CN114784224A - Reference electrode, three-electrode battery cell and lithium ion battery - Google Patents
Reference electrode, three-electrode battery cell and lithium ion battery Download PDFInfo
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- CN114784224A CN114784224A CN202210515385.XA CN202210515385A CN114784224A CN 114784224 A CN114784224 A CN 114784224A CN 202210515385 A CN202210515385 A CN 202210515385A CN 114784224 A CN114784224 A CN 114784224A
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- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 title claims abstract description 11
- 229910001416 lithium ion Inorganic materials 0.000 title claims abstract description 11
- 239000003792 electrolyte Substances 0.000 claims abstract description 42
- GELKBWJHTRAYNV-UHFFFAOYSA-K lithium iron phosphate Chemical compound [Li+].[Fe+2].[O-]P([O-])([O-])=O GELKBWJHTRAYNV-UHFFFAOYSA-K 0.000 claims abstract description 31
- 239000000758 substrate Substances 0.000 claims abstract description 25
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- 239000000463 material Substances 0.000 claims description 23
- 229910052759 nickel Inorganic materials 0.000 claims description 22
- -1 polypropylene Polymers 0.000 claims description 22
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 claims description 21
- 239000011267 electrode slurry Substances 0.000 claims description 19
- 239000004743 Polypropylene Substances 0.000 claims description 14
- 229920001155 polypropylene Polymers 0.000 claims description 14
- 229910052802 copper Inorganic materials 0.000 claims description 13
- 239000010949 copper Substances 0.000 claims description 13
- 239000002002 slurry Substances 0.000 claims description 13
- 229910052744 lithium Inorganic materials 0.000 claims description 12
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 claims description 11
- 239000000654 additive Substances 0.000 claims description 11
- 229910052782 aluminium Inorganic materials 0.000 claims description 9
- 230000000996 additive effect Effects 0.000 claims description 8
- 239000004698 Polyethylene Substances 0.000 claims description 7
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims description 7
- 239000011889 copper foil Substances 0.000 claims description 7
- 239000011888 foil Substances 0.000 claims description 7
- 229920000573 polyethylene Polymers 0.000 claims description 7
- 239000003575 carbonaceous material Substances 0.000 claims description 6
- 239000002131 composite material Substances 0.000 claims description 6
- 239000007773 negative electrode material Substances 0.000 claims description 6
- 239000006260 foam Substances 0.000 claims description 4
- 239000011356 non-aqueous organic solvent Substances 0.000 claims description 4
- 239000007774 positive electrode material Substances 0.000 claims description 4
- 239000002210 silicon-based material Substances 0.000 claims description 4
- 229910003002 lithium salt Inorganic materials 0.000 claims description 3
- 159000000002 lithium salts Chemical class 0.000 claims description 3
- 238000000034 method Methods 0.000 abstract description 11
- 238000007599 discharging Methods 0.000 abstract description 6
- 239000010410 layer Substances 0.000 description 46
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- 238000001035 drying Methods 0.000 description 7
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- 230000000052 comparative effect Effects 0.000 description 6
- 238000005520 cutting process Methods 0.000 description 5
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 4
- 239000011247 coating layer Substances 0.000 description 4
- 238000003475 lamination Methods 0.000 description 4
- 238000002156 mixing Methods 0.000 description 4
- 238000004806 packaging method and process Methods 0.000 description 4
- 229910052710 silicon Inorganic materials 0.000 description 3
- 239000000243 solution Substances 0.000 description 3
- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical compound CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 description 2
- 239000002033 PVDF binder Substances 0.000 description 2
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 2
- 239000002174 Styrene-butadiene Substances 0.000 description 2
- XLOMVQKBTHCTTD-UHFFFAOYSA-N Zinc monoxide Chemical compound [Zn]=O XLOMVQKBTHCTTD-UHFFFAOYSA-N 0.000 description 2
- 229910021383 artificial graphite Inorganic materials 0.000 description 2
- 229910052796 boron Inorganic materials 0.000 description 2
- 229910052791 calcium Inorganic materials 0.000 description 2
- 229910052799 carbon Inorganic materials 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
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- 229910002804 graphite Inorganic materials 0.000 description 2
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- 230000008595 infiltration Effects 0.000 description 2
- 238000001764 infiltration Methods 0.000 description 2
- 229910052748 manganese Inorganic materials 0.000 description 2
- 239000012528 membrane Substances 0.000 description 2
- 229910052758 niobium Inorganic materials 0.000 description 2
