CN114300644A - Negative plate, preparation method thereof and lithium ion battery - Google Patents
Negative plate, preparation method thereof and lithium ion battery Download PDFInfo
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- CN114300644A CN114300644A CN202111407886.8A CN202111407886A CN114300644A CN 114300644 A CN114300644 A CN 114300644A CN 202111407886 A CN202111407886 A CN 202111407886A CN 114300644 A CN114300644 A CN 114300644A
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- 229910001416 lithium ion Inorganic materials 0.000 title claims abstract description 29
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 title claims abstract description 28
- 238000002360 preparation method Methods 0.000 title abstract description 11
- 238000000576 coating method Methods 0.000 claims abstract description 116
- 239000011530 conductive current collector Substances 0.000 claims abstract description 36
- 239000013543 active substance Substances 0.000 claims abstract description 31
- 238000004519 manufacturing process Methods 0.000 claims abstract description 11
- 239000011149 active material Substances 0.000 claims description 190
- 239000010410 layer Substances 0.000 claims description 110
- 239000011248 coating agent Substances 0.000 claims description 95
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 87
- 229910002804 graphite Inorganic materials 0.000 claims description 81
- 239000010439 graphite Substances 0.000 claims description 81
- 239000002002 slurry Substances 0.000 claims description 60
- 239000011230 binding agent Substances 0.000 claims description 59
- 239000002245 particle Substances 0.000 claims description 33
- 239000011163 secondary particle Substances 0.000 claims description 28
- 239000011247 coating layer Substances 0.000 claims description 27
- 239000006258 conductive agent Substances 0.000 claims description 22
- 238000000034 method Methods 0.000 claims description 20
- 238000003756 stirring Methods 0.000 claims description 15
- 239000008367 deionised water Substances 0.000 claims description 13
- 229910021641 deionized water Inorganic materials 0.000 claims description 13
- 239000002904 solvent Substances 0.000 claims description 13
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 13
- 238000004804 winding Methods 0.000 claims description 13
- 229920002134 Carboxymethyl cellulose Polymers 0.000 claims description 8
- 229920003048 styrene butadiene rubber Polymers 0.000 claims description 8
- 238000001035 drying Methods 0.000 claims description 6
- 229920002125 Sokalan® Polymers 0.000 claims description 4
- 239000001768 carboxy methyl cellulose Substances 0.000 claims description 4
- 235000010948 carboxy methyl cellulose Nutrition 0.000 claims description 4
- 239000008112 carboxymethyl-cellulose Substances 0.000 claims description 4
- 229910021393 carbon nanotube Inorganic materials 0.000 claims description 3
- 239000002041 carbon nanotube Substances 0.000 claims description 3
- 229910021389 graphene Inorganic materials 0.000 claims description 3
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 claims description 3
- 239000002356 single layer Substances 0.000 claims description 2
- 230000000052 comparative effect Effects 0.000 description 13
- 238000002156 mixing Methods 0.000 description 10
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- 239000000203 mixture Substances 0.000 description 7
- 239000011267 electrode slurry Substances 0.000 description 6
- 230000008569 process Effects 0.000 description 6
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 4
- 229910052744 lithium Inorganic materials 0.000 description 4
- 238000007581 slurry coating method Methods 0.000 description 4
- 238000012360 testing method Methods 0.000 description 4
- 239000006256 anode slurry Substances 0.000 description 3
- 230000009286 beneficial effect Effects 0.000 description 3
- 230000005611 electricity Effects 0.000 description 3
- 239000007774 positive electrode material Substances 0.000 description 3
- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical compound CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 description 2
- 239000002033 PVDF binder Substances 0.000 description 2
- 229910021383 artificial graphite Inorganic materials 0.000 description 2
- 239000002131 composite material Substances 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000003487 electrochemical reaction Methods 0.000 description 2
- 239000003792 electrolyte Substances 0.000 description 2
- 230000006872 improvement Effects 0.000 description 2
- 238000003780 insertion Methods 0.000 description 2
- 230000037431 insertion Effects 0.000 description 2
- 229910021382 natural graphite Inorganic materials 0.000 description 2
- 229920002981 polyvinylidene fluoride Polymers 0.000 description 2
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- 229910012820 LiCoO Inorganic materials 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 239000006229 carbon black Substances 0.000 description 1
- 239000011889 copper foil Substances 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000003912 environmental pollution Methods 0.000 description 1
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- 238000002347 injection Methods 0.000 description 1
- 239000007924 injection Substances 0.000 description 1
- 238000009830 intercalation Methods 0.000 description 1
- 238000003475 lamination Methods 0.000 description 1
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- 239000000463 material Substances 0.000 description 1
- 230000003446 memory effect Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
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- 239000007773 negative electrode material Substances 0.000 description 1
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- 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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- Battery Electrode And Active Subsutance (AREA)
Abstract
The application provides a negative plate, a preparation method thereof and a lithium ion battery, wherein the negative plate comprises a conductive current collector, n layers of active substance coatings are stacked on the surface of the conductive current collector, and the length of the n layers of active substance coatings on the surface of the conductive current collector needs to satisfy L1＞L2、L2＞L3、…Ln‑1＞Ln(ii) a The technical scheme of this application can not only improve production efficiency, can effectively reduce electric core thickness moreover, improves battery energy density, promotes the big multiplying power charge-discharge performance of battery.
