CN113013414A - Cobalt-free positive electrode slurry, preparation method thereof, positive plate and lithium ion battery - Google Patents
Cobalt-free positive electrode slurry, preparation method thereof, positive plate and lithium ion battery Download PDFInfo
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Abstract
The invention provides a cobalt-free anode slurry, a preparation method thereof, an anode plate and a lithium ion battery. The cobalt-free cathode slurry comprises a cobalt-free cathode material, a conductive agent, a binder, a conductive polymer and a solvent. According to the cobalt-free anode slurry provided by the invention, the polymer material with conductivity is added, so that the conductivity of the cobalt-free anode plate is improved, and the internal resistance of a battery cell is reduced; the conductive polymer has higher ionic conductivity, forms a 3D fast ionic conductor network structure, improves the power performance of the battery, and further improves the surface density of the positive pole piece, thereby improving the energy density of the battery; in addition, the weak acid environment on the surface of the polymer neutralizes the alkalinity on the surface of the cobalt-free material, so that the residual metal dissolution phenomenon is reduced, the self-discharge phenomenon of the battery is reduced, and the safety factor of the battery is further improved.
Description
Technical Field
The invention belongs to the technical field of batteries, and relates to a positive electrode slurry and a preparation method thereof, a positive plate and a lithium ion battery, in particular to a cobalt-free positive electrode slurry and a preparation method thereof, a positive plate and a lithium ion battery.
Background
The lithium ion battery has the advantages of high energy density, no memory effect, wide use temperature, high voltage window and the like, and is widely applied to high-energy-density battery products. With the increasing demand of people on the energy density of the battery, the brand-open corner of the lithium ion battery adopting the lamination process has higher energy density and better cycle performance; with the intelligent development of the electrical appliance industry and the popularization of electric automobiles, the demand of people on lithium ion batteries is increased explosively, the energy density of the batteries is higher and higher, but the safety problem of the batteries is more and more prominent, and the production cost of the batteries is also rapidly improved; with the coming of the subsiding of the electric vehicle, the power battery industry is about to develop a price war, and various large battery manufacturers seek to improve the energy density of the battery, and meanwhile, the problem that how to reduce the production cost of the battery and improve the safety of the battery is urgently solved by each battery industry is solved.
The existing high-energy battery anode material is mainly concentrated on a ternary anode material, the main energy density carrier is lithium nickelate serving as a main body, and an NCM and NCA system; due to the shortage of cobalt resources, uneven distribution of the resources and other factors, the price of the cobalt resources is greatly fluctuated, the price of the ternary anode material is greatly fluctuated, and the cobalt cost is greatly occupied in the material. In addition, cobalt resources are scarce, and with the large-scale application of electric automobiles, the consumption of the cobalt resources is continuously increased, so that the problem of cobalt resource exhaustion is faced in the near future.
The existing common thick electrode coating technology for the cobalt-free anode is mainly wet coating, the electrode coating is thick, large gaps exist among active mass layers, and electrolyte is difficult to infiltrate into the inside of a pole piece due to the fact that the pole piece is thick, so that the ionic conductivity of the pole piece is reduced, and the reduction of the battery cycle performance and the performance in the multiplying power aspect is caused.
Secondly, polyvinylidene fluoride (PVDF) used for coating the positive electrode is an insulator of lithium ions/electrons, so that the electronic conductivity of the positive electrode is reduced, and lithium ions are prevented from being inserted into an active material; the thick electrode tends to cause an increase in PVDF usage, further reducing the ionic/conductivity of the pole piece.
Thirdly, because the main elements of the NMx cobalt-free positive electrode material are binary materials of Ni and Mn, the surface of the NMx cobalt-free positive electrode material has high metal residues, such as elements of nickel oxide/cobalt, and the like, and the materials are easily dissolved into the electrolyte in the battery circulation process and migrate to the surface of the negative electrode, so that metal foreign matters are caused, the self-discharge phenomenon of the battery is increased, and even the risk of short circuit exists.
