Single battery, energy storage device, energy storage system and power supply system

Abstract

The invention provides a single battery, an energy storage device, an energy storage system and a power supply system. The single battery comprises a plurality of roll cores, the roll cores are connected in parallel, each roll core comprises a positive pole piece, a diaphragm and a negative pole piece, and the diaphragm is located between the positive pole piece and the negative pole piece; and the thermal shrinkage rates of the diaphragms of at least two of the plurality of roll cores are different.

Description

Technical Field

[0001] This application relates to the field of energy storage, specifically to a single battery, an energy storage device, an energy storage system, and a power supply system. Background Technology

[0002] In related technologies, when a single battery cell in an energy storage device experiences thermal runaway, it is prone to excessive instantaneous gas production rate and low instantaneous gas exhaust rate. This causes the casing of the single battery cell to deform due to pressure difference, leading to casing breakage and failure, or even fire and ignition failure, thus reducing the safety of the single battery cell in use. Summary of the Invention

[0003] Therefore, this application provides a single-cell battery with high safety.

[0004] In a first aspect, embodiments of this application provide a single-cell battery, the single-cell battery comprising a plurality of winding cores connected in parallel, each winding core comprising a positive electrode sheet, a separator, and a negative electrode sheet, the separator being located between the positive electrode sheet and the negative electrode sheet; at least two of the winding cores have separators with different thermal shrinkage rates.

[0005] Furthermore, the single battery cell also includes a housing with a receiving cavity for accommodating the plurality of winding cores arranged sequentially; along the arrangement direction of the plurality of winding cores, the thermal shrinkage of the separator of the plurality of winding cores first gradually decreases and then gradually increases.

[0006] Furthermore, the diaphragm includes a base film and a coating, the coating being disposed on the surface of the base film, and the porosity of the base film of at least two of the plurality of cores being different, so that the thermal shrinkage rate of the diaphragm of at least two of the plurality of cores is different.

[0007] Furthermore, the plurality of cores includes a first core and a second core, wherein the porosity of the base film of the first core is P1 and the porosity of the base film of the second core is P2, and then 5% ≤ P2 - P1 ≤ 40%.

[0008] Furthermore, the porosity P1 of the base film of the first core is in the range of 40% ≤ P1 ≤ 60%, and the porosity P2 of the base film of the second core is in the range of 45% ≤ P2 ≤ 65%.

[0009] Furthermore, the diaphragm includes a base film and a coating. The coating is disposed on the surface of the base film. The coating includes a connected edge coating portion and a coating portion. Both the coating portion and the edge coating portion are located on the surface of the base film. The edge coating portion protrudes partially from the positive electrode sheet and partially from the negative electrode sheet. The areal density of the edge coating portion of at least two of the plurality of cores is different.

[0010] Furthermore, the plurality of cores includes a first core and a second core, wherein the areal density of the edge coating portion of the first core is ρ. 11 The areal density of the edge coating portion of the second core is ρ 21 Then 0.6≤ρ 21 / ρ 11 ≤0.9.

[0011] Furthermore, the areal density of the edge coating portion of the first core is ρ 11 The areal density of the coated portion of the first core is ρ 12 , then ρ 11 >ρ 12 ;

[0012] The areal density of the edge coating portion of the second core is ρ 21 The areal density of the coated portion of the second core is ρ 22 , then ρ 21 >ρ22.

[0013] Furthermore, the single cell satisfies the relationship: 1.1 ≤ ρ 11 / ρ 12 ≤1.6; and 1.1≤ρ 21 / ρ 22 ≤1.6.

[0014] Furthermore, the separator includes a base film and a coating. The coating is disposed on the surface of the base film. The coating includes a connected edge coating portion and a coating portion. Both the coating portion and the edge coating portion are located on the surface of the base film. The edge coating portion protrudes partially from the positive electrode sheet and partially from the negative electrode sheet. The edge coating portion includes a first adhesive and first ceramic particles. The first adhesive is used to bond the first ceramic particles together. The particle size distribution of the first ceramic particles in at least two of the plurality of cores is different.

[0015] Furthermore, if the plurality of winding cores includes a first winding core and a second winding core, then the single cell satisfies: 0.7≤D501 / D502≤0.9, and 1.1≤D901 / D902≤1.4;

[0016] Wherein, D501 is the particle size corresponding to the cumulative volume distribution number of the first ceramic particles in the first core reaching 50%, D502 is the particle size corresponding to the cumulative volume distribution number of the first ceramic particles in the second core reaching 50%, D901 is the particle size corresponding to the cumulative volume distribution number of the first ceramic particles in the first core reaching 90%, and D902 is the particle size corresponding to the cumulative volume distribution number of the first ceramic particles in the second core reaching 90%.

[0017] Furthermore, the coating portion includes a second adhesive and second ceramic particles, wherein the second adhesive is used to bond the second ceramic particles together; therefore, 0.6≤D501 / D503≤0.9; 1.1≤D901 / D903≤1.5;

[0018] Wherein, D503 is the particle size corresponding to when the cumulative volume distribution of the second ceramic particles in the first core reaches 50%, and D903 is the particle size corresponding to when the cumulative volume distribution of the second ceramic particles in the first core reaches 90%.

[0019] Furthermore, the coating portion includes a second adhesive and second ceramic particles, wherein the second adhesive is used to bond the second ceramic particles together; therefore, 0.6≤D502 / D504≤0.9; 1.1≤D902 / D904≤1.5;

[0020] Wherein, D504 is the particle size corresponding to when the cumulative volume distribution of the second ceramic particles in the second core reaches 50%, and D904 is the particle size corresponding to when the cumulative volume distribution of the second ceramic particles in the second core reaches 90%.

[0021] Furthermore, within the same core, the areal density of the edge coating portion is greater than the areal density of the coating portion, and along the arrangement direction of the edge coating portion and the coating portion, the widths of the edge coating portions of at least two cores among the plurality of cores are different.

[0022] Furthermore, the plurality of cores includes a first core and a second core. The heat shrinkage rate of the edge coating portion of the first core is less than that of the edge coating portion of the second core. Along the arrangement direction of the edge coating portion and the coating portion, the width of the edge coating portion of the first core is w1, and the width of the edge coating portion of the second core is w2. Then, 0.4≤w2 / w1≤1.

[0023] Secondly, embodiments of this application also provide an energy storage device, which includes: one or more single-cell batteries as described in embodiments of this application.

[0024] Thirdly, this application also provides an energy storage system, which includes: a high-voltage cable, a first power conversion device, a second power conversion device, and the energy storage device described in this application embodiment; the high-voltage cable is electrically connected to the energy storage device, the first power conversion device, and the second power conversion device respectively, the first power conversion device and the second power conversion device are both used to generate electrical energy, and the energy storage device is used to store the electrical energy.

[0025] Fourthly, embodiments of this application also provide a power supply system, which includes:

[0026] Electrical equipment; and

[0027] The energy storage device or energy storage system described in the embodiments of this application is used to supply power to the electrical equipment.

[0028] The single-cell battery described in this application embodiment includes multiple winding cores connected in parallel. Each winding core includes a positive electrode, a separator, and a negative electrode, with the separator located between the positive and negative electrode. At least two of the winding cores have separators with different thermal shrinkage rates. When the single-cell battery experiences thermal runaway, the separator with a higher thermal shrinkage rate among the winding cores exhibits more significant thermal shrinkage, leading to an earlier short circuit between the positive and negative electrode of that core and subsequent thermal runaway. Conversely, the separator with a lower thermal shrinkage rate among the winding cores exhibits less significant thermal shrinkage, resulting in a later short circuit between the positive and negative electrode of that core and subsequent thermal runaway. This avoids the instantaneous gas generation rate exceeding the maximum gas discharge rate of the single-cell battery when multiple winding cores experience simultaneous thermal runaway, preventing a rapid increase in heat generation and insufficient heat dissipation during thermal runaway. This better mitigates the risk of casing rupture, fire, or explosion, improving the safety of the single-cell battery. Furthermore, the single cell of this application includes multiple cores, which, compared to a single core solution, can better improve space utilization under limited space constraints and make fuller use of the space at the side corners of the single cell, thereby increasing the capacity and energy density of the single cell. Attached Figure Description

[0029] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 This is a schematic diagram of the structure of an energy storage system according to an embodiment of this application.

[0031] Figure 2 This is a schematic diagram of the power supply system according to an embodiment of this application.

[0032] Figure 3 This is a schematic diagram of the structure of an energy storage device according to an embodiment of this application.

[0033] Figure 4 This is a schematic diagram of the structure of a single battery cell according to an embodiment of this application.

[0034] Figure 5This application describes a single-cell battery according to an embodiment of the present application. Figure 4 A schematic diagram of the cross-sectional structure of AA.

[0035] Figure 6 This is a schematic diagram of the structure of a core according to an embodiment of this application.

[0036] Figure 7 This is a cross-sectional view of a diaphragm according to an embodiment of this application.

[0037] Figure 8 This is a structural schematic diagram of the arrangement of multiple cores according to an embodiment of this application.

[0038] Figure 9 This is a structural schematic diagram of the arrangement of multiple cores according to another embodiment of this application.

[0039] Figure 10 This is a cross-sectional view of the diaphragm according to another embodiment of this application.

[0040] Figure 11 This is a cross-sectional view of the first core and the second core according to an embodiment of this application.

[0041] Explanation of reference numerals in the attached figures:

[0042] 100 - Energy storage system; 110 - High-voltage cable; 120 - First energy conversion device; 130 - Second energy conversion device; 100' - Power supply system; 110' - Electrical equipment; 200 - Energy storage device; 300 - Single cell; 310 - Core; 310a - First core; 310b - Second core; 310c - Third core; 311 - Positive electrode; 312 - Separator; 3121 - Base film; 3122 - Coating; 31221 - Edge coating; 31222 - Coating part; 313 - Negative electrode; 320 - Housing; 321 - Reception cavity; 322 - First surface; 323 - Second surface; 330 - End cap assembly; 331 - Positive terminal; 332 - Negative terminal. Detailed Implementation

[0043] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present application.

[0044] The terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish different objects, not to describe a specific order. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or apparatus that includes a series of steps or units is not limited to the listed steps or units, but may optionally include steps or units not listed, or may optionally include other steps or units inherent to these processes, methods, products, or apparatuses.

[0045] The technical solutions in the embodiments of this application will now be described with reference to the accompanying drawings.

[0046] It should be noted that, for ease of explanation, the same reference numerals denote the same components in the embodiments of this application, and for the sake of brevity, detailed descriptions of the same components are omitted in different embodiments.

[0047] Because the energy we need is highly time- and space-dependent, in order to utilize energy rationally and improve energy efficiency, it is necessary to store one form of energy in the same way or by converting it into another, and then release it in a specific energy form based on future application needs. Currently, the main way to generate green electricity is to develop green energy sources such as photovoltaics and wind power to replace fossil fuels.

