Battery pack and electrical equipment

Abstract

A battery pack includes a housing, a battery cell assembly and a circuit board disposed in the housing. The battery cell assembly includes a plurality of stacked battery cells. Along the stacking direction of the battery cells, the tabs of the plurality of battery cells are connected to the circuit board. The battery pack further includes a first buffer member, and the first buffer member is disposed on one side of the battery cell assembly along the stacking direction of the battery cells. The first buffer member positions the battery cell assembly while absorbing the excessive expansion volume of the battery cells, solving the problems of lithium plating, shell rupture, and even the risks of thermal runaway or explosion caused by abnormal expansion of the battery. The present application also provides an electrical device having the above battery pack.

Description

Technical Field

[0001] The present application relates to the field of electrochemical devices, and particularly to a battery pack and an electrical device having the same. Background Art

[0002] With the development of the new energy industry, lithium batteries are increasingly widely used. After multiple lithium battery cells are connected in series and parallel to form a battery pack, during normal use, misuse, or abuse, the battery pack may cause abnormal swelling of multiple cells due to overcharging, short circuit, external extrusion, high-temperature cycling, high-temperature storage, etc., and then cause short circuit, lithium plating, shell rupture, or even the risk of thermal runaway or explosion in the battery pack. Summary of the Invention

[0003] In view of the above situation, the present application provides a battery pack and an electrical device having the same. By providing a first buffer member, the first buffer member absorbs the excessive swelling volume of the cells while positioning the cell assembly, thereby solving the risks of lithium plating, shell rupture, or even thermal runaway or explosion caused by abnormal swelling of the battery.

[0004] An embodiment of the present application provides a battery pack, including a housing, a cell assembly and a circuit board disposed in the housing. The cell assembly includes a plurality of stacked cells. Along the stacking direction of the cells, the tabs of the plurality of cells are connected to the circuit board. The battery pack further includes a first buffer member, and the first buffer member is disposed on one side of the cell assembly along the stacking direction of the cells.

[0005] The thickness of the first buffer member is D1, the compressibility ratio of the first buffer member is r1, the thickness of the cell is d, the abnormal swelling rate of the cell is r3, and the number of the plurality of cells is n. Wherein, D1≥(d×n×r3) / r1, and the abnormal swelling rate refers to the ratio of the total increased thickness of the plurality of cells in the case of abnormal swelling to the original total stacking thickness of the cells. The first buffer member absorbs the excessive swelling volume of the cells while positioning the cell assembly, thereby solving the risks of lithium plating, shell rupture, or even thermal runaway or explosion caused by abnormal swelling of the battery.

[0006] In some embodiments, L1>d×n×r2, L1<d×n×r3. L1 is the displacement of the first cell along the stacking direction of the cells when the tab of the first cell breaks, r2 is the normal swelling rate of the cell, and r3>r2.

[0007] In some embodiments, the first buffer member is made of an elastic material.

[0008] In some embodiments, the battery pack further includes a second buffer member disposed between adjacent battery cells. Along the stacking direction of the battery cells, the thickness of the first buffer member is greater than that of the second buffer member.

[0009] In some embodiments, the compressibility ratios of the first buffer member and the second buffer member are the same, being r1. The total thickness of the first buffer member and the second buffer member is D0, the normal expansion rate of the battery cells is r2, the number of the plurality of battery cells is n, and the thickness of the battery cell is d. Wherein, D0 > (d × n × r2) / r1.

[0010] In some embodiments, the thickness of the first buffer member is D1. When the tab of the first battery cell breaks, along the stacking direction of the battery cells, the displacement of the first battery cell is L1. By setting the upper limit value of L1, when the battery cells expand abnormally, the abnormal expansion rate of the battery cells is r3, and r3 > r2. Wherein, D1 > L1 × D0 / (d × n × r3), and this formula can be transformed into L1 < D1 / D0 × (d × n × r3). By setting the threshold upper limit value of L1, when the battery cells expand abnormally, the tab of the first battery cell is pulled and broken during the displacement of the battery cells, thereby disconnecting the internal circuit of the battery pack and reducing the risk of problems such as short circuit and thermal runaway.

[0011] When the battery cell assembly is charging normally, the tab of the first battery cell remains connected to the circuit board. Wherein, D1 / D0 × (d × n × r2) < L1 × D0 / (d × n × r2), and this formula can be transformed into L1 > D1 / D0 × (d × n × r2). By setting the threshold lower limit value of L1, when the battery cells expand normally, the tab of the first battery cell is not pulled and broken during the displacement of the battery cells, thereby avoiding the risk of disconnecting the internal circuit of the battery pack during normal charging of the battery cell assembly.

