Battery cell with winding lamination composite structure and preparation method of battery cell

Abstract

The invention discloses a battery cell with a winding lamination composite structure, which comprises a plurality of winding battery cell units and a plurality of lamination battery cell units, and two adjacent winding battery cell units are electrically connected through the lamination battery cell units; the laminated battery cell unit comprises a second positive plate, a second negative plate and a second diaphragm, the second diaphragm is folded in a Z-shaped reciprocating manner, and the second positive plate and the second negative plate are sequentially and alternately laminated on the two sides of the second diaphragm; the first positive plate and the first negative plate are respectively provided with a first positive tab and a first negative tab, the second positive plate and the second negative plate are respectively provided with a second positive tab and a second negative tab, the first positive tab and the second positive tab are electrically connected to form a first current collecting handle, and the first negative tab and the second negative tab are electrically connected to form a second current collecting handle. By adopting a winding lamination composite structure, the problem of non-uniform distribution of internal stress of the battery cell is solved. In addition, the invention also discloses a preparation method of the battery cell with the winding lamination composite structure.

Description

Technical Field

[0001] This invention belongs to the technical field of batteries, specifically relating to a battery cell with a wound and stacked composite structure and its preparation method. Background Technology

[0002] Currently, lithium-ion power battery cells are mainly manufactured using winding or stacking processes.

[0003] The wound structure has a mature technology, high efficiency, and low cost, but it suffers from problems such as uneven internal stress, high internal resistance, and limited rate performance. The laminated structure has a uniform stress distribution, longer cycle life, and better rate performance, but its manufacturing process is complex, inefficient, and has high equipment costs.

[0004] Lithium iron phosphate materials are widely used due to their high safety and long cycle life, but they also place higher demands on cell internal resistance and rate performance.

[0005] In the process of realizing this invention, the inventors discovered at least the following problems in the prior art: Existing battery cells use a single cell structure, resulting in uneven stress distribution within the cell, which makes them prone to deformation during battery cycling. Summary of the Invention

[0006] The purpose of this invention is to address the shortcomings of existing technologies by providing a battery cell with a wound lamination composite structure, which solves the problem of uneven stress distribution inside the battery cell.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: A battery cell with a wound and stacked composite structure includes multiple wound battery cell units and multiple stacked battery cell units. Two adjacent wound battery cell units are electrically connected through the stacked battery cell units. Each wound battery cell unit includes a first positive electrode, a first negative electrode, and a first separator. The first positive electrode, the first separator, and the first negative electrode are alternately stacked and wound to form the wound battery cell unit. Each stacked battery cell unit includes a second positive electrode, a second negative electrode, and a second separator. The second separator is folded in a "Z" shape. The second positive electrode and the second negative electrode are alternately stacked on both sides of the second separator. The first positive electrode and the first negative electrode are respectively provided with a first positive electrode tab and a first negative electrode tab. The second positive electrode and the second negative electrode are respectively provided with a second positive electrode tab and a second negative electrode tab. The first positive electrode tab and the second positive electrode tab are electrically connected to form a first current collector, and the first negative electrode tab and the second negative electrode tab are electrically connected to form a second current collector.

[0008] In some possible implementations, the first separator is located at the outermost ring of the wound cell unit, the second separator is located at the outermost layer of the stacked cell unit, and the ends of the first separator and the ends of the second separator are formed into an integral structure by thermal fusion.

[0009] In some possible implementations, there are multiple first positive tabs and multiple first negative tabs, and the projections of multiple first positive tabs and / or multiple first negative tabs overlap in the thickness direction.

[0010] In some possible implementations, there are multiple second positive electrode sheets and multiple second negative electrode sheets, each second positive electrode sheet is provided with a second positive electrode tab, each second negative electrode sheet is provided with a second negative electrode tab, and the projections of multiple second positive electrode tabs and / or multiple second negative electrode tabs overlap in the thickness direction.

[0011] In some possible implementations, the second diaphragm is folded multiple times to form multiple bends, and the second positive electrode and the second negative electrode are alternately placed in the multiple bends.

