A lithium battery winding structure and a lithium-ion battery

Abstract

The present invention discloses a winding structure of a lithium battery. The winding core has an X-fold, the first tab is located at the M-th fold, and the second tab is located at the N-th fold, where M < X and N < X; the length of the long film surface of the first electrode sheet is A, the distance between the first tab groove and the edge of the first electrode sheet in the length direction is a, the length of the long film surface of the second electrode sheet is B, and the distance between the second tab groove and the edge of the second electrode sheet in the length direction is b, satisfying the relational expressions: (M - 1) / X ≤ a / A ≤ M / X; (N - 1) / X ≤ b / B ≤ N / X. By optimizing the positions of the tabs, the present invention avoids the tabs and the adhesive tapes being on the same layer, which helps to reduce the risk of lithium plating on the electrode sheets. In addition, the present invention also discloses a lithium-ion battery.

Description

Technical Field

[0001] The present invention belongs to the technical field of batteries, and particularly relates to a lithium battery winding structure and a lithium-ion battery. Background Art

[0002] Lithium-ion batteries are widely used in power fields such as electric vehicles and consumer fields such as mobile phones, watches, tablets, and laptops because of their advantages of high specific energy, strong endurance, long cycle life, wide working range, short charging time, and large current discharge.

[0003] With the rapid development of lithium-ion batteries, lithium-ion batteries are gradually developing towards fast charging and high energy density. One of the existing technologies is to place the tab in the middle to improve the charging speed of the battery cell, but lithium deposition often occurs near the tab of the battery cell. Summary of the Invention

[0004] One of the purposes of the present invention is to provide a lithium battery winding structure to avoid the tab position adhesive tape being on the same layer by optimizing the position of the tab, which helps to reduce the risk of lithium deposition on the electrode sheet, aiming at the deficiencies of the existing fast charging technology.

[0005] In order to achieve the above purpose, the present invention adopts the following technical solutions:

[0006] A lithium battery winding structure includes a first electrode sheet, a second electrode sheet, and a separator. The first electrode sheet, the separator, and the second electrode sheet are sequentially stacked and wound to form a core; the first electrode sheet and the second electrode sheet are respectively provided with a first tab groove and a second tab groove, and a first tab and a second tab are respectively installed in the first tab groove and the second tab groove; the core has X folds, the first tab is located at the Mth fold, and the second tab is located at the Nth fold, where M < X and N < X; the length of the long film surface of the first electrode sheet is A, the distance between the first tab groove and the edge of the first electrode sheet in the length direction is a, the length of the long film surface of the second electrode sheet is B, and the distance between the second tab groove and the edge of the second electrode sheet in the length direction is b, satisfying the relational expressions: (M - 1) / X ≤ a / A ≤ M / X; (N - 1) / X ≤ b / B ≤ N / X; in the core, the second electrode sheet wraps the first electrode sheet, the first electrode sheet is located inside the core, and the second electrode sheet is located outside the core.

[0007] Preferably, when X is an even number and M = X / 2, the first tab is located at the middle fold of the first electrode sheet, and when N = X / 2, the second tab is located at the middle fold of the second electrode sheet.

[0008] Preferably, when X is an odd number and M = (X + 1) / 2, the first tab is located at the middle fold of the first electrode sheet, and when N = (X + 1) / 2, the second tab is located at the middle fold of the second electrode sheet.

[0009] Preferably, first adhesive tapes are respectively pasted above and below the first tab, and second adhesive tapes are respectively pasted above and below the second tab.

[0010] Preferably, when M - N ≥ 4 or N - M ≥ 2, the first adhesive tapes and the second adhesive tapes are in different layers of the core.

[0011] Preferably, both the first electrode sheet and the second electrode sheet include a current collector and a coating layer coated on the surface of the current collector.

[0012] Preferably, both the first tab groove and the second tab groove include a bottom and a side wall. The side wall extends upward from the bottom. The bottom is the current collector exposed on the surface of the electrode sheet, and the coating layer encloses the side wall.

