Method for measuring content of conductive component in composition

Abstract

The invention provides a method for measuring the content of a conductive component in a composition, which comprises the following steps of: setting thermogravimetric parameters according to a decomposition temperature interval of the conductive component, performing thermogravimetric decomposition on the composition in an inert atmosphere, collecting thermogravimetric decomposition data, and calculating to obtain the content of the conductive component, the invention provides a method capable of accurately measuring the content of conductive components in the composition, so that the technical problem of limitation in optimization analysis of the conductive components is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of conductive agent testing, and particularly relates to a method for determining the content of conductive components in a composition. Background Art

[0002] The positive electrode material of a lithium battery usually includes an active material, a binder, and a conductive material.

[0003] The conductive material in the battery is mainly used to improve the conductivity of the battery, thereby improving the charge and discharge performance and energy density of the battery. By effectively identifying and analyzing the conductive material, the type, dosage, and distribution of the conductive material can be optimized, thereby improving the overall performance of the battery.

[0004] However, at present, the analysis of the conductive material in the positive electrode material is more speculative, and it is impossible to efficiently and accurately determine and calculate the content of the conductive material. Therefore, there are limitations in the optimization analysis of the conductive material. Summary of the Invention

[0005] An embodiment of the present invention provides a method for determining the content of conductive components in a composition, which can solve the technical problem of limitations in the optimization analysis of conductive agents.

[0006] In a first aspect, an embodiment of the present invention provides a method for determining the content of conductive components in a composition,

[0007] The determination method includes the following steps:

[0008] Set the thermogravimetric parameters according to the decomposition temperature range of the conductive component, and under an inert atmosphere, perform thermogravimetric decomposition on the composition, collect the thermogravimetric decomposition data, and calculate the content of the conductive component.

[0009] In one embodiment, the determination method further includes:

[0010] Detect the positive electrode material by an electron microscope, and confirm the type of the conductive component by observing the morphology;

[0011] Obtain the decomposition temperature range of the conductive component according to the type of the conductive component.

[0012] In one embodiment, the method for setting the thermogravimetric parameters includes the following steps:

[0013] Heat up the composition to reach a first target temperature and keep it warm;

[0014] Heat up again to reach a second target temperature and keep it warm;

[0015] Continue to heat up to reach a third target temperature and keep it warm;

[0016] Wherein, the first target temperature is less than the second target temperature; and / or

[0017] The second target temperature is less than the third target temperature.

[0018] In one embodiment, the first target temperature is 450°C to 500°C; and / or

[0019] The second target temperature is 550°C to 650°C; and / or

[0020] The third target temperature is 680°C to 750°C.

[0021] In one embodiment, in the step of thermogravimetric decomposition, after each temperature increase, the heat preservation time is 30 min to 45 min.

[0022] In one embodiment, before reaching the first target temperature, it is preheated to a fourth target temperature, and the fourth target temperature is less than the first target temperature.

[0023] In one embodiment, the fourth target temperature is 150°C to 250°C.

[0024] In one embodiment, the inert atmosphere includes at least one of a nitrogen atmosphere, an argon atmosphere, and a helium atmosphere.

[0025] In one embodiment, the composition includes a mixture of an active component, multiple conductive components, a binder component, and a solvent;

[0026] Preferably, the composition includes a mixture of an active component and multiple conductive components.

[0027] In one embodiment, the conductive component includes a first conductive agent and a second conductive agent;

[0028] Wherein, the average decomposition temperature of the first conductive agent is less than that of the second conductive agent.

[0029] In one embodiment, the conductive component further includes a third conductive agent;

[0030] The average temperature of the third conductive agent is greater than the average decomposition temperature of the first conductive agent and less than that of the second conductive agent.

[0031] In one embodiment, the conductive component includes at least two of conductive carbon black, functionalized graphite, and carbon nanotubes.

[0032] In one embodiment, the composition is prepared by the following method:

[0033] Immerse the cathode material in a solvent and stir to obtain a first mixed solution;

[0034] Filter the first mixture, collect the filter cake and dry it to obtain the composition.

