Battery, battery formation method and energy storage device

Abstract

A battery, a battery formation method and an energy storage device. The battery comprises an electrode assembly and an electrolyte, wherein the electrode assembly comprises a positive electrode sheet, a separator and a negative electrode sheet; the battery satisfies the following relational expression: α=1 / (1+OI)×[a-(V / Cap)]×[b+c×d(GM-0.05)]≤3.61, wherein OI is the OI value of the negative electrode sheet, V / Cap is the electrolyte retention volume per unit capacity of the battery, and the unit is ml / Ah, GM is the thickness margin of the battery in a fully charged state, and a, b, c and d are all constants.

Description

Battery, formation method of battery and energy storage device

[0001] The present application claims priority to the Chinese patent application No. 202411139512.6, filed on August 19, 2024, entitled "Battery, formation method of battery and energy storage device", the whole content of which is incorporated herein by reference. TECHNICAL FIELD

[0002] The present application relates to the field of energy storage, in particular to a battery, a formation method of battery and an energy storage device. BACKGROUND

[0003] With the continuous development of lithium ion battery technology, compared with other types of batteries such as lead-acid, cadmium-nickel, lithium ion batteries have the advantages of large specific capacity, no memory effect, high working voltage, fast charging speed, wide working temperature range, long cycle life, small volume, light weight, etc. At present, lithium ion batteries have been widely used in mobile phones, notebook computers, electric vehicles, energy storage cabinets and other fields, and their application range is becoming more and more extensive.

[0004] A dry method separator (such as a bare polypropylene separator, referred to as a bare PP separator) is used in the battery to isolate the positive electrode sheet and the negative electrode sheet. The bare PP separator is composed of a crystal region and an amorphous region, and is in a fibrous form. This fibrous material will have a stress reduction phenomenon in the electrolyte, and the stress reduction will cause wrinkles (striations) to appear in the longitudinal direction, which is called sagging in the industry. The wrinkles of the separator can easily increase the gap between the positive electrode sheet and the negative electrode sheet, and the electrolyte is prone to break the bridge, so that the active material in this part cannot normally deintercalate lithium, causing part of the active material to be deactivated, resulting in purple stains, thereby affecting the interface effect, electrical performance and safety performance of the battery, etc. SUMMARY

[0005] The embodiments of the present application provide a battery which can better reduce the generation of purple stains and has a higher cycle life.

[0006] In a first aspect, the embodiments of the present application provide a battery, which comprises an electrode assembly and an electrolyte, the electrode assembly comprising a positive electrode sheet, a separator and a negative electrode sheet; the battery satisfies the relationship: α = 1 / (1+OI)×[a-(V / Cap)]×[b+c×d (GM-0.05) ]≤3.61;

[0007] Wherein, OI is the OI value of the negative electrode sheet, V / Cap is the liquid retention volume per unit capacity of the battery, in units of ml / Ah; GM is the thickness group margin of the battery in the full charge state, a, b, c, d are all constants.

[0008] In a second aspect, the embodiments of the present application further provide a formation method of a battery, the formation method comprising:

[0009] placing the battery in a negative pressure environment;

[0010] charging the battery at a first current to charge a first amount of electricity, and stopping charging for a first time;

[0011] charging the battery at a second current to charge a second amount of electricity, and stopping charging for a second time;

[0012] charging the battery at a third current to charge a third amount of electricity, and stopping charging for a third time; and

[0013] charging the battery at a fourth current to charge a fourth amount of electricity, and stopping charging for a fourth time;

[0014] wherein the first amount of electricity is less than the second amount of electricity, the second amount of electricity is less than the third amount of electricity, the second amount of electricity is less than the fourth amount of electricity, and the sum of the first amount of electricity, the second amount of electricity, the third amount of electricity and the fourth amount of electricity is 25% SOC to 35% SOC, wherein SOC is the proportion of the available amount of electricity in the battery to the nominal capacity.

[0015] In a third aspect, the embodiments of the present application further provide an energy storage device, the energy storage device comprising:

[0016] a box body; and

[0017] a plurality of batteries, the plurality of batteries being accommodated in the box body, the batteries being the battery of the first aspect or the battery obtained by using the formation method of the second aspect.

[0018] The battery of the embodiments of the present application is designed by taking the group margin of the battery in the full charge state, the liquid preservation volume of the unit capacity of the battery and the OI value of the negative electrode plate into consideration, so that 1 / (1+OI)×[a-(V / Cap)]×[b+c×d (GM-0.05)≤3.61, so that the negative electrode sheet of the battery is less prone to wrinkling and less prone to purple discoloration, thereby reducing the inactivation area of the negative active material of the negative active layer, improving the capacity development and energy density of the battery. In addition, the reduction of the purple discoloration area of the negative electrode sheet during lithium intercalation can improve the uniformity of lithium deintercalation during charging and discharging of the battery, reduce lithium precipitation around the purple discoloration, thereby reducing the loss of active lithium, slowing down the capacity decay of the battery, and improving the cycle life of the battery. Furthermore, the thickness expansion rate of the negative electrode sheet of different negative active materials from 0% SOC to 100% SOC is different, so even if the thickness group margin of two batteries is the same at the initial 0% SOC, the thickness group margin and the large surface restraint force they bear at the final 100% SOC will not be the same, and the wrinkling and purple discoloration of the negative electrode sheet will also be different. The present application uses the thickness group margin of the battery at 100% SOC for design, which can better reflect the final state of the large surface restraint force of the negative electrode sheet after expansion, better reflect the final form of the wrinkling and purple discoloration of the negative electrode sheet, and thus better control the wrinkling and purple discoloration of the negative electrode sheet of the battery, and better improve the cycle life of the battery. BRIEF DESCRIPTION OF DRAWINGS

[0019] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0020] FIG. 1 is a structural schematic diagram of an energy storage device according to an embodiment of the present application.

[0021] FIG. 2 is a structural schematic diagram of a battery according to an embodiment of the present application.

[0022] FIG. 3 is a structural schematic diagram of a battery according to an embodiment of the present application along the A-A direction in FIG. 2.

[0023] FIG. 4 is a structural schematic diagram of a positive electrode sheet according to an embodiment of the present application.

[0024] FIG. 5 is a structural schematic diagram of a negative electrode sheet according to an embodiment of the present application.

[0025] FIG. 6 is a formation method of a battery according to an embodiment of the present application.

[0026] FIG. 7 is a photograph of a negative electrode sheet of a battery according to Embodiment 1 of the present application at 100% SOC after 10 cycles of fresh charging and discharging.

[0027] FIG. 8 is a photograph of a negative electrode sheet of a battery according to Embodiment 2 of the present application at 100% SOC after 10 cycles of fresh charging and discharging.

[0028] Figure 9 is a photo of the negative electrode sheet of the battery of Comparative Example 1 of the present application at 100% SOC after 10 cycles of charge and discharge under fresh conditions.

[0029] Figure 10 is a photo of the negative electrode sheet of the battery of Comparative Example 3 of the present application at 100% SOC after 10 cycles of charge and discharge under fresh conditions.

[0030] Legend: 200 - energy storage device, 210 - box body, 211 - accommodating cavity, 100 - battery, 10 - electrode assembly, 11 - positive electrode sheet, 111 - positive current collector, 112 - positive active layer, 12 - separator, 13 - negative electrode sheet, 131 - negative current collector, 132 - negative active layer, 20 - shell assembly, 21 - accommodating cavity, 30 - insulating film. DETAILED DESCRIPTION

[0031] In order to make the personnel in the technical field better understand the scheme of the present application, the technical scheme in the embodiments of the present application will be clearly and completely described below in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by the person of ordinary skill in the art without creative labor fall within the scope of protection of the present application.

[0032] The terms "first", "second", and the like in the specification and claims of the present application and the above-described drawings are used to distinguish different objects, not to describe a specific order. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device including a series of steps or units is not limited to the listed steps or units, but can optionally include steps or units not listed or can optionally include other steps or units inherent to the process, method, product or device.