[0013] Preferably, the first tab and the second tab are respectively embedded in the first tab groove and the second tab groove.

[0014] Preferably, the first adhesive tape covers the first tab groove, and the second adhesive tape covers the second tab groove.

[0015] A second object of the present invention is to provide a lithium - ion battery, including the above - mentioned lithium - battery winding structure.

[0016] The beneficial effect of the present invention is that by providing the first tab groove and the second tab groove at preset positions on the first electrode sheet and the second electrode sheet, the first tab or the second tab can be installed in the middle of the electrode sheet, enabling electrons to be transmitted to the head and tail of both the positive and negative electrodes simultaneously. At this time, the electron transmission path is the shortest, which helps to improve the charging speed. At the same time, the first adhesive tapes and the second adhesive tapes are in different layers of the core, avoiding the formation of bridge holes when the first adhesive tapes and the second adhesive tapes are in the same layer, making the pressure uniform when the first electrode sheet or the second electrode sheet is formed, which helps to improve the fitting effect between the first electrode sheet, the separator, and the second electrode sheet, and reduces the probability of lithium deposition on the electrode sheet. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0018] Figure 1 It is a schematic diagram after the core of the present invention is unfolded.

[0019] Figure 2 It is one of the schematic structural diagrams of the core of the present invention.

[0020] Figure 3 It is one of the enlarged schematic diagrams at the first tab and the second tab of the core of the present invention.

[0021] Figure 4This is the second schematic structural view of the core of the present invention.

[0022] Figure 5 This is the second enlarged schematic view of the first tab and the second tab of the core of the present invention.

[0023] Figure 6 This is the third schematic structural view of the core of the present invention.

[0024] Figure 7 This is the third enlarged schematic view of the first tab and the second tab of the core of the present invention.

[0025] Among them, the reference numerals are explained as follows:

[0026] 1 - First pole piece; 10 - Core;

[0027] 2 - Second pole piece;

[0028] 3 - Separator;

[0029] 4 - First tab groove;

[0030] 5 - Second tab groove;

[0031] 6 - First tab;

[0032] 7 - Second tab;

[0033] 8 - First adhesive tape;

[0034] 9 - Second adhesive tape. Specific embodiments

[0035] For example, certain terms are used in the specification and claims to refer to specific components. Those skilled in the art should understand that hardware manufacturers may use different terms to refer to the same component. The specification and claims do not use the difference in names as a way to distinguish components, but use the difference in functions of components as the criterion for distinction. As mentioned throughout the specification and claims, "comprising" is an open-ended term and should be interpreted as "including but not limited to". "Substantially" means within an acceptable error range, and those skilled in the art can solve technical problems within a certain error range and basically achieve technical effects.

[0036] In addition, terms such as "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0037] In an invention, unless otherwise clearly specified and defined, terms such as "installed", "connected", "joined", "fixed", etc. shall be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two components. For those of ordinary skill in the art, the specific meanings of the above terms in this invention can be understood according to specific circumstances.

[0038] The following will further elaborate on the present invention in conjunction with the attached Figures 1-7 but it does not limit the present invention.

[0039] A lithium battery winding structure includes a first electrode tab 1, a second electrode tab 2, and a separator 3. The first electrode tab 1, the separator 3, and the second electrode tab 2 are stacked in sequence and wound to form a core 10; the first electrode tab 1 and the second electrode tab 2 are respectively provided with a first tab slot 4 and a second tab slot 5, and a first tab 6 and a second tab 7 are respectively installed in the first tab slot 4 and the second tab slot 5; the core 10 has an X-fold, the first tab 6 is located at the M-th fold, and the second tab 7 is located at the N-th fold, where M < X and N < X; the length of the long film surface of the first electrode tab 1 is A, the distance between the first tab slot 4 and the edge of the first electrode tab 1 in the length direction is a, the length of the long film surface of the second electrode tab 2 is B, and the distance between the second tab slot 5 and the edge of the second electrode tab 2 in the length direction is b, satisfying the relational expressions: (M - 1) / X ≤ a / A ≤ M / X; (N - 1) / X ≤ b / B ≤ N / X; in the core 10, the second electrode tab 2 wraps the first electrode tab 1, the first electrode tab 1 is located inside the core 10, and the second electrode tab 2 is located outside the core 10.

