Energy storage device and energy storage system

Abstract

Embodiments of the present application relate to the technical field of energy storage, and specifically disclose an energy storage device and an energy storage system, wherein the energy storage device comprises: a box body; a battery pack arranged in the box body, the battery pack having an expansion direction, and the battery pack being deformed by expansion along the expansion direction; an expansion constraint member arranged in the box body, the expansion constraint member being provided with a constraint groove, and the battery pack being embedded in the constraint groove; and a box cover covering the box body, and the box cover being connected with the expansion constraint member, the extension direction of the box cover being perpendicular to the expansion direction, and the box cover abutting against the battery pack. According to the present application, the expansion constraint member and the box cover are matched to jointly apply a pre-tightening force to the battery pack, which helps to improve the pre-tightening effect on the battery pack, efficiently controls the volume expansion of the battery pack during the charging and discharging process, and improves the cycle life of the battery pack.

Description

Technical Field

[0001] This application relates to the field of energy storage technology, and in particular to an energy storage device and energy storage system. Background Technology

[0002] With the rapid development of energy storage technology, batteries, as an important component of energy storage systems, are widely used in daily life and industrial production. However, the voltage of a single battery cell is too low to meet current usage requirements. Therefore, multiple single batteries are usually connected in series to form a battery pack, and then multiple battery packs are connected in series or in parallel to form an energy storage cabinet to meet usage requirements.

[0003] Individual battery cells undergo expansion during use, necessitating the application of pre-tightening force to their surfaces to suppress this expansion and extend cell life. Therefore, ensuring the effective pre-tightening of individual battery cells in energy storage devices is a pressing issue. Utility Model Content

[0004] The embodiments of this application provide an energy storage device and energy storage system, which helps to improve the pre-tightening effect of the battery pack, efficiently control the volume expansion of the battery pack during charging and discharging, and improve the cycle life of the battery pack.

[0005] To address the aforementioned technical problems, embodiments of this application disclose the following technical solutions:

[0006] On the one hand, an energy storage device is provided, including: a housing;

[0007] The battery pack is housed inside the casing. The battery pack has an expansion direction and expands and deforms along the expansion direction.

[0008] An expansion restraint component is installed inside the housing, and the expansion restraint component has a restraint groove, within which the battery pack is embedded; and

[0009] The cover seals the battery pack and is connected to the expansion restraint. The extension direction of the cover is perpendicular to the expansion direction, and the cover abuts against the battery pack.

[0010] In addition to one or more of the features disclosed above, or alternatively, the energy storage device has intersecting first and second directions;

[0011] The battery pack includes multiple individual cells, each of which includes two first outer wall surfaces disposed opposite each other in a first direction and two second outer wall surfaces disposed opposite each other in a second direction. The first and second outer wall surfaces are connected, and the first outer wall surface has a larger area than the second outer wall surface. The extension direction of the first outer wall surface is perpendicular to the expansion direction, and the cover abuts against the first outer wall surface.

[0012] In addition to one or more of the features disclosed above, or alternatively, the expansion constraint includes: a first constraint portion extending along a second direction; and

[0013] The second constraint part is provided in at least two, each of which extends along the first direction and is respectively connected to the two sides of the first constraint part that are disposed opposite to each other in the second direction. The first constraint part and the two second constraint parts together form a constraint groove with an opening.

[0014] The lid is connected to the side of the second restraint part near the opening, the first restraint part abuts against the first outer wall surface, and the second restraint part abuts against the second outer wall surface.

[0015] In addition to one or more of the features disclosed above, or alternatively, the energy storage device may also include: a converter disposed within the housing, wherein the converter and the battery pack are arranged sequentially in a second direction, and the converter and the battery pack are electrically connected.

[0016] In addition to one or more of the features disclosed above, or alternatively, the energy storage device also has a first reference plane perpendicular to the first direction;

[0017] Along the first direction, the projected area of ​​the battery pack on the first reference plane is S1 mm. 2 The orthographic projection area of ​​the converter on the first reference plane is S² mm. 2 The orthographic projection area of ​​the box on the first reference plane is S3 mm. 2 The orthographic projection area of ​​the box cover on the first reference plane is S4 mm. 2 The following conditions must be met: S1+S2<S3, and / or S1+S2≤S4.

[0018] In addition to one or more of the features disclosed above, or as an alternative, the converter and housing are integrally formed; or,

[0019] The converter and the enclosure are separate units, and the converter and the enclosure are fixedly connected.