[0048] Currently, the generation of green electricity generally relies on solar, wind, and hydropower. However, wind and solar power are generally characterized by strong intermittency and large fluctuations, which can cause grid instability, insufficient power during peak demand periods, and excessive power during off-peak periods. Unstable voltage can also damage the power grid. Therefore, insufficient electricity demand or insufficient grid capacity may lead to the problem of "wind and solar curtailment." Solving these problems requires energy storage. This involves converting electrical energy into other forms of energy through physical or chemical means and storing it. When needed, this energy can be converted back into electrical energy and released. Simply put, energy storage is like a large "power bank," storing electrical energy when solar and wind power are abundant and releasing the stored electricity when needed.

[0049] Taking electrochemical energy storage as an example, this solution provides an energy storage device for use in energy storage systems. The energy storage device is equipped with a set of chemical batteries, which mainly use the chemical elements in the batteries as energy storage media. The charging and discharging process is accompanied by the chemical reaction or change of the energy storage media. Simply put, the electrical energy generated by wind and solar energy is stored in the chemical batteries. When the use of external electrical energy reaches its peak, the stored electricity is released for use, or transferred to places with a shortage of electricity for use.

[0050] Current energy storage applications are quite widespread, including generation-side energy storage, grid-side energy storage, and consumption-side energy storage. The corresponding types of energy storage devices include:

[0051] (1) Large-scale energy storage power stations (including multiple prefabricated energy storage modules) applied to wind power and photovoltaic power stations can help renewable energy power generation meet grid connection requirements and improve the utilization rate of renewable energy. As a high-quality active / reactive power regulation power source on the power supply side, energy storage power stations can achieve load matching of power in time and space, enhance the absorption capacity of renewable energy, reduce instantaneous power changes, reduce the impact on the power grid, improve the absorption of new energy power generation, and are of great significance in power grid system backup, alleviating peak load power supply pressure and peak regulation and frequency regulation.

[0052] (2) The energy storage prefabricated cabin applied on the grid side mainly functions as peak regulation, frequency regulation and grid congestion relief. In terms of peak regulation, it can realize peak shaving and valley filling of electricity load, that is, charging the energy storage battery when the electricity load is low and releasing the stored electricity during the peak electricity load period, thereby achieving a balance between power production and consumption.

[0053] (3) Small energy storage cabinets applied to the electricity consumption side mainly function as self-consumption of electricity, peak-valley price arbitrage, capacity cost management, and improvement of power supply reliability. Depending on the application scenario, electricity consumption side energy storage can be divided into industrial and commercial energy storage cabinets, household energy storage devices, energy storage charging piles, etc., which are generally used in conjunction with distributed photovoltaics. Industrial and commercial users can use energy storage for peak-valley price arbitrage and capacity cost management. In the electricity market implementing peak-valley pricing, by charging the energy storage system when the electricity price is low and discharging the energy storage system when the electricity price is high, peak-valley price arbitrage can be achieved, reducing electricity costs. In addition, industrial enterprises subject to two-part tariffs can use energy storage systems to store energy during off-peak hours and discharge during peak loads, thereby reducing peak power and the maximum demand declared, achieving the goal of reducing capacity charges. Household photovoltaics with energy storage can improve the level of self-consumption of electricity. Due to high electricity prices and poor power supply stability, the demand for household photovoltaic installations is driven. Given that photovoltaic power generation occurs during the day, while user load is generally higher at night, configuring energy storage can better utilize photovoltaic power, improve self-consumption levels, and reduce electricity costs. Furthermore, energy storage is needed in areas such as communication base stations and data centers for backup power.

[0054] In some embodiments, see Figure 1 , Figure 1 This is a schematic diagram of the structure of an energy storage system 100 according to an embodiment of this application, and this application Figure 1 The embodiments are illustrated using a shared energy storage scenario on the power generation / distribution side as an example. The energy storage device 200 in this application is not limited to a prefabricated energy storage module in a power generation / distribution energy storage scenario.

[0055] This application provides an energy storage system 100, which includes: a high-voltage cable 110, a first power conversion device 120, a second power conversion device 130, and an energy storage device 200 provided in this application. In some embodiments of the power generation scenario, the second power conversion device 130 can be a wind power conversion device. Since the electricity generated by wind power conversion is volatile, random, and intermittent, the unstable electricity output by the wind power conversion device can be stored in the energy storage device 200 through grid connection. The energy storage device 200 is connected to the high-voltage cable 110 and outputs smooth electricity to the power consumption side of the distribution network, realizing peak shaving and frequency regulation, and stable grid operation; or, wind power conversion... The power conversion device is always connected to the high-voltage cable 110. Under normal power generation conditions, the power output of the wind power conversion device is supplied to the power consumption side of the distribution network through the high-voltage cable 110. When the current power load is low and the wind power conversion device generates excess power, the excess power is first stored in the energy storage device 200 to reduce wind and solar curtailment rates and improve the problem of new energy power generation consumption. When the power load is high, the power grid issues an instruction to transmit the power stored in the energy storage device 200 together with the high-voltage cable 110 in grid-connected mode to supply power to the power consumption side. This provides the power grid with various services such as peak shaving, frequency regulation, and backup, giving full play to the peak shaving role of the power grid, promoting peak shaving and valley filling, and alleviating the power supply pressure of the power grid.

[0056] In some embodiments on the distribution network side, the first power conversion device 120 can be a photovoltaic panel, and the energy storage device 200 is connected to the high-voltage cable 110 and installed downstream of the high-voltage cable 110 between the user load and the photovoltaic power conversion device. The electrical energy output by the photovoltaic power conversion device is stored in the energy storage device 200, which can respond in a timely manner to act as a backup power source when the power grid / distribution network fails; or, it can provide power supply support to alleviate line congestion when the high-voltage cable 110 transmission line is blocked, and to delay the economic pressure caused by the expansion of the power grid / distribution capacity when the power grid is planned to be expanded.

[0057] Optionally, the first power conversion device 120 may include, but is not limited to, a photovoltaic panel, and the second power conversion device 130 may include, but is not limited to, a wind power conversion device. The first power conversion device 120 and the second power conversion device 130 can convert at least one of solar energy, light energy, wind energy, thermal energy, tidal energy, biomass energy, and mechanical energy into electrical energy.

[0058] Optionally, the energy storage device 200 may include, but is not limited to, energy storage applications such as energy storage power stations, hydropower / thermal / wind power generation systems, solar power generation systems, mobile power systems, smart home systems, or temporary power supply systems, and may also be applied in multiple fields such as data centers, military equipment, aerospace, charging piles, and electric vehicles.

[0059] Figure 2This is a schematic diagram of the power supply system 100' according to an embodiment of this application.

[0060] This application embodiment also provides a power supply system 100', which includes an electrical device 110' and an energy storage device 200 or an energy storage system 100 as described in this application embodiment, wherein the energy storage device 200 or the energy storage system 100 is used to supply power to the electrical device 110'.

[0061] Optionally, the electrical equipment 110' can be, but is not limited to, at least one of the following: power grid, base station, household appliances (such as air conditioners, lamps, refrigerators, etc.), commercial charging equipment (such as photovoltaic storage charging stations).

[0062] It should be noted that when the power supply system 100' includes the energy storage system 100, the electrical equipment 110' is electrically connected to the high-voltage cable 110 of the energy storage system.

[0063] Please see Figure 3 , Figure 3 This is a schematic diagram of the structure of an energy storage device 200 according to an embodiment of this application.

[0064] Optionally, the energy storage device 200 may include, but is not limited to, one or more individual battery cells 300.

[0065] The term "multiple" refers to two or more, such as, but not limited to, 2, 5, 10, 30, 50, 100, 200, 300, 400, 800, 1000, etc. The number of individual battery cells 300 included in the energy storage device 200 can be determined based on the rated capacity of the individual battery cells 300 and the rated capacity to be achieved by the energy storage device 200.

[0066] It should be noted that when the energy storage device 200 includes a single battery cell 300, the energy storage device 200 can exist in the form of a single battery cell 300. When the energy storage device 200 includes multiple single batteries 300, the multiple single batteries 300 can be stacked, arranged, assembled, and other processes to form battery integrated systems such as battery modules, battery packs, battery clusters, power banks, energy storage cabinets / prefabricated energy storage compartments. In other words, the energy storage device 200 can exist in the form of, but is not limited to, battery integrated systems such as battery modules, battery packs, battery clusters, power banks, energy storage cabinets / prefabricated energy storage compartments. The actual application form of the energy storage device 200 provided in this application embodiment can be, but is not limited to, the listed products, and can also be other application forms. This application embodiment does not strictly limit the application form of the energy storage device 200.

[0067] Optionally, the single cell 300 can be, but is not limited to, at least one of cylindrical, square, prismatic, or other shaped cells.

[0068] Optionally, the single cell 300 can be a rechargeable battery, which refers to a single cell 300 that can be recharged after discharge to activate the active materials and continue to be used. The single cell 300 can be a lithium-ion battery, sodium-ion battery, sodium-lithium-ion battery, lithium metal battery, sodium metal battery, lithium-sulfur battery, magnesium-ion battery, nickel-metal hydride battery, nickel-cadmium battery, lead-acid battery, etc., and this application does not specifically limit it.

[0069] In related technologies, when a single battery cell in an energy storage device experiences thermal runaway, it is prone to excessive instantaneous gas production rate and low instantaneous gas exhaust rate. This causes the casing of the single battery cell to deform due to pressure difference, leading to casing breakage and failure, or even fire and ignition failure, thus reducing the safety of the single battery cell in use.

[0070] To achieve greater capacity and energy density and fully utilize the internal space of individual battery cells, for prismatic hard-shell cells (such as lithium-ion cells), two or more cores are typically connected in parallel under limited space constraints. Multiple cores can better utilize the limited space and make fuller use of the corner space, thus increasing capacity and energy density. However, in the event of thermal runaway, multiple cores in a multi-core cell are prone to simultaneously triggering short circuits and violent gas venting. This causes the instantaneous gas generation rate within the cell to exceed the effective instantaneous gas venting rate, easily leading to deformation of the cell casing due to pressure differences, resulting in cell failure due to casing rupture or even fire.

[0071] Figure 4 This is a schematic diagram of the structure of a single cell battery 300 according to an embodiment of this application. Figure 5 This application describes a single-cell battery 300 along one embodiment. Figure 4 A schematic diagram of the cross-sectional structure of AA. Figure 6 This is a schematic diagram of the structure of the core 310 according to an embodiment of this application.

[0072] Please see Figures 4 to 6 This application provides a single-cell battery 300, which includes a plurality of coils 310 connected in parallel. Each coil 310 includes a positive electrode 311, a separator 312, and a negative electrode 313. The separator 312 is located between the positive electrode 311 and the negative electrode 313. At least two of the coils 310 have different thermal shrinkage rates for their separators 312.

