CN114335554B - Lithium metal battery and application thereof - Google Patents
Lithium metal battery and application thereof Download PDFInfo
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- CN114335554B CN114335554B CN202210254732.8A CN202210254732A CN114335554B CN 114335554 B CN114335554 B CN 114335554B CN 202210254732 A CN202210254732 A CN 202210254732A CN 114335554 B CN114335554 B CN 114335554B
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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
- H01M4/136—Electrodes based on inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy
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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
- H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
- H01M2004/027—Negative electrodes
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- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
Abstract
The application discloses lithium metal battery, lithium metal battery includes positive pole, negative pole, barrier film and electrolyte, the negative pole includes composite construction, composite construction include the skeleton with lithium nitrate on the skeleton, the skeleton is three-dimensional porous structure or two-dimensional structure, composite construction's thickness is 25 mu m ~200 mu m. This application forms the composite construction who is applied to lithium metal battery negative pole on compounding lithium nitrate to two-dimensional structure or three-dimensional porous structure, the slow release function of lithium nitrate has been realized, make the lithium nitrate concentration in the electrolyte keep the saturated condition, lithium nitrate can increase the stability of SEI membrane in cycle process, slow down the consumption of lithium metal, reduce the side reaction of lithium metal and electrolyte, reduce the formation of lithium dendrite, thereby improve lithium metal battery's cyclicity performance and expansibility, promote lithium metal battery's coulomb efficiency.
Description
Technical Field
The application belongs to the technical field of lithium metal batteries, and particularly relates to a composite structure, and further relates to application of the composite structure in a lithium metal battery, and application of the lithium metal battery in an electronic device.
Background
The lithium metal battery has the advantages of high energy density, high working voltage, low self-discharge rate, small volume, light weight and the like, and has wide application in the field of consumer electronics. Currently, with the rapid development of electric vehicles and mobile electronic devices, there are increasingly high demands for energy density, safety, and cycle performance of lithium metal batteries.
Lithium metal has the smallest relative atomic mass and the lowest standard electrode potential among all metal elements, and simultaneously has higher theoretical specific capacity and mass specific energy. Therefore, the lithium metal is directly applied to the negative electrode, and the energy density and the working voltage of the battery can be greatly improved. However, when the lithium metal is directly applied to a negative electrode, there are problems that the lithium metal has high activity and is liable to undergo a side reaction with an electrolyte, formation of "dendrite" and "dead lithium" is liable to occur, and an electrode structure is broken due to infinite volume change, which causes a reduction in capacity, expansion performance, cycle performance, and the like of a battery.
Disclosure of Invention
In order to overcome the defects in the prior art, the lithium metal battery and the application thereof are provided. The negative pole of the lithium metal battery comprises a composite structure, the composite structure can continuously and slowly release lithium nitrate, the dissolving concentration of the lithium nitrate in electrolyte can be kept in a saturated state, the lithium nitrate can continuously play a role in the circulating process, the consumption of lithium metal is reduced, the occurrence of side reactions is reduced, and the capacity keeping, volume expansion and circulating performance of the lithium metal battery are improved.
In order to achieve the purpose, the technical scheme adopted by the application is as follows:
the lithium metal battery comprises a positive electrode, a negative electrode, an isolating membrane and electrolyte, and is characterized in that the negative electrode comprises a composite structure, the composite structure comprises a framework and lithium nitrate on the framework, the framework is of a three-dimensional porous structure or a two-dimensional structure, and the thickness of the composite structure is 25-200 mu m.
When the negative electrode in the lithium metal battery comprises the composite structure, lithium nitrate can generate an in-situ Solid Electrolyte Interface (SEI) layer on the surface of lithium metal to prevent the electrolyte from further contacting with the lithium metal to generate side reaction, and the lithium nitrate can generate Li on the surface of the lithium metal3N and LiNxOyThe method has the effects of repairing and stabilizing the SEI layer, improving the ionic conductivity and mechanical properties of the SEI layer, accelerating the transmission of lithium ions in the SEI layer, slowing down the side reaction in the battery, improving the expansion performance and cycle performance of the lithium metal battery and improving the coulombic efficiency of the lithium metal battery.
The inventor finds in experimental studies that the thickness has an influence on the use effect of the composite structure. When the thickness of the composite structure is 25-200 mu m, the cycle performance, the expansion performance and the capacity retention rate of the lithium metal battery can be improved. When the thickness of the framework is too low, the framework cannot accommodate the deposited lithium, the lithium metal is partially deposited on the surface of the framework, and the framework cannot limit the volume expansion; when the thickness of the skeleton is excessively large, the overall energy density of the lithium metal battery may be reduced. More preferably, the thickness of the composite structure is 45-80 μm, and the composite structure has a better effect of improving the expansion performance and the cycle performance of the lithium metal battery.
