CN116014058B - Preparation method of pole piece for winding type battery cell and winding type battery cell - Google Patents
Preparation method of pole piece for winding type battery cell and winding type battery cellInfo
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- CN116014058B CN116014058B CN202211633350.2A CN202211633350A CN116014058B CN 116014058 B CN116014058 B CN 116014058B CN 202211633350 A CN202211633350 A CN 202211633350A CN 116014058 B CN116014058 B CN 116014058B
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- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
- Y02P70/50—Manufacturing or production processes characterised by the final manufactured product
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Abstract
本发明涉及锂离子电池技术领域，公开了一种卷绕式电芯用极片制备方法及卷绕式电芯，方法包括：S1，分别制备正负极浆料；S2，将正负极浆料分别涂覆到正负极集流体两侧；S3，计算均匀涂覆情况下卷绕式电芯平坦区域的N/P值；S4，计算均匀涂覆情况下卷绕式电芯拐角区域的N/P值；计算卷绕式电芯拐角区域的N/P值与卷绕式电芯平坦区域的N/P值之间的差值，确定补偿值；根据补偿值，采用激光清洗工艺对相应的拐角区域的活性物质进行去除处理。通过本发明的技术方案，使得拐角区域的N/P值更加合理，改善拐角析锂现象，而且省略了一次涂覆流程，提高了生产效率，能够适用于相同设计、不同宽度的卷绕式电芯，通用性和灵活性更强。
The present invention relates to the technical field of lithium-ion batteries, and discloses a method for preparing an electrode sheet for a wound cell and a wound cell. The method comprises: S1, preparing positive and negative electrode slurries respectively; S2, coating the positive and negative electrode slurries on both sides of the positive and negative electrode current collectors respectively; S3, calculating the N/P value of the flat area of the wound cell under uniform coating; S4, calculating the N/P value of the corner area of the wound cell under uniform coating; calculating the difference between the N/P value of the corner area of the wound cell and the N/P value of the flat area of the wound cell to determine a compensation value; and using a laser cleaning process to remove the active material in the corresponding corner area according to the compensation value. Through the technical solution of the present invention, the N/P value of the corner area is made more reasonable, the lithium deposition phenomenon in the corner is improved, and a coating process is omitted, thereby improving production efficiency. The invention can be applied to wound cells of the same design and different widths, and has greater versatility and flexibility.
Description
Technical Field
The invention relates to the technical field of lithium ion batteries, in particular to a preparation method of a pole piece for a winding type battery cell and the winding type battery cell.
Background
Due to the rising of emerging electronic products such as flat plates, notebook computers and the like, the lithium batteries such as 3C and the like gradually develop to the directions of large capacity, high multiplying power, flexible batteries and the like, and the performance requirements on the use safety, reliability, service life and the like of the 3C lithium batteries are higher and higher.
Coating thickness of all areas on the pole piece in the winding type lithium ion battery is consistent, so that N/P value of a corner arc area is smaller than N/P value of a flat area, moreover, stress of the corner arc area in a formation stage is poor, contact effect between the pole pieces is poor, ion transmission resistance is easy to be large at a corner due to insufficient lithium intercalation space and poor contact between the pole pieces in a circulation process, lithium is easy to be separated out in the area in the later period of circulation, and secondary reaction is aggravated along with lithium separation, so that battery cell circulation failure is finally caused. In the related art, the cycle is improved by designing a "cathode and anode surface", generally increasing the N/P ratio of the outer ring of the anode, and improving the corner lithium precipitation, or the corner compensation area of the pole piece is coated first by adopting an extrusion coating method as in the patent document CN115084428a, and then the second layer of continuous coating is performed, so that the two layers of coating slurries are consistent and the coated pole piece is free from gaps. The following technical defects exist:
(1) The negative and positive surface design is achieved at the cost of losing the energy density of the battery cell, the coating weight of one side of the negative electrode is increased, and the thickness of the whole battery cell is increased.
(2) The corner compensation area of the pole piece is coated in an extrusion coating mode, and then each model in a second layer continuous coating mode needs to be coated twice, so that the production efficiency is low, and the slurry waste is serious.
Disclosure of Invention
In view of the above, it is necessary to provide a method for manufacturing a wound battery cell electrode sheet, a wound battery cell positive electrode sheet, a wound battery cell negative electrode sheet, and a wound battery cell, in which the N/P compensation value of a corner region is calculated based on the N/P value of a flat region, and the active material layer of the corner region corresponding to the positive electrode sheet or the negative electrode sheet is subjected to compensation treatment by a laser cleaning process, so that the N/P value of the corner region is more reasonable, the corner lithium precipitation phenomenon is improved, in addition, a primary coating process is omitted, the production efficiency is improved, and the method is applicable to wound battery cells of the same design and different widths, and has higher versatility and flexibility.
