WO2023197946A1 - Positive electrode plate, secondary battery, electronic device, and mobile equipment - Google Patents
Positive electrode plate, secondary battery, electronic device, and mobile equipment Download PDFInfo
- Publication number
- WO2023197946A1 WO2023197946A1 PCT/CN2023/086843 CN2023086843W WO2023197946A1 WO 2023197946 A1 WO2023197946 A1 WO 2023197946A1 CN 2023086843 W CN2023086843 W CN 2023086843W WO 2023197946 A1 WO2023197946 A1 WO 2023197946A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- positive electrode
- coating
- active material
- cathode
- binder
- Prior art date
Links
- 238000000576 coating method Methods 0.000 claims abstract description 245
- 239000011248 coating agent Substances 0.000 claims abstract description 238
- 239000011230 binding agent Substances 0.000 claims abstract description 57
- 239000007774 positive electrode material Substances 0.000 claims abstract description 46
- 239000006258 conductive agent Substances 0.000 claims abstract description 31
- 239000006182 cathode active material Substances 0.000 claims description 48
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- 229910052748 manganese Inorganic materials 0.000 claims description 5
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- 229910052797 bismuth Inorganic materials 0.000 claims description 3
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- 229910052746 lanthanum Inorganic materials 0.000 claims description 3
- 229910052750 molybdenum Inorganic materials 0.000 claims description 3
- 229910052711 selenium Inorganic materials 0.000 claims description 3
- 229910052712 strontium Inorganic materials 0.000 claims description 3
- 229910052714 tellurium Inorganic materials 0.000 claims description 3
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- 229910052721 tungsten Inorganic materials 0.000 claims description 3
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- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 17
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- 230000000052 comparative effect Effects 0.000 description 16
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- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 12
- 238000000034 method Methods 0.000 description 12
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- 238000010586 diagram Methods 0.000 description 8
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- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 7
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- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 2
- 229920003171 Poly (ethylene oxide) Polymers 0.000 description 2
- 239000004372 Polyvinyl alcohol Substances 0.000 description 2
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 2
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- 229910001416 lithium ion Inorganic materials 0.000 description 2
- GELKBWJHTRAYNV-UHFFFAOYSA-K lithium iron phosphate Chemical compound [Li+].[Fe+2].[O-]P([O-])([O-])=O GELKBWJHTRAYNV-UHFFFAOYSA-K 0.000 description 2
- 238000009782 nail-penetration test Methods 0.000 description 2
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- 229920001343 polytetrafluoroethylene Polymers 0.000 description 2
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- 239000010703 silicon Substances 0.000 description 2
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- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- IXPNQXFRVYWDDI-UHFFFAOYSA-N 1-methyl-2,4-dioxo-1,3-diazinane-5-carboximidamide Chemical compound CN1CC(C(N)=N)C(=O)NC1=O IXPNQXFRVYWDDI-UHFFFAOYSA-N 0.000 description 1
- 229920000049 Carbon (fiber) Polymers 0.000 description 1
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 description 1
- 229910000733 Li alloy Inorganic materials 0.000 description 1
- 229910013854 LiCo0.8Ni0.1Mn0.1O2 Inorganic materials 0.000 description 1
- 229910012851 LiCoO 2 Inorganic materials 0.000 description 1
- 229910013870 LiPF 6 Inorganic materials 0.000 description 1
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 description 1
- AFCARXCZXQIEQB-UHFFFAOYSA-N N-[3-oxo-3-(2,4,6,7-tetrahydrotriazolo[4,5-c]pyridin-5-yl)propyl]-2-[[3-(trifluoromethoxy)phenyl]methylamino]pyrimidine-5-carboxamide Chemical compound O=C(CCNC(=O)C=1C=NC(=NC=1)NCC1=CC(=CC=C1)OC(F)(F)F)N1CC2=C(CC1)NN=N2 AFCARXCZXQIEQB-UHFFFAOYSA-N 0.000 description 1
- 229910019142 PO4 Inorganic materials 0.000 description 1
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- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 description 1
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 1
- HCHKCACWOHOZIP-UHFFFAOYSA-N Zinc Chemical compound [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 description 1
- JXBAVRIYDKLCOE-UHFFFAOYSA-N [C].[P] Chemical compound [C].[P] JXBAVRIYDKLCOE-UHFFFAOYSA-N 0.000 description 1
- PFYQFCKUASLJLL-UHFFFAOYSA-N [Co].[Ni].[Li] Chemical compound [Co].[Ni].[Li] PFYQFCKUASLJLL-UHFFFAOYSA-N 0.000 description 1
- YWJVFBOUPMWANA-UHFFFAOYSA-H [Li+].[V+5].[O-]P([O-])([O-])=O.[O-]P([O-])([O-])=O Chemical compound [Li+].[V+5].[O-]P([O-])([O-])=O.[O-]P([O-])([O-])=O YWJVFBOUPMWANA-UHFFFAOYSA-H 0.000 description 1
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- 239000004917 carbon fiber Substances 0.000 description 1
- 239000000919 ceramic Substances 0.000 description 1
- CXULZQWIHKYPTP-UHFFFAOYSA-N cobalt(2+) manganese(2+) nickel(2+) oxygen(2-) Chemical compound [O--].[O--].[O--].[Mn++].[Co++].[Ni++] CXULZQWIHKYPTP-UHFFFAOYSA-N 0.000 description 1
- 238000004891 communication Methods 0.000 description 1
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- 239000008367 deionised water Substances 0.000 description 1
- 229910021641 deionized water Inorganic materials 0.000 description 1
- 238000003618 dip coating Methods 0.000 description 1
- 238000007599 discharging Methods 0.000 description 1
- PHAFDKCRJVKSSR-UHFFFAOYSA-N ethene hydrofluoride Chemical group F.C=C PHAFDKCRJVKSSR-UHFFFAOYSA-N 0.000 description 1
- 239000006232 furnace black Substances 0.000 description 1
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- 239000003273 ketjen black Substances 0.000 description 1
- 239000001989 lithium alloy Substances 0.000 description 1
- DMEJJWCBIYKVSB-UHFFFAOYSA-N lithium vanadium Chemical compound [Li].[V] DMEJJWCBIYKVSB-UHFFFAOYSA-N 0.000 description 1
- DVATZODUVBMYHN-UHFFFAOYSA-K lithium;iron(2+);manganese(2+);phosphate Chemical compound [Li+].[Mn+2].[Fe+2].[O-]P([O-])([O-])=O DVATZODUVBMYHN-UHFFFAOYSA-K 0.000 description 1
- 238000011068 loading method Methods 0.000 description 1
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- 239000012785 packaging film Substances 0.000 description 1
- 239000010452 phosphate Substances 0.000 description 1
- NBIIXXVUZAFLBC-UHFFFAOYSA-K phosphate Chemical compound [O-]P([O-])([O-])=O NBIIXXVUZAFLBC-UHFFFAOYSA-K 0.000 description 1
- 229920000573 polyethylene Polymers 0.000 description 1
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- 238000009517 secondary packaging Methods 0.000 description 1
- LIVNPJMFVYWSIS-UHFFFAOYSA-N silicon monoxide Chemical class [Si-]#[O+] LIVNPJMFVYWSIS-UHFFFAOYSA-N 0.000 description 1
- 229910052814 silicon oxide Inorganic materials 0.000 description 1
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- 229910052708 sodium Inorganic materials 0.000 description 1
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Classifications
-
- 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
-
- 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
- H01M10/054—Accumulators with insertion or intercalation of metals other than lithium, e.g. with magnesium or aluminium
-
- 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
- H01M10/36—Accumulators not provided for in groups H01M10/05-H01M10/34
-
- 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
-
- 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
- H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
-
- 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
- H01M4/1391—Processes of manufacture of electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/50—Current conducting connections for cells or batteries
- H01M50/572—Means for preventing undesired use or discharge
- H01M50/584—Means for preventing undesired use or discharge for preventing incorrect connections inside or outside the batteries
- H01M50/586—Means for preventing undesired use or discharge for preventing incorrect connections inside or outside the batteries inside the batteries, e.g. incorrect connections of electrodes
-
- 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
- H01M2004/028—Positive 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
Definitions
- Embodiments of the present application relate to the technical field of secondary batteries, and in particular to a positive electrode plate, secondary batteries, electronic equipment and mobile devices.
- Secondary batteries have been widely used in consumer electronics (such as mobile phones, tablets) and electric vehicles. However, secondary batteries can easily cause internal damage when they are continuously overcharged or damaged by external forces (such as punctures and collisions). Short circuit, and then thermal runaway occurs. Among them, the short circuit caused by the contact between the positive electrode current collector (such as aluminum foil) and the negative electrode is the most dangerous short circuit method of the battery. Therefore, reducing the risk of thermal runaway of secondary batteries is particularly important to promote their further widespread application.
- the safety coating mainly contains active materials with high safety performance (such as lithium iron phosphate). ), conductive agent and binder.
- embodiments of the present application provide a positive electrode plate and a secondary battery to effectively solve the problem of thermal runaway caused by the positive electrode current collector of the battery contacting the negative electrode without affecting the energy density of the battery.
- a first aspect of the embodiment of the present application provides a positive electrode sheet, including a positive electrode current collector and a first positive electrode coating and a second positive electrode coating sequentially laminated on at least one side surface of the positive electrode current collector;
- a positive electrode coating includes a first positive electrode active material, a first binder and a first conductive agent
- the second positive electrode coating includes a second positive electrode active material, a second binder and a second conductive agent; wherein, the The thickness of the first cathode coating is less than or equal to the second cathode coating, the tensile force or shear force of the first cathode coating is greater than the second cathode coating, and the first cathode active material
- the energy density is greater than or equal to the energy density of the second cathode active material.
- the positive electrode sheet provided in the embodiment of the present application controls the tensile force and/or shearing force of the first positive electrode coating close to the positive electrode current collector to be greater than the second positive electrode coating far away from the positive electrode current collector, and the first positive electrode coating
- the thickness is less than or equal to the second cathode coating, so that the difficulty of the first cathode coating falling off from the cathode current collector is greater than the difficulty of the second cathode coating falling off from the cathode plate.
- the first cathode coating can play a safety protection role.
- the first positive electrode coating when the second positive electrode coating peels off under abnormal conditions, the first positive electrode coating can still wrap and protect the positive electrode current collector to a certain extent, preventing it from direct contact with the negative electrode piece of the battery and causing thermal runaway.
- this application also controls that the energy density of the first positive electrode active material is not less than that of the second positive electrode active material, so that the first positive electrode coating can efficiently deintercalate lithium under normal operation of the battery, and its existence will not reduce the use of the positive electrode. Battery energy density of pole pieces.
- the thickness of the first cathode coating is greater than 0 and less than or equal to 50 ⁇ m. At this time, the first positive electrode coating is not easy to fall off from the positive electrode current collector, and has better safety performance.
- the mass proportion of the first binder in the first cathode coating is greater than the mass proportion of the second binder in the second cathode coating. This helps the first cathode coating have better bonding properties than the second cathode coating.
- the adhesive force of the first adhesive is greater than the adhesive force of the second adhesive. This also helps the first cathode coating have better bonding properties than the second cathode coating.
- the first adhesive and the second adhesive are made of the same material, and the molecular weight of the first adhesive is greater than that of the second adhesive.
- the mass proportion of the first binder in the first cathode coating is equal to the mass proportion of the second binder in the second cathode coating, and the The bonding force of the first adhesive is greater than the bonding force of the second adhesive. In this case, it can be ensured that the tensile force or shearing force of the first positive electrode coating is greater than that of the second positive electrode coating, which is conducive to its better performance of safety functions.
- the volume resistivity of the first cathode coating is greater than the volume resistivity of the second cathode coating.
- the first positive electrode coating can increase the ohmic polarization and electrochemical polarization of the positive electrode piece during the short circuit process, avoid the risk of thermal runaway caused by rapid heat accumulation, and can better passivate the positive electrode current collector and reduce its Thermal risk from contact with the negative battery tab.
- the first cathode coating includes the following mass percentages of each component: 85%-96.5% of the first cathode active material, 2.5%-10% of the first binder, 1% -5% first conductive agent.
- the sum of the mass proportions of the first binder and the first conductive agent does not exceed 15%, which can ensure that the capacity of the first positive electrode coating will not be too low, which will help it contribute energy and will not affect its safety function. .
- the mass proportion of the first binder in the first cathode coating is greater than the mass proportion of the first conductive agent in the first cathode coating.
- the first positive electrode coating itself has strong bonding performance, is not easy to fall off, and can effectively perform its safety function under abnormal conditions of the battery.
- the charging upper limit voltage of the first cathode active material is above 4.25V, the specific capacity is greater than or equal to 170mAh/g, and the compacted density of the first cathode coating is greater than or equal to 3.4g/cm 3 .
- the energy density of the first positive electrode active material contained in the first positive electrode coating is relatively large, so that the introduction of the first positive electrode coating will not reduce the energy density of the battery produced using the above-mentioned positive electrode sheet.
- the first cathode active material includes a material represented by the general formula LiCo 1-x M x O 2 , where 0 ⁇ x ⁇ 1, M is selected from Ni, Mn, Al, Ca, Mg, One or more of Sr, Ti, V, Cr, Fe, Cu, Zn, Mo, W, Y, La, Zr, Sn, Se, Te and Bi.
- the energy density of the first cathode active material conforming to this general formula is generally larger.
- the second aspect of the embodiments of the present application provides a secondary battery, including the positive electrode plate described in the first aspect of the present application.
- the secondary battery provided by the embodiment of the present application can take into account both good safety performance and high battery energy density.
- the third aspect of the embodiments of the present application provides an electronic device, including the secondary battery described in the second aspect of the present application.
- the fourth aspect of the embodiment of the present application also provides a mobile device, the mobile device includes the electrochemical device described in the fourth aspect of the embodiment of the present application.
- the above-mentioned electronic equipment or mobile device can enhance product competitiveness by using the electrochemical device provided by the embodiment of the present application for power supply.
- Figure 1 is a schematic diagram of a common structure of a secondary battery.
- Figure 2 is a schematic structural diagram of a positive electrode plate provided by an embodiment of the present application.
- Figure 3 is a schematic structural diagram of a secondary battery provided by an embodiment of the present application.
- FIG. 4 is a schematic structural diagram of an electronic device provided by an embodiment of the present application.
- FIG. 5 is another schematic structural diagram of a mobile device provided by an embodiment of the present application.
- the secondary battery can be used in 3C consumer products, such as mobile phones, tablets, laptops, smart watches and other wearable or mobile electronic devices, as well as electric vehicles.
- the secondary battery may be a lithium secondary battery, a sodium secondary battery, a potassium secondary battery, a magnesium secondary battery, an aluminum secondary battery, a zinc secondary battery, or the like.
- the secondary battery 100 in Figure 1 includes a positive electrode plate 10, a negative electrode plate 20, a separator 30 and an electrolyte (shown in the figure), as well as corresponding communication accessories and circuits.
- the positive electrode sheet 10 generally includes a positive electrode current collector 11 (usually aluminum foil) and a positive electrode active material layer 12 disposed on at least one side surface of the positive electrode current collector 11.
- the negative electrode sheet 20 has a similar structure.
- the positive electrode piece 10 and the negative electrode piece 20 are both housed in the battery case, and adjacent positive and negative electrodes are separated by a separator 30 in the case to maintain insulation between them and avoid Contact causes short circuit.
- the positive electrode sheet 10' provided by the embodiment of the present application includes a positive current collector 11 and a first positive electrode coating 121 and a second positive electrode coating 122 sequentially laminated on at least one side surface of the positive electrode current collector 11;
- the first positive electrode coating 121 includes a first positive electrode active material, a first binder and a first conductive agent
- the second positive electrode coating 122 includes a second positive electrode active material, a second binder and a second conductive agent
- the thickness of the first cathode coating 121 is less than or equal to the second cathode coating 122
- the tensile force and/or shear force of the first cathode coating 121 is greater than the second cathode coating 122
- the mass energy of the first cathode active material The density is greater than or equal to the mass energy density of the second cathode active material.
- the positive electrode sheet 10' provided in the embodiment of the present application adopts a double-layer positive electrode coating and controls the tensile force and/or shearing force of the first positive electrode coating 121 close to the positive electrode current collector 11 to be greater than that far away from the positive electrode current collector 11.
- the thickness of the first positive electrode coating 121 is less than or equal to the second positive electrode coating 122, so that the first positive electrode coating 121 can play a safety protection role, and it is difficult to fall off from the positive electrode current collector 11 It is more difficult for the second positive electrode coating 122 to fall off from the positive electrode piece 10', so that even if the second positive electrode coating 122 falls off when the battery is squeezed, collided, punctured, overcharged and other abnormal conditions, the first positive electrode coating 122 will fall off.
