Electrode sheet preparation method, electrode sheet and battery

Abstract

The present invention discloses an electrode sheet preparation method, an electrode sheet, and a battery, and relates to the field of battery technology. The electrode sheet preparation method comprises: using a dry film-forming method to form an outer electrode film from a mixture of a silicon-containing electrode material and a pore-forming filler, wherein the pore-forming filler comprises a high-temperature vaporizing material and / or an electrolyte-soluble material, the high-temperature vaporizing material is used to vaporize at a preset temperature, and the electrolyte-soluble material is used to dissolve in the electrolyte; using a dry film-forming method to form an inner electrode film from a carbon-containing electrode material; rolling the outer electrode film and the inner electrode film to obtain a composite laminate; and rolling the composite laminate onto a current collector to obtain an electrode sheet. The electrode sheet preparation method provided by the present invention can produce an electrode sheet with small volume rebound and stable performance.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and in particular to an electrode sheet preparation method, an electrode sheet and a battery. Background Art

[0002] At present, in order to improve energy density, lithium-ion batteries on the market often use a method of mixing silicon and graphite and then evenly coating the current collector to prepare electrode sheets.

[0003] The electrode sheet prepared by this method will have a large volume rebound after full charging due to the increased volume expansion of silicon, which will in turn affect the performance of the battery cell. This is especially true for negative electrode sheets with a high silicon content, where the rebound after volume expansion is more serious. Summary of the Invention

[0004] The object of the present invention is to provide a method for preparing an electrode sheet, which can produce an electrode sheet with small volume rebound and stable performance.

[0005] Another object of the present invention is to provide an electrode sheet having the characteristics of small volume rebound and stable performance.

[0006] Another object of the present invention is to provide a battery having more stable and reliable performance.

[0007] The embodiment of the present invention provides a technical solution:

[0008] A method for preparing an electrode sheet, comprising:

[0009] The outer electrode film is formed by a dry film forming method from a mixture of a silicon-containing electrode material and a pore-forming filler, wherein the pore-forming filler includes a high-temperature vaporizing material and / or an electrolyte-soluble material, the high-temperature vaporizing material is configured to vaporize at a preset temperature, and the electrolyte-soluble material is configured to dissolve in the electrolyte;

[0010] The carbon-containing electrode material is made into an inner electrode film by a dry film forming method;

[0011] Roll-combining the outer electrode film and the inner electrode film to obtain a composite laminate;

[0012] The composite laminate is rolled and laminated on a current collector to obtain an electrode sheet.

[0013] Furthermore, the high-temperature gasification material includes iodine and / or aluminum chloride.

[0014] Furthermore, the electrolyte dissolving material includes lithium salt and / or electrolyte additive.

[0015] Furthermore, the silicon-containing electrode material includes silicon material, a conductive agent and an adhesive.

[0016] Furthermore, the mass ratio of the pore-forming filler to the silicon material in the outer electrode film is greater than or equal to 0.5% and less than or equal to 60%.

[0017] Furthermore, the carbon-containing electrode material includes graphite, a conductive agent and an adhesive.

[0018] Furthermore, the step of rolling the composite laminate onto a current collector to obtain an electrode sheet includes:

[0019] The side of the composite laminate corresponding to the inner electrode film away from the outer electrode film is rolled and laminated on the current collector to obtain the electrode sheet.

[0020] Furthermore, the step of rolling the composite laminate onto a current collector to obtain an electrode sheet includes:

[0021] The two composite laminates are respectively rolled and laminated on both sides of the current collector to obtain the electrode sheet.

[0022] An embodiment of the present invention also provides an electrode sheet, which is prepared according to the electrode sheet preparation method, and the electrode sheet preparation method includes: using a dry film forming method to form an outer electrode film from a mixture of a silicon-containing electrode material and a pore-forming filler, wherein the pore-forming filler includes a high-temperature gasification material and / or an electrolyte-dissolving material, the high-temperature gasification material is used to gasify at a preset temperature, and the electrolyte-dissolving material is used to dissolve in the electrolyte; using a dry film forming method to form an inner electrode film from a carbon-containing electrode material; rolling the outer electrode film and the inner electrode film to obtain a composite laminate; rolling the composite laminate on a current collector to obtain an electrode sheet.

[0023] An embodiment of the present invention also provides a battery, comprising the electrode sheet, which is prepared according to the electrode sheet preparation method, the electrode sheet preparation method comprising: using a dry film-forming method to form an outer electrode film from a mixture of a silicon-containing electrode material and a pore-forming filler, wherein the pore-forming filler includes a high-temperature gasification material and / or an electrolyte-dissolving material, the high-temperature gasification material is used to gasify at a preset temperature, and the electrolyte-dissolving material is used to dissolve in the electrolyte; using a dry film-forming method to form an inner electrode film from a carbon-containing electrode material; roll-compounding the outer electrode film and the inner electrode film to obtain a composite laminate; roll-compounding the composite laminate on a current collector to obtain an electrode sheet.

