Battery cell and method of manufacturing the same, battery pack

Abstract

The application relates to the field of batteries, and discloses a battery cell, a manufacturing method thereof, and a battery pack. The battery cell comprises a shell, a pole group, an electrode terminal, and a metal reinforcing piece. The pole group is arranged in the shell and comprises an electrode main body and a tab connected to the electrode main body. The electrode terminal is arranged in the shell and is electrically connected to the tab. The metal reinforcing piece is welded with the tab and the electrode terminal. The three are fixed together to realize electrical connection through welding of the metal reinforcing piece with the tab and the electrode terminal. The metal reinforcing piece can not only improve the connection strength between the tab and the electrode terminal, improve the reliability of the battery cell, but also reduce the internal resistance at the connection position of the tab and the electrode terminal, improve the overcurrent capacity, and further improve the performance of the battery cell. Especially in the high-power or fast charging and discharging scene, the overcurrent capacity and reliability can also be met.

Description

Technical Field

[0001] This invention relates to the field of battery technology, specifically to battery cells and their manufacturing methods, and battery packs. Background Technology

[0002] With the rapid development of new energy technologies, higher requirements are being placed on the performance and reliability of batteries (such as lithium-ion batteries). In the battery manufacturing process, tab welding is one of the key processes in battery assembly. As the component that conducts current from inside the battery, the welding quality of the tab directly affects the battery's performance and reliability.

[0003] Currently, there are problems such as insufficient connection strength, poor welding, and high resistance at the weld mark when welding the tabs and terminals. These problems have an adverse effect on the battery's charging and discharging efficiency and energy output, and can cause local overheating at the weld mark, or even breakage and failure, resulting in performance degradation and poor reliability. Summary of the Invention

[0004] In view of this, the present invention provides a battery cell and its manufacturing method, and a battery pack, to solve the problems of poor reliability caused by insufficient welding strength between the tab and the terminal post, and poor performance caused by high resistance at the solder joint.

[0005] In a first aspect, the present invention provides a battery cell, comprising: a housing, an electrode assembly, electrode terminals, and a metal reinforcing member; the electrode assembly is disposed within the housing, the electrode assembly comprising an electrode body and a tab connected to the electrode body; the electrode terminals are disposed within the housing and electrically connected to the tabs; the metal reinforcing member is welded to the tabs and the electrode terminals.

[0006] Beneficial effects: By welding the metal reinforcing member to the tab and electrode terminal, the three are fixed together to achieve electrical connection. The metal reinforcing member can not only improve the connection strength between the tab and the electrode terminal and improve the reliability of the battery cell, but also reduce the internal resistance at the connection between the tab and the electrode terminal, improve the overcurrent capacity, and thus improve the performance of the battery cell. In particular, the battery cell can meet the overcurrent capacity and reliability requirements in high-power or fast charging and discharging scenarios.

[0007] In one optional embodiment, along the thickness direction of the tab, the tab is located between the metal reinforcement and the electrode terminal; the tab and the electrode terminal are welded together by a first welding part, and a solder mark area is formed on the side of the tab opposite to the electrode terminal; the metal reinforcement is disposed in the solder mark area and is welded to the tab and the electrode terminal by a second welding part.

[0008] Beneficial effects: The metal reinforcement, electrode, and electrode terminal are stacked along the thickness direction of the tab, which increases the contact area and improves the current carrying capacity. After the tab and electrode terminal are pre-welded, a preliminary bond is formed in the solder area, making the connection between the tab and electrode terminal tighter. The final welding of the metal reinforcement, electrode, and electrode terminal in the solder area can avoid uneven energy distribution caused by the thickness difference of the multi-layer materials (metal reinforcement, electrode, and electrode terminal) during synchronous welding, reducing the risk of poor welding, overheating, or insufficient penetration. It can also reduce the internal resistance of the solder area, improve the current carrying capacity, and reduce the temperature rise. Thus, it can further improve the connection strength between the tab and electrode terminal and the charge and discharge performance of the cell.

[0009] In one optional embodiment, the area of ​​the solder area is S1, and the orthographic projection area of ​​the metal reinforcement on the solder area along the thickness direction of the tab is S2, where 0.25 ≤ S2 / S1 < 1.

