CN116344742A - Fully lithiated negative electrode plate and preparation method thereof - Google Patents
Fully lithiated negative electrode plate and preparation method thereof Download PDFInfo
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- 238000002360 preparation method Methods 0.000 title abstract description 6
- 229910052744 lithium Inorganic materials 0.000 claims abstract description 75
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 claims abstract description 71
- 229910021385 hard carbon Inorganic materials 0.000 claims abstract description 56
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 46
- 229910002804 graphite Inorganic materials 0.000 claims abstract description 44
- 239000010439 graphite Substances 0.000 claims abstract description 44
- 229910052751 metal Inorganic materials 0.000 claims abstract description 37
- 239000002184 metal Substances 0.000 claims abstract description 37
- 238000006138 lithiation reaction Methods 0.000 claims abstract description 34
- 239000007773 negative electrode material Substances 0.000 claims abstract description 31
- 238000000034 method Methods 0.000 claims abstract description 22
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 claims abstract description 13
- 229910001416 lithium ion Inorganic materials 0.000 claims abstract description 13
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 claims abstract description 12
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 claims abstract description 11
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 claims abstract description 10
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims abstract description 10
- 229910052698 phosphorus Inorganic materials 0.000 claims abstract description 10
- 239000011574 phosphorus Substances 0.000 claims abstract description 10
- 229910052710 silicon Inorganic materials 0.000 claims abstract description 10
- 239000010703 silicon Substances 0.000 claims abstract description 10
- 239000003792 electrolyte Substances 0.000 claims description 27
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- 238000000576 coating method Methods 0.000 claims description 18
- 238000001035 drying Methods 0.000 claims description 18
- 239000011267 electrode slurry Substances 0.000 claims description 13
- 239000011149 active material Substances 0.000 claims description 8
- 239000006256 anode slurry Substances 0.000 claims description 6
- 238000006243 chemical reaction Methods 0.000 claims description 5
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- 239000006258 conductive agent Substances 0.000 claims description 4
- 229910003002 lithium salt Inorganic materials 0.000 claims description 4
- 159000000002 lithium salts Chemical class 0.000 claims description 4
- -1 super P Substances 0.000 claims description 4
- 238000004519 manufacturing process Methods 0.000 claims description 3
- OIFBSDVPJOWBCH-UHFFFAOYSA-N Diethyl carbonate Chemical compound CCOC(=O)OCC OIFBSDVPJOWBCH-UHFFFAOYSA-N 0.000 claims description 2
- KMTRUDSVKNLOMY-UHFFFAOYSA-N Ethylene carbonate Chemical compound O=C1OCCO1 KMTRUDSVKNLOMY-UHFFFAOYSA-N 0.000 claims description 2
- DPXJVFZANSGRMM-UHFFFAOYSA-N acetic acid;2,3,4,5,6-pentahydroxyhexanal;sodium Chemical compound [Na].CC(O)=O.OCC(O)C(O)C(O)C(O)C=O DPXJVFZANSGRMM-UHFFFAOYSA-N 0.000 claims description 2
- 239000002041 carbon nanotube Substances 0.000 claims description 2
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- 239000001768 carboxy methyl cellulose Substances 0.000 claims description 2
- IEJIGPNLZYLLBP-UHFFFAOYSA-N dimethyl carbonate Chemical compound COC(=O)OC IEJIGPNLZYLLBP-UHFFFAOYSA-N 0.000 claims description 2
- JBTWLSYIZRCDFO-UHFFFAOYSA-N ethyl methyl carbonate Chemical compound CCOC(=O)OC JBTWLSYIZRCDFO-UHFFFAOYSA-N 0.000 claims description 2
- 239000003273 ketjen black Substances 0.000 claims description 2
- 238000003475 lamination Methods 0.000 claims description 2
- 239000000203 mixture Substances 0.000 claims description 2
- RUOJZAUFBMNUDX-UHFFFAOYSA-N propylene carbonate Chemical compound CC1COC(=O)O1 RUOJZAUFBMNUDX-UHFFFAOYSA-N 0.000 claims description 2
- 235000019812 sodium carboxymethyl cellulose Nutrition 0.000 claims description 2
- 229920001027 sodium carboxymethylcellulose Polymers 0.000 claims description 2
- 229920003048 styrene butadiene rubber Polymers 0.000 claims description 2
- 239000000463 material Substances 0.000 abstract description 17
- 230000000694 effects Effects 0.000 abstract description 13
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- 150000002148 esters Chemical class 0.000 description 11
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- 239000012300 argon atmosphere Substances 0.000 description 3
- 238000000840 electrochemical analysis Methods 0.000 description 3
- 239000000843 powder Substances 0.000 description 3
- 239000013543 active substance Substances 0.000 description 2
- 239000006183 anode active material Substances 0.000 description 2
- 239000003575 carbonaceous material Substances 0.000 description 2
- 230000006872 improvement Effects 0.000 description 2
- 229910000733 Li alloy Inorganic materials 0.000 description 1
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 1
