CN113036069B - Method for improving capacity and stability of lithium battery, coating device and application - Google Patents
Method for improving capacity and stability of lithium battery, coating device and application Download PDFInfo
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- CN113036069B CN113036069B CN202110214976.9A CN202110214976A CN113036069B CN 113036069 B CN113036069 B CN 113036069B CN 202110214976 A CN202110214976 A CN 202110214976A CN 113036069 B CN113036069 B CN 113036069B
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- 229910052744 lithium Inorganic materials 0.000 title claims abstract description 106
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 title claims abstract description 98
- 239000011248 coating agent Substances 0.000 title claims abstract description 52
- 238000000576 coating method Methods 0.000 title claims abstract description 52
- 238000000034 method Methods 0.000 title claims abstract description 39
- 239000002904 solvent Substances 0.000 claims abstract description 82
- 239000003792 electrolyte Substances 0.000 claims abstract description 53
- 229910003002 lithium salt Inorganic materials 0.000 claims description 18
- 159000000002 lithium salts Chemical class 0.000 claims description 18
- 239000000463 material Substances 0.000 claims description 18
- JBTWLSYIZRCDFO-UHFFFAOYSA-N ethyl methyl carbonate Chemical compound CCOC(=O)OC JBTWLSYIZRCDFO-UHFFFAOYSA-N 0.000 claims description 16
- 229910001416 lithium ion Inorganic materials 0.000 claims description 14
- IEJIGPNLZYLLBP-UHFFFAOYSA-N dimethyl carbonate Chemical compound COC(=O)OC IEJIGPNLZYLLBP-UHFFFAOYSA-N 0.000 claims description 12
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 claims description 11
- OIFBSDVPJOWBCH-UHFFFAOYSA-N Diethyl carbonate Chemical compound CCOC(=O)OCC OIFBSDVPJOWBCH-UHFFFAOYSA-N 0.000 claims description 10
- -1 lithium hexafluorophosphate Chemical compound 0.000 claims description 6
- 239000000843 powder Substances 0.000 claims description 5
- FWLUTJHBRZTAMP-UHFFFAOYSA-N B([O-])([O-])F.B([O-])([O-])F.B([O-])([O-])F.B([O-])([O-])F.B([O-])([O-])F.B([O-])([O-])F.[Li+].[Li+].[Li+].[Li+].[Li+].[Li+].[Li+].[Li+].[Li+].[Li+].[Li+].[Li+] Chemical compound B([O-])([O-])F.B([O-])([O-])F.B([O-])([O-])F.B([O-])([O-])F.B([O-])([O-])F.B([O-])([O-])F.[Li+].[Li+].[Li+].[Li+].[Li+].[Li+].[Li+].[Li+].[Li+].[Li+].[Li+].[Li+] FWLUTJHBRZTAMP-UHFFFAOYSA-N 0.000 claims description 3
- 229910013188 LiBOB Inorganic materials 0.000 claims description 3
- 229910003473 lithium bis(trifluoromethanesulfonyl)imide Inorganic materials 0.000 claims description 3
- 229910001500 lithium hexafluoroborate Inorganic materials 0.000 claims description 3
- MHCFAGZWMAWTNR-UHFFFAOYSA-M lithium perchlorate Chemical compound [Li+].[O-]Cl(=O)(=O)=O MHCFAGZWMAWTNR-UHFFFAOYSA-M 0.000 claims description 3
- 229910001486 lithium perchlorate Inorganic materials 0.000 claims description 3
- QSZMZKBZAYQGRS-UHFFFAOYSA-N lithium;bis(trifluoromethylsulfonyl)azanide Chemical compound [Li+].FC(F)(F)S(=O)(=O)[N-]S(=O)(=O)C(F)(F)F QSZMZKBZAYQGRS-UHFFFAOYSA-N 0.000 claims description 3
- MCVFFRWZNYZUIJ-UHFFFAOYSA-M lithium;trifluoromethanesulfonate Chemical compound [Li+].[O-]S(=O)(=O)C(F)(F)F MCVFFRWZNYZUIJ-UHFFFAOYSA-M 0.000 claims description 3
- 229910052751 metal Inorganic materials 0.000 abstract description 10
- 239000002184 metal Substances 0.000 abstract description 10
- 230000008595 infiltration Effects 0.000 abstract description 6
- 238000001764 infiltration Methods 0.000 abstract description 6
- 238000005096 rolling process Methods 0.000 abstract description 6
- 238000004140 cleaning Methods 0.000 abstract description 4
- 230000002035 prolonged effect Effects 0.000 abstract description 4
- 238000005253 cladding Methods 0.000 abstract description 3
- 230000000052 comparative effect Effects 0.000 description 10
- 239000010410 layer Substances 0.000 description 7
- 239000013589 supplement Substances 0.000 description 5
- 238000004090 dissolution Methods 0.000 description 4
- 238000002161 passivation Methods 0.000 description 4
- 239000011888 foil Substances 0.000 description 3
- 239000007788 liquid Substances 0.000 description 3
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 2
- 239000011149 active material Substances 0.000 description 2
- 239000013543 active substance Substances 0.000 description 2
- 229910052782 aluminium Inorganic materials 0.000 description 2
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 238000001035 drying Methods 0.000 description 2
- 239000007772 electrode material Substances 0.000 description 2
