Cylindrical battery, battery pack and electric equipment

Abstract

The invention provides a cylindrical battery, a battery pack and electric equipment, the cylindrical battery comprises a cylindrical shell and a battery cell arranged in the cylindrical shell, a buffer layer is arranged between the battery cell and the cylindrical shell, the buffer layer comprises a first surface and a second surface which are oppositely arranged, the first surface is attached to the cylindrical shell, the second surface comprises an arc-shaped convex part, and the arc-shaped convex part is arranged between the first surface and the second surface. The arc-shaped protruding part is in contact with at least part of the circumferential surface of the battery cell, the vertical distance between the axis where the highest point of the arc-shaped protruding part is located and the edge of any side of the battery cell is A, the axial length of the battery cell is B, and A and B meet the condition that A is larger than or equal to 0.35 B and smaller than or equal to 0.5 B. The cylindrical battery provided by the invention can effectively relieve the non-uniform expansion of the pole core in the charging and discharging process, and avoids the deformation and fracture of the shell, thereby prolonging the service life of the battery.

Description

Technical Field

[0001] The present invention relates to the field of batteries, and in particular to a cylindrical battery, a battery pack and an electrical device. Background Art

[0002] During the use of lithium-ion batteries, the battery core will expand and contract during the charging and discharging process due to the temperature changes caused by the embedding and de-embedding of lithium ions and the heat generated inside the core. Under the repeated expansion of the electrode active material, the bonding force and electronic contact between the particles will deteriorate, resulting in the loss of active materials and the decrease of capacity. At the same time, the expansion impact of the core will be directly transmitted to the shell, which can easily cause deformation and rupture of the shell.

[0003] In order to suppress the expansion of the pole core, the prior art provides a buffer layer and / or a heat conducting plate between the battery housing and the battery core to play a buffering role when the battery expands. However, conventional buffer layers and / or heat conducting plates are usually uniform structures, which make it difficult to disperse the expansion stress of different parts of the pole core. For example, the expansion force in the center area and the two sides of a cylindrical battery core is quite 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, which includes a buffer layer with an arc-shaped protrusion, which can effectively alleviate the uneven expansion of the pole core during the charging and discharging process, avoid deformation and rupture of the shell, and extend the battery cycle life.

[0005] The present invention also provides a battery pack. Since the battery pack includes the battery, the battery pack has the advantages of long cycle life and high safety.

[0006] The present invention also provides an electric device. Since the electric device comprises the battery pack, the electric device 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 is elastic and comprises a first surface and a second surface arranged opposite to each other, the first surface is in contact with the cylindrical shell, the second surface comprises an arc-shaped protrusion, the arc-shaped protrusion is in contact with at least part of the circumferential surface of the battery cell, and the vertical distance between the axis at which the highest point of the arc-shaped protrusion is located and any side edge of the battery cell is A, the axial length of the battery cell is B, wherein A and B satisfy: 0.35B≤A≤0.5B.

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

[0009] Optionally, the arc-shaped protrusion includes N arc-shaped protrusion areas along the axial direction of the battery core, the thickness of each arc-shaped protrusion area gradually becomes thinner from the middle to the edges on both sides, 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 between the highest point of the (N+1) / 2th arc-shaped raised area and the battery cell is x, and the vertical distance between the highest point of any arc-shaped raised area except the (N+1) / 2th arc-shaped raised area and the battery cell is y, where x is greater than y.

[0011] Optionally, the arc-shaped raised areas other than the (N+1) / 2th arc-shaped raised areas are axially symmetrically distributed or approximately axially symmetrically distributed on both sides of the (N+1) / 2th arc-shaped raised area.

[0012] Optionally, the N arc-shaped raised areas are closely connected and arranged in the axial direction of the battery core, so that the buffer layer is corrugated along the axial cross section of the battery core.

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

[0014] Optionally, the vertical distance between the highest point of the third arc-shaped raised area and the battery core is 0.5-2 mm, and the vertical distance between the lowest point of the first arc-shaped raised area and the battery core is 0.1-0.4 mm.

[0015] Optionally, when N=1, the vertical distance between the highest point of the arc-shaped convex area and the battery core is 0.5-2 mm, and the vertical distance between the lowest point and the battery core is 0.25-0.4 mm.

[0016] Optionally, the buffer layer is thermally conductive.

