Battery cell and battery

Abstract

The invention relates to a battery cell and a battery. The battery cell comprises a pole piece, an outgoing tab is arranged on the pole piece; and the cross sectional area of the outgoing tab is gradually reduced from the connecting end to the free end of the outgoing tab. Under the condition that the material and the total mass of the outgoing tabs are not changed, the cross sectional area of the outgoing tabs on the pole piece is gradually reduced from the connecting ends to the free ends of the outgoing tabs, so that the cross sectional area of the outgoing tabs closer to the pole piece area is larger, the area of the tab area in direct contact with the pole piece is larger, and the contact area between the outgoing tabs and the pole piece area is larger. Therefore, the heat production quantity of the pole piece close to the outgoing tab area is reduced, the temperature distribution of the pole piece is more uniform, the hidden dangers of overhigh local temperature and the like are avoided, and the safety of the battery cell is higher.

Description

Technical Field

[0001] The present disclosure relates to the technical field of batteries, and in particular to a battery cell and a battery. Background Art

[0002] As one of the most promising industries in the new century, new energy has also ushered in a period of rapid development in various fields involved. In the field of batteries, lithium-ion batteries have the advantages of high voltage platform, high energy density, and long cycle life. Therefore, they are widely studied and are also the most commercialized secondary batteries. As the market share of lithium-ion batteries increases, the terminal application market has increasingly stringent requirements for their performance. In recent years, due to the surge in demand for fast charging of new energy equipment, the rate performance of lithium-ion batteries has attracted much attention.

[0003] In the related art, the battery cell includes a pole piece and a pole ear. The pole ear is used to realize the import and export of free electrons generated when the electrochemical reaction occurs in the pole piece. Since the size of the pole ear is much smaller than the area of ​​the pole piece, the current density in the pole ear is much greater than the current density in the pole piece in the adjacent area. According to Ohm's law, the pole ear will generate relatively hot heat when the battery cell is working. Through testing, it was found that the heat generated by the existing pole ear cannot be quickly transferred to the entire pole piece, causing the pole piece temperature in the area adjacent to the pole ear to be higher than other areas, resulting in uneven pole piece temperature distribution, which makes the battery cell have a higher safety risk. Summary of the invention

[0004] In order to solve the above technical problems, the present disclosure provides a battery cell and a battery.

[0005] The embodiment of the present disclosure provides a battery cell, including a pole piece;

[0006] The pole piece is provided with an outgoing pole ear;

[0007] The cross-sectional area of ​​the outgoing pole tab gradually decreases from the connecting end to the free end of the outgoing pole tab.

[0008] Optionally, the thickness of each region of the outgoing tab is the same;

[0009] The length of the outgoing pole tab gradually decreases from the connecting end to the free end of the outgoing pole tab.

[0010] Optionally, the outgoing pole lug is in a trumpet shape extending from the connecting end to the free end of the outgoing pole lug.

[0011] Optionally, a plurality of the outgoing pole ears are provided on the pole piece; the plurality of the outgoing pole ears are distributed at intervals along the length direction of the pole piece on which they are located.

[0012] Optionally, the electrode sheet includes a positive electrode sheet and a negative electrode sheet;

[0013] The positive electrode sheet and the negative electrode sheet are both provided with the outgoing pole lug;

[0014] The outgoing pole tabs on the positive pole sheet and the negative pole sheet are arranged in an offset manner.

[0015] Optionally, two current collection belts are also included;

[0016] The outgoing pole tab arranged on the positive electrode plate is welded to one of the current collecting belts. The outgoing pole tab arranged on the negative electrode plate is welded to the other current collecting belt.

[0017] Optionally, among all the outgoing pole tabs connected to the positive electrode plate, a free end of at least one of the outgoing pole tabs is provided with a current lead-out area; and / or,

[0018] Among all the outgoing pole tabs connected to the negative electrode plate, a current lead-out area is provided at the free end of at least one of the outgoing pole tabs.

[0019] Optionally, except for the current lead-out area and the area welded to the current collecting belt, all other areas of the outgoing pole lug are coated with an insulating layer.

