Preparation method of double-middle winding type lithium ion battery inner core

Abstract

The invention provides a preparation method of an inner core of a double-middle winding type lithium ion battery. The preparation method comprises the following steps: respectively welding a pre-prepared positive electrode pin and a pre-prepared negative electrode pin with a positive electrode foil material strip and a negative electrode foil material strip; sequentially laminating the electrolytic paper, the positive electrode foil material strip, the electrolytic paper, the negative electrode foil material strip and the electrolytic paper; winding by taking the welding part of the positive electrode foil material strip and the negative electrode foil material strip as a center to form a core roll; the wound core roll is fixed through dispensing or an adhesive tape and then sheared to form an inner core; and the inner cores are put into a detection plate for middle distance detection, and qualified inner cores are screened out. The structure is reasonable, and the rate capability, the power performance, the DCR during high-rate discharge and the heat effect of the battery cell can be effectively improved.

Description

Technical Field

[0001] The invention relates to the technical field of lithium ion battery preparation, in particular to a method for preparing a double-center-wound lithium ion battery inner core. Background Art

[0002] The advantages of soft-pack lithium-ion batteries mainly include good safety, light weight, large capacity, low internal resistance, flexible design, lightweight design, low internal resistance, high energy density, good safety, flexible design, light weight, low internal resistance, excellent heat dissipation performance, good fast charging capability, and significant cost-effectiveness; it is 40% lighter than steel-shell lithium batteries of the same capacity and 20% lighter than aluminum-shell batteries, which helps to reduce the weight of the entire vehicle and improve energy efficiency. Lithium-ion batteries are composed of inner core, outer shell, and pole ear (pole foot), among which: The impact of the internal resistance of the core on battery performance is mainly reflected in the following aspects: Discharge efficiency: Lower internal resistance helps reduce energy loss during charging and discharging, thereby improving the output power and efficiency of the battery. For example, by optimizing battery materials and structural design, the internal resistance can be significantly reduced, allowing the battery to provide higher current and longer use time during discharge.

[0003] Energy density: Batteries with high internal resistance may have higher energy density, but this is usually accompanied by greater internal resistance, which may lead to increased energy loss during the battery's charge and discharge process. Therefore, balancing internal resistance and energy density is the key to designing high-performance batteries.

[0004] Cycle life: The increase in battery internal resistance is often closely linked to the battery aging process, which can cause battery performance to degrade over time. Monitoring changes in battery internal resistance can help predict battery life and maintain battery health.

[0005] Temperature influence: Temperature is a key environmental parameter that affects the internal resistance of the battery. Under low temperature conditions, the ionic conductivity of the electrolyte decreases, resulting in an increase in the internal resistance of the battery. At a suitable temperature, the internal resistance of the battery will be relatively stable.

[0006] Usage conditions: Usage conditions such as charge and discharge status, usage duration, and load current also affect internal resistance. For example, frequent charge and discharge cycles may cause changes in the internal structure of the battery and increase internal resistance.

[0007] The traditional more efficient production method is winding lithium-ion batteries. The pole tabs (pole feet) are affected by the pole piece design, electrode expansion thickness, welding position, winding tightness, and winding needle size, resulting in unstable center distance of the pole tabs, which seriously affects the quality of the top and side seals of the product. Summary of the invention

[0008] The purpose of the present invention is to provide a double-center wound structure lithium-ion battery core and a preparation method with a reasonable structure that can effectively improve the rate performance, power performance, DCR and thermal effect of the battery cell during high-rate discharge, so that the same capacity and wound structure battery cells have superior rate, cycle, low internal resistance, and small thermal effect during charge and discharge.

[0009] To achieve the above object, the technical solution provided by the present invention is: a method for preparing a double-center wound lithium-ion battery core, which comprises the following steps: The first step: welding the pre-prepared positive electrode foot and negative electrode foot to the positive electrode foil strip and negative electrode foil strip respectively; The second step: stacking the electrolytic paper, the positive electrode foil strip, the electrolytic paper, the negative electrode foil strip, and the electrolytic paper in sequence; The third step is to wind the positive electrode foil strip and the negative electrode foil strip with their welding points as the center to form a core roll; Step 4: Fix the wound core roll by dispensing glue or tape and then cut it to form an inner core; Step 5: Place the inner core into the testing board for mid-range testing and select qualified inner cores.