- 239000003759 ester based solvent Substances 0.000 description 2
- 239000010439 graphite Substances 0.000 description 2
- 229910002804 graphite Inorganic materials 0.000 description 2
- 238000010438 heat treatment Methods 0.000 description 2
- 238000009830 intercalation Methods 0.000 description 2
- 230000002687 intercalation Effects 0.000 description 2
- 239000012528 membrane Substances 0.000 description 2
- 239000003960 organic solvent Substances 0.000 description 2
- 238000004806 packaging method and process Methods 0.000 description 2
- 238000002791 soaking Methods 0.000 description 2
- 239000007784 solid electrolyte Substances 0.000 description 2
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- HMDDXIMCDZRSNE-UHFFFAOYSA-N [C].[Si] Chemical compound [C].[Si] HMDDXIMCDZRSNE-UHFFFAOYSA-N 0.000 description 1
- 230000002238 attenuated effect Effects 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000004364 calculation method Methods 0.000 description 1
- 239000011247 coating layer Substances 0.000 description 1
- 239000011889 copper foil Substances 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000003487 electrochemical reaction Methods 0.000 description 1
- 239000011267 electrode slurry Substances 0.000 description 1
- 238000004146 energy storage Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 239000012212 insulator Substances 0.000 description 1
- 238000006138 lithiation reaction Methods 0.000 description 1
- GELKBWJHTRAYNV-UHFFFAOYSA-K lithium iron phosphate Chemical compound [Li+].[Fe+2].[O-]P([O-])([O-])=O GELKBWJHTRAYNV-UHFFFAOYSA-K 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 239000007773 negative electrode material Substances 0.000 description 1
- 230000010287 polarization Effects 0.000 description 1
- 239000007774 positive electrode material Substances 0.000 description 1
- 239000002002 slurry Substances 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 230000001502 supplementing effect Effects 0.000 description 1
Images
Classifications
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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
- H01M4/04—Processes of manufacture in general
- H01M4/0402—Methods of deposition of the material
- H01M4/0404—Methods of deposition of the material by coating on electrode collectors
-
- 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
- H01M4/04—Processes of manufacture in general
- H01M4/0402—Methods of deposition of the material
- H01M4/0409—Methods of deposition of the material by a doctor blade method, slip-casting or roller coating
-
- 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
- H01M4/04—Processes of manufacture in general
- H01M4/0402—Methods of deposition of the material
- H01M4/0416—Methods of deposition of the material involving impregnation with a solution, dispersion, paste or dry powder
-
- 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
- H01M4/04—Processes of manufacture in general
- H01M4/043—Processes of manufacture in general involving compressing or compaction
- H01M4/0435—Rolling or calendering
-
- 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
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
- Y02P70/50—Manufacturing or production processes characterised by the final manufactured product
Abstract
The invention provides a method for improving the capacity and stability of a lithium battery, a coating device and application, wherein the method comprises the following steps: after the negative plate is coated with lithium, the negative plate is sequentially soaked by the first solvent, dissolved by lithium in the electrolyte and cleaned by the second solvent under the traction of the driving roller. According to the invention, after the negative plate is coated with lithium, the negative plate is sequentially subjected to first solvent infiltration, electrolyte coating and second solvent cleaning under a rolling condition, wherein the first solvent fully infiltrates the negative plate in advance, the purpose of electrolyte coating is to dissolve metal lithium on the surface of the negative plate to form a compact SEI film, and the second solvent cleans residual electrolyte on the plate, so that the problem of capacity reduction caused by increase of the thickness of a battery cell after lithium cladding is solved, the capacity and the energy density of the battery cell are improved by more than 8%, the infiltration speed of the negative plate is accelerated, the SEI film formed on the surface of the negative plate is more uniform, and the cycle life of the battery cell is prolonged.
