A cylindrical battery, a battery pack, and an electric device

Abstract

The application provides a cylindrical battery, a battery pack and an electric device, the cylindrical battery comprising a cylindrical shell and an electrode core arranged in the cylindrical shell, a buffer layer is arranged between the electrode core and the cylindrical shell, the buffer layer comprises a first surface and a second surface arranged oppositely, the first surface is attached to the cylindrical shell, the second surface comprises an arc-shaped protruding part, the arc-shaped protruding part is in contact with at least part of the circumferential surface of the electrode core, the vertical distance between the axis of the highest point of the arc-shaped protruding part and the edge of any side of the electrode core is A, and the axial length of the electrode core is B, wherein A and B satisfy 0.35B≤A≤0.5B. The cylindrical battery provided by the application can effectively alleviate the uneven expansion of the electrode core during the charging and discharging process, avoid the deformation and rupture of the shell, and prolong the service life of the battery.

Description

Technical Field

[0001] This invention relates to the field of batteries, and more particularly to a cylindrical battery, a battery pack, and an electrical device. Background Technology

[0002] During the use of lithium-ion batteries, the battery core expands and contracts during charging and discharging due to the insertion and extraction of lithium ions and temperature changes caused by heat generation inside the core. Under repeated expansion, the adhesion between particles and the electronic contact of the electrode active materials deteriorate, resulting in loss of active materials and a decrease in capacity. At the same time, the impact force of the core expansion is directly transmitted to the casing, which can easily lead to deformation and cracking of the casing.

[0003] To suppress core expansion, existing technologies use a buffer layer and / or heat-conducting plate between the battery casing and the cell to cushion the expansion. However, conventional buffer layers and / or heat-conducting plates are usually of uniform structure, which makes it difficult to disperse the expansion stress in different parts of the core. For example, the expansion force in the central area and the two sides of a cylindrical cell is significantly different, which can easily lead to deformation and failure of the buffer layer. Summary of the Invention

[0004] The present invention provides a cylindrical battery including a buffer layer with arc-shaped protrusions, which can effectively alleviate the uneven expansion of the electrode core during charging and discharging, avoid deformation and cracking of the casing, and extend the cycle life of the battery.

[0005] The present invention also provides a battery pack, which, since it includes the above-mentioned battery, has the advantages of long cycle life and high safety.

[0006] The present invention also provides an electrical device that, because it includes the aforementioned battery pack, has good safety and a long service life.

[0007] In a first aspect, the present invention provides a cylindrical battery, comprising a cylindrical shell and a battery cell disposed inside the cylindrical shell, wherein a buffer layer is provided between the battery cell and the cylindrical shell, the buffer layer being elastic and comprising a first surface and a second surface disposed opposite to each other, the first surface being in contact with the cylindrical shell, the second surface comprising an arcuate protrusion, the arcuate protrusion being in contact with at least a portion of the peripheral surface of the battery cell, and the perpendicular distance between the axis of the highest point of the arcuate protrusion and any side edge of the battery cell being A, the axial length of the battery cell being B, wherein A and B satisfy: 0.35B≤A≤0.5B.

[0008] Optionally, the thickness of the buffer layer is 0.1-2 mm.

[0009] Optionally, the arc-shaped protruding part comprises N arc-shaped protruding regions along the axial direction of the battery cell, the thickness of each arc-shaped protruding region gradually decreases from the middle to the two edges, and N is a natural number greater than or equal to 1.

[0010] Optionally, N is an odd number greater than 1, the vertical distance from the highest point of the (N+1) / 2th arc-shaped protruding region to the battery cell is x, and the vertical distance from the highest point of any arc-shaped protruding region other than the (N+1) / 2th arc-shaped protruding region to the battery cell is y, wherein x is greater than y.

[0011] Optionally, the arc-shaped protruding regions other than the (N+1) / 2th arc-shaped protruding region are distributed on both sides of the (N+1) / 2th arc-shaped protruding region in axial symmetry or approximate axial symmetry.

