Cylindrical battery and method for preparing same

Abstract

The present disclosure provides a cylindrical battery and a method for preparing the same, which belongs to the technical field of batteries. The cylindrical battery according to the present disclosure includes a jelly roll, a housing, an upper cover plate, and a lower cover plate. There are at least two jelly rolls, and the (n+1)th jelly roll is wrapped around the outer wall of the nth jelly roll, where n is an integer greater than or equal to 1. Adjacent jelly rolls are separated by a housing, and the outer wall of the outermost jelly roll is covered by the housing. The upper cover plate is located on the upper surface of the jelly roll, and the lower cover plate is located on the lower surface of the jelly roll. The upper cover plate and the lower cover plate are respectively hermetically connected to the housing, so that each jelly roll is located in an independent sealed space. The cylindrical battery has good heat dissipation properties, greatly reducing the phenomenon of "internal accumulation" of heat in the battery. Different jelly rolls can be injected with electrolytes with different functions, reducing the phenomenon of uneven performance decay of the battery and extending the service life of the battery.

Description

[Technical Field]

[0001] FIELD OF THE DISCLOSURE The present disclosure is in the field of battery technology, and in particular relates to cylindrical batteries and methods for preparing same.

[0002] (CROSS-REFERENCE TO RELATED APPLICATIONS) This disclosure claims priority to a Chinese application entitled "Cylindrical Battery and Preparation Method Thereof," filed with the State Intellectual Property Office of the People's Republic of China on November 20, 2023, bearing application number 202311542976.7, the entire contents of which are incorporated herein by reference. [Background technology]

[0003] As is well known, during the charging and discharging process of a battery, the battery's energy is consumed due to battery impedance, resulting in irreversible heat generation. The optimal operating temperature for a lithium-ion battery is 20°C to 35°C, and as the temperature inside the battery increases, the battery's service life decreases exponentially with the gradual increase in temperature. Due to the special structure of cylindrical batteries, the heat generated inside the cylindrical battery during charging and discharging cannot be released in a timely manner, resulting in uneven heat distribution within the battery, with the temperature higher near the center of the battery. As a result, the relatively high temperature and uneven temperature distribution within the battery cause uneven decay within the battery, significantly reducing the battery's service life.

[0004] It is with this in mind that the present disclosure is provided. Summary of the Invention [Problem to be solved by the invention]

[0005] A first object of the present disclosure is to provide a cylindrical battery that can solve at least one of the above problems.

[0006] A second object of the present disclosure is to provide a method for preparing a cylindrical battery. [Means for solving the problem]

[0007] In a first aspect, the present disclosure provides a cylindrical battery, the cylindrical battery including a jelly roll, a housing, an upper cover plate, and a lower cover plate; There are at least two jelly rolls, and the n+1th jelly roll is wound around the outer wall of the nth jelly roll, n being an integer greater than or equal to 1, adjacent jelly rolls are separated by the housing, and the outer wall of the outermost jelly roll is covered with the housing; The upper cover plate is located on the upper surface of the jelly roll, and the lower cover plate is located on the lower surface of the jelly roll. The upper cover plate and the lower cover plate are each sealed and connected to the housing, so that each jelly roll is located in an independent sealed space.

[0008] In an alternative technical solution, the jelly roll is obtained by winding a first separator, a positive electrode plate, a second separator and a negative electrode plate.

[0009] In an alternative technical solution, the positive electrode active material of the positive electrode plate includes ternary NCM, lithium iron phosphate, or lithium cobalt oxide.

[0010] In an alternative technical solution, the negative electrode active material of the negative electrode plate includes graphite, hard carbon, soft carbon, silicon negative electrode, or lithium titanate.

[0011] In an optional technical solution, the upper cover plate or the lower cover plate is provided with an inlet hole and an explosion-proof valve; The injection hole is used to inject an electrolyte into the jelly roll, The explosion-proof valve is used to protect the jelly roll from explosion.

[0012] In an alternative technical solution, the housing includes an aluminum alloy housing or a nickel-plated steel housing.

[0013] In an alternative technical solution, the jelly rolls are connected in parallel.

[0014] In an alternative technical solution, the jelly roll is filled with an electrolyte; The electrolyte solution mainly includes a lithium salt, a solvent, and an additive, The lithium salts include LiPF6 and LiFSI, The solvents include EC (ethylene carbonate), EMC (ethyl methyl carbonate), DMC (dimethyl carbonate) and PC (propylene carbonate), The additives include VC (vinylene carbonate), DTD (ethylene sulfate), LiPO2F2 and FEC (fluoroethylene carbonate).

