CN115084428A - Method for improving lithium precipitation at corner of roll core, preparation process of battery and battery - Google Patents
Method for improving lithium precipitation at corner of roll core, preparation process of battery and battery Download PDFInfo
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- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 title claims abstract description 31
- 229910052744 lithium Inorganic materials 0.000 title claims abstract description 31
- 238000000034 method Methods 0.000 title claims abstract description 28
- 238000001556 precipitation Methods 0.000 title claims abstract description 18
- 238000002360 preparation method Methods 0.000 title claims description 8
- 238000000576 coating method Methods 0.000 claims abstract description 73
- 239000011248 coating agent Substances 0.000 claims abstract description 69
- 238000004804 winding Methods 0.000 claims abstract description 51
- 230000002441 reversible effect Effects 0.000 claims abstract description 8
- 238000007765 extrusion coating Methods 0.000 claims description 19
- 239000007888 film coating Substances 0.000 claims description 8
- 238000009501 film coating Methods 0.000 claims description 8
- 239000006255 coating slurry Substances 0.000 claims description 4
- 238000000605 extraction Methods 0.000 claims description 4
- 238000004519 manufacturing process Methods 0.000 claims 1
- 239000010410 layer Substances 0.000 description 20
- 238000004364 calculation method Methods 0.000 description 8
- 230000006872 improvement Effects 0.000 description 8
- 230000008901 benefit Effects 0.000 description 5
- 230000008021 deposition Effects 0.000 description 4
- 238000009826 distribution Methods 0.000 description 4
- 230000000694 effects Effects 0.000 description 3
- 239000011888 foil Substances 0.000 description 3
- 230000004048 modification Effects 0.000 description 3
- 238000012986 modification Methods 0.000 description 3
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 2
- 239000011247 coating layer Substances 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- NYPJDWWKZLNGGM-RPWUZVMVSA-N esfenvalerate Chemical compound C=1C([C@@H](C#N)OC(=O)[C@@H](C(C)C)C=2C=CC(Cl)=CC=2)=CC=CC=1OC1=CC=CC=C1 NYPJDWWKZLNGGM-RPWUZVMVSA-N 0.000 description 2
- 229910001416 lithium ion Inorganic materials 0.000 description 2
- 238000005457 optimization Methods 0.000 description 2
- 238000000926 separation method Methods 0.000 description 2
- 238000003860 storage Methods 0.000 description 2
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 239000011889 copper foil Substances 0.000 description 1
- 238000012938 design process Methods 0.000 description 1
- 238000001125 extrusion Methods 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 239000007773 negative electrode material Substances 0.000 description 1
- 239000007774 positive electrode material Substances 0.000 description 1
- 230000008569 process Effects 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 239000002699 waste material Substances 0.000 description 1
- 238000003466 welding Methods 0.000 description 1
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/04—Construction or manufacture in general
- H01M10/0431—Cells with wound or folded electrodes
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/058—Construction or manufacture
- H01M10/0587—Construction or manufacture of accumulators having only wound construction elements, i.e. wound positive electrodes, wound negative electrodes and wound separators
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
- H01M10/4235—Safety or regulating additives or arrangements in electrodes, separators or electrolyte
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Manufacturing & Machinery (AREA)
- Materials Engineering (AREA)
- Battery Electrode And Active Subsutance (AREA)
- Secondary Cells (AREA)
Abstract
The invention provides a method for improving lithium precipitation at a corner of a winding core, which comprises the following steps: s1, preparing a winding core, and calculating the corner arc length of each circle of negative pole pieces of the winding core to be S1 ═ π R1, and the corner arc length of each circle of positive pole pieces to be S2 ═ π R2; the length of the anode and the cathode is delta S ═ pi (R2-R1), S1 is the corner arc length of each circle of cathode sheets, S2 is the corner arc length of each circle of anode sheets, R1 is the arc radius of each circle of cathode sheets of the winding core, and R2 is the arc radius of each circle of anode sheets of the winding core; s2, passing
Calculating the compensation value of the N/P ratio of the corner of each turn of the winding core, and calculating the pole of each turnN/P ratio of corners and non-corners of the sheet, wherein the N/P ratio is the ratio of the capacity of the reversible surface of the negative electrode to the capacity of the reversible surface of the positive electrode, and alpha is a compensation value of the N/P ratio of each turn of the corner; by optimizing the surface coating structure of the pole piece, the N/P ratio of the positive pole piece region and the negative pole piece region is reasonably designed, and the risk of lithium precipitation at corners is reduced; meanwhile, the internal space of the winding core is reasonably utilized, and the energy density loss caused by coating of the 'sun and shade surfaces' is improved.
