Method for manufacturing secondary battery and forming method

Abstract

The invention provides a manufacturing method and a formation method of a secondary battery, the formation method of the secondary battery comprises a pre-charging step, an infiltration step carried out after the pre-charging step, and a negative pressure formation step carried out after the infiltration step, the pre-charging step comprises pre-charging with a pre-charging current I, 0.02 C < = I < 0.15 C, and the negative pressure formation step is carried out after the infiltration step. C is the designed capacity of the secondary battery. According to the technical scheme, the occurrence probability of the infiltration line phenomenon can be reduced at least, and the quick charge cycle performance of the battery is optimized.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and more particularly to a manufacturing method and a formation method of a secondary battery. Background Art

[0002] In the field of new energy power batteries, secondary batteries refer to rechargeable batteries, also known as renewable batteries or storage batteries. Unlike primary batteries, secondary batteries can be reverse charged for multiple charge and discharge cycles for reuse. Secondary batteries generally include electrode assemblies, shells, cover plates, etc. Cylindrical batteries refer to cylindrical wound core batteries, which include a shell and an electrode assembly. The electrode assembly includes a positive electrode sheet, a negative electrode sheet, and a separator located between the positive electrode sheet and the negative electrode sheet. These positive electrode sheets, negative electrode sheets, and separators are stacked on each other and wound into an electrode assembly, which is then encapsulated in a shell. In the production process of secondary batteries, it is usually necessary to undergo preparation processes such as formation, aging, capacity separation, and sorting. Summary of the Invention

[0003] In view of the problems existing in the related art, an object of the present invention is to provide a manufacturing method and a formation method of a secondary battery, so as to at least optimize the cycle performance of the secondary battery.

[0004] To achieve the above-mentioned object, the present invention provides a formation method for a secondary battery, which includes: a pre-charging step, an infiltration step performed after the pre-charging step, and a negative pressure formation step performed after the infiltration step, wherein the pre-charging step includes: pre-charging with a pre-charging current I, wherein 0.02C≤I<0.15C, and C is the design capacity of the secondary battery.

[0005] In some embodiments, the pre-charge current I satisfies: 0.05C≤I≤0.1C.

[0006] In some embodiments, in the pre-charging step, the time t1 for pre-charging with the pre-charging current I ranges from 10 minutes to 35 minutes.

[0007] In some embodiments, the infiltration step is performed at room temperature, and the temperature T of room temperature ranges from 22°C to 28°C.

[0008] In some embodiments, the time t2 for performing the infiltration step is in a range of greater than 18 hours and less than 24 hours.

[0009] In some embodiments, the negative pressure forming step is performed at room temperature, and the room temperature ranges from 22°C to 28°C.

[0010] In some embodiments, the voltage of the secondary battery after the pre-charging step is V1, and the voltage of the secondary battery after the soaking step is V2, wherein V2 is positively correlated with V1, negatively correlated with T and t2, and V2>1.5V.

[0011] In some embodiments, C=I×t1 is satisfied.

[0012] In some embodiments, the secondary battery is a cylindrical battery.

[0013] According to an embodiment of the present application, a method for manufacturing a secondary battery is also provided, which includes: a shelling step: providing an electrode assembly of a secondary battery and placing the electrode assembly in a shell; a liquid injection step: injecting an electrolyte into the shell; and performing the pre-charging step, the infiltration step, and the negative pressure formation step of any one of the above-mentioned formation methods on the secondary battery after liquid injection.

[0014] The beneficial technical effects of the present invention include:

[0015] Precharging with a precharge current I in the range of 0.02C to 0.15C can reduce the impact of precharging on electrode plates that have not yet been fully wetted, allowing the electrolyte to be evenly distributed between the electrode plates. This can reduce the probability of wetness lines, prevent significant lithium deposition and a decrease in the battery's reversible cycle capacity after fast charge cycles, and optimize the battery's fast charge cycle performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, a brief introduction will be given below to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0017] Figure 1 A schematic diagram showing an electronic device according to an embodiment of the present application is a vehicle.

[0018] Figure 2 A perspective view of a secondary battery according to an embodiment of the present application is shown.

[0019] Figure 3 A cross-sectional view of a secondary battery according to an embodiment of the present application is shown.

[0020] Figure 4 is a flowchart of a method for manufacturing a secondary battery according to an embodiment of the present application.

