CN114284471A - Negative pole piece and preparation method and application thereof - Google Patents
Negative pole piece and preparation method and application thereof Download PDFInfo
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- 125000002887 hydroxy group Chemical group [H]O* 0.000 claims abstract description 36
- 239000005416 organic matter Substances 0.000 claims abstract description 33
- DPXJVFZANSGRMM-UHFFFAOYSA-N acetic acid;2,3,4,5,6-pentahydroxyhexanal;sodium Chemical compound [Na].CC(O)=O.OCC(O)C(O)C(O)C(O)C=O DPXJVFZANSGRMM-UHFFFAOYSA-N 0.000 claims abstract description 29
- 229920005989 resin Polymers 0.000 claims abstract description 28
- 239000011347 resin Substances 0.000 claims abstract description 28
- 235000019812 sodium carboxymethyl cellulose Nutrition 0.000 claims abstract description 28
- 229920001027 sodium carboxymethylcellulose Polymers 0.000 claims abstract description 28
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 22
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- 239000000126 substance Substances 0.000 claims abstract description 8
- 239000010410 layer Substances 0.000 claims description 44
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- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 claims description 10
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- 238000010438 heat treatment Methods 0.000 claims description 8
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- 230000000052 comparative effect Effects 0.000 description 12
- KXGFMDJXCMQABM-UHFFFAOYSA-N 2-methoxy-6-methylphenol Chemical compound [CH]OC1=CC=CC([CH])=C1O KXGFMDJXCMQABM-UHFFFAOYSA-N 0.000 description 9
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- ISWSIDIOOBJBQZ-UHFFFAOYSA-N phenol group Polymers C1(=CC=CC=C1)O ISWSIDIOOBJBQZ-UHFFFAOYSA-N 0.000 description 4
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- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 2
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- GELKBWJHTRAYNV-UHFFFAOYSA-K lithium iron phosphate Chemical compound [Li+].[Fe+2].[O-]P([O-])([O-])=O GELKBWJHTRAYNV-UHFFFAOYSA-K 0.000 description 2
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Images
Abstract
The invention provides a negative pole piece and a preparation method and application thereof. The negative pole piece comprises a negative current collector and an electrode layer; in the negative current collector, an organic matter layer is arranged on the surface of one side close to the electrode layer, and the organic matter comprises a resin organic matter containing hydroxyl; the electrode layer comprises graphite, a conductive agent and sodium carboxymethyl cellulose. According to the invention, the resin organic matter containing hydroxyl is arranged on the surface of the negative current collector, the carboxyl in the sodium carboxymethyl cellulose and the hydroxyl in the resin form a chemical bond, so that the binding power is enhanced, and a styrene butadiene rubber binder is not required to be added, so that the mass ratio of a conductive agent to the binder in a negative electrode layer is reduced, the problem that a negative electrode plate is easy to fall off powder is effectively solved, and the high energy density and the good rapid charging cycle performance of a battery cell are ensured.
Description
Technical Field
The invention belongs to the technical field of lithium ion batteries, and relates to a negative pole piece and a preparation method and application thereof.
Background
The lithium ion battery has the advantages of high energy density, long cycle life, low self-discharge rate, no memory effect and the like, and becomes a main energy storage element of a pure electric automobile. However, the charging speed of the lithium ion battery is slow, the charging time of several hours is required in the general charging procedure, which causes inconvenience to the use of pure electric vehicles, mobile phones, and the like, and in order to increase the charging speed of the lithium ion battery, it becomes important to develop a new fast charging material and an advanced pole piece manufacturing process.
Since the solid phase diffusion coefficient of lithium in graphite is relatively small (usually only about 10)-10cm2/s) which facilitates solid phase diffusion of lithium within the graphite as a control step for the overall electrode reaction. The diffusion path of lithium ions is often reduced by reducing the particle size of the negative electrode material graphite and improving the granulation degree of the negative electrode material graphite, so that the diffusion resistance of the lithium ions is reduced, and the quick charging performance of the battery is improved.
