Cylindrical battery, energy storage device and energy storage system

Abstract

The invention provides a cylindrical battery, an energy storage device and an energy storage system. The cylindrical battery comprises an electrolyte, the electrolyte comprises an electrolyte salt, a first additive and an organic solvent, the sum of the mass fraction of the electrolyte salt and the mass fraction of the first additive in the electrolyte is X, and the first additive is a cyclic sulfate additive; the electrode assembly comprises an electrode plate, the electrode plate comprises a current collector and a plurality of tabs, the current collector and the tabs are electrically connected, the tabs are arranged on the same side of the current collector at intervals, and the distance between every two adjacent tabs is d; the electrode assembly is of a winding structure, the electrode assembly is provided with a center hole, the diameter of the center hole of the electrode assembly is L, the unit of d is mm, and the unit of L is mm; the cylindrical battery also meets the relational expression: d = k / X-L, and k is more than or equal to 0.4 mm and less than or equal to 2.175 mm.

Description

Technical Field

[0001] This application relates to the field of energy storage, and particularly to a cylindrical battery, an energy storage device and an energy storage system. Background Art

[0002] The cylindrical battery itself has the characteristics of good single consistency, high temperature resistance, safety and not easy to explode, high energy density and small internal resistance, making it occupy a certain proportion in actual working conditions. However, the overcharge temperature and thermal runaway temperature of the cylindrical battery in the related art are both relatively high, and the safety risk is relatively large. Summary of the Invention

[0003] An embodiment of this application provides a cylindrical battery, which has a lower overcharge temperature and thermal runaway temperature, and has higher safety.

[0004] In a first aspect, an embodiment of this application provides a cylindrical battery, which includes:

[0005] An electrolyte, which includes an electrolyte salt, a first additive and an organic solvent. The total mass fraction of the electrolyte salt and the first additive in the electrolyte is X, and the first additive is a cyclic sulfate additive; and

[0006] An electrode assembly, which includes electrode tabs. The electrode tabs include a current collector and a plurality of tabs that are electrically connected. The plurality of tabs are spaced apart on the same side of the current collector, and the distance between adjacent two tabs is d; the electrode assembly has a wound structure, the electrode assembly has a central hole, and the diameter of the central hole of the electrode assembly is L, where the unit of d is mm and the unit of L is mm;

[0007] The cylindrical battery also satisfies the relational expression: d = k / X - L, where the range of k is 0.4 mm ≤ k ≤ 2.175 mm.

[0008] Further, the structural formula of the cyclic sulfate additive is: Among them,, A is one of methyl, ethyl, propyl, isopropyl, and vinylene sulfate group; R is (CH 2 )n, and the range of n is 1 to 3.

[0009] Further, in the electrolyte, the range of the total mass fraction of the electrolyte salt and the first additive is: 8.85% ≤ X ≤ 14.5%.

[0010] Further, the electrolyte further includes a second additive, and the structural formula of the second additive is: In the electrolyte, the range of the mass fraction m of the second additive is: 0.1% ≤ m ≤ 1%.

[0011] Further, the distance d between two adjacent tabs ranges from 1 mm ≤ d ≤ 6 mm.

[0012] Further, the diameter L of the central hole of the electrode assembly ranges from 3 mm ≤ L ≤ 12 mm.

[0013] Further, the number of turns M of the electrode assembly winding is M turns, and M turns include N steps. Each step includes multiple turns. Each turn of the electrode tab includes multiple tabs. The sizes of the multiple tabs in each step are the same. From the outermost circle to the innermost circle of the electrode assembly, the widths of the tabs of different steps gradually decrease in gradient, and the heights of the tabs of different steps also gradually decrease in gradient, where M > N.

[0014] Further, the number N of steps of the electrode assembly ranges from 2 ≤ N ≤ 10.

[0015] Further, the number n of tabs of the electrode tab ranges from 400 ≤ n ≤ 2000.

[0016] Further, the height h1 of the tab of the step of the electrode assembly closest to the central hole ranges from 2 mm ≤ h1 ≤ 6 mm.

[0017] Further, when the electrode assembly is in a wound structure, the radial width w1 of the step farthest from the central hole ranges from 100 mm ≤ w1 ≤ 300 mm.

[0018] Further, the electrode tab includes a tabless area, and the tabless area is disposed close to the central hole and connected to the step closest to the central hole. When the electrode assembly is flattened, the length s1 of the tabless area ranges from 100 mm ≤ s1 ≤ 500 mm.

[0019] Further, the length s2 of the electrode tab corresponding to the innermost step of the electrode assembly when flattened ranges from 300 mm ≤ s2 ≤ 500 mm.

[0020] In a second aspect, an embodiment of the present application provides an energy storage device, which includes:

[0021] A box body; and

[0022] A plurality of cylindrical batteries according to the embodiments of the present application, and the plurality of cylindrical batteries are received in the box body.

[0023] In a third aspect, an embodiment of the present application provides an energy storage system, which includes:

[0024] The energy storage device according to the embodiment of the present application; and

[0025] An electric energy conversion device is electrically connected to the energy storage device. The electric energy conversion device is used to convert other forms of energy into electric energy, and the energy storage device is used to store the electric energy.

[0026] The cylindrical battery of the embodiment of the present application satisfies the relational expression d = k / X - L, where the range of k is 0.4 mm ≤ k ≤ 2.175 mm. By designing the relational expression d = k / X - L and the value of k, the cylindrical battery has better electrolyte wettability, so that the specific capacity of the cylindrical battery can be better exerted, the cylindrical battery has a higher normal temperature cycle capacity retention rate, and thus has a higher normal temperature cycle service life. In addition, the cylindrical battery also has higher safety performance. In this embodiment, by appropriately increasing the diameter of the central hole and using an electrolyte solution with a lower electrolyte salt concentration, the risk of side reactions during the safety test of the cylindrical battery (i.e., overcharge or thermal runaway) can be reduced. By adding a cyclic sulfate additive, the problem of accelerated consumption of electrolyte salts during the cycle caused by the lower electrolyte salt concentration can be improved. The cyclic sulfate additive can increase the content of inorganic sulfates in the interfacial film of the electrode plate, reduce the resistance of the interfacial film, reduce the heat generation during overcharge of the cylindrical battery, and improve the normal temperature cycle performance and high temperature cycle performance of the cylindrical battery. In addition, by appropriately increasing the distance d between two adjacent tab ears and the diameter L of the central hole, the gas generation path during the safe overcharge of the cylindrical battery can also be increased. Coupled with an electrolyte solution with a lower electrolyte salt concentration, the cylindrical battery has lower reaction consumption during the overcharge process at high voltage, so that the safety performance of the cylindrical battery can be improved, the wettability of the electrode assembly of the cylindrical battery can be improved, and the normal temperature cycle performance and high temperature cycle performance of the cylindrical battery can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0028] Figure 1 It is a schematic structural diagram of a cylindrical battery according to an embodiment of the present application.

[0029] Figure 2 It is along Figure 1 The cross-sectional structural diagram of the cylindrical battery in the present application in the A-A direction.

[0030] Figure 3 It is a schematic structural diagram when the electrode plate of an embodiment of the present application is unfolded.

[0031] Figure 4It is a top - view structural schematic diagram when the electrode assembly of an embodiment of the present application is wound.

[0032] Figure 5 It is a cross - sectional structural schematic diagram of the positive electrode tab of an embodiment of the present application.

[0033] Figure 6 It is a cross - sectional structural schematic diagram of the negative electrode tab of an embodiment of the present application.

[0034] Figure 7 It is a structural schematic diagram of an energy storage device of an embodiment of the present application.

[0035] Figure 8 It is a structural block diagram of an energy storage system of an embodiment of the present application.

[0036] Figure 9 It is an application scenario diagram of an energy storage system of an embodiment of the present application.

[0037] Explanation of reference numerals:

[0038] 100 - cylindrical battery, 10 - electrode assembly, 11 - electrode tab, 111 - current collector, 112 - tab, 11a - positive electrode tab, 111a - positive current collector, 112a - positive tab, 113a - positive active layer, 11b - negative electrode tab, 111b - negative current collector, 112b - negative tab, 113b - negative active layer, 12 - separator, 13 - central hole, 14 - tab - free area, 15 - step, 20 - housing, 30 - end - cover assembly, 200 - energy storage device, 210 - box body, 300 - energy storage system, 310 - power conversion device. Detailed implementation manners

[0039] In order to enable those skilled in the art to better understand the solution of the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present application.

[0040] The terms "first", "second", etc. in the specification and claims of the present application and the above - mentioned drawings are used to distinguish different objects, rather than 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 that includes a series of steps or units is not limited to the listed steps or units, but optionally further includes steps or units not listed, or optionally further includes other steps or units inherent to these processes, methods, products or devices.

[0041] The technical solutions in the embodiments of the present application will be described below in conjunction with the accompanying drawings.

[0042] It should be noted that for ease of description, in the embodiments of the present application, the same reference numerals represent the same components, and for the sake of brevity, in different embodiments, the detailed description of the same components is omitted.