[0021] Figure 5 It is a flowchart of a secondary battery formation method according to an embodiment of the present application.

[0022] Figure 6 is a graph showing the voltage change during the immersion step.

[0023] Figure 7 It is a graph showing the voltage change during the pre-charge step. DETAILED DESCRIPTION

[0024] In order to better understand the spirit of the embodiments of the present application, some preferred embodiments of the present application are further described below.

[0025] The embodiments of the present application will be described in detail below. Throughout this specification, identical or similar components and components having identical or similar functions are represented by similar reference numerals. The embodiments described herein with respect to the accompanying drawings are illustrative and diagrammatic and are intended to provide a basic understanding of the present application. The embodiments of the present application should not be construed as limiting the present application.

[0026] As used herein, the terms "substantially," "substantially," "essentially," and "about" are used to describe and account for small variations, such as variations within the margin of error for manufacturing processes. When used in conjunction with an event or circumstance, the terms may refer to instances where the event or circumstance occurred precisely as well as instances where the event or circumstance occurred very approximately.

[0027] In this specification, unless otherwise specified or limited, relative terms such as "central", "longitudinal", "lateral", "front", "rear", "right", "left", "inner", "outer", "lower", "higher", "horizontal", "vertical", "above", "below", "above", "below", "top", "bottom" and their derivatives (such as "horizontally", "downwardly", "upwardly", etc.) should be interpreted as referring to the directions described in the discussion or depicted in the drawings. These relative terms are only used for convenience of description and do not require that the present application be constructed or operated in a specific orientation.

[0028] For ease of description, “first,” “second,” “third,” etc. may be used herein to distinguish different components in a figure or a series of figures. “First,” “second,” “third,” etc. are not intended to describe the corresponding components.

[0029] The present application provides an electronic device 1000. For the convenience of description, the following embodiments are described by taking the electronic device 1000 as a vehicle as an example. Figure 1The vehicle is equipped with a battery pack 1002 inside. Battery pack 1002 can be located at the bottom, front, or rear of the vehicle body 1001. Battery pack 1002 can be used to power the vehicle, for example, as the vehicle's operating power source. The working portion of the electronic device 1000 is electrically connected to battery pack 1002 to obtain electrical energy. The vehicle can be a fuel-powered vehicle, a gas-powered vehicle, or a new energy vehicle. The new energy vehicle can be a pure electric vehicle, a hybrid vehicle, or an extended-range vehicle, among others, but is not limited thereto. The working portion is the vehicle body, with battery pack 1002 located at the bottom of the vehicle body and providing electrical energy for the vehicle's operation and for the operation of its electrical components. However, in other embodiments, the electronic device 1000 can also be a mobile phone, portable device, laptop computer, ship, spacecraft, electric toy, or electric tool, among others. Spacecraft include airplanes, rockets, space shuttles, and spacecraft, among others. The working portion can draw electrical energy from battery pack 1002 and perform corresponding operations, such as the blade rotation unit of a fan or the dust collection unit of a vacuum cleaner. Electric toys include fixed or mobile electric toys, such as game consoles, electric car toys, electric boat toys, and electric airplane toys; electric tools include metal cutting tools, grinding tools, assembly tools, and railway tools, such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators, and electric planers. The present embodiment of the present application does not impose any particular limitation on the electronic device 1000.

[0030] Figure 2 1 shows a perspective view of a secondary battery 100 according to an embodiment of the present application, Figure 3 FIG2 shows a cross-sectional view of a secondary battery 100 according to an embodiment of the present application. In this embodiment, the secondary battery 100 may be a cylindrical battery.

[0031] In one example of the secondary battery of the present invention, Figures 2 to 3As shown, the secondary battery 100 includes a shell 200, which includes a peripheral side wall 109 and an end wall 111 connected to one end of the peripheral side wall 109. The other end of the peripheral side wall 109 opposite to the end wall 111 is provided with an opening 205. The cover plate 220 covers the opening 205 of the shell 200 to be used to encapsulate the electrode assembly 120 and the electrolyte together with the shell 200. The material of the shell 200 can be any of a variety of available materials, such as copper, iron, aluminum, steel, aluminum alloy, etc. The shell 200 can be cylindrical and define a accommodating cavity, and the electrode assembly 120 is arranged in the accommodating cavity. The diameter of the shell 200 can be determined according to the specific diameter size of the electrode assembly 120, such as 18 mm, 21 mm, 46 mm, etc. In some embodiments, the secondary battery 100 may be a 4680 cylindrical battery (46 mm in diameter, 80 mm in height), or the secondary battery 100 may be a 4695 cylindrical battery (46 mm in diameter, 95 mm in height), or the secondary battery 100 may be a 46120 cylindrical battery (46 mm in diameter, 120 mm in height).

