CN116387509A - Composite positive electrode for lithium metal battery and preparation method thereof - Google Patents
Composite positive electrode for lithium metal battery and preparation method thereof Download PDFInfo
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- 239000002131 composite material Substances 0.000 title claims abstract description 33
- 238000002360 preparation method Methods 0.000 title abstract description 22
- 239000011230 binding agent Substances 0.000 claims abstract description 42
- 239000000843 powder Substances 0.000 claims abstract description 36
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 25
- 229910052799 carbon Inorganic materials 0.000 claims abstract description 24
- 239000002245 particle Substances 0.000 claims abstract description 24
- 239000013543 active substance Substances 0.000 claims abstract description 20
- 239000000463 material Substances 0.000 claims abstract description 18
- 229910015872 LiNi0.8Co0.1Mn0.1O2 Inorganic materials 0.000 claims abstract description 13
- 238000002156 mixing Methods 0.000 claims abstract description 12
- 239000011888 foil Substances 0.000 claims abstract description 7
- 206010016654 Fibrosis Diseases 0.000 claims abstract description 6
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- 229920001343 polytetrafluoroethylene Polymers 0.000 claims description 35
- 239000004810 polytetrafluoroethylene Substances 0.000 claims description 33
- 238000000034 method Methods 0.000 claims description 21
- 239000000853 adhesive Substances 0.000 claims description 12
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- 239000000835 fiber Substances 0.000 description 15
- 230000000052 comparative effect Effects 0.000 description 14
- 238000012360 testing method Methods 0.000 description 9
- 229910013716 LiNi Inorganic materials 0.000 description 8
- 239000007774 positive electrode material Substances 0.000 description 7
- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical compound CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 description 6
- 239000002002 slurry Substances 0.000 description 5
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 3
- 239000003792 electrolyte Substances 0.000 description 3
- 229910001416 lithium ion Inorganic materials 0.000 description 3
- 238000011068 loading method Methods 0.000 description 3
- 238000005096 rolling process Methods 0.000 description 3
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- 150000001875 compounds Chemical class 0.000 description 2
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- 238000004146 energy storage Methods 0.000 description 2
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- 239000007773 negative electrode material Substances 0.000 description 2
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- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 1
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- 229910003473 lithium bis(trifluoromethanesulfonyl)imide Inorganic materials 0.000 description 1
- QSZMZKBZAYQGRS-UHFFFAOYSA-N lithium;bis(trifluoromethylsulfonyl)azanide Chemical compound [Li+].FC(F)(F)S(=O)(=O)[N-]S(=O)(=O)C(F)(F)F QSZMZKBZAYQGRS-UHFFFAOYSA-N 0.000 description 1
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
- H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
- H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
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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
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/13—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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- 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
- H01M4/139—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
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
- H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
- H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
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- 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
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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Abstract
The invention belongs to the technical field of lithium metal batteries, and particularly relates to a composite positive electrode for a lithium metal battery and a preparation method thereof. The composite positive electrode for the lithium metal battery comprises an active substance, conductive carbon and a binder, wherein the active substance is ternary LiNi 0.8 Co 0.1 Mn 0.1 O 2 A powder; the LiNi 0.8 Co 0.1 Mn 0.1 O 2 The powder is spherical material formed by stacking small particles. The preparation method comprises the following steps: (1) pretreatment: fully grinding the active substances and the conductive carbon respectively; (2) mixing materials;(3) Fibrosis; (4) banburying; (5) open mill; and (6) compositely bonding the dry pole piece and the current collector foil. The prepared LiNi 0.8 Co 0.1 Mn 0.1 O 2 The positive electrode is applied to a lithium metal battery to realize high energy density.
Description
Technical Field
The invention belongs to the technical field of lithium metal batteries, and particularly relates to a composite positive electrode for a lithium metal battery and a preparation method thereof.
Background
Due to the increasing impact of global energy and fossil fuel demand, sustainable energy sources such as water and solar energy are attracting attention. Among them, lithium Ion Batteries (LIBs) have been widely studied due to their light weight and high energy density, and have been successfully applied to most portable electronic devices such as cellular phones, electronic watches, and digital cameras.
Although the application of lithium ion batteries has been expanded to larger areas, such as Electric Vehicles (EVs), hybrid vehicles, robots, etc., the high energy storage density (high weight and volumetric energy density) of these applications remains a significant challenge. In order to improve the performance of energy storage systems, researchers have been looking for new solutions beyond traditional lithium ion batteries.