The current cobalt-free battery thick electrode is mainly realized by increasing the density of a coating surface, and in order to ensure the thickness of a pole piece, a thick electrode pole piece is prepared by adopting a multi-rolling mode; however, the thick electrode plate prepared by the method has the defects of poor performance of an electrolyte wetting electrode plate and overlarge electrode rebound due to high compaction density. Secondly, the cobalt-free material is mainly Ni and Mn binary materials, so that the surface alkalinity is high, metal residues exist, and the metal residues have the risk of being dissolved into electrolyte, thereby bringing immeasurable risk factors to the safety of the battery.
CN112271285A discloses a preparation process of lithium ion battery anode slurry, which comprises the following steps: preparing anode powder; preparing polyvinylidene fluoride (PVDF) glue solution; uniformly adding a novel carbon black conductive agent ECP-600JD into a polyvinylidene fluoride glue solution, and fully stirring to obtain a carbon black conductive glue solution; uniformly adding the oil single-walled carbon nanotubes into the carbon black conductive glue solution, and stirring and dispersing to obtain composite conductive slurry; adding the anode powder into the composite conductive slurry for preliminary kneading; kneading and stirring for the second time; adding the rest PVDF glue solution and appropriate NMP, and crushing and dispersing at high speed.
CN112289995A discloses a composite positive electrode slurry, a positive electrode plate and a solid-state battery. The preparation method of the composite anode slurry comprises the following steps: mixing the positive active material with lithium-carbon boron oxide and sintering at 660-700 ℃ to obtain a pre-sintered material; and dissolving the obtained pre-sintered material, solid electrolyte, conductive agent, adhesive and lithium salt in a solvent, and mixing to obtain the composite anode slurry.
CN112234207A discloses a positive electrode slurry and a positive plate of a lithium iron phosphate battery and a preparation method thereof, wherein the positive electrode slurry of the lithium iron phosphate battery comprises the following components in parts by weight: 90-95 parts of positive active material, 4-6 parts of conductive agent, 5-7 parts of binder, 3-5 parts of dispersant, 2-4.2 parts of flexibilizer and 80-90 parts of solvent; the positive electrode active material is lithium iron phosphate, the binder is polyacrylic acid, the toughening agent is polymethyl methacrylate, and the weight ratio of the polyacrylic acid to the polymethyl methacrylate is 1: 0.4-0.6.
However, the above solutions all have a problem that the electrochemical performance needs to be further improved when the cobalt-free cathode material is used.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to provide cobalt-free anode slurry, a preparation method thereof, an anode plate and a lithium ion battery. The positive plate prepared from the cobalt-free positive slurry provided by the invention has the advantages of good conductivity, small electrode rebound, less surface metal residue and less side reaction of the positive material in electrolyte.
In order to achieve the purpose, the invention adopts the following technical scheme:
in a first aspect, the present invention provides a cobalt-free cathode slurry comprising a cobalt-free cathode material, a conductive agent, a binder, a conductive polymer, and a solvent.
In the cobalt-free anode slurry provided by the invention, the conductivity and ionic conductivity of the electrode plate are improved through the macromolecular crosslinking effect of the conductive polymer (the ionic conductivity refers to a measurement of conduction of a substance, and in the invention, refers to the speed of lithium ions transmitted on the electrode plate). In addition, the characteristics of the conductive polymer are utilized to neutralize the metal residue on the surface of the material, so that a metal complex is formed on the surface of the material, and the metal dissolved electrolyte is effectively relieved; meanwhile, the polymers effectively reduce the contact between the electrolyte and the anode material and reduce the side reaction of the anode material.
The cobalt-free anode slurry provided by the invention is mainly used for improving the conductivity and ionic conductivity of a high-surface-density pole piece. Meanwhile, the alkaline environment on the surface of the cobalt-free anode material is neutralized under the action of the high molecular polymer, the metal residue on the surface of the anode material is reduced to be dissolved into the electrolyte, and the safety of the battery cell is improved.
The following is a preferred technical solution of the present invention, but not a limitation to the technical solution provided by the present invention, and the technical objects and advantageous effects of the present invention can be better achieved and achieved by the following preferred technical solution.