Description
Technical Field
The invention relates to the technical field of new energy, in particular to a method for improving lithium precipitation at a corner of a roll core, a preparation process of a battery and the battery.
Background
The TWS earphone is a new intelligent wearable product in a new era, and has good market reaction; every TWS Bluetooth headset is randomly provided with a charging box matched with the TWS Bluetooth headset, and the charging box can provide power for the TWS Bluetooth headset and has the functions of storage and storage. The general design of box that charges is more exquisite, small in size, and duration requires highly, so in order to make full use of box inner space, the built-in electric core shape of it can be designed narrow again thick.
For the battery core, the battery core obtained by a conventional winding mode has a larger side arc area, and the N/P ratio of the positive electrode and the negative electrode at the corner of the outer ring of the pole piece is usually smaller than a design value, so that lithium is easily separated from the corner of the outer ring, and the safety and the cycle performance of the battery are influenced; the current solution is to design a cathode and anode surface, improve the corner lithium precipitation by increasing the N/P ratio of the cathode outer ring, thereby improving the cycle; however, this method is at the cost of energy density loss of the cell, and the single-side coating weight of the negative electrode increases, and the thickness of the whole cell increases.
In view of the above, it is necessary to provide a technical solution to the above problems.
Disclosure of Invention
The invention aims to: a method for improving lithium deposition at the corner of a winding core is provided to solve the problem that lithium deposition is easy to occur at the corner of the battery.
In order to achieve the purpose, the invention adopts the following technical scheme:
a method for improving lithium precipitation at the corner of a winding core comprises the following steps:
s1, preparing a winding core, and calculating the corner arc length of each circle of negative plates of the winding core to be S1 ═ π R1, and the corner arc length of each circle of positive plates to be S2 ═ π R2; the length of the positive and negative electrodes is delta S-pi (R2-R1), S1 is the corner arc length of each circle of negative electrode sheets, S2 is the corner arc length of each circle of positive electrode sheets, R1 is the arc radius of each circle of negative electrode sheets of the winding core, and R2 is the arc radius of each circle of positive electrode sheets of the winding core;
s2, passing
Acquiring a compensation value of the N/P ratio of each turn of corner of the winding core, and calculating the N/P ratio of the corner and the non-corner of each turn of pole piece, wherein the N/P ratio is the ratio of the capacity of the reversible surface of the negative electrode to the capacity of the reversible surface of the positive electrode, and alpha is the compensation value of the N/P ratio of each turn of corner;
and S3, calculating the corner area of each circle of the pole piece in the winding core, and coating and compensating one side of the corner area of each circle of the positive pole piece or the negative pole piece according to the obtained N/P ratio of the corner and the non-corner of each circle of the pole piece of the winding core and the compensation value in the pole piece coating process of the winding core.
As an improvement of the method for improving the lithium precipitation at the corner of the winding core, in step S3, the corner area side of each circle of the pole piece is compensated by adopting a squeeze coating mode according to the N/P ratio of the corner and the non-corner of each circle of the pole piece and the compensation value.
As an improvement of the method for improving the lithium deposition at the corner of the winding core, in step S3, the corner compensation area of the pole piece is coated by extrusion coating, and then the second layer of continuous coating is performed, wherein the two layers of coating slurry are consistent and the coated pole piece has no gap.
As an improvement of the method for improving lithium deposition at the corner of the winding core, in step S3, the non-corner region is coated intermittently by extrusion coating, and then the entire surface is coated continuously.
As an improvement of the method for improving the lithium precipitation at the corner of the winding core, in step S3, the extrusion coating speed is 10-20 m/min.
As a modification of the method for improving the lithium extraction at the corner of the winding core, in step S3, the tension of extrusion coating is 130-140N.
A preparation process of a battery comprises the method for improving lithium precipitation at the corner of the winding core.
A battery is prepared by adopting the preparation process of the battery.