In some embodiments, the framework is a three-dimensional porous structure built by fibers, and the lithium nitrate is loaded in the framework and/or on the surface of the framework.
Preferably, the lithium nitrate is loaded inside and on the surface of the fiber building the three-dimensional porous structure in an in-situ addition mode.
Preferably, the lithium nitrate is loaded on the surface of the three-dimensional porous structure in a manner of ectopic addition.
In other embodiments, the matrix is a two-dimensional structure, and the lithium nitrate is supported on the surface of the matrix.
Preferably, the two-dimensional structure comprises a lithium foil. Lithium nitrate is deposited on the surface of the lithium foil, so that the lithium nitrate can be slowly released in the battery circulation process, an SEI layer is generated on the surface of lithium metal, the electrolyte is prevented from further contacting with the lithium metal to generate side reaction, the consumption of the lithium metal is reduced, and the coulombic efficiency, the expansion performance and the cycle performance of the lithium metal battery are improved.
Preferably, the lithium nitrate is supported on the surface of the two-dimensional structure by means of ex-situ addition.
In the application, the in-situ addition mode comprises the steps of adding lithium nitrate into precursor liquid for preparing the framework to obtain a composite structure loaded with the lithium nitrate; the ectopic addition mode comprises the step of soaking the framework in a solution containing lithium nitrate to obtain a lithium nitrate-loaded composite structure.
The performance of the lithium metal battery can be improved by adopting the in-situ addition or the ex-situ addition in the three-dimensional porous structure, but compared with the ex-situ addition, the in-situ addition can wrap part of lithium nitrate in fibers for building the three-dimensional porous structure, so that the slow release effect of the lithium nitrate is better, and therefore the three-dimensional porous structure is more preferably loaded with the lithium nitrate by adopting the in-situ addition.
Compared with a two-dimensional structure, when the three-dimensional porous structure is adopted as the framework of the composite structure, the load of lithium nitrate can be more effectively controlled, the deposition of lithium metal can be better improved, the generation of lithium dendrites can be reduced, and the lithium metal battery has better cycle performance and expansion performance and higher coulombic efficiency.
Lithium nitrate in this application also can replace other electrolyte additives, for example one or more in lithium perchlorate, lithium tetrafluoroborate, lithium difluoro oxalate borate or two lithium oxalate borates, the mode of proposing in the usable this scheme is through normal position addition or dystopy addition mode, add to composite construction in, make in the circulation process of lithium metal battery, realize the continuous slowly-releasing of above-mentioned electrolyte additive, improve the deposit of lithium metal and the production of lithium dendrite, promote the cycle performance and the expansibility of lithium metal battery, and improve its coulomb efficiency.
Preferably, the porosity of the three-dimensional porous structure is 5% -90%, more preferably 40% -90%.
Preferably, the average pore size of the three-dimensional porous structure is 100 nm-4 μm, and more preferably 200 nm-2 μm.
Preferably, the three-dimensional porous structure is built by fibers. The three-dimensional porous structure can be built by adopting electrostatic spinning or 3D printing. The three-dimensional skeleton built by the fibers has low tortuosity and large aperture, and has larger space for accommodating lithium metal. In the process of charging lithium deposition, the framework can contain lithium metal and keep structural stability, and when the lithium metal is continuously removed in the discharging process, the framework can have higher mechanical strength, so that the negative electrode can not be subjected to severe expansion or contraction, and the expansion rate is reduced.
Further, the preparation material of the fiber comprises a conductive material or an insulating material.
Preferably, the preparation material of the fiber comprises at least one of a high molecular material and an inorganic material.
Wherein, the high molecular material can comprise at least one of polyvinylidene fluoride, polyimide, polyamide, polyacrylonitrile, polyethylene glycol, polyphenyl ether, polypropylene carbonate, polymethyl methacrylate, polyethylene terephthalate, polyethylene oxide, polyvinylidene fluoride-hexafluoropropylene and polyvinylidene fluoride-chlorotrifluoroethylene.
The inorganic material may include at least one of sodium silicate and derivatives thereof, alumina and derivatives thereof, silica and derivatives thereof, and carbon-based materials; the carbon-based material can comprise at least one of solid carbon spheres, hollow carbon spheres, porous carbon, single-layer carbon nanotubes, multi-layer carbon nanotubes, pure carbon fibers, doped carbon fibers (including oxide, sulfide, carbide, nitride, metal or functional group doping), graphene cages and derivatives thereof, doped graphene and derivatives thereof, wherein the diameters of all the carbon spheres can be 100 nm-200 mu m, the diameter of the tubular or fibrous carbon-based material can be 50 nm-50 mu m, the length of the tubular or fibrous carbon-based material can be any length, and the fibers can be solid or hollow.
