Battery cell and lithium ion battery

Abstract

The utility model discloses a battery cell and a lithium ion battery. The battery cell comprises a positive plate and a negative plate, the graphite sheet is arranged on the positive plate in an overlapping manner; wherein at least one side of the graphite sheet is provided with a first extension part which extends out of the positive plate along the width direction, and the first extension part is provided with a through first through hole. According to the utility model, the first extending part of the graphite sheet is provided with the through first through hole, so that the diffusion path of lithium ions entering the graphite sheet from electrolyte is shortened, and the lithium ions can be more quickly embedded into or separated from the internal area of the graphite sheet along with the electrolyte flowing into the first through hole; and the distribution uniformity of the lithium ion battery in the graphite flake is improved, so that the probability of lithium precipitation is reduced, and the interface problem caused by non-uniform lithium intercalation is quickly repaired.

Description

Technical Field

[0001] The utility model relates to the technical field of lithium ion batteries, in particular to a battery core and a lithium ion battery. Background Art

[0002] Lithium-ion batteries have an increasingly wide range of applications due to their advantages such as high specific energy, high operating voltage, long charge and discharge life, no memory effect, low environmental pollution, and low self-discharge rate. The requirements for the performance of lithium-ion batteries are also becoming higher and higher.

[0003] A large portion of existing lithium-ion battery cells use carbon materials as negative electrode materials, with artificial graphite being the primary carbon material. However, the transfer of lithium ions between graphite particles is difficult. Due to the interfacial resistance between the graphite particles, the diffusion rate of lithium on the negative electrode sheet is very slow. This can easily lead to uneven distribution of lithium ions on the negative electrode sheet and delay the lithium insertion and removal process in the redundant area of ​​the negative electrode sheet (also known as the overhang area, which refers to the portion of the negative electrode sheet that extends beyond the positive electrode sheet in length and width). This can cause lithium plating, which in turn leads to a decline in various performance aspects of the lithium-ion battery and poses a significant safety hazard. Utility Model Content

[0004] The main purpose of the utility model is to provide a battery cell, aiming to solve the problem that lithium deposition is easy to occur in the overhang area of ​​the negative electrode sheet in the existing battery cell.

[0005] To achieve the above objectives, the present invention provides a battery cell comprising:

[0006] positive electrode;

[0007] A graphite sheet, the graphite sheet being stacked on the positive electrode sheet;

[0008] At least one side of the graphite sheet is provided with a first extension portion extending to the outside of the positive electrode sheet along the width direction, and a first through hole is provided on the first extension portion.

[0009] In some embodiments, the first extension portion includes a first section close to the positive electrode sheet and a second section connected to the first section. The width of the first extension portion is L, the width D of the first section is 0.6L to 0.8L, and the first through hole is provided in the first section.

[0010] In some embodiments, the porosity of the first segment is 40-80%.

[0011] In some embodiments, a metal layer is disposed on the sidewall of the first through hole.

[0012] In some embodiments, the graphite sheet further includes a second extension portion extending outside the positive electrode sheet along a length direction, and a second through hole is provided on the second extension portion.

[0013] In some embodiments, the diameters of the first through holes and the second through holes are in the range of 0.1 to 100 μm.

[0014] In some embodiments, a spacing between the first through holes is 1-100 μm, and a spacing between the second through holes is 1-100 μm.

[0015] In some embodiments, the graphite sheet has a thickness of 0.1 to 200 μm.

[0016] In some embodiments, the first through hole and the second through hole are in the shape of an elliptical cylinder.

[0017] The present invention further provides a lithium-ion battery, comprising a housing and the battery cell described in the aforementioned embodiment, wherein the battery cell is disposed in the housing.

