Dry-method electrode powder fibrosis treatment method, dry-method electrode film, dry-method electrode plate and battery

Abstract

The invention discloses a dry-method electrode powder fibrosis treatment method, a dry-method electrode film, a dry-method electrode plate and a battery, and relates to the technical field of batteries. The method comprises the following steps: S1, obtaining a to-be-treated dry-method electrode powder sample, and performing fibrosis treatment on the to-be-treated dry-method electrode powder sample at different fibrosis time; s2, detecting the flowing energy of the sample at different fibrosis time; obtaining the fibrosis treatment preset time through the flow energy change; and S3, the dry electrode powder to be treated is subjected to fibration treatment, and the treatment time is controlled to be fibration treatment preset time. The method is short in measurement period, simple to operate, high in treatment precision and suitable for fibration treatment of powder in different material systems, and single detection can be completed in a short time; according to the method, the fibration degree of the powder can be evaluated in real time by measuring the flowing energy of the fibration powder, the uniformity of the fibration powder can be evaluated, and the optimal fibration time of the powder can be determined, so that the quality of a dry-method electrode membrane and an electrode plate and the performance of a battery are improved.

Description

Technical Field

[0001] This application relates to the field of battery material technology, and more specifically, to a method for dry electrode powder fiberization, a dry electrode film, a dry electrode sheet, and a battery. Background Technology

[0002] The dry electrode technology for lithium-ion batteries involves directly mixing the main material, conductive agent, and binder PTFE together. After shearing the powder, the PTFE is fibrousized. Through extrusion, a membrane with a certain strength can be directly synthesized. The membrane is then laminated onto the current collector to complete the electrode preparation process. Because this preparation method is fundamentally different from the wet electrode preparation method, some traditional detection methods for wet electrode process control are not applicable to dry electrode. In particular, there is still no accurate detection method to characterize the degree of fibrosis of powdered PTFE.

[0003] For the fabrication of dry electrodes, the degree of fibrosis in the powder is a crucial process that must be monitored. The degree and uniformity of fibrosis significantly impact subsequent processes and battery performance. Monitoring the degree of fibrosis is particularly important during the R&D phase of dry electrodes. Only by quantitatively characterizing the degree of fibrosis can we explore its relationship with subsequent processes and cell performance, enabling targeted optimization and further ensuring product performance and consistency.

[0004] Existing technologies disclose a method to characterize the degree of fiberization of fibrous powder by testing its specific surface area. The reason for using this detection method is that PTFE material is dispersed to a certain extent after fiberization, resulting in an increased specific surface area. However, the problem is that PTFE material itself is a non-polar material and cannot uniformly adsorb gases such as nitrogen. Therefore, there will inevitably be a large error in the detection process, leading to inaccurate process monitoring. Summary of the Invention

[0005] The main objective of this application is to provide a dry electrode powder fiberization treatment method, a dry electrode membrane, a dry electrode sheet, and a battery, in order to solve the problems of inaccurate powder fiberization degree detection results and complex operation in the prior art.

[0006] To achieve the above objectives, according to one aspect of this application, a method for dry electrode powder fiberization is provided, comprising the following steps:

[0007] Step S1: Obtain the dry electrode powder sample to be processed and perform fiberization treatment on it for different fiberization times;

[0008] Step S2: Detect the flow energy of samples at different fibrillation times; obtain the predetermined fibrillation time by measuring the change in flow energy;

[0009] Step S3: Perform fiberization treatment on the dry electrode powder to be processed, and control the processing time to the predetermined fiberization time.

[0010] Furthermore, in step S1, the dry electrode powder includes an active material, a conductive agent, and a binder.

[0011] Furthermore, the adhesive is a fiber-forming adhesive.

[0012] Furthermore, the adhesive is polytetrafluoroethylene.

[0013] Furthermore, the grade of polytetrafluoroethylene is 106.

[0014] Furthermore, the active material includes a positive electrode active material and a negative electrode active material; the positive electrode active material is at least one of ternary positive electrode materials, lithium iron phosphate, lithium cobalt oxide, and lithium manganese oxide; the negative electrode active material is at least one of graphite, hard carbon, and silicon-based materials.

[0015] Furthermore, the conductive agent includes at least one of superconducting carbon black, carbon nanotubes, and vapor-grown carbon fibers.