[0035] In one embodiment, in the step of immersing the cathode material in the solvent, the temperature is set to 50°C to 100°C; and / or

[0036] In the step of filtering the first mixture,

[0037] Shake the first mixture and then filter it;

[0038] Preferably, the temperature range for filtration is 60°C to 80°C.

[0039] In one embodiment, the thermogravimetric curve of the composition includes:

[0040] A first plateau, which appears in the first temperature range;

[0041] Wherein, the first plateau includes a plurality of sub-plateaus;

[0042] The temperature range of the sub-plateau is consistent with the decomposition temperature range of the conductive component.

[0043] In one embodiment, the first temperature range is 380°C to 750°C.

[0044] In one embodiment, the sub-plateau includes:

[0045] A first sub-plateau, which appears between 380°C and 480°C; and / or

[0046] A second sub-plateau, which appears between 500°C and 600°C; and / or

[0047] A third sub-plateau, which appears between 680°C and 750°C.

[0048] In one embodiment, the slope of the third sub-plateau is less than the slope of the first sub-plateau; and / or

[0049] The slope of the second sub-plateau is less than the slope of the first sub-plateau.

[0050] In one embodiment, the thermogravimetric curve of the mixture further includes:

[0051] A second plateau, which appears within the second temperature range;

[0052] The average temperature of the second temperature range is less than the average temperature of the first temperature range.

[0053] In one embodiment, the second temperature range is 100°C to 210°C.

[0054] Advantages of the embodiments of the present invention:

[0055] In the embodiments of the present invention, a method for determining the content of a conductive component in a composition is provided. According to the decomposition temperature range, thermogravimetric parameters are set, the composition is subjected to thermogravimetric decomposition, and through the collected thermogravimetric decomposition data, the content of the conductive component is calculated, realizing the accurate determination of the content of the conductive component in the composition, thereby improving the technical problem of the limitation in the optimization analysis of the conductive component. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those skilled in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0057] Figure 1 is a flowchart of the determination method provided by the embodiments of the present invention;

[0058] Figure 2 is a flowchart of the thermogravimetric parameter setting method provided by the embodiments of the present invention;

[0059] Figure 3 are scanning electron microscope images of the conductive components SP, FG-5 and CNT;

[0060] Figure 4 is a schematic diagram of the thermogravimetric curve provided by Embodiment 1 of the present invention;

[0061] Figure 5 is a schematic diagram of the thermogravimetric curve provided by Embodiment 5 of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0062] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative efforts belong to the scope of protection of the present invention. In addition, it should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention. In the present invention, unless otherwise stated, the orientation terms such as "upper" and "lower" usually refer to the upper and lower in the actual use or working state of the device, specifically the drawing direction in the drawings; and "inner" and "outer" refer to the outline of the device.

[0063] Common conductive materials include conductive carbon black, carbon nanotubes, functionalized graphite, etc.

[0064] Different conductive materials have different action mechanisms.

[0065] For example, carbon black forms a three-dimensional conductive network through nanoparticles, fills the gaps between active material particles, and shortens the electron transport path. Carbon nanotubes utilize a one-dimensional tubular structure to form a long-range conductive network, while providing mechanical support and enhancing the stability of the electrode structure. Functionalized graphite uses a two-dimensional sheet structure to cover the surface of the active material, forming an efficient conductive interface and suppressing volume expansion.

[0066] Therefore, the accurate measurement of the content of the conductive component in the battery is a key technical means for optimizing the battery performance, which is conducive to the R & D personnel to control the quality of the battery during the production process.

[0067] However, in the related technology, only the microscopic morphology of the conductive component is observed through a Scanning Electron Microscope (SEM) to achieve the speculative analysis of the conductive component, and the accurate analysis of the content of the conductive component cannot be carried out.

[0068] In view of this, the embodiments of the present application provide a method for determining the content of the conductive component in a composition.

[0069] The embodiments of the present application provide a method for determining the content of the conductive component in a composition, referring to Figure 1 , the determination method includes the following steps:

[0070] S100. Confirm the decomposition temperature range of the conductive component;

[0071] S200. Set the thermogravimetric parameters according to the decomposition temperature range of the conductive component, thermally decompose the composition in an inert atmosphere, collect the thermogravimetric decomposition data, and calculate the content of the conductive component.

