Battery and preparation method of lithium ion battery pole piece

Abstract

The invention relates to the technical field of lithium ion batteries, in particular to a battery and a preparation method of a lithium ion battery pole piece. The method comprises the following steps: confirming a first coating area and a second coating area of a current collector; coating the first coating area with graphite slurry or lithium cobalt oxide slurry to form an isolation coating; coating ternary material slurry on the second coating area and the isolation coating to form an active substance layer; in the thickness direction of the current collector, the isolation coating isolates the active substance layer from the current collector; and carrying out laser cleaning on the active material layer of the first coating area and the isolation coating until the part for welding the tab on the current collector is exposed, so as to prepare the pole piece. By adopting the mode, the cleaning difficulty can be reduced, and the laser cleaning optimal rate is increased.

Description

Technical Field

[0001] The invention relates to the technical field of lithium ion batteries, in particular to a battery and a method for preparing a lithium ion battery pole piece. Background Art

[0002] Lithium-ion batteries are widely used in electronic communications, energy storage, transportation and other fields due to their high energy density, long service life and good safety performance.

[0003] As people have higher requirements for the charging speed of lithium-ion batteries, the charging speed of lithium batteries can be effectively improved by reserving a collector slot for welding the tabs in the middle of the active material layer and welding the tabs in the middle of the slot. Before welding the tabs, the coating on the battery pole piece needs to be cleaned to leak out the bottom current collector before welding the tabs. The current mainstream coating cleaning method is laser cleaning.

[0004] Laser cleaning is a cleaning technology that uses a galvanometer to control the laser beam to scan the cleaning area at high speed multiple times, so that the coating on the surface of the material is heated, vaporized, ablated, and peeled off to achieve cleaning. However, when using laser to clean the coating of the pole piece, it is easy to burn or even perforate the current collector, causing the pole piece to be defective, thus affecting the subsequent welding of the pole ear and thus affecting the overall performance of the battery cell. Summary of the invention

[0005] The technical problem to be solved by the embodiments of the present invention is to provide a method for preparing a pole piece and a pole piece for a lithium-ion battery, which can reduce the difficulty of cleaning and increase the efficiency of laser cleaning.

[0006] The present invention discloses a method for preparing a lithium ion battery pole piece, the method comprising:

[0007] Identifying a first coating region and a second coating region of the current collector;

[0008] Applying graphite slurry or lithium cobalt oxide slurry on the first coating area to form an isolation coating;

[0009] Applying ternary material slurry on the second coating area and the isolation coating to form an active material layer; in the thickness direction of the current collector, the isolation coating isolates the active material layer from the current collector;

[0010] The active material layer in the first coating area and the isolation coating are laser cleaned until a portion on the current collector for welding the pole lug is exposed, so as to obtain a pole piece.

[0011] Optionally, the step of laser cleaning the active material layer and the isolation coating in the first coating area until a portion on the current collector for welding the electrode lug is exposed to obtain a pole piece comprises:

[0012] The active material layer and the isolation coating in the first coating area are laser cleaned until the current collector is exposed, and the active material layer and the isolation coating in the first coating area close to the second coating area are retained. The current collector, the isolation coating and the active material layer located on the surface of the isolation coating form a pole lug groove, and the portion of the current collector located at the bottom of the pole lug groove is used for welding the pole lug.

[0013] The pole ear groove is a rectangular groove that passes through one side of the pole piece in the width direction, and the first coating area is a square coating area that extends to the edge of the pole piece;

[0014] The size of the tab groove and the size of the isolation coating satisfy the following relationship:

[0015] 0 <c-a≤3mm

[0016] 0 <d-b≤3mm

[0017] Among them, a is the length of the pole ear groove; b is the width of the pole ear groove; c is the length of the isolation coating; d is the width of the isolation coating.

[0018] Optionally, the first coating area and the second coating area are respectively located on opposite sides of the current collector, the orthographic projections of the first coating areas on both sides overlap on the current collector, and the orthographic projections of the second coating areas on both sides overlap on the current collector.

[0019] Optionally, the composition of the graphite slurry satisfies the following relationship:

[0020] 0.2≤θ1≤0.6

[0021] X1+Y1+Z1=1

[0022] 0.5≤X1≤0.99

[0023] 0.01≤Y1≤0.1

[0024] 0.01≤Z1≤0.1

[0025] Wherein, in the above relationship, X1 is the mass ratio of graphite, Y1 is the mass ratio of styrene-butadiene rubber, Z1 is the mass ratio of carboxymethyl cellulose, the solvent is pure water, and θ1 is the solid content in the graphite slurry.