In order to achieve the purpose, the invention adopts the following technical scheme that the preparation method of the pole piece for the winding type battery cell comprises the following steps:
S1, respectively preparing positive electrode slurry and negative electrode slurry, wherein the weight percentage of active substances in the positive electrode slurry is W c, the gram capacity of the active substances in the positive electrode slurry is C c, the weight percentage of the active substances in the negative electrode slurry is W a, and the gram capacity of the active substances in the negative electrode slurry is C a;
S2, respectively coating positive electrode slurry and negative electrode slurry on two sides of a positive electrode current collector and a negative electrode current collector, wherein the density of a coating surface of the positive electrode current collector is rho c, and the density of a coating surface of the negative electrode current collector is rho a;
S3, calculating an N/P value of a winding type cell flat area under the condition of uniform coating, and recording the N/P value as (N/P) 0, wherein (N/P) 0＝(ρa*Wa*Ca)/(ρc*Wc*Cc;
S4, calculating N/P values of corner areas of the winding type battery cell under the condition of uniform coating, and recording the N/P values as (N/P) i, wherein ,(N/P)i＝(ρa*Wa*Ca*π*R1i)/(ρc*Wc*Cc*π*R2i),R1i is characterized by the arc radius of an ith circle of negative pole piece of the winding type battery cell, R2 i is characterized by the arc radius of an ith circle of positive pole piece of the winding type battery cell, and i=1, 2,3,..n;
s5, calculating a difference value between the N/P value of the corner area of the coiled battery cell and the N/P value of the flat area of the coiled battery cell, and determining a compensation value;
and S6, removing the active substances in the corresponding corner areas by adopting a laser cleaning process according to the compensation value.
Preferably, the active substances in the corresponding corner areas are removed by a laser cleaning process according to the compensation value, and the method comprises the following steps that if the positive plate in the corner areas is coated with the negative plate, the active substances in the corresponding corner areas of the positive plate are physically removed by the laser cleaning process according to the compensation value.
Preferably, the physical removal of the active material in the corresponding corner region of the positive electrode sheet by using a laser cleaning process comprises the following steps:
determining a first active material target area density of a corresponding corner area of the positive plate according to the compensation value;
Determining a first positive plate laser cleaning process parameter according to the first active material target surface density, and performing first laser cleaning and removing on active materials in corresponding corner areas of the positive plate according to the first positive plate laser cleaning process parameter, wherein the first positive plate laser cleaning process parameter comprises 4-5 kW of power, 11000-15000 mm/s of speed, 100-200 kHz of frequency, 30-90N of unreeling tension, 60-120N of reeling tension and 400-900 mm/s of tape moving speed;
and weighing and visually observing the positive plate subjected to the first laser cleaning, determining a second positive plate laser cleaning process parameter according to the first laser cleaning result, and performing second laser cleaning removal on active substances in corresponding corner areas of the positive plate according to the second positive plate laser cleaning process parameter, wherein the second positive plate laser cleaning process parameter comprises 4-5 kW of power, 14000-18000 mm/s of speed, 400-600 kHz of frequency, 30-90N of unreeling tension, 60-120N of reeling tension and 400-900 mm/s of tape conveying speed.
Preferably, the laser cleaning process is adopted to remove the active substances in the corresponding corner areas, and the method further comprises the step of physically removing the active substances in the corresponding corner areas of the negative electrode plate by adopting the laser cleaning process according to the compensation value if the negative electrode plate in the corner areas is coated with the positive electrode plate.
Preferably, the physical removal of the active material in the corresponding corner region of the negative electrode sheet by using a laser cleaning process comprises the following steps:
Determining the target surface density of the second active material in the corresponding corner area of the negative plate according to the compensation value;
determining a first negative electrode plate laser cleaning process parameter according to the second active material target surface density, and performing first laser cleaning and removing on active materials in corresponding corner areas of the negative electrode plate according to the first negative electrode plate laser cleaning process parameter, wherein the first negative electrode plate laser cleaning process parameter comprises 7.2-8 kW of power, 11000-15000 mm/s of speed, 100-200 kHz of frequency, 30-90N of unreeling tension, 60-120N of reeling tension and 400-900 mm/s of tape running speed;
Weighing and visually observing the anode plate subjected to the first laser cleaning, determining a second anode plate laser cleaning parameter according to the first laser cleaning result, and performing second laser cleaning and removing on active substances in corresponding corner areas of the anode plate according to the second anode plate laser cleaning process parameter, wherein the second anode plate laser cleaning process parameter comprises the power of 1.6 kW-2.4 kW, the speed of 11000 mm/s-15000 mm/s, the frequency of 400 kHz-600 kHz, the unreeling tension of 30N-90N, the reeling tension of 60N-120N and the tape conveying speed of 400 mm/s-900 mm/s.
Preferably, the active material in the positive electrode slurry is any one or a combination of at least two of lithium cobaltate, ternary material, lithium iron phosphate, lithium manganate and lithium-rich manganese.
Preferably, the active material in the negative electrode slurry is any one or a combination of at least two of a silicon material, mesophase carbon microspheres, hard carbon, soft carbon and lithium metal.
The positive plate for the coiled battery cell is prepared by adopting the preparation method of the pole piece for the coiled battery cell in the technical scheme and comprises a positive current collector, and a first active material layer and a second active material layer which are respectively coated on two sides of the positive current collector, wherein the first active material layer is distributed at intervals and corresponds to a flat area and a corner area of the coiled battery cell respectively.
The negative electrode plate for the coiled battery cell is prepared by adopting the preparation method of the pole piece for the coiled battery cell in the technical scheme and comprises a negative electrode current collector, and a third active material layer and a fourth active material layer which are respectively coated on two sides of the negative electrode current collector, wherein the fourth active material layer is distributed at intervals and corresponds to a flat area and a corner area of the coiled battery cell respectively.
A winding type battery cell is formed by winding a positive plate for the winding type battery cell and a negative plate for the winding type battery cell in the technical scheme.