Description
Technical Field
The application belongs to the technical field of lithium ion batteries, and particularly relates to a negative plate, a preparation method of the negative plate and a lithium ion battery.
Background
With the development of industry, fossil fuel is exhausted, and environmental pollution is serious, so that lithium ion batteries are one of environment-friendly energy sources and become a hot topic for people to research. The lithium ion battery has the advantages of high specific capacity, high working voltage, long service life, no memory effect and the like as a new energy source, and the power storage device for storing energy by the lithium ion battery for the automobile also draws attention. With the rise of new energy electric automobiles, the comprehensive performance of lithium ion secondary batteries is more and more emphasized by various large new energy automobile enterprises. How to maintain the high energy density of the lithium battery and improve the quick charging capability of the lithium battery becomes one of the problems to be solved in the whole industry.
In the case of pole pieces, increasing the energy density is to increase the active material content per unit volume and to increase the specific capacity of the active material. At present, the electrode generally increases the content of the positive active material, and the high content of the active material is coated on the surface of the conductive current collector by a coating method. The content of the positive active material is increased, the content of the negative active material is increased to the same extent, the conductive layer needs to be compacted to be thicker or firmer in order to achieve higher energy density, but under the condition of being thicker or compacted to be higher, the negative plate is easy to expand and fall off after the battery is injected with electrolyte for charge and discharge cycles, so that the performance attenuation and safety performance problems of lithium precipitation and the like are caused.
Disclosure of Invention
The application provides a negative plate, a preparation method thereof and a lithium ion battery, aiming at the problems of low energy density and low high-rate discharge performance of the conventional lithium ion battery.
The technical scheme adopted by the application for solving the technical problems is as follows:
in one aspect, the present application provides a negative plate, including the current collector that conducts electricity, the current collector surface piles up n layers of active material coating that forms, the active material coating length of n layers on current collector surface needs to satisfy L1＞L2、L2＞L3、…Ln-1＞Ln；
Wherein n is more than or equal to 2, and L is1For a first active material coating length applied to the surface of the conductive current collector, L2Length of the second active material coating applied on the first active material coating, LnIs the length of the n-th active material coating layer coated on the n-1 th active material coating layer.
Preferably, theThe length of n active material coating layers on the surface of the conductive current collector is required to satisfy L1-L2≥5mm、L2-L3≥5mm、…Ln-1-Ln≥5mm。
Preferably, said L1-L2More than or equal to 1 +/-2 mm and L2-L3Not less than 1 +/-2 mm and … Ln-1-LnThe folding length is more than or equal to 1 +/-2 mm, and the folding length of the folding length 1 is 1 in the winding structure.
Preferably, the active material coating comprises graphite, the graphite comprises single-particle graphite and/or secondary-particle graphite, the mass percentage of the graphite in a single-layer active material coating is 100%, the mass percentage of the secondary-particle graphite in an n-th active material coating is greater than that of the secondary-particle graphite in an n-1-th active material coating, and the average particle size of the secondary-particle graphite is greater than that of the single-particle graphite.
Preferably, the surfaces of the conductive current collectors are stacked to form three active material coatings, graphite in the active material coating of the first layer is single-particle graphite, graphite in the active material coating of the second layer is 25-75 wt% of single-particle graphite and 25-75 wt% of secondary-particle graphite, and graphite in the active material coating of the third layer is 100% of secondary-particle graphite.
Preferably, the face density ratio of the n active material coating layers is that of the first active material coating layer: second active material coating: third active material coating: fourth active material coating: … …: the nth layer of active material coating is 1-4: 1-4 … …:1 to 4.
In another aspect, the present application provides a method for preparing a negative electrode sheet, including: coating the first active material layer slurry on the conductive current collector, coating the second active material layer slurry on the first active material layer slurry, coating the third active material layer slurry on the second active material layer slurry, coating the nth active material layer slurry on the (n-1) th active material layer slurry, and drying after coating to obtain the negative plate coated with the n layers of active material coatings.
Preferably, the first active material layer slurry is prepared by the following method: uniformly stirring a first active material, a conductive agent, a binder and deionized water to obtain first active material layer slurry; the mass ratio of the first active substance to the conductive agent to the binder to the solvent is 90-98.5: 0-5: 1.5-5: 80-120 parts.
Preferably, the nth active material layer slurry is prepared by the following method: uniformly stirring the nth active substance, the conductive agent, the binder and the deionized water to obtain nth active substance layer slurry; the mass ratio of the nth active substance to the conductive agent to the binder to the solvent is 90-98.5: 0-5: 1.5-5: 80-120 parts.