As an improvement of the battery, the battery comprises a positive plate and a negative plate, and the positive/negative plates each comprise:
the current collector comprises a first film coating area and a second film coating area, and the first film coating area and the second film coating area are respectively positioned on two opposite sides of the current collector;
the first coating is arranged in the first coating area;
and the second coating is arranged in the second coating area.
Compared with the prior art, the invention has the beneficial effects that:
1) the invention provides a method for improving the corner lithium analysis of a roll core, which reasonably designs the N/P ratio of positive and negative pole piece areas by optimizing the surface coating structure of the pole pieces and reduces the risk of the corner lithium analysis; meanwhile, the internal space of the winding core is reasonably utilized, and the energy density loss caused by coating of the 'sun and shade surfaces' is improved.
Drawings
FIG. 1 is a flow chart of a method for improving lithium extraction at the corner of a winding core provided by the invention.
Fig. 2 is a schematic diagram of a pole piece structure of a battery according to the present invention.
Fig. 3 is a second schematic diagram of a pole piece structure of a battery according to the present invention.
In the figure: 1-current collector, 2-first coating, 3-second coating, 4-corner region, 5-straight region.
Detailed Description
In order to make the technical solutions and advantages of the present invention clearer, the present invention and its advantages will be described in further detail below with reference to the following detailed description and the accompanying drawings, but the embodiments of the present invention are not limited thereto.
In the description of the present invention, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "fixed" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral part; can be mechanically or electrically connected; either directly or indirectly through intervening media, either internally or in any other relationship. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.
The standard parts used in the invention can be purchased from the market, the special-shaped parts can be customized according to the description of the specification and the accompanying drawings, the specific connection mode of each part adopts conventional means such as bolts, rivets, welding and the like mature in the prior art, the machines, the parts and equipment adopt conventional models in the prior art, and the circuit connection adopts the conventional connection mode in the prior art, so that the detailed description is omitted.
In the design process of the battery, in order to ensure that no redundant lithium ions are precipitated and accumulated on the surface of the negative electrode in the charge and discharge process of the battery, the negative electrode material is more than the positive electrode material;
in the winding type lithium ion battery, two surfaces are arranged between layers, and a positive plate is in contact with a negative plate; the first surface is contacted, the positive plate is arranged on the outer ring of the negative plate, namely the positive electrode covers the negative electrode; the second surface is contacted, the negative plate is arranged on the outer ring of the positive plate, namely the negative plate covers the positive electrode; designing the N/P ratio of different areas contacted by the positive and negative pole pieces, reducing the risk of lithium precipitation at corners and simultaneously improving the ED of the battery cell;
generally, for the outer ring of the negative electrode, the positive electrode wraps the negative electrode, because of radian relation, the positive electrode and the negative electrode are opposite to each other, the length of the positive electrode is longer than that of the negative electrode, the N/P ratio is normally designed, the actual N/P ratio is smaller than the design value, and the lithium precipitation risk exists; similarly, for the inner ring of the negative electrode, the negative electrode wraps the positive electrode, the positive electrode and the negative electrode are opposite to the area due to radian relation, the length of the negative electrode is longer than that of the positive electrode, the actual N/P ratio is designed to be larger according to the normal N/P ratio, the actual N/P ratio is larger than the design value, material waste exists, and ED is not facilitated;
as shown in fig. 1, fig. 2 and fig. 3, a method for improving lithium extraction at the corner of a winding core comprises the following steps:
s1, preparing a winding core, and calculating the corner arc length of each circle of negative pole pieces of the winding core to be S1 ═ π R1, and the corner arc length of each circle of positive pole pieces to be S2 ═ π R2; the length of the positive and negative electrodes is delta S-pi (R2-R1), S1 is the corner arc length of each circle of negative electrode sheets, S2 is the corner arc length of each circle of positive electrode sheets, R1 is the arc radius of each circle of negative electrode sheets of the winding core, and R2 is the arc radius of each circle of positive electrode sheets of the winding core;
s2, passing
Acquiring a compensation value of the N/P ratio of each turn of corner of the winding core, and calculating the N/P ratio of the corner and the non-corner of each turn of pole piece, wherein the N/P ratio is the ratio of the capacity of the reversible surface of the negative electrode to the capacity of the reversible surface of the positive electrode, and alpha is the compensation value of the N/P ratio of each turn of corner;
and S3, calculating the corner area 4 of each circle of the pole piece in the winding core, and coating and compensating one side of the corner area 4 of each circle of the positive pole piece or the negative pole piece according to the obtained N/P ratio and compensation value of the corner and non-corner of each circle of the pole piece of the winding core in the pole piece coating process of the winding core.