- the layer 121 can still protect the positive electrode current collector 11 and can wrap the positive electrode current collector 11 to a certain extent to prevent it from being exposed, thereby preventing it from contacting the negative electrode plate of the battery and causing thermal runaway, thereby improving the safety performance of the battery.
- the first cathode coating 121 can also participate in the charging and discharging process of the battery under normal conditions, and efficiently remove/intercalate lithium, and the energy density of the first cathode active material contained in the first cathode coating 121 is not less than that of the second cathode active material.
- the positive electrode coating 122 contains the second positive electrode active material.
- the positive electrode sheet 10 of the embodiment of the present application has the same thickness. Has a relatively high energy density. Therefore, a battery using the positive electrode plate 10' can have both good safety performance and high battery energy density.
- the stacked structure of the first positive electrode coating 121 and the second positive electrode coating 122 constitutes the positive active material layer 12' of the positive electrode sheet 10' of the present application, and the positive active material layer 12' is disposed on at least one side of the positive current collector 11 Superficially, in FIG. 2 , there are cathode active material layers 12 ′ on both sides of the cathode current collector 11 .
- the thickness of the first positive electrode coating 121 is less than or equal to the thickness of the second positive electrode coating 122 .
- the first positive electrode coating 121 has better bonding performance and mainly plays a safety protection role.
- the second positive electrode coating 122 mainly contributes energy and controls the first positive electrode coating 121 which mainly plays a safety protection role.
- the thickness is no larger than the second positive electrode coating, which mainly contributes to the capacity, so that the safety performance of the battery is better.
- the thickness of the first positive electrode coating 121 is controlled to be greater than 0 and less than or equal to 50 ⁇ m.
- the thickness of the first positive electrode coating 121 may be 2 ⁇ m, 5 ⁇ m, 10 ⁇ m, 20 ⁇ m, 30 ⁇ m, 40 ⁇ m, etc.
- the thickness of the first cathode coating 121 is 10 ⁇ m-40 ⁇ m.
- the thickness of the first positive electrode coating 121 is more appropriate, which can not only ensure that it can effectively improve the safety performance of the battery when it is damaged by external forces, but also avoid its excessive thickness, which increases the amount of binder and reduces the strength of the first active material.
- the mass proportion further affects the specific capacity of the first positive electrode coating.
- the first cathode coating includes the following mass percentages of each component: 85%-96.5% of the first cathode active material, 2.5%-10% of the first binder, 1% -5% first conductive agent.
- the second cathode coating includes the following mass percentages of each component: 50%-98% of the second cathode active material, 1%-35% of the second binder, 0.5%-15% of the second cathode active material Conductive agent.
- the mass proportions of corresponding components in the two positive electrode coatings can be the same or different.
- Controlling the mass proportion of the cathode active material in each cathode coating to be high can prevent the specific capacity of the two cathode coatings from being too low; controlling the mass proportion of the binder in each cathode coating within the above range can prevent the two cathode coatings from being too low.
- the bonding performance of the positive electrode coating is high without reducing the proportion of active material too much.
- the mass proportion of the first binder in the first cathode coating 121 is greater than the mass proportion of the second binder in the second cathode coating 122 .
- the aforementioned condition "the tensile force and/or shear force of the first positive electrode coating 121 is greater than that of the second positive electrode coating 122" can still be satisfied. , which helps the first positive electrode coating 121 to effectively play a safety protection role in abnormal situations where the positive electrode piece is damaged by external force.
- the first conductive agent in the first cathode coating 121 When the mass proportion of the first binder in the first cathode coating 121 is greater than the mass proportion of the second binder in the second cathode coating 122 , the first conductive agent in the first cathode coating 121 The mass proportion of may be smaller than the mass proportion of the second conductive agent in the second positive electrode coating 122 . In this way, the volume resistivity of the first positive electrode coating 121 is greater than that of the second positive electrode coating 122, and the first positive electrode coating 121 with slightly poor conductivity can better survive abnormal conditions such as battery overcharging, acupuncture, and collision.
- the positive electrode current collector 11 is wrapped and passivated, thereby reducing the risk of thermal runaway caused by contact with the negative electrode piece of the battery.
- the mass proportion of the first binder in the first cathode coating 121 is greater than the mass proportion of the first conductive agent in the first cathode coating 121 .
- the first positive electrode coating 121 itself has strong adhesive force and is not easy to fall off from the positive electrode current collector 11.
- the second positive electrode coating 122 falls off under abnormal conditions of the battery, the first positive electrode coating 121 can still adhere to the positive electrode current collector 11.
- the fluid 11 plays a certain protective role to prevent it from directly contacting the negative electrode piece of the battery and causing thermal runaway.
- the mass proportion of the second binder in the second cathode coating 122 is smaller than the mass proportion of the second conductive agent in the second cathode coating 122 .
- the adhesive force of the first adhesive is greater than the adhesive force of the second adhesive. In this way, even if the mass proportion of the first binder in the first cathode coating 121 is equal to the mass proportion of the second binder in the second cathode coating 122, the stretching of the first cathode coating 121 can still be ensured.
- the force and/or shearing force is greater than that of the second positive electrode coating 122, which helps the first positive electrode coating 121 improve the battery safety performance when the positive electrode piece is damaged by external force.
- bonding force of the first adhesive agent can be understood as the shear force or tensile force of the first adhesive layer formed by the simple first adhesive agent
- the "adhesive force of the second adhesive agent” can be understood as It is understood as the shear force or stretching of the second adhesive layer formed by the simple second adhesive.
- the mass proportion of the first binder in the first positive electrode coating 121 is equal to the mass proportion of the second binder in the second positive electrode coating 122 , the first positive electrode coating 121 The shearing force or tensile force is greater than the shearing force or tensile force of the second positive electrode coating 122 with the same size.
- the mass proportion of the first binder in the first cathode coating 121 is equal to the mass proportion of the second binder in the second cathode coating 122; the bonding of the first binder The force is greater than the bonding force of the second adhesive. In this way, the bonding performance of the first positive electrode coating 121 is better than that of the second positive electrode coating 122 .
- the mass proportion of the first binder in the first cathode coating 121 is greater than the mass proportion of the second binder in the second cathode coating 122;
- the bonding force is greater than the bonding force of the second adhesive.
- the bonding performance of the first positive electrode coating 121 is better than that of the second positive electrode coating 122 .
- the mass proportion of the first and second active materials in each cathode coating are equal, the mass proportion of the first conductive agent in the first cathode coating 121 is smaller than that of the second conductive agent.
- the volume resistivity of the first positive electrode coating 121 is generally greater than the volume resistivity of the second positive electrode coating 122.
- the first cathode coating 121 with slightly poor conductivity can better wrap the cathode current collector 11 and passivate its conductivity under abnormal conditions of the battery, thereby reducing the risk of contact with the negative electrode plate of the battery. Risk of thermal runaway.
- the volume resistivity of the first positive electrode coating 121 is greater than the volume resistivity of the second positive electrode coating 122 .
- the first positive electrode coating 121 with slightly poor conductivity can better wrap and passivate the positive electrode current collector 11 under abnormal conditions such as battery overcharging, acupuncture, collision, etc., thereby reducing its contact with the negative electrode plate of the battery.
- the ohmic polarization and electrochemical polarization of the positive electrode during the short circuit process avoiding the risk of thermal runaway caused by rapid heat accumulation.
- the volume resistivity of the first positive electrode coating 121 may also be less than or equal to the volume resistivity of the second positive electrode coating 122 . As long as the volume resistivity of the first positive electrode coating 121 is greater than the volume resistivity of the positive electrode current collector 11 , it can block the electrical contact between the positive electrode current collector 11 and the negative electrode under abnormal conditions of the battery.
- the mass proportion of the first cathode active material in the first cathode coating 121 and the mass proportion of the second cathode active material in the second cathode coating 122 may be equal or different.
- the mass proportion of the first cathode active material in the first cathode coating 121 is equal to the mass proportion of the second cathode active material in the second cathode coating 122 .
- the energy density of the first cathode active material is greater than or equal to the energy density of the second cathode active material.
- "Energy density” here can specifically refer to “mass energy density” or "volume energy density”.
- the relationship between the energy density of the first cathode active material and the second cathode active material is mainly determined by the characteristics of each cathode active material. Specifically, the energy density of the cathode active material is its charging specific capacity, charging voltage, It is the result of comprehensive effects such as the compaction density of the positive active material layer (since the charging voltage, compaction density, etc. are also related to the positive active material, essentially it can be said that the energy density is related to the positive active material).
- the energy density of cathode active materials of different materials is generally different.
- the energy density of a battery that simply uses lithium cobalt oxide as the cathode active material is generally greater than the energy density of a battery that simply uses lithium nickel cobalt manganate as the cathode active material (for comparison).
- Energy density can be both mass energy density or volume energy density); the energy density of batteries that simply use nickel-containing ternary materials as positive active materials is generally greater than those that simply use phosphate materials (such as lithium iron phosphate, lithium manganese iron phosphate , lithium vanadium phosphate, lithium vanadium oxyphosphate) as the positive electrode active material battery energy density.
- the energy density of a certain cathode active material can be measured by the product of U ⁇ M ⁇ P, where U represents the charging upper limit voltage of the cathode active material, in volts (V), and Q represents the charging specific capacity, in unit mAh/g, P represents the compacted density of the cathode active material layer, the unit is g/cm 3 , the product of the three gives the energy of the cathode active material in Wh/L quantity density.
- the charging upper limit voltage of the first cathode active material in the first cathode coating 121 is above 4.25V, the charge specific capacity is greater than or equal to 170mAh/g, and the compacted density of the first cathode coating 121 is greater than or equal to 3.4g/cm 3 .
- the energy density of the first positive electrode active material defined according to the product of the aforementioned parameters is relatively large, which can be above 2456.5Wh/L. This means that the introduction of the first positive electrode coating will not reduce the energy density of the battery made with the above-mentioned positive electrode sheet. Energy Density.
- the first cathode active material includes a material represented by the general formula LiCo 1-x M x O 2 , where 0 ⁇ x ⁇ 1, M is selected from Ni, Mn, Al, Ca, Mg, One or more of Sr, Ti, V, Cr, Fe, Cu, Zn, Mo, W, Y, La, Zr, Sn, Se, Te and Bi.
- materials whose general formula conforms to LiCo 1-x M x O 2 generally have larger energy densities.
- the second cathode active material may also include a material represented by the general formula LiCo 1-x M x O 2 .
- the first and second cathode active materials may be the same or different materials, but the energy density of the first cathode active material needs to be greater than or equal to the second cathode active material.
- the positive electrode current collector 11 may include aluminum foil, aluminum alloy foil, aluminum-plated polymer film, carbon-coated copper foil, carbon-coated aluminum alloy foil, or carbon-coated aluminum-plated polymer film.
- the aluminum-plated polymer film refers to a polymer film with an aluminum layer plated on the surface.
- the polymer film can be, for example, polyethylene terephthalate (PET) or aluminum/polyimide (PI).
- PET polyethylene terephthalate
- PI aluminum/polyimide
- the positive electrode current collector 11 containing metallic aluminum has high electrical conductivity. When the battery is damaged by external force, it may cause thermal runaway due to the short distance between it and the negative electrode. Therefore, it is necessary to provide a first positive electrode coating 121 and a second positive electrode on its surface. Stack of coatings 122.
- the first binder contained in the first positive electrode coating 121 and the second binder contained in the second positive electrode coating 122 are independently selected from polytetrafluoroethylene (PTFE), polyvinylidene fluoride Ethylene (PVDF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP), polypropylene oxide (PPO), polyethylene oxide (PEO), polymethyl methacrylate (PMMA), polyacrylonitrile (PAN) ), one or more of polyacrylic acid (PAA), polyvinyl alcohol (PVA), polyimide (PI), styrene-butadiene rubber (SBR), carboxymethylcellulose (CMC), sodium alginate, etc. .
- the materials of the first adhesive and the second adhesive may be the same or different.
- the first conductive agent contained in the first positive electrode coating 121 and the second conductive agent contained in the second positive electrode coating 122 may be the same or different.
- the first conductive agent and the second conductive agent can be independently selected from at least one of conductive carbon black (such as acetylene black, Ketjen black), carbon nanotubes (CNT), graphene, carbon fiber, graphite, furnace black, etc. species, but not limited to this.
- the embodiments of the present application also provide a method for preparing the above-mentioned positive electrode sheet.
- the preparation method may specifically include:
- a second positive electrode slurry containing a second positive electrode active material, a second binder and a second conductive agent is coated on the surface of the first positive electrode coating. After drying, a second positive electrode coating is formed, and after pressing, a second positive electrode slurry is obtained.
- Positive electrode sheet wherein the mass energy density of the first cathode active material is greater than or equal to the mass energy density of the second cathode active material, and the thickness of the first cathode coating is less than or equal to the second cathode coating. layer, the tensile force or shearing force of the first cathode coating is greater than that of the second cathode coating.
- the solvents contained in the first cathode slurry and the second cathode slurry may be the same or different, and may be independently selected from N-methylpyrrolidone (NMP), dimethylformamide (DMF), water, and alcohols.
- NMP N-methylpyrrolidone
- DMF dimethylformamide
- One or more solvents such as ethanol, etc.
- the pressing method may specifically be roller pressing.
- the coating method may be one or a combination of spin coating, brush coating, spray coating, dip coating, blade coating, etc.
- the above-mentioned positive electrode current collector may be coated on one side or on both sides.
- one side surface of the cathode current collector may have a cathode active material layer composed of a first cathode coating layer and a second cathode coating layer, or the cathode current collector may have a first cathode layer on opposite sides of the surface. coating and a second positive electrode coating.
- the preparation method of the positive electrode piece is simple and the structure of the prepared positive electrode piece is novel and stable, which can effectively improve the safety performance of the battery without reducing the energy density.
- the above-mentioned positive electrode plate can be assembled to obtain a secondary battery by the following method: stacking the positive electrode plate, separator and negative electrode plate in sequence to form a battery core; placing the battery core in a battery case and injecting electrolyte, The battery case is then sealed to produce a lithium ion battery.
- the cells of the secondary battery can be of a wound type or a laminated type.
- the battery case can be aluminum-plastic film, copper-plastic film, steel-plastic film or other packaging films, or it can be aluminum shell, steel shell, other metal shell, etc., which can be selected according to the type of secondary battery required.
- an air bag is usually reserved so that the gas can be discharged through the air bag after the battery is formed.
- secondary packaging can be carried out, and then the capacity dividing process can be carried out to obtain a secondary battery that can be shipped out of the factory.
- An embodiment of the present application also provides a secondary battery, which includes the above-mentioned positive electrode plate as in the embodiment of the present application.
- Figure 3 is a schematic structural diagram of a secondary battery provided by an embodiment of the present application.
- the secondary battery 100' shown in Figure 3 is different from the secondary battery 100 shown in Figure 1 only in that the positive electrode plates used in the two are different, and the structures of other components are similar. Please refer to the previous description of this application. Since this secondary battery adopts the above-mentioned positive electrode plate 10' of the embodiment of the present application, it can achieve both high battery energy density and good safety performance.
- the negative electrode sheet 20 includes a negative current collector 21 and a negative active material layer 22 disposed on at least one side surface of the negative current collector 21 .
- the negative active material layer 22 includes a negative active material, a binder and an optional conductive agent. The range of the binder and conductive agent contained in the negative electrode piece 20 can be found in the above description of the positive electrode piece.
- the negative electrode current collector 21 includes but is not limited to metal foil, alloy foil, metal-plated film or metal foil with carbon coating on the surface, alloy foil, metal-plated film, etc.
- the negative electrode current collector 21 includes copper foil, copper alloy foil, stainless steel foil, copper-coated polymer film, carbon-coated copper foil, carbon-coated copper alloy foil, or carbon-coated copper-coated polymer film.
- the surface of the fluid 21 may be etched or roughened to form secondary structures to facilitate effective contact with the negative active material layer.
- the negative active material may include but is not limited to lithium titanate, metal lithium, lithium alloy, carbon-based materials, silicon-based materials, tin-based materials, and phosphorus-based materials. of one or more.
- carbon-based materials can include graphite (such as natural graphite, artificial graphite), non-graphitized carbon (soft carbon, hard carbon, etc.); silicon-based materials can include elemental silicon, silicon-based alloys, silicon oxides and silicon-carbon composite materials etc.; tin-based materials may include one or more of elemental tin, tin alloys, etc.; phosphorus-based materials may include elemental phosphorus (such as black phosphorus), phosphorus-carbon composite materials, etc.