[0018] During the charge and discharge process of a lithium-ion battery, lithium ions migrate between the positive and negative electrodes through the electrolyte. The utility model provides a through first through hole in the first extension portion of the graphite sheet, thereby shortening the diffusion path of lithium ions from the electrolyte into the interior of the graphite sheet. This allows lithium ions to be more quickly embedded in or removed from the interior area of ​​the graphite sheet as the electrolyte flows into the first through hole, thereby improving the uniformity of the distribution of lithium ion batteries in the graphite sheet, thereby reducing the probability of lithium plating and quickly repairing interface problems caused by uneven lithium embedding. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a structural diagram of an embodiment of a battery cell of the present utility model;

[0020] Figure 2 It is a cross-sectional view of the battery cell of the present invention.

[0021] Reference numerals:

[0022] 100 , positive electrode sheet; 200 , graphite sheet; 210 , first extension portion; 211 , first through hole; 211 a , metal layer; 212 , first section; 213 , second section; 220 , second extension portion; 221 , second through hole. DETAILED DESCRIPTION

[0023] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the schemes in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0024] It should be noted that all directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present invention are only used to explain the relative position relationship, movement status, etc. between the various components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0025] It should also be noted that when an element is referred to as being "fixed on" or "disposed on" another element, it may be directly on the other element or there may be an intermediate element. When an element is referred to as being "connected to" another element, it may be directly connected to the other element or there may be an intermediate element.

[0026] In addition, the terms "first," "second," and so on, used in this utility model are for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, features defined as "first" or "second" may explicitly or implicitly include at least one of such features. Furthermore, the technical solutions of various embodiments may be combined with each other, but this must be based on the ability of a person of ordinary skill in the art to implement them. If the combination of technical solutions contradicts or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this utility model.

[0027] The utility model proposes a battery cell, referring to Figure 1 and Figure 2 ,include:

[0028] Positive electrode sheet 100;

[0029] Graphite sheet 200, graphite sheet 200 is stacked on the positive electrode sheet 100;

[0030] A first extension portion 210 extending out of the positive electrode sheet 100 along the width direction is provided on at least one side of the graphite sheet 200 , and a first through hole 211 is provided on the first extension portion 210 .

[0031] Among them, the positive electrode sheet 100 generally includes a current collector and an active material. The active material can be arranged on only one surface of the current collector or on both surfaces of the current collector at the same time. For example, in this embodiment, aluminum foil is used as the current collector, and active materials are arranged on both sides. The prepared positive electrode sheet 100 is stacked together with the graphite sheet 200 to form a battery cell. It can be understood that the upper and lower positions between the positive electrode sheet 100 and the graphite sheet 200 are not fixed. The positive electrode sheet 100 can be on top or the graphite sheet 200 can be on top, and the positive electrode sheet 100 can be arranged in the middle part of the graphite sheet 200 so that the battery cell is symmetrically arranged. The positive electrode sheet 100 can also be relatively close to an edge of the graphite sheet 200. This embodiment does not limit this.

[0032] Graphite sheet 200 serves as the negative electrode of the battery cell and can be made of either artificial graphite or natural graphite. Because artificial graphite is typically composed of a blend of graphite particles, and the interfaces between graphite particles negatively impact the diffusion of lithium ions, this embodiment preferably utilizes a fully grown graphite sheet 200 as the negative electrode of the lithium-ion battery. This significantly increases the lateral diffusion rate of lithium ions within the graphite sheet 200.

[0033] In order to increase the diffusion rate of lithium ions in the graphite sheet 200, this embodiment provides a through first through hole 211 on the first extension portion 210 (i.e., the Overhang area) of the graphite sheet 200, so that the electrolyte can flow into the first through hole 211 and directly contact the inside of the graphite sheet 200, thereby increasing the contact area between the graphite sheet 200 and the electrolyte, shortening the distance for lithium ions to be embedded in or out of the graphite sheet 200, reducing the probability of lithium plating, and improving the safety of the lithium battery. In this embodiment, the shape of the first through hole 211 can be circular, square, or polygonal to meet different manufacturing process requirements. It is understandable that the first through hole 211 can also be an irregular shape, such as a curved serpentine shape, as long as the electrolyte can flow in.