The beneficial effects of the invention are as follows:
(1) According to the invention, the N/P compensation value of the corner area is calculated by taking the N/P value of the flat area as a reference, and the active material layer of the corner area corresponding to the positive electrode plate or the negative electrode plate is subjected to compensation treatment by a laser cleaning process, so that the N/P value of the corner area is more reasonable, the corner lithium precipitation phenomenon can be improved, and the coating slurry can be saved.
(2) Compared with the prior art, the method has the advantages that the coating flow is simpler, one-time coating process is reduced, and the production efficiency is greatly improved.
(3) The invention can adjust parameters according to the actual coating thickness, the surface density and the like, so that the N/P value of the corner area is more reasonable, and the performance of the winding type battery cell is improved.
(4) The same technological parameters in the invention can be applied to winding type battery cores with the same surface density design and different widths, and the universality and the flexibility are stronger.
(5) According to the invention, parameters such as laser cleaning can be adjusted according to different actual coating thickness and surface density, so that the N/P value is optimized, the performance of a coiled battery core is improved, the cycle life of a lithium battery is further prolonged, the surface density of positive and negative active substances can be changed by adjusting the laser cleaning parameters to perform physical removal, so that a more reasonable N/P value is realized, the target surface density of the active substances is further determined according to the calculated compensation value, the adjustment of the laser cleaning parameters is facilitated, the cleaning result is confirmed by means of visual observation, weighing and the like, and the laser cleaning process parameters are continuously adjusted, so that the target cleaning effect can be realized, and the effect of optimizing the N/P value is realized.
Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention.
Drawings
The foregoing and/or additional aspects and advantages of the invention will become apparent and may be better understood from the following description of embodiments taken in conjunction with the accompanying drawings in which:
fig. 1 shows a schematic flow chart of a method for preparing a pole piece for a coiled battery cell according to an embodiment of the present invention;
Fig. 2 is a schematic view showing the structure of a positive electrode sheet for a wound battery cell according to an embodiment of the present invention;
Fig. 3 is a schematic view showing the structure of a negative electrode sheet for a wound battery cell according to an embodiment of the present invention;
fig. 4 shows a schematic structural view of a wound cell according to an embodiment of the present invention;
fig. 5 shows a cycle life comparison of the wound cells obtained according to example 3 and comparative example 1 of the present invention;
figure 6 shows a comparative graph of the cycle life of the wound cells obtained according to example 6 and comparative example 2 of the invention,
Wherein, the correspondence between the reference numerals and the components in fig. 2 to 4 is:
202 positive electrode current collector, 204 first active material layer, 206 second active material layer, 302 negative electrode current collector, 304 third active material layer, 306 fourth active material layer, 402 flat region, 406 corner region.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the technical solutions of the present invention will be further clearly and completely described in the following in conjunction with the embodiments of the present invention. It should be noted that the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
As shown in fig. 1, the preparation method of the pole piece for the coiled battery cell according to the embodiment of the invention comprises the following steps:
S102, respectively preparing positive electrode slurry and negative electrode slurry, wherein the weight percentage of active substances in the positive electrode slurry is W c, the gram capacity of the active substances in the positive electrode slurry is C c, the weight percentage of the active substances in the negative electrode slurry is W a, the gram capacity of the active substances in the negative electrode slurry is C a, the positive electrode slurry and the negative electrode slurry can be prepared by a dry method or a wet method,
S104, respectively coating the positive electrode slurry and the negative electrode slurry on two sides of a positive electrode current collector and a negative electrode current collector, wherein the density of the coating surface of the positive electrode current collector is rho c, the density of the coating surface of the negative electrode current collector is rho a, the coating can be carried out by adopting an extrusion or transfer coating mode,
S106, calculating an N/P value of a winding type cell flat area under the condition of uniform coating, and marking the N/P value as (N/P) 0, wherein (N/P) 0＝(ρa*Wa*Ca)/(ρc*Wc*Cc;
S108, calculating N/P values of corner areas of the winding type battery cell under the condition of uniform coating, and recording the N/P values as (N/P) i, wherein ,(N/P)i＝(ρa*Wa*Ca*π*R1i)/(ρc*Wc*Cc*π*R2i),R1i is characterized by the arc radius of an ith circle of negative pole piece of the winding type battery cell, R2 i is characterized by the arc radius of an ith circle of positive pole piece of the winding type battery cell, and i=1, 2,3,..n;
s110, calculating a difference value between an N/P value of a corner region of the coiled battery cell and an N/P value of a flat region of the coiled battery cell, and determining a compensation value;
And S112, removing active substances in the corresponding corner areas by adopting a laser cleaning process according to the compensation value.
By taking the N/P value of the flat area as a reference, the N/P compensation value of the corner area is calculated, and the active material layer of the corner area corresponding to the positive electrode plate or the negative electrode plate is subjected to compensation treatment through a laser cleaning process, so that the N/P value of the corner area is more reasonable, the corner lithium precipitation phenomenon can be improved, and the coating slurry can be saved. The coating process is simpler, compared with the prior art, one-time coating process is reduced, and the production efficiency is greatly improved.
In the winding type battery cell, the positive electrode plate and the negative electrode plate between the layers are contacted with two surfaces, wherein the first surface is contacted with the outer ring of the negative electrode plate, namely the positive electrode is coated with the negative electrode, and the second surface is contacted with the outer ring of the positive electrode plate, namely the negative electrode is coated with the positive electrode. The N/P value is the ratio of the face-to-face negative reversible capacity to the positive reversible capacity.