[0020] In addition to one or more of the features disclosed above, or alternatively, the energy storage device also has a third direction, wherein the first direction, the second direction, and the third direction intersect each other;

[0021] The energy storage device also includes an electrical connector, installed on the third-facing side of the enclosure, and electrically connected to the battery pack.

[0022] In addition to one or more of the features disclosed above, or alternatively, the energy storage device also has a second reference plane perpendicular to a third direction;

[0023] Along the third direction, the orthographic projection of the electrical connector on the second reference plane does not coincide with the orthographic projection of the converter on the second reference plane.

[0024] In addition to one or more of the features disclosed above, or alternatively, the energy storage device also has a second reference plane perpendicular to a third direction;

[0025] Along the third direction, the orthographic projection of the electrical connector on the second reference plane at least partially coincides with the orthographic projection of the converter on the second reference plane.

[0026] On the other hand, a further energy storage system is disclosed, which, in addition to one or more of the features disclosed above, or alternatively, includes an energy storage device and an inverter as described in any of the preceding claims, wherein the inverter is electrically connected to the energy storage device.

[0027] One of the above technical solutions has the following advantages or beneficial effects: This application uses an expansion constraint to accommodate the battery pack, and sets the extension direction of the cover perpendicular to the expansion direction and abuts the cover against the battery pack. The expansion constraint and the cover work together to apply a pre-tightening force to the battery pack, which helps improve the pre-tightening effect and efficiently controls the volume expansion of the battery pack during charging and discharging, thus improving the cycle life of the battery pack. Simultaneously, this application eliminates the need for other components, reducing the number of components in the energy storage device, resulting in a high degree of integration in the overall design of the energy storage device, improving the assembly efficiency of the energy storage device, and consequently increasing the production efficiency and reducing production costs. Furthermore, the expansion constraint can also protect the battery pack, preventing damage under vibration or impact conditions, ensuring the normal use of the battery pack, and improving the safety performance of the energy storage device. Attached Figure Description

[0028] The technical solution and other beneficial effects of this application will become apparent from the following detailed description of specific embodiments in conjunction with the accompanying drawings.

[0029] Figure 1 This is a three-dimensional structural view of the energy storage device provided according to the embodiments of this application;

[0030] Figure 2 This is an exploded structural diagram of an energy storage device provided according to an embodiment of this application;

[0031] Figure 3 This is an exploded structural diagram of the energy storage device provided according to an embodiment of this application.

[0032] Explanation of reference numerals in the attached figures:

[0033] 100, Energy storage device; 110, Housing; 120, Battery pack; 121, Individual battery cell; 1211, First outer wall surface; 1212, Second outer wall surface; 130, Expansion restraint; 131, First restraint part; 132, Second restraint part; 133, Restraint groove; 134, Opening; 140, Housing cover; 150, Converter; 160, Electrical connector. Detailed Implementation

[0034] To make the objectives, technical solutions, and beneficial effects of this application clearer, the following detailed description, in conjunction with the accompanying drawings and specific embodiments, further illustrates this application. It should be understood that the specific embodiments described in this specification are merely for explaining this application and are not intended to limit it.

[0035] In the description of this application, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of the stated features. In the description of this application, "a plurality of" means two or more, unless otherwise explicitly specified.

[0036] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection, a direct connection, or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0037] In this application, unless otherwise expressly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0038] In existing energy storage devices, pre-tightening force is applied to the battery by setting end plates on the large surface of the battery and then using steel strips or other structures to fix it. Although the pre-tightening effect of this structure is good, it has too many parts, complicated assembly, and high cost.

[0039] In the embodiments of this application, reference is made to Figures 1 to 2 This application also provides an energy storage device 100 to overcome at least one of the above-mentioned technical problems.

[0040] The energy storage device 100 has a first direction X, a second direction Y, and a third direction Z that intersect each other in pairs. For example, the energy storage device 100 also has a first direction X, a second direction Y, and a third direction Z that are perpendicular to each other in pairs. Here, "perpendicular" refers to a state where the angle formed by two lines, a line and a surface, or a surface is 89° to 91°.

[0041] Specifically, refer to Figures 1 to 3 The energy storage device 100 includes: a housing 110, a battery pack 120, an expansion restraint 130, and a housing cover 140.