According to the invention, by optimizing the surface coating structure of the pole piece, the N/P ratio of the positive pole piece region and the negative pole piece region is reasonably designed, and the risk of lithium precipitation at corners is reduced; meanwhile, the internal space of the winding core is reasonably utilized, and the energy density loss caused by coating of the 'sun and shade surfaces' is improved.
More preferably, in step S3, the compensation is performed on the 4-side corner region of each turn of the pole piece by extrusion coating according to the N/P ratio of the corner and non-corner of each turn of the pole piece and the compensation value. Specifically, an extrusion coater is used.
More preferably, in step S3, the corner compensation area of the pole piece is coated by extrusion coating, and then the second layer of continuous coating is performed, wherein the two layers of coating slurry are the same and the coated pole piece has no gap. Specifically, when the negative plate is coated, the corner compensation area is coated twice in an extrusion coating mode, so that the coating effect is effectively improved, and the coating amount of the positive electrode in the corner area 4 can be increased.
More preferably, in step S3, the non-corner region 4 is intermittently coated by extrusion coating, and then the entire surface is continuously coated. Specifically, when the positive electrode plate is coated, the non-corner region 4 is coated intermittently, and then the whole surface is coated continuously, so that the coating amount of the corner region 4 of the negative electrode plate can be effectively increased by using the coating method.
More preferably, in step S3, the extrusion coating speed is 10 to 20 m/min. Specifically, the extrusion coating speed is within the range of 10-20 m/min and the uniform movement is adopted, so that the consistency of the coating thickness or the coating amount distribution in the coating area is effectively ensured, and the extrusion coating effect and the compensation effect are further improved.
More preferably, in step S3, the tension of extrusion coating is 130-140N.
A preparation process of a battery comprises the method for improving lithium precipitation at the corner of the winding core.
A battery is prepared by adopting the preparation process of the battery. Specifically, the battery adopts the method for improving the corner lithium separation of the winding core, so that the risk of lithium separation at the corner of the battery is reduced, the internal space of the winding core is reasonably utilized, the loss of energy density is greatly reduced, and the cycle performance and the safety of the battery are improved.
More preferably, the current collector comprises a positive plate and a negative plate, wherein the positive/negative plate comprises a current collector 1, a first coating 2 and a second coating 3, the current collector 1 comprises a first coating area and a second coating area, the first coating area and the second coating area are respectively located on two opposite sides of the current collector 1, the first coating 2 is arranged on the first coating area, and the second coating 3 is arranged on the second coating area.
The negative electrode in the following examples comprises a negative electrode current collector 1, a first coating area and a second coating area, wherein the first coating area and the second coating area are respectively arranged on two sides of the current collector 1, and the current collector 1 is a copper foil; the anode comprises an anode current collector 1, a first coating area and a second coating area, wherein the first coating area and the second coating area are respectively positioned on two sides of the current collector 1, and the current collector 1 is an aluminum foil. The first coating film area is coated with a first coating layer 2, and the second coating film area is coated with a second coating layer 3.
The whole winding type battery cell is divided into a straight area 5 and a corner area 4, when the anode wraps the cathode, the lengths of the anode and the cathode of the straight area 5 are equal, the N/P ratio is equal to the actually designed N/P ratio, and the lithium precipitation condition cannot exist; the positive electrode of the corner region 4 is slightly longer than the negative electrode, and the N/P ratio is smaller than the actual design N/P ratio.
Example 1
The improvement method of the embodiment comprises the steps of calculating the position distribution of the corners on the negative pole piece in a geometric mode, and then carrying out N/P ratio compensation on the coating at the corresponding position; the compensation calculation method is as follows:
1) the corner arc length S1 of each layer of the second coating of the negative electrode is pi R1(R1 is the circle arc radius).
2) The corner arc length S2 of each layer of the first positive electrode coating is pi R2(R2 is the radius of the circle arc), and the radius R of the circle arc is calculated according to the actual layer number and the thickness of the pole piece.
3) The length of the positive pole and the super negative pole in the corner area is delta S-pi (R2-R1) -pi d, (d is the thickness of the diaphragm).
