CN118299498B - Dry electrode membrane and method for detecting the degree of binder fibrosis therein - Google Patents
Dry electrode membrane and method for detecting the degree of binder fibrosis therein Download PDFInfo
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- 239000012528 membrane Substances 0.000 title claims abstract description 188
- 238000000034 method Methods 0.000 title claims abstract description 64
- 206010016654 Fibrosis Diseases 0.000 title claims abstract description 50
- 230000004761 fibrosis Effects 0.000 title claims abstract description 50
- 239000011230 binding agent Substances 0.000 title claims abstract description 38
- 239000004810 polytetrafluoroethylene Substances 0.000 claims abstract description 126
- 229920001343 polytetrafluoroethylene Polymers 0.000 claims abstract description 126
- -1 polytetrafluoroethylene Polymers 0.000 claims abstract description 75
- 239000006258 conductive agent Substances 0.000 claims abstract description 33
- 239000007772 electrode material Substances 0.000 claims abstract description 28
- 239000000853 adhesive Substances 0.000 claims abstract description 22
- 230000001070 adhesive effect Effects 0.000 claims abstract description 22
- VLTRZXGMWDSKGL-UHFFFAOYSA-N perchloric acid Chemical compound OCl(=O)(=O)=O VLTRZXGMWDSKGL-UHFFFAOYSA-N 0.000 claims description 74
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 claims description 52
- 230000029087 digestion Effects 0.000 claims description 36
- 239000000843 powder Substances 0.000 claims description 35
- 238000006243 chemical reaction Methods 0.000 claims description 34
- 239000007864 aqueous solution Substances 0.000 claims description 27
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 claims description 26
- 229910017604 nitric acid Inorganic materials 0.000 claims description 26
- 239000000243 solution Substances 0.000 claims description 16
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 15
- 239000007773 negative electrode material Substances 0.000 claims description 12
- 239000007774 positive electrode material Substances 0.000 claims description 11
- 230000035484 reaction time Effects 0.000 claims description 9
- 239000007800 oxidant agent Substances 0.000 claims description 6
- KFDQGLPGKXUTMZ-UHFFFAOYSA-N [Mn].[Co].[Ni] Chemical compound [Mn].[Co].[Ni] KFDQGLPGKXUTMZ-UHFFFAOYSA-N 0.000 claims description 5
- 229910002804 graphite Inorganic materials 0.000 claims description 5
- 239000010439 graphite Substances 0.000 claims description 5
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 claims description 4
- 238000001514 detection method Methods 0.000 claims description 4
- 229910052744 lithium Inorganic materials 0.000 claims description 4
- 230000001590 oxidative effect Effects 0.000 claims description 4
- 229920000049 Carbon (fiber) Polymers 0.000 claims description 3
- 239000006183 anode active material Substances 0.000 claims description 3
- 239000004917 carbon fiber Substances 0.000 claims description 3
- 229910021393 carbon nanotube Inorganic materials 0.000 claims description 3
- 239000002041 carbon nanotube Substances 0.000 claims description 3
- 229910021389 graphene Inorganic materials 0.000 claims description 3
- GELKBWJHTRAYNV-UHFFFAOYSA-K lithium iron phosphate Chemical compound [Li+].[Fe+2].[O-]P([O-])([O-])=O GELKBWJHTRAYNV-UHFFFAOYSA-K 0.000 claims description 3
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 claims description 3
- 229910052799 carbon Inorganic materials 0.000 claims description 2
- QHGJSLXSVXVKHZ-UHFFFAOYSA-N dilithium;dioxido(dioxo)manganese Chemical compound [Li+].[Li+].[O-][Mn]([O-])(=O)=O QHGJSLXSVXVKHZ-UHFFFAOYSA-N 0.000 claims description 2
- 229910021385 hard carbon Inorganic materials 0.000 claims description 2
- 239000004005 microsphere Substances 0.000 claims description 2
- 238000012544 monitoring process Methods 0.000 abstract description 3
- 238000012360 testing method Methods 0.000 description 36
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 20
- 239000000463 material Substances 0.000 description 18
- 238000003490 calendering Methods 0.000 description 14
- 238000001179 sorption measurement Methods 0.000 description 13
- 238000001035 drying Methods 0.000 description 12
- 239000000203 mixture Substances 0.000 description 12
- 238000004438 BET method Methods 0.000 description 10
- 239000007788 liquid Substances 0.000 description 10
- 239000011159 matrix material Substances 0.000 description 10
- 229910052757 nitrogen Inorganic materials 0.000 description 10
- 238000002360 preparation method Methods 0.000 description 8
- 230000000052 comparative effect Effects 0.000 description 7
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 6
- 238000010521 absorption reaction Methods 0.000 description 6
- QZPSXPBJTPJTSZ-UHFFFAOYSA-N aqua regia Chemical compound Cl.O[N+]([O-])=O QZPSXPBJTPJTSZ-UHFFFAOYSA-N 0.000 description 6
- 238000005520 cutting process Methods 0.000 description 6
- 239000008367 deionised water Substances 0.000 description 6
- 229910021641 deionized water Inorganic materials 0.000 description 6
- 238000004519 manufacturing process Methods 0.000 description 6
- 238000002156 mixing Methods 0.000 description 6
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 6
- 239000010405 anode material Substances 0.000 description 5
- 238000001816 cooling Methods 0.000 description 5
- 238000005485 electric heating Methods 0.000 description 5
- 238000001878 scanning electron micrograph Methods 0.000 description 5
- 238000005406 washing Methods 0.000 description 5
- 206010061592 cardiac fibrillation Diseases 0.000 description 4
- 230000002600 fibrillogenic effect Effects 0.000 description 4
- 239000013067 intermediate product Substances 0.000 description 4
- ZCYVEMRRCGMTRW-UHFFFAOYSA-N 7553-56-2 Chemical compound [I] ZCYVEMRRCGMTRW-UHFFFAOYSA-N 0.000 description 3
- 229910052786 argon Inorganic materials 0.000 description 3
- 238000012512 characterization method Methods 0.000 description 3
- 239000007789 gas Substances 0.000 description 3
- 239000011630 iodine Substances 0.000 description 3
- 229910052740 iodine Inorganic materials 0.000 description 3
- QSHDDOUJBYECFT-UHFFFAOYSA-N mercury Chemical compound [Hg] QSHDDOUJBYECFT-UHFFFAOYSA-N 0.000 description 3
- 229910052753 mercury Inorganic materials 0.000 description 3
