Square energy storage battery and preparation method thereof

Abstract

The invention provides a square energy storage battery and a preparation method thereof, and the preparation method comprises the following steps: respectively carrying out die cutting treatment on a positive plate and a negative plate to obtain a plurality of positive lug parts and negative lug parts, sequentially laminating the positive plate, a diaphragm, the negative plate and the diaphragm, and winding to obtain a single roll core; and preparing at least two single roll cores, carrying out core combination treatment to form a core package, putting the core package into a shell, and carrying out final welding on the shell and the cover plate assembly to obtain the square energy storage battery. According to the distance between two adjacent positive lug parts and negative lug parts, the wound positive lug parts are centrally aligned at one end of the single roll core and are uniformly distributed along the two sides of the central line in the width direction of the single roll core, and the wound negative lug parts are centrally aligned at the other end of the single roll core and are uniformly distributed along the two sides of the central line in the width direction of the single roll core. According to the invention, the tab position of the battery cell is designed in the middle of the roll core, so that the assembly process is simplified, and the winding qualification rate is improved.

Description

Technical Field

[0001] The present invention belongs to the field of new energy lithium batteries and relates to a square energy storage battery and a preparation method thereof. Background Art

[0002] The battery cell is a structure composed of a positive electrode sheet, a separator, a negative electrode sheet, and a separator. There are generally two types of core winding and stacking. It is the most critical and core component of square power and energy storage batteries, and directly affects the electrochemical performance of power and energy storage batteries. For conventional core winding, the thickness of a single core winding is 10 to 35 mm. The thicker the thickness, the longer the pole piece corresponding to the single core winding, the higher the resistance of the pole piece, and the greater the internal deformation of the core during the cycle, the stress increases, which is not conducive to the electrochemical performance of the battery cell, such as capacity, internal resistance, rate and cycle life.

[0003] The traditional 71173207-280Ah standard energy storage battery cell is composed of two coils, which are welded in parallel on the connecting piece, and then welded on the pole of the battery cover to achieve the parallel connection of two cells. For batteries with a thickness of more than 80mm, four coils are generally connected in parallel internally, and two are welded in parallel on the connecting piece, and then welded on the pole, so as to achieve the effect of four cells in parallel.

[0004] Conventional square battery shell assembly uses two mirror-image cells, which require two mirror-image winding devices to be wound simultaneously, or one winding device to make one cell, adjust parameters such as cutting position and tab spacing, and then make another cell. The first option requires twice the investment in equipment, and a single unit cannot operate alone; while the second option has discontinuous processes, and after one cell is completed, it is necessary to wait for the first cell to be paired and transferred down, reducing the efficiency of the latter assembly. In addition, the two mirror-image cells need to be paired one-to-one, which inevitably leads to scrap or defective problems, resulting in measurement and calculation errors, etc., resulting in inconsistent quantities of the two cells, which cannot be matched, resulting in losses in the number and cost of finished cells.

[0005] Therefore, it is necessary to provide a battery cell structure and a preparation method that can improve the assembly efficiency of square batteries. Summary of the invention

[0006] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a square energy storage battery and a preparation method thereof, in which the tab position of the battery cell is designed to be in the middle of the winding core, and a single winding core with an undifferentiated design is used to replace the two conventional battery cells that are mirror images of each other, thereby simplifying the assembly process and improving the winding qualification rate.

[0007] To achieve this object, the present invention adopts the following technical solutions:

[0008] In a first aspect, the present invention provides a method for preparing a square energy storage battery, the preparation method comprising:

[0009] The positive electrode sheet and the negative electrode sheet are die-cut respectively to obtain a plurality of positive electrode ears and negative electrode ears, and the positive electrode sheet, the separator, the negative electrode sheet and the separator are stacked in order and then wound to obtain a single winding core;

[0010] Prepare at least two single winding cores, and perform core-joining processing to form a core package, put the core package into the shell, and perform final welding with the cover plate assembly to obtain a square energy storage battery;

[0011] During the die-cutting process, according to the spacing between two adjacent positive ear portions and the spacing between two adjacent negative ear portions, the positive ear portions after winding are centered and gathered at one end of the monomer winding core, and are evenly distributed on both sides of the center line in the width direction of the monomer winding core to form a positive ear cluster. At the same time, the negative ear portions are centered and gathered at the other end of the monomer winding core, and are evenly distributed on both sides of the center line in the width direction of the monomer winding core to form a negative ear cluster.

[0012] The present invention controls the spacing between adjacent pole lugs so that the pole lugs of the single winding core are centered after winding, which has a compact structure and shortens the gap between layers, thus avoiding the problem of pulling the pole lugs during welding and causing the pole lugs to tear. In addition, a single winding core with an indifferent design is used to replace the two conventional mirror-image battery cells, which improves the efficiency of the rear-stage assembly, reduces the equipment investment cost, and improves the winding qualification rate.

[0013] It should be noted that in the present invention, the single winding core is wound in a racetrack shape, and the center line of the single winding core in the width direction refers to the center line of the maximum linear length in the width direction of the end surface of the single winding core.