Description
Technical Field
The invention belongs to the technical field of lithium batteries, relates to a method for improving the capacity and stability of a lithium battery, and particularly relates to a method for improving the capacity and stability of the lithium battery, a coating device and application.
Background
The lithium ion battery has the characteristics of small volume, large energy storage and the like, and can discharge large current permanently. Therefore, lithium ion batteries are widely used not only in digital devices such as music players, video cameras, and portable computers, but also in electric tools, electric bicycles, and electric vehicles.
With the widespread use of lithium ion power batteries, the energy density of the batteries is also increasingly required. For cylindrical lithium ion batteries, the energy density is increased within a specified limited space.
At present, the pre-lithiation technology capable of realizing industrialization is lithium-clad metal lithium foil, two layers of 2-6 μm ultrathin lithium foils with an A/B surface are generally clad on a negative electrode (graphite or silicon-carbon negative electrode), active lithium consumed by SEI film formation is compensated, and the capacity is improved by 8%. The lithium metal and the negative pole take place electrochemical reaction after annotating the liquid, imbed in the negative pole active material, because the dissolution of lithium metal, the clearance increase between the electrode slice leads to the utmost point to roll up loosely, and the utmost point is rolled up and is removed easily in the aluminum hull, simultaneously because the inside interval of utmost point book increases, the polarization of battery can increase.
CN110875499A discloses a method for supplementing lithium to a battery, which comprises the following steps: coating positive slurry containing a positive active material on the surface of a positive current collector, and drying to obtain a positive plate with a positive diaphragm arranged on the surface of the positive current collector; coating negative electrode slurry containing a negative electrode active substance on the surface of a negative electrode current collector, drying to obtain an initial negative electrode plate with a negative electrode diaphragm arranged on the surface of the negative electrode current collector, and then continuously arranging a layer of lithium metal on the surface of the negative electrode diaphragm to obtain a lithium-rich negative electrode plate; assembling the lithium-rich cathode plate, the isolating membrane and the anode plate into a lithium supplement core; soaking the lithium-supplement cell in an organic solvent for a period of time, wherein the organic solvent at least comprises a negative electrode film-forming component; and (4) placing the soaked lithium supplement battery core in a battery packaging shell, injecting electrolyte and packaging to obtain the lithium supplement battery. But does not address the problems of lower capacity and loose pole rolls.
CN110896140A discloses a lithium-rich negative plate, an electrical core, and a lithium ion battery, where the lithium-rich negative plate includes a negative current collector and a negative diaphragm that is disposed on the surface of the negative current collector and contains a negative active material, and the lithium-rich negative plate further includes a layer of lithium metal disposed on the surface of the negative diaphragm. Wherein, the negativeThe electrode diaphragm further includes a cyclic ester capable of forming a film on the negative electrode, the cyclic ester having a dielectric constant of 10 or more and being soluble in Li/Li+The reduction potential of (A) is 1.5V or less. The invention can improve the film forming effect on the surface of the negative electrode, control the lithium intercalation speed of the negative electrode, ensure the uniform lithium intercalation of the negative electrode piece and enhance the bonding strength between the negative electrode membrane and the negative electrode current collector. The problems of low capacity and loose pole rolls are still not solved.
The existing lithium ion batteries all have the problems of low capacity, loose pole roll and the like, so how to ensure the high capacity and the difficult loosening of the pole roll under the condition of ensuring the stability and the safety of the lithium ion batteries becomes the problem which needs to be solved urgently at present.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to provide a method, a coating device and a use for improving the capacity and the stability of a lithium battery.