- 238000005096 rolling process Methods 0.000 description 3
- 239000006230 acetylene black Substances 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 238000002474 experimental method Methods 0.000 description 2
- 239000003273 ketjen black Substances 0.000 description 2
- DVATZODUVBMYHN-UHFFFAOYSA-K lithium;iron(2+);manganese(2+);phosphate Chemical compound [Li+].[Mn+2].[Fe+2].[O-]P([O-])([O-])=O DVATZODUVBMYHN-UHFFFAOYSA-K 0.000 description 2
- 238000012545 processing Methods 0.000 description 2
- 239000002904 solvent Substances 0.000 description 2
- 239000011149 active material Substances 0.000 description 1
- 239000013543 active substance Substances 0.000 description 1
- 238000004140 cleaning Methods 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- 238000013329 compounding Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 239000000835 fiber Substances 0.000 description 1
- 238000004898 kneading Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 238000011084 recovery Methods 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 239000002002 slurry Substances 0.000 description 1
Classifications
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N15/00—Investigating characteristics of particles; Investigating permeability, pore-volume or surface-area of porous materials
- G01N15/08—Investigating permeability, pore-volume, or surface area of porous materials
- G01N15/088—Investigating volume, surface area, size or distribution of pores; Porosimetry
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/04—Processes of manufacture in general
- H01M4/043—Processes of manufacture in general involving compressing or compaction
- H01M4/0435—Rolling or calendering
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
- H01M4/139—Processes of manufacture
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M2004/021—Physical characteristics, e.g. porosity, surface area
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Abstract
The application relates to the technical field of new energy, in particular to a dry electrode membrane and a method for detecting the fibrosis degree of a binder in the dry electrode membrane. The dry electrode membrane comprises a polytetrafluoroethylene support framework, and electrode active materials and conductive agents adhered to the polytetrafluoroethylene support framework; the specific surface area S of the polytetrafluoroethylene support framework meets the following conditions: 12m 2/g≤S≤25m2/g. According to the application, the degree of fibrosis of the adhesive can be judged by monitoring the specific surface area of the polytetrafluoroethylene support framework in the dry electrode membrane, and when the specific surface area S of the polytetrafluoroethylene support framework meets the following conditions: at 12m 2/g≤S≤25m2/g, the binder has better degree of fibrosis, and the dry electrode membrane has better mechanical property.
Description
Technical Field
The application relates to the technical field of new energy, in particular to a dry electrode membrane, a preparation method thereof, an electrode pole piece and a method for detecting the fibrosis degree of a binder in a dry positive electrode membrane.
Background
The wet electrode membrane is generally prepared by mixing powder materials with solvents to prepare slurry, then performing procedures such as coating, drying, solvent recovery and the like, and the dry electrode membrane is generally formed into a self-supporting framework for adhering materials such as active substances by utilizing fibrillation of a binder. Compared with the wet process, the dry process has the advantages of high production efficiency, strong processing adaptability, no pollution, low cost and the like, but the electrode membrane formed by the dry process also has the problem of poor mechanical strength.
Disclosure of Invention
Based on the above, the first aspect of the present application provides a dry electrode membrane, which aims to improve the mechanical strength of the dry electrode membrane, and the technical scheme is as follows:
A dry electrode membrane comprises a polytetrafluoroethylene support framework, an electrode active material and a conductive agent, wherein the electrode active material and the conductive agent are adhered to the polytetrafluoroethylene support framework; the specific surface area S of the polytetrafluoroethylene support framework meets the following conditions: 12m 2/g≤S≤25m2/g.
The application provides a preparation method of a dry electrode membrane, which comprises the following steps:
The preparation method of the dry electrode membrane comprises the following steps:
mixing polytetrafluoroethylene powder, an electrode active material and a conductive agent to obtain a mixed material;
Calendaring the mixed material into a film, forming the polytetrafluoroethylene powder into a polytetrafluoroethylene support framework, and controlling the specific surface area S of the polytetrafluoroethylene support framework to meet the following conditions: 12m 2/g≤S≤25m2/g, and adhering the electrode active material and the conductive agent to the polytetrafluoroethylene supporting framework to obtain the dry electrode membrane.
The third aspect of the application provides an electrode slice, which has the following technical scheme:
An electrode sheet comprising a current collector and a dry electrode membrane located over the current collector, the dry electrode membrane being as described above or prepared by a method of preparation as described above.
The fourth aspect of the present application provides a method for detecting the degree of binder fibrosis in a dry electrode membrane, which has the following technical scheme:
a method of detecting the extent of binder fibrosis in a dry electrode membrane comprising the steps of:
Digestion treatment is carried out on the dry electrode membrane with polytetrafluoroethylene as a binder, so as to obtain a polytetrafluoroethylene supporting framework with a continuous framework structure;
Detecting the specific surface area S of the polytetrafluoroethylene support framework;
If the adhesive is 12m 2/g≤S≤25m2/g, the adhesive fibrosis degree is qualified, if S is less than 12m 2/g, the adhesive fibrosis degree is not qualified, and if S is more than 25m 2/g, the detection is invalid.
