CN111540880B - Negative plate, preparation method and lithium ion battery comprising negative plate - Google Patents
Negative plate, preparation method and lithium ion battery comprising negative plate Download PDFInfo
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- CN111540880B CN111540880B CN202010383202.4A CN202010383202A CN111540880B CN 111540880 B CN111540880 B CN 111540880B CN 202010383202 A CN202010383202 A CN 202010383202A CN 111540880 B CN111540880 B CN 111540880B
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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
- H01M4/133—Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
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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
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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
- H01M10/058—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
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- 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
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- H01M4/1393—Processes of manufacture of electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
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- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
- H01M2004/027—Negative electrodes
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- Y02E60/10—Energy storage using batteries
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- 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
Abstract
The invention provides a negative plate, a preparation method and a lithium ion battery comprising the negative plate. The negative plate comprises a negative current collector, and the negative current collector comprises a single-side coating area and a double-side coating area; in the double-sided coating area, the surfaces of two sides of the negative current collector are respectively provided with a second coating layer, the second coating layers comprise a first negative active material layer and a second negative active material layer, the second negative active material layer is arranged on the surface of the negative current collector, and the first negative active material layer is arranged on the surface of the second negative active material layer. The lithium ion battery comprising the negative plate has the following effects: (1) the lithium ion battery cathode single-side coating area lithium precipitation problem of the conventional winding structure can be effectively improved, the cycle life of the lithium ion battery is prolonged, and the cycle expansion of the lithium ion battery is reduced. (2) The compaction of the negative electrode is improved, and the energy density of the battery core is increased. (3) The dynamic performance of the negative electrode is improved, and the quick charging capacity of the battery is improved.
Description
Technical Field
The invention belongs to the technical field of lithium ion batteries, and particularly relates to a negative plate, a preparation method and a lithium ion battery comprising the negative plate.
Background
With the rapid development of modern society, portable electronic devices (mobile phones, computers, etc.) are increasingly widely used. Lithium ion batteries are widely applied to portable mobile electronic equipment terminals because of long cycle life and high power density, but as the pace of life of people becomes faster, people have higher requirements on endurance and charging speed, and it is currently seen that fast-charging lithium ion batteries are the main development trend of consumer lithium ion batteries. The development of the fast-charging lithium ion battery technology brings convenience to people and brings safety problems, lithium separation of a lithium ion battery cathode is easily caused when the lithium ion battery is in long circulation under a high-rate fast charging condition, particularly, a single-side coating area of the cathode is more serious, so that the problems of water jumping, expansion, air blowing and the like of the lithium ion battery in circulation are caused, and the service life of the lithium ion battery is greatly reduced.
Disclosure of Invention
In order to overcome the defects in the prior art, the invention provides a negative plate, a preparation method and a lithium ion battery comprising the negative plate. The negative plate is mainly used for solving the problem of lithium precipitation of a single-side coating area of the battery cell negative electrode of a winding structure in a long circulation process under a high-rate quick charging system.
The inventor of the application finds that the basic reason for lithium separation in the single-side coating area of the battery cell negative electrode with the existing winding structure is that the single-side coating area is close to a lug, so that the current density is high, the potential is low, and the dynamic performance of the negative electrode is insufficient. However, the improvement of the dynamic performance of the whole negative electrode inevitably leads to the reduction of the energy density of the lithium ion battery, and the invention provides the negative electrode sheet with the specific structure, and the dynamic performance of the single-side coating area of the negative electrode of the lithium ion battery is improved under the condition of not reducing the energy density of the battery by adjusting the dynamic performance of the active substance in the single-side coating area of the negative electrode of the winding type lithium ion battery and the dynamic performance of the active substance on the surface of the whole negative electrode, so that the polarization of the single-side coating area of the negative electrode and the surface of the whole negative electrode is reduced, the problem of lithium precipitation of the single-side coating area of the negative electrode of the conventional winding structure of the lithium ion battery is effectively improved, the cycle life of the lithium ion battery is prolonged on the premise of not reducing the energy density, the cycle expansion is improved, and the quick charge performance of the battery is improved. The negative plate can solve the problem of lithium precipitation of a single-side coating area of the battery cell negative electrode of a winding structure in a long circulation process under a high-rate charging system under the condition of not reducing energy density.