- 229920002981 polyvinylidene fluoride Polymers 0.000 description 2
- 239000011148 porous material Substances 0.000 description 2
- 229910052814 silicon oxide Inorganic materials 0.000 description 2
- 229910052712 strontium Inorganic materials 0.000 description 2
- 229920003048 styrene butadiene rubber Polymers 0.000 description 2
- 230000002195 synergetic effect Effects 0.000 description 2
- 229910052719 titanium Inorganic materials 0.000 description 2
- 229910052721 tungsten Inorganic materials 0.000 description 2
- 229910052720 vanadium Inorganic materials 0.000 description 2
- 238000004804 winding Methods 0.000 description 2
- 229910052725 zinc Inorganic materials 0.000 description 2
- 239000011701 zinc Substances 0.000 description 2
- 229910052726 zirconium Inorganic materials 0.000 description 2
- 229910019419 CoxMyO2 Inorganic materials 0.000 description 1
- 229910009731 Li2FeSiO4 Inorganic materials 0.000 description 1
- 229910010584 LiFeO2 Inorganic materials 0.000 description 1
- 229910052493 LiFePO4 Inorganic materials 0.000 description 1
- 229910002993 LiMnO2 Inorganic materials 0.000 description 1
- 229910013716 LiNi Inorganic materials 0.000 description 1
- 229910001290 LiPF6 Inorganic materials 0.000 description 1
- 229910001228 Li[Ni1/3Co1/3Mn1/3]O2 (NCM 111) Inorganic materials 0.000 description 1
- 229910002097 Lithium manganese(III,IV) oxide Inorganic materials 0.000 description 1
- 229910016289 MxO2 Inorganic materials 0.000 description 1
- 241000872198 Serjania polyphylla Species 0.000 description 1
- 229910000676 Si alloy Inorganic materials 0.000 description 1
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 1
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 1
- 229910003481 amorphous carbon Inorganic materials 0.000 description 1
- 239000006183 anode active material Substances 0.000 description 1
- 239000006256 anode slurry Substances 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- MTAZNLWOLGHBHU-UHFFFAOYSA-N butadiene-styrene rubber Chemical compound C=CC=C.C=CC1=CC=CC=C1 MTAZNLWOLGHBHU-UHFFFAOYSA-N 0.000 description 1
- 239000006229 carbon black Substances 0.000 description 1
- 239000006257 cathode slurry Substances 0.000 description 1
- 238000004891 communication Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000004146 energy storage Methods 0.000 description 1
- 229910003437 indium oxide Inorganic materials 0.000 description 1
- PJXISJQVUVHSOJ-UHFFFAOYSA-N indium(iii) oxide Chemical compound [O-2].[O-2].[O-2].[In+3].[In+3] PJXISJQVUVHSOJ-UHFFFAOYSA-N 0.000 description 1
- 238000002347 injection Methods 0.000 description 1
- 239000007924 injection Substances 0.000 description 1
- 238000010030 laminating Methods 0.000 description 1
- 239000004816 latex Substances 0.000 description 1
- 229920000126 latex Polymers 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- FUJCRWPEOMXPAD-UHFFFAOYSA-N lithium oxide Chemical compound [Li+].[Li+].[O-2] FUJCRWPEOMXPAD-UHFFFAOYSA-N 0.000 description 1
- 229910001947 lithium oxide Inorganic materials 0.000 description 1
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 1
- 229910021382 natural graphite Inorganic materials 0.000 description 1
- 239000011255 nonaqueous electrolyte Substances 0.000 description 1
- 238000011056 performance test Methods 0.000 description 1
- 239000011347 resin Substances 0.000 description 1
- 229920005989 resin Polymers 0.000 description 1
- 238000007086 side reaction Methods 0.000 description 1
- 239000010703 silicon Substances 0.000 description 1
- 239000011115 styrene butadiene Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- XOLBLPGZBRYERU-UHFFFAOYSA-N tin dioxide Chemical compound O=[Sn]=O XOLBLPGZBRYERU-UHFFFAOYSA-N 0.000 description 1
- 229910001887 tin oxide Inorganic materials 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
- 239000011787 zinc oxide Substances 0.000 description 1
Images
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
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
- H01M4/134—Electrodes based on metals, Si or alloys
-
- 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
- H01M4/136—Electrodes based on inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy
Abstract
The invention provides a reference electrode, a three-electrode battery cell and a lithium ion battery, wherein the reference electrode comprises a substrate with a porous structure and a lithium iron phosphate layer coated on the substrate framework. The reference electrode provided by the invention has high stability, and can ensure the fluidity of the electrolyte and the performance of a three-electrode cell; the three-electrode battery cell prepared by the reference electrode provided by the invention can more accurately identify whether the electrolyte component reacts at the positive electrode or the negative electrode in the charging and discharging process.
Description
Technical Field
The invention belongs to the technical field of lithium ion batteries, and particularly relates to a reference electrode, a three-electrode cell and a lithium ion battery.
