Energy storage device and energy storage system

Abstract

The application discloses an energy storage device and an energy storage system. The energy storage device comprises a shell, an end cover assembly, a pole, a battery cell and an adapter. The multi-layer tabs of the battery cell comprise a middle tab, a first side tab and a second side tab located on both sides of the middle tab. The first side tab and the second side tab are respectively bent towards the middle tab. The first side of the adapter is electrically connected with the first side tab, and the second side of the adapter is electrically connected with the pole. Taking the root of the second side tab as the origin, the thickness direction of the battery cell as the x-axis and the extension direction of the tab as the y-axis, a rectangular coordinate system is established. The coordinates of the root of any tab are (x, 0). When the first side of the multi-layer tab is set to face the battery cell without bending, the coordinates of the connection position of the first side tab are (a, b). When the first side of the multi-layer tab is set to face the battery cell after bending, the coordinates of the connection position are (c, d). Wherein, ((a-x) 2 +b 2 ) - {(c-x) 2 +d 2} > 0.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of energy storage, in particular to an energy storage device and an energy storage system. BACKGROUND

[0002] In the process of processing the battery cell, the adapter is usually arranged on one side of the multi-layer tab of the battery cell, and the multi-layer tab is pressed and combined with the adapter, and then the multi-layer tab and the adapter are welded to complete the assembly of the adapter and the multi-layer tab.

[0003] In the related art, when the tabs are formed by die cutting, the multi-layer tabs are usually die cut into tabs with the same height, that is, the height of each tab protruding relative to the battery cell is the same. When welding, the tabs on one side of the multi-layer tabs are pressed and combined with the adapter on the other side, and the end of the multi-layer tab away from the battery cell will have uneven problems, for example, the end of the multi-layer tab forms a stepped structure with a gradient increasing in the direction close to the adapter, and the welding area of the tab farthest from the adapter is greatly reduced. In order to ensure that the welding mark falls on each tab and ensure the welding quality of the tab, a tab with a higher height is required, which will increase the cost of the battery cell foil and increase the internal resistance of the tab, thereby affecting the performance of the battery cell. SUMMARY

[0004] The embodiments of the present application disclose an energy storage device and an energy storage system, which can reduce the height of the tab protruding relative to the battery cell to reduce the cost of the battery cell foil and reduce the internal resistance of the tab, thereby improving the performance of the battery cell. At the same time, it can also avoid pulling and tearing the tab.

[0005] To achieve the above-mentioned purpose, in a first aspect, the present application discloses an energy storage device, comprising:

[0006] a housing having an inner cavity and an opening communicating with the inner cavity;

[0007] an end cover assembly sealingly arranged in the opening, and the end cover assembly is provided with a through tab hole;

[0008] a tab, the tab is arranged in the tab hole;

[0009] a battery cell arranged in the inner cavity, the battery cell comprises a battery cell body and a multi-layer tab arranged on the battery cell body, the multi-layer tab is arranged in the thickness direction of the battery cell, and the multi-layer tab comprises a middle tab, a first side tab and a second side tab, the first side tab and the second side tab are respectively located on both sides of the middle tab in the thickness direction of the battery cell, and the first side tab and the second side tab are respectively bent towards the middle tab; and

[0010] The adapter has opposite first and second sides, the first side is electrically connected with the first side edge tab, and the second side is electrically connected with the pole;

[0011] The multi-layer tab can be bent from a first state to a second state, wherein the first state is configured as a state in which the multi-layer tab is not bent to arrange the first side towards the battery body, and the second state is configured as a state in which the multi-layer tab is bent to arrange the first side towards the battery body;

[0012] Each of the tabs has a root connected with the battery body, the first side edge tab has a connection position connected with the adapter, taking the root of the second side edge tab as the origin, the thickness direction of the battery as the x-axis, and the extension direction of the tab as the y-axis to establish a rectangular coordinate system, the coordinate of the root of any tab is (x, 0), the coordinate of the connection position is (a, b) when the multi-layer tab is in the first state, and the coordinate of the connection position is (c, d) when the multi-layer tab is in the second state; wherein ((a-x) 2 +b 2 )-((c-x) 2 +d 2 )>0.

[0013] In the energy storage device provided in the embodiments of the present application, by bending and pressing the first side edge tab and the second side edge tab on both sides of the middle tab towards the middle tab respectively, and then electrically connecting the first side of the adapter with the first side edge tab, compared with the way of only bending and pressing the second side edge tab towards the first side edge tab, the bending degree of the second side edge tab can be reduced, so that the second side edge tab has sufficient welding area after bending, while the height of each layer of tabs, especially the height of the second side edge tab, is reduced, thereby the cost of the battery foil can be reduced, the internal resistance of the tab is reduced, and the performance of the battery can be improved.

[0014] Meanwhile, the energy storage device satisfies the following relationship: ((a-x) 2 +b 2 )-((c-x) 2 +d 2) > 0, wherein b, c, d, k, x can be obtained according to actual battery testing, the range of a can be calculated through calculation of the above relationship, and the distance range of the connection position of the first side edge tab and the root thereof in the thickness direction of the battery can be determined after the first side edge tab is bent towards the middle tab, so that the bending degree of the first side edge tab bent towards the middle tab can be determined, over-pulling of the first side edge tab when the first side is arranged towards the battery through bending of the multi-layer tab can be avoided, over-bending of the first side edge tab can be avoided, and the situation of pulling and tearing the first side edge tab when the first side of the adapter is arranged towards the battery body through bending of the multi-layer tab can be avoided, so as to ensure the conductive reliability of the tab.

[0015] As an optional implementation, in the embodiment of the first aspect of the application, the expansion rate of the battery in the thickness direction thereof is k, and the energy storage device satisfies the following relationship:

[0016] ((a-x) 2 +b 2 )-((c-(1+k)x) 2 +d 2 ) > 0.

[0017] When the energy storage device satisfies the following relationship: ((a-x) 2 +b 2 )-((c-(1+k)x) 2 +d 2 ) > 0, over-pulling of the first side edge tab when the battery expands can be avoided, and the situation of pulling and tearing the first side edge tab when the battery expands can be avoided, so as to ensure the conductive reliability of the tab.

[0018] As an optional implementation, in the embodiment of the first aspect of the application, when neither the first side edge tab nor the second side edge tab is bent towards the middle tab, and the first side edge tab is not connected with the first side, the height of each tab protruding relative to the battery body is equal.

[0019] In this way, the height of each tab protruding relative to the battery body can be kept the same, and the tab does not need to be specially die-cut, so that the die-cutting process of the tab can be simplified.