[0072] By adopting the above scheme, it is first necessary to confirm the decomposition temperature range of the conductive component, then set the thermogravimetric parameters according to the decomposition temperature range, thermally decompose the composition, and calculate the content of the conductive component through the collected thermogravimetric decomposition data, realizing the accurate determination of the content of the conductive component in the composition, thereby improving the technical problem of the limitation in the optimization analysis of the conductive component.

[0073] In some embodiments of the present application, in step S100, confirming the decomposition temperature range of the conductive component may include:

[0074] S101. Detect through an electron microscope and confirm the type of the conductive component by observing the morphology;

[0075] S102. Obtain the decomposition temperature range of the conductive component according to the type of the conductive component.

[0076] By adopting the above solution, the morphology map after detection by an electron microscope is observed, the type of the conductive component in the composition is analyzed and confirmed, and the decomposition temperature range of the corresponding conductive component is determined according to the type.

[0077] In some embodiments of the present application, the electron microscope may be at least one of a scanning electron microscope and a transmission electron microscope.

[0078] In some embodiments of the present application, there may be two or more conductive components.

[0079] In some embodiments of the present application, the conductive component may include a first conductive agent and a second conductive agent, and the average decomposition temperature of the first conductive agent is less than that of the second conductive agent.

[0080] It should be noted that the decomposition temperature is generally a temperature range. By using the average decomposition temperature as a measurement standard, the comparison of the decomposition temperatures of multiple conductive components can be realized, and the average decomposition temperature is the median value of the decomposition temperature.

[0081] Exemplarily, the first conductive agent may include conductive carbon black (Super P, SP). The decomposition temperature range of the conductive carbon black is 380°C to 480°C, and the average decomposition temperature of the conductive carbon black is 415°C.

[0082] Exemplarily, the second conductive agent may include carbon nanotubes (Carbon Nanotube, CNT). The decomposition temperature range of the carbon nanotubes is 680°C to 750°C, and the average decomposition temperature of the carbon nanotubes is 715°C.

[0083] In some embodiments of the present application, the conductive component may further include a third conductive agent; wherein, the average decomposition temperature of the third conductive agent is greater than that of the first conductive agent; and the average decomposition temperature of the third conductive agent is less than that of the second conductive agent.

[0084] Exemplarily, the third conductive agent may be functionalized graphite (Functionalized Graphite-5, FG-5). The decomposition temperature range of the functionalized graphite is 500°C to 600°C, and the average decomposition temperature of the functionalized graphite is 550°C.

[0085] In some embodiments of the present application, in step S200, referring to Figure 2 , the method for setting the thermogravimetric parameters may include the following steps:

[0086] S201. Heat up the composition to reach the first target temperature and keep it warm;

[0087] S202. Heat up again to reach the second target temperature and keep it warm;

[0088] S203. Continue to increase the temperature to reach the third target temperature and keep it warm;

[0089] Among them, the first target temperature is less than the second target temperature; and

[0090] The second target temperature is less than the third target temperature.

[0091] In some embodiments of the present application, the first target temperature can be 450 °C to 500 °C. Further, the first target temperature can be 470 °C to 490 °C. Exemplarily, the first target temperature can be 470 °C, 472 °C, 475 °C, 478 °C, 480 °C, 482 °C, 485 °C, 487 °C, 490 °C, and any interval between two adjacent values above.

[0092] In some embodiments of the present application, the second target temperature can be 550 °C to 650 °C. Further, the second target temperature can be 570 °C to 630 °C. Exemplarily, the first target temperature can be 570 °C, 575 °C, 580 °C, 585 °C, 590 °C, 595 °C, 600 °C, 605 °C, 610 °C, 615 °C, 620 °C, 625 °C, 630 °C, and any interval between two adjacent values above.

[0093] In some embodiments of the present application, the third target temperature is 680 °C to 750 °C. Further, the third target temperature can be 700 °C to 730 °C. Exemplarily, the first target temperature can be 700 °C, 705 °C, 710 °C, 715 °C, 720 °C, 725 °C, 730 °C, and any interval between two adjacent values above.