More preferably, the fiber is made of a material selected from lithium ion conductor materials, such as at least one of polyvinylidene fluoride-hexafluoropropylene, polyvinylidene fluoride, polyacrylonitrile, polymethyl methacrylate, polyphenylene oxide, polypropylene carbonate, and polyethylene oxide.
Preferably, the composite structure is applied to a negative electrode of a lithium metal battery, and lithium can be supplemented to the composite structure in advance; the lithium can be supplemented in advance by one of cold pressing, hot pressing, electrochemical lithium supplementation and physical vapor deposition; the composite structure may be pre-lithiated using lithium metal powder.
In some embodiments, when the framework is a lithium foil, the negative electrode of the lithium metal battery may be composed of the composite structure and a negative electrode current collector. And when the backbone is in other cases described herein, the negative electrode of the lithium metal battery is composed of the composite structure, a lithium metal layer (e.g., lithium foil), and a negative electrode current collector. The negative current collector can adopt a copper foil, a nickel foil or a carbon-based current collector.
Preferably, the loading amount of the lithium nitrate is 1-99% of the weight of the composite structure.
Preferably, the loading amount of the lithium nitrate is 5-30% of the weight of the composite structure.
The loading capacity of the lithium nitrate in the composite structure can influence the slow release effect of the lithium nitrate in the electrolyte. Along with the reaction in the battery, the lithium nitrate is continuously consumed, and if the deposition amount of the lithium nitrate is too small, the lithium nitrate cannot be timely supplemented and dissolved into the electrolyte, so that the concentration of the lithium nitrate in the electrolyte is reduced, and the cycle and expansion performance of the lithium metal battery are influenced; however, if the deposition amount of lithium nitrate is too large, the concentration of lithium nitrate slowly released into the electrolyte is too high, and the resistance increases, thereby affecting the cycle performance of the battery. When the loading capacity of the lithium nitrate accounts for 1-99% of the weight of the composite structure, particularly 5-30% of the weight of the composite structure, the cycle performance of the lithium metal battery can be obviously improved, the side reaction of lithium metal and electrolyte can be reduced, the expansion performance of the lithium metal battery can be improved, and the coulombic efficiency of the lithium metal battery can be improved.
In the present application, the positive electrode, the separator, and the electrolyte of the lithium metal battery may be conventionally provided.
The positive electrode generally includes a current collector and a positive active material layer disposed on the current collector. The positive active material includes a compound that reversibly intercalates and deintercalates lithium ions. For example, the positive active material may be at least one selected from lithium cobaltate, lithium manganate, lithium iron phosphate, lithium iron manganese phosphate, lithium nickel cobalt manganate, lithium nickel cobalt aluminate, and lithium nickel manganate. The positive electrode active material may be subjected to doping and/or coating treatment; for example, the coating element used for the coating layer may be at least one selected from K, Na, Ca, Mg, B, Al, Co, Si, V, Ga, Sn, and Zr.
In some embodiments, the positive electrode active material layer further includes a binder and a conductive agent. For example, the binder may be selected from at least one of polyvinylidene fluoride, copolymers of vinylidene fluoride and hexafluoropropylene, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, styrene-acrylate copolymer, styrene-butadiene copolymer, polyamide, sodium carboxymethylcellulose, polyvinyl acetate, polyvinylpyrrolidone, polyvinyl ether, polytetrafluoroethylene, polyhexafluoropropylene, and polymethyl methacrylate. The conductive agent may be at least one selected from conductive carbon black, acetylene black, ketjen black, flake graphite, graphene, carbon nanotubes, and carbon fibers.
The isolating membrane is a membrane arranged between the anode and the cathode of the lithium metal battery and mainly plays a role in isolating to prevent short circuit. The release film includes a base material layer and a surface treatment layer. Examples of the inventionThe preparation material of the substrate layer can be at least one selected from polyethylene, polypropylene, polyethylene terephthalate, polyimide and aramid. Illustratively, the polyethylene may be selected from at least one of high density polyethylene, low density polyethylene, or ultra high molecular weight polyethylene. The surface treatment layer is mainly used for improving the heat resistance, the oxidation resistance or the electrolyte infiltration performance and the like of the isolating membrane and enhancing the adhesion between the isolating membrane and the pole piece. The surface treatment layer is typically disposed on at least one surface of the substrate layer, and may be an inorganic layer or a polymeric layer. The inorganic layer generally includes inorganic particles, which may be selected from, for example, alumina (Al), and a binder2O3) Silicon oxide (SiO)2) Magnesium oxide (MgO), titanium oxide (TiO)2) Hafnium oxide (HfO)2) Tin oxide (SnO)2) Cerium oxide (CeO)2) Nickel oxide (NiO), zinc oxide (ZnO), calcium oxide (CaO), zirconium oxide (ZrO)2) Yttrium oxide (Y)2O3) The binder may be at least one selected from polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, sodium carboxymethylcellulose, polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene, and polyhexafluoropropylene. The polymer material in the polymer layer may be selected from at least one of polyacrylonitrile, polyacrylate, polyamide, polyvinylidene fluoride, and polyvinylpyrrolidone.