[0012] Optionally, the N arc-shaped protruding regions are arranged closely in the axial direction of the battery cell, so that the buffer layer has a corrugated shape in the axial cross-section of the battery cell.

[0013] Optionally, N=5, the vertical distance from the highest point of the third arc-shaped protruding region to the battery cell is 1.3-2 times the vertical distance from the highest point of the first arc-shaped protruding region to the battery cell, and the vertical distance from the highest point of the second arc-shaped protruding region to the battery cell is 1-1.3 times the vertical distance from the highest point of the first arc-shaped protruding region to the battery cell.

[0014] Optionally, the vertical distance from the highest point of the third arc-shaped protruding region to the battery cell is 0.5-2 mm, and the vertical distance from the lowest point of the first arc-shaped protruding region to the battery cell is 0.1-0.4 mm.

[0015] Optionally, when N=1, the vertical distance from the highest point of the arc-shaped protruding region to the battery cell is 0.5-2 mm, and the vertical distance from the lowest point of the arc-shaped protruding region to the battery cell is 0.25-0.4 mm.

[0016] Optionally, the buffer layer has thermal conductivity.

[0017] Optionally, the thermal conductivity of the buffer layer is 10 W / m·K-500 W / m·K.

[0018] And / or, the compressive strength of the buffer layer is 5 MPa-50 MPa.

[0019] Optionally, the material of the buffer layer comprises graphite.

[0020] And / or, a high polymer material containing a thermal conductive filler.

[0021] Optionally, the heat-conductive filler is aluminum oxide and / or aluminum nitride, and the high-molecular material is a polyurethane material.

[0022] Optionally, the heat-conductive filler accounts for 20-30 wt% of the high-molecular material.

[0023] In a second aspect, the application provides a battery pack comprising the battery of the second aspect.

[0024] In a third aspect, the application provides an electrical device comprising the battery of the second aspect or the battery pack of the third aspect.

[0025] The cylindrical battery provided by the application can effectively relieve uneven expansion of the electrode core during charging and discharging, avoid deformation and rupture of the shell, and thus prolong the cycle life of the battery. BRIEF DESCRIPTION OF DRAWINGS

[0026] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the application and, together with the description, serve to explain the principles of the application.

[0027] Figure 1 FIG. 1 is a structural schematic diagram of a battery in an initial assembly state according to an embodiment of the application,

[0028] In the figure, 1 is a cylindrical shell, 2 is an electrode core, and 3 is a buffer layer.

[0029] Figure 2 FIG. 2 is a structural schematic diagram of a battery in a maximum expansion force state according to an embodiment of the application,

[0030] In the figure, 1 is a cylindrical shell, 2 is an electrode core, and 3 is a buffer layer.

[0031] Figure 3 FIG. 3 is a structural schematic diagram of a buffer layer according to an embodiment of the application,

[0032] In the figure, 4 is a first surface, 5 is a second surface, and 6 is an arc-shaped protruding part.

[0033] Figure 4 FIG. 4 is a structural schematic diagram of a buffer layer according to an embodiment of the application,

[0034] In the figure, 61 is a first arc-shaped protruding area, 62 is a second arc-shaped protruding area, 63 is a third arc-shaped protruding area, 64 is a fourth arc-shaped protruding area, and 65 is a fifth arc-shaped protruding area.

[0035] Figure 5 FIG. 5 is a capacity retention rate comparison diagram of batteries of Example 1 and Comparative Example 1.

[0036] Figure 6A temperature change comparison chart for the batteries of Example 1 and Comparative Example 1 of the present application.

