A battery cell with a single-side structure and a method for preparing the same

Abstract

The present invention discloses a battery cell with a single-side edge structure, comprising a battery cell pole group (1); the outer surface of the battery cell pole group (1) is encapsulated with a battery cell aluminum-plastic shell (2); the battery cell aluminum-plastic shell (2) has only one side sealing edge parallel to the pole ear (3) of the battery cell pole group (1). In addition, the present invention also discloses a method for preparing a battery cell with a single-side edge structure. The battery cell with a single-side edge structure and the method for preparing the same disclosed by the present invention are scientifically designed, and by adopting an optimized single-side sealing structure, the energy density of the battery cell can be reliably improved, and have great production practice significance.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium ion soft-pack batteries, and in particular to a battery cell with a single-side structure and a preparation method thereof. Background Art

[0002] Lithium-ion batteries are green and environmentally friendly, with long cycle life, good rate performance, safety and reliability, and are widely used in various energy storage products, consumer electronics and power battery products. As a rapidly developing new energy industry, under fierce market competition, customers' requirements for the energy density of lithium-ion batteries are getting higher and higher.

[0003] At present, the common polymer soft-pack lithium-ion batteries on the market are mostly packaged in the form of a top seal and two side seals. Batteries with this structure are widely used in various electronic products. However, for batteries with longer lengths and thicker thicknesses, this structure has the following two shortcomings.

[0004] First, for the double-side structure battery cells with a longer length. Figure 1a , Figure 1b The schematic diagram of the structure of the double-sided sealed battery cell before and after folding is shown. Taking the single folded edge of the aluminum-plastic shell with a thickness of 115um as an example, after the single folding of the side seal, each side seal 20 occupies about 0.315mm-0.5mm in the width direction of the battery cell, and the double-sided structure occupies about 0.63mm-1mm in the width of the battery cell. The longer the battery cell, the larger the energy-inefficient space occupied by the double-sided structure of the battery cell. The battery cell with a double-sided structure has certain limitations in terms of energy density. If the battery has a double-sided structure with double folded edges, this limitation will be more significant.

[0005] Second, for thicker double-side structure batteries. Designers usually design the aluminum plastic shell of thicker batteries into a double pit structure (see Figure 2a , Figure 2b as well as Figure 3a , Figure 3b , Figure 3a The battery core aluminum-plastic shell 2 has two pits for accommodating two battery core electrode groups 1. Figure 3b The battery cell aluminum-plastic shell 2 has a pit for accommodating a battery cell electrode group 1, and the pit is a groove for accommodating the battery cell electrode group). For conventional double-sided structure batteries, the double pits on the battery cell aluminum-plastic shell are arranged along the length direction of the battery cell, and the position where the double pits are connected (i.e. the position between the double pits) is used to accommodate the bottom of the wrapped battery cell electrode group. The chamfer is generally around 1.2-1.5mm. As the thickness of the battery increases, the shell depth of the battery cell aluminum-plastic shell will increase, and the risk of shell cracking of the battery cell aluminum-plastic shell will also increase accordingly. In order to avoid shell cracking, thicker aluminum-plastic is usually used. However, the thicker the aluminum-plastic is, the smaller the energy density of the battery cell with the same outer size will be.

[0006] Therefore, there is an urgent need to develop a technology that can solve the shortcomings of the above conventional technologies, optimize and innovate the battery cell structure, and further improve the energy density of the battery cell. Summary of the invention

[0007] The purpose of the present invention is to provide a battery cell with a single-side structure and a preparation method thereof in view of the technical defects existing in the prior art.

[0008] To this end, the present invention provides a battery cell with a single-side structure, characterized in that it includes a battery cell electrode group;

[0009] The outer surface of the battery cell electrode group is encapsulated with a battery cell aluminum plastic shell;

[0010] The aluminum-plastic shell of the battery cell only has a side sealing edge parallel to the pole ear of the battery cell pole group;

[0011] Among them, the specific packaging structure used between the battery core aluminum plastic shell and the electrode group is as follows:

[0012] The first packaging structure: when there are two pole ears on the same side of the battery cell pole group, the battery cell aluminum-plastic shell includes a top seal, a bottom seal and a side seal parallel to the pole ears; wherein the top seal, the bottom seal and the side seal parallel to the pole ears on the battery cell aluminum-plastic shell are respectively used to package the side containing the pole ears, the side without the pole ears and a side portion parallel to the pole ears on the battery cell pole group;

[0013] Or the second packaging structure: when there is a pole ear on the front and rear sides of the battery cell pole group respectively, the battery cell aluminum-plastic shell includes two top seals and a side seal parallel to the pole ear; wherein the two top seals on the battery cell aluminum-plastic shell are respectively used to encapsulate the front and rear sides of the battery cell pole group containing the pole ears; the side seal on the battery cell aluminum-plastic shell is used to encapsulate a side edge portion of the battery cell pole group parallel to the pole ear.

