CN116799390A - Lower plastic, end cover assembly, energy storage device and energy storage system - Google Patents

Abstract

The application provides a lower plastic, an end cover assembly, an energy storage device and an energy storage system. The lower plastic is adapted to be connected to an end cap of the end cap assembly. The lower plastic comprises a first lower plastic body and a second lower plastic body. The second lower plastic body comprises a body part and a buffer structure positioned on one side of the body part close to the first lower plastic body; the buffer structure is protruding to the direction of keeping away from the end cover relative body portion, and the one end that buffer structure kept away from body portion is located one side that the plastic body deviates from the end cover under, and along the relative first plastic body movable of the length direction of plastic down, buffer structure and the explosion-proof valve of end cover subassembly are relative and the interval setting. When the energy storage device is impacted by external force, the buffer structure can deform after being impacted by the electrode assembly, and the impact force of the electrode assembly can be absorbed through deformation, so that the second lower plastic body is prevented from being broken, the electrode assembly is prevented from directly impacting the explosion-proof valve, the explosion-proof valve is prevented from being triggered by mistake, and the safety, the stability and the service life of the energy storage device are improved.

Description

Lower plastic, end cover assembly, energy storage device and energy storage system

Technical Field

The application relates to the technical field of energy storage, in particular to a lower plastic, an end cover assembly, an energy storage device and an energy storage system.

Background

When the existing energy storage device is impacted by external force (such as unexpected falling or violent shaking), the electrode assembly impacts the lower plastic under the action of inertia, the existing lower plastic is easy to break under the impact of the electrode assembly, the electrode assembly is easy to impact the explosion-proof valve after the lower plastic breaks, and the explosion-proof valve is triggered by mistake.

Disclosure of Invention

The embodiment of the application provides lower plastic, an end cover assembly, an energy storage device and an energy storage system, which are used for solving the problem that the existing lower plastic is easy to break under the impact of an electrode assembly.

In a first aspect, the present application provides a lower plastic adapted to be connected to an end cap of an end cap assembly. The lower plastic comprises a first lower plastic body and a second lower plastic body. The second lower plastic body comprises a body part and a buffer structure which is positioned on one side of the body part close to the first lower plastic body and connected with the body part; the body portion has the body surface that deviates from the end cover, buffer structure for the body portion the body surface orientation is kept away from the direction of end cover is protruding, buffer structure deviates from the one end of body portion is located first plastic body deviates from one side of end cover, and follows plastic length direction is relative first plastic body is movable down, buffer structure with the explosion-proof valve of end cover subassembly is relative and the interval sets up.

According to the application, the buffer structure is formed by protruding outwards from the body part towards the direction away from the end cover based on the buffer structure arranged on one side of the body part close to the first lower plastic body, one end of the buffer structure away from the body part is positioned on one side of the first lower plastic body away from the end cover, which is movable relative to the first lower plastic body along the length direction of the lower plastic body, when the energy storage device is impacted by external force (such as accidental falling or violent shaking), the electrode assembly is extruded towards the end cover, the buffer structure can deform after being impacted by the electrode assembly upwards, the length dimension of the buffer structure along the length direction of the lower plastic body is increased, at the moment, the free end of the buffer structure away from the body part, which is overlapped with the first lower plastic body, on one side of the buffer structure away from the end cover can move towards the direction away from the body part, the buffer structure can absorb the impact force of the electrode assembly through deformation, so that the impact force of the second lower plastic body can be prevented from being broken due to the fact that the impact force of the upper pressure can not be released, and the buffer structure and the explosion-proof valve is arranged at intervals, the safety, stability and service life of the energy storage device can be prevented from being triggered by mistake.

With reference to the first aspect, in certain implementation manners of the first aspect, the buffer structure includes a buffer portion and an extension portion, the buffer portion is connected to the body portion, the buffer portion is arranged in an arch-shaped protruding manner towards a direction away from the end cover, and the extension portion extends from an end of the buffer portion away from the body portion along a length direction of the lower plastic body, and is overlapped on a side of the first lower plastic body away from the end cover. The buffer portion is configured as an arch shape to better exert an elastic buffer effect. The buffer part can elastically deform under the impact of the electrode assembly, the bending degree of the buffer part is reduced, so that the impact force of the electrode assembly is absorbed, when the impact of the electrode assembly to the buffer part disappears, the buffer part rebounds under the elastic recovery effect, and the bending degree of the buffer part is increased, so that the buffer part buffers the next impact of the electrode assembly. The existing flat split lower plastic is a thin plate plastic part, and after the lower plastic is used for a long time, the lower plastic is influenced by gravity of the lower plastic and by gas production and electrolyte in the energy storage device, so that the problem that valve opening accuracy and stability of the explosion-proof valve are negatively influenced due to the fact that tab fragments fall to the explosion-proof valve is caused, the arc-shaped buffer part can be decomposed and reduced along an arc-shaped surface due to gravity of the buffer part, and the first lower plastic body and the second lower plastic body can be overlapped and closely attached to the back of the end cover for a long time, so that the tab fragments are prevented from drifting to the position of the explosion-proof valve, the valve opening stability and reliability of the explosion-proof valve are ensured, and the service life of the energy storage device is prolonged.

With reference to the first aspect, in certain implementation manners of the first aspect, a side of the first molding compound facing away from the end cover is provided with a sliding guide groove, and the extension portion is in sliding fit with the sliding guide groove. The sliding direction of extension portion can be guided to the guide chute, makes extension portion can slide relatively first plastic body relatively better, is favorable to improving buffer structure's stability when taking place the deformation, makes buffer structure can effectually exert the cushioning effect.

With reference to the first aspect, in certain implementation manners of the first aspect, a buffer space is formed on a side, facing the end cover, of the buffer portion, and a plurality of first openings communicating with the buffer space are formed on the buffer portion. When the gas pressure in the energy storage device is overlarge, the gas can conveniently pass through the first opening and reach the position of the explosion-proof valve, so that the explosion-proof valve is opened, the energy storage device is prevented from explosion, and the safety and the reliability of the energy storage device are improved.

