CN111725484B - Negative plate, preparation method and battery - Google Patents
Negative plate, preparation method and battery Download PDFInfo
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- CN111725484B CN111725484B CN202010534524.4A CN202010534524A CN111725484B CN 111725484 B CN111725484 B CN 111725484B CN 202010534524 A CN202010534524 A CN 202010534524A CN 111725484 B CN111725484 B CN 111725484B
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- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 claims abstract description 53
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- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 claims description 35
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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
-
- 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
- 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
- H01M4/139—Processes of manufacture
- H01M4/1393—Processes of manufacture of electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
-
- 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
- H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
- H01M2004/027—Negative electrodes
-
- 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
- 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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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Manufacturing & Machinery (AREA)
- Battery Electrode And Active Subsutance (AREA)
Abstract
The invention provides a negative plate, a preparation method and a battery, wherein the negative plate comprises: the current collector comprises a current collector, a first slurry layer is coated on one side of the current collector, a second slurry layer and a third slurry layer are respectively coated on the other side of the current collector, and the area where the second slurry layer is located corresponds to the area where the first slurry layer is located; the first slurry layer, the second slurry layer and the third slurry layer respectively comprise a negative active material, a binder and a conductive agent; at least one of the negative electrode active material, the binder, and the conductive agent in the first slurry layer and the third slurry layer is different. According to the negative plate, at least one of the negative active material, the binder and the conductive agent in the first slurry layer and the third slurry layer is different, so that the difference exists between the first slurry layer and the third slurry layer, the problem of negative lithium separation in the battery cycle process is solved while the battery meets the requirement of high-energy-density and quick charging of the battery, the thickness expansion in the battery cycle is reduced, the battery capacity attenuation is slowed, and the cycle performance of the battery is ensured.
Description
Technical Field
The invention relates to the technical field of batteries, in particular to a negative plate, a preparation method and a battery.
Background
The lithium ion battery plays an increasingly important role in daily life of people as a secondary battery which is widely used at present, has the advantages of high specific energy, low self-discharge, long cycle life, no pollution to the environment and the like, and is widely applied to the power fields of electric tools, electric automobiles and the like and the digital fields of mobile phones, pen power and the like. With the light weight and miniaturization of electronic products and the desire of people for high electric energy conversion efficiency, the corresponding demand for high energy density of the lithium ion battery is stronger and stronger, and meanwhile, the requirement for the charging speed of the lithium ion battery is provided, so that the lithium ion battery is required to have the characteristic of high energy density and meet the characteristic of quick charging.
For a lithium ion battery, high energy density and quick charge are contradictory characteristics, the high energy density requires high active material loading capacity and high compaction design, the design is not favorable for the quick charge capacity of the battery, the problems of lithium precipitation of a negative plate, quick battery capacity attenuation, large battery thickness expansion and the like are caused, for the battery with a winding structure, a single-side paste coating area is close to a tab position, the current density is relatively concentrated, lithium precipitation is more likely to occur in a double-side area, the capacity loss is caused, and the quick charge capacity of the lithium ion battery under the high energy density is reduced.
Disclosure of Invention
In view of the above, the invention provides a negative electrode plate, a preparation method and a battery, which are used for solving the problems that the negative electrode plate is easy to precipitate lithium, the battery capacity is fast to attenuate, and the battery thickness is large in expansion.
In order to solve the technical problem, the invention adopts the following technical scheme:
in a first aspect, a negative electrode sheet according to an embodiment of the present invention includes:
the current collector comprises a current collector, a first slurry layer is coated on one side of the current collector, a second slurry layer and a third slurry layer are respectively coated on the other side of the current collector, and the area where the second slurry layer is located corresponds to the area where the first slurry layer is located;
the first slurry layer, the second slurry layer and the third slurry layer respectively comprise a negative electrode active material, a binder and a conductive agent;
at least one of the negative electrode active material, the binder, and the conductive agent in the first slurry layer and the third slurry layer is different.
Wherein the migration rate of lithium ions in the third slurry layer is greater than that of lithium ions in the first slurry layer.
Wherein a rate of deintercalation of lithium ions within the anode active material in the third slurry layer is greater than a rate of deintercalation within the anode active material in the first slurry layer.
Wherein, include respectively in first thick liquids layer, the second thick liquids layer and the third thick liquids layer:
90% -98% of a negative active material;
1% -5% of a binder;
0.02 to 5 percent of conductive agent.
The conductive agents in the first slurry layer and the second slurry layer respectively comprise first conductive agents, the conductive agents in the third slurry layer comprise first conductive agents and second conductive agents, and the conductivity of the first conductive agents is smaller than that of the second conductive agents.
Wherein, include respectively in first thick liquids layer, the second thick liquids layer and the third thick liquids layer: a thickening agent.
Wherein the resistance of the thickener in the third slurry layer is less than the resistance of the thickener in the first slurry layer, and the resistance of the thickener in the third slurry layer is less than the resistance of the thickener in the second slurry layer.
Wherein the anode active material includes:
at least one of graphite, hard carbon, soft carbon, silicon-based materials, tin-based materials, graphene, and the like; and/or
The adhesive comprises:
at least one of styrene butadiene rubber, polyacrylic acid, lithium polyacrylate, sodium polyacrylate and polyvinylidene fluoride; and/or
The conductive agent includes:
at least one of conductive carbon black, carbon nanotube, carbon black and carbon fiber.
