A method for slowing down the wrinkles of lithium battery pole pieces

Abstract

The present invention discloses a method for slowing down the wrinkles of lithium battery pole pieces, comprising the following steps: S1, adjusting the winding tension parameters of the winding machine, adjusting the size of the gap between pole pieces during winding according to the adjusted winding tension parameters, and winding the battery cell; S2, hot pressing the wound battery cell; S3, assembling and shelling the hot pressed winding core, and performing full capacity distribution; wherein the winding tension parameters include positive pole piece tension, negative pole piece tension, positive pole piece diaphragm tension and negative pole piece diaphragm tension, and obtaining two sets of tension difference values: positive pole piece tension-negative pole piece tension=Δ1; positive pole piece diaphragm tension-negative pole piece diaphragm tension=Δ2. In this way, by selecting a Δ value (tension difference) of a suitable size range, the wrinkles of the pole piece can be slowed down, thereby improving the consistency of battery performance and the safety performance of the battery.

Description

Technical Field

[0001] The present invention relates to the technical field, and in particular to a method for alleviating wrinkles on a lithium battery pole piece. Background Art

[0002] With the continuous progress of science and technology, lithium-ion batteries have become one of the new generation of green, environmentally friendly and recyclable new energy sources. Lithium-ion batteries are widely used in various fields. Lithium batteries refer to batteries containing lithium (including metallic lithium, lithium alloys, lithium ions, and lithium polymers) in the electrochemical system. In the preparation process of lithium batteries, winding or lamination equipment is usually used to assemble the positive electrode sheet, negative electrode sheet and diaphragm into a battery cell.

[0003] However, due to inconsistent battery performance or imperfect battery management systems, the proportion of battery cycle life, safety performance, and substandard capacity has become increasingly prominent. Therefore, how to improve the consistency of battery quality has become an important tackling difficulty at present. From the perspective of disassembling the interface of the wound battery, there are a large number of wrinkles on the interface (as we all know, the rebound rate of the negative electrode is greater than the rebound rate of the positive electrode. Since the rebound rates of the positive and negative electrodes are different, when the rebound rate of the negative electrode is too large, the positive electrode sheet will produce a binding force on the negative electrode. Under the action of the binding force, the negative electrode will curl up, that is, the negative electrode wrinkles), black spots, and the problem of lithium precipitation, which seriously affects the performance of the battery, and in the subsequent use process, the lithium precipitation problem further forms lithium dendrites, causing the risk of piercing the diaphragm and causing short circuits. Therefore, how to slow down the wrinkles of the electrode sheet after battery capacity division has become a problem that needs to be solved urgently by technicians in this field. Summary of the invention

[0004] In order to solve the technical problems existing in the background technology, the present invention proposes a method for alleviating the wrinkles of lithium battery pole pieces.

[0005] A method for slowing down the wrinkling of a lithium battery pole piece proposed by the present invention comprises the following steps:

[0006] S1, adjusting the winding tension parameter of the winding machine, adjusting the size of the gap between the electrode layers during winding according to the adjusted winding tension parameter, and winding the battery cell;

[0007] S2, hot pressing the wound battery cell;

[0008] S3, assembling and shelling the hot-pressed coil core, and performing full capacity charging;

[0009] Among them, the winding tension parameters include positive electrode sheet tension, negative electrode sheet tension, positive electrode sheet diaphragm tension and negative electrode sheet diaphragm tension, and two sets of tension differences are obtained: positive electrode sheet tension-negative electrode sheet tension=Δ1; positive electrode sheet diaphragm tension-negative electrode sheet diaphragm tension=Δ2.

[0010] Preferably, adjusting the winding tension parameters of the winding machine in step S1 includes:

[0011] S11, selecting appropriate values ​​of positive electrode sheet tension, negative electrode sheet tension, positive electrode sheet diaphragm tension and negative electrode sheet diaphragm tension, and performing electrode sheet tension difference and diaphragm tension difference tests on the lithium battery;

[0012] S12, selecting the optimal tension parameter based on the experiments in S11;

[0013] S13, selecting the pole piece tension difference according to the optimal tension parameter;

[0014] S14, select the diaphragm tension difference according to the optimal tension parameter

[0015] S15, conducting an orthogonal test by comprehensively considering the influencing factors of the above-mentioned positive and negative electrode tension differences and the diaphragm tension differences;

[0016] Among them, the influencing factors include positive electrode sheet tension, negative electrode sheet tension, positive electrode sheet diaphragm tension and negative electrode sheet diaphragm tension.

[0017] Preferably, in step S12, the electrode tension is selected to be between 350-650g; and the diaphragm tension is selected to be between 150-250g for verification.

[0018] Preferably, in step S13, the pole piece tension differences Δ11=30g, Δ12=50g, and Δ13=100g are selected.