[0037] By means of the above-described drawings, the specific embodiments of the present application have been shown, and will be described in more detail hereinafter. These drawings and written descriptions are not intended to limit the scope of the inventive concept by any means, but to illustrate the concept of the present application to those skilled in the art by referring to specific embodiments. DETAILED DESCRIPTION

[0038] The technical solutions in the embodiments of the present application will be described clearly and completely below in combination with the drawings in the embodiments of the present application. It should be understood that the following embodiments are only illustrative and explanatory of the present application, and should not be interpreted as limiting the scope of protection of the present application. Any technology realized based on the above description of the present application is covered by the scope of protection intended by the present application. In the drawings, the same components are denoted by the same reference numerals, and components similar in structure or function are denoted by similar reference numerals. The size and thickness of each component shown in the drawings are arbitrarily shown, and the present application does not limit the size and thickness of each component. In order to make the drawings clearer, the thickness of some components is appropriately exaggerated in some places in the drawings.

[0039] The same or similar reference numerals in the drawings of the embodiments of the present application correspond to the same or similar components; in the description of the present application, it should be understood that if the terms "upper", "lower", "left", "right" and the like indicate the orientation or positional relationship shown in the drawings, they are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or components referred to must have a particular orientation. The orientation and operation are therefore constructed and operated, and therefore the terms describing the positional relationship in the drawings are used only for illustrative purposes, and cannot be understood as limiting the present application. For those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.

[0040] In the present application, the terms "first", "second", and the like are mainly used to distinguish different devices, elements or components (the specific types and structures may be the same or different), and are not used to indicate or imply the relative importance and quantity of the devices, elements or components referred to.

[0041] The application finds that, during the charging and discharging process, the expansion of the cylindrical battery in space is uneven. With the increasing size of the cylindrical battery (such as 46 system large cylindrical battery, further such as 4680, 46150, 46210) and the increasing requirement of fast charging, the unevenness of the expansion force of the cylindrical battery also increases significantly, especially the expansion displacement of the center region is obviously higher than that of the two sides. The main reason is that the temperature difference between the center region and the edge region of the pole core is large, which leads to the increase of the unevenness of thermal expansion and breathing expansion. Specifically, the volume expansion will increase by 0.05% when the temperature of the pole core increases by 1℃. Therefore, the buffer layer with uniform or horizontal structure cannot effectively respond to the expansion difference between the center and edge of the pole core. If the stress of the center region cannot be effectively dispersed, it will lead to the deformation and rupture of the shell and the decrease of the cycle life.

[0042] To solve the above problems, the application provides the following technical scheme: in the first aspect, the application provides a cylindrical battery, Figure 1 For the structure schematic diagram of the battery in the initial assembly state of one embodiment of the application, the application provides a cylindrical battery, which comprises a cylindrical shell 1 and a pole core 2 arranged in the cylindrical shell, Figure 3 For the structure schematic diagram of the buffer layer of one embodiment of the application, the buffer layer has elasticity and comprises a first surface 4 and a second surface 5 arranged oppositely, the first surface 4 is attached to the cylindrical shell 1, the second surface 5 comprises an arc-shaped protruding part 6, the arc-shaped protruding part 6 is in contact with at least part of the peripheral surface of the pole core 2, and the vertical distance between the axis of the highest point of the arc-shaped protruding part and any one side edge of the pole core is A, the axial length of the pole core is B, and A, B satisfy: 0.35B≤A≤0.5B.