In a second aspect, a method for preparing a negative electrode sheet according to an embodiment of the present invention includes:
coating a first slurry layer on one side of a current collector;
coating a second slurry layer and a third slurry layer on the other side of the current collector respectively, wherein the area where the second slurry layer is located corresponds to the area where the first slurry layer is located;
drying the current collector coated with the slurry layer to obtain the negative plate;
the first slurry layer, the second slurry layer and the third slurry layer respectively comprise a negative electrode active material, a binder and a conductive agent;
at least one of the negative electrode active material, the binder, and the conductive agent in the first slurry layer and the third slurry layer is different.
In a third aspect, a battery according to an embodiment of the present invention includes the negative electrode tab described in the above embodiment.
The technical scheme of the invention has the following beneficial effects:
according to the negative plate of the embodiment of the invention, one side of a current collector is coated with a first slurry layer, the other side of the current collector is respectively coated with a second slurry layer and a third slurry layer, the area where the second slurry layer is located corresponds to the area where the first slurry layer is located, the first slurry layer, the second slurry layer and the third slurry layer respectively comprise a negative active material, a binder and a conductive agent, and at least one of the negative active material, the binder and the conductive agent in the first slurry layer and the third slurry layer is different. At least one of the negative active material, the binder and the conductive agent in the first slurry layer and the third slurry layer is different, so that the difference exists between the first slurry layer and the third slurry layer, the problem of lithium precipitation of the negative electrode in the battery circulation process can be solved while the high-energy-density quick charge of the battery is met, the thickness expansion in the battery circulation process is favorably reduced, the battery capacity attenuation is slowed, and the battery circulation performance is ensured.
Drawings
Fig. 1 is a schematic view of a negative electrode sheet according to an embodiment of the present invention;
fig. 2 is a schematic view of the connection of a first slurry layer with a tab;
fig. 3 is a schematic view of a third slurry layer in connection with a tab;
fig. 4 is a cycle curve of a cycle test performed with the charge and discharge current.
Reference numerals
A current collector 10;
a first slurry layer 11;
a second slurry layer 12;
a third slurry layer 13;
and a tab 14.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention are clearly and completely described below. It should be apparent that the described embodiments are only some of the embodiments of the present invention, and not all of them. All other embodiments, which can be derived by a person skilled in the art from the described embodiments of the invention, are within the scope of the invention.
The negative electrode sheet according to an embodiment of the present invention is described in detail below.
As shown in fig. 1, the negative electrode sheet according to the embodiment of the present invention includes a current collector 10, a first slurry layer 11 is coated on one side of the current collector 10, a second slurry layer 12 and a third slurry layer 12 are coated on the other side of the current collector 10, respectively, and the second slurry layer 12 is located in a region corresponding to the region where the first slurry layer 11 is located, wherein the first slurry layer 11, the second slurry layer 12 and the third slurry layer 13 respectively include a negative electrode active material, a binder and a conductive agent, and at least one of the negative electrode active material, the binder and the conductive agent in the first slurry layer 11 and the third slurry layer 13 is different.
That is, the negative electrode sheet may include a current collector 10, the current collector 10 may be a metal sheet, one side of the current collector 10 may be coated with a first slurry layer 11, the other side of the current collector 10 may be coated with a second slurry layer 12 and a third slurry layer 12, respectively, the second slurry layer 12 and the third slurry layer 12 may be connected, and the area where the second slurry layer 12 is located corresponds to the area where the first slurry layer 11 is located. The first slurry layer 11, the second slurry layer 12, and the third slurry layer 13 respectively include a negative electrode active material, a binder, and a conductive agent, at least one of the negative electrode active material, the binder, and the conductive agent in the first slurry layer 11 and the third slurry layer 13 is different, and the negative electrode active material, the binder, and the conductive agent in the first slurry layer 11 and the third slurry layer 13 are not completely the same, and may have different contents or different types of specific components, for example, the negative electrode active material in the first slurry layer 11 and the negative electrode active material in the third slurry layer 13 have different types or different contents, and the conductive agent in the first slurry layer 11 and the third slurry layer 13 has different types or different contents. At least one of the negative active materials, the binder and the conductive agent in the first slurry layer 11 and the third slurry layer 13 is different, so that the difference exists between the first slurry layer 11 and the third slurry layer 13, the problem of lithium precipitation of a negative electrode in the battery cycle process can be solved while the high energy density quick charge of the battery is met, the thickness expansion in the battery cycle is favorably reduced, the battery capacity attenuation is slowed, and the cycle performance of the battery is ensured.
In the practical process, the first slurry layer 11 can meet the high-capacity and high-compaction design, can improve the energy density of the battery, and meets the requirement of the charging rate of the battery; the second slurry layer 12 can be designed to be low in expansion, so that the thickness expansion of the battery in the circulation process can be reduced, and the charging capacity requirement of the battery can be met; as shown in fig. 2 and 3, the first slurry layer 11, the second slurry layer 12 and the third slurry layer 13 can be connected with the tab 14, the third slurry layer 13 can be arranged adjacent to the tab 14, the third slurry layer 13 has better dynamic performance, is superior to the first slurry layer 11 and the second slurry layer 12, and can not cause the problems of black spots, lithium precipitation and the like due to large current density near the tab, and especially can not cause the problem of too fast attenuation of battery capacity due to failure of paste coating caused by single-sided lithium precipitation in the circulation process, thereby ensuring the circulation performance of the battery.
