Electrode diaphragm, preparation method thereof and lithium battery
By pretreating and fiberizing polytetrafluoroethylene (PTFE) materials, the problem of poor dispersibility during electrode preparation was solved, thereby improving electrode performance, lithium battery capacity, and electrode peeling force.
Patent Information
- Application Number
- CN202511461763.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-10-13
- Publication Date
- 2026-02-10
AI Technical Summary
In the existing technology, commercially available high molecular weight polytetrafluoroethylene materials have a large particle size, which leads to poor dispersibility during electrode preparation and affects electrode performance.
By pretreating polytetrafluoroethylene (PTFE) material under preset low-temperature conditions, crushing and fiberizing it, the extension of molecular chains is inhibited, and the particle size and fiberization process are controlled to ensure its uniform dispersion in active and conductive materials.
This method achieves uniform dispersion of polytetrafluoroethylene (PTFE) material in the electrode, improves the electrode conductivity and electrode peeling force, and enhances the capacity and performance of the lithium battery.
Smart Images
Figure CN121506880A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of batteries, and more particularly to an electrode film, a method for preparing the same, and a lithium battery. Background Technology
[0002] Dry electrode fabrication technology has attracted much attention in the lithium-ion battery field due to its advantages such as solvent-free and environmentally friendly processes. Polytetrafluoroethylene (PTFE) material, as a key binder, directly affects electrode performance due to its dispersibility and degree of fibrosis.
[0003] In related technologies, to prevent agglomeration and facilitate transportation, commercially available high molecular weight (over 5 million) polytetrafluoroethylene (PTFE) materials typically have a larger particle size, failing to possess both high molecular weight and low particle size characteristics. During electrode fabrication, this type of PTFE material is difficult to disperse, leading to a decrease in electrode performance. Summary of the Invention
[0004] This application provides an electrode film, a method for preparing the same, and a lithium battery, aiming to improve the problem of electrode performance being affected by uneven dispersion of binder.
[0005] To achieve the above objectives, in a first aspect, embodiments of this application provide a method for preparing an electrode film, the method comprising the following steps: Polytetrafluoroethylene (PTFE) material is pretreated under preset conditions and then pulverized to obtain the first powder; wherein... The pretreatment is intended to suppress the stretching of the molecular chains of the polytetrafluoroethylene material. The first powder is mixed with an active material and a conductive material to obtain a mixed powder; The mixed powder is subjected to fibrosis treatment to obtain the electrode film.
[0006] Optionally, in some embodiments of this application, the preset conditions include a preset temperature; The preset temperature range is -70°C. o Below C; Preferably, the preset temperature ranges from -100°C. o C to -120 o C.
[0007] Optionally, in some embodiments of this application, the number-average molecular weight of the polytetrafluoroethylene material ranges from 6 million to 7 million; and / or The average particle size of the polytetrafluoroethylene material ranges from 450 μm to 550 μm; and / or The average particle size of the first powder ranges from 10 μm to 30 μm.
[0008] Optionally, in some embodiments of this application, the step of mixing the first powder with the active material and the conductive material includes: The first powder is mixed with the active material and the conductive material at a low temperature, wherein the low temperature mixing temperature range is less than or equal to 10°C. o C; The temperature range for the low-temperature mixing is -20°C. o C to 10 o C.
[0009] Optionally, in some embodiments of this application, the step of fibrousizing the mixed powder includes... The mixed powder is fiberized once in the first temperature range to obtain mixed fiberized powder; The mixed fiberized powder is subjected to secondary fiberization in a second temperature range to obtain the electrode film.
[0010] Optionally, in some embodiments of this application, the first temperature range is 60°C. o C to 100 o C; and / or The second temperature range is 115. o C to 120 o C.
[0011] Optionally, in some embodiments of this application, the diameter of the mixed fibrous powder ranges from 3 μm to 10 μm; and / or The diameter of the secondary fiber is in the range of 20nm to 200nm.
[0012] Optionally, in some embodiments of this application, the electrode membrane comprises 94 to 95.5 parts by weight of the active material, 3 to 5 parts by weight of the conductive material, and 0.5 to 2 parts by weight of the polytetrafluoroethylene material.
[0013] Optionally, in some embodiments of this application, the active material includes at least one of manganese dioxide, lithium nickel cobalt manganese oxide, lithium iron phosphate, and lithium manganese iron phosphate; and / or The conductive material includes at least one of conductive carbon black, acetylene black, Ketjen black, conductive graphite, and activated carbon.