[0043] In the application, by adding a specific buffer layer, the expansion difference of the cylindrical battery in the axial direction can be adapted, the expansion failure problem of the active material can be relieved, and the cycle life of the pole core can be effectively improved. In more detail, the application designs a buffer layer with an arc-shaped protruding part according to the expansion force difference between the center and the two sides of the cylindrical battery. The arc-shaped protruding part has the characteristics that the middle part is thick and the two sides are thin. By limiting 0.35B≤A≤0.5B, the highest point of the arc-shaped protruding part is located near the center of the pole core, and the central region of the buffer layer has stronger buffering capacity to cope with the larger expansion force of the pole core in the center region. Especially during the high-rate charging and discharging process, with the increase of the expansion force of the pole core in the center region, the central region of the buffer layer deforms, the contact area between the pole core and the buffer layer increases gradually, and when the expansion force of the pole core reaches the maximum, see Figure 2, the thickness of the central region of the arc-shaped protruding part of the buffer layer after deformation is basically consistent with the thickness of the two sides, and the entire buffer layer does not fail due to compression, at this time, the contact area of the pole core and the buffer layer reaches the maximum, the buffer layer can effectively disperse the difference in expansion force at different positions, the center of the arc-shaped protruding part provides the maximum elastic support force, and the two sides with smaller expansion force provide smaller elastic support force, the arc-shaped protruding part not only deforms in the radial direction, but also deforms in the axial direction, so that the structure design also provides a deformation space for the axial deformation, thereby avoiding deformation and rupture of the shell, relieving the expansion failure problem of the active material, and prolonging the cycle life of the battery cell.

[0044] As for other structural features of the cylindrical battery, the application is not specifically limited, and the skilled person can select appropriate cylindrical shells and battery cells according to the actual application scene, in some embodiments, the cylindrical battery comprises a cylindrical shell and a battery cell arranged in the cylindrical shell, and a positive cover plate and a negative cover plate sealedly connected to two ends of the cylindrical shell, the battery cell is wound by a positive plate, a negative plate and a separator, the positive plate is electrically connected to the positive current collector disc of the positive cover plate, the negative plate is electrically connected to the negative current collector disc of the negative cover plate, and the material of the cylindrical shell body can be aluminum, copper or stainless steel.

[0045] In some embodiments, the thickness of the buffer layer is 0.1-2mm.

[0046] In some embodiments, the thickness of the buffer layer is 0.1-2mm.

[0047] In some embodiments, the arc-shaped protruding part comprises N arc-shaped protruding regions along the axial direction of the battery cell, the thickness of each arc-shaped protruding region gradually thins from the middle to the two edges, and N is a natural number greater than or equal to 1.

[0048] In some embodiments, the thickness of the buffer layer is 0.1-2mm.

[0049] In some embodiments, N is an odd number greater than 1, the vertical distance between the highest point of the (N+1) / 2th arc-shaped protruding region and the battery cell is x, and the vertical distance between the highest point of any arc-shaped protruding region other than the (N+1) / 2th arc-shaped protruding region and the battery cell is y, wherein x is greater than y.

[0050] In the above-mentioned embodiments, by defining the vertical distance from the highest point of the (N+1) / 2th arc-shaped protruding region to the battery cell to be greater than the vertical distance from the highest point of other arc-shaped protruding regions to the battery cell, it can be ensured that the central region of the buffer layer has stronger buffering capacity to cope with the greater expansion force of the battery cell in the central region.

[0051] It can be understood that any arc-shaped protruding region other than the (N+1) / 2th arc-shaped protruding region is distributed on both sides of the (N+1) / 2th arc-shaped protruding region, which can be irregularly distributed or can be distributed in a gradient-decreasing manner with the maximum thickness.

[0052] In some embodiments, the arc-shaped protruding regions other than the (N+1) / 2th arc-shaped protruding region are distributed on both sides of the (N+1) / 2th arc-shaped protruding region in an axial symmetry or an approximate axial symmetry.

[0053] Since the expansion force of the cylindrical battery cell presents an overall trend of being higher in the middle and lower at both ends, the arc-shaped protruding regions distributed in an axial symmetry or an approximate axial symmetry can better disperse the expansion force on both sides and avoid stress concentration and active material expansion failure on one side.

[0054] In some embodiments, the N arc-shaped protruding regions are arranged closely in the axial direction of the battery cell, so that the buffer layer has a corrugated shape in the axial cross section of the battery cell.