The migration rate of lithium ions in the third slurry layer 13 can be greater than that of lithium ions in the first slurry layer 11, so that the dynamic performance of the third slurry layer 13 is superior to that of the first slurry layer 11, the problems of black spots, lithium precipitation and the like caused by high current density near the tab of the third slurry layer 13 are avoided, and the problem of too fast attenuation of the battery capacity caused by failure of the third slurry layer 13 due to single-sided lithium precipitation of the third slurry layer 13 in the circulation process is avoided.
In some embodiments of the present invention, the de-intercalation rate of lithium ions in the negative active material of the third slurry layer 13 is greater than the de-intercalation rate of lithium ions in the negative active material of the first slurry layer 11, so that the activity of the third slurry layer 13 is greater than the activity of the first slurry layer 11, and the dynamic performance of the third slurry layer 13 is better than that of the first slurry layer 11 and the second slurry layer 12, so that the third slurry layer 13 does not cause black spots, lithium deposition and other problems due to high current density near a tab, and the problem of too fast battery capacity attenuation due to failure of the third slurry layer 13 caused by single-sided lithium deposition of the third slurry layer 13 in the circulation process is avoided, thereby ensuring the circulation performance of the battery. The starting current of the lithium analysis window of the third slurry layer 13 may be greater than the starting current of the lithium analysis window of the first slurry layer 11, and the starting current of the lithium analysis window of the third slurry layer 13 may be greater than the starting current of the lithium analysis window of the second slurry layer 12, so that the dynamic performance of the third slurry layer 13 is superior to that of the first slurry layer 11, and the problems of black spots, lithium analysis and the like caused by the high current density of the third slurry layer 13 near the tab are avoided.
In other embodiments of the present invention, the first paste layer 11, the second paste layer 12, and the third paste layer 13 may include 90% to 98% of the negative active material, 1% to 5% of the binder, and 0.02% to 5% of the conductive agent, respectively. That is, the first slurry layer 11 includes: 90-98% of negative active material, 1-5% of binder and 0.02-5% of conductive agent; the second slurry layer 12 includes: 90-98% of negative electrode active material, 1-5% of binder and 0.02-5% of conductive agent; the third slurry layer 13 includes: 90-98% of negative electrode active material, 1-5% of binder and 0.02-5% of conductive agent, and the specific content of each component in each slurry layer can be selected according to actual needs.
According to some embodiments, the conductive agents in the first paste layer 11 and the second paste layer 12 may respectively include a first conductive agent, the conductive agent in the third paste layer 13 may include a first conductive agent and a second conductive agent, the conductivity of the first conductive agent is smaller than that of the second conductive agent, by adding the second conductive agent with the conductivity larger than that of the first conductive agent in the third paste layer 13, the improvement of the dynamic performance of the third paste layer 13 can be facilitated, the dynamic performance is superior to that of the first paste layer 11 and the second paste layer 12, and the third paste layer 13 cannot cause the problems of black spots, lithium precipitation and the like due to the fact that the current density is large near the tab.
According to other embodiments, the first slurry layer 11, the second slurry layer 12, and the third slurry layer 13 respectively include: the thickening agent can comprise one or more of carboxymethyl cellulose, sodium carboxymethyl cellulose and lithium carboxymethyl cellulose, and the thickening agent is added to adjust the consistency of the pulp and facilitate the coating of the pulp.
The impedance of the thickener in the third slurry layer 13 may be smaller than that of the thickener in the first slurry layer 11, and the impedance of the thickener in the third slurry layer 13 may be smaller than that of the thickener in the second slurry layer 12, which is beneficial to improving the dynamic performance of the third slurry layer 13, so that the problems of black spots, lithium deposition and the like caused by large current density near the tab cannot occur in the third slurry layer 13.
Alternatively, the conductivity of the thickener in the third slurry layer 13 may be greater than that of the thickener in the first slurry layer 11, the conductivity of the thickener in the third slurry layer 13 may be greater than that of the thickener in the second slurry layer 12, and by making the conductivity of the thickener in the third slurry layer 13 greater than that of the thickeners in the first slurry layer 11 and the second slurry layer 12, it is beneficial to improve the dynamic performance of the third slurry layer 13, so that the third slurry layer 13 does not cause the problems of black spots, lithium precipitation and the like due to large current density near the tab.
In an embodiment of the present invention, the negative active material may include: at least one of graphite, hard carbon, soft carbon, silicon-based materials, tin-based materials, graphene, and the like, for example, the negative active material may include graphite, or the negative active material may include graphite and hard carbon; and/or the binder may include: at least one of styrene butadiene rubber, polyacrylic acid, lithium polyacrylate, sodium polyacrylate and polyvinylidene fluoride, for example, the binder can be styrene butadiene rubber or polyacrylic acid; the binder can be lithium polyacrylate or sodium polyacrylate, which is beneficial to improving the conductivity; and/or the conductive agent may include: at least one of conductive carbon black, carbon nanotubes, carbon black, carbon fibers, for example, the conductive agent may include conductive carbon black or carbon nanotubes.
