Battery pack, energy storage apparatus and method for monitoring state of charge of battery pack

Abstract

Provided in the embodiments of the present application are a battery pack, an energy storage apparatus and a method for monitoring the state of charge of a battery pack. The battery pack comprises a plurality of battery cells, the plurality of battery cells each comprising a casing and, accommodated in the casing, a positive tab and a negative tab. The plurality of battery cells comprise sodium-ion batteries and lithium-ion batteries, the negative tabs of the sodium-ion batteries being electrically connected to the casings of the sodium-ion batteries, the positive tabs of the lithium-ion batteries being electrically connected to the casings of the lithium-ion batteries, and the casings of the sodium-ion batteries being electrically connected to the casings of the lithium-ion batteries. In the present application, the sodium-ion batteries are introduced into a lithium iron phosphate battery system so as to reduce costs, and when the sodium-ion batteries and the lithium iron phosphate batteries are integrated into a whole, no wire connection is required, thus reducing the complexity of connection and the total internal resistance. In addition, by means of a sodium-ion battery charge-discharge curve, the estimation accuracy of the SOC of the battery pack is estimated.

Description

Battery pack, energy storage device and method for monitoring state of charge of battery pack

[0001] The present application claims priority to the Chinese patent application No. 202410741141.2 filed on June 7, 2024, and entitled "Battery pack, energy storage device and method for monitoring state of charge of battery pack", the content of which is incorporated herein by reference in its entirety. TECHNICAL FIELD

[0002] The present application relates to the technical field of batteries, and in particular to a battery pack, an energy storage device and a method for monitoring the state of charge of the battery pack. BACKGROUND

[0003] In the related art, lithium ion batteries are widely used due to their suitable price and mature process. However, the lithium ion batteries have a long charging and discharging platform during the charging and discharging process. The voltage changes slowly along with the SOC-OCV (state of charge-voltage) curve of the charging and discharging process of the battery cell, and the slope is small. As a result, when the BMS monitors the SOC of the battery pack by means of the voltage of the lithium ion battery, there is a large error in the accuracy. The SOC of the battery pack is not accurately measured, which can cause the battery pack to be overcharged and discharged, and thus the battery pack is damaged. Moreover, the inaccurate measurement of the SOC of the battery pack can reduce the system performance and reliability of the energy storage system using the battery pack, and can also cause the vehicle using the battery pack to estimate the range incorrectly, so that the battery utilization efficiency is low. Therefore, the inaccurate measurement of the SOC of the battery pack seriously affects the use experience. SUMMARY

[0004] Embodiments of the present application provide a battery pack, an energy storage device and a method for monitoring the state of charge of the battery pack to improve the detection accuracy of the SOC of the battery pack.

[0005] In a first aspect, embodiments of the present application provide a battery pack. The battery pack includes a plurality of battery cells. Each of the plurality of battery cells includes a shell, a positive electrode tab and a negative electrode tab accommodated in the shell. The plurality of battery cells includes a sodium ion battery and a lithium ion battery. The negative electrode tab of the sodium ion battery and the shell of the sodium ion battery are electrically connected. The positive electrode tab of the lithium ion battery and the shell of the lithium ion battery are electrically connected. The shell of the sodium ion battery and the shell of the lithium ion battery are electrically connected.

[0006] In the embodiment, the shell of the sodium-ion battery can be regarded as the negative pole of the sodium-ion battery because the negative pole tab of the sodium-ion battery is electrically connected with the shell of the sodium-ion battery, and the shell of the lithium-ion battery can be regarded as the positive pole of the lithium-ion battery because the positive pole tab of the lithium-ion battery is electrically connected with the shell of the lithium-ion battery, so that when the shell of the sodium-ion battery and the shell of the lithium-ion battery are in contact, the negative pole of the sodium-ion battery and the positive pole of the lithium-ion battery are electrically connected, and the series connection of the sodium-ion battery and the lithium-ion battery can be regarded. Because the slope of the voltage change of the sodium-ion battery during the charging and discharging process is large, the voltage of the sodium-ion battery and the SOC state of the battery pack have a good corresponding relationship, so that the BMS can monitor the SOC state of the battery pack with higher precision and reliability. Therefore, in the embodiment, by connecting the sodium-ion battery and the lithium-ion battery in series, the SOC state of the battery pack can be accurately monitored by monitoring the voltage of the sodium-ion battery, thereby effectively solving the problem of low SOC state monitoring precision of the battery pack.

[0007] In some embodiments, the battery pack further comprises a battery management unit, and the battery management unit is configured to collect voltage data of the sodium-ion battery and calculate the state of charge of the battery pack according to the voltage data of the sodium-ion battery collected by the battery management unit. In the embodiment, because the slope of the voltage change of the sodium-ion battery during the charging and discharging process is large, the real-time voltage data of the sodium-ion battery during the charging and discharging process can be accurately detected, and then the voltage data of the sodium-ion battery is collected by the battery management unit and fed back to the data processing module, and the data processing module can calculate the state of charge of the battery pack according to the voltage data of the sodium-ion battery collected by the battery management unit. Therefore, the state of charge of the battery pack in the embodiment can be accurately monitored in real time.

[0008] In some embodiments, the battery management unit comprises a first voltage collection line and a second voltage collection line, the first voltage collection line is electrically connected with the positive pole of the sodium-ion battery, and the second voltage collection line is electrically connected with the shell of the sodium-ion battery or the shell of the lithium-ion battery.

[0009] In some embodiments, the voltage collection lines include a first voltage collection line, a third voltage collection line, and a second voltage collection line, the first voltage collection line is connected to the positive pole of the sodium-ion battery, the third voltage collection line is connected to the negative pole of the lithium iron phosphate battery; and the second voltage collection line is connected to the surface of the shell of the sodium-ion battery or the surface of the shell of the lithium-ion battery. In this embodiment, since the slope of the voltage of the sodium-ion battery during the charging and discharging process changes greatly, the voltage of the sodium-ion battery and the SOC state of the battery pack have a good corresponding relationship, so the voltage of the sodium-ion battery between the first voltage collection line and the second voltage collection line, and the total voltage of the series connection of the sodium-ion battery and the lithium iron phosphate battery between the third voltage collection line and the first voltage collection line can be accurately monitored, so that the SOC of the battery pack can be accurately predicted by monitoring the voltage of the sodium-ion battery between the first voltage collection line and the second voltage collection line, or the total voltage of the series connection of the sodium-ion battery and the lithium iron phosphate battery between the third voltage collection line and the first voltage collection line.

[0010] In some embodiments, the shells of the sodium-ion batteries and the shells of the lithium-ion batteries are arranged along a first direction, the length direction of the lithium-ion batteries is the same as the first direction, and the length direction of the sodium-ion batteries is the same as the first direction. In this embodiment, the shells of the sodium-ion batteries and the shells of the lithium-ion batteries are arranged along the first direction, which not only facilitates the connection of the sodium-ion batteries and the lithium-ion batteries, but also meets the arrangement requirements of the sodium-ion batteries and the lithium-ion batteries in some specific scenarios.

[0011] In some embodiments, the first direction is the same as the width direction of the battery pack. In this embodiment, since the first direction is the width direction of the battery pack, and the arrangement direction of the sodium-ion batteries and the lithium-ion batteries is the first direction, the arrangement of the sodium-ion batteries and the lithium-ion batteries can be more reasonable when the lengths of the sodium-ion batteries and the lithium-ion batteries are different.

[0012] In some embodiments, the width of the lithium-ion batteries is the same as the width of the sodium-ion batteries, the height of the lithium-ion batteries is the same as the height of the sodium-ion batteries, and the sodium-ion batteries and the lithium-ion batteries are arranged face to face in the first direction. In this embodiment, since the sodium-ion batteries and the lithium-ion batteries are arranged face to face in the first direction, it is beneficial to make the overall layout of the sodium-ion batteries and the lithium-ion batteries more reasonable.

[0013] In some embodiments, the length of the sodium-ion battery is greater than the length of the lithium-ion battery, the capacity of the sodium-ion battery is the same as the capacity of the lithium-ion battery, and the charge-discharge rate of the sodium-ion battery is the same as the charge-discharge rate of the lithium-ion battery. In this embodiment, the capacity of the sodium-ion battery is the same as the capacity of the lithium-ion battery, and the charge-discharge rate of the sodium-ion battery is the same as the charge-discharge rate of the lithium-ion battery, so that the series connection of the batteries can achieve more balanced current distribution and more efficient energy utilization. In this way, energy waste and inconsistent performance caused by differences between the battery cells can be avoided.

