared from the positive electrode plate slurry prepared in Comparative Example 1 has relatively obvious cracks at the indentation.

[0165] It can be seen that the positive electrode plate slurry prepared in Examples 1 and 2 can have better flexibility and processing performance.

[0166] Battery performance test:

[0167] As shown in the cycle performance test schematic diagram of the battery of Figure 4 The lithium ion battery containing the positive electrode plate prepared from the positive electrode plate slurry prepared in Examples 1 or 2 has higher gram capacity than the lithium ion battery containing the positive electrode plate prepared from the positive electrode plate slurry prepared in Comparative Example 1.

[0168] It can be seen that the positive electrode plate prepared by the positive electrode plate slurry prepared in Example 1 and Example 2 can make the battery have better electrochemical performance and higher energy density, so that better battery performance can be obtained by using the positive electrode plate slurry prepared by the application.

[0169] The above describes in detail the positive electrode plate slurry of a lithium ion battery, the preparation method of the positive electrode plate slurry of a lithium ion battery, the lithium ion battery, and the vehicle provided by the application. The principles and implementation manners of the application are described by using specific examples. The above description of the examples is only used to help understand the method of the application and its core idea. Meanwhile, for those skilled in the art, the specific implementation manners and application ranges can be changed according to the idea of the application. In summary, the content of the specification should not be understood as a limitation of the application.

Claims

1. A positive electrode sheet slurry for a lithium ion battery, characterized by, The positive electrode active material, the first binder, the second binder, the conductive agent, the second solvent, and the first solvent are included. The first binder includes a polyacrylic binder, the polyacrylic binder includes a polyacrylonitrile multi-copolymer and / or a copolymer of acrylic acid and acrylonitrile, the second binder includes an acrylate binder, the acrylate binder includes at least one of methoxy polyethylene glycol acrylate, polyethylene glycol diacrylate, and polybutyl acrylate, the first solvent includes deionized water, the second solvent includes an alcohol solvent, and the alcohol solvent includes ethanol and / or isopropyl alcohol; a mass ratio of the first binder and the second binder to the positive electrode active material is 2-5:90-96.

2. The cathode electrode slurry of claim 1, wherein, The conductive agent includes a first conductive agent, a second conductive agent, and a third conductive agent. The first conductive agent includes at least one of nanometer carbon fiber, carbon nanotube, and metal fiber, the second conductive agent includes acetylene black and / or conductive graphite, and the third conductive agent includes graphene; a mass ratio of the first conductive agent, the second conductive agent, and the third conductive agent to the positive electrode active material is 1-3:90-96.

3. The cathode electrode slurry of claim 1, wherein, The positive electrode active material includes at least one of lithium cobaltate, lithium manganate, lithium iron phosphate, lithium vanadium phosphate, lithium manganese phosphate, lithium nickel cobalt manganese oxide, and lithium nickel cobalt aluminum oxide.

4. A method of making a positive electrode slurry for a lithium-ion battery, characterized by, The method includes: The first binder and the second binder are mixed to obtain a composite binder; the first binder includes a polyacrylic binder, the polyacrylic binder includes a polyacrylonitrile multi-copolymer and / or a copolymer of acrylic acid and acrylonitrile, and the second binder includes an acrylate binder, the acrylate binder includes at least one of methoxy polyethylene glycol acrylate, polyethylene glycol diacrylate, and polybutyl acrylate; The conductive agent is dissolved in the first solvent to obtain a first mixed solution; the first solvent includes deionized water; The composite binder is dissolved in the first mixed solution to obtain a second mixed solution; The positive electrode active material is added to the second mixed solution, and after high-speed dispersion, a positive electrode sheet slurry is obtained; a mass ratio of the first binder and the second binder to the positive electrode active material is 2-5:90-96. The step of dissolving the conductive agent in the first solvent to obtain the first mixed solution includes: After the first solvent and the first conductive agent are mixed, the second solvent is added to obtain the first mixed solution; the second solvent includes an alcohol solvent, and the alcohol solvent includes ethanol and / or isopropyl alcohol.

5. The method of claim 4, wherein, The step of adding the positive electrode active material to the second mixed solution and uniformly dispersing at high speed to obtain the positive electrode sheet slurry includes: After the positive electrode active material, the second conductive agent, and the third conductive agent are uniformly mixed, they are added to the second mixed solution, and after high-speed dispersion, the positive electrode sheet slurry is obtained.

6. A lithium-ion battery, characterized by The lithium ion battery comprises a positive electrode sheet coated with the positive electrode sheet slurry as claimed in any one of claims 1-3, or comprises a positive electrode sheet coated with the positive electrode sheet slurry prepared by the preparation method as claimed in any one of claims 4-5.

7. A vehicle characterized by comprising: The vehicle comprises the lithium ion battery as claimed in claim 6.

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