In practice, the method for improving the dynamic performance of the third slurry layer may include changing the negative active material and other components, and the method for improving the dynamic performance of the third slurry layer by the negative active material may include, but is not limited to: performing material coating, doping and the like on the negative electrode active material; the kinetic properties of the third slurry layer can also be improved by changing the amount or type of the conductive agent, changing the amount or type of the binder, adding additives, and the like.
The embodiment of the invention provides a preparation method of a negative plate, which comprises the following steps:
coating a first slurry layer 11 on one side of a current collector 10;
coating a second slurry layer 12 and a third slurry layer 13 on the other side of the current collector 10 respectively, wherein the area of the second slurry layer 12 corresponds to the area of the first slurry layer 11;
drying the current collector 10 coated with the slurry layer to obtain the negative plate;
the first slurry layer 11, the second slurry layer 12, and the third slurry layer 13 respectively include a negative electrode active material, a binder, and a conductive agent, at least one of the negative electrode active material, the binder, and the conductive agent in the first slurry layer 11 and the third slurry layer 13 is different, and may have different contents or different types of specific components, for example, the negative electrode active material in the first slurry layer 11 and the negative electrode active material in the third slurry layer 13 have different types or different contents, and the conductive agent in the first slurry layer 11 and the third slurry layer 13 has different types or different contents. The negative electrode sheet in the embodiment can be prepared by the method, and at least one of the negative electrode active material, the binder and the conductive agent in the first slurry layer 11 and the third slurry layer 13 is different, so that the difference exists between the first slurry layer 11 and the third slurry layer 13, the problem of lithium precipitation of the negative electrode in the battery cycle process can be solved while the high energy density quick charge of the battery is met, the thickness expansion in the battery cycle can be reduced, and the battery capacity attenuation can be slowed down.
In the preparation process, the first slurry layer 11 is formed by the first slurry, the second slurry layer 12 is formed by the second slurry, and the third slurry layer 13 is formed by the third slurry, and the first slurry, the second slurry, and the third slurry can be prepared by the following methods. The preparation method of the slurry comprises the following steps:
(1) Adding required amount of negative active material and conductive agent into the batching tank, and premixing for 30min at a revolution speed of 10-25 r/min;
(2) Adding a required amount of thickening agent CMC and a certain amount of deionized water into a stirring tank, and stirring for 30min-3h at a revolution speed of 20-40 r/min and a dispersion speed of 400-1500 r/min;
(3) Adding required amount of adhesive and a certain amount of deionized water, stirring for 30min-1h at a revolution speed of 15-35 r/min and a dispersion speed of 400-1000 r/min, then closing dispersion, and vacuumizing for 30min to obtain slurry with the solid content of 38% -50% and the viscosity of 1500-6000mPa.s.
The preparation process of the negative plate can comprise the following steps:
coating the first slurry on one side of a current collector, and baking for 4 hours at 60-80 ℃ in vacuum to obtain a first slurry layer; and then respectively coating the second slurry and the third slurry on the other side of the current collector by using a double-gun nozzle, and baking for 8-12 h in vacuum at the temperature of 60-80 ℃ to obtain the required negative plate.
The migration rate of lithium ions in the third slurry layer 13 is greater than that of lithium ions in the first slurry layer 11, so that the activity of the third slurry layer 13 is greater than that of the first slurry layer 11, the dynamic performance of the third slurry layer 13 is superior to that of the first slurry layer 11, the problems of black spots, lithium precipitation and the like caused by high current density near a tab of the third slurry layer 13 are avoided, and the problem of too fast attenuation of the battery capacity caused by failure of the third slurry layer 13 due to single-sided lithium precipitation of the third slurry layer 13 in the circulating process is avoided.
The de-intercalation rate of lithium ions in the negative active material in the third slurry layer 13 can be greater than the de-intercalation rate in the negative active material in the first slurry layer 11, so that the activity of the third slurry layer 13 is greater than the activity of the first slurry layer 11, so that the dynamics of the third slurry layer 13 is better, and the de-intercalation rate can be superior to that of the first slurry layer 11 and the second slurry layer 12, so that the third slurry layer 13 cannot cause black spots, lithium precipitation and other problems due to the large current density near the tabs, the problem that the third slurry layer 13 fails due to the single-sided lithium precipitation of the third slurry layer 13 in the circulating process is avoided, the problem that the battery capacity is attenuated too fast is caused, and the circulating performance of the battery is ensured.
In an embodiment of the present invention, the first slurry layer 11, the second slurry layer 12, and the third slurry layer 13 may include 90% to 98% of a negative active material, 1% to 5% of a binder, and 0.02% to 5% of a conductive agent, respectively. The conductive agent in the first slurry layer 11 and the second slurry layer 12 can respectively comprise a first conductive agent, the conductive agent in the third slurry layer 13 can comprise a first conductive agent and a second conductive agent, the conductivity of the first conductive agent is smaller than that of the second conductive agent, the second conductive agent with the conductivity larger than that of the first conductive agent is added in the third slurry layer 13, the dynamic performance of the third slurry layer 13 can be favorably improved, the dynamic performance is superior to that of the first slurry layer 11 and the second slurry layer 12, and the third slurry layer 13 cannot cause the problems of black spots, lithium precipitation and the like due to the fact that the current density is close to the tab is large.
