Preparation method of battery cell with electrolyte rapid infiltration structure and battery

Abstract

The present application provides a method for preparing a battery cell and a battery with a structure for rapid electrolyte infiltration. The method for preparing the battery cell includes the following steps: S1, providing a positive electrode sheet, a separator, and a negative electrode sheet; S2, respectively opening holes on the positive electrode sheet and the negative electrode sheet to form a first through hole and a second through hole respectively; S3, stacking the positive electrode sheet in step S2, the separator in step S1, and the negative electrode sheet in step S2 in sequence, and then thermally compounding them to form a dry battery cell, wherein the area of ​​the first through hole is greater than the area of ​​the second through hole, and the first through hole and the second through hole are eccentrically arranged with respect to each other. The method of the embodiment of the present invention ensures that the area of ​​the positive electrode sheet after the opening is still smaller than the area of ​​the negative electrode sheet by designing the size and position of each through hole, so that there are more lithium insertion positions on the negative electrode sheet, and can effectively improve the defect of poor mechanical performance of the battery due to opening holes in the axial direction of the battery, which is beneficial to improving the performance and mechanical strength of the battery.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and in particular to a method for preparing a battery cell with a rapid electrolyte infiltration structure and a battery. Background Art

[0002] With the development of science and technology, the requirements for the performance and life of lithium batteries are becoming increasingly higher. In addition to the quality of the electrodes and raw materials, whether the electrolyte is fully infiltrated and evenly dispersed within the lithium battery is also particularly important. This is because only when the electrolyte fully infiltrates the positive and negative electrodes and the separator can it serve as a homogeneous lithium ion transmission medium. If the electrolyte is not fully infiltrated, the lithium battery will experience a partial lack of electrolyte in the middle and late stages of the cycle, or even in the early stages, thus affecting the cycle life of the lithium battery.

[0003] In the existing technology, in order to ensure that the electrode core is not loose and the positive and negative electrodes and diaphragms are not misaligned during the production process, the stacked core will be dry pressed to form a battery cell after lamination. Especially for power-type lithium batteries, the positive and negative electrode sheets have high surface density and high compaction density, and the steric hindrance of electrolyte infiltration is large, which is very unfavorable for uniform infiltration of the battery cell.

[0004] To solve this problem, vacuum injection, high-pressure infiltration and other methods can be used to improve the infiltration performance of the electrolyte, but this method is difficult to produce and has high production costs. Summary of the Invention

[0005] In view of this, the present invention provides a method for preparing a battery cell capable of improving the wettability of an electrolyte inside a battery.

[0006] The invention also provides a battery.

[0007] According to the first embodiment of the present invention, a method for preparing a battery cell having an electrolyte rapid infiltration structure comprises the following steps:

[0008] S1, provides positive electrode sheets, separators, and negative electrode sheets;

[0009] S2, drilling holes in the positive electrode sheet and the negative electrode sheet to form a first through hole and a second through hole respectively;

[0010] S3, stacking the positive electrode sheet in step S2, the separator in step S1, and the negative electrode sheet in step S2 in sequence and compounding them to form a dry cell.

[0011] The area of ​​the first through hole is greater than the area of ​​the second through hole, and the first through hole and the second through hole are eccentrically arranged with respect to each other.

[0012] Furthermore, in step S2, the first through hole and the second through hole are independently formed into a circle, a triangle, a square, a polygon, or a special shape.

[0013] Furthermore, in step S2, the distance between the center of any one of the first through hole and the second through hole and the edge of the layer where the center is located is greater than or equal to 0.1 mm.

[0014] Furthermore, step S3 includes:

[0015] S31, stacking the positive electrode sheet, the separator, and the negative electrode sheet with holes formed therein in sequence to form an electrode group, wherein the first through hole and the second through hole in each electrode group are eccentrically arranged.

[0016] S32, stacking a plurality of electrode groups with the separator therebetween;

[0017] S33, thermally compounding the stacked plurality of electrode groups to form the dry battery cell.

[0018] Further, in step S31, in projection in the stacking direction, the second through hole of each electrode group is located within the first through hole.

[0019] Furthermore, the centers of the through holes in the battery core are sequentially connected to form a sawtooth line, a slant line, or a disordered broken line.