In order to achieve the purpose, the invention adopts the following technical scheme:
in a first aspect, the present invention provides a method for improving capacity and stability of a lithium battery, the method comprising:
after the negative plate is coated with lithium, the negative plate is sequentially soaked by the first solvent, dissolved by lithium in the electrolyte and cleaned by the second solvent under the traction of the driving roller.
According to the invention, after the negative plate is coated with lithium, the negative plate is sequentially subjected to first solvent infiltration, electrolyte coating and second solvent cleaning under a rolling condition, wherein the first solvent fully infiltrates the negative plate in advance, the purpose of electrolyte coating is to dissolve metal lithium on the surface of the negative plate to form a compact SEI film, and the second solvent cleans residual electrolyte on the plate, so that the problem of capacity reduction caused by increase of the thickness of a battery cell after lithium cladding is solved, the capacity and the energy density of the battery cell are improved by more than 8%, the infiltration speed of the negative plate is accelerated, the SEI film formed on the surface of the negative plate is more uniform, and the cycle life of the battery cell is prolonged.
It should be noted that, in the first charge and discharge process of the liquid lithium ion battery, the electrode material and the electrolyte react on the solid-liquid interface to form a passivation layer covering the surface of the electrode material. The passivation layer is an interfacial layer, characterized by a solid electrolyte, which is an electronic insulator but Li+Of good electrical conductivity, Li+Can be freely inserted into and removed from the passivation layer, so that the passivation film is called a Solid Electrolyte Interface (SEI) film.
In a preferred embodiment of the present invention, the lithium coating quality of the negative electrode sheet is calculated from the coating layer of the positive electrode sheet, and the lithium coating quality per unit area of the negative electrode sheet is equal to the capacity per unit area of the positive electrode sheet (CB × (CB)1-CB2) X area of negative electrode sheet/(3861.3 mAh/g 85%), and the ratio of CB to surface area is set to be equal to1Is an initial cell capacity balance value of the cell, the CB2And (4) pre-lithium of the battery to obtain a battery capacity balance value.
Preferably, the lithium coating mass of the negative electrode sheet is 0.5 to 8% of the mass of the positive electrode sheet coating, such as 0.5%, 1.0%, 1.5%, 2.0%, 2.5%, 3.0%, 3.5%, 4.0%, 4.5%, 5.0%, 5.5%, 6.0%, 6.5%, 7.0%, 7.5% or 8.0%.
As a preferred embodiment of the present invention, the CB1Has a value of 1.16 to 2.16, e.g. CB1Has a value of 1.16, 1.26, 1.36, 1.46, 1.56, 1.66, 1.76, 1.86, 1.96, 2.06 or 2.16, CB1The unit area capacity of the positive plate is the initial charge capacity of the positive electrode x the initial coulomb efficiency of the negative electrode x the second cycle coulomb efficiency of the negative electrode x the third cycle coulomb efficiency of the negative electrode/the area of the positive plate.
As a preferred embodiment of the present invention, the CB2A value of ≧ 1.06, e.g., CB2Has a value of 1.06, 1.16, 1.26, 1.36, 1.46 or 1.56, CB2Capacity per unit area of negative electrode sheet-lithium coating mass per unit area of negative electrode sheet × 3861.3mAh/g × 80%)/capacity per unit area of positive electrode sheet.
Compared with the calculation method in the prior art, the method for calculating the lithium coating quality has the advantages of simplicity, convenience and convenience, and is convenient for guiding the theoretical design of lithium supplement amount.
As a preferred technical solution of the present invention, the lithium-coated material in the negative electrode sheet includes metallic lithium powder and/or a metallic lithium ribbon.
Preferably, the first solvent comprises a linear ester solvent.
Preferably, the linear ester-based solvent includes one or a combination of at least two of dimethyl carbonate, diethyl carbonate, or ethyl methyl carbonate.
In a preferred embodiment of the present invention, the concentration of the lithium salt in the electrolyte is 0.01 to 1.2mol/L, for example, the concentration of the lithium salt is 0.01mol/L, 0.1mol/L, 0.2mol/L, 0.3mol/L, 0.4mol/L, 0.5mol/L, 0.6mol/L, 0.7mol/L, 0.8mol/L, 0.9mol/L, 1.0mol/L, 1.1mol/L or 1.2mol/L, and more preferably 0.1 to 0.5 mol/L.