[0055] In some embodiments, a structural schematic diagram of the buffer layer is shown in Figure 4 , N=5, the vertical distance from the highest point of the third arc-shaped protruding region 63 to the battery cell is 1.3-2 times the vertical distance from the highest point of the first arc-shaped protruding region 61 to the battery cell, and the vertical distance from the highest point of the second arc-shaped protruding region 62 to the battery cell is 1-1.3 times the vertical distance from the highest point of the first arc-shaped protruding region 61 to the battery cell.

[0056] In some embodiments, the vertical distance from the highest point of the third arc-shaped protruding region to the battery cell is 0.5-2 mm, and the vertical distance from the lowest point of the first arc-shaped protruding region to the battery cell is 0.1-0.4 mm.

[0057] In some embodiments, when N=1, a structural schematic diagram of the buffer layer is shown in Figure 3 , the vertical distance from the highest point of the arc-shaped protruding region to the battery cell is 0.5-2 mm, and the vertical distance from the lowest point of the arc-shaped protruding region to the battery cell is 0.25-0.4 mm.

[0058] In some embodiments, the buffer layer has thermal conductivity.

[0059] When the buffer layer has thermal conductivity, it can also prevent the temperature of the electrode core from being too high, and the superposition of thermal conductivity and the elasticity of the buffer layer can further effectively improve the cycle life of the electrode core.

[0060] In some embodiments, the thermal conductivity is 10 W / m·K-500 W / m·K;

[0061] And / or, the compressive strength of the buffer layer is 5 MPa-50 MPa.

[0062] The thermal conductivity of the selected buffer layer in the above range not only has buffering capacity, but also quickly conducts heat, which helps to reduce the temperature rise of the electrode core and thus reduce thermal expansion; and the compressive strength of the selected buffer layer in the above range can further ensure that it has stronger buffering capacity to cope with the expansion force of the electrode core.

[0063] In some embodiments, the thermal conductivity of the buffer layer is tested by a Hot Disk thermal constant analyzer (model: TPS2500S). The specific test steps include: placing the Hot Disk sensor between the two parts of the sample to be tested, applying current heating, and recording the change of sensor temperature with time, and calculating the thermal conductivity by data analysis. The specific operation method can refer to the ISO 22007-2 standard.

[0064] In some embodiments, the compressive strength of the buffer layer is tested by a universal material testing machine (model: Instron 3369). The specific test steps include: placing the sample to be tested in the center position of the compression clamp, setting the loading speed and applying compression load to the sample until the sample breaks or deforms to a predetermined value. Record the relationship data between compression load and deformation during the test, and calculate the compressive strength. The specific operation method refers to the ASTM D695-15 standard.

[0065] In a specific embodiment, the material of the buffer layer includes graphite;

[0066] And / or, a high polymer material containing a thermal conductive filler.

[0067] The preparation of the buffer layer can be prepared by conventional methods, which are not particularly limited by the present application. In a specific embodiment, high-purity graphite is hot-pressed to form a buffer layer with an arc-shaped protruding part, and laser cutting is used. Further, the thermal conductivity of the buffer layer prepared by graphite is 300-500 W / m·K, and the compressive strength is 5-50 MPa. In another specific embodiment, the powder of the thermal conductive filler is added to the high polymer material matrix, and after stirring uniformly, it is molded by molding. Through special mold injection, a buffer layer with an arc-shaped protruding part can be obtained, and the thermal conductivity and mechanical properties can be adjusted by changing the proportion of the thermal conductive filler and the crosslinking degree of the high polymer material.

[0068] In some embodiments, the thermally conductive filler is aluminum oxide and / or aluminum nitride, and the high polymer material is a polyurethane material.

[0069] In some embodiments, the thermally conductive filler accounts for 20-30 wt% of the high polymer material.

[0070] The embodiments described above can make the thermal conductivity of the buffer layer reach 10-20 W / m·K, and the compressive strength is 10-25 MPa.

[0071] In a second aspect, the present application provides a battery pack comprising the battery of the second aspect.