[0042] Specifically, the battery pack 120 is disposed inside the housing 110, and the battery pack 120 has an expansion direction Q, and the battery pack 120 expands and deforms along the expansion direction Q; the expansion constraint member 130 is disposed inside the housing 110, and the expansion constraint member 130 has a constraint groove 133, in which the battery pack 120 is embedded; the housing cover 140 covers the housing 110, and the housing cover 140 is connected to the expansion constraint member 130, the extension direction of the housing cover 140 is perpendicular to the expansion direction Q, and the housing cover 140 abuts against the battery pack 120.

[0043] The enclosure 110 may be made of ordinary steel or aluminum, but is not limited to these materials.

[0044] The lid 140 may be made of metal, but is not limited to that.

[0045] The housing 110 and the cover 140 can be integrally formed, that is, the housing 110 and the cover 140 are an integral structure; the cover 140 can also be separately set, and the housing 110 and the cover 140 are fixed by welding or screwing to ensure the overall sealing performance of the energy storage device 100.

[0046] The expansion constraint 130 may be made of plastic injection molding, but is not limited to this.

[0047] Understandably, in this application, the battery pack 120 is first pre-assembled in the constraint groove 133 of the expansion constraint member 130, and then the cover 140 is connected to one end of the expansion constraint member 130 with an opening 134 so that the cover 140 abuts against the battery pack 120 so that the cover 140 and the expansion constraint member 130 cooperate to apply a pre-tightening force to the battery pack 120. Then, the assembly of the battery pack 120, the expansion constraint member 130 and the cover 140 is assembled into the housing 110, and the cover 140 is connected to the housing 110 to seal the housing 110, thus completing the assembly of the energy storage device 100.

[0048] This application incorporates an expansion constraint 130 to house the battery pack 120. A cover 140 extends perpendicularly to the expansion direction Q and abuts against the battery pack 120. The expansion constraint 130 and cover 140 work together to apply a pre-tightening force to the battery pack 120, improving the pre-tightening effect and efficiently controlling the volume expansion of the battery pack 120 during charging and discharging, thus extending its cycle life. Furthermore, this application eliminates the need for other components, reducing the number of parts in the energy storage device 100 and resulting in a high degree of integration. This improves assembly efficiency, thereby increasing production efficiency and reducing costs. Additionally, the expansion constraint 130 protects the battery pack 120 from damage during vibration or impact, ensuring its normal operation and enhancing the safety performance of the energy storage device 100.

[0049] In some embodiments, refer to Figures 2 to 3 The battery pack 120 includes a plurality of individual cells 121. Specifically, the plurality of individual cells 121 can be arranged sequentially along a first direction X to form the battery pack 120, and the plurality of individual cells 121 can also be arranged sequentially along a second direction Y to form the battery pack 120.

[0050] The single cell 121 can be a rechargeable battery, which refers to a single cell that can be recharged after discharge to activate the active materials and continue to be used. For example, the single cell 121 can be a lithium-ion battery, sodium-ion battery, sodium-lithium-ion battery, lithium metal battery, sodium metal battery, lithium-sulfur battery, magnesium-ion battery, nickel-metal hydride battery, or nickel-cadmium battery, but is not limited to these.

[0051] The single cell 121 can be a cylindrical cell, a prismatic cell, a pouch cell, or a cell of other shapes. For example, in this application, the single cell 121 is a square lithium-ion cell.

[0052] The single-cell battery 121 may include a casing, electrode assembly, electrolyte, end caps, terminals, and other functional components. The electrolyte can be a conventional electrolyte or a special electrolyte with additives, used to wet the electrode assembly. The electrode assembly is the component in the single-cell battery 121 where electrochemical reactions occur, and there may be one or more electrode assemblies. The electrode assembly is mainly formed by stacking or winding a positive electrode, a separator, and a negative electrode. The portions of the positive and negative electrode with active material constitute the electrode body, while the portions without active material each constitute a tab. During the charging and discharging process of the single-cell battery 121, the positive and negative active materials react with the electrolyte, and the tabs and terminals are electrically connected to form a current loop, enabling the single-cell battery 121 to function normally.

[0053] Specifically, refer to Figures 2 to 3 Each individual battery cell 121 includes two first outer wall surfaces 1211 disposed opposite to each other in the first direction X, and two second outer wall surfaces 1212 disposed opposite to each other in the second direction Y. The first outer wall surfaces 1211 and the second outer wall surfaces 1212 are connected, and the first outer wall surface 1211 has a larger area than the second outer wall surface 1212. The extension direction of the first outer wall surface 1211 is perpendicular to the expansion direction Q. The cover 140 abuts against the first outer wall surface 1211.

