Energy storage device and power utilization system

Abstract

The invention relates to an energy storage device and a power utilization system. The energy storage device comprises a first battery module and a second battery module, wherein the first battery module comprises a first diaphragm; the second battery module is connected with the first battery module in parallel, and the second battery module comprises a second diaphragm; the thermal shrinkage rate of the first diaphragm along a preset direction at 150 DEG C is smaller than that of the second diaphragm along the preset direction at 150 DEG C, and the preset direction is the height direction of the first battery module.

Description

Technical Field

[0001] The present application relates to the field of energy storage technology, and in particular to an energy storage device and an electricity consumption system. Background Art

[0002] With the continuous development of energy storage technology, the capacity of energy storage devices has gradually increased. However, large-capacity energy storage devices all have the safety problem of high temperature when the battery cell thermal runaway occurs, which is easy to cause the battery cell thermal runaway fire. Therefore, it is necessary to design the battery cell for safety, reduce the intensity of the reaction when the battery cell thermal runaway occurs, and reduce the maximum temperature of the module to improve the safety performance of the module. Summary of the invention

[0003] In view of this, the present application provides an energy storage device and an electricity consumption system, wherein the energy storage device has good safety performance.

[0004] The present application provides an energy storage device, which includes: a first battery module and a second battery module, the first battery module includes a first diaphragm; the second battery module is connected in parallel with the first battery module, and the second battery module includes a second diaphragm; the thermal shrinkage rate of the first diaphragm along a preset direction at 150°C is less than the thermal shrinkage rate of the second diaphragm along a preset direction at 150°C, wherein the preset direction is the height direction of the first battery module.

[0005] Furthermore, the thermal shrinkage rate of the first diaphragm along the preset direction at 150° C. is η1, and the thermal shrinkage rate of the second diaphragm along the preset direction at 150° C. is η2, and the relationship is satisfied: 0.14%≤η1 / η2≤66.67%.

[0006] Furthermore, the range of the heat shrinkage rate η1 of the first diaphragm along the preset direction at 150°C is: 0.1%≤η1≤20%, and the range of the heat shrinkage rate η2 of the second diaphragm along the preset direction at 150°C is: 30%≤η2≤70%.

[0007] Furthermore, the range of the time difference t between the first battery module and the second battery module reaching the maximum temperature of thermal runaway is: t≥1min, wherein thermal runaway refers to the temperature rise rate of the first battery module or the second battery module being greater than 3°C / s, and the temperature rise rate is the rate at which the temperature of the first battery module or the second battery module increases.

[0008] Furthermore, when the second battery module is short-circuited, the first battery module is discharged to reduce the remaining capacity of the first battery module.

[0009] Furthermore, the first battery module further comprises a first positive electrode sheet and a first negative electrode sheet, in which the first positive electrode sheet, the first diaphragm and the first negative electrode sheet are arranged in sequence; the second battery module further comprises a second positive electrode sheet and a second negative electrode sheet, in which the second positive electrode sheet, the second diaphragm and the second negative electrode sheet are arranged in sequence; the first positive electrode sheet comprises a first positive electrode active material, and the first positive electrode active material comprises lithium iron phosphate, lithium nickel cobalt manganese oxide, lithium cobalt oxide, iron pyrophosphate The first negative electrode plate comprises a first negative electrode active material, and the first negative electrode active material comprises at least one of graphite, silicon carbon, hard carbon, lithium titanate, and metallic lithium; the second positive electrode plate comprises a second positive electrode active material, and the second positive electrode active material comprises at least one of lithium iron phosphate, lithium nickel cobalt manganate, lithium cobaltate, sodium iron pyrophosphate, and sodium nickel cobalt manganate; the second negative electrode plate comprises a second negative electrode active material, and the second negative electrode active material comprises at least one of graphite, silicon carbon, hard carbon, lithium titanate, and metallic lithium.

[0010] Furthermore, the energy efficiency E of the energy storage device at 25° C. and 0.5P constant power charging and discharging is in the range of: 94%≤E<100%.

[0011] Furthermore, the energy storage device also includes a shell, the shell enclosing a accommodating cavity, and the accommodating cavity is used to accommodate the first battery module and the second battery module; the number of the first battery module is at least one, and the number of the second battery module is at least one; when the number of the first battery modules is multiple and the number of the second battery modules is multiple, the second battery module is arranged closer to the middle position of the accommodating cavity than the first battery module.

[0012] Furthermore, the first battery module is selected from at least one of a winding structure and a laminated structure, and the second battery module is selected from at least one of a winding structure and a laminated structure.

[0013] The present application also provides an electricity consumption system, which includes: an electricity-consuming device and an energy storage device provided in the present application, wherein the energy storage device is used to supply power to the electricity-consuming device.

[0014] In the present application, the first battery module and the second battery module are arranged in parallel, and when the energy storage device is in a normal charge and discharge cycle, the charge and discharge process of the first battery module and the charge and discharge process of the second battery module do not interfere with each other. In addition, the thermal shrinkage rate of the first diaphragm along the preset direction at 150°C is different from the thermal shrinkage rate of the second diaphragm along the preset direction at 150°C, so there is a difference between the first battery module and the second battery module. When one of the first battery module and the second battery module has thermal runaway, the other of the first battery module and the second battery module can delay the occurrence of thermal runaway or not have thermal runaway, so as to avoid the first battery module and the second battery module having thermal runaway at the same time, which makes it difficult to discharge the heat inside the energy storage device in time, thereby helping to reduce the maximum temperature inside the energy storage device, so as to reduce the probability of explosion and fire of the energy storage device due to excessive temperature, thereby improving the safety performance of the energy storage device. Specifically, the thermal shrinkage rate of the first diaphragm along the preset direction at 150°C is less than the thermal shrinkage rate of the second diaphragm along the preset direction at 150°C. At 150°C, the degree of thermal shrinkage of the first diaphragm in the preset direction is less than the degree of thermal shrinkage of the second diaphragm in the preset direction. Accordingly, the probability of short circuit inside the first battery module is less than the probability of short circuit inside the second battery module. The second battery module is more likely to have thermal runaway than the first battery module. When the second battery module has thermal runaway, the first battery module has not yet had thermal runaway, so that the heat generated by the second battery module when thermal runaway occurs can be dissipated through the housing, explosion-proof valve, exhaust channel, etc. of the energy storage device to slow down the temperature rise rate inside the energy storage device. Furthermore, the first battery module and the second battery module are arranged in parallel. When the second battery module has a short circuit due to thermal runaway, the first battery module will discharge to reduce the remaining power of the first battery module. If the remaining power of the first battery module decreases, that is, the charge of the first battery module decreases, it is helpful to reduce the reaction heat inside the first battery module, thereby extending the triggering time of thermal runaway of the first battery module, and / or reducing the severity of thermal runaway of the first battery module, and / or preventing the first battery module from thermal runaway, which is helpful to reduce the temperature rise rate inside the energy storage device. Even if the second battery module has thermal runaway, the temperature inside the energy storage device will not be too high. It is known that the smoke generated by the thermal runaway of the second battery module is a flammable gas, which can easily cause fire and explosion of the energy storage device under high temperature conditions.In the case of thermal runaway of the second battery module of the energy storage device of the present application, the differentiated design of the first battery module and the second battery module is adopted so that there is a time difference between the time when the thermal runaway occurs in the first battery module and the second battery module, and there is a time difference between the two large surfaces reaching the maximum temperature of thermal runaway, and there is also a time difference between the first battery module and the second battery module reaching the maximum temperature of thermal runaway, which greatly reduces the temperature rise rate inside the energy storage device, so that the temperature inside the energy storage device is not too high, which is beneficial to reduce the probability of fire and explosion of the energy storage device, so that the energy storage device has better safety performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the implementation will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0016] Figure 1 This is a schematic diagram of the structure of an energy storage device according to an embodiment of the present application;

[0017] Figure 2 A partial cross-sectional structural schematic diagram of a first battery module according to an embodiment of the present application;

[0018] Figure 3 A partial cross-sectional structural schematic diagram of a second battery module according to an embodiment of the present application;

[0019] Figure 4 Thermal runaway voltage and temperature curves for implementing device 1;

[0020] Figure 5 The thermal runaway voltage and temperature curves of device 1 are compared;

[0021] Figure 6 This is a schematic diagram of the structure of an electric power system according to an embodiment of the present application;

[0022] Figure 7 A circuit block diagram of an electric power system according to an embodiment of the present application.