[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 includes graphite;

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

[0021] Optionally, the thermal conductive filler is aluminum oxide and / or aluminum nitride, and the polymer material is a polyurethane material.

[0022] Optionally, the thermally conductive filler accounts for 20-30 wt % of the polymer material.

[0023] In a second aspect, the present invention provides a battery pack comprising the battery described in the second aspect.

[0024] In a third aspect, the present invention provides an electrical device, comprising the battery described in the second aspect or the battery pack described in the third aspect.

[0025] The cylindrical battery provided by the present invention comprises a buffer layer with an arc-shaped protrusion, which can effectively alleviate the uneven expansion of the pole core during the charging and discharging process, avoid deformation and rupture of the shell, and thus extend the battery cycle life. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0027] Figure 1 is a schematic structural diagram of a battery in an initial assembly state according to a specific embodiment of the present invention,

[0028] In the figure, 1-column shell, 2-battery core, 3-buffer layer;

[0029] Figure 2 This is a schematic diagram of the structure of a battery in a state of maximum expansion force according to a specific embodiment of the present invention.

[0030] In the figure, 1-column shell, 2-battery core, 3-buffer layer;

[0031] Figure 3 is a schematic structural diagram of a buffer layer according to a specific embodiment of the present invention,

[0032] In the figure, 4-first surface, 5-second surface, 6-arc-shaped protrusion;

[0033] Figure 4 is a schematic structural diagram of a buffer layer according to a specific embodiment of the present invention,

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

[0035] Figure 5 It is a comparison chart of the capacity retention rate of the batteries of Example 1 of the present invention and Comparative Example 1;

[0036] Figure 6It is a comparison chart of temperature changes of the batteries of Example 1 of the present invention and Comparative Example 1.

[0037] The above drawings have shown clear embodiments of the present invention, which will be described in more detail below. These drawings and text descriptions are not intended to limit the scope of the present invention in any way, but to illustrate the concept of the present invention for those skilled in the art by referring to specific embodiments. DETAILED DESCRIPTION

[0038] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. It should be understood that the following embodiments are only exemplary illustrations and explanations of the present invention, and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above contents of the present invention are covered within the scope that the present invention is intended to protect. In the accompanying drawings, components with the same structure are represented by the same numerical labels, and components with similar structures or functions are represented by similar numerical labels. The size and thickness of each component shown in the drawings are arbitrarily shown, and the present invention does not limit the size and thickness of each component. In order to make the illustration clearer, the thickness of the components is appropriately exaggerated in some places in the drawings.

[0039] The same or similar numbers in the drawings of the embodiments of the present invention correspond to the same or similar parts; in the description of the present invention, it should be understood that if the terms "upper", "lower", "left", "right" and the like indicate the orientation or positional relationship, they are based on the orientation or positional relationship shown in the drawings, which is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or component referred to must have a specific orientation. The device is constructed and operated in a specific orientation. Therefore, the terms describing the positional relationship in the drawings are only used for illustrative purposes and cannot be understood as a limitation on the present invention. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0040] In the present invention, the terms "first", "second", etc. 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 indicated devices, elements or components.

[0041] During the research of the present invention, it was found that during the charging and discharging process, the expansion of the cylindrical battery cell in space is uneven. With the continuous increase in the size of the cylindrical battery (such as the 46 series large cylindrical battery, and further such as 4680, 46150, 46210) and the continuous improvement of the fast charging requirements, the expansion force non-uniformity of the cylindrical battery cell has also increased significantly, especially the expansion displacement of the center area will be significantly higher than the expansion displacement on both sides. The main reason is that the temperature difference between the center area and the edge area of ​​the pole core is large, which leads to increased non-uniformity of thermal expansion and breathing expansion. Specifically, for every 1°C increase in the pole core temperature, the volume expansion will increase by 0.05%. Therefore, the buffer layer with uniform or horizontal structure cannot effectively cope with the expansion difference between the center and edge of the pole core. If the stress in the center area cannot be effectively dispersed, it will cause the shell to deform and crack and the cycle life to decrease.

