Electrode manufacturing method, electrode, and battery
By filling the negative electrode of lithium-ion batteries with oxygen and maintaining a slight positive pressure during the mixing process, combined with the use of lithium replenishing agents, the generation of inorganic matter in the SEI film is promoted, which solves the problem of insufficient SEI film density and improves the storage stability and lifespan of the battery.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-11
- Publication Date
- 2026-03-13
AI Technical Summary
In existing technologies, during the charging and discharging process of lithium-ion batteries, insufficient inorganic components are generated in the SEI film, resulting in an insufficiently dense film that affects the storage stability and lifespan of the battery.
A dry process is used to fill oxygen and maintain a slight positive pressure during the mixing of the negative electrode sheet. Combined with the use of lithium replenishment agent, sufficient oxygen is provided at the electrode-electrolyte interface to promote the formation of inorganic substances in the SEI film, resulting in a denser and more stable SEI film.
It improves the battery's calendar life, reduces side reactions in the cells during storage, and enhances the battery's chemical stability and capacity retention.
Smart Images
Figure CN121662747A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of battery manufacturing, and more specifically to an electrode manufacturing method, an electrode, and a battery. Background Technology
[0002] During the initial charge and discharge of a liquid lithium-ion battery, the electrode material and the electrolyte react at the solid-liquid interface, forming a passivation layer covering the surface of the electrode material. This passivation layer is an interface layer with the characteristics of a solid electrolyte. It is an electronic insulator but an excellent conductor of Li+. Li+ can freely insert and extract through this passivation layer. Therefore, this passivation film is called a "solid electrolyte interface" (SEI film) for short.
[0003] An electrolyte interphase (SEI) film can be formed at the interface between the graphite anode material and the electrolyte through interfacial reactions. Multiple analytical methods have confirmed the existence of the SEI film, with a thickness of approximately 100–120 nm. Its composition mainly consists of various inorganic components such as Li₂CO₃, LiF, Li₂O, and LiOH, and various organic components such as ROCO₂Li, ROLi, and (ROCO₂Li)₂. During battery formation, a two-electron reaction first occurs at the electrode-electron interface to form inorganic lithium salts. As the reaction proceeds, the inorganic lithium salt layer gradually thickens, making it more difficult for electrons to reach the reaction interface, thus leading to a single-electron reaction at the interface to form organic lithium salts. Inorganic lithium salts have advantages over organic lithium salts, such as denser structure, better chemical stability, and lower impedance. Therefore, in practical formation processes, it is preferable to form an SEI film with a higher proportion of inorganic lithium salt components. Summary of the Invention
[0004] This invention provides an electrode manufacturing method, an electrode, and a battery, which effectively promotes the formation of inorganic matter in the SEI film during the formation process, thereby forming a denser and more stable SEI film. This makes the battery cell less prone to side reactions during storage, thus improving its calendar life.
[0005] This application provides an electrode manufacturing method, comprising the following steps: preparing a negative electrode sheet and a positive electrode sheet respectively; providing a separator, and assembling the negative electrode sheet, the positive electrode sheet, and the separator into an electrode; wherein, the negative electrode sheet is prepared using a dry process, specifically including: (S11) adding a negative electrode active material, a first conductive agent, and a first binder into a closed mixer according to a preset weight ratio and mixing them; during the mixing process, the mixer is filled with oxygen and maintains a preset pressure; (S12) preparing the mixed material into a negative electrode film; (S13) combining the negative electrode film with a negative electrode current collector to obtain the negative electrode sheet.
[0006] The negative electrode preparation method adopts a dry process, in which the negative electrode active material adsorbs oxygen during mixing. During the subsequent formation process, sufficient oxygen is provided at the electrode-electrolyte interface, which can increase the proportion of inorganic matter in the SEI film, thereby forming a denser and more stable SEI film. This makes the cell less prone to side reactions during storage, thereby improving the calendar life.
[0007] Furthermore, in step (S11), the mixer is evacuated using a vacuum pump before oxygen is filled.
[0008] Furthermore, in step (S11), the preset pressure is 2kPa-5kPa.
[0009] Furthermore, in step (S12), the mixture is fed into a screw extruder, fibrillated at a preset temperature, and extruded into the negative electrode film; or, in step (S12), the mixture is calendered into the negative electrode film by calendering rolls.
[0010] Furthermore, the preset temperature is 70°C to 90°C.
