Energy storage battery pack and energy storage system

Abstract

The invention provides an energy storage battery pack and an energy storage system. The energy storage battery pack comprises at least one sodium ion battery cell and a plurality of lithium iron phosphate battery cells. The at least one sodium ion battery cell and the plurality of lithium iron phosphate battery cells are connected in series to form the hybrid battery pack, and the capacity of the sodium ion battery cell is greater than that of the lithium iron phosphate battery cell. According to the energy storage battery pack provided by the invention, the sodium ion battery cells are introduced, and the number ratio of the sodium ion battery cells in the energy storage battery pack is set to be 10-50%, so that the problem that the state of charge of an existing lithium iron phosphate battery cannot be accurately estimated is solved.

Description

Technical Field

[0001] The present application relates to the field of power electronics technology, and in particular to an energy storage battery pack and an energy storage system. Background Art

[0002] The state of charge (SOC) estimation of energy storage batteries is a core issue in battery management systems (BMS), so accurate estimation of the battery's state of charge will help extend the battery's service life.

[0003] At present, lithium iron phosphate batteries have excellent safety performance, so in recent years, more and more energy storage products using lithium iron phosphate batteries have been launched on the market. However, due to the characteristics of lithium iron phosphate plateau, it is impossible to accurately estimate the state of charge of the battery. Summary of the invention

[0004] In view of the above, the present application provides an energy storage battery pack and an energy storage system. The energy storage battery pack and the energy storage system of the present application can solve the problem that the existing lithium iron phosphate battery cannot accurately estimate its state of charge.

[0005] A first aspect of the present application provides an energy storage battery pack, the energy storage battery pack comprising: at least one sodium-ion battery cell; A plurality of lithium iron phosphate battery cells; at least one sodium ion battery cell and a plurality of lithium iron phosphate battery cells are connected in series to form a hybrid battery pack; Among them, the capacity of sodium-ion batteries is greater than that of lithium iron phosphate batteries, and the proportion of sodium-ion batteries in the energy storage battery pack is between 10% and 50%.

[0006] The energy storage battery pack of the present application is based on a mixed series connection of lithium iron phosphate cells and sodium ion cells to form an energy storage battery pack. Compared with the existing lithium iron phosphate battery pack, by introducing sodium ion cells into the energy storage battery pack, and by setting the number of sodium ion cells in the energy storage battery pack to between 10% and 50%, the problem that the existing lithium iron phosphate battery cannot accurately estimate its state of charge can be solved.

[0007] As an optional implementation, the operating voltage range of the lithium iron phosphate battery cell is within the operating voltage range of the sodium ion battery cell.

[0008] As an optional implementation, the capacity of the sodium ion battery cell is at least 1.5 times greater than the capacity of the lithium iron phosphate battery cell.

[0009] As an optional implementation, the discharge current of the sodium ion battery cell is greater than the discharge current of the lithium iron phosphate battery cell, and the charging current of the sodium ion battery cell is greater than the charging current of the lithium iron phosphate battery cell.

[0010] As an optional implementation, at least one sodium ion battery cell and a plurality of lithium iron phosphate battery cells are spatially arranged according to a first preset number of rows and a second preset number of columns.

[0011] A second aspect of the present application further provides an energy storage system, the energy storage system comprising a battery management system and at least one energy storage battery pack, the energy storage battery pack comprising: at least one sodium-ion battery cell; A plurality of lithium iron phosphate cells; at least one sodium ion cell is connected in series with a plurality of lithium iron phosphate cells to form a hybrid battery pack; wherein the capacity of the sodium ion cell is greater than the capacity of the lithium iron phosphate cell, and the number of sodium ion cells in the energy storage battery pack accounts for between 10% and 50%; The battery management system is electrically connected to the energy storage battery pack. The battery management system is used to obtain parameters of the sodium ion battery cell and parameters of multiple lithium iron phosphate battery cells, and determine the charge state of the energy storage system based on the parameters of the sodium ion battery cell and parameters of multiple lithium iron phosphate battery cells.

[0012] As an optional implementation, the operating voltage range of the lithium iron phosphate battery cell is within the operating voltage range of the sodium ion battery cell.

[0013] As an optional implementation, the capacity of the sodium ion battery cell is at least 1.5 times greater than the capacity of the lithium iron phosphate battery cell.

[0014] As an optional implementation, at least one sodium ion battery cell and a plurality of lithium iron phosphate battery cells are spatially arranged according to a first preset number of rows and a second preset number of columns.

[0015] As an optional implementation, the energy storage system also includes a power converter, which is electrically connected between the energy storage battery pack and the power generation system, or between the energy storage battery pack and the electrical equipment.