For the outer ring of the negative electrode, the positive electrode is coated with the negative electrode, and the positive electrode and the negative electrode are opposite to each other in terms of radian, the length of the positive electrode is longer than that of the negative electrode, and according to the N/P ratio of normal design, the actual N/P ratio is smaller than the design value, and the lithium precipitation risk exists.
For the inner ring of the negative electrode, the positive electrode is wrapped by the negative electrode, and the positive electrode and the negative electrode are opposite to the region, so that the length of the negative electrode is longer than that of the positive electrode, the actual N/P ratio is larger than the design value according to the N/P ratio of normal design, slurry material waste exists, and the energy density is not improved.
Example 1
Taking a specific model 506582 as an example, the model is 11 circles, the thickness of the isolation film is 9um, the thickness of the positive plate is 74um, the thickness of the negative plate is 91um, the winding type battery cell is of a bilateral symmetry structure, each circle is provided with two corners, and the corner compensation values of the same circles are the same.
For the negative electrode outer ring, the positive electrode coats the negative electrode, and the active material in the corner area corresponding to the positive electrode is physically removed, and the method comprises the following steps:
Calculating the N/P value of the flat area of the coiled cell under the condition of uniform coating, and recording the N/P value as (N/P) 0, wherein (N/P) 0＝(ρa*Wa*Ca)/(ρc*Wc*Cc), wherein rho a is characterized by the density of a coated surface of a negative electrode current collector, W a is characterized by the weight percentage of active substances in a negative electrode slurry, C a is characterized by the gram capacity of the active substances in the negative electrode slurry, rho c is characterized by the density of a coated surface of a positive electrode current collector, W c is characterized by the weight percentage of the active substances in the positive electrode slurry, C c is characterized by the gram capacity of the active substances in the positive electrode slurry, and the calculation result is shown in the following table 1, wherein the active substances in the positive electrode slurry are any one or a combination of at least two of lithium cobaltate, ternary materials, lithium iron phosphate, lithium manganate and lithium-rich manganese, and the active substances in the negative electrode slurry are any one or a combination of at least two of silicon materials, mesophase carbon microspheres, hard carbon, soft carbon and lithium metal.
Calculating the N/P value of the corner region of the coiled cell under the condition of uniform coating, and recording the N/P value as (N/P) i, wherein ,(N/P)i＝(ρa*Wa*Ca*π*R1i)/(ρc*Wc*Cc*π*R2i),R1i is characterized by the arc radius of the negative plate of the ith circle of the coiled cell, R2 i is characterized by the arc radius of the positive plate of the ith circle of the coiled cell, (N/P) i is characterized by the N/P value of the ith circle of the coiled cell, i=1, 2,3, and the calculation result is shown in the following table 1;
Calculating the difference between the N/P value of the corner region of the coiled cell and the N/P value of the flat region of the coiled cell, and determining a compensation value, wherein the calculation result is shown in the following table 1;
According to the compensation value, the active material in the corresponding corner area of the positive plate is physically removed by adopting a laser cleaning process, the laser cleaning process parameters are determined according to the active material target surface density determined by the compensation value, a corresponding relation table of the compensation value and the active material target surface density is established according to a large number of experimental researches in advance, the active material target surface density is determined by the compensation value, and the first positive plate laser cleaning process parameters are determined according to the active material target surface density, wherein the first positive plate laser cleaning process parameters comprise 4 kW-5 kW of power, the speed is 11000 mm/s-15000 mm/s, the frequency is 100 kHz-200 kHz, the unreeling tension is 30N-90N, the reeling tension is 60N-120N, and the taping speed is 400 mm/s-900 mm/s. Performing laser cleaning according to the first positive plate laser cleaning process parameters, weighing and visually observing the positive plate subjected to the first laser cleaning, and determining second positive plate laser cleaning process parameters according to the first laser cleaning result, wherein the second positive plate laser cleaning process parameters comprise 4-5 kW of power, 14000-18000 mm/s of speed, 400-600 Khz of frequency, 30-90N of unreeling tension, 60-120N of reeling tension and 400-900 mm/s of travelling speed. Laser cleaning and removing are continued according to the second positive plate laser cleaning process parameters, so that a target positive plate is obtained, and the structure of the positive plate is shown in fig. 2, and the positive plate comprises a positive current collector 202, a first active material layer 204 and a second active material layer 206 which are respectively coated on two sides of the positive current collector 202, wherein the first active material layers 204 are distributed at intervals, and correspond to a flat area 402 and a corner area 404 of a coiled battery cell respectively.
Table 1 results of calculating compensation values for different turns of positive electrode sheet
| Number of turns | N/P ratio | Compensation value |
| Flat area | 1.065 | 0.000 |
| Circle 1 | 1.161 | 0.096 |
| Circle 2 | 1.099 | 0.034 |
| Circle 3 | 1.086 | 0.021 |
| Circle 4 | 1.080 | 0.015 |
| Circle 5 | 1.077 | 0.012 |
| Circle 6 | 1.074 | 0.009 |
| Circle 7 | 1.073 | 0.008 |
| Circle 8 | 1.072 | 0.007 |
| Circle 9 | 1.071 | 0.006 |
| Circle 10 | 1.070 | 0.005 |
| 11 Th turn | 1.070 | 0.005 |
Example 2
Taking a specific model 506582 as an example, the model is 11 circles, the thickness of the isolation film is 9um, the thickness of the positive plate is 74um, the thickness of the negative plate is 91um, the winding type battery cell is of a bilateral symmetry structure, each circle is provided with two corners, and the corner compensation values of the same circles are the same.