[0024] Compared with the prior art, the electrode sheet preparation method provided by the present invention adds a pore-forming filler to the silicon-containing electrode material. The pore-forming filler includes a high-temperature vaporization material and / or an electrolyte-soluble material, and adopts a dry film-forming method to form an outer electrode film. The outer electrode film and the inner electrode film are roll-compounded on the current collector to obtain an electrode sheet. In actual applications, the electrode sheet prepared by this method can be vaporized by the high-temperature vaporization material in the pore-forming filler as the temperature of the electrode sheet increases, and the electrolyte-soluble material can be dissolved in the electrolyte, that is, the pore-forming filler can form multiple pores in the outer electrode film in actual applications, thereby providing expansion space for the silicon in the outer electrode film, absorbing the expansion of silicon, thereby avoiding changes in the volume of the electrode sheet, reducing or even avoiding the volume rebound of the electrode sheet, and ensuring the stability of the performance of the battery cell. Therefore, the beneficial effects of the electrode sheet preparation method provided by the present invention include: being able to prepare an electrode sheet with small volume rebound and stable performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] To more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly describes the drawings required for use in the embodiments. It should be understood that the following drawings illustrate only certain embodiments of the present invention and should not be construed as limiting the scope of the present invention. Those skilled in the art can, without inventive effort, derive other relevant drawings from these drawings.

[0026] Figure 1 A flowchart of a method for preparing an electrode sheet according to an embodiment of the present invention;

[0027] Figure 2 A schematic structural diagram of an electrode sheet provided in an embodiment of the present invention.

[0028] Icon: 100-electrode sheet; 110-current collector; 120-composite laminate; 121-inner electrode film; 122-outer electrode film; 1221-pore-forming filler. DETAILED DESCRIPTION

[0029] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more apparent, the technical solutions of the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings of the embodiments of the present invention. It should be understood that the described embodiments are only a portion of the embodiments of the present invention, not all of them. Generally, the components of the embodiments of the present invention described and illustrated in the drawings herein may be arranged and designed in a variety of different configurations.

[0030] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention as claimed, but rather merely represents selected embodiments of the present invention. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort shall fall within the scope of protection of the present invention.

[0031] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, it does not need to be further defined or explained in subsequent drawings.

[0032] In the description of the present invention, it should be understood that the terms "upper", "lower", "inside", "outside", "left", "right", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, or are the orientations or positional relationships in which the inventive product is conventionally placed when in use, or are the orientations or positional relationships conventionally understood by those skilled in the art. These are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or component referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0033] Furthermore, the terms “first”, “second”, etc. are merely used for distinguishing descriptions and should not be understood as indicating or implying relative importance.

[0034] In the description of the present invention, it should also be noted that, unless otherwise expressly specified or limited, terms such as "disposed" and "connected" should be understood in a broad sense. For example, "connected" can mean a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can also mean internal communication between two components. Those skilled in the art will be able to understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0035] The specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0036] Example

[0037] See also Figure 1 , Figure 1 The figure shows a flow chart of the electrode sheet preparation method provided in this embodiment. The electrode sheet preparation method may include the following steps:

[0038] In step S101 , a mixture of a silicon-containing electrode material and a pore-forming filler is formed into an outer electrode film by a dry film forming method.

[0039] It can be understood that the silicon-containing electrode material in this embodiment refers to a negative electrode active material with silicon as the main material, and the silicon-containing electrode material specifically includes silicon material, a conductive agent and an adhesive.

[0040] The pore-forming filler includes a high-temperature gasification material and / or an electrolyte-soluble material. The high-temperature gasification material is used to gasify at a preset temperature, and the electrolyte-soluble material is used to dissolve in the electrolyte.

[0041] In this embodiment, the pore-forming filler preferably includes a high-temperature vaporizing material and an electrolyte-soluble material, wherein the high-temperature vaporizing material includes iodine and / or aluminum chloride, and the electrolyte-soluble material includes a lithium salt and / or an electrolyte additive.

[0042] The lithium salt may include one or more of LiPF6, LiBF4, LiBOB, LiFSI, LiTFSI, LiDFOB, and LiPO2F2, and the electrolyte additive may include one or more of FEC, VC, PS, DTD, ES, and TMSP.

[0043] It should be noted that in order to ensure that the pores formed on the outer electrode membrane can effectively absorb the expansion of silicon in actual applications, thereby avoiding changes in the volume of the electrode sheet, it is necessary to ensure that the mass ratio of the pore-forming filler and the silicon material in the outer electrode membrane is greater than or equal to 0.5% and less than or equal to 60%.