Background
Lithium ion batteries have been widely used in communication, energy storage, and electric vehicles due to their advantages of high energy density, long cycle life, and the like. In order to judge the potential influence and change of the additive on the whole battery cell, a reference electrode needs to be introduced. At present, a three-electrode battery cell is obtained by directly using a copper wire, a copper strip plated with lithium or metallic lithium as a reference electrode. However, lithium metal reacts with the electrolyte and additives, and the reference electrode area is either too small or too large, which results in inaccurate potential data and poor cell performance.
Therefore, the reference electrode is reasonably designed, the flowability of the electrolyte and the performance of the battery cell are ensured while the reference electrode is not reacted with the electrolyte, and the battery cell prepared by the reference electrode can accurately reflect potential change.
Disclosure of Invention
In view of the defects in the prior art, the present invention aims to provide a reference electrode, a three-electrode cell and a lithium ion battery, which can ensure the stability of the reference electrode, prevent the reference electrode from reacting with an electrolyte, and simultaneously ensure the fluidity of the electrolyte and the performance of the three-electrode cell, and the three-electrode cell prepared by using the reference electrode can more accurately identify whether the electrolyte component reacts at the positive electrode or the negative electrode in the charging and discharging processes.
In order to achieve the purpose, the invention adopts the following technical scheme:
in a first aspect, the present invention provides a reference electrode, which includes a substrate having a porous structure and a lithium iron phosphate layer coated on a skeleton of the substrate.
The reference electrode provided by the invention takes a material with a porous structure as a base material, so that the fluidity of the electrolyte can be ensured, and the performance of a three-electrode cell is not influenced; the stable lithium iron phosphate layer is used as the coating layer of the base material framework, so that the problem that lithium serving as a reference electrode or the coating layer serving as the reference electrode in the prior art can react with electrolyte and additives is effectively solved, and the stability of the reference electrode is obviously improved. Therefore, the synergistic effect of the substrate with the porous structure and the lithium iron phosphate layer can ensure the stability of the reference electrode, does not react with the electrolyte, and can ensure the fluidity of the electrolyte and the performance of the three-electrode battery cell.
Further, the skeleton of the base material in the present invention means: the substantial portion of the substrate outside the pore structure is removed.
In a preferred embodiment of the present invention, the mesh number of the substrate is 20 to 250 meshes, and may be, for example, 20, 40, 60, 80, 100, 120, 140, 160, 180, 200, 220, 240 or 250 meshes, but is not limited to the above-mentioned values, and other values not listed in the above-mentioned value range are also applicable.
The mesh number of the base material is limited to be 20-250 meshes, and when the mesh number of the base material is lower than 20 meshes, the data is incomplete and unreal, because the two-dimensional structure of surface contact is formed between the pole pieces in the battery cell, the contact area of the reference electrode is small due to too small size, and the internal situation of the pole pieces cannot be comprehensively reflected; when the mesh number of the base material is higher than 250 meshes, no data signal can be caused, and the cell cannot work normally because the electrolyte is blocked by the small meshes.
As a preferable technical scheme of the invention, the mesh number of the base material is 80-200 meshes
In a preferred embodiment of the present invention, the substrate includes any one of copper foam, nickel foam, copper mesh, and nickel mesh.
In a second aspect, the invention provides a three-electrode battery cell, which comprises a shell, wherein a negative pole piece, a reference electrode and a positive pole piece are sequentially stacked in the shell, a first diaphragm is arranged between the negative pole piece and the reference electrode, and a second diaphragm is arranged between the reference electrode and the positive pole piece.
The reference electrode is the reference electrode of the first aspect.
The reference electrode provided by the invention is used for preparing the three-electrode battery cell, so that whether the electrolyte component reacts at the positive electrode or the negative electrode in the charging and discharging process can be identified more accurately. The reference electrode is provided with the stable lithium iron phosphate coating layer which does not react with the electrolyte and the additive, so that more accurate potential change can be obtained, and the three-electrode cell can more accurately identify whether the electrolyte component reacts at the positive electrode or the negative electrode in the charging and discharging process.
In a preferred embodiment of the present invention, the area of the substrate in the reference electrode is not less than 10%, for example, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90% or 100% based on 100% of the area of the negative electrode sheet, but is not limited to the above-mentioned values, and other values not listed in the above-mentioned range are also applicable.
The area of the base material in the reference electrode is limited to be not less than 10% of the area of the negative electrode piece, because the area of the reference electrode is too small, the measured potential is inaccurate, and therefore whether the electrolyte component reacts at the positive electrode or the negative electrode in the charging and discharging process cannot be accurately identified. In addition, the area of the substrate in the reference electrode cannot exceed the area of the negative electrode tab, since exceeding the negative electrode area is likely to cause internal short circuits and thus data failure. Meanwhile, the area of the base material in the invention refers to the area enclosed by four sides of the base material, and comprises the area of the solid skeleton and the area of the pore structure, namely the whole area of the base material, but not the area of the solid skeleton of the base material.