[0014] In some embodiments, the housing of the sodium-ion battery includes a first top wall, a first bottom wall, and a plurality of first side walls connected between the first top wall and the first bottom wall, the first top wall and the first bottom wall are oppositely arranged in a first direction, the first bottom wall, the first top wall and the plurality of first side walls enclose a first sealed cavity; the housing of the lithium-ion battery includes a second top wall and a plurality of second side walls, the second top wall and the first bottom wall are oppositely arranged in the first direction, the plurality of second side walls are connected between the first bottom wall and the second top wall, and the three walls enclose a second sealed cavity. In this embodiment, since the first bottom wall is part of the first sealed cavity and part of the second sealed cavity, and the sodium-ion battery and the lithium-ion battery are arranged along the first direction, the housing of the lithium-ion battery does not need to additionally provide a bottom wall for enclosing the second sealed cavity with the plurality of second side walls and the second top wall. If the bottom wall of the second housing is provided, it will have a certain thickness. Since the second housing does not need to additionally provide a bottom wall, the length of the second housing in the first direction can be effectively reduced, thereby effectively reducing the overall length of the sodium-ion battery and the lithium-ion battery arranged in the first direction. Thus, the energy density of the battery pack can be effectively improved. In addition, since the housing of the lithium-ion battery saves a bottom wall, the material cost of the housing can also be saved.

[0015] In some embodiments, the height of the housing of the lithium iron phosphate battery is H1, the width is T1, and the length is L1. The height of the housing of the sodium-ion battery is H2, the width is T2, and the length is L2. L2=XL2, wherein X=1.2-3, to ensure that the lithium iron phosphate battery and the sodium-ion battery are in the same voltage range, and the charge and discharge capacity of the lithium iron phosphate battery and the sodium-ion battery is the same.

[0016] In some embodiments, the first bottom wall is welded to the first side wall, and the first bottom wall is welded to the second side wall. In this embodiment, the first bottom wall, the first side wall and the second side wall can be connected together by welding. It can be understood that in other embodiments, the first bottom wall, the first side wall and the second side wall can also be integrally injection molded. The first bottom wall and the first side wall can be integrally injection molded, and the second side wall and the first bottom wall can be welded.

[0017] In some embodiments, the negative tab of the sodium-ion battery is electrically connected with the first bottom wall, and the positive tab of the lithium-ion battery is electrically connected with the first bottom wall. In this embodiment, since the negative tab of the sodium-ion battery is electrically connected with the first bottom wall, and the positive tab of the lithium-ion battery is electrically connected with the first bottom wall, the first bottom wall can be regarded as both the positive pole of the sodium-ion battery and the negative pole of the lithium-ion battery, and the series connection of the sodium-ion battery and the lithium-ion battery is achieved. Compared with the mode of indirectly achieving the electrical connection between the negative tab of the sodium-ion battery and the positive tab of the lithium-ion battery by the contact between the shell of the sodium-ion battery and the shell of the lithium-ion battery, in this embodiment, since the negative tab of the sodium-ion battery is electrically connected with the first bottom wall, and the positive tab of the lithium-ion battery is electrically connected with the first bottom wall, the contact resistance can be effectively reduced or avoided, so as to further reduce the internal loss of the sodium-ion battery and the lithium-ion battery.

[0018] In some embodiments, the sodium-ion battery further comprises a positive pole arranged on the first top wall, and the positive pole is electrically connected with the positive tab of the sodium-ion battery; and the lithium-ion battery further comprises a negative pole arranged on the second top wall, and the negative pole is electrically connected with the negative tab of the lithium-ion battery. In this way, the positions of the positive pole of the sodium-ion battery and the negative pole of the lithium-ion battery are designed, so that the sodium-ion battery and the lithium-ion battery can be reasonably arranged, and the overall structure of the sodium-ion battery and the lithium-ion battery after being connected is more reasonable. In addition, since the first direction is the same as the width direction of the battery pack, the positive pole is arranged on the first top wall, and the negative pole is arranged on the second top wall, so that the size of the battery pack in the height direction can be effectively reduced, so that when the battery pack is applied to a vehicle, the proportion of the battery pack in the vertical direction can be effectively reduced, and the size of the passenger compartment of the vehicle can be effectively increased.

[0019] In some embodiments, the lithium ion battery is a lithium iron phosphate battery, the shell of the sodium ion battery is an aluminum shell, the shell of the lithium iron phosphate battery is an aluminum shell, the negative tab of the sodium ion battery is electrically connected with the shell of the sodium ion battery, the positive tab of the lithium iron phosphate battery is electrically connected with the shell of the lithium iron phosphate battery, and the shell of the sodium ion battery is in contact with and electrically connected with the shell of the lithium iron phosphate battery. In this embodiment, since the shell of the sodium ion battery is an aluminum shell and the positive electrode material of the sodium ion battery is a compound or polymer containing sodium elements, the shell of the sodium ion battery will not react with sodium ions in the electrolyte of the sodium ion battery at high or low potentials, so that the negative tab of the sodium ion battery will not affect the stability of the overall sodium ion battery after being electrically connected with the shell of the sodium ion battery. Since the shell of the lithium ion battery is an aluminum shell and the positive electrode material of the lithium ion battery is a compound or polymer containing lithium elements, the shell of the lithium ion battery will not react with lithium ions at high potentials, so that the positive tab of the lithium ion battery can still ensure the stability of the lithium ion battery after being electrically connected with the shell of the lithium ion battery. The sodium ion battery and the lithium ion battery can be connected in series by contacting the shell of the sodium ion battery and the shell of the lithium ion battery, so as to avoid the use of wires, reduce the internal loss caused by the wires, and reduce the complexity of the series connection of the sodium ion battery and the lithium ion battery. Moreover, the stability of the sodium ion battery and the lithium ion battery can be ensured.

[0020] In addition, since the sodium ion battery is a sodium ion battery, the voltage of the sodium ion battery changes with a large slope during the charging and discharging process, and the voltage of the sodium ion battery and the SOC state of the battery pack have a good corresponding relationship, so that the BMS can more accurately and reliably monitor the SOC state of the battery pack by means of the voltage of the sodium ion battery. In this embodiment, since the sodium ion battery is a sodium ion battery and the sodium ion battery and the lithium ion battery are connected in series, the SOC state of the battery pack can be accurately monitored by monitoring the voltage of the sodium ion battery, thereby effectively solving the problem of low monitoring accuracy of the SOC state of the battery pack using only lithium iron phosphate batteries.

[0021] In some embodiments, the positive tab of the sodium-ion battery includes an aluminum foil and a positive material disposed on the aluminum foil, the positive material including a layered oxide and a polyanion, and the polyanion having a proportion of 0-40%, such as 0, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, etc. In this embodiment, the layered oxide can simultaneously consider the energy density and the cycle life. The layered oxide has the advantages of providing high specific capacity and good cycle performance, and the polyanion compound has the characteristics of three-dimensional structure diversity and structural stability, good long-term cycle stability, and high safety. Since the proportion of the polyanion in the positive material is 0-40%, within this range, it can meet the requirements of providing high specific capacity, good cycle performance, long-term cycle stability, and high safety. In addition, when the proportion of the polyanion in the positive material is within the range of 0-40%, the slope of the SOC-OCV (state of charge-voltage) curve of the sodium-ion battery during the charging and discharging process can be large enough to provide accurate voltage change measurement, so that the SOC of the battery pack can be accurately obtained by measuring the voltage of the sodium-ion battery.

[0022] In some embodiments, the lithium-ion battery includes a second bottom wall, a second top wall, and a second side wall connected between the second bottom wall and the second top wall. The second bottom wall, the second side wall, and the second top wall enclose a second sealed cavity. The sodium-ion battery and the lithium-ion battery are arranged along a first direction, and the first bottom wall and the second bottom wall are in contact and electrically connected.

[0023] In some embodiments, the lithium-ion battery includes a second bottom wall, a second top wall, and a second side wall connected between the second bottom wall and the second top wall. The second bottom wall, the second side wall, and the second top wall enclose a second sealed cavity for accommodating the positive tab, the negative tab, and the electrolyte of the lithium-ion battery. The sodium-ion battery and the lithium-ion battery are arranged along a second direction, wherein the second direction is perpendicular to the first direction, and the first side wall of the sodium-ion battery is in contact and electrically connected with the second side wall of the lithium-ion battery.

[0024] In some embodiments, the current collector of the positive tab and the current collector of the negative tab of the sodium-ion battery are both made of aluminum material, which can effectively reduce the cost of the sodium-ion battery. It can also effectively reduce the weight of the sodium-ion battery.

[0025] In some embodiments, the number of lithium iron phosphate batteries is a plurality, and the plurality of lithium iron phosphate batteries are connected in series. The shell of the sodium-ion battery is in contact and electrically connected with the shell of one of the lithium iron phosphate batteries. In this embodiment, one sodium-ion battery is connected in series with a plurality of lithium iron phosphate batteries connected in series, and the SOC of the battery pack can be accurately predicted by monitoring the voltage of the sodium-ion battery.

[0026] In some embodiments, the length of the sodium-ion battery is twice the length of the lithium-ion battery, the sodium-ion battery and one of the lithium-ion batteries are arranged along the first direction and form a first battery pack, and three lithium-ion batteries are arranged along the first direction and form a second battery pack, and the first battery pack and the second battery pack are arranged along the length direction of the battery pack. In this embodiment, since the length of the sodium-ion battery is twice the length of the lithium-ion battery, the size of the second battery pack formed by the arrangement of the three lithium-ion batteries and the first battery pack in the first direction is the same, so that the arrangement of the sodium-ion battery and the lithium-ion battery in the shell of the battery pack is more reasonable.