[0010] The electrolytic paper in the second step does not cover the welding parts of the positive electrode foil strip and the negative electrode foil strip.

[0011] The detection plate includes a bottom plate and screen bars, wherein the bottom plate is in the shape of a long strip, and its two sides in the length direction are concave to form an arc-shaped waist groove, a screen bar is fixed to the surface of one end of the bottom plate, a rectangular center distance screening groove is provided in the middle of the bottom plate, and pole ear screening grooves are provided on the screen bars on both sides of the center distance screening groove; there are two pole ear screening grooves, which are respectively located at the two ends of the screen bar, and the center line between the two pole ear screening grooves and the center line of the center distance screening groove are located on the same straight line.

[0012] The length direction of the center distance screening slot is consistent with the length direction of the bottom plate, and the center distance screening slot passes through the bottom plate from top to bottom; the screen bar is in the shape of a long strip, and its length direction is consistent with the width direction of the bottom plate.

[0013] The technical advantages of this solution are: First, the structure provided by this solution is simple and reasonable, can be directly used in solid-state and liquid batteries, and is easy to operate.

[0014] Second, this solution can significantly reduce the internal resistance of the battery cell, with an actual reduction of about 45~55%.

[0015] Third, this solution can significantly reduce the ohmic internal resistance of the battery cell, improve the battery cell rate performance, power performance, DCR and thermal effect during high-rate discharge, so that the same capacity, wound-structured battery cells have superior rate, cycle, low internal resistance, and low thermal effect during charge and discharge.

[0016] Fourthly, the center distance screening slot of the present solution can quickly compare and screen the center distance of the tabs, and at the same time, it can facilitate the operator to quickly and smoothly remove the checked and screened battery cells from the fixture, thereby improving work efficiency.

[0017] Fifth, adopt a single screen bar design and gently lift the battery cell with your fingers so that the surface of the battery cell will not be adsorbed on the fixture due to static electricity, and quickly detach from the fixture to avoid the outer surface of the battery cell being scratched by the fixture, resulting in poor product appearance. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of the positive electrode foot structure of the present invention.

[0019] Figure 2 It is a schematic diagram of the structure of the negative electrode leg of the present invention.

[0020] Figure 3 It is a schematic diagram of the overall structure of the present invention.

[0021] Figure 4 It is a schematic diagram of the overall structure of the present invention.

[0022] Figure 5 It is a schematic diagram of the tab screening trough of the present invention. DETAILED DESCRIPTION

[0023] The present invention is further described below in conjunction with all the accompanying drawings. The embodiments described in this embodiment with reference to the accompanying drawings are exemplary and are only used to explain this patent, and cannot be understood as limiting this patent.

[0024] In the description of this patent, it should be understood that the terms "center", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the drawings, and are only for the convenience of describing this patent and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on this patent.

[0025] In the description of this patent, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", and "set" should be understood in a broad sense, for example, it can be fixedly connected or set, or it can be detachably connected or set, or connected or set in one piece. For ordinary technicians in this field, the specific meanings of the above terms in this patent can be understood according to specific circumstances.

[0026] See attached Figure 1 To Attachment Figure 5 The method for preparing a double-center wound lithium-ion battery core described in this embodiment includes the following steps: The first step: welding the pre-prepared positive electrode foot and negative electrode foot to the positive electrode foil strip and negative electrode foil strip respectively; The second step: stacking the electrolytic paper, the positive electrode foil strip, the electrolytic paper, the negative electrode foil strip, and the electrolytic paper in sequence; the electrolytic paper does not cover the welding parts of the positive electrode foil strip and the negative electrode foil strip; The third step is to wind the positive electrode foil strip and the negative electrode foil strip with their welding points as the center to form a core roll; Step 4: Fix the wound core roll by dispensing glue or tape and then cut it to form an inner core; Step 5: Place the inner core into the testing board for mid-range testing and select qualified inner cores.