[0026] Optionally, when the isolation coating layer is made of graphite slurry, the thickness D1 of the isolation coating layer satisfies the following relationship:

[0027] 0.5um≤D1≤30um

[0028] Optionally, the composition of the lithium cobalt oxide slurry satisfies the following relationship:

[0029] 0.3≤θ2≤0.8

[0030] X2+Y2+Z2=1

[0031] 0.5≤X2≤0.99

[0032] 0.01≤Y2≤0.1

[0033] 0≤Z2≤0.1

[0034] Among them, in the above relationship, X2 is the mass ratio of lithium cobalt oxide, Y2 is the mass ratio of polyvinylidene fluoride, Z2 is the mass ratio of conductive carbon black, the solvent is pure water, and θ2 is the solid content in the lithium cobalt oxide slurry.

[0035] Optionally, when the isolation coating layer is made of lithium cobalt oxide slurry, the thickness D2 of the isolation coating layer satisfies the following relationship:

[0036] 10um≤d2≤60um

[0037] Optionally, the ternary material includes one of lithium nickel manganese cobalt oxide and lithium nickel cobalt aluminum oxide.

[0038] The present invention also discloses a battery, comprising a pole piece made by the method for preparing a lithium ion battery pole piece as described in any one of the above.

[0039] Compared with the prior art, the beneficial effect of the preparation method of the lithium-ion battery pole piece provided by the embodiment of the present invention is that after confirming the first coating area and the second coating area on the current collector, a graphite slurry or a lithium cobalt oxide slurry is coated at the position corresponding to the first coating area, thereby forming an isolation coating on the first coating area of ​​the current collector, and then the current collector can be coated with a ternary material slurry as a whole. At the position of the first coating area, since the isolation coating is formed in advance, the active material layer formed by the ternary material slurry at this position will not be directly in contact with the current collector. After the ternary material slurry is coated, when the first coating area needs to be laser cleaned, it is not necessary to adjust the cleaning temperature of the laser cleaning instrument to a higher temperature to destroy the adhesion between the isolation coating and the current collector. Even if there is a temperature fluctuation during the cleaning process, it will not reach the temperature that destroys the current collector, avoiding the problem of damage or perforation of the current collector during the cleaning process, thereby reducing the difficulty of cleaning and increasing the laser cleaning rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments, in which:

[0041] Figure 1It is a schematic diagram of the process of laser cleaning of lithium battery pole pieces provided by an embodiment of the present invention;

[0042] Figure 2 is a schematic diagram of a structure in which an isolation coating is applied to a current collector according to an embodiment of the present invention;

[0043] Figure 3 is Figure 2 A schematic diagram of a structure in which an active material layer is coated on a base;

[0044] Figure 4 is Figure 3 A schematic diagram of a structure in which an active material layer and an isolation coating are cleaned to form a tab groove;

[0045] Figure 5 It is a schematic diagram comparing the sizes of the tab groove and the isolation coating.

[0046] The reference numerals in the figures are:

[0047] 110, current collector; 112, tab groove; 120, isolation coating; 130, active material layer. DETAILED DESCRIPTION

[0048] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. Now, in conjunction with the accompanying drawings, the preferred embodiments of the present invention are described in detail.

[0049] The present invention provides a method for preparing a lithium-ion battery electrode. Figure 1 The method comprises:

[0050] S100 , confirming the first coating area and the second coating area of ​​the current collector 110 .

[0051] Specifically, according to the size of the winding core to be wound, the position on the current collector 110 where the electrode tab needs to be welded is determined, and this position is the first coating area, and the other positions are the second coating areas. After the first coating area and the second coating area are determined, it is convenient for subsequent orderly production and processing.

[0052] S200 , coating a graphite slurry or a lithium cobalt oxide slurry on a first coating area to form an isolation coating layer 120 .

[0053] Specifically, Figure 2As shown, it is a schematic diagram of graphite slurry or lithium cobalt oxide slurry forming an isolation coating 120 on the current collector 110. After the graphite slurry or lithium cobalt oxide slurry is coated on the current collector 110, it is relatively easy to separate from the current collector 110. When the graphite slurry or lithium cobalt oxide slurry is cleaned by a laser cleaning device, it is not necessary to adjust the cleaning temperature to a higher temperature. During the cleaning process, even if the laser cleaning temperature fluctuates, it will not cause damage to the current collector 110, which is conducive to ensuring the laser cleaning efficiency.

[0054] S300 , coating the ternary material slurry on the second coating area and the isolation coating 120 to form an active material layer 130 ; in the thickness direction of the current collector 110 , the isolation coating 120 isolates the active material layer 130 from the current collector 110 .