[0010] Beneficial effects: When S2 / S1 is greater than or equal to 0.25, the welding area between the metal reinforcement and the tab / electrode terminal is increased, improving the connection strength. When S2 / S1 is less than 1, the area of ​​the metal reinforcement is smaller than the area of ​​the solder area, which can avoid the risk of the metal reinforcement piercing the tab and causing it to break. Therefore, when 0.25≤S2 / S1<1, it can both increase the welding area between the metal reinforcement and the tab / electrode terminal, improving the connection strength, and avoid the risk of the metal reinforcement piercing the tab and causing it to break.

[0011] In one optional embodiment, the solder area is rectangular, with a length of L1 and a width of W1; the metal reinforcement is rectangular, with a length of L2 and a width of W2; wherein, 0.5*L1≤L2<L1, and / or, 0.5*W1≤W2<W1.

[0012] Beneficial effects: When L2 is greater than or equal to 0.5*L1, and / or W2 is greater than or equal to 0.5*W1, the welding area between the metal reinforcement and the tab / electrode terminal can be increased, improving connection strength. When L2 is less than L1, and / or W2 is less than W1, the risk of the metal reinforcement piercing the tab and causing tab breakage can be avoided, improving connection reliability. Therefore, when 0.5*L1≤L2<L1, and / or 0.5*W1≤W2<W1, both connection strength and connection reliability can be improved.

[0013] In one optional embodiment, the length L1 of the solder area satisfies 5mm≤L1≤50mm, and / or the width W1 of the solder area satisfies 3mm≤W1≤20mm.

[0014] Beneficial effects: When L1 is greater than or equal to 5mm, and / or W1 is greater than or equal to 3mm, the connection strength can be improved; when L1 is less than or equal to 50mm, and / or W1 is less than or equal to 20mm, the electrode lug deformation can be reduced; therefore, when 5mm≤L1≤50mm, and / or 3mm≤W1≤20mm, both welding strength and electrode lug deformation can be increased.

[0015] In one optional embodiment, the thickness of the metal reinforcement is T, which satisfies 0.1mm≤T≤5mm.

[0016] Beneficial effects: When T is greater than or equal to 0.1mm, it can improve connection strength and overcurrent capacity; when T is less than or equal to 5mm, it can reduce the space occupied by the casing and help improve the volumetric energy density of the cell; therefore, when 0.1mm≤T≤5mm, it can improve connection strength and overcurrent capacity, reduce the space occupied by the casing, and improve the volumetric energy density of the cell.

[0017] In one optional embodiment, the melting point of the metal reinforcement is not lower than 650°C; and / or, the electrical conductivity of the metal reinforcement is not lower than 1*10⁻⁶. 7 S / m.

[0018] Beneficial effects: The melting point of the metal reinforcement is not lower than 650℃, resulting in a smaller heat-affected zone during welding, preventing melting and deformation during welding, maintaining a certain level of rigidity, and improving connection reliability. The electrical conductivity of the metal reinforcement 40 is not lower than 1*10 7 S / m can improve current carrying capacity.

[0019] In one optional embodiment, the metal reinforcement is made of the same material as the tab; and / or, the metal reinforcement is made of at least one of aluminum, copper, magnesium, aluminum alloy, and nickel alloy.

[0020] Beneficial effects: When the material of the metal reinforcement is the same as that of the electrode tab, it can have better bonding performance during welding, reduce the risk of incomplete welding, and improve the reliability of the connection.

[0021] Secondly, the present invention also provides a battery pack comprising the battery cells described in any embodiment of the first aspect.

[0022] Beneficial effects: Since the battery pack contains the cells mentioned in the first aspect, the battery pack also has the same beneficial effects as the cells, which will not be elaborated here.

[0023] Thirdly, the present invention also provides a cell manufacturing method, applicable to the cell described in any embodiment of the first aspect, the cell manufacturing method comprising: pre-soldering the tab and the electrode terminal to form a solder area; placing the metal reinforcement in the solder area, and welding the metal reinforcement, the tab and the electrode terminal.