The graphite has larger particle size, so that the diffusion time is longer, and the quick charge performance of the graphite is influenced, while when the particle size of the graphite is reduced, the specific surface area is overlarge, so that the dispersant-grade adhesive is excessively consumed among particles, and the peeling strength between the particles and a foil is influenced.
CN102185130A discloses a lithium ion battery cathode batching method, which comprises weighing graphite, CMC, SBR latex and deionized water according to a certain proportion; adding a part of graphite into CMC for premixing treatment, wherein the weight of the premixed graphite is 2-3 times that of the CMC; adding deionized water into a vacuum stirring barrel, starting autorotation, gradually adding the pretreated mixed powder of CMC and graphite, stopping autorotation after no powder exists, vacuumizing, starting revolution and autorotation, and stirring; and (3) adding the rest graphite into a vacuum stirring barrel step by step, starting revolution and rotation, stopping stirring after no powder exists, vacuumizing, and starting revolution and rotation. However, the adhesive system in the document has a too high addition ratio, and reduces the capacity of the negative electrode plate, so that the energy density of the battery cell is integrally low.
CN104600318A discloses a modified CMC and a gel battery thereof, and the invention provides the application of the modified CMC in improving the bonding strength of a cathode and a diaphragm of a water system gel battery; the gel battery provided by the invention comprises a positive electrode, a negative electrode, a diaphragm and electrolyte, wherein in the preparation of the negative electrode, the used binder is the combination of modified CMC and SBR, and the solvent is deionized water. But the powder may detach from the foil at the end of the cycle.
Therefore, how to effectively solve the problem of powder falling of the negative pole piece and ensure the electrochemical performance of the negative pole piece is a technical problem to be solved urgently.
Disclosure of Invention
The invention aims to provide a negative pole piece and a preparation method and application thereof. According to the invention, the resin organic matter containing hydroxyl is arranged on the surface of the negative current collector, the carboxyl in the sodium carboxymethyl cellulose and the hydroxyl in the resin form a chemical bond, so that the binding power is enhanced, and a styrene butadiene rubber binder is not required to be added, so that the mass ratio of a conductive agent to the binder in a negative electrode layer is reduced, the problem that a negative electrode plate is easy to fall off powder is effectively solved, and the high energy density and the good rapid charging cycle performance of a battery cell are ensured.
In order to achieve the purpose, the invention adopts the following technical scheme:
in a first aspect, the present invention provides a negative electrode plate, comprising a negative current collector and an electrode layer; in the negative current collector, an organic matter layer is arranged on the surface of one side close to the electrode layer, and the organic matter comprises a resin organic matter containing hydroxyl; the electrode layer comprises graphite, a conductive agent and sodium carboxymethyl cellulose.
In the invention, the electrode layer can be arranged on one side of the current collector, and can also be arranged on two sides of the current collector, namely, as long as the electrode layer is arranged, namely, the organic matter layer of the hydroxyl-containing resin organic matter is arranged on the corresponding position of the current collector.
In the present invention, the hydroxyl-containing organic resin is suitable, and includes, but is not limited to, conventional straight-chain phenolic resins, epoxy phenolic resins, polyvinyl alcohol phenolic resins, polyamide-modified phenolic resins, dicyandiamide-modified phenolic resins, epoxy-modified phenolic resins, polyvinyl acetal-modified phenolic resins, and the like.
According to the invention, the resin organic matter containing hydroxyl is arranged on the surface of the negative current collector, the carboxyl in the sodium carboxymethyl cellulose and the hydroxyl in the resin form a chemical bond, so that the binding power is enhanced, and a styrene butadiene rubber binder is not required to be added, so that the mass ratio of a conductive agent to the binder in a negative electrode layer is reduced, the problem that a negative electrode plate is easy to fall off powder is effectively solved, and the high energy density and the good rapid charging cycle performance of a battery cell are ensured.
Compared with the conventional collocation of styrene butadiene rubber and carboxymethyl cellulose (CMC), the negative pole piece provided by the invention has the advantages of higher peel strength and higher mass ratio of main materials.