Preferably, the lithium salt comprises one or a combination of at least two of lithium perchlorate, lithium hexafluorophosphate, lithium hexafluoroborate, LiBOB, LiTFSI or LiTFS.
In a preferred embodiment of the present invention, the second solvent includes a linear ester solvent.
Preferably, the linear ester-based solvent includes one or a combination of at least two of dimethyl carbonate, diethyl carbonate, or ethyl methyl carbonate.
Preferably, the first solvent and the second solvent are the same or different.
In a second aspect, the invention provides a coating device for performing the method for improving the capacity and stability of the lithium battery in the first aspect, the coating device comprises a first solvent tank, an electrolyte tank and a second solvent tank which are sequentially arranged, at least one material roller is arranged in each of the first solvent tank, the electrolyte tank and the second solvent tank in a staggered manner, and the material rollers are used for conveying pole pieces.
As a preferable technical scheme of the invention, the material roller is a heating material roller.
Preferably, the coating device further comprises a guide roller assembly, wherein the guide roller assembly comprises at least four guide rollers, and the guide rollers are respectively positioned at the inlet end of the first solvent tank, between the first solvent tank and the electrolyte tank, between the electrolyte tank and the second solvent tank and at the outlet end of the second solvent tank.
In a third aspect, the present invention provides a use of the method for improving the capacity and stability of a lithium battery according to the first aspect, wherein the method is used in the field of lithium ion batteries.
The recitation of numerical ranges herein includes not only the above-recited numerical values, but also any numerical values between non-recited numerical ranges, and is not intended to be exhaustive or to limit the invention to the precise numerical values encompassed within the range for brevity and clarity.
Compared with the prior art, the invention has the beneficial effects that:
according to the invention, after the negative plate is coated with lithium, the negative plate is sequentially subjected to first solvent infiltration, electrolyte coating and second solvent cleaning under a rolling condition, wherein the first solvent fully infiltrates the negative plate in advance, the purpose of electrolyte coating is to dissolve metal lithium on the surface of the negative plate to form a compact SEI film, and the second solvent cleans residual electrolyte on the plate, so that the problem of capacity reduction caused by increase of the thickness of a battery cell after lithium cladding is solved, the capacity and the energy density of the battery cell are improved by more than 8%, the infiltration speed of the negative plate is accelerated, the SEI film formed on the surface of the negative plate is more uniform, and the cycle life of the battery cell is prolonged.
Drawings
Fig. 1 is a schematic structural view of a coating apparatus provided in an embodiment of the present invention.
Wherein, 1-a first solvent tank; 2-an electrolyte tank; 3-a second solvent tank; 4-a material roller; 5-guide rollers.
Detailed Description
It is to be understood that in the description of the present invention, the terms "central," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," and the like are used in an orientation or positional relationship indicated in the drawings for convenience in describing the present invention and to simplify the description, but are not intended to indicate or imply that the device or element so referred to must have a particular orientation, be constructed in a particular orientation, and be operated in a particular manner and therefore are not to be construed as limiting the invention. Furthermore, the terms "first," "second," and the like are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or to implicitly indicate a number of the indicated technical features. Thus, a feature defined as "first," "second," etc. may explicitly or implicitly include one or more of that feature. In the description of the present invention, "a plurality" means two or more unless otherwise specified.
It should be noted that, in the description of the present invention, unless otherwise explicitly specified or limited, the terms "disposed," "connected" and "connected" are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood by those of ordinary skill in the art through specific situations.
The technical solution of the present invention is further explained by the following embodiments.
In one embodiment, the invention provides a coating device, as shown in fig. 1, the coating device comprises a first solvent tank, an electrolyte tank and a second solvent tank which are arranged in sequence, at least one material roller is arranged in the first solvent tank, the electrolyte tank and the second solvent tank in a staggered manner, the material rollers are used for conveying pole pieces, and further, the material rollers are heating material rollers.
The coating device also comprises a guide roller assembly, wherein the guide roller assembly comprises at least four guide rollers, and the guide rollers are respectively positioned at the inlet end of the first solvent tank, between the first solvent tank and the electrolyte tank, between the electrolyte tank and the second solvent tank and at the outlet end of the second solvent tank.
