Secondary battery, battery pack, and electric device

Abstract

The invention discloses a secondary battery, a battery pack and electric equipment. The secondary battery includes a case, a plurality of electrode assemblies, and a terminal assembly. The plurality of electrode assemblies are accommodated in the shell and are stacked in a first direction, and each electrode assembly comprises a tab; the terminal assembly comprises a plurality of electrode terminals and at least one insulating layer, one end of each electrode terminal is positioned in the shell, the other end of each electrode terminal is positioned outside the shell, the plurality of electrode terminals are respectively connected to the tabs of different electrode assemblies, the plurality of electrode terminals are laminated and have the same polarity, and the insulating layer is arranged between the adjacent electrode terminals; the rated capacity of the secondary battery is a Ah, the resistance between the adjacent electrode terminals between which the insulating layers are arranged is b omega, a / b is 4 * 10 <-17 > to 6 * 10 <-13 >, and a is 30 to 200. The secondary battery can have both high capacity and high use reliability.

Description

Technical Field

[0001] This application relates to the field of batteries, and in particular to a secondary battery, a battery pack, and an electrical device. Background Technology

[0002] Secondary batteries are widely used in electronic devices such as mobile phones, laptops, electric vehicles, electric cars, electric airplanes, electric ships, and power tools.

[0003] Improving the reliability of secondary batteries is a research direction in battery technology. Summary of the Invention

[0004] This application provides a secondary battery, a battery pack, and an electrical device, wherein the secondary battery has both high capacity and high reliability.

[0005] In a first aspect, this application provides a secondary battery, comprising: a housing, multiple electrode assemblies, and a terminal assembly. The multiple electrode assemblies are housed within the housing and stacked along a first direction, each electrode assembly including a tab; the terminal assembly includes multiple electrode terminals and at least one insulating layer, one end of each electrode terminal being located inside the housing and the other end outside the housing, the multiple electrode terminals being respectively connected to the tabs of different electrode assemblies, the multiple electrode terminals being stacked and having the same polarity, and the insulating layer being disposed between adjacent electrode terminals; wherein, the rated capacity of the secondary battery is a Ah, the resistance between adjacent electrode terminals with insulating layers is b Ω, and a / b is 4 × 10⁻⁶. -17 Up to 6×10 -13 And a is between 30 and 200.

[0006] In the secondary battery of this application, multiple electrode assemblies are housed within a casing and stacked along a first direction. Each electrode assembly includes a tab. A terminal assembly includes multiple electrode terminals and at least one insulating layer. One end of each electrode terminal is located inside the casing, and the other end is located outside the casing. The multiple electrode terminals are respectively connected to the tabs of different electrode assemblies. The multiple electrode terminals are stacked and have the same polarity. The insulating layer is disposed between adjacent electrode terminals. Thus, the multiple electrode assemblies of the secondary battery can form a parallel structure. When a is 30 to 200, by ensuring that a / b is within 4 × 10⁻⁶, the secondary battery can achieve this. -17 Up to 6×10 -13 In the event of an accident such as a puncture in the secondary battery, the insulating layer can prevent current from accumulating between the various electrode components, increase the internal resistance of the secondary battery after a short circuit, reduce the current transmitted to the short circuit location, and limit the surge of short circuit current. This reduces heat generation inside the secondary battery, lowers the risk of localized high temperatures and thermal runaway, and thus enables the secondary battery to possess both high capacity and high reliability.

[0007] In some embodiments, the electrode assembly includes an electrode sheet, and an electrode tab is connected to the electrode sheet; there are multiple electrode sheets, and the multiple electrode sheets include a positive electrode sheet; in the secondary battery, the total number of layers of the positive electrode sheet stacked along the first direction is 30-80. This enables the secondary battery to have a high capacity and also reduces the number of internal short circuit points when the secondary battery is punctured, thus helping the secondary battery to have both high capacity and high reliability.

[0008] In some embodiments, b is 5 × 10 13 Up to 5×10 18 This effectively blocks current convergence between various electrode components, increases the internal resistance of the secondary battery after a short circuit, reduces heat generation inside the secondary battery, lowers the risk of localized high temperatures and thermal runaway, and improves the reliability of the secondary battery.

[0009] In some embodiments, the thickness of the electrode terminal is c mm, the thickness of the insulating layer is d mm, and the c / d ratio is 1 to 5. This allows the electrode terminal and the insulating layer to have suitable thicknesses, thereby enabling the electrode terminal to have good current carrying capacity and mechanical connection function, the insulating layer to have good barrier function, and enabling the secondary battery to have high energy density and reduce the risk of leakage of the secondary battery.

[0010] In some embodiments, the thickness of the insulating layer is 0.1mm-2mm, optionally 0.1mm-0.5mm. This enables the secondary battery to have both high energy density and high reliability, while also reducing the risk of leakage.

[0011] In some embodiments, the volume resistivity of the insulating layer is 1×10⁻⁶. 11 For values ​​above Ω.m, 1×10 can be selected. 14 Ω.m to 1×10 18 Ω.m. This allows the insulating layer to have both high resistance and small thickness.

[0012] In some embodiments, the dielectric strength of the insulating layer is 150 kV / mm or higher, optionally between 150 kV / mm and 200 kV / mm. This reduces the risk of electrical breakdown of the insulating layer when the local electric field strength is high, thus maintaining good insulation performance.

[0013] In some embodiments, the melting point of the insulating layer is 200°C-400°C. This reduces the risk of the insulating layer failing to block current when the local temperature is high, thus maintaining good insulation performance.

[0014] In some embodiments, the thicknesses of any two locations in the insulating layer are d1mm and d2mm, respectively, where d1≥d2, and the insulating layer satisfies: 0≤(d1-d2) / d1≤5%. This reduces the risk of current conduction at adjacent electrode terminals due to local breakdown of the insulating layer, thereby improving the reliability of the secondary battery.

[0015] In some embodiments, the defect density of the insulation layer is 0.1 defects / cm². 2 The following can reduce the risk of localized current conduction in the insulation layer and improve the reliability of the secondary battery.

