Battery pack and single batteries thereof

Abstract

The invention discloses a battery monomer which is characterized by comprising a battery shell and a battery cell, the battery cell is placed in the battery shell, an anti-explosion valve is arranged on the battery shell, the anti-explosion valve comprises a weak part, a blocking part is arranged on the battery shell, the blocking part is arranged on the periphery of the weak part, and the thickness of the blocking part is larger than that of the weak part. The blocking part comprises a blocking main body structure, the area surrounded by the weak part is S1, the area surrounded by the outer edge of the blocking part is S2, S1 and S2 meet the condition that S1 * (S2-S1) / (Q * h1 / h2) is larger than or equal to 0.03 * 104 and smaller than or equal to 20 * 104, Q is the battery capacity, h1 is the thickness of a shell provided with the anti-explosion valve, and h2 is the thickness sum of the battery shell and the blocking main body structure. According to the single battery, the probability that the adjacent single battery is burnt during thermal runaway of the single battery is reduced, and thermal spread during thermal runaway of the battery is reduced. The invention also discloses a battery pack.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and particularly to a battery pack and a battery cell thereof. Background Art

[0002] Battery thermal runaway refers to the phenomenon that the temperature inside the battery rises abnormally, resulting in the out-of-control of the internal chemical reaction of the battery, and ultimately may lead to battery failure, fire or even explosion. When the battery undergoes thermal runaway, the explosion-proof valve opens to release heat. Due to the large amount of heat released, the periphery of the explosion-proof valve is easily melted, and the heat transferred by the burning of the ejected flame reaches the adjacent battery cells, causing thermal spread and triggering thermal runaway of the adjacent batteries. Summary of the Invention

[0003] In view of this, the present invention provides a battery cell, which reduces the probability of the situation that the adjacent battery cells are burned when the battery cell undergoes thermal runaway, and reduces the occurrence of thermal spread during battery thermal runaway.

[0004] The present invention also provides a battery pack.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] A battery cell includes a battery case and an electrode core. The electrode core is placed inside the battery case. An explosion-proof valve is provided on the battery case. The explosion-proof valve includes a weak part. A barrier part is provided on the battery case. The barrier part is arranged on the periphery of the weak part. The thickness of the barrier part is greater than that of the weak part. The barrier part includes a barrier main structure. The area enclosed by the weak part is S1, and the area enclosed by the outer edge of the barrier part is S2. S1 and S2 satisfy 0.03×10 4 ≤S1×(S2 - S1) / (Q×h1 / h2)≤20×10 4 , where Q is the battery capacity in Ah, h1 is the thickness of the case where the explosion-proof valve is provided in mm, h2 is the sum of the thicknesses of the battery case and the barrier main structure in mm, and the units of S1 and S2 are mm 2 .

[0007] As can be seen from the above technical solution, for the battery cell provided by the present invention, a barrier portion is provided outside the weak portion of the explosion-proof valve. The barrier portion is disposed around the weak portion, and the thickness of the barrier portion is greater than that of the weak portion. Therefore, when a large amount of heat is released from the explosion-proof valve, the periphery of the explosion-proof valve is not easily melted, effectively reducing the risk that the jet flame burns through the large surface of the battery cell due to the melting of the periphery of the explosion-proof valve, reducing the probability of the situation where adjacent battery cells are burned when the battery cell is out of thermal control, and reducing the occurrence of thermal propagation when the battery is out of thermal control. For the battery cell of the present invention, by comprehensively considering the relationship between S1*(S2 - S1), Q, and h1 / h2, the risk that heat is transferred to adjacent batteries and causes adjacent batteries to get out of thermal control when the battery gets out of thermal control is reduced. The value of S1*(S2 - S1) / (Q*h1 / h2) cannot be too small. Because the heat generation inside the battery is large, if the value of the above formula is too small, the effect of the barrier portion blocking heat transfer is poor, increasing the risk of causing adjacent batteries to get out of thermal control; the value of the above formula cannot be too large, otherwise the energy density of the battery will decrease.

[0008] The present invention also provides a battery pack, which includes a plurality of battery cells stacked together. The battery cells are the above-mentioned battery cells, and a heat insulation pad is disposed between adjacent battery cells. The thickness of the heat insulation pad is 1 - 5 mm.

[0009] The battery pack of the present invention includes the above-mentioned battery cells, and thus has the advantages of the above-mentioned battery cells, which will not be elaborated here. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0011] Figure 1 It is a schematic structural diagram of a battery cell provided by an embodiment of the present invention from one angle;

[0012] Figure 2 It is a schematic structural diagram of the battery cell provided by an embodiment of the present invention from another angle;

[0013] Figure 3 For Figure 2 it is a cross-sectional structural diagram at the A - A position in

[0014] Figure 4 For Figure 3 it is a partial enlarged structural diagram of part B in

[0015] Figure 5Schematic diagram of the structure where the barrier platform provided by the embodiment of the present invention is directly connected to the protection patch;

[0016] Figure 6 Schematic diagram of the structure where the barrier platform provided by the embodiment of the present invention is provided with a first barrier platform;

[0017] Figure 7 Schematic diagram of the structure where the barrier platform provided by the embodiment of the present invention is connected to the protection patch through the first barrier platform;

[0018] Figure 8 Schematic diagram of the area of the weak part of the explosion-proof valve provided by an embodiment of the present invention;