- graphite such as natural graphite, artificial graphite
- silicon-based materials can include elemental silicon, silicon-based alloys, silicon oxides and silicon-carbon composite materials etc.
- tin-based materials may include one or more of elemental tin, tin alloys, etc.
- phosphorus-based materials may include elemental phosphorus (such as black phosphorus), phosphorus-carbon composite materials, etc.
- the separator 30 can be a polymer separator, non-woven fabric, etc., including but not limited to single-layer PP (polypropylene), single-layer PE (polyethylene), double-layer PP/PE, double-layer PP/PP, and three-layer PP. /PE/PP and other separators.
- the secondary battery provided by the embodiment of the present application can be used in terminal consumer products, such as mobile phones, tablet computers, mobile power supplies, portable machines, notebook computers, digital cameras and other wearable or mobile electronic devices, as well as drones and automobiles. and other products to improve product performance.
- terminal consumer products such as mobile phones, tablet computers, mobile power supplies, portable machines, notebook computers, digital cameras and other wearable or mobile electronic devices, as well as drones and automobiles. and other products to improve product performance.
- An embodiment of the present application also provides an electronic device including the above-mentioned secondary battery. Since the above-mentioned secondary battery provided by the embodiment of the present application has good safety performance and high energy density, electronic devices equipped with the secondary battery can have good safety performance, good product use experience, and outstanding market competitiveness.
- the electronic device may include various consumer electronic products, such as mobile phones, tablet computers, laptops, mobile power supplies, portable machines, smart watches and other wearable or removable electronic devices, televisions, DVD players, Video recorders, camcorders, radios, cassette players, combo speakers, record players, compact disc players, home office equipment, home electronic health care equipment, and automobiles and other electronic products.
- consumer electronic products such as mobile phones, tablet computers, laptops, mobile power supplies, portable machines, smart watches and other wearable or removable electronic devices, televisions, DVD players, Video recorders, camcorders, radios, cassette players, combo speakers, record players, compact disc players, home office equipment, home electronic health care equipment, and automobiles and other electronic products.
- this embodiment of the present application provides an electronic device 300, which includes a housing 301, electronic components (not shown in Figure 4) accommodated in the housing 301, and a battery 302.
- the battery 302 supplies power to the electronic device 300, and the battery 302 includes the secondary battery described in the embodiment of the present application.
- the housing 301 may include a front cover assembled on the front side of the terminal and The back shell is assembled on the rear side, and the battery 302 can be fixed on the inside of the back shell.
- the electronic device 300 shown in FIG. 4 is usually a small portable electronic device, such as a mobile phone.
- an embodiment of the present application also provides a mobile device 400, which includes the above-mentioned secondary battery provided by an embodiment of the present application.
- the mobile device 400 can be various movable devices used for loading, transportation, assembly, disassembly, security, etc., and can be various forms of vehicles.
- the mobile device 400 may include a vehicle body 401, a mobile component 402 (such as a wheel), and a driving component.
- the driving component includes a motor 403 and a battery system 404 for powering the motor 403.
- the battery system 404 includes the components provided by the embodiments of the present application. of the above-mentioned secondary batteries.
- the battery system 404 may be a battery pack of the above-mentioned secondary battery, which is housed at the bottom of the vehicle body and is electrically connected to the motor 403 . In this way, the battery system 404 can power the motor 403, and the motor 403 provides power to drive the moving component 402 of the mobile device 400 to move.
- Mobile devices using the secondary battery provided by embodiments of the present application have high battery life and good safety performance.
- a method for preparing a positive electrode sheet including the following steps:
- the positive electrode active material specifically lithium cobalt oxide LiCoO 2
- binder PVDF molecular weight: 700,000
- conductive carbon black is weighed according to the mass ratio of 95%: 2%: 3%, mixed with NMP, and stirred thoroughly to obtain the second positive electrode slurry;
- the schematic structural diagram of the positive electrode piece of Example 1 is shown in Figure 2.
- the cathode plate 10' includes a cathode current collector 11 and cathode active material layers 12' disposed on opposite side surfaces thereof.
- the cathode active material layer 12' includes a first cathode coating 121 close to the cathode current collector 11 and away from the cathode current collector 11.
- the second positive electrode coating 122 of the positive electrode current collector 11 wherein, the thickness of each first positive electrode coating 121 is 10 ⁇ m, the thickness of each second positive electrode coating 122 is 50 ⁇ m, and the tensile force of the first positive electrode coating 121 Or the shear force is greater than the second positive electrode coating, and the energy density of lithium cobalt oxide in the first positive electrode coating 121 is equal to the mass energy density of lithium cobalt oxide in the second positive electrode coating 122 .
- the volume resistivity of the first positive electrode coating 121 is greater than that of the second positive electrode coating 122 .
- the compacted density of the first positive electrode coating 121 is 4.15g/cm 3
- the charging specific capacity of 121 lithium cobalt oxide in the first positive electrode coating is about 180mAh/g
- the upper charging voltage is 4.45V.
- the energy density of lithium cobalt oxide calculated by product is approximately 3324.15Wh/L.
- Preparing the negative electrode sheet Mix the negative active material (specifically artificial graphite) with conductive carbon black, styrene-butadiene rubber (SBR) and carboxymethyl cellulose (CMC) in a mass ratio of 96%:1%:2%:1% Disperse in deionized water, stir evenly to obtain negative electrode slurry, apply the negative electrode slurry on copper foil, dry, compact, and slice to prepare negative electrode sheets;
- negative active material specifically artificial graphite
- SBR styrene-butadiene rubber
- CMC carboxymethyl cellulose
- Assemble the battery Use 1 mol/L LiPF 6 EC (ethylene carbonate) + DEC (diethyl carbonate) mixture (the volume ratio of EC and DEC is 1:1) as the electrolyte, and the ceramic-treated PE film as the separator , the positive electrode sheet, separator and negative electrode sheet of Example 1 are stacked in order to form a bare battery core.
- the bare battery core is packaged in an aluminum plastic film case, and then the electrolyte is injected into the battery case, and the electrolyte is formed and pumped. After gasification, it is packaged again and divided into volumes to prepare a lithium-ion battery.
- a positive electrode piece which is different from Embodiment 1 in that: in the positive electrode piece of Embodiment 2, the positive active materials in the first positive electrode coating 121 and the second positive electrode coating 122 are both nickel cobalt manganese oxide.
- Lithium the general structural formula is LiCo 0.8 Ni 0.1 Mn 0.1 O 2 .
- the energy density of lithium nickel cobalt manganate in the first positive electrode coating 121 is equal to the mass energy density of lithium nickel cobalt manganate in the second positive electrode coating 122 .
- the compacted density of the first positive electrode coating 121 is 3.6g/cm 3
- the charging specific capacity of the lithium nickel cobalt manganate in the first positive electrode coating 121 is about 200mAh/g
- the charging upper limit voltage is 4.25V.
- the energy density of lithium nickel cobalt manganate calculated by the product of these three is approximately 3060Wh/L.
- the positive electrode sheet of Example 2 was assembled into a lithium secondary battery.
- a positive electrode sheet which is different from Embodiment 1 in that: in the positive electrode sheet of Embodiment 3, the positive active material in the first positive electrode coating 121 is lithium cobalt oxide, and the positive electrode active material in the second positive electrode coating 122 is lithium cobalt oxide.
- the positive active material is lithium nickel cobalt manganate, and the energy density of lithium cobalt oxide in the first positive electrode coating 121 is greater than the energy density of lithium nickel cobalt manganate in the second positive electrode coating 122 .
- the general formula and energy density characteristics of lithium cobalt oxide and lithium nickel cobalt manganate used in Example 3 please refer to the descriptions in Examples 1 and 2.
- the positive electrode sheet of Example 3 was assembled into a lithium secondary battery.
- a positive electrode piece which is different from Embodiment 1 in that: in the positive electrode piece of Embodiment 4, the first binder in the first positive electrode coating 121 is PVDF with a molecular weight of about 1 million, and the second The second binder in the positive electrode coating 122 is PVDF with a molecular weight of about 700,000 (its binding force is smaller than that of the first binder), and the first positive electrode coating 121 and the second positive electrode coating 122 , the mass ratio of lithium cobalt oxide to the corresponding binder and conductive agent is 95%: 2%: 3%.
- the volume resistivity of the first positive electrode coating 121 is equal to the second positive electrode coating 122 .
- the positive electrode sheet of Example 4 was assembled into a lithium secondary battery.
- a lithium secondary battery is different from Example 1 in that: the structure of the positive electrode sheet used in Comparative Example 1 is as shown in Figure 1, and the positive active material layer on one side of the positive electrode current collector 11 is only one layer. Indicated by reference numeral 12, the thickness of the positive electrode active material layer 12 is 60 ⁇ m, and its composition is the same as the second positive electrode coating in Example 1 of the present application, that is, it includes lithium cobalt oxide in a mass ratio of 95%:2%:3%. , PVDF and conductive carbon black.
- a conventional lithium secondary battery differs from Example 2 in that: the structure of the positive electrode sheet used in Comparative Example 1 is shown in Figure 1.
- the positive active material layer on one side of the aluminum foil is only one layer, and its thickness is 60 ⁇ m, and its composition is the same as the second positive electrode coating in Example 2 of the present application, that is, it includes lithium nickel cobalt manganate, PVDF and conductive carbon black in a mass ratio of 95%: 2%: 3%.
- a lithium secondary battery differs from Example 1 in that: in the positive electrode sheet of Comparative Example 3, the positive active material in the first positive electrode coating 121 is lithium nickel cobalt manganate, and the second positive electrode coating 122 The positive active material is lithium cobalt oxide.
- the lithium secondary batteries of the above embodiments and comparative examples are Perform normal charge and discharge tests to measure energy density, as well as perform pinprick tests.
- the battery energy density test method is: charge each lithium secondary battery at a constant current rate of 0.2C to the corresponding full charge voltage for the first time, then charge at a constant voltage until the cut-off current is 0.025C, leave it aside for 10 minutes; discharge at a rate of 0.2C When the rated lower limit voltage is 3.0V, record the energy released by the battery.
- the ratio of this energy to the battery volume or mass is the volume or mass energy density of the battery.
- Battery acupuncture test After each secondary battery is fully charged at 0.2C, perform a nail penetration test. First, place each secondary battery on a flat surface, use a steel needle with a diameter of 2mm, and perform a nail penetration test at a speed of 100mm/s. Penetrate the battery in the direction of the battery poles. The steel needle pierces the battery and remains in the battery for 5 minutes or the battery indicates that the temperature drops to 50°C. The test will be stopped. If the battery does not catch fire or explode, it means the battery has passed the test. Each test is 5 Parallel samples are taken, and the ratio of the number of samples that pass the test to the total number of samples is regarded as the passing rate of the steel needle test.
- each positive electrode piece is cut into a sample of a certain size, the tape is adhered to the surface of the positive electrode piece sample (that is, adhered to the second positive electrode coating) and pressed tightly, and the top of the tape and the electrode are Leave an unadhered area at the bottom of the sample for stretching purposes.
- Use a tensile machine to test as follows:
- the tape is adhered to the first positive electrode coating and pressed tightly in a similar manner as above, and the top of the tape and the electrode piece are Leave an unadhered area at the bottom of the sample, and use a tensile machine to perform the test as above.
- the tape adheres to the first positive electrode coating when it is peeled off from the positive electrode current collector.
- the force is recorded as the tensile force of the first positive electrode coating; along the cross-sectional direction parallel to the pole piece sample, the force when the tape adheres to the first positive electrode coating is peeled off from the positive electrode current collector, is recorded as the first Shear force of positive electrode coating.
- Comparative Example 1-2 when Comparative Example 1-2 is provided with a single-layer positive electrode active material layer on one side of the positive electrode current collector (composing a second positive electrode coating similar to the example of this application), the tension of the active material layer is Tensile force and shear force both refer to the force peeled off from the positive electrode current collector.
- the battery produced by using the double-layer positive electrode coating cathode sheet provided in the embodiment of the present application has better safety performance when encountering external force damage (in Table 1, the acupuncture pass rate is higher ) without reducing the energy density of the battery under normal operating conditions.
- Table 1 the battery produced by using the double-layer positive electrode coating cathode sheet provided in the embodiment of the present application has better safety performance when encountering external force damage (in Table 1, the acupuncture pass rate is higher ) without reducing the energy density of the battery under normal operating conditions.
- Table 1 the comparison between Examples 1 and 4 and Comparative Example 1, and the comparison between Examples 2-3 and Comparative Example 2.
- the comparison between Example 3 and Comparative Example 2 illustrates that Example 3 controls the positive electrode active material in the positive electrode coating close to the positive electrode current collector to have a higher energy density than the positive electrode active material in the positive electrode coating far away from the positive electrode current collector.
- Comparative Example 3 shows that when the energy density of the positive active material in the positive electrode coating close to the positive electrode current collector side of the double-layer positive electrode coated pole piece is small (Comparative Example 3), this positive electrode is used.
- the energy density of a battery made from a sheet will be lower than that of a battery made from a cathode sheet that only uses a one-layer cathode active material layer that is the same composition as the second cathode coating that mainly contributes energy.
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Abstract
Embodiments of the present application provide a positive electrode plate, a secondary battery, an electronic device, and mobile equipment. The positive electrode plate comprises a positive electrode current collector, and a first positive electrode coating and a second positive electrode coating which are sequentially stacked on at least one side surface of the positive electrode current collector; the first positive electrode coating comprises a first positive electrode active material, a first binder and a first conductive agent; the second positive electrode coating comprises a second positive electrode active material, a second binder and a second conductive agent; the thickness of the first positive electrode coating is less than or equal to the second positive electrode coating, the tensile stress or shear stress of the first positive electrode coating is greater than that of the second positive electrode coating, and the energy density of the first positive electrode active material is greater than or equal to the second positive electrode active material. The secondary battery prepared by using the positive electrode plate can effectively solve the problem of thermal runaway caused by the positive electrode current collector of the battery being in contact with the negative electrode, without affecting the energy density of the battery.
Description
本申请要求于2022年4月14日提交至中国专利局、申请号为202210390904.4、申请名称为“正极极片、二次电池、电子设备和移动装置”的中国专利申请的优先权,其全部内容通过引用结合在本申请中。This application claims priority to the Chinese patent application submitted to the China Patent Office on April 14, 2022, with application number 202210390904.4 and the application name "Cathode Plate, Secondary Battery, Electronic Equipment and Mobile Device", and its entire contents incorporated herein by reference.
本申请实施例涉及二次电池技术领域,特别是涉及一种正极极片、二次电池、电子设备和移动装置。Embodiments of the present application relate to the technical field of secondary batteries, and in particular to a positive electrode plate, secondary batteries, electronic equipment and mobile devices.
二次电池已经在消费类电子产品(如手机、平板电脑)及电动汽车等领域得到广泛应用,但二次电池在持续过充、受外力破坏(如穿刺、碰撞)等情况下易引发电池内部短路,进而发生热失控,其中,正极集流体(如铝箔)与负极接触引起的短路是电池最危险的短路方式。因此,降低二次电池的热失控风险对推动其进一步广泛应用尤为重要。Secondary batteries have been widely used in consumer electronics (such as mobile phones, tablets) and electric vehicles. However, secondary batteries can easily cause internal damage when they are continuously overcharged or damaged by external forces (such as punctures and collisions). Short circuit, and then thermal runaway occurs. Among them, the short circuit caused by the contact between the positive electrode current collector (such as aluminum foil) and the negative electrode is the most dangerous short circuit method of the battery. Therefore, reducing the risk of thermal runaway of secondary batteries is particularly important to promote their further widespread application.
为避免正极集流体与负极直接接触导致热失控,业界一般是在正极集流体与正极活性材料层之间设置一安全涂层,该安全涂层主要包含安全性能高的活性材料(如磷酸铁锂)、导电剂和粘结剂,虽然该涂层可在电池受外力破坏时,避免正极集流体与负极直接接触,但由于该涂层占据电池一定的厚度空间,且其可贡献的单位质量或单位体积的能量一般是远低于正极活性材料层,使得其引入会降低电池的能量密度。In order to avoid thermal runaway caused by direct contact between the positive electrode current collector and the negative electrode, the industry generally installs a safety coating between the positive electrode current collector and the positive electrode active material layer. The safety coating mainly contains active materials with high safety performance (such as lithium iron phosphate). ), conductive agent and binder. Although this coating can avoid direct contact between the positive electrode current collector and the negative electrode when the battery is damaged by external force, because the coating occupies a certain thickness space of the battery, and the unit mass it can contribute or The energy per unit volume is generally much lower than that of the cathode active material layer, so its introduction will reduce the energy density of the battery.