[0016] Furthermore, the weight ratio of the binder, active material and conductive agent is (0.5~5):(92~99):(0.5~3).

[0017] Furthermore, the weight ratio of the binder, active material and conductive agent is (0.5~2):(95~99):(0.5~3).

[0018] Further, in step S1, the sample is subjected to a fiberization treatment for 30s to 20min.

[0019] Furthermore, in step S2, the flow energy of the sample is detected every 20s to 120s.

[0020] Further, in step S2, the fiberization time corresponding to the maximum flow energy is denoted as Tm, and (Tm-5min) to (Tm+5min) is used as the predetermined fiberization treatment time.

[0021] Further, in step S2, the curve of flow energy change with fiberization time is fitted, and the fiberization time corresponding to the maximum flow energy in the curve is recorded as Tm, and (Tm-2min)~(Tm+2min) is used as the predetermined fiberization treatment time.

[0022] Furthermore, the fiberization treatment conditions for the sample in step S1 and the dry electrode powder to be treated in step S2 are the same; the conditions include: fiberization treatment temperature of 60~120℃ and rotation speed of 3000~8000rpm.

[0023] Furthermore, in step S2, the flow energy of the fibrous powder shows a trend of first increasing to a peak and then decreasing as the fibrosis time increases.

[0024] Furthermore, in step S2, the predetermined time for the fiberization treatment is 1 to 10 minutes.

[0025] Furthermore, the fiberization treatment is scheduled for 1 to 8 minutes.

[0026] Furthermore, the fiberization treatment is scheduled for 1 to 5 minutes.

[0027] Furthermore, the kinetic energy was obtained using an FT4 powder rheometer.

[0028] Furthermore, the equipment for the fiberization process is a vertical mixer H350.

[0029] According to a second aspect of this application, a dry electrode membrane is provided, which is an electrode membrane obtained by sequentially subjecting raw materials to dry mixing, fiberization treatment and open mill rolling; wherein the fiberization treatment process adopts the above-mentioned dry electrode powder fiberization treatment method.

[0030] According to a third aspect of this application, a dry electrode sheet is provided, which is an electrode sheet obtained by hot rolling a dry electrode film and a current collector together; wherein the dry electrode film is the aforementioned dry electrode film.

[0031] According to a fourth aspect of this application, a battery is provided, including a dry electrode sheet; the dry electrode sheet is the aforementioned dry electrode sheet.

[0032] Compared with the prior art, this application has the following beneficial effects:

[0033] The dry electrode powder fiberization method provided in this application has a short operation cycle, can be completed in a short time for a single treatment, is simple to operate, and has high detection accuracy. This method has a wide range of applications and is suitable for detecting the fiberization effect of powders in different material systems. This method can not only evaluate the degree of powder fiberization in real time by measuring the flow energy of the fiberized powder, but also assess the uniformity of the fiberized powder and determine the optimal fiberization time, thereby improving the quality of dry electrode films and electrode sheets and battery performance. Attached Figure Description

[0034] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings:

[0035] Figure 1 This is a graph showing the change in flow energy of the dry electrode powder in Example 1 of this application at different fiberization times.

[0036] Figure 2 This is a scanning electron microscope image of the dry electrode powder fiberized for 1 minute according to Example 1 of this application;

[0037] Figure 3 This is a scanning electron microscope image of the dry electrode powder fiberized for 3 minutes according to Example 1 of this application;

[0038] Figure 4 This is a scanning electron microscope image of the dry electrode powder fiberized for 5 minutes according to Example 1 of this application;

[0039] Figure 5 This is a scanning electron microscope image of the dry electrode powder after 10 minutes of fiberization in Example 1 of this application.

[0040] Figure 6 This is a graph showing the change in flow energy of the fibrous powder in Example 6 of this application;

[0041] Figure 7 This is a photograph of the dry electrode film prepared using fibrous powder that has been fibrous for 1 minute, as shown in Example 7 of this application.

[0042] Figure 8 This is a photograph of the dry electrode film prepared using fibrous powder that has been fibrous for 2 minutes, as shown in Example 8 of this application.

[0043] Figure 9 This is a photograph of the dry electrode film prepared using fiberized powder that has been fiberized for 5 minutes, as shown in Example 9 of this application.

