A current collector and a lithium battery

Abstract

The utility model provides a kind of current collector, including foil, tapered hole extending along the thickness direction of foil is opened on foil, along the direction of foil front surface towards foil back, the opening area of tapered hole gradually reduces, and lithium supplement agent is filled in tapered hole.Using the above technical scheme, the structural stability of electrode can be significantly enhanced while ensuring the long-term stability of lithium supplement effect, and the safety performance of battery is further improved.The utility model also provides a lithium battery comprising the above current collector.The battery has high battery coulomb efficiency and cycle stability.

Description

Technical Field

[0001] This utility model relates to the field of battery technology, and in particular to a current collector and a lithium battery. Background Technology

[0002] During the first charge and discharge of a lithium-ion battery, the solid electrolyte interphase (SEI) film formed on the surface of the negative electrode irreversibly consumes 5%-20% of the lithium ions, leading to a decrease in battery coulombic efficiency and capacity loss. To address this, existing technologies often employ negative electrode pre-lithiation or the introduction of additives into the positive electrode for lithium replenishment, but both approaches have significant limitations. The negative electrode pre-lithiation method suffers from complex processing, while the method of directly mixing lithium-rich materials such as Li₂NiO₂ into the positive electrode is prone to causing side reactions between the lithium-rich materials and the electrolyte. Utility Model Content

[0003] The present invention provides the following technical solutions to solve the above-mentioned technical problems.

[0004] This utility model provides a current collector, including a foil, on which a tapered hole extending along the thickness direction of the foil is formed. The opening area of ​​the tapered hole gradually decreases along the direction from the front side of the foil to the back side of the foil, and the tapered hole is filled with a lithium replenishing agent.

[0005] By adopting the above technical solution, the structural stability of the electrode can be significantly enhanced while ensuring a long-lasting and stable lithium replenishment effect, thereby further improving the safety performance of the battery.

[0006] According to another specific embodiment of the present invention, the conical hole is cone-shaped.

[0007] According to another specific embodiment of the present invention, the taper of the cone is 1.2-3.0, and the taper is the ratio of the diameter of the base of the cone to its depth.

[0008] According to another specific embodiment of the present invention, the diameter of the bottom surface of the cone is 5-200μm.

[0009] According to another specific embodiment of the present invention, the cone angle of the tapered hole is 20-25°.

[0010] According to another specific embodiment of the present invention, the ratio of the depth of the conical hole to the thickness of the foil is 0.8-1.0.

[0011] According to another specific embodiment of the present invention, the number of the conical holes is multiple and the hole density is 10-1000 holes / cm².

[0012] According to another specific embodiment of the present invention, a sealing layer is coated at the maximum opening of the conical hole, and the sealing material in the sealing layer is selected from one of polyvinylidene fluoride (PVDF), polyacrylic acid (PAA), and alumina (Al2O3).

[0013] According to another specific embodiment of the present invention, the thickness of the sealing layer is 0.1-5μm.

[0014] This invention also provides a lithium battery, including the current collector in any of the above embodiments.

[0015] By adopting the above technical solution, the initial capacity and actual usable capacity of lithium batteries can be significantly improved, while the battery coulombic efficiency and cycle stability can be enhanced. Attached Figure Description

[0016] Figure 1 This shows a front view of the current collector in an embodiment of the present invention. Figure 1 ;

[0017] Figure 2 This shows a front view of the current collector in an embodiment of the present invention. Figure 2 . Detailed Implementation

[0018] The following specific embodiments illustrate the implementation of this utility model. Those skilled in the art can easily understand other advantages and effects of this utility model from the content disclosed in this specification. Although the description of this utility model will be presented in conjunction with preferred embodiments, this does not mean that the features of this utility model are limited to this embodiment. On the contrary, the purpose of describing the utility model in conjunction with the embodiments is to cover other options or modifications that may be derived based on the claims of this utility model. To provide a deep understanding of this utility model, many specific details will be included in the following description. This utility model may also be implemented without using these details. Furthermore, to avoid confusion or obscuring the focus of this utility model, some specific details will be omitted in the description. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of this utility model can be combined with each other.