[0019] Figure 9 Schematic cross-sectional structure diagram of the explosion-proof sheet provided by the embodiment of the present invention;

[0020] Figure 10 Schematic diagram of the area enclosed by the barrier part provided by the embodiment of the present invention;

[0021] Figure 11 Schematic diagram of the barrier platform provided by another embodiment of the present invention;

[0022] Figure 12 Schematic partial cross-sectional structure diagram of the position of the barrier groove provided by the embodiment of the present invention;

[0023] Figure 13 Schematic diagram of the structure after placing a heat-insulating member in the barrier groove provided by the embodiment of the present invention;

[0024] Figure 14 For Figure 13 Cross-sectional structure diagram at the E-E position in;

[0025] Figure 15 Schematic diagram of the explosion-proof sheet provided by an embodiment of the present invention;

[0026] Figure 16 For Figure 15 Schematic diagram of the area of the weak part of the explosion-proof valve in;

[0027] Figure 17 Schematic diagram of the explosion-proof sheet provided by another embodiment of the present invention;

[0028] Figure 18 For Figure 17 Schematic diagram of the area of the weak part of the explosion-proof valve in;

[0029] Figure 19 Schematic diagram of the difference between the area enclosed by the barrier part and the area of the weak part provided by the embodiment of the present invention.

[0030] Wherein:

[0031] 1. Battery housing

[0032] 101. Housing main body, 1011. Large surface side, 102. Cover plate, 103. Protrusion, 104. Barrier groove

[0033] 2. Protection patch

[0034] 3. Barrier platform

[0035] 301. First barrier platform, 302. Second barrier platform

[0036] 4. Battery cell

[0037] 5. Explosion-proof hole

[0038] 6. Explosion-proof film

[0039] 601. Weak part

[0040] 7. Heat insulation member Detailed implementation manners

[0041] The present invention discloses a battery cell, which reduces the probability of the situation that when the battery cell is out of thermal control, it burns the adjacent battery cells, and reduces the occurrence of thermal spread when the battery is out of thermal control.

[0042] The present invention also discloses a battery pack.

[0043] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0044] Refer to Figures 1 to 14 , the battery cell of the present invention includes a battery housing 1 and a battery cell 4. The battery housing 1 is arranged on the outermost side of the battery cell 4 to protect the battery cell 4. The material of the battery housing 1 can be selected but not limited to aluminum, steel, and aluminum alloy. Specifically, the material of the battery housing 1 can be aluminum-manganese alloy, aluminum-magnesium alloy, stainless steel, nickel-plated steel, carbon steel, or titanium, etc.

[0045] The battery cell 4 includes a positive electrode sheet, a negative electrode sheet, and a separator disposed therebetween. The positive electrode sheet, the negative electrode sheet, and the separator form a battery cell body by stacking. The positive electrode sheet includes a positive electrode current collector and positive electrode active material. The positive electrode current collector can be made of a metal material such as aluminum foil, nickel foil, or stainless steel; or the positive electrode current collector is a composite foil formed by combining a metal and an insulating material. The positive electrode active material includes a positive electrode active main material, a conductive agent, an adhesive, etc. The positive electrode active main material includes one or more of lithium-containing positive electrode active materials such as lithium iron phosphate, ternary materials containing nickel, cobalt, and manganese, and lithium manganese iron phosphate. The negative electrode sheet includes a negative electrode current collector and negative electrode active material. The negative electrode current collector can be made of a metal material such as copper foil, aluminum foil, stainless steel, or a composite foil formed by combining a metal and an insulating material. The negative electrode active material includes a negative electrode active main material, a conductive agent, an adhesive, etc. The negative electrode active main material includes one or more of negative electrode active main materials such as artificial graphite, natural graphite, silicon carbide, silicon oxide, and lithium titanate.

[0046] An explosion-proof valve is provided on the battery case 1. The explosion-proof valve includes a weak part 601. The weak part 601 is used for the explosion-proof valve to crack at the position of the weak part 601 when the battery undergoes thermal runaway, so as to release the heat, dust, etc. inside the battery. Specifically, the explosion-proof valve can be an explosion-proof hole 5 provided on the battery case 1. The explosion-proof valve includes an explosion-proof sheet 6, and the explosion-proof sheet 6 is connected to the explosion-proof hole 5. The weak part 601 on the explosion-proof valve can be a thinning area on the explosion-proof sheet 6. The weak part 601 can be provided in a circumferential manner or at non-circumferential intervals to prevent the explosion-proof sheet 6 from flying out.

[0047] The weak part 601 can be directly formed on the explosion-proof sheet 6 by stamping or by laser etching. The weak part 601 also has a notch structure. In this structure, first a groove is formed, and then a notch groove is formed by laser etching in the groove. The explosion-proof valve includes a weak part 601. A barrier part is provided on the battery case 1. The barrier part is disposed on the periphery of the weak part 601. Here, the periphery is the side away from the center position of the explosion-proof sheet 6. The barrier part is used to improve the heat resistance of the periphery of the explosion-proof valve. The thickness of the barrier part is greater than the thickness of the weak part 601, so as to improve the melting resistance around the explosion-proof valve. The barrier part includes a barrier main structure. The area surrounded by the weak part 601 is S1, as Figure 8 shown. The area surrounded by the outer edge of the barrier part is S2, as Figure 10 shown. Therefore, the effective area of the barrier part is S2 - S1, and S1 and S2 satisfy 0.03 * 10 4 ≤S1 * (S2 - S1) / (Q * h1 / h2) ≤ 20 * 10 4 , and specific values can be selected as 0.03 * 10 4 , 0.1 * 10 4, 2 * 10 4 or 5 * 10 4 . Wherein, Q is the battery capacity in Ah, h1 is the thickness of the battery case 1 where the explosion-proof valve is set in mm, h2 is the sum of the thickness of the battery case 1 and the thickness of the barrier main structure in mm, and the units of S1 and S2 are mm 2 .