[0016] In some embodiments, the peel strength between the insulating layer and the electrode terminals is 2 N / cm or higher. This reduces the risk of the electrode terminals separating from the insulating layer when pulled, thereby improving the sealing performance of the secondary battery casing and reducing the risk of secondary battery leakage.

[0017] In some embodiments, the insulating layer comprises polymeric materials and / or ceramic materials.

[0018] The polymer materials include one or more of polyimide, polyethylene terephthalate, polytetrafluoroethylene, and epoxy resin; the ceramic materials include one or more of alumina, Al2O3-ZrO2 composite ceramics, and ceramic-polymer composite ceramics.

[0019] The aforementioned materials not only possess high volume resistivity, dielectric strength, and thermal stability, but also exhibit high chemical inertness in electrolytes. Insulating layers comprising these materials maintain excellent insulation properties during secondary battery cycling or in the event of a short circuit, thereby contributing to improved battery reliability.

[0020] In some embodiments, there are multiple tabs, including a positive tab and a negative tab; there are multiple terminal assemblies, with a portion of the multiple terminal assemblies connected to the positive tab and another portion of the multiple terminal assemblies connected to the negative tab.

[0021] Secondly, this application provides a battery pack that includes a plurality of secondary batteries according to any embodiment of the first aspect.

[0022] In some embodiments, the battery pack further includes multiple busbars that electrically connect multiple secondary batteries; multiple electrode terminals of the terminal assembly are respectively connected to different busbars. By providing multiple busbars, the current from the multiple electrode terminals can be drawn out separately.

[0023] Thirdly, this application provides an electrical device that includes a battery pack according to any embodiment of the second aspect. Attached Figure Description

[0024] The features, advantages, and technical effects of exemplary embodiments of this application will now be described with reference to the accompanying drawings.

[0025] Figure 1 This is a schematic diagram of the structure of a secondary battery provided in some embodiments of this application; Figure 2 A partial cross-sectional schematic diagram of a secondary battery provided in some embodiments of this application; Figure 3 Schematic diagram of a battery pack provided for some embodiments of this application; Figure 4 This is a schematic diagram of an electrical device provided for some embodiments of this application.

[0026] The reference numerals in the accompanying drawings for the specific embodiments are as follows: 1. Secondary battery; 10. Electrode assembly; 11. Electrode; 11a. Positive electrode; 11b. Negative electrode; 12. Tab; 13. Separator; 20. Housing; 21. Packaging film; 30. Terminal assembly; 31. Electrode terminal; 32. Insulating layer; 33. Sealing element; 2. Busbar components; 3. Battery pack; 4. Electrical equipment; Z, First direction. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly described below with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of this application, but not all embodiments.

[0028] The terms "first," "second," "third," etc., used in the specification, claims, or accompanying drawings of this application are used to distinguish different objects, not to describe a specific order or hierarchy. In the embodiments of this application, the same reference numerals denote the same components, and for the sake of brevity, detailed descriptions of the same components are omitted in different embodiments.

[0029] In this application, the reference to "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment that is mutually exclusive with other embodiments.

[0030] In the description of this application, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0031] In the embodiments of this application, "parallel" includes not only the case of absolute parallelism, but also the case of approximate parallelism as commonly understood in engineering; similarly, "perpendicular" also includes not only the case of absolute perpendicularity, but also the case of approximate perpendicularity as commonly understood in engineering. For example, if the angle between two directions is 80°-90°, the two directions can be considered perpendicular; if the angle between two directions is 0°-10°, the two directions can be considered parallel.

[0032] The secondary battery of this application is described below with reference to the accompanying drawings.

[0033] Reference Figures 1 to 2 This application provides a secondary battery 1. The secondary battery 1 can refer to a battery that can be used again after being discharged by recharging to activate the active materials.

[0034] As an example, the secondary battery 1 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, etc.

[0035] As an example, the secondary battery 1 can be a prismatic battery, a pouch battery, or a battery of other shapes. Prismatic batteries include square-shell batteries, blade-shaped batteries, and multi-prismatic batteries, such as hexagonal prismatic batteries.

[0036] The secondary battery 1 includes a housing 20 and an electrode assembly 10 housed within the housing 20.

[0037] Electrode assembly 10 is a component in the secondary battery 1 where an electrochemical reaction occurs. The housing 20 may contain one or more electrode assemblies 10. Exemplarily, the electrode assembly 10 can be a wound structure or a stacked structure.

[0038] The electrode assembly 10 includes a positive electrode 11a, a negative electrode 11b, and a separator 13. The positive electrode 11a and the negative electrode 11b have opposite polarities, and the separator 13 separates the positive electrode 11a and the negative electrode 11b. During the charging and discharging process of the secondary battery 1, active ions (such as lithium ions) repeatedly insert and extract between the positive electrode 11a and the negative electrode 11b. The separator 13, disposed between the positive electrode 11a and the negative electrode 11b, serves to prevent short circuits between the positive and negative electrodes while allowing active ions to pass through.

[0039] The positive electrode 11a includes a positive current collector and a positive active material layer, the positive active material layer being disposed on the surface of the positive current collector. The negative electrode 11b includes a negative current collector and a negative active material layer, the negative active material layer being disposed on the surface of the negative current collector.

[0040] The positive electrode tab is connected to the positive current collector. In some examples, the positive electrode tab and the positive current collector are a single piece; for example, a layer of positive active material can be coated onto the surface of a metal foil first, and then the positive current collector and the positive electrode tab can be formed by die-cutting the metal foil after coating. In other examples, the positive electrode tab and the positive current collector are formed separately and connected separately; for example, the positive electrode tab is welded to the positive current collector.

[0041] The negative electrode tab is connected to the negative electrode current collector. In some examples, the negative electrode tab and the negative electrode current collector are a single piece; for example, a layer of negative electrode active material can be coated onto the surface of a metal foil first, and then the negative electrode current collector and the negative electrode tab can be formed by die-cutting the metal foil after coating. In other examples, the negative electrode tab and the negative electrode current collector are formed separately and connected; for example, the negative electrode tab is welded to the negative electrode current collector.