The purpose of the invention is realized by the following technical scheme:
a winding type negative plate, in particular to a winding type negative plate for a lithium ion battery, the negative plate comprises a negative current collector, and the negative current collector comprises a single-side coating area and a double-side coating area;
in the single-side coating area, a first coating layer is arranged on one side surface of the negative current collector, and the first coating layer comprises a first negative active material layer;
in the double-sided coating area, second coating layers are respectively arranged on the surfaces of two sides of the negative current collector, each second coating layer comprises a first negative active material layer and a second negative active material layer, each second negative active material layer is arranged on the surface of the negative current collector, and each first negative active material layer is arranged on the surface of each second negative active material layer;
the first anode active material layer includes a first anode active material, the second anode active material layer includes a second anode active material, and a lithium ion accepting rate of the first anode active material is larger than a lithium ion accepting rate of the second anode active material.
In the present invention, the kinetic performance of the first anode active material layer is superior to that of the second anode active material layer.
In the present invention, the single-sided coating region refers to a region where the negative electrode active material layer is coated on one of the two sides of the current collector. The double-sided coating area is formed by coating the negative active material layers on the surfaces of two sides of the current collector.
According to the invention, the kinetic performance refers to the de-intercalation speed of lithium ions, and the faster the de-intercalation speed, the better the kinetic performance. Factors affecting the deintercalation rate of lithium ions mainly include: (1) the supportable charging current of the active substance is larger, and the kinetic performance is better; (2) the amount of lithium ions received per unit time, i.e., the rate of receiving lithium ions, is higher, and the kinetic properties are better.
Illustratively, the first anode active material layer has a lithium ion deintercalation rate greater than that of the second anode active material layer.
Illustratively, the supportable charging current of the first anode active material layer is larger than the supportable charging current of the second anode active material layer.
Illustratively, the rate of accepting lithium ions by the first anode active material layer is greater than the rate of accepting lithium ions by the second anode active material layer.
According to the present invention, the content of the first conductive agent forming the first anode active material layer is larger than the content of the second conductive agent forming the second anode active material layer. The selection can ensure that the electron conductivity of the first negative electrode active material layer is better than that of the second negative electrode active material layer, and the addition of the conductive agent can not only improve the conductivity of the negative electrode active material, but also effectively improve Li+The ability to diffuse inside the anode active material, so this selection can ensure that the kinetic performance of the first anode active material layer is better than that of the second anode active material layer.
According to the invention, the negative current collector further comprises a tab area, and coating layers are not arranged on two sides of the negative current collector in the tab area.
According to the invention, the tab area, the single-side coating area and the double-side coating area are sequentially connected, namely, no blank area exists in the tab area, the single-side coating area and the double-side coating area.
According to the invention, the length and the width of the current collector are not specially defined, and the current collectors with different lengths and different widths are selected according to different required battery cores. Illustratively, for the 386283 battery, the length of the current collector is 500-1000mm, such as 885 + -2mm, and the width of the current collector is 400-900mm, such as 773 + -2 mm.
According to the invention, the length of the tab area, the length of the single-side coating area and the length of the double-side coating area are not particularly defined, and can be set according to different requirements, for example, the length of the double-side coating area is greater than that of the single-side coating area, and the length of the double-side coating area is greater than that of the tab area. Also for example, for an 386283 size battery, the length of the single-coated area is 113 ± 2 mm.
According to the invention, the tab area is provided with the negative tab, so that no coating layer is required to be arranged in the area.
According to the present invention, the distance between the negative electrode tab provided in the tab region and the single-side coated region is also not particularly limited, and is, for example, 10 to 100 mm; also for example, for an 386283 size battery, the negative tab disposed in the tab region is 35.5 ± 0.5mm from the single-sided coated region.
According to the present invention, the first anode active material layer of the first coating layer is connected to the first anode active material layer of the second coating layer.
According to the invention, in the double-sided coating area, the thicknesses of the second coating layers on two sides of the negative current collector are the same.
