Dry electrode binder, preparation method therefor, and use thereof

Abstract

The present application belongs to the technical field of lithium-ion batteries, and particularly relates to a dry electrode binder, a preparation method therefor, and a use thereof. The dry electrode binder comprises a bonding layer and a coating layer coated on a surface of the bonding layer. A bonding material used in the bonding layer comprises at least one of surface-modified polyvinylidene fluoride, gelatin, and polytetrafluoroethylene, the surface of the bonding material containing at least one of the elements oxygen, nitrogen, or hydrogen. A carbon material is used for the coating layer. By means of the foregoing improvements, the surface-modified polytetrafluoroethylene is more easily wetted by an electrolyte, and the carbon material wrapping the polytetrafluoroethylene can passivate the surface thereof, preventing irreversible decomposition of the polytetrafluoroethylene during charging and discharging, and maintaining the bonding effect, which is beneficial for improving battery cycling performance and increasing the initial Coulombic efficiency. Polytetrafluoroethylene tends to fibrillate under shear force, and the surface-modified polytetrafluoroethylene reduces the adverse effects of fibrillation on the carbon material coating effect, thereby effectively preventing the problem of increased electrode sheet impedance after polytetrafluoroethylene fibrillation.

Description

Dry-process electrode binder, preparation method and application thereof TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium ion batteries, in particular to a dry-process electrode binder, a preparation method and application thereof. BACKGROUND

[0002] It is known that the lithium ion battery process is generally prepared by a wet process; in the wet process, an organic solvent is prepared into a slurry and then coated and baked into an electrode sheet, but the baking and recovery of the organic solvent have huge cost consumption; and the use of the organic solvent can cause serious pollution to the environment; therefore, compared with the wet electrode, the dry electrode has more considerable application prospect and economic benefit.

[0003] The existing dry-process electrode preparation process is to mix the active material, the conductive agent and the fiberizable binder to form a self-supporting film after fiberization and rolling, and then to be combined with the current collector to finally form a dry-process electrode sheet; in the preparation process of the dry-process electrode sheet, the binder needs to go through the steps of mixing and fiberization, and the adhesion performance of the binder may be poor due to instability in the preparation process; although the proportion of the binder in the electrode is very small, the binder plays an important role in maintaining the stability of the electrode structure, and the instability of the adhesion effect can seriously affect the cycle stability of the battery and reduce the capacity of the battery; therefore, it is necessary to provide an improved binder which can better improve the performance of the battery when applied to the battery. TECHNICAL SOLUTION

[0004] The present application provides a dry-process electrode binder, a preparation method and application thereof to improve the performance of the battery.

[0005] To achieve the above-mentioned purpose, the first aspect of the present application provides a dry-process electrode binder, comprising a binder layer and a coating layer coated on the surface of the binder layer.

[0006] The binder layer is a binder material, and the binder material comprises at least one of surface-modified polyvinylidene fluoride, gelatin and polytetrafluoroethylene, and the binder material contains at least one of oxygen, nitrogen and hydrogen elements on the surface.

[0007] The coating layer is a carbon material.

[0008] In some embodiments, the content of the coating layer is 0.1% to 5% based on the total mass of the dry-process electrode binder being 100%.

[0009] In some embodiments, the content of the coating layer is 2% to 5%.

[0010] In some embodiments, the binder material is surface-modified polytetrafluoroethylene; the content of fluorine element in the surface-modified polytetrafluoroethylene is denoted as F, the mass content of oxygen element is denoted as O, the mass content of carbon element is denoted as C, and the mass content of nitrogen element is denoted as N; wherein 1.1≤F / C≤1.6, and 0.1≤(O+N) / C≤0.25.

[0011] In some embodiments, the carbon material includes at least one of conductive carbon black and graphite.

[0012] In some embodiments, the pH value of the carbon material is in the range of 3-5.

[0013] In some embodiments, the coating layer is obtained by mixing the carbon material with the binder material and then ball milling.