[0094] In some embodiments of the present application, in steps S201 - S203, the heat preservation time can be 30 min to 45 min. Further, the heat preservation time can be 35 min to 40 min. Exemplarily, the heat preservation time can be 35 min, 36 min, 37 min, 38 min, 39 min, 40 min, and any value between two adjacent values above.

[0095] In some embodiments of the present application, in step S201, before reaching the first target temperature, the temperature is raised to the fourth target temperature, and the fourth target temperature is less than the first target temperature.

[0096] In some embodiments of the present application, the fourth target temperature may be from 150°C to 250°C. Further, the fourth target temperature may be from 170°C to 230°C. Exemplarily, the fourth target temperature may be 170°C, 175°C, 180°C, 185°C, 190°C, 195°C, 200°C, 205°C, 210°C, 215°C, 220°C, 225°C, 230°C, and any value between two adjacent above-mentioned values.

[0097] In some embodiments of the present application, in step S200, the inert atmosphere may include at least one of a nitrogen atmosphere, an argon atmosphere, and a helium atmosphere.

[0098] By adopting the above scheme, the argon atmosphere is superior to the nitrogen atmosphere in terms of high-temperature inertness, high-temperature stability, and test accuracy.

[0099] In some embodiments of the present application, the composition may include an active component and a plurality of conductive components.

[0100] By adopting the above scheme, the active component is usually composed of a transition metal oxide, and its metal-oxygen bond is relatively strong and requires higher energy to break. While the conductive component generally has relatively weak carbon-carbon bonds or carbon-oxygen bonds and a lower decomposition temperature. Therefore, the inclusion of the active component in the mixture does not affect the determination of the content of the conductive component.

[0101] In some embodiments of the present application, the components of the mixture may be a composition of an active component, a binder component, a solvent, and a plurality of conductive components.

[0102] By adopting the above scheme, the decomposition temperatures of the binder component and the solvent are generally lower than that of the conductive component. Therefore, when the mixture includes the binder component and the solvent, it does not affect the determination of the content of the conductive component.

[0103] In some embodiments of the present application, in step S200, the composition may be prepared by the following method:

[0104] S210. Immerse the positive electrode material in a solvent and stir to obtain a first mixed solution;

[0105] S220. Filter the first mixed solution, collect the filter cake and dry it to obtain the composition.

[0106] In some embodiments of the present application, in step S210, the temperature may be from 50°C to 100°C. Further, the temperature may be from 60°C to 90°C. Exemplarily, the temperature may be 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, and any value between two adjacent above-mentioned values.

[0107] In some embodiments of the present application, in step S220, before filtering the first mixture, the first mixture can be shaken repeatedly for 10 minutes to 30 minutes, and then filtered.

[0108] In some embodiments of the present application, in step S220, the temperature range for filtration can be from 60°C to 80°C. Further, the temperature range for filtration can be from 65°C to 75°C. Exemplarily, the filtration temperature can be 65°C, 66°C, 67°C, 68°C, 69°C, 70°C, 71°C, 72°C, 73°C, 74°C, 75°C, and any value between two adjacent values above.

[0109] In some embodiments of the present application, in step S220, if there are white or yellow impurities in the color of the dried filter cake, the following steps need to be carried out:

[0110] Soak the composition in a solvent to obtain a second mixture;

[0111] Filter the second mixture through the solvent, collect the filter cake and dry it for standby.

[0112] By adopting the above scheme, continuously filtering the second mixture through the solvent is beneficial to the adhesive component being fully dissolved in the solvent, so as to minimize the residue of the adhesive component in the obtained composition, which is beneficial to the accuracy of subsequent tests.

[0113] In some embodiments of the present application, the thermogravimetric curve of the mixture can include:

[0114] A first plateau, which appears in the first temperature range.

[0115] Among them, the first plateau can include multiple sub-plateaus, and the temperature range of the sub-plateau is consistent with the decomposition temperature range of the conductive component.

[0116] By adopting the above scheme, thermogravimetric decomposition of the mixture of the present application is carried out, and a first plateau appears on the thermogravimetric curve. The first plateau is mainly generated by the decomposition of the conductive component in the mixture. Since there are multiple conductive components, the first plateau includes multiple sub-plateaus. The temperature range at which each sub-plateau appears corresponds to the decomposition temperature range of one of the conductive components. Measure the initial ordinate and the final ordinate of each sub-plateau, and calculate the difference to obtain the content of each conductive component, thereby realizing the accurate measurement of the content of the conductive component.