[0012] In some embodiments, in the battery cell assembly, one second buffer member is provided for every two battery cells; or one second buffer member is provided between any adjacent battery cells.

[0013] In some embodiments, the compressibility ratio of the first buffer member is r4, and the compressibility ratio of the second buffer member is r5. The total thickness of the first buffer member and the second buffer member is D0, the normal expansion rate of the battery cells is r2, the number of the plurality of battery cells is n, and the thickness of the battery cell is d. Wherein, D0 > (d × n × r2) / r6, wherein r6 is determined according to r4 and r5, and r4 and r5 are not equal.

[0014] In some embodiments, the thickness of the first buffer is D1. When the tab of the first battery cell breaks, along the stacking direction of the battery cells, the displacement of the first battery cell is L1. When the battery cell assembly is charging normally, the tab of the first battery cell remains connected to the circuit board, where D1 < L1×D0 / (d×n×r2).

[0015] In some embodiments, the tab of the first battery cell is provided with a groove for assisting the tab to break.

[0016] In some embodiments, the tab of the first battery cell includes a first tab and a second tab, and the grooves are respectively provided on the first tab and the second tab.

[0017] An embodiment of the present application further provides an electrical device, and the electrical device includes the battery pack described in the above embodiment.

[0018] By providing the first buffer in the battery provided in the present application, the first buffer absorbs the excessive expansion volume of the battery cells while positioning the battery cell assembly, avoiding the risk of lithium plating, shell rupture, and even thermal runaway or explosion caused by abnormal expansion of the battery. Moreover, by setting the lower threshold value of L1 and the upper threshold value of L1, the displacement of the first battery cell is maximized when the battery cells expand, so that the tab of the first battery cell is not pulled and broken during the displacement of the battery cells when the battery cells expand normally, and the tab of the first battery cell is pulled and broken during the displacement of the battery cells when the battery cells expand abnormally, thereby disconnecting the internal circuit of the battery pack and reducing the risk of problems such as short circuit and thermal runaway. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic structural diagram of a battery pack in an embodiment.

[0020] Figure 2 It is Figure 1 A schematic structural diagram of the battery pack shown after overcharging.

[0021] Figure 3 It is a schematic structural diagram of a battery pack in an embodiment.

[0022] Figure 4 It is Figure 3 A schematic structural diagram of the battery pack shown after overcharging.

[0023] Figure 5 It is Figure 3 A charging parameter curve diagram of a test site in the battery pack shown.

[0024] Figure 6 It is a schematic structural diagram of a battery pack in a comparative example.

[0025] Figure 7 It isFigure 6 Schematic diagram of the structure of the battery pack after overcharging.

[0026] Figure 8 Schematic diagram of the structure of the battery pack in a pair of ratios.

[0027] Figure 9 Schematic diagram of the structure of the battery cells of the battery pack in one embodiment.

[0028] Figure 10 Schematic diagram of the structure of the battery cells of the battery pack in one embodiment.

[0029] Figure 11 Schematic diagram of the structure of the battery cells of the battery pack in one embodiment.

[0030] Figure 12 Schematic diagram of the structure of the electrical device in one embodiment.

[0031] Description of main component symbols:

[0032]

[0033] Detailed implementation manners

[0034] Next, the technical solutions in the embodiments of the present application will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments.

[0035] It should be noted that when an element is referred to as being "fixed to" another element, it can be directly on the other element or there can also be an intermediate element. When an element is considered to be "connected" to another element, it can be directly connected to the other element or there may be an intermediate element at the same time. When an element is considered to be "disposed on" another element, it can be directly disposed on the other element or there may be an intermediate element at the same time. The terms "vertical", "horizontal", "left", "right" and similar expressions used herein are only for the purpose of illustration.

[0036] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific implementation manners and are not intended to limit this application. The term "or / and" used herein includes any and all combinations of one or more of the related listed items.