[0042] Optionally, the positive current collector is aluminum foil, and the negative current collector is copper foil.

[0043] In some embodiments, the secondary battery 1 is a pouch battery. A pouch battery can refer to a secondary battery 1 that uses a flexible packaging film 21 (such as aluminum-plastic film) as the casing 20. Compared with secondary batteries 1 with metal structure casings 20, pouch batteries have the advantages of lighter structural weight and more flexible external contour shapes.

[0044] The secondary battery 1 can be rectangular, square, or other irregularly shaped.

[0045] In some embodiments, the housing 20 includes two packaging films 21, forming a receiving cavity between the two packaging films 21, and the electrode assembly 10 is received in the receiving cavity.

[0046] In some embodiments, the two packaging films 21 are integrally formed. As an example, two packaging films 21 can be formed by folding a single aluminum-plastic film.

[0047] In some alternative embodiments, the two packaging films 21 are separate structures. As an example, the two packaging films 21 are two aluminum-plastic films.

[0048] Each packaging film 21 includes an encapsulation layer, a metal layer, and a protective layer. The encapsulation layers of two packaging films 21 are fused together to form a closed receiving cavity.

[0049] In some embodiments, the metal layer comprises aluminum, and the encapsulation layer and protective layer comprise resin materials.

[0050] In some embodiments, the encapsulation layer includes a polypropylene layer. The protective layer is made of one or more materials selected from nylon and polyethylene terephthalate.

[0051] In some embodiments, the secondary battery 1 includes a terminal assembly 30, which includes electrode terminals 31. One end of the electrode terminal 31 is located inside the housing 20, and the other end is located outside the housing 20. The electrode terminal 31 is connected to a tab 12 (positive tab or negative tab). The electrode terminal 31 is used to connect to an external circuit to enable charging and discharging of the secondary battery 1.

[0052] In some embodiments, electrode terminals 31 are soldered to tabs 12.

[0053] In some embodiments, the terminal assembly 30 further includes a seal 33 surrounding the electrode terminal 31 and disposed between the electrode terminal 31 and the housing 20. The seal 33 can be used to weld with the encapsulation layer of the packaging film 21 to achieve a sealed connection between the terminal assembly 30 and the housing 20.

[0054] In some embodiments, there are multiple terminal assemblies 30, with a portion of the multiple terminal assemblies 30 connected to the positive electrode tab and another portion of the multiple terminal assemblies 30 connected to the negative electrode tab.

[0055] In some embodiments, the secondary battery 1 includes a housing 20, a plurality of electrode assemblies 10, and a terminal assembly 30. The plurality of electrode assemblies 10 are housed within the housing 20 and stacked along a first direction Z, each electrode assembly 10 including a tab 12. The terminal assembly 30 includes a plurality of electrode terminals 31 and at least one insulating layer 32. One end of each electrode terminal 31 is located inside the housing 20, and the other end is located outside the housing 20. The plurality of electrode terminals 31 are respectively connected to the tabs 12 of different electrode assemblies 10. The plurality of electrode terminals 31 are stacked and have the same polarity, and the insulating layer 32 is disposed between adjacent electrode terminals 31.

[0056] The rated capacity of the secondary battery 1 is a Ah, and the resistance between adjacent electrode terminals 31 with an insulating layer 32 is b Ω, where a / b is 4 × 10⁻⁶. -17 Up to 6×10 -13 For example, a / b can be selected as 4×10 -17 5×10 -17 1×10 -16 1.5×10 -16 2×10 -16 5×10 -16 1×10 -15 1.5×10 -15 2×10 -15 2.5×10 -15 2.9×10 -15 3×10-15 5×10 -15 1×10 -14 3×10 -14 5×10 -14 1×10 -13 3×10 -13 6×10 -13 The rated capacity can be 30Ah, 50Ah, 70Ah, 90Ah, 100Ah, 110Ah, 130Ah, 150Ah, 170Ah, 190Ah, 200Ah, or any value between two values. Specifically, the rated capacity of secondary battery 1 can be as stated on the outer packaging or in the product specification sheet.

[0057] When secondary battery 1 is punctured by a sharp object (such as a steel nail), the puncturing object comes into direct contact with the electrode 11 of secondary battery 1, which may form an electronic channel, creating a short circuit point and causing a short circuit inside secondary battery 1. After the short-circuit electronic channel is formed, a short-circuit current will be generated instantaneously inside secondary battery 1, which will then be converted into Joule heat. Since the heat dissipation rate of secondary battery 1 is limited, if the heat generated by the short circuit is too large, it may cause localized high temperature and thermal runaway inside secondary battery 1, affecting the reliability of secondary battery 1 and creating a safety hazard.

[0058] Furthermore, with the development of secondary batteries 1, the requirements for their capacity are gradually increasing. However, as the capacity of secondary batteries 1 increases, the content of active materials inside them also increases, and the number of electrode layers 11 increases. This leads to an increase in the short-circuit current inside the secondary battery 1 when a puncture occurs, further exacerbating the safety hazards caused by the puncture.

[0059] In the secondary battery 1 of this application, multiple electrode assemblies 10 are housed within a housing 20 and stacked along a first direction Z. Each electrode assembly 10 includes a tab 12. A terminal assembly 30 includes multiple electrode terminals 31 and at least one insulating layer 32. One end of each electrode terminal 31 is located inside the housing 20, and the other end is located outside the housing 20. The multiple electrode terminals 31 are respectively connected to the tabs 12 of different electrode assemblies 10. The multiple electrode terminals 31 are stacked and have the same polarity. The insulating layer 32 is disposed between adjacent electrode terminals 31. Thus, the multiple electrode assemblies 10 of the secondary battery 1 can form a parallel structure. When a is 30 to 200, by making the secondary battery 1 satisfy a / b in the range of 4 × 10... -17 Up to 6×10 -13In the event of an accident such as puncture in the secondary battery 1, the insulating layer 32 can prevent current from accumulating between the various electrode components 10, increase the internal resistance of the secondary battery 1 after a short circuit, reduce the current transmitted to the short circuit location, and limit the surge of short circuit current. This reduces heat generation inside the secondary battery 1, lowers the risk of localized high temperatures and thermal runaway, and thus enables the secondary battery 1 to possess both high capacity and high reliability.