[0044] Figure 10 This is a comparison of the maximum tensile strength of dry electrode films prepared using different fibrous powders in Examples 7-9 of this application;

[0045] Figure 11 This is a graph showing the change in flow energy of the two powders in Example 10 of this application;

[0046] Figure 12 This is a graph showing the change in the flow energy of the powder at different fiberization times in Example 11 of this application. Detailed Implementation

[0047] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present application will now be described in detail with reference to the embodiments.

[0048] As mentioned in the background technology, the degree of fibrosis in dry electrode powder is a crucial process that must be monitored. The degree and uniformity of fibrosis significantly impact subsequent processes and battery performance. Monitoring the degree of fibrosis is particularly important during the development stage of dry electrodes. Only by quantitatively characterizing the degree of fibrosis can the relationship with subsequent processes and cell performance be determined, allowing for targeted optimization and further ensuring product performance and consistency. However, current technologies use the specific surface area method to detect and monitor the degree of fibrosis. This method has low accuracy and yields inaccurate results, and its improvement is needed.

[0049] Therefore, this application provides a dry electrode powder fiberization treatment method, comprising:

[0050] Step S1: Obtain the dry electrode powder sample to be processed and perform fiberization treatment on it for different fiberization times;

[0051] Step S2: Detect the flow energy of samples at different fibrillation times; obtain the predetermined fibrillation time by measuring the change in flow energy;

[0052] Step S3: Perform fiberization treatment on the dry electrode powder to be processed, and control the processing time to the predetermined fiberization time.

[0053] This application observes that the viscosity of the powder significantly increases after fiberization. The viscosity varies to some extent depending on the degree of fiberization. Based on experience with subsequent film-forming processes, the film-forming effect of the powder progresses from no film formation to a gradually increasing degree of film formation, reaching an optimal level, and then gradually decreasing in the latter. This trend is clearly correlated with the powder's viscosity. Therefore, the degree of fiberization of the powder can be evaluated by assessing its viscosity. In methods for evaluating powder viscosity, the flow energy of the powder can be measured; higher viscosity powders have higher flow energy.

[0054] This application innovatively proposes an efficient treatment scheme for the fibrous state of powder in dry electrode processes. The significant feature of this method is its ability to rapidly and accurately assess the degree of fibrousness. A single analysis can be completed within a very short time window, greatly improving production efficiency and process control flexibility. Simultaneously, its simplified operation process reduces implementation difficulty, making testing more convenient and easily applicable to widespread production lines. More importantly, the detection method of this application exhibits good versatility, not limited to specific material combinations, and can be flexibly applied to various electrode material systems, including but not limited to composite powders containing polytetrafluoroethylene (PTFE), ensuring its effectiveness in different electrode formulations. By quantifying the flow energy of the powder, not only can the fibrous level of the powder be fed back in real time, but the consistency of fibrousization can also be effectively monitored, thereby accurately locating the optimal fibrous treatment time, further optimizing the structural integrity of the dry electrode film and the overall performance of the electrode sheet, ultimately improving the efficiency and consistency of the battery.

[0055] The dry electrode powder detected in the above method of this application includes active material, conductive agent and binder; the binder is a fiberizable binder; for example, polytetrafluoroethylene, specifically grade 106; the active material includes positive electrode active material and negative electrode active material; the positive electrode active material is selected from at least one of ternary positive electrode materials (nickel cobalt manganese, nickel cobalt aluminum), lithium iron phosphate, lithium cobalt oxide and lithium manganese oxide; the negative electrode active material is selected from at least one of graphite, hard carbon and silicon-based materials; the conductive agent includes at least one of super conductive carbon black (SuperP), carbon nanotubes (CNT) and vapor-grown carbon fiber (VGCF); wherein, the weight ratio of binder, active material and conductive agent is (0.5~5):(92~99):(0.5~3); wherein, the amount of binder added is 0.5%~5%, for example, any value or any range between 0.5%, 1%, 1.5%, 2%, 3%, 4% and 5%; for example, (0.5~2):(95~99):(0.5~3). When the binder content is between 0.5% and 5%, the material has good adhesion and lower requirements for subsequent processing conditions. However, a higher binder content will affect the battery's energy density and other performance characteristics. Therefore, when the binder content is controlled between 0.5% and 2%, both good electrochemical performance and good adhesion performance can be ensured.