[0024] Beneficial effects: After the tabs and electrode terminals are pre-welded, a preliminary bond is formed in the solder area, making the connection between the tabs and electrode terminals tighter. The final welding of the metal reinforcement to the tabs and electrode terminals in the solder area can avoid uneven energy distribution caused by the thickness difference of the multi-layer materials (metal reinforcement, tabs and electrode terminals) during synchronous welding, reducing the risk of poor welding, overheating or insufficient penetration. It can also reduce the internal resistance of the solder area, improve the current carrying capacity, and reduce the temperature rise. Thus, it can further improve the connection strength between the tabs and electrode terminals and the charge and discharge performance of the battery cell. Attached Figure Description

[0025] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0026] Figure 1 This is a schematic diagram of the battery cell structure according to an embodiment of the present invention;

[0027] Figure 2 This is a partial structural diagram of the battery cell according to an embodiment of the present invention; the casing has been omitted for ease of illustration.

[0028] Figure 3 This is a schematic diagram of the electrode tab, electrode terminal, and metal reinforcement in the welded state according to an embodiment of the present invention.

[0029] Figure 4 This is a schematic diagram of the structure of the metal reinforcement component according to an embodiment of the present invention;

[0030] Figure 5 This is a simulation diagram of the temperature change of the tab of the metal-free reinforcing member according to an embodiment of the present invention;

[0031] Figure 6 This is a simulation diagram of the temperature change of the tab with metal reinforcement according to an embodiment of the present invention;

[0032] Figure 7 This is a schematic flowchart of a battery cell manufacturing method according to an embodiment of the present invention.

[0033] Explanation of reference numerals in the attached figures:

[0034] 100-Battery cell; 10-Outer casing; 11-Housing shell; 12-Cover; 20-Electrode group; 21-Electrode body; 22-Electrode tab; 30-Electrode terminal; 40-Metal reinforcement; A-Soldering area; A'-First welding part; B'-Second welding part; X-First direction; Y-Second direction; Z-Third direction. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0036] The welding process for battery tabs and electrode terminals (such as terminals) mainly employs methods such as laser welding, resistance welding, or ultrasonic welding. While these welding technologies can meet the production requirements of battery cells to some extent, in practical applications, due to the special properties of the materials (such as the high conductivity and high reflectivity of the tab materials), thermal stress during the welding process, and insufficient optimization of welding parameters, problems such as insufficient weld strength, incomplete welds, and high resistance at the weld joint often occur. These problems not only increase the internal resistance of the battery cell, affecting its charge and discharge efficiency and energy output, but may also cause localized overheating at the weld joint, leading to performance degradation or even breakage and failure of the battery cell. Therefore, the performance and reliability of the battery cell are poor.

[0037] To address the aforementioned issues, related technologies have improved welding quality by optimizing welding parameters, upgrading welding equipment, or using new welding materials. However, these methods often fail to fundamentally solve the problems of insufficient weld strength and high resistance at the weld joint, especially in high-power battery or fast-charging / discharging scenarios, where issues such as incomplete welds, high resistance, and even breakage still exist at the weld joint.

[0038] In response, this invention adds a metal reinforcing member to the solder area between the tab and the electrode terminal, which not only improves the connection strength of the solder area and enhances the reliability of the battery cell, but also reduces the resistance of the solder area and improves the performance of the battery cell.

[0039] The following is combined with Figures 1 to 7 The following describes embodiments of the present invention.

[0040] According to an embodiment of the present invention, in a first aspect, a battery cell 100 is provided, including a housing 10, an electrode assembly 20, electrode terminals 30, and a metal reinforcing member 40. The electrode assembly 20 is disposed within the housing 10, and includes an electrode body 21 and electrode tabs 22 connected to the electrode body 21. The electrode terminals 30 are disposed within the housing 10 and electrically connected to the electrode tabs 22. The metal reinforcing member 40 is welded to the electrode tabs 22 and the electrode terminals 30.