[0072] In a third aspect, the present application provides an electrical device comprising the battery of the second aspect or the battery pack of the third aspect.

[0073] It should be noted that the above-mentioned electrical device can be any conventional device that requires electricity, for example, but not limited to, a computer, an electric vehicle, an air conditioner, a refrigerator, a washing machine, a microwave oven, a printer, a fax machine, etc.

[0074] In order to further understand the present application, the technical solutions of the present application will be described in detail below in conjunction with specific embodiments. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative labor fall within the scope of protection of the present application.

[0075] Unless otherwise specified, the reagents involved in the embodiments of the present application are all commercially available and can be purchased through commercial channels.

[0076] The cylindrical battery for the following tests includes a battery cell. Specifically, the cylindrical battery is a 46150 model with a diameter of 46.0±0.5 mm and a height of 150±0.5 mm. The positive active material is lithium iron phosphate, the negative active material is graphite, the positive current collector is aluminum foil, the negative current collector is copper foil, the shell is aluminum, and the capacity is 35±0.5 Ah.

[0077] Example 1

[0078] This example provides a cylindrical battery, the structure diagram of which is shown in Figure 1 , which includes a shell 1 and a battery cell 2 placed inside the shell. A buffer layer 3 is provided between the battery cell and the shell, Figure 3As shown in the structural diagram of the buffer layer of one embodiment of the present application, the buffer layer has elasticity and comprises a first surface 4 and a second surface 5 arranged oppositely, the first surface 4 is attached to the peripheral surface of the cylindrical shell 1, and the second surface 5 comprises an arc-shaped protruding part 6, the arc-shaped protruding part 6 is in contact with at least part of the peripheral surface of the battery cell 2, the vertical distance between the axis of the highest point of the arc-shaped protruding part and any side edge of the battery cell is A, and the axial length of the battery cell is B, wherein A and B satisfy 0.5B=A; the arc-shaped protruding part has one arc-shaped protruding area, the thickness of which gradually decreases from the middle to the two side edges, the straight-line distance between the highest point of the arc-shaped protruding area and the battery cell is 0.5 mm, the straight-line distance between the lowest point of the arc-shaped protruding area and the battery cell is 0.25 mm, the material of the buffer layer is graphite, the thermal conductivity coefficient of the buffer layer is 482 W / m·K, and the compressive strength of the buffer layer is 14.6 MPa.

[0079] Example 2

[0080] This example provides a cylindrical battery, the structural diagram of which is shown in Figure 1 , which comprises a cylindrical shell 1 and a battery cell 2 arranged inside the cylindrical shell, and a buffer layer 3 arranged between the battery cell and the cylindrical shell, Figure 3 As shown in the structural diagram of the buffer layer of one embodiment of the present application, the buffer layer has elasticity and comprises a first surface 4 and a second surface 5 arranged oppositely, the first surface 4 is attached to the peripheral surface of the cylindrical shell 1, and the second surface 5 comprises an arc-shaped protruding part 6, the arc-shaped protruding part 6 is in contact with at least part of the peripheral surface of the battery cell 2, the vertical distance between the axis of the highest point of the arc-shaped protruding part and any side edge of the battery cell is A, and the axial length of the battery cell is B, wherein A and B satisfy 0.5B=A; the arc-shaped protruding part has one arc-shaped protruding area, the thickness of which gradually decreases from the middle to the two side edges, the straight-line distance between the highest point of the arc-shaped protruding area and the battery cell is 0.5 mm, the straight-line distance between the lowest point of the arc-shaped protruding area and the battery cell is 0.25 mm, the material of the buffer layer is graphite, the thermal conductivity coefficient of the buffer layer is 482 W / m·K, and the compressive strength of the buffer layer is 14.6 MPa. Figure 4 , the thickness of each of which gradually decreases from the middle to the two side edges, the first, second, fourth and fifth arc-shaped protruding areas are approximately axially symmetrically distributed on the two sides of the third arc-shaped protruding area, and the five arc-shaped protruding areas are closely arranged, so that the buffer layer has a corrugated shape in the axial cross section of the battery cell, the length ratio of the arc-shaped protruding areas in the axial direction is 1:2:4:2:1, the minimum thickness of the arc-shaped protruding part is 0.25 mm, the thickness of the highest point of the third arc-shaped protruding area (i.e. the vertical distance between the highest point and the battery cell) is 0.5 mm, the thickness of the highest point of the second and fourth arc-shaped protruding areas is 0.44 mm, the thickness of the highest point of the first and fifth arc-shaped protruding areas is 0.37 mm, the material of the buffer layer is graphite, the thermal conductivity coefficient of the buffer layer is 482 W / m·K, and the compressive strength of the buffer layer is 14.6 MPa.