[0019] It should be noted that in this specification, similar reference numerals and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0020] The terms “first”, “second”, etc., are used only to distinguish descriptions and should not be interpreted as indicating or implying relative importance.

[0021] In the description of this embodiment, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set up," "connected," and "linked" 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 or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this embodiment based on the specific circumstances.

[0022] To make the objectives, technical solutions, and advantages of this utility model clearer, the embodiments of this utility model will be described in further detail below with reference to the accompanying drawings.

[0023] like Figure 1 As shown, this utility model provides a current collector 1, including a foil 2, on which a current collector is formed along the thickness direction of the foil 2 (e.g., ...). Figure 1 The tapered hole 3 extends in the Y direction of the foil 2, along the direction from the front side of the foil 2 toward the back side of the foil 2 (see reference). Figure 2 (In the Y1 direction), the opening area of ​​the conical hole 3 gradually decreases. The conical hole 3 is filled with lithium replenishing agent.

[0024] Studies have found that while simply creating through holes and filling them with lithium replenishing agent on the current collector 1 can compensate for lithium loss caused by SEI film formation, the bonding force between the lithium replenishing agent and the current collector is weak. This defect leads to the lithium replenishing agent being easily detached or displaced from the through holes due to mechanical forces during the process of preparing the current collector into an electrode, or during critical stages of battery assembly (such as slurry coating, winding, and finished product transportation). This not only significantly weakens the long-term stability of the lithium replenishment effect but may also damage the structural integrity of the electrode, thereby increasing safety hazards such as internal short circuits in the battery. To address this, this invention provides a tapered hole 3 on the current collector 1 with a gradually decreasing opening area along the Y1 direction. After the lithium replenishing agent is filled into it, it achieves efficient lithium replenishment while the geometric constraint of the tapered hole allows the lithium replenishing agent to be firmly embedded in the hole. This effectively avoids problems such as detachment or displacement of the lithium replenishing agent during subsequent production processes or battery use, thus ensuring a long-lasting and stable lithium replenishment effect while significantly enhancing the structural stability of the electrode and further improving the safety performance of the battery.

[0025] Furthermore, such as Figure 1 As shown, in the above embodiment, the shape of the conical hole is a cone.

[0026] This technical solution sets the conical hole 3 to a conical shape, which not only improves the firmness of the lithium replenishing agent, but also allows the lithium replenishing agent to form a uniformly stressed and adhered state within the hole. This is beneficial for the stable release of lithium ions during charging and discharging, and can also prevent the lithium replenishing agent from cracking or falling off due to local stress concentration, thereby further ensuring the lithium replenishment effect and battery cycle stability.

[0027] Furthermore, in the above embodiment, the taper of the cone is 1.2-3.0. Wherein, the taper is the diameter of the base of the cone (e.g., ...). Figure 2 D in the middle) and depth (such as Figure 2 The ratio of H in the formula is used to ensure smooth filling of the lithium replenisher. This design also creates a reliable mechanical interlocking structure through a reasonable taper, further improving the bonding stability between the lithium replenisher and the current collector, while also ensuring the uniformity of lithium ion release.

[0028] Furthermore, in the above embodiments, the diameter D of the cone's base is 5-200 μm. Studies have found that if the diameter D of the cone's base is too large, it will significantly weaken the structural strength of the foil 2, thus affecting the overall mechanical stability of the current collector; if the diameter is too small, the space inside the hole will be insufficient to accommodate a sufficient amount of lithium replenishing agent, making it difficult to achieve the expected lithium replenishment effect. Controlling the diameter of the cone's base within the range of 5-200 μm ensures that the foil 2 has good mechanical strength, provides sufficient space to accommodate the required lithium replenishment dose, and adapts to subsequent process requirements such as electrode coating, thereby achieving a balance between the lithium replenishment effect and the current collector performance.