[0020] Optionally, a diaphragm is also included; the diaphragm is arranged between the positive electrode plate and the negative electrode plate.

[0021] The embodiment of the present disclosure further provides a battery pack, characterized in that it includes a battery cell fixing member and a plurality of battery cells as described above, wherein the battery cell fixing member is used to fix the plurality of battery cells after they are connected.

[0022] Compared with the prior art, the technical solution provided by the embodiments of the present disclosure has the following advantages:

[0023] In the solution provided by the embodiment of the present disclosure, since the material and total mass of the outgoing pole ear remain unchanged, when the cross-sectional area of ​​the outgoing pole ear on the pole piece is set to gradually decrease from the connection end with the pole piece to the free end, the closer the outgoing pole ear is to the connection end, the larger the cross-sectional area, that is, the closer the outgoing pole ear is to the connection end, the longer the length of the area, so the closer the outgoing pole ear is to the connection end, the larger the extension area, the smaller the current density of the outgoing pole ear, and when the battery cell current is constant, the closer the outgoing pole ear is to the pole piece area, the smaller the heat generated in the area. At the same time, since the cross-sectional area of ​​the outgoing pole ear is closer to the pole piece area, the larger the area of ​​the pole ear area in direct contact with the pole piece, the higher the efficiency of heat conduction, the heat generated by the outgoing pole ear can be transferred to the adjacent pole piece area more quickly, and then transferred from the adjacent pole piece area to other pole piece areas, thereby making the temperature gradient change of each area of ​​the pole piece as gentle as possible, avoiding hidden dangers such as excessive local temperature of the pole piece, and making the battery cell safer. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present disclosure and, together with the description, serve to explain the principles of the present disclosure.

[0025] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0026] Figure 1 A schematic diagram of current distribution of a single-pole positive electrode provided by the prior art;

[0027] Figure 2 A schematic diagram of a pole piece structure provided in an embodiment of the present disclosure;

[0028] Figure 3 A schematic diagram of another pole piece structure provided in an embodiment of the present disclosure;

[0029] Figure 4 A schematic diagram of another pole piece structure provided in an embodiment of the present disclosure;

[0030] Figure 5 A schematic diagram of another pole piece structure provided in an embodiment of the present disclosure;

[0031] Figure 6 A schematic diagram of another pole piece structure provided in an embodiment of the present disclosure;

[0032] Figure 7 A schematic diagram of a battery cell structure provided in an embodiment of the present disclosure;

[0033] Figure 8 A schematic diagram of another battery cell structure provided in an embodiment of the present disclosure;

[0034] Fig. 9 A schematic diagram of another battery cell structure provided in an embodiment of the present disclosure;

[0035] Fig.10 A schematic diagram of another pole piece structure provided in an embodiment of the present disclosure;

[0036] Fig.11 A schematic diagram of the structure of a positive electrode sheet and a negative electrode sheet provided in an embodiment of the present disclosure. DETAILED DESCRIPTION

[0037] In order to more clearly understand the above-mentioned objectives, features and advantages of the present disclosure, the scheme of the present disclosure will be further described below. It should be noted that the embodiments of the present disclosure and the features in the embodiments can be combined with each other without conflict.

[0038] In the following description, many specific details are set forth to facilitate a full understanding of the present disclosure, but the present disclosure may also be implemented in other ways different from those described herein; it is obvious that the embodiments in the specification are only part of the embodiments of the present disclosure, rather than all of the embodiments.

[0039] For the single-pole ear pole piece in the prior art, since the extension area of ​​the battery cell pole piece is large, the distances between each region of the pole piece and the potential extreme point are not the same. The pole piece in the area closest to the potential extreme point has a small internal resistance, and the pole piece in the area farthest from the potential extreme point has a large internal resistance, and

[0040] Figure 1 A schematic diagram of current distribution of a single-pole positive electrode provided by the prior art, such as Figure 1 As shown, the thicker the arrow line, the greater the current density. Figure 1 It can be seen that the current density in the lug area is relatively high, and the size of the lug area is relatively small, which makes it difficult for the heat generated in the lug area to be quickly transferred to the pole piece through heat conduction. During the charging and discharging process of the battery cell, the temperature of the lug area is too high, which makes the temperature of the pole piece area near the lug higher than that of other areas of the pole piece, making the temperature gradient on the pole piece larger and larger, which is easy to cause hidden dangers such as local overtemperature, making the battery cell have a higher safety risk.