[0081] Example 3

[0082] The same as example 1, except that the material of the buffer layer is polyurethane material filled with 28% of aluminum oxide, the thermal conductivity coefficient of the buffer layer is 11 W / m·K, and the compressive strength of the buffer layer is 11.2 MPa.

[0083] Example 4

[0084] The same as Example 1, except that the material of the buffer layer is polyurethane material filled with 28% aluminum nitride, the thermal conductivity is 17 W / m·K, and the compressive strength is 12.3 MPa.

[0085] Example 5

[0086] The same as Example 1, except that the buffer layer is replaced by a buffer layer made of polyurethane material only, the thermal conductivity is 0.1 W / m·K, and the compressive strength is 8.6 MPa.

[0087] Comparative Example 1

[0088] The same as Example 1, except that no buffer layer is provided.

[0089] Comparative Example 2

[0090] The same as Example 5, except that the buffer layer is uniform in thickness, all 0.5 mm, the thermal conductivity of the buffer layer is 0.1 W / m·K, and the compressive strength is 8.6 MPa.

[0091] Test Example

[0092] 1: Change of cell center temperature:

[0093] Test method: A K-type thermocouple is pre-implanted at the center of the cylindrical cell and fixed with thermal conductive glue, then the cell is placed in a constant temperature oven, and a specific working condition is applied to the cell through a charge-discharge test cabinet, then the real-time temperature change of the cell is recorded through a data acquisition system. Specifically, the cylindrical cell is first placed in a constant temperature oven at 25℃, then the SOC state of the cell is adjusted to 60%, then a 3C rate periodic pulse charge-discharge is carried out for 5s charging and 5s discharging, lasting for 10000s, and the change rule of the center temperature of the cylindrical cell with time is recorded, the results are shown in Table 1.

[0094] 2, Cycle life

[0095] Test method: The cylindrical cell is placed in a constant temperature oven, and the cell is subjected to cyclic charge-discharge through a charge-discharge test cabinet, while the discharge capacity is recorded through a data acquisition system, and the discharge capacity after each cycle is divided by the initial discharge capacity to obtain the capacity retention rate, i.e. cycle life. Specifically, the cylindrical cell is placed in a constant temperature oven at 45℃, first charged at 1C constant current to the upper limit voltage 3.75V, then discharged at 1C constant current to the lower limit voltage 2V, and the charge-discharge cycle is carried out for 1000 times, the discharge capacity of each time is recorded and the capacity retention rate is calculated, and whether the shell is deformed or cracked is observed, the results are shown in Table 1.

[0096] Table 1:

[0097]

[0098] As can be seen from Table 1, the cylindrical battery of the examples 1-5 has a heat-conducting buffer layer with an arc-shaped protruding part, and the temperature of the battery core center is lower after 3C 60% SOC 5s pulse charge and discharge at room temperature, which shows that the buffer layer of the examples can more significantly reduce the overall temperature rise rate of the battery core.