[0073] The term "multiple" refers to two or more.

[0074] Specifically, the number of winding cores 310 in the single battery cell 300 can be, but is not limited to, 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 14, 16, 18, 20, etc.

[0075] In some examples, the thermal shrinkage rates of the separator 312 of at least two of the plurality of cores 310 are different across the entire layer. In some examples, at least a portion of the separator 312 of at least two of the plurality of cores 310 (e.g., the overhang region, i.e., the portion of the separator 312 that protrudes from the positive electrode 311 and the negative electrode 313) and the portion near the overhang region have different thermal shrinkage rates.

[0076] Figure 7 This is a cross-sectional view of a diaphragm 312 according to an embodiment of this application.

[0077] Please see Figure 7 In some examples, the diaphragm 312 includes a base film 3121 and a coating 3122, the coating 3122 being disposed on the surface of the base film 3121, and the base film 3121 of at least two of the plurality of winding cores 310 has a different rate of thermal shrinkage. In still other examples, the diaphragm 312 includes a base film 3121 and a coating 3122, the coating 3122 being disposed on the surface of the base film 3121, and at least a portion of the coating 3122 of at least two of the plurality of winding cores 310 has a different rate of thermal shrinkage.

[0078] The single-cell battery 300 of this application embodiment includes a plurality of coils 310 connected in parallel. Each coil 310 includes a positive electrode 311, a separator 312, and a negative electrode 313. The separator 312 is located between the positive electrode 311 and the negative electrode 313. At least two of the coils 310 have different thermal shrinkage rates for their separators 312. When the single cell 300 experiences thermal runaway, the separator 312 with a higher thermal shrinkage rate among the multiple cores 310 undergoes more significant thermal shrinkage, causing the corresponding positive electrode 311 and negative electrode 313 to short-circuit earlier and experience thermal runaway earlier. Conversely, the separator 312 with a lower thermal shrinkage rate among the multiple cores 310 undergoes less significant thermal shrinkage, causing the corresponding positive electrode 311 and negative electrode 313 to short-circuit later and experience thermal runaway later. This avoids the instantaneous gas generation rate from exceeding the maximum exhaust rate of the single cell 300 when multiple cores 310 experience thermal runaway simultaneously, preventing a sharp increase in heat generation and insufficient heat dissipation during thermal runaway. This better avoids the risk of the single cell 300's casing rupture or even fire and explosion, improving the safety of the single cell 300 in use. Furthermore, the single cell 300 of this application includes multiple cores 310. Compared with the single core 310 solution, it can better improve the space utilization rate under limited space constraints, make fuller use of the space at the side corners of the single cell 300, and improve the capacity and energy density of the single cell 300.

[0079] Please see again Figure 4 and Figure 5 In some embodiments, the single battery cell 300 further includes a housing 320, the housing 320 having a receiving cavity 321 for receiving the plurality of winding cores 310 arranged in sequence; along the arrangement direction of the plurality of winding cores 310, the thermal shrinkage of the separator 312 of the plurality of winding cores 310 first gradually decreases and then gradually increases.

[0080] Understandably, the receiving cavity 321 is a receiving cavity 321 with one end open.

[0081] Understandably, along the arrangement direction of the plurality of cores 310, the thermal shrinkage rate of the diaphragm 312 of the core 310 closer to the housing 320 is greater, and the thermal shrinkage rate of the diaphragm 312 of the core 310 further away from the housing 320 is smaller.

[0082] Figure 8 This is a structural schematic diagram of the arrangement of multiple cores 310 according to an embodiment of this application.

[0083] Please see Figure 8In one example, the plurality of cores 310 include two first cores 310a and two second cores 310b. The heat shrinkage rate of the diaphragm 312 of the first core 310a is less than that of the diaphragm 312 of the second core 310b. The four cores 310 are arranged in the order of second core 310b, first core 310a, first core 310a, and second core 310b. That is, the second cores 310b with two diaphragms 312 having a higher heat shrinkage rate are located on the outer side (closer to the housing 320), and the first cores 310a with two diaphragms 312 having a lower heat shrinkage rate are located in the middle (closer to the inside of the core 310).

[0084] Figure 9 This is a structural schematic diagram of the arrangement of multiple cores 310 according to another embodiment of this application.

[0085] Please see Figure 9 In another example, the plurality of cores 310 include two first cores 310a, two second cores 310b, and two third cores 310c. The heat shrinkage rate of the diaphragm 312 of the first core 310a is less than that of the diaphragm 312 of the second core 310b, and the heat shrinkage rate of the diaphragm 312 of the second core 310b is less than that of the diaphragm 312 of the third core 310c. The six cores 310 are arranged in the order of third core 310c, second core 310b, first core 310a, first core 310a, second core 310b, and third core 310c. That is, the third core 310c with the maximum heat shrinkage rate of the two diaphragms 312 is located on the outermost side (closer to the housing 320), the second core 310b with the medium heat shrinkage rate of the two diaphragms 312 is located on the next outermost side, and the third core 310c with the minimum heat shrinkage rate of the two diaphragms 312 is located in the middle.

[0086] In this embodiment, along the arrangement direction of the plurality of winding cores 310, the thermal shrinkage of the separator 312 of the plurality of winding cores 310 gradually decreases first, and then gradually increases. Thus, when the single cell 300 has a large number of winding cores 310, when the single cell 300 has an external heat source and experiences thermal runaway, the multiple winding cores 310 can gradually experience thermal runaway from the outside in, better staggering the thermal runaway time of each winding core 310. This results in more stable gas production during thermal runaway of the single cell 300, better preventing the single cell 300 from exploding or catching fire due to excessively rapid instantaneous gas production.

[0087] Please see again Figure 4The single cell 300 further includes an electrolyte and an end cap assembly 330. The electrolyte is disposed in the receiving cavity 321 for wetting the plurality of winding cores 310. The end cap assembly 330 is connected to the housing 320 for sealing the opening of the receiving cavity 321. The end cap assembly 330 includes an insulated positive terminal 331 and a negative terminal 332. The positive terminal 331 is electrically connected to the positive electrode 311 of each winding core 310, and the negative terminal 332 is electrically connected to the negative electrode 313 of each winding core 310.

[0088] Optionally, the housing 320 has a first surface 322 and a second surface 323 arranged opposite to each other, wherein the first surface 322 and the second surface 323 are the two surfaces with the largest area among all the surfaces of the housing 320. The plurality of winding cores 310 are arranged sequentially along the arrangement direction of the first surface 322 and the second surface 323.

[0089] Optionally, the core 310 has a flat structure, and the core 310 has a cross-section parallel to the winding direction of the core 310. The cross-section has a long side and a short side, and the long side is parallel to the first surface 322 and / or the second surface 323.

[0090] Please see again Figure 7 In some embodiments, the diaphragm 312 includes a base film 3121 and a coating 3122, the coating 3122 being disposed on the surface of the base film 3121, and the porosity of the base film 3121 of at least two of the plurality of cores 310 is different, so that the thermal shrinkage rate of the diaphragm 312 of at least two of the plurality of cores 310 is different.

[0091] It should be noted that the smaller the porosity of the base membrane 3121, the smaller the thermal shrinkage rate of the base membrane 3121 and the diaphragm 312; the larger the porosity of the base membrane 3121, the larger the thermal shrinkage rate of the base membrane 3121 and the diaphragm 312.

[0092] In this embodiment, at least two of the plurality of winding cores 310 have different porosities in their base films 3121. When the single-cell battery 300 experiences thermal runaway, the winding core 310 with a higher porosity in its base film 3121 has a higher thermal shrinkage rate, and the separator 312 experiences more significant thermal shrinkage. The positive electrode 311 and negative electrode 313 corresponding to this winding core 310 will short-circuit earlier and experience thermal runaway earlier. Conversely, the winding core 310 with a lower porosity in its base film 3121 has a lower thermal shrinkage rate, and the separator 312 experiences less significant thermal shrinkage. The positive electrode 311 and negative electrode 313 corresponding to the core 310 short-circuit later and thermal runaway later; thus, when multiple cores 310 experience thermal runaway simultaneously, the instantaneous gas generation rate is too fast, exceeding the maximum exhaust rate of the single cell 300. This also prevents the heat generation from increasing sharply and the heat dissipation from being insufficient when the single cell 300 experiences thermal runaway. This better avoids the risk of the casing 320 of the single cell 300 cracking or even causing fire or explosion, and improves the safety of using the single cell 300.

[0093] Please see again Figure 5 and Figure 8 In some embodiments, the plurality of cores 310 includes a first core 310a and a second core 310b, wherein the porosity of the base film 3121 of the first core 310a is P1 and the porosity of the base film 3121 of the second core 310b is P2, and then 5% ≤ P2 - P1 ≤ 40%.

[0094] Understandably, in this embodiment, the porosity of the base film 3121 of the second core 310b is greater than the porosity of the base film 3121 of the first core 310a.

[0095] Specifically, P2-P1 can be, but is not limited to, 5%, 6%, 8%, 10%, 12%, 14%, 16%, 18%, 20%, 22%, 24%, 26%, 28%, 30%, 32%, 34%, 36%, 38%, 40%, etc.

[0096] In this embodiment, if P2-P1 is too small, when the single cell 300 experiences thermal runaway, the thermal runaway times of the first core 310a and the second core 310b will be too close and difficult to be completely staggered. This is not conducive to reducing the maximum instantaneous gas production of the single cell 300 and is not conducive to improving the safety of the single cell 300. If P2-P1 is too large, then P2 will be too large or P1 will be too small. If P2 is too large, the self-discharge of the second core 310b will increase, reducing the storage life of the second core 310b. If P1 is too small, the electrolyte wettability of the separator 312 of the first core 310a will be reduced, reducing the transport rate of metal ions (e.g., lithium ions, sodium ions), thus hindering the transport of metal ions and reducing the dynamic performance of the single cell 300. In addition, if P2-P1 is too large, the metal ion transport rate of the first core 310a and the second core 310b will not be consistent, so the capacity of the first core 310a with a lower metal ion transport rate cannot be fully utilized, reducing the cycle capacity retention rate of the single cell 300.

[0097] In some embodiments, the porosity P1 of the base film 3121 of the first core 310a is in the range of 40% ≤ P1 ≤ 60%, and the porosity P2 of the base film 3121 of the second core 310b is in the range of 45% ≤ P2 ≤ 65%.

[0098] Specifically, the porosity P1 of the base film 3121 of the first core 310a can be, but is not limited to, 40%, 42%, 44%, 46%, 48%, 50%, 52%, 54%, 56%, 58%, 60%, etc.

[0099] If the porosity P1 of the base film 3121 of the first core 310a is too low, the electrolyte wettability of the separator 312 of the first core 310a is reduced, the transport rate of metal ions (e.g., lithium ions, sodium ions) is reduced, the transport of metal ions is hindered, and the dynamic performance of the single cell 300 is reduced.