[0041] The present disclosure provides a battery cell. Figure 2 A schematic diagram of a pole piece structure provided in an embodiment of the present disclosure is shown in FIG. Figure 2 As shown, the battery cell includes a pole piece 100 , on which an outgoing pole ear 110 is disposed; the cross-sectional area of ​​the outgoing pole ear 110 gradually decreases from the connecting end 111 to the free end 112 of the outgoing pole ear 110 .

[0042] For example, Figure 3 A schematic diagram of a pole piece structure provided in an embodiment of the present disclosure is shown in FIG. Figure 3 As shown, since the material and total mass of the external pole tab 110 remain unchanged, when the cross-sectional area of ​​the external pole tab 110 on the pole piece 100 is set to gradually decrease from the connection end 111 to the free end 112, the closer the external pole tab 110 is to the connection end 111, the larger the cross-sectional area. Figure 3Reference numerals 113 and 114 are shown, reference numeral 113 is the cross section of the outgoing pole ear 110 close to the connection end 111, and reference numeral 114 is the cross section of the outgoing pole ear 110 away from the connection end 111. It can be seen that the area S1 of the cross section of the outgoing pole ear 110 close to the connection end 111 is greater than the area S2 of the cross section of the outgoing pole ear 110 away from the connection end 111, and the length A1 of the cross section of the outgoing pole ear 110 close to the connection end 111 is greater than the length A2 of the cross section of the outgoing pole ear 110 away from the connection end 111. Therefore, the closer the outgoing pole ear 110 is to the connection end 111, the larger the extensional area of ​​the region, and the smaller the current density of the outgoing pole ear 110. When the cell current is constant, the heat generated in the region closer to the pole piece of the outgoing pole ear 110 is smaller. At the same time, since the cross-sectional area of ​​the outgoing pole ear 110 is larger as it is closer to the pole piece area, and the area of ​​the pole ear area in direct contact with the pole piece 100 is larger, the efficiency of heat conduction is also higher. The heat generated by the outgoing pole ear 110 can be transferred to the adjacent pole piece area faster, and then conducted from the adjacent pole piece area to other pole piece areas, thereby making the temperature gradient changes in various areas of the pole piece 100 as gentle as possible, avoiding hidden dangers such as excessive local temperature of the pole piece 100, and making the battery cell safer.

[0043] Figure 4 A schematic diagram of another pole piece structure provided in an embodiment of the present disclosure is shown in FIG. Figure 4 As shown, the thickness of each region of the outgoing pole tab 110 is the same; the length of the outgoing pole tab 110 gradually decreases from the connecting end 111 to the free end 112 of the outgoing pole tab 110 .

[0044] For example, see Figure 4Reference numerals 115 and 116 are shown, reference numeral 115 is a cross section of the outgoing pole lug 110 close to the connection end 111, and reference numeral 116 is a cross section of the outgoing pole lug 110 away from the connection end 111. The area S3 of the cross section of the outgoing pole lug 110 close to the connection end 111 is greater than the area S4 of the cross section of the outgoing pole lug 110 away from the connection end 111. Since the thickness of each region of the outgoing pole lug 110 is the same, the length A3 of the cross section of the outgoing pole lug 110 close to the connection end 111 is greater than the length A4 of the cross section of the outgoing pole lug 110 away from the connection end 111. Therefore, the longer the length of the outgoing pole lug 110 is in the region closer to the connection end 111, the larger the extensional area of ​​the region closer to the connection end 111, and the smaller the current density of the outgoing pole lug 110. When the cell current is constant, the heat generated in the region closer to the pole piece region of the outgoing pole lug 110 is smaller. At the same time, since the cross-sectional area of ​​the outgoing pole ear 110 is larger as it is closer to the pole piece area, and the area of ​​the pole ear area in direct contact with the pole piece 100 is larger, the efficiency of heat conduction is also higher. The heat generated by the outgoing pole ear 110 can be transferred to the adjacent pole piece area faster, and then conducted from the adjacent pole piece area to other pole piece areas, thereby making the temperature gradient changes in various areas of the pole piece 100 as gentle as possible, avoiding hidden dangers such as excessive local temperature of the pole piece 100, and making the battery cell safer.