4) Compensation value
Suppose that: the N/P ratio of the flat region is calculated to be A, and A is more than 0.
Then: and when the N/P ratio of the corner region is equal to A + alpha, compensating the corner region of the second coating of the negative electrode, and keeping the positive electrode still.
Taking the specific model 971630 as an example for calculation: the thickness of the isolating film is 8um, the thickness of the negative pole piece is 100um, the thickness of the positive pole piece is 80um, and the thickness of the foil is ignored; there are 2 corners per turn, the same as the turn corner compensation value, and the following table is the N/P ratio compensation value calculation for each turn corner.
| Number of turns | Formula for calculating compensation value | Compensation value | Corner N/P |
| Circle | |||
| 1 | π＊8/1＊π＊(100+8) | 0.074 | 1.144 |
| |
π＊8/2＊π＊(100+80+8) | 0.021 | 1.091 |
| |
π＊8/3＊π＊(100+80+8) | 0.014 | 1.084 |
| 4 th turn | π＊8/4＊π＊(100+80+8) | 0.010 | 1.080 |
| |
π＊8/5＊π＊(100+80+8) | 0.008 | 1.078 |
| Circle 6 | π＊8/6＊π＊(100+80+8) | 0.007 | 1.077 |
| … | … | … | … |
| Circle 10 | π＊8/10＊π＊(100+80+8) | 0.004 | 1.074 |
| Circle 11 | π＊8/11＊π＊(100+80+8) | 0.0038 | 1.0738 |
| … | … | … | … |
| Circle 19 | π＊8/19＊π＊(100+80+8) | 0.0022 | 1.0722 |
| Loop 20 | π＊8/20＊π＊(100+80+8) | 0.0021 | 1.0721 |
Coating the negative electrode by adopting an extrusion coating mode according to the designed N/P ratio, coating a corner compensation area, and then continuously coating a second layer, wherein the two layers of coating slurry are consistent and the coated pole pieces have no gap, so that the coating amount of the anode at the corner can be increased; as shown in fig. 2: the arc lengths of two corners of the 1 st turn of A1 are equal; a2 is the two corners of turn 2, with equal arc lengths but slightly longer than the two corners of turn 1 by the difference: pi is multiplied by (the thickness of the 2 layers of diaphragms plus the thickness of the 1 layer of anodes) to be 3.01 mm; in the same way, the length of the arc of the nth circle is slightly longer than that of the arc of the (n-1) th circle by 3.01 mm; and calculating the position of each turn of corner, and performing the positive compensation optimization on the N/P ratio to obtain the target pole piece.
The battery core is assembled by the negative pole piece and the positive pole piece, the N/P ratio of the straight area does not need to be improved, the N/P ratio of the corner only needs to be compensated, the surface density of the negative pole is increased, the compensated part does not occupy the space of the battery core, the N/P of the straight area only needs to be normally designed, under the condition of fixing the size of the battery core, the capacity can be relatively improved, and the ED can also be improved.
Example 2
The improvement method of the embodiment comprises the steps of calculating the position distribution of the corner on the positive pole piece in a geometric mode, and then carrying out N/P ratio compensation on the coating at the corresponding position; the compensation calculation method is as follows:
1) the corner arc length S1 of each layer of the second coating of the negative electrode is pi R1(R1 is the circle arc radius).
2) The corner arc length S2 of each layer of the first positive electrode coating is pi R2(R2 is the radius of the circle arc), and the radius R of the circle arc is calculated according to the actual layer number and the thickness of the pole piece.
3) The length of the positive pole and the super negative pole in the corner area is delta S-pi (R2-R1) -pi d, (d is the thickness of the diaphragm).
4) Compensation value
Suppose that: the N/P ratio of the flat region is calculated to be A, and A is more than 0.
Then: when the N/P ratio at the corner is equal to A-alpha, the corner area of the positive first coating is compensated, and the negative electrode is fixed.