[0014] Secondly, embodiments of this application provide an electrode, wherein the electrode film is prepared using the electrode film preparation method described above.
[0015] Optionally, in some embodiments of this application, the electrode membrane is at 3 g / cm³. 3 The electrical conductivity at the compacted density is greater than or equal to 0.42 S / cm.
[0016] Thirdly, embodiments of this application provide a lithium battery, which includes the electrode film as described above.
[0017] Optionally, in some embodiments of this application, the capacity of the lithium battery ranges from 1520mAh to 1650mAh; and / or The electrode peeling force of the lithium battery is greater than or equal to 3.6N and less than or equal to 6.2N.
[0018] In the electrode preparation process of this application embodiment, the polytetrafluoroethylene material is pretreated before pulverization to suppress the molecular chain movement of the polytetrafluoroethylene material, making it easier for it to break rather than extend under pulverization. This can avoid premature fibrosis during pulverization, and the pulverized polytetrafluoroethylene material can be better dispersed in the active and conductive materials, thereby better ensuring the electrode performance. Attached Figure Description
[0019] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0020] Figure 1 This is a flowchart of the preparation method of the electrode film in some embodiments of this application; Figure 2 This is a particle size distribution diagram of the pulverized polytetrafluoroethylene material in some embodiments of this application; Figure 3 These are SEM images after step S200 in some embodiments of this application; Figure 4 These are SEM images of the primary fiberization process in step S310 of some embodiments of this application; Figure 5 These are SEM images of the secondary fiberization step S320 in some embodiments of this application. Detailed Implementation
[0021] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the protection scope of this application.
[0022] In related technologies, to prevent agglomeration and facilitate transportation, commercially available polytetrafluoroethylene (PTFE) materials with molecular weights (above 5 million) such as Gaodajin Fluorochemical F-106C and Chemours 601X typically have relatively large particle sizes, failing to possess both high molecular weight and low particle size characteristics. During electrode preparation, this type of PTFE material is not conducive to dispersion, leading to a decrease in electrode performance.
[0023] According to a first aspect of the embodiments of this application, a method for preparing an electrode film is provided, with reference to... Figure 1 The preparation method includes the following steps: S100. The polytetrafluoroethylene material is pretreated under preset conditions and then pulverized to obtain the first powder. The purpose of pretreatment is to inhibit the extension of the molecular chains of polytetrafluoroethylene (PTFE) materials. S200: The first powder is mixed with the active material and the conductive material to obtain a mixed powder; S300. The mixed powder is subjected to fibrous treatment to obtain an electrode film.
[0024] By adopting the above scheme, before mixing the polytetrafluoroethylene (PTFE) material with the active and conductive materials, the PTFE material is subjected to glassy treatment under preset conditions. The glassy state freezes the movement of the molecular chain segments of the PTFE material, and the rigidity of the crystalline region is enhanced. Under the action of crushing, it is easier to break rather than extend, that is, to achieve crushing alone rather than fiberization during crushing. The crushed PTFE material can be better dispersed in the active and conductive materials, thereby better ensuring the electrode performance of the membrane.
[0025] It is understandable that pulverization refers to the breaking of molecular chains, and the particles become smaller macroscopically; fibrosis refers to the slippage of PTFE molecular chains, which macroscopically changes from granular to fibrous.
[0026] It should be noted that if polytetrafluoroethylene (PTFE) material is pulverized at room temperature, the molecular chains of PTFE material are flexible and prone to slippage, and are prone to fibrosis under external force, at which point the particle size is uncontrollable; however, in the glassy state of PTFE material in the embodiments of this application, the molecular chains are frozen, which helps to enhance rigidity, thereby directly causing brittle fracture under external force, ensuring a more uniform and refined particle size.
[0027] In some embodiments of this application, the preset conditions include a preset temperature, wherein the preset temperature can range from -70°C. o Below C. Furthermore, the preset temperature range is -100. o C to -120 o C. For example, the preset condition can be -100. o C, -105 o C, -110o C, -115 o C, -120 o C and any value between the two adjacent values mentioned above.
[0028] It is understandable that the preset temperature can be the glass transition temperature, because polymer materials exhibit low ductility below their glass transition temperature, meaning they can only undergo very small elongation deformation before fracture, exhibiting brittleness.