The conductive agent comprises one of conductive carbon black, carbon nano tubes and graphene; the binder comprises a binder A and a binder B, wherein the binder A and the binder B are respectively and independently selected from any one of carboxymethyl cellulose, styrene-butadiene rubber, PAA-based binder or PAN-based binder, the mass percentage of the binder A in the active material layer slurry is 0.5-2%, and the mass percentage of the binder B in the active material layer slurry is 1-3%; the solvent is deionized water.
In another aspect, the present application provides a lithium ion battery, including the above negative electrode sheet.
The beneficial effect of this application:
the application provides a negative pole piece, including the current collector that conducts electricity, pile up n layers of active material coating that forms on the current collector surface that conducts electricity, the length of n layers of active material coating on current collector surface needs to satisfy L1＞L2、L2＞L3、…Ln-1＞Ln(ii) a According to the scheme, the production efficiency can be improved, the thickness of the battery cell can be effectively reduced, and the energy density of the battery is improved.
Drawings
FIG. 1 is a schematic structural diagram of a negative electrode sheet prepared by the present application;
FIG. 2 is a schematic structural diagram of a negative electrode sheet prepared in comparative example 1;
fig. 3 is a schematic structural view of the negative electrode sheet prepared in comparative example 2.
1. A conductive current collector; 2. a first active material coating; 3. a second active material coating; 4. a third active material coating; 5. and a negative tab.
Detailed Description
In order to make the technical problems, technical solutions and advantageous effects solved by the present application more clear, the present application is further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present application and are not intended to limit the present application.
The preparation method of the lithium ion cell comprises two modes of lamination and winding, for the pole piece of the lithium ion battery prepared by the conventional winding mode, the cathode lug is generally designed at the head or the tail of the cathode piece, and in the charging and discharging process of the battery, the closer to the pole lug, the higher the current density is, and the deeper the de-intercalation depth of the active substance at the position is; for the negative pole piece far away from the pole ear area, the extraction depth of the negative pole active substance is shallower in the process of charging and discharging the battery, and the active substance far away from the pole ear area is in a shallow charging and shallow discharging state; according to the principle that the disengagement and insertion depth far away from the tabs is shallower, the application provides a negative plate, a preparation method thereof and a lithium ion battery.
In one aspect, as shown in fig. 1, the present application provides a negative electrode sheet, including a conductive current collector, n active material coatings stacked on the surface of the conductive current collector, where the length of the n active material coatings on the surface of the conductive current collector is required to satisfy L1＞L2、L2＞L3、…Ln-1＞Ln；
Wherein n is more than or equal to 2, and L is1For the length of the first active material coating 2 applied on the surface of the conductive current collector 1, L2Is the length, L, of the second active material coating 3 applied on the first active material coating 2nIs the length of the n-th active material coating layer coated on the n-1 th active material coating layer.
FIG. 1 shows a schematic structure of n active material coatings, including a negative electrode tab 5, a first active material coating 2, and a second active material coating3. And a third active material coating layer 4, wherein N represents an omitted N-th active material coating layer. In some embodiments, the n active material coatings provided herein have a length L1＞L2、L2＞L3、…Ln-1＞LnTherefore, the production efficiency can be improved, the thickness of the battery cell can be effectively reduced, and the energy density of the battery can be improved.
In some preferred embodiments, the length of the n active material coating layers on the surface of the conductive current collector is required to satisfy L1-L2≥5mm、L2-L3≥5mm、…Ln-1-Ln≥5mm。
In the design of the lithium ion battery, the length of the n-1 th active material coating is 5mm longer than that of the n-th active material coating, so that the thickness of the battery core can be effectively reduced, and the energy density of the battery is improved.
In some preferred embodiments, said L1-L2More than or equal to 1 +/-2 mm and L2-L3Not less than 1 +/-2 mm and … Ln-1-LnThe length of the core is more than or equal to 1 fold plus or minus 2mm, and the 1 fold is 1 fold of the core in the winding structure.
Specifically, the battery cell is prepared in a winding mode, the length of 1 fold is the distance from the left side of the battery cell middle layer to the right side of the middle layer, and the middle layer refers to the number of battery cell layers corresponding to half of the total number of turns of the battery cell. If the number of winding turns of the battery core is 20, the middle layer is the layer of the 10 th turn of the winding core, the position of the 10 th turn is confirmed after 1 turn, the distance from the left side of the 10 th turn is taken as a reference, the right side of the 10 th turn is measured, a plurality of groups of data can be measured, the data are allowed to fluctuate, the fluctuation range of the data is less than or equal to 2mm, and the average value is calculated according to the data with the fluctuation range less than or equal to 2mm, so that the length data of 1 turn is obtained. If the number of turns of the battery cell is an odd number of turns, the middle layer can be half or more than half of the total number of turns of the battery cell, the distance from the left side to the right side of the middle layer is measured, a plurality of groups of data are measured, the data are allowed to fluctuate, the fluctuation range of the data is less than or equal to 2mm, the average value is calculated according to the data with the fluctuation range less than or equal to 2mm, and the length data of 1-fold is obtained. For the specific length of the 1-fold in the present application, refer to the above description. In some embodiments of the present invention, the,for cells produced by winding, L1-L2Not less than 1 +/-2 mm and … Ln-1-LnMore than or equal to 1 to +/-2 mm, namely the length of the active substance coating of the n-1 th layer is required to be 1 to +/-2 mm longer than that of the active substance coating of the n th layer, the thickness of the pole piece is reduced in different layers, and after the action of winding the battery core is finished, the diaphragm can be more favorably drawn out, so that the thickness of the winding core can be effectively reduced, the production efficiency of the winding process can be more favorably improved, and the energy density of the battery can be improved.