In various alternatives, the metal lithium has very high theoretical specific capacity (up to 3860 mAh.g -1 ) And the most negative electrochemical potential (3.04V compared to standard hydrogen electrodes), is recognized as a promising negative electrode material, but a positive electrode material matched to lithium metal is mostly wet coated. The wet-process-pasted pole piece manufacturing process consumes a large amount of N-methyl-2-pyrrolidone (NMP), and the preparation cost is increased, and meanwhile, serious pollution is generated to the environment, and particularly, a recovery device is required to be established to collect and treat evaporated NMP in the subsequent recovery and reuse process.
In addition, the thickness of the pole piece prepared by the wet coating process is limited, and problems such as electrode cracks, layering, poor flexibility and the like can occur when a thick electrode is prepared, so that the carrying capacity of the positive electrode active material of the battery and the performance of the whole energy density of the battery are greatly limited.
For this reason, it is necessary to solve how to increase the energy density of the composite positive electrode for lithium metal batteries.
Disclosure of Invention
The invention aims at overcoming the defects of the prior wet coating process, and aims at reducing the extra power and chemical consumption in the electrode manufacturing processThe invention provides a composite positive electrode for a lithium metal battery and a preparation method thereof, which are convenient for recycling the lithium metal battery due to consumption of stone energy and reduce environmental pollution, and the LiNi with higher active material loading is prepared by a dry process without using any solvent 0.8 Co 0.1 Mn 0.1 O 2 The positive plate solves the problems of lower energy density and the like on the basis of maintaining the electrochemical performance of a wet process, and the secondary battery with higher energy density is obtained. The prepared LiNi 0.8 Co 0.1 Mn 0.1 O 2 The positive electrode is applied to a lithium metal battery to realize high energy density.
The specific technical scheme of the invention is as follows:
a composite positive electrode for lithium metal battery comprises an active substance, conductive carbon and a binder, wherein the active substance is ternary LiNi 0.8 Co 0.1 Mn 0.1 O 2 A powder; the LiNi 0.8 Co 0.1 Mn 0.1 O 2 The powder is spherical material formed by stacking small particles.
In the invention, the binder in the composite positive electrode for the lithium metal battery is polytetrafluoroethylene with the particle size of 10-650 mu m and the average molecular weight of 400-600 ten thousand; preferably, the particle size of the binder polytetrafluoroethylene is 600-650 μm.
The larger the particle size of the binder Polytetrafluoroethylene (PTFE), the longer the fibrillated molecular chains thereof, i.e., the higher the fiberization strength. However, a binder having an excessively large particle diameter is difficult to achieve complete fiberization, and thus a particle diameter of 600 to 650 μm is preferable.
Polytetrafluoroethylene has a large molecular mass that provides sufficient fiberizing components to achieve fiberization under sufficient shear forces and high temperatures to uniformly complex the active species with the conductive carbon and maintain good mechanical properties. The dry electrode can be prepared by successfully fiberizing the binder with the minimum content while improving the energy density of the battery.
In the invention, the binder content in the composite positive electrode for the lithium metal battery is 1-5wt%. The content of the binder is more than or equal to 1 weight percent, so that the cracking of the rolled film can be prevented; the binder content of 5wt% or less is to ensure the energy density of the battery.
In the composite positive electrode for the lithium metal battery, active substances in mass ratio are as follows: conductive carbon: the binder is 90-98:1-5:1-5.
In the invention, the conductive carbon in the composite positive electrode for the lithium metal battery is Super P.
The preparation method of the composite positive electrode for the lithium metal battery comprises the following steps:
(1) Pretreatment: fully grinding the active substances and the conductive carbon respectively; ensuring uniform and fine particle size, being convenient for rolling and forming film uniformly, and the initial powder is pretreated into powder with finer and uniform particle size.
(2) Mixing: adding the pretreated active substances, conductive carbon and binder into a mixer according to a proportion, and uniformly mixing to obtain mixed powder;
(3) Fibrosis: adding the obtained mixed powder into a high-speed dispersing machine for high-speed dispersing, wherein the high-speed dispersing machine is arranged according to the following rotating speed gradient: firstly, running for 2-3min at the rotating speed of 3000-3500 rpm; then running for 2-3min at the rotating speed of 5000-5500 rpm; finally, running at 9500-10000rpm for 10-11min; the adhesive is fibrillated by increasing the rotating speed in a gradient way, the shearing force is gradually increased, and the degree of the adhesive is also gradually increased. And (3) after each dispersing, manually stirring to observe the aggregation state of the materials, and carrying out the next step when the materials slightly show aggregation and thread pulling.