[0011] Furthermore, the steps for preparing the positive electrode sheet include: (S21) adding the positive active material, lithium supplementer, second binder, and second conductive agent into an organic solvent according to a preset weight ratio and stirring to prepare a positive electrode slurry; (S22) coating the positive electrode slurry onto the positive current collector and drying and compacting it to obtain the positive electrode sheet.
[0012] Furthermore, the lithium replenishing agent is selected from at least one of Li2O, Li2O2, Li2NiO2, Li5FeO4, Li6CoO4, and Li2CuO2.
[0013] Furthermore, the weight ratio of the positive electrode active material, the lithium replenishing agent, the second binder, and the second conductive agent is 92:4:2:2.
[0014] This application also provides an electrode, which is manufactured using the electrode manufacturing method described in any of the above technical solutions.
[0015] Finally, this application also provides a battery comprising the electrodes described above. Attached Figure Description
[0016] Figure 1 This is a schematic diagram of the process for preparing the negative electrode sheet according to an embodiment of this application.
[0017] Figure 2 This is a schematic diagram of the process for preparing the positive electrode sheet according to an embodiment of this application.
[0018] Figure 3This is a schematic diagram of the structure of a dry-process equipment for manufacturing negative electrode sheets according to an embodiment of this application.
[0019] Figure 4 This is a schematic flowchart of an electrode manufacturing method in a specific embodiment of this application.
[0020] Figure 5 This is a comparison diagram of the experimental group and the control group in a specific embodiment of this application.
[0021] Figure 6 This is a comparison chart of the EIS curves of the experimental group and the control group in a specific embodiment of this application.
[0022] Figure 7 This is a comparison chart of the high-temperature storage performance of the experimental group and the control group in a specific embodiment of this application. Detailed Implementation
[0023] Numerous specific details are set forth in the following description to provide a full understanding of the invention. However, the invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.
[0024] In the description of this invention, it should be understood that the orientation descriptions, such as up, down, front, back, left, right, inside, outside, etc., are based on the orientation or positional relationship shown in the drawings and are only for the convenience of describing this application and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.
[0025] In the description of this invention, unless otherwise explicitly defined, terms such as "set up," "install," and "connect" should be interpreted broadly, and those skilled in the art can reasonably determine the specific meaning of the above terms in this invention in conjunction with the specific content of the technical solution.
[0026] In the description of this invention, references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some implementations," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example that are included in at least one embodiment or example of this invention.
[0027] See Figures 1 to 2 This application provides an electrode manufacturing method, comprising the following steps: (S1) preparing a negative electrode sheet using a dry process, maintaining a slightly positive pressure oxygen atmosphere during the mixing process; (S2) preparing a positive electrode sheet; (S3) providing a separator, and assembling the negative electrode sheet, the positive electrode sheet, and the separator into an electrode.
[0028] The specific steps for preparing the negative electrode sheet include: (S11) adding the negative electrode active material, the first conductive agent and the first binder into a closed mixer according to a preset weight ratio and mixing them; during the mixing process, the mixer is filled with oxygen and maintains a preset pressure; (S12) preparing the mixture after mixing into a negative electrode film; (S13) combining the negative electrode film with a negative electrode current collector to obtain the negative electrode sheet.
[0029] Therefore, a slightly positive pressure oxygen atmosphere is maintained during the mixing process of the negative electrode sheet preparation. During the mixing process, the raw materials are fully compacted, stirred and mixed. Oxygen molecules can be physically adsorbed by interacting with the surface of the active material through van der Waals forces. After the mixing is completed, the mixture is molded into an electrode film. Then, the negative electrode current collector, such as copper foil, and the negative electrode film are rolled together by a rolling process.
[0030] In other words, the negative electrode preparation method adopts a dry process, in which the negative electrode active material adsorbs oxygen during mixing. During the subsequent formation process, sufficient oxygen is provided at the electrode-electrolyte interface, which can increase the proportion of inorganic matter in the SEI film, thereby forming a denser and more stable SEI film. This makes the cell less prone to side reactions during storage, thereby improving the calendar life.
[0031] Oxygen molecules on the surface of the negative electrode active material react at the negative electrode to promote the formation of inorganic components in the SEI film. The chemical reaction is as follows:
[0032]
[0033] Where R is a hydrocarbon group, such as methyl or ethyl.
[0034] It is understandable that the order of steps (S1) and (S2) can be interchanged.