发明内容Contents of the invention
鉴于此,本申请实施例提供一种正极极片和二次电池,以在有效解决电池的正极集流体接触负极导致的热失控问题的同时,还不影响电池的能量密度。In view of this, embodiments of the present application provide a positive electrode plate and a secondary battery to effectively solve the problem of thermal runaway caused by the positive electrode current collector of the battery contacting the negative electrode without affecting the energy density of the battery.
本申请实施例第一方面提供了一种正极极片,包括正极集流体和依次层叠设置在所述正极集流体至少一侧表面上的第一正极涂层和第二正极涂层;所述第一正极涂层包括第一正极活性材料、第一粘结剂和第一导电剂,所述第二正极涂层包括第二正极活性材料、第二粘结剂和第二导电剂;其中,所述第一正极涂层的厚度小于或者等于所述第二正极涂层,所述第一正极涂层的拉伸力或剪切力大于所述第二正极涂层,所述第一正极活性材料的能量密度大于或者等于所述第二正极活性材料的能量密度。A first aspect of the embodiment of the present application provides a positive electrode sheet, including a positive electrode current collector and a first positive electrode coating and a second positive electrode coating sequentially laminated on at least one side surface of the positive electrode current collector; A positive electrode coating includes a first positive electrode active material, a first binder and a first conductive agent, and the second positive electrode coating includes a second positive electrode active material, a second binder and a second conductive agent; wherein, the The thickness of the first cathode coating is less than or equal to the second cathode coating, the tensile force or shear force of the first cathode coating is greater than the second cathode coating, and the first cathode active material The energy density is greater than or equal to the energy density of the second cathode active material.
本申请实施例提供的正极极片,通过控制靠近正极集流体的第一正极涂层的拉伸力和/或剪切力大于远离正极集流体的第二正极涂层,且第一正极涂层的厚度小于或等于第二正极涂层,这样第一正极涂层从正极集流体脱落的难度就大于第二正极涂层从该正极极片脱落的难度,第一正极涂层可起安全保护作用,当电池在异常下发生第二正极涂层脱落时,第一正极涂层仍能对正极集流体起一定的包裹、保护作用,避免其与电池的负极极片直接接触而引发热失控。此外,本申请还控制第一正极活性材料的能量密度不小于第二正极活性材料,这样第一正极涂层能在电池正常工作情况下高效地脱嵌锂,且其存在不会降低采用该正极极片的电池能量密度。
The positive electrode sheet provided in the embodiment of the present application controls the tensile force and/or shearing force of the first positive electrode coating close to the positive electrode current collector to be greater than the second positive electrode coating far away from the positive electrode current collector, and the first positive electrode coating The thickness is less than or equal to the second cathode coating, so that the difficulty of the first cathode coating falling off from the cathode current collector is greater than the difficulty of the second cathode coating falling off from the cathode plate. The first cathode coating can play a safety protection role. , when the second positive electrode coating peels off under abnormal conditions, the first positive electrode coating can still wrap and protect the positive electrode current collector to a certain extent, preventing it from direct contact with the negative electrode piece of the battery and causing thermal runaway. In addition, this application also controls that the energy density of the first positive electrode active material is not less than that of the second positive electrode active material, so that the first positive electrode coating can efficiently deintercalate lithium under normal operation of the battery, and its existence will not reduce the use of the positive electrode. Battery energy density of pole pieces.
本申请实施方式中,所述第一正极涂层的厚度大于0且小于或者等于50μm。此时,第一正极涂层不易从正极集流体脱落,具有较优的安全性能。In the embodiment of the present application, the thickness of the first cathode coating is greater than 0 and less than or equal to 50 μm. At this time, the first positive electrode coating is not easy to fall off from the positive electrode current collector, and has better safety performance.
本申请实施方式中,所述第一粘结剂在所述第一正极涂层中的质量占比大于所述第二粘结剂在所述第二正极涂层中的质量占比。这有助于使第一正极涂层的粘结性能优于第二正极涂层。In the embodiment of the present application, the mass proportion of the first binder in the first cathode coating is greater than the mass proportion of the second binder in the second cathode coating. This helps the first cathode coating have better bonding properties than the second cathode coating.
本申请实施方式中,所述第一粘结剂的粘结力大于所述第二粘结剂的粘结力。这也有助于使第一正极涂层的粘结性能优于第二正极涂层。In the embodiment of the present application, the adhesive force of the first adhesive is greater than the adhesive force of the second adhesive. This also helps the first cathode coating have better bonding properties than the second cathode coating.
本申请实施方式中,所述第一粘结剂与所述第二粘结的材质相同,且所述第一粘结剂的分子量大于所述第二粘结剂。In the embodiment of the present application, the first adhesive and the second adhesive are made of the same material, and the molecular weight of the first adhesive is greater than that of the second adhesive.
本申请实施方式中,所述第一粘结剂在所述第一正极涂层中的质量占比等于所述第二粘结剂在所述第二正极涂层中的质量占比,所述第一粘结剂的粘结力大于所述第二粘结剂的粘结力。此种情况下,可保证使第一正极涂层的拉伸力或剪切力大于第二正极涂层,利于其更好地发挥安全功用。In the embodiment of the present application, the mass proportion of the first binder in the first cathode coating is equal to the mass proportion of the second binder in the second cathode coating, and the The bonding force of the first adhesive is greater than the bonding force of the second adhesive. In this case, it can be ensured that the tensile force or shearing force of the first positive electrode coating is greater than that of the second positive electrode coating, which is conducive to its better performance of safety functions.
本申请实施方式中,所述第一正极涂层的体积电阻率大于所述第二正极涂层的体积电阻率。此时,第一正极涂层能增加短路过程中正极极片的欧姆极化与电化学极化,避免热迅速累积而引发热失控的风险,并能较好地钝化正极集流体,降低其与电池的负极极片接触带来的热风险。In an embodiment of the present application, the volume resistivity of the first cathode coating is greater than the volume resistivity of the second cathode coating. At this time, the first positive electrode coating can increase the ohmic polarization and electrochemical polarization of the positive electrode piece during the short circuit process, avoid the risk of thermal runaway caused by rapid heat accumulation, and can better passivate the positive electrode current collector and reduce its Thermal risk from contact with the negative battery tab.
本申请实施方式中,所述第一正极涂层包括以下质量百分含量的各组分:85%-96.5%的第一正极活性材料,2.5%-10%的第一粘结剂、1%-5%的第一导电剂。第一粘结剂和第一导电剂的质量占比之和不超过15%,可保证第一正极涂层的容量不会过低,利于其发挥贡献能量的作用,且不影响其发挥安全功能。In the embodiment of the present application, the first cathode coating includes the following mass percentages of each component: 85%-96.5% of the first cathode active material, 2.5%-10% of the first binder, 1% -5% first conductive agent. The sum of the mass proportions of the first binder and the first conductive agent does not exceed 15%, which can ensure that the capacity of the first positive electrode coating will not be too low, which will help it contribute energy and will not affect its safety function. .
本申请实施方式中,所述第一粘结剂在所述第一正极涂层中的质量占比大于所述第一导电剂在所述第一正极涂层中的质量占比。这样,第一正极涂层自身的粘结性能较强,不易脱落,能在电池异常情况下有效发挥安全功用。In the embodiment of the present application, the mass proportion of the first binder in the first cathode coating is greater than the mass proportion of the first conductive agent in the first cathode coating. In this way, the first positive electrode coating itself has strong bonding performance, is not easy to fall off, and can effectively perform its safety function under abnormal conditions of the battery.
本申请实施方式中,所述第一正极活性材料的充电上限电压在4.25V以上,比容量大于或等于170mAh/g,所述第一正极涂层的压实密度大于或者等于3.4g/cm3。此时,第一正极涂层中所含第一正极活性材料的能量密度较大,这使得第一正极涂层的引入不会降低采用上述正极极片制得的电池的能量密度。In the embodiment of the present application, the charging upper limit voltage of the first cathode active material is above 4.25V, the specific capacity is greater than or equal to 170mAh/g, and the compacted density of the first cathode coating is greater than or equal to 3.4g/cm 3 . At this time, the energy density of the first positive electrode active material contained in the first positive electrode coating is relatively large, so that the introduction of the first positive electrode coating will not reduce the energy density of the battery produced using the above-mentioned positive electrode sheet.
本申请实施方式中,所述第一正极活性材料包括通式表示为LiCo1-xMxO2的材料,其中,0≤x≤1,M选自Ni、Mn、Al、Ca、Mg、Sr、Ti、V、Cr、Fe、Cu、Zn、Mo、W、Y、La、Zr、Sn、Se、Te和Bi中的一种或多种。符合该通式的第一正极活性材料的能量密度一般较大。In the embodiment of the present application, the first cathode active material includes a material represented by the general formula LiCo 1-x M x O 2 , where 0≤x≤1, M is selected from Ni, Mn, Al, Ca, Mg, One or more of Sr, Ti, V, Cr, Fe, Cu, Zn, Mo, W, Y, La, Zr, Sn, Se, Te and Bi. The energy density of the first cathode active material conforming to this general formula is generally larger.
本申请实施例第二方面提供了一种二次电池,包括本申请第一方面所述的正极极片。The second aspect of the embodiments of the present application provides a secondary battery, including the positive electrode plate described in the first aspect of the present application.
本申请实施例提供的二次电池可以兼顾良好的安全性能和较高的电池能量密度。The secondary battery provided by the embodiment of the present application can take into account both good safety performance and high battery energy density.
本申请实施例第三方面提供了一种电子设备,包括如本申请第二方面所述的二次电池。The third aspect of the embodiments of the present application provides an electronic device, including the secondary battery described in the second aspect of the present application.
本申请实施例第四方面还提供了一种移动装置,所述移动装置包括本申请实施例第四方面所述的电化学装置。The fourth aspect of the embodiment of the present application also provides a mobile device, the mobile device includes the electrochemical device described in the fourth aspect of the embodiment of the present application.
上述电子设备或移动装置通过采用本申请实施例提供的电化学装置供电,能够提升产品竞争力。The above-mentioned electronic equipment or mobile device can enhance product competitiveness by using the electrochemical device provided by the embodiment of the present application for power supply.
图1为二次电池的一种常见结构示意图。Figure 1 is a schematic diagram of a common structure of a secondary battery.
图2为本申请实施例提供的正极极片的一种结构示意图。Figure 2 is a schematic structural diagram of a positive electrode plate provided by an embodiment of the present application.
图3为本申请实施例提供的二次电池的一种结构示意图。Figure 3 is a schematic structural diagram of a secondary battery provided by an embodiment of the present application.
图4为本申请实施例提供的电子设备的一种结构示意图。FIG. 4 is a schematic structural diagram of an electronic device provided by an embodiment of the present application.
图5为本申请实施例提供的移动装置的另一种结构示意图。FIG. 5 is another schematic structural diagram of a mobile device provided by an embodiment of the present application.
下面将结合附图,对本申请实施例的技术方案进行说明。The technical solutions of the embodiments of the present application will be described below with reference to the accompanying drawings.
请参见图1,图1为二次电池的示例性结构示意图。该二次电池可用于3C消费类产品,如手机、平板电脑、笔记本电脑、智能手表及其它可穿戴或可移动的电子设备,以及电动汽车等。该二次电池可以是锂二次电池、钠二次电池,钾二次电池,镁二次电池,铝二次电池,锌二次电池等。Please refer to Figure 1, which is a schematic structural diagram of an exemplary secondary battery. The secondary battery can be used in 3C consumer products, such as mobile phones, tablets, laptops, smart watches and other wearable or mobile electronic devices, as well as electric vehicles. The secondary battery may be a lithium secondary battery, a sodium secondary battery, a potassium secondary battery, a magnesium secondary battery, an aluminum secondary battery, a zinc secondary battery, or the like.
图1中的二次电池100包括正极极片10、负极极片20、隔膜30和电解液(图为示出),以及相应的连通辅件和回路。其中,正极极片10一般包括正极集流体11(通常是铝箔)和设置在正极集流体11至少一侧表面上的正极活性材料层12,负极极片20的结构与之类似。正极极片10和负极极片20都容置在电池的壳体中,且相邻的正、负极之间通过壳体内的隔膜30间隔开来,保持二者之间的绝缘性,避免二者接触引起短路。但当二次电池受外力破坏(如穿刺、碰撞)时,例如正极极片10发生破坏、正极活性材料层12从正极集流体上脱落时,正极集流体铝箔漏出,并与负极接触,这会引起电池发生最严重、最危险的短路,进而发生热失控。为解决电池的正极集流体接触负极导致的热失控问题,且不影响电池的能量密度,本申请实施例提供了一种正极极片。The secondary battery 100 in Figure 1 includes a positive electrode plate 10, a negative electrode plate 20, a separator 30 and an electrolyte (shown in the figure), as well as corresponding communication accessories and circuits. Among them, the positive electrode sheet 10 generally includes a positive electrode current collector 11 (usually aluminum foil) and a positive electrode active material layer 12 disposed on at least one side surface of the positive electrode current collector 11. The negative electrode sheet 20 has a similar structure. The positive electrode piece 10 and the negative electrode piece 20 are both housed in the battery case, and adjacent positive and negative electrodes are separated by a separator 30 in the case to maintain insulation between them and avoid Contact causes short circuit. However, when the secondary battery is damaged by external force (such as puncture, collision), for example, the positive electrode piece 10 is damaged and the positive active material layer 12 falls off from the positive current collector, the positive current collector aluminum foil leaks out and comes into contact with the negative electrode, which will This causes the most serious and dangerous short circuit in the battery, leading to thermal runaway. In order to solve the thermal runaway problem caused by the positive electrode current collector of the battery contacting the negative electrode without affecting the energy density of the battery, embodiments of the present application provide a positive electrode plate.
请参阅图2,本申请实施例提供的正极极片10’包括正极集流体11和依次层叠设置在正极集流体11至少一侧表面上的第一正极涂层121和第二正极涂层122;第一正极涂层121包括第一正极活性材料、第一粘结剂和第一导电剂,第二正极涂层122包括第二正极活性材料、第二粘结剂和第二导电剂;其中,第一正极涂层121的厚度小于或等于第二正极涂层122,第一正极涂层121的拉伸力和/或剪切力大于第二正极涂层122,第一正极活性材料的质量能量密度大于或者等于第二正极活性材料的质量能量密度。Referring to Figure 2, the positive electrode sheet 10' provided by the embodiment of the present application includes a positive current collector 11 and a first positive electrode coating 121 and a second positive electrode coating 122 sequentially laminated on at least one side surface of the positive electrode current collector 11; The first positive electrode coating 121 includes a first positive electrode active material, a first binder and a first conductive agent, and the second positive electrode coating 122 includes a second positive electrode active material, a second binder and a second conductive agent; wherein, The thickness of the first cathode coating 121 is less than or equal to the second cathode coating 122 , the tensile force and/or shear force of the first cathode coating 121 is greater than the second cathode coating 122 , and the mass energy of the first cathode active material The density is greater than or equal to the mass energy density of the second cathode active material.
本申请实施例提供的正极极片10’,通过采用双层式正极涂层,并控制靠近正极集流体11的第一正极涂层121的拉伸力和/或剪切力大于远离正极集流体11的第二正极涂层122,第一正极涂层121的厚度小于或等于第二正极涂层122,这样第一正极涂层121就可发挥安全保护作用,其从正极集流体11脱落的难度大于第二正极涂层122从该正极极片10’脱落的难度,可使得在电池受到挤压、碰撞、穿刺、过充等异常情况下即使第二正极涂层122发生脱落,第一正极涂层121也依然能对正极集流体11起保护作用,可在一定程度上包裹正极集流体11,避免其露出,进而避免其与电池的负极极片接触而引发热失控,改善电池的安全性能。此外,第一正极涂层121还能参与电池在正常情况下的充放电过程,高效地脱/嵌锂,且第一正极涂层121中含有的第一正极活性材料的能量密度不小于第二正极涂层122含有的第二正极活性材料,故相较于仅采用本申请第二正极涂层122作正极活性材料层的常规正极极片,在同等厚度下本申请实施例的正极极片10具有相对较高的能量密度。因此,采用正极极片10’的电池可以兼顾良好的安全性能和较高的电池能量密度。
The positive electrode sheet 10' provided in the embodiment of the present application adopts a double-layer positive electrode coating and controls the tensile force and/or shearing force of the first positive electrode coating 121 close to the positive electrode current collector 11 to be greater than that far away from the positive electrode current collector 11. 11 of the second positive electrode coating 122, the thickness of the first positive electrode coating 121 is less than or equal to the second positive electrode coating 122, so that the first positive electrode coating 121 can play a safety protection role, and it is difficult to fall off from the positive electrode current collector 11 It is more difficult for the second positive electrode coating 122 to fall off from the positive electrode piece 10', so that even if the second positive electrode coating 122 falls off when the battery is squeezed, collided, punctured, overcharged and other abnormal conditions, the first positive electrode coating 122 will fall off. The layer 121 can still protect the positive electrode current collector 11 and can wrap the positive electrode current collector 11 to a certain extent to prevent it from being exposed, thereby preventing it from contacting the negative electrode plate of the battery and causing thermal runaway, thereby improving the safety performance of the battery. In addition, the first cathode coating 121 can also participate in the charging and discharging process of the battery under normal conditions, and efficiently remove/intercalate lithium, and the energy density of the first cathode active material contained in the first cathode coating 121 is not less than that of the second cathode active material. The positive electrode coating 122 contains the second positive electrode active material. Therefore, compared with the conventional positive electrode sheet that only uses the second positive electrode coating 122 of the present application as the positive electrode active material layer, the positive electrode sheet 10 of the embodiment of the present application has the same thickness. Has a relatively high energy density. Therefore, a battery using the positive electrode plate 10' can have both good safety performance and high battery energy density.