With reference to the first aspect, in certain implementation manners of the first aspect, in a width direction of the lower plastic, a flow area of the first openings near a middle position of the lower plastic is larger than a flow area of the first openings near two sides of the lower plastic. In the use process of the energy storage device, along the width direction of the lower plastic, the electrode plate and electrolyte at the middle position of the electrode assembly are relatively high in temperature due to relatively poor heat dissipation, electrochemical reaction at the middle position is relatively active, the corresponding generated gas amount is relatively large, and conversely, the heat dissipation effect at the two side positions is good, the temperature is relatively low, the electrochemical reaction is relatively weak, and the gas production amount is relatively low. When the energy storage device expands accidentally, the gas production amount of the middle position of the electrode assembly is larger than that of the two side positions. According to the application, the flow area of the first opening close to the middle position of the lower plastic is larger than that of the first openings close to the two sides of the lower plastic, so that gas in the middle position of the electrode assembly can be more effectively gathered to the position of the explosion-proof valve through the first opening, the valve opening performance of the explosion-proof valve is improved, and the safety of the energy storage device is improved. In addition, the first open pore that is located the position that is close to lower plastic both sides department is closer to electrode assembly's edge position, first open pore that is close to both sides department and the first open pore interval setting that is close to intermediate position department, on the one hand, can strengthen the whole framework intensity of buffer, guarantee structural stability, on the other hand, there is the clearance in the position between core and the core in the electrode assembly, and the winding degree in the core outside is comparatively loose, the position between core and the core produces gas more easily, there is the clearance between core and the casing, also produce gas here easily, and the middle part position of core winds closely, be difficult to produce gas, the gas is mainly in electrode assembly's central point position and both sides position, through the intermediate position and both sides position that set up the interval setting respectively of plastic under the buffer, both sides position has enough structural strength in guaranteed, the gas that produces in the energy memory can be fast and effectual gathering to the position of explosion-proof valve again, the security and quick valve opening ability of improvement energy memory.

With reference to the first aspect, in certain implementation manners of the first aspect, a ratio of a first length of the first opening along a length direction of the lower plastic to a first width of the lower plastic is in a range of 1.2-3, so that the buffer portion has a better elastic deformation capability to effectively absorb an impact force of the electrode assembly, and has a better elastic recovery capability, so that the buffer portion can be better recovered. When the ratio of the first length to the first width is smaller than 1.2, the strength of the buffer portion corresponding to the position of the first opening is lower, and when the buffer portion is impacted by the electrode assembly, the deformation degree of the buffer portion is overlarge at the position of the first opening compared with other positions, and the buffer portion is easy to generate plastic deformation due to stress concentration, so that the buffer portion is difficult to restore by itself after the impact of the electrode assembly is eliminated. When the ratio of the first length to the first width is greater than 3, the ability of the buffer portion to resist deformation is too small, and the buffer portion cannot effectively absorb and absorb impact force of the buffer electrode assembly.

With reference to the first aspect, in certain implementation manners of the first aspect, the buffer structure further includes a fence structure disposed on a side of the buffer portion facing away from the end cover, and a plurality of second openings are disposed on the fence structure, at least a portion of the second openings are communicated with the first openings, and a flow area of the first openings is greater than a flow area of the second openings. When the gas pressure inside the energy storage device is too high, the gas can flow into the first opening or the buffer space through the second opening, so that the position of the explosion-proof valve is reached. The fence structure can stop objects such as an insulating film, a tab and the like in the energy storage device, and the situation that foreign matters such as the insulating film, the tab and the like reach the explosion-proof valve to influence the opening of the explosion-proof valve is avoided.

With reference to the first aspect, in certain implementations of the first aspect, a surface of a side of the barrier structure facing away from the end cover is a plane. When the electrode assembly impacts the buffer structure, the fence structure can enable the stress of the buffer part to be more uniform, local overlarge stress on the buffer part is avoided, and the electrode assembly is prevented from being damaged when pressed against the fence structure due to the fact that the energy storage device is rocked and falls down, and the electrode assembly is extruded towards the direction of the end cover.

With reference to the first aspect, in certain implementation manners of the first aspect, a ratio of the second length of the buffer portion along the length direction of the lower plastic to the third length of the fence structure along the length direction of the lower plastic ranges from 1.5 to 2, so that when the electrode assembly impacts the buffer structure, a sufficient contact area exists between the fence structure and the electrode assembly, and the buffer portion has a sufficient elastic deformation capability. When the ratio of the second length to the third length is smaller than 1.5, the fence structure easily enables the overall thickness of the buffer part to be too large, so that the elastic deformation capacity of the buffer part is poor, impact force of the electrode assembly cannot be effectively buffered, the overall weight of lower plastic is increased, and the energy density of the energy storage device is reduced. When the ratio of the second length to the third length is greater than 2, when the electrode assembly impacts the buffer structure, the contact area between the fence structure and the electrode assembly is insufficient, the fence structure cannot effectively transmit the impact force of the electrode assembly to the buffer part, the fence structure can easily cause the electrode assembly to locally deform, the number of second open holes which can be formed in the fence structure is small, the gas in the energy storage device is influenced to reach the explosion-proof valve through the second open holes, the valve opening of the explosion-proof valve is not facilitated, and the safety and the reliability of the energy storage device are influenced.

With reference to the first aspect, in some implementations of the first aspect, the first lower plastic body is provided with a first avoidance hole, the first avoidance hole is used for accommodating a sealing nail of the end cover assembly, and the extension part is provided with a second avoidance hole which is avoided from the sealing nail; the buffer structure further comprises a shielding part, the shielding part is arranged on one side, deviating from the first lower plastic body, of the extending part, the shielding part shields the sealing nails when the buffer structure is in a deformation state, and the shielding part is staggered with the sealing nails when the buffer structure is in a recovery state. The second avoidance hole can enable the extension part to avoid interference with the sealing nail when the extension part slides relative to the first lower plastic body, so that the sealing nail is damaged or the second lower plastic body is damaged. When buffer structure receives electrode assembly's impact and is in deformation state, shelter from the portion and shelter from the seal nail, avoid electrode assembly to support against the seal nail, lead to seal nail to deviate from the notes liquid hole of end cover to energy storage device's sealed inefficacy causes electrolyte to reveal, and seal nail can puncture electrode assembly and cause the damage to the structure wherein, if puncture the diaphragm leads to electrode assembly short circuit, influence battery safety. When the buffer structure is in a recovery state without being impacted by the electrode assembly, the shielding part and the sealing nails are staggered, for example, when electrolyte is filled, the buffer structure is in the recovery state, the shielding part and the sealing nails are staggered, the shielding part is prevented from stopping a path for the electrolyte to enter, the probability of back splash during electrolyte injection can be effectively reduced, and the electrolyte filling efficiency is improved.

With reference to the first aspect, in certain implementation manners of the first aspect, the shielding portion includes a strut and a stopper, the strut is connected to a side of the extension portion facing away from the end cover, the stopper is connected to a side of the strut facing away from the extension portion, and the stopper is located on a side of the second avoidance hole facing away from the end cover and has a gap with the sealing nail. When the lower plastic is in the first state, the stop block moves to one side of the sealing nail, which is far away from the end cover, along with the extension part so as to protect the sealing nail. When the lower plastic is in the second state, the stop block is driven by the extension part to be staggered with the sealing nail along the height direction of the lower plastic.