[0029] For example, the preset temperature can be obtained by refrigeration in a liquid nitrogen environment.
[0030] By adopting the above scheme, the preset conditions are -70. o Temperatures below a certain range help suppress the thermal activation effect during the pulverization process, preventing localized melting and adhesion. A liquid nitrogen environment helps maintain a relatively low temperature, further reducing the risk of thermal agglomeration.
[0031] In some embodiments of this application, airflow pulverization is used, and the airflow pressure ranges from greater than or equal to 0.8 MPa. Exemplarily, the airflow pressure can be 0.8 MPa, 0.9 MPa, 1.0 MPa, 1.1 MPa, 1.2 MPa, or any value between two adjacent values mentioned above.
[0032] By adopting the above scheme, the impact of a larger airflow pressure on the brittle polytetrafluoroethylene material helps to produce a uniform fracture surface, thereby ensuring the uniformity of the particle size of the material after crushing.
[0033] In some embodiments of this application, the number-average molecular weight of the polytetrafluoroethylene (PTFE) material ranges from 6 million to 7 million. Exemplarily, the number-average molecular weight of the PTFE material can be 6 million, 6.1 million, 6.2 million, 6.3 million, 6.4 million, 6.5 million, 6.6 million, 6.7 million, 6.8 million, 6.9 million, 7 million, or any value between two adjacent values.
[0034] By adopting the above scheme, the molecular weight of the polytetrafluoroethylene (PTFE) material is within a suitable range, resulting in a moderate molecular chain length, which is conducive to the formation of a continuous and strong fiber network, thereby effectively balancing the adhesiveness and dispersibility of the PTFE material. If the number-average molecular weight of the PTFE material is too small, the fibers formed after fiberization will be relatively loose, leading to insufficient adhesiveness; while if the number-average molecular weight of the PTFE material is too large, the molecular chains are prone to fiberization during premixing, resulting in uneven mixing.
[0035] In some embodiments of this application, the average particle size of the polytetrafluoroethylene (PTFE) material ranges from 450 μm to 550 μm. Exemplarily, the average particle size of the PTFE material can be 450 μm, 460 μm, 470 μm, 480 μm, 490 μm, 500 μm, 510 μm, 520 μm, 530 μm, 540 μm, 550 μm, or any value between two adjacent values.
[0036] It should be noted that this application addresses the limitation of high-molecular-weight polytetrafluoroethylene (PTFE) materials in simultaneously achieving low particle size. Due to the high molecular weight and tendency for low-particle-size PTFE to agglomerate, the material undergoes microscopic fibrosis under vibration and shearing forces during transportation and storage, resulting in macroscopic caking. Consequently, even if the powder is macroscopically homogeneous during dry powder mixing, micron-sized agglomerates may still exist, affecting the film-forming properties of the powder and the electrical properties of subsequent products. This is determined by the material's inherent characteristics. Producing low-particle-size PTFE increases production and transportation costs, and since PTFE's primary application is not in battery binders, material manufacturers have not yet developed dedicated models to address this issue. Therefore, to facilitate transportation, this application's embodiments aim to reduce the average particle size of high-molecular-weight, high-particle-size PTFE materials, thereby facilitating better mixing with active and conductive materials.
[0037] In some embodiments of this application, the average particle size of the first powder, according to ASTM D4895, ranges from 10 μm to 30 μm. Further, the average particle size of the first powder ranges from 15 μm to 25 μm. Exemplarily, the average particle size of the first powder can be 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, 21 μm, 22 μm, 23 μm, 24 μm, 25 μm, or any value between two adjacent values mentioned above.
[0038] Figure 2 This is a particle size distribution diagram of the first powder in some embodiments of this application, by... Figure 2 It can be seen that the average particle size of the first powder is between 10 μm and 30 μm.
[0039] By adopting the above scheme, an average particle size within a suitable range helps improve the dispersion uniformity of the first powder. Furthermore, during the fiberization stage, a first powder with a suitable particle size also facilitates precise control of fiberization, thereby ensuring improved electrode performance. If the average particle size of the first powder is too small, its specific surface area will be too large, leading to easy agglomeration during mixing. Moreover, in the subsequent fiberization process, a smaller particle size can also cause premature fiberization, resulting in a decrease in electrode performance. If the average particle size of the first powder is too large, it will lead to uneven dispersion during mixing. Additionally, during the fiberization process, large-particle-size first powder is difficult to fully fiberize during shearing, affecting electrode performance.