[0027] In some embodiments, the length direction of the lithium-ion battery is the same as the first direction, the length direction of the sodium-ion battery is the same as the first direction, one lithium-ion battery and one sodium-ion battery are arranged along the first direction and form a first battery pack, the first direction is perpendicular to the length direction of the battery pack, and a plurality of first battery packs are arranged along the length direction of the battery pack. In this embodiment, the first battery pack formed by the sodium-ion battery and the lithium-ion battery is arranged along the length direction of the battery pack, and the size of each first battery pack is consistent, so that the arrangement in the battery pack is more reasonable.

[0028] In some embodiments, the length direction of the lithium-ion battery is the same as the first direction, the length direction of the sodium-ion battery is the same as the first direction, one lithium-ion battery and one sodium-ion battery are arranged along the first direction and form a first battery pack, the first direction is parallel to the length direction of the battery pack, the battery pack further includes a plurality of lithium-ion batteries, the plurality of lithium-ion batteries are arranged along the length direction of the battery pack and form a second battery pack, and in the length direction of the battery pack, the length of the second battery pack is consistent with the length of the first battery pack. In this embodiment, since the length of the first battery pack and the length of the second battery pack are the same in the length direction of the battery pack, it is more convenient to reasonably arrange the first battery pack and the second battery pack in the battery pack.

[0029] In some embodiments, the lithium-ion battery is a ternary lithium battery, and the shell of the sodium-ion battery and the shell of the ternary lithium battery are both aluminum shells; the negative tab of the sodium-ion battery is electrically connected to the shell of the sodium-ion battery, the positive tab of the ternary lithium battery is electrically connected to the shell of the ternary lithium battery, and the shell of the sodium-ion battery is in contact with and electrically connected to the shell of the ternary lithium battery.

[0030] In a second aspect, the embodiments of the present application provide an energy storage device, which includes a battery management system and a plurality of battery packs according to any one of the first aspect, and the battery management system is used to collect voltage data of the sodium-ion battery and calculate the state of charge of the battery pack according to the collected voltage data of the sodium-ion battery.

[0031] In a third aspect, the embodiments of the present application provide a method for measuring the state of charge of the battery pack according to any one of the first aspect, the sodium-ion battery being a sodium-ion battery;

[0032] The method comprises:

[0033] collecting voltage data of the sodium-ion battery;

[0034] calculating the state of charge of the battery pack according to the collected voltage data of the sodium-ion battery.

[0035] In some embodiments, before the step of collecting voltage data of the sodium-ion battery, the method further comprises the following steps:

[0036] measuring and obtaining corresponding curves of the voltage of the sodium-ion battery and the state of charge of the battery pack at different states;

[0037] In the step of calculating the state of charge of the battery pack according to the collected voltage data of the sodium-ion battery, the state of charge of the battery pack is calculated based on the corresponding curves according to the collected voltage data of the sodium-ion battery.

[0038] In a fourth aspect, the embodiments of the present application provide a vehicle, which comprises a vehicle body and a plurality of battery packs according to any one of the first aspect arranged in the vehicle body. BRIEF DESCRIPTION OF DRAWINGS

[0039] In order to more clearly illustrate the technical solutions of the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description.

[0040] FIG. 1 is a simple structure schematic diagram of an energy storage device provided by the embodiments of the present application;

[0041] FIG. 2 is a structure schematic diagram of a battery pack provided by the embodiments of the present application;

[0042] FIG. 3 is a structure schematic diagram of a sodium-ion battery and a lithium-ion battery in the battery pack in the embodiment of FIG. 2;

[0043] FIG. 4 is a structure schematic diagram of a winding core of a battery cell in the embodiment of FIG. 3;

[0044] FIG. 5 is an exploded structure schematic diagram of a shell of the sodium-ion battery and the lithium-ion battery in FIG. 3;

[0045] FIG. 6 is a charging and discharging curve diagram of a lithium iron phosphate battery and a sodium-ion battery;

[0046] FIG. 7 is a top view of the sodium-ion battery and the lithium-ion battery in the embodiment of FIG. 3;

[0047] FIG. 8 is a front view of the sodium-ion battery and the lithium-ion battery in the embodiment of FIG. 3;

[0048] FIG. 9 is a structural schematic diagram of another sodium-ion battery and lithium-ion battery according to an embodiment of the present application;

[0049] FIG. 10 is a structural schematic diagram of still another sodium-ion battery and lithium-ion battery according to an embodiment of the present application;

[0050] FIG. 11A is a schematic diagram of connection of partial battery cells of another battery pack according to an embodiment of the present application;

[0051] FIG. 11B is a schematic diagram of connection of partial battery cells of another battery pack according to an embodiment of the present application;

[0052] FIG. 11C is a schematic diagram of connection of partial battery cells of another battery pack according to an embodiment of the present application;

[0053] FIG. 12 is a method for measuring state of charge of a battery pack according to an embodiment of the present application.

[0054] BRIEF DESCRIPTION OF DRAWINGS X, first direction; Y, second direction; 1, energy storage device; 2, box body; 3, battery pack; 4, shell; 5, battery cell; 6, sodium-ion battery; 7, lithium-ion battery; 8, battery management unit; 10, shell; 11, first bottom wall; 12, first top wall; 13, first side wall; 14, first sealed cavity; 15, second top wall; 16, second side wall; 17, second sealed cavity; 18, second bottom wall; 21, positive plate; 22, negative plate; 23, separator; 31, positive pole of sodium-ion battery; 32, negative pole of lithium-ion battery; 40, voltage collection line; 41, first voltage collection line; 42, second voltage collection line; 43, third voltage collection line; 91, first battery group; 92, second battery group. DETAILED DESCRIPTION

[0055] The following first explains some terms related to the embodiments of the present application.

[0056] The terms "first", "second", "third", "fourth" and the like in the description, claims, and drawings of the embodiments of the present application are used to distinguish similar objects, and do not necessarily have to be used to describe a particular order or sequence. It should be understood that the terms used in this way can be interchanged under appropriate circumstances, so that the embodiments of the present application described herein, for example, can be implemented in an order other than those illustrated or described herein. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion, for example, a process, method, system, product, or device including a series of steps or units does not have to be limited to only those steps or units clearly listed, but can include other steps or units not clearly listed or inherent to these processes, methods, products, or devices.

[0057] In this specification, the terms "vertical", "parallel" and the like are explained.

[0058] Vertical: The vertical defined in this application is not limited to the absolute vertical intersection (the angle is 90 degrees) relationship, and allows the relationship that is not the absolute vertical intersection due to factors such as assembly tolerance, design tolerance, and the influence of structure flatness, and allows the existence of a small angle range of errors, for example, within the assembly error range of 80 degrees to 100 degrees, which can be understood as a vertical relationship.

[0059] Parallel: The parallel defined in this application is not limited to absolute parallel, and the definition of this parallel can be understood as substantially parallel, allowing the case that is not absolutely parallel between the sliding fit part and the first door plate due to factors such as assembly tolerance, design tolerance, and the influence of structure flatness, which will lead to the case that is not absolutely parallel between the sliding fit part and the first door plate, but this application also defines that this case is parallel.

[0060] FIG. 1 is a simple structure schematic diagram of an energy storage device 1 provided by an embodiment of the present application.

[0061] Referring to FIG. 1, the energy storage device 1 includes a box body 2 and a plurality of battery packs 3 and a battery management system (BMS) arranged in the box body 2, and the plurality of battery packs 3 are stacked in the box body 2. The plurality of battery packs 3 can store or output electric energy. The battery management system is used for intelligently managing and maintaining each battery pack 3, preventing overcharging and overdischarging of the battery pack 3, prolonging the service life of the battery pack 3, and monitoring the state of the battery pack 3.

[0062] In order to facilitate understanding of the energy storage device 1 provided by the embodiment of the present application, the application scenario thereof will be introduced first. The energy storage device 1 is a system that can store electric energy through a certain medium and release the stored energy to generate electricity when needed, and can be applied to industrial and commercial parks, ground large power supply stations, or light storage systems and the like as load balancing devices and backup power sources. The application of the energy storage device 1 will be simply explained by taking the light storage system scenario as an example. The light storage system usually can include a photovoltaic assembly, an energy storage converter, an energy storage device 1 and a grid-connected inverter. Among them, the photovoltaic assembly can convert light energy into electric energy in the form of direct current and output to the grid-connected inverter; the grid-connected inverter can convert the electric energy in the form of direct current into electric energy in the form of alternating current, and transmit the electric energy in the form of alternating current to the power grid, so as to realize grid connection of the light storage system.

[0063] FIG. 2 is a structure schematic diagram of a battery pack 3 provided by an embodiment of the present application. The battery pack 3 in the embodiment of FIG. 2 can not only be applied to the energy storage device 1 in the embodiment of FIG. 1, but also can be applied to the field of vehicle-mounted or other fields requiring the use of the battery pack 3.