[0041] The outer casing 10 is used to accommodate the electrode assembly 20. Furthermore, the outer casing 10 may also contain electrolyte, etc. The outer casing 10 may include a housing 11 and a cover 12 disposed on at least one side of the housing 11 along a first direction X. In the figure, the first direction X represents the length direction of the battery cell 100, the second direction Y represents the width direction of the battery cell 100, and the third direction Z represents the height direction of the battery cell 100. The first direction X, the second direction Y, and the third direction Z are perpendicular to each other. The outer casing 10 may have an opening on only one side, with the cover 12 sealing one opening of the outer casing 10, thereby the cover 12 and the outer casing 10 together forming a storage space for accommodating the electrode assembly 20. The outer casing 10 may also have openings on both opposite sides, with a cover 12 disposed at each opening, the two covers 12 and the outer casing 10 together forming a storage space for accommodating the electrode assembly 20. The material of the outer casing 10 may be aluminum, aluminum alloy, stainless steel, etc. The outer casing 10 may be square, blade-shaped, etc.

[0042] Electrode terminals 30 are components that connect electrode assembly 20 to external circuitry for inputting and outputting electrical energy. Electrode terminals 30 can be disposed on cover 12, forming a top cover assembly with cover 12. Electrode terminals 30 can also be disposed on housing 11.

[0043] As an example, electrode terminal 30 can be a pole post, which includes a riveting block and a riveting post that are riveted together. The riveting post is located on the side of the cover 12 near the electrode group 20, and the riveting block is located on the side of the cover 12 away from the electrode group 20. The riveting block is used to connect to an external circuit, and the riveting post is used to electrically connect to the tab 22.

[0044] As another example, the electrode terminal 30 can also be an integral structural component, i.e., a non-riveted structure, which passes through the cover 12. One part of this component is located on the side of the cover 12 closer to the electrode assembly 20 for electrical connection with the electrode tab 22, while the other part is located on the side of the cover 12 away from the electrode assembly 20 for connection to an external circuit. An insulating component, such as a plastic gasket, can also be provided between the electrode terminal 30 and the cover 12. The cover 12 can also be provided with a liquid injection hole, a pressure relief mechanism (such as an explosion-proof valve), etc.

[0045] The electrode assembly 20 is a component in the battery cell 100 where a chemical reaction occurs to provide electrical energy. The electrode body 21 may include a positive electrode, a negative electrode, and a separator disposed between the positive and negative electrode. The electrode body 21 can be a wound structure or a stacked structure. A tab 22 can be led out from one end of the electrode body 21 or from opposite ends of the electrode body 21. When the tab 22 is led out from opposite ends of the electrode body 21, one end of the tab 22 can be a positive tab, and the other end of the tab 22 can be a negative tab. The positive tab is electrically connected to the electrode terminal 30 on the same side, and the negative tab is electrically connected to the electrode terminal 30 on the same side. The positive tab can be integrally formed with the positive current collector of the positive electrode, and the negative tab can be integrally formed with the negative current collector of the negative electrode. The positive tab can be made of aluminum, and the negative tab can be made of copper.

[0046] The metal reinforcing member 40 is welded to the tab 22 and the electrode terminal 30 to electrically connect the tab 22, the electrode terminal 30, and the metal reinforcing member 40. The metal reinforcing member 40, tab 22, and electrode terminal 30 can be welded together in one step or in stages. Staged welding involves first pre-welding the tab 22 to the electrode terminal 30, and then finally welding the metal reinforcing member 40 to both tab 22 and electrode terminal 30, i.e., two welding processes. Welding methods include laser welding, ultrasonic welding, and thermoforming welding.

[0047] The metal reinforcing member 40 can be made of aluminum, copper, magnesium, aluminum alloy, or nickel alloy, etc. The material of the metal reinforcing member 40 can be the same as or different from that of the tab 22. For example, the metal reinforcing member 40 welded to the positive tab can be made of aluminum, while the metal reinforcing member 40 welded to the negative tab can be made of copper. When the material of the metal reinforcing member 40 is the same as that of the tab 22, it can provide better bonding performance during welding, reduce the risk of incomplete soldering, and improve connection reliability.

[0048] It is worth noting that the metal reinforcement 40 is a component independent of the tab 22, and is not a structure on the tab 22 itself.

[0049] The metal reinforcement 40 is welded to the tab 22 and the electrode terminal 30, fixing the three together to achieve electrical connection. The metal reinforcement 40 can not only improve the connection strength between the tab 22 and the electrode terminal 30 and improve the reliability of the cell 100, but also reduce the internal resistance at the connection between the tab 22 and the electrode terminal 30, improve the overcurrent capacity, and thus improve the performance of the cell 100. In particular, the cell 100 can also meet the overcurrent capacity and reliability in high-power or fast charging and discharging scenarios.