- 229910001128 Sn alloy Inorganic materials 0.000 description 1
- HMDDXIMCDZRSNE-UHFFFAOYSA-N [C].[Si] Chemical compound [C].[Si] HMDDXIMCDZRSNE-UHFFFAOYSA-N 0.000 description 1
- 230000004888 barrier function Effects 0.000 description 1
- 239000010406 cathode material Substances 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
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- 230000002687 intercalation Effects 0.000 description 1
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- 239000013589 supplement Substances 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
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- H—ELECTRICITY
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- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
- H01M4/133—Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- 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
- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
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- H—ELECTRICITY
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- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
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- 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
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- H01M4/00—Electrodes
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- 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
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- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
Abstract
The invention belongs to the field of lithium ion batteries, and discloses a fully lithiated negative electrode plate and a preparation method thereof, wherein the fully lithiated negative electrode plate is obtained by directly lithiating a sandwich structure negative electrode with metal lithium, wherein the sandwich structure negative electrode sequentially comprises an upper layer, an intermediate layer and a lower layer from top to bottom, negative electrode active materials adopted by the upper layer and the lower layer are independently selected from hard carbon and lithium titanate, and negative electrode active materials adopted by the intermediate layer are selected from one or more of graphite, silicon-based negative electrode materials, tin-based negative electrode materials and phosphorus-based negative electrode materials. According to the invention, a sandwich structure is constructed (wherein the middle layer is a cathode active material with large volume expansion effect, the upper layer and the lower layer are materials with no volume expansion or small volume expansion effect), and in the subsequent direct lithiation process of contacting with metal lithium, the cathode does not generate heat, fall off or slag, so that the technical problems of heat generation, slag fall off and the like in the direct prelithiation of the existing cathode can be effectively solved.
Description
Technical Field
The invention belongs to the field of lithium ion batteries, and particularly relates to a fully lithiated negative electrode plate and a preparation method thereof.
Background
In the first charge and discharge process of the lithium ion battery, a solid electrolyte interface film (SEI) is formed on the surface of the negative electrode, and the SEI can irreversibly consume lithium from the positive electrode material and the electrolyte, and reduce the coulombic efficiency of the first cycle of the battery, so that a pre-lithiation scheme with reasonable design is needed to compensate the loss of irreversible lithium in the first cycle, and further the first efficiency of the lithium ion battery is improved and higher energy density is achieved.
Currently, there are many methods for pre-lithiation of the negative electrode, which can be largely divided into chemical, electrochemical and direct lithiation. The chemical lithiation generally uses a lithium-containing reagent or lithium alloy compound with strong reduction strength to supplement lithium to the anode material, but has high chemical reaction activity, serious potential safety hazard, incompatibility with the current electrode slurry preparation process taking NMP or water as a solvent, and faces a plurality of problems in practical application; electrochemical lithiation requires the participation of an electrolyte, and a simple electrochemical reaction between the negative electrode and metallic lithium occurs, similar to the negative electrode lithiation process of a battery. However, the electrochemical lithiated anode has high chemical reactivity, is complex in use process, cannot be stably stored in air, and is not suitable for large-scale industrial production; the direct lithiation is to use lithium powder, lithium foil or lithium sheet for lithiation, and the battery can be directly assembled continuously after the lithiation is completed, so that the operation is simpler. The stable lithium metal powder developed by the American FMC company is added in a mixing process or coated on the surface of the negative electrode plate, and the negative electrode is lithiated effectively by adjusting the amount of the added metal powder.