For the negative electrode inner ring, the negative electrode coats the positive electrode, and the active substances in the corner area corresponding to the negative electrode are physically removed, and the method comprises the following steps:
Calculating the N/P value of the flat area of the coiled cell under the condition of uniform coating, and recording the N/P value as (N/P) 0, wherein (N/P) 0＝(ρa*Wa*Ca)/(ρc*Wc*Cc), wherein rho a is characterized by the density of a coated surface of a negative electrode current collector, W a is characterized by the weight percentage of active substances in a negative electrode slurry, C a is characterized by the gram capacity of the active substances in the negative electrode slurry, rho c is characterized by the density of a coated surface of a positive electrode current collector, W c is characterized by the weight percentage of the active substances in the positive electrode slurry, C c is characterized by the gram capacity of the active substances in the positive electrode slurry, and the calculation result is shown in the following table 2, wherein the active substances in the positive electrode slurry are any one or a combination of at least two of lithium cobaltate, ternary materials, lithium iron phosphate, lithium manganate and lithium-rich manganese, and the active substances in the negative electrode slurry are any one or a combination of at least two of silicon materials, mesophase carbon microspheres, hard carbon, soft carbon and lithium metal.
Calculating the N/P value of the corner region of the coiled cell under the condition of uniform coating, and recording the N/P value as (N/P) i, wherein ,(N/P)i＝(ρa*Wa*Ca*π*R1i)/(ρc*Wc*Cc*π*R2i),R1i is characterized by the arc radius of the negative plate of the ith circle of the coiled cell, R2 i is characterized by the arc radius of the positive plate of the ith circle of the coiled cell, (N/P) i is characterized by the N/P value of the ith circle of the coiled cell, i=1, 2,3, and the calculation result is shown in the following table 2;
calculating the difference between the N/P value of the corner region of the coiled cell and the N/P value of the flat region of the coiled cell, and determining a compensation value, wherein the calculation result is shown in the following table 2;
According to the compensation value, the active material in the corresponding corner area of the negative electrode plate is physically removed by adopting a laser cleaning process, the laser cleaning process parameters are determined according to the active material target surface density determined by the compensation value, a corresponding relation table of the compensation value and the active material target surface density is established according to a large number of experimental researches in advance, the active material target surface density is determined by the compensation value, and the first negative electrode plate laser cleaning process parameters are determined according to the active material target surface density, wherein the first negative electrode plate laser cleaning process parameters comprise 7.2-8 kW of power, the speed of 11000-15000 mm/s, the frequency of 100-200 kHz, the unreeling tension of 30-90N, the reeling tension of 60-120N and the taping speed of 400-900 mm/s. According to the first negative electrode sheet laser cleaning process parameters, weighing and visually observing the negative electrode sheet after the first laser cleaning, and determining the second negative electrode sheet laser cleaning process parameters according to the first laser cleaning result, wherein the second negative electrode sheet laser cleaning process parameters comprise power of 1.6 kW-2.4 kW, speed of 11000 mm/s-15000 mm/s, frequency of 400 kHz-600 kHz, unreeling tension of 30N-90N, reeling tension of 60N-120N and tape feeding speed of 400 mm/s-900 mm/s. Laser cleaning and removing are continued according to the second anode piece laser cleaning process parameters, so that a target anode piece is obtained, and the structure of the anode piece is shown in fig. 3, wherein the anode piece comprises an anode current collector 302, a third active material layer 304 and a fourth active material layer 306 which are respectively coated on two sides of the anode current collector 302, and the fourth active material layer 306 is distributed at intervals in a height and respectively corresponds to a flat area 402 and a corner area 404 of a coiled battery cell.
Table 2 results of calculating the compensation values for different turns of the negative electrode sheet
Example 3
The target positive electrode sheet prepared in example 1 and the target negative electrode sheet prepared in example 2 were assembled to form a rolled cell, and as shown in fig. 4, a flat region 402 is formed in the middle, and symmetrical corner regions 404 are formed on both sides.
Example 4
Taking a specific model 496488 as an example, the model number is 9 circles, the thickness of the isolation film is 8um, the thickness of the positive plate is 91um, the thickness of the negative plate is 110um, the winding type battery cell is of a bilateral symmetry structure, each circle is provided with two corners, and the corner compensation values of the same circles are the same.
For the negative electrode outer ring, the positive electrode coats the negative electrode, and the active material in the corner area corresponding to the positive electrode is physically removed, and the method comprises the following steps:
Calculating the N/P value of the flat area of the coiled cell under the condition of uniform coating, and recording the N/P value as (N/P) 0, wherein (N/P) 0＝(ρa*Wa*Ca)/(ρc*Wc*Cc), wherein rho a is characterized by the density of a coated surface of a negative electrode current collector, W a is characterized by the weight percentage of active substances in a negative electrode slurry, C a is characterized by the gram capacity of the active substances in the negative electrode slurry, rho c is characterized by the density of a coated surface of a positive electrode current collector, W c is characterized by the weight percentage of the active substances in the positive electrode slurry, C c is characterized by the gram capacity of the active substances in the positive electrode slurry, and the calculation result is shown in the following table 1, wherein the active substances in the positive electrode slurry are any one or a combination of at least two of lithium cobaltate, ternary materials, lithium iron phosphate, lithium manganate and lithium-rich manganese, and the active substances in the negative electrode slurry are any one or a combination of at least two of silicon materials, mesophase carbon microspheres, hard carbon, soft carbon and lithium metal.