[0050] In some embodiments, along the thickness direction of the tab 22 ( Figure 2 and Figure 3In the direction of X, the metal reinforcement 40, the tab 22 and the electrode terminal 30 are stacked, with the tab 22 located between the metal reinforcement 40 and the electrode terminal 30; the tab 22 and the electrode terminal 30 are welded through the first welding part A', and a solder mark area A is formed on the side of the tab 22 away from the electrode terminal 30; the metal reinforcement 40 is disposed in the solder mark area A, and is welded to the tab 22 and the electrode terminal 30 through the second welding part B'.

[0051] Along the thickness direction of the tab 22, the tab 22 has a side facing away from the electrode terminal 30 and another side facing towards the electrode terminal 30. The side of the tab 22 facing towards the electrode terminal 30 is in contact with the electrode terminal 30. A first welding portion A' connects the tab 22 and the electrode terminal 30, and a solder area A is formed on the side facing away from the electrode terminal 30. The first welding portion A' is a molten structure formed when the tab 22 and the electrode terminal 30 are welded. It can be understood that the solder area A is a welding area composed of multiple first welding portions A'.

[0052] Along the thickness direction of tab 22 ( Figure 2 and Figure 3 In the direction of X (where X is located), the metal reinforcement 40 has a side facing away from the electrode tab 22 and another side facing towards the electrode tab 22. The side of the metal reinforcement 40 facing towards the electrode tab 22 is in contact with the electrode tab 22. A second weldment B' connects the metal reinforcement 40, the electrode tab 22, and the electrode terminal 30. Another solder area B is formed on the side of the metal reinforcement 40 facing away from the electrode tab 22. The second weldment B' is a molten structure formed when the metal reinforcement 40, the electrode tab 22, and the electrode terminal 30 are welded. This other solder area B can be a welding area composed of multiple second weldment B's.

[0053] First, the tab 22 and the electrode terminal 30 are pre-welded to form a solder area A (first solder area). Then, the metal reinforcement 40 is placed in the solder area A and finally soldered to the tab 22 and the electrode terminal 30 to form another solder area B (second solder area). The second welded portion B' on the second solder area at least partially overlaps with the first welded portion A' on the first solder area.

[0054] If ultrasonic welding is used, the frequency for the first pre-weld can be 10Hz~40Hz, and the frequency for the second final weld can be 20Hz~100Hz. If laser welding is used, the power for the first pre-weld can be 300W~800W, and the power for the second final weld can be 400W~1500W. If thermocompression welding is used, the pressure for the first pre-weld can be 0.4MPa~1MPa, and the pressure for the second pre-weld can be 0.2MPa~0.55MPa.

[0055] Along the thickness direction of tab 22 ( Figure 2 and Figure 3In the direction of X, the metal reinforcement 40, the tab 22, and the electrode terminal 30 are stacked to increase the contact area and improve the current carrying capacity. After the tab 22 and the electrode terminal 30 are pre-welded, they form an initial bond in the soldering area A, making the connection between the tab 22 and the electrode terminal 30 tighter. The final welding of the metal reinforcement 40 with the tab 22 and the electrode terminal 30 in the soldering area A can avoid uneven energy distribution caused by the thickness difference of the multi-layer materials (metal reinforcement 40, tab 22, and electrode terminal 30) during synchronous welding, reduce the risk of poor welding, overheating, or insufficient penetration, and also reduce the internal resistance of the soldering area A, improve the current carrying capacity, and reduce the temperature rise. Thus, the connection strength between the tab 22 and the electrode terminal 30 and the charging and discharging performance of the cell 100 can be further improved.

[0056] In some embodiments, the area of ​​the solder area A is S1, which is along the thickness direction of the tab 22 ( Figure 3 (In the direction of X), the orthographic projection area of ​​the metal reinforcing member 40 on the solder area A is S2, 0.25≤S2 / S1<1. S2 / S1 can be 0.25, 0.3, 0.35, 0.4, 0.5, 0.6, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 0.99 or any value range between the two.