In addition, since the potential of the metal lithium is low, lithium can be supplemented by using a lithium sheet or a lithium foil by utilizing a self-discharge mechanism. When the lithium ion battery is brought into contact with a negative electrode material due to the existence of a potential difference, electrons spontaneously move to the negative electrode, and lithium ions are intercalated into the negative electrode, which is the most suitable method for industrial mass production. However, in the direct lithiation method, materials such as negative electrode graphite and the like have obvious heating phenomena during actual mass production, and part of pole pieces also have the problem of material falling. Therefore, in order to further advance the industrial application of direct lithiation, a solution is required to solve these problems encountered in practical applications.
In the prior art, materials such as graphite and the like are also used for preparing the mixed cathode, but the materials are not aimed at the pre-lithiation process, and more importantly, the problems of heating, slag falling, falling and the like still occur in the pre-lithiation process in the prior art.
Disclosure of Invention
Aiming at the defects or improvement demands of the prior art, surrounding the battery pre-lithiation, the invention aims to provide a fully lithiated negative electrode plate and a preparation method thereof, and the technical problems of heating, slag falling, falling and the like of the traditional negative electrode during the direct pre-lithiation can be effectively solved by constructing a sandwich structure (wherein the middle layer is a negative electrode active material with large volume expansion effect, the upper layer and the lower layer are materials without volume expansion or small volume expansion effect) in the direct lithiation process of the subsequent contact with metal lithium.
In order to achieve the above object, according to one aspect of the present invention, there is provided a fully lithiated anode piece, which is characterized in that the fully lithiated anode piece is obtained by directly lithiating an anode of a sandwich structure with metallic lithium, wherein the anode of the sandwich structure is an upper layer, an intermediate layer and a lower layer sequentially from top to bottom, and anode active materials adopted in the upper layer and the lower layer are independently selected from hard carbon and lithium titanate, and anode active materials adopted in the intermediate layer are selected from one or more of graphite, a silicon-based anode material, a tin-based anode material and a phosphorus-based anode material.
As a further preferred aspect of the present invention, in the sandwich structure anode, the ratio of the thicknesses of the upper layer, the middle layer and the lower layer is 1: (1-12): 1.
as a further preferred aspect of the present invention, the metallic lithium includes a metallic lithium sheet or a metallic lithium foil.
According to another aspect of the present invention, the present invention provides a method for preparing the fully lithiated anode sheet, which is characterized by comprising the steps of:
(1) Preparing a lower-layer negative electrode slurry, wherein an active material is selected from hard carbon and lithium titanate;
preparing an intermediate layer negative electrode slurry, wherein an active material is one or more selected from graphite, a silicon-based negative electrode material, a tin-based negative electrode material and a phosphorus-based negative electrode material;
preparing upper-layer negative electrode slurry, wherein an active material is selected from hard carbon and lithium titanate;
(2) Coating the lower-layer negative electrode slurry on a current collector, and drying to form a lower layer on the current collector;
(3) Continuously coating the intermediate layer negative electrode slurry on the surface of the lower layer, and drying to obtain an intermediate layer;
(4) Coating the upper layer negative electrode slurry on the surface of the middle layer continuously, and drying to obtain an upper layer, thereby forming a sandwich structure negative electrode on the current collector;
(5) Attaching the upper layer of the negative electrode with the sandwich structure with metal lithium, wherein the dosage of the metal lithium is larger than or equal to the theoretical dosage of the metal lithium required by complete lithiation of the negative electrode plate, and the attaching surface is pre-applied with lithium ion battery electrolyte; and standing for reaction after lamination, so as to obtain the fully lithiated negative electrode plate.
As a further preferred aspect of the present invention, the lower layer anode slurry, the intermediate layer anode slurry, and the upper layer anode slurry each satisfy: the mass fraction of the active material is 90% -95%, the mass fraction of the conductive agent is 4% -6%, and the mass fraction of the binder is 1% -4%.
As a further preferred aspect of the present invention, the conductive agent is preferably at least one of ketjen black, super P, and carbon nanotubes, and the binder is preferably a mixture of sodium carboxymethyl cellulose and styrene-butadiene rubber of equal mass.
As a further preferred aspect of the present invention, in the step (5), the lithium ion battery electrolyte includes a solvent and a lithium salt, and the solvent is preferably one or more of ethylene carbonate, ethylmethyl carbonate, diethyl carbonate, propylene carbonate and dimethyl carbonate; the lithium salt is preferably lithium hexafluorophosphate.