[0044] In this embodiment, preferably, the mass ratio of the silicon material to the conductive agent, adhesive and pore-forming filler in the outer electrode film is 87:1:4:8.

[0045] Furthermore, the electrode sheet preparation method provided in this embodiment may further include:

[0046] Step S102 : using a dry film forming method to form an inner electrode film from the carbon-containing electrode material.

[0047] The carbon-containing electrode material in this embodiment refers to a negative electrode active material mainly composed of graphite, and the silicon-containing electrode material specifically includes graphite, a conductive agent, and a binder. Preferably, the mass ratio of graphite to the conductive agent and the binder in this embodiment is 96:1:3.

[0048] Furthermore, the electrode sheet preparation method provided in this embodiment may further include:

[0049] Step S103 , rolling the outer electrode film and the inner electrode film to form a composite laminate.

[0050] After the outer electrode film and the inner electrode film are prepared in steps S101 and S102, respectively, the outer electrode film and the inner electrode film are roll-laminated together to form a composite laminate. It is understood that in the composite laminate formed by roll-laminated bonding, one side of the outer electrode film in the thickness direction is closely attached to one side of the inner electrode film in the thickness direction.

[0051] Furthermore, the electrode sheet preparation method provided in this embodiment may further include:

[0052] Step S104 , rolling the composite laminate onto the current collector to obtain an electrode sheet.

[0053] In fact, in this embodiment, the side of the composite laminate corresponding to the inner electrode film away from the outer electrode film is rolled and laminated on the current collector to obtain an electrode sheet.

[0054] That is, the inner electrode film is located between the outer electrode film and the current collector. The inner electrode film has a high graphite content and a relatively soft texture. It can absorb and release the stress generated by the volume expansion of the silicon material in the outer electrode film during the charging and discharging process to a certain extent, prevent the outer electrode film from falling off, and further ensure the stability of the performance of the prepared electrode sheet and the battery cell used.

[0055] In this embodiment, two composite laminates are roll-laminated onto opposite sides of a current collector to form an electrode sheet. This means that the composite laminates are laminated onto opposite sides of the current collector in the thickness direction, further improving the energy density of the electrode sheet. Furthermore, the two inner electrode films corresponding to the two composite laminates are closely attached to opposite sides of the current collector, while the two outer electrode films corresponding to the two inner electrode films are closely attached to the sides facing away from the current collector.

[0056] In addition, this application takes the negative electrode sheet as an example, and also uses the negative electrode sheet prepared by the electrode sheet preparation method provided in this embodiment and the negative electrode sheets prepared by various comparative examples to form battery cells and compare them in combination with actual application scenarios. Among them, except for the different preparation methods of the negative electrode sheet, other factors including the preparation process of the positive electrode sheet remain consistent.

[0057] In this embodiment, 6 μm copper foil is selected as the current collector of the negative electrode sheet. The overall thickness of the prepared negative electrode sheet is 0.139 mm and the compaction density is 1.6 g / cm 3 .

[0058] 92 wt% positive electrode active material, 5 wt% conductive agent, and 3 wt% PVDF were mixed and uniformly mixed in NMP as solvent to form a positive electrode slurry. The positive electrode slurry was then extrusion coated onto the surface of a 12 μm thick aluminum foil current collector. The positive electrode active material layer was then dried at 85°C. The positive electrode sheet had a compaction density of 3.4 g / cm 3 , and then cut into different pieces according to the shape of the battery, and then dry them under vacuum conditions at 85° C. for 4 hours to obtain the positive electrode sheets required for this embodiment and multiple comparative examples.

[0059] Comparative Example 1

[0060] The outer electrode film was prepared without adding pore-forming fillers. Silicon material, conductive agent, and adhesive were mixed in a mixing tank at a mass ratio of 95:1:4, and then the outer electrode film was prepared using a dry film-forming method. The negative electrode sheet was then prepared using the same steps and material selection as steps S102 to S104 of this embodiment. The resulting negative electrode sheet had an overall thickness of 0.131 mm and a compacted density of 1.6 g / cm3 .

[0061] Comparative Example 2

[0062] 10% silicon material was mixed evenly with graphite, and the outer electrode film was prepared using a dry film forming method without adding pore-forming fillers. The negative electrode sheet was then prepared using the same steps and material selection as steps S102 to S104 of this embodiment. The overall thickness of the prepared negative electrode sheet was 0.131 mm, and the compacted density was 1.6 g / cm 3 .

[0063] Comparative Example 3

[0064] The negative electrode sheet is made using a wet coating process. 10% silicon and graphite are evenly mixed to form a silicon composite negative electrode. The negative electrode active material (graphite), conductive agent, plasticizer, and binder are mixed in a mass ratio of 96:1:1.5:1.5 according to traditional processes. They are slurried, coated, dried, and rolled to form the negative electrode sheet. The thickness of the negative electrode sheet is 0.132mm and the compaction density is 1.6g / cm 3 .