[0015] In the alternative technical solution, the composition ratio of each component in the electrolyte of each jelly roll is as follows: y1=k×(-0.011ln(n)+0.1001), k=0.9-1.05, 1 <n<1000、 y2=0.14-y1, y3=30%×ω, y4=(-0.039 ln(n)+0.351)×ω, y5=(0.0563 ln(n)+0.301)×ω, y6=(1-y3-y4-y5)×ω, ω=1-y1-y2-y7-y8-y9-y10, y7=0.000032n2-0.000485n+0.025452, y8=0.00235ln(n)+0.0002, y8≦1%, y9=-0.0005n+0.0025, 0≦y9≦0.2%, y10=0.3%, y1+y2+y3+y4+y5+y6+y7+y8+y9+y10=1, Here, y1 is the mass fraction of LiPF6, y2 is the mass fraction of LiFSI, y3 is the mass fraction of EC, y4 is the mass fraction of EMC, y5 is the mass fraction of DMC, y6 is the mass fraction of PC, y7 is the mass fraction of VC, y8 is the mass fraction of DTD, y9 is the mass fraction of LiPO2F2, and y10 is the mass fraction of FEC.

[0016] In a second aspect, the present disclosure provides a method for preparing the cylindrical battery described above, the method comprising: a step a) of winding a first separator, a first negative electrode plate, a first separator, and a first positive electrode plate of a first jelly roll around a core pin to form a first jelly roll, and placing the first jelly roll in a first housing; Step b: winding the first separator, the first negative electrode plate, the first separator, and the first positive electrode plate of the (n+1)th jelly roll around the (n+1)th jelly roll to form the (n+1)th jelly roll, and placing the (n+1)th jelly roll into the (n+1)th housing; and step c) after all the jelly rolls have been prepared, welding the upper and lower cover plates together, and then subjecting them to injection and chemical formation to obtain cylindrical batteries.

[0017] Compared with the prior art, the present disclosure has the following beneficial effects:

[0018] In the cylindrical battery of the present disclosure, the housing is hermetically connected to the upper and lower cover plates, so that each jelly roll is placed in its own sealed space, and adjacent jelly rolls are separated by the housing. Heat generated by the jelly rolls in each space can be released from the housing in a timely manner, reducing the total heat generated in the battery and significantly reducing the phenomenon of "internal heat accumulation" in the battery, thereby extending the service life of the battery.

[0019] The present disclosure allows different jelly rolls to be infused with electrolytes of different functions, allowing for appropriate responses based on the heat generation characteristics of the battery, thereby reducing uneven battery performance decay and extending the battery's service life.

[0020] The present disclosure makes it possible to avoid sharing electrolyte in the same battery system, significantly improves the performance degradation of batteries caused by inherent defects in conventional battery structural designs, realizes long-life batteries suitable for different applications, and meets the needs of applications through formulations, material combinations, and jelly roll designs in different jelly rolls, thereby avoiding the "inherent defects" in batteries. [Brief explanation of the drawings]

[0021] In order to more clearly describe the specific embodiments of the present disclosure or the technical solutions in the prior art, the drawings necessary for describing the specific embodiments or the prior art will be briefly described below. The drawings described only illustrate some embodiments of the present disclosure, and those skilled in the art can obtain other related drawings based on these drawings without using inventive ability.

[0022] [Figure 1] FIG. 2 is a schematic cross-sectional view of a battery. [Figure 2] FIG. 2 is a schematic diagram of the top cover plate of the battery. [Figure 3] FIG. 2 is a schematic diagram of the bottom cover plate of the battery. [Figure 4] 10 is a graph showing the results of temperature rise of a battery. [Figure 5] 10 is a graph showing the results of the capacity retention rate of the battery. DETAILED DESCRIPTION OF THE INVENTION

[0023] Hereinafter, the implementation of the present disclosure will be described in detail using embodiments and examples. Those skilled in the art will understand that the following embodiments and examples are merely for the purpose of illustrating the present disclosure and do not limit the scope of the present disclosure. All other examples obtained by those skilled in the art based on the examples in the present disclosure without using their inventive abilities fall within the scope of protection of the present disclosure. Where specific conditions are not specified, they can be carried out under conventional conditions or conditions recommended by the manufacturer. For reagents or equipment whose manufacturers are not specified, conventional products available on the market can be used.