[0029] Furthermore, in the above embodiments, the cone angle of the conical hole is 20°-25°. Here, the cone angle refers to the angle between the axis of the conical hole and the generatrix. Research has found that controlling the cone angle within the range of 20°-25° allows for reliable mechanical engagement through a moderate tilt angle, further ensuring a stable bond between the lithium replenisher and the current collector. It also balances the convenience of lithium replenisher filling with lithium-ion transport efficiency, further optimizing the lithium replenishment effect and battery performance.

[0030] Furthermore, in the above embodiments, the depth H of the tapered hole 3 is related to the foil thickness 9 (e.g., ...). Figure 2 The ratio of M to the thickness of the foil 2 is 0.8-1.0. Specifically, when the ratio of the depth of the conical hole 3 to the thickness of the foil 2 is 1.0, the conical hole is a through-hole penetrating the foil 2. When the ratio is less than 1.0, the conical hole 3 is a non-penetrating blind hole. Limiting this ratio within the above range ensures that the conical hole 3 has sufficient space to accommodate the lithium replenishing agent, meeting the lithium replenishment dosage requirements, while avoiding problems such as insufficient containment effect due to excessively shallow hole depth, or decreased foil structural strength due to excessively deep hole depth. It also optimizes the lithium ion transport path.

[0031] Furthermore, the number of conical holes 3 is multiple, and the hole density is 10-1000 holes / cm². Limiting the hole density within this range ensures sufficient total lithium replenishment loading through reasonable hole distribution to meet the lithium loss compensation requirements of the battery's first charge and discharge. It also avoids the problems of excessively high hole density leading to a significant decrease in the structural strength of the foil 2 and increased processing costs, or excessively low hole density leading to uneven distribution of lithium replenishment and insufficient lithium replenishment effect. At the same time, it can also take into account the uniformity of lithium ion release and the overall structural stability of the electrode, thereby achieving the optimal match between lithium replenishment efficiency and current collector performance.

[0032] Furthermore, in the above embodiments, a sealing layer is coated at the maximum opening of the conical hole (not shown in the figure). The sealing material in this sealing layer is selected from one of polyvinylidene fluoride (PVDF), polyacrylic acid (PAA), and alumina (Al2O3). This design effectively prevents premature contact between the lithium replenishing agent and the electrolyte, avoiding side reactions of the highly active lithium replenishing agent during non-charge / discharge stages, thus preventing lithium resource waste and the negative impact of impurities on battery performance. On the other hand, the sealing layer does not obstruct lithium-ion transport, reserving a smooth path for lithium ions during the first charge / discharge cycle, ensuring precise release of lithium ions by the lithium replenishing agent during critical stages. This design simultaneously meets the dual requirements of "isolating and protecting the lithium replenishing agent" and "ensuring efficient ion transport," further improving the lithium replenishment effect and overall battery stability.

[0033] Furthermore, in the above embodiments, the thickness of the sealing layer is 0.1-5 μm.

[0034] This design ensures that the sealing layer has sufficient barrier properties to effectively prevent side reactions caused by excessive contact between the lithium replenisher and the electrolyte. It also avoids problems such as excessive thickness hindering lithium-ion transport, or insufficient thickness leading to sealing failure and premature consumption of the lithium replenisher.

[0035] Furthermore, in the above embodiments, the lithium replenishing agents are classified into positive electrode lithium-rich salt lithium replenishing agents and negative electrode lithium-rich salt lithium replenishing agents according to the application scenario. The positive electrode lithium-rich salt lithium replenishing agent is selected from at least one of Li5FeO4, Li2NiO2, Li2MnO3, and Li6CoO4, and its lithium release potential is 3.0-4.5V; the negative electrode lithium-rich salt lithium replenishing agent is selected from at least one of Li5FeO4@C, Li3N, and LiC6H5O2, and its decomposition potential is ≤1.5V. Among them, Li5FeO4@C is a carbon-coated lithium ferrite composite lithium replenishing agent with an overall core-shell structure.