[0016] The energy storage system of the present application is based on a mixed series connection of lithium iron phosphate cells and sodium ion cells to form an energy storage battery pack. Compared with the existing lithium iron phosphate battery pack, sodium ion cells are introduced into the energy storage battery pack, and the proportion of sodium ion cells in the energy storage battery pack is set to between 10% and 50%. The state parameters of the entire energy storage system can be estimated by the charge state of the sodium ion cells, which can solve the problem that the existing lithium iron phosphate battery cannot accurately estimate its charge state. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0018] Figure 1 This is an application scenario diagram of an energy storage system provided in an embodiment of the present application.

[0019] Figure 2 This is another application scenario diagram of an energy storage system provided in an embodiment of the present application.

[0020] Figure 3 It is a schematic diagram of an energy storage system provided in an embodiment of the present application.

[0021] Figure 4 It is a schematic diagram of an energy storage battery pack provided in an embodiment of the present application.

[0022] Figure 5 This is another schematic diagram of an energy storage battery pack provided in an embodiment of the present application.

[0023] Figure 6 This is another schematic diagram of an energy storage battery pack provided in an embodiment of the present application.

[0024] Figure 7 This is another schematic diagram of an energy storage battery pack provided in an embodiment of the present application. DETAILED DESCRIPTION

[0025] In the embodiments of the present application, the words "first", "second", etc. are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance, nor can they be understood as indicating or implying order. For example, the first application, the second application, etc. are used to distinguish different applications, rather than to describe a specific order of applications. The features defined as "first" or "second" may explicitly or implicitly include one or more of the features.

[0026] The state of charge (SOC) estimation of energy storage batteries is a core issue in the battery management system (BMS), so accurate estimation of the battery's SOC will help extend the battery's service life.

[0027] At present, lithium iron phosphate batteries have excellent safety performance, so in recent years, more and more energy storage products using lithium iron phosphate batteries have been launched on the market. However, due to the characteristics of lithium iron phosphate plateau, it is impossible to accurately estimate the state of charge of the battery.

[0028] In view of the above problems, the embodiments of the present application provide an energy storage battery pack and an energy storage system. The present application can construct a hybrid series battery pack by using a hybrid series connection of lithium iron phosphate cells and sodium ion cells in the energy storage battery pack.

[0029] The present application is based on an energy storage battery pack in which lithium iron phosphate cells and sodium ion cells are mixed in series. Compared with lithium ion battery packs, the present application introduces sodium ion cells into the energy storage battery pack and sets the proportion of sodium ion cells in the energy storage battery pack to between 10% and 50%. The state parameters of the entire energy storage system can be estimated by the state of charge of the sodium ion cells, wherein the state parameters may include the state of charge (SOC), state of health (SOH), and state of power (SOP). The present application can solve the problem that the existing lithium iron phosphate battery cannot accurately estimate its state parameters, especially the state of charge.

[0030] See also Figure 1 , is an application schematic diagram of an energy storage system 200 provided in one embodiment of the present application.

[0031] In one application scenario, the energy storage system 200 is electrically connected to the power-consuming device 300. The energy storage system 200 can be used to supply power to the power-consuming device 300.

[0032] In the present application, the electrical equipment 300 refers to equipment powered by electric energy, including electric water heaters, electric fans, hair dryers, vacuum cleaners, sweeping robots and other household electrical appliances.

[0033] See also Figure 2 , is another application schematic diagram of the energy storage system 200 provided in one embodiment of the present application.

[0034] In another application scenario, the energy storage system 200 is electrically connected to the power generation system 400. The power generation system 400 can be used to supply power to the energy storage system 200.

[0035] It can be understood that in an optional implementation, the power generation system 400 can be a photovoltaic power generation system, which can convert solar energy into usable electrical energy, output the electrical energy to the energy storage system 200, and charge the energy storage system 200. In other optional implementations, the power generation system 400 can also be other new energy power generation systems or power grids.

[0036] See also Figure 3 , is a schematic diagram of an energy storage system 200 provided in one embodiment of the present application.

[0037] In this embodiment, the energy storage system 200 may include a power converter 201, a battery management system 202, and a plurality of energy storage battery packs connected in series. Figure 3Taking three energy storage battery packs 100a, 100b, and 100c as an example for illustration, in a possible embodiment, the number of energy storage battery packs may be more than three or less than three. Figure 3 As shown, multiple energy storage battery packs 100a, 100b, and 100c are connected in series. It can be understood that in other possible implementations, multiple energy storage battery packs 100a, 100b, and 100c can also be connected in parallel.

[0038] The energy storage battery pack 100a can be connected to the battery management system 202 through the communication bus 101a to achieve communication between the energy storage battery pack 100a and the battery management system 202. The energy storage battery pack 100b can be connected to the battery management system 202 through the communication bus 101b to achieve communication between the energy storage battery pack 100b and the battery management system 202. The energy storage battery pack 100c can be connected to the battery management system 202 through the communication bus 101c to achieve communication between the energy storage battery pack 100c and the battery management system 202. The battery management system 202 can also be connected to the power converter 201 through the communication bus 101d to achieve communication between the power converter 201 and the battery management system 202. In a possible example, the energy storage battery pack 100a is connected to the battery management system 202 through a controller area network (CAN) bus, the energy storage battery pack 100b can be connected to the battery management system 202 through a CAN communication bus, and the energy storage battery pack 100c can be connected to the battery management system 202 through a CAN communication bus. The battery management system 202 may also be connected to the power converter 201 via a CAN communication bus. It is understood that, in another possible example, the communication buses 101a, 101b, 101c, 101d may also be RS485 buses.