[0024] In a first aspect, the present disclosure provides a cylindrical battery including a jelly roll, a housing, an upper cover plate, and a lower cover plate.

[0025] There are at least two jelly rolls, and the (n+1)th jelly roll is wound around the outer wall of the nth jelly roll, where n is an integer greater than or equal to 1. Adjacent jelly rolls are separated by the housing, and the outer wall of the outermost jelly roll is covered by the housing.

[0026] The upper cover plate is located on the upper surface of the jelly roll, and the lower cover plate is located on the lower surface of the jelly roll, and the upper cover plate and the lower cover plate are each sealed and connected to the housing, so that each jelly roll is located in an independent sealed space.

[0027] In the cylindrical battery according to the present disclosure, the housing is hermetically connected to the upper and lower cover plates, so that each jelly roll is placed in its own sealed space, and adjacent jelly rolls are separated by the housing. Because solid-to-solid thermal conduction is superior to solid-to-gas thermal conduction, the present disclosure adds a solid-to-solid thermal conduction mechanism by using the housing between the jelly rolls, allowing heat generated by the jelly rolls in each space to be released from the housing in a timely manner, reducing the total amount of heat generated in the battery and significantly reducing the phenomenon of "internal heat accumulation" in the battery, thereby extending the service life of the battery.

[0028] The present disclosure allows different jelly rolls to be infused with electrolytes of different functions, allowing for appropriate responses based on the heat generation characteristics of the battery, thereby reducing uneven battery performance decay and extending the battery's service life.

[0029] The present disclosure makes it possible to avoid sharing electrolyte in the same battery system, significantly improves the performance degradation of batteries caused by inherent defects in conventional battery structural designs, realizes long-life batteries suitable for different applications, and meets the needs of applications through formulations, material combinations, and jelly roll designs in different jelly rolls, thereby avoiding the "inherent defects" in batteries.

[0030] In some alternative embodiments, the jelly roll is obtained by winding mainly a first separator, a positive electrode plate, a second separator, and a negative electrode plate.

[0031] In some alternative embodiments, the positive electrode active material of the positive plate includes, but is not limited to, ternary NCM, lithium iron phosphate, or lithium cobalt oxide, and other positive electrode active materials known in the art may also be used.

[0032] In some alternative embodiments, the negative electrode active material of the negative electrode plate includes, but is not limited to, graphite, hard carbon, soft carbon, silicon anode, or lithium titanate, and other negative electrode active materials known in the art may also be used.

[0033] In some alternative embodiments, the separator includes, but is not limited to, PE (polyethylene) or PP (polypropylene), although other battery separators known in the art may also be used.

[0034] In some alternative embodiments, the upper cover plate or the lower cover plate is provided with a liquid inlet and an explosion-proof valve.

[0035] The liquid injection holes are used to inject an electrolyte into the jelly roll, and include a first liquid injection hole, a second liquid injection hole, a third liquid injection hole, . . . an n-th liquid injection hole.

[0036] The explosion-proof valves are used to prevent explosions of jelly rolls, and include a first explosion-proof valve, a second explosion-proof valve, a third explosion-proof valve, ... an nth explosion-proof valve.

[0037] Since the jelly rolls are separated from one another, it is necessary to provide each jelly roll with its own inlet and explosion-proof valve in order to inject liquid into each jelly roll and to protect each jelly roll from explosion.

[0038] In some alternative embodiments, the upper and lower cover plates are welded to the housing to form a first weld area, a second weld area, a third weld area, . . . an nth weld area.

[0039] In some alternative embodiments, the housing comprises an aluminum alloy housing or a nickel-plated steel housing.

[0040] In some alternative embodiments, the jelly rolls are connected in parallel.

[0041] In the present disclosure, the connection between the tabs of the jelly roll and the cover plate may be made using a common connection method in the art, such as welding the positive electrode tab of the jelly roll to the bus bar and then connecting it to the positive electrode cover plate with a connecting member, or welding the negative electrode tab of the jelly roll to the bus bar and then connecting it to the negative electrode cover plate with a connecting member.

[0042] In some alternative embodiments, the jelly roll is filled with an electrolyte.