[0020] As an optional implementation, in the embodiment of the first aspect of the present application, when neither the first side edge tab nor the second side edge tab is bent towards the middle tab, and the first side edge tab is not connected to the first side surface, the height of the first side edge tab protruding relative to the battery body is greater than the height of the middle tab protruding relative to the battery body, and / or the height of the second side edge tab protruding relative to the battery body is greater than the height of the middle tab protruding relative to the battery body.

[0021] In this way, after the first side edge tab and the second side edge tab are respectively bent towards the middle tab and are pressed and connected, that is, after the multiple layers of tabs are pressed and connected, the middle tab, the first side edge tab and the second side edge tab are flush with each other away from one end of the battery. Compared with the mode in which the height of each tab is equal, at least the height of the middle tab can be reduced, thereby facilitating the reduction of the cost of the battery foil and the reduction of the internal resistance of the tab, so that the performance of the battery can be improved.

[0022] As an optional implementation, in the embodiment of the first aspect of the present application, when neither the first side edge tab nor the second side edge tab is bent towards the middle tab, and the first side edge tab is not connected to the first side surface, the height of the tab protruding relative to the battery body first decreases and then increases along the thickness direction of the battery.

[0023] In this way, after the first side edge tab and the second side edge tab are respectively bent towards the middle tab and are pressed and connected, that is, after the multiple layers of tabs are pressed and connected, the middle tab, the first side edge tab and the second side edge tab are flush with each other away from one end of the battery. Compared with the mode in which the height of each tab is equal, at least the height of the middle tab can be reduced, thereby facilitating the reduction of the cost of the battery foil and the reduction of the internal resistance of the tab, so that the performance of the battery can be improved.

[0024] As an optional implementation, in the embodiment of the first aspect of the present application, when neither the first side edge tab nor the second side edge tab is bent towards the middle tab, and the first side edge tab is not connected to the first side surface, the distance between any two adjacent layers of the tabs is equal, so that the layers of tabs can be arranged at equal intervals, thereby facilitating the guarantee of the charge and discharge performance and the comprehensive performance of the battery.

[0025] As an optional implementation, in the embodiment of the first aspect of the present application, when neither the first side edge tab nor the second side edge tab is bent towards the middle tab, and the first side edge tab is not connected to the first side surface, the height difference of any two adjacent layers of the tabs protruding relative to the battery body is equal.

[0026] In this way, the multi-layered tabs are not only more flat after being pressed, but also the height of the multi-layered tabs protruding from the battery body is arranged in an arithmetic progression, which can form a regular change, thereby facilitating the die cutting of each layer of tabs and achieving accurate control of the height of each layer of tabs.

[0027] As an optional implementation, in the embodiment of the first aspect of the present application, the energy storage device is a polygon battery or a cylindrical battery. It can be seen that the energy storage device in the present application is not limited to a specific shape of battery, and the shape of the energy storage device is various and flexible.

[0028] As an optional implementation, in the embodiment of the first aspect of the present application, the pole hole includes a first pole hole and a second pole hole.

[0029] The pole includes a positive pole and a negative pole, the positive pole is arranged in the first pole hole, and the negative pole is arranged in the second pole hole.

[0030] The battery includes a first battery and a second battery, the first battery includes a first battery body, a first positive tab arranged on the first battery body, and a first negative tab arranged on the first battery body, the second battery includes a second battery body, a second positive tab arranged on the second battery body, and a second negative tab arranged on the second battery body, the first battery body and the second battery body both include the battery body, and the first positive tab, the first negative tab, the second positive tab, and the second negative tab all include the multi-layered tabs.

[0031] The first battery and the second battery are arranged along the thickness direction of the battery, the first positive tab and the second positive tab are arranged opposite to each other along the thickness direction of the battery, the first negative tab and the second negative tab are arranged opposite to each other along the thickness direction of the battery, and / or the first positive tab and the first negative tab are located on the side of the first battery body away from the second battery body, and the second positive tab and the second negative tab are located on the side of the second battery body away from the first battery body along the thickness direction of the battery.

[0032] The adapter includes a first adapter component and a second adapter component, the first adapter component is electrically connected with the positive pole, the first positive tab, and the second positive tab respectively, and the second adapter component is electrically connected with the negative pole, the first negative tab, and the second negative tab respectively.

[0033] It can be understood that, in the assembling process of the battery cell, the first battery cell and the second battery cell are arranged in the height direction of the battery cell, and in the height direction of the battery cell, the first negative tab of the first battery cell and the second negative tab of the second battery cell can be arranged oppositely, and the first positive tab of the first battery cell and the second positive tab of the second battery cell can be arranged oppositely, thereby facilitating the welding of the first adapter component with the first positive tab and the second positive tab, and facilitating the welding of the second adapter component with the first negative tab and the second negative tab, which is beneficial to realize the welding of the first adapter with the first positive tab and the second positive tab, quickly realize the welding of the second adapter component with the first negative tab and the second negative tab, and save the welding time.

[0034] In addition, since the first positive tab of the first battery cell and the second positive tab of the second battery cell are both located on the outside of the battery cell, and the first negative tab of the first battery cell and the second negative tab of the second battery cell are both located on the outside of the battery cell, when the first battery cell and the second battery cell are arranged in the thickness direction of the battery cell, the positions of the first positive tab and the second positive tab are far apart, and the positions of the first negative tab and the second negative tab are far apart, which can avoid the first positive tab and the second positive tab from being overlapped to cause short circuit, and the first negative tab and the second negative tab from being overlapped to cause short circuit, and enable the first positive tab and the second positive tab to have a larger connection area with the first adapter component, and enable the first negative tab and the second negative tab to have a larger connection area with the second adapter component, thereby facilitating to improve the connection strength of the battery cell and the adapter, and avoiding the problem of conductive failure caused by the low connection strength of the battery cell and the adapter.

[0035] In a second aspect, the present application discloses a kind of energy storage systems, the energy storage system has the energy storage device of the first aspect described above. The energy storage system with the energy storage device of the first aspect can also reduce the height of the tab relative to the battery cell, reduce the cost of the battery cell foil and the internal resistance of the tab, thereby improving the performance of the battery cell; It can also avoid pulling and tearing the tab.

[0036] Compared with the prior art, the present application has the following beneficial effects:

[0037] The energy storage device and the energy storage system provided by the embodiments of the present application can reduce the bending degree of the second side tab by bending and pressing the first side tab and the second side tab on both sides of the middle tab towards the middle tab, and then electrically connecting the first side of the adapter to the first side tab, compared with the way of only bending and pressing the second side tab towards the first side tab, so that the second side tab has sufficient welding area after bending, while reducing the height of each layer of tabs, especially the height of the second side tab, thereby reducing the cost of the battery cell foil and the internal resistance of the tab, and improving the performance of the battery cell.