[0042] In order to solve the above problems, the present invention proposes the following technical solutions: In the first aspect, the present invention provides a cylindrical battery, Figure 1 The schematic diagram of the structure of a battery in an initial assembly state according to a specific embodiment of the present invention provides a cylindrical battery, comprising a cylindrical shell 1 and a battery cell 2 disposed inside the cylindrical shell, wherein a buffer layer 3 is disposed between the battery cell and the cylindrical shell. Figure 3 This is a schematic structural diagram of a buffer layer of a specific embodiment of the present invention, wherein the buffer layer is elastic and comprises a first surface 4 and a second surface 5 arranged opposite to each other, wherein the first surface 4 is in contact with the column shell 1, and the second surface 5 comprises an arcuate protrusion 6, wherein the arcuate protrusion 6 is in contact with at least a portion of the circumferential surface of the battery cell 2, and a vertical distance between an axis at which the highest point of the arcuate protrusion is located and an edge on any side of the battery cell is A, and an axial length of the battery cell is B, wherein A and B satisfy: 0.35B≤A≤0.5B.

[0043] In the present invention, by adding a specific buffer layer, it is possible to adapt to the axial expansion difference of the cylindrical battery cell, alleviate the expansion failure problem of the active material, and thus effectively improve the cycle life of the battery cell. In more detail, the present invention designs a buffer layer with an arc-shaped protrusion in view of the difference in expansion force between the center and the two sides of the cylindrical battery cell. The arc-shaped protrusion is thick in the middle and thin on both sides, and at the same time, by limiting 0.35B≤A≤0.5B, the highest point of the arc-shaped protrusion is controlled to be near the center of the battery cell, ensuring that the central area of ​​the buffer layer has a stronger buffering capacity to cope with the larger expansion force of the battery cell in the central area. Especially during high-rate charging and discharging, as the expansion force in the central area of ​​the battery cell increases, the central area of ​​the buffer layer deforms, and the contact area between the battery cell and the buffer layer gradually increases. When the expansion force of the battery cell reaches the maximum, see Figure 2The thickness of the central area of ​​the arc-shaped raised part of the buffer layer after deformation is basically the same as the thickness on both sides, and the entire buffer layer will not fail due to compression. At this time, the contact area between the pole core and the buffer layer reaches the maximum, and the buffer layer can effectively disperse the expansion force differences at different positions. The center of the arc-shaped raised part provides the largest elastic supporting force, while the two sides with smaller expansion force provide smaller elastic supporting force. The arc-shaped raised part will not only have radial deformation, but also axial deformation. Therefore, this structural design also provides deformation space for axial deformation, thereby avoiding deformation and rupture of the shell, alleviating the expansion failure problem of the active material, and extending the cycle life of the battery cell.

[0044] As for other structural features of the cylindrical battery, the present invention does not make specific limitations. Technicians can select suitable column shells and battery cells according to actual application scenarios. In some embodiments, the cylindrical battery includes a column shell and a battery cell arranged in the column shell, and a positive electrode cover plate and a negative electrode cover plate sealed and assembled at both ends of the column shell. The battery cell is wound by a positive electrode sheet, a negative electrode sheet and a diaphragm. The positive electrode sheet is electrically connected to the positive electrode collector disk of the positive electrode cover plate, and the negative electrode sheet is electrically connected to the negative electrode collector disk of the negative electrode cover plate. The material of the column shell body can be aluminum, copper or stainless steel.

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

[0046] Since the buffer layer of the present invention includes an arc-shaped protrusion, the thickness of each point of the buffer layer is not uniform, but the thickness of any point is within the range of 0.1-2 mm.

[0047] In some embodiments, the arc-shaped protrusion includes N arc-shaped protrusion areas along the axial direction of the battery core, the thickness of each arc-shaped protrusion area gradually becomes thinner from the middle to the edges on both sides, and N is a natural number greater than or equal to 1.

[0048] Among them, when the pole core expands, multiple arc-shaped raised areas can provide multi-point support compared to a single arc-shaped raised area, thereby having better buffering capacity and being able to adapt to the expansion force difference in the height direction of the cylindrical battery cell.

[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 raised area and the battery cell is x, and the vertical distance between the highest point of any arc-shaped raised area other than the (N+1) / 2th arc-shaped raised area and the battery cell is y, wherein x is greater than y.

[0050] In the embodiment as described above, by limiting the vertical distance between the highest point of the (N+1) / 2th arc-shaped protrusion area and the battery cell to be greater than the vertical distance between the highest point of the other arc-shaped protrusion areas and the battery cell, it can be ensured that the central area of ​​the buffer layer has a stronger buffering capacity to cope with the larger expansion force of the battery cell in the central area.