Compared with the traditional scheme, the application has the following beneficial effects:
According to the application, the degree of fibrosis of the adhesive can be judged by monitoring the specific surface area of the polytetrafluoroethylene support framework in the dry electrode membrane, and when the specific surface area S of the polytetrafluoroethylene support framework meets the following conditions: at 12m 2/g≤S≤25m2/g, the binder has better degree of fibrosis, and the dry electrode membrane has better mechanical property.
Drawings
In order to more clearly illustrate the technical solution in the embodiments of the present application and to more fully understand the present application and its advantageous effects, the following brief description will be given with reference to the accompanying drawings, which are required to be used in the description of the embodiments. It is evident that the figures in the following description are only some embodiments of the application, from which other figures can be obtained without inventive effort for a person skilled in the art.
FIG. 1 is a live view of PTFE powder of example 1;
FIG. 2 is an SEM image of PTFE powder of example 1;
FIG. 3 is a live view of a dry cathode membrane of example 1;
fig. 4 is an SEM image of the dry cathode membrane of example 1;
FIG. 5 is a live view of the PTFE support skeleton of example 1;
FIG. 6 is an SEM image of a PTFE support matrix of example 1;
FIG. 7 is a live view of the PTFE support skeleton of comparative example 2;
Fig. 8 is an SEM image of the PTFE support skeleton of comparative example 2.
Detailed Description
The present application will be described in further detail with reference to specific examples. The present application may be embodied in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the description of the application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.
Terminology
Unless otherwise indicated or contradicted, terms or phrases used herein have the following meanings:
in the present application, the terms "plurality", "plural", "multiple", and the like are used in terms of the number of the terms "plurality", "multiple", and the like, and are not particularly limited, but are greater than 2 or equal to 2 in number. For example, "one or more" means one kind or two or more kinds.
In the present application, reference to "optional", "optional" refers to the presence or absence of the "optional" or "optional" means either of the "with" or "without" side-by-side arrangements. If multiple "alternatives" occur in a technical solution, if no particular description exists and there is no contradiction or mutual constraint, then each "alternative" is independent.
In the present application, the terms "first", "second", "third", "fourth", etc. are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or quantity, nor as implying an importance or quantity of a technical feature indicated. Moreover, the terms "first," "second," "third," "fourth," and the like are used for non-exhaustive list description purposes only, and are not to be construed as limiting the number of closed forms.
In the present application, a numerical range (i.e., a numerical range) is referred to, and optional numerical distributions are considered to be continuous within the numerical range and include two numerical endpoints (i.e., a minimum value and a maximum value) of the numerical range and each numerical value between the two numerical endpoints unless otherwise specified.
The temperature parameter in the present application is not particularly limited, and may be a constant temperature treatment or may vary within a predetermined temperature range. It should be appreciated that the constant temperature process described allows the temperature to fluctuate within the accuracy of the instrument control. Allows for fluctuations within a range such as + -5 ℃, + -4 ℃, + -3 ℃, + -2 ℃, + -1 ℃. In the application, the room temperature refers to any temperature of 15-40 ℃.
A first aspect of the present application provides a dry electrode membrane, in some embodiments, comprising a Polytetrafluoroethylene (PTFE) support matrix and an electrode active material and a conductive agent adhered to the polytetrafluoroethylene support matrix; the specific surface area S of the polytetrafluoroethylene support framework meets the following conditions: 12m 2/g≤S≤25m2/g.
According to the application, the degree of fibrosis of the adhesive can be judged by monitoring the specific surface area of the polytetrafluoroethylene support framework in the dry electrode membrane, and when the specific surface area S of the polytetrafluoroethylene support framework meets the following conditions: at 12m 2/g≤S≤25m2/g, the binder has better degree of fibrosis, and the dry electrode membrane has better mechanical property.
Alternatively, the specific surface area of the polytetrafluoroethylene support skeleton in the dry electrode membrane was tested by the following method:
Digestion treatment is carried out on the dry electrode membrane to obtain a polytetrafluoroethylene supporting framework with a continuous framework structure;
and detecting the specific surface area S of the polytetrafluoroethylene support framework.
Alternatively, the method of detecting the specific surface area S of the polytetrafluoroethylene support skeleton includes, but is not limited to, a liquid nitrogen adsorption BET method, an argon adsorption method, a gas permeation method, a mercury absorption method, and an iodine absorption method.
And (3) carrying out digestion treatment on the dry electrode membrane, so that electrode active materials and conductive agents adhered to the polytetrafluoroethylene support framework can be removed, and the influence of the electrode active materials and the conductive agents on a test result is eliminated. The dry electrode membrane is prepared by a dry process, and can be a dry positive electrode membrane or a dry negative electrode membrane.
When the dry electrode membrane is a dry positive electrode membrane, the electrode active material is a positive electrode active material. Optionally, the positive electrode active material is selected from at least one of ternary nickel cobalt manganese, lithium manganese iron phosphate, lithium nickelate, lithium manganate and lithium cobaltate. The digestion treatment of the dry electrode membrane comprises the following steps: adding perchloric acid into the dry electrode membrane to remove the conductive agent, thereby obtaining an intermediate product; hydrochloric acid and nitric acid are added to the intermediate product to remove the positive electrode active material. Optionally, removing the conductive agent reaction conditions includes: the reaction temperature is 150-200 ℃ and the reaction time is 20-40 min. Optionally, the perchloric acid is provided by perchloric acid aqueous solution, the mass concentration of the perchloric acid aqueous solution is 70% -72%, and 8-15 mL of perchloric acid aqueous solution is added to each 9cm 2 area of dry electrode membrane. Optionally, the hydrochloric acid is provided by an aqueous hydrochloric acid solution, the nitric acid is provided by an aqueous nitric acid solution, and the volume ratio of the aqueous hydrochloric acid solution to the aqueous nitric acid solution is (2-4): 1, the mass concentration of the hydrochloric acid aqueous solution is 36% -38%, and the mass concentration of the nitric acid aqueous solution is 65% -68%. And adding 8-15 mL of a total volume of the aqueous solution of hydrochloric acid and the aqueous solution of nitric acid into each 9cm 2 area dry electrode membrane. Optionally, the reaction conditions for removing the positive electrode active material include: the reaction temperature is 15-40 ℃ and the reaction time is 10-30 min.