[0033] The technical scheme in the embodiments of the present application will be described below in combination with the drawings.

[0034] It should be noted that, for the sake of convenience, in the embodiments of the present application, the same reference signs represent the same parts, and for brevity, detailed description of the same parts is omitted in different embodiments.

[0035] Currently, green power generation generally relies on photovoltaic, wind power, water potential, etc., and wind power and solar power generally have strong intermittency and large volatility, which can cause unstable power grid, insufficient power during power consumption peak, excessive power during power consumption valley, and unstable voltage can also cause damage to power, thus causing "abandoned wind and light" problem due to insufficient power demand or insufficient power grid receiving capacity. To solve these problems, energy storage is needed. That is, the electrical energy is converted into other forms of energy by physical or chemical means and stored, and the energy is converted into electrical energy and released when needed. In simple terms, energy storage is similar to a large "power bank", which stores electrical energy when photovoltaic and wind power is sufficient, and releases the stored electrical energy when needed.

[0036] For example, an electrochemical energy storage device has a set of chemical batteries, which mainly use chemical elements in the battery as energy storage medium. The charging and discharging process is accompanied by chemical reaction or change of the energy storage medium. In simple terms, the electrical energy generated by wind power and solar power is stored in the chemical battery, and the stored electrical energy is released for use when the use of external electrical energy reaches the peak, or is transferred to a place where electrical energy is in short supply for use.

[0037] Referring to FIG. 1, an energy storage device 200 is provided, which includes a box body 210 and a plurality of batteries 100, wherein the plurality of batteries 100 are accommodated in the box body 210.

[0038] The energy storage device 200 can include, but is not limited to, a battery 100 module, a battery 100 pack, a battery 100 system, etc. The actual application form of the energy storage device 200 provided by the embodiments of the present application can be, but is not limited to, the listed products, and can also be other application forms. The embodiments of the present application do not strictly limit the application form of the energy storage device 200. The embodiments of the present application only take the energy storage device 200 including a plurality of batteries 100 as an example for description, and should not be understood as a limitation of the energy storage device 200 of the present application.

[0039] Optionally, the battery 100 can be, but is not limited to, a lithium ion secondary battery 100 (i.e., a lithium ion rechargeable battery 100), a lithium ion primary battery 100, a lithium-sulfur battery 100, a sodium lithium ion battery 100, a sodium ion battery 100, or a magnesium ion battery 100, an energy storage battery 100, etc. In the following description of the present application, a lithium ion secondary battery 100 is taken as an example for description, which should not be understood as a limitation of the battery 100 of the present application, nor as a limitation of the energy storage device 200 of the present application.

[0040] The term "a plurality of" means greater than or equal to two.

[0041] It can be understood that the plurality of batteries 100 of the energy storage device 200 can be connected in parallel with each other; or connected in series with each other; or partially connected in parallel and partially connected in series (in other words, the plurality of batteries 100 are connected in a hybrid manner); and the application does not make a specific limitation on the connection manner of the plurality of batteries 100 of the same energy storage device 200.

[0042] It can be understood that the box body 210 has a plurality of accommodation cavities 211, and the plurality of batteries 100 are accommodated in the plurality of accommodation cavities 211. In some embodiments, each of the plurality of accommodation cavities 211 accommodates one battery 100. In other embodiments, each of the plurality of accommodation cavities 211 accommodates a plurality of batteries 100.

[0043] Optionally, the plurality of batteries 100 can be stacked and arranged in a preset manner, or can be arranged in an array.

[0044] In the related art, a dry method separator (for example, a bare polypropylene separator, referred to as a bare PP separator) is used in the battery to isolate the positive electrode sheet and the negative electrode sheet. The bare PP separator is composed of a crystal region and an amorphous region, and has a fibrous shape. Such a fibrous material can cause stress reduction in the electrolyte, and the stress reduction can cause wrinkles (stripes) in the longitudinal direction, which is referred to as sagging in the industry. The wrinkles of the separator can easily increase the gap between the positive electrode sheet and the negative electrode sheet, and the electrolyte can easily appear to be broken, so that the active material in this part cannot normally deintercalate lithium, and part of the active material is deactivated, which produces purple spots, thereby affecting the interface effect, electrical performance, and safety performance of the battery.

[0045] Please refer to FIG. 2 and FIG. 3, an embodiment of the application provides a battery 100, which comprises an electrode assembly 10 and an electrolyte, the electrode assembly 10 comprises a positive electrode sheet 11, a separator 12 and a negative electrode sheet 13; the battery 100 satisfies the relationship formula: α = 1 / (1 + OI) × [a-(V / Cap)] × [b + c × d (GM-0.05) ]≤3.61;

[0046] Wherein, OI is the OI value of the negative electrode sheet 13, V / Cap is the liquid retention volume per unit capacity of the battery 100, and the unit is ml / Ah; GM is the thickness group margin of the battery 100 in the full charge state, and a, b, c and d are all constants.

[0047] It should be noted that the "full charge state" is the full power state, in other words, the state of the battery 100 at 100% State Of Charge (SOC), that is, 100% SOC.

[0048] The thickness group margin of the battery 100 in the full charge state refers to the ratio of the thickness D1 of the electrode assembly 10 (i.e., the total thickness after winding of the positive electrode tab 11, the separator 12, and the negative electrode tab 13) to the thickness D2 of the inner cavity of the battery 100 in the 100% SOC state, i.e., GM = D1 / D2 x 100%.

[0049] It should be noted that although the liquid retention volume per unit capacity of the battery 100 has a unit, in the above relationship, V / Cap refers to the value or numerical value of the liquid retention volume per unit capacity of the battery 100 when the unit is ml / Ah.

[0050] Optionally, the battery 100 further comprises a shell assembly 20 having a receiving cavity 21, and an insulating film 30, the electrode assembly 10 and the electrolyte are located in the receiving cavity 21, the insulating film 30 is located between the electrode assembly 10 and the shell assembly 20, for insulating the electrode assembly 10 and the shell assembly 20, and D2 is the thickness of the battery 100 excluding the thickness of the shell assembly 20 and the Mylar insulating film 30.

[0051] It can be understood that the liquid retention volume V / Cap per unit capacity of the battery 100 is the weight of the fresh battery 100 liquid retention / (density of the electrolyte x unit capacity of the battery 100).

[0052] "OI" is the ratio of the intensity of the 004 characteristic diffraction peak to the intensity of the 110 characteristic diffraction peak in the X-ray diffraction pattern of the negative electrode tab 13.

[0053] Further, 0 < 1 / (1+OI) x [a-(V / Cap)] x [b+c x d (GM-0.05) ]≤3.61. In other words, 0 < a ≤ 3.61.

[0054] Specifically, 1 / (1+OI) x [a-(V / Cap)] x [b+c x d (GM-0.05) ]may be, but is not limited to, 0.1, 0.3, 0.5, 0.8, 1.0, 1.3, 1.5, 1.8, 2.0, 2.3, 2.5, 2.8, 3.0, 3.3, 3.5, 3.61, etc. The smaller 1 / (1+OI) x [a-(V / Cap)] x [b+c x d (GM-0.05) ], the less likely the battery 100 is to produce purple spots during the charge and discharge cycle, and even if purple spots are produced, the smaller the area of the purple spots; 1 / (1+OI) x [a-(V / Cap)] x [b+c x d (GM-0.05)If the thickness of the negative electrode tab 13 is too large, the battery 100 is prone to purple discoloration during the charge and discharge cycle, causing the negative active material part of the negative electrode tab 13 to be deactivated, reducing the energy density of the battery 100; in addition, it also reduces the uniformity of lithium deintercalation during the charge and discharge process of the battery 100, increases the loss of active lithium, increases the capacity decay rate of the battery 100, and reduces the cycle capacity retention rate of the battery 100.