[0040] In some embodiments of this application, the step of mixing the first powder with the active material and the conductive material includes: The first powder is mixed with the active material and the conductive material at a low temperature; wherein the temperature range for low-temperature mixing is less than or equal to 10°C. o C. Furthermore, the temperature range for low-temperature mixing is -20°C. o C to 10 o C.
[0041] Figure 3 This is a SEM image of a mixed powder formed by mixing the first powder with an active material and a conductive material in some embodiments of this application. Figure 3 It can be seen that most of the mixed powders are in granular form.
[0042] By adopting the above scheme, the first powder reacts with the active material and the conductive material at -20°C. o C to 10 o Mixing is performed within temperature range C, where the PTFE material is in a triclinic crystal system with a large slip energy barrier, which helps prevent premature fiberization. If the mixing temperature is too high, it may approach the hexagonal phase transition point, leading to local crystal instability, reduced cohesive force between adjacent polymer chains, easier sliding along the chain axis, and a decrease in electrode capacity.
[0043] In some embodiments of this application, the step of fiberizing the mixed powder includes: S310. The mixed powder is fiberized once in the first temperature range to obtain mixed fiberized powder. S320. The mixed fiberized powder is subjected to secondary fiberization in the second temperature range to obtain the electrode.
[0044] Figure 4 These are SEM images of some embodiments of this application after one fiberization process, by... Figure 4 It can be seen that the molecular chains of the mixed powder undergo slippage and extension to form mixed fibrous powder, providing a primary skeleton. Figure 5These are SEM images of the mixed powder after secondary fiberization in some embodiments of this application. Figure 5 It is known that secondary fiberization can form a dense adhesive network, enabling the preparation of polytetrafluoroethylene materials with both good dispersibility and adhesion.
[0045] In some embodiments of this application, the first temperature range is 60°C. o C to 100 o C.
[0046] By adopting the above method, the material is at 60 o C to 100 o C undergoes a primary fiberization process to form coarse fibers, providing mechanical support. These coarse fibers should not be cut during mixing, which facilitates precise control of the fiberization process. If the temperature in the first temperature range is too low, film formation may fail due to insufficient fiberization; conversely, if the temperature in the first temperature range is too high, the fibers may become too fine, resulting in a decrease in electrode capacity.
[0047] In some embodiments of this application, the second temperature range is 115°C. o C to 120 o C.
[0048] By adopting the above scheme, the material, after one fiberization, reaches 115 o C to 120 o Secondary fiberization is carried out in the second temperature range of C, which refines the fiber diameter to the nanometer scale, helping to enhance the bonding strength of the PTFE material. If the temperature in the first temperature range is too high, the PTFE material will form fine fibers too early, which may be displaced and cut during the mixing stage, resulting in loss of bonding ability during rolling.
[0049] It should be noted that performing one fiberization in the first temperature range, while retaining the potential for further fiberization, helps to form a continuous network.
[0050] In some embodiments of this application, the diameter of the mixed fibrous powder ranges from 3 μm to 10 μm. Exemplarily, the diameter of the mixed fibrous powder can be 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, or any value between two adjacent values mentioned above.
[0051] By adopting the above-mentioned scheme, the mixed fibrous powder within the aforementioned diameter range has a moderate fineness, which ensures that it provides binding force after fibrosis while avoiding breakage due to excessive fibrosis. If the diameter of the mixed fibrous powder is too large, the excessive rigidity of the fibers may make it difficult to refine the fibers; if the diameter of the mixed fibrous powder is too small, the molecular chains of individual fibers will not be sufficiently entangled, and during the secondary fibrosis process, they are prone to overall slippage rather than plastic deformation.
[0052] In some embodiments of this application, the fiber diameter in the electrode membrane ranges from 20 nm to 200 nm. Exemplarily, the fiber diameter in the electrode membrane can be 20 nm, 30 nm, 45 nm, 50 nm, 65 nm, 80 nm, 95 nm, 100 nm, 115 nm, 130 nm, 135 nm, 140 nm, 150 nm, 155 nm, 160 nm, 170 nm, 180 nm, 190 nm, 200 nm, or any value between two adjacent values mentioned above.
[0053] By adopting the above scheme, the fiber diameter in the electrode film does not exceed 200nm. Polytetrafluoroethylene material within this diameter range can penetrate the gaps of the active material, which helps to form a fiber bridging structure, thereby ensuring that more active material is bonded at the same time.
