Cylindrical battery and method for manufacturing cylindrical battery

Abstract

The application relates to the technical field of batteries, and discloses a cylindrical battery and a preparation method of the cylindrical battery. The cylindrical battery comprises a first cylindrical battery cell and a second cylindrical battery cell. The first cylindrical battery cell comprises a first battery cell main body, a first tab and a second tab. The first tab and the second tab with opposite polarities extend from opposite ends of the first battery cell main body along a first direction and a second direction respectively. The first battery cell main body comprises a first center hole. The second cylindrical battery cell comprises a second battery cell main body, a third tab and a fourth tab. The third tab and the fourth tab with opposite polarities extend from opposite ends of the second battery cell main body along the first direction and the second direction respectively. The second battery cell main body comprises a second center hole, and the second cylindrical battery cell is arranged in the first center hole. The first tab and the third tab with opposite polarities are connected, so that the first cylindrical battery cell and the second cylindrical battery cell are connected in series, and the voltage of the cylindrical battery is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of battery, in particular to a cylindrical battery and a preparation method of the cylindrical battery. BACKGROUND

[0002] In the related art, since the voltage of a single cylindrical battery is low, when multiple cylindrical batteries are grouped, a large number of cylindrical batteries need to be connected in series to meet the voltage requirement of the battery group. SUMMARY

[0003] The present application provides a cylindrical battery and a preparation method of the cylindrical battery, which improves the voltage of the cylindrical battery.

[0004] According to a first aspect of the present application, a cylindrical battery is provided, the cylindrical battery comprising:

[0005] a first cylindrical battery cell comprising a first cell body, a first tab and a second tab, the first tab and the second tab being opposite in polarity and extending from opposite ends of the first cell body along a first direction and a second direction respectively, the first cell body comprising a first central hole;

[0006] a second cylindrical battery cell comprising a second cell body, a third tab and a fourth tab, the third tab and the fourth tab being opposite in polarity and extending from opposite ends of the second cell body along the first direction and the second direction respectively, the second cell body comprising a second central hole, the second cylindrical battery cell being arranged in the first central hole;

[0007] wherein the first tab and the third tab are connected to make the first cylindrical battery cell and the second cylindrical battery cell connected in series.

[0008] According to a second aspect of the present application, a preparation method of a cylindrical battery is provided, the preparation method comprising:

[0009] providing a first cylindrical battery cell comprising a first cell body, a first tab and a second tab, the first tab and the second tab being opposite in polarity and extending from opposite ends of the first cell body along a first direction and a second direction respectively, the first cell body comprising a first central hole;

[0010] providing a second cylindrical battery cell comprising a second cell body, a third tab and a fourth tab, the third tab and the fourth tab being opposite in polarity and extending from opposite ends of the second cell body along the first direction and the second direction respectively, the second cell body comprising a second central hole;

[0011] The second cylindrical cell is inserted into the first center hole of the first cylindrical cell, and the first tab and the third tab with opposite polarities are connected to make the first cylindrical cell and the second cylindrical cell series connected.

[0012] The cylindrical battery provided by the application comprises a first cylindrical cell and a second cylindrical cell, the first cylindrical cell and the second cylindrical cell are sleeved to form a cell, the first cylindrical cell and the second cylindrical cell are located at the same end and the tabs with opposite polarities are connected to make the first cylindrical cell and the second cylindrical cell series connected, the tabs with opposite polarities can be connected in a rubbing flat manner, the production efficiency is high, and the fault tolerance is high; the other pair of tabs with opposite polarities of the first cylindrical cell and the second cylindrical cell are located at the same end, the positive tab and the negative tab are distinct in area, the current density is uniform, and the internal insulation is facilitated; meanwhile, alignment is not required, the requirements for die cutting and winding are reduced, the process difficulty is reduced, and the product yield is improved; in addition, the requirement for the thickness consistency of the pole piece is low, the pole piece does not need to be die cut, in addition, the first cylindrical cell and the second cylindrical cell are separately arranged, and the gap therebetween can provide more expansion space for the cell; meanwhile, after the first cylindrical cell and the second cylindrical cell of the cylindrical battery are series connected, the voltage of the cylindrical battery is equivalent to being doubled. When a plurality of cylindrical batteries are grouped, the voltage requirement of the battery pack is high, the number of cylindrical batteries can be reduced, by relatively reducing the number of cylindrical batteries, the number of structural members such as a shell and a conductive row which do not provide energy density can be reduced, so that the energy density of the battery pack can be improved. BRIEF DESCRIPTION OF DRAWINGS

[0013] For better understanding of the present disclosure, reference can be made to the embodiments shown in the following drawings. The components in the drawings are not necessarily to scale, and related elements can be omitted in order to emphasize and clearly illustrate the technical features of the present disclosure. In addition, related elements or components can have different settings as known in the art. Furthermore, in the drawings, the same reference numerals represent the same or similar components throughout the drawings. Among them:

[0014] Figure 1 is a structural schematic diagram of a cylindrical battery according to an exemplary embodiment;

[0015] Figure 2 is a structural schematic diagram of a cell according to an exemplary embodiment;

[0016] Figure 3 is a top view of a cell according to an exemplary embodiment;

[0017] Figure 4 is a top view of a cell after being put into a shell according to an exemplary embodiment;

[0018] Figure 5This is a top view of a battery cell according to another exemplary embodiment;

[0019] Figure 6 This is a top view of a battery cell after it has been installed in a casing, according to another exemplary embodiment;

[0020] Figure 7 This is a flowchart illustrating a method for preparing a cylindrical battery according to an exemplary embodiment.