[0055] The battery 100 of the embodiment of the present application is designed by the group margin of the battery 100 in the full charge state, the liquid retention volume per unit capacity of the battery 100, and the OI value of the negative electrode tab 13, so that 1 / (1+OI)×[a-(V / Cap)]×[b+c×d (GM-0.05) ]≤3.61, so that the negative electrode tab 13 of the battery 100 is less prone to wrinkling and less prone to purple discoloration, thereby reducing the deactivation area of the negative active material of the negative active layer and improving the capacity development and energy density of the battery 100; in addition, the reduction of the purple discoloration area of the negative electrode tab 13 during lithium intercalation can improve the uniformity of lithium deintercalation during the charge and discharge process of the battery 100, reduce lithium precipitation around the purple discoloration, thereby reducing the loss of active lithium, slowing down the capacity decay of the battery 100, and improving the cycle life of the battery 100. Furthermore, the thickness expansion rate of the negative electrode tab 13 of different negative active materials from 0% SOC to 100% SOC is different, so even if the thickness group margin of two batteries 100 is the same at the initial 0% SOC, the thickness group margin and the large surface binding force they bear at the final 100% SOC will not be the same, and the wrinkling and purple discoloration of the negative electrode tab 13 will also be different; the thickness group margin of the battery 100 at 100% SOC is used for design in the present application, which can better reflect the final state of the large surface binding force of the negative electrode tab 13 after expansion, better reflect the final form of the wrinkling and purple discoloration of the negative electrode tab 13, and thus better control the wrinkling and purple discoloration of the negative electrode tab 13 of the battery 100, and better improve the cycle life of the battery 100.

[0056] Referring to FIG. 4, the positive electrode tab 11 can include a positive electrode current collector 111 and a positive electrode active layer 112, and the positive electrode active layer 112 is arranged on the surface of the positive electrode current collector 111. It can be understood that the positive electrode active layer 112 can cover one surface or opposite two surfaces of the positive electrode current collector 111.

[0057] Optionally, the positive electrode current collector 111 can be, but is not limited to, an aluminum sheet.

[0058] Optionally, the positive electrode active layer 112 can include positive electrode active material, positive electrode conductive agent, positive electrode binder, and positive electrode thickening agent.

[0059] Optionally, the positive active material can be, but is not limited to, lithium iron phosphate (LiFeP04).

[0060] Optionally, the positive conductive agent can be, but is not limited to, at least one of conductive carbon black, acetylene black, carbon nanotube, carbon fiber, graphene, and the like.

[0061] Optionally, the positive conductive agent can be, but is not limited to, at least one of conductive carbon black, acetylene black, carbon nanotube, carbon fiber, graphene, and the like.

[0062] Optionally, the positive conductive agent can be, but is not limited to, at least one of conductive carbon black, acetylene black, carbon nanotube, carbon fiber, graphene, and the like.

[0063] Optionally, the separator 12 can be, but is not limited to, at least one of a polypropylene film (PP film), a polyethylene film (PE film), a ceramic separator 12, and the like.

[0064] Referring to FIG. 5, optionally, the negative electrode tab 13 includes a negative current collector 131 and a negative active layer 132 disposed on a surface of the negative current collector 131. Understandably, the negative active layer 132 can cover one surface or opposite two surfaces of the negative current collector 131.

[0065] Optionally, the negative current collector 131 can be, but is not limited to, a copper sheet.

[0066] Optionally, the negative active layer 132 includes a negative active material, a negative conductive agent, a negative binder, and a negative thickening agent.

[0067] Optionally, the negative active material can be, but is not limited to, graphite.

[0068] Optionally, the negative conductive agent can be, but is not limited to, at least one of conductive carbon black (SP), acetylene black, carbon nanotube, carbon fiber, graphene, and the like.

[0069] Optionally, the negative electrode binder can be, but is not limited to, at least one of polyvinylidene fluoride, polyamide, polyacrylonitrile, polyacrylate, polyvinyl ether, polymethyl methacrylate, polyhexafluoropropylene, butadiene styrene rubber, etc.

[0070] Optionally, the negative electrode thickening agent can be, but is not limited to, at least one of sodium carboxymethyl cellulose (CMC for short), polyacrylamide (PAM), and polymethacrylate (PMA), etc.

[0071] Optionally, the electrolyte includes an electrolyte salt, an organic solvent, and a film-forming additive.

[0072] Optionally, the electrolyte salt can be a lithium salt, which can include at least one of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(oxalato)borate (LiBOB), lithium difluorophosphate dioxalate (LiODFP), lithium difluoro oxalate borate (LiODFB), lithium difluorophosphate (LiPO2F2), lithium triflate (CF3SO3Li), etc.

[0073] Optionally, the organic solvent includes at least one of a cyclic carbonate and a chain carbonate. The cyclic carbonate has a high dielectric constant and a high ionic conductivity, and can form a stable solid electrolyte interface film (SEI film for short) on the surface of the negative electrode tab 13, but has a relatively large viscosity. The chain carbonate has a lower viscosity than the cyclic carbonate and better electrochemical stability, and can improve the low-temperature performance of the electrolyte. Therefore, when a mixed solvent of a cyclic carbonate and a chain carbonate is used, the electrolyte can have a relatively suitable viscosity and low-temperature stability, and the battery 100 using the electrolyte can form a better film.

[0074] Optionally, the cyclic carbonate can include, but is not limited to, at least one of ethylene carbonate (EC for short), propylene carbonate (PC for short), etc. The dielectric constant of ethylene carbonate is much larger than that of propylene carbonate, and ethylene carbonate can better promote the formation of the SEI film.

[0075] Optionally, the chain carbonate can include, but is not limited to, at least one of dimethyl carbonate (DMC for short), diethyl carbonate (DEC for short), and methyl ethyl carbonate (EMC for short).

[0076] Optionally, the film-forming additive includes at least one of fluoroethylene carbonate (FEC), vinylene sulfate (DTD), vinylene carbonate (VC), vinyl ethylene carbonate (VEC), tris(trimethylsilyl)phosphate, tris(trimethylsilyl)borate, adiponitrile, succinonitrile, 1,3,6-hexanetricarbonitrile. When the electrolyte is applied to the battery 100, these film-forming additives can be used to promote the formation of an interfacial film in at least one of the positive electrode sheet 11 and the negative electrode sheet 13 and maintain the stability of the interfacial film.

[0077] In some embodiments, the thickness group margin GM of the battery 100 in the full charge state ranges from 90% to 97%.

[0078] Specifically, the thickness group margin GM of the battery 100 in the full charge state can be, but is not limited to, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, etc. If the thickness group margin GM of the battery 100 in the full charge state is too small, the energy density of the battery 100 is reduced, and the electrode assembly 10 is shaken in the case assembly 20, which is easy to tear the tab, in addition, the negative electrode sheet 13 is easy to wrinkle, so that the gap between the positive electrode sheet 11 and the negative electrode sheet 13 at the wrinkle position increases, and the electrolyte is easy to break the bridge, so that there is no lithium ion channel between the positive electrode sheet 11 and the negative electrode sheet 13 at the wrinkle position, and the reaction of deintercalation of lithium cannot be carried out, so that the negative active material at the wrinkle position is deactivated, thereby generating purple or black spots; as the group margin increases, the restraining force of the case assembly 20 (the large surface of the case assembly 20) on the electrode assembly 10 increases during the lithium intercalation expansion process, so that the negative electrode sheet 13 is less likely to wrinkle, thereby reducing the generation of purple spots; however, if the thickness group margin GM of the battery 100 in the full charge state is too large, the electrode assembly 10 is too thick, which is easy to enter the case assembly 20, even if it is installed in the case assembly 20, after the lithium intercalation expansion of the battery 100, the restraining force on the electrode assembly 10 is too large, so that the porosity of the negative electrode sheet 13 is reduced, the reaction site is reduced, the kinetic performance is reduced, and lithium precipitation is easy to occur, which deteriorates the cycle performance, in addition, it also makes the negative active material (such as graphite) of the negative electrode sheet 13 easy to break, the newly generated interface consumes lithium in the electrolyte, forms an SEI film, and reduces the capacity of the battery 100. In the present embodiment, the thickness group margin GM of the battery 100 in the full charge state ranges from 90% to 97%, which can better reduce the probability of the negative electrode sheet 13 being wrinkled and purple, reduce the deactivation of active lithium, and improve the cycle life of the battery 100.