[0027] The detection plate used in the above method includes a bottom plate 1 and a screen bar 2, wherein the bottom plate 1 is in the shape of a long strip, and its two sides in the length direction are concave to form an arc-shaped waist groove 3, and the screen bar 2 is fixed on one end surface of the bottom plate 1, and a rectangular center distance screening groove 4 is provided in the middle of the bottom plate 1, and a tab screening groove 5 is provided on the screen bar 2 on both sides of the center distance screening groove 4; there are two tab screening grooves 5, which are respectively located at both ends of the screen bar 2, and the center line between the two tab screening grooves 5 and the center line of the center distance screening groove 4 are located on the same straight line. The length direction of the center distance screening groove 4 is consistent with the length direction of the bottom plate 1, and the center distance screening groove 4 runs through the bottom plate 1 from top to bottom; the screen bar 2 is in the shape of a long strip, and its length direction is consistent with the width direction of the bottom plate 1.

[0028] After adopting the above scheme, the pole ear welding position is designed to be the middle of the pole piece, so that the current flows from both ends of the pole piece to the pole ear, which greatly shortens the current flow path, and the empty foil area is not rolled up to avoid uneven force during pressure formation caused by uneven thickness of the local battery cell. At the same time, the structure after adopting this scheme is reasonable, which can effectively improve the battery cell rate performance, power performance, DCR and thermal effect during high-rate discharge, so that the same capacity, wound-structured battery cells have superior rate, cycle, low internal resistance, and small thermal effect during charging and discharging.

[0029] After the inner core is wound, it is placed at the center distance screening groove, and the tabs are aligned (embedded) in the corresponding tab screening grooves for rapid screening. In this solution, the screen bar is arranged at one end of the bottom plate, so that the tabs can be put in and taken out more conveniently. The center distance screening grooves that run through the top and bottom are used to better position the inner core and prevent the inner core from being stuck on the bottom plate. At the same time, the center distance between the inner core and the tabs can be quickly screened. The two waist grooves are used for easy picking (just pinch the two waist grooves by hand), and the weight of the bottom plate is reduced, raw materials are saved, and the manufacturing cost of the fixture is reduced. The structure after adopting this solution is reasonable, and the operator can quickly and smoothly remove the checked and screened battery cells from the fixture, thereby improving work efficiency and avoiding the outer surface of the battery cell being scratched by the fixture, resulting in poor product appearance.

[0030] The embodiments described above are only preferred embodiments of the present invention and are not intended to limit the scope of implementation of the present invention. Therefore, all changes made according to the shape and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a double-center wound lithium-ion battery core, characterized in that: It includes the following steps: The first step: welding the pre-prepared positive electrode foot and negative electrode foot to the positive electrode foil strip and negative electrode foil strip respectively; The second step: stacking the electrolytic paper, the positive electrode foil strip, the electrolytic paper, the negative electrode foil strip, and the electrolytic paper in sequence; The third step is to wind the positive electrode foil strip and the negative electrode foil strip with their welding points as the center to form a core roll; Step 4: Fix the wound core roll by dispensing glue or tape and then cut it to form an inner core; Step 5: Place the inner core into the testing board for mid-range testing and select qualified inner cores.

2. The method for preparing a double-center wound lithium-ion battery core according to claim 1, characterized in that: The electrolytic paper in the second step does not cover the welding parts of the positive electrode foil strip and the negative electrode foil strip.

3. The method for preparing a double-center wound lithium-ion battery core according to claim 1, characterized in that: The detection plate comprises a bottom plate (1) and a screen bar (2), wherein the bottom plate (1) is in the shape of a long strip, and both sides of the bottom plate (1) are concave inwardly to form an arc-shaped waist groove (3) in the length direction, and the screen bar (2) is fixed to one end surface of the bottom plate (1), and a rectangular center distance screening groove (4) is provided in the middle of the bottom plate (1), and a tab screening groove (5) is provided on the screen bar (2) on both sides of the center distance screening groove (4); there are two tab screening grooves (5), which are respectively located at both ends of the screen bar (2), and the center line between the two tab screening grooves (5) and the center line of the center distance screening groove (4) are located on the same straight line.

4. The method for preparing a double-center wound lithium-ion battery core according to claim 3, characterized in that: The length direction of the center distance screening slot (4) is consistent with the length direction of the bottom plate (1), and the center distance screening slot (4) passes through the bottom plate (1) from top to bottom; the screen bar (2) is in the shape of a long strip, and its length direction is consistent with the width direction of the bottom plate (1).

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