CN113422006B - Positive pole piece, preparation method thereof and lithium ion battery - Google Patents
Positive pole piece, preparation method thereof and lithium ion battery Download PDFInfo
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- CN113422006B CN113422006B CN202110978218.4A CN202110978218A CN113422006B CN 113422006 B CN113422006 B CN 113422006B CN 202110978218 A CN202110978218 A CN 202110978218A CN 113422006 B CN113422006 B CN 113422006B
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- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
- H01M4/139—Processes of manufacture
- H01M4/1391—Processes of manufacture of electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
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- H01M10/00—Secondary cells; Manufacture thereof
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- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
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- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
- H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
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- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
- H01M2004/028—Positive electrodes
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Abstract
The invention provides a positive pole piece, a preparation method thereof and a lithium ion battery. The preparation method comprises the following steps: step S1, coating a conductive agent on the surface of the nickel-cobalt-manganese ternary positive electrode material by adopting a fluidized bed process to form a first coating layer, and then coating a binder to form a second coating layer, thereby forming active powder; and step S2, coating the active powder on the surface of the current collector by using a dry coating method, and then rolling to obtain the positive pole piece. The preparation method provided by the invention does not use NMP and other organic solvents, simplifies the process and reduces the cost. More importantly, the conductive agent and the binder are uniformly distributed, the particles are tightly arranged, the space utilization rate is improved, and the pole piece compaction density is improved, so that the energy density of the lithium ion battery is improved.
Description
Technical Field
The invention relates to the technical field of lithium ion batteries, in particular to a positive pole piece, a preparation method of the positive pole piece and a lithium ion battery.
Background
With the rapid development of new energy automobiles, the energy density of lithium ion power batteries is also continuously improved. The energy density of the power battery is improved by the main methods of improving the capacity of materials, improving the voltage and improving the density. At present, most researches are carried out on improving capacity and voltage, but the attention on improving the density of materials is less, particularly the compaction density of a positive pole piece. In the current lithium ion battery, the compaction density of the lithium cobaltate positive pole piece is the highest and can reach 4.2g/cm3The theoretical maximum density of the crystals is 5.2g/cm3The space utilization of the pole piece is about 80%. While the compacted density of nickel-cobalt-manganese ternary positive electrode materials is generally up to 3.5g/cm3The theoretical maximum density of the crystals is 4.8g/cm3The space utilization of the pole piece is about 73%. Therefore, the compaction density of the nickel-cobalt-manganese ternary cathode material has a large promotion space.
At present, the positive electrode manufacturing process in the lithium ion battery generally comprises the step of preparing positive electrode active micrometer particles, a conductive agent and a binder into a slurry with a certain viscosity in an NMP (N-methyl pyrrolidone) solvent. And then coating the slurry on an aluminum foil, rolling and cutting pieces to obtain the required positive pole piece. Although the method is an industry common technology, the NMP organic solvent of the technology causes cost rise, the layering phenomenon of the binder in the drying process of the NMP solvent influences the compaction density of the pole piece, and the uneven distribution of various materials such as a conductive agent, the binder and the like among particles also influences the compaction density of the pole piece. Therefore, the technology also has a space for improvement.
Patent CN103093969B reports a method for manufacturing a pole piece without using NMP solvent. The method is to mix and prepare the conductive agent, the binder, the anode active micron particles and the electrolyte salt powder. Because a plurality of powder materials are mixed together, the uniform distribution of the powder materials cannot be ensured, and the space of the pole piece cannot be fully and effectively utilized.
For the above reasons, there is a need to provide a new method capable of increasing the compaction density of the positive electrode sheet.
Disclosure of Invention
The invention mainly aims to provide a positive pole piece, a preparation method thereof and a lithium ion battery, and aims to solve the problem that the energy density of the battery is influenced by low compaction density of the positive pole piece in the prior art.
In order to achieve the above object, according to an aspect of the present invention, there is provided a method for preparing a positive electrode sheet, including the steps of: step S1, coating a conductive agent on the surface of the nickel-cobalt-manganese ternary positive electrode material by adopting a fluidized bed process to form a first coating layer, and then coating a binder to form a second coating layer, thereby forming active powder; and step S2, coating the active powder on the surface of the current collector by using a dry coating method, and then rolling to obtain the positive pole piece.