Taking the specific model 971630 as an example for calculation: the thickness of the isolating film is 8um, the thickness of the negative pole piece is 100um, the thickness of the positive pole piece is 80um, and the thickness of the foil is ignored; there are 2 corners per turn, the same as the corner compensation value for the turn, and the following table is the N/P ratio compensation value calculation for each corner turn.
| Number of turns | Formula for calculating compensation value | Compensation value | Corner N/ |
| 1 st circle | π＊8/1＊π＊(100+8) | 0.074 | 1.144 |
| |
π＊8/2＊π＊(100+80+8) | 0.021 | 1.091 |
| |
π＊8/3＊π＊(100+80+8) | 0.014 | 1.084 |
| 4 th turn | π＊8/4＊π＊(100+80+8) | 0.010 | 1.080 |
| |
π＊8/5＊π＊(100+80+8) | 0.008 | 1.078 |
| Circle 6 | π＊8/6＊π＊(100+80+8) | 0.007 | 1.077 |
| … | … | … | … |
| Circle 10 | π＊8/10＊T＊(100+80+8) | 0.004 | 1.074 |
| Circle 11 | π＊8/11＊π＊(100+80+8) | 0.0038 | 1.0738 |
| … | … | … | … |
| Circle 19 | π＊8/19＊π＊(100+80+8) | 0.0022 | 1.0722 |
| Loop 20 | π＊8/20＊π＊(100+80+8) | 0.0021 | 1.0721 |
According to the designed N/P ratio, the positive electrode is coated in an extrusion coating mode, a straight area is coated intermittently, and then the whole surface is coated continuously, so that the coating amount of the negative electrode in a corner area can be reduced, as shown in figure 3: the arc lengths of two corners of the 1 st turn of A1 are equal; a2 is the two corners of turn 2, with equal arc lengths but slightly longer than the two corners of turn 1 by the difference: pi times (thickness of 2 layers of diaphragms + thickness of 1 layer of positive electrodes) is 3.01 mm; in the same way, the length of the arc of the nth circle is slightly longer than that of the arc of the (n-1) th circle by 3.01 mm; and calculating the position of each turn of corner, and performing the negative compensation optimization on the N/P ratio to obtain the target pole piece.
The positive plate and the negative plate are assembled into a battery cell, the N/P ratio of the straight area is not increased, the surface density of the positive electrode of the straight area is not required to be reduced, and the surface density of the positive electrode of the corner area is only required to be reduced, so that the N/P ratio of the corner is compensated; the N/P ratio of the positive electrode and the negative electrode in the mode is smaller than that of the whole positive and negative surfaces, so that the capacity benefit is higher than that of capacity loss caused by corner reduction of the coating amount of the positive electrode, and therefore under the condition of fixing the size of the battery core, the capacity of the battery core is relatively improved on the whole, and ED is also improved.
Example 3
The embodiment 1 and the embodiment 2 are optimized on the basis that the anode is coated with the cathode, when the cathode is coated with the anode, the lengths of the anode and the cathode in a straight area are equal, the N/P ratio is equal to the actually designed N/P ratio, and the lithium precipitation condition can not occur; the length of the negative pole of the corner area is slightly longer than that of the positive pole, and the N/P ratio is larger than the actually designed N/P ratio;
in the embodiment, the position distribution of the corners on the pole piece is calculated in a geometric mode, and then N/P ratio compensation is carried out on the coating at the corresponding position; the compensation calculation method is as follows:
1) the corner arc length S1 ═ R1(R1 is the circle arc radius) of each layer of the positive secondary coating.
2) The corner arc length S2 of each layer of the first coating of the negative electrode is pi R2(R2 is the radius of the circle arc), and the radius R of the circle arc is calculated according to the actual layer number and the thickness of the pole piece.
3) And the length Delta S of the cathode and the anode in the corner region is pi (R2-R1).
4) Compensation value
Suppose that: the N/P ratio of the flat area is calculated to be A, and A is more than 0.
Then: when the N/P ratio at the corner is equal to A-alpha, the corner of the first coating of the cathode is compensated, and the anode is not moved, or when the N/P ratio at the corner is equal to A + alpha, the corner of the second coating of the anode is compensated, and the cathode is not moved.