[0032] The electrode assembly 120 is mainly formed by stacking and winding a first electrode sheet, a second electrode sheet, and a diaphragm located between the first electrode sheet and the second electrode sheet in sequence. The wound electrode assembly 120 has a winding center hole 120c. The electrode assembly 120 has a first electrode tab 121 and a second electrode tab 122 on opposite sides of its height direction H. The second electrode tab 122 faces the opening 205, and the first electrode tab 121 faces the end wall 111 of the shell 200 opposite to the opening 205. The direction from the second electrode tab 122 to the first electrode tab 121 is the height direction H of the electrode assembly 120. In some embodiments of the present application, the first electrode tab 121 is the positive electrode tab, and the second electrode tab 122 is the negative electrode tab. In some embodiments, the electrode assembly 120 may further include an insulating layer, such as an insulating tape, bonded to the outer ring of the first electrode sheet, the second electrode sheet, and the diaphragm after winding.

[0033] An inwardly protruding rolling groove 113 may be provided on the sidewall of the housing 200 adjacent to the opening 205. The electrode assembly 120 is disposed between the end wall 111 and the rolling groove 113, and the rolling groove 113 is capable of limiting movement of the electrode assembly 120 in the height direction H and the opposite direction between the end wall 111 and the rolling groove 113. The end of the peripheral sidewall 109 of the housing 200 on the side facing the opening 205 may be configured as a curling portion 32, which extends radially inwardly of the housing 200. The curling portion 32 is spaced apart from the rolling groove 113 along the height direction H, and the rolling groove 113 and the curling portion 32 can jointly clamp the cover plate 220.

[0034] The secondary battery 100 may further include a post 160 that passes through the end wall 111 and is insulated from the end wall 111. The post 160 may be electrically connected to the first tab 121 of the electrode assembly 120 via a first current collecting plate 301, thereby causing the post 160 to be charged, for example, positively charged. The second tab 122 may be electrically connected to the housing 200 via a second current collecting plate 302, thereby causing the housing 200 to be charged, for example, negatively charged.

[0035] In some embodiments, the positive electrode sheet (first electrode sheet) may include a positive electrode current collector and a positive electrode coating region, wherein the positive electrode coating region is coated on a portion of the surface of the positive electrode current collector. The positive electrode coating region is a positive electrode active material layer formed by coating the positive electrode active material. The portion of the positive electrode current collector not covered by the positive electrode coating region constitutes a positive electrode tab (first electrode tab 121). The negative electrode sheet (second electrode sheet) may include a negative electrode current collector and a negative electrode coating region, wherein the negative electrode coating region is coated on a portion of the surface of the negative electrode current collector. The negative electrode coating region is a negative electrode active material layer formed by coating the negative electrode active material. The portion of the negative electrode current collector not covered by the negative electrode coating region constitutes a negative electrode tab (second electrode tab 122).

[0036] Taking lithium-ion batteries as an example, the positive electrode current collector can be made of aluminum, and the positive electrode coating region can include a positive electrode active material, such as lithium cobalt oxide, lithium iron phosphate, ternary lithium, or lithium manganese oxide. The negative electrode current collector can be made of copper. The negative electrode coating region can include a negative electrode active material, such as carbon or silicon. The separator can be made of polypropylene (PP) or polyethylene (PE).

[0037] Figure 4 FIG is a flowchart of a method for manufacturing a secondary battery according to an embodiment of the present application. Figure 4 Shown and combined Figure 3 In an example of the secondary battery 100 of the present invention, the manufacturing method of the secondary battery 100 of the present invention includes the following steps:

[0038] Winding step S402: The first electrode sheet, separator, and second electrode sheet are stacked and wound to form a wound structure. The uncoated portions of the positive electrode current collector of the first electrode sheet and the negative electrode current collector of the second electrode sheet constitute the first and second electrode tabs 121 and 122. The first and second electrode tabs 121 and 122 are bent radially along the electrode assembly 120. The current collecting plates can then be welded to the electrode assembly. Specifically, the first and second current collecting plates 301 and 302 are welded to the surface areas of the bent first and second electrode tabs 121 and 122, respectively.