Preferably, the positive pole piece comprises a positive slurry layer and a positive current collector.
Preferably, the positive electrode slurry layer includes a positive electrode active material.
Preferably, the positive electrode active material includes a lithium-containing composite oxide.
In the present invention, the lithium-containing composite oxide may be LiMnO2、LiFeO2、LiMn2O4、Li2FeSiO4LiNi1/3Co1/ 3Mn1/3O2、LiFePO4And LiNi5Co2Mn3O2Any one of them.
The lithium-containing composite oxide may also be LizNi(1-x-y)CoxMyO2Wherein, 0.01 is less than or equal tox is less than or equal to 0.20, y is less than or equal to 0 and less than or equal to 0.20, z is more than or equal to 0.97 and less than or equal to 1.20, and further preferably, x is more than or equal to 0.01 and less than or equal to 0.15, y is more than or equal to 0 and less than or equal to 0.15, and z is more than or equal to 0.97 and less than or equal to 1.20; m is any one or the combination of at least two of B, Sr, Ti, Ca, Zr, Zn, Si, W, Mn, V, Mg, Mo, Nb or Al.
The lithium-containing composite oxide may also be LizCo(1-x)MxO2Wherein x is more than or equal to 0 and less than or equal to 0.1, z is more than or equal to 0.97 and less than or equal to 1.20, and M is any one or the combination of at least two of Ni, B, Sr, Ti, Ca, Zr, Zn, Si, W, Mn, V, Mg, Mo, Nb or Al.
Preferably, the thickness of the positive electrode current collector is 13 μm to 17 μm, and may be, for example, 13 μm, 14 μm, 15 μm, 16 μm or 17 μm, but is not limited to the values listed, and other values not listed in the range of the values are also applicable.
Preferably, the positive electrode current collector includes an aluminum foil.
As a preferred technical solution of the present invention, the negative electrode plate includes a negative electrode slurry layer and a negative electrode current collector.
Preferably, the anode slurry layer includes an anode active material. The negative electrode active material in the present invention is a material capable of inserting and extracting lithium.
Preferably, the negative electrode active material includes a carbon material and an oxide material, or a carbon material and a silicon material.
The carbon material may be, for example, crystalline carbon (natural graphite, artificial graphite, or the like), amorphous carbon, carbon-coated graphite, resin-coated graphite, or the like. The oxide material may be, for example, indium oxide, silicon oxide, tin oxide, lithium titanate, zinc oxide, lithium oxide, or the like. From the viewpoint of high energy density, the negative electrode active material may be a composite of a carbon material and a silicon material. The silicon material may be a simple substance of silicon, a silicon alloy, a silicon oxide, or the like.
Preferably, the thickness of the negative electrode current collector is 6 μm to 10 μm, and may be, for example, 6 μm, 7 μm, 8 μm, 9 μm or 10 μm, but is not limited to the values listed, and other values not listed in the range of the values are also applicable.
Preferably, the negative electrode current collector includes a copper foil.
As a preferable aspect of the present invention, each of the first separator and the second separator includes at least three layers.
Preferably, the first separator and the second separator each include a polypropylene layer, a polyethylene layer, and a polypropylene layer, which are sequentially laminated.
It should be noted that the structure and composition of the separator are not specifically required or limited, and the present invention provides a structure and composition of a separator, and separators commonly used in the field of lithium ion batteries can be used in the present invention. Thus, it will be appreciated that one skilled in the art can adapt the structure and composition of the diaphragm to the application scenario and test conditions.
As a preferable technical solution of the present invention, the case is further filled with an electrolyte.
Preferably, the electrolyte includes a non-aqueous organic solvent, a lithium salt, and an additive.
The invention provides an electrolyte, which comprises the following components: based on the mass fraction of the electrolyte as 100%, the mass fraction of the non-aqueous organic solvent is 70 wt% to 90 wt%, the mass fraction of the lithium salt is 5 wt% to 20 wt%, and the mass fraction of the additive is 0.05 wt% to 5 wt%.
It should be noted that the present invention does not specifically require or limit the composition of the electrolyte, and the present invention provides an exemplary composition of an electrolyte, and any electrolyte commonly used in the field of lithium ion batteries can be used in the present invention. Therefore, it can be understood that the composition of the electrolyte solution can be adaptively adjusted by those skilled in the art according to the use scenario and the test conditions.
In a third aspect, the present invention provides a lithium ion battery, which includes the three-electrode cell of the second aspect.
The present invention also provides a method for preparing the reference electrode of the first aspect, the method comprising:
and soaking the substrate in lithium iron phosphate slurry, drying, and forming the lithium iron phosphate layer on the framework of the substrate to obtain the reference electrode.