[0034] During the charge and discharge process of a lithium-ion battery, lithium ions migrate between the positive and negative electrodes through the electrolyte. The present invention shortens the diffusion path of lithium ions from the electrolyte into the interior of the graphite sheet 200 by providing a through first through hole 211 in the first extension portion 210 of the graphite sheet 200. This allows lithium ions to be more quickly embedded in or removed from the internal area of ​​the graphite sheet 200 as the electrolyte flows into the first through hole 211, thereby improving the uniformity of the distribution of lithium-ion batteries in the graphite sheet 200, thereby reducing the probability of lithium plating and quickly repairing interface problems caused by uneven lithium embedding.

[0035] like Figure 1As shown, in some embodiments, the first extension portion 210 includes a first section 212 close to the positive electrode sheet 100 and a second section 213 connected to the first section 212 , the width of the first extension portion 210 is L, the width D of the first section 212 is 0.6L~0.8L, and the first through hole 211 is set in the first section 212 .

[0036] In this embodiment, the first extension portion 210 is divided into a first section 212 and a second section 213, wherein the first section 212 is close to the positive electrode sheet 100, that is, compared with the second section 213, the first section 212 is closer to the interior of the graphite sheet 200. Therefore, under the same porosity, the first through hole 211 is set in the first section 212, so that the electrolyte can flow more into the area of ​​the graphite sheet 200 that is not easily embedded by lithium ions, thereby improving the effect of lithium ion embedding and extraction, thereby reducing the probability of lithium precipitation.

[0037] Furthermore, in this embodiment, the width of the first section 212 is set to 60% to 80% of the width of the first extension portion 210. If the width of the first section 212 is greater than 80% of the width of the first extension portion 210, some of the first through holes 211 are closer to the edge of the first extension portion 210, and the contact area between the edge of the first extension portion 210 and the electrolyte is already large. The first through holes 211 cannot play a good improvement role, and it is also easy to reduce the mechanical strength at the edge, causing the lithium-ion battery to be easily damaged during use, thereby affecting the safety of the lithium-ion battery and reducing its service life; if the width of the first section 212 is less than 60% of the width of the first extension portion 210, the proportion of the second end without the first through holes 211 is too large, the electrolyte cannot well infiltrate the interior of the first extension portion 210, and the effect of improving the insertion and extraction of lithium ions cannot be well played. Therefore, the width of the first section 212 is set to 60% to 80% of the width of the first extension portion 210. Preferably, the width of the first section 212 is 70% of the width of the first extension portion 210, that is, D = 0.7L, so that the electrolyte can flow through various parts of the interior of the first extension portion, improving the lithium deposition situation while ensuring that the graphite sheet 200 has a certain mechanical strength, thereby extending the service life of the lithium-ion battery.

[0038] In some embodiments, the porosity of the first section 212 is 40-80%.

[0039] The porosity in this embodiment refers to the percentage of the volume of the first through hole 211 and the volume of the first section 212. If the porosity of the first section 212 exceeds 80%, the number of the first through holes 211 is large and dense, which will greatly increase the difficulty of drilling and reduce the mechanical strength of the first section 212, resulting in easy breakage and increasing the scrap rate of the battery cell; if the porosity of the first section 212 is lower than 40%, the first through holes 211 occupy too small a volume of the first extension portion, and the electrolyte cannot effectively infiltrate the interior of the first extension portion 210, and cannot effectively play the role of improving the insertion and extraction of lithium ions. Therefore, the present invention controls the porosity of the first section 212 to be in the range of 40% to 80%. For example, the porosity of the first section 212 is set to 60%, so that the first through hole 211 occupies a sufficiently large volume of the first extension portion, and the electrolyte can be relatively evenly distributed throughout the first extension portion, so that lithium ions can be quickly embedded in or out of the interior of the first extension portion, reducing the probability of lithium plating. In addition, the first section 212 still has good mechanical strength, avoiding the situation where a slight collision causes the first extension portion to break off.