[0045] It should be noted that Figure 2 , Figure 3 and Figure 4 The case where the longitudinal section of the external pole tab is fan-shaped is only schematically drawn, and the shape of the longitudinal section of the external pole tab may also be other shapes such as a trapezoid, which is not specifically limited here.

[0046] It should be noted that Figure 3 and Figure 4 In order to facilitate the explanation of the gradual decrease in the cross-sectional area of ​​the outer pole ear and the gradual decrease in the length of the outer pole ear, reference numerals 113, 114, 115 and 116 are drawn accordingly. Those skilled in the art should understand that these are only examples.

[0047] In some embodiments, the external tab is in a trumpet shape extending from the connection end to the free end of the external tab.

[0048] For example, Figure 5 A schematic diagram of another pole piece structure provided in an embodiment of the present disclosure is shown in FIG. Figure 5As shown, while ensuring that the material and total mass of the outgoing pole ear 110 remain unchanged, the outgoing pole ear 110 is made into a trumpet shape, so that the extension area of ​​the area of ​​the outgoing pole ear 110 near the connection end 111 is larger than the extension area of ​​the area of ​​the outgoing pole ear 110 near the free end 112, thereby making the heat dissipation capacity of the area of ​​the outgoing pole ear 110 near the connection end 111 the strongest, thereby reducing the heat generation of the pole piece 100 near the outgoing pole ear 110 area, and the temperature distribution of the pole piece 100 is more uniform, making the battery cell safer. In addition, the trumpet-shaped outgoing pole ear is convenient for directly cutting the pole piece to generate the outgoing pole ear during production, and it is not easy to form a sharp corner area. At the same time, the trumpet-shaped smooth curve transition reduces the probability of stress concentration between the outgoing pole ear and the pole piece.

[0049] Figure 6 A schematic diagram of another pole piece structure provided in an embodiment of the present disclosure is shown in FIG. Figure 6 As shown, a plurality of outgoing pole tabs 110 are disposed on the pole piece 100 ; the plurality of outgoing pole tabs 110 are distributed at intervals along the length direction of the pole piece 100 where they are located.

[0050] Exemplarily, the pole piece 100 is provided with a plurality of outgoing pole ears 110 spaced apart along the length direction of the pole piece 100, and each outgoing pole ear 110 can be used to transmit current. The current inside the pole piece 100 can be transmitted through a plurality of outgoing pole ears 110 at the same time, so as to avoid the problem that the current is too concentrated when there is only a single pole ear and the current can only be transmitted through the same pole ear, thereby causing the heat of the pole piece to be concentrated in the single pole ear area.

[0051] For the battery cell pole piece, the pole ear arranged on the pole piece is the potential extreme point of the pole piece. The present disclosure arranges a plurality of outgoing pole ears 110 spaced apart along the length direction of the pole piece 100 on the pole piece 100, so that there are a plurality of potential extreme points on the pole piece 100, thereby making it possible for the current in each area of ​​the pole piece 100 to be transmitted outward from the nearest outgoing pole ear 110. Unlike a single-pole ear pole piece, the current in the pole piece area farther from the pole ear flows through a longer path than the current in the pole piece area closer to the pole ear. In this way, it can be ensured that the current distribution inside the pole piece 100 is more uniform, and the current density will not be too large, avoiding the problem of uneven temperature distribution caused by the concentration of heat in a certain area due to the excessive current density, thereby avoiding the hidden dangers of excessive local temperature, and making the battery cell safer. Because the number of tabs on the pole piece 100 increases, when the battery cell is working, the current inside the pole piece 100 can be transmitted through multiple external tabs 110 at the same time, so that the conductive path inside the battery cell is increased, and the charging rate of the battery cell is improved. In addition, the increase in the number of tabs also increases the total area of ​​the tabs accordingly, thereby enhancing the heat dissipation capacity of the tabs and reducing the temperature rise of the battery cell when charging.