[0038] At the same time, the energy storage device satisfies the following relationship: ((a-x)2 +b 2 )-((c-x) 2 +d 2 )>0, wherein b, c, d, k, and x can be obtained according to actual battery cell tests, the range of a can be calculated by calculating the above relationship, and the distance range between the connection position of the first side edge tab and the root thereof in the thickness direction of the battery cell can be determined after the first side edge tab is bent toward the middle tab, so that the bending degree of the first side edge tab bent toward the middle tab can be determined, excessive pulling of the first side edge tab when the first side edge tab is arranged toward the battery cell after the multi-layer tab is bent can be avoided, the first side edge tab is prevented from being excessively bent, and the first side edge tab is prevented from being pulled and torn when the first side of the adapter is arranged toward the battery cell after the multi-layer tab is bent, so that the conductivity reliability of the tab can be ensured. BRIEF DESCRIPTION OF DRAWINGS

[0039] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the embodiments will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0040] Figure 1 is a structural schematic diagram of the battery cell and the adapter in the related art;

[0041] Figure 2 is a structural schematic diagram of the battery cell in the related art;

[0042] Figure 3 is a first structural schematic diagram of the energy storage system disclosed by the embodiments of the present application;

[0043] Figure 4 is a second structural schematic diagram of the energy storage system disclosed by the embodiments of the present application;

[0044] Figure 5 is a structural schematic diagram of the energy storage device disclosed by the embodiments of the present application;

[0045] Figure 6 is an exploded structural schematic diagram of the energy storage device disclosed by the embodiments of the present application;

[0046] Figure 7 is a sectional view of the energy storage device disclosed by the embodiments of the present application along the N-N direction in Figure 5

[0047] Figure 8 is a structural schematic diagram of two battery cells disclosed by the embodiments of the present application;

[0048] Figure 9 ​is a structural schematic view of two battery cells and two adapter pieces disclosed by embodiments of the present application;

[0049] Figure 10 is a structural schematic view of two battery cells and two adapter pieces from another perspective disclosed by embodiments of the present application;

[0050] Figure 11 is a structural schematic view of a battery cell and an adapter piece disclosed by embodiments of the present application;

[0051] Figure 12 is Figure 7 is a partial enlarged view of M in

[0052] Figure 13 is a theoretical calculation schematic view for confirming a connection position of a first side edge tab and an adapter piece disclosed by embodiments of the present application;

[0053] Figure 14 is a first structural schematic view of a battery cell disclosed by embodiments of the present application;

[0054] Figure 15 is a second structural schematic view of a battery cell disclosed by embodiments of the present application;

[0055] Figure 16 is a third structural schematic view of a battery cell disclosed by embodiments of the present application;

[0056] Figure 17 is a fourth structural schematic view of a battery cell disclosed by embodiments of the present application.

[0057] Main figure mark explanation

[0058] 1000 - energy storage system;

[0059] 100 - energy storage device; 11 - shell; 111 - inner cavity; 112 - opening; 12 - end cap assembly; 12a - pole hole; 121a - first pole hole; 121b - second pole hole; 13 - pole; 131 - positive pole; 132 - negative pole; 14 - battery cell; 14a - first battery cell; 14a1 - first battery cell body; 14a2 - first positive tab; 14a3 - first negative tab; 14b - second battery cell; 14b1 - second battery cell body; 14b2 - second positive tab; 14b3 - second negative tab; 141 - battery cell body; 142 - tab; 142a - root; 1421 - middle tab; 1422 - first side edge tab; 1422a - connection position; 1423 - second side edge tab; 15 - adapter piece; 15a - first adapter component; 15b - second adapter component; 151 - first side; 152 - second side;

[0060] 200 - electric energy conversion device; 300 - first user load; 400 - second user load;

[0061] 210 - high voltage cable; 310 - first electric energy conversion device; 410 - second electric energy conversion device;

[0062] f1 - length direction; f2 - thickness direction; f3 - height direction. DETAILED DESCRIPTION

[0063] In order to make the objects, technical solutions and advantages of the present application clearer, the following will clearly and completely describe the exemplary embodiments of the present application with reference to the accompanying drawings. Obviously, the described exemplary embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. That is, the specific embodiments described herein are only used to explain the present application, and are not intended to limit the present application.

[0064] It should be noted that the brief description of the terms in the present application is only for the convenience of understanding the embodiments described next, and is not intended to limit the embodiments of the present application. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present application belongs. The terms used in the specification of the present application are only for the purpose of describing the specific embodiments of the present application, and are not intended to limit the present application.

[0065] In the description of the present application, it should be understood that the terms "center", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application.

[0066] The terms "first", "second", and the like can be used in the present application to describe various elements, but these elements are not limited by these terms. These terms are only used to distinguish the first element from another element. For example, without departing from the scope of the present application, the first side edge tab can be called the second side edge tab, and similarly, the second side edge tab can be called the first side edge tab. The first side edge tab and the second side edge tab are both side edge tabs, but they are not the same side edge tab.

[0067] In addition, the terms "first", "second", etc. are used only for the purpose of description, and should not be understood as indicating or implying relative importance or implying the number of the technical features indicated. Therefore, the features defined as "first", "second" can explicitly or implicitly include one or more of the features. In the description of the present application, the meaning of "a plurality of" is two or more, unless otherwise specified.

[0068] In the description of the present application, it should be noted that, unless otherwise specified and limited, the terms "mounting", "connecting", "connection" should be understood broadly, for example, it can be fixed connection, or detachable connection, or integral connection; it can be mechanical connection, or electrical connection; it can be direct connection, or indirect connection through intermediate medium, or internal communication of two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0069] In the description of the present application, it should be noted that the singular form "one", "an" and "said / this" can also include the plural form, unless the context clearly indicates otherwise. It should also be understood that the term "include / contain" or "have" and the like specifies the existence of the stated features, integers, steps, operations, components, parts or combinations thereof, but does not exclude the possibility of existence or addition of one or more other features, integers, steps, operations, components, parts or combinations thereof.

[0070] In addition, the term "and / or" used in the present specification includes any and all combinations of the related listed items, for example, A and / or B can mean that A exists alone, A and B exist together, B exists alone, that is, the term "and / or" used in the present specification includes any and all combinations of the related listed items.

[0071] Since the energy required by people has strong time and space, in order to reasonably use energy and improve the utilization rate of energy, it is necessary to store one form of energy into the same or another form of energy through a medium or device, and release it in a specific energy form based on future application needs. It is well known that the main way to generate green electricity at present is to develop green energy such as photovoltaic and wind power to replace fossil energy.