[0020] Furthermore, in step S32, the center of the first through hole in each of the electrode groups has the same offset distance relative to the center of the second through hole in the first direction / the second direction, and the offset distance Δ satisfies equation 1):

[0021]

[0022] Wherein, x is the larger vertical distance from the center of the first through hole / the second through hole in the first direction / the second direction to the edge of the electrode sheet, k is the ratio of the smaller vertical distance from the center of the first through hole / the second through hole in the first direction / the second direction to the edge of the electrode sheet to the distance between the two edges of the electrode sheet in the first direction / the second direction, m is the number of layers of negative electrode sheets in the electrode group, and n is the number of layers of positive electrode sheets in the electrode group; and the offset distance Δ satisfies formula 2):

[0023] Δ<R 2)

[0024] Wherein R is the distance between the center of the second through hole and its edge;

[0025] The first direction and the second direction are along the width direction and the length direction of the pole piece.

[0026] Furthermore, in step S33, in two adjacent electrode groups, the deviation directions of the line connecting the center of the first through hole and the center of the second through hole are opposite.

[0027] The battery according to the second embodiment of the present invention includes a plurality of battery cells prepared by the above method.

[0028] Furthermore, a positive electrode active layer is formed on the positive electrode sheet of the battery, and the positive electrode active layer contains a positive electrode active material, and the positive electrode active material is selected from one or more of lithium iron phosphate, lithium cobalt oxide, lithium manganese oxide, and ternary materials;

[0029] A negative electrode active layer is formed on the negative electrode sheet of the battery. The negative electrode active layer contains a negative electrode active material. The negative electrode active material is selected from one or more of graphite, silicon-based, transition metal oxides, and metallic lithium.

[0030] The above technical solution of the present invention has at least one of the following beneficial effects:

[0031] According to the preparation method of the battery cell with the electrolyte rapid infiltration structure of the embodiment of the present invention, the positive electrode sheet and the negative electrode sheet are respectively opened to form the first through hole and the second through hole, and the battery cell is formed by stacking them in sequence and pressing them, so that the electrolyte can infiltrate the corresponding positive electrode sheet and negative electrode sheet through the first through hole and the second through hole, shortening the infiltration path of the electrolyte and improving the infiltration speed. The area of ​​the first through hole is greater than the area of ​​the second through hole, and the first through hole and the second through hole are eccentrically arranged with each other. That is to say, by designing the size of each through hole, the positive electrode sheet is The area of ​​the first through hole opened on the sheet is greater than the area of ​​the second through hole on the negative electrode sheet, thereby ensuring that the area of ​​the positive electrode sheet after the hole is opened is still smaller than the area of ​​the negative electrode sheet, so that there are more lithium insertion positions on the negative electrode sheet, avoiding lithium dendrite short circuit caused by lithium precipitation during charging, and improving the performance and life of the battery; by designing the positions of each through hole, that is, the first through hole and the second through hole are eccentrically arranged to each other, compared with the straight through hole, the defect of poor mechanical performance of the battery due to opening the hole in the axial direction of the battery can be effectively improved, which is beneficial to improving the mechanical strength of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 Flowchart of a method for preparing a battery cell according to an embodiment of the present invention;

[0033] Figure 2 This is a schematic structural diagram of a battery cell according to an embodiment of the present invention;

[0034] Figure 3 This is a schematic structural diagram of a battery cell according to another embodiment of the present invention;

[0035] Figure 4Schematic diagram of the positional relationship of each through hole in the projection of the electrode group in the stacking direction in a battery cell according to an embodiment of the present invention;

[0036] Figure 5 Schematic diagram of the position of the first through hole of the electrode group according to an embodiment of the present invention.

[0037] Reference numerals: 100. positive electrode sheet; 110. first through hole; 200. separator; 300. negative electrode sheet; 310. second through hole. DETAILED DESCRIPTION

[0038] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the described embodiments of the present invention, all other embodiments derived by persons of ordinary skill in the art are within the scope of protection of the present invention.

[0039] Unless otherwise defined, the technical or scientific terms used in the present invention shall have the usual meanings understood by persons of ordinary skill in the field to which the present invention belongs. The words "first", "second" and similar terms used in the present invention do not indicate any order, quantity or importance, but are only used to distinguish different components. Similarly, words such as "one" or "a" do not indicate a quantity limitation, but rather indicate the existence of at least one. Words such as "connected" or "connected" are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the object being described changes, the relative positional relationship also changes accordingly.