[0014] The second aspect of the present application proposes a preparation method of a dry electrode binder, including the following steps:

[0015] The binder is subjected to plasma treatment to obtain a surface-modified binder.

[0016] The surface-modified binder is mixed with a carbon material as a binder layer and subjected to ball milling, so that the carbon material is coated on the surface of the binder layer to form a coating layer, thereby obtaining a dry electrode binder.

[0017] In some embodiments, the content of the coating layer is 2%-5% based on the total mass of the dry electrode binder; the carbon material includes at least one of conductive carbon black and graphite; and the binder includes at least one of polyvinylidene fluoride, gelatin, and polytetrafluoroethylene.

[0018] In some embodiments, the step of subjecting the binder to plasma treatment to obtain a surface-modified binder includes:

[0019] The binder is placed in a plasma treatment chamber.

[0020] At least one of oxygen, nitrogen, and hydrogen is injected into the plasma treatment chamber to react with the surface of the binder for 1-5 minutes.

[0021] The third aspect of the present application proposes a dry electrode sheet, which includes the above-mentioned dry electrode binder or the dry electrode binder prepared according to the above-mentioned preparation method of a dry electrode binder.

[0022] The fourth aspect of the present application proposes a lithium ion battery, which includes the above-mentioned dry electrode sheet.

[0023] Compared with the prior art, the present application has the following beneficial effects:

[0024] The dry-process electrode binder provided by the application comprises a bonding layer and a coating layer coated on the surface of the bonding layer, the bonding layer uses a bonding material, and the bonding material comprises at least one of surface-modified polyvinylidene difluoride (PVDF), gelatin and polytetrafluoroethylene (PTFE); the coating layer uses a carbon material; wherein the hydrophilicity of the PTFE can be improved and the surface tension can be increased through surface modification; the surface-modified PTFE is more easily infiltrated by electrolyte, the surface of the PTFE can be passivated by wrapping the PTFE with the carbon material, thereby preventing the irreversible consumption of Li ions by the PTFE during the charging and discharging process, inhibiting the continuous decomposition of the PTFE, stably maintaining the adhesion effect of the PTFE, and being beneficial to improving the cycle performance and the initial coulomb efficiency of the dry-process battery; the surface-modified PTFE also improves the adhesion to the carbon material; the PTFE will fibrillate under a huge shear force during the preparation of the dry-process battery, the surface-modified PTFE can further improve the coating effect of the carbon material on the PTFE, weaken the adverse effects of fibrillation on the coating effect, and effectively avoid the problem that the contact resistance between active particles increases after the PTFE fibrillates, thereby causing the impedance of the pole piece to be too high.

[0025] DETAILED DESCRIPTION

[0026] The technical solutions in the embodiments of the application will be clearly and completely described below. Obviously, the described embodiments are only some of the embodiments of the application but not all the embodiments. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the application.

[0027] The embodiments of the application provide a dry-process electrode binder, which comprises a bonding layer and a coating layer coated on the surface of the bonding layer.

[0028] The bonding layer is a bonding material, and the bonding material comprises at least one of surface-modified polyvinylidene difluoride, gelatin and polytetrafluoroethylene, and the bonding material contains at least one of oxygen, nitrogen and hydrogen elements on the surface.

[0029] The coating layer is a carbon material.

[0030] In some embodiments, the content of the coating layer is 0.1% to 5% based on 100% of the total mass of the dry-process electrode binder.

[0031] In some embodiments, the content of the coating layer is 2% to 5%; if the content of the coating layer is too small, the carbon material is not enough to coat the binder material, which will result in poor electrolyte wettability of the prepared negative electrode sheet and low conductivity, and the battery rate performance will decrease; if the content of the coating layer is too high, it will result in an excessively thick coating layer, and the prepared negative electrode sheet has low fiberization degree, and the battery cycle stability decreases; therefore, the appropriate content of the coating layer is the key to the battery with high rate performance and long cycle life, that is, in the present embodiment, the content of the coating layer is in the range of 2% to 5%, which can ensure that the battery prepared by the dry electrode binder has high rate performance and long cycle life.