[0048] In order to improve the energy density of the battery and pursue a larger battery capacity, when the battery undergoes thermal runaway, the amount of heat and gas generated will increase. After the batteries are stacked into a group, when one battery undergoes thermal runaway, due to the existence of thermal propagation, it is easy to cause adjacent batteries to also undergo thermal runaway. The battery cell of the present invention controls the relationship between the above parameters comprehensively, and adjusts the relationship between the area of the barrier part, the area of the weak part 601, the battery capacity, and the ratio of the thickness of the barrier part to the wall thickness of the housing. By setting the barrier part, heat transfer to adjacent batteries is blocked, thermal propagation is reduced, and the occurrence of adjacent batteries undergoing thermal runaway is avoided; at the same time, the battery energy density is not affected either.

[0049] For the battery cell of the present invention, a barrier part is provided outside the weak part 601 of the explosion-proof valve. The barrier part is arranged around the weak part 601, and the thickness of the barrier part is greater than the thickness of the weak part 601. Thus, when the heat release of the explosion-proof valve is very large, the periphery of the explosion-proof valve is not easily melted, effectively reducing the risk that the jet flame burns through the large surface of the battery cell due to the melting of the periphery of the explosion-proof valve, reducing the probability of the situation that the adjacent battery cell is burned when the battery cell undergoes thermal runaway, and reducing the occurrence of thermal propagation when the battery undergoes thermal runaway. For the battery cell of the present invention, by comprehensively considering the relationship between S1 * (S2 - S1), Q, and h1 / h2, the risk that heat is transferred to adjacent batteries and causes adjacent batteries to undergo thermal runaway when the battery undergoes thermal runaway is reduced. The value of S1 * (S2 - S1) / (Q * h1 / h2) cannot be too small, because the heat generation inside the battery is large. If the value of the above formula is too small, the effect of the barrier part blocking heat transfer is poor, increasing the risk of causing adjacent batteries to undergo thermal runaway; the value of the above formula cannot be too large. If the value of the above formula is too large, since the accommodation space inside the battery pack is fixed, if the set barrier part is too large, the placement space of the battery core will be reduced, affecting the internal space of the battery. When the internal space is insufficient, the gas emission is blocked, heat and gas are easily accumulated inside the battery case 1 and cannot be discharged smoothly. When thermal runaway occurs, the weight loss rate of the battery cannot meet the requirements, and heat and gas are not discharged in time.

[0050] Wherein, a battery pack generally consists of multiple battery cells used in a group. When the battery cells are grouped, the large surfaces of adjacent battery cells are arranged adjacent to each other. The large surface of the battery cell refers to the side with the largest area of the battery cell.

[0051] In one embodiment, the range of S1 is 100 - 1200 mm 2 , specifically it can be 200 mm 2 , 500 mm 2 or 800 mm 2 ; the range of S2 - S1 is 100 - 2850 mm 2 , specifically it can be 200 mm 2 , 400 mm 2 or 1000 mm 2 ; the range of Q is 20 - 600 Ah, specifically it can be 30 Ah, 100 Ah or 200 Ah, and the range of h1 / h2 is 0.1 - 0.8, specifically it can be 0.2, 0.3 or 0.5. By controlling the range of S1 and the range of (S2 - S1), when the battery undergoes thermal runaway, the risk of heat spreading to adjacent batteries is further reduced; by controlling the range of Q, both the battery energy density and the risk of triggering thermal runaway in adjacent batteries when thermal runaway occurs are considered; by further controlling the range of h1 / h2, when the battery undergoes thermal runaway, heat transfer to adjacent batteries is avoided, preventing adjacent battery thermal runaway, and at the same time avoiding affecting the internal space of the battery and the gas discharge channel, so that when the battery undergoes thermal runaway, heat and gas cannot be discharged smoothly, and heat accumulates inside the housing

[0052] Among them, the barrier main structure includes a barrier platform 3, as shown in Figure 1 , Figure 4 and Figure 5 . The barrier platform 3 protrudes on the outer surface of the battery housing 1. By setting the barrier platform 3, the thickness around the explosion-proof hole 5 is increased to reduce combined heat spread of the thermally runaway battery Figure 6 . The large surface side 1011 of the battery housing 1 refers to the side with the largest area of the battery housing 1. When multiple battery monomers are grouped, the large surface sides 1011 of adjacent battery monomers are in contact or are spaced apart by a heat insulation pad