[0100] If the porosity P1 of the base film 3121 of the first core 310a is too high, the thermal shrinkage rate of the separator 312 of the first core 310a and the thermal shrinkage rate of the separator 312 of the second core 310b will be similar. When the single cell 300 experiences thermal runaway, the thermal runaway times of the first core 310a and the second core 310b will be too close and difficult to be completely staggered. This is not conducive to reducing the maximum instantaneous gas production of the single cell 300 and improving the safety of the single cell 300. In addition, if the porosity P1 of the base film 3121 of the first core 310a is too high, the self-discharge of the first core 310a will increase, reducing the storage life of the first core 310a.

[0101] Specifically, the porosity P2 of the base film 3121 of the second core 310b can be, but is not limited to, 45%, 46%, 48%, 50%, 52%, 54%, 56%, 58%, 60%, 62%, 64%, 65%, etc.

[0102] If the porosity P2 of the base film 3121 of the second core 310b is too low, the thermal shrinkage rate of the separator 312 of the first core 310a and the thermal shrinkage rate of the separator 312 of the second core 310b will be similar. When the single cell 300 experiences thermal runaway, the thermal runaway times of the first core 310a and the second core 310b will be too close and difficult to be completely staggered. This is not conducive to reducing the maximum instantaneous gas production of the single cell 300 and is not conducive to improving the safety of the single cell 300. In addition, if the porosity P2 of the base film 3121 of the second core 310b is too low, it will reduce the electrolyte wettability of the separator 312 of the second core 310b, reduce the transport rate of metal ions (such as lithium ions and sodium ions), and hinder the transport of metal ions, thereby reducing the dynamic performance of the single cell 300.

[0103] If the porosity P2 of the base film 3121 of the second core 310b is too high, the self-discharge of the second core 310b will increase, reducing the storage life of the second core 310b.

[0104] Figure 10 This is a cross-sectional view of the diaphragm 312 according to another embodiment of this application.

[0105] Please see Figure 10 In some embodiments, the diaphragm 312 includes a base film 3121 and a coating 3122. The coating 3122 is disposed on the surface of the base film 3121. The coating 3122 includes an adjacent edge coating portion 31221 and a coating portion 31222. Both the coating portion 31222 and the edge coating portion 31221 are located on the surface of the base film 3121. The edge coating portion 31221 protrudes partially from the positive electrode sheet 311 and partially from the negative electrode sheet 313. The areal density of the edge coating portion 31221 of at least two of the plurality of cores 310 is different.

[0106] Optionally, there are two edge coating portions 31221, which are located on opposite sides of the coating portion 31222. It can be understood that the edge coating portions 31221, the coating portion 31222, and the edge coating portions 31221 are arranged sequentially.

[0107] It should be noted that the arrangement direction of the edge coating portion 31221 and the coating portion 31222 is perpendicular to the winding direction of the core 310. The edge coating portions 31221 on both sides of the diaphragm 312 partially protrude from the positive electrode plate 311 and partially protrude from the negative electrode plate 313.

[0108] It should be noted that the areal density (i.e., coating weight per unit area) of the edge coating portion 31221 of at least two of the plurality of cores 310 is different: it can be that the thickness of the edge coating portion 31221 of at least two of the plurality of cores 310 is different, but the compaction density is the same; it can also be that the thickness of the edge coating portion 31221 of at least two of the plurality of cores 310 is the same, but the compaction density or porosity is different.

[0109] It should be noted that the thermal shrinkage rate of coating 3122 is less than that of base film 3121. The greater the areal density of coating 3122, the smaller the thermal shrinkage rate of diaphragm 312; the smaller the areal density of coating 3122, the greater the thermal shrinkage rate of diaphragm 312.

[0110] It should be noted that the areal density of this application can be measured using the following gravimetric method, specifically: (1) a standard cutter (usually a round punch or square cutter) is used to cut samples of a specified area from different positions (such as head, middle, tail, left, center, and right) of the diaphragm 312; the cutter must be sharp to ensure neat edges and that the area is accurately known (it needs to be calibrated regularly); commonly used sample areas are 100 cm². 2 (approximately 113mm in diameter), 50cm 2 25cm 2 (2) Weigh the cut sample mass using a high-precision electronic balance (usually with an accuracy of 0.0001g or higher); (3) Calculate: surface density = (sample mass / sample area); the unit is usually g / m². 2 (grams per square meter)

[0111] In this embodiment, at least two of the plurality of cores 310 have different surface densities in the edge coating portion 31221. When the single cell 300 experiences thermal runaway, the core 310 with a smaller areal density of the edge coating 31221 among the plurality of cores 310 has a larger thermal shrinkage rate. The positive electrode 311 and negative electrode 313 corresponding to this core 310 will short-circuit earlier and experience thermal runaway earlier. Conversely, the core 310 with a larger areal density of the edge coating 31221 among the plurality of cores 310 has a smaller thermal shrinkage rate. The positive electrode 311 and negative electrode 313 corresponding to this core 310 will short-circuit later and experience thermal runaway later. This avoids the instantaneous gas generation rate from exceeding the maximum exhaust rate of the single cell 300 when multiple cores 310 experience thermal runaway simultaneously. It also prevents the heat generation from increasing rapidly and the heat dissipation from being insufficient when the single cell 300 experiences thermal runaway. This better avoids the risk of the casing 320 of the single cell 300 cracking or even causing fire or explosion, and improves the safety of the single cell 300 in use.

[0112] Please see again Figure 5 , Figure 8 and Figure 10 In some embodiments, the plurality of cores 310 includes a first core 310a and a second core 310b, wherein the areal density of the edge coating portion 31221 of the first core 310a is ρ. 11 The areal density of the edge coating portion 31221 of the second core 310b is ρ. 21 Then 0.6≤ρ 21 / ρ 11 ≤0.9.

[0113] Understandably, in this embodiment, the areal density of the edge coating portion 31221 of the first core 310a is ρ. 11 The areal density of the edge coating portion 31221, which is greater than that of the second core 310b, is ρ. 21 .

[0114] Specifically, ρ 21 / ρ 11 It can be, but is not limited to, 0.6, 0.62, 0.64, 0.66, 0.68, 0.7, 0.72, 0.74, 0.76, 0.78, 0.8, 0.82, 0.84, 0.86, 0.88, 0.9, etc.

[0115] It should be noted that, in this embodiment, the heat shrinkage rate of the edge coating portion 31221 corresponding to the diaphragm 312 of the first core 310a is different from that of the edge coating portion 31221 corresponding to the diaphragm 312 of the second core 310b. For example, the heat shrinkage rate of the edge coating portion 31221 of the first core 310a is less than that of the edge coating portion 31221 of the second core 310b. The heat shrinkage rate of the coating portion 31222 corresponding to the diaphragm 312 of the first core 310a is the same as that of the coating portion 31222 corresponding to the diaphragm 312 of the second core 310b, or they may be different. For example, the heat shrinkage rate of the coating portion 31222 corresponding to the diaphragm 312 of the first core 310a is less than that of the coating portion 31222 corresponding to the diaphragm 312 of the second core 310b.

[0116] Optionally, the areal density ρ of the edge coating portion 31221 of the first core 310a 11 The areal density ρ of the edge coating portion 31221 of the second core 310b is greater than that of the second core 310b. 21 The areal density ρ of the coating portion 31222 of the first core 310a 12 The areal density ρ of the coating portion 31222 of the second core 310b is greater than or equal to that of the second core 310b. 22 .

[0117] Optionally, the areal density ρ of the edge coating portion 31221 of the first core 310a 11 The range is 6g / cm 2 Up to 14g / cm 2 Specifically, the areal density ρ of the edge coating portion 31221 of the first core 310a 11 It can be, but is not limited to, 6g / cm³ 2 6.5g / cm 2 7g / cm 2 7.5g / cm 2 8g / cm 2 8.5g / cm 2 9g / cm 2 9.5g / cm 2 10g / cm 2 10.5g / cm 2 11g / cm 2 11.5g / cm 2 12g / cm 2 13g / cm 2 14g / cm 2 wait.

[0118] Optionally, the areal density ρ of the edge coating portion 31221 of the second core 310b 21 The range is 6g / cm2 Up to 14g / cm 2 Specifically, the areal density ρ of the edge coating portion 31221 of the second core 310b 21 It can be, but is not limited to, 6g / cm³ 2 6.5g / cm 2 7g / cm 2 7.5g / cm 2 8g / cm 2 8.5g / cm 2 9g / cm 2 9.5g / cm 2 10g / cm 2 10.5g / cm 2 11g / cm 2 11.5g / cm 2 12g / cm 2 13g / cm 2 14g / cm 2 wait.

[0119] In this embodiment, if ρ 21 / ρ 11 If the density ρ is too small, the areal density ρ of the edge coating portion 31221 of the first core 310a will be too small. 11 The areal density ρ of the edge coating portion 31221 of the second core 310b 21 If the difference is too large, the consistency between the first core 310a and the second core 310b will be poor. The second core 310b, with its lower areal density, will have a faster metal ion transport rate, while the first core 310a, with its higher areal density, will have a slower metal ion transport rate, resulting in reduced cycle performance. Furthermore, if the self-discharge difference between the first core 310a and the second core 310b is too large, the second core 310b, with its lower areal density, will have a larger self-discharge, leading to a reduced cycle life. If ρ 11 / ρ 21 If the thermal shrinkage rate is too large, the thermal shrinkage rate of the separator 312 corresponding to the edge coating 31221 of the first core 310a and the thermal shrinkage rate of the separator 312 corresponding to the edge coating 31221 of the second core 310b will be too close. When the single cell 300 experiences thermal runaway, the thermal runaway times of the first core 310a and the second core 310b will be too close and difficult to be completely staggered. This is not conducive to reducing the maximum instantaneous gas production of the single cell 300 and is not conducive to improving the safety of the single cell 300.

[0120] In some embodiments, the areal density of the edge coating portion 31221 of the first core 310a is ρ. 11 The areal density of the coating portion 31222 of the first core 310a is ρ. 12 , then ρ 11 >ρ12 ;

[0121] The areal density of the edge coating portion 31221 of the second core 310b is ρ 21 The areal density of the coating portion 31222 of the second core 310b is ρ. 22 , then ρ 21 >ρ 22 .