[0032] In some embodiments, the binder material is surface-modified polytetrafluoroethylene; the content of fluorine element in the surface-modified polytetrafluoroethylene is denoted as F, the mass content of oxygen element is denoted as O, the mass content of carbon element is denoted as C, and the mass content of nitrogen element is denoted as N; wherein, 1.1≤F / C≤1.6, 0.1≤(O+N) / C≤0.25; since the element content on the surface of the binder material needs to satisfy the same relationship in the surface-modified polytetrafluoroethylene binder material, it is limited in a suitable numerical range, the synergistic relationship is strong, and the performance of the dry electrode binder can be improved together, so that the prepared battery has higher rate performance and longer cycle life.

[0033] In some embodiments, the carbon material includes at least one of conductive carbon black and graphite.

[0034] In some embodiments, the pH value of the carbon material is in the range of 3 to 5; too high or too low pH value of the carbon material will affect the membrane resistance dispersion coefficient and the cycle performance of the battery; therefore, the appropriate pH value of the carbon material is the key to the battery with high rate performance and long cycle life, that is, in the present embodiment, the pH value of the carbon material is in the range of 3 to 5, which can ensure that the battery prepared by the dry electrode binder has high rate performance and long cycle life.

[0035] In some embodiments, the coating layer is obtained by mixing the carbon material and the binder material and then ball milling.

[0036] The present application also provides a preparation method of the dry electrode binder, which includes the following steps:

[0037] The binder is subjected to plasma treatment to obtain a surface-modified binder;

[0038] The surface-modified binder is mixed with the carbon material as a binder layer and subjected to ball milling, so that the carbon material coats the surface of the binder layer to form a coating layer, and a dry electrode binder is obtained.

[0039] In some embodiments, the content of the coating layer is 2% to 5% based on the total mass of the dry electrode binder; and the carbon material includes at least one of conductive carbon black and graphite; and the binder includes at least one of polyvinylidene fluoride, gelatin and polytetrafluoroethylene.

[0040] In some embodiments, the step of subjecting the binder to plasma treatment to obtain a surface-modified binder includes:

[0041] placing the binder in a plasma treatment chamber;

[0042] injecting at least one of oxygen, nitrogen and hydrogen into the plasma treatment chamber to react with the surface of the binder for 1 to 5 minutes.

[0043] The embodiments of the present application also provide a dry electrode sheet including the dry electrode binder or the dry electrode binder prepared according to the preparation method of the dry electrode binder.

[0044] The embodiments of the present application also provide a lithium ion battery including the dry electrode sheet.

[0045] Some examples of preparing the dry electrode binder are provided herein to show various cases of the material selection of the binder layer, the material selection of the coating layer, the treatment time selection of the binder layer material, the treatment method selection of the binder layer material, the content selection of the coating layer, and the pH value selection of the material of the coating layer in the preparation steps of the dry electrode binder. These examples all adopt reasonable collocations in accordance with the present application.

[0046] Example 1

[0047] The dry electrode binder is prepared according to the foregoing scheme, and the specific preparation steps are as follows:

[0048] The material of the binder layer is PTFE, and the PTFE is placed in a plasma treatment chamber;

[0049] A mixed gas of nitrogen and oxygen is injected into the plasma treatment chamber to react with the surface of the PTFE, and the plasma treatment time is 2 minutes;

[0050] The material of the coating layer is conductive carbon black (Super P, SP) with a pH value of 4, and the SP is mixed with the PTFE subjected to plasma treatment and then ball milled to realize the coating of the SP on the PTFE, thereby obtaining the dry electrode binder;

[0051] In the dry electrode binder, the content of the SP coated on the PTFE is 2% based on the total mass of the dry electrode binder.

[0052] Example 2

[0053] The difference from the dry electrode binder preparation example presented in Example 1 above is that the plasma treatment time of the PTFE is 1 minute.

[0054] Example 3

[0055] The difference from the dry electrode binder preparation example presented in Example 1 above is that the plasma treatment time of the PTFE is 3 minutes.