[0040] The following first describes in detail the method for preparing a battery cell with a rapid electrolyte infiltration structure according to an embodiment of the first aspect of the present invention.

[0041] like Figure 1 As shown, the method for preparing a battery cell according to an embodiment of the present invention includes the following steps:

[0042] S1 , providing a positive electrode sheet 100 , a separator 200 , and a negative electrode sheet 300 .

[0043] The positive electrode sheet 100, the separator 200, and the negative electrode sheet 300 can be prepared by conventional preparation methods, wherein a positive electrode active layer is formed on the positive electrode sheet 100, and the positive electrode active layer contains a positive electrode active material, and the positive electrode active material is selected from one or more of lithium iron phosphate, lithium cobalt oxide, lithium manganese oxide, and ternary materials; a negative electrode active layer is formed on the negative electrode sheet 300, and the negative electrode active layer contains a negative electrode active material, and the negative electrode active material is selected from one or more of graphite, silicon-based, transition metal oxide, and metallic lithium.

[0044] S2. Drill holes on the positive electrode sheet 100 and the negative electrode sheet 300 to form a first through hole 110 and a second through hole 310 respectively. The area of ​​the first through hole 110 is greater than the area of ​​the second through hole 310, and the first through hole 110 and the second through hole 310 are eccentrically arranged with respect to each other.

[0045] S3, stacking the positive electrode sheet 100 in step S2, the separator 200 in step S1, and the negative electrode sheet 300 in step S2 in sequence, and then compounding them to form a dry battery cell.

[0046] That is to say, first, holes are respectively opened on the positive electrode sheet 100 and the negative electrode sheet 300 to form the first through hole 110 and the second through hole 310 respectively, and then the first through hole 110 and the second through hole 310 are eccentrically arranged with respect to each other when stacking the sheets, and finally a dry battery cell is formed by pressing. Thereafter, when the dry battery cell is injected with liquid, the electrolyte can penetrate into each layer of the positive electrode sheet 100 and the negative electrode sheet 300 corresponding to the through hole through the first through hole 110 and the second through hole 310, thereby shortening the infiltration path of the electrolyte and improving the infiltration speed.

[0047] Furthermore, the area of ​​the first through hole 110 in the battery cell is greater than the area of ​​the second through hole 310. In other words, by designing the sizes of the through holes, the area of ​​the first through hole 110 on the positive electrode sheet 100 is greater than the area of ​​the second through hole 310 on the negative electrode sheet 300. This ensures that the area of ​​the positive electrode sheet 100 after the holes are opened is still smaller than that of the negative electrode sheet 300, providing more lithium insertion sites on the negative electrode sheet 300. This can prevent lithium dendrite short circuits caused by lithium deposition during charging, thereby improving battery performance and lifespan.

[0048] Moreover, by designing the positions of the through holes, that is, the first through hole 110 and the second through hole 310 are eccentrically arranged relative to each other, that is, in the process of stacking the positive electrode sheet 100, the diaphragm 200, and the negative electrode sheet 300 in sequence, by adjusting the lateral position between the positive electrode sheet 100 and the negative electrode sheet 300, the first through hole 110 on the positive electrode sheet 100 and the second through hole 310 on the negative electrode sheet 300 are eccentrically arranged relative to each other. Compared with straight-through holes, this can effectively improve the defect of poor mechanical performance of the battery caused by opening holes in the axial direction of the battery, thereby improving the mechanical strength of the battery.

[0049] As an embodiment of the present invention, based on the above-mentioned design of the sizes of the first through hole 110 and the second through hole 310, in step S2, the shape and position relationship of each through hole can be further limited to further improve the mechanical strength of the battery.

[0050] Regarding the shape of each through hole, corresponding to step S2, the first through hole 110 and the second through hole 310 are each independently formed into a circle, triangle, square, polygon, or irregular shape. In other words, the shape of the first through hole 110 and the second through hole 310 can be determined based on the difficulty of processing and the shape of the tool head in the actual punching process to improve production efficiency.