Then placing the materials after high-speed dispersion into a high-temperature oven, and heating at 200-300 ℃ for 0.5-1h to obtain fiberized powder; the high temperature heating at 200-300 ℃ further increases the degree of binder fibrosis and maintains its good fibrosis state.
The binder is fully fibrillated by high-speed dispersion and high-temperature heating, and the uniformly dispersed active substances and conductive carbon are in an agglomerated state under the winding action of the binder fiber filaments.
(4) Banburying: taking out the fiberized powder, and directly banburying for 5-6min at the temperature of more than or equal to 100 ℃ to obtain a dough-like dry material; too low banburying temperature can lead the adhesive fiber to be instantly cooled, so that brittleness of the adhesive fiber is increased, and the toughness of the pole piece is affected.
(5) Open mill: firstly, using an open mill to open-mill a dough-shaped dry material into a membrane; and then thinning the open-smelting membrane by using a horizontal roller press to obtain the dry pole piece. The dry pole piece has good toughness, the thickness of the rolled diaphragm is controllable by adjusting the spacing of the rollers, and the cracking phenomenon is avoided.
(6) And (3) bonding the dry pole piece and the current collector foil in a composite manner: mixing conductive adhesive and Super P according to a certain proportion, stirring to obtain bonding conductive paste, uniformly coating the bonding conductive paste on the foil by using an extrusion coater, and then covering the dry pole piece for drying.
In the invention, in the step (1) of the preparation method, grinding is carried out by adopting an air flow mill; the feeding pressure is 0.3-0.4MPa, and the crushing pressure is 0.2-0.3MPa.
In the invention, in the step (2) of the preparation method, a planetary mixer is adopted for mixing, the rotation speed of the mixer is 450-500rmp, and the mixing time is 30-35min.
In the invention, in the step (6) of the preparation method, the conductive adhesive is: the mass ratio of Super P is 99:1.
in the invention, the viscosity of the bonding conductive paste in the step (6) of the preparation method is 4000-4500 pa.s; the coating thickness of the bonding conductive paste is 100-120 μm.
The composite electrode for the lithium metal battery or the composite positive electrode for the lithium metal battery prepared by the preparation method is adopted in the lithium metal battery, and the energy density of the battery is more than or equal to 300Wh/kg.
The beneficial effects of the invention are as follows: the composite positive electrode for the lithium metal battery comprises an active substance ternary LiNi 0.8 Co 0.1 Mn 0.1 O 2 Powder, conductive carbon and binder. The content of the active substances directly influences the energy density of the battery, the conductive carbon influences the conductive performance of the dry pole piece, and the adhesive determines whether the dry pole piece can form a film smoothly.
The preparation method provided by the invention does not have the processes of pulling slurry and drying from powder to an electrode, but does not need to fiberize the powder and a binder material, then press the powder into a film, compound the film with a current collector coated with back glue, and introduce no liquid substance in the whole process, namely, no solvent in the pole piece preparation process, isolate and control the introduction of impurities, so that the formed film has high compaction density, can maximally require the thickness of the film and has high compound strength with the current collector.
Drawings
Fig. 1 is a flow chart of the dry process according to the invention.
FIG. 2 shows the LiNi of the present invention 0.8 Co 0.1 Mn 0.1 O 2 SEM pictures of positive electrode powder.
FIG. 3 is a composite positive electrode material of the present invention that is fully fibrillated after high temperature banburying.
FIG. 4 shows the LiNi prepared by the present invention 0.8 Co 0.1 Mn 0.1 O 2 Dry pole piece pattern. Wherein the surface wrinkles are generated for a fold-over test.
FIG. 5 is a graph of the pole piece cracked at the end of the roll pressing in comparative examples 3-5.
Fig. 6 is an energy density diagram of dry positive electrode and lithium metal assembled battery obtained in examples 1 to 4 and comparative example 1.
Detailed Description
The invention is directed to LiNi 0.8 Co 0.1 Mn 0.1 O 2 The positive electrode material researches the film forming effect of polytetrafluoroethylene with different particle sizes and different proportions under the same technological process, and performs performance test on the prepared dry electrode. The technical scheme of the invention is described in detail below with reference to the accompanying drawings.