[0056] Example 4

[0057] The difference from the dry electrode binder preparation example presented in Example 1 above is that the plasma treatment time of the PTFE is 4 minutes.

[0058] Example 5

[0059] The difference from the dry electrode binder preparation example presented in Example 1 above is that the plasma treatment time of the PTFE is 5 minutes.

[0060] Example 6

[0061] The difference from the dry electrode binder preparation example presented in Example 1 above is that the coating amount of SP on PTFE is 3%.

[0062] Example 7

[0063] The difference from the dry electrode binder preparation example presented in Example 1 above is that the coating amount of SP on PTFE is 4%.

[0064] Example 8

[0065] The difference from the dry electrode binder preparation example presented in Example 1 above is that the coating amount of SP on PTFE is 5%.

[0066] Example 9

[0067] The difference from the dry electrode binder preparation example presented in Example 1 above is that the material of the coating layer is graphite.

[0068] Example 10

[0069] The difference from the dry electrode binder preparation example presented in Example 1 above is that the binder material is surface-modified PVDF.

[0070] Comparative Example 1

[0071] The difference from the dry electrode binder preparation example presented in Example 1 above is that the dry electrode binder is PTFE.

[0072] Comparative Example 2

[0073] Compared with the dry electrode binder preparation example proposed in Example 1 above, the only difference is that the PTFE is not subjected to plasma treatment.

[0074] Comparative Example 3

[0075] Compared with the dry electrode binder preparation example proposed in Example 1 above, the only difference is that the PTFE subjected to surface modification is not coated with SP.

[0076] Comparative Example 4

[0077] Compared with the dry electrode binder preparation example proposed in Example 1 above, the only difference is that the plasma treatment time of the PTFE is 7 minutes.

[0078] Comparative Example 5

[0079] Compared with the dry electrode binder preparation example proposed in Example 1 above, the only difference is that the coating amount of SP on the PTFE is 0.1%.

[0080] Comparative Example 6

[0081] Compared with the dry electrode binder preparation example proposed in Example 1 above, the only difference is that the coating amount of SP on the PTFE is 1%.

[0082] Comparative Example 7

[0083] Compared with the dry electrode binder preparation example proposed in Example 1 above, the only difference is that the coating amount of SP on the PTFE is 6%.

[0084] Comparative Example 8

[0085] Compared with the dry electrode binder preparation example proposed in Example 1 above, the only difference is that the pH value of SP is selected to be 2.

[0086] Comparative Example 9

[0087] Compared with the dry electrode binder preparation example proposed in Example 1 above, the only difference is that the pH value of SP is selected to be 6.

[0088] In order to know the performance of the dry electrode binders prepared in Examples 1-10 and Comparative Examples 1-9, the dry electrode binders prepared in each example and comparative example are used to prepare dry electrode sheets, and the prepared dry electrode sheets are used to prepare lithium ion batteries.

[0089] After the PTFE obtained after the plasma treatment step in Examples 1-5, Comparative Example 1, and Comparative Example 4 is placed for 30 min to reach a stable state, the following operations are performed: the mass percentage of elements and chemical bonds on the surface is collected; the collection results are shown in Table 1; the collection means include but are not limited to spectroscopy and thermochemistry.

[0090] Table 1

[0091] The following operations were performed on the dry electrode sheets and lithium ion batteries prepared from the dry electrode binders in Examples 1-10 and Comparative Examples 1-7: the complete wetting time of the dry electrode sheets in electrolyte was tested, the sheet resistivity of the dry electrode sheets was tested, the first coulombic efficiency of the lithium ion batteries was tested, and the 500 cycle retention rate of the lithium ion batteries was tested; the results are shown in Table 2.

[0092] Table 2

[0093] The following operations were performed on the SP, dry electrode sheets, and lithium ion batteries in Example 1 and Comparative Examples 8 and 9: the proportion of oxygen-containing groups in the SP was tested, the sheet resistivity dispersion coefficient of the dry electrode sheets was tested, and the 500 cycle retention rate of the lithium ion batteries was tested; the results are shown in Table 3.