[0117] It should be noted that being consistent means that the temperature range of the sub-plateau can be exactly the same as the decomposition temperature range of the conductive component, or the temperature range of the sub-plateau can be close (being close means being within 10°C of the endpoint value of the temperature range) to the decomposition temperature range of the conductive component.

[0118] In some embodiments of the present application, the first temperature range may be from 380°C to 750°C.

[0119] By adopting the above solution, since the decomposition temperature ranges of several common conductive agents are within the above temperature range, therefore, the first temperature range is set to be from 380°C to 750°C.

[0120] In some embodiments of the present application, the sub-platform may include a first sub-platform, and the first sub-platform appears between 380°C and 450°C.

[0121] By adopting the above solution, since the decomposition temperature range of conductive carbon black is from 380°C to 450°C, the temperature range where the first sub-platform appears is between 380°C and 450°C.

[0122] In some embodiments of the present application, the sub-platform may include a second sub-platform, and the second sub-platform appears between 500°C and 600°C.

[0123] By adopting the above solution, since the decomposition temperature range of functionalized graphite is from 500°C to 600°C, the temperature range where the second sub-platform appears is between 500°C and 600°C.

[0124] In some embodiments of the present application, the sub-platform may include a third sub-platform, and the third sub-platform appears between 680°C and 750°C.

[0125] By adopting the above solution, since the decomposition temperature range of carbon nanotubes is from 680°C to 750°C, the temperature range where the third sub-platform appears is between 680°C and 750°C.

[0126] In the thermogravimetric curve, the slope represents the mass loss rate per unit time (or temperature). The slope can reflect the severity of material decomposition.

[0127] In some embodiments of the present application, the slope of the third sub-platform is less than the slope of the first sub-platform.

[0128] By adopting the above solution, since the first sub-platform is generated by the decomposition of conductive carbon black, and conductive carbon black is amorphous carbon with a large specific surface area and many surface defects, the oxidation reaction occurs violently and rapidly. Therefore, the slope of the first sub-platform is the largest. While carbon nanotubes have a highly graphitized structure, the oxidation decomposition requires breaking the interlayer bonding of the tube wall. The surface defect sites of carbon nanotubes are few and the decomposition rate is slow. Therefore, the slope of the third sub-platform is less than the slope of the first sub-platform.

[0129] In some embodiments of the present application, the slope of the second sub-platform is less than the slope of the first sub-platform.

[0130] By adopting the above solution, since the functionalized graphite surface contains functional groups such as carboxyl and hydroxyl groups, these functional groups can decompose at around 500 °C. After the functional groups decompose, the graphite layer begins to oxidize and decompose. Therefore, the slope of the second sub-platform is smaller than that of the first sub-platform.

[0131] In some embodiments of the present application, the thermogravimetric curve of the mixture may further include:

[0132] A second platform, which appears in the second temperature range;

[0133] wherein, the average temperature of the second temperature range is less than the average temperature of the first temperature range.

[0134] By adopting the above solution, when the mixture is thermogravimetrically decomposed, the free water and bound water in the mixture will decompose preferentially, thereby forming a second platform.

[0135] In some embodiments of the present application, the second temperature range may be 100 °C to 210 °C. Further, the second temperature range may be 130 °C to 210 °C.

[0136] By adopting the above solution, when the mixture is heated to 100 °C, the free water can decompose. When the temperature is further increased to 210 °C, the bound water may decompose, thereby forming a second platform within 210 °C.

[0137] The present application will be specifically described below through specific embodiments. The following embodiments are only partial embodiments of the present application and do not limit the present application. The raw materials used in the following embodiments are all commercially available products unless otherwise specified.