[0043] Currently, the generation of green electric energy generally relies on photovoltaics, wind power, water potential, etc. However, wind energy and solar energy generally have problems of strong intermittency and large volatility, which will cause instability of the power grid. There is not enough electricity during peak electricity consumption, and too much electricity during low electricity consumption. The unstable voltage will also damage the power. Therefore, the problems of "abandoning wind and light" may be caused due to insufficient electricity demand or insufficient grid acceptance capacity. To solve these problems, energy storage is required. That is, the electric energy is converted into other forms of energy and stored through physical or chemical means, and the energy is converted into electric energy and released when needed. Simply put, energy storage is similar to a large "portable charger". When photovoltaics and wind energy are sufficient, the electric energy is stored, and the stored energy is released when needed.

[0044] The cylindrical battery is the smallest energy storage unit of the energy storage device and the energy storage system, and the performance of the cylindrical battery directly affects the performance and application of the energy storage device and the energy storage system.

[0045] The cylindrical battery itself has the characteristics of good single consistency, high temperature resistance, safety and not easy to explode, high energy density, and small internal resistance, making it occupy a certain proportion in actual working conditions. However, the overcharge temperature and thermal runaway temperature of the cylindrical battery in the related art are both relatively high, and the safety risk is relatively large.

[0046] Please refer to Figures 1 to 3 , an embodiment of the present application provides a cylindrical battery 100, the cylindrical battery 100 includes an electrolyte and an electrode assembly 10. The electrolyte includes an electrolyte salt, a first additive and an organic solvent. The sum of the mass fractions of the electrolyte salt and the first additive in the electrolyte is X, and the first additive is a cyclic sulfate additive. The electrode assembly 10 includes an electrode tab 11, the electrode tab 11 includes a current collector 111 and a plurality of tabs 112 that are electrically connected. The plurality of tabs 112 are spaced apart on the same side of the current collector 111, and the distance between adjacent two tabs 112 is d; the electrode assembly 10 is in a wound structure, the electrode assembly 10 has a central hole 13, and the diameter of the central hole 13 of the electrode assembly 10 is L, where the unit of d is mm and the unit of L is mm; the cylindrical battery 100 also satisfies the relational expression: d = k / X - L, where the range of k is 0.4mm ≤ k ≤ 2.175mm.

[0047] The cylindrical battery 100 according to the embodiment of the present application can be applied to energy storage devices such as battery modules (also known as energy storage modules), small energy storage boxes, and large energy storage cabinets. The energy storage device is used to store electrical energy and can supply electrical loads such as street lamps and household appliances for use during peak electricity prices, or supply power when the power grid is powered off / out of power.

[0048] The term "a plurality of" means greater than or equal to two.

[0049] It should be noted that the electrode assembly 10 of the cylindrical battery 100 is wound using a winding needle. The winding needle has a certain diameter. Therefore, there is a cylindrical central hole 13 in the center of the wound electrode assembly 10, and the diameter of the central hole 13 is related to the diameter of the winding needle.

[0050] It should be noted that the distance d between two adjacent tab ears 112 in the embodiment of the present application refers to the minimum distance d between two adjacent tab ears 112 along the length direction of the electrode assembly 10 or the electrode tab 11 when the electrode assembly 10 or the electrode tab 11 is flattened. It can also be understood that the distance between the roots of two adjacent tab ears 112, in other words, the distance between the roots of two adjacent tab ears 112 connecting the current collector 111.

[0051] It should be noted that the central hole 13 of the electrode assembly 10 refers to the hollow hole in the middle position after the electrode assembly 10 is wound.

[0052] Optionally, the electrode assembly 10 includes a positive electrode tab 11a, a separator 12, and a negative electrode tab 11b. The separator 12 is located between the positive electrode tab 11a and the negative electrode tab 11b and is used to separate the positive electrode tab 11a from the negative electrode tab 11b. It should be noted that at least a part of the electrode assembly 10 is immersed in the electrolyte.

[0053] Optionally, the electrode tab 11 can be a positive electrode tab 11a or a negative electrode tab 11b; when the electrode tab 11 is a positive electrode tab 11a, the current collector 111 is a positive current collector 111a, and the tab ear 112 is a positive tab ear 112a; when the electrode tab 11 is a negative electrode tab 11b, the current collector 111 is a negative current collector 111b, and the tab ear 112 is a negative tab ear 112b. Optionally, multiple positive tab ears 112a of the cylindrical battery 100 are located on the same side of the cylindrical battery 100, and multiple negative tab ears 112b are all located on the other side of the cylindrical battery 100.

[0054] Optionally, the tab ear 112 in the embodiment of the present application can be, but is not limited to, a die-cut tab ear.

[0055] Specifically, the value of k can be, but is not limited to, 0.4 mm, 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, 1.0 mm, 1.1 mm, 1.2 mm, 1.3 mm, 1.4 mm, 1.5 mm, 1.6 mm, 1.7 mm, 1.8 mm, 1.9 mm, 2.0 mm, 2.1 mm, 2.175 mm, etc.

[0056] In this embodiment, when the k value is too low, it is necessary to make the total content of the electrolyte salt and the first additive in the electrolyte lower, and the diameter L of the central hole 13 and the distance d between two adjacent tab ears 112 smaller. When the content of the electrolyte salt and the first additive in the electrolyte is too low, it will lead to a decrease in the amount of migratable lithium ions in the electrolyte, a decrease in conductivity, an increase in the polarization of the electrode assembly 10, an increase in the consumption of the electrolyte. At the same time, the film-forming effect of the first additive will not be obvious, there will be defects at the interface of the electrode assembly 10, increasing the contact area between the electrolyte and the active material of the electrode plate 11 (such as the positive active material of the positive electrode plate 11a and the negative active material of the negative electrode plate 11b), increasing the side reaction of the cylindrical battery 100, and reducing the cycle life of the cylindrical battery 100; and when the diameter L of the central hole 13 is too small and the distance d between two adjacent tab ears 112 is too small, there will be insufficient channels for the electrolyte to be injected and infiltrated, and the infiltration will be insufficient.

[0057] In this embodiment, when the k value is too high, it is necessary to make the content of the electrolyte salt and the first additive in the electrolyte too high, and the diameter L of the central hole 13 and the distance d between two adjacent tab ears 112 larger. When the content of the electrolyte salt and the concentration of the first additive in the electrolyte are on the high side, it will increase the viscosity of the electrolyte, affect the wettability of the cylindrical battery 100, and at the same time reduce the thermal stability of the electrolyte, accelerating the side reaction on the surface of the electrode plate 11, and instead deteriorating the safety performance and cycle performance of the cylindrical battery 100; at the same time, designing a wider diameter L of the central hole 13 will squeeze the design area of the electrode plate 11, making the design of the electrode plate 11 tend to the high-compaction direction, affecting the infiltration of the electrode plate 11 and deteriorating the cycle performance of the cylindrical battery 100. Although a too large distance d between two adjacent tab ears 112 is beneficial for injection and infiltration, the area for welding the tab ears 112 will be smaller, which is likely to cause poor welding and the risk of false soldering.

[0058] The cylindrical battery 100 of the embodiment of the present application satisfies the relational expression d = k / X - L, where the range of k is 0.4 mm ≤ k ≤ 2.175 mm. By designing the relational expression d = k / X - L and the value of k, the cylindrical battery 100 has better electrolyte wettability, so that the gram capacity of the cylindrical battery 100 can be better exerted, the cylindrical battery 100 has a higher normal temperature cycle capacity retention rate, and thus has a higher normal temperature cycle service life. In addition, the cylindrical battery 100 also has higher safety performance. In this embodiment, by appropriately increasing the diameter of the central hole 13 and using an electrolyte with a lower electrolyte salt concentration, the risk of side reactions during the safety test of the cylindrical battery 100 (i.e., overcharge or thermal runaway) can be reduced. By adding a cyclic sulfate additive, the problem of accelerated consumption of electrolyte salts during the cycle caused by the lower electrolyte salt concentration can be improved. The cyclic sulfate additive can increase the content of inorganic sulfates in the interface film of the electrode tab 11, reduce the resistance of the interface film, reduce the heat generation during overcharge of the cylindrical battery 100, and improve the normal temperature cycle performance and high temperature cycle performance of the cylindrical battery 100. In addition, by appropriately increasing the distance d between two adjacent tabs 112 and the diameter L of the central hole 13, the gas generation path during the safe overcharge of the cylindrical battery 100 can be increased. Combined with an electrolyte with a lower electrolyte salt concentration, the cylindrical battery 100 has lower reaction consumption during overcharge at high voltage, so that the safety performance of the cylindrical battery 100 can be improved, the wettability of the electrode assembly 10 of the cylindrical battery 100 can be improved, and the normal temperature cycle performance and high temperature cycle performance of the cylindrical battery 100 can be improved.

[0059] Optionally, the electrolyte salt may be, but is not limited to, a lithium salt.

[0060] Optionally, the lithium salt may include, but is not limited to, lithium hexafluorophosphate (LiPF 6 ), lithium tetrafluoroborate (LiBF 4 ), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(oxalato)borate (LiBOB), lithium difluoro(oxalato)phosphate (LiODFP), lithium difluoro(oxalato)borate (LiODFB), lithium difluorophosphate (LiPO 2 F 2 ), lithium trifluoromethanesulfonate (CF 3 SO 3 Li), etc., at least one of which.

[0061] In some embodiments, the range of the mass fraction a of the electrolyte salt in the electrolyte is: 8.75% ≤ a ≤ 12.5%.