[0122] The portion of the separator 312 that is stacked with the positive electrode 311 and the negative electrode 313 is bound by the positive electrode 311 and the negative electrode 313. Therefore, when the material composition of the entire separator 312 is uniform, the thermal shrinkage rate of this portion of the separator 312 is relatively low. The binding force of the portion of the separator 312 that protrudes from the positive electrode 311 and the negative electrode 313 is relatively small. Therefore, when the material composition of the entire separator 312 is uniform, the thermal shrinkage rate of the portion of the separator 312 that protrudes from the positive electrode 311 and the negative electrode 313 is relatively high. This portion is usually the thermal runaway induction point (also known as the trigger point) of the core 310. After the core 310 is formed, the edge coating portion 31221 at least partially covers the portion of the base film 3121 that protrudes from the positive electrode 311 and the negative electrode 313, and the coating portion 31222 covers the portion of the base film 3121 that is stacked with the positive electrode 311 and the negative electrode 313. In this embodiment, the areal density of the edge coating portion 31221 of the first core 310a is greater than the areal density of the coating portion 31222 of the first core 310a, and the areal density of the edge coating portion 31221 of the second core 310b is greater than the areal density of the coating portion 31222 of the second core 310b. This makes the thermal shrinkage rate of the edge coating portion 31221 of the first core 310a less than the thermal shrinkage rate of the coating portion 31222 of the first core 310a, and the thermal shrinkage rate of the edge coating portion 31221 of the second core 310b is less than the thermal shrinkage rate of the coating portion 31222 of the second core 310b. The shrinkage rate is less than the thermal shrinkage rate of the coating portion 31222 of the second core 310b, thereby better reducing the thermal shrinkage rate of the diaphragm 312 of the corresponding edge coating portion 31221 of the first core 310a and the second core 310b, improving the heat resistance of the diaphragm 312 of the first core 310a and the diaphragm 312 of the second core 310b, thereby improving the overcharge resistance of the first core 310a and the second core 310b, and improving the pass rate of the overcharge test of the first core 310a and the second core 310b.

[0123] In some embodiments, the single cell 300 satisfies the relationship: 1.1 ≤ ρ 11 / ρ 12 ≤1.6; and 1.1≤ρ 21 / ρ 22 ≤1.6.

[0124] Specifically, ρ 11 / ρ 12It can be, but is not limited to, 1.1, 1.15, 1.2, 1.25, 1.3, 1.35, 1.4, 1.45, 1.5, 1.55, 1.6, etc. If ρ 11 / ρ 12 If the value is too small, the improvement in the heat resistance of the first core 310a and the pass rate of the overcharge test will be limited; if ρ 11 / ρ 12 If the thickness is too large, the edge coating portion 31221 of the diaphragm 312 of the first core 310a will be too thick. After the first core 310a is wound, during hot pressing, the layers of the first core 310a will not be pressed tightly, reducing the cycle life of the first core 310a.

[0125] Specifically, ρ 21 / ρ 22 It can be, but is not limited to, 1.1, 1.15, 1.2, 1.25, 1.3, 1.35, 1.4, 1.45, 1.5, 1.55, 1.6, etc. If ρ 21 / ρ 22 If the value is too small, the improvement in the heat resistance of the second core 310b and the pass rate of the overcharge test will be limited; if ρ 21 / ρ 22 If the thickness is too large, the edge coating portion 31221 of the diaphragm 312 of the second core 310b will be too thick. After the second core 310b is wound, during hot pressing, the layers of the second core 310b will not be pressed tightly together, reducing the cycle life of the second core 310b.

[0126] Optionally, the areal density ρ of the coating portion 31222 of the first core 310a 12 The range is 6g / cm 2 Up to 14g / cm 2 Specifically, the areal density ρ of the coating portion 31222 of the first core 310a 12 It can be, but is not limited to, 6g / cm³ 2 6.5g / cm 2 7g / cm 2 7.5g / cm 2 8g / cm 2 8.5g / cm 2 9g / cm 2 9.5g / cm 2 10g / cm 2 10.5g / cm 2 11g / cm 2 11.5g / cm 2 12g / cm 2 13g / cm 2 14g / cm 2 wait.

[0127] Optionally, the areal density ρ of the coating portion 31222 of the second core 310b 22 The range is 6g / cm 2 Up to 14g / cm 2 Specifically, the areal density ρ of the coating portion 31222 of the second core 310b 22 It can be, but is not limited to, 6g / cm³ 2 6.5g / cm 2 7g / cm 2 7.5g / cm 2 8g / cm 2 8.5g / cm 2 9g / cm 2 9.5g / cm 2 10g / cm 2 10.5g / cm 2 11g / cm 2 11.5g / cm 2 12g / cm 2 13g / cm 2 14g / cm 2 wait.

[0128] Please see again Figure 10 In some embodiments, the diaphragm 312 includes a base film 3121 and a coating 3122. The coating 3122 is disposed on the surface of the base film 3121. The coating 3122 includes a connected edge coating portion 31221 and a coating portion 31222. Both the coating portion 31222 and the edge coating portion 31221 are located on the surface of the base film 3121. The edge coating portion 31221 protrudes partially from the positive electrode 311 and partially from the negative electrode 313. The edge coating portion 31221 includes a first adhesive and first ceramic particles. The first adhesive is used to bond the first ceramic particles together. The particle size distribution of the first ceramic particles in at least two of the plurality of cores 310 is different.

[0129] It should be noted that when the particle size distribution of the first ceramic particles in the edge coating portion 31221 is wider, the first ceramic particles in the edge coating portion 31221 are more densely packed, and the first ceramic particles in the edge coating portion 31221 hinder the molecular chain movement of the base film 3121 more at high temperatures, resulting in a smaller thermal shrinkage rate of the diaphragm 312 at the position corresponding to the edge coating portion 31221. Conversely, when the particle size distribution of the first ceramic particles in the edge coating portion 31221 is narrower, the first ceramic particles in the edge coating portion 31221 are more loosely packed, and the first ceramic particles in the edge coating portion 31221 hinder the molecular chain movement of the base film 3121 less at high temperatures, resulting in a larger thermal shrinkage rate of the diaphragm 312 at the position corresponding to the edge coating portion 31221.

[0130] Optionally, the first adhesive may be, but is not limited to, at least one of polyvinylidene fluoride (PVDF), polymethyl methacrylate (PMMA), and polyacrylonitrile (PAN).

[0131] Optionally, the first ceramic particle may include, but is not limited to, at least one of alumina, silicon dioxide, etc.

[0132] Optionally, the mass fraction of the first binder in the edge coating portion 31221 ranges from 3% to 8%. Specifically, the mass fraction of the first binder in the edge coating portion 31221 can be, but is not limited to, 3%, 4%, 5%, 6%, 7%, 8%, etc. If the mass fraction of the first binder in the edge coating portion 31221 is too low, the adhesion of the coating 3122 will not be maintained, it will easily shed powder, the uniformity of the edge coating portion 31221 will be poor, and the bonding force between the edge coating portion 31221 and the base film 3121 will be weak. If the mass fraction of the first binder in the edge coating portion 31221 is too high, it will reduce the ionic conductivity of the edge coating portion 31221, increase the internal resistance of the edge coating portion 31221, reduce the porosity and air permeability of the edge coating portion 31221, and may also increase the brittleness of the edge coating portion 31221.

[0133] In this embodiment, by making the particle size distribution of the first ceramic particles different in at least two of the plurality of cores 310, the heat shrinkage rate of the diaphragm 312 corresponding to the edge coating portion 31221 of the core 310 with a narrower particle size distribution is greater. This results in a earlier short circuit between the positive electrode 311 and the negative electrode 313 of the core 310, leading to earlier thermal runaway. The diaphragm 312 with a lower heat shrinkage rate among the plurality of cores 310 exhibits less significant heat shrinkage. Conversely, the diaphragm 312 corresponding to the edge coating portion of the core 310 with a wider particle size distribution... The 31221 has a lower thermal shrinkage rate, and the positive electrode 311 and negative electrode 313 of the core 310 short-circuit later and thermal runaway later. This can avoid the instantaneous gas generation rate from being too fast when multiple cores 310 experience thermal runaway at the same time, exceeding the maximum exhaust rate of the single cell 300. It can also avoid the rapid increase in heat generation and insufficient heat dissipation when the single cell 300 experiences thermal runaway. This can better avoid the risk of the casing 320 of the single cell 300 cracking or even causing fire or explosion, and improve the safety of the single cell 300 in use.

[0134] Please see again Figure 5 , Figure 8 and Figure 10 In some embodiments, the plurality of winding cores 310 includes a first winding core 310a and a second winding core 310b, then the single cell 300 satisfies: 0.7≤D501 / D502≤0.9 and 1.1≤D901 / D902≤1.4;

[0135] Wherein, D501 is the particle size corresponding to the cumulative volume distribution number of the first ceramic particles in the first core 310a reaching 50%, D502 is the particle size corresponding to the cumulative volume distribution number of the first ceramic particles in the second core 310b reaching 50%, D901 is the particle size corresponding to the cumulative volume distribution number of the first ceramic particles in the first core 310a reaching 90%, and D902 is the particle size corresponding to the cumulative volume distribution number of the first ceramic particles in the second core 310b reaching 90%.

[0136] Understandably, D501 < D502, D901 > D902.

[0137] Specifically, D501 / D502 can be, but is not limited to, 0.7, 0.73, 0.75, 0.78, 0.8, 0.83, 0.85, 0.88, 0.9, etc. If D501 / D502 is too small, the particle size of the first ceramic particles of the first core 310a will be too small, making it difficult to manufacture and causing the first ceramic particles of the first core 310a to easily agglomerate, reducing the processing performance of the first ceramic particles of the first core 310a. If D501 / D502 is too large, the D501 and D502 of the first ceramic particles of the first core 310a will be too close, making it difficult to completely stagger the thermal runaway times of the first core 310a and the second core 310b when the single cell 300 experiences thermal runaway.

[0138] Specifically, D901 / D902 can be, but is not limited to, 1.1, 1.13, 1.15, 1.18, 1.2, 1.23, 1.25, 1.28, 1.3, 1.33, 1.35, 1.38, 1.4, etc. If D901 / D902 is too small, the D901 and D902 of the first ceramic particles of the first core 310a will be too close, making it difficult to completely stagger the thermal runaway times of the first core 310a and the second core 310b when thermal runaway occurs in the single cell 300. If D901 / D902 is too large, the particle size of the first ceramic particles of the first core 310a will be too small, making them difficult to manufacture and causing them to easily agglomerate, thus reducing their processing performance.

[0139] In this embodiment, the single cell 300 satisfies: 0.7≤D501 / D502≤0.9 and 1.1≤D901 / D902≤1.4, meaning that the particle size distribution of the first ceramic particles in the first core 310a is wider, the thermal shrinkage rate of the separator 312 of the first core 310a is smaller, and thermal runaway of the single cell 300 occurs later; the particle size distribution of the first ceramic particles in the second core 310b is narrower, the thermal shrinkage rate of the separator 312 of the first core 310a is larger, and thermal runaway of the single cell 300 occurs earlier. This avoids the instantaneous gas generation rate from being too fast when multiple cores 310 experience thermal runaway simultaneously, exceeding the maximum exhaust rate of the single cell 300, and prevents a sharp increase in heat generation and insufficient heat dissipation when the single cell 300 experiences thermal runaway. This better avoids the risk of the casing 320 of the single cell 300 cracking or even causing fire or explosion, and improves the safety of the single cell 300 in use.