In combination with the first aspect, in certain implementation manners of the first aspect, the supporting rod includes two first supporting rods and one second supporting rod, the two first supporting rods are arranged at two sides of the second avoidance hole along the width direction of the lower plastic, the second supporting rod is arranged at one side of the second avoidance hole along the length direction of the lower plastic, which is close to the buffer part, so that the stop block can be supported more stably, and compared with the mode of arranging the supporting rods into a semi-cylindrical supporting sheet, the supporting rods are arranged into the first supporting rods and the second supporting rods, so that the material consumption of the supporting rods can be reduced, the overall quality of the lower plastic is reduced, and the electrolyte retention on the stop block is avoided.

With reference to the first aspect, in certain implementation manners of the first aspect, a circumference of a side of the stopper facing away from the extension portion is provided with a rounded corner, so that burrs are avoided from being generated on the circumference of the stopper, and damage is caused to the electrode assembly.

In combination with the first aspect, in certain implementation manners of the first aspect, the first lower plastic body and the second lower plastic body are respectively provided with a boss portion along one side, away from the buffer structure, of the length direction of the lower plastic body, the boss portions extend towards a direction away from the end cover, and are arranged along the height direction of the lower plastic body, and the first height of the stop block relative to the end cover is smaller than the second height of the boss portions relative to the end cover, so that when the lower plastic body is extruded, the boss portions can be contacted with the electrode assembly first to buffer the impact force of the electrode assembly, and the shielding portion is prevented from being damaged by impact.

In combination with the first aspect, in some implementations of the first aspect, a diversion trench is provided on a side of the boss portion facing the end cover, a reinforcing rib is provided in the diversion trench, and a diversion hole communicating with the diversion trench is provided on a side of the boss portion facing away from the end cover. The reinforcing ribs can strengthen the overall strength of the boss part, improve the impact resistance of the boss part and avoid the boss part from being damaged under the impact of the electrode assembly. After the electrolyte flows into the diversion trench, the electrolyte can return to the electrode assembly through the diversion hole, so that the redistribution of the electrolyte in the energy storage device is promoted, and the service life of the energy storage device is prolonged.

In a second aspect, the present application provides an end cap assembly comprising an end cap and a lower plastic as defined in any one of the preceding claims, the lower plastic being attached to the end cap.

In a third aspect, the present application provides an energy storage device comprising an end cap assembly as described above.

In a fourth aspect, the present application provides an energy storage system comprising an energy storage device as described above, the energy storage device providing electrical energy to the energy storage system.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are needed in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and that other drawings can be obtained according to these drawings without inventive effort for a person skilled in the art.

Fig. 1 is a schematic structural diagram of a household energy storage system according to an embodiment of the present application.

Fig. 2 is a schematic structural diagram of an energy storage system according to an embodiment of the present application.

FIG. 3 is an exploded view of an end cap assembly provided in accordance with one embodiment of the present application.

Fig. 4 is a schematic structural diagram of the lower plastic in a first state according to an embodiment of the present application.

Fig. 5 is a cross-sectional view of the lower plastic of fig. 4 taken along line A-A.

Fig. 6 is an enlarged view at I in fig. 5.

Fig. 7 is a schematic structural diagram of the lower plastic in a second state according to an embodiment of the present application.

Fig. 8 is a partial cross-sectional view of the lower plastic in a second state according to an embodiment of the present application.

Fig. 9 is a top view of a lower plastic provided by an embodiment of the application.

Description of main reference numerals: an energy storage system 1; an electric energy conversion device 2; a first user load 3; a second user load 4; a high voltage cable 51; a first power conversion device 52; a second electric energy conversion device 53; an energy storage device 100; an end cap assembly 10; an end cap 11; an explosion-proof valve 12; a liquid injection hole 13; sealing nail 141; a seal cover 142; a lower plastic 20; a first lower molding compound 21; a guide chute 211; a first escape aperture 212; a second lower molding compound 22; a body portion 221; a body surface 221a; a buffer structure 222; a buffer space 220; a buffer portion 223; a first aperture 2231; an extension 224; a second avoidance hole 2241; a shielding portion 225; a strut 226; a first strut 2261; a second strut 2262; a stopper 227; rounded corners 2271; a fence structure 23; a second opening 231; a boss portion 24; a diversion trench 241; reinforcing ribs 242; deflector holes 243; a reinforcing portion 25; positioning structure 26.

The application will be further described in the following detailed description in conjunction with the above-described figures.

Detailed Description

The following description of the embodiments of the present application will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some, but not all embodiments of the present application. All other embodiments, which can be made by those skilled in the art based on the embodiments of the application without making any inventive effort, are intended to be within the scope of the application.

Reference herein to "an embodiment" or "implementation" means that a particular feature, structure, or characteristic described in connection with the embodiment or implementation may be included in at least one embodiment of the application. The appearances of such phrases in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments. Those of skill in the art will explicitly and implicitly appreciate that the embodiments described herein may be combined with other embodiments.

It is to be understood that the terminology used in the description and claims of the application and in the above description and drawings is for the purpose of describing particular embodiments only, and is not intended to be limiting of the application. The terms first, second and the like in the description and in the claims and in the above-described figures, are used for distinguishing between different objects and not necessarily for describing a sequential or chronological order.

Because of the strong timeliness and space properties of energy required by people, in order to reasonably utilize the energy and improve the utilization rate of the energy, one energy form needs to be stored by one medium or equipment and then converted into another energy form, and the energy is released in a specific energy form based on future application. At present, the main way of generating green electric energy is to develop green energy sources such as photovoltaic, wind power and the like to replace fossil energy sources.

At present, the generation of green electric energy generally depends on photovoltaic, wind power, water potential and the like, but wind energy, solar energy and the like generally have the problems of strong intermittence and large fluctuation, which can cause unstable power grid, insufficient peak electricity consumption, too much electricity consumption and unstable voltage can cause damage to the electric power, so that the problem of 'wind abandoning and light abandoning' possibly occurs due to insufficient electricity consumption requirement or insufficient power grid acceptance, and the problem needs to be solved by relying on energy storage. The energy is converted into other forms of energy through physical or chemical means and is stored, the energy is converted into electric energy when needed and released, in short, the energy storage is similar to a large-scale 'charge pal', the electric energy is stored when the photovoltaic and wind energy are sufficient, and the stored electric power is released when needed.

Taking electrochemical energy storage as an example, the present solution provides an energy storage device 100, in which a group of chemical batteries are disposed in the energy storage device 100, and chemical elements in the batteries are mainly used as energy storage media, and the charge and discharge process is accompanied with chemical reaction or change of the energy storage media, that is, the stored electric energy is released for use when the use of external electric energy reaches a peak, or is transferred to a place where the electric energy is short for reuse.

