Battery cell, battery module and battery pack

Abstract

The invention provides a battery cell, a battery module and a battery pack, and relates to the technical field of lithium ion batteries, all parts of the battery cell are provided with electric connection positions, and the two sides of the electric connection positions are electrically connected by adopting the same metal. The method has the beneficial effects that a scene of dissimilar metal contact is completely avoided, so that an electrode potential difference does not exist, the generation condition of a primary battery effect is blocked from the source, an electrochemical corrosion phenomenon is thoroughly avoided at an electric connection position, the electric connection structure can be ensured to keep structural integrity in the whole life cycle of a battery cell, and the service life of the battery cell is prolonged. And the long-term reliability of the electric connection part is obviously improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium ion batteries, in particular to a battery cell, a battery module and a battery pack. BACKGROUND

[0002] With the rapid development of new energy industry, the market has higher requirements for the energy density, rate discharge performance and cycle life of the battery cell. The electrical connection structure is the core link for efficient transmission of current between the internal parts (such as the current collector, the tab, and the electrode terminal) of the battery cell and the external circuit, and its performance directly determines the charge and discharge efficiency, cycle life and application safety of the battery cell.

[0003] Currently, for cylindrical battery cells, square aluminum shell battery cells or steel shell battery cells, the internal key electrical connection positions, such as the connection between the shell / cover plate and the tab, the connection between the tab and the positive / negative current collector, and the connection between the electrode terminal and the internal conductive part, generally adopt a design scheme of heterogeneous metal connection due to factors such as material property adaptation, assembly process compatibility or cost control.

[0004] However, the internal part of the battery cell is in a complex environment of electrolyte immersion for a long time, and in the process of charge and discharge cycle or high temperature working condition (such as high rate discharge heating, vehicle environment temperature fluctuation, etc.), the heterogeneous metal connection position will form a primary cell effect due to the difference in metal electrode potential, and then cause continuous electrochemical corrosion. This corrosion problem will have multidimensional negative effects on the performance and safety of the battery cell, which is specifically manifested as: 1. When the corrosion is mild, the corrosion product will adhere to the electrical connection interface or dissolve in the electrolyte, increasing the risk of micro-short circuit in the battery cell, causing abnormal increase in self-discharge rate of the battery cell, and significantly reducing the storage performance and cycle life; 2. When the corrosion is moderate, the corrosion will gradually destroy the structural integrity of the electrical connection position, significantly increasing the contact resistance of the connection part, not only intensifying the joule heat generated in the process of charge and discharge of the battery cell, but also forming a vicious cycle of accelerated corrosion caused by increased internal resistance, which further deteriorates the electrical performance of the battery cell; 3. When the corrosion is severe, the metal debris or flocculent corrosion product generated by electrochemical corrosion will migrate to the winding core area with the electrolyte flow, and if it penetrates the diaphragm structure in the winding core, it will directly cause short circuit of the positive and negative materials, causing serious safety accidents such as fire and explosion of the battery cell.

[0005] In summary, the electrochemical corrosion hidden danger of the heterogeneous metal electrical connection structure in the existing lithium ion battery cell has become a key bottleneck restricting the long-term reliability and application safety of the battery cell, and an electrical connection optimization scheme that can avoid this problem from the structural design level is urgently needed. SUMMARY

[0006] In view of the problems in the prior art, the application provides a battery cell, which has an electrical connection position between each component of the battery cell, and the same metal is used for electrical connection on both sides of the electrical connection position.

[0007] Preferably, each of the components includes a shell, positive and negative terminals arranged at both ends of the shell, and a winding core arranged in the shell.

[0008] Preferably, the shell is formed by combining an inner support layer and an outer conductive layer.

[0009] Preferably, a first through hole is arranged at one end of the shell, and the positive terminal extends out of the first through hole. The electrical connection position between the positive terminal and the first through hole is welded by the outer conductive layer at the first through hole.

[0010] Preferably, a cover plate is arranged at the other end of the shell, the cover plate and the inner support layer are made of the same metal, and the cover plate and the shell are welded at the electrical connection position by the side of the cover plate and the inner support layer of the shell.