[0039] In one example, one end of the power converter 201 is electrically connected to the positive electrode of the energy storage battery pack 100a, and the other end of the power converter 201 is also electrically connected to the negative electrode of the energy storage battery pack 100a. One end of the battery management system 202 is electrically connected to the connection point between the positive electrode of the energy storage battery pack 100a and the power converter 201, and the other end of the battery management system 202 is electrically connected to the connection point between the negative electrode of the energy storage battery pack 100a and the power converter 201.

[0040] Based on this approach, in an embodiment of the present application, the battery management system 202 can obtain battery parameters of the energy storage battery packs 100a, 100b, and 100c, and the battery management system 202 can also estimate state parameters of the energy storage system 200 based on the obtained parameters.

[0041] In a scenario where the energy storage system 200 supplies power to an electrical device 300 , the electrical device 300 is electrically connected to a power converter 201 , and the series-connected energy storage battery packs 100 a , 100 b , and 100 c provide electrical energy to the electrical device 200 through the power converter 201 .

[0042] In a scenario where the power generation system 400 supplies power to the energy storage system 200, the power generation system 400 is electrically connected to the power converter 201, and the power generation system 400 provides power to the series-connected energy storage battery packs 100a, 100b, and 100c through the power converter 201.

[0043] The energy storage battery pack 100a, the energy storage battery pack 100b and the energy storage battery pack 100c in this embodiment are hybrid battery packs. A hybrid battery pack refers to a battery pack formed by assembling two or more types of battery cells.

[0044] It is understood that the structures of the energy storage battery pack 100a, the energy storage battery pack 100b and the energy storage battery pack 100c are the same or different. In a preferred implementation, the structures of the energy storage battery pack 100a, the energy storage battery pack 100b and the energy storage battery pack 100c are the same. The structure of the energy storage battery pack 100a will be used as an example for illustration.

[0045] It can be understood that the energy storage battery pack in the present application may include at least one sodium ion battery cell and multiple lithium iron phosphate battery cells. At least one sodium ion battery cell can be connected in series with multiple lithium iron phosphate battery cells to form a hybrid battery pack. Among them, the capacity of the sodium ion battery cell is greater than the capacity of the lithium iron phosphate battery cell, and the number of sodium ion batteries in the energy storage battery pack accounts for between 10% and 50% (that is, the number of sodium ion batteries in the energy storage battery pack accounts for more than 10% and less than 50%).

[0046] The energy storage battery pack of the present application will be described in detail below in conjunction with specific embodiments.

[0047] See also Figure 4 , is a schematic diagram of an energy storage battery pack 100a provided in one embodiment of the present application.

[0048] like Figure 4 As shown, the energy storage battery pack 100a may include a plurality of battery cells. Specifically, the energy storage battery pack 100a includes at least one lithium iron phosphate battery cell and at least one sodium ion battery cell. Figure 4 One sodium ion battery cell and seven lithium iron phosphate battery cells are used as an example for illustration. It can be understood that in other possible embodiments, the number of lithium iron phosphate battery cells may be more than seven or less than seven, and the number of sodium ion battery cells may be greater than one.

[0049] In the specific implementation process, the energy storage battery pack 100a includes a sodium ion battery cell 21a, a lithium iron phosphate battery cell 31a, a lithium iron phosphate battery cell 32a, a lithium iron phosphate battery cell 33a, a lithium iron phosphate battery cell 34a, a lithium iron phosphate battery cell 35a, a lithium iron phosphate battery cell 36a, and a lithium iron phosphate battery cell 37a connected in series in sequence.

[0050] More specifically, the positive electrode of the lithium iron phosphate cell 31a is electrically connected to the negative electrode of the sodium ion cell 21a, the negative electrode of the lithium iron phosphate cell 31a is electrically connected to the positive electrode of the lithium iron phosphate cell 32a, the negative electrode of the lithium iron phosphate cell 32a is electrically connected to the positive electrode of the lithium iron phosphate cell 33a, the negative electrode of the lithium iron phosphate cell 33a is electrically connected to the positive electrode of the lithium iron phosphate cell 34a, the negative electrode of the lithium iron phosphate cell 34a is electrically connected to the positive electrode of the lithium iron phosphate cell 35a, the negative electrode of the lithium iron phosphate cell 35a is electrically connected to the positive electrode of the lithium iron phosphate cell 36a, and the negative electrode of the lithium iron phosphate cell 36a is electrically connected to the positive electrode of the lithium iron phosphate cell 37a. Therefore, the positive electrode of the sodium ion cell 21a can be used as the positive electrode of the energy storage battery pack 100a, and the negative electrode of the lithium iron phosphate cell 37a can be used as the negative electrode of the energy storage battery pack 100a. In an optional implementation, in order to ensure that the energy storage battery pack 100a can be assembled smoothly and reduce the volume of the energy storage battery pack 100a, the sodium ion battery cell 21a, the lithium iron phosphate battery cell 31a, the lithium iron phosphate battery cell 32a, the lithium iron phosphate battery cell 33a, the lithium iron phosphate battery cell 34a, the lithium iron phosphate battery cell 35a, the lithium iron phosphate battery cell 36a, and the lithium iron phosphate battery cell 37a can be arranged in an array structure.