[0065] The negative electrode sheets prepared in this embodiment, comparative example 1, comparative example 2 and comparative example 3 were respectively assembled with the same positive electrode sheets into cylindrical batteries, and the capacity and cycle tests were performed respectively. The test results are shown in the following table:

[0066]

[0067]

[0068] It can be seen that the thickness increment of the negative electrode sheet prepared by the electrode sheet preparation method provided in this embodiment is the smallest when fully charged, and the battery cell capacity is larger and the cycle performance is higher.

[0069] In summary, the electrode sheet preparation method provided in this embodiment can prepare an electrode sheet with small volume rebound and stable performance.

[0070] See also Figure 2 , Figure 2 FIG. 1 is a schematic structural diagram of the electrode sheet 100 provided in this embodiment.

[0071] The electrode sheet 100 provided in this embodiment is prepared by the electrode sheet preparation method of steps S101 to S104 described above. The electrode sheet 100 includes a current collector 110 and two composite laminates 120 located on opposite sides of the current collector 110. Each composite laminate 120 includes an inner electrode film 121 adjacent to the current collector 110 and an outer electrode film 122 distal from the current collector 110. The outer electrode film 122 includes silicon material, a conductive agent, an adhesive, and a pore-forming filler 1221.

[0072] The pore-forming filler 1221 includes a high-temperature vaporizing material and / or an electrolyte-soluble material. The high-temperature vaporizing material is used to vaporize at a preset temperature, and the electrolyte-soluble material is used to dissolve in the electrolyte.

[0073] In actual applications, the high-temperature vaporization material in the pore-forming filler 1221 can be vaporized as the temperature of the electrode sheet 100 increases, and the electrolyte-dissolving material can dissolve in the electrolyte, that is, the pore-forming filler 1221 can form multiple pores in the outer electrode film 122 in actual applications, thereby providing expansion space for the silicon in the outer electrode film 122, absorbing the expansion of silicon, thereby avoiding volume changes of the electrode sheet 100, reducing or even avoiding volume rebound of the electrode sheet 100, and ensuring stable performance of the battery cell.

[0074] Therefore, the electrode sheet 100 provided in this embodiment has the characteristics of small volume rebound and stable performance. In addition, the pores formed by the pore-forming filler 1221 within the outer electrode film 122 are also conducive to the storage and infiltration of the electrolyte. At the same time, to prevent the pore size from being too large and blocking the transmission path of electrons and ions, long-chain conductive agents such as carbon nanotubes and single-walled carbon tubes can be used. The micropore shape can be elongated, flat, or round, and the size is controlled within the range of 0.001μm to 3μm.

[0075] This embodiment further provides a battery, including the aforementioned electrode sheet 100 . Therefore, the battery has the characteristics of more stable and reliable performance.

[0076] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A method for preparing an electrode sheet, characterized in that: include: The outer electrode film is formed by a dry film forming method from a mixture of a silicon-containing electrode material and a pore-forming filler, wherein the pore-forming filler includes a high-temperature vaporizing material and an electrolyte-dissolving material, the high-temperature vaporizing material includes iodine and / or aluminum chloride and is configured to vaporize at a preset temperature, and the electrolyte-dissolving material is configured to dissolve in the electrolyte; The carbon-containing electrode material is made into an inner electrode film by a dry film forming method; Roll-combining the outer electrode film and the inner electrode film to obtain a composite laminate; Roll-pressing the composite laminate onto a current collector to obtain an electrode sheet; The silicon-containing electrode material includes silicon material, a conductive agent and an adhesive; the mass ratio of the pore-forming filler and the silicon material in the outer electrode film is greater than or equal to 0.5% and less than or equal to 60%.

2. The method for preparing an electrode sheet according to claim 1, wherein: The electrolyte dissolving material includes lithium salt and / or electrolyte additive.

3. The method for preparing an electrode sheet according to claim 1, wherein: The carbon-containing electrode material includes graphite, a conductive agent and an adhesive.

4. The method for preparing an electrode sheet according to claim 1, wherein: The step of rolling the composite laminate onto the current collector to obtain an electrode sheet comprises: The side of the composite laminate corresponding to the inner electrode film away from the outer electrode film is rolled and laminated on the current collector to obtain the electrode sheet.

5. The method for preparing an electrode sheet according to claim 1, wherein: The step of rolling the composite laminate onto the current collector to obtain an electrode sheet comprises: The two composite laminates are respectively rolled and laminated on both sides of the current collector to obtain the electrode sheet.

6. An electrode sheet, characterized in that: The electrode sheet is prepared according to the electrode sheet preparation method according to any one of claims 1 to 5.

7. A battery, characterized in that: Comprising the electrode sheet as claimed in claim 6.

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