1. The electrolyte is an ester electrolyte, preferably LiTFSI: EC: DMC: FEC=1:1:1, and the electrolyte dosage is determined according to the positive electrode active material loading, and the loading is in the range of 30-100 mu L under the condition of 5-40 mg.
2. The battery cathode uses a commercial lithium metal pole piece with the diameter of 16mm and the thickness of 450 mu m, and inert oxides possibly existing on the surface are removed before the battery cathode is used.
3. As the separator, a porous polymer separator, preferably a Celgard separator having a diameter of 18mm, is used. The battery assembly is carried out entirely in a glove box filled with inert gas.
4. And (3) testing the charge and discharge of the lithium metal battery: and (3) sequentially assembling and sealing a dry positive electrode material, a diaphragm and a lithium metal negative electrode which are compounded with a current collector by using a CR2032 battery shell to form a button battery, and carrying out charge and discharge test on the button battery in an incubator according to the requirements of national standard GB/T31484.
Example 1
The preparation method of the composite positive electrode for the lithium metal battery comprises the following steps:
(1) Pretreatment: liNi is added to 0.8 Co 0.1 Mn 0.1 O 2 Super P pulverizes particles by airflow, the feeding pressure is 0.4MPa, the pulverizing pressure is 0.2MPa, and the original powder can be sufficiently ground by the larger pulverizing pressure, so that the film forming uniformity is facilitated.
(2) Mixing: the powder material after air flow grinding is processed according to LiNi 0.8 Co 0.1 Mn 0.1 O 2 : super P: ptfe=90: 5:5, the mixture is added into a planetary mixer in proportion, the rotating speed is 500rmp, the mixing time is 30min, and the mixture is repeated for two to three times according to the material dispersion condition, wherein the particle size of PTFE is 600 mu m.
(3) Fibrosis: adding the mixed powder into a high-speed dispersing machine, starting a water cooling machine, and setting the rotating speed of the high-speed dispersing machine according to the gradient. This step was repeated two to three times, and after each dispersion was completed, manual stirring was performed using a spatula until the powder slightly appeared to be stringy agglomerated. The powder in this state was then transferred to a high temperature oven set at 230℃and heated for 1h, waiting for complete fiberization.
(4) Banburying: taking out the powder heated at high temperature, continuously kneading and banburying the powder by using a 200 ℃ banbury mixer when the powder is not completely cooled, and continuously banburying the PTFE fiber at higher temperature to ensure that the PTFE fiber can completely and effectively wrap the mixed materials such as anode powder, conductive carbon and the like, and forming the mixed powder into the aggregates with different sizes after the banburying is finished for 5min.
(5) Open mill: heating two rollers of an open mill to 230 ℃, adjusting the roller spacing to 500um by using a feeler gauge, and compounding scattered materials with different sizes into a dry film by the open mill. The temperature of the counter roller cannot be too low, and the physical properties of the ternary positive electrode material and the graphite negative electrode material are different, so that a higher temperature is required to keep the PTFE fiber state, the counter fiber state can be generated due to the too low temperature, and the rolled pole piece can be in a broken and cracked state.
After the open mill film forming, the pole piece is cut into a regular shape, the pole piece passes through a horizontal roller press, the distance between two rollers of the horizontal roller press is gradually reduced, and the dry pole piece with controllable thickness is obtained according to actual requirements. As shown in fig. 4.
(6) And (3) bonding the dry pole piece and the current collector foil in a composite manner: the conductive adhesive slurry is prepared by using a small planetary four-paddle stirrer, and the conductive adhesive and Super P are prepared according to the following steps of 99:1, and 300rmp for 30min, the resulting slurry viscosity was about 4000 pa.s. The slurry is added into a feed bin of an extrusion coater, the coating thickness is 100 mu m, the coating start and stop positions, the feeding speed is 3mm/s, and the coating speed is 15mm/s, so that the slurry is uniformly coated on a foil, and the dry pole piece is covered on the conductive adhesive and stands for infrared drying.
The process steps of the preparation method are shown in figure 1.
As can be seen from fig. 2, active material LiNi 0.8 Co 0.1 Mn 0.1 O 2 The spherical material formed by stacking small particles can increase the contact area of the active substance and polytetrafluoroethylene fiber, and the polytetrafluoroethylene fiber has more excellent coating property on the active substance and is beneficial to dry film forming.
As can be seen from fig. 3, the active material and the conductive agent are completely interwoven with the binder fiber yarn and slightly have a dough shape after high-temperature banburying, so that the subsequent open mill rolling is facilitated.