[0037] The present application provides a battery pack, which includes a housing, a battery cell assembly and a circuit board disposed in the housing. The battery cell assembly includes a plurality of stacked battery cells. Along the stacking direction of the battery cells, the tabs of the plurality of battery cells are connected to the circuit board. The battery pack further includes a first buffer member, which is disposed on one side of the battery cell assembly along the stacking direction of the battery cells. The first buffer member positions the battery cell assembly while absorbing the excessive expansion volume of the battery cells, avoiding the risk of lithium plating, shell rupture, or even thermal runaway or explosion caused by abnormal expansion of the battery.

[0038] The battery cell adjacent to the first buffer member is the first battery cell. If the volumes of the plurality of battery cells expand, along the stacking direction of the battery cells, the displacement of the first battery cell is the largest. The first battery cell displaces relative to the circuit board and squeezes the first buffer member, and the tab of the first battery cell is pulled and broken as the first battery cell displaces.

[0039] By providing the first buffer member, the above battery enables the first battery cell to have the largest displacement when the battery cells expand. The first buffer member positions the battery cell assembly while absorbing the excessive expansion volume of the battery cells, causing the tab of the first battery cell to be pulled and broken during the displacement of the battery cells, thereby disconnecting the internal circuit of the battery pack and reducing the risk of problems such as short circuit and thermal runaway.

[0040] Some embodiments of the present application will be described in detail. Without conflict, the following embodiments and the features in the embodiments can be combined with each other.

[0041] Please refer to Figure 1 and Figure 2 , in an embodiment, the battery pack 100 includes a housing 10, a battery cell assembly 20, a circuit board 30 and a first buffer member 40 disposed in the housing 10.

[0042] The battery cell assembly 20 includes a plurality of stacked battery cells 21. Each battery cell 21 includes a packaging shell 211, an electrode assembly and a tab 212. The electrode assembly is disposed in the packaging shell 211, and the tab 212 connects the electrode assembly and extends out of the packaging shell 211. In the embodiments of the present application, the tab 212 extends out from one end of the packaging shell 211 facing the circuit board 30. The tabs 212 of the plurality of battery cells 21 are connected according to a preset rule to achieve electrical connection between the plurality of battery cells 21. The electrical connection method includes but is not limited to series connection, or a combination of series and parallel connections, etc.

[0043] The circuit board 30 is electrically connected to the battery cell assembly 20. Specifically, along the stacking direction of the battery cells 21, the tabs 212 of multiple battery cells 21 are sequentially connected to the circuit board 30. A circuit (not shown in the figure) may be provided on the circuit board 30, and multiple tabs 212 are electrically connected to this circuit to achieve electrical connection between multiple battery cells 21. The circuit board 30 further includes an adapter board, and the tabs 212 of multiple battery cells 21 are connected to this adapter board.

[0044] The first buffer member 40 is disposed on one side of the battery cell assembly 20 along the stacking direction of the battery cells 21, and is used to position the battery cell assembly 20 within the housing 10 and absorb the expanded volume of the battery cells 21 after overcharging. The first buffer member 40 is made of an elastic material, including but not limited to foam. The battery cell 21 adjacent to the first buffer member 40 is the first battery cell 21'. When the battery cell assembly 20 generates gas due to overcharging, short circuit, external force extrusion, external force puncture, high-temperature cycling, high-temperature storage, etc., the volumes of multiple battery cells 21 expand excessively, so that multiple battery cells 21 all undergo different degrees of displacement relative to the circuit board 30. Due to the accumulation of displacements of multiple battery cells 21, along the stacking direction of the battery cells 21, the displacement of the first battery cell 21' is the largest. When the first battery cell 21' undergoes displacement relative to the circuit board 30 and squeezes the first buffer member 40, the first buffer member 40 is compressed, and the tab 212 of the first battery cell 21' is pulled and broken as the first battery cell 21' undergoes displacement.

[0045] In the prior art, cathode materials with high thermal stability, or electrolytes with high thermal stability, or the method of setting a pressure relief valve on the battery pack are used to suppress battery expansion and subsequent risks. However, cathode materials with high thermal stability and electrolytes with high thermal stability will reduce the battery energy density, increase the internal resistance of the battery cells, and can only delay gas production and expansion, and cannot fundamentally eliminate abnormal expansion and related risks. The pressure relief valve can only play a pressure relief role after the packaging shell of the battery cell is burst, and cannot prevent abnormal expansion and leakage, and similarly, cannot solve risks such as overcharging and short circuit.