[0014] As a preferred technical solution of the present invention, the die-cutting process includes:

[0015] Set the width of each pole ear to be equal;

[0016] Determine the distance from the first pole ear to the first end of the pole piece, and the distance from the last pole ear to the last end of the pole piece, and cut the first pole ear and the last pole ear;

[0017] According to the difference in the spacing between the two pole ears, first confirm the position of the pole ears at odd or even positions, and then determine the positions of the remaining pole ears for cutting, so that the several pole ears after winding are centered and gathered at one end of the single winding core, and are evenly distributed on both sides of the center line in the width direction of the single winding core.

[0018] Preferably, the positive electrode tab cluster and the negative electrode tab cluster are symmetrically arranged along a center line in the length direction of the monomer winding core.

[0019] That is, the present invention provides the following two solutions: (1) first confirm the position of each pole ear portion at an odd-numbered position, and then confirm the positions of the remaining pole ears at an even-numbered position; (2) first confirm the position of each pole ear portion at an even-numbered position, and then confirm the positions of the remaining pole ears at an odd-numbered position.

[0020] It should be noted that the pole piece in the present invention refers to a positive pole piece or a negative pole piece, and the pole ear portion refers to a positive pole ear portion or a negative pole ear portion, that is, when the positive pole piece is die-cut, the pole ear portion refers to the positive pole ear portion, and when the negative pole piece is die-cut, the pole ear portion refers to the negative pole ear portion. In addition, the center line in the length direction of the monomer core in the present invention refers to the center line of the maximum linear length along the length direction of the end face of the monomer core, and the length direction of the monomer core is perpendicular to the width direction of the monomer core.

[0021] As a preferred technical solution of the present invention, a method for calculating the distance between two adjacent pole ears includes:

[0022] The number of the pole lugs is set to n, where n is an integer and n>2;

[0023] The i-th pole ear is denoted as N i , i=2,3,···n, pole ear part N i The distance between the ear and the previous one is S i-1 , set S i-1 The corresponding winding radius is R i-1 ;

[0024] The difference between the distances between the two pole ears is S i -S i-2 =πd;

[0025] Then S i =S i-1 +2t+π×(R i-2 -d);

[0026] Among them, t is the distance between the first pole ear and the first fold after winding; L is the total length of the pole piece; d is the total thickness of the positive pole piece, the negative pole piece and the two layers of separator.

[0027] It should be noted that in the present invention, the positive electrode tab and the negative electrode tab are respectively located at the two ends of the single winding core, so the spacing between the tabs of the positive electrode sheet and the negative electrode sheet needs to be calculated respectively.

[0028] The single winding core of the present invention has a structure in which the winding radius increases from the inside to the outside. Each time the pole piece is wound, its two ends need to be bent twice to form a semicircle, that is, each turn corresponds to two winding radii that increase in sequence along the winding direction. In addition, each time the pole piece is wound, two pole ears are arranged within the distance.

[0029] It should also be noted that the difference in the spacing between the two pole ears described in the present invention refers to the difference between the spacing between the two pole ears set at intervals and the previous pole ears, respectively. Taking the second pole ear N2 and the fourth pole ear N4 set at intervals as an example, the difference in the spacing between the two pole ears refers to the difference between the spacing between the first pole ear N1 and the second pole ear N2 and the spacing between the third pole ear N3 and the fourth pole ear N4.

[0030] As a preferred technical solution of the present invention, the distance S from the center line of the first pole ear N1 to the first end of the pole piece is set to f , the final ear N n The distance from the center line to the end of the pole piece is S e ;

[0031] but

[0032] Preferably, S e ≥1 / 2L.

[0033] The end ear portion N of the pole piece in the present invention n The position corresponds to the middle pole lug portion of the pole sheet having the same number n of pole lug portions, where the number of pole lugs is n / 2.

[0034] As a preferred technical solution of the present invention, the preparation method further comprises: hot pressing and shaping the monomer core.

[0035] As a preferred technical solution of the present invention, the hot pressing shaping includes: performing preheating treatment and hot pressing treatment on the single winding core in sequence.

[0036] Preferably, the temperature of the preheat treatment is 80-100°C, for example, it can be 80°C, 82°C, 85°C, 86°C, 90°C, 93°C, 95°C, 98°C or 100°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0037] Preferably, the preheat treatment time is 15 to 25 minutes, for example, it can be 15 minutes, 16 minutes, 17 minutes, 18 minutes, 19 minutes, 20 minutes, 21 minutes, 22 minutes, 23 minutes, 24 minutes or 25 minutes, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0038] Preferably, the temperature of the hot pressing treatment is 80-100°C, for example, it can be 80°C, 82°C, 85°C, 86°C, 90°C, 93°C, 95°C, 98°C or 100°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0039] Preferably, the heat pressing treatment time is 45 to 90 s, for example, 45 s, 50 s, 55 s, 60 s, 65 s, 70 s, 75 s, 80 s, 85 s or 90 s, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0040] Preferably, the pressure of the hot pressing treatment is 2.5-8T, for example, it can be 2.5T, 3T, 3.5T, 4T, 4.5T, 5T, 5.5T, 6T, 6.5T, 7T, 7.5T or 8T, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0041] As a preferred technical solution of the present invention, the core closing process includes:

[0042] Performing a first welding on the monomer winding core, so that the positive electrode ear cluster and the negative electrode ear cluster are independently gathered toward the center line in the width direction of the monomer winding core, forming a positive electrode ear and a negative electrode ear respectively located at two ends of the monomer winding core;

[0043] Provide two connecting pieces, weld and fix the positive pole ears of the two single winding cores on one connecting piece, and weld and fix the negative pole ears of the two single winding cores on the other connecting piece;

[0044] The positive electrode ear and the negative electrode ear are bent respectively, and the two monomer winding cores are bonded and fixed to obtain the core package.