When the dry electrode membrane is a dry negative electrode membrane, the electrode active material is a negative electrode active material. Optionally, the negative electrode active material is selected from at least one of graphite, hard carbon, and mesophase carbon microspheres. The digestion treatment of the dry electrode membrane comprises the following steps: perchloric acid is added to the dry electrode film sheet to remove the negative electrode active material and the conductive agent. Optionally, the reaction conditions for removing the anode active material and the conductive agent include: the reaction temperature is 150-200 ℃ and the reaction time is 20-40 min. Optionally, the perchloric acid is provided by perchloric acid aqueous solution, the mass concentration of the perchloric acid aqueous solution is 70% -72%, and 8-15 mL of perchloric acid aqueous solution is added to each 9cm 2 area of dry electrode membrane.
Alternatively, the conductive agent is selected from at least one of acetylene black, conductive carbon black (SUPER-P), carbon nanotubes, carbon fibers, ketjen black, graphite, and graphene. It is understood that the conductive agents in the dry positive electrode membrane and the dry negative electrode membrane are each independently selected from at least one of acetylene black, conductive carbon black, carbon nanotubes, carbon fibers, ketjen black, graphite, and graphene.
Optionally, the mass ratio of the polytetrafluoroethylene support skeleton to the dry electrode membrane is 1% -5%. The above range can provide the required adhesiveness and satisfy the requirement of electrical conductivity.
The mass ratio of the polytetrafluoroethylene support skeleton to the dry electrode membrane is obtained by calculating the mass ratio of the polytetrafluoroethylene support skeleton after digestion treatment to the dry electrode membrane before digestion treatment.
Optionally, the mass ratio of the electrode active material to the dry electrode membrane is 90% -98%.
Optionally, the conductive agent accounts for 1% -5% of the dry electrode membrane by mass.
In a second aspect of the present application, there is provided a method of preparing a dry electrode membrane, in some embodiments, the method of preparing a dry electrode membrane comprising the steps of:
mixing polytetrafluoroethylene powder, an electrode active material and a conductive agent to obtain a mixed material;
Calendaring the mixed material into a film, forming the polytetrafluoroethylene powder into a polytetrafluoroethylene support framework, and controlling the specific surface area S of the polytetrafluoroethylene support framework to meet the following conditions: 12m 2/g≤S≤25m2/g, and adhering the electrode active material and the conductive agent to the polytetrafluoroethylene supporting framework to obtain the dry electrode film.
It can be understood that the specific surface area S of the polytetrafluoroethylene powder can be satisfied by controlling the specific surface area, the dosage and the technological parameters of calendaring to form a film: 12m 2/g≤S≤25m2/g polytetrafluoroethylene supporting framework. When the specific surface area S of the polytetrafluoroethylene supporting framework meets the following conditions: at 12m 2/g≤S≤25m2/g, the binder has better degree of fibrosis, and the dry electrode membrane has better mechanical property.
The specific surface areas of polytetrafluoroethylene powder of different types are different, the specific surface areas of polytetrafluoroethylene support frameworks after film rolling are different, in order to further know and master the fibrosis degree of the adhesive, the mechanical properties of the dry electrode membrane are further improved, and optionally, the specific surface areas of the polytetrafluoroethylene powder are S0, so that S/S0 meets the following conditions: S/S0 is more than or equal to 1.5. Further alternatively, let S/S0 satisfy: S/S0 > 2. Among them, the method for detecting the specific surface area S0 of the polytetrafluoroethylene powder includes, but is not limited to, a liquid nitrogen adsorption BET method, an argon adsorption method, a gas permeation method, a mercury absorption method, and an iodine absorption method.
Optionally, the polytetrafluoroethylene powder accounts for 1% -5% of the mass of the mixed material. The mass ratio of the polytetrafluoroethylene powder to the mixed material is obtained through the test by the method, and the mass ratio is not repeated here.
Optionally, the mass ratio of the electrode active material to the mixed material is 90% -98%. The electrode active material is as described above, and will not be described here again.
Optionally, the conductive agent accounts for 1% -5% of the mass of the mixed material. Wherein, the conductive agent is described above and will not be described here again.
The specific surface area of the polytetrafluoroethylene supporting framework in the dry electrode membrane is obtained through the test by the method, and the specific surface area is not repeated here.
In a third aspect the present application provides an electrode sheet, in some embodiments, comprising a current collector and a dry electrode membrane located over the current collector, the dry electrode membrane being as described above or prepared by a method of preparation as described above. The electrode sheet can be prepared by rolling a dry electrode membrane and a current collector. During the rolling process of the dry electrode membrane and the current collector, the polytetrafluoroethylene supporting framework is not damaged generally.