[0019] Preferably, in step S14, the diaphragm tension differences Δ21=5g, Δ22=10g, and Δ23=20g are selected.

[0020] Preferably, in step S15, the factors in step S13 and step S14 are combined according to an orthogonal test.

[0021] Preferably, the orthogonal test in step S15 includes the following steps:

[0022] S151, first keep the pole piece tension difference Δ11=30g constant in an orthogonal manner, and randomly match the diaphragm tension differences Δ21=5g, Δ22=10g, and Δ23=20g for verification, and record the corresponding core thickness and battery thickness data;

[0023] S152, firstly keep the pole piece tension difference Δ12=50g constant in an orthogonal manner, and randomly match the diaphragm tension differences Δ21=5g, Δ22=10g, and Δ23=20g for verification, and record the corresponding core thickness and battery thickness data;

[0024] S153, firstly keep the pole piece tension difference Δ13=100g constant in an orthogonal manner, and randomly match the diaphragm tension differences Δ21=5g, Δ22=10g, and Δ23=20g for verification, and record the corresponding core thickness and battery thickness data;

[0025] S154, based on the data recorded in the above steps, select the tension parameters that can improve the pole piece wrinkles.

[0026] Preferably, the hot pressing temperature of the battery cell is 80-90° C., the hot pressing time is 60-90 s, and the hot pressing pressure is 4000-6000 kgf.

[0027] In summary, the present invention has the following beneficial effects: by adjusting the winding tension parameters, positive electrode sheet tension - negative electrode sheet tension = Δ1; positive electrode sheet diaphragm tension - negative electrode sheet diaphragm tension = Δ2, by selecting a Δ value (tension difference) in a suitable range of sizes, the wrinkling of the electrode sheet can be reduced. When the positive electrode tension is greater than the negative electrode tension during winding (i.e., the electrode sheet tension difference, both positive and negative electrode tensions are <600g), the positive electrode will apply a binding force to the negative electrode in advance, resulting in a smaller interlayer spacing between the negative and positive electrodes; at the same time, it also ensures the corresponding diaphragm tension difference between the diaphragms, avoiding the problem of inconsistent binding force of the internal diaphragm caused by the binding between the pole pieces, thereby causing the binding of the diaphragm to cause the pole piece to wrinkle. By improving the tension between the pole pieces, the restraining force of the pole piece rebound is reduced, and the wrinkles of the pole piece after capacity division are improved, thereby improving the consistency of battery performance and the safety performance of the battery.

[0028] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 The present invention is a flow chart of a method for alleviating wrinkles on a lithium battery electrode according to an embodiment of the present invention. DETAILED DESCRIPTION

[0030] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar symbols throughout represent the same or similar elements or elements with the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be understood as limiting the present invention.

[0031] like Figure 1 As shown, a method for alleviating wrinkles of a lithium battery electrode sheet proposed in this embodiment includes the following steps:

[0032] S1, adjusting the winding tension parameter of the winding machine, adjusting the size of the gap between the electrode layers during winding according to the adjusted winding tension parameter, and winding the battery cell;

[0033] It should be noted that by adjusting the tension parameters and selecting the appropriate tension difference, the core can be wound with appropriate tightness during the winding process, thereby providing a reasonable space for the electrode to rebound during subsequent formation and capacity separation.

[0034] S2, hot pressing the wound battery cell;

[0035] Specifically, the hot pressing temperature of the battery cell is 80-90° C., the hot pressing time is 60-90 s, and the hot pressing pressure is 4000-6000 kgf.

[0036] S3, assembling and shelling the hot-pressed coil core, and performing full capacity charging;

[0037] It should be noted that the standing time is 8-12 minutes; the constant temperature is 23-27°C.

[0038] Among them, the winding tension parameters include positive electrode sheet tension, negative electrode sheet tension, positive electrode sheet diaphragm tension and negative electrode sheet diaphragm tension, and two sets of tension differences are obtained: positive electrode sheet tension - negative electrode sheet tension = Δ1; positive electrode sheet diaphragm tension - negative electrode sheet diaphragm tension = Δ2.

[0039] In this way, by adjusting the winding tension parameters, the positive electrode sheet tension - the negative electrode sheet tension = Δ1; the positive electrode sheet diaphragm tension - the negative electrode sheet diaphragm tension = Δ2, by selecting a Δ value (tension difference) of a suitable size range, the wrinkling of the electrode sheet can be reduced. When the positive electrode tension is greater than the negative electrode tension during winding (i.e. the electrode sheet tension difference, both the positive and negative electrode tensions are less than 600g), the positive electrode will apply a binding force to the negative electrode in advance, resulting in a smaller interlayer spacing between the negative and positive electrodes; at the same time, it also ensures the corresponding diaphragm tension difference between the diaphragms, avoiding the problem of inconsistent binding force of the internal diaphragm caused by the binding between the pole pieces, thereby causing the problem of wrinkling of the pole piece caused by the binding of the diaphragm. By improving the tension between the pole pieces, the restraining force of the pole piece rebound can be reduced, and the wrinkling of the pole piece after capacity division can be improved, thereby improving the consistency of battery performance and the safety performance of the battery.