[0062] Specifically, the mass fraction a of the electrolyte salt in the electrolyte can be, but is not limited to, 8.75 wt%, 9 wt%, 9.5 wt%, 10 wt%, 10.5 wt%, 11 wt%, 11.5 wt%, 12 wt%, 12.5 wt%, etc.

[0063] In this embodiment, appropriately reducing the content of the electrolyte salt in the electrolyte can reduce the heat generation of the cylindrical battery 100 during overcharge and thermal runaway, and improve the safety of overcharge and thermal runaway. However, if the mass fraction of the electrolyte salt in the electrolyte is too low, the amount of migratable lithium ions in the electrolyte decreases, the electrolyte ions, and the ionic conductivity of the electrolyte is too low, making the cylindrical battery 100 prone to polarization, increasing the consumption of the electrolyte, and easily causing insufficient cycle life of the cylindrical battery 100 in the later stage. If the mass fraction of the electrolyte salt in the electrolyte is too high, the viscosity of the electrolyte increases, reducing the wetting ability of the electrolyte and the wettability of the electrolyte to the electrode assembly 10, thereby reducing the discharge capacity of the cylindrical battery 100 and the cycle capacity retention rate of the cylindrical battery 100; in addition, it will also reduce the thermal stability of the electrolyte and accelerate the side reaction on the surface of the electrode plate 11, instead deteriorating the safety performance and cycle performance of the cylindrical battery 100.

[0064] In some embodiments, the structural formula of the cyclic sulfate additive is: wherein, A is one of methyl, ethyl, propyl, isopropyl, and vinylene sulfate group; R is (CH 2 )n, and the range of n is from 1 to 3.

[0065] It can be understood that the cyclic sulfate additive can be at least one of, but not limited to, a five-membered ring cyclic sulfate additive, a six-membered ring cyclic sulfate additive, and a seven-membered ring cyclic sulfate additive.

[0066] During the first charge and discharge process of the cylindrical battery 100, the cyclic sulfate additive can undergo a reduction reaction on the surface of the negative electrode plate 11b to form a stable solid electrolyte interface film (abbreviated as SEI film or interface film), preventing further decomposition of the electrolyte and the active material of the negative electrode plate 11b, extending the diving end point of the cylindrical battery 100, and improving the cycle life and safety of the cylindrical battery 100; at the same time, the cyclic sulfate additive can also optimize the structure of the SEI film, reduce the lithium ion migration resistance of the negative electrode plate 11b, and improve the rate performance of the cylindrical battery 100. Using the cyclic sulfate additive with the structural formula of this embodiment can better improve the cycle performance and safety performance of the cylindrical battery 100.

[0067] Optionally, the range of the mass fraction b of the cyclic sulfate additive (i.e., the first additive) in the electrolyte is: 0.1% ≤ b ≤ 2%.

[0068] Specifically, the mass fraction b of the cyclic sulfate additive in the electrolyte can be, but is not limited to, 0.1%, 0.2%, 0.3%, 0.4%, 0.6%, 0.8%, 1.0%, 1.2%, 1.4%, 1.6%, 1.8%, 2.0%, etc.

[0069] In this embodiment, when the mass fraction b of the cyclic sulfate additive in the electrolyte is too low, it is difficult for the cyclic sulfate additive to improve the stability of the SEI film, and the effect of improving the stability of the SEI film is not obvious; when the mass fraction b of the cyclic sulfate additive in the electrolyte is too high, the cyclic sulfate decomposes prior to the organic solvent, increasing the side reactions of the electrolyte, resulting in an overly thick SEI film on the negative electrode tab 11b, increasing the impedance of the negative electrode tab 11b, exacerbating the consumption of the electrolyte, and at the same time increasing the viscosity of the electrolyte, affecting the wettability of the electrolyte, and being disadvantageous to the cycling performance of the cylindrical battery 100.

[0070] In some embodiments, the range of the total mass fraction X of the electrolyte salt and the first additive in the electrolyte is: 8.85% ≤ X ≤ 14.5%.

[0071] It can be understood that X = a + b.

[0072] Specifically, the total mass fraction of the electrolyte salt and the first additive in the electrolyte can be, but is not limited to, 8.85%, 9%, 9.5%, 10%, 10.5%, 11%, 11.5%, 12%, 12.5%, 13%, 13.5%, 14%, 14.5%, etc.

[0073] When the content of the electrolyte salt and the first additive in the electrolyte is too low, it will lead to a reduction in the amount of migratable lithium ions in the electrolyte, a decrease in conductivity, an increase in the polarization of the electrode assembly 10, an increase in the consumption of the electrolyte, and at the same time, the film-forming effect of the first additive will not be obvious, there will be defects at the interface of the electrode assembly 10, increasing the contact area between the electrolyte and the active material of the electrode tab 11 (such as the positive active material of the positive electrode tab 11a and the negative active material of the negative electrode tab 11b), increasing the side reactions of the cylindrical battery 100, and reducing the cycling life of the cylindrical battery 100; when the content of the electrolyte salt and the total content of the first additive in the electrolyte are too high, it will increase the viscosity of the electrolyte, affect the wettability of the cylindrical battery 100, and at the same time reduce the thermal stability of the electrolyte, accelerating the side reactions on the surface of the electrode tab 11, and instead deteriorating the safety performance and cycling performance of the cylindrical battery 100.

[0074] In some embodiments, the electrolyte further includes a second additive, and the structural formula of the second additive is: In the electrolyte, the mass fraction m of the second additive ranges from 0.1% ≤ m ≤ 1%.

[0075] In this embodiment, the cyclic sulfate additive significantly improves the cycling performance and safety of the cylindrical battery 100 by forming a stable SEI film, inhibiting the decomposition of the electrolyte, improving the thermal stability of the electrolyte, enhancing the ionic conductivity, and suppressing gas generation; while the second additive can be a supplement to the cyclic sulfate additive under the film-forming conditions of the cyclic sulfate additive. At higher voltages, it can combine with active free radicals such as H and O, reduce the heat generation reaction of the cylindrical battery 100, reduce the consumption of the cyclic sulfate additive, and form a nitrogen-sulfur element interface network in the composition of the sulfur-containing inorganic interface film (i.e., SEI film) formed by the cyclic sulfate additive, enrich the nitrogen-containing inorganic salt components of the SEI film, adjust the interlayer structure of the interface layer, and improve the deterioration of high-temperature cycling caused by low electrolyte salts (such as low lithium salts), thereby increasing the cycle life of the cylindrical battery 100.

[0076] Specifically, the mass fraction m of the second additive in the electrolyte can be, but is not limited to, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, etc.

[0077] In this embodiment, if the mass fraction m of the second additive in the electrolyte is too low, the cross-linking effect of the interface film formed by the second additive and the first additive is not obvious, and the improvement of the high-temperature cycling performance of the cylindrical battery 100 is not obvious; if the mass fraction m of the second additive in the electrolyte is too high, the film-forming reaction of the negative electrode plate 11b of the cylindrical battery 100 will be aggravated, increasing the impedance of the interface film of the negative electrode plate 11b and reducing the energy efficiency of the cylindrical battery 100.

[0078] Optionally, the organic solvent includes at least one of cyclic carbonates and chain carbonates.

[0079] Optionally, the cyclic carbonate may include, but is not limited to, at least one of ethylene carbonate (abbreviated as EC), propylene carbonate (abbreviated as PC), 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 solid electrolyte interface membrane (abbreviated as SEI).

[0080] Optionally, the chain carbonate may include, but is not limited to, at least one of dimethyl carbonate (abbreviated as DMC), diethyl carbonate (abbreviated as DEC), ethyl methyl carbonate (abbreviated as EMC), etc.

[0081] In some embodiments, the mass ratio A of the cyclic carbonate to the linear carbonate in the electrolyte ranges from 0.17 ≤ A ≤ 0.67.

[0082] Specifically, the mass ratio A of the cyclic carbonate to the linear carbonate in the electrolyte can be, but is not limited to, 0.17, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.67, etc.

[0083] In this embodiment, if the mass ratio A of the cyclic carbonate to the linear carbonate in the electrolyte is too low, the dissociation ability of lithium ions is reduced, the conductivity of the electrolyte is reduced, and thus the kinetic performance of the cylindrical battery 100 is reduced; increasing the mass ratio A of the cyclic carbonate to the linear carbonate in the electrolyte can enable the electrolyte to have a higher ability to dissociate lithium ions, improve the conductivity of the electrolyte, and enhance the cycling performance of the cylindrical battery 100. However, when the mass ratio A of the cyclic carbonate to the linear carbonate in the electrolyte is too high, it will affect the viscosity and freezing point of the electrolyte of the cylindrical battery 100, thereby increasing the difficulty of electrolyte infiltration of the cylindrical battery 100 and also reducing the cycling capacity retention rate of the cylindrical battery 100.

[0084] Optionally, the organic solvent further includes at least one of ethyl acetate, propyl acetate, ethyl propionate, propyl propionate, γ-butyrolactone, and 2,2-difluoroethyl acetate. In the organic solvent, the total mass percentage of ethyl acetate, propyl acetate, ethyl propionate, propyl propionate, γ-butyrolactone, and 2,2-difluoroethyl acetate is from 0 to 20 wt%; specifically, it can be, but is not limited to, 0, 3 wt%, 5 wt%, 8 wt%, 10 wt%, 13 wt%, 15 wt%, 18 wt%, 20 wt%, etc.