[0079] Further, the thickness group margin GM of the battery 100 in the full charge state ranges from 91% to 96%. This can better reduce the probability of the negative electrode sheet 13 being wrinkled and purple, reduce the deactivation of active lithium, and improve the cycle life of the battery 100.

[0080] In some embodiments, the battery 100 has a liquid reserve volume per unit capacity V / Cap in the range of 1.5≤V / Cap≤4.1.

[0081] Specifically, the battery 100 has a liquid reserve volume per unit capacity V / Cap of, but not limited to, 1.5, 1.8, 2.0, 2.3, 2.5, 2.8, 3.0, 3.3, 3.5, 3.8, 4.0, 4.1, etc.

[0082] In the present embodiment, if the battery 100 has a liquid reserve volume per unit capacity that is too small, the wettability of the electrode assembly 10 is insufficient, which can cause some areas of the electrode assembly 10 to be not wetted by the electrolyte, so that the lithium deintercalation reaction cannot normally occur in these areas during the charge and discharge cycle, which can cause the negative electrode tab 13 to easily produce purple spots in the areas not wetted by the electrolyte, reduce the cycle performance of the battery 100, increase the impedance, and reduce the cycle capacity retention rate. As the liquid reserve volume per unit capacity V / Cap of the battery 100 increases, the occurrence of purple spots in the battery 100 can be reduced. However, if the liquid reserve volume per unit capacity of the battery 100 is too large, the amount of electrolyte injected into the battery 100 is too large, and the remaining space in the shell assembly 20 is too small. During the reaction of the electrode assembly 10, gas is generated, and the remaining space in the shell assembly 20 is not enough, which can cause the pressure in the battery 100 to be too large, the explosion-proof valve on the shell assembly 20 to be prematurely opened, affect the normal use of the battery 100, and reduce the service life of the battery 100. When the liquid reserve volume per unit capacity V / Cap of the battery 100 is in the range of 1.5≤V / Cap≤4.1, the battery 100 can have a relatively high liquid reserve volume, so that the electrolyte in the battery 100 has a relatively high liquid level, and the electrolyte is less likely to be disconnected below the liquid level. This can improve the purple spots, and in addition, the battery 100 can have a suitable remaining space, which can better avoid the pressure in the battery 100 being too large during the charge and discharge of the electrode assembly 10, the explosion-proof valve on the shell assembly 20 being prematurely opened, and the battery 100 having a longer service life.

[0083] Further, the battery 100 has a liquid reserve volume per unit capacity V / Cap in the range of 1.8≤V / Cap≤4.0. This can make the electrolyte more fully wet the electrode assembly 10, so that the battery 100 is less likely to produce purple spots during the charge and discharge cycle, has better cycle performance and cycle capacity retention rate, and can have a relatively appropriate remaining space in the battery 100, which can better avoid the pressure in the battery 100 being too large during the charge and discharge of the electrode assembly 10, the explosion-proof valve on the shell assembly 20 being prematurely opened, and the battery 100 having a longer service life.

[0084] In some embodiments, the OI value of the negative electrode tab 13 ranges from 0 < OI ≤ 60.

[0085] In other words, the ratio of the intensity of the 004 characteristic diffraction peak to the intensity of the 110 characteristic diffraction peak in the X-ray diffraction spectrum of the negative electrode tab 13 ranges from 0 to 60.

[0086] Specifically, the OI value of the negative electrode tab 13 can be, but is not limited to, 1, 3, 5, 8, 10, 13, 15, 18, 20, 23, 25, 28, 30, 33, 35, 38, 40, 43, 45, 48, 50, 53, 55, 58, 60, and the like.

[0087] The battery 100 usually adopts graphite as the negative electrode active material of the negative electrode tab 13. When the battery 100 is a lithium ion battery 100, the graphite has a multi-layer structure, and the graphite expands during lithium intercalation. The expansion of the graphite is disordered expansion, so that the negative electrode active layer 132 of the negative electrode tab 13 expands in all directions during lithium intercalation. The expansion in the direction parallel to the negative electrode tab 13 is easy to cause wrinkles of the negative electrode tab 13. The OI value reflects the expansion direction of the graphite crystal during lithium intercalation. The smaller the OI value, the more the expansion in the direction parallel to the negative electrode tab 13, the more wrinkles, and the higher the risk of purple stain at the wrinkles. When the OI value is high, although the purple stain phenomenon of the negative electrode tab 13 during lithium intercalation can be improved, the rate performance of the battery 100 is reduced. Therefore, when the OI value of the negative electrode tab 13 is 0 < OI ≤ 60, the battery 100 has good rate performance, and the risk of wrinkles and purple stain of the negative electrode tab 13 during lithium intercalation is better prevented, so that the battery 100 has a higher cycle life.

[0088] Further, the OI value of the negative electrode tab 13 ranges from 5 < OI ≤ 50. In this way, the battery 100 has good rate performance, and the risk of wrinkles and purple stain of the negative electrode tab 13 during lithium intercalation is better prevented, so that the battery 100 has a higher cycle life.

[0089] Still further, the OI value of the negative electrode tab 13 ranges from 5 < OI ≤ 20. In this way, the battery 100 has good rate performance, and the risk of wrinkles and purple stain of the negative electrode tab 13 during lithium intercalation is better prevented, so that the battery 100 has a higher cycle life.

[0090] In some embodiments, the constant a ranges from 2.6 ≤ a ≤ 5.6; the constant b ranges from 43 ≤ b ≤ 123; the constant c ranges from 1.2 × 10 27 ≤ c ≤ 4.2 × 10 27 ; and the constant d ranges from 3.3 × 10-30 ≤ c ≤ 11.3 x 10 -30 .

[0091] Specifically, the constant a can be, but is not limited to, 2.6, 2.8, 3.0, 3.2, 3.4, 3.6, 3.8, 4.0, 4.2, 4.4, 4.6, 4.8, 5.0, 5.2, 5.4, 5.6, etc. If the constant a is too large or too small, 1 / (1+OI) x [a-(V / Cap)] x [b+c x d (GM-0.05) ]≤3.61 cannot accurately reflect the purple stain condition of the battery 100.

[0092] Specifically, the constant b can be, but is not limited to, 43, 45, 50, 60, 70, 80, 90, 100, 110, 120, 123, etc. If the constant b is too large or too small, 1 / (1+OI) x [a-(V / Cap)] x [b+c x d (GM-0.05) ]≤3.61 cannot accurately reflect the purple stain condition of the battery 100.

[0093] Specifically, the constant c can be, but is not limited to, 1.2 x 10 27 , 1.4 x 10 27 , 1.6 x 10 27 , 1.8 x 10 27 , 2.0 x 10 27 , 2.2 x 10 27 , 2.4 x 10 27 , 2.5 x 10 27 , 2.6 x 10 27 , 2.8 x 10 27 , 3.0 x 10 27 , 3.2 x 10 27 , 3.4 x 10 27 , 3.6 x 10 27 , 3.8 x 10 27 , 4.0 x 10 27 , 4.2 x 10 27 , etc. If the constant c is too large or too small, 1 / (1+OI) x [a-(V / Cap)] x [b+c x d (GM-0.05) ]≤3.61 cannot accurately reflect the purple stain condition of the battery 100.