Further, step S1 includes: step S11, placing the nickel-cobalt-manganese ternary positive electrode material into a fluidized bed cavity, and introducing a first carrier gas into the cavity to enable the nickel-cobalt-manganese ternary positive electrode material to be in a fluidized state; step S12, atomizing and spraying the slurry of the conductive agent into the cavity of the fluidized bed to enable the slurry to be in contact with the fluidized nickel-cobalt-manganese ternary cathode material, and enabling the conductive agent to coat the surface of the nickel-cobalt-manganese ternary cathode material to form a first coating layer to obtain primary coating powder; and step S13, maintaining the primary coated powder to be in a fluidized state, atomizing and spraying a solution of the binder into the fluidized bed cavity to enable the solution to be in contact with the fluidized primary coated powder, and further enabling the binder to be coated on the surface of the primary coated powder to form a second coating layer, so as to obtain the active powder.
Further, in step S11, the flow rate of the first carrier gas is 0.15-0.23 m3The temperature is 80-150 ℃.
Further, in step S12, the solvent of the slurry of the conductive agent is water and/or NMP, and the viscosity of the slurry of the conductive agent is less than 2000m ps, preferably 500-1500 m ps; preferably, the slurry of the conductive agent is atomized and sprayed into the cavity of the fluidized bed by the second carrier gas, and more preferably, the atomization speed of the slurry of the conductive agent is 1-2 g/min.
Further, in step S13, the solvent of the slurry of the binder is NMP, and the viscosity of the slurry of the binder is 1000-2000 mP S; preferably, the slurry of the binder is atomized and sprayed into the cavity of the fluidized bed by a third carrier gas, and more preferably, the atomization speed of the slurry of the binder is 0.5-1.5 g/min; preferably, the first carrier gas, the second carrier gas and the third carrier gas are all nitrogen.
Further, step S2 includes: coating the active powder on the surface of the current collector in an electrostatic spraying mode, and then rolling to obtain a positive pole piece; preferably, an electrostatic spraying machine is used for electrostatic spraying, and the voltage of the electrostatic spraying machine is 10-100 KV; preferably, after electrostatic spraying, the temperature of a press roll in the rolling process is 70-150 ℃, and the pressure is 5-50 MPa; or carrying out first rolling on the active powder to form a front pole piece, and then carrying out second rolling on the front pole piece and the current collector to obtain a positive pole piece; preferably, before the step of performing first rolling on the active powder, adding 1-5 wt% of NMP into the active powder, wherein in the process of performing the first rolling, the temperature of a press roll is 80-130 ℃; preferably, in the second rolling process, the temperature of the press roll is 70-150 ℃, and the pressure is 5-100 MPa.
Further, the nickel content in the nickel-cobalt-manganese ternary cathode material is not less than 60wt%, preferably, the particle size D10 of the nickel-cobalt-manganese ternary cathode material is 1-5 micrometers, D50 is 2-15 micrometers, and D90 is 5-30 micrometers; more preferably, the specific surface area of the nickel-cobalt-manganese ternary positive electrode material is 0.1-1.5 m2/g。
Further, the conductive agent is one or more of carbon nano tube, carbon black and graphene; the binder is one or more of PVDF, PTFE, PEDOT and PAN; an aluminum or copper foil of the current collector; preferably, the weight of the conductive agent is 0.1-1% of the weight of the nickel-cobalt-manganese ternary cathode material, and the weight of the binder is 0.5-5% of the weight of the nickel-cobalt-manganese ternary cathode material.
According to another aspect of the invention, the invention also provides a positive pole piece which is prepared by the preparation method.
According to another aspect of the present invention, there is also provided a lithium ion battery, including a positive electrode plate, which is the positive electrode plate described above, or the positive electrode plate prepared by the above preparation method.
According to the invention, a conductive agent and a binder are sequentially coated on the surface of the ternary cathode material through a fluidized bed process in advance to form a first coating layer (conductive agent layer) coated on the surface of the ternary cathode material and a second coating layer (binder layer) on the surface of the first coating layer, and then the positive active material micron particles are directly subjected to dry coating on the current collector layer and then rolled, so that the high-compaction positive pole piece is obtained. Through experimental tests, the positive pole piece obtained by the method greatly reduces the distribution volume of the conductive agent and the binder in the pole piece, and the ternary positive pole material particles are tightly combined, so that the space utilization rate is high, and the compaction density of the positive pole piece is obviously improved compared with that of the positive pole piece obtained by the traditional slurry coating method, and even can reach 4.0g/cm3。
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate embodiments of the invention and, together with the description, serve to explain the invention and not to limit the invention. In the drawings:
fig. 1 shows a scanning electron micrograph of an active material layer in a positive electrode sheet prepared according to example 1 of the present invention; and
fig. 2 shows a scanning electron micrograph of an active material layer in the positive electrode sheet prepared in comparative example 1.
