A lithium ion battery cell and method of making the same

Abstract

The application discloses a lithium ion cell and a manufacturing method thereof, and belongs to the technical field of lithium ion batteries. The lithium ion cell comprises a laminated core and a shell, the two ends of the laminated core are respectively provided with a negative electrode tab and a positive electrode tab, the positive electrode tab is connected with the shell, and the shell is provided with a plurality of grooves. Before the manufacturing of the laminated core is completed, the shell is in a plane structure. After the manufacturing of the laminated core is completed, the shell is bent along the grooves to form a shell body with one end being opened, and the laminated core is covered in the shell body of the shell. The end of the shell close to the negative electrode tab is connected with a negative electrode cover plate, and the negative electrode tab is connected with the negative electrode cover plate. The manufacturing method of the lithium ion cell comprises the following steps: fixing and clamping the shell on a laminated core table; manufacturing the laminated core, and welding the positive electrode tab of the laminated core with the shell; and bending the shell along the grooves to form a cavity structure, and welding a splicing gap. The application can simplify the manufacturing process of the cell, and solve the problem of difficulty in putting the cell into the shell.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium ion battery, in particular to a lithium ion battery cell and a manufacturing method thereof. BACKGROUND

[0002] With the further development of electronic digital products and the gradual popularization of new energy vehicles, lithium ion batteries are applied more and more widely due to their green environmental protection, high energy density, good cycle performance, no memory effect and other advantages. The control of the manufacturing cost and quality of lithium ion batteries has also attracted more and more attention.

[0003] The manufacturing process of traditional hard-shell lithium ion batteries mainly includes sheet making, assembling, liquid injection and formation, etc. The assembling process can be divided into tab pre-welding, tab main welding, film wrapping, glue sticking, peripheral welding and other processes. The structural parts of the battery cell mainly include the shell, the positive cover plate, the negative cover plate, the stop frame, the insulating film and the like. The complicated manufacturing process and the large number of structural parts lead to great difficulty in process control and high manufacturing cost. Therefore, it is necessary to simplify the structure and manufacturing process of the battery cell.

[0004] In the prior art, for example, a square power battery cell insulation protection structure is disclosed in Chinese Patent No. CN206497940U, which comprises a shell, a battery cell arranged in the shell, and a top cover for sealing the shell. The top surface, two large side surfaces and the bottom surface of the battery cell are insulated from the shell by an insulation protection sheet, and the two small side surfaces of the battery cell are insulated from the shell by an insulation tape. The two pole columns of the patent are connected to the adapter piece, and the adapter piece and the top cover electrode are connected by welding. The welding process is relatively complicated.

[0005] For another example, a lithium battery and a manufacturing method thereof are disclosed in Chinese Patent No. CN111403822A. The lithium battery comprises a shell, a battery cell and a sealing plate assembly. The shell comprises a base plate and a surrounding wall, and the surrounding wall and the base plate form a containing cavity for containing the battery cell. The end of the surrounding wall away from the base plate forms an opening communicating with the containing cavity. The sealing plate assembly seals the opening. The sealing plate assembly comprises a body, and a first connecting piece and a second connecting piece are arranged on the body. An expansion space is formed between the first connecting piece and the second connecting piece and on the side of the body close to the containing cavity. One of the first connecting piece and the second connecting piece is insulated from the body. The first connecting piece has a first connecting part extending to the space between the battery cell and the surrounding wall, and one tab of the battery cell is connected to the first connecting part. The second connecting piece has a second connecting part extending to the space between the battery cell and the surrounding wall, and the other tab of the battery cell is connected to the second connecting part. The shell of the patent is a containing cavity structure comprising a base plate and a surrounding wall. When facing the battery cell with a stacked core structure, there is a problem of difficulty in putting the battery cell into the shell due to the fluffy structure of the battery cell. SUMMARY

[0006] 1. Technical problem to be solved by the present application

[0007] In order to solve the problem that the electric core of the prior art is difficult to enter the electric core shell, the application provides a lithium ion electric core, which can simplify the manufacturing process of the electric core and solve the problem of the electric core entering the shell.

[0008] The application further provides a manufacturing method of the lithium ion electric core, which solves the problem of the traditional lithium ion electric core entering the shell and reduces the manufacturing cost of the electric core.

[0009] 2. Technical scheme

[0010] In order to achieve the above-mentioned purpose, the application provides a lithium ion electric core, which comprises a core and a shell, and the two ends of the core are respectively provided with a negative electrode tab and a positive electrode tab, the positive electrode tab is connected with the shell, and the shell is provided with a plurality of grooves; before the core is manufactured, the shell is a planar structure; after the core is manufactured, the shell is bent along the grooves to form a shell body with one end being open, and the core is covered in the shell body of the shell; the end of the shell close to the negative electrode tab is connected with a negative electrode cover plate, and the negative electrode tab is connected with the negative electrode cover plate.