[0094] Table 3

[0095] During the plasma treatment, the mixed gas of nitrogen and oxygen is ionized into plasma in the plasma treatment chamber, and active particles and polar groups are generated during the initiation of the plasma. The active particles and polar groups can remove the F ions on the surface of the PTFE and generate free radicals, which can initiate cross-linking reactions or form unsaturated bonds on the surface of the PTFE, thereby introducing N and O elements and generating new functional groups on the surface of the PTFE. After the generation of functional groups containing H and O elements such as -NH, -N-C-O, and -COOH on the surface of the PTFE, the hydrophilicity and surface tension of the PTFE surface can be significantly improved, and the adhesion of the PTFE after fibrillation to the SP can be improved, thereby improving the wetting of the PTFE by the electrolyte and the coating effect of the SP on the PTFE. After the SP coats the PTFE, the stability of the PTFE during the electrochemical reaction can be improved, the side reactions or irreversible decomposition of the PTFE with other substances can be inhibited, and the problem of failure of the PTFE bonding function can be overcome. Thus, the electrochemical performance of the dry battery can be improved, and the first coulombic efficiency of the battery can be improved.

[0096] The element content of the PTFE after plasma treatment needs to meet 1.1≤F / C≤1.6 and 0.1≤(O+N) / C≤0.25 in the stable state; it can be known from the data of examples 1 to 5 in tables 1 and 2 that, in the case of meeting 1.1≤F / C≤1.6, the greater the value of F / C, the greater the film resistance discrete coefficient; because the increase of the value of F / C indicates that the F element on the surface of PTFE increases and the polar group decreases, which will make the SP coating uniformity and combination of PTFE poor, directly causing the uneven distribution of the film resistance, thereby leading to the large discrete coefficient of the film resistance; in the case of meeting 0.1≤(O+N) / C≤0.25, the greater the value of (O+N) / C, the smaller the film resistance discrete coefficient, because the increase of the value of -(O+N / C) indicates that more -CF2 bonds are broken and more functional groups containing H and O elements are generated, thereby improving the adhesion and hydrophilicity of the surface of PTFE, improving the ball milling coating effect of PTFE and SP, improving the film resistance uniformity, and reducing the discrete coefficient of the film resistance;

[0097] It can be known from tables 1 and 2 that, in comparative example 4, F / C<1.1 and (O+N) / C>0.25, when F / C<1.1 or (O+N) / C>0.25, the fiberization ability of PTFE is greatly weakened, the dry electrode sheet prepared has poor stability, and the cycle performance is greatly reduced; in comparative example 1, F / C>1.6 and (O+N) / C<0.1, when F / C>1.6 or (O+N) / C<0.1, on the one hand, the surface of PTFE is coated with more F atoms, which not only enhances the hydrophobic and oleophobic properties of the surface, but also reduces the number of exposed polar functional groups on the surface, making it difficult for the electrolyte to infiltrate; for example, in comparative example 1, the complete infiltration time of the electrolyte is 600s, which is much higher than that of other examples; on the other hand, the high F / C content indicates that the number of polar groups in the plasma-treated PTFE is small, and when the number of polar groups is not enough, the surface energy of PTFE is small, which will lead to the decrease of the bonding force between PTFE and SP, the poor uniformity of ball milling coating, and thus the uneven distribution of the film resistance of the electrode sheet prepared subsequently, causing the loss of cycle performance of the battery and other problems; for example, in comparative example 1, the discrete coefficient of the film resistance is 3.43%, which is much higher than that of other examples.

[0098] From the results in table 1, it can be seen that, in the case of meeting 0.1≤(O+N) / C≤0.25, the F / C ratio of the PTFE surface after plasma treatment for 2 minutes in example 1 is the lowest, and the value of -(O+N / C) is the highest; therefore, the surface adhesion of the PTFE in example 1 is stronger than that of other examples and comparative examples, and the electrolyte infiltration effect is better; it can be known that, under the condition of plasma treatment of PTFE for 2 minutes given in the present application, the surface-modified PTFE has strong surface adhesion and electrolyte infiltration effect.