[0021] The annotations in the attached figures are explained as follows:

[0022] 10. Cylindrical battery;

[0023] 100. Battery cell; 110. First cylindrical battery cell; 111. First center hole; 120. Second cylindrical battery cell; 121. Second center hole; 130. Third cylindrical battery cell; 131. Third center hole; 140. Fourth cylindrical battery cell; 141. Fourth center hole;

[0024] 200. Battery casing; 210. Storage space. Detailed Implementation

[0025] The technical solutions in the exemplary embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. The exemplary embodiments described herein are for illustrative purposes only and are not intended to limit the scope of protection of this disclosure. Therefore, it should be understood that various modifications and changes can be made to the exemplary embodiments without departing from the scope of protection of this disclosure.

[0026] In the description of this disclosure, unless otherwise expressly specified and limited, the terms “first” and “second” are used for descriptive purposes only and should not be construed as indicating or implying relative importance; the term “multiple” refers to two or more; and the term “and / or” includes any and all combinations of one or more associated listed items. In particular, references to “the / described” object or “a” object are also intended to indicate one of a possible plurality of such objects.

[0027] Unless otherwise specified or stated, the terms "connection," "fixed," etc., should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, an integral connection, an electrical connection, or a signal connection; "connection" can be a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this disclosure according to the specific circumstances.

[0028] Furthermore, it should be understood that the directional terms such as "upper," "lower," "inner," and "outer" described in the exemplary embodiments of this disclosure are used to describe the angles shown in the accompanying drawings and should not be construed as limiting the exemplary embodiments of this disclosure. It should also be understood that, in the context of a reference to an element or feature being connected to another element (one or more) "upper," "lower," "inner," or "outer," it can be directly connected to the other element (one or more) "upper," "lower," "inner," or "outer," or indirectly connected to the other element (one or more) "upper," "lower," "inner," or "outer" through an intermediate element.

[0029] The embodiments of this disclosure first provide a cylindrical battery, such as Figures 1-4 As shown, the cylindrical battery 10 includes: a first cylindrical cell 110 and a second cylindrical cell 120. The first cylindrical cell 110 includes a first cell body, a first tab, and a second tab. The first tab and the second tab with opposite polarities extend from opposite ends of the first cell body along a first direction and a second direction, respectively. The first cell body includes a first central hole 111. The second cylindrical cell 120 includes a second cell body, a third tab, and a fourth tab. The third tab and the fourth tab with opposite polarities extend from opposite ends of the second cell body along a first direction and a second direction, respectively. The second cell body includes a second central hole 121. The second cylindrical cell 120 passes through the first central hole 111. The first tab and the third tab with opposite polarities are connected to form a series connection between the first cylindrical cell 110 and the second cylindrical cell 120.

[0030] The cylindrical battery 10 disclosed herein includes a first cylindrical cell 110 and a second cylindrical cell 120. The first cylindrical cell 110 and the second cylindrical cell 120 are sleeved to form a cell 100. The first cylindrical cell 110 and the second cylindrical cell 120 are connected with tabs of opposite polarity at the same end, so that the first cylindrical cell 110 and the second cylindrical cell 120 are connected in series. The tabs of opposite polarity can be connected by flattening, resulting in high production efficiency and high fault tolerance. The first cylindrical cell 110 and the second cylindrical cell 120 are connected in series. The second cylindrical cell 120 has another pair of tabs with opposite polarities located at the same end, with clear distinction between the positive and negative tab areas, uniform current density, and convenient internal insulation. At the same time, no alignment is required, which reduces the requirements for die-cutting and winding, reduces the process difficulty, and improves the product yield. In addition, the requirements for the consistency of electrode thickness are lower, and electrode die-cutting is not required. Furthermore, the first cylindrical cell 110 and the second cylindrical cell 120 are set separately, and the gap between them can provide more expansion space for the cell 100.

[0031] Meanwhile, when the first cylindrical cell 110 and the second cylindrical cell 120 of the cylindrical battery 10 are connected in series, the voltage of the cylindrical battery 10 is effectively doubled. When multiple cylindrical batteries 10 are grouped together, if the voltage requirement of the battery pack is high (e.g., 800V), the number of cylindrical batteries 10 can be reduced. By relatively reducing the number of cylindrical batteries 10, the number of structural components that do not provide energy density, such as the casing and conductive busbars, can be reduced, thereby increasing the energy density of the battery pack.

[0032] In the embodiments of this application, the second cylindrical cell 120 and the first cylindrical cell 110 have a height difference, which reduces the risk of short circuits due to the opposite polarity of the electrodes of the second cylindrical cell 120 and the first cylindrical cell 110, facilitates the setting of internal insulation, and makes the internal insulation more reliable.

[0033] The second electrode tab has a height difference between the end of the second electrode tab furthest from the first cell body and the end of the fourth electrode tab furthest from the second cell body; the fourth electrode tab is positioned higher than the second electrode tab. By making the fourth electrode tab of the second cylindrical cell 120 higher than the second electrode tab of the first cylindrical cell 110, insulation between the second electrode tab and the fourth electrode tab is facilitated.

[0034] The fourth tab can be the positive tab, and the second tab can be the negative tab. The fourth tab can be connected to the positive terminal at the top of the casing, while the casing can be connected to the negative tab or not. Due to the height difference between the positive terminal and the second tab, short circuits between them are less likely to occur.

[0035] In this design, the end of the first electrode tab furthest from the first cell body is flush with the end of the third electrode tab furthest from the second cell body. By aligning the ends of the first and third electrodes furthest from the first and second cell bodies, a flattening method can be used to connect the first and third electrodes with opposite polarities, resulting in high production efficiency and high fault tolerance. Of course, the ends of the first and third electrodes furthest from the first and second cell bodies can also have a small height difference, and this disclosure does not impose any limitations on this.