[0053] Furthermore, the barrier platform 3 is disposed around the weak part 601. In one embodiment, the barrier platform 3 continuously surrounds the weak part 601. Here, the continuous surrounding means that the barrier platform 3 is continuously arranged in a circle around the weak part 601, as shown in Figure 6 . In this embodiment, the range of h1 / h2 is 0.1 - 0.7, and h1 / h2 can be 0.3 or 0.4. By continuously surrounding the barrier platform 3 around the weak part 601, the heat blocking effect of the barrier platform 3 is improved, and h1 / h2 is further controlled within the range of 0.1 - 0.7 to reduce the space occupied by the barrier platform 3 in the battery housing 1 and avoid affecting the exhaust space inside the battery housing 1 and the smooth pressure relief of the explosion-proof valve

[0054] In another embodiment, a plurality of barrier platforms 3 are provided, and the plurality of barrier platforms 3 are spaced apart and surround the weak part 601, that is, the barrier platforms 3 are not continuously arranged in a circumferential manner. The spaced arrangement of the barrier platforms 3 reduces the weight of the barrier platforms 3, and thus reduces the overall weight of the housing, which is beneficial to improving the battery energy density. However, since the barrier platforms 3 are not continuously arranged, the heat blocking effect is weakened. By controlling the range of h1 / h2, the risk of thermal runaway of adjacent batteries is further reduced. As Figure 11 shown, in this embodiment, the range of h1 / h2 is 0.3 - 0.8, and h1 / h2 can be 0.3, 0.4 or 0.7.

[0055] Correspondingly, the weak part 601 on the explosion-proof sheet 6 can be continuously arranged or discontinuously arranged. When the weak part 601 is continuously arranged, that is, the thinning area of the weak part 601 is continuously arranged along the circumference, so that the thinning area becomes a closed figure. In this case, the numerical range of h1 / h2 is 0.25 - 0.5, and specifically can be 0.25, 0.35 or 0.4. The weak part 601 can also be discontinuously arranged in a circumferential manner, that is, there are some non-thinned areas in the weak part 601, to avoid the risk of thermal runaway of adjacent batteries caused by the area of the explosion-proof sheet 6 located within the weak part 601 flying out and heating the adjacent batteries. In this case, the numerical range of h1 / h2 is 0.3 - 0.6, and specifically can be 0.35, 0.4 or 0.5.

[0056] Specifically, the spacing distance between adjacent barrier platforms 3 is 1 - 10 mm, and the spacing distance between adjacent barrier platforms 3 can be 3 mm, 5 mm or 8 mm. The distance between adjacent barrier platforms 3 cannot be too large, as this will increase the heat overflowing from the gaps between the barrier platforms 3 and affect the risk of adjacent batteries; if the spacing distance of the barrier platforms 3 is too small, the barrier platforms 3 are set too densely, which will also cause an increase in the weight of the battery housing 1 and affect the battery energy density. The width of the barrier platform 3 is 3 - 50 mm. Specifically, the width of the barrier platform 3 is 5 mm, 15 mm or 40 mm. The width of the barrier platform 3 refers to the spacing distance between the two sides of the barrier platform 3 close to and far from the weak part 601.

[0057] To improve the heat resistance performance, the barrier platform 3 includes a first barrier platform 301 and a second barrier platform 302. As Figure 6 shown, the first barrier platform 301 is arranged around the weak part 601, and the first barrier platform 301 is located between the second barrier platform 302 and the weak part 601. Among them, the height ratio of the first barrier platform 301 to the second barrier platform 302 is 0.6 - 6. The height ratio of the first barrier platform 301 to the second barrier platform 302 can be 0.9, 1.5 or 2.5.

[0058] Further, the interval distance between the first barrier platform 301 and the second barrier platform 302 is 0 - 1 mm. When the interval distance between the first barrier platform 301 and the second barrier platform 302 is 0 mm, the first barrier platform 301 and the second barrier platform 302 are arranged adjacent to each other. As Figure 7 shown, when the interval distance between the first barrier platform 301 and the second barrier platform 302 is greater than 0 mm, the first barrier platform 301 and the second barrier platform 302 are arranged at intervals, and the interval distance between the first barrier platform 301 and the second barrier platform 302 can be 0.5 mm.

[0059] In one embodiment, the first barrier platform 301 is arranged at a position close to the weak part 601 of the second barrier platform 302. The first barrier platform 301 is arranged around the weak part 601, and a protective patch 2 is connected to the surface of the first barrier platform 301 away from the second barrier platform 302. In this embodiment, the first barrier platform 301, the second barrier platform 302 and the battery case 1 can be an integral structure. As Figure 7 shown, they can also be a split structure. When the barrier platform 3 and the battery case 1 are of a split structure, the barrier platform 3 is bonded or welded to the battery case 1.

[0060] In another embodiment, the barrier platform 3 does not include the first barrier platform 301 and only includes the second barrier platform 302. As Figure 5 shown, the second barrier platform 302 is arranged around the side of the explosion-proof hole 5 away from the explosion-proof sheet 6. As Figure 1 and Figure 2 shown. As Figure 4 and Figure 5 shown, by arranging the second barrier platform 302 with a raised structure outside the explosion-proof hole 5, the thickness around the explosion-proof hole 5 is increased. A protective patch 2 is arranged at the end of the explosion-proof hole 5, and the protective patch 2 is bonded to the end of the second barrier platform 302 to protect the explosion-proof sheet 6 and prevent foreign objects from entering the explosion-proof hole 5.