[0011] Preferably, a positive current collector is further arranged at the side close to the positive terminal in the shell, a second through hole is arranged at the center of the positive current collector, and the positive terminal is fixed in and extends out of the second through hole. The electrical connection position between the positive terminal and the positive current collector is welded by the outer side surface of the pole of the positive terminal and the inner wall of the second through hole.

[0012] Preferably, a negative current collector is further arranged at the side close to the negative terminal in the shell, the negative current collector includes a center area and an edge area arranged in a circumferential direction at the edge of the center area, and a step is formed between the center area and the edge area. The electrical connection position between the negative tab and the negative current collector is welded by the center area of one surface of the negative current collector and the negative tab. The electrical connection position between the negative current collector and the cover plate is welded by the edge area of the other surface of the negative current collector and the side of the cover plate facing the winding core.

[0013] Preferably, the inner support layer is stainless steel or titanium steel, and the outer conductive layer is aluminum or copper.

[0014] The application further provides a battery module comprising the battery cell.

[0015] The application further provides a battery pack comprising the battery module.

[0016] The technical scheme has the following advantages or beneficial effects: 1) The same metal is used for electrical connection on both sides of the electrical connection position of each component in the battery cell, completely avoiding the scenario of contact between different metals, and thus there is no electrode potential difference, which breaks the condition for the generation of primary battery effect from the root, so that the electrical connection position completely avoids electrochemical corrosion, ensuring that the electrical connection structure can maintain structural integrity throughout the life cycle of the battery cell, significantly improving the long-term reliability of the electrical connection part; 2) The electrical connection position is welded by the same metal, and there is no premise for the generation of corrosion products, so the hidden danger of micro-short circuit caused by corrosion at the welding position can be completely avoided, so that the self-discharge rate of the battery cell is always maintained at a very low stable level, which not only ensures the capacity retention rate of the battery cell during long-term storage, but also avoids the problem of consistency decline of the battery cell caused by uneven self-discharge, and improves the overall performance stability of the battery pack; 3) The crystal structure and physical properties of the same metal are more matched, and a more dense and stronger connection interface can be formed during welding, and there is no interface impedance caused by material difference, so that the contact resistance of the electrical connection position can be significantly reduced, reducing the joule heat loss during charging and discharging of the battery cell, improving the energy conversion efficiency of the battery cell, and avoiding the problem of local overheating caused by the increase of contact resistance, especially suitable for high-rate charging and discharging scenarios, and ensuring the performance stability of the battery cell under high-power working conditions; 4) Since electrochemical corrosion is completely eliminated and no corrosion products are generated, the risk of corrosion products piercing the separator is completely eliminated, and the interface structure of the same metal welding is more stable and will not cause structural failure problems such as connection part fracture and falling off due to corrosion, further reducing the possibility of internal short circuit of the battery cell, greatly improving the safety redundancy of the battery cell in various application scenarios, and providing reliable technical support for fields such as power batteries and energy storage batteries which have high safety requirements. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 For a preferred embodiment of the present application, an overall cross-sectional view of a battery cell; Figure 2 For a preferred embodiment of the present application, an overall exploded view of a battery cell; Figure 3 For a preferred embodiment of the present application, a cross-sectional view of the part of the battery cell close to the positive terminal; Figure 4 For a preferred embodiment of the present application, a structural schematic view of the first through hole; Figure 5 For a preferred embodiment of the present application, a cross-sectional view of the part of the battery cell close to the negative terminal.

[0018] In the figure: 1. Shell; 11. First through hole; 12. Inner support; 13. Outer conductive layer; 2. Cover plate; 3. Positive terminal; 4. Negative terminal; 5. Core; 6. Positive current collector; 7. Negative current collector; 71. Central region; 72. Edge region. Detailed Implementation

[0019] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. The present invention is not limited to this embodiment; other embodiments that conform to the spirit of the present invention may also fall within the scope of the present invention.

[0020] In a preferred embodiment of the present invention, based on the above-mentioned problems existing in the prior art, a battery cell is provided, wherein each component of the battery cell has an electrical connection position, and the two sides of each electrical connection position are electrically connected by the same metal.