[0039] Shell insertion step S404: Install the electrode assembly 120 welded to the first current collecting plate 301 and the second current collecting plate 302 into the shell 200 through the opening 205. The method of installing the electrode assembly 120 in this step is not limited, for example, it can be installed manually or by a robot.

[0040] In the adapter plate welding step S406, the adapter plate of the second current collecting plate 302 is welded to the housing 200. Then, the pole 160 can be installed.

[0041] In the groove rolling step S408 , in some embodiments, the outer periphery of the shell 200 is rolled to form a groove 113 that is recessed toward the center of the shell 200 to limit the movement of the electrode assembly 120 in the height direction H.

[0042] In the liquid injection step S410, the electrolyte is injected into the shell 200. The injection method of the electrolyte is not limited. It can be injected at the opening 205 or by setting an injection hole on the end wall 111. Preferably, in this embodiment, the electrolyte is injected at the opening 205, which reduces the process of setting the injection hole on the end wall 111. The existing opening 205 can be directly used for injection, which simplifies the process and reduces the cost.

[0043] Formation step S412. Formation is the first charging of the battery, the purpose of which is to activate the battery. Formation has a very important impact on lithium-ion batteries, affecting the battery's cycle and safety performance. The formation step directly determines the quality of the battery performance. The specific implementation of the formation step S412 will be referred to below. Figure 5 Provide a detailed description.

[0044] Sealing step S414: Sealing the cover plate 220 onto the opening 205. A mechanical sealing process can be used to seal the cover plate 220 to form a curling portion 32, thereby sealing the cover plate 220 onto the opening 205 of the housing 200. This step is a mature process with low cost and high efficiency.

[0045] After the sealing step S414, an aging step S416, a resting step 418 and a volume separation step 420 may be performed in sequence.

[0046] Current secondary batteries are usually manufactured using the above method. In the formation step, a 0.33C current is used to charge to 4.25V (100% SOC (State of Charge)). However, in the prior art, after disassembling the electrode assembly, one or more darker infiltration lines will appear in the longitudinal middle of the electrode interface. The infiltration line is a linear dark area formed by the liquid-deficient area due to uneven infiltration of the electrode. This causes obvious lithium deposition on the infiltration line and its surroundings after a fast charge cycle, resulting in a decrease in the reversible cycle capacity of the battery, and even a rapid decrease in the fast charge cycle performance of the battery.

[0047] For 46 series large cylindrical batteries (such as the above-mentioned 4680, 4695, and 46120 cylindrical batteries), the 46 series large cylindrical batteries have a large height, which leads to uneven distribution of electrolyte during the injection and formation process. In particular, the middle part of the electrode in the height direction of the battery cell is prone to less electrolyte, resulting in poor charge and discharge dynamics in this area, forming dark infiltration lines, and gradually developing into lithium precipitation lines after fast charging cycles, resulting in a rapid decline in battery cycle performance. In addition, in order to increase the capacity level of large cylindrical batteries, the group margin of large cylindrical batteries (the group margin refers to the ratio of the diameter of the electrode assembly to the diameter of the shell) is set higher, the contact between the pole pieces is closer, and the space between the pole pieces is small, which makes it more difficult for the electrolyte to be evenly distributed therein, increasing the probability of the infiltration line phenomenon, and further deteriorating the fast charging cycle performance of the battery cell.

[0048] In order to improve the aforementioned wetting line problem and optimize the cycle performance of a secondary battery, an embodiment of the present application provides a formation method for a secondary battery. Figure 5 is a flow chart of a secondary battery formation method 500 according to an embodiment of the present application. The formation method 500 may correspond to Figure 4 The formation step 412 in FIG. Figure 5 As shown, the formation method 500 may include: a pre-charging step 510, an immersion step 520 performed after the pre-charging step 510, and a negative pressure formation step 530 performed after the immersion step 520. In some embodiments, the pre-charging step 510 includes: pre-charging with a pre-charging current I, where 0.02C≤I<0.15C, and C is the design capacity of the secondary battery in Ah (ampere-hour).