[0040] Since the existing winding structure is difficult to meet the charging requirements of the battery cell, by providing the first tab slot 4 and the second tab slot 5 at preset positions on the first electrode tab 1 and the second electrode tab 2, the first tab 6 or the second tab 7 can be installed in the middle of the electrode tab, enabling electrons to be transmitted to the head and tail of both the positive and negative electrodes simultaneously. At this time, the electron transmission path is the shortest, which helps to improve the charging speed. At the same time, the first adhesive tape 8 and the second adhesive tape 9 are in different layers of the core 10, preventing the first adhesive tape 8 and the second adhesive tape 9 from forming a bridge hole in the same layer, making the pressure uniform when the first electrode tab 1 or the second electrode tab 2 is formed, helping to improve the bonding effect between the first electrode tab 1, the separator 3, and the second electrode tab 2, and reducing the probability of lithium deposition on the electrode tab.

[0041] Among them, it is preferred that the first electrode tab 1 is a negative electrode tab and the second electrode tab 2 is a positive electrode tab, the first tab 6 is a negative tab, and the second tab 7 is a positive tab, or the first electrode tab 1 can be a positive electrode tab and the second electrode tab 2 can be a negative electrode tab, which is not limited here.

[0042] In the lithium battery winding structure according to the present invention, when X is an even number and M = X / 2, the first tab 6 is located at the middle fold of the first electrode sheet 1, and when N = X / 2, the second tab 7 is located at the middle fold of the second electrode sheet 2. Electrons can be transmitted to the head and tail of the positive and negative electrode sheets simultaneously. At this time, the electron transmission path is the shortest and the charging speed is the fastest. However, there is still a certain risk when M - N = 0, and it is necessary to satisfy M - N ≥ 4, or N - M ≥ 2 and |M - N| is an even number. At this time, the wound bare battery cell is a staggered layer design, that is, to prevent the first adhesive tape 8 and the second adhesive tape 9 from forming a bridge hole on the same layer, so that the pressure on the first electrode sheet 1 or the second electrode sheet 2 is uniform during formation, which helps to improve the fitting effect between the first electrode sheet 1, the separator 3 and the second electrode sheet 2, and reduces the probability of lithium deposition on the electrode sheet.

[0043] In the lithium battery winding structure according to the present invention, when X is an odd number and M = (X + 1) / 2, the first tab 6 is located at the middle fold of the first electrode sheet 1, and when N = (X + 1) / 2, the second tab 7 is located at the middle fold of the second electrode sheet 2. Electrons can also be transmitted to the head and tail of the positive and negative electrode sheets simultaneously. At this time, the electron transmission path is short and the charging speed is fast.

[0044] When M - N = 0 or 2, at this time, the battery cell winding structure is as Figure 2 shown. The enlarged views of the positive tab and the negative tab are as Figure 3 shown. There are two adhesive tapes at the positive tab and the negative tab on the same layer. When the designed tab spacing of the battery cell is small, that is, when L is small, the two adhesive tapes are close to each other, resulting in the anode and cathode between the two adhesive tapes being supported by the adhesive tapes, forming a structure similar to a bridge hole. After formation, due to the support of the adhesive tapes at the two tab positions, the pressure on the positive and negative electrode sheets at the middle of the tabs during formation is less than that in other regions, and the contact between the positive and negative electrode sheets and the separator 3 is poor. The lithium ion transmission path between the positive and negative electrode sheets at this place increases, and the time for lithium ions to transfer from the positive electrode to the negative electrode during the charging process increases, increasing the risk of lithium deposition and causing lithium deposition in the battery cell.