上述第一正极涂层121和第二正极涂层122的层叠结构构成本申请正极极片10’的正极活性材料层12’,该正极活性材料层12’设置在正极集流体11的至少一侧表面上,图2中以正极集流体11的两侧表面均有正极活性材料层12’进行示意。The stacked structure of the first positive electrode coating 121 and the second positive electrode coating 122 constitutes the positive active material layer 12' of the positive electrode sheet 10' of the present application, and the positive active material layer 12' is disposed on at least one side of the positive current collector 11 Superficially, in FIG. 2 , there are cathode active material layers 12 ′ on both sides of the cathode current collector 11 .
本申请中,第一正极涂层121的厚度小于或者等于第二正极涂层122的厚度。这样相对来说,第一正极涂层121的粘结性能更好,主要起安全保护作用,第二正极涂层122主要起贡献能量作用,控制主要起安全保护作用的第一正极涂层121的厚度不大于主要起贡献容量作用的第二正极涂层,可使电池的安全性能较优。In this application, the thickness of the first positive electrode coating 121 is less than or equal to the thickness of the second positive electrode coating 122 . In this way, relatively speaking, the first positive electrode coating 121 has better bonding performance and mainly plays a safety protection role. The second positive electrode coating 122 mainly contributes energy and controls the first positive electrode coating 121 which mainly plays a safety protection role. The thickness is no larger than the second positive electrode coating, which mainly contributes to the capacity, so that the safety performance of the battery is better.
为保证第一正极涂层具有较优的安全性能,本申请一些实施方式中,控制第一正极涂层121的厚度大于0且小于或者等于50μm。例如,第一正极涂层121的厚度具体可以是2μm、5μm、10μm、20μm、30μm、40μm等。在一些实施例中,第一正极涂层121的厚度为10μm-40μm。此时,第一正极涂层121的厚度更合适,既可保证其有效提升电池遭外力破坏时的安全性能,又可避免其厚度过大而增加粘结剂的用量、降低第一活性材料的质量占比,进而影响第一正极涂层的比容量。In order to ensure that the first positive electrode coating has excellent safety performance, in some embodiments of the present application, the thickness of the first positive electrode coating 121 is controlled to be greater than 0 and less than or equal to 50 μm. For example, the thickness of the first positive electrode coating 121 may be 2 μm, 5 μm, 10 μm, 20 μm, 30 μm, 40 μm, etc. In some embodiments, the thickness of the first cathode coating 121 is 10 μm-40 μm. At this time, the thickness of the first positive electrode coating 121 is more appropriate, which can not only ensure that it can effectively improve the safety performance of the battery when it is damaged by external forces, but also avoid its excessive thickness, which increases the amount of binder and reduces the strength of the first active material. The mass proportion further affects the specific capacity of the first positive electrode coating.
本申请实施方式中,所述第一正极涂层包括以下质量百分含量的各组分:85%-96.5%的第一正极活性材料,2.5%-10%的第一粘结剂、1%-5%的第一导电剂。所述第二正极涂层包括以下质量百分含量的各组分:50%-98%的第二正极活性材料,1%-35%的第二粘结剂、0.5%-15%的第二导电剂。其中,两正极涂层中,各对应成分的质量占比可以相同,或者不同。控制正极活性材料在各正极涂层中的质量占比较高,可使两正极涂层的比容量不致过低;控制粘结剂在各正极涂层中的质量占比在上述范围,可使两正极涂层的粘结性能较高,且不会过多降低活性材料的占比。In the embodiment of the present application, the first cathode coating includes the following mass percentages of each component: 85%-96.5% of the first cathode active material, 2.5%-10% of the first binder, 1% -5% first conductive agent. The second cathode coating includes the following mass percentages of each component: 50%-98% of the second cathode active material, 1%-35% of the second binder, 0.5%-15% of the second cathode active material Conductive agent. Among them, the mass proportions of corresponding components in the two positive electrode coatings can be the same or different. Controlling the mass proportion of the cathode active material in each cathode coating to be high can prevent the specific capacity of the two cathode coatings from being too low; controlling the mass proportion of the binder in each cathode coating within the above range can prevent the two cathode coatings from being too low. The bonding performance of the positive electrode coating is high without reducing the proportion of active material too much.
本申请一些实施方式中,所述第一粘结剂在第一正极涂层121中的质量占比大于所述第二粘结剂在第二正极涂层122中的质量占比。这样即使在第一粘结剂与第二粘结剂的粘结性能相当时,仍能满足前述条件“第一正极涂层121的拉伸力和/或剪切力大于第二正极涂层122,利于第一正极涂层121在正极极片遭外力破坏的异常情况下有效发挥安全保护作用。In some embodiments of the present application, the mass proportion of the first binder in the first cathode coating 121 is greater than the mass proportion of the second binder in the second cathode coating 122 . In this way, even when the bonding properties of the first binder and the second binder are equivalent, the aforementioned condition "the tensile force and/or shear force of the first positive electrode coating 121 is greater than that of the second positive electrode coating 122" can still be satisfied. , which helps the first positive electrode coating 121 to effectively play a safety protection role in abnormal situations where the positive electrode piece is damaged by external force.
当第一粘结剂在第一正极涂层121中的质量占比大于第二粘结剂在第二正极涂层122中的质量占比时,第一导电剂在第一正极涂层121中的质量占比可以小于第二导电剂在第二正极涂层122中的质量占比。这样,第一正极涂层121的体积电阻率就大于第二正极涂层122,导电性略差的第一正极涂层121就能在电池过充、针刺、碰撞等异常情况下更好地起包裹、钝化正极集流体11,进而降低其与电池的负极极片接触而引发热失控的风险。When the mass proportion of the first binder in the first cathode coating 121 is greater than the mass proportion of the second binder in the second cathode coating 122 , the first conductive agent in the first cathode coating 121 The mass proportion of may be smaller than the mass proportion of the second conductive agent in the second positive electrode coating 122 . In this way, the volume resistivity of the first positive electrode coating 121 is greater than that of the second positive electrode coating 122, and the first positive electrode coating 121 with slightly poor conductivity can better survive abnormal conditions such as battery overcharging, acupuncture, and collision. The positive electrode current collector 11 is wrapped and passivated, thereby reducing the risk of thermal runaway caused by contact with the negative electrode piece of the battery.
本申请一些实施方式中,所述第一粘结剂在第一正极涂层121中的质量占比大于所述第一导电剂在第一正极涂层121中的质量占比。这样,第一正极涂层121自身的粘结力较强,不易从正极集流体11脱落,当电池在异常下发生第二正极涂层122脱落时,第一正极涂层121仍能对正极集流体11起一定的保护作用,避免其与电池的负极极片直接接触而引发热失控。在一些实施方式中,所述第二粘结剂在第二正极涂层122中的质量占比小于所述第二导电剂在第二正极涂层122中的质量占比。In some embodiments of the present application, the mass proportion of the first binder in the first cathode coating 121 is greater than the mass proportion of the first conductive agent in the first cathode coating 121 . In this way, the first positive electrode coating 121 itself has strong adhesive force and is not easy to fall off from the positive electrode current collector 11. When the second positive electrode coating 122 falls off under abnormal conditions of the battery, the first positive electrode coating 121 can still adhere to the positive electrode current collector 11. The fluid 11 plays a certain protective role to prevent it from directly contacting the negative electrode piece of the battery and causing thermal runaway. In some embodiments, the mass proportion of the second binder in the second cathode coating 122 is smaller than the mass proportion of the second conductive agent in the second cathode coating 122 .
本申请一些实施方式中,所述第一粘结剂的粘结力大于所述第二粘结剂的粘结力。这样即使第一粘结剂在第一正极涂层121中的质量占比等于第二粘结剂在第二正极涂层122中的质量占比,仍能保证第一正极涂层121的拉伸力和/或剪切力大于第二正极涂层122,利于第一正极涂层121提升正极极片遭外力破坏时的电池安全性能。In some embodiments of the present application, the adhesive force of the first adhesive is greater than the adhesive force of the second adhesive. In this way, even if the mass proportion of the first binder in the first cathode coating 121 is equal to the mass proportion of the second binder in the second cathode coating 122, the stretching of the first cathode coating 121 can still be ensured. The force and/or shearing force is greater than that of the second positive electrode coating 122, which helps the first positive electrode coating 121 improve the battery safety performance when the positive electrode piece is damaged by external force.
上述“第一粘结剂的粘结力”可理解为单纯的第一粘结剂形成的第一粘结层的剪切力或拉伸力,“第二粘结剂的粘结力”可理解为单纯的第二粘结剂形成的第二粘结层的剪切力或拉伸
力,在第一粘结层、第二粘结层的尺寸相同时,第一粘结层的剪切力大于第二粘结层的剪切力,第一粘结层的拉伸力大于第二粘结层的拉伸力。也可理解为,在第一粘结剂在第一正极涂层121中的质量占比与第二粘结剂在第二正极涂层122中的质量占比相等时,第一正极涂层121的剪切力或拉伸力大于尺寸相同的第二正极涂层122的剪切力或拉伸力。The above-mentioned "bonding force of the first adhesive agent" can be understood as the shear force or tensile force of the first adhesive layer formed by the simple first adhesive agent, and the "adhesive force of the second adhesive agent" can be understood as It is understood as the shear force or stretching of the second adhesive layer formed by the simple second adhesive. When the first adhesive layer and the second adhesive layer have the same size, the shear force of the first adhesive layer is greater than the shear force of the second adhesive layer, and the tensile force of the first adhesive layer is greater than that of the second adhesive layer. The tensile force of the second bonding layer. It can also be understood that when the mass proportion of the first binder in the first positive electrode coating 121 is equal to the mass proportion of the second binder in the second positive electrode coating 122 , the first positive electrode coating 121 The shearing force or tensile force is greater than the shearing force or tensile force of the second positive electrode coating 122 with the same size.
在一些实施例中,第一粘结剂在第一正极涂层121中的质量占比等于第二粘结剂在第二正极涂层122中的质量占比;第一粘结剂的粘结力大于第二粘结剂的粘结力。这样,第一正极涂层121的粘结性能就比第二正极涂层122优。In some embodiments, the mass proportion of the first binder in the first cathode coating 121 is equal to the mass proportion of the second binder in the second cathode coating 122; the bonding of the first binder The force is greater than the bonding force of the second adhesive. In this way, the bonding performance of the first positive electrode coating 121 is better than that of the second positive electrode coating 122 .
在另一些实施例中,第一粘结剂在第一正极涂层121中的质量占比大于第二粘结剂在第二正极涂层122中的质量占比;第一粘结剂的粘结力大于第二粘结剂的粘结力。此种情况下,第一正极涂层121的粘结性能比第二正极涂层122更优。此外,在这种情况下,若第一、第二活性材料在各正极涂层中的质量占比相等,则第一导电剂在第一正极涂层121中的质量占比小于第二导电剂在第二正极涂层122中的质量占比,如上所述,第一正极涂层121的体积电阻率一般大于第二正极涂层122的体积电阻率。这样导电性略差的第一正极涂层121就能在电池异常情况下更好地起包裹正极集流体11,并钝化其导电性的作用,进而降低其与电池的负极极片接触而引发热失控的风险。In other embodiments, the mass proportion of the first binder in the first cathode coating 121 is greater than the mass proportion of the second binder in the second cathode coating 122; The bonding force is greater than the bonding force of the second adhesive. In this case, the bonding performance of the first positive electrode coating 121 is better than that of the second positive electrode coating 122 . Furthermore, in this case, if the mass proportions of the first and second active materials in each cathode coating are equal, the mass proportion of the first conductive agent in the first cathode coating 121 is smaller than that of the second conductive agent. As for the mass proportion in the second positive electrode coating 122, as mentioned above, the volume resistivity of the first positive electrode coating 121 is generally greater than the volume resistivity of the second positive electrode coating 122. In this way, the first cathode coating 121 with slightly poor conductivity can better wrap the cathode current collector 11 and passivate its conductivity under abnormal conditions of the battery, thereby reducing the risk of contact with the negative electrode plate of the battery. Risk of thermal runaway.
如上所述,本申请一些实施方式中,第一正极涂层121的体积电阻率大于第二正极涂层122的体积电阻率。这样导电性略差的第一正极涂层121就能在电池过充、针刺、碰撞等异常情况下更好地起包裹、钝化正极集流体11,进而降低其与电池的负极极片接触,同时也增加短路过程中正极的欧姆极化与电化学极化,避免热迅速累积而引发热失控的风险。As mentioned above, in some embodiments of the present application, the volume resistivity of the first positive electrode coating 121 is greater than the volume resistivity of the second positive electrode coating 122 . In this way, the first positive electrode coating 121 with slightly poor conductivity can better wrap and passivate the positive electrode current collector 11 under abnormal conditions such as battery overcharging, acupuncture, collision, etc., thereby reducing its contact with the negative electrode plate of the battery. , and also increases the ohmic polarization and electrochemical polarization of the positive electrode during the short circuit process, avoiding the risk of thermal runaway caused by rapid heat accumulation.
当然,本申请其他实施方式中,第一正极涂层121的体积电阻率也可以小于或者等于第二正极涂层122的体积电阻率。只要第一正极涂层121的体积电阻率大于正极集流体11的体积电阻率,其就能阻隔正极集流体11与负极在电池异常情况下的电接触。Of course, in other embodiments of the present application, the volume resistivity of the first positive electrode coating 121 may also be less than or equal to the volume resistivity of the second positive electrode coating 122 . As long as the volume resistivity of the first positive electrode coating 121 is greater than the volume resistivity of the positive electrode current collector 11 , it can block the electrical contact between the positive electrode current collector 11 and the negative electrode under abnormal conditions of the battery.
如本申请前文所述,第一正极活性材料在第一正极涂层121中的质量占比与第二正极活性材料在第二正极涂层122中的质量占比可以相等,或者不等。本申请一些实施方式中,所述第一正极活性材料在第一正极涂层121中的质量占比等于所述第二正极活性材料在第二正极涂层122中的质量占比。此时,有利于缩小两正极涂层在电池正常工作状态下提供的能量差距。As mentioned previously in this application, the mass proportion of the first cathode active material in the first cathode coating 121 and the mass proportion of the second cathode active material in the second cathode coating 122 may be equal or different. In some embodiments of the present application, the mass proportion of the first cathode active material in the first cathode coating 121 is equal to the mass proportion of the second cathode active material in the second cathode coating 122 . At this time, it is helpful to narrow the energy gap provided by the two positive electrode coatings under normal operating conditions of the battery.