In some preferred embodiments, the active material coating layer comprises graphite, the graphite comprises single-particle graphite and/or secondary-particle graphite, the mass percentage of the secondary-particle graphite in the active material coating layer of the nth layer is larger than that of the secondary-particle graphite in the active material coating layer of the (n-1) th layer, and the average particle diameter of the secondary-particle graphite is larger than that of the single-particle graphite, based on 100% of the mass of the graphite in the active material coating layer.
In some embodiments, the secondary particulate graphite is secondary particulate graphite obtained by agglomerating smaller single particles of graphite having an average particle size less than the average particle size of the secondary particulate graphite. The ratio of the secondary particle graphite in the nth active material coating is greater than that in the (n-1) th active material coating, that is, the average particle size of the graphite in the active material coating closer to the conductive current collector 1 is smaller, and the average particle size of the graphite in the active material coating farther from the conductive current collector 1 is larger. During the charging and discharging process of the battery, lithium ions are removed from the positive electrode and are embedded into the hexagonal structure of the negative electrode graphite through the diaphragm and the electrolyte, the proportion of the secondary particle graphite in the active material coating layer which is farther away from the conductive current collector 1 is increased, the OI value of the surface active material particles is reduced, and the high-rate charging and discharging and the reduction of the expansion effect are facilitated.
In some preferred embodiments, the surfaces of the conductive current collector 1 are stacked to form three active material coatings, the graphite in the first active material coating 2 is single-particle graphite, the graphite in the second active material coating 3 is 25-75 wt% of single-particle graphite and 25-75 wt% of secondary-particle graphite, and the graphite in the third active material coating 4 is 100% of secondary-particle graphite.
In some embodiments, the surface of the negative plate conductive current collector 1 is stacked to form three active material coatings, the graphite in the first material coating is single-particle graphite, the average particle size is small, more lithium ions can be loaded, and the safety performance of the battery can be effectively improved in the battery charging and discharging process. The graphite in the second active material coating 3 is 25-75 wt% of single-particle graphite and 25-75 wt% of secondary-particle graphite, the graphite in the third active material coating 4 is secondary-particle graphite, all the graphite in the third active material coating 4 is secondary-particle graphite, and the OI value of the active material particles is the lowest, so that the lithium ion can be embedded more easily, and the rate capability of the battery can be improved more easily.
The surface density ratio of the n active material coating layers is that of the first active material coating layer: second active material coating: third active material coating: fourth active material coating: … …: the nth layer of active material coating is 1-4: 1-4 … …:1 to 4.
In some embodiments, the ratio of the areal densities of the n active material coatings applied to the surface of the conductive current collector 1 may be the same or different, but the ratio of the areal densities of the coatings needs to satisfy the first active material coating: second active material coating: third active material coating: fourth active material coating: … …: the nth layer of active material coating is 1-4: 1-4 … …:1 to 4. Experiments show that if the surface densities of the coatings are not consistent, the rate performance of the prepared battery is improved more obviously because the electrochemical reaction in the graphite layer far away from the conductive current collector 1 is more severe in the charging and discharging process, and particularly when the proportion of secondary particles in the nth active material coating of the negative plate is highest and the surface density is higher. The reason is that the outermost active material layer in the direction away from the conductive current collector 1 is close to the diaphragm side and is closest to the positive plate, the proportion of secondary particles is high, the lithium ions are more favorably embedded, the electrochemical reaction is more severe, and if the surface density of the outermost layer is higher, the graphite content is higher, the more the lithium ions can be embedded, and the higher the rate charge and discharge performance of the battery is favorably improved.
In another aspect, the present invention provides a method for preparing a negative electrode sheet, including: coating the first active material layer slurry on the conductive current collector 1, coating the second active material layer slurry on the first active material layer slurry, coating the third active material layer slurry on the second active material layer slurry, coating the nth active material layer slurry on the (n-1) th active material layer slurry, and drying after coating to obtain the negative plate coated with the n-layer active material coating.