[0052] It should be noted that Figure 6 Only three external pole tabs 110 are shown as being arranged on the pole piece 100 for exemplary purposes. The external pole tabs may be arranged in different numbers and positions according to actual needs, which are not specifically limited here.

[0053] Figure 7 A schematic diagram of a battery cell structure provided in an embodiment of the present disclosure is shown in FIG. Figure 7 As shown, the electrode sheet 100 includes a positive electrode sheet 101 and a negative electrode sheet 102 ; both the positive electrode sheet 101 and the negative electrode sheet 102 are provided with external electrode tabs 110 ; the external electrode tabs 110 on the positive electrode sheet 101 and the negative electrode sheet 102 are staggered and spaced apart.

[0054] For example, Figure 7 Taking the laminated cell as an example, a plurality of outgoing pole tabs 110 are schematically drawn to be arranged on a positive pole sheet 101 and a negative pole sheet 102. The plurality of outgoing pole tabs 110 arranged on the positive pole sheet 101 and the plurality of outgoing pole tabs 110 arranged on the negative pole sheet 102 are staggered and spaced apart, so that when each outgoing pole tab is folded to one side, the plurality of outgoing pole tabs 110 arranged on the positive pole sheet 101 and the plurality of outgoing pole tabs 110 arranged on the negative pole sheet 102 will not contact, thereby avoiding a short circuit caused by the contact of the pole tabs when the positive pole sheet and the negative pole sheet are folded, thereby improving the safety of the cell.

[0055] It should be noted that Figure 7 It is only schematically shown that three external pole tabs 110 are respectively arranged on a positive pole sheet 101 and a negative pole sheet 102. The specific number of pole sheets of the battery cell and the number of pole tabs arranged on the pole sheets can be set according to actual needs and are not specifically limited here.

[0056] Figure 8 A schematic diagram of another battery cell structure provided in an embodiment of the present disclosure is shown in FIG. Figure 8 As shown, two current collecting strips 120 are also included.

[0057] The outgoing pole tab 110 disposed on the positive electrode sheet 101 is welded to one of the current collecting strips 120 ; the outgoing pole tab 110 disposed on the negative electrode sheet 102 is welded to the other current collecting strip 120 .

[0058] Exemplarily, one current collecting belt 120 conductively connects all the outgoing pole ears 110 on the positive electrode plate 101 by welding, and another current collecting belt 120 conductively connects all the outgoing pole ears 110 on the negative electrode plate 102 by welding, thereby allowing the current collecting belt 120 to collect the current output by all the outgoing pole ears 110 and output it to the external circuit, or evenly distribute the current input by the external circuit to each outgoing pole ear 110.

[0059] In some embodiments, among all the outgoing pole ears connected to the positive electrode plate, at least one outgoing pole ear has a free end provided with a current lead-out area; and / or, among all the outgoing pole ears connected to the negative electrode plate, at least one outgoing pole ear has a free end provided with a current lead-out area.

[0060] For example, see Figure 8 A current lead-out area 130 is provided on the free end 112 of the outermost outgoing pole tab 110 of the positive pole sheet 101 and the negative pole sheet 102. The current lead-out area 140 is conductively connected to each outgoing pole tab 110 through a current collection belt 120. The connection path between each outgoing pole tab 110 and the current lead-out area 130 constitutes a conductive path, thereby increasing the number of conductive paths of the battery cell and further improving the rate performance of the battery cell during charging.

[0061] In some embodiments, except for the current lead-out area and the area welded to the current collecting belt, all other areas of the external tab are coated with an insulating layer.

[0062] For example, Fig. 9 A schematic diagram of another battery cell structure provided in an embodiment of the present disclosure is shown in FIG. Fig. 9 As shown, the adjacent outgoing pole tabs 110 can be electrically connected by welding using the current collection belt 120. A welding area 140 can be provided on the outgoing pole tab 110, and the current collection belt 120 is welded to the welding area 140 of the adjacent outgoing pole tab 110, so that the adjacent outgoing pole tabs 110 are welded and connected through the current collection belt 120 corresponding to the welding area 140, so that the current collection belt 120 can collect the current output from the outgoing pole tab 110 and output it to the external circuit, or evenly distribute the current input from the external circuit to each outgoing pole tab 110. In the outgoing pole tab 110, other areas except the current lead-out area 130 and the area welded and connected with the current collection belt 120 can be coated with an insulating layer. The insulating coating can isolate the current collection belt 120 outside the connection area from the external environment, prevent electric sparks from occurring when the current passes through the current collection belt 120, thereby causing the battery cell to burn, thereby ensuring the safety of the battery cell.