The solvent of the electrolyte adopts an organic solvent, and the organic solvent comprises a carbonate solvent, a carboxylic ester solvent, an ether solvent or a sulfone solvent and the like. Illustratively, the carbonate-based solvent may be selected from dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, dipropyl carbonate, ethylene carbonate, propylene carbonate, or the like. The carboxylic ester solvent may be selected from gamma-butyrolactone, ethyl formate, ethyl acetate, propyl formate, valerolactone, or the like. The ether solvent may be selected from dioxolane, tetrahydrofuran, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, 1, 4-dioxane, 1, 3-dioxane, etc. The sulfone solvent may be selected from sulfolane, dimethyl sulfoxide, methyl sulfolane, etc. The solvent of the electrolyte may be selected from other organic solvents such as 1, 3-dimethyl-2-imidazolidinone, N-methyl-2-pyrrolidone, formamide, dimethylformamide, acetonitrile, trimethyl phosphate, triethyl phosphate, trioctyl phosphate, and phosphate.
The lithium salt for preparing the electrolyte may be selected from lithium hexafluorophosphate (LiPF)6) Lithium bis (oxalato) borate (LiB (C)2O4)2LiBOB), lithium difluorooxalato borate (LiBF)2(C2O4) LiDFOB), lithium tetrafluoroborate (LiBF)4) Lithium hexafluoroantimonate (LiSbF)6) Lithium hexafluoroarsenate (LiAsF)6) Lithium perfluorobutylsulfonate (LiC)4F9SO3) Lithium perchlorate (LiClO)4) Lithium aluminate (LiAlO)2) Lithium aluminum tetrachloride (LiAlCl)4) Lithium bis (sulfonimide) (LiN (C)xF2x+1SO2)(CyF2y+1SO2) Wherein x and y are natural numbers), LiFSI (lithium bis (fluorosulfonyl) imide), LiTFSI (lithium bis (trifluoromethanesulfonic) imide), lithium chloride (LiCl), lithium fluoride (LiF). Illustratively, the concentration of the lithium salt in the electrolyte is 0.5-5 mol/L.
The lithium metal battery can be prepared according to the conventional method, and can be made into a button lithium metal battery or a soft package lithium metal battery. The soft package lithium metal battery is prepared by sequentially stacking a positive electrode, an isolating film and a negative electrode, enabling the isolating film to be positioned between the positive electrode and the negative electrode, stacking to obtain a bare cell, welding a tab, packaging the bare cell with an aluminum plastic film, injecting electrolyte, performing vacuum packaging, standing and shaping, and thus obtaining the soft package lithium metal battery.
The application also provides an electronic device which comprises the lithium metal battery. Exemplary, the electronic devices include, but are not limited to: a notebook computer, a portable phone, a portable facsimile machine, a portable copier, a portable printer, a liquid crystal television, a portable CD machine, a portable cleaner, a headphone, a mobile computer, a calculator, a memory card, a motor, an automobile, a motorcycle, a game machine, an electric power tool, a camera, or the like.
Compared with the prior art, the beneficial effect of this application is: according to the lithium metal battery cathode, the lithium nitrate is added to the framework to form the composite structure applied to the lithium metal battery cathode, the slow release function of the lithium nitrate is realized, the concentration of the lithium nitrate in the electrolyte is kept in a saturated state, the circulation and expansion of the lithium metal battery are improved, and the coulomb efficiency of the lithium metal battery is improved. The sustained release of the lithium nitrate can also repair an SEI film in the circulation process, increase the stability of the SEI film, slow down the consumption of lithium metal, reduce the side reaction of the lithium metal and electrolyte, the formation of lithium dendrites and dead lithium, better improve the expansion and contraction of the volume of a pole piece, and improve the circulation performance and the coulombic efficiency of the lithium metal battery.
Drawings
FIG. 1 is a schematic structural view of a three-dimensional porous structure described herein;
FIG. 2 is an SEM image of a three-dimensional porous structure (comparative example 3) not loaded with lithium nitrate;
FIG. 3 is an SEM image of a three-dimensional porous structure (example 1) loaded with lithium nitrate in situ;
fig. 4 is an SEM image of a three-dimensional porous structure ex-situ supported with lithium nitrate (example 7).
Detailed Description
The technical solutions of the present application will be further described with reference to the accompanying drawings and embodiments, and it is obvious that the described embodiments are only a part of the embodiments of the present application, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application. The reagents and raw materials used in the examples and comparative examples were all commercially available, and the same species was used in the parallel experiments.