In some embodiments, a first active material layer slurry is coated on the conductive current collector 1, a second active material layer slurry is coated on the first active material layer slurry, and so on, an nth active material layer slurry is coated on the (n-1) th active material layer slurry, and after the coating is finished and the drying treatment is carried out, the negative plate coated with n active material layers is obtained, wherein the length of the n active material layers satisfies L1-L2≥5mm、L2-L3≥5mm、…Ln-1-LnNot less than 5 mm; wherein n is more than or equal to 2, L1For the first active material coating 2 length, L, coated on the surface of the conductive current collector 12Is the length, L, of the second active material coating 3 applied on the first active material coating 2nIs the length of the n-th active material coating layer coated on the n-1 th active material coating layer.
The first active material layer slurry is prepared by adopting the following method: uniformly stirring a first active material, a conductive agent, a binder and deionized water to obtain first active material layer slurry; the mass ratio of the first active substance to the conductive agent to the binder to the solvent is 90-98.5: 0-5: 1.5-5: 80-120 parts.
In some embodiments, the first active material is one of natural graphite and artificial graphite, wherein the graphite is single-particle graphite. The method comprises the following steps of (1) mixing a first active substance, a conductive agent, a binder and a solvent according to a mass ratio of 90-98.5: 0-5: 1.5-5: 80-120, adding the mixture into a stirring tank, and uniformly stirring to obtain a first active material layer slurry.
The nth active material layer slurry is prepared by adopting the following method: uniformly stirring the nth active substance, the conductive agent, the binder and the deionized water to obtain nth active substance layer slurry; the mass ratio of the nth active substance to the conductive agent to the binder to the solvent is 90-98.5: 0-5: 1.5-5: 80-120 parts.
In some embodiments, the nth active material is one of natural graphite, artificial graphite, or a mixture of single-particle graphite and secondary-particle graphite, and it is required that the nth active material graphite has an average particle size larger than that of the (n-1) th active material graphite. Mixing an nth active substance, a conductive agent, a binder and a solvent according to a mass ratio of 90-98.5: 0-5: 1.5-5: 80-120, adding the mixture into a stirring tank, and uniformly stirring and stirring to obtain the nth active material layer slurry.
The conductive agent comprises one of conductive carbon black, carbon nano tubes and graphene; the binder comprises a binder A and a binder B, wherein the binder A and the binder B are respectively and independently selected from any one of carboxymethyl cellulose, styrene-butadiene rubber, PAA-based binder or PAN-based binder, the mass percentage of the binder A in the active material layer slurry is 0.5-2%, and the mass percentage of the binder B in the active material layer slurry is 1-3%; the solvent is deionized water.
In some embodiments, the binder is a composite binder, the composite binder comprises a binder A and a binder B, and the binder A and the binder B are respectively and independently selected from any one of carboxymethyl cellulose, styrene-butadiene rubber, PAA-based binder or PAN-based binder; the binder a and the binder B may be the same or different in kind. The mass ratio of the binder a in the active material layer slurry is 0.5% to 2%, the mass ratio of the binder B in the active material layer slurry is 1% to 3%, and 0.5% to 2% and 1% to 3% of these are mass ratio data including no solvent.
On the other hand, the application provides a lithium ion battery, which comprises a positive plate and a multilayer negative plate prepared by the method.
In some embodiments, the lithium ion battery prepared from the negative plate obtained by the method has the advantages of effectively reducing the thickness of the battery core and improving the energy density and the high-rate charge and discharge performance of the battery.
The present application is further described in detail by the following examples, wherein the negative electrode sheet is prepared by coating 3 active material layers on the conductive current collector 1, and the preparation method of the lithium ion battery is specifically described.
Example 1:
preparing positive electrode slurry: the positive electrode active material lithium cobaltate (LiCoO)2) The conductive agent carbon black, the binder polyvinylidene fluoride (PVDF) and the solvent N-methyl pyrrolidone (NMP) are uniformly mixed according to the weight ratio of 96:2.5:1.5:80 to obtain the anode slurry to be coated.
Preparing anode slurry:
preparation of first active material layer slurry: mixing a first active substance, a conductive agent, a binder carboxymethyl cellulose (CMC), Styrene Butadiene Rubber (SBR) and deionized water according to a mass ratio of 97: 0.5: 1.2: 1.3: and 100, adding the mixture into a stirrer, mixing and stirring, and uniformly dispersing to obtain the first active material layer slurry to be coated.
Preparation of second active material layer slurry: mixing a second active substance, a conductive agent, a binder carboxymethyl cellulose (CMC), Styrene Butadiene Rubber (SBR) and deionized water according to a mass ratio of 97: 0.5: 1.2: 1.3: and 100, adding the mixture into a stirrer, mixing and stirring, and uniformly dispersing to obtain a second active material layer slurry to be coated.
Preparation of third active material layer slurry: mixing a third active substance, a conductive agent, a binder carboxymethyl cellulose (CMC), Styrene Butadiene Rubber (SBR) and deionized water according to a mass ratio of 97: 0.5: 1.2: and (1.3) adding the mixture into a stirrer, mixing and stirring, and uniformly dispersing to obtain third active material layer slurry to be coated.