Dry electrode membranes generally utilize fibrillation of the binder to form a self-supporting framework that binds the active material or other materials. The degree of fibrosis of the binder is a key factor affecting the film formation of the electrode membrane and various properties after film formation. The traditional characterization method of the fibrosis degree of the binder is to evaluate and monitor by combining with an SEM image, and the method has large human error and is not beneficial to mass production development. In general, during the mixing stage of polytetrafluoroethylene powder, electrode active material and conductive agent, polytetrafluoroethylene produces fibrillation, but the degree of fibrillation during the mixing stage is relatively low, and polytetrafluoroethylene is fully fibrillated to form a self-supporting membrane mainly by virtue of the mixing, kneading and calendaring film-forming stage. Therefore, testing the extent of binder fibrosis during the compounding stage is not significant to subsequent film production guidelines. According to the fourth aspect of the application, a method for detecting the fibrosis degree of the adhesive in the dry electrode membrane is provided, and the fibrosis degree of the adhesive is tested after calendaring to form a membrane, so that human factor errors can be avoided, quantitative comparison can be performed, the quality of the dry electrode membrane can be monitored in real time, the subsequent membrane production can be guided, the rejection rate can be reduced, and the processing performance of the pole piece can be improved. In some embodiments, a method of detecting the degree of binder fibrosis in a dry electrode membrane comprises the steps of:
Digestion treatment is carried out on the dry electrode membrane with polytetrafluoroethylene as a binder, so as to obtain a polytetrafluoroethylene supporting framework with a continuous framework structure;
Detecting the specific surface area S of the polytetrafluoroethylene support framework;
If the adhesive is 12m 2/g≤S≤25m2/g, the adhesive fibrosis degree is qualified, if S is less than 12m 2/g, the adhesive fibrosis degree is not qualified, and if S is more than 25m 2/g, the detection is invalid.
The combination experiment shows that when the dry electrode membrane is 12m 2/g≤S≤25m2/g, the tensile strength of the dry electrode membrane can reach more than 1MPa, and the degree of the binder fibrosis is judged to be qualified. When S is smaller than 12m 2/g and the tensile strength of the dry electrode membrane is lower than 1MPa, the production quality requirement is not met at the moment, and the degree of the binder fibrosis is judged to be unqualified. When the digestion treatment is incomplete, S > 25m 2/g will occur, at which point the detection is ineffective.
According to the application, the specific surface area of the polytetrafluoroethylene support skeleton in the dry electrode membrane is monitored, so that the degree of fibrosis of the adhesive can be judged, however, the polytetrafluoroethylene support skeleton is an internal structure of the dry electrode membrane, the specific surface area of the polytetrafluoroethylene support skeleton cannot be directly obtained through testing the dry electrode membrane, and the polytetrafluoroethylene support skeleton is successfully obtained through digestion treatment of the dry electrode membrane by further research. The method has the advantages that the specific surface area of the polytetrafluoroethylene supporting framework is detected, the degree of fibrosis of the dry electrode membrane after calendaring to form a membrane is judged, so that artificial factor errors can be avoided, quantitative comparison can be carried out, the quality of the dry electrode membrane can be monitored in real time, subsequent membrane production can be guided, rejection rate is reduced, and the processability of the pole piece is improved.
Considering the specific surface areas of polytetrafluoroethylene powder of different types, the specific surface areas of polytetrafluoroethylene support frameworks after calendaring and film forming are different, so as to further know and master the degree of fibrosis of the adhesive. Optionally, the preparation raw materials of the dry electrode membrane comprise polytetrafluoroethylene powder, wherein the specific surface area of the polytetrafluoroethylene powder is S0, and if 12m 2/g≤S≤25m2/g and S/S0 is more than 2, the fibrosis degree of the adhesive is optimal; if 12m 2/g≤S≤25m2/g and 1.5.ltoreq.S/S0.ltoreq.2, the binder has a good degree of fibrosis.
The combination experiment shows that when 12m 2/g≤S≤25m2/g and S/S0 is more than 2, the tensile strength of the dry electrode membrane can reach more than 1.5MPa, and the fiber degree of the adhesive is judged to be good. When 12m 2/g≤S≤25m2/g and 1.5.ltoreq.S/S0.ltoreq.2, the tensile strength of the dry electrode membrane is between 1MPa and 1.5MPa, and the degree of the binder fibrosis is judged to be good.
And (3) carrying out digestion treatment on the dry electrode membrane taking polytetrafluoroethylene as an adhesive, so that electrode active materials and conductive agents adhered to the polytetrafluoroethylene support framework can be removed, and the influence of the electrode active materials and the conductive agents on a test result is eliminated. And the digestion treatment is carried out until a polytetrafluoroethylene supporting framework with a continuous framework is obtained, so that the influence of the digestion treatment on the specific surface area of the polytetrafluoroethylene supporting framework can be reduced.
Optionally, the digestion treatment is carried out on the dry electrode membrane taking polytetrafluoroethylene as a binder, and the digestion treatment comprises the following steps: and adding an oxidant into the dry electrode membrane to remove the electrode active material and the conductive agent in the dry electrode membrane.
The dry electrode membrane is prepared by a dry process, and can be a dry positive electrode membrane or a dry negative electrode membrane.
When the dry electrode membrane is a dry positive electrode membrane, the electrode active material is a positive electrode active material. The oxidizing agent comprises perchloric acid, hydrochloric acid and nitric acid. Optionally, the perchloric acid is utilized to remove the conductive agent in the dry electrode membrane, and the reaction conditions comprise a reaction temperature of 150-200 ℃ and a reaction time of 20-40 min. Optionally, the hydrochloric acid and the nitric acid are used to remove the positive electrode active material in the dry electrode membrane, and the reaction conditions include: the reaction temperature is 15-40 ℃ and the reaction time is 10-30 min. Optionally, the perchloric acid is provided by perchloric acid aqueous solution, the mass concentration of the perchloric acid aqueous solution is 70% -72%, and 8-15 mL of perchloric acid aqueous solution is added to each 9cm 2 area of dry electrode membrane. Optionally, the hydrochloric acid is provided by an aqueous hydrochloric acid solution, the nitric acid is provided by an aqueous nitric acid solution, and the volume ratio of the aqueous hydrochloric acid solution to the aqueous nitric acid solution is (2-4): 1, the mass concentration of the hydrochloric acid aqueous solution is 36% -38%, and the mass concentration of the nitric acid aqueous solution is 65% -68%. And adding 8-15 mL of a total volume of the aqueous solution of hydrochloric acid and the aqueous solution of nitric acid into each 9cm 2 area dry electrode membrane.