Detailed Description
It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict. The present invention will be described in detail below with reference to the embodiments with reference to the attached drawings.
In order to improve the compaction density of the positive pole piece, the invention provides a preparation method of the positive pole piece, which comprises the following steps: step S1, coating a conductive agent on the surface of the nickel-cobalt-manganese ternary positive electrode material by adopting a fluidized bed process to form a first coating layer, and then coating a binder to form a second coating layer, thereby forming active powder; and step S2, coating the active powder on the surface of the current collector by using a dry coating method, and then rolling to obtain the positive pole piece.
According to the invention, a conductive agent and a binder are sequentially coated on the surface of the ternary cathode material through a fluidized bed process in advance to form a first coating layer (conductive agent layer) coated on the surface of the ternary cathode material and a second coating layer (binder layer) on the surface of the first coating layer, and then the positive active material micron particles are directly subjected to dry coating on the current collector layer and then rolled, so that the high-compaction positive pole piece is obtained. Through experimental tests, the positive pole piece obtained by the method greatly reduces the distribution volume of the conductive agent and the binder in the pole piece, and the ternary positive pole material particles are tightly combined, so that the space utilization rate is high, and the compaction density of the positive pole piece is obviously improved compared with that of the positive pole piece obtained by the traditional slurry coating method, and even can reach 4.0g/cm3。
In a preferred embodiment, the step S1 includes: step S11, placing the nickel-cobalt-manganese ternary positive electrode material into a fluidized bed cavity, and introducing a first carrier gas into the cavity to enable the nickel-cobalt-manganese ternary positive electrode material to be in a fluidized state; step S12, atomizing and spraying the slurry of the conductive agent into the cavity of the fluidized bed to enable the slurry to be in contact with the fluidized nickel-cobalt-manganese ternary cathode material, and enabling the conductive agent to coat the surface of the nickel-cobalt-manganese ternary cathode material to form a first coating layer to obtain primary coating powder; and step S13, maintaining the primary coated powder to be in a fluidized state, atomizing and spraying a solution of the binder into the fluidized bed cavity to enable the solution to be in contact with the fluidized primary coated powder, and further enabling the binder to be coated on the surface of the primary coated powder to form a second coating layer, so as to obtain the active powder.
In the actual operation process, high-temperature compressed nitrogen is utilized to throw nickel-cobalt-manganese ternary positive electrode material particles into a cavity to turn over at a high speed, and then slurry of a conductive agent is atomized and sprayed to be in contact with fluidized powder. In the fluidized state, the solvent in the slurry is quickly volatilized, and the conductive agent is remained on the surface of the anode material particles to form a coating. Secondly, the primary coated powder is maintained to be in a fluidized state continuously, the slurry of the binder is atomized and sprayed into the primary coated powder and contacts with the fluidized primary coated powder, similarly, the solvent in the slurry is volatilized quickly, the binder is further coated on the surface of the primary coated powder, and finally the active powder is obtained.
Through the two-step fluidized bed process, the conductive agent and the binder form good coating on the surface of the positive electrode material particles, so that the space utilization rate of the particles on the surface of the current collector is further improved, and the improvement of the compaction density of the positive electrode plate is promoted better.
In order to maintain the anode material particles in a more stable fluidized state while allowing the atomized slurry to more sufficiently contact with the particles and promoting the solvent evaporation, in a preferred embodiment, in step S11, the flow rate of the first carrier gas is 0.15 to 0.23m3The temperature is 80-150 ℃.
Preferably, in step S12, the solvent of the slurry of the conductive agent is water and/or NMP, and the viscosity of the slurry of the conductive agent is less than 2000mP · S, preferably 500 to 1500mP · S (for example, carbon nanotubes are used as the conductive agent, and the concentration thereof is 0.2 to 0.6%). The viscosity is controlled within the range, so that the atomization effect is better, and the problem of too low coating speed caused by over-dilution of the slurry is avoided. More preferably, the slurry of the conductive agent is atomized and sprayed into the cavity of the fluidized bed by the second carrier gas, and the atomization speed of the slurry of the conductive agent is more preferably 1-2 g/min.