Calculating the N/P value of the corner region of the coiled cell under the condition of uniform coating, and recording the N/P value as (N/P) i, wherein ,(N/P)i＝(ρa*Wa*Ca*π*R1i)/(ρc*Wc*Cc*π*R2i),R1i is characterized by the arc radius of the negative plate of the ith circle of the coiled cell, R2 i is characterized by the arc radius of the positive plate of the ith circle of the coiled cell, (N/P) i is characterized by the N/P value of the ith circle of the coiled cell, i=1, 2,3, and the calculation result is shown in the following table 1;
Calculating the difference between the N/P value of the corner region of the coiled cell and the N/P value of the flat region of the coiled cell, and determining a compensation value, wherein the calculation result is shown in the following table 3;
According to the compensation value, the laser cleaning process parameters are determined according to the target surface density of the active substance determined by the compensation value, a corresponding relation table of the compensation value and the target surface density of the active substance is established according to a large number of experimental researches in advance, the target surface density of the active substance is determined by the compensation value, and the first positive plate laser cleaning process parameters are determined according to the target surface density of the active substance, wherein the first positive plate laser cleaning process parameters comprise power of 4 kW-5 kW, speed of 11000 mm/s-15000 mm/s, frequency of 100 kHz-200 kHz, unreeling tension of 30N-90N, reeling tension of 60N-120N and tape feeding speed of 400 mm/s-900 mm/s. And carrying out laser cleaning according to the first positive plate laser cleaning process parameters, weighing and visually observing the positive plate subjected to the first laser cleaning, and determining the second positive plate laser cleaning process parameters according to the first laser cleaning result, wherein the second positive plate laser cleaning process parameters comprise power of 4 kW-5 kW, speed of 14000 mm/s-18000 mm/s, frequency of 400 kHz-600 Khz, unreeling tension of 30N-90N, reeling tension of 60N-120N and tape feeding speed of 400 mm/s-900 mm/s. Laser cleaning and removal are continued according to the second positive plate laser cleaning process parameters to obtain a target positive plate, wherein the structure of the positive plate is shown in fig. 2, and the positive plate comprises a positive current collector 202, a first active material layer 204 and a second active material layer 206 which are respectively coated on two sides of the positive current collector 202, and the first active material layers 204 are distributed at intervals in a height and respectively correspond to a flat area 402 and a corner area 404 of a coiled cell.
TABLE 3 calculation results of compensation values for different turns of positive plate
Example 5
Taking a specific model 496488 as an example, the model number is 9 circles, the thickness of the isolation film is 8um, the thickness of the positive plate is 91um, the thickness of the negative plate is 110um, the winding type battery cell is of a bilateral symmetry structure, each circle is provided with two corners, and the corner compensation values of the same circles are the same.
For the negative electrode inner ring, the negative electrode coats the positive electrode, and the active substances in the corner area corresponding to the negative electrode are physically removed, and the method comprises the following steps:
Calculating the N/P value of the flat area of the coiled cell under the condition of uniform coating, and recording the N/P value as (N/P) 0, wherein (N/P) 0＝(ρa*Wa*Ca)/(ρc*Wc*Cc), wherein rho a is characterized by the density of a coated surface of a negative electrode current collector, W a is characterized by the weight percentage of active substances in a negative electrode slurry, C a is characterized by the gram capacity of the active substances in the negative electrode slurry, rho c is characterized by the density of a coated surface of a positive electrode current collector, W c is characterized by the weight percentage of the active substances in the positive electrode slurry, C c is characterized by the gram capacity of the active substances in the positive electrode slurry, and the calculation result is shown in the following table 2, wherein the active substances in the positive electrode slurry are any one or a combination of at least two of lithium cobaltate, ternary materials, lithium iron phosphate, lithium manganate and lithium-rich manganese, and the active substances in the negative electrode slurry are any one or a combination of at least two of silicon materials, mesophase carbon microspheres, hard carbon, soft carbon and lithium metal.
