Silicon-containing electrode sheet, method for manufacturing the same, and lithium ion battery
By using a press-fit-side welding method involving carbon fiber current collectors and conductive foils, the problem of electrode performance degradation caused by the volume expansion of silicon materials was solved, thereby improving the cycle stability and energy storage capacity of lithium-ion batteries.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- SHANGHAI INST OF SPACE POWER SOURCES
- Filing Date
- 2024-12-04
- Publication Date
- 2026-06-16
Smart Images
Figure CN119786617B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of secondary battery technology, and in particular to a silicon-containing electrode sheet and its manufacturing method, and a lithium-ion battery. Background Technology
[0002] As living standards improve, people have increasingly higher requirements for the energy density of lithium-ion batteries. Currently, the theoretical specific capacity of graphite anode materials for widely commercialized lithium-ion batteries is only 372 mAh / g. Silicon anodes, on the other hand, have a theoretical capacity of 4200 mAh / g, and compared to Li / Li... + Silicon has a low potential, which can significantly improve the energy density of batteries, making it the ideal material for the anode of next-generation high-capacity lithium-ion batteries. However, silicon anode materials still face significant challenges in commercial applications. This is mainly due to the large volume change rate of silicon materials during cycling, especially pure silicon, which experiences a volume change exceeding 300%. Even silicon oxide materials exhibit a volume change of up to 150%, far exceeding that of graphite. This leads to problems such as particle breakage, easy delamination of the electrode from the current collector, and unstable electrode interfaces. Summary of the Invention
[0003] The purpose of this invention is to provide a silicon-containing electrode sheet and its manufacturing method, as well as a lithium-ion battery, to overcome the problem of large volume expansion of existing silicon-containing negative electrodes leading to a sharp decline in electrode performance, and to improve the cycle stability of the silicon-containing electrode sheet.
[0004] To achieve the above objectives, in a first aspect, the present invention provides a silicon-containing electrode sheet, comprising:
[0005] The current collector is a carbon fiber current collector, comprising: an electrode body and a first electrode tab disposed at one end of the electrode body;
[0006] A negative electrode material layer is coated on the front and back of the current collector for energy storage.
[0007] A conductive foil is wrapped around the surface of the first electrode to collect and discharge the electrical energy stored in the current collector.
[0008] Optionally, the conductive foil is a metal foil with a flat surface structure, which is a planar structure with a smooth and flat surface.
[0009] Optionally, the conductive foil is a perforated and burred metal foil. The surface of the perforated and burred metal foil is provided with a plurality of through holes, and each through hole has a plurality of uniformly arranged burrs at its edge, and all burrs are provided on the same side of the conductive foil.
[0010] Optionally, the thickness of the conductive foil is 30μm-500μm, and the length of the conductive foil is 1mm-8mm longer than the length of the first tab, and the width of the conductive foil is more than twice the width of the first tab.
[0011] Optionally, the thickness of the conductive foil is 50μm-300μm, and the length of the conductive foil is 2mm-4mm longer than the length of the first tab.
[0012] Secondly, the present invention provides a method for manufacturing a silicon-containing electrode sheet, comprising:
[0013] Step 1: Prepare a silicon-containing negative electrode slurry using silicon-containing active components, conductive agents, and binders; wherein the mass ratio of the binder, conductive agent, and silicon-containing active components is (2%-7%):(1%-3%):(90%-97%), and the mass ratio of the silicon-containing active components, including silicon-containing powder and graphite materials, is (10%-70%):(0-30%).