[0023] Description of reference numerals:

[0024] 100-energy storage device, 110-first battery module, 111-first positive electrode plate, 112-first diaphragm, 113-first negative electrode plate, 120-second battery module, 121-second positive electrode plate, 122-second diaphragm, 123-second negative electrode plate, 130-housing, 131-accommodating chamber, 200-electrical system, 210-electrical equipment. DETAILED DESCRIPTION

[0025] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0026] The terms "first", "second", etc. in the specification and claims of this application and the above-mentioned drawings are used to distinguish different objects, rather than to describe a specific order. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not limited to the listed steps or units, but optionally includes steps or units that are not listed, or optionally includes other steps or units inherent to these processes, methods, products or devices.

[0027] Reference to "embodiment" or "implementation" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiment or implementation may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0028] With the continuous development of energy storage technology, the capacity of energy storage devices has gradually increased. For example, the capacity of current energy storage devices can reach 280Ah, 300Ah, 314Ah, etc. However, large-capacity energy storage devices all have the safety problem of high temperature when the battery cell thermal runaways, which can easily cause thermal runaway and fire of the battery cell. Specifically, when multiple battery cells are assembled into a module, due to the large number of battery cells, the heat dissipation performance of the module is relatively poor compared to the heat dissipation performance of a single battery cell. When the battery cell thermal runaway occurs, it is more likely to cause a large temperature rise in the module, making the temperature of the module too high (usually greater than 700°C) when the module thermal runaways, increasing the risk of fire and explosion of the module. Therefore, it is necessary to design the battery cell for safety, reduce the maximum temperature of the module when the battery cell thermal runaways, and improve the safety performance of the module.

[0029] See also Figure 1 The present application provides an energy storage device 100, the energy storage device 100 comprising: a first battery module 110 and a second battery module 120, the first battery module 110 comprising a first diaphragm 112; the second battery module 120 is connected in parallel with the first battery module 110, the second battery module 120 comprising a second diaphragm 122; the first diaphragm 112 is arranged along a preset direction (such as Figure 1 The thermal shrinkage rate of the second diaphragm 122 along a preset direction at 150° C. is smaller than the thermal shrinkage rate of the second diaphragm 122 along a preset direction at 150° C., wherein the preset direction is the height direction of the first battery module 110.

[0030] It can be understood that the heat shrinkage rate of the first diaphragm 112 along a preset direction at 150° C. is the ratio of the length of the first diaphragm 112 after heat shrinkage to the length of the first diaphragm 112 before heat shrinkage at 150° C.

[0031] It can be understood that the heat shrinkage rate of the second diaphragm 122 along a preset direction at 150° C. is the ratio of the length of the second diaphragm 122 after heat shrinkage to the length of the second diaphragm 122 before heat shrinkage at 150° C.

[0032] It can be understood that the preset direction is the height direction of the first battery module 110, the preset direction can be the height direction of the second battery module 120, the preset direction can be the transverse (TD) direction of the first diaphragm 112, or the preset direction can be the transverse (TD) direction of the second diaphragm 122.

[0033] It can be understood that the thermal shrinkage rate of the first diaphragm 112 along the preset direction at 150°C can characterize the thermal runaway characteristics of the first battery module 110 when the temperature reaches 150°C. If the thermal shrinkage rate of the first diaphragm 112 along the preset direction at 150°C is greater, the severity and probability of thermal runaway of the first battery module 110 when the temperature reaches 150°C will be greater; similarly, the thermal shrinkage rate of the second diaphragm 122 along the preset direction at 150°C can characterize the thermal runaway characteristics of the second battery module 120 when the temperature reaches 150°C. If the thermal shrinkage rate of the second diaphragm 122 along the preset direction at 150°C is greater, the severity and probability of thermal runaway of the second battery module 120 when the temperature reaches 150°C will be greater.

[0034] Optionally, the difference in heat shrinkage performance between the first diaphragm 112 and the second diaphragm 122 is mainly caused by the difference in material selection, formulation and preparation process of the first diaphragm 112 and the second diaphragm 122, which is not limited here.

[0035] In this embodiment, the first battery module 110 and the second battery module 120 are arranged in parallel. When the energy storage device 100 is in a normal charge and discharge cycle, the charge and discharge process of the first battery module 110 and the charge and discharge process of the second battery module 120 do not interfere with each other, and the first battery module 110 and the second battery module 120 can perform charge and discharge cycles independently. In addition, if the thermal shrinkage rate of the first diaphragm 112 along a preset direction at 150°C is different from the thermal shrinkage rate of the second diaphragm 122 along a preset direction at 150°C, there is a difference between the first battery module 110 and the second battery module 120. When one of the first battery module 110 and the second battery module 120 has thermal runaway, the other of the first battery module 110 and the second battery module 120 can delay the occurrence of thermal runaway or avoid thermal runaway, so as to avoid the first battery module 110 and the second battery module 120 having thermal runaway at the same time, which makes it difficult to discharge the heat inside the energy storage device 100 in time, thereby helping to reduce the maximum temperature inside the energy storage device 100, so as to reduce the probability of explosion or fire of the energy storage device 100 due to excessive temperature, thereby improving the safety performance of the energy storage device 100. Specifically, the thermal shrinkage rate of the first diaphragm 112 along the preset direction at 150°C is less than the thermal shrinkage rate of the second diaphragm 122 along the preset direction at 150°C. At 150°C, the degree of thermal shrinkage of the first diaphragm 112 in the preset direction is less than the degree of thermal shrinkage of the second diaphragm 122 in the preset direction. Accordingly, the probability of a short circuit inside the first battery module 110 is less than the probability of a short circuit inside the second battery module 120. Therefore, the second battery module 120 is more likely to have thermal runaway than the first battery module 110. When the second battery module 120 has thermal runaway, the first battery module 110 has not yet had thermal runaway, so that the heat generated when the second battery module 120 has thermal runaway can be dissipated through the housing 130, explosion-proof valve, exhaust channel, etc. of the energy storage device 100 to slow down the temperature rise rate inside the energy storage device 100. Furthermore, the first battery module 110 and the second battery module 120 are arranged in parallel. When the second battery module 120 is short-circuited due to thermal runaway, the first battery module 110 will be discharged to reduce the remaining power of the first battery module 110.If the remaining power of the first battery module 110 decreases, that is, the charge of the first battery module 110 decreases, it is beneficial to reduce the reaction heat inside the first battery module 110, thereby extending the triggering time of thermal runaway of the first battery module 110, and / or reducing the severity of thermal runaway of the first battery module 110, and / or preventing the first battery module 110 from thermal runaway, which is beneficial to reduce the temperature rise rate inside the energy storage device 100. Even if the second battery module 120 has thermal runaway, the temperature inside the energy storage device 100 will not be too high. It is known that the smoke generated by the thermal runaway of the second battery module 120 is a flammable gas, which is easy to cause fire and explosion of the energy storage device 100 under high temperature conditions. In the case of thermal runaway of the second battery module 120 of the energy storage device 100 of the present embodiment, the first battery module 110 and the second battery module 120 are designed differently so that there is a time difference between the time when the first battery module 110 and the second battery module 120 experience thermal runaway, and there is a time difference between the time when the two large surfaces of the first battery module 110 and the second battery module 120 reach the maximum temperature of thermal runaway, and there is also a time difference between the time when the first battery module 110 and the second battery module 120 reach the maximum temperature of thermal runaway, which greatly reduces the temperature rise rate inside the energy storage device 100, so that the temperature inside the energy storage device 100 is not too high, which is beneficial to reduce the probability of fire and explosion of the energy storage device 100, so that the energy storage device 100 has better safety performance.

[0036] It can be understood that, in the terminology of the present application, “two large surfaces of the first battery module 110 and the second battery module 120 ” refers to two surfaces of the first battery module 110 and the second battery module 120 that are arranged opposite to each other.

[0037] It can be understood that in the terminology of the present application, "thermal runaway" means that the temperature rise rate of the first battery module 110 or the second battery module 120 is greater than 3°C / s. The test standard is GB / T 36276 for lithium-ion batteries. The temperature rise rate of the first battery module 110 or the second battery module 120 is greater than 3°C / s, which means that the temperature rise rate of the first battery module 110 or the second battery module 120 is greater than 3°C / s for three consecutive tests.

[0038] It can be understood that the reason why the first diaphragm 112 undergoes thermal shrinkage and causes a short circuit inside the first battery module 110 is that the first battery module 110 also includes a first positive electrode sheet 111 and a first negative electrode sheet 113, and the first diaphragm 112 is arranged between the first positive electrode sheet 111 and the first negative electrode sheet 113. When the first diaphragm 112 undergoes thermal shrinkage, at least a portion of the first positive electrode sheet 111 and at least a portion of the first negative electrode sheet 113 are in contact, thereby causing the first positive electrode sheet 111 to short-circuit with the first negative electrode sheet 113.