[0060] By adjusting the material and thickness of the insulating layer 32, the resistance between adjacent electrode terminals 31 with the insulating layer 31 between them can be adjusted, thereby adjusting the value of a / b.

[0061] The resistance between adjacent electrode terminals 31 can be measured using a high-resistance meter. During testing, the high-voltage electrode of the high-resistance meter should be placed firmly against the surface of one of the adjacent electrode terminals, and the ground electrode of the high-resistance meter should be placed firmly against the surface of the other adjacent electrode terminal, ensuring uniform contact (a slight pressure can be applied, but avoid damaging the sample). Apply a DC voltage of 100V-500V (e.g., 100V, 250V, or 500V DC voltage can be applied) to the high-resistance meter and measure the leakage current. Calculate the resistance value R in Ω using R=U / I, where U is the applied DC voltage in V and I is the leakage current in A. The value of b can then be determined based on R.

[0062] In some embodiments, the electrode assembly 10 includes an electrode 11, and a tab 12 is connected to the electrode 11. There are multiple electrode 11s, and the multiple electrode 11s include a positive electrode 11a. In the secondary battery 1, the total number of layers of the positive electrode 11a stacked along the first direction Z can be 30-80. For example, the total number of layers of the positive electrode 11a stacked along the first direction Z in the secondary battery 1 can be selected as 30, 32, 34, 36, 38, 40, 42, 44, 46, 48, 50, 52, 54, 56, 58, 60, 62, 64, 68, 70, 72, 75, 78, 80, or any value range between the two.

[0063] In some examples, the electrode assembly 10 is a wound structure, with the positive electrode 11a and the negative electrode 11b forming a multi-layer structure through winding. In other examples, the electrode assembly 10 is a stacked structure, with each positive electrode 11a forming one layer and each negative electrode 11b forming one layer.

[0064] The total number of electrode sheets 11 stacked along the first direction Z in the secondary battery 1 meets the given range, which enables the secondary battery 1 to have a high capacity and also reduces the number of internal short circuit points when the secondary battery 1 is punctured, thus making it beneficial for the secondary battery 1 to have both high capacity and high reliability.

[0065] In the embodiments of this application, the total number of positive electrode sheets 11a of the multiple electrode components 10 stacked along the first direction Z can be the same or different.

[0066] Optionally, in a single electrode assembly 10, the total number of layers of the positive electrode 11a stacked along the first direction Z can be 15-40. For example, the total number of layers of the positive electrode 11a stacked along the first direction Z in the electrode assembly 10 can be selected as 15, 17, 19, 20, 21, 23, 25, 27, 29, 30, 31, 33, 35, 37, 39, 40, or any value range between the two. Therefore, when the secondary battery 1 is punctured, the number of short-circuit points inside a single electrode assembly 10 is relatively small, which can reduce the short-circuit current of a single electrode assembly 10, thereby helping to reduce the short-circuit current of the secondary battery 1 and improving the reliability of the secondary battery 1.

[0067] In some embodiments, b can be 5 × 10 13 Up to 5×10 18 For example, the resistance between adjacent electrode terminals 31 can be selected as 5 × 10⁻⁶. 13 Ω, 8×10 13 Ω, 1×10 14 Ω, 2×10 14 Ω, 5×10 14 Ω, 8×10 14 Ω, 1×10 15 Ω, 2×10 15 Ω, 5×10 15 Ω, 8×10 15 Ω, 1×10 16 Ω, 2×10 16 Ω, 5×10 16 Ω, 8×10 16 Ω, 1×10 17 Ω, 2×10 17 Ω, 5×10 17 Ω, 8×10 17 Ω, 1×10 18 Ω, 2×10 18 Ω, 5×10 18 Ω, or the range of values ​​between any two.

[0068] The resistance between adjacent electrode terminals 31 is within the aforementioned range, effectively preventing current convergence between the various electrode components 10, increasing the internal resistance of the secondary battery 1 after a short circuit, and limiting the surge in short-circuit current. This, in turn, reduces heat generation within the secondary battery 1, lowers the risk of localized high temperatures and thermal runaway, and improves the reliability of the secondary battery 1.

[0069] In some embodiments, the thickness of the electrode terminal 31 is c mm, the thickness of the insulating layer 32 is d mm, and the secondary battery 1 can satisfy: c / d is 1 to 5, for example, c / d can be selected as 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, or any value range between the two.

[0070] When the c / d ratio is large, the electrode terminal 31 is relatively thick, and the insulating layer 32 is relatively thin. A thicker electrode terminal 31 affects the energy density of the secondary battery 1 and the sealing performance of the casing 20. A thinner insulating layer 32 has limited dielectric strength and thermal stability; when the local electric field strength or temperature is too high, the current-blocking effect of the insulating layer 32 may decrease. When the c / d ratio is small, the electrode terminal 31 is relatively thin, and the insulating layer 32 is relatively thick. A thinner electrode terminal 31 has poor mechanical strength and current-carrying capacity; a thicker insulating layer 32 affects the energy density of the secondary battery 1 and the sealing performance of the casing 20. A c / d ratio between 1 and 5 allows the electrode terminal 31 and the insulating layer 32 to have suitable thicknesses, resulting in good current-carrying capacity and mechanical connection function for the electrode terminal 31, good barrier function for the insulating layer 32, and a higher energy density for the secondary battery 1, while reducing the risk of leakage.

[0071] The thickness of the electrode terminal 31 and the thickness of the insulating layer 32 mentioned above represent the average thickness of the electrode terminal 31 and the average thickness of the insulating layer 32, respectively. During testing, the thickness of five points can be measured and the average value is taken.