[0057] When S2 / S1 is greater than or equal to 0.25, the welding area between the metal reinforcement 40 and the tab 22 and electrode terminal 30 can be increased, improving the connection strength and reducing the internal resistance of the tab 22. When S2 / S1 is less than 1, the area of ​​the metal reinforcement 40 is smaller than the area of ​​the solder area A, which can avoid the risk of the metal reinforcement 40 piercing the tab 22 and causing the tab 22 to break. Therefore, when 0.25≤S2 / S1<1, the welding area between the metal reinforcement 40 and the tab 22 and electrode terminal 30 can be increased, improving the connection strength and reducing the internal resistance of the tab 22, while also avoiding the risk of the metal reinforcement 40 piercing the tab 22 and causing the tab 22 to break.

[0058] In some embodiments, the soldering area A is rectangular, with a length of L1 and a width of W1; the metal reinforcement 40 is rectangular, with a length of L2 and a width of W2; wherein, 0.5*L1≤L2<L1, and / or, 0.5*W1≤W2<W1.

[0059] When L2 is greater than or equal to 0.5*L1, and / or W2 is greater than or equal to 0.5*W1, the welding area between the metal reinforcement 40 and the tab 22 and electrode terminal 30 can be increased, thus improving the connection strength. When L2 is less than L1, and / or W2 is less than W1, the risk of the metal reinforcement 40 piercing the tab 22 and causing it to break can be avoided, thus improving the connection reliability. Therefore, when 0.5*L1≤L2<L1, and / or 0.5*W1≤W2<W1, both connection strength and connection reliability can be improved.

[0060] In some embodiments, 5mm ≤ L1 ≤ 50mm, and / or 3mm ≤ W1 ≤ 20mm. L1 can be 5mm, 15mm, 20mm, 30mm, 35mm, 40mm, 45mm, 50mm, or any value between two of these. W1 can be 3mm, 5mm, 7mm, 10mm, 15mm, 20mm, or any value between two of these.

[0061] When L1 is greater than or equal to 5mm, and / or W1 is greater than or equal to 3mm, the connection strength can be improved; when L1 is less than or equal to 50mm, and / or W1 is less than or equal to 20mm, the deformation of the tab 22 can be reduced; therefore, when 5mm≤L1≤50mm, and / or 3mm≤W1≤20mm, both the welding strength and the deformation of the tab 22 can be increased.

[0062] In some embodiments, the thickness of the metal reinforcement 40 is T, where 0.1 mm ≤ T ≤ 5 mm. T can be 0.1 mm, 0.5 mm, 0.8 mm, 1 mm, 1.5 mm, 2 mm, 3 mm, 4 mm, 4.5 mm, 5 mm, or any value between the two.

[0063] When T is greater than or equal to 0.1 mm, it can improve the connection strength and overcurrent capacity; when T is less than or equal to 5 mm, it can reduce the space occupied by the casing 10, which helps to improve the volumetric energy density of the cell 100; therefore, when 0.1 mm ≤ T ≤ 5 mm, it can improve the connection strength and overcurrent capacity, reduce the space occupied by the casing 10, and improve the volumetric energy density of the cell 100.

[0064] In some embodiments, the melting point of the metal reinforcement 40 is not lower than (i.e., greater than or equal to) 650°C; and / or, the electrical conductivity of the metal reinforcement 40 is not lower than (i.e., greater than or equal to) 1*10 7 S / m.

[0065] The metal reinforcing member 40 has a melting point of not less than 650°C, resulting in a smaller heat-affected zone during welding, preventing melting and deformation during welding, maintaining a certain level of rigidity, and improving connection reliability. For example, the metal reinforcing member 40 may be made of aluminum, which has a melting point of approximately 660°C; or it may be made of copper, which has a melting point of approximately 1085°C.

[0066] The electrical conductivity of the metal reinforcement 40 is not less than 1*10 7 The S / m value improves current carrying capacity. The conductivity of the metal reinforcement 40 can be measured at room temperature using an AC micro-resistance meter.