[0014] Preferably, the cross-sectional shape of the battery cell electrode group is circular, arc-shaped, elliptical or rectangular.

[0015] Preferably, when the aluminum-plastic shell of the battery cell is a double-pit structure, the side sealing edge is folded toward one side of the deep hole or the shallow pit in the double pit.

[0016] In addition, the present invention also provides a method for preparing a battery cell with a single-side structure, comprising the following steps:

[0017] The first step is winding: the positive electrode, negative electrode and separator are wound around the winding needle in a spiral winding manner to form a battery cell group;

[0018] The second step is punching the shell: according to the design size of the battery cell pole group, determine the convex and concave die sizes of the shell punching die, and then complete the punching of the battery cell aluminum plastic shell on the fully automatic shell punching machine;

[0019] The third step is to package the electrode group into the shell: the battery cell electrode group is placed into the matching battery cell aluminum plastic shell, and the top, bottom or double top packaging is completed, and the protective paper is affixed to the packaged battery cell electrode group;

[0020] Step 4: Drying: Place the battery cell group after the protective paper is pasted in a drying box at a temperature of 90°C and an air pressure of less than -0.09MPa for 14 hours. When the battery moisture value is not higher than 150ppm, proceed to step 5.

[0021] Step 5: Liquid injection: In a liquid injection workshop where the ambient dew point temperature is less than -34.5°C, liquid is injected into the battery cell group;

[0022] Step 6: Hot pressing: After the battery cell electrode group with liquid injection is left to stand at a high temperature of 40°C for 24 hours, the battery cell electrode group is hot pressed and shaped at a temperature of 80°C to 110°C for 3 to 10 minutes, and then cold pressed at 25°C for 3 to 10 minutes.

[0023] Step 7: Formation: The battery cell groups are charged with small current step charging in sequence, with charging currents of 0.05C, 0.1C, and 0.2C, and charging times of 30min, 60min, and 90min, respectively.

[0024] Step 8: Final edge sealing: Use existing packaging equipment to perform final edge sealing on the battery cell electrode group;

[0025] The ninth step is folding edges and corners: first fold the side sealing edge on the aluminum-plastic shell of the battery cell, then fold the upper and lower side corners of the side sealing edge, and then fold the two side corners of the two top sealing edges in succession, or first fold the two side corners of a top sealing edge, then hot fold a bottom sealing edge, fold the two side corners of the bottom sealing edge, and finally hot iron the edge to finalize the shape to obtain a battery cell with a single-side structure.

[0026] Preferably, in the first step, the cross-sectional shape of the battery cell electrode group is circular, elliptical or rectangular.

[0027] Preferably, in the first step, the positive electrode ear and the negative electrode ear of the battery cell electrode group are in the same direction or in different directions.

[0028] It can be seen from the technical solution provided by the present invention that, compared with the prior art, the present invention provides a battery cell with a single-sided edge structure and a preparation method thereof, which is scientifically designed and can reliably improve the energy density of the battery cell by adopting an optimized single-sided edge sealing structure, and has great production practical significance. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1a This is a schematic diagram of the structure of a traditional soft-pack battery cell with double-sided sealing after the folding is completed;

[0030] Figure 1b This is a schematic diagram of the structure of a traditional soft-pack battery cell with double-sided sealing before folding;

[0031] Figure 2a This is a schematic diagram of the cross-sectional structure of a conventional double-side sealed battery cell with a traditional deep pit side folding, and two side seals after folding;

[0032] Figure 2b This is a schematic diagram of the cross-sectional structure of a conventional double-side sealed battery cell with a traditional deep pit side folding, and two side seals before folding;

[0033] Figure 3a It is a structural schematic diagram of a traditional double-sided battery shell (conventional battery cell shell), and the aluminum-plastic shell in the figure has a double-pit structure;

[0034] Figure 3b It is a structural schematic diagram of a traditional double-sided battery shell (conventional battery cell shell), and the aluminum-plastic shell in the figure is a single-pit structure;

[0035] Figure 4a A schematic diagram of the structure of a battery cell with a single-side edge structure provided by the present invention after the edge is folded;

[0036] Figure 4b A schematic diagram of the structure of a battery cell with a single-side structure provided by the present invention, when the tabs are on the same side and the aluminum-plastic shell of the battery cell is before folding;

[0037] Figure 4c A schematic diagram of the structure of a battery cell with a single-side structure provided by the present invention, when the tabs are on opposite sides and the aluminum-plastic shell of the battery cell is before folding;