[0051] In an optional implementation, the lithium iron phosphate cells and sodium ion cells in the energy storage battery pack 100a may be spatially arranged in a preset number of rows and columns.

[0052] As an example, the multiple cells of the energy storage battery pack 100a in the embodiment of the present application can be arranged in an array structure of 2 rows and 4 columns. Figure 4 As shown in the spatial arrangement, the first row from left to right is 1 sodium ion battery cell and 3 lithium iron phosphate battery cells, and the second row is arranged in sequence with 4 lithium iron phosphate battery cells. It can be understood that due to the plateau characteristics of the open circuit voltage (OCV) curve of the lithium iron phosphate battery cell, this will lead to a large error in the estimation of the state of charge of the lithium iron phosphate battery cell, especially in low temperature conditions, the capacity of the lithium iron phosphate battery cell changes greatly, and the deviation of the estimated state of charge of the lithium iron phosphate battery cell will be even greater. The OCV curve of the sodium ion battery cell is a positively proportional curve, that is, the OCV curve of the sodium ion battery cell does not have a plateau period. In the present application, the energy storage battery pack 100a is a hybrid battery pack of sodium ion batteries and lithium iron phosphate batteries, that is, the sodium ion battery cell is connected in series with multiple lithium iron phosphate batteries. Therefore, in the present application, the battery management system 202 can accurately estimate the state of charge of the energy storage system 200 through the state of charge of the sodium ion battery cell.

[0053] In the specific implementation process, the energy storage battery pack 100a includes a controller (not shown in the figure), which will collect the voltage of the sodium ion battery cell and the voltage of the lithium iron phosphate battery cell, and transmit the collected voltage of the sodium ion battery cell and the voltage of the lithium iron phosphate battery cell to the battery management system 202 through the communication bus. The battery management system 202 can sample the parameters of the sodium ion battery cell (i.e., the voltage, current, and temperature parameters of the sodium ion battery cell) and the parameters of multiple lithium iron phosphate battery cells (i.e., the voltage, current, and temperature parameters of multiple lithium iron phosphate battery cells), and obtain the state of charge parameters of the sodium ion battery cell according to the parameters of the sodium ion battery cell, and obtain the state of charge parameters of multiple lithium iron phosphate battery cells according to the parameters of multiple lithium iron phosphate battery cells. The battery management system 202 can perform fusion operations based on the state of charge of the sodium ion battery cell, the highest state of charge among the multiple lithium iron phosphate battery cells, and the lowest state of charge among the multiple lithium iron phosphate battery cells, so as to accurately estimate the state of charge of the energy storage system 200.

[0054] In an optional implementation, in order to fully release the power of the energy storage battery pack, the capacity of the sodium ion battery cell is greater than the capacity of the lithium iron phosphate battery cell. Taking the sodium ion battery cell 21a and the lithium iron phosphate battery cell 31a as an example, the capacity of the sodium ion battery cell 21a is greater than the capacity of the lithium iron phosphate battery cell 31a.

[0055] In another more specific implementation, the capacity of the sodium ion battery is at least 1.5 times greater than the capacity of the lithium iron phosphate battery. Taking the sodium ion battery 21a and the lithium iron phosphate battery 31a as examples, the capacity of the sodium ion battery 21a is at least 1.5 times greater than the capacity of the lithium iron phosphate battery 31a.

[0056] In an optional implementation, the operating voltage range of the lithium-ion battery cell covers the operating voltage range of the lithium iron phosphate battery cell, that is, the operating voltage range of the lithium iron phosphate battery cell is within the operating voltage range of the lithium-ion battery cell. As an example, taking the sodium ion battery cell 21a and the lithium iron phosphate battery cell 31a as examples, the operating voltage of the lithium iron phosphate battery cell 31a is greater than the first voltage threshold and less than the second voltage threshold. The minimum value of the operating voltage of the sodium ion battery cell 21a is less than or equal to the first threshold, and the maximum value of the operating voltage of the sodium ion battery cell 21a is greater than or equal to the second threshold. For example, the operating voltage of the lithium iron phosphate battery cell 31a is greater than 2.5V and less than 3.6V. The minimum value of the operating voltage of the sodium ion battery cell 21a is less than or equal to 2.5V, and the maximum value of the operating voltage of the sodium ion battery cell 21a is greater than or equal to 3.6V.