[0055] Specifically, Figure 3 As shown, it is a schematic diagram of the structure that after the graphite slurry or lithium cobalt oxide slurry is coated on the first coating area of ​​the current collector 110 to form the isolation coating 120, the ternary material slurry is coated on the second coating area and the isolation coating 120. In the above method, in the second coating area on the current collector 110, the active material layer 130 is in direct contact with the current collector 110. In the first coating area on the current collector 110, the active material layer 130 is isolated by the isolation coating 120 to prevent the active material layer 130 from directly contacting the current collector 110, so as to reduce the difficulty of laser cleaning.

[0056] S400 , laser cleaning the active material layer 130 and the isolation coating layer 120 in the first coating area until a portion on the current collector 110 for welding the electrode lug is exposed, so as to obtain an electrode sheet.

[0057] Specifically, Figure 4 , which is a schematic diagram of the structure of the current collector 110 exposed after the first coating area is cleaned. After the first coating area of ​​the current collector 110 is cleaned by a laser cleaning device, the subsequent tabs are directly welded on the current collector 110.

[0058] The method for preparing a lithium-ion battery pole piece provided in the embodiment of the present application, after confirming the first coating area and the second coating area on the current collector 110, a graphite slurry or a lithium cobalt oxide slurry is coated at a position corresponding to the first coating area, thereby forming an isolation coating 120 on the first coating area of ​​the current collector 110, and then the current collector 110 can be coated with a ternary material slurry as a whole. At the position of the first coating area, the isolation coating 120 is formed due to the graphite slurry or lithium cobalt oxide slurry coated in advance, and the active material layer 130 formed by the ternary material slurry at this position will not be directly in contact with the current collector 110. After the ternary material slurry is coated, when the first coating area needs to be laser cleaned, the adhesion between the isolation coating 120 and the current collector 110 can be destroyed without adjusting the cleaning temperature of the laser cleaning instrument to a higher temperature. Even if there is a temperature fluctuation during the cleaning process, it will not reach the temperature that destroys the current collector 110, avoiding the problem of damage or perforation of the current collector 110 during the cleaning process, thereby reducing the cleaning difficulty and increasing the laser cleaning rate.

[0059] Optionally, in step S400, the step of laser cleaning the active material layer 130 and the isolation coating 120 in the first coating area until a portion on the current collector 110 for welding the electrode lug is exposed to obtain the electrode sheet includes:

[0060] S410, laser cleaning the active material layer 130 and the isolation coating 120 in the first coating area until the current collector 110 is exposed, and retaining the active material layer 130 and the isolation coating 120 in the first coating area close to the second coating area. The current collector 110, the isolation coating 120 and the active material layer 130 located on the surface of the isolation coating 120 enclose a pole lug groove 112, and the portion of the current collector 110 located at the bottom of the pole lug groove 112 is used for welding the pole lug.

[0061] In this way, when welding the tabs, the reliability of welding can be guaranteed, thereby improving the stability during use.

[0062] In an optional embodiment of the present application, Figure 5 As shown, the tab groove 112 is a rectangular groove that runs through one side of the pole piece in the width direction, and the first coating area is a square coating area that extends to the edge of the pole piece; the size of the tab groove 112 and the size of the isolation coating 120 satisfy the following relationship:

[0063] 0 <c-a≤3mm

[0064] 0 <d-b≤3mm

[0065] Wherein, a is the length of the tab groove 112 ; b is the width of the tab groove 112 ; c is the length of the isolation coating 120 ; and d is the width of the isolation coating 120 .

[0066] By adopting the above-mentioned form, it is possible to ensure that the size of the tab groove 112 is expanded as much as possible within the range of the isolation coating 120, so as to ensure that the tab groove 112 has a larger contact area when welding with the tab, so as to ensure the reliability of the welding connection.

[0067] In an optional embodiment of the present application, the first coating area and the second coating area are respectively located on opposite sides of the current collector 110, the orthographic projections of the first coating areas on the two sides on the current collector 110 overlap, and the orthographic projections of the second coating areas on the two sides on the current collector 110 overlap.

[0068] Specifically, in order to ensure the capacity of the final battery, a double-layer coating process is used when coating the current collector 110, and when laser cleaning is used, both sides of the current collector 110 need to be cleaned to ensure the reliability of subsequent tab welding. When welding the tab, the tab can be directly welded at the tab groove 112 on one side of the current collector.