According to the technical scheme, compared with the prior art, the sandwich structure negative electrode is constructed by constructing the sandwich structure negative electrode, namely, constructing the upper layer and the lower layer in the sandwich structure by using materials (such as hard carbon and lithium titanate) with no volume expansion or small volume expansion effect (that is, the materials adopted by the upper layer are single active substances, the materials adopted by the lower layer are single active substances, and are independently selected from hard carbon and lithium titanate), and directly lithiating the sandwich structure negative electrode by using materials (such as graphite, silicon-based negative electrode materials, tin-based negative electrode materials and phosphorus-based negative electrode materials, wherein the silicon-based negative electrode materials comprise silicon oxide, pure silicon, silicon-carbon materials and the like, the tin-based negative electrode materials comprise metal tin, tin alloy, nano tin and the like, the phosphorus-based negative electrode materials comprise elemental phosphorus, metal phosphide and the like, and the volume expansion refers to volume change of the materials when lithium ions are embedded into the sandwich structure negative electrode, the upper layer and the lower layer are wrapped by the intermediate layer, and then, the sandwich structure negative electrode is directly lithiated by contacting the metal lithium, so that the lithiated positive electrode is obtained, and no heat is generated in a direct lithiation process, and no slag is generated in a process of falling off.
When the graphite cathode is subjected to mass lithiation in industry, a certain technical barrier exists no matter a chemical method or an electrochemical method is used, and the feasibility is low. For direct lithiation, the prior art uses a single-layer negative electrode, and when the single-layer negative electrode is subjected to direct prelithiation, phenomena such as pole piece heating, slag falling and falling can occur (for example, if pure graphite, silicon-based negative electrode materials, tin-based negative electrode materials and phosphorus-based negative electrode material single-layer negative electrodes are used, the single-layer negative electrodes can fall off, heat and the like during lithiation, so that the subsequent use is affected).
In the sandwich structure of the present invention, the intermediate layer (e.g., graphite, silicon-based negative electrode material, tin-based negative electrode material, phosphorus-based negative electrode material) is used as the main material of the negative electrode of the sandwich structure, so that the thickness of the intermediate layer can be preferably controlled to be equal to or greater than the thickness of the upper layer and the lower layer. Based on the invention, the sandwich structure cathode after lithiation is completed can well exert the advantages of the interlayer material in the subsequent battery test; meanwhile, the upper layer and the lower layer can exert the advantages of the upper layer and the lower layer, so that the first effect is improved, and the cycle performance, the safety performance and the like are also greatly improved. Aiming at the problems of heat generation and falling off caused by the traditional direct prelithiation, the invention uses materials (such as hard carbon and lithium titanate) with no volume expansion effect or small volume expansion effect as an upper layer and a lower layer, so that the pole piece and the current collector are firmly adhered in the lithiation process, and the problems of heat generation of the pole piece are effectively solved by the upper layer and the lower layer of the cathode material wrapping the main body. According to the invention, materials (such as hard carbon and lithium titanate) with no or small volume expansion effect are preferentially attached to the current collector, and the advantage that the structure is not remarkably expanded during lithium intercalation is utilized, so that the problem of pole piece slag and falling is effectively solved. The sandwich structure electrode can perfectly combine the respective advantages of several materials, such as stable charge and discharge cycle performance and excellent multiplying power performance of a hard carbon material, excellent multiplying power performance of a lithium titanate material, high safety and the like, and the lithiated negative electrode plate ensures that the lithium ion battery is improved firstly, the multiplying power performance of the lithium ion battery is also obviously improved, and the cycle performance is stable.
The invention carries out lithiation by directly contacting the negative electrode with metal lithium (such as lithium foil or lithium sheet), and the method is simple and convenient and has rapid reaction. By utilizing the characteristic of low lithium metal potential, after electrolyte is added on the contact surface of the negative electrode of the sandwich structure and the metal lithium, the lithium can be effectively supplemented by spontaneous discharge, the operation is simple, and the reaction is rapid.
Drawings
FIG. 1 is a schematic diagram of the lithiated product of comparative example 1; the apparent shedding phenomenon can be seen from the figure.
FIG. 2 is a diagram of the lithiated product of example 1; no obvious falling off is caused in the figure.
FIG. 3 is a diagram showing the lithiated product of comparative example 2; slag can be removed from the figure.
Fig. 4 is a graph of electrochemical performance test results of the assembled battery of example 1.
Fig. 5 is a graph of electrochemical performance test results of the assembled battery of example 2.
Fig. 6 is a graph of electrochemical performance test results of the assembled battery of example 3.