[0046] By providing the first buffer member 40, the battery pack 100 of the present application can absorb the abnormal expanded volume of the battery cells 21 while positioning the battery cell assembly 20, so that the tab 212 of the first battery cell 21' is pulled and broken during the displacement of the battery cells, thereby disconnecting the electrical connection relationship between multiple battery cells 21, cutting off the internal circuit of the battery pack 100, and effectively reducing the risk of problems such as short circuit and thermal runaway.

[0047] In an embodiment of the present application, the thickness of the first buffer member 40 when not compressed is D1, and the thickness of the first buffer member 40 when compressed to the limit without damage is D1'. The compressibility ratio of the first buffer member 40 is r1, where r1 = (D1 - D1') / D1. The thickness of a single battery cell 21 when not expanded is d, the normal expansion rate of the battery cell 21 is r2, and the abnormal expansion rate is r3, and r3 > r2. The number of multiple battery cells 21 is n, and n is a positive number. When the tab 212 of the first battery cell 21' is broken, the displacement of the first battery cell 21' along the stacking direction of the battery cells 21 is L1.

[0048] D1, D1', d, n, and L1 can be obtained through actual measurement, and r1, r2, and r3 are calculated and set according to material properties and actual design requirements.

[0049] When the battery cell 21 expands normally during the usage period, the displacement of the battery cell 21 is not sufficient to break the tab 212 to ensure the normal use of the battery cell assembly 20. At this time, it should satisfy L1 > d × n × r2.

[0050] After the battery cell assembly 20 expands, the actual displacement of the first battery cell 21' is L2, where L2 = d × n × r2, or L2 = d × n × r3. To ensure that the tab 212 of the first battery cell 21' can be broken when the battery cell assembly 20 expands abnormally, it should satisfy L1 ≤ d × n × r3, and at the same time D1 × r1 ≥ L1, that is, satisfy the formula:

[0051] D1 ≥ (d × n × r3) / r1.

[0052] Please refer to Figure 3 and Figure 4 , in another embodiment, the battery pack 100 further includes a second buffer member 50. The second buffer member 50 is disposed between adjacent battery cells 21 and is used to absorb part of the expansion volume of the battery cells 21 and reduce the probability of the tab 212 of the first battery cell 21' being accidentally broken. If the battery cell 21 expands, the second buffer member 50 can also displace along the stacking direction of the battery cells 21 to ensure the maximum displacement of the first battery cell 21'. The second buffer member 50 includes, but is not limited to, compressible materials such as foam. Along the stacking direction of the battery cells 21, the thickness of the first buffer member 40 is greater than the thickness of the second buffer member 50.

[0053] Please continue to refer to Figure 5 , Figure 5It is the overcharge test curve of the battery pack 100 under the conditions of 0.5C / 65V, which includes the voltage curve, temperature curve and current curve of the test points. It can be seen from the test curve graph that as the overcharge progresses (the charging current is 7.5A), the voltage and temperature of the test points in the battery pack 100 gradually increase. At this time, the battery cell 21 starts to expand abnormally, and the safety risk starts to increase. Approximately around forty minutes of charging, the tab 212 disconnects in time, cutting off the charging circuit, the current immediately drops to zero, the battery pack 100 stops overcharging, and the temperature no longer increases, effectively reducing the risk of problems such as short circuit and thermal runaway.

[0054] The number of the second buffer members 50 is multiple, and the multiple second buffer members 50 are arranged in the battery cell assembly 20 evenly or relatively evenly. Specifically, please refer to Figure 6 , in this embodiment, one second buffer member 50 is arranged between any adjacent battery cells 21, so that the multiple second buffer members 50 are evenly arranged in the battery cell assembly 20. In another embodiment, please refer to Figure 8 , one second buffer member 50 can also be arranged every two battery cells 21, so that the multiple second buffer members 50 are relatively evenly arranged in the battery cell assembly 20.

[0055] The compressibility ratios of the first buffer member 40 and the second buffer member 50 are the same, which is r1. The total thickness of the first buffer member 40 and the second buffer member 50 when not compressed is D0, where D1 ≤ D0. In order to meet the normal expansion requirements of the battery cell assembly 20, the value range of D0 should satisfy the formula: D0 > (d × n × r2) / r1.

[0056] After adding the second buffer member 50, after the battery cell assembly 20 expands, the actual displacement L2 of the first battery cell 21' satisfies: L2 = (d × n × r2) × (D1 / D0), or L2 = (d × n × r3) × (D1 / D0).