In another embodiment, the present invention provides a method for increasing the capacity and stability of a lithium battery, comprising:
after the negative plate is coated with lithium, the negative plate is sequentially soaked by the first solvent, dissolved by lithium in the electrolyte and cleaned by the second solvent under the traction of the driving roller.
The lithium coating quality of the negative plate is calculated by the coating of the positive plate, and the lithium coating quality per unit area of the negative plate is equal to the capacity per unit area of the positive plate x (CB)1-CB2) /(3861.3 mAh/g.times.85%) the CB1Is an initial cell capacity balance value of the cell, the CB2The lithium coating quality of the negative plate is 0.5-8% of the coating quality of the positive plate.
CB1Has a value of 1.16 to 2.16, CB1The capacity per unit area of the negative electrode sheet/the capacity per unit area of the positive electrode sheet, and the capacity per unit area of the positive electrode sheet, the first charge capacity of the positive electrode, the first coulombic efficiency of the negative electrode, the second coulombic efficiency of the negative electrode, the third coulombic efficiency of the negative electrode, and the area of the positive electrode sheet.
CB2The value of (A) is more than or equal to 1.06, CB2Capacity per unit area of negative electrode sheet-lithium coating mass per unit area of negative electrode sheet × 3861.3mAh/g × 80%)/capacity per unit area of positive electrode sheet.
The lithium coating material in the negative plate comprises metal lithium powder and/or a metal lithium belt, the first solvent comprises a linear ester solvent, and the linear ester solvent comprises one or a combination of at least two of dimethyl carbonate, diethyl carbonate and methyl ethyl carbonate.
Further, the concentration of the lithium salt in the electrolyte is 0.01-1.2 mol/L, and more preferably 0.1-0.5 mol/L, and the lithium salt comprises one or a combination of at least two of lithium perchlorate, lithium hexafluorophosphate, lithium hexafluoroborate, LiBOB, LiTFSI and LiTFS. The second solvent includes a linear ester solvent including one or a combination of at least two of dimethyl carbonate, diethyl carbonate, or ethyl methyl carbonate. The first solvent and the second solvent are the same or different.
In the following examples and comparative examples, the electrolyte was a conventional electrolyte in which the lithium salt was lithium hexafluorophosphate. The current collector of the positive plate is made of aluminum foil, and the active material is lithium iron phosphate; the current collector of the negative plate is made of copper foil, and the active substance is graphite.
Example 1
The embodiment provides a method for improving the capacity and stability of a lithium battery, which comprises the following steps:
after the negative plate is coated with lithium, the negative plate is sequentially soaked by the first solvent, dissolved by lithium in the electrolyte and cleaned by the second solvent under the traction of the driving roller.
Wherein, CB of the battery1Value 1.66, CB2The value was 1.06. The lithium coating mass of the negative plate is 5 percent of the mass of the positive plate.
Wherein the first solvent is dimethyl carbonate. The concentration of lithium salt in the electrolyte was 0.3 mol/L. The second solvent is diethyl carbonate, and the lithium coating material in the negative plate is metal lithium powder.
Example 2
The embodiment provides a method for improving the capacity and stability of a lithium battery, which comprises the following steps:
after the negative plate is coated with lithium, the negative plate is sequentially soaked by the first solvent, coated by the electrolyte and washed by the second solvent under the rolling condition.
Wherein, CB of the battery1Value 2.16, CB2The value was 1.26. The lithium coating mass of the negative plate is 7.5 percent of the mass of the positive plate.
Wherein the first solvent is diethyl carbonate. The concentration of lithium salt in the electrolyte was 0.5 mol/L. The second solvent is methyl ethyl carbonate, and the lithium-coated material in the negative plate is a metal lithium belt.
Example 3
The embodiment provides a method for improving the capacity and stability of a lithium battery, which comprises the following steps:
after the negative plate is coated with lithium, the negative plate is sequentially soaked by the first solvent, coated by the electrolyte and washed by the second solvent under the rolling condition.
Wherein, CB of the battery1Value 1.36, CB2The value was 1.26. The lithium coating mass of the negative plate is 0.8 percent of the mass of the positive plate.