The first slurry layer 11, the second slurry layer 12 and the third slurry layer 13 respectively comprise thickening agents, the thickening agents can comprise one or more of carboxymethyl cellulose, sodium carboxymethyl cellulose and lithium carboxymethyl cellulose, and the thickening agents are added to adjust the consistency of the slurry and facilitate the coating of the slurry. The impedance of the thickener in the third slurry layer 13 is smaller than that of the thickener in the first slurry layer 11, the impedance of the thickener in the third slurry layer 13 is smaller than that of the thickener in the second slurry layer 12, and the impedance of the thickener in the third slurry layer 13 is smaller than that of the thickeners in the first slurry layer 11 and the second slurry layer 12, so that the dynamic performance of the third slurry layer 13 is improved, and the problems of black spots, lithium precipitation and the like caused by large current density close to the tab cannot occur in the third slurry layer 13. In some embodiments, the conductivity of the thickener in the third slurry layer 13 may be greater than that of the thickener in the first slurry layer 11, and the conductivity of the thickener in the third slurry layer 13 may be greater than that of the thickener in the second slurry layer 12, so that by making the conductivity of the thickener in the third slurry layer 13 greater than those of the thickeners in the first slurry layer 11 and the second slurry layer 12, it is beneficial to improve the dynamic performance of the third slurry layer 13, so that the third slurry layer 13 does not cause black spots, lithium precipitation and other problems due to high current density near the tab.
The anode active material may include: at least one of graphite, hard carbon, soft carbon, silicon-based materials, tin-based materials, graphene, and the like, for example, the negative active material may include graphite, or the negative active material may include graphite and hard carbon; and/or the binder may include: at least one of styrene-butadiene rubber, polyacrylic acid, lithium polyacrylate, sodium polyacrylate and polyvinylidene fluoride, for example, the binder can be styrene-butadiene rubber or polyacrylic acid; the binder can be lithium polyacrylate or sodium polyacrylate, which is beneficial to improving the conductivity; and/or the conductive agent may include: at least one of conductive carbon black, carbon nanotubes, carbon black, carbon fibers, for example, the conductive agent may include conductive carbon black or carbon nanotubes.
An embodiment of the present invention provides a battery, and the battery includes the negative electrode sheet described in the above embodiment. The battery with the negative plate can meet the requirement of high-energy-density quick charging of the battery, solves the problem of lithium precipitation of the negative electrode in the battery cycle process, is favorable for reducing the thickness expansion in the battery cycle, and slows down the capacity attenuation of the battery.
The invention is further illustrated by the following specific examples.
Example 1
Coating a first slurry layer on one side of a current collector;
coating a second slurry layer and a third slurry layer on the other side of the current collector respectively, wherein the area where the second slurry layer is located corresponds to the area where the first slurry layer is located;
drying the current collector coated with the slurry layer to obtain the negative plate;
wherein, the first slurry layer comprises:
90% of a negative electrode active material, 5% of a binder and 5% of a conductive agent;
the negative active material is graphite, the binder is styrene butadiene rubber, and the conductive agent is carbon black;
the second slurry layer comprises:
90% of a negative electrode active material, 5% of a binder and 5% of a conductive agent;
the negative active material is graphite, the binder is styrene butadiene rubber, and the conductive agent is carbon black;
the third slurry layer comprises:
90% of a negative electrode active material, 5% of a binder and 5% of a conductive agent;
the negative active material is graphene, the binder is styrene butadiene rubber, and the conductive agent is carbon black.
Example 2
Coating a first slurry layer on one side of a current collector;
coating a second slurry layer and a third slurry layer on the other side of the current collector respectively, wherein the area where the second slurry layer is located corresponds to the area where the first slurry layer is located;
drying the current collector coated with the slurry layer to obtain the negative plate;
wherein, the first slurry layer comprises:
98% of a negative electrode active material, 1% of a binder and 1% of a conductive agent;
the negative active material is graphite, the binder is styrene butadiene rubber, and the conductive agent is carbon black;
the second slurry layer comprises:
98% of a negative electrode active material, 1% of a binder and 1% of a conductive agent;
the negative active material is graphite, the binder is styrene butadiene rubber, and the conductive agent is carbon black;
the third slurry layer comprises:
98% of a negative electrode active material, 1% of a binder and 1% of a conductive agent;
the negative electrode active material is graphite doped graphene, the binder is polyacrylic acid, and the conductive agent is carbon black.
Example 3
Coating a first slurry layer on one side of a current collector;
coating a second slurry layer and a third slurry layer on the other side of the current collector respectively, wherein the area where the second slurry layer is located corresponds to the area where the first slurry layer is located;
drying the current collector coated with the slurry layer to obtain the negative plate;
wherein, the first slurry layer comprises:
95% of a negative electrode active material, 3% of a binder and 2% of a conductive agent;
the negative active material is graphite, the binder is styrene butadiene rubber, and the conductive agent is carbon black;
the second slurry layer comprises:
95% of negative electrode active material, 3% of binder and 2% of conductive agent;
the negative active material is graphite, the binder is styrene butadiene rubber, and the conductive agent is carbon black;
the third slurry layer comprises:
95% of negative electrode active material, 3% of binder and 2% of conductive agent;
the cathode active material is hard carbon, the binder is sodium polyacrylate, and the conductive agent is carbon nano tubes.