[0138] Example 1

[0139] A method for determining the content of the conductive component in a composition, the method comprising the following steps:

[0140] S100. Observe the positive electrode material through SEM to preliminarily confirm the type of the conductive component; refer to Figure 3 , in this embodiment, the types of the conductive components are SP, FG-5, and CNT;

[0141] S200. Set the corresponding decomposition temperature parameters according to the decomposition temperatures of SP, FG-5, and CNT. Among them, the decomposition temperature of SP is 380 °C to 450 °C, the decomposition temperature of FG-5 is 500 °C to 600 °C, and the decomposition temperature of CNT is 680 °C to 750 °C;

[0142] S300. Place the mixture in a thermogravimetric analyzer, and perform thermogravimetric decomposition under an argon atmosphere, collect the thermogravimetric decomposition data, and calculate the content of each conductive component;

[0143] Among them, the parameter range of thermogravimetric decomposition is set as follows:

[0144] Heat up the mixture at a heating rate of 5 °C / min until it reaches 250 °C, and keep it at this temperature for 45 min.

[0145] Heat up to 500 °C and keep it at this temperature for 45 min.

[0146] Continue to heat up to 650 °C and keep it at this temperature for 45 min.

[0147] Heat up to 750 °C again and keep it at this temperature for 45 min.

[0148] In this embodiment, the mixture is prepared by the following steps:

[0149] S10. Place the cathode material in an oven at 80 °C, soak the cathode material in N-methylpyrrolidone, and shake for 30 min to obtain a first mixed solution.

[0150] S20. Filter the first mixed solution until the filtrate becomes clear, collect the upper powder cake and dry it to obtain the mixture.

[0151] Example 2

[0152] A method for determining the content of conductive components in a composition, which is different from Example 1 in that the thermogravimetric parameter range in step S300 is different. In this embodiment, the parameter range of thermogravimetric decomposition is set as follows:

[0153] Heat up the mixture at a heating rate of 10 °C / min until it reaches 250 °C, and keep it at this temperature for 45 min.

[0154] Heat up to 500 °C and keep it at this temperature for 45 min.

[0155] Continue to heat up to 650 °C and keep it at this temperature for 45 min.

[0156] Heat up to 750 °C again and keep it at this temperature for 45 min.

[0157] Example 3

[0158] A method for determining the content of conductive components in a composition, which is different from Example 1 in that the thermogravimetric parameter range in step S300 is different. In this embodiment, the parameter range of thermogravimetric decomposition is set as follows:

[0159] Heat up the mixture at a heating rate of 15 °C / min until it reaches 250 °C, and keep it at this temperature for 45 min.

[0160] Continue to heat up to 500 °C and keep it at this temperature for 45 min.

[0161] Continue to heat up to 650 °C and keep it at this temperature for 45 min.

[0162] Heat it up to 750 °C again and keep it warm for 45 min.

[0163] Example 4

[0164] A method for determining the content of the conductive component in a composition, which is different from that of Example 1 in that the range of thermogravimetric parameters in step S300 is different. In this example, the range of parameters for thermogravimetric decomposition is set as:

[0165] Heat up the mixture at a heating rate of 20 °C / min to 250 °C and keep it warm for 45 min;

[0166] Heat it up to 500 °C and keep it warm for 45 min;

[0167] Continue to heat it up to 650 °C and keep it warm for 45 min;

[0168] Heat it up to 750 °C again and keep it warm for 45 min.

[0169] Example 5

[0170] A method for determining the content of the conductive component in a composition, which is different from that of Example 1 in that the range of thermogravimetric parameters in step S300 is different. In this example, the range of parameters for thermogravimetric decomposition is set as:

[0171] Heat up the mixture at a heating rate of 30 °C / min to 250 °C and keep it warm for 45 min;

[0172] Heat it up to 500 °C and keep it warm for 45 min;

[0173] Continue to heat it up to 650 °C and keep it warm for 45 min;

[0174] Heat it up to 750 °C again and keep it warm for 45 min.

[0175] Example 6

[0176] A method for determining the content of the conductive component in a composition, which is different from that of Example 1 in that the range of thermogravimetric parameters in step S300 is different. In this example, the range of parameters for thermogravimetric decomposition is set as:

[0177] Heat up the mixture at a heating rate of 5 °C / min to 250 °C and keep it warm for 45 min;

[0178] Continue to heat it up to 500 °C and keep it warm for 45 min;

[0179] Heat it up to 600 °C and keep it warm for 45 min;

[0180] Heat it up to 700 °C and keep it warm for 45 min;

[0181] Heat up to 750 °C again and hold for 45 min.