[0085] Optionally, in the electrolyte, the mass fraction of the organic solvent is 60 wt% to 85 wt%. Specifically, it can be, but is not limited to, 60 wt%, 65 wt%, 70 wt%, 75 wt%, 80 wt%, 85 wt%, etc.

[0086] Optionally, the electrolyte further includes a film-forming additive. When the cylindrical battery 100 is a lithium-ion cylindrical battery 100, the film-forming additive can be used to promote the formation of the interface film on at least one of the positive electrode plate 11a and the negative electrode plate 11b and maintain the stability of the interface film.

[0087] Optionally, the film-forming additive may include, but is not limited to, at least one of propargylbenzenesulfonic acid, vinylene carbonate (VC), fluoroethylene carbonate (FEC), ethylene sulfite (DTD), methylene methanedisulfonate (MMDS), butylsulfonic acid lactone (BS), 1,3-propylene sulfonic acid lactone (PST), etc.

[0088] Optionally, the mass fraction of the film-forming additive in the electrolyte ranges from 0.1 wt% to 10 wt%. Specifically, the mass fraction of the film-forming additive may be, but is not limited to, 0.1 wt%, 0.3 wt%, 0.5 wt%, 0.8 wt%, 1 wt%, 1.5 wt%, 2 wt%, 2.5 wt%, 3 wt%, 3.5 wt%, 4 wt%, 4.5 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, etc.

[0089] Please refer to Figure 3 , in some embodiments, the distance d between two adjacent tabs 112 ranges from: 1 mm ≤ d ≤ 6 mm.

[0090] Specifically, the distance d between two adjacent tabs 112 may be, but is not limited to, 1 mm, 1.3 mm, 1.5 mm, 1.8 mm, 2 mm, 2.3 mm, 2.5 mm, 2.8 mm, 3 mm, 3.3 mm, 3.5 mm, 3.8 mm, 4.0 mm, 4.3 mm, 4.5 mm, 4.8 mm, 5 mm, 5.0 mm, 5.3 mm, 5.5 mm, 5.8 mm, 6 mm.

[0091] In this embodiment, the distance between two adjacent tabs 112 in the cylindrical battery 100 is related to the size of the reserved pores after the electrode assembly 10 is wound and the wetting ability of the electrolyte in the cylindrical battery 100 after injection. The larger the distance d between two adjacent tabs 112, the stronger the wetting ability of the electrolyte. Therefore, when the distance d between two adjacent tabs 112 is too small, the electrolyte is not easily permeated to the electrode tab 11 at the central position of the electrode assembly 10, which will reduce the wetting ability of the electrolyte, affect the specific capacity of the electrode assembly 10, and reduce the cycle capacity retention rate of the cylindrical battery 100. In addition, it will also make it too difficult for the cylindrical battery 100 to safely relieve pressure, reducing the safety performance of the cylindrical battery 100. When the distance d between two adjacent tabs 112 is too large, the area of the tab 112 is too narrow, affecting the welding area between the tab 112 and the current collector plate of the cylindrical battery 100 and the welding strength between the tab 112 and the current collector plate, and will make the current distribution between the electrode tabs 11 uneven, reducing the electron transfer speed on the electrode tab 11, resulting in ineffective utilization of the capacity of the cylindrical battery 100 and reducing the kinetic performance of the cylindrical battery 100. In addition, it makes the resistance value of the welding area between the tab 112 and the current collector plate too low, increasing the risk of overcurrent fusing.

[0092] Please refer to again Figure 2 , in some embodiments, the diameter L of the central hole 13 of the electrode assembly 10 ranges from 3 mm ≤ L ≤ 12 mm.

[0093] Specifically, the diameter L of the central hole 13 of the electrode assembly 10 can be, but is not limited to, 3 mm, 4 mm, 5 mm, 5.5 mm, 6 mm, 6.5 mm, 7 mm, 7.5 mm, 8 mm, 8.5 mm, 9 mm, 9.5 mm, 10 mm, 11 mm, 12 mm, etc.

[0094] In this embodiment, if the diameter L of the central hole 13 of the electrode assembly 10 is too small, the size of the channel reserved for the electrolyte in the electrode assembly 10 is too small, reducing the wetting ability of the electrolyte, thereby affecting the specific capacity of the electrode assembly 10 and reducing the cycle capacity retention rate of the cylindrical battery 100. Increasing the diameter L of the central hole 13 of the electrode assembly 10 can increase the wetting area of the electrode assembly 10 and the wetting ability of the electrolyte, and the longer the diameter L of the central hole 13, the faster the pressure relief rate after the cylindrical battery 100 fails safely. However, if the diameter L of the central hole 13 of the electrode assembly 10 is too large, it will excessively reduce the volume energy density of the cylindrical battery 100, and will crush the design of the electrode tab 11, reducing the design redundancy of the thickness of the electrode tab 11, and a higher compaction design of the electrode tab 11 is required to meet the required capacity.

[0095] Please refer to together Figure 3 and Figure 4, in some embodiments, the number of turns of the wound electrode assembly 10 is M turns, and M turns include N steps 15. Each step 15 includes multiple turns. Each turn of the electrode tab 11 includes multiple tabs 112. The sizes of the multiple tabs 112 of each step 15 are the same. From the outermost circle to the innermost circle of the electrode assembly 10, the widths of the tabs 112 of different steps 15 gradually decrease in a gradient manner, and the heights of the tabs 112 of different steps 15 also gradually decrease in a gradient manner, where M > N.

[0096] It should be noted that the width of the tab 112 refers to the width of the tab 112 along the arrangement direction of the multiple tabs 112. The height of the tab 112 refers to the height of the tab 112 along the direction perpendicular to the arrangement direction of the multiple tabs 112 (i.e., along the arrangement direction of the tab 112 and the current collector 111).

[0097] It can be understood that the width of the tab 112 of the outermost step 15 is the largest and the height is the highest, and the width of the tab 112 of the step 15 closest to the central hole 13 is the smallest and the height is the lowest.

[0098] It can be understood that the widths of the multiple tabs 112 on the same step 15 are equal and the heights are also equal.

[0099] It should be noted that among the multiple tabs 112 on the electrode tab 11, the distance between any two adjacent tabs 112 is equal.

[0100] In this embodiment, by making the widths of the tabs 112 of different steps 15 gradually decrease in a gradient manner and the heights of the tabs 112 of different steps 15 also gradually decrease in a gradient manner from the outermost circle to the innermost circle of the electrode assembly 10, and the gradient changes in the widths and heights of the tabs 112 on different steps 15, the tabs 112 and the current collecting plate can be better welded, the welding strength between the tabs 112 and the current collecting plate can be improved, it is easy to make the current distribution on the current collector 111 uneven, reduce the electron transfer speed on the electrode tab 11, and reduce the dynamic performance of the cylindrical battery 100.

[0101] In some embodiments, the range of the number N of steps 15 of the electrode assembly 10 is: 2 ≤ N ≤ 10.

[0102] Specifically, the number N of steps 15 of the electrode assembly 10 can be, but is not limited to, 2, 3, 4, 5, 6, 7, 8, 9, 10, etc.

[0103] In this embodiment, if the number N of the steps 15 of the electrode assembly 10 is too small, the difficulty of die-cutting the tab 112 is increased, resulting in a decrease in the amount of welding in the short tab 112 area (the area where the height of the tab 112 is relatively small, i.e., the tab 112 on the step 15 close to the central hole 13). Therefore, when the tab 112 is welded to the current collector 111, poor welding is likely to occur, causing virtual soldering and reducing the production yield of the cylindrical battery 100. If the number N of the steps 15 of the electrode assembly 10 is too large, the number of die-cut tabs 112 increases, and the number of short tabs 112 increases, increasing the difficulty of die-cutting the tab 112.

[0104] In some embodiments, the range of the number n of the tabs 112 of the electrode tab 11 is: 400 ≤ n ≤ 2000.

[0105] It should be noted that n > M.

[0106] It can be understood that the range of the total number of tabs 112 on each electrode tab 11 is from 400 to 2000. For example, when the electrode tab 11 is the positive electrode tab 11a, the range of the number of tabs 112 on the positive electrode tab 11a is from 400 to 2000. Another example, when the electrode tab 11 is the negative electrode tab 11b, the range of the number of tabs 112 on the negative electrode tab 11b is from 400 to 2000.

[0107] Specifically, the number n of the tabs 112 of the electrode tab 11 can be, but is not limited to, 400, 450, 500, 600, 700, 800, 900, 1000, 1100, 1200, 1300, 1400, 1500, 1600, 1700, 1800, 1900, 2000, etc.

[0108] In this embodiment, if the number of tabs 112 on the electrode tab 11 is too small, the width of each tab 112 is too wide. When the tab 112 is welded to the current collector 111, it is easy to cause protrusions and wrinkles between adjacent die-cut tabs 112, thus easily resulting in poor welding of the tab 112, bending and squeezing of the tab 112 inward, and short circuit of the electrical connection between the positive electrode tab 11a and the negative electrode tab 11b. In this embodiment, if the number of tabs 112 on the electrode tab 11 is too large, the difficulty of the tab 112 die-cutting process is increased. When die-cutting the tab 112, the tab 112 is easily bent or broken, reducing the production yield of the electrode assembly 10.