[0045] As a preferred technical solution of the present invention, the final welding includes: laser welding the connecting piece and the cover plate assembly.

[0046] In a second aspect, the present invention provides a square energy storage battery, which is prepared by the preparation method described in the first aspect, and comprises a shell, a cover plate assembly and a core package, wherein the cover plate assembly is buckled on the shell, the core package is located in the shell, and the core package is electrically connected to the cover plate assembly; the core package comprises at least two monomer winding cores arranged side by side, and the monomer winding core is provided with a positive electrode ear and a negative electrode ear, wherein the positive electrode ear and the negative electrode ear are respectively located at two ends of the monomer winding core and are centered in the width direction of the monomer winding core.

[0047] The battery used in the present invention is a structure with a single winding core with the tab centered as the main body, replacing the existing mirror-image winding core structure, simplifying the matching requirements of the subsequent assembly stage, thereby improving the matching qualification rate and facilitating improving the efficiency of the assembly stage process.

[0048] As a preferred technical solution of the present invention, the core package also includes a first connecting piece and a second connecting piece, the positive electrode ear of the single core is connected to the first connecting piece, the negative electrode ear of the single core is connected to the second connecting piece, and the first connecting piece and the second connecting piece are independently connected to the cover plate assembly.

[0049] Compared with the prior art, the present invention has the following beneficial effects:

[0050] The present invention provides a square energy storage battery and a preparation method thereof. By designing the spacing between the pole ears of the pole piece, a single winding core with the pole ear centered is manufactured as the main structure of the battery, which greatly improves the efficiency of the rear-stage assembly, reduces the equipment investment cost by 50%, and achieves a 100% winding qualification rate of a single winding core. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 This is a schematic structural diagram of a single winding core provided by the present invention.

[0052] Figure 2 This is a top view of the single winding core provided by the present invention.

[0053] Figure 3 This is a left side view of the single winding core provided by the present invention.

[0054] Figure 4 A side view of a single winding core provided by the present invention.

[0055] Figure 5 This is a schematic diagram of the structure of a single winding core after the tab clusters provided by the present invention are folded.

[0056] Figure 6 It is a left view of the single winding core after the tab cluster provided by the present invention is folded.

[0057] Figure 7 It is a side view of the single winding core after the tab cluster provided by the present invention is folded.

[0058] Figure 8 This is a schematic diagram of the connection between the single winding core and the connecting piece provided by the present invention.

[0059] Fig. 9 for Figure 8 Side view of.

[0060] Fig.10 A schematic diagram of the connection between the connecting piece and the cover plate assembly provided by the present invention.

[0061] Fig.11 A top view of the winding core A provided by the present invention.

[0062] Fig.12 A top view of the winding core B provided by the present invention.

[0063] Fig.13 This is a schematic structural diagram of the winding core A provided by the present invention.

[0064] Fig.14 A side view of the winding core A provided by the present invention.

[0065] Fig.15 This is a schematic structural diagram of the winding core B provided by the present invention.

[0066] Fig.16 A side view of the winding core B provided by the present invention.

[0067] Fig.17 It is a left view of the winding core A after the tab cluster provided by the present invention is folded.

[0068] Fig.18 It is a left view of the winding core B after the tab cluster provided by the present invention is folded.

[0069] Fig.19 Schematic diagram of the connection between the winding core A and the winding core B provided by the present invention and the connecting piece respectively.

[0070] Fig. 20 A schematic diagram of the connection between the winding core A, winding core B, connecting sheet and cover plate assembly provided by the present invention.

[0071] Among them, 100-single winding core; 200-positive electrode ear; 300-negative electrode ear; 201-positive electrode ear cluster; 301-negative electrode ear cluster; 400-first connecting piece; 500-second connecting piece; 600-cover plate assembly; 700-winding core A; 800-winding core B. DETAILED DESCRIPTION

[0072] It should be understood that, in the description of the present invention, the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In addition, the terms "first", "second", etc. are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first", "second", etc. may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0073] It should be noted that in the description of the present invention, unless otherwise clearly specified and limited, the terms "disposed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood by specific circumstances.

[0074] The technical solution of the present invention is further described below with reference to the accompanying drawings and through specific implementation methods.

[0075] In a specific embodiment, the present invention provides a method for preparing a square energy storage battery, the preparation method comprising:

[0076] Step (i) The positive electrode sheet and the negative electrode sheet are die-cut respectively to obtain a plurality of positive electrode ears and negative electrode ears, and the positive electrode sheet, the separator, the negative electrode sheet and the separator are stacked in order and then wound to obtain a single winding core 100.