[0063] In some embodiments, the material of the current collecting belt and the current leading-out area may be a high-conductivity material.

[0064] In some embodiments, the plurality of outgoing pole ears are evenly spaced along the length direction of the pole piece where they are located, and the outgoing pole ears farther from the current extraction area have a larger extension area.

[0065] For example, Fig.10 A schematic diagram of another pole piece structure provided in an embodiment of the present disclosure is shown in FIG. Fig.10As shown, the farther the outgoing pole lug 110 on the pole piece 100 is from the outgoing pole lug 110 where the current lead-out area 130 is disposed, the larger the extensional area of ​​the outgoing pole lug 110 is.

[0066] According to the law of resistance:

[0067]

[0068] The resistance R1 of the outgoing tab and the resistance R2 of the current collection belt can be calculated respectively. The actual resistance R of the tabs at different positions is the sum of the resistance R1 of the outgoing tab and the resistance R2 of the current collection belt, that is, R=R1+R2, where:

[0069]

[0070] ρ1 is the material conductivity of the outgoing pole ear, L1 is the width of the outgoing pole ear, S5 is the cross-sectional area in the width direction of the outgoing pole ear, and the cross-sectional area S5 in the width direction of the outgoing pole ear can be found in Figure 6 Reference numeral 210 ;

[0071]

[0072] ρ2 is the material conductivity of the current collection belt, L2 is the length of the current collection belt from the outgoing pole ear provided with the current lead-out area to the corresponding outgoing pole ear, S6 is the cross-sectional area of ​​the current collection belt in the length direction, and the cross-sectional area S6 of the current collection belt in the length direction is shown in FIG. Figure 7 220 of the figure.

[0073] Since the electron current will preferentially choose the path with the least impedance, in order to ensure that the current passing through each pole ear is the same, it is necessary to ensure that the resistance of each pole ear is the same. Therefore, when calculating, since the width L1 of the outgoing pole ear and the cross-sectional area S6 in the length direction of the current collection belt are both constant values, when the actual resistance R of the pole ear remains unchanged, the greater the length L2 of the current collection belt between the outgoing pole ear with the current lead-out area and the corresponding outgoing pole ear, the greater the cross-sectional area S5 in the width direction of the outgoing pole ear. When the thickness B of each area of ​​the outgoing pole ear is the same, the greater the cross-sectional area S5 in the width direction of the outgoing pole ear, the greater the length A of the cross section in the width direction of the outgoing pole ear, and thus the longer the length of the outgoing pole ear 110, the greater the extension area of ​​the outgoing pole ear 110 while keeping the height of all the outgoing pole ears 110 the same.

[0074] It should be noted that the battery cell includes a plurality of positive electrode sheets and a plurality of negative electrode sheets during its configuration and manufacture. Fig.10For the convenience of illustrating the calculation, only one pole piece is drawn; and for the convenience of understanding the cross-sectional area S5 of the external pole ear in the width direction and the cross-sectional area S6 of the current collection belt in the length direction, the figure mark 210 and the figure mark 220 are drawn accordingly. Those skilled in the art should understand that these are only examples.