[0109] In some embodiments, the range of the height h1 of the tab 112 on the step 15 of the electrode assembly 10 closest to the central hole 13 is: 2 mm ≤ h1 ≤ 6 mm.

[0110] Understandably, on the electrode tab 11, the height h1 of the tab 112 with the minimum height ranges from 2 mm ≤ h1 ≤ 6 mm.

[0111] Specifically, the height h1 of the tab 112 on the step 15 of the electrode assembly 10 closest to the central hole 13 can be, but is not limited to, 2.0 mm, 2.5 mm, 3.0 mm, 3.5 mm, 4.0 mm, 4.5 mm, 5.0 mm, 5.5 mm, 6.0 mm, etc.

[0112] In this embodiment, if the height h1 of the tab 112 on the step 15 of the electrode assembly 10 closest to the central hole 13 is too low, it is likely to cause poor welding when the innermost tab 112 is welded to the current collector plate, resulting in uneven current density distribution of the current collector 111, slow electron transfer speed at the position of the current collector 111 of the electrode tab 11 close to the central hole 13, and reduced kinetic performance of the cylindrical battery 100; if the height h1 of the tab 112 on the step 15 of the electrode assembly 10 closest to the central hole 13 is too high, after the electrode assembly 10 is wound into a cylindrical shape, the tab 112 will be bent relative to the current collector 111 and then welded to the current collector plate. After the tab 112 is bent, the bent tab 112 is likely to overlap with the tabless area in the inner circle, so that the positive tab 112a overlaps with the negative current collector 111b or the negative tab 112b overlaps with the positive current collector 111a, resulting in a short circuit of the cylindrical battery 100.

[0113] In some embodiments, when the electrode assembly 10 is in a wound structure, the radial width w1 of the step 15 farthest from the central hole 13 ranges from 100 mm ≤ w1 ≤ 300 mm.

[0114] Understandably, in the radial direction of the wound electrode assembly 10, among the N steps 15 of the electrode assembly 10, the width w1 of the outermost step 15 of the electrode assembly 10 ranges from 100 mm ≤ w1 ≤ 300 mm. It is also understandable that when the electrode assembly 10 is in a wound structure, the radial width w1 of the outermost step 15 ranges from 100 mm ≤ w1 ≤ 300 mm.

[0115] Specifically, when the electrode assembly 10 is in a wound structure, the radial width w1 of the step 15 farthest from the central hole 13 can be, but is not limited to, 100 mm, 120 mm, 140 mm, 160 mm, 180 mm, 200 mm, 220 mm, 240 mm, 260 mm, 280 mm, 300 mm, etc.

[0116] In this embodiment, if the radial width w1 of the step 15 that is farthest from the central hole 13 when the electrode assembly 10 is in a wound structure is too small, it is likely that poor welding will occur when the tab 112 on the outermost step 15 of the electrode assembly 10 is welded to the current collector plate. If the radial width w1 of the step 15 that is farthest from the central hole 13 when the electrode assembly 10 is in a wound structure is too large, it is likely that the welding of the tab 112 on the inner ring close to the central hole 13 to the current collector plate is insufficient, resulting in uneven current density distribution of the current collector 111, slow electron transfer speed at the position of the current collector 111 of the electrode tab 11 close to the central hole 13, and reduction of the dynamic performance of the cylindrical battery 100.

[0117] Please refer to Figure 3 , in some embodiments, the electrode tab 11 includes a tabless region 14, the tabless region 14 is disposed close to the central hole 13 and connected to the step 15 closest to the central hole 13. When the electrode assembly 10 is flattened, the range of the length s1 of the tabless region 14 is: 100 mm ≤ s1 ≤ 500 mm.

[0118] It should be noted that when the electrode assembly 10 is in a wound structure, the tabless region 14 is located within the innermost step 15, that is, the innermost step 15 surrounds the outer periphery of the tabless region 14.

[0119] Specifically, the length s1 of the tabless region 14 when the electrode assembly 10 is flattened may be, but is not limited to, 100 mm, 150 mm, 200 mm, 250 mm, 300 mm, 350 mm, 400 mm, 450 mm, 500 mm, etc.

[0120] In this embodiment, when the length s1 of the tabless region 14 is too small when the electrode assembly 10 is flattened, after the electrode assembly 10 is formed, the tab 112 will be bent relative to the current collector 111 and then welded to the current collector plate. After the tab 112 is bent, the innermost tab 112 is likely to overlap with the tabless region 14 after bending, so that the positive tab 112a overlaps with the negative current collector 111b or the negative tab 112b overlaps with the positive current collector 111a, resulting in a short circuit of the cylindrical battery 100. When the length s1 of the tabless region 14 is too large when the electrode assembly 10 is flattened, the welding area of the tab 112 on the step 15 closest to the central hole 13 of the electrode assembly 10 to the current collector plate is insufficient, resulting in uneven current density distribution of the electrode tab 11 corresponding to the tabless region 14, and easy capacity loss of the cylindrical battery 100 during charge and discharge.

[0121] In some embodiments, the range of the length s2 of the electrode tab 11 corresponding to the innermost step 15 of the electrode assembly 10 when flattened is: 300 mm ≤ s2 ≤ 500 mm.

[0122] Understandably, the range of the length s2 of the electrode tab 11 corresponding to the step 15 connecting the tabless region 14 when flattened is: 300 mm ≤ s2 ≤ 500 mm.

[0123] Specifically, the length s2 of the electrode tab 11 corresponding to the innermost step 15 of the electrode assembly 10 when flattened can be, but is not limited to, 300 mm, 320 mm, 340 mm, 360 mm, 380 mm, 400 mm, 420 mm, 440 mm, 460 mm, 480 mm, 500 mm, etc.

[0124] In this embodiment, when the length s2 of the electrode tab 11 corresponding to the innermost step 15 of the electrode assembly 10 is too short during flattening, it is likely that the welding of the tab 112 of the innermost step 15 to the current collector plate is insufficient, resulting in an overly long current passing path and a too low current density for the electrode tab 11 corresponding to the innermost step 15; when the length s2 of the electrode tab 11 corresponding to the innermost step 15 of the electrode assembly 10 is too long during flattening, it is likely that when the tab 112 on the innermost step 15 of the electrode assembly 10 is bent, it will overlap with the electrode tab 11 within the tabless region 14, thus causing a short circuit between the positive electrode tab 11a and the negative electrode tab 11b.

[0125] Please refer to Figure 5 , optionally, the positive electrode tab 11a further includes a positive electrode active layer 113a, and the positive electrode active layer 113a is disposed on the surface of the positive electrode current collector 111a. Understandably, the positive electrode active layer 113a can cover one surface or two opposite surfaces of the positive electrode current collector 111a.

[0126] Understandably, the positive electrode tab 11a includes a positive electrode current collector 111a, a positive electrode tab 112a, and a positive electrode active layer 113a.

[0127] Optionally, the positive electrode current collector 111a can be, but is not limited to, an aluminum sheet.

[0128] Optionally, the positive electrode active layer 113a includes a positive electrode active material, a positive electrode conductive agent, a positive electrode binder, and a positive electrode thickening agent.

[0129] Optionally, the positive electrode active material can be, but is not limited to, lithium iron phosphate.

[0130] Optionally, the positive electrode conductive agent can be, but is not limited to, at least one of conductive carbon black, acetylene black, carbon nanotubes, carbon fibers, graphene, etc.

[0131] Optionally, the positive electrode binder may be, but is not limited to, at least one of polyvinylidene fluoride (PVDF for short), polyamide (PA for short), polyacrylonitrile (PAN for short), polyacrylate, polyvinylether, polymethylmethacrylate (PMMA for short), polyhexafluoropropylene, polymerized styrene butadiene rubber (SBR for short), etc.

[0132] Optionally, in the positive electrode active layer 113a, the mass fraction of the positive electrode binder ranges from 2 wt% to 4 wt%. Specifically, in the positive electrode active layer 113a, the mass fraction of the positive electrode binder may be, but is not limited to, 2 wt%, 2.5 wt%, 3 wt%, 3.5 wt%, 4 wt%, etc. If the mass fraction of the positive electrode binder is too small, the positive electrode active layer 113a is likely to powder or shed; if the mass fraction of the positive electrode binder is too large, the energy density of the positive electrode plate 11a is reduced.

[0133] Optionally, the positive electrode thickener may be, but is not limited to, at least one of sodium carboxymethyl cellulose (CMC for short), polyacrylamide (PAM), polymethacrylate (PMA), etc.

[0134] Optionally, the separator 12 may be, but is not limited to, at least one of a polypropylene film (PP film for short), a polyethylene film (PE film for short), a ceramic separator 12, etc.

[0135] Optionally, the thickness of the separator 12 is 14 μm to 18 μm. Specifically, the thickness of the separator 12 may be, but is not limited to, 14 μm, 14.5 μm, 15 μm, 15.5 μm, 16 μm, 16.5 μm, 17 μm, 17.5 μm, and 18 μm, etc.

[0136] Please refer to Figure 6 , optionally, the negative electrode plate 11b further includes a negative electrode active layer 113b, and the negative electrode active layer 113b is disposed on the surface of the negative electrode current collector 111b. It can be understood that the negative electrode active layer 113b may cover one surface or two opposite surfaces of the negative electrode current collector 111b.