[0061] In another embodiment, the barrier platform 3 is only arranged at the position of the large surface side 1011 of the explosion-proof hole 5 close to the battery cell. As Figure 11 shown, there are two barrier platforms 3, and both of the two barrier platforms 3 are arranged at the position of the large surface side 1011 of the weak part 601 close to the battery cell, so as to increase the thickness of the explosion-proof valve close to the large surface side 1011 and reduce the ignition of adjacent battery cells when the battery cell is out of control thermally.

[0062] In order to facilitate the arrangement of the barrier platform 3 with a consistent width in a surrounding structure, the width D1 of the barrier platform 3 is not greater than the distance between the explosion-proof hole 5 and the large surface side 1011 of the battery case 1. In one embodiment, the width D1 of the barrier platform 3 is less than the distance between the explosion-proof hole 5 and the large surface side 1011 of the battery case 1, that is, the distance D2 between the barrier platform 3 and the large surface side 1011 of the battery cell is greater than zero, so as to form the barrier platform 3.

[0063] Among them, the ratio of the height of the barrier platform 3 to the thickness of the battery housing 1 is 0.25 - 6, specifically it can be 0.3, 1 or 4. The height of the barrier platform 3 is 0.5 - 3.5 mm, and it can be 1 mm, 2 mm or 3 mm; the wall thickness of the battery housing 1 is 0.5 - 3 mm, and it can be 1 mm, 1.5 mm or 2.5 mm. The ratio of the thickness of the barrier platform 3 to the thickness of the battery housing 1 cannot be too large. Since the accommodation space inside the battery pack is fixed, a too large barrier platform 3 will cause the placement space of the battery cell to decrease, and too small of the above ratio will affect the effect of isolating thermal runaway.

[0064] In another embodiment, the barrier main structure is protruded from the surface of the battery housing 1 facing the battery cell 4 to form a barrier groove 104. The barrier groove 104 is arranged on the outer surface of the battery housing 1. The barrier main structure includes the barrier groove 104, that is, the barrier groove 104 is arranged on the surface of the barrier main structure away from the battery cell 4, and a heat insulation member 7 is arranged in the barrier groove 104. The barrier groove 104 protrudes towards the side of the battery housing 1 close to the battery cell 4, as Figure 14 shown, reducing the influence of the setting of the barrier groove 104 structure on the structural strength of the battery housing 1. Referring to Figures 12 to 14 , the barrier groove 104 is arranged around the weak part 601, specifically the barrier groove 104 is arranged around the explosion-proof hole 5. By arranging the barrier groove 104 structure around the explosion-proof hole 5 on the battery housing 1, the conduction of heat during the explosion of the explosion-proof valve can be effectively reduced, the influence on the large surface side 1011 of the battery cell during the explosion of the explosion-proof valve can be reduced, and the risk of melting of the large surface side 1011 is reduced. The heat insulation member 7 is arranged in the barrier groove 104, and the heat insulation member 7 fills the barrier groove 104, further reducing the conduction of heat during the explosion of the explosion-proof valve, greatly reducing the risk of outward diffusion when the explosion-proof valve melts, and effectively preventing the heat generated by the explosion of the explosion-proof valve from affecting the structure of the battery housing 1 away from the explosion-proof valve. Further, a first barrier platform 301 is arranged around the explosion-proof hole 5.

[0065] In one embodiment, the barrier groove 104 is a groove structure punched on the battery housing 1. The barrier groove 104 forms a protruding part 103 that protrudes towards the side of the battery housing 1 close to the battery cell 4, as Figure 12 and Figure 14 shown, the height D3 of the protruding part 103 is the same as the groove depth D5 of the barrier groove 104.

[0066] Furthermore, the groove depth of the barrier groove 104 is 0.5 - 3.5 mm, specifically it can be 1.5 mm, 2.5 mm or 3 mm. To ensure the structural strength of the battery housing 1, the groove depth of the barrier groove 104 cannot be too large. If the groove depth is too large, it will occupy a relatively large space inside the battery housing 1, affecting the internal gas emission. When thermal runaway occurs, the heat and gas emission will be blocked, and the heat will accumulate inside the battery housing 1. To have a good heat insulation effect, the groove depth of the barrier groove 104 cannot be too small either. The groove width of the barrier groove 104 is 3 - 50 mm. The groove width of the barrier groove 104 is 5 mm, 15 mm or 40 mm. The groove width of the barrier groove 104 refers to the interval distance between the two groove side surfaces of the barrier groove 104 close to and far from the weak part 601. If the width of the groove width of the barrier groove 104 is too small, it is not easy to block the heat conduction through the barrier groove 104. If the width of the barrier groove 104 is too large, it will cause a greater weakening of the structural strength of the battery housing 1.

[0067] Among them, the melting point of the heat insulation member 7 is higher than that of the battery housing 1, so that when the battery housing 1 around the weak part 601 melts, the heat insulation member 7 can maintain its shape to prevent the melting of the battery housing 1 and avoid the further spread of the melting. The melting point of the heat insulation member 7 is greater than or equal to 700 °C.