In a preferred embodiment of the present invention, the conductive polymer is a single-stranded polymer. In the invention, the single-chain polymer has the advantages that the polymer has good ionic conductivity and ionic conductivity, thereby forming a polymer layer with a net-shaped cross-linked structure and improving the conductivity and ionic conductivity of the pole piece; the polymer material which is conductive and ionic is used for manufacturing the cobalt-free anode material pole piece.
Preferably, the conductive polymer includes any one of polyvinyl formal, polyaniline, polyacrylate, polyimide, polyacrylonitrile, polysilicone, or polyethylene oxide resin, or a combination of at least two thereof, preferably polyvinyl formal (PVFM). The above-mentioned kinds of conductive polymers are all single-chain polymers.
The polyvinyl formal can be used as a binder and an ion conductive agent, and although the conductivity of the polyvinyl formal is probably slightly lower than that of polyaniline, the polyvinyl formal is not easy to be oxidized and decomposed, and is more suitable for cobalt-free anode slurry.
Preferably, the solvent is an organic solvent.
Preferably, the organic solvent comprises any one of N-methyl pyrrolidone, dimethyl sulfoxide, acetone or ethylene glycol or a combination of at least two thereof.
Preferably, the binder comprises polyvinylidene fluoride and/or sodium hydroxymethyl cellulose.
Preferably, the cobalt-free cathode material is a cathode material containing no cobalt element, and comprises lithium Nickel Manganese (NM)x) Lithium iron phosphate (LiFePO)4) Lithium manganate (LiMn)xO2) Or lithium nickelate (LiNi)xO2) Any one or a combination of at least two of them.
As a preferred embodiment of the present invention, the conductive agent includes any one or a combination of at least two of carbon nanotubes, conductive carbon black, and graphene.
Preferably, the conductive agent is a combination of carbon nanotubes and conductive carbon black.
Preferably, in the combination of the conductive carbon black and the carbon nano tubes, the mass ratio of the conductive carbon black to the carbon nano tubes is 6:4-8: 2.
In a preferred embodiment of the present invention, the mass ratio of the cobalt-free positive electrode material, the conductive agent, the conductive polymer and the binder is 90 (0.9-1.1): (6-8): 0.1-0.3), for example, 90:0.9:6:0.1, 90:1:7:0.2, 90:0.9:8:0.3, 90:1.1:6:0.1, 90:1:6:0.3 or 90:1.1:8: 0.2.
In the invention, if the conductive polymer is too much, the polymer can be agglomerated, the good dispersion effect can not be achieved, and the conductivity of the pole piece is influenced; if the conductive polymer is too little, the conductive polymer is less distributed on the surface of the active material, and a stable mesh conductive structure cannot be well formed, so that the conductivity of the pole piece is reduced. .
Preferably, the cobalt-free cathode slurry has a solids content of 50-80%, such as 50%, 60%, 70%, or 80%, etc., preferably a solids content of 68-72%.
In a second aspect, the present invention provides a method for preparing a cobalt-free cathode slurry as described in the first aspect, the method comprising the steps of:
(1) mixing a conductive polymer and a first solvent to obtain a first mixed glue solution, and mixing a binder and a second solvent to obtain a second mixed glue solution;
(2) and (2) mixing a cobalt-free anode material, a conductive agent, the first mixed glue solution and the second mixed glue solution in the step (1) to obtain the cobalt-free anode slurry.
The method provided by the invention is simple and feasible and has the advantage of low cost.
In the preparation method provided by the invention, the first mixed glue solution and the second mixed glue solution are prepared, but the conductive polymer, the binder and the solvent are not directly mixed together, and the purpose is that the conductive polymer is a chain polymer and is easy to cause agglomeration, and the conductive polymer is uniformly dispersed under the action of the solvent.
As a preferable technical scheme of the invention, the first solvent in the step (1) comprises N-methyl pyrrolidone.