[0072] 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 peak power consumption, excessive power during low power consumption, and unstable voltage can also cause damage to power, thus causing "abandoned wind and light" problems due to insufficient power demand or insufficient power grid receiving capacity. To solve these problems, energy storage is needed, that is, the power is stored in other forms of energy through physical or chemical means, and the energy is converted into electric energy for release when needed. In simple terms, energy storage is similar to a large "power bank", which stores power when photovoltaic and wind power are sufficient, and releases the stored power when needed.

[0073] Taking electrochemical energy storage as an example, the embodiment of the present application provides an energy storage device, which is provided with a group of energy storage batteries, mainly using chemical elements in the battery as energy storage medium, and the charging and discharging process is accompanied by chemical reaction or change of the energy storage medium. In simple terms, the power generated by wind and solar energy is stored in a chemical battery, and the stored power is released for use when the use of external power reaches a peak, or is transferred to a place where power is in short supply for use.

[0074] The current energy storage (i.e. energy storage) application scenarios are relatively wide, including power generation side energy storage, power grid side energy storage, renewable energy grid-connected energy storage, and user side energy storage, and the corresponding types of energy storage devices include:

[0075] ① Large energy storage containers applied in power grid side energy storage scenarios, which can be used as high-quality active and reactive power regulation power sources in the power grid, realize load matching of power in time and space, enhance renewable energy consumption capacity, and have great significance in power grid system backup, relieving peak load power supply pressure and peak regulation.

[0076] ② Medium and small energy storage cabinets applied in user side industrial and commercial energy storage scenarios (banks, shopping malls, etc.) and small household energy storage boxes applied in user side household energy storage scenarios, the main operation mode of which is "peak load shifting". Due to the large price difference between the electricity price at the peak and the valley according to the electricity demand, after the user has energy storage equipment, in order to reduce the cost, the energy storage cabinet / box is usually charged during the low price valley period; the power in the energy storage equipment is discharged for use during the high price peak period, so as to achieve the purpose of saving electricity cost. In addition, in remote areas and areas where earthquakes, hurricanes and other natural disasters are prone to occur, the existence of household energy storage devices is equivalent to providing the user and the power grid with a backup power source, which eliminates the inconvenience caused by frequent power outages due to disasters or other reasons.

[0077] In the production process of the energy storage device, the assembly process has a crucial influence on the quality, cost and performance of the battery cell product. The tab is an important connecting structure for connecting the winding core and the pole of the end cover. Its main function is to collect electrons and transmit electrons. The height design of the tab relative to the battery cell has a significant impact on the cost and internal resistance of the battery cell. In the case of ensuring the assembly process, the height of the tab is reduced as much as possible, which is conducive to reducing the cost of the battery cell foil and the internal resistance of the tab, and thus improving the performance of the battery cell.

[0078] In the related art, in order to ensure the battery performance of the energy storage device, a adapter is usually used to realize the electrical connection between the tab of the battery cell and the pole of the end cover. In the related art, the adapter is usually arranged on one side of the multi-layer tab of the battery cell during the processing process. The multi-layer tab is pressed on the adapter, and then the multi-layer tab and the adapter are welded to complete the assembly of the adapter and the multi-layer tab. As shown in Figure 1 , the multi-layer tab 142 is concentrated on one side of the battery cell body 141. The multi-layer tab 142 can be connected with the adapter 15 by welding (such as ultrasonic welding).

[0079] Since the height of each layer of tab is the same after die cutting, pressing the multi-layer tab during welding will cause the multi-layer tab to present a gradient increasing phenomenon from the upper layer to the lower layer, as shown in Figure 2 . In order to ensure that the welding mark can completely fall on each tab, the edge of the welding mark and the edge of the uppermost tab will be reserved a certain distance h in the direction of the tab protruding relative to the battery cell body. That is, the uppermost tab after bending needs to reserve enough welding area for welding to ensure the welding quality of the tab, which results in a higher height of the required tab, which is not conducive to reducing the cost of the battery cell foil and the internal resistance of the tab.

[0080] In order to overcome the above problems, the applicant has found that by pressing the two side tabs of the multi-layer tab towards the middle tab, and welding the tab on one side of the multi-layer tab with the adapter, the bending degree of the tab farthest from the adapter can be reduced, so that the tab farthest from the adapter has enough welding area after bending, while reducing the height of each layer of tab, especially the height of the tab farthest from the adapter, thereby reducing the cost of the battery cell foil and the internal resistance of the tab, and improving the performance of the battery cell.

[0081] Meanwhile, the applicant has also found that after the tab and the adapter are welded, the tab needs to be bent to bend the adapter on the top of the battery cell body, so as to facilitate the welding of the adapter and the pole on the end cover. Since in this process, the tab near the adapter needs to be bent in the opposite direction, the two bending directions of the tab near the adapter are opposite, which is easy to pull and tear the tab.

[0082] Therefore, the energy storage device provided in the embodiments of the present application can reduce the cost of the cell foil and the tab internal resistance, and avoid tearing and tearing the tab.

[0083] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present application.

[0084] Please refer to Figure 3 , Figure 3 The energy storage system provided in an embodiment of the present application is used as a structural schematic diagram of a household energy storage system, and the energy storage system provided in the present application Figure 3 The embodiments take a household energy storage scenario in user-side energy storage as an example for illustration, and the energy storage device provided in the present application is not limited to the household energy storage scenario.

[0085] As shown in Figure 3 , the energy storage system 1000 provided in the embodiments of the present application includes an energy storage device 100 and an electric energy conversion device 200 (a photovoltaic panel), a first user load 300 (a street lamp), and a second user load 400 (for example, a household appliance such as an air conditioner, etc.). The energy storage device 100 is a small energy storage box, which can be installed on an outdoor wall by a wall-hanging manner. Specifically, the photovoltaic panel can convert solar energy into electric energy during a low electricity price period, the energy storage device 100 is used to store the electric energy and supply the street lamp and the household appliance for use during a high electricity price period, or supply power during a power grid outage.

[0086] Please refer to Figure 4 , Figure 4 An exemplary structural schematic diagram of an energy storage system provided in another embodiment of the present application, and the energy storage system provided in the present application Figure 4 The embodiments take a distribution / transmission side shared energy storage scenario as an example for illustration, and the energy storage device 100 provided in the present application is not limited to the distribution / transmission side energy storage scenario.