[0049] As mentioned above, during the formation process, whether the electrolyte after injection is evenly distributed between the pole pieces will ultimately affect the performance of the electrode assembly. In the above-mentioned formation method of the present application, pre-charging is performed with a pre-charge current I in the range of 0.02C to 0.15C, which can reduce the impact of pre-charging on the pole pieces that have not been fully wetted, so that the electrolyte can be evenly distributed between the pole pieces. Therefore, the probability of the occurrence of the wet line phenomenon can be reduced, and after the fast charge cycle, the obvious lithium precipitation phenomenon and the decrease in the reversible cycle capacity of the battery are prevented, thereby optimizing the fast charge cycle performance of the battery.

[0050] In some embodiments, the pre-charge current I satisfies the following: 0.05C≤I≤0.1C. Such a small pre-charge current I can effectively reduce the impact of pre-charging on electrode sheets that have not been fully wetted, reduce the probability of the wet-line phenomenon, and optimize the battery's fast-charge cycle performance. For cylindrical batteries with a high group margin, such a small pre-charge current I configuration can effectively reduce the probability of the wet-line phenomenon in the cylindrical battery, prevent obvious lithium deposition and a decrease in the reversible cycle capacity of the cylindrical battery, and optimize the fast-charge cycle performance of the cylindrical battery.

[0051] In some embodiments, in the pre-charging step 510, the pre-charging time t1 with the pre-charging current I ranges from 10 minutes to 35 minutes. If the pre-charging time t1 is too short, the required pre-charging voltage may not be achieved; if the pre-charging time t1 is too long, it may have an adverse effect on the electrode that is not fully wetted. The pre-charging time t1 ranges from 10 minutes to 35 minutes. While achieving the required pre-charging voltage, it can avoid the effect of the pre-charging time on the electrode that is not fully wetted, thereby reducing the probability of the wet line phenomenon, preventing the occurrence of obvious lithium plating and the reduction of the reversible cycle capacity of the battery, and optimizing the fast charging cycle performance of the battery.

[0052] Regarding the infiltration step 520 , the parameter selection in the infiltration step 520 is associated with the priming step 510 . Figure 6 is a graph showing the voltage change during the soaking step. Figure 6 In the figure, the horizontal axis represents the time t2 of the soaking step, in h; the vertical axis represents the voltage, in V; the ambient temperature during soaking is T. Figure 6 As shown, after the pre-charging step 510, the voltage of the secondary battery is V1. As time t2 increases, the voltage gradually decreases. After the infiltration step 520, the voltage of the secondary battery is V2. V2 is positively correlated with V1, that is, the greater the voltage V1 of the secondary battery after the pre-charging, the greater the voltage V2 of the secondary battery after the infiltration step 520. V2 is negatively correlated with both T and t2. That is, the higher the temperature T during infiltration, the lower V2; the longer the infiltration time t2, the lower V2. However, it is generally required that V2 should not be too low. In some embodiments, V2 should be greater than 1.5V (V2>1.5V) to avoid undesirable oxidation of metal elements during the infiltration process.

[0053] As described above, the temperature T and time t2 during the soaking step 520 affect the voltage V2 of the secondary battery after the soaking step. According to some embodiments of the present application, the soaking step 520 is performed at room temperature, where the temperature T may range from 22°C to 28°C. Compared to the prior art, which typically performs soaking at high temperatures, the present application performs the soaking step 520 at room temperature, thereby preventing the voltage from dropping too quickly during the soaking step.

[0054] In some embodiments, the time t2 for performing the soaking step 520 is greater than 18 hours and less than 24 hours, i.e., 18 hours < t2 < 24 hours. If time t2 is too short, the electrolyte may not fully soak into the battery. If the pre-charge time t1 is too long, the voltage may drop too much and fail to reach the required voltage V2. Configuring time t2 to be 18 hours < t2 < 24 hours ensures that the electrolyte fully soaks into the battery while achieving the required voltage V2, allowing the electrolyte to be evenly distributed between the electrodes.