[0077] During the die-cutting process, according to the spacing between two adjacent positive ear portions and the spacing between two adjacent negative ear portions, the plurality of positive ear portions after winding are centered and gathered at one end of the single winding core 100, and are evenly distributed on both sides of the center line in the width direction of the single winding core 100 to form a positive ear cluster 201. At the same time, the plurality of negative ear portions are centered and gathered at the other end of the single winding core 100, and are evenly distributed on both sides of the center line in the width direction of the single winding core 100 to form a negative ear cluster 301.

[0078] The positive electrode sheet described in the present invention includes a positive electrode current collector well known to those skilled in the art, and a positive electrode active material layer coated on one side surface or both sides of the positive electrode current collector, a blank area is left at one end of the positive electrode active material layer, and the blank area is die-cut to obtain the positive electrode ear. The negative electrode sheet includes a negative electrode current collector well known to those skilled in the art, and a negative electrode active material layer coated on one side surface or both sides of the negative electrode current collector, a blank area is left at one end of the negative electrode active material layer, and the blank area is die-cut to obtain the negative electrode ear. The diaphragm is located between the positive electrode sheet and the negative electrode sheet, and plays an insulating role to avoid short circuit. The present invention does not specifically limit the material of the diaphragm, and at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride commonly used in the art can be used.

[0079] The winding direction of the single winding core 100 in the present invention can be clockwise or counterclockwise, which is not specifically limited in the present invention. The single winding core is wound in a racetrack shape, and the width of the single winding core refers to the maximum linear length of the front and rear ends of the single winding core end surface in the connecting width direction.

[0080] The die-cutting process may adopt laser die-cutting commonly used by those skilled in the art.

[0081] In some embodiments, the die cutting process includes:

[0082] S1: Set the width of each pole ear to be equal;

[0083] S2: Determine the distance from the first pole ear to the first end of the pole piece, and the distance from the last pole ear to the last end of the pole piece, and cut the first pole ear and the last pole ear;

[0084] S3: According to the difference in the spacing between the two pole ears, first confirm the position of the pole ears at the odd or even positions, and then determine the positions of the remaining pole ears and then cut them, so that the several pole ears after winding are centered and gathered at one end of the single winding core 100, and are evenly distributed on both sides of the center line in the width direction of the single winding core 100.

[0085] In step S1, the present invention does not specifically limit the width of the electrode ear portion, and those skilled in the art can adjust it according to actual conditions. It should be noted that the width of the positive electrode ear portion in the present invention is equal to the width of the negative electrode ear portion.

[0086] In step S2, the distance from the first pole ear to the first end of the pole piece in the present invention may refer to the distance from the center line of the first pole ear to the first end of the pole piece, or the distance from the end of the first pole ear to the first end of the pole piece, and correspondingly, the distance from the last pole ear to the tail end of the pole piece may refer to the distance from the center line of the last pole ear to the tail end of the pole piece, or the distance from the end of the last pole ear to the tail end of the pole piece. The pole ear refers to the positive pole ear or the negative pole ear.

[0087] The present invention first determines the positions of the first pole ear and the last pole ear, and then determines the positions of the remaining pole ears located in the middle. When determining the positions of the remaining pole ears, the spacing can be calculated based on the center line of each pole ear or the end of the same side of each pole ear.

[0088] In step S3, the monomer winding core 100 of the present invention is a structure that is wound in circles from the inside to the outside along the winding direction, and the middle part of a circle is a parallel line, and the two ends of the parallel line are bent into a semicircle with a small winding radius and a large winding radius respectively. As the number of turns increases, the increase in the thickness direction of each turn is equal, which is the total thickness of a layer of positive electrode sheet, a layer of negative electrode sheet and two layers of separator, so that the winding radius increases successively, and then the circumference of the semicircle at the same end of the parallel line changes in an arithmetic increment. Figure 1 and Figure 2 It can be seen that the difference between the spacings of the two pole ears is the change in the circumference of a corresponding semicircle. For example, the difference between the spacings of the first pole ear and the second pole ear and the spacings of the third pole ear and the fourth pole ear is the change in the circumference of the corresponding two semicircles.

[0089] In the present invention, when the first pole ear and the last pole ear are determined, the pole ear at the middle position is first determined by the difference in the distance between the two pole ears, and then another part of the pole ears is inserted at a suitable position to ensure that the difference in the distance also meets the requirements, so as to obtain the position of all the pole ears. To this end, the present invention provides the following two solutions:

[0090] (1) First confirm the position of each pole ear at an odd number, and then confirm the position of the remaining pole ears at an even number. For example, if the position of the first pole ear is an odd number, first confirm the third, fifth, seventh, etc. pole ears at odd numbers, and then insert the second, fourth, sixth, etc. pole ears at even numbers, to ensure that the difference in their spacings also meets the requirements.

[0091] (2) First confirm the position of each even-numbered lug, and then confirm the position of the remaining odd-numbered lugs. For example, based on the position of the first lug, first confirm the second, fourth, sixth, and so on, and then insert the third, fifth, seventh, and so on, and so on, and then insert the third, fifth, seventh, and so on, and so on, and ensure that the difference in their spacing also meets the requirements.

[0092] After winding, the positive electrode ear cluster 201 and the negative electrode ear cluster 301 are symmetrically arranged along the center line in the length direction of the monomer winding core 100. The length of the monomer winding core refers to the maximum linear length of the left and right ends of the connecting length direction of the end face of the monomer winding core.