[0075] Fig.11 A schematic diagram of a positive electrode sheet and a negative electrode sheet structure provided in an embodiment of the present disclosure is shown in FIG. Fig.11 As shown, Fig.11 The current distribution in the positive electrode and negative electrode of the multi-electrode battery cell provided by this solution is provided. Fig.11 It can be seen that in the multi-ear battery cell provided by this scheme, the current in the pole piece can be transmitted through multiple pole pieces, and will not be concentrated at a certain pole piece, and the current density of each pole piece is not greatly different, so the heat generated by each pole piece is almost the same, avoiding the problem of uneven temperature distribution caused by uneven current distribution in the pole piece in the single-pole ear pole piece. Also because the number of pole pieces on the pole piece increases, when the battery cell is working, the current inside the positive pole piece and the negative pole piece can be transmitted through multiple outgoing pole pieces at the same time, so that the conductive path inside the battery cell is increased, and the charging rate of the battery cell is improved. And the increase in the number of pole pieces also increases the total area of ​​the pole pieces accordingly, thereby enhancing the heat dissipation capacity of the pole pieces and reducing the temperature rise of the battery cell when charging. In addition, since the larger the extension area of ​​the outgoing pole piece, the smaller the current density of the outgoing pole piece, when the battery cell current is constant, the smaller the heat generated in the area where the outgoing pole piece is closer to the pole piece area. At the same time, since the cross-sectional area of ​​the outgoing pole ear is larger as it is closer to the pole piece area, the area of ​​the pole ear in direct contact with the pole piece is larger, and the efficiency of heat conduction is higher. The heat generated by the outgoing pole ear can be transferred to the adjacent pole piece area faster, and then conducted from the adjacent pole piece area to other pole piece areas, thereby making the temperature gradient changes in various areas of the pole piece as gentle as possible, avoiding hidden dangers such as excessive local temperature of the pole piece, and making the battery cell safer.

[0076] In some embodiments, see Figure 8 and Fig. 9 The battery cell further includes a separator 103 ; the separator 103 is disposed between the positive electrode sheet 101 and the negative electrode sheet 102 .

[0077] The positive electrode sheet 101 includes a positive electrode current collector and a positive electrode active material coated on the positive electrode current collector, and the negative electrode sheet 102 includes a negative electrode current collector and a negative electrode active material coated on the negative electrode current collector.

[0078] For example, Figure 8 and Fig. 9The provided battery cell is formed by laminating a plurality of positive electrode sheets 101, a plurality of negative electrode sheets 102 and a plurality of separators 103 in the order of positive electrode sheets, separators and negative electrode sheets through a lamination process. The positive electrode sheet 101 is formed by coating a positive electrode active material on a positive electrode current collector and then rolling it, and the negative electrode sheet 102 is formed by coating a negative electrode active material on a negative electrode current collector and then rolling it. The plurality of outgoing pole tabs 110 on the positive electrode sheet 101 are formed by cutting the positive electrode current collector, and the plurality of outgoing pole tabs 110 on the negative electrode sheet 102 are formed by cutting the negative electrode current collector. After forming a plurality of outgoing pole ears 110 on the pole piece, all outgoing pole ears 110 on the positive pole piece 101 and all outgoing pole ears 110 on the negative pole piece 102 are folded to one side. After folding, the adjacent outgoing pole ears 110 are conductively connected through the current collection belt 120 by welding, and a current lead-out area 130 is set on the outermost outgoing pole ear 110.

[0079] Since the current inside the positive electrode plate 101 and the negative electrode plate 102 can be transmitted through multiple external pole ears 110 at the same time, it is possible to avoid the problem that the current is too concentrated when there is only a single pole ear and the current can only be transmitted through the same pole ear, thereby causing the heat of the pole plate to be concentrated in the single pole ear area.