[0036] In the embodiments of this application, the expansion coefficient of the first cylindrical cell 110 is smaller than that of the second cylindrical cell 120. By making the expansion coefficient of the first cylindrical cell 110 smaller than that of the second cylindrical cell 120, the expansion force generated by the outer electrode of the cell 100 is smaller, making the outer structure of the cell 100 stable and able to assist the battery casing 200 in providing a binding effect on the inner layer of the cell 100.

[0037] It should be noted that the main body of the battery cell has positive and negative electrode plates stacked on top of each other, as well as a separator plate disposed between the positive and negative electrode plates. The positive and negative electrode plates and the separator plate disposed between the positive and negative electrode plates are wound together to form a wound battery cell. The positive electrode tab of the cylindrical battery cell is connected to the positive electrode plate, and the negative electrode tab is connected to the negative electrode plate.

[0038] The coefficient of expansion of a cylindrical cell is calculated as the negative electrode thickness at 100% SOC / the negative electrode thickness at 0% SOC. 100% SOC (State of Charge) indicates that the cell is fully charged, while 0% SOC indicates that the cell is fully discharged.

[0039] Wherein, the thickness of the negative electrode at 100% SOC = the thickness of the negative electrode (1+100% SOC negative electrode coating expansion rate), negative electrode thickness at 0% SOC = negative electrode thickness (1+0% SOC negative electrode coating expansion rate).

[0040] Among them, the first cylindrical cell 110 is the first silicon-based cell, and the second cylindrical cell 120 is the second silicon-based cell.

[0041] In this process, the silicon content of the active material in the first silicon-based battery cell is less than that in the second silicon-based battery cell. By making the silicon content of the active material in the first silicon-based battery cell less than that in the second silicon-based battery cell, the coefficient of thermal expansion of the first silicon-based battery cell is less than that of the second silicon-based battery cell. This stabilizes the outer layer structure of the battery cell 100 and helps the battery casing to provide a binding effect on the inner layer of the battery cell 100.

[0042] In the embodiments of this application, there is a gap between the first cell body and the second cell body, that is, there is a gap between the first silicon-based cell and the second silicon-based cell. By creating a gap between the first silicon-based cell and the second silicon-based cell, a cell expansion space is formed in the second central hole 121 of the second silicon-based cell. At the same time, the gap between the first silicon-based cell and the second silicon-based cell forms a cell expansion space, making the stress on the inner and outer electrode sheets relatively uniform. This reduces the pressure on the intermediate layer of the cell 100, avoiding problems such as collapse and lithium plating caused by uneven stress on the intermediate layer electrode sheets of the cell 100, and improving the performance of the cylindrical battery 10.

[0043] The gap between the second silicon-based cell and the first silicon-based cell is 0.1mm to 2mm, for example, 0.1mm, 0.2mm, 0.5mm, 0.7mm, 1mm, 1.2mm, 1.5mm, 1.7mm, 2.0mm, etc., which will not be listed here. By making the gap between the second silicon-based cell and the first silicon-based cell 0.1mm to 2mm, sufficient cell expansion space is ensured between the first and second silicon-based cells, and the energy density of the cell 100 is also guaranteed. Of course, the gap between the second silicon-based cell and the first silicon-based cell can also be greater than 2mm or less than 0.1mm, as long as a certain cell expansion space is formed, and this disclosure does not impose any restrictions on this.

[0044] In the radial direction of the cell 100, the gap distance between the second silicon-based cell and the first silicon-based cell may be the same or different, and the second silicon-based cell and the first silicon-based cell may be set with equal gaps or non-equal gaps.

[0045] Wherein, at any height in the axial direction of the cell 100, the gap between the second silicon-based cell and the first silicon-based cell in the radial direction of the cell 100 is equal, so as to ensure that the cell expansion space formed by the gap between the second silicon-based cell and the first silicon-based cell at any height in the axial direction of the cell 100 is the same, further ensuring the effect of reducing the pressure of the intermediate layer of the cell 100.

[0046] The first silicon-based battery cell can be a battery cell of equal diameter, and the first central hole 111 formed therein can be a through hole of equal diameter; the second silicon-based battery cell can be a battery cell of equal diameter, and the second central hole 121 formed therein can be a through hole of equal diameter.

[0047] It should be noted that the gap between the first silicon-based battery cell and the second silicon-based battery cell is 0.1mm to 2mm. The first silicon-based battery cell and the second silicon-based battery cell can be fixed by the battery casing, thereby ensuring that the gap between the first silicon-based battery cell and the second silicon-based battery cell is 0.1mm to 2mm. Alternatively, the first silicon-based battery cell and the second silicon-based battery cell can be fixed by an electrical adapter structure connected to them. Alternatively, there can be a buffer structure between the first silicon-based battery cell and the second silicon-based battery cell, thereby limiting the position of the first silicon-based battery cell and the second silicon-based battery cell, while ensuring that there is a gap between the first silicon-based battery cell and the second silicon-based battery cell.

[0048] The buffer structure has a certain degree of elasticity to absorb expansion force and avoid hindering the expansion of the battery cell. In addition, the buffer structure is made of a material that is resistant to electrolyte corrosion and has a certain liquid absorption capacity to store electrolyte.

[0049] In the embodiments of this application, such as Figure 4As shown, the cylindrical battery 10 also includes a battery casing 200, which is also cylindrical and matches the cylindrical battery 10. The first cylindrical cell 110 and the second cylindrical cell 120 are disposed within the receiving space 210 of the battery casing 200.