Preferably, in the first mixed glue solution in step (1), the mass ratio of the conductive polymer to the first solvent is 1:100-15:100, such as 1:100, 2:100, 3:100, 4:100, 5:100, 6:100, 7:100, 8:100, 9:100, 10:100, 11:100, 12:100, 13:100, 14:100, or 15: 100.
Preferably, the second solvent in step (1) comprises any one of N-methyl pyrrolidone, dichloroethane or dimethyl sulfoxide or a combination of at least two of the same.
Preferably, in the second mixed glue solution in the step (1), the mass ratio of the binder to the second solvent is 3:100-9: l00, such as 3:100, 4:100, 5:100, 6:100, 7:100, 8:100, or 9: 100.
In the step (2), the mass ratio of the cobalt-free cathode material, the conductive agent, the conductive polymer in the first mixed colloidal solution and the binder in the second mixed colloidal solution is 90 (0.9-1.1): 6-8): 0.1-0.3, for example, 90:0.9:6:0.1, 90:1:7:0.2, 90:0.9:8:0.3, 90:1.1:6:0.1, 90:1:6:0.3 or 90:1.1:8: 0.2.
Preferably, in step (2), the mixing comprises stirring.
Preferably, the agitation mixing comprises dry homogenization and/or wet homogenization.
As a further preferable technical scheme of the preparation method, the method comprises the following steps:
(1) mixing a conductive polymer and a first solvent to obtain a first mixed glue solution, and mixing a binder and a second solvent to obtain a second mixed glue solution;
wherein the conductive polymer of step (1) comprises polyvinyl formal;
in the first mixed glue solution, the mass ratio of the conductive polymer to the first solvent is 1:100-15: 100;
in the second mixed glue solution in the step (1), the mass ratio of the binder to the second solvent is 3:100-9: l 00;
(2) mixing a cobalt-free anode material, a conductive agent, the first mixed glue solution and the second mixed glue solution in the step (1) to obtain cobalt-free anode slurry; wherein the mass ratio of the cobalt-free anode material, the conductive agent, the conductive polymer in the first mixed glue solution and the binder in the second mixed glue solution is 90 (0.9-1.1): 6-8): 0.1-0.3.
In a third aspect, the present invention provides a positive electrode sheet coated with the cobalt-free positive electrode slurry according to the first aspect.
In a fourth aspect, the present invention provides a lithium ion battery comprising the positive electrode sheet according to the third aspect.
Compared with the prior art, the invention has the following beneficial effects:
(1) according to the cobalt-free anode slurry provided by the invention, the polymer material with conductivity is added, so that the conductivity of the cobalt-free anode plate is improved, and the internal resistance of a battery cell is reduced; the conductive polymer has higher ionic conductivity, forms a 3D fast ionic conductor network structure, improves the power performance of the battery, and further improves the surface density of the positive pole piece, thereby improving the energy density of the battery; in addition, the weak acid environment on the surface of the polymer neutralizes the alkalinity on the surface of the cobalt-free material, so that the residual metal dissolution phenomenon is reduced, the self-discharge phenomenon of the battery is reduced, and the safety factor of the battery is further improved.
(2) The preparation method provided by the invention is simple and feasible, and has the advantage of low cost.
Detailed Description
In order to better illustrate the present invention and facilitate the understanding of the technical solutions of the present invention, the present invention is further described in detail below. The following examples are merely illustrative of the present invention and do not represent or limit the scope of the claims, which are defined by the claims.
The following are typical but non-limiting examples of the invention:
example 1
The present embodiment provides a cobalt-free cathode slurry, which is composed of a cobalt-free cathode material, a conductive agent, a binder, a conductive polymer, and a solvent.