[0043] The electrolyte mainly includes a lithium salt, a solvent, and an additive.

[0044] The lithium salts include LiPF6 and LiFSI.

[0045] The solvents include EC (ethylene carbonate), EMC (ethyl methyl carbonate), DMC (dimethyl carbonate) and PC (propylene carbonate).

[0046] The additives include VC (vinylene carbonate), DTD (ethylene sulfate), LiPO2F2 and FEC (fluoroethylene carbonate).

[0047] In some alternative embodiments, the blending ratio of each component in the electrolyte of each jelly roll is as follows: y1=k×(-0.011ln(n)+0.1001), k=0.9-1.05, 1 <n<1000、 y2=0.14-y1, y3=30%×ω, y4=(-0.039 ln(n)+0.351)×ω, y5=(0.0563 ln(n)+0.301)×ω, y6=(1-y3-y4-y5)×ω, ω=1-y1-y2-y7-y8-y9-y10, y7=0.000032n2-0.000485n+0.025452, y8=0.00235ln(n)+0.0002, y8≦1%, y9=-0.0005n+0.0025, 0≦y9≦0.2%, y10=0.3%, y1+y2+y3+y4+y5+y6+y7+y8+y9+y10=1. Here, y1 is the mass fraction of LiPF6, y2 is the mass fraction of LiFSI, y3 is the mass fraction of EC, y4 is the mass fraction of EMC, y5 is the mass fraction of DMC, y6 is the mass fraction of PC, y7 is the mass fraction of VC, y8 is the mass fraction of DTD, y9 is the mass fraction of LiPO2F2, and y10 is the mass fraction of FEC.

[0048] In a second aspect, the present disclosure provides a method for preparing the cylindrical battery described above, the method comprising the steps of:

[0049] Step a: The first separator, the first negative electrode plate, the first separator, and the first positive electrode plate of the first jelly roll are wound around a core pin to form a first jelly roll (a center hole is formed after the core pin is removed), and the first jelly roll is placed into a first housing.

[0050] Step b: The first separator, the first negative electrode plate, the first separator, and the first positive electrode plate of the (n+1)th jelly roll are wound around the (n+1)th jelly roll to form the (n+1)th jelly roll, and the (n+1)th jelly roll is placed into the (n+1)th housing.

[0051] Step c: After all the jelly rolls are prepared, the upper and lower cover plates are welded together, and then a cylindrical battery is obtained through injection and chemical formation.

[0052] The preparation method according to the present disclosure is simple and easy, and the prepared cylindrical battery has good heat dissipation and a long service life.

[0053] The present disclosure will be further described below using specific examples and comparative examples, which are provided for the purpose of further illustration only and are not intended to limit the present disclosure.

[0054] Example 1 As shown in FIGS. 1 to 3, the cylindrical battery includes a jelly roll, a housing, an upper cover plate, and a lower cover plate.

[0055] The jelly roll is mainly obtained by winding a first separator, a positive electrode plate, a second separator, and a negative electrode plate. There are three jelly rolls, each connected in parallel, with the second jelly roll wound around the outer wall of the first jelly roll, the third jelly roll wound around the outer wall of the second jelly roll, adjacent jelly rolls separated by a housing, and the outer wall of the outermost jelly roll covered by the housing.

[0056] The positive electrode plate is a lithium iron phosphate positive electrode plate, the negative electrode plate is a graphite negative electrode plate, the separator is a PP separator, and the housing is an aluminum alloy housing.

[0057] The upper cover plate is located on the upper surface of the jelly roll, and the lower cover plate is located on the lower surface of the jelly roll. The upper cover plate and the lower cover plate are respectively hermetically welded to the housing, so that each jelly roll is located in an independent sealed space. The upper cover plate is provided with a liquid injection hole and an explosion-proof valve corresponding to each jelly roll.

[0058] The blending ratio of each component in the electrolyte of each jelly roll is shown in Table 1.

[0059] The preparation method is as follows.

[0060] Step a: The first separator, the first negative electrode plate, the first separator and the first positive electrode plate of the first jelly roll were wound around a core pin to form a first jelly roll, and the first jelly roll was placed in a first housing.

[0061] Step b: The first separator, the first negative electrode plate, the first separator, and the first positive electrode plate of a second jelly roll were wound around the first jelly roll to form a second jelly roll, and the second jelly roll was placed into a second housing.