[0012] In some possible implementations, the end of the second diaphragm extends from the bottom of the stacked cell unit to the top of the stacked cell unit.

[0013] In some possible implementations, the end of the first separator is disposed around the outermost ring of the wound cell unit, and the end of the first separator is thermally fused with the second separator located on top of the stacked cell unit to form an integral structure. In some possible implementations, the number of wound cell units is N, where N is a positive integer greater than or equal to N.

[0014] In some possible implementations, the Nth winding cell unit and the N-th winding cell unit are symmetrically arranged on both sides of the stacked cell unit in the thickness direction.

[0015] On the other hand, a method for preparing a battery cell with a wound and stacked composite structure is provided, comprising: Step 1: Fabrication of wound cell units and stacked cell units; Step 2: Alternately arrange the wound cell units and the stacked cell units and hot-press them together; Step 3: Weld the first positive electrode tab and the second positive electrode tab together to form the first current collector, and then weld the first negative electrode tab and the second negative electrode tab together to form the second current collector. Step 4: Complete the subsequent shell insertion and liquid injection processes in sequence.

[0016] One of the above technical solutions has the following beneficial effects: This invention employs a wound and laminated composite structure, combining at least two wound cell units with a laminated cell unit located between them. The laminated cell unit acts as a buffer, absorbing internal stress and suppressing deformation during cell cycling, thus helping to extend the cell's cycle life. Simultaneously, the tabs of the wound and laminated cell units are welded together using ultrasonic welding or laser re-welding processes to form a low-impedance shared current collector, which reduces the cell's internal resistance and helps improve the cell's rate performance and fast charging performance. Attached Figure Description

[0017] The features, advantages and technical effects of exemplary embodiments of the present invention will now be described with reference to the accompanying drawings.

[0018] Figure 1 This is a schematic diagram of the structure of Embodiment 1 of the present invention.

[0019] Figure 2 This is a schematic diagram of the structure of Embodiment 2 of the present invention.

[0020] Figure 3 This is a schematic diagram of the structure of Embodiment 3 of the present invention.

[0021] The reference numerals in the attached figures are explained as follows: Winded battery cell unit; 11-First positive electrode plate; 12-First negative electrode plate; 13-First separator; 111-First positive electrode tab; 121-First negative electrode tab; Laminated battery cell unit; 21-Second positive electrode; 22-Second negative electrode; 23-Second separator; 211-Second positive electrode tab; 221-Second negative electrode tab; Bend; H - Thickness direction. Detailed Implementation

[0022] If certain terms are used in the specification and claims to refer to specific components, those skilled in the art will understand that hardware manufacturers may use different names to refer to the same component. This specification and claims do not distinguish components based on differences in name, but rather on differences in function. The term "comprising" as used throughout the specification and claims is an open-ended term and should be interpreted as "comprising but not limited to." "Approximately" means that within an acceptable margin of error, those skilled in the art can solve the technical problem and substantially achieve the technical effect within a certain margin of error.

[0023] Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be interpreted as indicating or implying relative importance.

[0024] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0025] The present invention will be further described in detail below with reference to the accompanying drawings, but this is not intended to limit the scope of the invention.

[0026] Example 1 Because existing battery cells use a single cell structure, the internal stress distribution of the cell is uneven, making it prone to deformation during battery cycling.