In the invention, the surface of the current collector of the negative pole piece is not provided with the organic layer, so that the pole piece can not fall off when the particle size of the negative pole is too small.
Preferably, the organic layer has a thickness of 0.5 to 2 μm, such as 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.7 μm, 1.8 μm, 1.9 μm, 2 μm, or the like.
In the invention, the organic layer is too thin to facilitate the adhesion of the material layer and the foil, and the pole piece resistance is too high due to too thick organic layer.
Preferably, the hydroxyl group-containing resin organic is a thermoplastic resin.
In the present invention, the thermoplastic resin is selected to achieve softening at high temperatures.
Preferably, the graphite has a median particle diameter of 5 to 8 μm, such as 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm, or 8 μm.
Preferably, the total mass of the conductive agent and the sodium carboxymethyl cellulose is 1.2-2.5% of the mass of the electrode layer, such as 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, and the like.
In the invention, the total mass of the conductive agent and the sodium carboxymethyl cellulose is too small, so that the adhesion between a material layer and a foil is difficult to realize, and the energy density is reduced due to too large mass.
Preferably, the mass ratio of the conductive agent to the sodium carboxymethyl cellulose is 1 (1-2), such as 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5, 1:1.6, 1:1.7, 1:1.8, 1:1.9, or 1: 2.
In the invention, excessive conductive agent in the conductive agent and the sodium carboxymethyl cellulose is not beneficial to the adhesion of a material layer and a foil material, and too little conductive agent can cause poor conductivity of a pole piece and increase of resistance of the pole piece
In a second aspect, the present invention provides a method for preparing a negative electrode plate according to the first aspect, where the method for preparing the negative electrode plate includes:
coating a liquid resin organic matter containing hydroxyl on the surface of a negative current collector to obtain a current collector with an organic matter layer arranged on the surface, and coating negative slurry on the surface of the organic matter layer to obtain a negative pole piece;
the negative electrode slurry comprises graphite, a conductive agent, a solvent and sodium carboxymethyl cellulose.
Preferably, the preparation method of the liquid hydroxyl-containing resinous organic substance comprises:
and carrying out heat treatment on the resin organic matter containing hydroxyl groups to obtain the liquid resin organic matter containing hydroxyl groups.
In the present invention, softening of the resin is achieved by heat treatment.
Preferably, the temperature of the heat treatment is 150 to 500 ℃, for example, 150 ℃, 200 ℃, 250 ℃, 300 ℃, 350 ℃, 400 ℃, 450 ℃ or 500 ℃.
In a third aspect, the present invention provides a lithium ion battery, including the negative electrode tab according to the first aspect.
Compared with the prior art, the invention has the following beneficial effects:
according to the invention, the resin organic matter containing hydroxyl is arranged on the surface of the negative current collector, the carboxyl in the sodium carboxymethyl cellulose and the hydroxyl in the resin form a chemical bond, so that the binding power is enhanced, and a styrene butadiene rubber binder is not required to be added, so that the mass ratio of a conductive agent to the binder in a negative electrode layer is reduced, the problem that a negative electrode plate is easy to fall off powder is effectively solved, and the high energy density and the good rapid charging cycle performance of a battery cell are ensured. The stripping force of the negative pole piece provided by the invention is more than 0.28N, the energy density of the battery provided by the invention can reach more than 172.4Wh/kg, the charging is carried out according to the processes of 5C-30%, 4.5C-50%, 4C-60%, 3.5C-70%, 3C-80% and 0.5C-100%, and the capacity retention rate can reach more than 80.9% after 1000 cycles under the mechanism of 1C-100% discharging.
Drawings
Fig. 1 is an SEM image of the artificial graphite in example 1.
Fig. 2 is a graph of the rapid charge cycle performance of the battery provided in example 1.
Fig. 3 is a negative electrode tab of the battery after the charge-discharge test in example 1.
Fig. 4 is a negative electrode tab of the battery after the charge-discharge test in comparative example 2.
Detailed Description
The technical solution of the present invention is further explained by the following embodiments. It should be understood by those skilled in the art that the examples are only for the understanding of the present invention and should not be construed as the specific limitations of the present invention.