[0062] Step c: The first separator, the first negative electrode plate, the first separator, and the first positive electrode plate of a third jelly roll were wound around the second jelly roll to form a third jelly roll, and the third jelly roll was placed in a third housing.

[0063] Step d: After all the jelly rolls were prepared, the upper and lower cover plates were welded together, and then the cylindrical batteries were obtained through injection and chemical formation.

[0064] The connection between the jelly roll tab and the cover plate was made using conventional methods.

[0065] Example 2 The cylindrical batteries differ from Example 1 in that the blending ratios of the components in the electrolyte of each jelly roll are different. The blending ratios of the components are shown in Table 1.

[0066] Example 3 The cylindrical batteries differ from Example 1 in that the blending ratios of the components in the electrolyte of each jelly roll are different. The blending ratios of the components are shown in Table 1.

[0067] [Table 1]

[0068] Comparative Example 1 The cylindrical battery differs from Example 1 in that no housing was placed between the jelly rolls and the electrolyte from the first jelly roll according to Example 1 was used as the electrolyte.

[0069] Comparative Example 2 The cylindrical battery differs from Example 1 in that no housing was placed between the jelly rolls and the electrolyte from the second jelly roll according to Example 1 was used as the electrolyte.

[0070] Comparative Example 3 The cylindrical battery differs from Example 1 in that no housing was placed between the jelly rolls and the electrolyte from the third jelly roll according to Example 1 was used as the electrolyte.

[0071] Example 4 The cylindrical battery differs from Example 1 in that the electrolyte of the second jelly roll according to Example 1 was used as the electrolyte in each jelly roll.

[0072] Test Example 1 Tests were carried out on the battery cells according to Examples 1 to 4 and Comparative Examples 1 to 3. The battery cell system was an LFP / Gr system, and the nominal capacity of the battery cell was 10 Ah. The test contents and results are as follows:

[0073] 1. The battery cell was discharged from 100% SOC to 2.5V at 1.0C at 25°C, and the temperature rise of the battery cell is shown in Figure 4.

[0074] 4, the battery cells according to Examples 1 to 4 had a smaller temperature rise than the battery cells according to Comparative Examples 1 to 3. Therefore, the battery cells according to the present disclosure further improved the heat dissipation performance of the battery cells by installing a housing between the jelly rolls. The temperatures of the battery cells according to Examples 1 to 3 were lower than that of Example 4. The present disclosure further improved the heat dissipation effect of the battery by designing an electrolyte suitable for the battery in accordance with the heat generation characteristics of the battery.

[0075] 2. The battery cell was charged and discharged at 1.0 C at 25°C, with a charge cutoff voltage of 3.65 V and a discharge cutoff voltage of 2.5 V. The test results are shown in Figure 5.

[0076] As can be seen from the drawings, the battery cells according to Examples 1 to 4 have a higher capacity retention rate at the same number of cycles than the battery cells according to Comparative Examples 1 to 3. In other words, the battery cells according to the present disclosure can further extend the cycle life of the battery cells by installing a housing between the jelly rolls. The battery cells according to Examples 1 to 3 have a higher capacity retention rate at 2400 cycles than Example 4. In other words, the present disclosure can further extend the cycle life of a battery by designing an electrolyte suitable for the battery.

[0077] The above embodiments are merely for illustrating the technical solutions of the present disclosure and are not intended to limit the same. Although the above embodiments are used to describe the present disclosure in detail, those skilled in the art may modify the technical solutions described in the above embodiments and make equivalent substitutions for some or all of the technical features therein. These modifications or substitutions do not deviate from the essence of the technical solutions and the scope of the technical solutions of the embodiments of the present disclosure.

[0078] Industrial Applicability The present disclosure provides a cylindrical battery and a method for preparing the same, which belong to the battery technical field. The cylindrical battery according to the present disclosure includes a jelly roll, a housing, an upper cover plate, and a lower cover plate. There are at least two jelly rolls. The (n+1)th jelly roll is wrapped around the outer wall of the nth jelly roll, where n is an integer greater than or equal to 1. Adjacent jelly rolls are separated by the housing, and the outer wall of the outermost jelly roll is covered by the housing. The upper cover plate is located on the upper surface of the jelly roll, and the lower cover plate is located on the lower surface of the jelly roll. The upper cover plate and the lower cover plate are respectively hermetically connected to the housing, so that each jelly roll is located in an independent sealed space. The cylindrical battery has good heat dissipation properties, greatly reducing the phenomenon of "internal accumulation" of heat in the battery. It allows different jelly rolls to be injected with electrolytes with different functions, reducing the phenomenon of uneven performance decay of the battery and extending the service life of the battery.