[0099] Further, through the 45℃ high-temperature cycle test, it can be known that the cylindrical battery of the examples has a buffer layer with an arc-shaped protruding part, which can better adapt to the difference in expansion force in the axial direction of the cylindrical battery core, and shows better cycle life, which is specifically shown in that the capacity retention rate after 1000 cycles is much higher than that of the comparative examples.

[0100] Further, the cylindrical battery of the comparative example 1 has no buffer layer, and the cycle inflection point occurs, the life sharply decreases, and the shell cracking occurs during the cycle.

[0101] Finally, it should be pointed out that: the above examples are only used to illustrate the technical solutions of the present application, but not to limit them; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing examples, or make equivalent replacement for part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the examples of the present application.

Claims

1. A cylindrical battery comprising a cylindrical case and an electrode group disposed inside the cylindrical case, a buffer layer being provided between the electrode group and the cylindrical case, the buffer layer having elasticity and comprising a first face and a second face disposed opposite to each other, characterized in that, The first surface is attached to the cylindrical shell, the second surface comprises an arc-shaped protruding part, the arc-shaped protruding part is in contact with at least part of the circumferential surface of the battery cell, and the vertical distance between the axis of the thickest part of the arc-shaped protruding part and any side edge of the battery cell is A, and the axial length of the battery cell is B, wherein A and B satisfy: 0.35B≤A≤0.5B. The arc-shaped protruding part comprises N arc-shaped protruding regions along the axial direction of the battery cell, the thickness of each arc-shaped protruding region gradually decreases from the middle to the side edges, N is an odd number greater than 1, the thickness of the thickest part of the (N+1) / 2th arc-shaped protruding region is x, and the thickness of the thickest part of any arc-shaped protruding region other than the (N+1) / 2th arc-shaped protruding region is y, wherein x is greater than y.

2. The cylindrical battery according to claim 1, characterized by The thickness of the buffer layer is 0.1-2mm.

3. The cylindrical battery according to claim 1, characterized by, The arc-shaped protruding regions other than the (N+1) / 2th arc-shaped protruding region are distributed in axial symmetry on both sides of the (N+1) / 2th arc-shaped protruding region.

4. The cylindrical battery according to claim 1, characterized by, The N arc-shaped protruding regions are arranged closely in the axial direction of the battery cell, so that the buffer layer has a corrugated shape in the axial cross-section of the battery cell.

5. The cylindrical battery according to claim 1, characterized by, N=5, along the axial direction of the battery cell, the thickness of the thickest part of the 3rd arc-shaped protruding region is 1.3-2 times the thickness of the thickest part of the 1st arc-shaped protruding region, and the thickness of the thickest part of the 2nd arc-shaped protruding region is 1-1.3 times the thickness of the thickest part of the 1st arc-shaped protruding region.

6. The cylindrical battery according to claim 5, characterized by The thickness of the thickest part of the 3rd arc-shaped protruding region is 0.5-2mm, and the thickness of the thinnest part of the 1st arc-shaped protruding region is 0.1-0.4mm.

7. The cylindrical battery according to any one of claims 1 to 6, characterized by, The buffer layer has thermal conductivity.

8. The cylindrical battery according to claim 7, characterized by The thermal conductivity coefficient of the buffer layer is 10 W / m·K-500 W / m·K. And / or, the compressive strength of the buffer layer is 5 MPa-50 MPa.

9. The cylindrical battery according to claim 8, characterized by The material of the buffer layer comprises graphite. And / or, a high polymer material containing a thermal conductive filler.

10. The cylindrical battery according to claim 9, characterized by The thermal conductive filler is alumina and / or aluminum nitride, and the high polymer material is a polyurethane material.

11. The cylindrical battery according to claim 10, characterized by The thermal conductive filler accounts for 20-30 wt% of the high polymer material.

12. A battery pack, characterized by A cylindrical battery according to any one of claims 1-11.

13. An electrical device, characterized by A cylindrical battery according to any one of claims 1-11 or a battery pack according to claim 12.

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