The present energy storage (i.e. energy storage) application scenario is relatively wide, including aspects such as power generation side energy storage, grid side energy storage, and power utilization side energy storage, the types of the corresponding energy storage device 100 include:

(1) The large energy storage power station applied to the wind power and photovoltaic power station side can assist renewable energy sources to generate electricity to meet grid-connected requirements, and meanwhile, the utilization rate of the renewable energy sources is improved; the energy storage power station is used as a high-quality active/reactive power regulating power supply in a power supply side, so that the load matching of electric energy in time and space is realized, the capacity of absorbing renewable energy sources is enhanced, the instantaneous power change is reduced, the impact on a power grid is reduced, the problem of generating and absorbing new energy sources is solved, and the energy storage power station has great significance in the aspects of standby of a power grid system, relieving peak load power supply pressure and peak regulation and frequency modulation;

(2) The energy storage container applied to the power grid side has the functions of mainly peak regulation, frequency modulation and power grid blocking and peak regulation relieving, and can realize peak clipping and valley filling of the power consumption load, namely the energy storage battery is charged when the power consumption load is low, and the stored electric quantity is released in the peak period of the power consumption load, so that the balance between power production and power consumption is realized;

(3) The small energy storage cabinet applied to the electricity utilization side has the main functions of spontaneous electricity utilization, peak Gu Jiacha arbitrage, capacity cost management and power supply reliability improvement. According to the different application scenes, the electricity-side energy storage can be divided into an industrial and commercial energy storage cabinet, a household energy storage device, an energy storage charging pile and the like, and is generally matched with the distributed photovoltaic. The energy storage can be used by industrial and commercial users for valley peak price difference arbitrage and capacity cost management. In the electric power market implementing peak-valley electricity price, the energy storage system is charged when the electricity price is low, and the energy storage system is discharged when the electricity price is high, so that peak-valley electricity price difference arbitrage is realized, and the electricity cost is reduced. In addition, the energy storage system is suitable for two industrial enterprises with electricity price, can store energy when electricity is used in low valley and discharge the energy when the electricity is used in peak load, so that peak power and the declared maximum demand are reduced, and the purpose of reducing the capacity electricity fee is achieved. The household photovoltaic distribution and storage can improve the spontaneous self-use level of the electric power. Due to high electricity prices and poor power supply stability, the photovoltaic installation requirements of users are pulled. Considering that the photovoltaic power generation is performed in daytime, and the load of a user is generally higher at night, the photovoltaic power can be better utilized through configuration of energy storage, the spontaneous self-use level is improved, and meanwhile the power consumption cost is reduced. In addition, the fields of communication base stations, data centers and the like need to be configured with energy storage for standby power.

Referring to fig. 1, fig. 1 is a schematic structural diagram of a household energy storage system 1 according to an embodiment of the present application, and the embodiment of fig. 1 of the present application is illustrated by taking a household energy storage scenario in a user side energy storage as an example, and the energy storage device of the present application is not limited to the household energy storage scenario.

The application provides a household energy storage system 1, wherein the household energy storage system 1 comprises an electric energy conversion device 2 (photovoltaic panel), a first user load 3 (street lamp), a second user load 4 (such as an air conditioner and other household appliances) and the like, and an energy storage device 100, wherein the energy storage device 100 is a small energy storage box and can be installed on an outdoor wall in a wall-mounted mode. The energy storage device 100 provides electrical energy to the energy storage system 1. In particular, the photovoltaic panel may convert solar energy into electric energy during the low electricity price period, and the energy storage device 100 is used to store the electric energy and supply the electric energy to the street lamp and the household appliances for use during the electricity price peak or supply the electric power during the power outage/power failure of the electric network.

Referring to fig. 2, fig. 2 is a schematic structural diagram of an energy storage system 1 according to an embodiment of the present application, and the embodiment of fig. 2 is illustrated by taking a power generation/distribution side shared energy storage scenario as an example, and the energy storage device 100 of the present application is not limited to the power generation/distribution side energy storage scenario.

The present application provides an energy storage system 1, the energy storage system 1 comprising: the high-voltage cable 51, the first electric energy conversion device 52, the second electric energy conversion device 53 and the energy storage device 100 provided by the application. In the power generation, the first power conversion device 52 and the second power conversion device 53 are used for converting other forms of energy into electric energy, and are connected to the high-voltage cable 51 and supplied to the power distribution network. When the power load is low and the power generation of the first power conversion device 52 and the second power conversion device 53 is excessive, the multiple generated power is stored in the energy storage device 100, so that the wind and light rejection rate is reduced, and the problem of power generation and absorption of new energy is solved; when the power consumption load is high, the power grid gives an instruction, the electric quantity stored by the energy storage device 100 is cooperated with the high-voltage cable 51 to transmit electric energy to the power consumption side for use in a grid-connected mode, various services such as peak regulation, frequency modulation and standby are provided for the operation of the power grid, the peak regulation effect of the power grid is fully exerted, peak clipping and valley filling of the power grid are promoted, and the power supply pressure of the power grid is relieved.

Alternatively, the first and second electric energy conversion devices 52 and 53 may convert at least one of solar energy, optical energy, wind energy, thermal energy, tidal energy, biomass energy, mechanical energy, and the like into electric energy.

The number of the energy storage devices 100 may be plural, and the plurality of energy storage devices 100 may be connected in series or parallel, and the plurality of energy storage devices 100 may be supported by a separator (not shown) and electrically connected. In the present embodiment, "a plurality of" means two or more. The energy storage device 100 may further be provided with an energy storage box for accommodating the energy storage device 100.

Alternatively, the energy storage device 100 may include, but is not limited to, a battery cell, a battery module, a battery pack, a battery system, and the like. The practical application form of the energy storage device 100 provided in the embodiment of the present application may be, but is not limited to, the listed products, and may be other application forms, and the embodiment of the present application does not strictly limit the application form of the energy storage device 100. The embodiment of the present application will be described by taking the energy storage device 100 as a multi-core battery. When the energy storage device 100 is a single battery, the energy storage device 100 may be at least one of a cylindrical battery, a prismatic battery, and the like.

In the present application, for the sake of more clear description, the X-axis direction is defined as the length direction of the lower plastic, the Y-axis direction is defined as the width direction of the lower plastic, and the Z-axis direction is defined as the height direction of the lower plastic. The length direction, the width direction and the height direction of the lower plastic are mutually perpendicular.