[0027] See Figure 1 As shown, the battery cell of the present invention with a wound and laminated composite structure includes multiple wound battery cell units 1 and multiple laminated battery cell units 2. Two adjacent wound battery cell units 1 are electrically connected through laminated battery cell units 2. The wound battery cell unit 1 includes a first positive electrode 11, a first negative electrode 12 and a first separator 13. The first positive electrode 11, the first separator 13 and the first negative electrode 12 are alternately layered and wound to form the wound battery cell unit 1. The laminated battery cell unit 2 includes a second positive electrode 21, a second negative electrode 22 and a second separator 23. The second separator 23... The second positive electrode 21 and the second negative electrode 22 are alternately stacked on both sides of the second diaphragm 23 in a "Z" shape. The first positive electrode 11 and the first negative electrode 12 are respectively provided with a first positive electrode tab 111 and a first negative electrode tab 121. The second positive electrode 21 and the second negative electrode 22 are respectively provided with a second positive electrode tab 211 and a second negative electrode tab 221. The first positive electrode tab 111 and the second positive electrode tab 211 are electrically connected to form a first current collector, and the first negative electrode tab 121 and the second negative electrode tab 221 are electrically connected to form a second current collector. This invention employs a wound and stacked composite structure, combining at least two wound cell units 1 with a stacked cell unit 2 located between them. The stacked cell unit 2 acts as a buffer, absorbing internal stress and suppressing deformation during cell cycling, thus helping to extend the cell's cycle life. Simultaneously, the tabs of the wound cell unit 1 and the stacked cell unit 2 are welded together using ultrasonic welding or laser re-welding processes to form a low-impedance shared current collector, which reduces the cell's internal resistance and helps improve the cell's rate performance and fast charging performance.

[0028] It should be noted that the first positive electrode tab 111 and the second positive electrode tab 211 are welded together using ultrasonic welding or laser re-welding to form the first current collector, and the first negative electrode tab 121 and the second negative electrode tab 221 are welded together using ultrasonic welding or laser re-welding to form the second current collector. This reduces the temperature rise during 3C continuous discharge, improving the battery's thermal safety and high-temperature performance. Furthermore, the composite cell structure employs a winding process, using stacked cell units only at the connection points. While achieving the performance advantages of a stacked structure, the production efficiency loss is lower than that of a fully stacked cell using a single cell structure, helping to control the overall cell cost. Specifically, each turn of the first positive electrode 11 or the first negative electrode 12 of the wound cell unit 1 leads to a tab, which is then joined with the second positive electrode tab 211 or the second negative electrode tab 221 to form a current collector.

[0029] In the battery cell with the wound and stacked composite structure according to the present invention, the first separator 13 is located at the outermost ring of the wound battery cell unit 1, and the second separator 23 is located at the outermost layer of the stacked battery cell unit 2. The ends of the first separator 13 and the ends of the second separator 23 are formed into an integral structure by hot melting. Specifically, the first diaphragm 13 and the second diaphragm 23 are designed with PVDF coatings. The end of the second diaphragm 23 extends from the bottom of the stacked cell unit 2 to the top of the stacked cell unit 2. The end of the first diaphragm 13 is arranged around the outermost ring of the wound cell unit 1. The end of the first diaphragm 13 and the second diaphragm 23 located on the top of the stacked cell unit 2 are thermally fused to form an integral structure. The ends of the first diaphragm 13 and the second diaphragm 23 serve to connect the two cell units. Through the diaphragm thermal fusion process, the ends of the first diaphragm 13, the ends of the second diaphragm 23, and the second diaphragm 23 located on the top of the stacked cell unit 2 are thermally fused to form a complete and continuous diaphragm, which wraps the wound cell unit 1 and the stacked cell unit 2 inside.

[0030] In the battery cell with the wound laminated composite structure according to the present invention, there are multiple second positive electrode plates 21 and second negative electrode plates 22. Each second positive electrode plate 21 is provided with a second positive electrode tab 211, and each second negative electrode plate 22 is provided with a second negative electrode tab 221. The projections of multiple second positive electrode tabs 211 and / or multiple second negative electrode tabs 221 overlap in the thickness direction H. Specifically, the second positive electrode 21 and the second negative electrode 22 are punched into sheet-like structures and alternately placed in the bend 3 formed by the second diaphragm 23. Each second positive electrode 21 is designed with a second positive electrode tab 211, and each second negative electrode 22 is designed with a second negative electrode tab 221. This can be understood as each electrode having one tab. The second positive electrode tab 211 and the second negative electrode 22 are electrically connected to the two tabs of the wound cell unit 1, respectively. The projections of multiple second positive electrode tabs 211 and / or multiple second negative electrode tabs 221 in the thickness direction H overlap, which facilitates stacking multiple second positive electrode tabs 211 or multiple second negative electrode tabs 221 into an integral structure for welding, thus helping to improve the electrode tab welding effect.