[0137] It can be understood that the negative electrode plate 11b includes a negative electrode current collector 111b, a negative electrode tab 112b, and a negative electrode active layer 113b.

[0138] Optionally, the negative electrode current collector 111b can be, but is not limited to, a copper sheet.

[0139] Optionally, the negative electrode active layer 113b includes a negative electrode active material, a negative electrode conductive agent, a negative electrode binder, and a negative electrode thickener.

[0140] Optionally, the negative electrode active material can be, but is not limited to, graphite.

[0141] Optionally, the negative electrode conductive agent can be, but is not limited to, at least one of conductive carbon black (abbreviated as SP), acetylene black, carbon nanotubes, carbon fibers, graphene, etc.

[0142] Optionally, the negative electrode binder can be, but is not limited to, at least one of polyvinylidene fluoride, polyamide, polyacrylonitrile, polyacrylate, polyethylene ether, polymethyl methacrylate, polyhexafluoropropylene, styrene-butadiene rubber, etc.

[0143] Optionally, in the negative electrode active layer 113b, the mass fraction range of the negative electrode binder is 2 wt% to 4 wt%. Specifically, in the negative electrode active layer 113b, the mass fraction of the negative electrode binder can be, but is not limited to, 2 wt%, 2.5 wt%, 3 wt%, 3.5 wt%, 4 wt%, etc. If the mass fraction of the negative electrode binder is too small, the negative electrode active layer 113b is prone to powdering or chipping; if the mass fraction of the negative electrode binder is too large, the energy density of the negative electrode plate 11b is reduced.

[0144] Optionally, the negative electrode thickener can be, but is not limited to, at least one of sodium carboxymethyl cellulose (abbreviated as CMC), polyacrylamide (PAM), and polymethacrylate (PMA), etc.

[0145] Please refer to again Figure 1 and Figure 2 , optionally, the cylindrical battery 100 further includes a housing 20 and an end cap assembly 30. The housing 20 and the end cap assembly 30 enclose a receiving cavity (not shown in the figure), and the receiving cavity is used to receive the electrolyte, the positive electrode plate 11a, the separator 12, and the negative electrode plate 11b described above.

[0146] The following further introduces the cylindrical battery 100 of the present application through specific examples.

[0147] Examples 1 to 28, Comparative Examples 1 to 4

[0148] The cylindrical batteries 100 of each example and comparative example are prepared through the following steps:

[0149] (1) Preparation of electrolyte: In an argon atmosphere glove box with a water content ≤ 1 ppm, according to the designed solvent ratio, a mixed solution of ethylene carbonate (EC, cyclic carbonate), ethyl methyl carbonate (EMC, chain carbonate), and dimethyl carbonate (DMC, chain carbonate) solvents was prepared, and the mass ratio of EC, EMC, and DMC was 1:1:2; after sealing to isolate water, it was placed in a 0 °C freezer and stabilized for 2 h, then quickly transferred to the glove box, lithium hexafluorophosphate, the electrolyte salt, was added, and stirred until the solute was completely dissolved and uniform. After the temperature stabilized, vinylene carbonate (VC, mass fraction 3 wt%), fluoroethylene carbonate (FEC, mass fraction 1.5 wt%), and cyclic sulfate ester additive (the first additive) were added and mixed evenly to obtain the electrolyte. In the electrolytes of each example and comparative example, the type and mass fraction a of the electrolyte salt, the type and mass fraction b of the cyclic sulfate ester additive, and the mass fraction m of the second additive are shown in Table 1 below.

[0150] (2) Preparation of the positive electrode plate 11a: The positive electrode active material lithium iron phosphate (LiFePO 4 )), conductive carbon black (Super-P, positive electrode conductive agent), and PVDF (positive electrode binder) were mixed in a mass ratio of 94:3:3; then N-methylpyrrolidone (NMP) was added as a solvent to prepare a positive electrode slurry with a solid content of 60 wt%, and stirred evenly. Then the positive electrode slurry was evenly coated on one surface of a 10-μm-thick positive electrode current collector 111a aluminum foil, and after drying, cold pressing, slitting, and die cutting, the positive electrode plate 11a to be wound was obtained; the single-sided thickness of the positive electrode active layer 113a was 100 μm.

[0151] (3) Preparation of the negative electrode plate 11b: The negative electrode active material artificial graphite, sodium carboxymethyl cellulose (CMC, thickener), conductive carbon black (Super-P, negative electrode conductive agent), and styrene-butadiene rubber latex (SBR, negative electrode binder) were mixed in a mass ratio of 96:2:1:1, deionized water was added to prepare a negative electrode slurry with a solid content of 50 wt%, and stirred evenly; the negative electrode slurry was evenly coated on one surface of a 6-μm-thick negative electrode current collector 111b copper foil, and after drying, cold pressing, slitting, and die cutting, the negative electrode plate 11b to be wound was obtained; the single-sided thickness of the negative electrode active layer 113b was 70 μm.

[0152] (4) Preparation of the separator 12: A 16-μm-thick polyethylene film (PE) was used as the separator 12.

[0153] (5) Assembly of the cylindrical battery 100: Stack the above-mentioned positive electrode plate 11a, separator 12, and negative electrode plate 11b in sequence, with the separator 12 placed between the positive electrode plate 11a and the negative electrode plate 11b to play an insulating role, and then wind them into a cylindrical bare battery cell; after welding the tab 112, place the bare cylindrical battery 100 in the outer packaging shell, inject the above-mentioned electrolyte after drying, and go through processes such as standing at room temperature, forming, second injection, aging, welding, helium leak detection, capacity and OCV testing, etc., and finally prepare the cylindrical battery 100.

[0154] The number of turns M of the winding of the electrode assembly 10 of the cylindrical battery 100 is 80, the M turns include N steps 15, and the number N of the steps 15 of the electrode assembly 10 is 5; the number n of the tabs 112 of the electrode plate 11 is 1600; the height h1 of the tab 112 of the step 15 closest to the central hole 13 of the electrode assembly 10 is 4 mm; when the electrode assembly 10 is in a wound structure, the radial width w1 of the step 15 farthest from the central hole 13 is 200 mm; the tabless area 14 is arranged close to the central hole 13 and is connected to the step 15 closest to the central hole 13. When the electrode assembly 10 is flattened, the length s1 of the tabless area 14 is 300 mm; the length s2 of the electrode plate 11 corresponding to the innermost step 15 of the electrode assembly 10 when flattened is 350 mm.

[0155] The diameter L of the central hole 13 and the distance d between adjacent two tabs 112 of the cylindrical battery 100 in each example and comparative example are shown in Table 1 below.

[0156] Perform the following various performance tests on the cylindrical battery 100 in each example and comparative example.

[0157] (1) Overcharge test: Charge the cylindrical battery 100 at a constant current of 1C until the voltage of the cylindrical battery 100 monomer reaches 5.475V (1.5 times) or the time reaches 1h, and then stop charging. Stop when either of the two reaches the requirement. There is no phenomenon of fire, cracking, or explosion, and observe for one hour. Record the highest temperature during the entire test process as the overcharge temperature. The higher the overcharge temperature of the cylindrical battery 100, the higher the heat accumulation of the cylindrical battery 100 during the overcharge stage and the greater the safety risk.

[0158] (2) Thermal runaway test: Charge the cylindrical battery 100 at a constant current of 1C until it reaches a fully charged state (i.e., 100% SOC, or the remaining charge is 100%), then charge it for another 12 minutes, and then heat it until the cylindrical battery 100 undergoes thermal runaway or the temperature at the detection point reaches 300°C; Thermal runaway determination conditions: The cylindrical battery 100 generates a voltage drop and the temperature rise rate of the cylindrical battery 100 ≥ 1°C / s; or reaches the protection temperature of the cylindrical battery 100 and the temperature rise rate of the cylindrical battery 100 ≥ 1°C / s; Observe for one hour after the test, and record the highest temperature during the thermal runaway process as the thermal runaway temperature. The higher the thermal runaway temperature of the cylindrical battery 100, the easier it is to cause the electrolyte to reach the ignition point, exacerbate the decomposition of lithium salts, and at the same time, the risk of direct short-circuiting of the positive electrode plate 11a and the negative electrode plate 11b due to the thermal shrinkage of the separator 12 caused by the temperature increase is further increased; resulting in safety risks such as fire and explosion.

[0159] (3) 25°C charge and discharge cycle test: Perform a constant current charge and discharge cycle test on the cylindrical batteries 100 obtained in the above-mentioned examples and comparative examples on a Blue Power Tester. The test temperature is 25°C, the charge and discharge rate is 1C, and the charge and discharge voltage window is 2.5V to 3.65V. Calculate the capacity retention rate after 500 cycles. The calculation formula is: Capacity retention rate after the 500th cycle = (Discharge capacity after the 500th cycle / Discharge capacity of the first cycle) × 100%. Among them, usually, a complete charge and discharge is called a charge and discharge cycle, that is, the cylindrical battery 100 is first charged from 2.5V to 3.65V, and then discharged from 3.65V to 2.5V, thus forming a charge and discharge cycle. Repeating the above process 500 times means performing 500 charge and discharge cycles.