[0072] In some embodiments, the thickness of the insulating layer 32 can be 0.1mm-2mm, for example, 0.1mm, 0.3mm, 0.5mm, 0.7mm, 0.9mm, 1mm, 1.2mm, 1.4mm, 1.6mm, 1.8mm, 2mm, or any value range between the two.

[0073] Within the aforementioned thickness range, the insulating layer 32 possesses excellent current blocking properties and also helps reduce its volume and mass proportion within the secondary battery 1, thereby increasing the energy density of the secondary battery 1. Furthermore, the thickness of the insulating layer 32 within the aforementioned range also enhances the sealing effect at the opening of the casing 20, reducing the risk of leakage from the secondary battery 1.

[0074] Optionally, the thickness of the insulating layer 32 can be 0.1mm-0.5mm, for example, 0.1mm, 0.15mm, 0.2mm, 0.25mm, 0.3mm, 0.35mm, 0.4mm, 0.45mm, 0.5mm, or any value range between the two.

[0075] In some embodiments, the volume resistivity of the insulating layer 32 may be 1×10⁻⁶. 11 Ω.m and above, for example, 1×10 can be selected. 11 Ω.m, 1.3×10 11 Ω.m, 2.5×10 11 Ω.m, 5×10 11 Ω.m, 7.5×10 11 Ω.m, 1×10 12 Ω.m, 2.5×10 12 Ω.m, 5×10 12 Ω.m, 7.5×10 12 Ω.m, 1×10 13 Ω.m, 2.5×10 13 Ω.m, 5×10 13 Ω.m, 7.5×10 13 Ω.m, 1×10 14 Ω.m, 2.5×10 14 Ω.m, 5×10 14 Ω.m, 7.5×10 14 Ω.m, 1×10 15 Ω.m, 2.5×10 15 Ω.m, 5×10 15 Ω.m, 7.5×10 15 Ω.m, 1×10 16 Ω.m, 5×10 16 Ω.m, 1×10 17 Ω.m, 5×10 17 Ω.m, 1×10 18 Ω.m, 2.5×10 18 Ω.m.

[0076] The volume resistivity of the insulating layer 32 is within the above range, which allows the insulating layer 32 to have both high resistance and low thickness.

[0077] Optionally, the volume resistivity of the insulating layer 32 can be 1×10⁻⁶. 14 Ω.m to 1×10 18 Ω.m, for example, can be selected as 1×10 14 Ω.m, 3×10 14 Ω.m, 6×10 14 Ω.m, 8×10 14 Ω.m, 1×10 15 Ω.m, 3×10 15 Ω.m, 6×10 15 Ω.m, 8×10 15 Ω.m, 1×10 16 Ω.m, 3×1016 Ω.m, 6×10 16 Ω.m, 8×10 16 Ω.m, 1×10 17 Ω.m, 3×10 17 Ω.m, 6×10 17 Ω.m, 8×10 17 Ω.m, 1×10 18 Ω.m, or any range of values ​​between the two.

[0078] In some embodiments, the dielectric strength of the insulating layer 32 can be 150 kV / mm or higher, for example, 150 kV / mm, 160 kV / mm, 170 kV / mm, 180 kV / mm, 190 kV / mm, 200 kV / mm, or any value range between the two.

[0079] The dielectric strength of the insulating layer 32 is within the aforementioned range, which reduces the risk of electrical breakdown of the insulating layer 32 when the local electric field strength is high. Therefore, the insulating layer 32 can maintain good insulation performance, thereby reducing the risk of excessive internal short-circuit current in the secondary battery 1 during puncture and improving the reliability of the secondary battery 1.

[0080] Optionally, the dielectric strength of the insulating layer 32 can be 150kV / mm-200kV / mm, for example, 150kV / mm, 155kV / mm, 160kV / mm, 165kV / mm, 170kV / mm, 175kV / mm, 180kV / mm, 185kV / mm, 190kV / mm, 195kV / mm, 200kV / mm, or any value range between the two.

[0081] In some embodiments, the melting point of the insulating layer 32 may be 200°C-400°C.

[0082] The melting point of the insulating layer 32 is within the aforementioned range, which reduces the risk of the insulating layer 32 failing to block current when the local temperature is high. Therefore, the insulating layer 32 can maintain good insulation performance, thereby reducing the risk of excessive internal short-circuit current in the secondary battery 1 during puncture and improving the reliability of the secondary battery 1.

[0083] In some embodiments, the thicknesses of any two positions in the insulating layer 32 are d1mm and d2mm, respectively, d1≥d2, and the insulating layer 32 satisfies: 0≤(d1-d2) / d1≤5%.

[0084] The insulating layer 32 satisfies the condition that (d1-d2) / d1 is between 0 and 5%, and its thickness is highly consistent throughout. This reduces the risk of stress concentration damage or breakdown due to lower dielectric strength in thinner areas when thickness variations are excessive. Furthermore, it reduces the risk of current conduction occurring between adjacent electrode terminals 31 due to localized breakdown of the insulating layer 32, thus improving the reliability of the secondary battery 1.

[0085] In some embodiments, the defect density of the insulating layer 32 is 0.1 defects / cm². 2 the following.

[0086] If the defect density of the insulating layer 32 is within the above range, the risk of local current conduction in the insulating layer 32 can be reduced, thereby improving the reliability of the secondary battery 1.

[0087] In this embodiment, a defect in the insulating layer 32 can refer to a hole with an equivalent circular area diameter greater than 5 μm. The equivalent circular area diameter can be defined as the diameter of a circle with an area equal to that of the hole. This can be measured using a CCD visual inspection device, with a test area of ​​1 cm². 2 During testing, multiple test areas (e.g., 5 test areas) can be selected, and the average defect density of the multiple test areas can be taken as the defect density test result of the insulation layer 32.

[0088] In some embodiments, the peel strength between the insulating layer 32 and the electrode terminal 31 can be 2 N / cm or higher.