Example 4
Coating a first slurry layer on one side of a current collector;
coating a second slurry layer and a third slurry layer on the other side of the current collector respectively, wherein the area where the second slurry layer is located corresponds to the area where the first slurry layer is located;
drying the current collector coated with the slurry layer to obtain the negative plate;
wherein, the first slurry layer comprises:
96% of negative electrode active material, 3.98% of binder and 0.02% of conductive agent;
the negative active material is graphite, the binder is styrene butadiene rubber, and the conductive agent is carbon black;
the second slurry layer comprises:
96% of negative electrode active material, 3.98% of binder and 0.02% of conductive agent;
the negative active material is graphite, the binder is styrene butadiene rubber, and the conductive agent is carbon black;
the third slurry layer comprises:
96% of negative electrode active material, 3.98% of binder and 0.02% of conductive agent;
the cathode active material is hard carbon, the binder is sodium polyacrylate, and the conductive agent is carbon black and carbon nano tubes.
Example 5
Coating a first slurry layer on one side of a current collector;
coating a second slurry layer and a third slurry layer on the other side of the current collector respectively, wherein the area where the second slurry layer is located corresponds to the area where the first slurry layer is located;
drying the current collector coated with the slurry layer to obtain the negative plate;
wherein, the first slurry layer comprises:
96% of negative electrode active material, 1% of thickening agent, 1% of binder and 2% of conductive agent;
the cathode active material is graphite, the thickening agent is carboxymethyl cellulose, the binder is styrene butadiene rubber, and the conductive agent is carbon black;
the second slurry layer comprises:
96% of a negative electrode active material, 1% of a thickening agent, 1% of a binder and 2% of a conductive agent;
the negative active material is graphite, the thickening agent is carboxymethyl cellulose, the binder is styrene butadiene rubber, and the conductive agent is carbon black;
the third slurry layer comprises:
96% of a negative electrode active material, 1% of a thickening agent, 1% of a binder and 2% of a conductive agent;
the negative electrode active material is graphite, the thickening agent is sodium carboxymethylcellulose, the binder is lithium polyacrylate, and the conductive agent is carbon black.
Comparative example
Preparing anode slurry:
adding 96.0wt% of negative electrode active material a, 1.5wt% of binder SBR (styrene butadiene rubber), 1.5wt% of thickener CMCNa (sodium carboxymethylcellulose), 1.0wt% of conductive agent SP (carbon black conductive agent) and a certain amount of deionized water into a planetary stirring tank, and stirring for 8 hours at a stirring speed of revolution of 35Hz and dispersion of 1500Hz, so that uniform negative electrode slurry with the viscosity of 1500-6000mPa.s is prepared by fully mixing the materials. And coating the negative electrode slurry on the two side layers of the current collector, and drying in a vacuum drying oven at 80 ℃ to prepare the required negative electrode plate.
The positive active substance of the selected positive plate is lithium cobaltate, the diaphragm is a conventional base material diaphragm for a lithium battery, and the electrolyte is commercial liquid electrolyte for the lithium ion battery.
And (3) preparing the lithium ion battery by matching the prepared negative plate, positive plate and diaphragm with liquid electrolyte by adopting a winding process.
Example 6
Preparing a first slurry: adding 96.0wt% of negative electrode active material a, 1.5wt% of binder SBR, 1.5wt% of thickener CMCNa, 1.0wt% of conductive agent SP and a certain amount of deionized water into a planetary stirring tank, stirring for 8 hours at a stirring speed of revolution of 35Hz and dispersion of 1500Hz, and fully mixing to prepare uniform negative electrode slurry with the viscosity of 1500-6000mPa.s.
Preparing a second slurry: the difference from the first slurry is that b is replaced with a negative active material.
Preparing a third slurry: the difference from the first slurry is that the anode active material is changed into c1, and the dynamics of c1 is only slightly better than that of a; a represents graphite, b represents graphite, and c1 represents graphite doped with 10% of hard carbon;
coating the first slurry on one side of a current collector, and baking for 4 hours at 60-80 ℃ in vacuum to obtain a first slurry layer; then coating the second slurry and the third slurry on the other side of the current collector by using a double-gun nozzle to form a second slurry layer and a third slurry layer, wherein the area where the second slurry layer is located corresponds to the area where the first slurry layer is located, and carrying out vacuum baking for 8-12 h at the temperature of 60-80 ℃ to obtain the required negative plate;
the selected positive active substance of the positive plate is lithium cobaltate, the diaphragm is a conventional base material diaphragm for a lithium battery, and the electrolyte is commercial liquid electrolyte for the lithium ion battery;
and (3) preparing the negative plate, the positive plate and the diaphragm which are prepared by adopting a winding process and matching with liquid electrolyte to prepare the lithium ion battery.