[0140] In some embodiments, the coating portion 31222 includes a second adhesive and second ceramic particles, the second adhesive being used to bond the second ceramic particles; then 0.6≤D501 / D503≤0.9; 1.1≤D901 / D903≤1.5;

[0141] Wherein, D501 is the particle size corresponding to the cumulative volume distribution number of the first ceramic particles of the first core 310a reaching 50%, D503 is the particle size corresponding to the cumulative volume distribution number of the second ceramic particles of the first core 310a reaching 50%, D901 is the particle size corresponding to the cumulative volume distribution number of the first ceramic particles of the first core 310a reaching 90%, and D903 is the particle size corresponding to the cumulative volume distribution number of the second ceramic particles of the first core 310a reaching 90%.

[0142] Optionally, the second adhesive may be, but is not limited to, at least one of polyvinylidene fluoride (PVDF), polymethyl methacrylate (PMMA), and polyacrylonitrile (PAN).

[0143] Optionally, the second ceramic particles may include, but are not limited to, at least one of alumina, silicon dioxide, etc.

[0144] Optionally, the mass fraction of the second binder in the coating portion 31222 ranges from 3% to 8%. Specifically, the mass fraction of the second binder in the coating portion 31222 can be, but is not limited to, 3%, 4%, 5%, 6%, 7%, 8%, etc. If the mass fraction of the second binder in the coating portion 31222 is too low, the adhesion of the coating 3122 will not be maintained, it will easily shed powder, the uniformity of the coating portion 31222 will be poor, and the bonding force between the coating portion 31222 and the base film 3121 will be weak. If the mass fraction of the second binder in the coating portion 31222 is too high, it will reduce the ionic conductivity of the coating portion 31222, increase the internal resistance of the coating portion 31222, reduce the porosity and air permeability of the coating portion 31222, and may also increase the brittleness of the coating portion 31222.

[0145] Optionally, D501 < D503; D901 > D903.

[0146] Specifically, D501 / D503 can be, but is not limited to, 0.6, 0.63, 0.65, 0.68, 0.7, 0.73, 0.75, 0.78, 0.8, 0.83, 0.85, 0.88, 0.9, etc. If D501 / D503 is too small, the particle size of the first ceramic particles in the first core 310a will be too small, making it difficult to prepare and causing the first ceramic particles in the first core 310a to easily agglomerate, reducing the processing performance of the first ceramic particles in the first core 310a. If D501 / D503 is too large, the difference between the particle size distribution width of the first ceramic particles in the first core 310a and the particle size distribution width of the second ceramic particles in the first core 310a will be too small, which will have limited effect on improving the heat resistance and overcharge test pass rate of the first core 310a.

[0147] Specifically, D901 / D903 can be, but is not limited to, 1.1, 1.13, 1.15, 1.18, 1.2, 1.23, 1.25, 1.28, 1.3, 1.33, 1.35, 1.38, 1.4, 1.43, 1.45, 1.48, 1.5, etc. If D901 / D903 is too small, the difference between the particle size distribution width of the first ceramic particles of the first core 310a and the particle size distribution width of the second ceramic particles of the first core 310a will be too small, which will have limited effect on improving the heat resistance and overcharge test pass rate of the first core 310a. If D901 / D903 is too large, the particle size of the second ceramic particles of the first core 310a will be too small, making it difficult to prepare and causing the second ceramic particles of the first core 310a to easily agglomerate, reducing the processing performance of the second ceramic particles of the first core 310a.

[0148] The portion of the separator 312 that is stacked with the positive electrode 311 and the negative electrode 313 is bound by the positive electrode 311 and the negative electrode 313. Therefore, when the material composition of the entire separator 312 is uniform, the thermal shrinkage rate of this portion of the separator 312 is relatively low. The binding force of the portion of the separator 312 that protrudes from the positive electrode 311 and the negative electrode 313 is relatively small. Therefore, when the material composition of the entire separator 312 is uniform, the thermal shrinkage rate of the portion of the separator 312 that protrudes from the positive electrode 311 and the negative electrode 313 is relatively high. This portion is usually the thermal runaway induction point (also known as the trigger point) of the core 310. After the core 310 is formed, the edge coating portion 31221 at least partially covers the portion of the base film 3121 that protrudes from the positive electrode 311 and the negative electrode 313, and the coating portion 31222 covers the portion of the base film 3121 that is stacked with the positive electrode 311 and the negative electrode 313.

[0149] In this embodiment, the particle size distribution width of the first ceramic particles in the edge coating portion 31221 of the first core 310a is greater than the particle size distribution width of the second ceramic particles in the coating portion 31222 of the first core 310a. This makes the thermal shrinkage rate of the edge coating portion 31221 of the first core 310a less than that of the coating portion 31222 of the first core 310a. This can better reduce the thermal shrinkage rate of the diaphragm 312 corresponding to the edge coating portion 31221 of the first core 310a, improve the heat resistance of the diaphragm 312 of the first core 310a, thereby improving the overcharge resistance of the first core 310a and increasing the pass rate of the overcharge test of the first core 310a.

[0150] In some embodiments, the coating portion 31222 includes a second adhesive and second ceramic particles, the second adhesive being used to bond the second ceramic particles; then 0.6≤D502 / D504≤0.9; 1.1≤D902 / D904≤1.5;

[0151] Wherein, D504 is the particle size corresponding to the cumulative volume distribution number of the second ceramic particles in the second core 310b reaching 50%, and D904 is the particle size corresponding to the cumulative volume distribution number of the second ceramic particles in the second core 310b reaching 90%.

[0152] Optionally, D502 < D504; D902 > D904.

[0153] Specifically, D502 / D504 can be, but is not limited to, 0.6, 0.63, 0.65, 0.68, 0.7, 0.73, 0.75, 0.78, 0.8, 0.83, 0.85, 0.88, 0.9, etc. If D502 / D504 is too small, the particle size of the first ceramic particles in the second core 310b will be too small, making it difficult to prepare and causing the first ceramic particles in the second core 310b to easily agglomerate, reducing the processing performance of the first ceramic particles in the second core 310b. If D502 / D504 is too large, the difference between the particle size distribution width of the first ceramic particles in the second core 310b and the particle size distribution width of the second ceramic particles in the second core 310b will be too small, which will have limited effect on improving the heat resistance and overcharge test pass rate of the second core 310b.

[0154] Specifically, D902 / D904 can be, but is not limited to, 1.1, 1.13, 1.15, 1.18, 1.2, 1.23, 1.25, 1.28, 1.3, 1.33, 1.35, 1.38, 1.4, 1.43, 1.45, 1.48, 1.5, etc. If D902 / D904 is too small, the difference between the particle size distribution width of the first ceramic particles of the second core 310b and the particle size distribution width of the second ceramic particles of the second core 310b will be too small, which will have limited effect on improving the heat resistance and overcharge test pass rate of the second core 310b. If D902 / D904 is too large, the particle size of the second ceramic particles of the second core 310b will be too small, making it difficult to prepare and causing the second ceramic particles of the second core 310b to easily agglomerate, reducing the processing performance of the second ceramic particles of the second core 310b.

[0155] In this embodiment, the particle size distribution width of the first ceramic particles in the edge coating portion 31221 of the second core 310b is greater than the particle size distribution width of the second ceramic particles in the coating portion 31222 of the second core 310b. This makes the thermal shrinkage rate of the edge coating portion 31221 of the second core 310b less than that of the coating portion 31222 of the second core 310b. This can better reduce the thermal shrinkage rate of the diaphragm 312 corresponding to the edge coating portion 31221 of the second core 310b, improve the heat resistance of the diaphragm 312 of the second core 310b, thereby improving the overcharge resistance of the second core 310b and increasing the pass rate of the overcharge test of the second core 310b.

[0156] It should be noted that the particle size distribution widths, D501, D502, D503, D504, D901, D902, D903, D904, etc. of the first ceramic particles of the edge coating portion 31221 and the second ceramic particles of the coating portion 31222 in this application embodiment can be measured by one of the following two methods: (1) Using laser diffraction / particle size analyzer, the first ceramic particles or the second ceramic particles are suspended in a liquid (DI water can be used) or a gas (dry method) and passed through a laser beam. The first ceramic particles or the second ceramic particles of different sizes produce scattered light at different angles to the laser. The detector measures the distribution of the intensity of the scattered light with the angle, and calculates the particle size distribution, D501, D502, D503, D504, D901, D902, D903, D904, etc. of the first ceramic particles or the second ceramic particles through Mie theory or Fraunhofer diffraction theory. (2) Using a scanning electron microscope (SEM) or a transmission electron microscope (TEM) to scan the sample surface or penetrate thin samples with a high-energy electron beam to generate various signal imaging, the morphology, size and distribution of the first ceramic particles or the second ceramic particles can be directly observed.

[0157] Please see again Figure 5 , Figure 8 and Figure 10 In some embodiments, in the same core 310, the areal density of the edge coating portion 31221 is greater than the areal density of the coating portion 31222, and along the arrangement direction of the edge coating portion 31221 and the coating portion 31222, the width of the edge coating portion 31221 of at least two cores 310 is different.

[0158] Understandably, the heat shrinkage rate of the edge coating portion 31221 is different from that of the coating portion 31222. Optionally, the heat shrinkage rate of the edge coating portion 31221 is less than that of the coating portion 31222.

[0159] It should be noted that, in other embodiments, the width of the edge coating portion 31221 of the plurality of cores 310 may be the same.

[0160] In this embodiment, at least two of the plurality of cores 310 have different widths of the edge coating portion 31221. When the single cell 300 experiences thermal runaway, and the thermal shrinkage rate of the edge coating portion 31221 is less than the thermal shrinkage rate of the coating portion 31222, the separator 312 of the core 310 with the smaller edge coating portion 31221 has a higher thermal shrinkage rate and experiences thermal runaway earlier, while the separator 312 of the core 310 with the larger edge coating portion 31221 has a lower thermal shrinkage rate and experiences thermal runaway later. This avoids the instantaneous gas generation rate from exceeding the maximum exhaust rate of the single cell 300 when multiple cores 310 experience thermal runaway simultaneously, thus preventing a sharp increase in heat generation and insufficient heat dissipation when the single cell 300 experiences thermal runaway. This better avoids the risk of the casing 320 of the single cell 300 rupturing or even causing fire or explosion, improving the safety of the single cell 300 in use.

[0161] Figure 11 This is a cross-sectional view of the first core 310a and the second core 310b according to an embodiment of this application.

[0162] Please see Figure 11 In some embodiments, within the same core 310, the areal density of the edge coating portion 31221 is greater than the areal density of the coating portion 31222. The plurality of cores 310 include a first core 310a and a second core 310b. Along the arrangement direction of the edge coating portion 31221 and the coating portion 31222, the width of the edge coating portion 31221 of the first core 310a is w1, and the width of the edge coating portion 31221 of the second core 310b is w2. Then, 0.4 ≤ w2 / w1 ≤ 1.