In the present application, the average pore size and porosity of the three-dimensional porous structure are measured as follows:
1. average pore diameter
The capillary flow analyzer is used for testing, and the specific testing steps are as follows:
wetting and filling the pore channel of the sample completely by using wetting liquid, and forming positive pressure in the pore channel due to capillary phenomenon;
secondly, putting the sample into a closed groove, pressurizing by gas pressure to extrude liquid out of a capillary channel;
thirdly, according to the relative relation between the pressure applied when the liquid in the single pore channel is completely extruded from the inside of the capillary channel and the diameter of the pore channel, the average pore diameter of the sample can be obtained according to the Laplace equation.
The test conditions were: the capillary flow analyzer Porolux 1000, the wetting liquid with surface tension of 15.9mN/m and pressure of 3.5 MPa.
2. Porosity of the material
Adopting a liquid absorption method: cutting a three-dimensional structure sample with a proper area and recording the mass of the three-dimensional structure sample as mu0(in g), completely soaking the sample in absolute ethyl alcohol for a period of time, then quickly taking out, lightly rubbing the absolute ethyl alcohol on the surface of the sample by using filter paper, and weighing and recording the mass of the sample to be mu (in g). The porosity of the composite structure is calculated according to the following formula:
porosity P =
100% of rho (unit: kg/m)3) Is the density, rho, of the fibrous material in the composite structure0Is the density of absolute ethyl alcohol (unit is kg/m)3）
Example 1
(1) Preparation of composite structures
Adding 0.022g of lithium nitrate into 20mL of N, N-dimethylformamide, stirring and dissolving, then adding 2.2g of PVDF, and stirring for 12 hours at 40 ℃ until the solution is in a uniform and clear state; and transferring the solution into a needle cylinder for electrostatic spinning to prepare a lithium nitrate-loaded three-dimensional porous structure, namely a composite structure. Parameters of the electrostatic spinning process: the negative pressure is-4 kV, the positive pressure is 18 kV, the liquid inlet speed is 0.3mL/h, and the distance between the collecting plate and the needle head is 15 cm-20 cm; the collecting drum was rotated at 2000 rpm. And standing the composite structure prepared by spinning for 24 hours at normal temperature and normal humidity, and transferring the composite structure to a vacuum drying oven to be dried for 12 hours at 80 ℃ for later use.
The composite structure had a thickness of 60 μm, a porosity of 85% and an average pore size of 800 nm.
And (3) supplementing lithium to the prepared composite structure by a cold pressing mode, wherein the thickness of a lithium supplementing layer is 20 micrometers.
(2) Preparation of negative pole piece
And (3) stacking the pre-lithium-supplemented composite structure, the lithium foil and the copper foil current collector in sequence, cold-pressing, and punching into a wafer with the diameter of 18mm for later use. Wherein the thickness of the composite structure is 60 μm, the thickness of the lithium foil is 20 μm, and the thickness of the copper foil current collector is 12 μm.
(3) Preparation of positive pole piece
Lithium iron phosphate (LiFePO) as a positive electrode active material4) Mixing conductive carbon black (Super P) and PVDF according to the weight ratio of 97.5:1.0:1.5, adding N-methylpyrrolidone (NMP) as a solvent, blending into slurry with the solid content of 75%, and uniformly stirring. And uniformly coating the slurry on an aluminum foil of the positive current collector, and drying at 90 ℃ to obtain the positive pole piece. The loading capacity is 1mAh/cm2. After coating, the pole pieces were cut into disks 14mm in diameter for use.
(4) Preparation of the electrolyte
In a dry argon atmosphere, firstly, mixing Dioxolane (DOL) and ethylene glycol dimethyl ether (DME) in a volume ratio of 1:1, then adding lithium salt LiTFSI (lithium bistrifluoromethylenesulfonic acid imide) to dissolve and uniformly mix, and obtaining an electrolyte with the lithium salt concentration of 1M.
(5) Lithium metal battery preparation
And (3) selecting a porous polyethylene film with the thickness of 15 mu m to be placed in the middle as an isolating film, and assembling the prepared negative pole piece, positive pole piece and electrode solution into the button cell.
Example 2
Preparation of composite structures
Adding 0.044g of lithium nitrate into 20mL of N, N-dimethylformamide, stirring and dissolving, then adding 2.2g of PVDF, and stirring for 12 hours at 40 ℃ until the solution is in a uniform and clear state; and transferring the solution into a needle cylinder for electrostatic spinning according to the method in the embodiment 1 to prepare a lithium nitrate-loaded three-dimensional porous structure, namely a composite structure. And standing the composite structure prepared by spinning for 24 hours at normal temperature and normal humidity, and transferring the composite structure to a vacuum drying oven to be dried for 12 hours at 80 ℃ for later use.
The composite structure had a thickness of 60 μm, a porosity of 85% and an average pore size of 800 nm.
And (3) supplementing lithium to the prepared composite structure by a cold pressing mode, wherein the thickness of a lithium supplementing layer is 20 micrometers.