Referring to fig. 3, fig. 3 is an exploded view of an end cap assembly 10 according to an embodiment of the present application. The energy storage device 100 includes a case, an electrode assembly, and an end cap assembly 10. The end cap assembly 10 covers the opening of the case to enclose the electrolyte and the electrode assembly within the case. The end cap assembly 10 includes an end cap 11 and a lower plastic 20. The end cap 11 is provided with an explosion-proof valve 12. The lower plastic 20 is adapted to be connected to the end cap 11. The lower plastic 20 includes a first lower plastic body 21 and a second lower plastic body 22 disposed along a length direction X of the lower plastic 20. The second lower molding body 22 includes a body 221 and a buffer structure 222 disposed on a side of the body 221 adjacent to the first lower molding body 21 and connected to the body 221. The body portion 221 has a body surface 221a facing away from the end cap 11, and the cushioning structure 222 projects relative to the body surface 221a of the body portion 221 in a direction away from the end cap 11. One end of the buffer structure 222 facing away from the body 221 is located on a side of the first lower plastic body 21 facing away from the end cover 11, and is movable relative to the first lower plastic body 21 along the length direction X of the lower plastic 20. The cushioning structure 222 is disposed opposite and spaced apart from the explosion proof valve 12 of the end cap assembly 10.

When the energy storage device 100 is impacted by external force (such as unexpected falling or violent shaking), the electrode assembly is extruded towards the end cover 11, the buffer structure 222 can deform after being impacted by the electrode assembly upwards, the length dimension of the buffer structure 222 along the length direction X of the lower plastic 20 is increased, at the moment, the free end, which is far away from the body 221, of the buffer structure 222, which is lapped on one side, which is far away from the end cover 11, of the first lower plastic body 21 can move towards the direction away from the body 221, the buffer structure 222 can absorb the impact force of the electrode assembly through deformation, so that the second lower plastic body 22 cannot release stress due to the impact force of the upper pressure is prevented from being broken, and the buffer structure 222 and the explosion-proof valve 12 are arranged at intervals, so that the explosion-proof valve 12 can be prevented from being directly impacted by the electrode assembly, and the explosion-proof valve 12 is prevented from being triggered by mistake, and the safety, stability and service life of the energy storage device 100 are improved.

Referring to fig. 4, fig. 5, fig. 6, fig. 7 and fig. 8, fig. 4 is a schematic structural diagram of the lower plastic 20 in a first state according to an embodiment of the application; FIG. 5 is a cross-sectional view of the lower plastic 20 of FIG. 4 taken along line A-A; FIG. 6 is an enlarged view at I in FIG. 5; fig. 7 is a schematic structural diagram of the lower plastic 20 in a second state according to the embodiment of the present application; fig. 8 is a partial cross-sectional view of the lower plastic 20 in a second state according to an embodiment of the present application. The lower plastic 20 includes a first state and a second state. When the energy storage device 100 is in the normal state, the lower plastic 20 is in the first state when not impacted by the electrode assembly, and at this time, the buffer structure 222 is in a protruding state relative to the body surface 221a in a direction away from the end cover 11, and a maximum distance between a side of the buffer structure 222 away from the end cover 11 and the end cover 11 is a first distance D1. When the energy storage device 100 is impacted by an external force (such as unexpected falling or violent shaking), the lower plastic 20 is in the second state after being impacted by the electrode assembly, at this time, the buffer structure 222 is pressed by the electrode assembly towards the end cover 11, and the maximum distance between the side of the buffer structure 222 away from the end cover 11 and the end cover 11 is the second distance D2. Wherein the first distance D1 is greater than the second distance D2.

Specifically, the cushioning structure 222 includes a cushioning portion 223 and an extension portion 224. The buffer portion 223 is connected to the main body portion 221. The buffer portion 223 is provided in an arch-like projection with respect to the body surface 221a toward a direction away from the end cover 11. The extending portion 224 extends from one end of the buffer portion 223 away from the main portion 221 along the length direction X of the lower plastic 20, and is overlapped on a side of the first lower plastic 21 facing away from the end cover 11. The buffer portion 223 is formed with a buffer space 220 toward one side of the cap 11. The explosion proof valve 12 is located in the buffer space 220. After the buffer portion 223 receives the impact of the electrode assembly, the degree of bending of the buffer portion 223 becomes smaller, the buffer space 220 becomes smaller, and the buffer portion 223 pushes the extension portion 224 to slide in a direction away from the body portion 221 at a side of the first lower molding body 21 facing away from the end cap 11. Wherein the buffer portion 223 has an elastic structure. The buffer 223 is configured in an arch shape to better perform an elastic buffer function. The buffer portion 223 may elastically deform under the impact of the electrode assembly, the bending degree of the buffer portion 223 becomes smaller, so as to absorb the impact force of the electrode assembly, when the impact of the electrode assembly to the buffer portion 223 disappears, the buffer portion 223 rebounds under the elastic recovery effect, the bending degree of the buffer portion 223 becomes larger, so that the buffer portion 223 buffers the next impact of the electrode assembly, and the safety, stability and service life of the energy storage device 100 are improved. The extension portion 224 can guide the moving direction of the end of the buffer portion 223 away from the body portion 221, so as to move in the direction away from the body portion 221, so as to avoid the end of the buffer portion 223 away from the body portion 221 moving in the direction close to the body portion 221, which causes the buffer portion 223 to break, and thus the buffer structure 222 effectively plays a role of buffering. The existing split lower plastic in a flat plate shape is influenced by self gravity and by gas and electrolyte in the energy storage device after being used for a long time, so that the lower plastic can age and droop, and the problem that the valve opening accuracy and stability of the explosion-proof valve are negatively influenced due to the fact that tab fragments fall to the explosion-proof valve position exists.

The side of the first lower molding body 21, which is far away from the end cover 11, is provided with a guide chute 211. The extension 224 is in sliding engagement with the guide slot 211. When the buffer structure 222 is impacted by the electrode assembly, the extension portion 224 may slide along the sliding guide groove 211 under the pushing of the buffer portion 223, so that the buffer portion 223 extends to absorb the impact force of the electrode assembly. The sliding guide groove 211 can guide the sliding direction of the extension portion 224, so that the extension portion 224 can better slide relative to the first molding body 21, which is beneficial to improving the stability of the buffer structure 222 when the buffer structure 222 is deformed, and the buffer structure 222 can effectively play a role in buffering. The two sidewalls of the guiding slot 211 along the width direction Y of the lower plastic 20 can also avoid the interference between the extending portion 224 and other structures in the energy storage device 100.

The buffer portion 223 is provided with a plurality of first openings 2231 communicated with the buffer space 220, so that when the gas pressure in the energy storage device 100 is too high, the gas can conveniently pass through the first openings 2231 and reach the position of the explosion-proof valve 12, thereby opening the explosion-proof valve 12, avoiding explosion of the energy storage device 100 and improving the safety and reliability of the energy storage device 100. The first openings 2231 are arranged along the width direction Y of the lower plastic 20. Along the height direction Z of the lower plastic 20, at least one first opening 2231 is disposed opposite the explosion-proof valve 12. The first opening 2231 is also advantageous in improving the elastic ability of the buffer 223 so that the buffer 223 can better absorb the impact force of the electrode assembly.