[0094] Specifically, the constant d can be, but is not limited to, 3.3 x 10 -30 , 3.4 x 10 -30 , 3.6 x 10 -30 , 3.8 x 10 -30 , 4.0 x 10 -30 , 4.2 x 10 -30 , 5 x 10-30 , 6 x 10 -30 , 7 x 10 -30 , 8 x 10 -30 , 9 x 10 -30 , 10 x 10 -30 , 11 x 10 -30 , 11.3 x 10 -30 , etc. If the constant d is too large or too small, it will not accurately reflect the purple stain condition of the battery 100, i.e., 1 / (1+OI) x [a-(V / Cap)] x [b+c x d (GM-0.05) ]≤3.61.

[0095] In some embodiments, the battery 100 has a purple stain area ratio of the negative electrode tab 13 in the area stacked with the positive electrode tab 11 of ≤0.015% at 100% SOC after 10 cycles of fresh charge and discharge, wherein SOC is the proportion of available capacity in the battery 100 to the nominal capacity.

[0096] It should be noted that the battery 100 has a purple stain area ratio of the negative electrode tab 13 in the area stacked with the positive electrode tab 11 of ≤0.015% at full charge after 10 cycles of fresh charge and discharge from 0% SOC to 100% SOC.

[0097] Optionally, during charging, one of the following can be used, but is not limited to: constant current charging (CC, i.e., the current is constant throughout the charging process), constant voltage charging (CV, i.e., the current is at a peak value after the instantaneous voltage reaches a set value), constant current and constant voltage charging (CC-CV, i.e., the current is first kept constant, the voltage is charged to the upper limit, then the voltage is kept constant, and finally the current is gradually reduced to a set value before the charging ends), etc.

[0098] Optionally, during discharging, one of the following can be used, but is not limited to: constant current discharging, constant voltage discharging, constant current and constant voltage discharging, etc.

[0099] It should be noted that the area of the negative electrode tab 13 stacked with the positive electrode tab 11 refers to the area of the negative electrode tab 13 covered by the orthographic projection of the positive electrode tab 11 on the surface of the negative electrode tab 13. In order to better prevent the negative electrode tab 13 from undergoing lithium precipitation during lithium intercalation, the area of the negative electrode tab 13 is usually designed to be larger than that of the positive electrode tab 11, i.e., the outer periphery of the negative electrode tab 13 exceeds that of the positive electrode tab 11.

[0100] Specifically, the battery 100 has a purple stain area ratio of the negative electrode tab 13 in the region stacked with the positive electrode tab 11 of ≤0.015%, ≤0.014%, ≤0.013%, ≤0.012%, ≤0.010%, ≤0.009%, ≤0.008%, ≤0.007%, ≤0.006%, ≤0.005%, ≤0.004%, ≤0.003%, ≤0.002%, ≤0.001%, etc. after 10 cycles of charge and discharge under fresh conditions in a full charge state.

[0101] In this embodiment, the battery 100 has a purple stain area ratio of the negative electrode tab 13 in the region stacked with the positive electrode tab 11 of ≤0.015% after 10 cycles of charge and discharge under fresh conditions in a full charge state. The battery 100 has a small purple stain area ratio when lithium is embedded, and the region of the negative electrode active layer 132 of the negative electrode tab 13 is small, thereby making the energy density of the battery 100 better, reducing the capacity decay rate of the battery 100, and making the battery 100 have a higher cycle capacity retention rate.

[0102] After the lithium ion battery is prepared, formation treatment needs to be performed to activate the active material in the battery, and a dense solid electrolyte interface film (SEI film for short) is generated on the surface of the electrode material (usually on the surface of the anode material). During the formation process of the lithium ion battery, gas is generated, which affects the quality of the SEI film and thus the cycle performance of the battery.

[0103] Referring to FIG. 6, the application also provides a formation method of a battery 100, which comprises:

[0104] S201, placing the battery 100 in a negative pressure environment;

[0105] Optionally, the negative pressure environment can be -100 KPa to -60 KPa, that is, the pressure is 1.325 KPa to 41.325 KPa. Specifically, the pressure can be, but is not limited to, 1.325 KPa, 5 KPa, 10 KPa, 15 KPa, 20 KPa, 25 KPa, 30 KPa, 35 KPa, 40 KPa, 41.325 KPa, etc. If the pressure is too small, the requirement for the equipment is too high, and even it cannot meet the requirement; if the pressure is too large, the gas generated during the formation process of the battery 100 is not easy to discharge, and the residual gas in the battery 100 is easy to cause the local breakage between the positive electrode tab 11 and the negative electrode tab 13, thereby making the active material corresponding to the part not react during the charge and discharge process, the active material in the part is deactivated, the position of the negative electrode tab 13 corresponding to the part produces a purple stain, and the cycle service life of the battery 100 is reduced.

[0106] S202, charging with a first current to charge a first electric quantity, stopping charging for a first time;

[0107] It can be understood that the first constant current charging is performed.

[0108] Optionally, the time of the first constant current charging is 5 min to 10 min. Specifically, the time of the first constant current charging can be, but is not limited to, 5 min, 6 min, 7 min, 8 min, 9 min, 10 min, etc. If the time of the first constant current charging is too short, the first electric quantity charged by the first constant current charging is too small, the SEI film of the battery 100 has not been completely formed, which affects the film forming quality of the SEI film, thereby affecting the cycle performance and service life of the battery 100. If the time of the first constant current charging is too long, the first electric quantity charged by the first constant current charging is too large, which will not improve the quality of the SEI film, but will reduce the production efficiency.

[0109] S203, charging with a second current to charge a second electric quantity, stopping charging for a second time;

[0110] It can be understood that the second constant current charging is performed.

[0111] Optionally, the time of the second constant current charging is 5 min to 20 min. Specifically, the time of the second constant current charging can be, but is not limited to, 5 min, 6 min, 7 min, 8 min, 9 min, 10 min, 12 min, 14 min, 16 min, 18 min, 20 min, etc. If the time of the second constant current charging is too short, the second electric quantity charged by the second constant current charging is too small, the battery 100 does not produce gas sufficiently, after the sealing nail of the shell assembly 20 is welded, the battery 100 continues to produce gas inside, which is easy to cause the battery 100 to swell, increase the internal pressure, and cause the valve to burst in advance, thereby reducing the service life of the battery 100. If the time of the second constant current charging is too long, the second electric quantity charged by the second constant current charging is too large, which will not affect the gas production of the battery 100, but will reduce the production efficiency of the battery 100 and increase the production cost of the battery 100.

[0112] S204, charging with a third current to charge a third electric quantity, stopping charging for a third time; and

[0113] It can be understood that the third constant current charging is performed.

[0114] Optionally, the time of the third constant current charging is 10 min to 30 min. Specifically, the time of the third constant current charging can be, but is not limited to, 10 min, 12 min, 14 min, 16 min, 18 min, 20 min, 22 min, 24 min, 26 min, 28 min, 30 min, etc. If the time of the third constant current charging is too short, the third electric quantity charged by the third constant current charging is too small, and the battery 100 does not produce gas sufficiently. After the sealing nail on the shell assembly 20 is welded, the battery 100 continues to produce gas inside, which easily causes the battery 100 to swell, the internal pressure increases, the valve bursts in advance, and the service life of the battery 100 is reduced. If the time of the third constant current charging is too long, the third electric quantity charged by the third constant current charging is too large, and the battery 100 will not be affected by the gas production. However, the production efficiency of the battery 100 is reduced, and the production cost of the battery 100 is increased.

[0115] S205, constant current charging at a fourth current to charge a fourth electric quantity, and stopping charging for a fourth time; wherein the first electric quantity is less than the second electric quantity, the second electric quantity is less than the third electric quantity, the second electric quantity is less than the fourth electric quantity, and the sum of the first electric quantity, the second electric quantity, the third electric quantity and the fourth electric quantity is 25% SOC to 35% SOC, wherein SOC is the proportion of the available electric quantity in the battery 100 to the nominal capacity.