[0055] Figure 7 is a graph of the voltage changes during the precharge step. Figure 7 In the chart, the horizontal axis represents C in Ah, and the vertical axis represents voltage in V. Figure 7 As shown, the voltage V1 of the secondary battery after pre-charging can be determined based on the voltage V2, the soaking temperature T, and the soaking time t2. Furthermore, the value of C can be determined according to C = I × t1. After determining C, the pre-charge current I can be selected to be as small as possible while ensuring process efficiency, for example, 0.02C ≤ I < 0.15C.

[0056] In the negative pressure formation step 530, the secondary battery soaked in electrolyte is subjected to negative pressure formation under a negative pressure environment. In some embodiments, the negative pressure formation step 530 is performed at room temperature, and the temperature range of normal temperature is 22°C to 28°C. The inventors have found that if negative pressure formation is performed at high temperature, it may also cause obvious soaking lines. The present application can further reduce the probability of the soaking line phenomenon by performing the negative pressure formation step 530 at room temperature.

[0057] Table 1 is a comparison table of several specific examples of chemical formation methods.

[0058] Table 1

[0059]

[0060] As shown in Reference Table 1, large pre-charge current I, high temperature infiltration and high temperature negative pressure formation (see Example 1) will cause a clear black infiltration line in the middle of the electrode. See Example 2, by reducing the pre-charge current I, for example, to 0.1C, the infiltration line can be made slight. Further, see Example 3, reduce the pre-charge current I to 0.05C, and appropriately extend the pre-charge time t2, there can be almost no infiltration line in the middle of the electrode. And as mentioned above: C = I × t1, it can be seen that the C values ​​in Examples 2 and 3 are the same. Therefore, when C is the same, using a smaller pre-charge current I and appropriately extending the pre-charge time t2 can effectively avoid the formation of infiltration lines.

[0061] Furthermore, see Example 4. By performing infiltration and negative pressure formation at room temperature, there can be almost no infiltration line in the middle of the electrode. And by performing infiltration and negative pressure formation at room temperature, the pre-charge time can be shortened while ensuring that there is almost no infiltration line in the middle of the electrode. The technical solution of the present application can significantly improve the 100% SOC negative electrode interface infiltration line problem of cylindrical batteries, and make the battery have better cycle stability in fast charging cycles (10-80% DOD (depth of discharge), charging time 22 minutes).

[0062] The embodiments of the present application also provide a secondary battery formed using the aforementioned secondary battery formation method. The manufactured secondary battery has no wettability lines on its electrode plates, no significant lithium deposition after fast charge cycles, and has optimized fast charge cycle performance.

[0063] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A secondary battery formation method, characterized in that: include: a pre-filling step, an infiltration step performed after the pre-filling step, and a negative pressure forming step performed after the infiltration step, The pre-charging step includes: pre-charging with a pre-charging current I, wherein 0.02C≤I<0.15C, and C is the designed capacity of the secondary battery.

2. The secondary battery formation method according to claim 1, wherein: The pre-charge current I satisfies: 0.05C≤I≤0.1C.

3. The secondary battery formation method according to claim 1, wherein: In the pre-charging step, the time t1 for pre-charging with the pre-charging current I ranges from 10 minutes to 35 minutes.

4. The secondary battery formation method according to claim 1, wherein: The infiltration step is performed at room temperature, and the temperature T of the room temperature ranges from 22°C to 28°C.

5. The secondary battery formation method according to claim 4, characterized in that: The time t2 for performing the infiltration step is in the range of more than 18 hours and less than 24 hours.

6. The secondary battery formation method according to claim 1, characterized in that: The negative pressure forming step is performed at room temperature, and the temperature range of room temperature is 22°C to 28°C.

7. The secondary battery formation method according to claim 5, characterized in that: The voltage of the secondary battery after the pre-charging step is V1, and the voltage of the secondary battery after the soaking step is V2, wherein V2 is positively correlated with V1, negatively correlated with T and t2, and V2>1.5V.

8. The secondary battery formation method according to claim 3, characterized in that: Satisfies: C = I × t1.

9. The secondary battery formation method according to claim 1, characterized in that: The secondary battery is a cylindrical battery.

10. A method for manufacturing a secondary battery, characterized in that: include: Shelling step: providing an electrode assembly of a secondary battery and placing the electrode assembly in a shell; Liquid injection step: injecting electrolyte into the shell; as well as The secondary battery after liquid injection is subjected to the pre-charging step, the impregnation step and the negative pressure formation step in the formation method according to any one of claims 1 to 9.

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