[0051] As for the positional relationship of each through hole in its respective layer, corresponding to step S2, the distance between the center of the first through hole 110 and the center of the second through hole 310 and the edge of the layer in which it is located is greater than or equal to 0.1 mm. In other words, the distance from the center of the first through hole 110 to the edge of the positive electrode sheet 100 and the distance from the second through hole 310 to the edge of the negative electrode sheet 300 are both greater than or equal to 0.1 mm to ensure the mechanical properties of the battery. As a preferred embodiment, the distance from the center of the first through hole 110 to the edge of the positive electrode sheet 100 and the distance from the second through hole 310 to the edge of the negative electrode sheet 300 can also be greater than or equal to 0.5 mm to further improve the mechanical strength of the battery.

[0052] Further, if Figure 2 、 Figure 3 As shown, the negative electrode sheet 300, separator 200, and positive electrode sheet 100 constitute an electrode group. The battery cell includes multiple electrode groups connected in series, wherein two adjacent electrode groups are separated by separator 200. The first through-hole 110 and the second through-hole 310 in each electrode group are eccentrically arranged. In other words, by eccentrically arranging each through-hole, the mechanical strength of the electrode group can be maintained as high as possible. Furthermore, the eccentric arrangement of each through-hole in each electrode group ensures that the battery cell formed by connecting multiple electrode groups in series also maintains high mechanical strength.

[0053] Furthermore, the centers of the through holes in the battery cell are sequentially connected to form a sawtooth line, a slant line, or a random fold line. In other words, the eccentric distance and eccentric direction of the centers of the through holes can be the same or different between layers.

[0054] Specifically, when the eccentricity directions of two adjacent electrode groups, between layers, or between electrode groups are different, the centers of the through holes in the battery cell are connected in sequence to form the following: Figure 2 When the eccentric directions of the through holes between two adjacent electrode groups are the same and the eccentric distances are the same, the centers of the through holes in the battery cell are connected in sequence to form the following: Figure 3When the eccentric distances and eccentric directions of the through holes in two adjacent electrode groups are randomly the same or different, the centers of the through holes in the battery cell are sequentially connected to form a disordered broken line (not shown in the figure).

[0055] In some embodiments, in each electrode group, the center of the first through hole 110 is offset from the center of the second through hole 310 by the same distance in the first direction / second direction, and the first direction and the second direction are along the width direction and the length direction of the electrode sheet. In other words, in each electrode group of the battery cell, the center of the first through hole 110 is offset equidistantly from the center of the second through hole 310. This structure facilitates the control of the punching process. Specifically, during the punching process, the offset distance Δ of the center of the first through hole 110 relative to the center of the second through hole 310 satisfies formula 1): Here, x is the larger vertical distance from the center of the first through hole 110 / second through hole 310 to the edge of the electrode sheet in the first direction / second direction, k is the ratio of the smaller vertical distance from the center of the first through hole 110 / second through hole 310 to the edge of the electrode sheet in the first direction / second direction to the distance between the two edges of the electrode sheet in the first direction / second direction, m is the number of layers of negative electrode sheets 300 in the electrode assembly, and n is the number of layers of positive electrode sheets 100 in the electrode assembly. Furthermore, the deviation distance Δ satisfies equation 2): Δ<R, where R is the distance between the center of the second through hole 310 and its edge. In other words, once the number of electrode assemblies in the battery cell and the overall eccentricity are determined, the plane coordinates of the centers of the first through holes 110 and the second through holes 310 in each layer in the first and second directions can be calculated using equations 1) and 2). After punching by a punching device, the electrolyte can be fully infiltrated between the layers, further improving the performance and service life of the battery.