[0087] As shown in Figure 4As shown, the energy storage system 1000 provided by the embodiment of the present application can include an energy storage device 100, a high-voltage cable 210, a first electric energy conversion device 310, and a second electric energy conversion device 410. In the power generation condition, the first electric energy conversion device 310 and the second electric energy conversion device 410 are used to convert other forms of energy into electric energy, and are connected with the high-voltage cable 210 and used by the power distribution network side. When the power consumption load is low, the first electric energy conversion device 310 and the second electric energy conversion device 410 generate excess power, and the excess power is stored in the energy storage device 100, thereby reducing the wind and light abandonment rate and improving the new energy power generation consumption problem. When the power consumption load is high, the power grid issues an instruction, and the energy storage device 100 stores the electric energy in cooperation with the high-voltage cable 210 to transmit electric energy in the grid-connected mode to supply the power consumption side, thereby providing peak shaving, frequency modulation, backup and other services for the power grid operation, fully playing the role of the power grid peak shaving, promoting the power grid peak shaving and valley filling, and relieving the power supply pressure of the power grid.

[0088] Optionally, the first electric energy conversion device 310 and the second electric energy conversion device 410 can convert at least one of solar energy, light energy, wind energy, heat energy, tidal energy, biomass energy, and mechanical energy into electric energy. In the present application, the number of energy storage devices 100 can be multiple, and multiple energy storage devices 100 are connected in series or parallel with each other, and multiple energy storage devices 100 are supported and electrically connected by an isolation plate (not shown). In the embodiment, "multiple" means two or more. The energy storage device 100 can also be provided with an energy storage box outside for accommodating the energy storage device 100.

[0089] Optionally, the energy storage device 100 can include but is not limited to a battery cell, a battery module, a battery pack, a battery system, etc. The actual application form of the energy storage device 100 provided by the embodiment of the present application can be but is not limited to the listed products, and can also be other application forms. The embodiment of the present application does not strictly limit the application form of the energy storage device 100.

[0090] The embodiment of the present application only takes the energy storage device 100 as an example of a battery cell.

[0091] Optionally, the energy storage device 100 can be a polygonal battery, a cylindrical battery, etc., which can be selected according to actual conditions and is not specifically limited in the embodiment. It can be seen that the energy storage device 100 in the present application is not limited to a battery of a certain specific shape, and the shape of the energy storage device 100 is various and flexible.

[0092] The polygonal battery includes a square battery, a pentagonal battery, a hexagonal battery, etc.

[0093] In order to more conveniently describe the energy storage device 100 provided by the embodiment of the present application, as an example but not limitation, the energy storage device 100 will be taken as a square battery in the following to describe the technical solution of the present application in detail.

[0094] Please refer to Figures 5 to 8 , Figure 5 The energy storage device in the present application is a square battery, Figure 6 is a schematic diagram of the exploded structure of the energy storage device in one embodiment, Figure 7 is a sectional view of the energy storage device in one embodiment along the N-N direction in Figure 5 , Figure 8 is a schematic diagram of the arrangement of two battery cells along their thickness direction.

[0095] As shown in Figures 5 to 8 , the energy storage device 100 provided by the embodiments of the present application includes a shell 11, an end cover assembly 12, a pole 13, a battery cell 14 and an adapter 15, wherein the shell 11 has an inner cavity 111 and an opening 112 communicating with the inner cavity 111, the end cover assembly 12 is sealingly arranged at the opening 112, and the end cover assembly 12 is provided with a through pole hole 12a, the pole 13 is arranged in the pole hole 12a, the battery cell 14 is arranged in the inner cavity 111, and the battery cell 14 has a length direction f1, a thickness direction f2 and a height direction f3.

[0096] In the present application, the battery cell 14 includes a battery cell body 141 and a plurality of layers of tabs 142 arranged on the battery cell body 141, the plurality of layers of tabs 142 are arranged at intervals along the thickness direction f2 of the battery cell 14, and the adapter 15 is electrically connected with the pole 13 and the plurality of layers of tabs 142 respectively, so as to realize the electrical connection between the battery cell 14 and the pole 13, so as to facilitate the output of the current stored in the battery cell 14 through the pole 13, or facilitate the introduction of the external current into the battery cell 14 through the pole 13 and store it in the battery cell 14.

[0097] Optionally, the shell 11 is a metal shell, such as an aluminum shell. Of course, the shell 11 can also be made of other materials. The end cover assembly 12 can at least include an end cover plate, and in other embodiments, the end cover assembly 12 can also include a lower plastic and / or an upper plastic.

[0098] Optionally, the battery cell 14 can be formed by a plurality of positive electrode plates, a plurality of separators and a plurality of negative electrode plates arranged in a stack, or can be formed by a positive electrode plate, a separator and a negative electrode plate through a winding process, which can be selected according to actual conditions, and is not limited in the present embodiment.

[0099] In some embodiments, the number of battery cells 14 can be multiple, such as two, three, four, five, six or more, and the plurality of battery cells 14 can be connected in parallel or in series.

[0100] It should be noted that Figure 6The purpose of the connection relationship between the shell 11 and the end cover assembly 12 is only to schematically describe the connection position, specific structure and quantity of each component, and does not constitute a specific limitation on the connection position, specific structure and quantity of each component. The structure schematically shown in the embodiments of the present application does not constitute a specific limitation on the energy storage device 100. In other embodiments of the present application, the energy storage device 100 includes more or fewer components than those shown, or combines some components, or splits some components, or different component arrangements. Figure 6 The components shown can be implemented in hardware, software or a combination of software and hardware. Figure 6 The components shown can be implemented in hardware, software or a combination of software and hardware.

[0101] As shown in Figure 6 , Figure 7 and Figure 8 , the pole hole 12a on the end cover assembly 12 can include a first pole hole 121a and a second pole hole 121b; the pole 13 can include a positive pole 131 and a negative pole 132, wherein the positive pole 131 is inserted into the first pole hole 121a, and the negative pole 132 is inserted into the second pole hole 121b; the cell 14 can include a first cell 14a and a second cell 14b, the first cell 14a includes a first cell body 14a1, a first positive tab 14a2 and a first negative tab 14a3 arranged on the first cell body 14a1, and the second cell 14b includes a second cell body 14b1, a second positive tab 14b2 and a second negative tab 14b3 arranged on the second cell body 14b1, the first cell body 14a1 and the second cell body 14b1 both include the aforementioned cell body 141, and the first positive tab 14a2, the first negative tab 14a3, the second positive tab 14b2 and the second negative tab 14b3 all include the aforementioned multi-layer tab 142; the adapter 15 can include a first adapter component 15a and a second adapter component 15b, the first adapter component 15a is electrically connected to the positive pole 131, the first positive tab 14a2 and the second positive tab 14b2 respectively, and the second adapter component 15b is electrically connected to the negative pole 132, the first negative tab 14a3 and the second negative tab 14b3 respectively, so that the current can be led out or led in through the positive pole 131 and the negative pole 132.