The conductive polymer is polyvinyl formal, the cobalt-free positive electrode material is lithium nickelate (NMx), the binder is polyvinylidene fluoride, the conductive agent is carbon nano tubes and conductive carbon black (the mass ratio is 3:7), and the solvent is N-methyl pyrrolidone. The mass ratio of the cobalt-free anode material to the conductive agent to the conductive polymer to the binder is 93.8:1:5:0.2, and the solid content of the cobalt-free anode slurry is 70 percent
This example prepares a cobalt-free positive electrode slurry as follows:
(1) mixing a conductive polymer with a first solvent (N-methyl pyrrolidone) to obtain a first mixed glue solution, and mixing a binder with a second solvent (N-methyl pyrrolidone) to obtain a second mixed glue solution;
in the first mixed glue solution, the mass ratio of the conductive polymer to the first solvent is 7: 100;
in the second mixed glue solution in the step (1), the mass ratio of the binder to the second solvent is 6: l 00;
(2) and (2) stirring, mixing and homogenizing the cobalt-free anode material, the conductive agent, the first mixed glue solution and the second mixed glue solution in the step (1) according to the formula ratio to obtain the cobalt-free anode slurry. The mass ratio of the cobalt-free anode material to the conductive agent to the conductive polymer in the first mixed glue solution to the binder in the second mixed glue solution is 90:1:7: 0.2.
Example 2
The present embodiment provides a cobalt-free cathode slurry, which is composed of a cobalt-free cathode material, a conductive agent, a binder, a conductive polymer, and a solvent.
The conductive polymer is polyvinyl formal, the cobalt-free positive electrode material is lithium nickelate (NMx), the binder is polyvinylidene fluoride, the conductive agent is carbon nano tubes and conductive carbon black (the mass ratio is 4:6), and the solvent is N-methyl pyrrolidone. The mass ratio of the cobalt-free anode material to the conductive agent to the conductive polymer to the binder is 90:0.9:8:0.1, and the solid content of the cobalt-free anode slurry is 50%.
This example prepares a cobalt-free positive electrode slurry as follows:
(1) mixing a conductive polymer with a first solvent (N-methyl pyrrolidone) to obtain a first mixed glue solution, and mixing a binder with a second solvent (N-methyl pyrrolidone) to obtain a second mixed glue solution;
in the first mixed glue solution, the mass ratio of the conductive polymer to the first solvent is 1: 100;
in the second mixed glue solution in the step (1), the mass ratio of the binder to the second solvent is 3: l 00;
(2) and (2) stirring, mixing and homogenizing the cobalt-free anode material, the conductive agent, the first mixed glue solution and the second mixed glue solution in the step (1) according to the formula ratio to obtain the cobalt-free anode slurry. The mass ratio of the cobalt-free anode material, the conductive agent, the conductive polymer in the first mixed glue solution and the binder in the second mixed glue solution is 91:0.9:8: 0.1.
Example 3
The present embodiment provides a cobalt-free cathode slurry, which is composed of a cobalt-free cathode material, a conductive agent, a binder, a conductive polymer, and a solvent.
Wherein the conductive polymer is polyvinyl formal, and the cobalt-free anode material is lithium manganate (LiMnO)2) The adhesive is polyvinylidene fluoride, the conductive agent is carbon nano tube and conductive carbon black (mass ratio is 2:8), and the solvent is N-methyl pyrrolidone. The mass ratio of the cobalt-free anode material to the conductive agent to the conductive polymer to the binder is 90:1.1:6:0.3, and the solid content of the cobalt-free anode slurry is 80%.
This example prepares a cobalt-free positive electrode slurry as follows:
(1) mixing a conductive polymer with a first solvent (N-methyl pyrrolidone) to obtain a first mixed glue solution, and mixing a binder with a second solvent (N-methyl pyrrolidone) to obtain a second mixed glue solution;
in the first mixed glue solution, the mass ratio of the conductive polymer to the first solvent is 15: 100;
in the second mixed glue solution in the step (1), the mass ratio of the binder to the second solvent is 9: l 00;
(2) and (2) stirring, mixing and homogenizing the cobalt-free anode material, the conductive agent, the first mixed glue solution and the second mixed glue solution in the step (1) according to the formula ratio to obtain the cobalt-free anode slurry. The mass ratio of the cobalt-free positive electrode material, the conductive agent, the conductive polymer in the first mixed glue solution and the binder in the second mixed glue solution is 92. 6:1.1:6:0.3.