Example 1
The embodiment provides a negative pole piece, which comprises a copper foil and an electrode layer, wherein an organic matter layer with the thickness of 1 micrometer is arranged on the surface of one side, close to the electrode layer, of the copper foil, and the organic matter is linear phenolic resin containing hydroxyl; the electrode layer is composed of artificial graphite (with a median particle size of 5.5 μm as shown in fig. 1), conductive carbon black and sodium carboxymethyl cellulose (CMC);
the total mass of the conductive carbon black and the sodium carboxymethyl cellulose is 2% of the mass of the electrode layer, and the mass ratio of the conductive carbon black to the sodium carboxymethyl cellulose is 1:1.
The preparation method of the negative pole piece comprises the following steps:
carrying out heat treatment on the linear phenolic resin containing hydroxyl at the temperature of 200 ℃ to obtain liquid thermoplastic phenolic resin containing hydroxyl, coating the liquid thermoplastic phenolic resin containing hydroxyl on the surface of copper foil, cooling to be solid, coating the negative electrode slurry on the surface of resin, drying and rolling to obtain the negative electrode plate;
the preparation method of the anode slurry comprises the following steps:
mixing artificial graphite, conductive carbon black and CMC (the mass ratio of the artificial graphite to the conductive carbon black to the CMC is 98:1:1), adding water, and homogenizing to obtain negative electrode slurry with the solid content of 55%.
Fig. 2 shows a diagram of the quick charge cycle performance of the battery provided in example 1, and it can be seen from fig. 2 that after the particle size of graphite is reduced and the quick charge capacity is increased, the quick charge cycle life of the battery can reach more than 2000 times, and the phenomenon of rapid attenuation caused by powder falling in the cycle process does not occur.
Example 2
The embodiment provides a negative electrode plate, which comprises a copper foil and an electrode layer, wherein an organic matter layer with the thickness of 0.5 μm is arranged on the surface of one side, close to the electrode layer, of the copper foil, and the organic matter is epoxy type phenolic resin containing hydroxyl; the electrode layer is composed of artificial graphite (with a median particle size of 6.3 μm), conductive carbon black and sodium carboxymethyl cellulose (CMC);
the total mass of the conductive carbon black and the sodium carboxymethyl cellulose is 1.2 percent of the mass of the electrode layer, and the mass ratio of the conductive carbon black to the sodium carboxymethyl cellulose is 1: 2.
The preparation method of the negative pole piece comprises the following steps:
carrying out heat treatment on the epoxy phenolic resin containing hydroxyl at 300 ℃ to obtain liquid thermoplastic phenolic resin containing hydroxyl, coating the liquid thermoplastic phenolic resin containing hydroxyl on the surface of copper foil, cooling to be solid, coating the negative electrode slurry on the surface of resin, drying and rolling to obtain the negative electrode plate;
the preparation method of the anode slurry comprises the following steps:
mixing artificial graphite, conductive carbon black and CMC (the mass ratio of the artificial graphite to the conductive carbon black to the CMC is 98.8:0.4:0.8), adding water, and homogenizing to obtain negative electrode slurry with the solid content of 55%.
Example 3
The embodiment provides a negative pole piece, which comprises a copper foil and an electrode layer, wherein an organic matter layer with the thickness of 2 micrometers is arranged on the surface of one side, close to the electrode layer, of the copper foil, and the organic matter is polyurethane resin; the electrode layer is composed of artificial graphite (the median particle size is 8 mu m), conductive carbon black and sodium carboxymethyl cellulose (CMC);
the total mass of the conductive carbon black and the sodium carboxymethyl cellulose is 2.5 percent of the mass of the electrode layer, and the mass ratio of the conductive carbon black to the sodium carboxymethyl cellulose is 1: 1.5.