[0056] Before the fiberization process, the active material, conductive agent, and binder powder are placed in a mixer and premixed at low temperature and low speed to ensure that the binder powder is as evenly dispersed as possible inside the cavity before the fiberization process.

[0057] In step S1, the sample is first subjected to fiberization treatment to screen the optimal fiberization time; in step S2, the optimal fiberization time screened in step S1 is used to treat the dry electrode powder to be tested; in both processes, the fiberization treatment conditions are the same, for example, the fiberization treatment is carried out in a mixer with a rotation speed of 3000~8000 rpm; the mixer can be a small high-speed mixer (model RKT010) or a pilot high-speed mixer (model vertical mixer H350); the temperature of the mixture during fiberization treatment is 60~120℃.

[0058] In some embodiments, in step S1, the sample is subjected to a fiberization treatment for 30 seconds to 20 minutes; in step S2, the flow energy of the sample is detected every 20 to 120 seconds, for example, every 30 to 60 seconds. The fiberization treatment time of the sample can be adjusted according to the different properties of the actual dry electrode powder. In step S1, the sample is first subjected to fiberization treatment to screen out a suitable predetermined fiberization time with the maximum flow energy, the best degree of fiberization, and the best powder viscosity.

[0059] In some embodiments, in step S2, the fiberization time corresponding to the maximum flow energy is denoted as Tm, and (Tm-5min) to (Tm+5min) is used as the predetermined fiberization treatment time. After step S2 uses the same material sample to screen out a suitable predetermined fiberization treatment time, this predetermined time is then used in the formal fiberization treatment process of the dry electrode powder to be tested in step S3, so that the degree of fiberization of the dry electrode powder to be tested reaches the optimal state. Specifically, the change curve of flow energy with fiberization time can be fitted (the horizontal axis is fiberization time, and the vertical axis is powder flow energy), and the fiberization time corresponding to the maximum flow energy in the change curve is denoted as Tm, and (Tm-2min) to (Tm+2min) is used as the predetermined fiberization treatment time.

[0060] In some embodiments, during step S2, the flow energy of the fiberized powder during the dry electrode powder fiberization process first increases to a peak and then decreases as the fiberization time increases. The type of active material affects the optimal fiberization time; for example, the optimal time for negative electrode graphite electrode powder is between 2 and 5 minutes, and the optimal time for ternary material electrode powder is between 5 and 15 minutes, further between 5 and 10 minutes. Specifically, for dry electrode powder with polytetrafluoroethylene (PTFE) as the binder, the ideal fiberization time for the fiberized powder is 1–10 min, and more specifically 1–8 min. Within this fiberization time range, the flow energy is relatively high, reaching 200–1500 mJ, resulting in better adhesion and facilitating the formation of a stable dry electrode film structure. Within this range, the ideal fiberization time can be any value from 1, 2, 3, 4, 5, 6, 7, to 8 min, or any value between any two. Furthermore, when the fiberization time is 1–5 min, the material flow energy is even greater, reaching 500–1500 mJ, resulting in better material adhesion and further facilitating the formation of subsequent dry electrode films and electrode sheets. For example, a fiberization time of 1–4 min… At 1 min and 1.5-3 min, the material flow energy gradually increases, reaching 700-1500 mJ and 800-1500 mJ respectively, further improving the material's adhesion and facilitating subsequent processes. For example, when the fiberization time is 2 min, the material flow energy reaches its peak, such as 1500 mJ. At this point, the material adhesion reaches its optimal state, providing a good foundation for the subsequent preparation of dry electrode films and dry electrode sheets, and helping to improve the electrochemical performance of the final battery.

[0061] In some embodiments, in step S2, when the fiberization time of the fibrous powder is 3-10 minutes, the homogenization degree of the fibrous powder reaches an ideal state. Within this fiberization time, the flow energy of the material is repeatedly measured for the same fiberization time. If the flow energy change is small, the fiberization degree of the fibrous powder can be considered relatively uniform. Furthermore, when the material fiberization time is 4-10 minutes, the flow energy of the material is repeatedly measured for the same fiberization time. If the flow energy change is even smaller, the uniformity of the material fiberization degree is even more uniform. When the material fiberization time is 5-10 minutes, the flow energy is almost the same after 9 repeated measurements, indicating that the uniformity of the material fiberization degree has reached the optimal state. Therefore, the degree of fiberization uniformity of the fibrous material can be determined by repeatedly measuring the change in flow energy of the fibrous material within a specific fiberization time. Therefore, based on the ideal fiberization time and ideal uniformity fiberization time of the fibrous powder, a fiberization time that balances ideal fiberization degree and ideal fiberization uniformity can be determined, for example, 2-8 minutes, or even 4-6 minutes.