[0014] Step 2: Coat the silicon-containing anode slurry onto the front and back sides of the current collector, so that the areal loading of the silicon-containing anode slurry coated on both sides of the current collector is 6 mg / cm². 2 -40mg / cm 2 After drying the current collector, a silicon-containing negative electrode to be processed is obtained; wherein, the current collector is a carbon fiber current collector;
[0015] Step 3: The silicon-containing negative electrode to be processed is punched to form a first electrode tab; the first electrode tab is covered by symmetrically folding of conductive foil; the conductive foil is deformed and attached to the surface of the first electrode tab by pressing technology; the conductive foil is fixed on the first electrode tab by side welding at one edge of the folded conductive foil to obtain the silicon-containing electrode sheet; wherein, the width of the side welding is 1mm-5mm.
[0016] Optionally, in step 3, when the metal foil with the punched protrusion structure is used to cover the first electrode tab, the surface of the metal foil with the punched protrusion structure on the side of the through hole surrounded by protrusions is symmetrically folded so that the protrusions of the metal foil with the punched protrusion structure are placed opposite each other; at the same time, the first electrode tab is covered between the metal foils with the punched protrusion structure so that the protrusions of the metal foil with the punched protrusion structure contact the surface of the first electrode tab and penetrate the carbon fiber current collector.
[0017] Optionally, in step 3, the width of the side weld is 2mm-3mm.
[0018] Optionally, in step 2, the double-sided surface loading of the coating is in the range of 8 mg / cm³. 2 -24mg / cm 2 .
[0019] Thirdly, the present invention provides a lithium-ion battery comprising: the silicon-containing electrode sheet obtained using the above-described method for manufacturing silicon-containing electrode sheets.
[0020] Compared with the prior art, the technical solution of the present invention has at least the following beneficial effects:
[0021] (1) The current collector of the silicon-containing electrode sheet of the present invention is a carbon fiber current collector. The three-dimensional structure of carbon fiber provides usable space for the volume expansion of the silicon-containing negative electrode material layer, reduces the influence of the high volume effect of the silicon-containing active component on the electrode stability, and is beneficial to improving the cycle stability of the silicon-containing electrode sheet.
[0022] (2) The present invention fixes the conductive foil to the surface of the first tab of the carbon fiber current collector by pressing and side welding, and transforms the first tab of the carbon fiber material into a second tab covered with conductive foil, which solves the problem that the first tab of the carbon fiber material cannot be directly welded and current collected and discharged, so that the silicon-containing electrode sheet can be used in lithium-ion batteries and has high cycle stability. Attached Figure Description
[0023] Figure 1 This is a schematic diagram of the structure of the silicon-containing electrode sheet described in this invention.
[0024] Figure 2 This is a perspective view of the conductive foil in the silicon-containing electrode sheet described in this invention.
[0025] Figure 3 This is a schematic diagram of the perforated and burred structure of the metal foil containing the silicon electrode sheet according to the present invention.
[0026] Figure 4 This is the charge-discharge curve of the silicon-containing electrode sheet in Embodiment 1 of the present invention.
[0027] In the figure, 1-conductive foil, 11-metal foil with punched protrusions, 12-through hole, 13-protrusions, 2-first electrode tab, 3-electrode body, 4-welding position. Detailed Implementation
[0028] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0029] In the description of this invention, it should be noted that the terms "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.
[0030] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.
[0031] Firstly, such as Figure 1 As shown, the present invention provides a silicon-containing electrode sheet, which includes a negative electrode material layer, a current collector, and a conductive foil 1. The current collector serves as a carrier for the negative electrode of the battery. The negative electrode material layer is coated on both the front and back sides of the current collector for energy storage. The conductive foil 1 covers one end of the current collector for collecting and discharging the electrical energy stored in the current collector.
[0032] The negative electrode material layer is coated on both the front and back sides of the current collector, and the negative electrode material layer includes: a silicon-containing active component, a conductive agent, and a binder. The silicon-containing active component includes silicon powder and graphite material, and the silicon powder includes at least one of nano-Si, micro-Si, SiOx, pre-lithiated SiOx, and pre-lithiated Si.