[0054] In some embodiments of this application, the particle size of the conductive material is 30 nm to 80 nm.
[0055] By adopting the above scheme, the particle size of the conductive material is similar to the diameter of the fiber in the electrode, and the conductive material and the fiber in the electrode can coexist in an interwoven manner, which is beneficial to shortening the electron conduction path.
[0056] In some embodiments of this application, the electrode membrane comprises 94 to 95.5 parts by weight of an active material, 3 to 5 parts by weight of a conductive material, and 0.5 to 2 parts by weight of a polytetrafluoroethylene (PTFE) material. Exemplarily, the electrode comprises 94% to 95.5% active material, 3% to 5% conductive material, and 0.5% to 2% PTFE material.
[0057] By adopting the above solution, the electrode membrane of this application embodiment includes a high content of active material, while using a low amount of polytetrafluoroethylene material, thereby ensuring that the electrode achieves a high peel force with a low amount of polytetrafluoroethylene material.
[0058] In some embodiments of this application, the active material includes at least one of manganese dioxide, lithium nickel cobalt manganese oxide, lithium iron phosphate, and lithium manganese iron phosphate.
[0059] In some embodiments of this application, the conductive material includes at least one of conductive carbon black, acetylene black, Ketjen black, conductive graphite, and activated carbon.
[0060] According to a second aspect of the embodiments of this application, an electrode diaphragm is provided, the electrode diaphragm being prepared using the electrode diaphragm preparation method described above.
[0061] By adopting the above scheme, the electrode possesses all the features and advantages of the aforementioned electrode film preparation method, which will not be repeated here. In summary, it ensures at least a high content of active material in the electrode while using a low amount of binder material.
[0062] In some embodiments of this application, the electrode membrane is at 3 g / cm 3 The electrical conductivity at the compacted density is greater than or equal to 0.42 S / cm.
[0063] According to a third aspect of the embodiments of this application, a lithium battery is provided, which may include the electrode film as described above.
[0064] By adopting the above-described scheme, the lithium battery possesses all the characteristics and advantages of the aforementioned electrode films, which will not be repeated here. In summary, it at least ensures that the lithium battery has a large capacity, while also exhibiting high electrode peeling force.
[0065] In some embodiments of this application, the capacity of the lithium battery ranges from 1520mAh to 1650mAh. For example, the capacity of the lithium battery can be 1520mAh, 1550mAh, 1570mAh, 1590mAh, 1610mAh, 1650mAh, or any value between two adjacent values.
[0066] In some embodiments of this application, the electrode peeling force of the lithium battery is greater than or equal to 3.6N and less than or equal to 6.2N. Exemplarily, the electrode peeling force of the lithium battery can be 3.6N, 3.8N, 4.0N, 4.2N, 4.5N, 4.8N, 5N, 5.2N, 5.4N, 5.6N, 5.8N, 6N, 6.2N, or any value between two adjacent values.
[0067] The present application will be specifically described below through specific embodiments. These embodiments are only some embodiments of the present application and are not intended to limit the present application. Unless otherwise specified, the raw materials used in the following embodiments are all commercially available products.
[0068] Example 1 A lithium battery is prepared using the following method: Electrode preparation: Polytetrafluoroethylene (PTFE) material was refrigerated in liquid nitrogen for 4 hours. When the temperature was below -100°C... o At temperature C, PTFE becomes glassy. The glassy PTFE is then pulverized to an average particle size of 20 μm using an air jet mill. The grinding pressure of the air jet mill is greater than 0.8 MPa to obtain the first powder. Then, 1.2% of the first powder, 94.8 wt% of manganese dioxide, and 4 wt% of conductive carbon black were mixed at -10°C. o Low-temperature mixing at C yields a mixed powder; Mix the powder at 70 o C undergoes a single fiberization process to obtain a mixed fiberized powder. The mixed fibrous powder was heated at 120°C. o C is subjected to secondary fiberization by rolling to obtain an electrode film; The electrode film is composited on both sides of the current collector to form the initial electrode, and then pressed by a 150T pressure roller to form a finished positive electrode roll with high compaction density. PTFE has a number-average molecular weight of 6.5 million, a particle size of 450 μm to 550 μm, and a melting point of 326°C. o C to 328 o C.