[0056] Specifically, if Figure 5 As shown, the centers of the two through holes are calculated in the first direction (corresponding to Figure 5As an example, assume that the distance between the two edges of the electrode in the first direction is 5, and the smaller vertical distance y between the center of the first through hole 110 of the first layer of positive electrode sheet and the edge in the first direction is 2, then the larger vertical distance x from the center of the first through hole 110 of the first layer of positive electrode sheet to the edge of the electrode in the first direction is 3, so that for the second through hole 310 of the second layer of negative electrode sheet, the ratio of the smaller vertical distance from the center of the first through hole 110 to the edge of the electrode in the first direction to the distance z between the two edges of the electrode in the first direction is: k=2 / 5=0.4, the number of positive electrode sheet layers n in the electrode group is 1, and the number of negative electrode sheet layers m is 1, and the deviation distance Δ in the first direction relative to the center of the first through hole of the first layer of positive electrode sheet is 0.4*3 / 2=0.6, that is, the center of the second through hole 310 of the second layer of negative electrode sheet is 0.4*3 / 2=0.6 in the first direction. The coordinates on are 2+0.6=2.6, that is, the smaller vertical distance y of the center of the second through hole 310 of the second layer of negative electrode sheet from the edge in the first direction is 2.4, and the larger vertical distance x is 2.6. Then, for the first through hole of the third layer of positive electrode sheet, k=2.4 / 5=0.48, the number of positive electrode sheet layers n in the electrode sheet group is 2, and the number of negative electrode sheet layers m is 1, and the offset distance Δ in the first direction relative to the center of the second through hole of the negative electrode sheet of the second layer is 0.48*2.6 / 3=0.416, that is, the coordinates of the center of the first through hole 110 of the third layer in the first direction are 2.6+0.416=3.016, that is, the smaller vertical distance y of the center of the first through hole 110 of the third layer from the edge in the first direction is 1.984, and the larger vertical distance x is 3.016.

[0057] According to the above design, and making the deviation direction of the line connecting the center of the first through hole 110 and the center of the second through hole 310 in two adjacent electrode groups the same, after punching by the punching device, the centers of the through holes are sequentially connected to form an oblique line.

[0058] In some embodiments, the lines connecting the centers of the first through-holes 110 and the second through-holes 310 in two adjacent electrode groups deviate in opposite directions. That is, based on the above design, the lines connecting the centers of the adjacent first through-holes 110 and the centers of the second through-holes 310 in two adjacent electrode groups in the battery cell deviate in opposite directions. Thus, connecting the centers of the through-holes in sequence can form a zigzag line or a random fold line, thereby allowing the electrolyte to fully penetrate between the layers, further improving the performance and service life of the battery.

[0059] As a specific example, Figure 2For example, in each electrode group, the center of the first through hole 110 and the center of the second through hole 310 are on an oblique line (that is, the eccentric directions and eccentric distances between layers are the same), and the inclination directions of the oblique lines between two adjacent electrode groups are different (that is, the eccentric directions between electrode groups are different), thereby forming a regular sawtooth line.

[0060] After each layer is opened, the positive electrode sheet, the separator, and the negative electrode sheet with holes are stacked in sequence and then compounded to form a dry battery cell, which is step S3.

[0061] In some embodiments of the present application, step S3 may include:

[0062] S31, stacking the perforated positive electrode sheet 100, the separator 200, and the perforated negative electrode sheet 300 in sequence to form an electrode group, wherein the first through hole 110 and the second through hole 310 in each electrode group are eccentrically arranged;

[0063] S32, stacking a plurality of electrode groups with the separator 200 therebetween;

[0064] S33, thermally compounding the stacked multiple electrode groups to form a dry battery cell.

[0065] That is to say, in step S31, the positive electrode sheet 100, the separator 200, and the negative electrode sheet 300 are stacked in sequence. By designing the punching position accordingly in the punching stage (step S2), or by adjusting the lateral position between the positive electrode sheet 100 and the negative electrode sheet 300 during the stacking process, the first through hole 110 on the positive electrode sheet 100 and the second through hole 310 on the negative electrode sheet 300 can be eccentrically arranged with respect to each other, thereby further improving the mechanical strength of the electrode group.

[0066] Furthermore, in step S32, the second through hole 310 of each electrode group is located inside the first through hole 110 in the projection in the stacking direction. Figure 4 As shown, on the basis that the area of ​​the first through hole 110 is greater than the area of ​​the second through hole 310, the first through hole 110 and the second through hole 310 correspond to Figure 4 In the case of the two circular holes that gradually decrease in size from the outside to the inside, when projected in the stacking direction of any electrode group, the first through-hole 110 and the second through-hole 310 overlap. Take any point O inside the area where the first through-hole 110 and the second through-hole 310 overlap, and draw line segments L1 and L2 extending from point O along any direction to the edge of the negative electrode sheet 300 and the edge of the positive electrode sheet 100, respectively. The length of L1 is less than the length of L2. In other words, by designing the positions of the through-holes, the centers of the through-holes in each electrode group are eccentric relative to each other.