[0160] (4) 45°C charge and discharge cycle test: Perform a constant current charge and discharge cycle test on the cylindrical batteries 100 obtained in the above-mentioned examples on a Blue Power Tester. The test temperature is 45°C, the charge and discharge rate is 1C, and the charge and discharge voltage window is 2.5V to 3.65V. Calculate the capacity retention rate after 500 cycles. The calculation formula is: Capacity retention rate after the 500th cycle = (Discharge capacity after the 500th cycle / Discharge capacity of the first cycle) × 100%. Among them, usually, a complete charge and discharge is called a charge and discharge cycle, that is, the cylindrical battery 100 is first charged from 2.5V to 3.65V, and then discharged from 3.65V to 2.5V, thus forming a charge and discharge cycle. Repeating the above process 500 times means performing 500 charge and discharge cycles.

[0161] (5) Spacing d between the roots of adjacent tabs 112: The die-cutting equipment cuts out the requirements of the designed tabs 112 on the full tabs 112 through program control. The spacing between the roots of the die-cut tabs 112 can be directly read through the die-cutting equipment or measured using a film ruler for the trapezoidal tabs 112.

[0162] (6) Diameter L of the central hole 13: The electrode assembly 10 is wound by a winding needle, and the value of L can be measured by a digital display vernier caliper.

[0163] The parameters of the cylindrical battery 100 in each embodiment and comparative example are shown in Table 1 and Table 2 below.

[0164] Table 1 Performance parameters of the cylindrical battery 100 in each embodiment and comparative example

[0165]

[0166] Table 2 Performance parameters of the cylindrical battery 100 in each embodiment and comparative example

[0167]

[0168]

[0169] From the test data of Embodiment 1 to Embodiment 5, it can be seen that as the mass fraction of the electrolyte salt in the electrolyte increases, the overcharge temperature of the cylindrical battery 100 first gradually decreases and then gradually increases; the thermal runaway temperature of the cylindrical battery 100 also first gradually increases and then gradually decreases. The cycle capacity retention rate of the cylindrical battery 100 after 500 cycles at 25°C first gradually increases and then gradually decreases, and the cycle capacity retention rate after 500 cycles at 45°C gradually increases. Therefore, when the mass fraction range of the electrolyte salt in the electrolyte is 8.75% to 12.5%, the cylindrical battery 100 can have a lower overcharge temperature and a lower thermal runaway temperature, thus having higher safety performance. In addition, the cylindrical battery 100 can also have a higher cycle capacity retention rate at room temperature (25°C) and a higher cycle capacity retention rate at high temperature (45°C).

[0170] From the test results of Comparative Example 1 and Example 6, it can be seen that adding a cyclic sulfate additive to the electrolyte has little effect on the overcharge temperature of the cylindrical battery 100, but can greatly reduce the thermal runaway temperature of the cylindrical battery 100 and improve the safety performance of the cylindrical battery 100; in addition, it can also improve the normal temperature cycle capacity retention rate and high temperature cycle capacity retention rate of the cylindrical battery 100. When the content of the cyclic sulfate additive in the electrolyte is small, the improvement of the safety performance and cycle capacity retention rate of the cylindrical battery 100 is small. From the test results of Example 3, Example 6 to Example 12, it can be seen that as the cyclic sulfate additive in the electrolyte increases, the overcharge temperature of the cylindrical battery 100 first gradually decreases and then gradually increases, and the thermal runaway temperature of the cylindrical battery 100 also first gradually decreases and then gradually increases, indicating that the safety performance of the cylindrical battery 100 first gradually improves and then gradually deteriorates as the content of the cyclic sulfate additive increases. The cycle capacity retention rate of the cylindrical battery 100 after 500 cycles at 25 °C first gradually increases and then gradually decreases, and the cycle capacity retention rate after 500 cycles at 45 °C also first gradually increases and then gradually decreases. Therefore, when the mass fraction range of the cyclic sulfate additive in the electrolyte is 0.1% to 3%, the cylindrical battery 100 can have a lower overcharge temperature and a lower thermal runaway temperature, thereby having higher safety performance. In addition, the cylindrical battery 100 can also have a higher normal temperature (25 °C) cycle capacity retention rate and high temperature (45 °C) cycle capacity retention rate.

[0171] From the test results of Comparative Example 2 and Example 3, it can be seen that adding a second additive to the electrolyte can greatly reduce the overcharge temperature and thermal runaway temperature of the cylindrical battery 100 and improve the safety performance of the cylindrical battery 100; in addition, it can also improve the normal temperature cycle capacity retention rate and high temperature cycle capacity retention rate of the cylindrical battery 100. From the test results of Example 3, Example 13 to Example 15, it can be seen that as the content of the second additive in the electrolyte increases, the overcharge temperature of the cylindrical battery 100 gradually increases, and the thermal runaway temperature of the cylindrical battery 100 also gradually increases. The cycle capacity retention rate of the cylindrical battery 100 after 500 cycles at 25 °C gradually decreases, and the cycle capacity retention rate after 500 cycles at 45 °C also gradually decreases. Therefore, when the mass fraction range of the second additive in the electrolyte is 0.1% to 1%, the cylindrical battery 100 can have a lower overcharge temperature and a lower thermal runaway temperature, thereby having higher safety performance. In addition, the cylindrical battery 100 can also have a higher normal temperature (25 °C) cycle capacity retention rate and high temperature (45 °C) cycle capacity retention rate.

[0172] As can be seen from the test results of Example 3 and Examples 16 to 19, as the diameter L of the central hole 13 of the electrode assembly 10 increases, the overcharge temperature of the cylindrical battery 100 first gradually decreases and then gradually increases, and the thermal runaway temperature of the cylindrical battery 100 also first gradually decreases and then gradually increases, indicating that the safety performance of the cylindrical battery 100 first gradually improves and then gradually deteriorates as the diameter L of the central hole 13 of the electrode assembly 10 increases. The cycle capacity retention rate of the cylindrical battery 100 after 500 cycles at 25 °C first gradually increases and then gradually decreases, and the cycle capacity retention rate after 500 cycles at 45 °C also first gradually increases and then gradually decreases. Therefore, when the diameter L of the central hole 13 of the electrode assembly 10 ranges from 2 mm to 12 mm, the cylindrical battery 100 can have a lower overcharge temperature and a lower thermal runaway temperature, thus having higher safety performance. In addition, the cylindrical battery 100 can also have a higher cycle capacity retention rate at room temperature (25 °C) and a higher cycle capacity retention rate at high temperature (45 °C).

[0173] As can be seen from the test results of Example 3 and Examples 20 to 23, as the distance d between two adjacent tab ears 112 increases, the overcharge temperature of the cylindrical battery 100 first gradually decreases and then gradually increases, and the thermal runaway temperature of the cylindrical battery 100 first gradually decreases and then gradually increases, indicating that the safety performance of the cylindrical battery 100 first gradually improves and then gradually deteriorates as the distance d between two adjacent tab ears 112 increases. The cycle capacity retention rate of the cylindrical battery 100 after 500 cycles at 25 °C first gradually increases and then gradually decreases, and the cycle capacity retention rate after 500 cycles at 45 °C also first gradually increases and then gradually decreases. Therefore, when the distance d between two adjacent tab ears 112 ranges from 1 mm to 6 mm, the cylindrical battery 100 can have a lower overcharge temperature and a lower thermal runaway temperature, thus having higher safety performance. In addition, the cylindrical battery 100 can also have a higher cycle capacity retention rate at room temperature (25 °C) and a higher cycle capacity retention rate at high temperature (45 °C).

[0174] As can be seen from the test results of Example 3, Examples 24 to 26 and Comparative Example 2, different cyclic sulfate additives with the structural formula of the present application can all reduce the thermal runaway temperature of the cylindrical battery 100, improve the safety performance of the cylindrical battery 100, and can also improve the cycle capacity retention rate of the cylindrical battery 100 at room temperature (25 °C) and at high temperature (45 °C), making the cylindrical battery 100 have better cycle performance and safety performance. Compared with 4-ethyl vinyl sulfate, 4-isopropyl vinyl sulfate and 4-butyl vinyl sulfate, 4-ethyl methyl sulfate has a more obvious improvement effect on the safety performance and cycle performance of the cylindrical battery 100.

[0175] From the test results of Example 3 and Examples 27 to 28, it can be seen that using lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, and lithium bis(trifluoromethanesulfonyl)imide as electrolyte salts can all enable the cylindrical battery 100 to have a relatively low overcharge heat generation, a relatively high normal temperature cycle capacity retention rate, and a relatively high high temperature cycle capacity retention rate. However, compared with lithium bis(fluorosulfonyl)imide and lithium bis(trifluoromethanesulfonyl)imide, using lithium bis(fluorosulfonyl)imide hexafluorophosphate as the electrolyte salt can enable the cylindrical battery 100 to have a lower overcharge temperature and a lower thermal runaway temperature, and a relatively high normal temperature cycle capacity retention rate and a relatively high high temperature cycle capacity retention rate.