[0057] When the battery cell assembly 20 is charging normally, the tab 212 of the first battery cell 21' remains connected to the circuit board 30. The actual displacement L2 of the first battery cell 21' should be less than the displacement L1 of the first battery cell 21' when the tab 212 breaks, that is, (d × n × r2) × (D1 / D0) < L1, so that the thickness D1 of the first buffer member 40 satisfies the formula:

[0058] D1 < L1 × D0 / (d × n × r2).

[0059] When the battery cell assembly 20 expands abnormally, the actual displacement L2 of the first battery cell 21' should meet the requirement of pulling off the tab 212, that is, it is required that L2 > L1, that is, (d × n × r3) × (D1 / D0) > L1, so that the thickness D1 of the first buffer member 40 further satisfies the formula:

[0060] D1 > L1×D0 / (d×n×r3).

[0061] In another embodiment, the compressibility ratios of the first buffer member 40 and the second buffer member 50 are not equal. The compressibility ratio of the first buffer member 40 is r4, and the compressibility ratio of the second buffer member 50 is r5, where r4 is not equal to r5. The total thickness of the first buffer member 40 and the second buffer member 50 is D0, and the thickness of the first buffer member 40 is D1. The combined compressibility ratio of the first buffer member 40 and the second buffer member 50 is r6, where r6 is determined according to r4 and r5, specifically:

[0062] r6×D0 = r4×D1 + r5×(D0 - D1), and further it can be deduced that:

[0063] r6 = [r4×D1 + r5×(D0 - D1)] / D0.

[0064] To meet the normal expansion requirements of the battery cell assembly 20, the value range of D0 should satisfy the formula: D0 > (d×n×r2) / r6, that is, r4×D1 + r5×(D0 - D1) > d×n×r2, and further it can be deduced that:

[0065] D0 > D1 + [(d×n×r2 - r4×D1) / r5].

[0066] The number of the plurality of battery cells 21 is n, and the thickness of the battery cell 21 is d. When the battery cell assembly 20 is normally charged, the normal expansion rate of the battery cell 21 is r2. The tab 212 of the first battery cell 21' remains connected to the circuit board 30, and the actual displacement L2 of the first battery cell 21' should be less than the displacement L1 of the first battery cell 21' when the tab 212 breaks, that is, (d×n×r2)×(D1 / D0) < L1, so that the thickness D1 of the first buffer member 40 satisfies the formula:

[0067] D1 < L1×D0 / (d×n×r2).

[0068] When the battery cell assembly 20 expands abnormally, the abnormal expansion rate of the battery cell 21 is r3, where r3 > r2. The actual displacement L2 of the first battery cell 21' should meet the requirement of pulling off the tab 212, that is, it is required that L2 > L1, that is, (d×n×r3)×(D1 / D0) > L1, so that the thickness D1 of the first buffer member 40 further satisfies the formula:

[0069] D1 > L1×D0 / (d×n×r3).

[0070] Please refer to Figure 6 and Figure 7, in a pair of comparative examples, the first buffer member 40 is not provided in the battery pack 100'. A plurality of second buffer members 50 are evenly arranged in the battery cell assembly 20, that is, one second buffer member 50 is arranged between any adjacent battery cells 21. Since the battery cells 21 and the second buffer members 50 are evenly placed, each second buffer member 50 can timely absorb the expansion volume of the adjacent battery cells 21, and the expansion of the battery cells 21 will not cause the relative position of the battery cells 21 in the housing 10 to move. Therefore, even if abnormal expansion occurs, the ear 212 will not break, and the risks of short circuit and thermal runaway are significantly increased.

[0071] Please refer to Figure 8 , in another pair of comparative examples, the first buffer member 40 is also not provided in the battery pack 100'. A plurality of second buffer members 50 are relatively evenly arranged in the battery cell assembly 20, that is, one second buffer member 50 is arranged every two battery cells 21. Since the battery cells 21 and the second buffer members 50 are relatively evenly placed, the second buffer members 50 at different positions can timely absorb the expansion volume of their adjacent battery cells 21, and the expansion of the battery cells 21 will not cause the relative position of the battery cells 21 in the housing 10 to move. Therefore, even if abnormal expansion occurs, the ear 212 will not break, and the risks of short circuit and thermal runaway are significantly increased.