[0062] According to a second aspect of this application, a dry electrode membrane is provided. The materials are dry-mixed and then subjected to fiberization treatment, followed by rolling to a preset thickness after open milling, to obtain the dry electrode membrane. The fiberization treatment method is kneading. The fiberization process employs the aforementioned dry electrode powder fiberization treatment method. The dry electrode membrane can be prepared using a suitable method according to actual needs, such as a suitable open milling temperature of 60-80℃ and a preset thickness of 300-400μm. By employing the powder fiberization treatment method, the degree of fiberization of the powder can be monitored in real time and accurately, thereby ensuring precise control of the fiberization process. This helps optimize the parameters of the kneading process, such as time, temperature, and pressure, to ensure that the fiberization of the electrode membrane reaches its optimal state. Precise control of the degree of fiberization directly affects the structural integrity and mechanical properties of the dry electrode membrane. Therefore, this method helps improve the quality and consistency of the dry electrode membrane and reduce the scrap rate during production.

[0063] According to a third aspect of this application, a dry electrode sheet is provided, which is obtained by pressing a dry electrode film and a current collector together using a roller press; wherein the dry electrode film is the aforementioned dry electrode film. The preparation method of the dry electrode sheet can be selected from existing technologies according to actual needs; for example, the negative electrode current collector is a carbon-coated copper foil, the positive electrode is a carbon-coated aluminum foil, the roller pressing pressure is 6~12MPa, and the roller temperature is 60~120℃. Since the preparation of the dry electrode film has been optimized through monitoring the degree of fibrosis, ensuring that the fibrosis state of the film is within the optimal range, this provides a high-quality base material for the subsequent preparation of the electrode sheet, thereby improving the consistency and overall quality of the electrode sheet. When the optimized dry electrode film is pressed with the current collector, due to its good fibrosis state and uniformity, a tighter and more stable contact interface can be formed, which is beneficial to improving the electron and ion transport efficiency, thereby improving the electrochemical performance of the electrode sheet, such as increasing energy density and cycle life.

[0064] According to a fourth aspect of this application, a battery is provided, including a dry-process electrode sheet; the dry-process electrode sheet is the aforementioned dry-process electrode film. Optimizing the electrode film fibrosis process helps improve the electrode film performance, thereby enhancing the battery's electrochemical performance. The preparation process of the dry-process electrode sheet strictly controls the degree of fibrosis and uniformity of the powder, which directly translates into better energy density, higher cycle life, and better rate performance of the battery. The optimized electrode structure ensures good contact between the active material and the conductive agent and binder, improving the electron and ion transport paths.

[0065] The present application will be further described in detail below with reference to specific embodiments, which should not be construed as limiting the scope of protection claimed in the present application.

[0066] Example 1

[0067] The negative electrode active material graphite, conductive agent SuperP, and binder polytetrafluoroethylene (PTFE) were added to a small high-speed mixer (model RKT010, volume 800mL) at a weight ratio of 97:1:2 and mixed evenly to obtain a premix for dry electrode powder. The premix was subjected to fiberization treatment for different times from 0 to 20 minutes, with the temperature controlled at 80℃ and the rotation speed at 8000 rpm, to obtain fiberized powder. The flow energy of the fiberized powder was measured and recorded using a powder rheometer (model FT4) at 10s, 1min, 2min, 3min, 4min, 5min, 6min, 7min, 8min, 9min, 10min, 11min, 12min, 13min, 14min, 15min, 16min, 17min, 18min, 19min, and 20min. The test results are shown in Table 1. Figure 1 , Figure 2 , Figure 3 , Figure 4 , Figure 5 As shown.

[0068] Example 2

[0069] The difference between Example 2 and Example 1 is that the amount of adhesive added is replaced with 0.5 wt%; the flow energy test results are shown in Table 1.

[0070] Example 3

[0071] The difference between Example 3 and Example 1 is that the amount of adhesive added was replaced with 5 wt%; the flow energy test results are shown in Table 1.