[0038] Figure 5a A schematic diagram of the cross-sectional structure of a single side sealing edge after folding the shallow pit side of a battery cell with a single side edge structure provided by the present invention;

[0039] Figure 5b A schematic diagram of the cross-sectional structure of a single side sealing edge before folding the shallow pit side of a battery cell with a single side edge structure provided by the present invention;

[0040] Figure 6a A schematic diagram of the cross-sectional structure of a single side sealing edge after folding the deep pit side of a battery cell with a single side edge structure provided by the present invention;

[0041] Figure 6bA schematic diagram of the cross-sectional structure of a single side sealing edge before folding the deep pit side of a battery cell with a single side edge structure provided by the present invention;

[0042] Figure 7a A schematic diagram of the structure of a battery cell shell with a single-side structure provided by the present invention, wherein the battery cell aluminum-plastic shell in the figure has a double-pit structure;

[0043] Figure 7b A schematic diagram of the structure of a battery cell housing with a single-side structure provided by the present invention, wherein the battery cell aluminum-plastic housing in the figure is a single-pit structure;

[0044] Figure 8 A schematic diagram of the structure of a battery cell electrode group with a same-side electrode ear in a battery cell with a single-side structure provided by the present invention;

[0045] Fig. 9 A schematic diagram of the structure of a battery cell electrode group with a pole ear on the opposite side in a battery cell with a single-side structure provided by the invention;

[0046] In the figure: 1 is the battery cell pole group, 2 is the battery cell aluminum plastic, 20 is the side sealing edge, 21 is the top sealing edge, 22 is the bottom sealing edge; 3 is the pole ear. DETAILED DESCRIPTION

[0047] In order to enable those skilled in the art to better understand the scheme of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and implementation modes.

[0048] See also Figures 4a to 9 , the present invention provides a battery cell with a single-side structure, comprising a battery cell electrode group 1;

[0049] The outer surface of the battery cell electrode group 1 is encapsulated with a battery cell aluminum plastic shell 2;

[0050] The specific packaging structure used between the battery core aluminum plastic shell 2 and the electrode group 1 is as follows:

[0051] The first packaging structure: when there are two pole ears 3 (specifically including a positive pole ear and a negative pole ear) on the same side (for example, the front side or the rear side) of the battery cell electrode group 1, the battery cell aluminum-plastic shell 2 includes a top seal 21, a bottom seal 22, and a side seal 20 parallel to the pole ear 3; wherein the top seal 21, the bottom seal 22, and the side seal 20 parallel to the pole ear on the battery cell aluminum-plastic shell 2 are respectively used to package the side containing the pole ear 3, the side without the pole ear, and a side portion (i.e., the left side or the right side) parallel to the pole ear on the battery cell electrode group 1;

[0052] It should be noted that a conventional linear head or a special-shaped head can be used for packaging.

[0053] Or the second packaging structure: when the front and rear sides of the battery cell electrode group 1 each have a pole ear 3 (a positive pole ear or a negative pole ear), the battery cell aluminum-plastic shell 2 includes two top sealing edges 21 and a side sealing edge 20 parallel to the pole ear 3; wherein the two top sealing edges 21 on the battery cell aluminum-plastic shell 2 are respectively used to package the front and rear sides containing the pole ear 3 on the battery cell electrode group 1; the side sealing edge 20 on the battery cell aluminum-plastic shell 2 is used to package a side edge (i.e., the left side or the right side) on the battery cell electrode group 1 that is parallel to the pole ear.

[0054] It should be noted that both the first packaging structure and the second packaging structure only have one side sealing edge, that is, the battery cell aluminum-plastic shell 2 only has one side sealing edge structure parallel to the pole ear 3 of the battery cell pole group 1 .

[0055] That is to say, for the present invention, there are two packaging forms between the battery core aluminum plastic shell 2 and the battery core electrode group 1: when the positive and negative electrodes are led out on the same side, there is a top seal, a bottom seal and a side seal structure (such as Figure 4b When the positive and negative ears are led out from different sides, the battery core aluminum plastic shell has a double top seal and one side seal structure (as shown in Figure 4c shown).

[0056] Here, it should be noted that the package with a tab side is usually called a top seal, the package without a tab side and perpendicular to the top seal is usually called a side seal, and the package without a tab side and parallel to the top seal is usually called a bottom seal.

[0057] In the present invention, in a specific implementation, the cross-sectional shape of the battery cell electrode group 1 is circular, arc-shaped, elliptical or rectangular.

[0058] In the present invention, in a specific implementation, the positive electrode ear and the negative electrode ear of the battery cell electrode group 1 can be in the same direction or in different directions, such as Figure 8 , Fig. 9 shown.