According to the present invention, in the second coating layer, the thickness of the first anode active material layer is 5 to 30 μm, for example, 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, or 30 μm; the thickness of the second negative electrode active material layer is 90 to 115 μm, for example, 90 μm, 95 μm, 100 μm, 105 μm, 110 μm, or 115 μm; and the sum of the thickness of the first anode active material layer and the thickness of the second anode active material layer is 95 to 120 μm.
According to the present invention, in the single-sided coating region, the thickness of the first coating layer, i.e., the thickness of the first anode active material layer, is 120 μm or less, for example, 95 μm, 100 μm, 105 μm, 110 μm, or 115 μm.
According to the present invention, the first coating layer and the second coating layer have the same thickness.
According to the present invention, the surface of the negative current collector optionally further includes a blank region provided on the other side of the double-coated region connected to the single-coated region, the blank region being generated, for example, in order to avoid clipping of the active material layer to the surface of the negative current collector during production of the negative electrode sheet, and the length of the blank region may be, for example, 0.5 to 2mm, such as 1 mm.
According to the invention, as shown in fig. 1, the negative current collector comprises a tab area, a single-side coating area and a double-side coating area which are sequentially arranged from one end of the negative current collector and along the length direction of the negative current collector;
coating a first coating layer including a first negative electrode active material layer on one side surface of a negative electrode current collector in a single-side coating region, namely a BC section region in an M side; coating a second coating layer comprising a first negative electrode active material layer and a second negative electrode active material layer on the two side surfaces of the negative electrode current collector in a double-surface coating area, namely an AB section area in an M surface and an ED section area in an N surface, wherein the second negative electrode active material layer is coated on the surface of the negative electrode current collector, and the first negative electrode active material layer is coated on the surface of the second negative electrode active material layer;
in the negative electrode sheet having the above-described structure, in the preparation process, for example, the slurry for forming the first negative electrode active material layer and the slurry for forming the second negative electrode active material layer may be coated together from the negative electrode current collector a, and the slurry for forming the second negative electrode active material layer is close to the negative electrode current collector, and the slurry for forming the first negative electrode active material layer is far from the negative electrode current collector; the application of the slurry for forming the second anode active material layer to point B is completed, the slurry for forming the first anode active material layer is applied up to point C, and the thickness of the first coating layer in the single-sided coating region and the second coating layer in the double-sided coating region are ensured to be the same.
In the negative electrode sheet having the above-described structure, in the production process, for example, the slurry for forming the first negative electrode active material layer and the slurry for forming the second negative electrode active material layer may be coated together from the negative electrode current collector E, and the slurry for forming the second negative electrode active material layer is close to the negative electrode current collector, and the slurry for forming the first negative electrode active material layer is far from the negative electrode current collector; coating the slurry for forming the second negative electrode active material layer to a point D, or coating the slurry for forming the first negative electrode active material layer and the slurry for forming the second negative electrode active material layer together from the point D of the negative electrode current collector, wherein the slurry for forming the second negative electrode active material layer is close to the negative electrode current collector, and the slurry for forming the first negative electrode active material layer is far away from the negative electrode current collector; the application of the slurry for forming the second anode active material layer to point E is completed; and the connecting line of the point E and the point A is vertical to the negative current collector, in the actual preparation process, the dislocation of about 0-1mm exists between the point E and the point A, the connecting line of the point D and the point B is vertical to the negative current collector, and in the actual preparation process, the dislocation of about 0-1mm exists between the point D and the point B, so that a tab area, a single-side coating area and a double-side coating area can be formed in the negative plate.
According to the present invention, the first anode active material layer includes a first anode active material, a first conductive agent, and a first binder, and the second anode active material layer includes a second anode active material, a second conductive agent, and a second binder. Wherein the first and second anode active materials forming the first and second anode active material layers are the same or different, the first and second conductive agents are the same or different, and the first and second binders are the same or different.
According to the invention, the first negative electrode active material layer comprises the following components in percentage by mass:
70-97 wt% of a first negative electrode active material, 2.5-15 wt% of a first conductive agent, and 0.5-15 wt% of a first binder.
Preferably, the first negative electrode active material layer comprises the following components in percentage by mass:
90.5-96.5 wt% of a first negative electrode active material, 2.5-4.5 wt% of a first conductive agent, and 1-5 wt% of a first binder.