[0011] Further, the shell is provided with a liquid injection hole located close to the positive electrode tab.

[0012] Further, the shell is provided with an explosion-proof valve.

[0013] Further, the core comprises a diaphragm, a negative electrode sheet and a positive electrode sheet, which are sequentially stacked in a Z-shaped sheet stacking mode, and the uppermost layer and the lowermost layer of the core are both diaphragms.

[0014] Further, the outer surface of the core is wrapped with an insulating film.

[0015] Further, the length of the insulating film is greater than the length of the core, and the width of the insulating film is greater than the circumference of the core.

[0016] Further, the free end of the insulating film is fixed by a fixing belt.

[0017] Further, the negative electrode cover plate is provided with a stop frame on the side facing the negative electrode tab.

[0018] The application further provides a manufacturing method of the lithium ion electric core, which is used for manufacturing the above-mentioned lithium ion electric core and comprises the following steps:

[0019] An explosion-proof valve is installed on the pre-prepared planar structure shell, and a liquid injection hole is reserved;

[0020] The shell is fixed and clamped on a sheet stacking table, the insulating film is laid on the shell and is pressed tightly;

[0021] The core is manufactured, and the positive electrode tab of the core is welded with the shell;

[0022] Bending the shell along the groove to form a cavity structure, and welding the splicing gap;

[0023] Welding the negative tab with the negative cover plate, and then welding the negative cover plate with the shell to seal the shell;

[0024] The assembled battery cell is subjected to baking, liquid injection, formation and film coating processes to complete the production and delivery.

[0025] Further, the step of making the core stack includes: making positive and negative tabs through slurry mixing, coating, roll cutting and die cutting;

[0026] The separator, negative electrode and positive electrode are stacked in the preset number of layers in the "Z" type tab stacking mode, and the uppermost layer and the lowermost layer are separators.

[0027] The core stack is wrapped with an insulating film and fixed with a fixing belt.

[0028] Further, in the step of welding the splicing gap, the core stack is first pressed tightly with a tool to ensure good welding seam connection, then pre-welding is performed, and finally full welding is performed.

[0029] 3. Beneficial effects

[0030] Compared with the prior art, the technical scheme provided by the present application has the following beneficial effects:

[0031] (1) The lithium ion battery cell of the present application has a flat shell structure, which is convenient for processing and storage and is not prone to deformation. The positive tab is connected with the shell, and there is no need for a positive cover plate, which reduces the welding process and reduces the manufacturing cost. The shell can be bent along the groove to cover the outer side of the core stack and the end face where the positive tab is located in the cavity formed by the shell bending. The shell is bent and formed after the core stack is completed, which better adapts to the specifications of the core stack and solves the problem of difficulty in inserting the traditional core stack structure into the shell. The positive tab is directly connected with the shell, which makes the shell have a positive potential and prevents electrochemical corrosion of the shell. The positive tab is directly connected with the shell, and the negative tab is separately connected with the negative cover plate, which omits the traditional positive cover plate and other components inside the positive cover plate. The length of the tab can be increased by 5-7mm under the same battery size, which greatly improves the capacity of the battery.

[0032] (2) The lithium ion battery cell of the present application has a liquid injection hole for conveniently injecting electrolyte into the battery cell, and a pressure relief valve that can prevent the explosion-proof membrane from being detached and broken when the battery temperature rises and the internal gas expands and the pressure increases to a certain extent, thereby preventing the battery from exploding and increasing the safety performance of the battery.

[0033] (3) The lithium ion cell of the present application, the stacked core is stacked by "Z" type laminated mode in sequence with the separator, negative electrode sheet and positive electrode sheet, the laminated structure has more uniform current density, excellent internal heat dissipation performance and more suitable for high power discharge. The uppermost layer and the lowermost layer of the stacked core are both the separator, avoiding the contact of the electrode sheet and the shell, which can play the role of insulation. The outer surface of the stacked core is wrapped with an insulating film, further increasing the insulation of the stacked core. The length of the insulating film is greater than the length of the stacked core, and the width of the insulating film is greater than the circumference of the stacked core, which can ensure that the insulating film completely wraps the stacked core, and the fixing belt fixes the free end of the insulating film, increasing the tightness of the insulating film wrapping. The stop frame mainly plays the role of insulating the negative electrode tab and the negative electrode cover plate.