[0089] During cycling, the secondary battery 1 undergoes volume changes, causing the casing 20 of the secondary battery 1 to deform and pull on the electrode terminals 31. The peel strength between the insulating layer 32 and the electrode terminals 31 is within the aforementioned range, which reduces the risk of the electrode terminals 31 separating from the insulating layer 32 when pulled, thereby improving the sealing performance of the casing 20 of the secondary battery 1 and reducing the risk of leakage.

[0090] In some embodiments, the insulating layer 32 may include polymeric materials and / or ceramic materials.

[0091] The polymer materials include one or more of polyimide (PI), polyethylene terephthalate (PET), polytetrafluoroethylene (PTFE), and epoxy resin.

[0092] The ceramic materials include one or more of alumina, Al2O3-ZrO2 composite ceramics, and ceramic-polymer composite ceramics. Ceramic-polymer composite ceramics may be, for example, one or more of Al2O3-epoxy resin composite ceramics and Al2O3-polyvinylidene fluoride (PVDF) composite ceramics.

[0093] The aforementioned materials not only possess high volume resistivity, dielectric strength, and thermal stability, but also exhibit high chemical inertness in the electrolyte. The insulating layer 32, comprising these materials, maintains good insulation performance during the cycling process of the secondary battery 1 or in the event of a short circuit, thereby contributing to improved reliability of the secondary battery 1.

[0094] The insulating layer 32, comprising the aforementioned materials, can be bonded to the electrode terminals 31 in any manner. As an example, the insulating layer 32 may include one or more of polyimide, polyethylene terephthalate, and polytetrafluoroethylene. The insulating layer 32 can be placed between two adjacent electrode terminals 31, and bonded to the electrode terminals 31 via a hot-pressing process. As another example, the insulating layer 32 may include epoxy resin. Uncured epoxy resin can be coated between two adjacent electrode terminals 31, and cured via a thermosetting or photocuring process, thereby achieving bonding between the insulating layer 32 and the electrode terminals 31. As yet another example, the insulating layer 32 may include a ceramic material. The ceramic material can be mixed with an adhesive and then bonded to the electrode terminals 31.

[0095] In some embodiments, there are multiple electrodes 12, and the multiple electrodes 12 include positive electrodes and negative electrodes.

[0096] There are multiple terminal assemblies 30, with a portion of each terminal assembly 30 connected to the positive electrode tab and another portion of each terminal assembly 30 connected to the negative electrode tab.

[0097] For example, the terminal assembly 30 connected to the positive tab is defined as the positive terminal assembly, and the terminal assembly 30 connected to the negative tab is defined as the negative terminal assembly.

[0098] The positive and negative terminal components can be led out from the same side of the housing 20, or they can be led out from opposite sides of the housing 20. For example, as Figure 1 As shown, two terminal assemblies 30 extend from both sides of the housing 20.

[0099] According to the second aspect of this application, please refer to Figure 3 This application also provides a battery pack 3, which includes a plurality of secondary batteries 1 provided according to any embodiment of this application.

[0100] In some embodiments, the battery pack 3 further includes a plurality of busbar components 2, which electrically connect a plurality of secondary batteries 1.

[0101] Multiple busbar components 2 can connect multiple secondary batteries 1 in series, parallel, or mixed connections. Mixed connection means that there are both series and parallel connections.

[0102] In some embodiments, the plurality of electrode terminals 31 of the terminal assembly 30 are respectively connected to different busbars 2. In this embodiment, although the insulating layer 32 insulates adjacent electrode terminals 31, the current from the plurality of electrode terminals 31 can be drawn out separately by providing a plurality of busbars 2.

[0103] In some examples, two secondary batteries 1 are connected in series via two busbars 2. For example, one busbar 2 is connected to one electrode terminal 31 of the positive terminal assembly 30 of one secondary battery 1 and one electrode terminal 31 of the negative terminal assembly 30 of the other secondary battery 1, and the other busbar 2 is connected to the other electrode terminal 31 of the positive terminal assembly 30 of one secondary battery 1 and the other electrode terminal 31 of the negative terminal assembly 30 of the other secondary battery 1.

[0104] This application also provides an electrical device 4, which includes the battery pack 3 provided in any of the foregoing embodiments. The battery pack 3 can provide electrical energy for the operation of the electrical device 4.

[0105] The electrical device 4 in this application embodiment can be a portable device, a laptop computer, an electric toy, a drone, a power tool, an energy storage system, etc. Power tools include metal cutting power tools, cleaning tools, etc., such as electric drills, electric wrenches, vacuum cleaners, robot vacuum cleaners, etc. This application embodiment does not impose any special limitations on the aforementioned electrical device 4.

[0106] Example The following examples describe the disclosure of this invention in more detail. These examples are merely illustrative, as various modifications and variations will be apparent to those skilled in the art within the scope of this disclosure. Unless otherwise stated, all parts, percentages, and ratios reported in the following examples are based on mass, and all reagents used in the examples are commercially available or synthesized by conventional methods and can be used directly without further processing. The instruments used in the examples are also commercially available.

[0107] Example 1 Preparation of positive electrode LiNi, the positive electrode active material 0.6 Co 0.2 Mn 0.2O2 (NCM622), positive electrode conductive agent carbon black (SP), positive electrode conductive agent carbon nanotubes (CNT), and positive electrode binder polyvinylidene fluoride (PVDF) are dispersed in solvent N-methylpyrrolidone (NMP) at a mass ratio of 96.4:1.4:0.8:1.4 and thoroughly mixed to form positive electrode slurry one with a solid content of 65%. Lithium iron manganese phosphate, positive electrode conductive agent carbon black SP, positive electrode conductive agent CNT, and positive electrode binder PVDF are dispersed in solvent NMP at a mass ratio of 96.5:0.6:0.4:2.5 and thoroughly mixed to form positive electrode slurry two with a solid content of 65%. Positive electrode slurry two was coated onto one surface of a 13 μm thick aluminum foil used as a positive electrode current collector. Then, positive electrode slurry one was coated onto positive electrode slurry two, forming a double-layer slurry layer with positive electrode slurry one on top and positive electrode slurry two on the bottom. This layer was dried at 120°C to obtain a positive electrode sheet with a single-sided coating of positive electrode material. In this single-sided positive electrode material layer, the mass ratio of NCM622 to lithium iron manganese phosphate was 7:3. The above steps were then repeated on the other surface of the aluminum foil to obtain a positive electrode sheet with a double-sided coating of positive electrode material. After cold pressing, cutting, and slitting, the positive electrode sheet was formed with multiple die-cut tabs. It was then dried under vacuum at 120°C for 10 minutes to obtain the final positive electrode sheet for use. The single-sided coating weight of the positive electrode material layer was 17 mg / cm³. 2 The thickness of the single-sided positive electrode material layer is 57 μm.