[0067] It should be noted that the relative positions of the above-mentioned holes can be designed in advance and then realized by drilling holes at corresponding positions in the punching stage, that is, in step S2, or can be realized by adjusting the lateral positions of each layer when stacking in step S3 and performing corresponding cutting after stacking.

[0068] After obtaining the dry cell, liquid injection, packaging, etc. are performed to obtain the cell for battery use.

[0069] A battery according to a second embodiment of the present invention comprises a plurality of battery cells obtained by the preparation method of the first embodiment. Specifically, the battery cells are obtained by the preparation method of the battery cell having a rapid electrolyte infiltration structure according to the first embodiment, and then connected in series to form a battery. Because the battery comprises the battery cells of any of the above embodiments, the battery exhibits similar effects to those of the battery cells, and a detailed description thereof is omitted herein.

[0070] In order to make the objectives, technical solutions and advantages of the present invention more clear, the embodiments of the present invention will be described in further detail below.

[0071] First, the following describes in detail the distribution ratios of the positive electrode slurry and the negative electrode slurry components of Examples 1-24 and Comparative Examples 1-3, the proportion of the negative electrode active material in the negative electrode slurry, the structure of the first through hole 110 and the second through hole 310 of Examples 1-24, and the shape, size, deviation distance Δ, and deviation direction of each through hole.

[0072] First, 95 wt% of the positive electrode active material, 2 wt% of the superconducting carbon and 3 wt% of the polyvinylidene fluoride were added to N-methylpyrrolidone and stirred evenly to form a positive electrode slurry; 90 wt% of the negative electrode active material, 2 wt% of the superconducting carbon, 7 wt% of the polyacrylic acid and 1 wt% of the styrene-butadiene rubber were added to deionized water and stirred evenly to form a negative electrode slurry.

[0073] Next, Table 1 shows the proportion of negative electrode active materials in the negative electrode slurries of Examples 1-24 and Comparative Examples 1-3, as well as the structures of the first through holes 110 and the second through holes 310 of Examples 1-24, and the shape, size, deviation distance, and deviation direction of each through hole.

[0074] Table 1 Negative electrode components and through-hole structure designs of Examples 1-24 and Comparative Examples 1-3

[0075]

[0076]

[0077] The cells of Examples 1-24 and Comparative Examples 1-3 were prepared according to the process parameters in Table 1. The cells were then stacked to form batteries of Examples 1-24 and Comparative Examples 1-3. Internal resistance tests were performed on the batteries of Examples 1-24 and Comparative Examples 1-3. The results are shown in Table 2.

[0078] Table 2 Internal resistance of the batteries of Examples 1-24 and Comparative Examples 1-3

[0079] serial number Internal resistance / mΩ serial number Internal resistance / mΩ serial number Internal resistance / mΩ Example 1 43 Example 2 36.2 Example 3 24 Example 4 41.5 Example 5 35 Example 6 23.7 Example 7 40.9 Example 8 34.3 Example 9 22.5 Example 10 39.5 Example 11 33 Example 12 21 Example 13 43.6 Example 14 35.8 Example 15 23.8 Example 16 41.8 Example 17 34.9 Example 18 23.5 Example 19 40.7 Example 20 33.6 Example 21 22 Example 22 39.9 Example 23 32 Example 24 21.5 Comparative Example 1 45 Comparative Example 2 38 Comparative Example 3 25

[0080] As can be seen from Table 1-2, the internal resistance of the batteries of Examples 1-24 of the present invention is significantly lower than that of the batteries of Comparative Examples 1-3. That is, for different negative electrode active material ratios, the internal resistance of the batteries of Examples 1-24 of the present invention is significantly lower than that of the comparative examples with the same composition. This is because the first through-holes 110 and second through-holes 310 formed in the positive electrode sheet 100 and the negative electrode sheet 300, respectively, allow the electrolyte to penetrate into each layer of the battery cell through each through-hole, shortening the electrolyte infiltration path. This not only increases the infiltration speed but also significantly improves the infiltration effect. At the same time, the eccentric arrangement of the first through-holes 110 and the second through-holes 310 improves the mechanical strength of the battery.