[0057] In an optional implementation, the charging current of the sodium ion battery is greater than the charging current of the lithium iron phosphate battery. The discharging current of the sodium ion battery is greater than the discharging current of the lithium iron phosphate battery.

[0058] In the above Figure 4 In the embodiment shown, the sodium ion battery cell is located at the positive terminal of the energy storage battery pack 100a. In addition, the number of sodium ion batteries in the energy storage battery pack 100a is 1, and the number of lithium iron phosphate batteries is 8, that is, the number of sodium ion batteries in the energy storage battery pack 100a accounts for 12.5%. In other words, in the energy storage battery pack in this embodiment, the number of sodium ion batteries in the energy storage battery pack 100a accounts for between 10% and 50%.

[0059] See also Figure 5 , is a schematic diagram of an energy storage battery pack 100a provided in another embodiment of the present application.

[0060] and Figure 4 The embodiment shown differs in that Figure 5 As shown, in this embodiment, the energy storage battery pack 100a includes two sodium ion cells, and the two sodium ion cells are respectively located at the positive terminal and the negative terminal of the energy storage battery pack 100a.

[0061] Specifically, the energy storage battery pack 100a in this embodiment includes a sodium ion battery cell 21a, a lithium iron phosphate battery cell 31a, a lithium iron phosphate battery cell 32a, a lithium iron phosphate battery cell 33a, a lithium iron phosphate battery cell 34a, a lithium iron phosphate battery cell 35a, a lithium iron phosphate battery cell 36a, and a sodium ion battery cell 22a connected in series in sequence.

[0062] More specifically, the positive electrode of the lithium iron phosphate cell 31a is electrically connected to the negative electrode of the sodium ion cell 21a, the negative electrode of the lithium iron phosphate cell 31a is electrically connected to the positive electrode of the lithium iron phosphate cell 32a, the negative electrode of the lithium iron phosphate cell 32a is electrically connected to the positive electrode of the lithium iron phosphate cell 33a, the negative electrode of the lithium iron phosphate cell 33a is electrically connected to the positive electrode of the lithium iron phosphate cell 34a, the negative electrode of the lithium iron phosphate cell 34a is electrically connected to the positive electrode of the lithium iron phosphate cell 35a, the negative electrode of the lithium iron phosphate cell 35a is electrically connected to the positive electrode of the lithium iron phosphate cell 36a, and the negative electrode of the lithium iron phosphate cell 36a is electrically connected to the positive electrode of the sodium ion cell 22a. Therefore, the positive electrode of the sodium ion cell 21a can be used as the positive electrode of the energy storage battery pack 100a, and the negative electrode of the sodium ion cell 22a can be used as the negative electrode of the energy storage battery pack 100a.

[0063] In this embodiment, the multiple cells of the energy storage battery pack 100a are arranged in an array structure of 2 rows and 4 columns. Figure 5 As shown in the spatial arrangement, the first row from left to right is 1 sodium-ion battery cell and 3 lithium iron phosphate battery cells, and the second row from right to left is 3 lithium iron phosphate battery cells and 1 sodium-ion battery cell.

[0064] It can be understood that in this embodiment, six lithium iron phosphate cells are spaced between the two sodium ion cells 21 a and 22 a.

[0065] In the above Figure 5 In the embodiment shown, two sodium ion cells are respectively located at the positive terminal and the negative terminal of the energy storage battery pack 100a. In addition, the number of sodium ion cells in the energy storage battery pack 100a is 2, and the number of lithium iron phosphate cells is 6, that is, the number of sodium ion cells in the energy storage battery pack 100a accounts for 25%. In other words, in the energy storage battery pack in this embodiment, the number of sodium ion cells in the energy storage battery pack 100a accounts for between 10% and 50%.

[0066] See also Figure 6 , is a schematic diagram of an energy storage battery pack 100a provided in another embodiment of the present application.

[0067] and Figure 5 The embodiment shown differs in that Figure 6 As shown, in this embodiment, the energy storage battery pack 100a includes four sodium ion cells, and the four sodium ion cells are located at four corners of the array structure.

[0068] Specifically, the energy storage battery pack 100a in this embodiment includes a sodium ion cell 21a, a lithium iron phosphate cell 30a, a lithium iron phosphate cell 35a, a lithium iron phosphate cell 32a, a sodium ion cell 22a, a sodium ion cell 23a, a lithium iron phosphate cell 33a, a lithium iron phosphate cell 36a, a lithium iron phosphate cell 34a and a sodium ion cell 24a connected in series in sequence.