[0036] Furthermore, in the above embodiments, the current collector preparation process includes: preparing through holes on the surface of the current collector by laser etching or electrochemical etching, then filling the through holes with lithium-rich acid salt slurry; then drying at 80-150°C to form a lithium replenishing agent filler, and finally coating the filler surface with a sealing layer solution and curing it.

[0037] Furthermore, in the above embodiments, the preparation process of the current collector specifically includes the following steps:

[0038] 1) A tapered hole of a predetermined specification is formed on the surface of the foil by laser etching or electrochemical etching process;

[0039] 2) Fill the conical hole with lithium replenishing agent slurry evenly;

[0040] 3) Dry the lithium supplement slurry at a temperature of 80-150℃ to solidify it and form a stable lithium supplement filler.

[0041] 4) Apply a sealing layer solution to the surface of the lithium replenishing agent filler (i.e., the largest opening of the conical hole), and form a sealing layer after the solution solidifies.

[0042] The process is simple and controllable, ensuring the precision of the tapered hole machining and the uniformity of the lithium replenishing agent filling. Through a specific temperature drying and sealing layer curing process, it ensures the stable bonding between the lithium replenishing agent and the current collector and the protective effect of the sealing layer, making it suitable for industrial production needs.

[0043] This utility model also provides a lithium battery including any of the above embodiments.

[0044] By adopting the above technical solution, the lithium replenishing agent filled in the conical hole of the current collector can be used to compensate for the irreversible loss of lithium ions during the formation of the SEI film. At the same time, the conical structure ensures the stable fixation and directional release of the lithium replenishing agent. This can effectively reduce the capacity loss during the first charge and discharge, significantly improve the initial capacity and actual usable capacity of the lithium battery, and improve the battery coulombic efficiency and cycle stability.

[0045] The technical solution of this utility model will be further described below with reference to the embodiments.

[0046] Example 1:

[0047] Preparation of positive electrode current collector:

[0048] 1) Laser Drilling: Aluminum foil with a thickness of 20μm and a purity >99.6% is selected as the substrate and processed using a 355nm ultraviolet laser drilling machine. The parameters are set as follows: bottom diameter 50±2μm, cone angle 15°. This forms uniformly distributed holes on the aluminum foil surface, with the inlet diameter larger than the outlet diameter. Figure 1The conical hole shown is cone-shaped with a taper of 2. The ratio of the depth of the conical hole to the thickness of the foil is 0.8, and the hole density is 200 holes / cm².

[0049] 2) Lithium-rich salt lithium replenishment agent filling: Prepare lithium replenishment slurry with the following composition: Li5FeO4 powder, PVDF binder and NMP solvent; fill the slurry using "dosage coating + negative pressure adsorption" process (vacuum degree controlled at -80kPa).

[0050] 3) Then place it in a 120℃ oven to dry for 10 minutes to allow the slurry to solidify and form a dense lithium supplement filler.

[0051] 4) Sealing layer encapsulation: Prepare a 5wt% PVDF / acetone solution (5% by mass of polyvinylidene fluoride-acetone solution) as the sealing layer coating liquid, and apply it to the surface of the lithium replenishing agent filler by micro-gravure roller coating (wet film thickness 5μm); after drying with hot air at 100℃, a sealing layer with a thickness of 1μm is formed.

[0052] 5) Positive electrode coating: Following conventional processes, NCM positive electrode active material is coated onto the surface of the treated current collector.

[0053] Example 2:

[0054] Preparation of negative electrode current collector

[0055] 1) Laser drilling: A copper foil with a thickness of 12μm and a tensile strength ≥300MPa is selected as the substrate; a picosecond laser drilling machine with a wavelength of 1064nm and a pulse width of 10ps is used for processing. The parameters are set as follows: bottom diameter 15±1μm, hole density 400 holes / cm², forming holes with an inlet diameter larger than the outlet diameter. Figure 1 The conical hole shown is conical in shape with a cone angle of 10° and a taper of 2. The ratio of the depth of the conical hole to the thickness of the foil is 0.8.