[0059] In the present invention, in specific implementation, the battery core aluminum-plastic shell 2 can be a single-pit structure or a double-pit structure. Figure 7a , Figure 7b As shown, Figure 7a The battery core aluminum plastic shell 2 has two pits (i.e., grooves) for accommodating two battery core electrode groups 1. Figure 7b The battery core aluminum-plastic shell 2 has a pit for accommodating a battery core electrode group 1.

[0060] In the present invention, in a specific implementation, when the battery core aluminum-plastic shell 2 is a double-pit structure, the pit depths of the two pits of the battery core aluminum-plastic shell 2 can be the same depth or different depths.

[0061] In specific implementation, when the battery core aluminum-plastic shell 2 is a double-pit structure, the side sealing edge 20 can be folded toward one side of the deep hole or the shallow pit in the double pit.

[0062] For example, when the battery core aluminum-plastic shell 2 is a double-pit structure, if the pit depths of the two pits of the battery core aluminum-plastic shell 2 are different, the side seal 20 is folded toward the shallow pit with a shallower depth, and the folded edge of the side seal 20 does not exceed the depth of the shallow pit.

[0063] For example, when the battery cell aluminum-plastic shell 2 has a double-pit structure, if the pit depths of the two pits of the battery cell aluminum-plastic shell 2 are different, the side seal 20 can also be folded to the side of the deeper pit, and the folded edge of the side seal 20 does not exceed the depth of the deep pit.

[0064] In the present invention, in a specific implementation, when the battery cell aluminum-plastic shell 2 is a battery cell aluminum-plastic shell without pits, the side sealing edge 20 is folded toward the thickness direction of the battery cell electrode group 1 .

[0065] It should be noted that if the side sealing edge 20 of the battery cell aluminum-plastic shell 2 is folded in the thickness direction of the battery cell electrode group 1 on the non-pit side, the folded width portion is tightly attached to the thickness direction of the battery cell electrode group after folding.

[0066] It should be noted that, compared with the prior art, the battery cell with a single-side structure provided by the present invention has the following advantages:

[0067] First, the single-side edge structure that folds toward the deep pit side can improve the energy efficiency space of the battery cell. The present invention transfers one of the side seals of the double-side edge structure to the bottom side. After the bottom seal is folded and folded toward the deep pit side, the additional contribution of the sealing structure on the bottom side to the battery length is about 0.5mm (115um thick aluminum-plastic shell). For batteries with double-side edge structures of the same aluminum-plastic thickness, the additional contribution of each folded side of the single-side edge sealing structure to the width of the battery is 0.2mm (115um thick aluminum-plastic shell). Therefore, for existing batteries with double-folded edge structures (such as Figure 2a , Figure 2b As shown), when the aspect ratio of the battery is greater than 2.5 / 1.25, the lithium-ion soft-pack battery manufactured using the single-side sealing packaging structure provided by the present invention has greater advantages in energy utilization.

[0068] Second, the single-side structure with shallow pit side folding can further improve the energy efficiency space of the battery cell. In order to ensure the reliability of packaging, the width of the side of the battery cell is generally at least 2mm. For batteries with double pit punching depths greater than 2mm, when the side is folded toward the shallow pit side, the widest position of the battery cell pole group does not overlap with the folding edge. In this case, the folding edge does not contribute to the width of the battery. The battery cell space utilization rate of this structure is maximized, and the energy density is higher than that of the ordinary double-side structure of the same size.

[0069] Third, the battery cell with a single-sided structure of the present invention is more conducive to shell forming. The double pits of the conventional double-sided structure battery cell are arranged along the length direction of the battery cell, and the position where the double pits are connected is used to accommodate the bottom / top of the wrapped electrode group, and the chamfer is generally less than or equal to 1.5mm. The battery cell with a single-sided structure provided by the present invention has a double pit on the battery cell aluminum-plastic shell 2 arranged along the width direction of the battery cell electrode group 1, and the position where the double pits are connected is used to accommodate the side of the wrapped electrode group, and the chamfer is usually greater than 2mm. The battery cell with a single-sided structure of the present invention is more conducive to shell forming than the battery cell with a double-sided structure.

[0070] In order to prepare the battery cell with a single-sided structure provided by the present invention, the present invention also provides a method for preparing a battery cell with a single-sided structure, comprising the following steps:

[0071] The first step is winding: the positive electrode, negative electrode and separator are wound around the winding needle in a spiral winding manner to form a battery cell group;

[0072] The second step is punching the shell: according to the design size of the battery cell pole group, determine the size of the male and female dies of the shell punching die, and then complete the punching of the battery cell aluminum plastic shell 2 on the fully automatic shell punching machine;

[0073] The third step is to package the electrode group into the shell: the battery cell electrode group is placed into the matching battery cell aluminum-plastic shell 2, and the top, bottom or double top packaging is completed, and the packaged battery cell electrode group is affixed with protective paper;

[0074] Step 4: Drying: Place the battery cell group after the protective paper is pasted in a drying box at a temperature of 90°C and an air pressure of less than -0.09MPa for 14 hours. When the battery moisture value is not higher than 150ppm, proceed to step 5.