[0031] In the battery cell with the wound and stacked composite structure according to the present invention, the second separator 23 is folded multiple times to form a plurality of bends 3, and the second positive electrode 21 and the second negative electrode 22 are alternately placed in the plurality of bends 3. Specifically, each bend 3 adopts a U-shaped structure, and the length and width of the bend 3 match the size of the electrode, which is preferably 100*80mm.

[0032] The working principle of this invention is: This invention employs a wound and stacked composite structure, combining at least two wound cell units 1 with a stacked cell unit 2 located between them. The stacked cell unit 2 acts as a buffer, absorbing internal stress and suppressing deformation during cell cycling, thus helping to extend the cell's cycle life. Simultaneously, the tabs of the wound cell unit 1 and the stacked cell unit 2 are welded together using ultrasonic welding or laser re-welding processes to form a low-impedance shared current collector, which reduces the cell's internal resistance and helps improve the cell's rate performance and fast charging performance.

[0033] The composite structure of the battery cell in this embodiment uses two wound cell units 1 and one stacked cell unit 2, with a capacity of 25Ah. The wound cell unit 1 has 45 layers wound, with a single capacity of 12.5Ah and dimensions of 10*80*120mm. The stacked cell unit has 15 repeating units, with an electrode size of 100*80mm. The electrodes are welded using ultrasonic or laser re-welding. The internal resistance of the composite structure battery cell in this embodiment is 0.88mΩ; the 3C temperature rise is 12.1°C; and the cycle life is 3180 cycles. Compared with the existing single cell structure, the internal resistance is reduced by 0.37mΩ, the temperature rise is reduced by 6.4°C, and the cycle life is increased by 830 cycles.

[0034] Example 2 Unlike Embodiment 1, this embodiment has multiple first positive tabs 111 and first negative tabs 121, and the projections of the multiple first positive tabs 111 and / or multiple first negative tabs 121 overlap in the thickness direction H. Specifically, each turn of the first positive electrode 11 or the first negative electrode 12 of the wound cell unit 1 leads out two tabs. Compared with the structure of Embodiment 1, by increasing the number of first positive tabs 111 and first negative tabs 121, it helps to shorten the path for electrons to converge to the tabs, thereby reducing the cell impedance. Moreover, the overlapping projections of the multiple first positive tabs 111 and / or multiple first negative tabs 121 in the thickness direction H facilitate the stacking of multiple first positive tabs 111 or multiple first negative tabs 121 into a single structure for welding, which helps to improve the tab welding effect.

[0035] See Figure 2 As shown, the composite structure cell in this embodiment uses two wound cell units 1 and one stacked cell unit 2, with a capacity of 25Ah. The wound cell unit 1 has 45 layers wound, with a single capacity of 12.5Ah and dimensions of 10*80*120mm. The stacked cell unit has 15 repeating units, with an electrode size of 100*80mm. Each turn of the electrode in the wound cell unit 1 has two tabs, which can be understood as a bitab design. The tabs are welded using ultrasonic or laser welding. The internal resistance of the composite structure cell in this embodiment is 0.75mΩ; the 3C temperature rise is 10.8°C; and the cycle life is 3350 cycles. Compared with the existing single cell structure, the internal resistance is reduced by 0.50mΩ, the temperature rise is reduced by 7.7°C, and the cycle life is increased by 1000 cycles.

[0036] The other structures are the same as in Example 1, and will not be described again here.

[0037] Example 3 Unlike Embodiment 1, this embodiment has N winding cell units 1, where N is a positive integer greater than or equal to 2. The Nth winding cell unit 1 and the (N-1)th winding cell unit 1 are symmetrically arranged on both sides of the stacked cell unit 2 in the thickness direction H.