[0050] There is a gap between the circumferential outer surface of the first cylindrical cell 110 and the battery casing 200. After the first cylindrical cell 110 and the second cylindrical cell 120 are fitted together to form a cell 100 and disposed in the battery housing 200, there is a gap between the circumferential outer surface of the cell 100 and the battery housing 200. Thus, a first expansion space of the cell 100 is formed through the second central hole 121 of the second cylindrical cell 120. A second expansion space of the cell 100 is formed through the gap between the first cylindrical cell 110 and the second cylindrical cell 120. Furthermore, a third expansion space of the cell 100 is formed through the gap between the circumferential outer surface of the first cylindrical cell 110 and the inner wall of the battery housing 200. The expansion of the electrode plates of the cell 100 is absorbed by the three expansion spaces, so that the stress on the inner and outer electrode plates of the cell 100 is more uniform, avoiding excessive pressure on the middle layer electrode plates. At the same time, it avoids the large expansion force of the outer layer from acting directly on the inner wall of the battery housing 200, which could lead to the battery housing 200 cracking and electrode tearing, thus improving the performance of the battery.

[0051] The gap between the outer circumferential surface of the first cylindrical cell 110 and the battery casing 200 is 0.1mm to 2mm, for example, 0.1mm, 0.2mm, 0.5mm, 0.7mm, 1mm, 1.2mm, 1.5mm, 1.7mm, 2.0mm, etc., which will not be listed here. By maintaining a gap of 0.1mm to 2mm between the outer circumferential surface of the first cylindrical cell 110 and the battery casing 200, sufficient cell expansion space is ensured between the first cylindrical cell 110 and the battery casing 200, and the energy density of the battery is also guaranteed. Of course, the gap between the outer circumferential surface of the first cylindrical cell 110 and the battery casing 200 can also be greater than 2mm or less than 0.1mm, as long as a certain cell expansion space is formed; this disclosure does not impose any restrictions on this.

[0052] In the radial direction of the cell 100, the gap between the circumferential outer surface of the first cylindrical cell 110 and the battery casing 200 may be the same or different, and the circumferential outer surface of the first cylindrical cell 110 and the battery casing 200 may be set with equal gaps or with non-equal gaps.

[0053] Specifically, at any height in the axial direction of the cell 100, the gaps in the radial direction between the circumferential outer surface of the first cylindrical cell 110 and the battery casing 200 are equal, so as to ensure that the cell expansion space formed by the gap between the circumferential outer surface of the first cylindrical cell 110 and the battery casing 200 at any height in the axial direction of the cell 100 is the same, further ensuring the absorption of the larger expansion force of the outer layer.

[0054] In the embodiments of this application, the capacity of the first cylindrical cell 110 is the same as the capacity of the second cylindrical cell 120. Since the first cylindrical cell 110 and the second cylindrical cell 120 are connected in series, by making the capacity of the first cylindrical cell 110 and the capacity of the second cylindrical cell 120 the same, the series voltage distribution can be made uniform, preventing overcharging of the cylindrical cell with a large voltage distribution. Of course, the capacity of the first cylindrical cell 110 and the capacity of the second cylindrical cell 120 can also be different, and this disclosure does not limit this.

[0055] In the embodiments of this application, such as Figure 5 and Figure 6 As shown, the cylindrical battery 10 may further include a third cylindrical cell 130 and a fourth cylindrical cell 140. The third cylindrical cell 130 may be a third silicon-based cell, and the fourth cylindrical cell 140 may be a fourth silicon-based cell. The third cylindrical cell 130 includes a third central hole 131, and the fourth cylindrical cell 140 includes a fourth central hole 141. The third silicon-based cell passes through the second central hole 121 of the second cylindrical cell 120, and the fourth silicon-based cell passes through the third central hole 131 of the third cylindrical cell 130. By setting the third silicon-based cell and the fourth silicon-based cell, with the third silicon-based cell placed in the second central hole 121 of the second silicon-based cell and the fourth silicon-based cell placed in the third central hole 131 of the third silicon-based cell, the first silicon-based cell, the second silicon-based cell, the third silicon-based cell, and the fourth silicon-based cell are nested together to form a cell 100.

[0056] The third cylindrical battery cell 130 includes a third battery cell body, a fifth tab, and a sixth tab. The fifth and sixth tabs, with opposite polarities, extend from opposite ends of the third battery cell body along a first direction and a second direction, respectively. The third battery cell body includes a third central hole 131. The fourth cylindrical battery cell 140 includes a fourth battery cell body, a seventh tab, and an eighth tab. The seventh and eighth tabs, with opposite polarities, extend from opposite ends of the fourth battery cell body along a first direction and a second direction, respectively. The fourth battery cell body includes a third central hole 131.

[0057] The first, third, fifth, and seventh tabs are located at one end of the cell 100, while the second, fourth, sixth, and eighth tabs are located at the other end of the cell 100. The first and third tabs with opposite polarities are connected together, the fourth and sixth tabs with opposite polarities are connected together, and the fifth and seventh tabs with opposite polarities are connected together, so that the first cylindrical cell 110, the second cylindrical cell 120, the third cylindrical cell 130, and the fourth cylindrical cell 140 are connected in series.

[0058] There are gaps between the first silicon-based cell and the second silicon-based cell, between the second silicon-based cell and the third silicon-based cell, and between the third silicon-based cell and the fourth silicon-based cell. That is, there are three gaps in the middle layer of the cell 100, forming three cell expansion spaces in the middle layer of the cell 100. This makes the stress on the inner and outer electrodes relatively uniform, and the pressure on the middle layer of the cell 100 is smaller. This further avoids problems such as collapse and lithium plating caused by uneven stress on the middle layer electrodes, thus improving the performance of the cylindrical battery 10.