The first active substance, the second active substance and the third active substance are different kinds of graphite, the first active substance is single-particle graphite, the second active substance is 25% of single-particle graphite and 75% of secondary-particle graphite, and the third active substance is pure secondary-particle graphite.
Preparing a negative plate: as shown in fig. 1, a first active material layer slurry was uniformly coated on a copper foil current collector having a thickness of 8 μm, a second active material layer slurry was simultaneously coated on the first active material layer slurry, wherein the second active material layer slurry coating length was 1-fold shorter than the first active material layer slurry coating length, and a third active material layer slurry was coated on the second active material layer slurry, wherein the third active material layer slurry coating length was 1-fold +2mm shorter than the second active material layer slurry coating length. First active material layer density: second active material layer density: and (5) the layer density of the third active material is 1:1:1, and the negative plate to be rolled is obtained after the coating and drying treatment is completed.
Preparing a positive plate: in order to ensure that the negative electrode is excessive, the positive electrode slurry is matched with the negative electrode plate, the coating sequence of the negative electrode plate is referred, three times of coating are respectively carried out on an aluminum foil current collector with the thickness of 13 mu m, the slurry coated for the three times is the same, the surface density corresponds to that of the negative electrode plate, the coating length is matched with that of the negative electrode plate, and the positive electrode to be rolled is obtained after drying treatment is carried out after the three times of coating.
Manufacturing the lithium ion battery: the coated positive and negative pole pieces are baked and then are prepared by the steps of rolling, slitting, sheet making, winding, packaging, baking, liquid injection, formation and the like.
Examples 2 to 4: examples 2-4 differ from example 1 in the areal density ratio of the three active material coatings, with specific reference to table 1.
Comparative example 1
The positive electrode slurry was prepared in the same manner as in example 1.
Preparing anode slurry: mixing a first active substance, a conductive agent, a binder carboxymethyl cellulose (CMC), Styrene Butadiene Rubber (SBR) and deionized water according to a mass ratio of 97: 0.5: 1.2: 1.3: and 100, adding the mixture into a stirrer, mixing and stirring, and uniformly dispersing to obtain the first active material layer negative electrode slurry to be coated.
Manufacturing positive and negative pole pieces: performing primary coating, namely coating the prepared positive and negative electrode slurry on a current collector, wherein the coating surface density is the sum of the 3-time coating surface densities of the embodiment 1; the structure of the negative plate is shown in fig. 2.
Manufacturing the lithium ion battery: same as in example 1.
Comparative example 2
The positive and negative electrode pastes were prepared in the same manner as in example 1.
Manufacturing a positive plate: and coating the prepared positive electrode slurry on a current collector.
And (3) manufacturing a negative plate: as shown in fig. 3, the coating method was the same as in example 1 except that the first active material layer coating length was the second active material layer coating length and the third active material layer coating length.
And (3) manufacturing a finished battery: same as in example 1.
Table 1 areal density ratios of negative plates of examples 1-4 are given in the table below
The lithium ion batteries prepared in the above examples 1 to 4 and comparative examples 1 to 2 were subjected to the following performance tests:
(1) testing the capacity, thickness and volume energy density of the battery cell;
the battery was fully charged at a constant current and a constant voltage at 25 ℃ and then discharged to 3.0V at 0.2C, and the discharged capacity was recorded as the battery capacity.
The battery thus produced was charged to 50% SOC at 25 ℃ and the thickness of the battery was measured using 500g of ppg.
The volumetric energy density is calculated as the cell capacity x plateau voltage/length/width/thickness of the cell, and for a 4.45V system, the plateau voltage is uniformly considered to be 3.87V.
(2) Rate capability test
The prepared battery is charged under different multiplying powers of 0.2C, 0.5C, 1.5C and 3C at the temperature of 25 ℃, and the constant current rush-in ratio data during charging is recorded.
The test results are shown in tables 2 and 3:
table 2 test data for capacity, thickness and energy density of the batteries prepared in comparative examples 1-2 and examples 1-4 are shown in the following table:
| battery capacity/mAh | Thickness of battery/mm | Energy Density/Wh/L | |
| Comparative example 1 | 3705 | 3.88 | 722.19 |
| Comparative example 2 | 3728 | 3.897 | 723.50 |
| Example 1 | 3720 | 3.875 | 726.04 |
| Example 2 | 3735 | 3.867 | 730.48 |
| Example 3 | 3725 | 3.873 | 727.40 |
| Example 4 | 3715 | 3.875 | 725.07 |
Table 3 constant current ratio data at different rates for the cells prepared in comparative examples 1-2 and examples 1-4 are shown below:
as can be seen from table 2, the capacity and energy density of examples 1 to 4 are both significantly improved compared with those of comparative example 1, because the graphite particles far from the conductive current collector 1 are large in size, which is beneficial to the insertion of lithium ions, and the battery capacity is improved, and meanwhile, the coating lengths of the active material coatings are different, so that the battery thickness is effectively reduced, and the energy density of the battery is improved. The cell thickness of examples 1-4 was somewhat reduced compared to comparative example 2, and the energy density of the examples was significantly increased compared to the comparative example.