[0038] See Figure 3As shown, the composite structure cell in this embodiment uses four wound cell units 1 and two stacked cell units 2, with a capacity of 100Ah. The wound cell unit 1 has 35 layers of winding, a single capacity of 25Ah, and dimensions of 12*100*180mm. The stacked cell unit has 15 repeating units, with an electrode size of 120*100mm. Each turn of the electrode in the wound cell unit 1 has two tabs, which can be understood as a bitab design. The tabs are welded using ultrasonic or laser re-welding. The internal resistance of the composite structure cell in this embodiment is 0.38mΩ; the 3C temperature rise is 8.5°C; and the cycle life is 5200 cycles. Compared with the existing single cell structure, the internal resistance is reduced by 0.27mΩ, the temperature rise is reduced by 6.5°C, and the cycle life is increased by 1350 cycles.

[0039] The other structures are the same as in Example 1, and will not be described again here.

[0040] Compared with existing structures, the present invention has the following advantages: 1. Reduced internal resistance: Example tests show that the internal resistance can be reduced by 0.27-0.50mΩ, which greatly improves the rate performance and meets the fast charging requirements.

[0041] 2. Cyclic performance: The stacked cell unit 2 acts as a stress buffer, suppressing the overall aging deformation of the cell, and the cycle life can be increased by more than 830 cycles compared with the traditional winding structure.

[0042] 3. Temperature rise control: The temperature rise during 3C continuous discharge can be reduced by 6.5-7.7°C, which improves the thermal safety and high-temperature performance of the battery.

[0043] Method for fabricating battery cells with wound and laminated composite structures This invention also discloses a method for preparing a battery cell with a wound and stacked composite structure, comprising: Step 1: Prepare wound cell unit 1 and laminated cell unit 2; Step 2: Alternately arrange the wound cell unit 1 and the stacked cell unit 2 and hot-press them together; Step 3: Weld the first positive electrode tab 111 and the second positive electrode tab 211 to form the first current collector, and then weld the first negative electrode tab 121 and the second negative electrode tab 221 to form the second current collector. Step 4: Complete the subsequent shell insertion and liquid injection processes in sequence.

[0044] It should be noted that in step three, the tabs of each unit (using a multi-tab or all-tab design) are welded to the current collector or pole piece by ultrasonic welding and laser re-welding processes to form a low-impedance common current collector. The ultrasonic parameters are a frequency of 15-25kHz, a welding pressure of 300-500N, and a welding time of 150-250ms. In the laser re-welding, a fiber laser with a power / speed of 700-900W / 80-120mm / s is used; the spot / line spacing is 100-200μm / 100-150μm; and the waveform is a modulated pulse with a gradual rise and fall.

[0045] Because the interlocking between layers in the wound structure is very tight, the τ_max is very high, making slippage difficult. However, the "Z-shaped" bends in the laminated structure have more free space and a more complex stress distribution, reducing the effective τ_max and making slippage more likely to occur when the cell needs it. The transition region between winding and lamination, as well as the bending angles of the laminations, are stress concentration points. These areas are most likely to reach the slippage critical condition first, becoming the preferred stress release windows. The entire composite structure has a large number of internal interfaces, which can slip asynchronously and locally, forming a distributed, flexible stress dissipation network. Furthermore, this invention overcomes the work done by static friction, converting some mechanical energy (stress energy) into heat energy for dissipation. When slippage occurs, the constraints between layers are instantly released, and the accumulated shear stress τ drops rapidly. This can be understood as two people pushing each other; if one suddenly releases force, the other will stagger forward, and the previous pushing force is released. In the next stage of charging and discharging, the direction of volume change may change, stress may accumulate again, and the slip critical point may be reached again. This process repeats, which acts as a buffer, absorbs the internal stress of the cell, suppresses the deformation of the cell during the cycle, and helps to extend the cycle life of the cell.

[0046] Based on the disclosure and teachings of the foregoing specification, those skilled in the art can make changes and modifications to the above embodiments. Therefore, the present invention is not limited to the specific embodiments described above, and any obvious improvements, substitutions, or modifications made by those skilled in the art based on the present invention are within the scope of protection of the present invention. Furthermore, although some specific terms are used in this specification, these terms are only for convenience of explanation and do not constitute any limitation on the present invention.