[0075] Step 5: Liquid injection: In a liquid injection workshop where the ambient dew point temperature is less than -34.5°C, liquid is injected into the battery cell group;

[0076] It should be noted that the existing conventional liquid injection process is: loading → scanning → weighing → shaping → blowing → liquid injection → vacuum holding (completed in three steps, namely: vacuum holding 1, vacuum holding 2, vacuum holding 3) → packaging → weighing → unloading.

[0077] Step 6: Hot pressing: After the battery cell electrode group with liquid injection is left to stand at a high temperature of 40°C for 24 hours, the battery cell electrode group is hot pressed and shaped at a temperature of 80°C to 110°C for 3 to 10 minutes, and then cold pressed at 25°C for 3 to 10 minutes.

[0078] The seventh step is formation: the battery cell electrode group is charged with small current step charging in sequence. The charging current is 0.05C, 0.1C, and 0.2C respectively, and the charging time is 30min, 60min, and 90min respectively.

[0079] Step 8: Final edge sealing: Use existing packaging equipment (such as fully automatic Degas equipment) to perform final edge sealing on the battery cell electrode group, specifically: set the packaging time parameter to 2 to 4 seconds at a packaging temperature of 165-185°C and a packaging pressure of 0.3-0.5Mpa;

[0080] The ninth step is folding the edges and corners: first fold the side sealing edge 20 on the battery cell aluminum-plastic shell 2, then fold the upper and lower side corners of the side sealing edge 20, and then fold the two side corners of the two top sealing edges 21 in succession, or first fold the two side corners of a top sealing edge 21, then hot fold a bottom sealing edge 22, and fold the two side corners of the bottom sealing edge 22 (i.e. corresponding to two different forms of single-sided packaging structures), and finally hot iron the edges to finalize the shape to obtain a battery cell with a single-sided structure.

[0081] In the first step, the cross-sectional shape of the battery cell electrode group is circular, elliptical or rectangular.

[0082] In the first step, the positive electrode ear and the negative electrode ear of the battery cell group can be in the same direction or in different directions.

[0083] In the third step, there are two packaging forms between the battery core aluminum plastic shell and the electrode group:

[0084] The first packaging form is: when the positive and negative tabs are led out on the same side of the battery cell electrode group, it is a top seal, a bottom seal and a side seal structure;

[0085] The second packaging form is: when the positive and negative pole ears are led out from different sides, the battery core aluminum-plastic shell is a double top-sealed and one-side-sealed structure.

[0086] Here, it should be noted that the package containing the tab is generally called the top seal, the package opposite to the tab side and without the tab is called the bottom seal, and the two side packages perpendicular to the top seal / bottom seal are called side seals.

[0087] It should be noted that both of the above-mentioned two packaging structures have a side seal. In order to ensure the reliability of packaging, the side seal of the battery cell is generally at least 2mm wide. For the battery cell when the double pit punching depth is greater than 2mm, there are two types of folding edges: folding toward the deep pit side and folding toward the shallow pit side. Preferably, when the side is folded toward the shallow pit side, the widest position of the battery cell electrode group does not overlap with the folded edge. In this case, the folding edge does not contribute to the width of the battery. The space utilization of the battery cell with this structure is maximized, and the energy density is higher than that of the ordinary double-side structure of the same size.

[0088] In the present invention, in specific implementation, the battery core aluminum-plastic shell 2 has the following advantages during molding:

[0089] Compared with the traditional double-sided battery cell shell, the punch radius of the deep pit at the junction of the deep and shallow pit / deep pit and the flat pit is generally designed to be less than or equal to 1.5mm, while the shell of the single-sided battery cell of the present invention, the punch radius of the deep pit at the junction of the deep and shallow pit / deep pit and the flat pit is generally designed to be greater than or equal to 2mm. The larger the radius, the more conducive to shell forming, and effectively solves the problem of light leakage when the shell is deep.

[0090] In addition, the core difference between the battery cell prepared according to the present invention and the traditional battery cell is that the battery cell has a larger energy efficiency space and a higher reliability in shell punching and molding.

[0091] In order to more clearly understand the technical solution of the present invention, the technical solution of the present invention is described below in conjunction with specific embodiments.

[0092] Example 1.

[0093] Take the polymer battery cell with single folded edge structure with the same side tab as an example:

[0094] The battery cell with a single folded edge structure provided by the present invention comprises an aluminum-plastic shell and a battery cell pole group. The battery cell has a side sealing edge structure which is parallel to the pole ear of the battery cell pole group.