[0033] The current collector includes an electrode body 3 and a first tab 2. Both the front and back of the electrode body 3 are coated with a negative electrode material layer. The first tab 2 is rectangular in shape and is located at one end of the electrode body 3, used to conduct electrical energy from the negative electrode of the battery. The current collector of this invention is a carbon fiber current collector, mainly made of graphitized carbon fiber (GCF). The three-dimensional structure of the carbon fiber provides usable space for the volume expansion of the silicon-containing active components in the negative electrode material layer, reducing the impact of the high volume effect of the silicon-containing electrode on electrode stability, which is beneficial to improving the cycle stability of the silicon-containing electrode and simultaneously increasing the energy storage capacity of the silicon-containing battery.
[0034] The conductive foil 1 is symmetrically folded to enclose the first tab 2 of the current collector, forming the second tab of the current collector. This prevents the first tab 2 of the carbon fiber current collector material from breaking during the current collector processing. The conductive foil 1 is typically a metal foil with a thickness of 30μm-500μm; and as... Figure 2 As shown ( Figure 2 This indicates that the length of the conductive foil is greater than the length of the first electrode tab, and the second electrode tab structure, composed of the conductive foil and the first electrode tab, is as follows: Figure 1 As shown, the length of the conductive foil 1 is greater than the length of the first tab 2, typically 1mm-8mm longer than the first tab 2, and the width of the conductive foil 1 is more than twice the width of the first tab, ensuring that the conductive foil 1 can completely cover the first tab 2 and has a position on the conductive foil 1 that can be welded and fixed to the first tab 2.
[0035] Specifically, in one embodiment, the conductive foil 1 is selected as a metal foil with a flat surface structure; the metal foil with a flat surface structure is a planar structure with a smooth and flat surface.
[0036] Specifically, in another embodiment, such as Figure 3 As shown, the conductive foil 1 is a metal foil 11 with a perforated and burred structure. The surface of the metal foil 11 with the perforated and burred structure is provided with a plurality of through holes 12, and the edge of each through hole 12 is provided with a plurality of uniformly arranged burrs 13, and all the burrs 13 are provided on the same side of the conductive foil 1, so that one side surface of the metal foil 11 with the perforated and burred structure is a three-dimensional structure with a plurality of through holes 12 surrounded by burrs 13, and the other side surface of the metal foil 11 with the perforated and burred structure is a smooth structure with a plurality of through holes 12.
[0037] Furthermore, when the metal foil 11 with the perforated protrusion structure is used to cover the first electrode tab 2, the surface of the metal foil 11 with the perforated protrusion structure on one side of the through hole 12 surrounded by protrusions 13 is symmetrically folded so that the protrusions 13 of the metal foil 11 with the perforated protrusion structure are placed opposite each other; at the same time, the first electrode tab 2 is covered between the metal foils 11 with the perforated protrusion structure so that the protrusions 13 of the metal foil 11 with the perforated protrusion structure are in contact with the surface of the first electrode tab 2 and penetrate the carbon fiber current collector, thereby increasing the conductive area between the metal foil 11 with the perforated protrusion structure and the first electrode tab 2.
[0038] The conductive foil 1 and the first tab 2 are fixed together using a crimping-side welding technique. After the conductive foil 1 is folded and covers the first tab 2, a crimping joint is used to crimp the conductive foil 1 and the first tab 2, enhancing the contact between the surface of the conductive foil 1 and the surface of the first tab 2 and reducing the contact resistance between them. By heating the crimping joint, the conductive foil 1 in contact with the joint melts and deforms, thus adhering to the first tab 2. Welding is then used to fix one side of the conductive foil 1 covering the first tab 2. The edges of the two layers of conductive foil formed by folding a piece of conductive foil 1 are welded together, fixing the conductive foil 1 and the first tab 2 together. Since the carbon fiber current collector may break during welding, the welding position 4 cannot be directly above the first tab 2, but must be on the edge of the conductive foil 1, where the welding position 4 does not contact the first tab 2. Therefore, the side weld width of the conductive foil 1 is 1mm-5mm to ensure that the conductive foil 1 is fixed to the surface of the first tab 2.