The preparation method of the negative pole piece comprises the following steps:
carrying out heat treatment on the hydroxyl-containing polyurethane resin at 250 ℃ to obtain liquid hydroxyl-containing thermoplastic phenolic resin, coating the liquid hydroxyl-containing thermoplastic phenolic resin on the surface of copper foil, cooling to be solid, coating the negative electrode slurry on the surface of the resin, and drying and rolling to obtain the negative electrode plate;
the preparation method of the anode slurry comprises the following steps:
mixing artificial graphite, conductive carbon black and CMC (the mass ratio of the artificial graphite to the conductive carbon black to the CMC is 97.5:1:1.5), adding water, and homogenizing to obtain negative electrode slurry with the solid content of 55%.
Example 4
The present example is different from example 1 in that the thickness of the organic layer in the present example is 3 μm.
The remaining preparation methods and parameters were in accordance with example 1.
Example 5
The difference between the embodiment 1 and the embodiment 1 is that the total mass of the conductive carbon black and the sodium carboxymethyl cellulose is 1% of the mass of the electrode layer, and the mass ratio of the artificial graphite, the conductive carbon black and the CMC in the negative electrode slurry is 99:0.5: 0.5.
The remaining preparation methods and parameters were in accordance with example 1.
Example 6
The difference between the embodiment 1 and the embodiment 1 is that the total mass of the conductive carbon black and the sodium carboxymethyl cellulose is 3% of the mass of the electrode layer, and the mass ratio of the artificial graphite, the conductive carbon black and the CMC in the negative electrode slurry is 97:1.5: 1.5.
The remaining preparation methods and parameters were in accordance with example 1.
Comparative example 1
The comparative example is different from example 1 in that the comparative example does not contain an organic layer, and the negative electrode slurry is directly coated on the surface of the copper foil in the preparation method.
The remaining preparation methods and parameters were in accordance with example 1.
Comparative example 2
The negative pole piece comprises a copper foil and an electrode layer positioned on the surface of the copper foil, wherein the electrode layer is composed of artificial graphite (the median particle size is 5.5 mu m), conductive carbon black styrene-butadiene rubber and sodium carboxymethylcellulose (CMC).
The preparation method of the negative pole piece comprises the following steps:
coating negative electrode slurry on the surface of the copper foil, and drying and rolling to obtain the negative electrode piece;
the preparation method of the anode slurry comprises the following steps:
mixing artificial graphite, conductive carbon black, CMC and SBR according to the mass ratio of 97:1:1:1, adding water, and homogenizing to obtain negative electrode slurry with the solid content of 53%.
Fig. 3 shows the negative electrode sheet of the battery after the charge-discharge test in example 1; fig. 4 shows the negative electrode plate of the battery after the charge and discharge test in the comparative example 2, and it can be seen from the comparison between fig. 3 and fig. 4 that the negative electrode plate provided by the present invention has no powder falling phenomenon during the charge and discharge processes of the battery, while the negative electrode plate provided by the comparative example 2 has an obvious powder falling phenomenon as shown by the circle in fig. 4, so that the negative electrode plate provided by the present invention solves the problem that the small-particle-size fast-charging graphite negative electrode plate is easy to fall powder.
And (3) assembling the lithium iron phosphate positive plate as a negative electrode and the lithium iron phosphate positive plate as a positive electrode to obtain the battery by taking the examples 1-6 and the comparative examples 1-2 as negative electrodes.
Electrochemical performance tests were performed on the batteries provided in examples 1-6 and comparative examples 1-2 under the following test conditions:
the battery is charged according to the processes of 5C-30%, 4.5C-50%, 4C-60%, 3.5C-70%, 3C-80% and 0.5C-100%, and discharged according to 1C-100%, and the cycle is cycled according to the rapid charging system to obtain a cycle curve diagram, wherein a table 1 shows the stripping force of the negative pole piece, the rapid charging cycle performance (1000-cycle capacity retention rate) and the energy density of the battery.
TABLE 1
Remarking: comparative example 1 could not form a battery, so the energy density and the fast charge cycle performance could not be quantified;
from the data results of example 1 and example 4, it is understood that when the thickness of the organic material layer is too large, the sheet resistance is too large, which is not favorable for rapid charging, and the energy density is reduced.