[0059] The expansion coefficient of the second silicon-based cell is smaller than that of the third silicon-based cell, and the expansion coefficient of the third silicon-based cell is smaller than that of the fourth silicon-based cell. By making the expansion coefficient of the second silicon-based cell smaller than that of the third silicon-based cell, and the expansion coefficient of the third silicon-based cell smaller than that of the fourth silicon-based cell, the expansion force generated by the outer electrode of the cell 100 is smaller, which makes the outer structure of the cell 100 more stable and can help the battery casing 200 to provide a binding effect on the inner layer of the cell 100.

[0060] In this process, the silicon content of the active material in the second silicon-based cell is less than that in the third silicon-based cell, and the silicon content of the active material in the third silicon-based cell is less than that in the fourth silicon-based cell. By making the silicon content of the active material in the second silicon-based cell less than that in the third silicon-based cell, and the silicon content of the active material in the third silicon-based cell less than that in the fourth silicon-based cell, the expansion coefficient of the second silicon-based cell is less than that of the third silicon-based cell, and the expansion coefficient of the third silicon-based cell is less than that of the fourth silicon-based cell. This stabilizes the outer structure of the cell 100 and helps the battery casing 200 to provide a binding effect on the inner layer of the cell 100.

[0061] Embodiments of this application also provide a method for preparing a cylindrical battery, such as... Figure 7 As shown, the preparation method includes:

[0062] Step S100: Provide a first cylindrical battery cell. The first cylindrical battery cell includes a first battery cell body, a first electrode, and a second electrode. The first electrode and the second electrode with opposite polarities extend from opposite ends of the first battery cell body along a first direction and a second direction, respectively. The first battery cell body includes a first central hole.

[0063] Step S200: Provide a second cylindrical battery cell. The second cylindrical battery cell includes a second battery cell body, a third tab, and a fourth tab. The third tab and the fourth tab, which have opposite polarities, extend from opposite ends of the second battery cell body along a first direction and a second direction, respectively. The second battery cell body includes a second central hole.

[0064] Step S300: Insert the second cylindrical battery cell into the first central hole of the first cylindrical battery cell, and connect the first and third tabs with opposite polarities to connect the first and second cylindrical battery cells in series.

[0065] The method for manufacturing a cylindrical battery disclosed herein involves nesting a first cylindrical cell and a second cylindrical cell to form a battery cell. The first and second cylindrical cells are connected at the same end with opposite polarities via tabs, thus connecting them in series. The opposite polarities can be connected by flattening, resulting in high production efficiency and high tolerance. Another pair of opposite polarities tabs of the first and second cylindrical cells are located at the same end, clearly distinguishing the positive and negative tab areas, ensuring uniform current density, and facilitating internal insulation. Furthermore, alignment is unnecessary, reducing the requirements for die-cutting and winding, lowering the manufacturing process difficulty, and improving product yield. In addition, the requirements for electrode thickness consistency are lower, eliminating the need for electrode die-cutting. Moreover, the separate arrangement of the first and second cylindrical cells provides more expansion space between them.

[0066] The following will describe in detail each step of the preparation method of the cylindrical battery provided in this disclosure.

[0067] In step S100, a first cylindrical battery cell is provided. The first cylindrical battery cell includes a first battery cell body, a first electrode, and a second electrode. The first electrode and the second electrode with opposite polarities extend from opposite ends of the first battery cell body along a first direction and a second direction, respectively. The first battery cell body includes a first central hole.

[0068] In embodiments of this disclosure, a first cylindrical cell 110 is provided, comprising: providing a first current collector and forming a first active material coating on the surface of the first current collector in the thickness direction to form a first negative electrode.

[0069] The silicon content in the first active material coating is 0-10%, for example, 0, 1%, 3%, 5%, 8%, 10%, etc.

[0070] For example, when preparing the negative electrode of the first cylindrical battery cell 110, and when the silicon content percentage is the same at all positions of the negative electrode of the first cylindrical battery cell 110, the raw materials include silicon material, graphite, SP (conductive carbon black), CMC (sodium carboxymethyl cellulose), and PAA (polyacrylic acid). The mass percentage of silicon material can be 0-10%, the mass percentage of graphite can be 85%-95%, the mass percentage of SP can be 0.5%-1.5%, the mass percentage of CMC can be 0.5%-1.5%, and the mass percentage of PAA can be 1%-3%. Specifically, the preparation of the negative electrode sheet of the first cylindrical cell 110 may include the following steps: (1) Dry mixing of powder: Silicon material, graphite and SP are added to the mixing vessel according to the above negative electrode slurry formula, and dry mixing is carried out to obtain dry powder; (2) Preparation of CMC adhesive solution: CMC is dissolved in deionized water according to the proportion, and dispersed by rotation at 1500 rpm to 2000 rpm for 100 min to 140 min to obtain CMC adhesive solution with a solid content of 1% to 2%; (3) Slurry mixing: The dry powder and SP in step (1) are mixed according to the formula. In step (2), 50% of the CMC adhesive and solvent (deionized water) are stirred and dispersed for 50 min to 70 min; then the remaining 50% of the CMC adhesive and solvent are added and stirred for another 50 min to 70 min; then PAA is added and stirred for another 50 min to 70 min; finally, an appropriate amount of deionized water is added to adjust the viscosity to 3000 mPa·s to 5000 mPa·s to obtain the first battery negative electrode slurry; (4) Negative electrode coating-rolling: The first battery negative electrode slurry prepared above is coated on copper foil (current collector). After coating is completed, it is rolled to obtain a negative electrode sheet with a silicon content of 0% to 10%.