[0040] like Figure 2 As shown, in some embodiments, a metal layer 211 a is disposed on the sidewall of the first through hole 211 .

[0041] The metal layer 211a can be formed from a highly conductive metal material such as copper, nickel, silver, or gold, and laid on the sidewalls of the first through-hole 211 by electroplating, vapor deposition, or the like. Specifically, during the battery charge and discharge process, the metal layer 211a on the sidewalls of the first through-hole 211 can provide a low-resistance electron conduction channel, allowing electrons to move more efficiently between the graphite sheet 200 and the positive electrode sheet 100, effectively reducing the internal resistance of the lithium-ion battery, thereby improving the charge and discharge speed and energy conversion efficiency of the lithium-ion battery. At the same time, the metal layer 211a can also enhance the mechanical strength of the graphite sheet 200 to a certain extent, enhance the structural stability of the graphite sheet 200, reduce the probability of deformation or damage of the graphite sheet 200 during repeated charge and discharge, and extend the service life of the graphite sheet 200.

[0042] like Figure 1 As shown, in some embodiments, at least one side of the graphite sheet 200 is provided with a second extension portion 220 extending to the outside of the positive electrode sheet 100 along the length direction, and the second extension portion 220 is provided with a through second through hole 221 .

[0043] Similar to the first extension 210, the graphite sheet 200 also has a portion extending beyond the positive electrode sheet 100 in the longitudinal direction, namely the second extension 220. By providing a second through hole 221 through the second extension 220, the efficiency of lithium ion insertion and extraction in the second extension 220 can be improved. The specific configuration of the second extension 220 can be referred to in the previous embodiment and will not be repeated here.

[0044] In some embodiments, the diameter of the first through hole 211 and the second through hole 221 is 0.1-100 μm.

[0045] When the porosity is constant, the pore size has a significant impact on the number of the first through holes 211 and the second through holes 221. The smaller the pore size, the greater the number, and the corresponding contact area between the electrolyte and the graphite sheet 200 is also larger, which is better for improving the insertion or removal of lithium ions from the graphite sheet 200. However, if the pore size of the first through hole 211 and the second through hole 221 is less than 0.1 μm, the processing difficulty is greater, the cost is higher, and it will increase the difficulty of the electrolyte infiltrating the first through hole 211 and the second through hole 221. Therefore, preferably, in this embodiment, the pore size of the first through hole 211 and the second through hole 221 is set to 1 μm, ensuring that the contact area between the electrolyte and the graphite sheet 200 is sufficient, while the electrolyte can more easily penetrate into the hole, and the pore size of 1 μm is easier to process.

[0046] In some embodiments, the intervals between the first through holes 211 are 1-100 μm, and the intervals between the second through holes 221 are 1-100 μm.

[0047] Taking the first through holes 211 as an example, if the spacing between the first through holes 211 is less than 1 μm, the first through holes 211 that are too close together make the sidewalls between the two adjacent first through holes 211 too thin, resulting in the first extension portion 210 having a low mechanical strength and being prone to breakage; if the spacing between the first through holes 211 is greater than 100 μm, the sidewalls between the two adjacent first through holes 211 are too thick. Although it has a high mechanical strength, it also has a poor effect on improving the diffusion rate of lithium ions. Preferably, in this embodiment, the spacing between the first through holes 211 is set to 5 μm, which not only ensures the mechanical strength of the first extension portion 210, but also ensures that lithium ions can be quickly embedded in or out of the interior of the first extension portion 210, and the diffusion rate is faster. The second through hole 221 is similar to the first through hole 211 and will not be described here.

[0048] In some embodiments, the thickness of the graphite sheet 200 is 0.1-200 μm.