Example 4
This example is different from example 1 in that the conductive polymer in the cobalt-free cathode slurry is polyaniline.
Example 5
The present example is different from example 1 in that the mass ratio of the cobalt-free cathode material, the conductive agent, the conductive polymer, and the binder is 90:1:10: 0.2.
Example 6
The present example is different from example 1 in that the mass ratio of the cobalt-free cathode material, the conductive agent, the conductive polymer, and the binder is 94:1:3: 1.
Comparative example 1
This comparative example differs from example 1 in that the cobalt-free positive electrode slurry does not contain a conductive polymer.
The cobalt-free anode material, the conductive agent and the binder in the formula amount are mixed according to the mass ratio: 95:3:2, adding a proper amount of NMP, and uniformly stirring.
The test method comprises the following steps:
the cobalt-free positive electrode slurry provided in each example and comparative example was prepared into a positive electrode sheet as follows: coating the slurry on aluminum foil, baking at 60 deg.C under vacuum, rolling, and cutting into pole pieces with appropriate size and surface density of 4mg/cm2。
Mixing the prepared positive plate with a negative electrode (lithium plate), a diaphragm (PP diaphragm) and electrolyte (1mol/L LiPF)6Test cells were assembled with/EC + DMC + EMC (v/v ═ 1:1:1)) and subjected to electrochemical testing. The first discharge capacity, the first coulombic efficiency, the capacity retention rate after 100 cycles and the alternating current resistance (DCR) after 100 cycles of the battery were measured under the above-mentioned charging and discharging conditions of 0.2C, and table 1 is shown below.
The test results are shown in the following table:
TABLE 1
It can be known from the above examples and comparative examples that the cobalt-free positive electrode slurry provided in examples 1 to 4 improves the conductivity of the cobalt-free positive electrode plate and reduces the internal resistance of the cell by adding the polymer material with conductivity; the conductive polymer has higher ionic conductivity, forms a 3D fast ionic conductor network structure, improves the power performance of the battery, and further improves the surface density of the positive pole piece, thereby improving the energy density of the battery; in addition, the weak acid environment on the surface of the polymer neutralizes the alkalinity on the surface of the cobalt-free material, so that the residual metal dissolution phenomenon is reduced, the self-discharge phenomenon of the battery is reduced, and the safety factor of the battery is further improved.
However, polyaniline, which has better conductivity than polyvinyl formal, was used in example 4; however, polyaniline is not the most preferred material in this application due to the fact that the energy of polyaniline HUMO is better than that of polyvinyl formal, which means that polyaniline is more easily oxidized and decomposed.
The conductive polymer of example 5 was too much in the slurry, resulting in poor battery performance, probably because the conductive polymer was more and easy to agglomerate, resulting in uneven conductivity of the electrode sheet.
The conductive polymer of example 6 was too little in the slurry, resulting in a lower capacity retention of the pole piece, which may be caused by non-uniformity of the conductive network.
Comparative example 1 the capacity retention of the positive electrode material and the DCR values were inferior to those of the examples because no conductive polymer was used.
The applicant states that the present invention is illustrated in detail by the above examples, but the present invention is not limited to the above detailed methods, i.e. it is not meant that the present invention must rely on the above detailed methods for its implementation. It should be understood by those skilled in the art that any modification of the present invention, equivalent substitutions of the raw materials of the product of the present invention, addition of auxiliary components, selection of specific modes, etc., are within the scope and disclosure of the present invention.
Claims (10)
1. The cobalt-free cathode slurry is characterized by comprising a cobalt-free cathode material, a conductive agent, a binder, a conductive polymer and a solvent.