The number of the first openings 2231 ranges from 3 to 7, so that gas can reach the explosion-proof valve 12 through the first openings 2231, the buffer part 223 can effectively play a role in buffering the electrode assembly, and when the buffer part 223 is deformed, the first openings 2231 can well release internal stress caused by the deformation process, so that the buffer part 223 is prevented from being cracked. Illustratively, the number of the first openings 2231 is 3 in this embodiment. In some embodiments, the number of first apertures 2231 may also be 4, 5, 6, 7. When the number of the first openings 2231 is less than 3, it is disadvantageous that gas rapidly passes through the first openings 2231 to reach the explosion-proof valve 12, and the elastic deformability of the buffer portion 223 is poor, and the buffering effect on the electrode assembly is poor. When the number of the first openings 2231 is greater than 7, the capacity of the buffer portion 223 against deformation is too small, the buffer portion 223 cannot effectively absorb and buffer the impact force of the electrode assembly, the electrode assembly is easily directly impacted to the explosion-proof valve 12, the explosion-proof valve 12 is erroneously triggered, the rebound capacity of the buffer portion 223 is poor, and when the impact of the electrode assembly is eliminated, the buffer portion 223 is difficult to restore by itself.

In some embodiments, in the width direction Y of the lower plastic 20, the flow area of the first openings 2231 near the middle of the lower plastic 20 is larger than the flow area of the first openings 2231 near both sides of the lower plastic 20 among the plurality of first openings 2231. The explosion-proof valve 12 is disposed at an intermediate position of the end cap 11 in the width direction Y of the lower plastic 20. In the use process of the energy storage device 100, along the width direction Y of the lower plastic 20, the electrode plate and the electrolyte at the middle position of the electrode assembly have higher temperature due to poor heat dissipation, the electrochemical reaction at the middle position is more active, the corresponding generated gas amount is larger, and conversely, the heat dissipation effect at the two side positions is good, the temperature is lower, the electrochemical reaction is weaker, and the gas yield is relatively lower. When the energy storage device 100 is accidentally expanded, the gas production amount at the middle position of the electrode assembly is greater than that at the two side positions. In the present application, the flow area of the first opening 2231 near the middle position of the lower plastic 20 is larger than the flow area of the first openings 2231 near the two sides of the lower plastic 20, so that the gas at the middle position of the electrode assembly can be more effectively collected to the position of the explosion-proof valve 12 through the first openings 2231, and the valve opening performance of the explosion-proof valve 12 is improved, thereby improving the safety of the energy storage device 100. In addition, the first openings 2231 located at two sides of the lower plastic 20 are closer to the edge of the electrode assembly, the first openings 2231 located at two sides of the electrode assembly are spaced from the first openings 2231 located at two sides of the electrode assembly, so that on one hand, the overall structural strength of the buffer portion 223 can be enhanced, and the structural stability is ensured, on the other hand, gaps exist between the winding cores in the electrode assembly, the winding degree on the outer side of the winding cores is loose, gas is easier to generate at the positions between the winding cores, gaps exist between the winding cores and the shell, gas is easy to generate at the positions, the middle position of the winding cores is tightly wound, gas is difficult to generate, and the gas in the electrode assembly is mainly arranged at the center position and the two sides of the electrode assembly, and through the first openings 2231 which are arranged at intervals are respectively arranged at the middle position and the two sides of the buffer portion 223 corresponding to the lower plastic 20, so that the buffer portion 223 can be ensured to have sufficient structural strength, meanwhile, the gas generated in the energy storage device 100 can be quickly and effectively gathered to the position of the explosion-proof valve 12, the safety of the explosion-proof valve 12 is improved, the safety and the quick valve opening capability of the explosion-proof valve 100 is improved, and the safety of the energy storage device 100 is improved.

Referring to fig. 9, fig. 9 is a top view of a lower plastic 20 according to an embodiment of the application. The ratio of the first length L1 of the first opening 2231 along the length direction X of the lower plastic 20 to the first width W1 along the width direction Y of the lower plastic 20 is in the range of 1.2-3. For example, the ratio of the first length L1 to the first width W1 may be 1.2, 1.3, 1.4, 1.5, 1.6, 1.8, 2.0, 2.5, 3, and so on. When the ratio of the first length L1 to the first width W1 ranges from 1.2 to 3, the buffer portion 223 may have a good elastic deformation capability to effectively absorb the impact force of the electrode assembly, and a good elastic recovery capability, so that the buffer portion 223 may be better recovered. When the ratio of the first length L1 to the first width W1 is less than 1.2, the strength of the buffer portion 223 at the position corresponding to the first opening 2231 is low, and when the impact of the electrode assembly is received, the deformation degree of the buffer portion 223 at the position of the first opening 2231 is excessively large compared with other positions, and the buffer portion 223 is easily plastically deformed due to stress concentration, so that the buffer portion 223 is difficult to restore by itself after the impact of the electrode assembly is eliminated. When the ratio of the first length L1 to the first width W1 is greater than 3, the ability of the buffer portion 223 to resist deformation is excessively small, and the buffer portion 223 cannot effectively absorb the impact force of the buffer electrode assembly.

Referring to fig. 4 and 6, the buffer structure 222 further includes a fence structure 23 disposed on a side of the buffer portion 223 facing away from the end cap 11. The fence structure 23 is provided with a plurality of second openings 231. At least a portion of the second aperture 231 communicates with the first aperture 2231. The flow area of the first aperture 2231 is greater than the flow area of the second aperture 231. When the gas pressure inside the energy storage device 100 is excessively high, the gas may flow into the first opening 2231 or the buffer space 220 through the second opening 231, thereby reaching the position of the explosion-proof valve 12. The fence structure 23 can stop objects such as an insulating film and a tab in the energy storage device 100, so as to prevent the foreign matters such as the insulating film and the tab from reaching the explosion-proof valve 12 and affecting the opening of the explosion-proof valve 12.

The second openings 231 are arranged in a plurality of rows and columns. In some embodiments, the second openings 231 near the center of the lower plastic 20 are arranged at a greater density than the second openings 231 near the two sides along the width direction Y of the lower plastic 20, so that the gas is concentrated at the center of the lower plastic 20 and the gas is pushed up against the explosion-proof valve 12. In some embodiments, the plurality of second openings 231 may be uniformly arranged along the width direction Y of the lower plastic 20.

The fence structure 23 is set to a plane on one side surface deviating from the buffer portion 223 and is parallel to one side surface of the end cover 11 facing the lower plastic 20, so that when the electrode assembly impacts the buffer portion 222, the fence structure 23 can enable the stress of the buffer portion 223 to be more uniform, local overlarge stress on the buffer portion 223 is avoided, and when the electrode assembly presses against the fence structure 23 due to shaking and falling of the energy storage device 100, the plane of the fence structure 23 can avoid damage to the electrode assembly. The distance between the surface of the side of the barrier structure 23 facing away from the buffer portion 223 and the surface of the side of the end cover 11 facing the lower plastic 20 is the maximum distance between the side of the buffer structure 222 facing away from the end cover 11 and the end cover 11.