The following table is the N/P ratio offset calculation for each corner turn.
| Number of turns | Formula for calculating compensation value | Compensation value | Corner N/P |
| Circle | |||
| 1 | π＊8/1＊π＊(100+8) | 0.074 | 1.144 |
| |
π＊8/2＊π＊(100+80+8) | 0.021 | 1.091 |
| |
π＊8/3＊π＊(100+80+8) | 0.014 | 1.084 |
| 4 th turn | π＊8/4＊π＊(100+80+8) | 0.010 | 1.080 |
| |
π＊8/5＊π＊(100+80+8) | 0.008 | 1.078 |
| Circle 6 | π＊8/6＊π＊(100+80+8) | 0.007 | 1.077 |
| … | … | … | … |
| Circle 10 | π＊8/10＊π＊(100+80+8) | 0.004 | 1.074 |
| Circle 11 | π＊8/11＊π＊(100+80+8) | 0.0038 | 1.0738 |
| … | … | … | … |
| Circle 19 | π＊8/19＊π＊(100+80+8) | 0.0022 | 1.0722 |
| Loop 20 | π＊8/20＊π＊(100+80+8) | 0.0021 | 1.0721 |
The above embodiment 3 can be applied to the pole piece structure simultaneously with the embodiment 1.
The above embodiment 3 can be applied to the pole piece structure simultaneously with the embodiment 2.
The patent benefits of the invention are mainly capacity benefits: taking 971630 as an example, when the whole surface of the cathode and the anode is designed, the cathode is not moved, the N/P ratio of the outer ring of the cathode is 1.10, and the N/P ratio of the inner ring is 1.07; when the design of the cathode and the anode surfaces of the corner is carried out, the design of the inner ring and the outer ring of the cathode is 1.07.
Variations and modifications to the above-described embodiments may also occur to those skilled in the art, which fall within the scope of the invention as disclosed and taught herein. Therefore, the present invention is not limited to the above-mentioned embodiments, and any obvious improvement, replacement or modification made by those skilled in the art based on the present invention is within the protection scope of the present invention. Furthermore, although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.
Claims (9)
1. The method for improving lithium precipitation at the corner of the winding core is characterized by comprising the following steps:
s1, preparing a winding core, and calculating the corner arc length of the negative plate of each circle of the winding core toS 1 ＝πR 1 The arc length of the corner of each circle of positive plate is S 2 ＝πR 2 (ii) a The length of the positive pole and the super negative pole is delta S-pi (R) 2 -R 1 )，S 1 Is the corner arc length of each circle of the negative pole piece, S 2 The arc length of the corner of each circle of positive plate, R1 is the arc radius of each circle of negative plate of the winding core, and R2 is the arc radius of each circle of positive plate of the winding core;
s2, passing
Acquiring a compensation value of the N/P ratio of each turn of corner of the winding core, and calculating the N/P ratio of the corner and the non-corner of each turn of pole piece, wherein the N/P ratio is the ratio of the capacity of the reversible surface of the negative electrode to the capacity of the reversible surface of the positive electrode, and alpha is the compensation value of the N/P ratio of each turn of corner;
and S3, calculating the corner area of each circle of the pole piece in the winding core, and coating and compensating one side of the corner area of each circle of the positive pole piece or the negative pole piece according to the obtained N/P ratio of the corner and the non-corner of the pole piece of each circle of the winding core and the compensation value in the pole piece coating process of the winding core.
2. The method of claim 1, wherein in step S3, the compensation is performed on one side of the corner region of each turn of the pole piece by extrusion coating according to the N/P ratio of the corner and the non-corner of each turn of the pole piece and the compensation value.
3. The method of claim 2, wherein in step S3, the corner compensation region of the pole piece is coated by extrusion coating, and then the second layer of continuous coating is performed, wherein the two layers of coating slurry are the same and the coated pole piece has no gap.
4. The method of claim 2, wherein in step S3, the non-corner region is coated intermittently by extrusion coating, and then the entire surface is coated continuously.
5. The method for improving the lithium extraction at the corner of the winding core according to claim 2, wherein in the step S3, the extrusion coating speed is 10-20 m/min.
6. The method as claimed in claim 5, wherein the extrusion coating tension is 130-140N in step S3.
7. A preparation process of a battery, which is characterized by comprising the method for improving lithium precipitation at the corner of a roll core according to any one of claims 1 to 6.
8. A battery prepared by the process for preparing a battery according to claim 8.
9. The battery according to claim 9, comprising a positive plate and a negative plate, wherein the positive/negative plates each comprise:
the current collector comprises a first film coating area and a second film coating area, and the first film coating area and the second film coating area are respectively positioned on two opposite sides of the current collector;
the first coating is arranged in the first coating area;
and the second coating is arranged in the second coating area.
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