[0116] Optionally, the time of the fourth constant current charging is 10 min to 30 min. Specifically, the time of the fourth constant current charging can be, but is not limited to, 10 min, 12 min, 14 min, 16 min, 18 min, 20 min, 22 min, 24 min, 26 min, 28 min, 30 min, etc. If the time of the fourth constant current charging is too short, the fourth electric quantity charged by the fourth constant current charging is too small, and the battery 100 does not produce gas sufficiently. After the sealing nail on the shell assembly 20 is welded, the battery 100 continues to produce gas inside, which easily causes the battery 100 to swell, the internal pressure increases, the valve bursts in advance, and the service life of the battery 100 is reduced. If the time of the fourth constant current charging is too long, the fourth electric quantity charged by the fourth constant current charging is too large, and the battery 100 will not be affected by the gas production. However, the production efficiency of the battery 100 is reduced, and the production cost of the battery 100 is increased.

[0117] Specifically, the sum of the first electric quantity, the second electric quantity, the third electric quantity and the fourth electric quantity can be, but is not limited to, 25% SOC, 26% SOC, 27% SOC, 28% SOC, 29% SOC, 30% SOC, 31% SOC, 32% SOC, 33% SOC, 34% SOC, 35% SOC, etc. If the sum of the first electric quantity, the second electric quantity, the third electric quantity and the fourth electric quantity is too low, the gas production is insufficient, and the battery 100 will continue to produce gas during the charging and discharging process after the sealing nail welding, which will cause the gas pressure in the battery 100 to rise, the explosion-proof valve to open in advance, and the cycle life of the battery 100 to decrease; if the sum of the first electric quantity, the second electric quantity, the third electric quantity and the fourth electric quantity is too high, the production efficiency will be reduced.

[0118] The formation method of the battery 100 of the embodiment of the present application includes a four-stage constant current charging process. By making the first electric quantity less than the second electric quantity, the second electric quantity less than the third electric quantity, the second electric quantity less than the fourth electric quantity, and the sum of the first electric quantity, the second electric quantity, the third electric quantity and the fourth electric quantity being 25% SOC to 35% SOC, the surface of the positive electrode sheet 11 and the negative electrode sheet 13 of the battery 100 can form a better SEI film, the consumption of the SEI film of the battery 100 during the charging and discharging cycle process is reduced, and thus the battery 100 has higher cycle performance and cycle life. In addition, by designing the electric quantity charged in each stage of the four-stage constant current charging process and the total electric quantity charged in the four-stage constant current charging process, the battery 100 can produce more complete gas during the formation process, the generated gas can be better discharged, the incomplete discharge of the gas is avoided, the purple stain is easily produced in the battery 100 during the charging and discharging cycle process, the power attenuation rate of the battery 100 is reduced, and the service life of the battery 100 is improved. Furthermore, the battery 100 is formed in a negative pressure environment, which can better discharge the gas generated in the battery 100 during the formation process, better avoid the incomplete discharge of the gas, the purple stain is easily produced in the battery 100 during the charging and discharging cycle process, the power attenuation rate of the battery 100 is reduced, and the service life of the battery 100 is improved.

[0119] In some embodiments, the first electric quantity Q1 is in the range of 0.5% SOC≤Q1≤2% SOC.

[0120] Specifically, the first electric quantity Q1 can be, but is not limited to, 0.5% SOC, 0.6% SOC, 0.8% SOC, 1% SOC, 1.2% SOC, 1.4% SOC, 1.6% SOC, 1.8% SOC, 2% SOC, etc. If the first electric quantity charged by the first constant current charging is too small, the SEI film of the battery 100 has not been completely formed, which affects the film forming quality of the SEI film, thereby affecting the cycle performance and service life of the battery 100; if the first electric quantity charged by the first constant current charging is too large, the quality of the SEI film will not be improved, but the production efficiency will be reduced.

[0121] Optionally, the second electric quantity Q2 ranges from 3% SOC to 10% SOC.

[0122] Specifically, the second electric quantity Q2 can be, but is not limited to, 3% SOC, 4% SOC, 5% SOC, 6% SOC, 7% SOC, 8% SOC, 9% SOC, 10% SOC, etc. If the second electric quantity Q2 charged by the second constant current charging is too small, the battery 100 has insufficient gas production, and after the sealing nail welding on the shell assembly 20, the battery 100 continues to produce gas inside, which is easy to cause the battery 100 to swell, increase the internal pressure, and prematurely burst the valve, thereby reducing the service life of the battery 100; if the second electric quantity Q2 charged by the second constant current charging is too large, the battery 100 has no influence on the gas production, but the production efficiency of the battery 100 is reduced, and the production cost of the battery 100 is increased.

[0123] Optionally, the third electric quantity Q3 ranges from 5% SOC to 20% SOC.

[0124] Specifically, the third electric quantity Q3 can be, but is not limited to, 5% SOC, 6% SOC, 7% SOC, 8% SOC, 9% SOC, 10% SOC, 12% SOC, 14% SOC, 16% SOC, 18% SOC, 20% SOC, etc. If the third electric quantity Q3 charged by the third constant current charging is too small, the battery 100 has insufficient gas production, and after the sealing nail welding on the shell assembly 20, the battery 100 continues to produce gas inside, which is easy to cause the battery 100 to swell, increase the internal pressure, and prematurely burst the valve, thereby reducing the service life of the battery 100; if the third electric quantity Q3 charged by the third constant current charging is too large, the battery 100 has no influence on the gas production, but the production efficiency of the battery 100 is reduced, and the production cost of the battery 100 is increased.

[0125] Optionally, the fourth electric quantity Q4 ranges from 5% SOC to 20% SOC.

[0126] Specifically, the fourth electric quantity Q4 can be, but is not limited to, 5% SOC, 6% SOC, 7% SOC, 8% SOC, 9% SOC, 10% SOC, 12% SOC, 14% SOC, 16% SOC, 18% SOC, 20% SOC, etc. If the fourth electric quantity Q4 charged by the fourth constant current charging is too small, the battery 100 is not sufficient in gas production, and after the sealing nail welding on the shell assembly 20, the battery 100 continues to produce gas inside, which is easy to cause the battery 100 to swell, increase the internal pressure, and cause the valve to burst in advance, thereby reducing the service life of the battery 100. If the fourth electric quantity Q4 charged by the fourth constant current charging is too large, the battery 100 will not be affected by the gas production, but the production efficiency of the battery 100 is reduced, and the production cost of the battery 100 is increased.

[0127] In some embodiments, the first stopping charging time includes a first static time; or the first stopping charging time includes a first centrifugal time at a first centrifugal acceleration;

[0128] The second stopping charging time includes a second static time; or the second stopping charging time includes a second centrifugal time at a second centrifugal acceleration;

[0129] The third stopping charging time includes a third static time; or the third stopping charging time includes a third centrifugal time at a third centrifugal acceleration;

[0130] The fourth stopping charging time includes a fourth static time; or the fourth stopping charging time includes a fourth centrifugal time at a fourth centrifugal acceleration.

[0131] In the related art, the battery is discharged after the entire formation is completed, and then the gas generated during the formation process is easy to form bubbles on the positive and negative electrode plates, so that the positive and negative electrode plates cannot be formed on the bubble position, thereby affecting the cycle performance and capacity of the battery.

[0132] In the present embodiment, after each segment of charging is completed, a static time or a centrifugal time is set, so that the gas generated during the formation of the battery 100 is better discharged, and the gas is not completely discharged and remains in the battery 100, so that the battery 100 is easy to produce purple spots during the charging and discharging cycle, thereby reducing the electric quantity decay rate of the battery 100 and improving the service life of the battery 100. In addition, compared with the static time, the centrifugal time can increase the buoyancy of the bubbles, so that the gas is more easily discharged, the battery 100 is more completely discharged, and has a better discharge effect. Furthermore, the segmented stopping charging for discharging can reduce the influence of the bubbles generated by the previous segment of formation on the subsequent activation formation, avoid the bubbles generated by the previous segment of formation to form bubbles on the positive and negative electrode plates 11 and 13, so that the bubble position cannot be formed, thereby better improving the formation effect and uniformity.