[0068] Specifically, the battery housing 1 includes a housing main body 101 and a cover plate 102. The housing main body 101 is a rectangular housing, and the battery cell 4 is placed in the cavity of the housing main body 101. The cover plate 102 is connected to the top opening position of the housing main body 101. When the battery housing 1 is a square housing, the battery housing 1 includes a first surface and a second surface. There are two first surfaces, and the two first surfaces are arranged oppositely. Among the four second surfaces, two are arranged oppositely. The area of the first surface is larger than that of the second surface. The barrier main structure is arranged on the second surface between the two first surfaces. Here, the first surface refers to the large surface side 1011 mentioned above. The distance between the barrier main structure and the large surface side 1011 is 3 - 20 mm, and the barrier main structure is at least arranged at the position of the weak part 601 close to the large surface side 1011. The distance between the barrier main structure and the large surface side 1011 is specifically 4 mm, 10 mm or 15 mm. By controlling the distance between the barrier main structure and the large surface side 1011 of the battery, it is avoided that the barrier main structure is set too close to the edge and is not easy to be formed; it is also avoided that the distance of the barrier main structure is too far, resulting in too small a width of the barrier main structure and affecting the effect of blocking heat transfer. In one embodiment, the explosion-proof valve is arranged on the cover plate 102, as Figure 6 shown. In another embodiment, the explosion-proof valve is arranged on the housing main body 101.

[0069] In other embodiments, the battery housing 1 can also be a cylindrical shell, and the explosion-proof valve is arranged on the end face of the cylindrical shell. In the radial direction, the distance between the outer edge of the barrier main structure and the edge of the end face of the battery housing 1 is 0.5-10 mm. In one embodiment, the distance between the barrier main structure and the edge of the end face of the battery housing 1 is 1 mm, 4 mm or 6 mm.

[0070] There are various types of lithium batteries. When the battery cell is a ternary lithium battery, the ternary lithium battery specifically refers to nickel cobalt manganese ternary or nickel cobalt aluminum ternary materials. The ternary structure of the ternary lithium battery is LiNi x Co y Mn z O2, where x is greater than or equal to 0.5, y is greater than 0 and less than 0.5, z is greater than 0 and less than 0.5, and y + z = 0.5; in addition, there can also be a doping element M, and the element M is Zr, Ti, Si, Mo, La, Ce, Te, Nb, Ta, Si, Al, W, Sr, V, Y, Mg, Co, F, Cl, S, L. When the battery cell is a ternary lithium battery, the ratio range of h1 to h2 is 0.1-0.65, and can specifically be 0.2 or 0.3. When the nickel content in the positive electrode of the ternary lithium battery is greater than or equal to 0.7, the ratio range of h1 to h2 is 0.1-0.58, specifically 0.3, 0.35 or 0.5.

[0071] When the battery cell is a lithium iron phosphate battery, its positive electrode material is LiFePO4, and the lithium iron phosphate can also have doping elements, and the doping elements can be Ti, V. The ratio range of h1 to h2 is 0.2-0.75, specifically 0.3, 0.4 or 0.5.

[0072] When the weak part 601 is a closed structure, the area of the region surrounded by the weak part 601 is S1, as shown by the shaded part in Figure 8 ; when the weak part 601 is a non-closed structure, as shown in Figure 15 and Figure 17 shown, the area of the region surrounded by the connecting line of the edges of the weak part 601 and the weak part 601 is S1, as shown by the shaded parts in Figure 16 and Figure 18 shown. The area of the region of S2 - S1 is shown in Figure 19 , Figure 19 shown, the slanted line region in

[0073] For the battery cell of the present invention, by providing a first barrier platform 301 and / or a second barrier platform 302 around the explosion-proof hole 5, or a barrier groove 104 in which a heat-insulating member 7 is placed, when the explosion-proof valve opens during thermal runaway, the periphery of the explosion-proof valve is not easily melted, reducing the probability that the flame ejected by the explosion-proof valve burns adjacent battery cells and reducing the occurrence of thermal propagation.

[0074] In one embodiment, the preparation process of a battery with the positive electrode active material being LiNi 0.6 Co 0.2 Mn 0.2 O2 includes the following steps:

[0075] Preparation of the positive electrode sheet: Mix the positive electrode active material LiNi 0.6 Co 0.2 Mn 0.2 O2, the conductive agent acetylene black, and the binder PVDF in a mass ratio of 95:3:2, add the solvent NMP, and stir under the action of a vacuum mixer until the system becomes homogeneous to obtain a positive electrode slurry; uniformly coat the positive electrode slurry on both surfaces of the positive electrode current collector aluminum foil, air-dry at room temperature and then transfer to an oven for further drying, and then obtain the positive electrode sheet through cold pressing and slitting;

[0076] Preparation of the negative electrode sheet: Mix the negative electrode active material graphite, the conductive agent acetylene black, the thickener CMC, and the binder SBR in a mass ratio of 96:1:1.5:1.5, add the solvent deionized water, and stir under the action of a vacuum mixer until the system becomes homogeneous to obtain a negative electrode slurry; uniformly coat the negative electrode slurry on both surfaces of the negative electrode current collector copper foil, air-dry at room temperature and then transfer to an oven for further drying, and then obtain the negative electrode sheet through cold pressing and slitting;

[0077] Preparation of the electrolyte: Mix ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) in a volume ratio of 1:1:1 to obtain an organic solvent, and then dissolve the fully dried lithium salt LiPF6 in the mixed organic solvent to prepare an electrolyte with a concentration of 1 mol / L;

[0078] Preparation of the separator: Select a polyethylene film as the separator;

[0079] Preparation of the lithium-ion battery: Stack the positive electrode sheet, separator, and negative electrode sheet in the above steps in sequence through a lamination process, with the separator placed between the positive and negative electrode sheets to play an isolation role. After the battery core is prepared, the battery core is put into a shell, the battery cover plate is welded, and processes such as electrolyte injection, formation, and constant volume are carried out on the battery.