[0040] Furthermore, in step S1, adjusting the winding tension parameters of the winding machine includes:

[0041] S11, selecting appropriate values ​​of positive electrode sheet tension, negative electrode sheet tension, positive electrode sheet diaphragm tension and negative electrode sheet diaphragm tension, and performing electrode sheet tension difference and diaphragm tension difference tests on the lithium battery;

[0042] Among them, the appropriate values ​​of the positive electrode sheet tension, the negative electrode sheet tension, the positive electrode sheet diaphragm tension and the negative electrode sheet diaphragm tension are selected according to the lowest winding tension of the electrode sheet and the diaphragm during the winding operation, that is, there will be no poor coating or misalignment under low tension; when verifying the maximum tension step by step, the winding core will be too tight, resulting in rebound deformation.

[0043] S12, selecting the optimal tension parameter based on the experiments in S11;

[0044] Among them, the pole piece tension and diaphragm tension should be verified at no less than 300g and 100g respectively. If the winding does not fail to operate under this tension, such as poor coating, the tension of the two factors should be reduced to further explore the minimum tension; the pole piece tension and diaphragm tension should be verified at 700g and 300g respectively. If the winding core wound under this tension does not show obvious deformation due to the rebound of the negative electrode for a period of time after hot pressing, the tension of the two factors should be increased to further explore the maximum tension. Specifically, in order to further elaborate on the effects of the pole piece tension and diaphragm tension on winding in step S12, this test tentatively sets the pole piece tension to between 350-650g; the diaphragm tension is tentatively set to between 150-250g for verification.

[0045] S13, selecting the pole piece tension difference according to the optimal tension parameter;

[0046] Specifically, the pole piece tension differences Δ11=30g, Δ12=50g, and Δ13=100g are selected.

[0047] S14, selecting the diaphragm tension difference according to the optimal tension parameter;

[0048] Specifically, the diaphragm tension differences Δ21 = 5 g, Δ22 = 10 g, and Δ23 = 20 g are selected.

[0049] S15, conducting an orthogonal test by comprehensively considering the influencing factors of the above-mentioned positive and negative electrode tension differences and the diaphragm tension differences;

[0050] Among them, the influencing factors include positive electrode sheet tension, negative electrode sheet tension, positive electrode sheet diaphragm tension and negative electrode sheet diaphragm tension.

[0051] According to the above verification scheme, the method for alleviating the wrinkles of the lithium battery pole piece in this embodiment can significantly improve the wrinkles of the pole piece of the lithium-ion battery after full charge, thereby preventing the occurrence of battery wrinkles and capacity attenuation.

[0052] Furthermore, in step S15, the factors in step S13 and step S14 are combined according to an orthogonal test.

[0053] Specifically, the orthogonal test in step S15 includes the following steps:

[0054] S151, first keep the pole piece tension difference Δ11=30g constant in an orthogonal manner, and randomly match the diaphragm tension differences Δ21=5g, Δ22=10g, and Δ23=20g for verification, and record the corresponding core thickness and battery thickness data;

[0055] S152, firstly keep the pole piece tension difference Δ12=50g constant in an orthogonal manner, and randomly match the diaphragm tension differences Δ21=5g, Δ22=10g, and Δ23=20g for verification, and record the corresponding core thickness and battery thickness data;

[0056] S153, firstly keep the pole piece tension difference Δ13=100g constant in an orthogonal manner, and randomly match the diaphragm tension differences Δ21=5g, Δ22=10g, and Δ23=20g for verification, and record the corresponding core thickness and battery thickness data;

[0057] S154, based on the data recorded in the above steps, select the tension parameters that can improve the pole piece wrinkles.

[0058] Among them, the data record table of core thickness and battery thickness is as follows:

[0059]

[0060]

[0061] Judging from the core thickness processed in the above table, the average thickness of the cores in groups B and F is the largest among the 10 groups of cores, while the core thickness of other groups is smaller than these two groups. The corresponding average battery thickness decreases with the increase of the average core thickness, which means that when the pole piece tension difference is 30g, 50g and the corresponding diaphragm tension difference is 10g, 20g, the gap between the pole pieces is expanding, and after the capacity is fully charged, there will be enough space for the pole piece to rebound, so there will be no insufficient gap for the inward folded pole piece to rebound and cause wrinkles. According to the situation analysis, the pole piece tension difference Δ1 is 30-50g, and the diaphragm tension difference Δ2 is 10-20g, which has a better effect on improving the pole piece wrinkles. At the same time, ensure that the size of the gap between the pole pieces is adjusted appropriately when the tension difference is adjusted, and study other tension differences that refer to the battery inward fold wrinkles.