The thickness of the lithium iron phosphate layer is adjusted by controlling the solid content of the lithium iron phosphate slurry and the infiltration time of the base material in the lithium iron phosphate slurry, and the preparation method is simple and convenient to popularize.
In a preferred embodiment of the present invention, the solid content of the lithium iron phosphate slurry is 60 wt% to 90 wt%, and may be, for example, 60 wt%, 62 wt%, 65 wt%, 68 wt%, 70 wt%, 72 wt%, 75 wt%, 78 wt%, 80 wt%, 82 wt%, 85 wt%, 88 wt%, or 90 wt%, but is not limited to the above-mentioned values, and other values not listed in the above-mentioned value range are also applicable.
Preferably, the time for soaking the substrate in the lithium iron phosphate slurry is 0 to 5 hours, and does not include 0, and for example, the time can be 0.5 hour, 0.8 hour, 1 hour, 1.2 hour, 1.5 hour, 1.8 hour, 2 hour, 2.2 hour, 2.5 hour, 2.8 hour, 3 hour, 3.2 hour, 3.5 hour, 3.8 hour, 4 hour, 4.2 hour, 4.5 hour, 4.8 hour or 5 hour, but is not limited to the enumerated values, and other non-enumerated values in the numerical range are also applicable; further preferably 1 to 2.5 hours.
Preferably, the drying temperature is from 30 ℃ to 150 ℃, for example 30 ℃, 40 ℃, 50 ℃, 60 ℃, 70 ℃, 80 ℃, 90 ℃, 100 ℃, 110 ℃, 120 ℃, 130 ℃, 1400 ℃ or 150 ℃, but is not limited to the recited values, and other unrecited values within this range are equally applicable.
The invention also provides a preparation method of the three-electrode battery cell of the second aspect, which comprises the following steps:
and arranging the negative pole piece, the first diaphragm, the reference electrode, the second diaphragm and the positive pole piece in a winding or laminating manner in sequence, putting the negative pole piece, the first diaphragm, the reference electrode, the second diaphragm and the positive pole piece into the shell, then injecting electrolyte into the shell, and packaging to obtain the three-electrode battery cell.
Compared with the prior art, the invention has the following beneficial effects:
the reference electrode and the three-electrode cell provided by the invention can ensure the stability of the reference electrode, do not react with electrolyte and additives, and simultaneously can ensure the fluidity of the electrolyte and the performance of the three-electrode cell, and the three-electrode cell prepared by adopting the reference electrode provided by the invention can more accurately identify whether the electrolyte component reacts at the positive electrode or the negative electrode in the charging and discharging process. In addition, the reference electrode and the three-electrode battery cell provided by the invention have simple preparation methods and are convenient to operate and popularize.
Drawings
Fig. 1 is a schematic structural diagram of a three-electrode cell provided in embodiments 1 to 5 of the present invention.
Reference numerals are as follows: 1-negative pole piece; 2-a first membrane; 3-a reference electrode; 4-a second membrane; 5-positive pole piece.
Detailed Description
It is to be understood that in the description of the present invention, the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate orientations or positional relationships based on those shown in the drawings, and are used only for convenience in describing the present invention and for simplicity in description, and do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, should not be taken as limiting the present invention. Furthermore, the terms "first," "second," and the like are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or to implicitly indicate a number of the indicated technical features. Thus, a feature defined as "first," "second," etc. may explicitly or implicitly include one or more of that feature. In the description of the present invention, "a plurality" means two or more unless otherwise specified.
It should be noted that, unless explicitly stated or limited otherwise, the terms "disposed," "connected" and "connected" in the description of the present invention are to be construed broadly and may include, for example, a fixed connection, a detachable connection, or an integral connection; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meaning of the above terms in the present invention can be understood by those of ordinary skill in the art through specific situations.
The technical solution of the present invention is further explained by the following embodiments. It should be understood by those skilled in the art that the examples are only for the understanding of the present invention and should not be construed as the specific limitation of the present invention.
In one embodiment, the present invention provides a method for preparing the positive electrode slurry, the method comprising: based on the total mass of the positive electrode slurry, 97 wt% of LiNi is added0.3Co0.3Mn0.4O2Adding carbon black with the mass fraction of 2 wt% and polyvinylidene fluoride (PVDF) with the mass fraction of 1 wt% into N-methylpyrrolidone (NMP) and mixing to obtain the positive electrode slurry.
The invention also provides a preparation method of the cathode slurry, which comprises the following steps: on the basis of the total mass of the negative electrode slurry, 97 wt% of artificial graphite, 1 wt% of styrene-butadiene latex (SBR, AL3001A) and 1 wt% of conductive carbon black are dissolved in water to obtain the negative electrode slurry.