[0080] Using the above LiNi 0.6 Co 0.2 Mn 0.2The O2 battery was tested, and the obtained data are shown in Examples 2 to 5, Examples 7 to 12, Example 14, and Comparative Examples 1 and 2 in the following table. Examples 1, 6, 13, and 15 in the following table used LiNi 0.9 Co 0.05 Mn 0.05 O2 battery for testing. The preparation steps of the LiNi 0.9 Co 0.05 Mn 0.05 O2 battery are the same as those of the LiNi 0.9 Co 0.05 Mn 0.05 O2 battery. Examples 16 - 19 and Comparative Examples 3 and 4 are the data obtained from testing batteries using lithium iron phosphate as the positive electrode active material. Among them, the battery capacity Q can be adjusted by the surface density of the positive electrode sheet being 180 - 600 g / cm 2 ; the thickness of the positive electrode sheet being 80 - 200 μm; the number of positive electrode sheet layers being 60 - 400 layers. Regarding the above limitations on the surface density, the thickness of the positive electrode sheet, and the number of positive electrode sheet layers, they can be comprehensively adjusted in combination with the capacity, and the present application does not make any limitations.

[0081]

[0082] Performance Test 1: Test for whether adjacent batteries are triggered to undergo thermal runaway: Use a planar or rod-shaped heating device, and its surface should be covered with a ceramic, metal, or insulating layer. Directly contact the heating surface of the heating device with the surface of the battery cell. Start the heating device within 24 hours and heat the triggering object at the maximum power of the heating device. A temperature sensor is arranged at the position of the battery explosion-proof valve / on the large surface side 1011 of the battery. When a thermal runaway phenomenon occurs, if the distance between the edge of the burned position on the surface of the housing where the explosion-proof valve is set and the edge of the housing is greater than or equal to 3 mm, it is determined as no, and it will not trigger adjacent batteries to undergo thermal runaway; if it is less than 3 mm, it is judged as yes, and it will trigger adjacent batteries to undergo thermal runaway. If it is a square battery, then this distance refers to the distance from the large surface side 1011 of the battery. If it is a cylindrical battery, then this distance refers to the distance from the edge of the cylinder.

[0083] Performance Test 2, Weight Loss Rate Test: Use a planar or rod-shaped heating device, and its surface should be covered with a ceramic, metal, or insulating layer. Directly contact the heating surface of the heating device with the surface of the battery cell. Start the heating device within 24 hours and heat the triggering object at the maximum power of the heating device. Arrange temperature sensors at the explosion-proof valve opening of the battery / the large surface side 1011 of the battery, calculate the mass before and after thermal runaway. Among them, the mass of the battery cell before thermal runaway is m1, and the mass of the battery cell after thermal runaway is m2. Obtain the value of (m1 - m2) / m1. If this value is less than 40%, it is unqualified, and there is no eruption inside the housing, but the temperature inside the housing is too high; if this value is greater than or equal to 40%, it is qualified, and the heat can be smoothly discharged through the explosion-proof valve to avoid excessive heat inside the battery. Among them, the determination conditions for thermal runaway triggering are as follows: a) The triggering object generates a voltage drop, and the drop value exceeds 25% of the initial voltage; b) The temperature at the monitoring point reaches the maximum operating temperature specified by the manufacturer; c) The temperature rise rate dT / dt at the monitoring point ≥ 1 °C / s and lasts for more than 3 s. When a) and c) or b) and c) occur, it is determined that thermal runaway has occurred.

[0084] The present invention also provides a battery pack, which includes a plurality of battery cells stacked together. The battery cells are the above-mentioned battery cells, and a heat insulation pad is arranged between adjacent battery cells. The thickness of the heat insulation pad is 1 - 5 mm. Specifically, the thickness of the heat insulation pad can be 1 mm, 2.5 mm, or 4 mm.

[0085] In the description of this solution, it should be understood that the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of these features. In the description of this solution, the meaning of "a plurality" is two or more, unless otherwise specifically defined.

[0086] The various embodiments in this specification are described in a progressive manner. Each embodiment focuses on the differences from other embodiments. The same or similar parts among the various embodiments can be referred to each other.

[0087] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be obvious to those skilled in the art. The general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to these embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A battery cell, characterized in that, It includes a battery housing and a battery cell. The battery cell is placed inside the battery housing. An explosion-proof valve is provided on the battery housing. The explosion-proof valve includes a weak part. A barrier part is provided on the battery housing. The barrier part is arranged around the weak part. The thickness of the barrier part is greater than that of the weak part. The barrier part includes a barrier main structure. The area enclosed by the weak part is S1, and the area enclosed by the outer edge of the barrier part is S2. S1 and S2 satisfy 0.03*10 4 ≤S1*(S2 - S1) / (Q*h1 / h2)≤20*10 4 , where Q is the battery capacity in Ah, h1 is the thickness of the housing where the explosion-proof valve is provided in mm, h2 is the sum of the thicknesses of the battery housing and the barrier main structure in mm, and the units of S1 and S2 are mm 2 .