[0069] More specifically, in the embodiment of the present application, the positive electrode of the lithium iron phosphate battery cell 30a is electrically connected to the negative electrode of the sodium ion battery cell 21a, the negative electrode of the lithium iron phosphate battery cell 30a is electrically connected to the positive electrode of the lithium iron phosphate battery cell 35a, the negative electrode of the lithium iron phosphate battery cell 35a is electrically connected to the positive electrode of the lithium iron phosphate battery cell 32a, the negative electrode of the lithium iron phosphate battery cell 32a is electrically connected to the positive electrode of the sodium ion battery cell 22a, the negative electrode of the sodium ion battery cell 22a is electrically connected to the positive electrode of the sodium ion battery cell 23a, the negative electrode of the sodium ion battery cell 23a is electrically connected to the positive electrode of the lithium iron phosphate battery cell 33a, the negative electrode of the lithium iron phosphate battery cell 33a is electrically connected to the positive electrode of the lithium iron phosphate battery cell 36a, the negative electrode of the lithium iron phosphate battery cell 36a is electrically connected to the positive electrode of the lithium iron phosphate battery cell 34a, and the negative electrode of the lithium iron phosphate battery cell 34a is electrically connected to the positive electrode of the sodium ion battery cell 24a. Therefore, the positive electrode of the sodium ion battery cell 21a can be used as the positive electrode of the energy storage battery pack 100a, and the negative electrode of the sodium ion battery cell 24a can be used as the negative electrode of the energy storage battery pack 100a.

[0070] In the embodiment of the present application, the multiple cells of the energy storage battery pack 100a are arranged in an array structure of 2 rows and 4 columns. Figure 6 As shown in the spatial arrangement, the first row from left to right includes 1 sodium ion battery cell, 3 lithium iron phosphate battery cells and 1 sodium ion battery cell, and the second row from right to left includes 1 sodium ion battery cell, 3 lithium iron phosphate battery cells and 1 sodium ion battery cell.

[0071] It can be understood that in this embodiment, there are three lithium iron phosphate cells between the sodium ion battery cell 21a and the sodium ion battery cell 22a, and there are three lithium iron phosphate cells between the sodium ion battery cell 23a and the sodium ion battery cell 24a.

[0072] It can be understood that if the number of sodium ion cells in the energy storage battery pack is greater than 2, in addition to placing 2 sodium ion cells at both ends of the energy storage battery pack, the remaining sodium ion cells need to be evenly interspersed between the lithium iron phosphate cells. Figure 6 In the illustrated embodiment, four sodium ion cells are located at the four corners of the array structure, and two sodium ion cells are located at the positive terminal and the negative terminal of the energy storage battery pack 100a, respectively, so that the energy storage battery pack 100a is balanced as a whole. In addition, the number of sodium ion cells in the energy storage battery pack 100a is 4, and the number of lithium iron phosphate cells is 6, that is, the number of sodium ion cells in the energy storage battery pack 100a accounts for 40%. In other words, in the energy storage battery pack in this embodiment, the number of sodium ion cells in the energy storage battery pack 100a accounts for between 10% and 50%.

[0073] See also Figure 7 , is a schematic diagram of an energy storage battery pack 100a provided in another embodiment of the present application.

[0074] and Figure 5 The embodiment shown differs in that Figure 7 As shown, in this embodiment, the energy storage battery pack 100a includes two sodium ion cells, the two sodium ion cells are located in the middle of the array structure, and four lithium iron phosphate cells are located at the four corners of the array structure.

[0075] The energy storage battery pack 100a in this embodiment includes a lithium iron phosphate cell 31a, a sodium ion cell 21a, a lithium iron phosphate cell 32a, a lithium iron phosphate cell 33a, a lithium iron phosphate cell 34a, a lithium iron phosphate cell 35a, a sodium ion cell 22a, and a lithium iron phosphate cell 36a connected in series in sequence.

[0076] Specifically, the positive electrode of the sodium ion battery cell 21a is electrically connected to the negative electrode of the lithium iron phosphate battery cell 31a, the negative electrode of the sodium ion battery cell 21a is electrically connected to the positive electrode of the lithium iron phosphate battery cell 32a, the negative electrode of the lithium iron phosphate battery cell 32a is electrically connected to the positive electrode of the lithium iron phosphate battery cell 33a, the negative electrode of the lithium iron phosphate battery cell 33a is electrically connected to the positive electrode of the lithium iron phosphate battery cell 34a, the negative electrode of the lithium iron phosphate battery cell 34a is electrically connected to the positive electrode of the lithium iron phosphate battery cell 35a, the negative electrode of the lithium iron phosphate battery cell 35a is electrically connected to the positive electrode of the sodium ion battery cell 22a, and the negative electrode of the sodium ion battery cell 22a is electrically connected to the positive electrode of the lithium iron phosphate battery cell 36a. Therefore, the positive electrode of the lithium iron phosphate battery cell 31a can be used as the positive electrode of the energy storage battery pack 100a, and the negative electrode of the lithium iron phosphate battery cell 36a can be used as the negative electrode of the energy storage battery pack 100a.

[0077] It can be understood that in this embodiment, there are four lithium iron phosphate cells between the sodium ion cell 21 a and the sodium ion cell 22 a .