[0039] It can be understood that the reason why the second diaphragm 122 undergoes thermal shrinkage and causes a short circuit inside the second battery module 120 is that the second battery module 120 also includes a second positive electrode sheet 121 and a second negative electrode sheet 123, and the second diaphragm 122 is arranged between the second positive electrode sheet 121 and the second negative electrode sheet 123. When the second diaphragm 122 undergoes thermal shrinkage, at least a portion of the second positive electrode sheet 121 and at least a portion of the second negative electrode sheet 123 are in direct contact, thereby causing the second positive electrode sheet 121 to short-circuit with the second negative electrode sheet 123.

[0040] It can be understood that in the terminology of this application, "charge" refers to the ratio of the remaining dischargeable capacity of the battery module to the charge in its fully charged state, that is, the remaining charge of the battery module, which can be represented by SOC. For example, 100% SOC means that the ratio of the charge state of the battery module to the charge in its fully charged state is 100%, that is, the battery module is in a fully charged state.

[0041] Optionally, the preset direction is perpendicular to an arrangement direction of the first battery module 110 and the second battery module 120 .

[0042] Optionally, in the energy storage device 100, the number of the first battery modules 110 is one or more, and the number of the second battery modules 120 is one or more. When the number of the first battery modules 110 is multiple, the multiple first battery modules 110 are arranged in parallel; when the number of the second battery modules 120 is multiple, the multiple second battery modules 120 are arranged in parallel.

[0043] Optionally, in some embodiments, the first diaphragm 112 includes a first base film and a first ceramic coating, the first ceramic coating is disposed on the surface of the first base film, the material of the first base film is selected from at least one of polyethylene, polypropylene, polyimide, etc., and the first ceramic coating has a plurality of first micropores to facilitate the transmission of lithium ions.

[0044] Optionally, the thermal shrinkage rate of the first diaphragm 112 along a preset direction at 150° C. can be adjusted by selecting the material of the first diaphragm 112 and the material of the first ceramic coating, which is not limited here.

[0045] Optionally, in some embodiments, the second diaphragm 122 includes a second base film and a second ceramic coating, the second ceramic coating is disposed on the surface of the second base film, the material of the second base film is selected from at least one of polyethylene, polypropylene, polyimide, etc., and the second ceramic coating has a plurality of second micropores to facilitate the transmission of lithium ions.

[0046] It can be understood that the thermal shrinkage performance of polyimide is better than that of polypropylene, and the thermal shrinkage performance of polypropylene is better than that of polyethylene. The first base film can be mixed with polyethylene, polypropylene and polyimide in a certain proportion to adjust the thermal shrinkage performance of the first base film, thereby adjusting the thermal shrinkage performance of the first diaphragm 112; similarly, the second base film can be mixed with polyethylene, polypropylene and polyimide in a certain proportion to adjust the thermal shrinkage performance of the second base film, thereby adjusting the thermal shrinkage performance of the second diaphragm 122.

[0047] Optionally, the thermal shrinkage rate of the second diaphragm 122 along a preset direction at 150° C. can be adjusted by selecting the material of the second diaphragm 122 and the material of the second ceramic coating, which is not limited here.

[0048] In some embodiments, the thermal shrinkage rate of the first diaphragm 112 along a preset direction at 150° C. is η1, and the thermal shrinkage rate of the second diaphragm 122 along a preset direction at 150° C. is η2, which satisfies the relationship: 0.14%≤η1 / η2≤66.67%.

[0049] Specifically, the value of η1 / η2 can be but is not limited to 0.14%, 0.2%, 0.8%, 1%, 5%, 8%, 10%, 12%, 15%, 18%, 20%, 30%, 35%, 40%, 45%, 50%, 55%, 58%, 60% and 66.67%, etc.

[0050] In this embodiment, when the heat shrinkage rate η1 of the first diaphragm 112 along the preset direction at 150°C and the heat shrinkage rate η2 of the second diaphragm 122 along the preset direction at 150°C satisfy the relationship 0.14%≤η1 / η2≤66.67%, the difference between the degree of heat shrinkage of the first diaphragm 112 in the preset direction and the degree of heat shrinkage of the second diaphragm 122 in the preset direction is within a reasonable range. On the one hand, the second battery module 120 can be prevented from prematurely experiencing thermal runaway, thereby improving the performance of the second battery module 120. On the other hand, when the second battery module 120 experiences thermal runaway and an internal short circuit occurs, the first battery module 110 can delay the occurrence of thermal runaway or prevent thermal runaway, so that the heat dissipated when the second battery module 120 experiences thermal runaway can be dissipated from the energy storage device 100, thereby slowing down the temperature rise rate inside the energy storage device 100, reducing the risk of explosion and fire of the energy storage device 100, and ultimately improving the service life of the energy storage device 100. When the value of η1 / η2 is too large, when the thermal shrinkage rate of the first diaphragm 112 along the preset direction at 150°C is less than the thermal shrinkage rate of the second diaphragm 122 along the preset direction at 150°C, the thermal shrinkage rate of the first diaphragm 112 along the preset direction at 150°C is too large, and / or the thermal shrinkage rate of the second diaphragm 122 along the preset direction at 150°C is too small. In other words, the difference between the degree of thermal shrinkage of the first diaphragm 112 in the preset direction and the degree of thermal shrinkage of the second diaphragm 122 in the preset direction is too small. When the second battery module 120 has an internal short circuit due to thermal runaway, the first battery module 110 also has thermal runaway, which may cause the first battery module 110 and the second battery module 120 to have thermal runaway at the same time or almost at the same time. The heat emitted by the first battery module 110 and the second battery module 120 when thermal runaway occurs cannot be discharged from the energy storage device 100 in time, and the maximum temperature inside the energy storage device 100 increases sharply, increasing the probability of explosion and fire of the energy storage device 100. When the value of η1 / η2 is too small, the thermal shrinkage rate of the first diaphragm 112 along the preset direction at 150°C is too small, and / or the thermal shrinkage rate of the second diaphragm 122 along the preset direction at 150°C is too large. If the thermal shrinkage rate of the first diaphragm 112 along the preset direction at 150°C is too small, the current industry-scale production technology cannot be prepared, and more advanced technology is required to achieve an extremely low thermal shrinkage rate, which greatly increases the cost and cannot be mass-produced.If the thermal shrinkage rate of the second diaphragm 122 along a preset direction at 150°C is too large, then during the charging and discharging process of the second battery module 120, as the temperature of the second battery module 120 increases, the second diaphragm 122 thermally shrinks to a greater extent, and the second battery module 120 is more susceptible to short circuit and thermal runaway, thereby reducing the performance of the second battery module 120.

[0051] In some embodiments, the thermal shrinkage rate η1 of the first diaphragm 112 along a preset direction at 150° C. is in the range of 0.1%≤η1≤20%.

[0052] Specifically, the thermal shrinkage rate η1 of the first diaphragm 112 along a preset direction at 150°C can be, but is not limited to, 0.1%, 0.5%, 1%, 1.5%, 2%, 3%, 5%, 6%, 8%, 10%, 11%, 12%, 14%, 15%, 16%, 17%, 18%, 19% and 20%, etc.

[0053] In this embodiment, when the thermal shrinkage rate η1 of the first diaphragm 112 along a preset direction at 150°C satisfies the range of 0.1%≤η1≤20%, compared with the second diaphragm 122, the degree of thermal shrinkage of the first diaphragm 112 at 150°C is smaller and within a reasonable range. When the second battery module 120 has thermal runaway or is in a critical state of thermal runaway, the second battery module 120 dissipates heat and causes the temperature inside the energy storage device 100 to rise, while the first diaphragm 112 can still maintain a small thermal shrinkage rate to isolate the first positive electrode plate 111 and the first negative electrode plate 113, thereby avoiding a short circuit inside the first battery module 110, thereby delaying the time for the first battery module 110 to have thermal runaway or ultimately preventing the first battery module 110 from having thermal runaway. Compared with a solution in which the first battery module 110 and the second battery module 120 in the energy storage device 100 simultaneously or almost simultaneously experience thermal runaway, the first battery module 110 and the second battery module 120 in this embodiment have a larger time difference in reaching the maximum temperature of thermal runaway, which is beneficial for timely dissipation of heat generated when the second battery module 120 experiences thermal runaway, thereby reducing the risk of explosion or fire of the energy storage device 100 due to excessively high internal temperature of the energy storage device 100, and the energy storage device 100 has better safety performance. When the value of the thermal shrinkage rate η1 of the first diaphragm 112 along the preset direction at 150°C is too large, then when the thermal shrinkage rate of the first diaphragm 112 along the preset direction at 150°C is less than the thermal shrinkage rate of the second diaphragm 122 along the preset direction at 150°C, the difference between the thermal shrinkage performance of the first diaphragm 112 at 150°C and the thermal shrinkage performance of the second diaphragm 122 at 150°C is too small. In other words, the first battery module 110 and the second battery module 120 may experience thermal runaway at the same time or almost at the same time. When thermal runaway occurs in the first battery module 110 and the second battery module 120, most of the heat will be generated in the energy storage device 100 and it will be difficult to dissipate it in time, thereby causing the temperature inside the energy storage device 100 to rise sharply, increasing the risk of explosion or fire of the energy storage device 100 due to excessive temperature. When the value of the thermal shrinkage rate η1 of the first diaphragm 112 along the preset direction at 150°C is too small, the requirements for the preparation technology of the first diaphragm 112 are increased. The current industry-scale production technology cannot prepare it. More advanced technology is required to achieve an extremely low thermal shrinkage rate, which greatly increases the cost and cannot be mass-produced.