2. The cobalt-free cathode slurry according to claim 1, wherein the conductive polymer is a single-chain polymer;
preferably, the conductive polymer comprises any one of polyvinyl formal, polyaniline, polyacrylate, polyimide, polyacrylonitrile, polysilicone or polyethylene oxide resin or a combination of at least two of the polyvinyl formal, the polyaniline, the polyacrylate, the polyimide, the polypropylene cyanide, the polysiloxane and the polyethylene oxide resin;
preferably, the solvent is an organic solvent;
preferably, the organic solvent comprises any one of N-methyl pyrrolidone, dimethyl sulfoxide, acetone or ethylene glycol or a combination of at least two of the above;
preferably, the binder comprises polyvinylidene fluoride and/or sodium carboxymethylcellulose;
preferably, the cobalt-free cathode material comprises any one of lithium nickel manganese oxide, lithium iron phosphate, lithium manganese oxide or lithium nickel oxide or a combination of at least two of the lithium nickel manganese oxide, the lithium iron phosphate, the lithium manganese oxide or the lithium nickel oxide.
3. The cobalt-free cathode slurry according to claim 1 or 2, wherein the conductive agent comprises any one of or a combination of at least two of carbon nanotubes, conductive carbon black, or graphene;
preferably, the conductive agent is a combination of carbon nanotubes and conductive carbon black;
preferably, in the combination of the conductive carbon black and the carbon nano tubes, the mass ratio of the conductive carbon black to the carbon nano tubes is 6:4-8: 2.
4. The cobalt-free cathode slurry according to any one of claims 1 to 3, wherein the mass ratio of the cobalt-free cathode material, the conductive agent, the conductive polymer and the binder is 90 (0.9-1.1): 6-8: 0.1-0.3;
preferably, the cobalt-free cathode slurry has a solid content of 50-80%, preferably 68-72%.
5. A method of preparing a cobalt-free positive electrode slurry according to any one of claims 1 to 4, comprising the steps of:
(1) mixing a conductive polymer and a first solvent to obtain a first mixed glue solution, and mixing a binder and a second solvent to obtain a second mixed glue solution;
(2) and (2) mixing a cobalt-free anode material, a conductive agent, the first mixed glue solution and the second mixed glue solution in the step (1) to obtain the cobalt-free anode slurry.
6. The method according to claim 5, wherein the first solvent of step (1) comprises any one or a combination of at least two of N-methylpyrrolidone, acetone, ethanol, dimethyl sulfoxide, or dichloroethane;
preferably, in the first mixed glue solution in the step (1), the mass ratio of the conductive polymer to the first solvent is 1:100-15: 100;
preferably, the second solvent in step (1) comprises any one or a combination of at least two of N-methylpyrrolidone, dichloroethane or dimethyl sulfoxide;
preferably, in the second mixed glue solution in the step (1), the mass ratio of the binder to the second solvent is 3:100-9: l 00.
7. The method as claimed in claim 5 or 6, wherein in the step (2), the mass ratio of the cobalt-free cathode material, the conductive agent, the conductive polymer in the first mixed glue solution and the binder in the second mixed glue solution is 90 (0.9-1.1): 6-8): 0.1-0.3;
preferably, in step (2), the mixing comprises stirring;
preferably, the agitation mixing comprises dry homogenization and/or wet homogenization.
8. Method according to any of claims 5-7, characterized in that the method comprises the steps of:
(1) mixing a conductive polymer and a first solvent to obtain a first mixed glue solution, and mixing a binder and a second solvent to obtain a second mixed glue solution;
wherein the conductive polymer of step (1) comprises polyvinyl formal;
in the first mixed glue solution, the mass ratio of the conductive polymer to the first solvent is 1:100-15: 100;
in the second mixed glue solution in the step (1), the mass ratio of the binder to the second solvent is 3:100-9: l 00;
(2) mixing a cobalt-free anode material, a conductive agent, the first mixed glue solution and the second mixed glue solution in the step (1) to obtain cobalt-free anode slurry; wherein the mass ratio of the cobalt-free anode material, the conductive agent, the conductive polymer in the first mixed glue solution and the binder in the second mixed glue solution is 90 (0.9-1.1): 6-8): 0.1-0.3.
9. A positive electrode sheet, characterized in that the cobalt-free positive electrode slurry according to claims 1 to 4 is coated on the positive electrode sheet.
10. A lithium ion battery, characterized in that it comprises the positive electrode sheet according to claim 9.
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