[0039] In a preferred embodiment, the thickness of the conductive foil 1 is 50μm-300μm. This effectively prevents the conductive foil 1 from being too thick, which would make it difficult to deform during the pressing process, thereby increasing the contact resistance of the silicon electrode sheet and causing the silicon electrode sheet to have an excessive mass, thus reducing the energy density of the silicon electrode sheet. At the same time, it prevents the conductive foil 1 from being too thin, which would result in excessive contact resistance between the conductive foil 1 and the first tab 2, affecting the cycle stability of the battery.
[0040] In a preferred embodiment, the length of the conductive foil 1 is 2mm-4mm longer than the length of the first tab 2. This ensures that the conductive foil 1 can completely cover the first tab 2 and has sufficient side solder width for soldering the conductive foil 1; at the same time, it prevents the length of the conductive foil 1 from being too large, which would increase the mass of the silicon-containing electrode sheet and reduce the energy density of the silicon-containing electrode sheet.
[0041] In a preferred embodiment, the conductive foil 1 is made of at least one of copper, pure copper, nickel-plated copper, and copper alloys to improve the conductivity of the conductive foil 1.
[0042] In a preferred embodiment, the side welding method includes: ultrasonic welding, spot welding, and laser welding.
[0043] In a preferred embodiment, the side solder width of the conductive foil 1 is 2mm-3mm. This effectively prevents the side solder width from being too small, which would lead to poor soldering and poor contact between the surface of the conductive foil 1 and the surface of the first electrode tab 2, thereby increasing the contact resistance between the conductive foil 1 and the first electrode tab 2. At the same time, it prevents the side solder width from being too large, which would increase the mass of the negative electrode and reduce the energy density of the negative electrode.
[0044] In a preferred embodiment, the crimping connector includes: a flat-head connector, a corrugated connector, and a connector with raised dots. Since the flat-head connector has poor deformation effect on the conductive foil 1, corrugated connectors or connectors with raised dots are more commonly used when crimping metal foils with flat surfaces. This increases the contact area between the metal foil with flat surfaces and the first tab 2, reducing the contact resistance between the conductive foil 1 and the first tab 2. Because the protrusions 13 of the perforated metal foil 11 can penetrate the first tab 2 (i.e., the carbon fiber current collector), the problem of a small contact area between the conductive foil 1 and the first tab 2 due to the use of a flat-head connector is not considered.
[0045] Secondly, the present invention also provides a lithium-ion battery, which includes at least the silicon-containing electrode sheet as described above. Specifically, the types of the lithium-ion battery include: pouch cell, aluminum-cased prismatic cell, and rigid-cased prismatic cell.
[0046] Thirdly, the present invention also provides a method for manufacturing a silicon-containing electrode sheet, the specific steps of which include:
[0047] Step 1: Preparation of silicon-containing anode slurry.
[0048] Weigh silicon-containing powder and graphite material at a mass ratio of (10%-70%):(0-30%) to obtain the silicon-containing active component. Then, based on the mass of the silicon-containing active component, weigh the binder, conductive agent, and silicon-containing active component at a mass ratio of (2%-7%):(1%-3%):(90%-97%).
[0049] First, the binder and deionized water are mixed evenly, then the conductive agent is added and stirred. Then, graphite material is added first, followed by silicon powder. After stirring evenly, silicon-containing negative electrode slurry is obtained.
[0050] Step 2: Coating with silicon-containing anode slurry.
[0051] The silicon-containing anode slurry obtained in step 1 is coated onto the front and back sides of the current collector, so that the areal loading of the silicon-containing anode slurry coated onto the current collector is 6 mg / cm². 2 -40mg / cm 2 The current collector coated with silicon-containing anode slurry is dried, so that the silicon-containing anode slurry forms a silicon-containing material layer coated on the front and back of the current collector after drying, and the silicon-containing anode to be processed is obtained.