[0054] In some embodiments, the heat shrinkage rate η2 of the second diaphragm 122 along a preset direction at 150° C. is in the range of 30%≤η2≤70%.

[0055] Specifically, the thermal shrinkage rate η2 of the second diaphragm 122 along a preset direction at 150°C can be but is not limited to 30%, 32%, 34%, 35%, 38%, 40%, 42%, 45%, 48%, 50%, 52%, 55%, 60%, 62%, 65%, 68% and 70%, etc.

[0056] In this embodiment, when the heat shrinkage rate η2 of the second diaphragm 122 along the preset direction at 150°C satisfies the range of 30%≤η2≤70%, compared with the first diaphragm 112, the degree of heat shrinkage of the second diaphragm 122 at 150°C is greater and within a reasonable range. During the charge and discharge process of the first battery module 110 and the second battery module 120, as the temperature rises, the degree of heat shrinkage of the second diaphragm 122 is greater than that of the first diaphragm 112, and the second battery module 120 is more prone to thermal runaway and short circuit, and the time difference between the first battery module 110 and the second battery module 120 reaching the maximum temperature of thermal runaway is large, which facilitates the timely dissipation of the heat generated when the second battery module 120 has thermal runaway, thereby making the maximum temperature inside the energy storage device 100 low, reducing the risk of explosion, fire, etc. of the energy storage device 100, and the energy storage device 100 has good safety performance. When the thermal shrinkage rate η2 of the second diaphragm 122 along the preset direction at 150°C is too large, then during the charging and discharging process of the second battery module 120, as the temperature of the second battery module 120 increases, the second diaphragm 122 undergoes thermal shrinkage to a greater extent, and the second positive electrode plate 121 and the second negative electrode plate 123 in the second battery module 120 are prone to direct contact, resulting in short circuit and thermal runaway, thereby reducing the performance of the second battery module 120. When the value of the thermal shrinkage rate η2 of the second diaphragm 122 along the preset direction at 150°C is too small, then when the thermal shrinkage rate of the first diaphragm 112 along the preset direction at 150°C is less than the thermal shrinkage rate of the second diaphragm 122 along the preset direction at 150°C, the difference between the thermal shrinkage performance of the first diaphragm 112 at 150°C and the thermal shrinkage performance of the second diaphragm 122 at 150°C is too small. In other words, the first battery module 110 and the second battery module 120 may experience thermal runaway at the same time or almost at the same time. When the first battery module 110 and the second battery module 120 experience thermal runaway, most of the heat will be generated in the energy storage device 100 and it will be difficult to dissipate it in time, thereby causing the temperature inside the energy storage device 100 to rise sharply, increasing the risk of explosion or fire of the energy storage device 100 due to excessively high temperature, and reducing the safety performance of the energy storage device 100.

[0057] In some embodiments, the time difference t between the first battery module 110 and the second battery module 120 reaching the maximum temperature of thermal runaway is in the range of: t≥1min, wherein thermal runaway refers to a temperature rise rate of the first battery module 110 or the second battery module 120 being greater than 3°C / s, and the temperature rise rate is the rate at which the temperature of the first battery module 110 or the second battery module 120 increases.

[0058] Specifically, the time difference t between the first battery module 110 and the second battery module 120 reaching the maximum temperature of thermal runaway may be, but is not limited to, 1 min, 1.2 min, 1.25 min, 1.3 min, 1.35 min, 1.38 min, etc.

[0059] It can be understood that the test standard for thermal runaway of the first battery module 110 and the second battery module 120 is lithium-ion battery GB / T 36276. The temperature rise rate of the first battery module 110 or the second battery module 120 is greater than 3°C / s means that the temperature rise rate of the first battery module 110 or the second battery module 120 is greater than 3°C / s for three consecutive tests.

[0060] It can be understood that if the thermal shrinkage rate of the first diaphragm 112 along a preset direction at 150°C is smaller than the thermal shrinkage rate of the second diaphragm 122 along a preset direction at 150°C, the second battery module 120 is more likely to experience thermal runaway than the first battery module 110, and the time when the thermal runaway of the first battery module 110 occurs is later than the time when the thermal runaway of the second battery module 120 occurs, and the first battery module 110 may not experience thermal runaway.

[0061] In this embodiment, the first diaphragm 112 of the first battery module 110 and the second diaphragm 122 of the second battery module 120 are differentially designed so that the time difference t between the first battery module 110 and the second battery module 120 reaching the maximum temperature of thermal runaway satisfies the range t≥1min, and the time difference between the first battery module 110 and the second battery module 120 reaching the maximum temperature of thermal runaway is large. As the temperature inside the energy storage device 100 increases, the second battery module 120 first undergoes thermal runaway, and the first battery module 110 delays thermal runaway or does not undergo thermal runaway, so that the heat generated when the second battery module 120 undergoes thermal runaway can be dissipated from the inside of the energy storage device 100 in time, slowing down the rate of temperature increase inside the energy storage device 100 and improving the safety performance of the energy storage device 100. If the time difference between the first battery module 110 and the second battery module 120 reaching the maximum temperature of thermal runaway is too small, then after the second battery module 120 undergoes thermal runaway, the first battery module 110 will immediately undergo thermal runaway, and the first battery module 110 and the second battery module 120 will dissipate excessive heat, causing the temperature inside the energy storage device 100 to rise sharply, thereby increasing the risk of explosion or fire of the energy storage device 100, thereby causing the safety performance of the energy storage device 100 to be poor.

[0062] In some embodiments, when the second battery module 120 is short-circuited, the first battery module 110 is discharged to reduce the remaining capacity of the first battery module 110 .

[0063] In this embodiment, the first battery module 110 and the second battery module 120 are connected in parallel. When the second battery module 120 has thermal runaway, the second diaphragm 122 undergoes thermal contraction, and the second positive electrode plate 121 and the second negative electrode plate 123 are in direct contact and short-circuited, that is, a short circuit occurs inside the second battery module 120, and the first battery module 110 will be discharged, thereby reducing the remaining capacity of the first battery module 110. As the remaining capacity of the first battery module 110 decreases, the charge of the first battery module 110 decreases, which is beneficial to reducing the reaction heat inside the first battery module 110. The first battery module 110 with a low charge requires more external heat to reach the critical temperature of thermal runaway, which is beneficial to increase the critical temperature of thermal runaway of the first battery module 110, so that the first battery module 110 delays the occurrence of thermal runaway or does not occur thermal runaway. On the one hand, it can delay the use performance of the first battery module 110, and on the other hand, it can also improve the safety performance of the energy storage device 100.

[0064] See also Figure 2In some embodiments, the first battery module 110 further includes a first positive electrode sheet 111 and a first negative electrode sheet 113. In the first battery module 110, the first positive electrode sheet 111, the first separator 112 and the first negative electrode sheet 113 are arranged in sequence; the first positive electrode sheet 111 includes a first positive electrode active material, and the first positive electrode active material includes at least one of lithium iron phosphate, lithium nickel cobalt manganese oxide, lithium cobalt oxide, sodium iron pyrophosphate, and sodium nickel cobalt manganese oxide; the first negative electrode sheet 113 includes a first negative electrode active material, and the first negative electrode active material includes graphite, silicon carbon, hard carbon, lithium titanate (Li4Ti5O 12 ), at least one of metallic lithium.

[0065] It can be understood that the first positive electrode sheet 111 , the first separator 112 and the first negative electrode sheet 113 are stacked in sequence. In other words, the first separator 112 is sandwiched between the first positive electrode sheet 111 and the first negative electrode sheet 113 .