[0080] For the battery cell pole piece, the pole ear provided on the pole piece is the potential extreme point of the pole piece. The present disclosure provides multiple outgoing pole ears 110 spaced apart along the length direction on the positive pole piece 101 and the negative pole piece 102, so that there are multiple potential extreme points on the positive pole piece 101 and the negative pole piece 102, thereby allowing the current in each area of ​​the positive pole piece 101 and the negative pole piece 102 to be transmitted outward from the nearest outgoing pole ear 110. Unlike a single-pole ear pole piece, the current in the pole piece area farther from the pole ear flows through a longer path than the current in the pole piece area closer to the pole ear. In this way, it can be ensured that the current distribution inside the positive pole piece 101 and the negative pole piece 102 is more uniform, and the current density will not be too large, thereby avoiding the problem of uneven temperature distribution caused by the heat concentrated in a certain area due to the excessive current density. Also, because the number of tabs on the positive pole piece 101 and the negative pole piece 102 increases, when the battery cell is working, the current inside the positive pole piece 101 and the negative pole piece 102 can be transmitted through multiple external tabs 110 at the same time, so that the conductive path inside the battery cell is increased, and the charging rate of the battery cell is improved. In addition, the increase in the number of tabs also increases the total area of ​​the tabs accordingly, thereby enhancing the heat dissipation capacity of the tabs and reducing the temperature rise when the battery cell is charged. In addition, since the larger the extension area of ​​the external tab, the smaller the current density of the external tab, when the battery cell current is constant, the heat generated in the area where the external tab is closer to the pole piece area is smaller. At the same time, since the cross-sectional area of ​​the outgoing pole ear is larger as it is closer to the pole piece area, the area of ​​the pole ear in direct contact with the pole piece is larger, and the efficiency of heat conduction is higher. The heat generated by the outgoing pole ear can be transferred to the adjacent pole piece area faster, and then conducted from the adjacent pole piece area to other pole piece areas, thereby making the temperature gradient changes in various areas of the pole piece as gentle as possible, avoiding hidden dangers such as excessive local temperature of the pole piece, and making the battery cell safer.

[0081] The embodiment of the present disclosure further provides a battery pack, comprising a battery cell fixing member and a plurality of the above-mentioned battery cells, wherein the battery cell fixing member is used to fix the plurality of the battery cells after they are connected.

[0082] The battery disclosed in the above embodiments has the same or corresponding beneficial effects as the above-mentioned battery cell, which will not be described again here to avoid repetition.

[0083] It should be noted that, in this article, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the existence of other identical elements in the process, method, article or device including the elements.

[0084] The above are only specific embodiments of the present disclosure, so that those skilled in the art can understand or implement the present disclosure. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present disclosure. Therefore, the present disclosure will not be limited to these embodiments 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: Including pole piece; The pole piece is provided with an outgoing pole ear; The cross-sectional area of ​​the outgoing pole tab gradually decreases from the connecting end to the free end of the outgoing pole tab.

2. The battery cell according to claim 1, characterized in that: The thickness of each area of ​​the outgoing tab is the same; The length of the outgoing pole tab gradually decreases from the connecting end to the free end of the outgoing pole tab.

3. The battery cell according to claim 2, characterized in that: The outgoing pole lug is in a trumpet shape extending from the connecting end to the free end of the outgoing pole lug.

4. The battery cell according to any one of claims 1 to 3, characterized in that: A plurality of outgoing pole tabs are arranged on the pole piece; the plurality of outgoing pole tabs are distributed at intervals along the length direction of the pole piece where they are located.

5. The battery cell according to claim 4, characterized in that: The pole pieces include a positive pole piece and a negative pole piece; The positive electrode sheet and the negative electrode sheet are both provided with the outgoing pole lug; The outgoing pole tabs on the positive pole sheet and the negative pole sheet are arranged in an offset manner.

6. The battery cell according to claim 5, characterized in that: Also included are two current collection strips; The outgoing pole tab arranged on the positive electrode plate is welded and connected to one of the current collecting belts; the outgoing pole tab arranged on the negative electrode plate is welded and connected to the other current collecting belt.

7. The battery cell according to claim 6, characterized in that: Among all the outgoing pole tabs connected to the positive electrode sheet, at least one of the outgoing pole tabs has a free end provided with a current lead-out area; and / or, Among all the outgoing pole tabs connected to the negative electrode plate, a current lead-out area is provided at the free end of at least one of the outgoing pole tabs.

8. The battery cell according to claim 7, characterized in that: Except for the current lead-out area and the area welded to the current collecting belt, all other areas of the outgoing pole lug are coated with an insulating layer.

9. The battery cell according to claim 8, characterized in that: It also includes a diaphragm; the diaphragm is arranged between the positive electrode sheet and the negative electrode sheet.

10. A battery pack, characterized in that: It comprises a battery cell fixing part and a plurality of battery cells as claimed in claims 1 to 9, wherein the battery cell fixing part is used for fixing the plurality of battery cells after they are connected.

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