[0052] In a preferred embodiment, the double-sided surface loading of the coating is in the range of 8 mg / cm². 2 -24mg / cm 2The bifacial loading capacity is related to the load-bearing capacity of the current collector (i.e., the carbon fiber current collector). If the bifacial loading capacity is too high, it will result in too many silicon-containing active components forming particles on the surface of the carbon fiber current collector. These particles cannot utilize the three-dimensional structure of the carbon fiber, which reduces the buffering effect of the current collector on the expansion effect of the silicon-containing material system, thus hindering the capacity utilization of the negative electrode material layer and the cycle stability of the battery.
[0053] Step 3: Further process the silicon-containing anode to be processed.
[0054] The silicon-containing anode obtained in step 2 is punched to form the first tab 2 in the current collector of the silicon-containing anode.
[0055] The conductive foil 1 is symmetrically folded and the first electrode tab 2 is wrapped around it. The conductive foil 1 is deformed by pressing and attached to the surface of the first electrode tab 2. The conductive foil 1 is fixed to the first electrode tab 2 by side welding at one edge of the folded conductive foil 1 to obtain the silicon-containing electrode sheet.
[0056] Example 1
[0057] Step S1: Preparation of silicon-containing anode slurry.
[0058] In this embodiment, the silicon-containing powder is pre-lithiated SiOx, and the silicon-containing active component is prepared with a mass ratio of silicon-containing powder to graphite material of 45%:55%. The silicon-containing anode slurry is prepared with a mass ratio of binder, conductive agent and silicon-containing active component of 5%:1.5%:93.5%.
[0059] Specifically, after the binder and deionized water are mixed evenly, a conductive agent is added and stirred. Then, graphite material is added first, followed by silicon powder. After stirring evenly, a silicon-containing anode slurry is obtained.
[0060] Step S2: Coating of silicon-containing anode slurry.
[0061] In this embodiment, a carbon fiber current collector is selected. The prepared silicon-containing anode slurry is prepared with a double-sided areal loading of 16 mg / cm². 2 The coating is applied to the front and back of the carbon fiber current collector, and after drying, a silicon-containing anode is obtained for processing.
[0062] Step S3: Further process the silicon-containing anode to be processed.
[0063] The silicon-containing anode obtained in step S2 is punched to form the first tab 2 in the current collector of the silicon-containing anode.
[0064] In this embodiment, the conductive foil 1 is made of copper foil with a flat surface, and the thickness of the conductive foil 1 is 100 μm, and its length is 3 mm longer than the length of the first tab 2. The conductive foil 1 is symmetrically folded so that the first tab 2 is wrapped around the conductive foil 1.
[0065] A corrugated connector is used to press the conductive foil 1 covering the first electrode tab 2, deforming the conductive foil 1 so that it can better adhere to the surface of the first electrode tab. Ultrasonic welding is then used to weld (i.e., side welding) one edge of the conductive foil 1 covering the first electrode tab 2, fixing the conductive foil 1 to the first electrode tab 2, thus transforming the first electrode tab 2 on the current collector into a second electrode tab covering the conductive foil 1. The width of the side weld is 2.5 mm.
[0066] Furthermore, a standard battery was constructed by combining silicon-containing electrode sheets with lithium metal. The specific capacity of the silicon-containing electrode sheets was tested under 0.1C charging and 0.1C discharging conditions. The test charge-discharge curves are shown below. Figure 4 As shown, the silicon electrode sheet exhibits high electrochemical performance when carbon fiber current collector is used as the current collector.