In one embodiment, the digestion treatment of the dry electrode membrane comprises the steps of: adding perchloric acid into the dry electrode membrane to remove the conductive agent, thereby obtaining an intermediate product; hydrochloric acid and nitric acid are added to the intermediate product to remove the positive electrode active material.
When the dry electrode membrane is a dry negative electrode membrane, the electrode active material is a negative electrode active material. The oxidizing agent comprises perchloric acid. Optionally, the perchloric acid is used to remove the negative electrode active material and the conductive agent in the dry electrode membrane, and the reaction conditions include: the reaction temperature is 150-200 ℃ and the reaction time is 20-40 min. Optionally, the perchloric acid is provided by perchloric acid aqueous solution, the mass concentration of the perchloric acid aqueous solution is 70% -72%, and 8-15 mL of perchloric acid aqueous solution is added to each 9cm 2 area of dry electrode membrane.
In one embodiment, the digestion treatment of the dry electrode membrane comprises the steps of: perchloric acid is added to the dry electrode film sheet to remove the negative electrode active material and the conductive agent.
The selection and the amount of the positive electrode active material, the negative electrode active material and the conductive agent, the polytetrafluoroethylene powder and the polytetrafluoroethylene supporting framework are as described above, and are not described herein.
Alternatively, the method of detecting the specific surface area S of the polytetrafluoroethylene support skeleton includes, but is not limited to, a liquid nitrogen adsorption BET method, an argon adsorption method, a gas permeation method, a mercury absorption method, and an iodine absorption method.
The following examples and comparative examples are further illustrated by the fact that the materials used, unless otherwise indicated, are commercially available and that the equipment used, unless otherwise indicated, are commercially available and that the processes involved, unless otherwise indicated, are routine selections by those skilled in the art.
Example 1
The embodiment provides a dry positive electrode membrane, a preparation method thereof and a method for detecting the fibrosis degree of a binder in the dry positive electrode membrane, which comprises the following steps:
And step 1, taking 0.25g SUPER-P and 9.45g ternary nickel cobalt manganese anode material, and premixing for 2min at the rotating speed of 600rpm to obtain premix. 0.3g PTFE powder was added to the premix, and the mixture was centrifugally dispersed at 1500rpm for 5 minutes to obtain a mixed material. The mixture was calendered 5-6 times at 100 ℃ to form a dry positive membrane 60 μm thick.
And 2, cutting a dry-method positive electrode membrane of 3 multiplied by 3 (cm multiplied by cm), putting the membrane into a 150mL beaker, adding 10mL of perchloric acid aqueous solution (the mass concentration is 72%), covering a surface dish, placing the membrane on an electric heating furnace at 190 ℃ for reaction for 30min, taking down the membrane, cooling the membrane to room temperature, adding 10mL of aqua regia (concentrated hydrochloric acid (the mass concentration is 38%):concentrated nitric acid (the mass concentration is 68%) =3:1, v:v) for reaction for 20min, taking out the membrane after the reaction is finished, washing the membrane for 2-3 times by using deionized water, and placing the membrane in an oven at 70 ℃ for drying for 2-3 h to obtain the PTFE support skeleton.
Test 1, the specific surface areas of PTFE powder and PTFE supporting framework are respectively tested by a liquid nitrogen adsorption BET method, the mass ratio of PTFE supporting framework after digestion treatment to dry-method positive electrode membrane before digestion treatment is tested, and the test results are shown in Table 1.
Test 2 SEM characterization of PTFE powder, dry positive membrane and PTFE support skeleton, fig. 1 is a live view of PTFE powder, fig. 2 is a SEM view of PTFE powder, fig. 3 is a live view of dry positive membrane, fig. 4 is a SEM view of dry positive membrane, fig. 5 is a live view of PTFE support skeleton, and fig. 6 is a SEM view of PTFE support skeleton.
As can be seen in conjunction with fig. 5 and 6, the PTFE support matrix has a continuous matrix structure, indicating that the digestion treatment described above does not damage the PTFE support matrix.
Test 3, with reference to GB/T1040.3-2006 standard, tensile properties of the dry cathode film were tested, and the test results are shown in Table 1.
Example 2
The embodiment provides a dry positive electrode membrane, a preparation method thereof and a method for detecting the fibrosis degree of a binder in the dry positive electrode membrane, which comprises the following steps:
Step 1, premixing 0.25g of Keqin black and 9.45g of lithium iron manganese phosphate anode material for 2min at the rotating speed of 600rpm to obtain a premix; 0.3g PTFE powder was added to the premix, and the mixture was centrifugally dispersed at 1500rpm for 5 minutes to obtain a mixed material. The mixture is calendered for 5-6 times at 100 ℃ to form a dry positive membrane with the thickness of 100 mu m.
And 2, cutting a dry-method positive electrode membrane of 3 multiplied by 3 (cm multiplied by cm), putting the membrane into a 150mL beaker, adding 10mL of perchloric acid aqueous solution (the mass concentration is 72%), covering a surface dish, placing the membrane on an electric heating furnace at 190 ℃ for reaction for 30min, taking down the membrane, cooling the membrane to room temperature, adding 10mL of aqua regia (concentrated hydrochloric acid (the mass concentration is 38%):concentrated nitric acid (the mass concentration is 68%) =3:1, v:v) for reaction for 20min, taking out the membrane after the reaction is finished, washing the membrane for 2-3 times by using deionized water, and placing the membrane in an oven at 70 ℃ for drying for 2-3 h to obtain the PTFE support skeleton.
Test 1, the specific surface areas of PTFE powder and PTFE supporting framework are respectively tested by a liquid nitrogen adsorption BET method, the mass ratio of PTFE supporting framework after digestion treatment to dry-method positive electrode membrane before digestion treatment is tested, and the test results are shown in Table 1.
Test 2, with reference to GB/T1040.3-2006 standard, tensile properties of dry cathode films were tested, and the test results are shown in Table 1.