And after the coating of the conductive agent is finished, keeping the first coating powder in a fluidized state, and then spraying slurry of the binder into the first coating powder in an atomized manner to finish the coating of the binder. In the actual operation process, in order to further improve the atomization effect of the adhesive slurry, the solvent of the adhesive slurry is preferably NMP, and the viscosity of the adhesive slurry is 1000-2000 mP & s; preferably, the slurry of the binder is atomized and sprayed into the cavity of the fluidized bed by a third carrier gas, and more preferably, the atomization speed of the slurry of the binder is 0.5-1.5 g/min; preferably, the first carrier gas, the second carrier gas and the third carrier gas are all nitrogen.
In a preferred embodiment, step S2 includes: coating the active powder on the surface of the current collector in an electrostatic spraying mode, and then rolling to obtain a positive pole piece; preferably, the electrostatic spraying is carried out by using an electrostatic spraying machine, and the voltage of the electrostatic spraying machine is 10-100 KV. By means of electrostatic spraying, the active powder can be coated on the surface of the current collector layer in a dry method under the action of an electric field. And because the surface of the positive electrode material is coated with the conductive agent, the electrostatic force of the powder is uniform in the electrostatic spraying process, and the powder layer coated on the surface of the current collector is uniformly and compactly distributed, so that the compaction density of the positive electrode plate is further improved. Preferably, after the electrostatic spraying, the temperature of the press roll is 70-150 ℃ and the pressure is 5-50 MPa in the rolling process. The temperature and pressure conditions of the compression roller are controlled within the range, so that the mutual adhesion of the binding agents is facilitated, and a more compact active material layer is formed on the surface of the current collector. In practical operation, the preferable rolling comprises 3-5 times of rolling.
In another embodiment, dry coating may also be performed in the following manner: and carrying out first rolling on the active powder to form a front pole piece, and then carrying out second rolling on the front pole piece and the current collector to obtain the positive pole piece. Preferably, before the step of performing the first rolling on the active powder, 1-5 wt% of NMP is added into the active powder, and in the process of the first rolling, the temperature of the press roll is 80-130 ℃. And a trace amount of solvent NMP is added, so that a coating layer on the surface of the positive electrode material is not damaged, an integral prepressing layer is formed in the first rolling process, and the positive electrode material is directly placed on the current collector layer for second rolling treatment, so that a stable positive electrode plate with high compaction density can be formed. Preferably, in the second rolling process, the temperature of the press roll is 70-150 ℃, and the pressure is 5-100 MPa. In practice, the second rolling preferably comprises 3 to 5 times of rolling.
In a preferred embodiment, the nickel content in the nickel-cobalt-manganese ternary cathode material is more than or equal to 60 wt%. The compact density improvement effect of the method is more obvious for the high-nickel ternary cathode material, and specific nickel-cobalt-manganese ternary cathode materials can be of the types commonly used in the field, such as LiNi0.83Co0.11Mn0.06O2, LiNi0.6Co0.1Mn0.3O2, LiNi0.6Co0.2Mn0.2O2 and the like. Preferably, the particle size D10 of the nickel-cobalt-manganese ternary positive electrode material is 1-5 micrometers, the particle size D50 is 2-15 micrometers, and the particle size D90 is 5-30 micrometers. The nickel-cobalt-manganese ternary positive electrode material with the particle size is more uniform and suitable, the subsequent coating effect of the conductive agent and the binder is more uniform, and the space utilization rate on the surface of the current collector is higher. More preferably, the specific surface area of the nickel-cobalt-manganese ternary positive electrode material is 0.1-1.5 m2/g。
In the actual manufacturing process, the moisture of the nickel-cobalt-manganese ternary positive electrode material can be dried to be less than 0.1% in advance, and then the nickel-cobalt-manganese ternary positive electrode material is coated. More preferably, the pH value of the positive electrode material is 10.5-12.5. Preferably, after dry coating, the thickness of the pole piece is 50-200 microns, and after rolling, the thickness of the final positive pole piece is 30-180 microns.