[0176] From the test results of Examples 1 to 28, it can be seen that when 0.4 mm ≤ k ≤ 2.175 mm, the cylindrical battery 100 has a relatively low overcharge temperature and a relatively low thermal runaway temperature, and a relatively high normal temperature cycle capacity retention rate and a relatively high high temperature cycle capacity retention rate. From the test result of Comparative Example 3, it can be seen that when k is less than 0.4 mm, both the overcharge temperature and the thermal runaway temperature of the cylindrical battery 100 are relatively high, indicating that the safety performance of the cylindrical battery 100 is reduced and the risk of explosion during thermal runaway increases; in addition, the cycle capacity retention rate of the cylindrical battery 100 after 500 cycles at 25°C is reduced to a large extent, and the cycle capacity retention rate after 500 cycles at 45°C drops directly. From the test result of Comparative Example 4, it can be seen that when k is greater than 2.175 mm, both the overcharge temperature and the thermal runaway temperature of the cylindrical battery 100 increase to a large extent, indicating that the safety performance of the cylindrical battery 100 is reduced and the risk of explosion during thermal runaway increases; in addition, both the cycle capacity retention rate of the cylindrical battery 100 after 500 cycles at 25°C and the cycle capacity retention rate after 500 cycles at 45°C drop significantly.

[0177] Please refer to Figure 7 , the embodiment of the present application further provides an energy storage device 200, which includes a box body 210 and a plurality of cylindrical batteries 100 described in the embodiments of the present application, and the plurality of cylindrical batteries 100 are received in the box body 210.

[0178] It can be understood that the plurality of cylindrical 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 in parallel and partially in series (in other words, in a mixed connection). For the connection manner of the plurality of cylindrical batteries 100 of the same energy storage device 200, the present application does not make a specific limitation.

[0179] Optionally, the energy storage device 200 can be at least one of a small energy storage box, a large energy storage cabinet, an energy storage module, etc. The present application does not make a specific limitation on the form of the energy storage device 200. The form of the energy storage device 200 in the present application is only one of its many forms and should not be construed as a limitation on the energy storage device 200 of the present application.

[0180] It should be noted that the stacking of the plurality of cylindrical batteries 100 can be arranged such that the plurality of cylindrical batteries 100 are sequentially abutted against each other, or the plurality of cylindrical batteries 100 are sequentially arranged with intervals. In addition, the plurality of cylindrical batteries 100 can be stacked in the horizontal direction (such as the horizontal direction) or the vertical direction (such as the gravity direction). The stacking method and stacking direction of the plurality of cylindrical batteries 100 can be designed according to actual situations.

[0181] Understandably, the box body 210 has a receiving cavity (not shown in the figure), and the plurality of cylindrical batteries 100 are received in the receiving cavity. In some embodiments, each receiving cavity receives one cylindrical battery 100. In other embodiments, each receiving cavity receives a plurality of cylindrical batteries 100.

[0182] Please refer to Figure 8 and Figure 9 In addition, the embodiment of the present application further provides an energy storage system 300, which includes the energy storage device 200 described in the embodiment of the present application; and a power conversion device 310, the power conversion device 310 is electrically connected to the energy storage device 200, and the power conversion device 310 is used to convert other forms of energy into electrical energy, and the energy storage device 200 is used to store the electrical energy.

[0183] Energy storage (i.e., energy storage) has a wide range of application scenarios, including power generation side energy storage, grid side energy storage, and user side energy storage, etc. The energy storage system 300 of the embodiment of the present application takes the power generation side energy storage as an example to introduce the energy storage system 300 of the embodiment of the present application in detail, and should not be understood as a limitation on the energy storage system 300 of the embodiment of the present application, nor should it be understood as a limitation on the energy storage device 200 and the cylindrical battery 100 of the embodiment of the present application.

[0184] Optionally, the power conversion device 310 can convert at least one of other forms of energy such as solar energy, light energy, wind energy, thermal energy, tidal energy, biomass energy, and mechanical energy into electrical energy.

[0185] Optionally, the number of the power conversion devices 310 can be one or more. When there are multiple power conversion devices 310, the multiple power conversion devices 310 can be connected in series, parallel, or in a hybrid connection, and the present application does not make specific limitations.

[0186] Optionally, the power conversion device 310 can be at least one of, but not limited to, a photovoltaic panel, a wind power generation device, a water power generation device, etc.

[0187] Optionally, the number of the energy storage devices 200 can be one or more. When the number of the energy storage devices 200 is multiple, the multiple energy storage devices 200 are connected in series or parallel with each other, and the present application does not make specific limitations.

[0188] During operation, the power conversion device 310 is used to convert other forms of energy into electrical energy and store it in the energy storage device 200. The electrical energy stored in the energy storage device 200 can be supplied to electrical loads such as street lights and household appliances for use during peak electricity prices, or for power supply when the power grid is powered off / out of power. The electrical energy generated by the power conversion device 310 can also be supplied to the power grid through high-voltage cables to relieve the power supply pressure during peak grid periods.

[0189] In this application, the mention of "embodiment" and "implementation manner" means that the specific features, structures, or characteristics described in connection with the embodiment can be included in at least one embodiment of this application. The phrase appears in various positions in the specification and does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art explicitly and implicitly understand that the embodiments described in this application can be combined with other embodiments. In addition, it should also be understood that the features, structures, or characteristics described in each embodiment of this application can be combined arbitrarily without contradiction to form another embodiment that does not depart from the spirit and scope of the technical solution of this application.

[0190] Finally, it should be noted that the above implementation manners are only used to illustrate the technical solutions of this application and not to limit them. Although the technical solutions of this application have been described in detail with reference to the above preferred implementation manners, those of ordinary skill in the art should understand that modifications or equivalent replacements of the technical solutions of this application should not depart from the spirit and scope of the technical solutions of this application.

Claims

1. A cylindrical battery, characterized in that: The cylindrical battery comprises: An electrolyte, the electrolyte comprising an electrolyte salt, a first additive and an organic solvent, the sum of the mass fractions of the electrolyte salt and the first additive in the electrolyte is X, and the first additive is a cyclic sulfate additive; and An electrode assembly, wherein the electrode assembly comprises an electrode plate, wherein the electrode plate comprises an electrically connected current collector and a plurality of tabs, wherein the plurality of tabs are arranged at intervals on the same side of the current collector, and the spacing between two adjacent tabs is d; the electrode assembly is in a winding structure, and the electrode assembly has a central hole, and the diameter of the central hole of the electrode assembly is L, wherein the unit of d is mm, and the unit of L is mm; The cylindrical battery also satisfies the relationship: d=k / XL, wherein the range of k is 0.4 mm≤k≤2.175 mm.

2. The cylindrical battery according to claim 1, characterized in that: The structural formula of the cyclic sulfate additive is: Wherein, A is one of methyl, ethyl, propyl, isopropyl, and vinyl sulfate; R is (CH2)n, and n ranges from 1 to 3.

3. The cylindrical battery according to claim 1, characterized in that: In the electrolyte, the sum of the mass fractions of the electrolyte salt and the first additive is in the range of 8.85%≤X≤14.5%.

4. The cylindrical battery according to claim 1, characterized in that: The electrolyte further includes a second additive, the structural formula of which is: In the electrolyte, the mass fraction m of the second additive is in the range of 0.1%≤m≤1%.

5. The cylindrical battery according to claim 1, characterized in that: The range of the distance d between two adjacent tabs is: 1mm≤d≤6mm.

6. The cylindrical battery according to claim 1, characterized in that: The diameter L of the central hole of the electrode assembly is in the range of 3 mm ≤ L ≤ 12 mm.

7. The cylindrical battery according to claim 1, characterized in that: The number of turns of the electrode assembly is M, M turns include N steps, each step includes multiple turns, the electrode plate of each turn includes multiple pole ears, the multiple pole ears of each step have the same size, and from the outermost turn of the electrode assembly to the innermost turn, the width of the pole ears at different steps gradually decreases and the height of the pole ears at different steps also gradually decreases, wherein M>N.

8. The cylindrical battery according to claim 7, characterized in that: The number N of steps of the electrode assembly is in the range of 2≤N≤10.

9. The cylindrical battery according to claim 7, characterized in that: The number n of the electrode tabs of the electrode plate is in the range of 400≤n≤2000.

10. The cylindrical battery according to claim 7, characterized in that: The height h1 of the electrode tab of the step of the electrode assembly closest to the central hole is in the range of 2 mm ≤ h1 ≤ 6 mm.

11. The cylindrical battery according to claim 7, characterized in that: When the electrode assembly is in a winding structure, the radial width w1 of the step farthest from the central hole is in the range of 100 mm≤w1≤300 mm.

12. The cylindrical battery according to claim 7, characterized in that: The electrode plate includes a non-polar lug area, which is arranged close to the central hole and connected to the step closest to the central hole. When the electrode assembly is flattened, the length s1 of the non-polar lug area is in the range of 100mm≤s1≤500mm.

13. The cylindrical battery according to claim 7, characterized in that: The length s2 of the electrode pole piece corresponding to the innermost step of the electrode assembly when flattened is in the range of: 300mm≤s2≤500mm.

14. An energy storage device, characterized in that: include: Box; as well as A plurality of cylindrical batteries according to any one of claims 1 to 13, wherein the plurality of cylindrical batteries are housed in the box.

15. An energy storage system, characterized in that: include: The energy storage device according to claim 14; as well as An electric energy conversion device, wherein the electric energy conversion device is electrically connected to the energy storage device, the electric energy conversion device is used to convert other forms of energy into electric energy, and the energy storage device is used to store the electric energy.

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