[0067] Below, taking the blade battery cell 100 with tabs 22 at both ends as an example, the charging strategy remains the same (charging current is the same). The metal reinforcing member 40 connected to the positive tab is made of aluminum, and the metal reinforcing member 40 connected to the negative tab is made of copper. The welding method is laser welding, and the welding area between the metal reinforcing member 40 and the tabs 22 and electrode terminals 30 is 100mm². 2 The resistance of the 22-ohm electrode of the electrode with and without the metal reinforcement 40 is compared with that of the electrode with the metal reinforcement 40 (Table 1) and the temperature change. Figure 5 , Figure 6 Table 2 shows the influence of the ratio of the orthographic projection area S2 of the metal reinforcement 40 on the solder area A to the area S1 of the solder area on the internal resistance of the tab and the degree of tab breakage risk in different embodiments and comparative examples.

[0068] Table 1

[0069]

[0070] Table 2

[0071]

[0072] As shown in Table 1, the ohmic resistance of the positive electrode tab of the non-metallic reinforcing member 40 at the solder mark is 7.25 × 10⁻⁶. -5 The negative electrode tab of the non-metallic reinforcing member 40 has an ohmic resistance of 5.57*10 at the solder joint. -5 The positive electrode tab with metal reinforcement 40 has an ohmic resistance of 1.23*10 Ω at the solder joint. -5 The negative electrode tab with metal reinforcement 40 has an ohmic resistance of 5.47*10 at the solder joint. -6 Ω. It can be seen that the ohmic resistance at the solder joint of the positive and negative electrodes with metal reinforcement is significantly lower than that of the positive and negative electrodes without metal reinforcement. Therefore, the positive and negative electrodes with metal reinforcement can achieve better charge and discharge performance.

[0073] The method for measuring ohmic resistance is as follows: Based on the simulation software (COMSOL Multiphysics), current is input into the outer surface of electrode terminal 30, and current is output at the bottom of tab 22 (the connection position between tab 22 and electrode body 21) to obtain the ohmic resistance of tab 22.

[0074] Figure 5 , Figure 6 A comparison of the temperature changes of the tabs in the cell with and without the metal reinforcement 40 in the soldering area A (taking the negative tab as an example) is shown. The fast charging conditions and ambient temperature (such as 20°~25°) are kept consistent.

[0075] The temperature measurement method is as follows: the ambient temperature is 20°C to 25°C; the fast charging mode uses stepped fast charging; the charging voltage is 800V; the maximum current is 700A; and the charging time is until full charge. A multiphysics model including electric and thermal fields is constructed using simulation software (COMSOL Multiphysics) to simulate the heat generated when current passes through the material and the resulting temperature change. Figure 5 and Figure 6 .

[0076] The temperature distribution results show that Figure 5 The maximum temperature of the solder area of ​​the negative electrode tab of the non-metallic reinforcing member 40 is approximately 53.16℃. Figure 6 The maximum temperature of the solder area of ​​the negative electrode tab with metal reinforcement 40 is approximately 52.16℃, which is about 1℃ lower than the maximum temperature of the solder area of ​​the negative electrode tab without metal reinforcement 40. Figure 5 and Figure 6 The maximum temperature occurs at the connection point between the tab 22 and the electrode body 21, that is, at the root of the tab 22, while the minimum temperature occurs at the top cover.

[0077] As shown in Table 2, when S2 / S1 is 0.25, 0.5, and 0.9, the resistance of the positive and negative electrodes with metal reinforcement is lower than that of the positive and negative electrodes without metal reinforcement, and also lower than the resistance when S2 / S1 is 0.1. When S2 / S1 is 0.1, although the resistance of the positive and negative electrodes with metal reinforcement is lower than that of the positive and negative electrodes without metal reinforcement, there is a risk of unstable connection strength. When S2 / S1 is 1 or 1.5, there is a risk of electrode breakage.

[0078] According to an embodiment of the present invention, in a second aspect, a battery pack is provided, including a battery cell 100 according to any embodiment of the first aspect.

[0079] The battery pack may include a housing, in which the battery modules are housed. The housing may be part of the vehicle's chassis structure. For example, a portion of the housing may be at least a part of the vehicle's floor, or a portion of the housing may be at least a part of the vehicle's crossbeams and longitudinal beams.

[0080] Battery packs can be used in vehicles, energy storage, and other fields. Vehicles can be gasoline vehicles, natural gas vehicles, or new energy vehicles. New energy vehicles can be pure electric vehicles, hybrid vehicles, or range-extended vehicles, etc.