[0093] Furthermore, the calculation method of the distance between two adjacent pole ears includes:

[0094] S01: Set the number of pole lugs to n, where n is an integer and n>2.

[0095] S02: The i-th pole ear is recorded as N i , i=2,3,···n, pole ear part N i The distance between the ear and the previous one is S i-1 , set S i-1 The corresponding winding radius is R i-1 That is, in the present invention, the distance between the first pole ear portion and the second pole ear portion N2 is S1, the distance between the second pole ear portion N2 and the third pole ear portion N3 is S2, the distance between the third pole ear portion N3 and the fourth pole ear portion N4 is S3, and so on. n-1 With the final ear N n The spacing is S n-1 The S in the present invention i-1 The corresponding winding radius is R i-1 Refers to the N located at the ear i With its previous ear N i-1 The radius of the semicircle between them.

[0096] like Figure 2 As shown, S1 = πR1, S3-S1 = π×(R3-R2) = πd, S5-S3 = π×(R5-R3) = πd, and so on. The difference S between the two pole ears is i -S i-2 =π×(R i -R i-2 )=πd, then S i =S i-1 +2t+π×(R i-2 -d).

[0097] Among them, t is the distance between the first pole ear and the first fold after winding; L is the total length of the pole piece; d is the total thickness of the positive pole piece, the negative pole piece and the two layers of separator.

[0098] Furthermore, the distance S from the center line of the first pole ear N1 to the first end of the pole piece is set to f , the final ear N n The distance from the center line to the end of the pole piece is S e ;

[0099] but

[0100] Among them, S e ≥1 / 2L, the end ear N in the present invention n The position corresponds to the middle pole lug at the position n / 2 of the number of pole lugs of a pole sheet with a conventional number of n pole lugs.

[0101] Step (ii) prepares at least two single winding cores 100, and performs core-closing processing to form a core package, places the core package into the shell, and performs final welding with the cover plate assembly to obtain a square energy storage battery.

[0102] In some embodiments, the preparation method further comprises: hot pressing and shaping the single winding core 100 .

[0103] Furthermore, the specific method of the hot pressing shaping includes: performing preheating treatment and hot pressing treatment on the single winding core 100 in sequence.

[0104] The preheating treatment is performed at a temperature of 80 to 100° C. for 15 to 25 minutes, the hot pressing treatment is performed at a temperature of 80 to 100° C. for 45 to 90 seconds, and the hot pressing treatment is performed at a pressure of 2.5 to 8T.

[0105] Specifically, the preheating treatment may be performed by using a preheating furnace commonly used in the art to heat the single winding core 100 , and the hot pressing treatment may be performed by using a hot press commonly used in the art to perform the pressing treatment.

[0106] In some embodiments, the core closing process includes:

[0107] S21: performing a first welding on the monomer winding core 100, so that the positive electrode ear cluster 201 and the negative electrode ear cluster 301 are independently gathered toward the center line in the width direction of the monomer winding core 100, so as to form the positive electrode ear 200 and the negative electrode ear 300 respectively located at two ends of the monomer winding core 100;

[0108] S22: providing two connecting sheets, welding and fixing the positive electrode tabs 200 of the two single winding cores 100 on one connecting sheet, and welding and fixing the negative electrode tabs 300 of the two single winding cores 100 on the other connecting sheet;

[0109] S23: bend the positive electrode tab 200 and the negative electrode tab 300 respectively, so that the two single winding cores 100 are attached to each other and then bonded and fixed to obtain the core package.

[0110] The present invention does not specifically limit the welding process of the first welding and the second welding, and ultrasonic welding well known to those skilled in the art may be used.

[0111] In some embodiments, the final welding includes: laser welding the connecting piece to the cover plate assembly 600. In the present invention, the cover plate assembly 600 is provided with a positive electrode column and a negative electrode column. In the final welding process, the connecting piece connected to the positive electrode ear 200 is laser welded to the positive electrode column, and the connecting piece connected to the negative electrode ear 300 is laser welded to the negative electrode column.

[0112] After the final welding of the square energy storage battery of the present invention, it is necessary to undergo conventional processes such as baking, liquid injection and formation, which are well known to those skilled in the art, before a complete lithium battery can be obtained for application.

[0113] In another specific embodiment, the present invention provides a square energy storage battery, which is prepared by the preparation method described in a specific embodiment. The square energy storage battery includes a shell, a cover assembly 600 and a core package, the cover assembly 600 is buckled on the shell, the core package is located in the shell, and the core package is electrically connected to the cover assembly 600. The core package includes at least two monomer cores 100 arranged side by side, and the monomer core 100 is provided with a positive electrode ear 200 and a negative electrode ear 300, and the positive electrode ear 200 and the negative electrode ear 300 are respectively located at the two ends of the monomer core 100, and are arranged in the center in the width direction of the monomer core 100.

[0114] At least one end of the shell is an open structure, and the shell may be a hard shell, including but not limited to hard plastic shells, aluminum shells, steel shells, etc. commonly used in the art.