Example 2
Electrodes were prepared and battery tests were performed using the method of example 1, except that the dry electrode preparation procedure LiNi in this example 0.8 Co 0.1 Mn 0.1 O 2 The corresponding proportions of Super P, PTFE are 93:3:4, the particle size of the PTFE powder was 600. Mu.m, which remained unchanged.
Example 3
Electrodes were prepared and electrically conducted by the method of example 1Cell testing, except for the dry electrode preparation process LiNi in this example 0.8 Co 0.1 Mn 0.1 O 2 The corresponding ratio of Super P to PTFE is 95:2: the particle size of the PTFE powder was 600. Mu.m, which remained unchanged.
Example 4
Electrodes were prepared and battery tests were performed using the method of example 1, except that the dry electrode preparation procedure LiNi in this example 0.8 Co 0.1 Mn 0.1 O 2 The corresponding proportions of Super P, PTFE are 97:1:2, the particle size of the PTFE powder was 600. Mu.m, which remained unchanged.
Comparative example 1
The foregoing mentions that the energy density of the battery is increased, and the content of the binder may not be more than 5%. To demonstrate this, electrodes were prepared and battery tests were performed using the method of example 1, except that in this comparative example, the dry electrode preparation process LiNi 0.8 Co 0.1 Mn 0.1 O 2 The corresponding proportions of Super P, PTFE are 80:10:10 the particle size of the PTFE powder was 600. Mu.m, which remained unchanged.
Examples 1 to 4 and comparative example 1 each had a complete film forming ability when the content of the binder was 2% or more and dry pole pieces of the same thickness could be produced, but as shown in fig. 6, the energy density of the battery gradually decreased as the content of the PTFE binder increased. Therefore, in order to prepare the battery pole piece with high energy density, the percentage content of active substances needs to be increased as much as possible, and the content of the binder and the conductive carbon only needs to meet the minimum requirements of the conductivity and the film forming property of the pole piece. For the wearable flexible battery, the content of the binder needs to be increased on the basis of the minimum PTFE consumption so as to ensure the flexibility of the pole piece.
Comparative example 2
Electrodes were prepared and battery tests were performed using the method of example 1, except that the dry electrode preparation procedure LiNi in this example 0.8 Co 0.1 Mn 0.1 O 2 The corresponding proportions of Super P, PTFE are 99:0.5:0.5, the particle size of the PTFE powder remains unchanged at 600. Mu.m.
The final film formation of the different PTFE powder contents was compared with the same process parameters, and it was found that the 0.5% binder content in this comparative example was not normally film-forming, and the active material remained in a loose powder form even after the end of banburying, and no fibrous state was observed. This is due to the limited amount of fiber produced by the low binder content and the inability to crosslink coat large amounts of active material and conductive carbon.
The above LiNi is used below 0.8 Co 0.1 Mn 0.1 O 2 Super P, ptfe=97: 1:2, the influence of PTFE binders with different particle sizes on dry film formation was investigated.
Comparative example 3
An electrode was prepared and tested for a battery using the method of example 4, with a ratio of active material, conductive carbon, and binder of 97:1:2. in the present example, a 10 μm PTFE powder was used as the binder.
Comparative example 4
An electrode was prepared and tested for a battery using the method of example 4, with a ratio of active material, conductive carbon, and binder of 97:1:2. in this comparative example, a 50 μm PTFE powder was used as the binder.
Comparative example 5
An electrode was prepared and tested for a battery using the method of example 4, with a ratio of active material, conductive carbon, and binder of 97:1:2. in this comparative example, a 100 μm PTFE powder was used as the binder.
Comparative example 6
An electrode was prepared and tested for a battery using the method of example 4, with a ratio of active material, conductive carbon, and binder of 97:1:2. in the present comparative example, a 300 μm PTFE powder was used as the binder.
Dry pole pieces were prepared using PTFE of different particle sizes, and it was found that no film was formed using PTFE binders of particle size 100 μm or less, and the active material was dried and disintegrated by rolling, as shown in fig. 5. This is attributed to the fact that the small particle size binder forms shorter fiber chains, which cannot be fully cross-linked coated at higher active substance levels.
The adhesive with the particle size of 300 μm can form a film but is broken after a folding test, and has poor mechanical properties. The fiber chain of the binder can crosslink and coat the active substance and the conductive carbon, but the fiber has poor flexibility due to limited chain length and weak toughness of fiber filaments, and the requirement cannot be met.