[0067] Further, the silicon-containing electrode sheet obtained in step S3 is combined with a high-nickel ternary cathode sheet, a separator, and an electrolyte to fabricate a 5Ah pouch lithium-ion battery. The 5Ah pouch lithium-ion battery is subjected to capacity and coulombic efficiency tests under 0.1C charging and discharging conditions; it is also subjected to cycle tests under 0.2C charging and discharging conditions, and the capacity retention rate after 500 cycles is statistically analyzed. The energy density, initial coulombic efficiency, and cycle performance (i.e., capacity retention rate) of this 5Ah pouch lithium-ion battery are shown in Table 1.
[0068] Table 1 Battery performance parameters of Examples 1 to Comparative Examples 4
[0069] Battery energy density (Wh / kg) First-time coulomb efficiency (%) 500-cycle capacity retention rate (%) Example 1 283.5 87.5％ 86.5％ Example 2 298.5 87.8％ 87.3％ Example 3 278.4 87.1％ 82.9％ Example 4 270.5 87.2％ 84.7％ Comparative Example 1 300.5 86.3％ 70.4％ Comparative Example 2 287.5 85.5％ 72.5％ Comparative Example 3 275.8 86.1％ 68.3％ Comparative Example 4 275.4 84.9％ 62.6％
[0070] Example 2
[0071] The specific implementation process of this embodiment is the same as that of Embodiment 1, except that: the conductive foil 1 is a copper foil with a punched and burred structure, with a thickness of 60μm and a length that is 2mm longer than the length of the first tab 2; during the pressing process, the pressing joint adopts a flat-head joint to press the conductive foil 1 onto the surface of the first tab 2 to form the second tab.
[0072] As shown in Table 1, the energy density, initial coulombic efficiency, and capacity retention of the 5Ah soft-pack lithium-ion battery obtained by the silicon-containing electrode sheet in this embodiment are all better than those of the 5Ah soft-pack lithium-ion battery obtained in Example 1. This indicates that the battery performance of the silicon-containing electrode sheet obtained by using the perforated and burred metal foil 11 as the conductive foil 1 is better than that of the conductive foil 1 with a flat surface structure.
[0073] Example 3
[0074] The specific implementation process of this embodiment is the same as that of Embodiment 1, except that: the silicon-containing powder is pre-lithiated Si, and the mass ratio of pre-lithiated Si to graphite material is 55%:45% as the silicon-containing active component. The binder, conductive agent, and active material are weighed in a mass ratio of 4%:1.5%:94.5%, and a silicon-containing anode slurry is obtained in step S1 of Embodiment 1. Furthermore, the prepared silicon-containing anode slurry is subjected to a double-sided surface loading of 24 mg / cm². 2 The coating is applied to the front and back sides of the electrode body 3 of the current collector.
[0075] As shown in Table 1, compared with Example 1, the 5Ah soft-pack lithium-ion battery prepared by the silicon-containing electrode sheet obtained in this example has lower battery energy density, initial coulombic efficiency, and capacity retention rate, indicating that the battery performance is worse than that of the silicon-containing electrode sheet prepared by using pre-lithiated Si as silicon powder. At the same time, increasing the double-sided areal loading of the silicon-containing negative electrode slurry on the current collector is not conducive to the release of material capacity of the negative electrode material layer, thus affecting the battery performance.
[0076] Example 4
[0077] The specific implementation process of this embodiment is the same as that of Embodiment 1, except that spot welding is used for the side welding of the edge of the conductive foil 1, and the side welding width is 2mm.
[0078] As shown in Table 1, compared with Example 1, the initial coulombic efficiency of the 5Ah pouch lithium-ion battery prepared by the silicon-containing electrode sheet obtained in this example is close to that of Example 1. However, the energy density and capacity retention of the 5Ah pouch lithium-ion battery prepared in this example are worse than those of Example 1. This indicates that spot welding to fix the conductive foil 1 and the first tab 2 can also enable the current collector to obtain better battery performance. However, because spot welding reduces the contact area of the welding position 4 on the conductive foil 1 and increases the spacing between adjacent welding positions 4, it leads to a decrease in the capacity of the 5Ah pouch lithium-ion battery, thereby affecting the energy density and cycle performance of the 5Ah pouch lithium-ion battery.