[0064] Referring to FIG. 2, the battery pack 3 comprises a shell 4 and a plurality of battery cells 5 arranged in the shell 4. It can be understood that the plurality of battery cells 5 can be arranged in one row or in multiple rows.

[0065] In some embodiments, the plurality of battery cells 5 are connected in series. In other embodiments, the plurality of battery cells 5 can also be connected in parallel, or some battery cells 5 can be connected in series and some battery cells 5 can be connected in parallel.

[0066] In some embodiments, the shell of the battery cell 5 is a metal shell, such as an aluminum shell.

[0067] In some embodiments, the battery cell 5 is substantially cuboid. Of course, in other embodiments, the battery cell 5 can also be in other shapes.

[0068] FIG. 3 is a structural schematic diagram of the sodium-ion battery 6 and the lithium-ion battery 7 in the battery pack 3 in the embodiment of FIG. 2; FIG. 4 is a structural schematic diagram of the winding core of the battery cell 5 in the embodiment of FIG. 3; FIG. 5 is an exploded structural schematic diagram of the shell 10 of the sodium-ion battery 6 and the lithium-ion battery 7 in FIG. 3; and FIG. 6 is a charge-discharge curve diagram of the lithium-iron-phosphate battery and the sodium-ion battery 6; wherein the horizontal coordinate is the charge ratio or discharge ratio of the lithium-iron-phosphate battery and the sodium-ion battery 6, and the vertical coordinate is the voltage value, wherein the positive slope is charging and the negative slope is discharging. The battery cell 5 in FIG. 3 is applied to the battery pack 3 in the embodiment of FIG. 2.

[0069] Referring to FIGS. 4 and 5, in some embodiments, the plurality of battery cells 5 of the battery pack 3 each comprise a shell 10, and an electrolyte, a positive tab (not shown in the figure), a negative tab (not shown in the figure), a positive plate 21, a negative plate 22, and a separator 23 located between the positive plate 21 and the negative plate 22 accommodated in the shell 10, the positive tab and the positive plate 21 being connected, and the negative tab and the negative plate 22 being connected.

[0070] Referring to FIGS. 3-5, in some embodiments, the plurality of battery cells 5 comprise a sodium-ion battery 6 and a lithium-ion battery 7, such as a lithium-iron-phosphate battery or a ternary lithium battery.

[0071] The negative tab of the sodium-ion battery 6 is electrically connected to the shell 10 of the sodium-ion battery 6, and the positive tab of the sodium-ion battery 6 is electrically connected to the positive post 31 of the sodium-ion battery 6. Since the negative tab of the sodium-ion battery 6 is electrically connected to the shell 10 of the sodium-ion battery 6, the shell 10 of the sodium-ion battery 6 can be regarded as a negative post of the sodium-ion battery 6, and there is a potential difference between the positive post 31 of the sodium-ion battery 6 and the shell 10 of the sodium-ion battery 6.

[0072] The positive tab of the lithium ion battery 7 is electrically connected with the shell 10 of the lithium ion battery 7, and the negative tab of the lithium ion battery 7 is electrically connected with the negative post 32 of the lithium ion battery 7. Since the positive tab of the lithium ion battery 7 is electrically connected with the shell 10 of the lithium ion battery 7, the shell 10 of the lithium ion battery 7 can be regarded as the positive post of the lithium ion battery 7, and there is a potential difference between the shell 10 of the lithium ion battery 7 and the negative post 32 of the lithium ion battery 7.

[0073] In some embodiments, the shell 10 of the sodium ion battery 6 is made of aluminum, and aluminum does not alloy with the electrolyte of the sodium ion battery 6 at high potential and low potential, that is, the sodium ions in the electrolyte of the sodium ion battery 6 do not embed into the aluminum shell to form sodium-aluminum alloy, so that the shell 10 of the sodium ion battery 6 is not corroded by the electrolyte of the sodium ion battery 6 at high potential and low potential, thereby ensuring the stability of the sodium ion battery 6. It can be understood that in other embodiments, the shell 10 of the sodium ion battery 6 can also be made of other materials, but the shell 10 of the sodium ion battery 6 should not alloy with the sodium ions in the electrolyte of the sodium ion battery 6 at low potential when the negative tab of the sodium ion battery 6 is connected with the shell 10 of the sodium ion battery 6.

[0074] In some embodiments, the shell 10 of the lithium ion battery 7 is made of aluminum, and aluminum does not alloy with the lithium ions in the electrolyte of the lithium ion battery 7 at high potential, that is, the lithium ions in the electrolyte of the lithium ion battery 7 do not embed into the aluminum to form aluminum-lithium alloy, so that the shell 10 of the lithium ion battery 7 is not corroded by the electrolyte of the lithium ion battery 7 at high potential, thereby ensuring the stability of the shell 10 of the lithium ion battery 7. It can be understood that in other embodiments, the shell 10 of the lithium ion battery 7 can also be made of other materials, but the shell 10 of the lithium ion battery 7 should not alloy with the lithium ions in the electrolyte of the lithium ion battery 7 at high potential when the positive tab of the lithium ion battery 7 is connected with the shell 10 of the lithium ion battery 7.

[0075] In some embodiments, the shell 10 of the sodium ion battery 6 and the shell 10 of the lithium ion battery 7 are electrically connected. Since the slope of the voltage change of the sodium ion battery during charging and discharging is large (referring to FIG. 6), the voltage of the sodium ion battery and the SOC state of the battery pack 3 have a good corresponding relationship, so that the BMS can more accurately and reliably monitor the SOC state of the battery pack 3 by means of the voltage of the sodium ion battery. Therefore, in this embodiment, by connecting the sodium ion battery 6 and the lithium ion battery 7 in series, the SOC state of the battery pack 3 can be accurately monitored by monitoring the voltage of the sodium ion battery 6, thereby effectively solving the problem of low monitoring accuracy of the SOC state of the battery pack 3.

[0076] In the related art, lithium iron phosphate batteries are widely used in the energy storage field due to their suitable price and mature process. However, the positive system of the lithium iron phosphate battery has a long charge-discharge platform during the charge-discharge process (see FIG. 6), and the SOC-OCV (state of charge-voltage) curve of the voltage charge-discharge process is very flat, with a small slope, which results in a large error in the accuracy of the SOC monitoring of the battery pack 3 by the BMS with the voltage of the lithium iron phosphate battery. The capacity estimation difference will affect the application experience.

[0077] In some embodiments, the lithium ion battery 7 is a lithium iron phosphate battery, and the shell 10 of the sodium ion battery 6 and the shell 10 of the lithium ion battery 7 are both aluminum shells, so as to ensure the stability of the negative tab of the shell 10 of the sodium ion battery 6 after being electrically connected with the shell 10 of the sodium ion battery 6, and the stability of the shell 10 of the lithium ion battery 7 after being electrically connected with the positive tab of the lithium ion battery 7. In addition, since the slope of the voltage charge-discharge process of the sodium ion battery 6 is large (see FIG. 6), the voltage of the sodium ion battery 6 and the SOC state of the battery pack 3 have a good corresponding relationship, so that the accuracy of the SOC state monitoring of the battery pack 3 by the BMS with the voltage of the sodium ion battery 6 is more accurate and reliable. In this embodiment, by connecting the sodium ion battery 6 and the lithium iron phosphate battery in series, the SOC state of the battery pack 3 can be accurately monitored by monitoring the voltage of the sodium ion battery 6, thereby effectively solving the problem of low SOC state monitoring accuracy of the battery pack 3 using only lithium iron phosphate batteries. At the same time, since the lithium iron phosphate battery has a suitable price and a mature process, the cost can be reduced and the safety performance can be improved.

[0078] In some embodiments, the shell 10 of the sodium-ion battery 6 and the shell 10 of the lithium-ion battery 7 are in contact and electrically connected. Since the shell 10 of the sodium-ion battery 6 can be regarded as the negative pole of the sodium-ion battery 6, and the shell 10 of the lithium-ion battery 7 can be regarded as the positive pole of the lithium-ion battery 7, when the shell 10 of the sodium-ion battery 6 and the shell 10 of the lithium-ion battery 7 are in contact, it can be regarded that the negative pole of the sodium-ion battery 6 and the positive pole of the lithium-ion battery 7 are electrically connected, and thus it can be regarded that the sodium-ion battery 6 and the lithium-ion battery 7 are connected in series. By means of the shell 10 of the sodium-ion battery 6 and the shell 10 of the lithium-ion battery 7 being in contact and electrically connected, the use of wires to connect the sodium-ion battery 6 and the lithium-ion battery 7 in series can be avoided, so that not only the electrical connection between the shell 10 of the sodium-ion battery 6 and the shell 10 of the lithium-ion battery 7 is facilitated, and the complexity of the connection between the sodium-ion battery 6 and the lithium-ion battery 7 is reduced, but also the stability of the connection between the shell 10 of the sodium-ion battery 6 and the shell 10 of the lithium-ion battery 7 can be improved, and the connection will not be easily disconnected as in the case of wire connection. Moreover, since the use of wires is avoided, the internal resistance caused by the wires can be effectively reduced, and the internal loss caused by the wires can be effectively avoided, so that the energy output of the battery pack 3 as a whole can be improved.