[0071] For example, in preparing the positive electrode sheet of the first cylindrical battery cell 110, the raw materials include ternary main material LiNi5Co2Mn3, SP, conductive agent CNT, and binder PVDF. The mass percentage of ternary main material LiNi5Co2Mn3 can be 90%~98%, the mass percentage of SP can be 0.5%~1.5%, the mass percentage of conductive agent CNT can be 0.1%~1%, and the mass percentage of binder PVDF can be 1%~3%. The positive electrode slurry is uniformly coated on carbon-coated aluminum foil and dried, and then rolled to obtain the positive electrode sheet.

[0072] For example, the above-mentioned positive electrode, separator, and negative electrode are wound together to form a first cylindrical battery cell 110. For example, a 22mm diameter winding needle is used to wind the battery cell 100 to a diameter of 44mm, thus obtaining the first cylindrical battery cell 110.

[0073] When the silicon content ratio at different positions of the first active material coating on the negative electrode sheet of the first cylindrical cell 110 is different, the above steps can be used to form a battery negative electrode slurry with a different silicon content ratio, and the battery negative electrode slurry with a different silicon content ratio can be coated on the corresponding position of the current collector.

[0074] When the silicon content of the first active material coating on the negative electrode sheet of the first cylindrical cell 110 gradually changes, the above steps can be used to form two battery negative electrode slurries with different silicon content ratios. The two battery negative electrode slurries with different silicon content ratios are mixed and continuously coated on the negative electrode current collector. The mixing ratio changes continuously from 1 to 0. After the coating is completed, the negative electrode sheet with the silicon content continuously decreasing along the winding direction is obtained.

[0075] In step S200, a second cylindrical battery cell is provided. The second cylindrical battery cell includes a second battery cell body, a third tab, and a fourth tab. The third tab and the fourth tab, which have opposite polarities, extend from opposite ends of the second battery cell body along a first direction and a second direction, respectively. The second battery cell body includes a second central hole.

[0076] In embodiments of this disclosure, providing a second cylindrical battery cell includes: providing a second current collector and forming a second active material coating on the surface of the second current collector in the thickness direction to form a second negative electrode.

[0077] Wherein, the coefficient of expansion of the second active material coating of the second cylindrical cell 120 is equal to the coefficient of expansion of the first active material coating of the first cylindrical cell 110; or, the coefficient of expansion of the second active material coating of the second cylindrical cell 120 is greater than the coefficient of expansion of the first active material coating of the first cylindrical cell 110.

[0078] When the coefficient of thermal expansion of the second active material coating of the second cylindrical cell 120 is greater than the coefficient of thermal expansion of the first active material coating of the first cylindrical cell 110, the silicon content of the second negative electrode paste is greater than the silicon content of the first negative electrode paste. The silicon content in the second active material coating is 5% to 25%, such as 5%, 10%, 15%, 20%, 25%, etc.

[0079] For example, when preparing the second battery negative electrode slurry coated on the second region 112, the mass percentage of silicon material can be 5%~25%, the mass percentage of graphite can be 80%~90%, the mass percentage of SP can be 0.5%~1.5%, the mass percentage of CMC can be 0.5%~1.5%, and the mass percentage of PAA can be 1%~3%. Specifically, the preparation of the negative electrode sheet of the second cylindrical cell 120 may include the following steps: (1) Dry mixing of powder: according to the above negative electrode slurry formula, silicon material, graphite, and SP are added to the stirring vessel and stirred and dry mixed to obtain dry powder; (2) CMC adhesive preparation: CMC is dissolved in deionized water according to the proportion and dispersed by rotation at 1500 rpm~2000 rpm for 100 min~140 min to obtain CMC adhesive with a solid content of 1%~2%; (3) Slurry mixing: according to the formula, the dry powder in step (1) and the powder in step (2) are mixed. In step (2), 50% of the CMC adhesive and solvent (deionized water) are stirred and dispersed for 50 min to 70 min; then the remaining 50% of the CMC adhesive and solvent are added and stirred for another 50 min to 70 min; then PAA is added and stirred for another 50 min to 70 min; finally, an appropriate amount of deionized water is added to adjust the viscosity to 3000 mPa·s to 5000 mPa·s to obtain the second battery negative electrode slurry; (4) Negative electrode coating-rolling: The second battery negative electrode slurry prepared above is coated on copper foil (current collector). After coating is completed, it is rolled to obtain a negative electrode sheet with a silicon content of 5% to 25%.

[0080] For example, in preparing the positive electrode sheet of the second cylindrical battery cell 120, the raw materials include ternary main material LiNi5Co2Mn3, SP, conductive agent CNT, and binder PVDF. The mass percentage of ternary main material LiNi5Co2Mn3 can be 90%~98%, the mass percentage of SP can be 0.5%~1.5%, the mass percentage of conductive agent CNT can be 0.1%~1%, and the mass percentage of binder PVDF can be 1%~3%. The positive electrode slurry is uniformly coated on carbon-coated aluminum foil and dried, and then rolled to obtain the positive electrode sheet.

[0081] For example, the above-mentioned positive electrode, separator, and negative electrode are wound together to form a second cylindrical cell 120. For example, a 6mm diameter winding needle is used to wind the cells until the diameter of the cell 100 is 20mm, thus obtaining the second cylindrical cell 120. At this time, it is necessary to ensure that the outer diameter of the second cylindrical cell 120 is less than or equal to the diameter of the first central hole 111 in the first cylindrical cell 110.

[0082] When the silicon content ratio at different positions of the second active material coating on the negative electrode sheet of the second cylindrical cell 120 is different, the above steps can be used to form a battery negative electrode slurry with a different silicon content ratio, and the battery negative electrode slurry with a different silicon content ratio can be coated on the corresponding position of the current collector.