Fig. 7 is a schematic diagram of the structure of the negative electrode tab fully lithiated in example 1 embodying the present invention. The meaning of the reference numerals in the figures is as follows: 1 is copper foil, 21 is a hard carbon layer, 3 is a graphite layer, 22 is a hard carbon layer, and 4 is a metallic lithium foil.
Detailed Description
The present invention will be described in further detail with reference to the drawings and examples, in order to make the objects, technical solutions and advantages of the present invention more apparent. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention. In addition, the technical features of the embodiments of the present invention described below may be combined with each other as long as they do not collide with each other.
Example 1:
for example, as shown in fig. 7, a sandwich structure comprising a hard carbon layer 21/graphite layer 3/hard carbon layer 22 is formed by using a sandwich structure cathode made of hard carbon and graphite materials, and specifically comprises the following steps:
(1) Preparing hard carbon slurry, wherein the mass ratio of the hard carbon in the slurry is 90%, coating the slurry on the copper foil 1, and drying to prepare a hard carbon layer 21 with the thickness of 10 mu m;
(2) Preparing graphite slurry, wherein the mass ratio of graphite in the slurry is 90%, coating the graphite slurry on the surface of the hard carbon layer 21, and drying to prepare an intermediate layer, namely a graphite layer 3, with the thickness of 80 mu m;
(3) Preparing hard carbon slurry with the same proportion again, coating the hard carbon slurry on the graphite layer 3 obtained in the step (2), and drying to obtain a hard carbon layer 22 with the thickness of 10 mu m; thereby obtaining a graphite anode with a hard carbon layer 21/graphite layer 3/hard carbon layer 22 sandwich structure;
(4) And (3) dropwise adding an ester electrolyte (the specific model of the electrolyte adopted in the embodiment is LB015, and other conventional electrolytes can be adopted), then attaching a metal lithium foil 4, completely attaching the prepared sandwich-structure cathode and the metal lithium foil 4 together, standing for 12 hours, and completely lithiating the cathode pole piece, wherein the obtained lithiation product is shown in figure 2. Of course, the ester electrolyte may be dropped onto the metal lithium foil 4, and then the prepared sandwich structure anode may be attached to the metal lithium foil.
(5) And assembling 2032 a button type half battery with the obtained fully lithiated sandwich structure pole piece on a metal lithium sheet battery under the condition of argon atmosphere, wherein electrolyte is ester electrolyte (LB 015 is also adopted), carrying out electrochemical performance test on the obtained button type half battery by using a blue electrochemical test system, carrying out charge and discharge at a current density of 0.1C, and obtaining the lithiation degree of the negative electrode according to the first-cycle charge specific capacity. The charge and discharge cut-off voltages are respectively: 0.01V and 1.5V as shown in fig. 4.
Wherein the dosage of the metal lithium foil 4 in the step (4) is larger than or equal to the theoretical dosage of the metal lithium required by the complete lithiation of the negative electrode plate, namely, according to the density and theoretical specific capacity of lithium metal, 1mAh cm can be calculated -2 And requires about 5 microns thick of metallic lithium. Further, when the amount of the lithium metal foil 4 is equal to the theoretical value, the step (5) may be directly performed after the step (4) is completed; when the amount of the metal lithium foil 4 is greater than the theoretical value, after the end of the step (4), the excess lithium may be removed, and then the step (5) may be performed. Subsequent embodiments are also similar.
Example 2:
for example, as shown in fig. 7, a sandwich structure comprising a hard carbon layer 21/graphite layer 3/hard carbon layer 22 is formed by using a sandwich structure cathode made of hard carbon and graphite materials, and specifically comprises the following steps:
(1) Preparing hard carbon slurry, wherein the mass ratio of the hard carbon in the slurry is 90%, coating the slurry on the copper foil 1, and drying to obtain a hard carbon layer 21 with the thickness of 7 mu m;
(2) Preparing graphite slurry, wherein the mass ratio of graphite in the slurry is 90%, coating the graphite slurry on the surface of the hard carbon layer 21, and drying to obtain an intermediate layer, namely a graphite layer 3, with the thickness of 84 mu m;
(3) Preparing hard carbon slurry with the same proportion again, coating the hard carbon slurry on the graphite layer 3 obtained in the step (2), and drying to obtain a hard carbon layer 22 with the thickness of 7 mu m; thereby obtaining a graphite anode with a hard carbon layer 21/graphite layer 3/hard carbon layer 22 sandwich structure;
(4) And (3) dropwise adding an ester electrolyte (the specific model of the electrolyte adopted in the embodiment is LB015, and other conventional electrolytes can be adopted), then attaching a metal lithium foil 4, completely attaching the prepared sandwich-structure cathode and the metal lithium foil 4 together, standing for 12h, and completely lithiating the cathode pole piece to obtain a lithiated product. Of course, the ester electrolyte may be dropped onto the metal lithium foil 4, and then the prepared sandwich structure anode may be attached to the metal lithium foil.