The invention also provides a formula of the electrolyte, which comprises the following components in percentage by weight: mixing the components of EC/EMC/DMC/PC in a ratio of about 3:4:3:0 to form a non-aqueous organic solvent, and mixing with 14 wt% LiPF6After mixing, and adding 1 wt% VC based on 100 parts by weight of the non-aqueous electrolyte solution to prepare an electrolyte solution.
Example 1
The embodiment provides a preparation method of a three-electrode battery cell, which comprises the following steps:
(1) coating the positive electrode slurry (prepared in the above embodiment) on the surface of an aluminum foil with the thickness of 15 μm to obtain a positive electrode plate 5; coating the negative electrode slurry (prepared in the above embodiment) on the surface of copper foil with the thickness of 8 μm to obtain a negative electrode plate 1; the first diaphragm 2 and the second diaphragm 4 are each composed of three layers of a polypropylene layer, a polyethylene layer, and a polypropylene layer, which are sequentially laminated;
(2) cutting a nickel screen with the mesh number of 150 meshes into a material with the area of 50% of that of the negative pole piece 1; soaking a nickel screen in lithium iron phosphate slurry with the solid content of 70 wt% for 2h, then drying at 80 ℃, and forming a lithium iron phosphate layer on a framework of the nickel screen to obtain a reference electrode 3 with the lithium iron phosphate layer coated on the framework of the nickel screen;
(3) the negative electrode plate 1, the first diaphragm 2, the reference electrode 3, the second diaphragm 4 and the positive electrode plate 5 are sequentially arranged in a lamination manner and placed inside the shell, then electrolyte (consisting of the formula of the above specific embodiment) is injected into the shell, and the three-electrode battery cell is obtained after encapsulation, as shown in fig. 1.
Example 2
The embodiment provides a preparation method of a three-electrode battery cell, which comprises the following steps:
(1) coating the positive electrode slurry (prepared in the above embodiment) on the surface of an aluminum foil with the thickness of 13 μm to obtain a positive electrode plate 5; coating the negative electrode slurry (prepared in the above embodiment) on the surface of a copper foil with the thickness of 6 μm to obtain a negative electrode plate 1; the first diaphragm 2 and the second diaphragm 4 are respectively composed of three layers of a polypropylene layer, a polyethylene layer and a polypropylene layer which are sequentially laminated;
(3) cutting a copper mesh with the mesh number of 20 meshes into 100% of the area of the negative pole piece 1; soaking the copper mesh substrate in lithium iron phosphate slurry with the solid content of 60 wt% for 10min, then drying at 30 ℃, and forming a lithium iron phosphate layer on the framework of the copper mesh substrate to obtain a reference electrode 3 with the lithium iron phosphate layer coated on the framework of the copper mesh substrate;
(3) arranging a negative electrode plate 1, a first diaphragm 2, a reference electrode 3, a second diaphragm 4 and a positive electrode plate 5 in a lamination manner in sequence, placing the negative electrode plate, the first diaphragm 2, the reference electrode 3, the second diaphragm 4 and the positive electrode plate into a shell, then injecting electrolyte into the shell (the electrolyte composition is the formula of the specific embodiment), and packaging to obtain the three-electrode battery core, as shown in fig. 1.
Example 3
The embodiment provides a preparation method of a three-electrode battery cell, which comprises the following steps:
(1) coating the positive electrode slurry (prepared in the above-mentioned embodiment) on the surface of an aluminum foil with a thickness of 17 μm to obtain a positive electrode sheet 5; coating the negative electrode slurry (prepared in the above embodiment) on the surface of a copper foil with the thickness of 10 μm to obtain a negative electrode plate 1; the first diaphragm 2 and the second diaphragm 4 are each composed of three layers of a polypropylene layer, a polyethylene layer, and a polypropylene layer, which are sequentially laminated;
(2) cutting the foamed nickel with the mesh number of 250 meshes into a material with the area of 1 percent of that of the negative pole piece; soaking the foamed nickel in lithium iron phosphate slurry with the solid content of 90 wt% for 5 hours, and then drying at 150 ℃ to form a lithium iron phosphate layer on a skeleton of the foamed nickel, so as to obtain a reference electrode 3 with the foamed nickel skeleton coated with the lithium iron phosphate layer;
(3) the negative electrode plate 1, the first diaphragm 2, the reference electrode 3, the second diaphragm 4 and the positive electrode plate 5 are sequentially arranged in a winding manner and placed inside the shell, then electrolyte (the electrolyte composition is the formula of one embodiment) is injected into the shell, and the three-electrode battery cell is obtained after packaging, as shown in fig. 1.