[0045] In the lithium battery winding structure according to the present invention, the first adhesive tape 8 is respectively pasted above and below the first tab 6, and the second adhesive tape 9 is respectively pasted above and below the second tab 7. Specifically, the first adhesive tape 8 includes a negative tab position protection adhesive tape and a negative tab protection adhesive tape on the positive electrode sheet. After winding, the negative tab protection adhesive tape on the positive electrode sheet is located on the surface of the negative tab position protection adhesive tape and is separated by the separator 3 in the middle. The negative tab protection adhesive tape covers the negative tab position protection adhesive tape. The second adhesive tape 9 includes a positive tab position protection adhesive tape and a negative tab protection adhesive tape on the positive electrode sheet. After winding, the negative tab protection adhesive tape on the positive electrode sheet is located on the surface of the positive tab position protection adhesive tape and is separated by the separator 3 in the middle. The negative tab protection adhesive tape does not completely cover the positive tab position protection adhesive tape.

[0046] In the lithium battery winding structure according to the present invention, when M - N ≥ 4 or N - M ≥ 2, the first adhesive tape 8 and the second adhesive tape 9 are in different layers of the core 10. The positions of the adhesive tapes at the positive and negative electrode tabs are as Figure 4 and 5 shown. There are two adhesive tapes at each of the positive and negative electrode tabs that are not in the same layer. Even if the distance between the electrode tabs is small, since the adhesive tapes are not in the same layer, no bridge holes will be formed in the same layer. During formation, only the thickness of the electrode tab position in the layer of the negative electrode tab is relatively thick and has a supporting effect. The formation pressure in other areas of this layer is uniform, and the fitting effect between the positive and negative electrodes and the separator 3 is better. The same is true for the positive electrode tab position, which helps to reduce the risk of lithium deposition on the electrode sheet. When N - M ≥ 2, for the adhesive tapes at the positive and negative electrode tabs in the winding structure of the battery cell at this time, as Figure 6 and Figure 7 shown. There are two adhesive tapes at each of the positive and negative electrode tabs that are not in the same layer, and the effect is the same as when M - N ≥ 4.

[0047] In the lithium battery winding structure according to the present invention, the first electrode sheet 1 and the second electrode sheet 2 both include a current collector and a coating coated on the surface of the current collector. The first electrode tab groove 4 and the second electrode tab groove 5 both include a bottom and a side wall. The side wall extends upward from the bottom, and the bottom is the current collector exposed on the surface of the electrode sheet, and the coating surrounds the side wall. Specifically, the first electrode tab groove 4 and the second electrode tab groove 5 both have four side walls. The four side walls and the bottom enclose the first electrode tab groove 4 and the second electrode tab groove 5. The bottom is the current collector exposed outside, and the first electrode tab 6 and the second electrode tab 7 are welded to the current collector.

[0048] In the lithium battery winding structure according to the present invention, the first electrode tab 6 and the second electrode tab 7 are respectively embedded in the first electrode tab groove 4 and the second electrode tab groove 5.

[0049] In the lithium battery winding structure according to the present invention, the first adhesive tape 8 covers the first electrode tab groove 4, and the second adhesive tape 9 covers the second electrode tab groove 5. Specifically, the first adhesive tape 8 includes a negative electrode tab position protection adhesive tape and a negative electrode tab protection adhesive tape on the positive electrode sheet. The negative electrode tab protection adhesive tape covers the negative electrode tab position protection adhesive tape. The second adhesive tape 9 includes a positive electrode tab position protection adhesive tape and a negative electrode tab protection adhesive tape on the positive electrode sheet. The negative electrode tab protection adhesive tape does not completely cover the positive electrode tab position protection adhesive tape.