[0095] The cross-sectional shapes of the battery cell pole group are circular, elliptical and rectangular.

[0096] In specific implementation, the positive and negative pole ears of the battery cell electrode group are led out in the same direction.

[0097] The packaging forms between the aluminum plastic shell of the battery cell and the pole group: a top seal, a bottom seal and a side seal structure. It should be noted that the package containing the pole ear is generally called the top seal, the package opposite to the pole ear side and without the pole ear is called the bottom seal, and the two side packages perpendicular to the top seal / bottom seal are called side seals.

[0098] In specific implementation, in order to ensure the reliability of packaging, the side sealing edge of the battery cell is generally at least 2mm wide. For the battery cells when the double pit punching depth is greater than 2mm, there are two types of folding: folding toward the deep pit side and folding toward the shallow pit side. Preferably, when the side is folded toward the shallow pit side, the widest position of the battery cell electrode group does not overlap with the folded edge. In this case, the folding edge does not contribute to the width of the battery. The space utilization of the battery cell with this structure is maximized, and the energy density is higher than that of the ordinary double-side structure of the same size.

[0099] In specific implementation, the aluminum-plastic shell of the battery cell has the following advantages during molding: compared with the shell of the traditional double-sided battery cell, the punch radius of the deep pit at the junction of the deep and shallow pit / deep pit and the flat pit is generally designed to be less than or equal to 1.5mm, while the shell of the single-sided battery cell of the present invention, the punch radius of the deep pit at the junction of the deep and shallow pit / deep pit and the flat pit is generally designed to be greater than or equal to 2mm. The larger the radius, the more conducive to the shell molding, which effectively solves the problem of light leakage when the shell is deep.

[0100] The core difference between the battery cell obtained according to the present invention and the traditional battery cell is that the battery cell has a larger energy efficiency space and a higher reliability in shell punching and molding.

[0101] The manufacturing process of the battery cell obtained according to the present invention includes:

[0102] The first step is winding: the positive electrode, the negative electrode and the separator are wound around a winding needle in a spiral manner to form an electrode group, as shown in FIG6 , and the electrode ears of the electrode group are in the same direction.

[0103] The second step is punching the shell: design the convex and concave die sizes of the shell punching mold according to the size of the pole group, and then complete the stamping of the shell on the fully automatic shell punching machine.

[0104] The third step is to package the electrode assembly into a shell: Place the electrode assembly into a matching shell and complete the top and bottom packaging, and stick protective paper on the packaged battery cell.

[0105] The fourth step is drying: the battery cell with protective paper needs to be placed in a drying box with a temperature of 90°C and an air pressure less than -0.09MPa for 14 hours. The battery moisture value is not higher than 150ppm before liquid injection can be carried out.

[0106] The fifth step, liquid injection: It needs to be carried out in a liquid injection workshop with an ambient dew point temperature less than -34.5℃. The liquid injection process is as follows: loading → scanning → weighing → shaping → blowing → liquid injection → vacuum holding (completed in 3 steps, namely: vacuum holding 1, vacuum holding 2, vacuum holding 3) → packaging → weighing → unloading.

[0107] Step 6: Hot pressing: After the battery cell is filled with liquid and left to stand at high temperature for 24 hours, it needs to be hot pressed and shaped at 80℃-110℃.

[0108] Step 7: Formation: Charge the battery with a small current.

[0109] Step 8: Final edge sealing: Use fully automatic Degas equipment to perform final edge sealing on the battery cell under set parameters.

[0110] Step 9: Fold the edges and corners.

[0111] Example 2.

[0112] Take the polymer battery cell with single folded edge structure with opposite side tabs as an example:

[0113] The battery cell with a single folded edge structure provided by the present invention comprises an aluminum-plastic shell and a battery cell pole group. The battery cell has a side sealing edge structure which is parallel to the pole ear of the battery cell pole group.

[0114] The cross-sectional shapes of the battery cell pole group are circular, elliptical and rectangular.

[0115] In specific implementation, the positive and negative pole ears of the battery cell electrode group are in different directions.

[0116] In specific implementation, the packaging form between the battery cell aluminum plastic shell and the battery cell electrode group: double top seal and one side seal structure. It should be noted that the package containing the pole ear is generally called the top seal, the package opposite to the pole ear side and without the pole ear is called the bottom seal, and the two side packages perpendicular to the top seal / bottom seal are called side seals.