[0108] Preparation of negative electrode Artificial graphite (negative electrode active material), carbon black (negative electrode conductive agent), sodium carboxymethyl cellulose (CMC-Na) (thickener), and styrene-butadiene rubber (SBR) (negative electrode binder) were dispersed in deionized water at a mass ratio of 97.2:0.4:1:1.4 and thoroughly mixed to form a negative electrode slurry with a solid content of 40%. This negative electrode slurry was coated onto a 6 μm thick copper foil current collector and dried at 100°C to obtain a negative electrode sheet with a single-sided coating of the negative electrode material layer. The above steps were then repeated on the other side of the copper foil to obtain a negative electrode sheet with a double-sided coating of the negative electrode material layer. After cold pressing, cutting, and slitting, the negative electrode sheet was formed with multiple die-cut tabs. It was then dried under vacuum at 100°C for 30 minutes to obtain the final negative electrode sheet for use. The single-sided coating weight of the negative electrode material layer was 8 mg / cm³. 2 The thickness of the single-sided negative electrode material layer is 55 μm.

[0109] Preparation of electrolyte In an environment with a water content of less than 10 ppm, dimethyl carbonate, diethyl carbonate, and ethylene carbonate were mixed in a mass ratio of 1:1:1 to obtain an organic solvent. Then, the electrolyte salt LiPF6 was added to the organic solvent and mixed thoroughly to obtain the electrolyte. Based on the mass of the electrolyte, the electrolyte salt comprised 12.5% ​​by mass, with the remainder being the organic solvent.

[0110] Separating membrane A 10μm thick polyethylene film (supplied by Celgard) was used as the separator.

[0111] Preparation of secondary batteries The prepared positive electrode sheet, negative electrode sheet, and separator are wound into an electrode assembly. The positive electrode tabs of the two electrode assemblies are respectively welded to the two electrode terminals (made of aluminum) of a terminal assembly, with a PET insulating layer between the two electrode terminals. The negative electrode tabs of the two electrode assemblies are respectively welded to the two electrode terminals (made of nickel-plated copper) of another terminal assembly, with a PET insulating layer between the two electrode terminals. The two electrode assemblies are placed into an aluminum-plastic film for top and side sealing, then electrolyte is injected and sealed. After sequentially undergoing processes such as standing, hot and cold pressing, formation, shaping, and capacity testing, a secondary battery with a rated capacity of 30 Ah is obtained.

[0112] Examples 2-5 Except for adjusting the insulating layer material as shown in Table 1, the preparation of the secondary battery is the same as in Example 1. Specifically, the insulating layer materials in Examples 2-3 are PI and PTFE, respectively; the insulating layer in Example 4 comprises 90% Al2O3-PVDF composite ceramic and 10% PVDF binder; and the insulating layer in Example 5 comprises 90% Al2O3 ceramic and 10% PVDF binder.

[0113] Example 6 Except for adjusting the thickness of the positive electrode material layer and the negative electrode material layer to change the rated capacity of the secondary battery, the preparation of the secondary battery is the same as in Example 1.

[0114] Examples 7-10 Except for adjusting the thickness of the positive electrode material layer and the negative electrode material layer, as well as the number of turns of the electrode assembly to change the rated capacity of the secondary battery, the preparation of the secondary battery is the same as in Example 1.

[0115] Example 11 Except for adjusting the thickness of the positive electrode material layer and the negative electrode material layer, the number of turns of the electrode assembly to change the rated capacity of the secondary battery, and adjusting the material and thickness of the insulating layer, the preparation of the secondary battery is the same as in Example 1. The insulating layer material in Example 11 is PTFE.

[0116] Examples 12-13 Except for adjusting the thickness of the insulating layer, the preparation of the secondary battery is the same as in Example 1.

[0117] Comparative Example 1 Preparation of secondary batteries The prepared positive electrode sheet, negative electrode sheet, and separator are wound into an electrode assembly; the positive electrode tab of the electrode assembly is welded to one electrode terminal, and the negative electrode tab is welded to another electrode terminal; the individual electrode assembly is placed into an aluminum-plastic film for top and side sealing, then electrolyte is injected and sealed, and then the assembly undergoes a series of processes such as standing, hot and cold pressing, formation, shaping, and capacity testing to obtain a secondary battery with a rated capacity of 30Ah.

[0118] Comparative Example 2 Except for adjusting the thickness of the positive electrode material layer and the negative electrode material layer, as well as the number of turns of the electrode assembly to change the rated capacity of the secondary battery, the preparation of the secondary battery is the same as that of Comparative Example 1.

[0119] Test section The secondary batteries from each embodiment and comparative example were subjected to a nail penetration test. 100 batteries from each embodiment and comparative example were charged at a constant current of 0.5C to 4.3V at 25°C, and then charged at a constant voltage of 4.3V to the current cutoff point of 0.05C.

[0120] A nail penetration test was conducted on the secondary battery at 25℃ using a 5mm diameter carbon steel nail with a 45mm taper and a total length of 100mm. The nail penetration speed was set to 25mm / s, and the penetration depth was determined by the nail's taper penetrating the secondary battery. The state of the secondary battery during the test was observed, and the battery was deemed to have passed the nail penetration test if it did not burn or explode. The number of secondary batteries that passed the nail penetration test was recorded. The pass rate of the nail penetration test characterizes the reliability of the secondary battery. A higher pass rate indicates better reliability of the secondary battery.