[0072] Example 4

[0073] The difference between Example 4 and Example 1 is that the negative electrode active material is replaced with the positive electrode active material, ternary material nickel-cobalt-manganese 622; the flow energy detection results are shown in Table 1.

[0074] Example 5

[0075] Example 5 differs from Example 1 in that the conductive agent is replaced with carbon nanotubes (CNTs); the flow energy detection results are shown in Table 1.

[0076] Example 6

[0077] Example 6 differs from Example 1 in that the small-scale high-speed mixer was replaced with a pilot-scale high-speed mixer, with the temperature controlled at 80℃ and the rotation speed at 5000 rpm, to obtain fibrous powder; the flow energy test results are shown in Table 1 and... Figure 6 As shown.

[0078] Example 7

[0079] The fiberized powder from Example 1, after 1 minute of fiberization, was milled on a two-roll mill to prepare a 400 μm dry electrode membrane. Samples were taken to test the maximum tensile strength of the membrane; the test results are as follows. Figure 7 and Figure 10 As shown.

[0080] Example 8

[0081] Example 8 differs from Example 7 in that the powder that was fiberized for 1 minute was replaced with powder that was fiberized for 2 minutes. A dry electrode film was prepared and its maximum tensile strength was tested. The test results are as follows: Figure 8 and Figure 10 As shown.

[0082] Example 9

[0083] Example 9 differs from Example 7 in that the powder that was fiberized for 1 minute was replaced with powder that was fiberized for 5 minutes. A dry electrode film was prepared and its maximum tensile strength was tested. The test results are as follows: Figure 9 and Figure 10 As shown.

[0084] Example 10

[0085] The flow energy of the premixed powder (mixture before fiberization) and graphite raw material of the dry electrode powder in Example 1 were measured separately, repeated 8 times; the test results are shown in Table 2 and... Figure 11 As shown.

[0086] Example 11

[0087] The flow energy of the premixed dry electrode powder (mixture before fiberization) and the fiberized powder from Example 1 after 2 min, 5 min, and 10 min of fiberization were measured respectively; the results are shown in Table 3 and Figure 12 As shown.

[0088] Comparative Example 1

[0089] The method for detecting the degree of fiberization of binders in dry-process positive electrode films using the specific surface area method comprises the following steps:

[0090] A dry-process electrode membrane using polytetrafluoroethylene (PTFE) as a binder is digested to obtain a continuous PTFE support framework. The digestion process includes the following steps: adding an oxidant to the dry-process electrode membrane to remove the electrode active material and conductive agent; measuring the specific surface area S of the PTFE support framework; if 12m 2 / g≤S≤25m 2 If S < 12m, the degree of fiberization of the adhesive is acceptable. 2 If S > 25m, the degree of fiberization of the adhesive is unqualified.2 If / g, then this test is invalid.

[0091] Application examples

[0092] Fiberized powders of negative electrode powder from Example 1 with fiberization times of 1, 2, 5, and 10 min (this is one set of fiberization times) were taken respectively. Using a pair of rollers with a diameter of 200 mm, the roller temperature was set to 60°C, and the rotation speed was 5 m / min, the open milling rollers pressed the negative electrode film into an electrode film. The negative electrode film and the carbon-coated copper foil were then hot-rolled to form a negative electrode sheet. The positive electrode slurry (nickel cobalt manganese 622: super conductive carbon black: polyvinylidene fluoride binder = 97:1.5:1.5, solvent is NMP, solid content is 73 wt%) was coated on aluminum foil, baked, and rolled to obtain a positive electrode sheet (wet process). The separator was a Jinli wet process separator. The soft-pack battery cell was assembled in a drying chamber.

[0093] The three sets of fibrosis times from Example 1 were used to repeat the above preparation process three times to prepare three sets of test batteries, which were denoted as Example 1-1, Example 1-2, and Example 1-3. The electrochemical performance of the above three sets of batteries was tested using a Xinwei test cabinet.

[0094] Performance testing:

[0095] (1) Cyclic stability at 45℃: Charged at a constant current of 1C to 4.3V and discharged at a constant current of 1C to 2.75V, this is one cycle. After 100 cycles, the test results are shown in Table 4.

[0096] Table 1.

[0097]

[0098] Table 2.

[0099]

[0100] Table 3.

[0101]

[0102] Table 4.