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

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

[0053] Since the expansion force of cylindrical battery cells shows an overall trend of being high in the middle and low at both ends, setting an arc-shaped convex area with an axisymmetric distribution or a nearly axisymmetric distribution can better disperse the expansion force on both sides, avoiding local stress concentration on one side and expansion failure of the active material.

[0054] In some embodiments, the N arc-shaped raised areas are closely connected and arranged in the axial direction of the battery core, so that the buffer layer is corrugated along the axial cross section of the battery core.

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

[0056] In some embodiments, the vertical distance between the highest point of the third arc-shaped raised area and the battery core is 0.5-2 mm, and the vertical distance between the lowest point of the first arc-shaped raised area and the battery core is 0.1-0.4 mm.

[0057] In some embodiments, when N=1, the schematic diagram of the structure of the buffer layer is shown in Figure 3 The vertical distance between the highest point of the arc-shaped convex area and the battery core is 0.5-2 mm, and the vertical distance between the lowest point and the battery core is 0.25-0.4 mm.

[0058] In some embodiments, the buffer layer is thermally conductive.

[0059] When the buffer layer has thermal conductivity, it can also prevent the core temperature from being too high. The combination of thermal conductivity and elasticity of the buffer layer can more effectively improve the cycle life of the battery cell.

[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 within the above range not only has buffering capacity, but also can quickly dissipate heat, which helps to reduce the temperature rise of the battery cell and thus reduce thermal expansion; and the compression strength of the selected buffer layer within the above range can further ensure that it has stronger buffering capacity to cope with the expansion force of the battery cell.

[0063] In some embodiments, the thermal conductivity of the buffer layer is tested using a Hot Disk thermal constant analyzer (model: TPS2500S). The specific test steps include: placing a Hot Disk sensor between two parts of the sample to be tested, applying current for heating, and recording the change in sensor temperature over time, and calculating the thermal conductivity through 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 using a universal material testing machine (model: Instron 3369), and the specific test steps include: placing the sample to be tested in the center of the compression fixture, setting the loading speed and applying a compressive load to the sample until the sample breaks or the deformation reaches a predetermined value. The relationship data between the compressive load and the deformation during the test is recorded, and the compressive strength is calculated. 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 polymer material containing a thermally conductive filler.

[0067] The preparation of the buffer layer can be prepared by conventional methods, and the present invention is not particularly limited to this. In one specific embodiment, high-purity graphite can be hot-pressed and laser-cut into a buffer layer with an arc-shaped protrusion; further, the thermal conductivity of the buffer layer prepared by graphite is 300-500 W / m·K and the compression strength is 5-50 MPa. In another specific embodiment, the powder of the thermal conductive filler is added to the polymer material matrix, and the powder is molded after being stirred evenly. The buffer layer with an arc-shaped protrusion can be obtained by injection molding with a special mold. The thermal conductivity and mechanical properties of the buffer layer can be adjusted by changing the proportion of the thermal conductive filler and the cross-linking degree of the polymer material.

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

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

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

[0071] In a second aspect, the present invention provides a battery pack comprising the battery described in the second aspect.

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

[0073] It should be noted that the above-mentioned electrical equipment can be any conventional equipment that requires electricity, for example, including but not limited to computers, electric cars, air conditioners, refrigerators, washing machines, microwave ovens, printers, fax machines, etc.

[0074] In order to further understand the present invention, the technical solution of the present invention will be clearly and completely described below in conjunction with specific embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

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

[0076] Among them, the cylindrical battery tested below includes a battery cell. Specifically, the cylindrical battery is a 46150 model with a diameter of 46.0±0.5mm and a height of 150±0.5mm. Its positive electrode active material is lithium iron phosphate, and its negative electrode active material is graphite. The positive electrode collector is aluminum foil, the negative electrode collector is copper foil, the column shell is an aluminum shell, and the capacity is 35±0.5Ah.