[0079] It can be understood that the electrical connection between the shell 10 of the sodium-ion battery 6 and the shell 10 of the lithium-ion battery 7 in the present embodiment is subject to certain conditions, i.e., the electrical connection between the shell 10 of the sodium-ion battery 6 and the negative tab of the sodium-ion battery 6 must be stable, and the electrical connection between the shell 10 of the lithium-ion battery 7 and the positive tab of the lithium-ion battery 7 must be stable.

[0080] In some embodiments, the positive electrode material of the sodium-ion battery can be a compound or a polymer containing sodium elements, such as a positive electrode material of some sodium-ion batteries formed by mixing layered oxides and polyanions. The layered oxides can include transition metals such as nickel, iron, manganese, and copper, and the polyanions can be sodium iron pyrophosphate.

[0081] In some embodiments, the positive electrode material of the lithium-ion battery is a compound or a polymer containing lithium elements, such as lithium iron phosphate for some lithium-ion batteries, or ternary polymers of lithium nickel cobalt manganese oxide or lithium nickel cobalt aluminum oxide for some lithium-ion batteries.

[0082] In some embodiments, the positive electrode sheet 21 of the sodium-ion battery 6 includes an aluminum foil and a positive electrode material disposed on the aluminum foil, and the positive electrode material includes a layered oxide and a polyanion, wherein the proportion of the polyanion in the positive electrode material is 0-40%, such as 0, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, etc. The layered oxide can balance the energy density and cycle life. The layered oxide has the advantages of providing high specific capacity and good cycle performance, and the polyanion compound has the characteristics of three-dimensional structure diversity and structural stability, good long-term cycle stability, and high safety. The proportion of the polyanion in the positive electrode material is 0-40%, which can meet the requirements of providing high specific capacity, good cycle performance, long-term cycle stability, and high safety. In addition, when the proportion of the polyanion in the positive electrode material is 0-40%, the slope of the SOC-OCV (state of charge-voltage) curve of the sodium-ion battery 6 during charging and discharging can be large enough to provide accurate voltage change measurement, so that the SOC of the battery pack 3 can be accurately obtained by measuring the voltage of the sodium-ion battery 6.

[0083] In some embodiments, the current collector of the positive electrode sheet 21 of the sodium-ion battery 6 and the current collector of the negative electrode sheet 22 can both use aluminum materials to effectively reduce the cost of the sodium-ion battery 6. It can also effectively reduce the weight of the sodium-ion battery 6.

[0084] Referring to FIGS. 3 and 5, in some embodiments, the shell 10 of the sodium-ion battery 6 and the shell 10 of the lithium-ion battery 7 are arranged along the first direction X, wherein the length direction of the lithium-ion battery 7 is the same as the first direction X, and the length direction of the sodium-ion battery 6 is the same as the first direction X. This arrangement not only facilitates the connection of the sodium-ion battery 6 and the lithium-ion battery 7, but also meets the arrangement requirements of the sodium-ion battery 6 and the lithium-ion battery 7 in some specific scenarios.

[0085] In some embodiments, the first direction X is the same as the width direction b of the battery pack 3. Since the first direction X is the width direction b of the battery pack 3, and the arrangement direction of the sodium-ion battery 6 and the lithium-ion battery 7 is the first direction X, the arrangement of the sodium-ion battery 6 and the lithium-ion battery 7 is more reasonable when the lengths of the sodium-ion battery 6 and the lithium-ion battery 7 are different.

[0086] In order to effectively reduce the overall length of the sodium-ion battery 6 and the lithium-ion battery 7 arranged in the first direction X. In some embodiments, the shell 10 of the sodium-ion battery 6 comprises a first bottom wall 11, a first top wall 12, and a plurality of first side walls 13 connected between the first bottom wall 11 and the first top wall 12, the first bottom wall 11, the first top wall 12, and the plurality of first side walls 13 enclose a first sealed cavity 14, and the first direction X is the direction opposite to the first bottom wall 11 and the first top wall 12. The shell 10 of the lithium-ion battery 7 comprises a second top wall 15 and a plurality of second side walls 16 connected to the periphery of the second top wall 15, the first bottom wall 11 and the second top wall 15 are arranged opposite to each other in the first direction X, the second side walls 16 are connected between the first bottom wall 11 and the second top wall 15, and the first bottom wall 11, the second top wall 15, and the plurality of second side walls 16 enclose a second sealed cavity 17. In this embodiment, since the first bottom wall 11 is part of the first sealed cavity 14 and part of the second sealed cavity 17, and the sodium-ion battery 6 and the lithium-ion battery 7 are arranged along the first direction X, the shell 10 of the lithium-ion battery 7 does not need to additionally provide a bottom wall for enclosing the second sealed cavity 17 with the second side wall 16 and the second top wall 15. If the bottom wall of the second shell 10 is provided, it will have a certain thickness. Since the second shell 10 does not need to additionally provide a bottom wall, the length of the second shell 10 in the first direction X can be effectively reduced, thereby effectively reducing the overall length of the sodium-ion battery 6 and the lithium-ion battery 7 arranged in the first direction X. Thus, the energy density of the battery pack 3 can be effectively improved. In addition, since the shell 10 of the lithium-ion battery 7 saves a bottom wall, the material cost of the shell 10 can also be saved. In addition, since the shell 10 of the sodium-ion battery 6 and the shell 10 of the lithium-ion battery 7 are arranged along the first direction X, the shell 10 of the lithium-ion battery 7 does not need to be provided with a bottom wall. Not providing a bottom wall on the shell 10 of the lithium-ion battery 7 not only does not need additional process to remove the bottom wall, but also saves the step of welding the bottom wall of the shell 10 of the lithium-ion battery 7. Therefore, since the shell 10 of the sodium-ion battery 6 and the shell 10 of the lithium-ion battery 7 are arranged along the first direction X, the manufacturing of the second shell 10 is facilitated.

[0087] In some embodiments, the first bottom wall 11 is welded with the first side wall 13, and the first bottom wall 11 is welded with the second side wall 16. In this embodiment, the first bottom wall 11, the first side wall 13, and the second side wall 16 can be conveniently and quickly connected together by welding.

[0088] It can be understood that in other embodiments, the first bottom wall 11, the first side wall 13, and the second side wall 16 can also be integrally injection molded. The first bottom wall 11 and the first side wall 13 can be integrally injection molded, and the second side wall 16 can be welded with the first bottom wall 11.

[0089] In some embodiments, the negative tab of the sodium-ion battery 6 is electrically connected with the first bottom wall 11, and the positive tab of the lithium-ion battery 7 is electrically connected with the first bottom wall 11. In the present embodiment, since the negative tab of the sodium-ion battery 6 is electrically connected with the first bottom wall 11, and the positive tab of the lithium-ion battery 7 is electrically connected with the first bottom wall 11, the first bottom wall 11 can be regarded as both the positive pole 31 of the sodium-ion battery 6 and the negative pole 32 of the lithium-ion battery 7, and the series connection of the sodium-ion battery 6 and the lithium-ion battery 7 is achieved. Moreover, since the first bottom wall 11 can be directly electrically connected with the negative tab of the sodium-ion battery 6 and the positive tab of the lithium-ion battery 7 to achieve the series connection of the sodium-ion battery 6 and the lithium-ion battery 7, the contact resistance can be effectively reduced or avoided, and the internal loss of the sodium-ion battery 6 and the lithium-ion battery 7 can be further reduced. It can be understood that, in the present embodiment, the first bottom wall 11 can be regarded as both the positive pole 31 of the sodium-ion battery 6 and the negative pole 32 of the lithium-ion battery 7, and the first side wall 13, the first top wall 12, the second side wall 16 and the second top wall 15 connected with the first bottom wall 11 have the same potential as the first bottom wall 11, and can be regarded as both the positive pole 31 of the sodium-ion battery 6 and the negative pole 32 of the lithium-ion battery 7.

[0090] FIG. 7 is a top view of the sodium-ion battery 6 and the lithium-ion battery 7 in the embodiment of FIG. 3, and FIG. 8 is a front view of the sodium-ion battery 6 and the lithium-ion battery 7 in the embodiment of FIG. 3.