[0163] Optionally, the heat shrinkage rate of the edge coating portion 31221 of the first core 310a is less than the heat shrinkage rate of the edge coating portion 31221 of the second core 310b.

[0164] Specifically, w2 / w1 can be, but is not limited to, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 1, etc. If w2 / w1 is too small, the width of the edge coating portion 31221 of the second core 310b will be too small, reducing the heat resistance of the second core 310b and reducing the pass rate of the overcharge test of the second core 310b.

[0165] In this embodiment, the difference in width between the edge coating portion 31221 of the first core 310a and the edge coating portion 31221 of the second core 310b can better stagger the thermal runaway times of the first core 310a and the second core 310b.

[0166] Optionally, the width w1 of the edge coating portion 31221 of the first core 310a is in the range of 1mm ≤ w1 ≤ 100mm. Specifically, the width w1 of the edge coating portion 31221 of the first core 310a can be, but is not limited to, 1mm, 2mm, 3mm, 4mm, 5mm, 8mm, 10mm, 15mm, 20mm, 30mm, 40mm, 50mm, 60mm, 70mm, 80mm, 90mm, 100mm, etc. If the width w1 of the edge coating portion 31221 of the first core 310a is too narrow, it has limited effect on improving the heat resistance and overcharge test pass rate of the first core 310a; if the width w1 of the edge coating portion 31221 of the first core 310a is too wide, it increases the manufacturing cost of the first core 310a.

[0167] Optionally, the width w2 of the edge coating portion 31221 of the second core 310b is in the range of 1mm ≤ w2 ≤ 100mm. Specifically, the width w2 of the edge coating portion 31221 of the second core 310b can be, but is not limited to, 1mm, 2mm, 3mm, 4mm, 5mm, 8mm, 10mm, 15mm, 20mm, 30mm, 40mm, 50mm, 60mm, 70mm, 80mm, 90mm, 100mm, etc. If the width w2 of the edge coating portion 31221 of the second core 310b is too narrow, it has limited effect on improving the heat resistance and overcharge test pass rate of the second core 310b; if the width w2 of the edge coating portion 31221 of the second core 310b is too wide, it increases the manufacturing cost of the second core 310b.

[0168] The following specific embodiments further describe the single cell 300 of this application.

[0169] Examples 1 to 3 and Comparative Example 1

[0170] The single-cell battery 300 in each embodiment and comparative example includes two cores 310, which are arranged in parallel. Each core 310 includes a positive electrode 311, a separator 312, and a negative electrode 313. The separator 312 is located between the positive electrode 311 and the negative electrode 313. The separator 312 includes a base film 3121 and two coatings 3122. The two coatings 3122 are disposed opposite to each other on two opposite surfaces of the base film 3121. Each coating 3122 includes two edge coating portions 31221 and a coating portion 31222. The two edge coating portions 31221 are respectively located on opposite sides of the coating portion 31222.

[0171] The two cores 310 include a first core 310a and a second core 310b. The difference between Embodiments 1 to 3 and Comparative Example 1 is that the areal density of the edge coating portion 31221 of the first core 310a and the edge coating portion 31221 of the second core 310b, and the areal density of the coating portion 31222 of the first core 310a and the coating portion 31222 of the second core 310b are different. The areal density of the edge coating portion 31221 of the first core 310a and the edge coating portion 31221 of the second core 310b, and the areal density of the coating portion 31222 of the first core 310a and the coating portion 31222 of the second core 310b in each embodiment and comparative example are shown in Table 1 below.

[0172] Example 4

[0173] The difference between this embodiment and embodiment 2 is that the single cell 300 in this embodiment includes four cores 310, and the four cores 310 include two first cores 310a and two second cores 310b. The two first cores 310a and the two second cores 310b are arranged in the order of first core 310a, first core 310a, second core 310b, second core 310b.

[0174] Example 5

[0175] The difference between this embodiment and embodiment 2 is that the single cell 300 in this embodiment includes four cores 310. The four cores 310 include two first cores 310a and two second cores 310b. The two first cores 310a and the two second cores 310b are arranged in the order of second core 310b, first core 310a, first core 310a, and second core 310b.

[0176] Comparative Example 2

[0177] The difference between this comparative example and Example 2 is that the single cell 300 in this example includes two second cores 310b.

[0178] Thermal runaway tests were conducted on the individual cells 300 of each embodiment and comparative example according to UL9540A to obtain the time intervals at which different cores 310 in the individual cells 300 experienced thermal runaway. The larger the time interval, the longer the thermal runaway exhaust time, and the less likely the individual cells 300 are to catch fire or explode.

[0179] Table 1 Performance parameters of single-cell batteries 300 in Examples 1 to 5, and Comparative Examples 1 and 2

[0180]

[0181] From the test results of Examples 1 to 5, Comparative Examples 1 and 2 in Table 1, it can be seen that in Comparative Example 1, the areal density of the edge coating portion 31221 of the first core 310a is equal to that of the edge coating portion 31221 of the second core 310b, and the areal density of the coating portion 31222 of the first core 310a is equal to that of the coating portion 31222 of the second core 310b. In Comparative Example 2, the areal density of the edge coating portion 31221 of the first core 310a is... Although the areal density of the coating portion 31221 of the first core 310a is not equal to that of the coating portion 31221 of the second core 310b, they are very close. Furthermore, the areal density of the coating portion 31222 of the first core 310a is equal to that of the coating portion 31222 of the second core 310b. Therefore, in Comparative Examples 1 and 2, when the single-cell battery 300 experiences thermal runaway, the interval between thermal runaway of the first core 310a and the second core 310b is relatively short. In Examples 1 to 5, the areal density of the coating portion 31221 of the first core 310a is greater than that of the coating portion 31221 of the second core 310b. This results in a longer interval between thermal runaways of different cores 310a in the single-cell battery 300, which can better reduce the maximum instantaneous gas production during thermal runaway and improve the safety of the single-cell battery 300.

[0182] Furthermore, the test results of Examples 4 and 5 show that, compared to the scheme in Example 4 where the first core 310a is set on one side and the second core 310b is set on the other side, in Example 5, along the arrangement direction of the multiple cores 310, the surface density of the edge coating portion 31221 of the multiple cores 310 gradually increases and then gradually decreases (i.e., when thermal shrinkage first decreases and then increases), when the single cell 300 experiences thermal runaway, the interval between the multiple cores 310 experiencing thermal runaway is longer, which can better reduce the maximum instantaneous gas production when the single cell 300 experiences thermal runaway and improve the safety of using the single cell 300.

[0183] Examples 6 to 8, Comparative Examples 3 to 4

[0184] The single-cell battery 300 in each embodiment and comparative example includes two cores 310, which are arranged in parallel. Each core 310 includes a positive electrode 311, a separator 312, and a negative electrode 313. The separator 312 is located between the positive electrode 311 and the negative electrode 313. The separator 312 includes a base film 3121 and two coatings 3122. The two coatings 3122 are disposed opposite to each other on two opposite surfaces of the base film 3121. Each coating 3122 includes two edge coating portions 31221 and a coating portion 31222. The two edge coating portions 31221 are respectively located on opposite sides of the coating portion 31222.

[0185] The edge coating portion 31221 includes a first adhesive and first ceramic particles, wherein the first adhesive is used to bond the first ceramic particles together; the coating portion 31222 includes a second adhesive and second ceramic particles, wherein the second adhesive is used to bond the second ceramic particles together.

[0186] The two cores 310 include a first core 310a and a second core 310b. The differences between the embodiments and comparative examples are that the particle size distribution of the first ceramic particles and the second ceramic particles in the first core 310a is different from that in the second core 310b, as shown in Table 2 below.

[0187] Thermal runaway tests were conducted on the individual cells 300 of each embodiment and comparative example according to UL9540A to obtain the time intervals at which different cores 310 in the individual cells 300 experienced thermal runaway. The larger the time interval, the longer the thermal runaway exhaust time, and the less likely the individual cells 300 are to catch fire or explode.

[0188] Table 2 Performance parameters of single-cell batteries 300 from Examples 6 to 8 and Comparative Examples 3 to 4 (Examples 6 to 8, Comparative Examples 3 to 4)

[0189]

[0190]

[0191] From the test results of Examples 6 to 8, Comparative Examples 3 and 4 in Table 2, it can be seen that in Comparative Example 3, D501 / D502 = 1 and D901 / D902 = 1, meaning that the first ceramic particles of the first core 310a and the second core 310b are the same. When the single cell 300 experiences thermal runaway, the thermal runaway interval between the first core 310a and the second core 310b is relatively short. In Comparative Example 4, D501 / D502 and D901 / D902 are too small. When the single cell 300 experiences thermal runaway, the thermal runaway interval between the first core 310a and the second core 310b is relatively increased, but still relatively short. In Examples 6 to 8, 0.7≤D501 / D502≤0.9 and 1.1≤D901 / D902≤1.4, when the single cell 300 experiences thermal runaway, the time interval between the thermal runaway of the first core 310a and the second core 310b is greater than or equal to 2.7 min. The longer interval between the thermal runaway of the first core 310a and the second core 310b can better reduce the maximum instantaneous gas production when the single cell 300 experiences thermal runaway and improve the safety of the single cell 300.

[0192] Examples 9 to 11 and Comparative Example 5

[0193] The single-cell battery 300 in each embodiment and comparative example includes two cores 310, which are arranged in parallel. Each core 310 includes a positive electrode 311, a separator 312, and a negative electrode 313. The separator 312 is located between the positive electrode 311 and the negative electrode 313. The separator 312 includes a base film 3121 and two coatings 3122. The two coatings 3122 are disposed opposite to each other on two opposite surfaces of the base film 3121. Each coating 3122 includes two edge coating portions 31221 and a coating portion 31222. The two edge coating portions 31221 are respectively located on opposite sides of the coating portion 31222.

[0194] The two cores 310 include a first core 310a and a second core 310b. In each embodiment and comparative example, the areal density of the edge coating portion 31221 of the first core 310a is 8.3 g / m². 2 The areal density of the coating portion 31222 of the first core 310a is 7.3 g / m³. 2 The areal density of the edge coating 31221 of the second core 310b is 7.3 g / m³. 2 The areal density of the coating portion 31222 of the second core 310b is 7.3 g / m². 2The difference between Examples 9 to 11 and Comparative Example 5 is that the width of the edge coating portion 31221 of the first core 310a is different from the width of the edge coating portion 31221 of the second core 310b. The width of the edge coating portion 31221 of each embodiment and comparative example is shown in Table 3 below.