[0077] Example 1

[0078] This example provides a cylindrical battery, and its structural schematic diagram is shown in Figure 1 , comprising a column shell 1 and a battery core 2 disposed inside the column shell, a buffer layer 3 being disposed between the battery core and the column shell, Figure 3It is a structural schematic diagram of a buffer layer of a specific embodiment of the present invention, wherein the buffer layer is elastic and comprises a first surface 4 and a second surface 5 arranged opposite to each other, wherein the first surface 4 is in contact with the peripheral surface of the column shell 1, and the second surface 5 comprises an arcuate protrusion 6, wherein the arcuate protrusion 6 contacts at least part of the peripheral surface of the battery cell 2, and the vertical distance between the axis where the highest point of the arcuate protrusion is located and the edge of any side 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 arcuate protrusion has an arcuate protrusion area, and its thickness gradually becomes thinner from the middle to the edges on both sides, and specifically, the highest point of the arcuate protrusion area is 0.5 mm away from the battery cell in a straight line, and the lowest point is 0.25 mm away from the battery cell in a straight line, and the material of the buffer layer is graphite, with a thermal conductivity of 482 W / m·K and a compressive strength of 14.6 MPa.

[0079] Example 2

[0080] This example provides a cylindrical battery, and its structural schematic diagram is shown in Figure 1 , comprising a column shell 1 and a battery core 2 disposed inside the column shell, a buffer layer 3 being disposed between the battery core and the column shell, Figure 3 The schematic diagram of the structure of a buffer layer of a specific embodiment of the present invention is elastic, and includes a first surface 4 and a second surface 5 arranged opposite to each other, the first surface 4 is in contact with the peripheral surface of the column shell 1, the second surface 5 includes an arc-shaped protrusion 6, the arc-shaped protrusion 6 is in contact with at least part of the peripheral surface of the battery cell 2, and the vertical distance between the axis where the highest point of the arc-shaped protrusion is located and the edge of any side 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 protrusion has 5 arc-shaped protrusion areas, see Figure 4 The thickness of each one gradually becomes thinner from the middle to the edges on both sides. The first, second, fourth and fifth arc-shaped raised areas are approximately axially symmetrically distributed on both sides of the third arc-shaped raised area, and the five arc-shaped raised areas are closely connected and arranged, so that the buffer layer is corrugated along the axial cross-section of the battery cell. The length ratio of each arc-shaped raised area in the axial direction is set to 1:2:4:2:1, the minimum thickness of the arc-shaped raised part is set to 0.25 mm, the thickness of the highest point of the third arc-shaped raised area (that is, the vertical distance from the highest point to the battery cell) is set to 0.5 mm, the thickness of the highest point of the second and fourth arc-shaped raised areas is 0.44 mm, and the thickness of the highest point of the first and fifth arc-shaped raised areas is 0.37 mm. The material of the buffer layer is graphite, the thermal conductivity is 482 W / m·K, and the compressive strength is 14.6 MPa.

[0081] Example 3

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

[0083] Example 4

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

[0085] Example 5

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

[0087] Comparative Example 1

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

[0089] Comparative Example 2

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

[0091] Test Case

[0092] 1: Change of battery core center temperature:

[0093] Test method: A K-type thermocouple is pre-implanted in the center of the cylindrical battery cell and fixed with thermal conductive glue, and then the battery cell is placed in a constant temperature box, and a specific working condition is applied to the battery cell through a charge and discharge test cabinet, and then the real-time temperature change of the battery cell is recorded through a data acquisition system. Specifically, the present invention first places the cylindrical battery cell in a constant temperature box at 25°C, then adjusts the SOC state of the battery cell to 60%, and then performs periodic pulse charge and discharge at a rate of 3C with 5s charging and 5s discharging for 10,000s, and records the change of the center temperature of the cylindrical battery cell over time. The results are shown in Table 1.

[0094] 2. Cycle life

[0095] Test method: Place the cylindrical battery cell in a constant temperature box, perform cyclic charge and discharge on the battery cell through a charge and discharge test cabinet, and record the discharge capacity through a data acquisition system. Divide the discharge capacity after each cycle by the initial discharge capacity to obtain the capacity retention rate, i.e., the cycle life. Specifically, the present invention places the cylindrical battery cell in a constant temperature box at 45°C, first charges it with a 1C constant current to an upper limit voltage of 3.75V, and then discharges it with a 1C constant current to a lower limit voltage of 2V, performs 1000 charge and discharge cycles, records the discharge capacity each time and calculates the capacity retention rate, and observes whether the shell is deformed or cracked. The results are shown in Table 1.