[0081] Afterwards, the room temperature long cycle capacity retention rate of the battery was measured under the conditions of room temperature, charge and discharge rates of 1C and 1C, and 800 charge and discharge cycles; the high temperature long cycle capacity retention rate of the battery was measured under the conditions of 55°C, charge and discharge rates of 1C and 1C, and 600 charge and discharge cycles. The results are shown in Table 3 below.

[0082] Table 3 Battery capacity retention rate after normal temperature and high temperature cycles of each embodiment and comparative example

[0083]

[0084]

[0085] As can be seen from Table 3, compared with the battery of Comparative Example 3, the batteries of Examples 3, 6, 9, 12, 15, 18, 21, and 24 of the present invention have improved capacity retention rates under the conditions of charge and discharge rates of 1C and 1C, 800 charge and discharge cycles at room temperature, and 600 charge and discharge cycles at 55°C, respectively. This indicates that good wettability is maintained in the middle and late stages of the charge and discharge cycle, and no localized liquid starvation occurs inside the battery.

[0086] The above is a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for preparing a battery cell having a rapid electrolyte infiltration structure, characterized in that: The steps include: S1, provides positive electrode sheets, separators, and negative electrode sheets; S2, drilling holes in the positive electrode sheet and the negative electrode sheet to form a first through hole and a second through hole respectively; S3, stacking the positive electrode sheet in step S2, the separator in step S1, and the negative electrode sheet in step S2 in sequence, and then compounding them to form a dry cell. The area of ​​the first through hole is greater than the area of ​​the second through hole, and the first through hole and the second through hole are eccentrically arranged with respect to each other; The step S3 comprises: S31, stacking the positive electrode sheet, the separator, and the negative electrode sheet with holes formed therein in sequence to form an electrode group, wherein the first through hole and the second through hole in each electrode group are eccentrically arranged. S32, stacking a plurality of the electrode groups with the separator therebetween; S33, thermally combining the stacked plurality of electrode groups to form the dry battery cell; The centers of the through holes in the battery core are sequentially connected to form a sawtooth line or a diagonal line.

2. The method according to claim 1, characterized in that In the step S2, the first through hole and the second through hole are independently formed into a circle, a triangle, a square, a polygon, or a special shape.

3. The method according to claim 1, characterized in that In step S2, the distance between the center of any one of the first through hole and the second through hole and the edge of the layer where the center is located is greater than or equal to 0.1 mm.

4. The method according to claim 1, wherein In projection in the stacking direction, the second through hole of each electrode group is located within the first through hole.

5. The method according to claim 1, wherein The center of the first through hole in each of the electrode groups is offset from the center of the second through hole by the same distance in the first direction / the second direction, and the offset distance Δ satisfies formula 1): Wherein, x is the larger vertical distance from the center of the first through hole / the second through hole in the first direction / the second direction to the edge of the electrode sheet, k is the ratio of the smaller vertical distance from the center of the first through hole / the second through hole in the first direction / the second direction to the edge of the electrode sheet to the distance between the two edges of the electrode sheet in the first direction / the second direction, m is the number of layers of negative electrode sheets in the electrode group, and n is the number of layers of positive electrode sheets in the electrode group; And the deviation distance Δ satisfies formula 2): Δ<R 2) Wherein R is the distance between the center of the second through hole and its edge; The first direction and the second direction are along the width direction and the length direction of the pole piece.

6. The method according to claim 1, characterized in that In step S33, in two adjacent electrode groups, the deviation directions of the line connecting the center of the first through hole and the center of the second through hole are opposite.

7. A battery, characterized in that: include: A plurality of battery cells prepared by the method according to any one of claims 1 to 6.

8. The battery according to claim 7, characterized in that A positive electrode active layer is formed on the positive electrode sheet of the battery, and the positive electrode active layer contains a positive electrode active material, and the positive electrode active material is selected from one or more of lithium iron phosphate, lithium cobalt oxide, lithium manganese oxide, and ternary materials; A negative electrode active layer is formed on the negative electrode sheet of the battery. The negative electrode active layer contains a negative electrode active material. The negative electrode active material is selected from one or more of graphite, silicon-based, transition metal oxides, and metallic lithium.

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