According to the invention, the second anode active material layer comprises the following components in percentage by mass:
83-99 wt% of a second negative electrode active material, 0.5-2 wt% of a second conductive agent, and 0.5-15 wt% of a second binder.
Preferably, the second anode active material layer comprises the following components in percentage by mass:
90-98 wt% of a second negative electrode active material, 1-2 wt% of a second conductive agent, and 1-8 wt% of a second binder.
Wherein the first conductive agent and the second conductive agent are the same or different and are independently selected from at least one of conductive carbon black, acetylene black, Ketjen black, conductive graphite, conductive carbon fiber, carbon nanotube, metal powder and carbon fiber.
Wherein the first binder and the second binder are the same or different and are independently selected from at least one of sodium carboxymethylcellulose, styrene-butadiene latex, polytetrafluoroethylene and polyethylene oxide.
Wherein the first negative electrode active material and the second negative electrode active material are the same or different and are independently selected from at least one of artificial graphite, natural graphite, mesocarbon microbeads and lithium titanate.
Wherein the particle size distribution of the first and second negative electrode active materials is 3 μm<D10<8μm，5μm<D50<14μm，17μm<D90<25μm。
The invention also provides a preparation method of the negative plate, which comprises the following steps:
1) preparing a slurry for forming a first negative electrode active material layer and a slurry for forming a second negative electrode active material layer, respectively;
2) and coating the slurry for forming the first negative electrode active material layer and the slurry for forming the second negative electrode active material layer on the surfaces of the two sides of the negative electrode current collector by using a double-layer coating machine to prepare the negative electrode sheet.
According to the present invention, in step 1), the solid contents of the slurry for forming the first anode active material layer and the slurry for forming the second anode active material layer are 40 wt% to 45 wt%.
According to the present invention, in step 2), the slurry forming the first negative electrode active material layer and the slurry forming the second negative electrode active material layer are coated together from the negative electrode current collector a on one side surface of the negative electrode current collector, and the slurry forming the second negative electrode active material layer is close to the negative electrode current collector, and the slurry forming the first negative electrode active material layer is far from the negative electrode current collector; the slurry for forming the second anode active material layer is applied to the point B, and the slurry for forming the first anode active material layer is applied to the point C, wherein a double-coated area is formed between AB, a single-coated area is formed between BC, and the thickness of the first coating layer in the single-coated area is the same as that of the second coating layer in the double-coated area.
According to the present invention, in step 2), the slurry for forming the first negative electrode active material layer and the slurry for forming the second negative electrode active material layer are coated together from the point E of the negative electrode current collector on the other side surface of the negative electrode current collector, and the slurry for forming the second negative electrode active material layer is close to the negative electrode current collector, and the slurry for forming the first negative electrode active material layer is far away from the negative electrode current collector; coating the slurry for forming the second negative electrode active material layer to a point D, or coating the slurry for forming the first negative electrode active material layer and the slurry for forming the second negative electrode active material layer together from the point D of the negative electrode current collector, wherein the slurry for forming the second negative electrode active material layer is close to the negative electrode current collector, and the slurry for forming the first negative electrode active material layer is far away from the negative electrode current collector; the application of the slurry for forming the second anode active material layer to point E is completed; and the connecting line of the point E and the point A is vertical to the negative current collector, in the actual preparation process, the dislocation of about 0-1mm exists between the point E and the point A, the connecting line of the point D and the point B is vertical to the negative current collector, and in the actual preparation process, the dislocation of about 0-1mm exists between the point D and the point B, so that a tab area, a single-side coating area and a double-side coating area can be formed in the negative plate.
The invention also provides a lithium ion battery, which comprises the negative plate.
According to the present invention, the battery further includes a positive electrode sheet and a separator.
The invention has the beneficial effects that:
the invention provides a negative plate, a preparation method and a lithium ion battery comprising the negative plate. The lithium ion battery comprising the negative plate has the following effects:
(1) the lithium ion battery cathode single-side coating area lithium precipitation problem of the conventional winding structure can be effectively improved, the cycle life of the lithium ion battery is prolonged, and the cycle expansion of the lithium ion battery is reduced.