[0091] Referring to FIGS. 7 and 8, in some embodiments, the shell 10 of the sodium-ion battery 6 is substantially cuboid, the shell 10 of the lithium-ion battery 7 is substantially cuboid, the first direction X is the same as the length direction of the sodium-ion battery 6 and the length direction of the lithium-ion battery 7, the width of the shell 10 of the sodium-ion battery 6 is the same as the width of the shell 10 of the lithium-ion battery 7, and the height of the shell 10 of the sodium-ion battery 6 is the same as the height of the shell 10 of the lithium-ion battery 7. The sodium-ion battery 6 and the lithium-ion battery 7 are arranged in the first direction X, that is, the height direction of the sodium-ion battery 6 is the same as the height direction of the lithium-ion battery 7, the width direction of the sodium-ion battery 6 is the same as the width direction of the lithium-ion battery 7, and the outer surfaces of the first side wall 13 and the second side wall 16 are flush. Since the sodium-ion battery 6 and the lithium-ion battery 7 are arranged in the first direction X, the overall layout of the sodium-ion battery 6 and the lithium-ion battery 7 can be more reasonable.

[0092] In some embodiments, the lithium ion battery 7 is a lithium iron phosphate battery, the length of the housing 10 of the sodium ion battery 6 is greater than the length of the housing 10 of the lithium ion battery 7, the capacity of the sodium ion battery 6 is the same as the capacity of the lithium ion battery 7, and the charge-discharge rate of the sodium ion battery 6 is the same as the charge-discharge rate of the lithium ion battery 7. For example, when the sodium ion battery 6 is a sodium ion battery and the lithium ion battery 7 is a lithium iron phosphate battery, in order to achieve the same capacity of the sodium ion battery 6 and the lithium ion battery 7 and the same charge-discharge rate of the sodium ion battery 6 and the lithium ion battery 7, the length of the housing 10 of the sodium ion battery 6 needs to be greater than the length of the housing 10 of the lithium ion battery 7. It can be understood that if the capacities of the two cells 5 are different, the battery pack after being connected in series will be limited by the cell 5 with the smallest capacity, resulting in that the cell 5 with large capacity cannot be fully utilized, and the cell 5 with small capacity may be over-discharged. This situation not only causes the reduction of energy utilization rate, but also may adversely affect the life and performance. If the charge-discharge rates of the two cells 5 are different, during discharging, since the current flows through each cell 5 connected in series, the cell 5 with small charge-discharge rate will limit the current output of the entire battery pack, thereby affecting the performance and efficiency of the battery pack 3. Since the capacity of the sodium ion battery 6 in the present embodiment is the same as the capacity of the lithium ion battery 7, and the charge-discharge rate of the sodium ion battery 6 is the same as the charge-discharge rate of the lithium ion battery 7, the battery pack after being connected in series can achieve more balanced current distribution and more efficient energy utilization. In this way, energy waste and inconsistent performance caused by the difference between the cells 5 can be avoided.

[0093] Since there is a difference in volumetric energy density between the lithium iron phosphate battery and the sodium ion battery, but the lithium iron phosphate battery and the sodium ion battery are connected in series with the same overcurrent, the sizes of the housings 10 of the lithium iron phosphate battery and the sodium ion battery are different. The height of the housing 10 of the lithium iron phosphate battery is H1, the width is T1, and the length is L1. The height of the housing 10 of the sodium ion battery is H2, the width is T2, and the length is L2. L2 = XL2, where X = 1.2-3, to ensure that the lithium iron phosphate battery and the sodium ion battery are within the same voltage range, and the charge-discharge capacity of the lithium iron phosphate battery and the sodium ion battery is the same. For example, the lithium iron phosphate battery is at 2.0-3.65V 0.2C. Then the sodium ion battery is also at 2.0-3.65V 0.2C.

[0094] It can be understood that in some other embodiments, the sodium ion battery 6 and the lithium ion battery 7 can also not be arranged in the first direction X. The width of the sodium ion battery 6 and the width of the lithium ion battery 7 can also be different, the height of the sodium ion battery 6 and the height of the lithium ion battery 7 can also be different. The length of the sodium ion battery 6 and the length of the lithium ion battery 7 can also be the same.

[0095] Referring to FIGS. 7 and 8, in some embodiments, the positive pole column 31 of the sodium-ion battery 6 is arranged on the first top wall 12, and the positive pole column 31 of the sodium-ion battery 6 is electrically connected with the positive pole lug of the sodium-ion battery 6, and the negative pole column 32 of the lithium-ion battery 7 is arranged on the second top wall 15, and the negative pole column 32 of the lithium-ion battery 7 is electrically connected with the negative pole lug of the lithium-ion battery 7. By designing the position of the positive pole column 31 of the sodium-ion battery 6 and the negative pole column 32 of the lithium-ion battery 7, the sodium-ion battery 6 and the lithium-ion battery 7 can be reasonably arranged, and the overall structure of the sodium-ion battery 6 and the lithium-ion battery 7 after being connected is more reasonable.

[0096] In addition, since the first direction X is the same as the width direction b of the battery pack 3, the positive pole column 31 is arranged on the first top wall 12 and the negative pole column 32 is arranged on the second top wall 15, which can effectively reduce the size of the battery pack 3 in the height direction c, thereby effectively reducing the proportion of the battery pack 3 in the vertical direction when the battery pack 3 is applied to a vehicle, thereby effectively increasing the size of the passenger compartment of the vehicle.

[0097] It can be understood that in other embodiments, the positive pole column 31 of the sodium-ion battery 6 can also be arranged on the first side wall 13, and the negative pole column 32 of the lithium-ion battery 7 can also be arranged on the second side wall 16. It can be understood that the positive pole column 31 of the sodium-ion battery 6 is arranged in insulation with the shell 10 of the sodium-ion battery 6, and the negative pole column 32 of the lithium-ion battery 7 is arranged in insulation with the shell 10 of the lithium-ion battery 7.

[0098] In some embodiments, the battery pack 3 further comprises a battery management unit (BMU) 8, the battery management unit 8 is used to collect voltage data of the sodium-ion battery 6, and the collected voltage data of the sodium-ion battery 6 is fed back to a data processing module, and the data processing module is used to calculate the state of charge (SOC) of the battery pack 3 according to the voltage data of the sodium-ion battery 6 collected by the battery management unit 8. The data processing module belongs to a module in the battery management system (BMS) of the energy storage device. In this embodiment, since the voltage change slope of the sodium-ion battery 6 during charging and discharging is large, the real-time voltage data of the sodium-ion battery 6 during charging and discharging can be accurately detected, and then the voltage data of the sodium-ion battery 6 is collected by the battery management unit 8 and fed back to the data processing module, and the data processing module can calculate the state of charge of the battery pack 3 according to the voltage data of the sodium-ion battery 6 collected by the battery management unit 8. Thus, the state of charge of the battery pack 3 in this embodiment can be accurately monitored in real time.

[0099] In some embodiments, the battery management unit 8 comprises a voltage collection line 40 for monitoring the voltage of the sodium-ion battery 6 and / or the voltage of the lithium-ion battery 7 and / or the total voltage of the series connection of the sodium-ion battery 6 and the lithium-ion battery 7.

[0100] In some embodiments, the voltage collection line 40 comprises a first voltage collection line 41, a second voltage collection line 42 and a third voltage collection line 43, the first voltage collection line 41 is connected to the positive pole of the sodium-ion battery, the third voltage collection line 43 is connected to the negative pole of the lithium-ion battery 7; the second voltage collection line 42 can be connected to the surface of the shell 10 of the sodium-ion battery 6, and the second voltage collection line 42 can also be connected to the surface of the shell 10 of the lithium-ion battery 7. Specifically, the second voltage collection line 42 can be connected to any one of the first bottom wall 11, the first side wall 13, the first top wall 12, the second side wall 16 and the second top wall 15. The voltage between the third voltage collection line 43 and the first voltage collection line 41 is the total voltage of the series connection of the sodium-ion battery and the lithium-ion battery 7, the voltage between the first voltage collection line 41 and the second voltage collection line 42 is the voltage of the sodium-ion battery; the voltage between the second voltage collection line 42 and the third voltage collection line 43 is the voltage of the lithium-ion battery 7. In this embodiment, since the slope of the voltage change of the sodium-ion battery during charging and discharging is large, there is a good corresponding relationship between the voltage of the sodium-ion battery and the SOC state of the battery pack 3, so that the voltage of the sodium-ion battery between the first voltage collection line 41 and the second voltage collection line 42 and the total voltage of the series connection of the sodium-ion battery and the lithium-ion battery 7 between the third voltage collection line 43 and the first voltage collection line 41 can be accurately monitored, so that the SOC of the battery pack 3 can be accurately predicted by monitoring the voltage of the sodium-ion battery between the first voltage collection line 41 and the second voltage collection line 42 or the total voltage of the series connection of the sodium-ion battery and the lithium-ion battery 7 between the third voltage collection line 43 and the first voltage collection line 41.

[0101] FIG. 9 is a structural schematic diagram of another sodium-ion battery 6 and lithium-ion battery 7 provided by an embodiment of the present application. The main difference between the embodiment of FIG. 9 and the embodiment of FIG. 3 is that the lithium-ion battery 7 further comprises a second bottom wall 18.

[0102] Referring to FIG. 9, in some embodiments, the lithium-ion battery 7 comprises a second bottom wall 18, a second top wall 15 and a plurality of second side walls 16 connected between the second bottom wall 18 and the second top wall 15. The second bottom wall 18, the plurality of second side walls 16 and the second top wall 15 enclose a second sealed cavity 17 for accommodating the positive pole sheet 21, the negative pole sheet 22 and the electrolyte of the lithium-ion battery 7.