[0102] As shown in Figure 8 , the first cell 14a and the second cell 14b are arranged along the thickness direction f2 of the cell 14, along the thickness direction f2 of the cell 14, the first positive tab 14a2 is arranged opposite to the second positive tab 14b2, and the first negative tab 14a3 is arranged opposite to the second negative tab 14b3, and / or along the thickness direction f2 of the cell 14, the first positive tab 14a2 and the first negative tab 14a3 are located on the side of the first cell body 14a1 facing the second cell body 14b1, and the second positive tab 14b2 and the second negative tab 14b3 are located on the side of the second cell body 14b1 facing the first cell body 14a1.

[0103] It can be understood that, in the assembling process of the battery cell 14, as shown in Figure 9 , the first battery cell 14a and the second battery cell 14b are arranged along the height direction f3 of the battery cell 14, and as shown in Figure 10 , in the height direction f3 of the battery cell 14, the first negative tab 14a3 of the first battery cell 14a and the second negative tab 14b3 of the second battery cell 14b can be oppositely arranged, and the first positive tab 14a2 of the first battery cell 14a and the second positive tab 14b2 of the second battery cell 14b can be oppositely arranged, thereby facilitating the welding of the first adapter component 15a with the first positive tab 14a2 and the second positive tab 14b2, and facilitating the welding of the second adapter component 15b with the first negative tab 14a3 and the second negative tab 14b3, which is conducive to realizing the welding of the first adapter 15 with the first positive tab 14a2 and the second positive tab 14b2, quickly realizing the welding of the second adapter component 15b with the first negative tab 14a3 and the second negative tab 14b3, and saving welding time.

[0104] In addition, as shown in Figure 8 , since the first positive tab 14a2 of the first battery cell 14a and the second positive tab 14b2 of the second battery cell 14b are both located on the outside of the battery cell 14, and the first negative tab 14a3 of the first battery cell 14a and the second negative tab 14b3 of the second battery cell 14b are also both located on the outside of the battery cell 14, when the first battery cell 14a and the second battery cell 14b are arranged along the thickness direction f2 of the battery cell 14, the positions of the first positive tab 14a2 and the second positive tab 14b2 are far apart, and the positions of the first negative tab 14a3 and the second negative tab 14b3 are also far apart, which can avoid the situation that the first positive tab 14a2 and the second positive tab 14b2 are overlapped to cause short circuit, and the first negative tab 14a3 and the second negative tab 14b3 are overlapped to cause short circuit, and enable the first positive tab 14a2 and the second positive tab 14b2 to have a larger connection area with the first adapter component 15a, and enable the first negative tab 14a3 and the second negative tab 14b3 to have a larger connection area with the second adapter component 15b, thereby facilitating to improve the connection strength of the battery cell 14 and the adapter 15, and avoiding the problem of conductive failure caused by too low connection strength of the battery cell 14 and the adapter 15.

[0105] Please refer to Figure 11 and Figure 12The multi-layered tab 142 can include a middle tab 1421, a first side tab 1422 and a second side tab 1423, the first side tab 1422 and the second side tab 1423 are respectively located on two sides of the middle tab 1421 in the thickness direction f2 of the battery cell 14, and the first side tab 1422 and the second side tab 1423 are respectively bent towards the middle tab 1421. The adapter 15 has opposite first and second side surfaces 151 and 152, the first side surface 151 is electrically connected with the first side tab 1422, and the second side surface 152 is electrically connected with the pole 13.

[0106] In the above scheme, the first side tab 1422 and the second side tab 1423 on both sides of the middle tab 1421 are respectively bent and pressed towards the middle tab 1421, and then the first side surface 151 of the adapter 15 is attached and electrically connected with the first side tab 1422. Compared with the way of only bending and pressing the second side tab 1423 towards the first side tab 1422, the bending degree of the second side tab 1423 can be reduced, so that the second side tab 1423 has sufficient welding area after bending, while for example, the distance h between the edge of the welding mark and the edge of the second side tab 1423 in the direction of the tab 142 protruding from the battery cell body 141 is unchanged, the height of each layer of the tab 142, especially the height of the second side tab 1423, is reduced, thereby the cost of the battery cell foil can be reduced, and the internal resistance of the tab 142 is reduced, so that the performance of the battery cell can be improved.

[0107] Optionally, the number of the middle tab 1421, the first side tab 1422 and the second side tab 1423 can be the same or different, and the number of the middle tab 1421 can be one or more, the number of the first side tab 1422 can be one or more, and the number of the second side tab 1423 can be one or more.

[0108] In the present application, the multi-layered tab 142 can be bent from a first state to a second state, wherein the first state is configured as a state that the first side surface 151 is connected (e.g. welded) with the first side tab 1422, and the multi-layered tab 142 is not bent to set the first side surface 151 towards the battery cell body 141 (as shown in Figure 11 ), and the second state is configured as a state that the multi-layered tab 142 is bent to set the first side surface 151 towards the battery cell body 141 (as shown in Figure 12 ).

[0109] In the present application, each tab 142 has a root 142a connected with the battery cell body 141, and the first side tab 1422 has a connection site 1422a connected with the adapter 15, for example, a welding point where the first side tab 1422 is welded with the adapter 15.

[0110] To facilitate the determination of the distance L0 between the connecting position 1422a of the first side edge tab 1422 and the root 142a of the first side edge tab 1422 in the thickness direction f2 of the battery cell 14 after the first side edge tab 1422 is bent towards the middle tab 1421, the embodiment of the present application exemplarily takes the root 142a of the second side edge tab 1423 as the origin, the thickness direction f2 of the battery cell 14 as the x-axis, and the extension direction of the tab 142 as the y-axis to establish a rectangular coordinate system, so that the coordinates of the root 142a of any tab 142 are (x, 0), the coordinates of the root 142a of the first side edge tab 1422 are (A1, 0), x is between 0 and A1, i.e. 0≤x≤A1, in other words, x does not exceed half of the thickness of the battery cell body 141; when the plurality of tabs 142 are not bent to set the first side 151 towards the battery cell 14, i.e. when the plurality of tabs 142 are in the first state, the coordinates of the connecting position 1422a are (a, b), and when the plurality of tabs 142 are bent to set the first side 151 towards the battery cell 14, i.e. when the plurality of tabs 142 are in the second state, the coordinates of the connecting position 1422a are (c, d). Wherein, L0=A1-a. Figures 11 to 13

[0111] Wherein, when the plurality of tabs 142 are not bent to set the first side 151 towards the battery cell 14, the distance L1 between the connecting position 1422a and the root 142a of any tab 142 is ((a-x) 2 +b 2 ) 1 / 2 , and when the plurality of tabs 142 are bent to set the first side 151 towards the battery cell 14, the distance L2 between the connecting position 1422a and the root 142a of any tab 142 is ((c-x) 2 +d 2 ) 1 / 2 When L1>L2, the first side edge tab 1422 can be prevented from being excessively pulled when the plurality of tabs 142 are bent to set the first side 151 towards the battery cell 14, so as to prevent the first side edge tab 1422 from being excessively bent, and further prevent the first side edge tab 1422 from being pulled or torn when the plurality of tabs 142 need to be bent to set the first side 151 of the adapter 15 towards the battery cell 14, so as to ensure the conductive reliability of the tabs 142.