[0115] Furthermore, the core package also includes a first connecting sheet 400 and a second connecting sheet 500, the positive electrode ear 200 of the single core 100 is connected to the first connecting sheet 400, the negative electrode ear 300 of the single core 100 is connected to the second connecting sheet 500, and the first connecting sheet 400 and the second connecting sheet 500 are independently connected to the cover plate assembly 600.

[0116] Example 1

[0117] The present embodiment provides a square energy storage battery and a preparation method thereof, comprising a shell, a cover plate assembly 600 and a core package. One end of the shell is an open structure, the cover plate assembly 600 is buckled on the shell, and the core package is located inside the shell. The core package includes a first connecting piece 400, a second connecting piece 500 and two monomer cores 100 arranged side by side. The monomer core 100 is provided with a positive electrode ear 200 and a negative electrode ear 300, which are respectively located at the left and right ends of the monomer core 100 and are centered in the width direction of the monomer core 100. The positive electrode ears 200 of the two monomer cores 100 are both connected to one side surface of the first connecting piece 400, and the other side surface of the first connecting piece 400 is connected to the positive pole of the cover plate assembly 600; the negative electrode ears 300 of the two monomer cores 100 are both connected to one side surface of the second connecting piece 500, and the other side surface of the second connecting piece 500 is connected to the negative pole of the cover plate assembly 600.

[0118] The preparation method of the square energy storage battery provided in this embodiment specifically includes the following steps:

[0119] (1) The width of each positive electrode ear and negative electrode ear is set to be equal, and the number of positive electrode ears and negative electrode ears is n, n is an integer, and n>2; the i-th electrode ear is recorded as N i , i=2,3,···n, pole ear part N i The distance between the ear and the previous one is S i-1 , set S i-1 The corresponding winding radius is R i-1 ;

[0120] (2) Determine the distance S from the first pole ear N1 to the first end of the positive electrode f , and the final ear N n Distance S to the end of the positive electrode e , perform die-cutting of the first and last pole ears of the positive electrode sheet; Figure 2 As shown, according to the difference in the distance between the two positive ear parts, πd, the third positive ear part N3, the fifth positive ear part N5, the seventh positive ear part N7, etc., are first confirmed in turn, and die-cut; then, according to the calculation formula S i =S i-1 +2t+π×(R i-2 -d), calculate the second positive electrode ear N2, the fourth positive electrode ear N4, the sixth positive electrode ear N6, etc., and perform die-cutting, where t is the distance between the first positive electrode ear and the first circle fold after winding, L is the total length of the electrode sheet, and d is the total thickness of the positive electrode sheet, the negative electrode sheet and the two layers of the separator; and S e ≥1 / 2L and meet

[0121]

[0122] (3) using the calculation method of step (2) to obtain the positions of all negative electrode ears on the negative electrode sheet, and performing die-cutting of the negative electrode sheet;

[0123] (4) Figure 1 , Figure 2 , Figure 3 and Figure 4 As shown, the positive electrode sheet, the separator, the negative electrode sheet and the separator are stacked in a clockwise direction in the order and then wound to obtain a single winding core 100, so that the n positive electrode ears after winding are centered and gathered at the left end of the single winding core 100, and are evenly distributed on both sides of the center line in the width direction of the single winding core 100 to form a positive electrode ear cluster 201; at the same time, the n negative electrode ears are centered and gathered at the right end of the single winding core 100, and are evenly distributed on both sides of the center line in the width direction of the single winding core 100 to form a negative electrode ear cluster 301;

[0124] (5) Preheating and hot pressing the single core 100 in sequence, wherein the preheating temperature is 90° C. for 20 min, and the hot pressing temperature is 90° C. for 60 s and the pressure is 5 T;

[0125] (6) According to steps (1) to (5), two monomer cores 100 with completely identical structures are prepared;

[0126] (7) Figure 5 , Figure 6 and Figure 7 As shown, the positive electrode ear cluster 201 and the negative electrode ear cluster 301 of the monomer winding core 100 are ultrasonically welded respectively, so that the positive electrode ear cluster 201 is gathered toward the center line in the width direction of the monomer winding core 100, forming the positive electrode ear 200 located at the left end of the monomer winding core 100; at the same time, the negative electrode ear cluster 301 is gathered toward the center line in the width direction of the monomer winding core 100, forming the negative electrode ear 300 located at the right end of the monomer winding core 100;

[0127] (8) Figure 8 and Fig. 9 As shown, the positive electrode tabs 200 of the two single winding cores 100 are ultrasonically welded to the first connecting sheet 400, and the negative electrode tabs 300 of the two single winding cores 100 are ultrasonically welded to the second connecting sheet 500, and then the positive electrode tabs 200 and the negative electrode tabs 300 are bent respectively, so that the two single winding cores 100 are bonded and fixed to obtain a core package;

[0128] (9) Fig.10 As shown, the first connecting piece 400 is laser welded to the positive pole of the cover plate assembly 600, and then the second connecting piece 500 is laser welded to the negative pole of the cover plate assembly 600 to obtain a square energy storage battery.