[0069] In an optional embodiment of the present application, the composition of the graphite slurry satisfies the following relationship:

[0070] 0.2≤θ1≤0.6

[0071] X1+Y1+Z1=1

[0072] 0.5≤X1≤0.99

[0073] 0.01≤Y1≤0.1

[0074] 0.01≤Z1≤0.1

[0075] Wherein, in the above relationship, X1 is the mass ratio of graphite, Y1 is the mass ratio of styrene-butadiene rubber, Z1 is the mass ratio of carboxymethyl cellulose, the solvent is pure water, and θ1 is the solid content in the graphite slurry.

[0076] Specifically, graphite is conducive to lowering the melting point of the isolation coating 120, so that the isolation coating 120 is more easily broken after being heated, so as to detach from the current collector 110, and can also maintain a certain conductivity to avoid heat accumulation. Styrene-butadiene rubber and carboxymethyl cellulose are used to ensure the viscosity and adhesion of the isolation coating 120 during coating, ensure the operability of the coating process, reduce the difficulty of coating, and avoid accidental detachment of the unwashed part, which is conducive to ensuring the reliability of the prepared pole piece during use. Among them, in the preferred embodiment of the present application, the mass ratio of graphite is 0.98, the mass ratio of styrene-butadiene rubber is 0.01, and the mass ratio of carboxymethyl cellulose is 0.01; or the mass ratio of graphite is 0.89, the mass ratio of styrene-butadiene rubber is 0.01, and the mass ratio of carboxymethyl cellulose is 0.1; or the mass ratio of graphite is 0.89, the mass ratio of styrene-butadiene rubber is 0.1, and the mass ratio of carboxymethyl cellulose is 0.01; or the mass ratio of graphite is 0.80, the mass ratio of styrene-butadiene rubber is 0.1, and the mass ratio of carboxymethyl cellulose is 0.1.

[0077] In an optional embodiment of the present application, when the isolation coating 120 is made of graphite slurry, the thickness D1 of the isolation coating 120 satisfies the following relationship:

[0078] 0.5um≤D1≤30um

[0079] For example, when the isolation coating 120 is made of graphite slurry, the thinnest coating thickness of the isolation coating 120 can be 0.5um, and the thickest coating thickness can be 30um. The coating thickness can also be set to 10um or 20um. If the thickness of the isolation coating 120 is too thin, it will not be conducive to the stable isolation of the active material layer 130, and will increase the difficulty of cleaning. If the thickness of the isolation coating 120 is too thick, it will be detrimental to the subsequent winding operation.

[0080] In an optional embodiment of the present application, the composition of the lithium cobalt oxide slurry satisfies the following relationship:

[0081] 0.3≤θ2≤0.8

[0082] X2+Y2+Z2=1

[0083] 0.5≤X2≤0.99

[0084] 0.01≤Y2≤0.1

[0085] 0≤Z2≤0.1

[0086] Among them, in the above relationship, X2 is the mass ratio of lithium cobalt oxide, Y2 is the mass ratio of polyvinylidene fluoride, Z2 is the mass ratio of conductive carbon black, the solvent is pure water, and θ2 is the solid content in the lithium cobalt oxide slurry.

[0087] Specifically, lithium cobalt oxide can reduce the melting point of the isolation coating 120, and increase the viscosity and adhesion during coating through polyvinylidene fluoride. At the same time, the conductive carbon black and lithium cobalt oxide ensure the conductivity of the isolation coating 120. To ensure the operability of the coating process, reduce the difficulty of coating, and avoid accidental detachment of the uncleaned part, it is beneficial to ensure the reliability of the prepared electrode when in use. In the preferred embodiment of the present application, the mass ratio of lithium cobalt oxide is 0.98, the mass ratio of polyvinylidene fluoride is 0.01, and the mass ratio of conductive carbon black is 0.01; or the mass ratio of lithium cobalt oxide is 0.80, the mass ratio of polyvinylidene fluoride is 0.1, and the mass ratio of conductive carbon black is 0.1; or the mass ratio of lithium cobalt oxide is 0.90, the mass ratio of polyvinylidene fluoride is 0.05, and the mass ratio of conductive carbon black is 0.05.

[0088] In an optional embodiment of the present application, when the isolation coating 120 is made of lithium cobalt oxide slurry, the thickness D2 of the isolation coating 120 satisfies the following relationship:

[0089] 10um≤d2≤60um

[0090] For example, when the isolation coating 120 is made of lithium cobalt oxide slurry, the thinnest coating thickness of the isolation coating 120 may be 10 um, and the thickest coating thickness may be 60 um. The coating thickness may also be set to 20 um or 40 um according to the actual application environment.

[0091] In an optional embodiment of the present application, the ternary material includes one of lithium nickel manganese cobalt oxide and lithium nickel cobalt aluminum oxide. In actual production applications, it can be flexibly set as needed, as long as the economy and performance of the lithium battery can be guaranteed.