[0034] (4) The manufacturing method of the lithium ion cell of the present application, the shell is fixed on the laminated table in advance, the in-situ welding of the shell and the positive electrode tab of the stacked core can be realized on the laminated table, simplifying the manufacturing process. Then the shell is bent along the groove, at this time the stacked core has been located on the shell, and the cavity structure formed by the bending of the shell can cover the stacked core. Compared with the traditional process of manufacturing the shell first and then putting the stacked core into the shell, the problem of difficult entry of the traditional lithium ion cell into the shell is solved, and the manufacturing cost of the cell is reduced. BRIEF DESCRIPTION OF DRAWINGS

[0035] In the drawings, the size and proportion do not represent the actual size and proportion of the product. The drawings are only illustrative, and some unnecessary elements or features are omitted for the sake of clarity.

[0036] Figure 1 is the structure schematic view of the stacked core and the planar shell of the embodiment of the present application;

[0037] Figure 2 is the structure schematic view of the shell after folding and welding, and the negative electrode tab and the negative electrode cover plate after welding of the embodiment of the present application;

[0038] Figure 3 is the structure schematic view of the shell and the negative electrode cover plate after welding of the embodiment of the present application.

[0039] Explanation of the reference numerals in the schematic view:

[0040] 1, stacked core; 101, negative electrode tab; 102, positive electrode tab; 103, insulating film; 104, fixing belt; 2, shell; 201, groove; 3, liquid injection hole; 4, explosion-proof valve; 5, negative electrode cover plate; 501, stop frame. DETAILED DESCRIPTION

[0041] For further understanding of the present application, the application will be described in detail with reference to the drawings and embodiments. The description herein is only based on the preferred embodiments of the present application, and other ways that can achieve the present application can be conceived by those skilled in the art based on the preferred embodiments, and the other ways also fall within the scope of the present application.

[0042] In the description of the present application, it should be noted that the terms "center", "middle", "upper", "lower", "left", "right", "inner", "outer", "top", "bottom", "side", "vertical", "liquid level" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application. In addition, the terms "first", "second", "third", "fourth", "fifth", "sixth" are only for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0043] Embodiments

[0044] Reference Figures 1-3 The present embodiment provides a lithium ion cell, which comprises a stacked core 1 and a shell 2. The shell 2 is a metal shell, which can be made of steel or aluminum material. The stacked core 1 is provided with a negative tab 101 and a positive tab 102 on both sides, respectively. The positive tab 102 is connected with the shell 2, without the need for a positive cover plate, reducing the welding process and reducing the manufacturing cost. Before the stacked core 1 is completed, the shell 2 is a flat structure, which is convenient for processing and storage and is not easy to deform. The shell 2 is provided with multiple grooves 201 and can be bent along the grooves 201. When the stacked core 1 is completed, the shell 2 is bent along the grooves 201 to form a shell with one end open. The outer side surface of the stacked core 1 and the end surface where the positive tab 102 is located can be covered in the shell formed by bending the shell 2. The shell 2 is bent and formed after the stacked core 1 is completed, which better adapts to the specifications of the stacked core 1. It should be noted that the structure of the stacked core 1 of the lithium battery is relatively fluffy. The traditional cell shell is a pre-fabricated cavity structure, which needs to be inserted into the shell. The stacked core 1 is difficult to enter the shell. The shell 2 in the present embodiment is a flat structure before the cell is assembled. After the stacked core 1 is completed on the shell 2, the flat structure of the shell 2 is bent to cover the outer surface of the stacked core 1, solving the problem of difficulty in inserting the traditional stacked core 1 structure into the lithium ion cell.

[0045] The shell 2 is connected with a negative cover plate 5 near one end of the negative tab 101, and the negative tab 101 is laser welded with the negative cover plate 5. Since the shell 2 is in direct contact with the internal electrolyte after assembly, the shell 2 is prone to electrochemical corrosion under low potential. The positive tab 102 is directly welded with the shell 2, so that the shell 2 has a positive potential, which can prevent the shell 2 from electrochemical corrosion. In order to avoid the possibility that the entire shell 2 has a positive potential and causes internal short circuit when the negative pole of the battery is in direct contact with the shell 2, the staff will wrap an insulating film on the outside of the shell 2 when the battery is offline, so as to avoid the problem of short circuit. In addition, the positive tab 102 is directly welded with the shell 2, and the negative tab 101 is connected with the negative cover plate 5 separately. Compared with the traditional lithium ion battery with a positive cover plate, the battery structure of the present embodiment can omit the positive cover plate structure, and also can omit the weak conductive plate structure on the positive cover plate, so that the length of the pole piece can be increased by 5-7mm under the same battery volume, which greatly improves the capacity of the battery. It should be noted that the side of the negative cover plate 5 facing the negative tab 101 is provided with a stop frame 501 made of plastic and integrated on the negative cover plate 5, so that the negative tab 101 is insulated from the shell 2.