本申请实施方式中,所述第一正极活性材料的能量密度大于或者等于所述第二正极活性材料的能量密度。这里的“能量密度”可以具体同指“质量能量密度”或“体积能量密度”。第一正极活性材料、第二正极活性材料的能量密度的大小关系,这主要依据各正极活性材料自身的特性来定,具体来说,正极活性材料的能量密度是其充电比容量、充电电压、所在正极活性材料层的压实密度等综合作用的结果(由于充电电压、压实密度等也是与正极活性材料相关,本质上也可以说能量密度是与正极活性材料相关)。不同材质的正极活性材料的能量密度一般不同,例如单纯采用钴酸锂作正极活性材料的电池的能量密度,一般大于单纯采用镍钴锰酸锂作正极活性材料的电池的能量密度(进行比较的能量密度可以同是质量能量密度或同是体积能量密度);单纯采用含镍三元材料作正极活性材料的电池的能量密度,一般大于单纯采用磷酸盐材料(如磷酸铁锂、磷酸锰铁锂、磷酸钒锂、磷酸钒氧锂)作正极活性材料的电池能量密度。In an embodiment of the present application, the energy density of the first cathode active material is greater than or equal to the energy density of the second cathode active material. "Energy density" here can specifically refer to "mass energy density" or "volume energy density". The relationship between the energy density of the first cathode active material and the second cathode active material is mainly determined by the characteristics of each cathode active material. Specifically, the energy density of the cathode active material is its charging specific capacity, charging voltage, It is the result of comprehensive effects such as the compaction density of the positive active material layer (since the charging voltage, compaction density, etc. are also related to the positive active material, essentially it can be said that the energy density is related to the positive active material). The energy density of cathode active materials of different materials is generally different. For example, the energy density of a battery that simply uses lithium cobalt oxide as the cathode active material is generally greater than the energy density of a battery that simply uses lithium nickel cobalt manganate as the cathode active material (for comparison). Energy density can be both mass energy density or volume energy density); the energy density of batteries that simply use nickel-containing ternary materials as positive active materials is generally greater than those that simply use phosphate materials (such as lithium iron phosphate, lithium manganese iron phosphate , lithium vanadium phosphate, lithium vanadium oxyphosphate) as the positive electrode active material battery energy density.
本申请中可以用U×M×P的乘积来衡量某一正极活性材料的能量密度,其中,U代表正极活性材料的充电上限电压,单位是伏特(V),Q代表充电比容量,单位是mAh/g,P代表正极活性材料层的压实密度,单位是g/cm3,三者的乘积得到以Wh/L计的正极活性材料的能
量密度。本申请实施方式中,第一正极涂层121中第一正极活性材料的充电上限电压在4.25V以上,充电比容量大于或等于170mAh/g,第一正极涂层121的压实密度大于或者等于3.4g/cm3。此时,根据前述参数乘积定义的第一正极活性材料的能量密度较大,可在2456.5Wh/L以上,这使得第一正极涂层的引入不会降低采用上述正极极片制得的电池的能量密度。In this application, the energy density of a certain cathode active material can be measured by the product of U×M×P, where U represents the charging upper limit voltage of the cathode active material, in volts (V), and Q represents the charging specific capacity, in unit mAh/g, P represents the compacted density of the cathode active material layer, the unit is g/cm 3 , the product of the three gives the energy of the cathode active material in Wh/L quantity density. In the embodiment of the present application, the charging upper limit voltage of the first cathode active material in the first cathode coating 121 is above 4.25V, the charge specific capacity is greater than or equal to 170mAh/g, and the compacted density of the first cathode coating 121 is greater than or equal to 3.4g/cm 3 . At this time, the energy density of the first positive electrode active material defined according to the product of the aforementioned parameters is relatively large, which can be above 2456.5Wh/L. This means that the introduction of the first positive electrode coating will not reduce the energy density of the battery made with the above-mentioned positive electrode sheet. Energy Density.
本申请实施方式中,所述第一正极活性材料包括通式表示为LiCo1-xMxO2的材料,其中,0≤x≤1,M选自Ni、Mn、Al、Ca、Mg、Sr、Ti、V、Cr、Fe、Cu、Zn、Mo、W、Y、La、Zr、Sn、Se、Te和Bi中的一种或多种。在一些实施方式中,第一正极活性材料包括钴酸锂(对应x=0)、镍钴锰酸锂(对应0<x<1,M为Ni和Mn)、镍钴锰铝酸锂(对应0<x<1,M为Ni、Mn和Al)、镍钴铝酸锂(对应0<x<1,M为Ni和Al)、镍酸锂(对应x=1,M为Ni)。其中,通式符合LiCo1-xMxO2的材料的能量密度一般较大。类似地,所述第二正极活性材料也可以包括通式表示为LiCo1-xMxO2的材料。第一、第二正极活性材料可以是相同或者不同的材料,但需要满足第一正极活性材料的能量密度大于或者等于第二正极活性材料。In the embodiment of the present application, the first cathode active material includes a material represented by the general formula LiCo 1-x M x O 2 , where 0≤x≤1, M is selected from Ni, Mn, Al, Ca, Mg, One or more of Sr, Ti, V, Cr, Fe, Cu, Zn, Mo, W, Y, La, Zr, Sn, Se, Te and Bi. In some embodiments, the first positive active material includes lithium cobalt oxide (corresponding to x=0), lithium nickel cobalt manganate (corresponding to 0<x<1, M is Ni and Mn), lithium nickel cobalt manganate (corresponding to 0<x<1, M is Ni, Mn and Al), lithium nickel cobalt aluminate (corresponding to 0<x<1, M is Ni and Al), lithium nickelate (corresponding to x=1, M is Ni). Among them, materials whose general formula conforms to LiCo 1-x M x O 2 generally have larger energy densities. Similarly, the second cathode active material may also include a material represented by the general formula LiCo 1-x M x O 2 . The first and second cathode active materials may be the same or different materials, but the energy density of the first cathode active material needs to be greater than or equal to the second cathode active material.
本申请实施方式中,正极集流体11可以包括铝箔、铝合金箔、镀铝聚合物膜、涂碳铜箔,涂碳铝合金箔、或涂碳的镀铝聚合物膜等。其中,镀铝聚合物膜是指表面镀有铝层的聚合物薄膜,该聚合物薄膜例如可以是聚对苯二甲酸乙二醇酯(PET)或铝/聚酰亚胺(PI)。含金属铝的正极集流体11的导电性高,其在电池遭外力破坏时与负极之间因短路易发生热失控的危害大,故需要在其表面设置第一正极涂层121和第二正极涂层122的叠层。In the embodiment of the present application, the positive electrode current collector 11 may include aluminum foil, aluminum alloy foil, aluminum-plated polymer film, carbon-coated copper foil, carbon-coated aluminum alloy foil, or carbon-coated aluminum-plated polymer film. The aluminum-plated polymer film refers to a polymer film with an aluminum layer plated on the surface. The polymer film can be, for example, polyethylene terephthalate (PET) or aluminum/polyimide (PI). The positive electrode current collector 11 containing metallic aluminum has high electrical conductivity. When the battery is damaged by external force, it may cause thermal runaway due to the short distance between it and the negative electrode. Therefore, it is necessary to provide a first positive electrode coating 121 and a second positive electrode on its surface. Stack of coatings 122.
本申请实施方式中,第一正极涂层121中含有的第一粘结剂、第二正极涂层122中含有的第二粘结剂独立地选自聚四氟乙烯(PTFE)、聚偏氟乙烯(PVDF)、聚偏氟乙烯-六氟丙烯共聚物(PVDF-HFP)、聚氧化丙烯(PPO)、聚氧化乙烯(PEO)、聚甲基丙烯酸甲酯(PMMA)、聚丙烯腈(PAN)、聚丙烯酸(PAA)、聚乙烯醇(PVA)、聚酰亚胺(PI)、丁苯橡胶(SBR)、羧甲基纤维素(CMC)和海藻酸钠等中的一种或多种。第一粘结剂、第二粘结剂的材料可以相同,或者不同。In the embodiment of the present application, the first binder contained in the first positive electrode coating 121 and the second binder contained in the second positive electrode coating 122 are independently selected from polytetrafluoroethylene (PTFE), polyvinylidene fluoride Ethylene (PVDF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP), polypropylene oxide (PPO), polyethylene oxide (PEO), polymethyl methacrylate (PMMA), polyacrylonitrile (PAN) ), one or more of polyacrylic acid (PAA), polyvinyl alcohol (PVA), polyimide (PI), styrene-butadiene rubber (SBR), carboxymethylcellulose (CMC), sodium alginate, etc. . The materials of the first adhesive and the second adhesive may be the same or different.
本申请实施方式中,第一正极涂层121中含有的第一导电剂、第二正极涂层122中含有的第二导电剂可以相同,或者不同。其中,第一导电剂、第二导电剂可以独立地选自导电炭黑(如乙炔黑、科琴黑)、碳纳米管(CNT)、石墨烯、碳纤维、石墨、炉黑等中的至少一种,但不限于此。In the embodiment of the present application, the first conductive agent contained in the first positive electrode coating 121 and the second conductive agent contained in the second positive electrode coating 122 may be the same or different. Wherein, the first conductive agent and the second conductive agent can be independently selected from at least one of conductive carbon black (such as acetylene black, Ketjen black), carbon nanotubes (CNT), graphene, carbon fiber, graphite, furnace black, etc. species, but not limited to this.
本申请实施例还提供了上述正极极片的一种制备方法。该制备方法具体可以包括:The embodiments of the present application also provide a method for preparing the above-mentioned positive electrode sheet. The preparation method may specifically include:
在正极集流体的至少一侧表面上涂布含第一正极活性材料、第一粘结剂和第一导电剂的第一正极浆料,干燥后形成第一正极涂层;Coating a first positive electrode slurry containing a first positive electrode active material, a first binder and a first conductive agent on at least one side surface of the positive electrode current collector, and forming a first positive electrode coating after drying;
在所述第一正极涂层的表面涂布含第二正极活性材料、第二粘结剂和第二导电剂的第二正极浆料,干燥后,形成第二正极涂层,经压制,得到正极极片;其中,所述第一正极活性材料的质量能量密度大于或者等于所述第二正极活性材料的质量能量密度,所述第一正极涂层的厚度小于或者等于所述第二正极涂层,所述第一正极涂层的拉伸力或剪切力大于所述第二正极涂层。A second positive electrode slurry containing a second positive electrode active material, a second binder and a second conductive agent is coated on the surface of the first positive electrode coating. After drying, a second positive electrode coating is formed, and after pressing, a second positive electrode slurry is obtained. Positive electrode sheet; wherein the mass energy density of the first cathode active material is greater than or equal to the mass energy density of the second cathode active material, and the thickness of the first cathode coating is less than or equal to the second cathode coating. layer, the tensile force or shearing force of the first cathode coating is greater than that of the second cathode coating.
其中,第一正极浆料、第二正极浆料中所含有的溶剂可以相同或者不同,可独立地选自N-甲基吡咯烷酮(NMP)、二甲基甲酰胺(DMF)、水、醇类溶剂(如乙醇等)等中的一种或多种。压制的方法可以具体是辊压。涂布的方式可以是旋涂、刷涂、喷涂、浸涂、刮涂等一种或多种方式的组合。上述正极集流体可以是单面涂布,或者双面涂布。换句话说,可以是正极集流体的一侧表面具有第一正极涂层和第二正极涂层层叠构成的正极活性材料层,也可以是正极集流体的相对两侧表面上均具有第一正极涂层和第二正极涂层的叠层。
The solvents contained in the first cathode slurry and the second cathode slurry may be the same or different, and may be independently selected from N-methylpyrrolidone (NMP), dimethylformamide (DMF), water, and alcohols. One or more solvents (such as ethanol, etc.). The pressing method may specifically be roller pressing. The coating method may be one or a combination of spin coating, brush coating, spray coating, dip coating, blade coating, etc. The above-mentioned positive electrode current collector may be coated on one side or on both sides. In other words, one side surface of the cathode current collector may have a cathode active material layer composed of a first cathode coating layer and a second cathode coating layer, or the cathode current collector may have a first cathode layer on opposite sides of the surface. coating and a second positive electrode coating.
该正极极片的制备方法工艺简单,制备得到的正极极片的结构新颖且稳定,能有效发挥提升电池安全性能和不降低能量密度的作用。The preparation method of the positive electrode piece is simple and the structure of the prepared positive electrode piece is novel and stable, which can effectively improve the safety performance of the battery without reducing the energy density.
上述正极极片可通过以下方法装配得到二次电池:将正极极片、隔膜和负极极片依次层叠设置,制成电芯;将该电芯容置在电池壳体中,并注入电解液,然后将电池壳体密封,制得锂离子电池。The above-mentioned positive electrode plate can be assembled to obtain a secondary battery by the following method: stacking the positive electrode plate, separator and negative electrode plate in sequence to form a battery core; placing the battery core in a battery case and injecting electrolyte, The battery case is then sealed to produce a lithium ion battery.
其中,二次电池的电芯可以是卷绕式或叠片式。电池壳体可以是铝塑膜、铜塑膜、钢塑膜或其他包装膜,还可以是铝壳、钢壳、其他金属壳等,具体可根据所需二次电池的种类进行选择。在将电池壳体密封时,通常会预留气袋,以在电池化成后将气体通过气袋排出。在化成后可进行二次封装,再进入分容工序,得到可出厂的二次电池。Among them, the cells of the secondary battery can be of a wound type or a laminated type. The battery case can be aluminum-plastic film, copper-plastic film, steel-plastic film or other packaging films, or it can be aluminum shell, steel shell, other metal shell, etc., which can be selected according to the type of secondary battery required. When sealing the battery case, an air bag is usually reserved so that the gas can be discharged through the air bag after the battery is formed. After formation, secondary packaging can be carried out, and then the capacity dividing process can be carried out to obtain a secondary battery that can be shipped out of the factory.
本申请实施例还提供了一种二次电池,其包括如本申请实施例的上述正极极片。An embodiment of the present application also provides a secondary battery, which includes the above-mentioned positive electrode plate as in the embodiment of the present application.
参见图3,图3为本申请实施例提供的二次电池的一种结构示意图。图3示出的二次电池100’与图1示出的二次电池100的不同之处仅在于,二者所采用的正极极片不同,其他部件结构类似,可参见本申请前文的描述。该二次电池由于其采用了本申请实施例的上述正极极片10’,其可以兼顾较高的电池能量密度和良好的安全性能。Referring to Figure 3, Figure 3 is a schematic structural diagram of a secondary battery provided by an embodiment of the present application. The secondary battery 100' shown in Figure 3 is different from the secondary battery 100 shown in Figure 1 only in that the positive electrode plates used in the two are different, and the structures of other components are similar. Please refer to the previous description of this application. Since this secondary battery adopts the above-mentioned positive electrode plate 10' of the embodiment of the present application, it can achieve both high battery energy density and good safety performance.
其中,负极极片20包括负极集流体21和设置在负极集流体21至少一侧表面上的负极活性材料层22,负极活性材料层22包括负极活性材料、粘结剂和可选的导电剂。负极极片20中含有的粘结剂、导电剂的范围可参见上文对正极极片的描述。负极集流体21包括但不仅限于金属箔材、合金箔材、镀金属薄膜或表面具有碳涂层的金属箔材、合金箔材、镀金属薄膜等。在一些实施方式中,负极集流体21包括铜箔、铜合金箔、不锈钢箔、镀铜聚合物膜、涂碳铜箔,涂碳铜合金箔、或涂碳镀铜聚合物膜等,负极集流体21的表面可被蚀刻处理或粗化处理,以形成次级结构,便于和负极活性材料层形成有效接触。The negative electrode sheet 20 includes a negative current collector 21 and a negative active material layer 22 disposed on at least one side surface of the negative current collector 21 . The negative active material layer 22 includes a negative active material, a binder and an optional conductive agent. The range of the binder and conductive agent contained in the negative electrode piece 20 can be found in the above description of the positive electrode piece. The negative electrode current collector 21 includes but is not limited to metal foil, alloy foil, metal-plated film or metal foil with carbon coating on the surface, alloy foil, metal-plated film, etc. In some embodiments, the negative electrode current collector 21 includes copper foil, copper alloy foil, stainless steel foil, copper-coated polymer film, carbon-coated copper foil, carbon-coated copper alloy foil, or carbon-coated copper-coated polymer film. The surface of the fluid 21 may be etched or roughened to form secondary structures to facilitate effective contact with the negative active material layer.
在图3的二次电池具体为锂二次电池时,其负极活性材料可以包括但不限于钛酸锂、金属锂、锂合金、碳基材料、硅基材料、锡基材料、磷基材料中的一种或多种。其中,碳基材料可包括石墨(如天然石墨、人造石墨)、非石墨化炭(软碳、硬碳等);硅基材料可包括单质硅、硅基合金、硅氧化物和硅碳复合材料等中的一种或多种;锡基材料可包括单质锡、锡合金等中的一种或多种;磷基材料可包括磷单质(如黑磷)、磷碳复合材料等。此外,隔膜30可以是聚合物隔膜、无纺布等,包括但不限于单层PP(聚丙烯)、单层PE(聚乙烯)、双层PP/PE、双层PP/PP和三层PP/PE/PP等隔膜。When the secondary battery in Figure 3 is specifically a lithium secondary battery, the negative active material may include but is not limited to lithium titanate, metal lithium, lithium alloy, carbon-based materials, silicon-based materials, tin-based materials, and phosphorus-based materials. of one or more. Among them, carbon-based materials can include graphite (such as natural graphite, artificial graphite), non-graphitized carbon (soft carbon, hard carbon, etc.); silicon-based materials can include elemental silicon, silicon-based alloys, silicon oxides and silicon-carbon composite materials etc.; tin-based materials may include one or more of elemental tin, tin alloys, etc.; phosphorus-based materials may include elemental phosphorus (such as black phosphorus), phosphorus-carbon composite materials, etc. In addition, the separator 30 can be a polymer separator, non-woven fabric, etc., including but not limited to single-layer PP (polypropylene), single-layer PE (polyethylene), double-layer PP/PE, double-layer PP/PP, and three-layer PP. /PE/PP and other separators.