Example 3
Step 1, premixing 0.25g SUPER-P and 9.45g lithium iron phosphate anode material for 2min at the rotating speed of 600rpm to obtain premix; 0.3g PTFE powder was added to the premix, and the mixture was centrifugally dispersed at 1500rpm for 5 minutes to obtain a mixed material. The mixture is calendered for 5-6 times at 100 ℃ to form a dry positive membrane with the thickness of 100 mu m.
And 2, cutting a dry-method positive electrode membrane of 3 multiplied by 3 (cm multiplied by cm), putting the membrane into a 150mL beaker, adding 10mL of perchloric acid aqueous solution (the mass concentration is 72%), covering a surface dish, placing the membrane on an electric heating furnace at 190 ℃ for reaction for 30min, taking down the membrane, cooling the membrane to room temperature, adding 10mL of aqua regia (concentrated hydrochloric acid (the mass concentration is 38%):concentrated nitric acid (the mass concentration is 68%) =3:1, v:v) for reaction for 20min, taking out the membrane after the reaction is finished, washing the membrane for 2-3 times by using deionized water, and placing the membrane in an oven at 70 ℃ for drying for 2-3 h to obtain the PTFE support skeleton.
Test 1, the specific surface areas of PTFE powder and PTFE supporting framework are respectively tested by a liquid nitrogen adsorption BET method, the mass ratio of PTFE supporting framework after digestion treatment to dry-method positive electrode membrane before digestion treatment is tested, and the test results are shown in Table 1.
Test 2, with reference to GB/T1040.3-2006 standard, tensile properties of dry cathode films were tested, and the test results are shown in Table 1.
Example 4
And step 1, taking 0.25g SUPER-P and 9.45g ternary nickel cobalt manganese anode material, and premixing for 2min at the rotating speed of 600rpm to obtain premix. 0.3g PTFE powder was added to the premix, and the mixture was centrifugally dispersed at 1500rpm for 5 minutes to obtain a mixed material. The mixture was calendered 3-4 times at 100 ℃ to form a dry positive membrane 80 μm thick.
And 2, cutting a dry-method positive electrode membrane of 3 multiplied by 3 (cm multiplied by cm), putting the membrane into a 150mL beaker, adding 10mL of perchloric acid aqueous solution (the mass concentration is 72%), covering a surface dish, placing the membrane on an electric heating furnace at 190 ℃ for reaction for 30min, taking down the membrane, cooling the membrane to room temperature, adding 10mL of aqua regia (concentrated hydrochloric acid (the mass concentration is 38%):concentrated nitric acid (the mass concentration is 68%) =3:1, v:v) for reaction for 20min, taking out the membrane after the reaction is finished, washing the membrane for 2-3 times by using deionized water, and placing the membrane in an oven at 70 ℃ for drying for 2-3 h to obtain the PTFE support skeleton.
Test 1, the specific surface areas of PTFE powder and PTFE supporting framework are respectively tested by a liquid nitrogen adsorption BET method, the mass ratio of PTFE supporting framework after digestion treatment to dry-method positive electrode membrane before digestion treatment is tested, and the test results are shown in Table 1.
Test 2, with reference to GB/T1040.3-2006 standard, tensile properties of dry cathode films were tested, and the test results are shown in Table 1.
Example 5
Step 1, premixing 0.25g SUPER-P and 9.45g lithium iron phosphate anode for 2min at the rotating speed of 600rpm to obtain premix; 0.3g PTFE powder was added to the premix, and the mixture was centrifugally dispersed at 1500rpm for 5 minutes to obtain a mixed material. The mixture was calendered 5-6 times at 100 ℃ to form a dry positive membrane 60 μm thick.
And 2, cutting a dry-method positive electrode membrane of 3 multiplied by 3 (cm multiplied by cm), putting the membrane into a 150mL beaker, adding 10mL of perchloric acid aqueous solution (the mass concentration is 72%), covering a surface dish, placing the membrane on an electric heating furnace for reaction for 40min at 150 ℃, taking down the membrane, cooling the membrane to room temperature, adding 10mL of aqua regia (concentrated hydrochloric acid (the mass concentration is 38%):concentrated nitric acid (the mass concentration is 68%) =3:1, v:v) for reaction for 20min, taking out the membrane after the reaction is finished, washing the membrane for 2-3 times by using deionized water, and placing the membrane in an oven at 70 ℃ for 2-3 h for drying to obtain the PTFE support skeleton.
Test 1, the specific surface areas of PTFE powder and PTFE supporting framework are respectively tested by a liquid nitrogen adsorption BET method, the mass ratio of PTFE supporting framework after digestion treatment to dry-method positive electrode membrane before digestion treatment is tested, and the test results are shown in Table 1.
Test 2, with reference to GB/T1040.3-2006 standard, tensile properties of dry cathode films were tested, and the test results are shown in Table 1.
Comparative example 1
This comparative example provides a dry cathode membrane, a method of preparing the same, and a method of detecting the degree of binder fibrosis in the dry cathode membrane, substantially the same as in example 1, with the main differences: the parameters of the calendering stage are different. The step 1 is as follows:
and step 1, taking 0.25g SUPER-P and 9.45g ternary nickel cobalt manganese anode material, and premixing for 2min at the rotating speed of 600rpm to obtain premix. 0.3g PTFE powder was added to the premix, and the mixture was centrifugally dispersed at 1500rpm for 5 minutes to obtain a mixed material. The mixture was calendered 3-4 times at 80 ℃ to form a dry positive membrane 100 μm thick.
Test 1, the specific surface areas of PTFE powder and PTFE supporting framework are respectively tested by a liquid nitrogen adsorption BET method, the mass ratio of PTFE supporting framework after digestion treatment to dry-method positive electrode membrane before digestion treatment is tested, and the test results are shown in Table 1.
Test 2, with reference to GB/T1040.3-2006 standard, tensile properties of dry cathode films were tested, and the test results are shown in Table 1.