As can be seen from table 3, the rate performance of examples 1 to 4 is improved to a certain extent compared with comparative examples 1 to 2, because the graphite particle size far from the conductive current collector 1 is large, and the OI value of the active material is low, which is beneficial to large-rate charge and discharge. Example 1 compares with example 3, and example 1 compares with example 4, and the rate performance improvement is more obvious with the increase of the layer density of the active material away from the conductive current collector 1.
The above description is only exemplary of the present application and should not be taken as limiting the present application, as any modification, equivalent replacement, or improvement made within the spirit and principle of the present application should be included in the protection scope of the present application.
Claims (10)
1. The negative plate is characterized by comprising a conductive current collector, wherein n layers of active material coatings are stacked on the surface of the conductive current collector, and the length of the n layers of active material coatings on the surface of the conductive current collector needs to satisfy L1＞L2、L2＞L3、…Ln-1＞Ln；
Wherein n is more than or equal to 2, and L is1For a first active material coating length applied to the surface of the conductive current collector, L2Length of the second active material coating applied on the first active material coating, LnIs the length of the n-th active material coating layer coated on the n-1 th active material coating layer.
2. A negative electrode sheet according to claim 1, wherein the length of the n active material layers on the surface of the conductive current collector is such that L is the same as L1-L2≥5mm、L2-L3≥5mm、…Ln-1-Ln≥5mm。
3. Negative electrode sheet according to claim 1, wherein said L is1-L2More than or equal to 1 +/-2 mm and L2-L3Not less than 1 +/-2 mm and … Ln-1-LnThe folding length is more than or equal to 1 +/-2 mm, and the folding length of the folding length 1 is 1 in the winding structure.
4. The negative electrode sheet according to claim 1, wherein the active material coating layer comprises graphite, the graphite comprises single-particle graphite and/or secondary-particle graphite, the mass percentage of the secondary-particle graphite in the active material coating layer of the nth layer is greater than the mass percentage of the secondary-particle graphite in the active material coating layer of the (n-1) th layer, based on 100% by mass of the graphite in the active material coating layer of a single layer, and the average particle diameter of the secondary-particle graphite is greater than the average particle diameter of the single-particle graphite.
5. The negative electrode sheet according to claim 4, wherein the surfaces of said conductive current collectors are stacked to form three active material coatings, wherein the graphite in the first active material coating is single-particle graphite, the graphite in the second active material coating is 25-75 wt% of single-particle graphite and 25-75 wt% of secondary-particle graphite, and the graphite in the third active material coating is secondary-particle graphite.
6. A negative electrode sheet according to claim 1, wherein the n active material coating layers have a surface density ratio of the first active material coating layer: second active material coating: third active material coating: fourth active material coating: … …: the nth layer of active material coating is 1-4: 1-4 … …:1 to 4.
7. The method for preparing a negative electrode sheet according to any one of claims 1 to 6, wherein the method comprises: coating the first active material layer slurry on the conductive current collector, coating the second active material layer slurry on the first active material layer slurry, coating the third active material layer slurry on the second active material layer slurry, coating the nth active material layer slurry on the (n-1) th active material layer slurry, and drying after coating to obtain the negative plate coated with the n layers of active material coatings.
8. The method for manufacturing a negative electrode sheet according to claim 7, wherein the first active material layer slurry is prepared by: uniformly stirring a first active material, a conductive agent, a binder and deionized water to obtain first active material layer slurry; the mass ratio of the first active substance to the conductive agent to the binder to the solvent is 90-98.5: 0-5: 1.5-5: 80-120 parts;
the nth active material layer slurry is prepared by adopting the following method: uniformly stirring the nth active substance, the conductive agent, the binder and the deionized water to obtain nth active substance layer slurry; the mass ratio of the nth active substance to the conductive agent to the binder to the solvent is 90-98.5: 0-5: 1.5-5: 80-120 parts.
9. The method for preparing a negative electrode sheet according to claim 8, wherein the conductive agent comprises one of conductive carbon black, carbon nanotubes and graphene; the binder comprises a binder A and a binder B, wherein the binder A and the binder B are respectively and independently selected from any one of carboxymethyl cellulose, styrene-butadiene rubber, PAA-based binder or PAN-based binder, the mass percentage of the binder A in the active material layer slurry is 0.5-2%, and the mass percentage of the binder B in the active material layer slurry is 1-3%; the solvent is deionized water.