本申请实施例提供的二次电池,可用于终端消费产品,如手机、平板电脑、移动电源、便携机、笔记本电脑、数码相机以及其它可穿戴或可移动的电子设备、以及无人机、汽车等产品,以提高产品性能。The secondary battery provided by the embodiment of the present application can be used in terminal consumer products, such as mobile phones, tablet computers, mobile power supplies, portable machines, notebook computers, digital cameras and other wearable or mobile electronic devices, as well as drones and automobiles. and other products to improve product performance.
本申请实施例还提供一种包含有上述二次电池的电子设备。由于本申请实施例提供的上述二次电池具有良好的安全性能及较高的能量密度,可使得带有该二次电池的电子设备的安全性能好、产品使用体验好、市场竞争力突出。An embodiment of the present application also provides an electronic device including the above-mentioned secondary battery. Since the above-mentioned secondary battery provided by the embodiment of the present application has good safety performance and high energy density, electronic devices equipped with the secondary battery can have good safety performance, good product use experience, and outstanding market competitiveness.
具体地,该电子设备可以是包括各种消费类电子产品,如手机、平板电脑、笔记本电脑、移动电源、便携机、智能手表以及其它可穿戴或可移动的电子设备、电视机、影碟机、录像机、摄录机、收音机、收录机、组合音响、电唱机、激光唱机、家庭办公设备、家用电子保健设备以及汽车等电子产品。Specifically, the electronic device may include various consumer electronic products, such as mobile phones, tablet computers, laptops, mobile power supplies, portable machines, smart watches and other wearable or removable electronic devices, televisions, DVD players, Video recorders, camcorders, radios, cassette players, combo speakers, record players, compact disc players, home office equipment, home electronic health care equipment, and automobiles and other electronic products.
一些实施方式中,参见图4,本申请实施例提供了一种电子设备300,其包括壳体301和容纳于壳体301内的电子元器件(图4中未示出)和电池302,电池302为电子设备300供电,电池302包括本申请实施例上述的二次电池。壳体301可包括组装在终端前侧的前盖和
组装在后侧的后壳,电池302可固定在后壳内侧。图4示出的电子设备300通常为体积较小的便携式电子设备,如手机等。In some embodiments, referring to Figure 4, this embodiment of the present application provides an electronic device 300, which includes a housing 301, electronic components (not shown in Figure 4) accommodated in the housing 301, and a battery 302. The battery 302 supplies power to the electronic device 300, and the battery 302 includes the secondary battery described in the embodiment of the present application. The housing 301 may include a front cover assembled on the front side of the terminal and The back shell is assembled on the rear side, and the battery 302 can be fixed on the inside of the back shell. The electronic device 300 shown in FIG. 4 is usually a small portable electronic device, such as a mobile phone.
参见图5,本申请实施例还提供了一种移动装置400,其包括本申请实施例提供的上述二次电池。该移动装置400可以是各种用于装载、运输、组装、拆卸、安防等的可移动装置,可以是各种形式的车辆。具体地,该移动装置400可包括车体401、移动组件402(如车轮)、驱动组件,驱动组件包括电机403和用于给电机403供电的电池***404,电池***404包括本申请实施例提供的上述二次电池。其中,电池***404可以是上述二次电池的电池包,其容置在车辆的车体底部,并与电机403电连接。这样电池***404可以为电机403供电,电机403提供动力以驱动移动装置400的移动组件402移动。Referring to Figure 5, an embodiment of the present application also provides a mobile device 400, which includes the above-mentioned secondary battery provided by an embodiment of the present application. The mobile device 400 can be various movable devices used for loading, transportation, assembly, disassembly, security, etc., and can be various forms of vehicles. Specifically, the mobile device 400 may include a vehicle body 401, a mobile component 402 (such as a wheel), and a driving component. The driving component includes a motor 403 and a battery system 404 for powering the motor 403. The battery system 404 includes the components provided by the embodiments of the present application. of the above-mentioned secondary batteries. The battery system 404 may be a battery pack of the above-mentioned secondary battery, which is housed at the bottom of the vehicle body and is electrically connected to the motor 403 . In this way, the battery system 404 can power the motor 403, and the motor 403 provides power to drive the moving component 402 of the mobile device 400 to move.
采用本申请实施例提供的二次电池的移动装置,具有较高的续航能力和良好的安全性能。Mobile devices using the secondary battery provided by embodiments of the present application have high battery life and good safety performance.
下面分多个实施例对本申请实施例进行进一步的说明。The embodiments of the present application will be further described below in multiple embodiments.
实施例1Example 1
一种正极极片的制备方法,包括以下步骤:A method for preparing a positive electrode sheet, including the following steps:
将正极活性材料(具体是钴酸锂LiCoO2)、粘结剂PVDF(分子量为70万)、导电炭黑按95%:3%:2%的质量比称取,并与NMP混合,充分搅拌,得到第一正极浆料;将正极活性材料钴酸锂(与第一正极浆料中的钴酸锂相同)、粘结剂PVDF(与第一正极浆料中的PVDF分子量相同,粘结力相同)、导电炭黑按95%:2%:3%的质量比称取,并与NMP混合,充分搅拌,得到该第二正极浆料;Weigh the positive electrode active material (specifically lithium cobalt oxide LiCoO 2 ), binder PVDF (molecular weight: 700,000), and conductive carbon black at a mass ratio of 95%:3%:2%, mix them with NMP, and stir thoroughly , obtain the first positive electrode slurry; combine the positive active material lithium cobalt oxide (the same as the lithium cobalt oxide in the first positive electrode slurry), the binder PVDF (the same molecular weight as the PVDF in the first positive electrode slurry, the binding force Same), conductive carbon black is weighed according to the mass ratio of 95%: 2%: 3%, mixed with NMP, and stirred thoroughly to obtain the second positive electrode slurry;
选取铝箔作为正极集流体,在其相对两侧表面上涂布第一正极浆料,干燥后形成第一正极涂层;再在第一正极涂层的表面涂布上述第二正极浆料,干燥后,形成第二正极涂层,经辊压,得到正极极片。Select aluminum foil as the positive electrode current collector, apply the first positive electrode slurry on the opposite sides of the surface, and dry to form the first positive electrode coating; then apply the above-mentioned second positive electrode slurry on the surface of the first positive electrode coating, and dry Finally, a second positive electrode coating is formed, and the positive electrode sheet is obtained by rolling.
实施例1的正极极片的结构示意图如图2所示。该正极极片10’包括正极集流体11和设置在其相对两侧表面上的正极活性材料层12’,该正极活性材料层12’包括靠近正极集流体11的第一正极涂层121和远离正极集流体11的第二正极涂层122;其中,每一第一正极涂层121的厚度为10μm,每一第二正极涂层122的厚度为50μm,第一正极涂层121的拉伸力或剪切力大于第二正极涂层,第一正极涂层121中钴酸锂的能量密度等于第二正极涂层122中钴酸锂的质量能量密度。此外,第一正极涂层121的体积电阻率大于第二正极涂层122。其中,第一正极涂层121的压实密度为4.15g/cm3,第一正极涂层中121钴酸锂的充电比容量约为180mAh/g,充电上限电压为4.45V,通过这三者乘积算得的钴酸锂的能量密度约为3324.15Wh/L。The schematic structural diagram of the positive electrode piece of Example 1 is shown in Figure 2. The cathode plate 10' includes a cathode current collector 11 and cathode active material layers 12' disposed on opposite side surfaces thereof. The cathode active material layer 12' includes a first cathode coating 121 close to the cathode current collector 11 and away from the cathode current collector 11. The second positive electrode coating 122 of the positive electrode current collector 11; wherein, the thickness of each first positive electrode coating 121 is 10 μm, the thickness of each second positive electrode coating 122 is 50 μm, and the tensile force of the first positive electrode coating 121 Or the shear force is greater than the second positive electrode coating, and the energy density of lithium cobalt oxide in the first positive electrode coating 121 is equal to the mass energy density of lithium cobalt oxide in the second positive electrode coating 122 . In addition, the volume resistivity of the first positive electrode coating 121 is greater than that of the second positive electrode coating 122 . Among them, the compacted density of the first positive electrode coating 121 is 4.15g/cm 3 , the charging specific capacity of 121 lithium cobalt oxide in the first positive electrode coating is about 180mAh/g, and the upper charging voltage is 4.45V. Through these three The energy density of lithium cobalt oxide calculated by product is approximately 3324.15Wh/L.
锂二次电池的制备,包括:Preparation of lithium secondary batteries, including:
制备负极极片:将负极活性材料(具体为人造石墨)与导电炭黑、丁苯橡胶(SBR)以及羧甲基纤维素(CMC)按96%:1%:2%:1%的质量比分散在去离子水中,搅拌均匀得到负极浆料,将该负极浆料涂敷铜箔上,经烘干、压实、切片,制得负极极片;Preparing the negative electrode sheet: Mix the negative active material (specifically artificial graphite) with conductive carbon black, styrene-butadiene rubber (SBR) and carboxymethyl cellulose (CMC) in a mass ratio of 96%:1%:2%:1% Disperse in deionized water, stir evenly to obtain negative electrode slurry, apply the negative electrode slurry on copper foil, dry, compact, and slice to prepare negative electrode sheets;
组装电池:使用1mol/L LiPF6的EC(碳酸乙烯酯)+DEC(碳酸二乙酯)混合液(EC、DEC的体积比为1:1)作电解液,陶瓷处理后的PE膜作隔膜,将实施例1的正极极片、隔膜与负极极片按顺序叠放成裸电芯,将该裸电芯采用铝塑膜壳体封装,随后向电池壳体注入电解液,经化成、抽气后,再二次封装,分容后,制得锂离子电池。Assemble the battery: Use 1 mol/L LiPF 6 EC (ethylene carbonate) + DEC (diethyl carbonate) mixture (the volume ratio of EC and DEC is 1:1) as the electrolyte, and the ceramic-treated PE film as the separator , the positive electrode sheet, separator and negative electrode sheet of Example 1 are stacked in order to form a bare battery core. The bare battery core is packaged in an aluminum plastic film case, and then the electrolyte is injected into the battery case, and the electrolyte is formed and pumped. After gasification, it is packaged again and divided into volumes to prepare a lithium-ion battery.
实施例2
Example 2
一种正极极片,其与实施例1的不同之处在于:实施例2的正极极片中,第一正极涂层121、第二正极涂层122中的正极活性材料均为镍钴锰酸锂,结构通式为LiCo0.8Ni0.1Mn0.1O2。A positive electrode piece, which is different from Embodiment 1 in that: in the positive electrode piece of Embodiment 2, the positive active materials in the first positive electrode coating 121 and the second positive electrode coating 122 are both nickel cobalt manganese oxide. Lithium, the general structural formula is LiCo 0.8 Ni 0.1 Mn 0.1 O 2 .
其中,实施例2的正极极片中,第一正极涂层121中镍钴锰酸锂的能量密度等于第二正极涂层122中镍钴锰酸锂的质量能量密度。其中,第一正极涂层121的压实密度为3.6g/cm3,第一正极涂层中121中镍钴锰酸锂的充电比容量约为200mAh/g,充电上限电压为4.25V,通过这三者乘积算得的镍钴锰酸锂的能量密度约为3060Wh/L。Among them, in the positive electrode sheet of Example 2, the energy density of lithium nickel cobalt manganate in the first positive electrode coating 121 is equal to the mass energy density of lithium nickel cobalt manganate in the second positive electrode coating 122 . Among them, the compacted density of the first positive electrode coating 121 is 3.6g/cm 3 , the charging specific capacity of the lithium nickel cobalt manganate in the first positive electrode coating 121 is about 200mAh/g, and the charging upper limit voltage is 4.25V. The energy density of lithium nickel cobalt manganate calculated by the product of these three is approximately 3060Wh/L.
根据实施例1记载的方法,将实施例2的正极极片组装成锂二次电池。According to the method described in Example 1, the positive electrode sheet of Example 2 was assembled into a lithium secondary battery.
实施例3Example 3
一种正极极片,其与实施例1的不同之处在于:实施例3的正极极片中,第一正极涂层121中的正极活性材料为钴酸锂,第二正极涂层122中的正极活性材料为镍钴锰酸锂,第一正极涂层121中钴酸锂的能量密度大于第二正极涂层122中镍钴锰酸锂的能量密度。实施例3所用钴酸锂、镍钴锰酸锂的通式、能量密度特性等可参考实施例1、2的描述。A positive electrode sheet, which is different from Embodiment 1 in that: in the positive electrode sheet of Embodiment 3, the positive active material in the first positive electrode coating 121 is lithium cobalt oxide, and the positive electrode active material in the second positive electrode coating 122 is lithium cobalt oxide. The positive active material is lithium nickel cobalt manganate, and the energy density of lithium cobalt oxide in the first positive electrode coating 121 is greater than the energy density of lithium nickel cobalt manganate in the second positive electrode coating 122 . For the general formula and energy density characteristics of lithium cobalt oxide and lithium nickel cobalt manganate used in Example 3, please refer to the descriptions in Examples 1 and 2.
根据实施例1记载的方法,将实施例3的正极极片组装成锂二次电池。According to the method described in Example 1, the positive electrode sheet of Example 3 was assembled into a lithium secondary battery.
实施例4Example 4
一种正极极片,其与实施例1的不同之处在于:实施例4的正极极片中,第一正极涂层121中的第一粘结剂是分子量约为100万的PVDF,第二正极涂层122中的第二粘结剂是分子量约为70万的PVDF(其粘结力小于第一粘结剂的粘结力),且第一正极涂层121、第二正极涂层122中,钴酸锂与对应粘结剂、导电剂的质量比均为95%:2%:3%。此外,第一正极涂层121的体积电阻率等于第二正极涂层122。A positive electrode piece, which is different from Embodiment 1 in that: in the positive electrode piece of Embodiment 4, the first binder in the first positive electrode coating 121 is PVDF with a molecular weight of about 1 million, and the second The second binder in the positive electrode coating 122 is PVDF with a molecular weight of about 700,000 (its binding force is smaller than that of the first binder), and the first positive electrode coating 121 and the second positive electrode coating 122 , the mass ratio of lithium cobalt oxide to the corresponding binder and conductive agent is 95%: 2%: 3%. In addition, the volume resistivity of the first positive electrode coating 121 is equal to the second positive electrode coating 122 .
根据实施例1记载的方法,将实施例4的正极极片组装成锂二次电池。According to the method described in Example 1, the positive electrode sheet of Example 4 was assembled into a lithium secondary battery.
为突出本申请实施例的有益效果,提供以下对比例1-2。In order to highlight the beneficial effects of the embodiments of the present application, the following Comparative Examples 1-2 are provided.
对比例1Comparative example 1
一种锂二次电池,与实施例1的不同之处在于:对比例1所用的正极极片的结构如图1所示,正极集流体11一侧上的正极活性材料层仅为一层,以标号12表示,正极活性材料层12的厚度为60μm,且其组成与本申请实施例1的第二正极涂层相同,即,包括质量比的95%:2%:3%的钴酸锂、PVDF和导电炭黑。A lithium secondary battery is different from Example 1 in that: the structure of the positive electrode sheet used in Comparative Example 1 is as shown in Figure 1, and the positive active material layer on one side of the positive electrode current collector 11 is only one layer. Indicated by reference numeral 12, the thickness of the positive electrode active material layer 12 is 60 μm, and its composition is the same as the second positive electrode coating in Example 1 of the present application, that is, it includes lithium cobalt oxide in a mass ratio of 95%:2%:3%. , PVDF and conductive carbon black.
对比例2Comparative example 2
一种常规锂二次电池,与实施例2的不同之处在于:对比例1所用的正极极片的结构如图1所示,铝箔一侧上的正极活性材料层仅为一层,其厚度为60μm,且其组成与本申请实施例2的第二正极涂层相同,即,包括质量比的95%:2%:3%的镍钴锰酸锂、PVDF和导电炭黑。A conventional lithium secondary battery differs from Example 2 in that: the structure of the positive electrode sheet used in Comparative Example 1 is shown in Figure 1. The positive active material layer on one side of the aluminum foil is only one layer, and its thickness is 60 μm, and its composition is the same as the second positive electrode coating in Example 2 of the present application, that is, it includes lithium nickel cobalt manganate, PVDF and conductive carbon black in a mass ratio of 95%: 2%: 3%.