[0066] In this embodiment, the first diaphragm 112 is disposed between the first positive electrode sheet 111 and the first negative electrode sheet 113 to isolate the first positive electrode sheet 111 and the first negative electrode sheet 113, and prevent the first positive electrode sheet 111 from directly contacting the first negative electrode sheet 113 and causing a short circuit. The first diaphragm 112 has a small thermal shrinkage rate along a preset direction at 150°C, so that when the temperature inside the energy storage device 100 is high, the thermal shrinkage degree of the first diaphragm 112 is small, which can slow down the occurrence of thermal runaway of the first battery module 110 or prevent thermal runaway, increase the time difference between the occurrence of thermal runaway of the second battery module 120, thereby increasing the time difference between the first battery module 110 and the second battery module 120 reaching the maximum temperature of thermal runaway, and improving the safety performance of the energy storage device 100. The first positive electrode active material includes at least one of lithium iron phosphate, lithium nickel cobalt manganese oxide, lithium cobalt oxide, sodium iron pyrophosphate, and sodium nickel cobalt manganese oxide to provide more active lithium ions for the first battery module 110. The first negative electrode active material includes graphite, silicon carbon, hard carbon, lithium titanate (Li4Ti5O 12 ) and at least one of metallic lithium, which facilitates the insertion and extraction of lithium ions, so that the first battery module 110 and the energy storage device 100 have better cycle performance.

[0067] See also Figure 3In some embodiments, the second battery module 120 further includes a second positive electrode sheet 121 and a second negative electrode sheet 123. In the second battery module 120, the second positive electrode sheet 121, the second separator 122 and the second negative electrode sheet 123 are arranged in sequence; the second positive electrode sheet 121 includes a second positive electrode active material, and the second positive electrode active material includes at least one of lithium iron phosphate, lithium nickel cobalt manganese oxide, lithium cobalt oxide, sodium iron pyrophosphate, and sodium nickel cobalt manganese oxide; the second negative electrode sheet 123 includes a second negative electrode active material, and the second negative electrode active material includes graphite, silicon carbon, hard carbon, lithium titanate (Li4Ti5O 12 ) 、 At least one of metallic lithium.

[0068] It can be understood that the second positive electrode sheet 121 , the second separator 122 and the second negative electrode sheet 123 are stacked in sequence. In other words, the second separator 122 is sandwiched between the second positive electrode sheet 121 and the second negative electrode sheet 123 .

[0069] In this embodiment, the second diaphragm 122 is disposed between the second positive electrode sheet 121 and the second negative electrode sheet 123 to isolate the second positive electrode sheet 121 and the second negative electrode sheet 123, and prevent the second positive electrode sheet 121 from directly contacting the second negative electrode sheet 123 and causing a short circuit. The second diaphragm 122 has a large thermal shrinkage rate along a preset direction at 150°C, so that when the temperature inside the energy storage device 100 is high, the thermal shrinkage degree of the second diaphragm 122 is large, the second positive electrode sheet 121 contacts the second negative electrode sheet 123 and causes a short circuit in the second battery module 120. In other words, the second battery module 120 is more susceptible to thermal runaway than the first battery module 110, which is conducive to increasing the time difference between the second battery module 120 reaching the highest temperature of thermal runaway and improving the safety performance of the energy storage device 100. The second positive electrode active material includes at least one of lithium iron phosphate, lithium nickel cobalt manganese oxide, lithium cobalt oxide, sodium iron pyrophosphate, and sodium nickel cobalt manganese oxide to provide more active lithium ions for the second battery module 120. The second negative electrode active material includes graphite, silicon carbon, hard carbon, lithium titanate (Li4Ti5O 12 ) 、 At least one of the metallic lithium facilitates the insertion and extraction of lithium ions, so that the second battery module 120 and the energy storage device 100 have better cycle performance.

[0070] Optionally, in some embodiments, the first positive electrode active material and the second positive electrode active material are the same. When the first positive electrode active material and the second positive electrode active material are the same, it is beneficial to improve the uniformity of the energy storage device 100, and can also save the preparation process of the first positive electrode active material and the second positive electrode active material, and reduce the preparation cost of the first positive electrode active material and the second positive electrode active material; in other embodiments, the first positive electrode active material and the second positive electrode active material are different.

[0071] Optionally, in some embodiments, the first negative electrode active material and the second negative electrode active material are the same. When the first negative electrode active material and the second negative electrode active material are the same, it is beneficial to improve the uniformity of the energy storage device 100, and can also save the preparation process of the first negative electrode active material and the second negative electrode active material, and reduce the preparation cost of the first negative electrode active material and the second negative electrode active material; in other embodiments, the first negative electrode active material and the second negative electrode active material are different.

[0072] In some embodiments, the energy efficiency E of the energy storage device 100 at 25° C. and 0.5P constant power charging and discharging is in the range of 94%≤E<100%.

[0073] Specifically, the energy efficiency E of the energy storage device 100 charged and discharged at a constant power of 0.5P at 25°C can be, but is not limited to, 94%, 94.5%, 95%, 95.5%, 96%, 96.5%, 96.8%, 97%, 97.5%, 98%, 98.5% and 99%, etc.

[0074] In this embodiment, the energy efficiency E of the energy storage device 100 charged and discharged at a constant power of 0.5P at 25°C satisfies the range of 94%≤E<100%, so the energy loss of the energy storage device 100 during the charging and discharging process is small, and the efficiency of energy conversion and utilization is high. In addition, by performing differentiated design on the first battery module 110 and the second battery module 120 of the energy storage device 100, so that there is a time difference between the time when the first battery module 110 and the second battery module 120 reach the maximum temperature of thermal runaway, the temperature rise rate inside the energy storage device 100 is greatly reduced, so that the temperature inside the energy storage device 100 is not too high, which is conducive to reducing the probability of fire and explosion of the energy storage device 100, so that the energy storage device 100 has both good safety performance and high energy efficiency.

[0075] In some embodiments, the energy storage device 100 also includes a shell 130, the shell 130 encloses a accommodating cavity 131, and the accommodating cavity 131 is used to accommodate the first battery module 110 and the second battery module 120; the number of the first battery module 110 is at least one, and the number of the second battery module 120 is at least one; when the number of the first battery module 110 is multiple and the number of the second battery module 120 is multiple, the second battery module 120 is arranged closer to the middle position of the accommodating cavity 131 than the first battery module 110.

[0076] It can be understood that, in the terminology of the present application, "at least one" means one or more, and "plurality" means greater than or equal to two, which can be but is not limited to two, three, four, etc.

[0077] It can be understood that when the number of the first battery module 110 is one and the number of the second battery module 120 is one, one first battery module 110 and one second battery module 120 are arranged side by side in the accommodating cavity 131 of the shell 130 .

[0078] In the present embodiment, the shell 130 encloses a housing cavity 131, and the housing cavity 131 is used to accommodate the first battery module 110 and the second battery module 120. The temperature in the middle of the housing cavity 131 is relatively high. In the present embodiment, as the temperature inside the energy storage device 100 gradually increases, the second battery module 120 is more likely to experience thermal runaway than the first battery module 110. The second battery module 120 is arranged closer to the middle of the housing cavity 131 than the first battery module 110, so the temperature of the environment in which the second battery module 120 is located is slightly higher than the temperature of the environment in which the first battery module 110 is located. When the critical temperature of the second battery module 120 experiencing thermal runaway is reached, the thermal runaway of the second battery module 120 can be accelerated. Thermal runaway is achieved by further increasing the time difference between the occurrence of thermal runaway of the first battery module 110 and the occurrence of thermal runaway of the second battery module 120, so that the time difference between the first battery module 110 and the second battery module 120 reaching the maximum temperature of thermal runaway is relatively large, thereby avoiding the first battery module 110 and the second battery module 120 from having thermal runaway at the same time and causing the internal temperature of the energy storage device 100 to be too high, which is beneficial to reducing the probability of fire and explosion of the energy storage device 100, so that the energy storage device 100 has better safety performance.

[0079] In some embodiments, the first battery module 110 is selected from at least one of a winding structure and a laminated structure, and the second battery module 120 is selected from at least one of a winding structure and a laminated structure. The first battery module 110 and the second battery module 120 have good performance.

[0080] The technical solution of this application is further introduced in the following with multiple embodiments:

[0081] Example 1 to Example 4, Comparative Example 1 to Comparative Example 4:

[0082] 1. Preparation of the first diaphragm 112 and the second diaphragm 122:

[0083] (1) Preparation of the first diaphragm 112:

[0084] Alumina ceramic powder, dispersant and adhesive are mixed evenly, and then sprayed onto a first base film (polyethylene film, PE film) to form a first ceramic coating, thereby obtaining the first diaphragm 112 of Examples 1 to 4 and Comparative Examples 1 to 4.