[0021] Specifically, such as Figures 1 to 5 As shown, each component includes a housing 1, one end of which has a first through hole 11 and the other end is covered with a cover plate 2. It also includes a positive terminal 3 and a negative terminal 4 disposed at both ends of the housing 1, a core 5 disposed inside the housing 1, a positive current collector 6 corresponding to the positive terminal 3 and a negative current collector 7 corresponding to the negative terminal 4, and the positive terminal 3 extends out from the first through hole 11. The electrical connection positions include at least one of the following: connection position a between the positive terminal 3 and the first through hole 11; connection position b between the positive terminal 3 and the positive current collector 6; connection position c between the positive electrode tab of the core 5 and the positive current collector 6; connection position d between the negative electrode tab of the core 5 and the negative current collector 7; connection position e between the negative current collector 7 and the cover plate 2; and connection position f between the cover plate 2 and the housing 1.

[0022] More specifically, the shell 1 is formed by an inner support layer 12 and an outer conductive layer 13, forming a whole. The inner support layer 12 can be stainless steel or titanium steel, or other metals with excellent chemical stability and supporting function. Compared with the problems of traditional pure aluminum shells being easily corroded by electrolytes and pure steel shells being heavy, the inner support layer 12 formed by stainless steel or titanium steel can directly contact the electrolyte environment inside the battery cell. It can effectively resist the corrosion of electrolytes, extend the service life of the shell 1, and provide stable support for the core 5, preventing structural deformation of the battery cell under vibration, impact and other conditions.

[0023] The outer conductive layer 13 can be aluminum or copper, or other highly conductive metals. Its conductivity is much higher than that of the inner support layer 12. Compared with the problem that the overcurrent internal resistance of the traditional pure steel shell exceeds 70%, the composite shell can significantly reduce the overall conductivity resistance of the shell 1 through the high conductivity of the outer conductive layer 13, thereby reducing Joule heat loss during the charging and discharging process of the battery cell, and is especially suitable for high-rate charging and discharging scenarios.

[0024] Further, due to the adoption of the composite structure of the inner supporting layer 12 and the outer conductive layer 13, the strength can be achieved without relying on the thick structure of the pure steel shell, and the additional corrosion-resistant coating of the pure aluminum shell is not needed, and compared with the pure steel shell of the same strength, the weight of the structural member can be reduced by 30%, directly improving the energy density of the battery cell.

[0025] Further, the same metal matching is achieved for the electrical connection positions between the components of the battery cell, which fundamentally blocks the primary cell effect caused by the contact of dissimilar metals, and at the same time, the connection reliability and conductivity are strengthened, specifically including: 1. For the electrical connection position related to the positive electrode terminal 1) Connection position a: connection position of the positive electrode terminal 3 and the first through hole 11 As shown in Figure 3 and Figure 4 , the positive electrode terminal 3 and the first through hole 11 are connected by welding the outer conductive layer 13 of the positive electrode terminal 3 and the first through hole 11 at the connection position a.

[0026] Among them, the positive output end of the positive electrode terminal 3 and the outer conductive layer 13 of the shell side wall at the first through hole 11 adopt the same metal, preferably Al, or copper, which is not limited here, as long as it has good wire performance. The crystal structure and physical properties of the same metal are consistent, and a dense connection interface without gaps and brittle compounds can be formed during welding, which not only avoids the problems of virtual welding and gaps that easily occur during welding of dissimilar metals, but also completely eliminates the electrode potential difference, without the risk of electrochemical corrosion; at the same time, the high-conductive connection of Al / Al or Cu / Cu effectively reduces the contact resistance at this position, ensuring the transmission efficiency of the positive electrode current from the pole to the outer conductive layer of the shell.

[0027] 2) Connection position b: connection position of the positive electrode terminal 3 and the positive electrode current collector 6 In the preferred embodiment of the present application, as shown in Figure 3 , a second through hole is provided in the center of the positive electrode current collector 6, and the positive electrode terminal 3 is fixed in the second through hole and extends out of the second through hole; The positive electrode terminal 3 and the positive electrode current collector 6 are connected by welding the outer side surface of the pole 31 of the positive electrode terminal 3 and the inner wall of the second through hole at the connection position b.