对比例3Comparative example 3
一种锂二次电池,与实施例1的不同之处在于:对比例3的正极极片中,第一正极涂层121中的正极活性材料为镍钴锰酸锂,第二正极涂层122中的正极活性材料为钴酸锂。A lithium secondary battery differs from Example 1 in that: in the positive electrode sheet of Comparative Example 3, the positive active material in the first positive electrode coating 121 is lithium nickel cobalt manganate, and the second positive electrode coating 122 The positive active material is lithium cobalt oxide.
为对本申请实施例的有益效果进行有力支持,对以上各实施例和各对比例的锂二次电池
进行正常充放电测试以测得能量密度,以及进行针刺测试。In order to strongly support the beneficial effects of the embodiments of the present application, the lithium secondary batteries of the above embodiments and comparative examples are Perform normal charge and discharge tests to measure energy density, as well as perform pinprick tests.
其中,电池能量密度的测试方法为:将各锂二次电池首次以0.2C倍率恒流充电到对应的满充电压,再恒压充电到截止电流为0.025C,搁置10min;采用0.2C倍率放电到额定下限电压3.0V,记录电池放出的能量,该能量与电池体积或质量的比值即为电池的体积或质量能量密度。Among them, the battery energy density test method is: charge each lithium secondary battery at a constant current rate of 0.2C to the corresponding full charge voltage for the first time, then charge at a constant voltage until the cut-off current is 0.025C, leave it aside for 10 minutes; discharge at a rate of 0.2C When the rated lower limit voltage is 3.0V, record the energy released by the battery. The ratio of this energy to the battery volume or mass is the volume or mass energy density of the battery.
电池的针刺测试:将各二次电池以0.2C充满电后进行穿钉测试,先把各二次电池放置于一平面上,采用直径为2mm的钢针,以100mm/s的速度从垂直于电池极片的方向贯穿电池,钢针刺穿电池后续继续保留于电池内5min或电池表明温度降至50℃则停止测试,若电池不起火、不***则表示电池通过测试,每次测试5个平行样品,将通过测试的样品数量与总样品数量的比值作为该钢针测试的通过率。Battery acupuncture test: After each secondary battery is fully charged at 0.2C, perform a nail penetration test. First, place each secondary battery on a flat surface, use a steel needle with a diameter of 2mm, and perform a nail penetration test at a speed of 100mm/s. Penetrate the battery in the direction of the battery poles. The steel needle pierces the battery and remains in the battery for 5 minutes or the battery indicates that the temperature drops to 50°C. The test will be stopped. If the battery does not catch fire or explode, it means the battery has passed the test. Each test is 5 Parallel samples are taken, and the ratio of the number of samples that pass the test to the total number of samples is regarded as the passing rate of the steel needle test.
此外,还测试本申请实施例的正极极片的两正极涂层的剪切力、拉伸力。具体地,将各正极极片裁切出一定尺寸的样品,将胶带粘附在正极极片样品的表面(即,粘在第二正极涂层上)并压紧,且在胶带的顶端和极片样品的底端分别留一个未粘附区域,用作拉伸用,使用拉力机按照如下方法进行测试:In addition, the shear force and tensile force of the two positive electrode coatings of the positive electrode sheet in the embodiment of the present application were also tested. Specifically, each positive electrode piece is cut into a sample of a certain size, the tape is adhered to the surface of the positive electrode piece sample (that is, adhered to the second positive electrode coating) and pressed tightly, and the top of the tape and the electrode are Leave an unadhered area at the bottom of the sample for stretching purposes. Use a tensile machine to test as follows:
1)垂直于极片样品的横截面方向(即,平行于极片样品的厚度方向),分别向两个对立方向拉伸(如图2中示出的2个F方向),胶带粘附着第二正极涂层从极片样品上剥离下来时所对应的力,记作第二正极涂层的拉伸力;1) Perpendicular to the cross-sectional direction of the pole piece sample (i.e., parallel to the thickness direction of the pole piece sample), stretch in two opposite directions (the 2 F directions shown in Figure 2), and the tape adheres The corresponding force when the second positive electrode coating is peeled off from the electrode sample is recorded as the tensile force of the second positive electrode coating;
2)平行于极片样品的横截面方向,分别向两个对立方向拉伸(如图2中示出的2个F’方向),胶带粘附着第二正极涂层从极片样品剥离下来时所对应的力,记作第二正极涂层的剪切力。2) Parallel to the cross-sectional direction of the pole piece sample, stretch in two opposite directions (the two F' directions shown in Figure 2). The tape adheres to the second positive electrode coating and is peeled off from the pole piece sample. The corresponding force is recorded as the shear force of the second positive electrode coating.
类似地,在各正极极片样品上的第二正极涂层剥离下来后,再按上述类似的方式,将胶带粘附在第一正极涂层上并压紧,且在胶带的顶端和极片样品的底端分别留一个未粘附区域,用拉力机进行如上述测试,其中,沿垂直于正极片样品的横截面方向,胶带粘附着第一正极涂层从正极集流体上剥离下来时的力,记作第一正极涂层的拉伸力;沿平行于极片样品的横截面方向,胶带粘附着第一正极涂层从正极集流体上剥离下来时的力,记作第一正极涂层的剪切力。Similarly, after the second positive electrode coating on each positive electrode piece sample is peeled off, the tape is adhered to the first positive electrode coating and pressed tightly in a similar manner as above, and the top of the tape and the electrode piece are Leave an unadhered area at the bottom of the sample, and use a tensile machine to perform the test as above. In the direction perpendicular to the cross-section of the positive electrode sheet sample, the tape adheres to the first positive electrode coating when it is peeled off from the positive electrode current collector. The force is recorded as the tensile force of the first positive electrode coating; along the cross-sectional direction parallel to the pole piece sample, the force when the tape adheres to the first positive electrode coating is peeled off from the positive electrode current collector, is recorded as the first Shear force of positive electrode coating.
需要说明的是,当对比例1-2在正极集流体的一侧设置的是单层式的正极活性材料层时(组成类似本申请示例的第二正极涂层),其活性材料层的拉伸力、剪切力均是指从正极集流体上剥离下来的力。It should be noted that when Comparative Example 1-2 is provided with a single-layer positive electrode active material layer on one side of the positive electrode current collector (composing a second positive electrode coating similar to the example of this application), the tension of the active material layer is Tensile force and shear force both refer to the force peeled off from the positive electrode current collector.
各实施例和对比例的测试结果汇总在下表1中。The test results of each Example and Comparative Example are summarized in Table 1 below.
表1
Table 1
Table 1
从表1可以获知,采用本申请实施例提供的双层正极涂层的正极极片制得的电池,其在遭遇外力破坏时的安全性能较好(表1中是以针刺通过率较高体现),又不降低电池在正常工作状态下的能量密度,这可由实施例1、4与对比例1的对比、实施例2-3与对比例2的对比能明显看出。此外,实施例3与对比例2的对比说明,实施例3通过控制靠近正极集流体的正极涂层中的正极活性材料比远离正极集流体的正极涂层中的正极活性材料的能量密度高,同时提升靠近正极集流体侧的第一正极涂层的拉伸力或剪切力,可以有效提升电池能量密度,以及提升电池安全效果。而对比例3与对比例1的对比说明,当双层正极涂层式极片中靠近正极集流体侧的正极涂层中正极活性材料的能量密度较小时(对比例3),采用该正极极片制得的电池的能量密度会降低,其能量密度低于仅采用与主要起贡献能量的第二正极涂层组成相同的一层式正极活性材料层的正极极片制得的电池。It can be known from Table 1 that the battery produced by using the double-layer positive electrode coating cathode sheet provided in the embodiment of the present application has better safety performance when encountering external force damage (in Table 1, the acupuncture pass rate is higher ) without reducing the energy density of the battery under normal operating conditions. This can be clearly seen from the comparison between Examples 1 and 4 and Comparative Example 1, and the comparison between Examples 2-3 and Comparative Example 2. In addition, the comparison between Example 3 and Comparative Example 2 illustrates that Example 3 controls the positive electrode active material in the positive electrode coating close to the positive electrode current collector to have a higher energy density than the positive electrode active material in the positive electrode coating far away from the positive electrode current collector. At the same time, increasing the tensile force or shear force of the first positive electrode coating close to the positive electrode current collector side can effectively increase the battery energy density and improve the battery safety effect. The comparison between Comparative Example 3 and Comparative Example 1 shows that when the energy density of the positive active material in the positive electrode coating close to the positive electrode current collector side of the double-layer positive electrode coated pole piece is small (Comparative Example 3), this positive electrode is used. The energy density of a battery made from a sheet will be lower than that of a battery made from a cathode sheet that only uses a one-layer cathode active material layer that is the same composition as the second cathode coating that mainly contributes energy.
以上所述仅表达了本申请的几种示例性实施方式,其描述较为具体和详细,但并不能因此而理解为对本申请专利范围的限制。应当指出的是,对于本领域的普通技术人员来说,在不脱离本申请构思的前提下,还可以做出若干变形和改进,这些都属于本申请的保护范围。因此,本申请专利的保护范围应以所附权利要求为准。
The above description only expresses several exemplary embodiments of the present application. The descriptions are relatively specific and detailed, but should not be construed as limiting the patent scope of the present application. It should be noted that, for those of ordinary skill in the art, several modifications and improvements can be made without departing from the concept of the present application, and these all fall within the protection scope of the present application. Therefore, the protection scope of this patent application should be determined by the appended claims.
Claims (14)
- 一种正极极片,其特征在于,所述正极极片包括正极集流体和依次层叠设置在所述正极集流体至少一侧表面上的第一正极涂层和第二正极涂层;所述第一正极涂层包括第一正极活性材料、第一粘结剂和第一导电剂,所述第二正极涂层包括第二正极活性材料、第二粘结剂和第二导电剂;其中,所述第一正极涂层的厚度小于或者等于所述第二正极涂层,所述第一正极涂层的拉伸力或剪切力大于所述第二正极涂层,所述第一正极活性材料的能量密度大于或者等于所述第二正极活性材料的能量密度。A positive electrode sheet, characterized in that the positive electrode sheet includes a positive electrode current collector and a first positive electrode coating and a second positive electrode coating sequentially laminated on at least one side surface of the positive electrode current collector; the third A positive electrode coating includes a first positive electrode active material, a first binder and a first conductive agent, and the second positive electrode coating includes a second positive electrode active material, a second binder and a second conductive agent; wherein, the The thickness of the first cathode coating is less than or equal to the second cathode coating, the tensile force or shear force of the first cathode coating is greater than the second cathode coating, and the first cathode active material The energy density is greater than or equal to the energy density of the second cathode active material.
- 如权利要求1所述的正极极片,其特征在于,所述第一正极涂层的厚度大于0且小于或者等于50μm。The positive electrode sheet according to claim 1, wherein the thickness of the first positive electrode coating is greater than 0 and less than or equal to 50 μm.
- 如权利要求1或2所述的正极极片,其特征在于,所述第一粘结剂在所述第一正极涂层中的质量占比大于所述第二粘结剂在所述第二正极涂层中的质量占比。The positive electrode sheet according to claim 1 or 2, characterized in that the mass proportion of the first binder in the first positive electrode coating is greater than that of the second binder in the second The mass proportion of the positive electrode coating.
- 如权利要求1-3任一项所述的正极极片,其特征在于,所述第一粘结剂的粘结力大于所述第二粘结剂的粘结力。The positive electrode sheet according to any one of claims 1 to 3, characterized in that the adhesive force of the first adhesive agent is greater than the adhesive force of the second adhesive agent.
- 如权利要求4所述的正极极片,其特征在于,所述第一粘结剂与所述第二粘结的材质相同,且所述第一粘结剂的分子量大于所述第二粘结剂。The positive electrode sheet according to claim 4, wherein the first adhesive and the second adhesive are made of the same material, and the molecular weight of the first adhesive is greater than that of the second adhesive. agent.
- 如权利要求1或2所述的正极极片,其特征在于,所述第一粘结剂在所述第一正极涂层中的质量占比等于所述第二粘结剂在所述第二正极涂层中的质量占比,所述第一粘结剂的粘结力大于所述第二粘结剂的粘结力。The positive electrode sheet according to claim 1 or 2, characterized in that the mass proportion of the first binder in the first positive electrode coating is equal to the mass proportion of the second binder in the second The mass proportion of the positive electrode coating, the bonding force of the first binder is greater than the bonding force of the second binder.
- 如权利要求1-6任一项所述的正极极片,其特征在于,所述第一正极涂层的体积电阻率大于所述第二正极涂层的体积电阻率。The positive electrode sheet according to any one of claims 1 to 6, wherein the volume resistivity of the first positive electrode coating is greater than the volume resistivity of the second positive electrode coating.
- 如权利要求1-7任一项所述的正极极片,其特征在于,所述第一正极涂层包括以下质量百分含量的各组分:85%-96.5%的第一正极活性材料,2.5%-10%的第一粘结剂、1%-5%的第一导电剂。The positive electrode sheet according to any one of claims 1 to 7, characterized in that the first positive electrode coating includes the following mass percentages of each component: 85%-96.5% of the first positive electrode active material, 2.5%-10% first binder, 1%-5% first conductive agent.
- 如权利要求8所述的正极极片,其特征在于,所述第一粘结剂在所述第一正极涂层中的质量占比大于所述第一导电剂在所述第一正极涂层中的质量占比。The positive electrode sheet according to claim 8, wherein the mass proportion of the first binder in the first positive electrode coating is greater than the mass proportion of the first conductive agent in the first positive electrode coating. The quality ratio in .
- 如权利要求1-9任一项所述的正极极片,其特征在于,所述第一正极活性材料的充电上限电压在4.25V以上,比容量大于或等于170mAh/g,所述第一正极涂层的压实密度大于或者等于3.4g/cm3。The positive electrode sheet according to any one of claims 1 to 9, characterized in that the charging upper limit voltage of the first positive active material is above 4.25V, and the specific capacity is greater than or equal to 170mAh/g. The compacted density of the coating is greater than or equal to 3.4g/cm 3 .
- 如权利要求10所述的正极极片,其特征在于,所述第一正极活性材料包括通式表示为LiCo1-xMxO2的材料,其中,0≤x≤1,M选自Ni、Mn、Al、Ca、Mg、Sr、Ti、V、Cr、Fe、Cu、Zn、Mo、W、Y、La、Zr、Sn、Se、Te和Bi中的一种或多种。The cathode plate according to claim 10, wherein the first cathode active material includes a material represented by the general formula LiCo 1-x M x O 2 , where 0≤x≤1 and M is selected from Ni , one or more of Mn, Al, Ca, Mg, Sr, Ti, V, Cr, Fe, Cu, Zn, Mo, W, Y, La, Zr, Sn, Se, Te and Bi.
- 一种二次电池,其特征在于,包括如权利要求1-11任一项所述的正极极片。A secondary battery, characterized by comprising the positive electrode plate according to any one of claims 1-11.
- 一种电子设备,其特征在于,包括如权利要求12所述的二次电池。An electronic device, characterized by including the secondary battery according to claim 12.
- 一种移动装置,其特征在于,包括如权利要求12所述的二次电池。 A mobile device, characterized by comprising the secondary battery according to claim 12.
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KR20190064462A (en) * | 2017-11-30 | 2019-06-10 | 주식회사 엘지화학 | Cathode Having Double Active Material Layers and Lithium Secondary Battery Comprising the Same |
CN111916752A (en) * | 2020-06-19 | 2020-11-10 | 欣旺达电动汽车电池有限公司 | Positive pole piece, manufacturing method thereof and secondary battery |
CN112582581A (en) * | 2020-12-14 | 2021-03-30 | 珠海冠宇电池股份有限公司 | Positive plate and lithium ion battery comprising same |
CN112599722A (en) * | 2020-12-14 | 2021-04-02 | 珠海冠宇电池股份有限公司 | Positive plate and lithium ion battery comprising same |
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KR20190064462A (en) * | 2017-11-30 | 2019-06-10 | 주식회사 엘지화학 | Cathode Having Double Active Material Layers and Lithium Secondary Battery Comprising the Same |
CN111916752A (en) * | 2020-06-19 | 2020-11-10 | 欣旺达电动汽车电池有限公司 | Positive pole piece, manufacturing method thereof and secondary battery |
CN112582581A (en) * | 2020-12-14 | 2021-03-30 | 珠海冠宇电池股份有限公司 | Positive plate and lithium ion battery comprising same |
CN112599722A (en) * | 2020-12-14 | 2021-04-02 | 珠海冠宇电池股份有限公司 | Positive plate and lithium ion battery comprising same |
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