2. The battery cell according to claim 1, wherein In the formula S1*(S2 - S1) / (Q*h1 / h2), the range of S1 is 100 - 1200 mm 2 , the range of S2 - S1 is 100 - 2850 mm 2 , the range of Q is 20 - 600 Ah, and the range of h1 / h2 is 0.1 - 0.

8.

3. The battery cell according to claim 1, wherein, The barrier main structure includes a barrier platform, and the barrier platform protrudes on the outer surface of the battery housing.

4. The battery cell according to claim 3, wherein The barrier platform is disposed around the weak part.

5. The battery cell according to claim 4, wherein The barrier platform continuously surrounds the weak part, and the range of h1 / h2 is 0.1 - 0.

7.

6. The battery cell according to claim 4, wherein There are several barrier platforms, and multiple barrier platforms are spaced around the weak part, and the range of h1 / h2 is 0.3 - 0.

8.

7. The battery cell according to claim 6, wherein The spacing distance between adjacent barrier platforms is 1 - 10 mm.

8. The battery cell according to claim 3 or 4, characterized in that, The width of the barrier platform is 3 - 50 mm.

9. The battery cell according to claim 3 or 4, characterized in that, The barrier platform includes a first barrier platform and a second barrier platform. The first barrier platform is arranged around the weak part, and the first barrier platform is located between the second barrier platform and the weak part.

10. The battery cell according to claim 9, wherein The height ratio of the first barrier platform to the second barrier platform is 0.6 - 6.

11. The battery cell according to claim 9, wherein, The spacing distance between the first barrier platform and the second barrier platform is 0 - 1 mm.

12. The battery cell according to claim 9, wherein, The first barrier platform is disposed at a position close to the weak part of the second barrier platform, and a protective patch is connected to the surface of the first barrier platform away from the battery cell.

13. The battery cell according to claim 3 or 4, characterized in that, The ratio of the height of the barrier platform to the thickness of the battery housing is 0.25 - 6.

14. The battery cell according to claim 3 or 4, characterized in that, The barrier platform and the battery housing are of an integral structure.

15. The battery cell according to claim 3 or 4, characterized in that, The barrier platform and the battery housing are of a split structure, and the barrier platform is connected to the battery housing.

16. The battery cell according to claim 1, characterized in that, The barrier main structure protrudes from the battery housing towards the battery cell to form a barrier groove. The barrier groove is arranged on the outer surface of the battery housing, and a heat insulation member is arranged in the barrier groove.

17. The battery cell according to claim 16, characterized in that, The barrier groove is arranged around the weak part.

18. The battery cell according to claim 16, wherein, The depth of the barrier groove is 0.5 - 3.5 mm, and the width of the barrier groove is 3 - 50 mm.

19. The battery cell according to claim 16, characterized in that, The melting point of the heat insulation member is higher than that of the battery housing, and the melting point of the heat insulation member is greater than or equal to 700 °C.

20. The battery cell according to claim 1, characterized in that, The battery housing includes a housing main body and a cover plate, and the explosion-proof valve is arranged on the cover plate.

21. The battery cell according to claim 1, characterized in that, The battery housing includes a housing main body and a cover plate, and the explosion-proof valve is arranged on the housing main body.

22. The battery cell according to claim 2, wherein, An explosion-proof hole is arranged on the battery housing. The explosion-proof valve includes an explosion-proof sheet, and the explosion-proof sheet is connected to the explosion-proof hole. The explosion-proof sheet includes the weak part, and the weak part is continuously arranged around the circumference, and the numerical range of h1 / h2 is 0.25 - 0.

5.

23. The battery cell according to claim 2, characterized in that, An explosion-proof hole is arranged on the battery housing. The explosion-proof valve includes an explosion-proof sheet, and the explosion-proof sheet is connected to the explosion-proof hole. The explosion-proof sheet includes the weak part, and the weak part is discontinuously arranged around the circumference, and the numerical range of h1 / h2 is 0.3 - 0.

6.

24. The battery cell according to claim 1, wherein, The battery housing is a cylindrical shell, and the explosion-proof valve is arranged on the end face of the cylindrical shell. In the radial direction, the distance between the outer edge of the barrier main structure and the edge of the end face of the battery housing is 0.5 - 10 mm.

25. The battery cell according to claim 1, wherein The battery housing is a square shell. The battery housing includes a first face and a second face. There are two first faces, and the two first faces are arranged oppositely. Among the four second faces, two are arranged oppositely. The area of the first face is larger than that of the second face, and the barrier main structure is arranged on the second face between the two first faces.

26. The battery cell according to claim 25, characterized in that, The distance between the barrier main body structure and the first surface is 3-20 mm, and the barrier main body structure is at least arranged at a position of the weak part close to the first surface.

27. The battery cell according to claim 2, characterized in that, The battery cell is a ternary lithium battery, and the ratio range of h1 to h2 is 0.1-0.

65.

28. The battery cell according to claim 27, characterized in that, The nickel content of the positive electrode of the ternary lithium battery is greater than or equal to 0.7, and the ratio range of h1 to h2 is 0.1-0.

58.

29. The battery cell according to claim 2, wherein The battery cell is a lithium iron phosphate battery, and the ratio range of h1 to h2 is 0.2-0.

75.

30. A battery pack includes a plurality of battery cells stacked together, characterized in that, The battery cell is the battery cell according to any one of claims 1-29, and a heat insulation pad is arranged between adjacent battery cells, and the thickness of the heat insulation pad is 1-5 mm.

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