(2) The compaction density of the negative electrode is improved, and the energy density of the battery core is increased.
(3) The dynamic performance of the negative electrode is improved, and the quick charging capacity of the battery is improved.
Drawings
Fig. 1 is a negative electrode sheet structure according to a preferred embodiment of the present invention, in which 1 is a first negative electrode active material layer and 2 is a second negative electrode active material layer.
Fig. 2 is a conventional negative electrode sheet structure.
Detailed Description
The present invention will be described in further detail with reference to specific examples. It is to be understood that the following examples are only illustrative and explanatory of the present invention and should not be construed as limiting the scope of the present invention. All the technologies realized based on the above-mentioned contents of the present invention are covered in the protection scope of the present invention.
The experimental methods used in the following examples are all conventional methods unless otherwise specified; reagents, materials and the like used in the following examples are commercially available unless otherwise specified.
In the description of the present invention, it should be noted that the terms "first", "second", etc. are used for descriptive purposes only and do not indicate or imply relative importance.
The negative electrode sheet prepared in the following example was used for an 386283-type battery, in which the distance between the negative electrode tab disposed in the tab region and the single-sided coating region was 35.5 ± 0.5mm, the length of the single-sided coating region was 113 ± 2mm, the length of the current collector was 885 ± 2mm, and the width of the current collector was 773 ± 2 mm.
Example 1
The first step is as follows: preparing a slurry for forming a first anode active material layer: adding a first negative electrode active substance (artificial graphite), a first conductive agent (conductive carbon black) and a first binder (sodium carboxymethylcellulose) into a stirring tank according to a mass ratio of 94:4.5:1.5, and adding deionized water to prepare slurry for forming a first negative electrode active substance layer, wherein the solid content of the negative electrode slurry is 40-45 wt%;
the second step is that: preparing a slurry for forming the second anode active material layer: adding a second negative electrode active substance (artificial graphite), a second conductive agent (conductive carbon black) and a second binder (sodium carboxymethylcellulose) into a stirring tank according to the mass ratio of 97.5:1:1.5, and adding deionized water to prepare slurry for forming a second negative electrode active substance layer, wherein the solid content of the negative electrode slurry is 40-45 wt%;
the third step: coating the slurry for forming the first negative electrode active material layer and the slurry for forming the second negative electrode active material layer on the surface of the negative electrode current collector using a two-layer coater, specifically:
as shown in fig. 1, on the side surface M of the negative electrode current collector, the slurry for forming the first negative electrode active material layer and the slurry for forming the second negative electrode active material layer are coated together from the point a of the negative electrode current collector, and the slurry for forming the second negative electrode active material layer is close to the negative electrode current collector, and the slurry for forming the first negative electrode active material layer is far from the negative electrode current collector; finishing the application of the slurry for forming the second anode active material layer to the point B, and applying the slurry for forming the first anode active material layer to the point C, wherein a double-sided coating area is formed between AB, a single-sided coating area is formed between BC, and the thicknesses of the first coating layer in the single-sided coating area and the second coating layer in the double-sided coating area are the same;
coating the slurry for forming the first negative electrode active material layer and the slurry for forming the second negative electrode active material layer on the surface N on the other side of the negative electrode current collector from a point E of the negative electrode current collector, wherein the slurry for forming the second negative electrode active material layer is close to the negative electrode current collector, and the slurry for forming the first negative electrode active material layer is far away from the negative electrode current collector; coating the slurry for forming the second negative electrode active material layer to a point D, or coating the slurry for forming the first negative electrode active material layer and the slurry for forming the second negative electrode active material layer together from the point D of the negative electrode current collector, wherein the slurry for forming the second negative electrode active material layer is close to the negative electrode current collector, and the slurry for forming the first negative electrode active material layer is far away from the negative electrode current collector; the application of the slurry for forming the second anode active material layer to point E is completed; a connecting line of the point E and the point A is perpendicular to the negative current collector, and a connecting line of the point D and the point B is perpendicular to the negative current collector, so that a tab area, a single-side coating area and a double-side coating area can be formed in the negative plate; drying the prepared negative plate at the temperature of 100 ℃;
the fourth step: preparing a positive plate: lithium cobaltate is taken as a positive electrode active material, then the positive electrode active material, a conductive agent (acetylene black) and a binder (polyvinylidene fluoride) are added into a stirring tank according to the mass ratio of 97.2:1.5:1.3, an NMP solvent is added, the mixture is fully stirred, the mixture is sieved by a 200-mesh sieve to prepare positive electrode slurry, the solid content of the positive electrode slurry is 70-75 wt%, the slurry is coated on an aluminum foil by a coating machine, and the aluminum foil is dried at the temperature of 120 ℃ to obtain a positive electrode sheet;
the fifth step: assembling the battery cell: and (3) winding the negative plate prepared in the first step to the third step, the positive plate prepared in the fourth step and the diaphragm together to form a winding core, packaging the winding core by using an aluminum plastic film, baking the winding core to remove moisture, injecting electrolyte, and forming the winding core by adopting a hot pressing formation process to obtain the battery core.