[0083] When the silicon content of the second active material coating on the negative electrode sheet of the second cylindrical cell 120 gradually changes, the above steps can be used to form two battery negative electrode slurries with different silicon content ratios. The two battery negative electrode slurries with different silicon content ratios are mixed and continuously coated on the negative electrode current collector. The mixing ratio changes continuously from 1 to 0. After the coating is completed, the negative electrode sheet with silicon content continuously decreasing along the winding direction is obtained.

[0084] In step S300, the second cylindrical battery cell is inserted into the first central hole of the first cylindrical battery cell, and the first and third tabs with opposite polarities are connected together so that the first and second cylindrical battery cells are connected in series.

[0085] In the embodiments of this disclosure, a second cylindrical cell 120 is inserted into the first central hole 111 of the first cylindrical cell 110, and a gap is formed between the circumferential outer surface of the first cylindrical cell 110 and the battery casing 200. The cell 100 is formed by the first cylindrical cell 110 and the second cylindrical cell 120 being fitted together. The second cylindrical cell 120 includes a second central hole 121, and a gap exists between the first cylindrical cell 110 and the second cylindrical cell 120. This creates a cell expansion space within the second central hole 121 of the second cylindrical cell 120. Simultaneously, the gap between the first cylindrical cell 110 and the second cylindrical cell 120 creates a cell expansion space, resulting in relatively uniform stress on the inner and outer electrode sheets. This reduces the pressure on the intermediate layer of the cell 100, preventing problems such as collapse and lithium plating caused by uneven stress on the intermediate layer electrode sheets, thus improving the safety of the cylindrical battery 10.

[0086] In the embodiments of this disclosure, the second cylindrical battery cell 120 is inserted into the first central hole 111, and the end of the second electrode tab away from the first battery cell body and the end of the fourth electrode tab away from the second battery cell body have a height difference; wherein the second electrode tab is set higher than the fourth electrode tab. By making the fourth electrode tab of the second cylindrical battery cell 120 higher than the second electrode tab of the first cylindrical battery cell 110, insulation between the second electrode tab and the fourth electrode tab is facilitated.

[0087] In the embodiments of this disclosure, the end of the first electrode tab furthest from the first cell body is aligned with the end of the third electrode tab furthest from the second cell body. By aligning the end of the first electrode tab furthest from the first cell body with the end of the third electrode tab furthest from the second cell body, the first and third electrodes with opposite polarities can be connected using a flattening method, resulting in high production efficiency and high fault tolerance. Of course, the end of the first electrode tab furthest from the first cell body and the end of the third electrode tab furthest from the second cell body can also have a small height difference, and this disclosure does not impose any limitations on this.

[0088] In the embodiments of this disclosure, the cylindrical battery manufacturing method further includes: placing a first cylindrical cell 110 and a second cylindrical cell 120 within the receiving space 210 of the battery casing 200, and creating a gap between the circumferential outer surface of the first cylindrical cell 110 and the battery casing 200. After the first cylindrical cell 110 and the second cylindrical cell 120 are fitted together to form a cell 100 and placed in the battery housing 200, there is a gap between the circumferential outer surface of the cell 100 and the battery housing 200. Thus, a first expansion space of the cell 100 is formed through the second central hole 121 of the second cylindrical cell 120, a second expansion space of the cell 100 is formed through the gap between the first cylindrical cell 110 and the second cylindrical cell 120, and a third expansion space of the cell 100 is formed through the gap between the circumferential outer surface of the first cylindrical cell 110 and the inner wall of the battery housing 200. The expansion of the cell electrode plates is absorbed by the three expansion spaces, so that the stress on the inner and outer electrode plates of the cell 100 is more uniform, avoiding excessive pressure on the middle layer electrode plates. At the same time, it avoids the large expansion force of the outer layer from acting directly on the inner wall of the battery housing 200, which could lead to the battery housing 200 cracking and electrode plate tearing, thus improving the performance of the battery.

[0089] An embodiment of the present invention also provides a battery pack including the cylindrical battery 10 described above.

[0090] One embodiment of the battery pack of the present invention includes a cylindrical battery 10, which includes a first cylindrical cell 110 and a second cylindrical cell 120. The first cylindrical cell 110 and the second cylindrical cell 120 are sleeved to form a cell 100. The first cylindrical cell 110 and the second cylindrical cell 120 are connected with tabs of opposite polarity at the same end, so that the first cylindrical cell 110 and the second cylindrical cell 120 are connected in series. The tabs of opposite polarity can be connected by flattening, which has high production efficiency and high fault tolerance. The cylindrical cell 110 and the second cylindrical cell 120 have another pair of tabs with opposite polarities located at the same end, with clear distinction between the positive and negative tab areas and uniform current density, which facilitates internal insulation. At the same time, no alignment is required, which reduces the requirements for die-cutting and winding, reduces the process difficulty, and improves the product yield. In addition, the requirements for the consistency of electrode thickness are lower, and electrode die-cutting is not required. Furthermore, the first cylindrical cell 110 and the second cylindrical cell 120 are set separately, and the gap between them can provide more expansion space for the cell 100.

[0091] In one embodiment, the battery pack is a battery module or a battery pack.

[0092] The battery module includes multiple cylindrical batteries 10, which can be mounted on a tray to form the battery module.

[0093] The battery pack includes multiple cylindrical batteries 10 and a battery housing, which is used to secure the multiple cylindrical batteries 10.

[0094] It should be noted that the battery pack includes batteries, and there can be multiple cylindrical batteries 10, which are housed within the battery casing. Alternatively, the multiple cylindrical batteries 10 can be assembled into a battery module and then installed within the battery casing. Or, the multiple cylindrical batteries 10 can be directly housed within the battery casing, eliminating the need to group them together; the battery casing can be used to secure the multiple batteries.