In a preferred embodiment, the conductive agent is one or more of carbon nanotubes, carbon black and graphene; the binder is one or more of PVDF, PTFE, PEDOT and PAN; an aluminum or copper foil of the current collector; preferably, the weight of the conductive agent is 0.1-1% of the weight of the nickel-cobalt-manganese ternary cathode material, and the weight of the binder is 0.5-5% of the weight of the nickel-cobalt-manganese ternary cathode material.
In a word, the preparation method provided by the invention does not use NMP and other organic solvents, simplifies the process and reduces the cost. More importantly, the conductive agent and the binder are uniformly distributed, the particles are tightly arranged, the space utilization rate is improved, and the pole piece compaction density is improved, so that the energy density of the battery cell is improved.
According to another aspect of the invention, the invention also provides a positive pole piece which is prepared by the preparation method.
According to another aspect of the present invention, there is also provided a lithium ion battery, including a positive electrode plate, which is the positive electrode plate described above, or the positive electrode plate prepared by the above preparation method.
The present application is described in further detail below with reference to specific examples, which should not be construed as limiting the scope of the invention as claimed.
Example 1
Raw materials:
the nickel-cobalt-manganese ternary positive electrode material LiNi0.83Co0.11Mn0.06O2 has the particle size D10 of 1-5 microns, D50 of 2-15 microns and D90 of 5-30 microns. The specific surface area of the anode material is 0.1-1.5 m2The water content is less than 0.1 percent, and the pH value is 10.5-12.5.
Conductive agent: a carbon nanotube;
conductive agent slurry: the mass concentration of the slurry formed by the carbon nano tube and the water is 0.6 percent, and the viscosity is 800mP & s;
adhesive: PVDF;
binder slurry: an NMP solution of PVDF with the mass concentration of 0.8% and the viscosity of 1200mP & s;
the preparation method comprises the following steps:
500 g of the anode material is put into a cavity of a fluidized bed, and high-temperature compressed nitrogen (with the flow rate of 0.23 m) at 120 ℃ is introduced3H) throwing the high-nickel anode material in the cavity, and turning over at high speed to form a fluidized state; high-pressure nitrogen is used for atomizing and spraying conductive agent slurry (the conductive agent accounts for 1 percent of the weight of the anode material) into a fluidized bed cavity (1 g/min), and the conductive agent slurry is fully connected with powder in the cavityContacting; and (3) rapidly volatilizing water under a high-temperature condition, and leaving the carbon nano tube on the surface of the anode to finish the uniform coating of the carbon nano tube to obtain primary coated powder. Maintaining the powder in a fluidized state, atomizing and spraying a binder slurry (the binder accounts for 1.5 percent of the weight of the anode material) into a fluidized bed cavity (1.5 g/min) through high-pressure nitrogen, rapidly volatilizing NMP, and leaving the binder on the surface of the primary coated powder to form active powder.
Using an electrostatic spraying machine to spray active split static on the surface of the aluminum foil, wherein the voltage of the electrostatic spraying machine is 20KV, and the thickness of a coated pole piece is controlled to be 120 micrometers; after electrostatic spraying, the temperature of the press roll is 120 ℃ and the pressure is 12MPa in the rolling process, the positive pole piece is formed by rolling for 3 times, and the scanning electron microscope picture of the positive pole piece is shown in figure 1.
Example 2
The only difference from example 1 is that: the conductive agent slurry is formed by the carbon nano tube and water, the mass concentration of the conductive agent slurry is 0.8%, and the viscosity of the conductive agent slurry is 1500mP & s. The binder slurry was a PVDF NMP solution with a mass concentration of 1.2% and a viscosity of 2000mP · s. The manufacturing process comprises the following steps: the temperature of the high-temperature compressed nitrogen is 80 ℃, and the flow rate is 0.23m3The atomized spraying speed of the conductive agent slurry is 2g/min, and the atomized spraying speed of the binder slurry is 0.5 g/min. The voltage for electrostatic spraying was 10 KV.
Example 3
The only difference from example 1 is that: the conductive agent slurry is formed by the carbon nano tube and water, the mass concentration of the conductive agent slurry is 0.3%, and the viscosity of the conductive agent slurry is 500mP & s. The binder slurry was a PVDF NMP solution with a mass concentration of 0.5% and a viscosity of 1000mP · s. The manufacturing process comprises the following steps: the temperature of the high-temperature compressed nitrogen is 150 ℃, and the flow rate is 0.15m3The atomized spraying speed of the conductive agent slurry is 1.5g/min, and the atomized spraying speed of the binder slurry is 0.8 g/min. The voltage for electrostatic spraying was 50 KV.