[0195] Thermal runaway tests were conducted on the individual cells 300 of each embodiment and comparative example according to UL9540A to obtain the time intervals at which different cores 310 in the individual cells 300 experienced thermal runaway. The larger the time interval, the longer the thermal runaway exhaust time, and the less likely the individual cells 300 are to catch fire or explode.

[0196] Table 3 Performance parameters of the single cell 300 in Examples 9 to 11 and Comparative Example 5

[0197]

[0198]

[0199] As can be seen from the test results of Examples 9 to 11 in Table 3, the areal density of the edge coating portion 31221 of the first core 310a is greater than that of the edge coating portion 31221 of the second core 310b. Compared with the scheme in Example 11 where the width of the edge coating portion 31221 of the first core 310a is equal to the width of the edge coating portion 31221 of the second core 310b, when the width of the edge coating portion 31221 of the first core 310a is greater than that of the edge coating portion 31221 of the second core 310b, the interval time of thermal runaway between the first core 310a and the second core 310b can be better staggered. In Comparative Example 5, although the width of the edge coating portion 31221 of the first core 310a differs significantly from the width of the edge coating portion 31221 of the second core 310b, the narrow width of the edge coating portion 31221 of the second core 310b results in excessively severe thermal runaway of the second core 310b, generating more heat. This causes the temperature of the first core 310a to rise faster, accelerating the thermal runaway of the first core 310a. Consequently, the interval between the thermal runaway of the first core 310a and the second core 310b becomes shorter.

[0200] Examples 12 to 14 and Comparative Example 6

[0201] The single cell 300 in each embodiment and comparative example includes two cores 310, which are arranged in parallel. Each core 310 includes a positive electrode 311, a separator 312, and a negative electrode 313. The separator 312 is located between the positive electrode 311 and the negative electrode 313. The separator 312 includes a base film 3121 and two coatings 3122, which are disposed opposite to each other on two opposite surfaces of the base film 3121.

[0202] The two cores 310 include a first core 310a and a second core 310b. The difference between Examples 12 to 14 and Comparative Example 6 is that the porosity of the base film 3121 of the first core 310a and the base film 3121 of the second core 310b are different. The porosity of the base film 3121 of the first core 310a and the base film 3121 of the second core 310b in each example and comparative example is shown in Table 4 below.

[0203] Thermal runaway tests were conducted on the individual cells 300 of each embodiment and comparative example according to UL9540A to obtain the time intervals at which different cores 310 in the individual cells 300 experienced thermal runaway. The larger the time interval, the longer the thermal runaway exhaust time, and the less likely the individual cells 300 are to catch fire or explode.

[0204] Table 4 Performance parameters of the single cell 300 in Examples 12 to 14 and Comparative Example 6

[0205]

[0206] As can be seen from the test results of Examples 12 to 14 and Comparative Example 6 in Table 4, when the porosity of the base film 3121 of the first core 310a is equal to that of the base film 3121 of the second core 310b (as in Comparative Example 6), the thermal runaway interval between the first core 310a and the second core 310b is shorter when the single cell 300 experiences thermal runaway. As can be seen from the test results of Examples 12 to 14, when the porosity of the base film 3121 of the first core 310a is different from that of the base film 3121 of the second core 310b, when the single cell 300 experiences thermal runaway, the time interval between the thermal runaway of the first core 310a and the second core 310b increases. Furthermore, as the difference between the porosity P2 of the base film 3121 of the second core 310b and the porosity P1 of the base film 3121 of the first core 310a increases, the time interval between the thermal runaway of the first core 310a and the second core 310b gradually increases when the single cell 300 experiences thermal runaway.

[0207] In this application, the terms "embodiment" and "implementation" mean that a specific feature, structure, or characteristic described in connection with an embodiment can be included in at least one embodiment of this application. The appearance of these phrases in various locations throughout the specification does not necessarily refer to the same embodiment, nor are they independent or alternative embodiments mutually exclusive with other embodiments. Those skilled in the art will understand, explicitly and implicitly, that the embodiments described in this application can be combined with other embodiments. Furthermore, it should be understood that the features, structures, or characteristics described in the various embodiments of this application can be arbitrarily combined to form yet another embodiment that does not depart from the spirit and scope of the technical solution of this application, provided there is no contradiction between them.

[0208] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application and are not intended to limit it. Although this application has been described in detail with reference to the above preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions to the technical solutions of this application should not depart from the spirit and scope of the technical solutions of this application.

Claims

1. A single cell, characterized by, The monomer battery comprises a plurality of winding cores connected in parallel, the winding core comprises a positive pole piece, a diaphragm and a negative pole piece, the diaphragm is located between the positive pole piece and the negative pole piece; the thermal shrinkage rates of the diaphragms of at least two winding cores in the plurality of winding cores are different.

2. The cell according to claim 1, wherein The monomer battery further comprises a shell having a receiving cavity for receiving the plurality of winding cores, the plurality of winding cores are arranged in sequence; along the arrangement direction of the plurality of winding cores, the thermal shrinkage rates of the diaphragms of the plurality of winding cores gradually decrease first and then gradually increase.

3. The cell according to claim 1, wherein The diaphragm comprises a base film and a coating layer, the coating layer is arranged on the surface of the base film, the porosities of the base films of at least two winding cores in the plurality of winding cores are different, so that the thermal shrinkage rates of the diaphragms of at least two winding cores in the plurality of winding cores are different.

4. The cell according to claim 3, wherein The plurality of winding cores comprises a first winding core and a second winding core, the porosity of the base film of the first winding core is P1, the porosity of the base film of the second winding core is P2, and 5%≤P2-P1≤40%.

5. The cell according to claim 4, wherein The porosity P1 of the base film of the first winding core ranges from 40% to 60%, and the porosity P2 of the base film of the second winding core ranges from 45% to 65%.

6. The cell according to claim 1, wherein The diaphragm comprises a base film and a coating layer, the coating layer is arranged on the surface of the base film, the coating layer comprises a connected edge coating part and a coating part, the coating part and the edge coating part are both located on the surface of the base film, and the edge coating part partially protrudes from the positive pole piece and partially protrudes from the negative pole piece; the area densities of the edge coating parts of at least two winding cores in the plurality of winding cores are different.

7. The cell according to claim 6, wherein The plurality of winding cores includes a first winding core and a second winding core, a face density of the edge coating portion of the first winding core is p 11 , a face density of the edge coating portion of the second winding core is p 21 , and 0.6≤p 21 / p 11 ≤0.

9.

8. The cell according to claim 6, wherein The plurality of winding cores includes a first winding core and a second winding core, a face density of the edge coated portion of the first winding core is p 11 , a face density of a coated portion of the first winding core is p 12 , and p 11 > p12. The areal density of the edge coated portion of the second core is p 21 The areal density of the coated portion of the second core is p 22 Then p 21 > p22.

9. The cell according to claim 8, wherein The monobloc cell satisfies the relationship: 1.1≤ρ 11 / ρ 12 ≤1.6; and 1.1≤ρ 21 / ρ 22 ≤1.

6.

10. The cell according to claim 1, wherein The diaphragm comprises a base film and a coating layer, the coating layer is arranged on the surface of the base film, the coating layer comprises a connected edge coating part and a coating part, the coating part and the edge coating part are both located on the surface of the base film, the edge coating part partially protrudes from the positive pole piece and partially protrudes from the negative pole piece, the edge coating part comprises a first adhesive and first ceramic particles, and the first adhesive is used for bonding the first ceramic particles; the particle size distributions of the first ceramic particles of at least two winding cores in the plurality of winding cores are different.

11. The cell according to claim 10, wherein The plurality of winding cores comprises a first winding core and a second winding core, and the monomer battery satisfies 0.7≤D501 / D502≤0.9 and 1.1≤D901 / D902≤1.4; wherein D501 is the particle size corresponding to the cumulative volume distribution number of the first ceramic particles of the first winding core reaching 50%, D502 is the particle size corresponding to the cumulative volume distribution number of the first ceramic particles of the second winding core reaching 50%, D901 is the particle size corresponding to the cumulative volume distribution number of the first ceramic particles of the first winding core reaching 90%, and D902 is the particle size corresponding to the cumulative volume distribution number of the first ceramic particles of the second winding core reaching 90%.

12. The cell of claim 10, wherein, The plurality of winding cores comprises a first winding core and a second winding core, the coating part comprises a second binder and second ceramic particles, the second binder is used to bond the second ceramic particles; then 0.6≤D501 / D503≤0.9; 1.1≤D901 / D903≤1.5; Wherein, D501 is the particle size corresponding to the cumulative volume distribution number of 50% of the first ceramic particles of the first winding core, D503 is the particle size corresponding to the cumulative volume distribution number of 50% of the second ceramic particles of the first winding core, D901 is the particle size corresponding to the cumulative volume distribution number of 90% of the first ceramic particles of the first winding core, and D903 is the particle size corresponding to the cumulative volume distribution number of 90% of the second ceramic particles of the first winding core.

13. The cell of claim 10, wherein, The plurality of winding cores comprises a first winding core and a second winding core, the coating part comprises a second binder and second ceramic particles, the second binder is used to bond the second ceramic particles; then 0.6≤D502 / D504≤0.9; 1.1≤D902 / D904≤1.5; Wherein, D502 is the particle size corresponding to the cumulative volume distribution number of 50% of the first ceramic particles of the second winding core, D504 is the particle size corresponding to the cumulative volume distribution number of 50% of the second ceramic particles of the second winding core, D902 is the particle size corresponding to the cumulative volume distribution number of 90% of the first ceramic particles of the second winding core, and D904 is the particle size corresponding to the cumulative volume distribution number of 90% of the second ceramic particles of the second winding core.

14. The monobloc cell of any one of claims 6-13, wherein, In the same winding core, the area density of the edge coating part is greater than the area density of the coating part, and the widths of the edge coating parts of at least two winding cores in the arrangement direction of the edge coating part and the coating part are different.

15. The cell of claim 14, wherein, The plurality of winding cores comprises a first winding core and a second winding core, the thermal shrinkage rate of the edge coating part of the first winding core is less than the thermal shrinkage rate of the edge coating part of the second winding core, the width of the edge coating part of the first winding core is w1, the width of the edge coating part of the second winding core is w2, then 0.4≤w2 / w1≤1.

16. An energy storage device, comprising: Comprising: One or more monomer batteries according to any one of claims 1-15.

17. An energy storage system characterized by, Comprising: A high-voltage cable, a first electric energy conversion device, a second electric energy conversion device, and the energy storage device according to claim 16; the high-voltage cable is electrically connected to the energy storage device, the first electric energy conversion device, and the second electric energy conversion device respectively, the first electric energy conversion device and the second electric energy conversion device are both used to generate electric energy, and the energy storage device is used to store the electric energy.

18. A power supply system characterized by comprising: Comprising: An electric device; And The energy storage device according to claim 16 or the energy storage system according to claim 17, wherein the energy storage device or the energy storage system is used to supply power to the electric device.

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