Example 4
The embodiment provides a preparation method of a three-electrode battery cell, which comprises the following steps:
(1) coating the positive electrode slurry (prepared in the above embodiment) on the surface of an aluminum foil with the thickness of 15 μm to obtain a positive electrode plate 5; coating the negative electrode slurry (prepared in the above embodiment) on the surface of copper foil with the thickness of 8 μm to obtain a negative electrode plate 1; the first diaphragm 2 and the second diaphragm 4 are respectively composed of three layers of a polypropylene layer, a polyethylene layer and a polypropylene layer which are sequentially laminated;
(2) cutting the 80-mesh foamy copper into 50% of the area of the negative electrode plate 1; soaking foamy copper in lithium iron phosphate slurry with solid content of 70 wt% for 1h, then drying at 80 ℃, forming a lithium iron phosphate layer on a skeleton of the foamy copper, and obtaining a reference electrode 3 with the lithium iron phosphate layer coated on the skeleton of the foamy copper;
(3) the negative electrode plate 1, the first diaphragm 2, the reference electrode 3, the second diaphragm 4 and the positive electrode plate 5 are sequentially arranged in a lamination mode, placed inside the shell, then electrolyte (comprising the formula of one specific embodiment) is injected into the shell, and the three-electrode battery cell is obtained after packaging, as shown in fig. 1.
Example 5
The embodiment provides a preparation method of a three-electrode battery cell, which comprises the following steps:
(1) coating the positive electrode slurry (prepared in the above embodiment) on the surface of an aluminum foil with the thickness of 15 μm to obtain a positive electrode plate 5; coating the negative electrode slurry (prepared in the above embodiment) on the surface of copper foil with the thickness of 8 μm to obtain a negative electrode plate 1; the first diaphragm 2 and the second diaphragm 4 are respectively composed of three layers of a polypropylene layer, a polyethylene layer and a polypropylene layer which are sequentially laminated;
(2) cutting a nickel screen with 200 meshes into an area which is 50% of the area of the negative pole piece 1; soaking a nickel screen in lithium iron phosphate slurry with the solid content of 70 wt% for 2h, then drying at 80 ℃, and forming a lithium iron phosphate layer on a framework of the nickel screen to obtain a reference electrode 3 with the lithium iron phosphate layer coated on the framework of the nickel screen;
(3) the negative electrode plate 1, the first diaphragm 2, the reference electrode 3, the second diaphragm 4 and the positive electrode plate 5 are sequentially arranged in a lamination manner and placed inside the shell, then electrolyte (consisting of the formula of the above specific embodiment) is injected into the shell, and the three-electrode battery cell is obtained after encapsulation, as shown in fig. 1.
Examples 6 and 7 provide methods for preparing three-electrode cells, which are the same as example 1 except that the mesh number of the nickel mesh is changed as shown in table 2.
The preparation method of the three-electrode battery cell provided in example 8 is the same as that of example 1 except that the area of the nickel mesh substrate in table 3 is changed.
The preparation methods of the three-electrode cell provided in comparative examples 1 and 2 were the same as those of example 1 except that the kind of the reference electrode 3 in table 4 was changed.
The performance test parameters of the invention are as follows: the three-electrode cells prepared in examples 1 to 8 and comparative examples 1 to 2 were charged to 50% SOC at a current density of 0.33C, and then the electrode potentials were compared.
After the three-electrode cells prepared in examples 1 to 8 and comparative examples 1 to 2 were charged to 50% SOC, the respective electrode potentials were compared as shown in tables 1 to 4.
TABLE 1
TABLE 2
TABLE 3
TABLE 4
From the data in tables 1 to 4, it can be seen:
(1) the three-electrode cell in embodiments 1 to 5 can accurately reflect the potential changes of the positive electrode and the negative electrode, so as to determine whether the additive acts on the positive electrode or the negative electrode, and distinguish the influence caused by the additive, and the three-electrode cell provided in embodiments 1 to 5 has higher stability, so that the synergistic effect between the porous structure substrate and the lithium iron phosphate layer in the reference electrode 3 provided by the invention can ensure the stability of the reference electrode 3, and can ensure the fluidity of the electrolyte and the performance of the three-electrode cell while not reacting with the electrolyte, so that the three-electrode cell can accurately reflect the potential changes of the positive electrode and the negative electrode, and further determine whether the additive acts on the positive electrode or the negative electrode.
(2) In both the embodiment 6 and the embodiment 7, a three-electrode battery cell with stable performance cannot be obtained, and the potential changes of the positive electrode and the negative electrode cannot be accurately reflected, because the mesh number of the nickel mesh substrate in the embodiment 6 is too large, the electrolyte cannot circulate, so that a loop cannot be formed, and the battery cell cannot normally work; in example 7, the mesh size of the nickel mesh substrate is too small, which results in a small contact area of the reference electrode 3, and cannot reflect the effect of electrolyte infiltration and the side reaction change of film formation inside the battery cell after liquid injection. Therefore, the stable performance of the three-electrode cell can be better achieved and the effect of accurately reflecting the potential change of the positive electrode and the negative electrode can be better achieved only within the range of proper porosity of the nickel screen.