[0117] In specific implementation, in order to ensure the reliability of packaging, the side sealing edge of the battery cell is generally at least 2mm wide. For the battery cells when the double pit punching depth is greater than 2mm, there are two types of folding: folding toward the deep pit side and folding toward the shallow pit side. Preferably, when the side is folded toward the shallow pit side, the widest position of the battery cell electrode group does not overlap with the folded edge. In this case, the folding edge does not contribute to the width of the battery. The space utilization of the battery cell with this structure is maximized, and the energy density is higher than that of the ordinary double-side structure of the same size.

[0118] In specific implementation, the aluminum-plastic shell of the battery cell has the following advantages during molding: compared with the shell of the traditional double-sided battery cell, the punch radius of the deep pit at the junction of the deep and shallow pit / deep pit and the flat pit is generally designed to be less than or equal to 1.5mm, while the shell of the single-sided battery cell of the present invention, the punch radius of the deep pit at the junction of the deep and shallow pit / deep pit and the flat pit is generally designed to be greater than or equal to 2mm. The larger the radius, the more conducive to the shell molding, which effectively solves the problem of light leakage when the shell is deep.

[0119] The core difference between the battery cell obtained according to the present invention and the traditional battery cell is that the battery cell has a larger energy efficiency space and a higher reliability in shell punching and molding.

[0120] The manufacturing process of the battery cell obtained according to the present invention includes:

[0121] The first step is winding: the positive electrode, the negative electrode and the separator are wound around a winding needle in a spiral manner to form an electrode group, as shown in FIG6 , and the electrode ears of the electrode group are in the same direction.

[0122] The second step is punching the shell: design the convex and concave die sizes of the shell punching mold according to the size of the pole group, and then complete the stamping of the shell on the fully automatic shell punching machine.

[0123] The third step is to package the electrode assembly into a shell: Place the electrode assembly into a matching shell and complete the top and bottom packaging, and stick protective paper on the packaged battery cell.

[0124] The fourth step is drying: the battery cell with protective paper needs to be placed in a drying box with a temperature of 90°C and an air pressure less than -0.09MPa for 14 hours. The battery moisture value is not higher than 150ppm before liquid injection can be carried out.

[0125] The fifth step, liquid injection: It needs to be carried out in a liquid injection workshop with an ambient dew point temperature less than -34.5℃. The liquid injection process is as follows: loading → scanning → weighing → shaping → blowing → liquid injection → vacuum holding (completed in 3 steps, namely: vacuum holding 1, vacuum holding 2, vacuum holding 3) → packaging → weighing → unloading.

[0126] Step 6: Hot pressing: After the battery cell is filled with liquid and left to stand at high temperature for 24 hours, it needs to be hot pressed and shaped at 80℃-120℃.

[0127] Step 7: Formation: Charge the battery with a small current.

[0128] Step 8: Final edge sealing: Use fully automatic Degas equipment to perform final edge sealing on the battery cell under set parameters.

[0129] Step 9: Fold the edges and corners.

[0130] Based on the above technical solutions, it can be known that the present invention discloses a new type of battery cell, which is intended to solve the shortcomings of conventional double-sided structure batteries in improving energy density and battery safety and reliability. One of the side seals of the double-sided structure is transferred to the bottom side, and after the bottom seal is folded at the corner, the additional contribution of the sealing structure on the bottom side to the length of the battery is about 0.5mm (115um thickness aluminum-plastic shell). For batteries with double-sided structures of the same aluminum-plastic thickness, the additional contribution of each folded side of the battery cell with a single-sided side sealing structure to the width of the battery is 0.2mm (115um thickness aluminum-plastic shell). Therefore, for batteries with a single-sided / double-sided folding structure, when the aspect ratio of the battery is greater than 2.5 / 1.25, the lithium-ion soft-pack battery made with a single-sided sealing packaging structure provided by the present invention has greater advantages in energy utilization.

[0131] In addition, when the battery cell is thicker and longer, the double-sided structure is more prone to shell cracking when punching the shell because the bottom transition fillet of the shell is smaller than the side transition fillet. In order to avoid shell cracking, thicker aluminum plastic is usually selected, but the thicker the aluminum plastic is, the lower the energy density of the battery cell with the same external size. Therefore, the battery cell with a single-sided structure provided by the present invention has greater advantages than the battery cell with a double-sided structure in terms of both energy density improvement and shell safety and reliability.

[0132] In summary, compared with the prior art, the present invention provides a battery cell with a single-sided edge structure and a preparation method thereof, which is scientifically designed and can reliably improve the energy density of the battery cell by adopting an optimized single-sided edge sealing structure, and has great production practice significance.