[0121] The preparation parameters and test results of the examples and comparative examples are shown in Tables 1 and 2. In Table 1, the number of positive electrode layers indicates the total number of positive electrode layers stacked along the first direction Z. For example, the number of positive electrode layers in Example 1 is "15&15", which means that in the two electrode assemblies of Example 1, the total number of positive electrode layers stacked along the first direction Z in each electrode assembly is 15. aAh represents the rated capacity of the secondary battery, bΩ represents the resistance between adjacent electrode terminals, dmm represents the thickness of the insulating layer, ρvΩ.m represents the volume resistivity of the insulating layer, and " / " indicates that there is no corresponding parameter.

[0122] Table 1

[0123] Table 2

[0124] The test results in Tables 1 and 2 show that when the capacity of the secondary battery is between 30Ah and 200Ah, by including multiple electrode assemblies in the secondary battery, with an insulating layer between adjacent electrode terminals corresponding to the multiple electrode assemblies, and controlling a / b to be 4×10, -17 Up to 6×10 -13 During the pin-through test, the insulating layer can prevent current convergence between the various electrode components, increase the internal resistance of the secondary battery after a short circuit, reduce the current transmitted to the short circuit location, and limit the surge of short circuit current. This reduces heat generation inside the secondary battery, lowers the risk of localized high temperatures and thermal runaway, thus enabling the secondary battery 1 to possess both high capacity and high reliability.

[0125] In contrast, Comparative Examples 1 and 2 both consist of secondary batteries containing only a single electrode assembly. During the nail penetration test, the steel nail directly contacts the electrode of the secondary battery. After a short circuit occurs, the current inside the secondary battery can be conducted through the electrode terminals. Since the electrode terminals themselves have low resistance, the current in the secondary battery easily converges at the short circuit point, causing a surge in short circuit current. As a result, Comparative Examples 1 and 2 have low nail penetration rates and poor secondary battery reliability.

[0126] Although this application has been described with reference to preferred embodiments, various modifications can be made thereto and components can be replaced with equivalents without departing from the scope of this application. In particular, the technical features mentioned in the various embodiments can be combined in any manner, provided there is no structural conflict. This application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A secondary battery, characterized in that, include: case; Multiple electrode assemblies are housed within the housing and stacked along a first direction, each electrode assembly including a tab; A terminal assembly includes a plurality of electrode terminals and at least one insulating layer. One end of each electrode terminal is located inside the housing and the other end is located outside the housing. The plurality of electrode terminals are respectively connected to the tabs of different electrode assemblies. The plurality of electrode terminals are stacked and have the same polarity. The insulating layer is disposed between adjacent electrode terminals. The rated capacity of the secondary battery is a Ah, the resistance between adjacent electrode terminals with the insulating layer is b Ω, and a / b is 4 × 10⁻⁶. -17 Up to 6×10 -13 And a is between 30 and 200.

2. The secondary battery according to claim 1, characterized in that, The electrode assembly includes an electrode plate, and the electrode tab is connected to the electrode plate; there are multiple electrode plates, and the multiple electrode plates include a positive electrode plate; In the secondary battery, the total number of positive electrode layers stacked along the first direction is 30-80.

3. The secondary battery according to any one of claims 1-2, characterized in that, b is 5 × 10 13 Up to 5×10 18 .

4. The secondary battery according to any one of claims 1-3, characterized in that, The electrode terminal has a thickness of c mm, the insulating layer has a thickness of d mm, and the c / d ratio is 1 to 5.

5. The secondary battery according to any one of claims 1-4, characterized in that, The thickness of the insulating layer is 0.1mm-2mm, and can be selected as 0.1mm-0.5mm.

6. The secondary battery according to any one of claims 1-5, characterized in that, The volume resistivity of the insulating layer is 1×10⁻⁶. 11 For values ​​above Ω.m, 1×10 can be selected. 14 Ω.m to 1×10 18 Ω.m.

7. The secondary battery according to any one of claims 1-6, characterized in that, The dielectric strength of the insulating layer is above 150kV / mm, and can be selected as 150kV / mm-200kV / mm.

8. The secondary battery according to any one of claims 1-7, characterized in that, The melting point of the insulating layer is 200℃-400℃.

9. The secondary battery according to any one of claims 1-8, characterized in that, The thickness of any two positions in the insulating layer is d1mm and d2mm, respectively, where d1≥d2, and the insulating layer satisfies: 0≤(d1-d2) / d1≤5%.

10. The secondary battery according to any one of claims 1-9, characterized in that, The defect density of the insulating layer is 0.1 defects / cm². 2 the following.

11. The secondary battery according to any one of claims 1-10, characterized in that, The peel strength between the insulating layer and the electrode terminal is greater than 2 N / cm.

12. The secondary battery according to claim 1, characterized in that, The insulating layer comprises polymer materials and / or ceramic materials; The polymer material includes one or more of polyimide, polyethylene terephthalate, polytetrafluoroethylene, and epoxy resin; The ceramic material includes one or more of alumina, Al2O3-ZrO2 composite ceramics, and ceramic-polymer composite ceramics.

13. The secondary battery according to any one of claims 1-11, characterized in that, The electrode tabs are multiple, and the multiple electrode tabs include positive electrode tabs and negative electrode tabs; The terminal assembly comprises multiple components, with a portion of each terminal assembly connected to the positive electrode tab and another portion of each terminal assembly connected to the negative electrode tab.

14. A battery pack, characterized in that, It includes multiple secondary batteries according to any one of claims 1-13.

15. The battery pack according to claim 14, characterized in that, The battery pack also includes multiple busbars that electrically connect multiple secondary batteries; The plurality of electrode terminals of the terminal assembly are respectively connected to different busbar components.

16. An electrical appliance, characterized in that, Includes the battery pack according to claim 14 or 15.

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