Example 4
The only difference from example 1 is that: adding trace NMP (accounting for 1% of the weight of the powder) into the active powder, rolling at the temperature of 80 ℃ and the pressure of 5MPa to form a front pole piece, and then carrying out second rolling on the front pole piece and an aluminum foil (respectively placing a layer of front pole piece above and below the aluminum foil) at the temperature of 150 ℃ and the pressure of 5MPa to obtain a positive pole piece.
Example 5
The only difference from example 1 is that: adding trace NMP (accounting for 5% of the weight of the powder) into the active powder, rolling at the compression roller temperature of 130 ℃ and under the pressure of 130MPa to form a front pole piece, and then performing second rolling on the front pole piece and an aluminum foil (a layer of front pole piece is respectively placed on the upper side and the lower side of the aluminum foil) at the compression roller temperature of 70 ℃ and under the pressure of 100MPa to obtain a positive pole piece.
Example 6
The only difference from example 1 is that: the nickel-cobalt-manganese ternary positive electrode material LiNi0.6Co0.1Mn0.3O2 has the particle size D10 of 1-5 microns, the particle size D50 of 2-15 microns and the particle size D90 of 5-30 microns. The specific surface area of the anode material is 0.1-1.5 m2The water content is less than 0.1 percent, and the pH value is 10.5-12.5. The conductive agent is conductive carbon black, and the conductive agent slurry is slurry formed by the conductive carbon black and water and having the viscosity of 800mP & s; the binder is PAN, and the binder slurry is a slurry formed by dissolving PAN in NMP and having a viscosity of 1200mP & s.
Comparative example 1
The difference from example 1 is that the manufacturing method is as follows: the positive electrode material, the conductive agent, the binder and the solvent NMP were mixed to form a mixed slurry, wherein the weight ratio of the positive electrode material, the conductive agent and the binder was the same as that in example 1. The mixed slurry is coated on the surface of an aluminum foil, and after drying and curing, a positive pole piece with the thickness of 110 microns is formed, and a scanning electron microscope photo of the positive pole piece is shown in figure 2.
Comparative example 2
The difference from example 6 is that the manufacturing method is as follows: the positive electrode material, the conductive agent, the binder and the solvent NMP were mixed to form a mixed slurry, wherein the weight ratio of the positive electrode material, the conductive agent and the binder was the same as that in example 6. And coating the mixed slurry on the surface of an aluminum foil, and drying and curing to form a positive pole piece with the thickness of 110 microns.
Comparative example 3
The difference from example 1 is that: the nickel-cobalt-manganese anode material and the conductive agent carbon nano tube are dry-mixed in a fluidized bed instead of making the conductive agent into slurry and spraying the slurry in an atomizing manner. And then, spraying the binder slurry into a fluidization cavity to spray and coat the binder on the dry-mixed anode material and the conductive agent, and maintaining the dry-mixed powder of the anode material and the conductive agent in a fluidization state.
And (3) performance testing:
testing of compacted density: 1) cutting 5 pieces of 20cm × 20cm, measuring the surface density of the pole piece, and averaging to obtain M (unit g/cm)2) (ii) a 2) Measuring the thickness of the pole piece at 10 positions, and averaging to obtain h (unit cm); 3) according to ρ = (M-M)Aluminium)/(h-hAluminium) Calculating the compacted density in g/cm3(ii) a Wherein h isAluminiumIs the thickness of the aluminum foil, MAluminium（=ρAluminium×hAluminium) Is the aluminum foil surface density.
Energy density of the battery: the positive pole pieces prepared by different schemes are assembled into a liquid soft package battery (the capacity is about 5 Ah), the negative pole adopts artificial graphite, and the electrolyte component is 1mol/L LiPF6The test current employed was 0.33C (discharge time 3 hours).