A negative electrode sheet, a positive electrode sheet, an electrolyte and a button cell were prepared according to the method of example 1.
Example 3
Preparation of composite structures
Adding 0.11g of lithium nitrate into 20mL of N, N-dimethylformamide, stirring for dissolving, adding 2.2g of PVDF, and stirring for 12 hours at 40 ℃ until the solution is in a uniform and clear state; and transferring the solution into a needle cylinder for electrostatic spinning according to the method in the embodiment 1 to prepare a lithium nitrate-loaded three-dimensional porous structure, namely a composite structure. And standing the composite structure prepared by spinning for 24 hours at normal temperature and normal humidity, and transferring the composite structure to a vacuum drying oven to be dried for 12 hours at 80 ℃ for later use.
The composite structure had a thickness of 60 μm, a porosity of 85% and an average pore size of 800 nm.
And (3) supplementing lithium to the prepared composite structure by a cold pressing mode, wherein the thickness of a lithium supplementing layer is 20 micrometers.
A negative electrode sheet, a positive electrode sheet, an electrolyte and a button cell were prepared according to the method of example 1.
Example 4
Preparation of composite structures
Adding 0.33g of lithium nitrate into 20mL of N, N-dimethylformamide, stirring and dissolving, then adding 2.2g of PVDF, and stirring for 12 hours at 40 ℃ until the solution is in a uniform and clear state; and transferring the solution into a needle cylinder for electrostatic spinning according to the method in the embodiment 1 to prepare a lithium nitrate-loaded three-dimensional porous structure, namely a composite structure. And standing the composite structure prepared by spinning for 24 hours at normal temperature and normal humidity, and transferring the composite structure to a vacuum drying oven to be dried for 12 hours at 80 ℃ for later use.
The composite structure had a thickness of 60 μm, a porosity of 85% and an average pore size of 800 nm.
And (3) supplementing lithium to the prepared composite structure by a cold pressing mode, wherein the thickness of a lithium supplementing layer is 20 micrometers.
Negative electrode sheets, positive electrode sheets, electrolyte and button cells were prepared according to the method of example 1.
Example 5
Preparation of composite structures
Adding 0.44g of lithium nitrate into 20mL of N, N-dimethylformamide, stirring and dissolving, then adding 2.2g of PVDF, and stirring for 12 hours at 40 ℃ until the solution is in a uniform and clear state; and transferring the solution into a needle cylinder to carry out electrostatic spinning according to the method in the embodiment 1 to prepare a lithium nitrate-loaded three-dimensional porous structure, namely the composite structure. And standing the composite structure prepared by spinning for 24 hours at normal temperature and normal humidity, and transferring the composite structure to a vacuum drying oven to be dried for 12 hours at 80 ℃ for later use.
The composite structure had a thickness of 60 μm, a porosity of 85% and an average pore size of 800 nm.
And (3) supplementing lithium to the prepared composite structure by a cold pressing mode, wherein the thickness of a lithium supplementing layer is 20 micrometers.
Negative electrode sheets, positive electrode sheets, electrolyte and button cells were prepared according to the method of example 1.
Example 6
Preparation of composite structures
Adding 0.66g of lithium nitrate into 20mL of N, N-dimethylformamide, stirring and dissolving, then adding 2.2g of PVDF, and stirring for 12 hours at 40 ℃ until the solution is in a uniform and clear state; and transferring the solution into a needle cylinder for electrostatic spinning according to the method in the embodiment 1 to prepare a lithium nitrate-loaded three-dimensional porous structure, namely a composite structure. And standing the composite structure prepared by spinning for 24 hours at normal temperature and normal humidity, and transferring the composite structure to a vacuum drying oven to be dried for 12 hours at 80 ℃ for later use.
The composite structure had a thickness of 60 μm, a porosity of 85% and an average pore size of 800 nm.
And (3) supplementing lithium to the prepared composite structure by a cold pressing mode, wherein the thickness of a lithium supplementing layer is 20 micrometers.
A negative electrode sheet, a positive electrode sheet, an electrolyte and a button cell were prepared according to the method of example 1.
Example 7
Preparation of composite structures
2.2g of PVDF is dissolved in 20mL of N, N-dimethylformamide and stirred for 12 hours at 40 ℃ until the solution is in a uniform and clear state; the solution was transferred to a cylinder and electrospun according to the method of example 1 to produce a three-dimensional porous structure. And standing the three-dimensional porous structure prepared by spinning for 24 hours at normal temperature and normal humidity, and transferring the three-dimensional porous structure to a vacuum drying oven to be dried for 12 hours at 80 ℃ for later use. Lithium nitrate was dissolved in 50mL of N-methylpyrrolidone to prepare a 0.01M lithium nitrate solution. And soaking the prepared three-dimensional porous structure in a lithium nitrate solution, taking out after 10min, naturally drying, transferring to a vacuum drying oven, and drying at 80 ℃ for 12h for later use to prepare the lithium nitrate-loaded three-dimensional porous structure, namely the composite structure.