Example 7
The other steps are the same as those in example 6, except that: the negative active material for preparing the third slurry is replaced by c2 with better dynamic performance, and the dynamic performance of c2 is far better than that of a, namely: adding 96.0wt% of negative electrode active material c2, 1.5wt% of binder SBR, 1.5wt% of thickener CMCNa, 0.5wt% of conductive agent SP, 0.5wt% of conductive agent CNT (carbon nano tube) and a certain amount of deionized water into a planetary stirring tank, stirring for 8 hours at the stirring speed of revolution 35Hz and dispersion 1500Hz, and fully mixing to prepare uniform slurry with the viscosity of 1500-6000mPa.s; c2 represents that the graphite is doped with 30% of hard carbon;
example 8
The other steps are the same as those in example 6, except that: the formula of the conductive agent for preparing the third slurry is changed, and the CNT conductive network is better added, namely: adding 96.0wt% of negative electrode active material c1, 1.5wt% of binder SBR, 1.5wt% of thickener CMCNa, 0.5wt% of conductive agent SP, 0.5wt% of conductive agent CNT and a certain amount of deionized water into a planetary stirring tank, stirring for 8 hours at the stirring speed of revolution of 35Hz and dispersion of 1500Hz, and fully mixing to prepare uniform slurry with the viscosity of 1500-6000mPa.
Example 9
The other points are the same as those in example 6: the formula of the binder for preparing the third slurry is changed into polyacrylic acid with better viscosity and smaller impedance, and the CMCNa is changed into CMCLi (carboxymethyl cellulose lithium) with better ionic conductivity, and the dosage of the two is reduced at the same time, namely: 97.0wt% of negative electrode active material c1, 1.0wt% of binder polyacrylic acid, 1.0wt% of thickener CMCLi, 1.0wt% of conductive agent SP and a certain amount of deionized water are added into a planetary stirring tank, and stirred for 8 hours at the stirring speed of revolution of 35Hz and dispersion of 1500Hz, so that the materials are fully mixed to prepare uniform slurry with the viscosity of 1500-6000mPa.s.
The lithium ion batteries prepared in the comparative example and the examples 6 to 9 are subjected to a cycle test at a normal temperature and at a temperature of 25 ℃ by using a charge and discharge current of 1.5C/1C to obtain a cycle curve shown in a figure 4; the swelling data and the lithium out on charge windows for the cells during the corresponding cycles in examples 1-9 are shown in table 1 below. The lithium ion batteries were prepared by using the negative electrode sheets in examples 1 to 5, and specifically, the lithium ion batteries were prepared by referring to the method in example 6.
TABLE 1 results of battery thickness expansion during cycling and window for lithium ion batteries prepared in comparative examples and examples 1-9
As shown in fig. 4, the cycle performance curve of the lithium ion battery obtained from the negative electrode sheet of the present invention is shown, where curve N represents a comparative example, curve N6 represents example 6, curve N7 represents example 7, curve N8 represents example 8, and curve N9 represents example 9. The cycle curves in the comparative example and the example 6 have an inflection point, and the inflection point is generated because lithium precipitation in a single-sided area is better than that in a cycle process, so that single-sided capacity failure is caused, and a step is generated due to sudden capacity loss, so that the final cycle capacity retention rate is influenced, and the thickness expansion of the battery is also unfavorable.
From the test result of fig. 4, it can be seen that the dynamic performance of the single-side-region active material in the embodiment 6 is slightly improved compared with that of the comparative example, the number of times of reaching the inflection point is obviously delayed, the inflection point is improved from 180 weeks to about 250 weeks in the comparative example, and the capacity retention rate is improved; in example 7, the single-sided region is replaced with the active material with better dynamic performance, the inflection point disappears completely, and the capacity retention rate is higher, which shows that the dynamic performance of the single-sided region paste coating can be improved by improving the dynamic performance of the active material, so that the cycle performance of the battery is improved; examples 8 and 9 show that the dynamic performance of single-sided area pasting can be well improved and the battery cycle performance can be improved by improving the slurry formula of the negative plate provided by the invention.
Table 1 corresponds to the change in the thickness of the battery during the cycles of comparative example and examples 1 to 9, and the change in the thickness of the battery in the example of the present invention is lower than that in the comparative example. Compared with the prior art that inflection points appear at 180 weeks and 250 weeks respectively, the single-sided lithium separation problem occurs in the cell in the comparative example, so that the thickness change of the comparative example tested at 200 weeks and the thickness change of the example 6 tested at 300 weeks have large mutation, the final cycle thickness change is large, the single-sided zone dynamic performance of the example 6 is slightly better, and the expansion is smaller than that of the comparative example.
In examples 7 to 9, due to the selection of an active material with better dynamic performance or a conductive agent formula and a binder formula which can improve the dynamic performance, the problem of single-sided lithium separation in the battery cycle process is solved, the inflection point disappears, and the battery thickness expansion is small, which indicates that the negative plate provided by the invention can effectively solve the problem of single-sided lithium separation in the battery high-rate charging process, thereby being beneficial to reducing the battery cycle thickness expansion.
As can be seen from table 1, the charging lithium precipitation window of the lithium ion batteries prepared in examples 1 to 9 is larger than that of the lithium ion battery in the comparative example, and the lithium ion batteries in examples 1 to 9 are not easy to precipitate lithium, so that the problem of lithium precipitation of the negative electrode in the battery cycle process is solved, the thickness expansion in the battery cycle is reduced, and the battery capacity fading is slowed down. In the above embodiment, the migration rate of lithium ions in the third slurry layer is greater than that of lithium ions in the first slurry layer, so that the activity of the third slurry layer is greater than that of the first slurry layer, the dynamic performance of the third slurry layer can be superior to that of the first slurry layer, the problems of black spots, lithium deposition and the like caused by large current density near the tab of the third slurry layer are avoided, and the problem of too fast attenuation of the battery capacity caused by failure of the third slurry layer due to single-sided lithium deposition of the third slurry layer in the circulation process is avoided.