[0028] Among them, the second through hole is covered by the positive electrode terminal 3 extending out of it, which is not shown in the figure. The material of the positive electrode current collector 6 is preferably Al (consistent with the material of the positive output end), and the inner wall of the second through hole provided in the center and the outer side surface of the pole 31 of the positive electrode terminal 3 are both Al, which are connected by laser welding. The high-precision laser welding with the same Al material can achieve seamless connection of the pole 31 and the positive electrode current collector 6, not only avoiding the increase of contact resistance caused by corrosion, but also preventing the infiltration of electrolyte from the connection gap into the pole area, improving the sealing reliability.

[0029] 3) Connection position c: connection position of the positive electrode tab of the winding core 5 and the positive electrode current collector disc 6 As shown in the figure, the material of the positive electrode tab of the winding core 5 is preferably Al, which is fully matched with the Al material of the positive electrode current collector disc 6, and a unified conductive path is formed after welding, which avoids the generation of corrosion products (such as Al-Cu intermetallic compounds) compared with the heterogeneous connection of traditional Al tabs and Cu current collector discs, thereby avoiding the risk of self-discharge caused by micro-short circuit due to corrosion and ensuring the current collection efficiency from the positive electrode tab to the positive electrode current collector disc 6 and reducing local heating. Figure 3 2) Connection position e: connection position of the negative electrode current collector disc 7 and the cover plate 2

[0030] 1) Connection position d: connection position of the negative electrode tab of the winding core 5 and the negative electrode current collector disc 7 In the preferred embodiment of the present application, the negative electrode current collector disc 7 comprises a central region 71 and an edge region 72 arranged circumferentially at the edge of the central region 71, and a step is formed between the central region 71 and the edge region 72; The negative electrode tab and the negative electrode current collector disc 7 are welded at the connection position d through the central region 71 of one surface of the negative electrode current collector disc 7. In the preferred embodiment of the present application, the negative electrode tab of the winding core 5 is preferably made of Cu, and the central region 71 of the negative electrode current collector disc 7 is also made of Cu, and the two are welded together. The welding interface of the same Cu material has excellent conductivity and no risk of electrochemical corrosion, which can avoid the performance degradation of the battery cell caused by the dissolution of corrosion products (such as Cu oxides) in the electrolyte when the traditional Cu tab is connected with the stainless steel current collector disc, and the high conductivity of Cu further reduces the internal resistance of the negative electrode current collector disc; 2) Connection position e: connection position of the negative electrode current collector disc 7 and the cover plate 2

[0031] In the preferred embodiment of the present application, the negative electrode current collector disc 7 and the cover plate 2 are welded at the connection position e through the edge region 72 of the other surface of the negative electrode current collector disc 7 and the side of the cover plate 2 facing the winding core 5. In the preferred embodiment of the present application, the negative electrode current collector disc 7 and the cover plate 2 are welded at the connection position e through the edge region 72 of the other surface of the negative electrode current collector disc 7 and the side of the cover plate 2 facing the winding core 5.

[0032] In the preferred embodiment of the present application, the negative electrode current collector disc 7 and the cover plate 2 are welded at the connection position e through the edge region 72 of the other surface of the negative electrode current collector disc 7 and the side of the cover plate 2 facing the winding core 5.

[0033] 3) Connection position f: connection position of the cover plate 2 and the shell 1 In the preferred embodiment of the present application, the cover plate 2 and the inner support layer 12 are made of the same metal, and the cover plate 2 is welded to the inner support layer 12 of the shell 1 at the connecting position f through the side edge of the cover plate 2.

[0034] The cover plate 2 and the inner support layer 12 of the shell 1 are made of the same metal, and the side edge of the cover plate 2 is connected to the inner support layer 12 of the shell 1 by laser welding. The deep penetration characteristics of laser welding are compatible with the same metal, which can form a fully sealed welding seam. This not only avoids the risk of sealing failure (such as electrolyte leakage) when welding different metals, but also prevents the connecting position of the shell and the cover plate from being corroded by the internal electrolyte, further improving the overall sealing performance and service life of the battery cell.