Examples 2 to 4 and comparative examples 1 to 2
The other operation steps are the same as those of example 1, except that the mass percentage contents of the respective components in the first anode active material layer and the second anode active material layer are different, specifically as shown in table 1, and the thickness of the first anode active material layer and the second anode active material layer in the single-side coated region and the thickness of the first anode active material layer and the second anode active material layer in the double-side coated region are different, and only the first anode active material layer is coated in comparative example 1 (the specific structure is shown in fig. 2), and only the second anode active material layer is coated in comparative example 2 (the specific structure is shown in fig. 2), specifically as shown in table 2.
Table 1 mass% of active material layer in negative electrode sheets of examples 1 to 4 and comparative examples 1 to 2
| First negative electrode activityThe mass percentage of each component in the material layer | The mass percentage of each component in the second negative electrode active material layer | |
| Example 1 | 94.0:4.5:1.5 | 97.5:1:1.5 |
| Example 2 | 95.5:3.0:1.5 | 97:1.5:1.5 |
| Example 3 | 96.0:2.5:1.5 | 97:1.5:1.5 |
| Example 4 | 95.5:3.0:1.5 | 97:1.5:1.5 |
| Comparative example 1 | / | 97:1.5:1.5 |
| Comparative example 2 | 94:4.5:1.5 | / |
Table 2 structural parameters of the negative electrode sheets of examples 1 to 4 and comparative examples 1 to 2
The negative electrode sheets prepared in the embodiments are compacted identically, and a soft package battery cell with the model number of 386283 is assembled, the energy density of the soft package battery cell is tested by performing 0.2C/0.2C charging and discharging at 25 ℃, 2.5C charging/0.7C discharging is performed on each soft package battery cell manufactured at 25 ℃, the battery is disassembled at different cycle times to confirm the single-side coating area of the negative electrode of the battery and the lithium precipitation condition of the surface of the negative electrode, and the disassembling result and the energy density are shown in the following table 3:
TABLE 3 energy density of the batteries of the examples and data on lithium deposition, capacity retention and swelling during cycling in the single-side coated region of the negative electrode
In Table 3, the single-side coated area slightly separated lithium, the lithium separation area of the single-side coated area is less than 10% of the total area of the single-side coated area; single-side coated area lithium deposition: the lithium precipitation area of the single-side coating area accounts for 10-30% of the total area of the single-side coating area; single-sided coated areas were heavily lithiated: the lithium precipitation area of the single-side coating area is more than 50% of the total area of the single-side coating area;
slightly separating lithium from the surface of the negative electrode, wherein the lithium separation area accounts for less than 10% of the surface area of the whole negative electrode; lithium precipitation on the surface of the negative electrode: the lithium precipitation area accounts for 10-30% of the whole surface area of the negative electrode; the negative electrode surface was heavily lithiated: the lithium deposition area accounts for more than 50% of the whole surface area of the negative electrode.
From table 3, it can be seen that the battery core prepared by the method of the present invention effectively improves the problem of single-sided lithium precipitation of the negative electrode of the conventional winding structure of the lithium battery under the condition of not reducing the energy density of the battery, improves the cycle life of the lithium ion battery, improves the cycle expansion, and simultaneously improves the quick charging performance of the battery. The use amount of the negative electrode conductive agent is simply increased, so that the negative dynamic performance is improved, the problem of lithium precipitation of a single surface of the negative electrode in a long-cycle process can be effectively solved, and the energy density of the negative electrode is reduced.