[0112] That is, the energy storage device 100 satisfies the following relationship: L1 2 -L2 2 =((a-x) 2 +b 2 )-((c-x) 2 +d 2 ​) > 0, wherein b, c, d, x can be obtained according to actual battery testing, the range of a can be calculated by calculating the above relationship, and thus the range of L0 can be determined, that is, the distance range of the connecting position 1422a of the first side edge tab 1422 and the root 142a thereof in the thickness direction f2 of the battery 14 can be determined after the first side edge tab 1422 is bent toward the middle tab 1421, so that the bending degree of the first side edge tab 1422 bent toward the middle tab 1421 can be determined, the first side edge tab 1422 is prevented from being excessively bent, and thus the first side edge tab 1422 is prevented from being pulled and torn when the multi-layer tabs 142 are bent to arrange the first side of the adapter 15 toward the battery, so as to ensure the conductive reliability of the tabs 142.

[0113] Since the battery 14 inevitably expands during charging and discharging, and the expansion rate of the battery 14 in the thickness direction f2 thereof is k, when the multi-layer tabs 142 are bent to arrange the first side toward the battery 14, and the battery 14 expands, the coordinates of the root 142a of any tab 142 are ((1+k)x, 0), and the distance L3 between the connecting position 1422a and the root 142a of any tab 142 is ((c-(1+k)x) 2 +d 2 ) 1 / 2 When L1 > L3, that is, when the energy storage device 100 satisfies the following relationship: L1 2 -L3 2 =((a-x) 2 +b 2 )-((c-(1+k)x) 2 +d 2 ) > 0, the first side edge tab 1422 is prevented from being excessively pulled when the battery 14 expands, and thus the first side edge tab 1422 is prevented from being pulled and torn when the battery 14 expands, so as to ensure the conductive reliability of the tabs 142.

[0114] As a first optional embodiment, as shown in Figure 14 , when neither the first side edge tab 1422 nor the second side edge tab 1423 is bent toward the middle tab 1421, and the first side edge tab 1422 is not connected to the first side, the height of each tab 142 protruding relative to the battery 14 is equal. Thus, the height of each tab 142 protruding relative to the battery 14 remains the same, and the tabs 142 do not need to be specially die-cut, so as to facilitate simplifying the die-cutting process of the tabs 142.

[0115] As a second optional embodiment, as shown in Figure 15As shown, when neither the first side tab 1422 nor the second side tab 1423 is bent toward the middle tab 1421, and the first side tab 1422 is not connected to the first side, the height of the first side tab 1422 protruding relative to the cell body 141 is greater than the height of the middle tab 1421 protruding relative to the cell body 141. After the first side tab 1422 and the second side tab 1423 are bent and pressed toward the middle tab 1421, that is, after the multi-layer tabs are pressed and connected, the ends of the middle tab 1421 and the first side tab 1422 away from the cell body 141 are flush. Compared with the method where the height of each tab 142 is equal, the height of the middle tab 1421 can be reduced, which is beneficial to reduce the cost of the cell foil and reduce the internal resistance of the tab, so that the cell performance can be improved.

[0116] As a third alternative implementation method, such as Figure 16 As shown, when neither the first side tab 1422 nor the second side tab 1423 is bent toward the middle tab 1421, and the first side tab 1422 is not connected to the first side, the height of the second side tab 1423 protruding relative to the cell body 141 is greater than the height of the middle tab 1421 protruding relative to the cell body 141. After the first side tab 1422 and the second side tab 1423 are bent and pressed toward the middle tab 1421, that is, after the multi-layer tabs are pressed and connected, the ends of the middle tab 1421 and the second side tab 1423 away from the cell 14 are flush. Compared with the method where the height of each tab 142 is equal, the height of the middle tab 1421 can be reduced, which is beneficial to reduce the cost of the cell foil and reduce the internal resistance of the tab 142, so that the cell performance can be improved.

[0117] As a fourth optional implementation method, such as Figure 17As shown, when the first side edge tab 1422 and the second side edge tab 1423 are not bent towards the middle tab 1421, and the first side edge tab 1422 is not connected to the first side surface, the height of the first side edge tab 1422 protruding from the battery cell body 141 is greater than the height of the middle tab 1421 protruding from the battery cell body 141, and the height of the second side edge tab 1423 protruding from the battery cell body 141 is greater than the height of the middle tab 1421 protruding from the battery cell body 141. After the first side edge tab 1422 and the second side edge tab 1423 are bent towards the middle tab 1421 and are pressed and connected, that is, after the multiple layers of tabs are pressed and connected, the ends of the middle tab 1421, the first side edge tab 1422, and the second side edge tab 1423 away from the battery cell body 141 are flush. Compared with the mode in which the height of each tab 142 is equal, at least the height of the middle tab 1421 can be reduced, thereby facilitating the reduction of the cost of the battery cell foil and the reduction of the internal resistance of the tab 142, so that the performance of the battery cell can be improved.

[0118] In some embodiments, when the first side edge tab 1422 and the second side edge tab 1423 are not bent towards the middle tab 1421, and the first side edge tab 1422 is not connected to the first side surface, the height of the tab 142 protruding from the battery cell body 141 first decreases and then increases along the thickness direction f2 of the battery cell 14, that is, in the direction in which the middle tab 1421 points to the first side edge tab 1422, the height of the tab 142 protruding from the battery cell body 141 gradually increases, and in the direction in which the middle tab 1421 points to the second side edge tab 1423, the height of the tab 142 protruding from the battery cell body 141 gradually increases. After the first side edge tab 1422 and the second side edge tab 1423 are bent towards the middle tab 1421 and are pressed and connected, that is, after the multiple layers of tabs are pressed and connected, the ends of the layers of tabs 142 away from the battery cell 14 are flush. Not only can the appearance and fixation of the tabs be improved, but also compared with the mode in which the height of each tab 142 is equal, the height of the tab 142 can be reduced, thereby facilitating the reduction of the cost of the battery cell foil and the reduction of the internal resistance of the tab 142, so that the performance of the battery cell can be improved.