[0054] Understandably, during the charge-discharge cycle of the single cell 121, lithium ions are embedded in the layered material, which increases the thickness of the negative electrode. At the same time, gas is generated during the formation process of the single cell 121, causing the single cell 121 to expand and increase in volume.

[0055] When the single cell 121 expands during use, the first outer wall surface 1211 of the single cell 121 expands along the expansion direction Q to apply a compressive force to the expansion constraint member 130 and the cover 140. This causes the expansion constraint member 130 and the cover 140 to exert a force on the single cell 121, thereby controlling the volume expansion of the single cell 121 during charging and discharging. This reduces the shedding of electrode active materials during the cycle of the single cell 121, constrains the displacement of the electrode and separator during charging and discharging, prevents the internal structure of the single cell 121 from loosening, maintains tight contact between the electrode and separator, and improves the cycle life of the single cell 121. At the same time, it prevents the generation of excess space inside the single cell 121, so that the single cell 121 does not shake, increasing the reliability and safety of the single cell 121.

[0056] In some embodiments, refer to Figure 3 The expansion constraint 130 includes a first constraint part 131 and a second constraint part 132.

[0057] Specifically, the first constraint part 131 extends along the second direction Y; at least two second constraint parts 132 are provided, each of the second constraint parts 132 extends along the first direction X, and each of the second constraint parts 132 is respectively connected to the two sides of the first constraint part 131 that are opposite to each other in the second direction Y. The first constraint part 131 and the two second constraint parts 132 enclose a constraint groove 133 with an opening 134; the box cover 140 is connected to the side of the second constraint part 132 near the opening 134, the first constraint part 131 abuts against the first outer wall surface 1211, and the second constraint part 132 abuts against the second outer wall surface 1212.

[0058] The first constraint part 131 and the second constraint part 132 can be integrally formed, meaning they are a single, integrated structure. Alternatively, the first constraint part 131 and the second constraint part 132 can be separately configured and fixedly connected. For example, the second constraint part 132 is fixedly connected to the first constraint part 131 by processes such as bonding, snap-fitting, riveting, or screwing. This application does not impose specific limitations and can be configured according to actual circumstances. For example, the first constraint part 131 and the second constraint part 132 are integrally injection molded, but this is not a limitation.

[0059] Understandably, when the single cell 121 expands during use, the first outer wall surface 1211 of the single cell 121 expands to exert pressure on the first constraint part 131 and the cover 140, and the second outer wall surface 1212 of the single cell 121 expands to exert pressure on the second constraint part 132. This causes the first constraint part 131, the second constraint part 132, and the cover 140 to exert forces on the single cell 121, thereby controlling the volume expansion of the single cell 121 during charging and discharging, reducing the shedding of electrode active materials during the cycle of the single cell 121, constraining the displacement of the electrode and separator during the charging and discharging of the single cell 121, preventing the internal structure of the single cell 121 from loosening, maintaining tight contact between the electrode and the separator, and improving the cycle life of the single cell 121.

[0060] In some embodiments, the maximum dimension of the battery pack 120 in the first direction X is greater than the maximum dimension of the second constraint portion 132 in the first direction X, so that when the battery pack 120 is assembled in the constraint groove 133, some individual battery cells 121 are located outside the constraint groove 133, thereby facilitating the contact between the cover 140 and the first outer wall surface 1211, so that the cover 140 and the expansion constraint member 130 cooperate to provide pre-tightening force to the individual battery cells 121.

[0061] In some embodiments, refer to Figure 2 The energy storage device 100 also includes a converter 150, which is disposed inside the housing 110 and electrically connected to the battery pack 120. The converter 150 is used to realize bidirectional and efficient energy conversion of the battery pack 120. The converter 150 and the battery pack 120 are arranged sequentially in the second direction Y, that is, the converter 150 and the battery pack 120 are completely staggered in the second direction Y, so as to facilitate the modular design of the energy storage device 100, making the assembly and maintenance process of the energy storage device 100 more efficient and improving the production efficiency of the energy storage device 100.

[0062] The converter 150 can be a DC / DC converter, but is not limited to this.

[0063] In some embodiments, refer to Figure 2 The energy storage device 100 also has a first reference plane P perpendicular to the first direction X.