[0050] A lithium ion battery includes the above-mentioned lithium battery winding structure.

[0051] In order to avoid short - circuit between the positive and negative electrode sheets, a separator 3 is provided between every two adjacent electrode sheets, and the electrode sheets with opposite polarities are electrically isolated by the separator 3.

[0052] Example 1

[0053] Preparation of the negative electrode sheet:

[0054] Graphite, conductive carbon black, thickening agent sodium carboxymethyl cellulose (CMC), and binder styrene-butadiene rubber (SBR) are made into a slurry according to a mass ratio of 96:2.0:1.0:1.0. The rubber compound is evenly coated on the current collector copper foil and dried at 90 °C. After coating, the length of the electrode sheet is converted into 20 folds of the electrode sheet. The dried electrode sheet is roll-pressed and slit. After slitting, the electrode sheet is laser-cleaned to obtain corresponding slots on the electrode sheet. The position of the laser-cleaned slot is on the 10th fold. After laser cleaning, the electrode sheet is welded with an electrode tab and pasted with adhesive tape to make the negative electrode sheet of the lithium-ion battery.

[0055] Preparation of the positive electrode sheet:

[0056] Lithium cobaltate, conductive carbon black, and binder polyvinylidene fluoride are mixed evenly according to a mass ratio of 96:2.5:1.5 to make the positive electrode slurry of the lithium-ion battery with a preset viscosity. The slurry is coated on the current collector aluminum foil and dried at 110 °C. The coated length of the electrode sheet is converted into 20 folds of the electrode sheet. The dried electrode sheet is laser-cleaned. The cleaning slot is located at the 6th fold. After laser cleaning, the electrode sheet is roll-pressed, trimmed, and slit. After slitting, it is dried at 110 °C for 4 hours under vacuum conditions, welded with an electrode tab, and pasted with adhesive tape to make the positive electrode sheet of the lithium-ion battery.

[0057] Preparation of the electrolyte:

[0058] Lithium hexafluorophosphate (LiPF6) is dissolved in a mixed solvent composed of ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC). The mass ratio of the three is 1:2:1 to obtain an electrolyte with a concentration of 1 mol / L.

[0059] Preparation of the lithium-ion battery:

[0060] The above positive electrode sheet, separator 3, and negative electrode sheet are wound into an electrode core. The winding method refers to Figure 2 and Figure 3 , the separator 3 is located between the positive electrode sheet and the negative electrode sheet. The positive electrode is led out by spot welding of the aluminum electrode tab, and the negative electrode is led out by spot welding of the nickel electrode tab; then the electrode core is placed in an aluminum-plastic packaging bag, the above electrolyte is injected, and after processes such as encapsulation, formation, and capacity, the lithium-ion battery is made.

[0061] Example 2

[0062] The difference from Example 1 is that the positive electrode laser cleaning slot in this example is located at the 12th fold of the electrode sheet.

[0063] Other structures are the same as those in Example 1 and will not be elaborated here.

[0064] Example 3

[0065] The difference from Example 1 is that the positive electrode tab in this example is located at the 10th fold.

[0066] The other structures are the same as those in Embodiment 1 and will not be described herein again.

[0067] Embodiment 4

[0068] Different from Embodiment 3, the negative electrode tab of this embodiment is located at the 8th fold.

[0069] The other structures are the same as those in Embodiment 3 and will not be described herein again.

[0070] Embodiment 5

[0071] Different from Embodiment 3, the negative electrode tab of this embodiment is located at the 14th fold.

[0072] The other structures are the same as those in Embodiment 3 and will not be described herein again.