[0072] Please refer to Figure 9 and Figure 10 , in an optional embodiment, a groove 213 is further provided on the ear 212 of the battery cell 21. During the pulling process of the ear 212, stress concentration will occur at the groove 213 to assist the ear 212 to break. In the embodiment of the present application, the groove 213 is provided on the ear 212 of the first battery cell 21'. In other embodiments, the groove 213 can also be provided on the ears 212 of other battery cells 21. Further, the ear 212 of each battery cell 21 includes a first ear 2121 and a second ear 2122 arranged at intervals. The groove 213 can be only provided on the side of the first ear 2121, or the groove 213 is respectively provided on the first ear 2121 and the second ear 2122. The present application does not limit the number and position of the groove 213, as long as the design requirements are met.

[0073] Please refer to Figure 9 and Figure 11 , in the embodiment of the present application, the shape of the groove 213 is generally triangular. In other embodiments, the shape of the groove 213 can also be square, circular or other irregular shapes.

[0074] Table 1 Pass rate of overcharge test for examples and comparative examples

[0075]

[0076] Table 1 shows the overcharge test results of the battery pack 100 in different embodiments and comparative examples. The specific settings of the battery pack 100 in each embodiment and comparative example are as follows:

[0077] Embodiment 1: In the battery pack 100, the first buffer member 40 is disposed on the side of the total positive electrode of the battery cell assembly 20, and a plurality of second buffer members 50 are evenly distributed between the battery cells 21, that is, one second buffer member 50 is disposed between any adjacent battery cells 21, and the entire battery pack 100 is subjected to an overcharge test of 0.5C / 65V.

[0078] Embodiment 2: In the battery pack 100, the first buffer member 40 is disposed on the side of the total positive electrode of the battery cell assembly 20, and a plurality of second buffer members 50 are relatively evenly distributed between the battery cells 21, that is, one second buffer member 50 is disposed every two battery cells 21, and the entire battery pack 100 is subjected to an overcharge test of 0.5C / 65V.

[0079] Embodiment 3: In the battery pack 100, the first buffer member 40 is disposed on the side of the total positive electrode of the battery cell assembly 20, and a plurality of second buffer members 50 are relatively evenly distributed between the battery cells 21, that is, one second buffer member 50 is disposed every two battery cells 21, and notches are prefabricated on the tabs 212 of the battery cells 21, and the entire battery pack 100 is subjected to an overcharge test of 0.5C / 65V.

[0080] Embodiment 4: In the battery pack 100, the first buffer member 40 is disposed on the side of the total negative electrode of the battery cell assembly 20, and a plurality of second buffer members 50 are evenly distributed between the battery cells 21, that is, one second buffer member 50 is disposed between any adjacent battery cells 21, and the entire battery pack 100 is subjected to an overcharge test of 0.5C / 65V.

[0081] Embodiment 5: In the battery pack 100, the first buffer member 40 is disposed on the side of the total negative electrode of the battery cell assembly 20, and a plurality of second buffer members 50 are relatively evenly distributed between the battery cells 21, that is, one second buffer member 50 is disposed every two battery cells 21, and the entire battery pack 100 is subjected to an overcharge test of 0.5C / 65V.

[0082] Embodiment 6: In the battery pack 100, the first buffer member 40 is disposed on the side of the total negative electrode of the battery cell assembly 20, and a plurality of second buffer members 50 are relatively evenly distributed between the battery cells 21, that is, one second buffer member 50 is disposed every two battery cells 21, and notches are prefabricated on the tabs 212 of the battery cells 21, and the entire battery pack 100 is subjected to an overcharge test of 0.5C / 65V.

[0083] Comparative Example 1: In the battery pack 100', the first buffer member 40 is not provided, and a plurality of second buffer members 50 are evenly distributed among the plurality of battery cells 21, and the entire battery pack 100' is subjected to an overcharge test of 0.5C / 65V.

[0084] Comparative Example 2: The first buffer member 40 is not provided in the battery pack 100'. A plurality of second buffer members 50 are evenly distributed among the plurality of battery cells 21. The battery cells 21 use a cathode material with high thermal stability. The entire battery pack 100' is subjected to an overcharge test at 0.5C / 65V.

[0085] Comparative Example 3: The first buffer member 40 is not provided in the battery pack 100'. A plurality of second buffer members 50 are evenly distributed among the plurality of battery cells 21. The battery cells 21 use an electrolyte with high thermal stability. The entire battery pack 100' is subjected to an overcharge test at 0.5C / 65V.