[0103]

[0104] Table 1 shows that in Examples 1-6, with the extension of fiberization time, the flow energy of the fiberized powder exhibits a clear trend of first increasing to a peak and then decreasing; this is consistent with the trend of powder film formation in subsequent Examples 7-9; among them, Figure 1 The graph shows the change in flow energy of the fibrous powder over time in Example 1. Test 1 and Test 2 are repeated tests at two different test points to ensure that the data is stable and reliable.

[0105] Depend on Figures 2-3 As can be seen in the image, obvious fibrous strands gradually appear, indicating that the degree of fiberization is gradually increasing. Figures 4-5 It can be seen that the fiber-drawing phenomenon gradually decreases, indicating that the degree of fiberization gradually decreases; this further illustrates that the fiberization effect is good when the fiberization time is 1~10min, even better when it is 1~5min, and the best fiberization effect is achieved when it is 1~3min.

[0106] Figure 7 and Figure 10 The results show that the membrane prepared by using powder that has been fiberized for 1 minute in Example 7 is prone to small cracks inside; the maximum tensile strength is 6.15 N / 150 mm.

[0107] Figure 8 and Figure 10 The results show that the membrane prepared by using powder that has been fiberized for 2 minutes in Example 8 has a smooth and regular appearance with no defects; the maximum tensile strength is 9.3 N / 150 mm.

[0108] Figure 9 and Figure 10 The results show that although the membrane prepared by the powder that has been fiberized for 5 minutes in Example 9 has no obvious defects, the maximum tensile strength is 4.725 N / 150 mm, and the membrane is very easy to break.

[0109] By comparing the average maximum tensile strength of the dry electrode films in Examples 7-9, the results show a consistent trend with the flow energy results of the fibrous powder in Example 1; the ideal fibrosis time can be determined to be 1-8 min; further, 1-5 min; and even further, 1.5-3 min. The above test results indicate that by detecting the relationship between the change in the flow energy of the fibrous powder and the degree of powder fibrosis, the present application can determine the predetermined fibrosis time for the optimal degree of fibrosis, and then use this predetermined time for powder fibrosis treatment to improve the performance of the dry electrode film.

[0110] Figure 6 The graph shows the flow energy of the fibrous powder in Example 6 as a function of time. Test 1 and Test 2 are two repeated tests where the test points were not passed. Example 6 used a pilot-scale high-speed mixer to fibrose the material, and the trend of the flow energy was tested. Figure 6 The trend of the fibrous powder in the small high-speed mixer in Example 1 is similar to that in Example 1. Figure 1 The results were consistent, except that the maximum peak value of the detected flow energy was relatively low; and the film-forming effect of the fiberized powder in this device was worse than that of the fiberized powder in Example 1. This indicates that using flow energy to detect the degree of fiberization of powder is effective and that the method has good sensitivity.

[0111] Table 2 and Figure 11The results show that in Example 10, the flow energy of the unfibrillated premix and graphite raw material from Example 1 were tested 8 times. The results show that the graphite raw material was stable in repeated tests, while the flow energy of the premix with added PEFT changed relative to the graphite. This indicates that the method of monitoring the degree of fibrillation by detecting the flow energy of the fibrillated powder in this application is sensitive and reliable.

[0112] Table 3 and Figure 12 As shown in Example 11, it was clearly observed that in the same equipment, the uniformity of the degree of fiberization gradually weakened and then strengthened as the fiberization time increased. Therefore, this embodiment of the application determined that the uniformity of the fiberized powder reached an ideal state when the fiberization time was 3~10 min, and further 5~10 min, by detecting the relationship between the change in the flow energy of the fiberized powder and the degree of fiberization and the fiberization uniformity of the powder mixed once.

[0113] Table 4 shows that when the fiberization time is 1~10 min, the degree of fiberization is good, and the prepared dry electrode film, electrode sheet and battery have good electrochemical performance. Furthermore, when the fiberization time is 1~5 min, the degree of fiberization gradually increases, and the cycle stability and capacity retention of the prepared lithium-ion battery are improved.

[0114] Comparative Example 1 uses the specific surface area method to detect the degree of fiberization of the binder. This method involves using an oxidant to digest the dry electrode membrane, and then measuring the specific surface area of ​​the binder support skeleton. The degree of fiberization of the binder is judged by the size of the specific surface area. This method is obviously complicated to operate, requires an oxidant, is inconvenient to operate, and has poor safety.