[0099] The test results of Comparative Examples 1-3 in Table 2 show that the electrolyte infiltration speed of the dry electrode sheet in Comparative Example 2 and Comparative Example 3 is significantly better than that in Comparative Example 1, the sheet resistivity is significantly smaller than that in Comparative Example 1, and the first coulombic efficiency and the capacity retention rate after 500 cycles of the lithium ion battery in Comparative Example 2 and Comparative Example 3 are significantly better than those in Comparative Example 1;

[0100] Compared with Comparative Example 2, Example 1 selects a ball milling method to coat the carbon material outside the binder material; when the binder material is surface-modified PTFE, the surface of the PTFE has a fiberizable part and a non-fiberizable part after plasma treatment; in the process of coating the carbon material by using the mixed ball milling method, the fiberizable part of the PTFE surface can be pre-fiberized, which can further increase the aspect ratio of the PTFE fibers in the subsequent film thinning process of the dry electrode sheet, and also can increase the surface area of the active material exposed outside to realize the long-range connection between the active particles; at the same time, the carbon material can be uniformly coated in the non-fiberizable part of the PTFE containing polar groups, i.e., the part treated by plasma; because the surface energy of the carbon material is relatively high, the bonding force between the carbon material and the non-fiberizable part of the PTFE with increased surface energy after plasma treatment is also enhanced, which can withstand a larger shear force, further ensuring the uniformity and stability of the conductive network; therefore, coating the carbon material outside the binder material by using the mixed ball milling method can effectively improve the fiber performance of the PTFE and further improve the structural performance of the dry electrode binder.

[0101] Compared with Comparative Example 3, Example 1 selects to first perform plasma treatment on polytetrafluoroethylene and then mix and ball mill the polytetrafluoroethylene with the carbon material for coating; if the PTFE is not treated by plasma and directly coated with the carbon material, the bonding force between the PTFE and the carbon material is weak due to the F atom coating on the surface of the PTFE, the coating effect is poor, and the coating layer is easily damaged in the subsequent film thinning process; in addition, the surface of the PTFE not treated by plasma exposed on the surface layer of the electrode sheet has hydrophobic and oleophobic properties, which also causes difficulty in electrolyte infiltration; in summary, the PTFE after being treated by the two modification methods of plasma treatment and SP coating provided in the present application can improve the electrolyte infiltration of the dry electrode binder containing the PTFE and the dry electrode sheet prepared therefrom, and the first coulombic efficiency and the cycle performance of the lithium ion battery prepared from the dry electrode sheet are also improved, which proves the superiority of the performance of the modified dry electrode binder.

[0102] Secondly, as can be seen from the test results of Example 1 and Examples 6-8 and Comparative Examples 5-7 in Table 2, as the amount of SP coating PTFE increases in the dry electrode binder, the electrolyte wettability of the dry electrode sheet prepared therefrom is better, the conductivity is stronger, and the first coulombic efficiency and cycle efficiency of the lithium ion battery prepared therefrom are also higher. However, in Comparative Example 7, when the amount of SP coating exceeds 5%, the battery performance test results are actually worse, because at this time the coating layer is too thick, the polar surface of PTFE treated by plasma is coated by SP, and the fiberizability of PTFE is greatly weakened due to the coating of SP, resulting in low fiberization degree of the prepared electrode sheet and decreased cycle stability of the battery.

[0103] Furthermore, as can be seen from the test results of Example 1 and Example 9, the surface modification effect of PTFE after graphite coating is not as good as that of SP coating. On the one hand, SP has stronger conductivity and smaller particle size than graphite, and the coating is more uniform. On the other hand, the surface energy of SP is closer to that of PTFE, and the combination between them is better, which promotes the electrolyte wettability of the dry electrode binder. In the present application, when the surface-modified PTFE is used in the bonding layer and the conductive carbon black is used in the coating layer, better coating effect can be achieved.