[0046] In the present embodiment, referring to Figure 1 , the shell 2 is provided with a liquid injection hole 3 located near the positive tab 102, which facilitates the injection of electrolyte into the inside of the battery. The shell 2 is provided with an explosion-proof valve 4, which can prevent the battery from exploding and increase the safety performance of the battery when the internal gas of the battery expands and the pressure increases to a certain extent, causing the explosion-proof membrane to be detached and broken, and the gas to be released and pressure relieved.

[0047] It should be noted that the stacked core 1 includes a separator, a negative pole piece and a positive pole piece, which are stacked in a "Z" type stacking manner. The stacked core structure has more uniform current density, excellent internal heat dissipation performance and more suitable for high-power discharge. The uppermost layer and the lowermost layer of the stacked core 1 are both separators, which can avoid the contact between the pole piece and the shell 2 and play an insulating role.

[0048] Referring to Figure 1The outer surface of the core 1 is wrapped with an insulating film 103, further increasing the insulation of the core 1. In the embodiment, the length of the insulating film 103 is greater than the length of the core 1, and the width of the insulating film 103 is greater than the circumference of the core 1, so that the insulating film 103 can completely wrap the body of the core 1. Specifically, the length of the insulating film 103 exceeds the body of the core 1 by 2-5 mm, and the width of the insulating film 103 exceeds the circumference of the core 1 by 5-10 mm. The length and width can be determined according to the size of the core 1. The insulating film 103 is preferably made of heat-resistant material. In order to increase the tightness of the wrapping of the insulating film 103, the free end of the insulating film 103 is fixed by a fixing tape 104. The fixing tape 104 used here is a high-temperature adhesive tape, which is made of PET or polyimide. The width of the high-temperature adhesive tape is 25-35 mm, and the length is 30-50 mm. The length and width can also be determined according to the size and position of the core 1 and the insulating film 103.

[0049] A second object of the embodiment is to provide a manufacturing method of a lithium ion cell, which performs welding of the shell 2 and the positive tab 102 in situ on the lamination table, simplifying the manufacturing process. The manufacturing method scheme is as follows:

[0050] The shell 2 has an integrated prefabricated planar structure, and is made of steel or aluminum. The shell 2 is pre-installed with an explosion-proof valve 4 and has a reserved liquid injection hole 3. The cell manufacturing steps include:

[0051] Step one: complete the production of positive and negative plates through slurry mixing, coating, roll pressing, and die cutting. In the embodiment, the size of the positive plate is 200 mm*100 mm, the size of the negative plate is 202 mm*102 mm, the size of the positive tab (102) is 40 mm*20 mm, and the size of the negative tab (101) is 40 mm*30 mm.

[0052] Step two: pre-position the shell 2 at the fixed position of the lamination table and clamp it tightly. An insulating film 103 is placed above the shell 2 and pressed tightly.

[0053] Step three: use the "Z" type lamination method to stack the separator, negative electrode, and positive electrode in sequence to the preset number of layers. The uppermost layer and the lowermost layer are separators. The size of the separator is 205*103 mm.

[0054] Step four: wrap the core 1 with a heat-resistant insulating film 103 and fix it with a high-temperature adhesive tape. Then, directly weld the positive tab 102 with the shell 2 by ultrasonic welding.

[0055] Step five: bend the shell 2 along the groove 201 to form a rectangular structure. Use laser welding technology to weld the shell 2 into a sealed whole structure.

[0056] Step six: weld the negative tab 101 with the negative cover plate 5, and then seal the negative cover plate 5 with the shell 2 by laser welding.

[0057] Step seven: the assembled battery cell is baked, injected, formed, and coated to be ready for delivery.