[0095] Other embodiments of this disclosure will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This disclosure is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of this disclosure and include common knowledge or customary techniques in the art not disclosed herein. The specification and exemplary embodiments are to be considered exemplary only, and the true scope and spirit of this disclosure are indicated by the appended claims.

[0096] It should be understood that this disclosure is not limited to the precise structures described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of protection of this disclosure is limited only by the appended claims.

Claims

1. A cylindrical battery, characterized in that, include: The first cylindrical battery cell (110) includes a first battery cell body, a first electrode tab and a second electrode tab. The first electrode tab and the second electrode tab with opposite polarities extend from opposite ends of the first battery cell body along a first direction and a second direction, respectively. The first battery cell body includes a first central hole (111). The second cylindrical battery cell (120) includes a second battery cell body, a third electrode, and a fourth electrode. The third electrode and the fourth electrode, which have opposite polarities, extend from opposite ends of the second battery cell body along the first direction and the second direction, respectively. The second battery cell body includes a second central hole (121), and the second cylindrical battery cell (120) passes through the first central hole (111). The first and third electrodes with opposite polarities are connected to each other so that the first cylindrical cell (110) and the second cylindrical cell (120) are connected in series. The end of the second electrode away from the body of the first cell has a height difference with the end of the fourth electrode away from the body of the second cell. The end of the first electrode away from the body of the first cell is flush with the end of the third electrode away from the body of the second cell. The first electrode with opposite polarities is connected to the third electrode by flattening.

2. The cylindrical battery according to claim 1, characterized in that, The first cylindrical cell (110) and the second cylindrical cell (120) have a height difference.

3. The cylindrical battery according to claim 2, characterized in that, The fourth electrode is positioned higher than the second electrode.

4. The cylindrical battery according to claim 1, characterized in that, The capacity of the first cylindrical cell (110) is the same as that of the second cylindrical cell (120).

5. The cylindrical battery according to claim 1, characterized in that, The expansion coefficient of the first cylindrical cell (110) is smaller than that of the second cylindrical cell (120).

6. The cylindrical battery according to claim 5, characterized in that, The first cylindrical cell (110) is a first silicon-based cell, and the second cylindrical cell (120) is a second silicon-based cell.

7. The cylindrical battery according to claim 6, characterized in that, The silicon content of the active material in the first cylindrical cell (110) is less than the silicon content of the active material in the second cylindrical cell (120).

8. The cylindrical battery according to any one of claims 1 to 7, characterized in that, There is a gap between the first cell body and the second cell body.

9. The cylindrical battery according to any one of claims 1 to 7, characterized in that, The cylindrical battery also includes a battery casing (200), and the first cylindrical cell (110) and the second cylindrical cell (120) are disposed inside the battery casing (200); There is a gap between the circumferential outer surface of the first cell body and the battery casing (200).

10. A method for preparing a cylindrical battery, characterized in that, include: A first cylindrical battery cell (110) is provided. The first cylindrical battery cell (110) includes a first battery cell body, a first electrode tab and a second electrode tab. The first electrode tab and the second electrode tab with opposite polarities extend from opposite ends of the first battery cell body along a first direction and a second direction, respectively. The first battery cell body includes a first central hole (111). A second cylindrical battery cell (120) is provided. The second cylindrical battery cell (120) includes a second battery cell body, a third tab and a fourth tab. The third tab and the fourth tab, which have opposite polarities, extend from opposite ends of the second battery cell body along the first direction and the second direction, respectively. The second battery cell body includes a second central hole (121). The second cylindrical battery cell (120) is inserted into the first central hole (111) of the first cylindrical battery cell (110), and the first and third electrodes with opposite polarities are connected to each other so that the first cylindrical battery cell (110) and the second cylindrical battery cell (120) are connected in series. The end of the second electrode away from the body of the first battery cell has a height difference with the end of the fourth electrode away from the body of the second battery cell. The end of the first electrode away from the body of the first battery cell is flush with the end of the third electrode away from the body of the second battery cell. The first electrode with opposite polarities is connected to the third electrode by flattening.

11. The method for preparing a cylindrical battery according to claim 10, characterized in that, Providing a first cylindrical cell (110) includes: providing a first current collector and forming a first active material coating on the surface of the first current collector in the thickness direction to form a first negative electrode sheet; Providing a second cylindrical cell (120) includes: providing a second current collector and forming a second active material coating on the surface of the second current collector in the thickness direction to form a second negative electrode sheet; The coefficient of thermal expansion of the first active material coating is smaller than that of the second active material coating.

12. The method for preparing a cylindrical battery according to claim 11, characterized in that, Forming a first active material coating on the surface of the first current collector in the thickness direction includes: coating the first current collector with a first negative electrode slurry to form the first active material coating; Forming a second active material coating on the surface of the second current collector in the thickness direction includes: coating the second current collector with a second negative electrode slurry to form the second active material coating; The silicon content of the first negative electrode slurry is less than that of the second negative electrode slurry.

13. The method for preparing a cylindrical battery according to claim 10, characterized in that, The second cylindrical cell (120) is inserted into the first central hole (111) of the first cylindrical cell (110), and a gap is formed between the axial outer surface of the second cylindrical cell (120) and the inner wall of the first central hole (111).

14. The method for preparing a cylindrical battery according to claim 10 or 13, characterized in that, The preparation method further includes: The first cylindrical cell (110) and the second cylindrical cell (120) are disposed inside the battery housing (200), and a gap is formed between the circumferential outer surface of the first cylindrical cell (110) and the battery housing (200).

15. The method for preparing a cylindrical battery according to claim 10, characterized in that, The second electrode is positioned higher than the fourth electrode.

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