[0182] Example 7

[0183] A method for determining the content of conductive components in a composition, which is different from Example 1 in that the holding time in step S300 is different. In this example, the holding time is 30 min.

[0184] Example 8

[0185] A method for determining the content of conductive components in a composition, which is different from Example 1 in that the holding time in step S300 is different. In this example, the holding time is 20 min.

[0186] Example 9

[0187] A method for determining the content of conductive components using a mixture, which is different from Example 1 in that the inert atmosphere in step S300 is different. The inert atmosphere in this example is a nitrogen atmosphere.

[0188] Detection method:

[0189] 1. SEM: The sample is irradiated with a Hitachi SU8010 scanning electron microscope, the acceleration voltage is set to 5 - 20 kV, the surface morphology of the sample is observed, and the type of conductive components is confirmed according to the morphology.

[0190] 2. Thermogravimetry: Take 10 mg of the sample, perform thermogravimetric decomposition on the sample using a TA Instruments Q500 thermogravimetric analyzer, heat up from room temperature (25 °C) according to the measurement steps described in the example, and the flow rate of the inert atmosphere is 50 mL / min.

[0191] The detection results are shown in Table 1:

[0192] Table 1

[0193]

[0194] Comparing Examples 2 - 5 with Example 1, Examples 2 - 5 changed the heating rate in the thermogravimetric decomposition. Specifically, from Example 1 to Example 5, the heating rate increased successively. Combining the detection results in Table 1, it can be seen that as the heating rate increases, the measurement result of the content of conductive components is on the small side; while when the heating rate is small, the measurement result of the content of conductive components is on the large side. Combining Figure 4 it can be known that the thermogravimetric curve of Example 1 shows a first plateau between 400 °C and 750 °C, and the first plateau slopes downward. Combining Figure 5It can be seen that the sample of Example 5 shows a first plateau between 400°C and 750°C. However, the first plateau slopes upward, which affects the accuracy of the determination of the carbon nanotube content. Therefore, the heating rate is preferably 5°C to 20°C.

[0195] Comparing Example 6 with Example 1, in Example 6, the thermogravimetric parameters are changed. The heating to 650°C and holding for 45 minutes are adjusted to two stages. The first stage is heating to 600°C and holding for 45 minutes, and the second stage is heating to 700°C and holding for 45 minutes. From the detection results in Table 1, it can be seen that the measured content of FG-5 is on the low side, and the contents of SP and CNT remain unchanged.

[0196] Comparing Examples 7-8 with Example 1, in Examples 7-8, the holding time is reduced. The holding time in Example 7 is 30 minutes, and the holding time in Example 8 is 20 minutes. From the detection results in Table 1, it can be seen that the measurement data of Example 7 are the same as those of Example 1, indicating that the holding time from 30 minutes to 45 minutes has little effect on the accuracy of the determination of the conductive component content.

[0197] Comparing Example 9 with Example 1, in Example 9, the type of inert gas is changed, and a nitrogen atmosphere is used as the protective gas for thermogravimetric decomposition. From the detection results in Table 1, it can be seen that the content of the conductive component in Example 9 is generally on the low side, indicating that the high-temperature stability of the nitrogen atmosphere is poor and has a certain impact on the test results.

[0198] The embodiments of the present invention have been introduced in detail above. Specific examples are used in this article to elaborate on the principle and implementation manner of the present invention. The description of the above embodiments is only used to help understand the method and its core idea of the present invention; at the same time, for those skilled in the art, based on the idea of the present invention, there will be changes in the specific implementation manner and application scope. In summary, the content of this specification should not be construed as a limitation to the present invention.

Claims

1. A method for determining the content of conductive components in a composition, characterized in that, the determination method comprises the following steps: Set the thermogravimetric parameters according to the decomposition temperature range of the conductive components. Under an inert atmosphere, perform thermogravimetric decomposition on the composition, collect the thermogravimetric decomposition data, and calculate to obtain the content of the conductive components.

2. The method for determining the content of conductive components in a composition according to claim 1, characterized in that, the determination method further comprises: Detect the cathode material by an electron microscope and confirm the type of conductive components by observing the morphology; Obtain the decomposition temperature range of the conductive components according to the type of conductive components.