[0081] According to an embodiment of the present invention, a third aspect provides a method for manufacturing a battery cell, applicable to a battery cell 100 in any embodiment of the first aspect, the method comprising steps S11 and S12.

[0082] Step S11: Pre-solder the tab 22 and the electrode terminal 30 to form a first solder area A on the surface of the tab 22.

[0083] Step S12: Place the metal reinforcement 40 in the first soldering area A, and solder the metal reinforcement 40, the tab 22 and the electrode terminal 30.

[0084] As mentioned above, the welding connection between the metal reinforcing member 40, the tab 22, and the electrode terminal 30 is a step-by-step welding process. First, the tab 22 and the electrode terminal 30 are pre-welded, and then the metal reinforcing member 40 is finally welded to the tab 22 and the electrode terminal 30, requiring two welding operations. The welding can be laser welding, ultrasonic welding, or thermoforming welding, etc.

[0085] After the tab 22 and the electrode terminal 30 are pre-welded, a preliminary bond is formed in the soldering area A, making the connection between the tab 22 and the electrode terminal 30 tighter. The final welding of the metal reinforcement 40 with the tab 22 and the electrode terminal 30 is carried out in the soldering area A. This can avoid uneven energy distribution caused by the thickness difference of the multi-layer materials (metal reinforcement 40, tab 22 and electrode terminal 30) during synchronous welding, reduce the risk of poor welding, overheating or insufficient penetration, and also reduce the internal resistance of the soldering area A, improve the current carrying capacity and reduce the temperature rise. As a result, the connection strength between the tab 22 and the electrode terminal 30 and the charging and discharging performance of the cell 100 can be further improved.

[0086] Unless otherwise stated, the values ​​of all parameters mentioned in this application can be determined using testing methods commonly used in the art. Unless otherwise stated, the test temperature for all parameters is 25°C.

[0087] Although embodiments of the present invention have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the present invention, and all such modifications and variations fall within the scope of the present invention.

Claims

1. A battery cell, characterized in that, include: shell; An electrode assembly is disposed within the housing, the electrode assembly comprising an electrode body and tabs connected to the electrode body; Electrode terminals are disposed on the housing and electrically connected to the electrode tabs; A metal reinforcing member is welded to the electrode tab and the electrode terminal; along the thickness direction of the electrode tab, the electrode tab is located between the metal reinforcing member and the electrode terminal; The tab and the electrode terminal are pre-welded through the first welding part, and a solder area is formed on the side of the tab away from the electrode terminal; The metal reinforcing member is disposed in the soldering area and is welded to the tab and the electrode terminal through the second welding part; the area of ​​the soldering area is S1, and the orthogonal projection area of ​​the metal reinforcing member on the soldering area along the thickness direction of the tab is S2, satisfying 0.25≤S2 / S1<1.

2. The battery cell according to claim 1, characterized in that, The soldering area is rectangular, with a length of L1 and a width of W1. The metal reinforcing member is rectangular, with a length of L2 and a width of W2. Where 0.5*L1≤L2<L1, and / or 0.5*W1≤W2<W1.

3. The battery cell according to claim 2, characterized in that, The length L1 of the solder area satisfies 5mm≤L1≤50mm, and / or the width W1 of the solder area satisfies 3mm≤W1≤20mm.

4. The battery cell according to any one of claims 1-3, characterized in that, The thickness of the metal reinforcement is T, which satisfies 0.1mm≤T≤5mm.

5. The battery cell according to any one of claims 1-3, characterized in that, The melting point of the metal reinforcement is not lower than 650°C; and / or, The electrical conductivity of the metal reinforcement is not less than 1*10. 7 S / m.

6. The battery cell according to any one of claims 1-3, characterized in that, The metal reinforcing member is made of the same material as the electrode tab; and / or, The metal reinforcement is made of at least one of aluminum, copper, magnesium, aluminum alloy, and nickel alloy.

7. A battery pack, characterized in that, Includes the battery cell described in any one of claims 1-6.

8. A method for manufacturing a battery cell, characterized in that, The method of manufacturing the battery cell, applicable to any one of claims 1-6, comprises: The tabs and electrode terminals are pre-welded to form solder areas; The metal reinforcement is placed in the soldering area, and the metal reinforcement, the tab, and the electrode terminal are soldered.

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