[0035] See Figure 3 This is a schematic diagram of a dry process equipment for manufacturing negative electrode sheets. The dry process equipment includes an oxygen storage tank 1, a booster pump 2, a vacuum pump 3, and a mixer 4. The oxygen storage tank 1 is connected to the mixer 4 through the booster pump 2, and the vacuum pump 3 is connected to the mixer 4. The mixer 4 includes a sealed container with stirring blades inside.
[0036] The negative electrode active material, the first conductive agent, and the first binder are added to a sealed mixer 4 according to a preset weight ratio and mixed. Before oxygen is introduced into the mixer 4, a vacuum pump 3 is used to evacuate the mixer, and then a booster pump 2 is used to introduce oxygen from the oxygen storage tank 1 into the mixer 4, maintaining a preset pressure. For example, the preset pressure of oxygen is maintained at 2 kPa-5 kPa, such as 2 kPa, 3 kPa, 4 kPa, 5 kPa, etc.
[0037] See also Figure 3 The dry process equipment also includes a screw extruder 5 located downstream of the mixer 4. The mixture after being stirred and mixed by the mixer 4 is fed into the screw extruder 5, where it is fibrillated and extruded into a negative electrode film 6 at a preset temperature. The negative electrode film 6 is then laminated with a negative electrode current collector 7, such as copper foil, via a pressure roller 8 in a composite mechanism to obtain a negative electrode sheet 9. For example, the stirring speed of the mixer is 10-40 m / s; the preset temperature for fibrillation is 70°C to 90°C, for example, 80°C.
[0038] Of course, in other embodiments, the mixture after being stirred and mixed by mixer 4 can also be calendered into a negative electrode film by calendering rolls. For example, calendering and thinning can be performed by multi-stage calendering rolls, which does not depart from the essence of the present invention.
[0039] Therefore, a negative electrode sheet adsorbed with oxygen molecules can be prepared. During subsequent formation, providing sufficient oxygen at the electrode-electrolyte interface increases the proportion of inorganic matter in the SEI film, resulting in a denser and more stable SEI film, thereby improving calendar life. Furthermore, it can be understood that a slightly positive pressure oxygen atmosphere during stirring and mixing is particularly suitable for dry processes. In wet processes, due to the viscosity of the wet slurry, applying a slightly positive pressure oxygen atmosphere would cause air bubbles to remain inside the slurry, hindering the effective completion of subsequent coating processes. In other words, this invention effectively integrates the dry process with a slightly positive pressure oxygen atmosphere, providing oxygen molecules at the electrode-electrolyte interface during subsequent formation.
[0040] See also Figure 2 The step (S2) for preparing the positive electrode sheet specifically includes: (S21) adding the positive active material, lithium supplementer, second binder and second conductive agent into an organic solvent according to a preset weight ratio and stirring to prepare a positive slurry; (S22) coating the positive slurry onto the positive current collector and drying and compacting it to obtain the positive electrode sheet.
[0041] For example, the lithium supplement is selected from at least one of Li₂O, Li₂O₂, Li₂NiO₂, Li₅FeO₄, Li₆CoO₄, and Li₂CuO₂. For example, it is carbon-coated Li₂O.
[0042] In other words, the positive electrode uses a wet mixing process, adding a lithium replenishing agent during mixing. This agent not only provides an irreversibly lost Li source for SEI film formation, but the oxygen generated after oxidation can also reach the negative electrode surface through crosstalk. This process creates an oxygen-rich atmosphere on the electrode material surface, providing sufficient oxygen at the electrode-electrolyte interface during subsequent formation. This further increases the proportion of inorganic matter in the SEI film, resulting in a denser and more stable SEI film. This makes the cell less prone to side reactions during storage, thereby further improving calendar life.
[0043] For example, the reaction in which the positive electrode lithium supplement Li2O reacts to generate oxygen is as follows:
[0044] Li₂O→¹ / ²O₂ + 2e⁻ - +2Li + .
[0045] See Figure 4 In one specific embodiment, the steps for preparing the negative electrode sheet include: adding the negative electrode active material graphite, conductive agent carbon black and CNT, and binder PTFE into a mixer 4 at a weight ratio of 89:3:8 and mixing them at a stirring speed of 25 m / s. During the stirring process, the oxygen pressure is maintained at 2 kPa, and oxygen molecules are fully adsorbed on the surface of the negative electrode active material particles. Then, the mixture is put into a screw extruder and fibrillated at 80°C and extruded into a negative electrode film. The negative electrode film is rolled and pressed with copper foil to form an electrode sheet, and the negative electrode sheet is obtained by slitting and cutting.