[0096] Table 1:

[0097]

[0098] It can be seen from Table 1 that since the cylindrical batteries of Examples 1-5 are provided with a heat-conductive buffer layer with an arc-shaped protrusion compared to Comparative Examples 1-2, the center temperature of the battery cell is lower after pulse charge and discharge at 3C 60% SOC 5s at room temperature. It can be seen that the buffer layer of the embodiment can more significantly reduce the overall heating rate of the battery cell.

[0099] Furthermore, through the 45°C high-temperature cycle test, it can be seen that the cylindrical battery of the embodiment can better adapt to the difference in expansion force in the axial direction of the cylindrical battery cell due to the buffer layer provided with an arc-shaped protrusion, and it shows a better cycle life, which is specifically manifested in that the capacity retention rate after 1000 cycles is much higher than that of the control example.

[0100] Furthermore, the cylindrical battery of Comparative Example 1 had a cycle inflection point due to the lack of a buffer layer, and its life dropped sharply, and the shell cracked during the cycle.

[0101] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A cylindrical battery, comprising a cylindrical shell and a battery cell disposed inside the cylindrical shell, wherein a buffer layer is disposed between the battery cell and the cylindrical shell, the buffer layer is elastic and comprises a first surface and a second surface disposed opposite to each other, characterized in that: The first surface is fitted with the column shell, and the second surface includes an arc-shaped protrusion, which contacts at least part of the circumferential surface of the battery cell, and the vertical distance between the axis where the highest point of the arc-shaped protrusion is located and the edge of any side 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.

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

3. The cylindrical battery according to any one of claims 1 or 2, characterized in that: The arc-shaped protrusion includes N arc-shaped protrusion areas along the axial direction of the battery core, and the thickness of each arc-shaped protrusion area gradually becomes thinner from the middle to the edges on both sides, and N is a natural number greater than or equal to 1.

4. The cylindrical battery according to claim 3, characterized in that: N is an odd number greater than 1, the vertical distance between the highest point of the (N+1) / 2th arc-shaped raised area and the battery cell is x, and the vertical distance between the highest point of any arc-shaped raised area other than the (N+1) / 2th arc-shaped raised area and the battery cell is y, wherein x is greater than y.

5. The cylindrical battery according to claim 4, characterized in that: The arc-shaped convex areas other than the (N+1) / 2th arc-shaped convex area are axially symmetrically distributed or approximately axially symmetrically distributed on both sides of the (N+1) / 2th arc-shaped convex area.

6. The cylindrical battery according to claim 4 or 5, characterized in that: The N arc-shaped raised areas are closely connected and arranged in the axial direction of the battery core, so that the buffer layer is corrugated along the axial cross section of the battery core.

7. The cylindrical battery according to any one of claims 4 to 6, characterized in that: N=5, along the axial direction of the battery cell, the vertical distance from the highest point of the third arc-shaped raised area to the battery cell is 1.3-2 times the vertical distance from the highest point of the first arc-shaped raised area to the battery cell, and the vertical distance from the highest point of the second arc-shaped raised area to the battery cell is 1-1.3 times the vertical distance from the highest point of the first arc-shaped raised area to the battery cell.

8. The cylindrical battery according to claim 7, characterized in that: The vertical distance between the highest point of the third arc-shaped raised area and the battery core is 0.5-2 mm, and the vertical distance between the lowest point of the first arc-shaped raised area and the battery core is 0.1-0.4 mm.

9. The cylindrical battery according to claim 3, characterized in that: When N=1, the vertical distance between the highest point of the arc-shaped convex area and the battery core is 0.5-2 mm, and the vertical distance between the lowest point and the battery core is 0.25-0.4 mm.

10. The cylindrical battery according to any one of claims 1 to 9, characterized in that: The buffer layer has thermal conductivity.

11. The cylindrical battery according to claim 10, characterized in that: The thermal conductivity 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.

12. The cylindrical battery according to claim 11, characterized in that: The material of the buffer layer includes graphite; And / or, a polymer material containing a thermally conductive filler.

13. The cylindrical battery according to claim 12, characterized in that: The thermal conductive filler is aluminum oxide and / or aluminum nitride, and the polymer material is polyurethane material; Preferably, the thermally conductive filler accounts for 20-30 wt % of the polymer material.

14. A battery pack, characterized in that: A cylindrical battery comprising any one of claims 1-13.

15. An electrical equipment, characterized in that: It comprises the cylindrical battery according to any one of claims 1 to 13 or the battery pack according to claim 14.

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