[0078] In the above Figure 7 In the embodiment shown, two lithium iron phosphate cells are respectively located at the positive terminal and the negative terminal of the energy storage battery pack 100a. In addition, the number of sodium ion cells in the energy storage battery pack 100a is 2, and the number of lithium iron phosphate cells is 6, that is, the number of sodium ion cells in the energy storage battery pack 100a accounts for 25%. In other words, in the energy storage battery pack in this embodiment, the number of sodium ion cells in the energy storage battery pack 100a accounts for between 10% and 50%.

[0079] Understandably, Figure 5 The embodiment of the present invention arranges the sodium ion battery cell at the positive terminal and the negative terminal of the battery pack, and Figure 5 The difference of the embodiment is that Figure 7 In an embodiment, the sodium ion battery cell is arranged in the middle of the six lithium iron phosphate battery cells. Figure 5 Examples and Figure 7 The energy storage battery pack of the embodiment has a similar effect on the state of charge estimation.

[0080] Sodium-ion cells have better thermal stability than lithium iron phosphate cells. When placed in the middle of the energy storage battery pack, sodium-ion cells experience a significant temperature rise and have a poor cycle life. If they are exposed to high temperatures for a long time, their health status will decline rapidly, which will adversely affect the estimation of the state of charge. Therefore, in some possible implementations, for example Figure 5 In the energy storage battery pack 100a shown in the embodiment, the sodium ion battery cell is arranged at the positive terminal or the negative terminal, so as to ensure that the sodium ion battery cell can be at a more suitable temperature.

[0081] It is understandable that the above Figure 4 Embodiments of Figure 5 Embodiments of Figure 6 Examples and Figure 7 The energy storage battery pack 100a shown in the embodiment is a possible example of the energy storage battery pack structure. The present application does not limit the number and position of the sodium ion cells and lithium iron phosphate cells in the energy storage battery pack.

[0082] It is understandable that in some traditional energy storage battery pack structures, if the number of sodium ion cells in the energy storage battery pack is less than 10%, that is, the state of charge of one sodium ion cell needs to correct the state of charge of multiple (for example, 15 or 20) lithium iron phosphate batteries, the correction effect will be affected by the slight inconsistency within these lithium iron phosphate batteries, and the correction effect is poor and the stability is not high, making the battery's estimate of the state of charge not very accurate. If the number of sodium ion cells in the energy storage battery pack is greater than 50%, since the cycle life of sodium ion cells is shorter than that of lithium iron phosphate batteries, if too many sodium ion cells are placed in an energy storage battery pack, the health state of the batteries in the energy storage battery pack will be uneven because the life of the sodium ion cells decays faster than that of the lithium iron phosphate cells, which affects the health state of the energy storage battery pack, thereby affecting the accuracy of the energy storage battery pack's state of charge estimation.

[0083] It can be understood that compared with the traditional energy storage battery pack structure, the above Figure 4 Example Figure 5 Example Figure 6 Examples and Figure 7 In the energy storage battery pack 100a shown in the embodiment, the number of sodium ion cells in the energy storage battery pack 100a accounts for between 10% and 50%. Such a design can make the energy storage battery pack estimate the state of charge more accurately.

[0084] In order to make the invention purpose, technical scheme and technical effect of the present application clearer, the present application is further described in detail in combination with comparative examples and embodiments. The comparative examples 1 and 2 described below both use the energy storage battery pack structure in the prior art to estimate the state of charge. Embodiment 1 uses the energy storage battery pack structure of the present application to estimate the state of charge.

[0085] Comparative Example 1 It should be noted that what is disclosed in Comparative Example 1 is an energy storage battery pack structure using the prior art to perform state of charge estimation.

[0086] In comparative example 1, the energy storage battery pack includes 1 sodium ion battery cell and 15 lithium iron phosphate battery cells, wherein 1 sodium ion battery cell and 15 lithium iron phosphate battery cells are connected in series, and the sodium ion battery cell is located at the positive terminal of the energy storage battery pack. In the energy storage battery pack of comparative example 1, the number of sodium ion batteries in the energy storage battery pack accounts for 6.25%.

[0087] Comparative Example 2 It should be noted that what is disclosed in Comparative Example 2 is an energy storage battery pack structure using the prior art to perform state of charge estimation.

[0088] In comparative example 2, the energy storage battery pack includes 8 lithium iron phosphate cells connected in series. In other words, the energy storage battery pack of comparative example 2 does not include sodium ion cells.

[0089] Example 1 It should be noted that the embodiment 1 discloses the use of Figure 4 The energy storage battery pack structure shown is used to perform the state of charge estimation.

[0090] In Example 1, the energy storage battery pack 100a includes 1 sodium ion battery cell and 7 lithium iron phosphate battery cells, wherein 1 sodium ion battery cell and 7 lithium iron phosphate battery cells are connected in series, and the sodium ion battery cell is located at the positive terminal of the energy storage battery pack. In the energy storage battery pack of Example 1, the number of sodium ion batteries in the energy storage battery pack accounts for 12.5%.