[0133] The above is only 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 principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A battery cell with a single-side structure, characterized in that: It comprises a battery cell electrode group (1); The outer surface of the battery cell electrode group (1) is encapsulated with a battery cell aluminum plastic shell (2); The battery cell aluminum-plastic shell (2) only has a side sealing edge which is parallel to the pole ear (3) of the battery cell pole group (1); The specific packaging structure adopted between the battery core aluminum-plastic shell (2) and the electrode group (1) is as follows: A first packaging structure: when the same side of the battery cell electrode group (1) has two pole ears (3), the battery cell aluminum-plastic shell (2) comprises a top sealing edge (21), a bottom sealing edge (22), and a side sealing edge (20) that is parallel to the pole ears (3); wherein the top sealing edge (21), the bottom sealing edge (22), and the side sealing edge (20) that is parallel to the pole ears on the battery cell aluminum-plastic shell (2) are respectively used to package a side of the battery cell electrode group (1) that contains the pole ears (3), a side that does not contain the pole ears, and a side portion that is parallel to the pole ears; Or a second packaging structure: when the front and rear sides of the battery cell electrode group (1) each have a pole ear (3), the battery cell aluminum-plastic shell (2) comprises two top sealing edges (21) and a side sealing edge (20) that is parallel to the pole ear (3); wherein the two top sealing edges (21) on the battery cell aluminum-plastic shell (2) are respectively used to package the front and rear sides of the battery cell electrode group (1) containing the pole ear (3); and the side sealing edge (20) on the battery cell aluminum-plastic shell (2) is used to package a side edge portion of the battery cell electrode group (1) that is parallel to the pole ear; When the battery core aluminum-plastic shell (2) is a double-pit structure, the side sealing edge (20) is folded toward the deep hole or the shallow pit in the double pit; The double-pit structure comprises two pits, each of which is used to accommodate one side of a battery cell electrode group (1); The double-pit structure on the battery cell aluminum-plastic shell (2) is arranged along the width direction of the battery cell electrode group (1), and the position where the double-pit is connected is used to accommodate the side of the battery cell electrode group (1); If the side sealing edge (20) is folded toward the shallow pit, the folded edge of the side sealing edge (20) does not exceed the depth of the shallow pit; if the side sealing edge (20) is folded toward the deep pit, the folded edge of the side sealing edge (20) does not exceed the depth of the deep pit.

2. The battery cell with a single-side structure as claimed in claim 1, characterized in that: The cross-sectional shape of the battery cell electrode group (1) is circular, arc-shaped, elliptical or rectangular.

3. A method for preparing a battery cell with a single-side structure as claimed in claim 1 or 2, characterized in that: The following steps are involved: first step , Winding: The positive electrode, negative electrode and separator are wound around the winding needle in a spiral winding manner to form a battery cell group; The second step is punching the shell: according to the design size of the battery cell electrode group, the convex and concave mold sizes of the shell punching mold are determined, and then the aluminum plastic shell (2) of the battery cell is punched and produced on a fully automatic shell punching machine; The third step is to package the electrode assembly into a shell: the electrode assembly of the battery cell is placed into a matching battery cell aluminum-plastic shell (2), and the top, bottom or double top packaging is completed, and protective paper is affixed to the packaged electrode assembly of the battery cell; Step 4: Drying: Place the battery cell group after the protective paper is pasted in a drying box at a temperature of 90°C and an air pressure of less than -0.09MPa for 14 hours. When the battery moisture value is not higher than 150ppm, proceed to step 5. Step 5: Liquid injection: In a liquid injection workshop where the ambient dew point temperature is less than -34.5°C, liquid is injected into the battery cell group; Step 6: Hot pressing: After the battery cell electrode group with liquid injection is left to stand at a high temperature of 40°C for 24 hours, the battery cell electrode group is hot pressed and shaped at a temperature of 80°C to 110°C for 3 to 10 minutes, and then cold pressed at 25°C for 3 to 10 minutes. Step 7: Formation: The battery cell groups are charged with small current step charging in sequence, with charging currents of 0.05C, 0.1C, and 0.2C, and charging times of 30min, 60min, and 90min, respectively. Step 8: Final edge sealing: Use existing packaging equipment to perform final edge sealing on the battery cell electrode group; The ninth step is folding the edges and corners: first fold the side sealing edge (20) on the battery cell aluminum-plastic shell (2), then fold the upper and lower side corners of the side sealing edge (20) by means of a hot corner folding device, and then fold the two side corners of the two top sealing edges (21) in sequence, or first fold the two side corners of a top sealing edge (21), then hot fold a bottom sealing edge, fold the two side corners of the bottom sealing edge, and finally hot iron the edge to finalize the shape to obtain a battery cell with a single side edge structure.

4. The preparation method according to claim 3, characterized in that: In the first step, the cross-sectional shape of the battery cell electrode group is circular, elliptical or rectangular.

5. The preparation method according to claim 3, characterized in that: In the first step, the positive and negative ears of the battery cell group are in the same direction or in different directions.

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