[0079] In addition, the cylindrical battery and the preparation method thereof according to the present disclosure can be implemented and applied to various industrial applications, for example, the cylindrical battery and the preparation method thereof according to the present disclosure can be applied to the field of battery technology.

Claims

1. a jelly roll, a housing, an upper cover plate, and a lower cover plate; There are at least two jelly rolls, an (n+1)th jelly roll is wound around the outer wall of an nth jelly roll, n is an integer of 1 or greater, adjacent jelly rolls are separated by the housing, and the outer wall of the outermost jelly roll is covered with the housing; The upper cover plate is located on the upper surface of the jelly roll, and the lower cover plate is located on the lower surface of the jelly roll. The upper cover plate and the lower cover plate are each sealed to the housing, so that each jelly roll is located in an independent sealed space. A cylindrical battery characterized by:

2. The jelly roll is obtained by winding a first separator, a positive electrode plate, a second separator, and a negative electrode plate.

2. The cylindrical battery according to claim 1 .

3. The positive electrode active material of the positive electrode plate includes ternary NCM, lithium iron phosphate, or lithium cobalt oxide.

3. The cylindrical battery according to claim 2.

4. The negative electrode active material of the negative electrode plate includes graphite, hard carbon, soft carbon, silicon negative electrode, or lithium titanate.

3. The cylindrical battery according to claim 2.

5. The upper cover plate or the lower cover plate is provided with a liquid inlet and an explosion-proof valve, The injection hole is used to inject an electrolyte into the jelly roll, The explosion-proof valve is used to prevent explosion of a jelly roll.

2. The cylindrical battery according to claim 1 .

6. The housing includes an aluminum alloy housing or a nickel-plated steel housing.

2. The cylindrical battery according to claim 1 .

7. Each jelly roll is connected in parallel 2. The cylindrical battery according to claim 1 .

8. the jelly roll is filled with an electrolyte; The electrolyte solution mainly includes a lithium salt, a solvent, and an additive, The lithium salt is LiPF ６ and LiFSI, The solvents include EC, EMC, DMC and PC; The additives include VC, DTD, and LiPO ２ F ２ and FEC 2. The cylindrical battery according to claim 1 .

9. The composition ratio of each component in the electrolyte of each jelly roll is as follows: y1=k×(-0.011ln(n)+0.1001), k=0.9-1.05, 1<n<1000, y2=0.14-y1, y3=30%×ω, y4=(-0.039 ln(n)+0.351)×ω, y5=(0.0563 ln(n)+0.301)×ω, y6=(1-y3-y4-y5)×ω, ω=1-y1-y2-y7-y8-y9-y10, y7=0.000032n2-0.000485n+0.025452, y8=0.00235ln(n)+0.0002, y8≦1%, y9=-0.0005n+0.0025, 0≦y9≦0.2%, y10=0.3%, y1+y2+y3+y4+y5+y6+y7+y8+y9+y10=1, where y1 is LiPF ６ y2 is the mass proportion of LiFSI, y3 is the mass proportion of EC, y4 is the mass proportion of EMC, y5 is the mass proportion of DMC, y6 is the mass proportion of PC, y7 is the mass proportion of VC, y8 is the mass proportion of DTD, and y9 is LiPO ２ F ２ is the mass ratio of FEC, and y10 is the mass ratio of FEC.

8. The cylindrical battery according to claim 7.

10. A method for preparing a cylindrical battery according to any one of claims 1 to 9, comprising: a step a) of winding a first separator, a first negative electrode plate, a first separator, and a first positive electrode plate of a first jelly roll around a core pin to form a first jelly roll, and placing the first jelly roll in a first housing; Step b: winding the first separator, the first negative electrode plate, the first separator, and the first positive electrode plate of the (n+1)th jelly roll around the (n+1)th jelly roll to form the (n+1)th jelly roll, and placing the (n+1)th jelly roll into the (n+1)th housing; and c) after preparing all the jelly rolls, welding the upper and lower cover plates together, and then subjecting the resultant to injection and chemical formation to obtain a cylindrical battery. A method for preparing a cylindrical battery, comprising:

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