[0056] 2) Lithium-rich salt lithium replenishing agent filling: Prepare lithium replenishing slurry with the following composition: Li5FeO4 powder, PVDF binder and NMP solvent; fill the slurry using "dosage coating + negative pressure adsorption" process (vacuum degree controlled at -80kPa), and then place it in a 120℃ oven to dry for 10min to solidify the slurry into a dense lithium replenishing agent filler.

[0057] 3) Sealing layer encapsulation: Prepare a 5wt% PVDF / acetone solution as the sealing layer coating liquid, and apply it to the surface of the lithium replenishing agent filler by micro-gravure roller coating (wet film thickness 5μm); after drying with hot air at 100℃, a sealing layer with a thickness of 1μm is formed.

[0058] Negative electrode coating: A non-aqueous solvent-based negative electrode slurry is used, and C negative electrode active material is coated on the surface of the treated current collector according to conventional processes.

[0059] The next steps involve electrolyte selection, battery assembly, and performance testing. The specific steps are as follows:

[0060] 1) Electrolyte selection: Use 1M LiPF6 in EC:EMC (volume ratio 3:7) electrolyte. Wherein, 1M means 1 mole per liter (mol / L), in means "dissolved in", EC:EMC is a mixture of two carbonate solvents, ":" represents the volume ratio, EC is ethylene carbonate, and EMC is methyl ethyl carbonate.

[0061] 2) Battery assembly: The positive electrode sheet of Example 1 and the negative electrode sheet of Example 2 are rolled and slit in sequence. Then, the electrode tab welding, winding (or stacking), casing, outer casing welding, sealing, electrolyte injection, aging, formation, sorting, cleaning and coating are completed according to conventional processes to finally obtain the lithium-ion battery.

[0062] Performance testing results: Tests showed that the key performance indicators of this lithium-ion battery are significantly superior to those of conventional batteries. Specifically, the initial coulombic efficiency is ≥92%, while that of conventional batteries is only 85%-88%. Furthermore, the capacity retention rate of this lithium-ion battery is >90% after 500 cycles.

[0063] Although the present invention has been illustrated and described with reference to certain preferred embodiments, those skilled in the art should understand that the above description is a further detailed explanation of the present invention in conjunction with specific embodiments, and should not be construed as limiting the specific implementation of the present invention to these descriptions. Those skilled in the art can make various changes in form and detail, including some simple deductions or substitutions, without departing from the spirit and scope of the present invention.

Claims

1. A current collector, characterized in that, The device includes a foil material having a tapered hole extending along the thickness direction of the foil material. The opening area of ​​the tapered hole gradually decreases along the direction from the front side of the foil material to the back side of the foil material, and the tapered hole is filled with a lithium replenishing agent.

2. The current collector according to claim 1, characterized in that, The conical hole is cone-shaped.

3. The current collector according to claim 2, characterized in that, The cone has a taper of 1.2-3.0, where the taper is the ratio of the diameter of the cone's base to its depth.

4. The current collector according to claim 2, characterized in that, The diameter of the base of the cone is 5-200 μm.

5. The current collector according to claim 1, characterized in that, The cone angle of the tapered hole is 20-25°.

6. The current collector according to claim 1, characterized in that, The ratio of the depth of the tapered hole to the thickness of the foil is 0.8-1.

0.

7. The current collector according to claim 1, characterized in that, The number of tapered holes is multiple and the hole density is 10-1000 holes / cm².

8. The current collector according to claim 1, characterized in that, The maximum opening of the conical hole is coated with a sealing layer, and the sealing material in the sealing layer is selected from one of polyvinylidene fluoride (PVDF), polyacrylic acid (PAA), and alumina (Al2O3).

9. The current collector according to claim 8, characterized in that, The thickness of the sealing layer is 0.1-5 μm.

10. A lithium battery, characterized in that, The current collector includes any one of claims 1-9.

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