[0079] Comparative Example 1
[0080] The specific implementation process of this comparative example is the same as that of Example 1, except that: the conductive foil 1 is made of copper foil with a flat surface structure, and the thickness of the conductive foil 1 is 25μm, and its length is 0.8mm longer than the length of the first electrode 2.
[0081] As shown in Table 1, compared with Example 1, the 5Ah pouch lithium-ion battery prepared with the silicon-containing electrode sheet obtained in this comparative example has higher battery energy density and initial coulombic efficiency, but poorer cycle performance. This indicates that reducing the thickness and size of the conductive foil 1 can improve the battery energy density and initial coulombic efficiency, but it also increases the contact resistance of the negative electrode electrical connection, affecting the stability of battery cycling and reducing capacity retention.
[0082] Comparative Example 2
[0083] The specific implementation process of this comparative example is the same as that of Example 1, except that: the prepared silicon-containing anode slurry is prepared according to a double-sided areal loading of 42 mg / cm². 2 The coating is applied to the front and back sides of the electrode body 3 of the current collector.
[0084] As shown in Table 1, compared with Example 1, the 5Ah soft-pack lithium-ion battery prepared by the silicon-containing electrode sheet obtained in this comparative example has lower battery energy density, first coulombic efficiency, and capacity retention rate. This indicates that the excessively high bifacial loading of the silicon-containing anode slurry on the current collector is not conducive to the utilization of the material capacity of the anode material layer and the cycle stability of the battery, thereby affecting the battery energy density, first coulombic efficiency, and capacity retention rate.
[0085] Comparative Example 3
[0086] The specific implementation process of this comparative example is the same as that of Example 1, except that the width of the conductive foil 1 side solder is 0.5mm.
[0087] As shown in Table 1, compared with Example 1, the 5Ah soft-pack lithium-ion battery prepared with silicon-containing electrode sheets obtained in this comparative example has lower energy density, initial coulombic efficiency, and capacity retention. In particular, the 5Ah soft-pack lithium-ion battery in this comparative example exhibits poor cycle performance. This indicates that an insufficiently narrow side weld width easily leads to incomplete soldering, resulting in poor contact between the conductive foil 1 and the first tab 2, thus affecting the battery's cycle stability.
[0088] Comparative Example 4
[0089] The specific implementation process of this comparative example is the same as that of Example 1, except that: the silicon-containing powder is pre-lithiated Si, and the pre-lithiated Si and graphite material are weighed in a mass ratio of 85%:15% as the silicon-containing active component. The binder, conductive agent and active material are weighed in a mass ratio of 2%:1.5%:96.5%, and stirred according to step S1 in Example 1 to obtain the silicon-containing negative electrode slurry.
[0090] As shown in Table 1, compared with Examples 1 and 3, the 5Ah pouch lithium-ion battery prepared from the silicon-containing electrode sheet obtained in this comparative example has lower energy density, initial coulombic efficiency, and capacity retention. In particular, the 5Ah pouch lithium-ion battery in this comparative example exhibits poor cycle performance. This indicates that an excessively high mass ratio of silicon powder in the silicon-containing active component will affect the utilization of the negative electrode capacity, thereby impacting the battery's energy density, initial coulombic efficiency, and cycle stability.
[0091] In summary, the current collector of the silicon-containing electrode sheet of the present invention is a carbon fiber current collector. The conductive foil is fixed to the surface of the first tab of the carbon fiber current collector by a press-fit-side welding method, which overcomes the problem of large volume expansion of existing silicon-containing negative electrodes leading to a sharp decline in electrode performance and improves the cycle stability of the silicon-containing electrode sheet.