[0092] The present invention also discloses a battery, including a pole piece made by the method for making a lithium-ion battery pole piece in the above embodiment. The pole piece can reduce the probability of being burned or even perforated during laser cleaning, which is beneficial to improving the reliability of welding the pole piece to the pole ear, so as to ensure the overall performance of the battery finally made.

[0093] It should be understood that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. For those skilled in the art, the technical solutions described in the above embodiments can be modified, or some of the technical features therein can be replaced by equivalents; and all these modifications and replacements should fall within the scope of protection of the claims attached to the present invention.

Claims

1. A method for preparing a lithium-ion battery pole piece, characterized in that: The method comprises: Identifying a first coating region and a second coating region of the current collector; Applying graphite slurry or lithium cobalt oxide slurry on the first coating area to form an isolation coating; Applying ternary material slurry on the second coating area and the isolation coating to form an active material layer; in the thickness direction of the current collector, the isolation coating isolates the active material layer from the current collector; The active material layer in the first coating area and the isolation coating are laser cleaned until a portion on the current collector for welding the pole lug is exposed, so as to obtain a pole piece.

2. The method for preparing a lithium-ion battery pole piece according to claim 1, characterized in that: The step of laser cleaning the active material layer and the isolation coating in the first coating area until the portion on the current collector for welding the pole lug is exposed to obtain the pole piece comprises: The active material layer and the isolation coating in the first coating area are laser cleaned until the current collector is exposed, and the active material layer and the isolation coating in the first coating area close to the second coating area are retained. The current collector, the isolation coating and the active material layer located on the surface of the isolation coating form a pole lug groove, and the portion of the current collector located at the bottom of the pole lug groove is used for welding the pole lug.

3. The method for preparing a lithium-ion battery pole piece according to claim 1, characterized in that: The pole ear groove is a rectangular groove that passes through one side of the pole piece in the width direction, and the first coating area is a square coating area that extends to the edge of the pole piece; The size of the tab groove and the size of the isolation coating satisfy the following relationship: 0 <c-a≤3mm 0 <d-b≤3mm Among them, a is the length of the pole ear groove; b is the width of the pole ear groove; c is the length of the isolation coating; d is the width of the isolation coating.

4. The method for preparing a lithium-ion battery pole piece according to claim 3, characterized in that: The first coating area and the second coating area are respectively located on opposite sides of the current collector, the orthographic projections of the first coating areas on the two sides overlap on the current collector, and the orthographic projections of the second coating areas on the two sides overlap on the current collector.

5. The method for preparing a lithium-ion battery pole piece according to claim 1, characterized in that: The composition of the graphite slurry satisfies the following relationship: 0.2≤θ1≤0.6 X1+Y1+Z1=1 0.5≤X1≤0.99 0.01≤Y1≤0.1 0.01≤Z1≤0.1 Wherein, in the above relationship, X1 is the mass ratio of graphite, Y1 is the mass ratio of styrene-butadiene rubber, Z1 is the mass ratio of carboxymethyl cellulose, the solvent is pure water, and θ1 is the solid content in the graphite slurry.

6. The method for preparing a lithium-ion battery pole piece according to any one of claims 1 to 5, characterized in that: When the isolation coating layer is made of graphite slurry, the thickness D1 of the isolation coating layer satisfies the following relationship: 0.5um≤D1≤30um.

7. The method for preparing a lithium-ion battery pole piece according to claim 1, characterized in that: The composition of the lithium cobalt oxide slurry satisfies the following relationship: 0.3≤θ2≤0.8 X2+Y2+Z2=1 0.5≤X2≤0.99 0.01≤Y2≤0.1 0≤Z2≤0.1 Among them, in the above relationship, X2 is the mass ratio of lithium cobalt oxide, Y2 is the mass ratio of polyvinylidene fluoride, Z2 is the mass ratio of conductive carbon black, the solvent is pure water, and θ2 is the solid content in the lithium cobalt oxide slurry.

8. The method for preparing a lithium-ion battery pole piece according to any one of claims 1 to 4 or 7, characterized in that: When the isolation coating layer is made of lithium cobalt oxide slurry, the thickness D2 of the isolation coating layer satisfies the following relationship: 10um≤d2≤60um.

9. The method for preparing a lithium-ion battery pole piece according to claim 8, characterized in that: The ternary material includes one of lithium nickel manganese cobalt oxide and lithium nickel cobalt aluminum oxide.

10. A battery, characterized in that: A pole piece made by the method according to any one of claims 1 to 9.

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