[0073] Table 1. Electrochemical test results of the lithium-ion batteries prepared in Embodiments 1-5

[0074] Item Example 1 Example 2 Example 3 Example 4 Example 5 Charging time 63.11 62.92 62.31 66.8 71.3 Charging temperature rise 17.82 17.51 17.40 17.62 18.91 Internal resistance of battery cell 17.67 16.92 16.13 17.92 18.32 Lithium deposition during cycling No No Yes No No

[0075] As can be seen from the above table, the charging time and internal resistance of the battery cells in Embodiments 1 to 3 are better than those in Embodiments 4 to 5. That is, when the negative electrode tab is located in the middle of the electrode sheet, and the positive electrode tab is 2 folds behind or 4 folds in front of the negative electrode tab, it can not only meet a faster charging speed, smaller charging temperature rise and internal resistance of the battery cell, but also no lithium deposition occurs during the cycling process.

[0076] According to the disclosure and teachings of the above specification, those skilled in the art to which the present invention pertains can also make changes and modifications to the above embodiments. Therefore, the present invention is not limited to the above specific embodiments, and any obvious improvements, substitutions or variations made by those skilled in the art on the basis of the present invention all fall within the protection scope of the present invention. In addition, although some specific terms are used in this specification, these terms are only for convenience of description and do not constitute any limitation to the present invention.

Claims

1. A lithium battery winding structure, characterized in that, It includes a first pole piece (1), a second pole piece (2) and a separator (3), and the first pole piece (1), the separator (3) and the second pole piece (2) are stacked and wound in sequence to form a core (10); The first pole piece (1) and the second pole piece (2) are respectively provided with a first tab slot (4) and a second tab slot (5), and a first tab (6) and a second tab (7) are respectively installed in the first tab slot (4) and the second tab slot (5); The core (10) has X folds, the first tab (6) is located at the Mth fold, and the second tab (7) is located at the Nth fold, where M < X and N < X; The length of the long film surface of the first pole piece (1) is A, the distance from the first tab slot (4) to the edge of the first pole piece (1) in the length direction is a, the length of the long film surface of the second pole piece (2) is B, and the distance from the second tab slot (5) to the edge of the second pole piece (2) in the length direction is b, satisfying the relational expressions: (M - 1) / X ≤ a / A ≤ M / X; (N - 1) / X ≤ b / B ≤ N / X; In the core (10), the second pole piece (2) wraps the first pole piece (1), the first pole piece (1) is located inside the core (10), and the second pole piece (2) is located outside the core (10); First adhesive tapes (8) are respectively pasted above and below the first tab (6), and second adhesive tapes (9) are respectively pasted above and below the second tab (7); When M - N ≥ 4 or N - M ≥ 2, the first adhesive tapes (8) and the second adhesive tapes (9) are in different layers of the core (10).

2. The winding structure of a lithium battery according to claim 1, wherein: When X is an even number and M = X / 2, the first tab (6) is located at the middle fold of the first pole piece (1), and when N = X / 2, the second tab (7) is located at the middle fold of the second pole piece (2).

3. A lithium battery winding structure according to claim 1, characterized in that: When X is an odd number and M = (X + 1) / 2, the first tab (6) is located at the middle fold of the first pole piece (1), and when N = (X + 1) / 2, the second tab (7) is located at the middle fold of the second pole piece (2).

4. A lithium battery winding structure according to claim 1, characterized in that: Both the first pole piece (1) and the second pole piece (2) include a current collector and a coating coated on the surface of the current collector.

5. A lithium battery winding structure according to claim 4, characterized in that: Both the first tab slot (4) and the second tab slot (5) include a bottom and a side wall, the side wall extends upward from the bottom, the bottom is the current collector exposed on the surface of the pole piece, and the coating encloses the side wall.

6. The winding structure of a lithium battery according to claim 4, wherein: The first tab (6) and the second tab (7) are respectively embedded in the first tab slot (4) and the second tab slot (5).

7. A lithium battery winding structure according to claim 1, characterized in that: The first adhesive tape (8) covers the first tab slot (4), and the second adhesive tape (9) covers the second tab slot (5).

8. A lithium-ion battery, characterized in that: It includes the lithium battery winding structure according to any one of claims 1 - 7.

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