[0085] The thermal shrinkage performance of the first diaphragm 112 can be adjusted by changing the material of the first ceramic coating, or by adjusting the particle size of the alumina ceramic powder and the material of the first base film. The method of adjusting the thermal shrinkage performance of the first diaphragm 112 is not limited here. For example, the smaller the particle size of the alumina ceramic powder in the first ceramic coating, the better the thermal shrinkage performance of the first diaphragm 112, and the greater the thermal shrinkage rate of the first diaphragm 112 along the preset direction at 150°C; the larger the particle size of the alumina ceramic powder in the first ceramic coating, the worse the thermal shrinkage performance of the first diaphragm 112, and the smaller the thermal shrinkage rate of the first diaphragm 112 along the preset direction at 150°C.

[0086] (2) Preparation of the second diaphragm 122:

[0087] Alumina ceramic powder, dispersant and adhesive are mixed evenly, and then sprayed onto a second base film (polyethylene film, PE film) to form a second ceramic coating, thereby obtaining the second diaphragm 122 of Examples 1 to 4 and Comparative Examples 1 to 4.

[0088] The thermal shrinkage performance of the second diaphragm 122 can be adjusted by changing the material of the second ceramic coating, or by adjusting the particle size of the alumina ceramic powder and the material of the second base film. The method of adjusting the thermal shrinkage performance of the second diaphragm 122 is not limited here. For example, the smaller the particle size of the alumina ceramic powder in the second ceramic coating, the better the thermal shrinkage performance of the second diaphragm 122, and the greater the thermal shrinkage rate of the second diaphragm 122 along the preset direction at 150°C; the larger the particle size of the alumina ceramic powder in the second ceramic coating, the worse the thermal shrinkage performance of the second diaphragm 122, and the smaller the thermal shrinkage rate of the second diaphragm 122 along the preset direction at 150°C.

[0089] (3) Testing of thermal shrinkage performance of the first diaphragm 112 and the second diaphragm 122:

[0090] Step 1: Take the first diaphragm 112 or the second diaphragm 122 with a length×width of 10 cm×10 cm, and place it between two sheets of paper without heat shrinkage performance to form a test sample with a sandwich structure;

[0091] Step 2: Place the test sample of the sandwich structure into a vacuum oven, heat it to 150°C at a heating rate of 5°C / min, keep it warm for 30 minutes, and cool it to room temperature;

[0092] Step three: Take out the first diaphragm 112 or the second diaphragm 122, measure the length of the first diaphragm 112 or the second diaphragm 122 in the TD / transverse direction, and calculate the heat shrinkage rate of the first diaphragm 112 or the second diaphragm 122 by dividing the length after shrinkage by the initial length.

[0093] Among them, the values ​​of the thermal shrinkage rate η1 of the first diaphragm 112 along the preset direction at 150°C and the values ​​of the thermal shrinkage rate η2 of the second diaphragm 122 along the preset direction at 150°C in Examples 1 to 4 and Comparative Examples 1 to 4 are shown in Table 1.

[0094] 2. Preparation of the first positive electrode sheet 111 and the second positive electrode sheet 121:

[0095] (1) Preparation of the first positive electrode sheet 111:

[0096] The first positive electrode active material lithium iron phosphate, the first positive electrode conductive agent conductive carbon black (SP), and the first positive electrode binder polyvinylidene fluoride (PVDF) are dispersed in a solvent N-methylpyrrolidone (NMP) in a mass ratio of 97:0.7:2.3, and mixed evenly to obtain a first positive electrode slurry with a solid content of 60wt%; the first positive electrode slurry is coated on the first positive electrode collector layer (carbon-coated aluminum foil), and after drying, cold pressing, slitting, and cutting, a first positive electrode material layer is formed to obtain the first positive electrode sheets 111 of Examples 1 to 4 and Comparative Examples 1 to 4.

[0097] (2) Preparation of the second positive electrode sheet 121:

[0098] The second positive electrode active material lithium iron phosphate, the second positive electrode conductive agent conductive carbon black (SP), and the second positive electrode binder polyvinylidene fluoride (PVDF) are dispersed in a solvent N-methylpyrrolidone (NMP) in a mass ratio of 97:0.7:2.3, and mixed evenly to obtain a second positive electrode slurry with a solid content of 60wt%; the second positive electrode slurry is coated on the second positive electrode collector layer (aluminum foil), and after drying, cold pressing, slitting, and cutting, a second positive electrode material layer is formed to obtain the second positive electrode sheets 121 of Examples 1 to 4 and Comparative Examples 1 to 4.

[0099] 3. Preparation of the first negative electrode sheet 113 and the second negative electrode sheet 123:

[0100] (1) Preparation of the first negative electrode sheet 113:

[0101] The first negative electrode active material artificial graphite, the first negative electrode conductive agent conductive carbon black (SP), the first negative electrode thickener carboxymethyl cellulose (CMC) and the first negative electrode binder styrene butadiene rubber (SBR) are dispersed in deionized water at a mass ratio of 96.5:0.5:1:2 and mixed evenly to obtain a first negative electrode slurry with a solid content of 50wt%. The first negative electrode slurry is coated on the first negative electrode collector layer (copper foil), and after drying, cold pressing, slitting and cutting, a first negative electrode material layer is formed to obtain the first negative electrode sheets 113 of Examples 1 to 4 and Comparative Examples 1 to 4.

[0102] (2) Preparation of the second negative electrode sheet 123:

[0103] The second negative electrode active material artificial graphite, the second negative electrode conductive agent conductive carbon black (SP), the second negative electrode thickener carboxymethyl cellulose (CMC) and the second negative electrode binder styrene butadiene rubber (SBR) are dispersed in deionized water at a mass ratio of 96.5:0.5:1:2 and mixed evenly to obtain a second negative electrode slurry with a solid content of 50wt%. The second negative electrode slurry is coated on the second negative electrode collector layer (copper foil), and after drying, cold pressing, slitting and cutting, a second negative electrode material layer is formed to obtain the second negative electrode sheets 123 of Examples 1 to 4 and Comparative Examples 1 to 4.

[0104] 4. Preparation of electrolyte:

[0105] In an argon atmosphere glove box with a moisture content of ≤1ppm, ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) are mixed in a mass ratio of 2:1:2, and then the dry electrolyte lithium hexafluorophosphate is dissolved in the solvent and stirred until completely dissolved and uniformly dissolved, and fluoroethylene carbonate (FEC) and ethylene carbonate (VC) are added to obtain an electrolyte.

[0106] 5. Preparation of energy storage device 100:

[0107] (1) Preparation of the first battery module 110:

[0108] The prepared first positive electrode sheet 111, the first separator 112 and the first negative electrode sheet 113 are stacked in order so that the first separator 112 is located between the first positive electrode sheet 111 and the first negative electrode sheet 113, and a bare cell is obtained after winding, and the tabs are welded on the bare cell to obtain the first battery module 110 of Examples 1 to 4 and Comparative Examples 1 to 4. Among them, the first separator 112 of Example 1 is applied to the first battery module 110 of Example 1, the first separator 112 of Example 2 is applied to the first battery module 110 of Example 2, the first separator 112 of Comparative Example 1 is applied to the first battery module 110 of Comparative Example 1, and so on.

[0109] (2) Preparation of the second battery module 120:

[0110] The prepared second positive electrode sheet 121, second separator 122 and second negative electrode sheet 123 are stacked in order so that the second separator 122 is located between the second positive electrode sheet 121 and the second negative electrode sheet 123, and a bare cell is obtained after winding, and the pole tabs are welded on the bare cell to obtain the second battery module 120 of Examples 1 to 4 and Comparative Examples 1 to 4. Among them, the second separator 122 of Example 1 is applied to the second battery module 120 of Example 1, the second separator 122 of Example 2 is applied to the second battery module 120 of Example 2, the second separator 122 of Comparative Example 1 is applied to the second battery module 120 of Comparative Example 1, and so on.

[0111] (3) Preparation of energy storage device 100:

[0112] The first battery module 110 and the second battery module 120 are assembled into the accommodating cavity 131 formed by the shell 130. The second battery module 120 is arranged closer to the middle position of the accommodating cavity 131 than the first battery module 110. The prepared electrolyte is injected, and the energy storage device 100 is packaged, allowed to stand, formed, shaped, and capacity tested, etc., to finally prepare implementation devices 1 to implementation devices 4 and comparison devices 1 to comparison devices 4.