[0049] If the thickness of the graphite sheet 200 is less than 0.1 μm, its inherent strength is poor and it is easily damaged by mechanical stress during the manufacturing and assembly process. In addition, the capacity of the graphite sheet 200 that is too thin is limited, affecting the total energy density of the battery and making it more difficult to process. If the thickness of the graphite sheet 200 is greater than 200 μm, the diffusion path of lithium ions inside the graphite sheet 200 becomes longer, and the time required for lithium ions to penetrate from the electrolyte to the deep part of the graphite sheet 200 increases, resulting in a decrease in the charge and discharge rate of the battery. In addition, an overly thick graphite sheet 200 requires more internal space in the battery, reducing the volume of active material that can be filled, thereby affecting the total capacity of the battery. Preferably, the thickness of the graphite sheet 200 is set to 10 μm, ensuring that the graphite sheet 200 has sufficient strength while shortening the lithium ion penetration path, allowing it to diffuse more easily into the graphite sheet 200.

[0050] In some embodiments, the first through hole 211 and the second through hole 221 are in the shape of an elliptical cylinder.

[0051] Compared to cylinders or prisms, the elliptical cylindrical first through hole 211 and the second through hole 221 have a smaller volume and a larger surface area of ​​the side wall, that is, the contact area between the graphite sheet 200 and the electrolyte is larger, making it easier for lithium ions to diffuse into the interior of the graphite sheet 200, thereby improving the charge and discharge efficiency of the battery.

[0052] The present invention further provides a battery comprising a housing and a cell. The specific structure of the cell is similar to that of the above-described embodiments. Since the battery utilizes all technical solutions of all of the above-described embodiments, it at least has all the technical effects provided by the technical solutions of the above-described embodiments, and a detailed description thereof will not be repeated here. The cell is disposed within the housing. The housing may be an aluminum-plastic film, a steel shell, or other shell, and the specific selection can be based on the type of lithium-ion battery.

[0053] The above description is only part or preferred embodiments of the present invention. Neither the text nor the drawings can limit the scope of protection of the present invention. All equivalent structural transformations made by using the contents of the present invention specification and drawings under the overall concept of the present invention, or direct / indirect application in other related technical fields are included in the scope of protection of the present invention.

Claims

1. A battery cell, characterized in that: include: positive electrode; A graphite sheet, the graphite sheet being stacked on the positive electrode sheet; At least one side of the graphite sheet is provided with a first extension portion extending to the outside of the positive electrode sheet along the width direction, and a first through hole is provided on the first extension portion.

2. The battery cell according to claim 1, characterized in that The first extension portion includes a first section close to the positive electrode sheet and a second section connected to the first section. The width of the first extension portion is L, the width D of the first section is 0.6L to 0.8L, and the first through hole is provided in the first section.

3. The battery cell according to claim 2, characterized in that The porosity of the first section is 40-80%.

4. The battery cell according to claim 1, characterized in that A metal layer is provided on the sidewall of the first through hole.

5. The battery cell according to any one of claims 1 to 4, characterized in that: The graphite sheet further includes a second extension portion extending outside the positive electrode sheet along a length direction, and a second through hole is provided on the second extension portion.

6. The battery cell according to claim 5, characterized in that The apertures of the first through holes and the second through holes are 0.1 to 100 μm.

7. The battery cell according to claim 5, characterized in that The spacing between the first through holes is 1 to 100 μm, and the spacing between the second through holes is 1 to 100 μm.

8. The battery cell according to claim 5, characterized in that The first through hole and the second through hole are in an elliptical column shape.

9. The battery cell according to any one of claims 1 to 4, characterized in that: The thickness of the graphite sheet is 0.1-200 μm.

10. A lithium ion battery, characterized in that: The invention comprises a housing and the battery core according to any one of claims 1 to 9, wherein the battery core is arranged in the housing.

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