[0103] The sodium-ion battery 6 and the lithium-ion battery 7 are arranged along the first direction X, and the first bottom wall 11 and the second bottom wall 18 are in contact and electrically connected. For example, in some embodiments, the first bottom wall 11 and the second bottom wall 18 can be welded. In this embodiment, the sodium-ion battery 6 and the lithium-ion battery 7 can be independently manufactured, and then contacted and electrically connected together through subsequent processes. The production efficiency can be effectively improved.

[0104] It should be noted that the sodium-ion battery 6, the first bottom wall 11, the second top wall 15, the second side wall 16, the second sealed cavity 17, the first direction X, and the like in this embodiment can refer to the previous embodiments, and will not be repeated here.

[0105] FIG. 10 is a structural schematic diagram of another sodium-ion battery 6 and lithium-ion battery 7 provided in an embodiment of the present application. The main difference between the embodiment of FIG. 10 and the embodiment of FIG. 3 is that the lithium-ion battery 7 further includes a second bottom wall 18, and the arrangement direction of the sodium-ion battery 6 and the lithium-ion battery 7 is different.

[0106] Referring to FIG. 10, in some embodiments, the lithium-ion battery 7 includes a second bottom wall 18, a second top wall 15, and a plurality of second side walls 16 connected between the second bottom wall 18 and the second top wall 15. The second bottom wall 18, the plurality of second side walls 16, and the second top wall 15 enclose a second sealed cavity 17 for accommodating the positive electrode sheet 21, the negative electrode sheet 22, and the electrolyte of the lithium-ion battery 7.

[0107] The sodium-ion battery 6 and the lithium-ion battery 7 are arranged along the second direction Y, wherein the second direction Y is perpendicular to the first direction X, and the first side wall 13 of the sodium-ion battery 6 is in contact and electrically connected with the second side wall 16 of the lithium-ion battery 7.

[0108] In some embodiments, the first top wall 12 and the second top wall 15 are arranged flush. Thus, the positive electrode column arranged on the first top wall 12 and the negative electrode column arranged on the second top wall 15 are both directed to the same direction, and the distance is effectively shortened, thereby facilitating the connection of the voltage acquisition line 40 and reducing the length of the voltage acquisition line 40.

[0109] It should be noted that the sodium-ion battery 6, the first side wall 13, the first top wall 12, the second top wall 15, the second side wall 16, the second sealed cavity 17, the first direction X, the voltage acquisition line 40, the positive electrode column 31 of the sodium-ion battery 6, and the negative electrode column 32 of the lithium-ion battery 7, and the like in this embodiment can refer to the previous embodiments, and will not be repeated here.

[0110] It can be understood that FIG. 3, FIG. 9 and FIG. 10 are only three arrangements of the sodium ion battery 6 and the lithium ion battery 7, and the sodium ion battery 6 and the lithium ion battery 7 in the embodiments of the present application can also be arranged in other manners as long as the shell 10 of the sodium ion battery 6 and the shell 10 of the lithium ion battery 7 are in contact and electrically connected.

[0111] FIG. 11A is a schematic diagram of the connection of part of the battery cell 5 of another battery pack 3 provided in the embodiments of the present application.

[0112] Referring to FIG. 11A, in some embodiments, the number of the lithium ion battery 7 is multiple, and the multiple lithium ion batteries 7 are arranged in series, and the shell 10 of the sodium ion battery 6 is in contact and electrically connected with the shell 10 of one of the lithium ion batteries 7. The lithium ion battery 7 can be a lithium iron phosphate battery or a ternary lithium battery. In the embodiments, one sodium ion battery 6 is arranged in series in the multiple lithium ion batteries 7 arranged in series, and the voltage of the sodium ion battery 6 can be monitored to accurately predict the SOC of the battery pack 3.

[0113] It can be understood that the multiple lithium ion batteries 7 can be arranged in series by wires.

[0114] In some embodiments, the length of the sodium ion battery 6 is twice the length of the lithium ion battery 7, the sodium ion battery 6 and one of the lithium ion batteries 7 are arranged along the first direction X and constitute a first battery group 91, and three lithium ion batteries 7 are arranged along the first direction X and constitute a second battery group 92, and the first battery group 91 and the second battery group 92 are arranged in the length direction a of the battery pack 3. In the embodiments, since the length of the sodium ion battery 6 is twice the length of the lithium ion battery 7, the second battery group 92 arranged by the three lithium ion batteries 7 and the first battery group 91 have the same size in the first direction X, so that the arrangement of the sodium ion battery 6 and the lithium ion battery 7 in the shell 4 of the battery pack 3 is more reasonable.

[0115] It can be understood that the number of the first battery group 91 and the number of the second battery group 92 can be multiple, or there can be only one.

[0116] FIG. 11B is a schematic diagram of the connection of part of the battery cell 5 of another battery pack 3 provided in the embodiments of the present application.

[0117] Referring to FIG. 11B, in some embodiments, the number of sodium-ion batteries 6 is multiple, the number of lithium-ion batteries 7 is multiple, and the shell 10 of the sodium-ion battery 6 is in contact with and electrically connected to the shell 10 of the lithium-ion battery 7. One lithium-ion battery 7 and one sodium-ion battery 6 are arranged along a first direction X and form a first battery pack 91, and the first direction X is perpendicular to the length direction a of the battery pack 3. A plurality of first battery packs 91 are arranged along the length direction a of the battery pack 3. In this embodiment, the first battery pack 91 composed of the sodium-ion battery 6 and the lithium-ion battery 7 is arranged along the length direction a of the battery pack 3, and the size of each first battery pack 91 is consistent, so that the arrangement in the battery pack 3 can be more reasonable.

[0118] In order to facilitate the series connection between the two adjacent first battery packs 91 in the length direction a of the battery pack 3, the positions of the sodium-ion battery 6 and the lithium-ion battery 7 of the two adjacent first battery packs 91 in the length direction a of the battery pack 3 are opposite, so that the positions of the positive and negative electrodes of the two adjacent first battery packs 91 are just opposite, thereby facilitating the series connection of the two adjacent first battery packs 91.

[0119] FIG. 11C is a schematic diagram of the connection of part of the battery cell 5 of another battery pack 3 provided by the embodiments of the present application.

[0120] Referring to FIG. 11C, in some embodiments, the shell 10 of the sodium-ion battery 6 is in contact with and electrically connected to the shell 10 of the lithium-ion battery 7. One lithium-ion battery 7 and one sodium-ion battery 6 are arranged along a first direction X and form a first battery pack 91, and the first direction X is consistent with the length direction a of the battery pack 3. The battery pack 3 further comprises a plurality of lithium-ion batteries 9, and the plurality of lithium-ion batteries 9 are arranged along the length direction a of the battery pack 3 and form a second battery pack 92. The length of the second battery pack 92 in the length direction a of the battery pack 3 is the same as the length of the first battery pack 91. Since the length of the first battery pack 91 and the length of the second battery pack 92 are the same in the length direction a of the battery pack 3, the first battery pack 91 and the second battery pack 92 can be more reasonably arranged in the battery pack 3.

[0121] Specifically, in the first direction X, the total length of one sodium-ion battery 6 and one lithium-ion battery 7 is an integer multiple of the length of one lithium-ion battery 9. For example, in the first direction X, the total length of one sodium-ion battery 6 and one lithium-ion battery 7 is 4 times the length of one lithium-ion battery 9. Thus, the sodium-ion battery 6, the lithium-ion battery 7 and the lithium-ion battery 9 can be reasonably arranged.

[0122] In some embodiments, the positive electrode column and the negative electrode column of the lithium-ion battery 9 are both arranged on the top wall of the lithium-ion battery 9, so as to facilitate the series connection between the adjacent lithium-ion batteries 9.

[0123] In some embodiments, the height of the lithium-ion battery 9 is the same as the width of the lithium-ion battery 7, and the width of the sodium-ion battery 6 is the same as the height of the lithium-ion battery 9. The arrangement direction of the plurality of lithium-ion batteries 9 in the second battery pack 92 is consistent with the width direction of the lithium-ion battery 9. The total length of one sodium-ion battery 6 and one lithium-ion battery 7 is an integer multiple of the width of one lithium-ion battery 9.

[0124] FIG. 12 is a method for measuring the state of charge (SOC) of the battery pack 3 according to an embodiment of the present application. The battery pack 3 in the embodiment of FIG. 12 includes the sodium-ion battery 6 and the lithium-ion battery 7 described above, wherein the sodium-ion battery 6 is the sodium-ion battery 6.