[0113] Among them, the first battery module 110 and the second battery module 120 of Example 1 are applied to implementation device 1, the first battery module 110 and the second battery module 120 of Example 2 are applied to implementation device 2, the first battery module 110 and the second battery module 120 of Comparative Example 1 are applied to Comparative Device 1, and so on.

[0114] The following Table 1 shows the structural parameters of the first diaphragm 112 and the second diaphragm 122 of Examples 1 to 4 and Comparative Examples 1 to 4.

[0115] Table 1: Structural parameters of the first diaphragm 112 and the second diaphragm 122 of Examples 1 to 4 and Comparative Examples 1 to 4.

[0116]

[0117] Testing of thermal runaway performance of the energy storage device 100:

[0118] Step 1: Use 0.5P power, within the charge and discharge voltage range of 2.5 to 3.65V, and perform 4 cycles of discharge followed by charge, so that the first battery module 110 and the second battery module 120 are finally in a fully charged state;

[0119] Step 2: Add a 2 mm thermal insulation pad on both sides of the first battery module 110 and the second battery module 120, wherein the thermal conductivity of the thermal insulation pad at 25°C is less than or equal to 0.02 W / m·K, the thermal conductivity at 300°C is less than or equal to 0.035 W / m·K, and the thermal conductivity at 500°C is less than or equal to 0.055 W / m·K. The thermal conductivity test refers to GB / T10295-2008. The temperature sensing line is arranged at the center of the large surface of the energy storage device 100 to measure the maximum temperature inside the energy storage device 100 after thermal runaway;

[0120] Step 3: 0.5C constant current charging until the energy storage device 100 thermal runaway, the thermal runaway judgment condition is that the temperature rise rate of 3 consecutive points is greater than 3℃ / s;

[0121] Step 4: Observe the thermal runaway of the energy storage device 100 to see if fire or explosion occurs.

[0122] If the energy storage device 100 does not catch fire or explode during the test, the test is determined to have passed; if the energy storage device 100 catches fire and / or explodes during the test, the test is determined to have failed.

[0123] Among them, the maximum temperature values, test qualified stability and fire conditions of implementation devices 1 to implementation devices 4 and comparison devices 1 to comparison devices 4 after thermal runaway are shown in Table 2.

[0124] The following Table 2 shows the thermal runaway performance parameters of Implementation Devices 1 to Implementation Devices 4 and Comparative Devices 1 to 4.

[0125] Table 2: Thermal runaway performance parameters of implementation devices 1 to 4 and comparison devices 1 to 4.

[0126]

[0127]

[0128] It can be understood that in Table 2, the higher the maximum temperature of the energy storage device 100 after thermal runaway, the greater the risk of fire or explosion of the energy storage device 100 due to excessive temperature.

[0129] Please refer to Table 1 and Table 2. It can be seen from the data of Example 1, Comparative Example 1 and Comparative Example 2 that the heat shrinkage rate η1 of the first diaphragm 112 in the preset direction at 150°C of Example 1 satisfies the range of 0.1%≤η1≤20%, and the heat shrinkage rate η2 of the second diaphragm 122 in the preset direction at 150°C satisfies the range of 30%≤η2≤70%, while in Comparative Example 1, the first diaphragm 112 and the second diaphragm 122 are the same, and the heat shrinkage rates of the first diaphragm 112 and the second diaphragm 122 in the preset direction at 150°C are both Smaller; in Comparative Example 2, the first diaphragm 112 and the second diaphragm 122 are the same, and the thermal shrinkage rates of the first diaphragm 112 and the second diaphragm 122 along the preset direction at 150 are both large, which makes the maximum temperature of the implementation device 1 after thermal runaway much lower than the maximum temperature of the comparison device 1 and the comparison device 2 after thermal runaway, and the implementation device 1 has a higher test qualified stability and does not catch fire in the thermal runaway test, while the test qualified stability of the comparison device 1 and the comparison device 2 is poor, and both catch fire in the thermal runaway test. This is because: in Example 1, the first diaphragm 112 and the second diaphragm 122 are designed differently so that the first diaphragm 112 and the second diaphragm 122 have different thermal shrinkage properties, so that the first battery module 110 and the second battery module 120 are different. When the second battery module 120 has thermal runaway, the first battery module 110 has not yet had thermal runaway, so that the heat generated when the second battery module 120 has thermal runaway can be dissipated through the housing 130, explosion-proof valve, exhaust channel, etc. of the energy storage device 100 to slow down the temperature rise rate inside the energy storage device 100. Further, the first battery module 110 and the second battery module 120 are arranged in parallel, and when the second battery module 120 is short-circuited due to thermal runaway, the first battery module 110 will discharge so that the remaining power of the first battery module 110 is reduced. If the remaining power of the first battery module 110 decreases, that is, the charge of the first battery module 110 decreases, it is beneficial to reduce the reaction heat inside the first battery module 110, thereby reducing the maximum temperature of the implementation device 1 during thermal runaway, and the implementation device 1 did not catch fire during the thermal runaway test, and the implementation device 1 has good safety and stability. In comparative examples 1 and 2, the first diaphragm 112 and the second diaphragm 122 are not designed differently, so that the first battery module 110 and the second battery module 120 may have thermal runaway at the same time or almost at the same time, and the heat emitted by the first battery module 110 and the second battery module 120 during thermal runaway is difficult to dissipate in time, so that the maximum temperature of the comparative device 1 and the comparative device 2 during thermal runaway is higher.In addition, the smoke generated by the first battery module 110 and the second battery module 120 when thermal runaway occurs is flammable gas. Under high temperature conditions, the comparative device 1 and the comparative device 2 are more likely to catch fire, and the safety performance of the comparative device 1 and the comparative device 2 is poor.

[0130] Please refer to Examples 2 to 4, Comparative Examples 3 and 4. The thermal shrinkage rates η1 of the first diaphragm 112 in Examples 2 to 4, Comparative Examples 3 and 4 along the preset direction at 150°C all satisfy the range of 0.1%≤η1≤20%, and the thermal shrinkage rates η2 of the second diaphragm 122 along the preset direction at 150°C all satisfy the range of 30%≤η2≤70%. However, in Examples 2 to 4, the first diaphragm 112 and the second diaphragm 122 also satisfy the relationship of 0.14%≤η1 / η2≤66.67%. In Comparative Examples 3 and 4, the values ​​of η1 / η2 are too small, which makes the maximum temperatures of Implementation Devices 2 to Implementation Devices 4 after thermal runaway lower than the maximum temperatures of Comparative Devices 3 and 4 after thermal runaway, and Implementation Devices 2 to Implementation Devices 4 have It has good test passing stability and does not catch fire in the thermal runaway test, while the test passing stability of the comparison device 3 and the comparison device 4 is poor and catches fire in the thermal runaway test. In other words, the implementation devices 2 to 4 have good thermal stability and safety performance, while the thermal stability and safety performance of the comparison devices 3 and 4 are poor. This is because: in Examples 2 to 4, when the first diaphragm 112 and the second diaphragm 122 satisfy the relationship 0.14%≤η1 / η2≤66.67%, the difference between the degree of heat shrinkage of the first diaphragm 112 in the preset direction and the degree of heat shrinkage of the second diaphragm 122 in the preset direction is within a reasonable range. On the one hand, it can prevent the second battery module 120 from prematurely experiencing thermal runaway, thereby improving the performance of the second battery module 120. On the other hand, when the second battery module 120 has thermal runaway and an internal short circuit occurs, the first battery module 110 can delay thermal runaway or not have thermal runaway, so that the heat dissipated when the second battery module 120 has thermal runaway can be dissipated from the energy storage device 100, thereby slowing down the temperature rise rate inside the energy storage device 100, reducing the risk of explosion and fire of the energy storage device 100, and finally making the implementation device 2 to the implementation device 4 have good thermal stability and safety performance. In the comparative device 3 and the comparative device 4, if the value of η1 / η2 is too small, the thermal shrinkage rate of the first diaphragm 112 along the preset direction at 150°C is too small, and / or the thermal shrinkage rate of the second diaphragm 122 along the preset direction at 150°C is too large. If the thermal shrinkage rate of the first diaphragm 112 along the preset direction at 150°C is too small, the manufacturing difficulty of the first diaphragm 112 will be increased, and the manufacturing cost of the first diaphragm 112 will be increased.If the thermal shrinkage rate of the second diaphragm 122 along a preset direction at 150°C is too large, then during the charging and discharging process of the second battery module 120, as the temperature of the second battery module 120 increases, the second diaphragm 122 thermally shrinks to a greater extent, and the second battery module 120 is more susceptible to short circuit and thermal runaway, thereby reducing the performance of the second battery module 120, thereby causing the thermal temperature performance and safety performance of the comparison devices 3 and 4 to be poor.