Calculating the N/P value of the corner region of the coiled cell under the condition of uniform coating, and recording the N/P value as (N/P) i, wherein ,(N/P)i＝(ρa*Wa*Ca*π*R1i)/(ρc*Wc*Cc*π*R2i),R1i is characterized by the arc radius of the negative plate of the ith circle of the coiled cell, R2 i is characterized by the arc radius of the positive plate of the ith circle of the coiled cell, (N/P) i is characterized by the N/P value of the ith circle of the coiled cell, i=1, 2,3, and the calculation result is shown in the following table 2;
Calculating the difference between the N/P value of the corner region of the coiled cell and the N/P value of the flat region of the coiled cell, and determining a compensation value, wherein the calculation result is shown in the following table 4;
according to the compensation value, the active material in the corresponding corner area of the negative electrode plate is physically removed by adopting a laser cleaning process, the laser cleaning process parameters are determined according to the active material target surface density determined by the compensation value, a corresponding relation table of the compensation value and the active material target surface density is established according to a large number of experimental researches in advance, the active material target surface density is determined by the compensation value, and the first negative electrode plate laser cleaning process parameters are determined according to the active material target surface density, wherein the first negative electrode plate laser cleaning process parameters comprise 7.2-8 kW of power, the speed of 11000-15000 mm/s, the frequency of 100-200 kHz, the unreeling tension of 30-90N, the reeling tension of 60-120N and the taping speed of 400-900 mm/s. Performing laser cleaning according to the first negative electrode sheet laser cleaning process parameters, weighing and visually observing the negative electrode sheet subjected to the first laser cleaning, determining the second negative electrode sheet laser cleaning process parameters according to the first laser cleaning result, wherein the power is 1.6 kW-2.4 kW, the speed is 11000 mm/s-15000 mm/s, the frequency is 400 kHz-600 kHz, the unreeling tension is 30N-90N, the reeling tension is 60N-120N, and the tape moving speed is 400 mm/s-900 mm/s. Laser cleaning and removing are continued according to the second anode piece laser cleaning process parameters, so that a target anode piece is obtained, and the structure of the anode piece is shown in fig. 3, wherein the anode piece comprises an anode current collector 302, a third active material layer 304 and a fourth active material layer 306 which are respectively coated on two sides of the anode current collector 302, and the fourth active material layer 306 is distributed at intervals in a height and respectively corresponds to a flat area 402 and a corner area 404 of a coiled battery cell.
Table 4 results of calculating the compensation values for different turns of the negative electrode sheet
Example 6
The target positive electrode sheet prepared in example 4 and the target negative electrode sheet prepared in example 5 were assembled to form a rolled cell, and as shown in fig. 4, a flat region 402 is formed in the middle, and symmetrical corner regions 404 are formed on both sides.
Comparative example 1
Coating the same positive electrode slurry as in the embodiment 1 on two sides of a positive electrode current collector according to a set value, and carrying out no compensation treatment on corner areas of the positive electrode plate to obtain a target positive electrode plate;
coating the same cathode slurry as in example 2 on both sides of a cathode current collector according to a set value, and performing no compensation treatment on corner regions of the cathode sheet to obtain a target cathode sheet;
and assembling the target positive plate and the target negative plate into a winding type battery cell.
Comparative example 2
Coating the same positive electrode slurry as in example 4 on both sides of a positive electrode current collector according to a set value, and performing no compensation treatment on corner areas of the positive electrode sheet to obtain a target positive electrode sheet;
coating the same cathode slurry as in example 5 on both sides of a cathode current collector according to a set value, and performing no compensation treatment on corner regions of the cathode sheet to obtain a target cathode sheet;
and assembling the target positive plate and the target negative plate into a winding type battery cell.
The cycle performance test is performed on the coiled battery cells obtained in the example 3 and the comparative example 1, the test result is shown in fig. 5, and it can be seen from fig. 5 that the coiled battery cell prepared in the example 3 has longer cycle life, although the difference in the initial cycle period is not obvious, the cycle performance of the example 3 is obviously better than that of the comparative example 1 until the later cycle period, lithium is more and more separated at the corners, the contact effect between pole pieces is worse and worse, the battery cells are easy to be lost in cycle, the lithium separation problem at the corners is obviously improved in the example 3, the contact effect between pole pieces is better, the cycle period is longer, the cycle period is 500 weeks, and the capacity retention rate can still reach about 95%.
The cycle performance test is performed on the coiled battery cells obtained in the example 6 and the comparative example 2, the test result is shown in fig. 6, and it is seen from fig. 6 that the coiled battery cell prepared in the example 6 has longer cycle life, although the difference in the initial cycle period is not obvious, the cycle performance of the example 6 is obviously better than that of the comparative example 2 until the later cycle period, lithium is more and more separated at the corners, the contact effect between pole pieces is worse and worse, the cycle failure of the battery cells is easy to cause, the lithium separation problem at the corners is obviously improved in the example 6, the contact effect between pole pieces is better, the cycle period is longer, the cycle period is 500 weeks, and the capacity retention rate can still reach about 85%.
The foregoing examples illustrate only a few embodiments of the invention and are described in detail herein without thereby limiting the scope of the invention. It should be noted that it will be apparent to those skilled in the art that several variations and modifications can be made without departing from the spirit of the invention, which are all within the scope of the invention. Accordingly, the scope of protection of the present invention is to be determined by the appended claims.
Claims (10)
1. The preparation method of the pole piece for the winding type battery cell is characterized by comprising the following steps of:
S1, respectively preparing positive electrode slurry and negative electrode slurry, wherein the weight percentage of active substances in the positive electrode slurry is W c, the gram capacity of the active substances in the positive electrode slurry is C c, the weight percentage of the active substances in the negative electrode slurry is W a, and the gram capacity of the active substances in the negative electrode slurry is C a;
S2, respectively coating positive electrode slurry and negative electrode slurry on two sides of a positive electrode current collector and a negative electrode current collector, wherein the density of a coating surface of the positive electrode current collector is rho c, and the density of a coating surface of the negative electrode current collector is rho a;
S3, calculating an N/P value of a winding type cell flat area under the condition of uniform coating, and recording the N/P value as (N/P) 0, wherein (N/P) 0＝(ρa*Wa*Ca)/(ρc*Wc*Cc;
s4, calculating N/P values of corner areas of the winding type battery cell under the condition of uniform coating, and recording the N/P values as (N/P) i, wherein ,(N/P)i＝(ρa*Wa*Ca*π*R1i)/(ρc*Wc*Cc*π*R2i),R1i is characterized by the arc radius of an ith circle of negative pole piece of the winding type battery cell, R2 i is characterized by the arc radius of an ith circle of positive pole piece of the winding type battery cell, (N/P) i is characterized by the N/P values of the ith circle of the winding type battery cell, i=1, 2,3, & gt;
s5, calculating a difference value between the N/P value of the corner area of the coiled battery cell and the N/P value of the flat area of the coiled battery cell, and determining a compensation value;
And S6, removing active substances in the corresponding corner areas by adopting a laser cleaning process according to the compensation value.