[0058] It should be noted that the shell 2 is a flat structure before assembly, and the thickness of the shell 2 is too small to affect the strength and processing performance, and the thickness is too large to occupy more volume and weight of the battery cell, affecting the energy density of the battery cell. The thickness of the shell 2 is designed to be 0.3-1mm, which is a more appropriate range. The shell 2 is reserved with a liquid injection hole 3, and the hole diameter of the liquid injection hole 3 is too small to affect the exhaust and injection in the process, and the hole diameter is too large to be not conducive to sealing welding. The hole diameter is designed to be 1-2mm. The metal shell 2 has a groove 201 at the bending part, the depth of the groove 201 is 10%-30% of the thickness of the shell 2, and the width of the groove 201 is 2 times the thickness of the shell 2. The size parameters of the groove 201 are within the above range, which can ensure the strength after bending on the one hand, and on the other hand, the difficulty of bending is considered, and the design is easier to bend. Laser welding, first use the tool to press the stacked core 1 tightly to ensure good connection at the weld, then pre-point welding, and finally full welding. This welding method can facilitate the positioning of the shell 2 after bending, making it easier to form a cavity structure. In addition, the welding slag is a common problem in the current aluminum shell battery, and we will have dust removal facilities during welding, such as positive / negative pressure dust removal facilities, and the bare battery is also provided with an insulating film 103 to avoid the welding slag directly contacting the stacked core 1, ensuring the reliability of the quality of the stacked core 1.

[0059] The above describes the present application and its embodiments in a schematic manner, which is not limited, and the drawings shown are only one of the embodiments of the present application, and the actual structure is not limited thereto. Therefore, if a person skilled in the art is inspired thereby, without departing from the spirit of the present application, similar structural methods and embodiments can be designed without creativity, which shall belong to the protection scope of the present application.

Claims

1. A lithium ion battery cell comprising a core stack (1) and a housing (2), both ends of the core stack (1) are respectively provided with a negative electrode tab (101) and a positive electrode tab (102), characterized in that, The positive tab (102) is connected with the shell (2), the shell (2) is provided with a plurality of grooves (201); before the production of the core (1) is completed, the shell (2) is a plane structure; when the core (1) is produced on the shell (2) and completed, the positive tab (102) of the core (1) is welded with the shell (2), the shell (2) is bent along the groove (201) to form a shell with one end opening, and the core (1) is covered in the shell of the shell (2); the shell (2) is connected with the negative cover plate (5) at one end close to the negative tab (101), and the negative tab (101) is connected with the negative cover plate (5).

2. The lithium-ion cell of claim 1, wherein, The shell (2) is provided with a liquid injection hole (3) close to the positive tab (102).

3. The lithium-ion cell of claim 1, wherein, The shell (2) is provided with an explosion-proof valve (4).

4. The lithium-ion electric cell of claim 1, wherein, The core (1) comprises a diaphragm, a negative tab and a positive tab, which are stacked in a "Z" type in sequence, and the uppermost layer and the lowermost layer of the core (1) are diaphragms.

5. The lithium-ion electric cell of claim 4, wherein, The outer surface of the core (1) is wrapped with an insulating film (103).

6. The lithium-ion electric cell of claim 5, wherein, The length of the insulating film (103) is greater than the length of the core (1), and the width of the insulating film (103) is greater than the circumference of the core (1).

7. The lithium-ion electric cell of claim 6, wherein, The free end of the insulating film (103) is fixed by a fixing belt (104).

8. The lithium-ion battery cell of claim 1, wherein, The negative cover plate (5) is provided with a stop frame (501) on the side facing the negative tab (101).

9. A method of making a lithium-ion cell, comprising: A method for producing the lithium ion core as claimed in any one of claims 1-8 comprises the following steps: An explosion-proof valve (4) is installed on the pre-prepared plane structure shell (2), and a liquid injection hole (3) is reserved; The shell (2) is fixed and clamped on the laminated core table, and the insulating film (103) is laid on the shell (2) and pressed tightly; The core (1) is produced, and the positive tab (102) of the core (1) is welded with the shell (2); The shell (2) is bent along the groove (201) to form a cavity structure, and the splicing gap is welded; The negative tab (101) is welded with the negative cover plate (5), and then the negative cover plate (5) is welded with the shell (2) to seal the shell (2); The assembled core is subjected to baking, liquid injection, formation and film coating processes to complete production and go offline.

10. The method of claim 9, wherein the step of forming the lithium ion battery cell further comprises the step of: The step of producing the core (1) comprises the following steps: slurry mixing, coating, roll cutting and die cutting to produce positive and negative tabs; ​ The diaphragm, negative tab and positive tab are stacked in a "Z" type to a predetermined number of layers, and the uppermost layer and the lowermost layer are diaphragms; The core (1) is wrapped with an insulating film (103), and fixed with a fixing belt (104).

11. The method of claim 9, wherein the step of forming the lithium ion battery cell further comprises the step of: In the step of welding the splicing gap, the core (1) is pressed tightly with a tool to ensure good connection of the welding seam, then pre-welding is performed, and finally full welding is performed. ​

Images