Comparative example 2
This comparative example provides a dry cathode membrane, a method of preparing the same, and a method of detecting the degree of binder fibrosis in the dry cathode membrane, substantially the same as in example 1, with the main differences: the digestion method is different, and the step2 is as follows:
and 2, cutting a dry-method positive electrode membrane of 3 multiplied by 3 (cm multiplied by cm), adding 10mL of aqua regia (concentrated hydrochloric acid (the mass concentration is 38%):concentrated nitric acid (the mass concentration is 68%) =3:1, v:v) for reacting for 20min, taking out the membrane after the reaction is finished, cleaning the membrane for 2-3 times by using deionized water, and placing the membrane in a drying oven at 70 ℃ for 2-3 hours for drying to obtain the PTFE supporting framework.
Test 1, the specific surface areas of PTFE powder and PTFE supporting framework are respectively tested by a liquid nitrogen adsorption BET method, the mass ratio of PTFE supporting framework after digestion treatment to dry-method positive electrode membrane before digestion treatment is tested, and the test results are shown in Table 1.
Test 2 SEM characterization of PTFE support matrix, fig. 7 is a live view of PTFE support matrix, and fig. 8 is an SEM of PTFE support matrix. As can be seen from fig. 7 and 8, the digestion is insufficient, and the PTFE support matrix also remains with the conductive agent.
Test 3, with reference to GB/T1040.3-2006 standard, tensile properties of the dry cathode film were tested, and the test results are shown in Table 1.
TABLE 1
The technical features of the above-described embodiments may be arbitrarily combined, and all possible combinations of the technical features in the above-described embodiments are not described for brevity of description, however, as long as there is no contradiction between the combinations of the technical features, they should be considered as the scope of the description.
The above examples illustrate only a few embodiments of the application, which are described in detail and are not to be construed as limiting the scope of the application. It should be noted that it will be apparent to those skilled in the art that several variations and modifications can be made without departing from the spirit of the application, which are all within the scope of the application. Accordingly, the scope of protection of the present application is to be determined by the appended claims.
Claims (8)
1. A method for detecting the degree of binder fibrosis in a dry electrode membrane comprising the steps of:
Carrying out digestion treatment on a dry electrode membrane with polytetrafluoroethylene as a binder until a polytetrafluoroethylene supporting framework with a continuous framework structure is obtained, wherein the digestion treatment comprises the following steps: adding an oxidant into the dry electrode membrane to remove electrode active materials and conductive agents in the dry electrode membrane;
Detecting the specific surface area S of the polytetrafluoroethylene support framework;
If the adhesive is 12m 2/g≤S≤25m2/g, the adhesive fibrosis degree is qualified, if the adhesive fibrosis degree is less than 12m 2/g, the adhesive fibrosis degree is not qualified, and if the adhesive fibrosis degree is more than 25m 2/g, the detection is invalid;
the conductive agent is at least one selected from conductive carbon black, carbon nanotubes, carbon fibers, graphite and graphene;
The electrode active material is an anode active material, the anode active material is selected from at least one of ternary nickel cobalt manganese, lithium iron phosphate, lithium nickelate, lithium manganate and lithium cobaltate, and the oxidant comprises perchloric acid, hydrochloric acid and nitric acid;
Or the electrode active material is a negative electrode active material, the negative electrode active material is selected from at least one of graphite, hard carbon and mesophase carbon microspheres, and the oxidant comprises perchloric acid.
2. The method for detecting the degree of binder fibrosis in a dry electrode membrane according to claim 1, wherein the dry electrode membrane is prepared from polytetrafluoroethylene powder with a specific surface area of S0, and the degree of binder fibrosis is preferably 12m 2/g≤S≤25m2/g and S/S0 > 2; if 12m 2/g≤S≤25m2/g and 1.5.ltoreq.S/S0.ltoreq.2, the binder has a good degree of fibrosis.
3. The method for detecting the degree of binder fibrosis in a dry electrode membrane according to claim 1, wherein when the electrode active material is a positive electrode active material, the perchloric acid is used to remove the conductive agent in the dry electrode membrane, and the reaction conditions include a reaction temperature of 150 ℃ to 200 ℃ and a reaction time of 20min to 40min.
4. The method of detecting the degree of binder fibrosis in a dry electrode membrane of claim 1 wherein the hydrochloric acid and nitric acid are utilized to remove the positive active material in the dry electrode membrane, the reaction conditions comprising: the reaction temperature is 15-40 ℃ and the reaction time is 10-30 min.
5. The method for detecting the degree of binder fibrosis in a dry electrode membrane according to claim 1, wherein when the electrode active material is a positive electrode active material, the perchloric acid is supplied from an aqueous perchloric acid solution having a mass concentration of 70% to 72%.
6. The method for detecting the degree of binder fibrosis in a dry electrode membrane according to claim 1, wherein the hydrochloric acid is provided by an aqueous hydrochloric acid solution, the nitric acid is provided by an aqueous nitric acid solution, and the volume ratio of the aqueous hydrochloric acid solution to the aqueous nitric acid solution is (2-4): 1, the mass concentration of the hydrochloric acid aqueous solution is 36% -38%, and the mass concentration of the nitric acid aqueous solution is 65% -68%.
7. The method for detecting the degree of binder fibrosis in a dry electrode membrane of claim 1 wherein when the electrode active material is a negative electrode active material, the perchloric acid is used to remove the negative electrode active material and the conductive agent in the dry electrode membrane, the reaction conditions comprising: the reaction temperature is 150-200 ℃ and the reaction time is 20-40 min.
8. The method for detecting the degree of binder fibrosis in a dry electrode membrane according to claim 1, wherein when the electrode active material is a negative electrode active material, the perchloric acid is supplied from an aqueous perchloric acid solution having a mass concentration of 70% to 72%.
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