Claims

1. A battery cell with a wound and laminated composite structure, characterized in that: It includes multiple wound cell units (1) and multiple stacked cell units (2), with two adjacent wound cell units (1) electrically connected through the stacked cell units (2); The wound cell unit (1) includes a first positive electrode (11), a first negative electrode (12) and a first separator (13), wherein the first positive electrode (11), the first separator (13) and the first negative electrode (12) are alternately stacked and wound to form the wound cell unit (1); The stacked cell unit (2) includes a second positive electrode (21), a second negative electrode (22), and a second separator (23). The second separator (23) is folded back and forth in a "Z" shape. The second positive electrode (21) and the second negative electrode (22) are alternately stacked on both sides of the second separator (23). The first positive electrode (11) and the first negative electrode (12) are respectively provided with a first positive electrode tab (111) and a first negative electrode tab (121), and the second positive electrode (21) and the second negative electrode (22) are respectively provided with a second positive electrode tab (211) and a second negative electrode tab (221). The first positive electrode tab (111) and the second positive electrode tab (211) are electrically connected to form a first current collector, and the first negative electrode tab (121) and the second negative electrode tab (221) are electrically connected to form a second current collector.

2. The battery cell with a wound and laminated composite structure as described in claim 1, characterized in that: The first diaphragm (13) is located on the outermost ring of the wound cell unit (1), and the second diaphragm (23) is located on the outermost layer of the stacked cell unit (2). The ends of the first diaphragm (13) and the ends of the second diaphragm (23) are formed into an integral structure by hot melting.

3. A battery cell with a wound and laminated composite structure as described in claim 2, characterized in that: There are multiple first positive tabs (111) and multiple first negative tabs (121), and the projections of multiple first positive tabs (111) and / or multiple first negative tabs (121) overlap in the thickness direction.

4. A battery cell with a wound and laminated composite structure as described in claim 3, characterized in that: The number of the second positive electrode (21) and the second negative electrode (22) is multiple. Each second positive electrode (21) is provided with a second positive electrode tab (211), and each second negative electrode (22) is provided with a second negative electrode tab (221). The projections of multiple second positive electrode tabs (211) and / or multiple second negative electrode tabs (221) overlap in the thickness direction.

5. A battery cell with a wound and laminated composite structure as described in claim 2, characterized in that: The second diaphragm (23) is folded multiple times to form multiple bends, and the second positive electrode (21) and the second negative electrode (22) are alternately placed in the multiple bends.

6. A battery cell with a wound and laminated composite structure as described in claim 5, characterized in that: The end of the second diaphragm (23) extends from the bottom of the stacked cell unit (2) to the top of the stacked cell unit (2).

7. A battery cell with a wound and laminated composite structure as described in claim 6, characterized in that: The end of the first diaphragm (13) is disposed around the outermost ring of the wound cell unit (1), and the end of the first diaphragm (13) is thermally fused with the second diaphragm (23) located on top of the stacked cell unit (2) to form an integral structure.

8. A battery cell with a wound and laminated composite structure as described in claim 4, characterized in that: The number of wound battery cell units (1) is N, where N is a positive integer greater than or equal to 2.

9. A battery cell with a wound and laminated composite structure as described in claim 8, characterized in that: The Nth winding cell unit (1) and the (N-1)th winding cell unit (1) are symmetrically arranged on both sides of the stacked cell unit (2) in the thickness direction.

10. A method for preparing a battery cell with a wound and stacked composite structure, characterized in that, include: Step 1: Prepare the wound cell unit (1) and the stacked cell unit (2); Step 2: Alternately arrange the wound cell unit (1) and the stacked cell unit (2) and hot-press them together; Step 3: Weld the first positive electrode tab (111) and the second positive electrode tab (211) to form the first current collector, and then weld the first negative electrode tab (121) and the second negative electrode tab (221) to form the second current collector; Step 4: Complete the subsequent shell insertion and liquid injection processes in sequence.

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