[0129] Comparative Example 1

[0130] This comparative example provides a square energy storage battery and a preparation method thereof, which is different from Example 1 in that the core package is composed of a winding core A700 and a winding core B800 which are mirror images of each other. Fig.11 and Fig.12 As shown, the positive electrode ear 200 and the negative electrode ear 300 of the core A700 are respectively located at the left and right ends of the single core 100, and are gathered at the front end of the center line in the width direction of the core A700, while the positive electrode ear 200 and the negative electrode ear 300 of the core B800 are respectively located at the left and right ends of the core B800, and are gathered at the rear end of the center line in the width direction of the core B800. The rest of the structure is the same as that of Example 1.

[0131] The preparation method of the square energy storage battery provided in this comparative example comprises the following steps:

[0132] (1) The width of each positive electrode ear and negative electrode ear of the winding core A700 is set to be equal, and the number of positive electrode ears and negative electrode ears is n, where n is an integer and n>2; the i-th electrode ear is recorded as N i , i=2,3,···n, pole ear part N i The distance between the ear and the previous one is D i-1 , set D i-1 The corresponding winding radius is R i-1 ;

[0133] (2) Determine the distance D from the first pole ear N1 to the first end of the positive electrode f , the die-cutting process of the first ear of the positive electrode sheet is carried out, where D f =S f , and N n / 2 The position of is the same as the position of the last ear in the single winding core 100 of Example 1; then, according to the difference of the distance between the positive ear parts, which is πd, the position of each positive ear part is determined for die-cutting, where d is the total thickness of the positive electrode sheet, the negative electrode sheet and the two layers of separators; then, according to the same calculation method, the positions of all the negative electrode ears are obtained, and the negative electrode sheet is die-cut;

[0134] (3) Fig.13 and Fig.14 As shown, the positive electrode sheet, the separator, the negative electrode sheet and the separator are wound in a clockwise direction in the order to obtain the winding core A700, so that the n positive electrode ears after winding are gathered at the left end of the winding core A700 and located at the front end of the center line in the width direction of the winding core A700 to form a positive electrode ear cluster 201; at the same time, the n negative electrode ears are gathered at the right end of the winding core A700 and located at the front end of the center line in the width direction of the winding core A700 to form a negative electrode ear cluster 301;

[0135] (4) Fig.15 and Fig.16 As shown, the winding core B800 is manufactured according to steps (1) to (3), wherein the positive electrode sheet, the separator, the negative electrode sheet and the separator in the winding core B800 are wound in a counterclockwise direction, and the n positive electrode ears after winding are gathered at the left end of the winding core B800 and located at the rear end of the center line in the width direction of the winding core B800 to form a positive electrode ear cluster 201; at the same time, the n negative electrode ears are gathered at the right end of the winding core B800 and located at the rear end of the center line in the width direction of the winding core A700 to form a negative electrode ear cluster 301;

[0136] (5) Preheating and hot pressing the core A700 and the core B800 in turn, wherein the preheating temperature is 90° C. for 20 min, and the hot pressing temperature is 90° C. for 60 s and the pressure is 5 T;

[0137] (6) Fig.17and Fig.18 As shown, the positive electrode ear cluster 201 and the negative electrode ear cluster 301 of the winding core A700 are ultrasonically welded respectively, so that the positive electrode ear cluster 201 and the negative electrode ear cluster 301 are independently oriented to the edge of the front end of the center line in the width direction of the single winding core 100, forming the positive electrode ear 200 and the negative electrode ear 300; at the same time, the positive electrode ear cluster 201 and the negative electrode ear cluster 301 of the winding core B800 are ultrasonically welded respectively, so that the positive electrode ear cluster 201 and the negative electrode ear cluster 301 are independently oriented to the edge of the rear end of the center line in the width direction of the single winding core 100, forming the positive electrode ear 200 and the negative electrode ear 300;

[0138] (7) Fig.19 As shown, the positive electrode tabs 200 of the core A700 and the core B800 are ultrasonically welded to the first connecting sheet 400, and the negative electrode tabs 300 of the core A700 and the core B800 are ultrasonically welded to the second connecting sheet 500, and then the positive electrode tabs 200 and the negative electrode tabs 300 are bent respectively, so that the core A700 and the core B800 are bonded and fixed to obtain a core package;

[0139] (8) Fig. 20 As shown, the first connecting piece 400 is laser welded to the positive pole of the cover plate assembly 600, and then the second connecting piece 500 is laser welded to the negative pole of the cover plate assembly 600 to obtain a square energy storage battery.

[0140] Compared with Example 1, since the structures of the core A700 and the core B800 used in Comparative Example 1 are different, two mirror-image winding machines are used for winding in the preparation process, and the equipment investment is doubled, and the entire assembly steps are complicated and inefficient. It is also easy to have the problem that the core A700 and the core B800 cannot be 100% matched, which leads to the loss of the number and cost of the finished core. In contrast, Example 1 uses two single cores 100 with exactly the same structure, and the positions of the positive electrode ear 200 and the negative electrode ear 300 are designed in the middle of the single core 100, which can eliminate the differences between the two cores A700 and B800 and the dependence and requirements of the subsequent assembly process on the core structure, thereby achieving 100% matching of a single core, 100% improving the efficiency of the rear-stage assembly, and reducing the equipment investment cost by 50%. In addition, the structure of the pole ear in Example 1 is compact, and the gap between the layers is small. Compared with Comparative Example 1, it is less likely to pull the pole ear during welding and closing, causing the pole ear to tear.