[0046] The steps for preparing the positive electrode sheet include: adding lithium cobalt oxide (positive electrode active material), carbon-coated Li2O (lithium supplementer), polyvinylidene fluoride (PVDF) (binder), and Super-P (conductive agent) to N-methylpyrrolidone (NMP) in a weight ratio of 92:4:2:2 and stirring to form a positive electrode slurry at a stirring speed of 15 m / s; coating the positive electrode slurry on both sides onto a positive electrode current collector, such as aluminum foil; and then drying, compacting, slitting, and cutting the slurry to obtain the positive electrode sheet.
[0047] The negative electrode, positive electrode, and separator are assembled into an electrode.
[0048] The electrodes are wound or stacked and placed into the battery casing, and then electrolyte is injected to manufacture the battery.
[0049] During the formation of the manufactured battery, in the manufacturing method of the present invention, the oxygen molecules generated by the reaction of oxygen molecules on the surface of the negative electrode active material with the positive electrode lithium replenishing agent can promote the formation of inorganic components in the SEI film. The generated inorganic lithium salt has advantages such as dense structure, good chemical stability and low impedance, thereby improving the battery's calendar life.
[0050] Figures 5 to 7 The performance comparison of the battery cells manufactured using the manufacturing process of this embodiment (i.e., the experimental group) and the conventional process (i.e., the control group) is shown. The conventional process refers to the preparation of positive and negative electrode sheets using the traditional wet process, which does not have a positive pressure oxygen atmosphere and does not add lithium replenishing agent.
[0051] Analysis revealed that the experimental group's cells exhibited higher capacity retention compared to the control group's cells after 500 cycles. Simultaneously, the EIS curves showed that the experimental group's cells had lower impedance than the control group's cells, demonstrating that sufficient O2 molecules at the electrode-electrolyte interface of this embodiment promoted the formation of inorganic lithium salts on the surface of the negative electrode material. The resulting SEI film possesses advantages such as dense structure, good chemical stability, and low impedance. Furthermore, data from cell storage at 45°C showed that the experimental group's cells effectively improved cell calendar life; after 60 days of high-temperature storage, the capacity retention rate of the experimental group's cells remained at 98%.
[0052] It should be noted that although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make possible changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope defined in the claims of the present invention.
Claims
1. A method for manufacturing an electrode, characterized in that, Includes the following steps: Negative and positive electrode sheets were prepared separately. A diaphragm is provided, and the negative electrode, the positive electrode, and the diaphragm are assembled into an electrode; The preparation of the negative electrode sheet using a dry process specifically includes: (S11) The negative electrode active material, the first conductive agent and the first binder are added to a closed mixer in a preset weight ratio and stirred and mixed; during the stirring process, the mixer is filled with oxygen and maintained at a preset pressure; (S12) Prepare a negative electrode film from the stirred mixture; (S13) The negative electrode film is combined with the negative electrode current collector to obtain the negative electrode sheet.
2. The electrode manufacturing method according to claim 1, characterized in that, In step (S11), the mixer is evacuated using a vacuum pump before oxygen is filled.
3. The electrode manufacturing method according to claim 2, characterized in that, In step (S11), the preset pressure is 2kPa-5kPa.
4. The electrode manufacturing method according to claim 1, characterized in that, In step (S12), the mixture is fed into a screw extruder, fibrillated at a preset temperature, and extruded into the negative electrode film; Alternatively, in step (S12), the mixture is calendered into the negative electrode film by calendering rolls.
5. The electrode manufacturing method according to claim 4, characterized in that, The preset temperature is 70°C to 90°C.
6. The electrode manufacturing method according to claim 1, characterized in that, The steps for preparing the positive electrode sheet include: (S21) The positive electrode active material, lithium supplementer, second binder and second conductive agent are added to an organic solvent according to a preset weight ratio and stirred to prepare a positive electrode slurry; (S22) The positive electrode slurry is coated onto the positive electrode current collector and then dried and compacted to obtain the positive electrode sheet.
7. The electrode manufacturing method according to claim 6, characterized in that, The lithium supplement is selected from at least one of Li2O, Li2O2, Li2NiO2, Li5FeO4, Li6CoO4, and Li2CuO2.
8. The electrode manufacturing method according to claim 6, characterized in that, The weight ratio of the positive electrode active material, the lithium replenishing agent, the second binder, and the second conductive agent is 92:4:2:
2.
9. An electrode, characterized in that, The electrode is manufactured using the electrode manufacturing method as described in any one of claims 1-8.
10. A battery, characterized in that, The battery includes the electrodes as described in claim 9.