[0062] In summary, the method for slowing down the wrinkling of lithium battery pole pieces in this embodiment includes controlling a single factor variable, ensuring that other factors remain unchanged, and further reducing the restraining force between the layers of the wound battery by using the tension difference between the positive and negative pole pieces and the tension difference between the diaphragms, thereby expanding the interlayer gap between the negative pole piece and the diaphragm, and between the diaphragm and the positive pole piece, so that the positive and negative pole pieces are allowed to have a certain rebound space for the rebound after wetting and the thickness of the charging rebound after formation and capacity division, so as to avoid excessive restraint causing the pole pieces to curl up and wrinkle. This method mainly verifies that the positive pole piece tension - the negative pole piece tension = the pole piece difference Δ1, the upper diaphragm tension - the lower diaphragm tension = the diaphragm difference Δ2, and the scheme needs to further verify the effect by disassembling the battery for final capacity division and checking the interface.

[0063] It should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0064] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0065] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral one; it can be a mechanical connection, an electrical connection, or communication with each other; it can be a direct connection, or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0066] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being "above", "above" or "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below", "below" or "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0067] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A method for slowing down the wrinkling of a lithium battery pole piece, characterized in that: The following steps are involved: S1, adjusting the winding tension parameter of the winding machine, adjusting the size of the gap between the electrode layers during winding according to the adjusted winding tension parameter, and winding the battery cell; S2, hot pressing the wound battery cell; S3, assembling and shelling the hot-pressed coil core, and performing full capacity charging; The winding tension parameters include positive electrode sheet tension, negative electrode sheet tension, positive electrode sheet diaphragm tension and negative electrode sheet diaphragm tension, and two sets of tension differences are obtained: positive electrode sheet tension - negative electrode sheet tension = Δ1; positive electrode sheet diaphragm tension - negative electrode sheet diaphragm tension = Δ2; The step S1 of adjusting the winding tension parameters of the winding machine includes: S11, selecting certain values ​​of positive electrode sheet tension, negative electrode sheet tension, positive electrode sheet diaphragm tension and negative electrode sheet diaphragm tension, and performing electrode sheet tension difference and diaphragm tension difference tests on lithium batteries; S12, selecting the optimal tension parameter based on the experiments in S11; In the step S12, the electrode tension is selected to be between 350-650g; the diaphragm tension is selected to be between 150-250g for verification; S13, selecting the pole piece tension difference according to the optimal tension parameter; S14, selecting the diaphragm tension difference according to the optimal tension parameter; S15, conduct orthogonal test based on the influence factors of the difference in tension between the positive and negative electrodes and the difference in tension between the diaphragms, and select the tension parameters that can improve the wrinkles of the electrode according to the core thickness and battery thickness data; Among them, the influencing factors include positive electrode sheet tension, negative electrode sheet tension, positive electrode sheet diaphragm tension and negative electrode sheet diaphragm tension.

2. The method for alleviating wrinkles of a lithium battery pole piece according to claim 1, characterized in that: In step S13, the pole piece tension differences Δ11=30g, Δ12=50g, and Δ13=100g are selected.

3. The method for alleviating wrinkles of a lithium battery pole piece according to claim 1, characterized in that: In step S14, the diaphragm tension differences Δ21 = 5 g, Δ22 = 10 g, and Δ23 = 20 g are selected.

4. The method for alleviating wrinkles of a lithium battery pole piece according to claim 3, characterized in that: In step S15, the factors in step S13 and step S14 are combined according to an orthogonal test.

5. The method for alleviating wrinkles of a lithium battery pole piece according to claim 4, characterized in that: The orthogonal test of step S15 includes the following steps: S151, first keep the pole piece tension difference Δ11=30g constant in an orthogonal manner, and randomly match the diaphragm tension differences Δ21=5g, Δ22=10g, and Δ23=20g for verification, and record the corresponding core thickness and battery thickness data; S152, first keep the pole piece tension difference Δ12=50g constant in an orthogonal manner, and randomly match the diaphragm tension differences Δ21=5g, Δ22=10g, and Δ23=20g for verification, and record the corresponding core thickness and battery thickness data; S153, firstly keep the pole piece tension difference Δ13=100g constant in an orthogonal manner, and randomly match the diaphragm tension differences Δ21=5g, Δ22=10g, and Δ23=20g for verification, and record the corresponding core thickness and battery thickness data; S154, based on the data recorded in the above steps, select the tension parameters that can improve the pole piece wrinkles.

6. The method for alleviating wrinkles of a lithium battery pole piece according to claim 1, characterized in that: The hot pressing temperature of the battery cell is 80-90° C., the hot pressing time is 60-90s, and the hot pressing pressure is 4000-6000kgf.

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