3. The method for determining the content of conductive components in a composition according to claim 1, characterized in that, the method for setting the thermogravimetric parameters comprises the following steps: Heat up the composition to reach the first target temperature and keep it warm; Heat up again to reach the second target temperature and keep it warm; Continue to heat up to reach the third target temperature and keep it warm; wherein, the first target temperature is less than the second target temperature; and the second target temperature is less than the third target temperature.

4. The method for determining the content of conductive components in a composition according to claim 3, characterized in that, the first target temperature is 450 °C to 500 °C; and / or the second target temperature is 550 °C to 650 °C; and / or the third target temperature is 680 °C to 750 °C.

5. The method for determining the content of conductive components in a composition according to claim 3, characterized in that, in the step of thermogravimetric decomposition, after each heating up, the holding time is 30 min to 45 min.

6. The method for determining the content of conductive components in a composition according to any one of claims 3 to 5, characterized in that, before reaching the first target temperature, heat up to the fourth target temperature, and the fourth target temperature is less than the first target temperature.

7. The method for determining the content of conductive components in a composition according to claim 6, characterized in that, the fourth target temperature is 150 °C to 250 °C.

8. The method for determining the content of conductive components in a composition according to claim 1, characterized in that, the inert atmosphere includes at least one of a nitrogen atmosphere, an argon atmosphere, and a helium atmosphere.

9. The method for determining the content of conductive components in a composition according to claim 1, characterized in that, the composition includes a mixture of an active component, a plurality of conductive components, a binder component, and a solvent; preferably, the composition includes a mixture of an active component and a plurality of conductive components.

10. The method for determining the content of conductive components in a composition according to claim 9, characterized in that, the conductive components include a first conductive agent and a second conductive agent; wherein, the average decomposition temperature of the first conductive agent is less than the average decomposition temperature of the second conductive agent.

11. The method for determining the content of conductive components in a composition according to claim 10, characterized in that, the conductive components further include a third conductive agent; the average temperature of the third conductive agent is greater than the average decomposition temperature of the first conductive agent and less than the average decomposition temperature of the second conductive agent.

12. The method for determining the content of the conductive component in the composition according to any one of claims 9 to 11, characterized in that the conductive component includes at least two of conductive carbon black, functionalized graphite, and carbon nanotubes.

13. The method for determining the content of the conductive component in the composition according to claim 1, characterized in that the composition is prepared by the following method: Immerse the cathode material in a solvent and stir to obtain a first mixture; Filter the first mixture, collect the filter cake and dry it to obtain the composition.

14. The method for determining the content of the conductive component in the composition according to claim 13, characterized in that in the step of immersing the cathode material in the solvent, the temperature is set to 50°C to 100°C; and / or in the step of filtering the first mixture, shake the first mixture and then filter it; Preferably, the temperature range for filtration is 60°C to 80°C.

15. The method for determining the content of the conductive component in the composition according to any one of claims 1 to 14, characterized in that the thermogravimetric curve of the composition includes: a first plateau, which appears in a first temperature range; wherein, the first plateau includes multiple sub-platforms; the temperature range of the sub-platform is consistent with the decomposition temperature range of the conductive component.

16. The method for determining the content of the conductive component in the composition according to claim 15, characterized in that the first temperature range is 380°C to 750°C.

17. The method for determining the content of the conductive component in the composition according to claim 15, characterized in that the sub-platforms include: a first sub-platform, which appears between 380°C and 480°C; and / or a second sub-platform, which appears between 500°C and 600°C; and / or a third sub-platform, which appears between 680°C and 750°C.

18. The method for determining the content of the conductive component in the composition according to claim 17, characterized in that the slope of the third sub-platform is less than the slope of the first sub-platform; and / or the slope of the second sub-platform is less than the slope of the first sub-platform.

19. The method for determining the content of the conductive component in the composition according to claim 15, characterized in that the thermogravimetric curve of the mixture further includes: a second plateau, which appears within a second temperature range; the average temperature of the second temperature range is less than the average temperature of the first temperature range.

20. The method for determining the content of the conductive component in the composition according to claim 19, characterized in that the second temperature range is 100°C to 210°C.

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