10. A lithium ion battery comprising the negative electrode sheet according to any one of claims 1 to 6.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114678491A (en) * | 2022-04-12 | 2022-06-28 | 浙江极氪智能科技有限公司 | Negative pole piece, preparation method thereof and electrochemical device |
Citations (12)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109830690A (en) * | 2019-01-30 | 2019-05-31 | 深圳鸿鹏新能源科技有限公司 | Collector and pole piece and lithium battery with the collector |
| CN109935793A (en) * | 2017-12-15 | 2019-06-25 | 东莞市凯金新能源科技股份有限公司 | A kind of preparation method of lithium ion cell high-capacity high magnification composite graphite alkene negative electrode material |
| CN110024196A (en) * | 2017-06-09 | 2019-07-16 | 株式会社Lg化学 | Electrode and secondary cell including the electrode |
| CN110462885A (en) * | 2017-11-09 | 2019-11-15 | 株式会社Lg化学 | Strip electrode for cylindrical core and the lithium secondary battery comprising it |
| CN110660965A (en) * | 2019-08-29 | 2020-01-07 | 孚能科技(赣州)股份有限公司 | Negative plate and preparation method thereof, lithium ion battery and preparation method and application thereof |
| CN111600066A (en) * | 2020-06-29 | 2020-08-28 | 天津市捷威动力工业有限公司 | Quick-charging type high-energy-density lithium ion battery |
| CN111620331A (en) * | 2020-05-29 | 2020-09-04 | 湖北亿纬动力有限公司 | Artificial graphite negative electrode material, preparation method thereof and application thereof in lithium ion battery |
| CN211879509U (en) * | 2020-04-02 | 2020-11-06 | 宁德新能源科技有限公司 | Electrode pole piece, electrochemical device and electronic device comprising same |
| CN111916668A (en) * | 2020-07-27 | 2020-11-10 | 珠海冠宇电池股份有限公司 | Negative plate, preparation method thereof and lithium ion battery comprising negative plate |
| CN112701250A (en) * | 2020-12-29 | 2021-04-23 | 珠海冠宇电池股份有限公司 | Lithium ion battery |
| CN113140696A (en) * | 2021-04-22 | 2021-07-20 | 珠海冠宇电池股份有限公司 | Negative plate, lithium ion battery and preparation method of negative plate |
| CN113363418A (en) * | 2021-06-08 | 2021-09-07 | 江西安驰新能源科技有限公司 | High-rate lithium ion battery negative plate and preparation method thereof, and lithium ion battery |
-
2021
- 2021-11-24 CN CN202111407886.8A patent/CN114300644A/en active Pending
Patent Citations (13)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110024196A (en) * | 2017-06-09 | 2019-07-16 | 株式会社Lg化学 | Electrode and secondary cell including the electrode |
| US20200058962A1 (en) * | 2017-06-09 | 2020-02-20 | Lg Chem, Ltd. | Electrode and Secondary Battery Comprising the Same |
| CN110462885A (en) * | 2017-11-09 | 2019-11-15 | 株式会社Lg化学 | Strip electrode for cylindrical core and the lithium secondary battery comprising it |
| CN109935793A (en) * | 2017-12-15 | 2019-06-25 | 东莞市凯金新能源科技股份有限公司 | A kind of preparation method of lithium ion cell high-capacity high magnification composite graphite alkene negative electrode material |
| CN109830690A (en) * | 2019-01-30 | 2019-05-31 | 深圳鸿鹏新能源科技有限公司 | Collector and pole piece and lithium battery with the collector |
| CN110660965A (en) * | 2019-08-29 | 2020-01-07 | 孚能科技(赣州)股份有限公司 | Negative plate and preparation method thereof, lithium ion battery and preparation method and application thereof |
| CN211879509U (en) * | 2020-04-02 | 2020-11-06 | 宁德新能源科技有限公司 | Electrode pole piece, electrochemical device and electronic device comprising same |
| CN111620331A (en) * | 2020-05-29 | 2020-09-04 | 湖北亿纬动力有限公司 | Artificial graphite negative electrode material, preparation method thereof and application thereof in lithium ion battery |
| CN111600066A (en) * | 2020-06-29 | 2020-08-28 | 天津市捷威动力工业有限公司 | Quick-charging type high-energy-density lithium ion battery |
| CN111916668A (en) * | 2020-07-27 | 2020-11-10 | 珠海冠宇电池股份有限公司 | Negative plate, preparation method thereof and lithium ion battery comprising negative plate |
| CN112701250A (en) * | 2020-12-29 | 2021-04-23 | 珠海冠宇电池股份有限公司 | Lithium ion battery |
| CN113140696A (en) * | 2021-04-22 | 2021-07-20 | 珠海冠宇电池股份有限公司 | Negative plate, lithium ion battery and preparation method of negative plate |
| CN113363418A (en) * | 2021-06-08 | 2021-09-07 | 江西安驰新能源科技有限公司 | High-rate lithium ion battery negative plate and preparation method thereof, and lithium ion battery |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114678491A (en) * | 2022-04-12 | 2022-06-28 | 浙江极氪智能科技有限公司 | Negative pole piece, preparation method thereof and electrochemical device |
| CN114678491B (en) * | 2022-04-12 | 2023-09-05 | 浙江极氪智能科技有限公司 | Negative electrode plate, preparation method thereof and electrochemical device |
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