2. The method for manufacturing a wound-type battery cell electrode sheet according to claim 1, wherein the active material removal process for the corresponding corner region by using the laser cleaning process according to the compensation value comprises the steps of:
And if the positive plate in the corner area is coated with the negative plate, physically removing the active substances in the corresponding corner area of the positive plate by adopting a laser cleaning process according to the compensation value.
3. The method for manufacturing a wound-type battery cell electrode sheet according to claim 2, wherein the physical removal of the active material in the corresponding corner region of the positive electrode sheet by using the laser cleaning process comprises the steps of:
determining a first active material target area density of a corresponding corner area of the positive plate according to the compensation value;
Determining a first positive plate laser cleaning process parameter according to the first active material target surface density, and performing first laser cleaning and removing on active materials in corresponding corner areas of the positive plate according to the first positive plate laser cleaning process parameter, wherein the first positive plate laser cleaning process parameter comprises 4-5 kW of power, 11000-15000 mm/s of speed, 100-200 kHz of frequency, 30-90N of unreeling tension, 60-120N of reeling tension and 400-900 mm/s of tape moving speed;
and weighing and visually observing the positive plate subjected to the first laser cleaning, determining a second positive plate laser cleaning process parameter according to the first laser cleaning result, and performing second laser cleaning removal on active substances in corresponding corner areas of the positive plate according to the second positive plate laser cleaning process parameter, wherein the second positive plate laser cleaning process parameter comprises 4-5 kW of power, 14000-18000 mm/s of speed, 400-600 kHz of frequency, 30-90N of unreeling tension, 60-120N of reeling tension and 400-900 mm/s of tape conveying speed.
4. A method of manufacturing a wound-type battery cell electrode sheet according to any one of claims 1 to 3, wherein the active material in the corner regions is removed by a laser cleaning process, further comprising the steps of:
And if the anode plate is coated on the corner region anode plate, physically removing the corresponding corner region active substances of the anode plate by adopting a laser cleaning process according to the compensation value.
5. The method for manufacturing a wound-type battery cell electrode sheet according to claim 4, wherein the step of physically removing the active material in the corner region of the negative electrode sheet by using a laser cleaning process comprises the steps of:
Determining the target surface density of the second active material in the corresponding corner area of the negative plate according to the compensation value;
determining a first negative electrode plate laser cleaning process parameter according to the second active material target surface density, and performing first laser cleaning and removing on active materials in corresponding corner areas of the negative electrode plate according to the first negative electrode plate laser cleaning process parameter, wherein the first negative electrode plate laser cleaning process parameter comprises 7.2-8 kW of power, 11000-15000 mm/s of speed, 100-200 kHz of frequency, 30-90N of unreeling tension, 60-120N of reeling tension and 400-900 mm/s of tape running speed;
Weighing and visually observing the anode plate subjected to the first laser cleaning, determining a second anode plate laser cleaning parameter according to the first laser cleaning result, and performing second laser cleaning and removing on active substances in corresponding corner areas of the anode plate according to the second anode plate laser cleaning process parameter, wherein the second anode plate laser cleaning process parameter comprises the power of 1.6 kW-2.4 kW, the speed of 11000 mm/s-15000 mm/s, the frequency of 400 kHz-600 kHz, the unreeling tension of 30N-90N, the reeling tension of 60N-120N and the tape conveying speed of 400 mm/s-900 mm/s.
6. The method for preparing a wound-type battery cell electrode sheet according to claim 5, wherein,
The active material in the positive electrode slurry is any one or a combination of at least two of lithium cobaltate, ternary material, lithium iron phosphate, lithium manganate and lithium-rich manganese.
7. The method for preparing a wound-type battery cell electrode sheet according to claim 6, wherein,
The active substance in the negative electrode slurry is any one or a combination of at least two of silicon materials, mesophase carbon microspheres, hard carbon, soft carbon and lithium metal.
8. The positive plate for the coiled battery cell is characterized by being prepared by adopting the preparation method of the positive plate for the coiled battery cell according to any one of claims 1 to 7, and comprising a positive current collector, and a first active material layer and a second active material layer which are respectively coated on two sides of the positive current collector, wherein the first active material layers are distributed at intervals and correspond to a flat area and a corner area of the coiled battery cell respectively.
9. The negative electrode plate for the coiled battery cell is characterized by being prepared by adopting the preparation method of the negative electrode plate for the coiled battery cell according to any one of claims 1 to 7, and comprising a negative electrode current collector, and a third active material layer and a fourth active material layer which are respectively coated on two sides of the negative electrode current collector, wherein the fourth active material layers are distributed at intervals and correspond to a flat area and a corner area of the coiled battery cell respectively.
10. A wound battery cell, which is formed by winding the positive electrode sheet for a wound battery cell according to claim 8 and the negative electrode sheet for a wound battery cell according to claim 9.
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