The first solvent is a combination of dimethyl carbonate and diethyl carbonate, and the mass ratio of the dimethyl carbonate to the diethyl carbonate is 1: 1. The concentration of lithium salt in the electrolyte was 0.01 mol/L. The second solvent is dimethyl carbonate, and the lithium coating material in the negative plate is metal lithium powder.
Example 4
The embodiment provides a method for improving the capacity and stability of a lithium battery, which comprises the following steps:
after the negative plate is coated with lithium, the negative plate is sequentially soaked by the first solvent, coated by the electrolyte and washed by the second solvent under the rolling condition.
Wherein, CB of the battery1Value 1.36, CB2The value was 1.06. The lithium coating mass of the negative plate is 2.5 percent of the mass of the positive plate.
Wherein the first solvent is dimethyl carbonate. The concentration of lithium salt in the electrolyte was 1.2 mol/L. The second solvent is dimethyl carbonate, and the lithium coating material in the negative plate is a metal lithium belt.
Example 5
This example provides a method for improving the capacity and stability of a lithium battery, based on the method described in example 1, except that the concentration of lithium salt in the electrolyte is 0.05mol/L, and the rest of the operation steps and parameters are the same as those in example 1.
Example 6
This example provides a method for improving the capacity and stability of a lithium battery, based on the method described in example 1, except that the concentration of lithium salt in the electrolyte is 0.7mol/L, and the rest of the operation steps and parameters are exactly the same as those in example 1.
Comparative example 1
The present comparative example provides a negative electrode sheet and a positive electrode sheet, and compared with example 1, the difference is that after the negative electrode sheet and the positive electrode sheet are coated with lithium, the negative electrode sheet is sequentially subjected to electrolyte coating and second solvent cleaning, and the remaining parameters are completely the same as those of example 1.
Comparative example 2
Compared with the embodiment 1, the negative plate and the positive plate are different in that after the negative plate and the positive plate are coated with lithium, the negative plate is soaked in the first solvent and coated with the electrolyte in sequence, and other parameters are completely the same as those in the embodiment 1.
Comparative example 3
Compared with the embodiment 1, the negative plate and the positive plate are different in that after the negative plate and the positive plate are coated with lithium, the negative plate is soaked in the first solvent and washed by the second solvent in sequence, and other parameters are completely the same as those in the embodiment 1.
Preparing the negative plate and the positive plate prepared in the above examples and comparative examples into a rolled core battery, and measuring the battery capacity of the rolled core battery, wherein the measuring method comprises the following steps:
the test uses Xinwei charge-discharge equipment and a soft package battery with the designed capacity of 1.8Ah, and charges with CC-CV of current of 2A, the cut-off current is 0.1A, and the cut-off voltage is 3.65V; the discharge was carried out at 2A current DC, cutoff current 2.5V, capacity test temperature 25 deg.C, and cycle test ambient temperature 45 deg.C.
The measurement results are shown in table 1.
TABLE 1
As can be seen from the above table:
(1) in example 1, compared with examples 5 and 6, the battery capacity of example 1 is higher than that of example 6, and the cycle life is longer than that of examples 5 and 6, so that it can be seen that the concentration of the lithium salt in the electrolyte is more preferably 0.1 to 0.5mol/L, which has the advantages of both lithium dissolution efficiency and film formation quality, and when the concentration of the lithium salt in the electrolyte is less than 0.1mol/L, the lithium dissolution time is insufficient, resulting in a problem of lithium remaining; when the concentration of lithium salt in the electrolyte is higher than 0.5mol/L, the problem that the SEI film is formed at a high speed, so that the capacity is attenuated too fast and the like exists.