[0035] Further, the aluminum column of the positive terminal 3 is an integrated body formed by riveting the positive current collector, insulator, sealing body, steel riveting ring, and aluminum column. The aluminum column and the positive current collector (Al) are connected by laser welding, and the welding of the same Al material ensures the electrical continuity between the aluminum column and the current collector, avoiding the increase of contact resistance when riveting different metals. The matching of the steel riveting ring and the related stainless steel parts of the shell further strengthens the structural stability of the integrated body, which can adapt to the internal electrolyte environment without additional corrosion prevention treatment.

[0036] In summary, through the cooperative design of the composite shell and the connection of each electrical connection position by the same metal, on the one hand, the electrical resistance of the shell 1 and the contact resistance of each connection position are effectively reduced, which further improves the charging and discharging efficiency of the battery cell, reduces the temperature rise during high-rate discharge, and realizes the improvement of electrical performance. On the other hand, the risk of electrochemical corrosion is completely eliminated, thereby prolonging the cycle life of the battery cell, reducing the self-discharge rate of the battery cell, and realizing the improvement of the reliability of the battery cell. In addition, since no corrosion products are generated, the risk of short circuit caused by corrosion products piercing the separator of the winding core is eliminated, the sealing structure of the composite shell and the same metal welding effectively reduces the electrolyte leakage rate, and the safety of the battery cell is improved. The weight of the structural part is reduced by 30%, all connection methods (laser welding, seam welding) are compatible with the existing battery cell production line, and mass production can be realized without large-scale equipment modification, which takes into account the performance and cost advantages.

[0037] The present application also provides a battery module comprising the above-mentioned battery cell.

[0038] The present application also provides a battery pack comprising the above-mentioned battery module.

[0039] The above description is only a preferred embodiment of the present application, and is not intended to limit the implementation and protection scope of the present application. Those skilled in the art should be able to realize that any equivalent replacement and obvious changes made according to the present application and the drawings should be included in the protection scope of the present application.

Claims

1. A battery cell, wherein the components of the battery cell have electrical connection points, characterized in that, The electrical connection points are made of the same type of metal on both sides.

2. The battery cell according to claim 1, characterized in that, Each of the components includes a housing, positive and negative terminals disposed at both ends of the housing, and a winding core disposed inside the housing.

3. The battery cell according to claim 2, characterized in that, The shell is formed by an inner support layer and an outer conductive layer.

4. The battery cell according to claim 3, characterized in that, A first through hole is provided at one end of the housing, and the positive terminal protrudes from the first through hole; The electrical connection between the positive terminal and the first through hole is achieved by welding the positive terminal to the outer conductive layer at the first through hole.

5. The battery cell according to claim 3, characterized in that, The other end of the housing is covered with a cover plate, which is made of the same metal as the inner support layer, and the cover plate is welded to the inner support layer of the housing at the electrical connection position through the side of the cover plate.

6. The battery cell according to claim 3, characterized in that, Inside the housing, near the positive terminal, there is a positive current collector plate. A second through hole is opened in the center of the positive current collector plate. The positive terminal is fixed in the second through hole and extends out of the second through hole. The positive terminal is electrically connected to the positive current collector at the connection point via the outer side of the positive terminal post and welded to the inner wall of the second through hole.

7. The battery cell according to claim 5, characterized in that, The housing is further provided with a negative electrode current collector plate near the negative terminal. The negative electrode current collector plate includes a central region and an edge region circumferentially arranged connecting the edge of the central region. A step is formed between the central region and the edge region. The negative electrode tab and the negative electrode current collector are electrically connected at the connection point by welding the negative electrode tab to the central area of ​​one side of the negative electrode current collector. The negative electrode current collector and the cover plate are electrically connected at the connection point through the edge region of the other side of the negative electrode current collector to the side of the cover plate facing the core.

8. The battery cell according to claim 3, characterized in that, The inner support layer is made of stainless steel or titanium steel, and the outer conductive layer is made of aluminum or copper.

9. A battery module, characterized in that, Includes the battery cell as described in any one of claims 1-8.

10. A battery pack, characterized in that, Includes the battery module described in claim 9.

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