(5) And assembling 2032 a button type half battery with the obtained fully lithiated sandwich structure pole piece on a metal lithium sheet battery under the condition of argon atmosphere, wherein electrolyte is ester electrolyte (LB 015 is also adopted), carrying out electrochemical performance test on the obtained button type half battery by using a blue electrochemical test system, carrying out charge and discharge at a current density of 0.1C, and obtaining the lithiation degree of the negative electrode according to the first-cycle charge specific capacity. The charge and discharge cut-off voltages are respectively: 0.01V and 1.5V as shown in fig. 5.
Example 3:
for example, as shown in fig. 7, a sandwich structure comprising a hard carbon layer 21/graphite layer 3/hard carbon layer 22 is formed by using a sandwich structure cathode made of hard carbon and graphite materials, and specifically comprises the following steps:
(1) Preparing hard carbon slurry, wherein the mass ratio of the hard carbon in the slurry is 90%, coating the slurry on the copper foil 1, and drying to prepare a hard carbon layer 21 with the thickness of 14 mu m;
(2) Preparing graphite slurry, wherein the mass ratio of graphite in the slurry is 90%, coating the graphite slurry on the surface of the hard carbon layer 21, and drying to obtain an intermediate layer, namely a graphite layer 3, with the thickness of 70 mu m;
(3) Preparing hard carbon slurry with the same proportion again, coating the hard carbon slurry on the graphite layer 3 obtained in the step (2), and drying to obtain a hard carbon layer 22 with the thickness of 14 mu m; thereby obtaining a graphite anode with a hard carbon layer 21/graphite layer 3/hard carbon layer 22 sandwich structure;
(4) And (3) dropwise adding an ester electrolyte (the specific model of the electrolyte adopted in the embodiment is LB015, and other conventional electrolytes can be adopted), then attaching a metal lithium foil 4, completely attaching the prepared sandwich-structure cathode and the metal lithium foil 4 together, standing for 12h, and completely lithiating the cathode pole piece to obtain a lithiated product. Of course, the ester electrolyte may be dropped onto the metal lithium foil 4, and then the prepared sandwich structure anode may be attached to the metal lithium foil.
(5) And assembling 2032 a button type half battery with the obtained fully lithiated sandwich structure pole piece on a metal lithium sheet battery under the condition of argon atmosphere, wherein electrolyte is ester electrolyte (LB 015 is also adopted), carrying out electrochemical performance test on the obtained button type half battery by using a blue electrochemical test system, carrying out charge and discharge at a current density of 0.1C, and obtaining the lithiation degree of the negative electrode according to the first-cycle charge specific capacity. The charge and discharge cut-off voltages are respectively: 0.01V and 1.5V as shown in fig. 6.
Comparative example 1:
taking a single-layer structure cathode made of graphite material as an example, the method specifically comprises the following steps:
(1) Preparing graphite slurry, wherein the mass proportion of graphite in the slurry is 90%, coating the slurry on a copper foil, and drying to prepare a single-layer graphite pole piece with the thickness of 100 mu m;
(2) And completely attaching the prepared graphite pole piece and the metal lithium foil together, adding a proper amount of ester electrolyte in the middle, standing for 12 hours, and observing the lithiation condition, wherein the effect is shown in figure 1. As can be seen from fig. 1, after the negative electrode is completely lithiated, there is a significant drop-off phenomenon, and the drop-off degree is the most serious.