[0133] In some embodiments, the first time T1 is less than the second time T2; the second time T2 is less than the third time T3; and the fourth time T4 is less than the third time T3. The present embodiment can make the gas generated in the formation process of the battery 100 better discharged, and the exhaust effect is better, and the gas discharge is not completely avoided. The battery 100 is easy to produce purple stain in the charging and discharging cycle process, reduces the power attenuation speed of the battery 100, and improves the service life of the battery 100.

[0134] In some embodiments, the first time T1 is in the range of 0 < T1 ≤ 3 min. Optionally, the second time T2 is in the range of 0 < T2 ≤ 5 min. Optionally, the third time T3 is in the range of 0 < T3 ≤ 10 min. Optionally, the fourth time T4 is in the range of 0 < T4 ≤ 5 min. Specifically, the first time T1 can be, but is not limited to, 0.5 min, 1 min, 1.5 min, 2 min, 2.5 min, 3 min, etc. Specifically, the second time T2 can be, but is not limited to, 0.5 min, 1 min, 1.5 min, 2 min, 2.5 min, 3 min, 4 min, 4.5 min, 5 min, etc. Specifically, the third time T3 can be, but is not limited to, 0.5 min, 1 min, 1.5 min, 2 min, 2.5 min, 3 min, 4 min, 4.5 min, 5 min, 6 min, 7 min, 8 min, 9 min, 10 min, etc. Specifically, the fourth time T4 can be, but is not limited to, 0.5 min, 1 min, 1.5 min, 2 min, 2.5 min, 3 min, 4 min, 4.5 min, 5 min, etc.

[0135] In the present embodiment, the first time, the second time, the third time and the fourth time are too short to reduce the exhaust effect of the battery 100, and the first time, the second time, the third time and the fourth time are too long to increase the production cost of the battery 100. The present application designs the first time, the second time, the third time and the fourth time, so that the gas generated in the formation process of the battery 100 can be more fully discharged, and has better exhaust effect, and has higher production efficiency.

[0136] In some embodiments, the first centrifugal acceleration A1 is greater than the second centrifugal acceleration A2, the second centrifugal acceleration A2 is greater than or equal to the third centrifugal acceleration A3, and the second centrifugal acceleration A2 is greater than or equal to the fourth centrifugal acceleration A4. By designing the relationship of the centrifugal acceleration after constant current charging for four sections, the gas generated in the formation process of the battery 100 can be better discharged in this embodiment, the exhaust effect is better, and the gas discharge is not completely avoided. Residual in the battery 100, so that the battery 100 is easy to produce purple stain in the charge and discharge cycle process, reduces the power attenuation speed of the battery 100, and improves the service life of the battery 100.

[0137] In some embodiments, the first centrifugal acceleration A1 is in the range of 0 < A1≤ 50 m / s 2 . Optionally, the second centrifugal acceleration A2 is in the range of 0 < A2≤ 50 m / s 2 . Optionally, the third centrifugal acceleration A3 is in the range of 0 < A3≤ 50 m / s 2 . Optionally, the fourth centrifugal acceleration A4 is in the range of 0 < A4≤ 50 m / s 2 .

[0138] Specifically, the first centrifugal acceleration A1 can be, but is not limited to, 1 m / s 2 , 5 m / s 2 , 10 m / s 2 , 15 m / s 2 , 20 m / s 2 , 25 m / s 2 , 30 m / s 2 , 35 m / s 2 , 40 m / s 2 , 45 m / s 2 , 50 m / s 2 , etc. Specifically, the second centrifugal acceleration A2 can be, but is not limited to, 1 m / s 2 , 5 m / s 2 , 10 m / s 2 , 15 m / s 2 , 20 m / s 2 , 25 m / s 2 , 30 m / s 2 , 35 m / s 2 , 40 m / s 2 , 45 m / s 2 , 50 m / s 2 , etc. Specifically, the third centrifugal acceleration A3 can be, but is not limited to, 1 m / s 2 , 5 m / s 2 , 10 m / s 2, 15 m / s 2 , 20 m / s 2 , 25 m / s 2 , 30 m / s 2 , 35 m / s 2 , 40 m / s 2 , 45 m / s 2 , 50 m / s 2 , etc. Specifically, the fourth centrifugal acceleration A4 can be, but is not limited to, 1 m / s 2 , 5 m / s 2 , 10 m / s 2 , 15 m / s 2 , 20 m / s 2 , 25 m / s 2 , 30 m / s 2 , 35 m / s 2 , 40 m / s 2 , 45 m / s 2 , 50 m / s 2 , etc.

[0139] The embodiment can make the gas generated in the formation process of the battery 100 better discharged, has better exhaust effect, better avoids the gas not completely discharged and remaining in the battery 100, makes the battery 100 easy to produce purple stain in the charge and discharge cycle process, reduces the power attenuation speed of the battery 100, and improves the service life of the battery 100.

[0140] In some embodiments, the first current is less than the second current, the first current is less than the third current, and the first current is less than the fourth current. In the embodiment, by designing the relationship of the first current, the second current, the third current and the fourth current, the quality of the SEI film formed in the formation process of the battery 100 is better, so that the battery 100 has a higher service life; in addition, the reaction in the formation process of the battery 100 is more uniform, and the gas generation is more sufficient, so that after the liquid injection hole on the shell assembly 20 is sealed by the sealing nail, the battery 100 still continues to generate gas.

[0141] Optionally, the first current I1 is in the range of 0.05C≤I1≤0.3C. Specifically, the first current I1 can be, but is not limited to, 0.05C, 0.08C, 0.1C, 0.13C, 0.15C, 0.18C, 0.2C, 0.23C, 0.25C, 0.28C, 0.3C, etc. The first charging process is the process of the SEI film of the electrode assembly 10 of the battery 100, and too large or too small first current I1 will affect the film forming quality of the SEI film of the electrode assembly 10, and reduce the cycle performance of the battery 100. When the first current I1 is in the range of 0.05C to 0.3C, the quality of the SEI film is better improved, so that the battery 100 has better cycle performance.

[0142] Optionally, the second current I2 is in the range of 0.1C≤I2≤1C. Specifically, the second current I2 can be, but is not limited to, 0.1C, 0.2C, 0.3C, 0.4C, 0.5C, 0.6C, 0.7C, 0.8C, 0.9C, 1C, etc. Too small second current I2 will make the formation time of the battery 100 too long, reducing the production efficiency of the battery 100; too large second current I2 will make the battery 100 prone to lithium precipitation, the reaction in the battery 100 is not uniform, and the gas production is insufficient, so that after the injection hole is sealed by the sealing nail, the battery 100 still continues to produce gas, and the battery 100 is prone to swelling during the charge and discharge cycle, and the explosion-proof valve is broken early, reducing the service life of the battery 100.

[0143] The battery 100 of the present application is further described below through specific examples.

[0144] Examples 1, 2, Comparative Examples 1 to 5

[0145] The battery 100 of each example and comparative example is made into a square battery 100 in a winding manner, with aluminum foil as the positive current collector 111, lithium iron phosphate as the positive active material, copper foil as the negative current collector 131, graphite as the negative active material, and polypropylene as the separator 12. Lithium hexafluorophosphate is used as the electrolyte salt, and methyl ethyl carbonate (abbreviated as EMC), ethylene carbonate (abbreviated as EC), and dimethyl carbonate (abbreviated as DMC) in a mass ratio of 2:2:1 are used as organic solvents to configure an electrolyte, and the molar concentration of lithium hexafluorophosphate in the electrolyte is 1 mol / L.

[0146] The thickness group margin GM of the battery 100 of each example and comparative example in a full charge state, the OI value of the negative electrode sheet 13, the liquid retention volume V / Cap per unit capacity of the battery 100, and the value of a are shown in Table 1 below.