[0119] In some embodiments, when the first side edge tab 1422 and the second side edge tab 1423 are not bent towards the middle tab 1421, and the first side edge tab 1422 is not connected to the first side surface, the distance between any two adjacent layers of tabs 142 is equal, so that the layers of tabs 142 are arranged at equal intervals, thereby facilitating the guarantee of the charging and discharging performance and the comprehensive performance of the battery cell 14.

[0120] In order to improve the flatness of the multi-layered tab 142 after pressing, in some embodiments, the height difference of any two adjacent layers of the tab 142 protruding relative to the battery body 141 is equal when the first side tab 1422 is not connected to the first side, that is, the height of the multi-layered tab 142 protruding relative to the battery body 141 is arranged in an arithmetic progression. In this way, the multi-layered tab 142 can be more flat after pressing, and the height of the multi-layered tab 142 protruding relative to the battery body 141 is arranged in an arithmetic progression, which can form a regular change, thus facilitating the die cutting of each layer of the tab 142 and realizing the accurate control of the height of each layer of the tab 142.

[0121] The technical features of the above embodiments can be combined in any manner. In order to make the description simple, all possible combinations of the technical features in the above embodiments are not described, but as long as the combinations of the technical features do not contradict, they should be considered as the scope of the present disclosure.

[0122] In addition, the above-described embodiments only express several implementation manners of the present application, and the description is more specific and detailed, but it should not be understood as a limitation on the scope of the patent of the present application. It should be pointed out that for ordinary skilled in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which are all within the protection scope of the present application. Therefore, the content of the present specification should not be understood as a limitation on the present application, and the protection scope of the present application should be subject to the appended claims.

Claims

1. An energy storage device, characterized by, The energy storage device comprises: a housing having an inner cavity and an opening communicating with the inner cavity; an end cover assembly sealingly arranged at the opening and provided with a through pole hole; a pole arranged in the pole hole; an electric core arranged in the inner cavity, the electric core comprising an electric core body and a plurality of layers of tabs arranged at the electric core body, the plurality of layers of tabs being arranged at intervals along a thickness direction of the electric core, and the plurality of layers of tabs comprising a middle tab, a first side tab and a second side tab, the first side tab and the second side tab being respectively located on two sides of the middle tab in the thickness direction of the electric core, and the first side tab and the second side tab being respectively bent towards the middle tab; and an adapter having opposite first and second sides, the first side being electrically connected to the first side tab, and the second side being electrically connected to the pole; the plurality of layers of tabs can be bent from a first state to a second state, wherein the first state is configured as a state in which the plurality of layers of tabs are not bent and the first side is arranged towards the electric core body, and the second state is configured as a state in which the plurality of layers of tabs are bent and the first side is arranged towards the electric core body; each of the tabs has a root connected to the electric core body, the first side tab has a connection site connected to the adapter, and taking the root of the second side tab as an origin, a thickness direction of the electric core as an x-axis, and an extension direction of the tab as a y-axis to establish a rectangular coordinate system, a coordinate of the root of any one of the tabs is (x, 0), a coordinate of the connection site is (a, b) when the plurality of layers of tabs are in the first state, and a coordinate of the connection site is (c, d) when the plurality of layers of tabs are in the second state; wherein ((a-x) 2 + b 2 )- ((c-x) 2 + d 2 ) > 0, b, c, d, x are obtained according to actual battery testing, and the range of a is calculated through the above relationship.

2. The energy storage device of claim 1, wherein, an expansion rate of the electric core in the thickness direction thereof is k, wherein the energy storage device satisfies the following relationship: ((a - x) 2 + b 2 )- ((c - (1 + k)x) 2 + d 2 ) > 0.

3. The energy storage device of claim 1, wherein, when neither the first side tab nor the second side tab is bent towards the middle tab, and the first side tab is not connected to the first side, a height of each of the tabs protruding relative to the electric core body is equal.

4. The energy storage device of claim 1, wherein, when neither the first side tab nor the second side tab is bent towards the middle tab, and the first side tab is not connected to the first side; a height of the first side tab protruding relative to the electric core body is greater than a height of the middle tab protruding relative to the electric core body, and / or a height of the second side tab protruding relative to the electric core body is greater than the height of the middle tab protruding relative to the electric core body.

5. The energy storage device of claim 4, wherein, when neither the first side tab nor the second side tab is bent towards the middle tab, and the first side tab is not connected to the first side, the height of the tab protruding relative to the electric core body first decreases and then increases along the thickness direction of the electric core.

6. The energy storage device of claim 5, wherein, In the case that neither of the first side edge tab and the second side edge tab is bent towards the middle tab, and the first side edge tab is not connected with the first side surface, the distance between any two adjacent layers of the tabs is equal.

7. The energy storage device of claim 5, wherein, In the case that neither of the first side edge tab and the second side edge tab is bent towards the middle tab, and the first side edge tab is not connected with the first side surface, the height difference of any two adjacent layers of the tabs protruding from the cell body is equal.

8. The energy storage device of any one of claims 1-7, wherein, The energy storage device is a polygonal battery or a cylindrical battery.

9. The energy storage device of any one of claims 1-7, wherein, The pole hole includes a first pole hole and a second pole hole. The pole includes a positive pole and a negative pole, the positive pole is arranged in the first pole hole, and the negative pole is arranged in the second pole hole. The cell includes a first cell and a second cell, the first cell includes a first cell body, a first positive tab and a first negative tab arranged on the first cell body, the second cell includes a second cell body, a second positive tab and a second negative tab arranged on the second cell body, the first cell body and the second cell body both include the cell body, and the first positive tab, the first negative tab, the second positive tab and the second negative tab all include the multi-layered tabs. The first cell and the second cell are arranged along the thickness direction of the cell, the first positive tab and the second positive tab are arranged oppositely along the thickness direction of the cell, the first negative tab and the second negative tab are arranged oppositely along the thickness direction of the cell, and / or the first positive tab and the first negative tab are located on the side of the first cell body away from the second cell body, and the second positive tab and the second negative tab are located on the side of the second cell body away from the first cell body along the thickness direction of the cell. The adapter includes a first adapter component and a second adapter component, the first adapter component is electrically connected with the positive pole, the first positive tab and the second positive tab respectively, and the second adapter component is electrically connected with the negative pole, the first negative tab and the second negative tab respectively.

10. An energy storage system characterized by, The energy storage system has the energy storage device as claimed in any one of claims 1-9.

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