Unless otherwise defined, technical or scientific terms used herein shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention belongs. The use of "first," "second," and similar terms in the present application do not denote any order, quantity, or importance, but rather the terms are used to distinguish one element from another. The terms "connected" or "coupled" and the like are not restricted to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "upper", "lower", "left", "right", and the like are used merely to indicate relative positional relationships, and when the absolute position of the object being described is changed, the relative positional relationships are changed accordingly.
While the foregoing is directed to the preferred embodiment of the present invention, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined in the appended claims.
Claims (9)
1. A negative electrode sheet, comprising:
the current collector comprises a current collector, wherein one side of the current collector is coated with a first slurry layer, the other side of the current collector is respectively coated with a second slurry layer and a third slurry layer, the area where the second slurry layer is located corresponds to the area where the first slurry layer is located, and the area, opposite to the third slurry layer, on one side of the current collector is a blank area which is not coated with the slurry layers;
the first slurry layer, the second slurry layer and the third slurry layer respectively comprise a negative electrode active material, a binder and a conductive agent;
at least one of the negative electrode active material, the binder and the conductive agent in the first slurry layer and the third slurry layer is different;
the migration rate of lithium ions in the third slurry layer is greater than that of the lithium ions in the first slurry layer;
and the third slurry layer is arranged close to the tab.
2. The negative electrode sheet according to claim 1, wherein a desorption rate of lithium ions in the negative electrode active material in the third slurry layer is greater than a desorption rate in the negative electrode active material in the first slurry layer.
3. The negative electrode sheet according to claim 1, wherein the first slurry layer, the second slurry layer and the third slurry layer each comprise:
90% -98% of a negative active material;
1% -5% of a binder;
0.02 to 5 percent of conductive agent.
4. The negative electrode sheet according to claim 1, wherein the conductive agents in the first paste layer and the second paste layer respectively comprise a first conductive agent, and the conductive agents in the third paste layer comprise a first conductive agent and a second conductive agent, and the conductivity of the first conductive agent is smaller than that of the second conductive agent.
5. The negative electrode sheet according to claim 1, wherein the first slurry layer, the second slurry layer and the third slurry layer each comprise: a thickening agent.
6. Negative electrode sheet according to claim 5, characterized in that the resistance of the thickener in the third slurry layer is smaller than the resistance of the thickener in the first slurry layer, and the resistance of the thickener in the third slurry layer is smaller than the resistance of the thickener in the second slurry layer.
7. The negative electrode sheet according to claim 1, wherein the negative active material comprises:
at least one of graphite, hard carbon, soft carbon, silicon-based materials, tin-based materials, graphene, and the like; and/or
The adhesive comprises:
at least one of styrene butadiene rubber, polyacrylic acid, lithium polyacrylate, sodium polyacrylate and polyvinylidene fluoride; and/or
The conductive agent includes:
at least one of conductive carbon black, carbon nanotube, carbon black and carbon fiber.
8. A preparation method of a negative plate is characterized by comprising the following steps:
coating a first slurry layer on one side of a current collector;
coating a second slurry layer and a third slurry layer on the other side of the current collector respectively, wherein the area where the second slurry layer is located corresponds to the area where the first slurry layer is located, and the area on one side of the current collector, which is opposite to the third slurry layer, is a blank area which is not coated with the slurry layer;
drying the current collector coated with the slurry layer to obtain the negative plate;
the first slurry layer, the second slurry layer and the third slurry layer respectively comprise a negative electrode active material, a binder and a conductive agent;
at least one of the negative electrode active material, the binder and the conductive agent in the first slurry layer and the third slurry layer is different;
the migration rate of lithium ions in the third slurry layer is greater than that of lithium ions in the first slurry layer;
and the third slurry layer is arranged close to the tab.
9. A battery comprising the negative electrode sheet according to any one of claims 1 to 7.
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| CN112750976B (en) * | 2020-12-29 | 2022-08-23 | 珠海冠宇电池股份有限公司 | Lithium battery core and lithium ion battery |
| CN112701250A (en) * | 2020-12-29 | 2021-04-23 | 珠海冠宇电池股份有限公司 | Lithium ion battery |
| CN112736217A (en) * | 2020-12-29 | 2021-04-30 | 珠海冠宇电池股份有限公司 | Lithium battery negative plate, winding type battery cell and lithium ion battery |
| CN112968177B (en) * | 2021-03-01 | 2022-02-22 | 广州鹏辉能源科技股份有限公司 | Water-based anode slurry composition, water-based anode slurry, preparation method of water-based anode slurry, anode plate, lithium ion battery and power utilization equipment |
| CN113097441B (en) * | 2021-03-31 | 2023-03-21 | 宁德新能源科技有限公司 | Electrochemical device and electronic device |
| CN113410425B (en) * | 2021-06-21 | 2024-10-15 | 珠海冠宇电池股份有限公司 | Battery cell and battery |
| CN114142038B (en) * | 2021-11-29 | 2023-11-24 | 珠海冠宇电池股份有限公司 | Negative plate and lithium battery |
| CN114597415A (en) * | 2022-03-23 | 2022-06-07 | 珠海冠宇电池股份有限公司 | Negative plate and lithium ion battery |
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