The ratio of the second length L2 of the lower plastic 20 in the length direction X of the buffer portion 223 to the third length L3 of the barrier structure 23 along the length direction X of the lower plastic 20 is in the range of 1.5-2, so that when the electrode assembly impacts the buffer structure 222, a sufficient contact area is provided between the barrier structure 23 and the electrode assembly, and the buffer portion 223 has a sufficient elastic deformation capability. For example, the ratio of the second length L2 to the third length L3 may be 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, etc. When the ratio of the second length L2 to the third length L3 is smaller than 1.5, the fence structure 23 easily makes the overall thickness of the buffer portion 223 too large, resulting in poor elastic deformation capability of the buffer portion 223, failing to effectively buffer the impact force of the electrode assembly, and resulting in an increase in the overall weight of the lower plastic 20, and reducing the energy density of the energy storage device 100. When the ratio of the second length L2 to the third length L3 is greater than 2, when the electrode assembly impacts the buffer structure 222, the contact area between the barrier structure 23 and the electrode assembly is insufficient, the barrier structure 23 cannot effectively transmit the impact force of the electrode assembly to the buffer portion 223, and the barrier structure 23 easily causes local deformation of the electrode assembly, and the number of the second openings 231 which can be formed in the barrier structure 23 is small, so that the gas in the energy storage device 100 reaches the explosion-proof valve 12 through the second openings 231, which is not beneficial to opening the explosion-proof valve 12, and the safety and reliability of the energy storage device 100 are affected. Along the length direction X of the lower plastic 20, the third length L3 of the barrier structure 23 is smaller than the first length L1 of the first opening 2231, so that the gas can reach the explosion-proof valve 12 more quickly.

Referring to fig. 3, 4 and 6, the end cap 11 is provided with a liquid injection hole 13, and the electrolyte can be injected into the energy storage device 100 through the liquid injection hole 13. The end cap assembly 10 further includes a sealing pin 141 and a sealing cap 142 disposed on the end cap 11. The sealing nail 141 is used to block the liquid injection hole 13 to avoid leakage of the electrolyte in the energy storage device 100. The sealing cap 142 is welded to the end cap 11 to define the sealing nail 141 in the injection hole 13 and to close the injection hole 13 after the electrolyte is injected.

The first lower plastic body 21 is provided with a first avoiding hole 212 at a position corresponding to the liquid injection hole 13. The first relief aperture 212 is adapted to receive the sealing pin 141 of the end cap assembly 10. The extension 224 is provided with a second avoidance hole 2241 that is formed to avoid the sealing pin 141. The second avoidance holes 2241 may allow the extension 224 to avoid interference with the sealing pin 141 when sliding relative to the first lower molding body 21, resulting in damage to the sealing pin 141 or damage to the second lower molding body 22. The second avoidance hole 2241 is opened from one end of the extension portion 224 away from the buffer portion 223 toward the buffer portion 223.

The cushioning structure 222 also includes a shield 225. The shielding portion 225 is disposed on a side of the extending portion 224 facing away from the first lower molding body 21. When the lower plastic 20 is in the first state, the buffer structure 222 is impacted by the electrode assembly and is in a deformation state, at the moment, the shielding part 225 shields the sealing nail 141, so that the electrode assembly is prevented from propping against the sealing nail 141, the sealing nail 141 is propped against the sealing cover 142, the sealing cover 142 is in failure in connection with the end cover 11, the sealing nail 141 is separated from the liquid injection hole 13 of the end cover 11, the sealing of the energy storage device 100 is failed, electrolyte leakage is caused, and the sealing nail 141 pierces the electrode assembly to damage the structure therein, such as the electrode assembly is short-circuited due to the piercing of a diaphragm, and the safety of the energy storage device 100 is affected. When the lower plastic 20 is in the second state, the buffer structure 222 is in the restored state without being impacted by the electrode assembly, and the shielding portion 225 is disposed offset from the sealing nail 141. For example, when electrolyte is filled, the buffer structure 222 is in a recovery state, the shielding part 225 and the sealing nails 141 are staggered, so that the path for the electrolyte to enter is avoided by the shielding part 225, the probability of back splash during electrolyte injection can be effectively reduced, and the electrolyte filling efficiency is improved.

The shield 225 includes a post 226 and a stop 227. The strut 226 is connected to the side of the extension 224 facing away from the end cap 11. Stop 227 is attached to the side of post 226 facing away from extension 224. The stopper 227 is located on a side of the second avoidance hole 2241 facing away from the end cap 11. Along the height direction X of the lower plastic 20, a gap is formed between the stop 227 and the sealing nail 141 to avoid interference between the stop 227 and the sealing nail 141. When the lower plastic 20 is in the first state, the stopper 227 moves with the extension 224 to the side of the sealing nail 141 away from the end cap 11 to protect the sealing nail 141. When the lower plastic 20 is in the second state, the stop block 227 is driven by the extension portion 224 to be staggered with the sealing nail 141 along the height direction Z of the lower plastic 20. The periphery of the side of the stop 227 facing away from the extension 224 is provided with a rounded corner 2271 to avoid burrs from being generated on the periphery of the stop 227 and damage to the electrode assembly.

The struts 226 include two first struts 2261 and one second strut 2262. The two first struts 2261 are disposed at both sides of the second avoidance hole 2241 in the width direction Y of the lower plastic 20. The second strut 2262 is disposed at a side of the second avoidance hole 2241 near the buffer portion 223 along the length direction X of the lower plastic 20. The first support rod 2261 and the second support rod 2262 are arranged around the second avoidance hole 2241 at intervals of 90 degrees, so that the stop block 227 can be supported more stably, and compared with the mode of arranging the support rod 226 into a semi-cylindrical supporting sheet, the support rod 226 is arranged into the first support rod 2261 and the second support rod 2262, so that the material consumption of the support rod 226 can be reduced, the overall mass of the lower plastic 20 is reduced, and the electrolyte retention on the stop block 227 is avoided.

Referring to fig. 3, 5 and 6, the first lower molding body 21 and the second lower molding body 22 are respectively provided with a boss 24 along a side of the length direction X of the lower plastic 20 away from the buffer structure 222. The boss portion 24 is provided to extend in a direction away from the end cover 11. Along the height direction Z of the lower plastic 20, the first height H1 of the stopper 227 relative to the end cover 11 is smaller than the second height H2 of the boss portion 24 relative to the end cover 11, so that when the lower plastic 20 is extruded, the boss portion 24 can contact the electrode assembly first to buffer the impact force of the electrode assembly, so as to avoid the shielding portion 225 from being damaged by impact.