[0064] Specifically, along the first direction X, the orthographic projection area of ​​the battery pack 120 on the first reference plane P is S1 mm. 2 The orthographic projection area of ​​converter 150 on the first reference plane P is S2 mm. 2 The orthographic projection area of ​​the box 110 on the first reference plane P is S3 mm. 2The condition is satisfied that S1 + S2 < S3, meaning the orthogonal projected area of ​​battery pack 120 on the first reference plane P is S1 mm. 2 The orthogonal projected area of ​​converter 150 on the first reference plane P is S2 mm. 2 The sum is less than the orthographic projection area S3 mm of the box 110 on the first reference plane P. 2 This allows for a more modular design of the energy storage device 100, resulting in more efficient assembly and maintenance processes and improved production efficiency.

[0065] Among them, the orthogonal projection area of ​​the battery pack 120 on the first reference plane P is S1 mm. 2 The actual energy storage device 100 can be disassembled, and the image area of ​​the battery pack 120 along the first direction X can be measured multiple times using a projection measurement device (such as a digital microscope or image measuring instrument) to obtain the orthogonal projection area S1 mm of the battery pack 120 on the first reference plane P. 2 However, it is not limited to this.

[0066] The orthogonal projected area of ​​converter 150 on the first reference plane P is S2 mm. 2 The measurement method, the orthographic projection area S3 mm of the box 110 on the first reference plane P. 2 The measurement method and the orthographic projection area S1 mm of the battery pack 120 on the first reference plane P 2 The measurement method is the same, and will not be elaborated here. Please refer to the description above.

[0067] In some embodiments, refer to Figure 2 Along the first direction X, the orthographic projection area of ​​the battery pack 120 on the first reference plane P is S1 mm. 2 The orthographic projection area of ​​converter 150 on the first reference plane P is S2mm. 2 The orthographic projection area of ​​the box cover 140 on the first reference plane P is S4 mm. 2 The following condition is satisfied: S1 + S2 ≤ S4, that is, the orthogonal projection area of ​​battery pack 120 on the first reference plane P is S1 mm. 2 The orthogonal projected area of ​​converter 150 on the first reference plane P is S2 mm. 2 The sum of these values ​​is not greater than the orthographic projection area S4 mm of the box cover 140 on the first reference plane P. 2 This allows for a more modular design of the energy storage device 100, resulting in more efficient assembly and maintenance processes and improved production efficiency.

[0068] The orthographic projection area of ​​the cover 140 on the first reference plane P is S4 mm. 2The measurement method and the orthographic projection area S1 mm of the battery pack 120 on the first reference plane P 2 The measurement method is the same, and will not be elaborated here. Please refer to the description above.

[0069] In some embodiments, the converter 150 and the housing 110 are integrally formed to facilitate processing, reduce processing steps, and improve the overall processing efficiency of the energy storage device 100.

[0070] In other embodiments, the converter 150 and the housing 110 are separately arranged, and the converter 150 and the housing 110 are fixedly connected to facilitate the assembly between the converter 150 and the housing 110, thereby improving the overall assembly efficiency of the energy storage device 100.

[0071] In some embodiments, refer to Figures 2 to 3 The energy storage device 100 also includes an electrical connector 160, which is installed on one side of the housing 110 in the third direction Z and is electrically connected to the battery pack 120. The electrical connector 160 is used to connect the energy storage device 100 to external electrical components or to realize the electrical connection between two energy storage devices 100.

[0072] The electrical connector 160 can be either an air-plug port or a hot-plug port, but is not limited to either.

[0073] In some embodiments, the energy storage device 100 further has a second reference plane O perpendicular to the third direction Z.

[0074] Specifically, along the third direction Z, the orthographic projection of the electrical connector 160 on the second reference plane O does not coincide with the orthographic projection of the converter 150 on the second reference plane O. That is, the electrical connector 160 and the converter 150 are completely misaligned. This further enables the modular design of the energy storage device 100, making the assembly and maintenance processes of the energy storage device 100 more efficient and improving the production efficiency of the energy storage device 100.

[0075] In other embodiments, along the third direction Z, the orthographic projection of the electrical connector 160 on the second reference plane O at least partially coincides with the orthographic projection of the converter 150 on the second reference plane O, that is, the orthographic projection of the electrical connector 160 on the second reference plane O and the orthographic projection of the converter 150 on the second reference plane O can partially coincide, and the electrical connector 160 and the converter 150 are partially misaligned; the orthographic projection of the electrical connector 160 on the second reference plane O and the orthographic projection of the converter 150 on the second reference plane O can also completely coincide.