The composite structure had a thickness of 60 μm, a porosity of 85% and an average pore size of 800 nm.
And (3) supplementing lithium to the prepared composite structure by a cold pressing mode, wherein the thickness of a lithium supplementing layer is 20 micrometers.
Negative electrode sheets, positive electrode sheets, electrolyte and button cells were prepared according to the method of example 1.
Example 8
Preparation of composite structures
2.2g of PVDF is dissolved in 20mL of N, N-dimethylformamide and stirred for 12 hours at 40 ℃ until the solution is in a uniform and clear state; the solution was transferred to a cylinder and electrospun according to the method of example 1 to produce a three-dimensional porous structure. And standing the three-dimensional porous structure prepared by spinning for 24 hours at normal temperature and normal humidity, and transferring the three-dimensional porous structure to a vacuum drying oven to be dried for 12 hours at 80 ℃ for later use. Lithium nitrate was dissolved in 50mL of N-methylpyrrolidone to prepare a 0.02M lithium nitrate solution. And soaking the prepared three-dimensional porous structure in a lithium nitrate solution, taking out after 10min, naturally drying, transferring to a vacuum drying oven, and drying at 80 ℃ for 12h for later use to prepare the lithium nitrate-loaded three-dimensional porous structure, namely the composite structure.
The composite structure had a thickness of 60 μm, a porosity of 85% and an average pore size of 800 nm.
And (3) supplementing lithium to the prepared composite structure by a cold pressing mode, wherein the thickness of a lithium supplementing layer is 20 micrometers.
Negative electrode sheets, positive electrode sheets, electrolyte and button cells were prepared according to the method of example 1.
Example 9
Preparation of composite structures
2.2g of PVDF is dissolved in 20mL of N, N-dimethylformamide and stirred for 12 hours at 40 ℃ until the solution is in a uniform and clear state; the solution was transferred to a cylinder and electrospun according to the method of example 1 to produce a three-dimensional porous structure. And standing the three-dimensional porous structure prepared by spinning for 24 hours at normal temperature and normal humidity, and transferring the three-dimensional porous structure to a vacuum drying oven to be dried for 12 hours at 80 ℃ for later use. Lithium nitrate was dissolved in 50mL of N-methylpyrrolidone to prepare a 0.05M lithium nitrate solution. And soaking the prepared three-dimensional porous structure in a lithium nitrate solution, taking out after 10min, naturally drying, transferring to a vacuum drying oven, and drying at 80 ℃ for 12h for later use to prepare the lithium nitrate-loaded three-dimensional porous structure, namely the composite structure.
The composite structure had a thickness of 60 μm, a porosity of 85% and an average pore size of 800 nm.
And (3) supplementing lithium to the prepared composite structure by a cold pressing mode, wherein the thickness of a lithium supplementing layer is 20 micrometers.
Negative electrode sheets, positive electrode sheets, electrolyte and button cells were prepared according to the method of example 1.
Example 10
Preparation of composite structures
2.2g of PVDF is dissolved in 20mL of N, N-dimethylformamide and stirred for 12 hours at 40 ℃ until the solution is in a uniform and clear state; the solution was transferred to a cylinder and electrospun according to the method of example 1 to produce a three-dimensional porous structure. And standing the three-dimensional porous structure prepared by spinning for 24 hours at normal temperature and normal humidity, and transferring the three-dimensional porous structure to a vacuum drying oven to be dried for 12 hours at 80 ℃ for later use. Lithium nitrate was dissolved in 50mL of N-methylpyrrolidone to prepare a 0.15M lithium nitrate solution. And soaking the prepared three-dimensional porous structure in a lithium nitrate solution, taking out after 10min, naturally drying, transferring to a vacuum drying oven, and drying at 80 ℃ for 12h for later use to prepare the lithium nitrate-loaded three-dimensional porous structure, namely the composite structure.
The composite structure had a thickness of 60 μm, a porosity of 85% and an average pore size of 800 nm.
And (3) supplementing lithium to the prepared composite structure by a cold pressing mode, wherein the thickness of a lithium supplementing layer is 20 micrometers.
A negative electrode sheet, a positive electrode sheet, an electrolyte and a button cell were prepared according to the method of example 1.
Example 11
Preparation of composite structures
2.2g of PVDF is dissolved in 20mL of N, N-dimethylformamide and stirred for 12 hours at 40 ℃ until the solution is in a uniform and clear state; the solution was transferred to a cylinder and electrospun according to the method of example 1 to produce a three-dimensional porous structure. And standing the three-dimensional porous structure prepared by spinning for 24 hours at normal temperature and normal humidity, and transferring the three-dimensional porous structure to a vacuum drying oven to be dried for 12 hours at 80 ℃ for later use. Lithium nitrate was dissolved in 50mL of N-methylpyrrolidone to prepare a 0.2M lithium nitrate solution. And soaking the prepared three-dimensional porous structure in a lithium nitrate solution, taking out after 10min, naturally drying, transferring to a vacuum drying oven, and drying at 80 ℃ for 12h for later use to prepare the lithium nitrate-loaded three-dimensional porous structure, namely the composite structure.