The test results are shown in table 1:
from the above description, it can be seen that the above-described embodiments of the present invention achieve the following technical effects:
compared with the pole piece of the scheme and the traditional method (high-nickel anode material, NMP, adhesive and conductive agent for pulping and coating), the pole piece of the scheme has the advantages that the grain combination is compact, and the compaction can reach 3.8-4.0g/cm3Even higher. The particles of the traditional method are loosely combined, and the compaction density is about 3.4-3.6g/cm3。
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (8)
1. A preparation method of a positive pole piece is characterized by comprising the following steps:
step S1, coating a conductive agent on the surface of the nickel-cobalt-manganese ternary positive electrode material by adopting a fluidized bed process to form a first coating layer, and then coating a binder to form a second coating layer, thereby forming active powder;
step S2, coating the active powder on the surface of a current collector by using a dry coating method, and then rolling to obtain a positive pole piece;
the step S1 includes:
step S11, placing the nickel-cobalt-manganese ternary cathode material into a fluidized bed cavity, and introducing a first carrier gas into the fluidized bed cavity to enable the nickel-cobalt-manganese ternary cathode material to be in a fluidized state;
step S12, atomizing and spraying the slurry of the conductive agent into the fluidized bed cavity to enable the slurry to be in contact with the fluidized nickel-cobalt-manganese ternary cathode material, and enabling the conductive agent to coat the surface of the nickel-cobalt-manganese ternary cathode material to form the first coating layer to obtain primary coating powder;
step S13, maintaining the primary coated powder to be in a fluidized state continuously, then atomizing and spraying the solution of the binder into the fluidized bed cavity to enable the solution of the binder to be in contact with the fluidized primary coated powder, and enabling the binder to coat the surface of the primary coated powder to form a second coating layer, so as to obtain the active powder;
the step S2 includes:
coating the active powder on the surface of the current collector in an electrostatic spraying mode, and then performing rolling to obtain the positive pole piece; alternatively, the first and second electrodes may be,
and carrying out first rolling on the active powder to form a front pole piece, and then carrying out second rolling on the front pole piece and the current collector to obtain the positive pole piece.
2. The method of claim 1, wherein the method comprisesCharacterized in that, in the step S11, the flow speed of the first carrier gas is 0.15-0.23 m3The temperature is 80-150 ℃.
3. The method according to claim 2, wherein in step S12, the solvent of the slurry of the conductive agent is water and/or NMP, and the viscosity of the slurry of the conductive agent is lower than 2000 mP-S;
and atomizing the slurry of the conductive agent into the cavity of the fluidized bed by using a second carrier gas, wherein the atomization speed of the slurry of the conductive agent is 1-2 g/min.
4. The method according to claim 3, wherein in the step S13, the solvent of the binder slurry is NMP, and the viscosity of the binder slurry is 1000 to 2000 mP-S;
atomizing the slurry of the binder into the fluidized bed cavity by using third carrier gas, wherein the atomizing speed of the slurry of the binder is 0.5-1.5 g/min;
the first carrier gas, the second carrier gas, and the third carrier gas are all nitrogen.
5. The preparation method of any one of claims 1 to 4, wherein the nickel content in the nickel-cobalt-manganese ternary cathode material is not less than 60wt%, the particle size D10 of the nickel-cobalt-manganese ternary cathode material is 1-5 micrometers, the particle size D50 of the nickel-cobalt-manganese ternary cathode material is 2-15 micrometers, and the particle size D90 of the nickel-cobalt-manganese ternary cathode material is 5-30 micrometers.
6. The production method according to any one of claims 1 to 4, characterized in that the conductive agent is one or more of carbon nanotubes, carbon black, and graphene; the binder is one or more of PVDF, PTFE, PEDOT and PAN; an aluminum foil or a copper foil of the current collector;
the weight of the conductive agent is 0.1-1% of that of the nickel-cobalt-manganese ternary positive electrode material, and the weight of the binder is 0.5-5% of that of the nickel-cobalt-manganese ternary positive electrode material.
7. A positive electrode plate, characterized by being prepared by the preparation method of any one of claims 1 to 6.
8. A lithium ion battery, comprising a positive electrode plate, wherein the positive electrode plate is the positive electrode plate of claim 7.
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| CN202110978218.4A CN113422006B (en) | 2021-08-25 | 2021-08-25 | Positive pole piece, preparation method thereof and lithium ion battery |
| PCT/CN2022/106540 WO2023024765A1 (en) | 2021-08-25 | 2022-07-19 | Positive electrode plate and preparation method therefor, and lithium ion battery |
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| CN114122393A (en) * | 2021-11-11 | 2022-03-01 | 深圳市翔丰华科技股份有限公司 | Preparation method of high-power-density negative electrode material for lithium ion battery |
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