The boss portion 24 is provided with a diversion trench 241 on a side facing the end cover 11. The flow guide groove 241 is internally provided with a reinforcing rib 242. The reinforcing ribs 242 can strengthen the overall strength of the boss portion 24, improve the impact resistance of the boss portion 24, and prevent the boss portion 24 from being damaged under the impact of the electrode assembly. The boss portion 24 is provided with a diversion hole 243 communicating with the diversion trench 241 on a side facing away from the end cover 11. After flowing into the flow guide groove 241, the electrolyte may be returned to the electrode assembly through the flow guide hole 243, thereby promoting redistribution of the electrolyte within the energy storage device 100 and improving the service life of the energy storage device 100.

The boss portion 24 is provided with reinforcing portions 25 along both sides of the width direction Y of the lower plastic 20. The reinforcement portion 25 extends from the boss portion 24 in the longitudinal direction X of the lower plastic 20 toward the buffer structure 222. The reinforcement portion 25 can enhance the overall strength of the first lower molding body 21 and the second lower molding body 22, and increase the connection area between the mayar protective film for accommodating the electrode assembly and the first lower molding body 21 and the second lower molding body 22 in the energy storage device 100, thereby improving the connection reliability between the mayar protective film and the lower plastic 20.

In some embodiments, the side of the first lower plastic body 21 and the second lower plastic body 22 facing the end cover 11 is provided with a positioning structure 26, the side of the end cover 11 facing the lower plastic body 20 is provided with a matching structure matching with the positioning structure 26, and the connection stability of the first lower plastic body 21 and the second lower plastic body 22 and the end cover 11 can be improved through the matching of the positioning structure 26 and the matching structure, and the dislocation of the first lower plastic body 21 and the second lower plastic body 22 relative to the end cover 11 during installation is avoided, so that the assembly efficiency of the end cover assembly 10 is improved. The positioning structure 26 may be configured as a protrusion protruding from the side of the first lower plastic body 21 and the second lower plastic body 22 facing the end cover 11, and the mating structure may be configured as a groove formed on the end cover 11. When the lower plastic 20 is assembled on the end cap 11, the protrusions are accommodated in the grooves. In some embodiments, the locating structure 26 may also be configured as a groove and the mating structure may also be configured as a protrusion.

While the application has been described with reference to certain preferred embodiments, it will be understood by those skilled in the art that various changes and substitutions of equivalents may be made and equivalents will be apparent to those skilled in the art without departing from the scope of the application. Therefore, the protection scope of the application is subject to the protection scope of the claims.

Claims (18)

1. A lower plastic adapted to be connected to an end cap of an end cap assembly, comprising:

a first lower molding compound; and

the second lower plastic body comprises a body part and a buffer structure which is positioned on one side of the body part close to the first lower plastic body and connected with the body part; the body portion has the body surface that deviates from the end cover, buffer structure for the body portion the body surface orientation is kept away from the direction of end cover is protruding, buffer structure deviates from the one end of body portion is located first plastic body deviates from one side of end cover, and follows plastic length direction is relative first plastic body is movable down, buffer structure with the explosion-proof valve of end cover subassembly is relative and the interval sets up.

2. The lower plastic of claim 1, wherein the buffer structure comprises a buffer portion and an extension portion, the buffer portion is connected to the body portion, the buffer portion is arranged in an arch-shaped protruding manner towards a direction away from the end cover, and the extension portion extends from one end of the buffer portion away from the body portion along a length direction of the lower plastic and is overlapped with one side of the first lower plastic body away from the end cover.

3. The lower plastic of claim 2, wherein a side of the first lower plastic body facing away from the end cap is provided with a guide chute, and the extension portion is slidably engaged with the guide chute.

4. The lower plastic according to claim 2, wherein a buffer space is formed on a side of the buffer portion facing the end cover, and a plurality of first openings are formed in the buffer portion and are communicated with the buffer space.

5. The lower plastic of claim 4, wherein a flow area of the first openings near a middle position of the lower plastic among the plurality of first openings in a width direction of the lower plastic is larger than a flow area of the first openings near both sides of the lower plastic.

6. The lower plastic of claim 4, wherein a ratio of a first length of the first opening along a length direction of the lower plastic to a first width along a width direction of the lower plastic is in a range of 1.2-3.

7. The lower plastic of claim 4, wherein the buffer structure further comprises a barrier structure disposed on a side of the buffer portion facing away from the end cap, the barrier structure having a plurality of second openings, at least a portion of the second openings being in communication with the first openings, the first openings having a flow area greater than a flow area of the second openings.

8. The lower plastic of claim 7, wherein the surface of the side of the barrier structure facing away from the end cap is planar.

9. The lower plastic of claim 8, wherein a ratio of the second length of the buffer portion along the length direction of the lower plastic to the third length of the barrier structure along the length direction of the lower plastic is in a range of 1.5-2.

10. The lower plastic of claim 2, wherein the first lower plastic body is provided with a first avoidance hole for accommodating a sealing nail of the end cover assembly, and the extension part is provided with a second avoidance hole for avoiding the sealing nail; the buffer structure further comprises a shielding part, the shielding part is arranged on one side, deviating from the first lower plastic body, of the extending part, the shielding part shields the sealing nails when the buffer structure is in a deformation state, and the shielding part is staggered with the sealing nails when the buffer structure is in a recovery state.

11. The lower plastic of claim 10, wherein the shielding portion includes a strut and a stop, the strut being connected to a side of the extension facing away from the end cap, the stop being connected to a side of the strut facing away from the extension, the stop being located on a side of the second relief hole facing away from the end cap and having a gap from the sealing spike.

12. The lower plastic of claim 11, wherein the struts include two first struts and one second strut, the two first struts are disposed on two sides of the second avoidance hole along the width direction of the lower plastic, and the second struts are disposed on one side of the second avoidance hole along the length direction of the lower plastic, which is close to the buffer portion.

13. The lower plastic of claim 11, wherein a periphery of a side of the stopper facing away from the extension is provided with rounded corners.

14. The lower plastic of claim 11, wherein the first lower plastic body and the second lower plastic body are respectively provided with a boss portion along a side of the length direction of the lower plastic body away from the buffer structure, the boss portions extend towards a direction away from the end cover, and along the height direction of the lower plastic body, the first height of the stopper relative to the end cover is smaller than the second height of the boss portions relative to the end cover.

15. The lower plastic of claim 14, wherein a diversion trench is formed in a side of the boss portion facing the end cover, a reinforcing rib is arranged in the diversion trench, and a diversion hole communicated with the diversion trench is formed in a side of the boss portion facing away from the end cover.

16. An end cap assembly comprising an end cap and a lower plastic of any one of claims 1-15, said lower plastic being attached to said end cap.

17. An energy storage device comprising the end cap assembly of claim 16.

18. An energy storage system comprising the energy storage device of claim 17, wherein the energy storage device provides electrical energy to the energy storage system.