[0125] Referring to FIG. 12, the method for measuring the state of charge of the battery pack 3 includes the following steps:

[0126] S100, measure and obtain the corresponding curve of the voltage of the sodium-ion battery 6 at different states and the state of charge of the battery pack 3. The corresponding curve of the voltage of the sodium-ion battery 6 at different states and the state of charge of the battery pack 3 in the S100 step is usually measured and obtained before the battery pack 3 leaves the factory, so that the battery pack 3 can be directly applied by the battery management system BMS when it is applied to an energy storage device or a vehicle later. Specifically, the corresponding curve of the voltage of the sodium-ion battery 6 at different states and the state of charge of the battery pack 3 can be obtained by an experimental method, for example, the voltage of the sodium-ion battery 6 after being fully charged and standing, and the voltage of the sodium-ion battery 6 after being fully discharged and standing. Then, according to the two voltages, the corresponding curve of the voltage of the sodium-ion battery 6 and the state of charge of the battery pack 3 can be estimated by using an appropriate method.

[0127] S200, collect the voltage data of the sodium-ion battery 6, and / or monitor the total voltage of the sodium-ion battery 6 and the lithium-ion battery 7. In this step, the battery management unit 8 can collect the voltage data of the sodium-ion battery 6, and / or monitor the total voltage of the sodium-ion battery 6 and the lithium-ion battery 7.

[0128] For example, the voltage data can be collected through the first voltage collection line 41, the third voltage collection line 43 and the second voltage collection line 42. The first voltage collection line 41 is connected to the positive pole of the sodium ion battery 6, and the third voltage collection line 43 is connected to the negative pole of the lithium ion battery 7. The second voltage collection line 42 can be connected to the surface of the shell 10 of the sodium ion battery 6, or connected to the surface of the shell 10 of the lithium ion battery 7. The voltage between the third voltage collection line 43 and the first voltage collection line 41 is the total voltage of the sodium ion battery 6 and the lithium ion battery 7 connected in series, the voltage between the first voltage collection line 41 and the second voltage collection line 42 is the voltage of the sodium ion battery 6, and the voltage between the second voltage collection line 42 and the third voltage collection line 43 is the voltage of the lithium ion battery 7. In this step, since the slope of the voltage change of the sodium ion battery 6 during charging and discharging is large, the voltage of the sodium ion battery 6 and the SOC state of the battery pack 3 have a good corresponding relationship, so the voltage of the sodium ion battery 6 between the first voltage collection line 41 and the second voltage collection line 42 and the total voltage of the sodium ion battery 6 and the lithium ion battery 7 connected in series between the third voltage collection line 43 and the first voltage collection line 41 can be accurately monitored, so that the SOC of the battery pack 3 can be accurately predicted by monitoring the voltage of the sodium ion battery 6 between the first voltage collection line 41 and the second voltage collection line 42 or the total voltage of the sodium ion battery 6 and the lithium ion battery 7 connected in series between the third voltage collection line 43 and the first voltage collection line 41.

[0129] S300, calculating the state of charge of the battery pack 3 according to the collected voltage data of the sodium ion battery 6.

[0130] Before step S200, the corresponding curve of the voltage of the sodium ion battery 6 and the SOC of the battery pack 3 has been obtained, and then the data processing module can calculate the SOC value of the battery pack 3 based on the corresponding curve of the voltage of the sodium ion battery 6 and the SOC of the battery pack 3.

[0131] It should be noted that when estimating the SOC of the battery pack 3, the influence of other factors such as working temperature, charging and discharging current, etc. also needs to be considered.

[0132] When estimating the SOC, other factors such as the working temperature of the battery, the charging and discharging current, etc. also need to be considered. Changes in these factors will affect the voltage of the battery, thereby affecting the estimation result of the SOC.

[0133] It can be understood that the method of detecting the SOC of the battery pack 3 in the embodiment can also be combined with the ampere-hour integration method to improve the prediction accuracy of the SOC of the battery pack 3.

[0134] The above merely illustrates the specific embodiments of the present application, but the protection scope of the present application is not limited thereto, any person skilled in the art can easily think of the changes or replacements within the technical range disclosed by the present application, which should be covered in the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A battery pack, characterized by, The battery pack comprises a battery management unit and a plurality of battery cells, each of the plurality of battery cells comprises a shell and a positive and negative tab accommodated in the shell, the plurality of battery cells comprises a sodium ion battery and a lithium ion battery, the negative tab of the sodium ion battery and the shell of the sodium ion battery are electrically connected, the positive tab of the lithium ion battery and the shell of the lithium ion battery are electrically connected, and the shell of the sodium ion battery and the shell of the lithium ion battery are electrically connected. The battery management unit is used to collect voltage data of the sodium ion battery, and the state of charge of the battery pack is calculated according to the voltage data of the sodium ion battery collected by the battery management unit.

2. The battery pack of claim 1, wherein, The battery management unit comprises a first voltage collection line and a second voltage collection line, the first voltage collection line is electrically connected to the positive post of the sodium ion battery, and the second voltage collection line is electrically connected to the shell of the sodium ion battery or the shell of the lithium ion.

3. The battery pack of claim 1 or 2, wherein, The shell of the sodium ion battery and the shell of the lithium ion battery are arranged along a first direction, the length direction of the lithium ion battery is the same as the first direction, the length direction of the sodium ion battery is the same as the first direction, and the first direction is the same as the width direction of the battery pack.

4. The battery pack of claim 3, wherein, The width of the lithium ion battery is the same as the width of the sodium ion battery, the height of the lithium ion battery is the same as the height of the sodium ion battery, the sodium ion battery and the lithium ion battery are arranged in the first direction, the length of the sodium ion battery is greater than the length of the lithium ion battery.

5. The battery pack of claim 3 or 4, wherein, The shell of the sodium ion battery comprises a first top wall, a first bottom wall and a plurality of first side walls connected between the first top wall and the first bottom wall, the first top wall and the first bottom wall are arranged opposite to each other in the first direction, and the first bottom wall, the first top wall and the plurality of first side walls form a first sealed cavity. The shell of the lithium ion battery comprises a second top wall and a plurality of second side walls, the second top wall and the first bottom wall are arranged opposite to each other in the first direction, the plurality of second side walls are connected between the first bottom wall and the second top wall, and the first bottom wall, the second top wall and the plurality of second side walls form a second sealed cavity.

6. The battery pack of claim 5, wherein, The sodium ion battery further comprises a positive post arranged on the first top wall, and the positive post is electrically connected to the positive tab of the sodium ion battery, and the lithium ion battery further comprises a negative post arranged on the second top wall, and the negative post is electrically connected to the negative tab of the lithium ion battery.

7. The battery pack of any one of claims 1-6, wherein, The positive tab of the sodium ion battery comprises an aluminum foil and a positive material arranged on the aluminum foil, the positive material comprises a layered oxide and a polyanion, and the proportion of the polyanion is 0-40%.

8. The battery pack of claim 3, wherein, The number of the lithium ion batteries is a plurality, and the plurality of lithium ion batteries are arranged in series, the shell of the sodium ion battery is in contact with and electrically connected to the shell of one of the lithium ion batteries.

9. The battery pack of claim 8, wherein, The length of the sodium-ion battery is twice the length of the lithium-ion battery, one of the sodium-ion battery and one of the lithium-ion battery are arranged along the first direction and form a first battery pack; three of the lithium-ion batteries are arranged along the first direction and form a second battery pack, the first battery pack and the second battery pack are arranged along the length direction of the battery pack.

10. The battery pack of claim 3, wherein, One of the lithium-ion battery and one of the sodium-ion battery are arranged along the first direction and form a first battery pack, the first direction is perpendicular to the length direction of the battery pack, and a plurality of the first battery packs are arranged along the length direction of the battery pack.

11. The battery pack of claim 1 or 2, wherein, The shell of the sodium-ion battery and the shell of the lithium-ion battery are arranged along the first direction, one of the lithium-ion battery and one of the sodium-ion battery are arranged along the first direction and form a first battery pack, the first direction is parallel to the length direction of the battery pack, the battery pack further comprises a plurality of lithium-ion batteries, the plurality of lithium-ion batteries are arranged along the length direction of the battery pack and form a second battery pack, and the length of the second battery pack is consistent with the length of the first battery pack along the length direction of the battery pack.

12. An energy storage device, characterized by The energy storage device comprises a battery management system and a plurality of battery packs according to any one of claims 1-11, and the battery management system is used to collect voltage data of the sodium-ion battery and calculate the state of charge of the battery pack according to the collected voltage data of the sodium-ion battery.

13. A method for measuring the state of charge of a battery pack as claimed in any one of the preceding claims 1-11, characterized by, The method comprises: Collecting voltage data of the sodium-ion battery; According to the collected voltage data of the sodium-ion battery, the state of charge of the battery pack is calculated.

14. The method of measuring state of charge of a battery pack of claim 13, wherein, Before the step of collecting voltage data of the sodium-ion battery, the method further comprises the following steps: Measuring and obtaining the corresponding curves of the voltage of the sodium-ion battery and the state of charge of the battery pack under different states; In the step of calculating the state of charge of the battery pack according to the collected voltage data of the sodium-ion battery, the voltage data of the sodium-ion battery collected is used to calculate the state of charge of the battery pack based on the corresponding curves.

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