[0092] Although the present invention has been described in detail through the preferred embodiments above, it should be understood that the above description should not be considered as a limitation of the present invention. Various modifications and substitutions to the present invention will be apparent to those skilled in the art after reading the above description. Therefore, the scope of protection of the present invention should be defined by the appended claims.
Claims
1. A silicon-containing electrode sheet, characterized in that, include: The current collector is a carbon fiber current collector, comprising: an electrode body and a first electrode tab disposed at one end of the electrode body; A negative electrode material layer is coated on the front and back of the current collector for energy storage. A conductive foil completely covers the surface of the first electrode tab, collecting and discharging the electrical energy stored in the current collector; wherein the width of the conductive foil is greater than twice the width of the first electrode tab, and the length of the conductive foil is greater than the length of the first electrode tab.
2. The silicon-containing electrode sheet according to claim 1, characterized in that, The conductive foil is a metal foil with a flat surface structure, which is a planar structure with a smooth and flat surface.
3. The silicon-containing electrode sheet according to claim 1, characterized in that, The conductive foil is a perforated and burred metal foil. The surface of the perforated and burred metal foil is provided with several through holes, and each through hole has several uniformly arranged burrs at its edge, and all burrs are provided on the same side of the conductive foil.
4. The silicon-containing electrode sheet according to claim 1, characterized in that, The thickness of the conductive foil is 30μm-500μm, and the length of the conductive foil is 1mm-8mm longer than the length of the first tab.
5. The silicon-containing electrode sheet according to claim 4, characterized in that, The thickness of the conductive foil is 50μm-300μm, and the length of the conductive foil is 2mm-4mm longer than the length of the first electrode tab.
6. A method for manufacturing a silicon-containing electrode sheet as described in any one of claims 1-5, characterized in that, include: Step 1: Prepare a silicon-containing negative electrode slurry using silicon-containing active components, conductive agents, and binders; wherein the mass ratio of the binder, conductive agent, and silicon-containing active components is (2%-7%):(1%-3%):(90%-97%), and the mass ratio of the silicon-containing active components, including silicon-containing powder and graphite materials, is (10%-70%):(0-30%). Step 2: Coat the silicon-containing anode slurry onto the front and back sides of the current collector, so that the areal loading of the silicon-containing anode slurry coated on both sides of the current collector is 6 mg / cm². 2 -40 mg / cm 2 After drying the current collector, a silicon-containing negative electrode to be processed is obtained; wherein, the current collector is a carbon fiber current collector; Step 3: The silicon-containing negative electrode to be processed is punched to form a first electrode tab; a conductive foil is symmetrically folded to cover the first electrode tab; the conductive foil is deformed and attached to the surface of the first electrode tab by pressing technology; the conductive foil is welded to one side edge of the folded conductive foil by side welding to fix the conductive foil to the first electrode tab, thereby obtaining the silicon-containing electrode sheet; wherein, the width of the side welding is 1mm-5mm.
7. The method for fabricating a silicon-containing electrode sheet according to claim 6, characterized in that, In step 3, when the metal foil with the punched protrusion structure is used to cover the first electrode tab, the surface of the metal foil with the punched protrusion structure on the side of the through hole surrounded by protrusions is symmetrically folded so that the protrusions of the metal foil with the punched protrusion structure are placed opposite each other; at the same time, the first electrode tab is covered between the metal foils with the punched protrusion structure so that the protrusions of the metal foil with the punched protrusion structure come into contact with the surface of the first electrode tab and penetrate the carbon fiber current collector.
8. The method for fabricating a silicon-containing electrode sheet according to claim 6, characterized in that, In step 3, the width of the side weld is 2mm-3mm.
9. The method for fabricating a silicon-containing electrode sheet according to claim 6, characterized in that, In step 2, the coating surface loading range is 8 mg / cm². 2 -24mg / cm 2 .
10. A lithium-ion battery, characterized in that, include: The silicon-containing electrode sheet is obtained using the method for manufacturing a silicon-containing electrode sheet according to any one of claims 6-9.