[0115] The dry electrode powder fiberization treatment method of this application features a short measurement cycle, allowing for quick completion of a single test. It is simple to operate, highly accurate, and widely applicable, suitable for detecting the fiberization effect of powders in various material systems. This method not only monitors and evaluates the degree of powder fiberization in real time by measuring the flow energy of the fiberized powder, but also monitors the uniformity of the fiberized powder and determines the optimal fiberization time, thereby improving the quality of dry electrode films and sheets, and enhancing battery performance.

[0116] It should be noted that the terms "first," "second," etc., used in the specification and claims of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such terms can be used interchangeably where appropriate so that the embodiments of this application described herein can be implemented, for example, in a sequence other than those described herein.

[0117] The above are merely preferred embodiments of this application and are not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A dry electrode powder fibrousizing process characterized by, The processing method comprises the following steps: Step S1: obtaining a sample of dry-process electrode powder to be processed, and performing fiberization treatment on the sample for different fiberization times; Step S2: detecting the flow energy of the sample under different fiberization times; obtaining a predetermined fiberization time by the change of the flow energy; Step S3: performing fiberization treatment on the dry-process electrode powder to be processed, and controlling the processing time to be the predetermined fiberization time.

2. The dry electrode powder fibriiization process of claim 1 wherein, In the step S1, the dry-process electrode powder comprises an active material, a conductive agent and a binder; Preferably, the binder is a fiberizable binder; further preferably, polytetrafluoroethylene; and more preferably, polytetrafluoroethylene with a brand of 106. Preferably, the active material comprises a positive active material and a negative active material; the positive active material is at least one of ternary positive materials, lithium iron phosphate, lithium cobaltate and lithium manganate; and the negative active material is at least one of graphite, hard carbon and silicon-based materials. Preferably, the conductive agent comprises at least one of super-conductive carbon black, carbon nanotubes and vapor-phase grown carbon fibers. Preferably, the weight ratio of the binder, the active material and the conductive agent is (0.5-5):(92-99):(0.5-3); and further preferably, (0.5-2):(95-99):(0.5-3).

3. The dry electrode powder fibriiization process of claim 1 or 2, characterized in that, In the step S1, the sample is subjected to fiberization treatment for 30 seconds to 20 minutes. In the step S2, the flow energy of the sample is detected every 20 seconds to 120 seconds.

4. The dry electrode powder fibriiization process method according to any one of claims 1 to 3, characterized in that, In the step S2, the fiberization time corresponding to the maximum flow energy is recorded as Tm, and (Tm-5min) to (Tm+5min) is taken as the predetermined fiberization time.

5. The dry electrode powder fibriiization process of claim 4, wherein, In the step S2, the curve of the change of the flow energy with the fiberization time is fitted, the fiberization time corresponding to the maximum flow energy in the curve is recorded as Tm, and (Tm-2min) to (Tm+2min) is taken as the predetermined fiberization time.

6. The dry electrode powder fibriiization process method according to any one of claims 1 to 5, characterized in that, The fiberization treatment conditions of the sample in the step S1 and the dry-process electrode powder to be processed in the step S2 are the same; the conditions comprise that the fiberization treatment temperature is 60-120°C, and the rotation speed is 3000-8000 rpm.

7. The dry electrode powder fibriiization process method according to any one of claims 1 to 6, characterized in that, In the step S2, the flow energy of the fiberized powder increases to a peak value and then decreases with the extension of the fiberization time. In the step S2, the predetermined fiberization time is 1-10 minutes; further preferably, 1-8 minutes; and more preferably, 1-5 minutes. The flow energy is detected by a powder FT4 powder rheometer. The fiberization treatment device is a vertical mixer H350.

8. A dry electrode film characterized by, The dry-process electrode film is obtained by sequentially performing dry-process mixing, fiberization treatment and open mill pressing on each raw material; wherein the fiberization treatment adopts the dry-process electrode powder fiberization treatment method according to any one of claims 1 to 7.

9. A dry electrode sheet, characterized by The dry electrode sheet is an electrode sheet obtained by hot-rolling and pressing the dry electrode film and the current collector; wherein the dry electrode film is the dry electrode film according to claim 8.

10. A battery comprising a dry electrode sheet; characterized by, The dry electrode sheet is the dry electrode sheet according to claim 9.

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