Claims (10)
1. The composite positive electrode for the lithium metal battery is characterized by comprising an active substance, conductive carbon and a binder, wherein the active substance is ternary LiNi 0.8 Co 0.1 Mn 0.1 O 2 A powder; the LiNi 0.8 Co 0.1 Mn 0.1 O 2 The powder is spherical material formed by stacking small particles.
2. The composite positive electrode for lithium metal battery according to claim 1, wherein the binder is polytetrafluoroethylene having a particle diameter of 10 μm to 650 μm and an average molecular weight of 400 to 600 tens of thousands.
3. The composite positive electrode for a lithium metal battery according to claim 1, wherein the binder content is 1 to 5wt%.
4. The composite positive electrode for lithium metal battery according to claim 1, wherein the active material is as follows in mass ratio: conductive carbon: the binder is 90-98:1-5:1-5.
5. The composite positive electrode for a lithium metal battery according to claim 1, wherein the conductive carbon is Super P.
6. A method for preparing a composite positive electrode for a lithium metal battery according to any one of claims 1 to 5, comprising the steps of:
(1) Pretreatment: fully grinding the active substances and the conductive carbon respectively;
(2) Mixing: adding the pretreated active substances, conductive carbon and binder into a mixer according to a proportion, and uniformly mixing to obtain mixed powder;
(3) Fibrosis: firstly, adding the obtained mixed powder into a high-speed dispersing machine for high-speed dispersing, wherein the high-speed dispersing machine is arranged according to the following rotating speed gradient: firstly, running for 2-3min at the rotating speed of 3000-3500 rpm; then running for 2-3min at the rotating speed of 5000-5500 rpm; finally, running at 9500-10000rpm for 10-11min;
then placing the materials after high-speed dispersion into a high-temperature oven, and heating at 200-300 ℃ for 0.5-1h to obtain fiberized powder;
(4) Banburying: taking out the fiberized powder, and directly banburying for 5-6min at the temperature of more than or equal to 100 ℃ to obtain a dough-like dry material;
(5) Open mill: firstly, using an open mill to open-mill a dough-shaped dry material into a membrane; then, thinning the open mill diaphragm by using a horizontal roller press to obtain a dry pole piece;
(6) And (3) bonding the dry pole piece and the current collector foil in a composite manner: mixing conductive adhesive and Super P according to a proportion, stirring to prepare bonding conductive paste, uniformly coating the bonding conductive paste on a foil by using an extrusion coater, and then covering a dry pole piece for drying to obtain the composite anode.
7. The method for producing a composite positive electrode for a lithium metal battery according to claim 6, wherein the grinding is performed by an air flow mill in the step (1); the feeding pressure is 0.3-0.4MPa, and the crushing pressure is 0.2-0.3MPa.
8. The method for preparing a composite positive electrode for a lithium metal battery according to claim 6, wherein the step (2) is performed by adopting a planetary mixer, the rotation speed of the mixer is 450-500rmp, and the mixing time is 30-35min.
9. The method of manufacturing a composite positive electrode for a lithium metal battery according to claim 6, wherein the conductive paste in step (6): the mass ratio of Super P is 99:1, a step of; the viscosity of the obtained bonding conductive paste is 4000-4500 pa.s; the coating thickness of the bonding conductive paste is 100-120 μm.
10. A lithium metal battery characterized in that a composite electrode for a lithium metal battery according to any one of claims 1 to 5 or a composite positive electrode for a lithium metal battery produced by the production method according to any one of claims 6 to 9 is used; the energy density of the lithium metal battery is more than or equal to 300Wh/kg.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN117199261A (en) * | 2023-09-12 | 2023-12-08 | 深圳市贝特瑞新能源技术研究院有限公司 | Dry pole piece, preparation method thereof and secondary battery |
| CN117393704A (en) * | 2023-12-12 | 2024-01-12 | 山东东岳高分子材料有限公司 | Preparation method of dry pole piece |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN117199261A (en) * | 2023-09-12 | 2023-12-08 | 深圳市贝特瑞新能源技术研究院有限公司 | Dry pole piece, preparation method thereof and secondary battery |
| CN117393704A (en) * | 2023-12-12 | 2024-01-12 | 山东东岳高分子材料有限公司 | Preparation method of dry pole piece |
| CN117393704B (en) * | 2023-12-12 | 2024-04-16 | 山东东岳高分子材料有限公司 | Preparation method of dry pole piece |
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