[0141] The present invention unifies the cell structure within the core package, takes the single core with the pole ear centered as the main body, performs laser die-cutting, winding and core assembly of the positive and negative electrode sheets, eliminates the mirror-image cores A and B in conventional square batteries, and greatly improves the winding qualification rate.

[0142] The applicant declares that the above is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention shall fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for preparing a square energy storage battery, characterized in that: The preparation method comprises: The positive electrode sheet and the negative electrode sheet are die-cut respectively to obtain a plurality of positive electrode ears and negative electrode ears, and the positive electrode sheet, the separator, the negative electrode sheet and the separator are stacked in order and then wound to obtain a single winding core; Prepare at least two single winding cores, and perform core-joining processing to form a core package, put the core package into the shell, and perform final welding with the cover plate assembly to obtain a square energy storage battery; During the die-cutting process, according to the spacing between two adjacent positive ear portions and the spacing between two adjacent negative ear portions, the positive ear portions after winding are centered and gathered at one end of the monomer winding core, and are evenly distributed on both sides of the center line in the width direction of the monomer winding core to form a positive ear cluster. At the same time, the negative ear portions are centered and gathered at the other end of the monomer winding core, and are evenly distributed on both sides of the center line in the width direction of the monomer winding core to form a negative ear cluster.

2. The preparation method according to claim 1, characterized in that: The die-cutting process includes: Set the width of each pole ear to be equal; Determine the distance from the first pole ear to the first end of the pole piece, and the distance from the last pole ear to the last end of the pole piece, and cut the first pole ear and the last pole ear; According to the difference in the distance between the two pole ears, the position of the pole ears at the odd or even position is first determined, and then the positions of the remaining pole ears are determined and cut, so that the pole ears after winding are centered and collected at one end of the single winding core, and are evenly distributed on both sides of the center line in the width direction of the single winding core; Preferably, the positive electrode tab cluster and the negative electrode tab cluster are symmetrically arranged along a center line in the length direction of the monomer winding core.

3. The preparation method according to claim 2, characterized in that: The calculation method of the distance between two adjacent pole ears includes: The number of the pole lugs is set to n, where n is an integer and n>2; The i-th pole ear is denoted as N i , i=2,3,···n, pole ear part N i The distance between the ear and the previous ear is S i-1 , set S i-1 The corresponding winding radius is R i-1 ; The difference between the distances between the two pole ears is S i -S i-2 =πd; Then S i =S i-1 +2t+π×(R i-2 -d); Among them, t is the distance between the first pole ear and the first fold after winding; L is the total length of the pole piece; d is the total thickness of the positive pole piece, the negative pole piece and the two layers of separator.

4. The preparation method according to claim 3, characterized in that: Set the distance S from the center line of the first pole ear N1 to the first end of the pole piece f , the final ear N n The distance from the center line to the end of the pole piece is S e ; but Preferably, S e ≥1 / 2L.

5. The preparation method according to any one of claims 1 to 4, characterized in that: The preparation method further comprises: hot pressing and shaping the monomer core.

6. The preparation method according to claim 5, characterized in that: The hot pressing shaping comprises: sequentially performing preheating treatment and hot pressing treatment on the single winding core; Preferably, the temperature of the preheating treatment is 80-100°C; Preferably, the preheating time is 15 to 25 minutes; Preferably, the temperature of the hot pressing treatment is 80-100°C; Preferably, the heat pressing treatment time is 45 to 90 seconds; Preferably, the pressure of the hot pressing treatment is 2.5-8T.

7. The preparation method according to claim 1, characterized in that: The core closing process includes: Performing a first welding on the monomer winding core, so that the positive electrode ear cluster and the negative electrode ear cluster are independently gathered toward the center line in the width direction of the monomer winding core, forming a positive electrode ear and a negative electrode ear respectively located at two ends of the monomer winding core; Provide two connecting pieces, weld and fix the positive pole ears of the two single winding cores on one connecting piece, and weld and fix the negative pole ears of the two single winding cores on the other connecting piece; The positive electrode ear and the negative electrode ear are bent respectively, and the two monomer winding cores are bonded and fixed to obtain the core package.

8. The preparation method according to claim 7, characterized in that: The final welding includes: laser welding the connecting piece and the cover plate assembly.

9. A square energy storage battery, characterized in that: The square energy storage battery is prepared by the preparation method according to any one of claims 1 to 8, and comprises a shell, a cover plate assembly and a core pack, wherein the cover plate assembly is buckled on the shell, the core pack is located in the shell, and the core pack is electrically connected to the cover plate assembly; The core package includes at least two single winding cores arranged side by side, and the single winding core is provided with a positive electrode ear and a negative electrode ear. The positive electrode ear and the negative electrode ear are respectively located at two ends of the single winding core and are arranged in the center in the width direction of the single winding core.

10. The square energy storage battery according to claim 9, characterized in that: The core package further includes a first connecting piece and a second connecting piece, the positive electrode ear of the single winding core is connected to the first connecting piece, the negative electrode ear of the single winding core is connected to the second connecting piece, and the first connecting piece and the second connecting piece are independently connected to the cover plate assembly.

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