Comparative example 2:
taking a double-layer structure cathode made of hard carbon and graphite material as an example, the method specifically comprises the following steps:
(1) Preparing hard carbon slurry, wherein the mass ratio of hard carbon in the slurry is 90%, coating the slurry on a copper foil, and drying to obtain a hard carbon layer with the thickness of 10 mu m;
(2) Preparing graphite slurry, wherein the mass ratio of graphite in the slurry is 90%, coating the graphite slurry on the surface of a hard carbon layer, and drying to obtain a double-layer structured graphite anode with the thickness of 90 mu m;
(3) And (3) completely attaching the prepared double-layer negative electrode and the metal lithium foil together, enabling the hard carbon layer to contact the lithium foil, adding a proper amount of ester electrolyte in the middle, standing for 12 hours, and observing lithiation. After the negative electrode is completely lithiated, the negative electrode may be partially exfoliated, and the degree of exfoliation may be less severe.
The present invention also uses different negative electrode materials, and similar treatment operations were performed with reference to comparative example 1, comparative example 2, and example 1, with the effects shown in table 1 below.
Note that: the effects described in the above table correspond to the negative electrode after complete lithiation.
It will be readily appreciated by those skilled in the art that the foregoing description is merely a preferred embodiment of the invention and is not intended to limit the invention, but any modifications, equivalents, improvements or alternatives falling within the spirit and principles of the invention are intended to be included within the scope of the invention.
Claims (7)
1. The fully lithiated negative electrode plate is characterized in that the fully lithiated negative electrode plate is obtained by directly lithiating a sandwich-structure negative electrode with metal lithium, wherein the sandwich-structure negative electrode is sequentially an upper layer, a middle layer and a lower layer from top to bottom, negative electrode active materials adopted by the upper layer and the lower layer are independently selected from hard carbon and lithium titanate, and negative electrode active materials adopted by the middle layer are selected from one or more of graphite, silicon-based negative electrode materials, tin-based negative electrode materials and phosphorus-based negative electrode materials.
2. The fully lithiated anode electrode of claim 1, wherein the sandwich structured anode has a ratio of thicknesses of upper, middle, and lower layers of 1: (1-12): 1.
3. the fully lithiated negative electrode pad of claim 1, wherein the metallic lithium comprises a metallic lithium sheet or foil.
4. A method of preparing a fully lithiated negative electrode sheet as claimed in any one of claims 1 to 3, comprising the steps of:
(1) Preparing a lower-layer negative electrode slurry, wherein an active material is selected from hard carbon and lithium titanate;
preparing an intermediate layer negative electrode slurry, wherein an active material is one or more selected from graphite, a silicon-based negative electrode material, a tin-based negative electrode material and a phosphorus-based negative electrode material;
preparing upper-layer negative electrode slurry, wherein an active material is selected from hard carbon and lithium titanate;
(2) Coating the lower-layer negative electrode slurry on a current collector, and drying to form a lower layer on the current collector;
(3) Continuously coating the intermediate layer negative electrode slurry on the surface of the lower layer, and drying to obtain an intermediate layer;
(4) Coating the upper layer negative electrode slurry on the surface of the middle layer continuously, and drying to obtain an upper layer, thereby forming a sandwich structure negative electrode on the current collector;
(5) Attaching the upper layer of the negative electrode with the sandwich structure with metal lithium, wherein the dosage of the metal lithium is larger than or equal to the theoretical dosage of the metal lithium required by complete lithiation of the negative electrode plate, and the attaching surface is pre-applied with lithium ion battery electrolyte; and standing for reaction after lamination, so as to obtain the fully lithiated negative electrode plate.
5. The method of manufacturing according to claim 4, wherein the lower layer anode slurry, the intermediate layer anode slurry, and the upper layer anode slurry each satisfy: the mass fraction of the active material is 90% -95%, the mass fraction of the conductive agent is 4% -6%, and the mass fraction of the binder is 1% -4%.
6. The method according to claim 5, wherein the conductive agent is at least one of ketjen black, super P, and carbon nanotubes, and the binder is a mixture of sodium carboxymethyl cellulose and styrene-butadiene rubber.
7. The method of claim 4, wherein in step (5), the lithium ion battery electrolyte comprises a solvent and a lithium salt, and the solvent is preferably one or more of ethylene carbonate, methylethyl carbonate, diethyl carbonate, propylene carbonate and dimethyl carbonate; the lithium salt is preferably lithium hexafluorophosphate.
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| CN116666561A (en) * | 2023-07-28 | 2023-08-29 | 宁德时代新能源科技股份有限公司 | Negative electrode plate, secondary battery comprising same and power utilization device |
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| CN116666561A (en) * | 2023-07-28 | 2023-08-29 | 宁德时代新能源科技股份有限公司 | Negative electrode plate, secondary battery comprising same and power utilization device |
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