[0131] In particular, see Figure 4 and Figure 5 , Figure 4 The thermal runaway voltage and temperature curve of the device 1 implemented in this application, Figure 5 For the thermal runaway voltage and temperature curve of the comparison device 1 of the present application, in the implementation device 1, the first battery module 110 and the second battery module 120 are designed differently, so that there is a time difference between the time when the first battery module 110 and the second battery module 120 reach the maximum temperature of thermal runaway, Figure 4 The temperature variation curve of the large surface of the first battery module 110, the temperature variation curve of the large surface of the second battery module 120, and the voltage variation curve of the implementation device 1 are shown. In the comparative device 1, the first battery module 110 and the second battery module 120 are not designed differently, so that the first battery module 110 and the second battery module 120 have thermal runaway at the same time or almost at the same time. Figure 5 The temperature variation curve of the large surface of the first battery module 110, the temperature variation curve of the large surface of the second battery module 120, and the voltage variation curve of the comparative device 1 are shown. Figure 4 and Figure 5It can be seen that compared with the comparison device 1, when the first battery module 110 and the second battery module 120 of the implementation device 1 have thermal runaway, the time difference between the large surface of the first battery module 110 and the large surface of the second battery module 120 reaching the maximum temperature is different. The time difference between the first battery module 110 and the second battery module 120 reaching the maximum temperature of thermal runaway in the implementation device 1 is 1.8min. When the first battery module 110 and the second battery module 120 of the comparison device 1 have thermal runaway, the time difference between the large surface of the first battery module 110 and the large surface of the second battery module 120 reaching the maximum temperature is closer. The time difference between the first battery module 110 and the second battery module 120 reaching the maximum temperature of thermal runaway in the comparison device 1 is 0.9min. This shows that the time difference between the large surface of the first battery module 110 and the large surface of the second battery module 120 reaching the maximum temperature in the implementation device 1 and the comparison device 1 is nearly twice. In addition, the temperature rise rate of thermal runaway of the implementation device 1 is significantly lower than the temperature rise rate of thermal runaway of the comparison device 1. Therefore, the intensity of the reaction during thermal runaway of the implementation device 1 is significantly weaker than the intensity of the reaction during thermal runaway of the comparison device 1, thereby greatly reducing the probability of fire or explosion of the implementation device 1.

[0132] See also Figure 6 and Figure 7 The present application also provides an electric power system 200 , which includes: an electric power device 210 and an energy storage device 100 provided in the present application, and the energy storage device 100 is used to supply power to the electric power device 210 .

[0133] It can be understood that the electrical device 210 is electrically connected to the energy storage device 100 .

[0134] In this embodiment, the energy storage device 100 performs differentiated design on the first battery module 110 and the second battery module 120, so that there is a time difference between the first battery module 110 and the second battery module 120 reaching the highest temperature of thermal runaway, which greatly reduces the temperature rise rate inside the energy storage device 100, so that the temperature inside the energy storage device 100 is not too high, which is conducive to reducing the probability of fire and explosion of the energy storage device 100, so that the energy storage device 100 has better safety performance and a longer service life. When the energy storage device 100 is applied to the power system 200, the energy storage device 100 can provide stable power for the power equipment 210, which is conducive to improving the user experience.

[0135] Optionally, the power system 200 of the embodiment of the present application can be, but is not limited to, a portable electronic device such as a mobile phone, a tablet computer, a laptop computer, a desktop computer, a smart bracelet, a smart watch, an e-reader, a game console, etc. It can also be a means of transportation such as a car, a truck, a car, a truck, a truck, a motor vehicle, a high-speed train, an electric vehicle, etc. In addition, it can also be various household appliances, etc. The present application Figure 6 The power consumption system 200 of the embodiment is an energy storage battery cabinet.

[0136] It can be understood that the power system 200 described in this embodiment is merely a form of the power system 200 used by the energy storage device 100, and should not be understood as a limitation on the power system 200 provided in the present application, nor should it be understood as a limitation on the power system 200 provided in each embodiment of the present application.

[0137] Mentioning "embodiment" and "implementation method" in this application means that the specific features, structures or characteristics described in conjunction with the embodiment may be included in at least one embodiment of the present application. The appearance of the phrases in various places in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described in this application can be combined with other embodiments. In addition, it should also be understood that the features, structures or characteristics described in the various embodiments of the present application can be arbitrarily combined to form another embodiment that does not deviate from the spirit and scope of the technical solution of the present application, provided that there is no contradiction between them.

[0138] Finally, it should be noted that the above implementation modes are only used to illustrate the technical solution of the present application and are not intended to limit it. Although the present application has been described in detail with reference to the above preferred implementation modes, a person of ordinary skill in the art should understand that the technical solution of the present application may be modified or replaced by equivalents without departing from the spirit and scope of the technical solution of the present application.

Claims

1. An energy storage device, characterized in that: The energy storage device comprises: a first battery module, the first battery module comprising a first separator; and a second battery module, the second battery module being connected in parallel with the first battery module, the second battery module comprising a second diaphragm; The thermal shrinkage rate of the first diaphragm along a preset direction at 150° C. is smaller than the thermal shrinkage rate of the second diaphragm along a preset direction at 150° C., wherein the preset direction is a height direction of the first battery module.

2. The energy storage device according to claim 1, characterized in that: The thermal shrinkage rate of the first diaphragm along the preset direction at 150° C. is η1, and the thermal shrinkage rate of the second diaphragm along the preset direction at 150° C. is η2, which satisfies the relationship: 0.14%≤η1 / η2≤66.67%.

3. The energy storage device according to claim 2, characterized in that: The range of the heat shrinkage rate η1 of the first diaphragm along the preset direction at 150° C. is: 0.1%≤η1≤20%, and the range of the heat shrinkage rate η2 of the second diaphragm along the preset direction at 150° C. is: 30%≤η2≤70%.

4. The energy storage device according to claim 1, characterized in that: The range of the time difference t between the first battery module and the second battery module reaching the maximum temperature of thermal runaway is: t≥1min, wherein thermal runaway refers to the temperature rise rate of the first battery module or the second battery module being greater than 3°C / s, and the temperature rise rate is the rate at which the temperature of the first battery module or the second battery module increases.

5. The energy storage device according to claim 4, characterized in that: When the second battery module is short-circuited, the first battery module is discharged to reduce the remaining capacity of the first battery module.

6. The energy storage device according to any one of claims 1 to 5, characterized in that: The first battery module further includes a first positive electrode sheet and a first negative electrode sheet. In the first battery module, the first positive electrode sheet, the first separator and the first negative electrode sheet are sequentially arranged. The second battery module further includes a second positive electrode sheet and a second negative electrode sheet. In the second battery module, the second positive electrode sheet, the second separator and the second negative electrode sheet are sequentially arranged. The first positive electrode plate includes a first positive electrode active material, the first positive electrode active material includes at least one of lithium iron phosphate, lithium nickel cobalt manganese oxide, lithium cobalt oxide, sodium iron pyrophosphate, and sodium nickel cobalt manganese oxide; the first negative electrode plate includes a first negative electrode active material, the first negative electrode active material includes at least one of graphite, silicon carbon, hard carbon, lithium titanate, and metallic lithium; the second positive electrode plate includes a second positive electrode active material, the second positive electrode active material includes at least one of lithium iron phosphate, lithium nickel cobalt manganese oxide, lithium cobalt oxide, sodium iron pyrophosphate, and sodium nickel cobalt manganese oxide; the second negative electrode plate includes a second negative electrode active material, the second negative electrode active material includes graphite, silicon carbon, hard carbon, lithium titanate, and lithium metal. 、 At least one of metallic lithium.

7. The energy storage device according to any one of claims 1 to 5, characterized in that: The energy efficiency E of the energy storage device when charging and discharging at a constant power of 0.5P at 25°C is in the range of 94%≤E<100%.

8. The energy storage device according to any one of claims 1 to 5, characterized in that: The energy storage device also includes a shell, which encloses a housing cavity, and the housing cavity is used to accommodate the first battery module and the second battery module; the number of the first battery module is at least one, and the number of the second battery module is at least one; when the number of the first battery modules is multiple and the number of the second battery modules is multiple, the second battery module is arranged closer to the middle position of the housing cavity than the first battery module.

9. The energy storage device according to any one of claims 1 to 5, characterized in that: The first battery module is selected from at least one of a winding structure and a stacked structure, and the second battery module is selected from at least one of a winding structure and a stacked structure.

10. An electricity system, characterized in that: The power system comprises: Electrical equipment; and The energy storage device according to any one of claims 1 to 9, wherein the energy storage device is used to supply power to the electrical equipment.

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