(3) The three-electrode cell in example 8 cannot accurately reflect the potential changes of the positive electrode and the negative electrode, because the electrode of the reference electrode 3 in example 8 is too small, the potential change cannot be measured, and thus the actual conditions inside the cell cannot be accurately reflected.
(4) The three-electrode cell in comparative examples 1-2 cannot accurately reflect the potential changes of the positive electrode and the negative electrode, and the stability of the three-electrode cell is much lower than that of example 1, because the coating process of a lithium iron phosphate layer is omitted in comparative example 1, and a nickel mesh is directly used as a reference electrode 3 in the three-electrode cell; in comparative example 2, metallic lithium was used directly as the reference electrode 3 of the three-electrode cell. Therefore, according to the invention, the porous structure material is used as the base material of the reference electrode 3, and the lithium iron phosphate layer is used as the coating layer of the reference electrode 3, so that the stability of the three-electrode cell can be obviously improved, and the accuracy of reflecting the potential changes of the positive electrode and the negative electrode can be obviously improved.
The applicant declares that the above description is only a specific embodiment of the present invention, but the scope of the present invention is not limited thereto, and it should be understood by those skilled in the art that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are within the scope and disclosure of the present invention.
Claims (10)
1. The reference electrode is characterized by comprising a substrate with a porous structure and a lithium iron phosphate layer coated on the framework of the substrate.
2. The reference electrode of claim 1, wherein the substrate has a mesh size of 20 to 250 mesh.
3. The reference electrode of claim 2, wherein the substrate has a mesh size of 80 to 200 mesh.
4. The reference electrode of claim 1, wherein the substrate comprises any one of copper foam, nickel foam, copper mesh, or nickel mesh.
5. A three-electrode battery cell is characterized by comprising a shell, wherein a negative pole piece, a reference electrode and a positive pole piece are sequentially stacked in the shell, a first diaphragm is arranged between the negative pole piece and the reference electrode, and a second diaphragm is arranged between the reference electrode and the positive pole piece;
the reference electrode is the reference electrode of any one of claims 1 to 4.
6. The three-electrode cell of claim 5, wherein the three-electrode cell satisfies at least one of (a) to (e) below:
(a) the positive pole piece comprises a positive slurry layer and a positive current collector;
(b) the positive electrode slurry layer comprises a positive electrode active material;
(c) the positive electrode active material includes a lithium-containing composite oxide;
(d) the thickness of the positive electrode current collector is 13-17 μm;
(e) the positive current collector includes an aluminum foil.
7. The three-electrode cell of claim 5, wherein the three-electrode cell satisfies at least one of the following conditions (f) to (k):
(f) the area of the negative electrode plate is 100%, and the area of the base material in the reference electrode is more than or equal to 10%;
(g) the negative pole piece comprises a negative slurry layer and a negative current collector;
(h) the negative electrode slurry layer includes a negative electrode active material;
(i) the negative electrode active material includes a carbon material and an oxide material, or the negative electrode active material includes a carbon material and a silicon material;
(j) the thickness of the negative current collector is 6-10 μm;
(k) the negative current collector comprises a copper foil.
8. The three-electrode cell of claim 5, wherein the three-electrode cell satisfies at least one of the following conditions (l) to (m):
(l) The first diaphragm and the second diaphragm each include at least three layers;
(m) each of the first and second separators includes a polypropylene layer, a polyethylene layer, and a polypropylene layer, which are sequentially stacked.
9. The three-electrode cell of claim 5, wherein the three-electrode cell satisfies at least one of (n) to (o) in the following conditions:
(n) electrolyte is also injected into the shell;
(o) the electrolyte includes a non-aqueous organic solvent, a lithium salt, and an additive.
10. A lithium-ion battery, characterized in that it comprises a three-electrode cell according to any of claims 5 to 9.
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Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
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| US20140375325A1 (en) * | 2013-06-20 | 2014-12-25 | Hrl Laboratories, Llc | Battery with reference electrode for voltage monitoring |
| CN216052084U (en) * | 2021-08-30 | 2022-03-15 | 比亚迪股份有限公司 | Reference electrode and lithium battery with same |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20140375325A1 (en) * | 2013-06-20 | 2014-12-25 | Hrl Laboratories, Llc | Battery with reference electrode for voltage monitoring |
| CN216052084U (en) * | 2021-08-30 | 2022-03-15 | 比亚迪股份有限公司 | Reference electrode and lithium battery with same |
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