[0069] The finished positive electrode coil is slit and cut into electrode sheets of corresponding sizes; The electrode sheets are ultrasonically cleaned, the tabs are spot-welded, and then the separator and negative electrode are sequentially stacked and wound into a core. After the core is put into the shell, the cap is welded and the electrolyte is injected to make a complete battery cell.
[0070] Example 2 A lithium battery, differing from Example 1 in that it is placed in a liquid nitrogen environment at a temperature of -130°C. o C. The remaining steps are consistent with those in Example 1.
[0071] Example 3 A lithium battery, differing from Example 1 in that it is placed in a liquid nitrogen environment at a temperature reaching -70°C. o C. The remaining steps are consistent with those in Example 1.
[0072] Example 4 A lithium battery, differing from Example 1 in that the cryogenic mixing temperature is 19°C. o C. The remaining steps are consistent with those in Example 1.
[0073] Example 5 A lithium battery, differing from Example 1 in that the primary fibrosis temperature is 80°C. o C. The remaining steps are consistent with those in Example 1.
[0074] Example 6 A lithium battery differs from Example 1 in that the primary fibrosis temperature is 60°C. o C. The remaining steps are consistent with those in Example 1.
[0075] Example 7 A lithium battery, differing from Example 1 in that the primary fibrosis temperature is 100°C. o C. The remaining steps are consistent with those in Example 1.
[0076] Example 8 A lithium battery differs from Example 1 in that the secondary fibrosis temperature is 100°C. o C. The remaining steps are consistent with those in Example 1.
[0077] Example 9 A lithium battery differs from Example 1 in that the polytetrafluoroethylene material used has a number-average molecular weight of 7 million, while the remaining steps are the same as in Example 1.
[0078] Example 10 A lithium battery differs from Example 1 in that the polytetrafluoroethylene material used has a number-average molecular weight of 6 million, while the remaining steps are the same as in Example 1.
[0079] Example 11 A lithium battery differs from Example 1 in that the polytetrafluoroethylene material used has a number-average molecular weight of 5 million, while the remaining steps are the same as in Example 1.
[0080] Example 12 A lithium battery differs from Example 1 in that the polytetrafluoroethylene material used has a number-average molecular weight of 7.7 million, while the remaining steps are the same as in Example 1.
[0081] Example 13 A lithium battery differs from Example 1 in that the amount of polytetrafluoroethylene material used is 2%, and the amount of manganese dioxide used is 94%, while the remaining steps are the same as in Example 1.
[0082] Example 14 A lithium battery differs from Example 1 in that the amount of polytetrafluoroethylene material used is 0.5%, and the amount of manganese dioxide used is 95.5%, while the remaining steps are the same as in Example 1.
[0083] Comparative Example 1 A lithium battery differs from Example 1 in that it lacks the liquid nitrogen environment treatment process, while the remaining steps are consistent with Example 1.
[0084] Materials and performance testing: (1) Average particle size: The first powder was measured using a dry laser particle size analyzer to obtain the D50 data; (2) Fiber diameter: Measured using ImageJ software with an electronic ruler under scanning electron microscope at 50x magnification; (3) Capacity: at room temperature 21±3 o C. At humidity less than 60%, the 100Ω constant resistance discharge capacity was tested, and the termination voltage was 2.0V. (4) Powder conductivity: The PRD1100 powder resistivity meter was used to measure the compaction density of the sample at 3.0 g / cm³. 3 The value is taken under the given conditions, and the average value is taken after 5 tests. (5) Electrode peel force: Cut the electrode into strips with a width of 25mm and a length of 150mm. Use tape to measure the peel force between the active layer and the current collector. Clamp the current collector at one end and the tape at the other end. Stick the tape to the active material layer so that the tape and the active material layer form a whole. After peel force test, the adhesion is firm. Peel the tape and the electrode at a constant rate of 100mm / min on a universal testing machine.
[0085] The test results are shown in Table 1: Table 1
[0086] Compared with Comparative Example 1, Examples 1-14 use a liquid nitrogen environment to freeze the polytetrafluoroethylene material, while Comparative Example 1 lacks a liquid nitrogen environment. As shown in Table 1, Examples 1-14 can suppress the molecular chain movement of the polytetrafluoroethylene material, making it easier to break rather than extend under the crushing action. That is, it achieves crushing alone rather than fiberization at the same time as crushing. The crushed polytetrafluoroethylene material is fully fiberized and can be better dispersed in the active and conductive materials, thereby better ensuring the electrode performance of the electrode film.