[0091] The estimated results of the state of charge of the energy storage battery packs of Comparative Examples 1, 2 and Example 1 are recorded and recorded in Table 1 below.

[0092] It can be seen from Table 1 above that the number of sodium ion cells in Comparative Examples 1 and 2 in the energy storage battery pack is not between 10%-50%, and the number of sodium ion cells in Example 1 in the energy storage battery pack 100a is between 10%-50%. The state of charge estimation effect of the energy storage battery packs of Example 1 and Comparative Example 1 is better than the state of charge estimation effect of the energy storage battery pack of Comparative Example 2. The energy storage battery pack of Comparative Example 1 has a large jitter at a high state of charge or a low state of charge, and the stability of the state of charge estimation effect is not high. The energy storage battery pack of Example 1 is also more accurate in the estimation during the plateau period. Compared with the energy storage battery pack structure of Comparative Example 1, the average error of the energy storage battery pack of Example 1 is smaller, and the state of charge estimation effect of the energy storage battery pack of Example 1 is more stable. The estimation of the state of charge of the energy storage battery packs of Comparative Examples 1 and 2 has a large deviation compared with the estimation of the state of charge of the energy storage battery pack of Example 1.

[0093] The present application is based on an energy storage battery pack in which lithium iron phosphate cells and sodium ion cells are mixed in series. Compared with the existing lithium iron phosphate battery pack, sodium ion cells are introduced, and the proportion of sodium ion cells in the energy storage battery pack is set between 10% and 50%. The state of charge of the sodium ion cells can be used to estimate the state parameters of the entire energy storage system, which can solve the problem that the existing lithium iron phosphate battery cannot accurately estimate its state of charge.

[0094] It is obvious to those skilled in the art that the present application is not limited to the details of the above exemplary embodiments, and that the present application can be implemented in other specific forms without departing from the spirit or basic features of the present application. Therefore, as long as they are within the scope of the essence and spirit of the present application, appropriate changes and modifications made to the above embodiments should fall within the scope of protection claimed in the present application.

Claims

1. An energy storage battery pack, characterized in that: The energy storage battery pack comprises: at least one sodium-ion battery cell; A plurality of lithium iron phosphate battery cells; the at least one sodium ion battery cell is connected in series with the plurality of lithium iron phosphate battery cells to form a hybrid battery pack; Among them, the capacity of the sodium ion battery cell is greater than that of the lithium iron phosphate battery cell, and the number of the sodium ion battery cells in the energy storage battery pack accounts for between 10% and 50%.

2. The energy storage battery pack according to claim 1, characterized in that: The operating voltage range of the lithium iron phosphate battery cell is within the operating voltage range of the sodium ion battery cell.

3. The energy storage battery pack according to claim 1 or 2, characterized in that: The capacity of the sodium ion battery cell is at least 1.5 times greater than the capacity of the lithium iron phosphate battery cell.

4. The energy storage battery pack according to claim 1, characterized in that: The discharge current of the sodium ion battery cell is greater than the discharge current of the lithium iron phosphate battery cell, and the charging current of the sodium ion battery cell is greater than the charging current of the lithium iron phosphate battery cell.

5. The energy storage battery pack according to claim 1, characterized in that: The at least one sodium ion battery cell and the plurality of lithium iron phosphate battery cells are spatially arranged according to a first preset number of rows and a second preset number of columns.

6. An energy storage system, characterized in that: The energy storage system includes a battery management system and at least one energy storage battery pack, and the energy storage battery pack includes: at least one sodium-ion battery cell; A plurality of lithium iron phosphate cells; the at least one sodium ion cell is connected in series with the plurality of lithium iron phosphate cells to form a hybrid battery pack; wherein the capacity of the sodium ion cell is greater than the capacity of the lithium iron phosphate cell, and the number of the sodium ion cells in the energy storage battery pack accounts for between 10% and 50%; The battery management system is electrically connected to the energy storage battery pack, and is used to obtain parameters of the sodium ion battery cell and parameters of the multiple lithium iron phosphate battery cells, and determine the charge state of the energy storage system according to the parameters of the sodium ion battery cell and the parameters of the multiple lithium iron phosphate battery cells.

7. The energy storage system according to claim 6, characterized in that: The operating voltage range of the lithium iron phosphate battery cell is within the operating voltage range of the sodium ion battery cell.

8. The energy storage system according to claim 6, characterized in that: The capacity of the sodium ion battery cell is at least 1.5 times greater than the capacity of the lithium iron phosphate battery cell.

9. The energy storage system according to claim 6, characterized in that: The at least one sodium ion battery cell and the plurality of lithium iron phosphate battery cells are spatially arranged according to a first preset number of rows and a second preset number of columns.

10. The energy storage system according to claim 6, characterized in that: Also includes a power converter, The power converter is electrically connected between the energy storage battery pack and the power generation system, or the power converter is electrically connected between the energy storage battery pack and the electrical equipment.

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