[0147] For the battery 100 of each example and comparative example, a = 4.1, b = 82.6, c = 2.05865 x 1027 d = 7.2722 x 10 -30 .

[0148] The batteries 100 of each of the above examples and comparative examples were subjected to performance tests.

[0149] (1) Purple stain test: the battery 100 was charged at a temperature of 25±2°C to 3.65V at a constant current of 1C, charged to 3.65V at a constant voltage of 0.05C, and rested for 30min; and discharged to 2.5V at a constant current of 1C, and rested at 2.5V. One cycle was performed once, and after repeating the cycle 10 times, the battery 100 was disassembled, and the purple stain area was calculated. The purple stain area can be measured by a ruler, or the edge of the purple stain can be circled by area measurement software such as Image J, and the area of the purple stain is automatically calculated.

[0150] Among them, the photograph of the negative electrode sheet 13 of the battery 100 of Example 1 after disassembly is shown in FIG. 7. The photograph of the negative electrode sheet 13 of the battery 100 of Example 2 after disassembly is shown in FIG. 8. The photograph of the negative electrode sheet 13 of the battery 100 of Comparative Example 1 after disassembly is shown in FIG. 9. The photograph of the negative electrode sheet 13 of the battery 100 of Comparative Example 3 after disassembly is shown in FIG. 10.

[0151] The test results of each of the examples and comparative examples are shown in Table 1 below:

[0152] Table 1 Test data of the battery 100 of each of the examples and comparative examples

[0153] From the test results of Example 1, Example 2, Comparative Example 1 and Comparative Example 2, when α = 1 / (1+OI)×[a-(V / Cap)]×[b+c×d (GM-0.05) ]≤3.61, the battery 100 is not prone to produce purple stains after 10 cycles of charge and discharge, such as the batteries 100 of Example 1 and Example 2. When α = 1 / (1+OI)×[a-(V / Cap)]×[b+c×d (GM-0.05) ] is too large (such as Comparative Examples 1 to 5), the probability of the battery 100 producing purple stains during the charge and discharge cycle increases, and as α = 1 / (1+OI)×[a-(V / Cap)]×[b+c×d (GM-0.05) ] increases, the number of purple stains increases.

[0154] The term "in an embodiment" or "in embodiments" appearing in various locations throughout this application refers to various embodiments of the application described in the specification. The presence of this term in a given location does not necessarily refer to the same embodiment in every instance. It is explicitly contemplated that one or more embodiments of the application can include some features, structures, or characteristics described in connection with one or more embodiments while excluding others. Furthermore, it is also contemplated that one or more embodiments of the application can include some features, structures, or characteristics of the disclosure while excluding others. Accordingly, no limitation - expressed or implied - is placed on the scope of the application described in the claims.

[0155] Finally, it should be noted that the above-mentioned embodiments are merely used to illustrate the technical solutions of the present application, but not to limit the present application. Although the present application is described in detail with reference to the above preferred embodiments, it should be understood by those skilled in the art that the technical solutions of the present application can be modified or replaced by equivalents without departing from the spirit and scope of the present application.

Claims

1. A battery, wherein, Comprising: An electrode assembly including a positive electrode sheet, a separator, and a negative electrode sheet, and an electrolyte, the battery satisfying the relationship: α = 1 / (1 + OI) x [a - (V / Cap)] x [b + c x d] ≤ 3.61 (GM-0.05) ]≤3.61; wherein, OI is the OI value of the negative electrode sheet, V / Cap is the liquid retention volume per unit capacity of the battery, in units of ml / Ah; GM is the thickness group margin of the battery in full charge state, a, b, c, d are all constants.

2. The battery of claim 1, wherein, The thickness group margin GM of the battery in full charge state ranges from 90% to 97%.

3. The battery of claim 1, wherein, The liquid retention volume V / Cap per unit capacity of the battery ranges from 1.5≤V / Cap≤4.

1.

4. The battery of claim 1, wherein, The OI value of the negative electrode sheet ranges from 0 5. The battery of claim 1, wherein, The constant a ranges from 2.6 < a < 5.6; the constant b ranges from 43 < b < 123; the constant c ranges from 1.2 x 10 27 ≤ c < 4.2 x 10 27 ; and the constant d ranges from 3.3 x 10 -30 ≤ c < 11.3 x 10 -30 .

6. The battery of claim 1, wherein, After 10 cycles of charge and discharge under fresh conditions, the proportion of purple stain area of the negative electrode sheet in the region stacked with the positive electrode sheet is ≤0.015% at 100% SOC, wherein SOC is the proportion of available capacity in the battery to the nominal capacity.

7. A method of forming a battery, wherein, The formation method comprises: placing the battery in a negative pressure environment; constant current charging at a first current to charge a first amount of electricity, stopping charging for a first time; constant current charging at a second current to charge a second amount of electricity, stopping charging for a second time; constant current charging at a third current to charge a third amount of electricity, stopping charging for a third time; and constant current charging at a fourth current to charge a fourth amount of electricity, stopping charging for a fourth time; wherein the first amount of electricity is less than the second amount of electricity, the second amount of electricity is less than the third amount of electricity, the second amount of electricity is less than the fourth amount of electricity, and the sum of the first amount of electricity, the second amount of electricity, the third amount of electricity and the fourth amount of electricity is 25% SOC to 35% SOC, wherein SOC is the proportion of available capacity in the battery to the nominal capacity.

8. The method of forming of a battery according to claim 7, wherein, The first amount of electricity Q1 ranges from 0.5% SOC≤Q1≤2% SOC; the second amount of electricity Q2 ranges from 3% SOC≤Q2≤10% SOC; the third amount of electricity Q3 ranges from 5% SOC≤Q3≤20% SOC; and the fourth amount of electricity Q4 ranges from 5% SOC≤Q4≤20% SOC.

9. The method of forming a battery of claim 7, wherein, The first stopping charging time includes a first standing time; or the first stopping charging time includes centrifuging at a first centrifugal acceleration for a first centrifuging time; The second stopping charging time includes a second standing time; or the second stopping charging time includes centrifuging at a second centrifugal acceleration for a second centrifuging time; The third stopping charging time includes a third standing time; or the third stopping charging time includes centrifuging at a third centrifugal acceleration for a third centrifuging time; The fourth stopping charging time includes a fourth standing time; or the fourth stopping charging time includes centrifuging at a fourth centrifugal acceleration for a fourth centrifuging time.

10. The method of forming a battery of claim 9, wherein, The first time T1 is less than the second time T2; the second time T2 is less than the third time T3; and the fourth time T4 is less than the third time T3.

11. The method of forming of a battery according to claim 10, wherein, The first time T1 ranges from 0 The second time T2 ranges from 0 The third time T3 ranges from 0 The fourth time T4 ranges from 0 12. The method of forming of a battery according to claim 9, wherein, The first centrifugal acceleration A1 is greater than the second centrifugal acceleration A2, the second centrifugal acceleration A2 is greater than or equal to the third centrifugal acceleration A3, and the second centrifugal acceleration A2 is greater than or equal to the fourth centrifugal acceleration A4.

13. The method of forming of a battery according to claim 12, wherein, said first centrifugal acceleration A1 ranges from 0 < A1 < 50 m / s 2 said second centrifugal acceleration A2 ranges from 0 < A2 < 50 m / s 2 said third centrifugal acceleration A3 ranges from 0 < A3 < 50 m / s 2 said fourth centrifugal acceleration A4 ranges from 0 < A4 < 50 m / s 2 .

14. The method of forming of a battery according to claim 7, wherein, The first current is less than the second current, the first current is less than the third current, and the first current is less than the fourth current.

15. An energy storage device, wherein, The energy storage device comprises: a box; and a plurality of batteries housed in the box, the batteries being the batteries of any one of claims 1-6 or the batteries being obtained by the formation method of the batteries of any one of claims 7-14.

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