[0087] Compared with Examples 1 and 9-12, the number-average molecular weight of PTFE was changed. Under the same shear force, PTFE with a larger molecular weight is more prone to fiberization. The higher the degree of fiberization, the more likely it is to cause a decrease in powder conductivity, an increase in electrode resistance, and a low capacity utilization rate. PTFE with a smaller molecular weight has poor bonding performance, and the active material layer peels off during discharge, making it unable to exert the corresponding capacity.
[0088] Compared with Examples 1 and 13-14, the amount of PTFE was changed. As shown in Table 1, the higher the amount of binder, the higher the degree of fiberization, the worse the degree of dispersion, and the lower the powder conductivity. When the amount of binder is less, the electrode sheet will have powder shedding and discharge interruption at the end of the discharge period, and the capacity cannot be fully utilized.
[0089] The electrode film, its preparation method, and lithium battery provided in the embodiments of this application have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the methods and core ideas of this application. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this application. Therefore, the content of this specification should not be construed as a limitation of this application.
Claims
1. A method for preparing an electrode diaphragm, characterized in that, The preparation method includes the following steps: Polytetrafluoroethylene (PTFE) material is pretreated under preset conditions and then pulverized to obtain the first powder; wherein... The pretreatment is intended to suppress the stretching of the molecular chains of the polytetrafluoroethylene material. The first powder is mixed with an active material and a conductive material to obtain a mixed powder; The mixed powder is subjected to fibrosis treatment to obtain the electrode film.
2. The method for preparing the electrode film according to claim 1, characterized in that, The preset conditions include a preset temperature; The preset temperature range is -70°C. o Below C; Preferably, the preset temperature ranges from -100°C. o C to -120 o C.
3. The method for preparing the electrode film according to claim 1, characterized in that, The number-average molecular weight of the polytetrafluoroethylene material ranges from 6 million to 7 million; and / or The average particle size of the polytetrafluoroethylene material ranges from 450 μm to 550 μm; and / or The average particle size of the first powder ranges from 10 μm to 30 μm.
4. The method for preparing the electrode film according to claim 1, characterized in that, The step of mixing the first powder with the active material and the conductive material includes: The first powder is mixed with the active material and the conductive material at a low temperature, wherein the low temperature mixing temperature range is less than or equal to 10°C. o C; The temperature range for the low-temperature mixing is -20°C. o C to 10 o C.
5. The method for preparing the electrode film according to claim 4, characterized in that, The step of fibrousizing the mixed powder includes The mixed powder is fiberized once in the first temperature range to obtain mixed fiberized powder; The mixed fiberized powder is subjected to secondary fiberization in a second temperature range to obtain the electrode film.
6. The method for preparing the electrode film according to claim 5, characterized in that, The first temperature range is 60 o C to 100 o C; and / or The second temperature range is 115. o C to 120 o C.
7. The method for preparing the electrode film according to claim 5, characterized in that, The diameter of the mixed fibrous powder ranges from 3 μm to 10 μm; and / or The diameter of the secondary fiber is in the range of 20nm to 200nm.
8. The method for preparing the electrode film according to any one of claims 1 to 7, characterized in that, The electrode membrane comprises 94 to 95.5 parts by weight of the active material, 3 to 5 parts by weight of the conductive material, and 0.5 to 2 parts by weight of the polytetrafluoroethylene material.
9. The method for preparing the electrode film according to claim 8, characterized in that, The active material includes at least one of manganese dioxide, lithium nickel cobalt manganese oxide, lithium iron phosphate, and lithium manganese iron phosphate; and / or The conductive material includes at least one of conductive carbon black, acetylene black, Ketjen black, conductive graphite, and activated carbon.
10. An electrode diaphragm, characterized in that, The electrode is prepared by the method for preparing an electrode film as described in any one of claims 1 to 9.
11. The electrode diaphragm according to claim 10, characterized in that, The electrode membrane is at 3g / cm 3 The electrical conductivity at the compacted density is greater than or equal to 0.42 S / cm.
12. A lithium battery, characterized in that, The lithium battery includes the electrode film as described in claim 10 or 11.
13. The lithium battery according to claim 12, characterized in that... The capacity of the lithium battery ranges from 1520mAh to 1650mAh; and / or The electrode peeling force of the lithium battery is greater than or equal to 3.6N and less than or equal to 6.2N.