(2) Compared with comparative examples 1, 2 and 3, the capacity of the battery in example 1 is higher than that in comparative example 3, the cycle life is longer than that in comparative examples 1 and 3, and the residual electrolyte in comparative example 2 cannot be used for the next step, so that the invention can be seen in the fact that after the lithium is coated on the negative plate, the negative plate is sequentially soaked by the first solvent, coated by the electrolyte and cleaned by the second solvent under the condition of roller traction, wherein the first solvent fully soaks the negative plate in advance, the purpose of coating the electrolyte is to dissolve metallic lithium on the surface of the negative plate to form a compact SEI film, the slower the dissolution time of the lithium belt is, the better the film forming quality is, the longer the service life is, the second solvent cleans the residual electrolyte on the plate, the problem of capacity reduction caused by the increase of the thickness of the battery core after the lithium coating is solved, the capacity and the energy density of the battery core are improved by more than 8%, and the soaking speed of the negative plate is accelerated, the SEI film formed on the surface of the negative electrode is more uniform, and the cycle life of the battery cell is prolonged.
The applicant declares that the above description is only a specific embodiment of the present invention, but the scope of the present invention is not limited thereto, and it should be understood by those skilled in the art that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention disclosed herein fall within the scope and disclosure of the present invention.
Claims (15)
1. A method for improving the capacity and stability of a lithium battery is characterized by comprising the following steps:
after the negative plate is coated with lithium, the negative plate is sequentially soaked by a first solvent, dissolved by lithium in electrolyte and cleaned by a second solvent under the traction of a driving roller;
the lithium coating quality of the negative plate is calculated by the coating of the positive plate, and the unit surface of the negative plateMass of lithium deposited is equal to unit area capacity of positive plate x (CB)1-CB2) /(3861.3 mAh/g.times.85%) the CB1Is an initial cell capacity balance value of the cell, the CB2Pre-lithium is carried out on the battery to obtain a battery capacity balance value;
the CB1Has a value of 1.16 to 2.16, the CB1The unit area capacity of the positive plate is the first charge capacity of the positive electrode x the first coulombic efficiency of the negative electrode x the second coulombic efficiency of the negative electrode x the third coulombic efficiency of the negative electrode/the area of the positive plate;
the CB2The number of (b) is not less than 1.06, said CB2Capacity per unit area of negative electrode sheet-lithium coating mass per unit area of negative electrode sheet × 3861.3mAh/g × 80%)/capacity per unit area of positive electrode sheet.
2. The method according to claim 1, wherein the lithium coating quality of the negative plate is 0.5-8% of the quality of the positive plate coating.
3. The method according to claim 1, wherein the lithium-coated material in the negative electrode sheet comprises metallic lithium powder and/or a metallic lithium ribbon.
4. The method of claim 1, wherein the first solvent comprises a linear ester solvent.
5. The method according to claim 4, wherein the linear ester solvent comprises one or a combination of at least two of dimethyl carbonate, diethyl carbonate, or ethyl methyl carbonate.
6. The method of claim 1, wherein the concentration of the lithium salt in the electrolyte is 0.01 to 1.2 mol/L.
7. The method of claim 1, wherein the concentration of the lithium salt in the electrolyte is 0.1-0.5 mol/L.
8. The method of claim 6 or 7, wherein the lithium salt comprises one or a combination of at least two of lithium perchlorate, lithium hexafluorophosphate, lithium hexafluoroborate, LiBOB, LiTFSI, or LiTFS.
9. The method of claim 1, wherein the second solvent comprises a linear ester solvent.
10. The method of claim 9, wherein the linear ester solvent comprises one or a combination of at least two of dimethyl carbonate, diethyl carbonate, or ethyl methyl carbonate.
11. The method of claim 1, wherein the first solvent and the second solvent are the same or different.
12. A coating apparatus for performing the method of improving the capacity and stability of a lithium ion battery according to any one of claims 1 to 11, wherein the coating apparatus comprises a first solvent tank, an electrolyte tank and a second solvent tank, which are arranged in sequence, and at least one material roller is arranged in each of the first solvent tank, the electrolyte tank and the second solvent tank in a staggered manner, and the material roller is used for conveying a pole piece.
13. A coating apparatus as in claim 12 wherein said rollers are heated rollers.
14. The coating apparatus of claim 12 further comprising a guide roller assembly, said guide roller assembly comprising at least four guide rollers, said guide rollers being positioned at an inlet end of the first solvent bath, between the first solvent bath and the electrolyte bath, between the electrolyte bath and the second solvent bath, and at an outlet end of the second solvent bath.
15. Use of a method for increasing the capacity and stability of a lithium battery according to any one of claims 1 to 11, characterized in that the method is used in the field of lithium ion batteries.
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