From the data results of example 1 and examples 5 and 6, it is understood that the sum of the mass of the conductive carbon black and the carboxymethyl cellulose sodium is too small, the peeling force is low, and too large, which in turn causes a decrease in the energy density.
From the data results of the example 1 and the comparative example 1, it can be seen that the formation of chemical bonds can not be realized without adding an organic layer, resulting in low peeling force, serious powder dropping, and failure to obtain a normally usable negative electrode plate.
From the data results of the example 1 and the comparative example 2, it can be known that, compared with the battery prepared by the conventional graphite negative pole piece, the battery provided by the invention has both high energy density and quick charging performance.
In conclusion, the resin organic matter containing hydroxyl is arranged on the surface of the negative current collector, the carboxyl in the sodium carboxymethyl cellulose and the hydroxyl in the resin form a chemical bond, the binding power is enhanced, a styrene butadiene rubber binder is not required to be added, the mass ratio of the conductive agent to the binder in the negative electrode layer is reduced, the problem that the negative electrode pole piece is easy to fall off powder is effectively solved, and meanwhile, the high energy density and the good rapid charging cycle performance of the battery cell are ensured. The stripping force of the negative pole piece provided by the invention is more than 0.28N, the energy density of the battery provided by the invention can reach more than 172.4Wh/kg, the charging is carried out according to the processes of 5C-30%, 4.5C-50%, 4C-60%, 3.5C-70%, 3C-80% and 0.5C-100%, and the capacity retention rate can reach more than 80.9% after 1000 cycles under the mechanism of 1C-100% discharging.
The applicant declares that the above description is only a specific embodiment of the present invention, but the scope of the present invention is not limited thereto, and it should be understood by those skilled in the art that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are within the scope and disclosure of the present invention.
Claims (10)
1. The negative pole piece is characterized by comprising a negative pole current collector and an electrode layer; in the negative current collector, an organic matter layer is arranged on the surface of one side close to the electrode layer, and the organic matter comprises a resin organic matter containing hydroxyl; the electrode layer comprises graphite, a conductive agent and sodium carboxymethyl cellulose.
2. The negative electrode plate as claimed in claim 1, wherein the organic layer has a thickness of 0.5-2 μm.
3. The negative electrode tab according to claim 1 or 2, wherein the hydroxyl group-containing resin organic substance is a thermoplastic resin.
4. The negative electrode plate as claimed in any one of claims 1 to 3, wherein the graphite has a median particle diameter of 5 to 8 μm.
5. The negative electrode plate as claimed in any one of claims 1 to 4, wherein the total mass of the conductive agent and the sodium carboxymethyl cellulose is 1.2 to 2.5% of the mass of the electrode layer.
6. The negative electrode plate as claimed in any one of claims 1 to 5, wherein the mass ratio of the conductive agent to the sodium carboxymethyl cellulose is 1 (1-2).
7. The preparation method of the negative electrode plate as claimed in any one of claims 1 to 6, wherein the preparation method comprises the following steps:
coating a liquid resin organic matter containing hydroxyl on the surface of a negative current collector to obtain a current collector with an organic matter layer arranged on the surface, and coating negative slurry on the surface of the organic matter layer to obtain a negative pole piece;
the negative electrode slurry comprises graphite, a conductive agent, a solvent and sodium carboxymethyl cellulose.
8. The method for preparing the negative electrode plate of claim 7, wherein the method for preparing the liquid hydroxyl-containing resin organic matter comprises the following steps:
and carrying out heat treatment on the resin organic matter containing hydroxyl groups to obtain the liquid resin organic matter containing hydroxyl groups.
9. The preparation method of the negative electrode plate according to claim 8, wherein the temperature of the heat treatment is 150-500 ℃.
10. A lithium ion battery, characterized in that the lithium ion battery comprises the negative electrode plate of any one of claims 1 to 6.
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| CN202111590973.1A CN114284471A (en) | 2021-12-23 | 2021-12-23 | Negative pole piece and preparation method and application thereof |
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| CN202111590973.1A CN114284471A (en) | 2021-12-23 | 2021-12-23 | Negative pole piece and preparation method and application thereof |
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Cited By (1)
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