[0086] Please refer to Figure 12 , an embodiment of the present application further provides an electrical device 200, and the electrical device 200 includes the battery pack 100 described in the above embodiment. The electrical device includes the aforementioned battery pack and a load, and the battery pack is used to supply power to the load.

[0087] The electrical device 200 is a unicycle or an electric vehicle with two or more wheels, or a drone, or an electric tool, etc.

[0088] The above embodiments are only used to illustrate the technical solutions of the present application and are not intended to limit them. Although the present application has been described in detail with reference to the above preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present application can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the present application.

Claims

1. A battery pack, comprising a housing, and a battery cell assembly and a circuit board disposed within the housing; Characterized in that, The battery cell assembly includes a plurality of stacked battery cells; Along the stacking direction of the battery cells, the tabs of the plurality of battery cells are connected to the circuit board; The battery pack further includes a first buffer member disposed on one side of the battery cell assembly along the stacking direction of the battery cells, and the battery cell adjacent to the first buffer member is the first battery cell; The thickness of the first buffer member is D1, the compressibility ratio of the first buffer member is r1, the thickness of the battery cell is d, the abnormal expansion rate of the battery cell is r3, and the number of the plurality of battery cells is n. Wherein, D1≥(d×n×r3) / r1, and the abnormal expansion rate refers to the ratio of the total increased thickness of the plurality of battery cells in the case of abnormal expansion to the original total stacked thickness of the battery cells; L1>d×n×r2, L1≤d×n×r3, wherein, L1 is the displacement of the first battery cell along the stacking direction of the battery cells when the tab of the first battery cell breaks, r2 is the normal expansion rate of the battery cell, and r3>r2.

2. The battery pack according to claim 1, Characterized in that, The battery pack further includes a second buffer member disposed between adjacent battery cells, and along the stacking direction of the battery cells, the thickness of the first buffer member is greater than the thickness of the second buffer member.

3. The battery pack according to claim 2, Characterized in that, The first buffer member and the second buffer member have the same compressibility ratio, which is r1, the total thickness of the first buffer member and the second buffer member is D0, the normal expansion rate of the battery cell is r2, the number of the plurality of battery cells is n, and the thickness of the battery cell is d. Wherein, D0>(d×n×r2) / r1.

4. The battery pack according to claim 3, Characterized in that, The thickness of the first buffer member is D1, and when the tab of the first battery cell breaks, the displacement of the first battery cell along the stacking direction of the battery cells is L1. When the battery cell assembly is normally charged, the tab of the first battery cell is electrically connected to the circuit board. Wherein, D1<L1×D0 / (d×n×r2).

5. The battery pack according to claim 4, Characterized in that, The abnormal expansion rate of the battery cell is r3, r3>r2. Wherein, D1>L1×D0 / (d×n×r3).

6. The battery pack according to claim 2, Characterized in that, In the battery cell assembly, one second buffer member is provided for every two battery cells; or one second buffer member is provided between any adjacent battery cells.

7. The battery pack according to claim 2, Characterized in that, The compressibility ratio of the second buffer member is r5, the total thickness of the first buffer member and the second buffer member is D0, the normal expansion rate of the battery cell is r2, the number of the plurality of battery cells is n, and the thickness of the battery cell is d. Wherein, D0>(d×n×r2) / r6, wherein, r6 = [D1×r1+(D0 - D1)×r5] / D0, and r1 is not equal to r5.

8. The battery pack according to claim 7, It is characterized in that the thickness of the first buffer is D1. When the tab of the first battery cell breaks, along the stacking direction of the battery cells, the displacement of the first battery cell is L1. When the battery cell assembly is normally charged, the tab of the first battery cell is electrically connected to the circuit board, where D1 < L1×D0 / (d×n×r2).

9. The battery pack according to claim 8, It is characterized in that the abnormal expansion rate of the battery cell is r3, r3 > r2, where D1 > L1×D0 / (d×n×r3).

10. The battery pack according to claim 1, It is characterized in that a groove is provided on the tab of the first battery cell to assist in breaking the tab.

11. The battery pack according to claim 10, It is characterized in that the tab of the first battery cell includes a first tab and a second tab, and the grooves are respectively provided on the first tab and the second tab.

12. An electrical device, It is characterized in that the electrical device includes the battery pack according to any one of claims 1-11 and a load, and the battery pack is used to supply power to the load.

13. The electrical device according to claim 12, It is characterized in that the electrical device includes a unicycle or an electric vehicle with two or more wheels.

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