[0104] As can be seen from the test results of Example 1 and Comparative Examples 8 and 9, the proportion of oxygen-containing groups in the SP of Comparative Examples 8 and 9 is much lower than that of Example 1, and the pH value of SP in Comparative Examples 8 and 9 is too high or too low, which will affect the film resistance dispersion coefficient and the cycle performance of the battery. In the present application, the carbon material with a pH value in the range of 3-5 is selected for the coating layer, because the number of oxygen-containing groups of the carbon material is appropriate, and the number of oxygen-containing groups directly affects the surface energy of the carbon material, so that the surface energy of the carbon material and the modified PTFE is more suitable. At this time, the binding force of the carbon material and the PTFE ball-milled with a high N / H content after plasma treatment is stronger, the stability and uniformity of the dry electrode binder material can be steadily improved, the resistance dispersion coefficient of the film after the electrode sheet is prepared is greatly reduced, and the resistance consistency and the cycle performance of the battery cell can be improved.

[0105] Based on the disclosure and teachings of the above specification, a person of ordinary skill in the art can make modifications and variations to the above embodiments. Therefore, the present application is not limited to the specific embodiments described above, and any obvious improvements, replacements or modifications made by those skilled in the art based on the present application shall fall within the scope of the present application. In addition, although some specific terms are used in the specification, these terms are only for convenience of description and do not constitute any limitation on the present application.

Claims

1. A dry electrode binder characterized by, The adhesive layer is an adhesive material, and the adhesive material comprises at least one of surface-modified polyvinylidene fluoride, gelatin and polytetrafluoroethylene, and the surface of the adhesive material contains at least one of oxygen, nitrogen and hydrogen elements. The coating layer is a carbon material. The content of the coating layer is 0.1% to 5% based on the total mass of the dry electrode binder.

2. The dry electrode binder of claim 1, wherein, The content of the coating layer is 2% to 5%.

3. The dry electrode binder of claim 2, wherein, The adhesive material is surface-modified polytetrafluoroethylene, the mass content of fluorine elements in the surface-modified polytetrafluoroethylene is denoted as F, the mass content of oxygen elements is denoted as O, the mass content of carbon elements is denoted as C, and the mass content of nitrogen elements is denoted as N; wherein 1.1≤F / C≤1.6 and 0.1≤(O+N) / C≤0.

25.

4. The dry electrode binder of claim 3, wherein, The carbon material comprises at least one of conductive carbon black and graphite.

5. The dry electrode binder of claim 3 or 4, wherein, The pH value of the carbon material is in the range of 3 to 5.

6. The dry electrode binder of claim 5, wherein, The coating layer is obtained by mixing the carbon material and the adhesive material and then ball milling.

7. The dry electrode binder of claim 5, wherein, The method comprises the following steps:

8. A method of making a dry electrode binder, characterized by, The adhesive is subjected to plasma treatment to obtain a surface-modified adhesive; The surface-modified adhesive is mixed with a carbon material as an adhesive layer and subjected to ball milling, so that the carbon material is coated on the surface of the adhesive layer to form a coating layer, thereby obtaining a dry electrode binder. The content of the coating layer is 2% to 5% based on the total mass of the dry electrode binder; the carbon material comprises at least one of conductive carbon black and graphite; and the adhesive comprises at least one of polyvinylidene fluoride, gelatin and polytetrafluoroethylene.

9. The method of making a dry electrode binder according to claim 8, wherein, The step of subjecting the adhesive to plasma treatment to obtain a surface-modified adhesive comprises:

10. The method of making a dry electrode binder according to claim 9, wherein, The adhesive is placed in a plasma treatment chamber; At least one of oxygen, nitrogen and hydrogen is injected into the plasma treatment chamber to react with the surface of the adhesive for 1 to 5 minutes. A dry electrode binder as claimed in any one of claims 1 to 7 or prepared according to the method as claimed in any one of claims 8 to 10.

11. A dry electrode sheet characterized by A dry electrode sheet as claimed in claim 11.

12. A lithium-ion battery, characterized by, ​

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