[0076] This application further modularizes the energy storage device 100 by limiting the orthographic projection of the electrical connector 160 on the second reference plane O to at least partially overlap with the orthographic projection of the converter 150 on the second reference plane O, thereby making the assembly and maintenance processes of the energy storage device 100 more efficient and improving the production efficiency of the energy storage device 100.

[0077] In the embodiments of this application, this application also provides an energy storage system, including: an energy storage device 100 as described in any of the above embodiments and an inverter, wherein the inverter is electrically connected to the energy storage device 100, and the inverter is used to convert the DC power output by the energy storage device 100 into AC power for output to an external load or the power grid, and / or, the inverter is used to convert the AC power output by the power grid into DC power for output to the energy storage device 100.

[0078] The above steps are provided only to help understand the method, structure, and core ideas of this application. Those skilled in the art can make various improvements and modifications to this application without departing from its principles, and these improvements and modifications also fall within the scope of protection of the claims.

Claims

1. An energy storage device, characterized in that, include: Box; A battery pack is disposed inside the housing, the battery pack has an expansion direction, and the battery pack expands and deforms along the expansion direction; An expansion constraint member is disposed within the housing, the expansion constraint member having a constraint groove, and the battery pack is embedded within the constraint groove; and A lid covers the housing and is connected to the expansion constraint. The extension direction of the lid is perpendicular to the expansion direction, and the lid abuts against the battery pack.

2. The energy storage device as described in claim 1, characterized in that, The energy storage device has intersecting first and second directions; The battery pack includes multiple individual cells, each of which includes two first outer wall surfaces disposed opposite to each other in the first direction and two second outer wall surfaces disposed opposite to each other in the second direction. The first outer wall surfaces and the second outer wall surfaces are connected, and the first outer wall surface has a larger area than the second outer wall surface. The extension direction of the first outer wall surface is perpendicular to the expansion direction, and the cover abuts against the first outer wall surface.

3. The energy storage device as described in claim 2, characterized in that, The expansion constraint member includes: a first constraint portion extending along the second direction; and... The second constraint part is provided in at least two, each of the second constraint parts extending along the first direction, and each of the second constraint parts is respectively connected to the two sides of the first constraint part that are disposed opposite to each other in the second direction. The first constraint part and the two second constraint parts together form the constraint groove with an opening. The lid is connected to the side of the second constraint part near the opening, the first constraint part abuts against the first outer wall surface, and the second constraint part abuts against the second outer wall surface.

4. The energy storage device as described in claim 2, characterized in that, The energy storage device further includes: a converter, which is disposed in the housing, and the converter and the battery pack are arranged sequentially in the second direction, and the converter is electrically connected to the battery pack.

5. The energy storage device as described in claim 4, characterized in that, The energy storage device also has a first reference plane perpendicular to the first direction; Along the first direction, the projected area of ​​the battery pack on the first reference plane is S1mm. 2 The orthographic projection area of ​​the converter on the first reference plane is S² mm. 2 The orthographic projection area of ​​the box body on the first reference plane is S3 mm. 2 The orthographic projection area of ​​the box cover on the first reference plane is S4 mm. 2 The following conditions must be met: S1+S2<S3, and / or S1+S2≤S4.

6. The energy storage device as described in claim 4, characterized in that, The converter is integrally formed with the housing; or... The converter and the housing are separate components, and the converter and the housing are fixedly connected.

7. The energy storage device as described in claim 4, characterized in that, The energy storage device also has a third direction, wherein the first direction, the second direction, and the third direction intersect each other in pairs; The energy storage device further includes an electrical connector, which is installed on the third-party upward side of the housing, and the electrical connector is electrically connected to the battery pack.

8. The energy storage device as described in claim 7, characterized in that, The energy storage device also has a second reference plane perpendicular to the third direction; Along the third direction, the orthographic projection of the electrical connector on the second reference plane does not coincide with the orthographic projection of the converter on the second reference plane.

9. The energy storage device as described in claim 7, characterized in that, The energy storage device also has a second reference plane perpendicular to the third direction; Along the third direction, the orthographic projection of the electrical connector on the second reference plane at least partially coincides with the orthographic projection of the converter on the second reference plane.

10. An energy storage system, characterized in that, include: The energy storage device and inverter as described in any one of claims 1 to 9, wherein the inverter is electrically connected to the energy storage device.

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