The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiment. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (8)
1. A coiled negative plate comprises a negative current collector, wherein the negative current collector comprises a single-sided coating area and a double-sided coating area;
in the single-side coating area, a first coating layer is arranged on one side surface of the negative current collector, and the first coating layer comprises a first negative active material layer;
in the double-sided coating area, second coating layers are respectively arranged on the surfaces of two sides of the negative current collector, each second coating layer comprises a first negative active material layer and a second negative active material layer, each second negative active material layer is arranged on the surface of the negative current collector, and each first negative active material layer is arranged on the surface of each second negative active material layer;
the first anode active material layer includes a first anode active material, the second anode active material layer includes a second anode active material, and a lithium ion accepting rate of the first anode active material is larger than a lithium ion accepting rate of the second anode active material; the content of the first conductive agent forming the first anode active material layer is larger than the content of the second conductive agent forming the second anode active material layer.
2. The negative electrode sheet according to claim 1, wherein the first negative electrode active material layer of the first coating layer is connected to the first negative electrode active material layer of the second coating layer.
3. The negative electrode sheet according to claim 1, wherein the first coating layer and the second coating layer have the same thickness.
4. The negative electrode sheet according to any one of claims 1 to 3, wherein the thickness of the second coating layer is the same on both sides of the negative electrode current collector in the double-sided coating region.
5. The negative electrode sheet according to any one of claims 1 to 3, wherein in the second coating layer, the thickness of the first negative electrode active material layer is 5 to 30 μm, and the thickness of the second negative electrode active material layer is 90 to 115 μm; and the sum of the thickness of the first anode active material layer and the thickness of the second anode active material layer is 95 to 120 μm.
6. The negative electrode sheet according to claim 1, wherein the first negative electrode active material layer further comprises a first conductive agent and a first binder;
the first negative electrode active material layer comprises the following components in percentage by mass:
70-97 wt% of a first negative electrode active material, 2.5-15 wt% of a first conductive agent, and 0.5-15 wt% of a first binder.
7. The negative electrode sheet according to claim 1, wherein the second negative electrode active material layer further comprises a second conductive agent and a second binder;
the second negative electrode active material layer comprises the following components in percentage by mass:
83-99 wt% of a second negative electrode active material, 0.5-2 wt% of a second conductive agent, and 0.5-15 wt% of a second binder.
8. A lithium ion battery comprising the negative electrode sheet of any one of claims 1 to 7.
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| CN112750974B (en) * | 2020-12-29 | 2022-08-09 | 珠海冠宇电池股份有限公司 | Lithium battery positive plate, winding type battery cell and lithium ion battery |
| CN112736218B (en) * | 2020-12-29 | 2022-10-21 | 珠海冠宇电池股份有限公司 | Lithium battery negative plate, winding type battery cell and lithium ion battery |
| CN112968148B (en) * | 2021-03-29 | 2023-07-14 | 欣旺达惠州动力新能源有限公司 | Lithium ion battery negative plate and lithium ion battery |
| CN113097428A (en) * | 2021-03-30 | 2021-07-09 | 珠海冠宇电池股份有限公司 | Negative plate, battery and preparation method of negative plate |
| CN113097427A (en) * | 2021-03-30 | 2021-07-09 | 珠海冠宇电池股份有限公司 | Negative plate and battery |
| CN113707842A (en) * | 2021-08-30 | 2021-11-26 | 维沃移动通信有限公司 | Electrode pole piece, manufacturing method thereof and battery cell |
| CN114094050A (en) * | 2021-11-25 | 2022-02-25 | 珠海冠宇电池股份有限公司 | Negative plate, lithium ion battery and electronic equipment |
| CN114242936B (en) * | 2021-12-16 | 2024-01-30 | 珠海冠宇电池股份有限公司 | Electrode assembly and application thereof |
| CN114551980A (en) * | 2022-02-28 | 2022-05-27 | 宁德新能源科技有限公司 | Electrochemical device and electronic device |
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