The composite structure had a thickness of 60 μm, a porosity of 85% and an average pore size of 800 nm.
And (3) supplementing lithium to the prepared composite structure by a cold pressing mode, wherein the thickness of a lithium supplementing layer is 20 micrometers.
Negative electrode sheets, positive electrode sheets, electrolyte and button cells were prepared according to the method of example 1.
Example 12
Preparation of composite structures
2.2g of PVDF is dissolved in 20mL of N, N-dimethylformamide and stirred for 12 hours at 40 ℃ until the solution is in a uniform and clear state; the solution was transferred to a cylinder and electrospun according to the method of example 1 to produce a three-dimensional porous structure. And standing the three-dimensional porous structure prepared by spinning for 24 hours at normal temperature and normal humidity, and transferring the three-dimensional porous structure to a vacuum drying oven to be dried for 12 hours at 80 ℃ for later use. Lithium nitrate was dissolved in 50mL of N-methylpyrrolidone to prepare a 0.3M lithium nitrate solution. And soaking the prepared three-dimensional porous structure in a lithium nitrate solution, taking out after 10min, naturally drying, transferring to a vacuum drying oven, and drying at 80 ℃ for 12h for later use to prepare the lithium nitrate-loaded three-dimensional porous structure, namely the composite structure.
The composite structure had a thickness of 60 μm, a porosity of 85% and an average pore size of 800 nm.
And (3) supplementing lithium to the prepared composite structure by a cold pressing mode, wherein the thickness of a lithium supplementing layer is 20 micrometers.
Negative electrode sheets, positive electrode sheets, electrolyte and button cells were prepared according to the method of example 1.
Example 13
Preparation of composite structures
Adding 0.11g of lithium nitrate into 20mL of N, N-dimethylformamide, stirring and dissolving, then adding 2.2g of PVDF, and stirring for 12 hours at 40 ℃ until the solution is in a uniform and clear state; the solution was transferred to a syringe and electrospun according to the method of example 1 to produce a lithium nitrate-loaded three-dimensional porous structure. And standing the composite structure prepared by spinning for 24h at normal temperature and normal humidity, transferring the composite structure to a vacuum drying oven for drying for 12h at the temperature of 80 ℃, heating to 800 ℃ at the speed of 5 ℃/min in a nitrogen atmosphere by using a tube furnace, and preserving heat for 6 h to obtain the hollow porous carbon nanofiber tube (namely the composite structure) for later use.
The composite structure had a thickness of 60 μm, a porosity of 85% and an average pore size of 800 nm.
And (3) supplementing lithium to the prepared composite structure by a cold pressing mode, wherein the thickness of a lithium supplementing layer is 20 micrometers.
A negative electrode sheet, a positive electrode sheet, an electrolyte and a button cell were prepared according to the method of example 1.
Example 14
Preparation of composite structures
2.2g of PVDF is dissolved in 20mL of N, N-dimethylformamide and stirred for 12 hours at 40 ℃ until the solution is in a uniform and clear state; the solution was transferred to a cylinder and electrospun according to the method of example 1 to produce a three-dimensional porous structure. And standing the fiber framework prepared by spinning at normal temperature and normal humidity for 24h, transferring the fiber framework into a vacuum drying oven to be dried for 12h at the temperature of 80 ℃, heating to 800 ℃ at the speed of 5 ℃/min in a nitrogen atmosphere by using a tube furnace, and preserving heat for 6 h to obtain the hollow porous carbon nanofiber tube for later use.
0.05M of lithium nitrate is prepared and dissolved in 50mL of N-methylpyrrolidone, and the solution is fully stirred and dissolved to obtain a lithium nitrate solution. And soaking the prepared carbon nanofiber pipe in a lithium nitrate solution, taking out after 10min, naturally drying, transferring to a vacuum drying oven, and drying at 80 ℃ for 12h for later use to prepare the carbon nanofiber pipe loaded with lithium nitrate, namely the composite structure.
The composite structure had a thickness of 60 μm, a porosity of 85% and an average pore size of 800 nm.
And (3) supplementing lithium to the prepared composite structure by a cold pressing mode, wherein the thickness of a lithium supplementing layer is 20 micrometers.
Negative electrode sheets, positive electrode sheets, electrolyte and button cells were prepared according to the method of example 1.
Example 15
Preparation of composite structures
Dissolving lithium nitrate in 50mL of N-methylpyrrolidone to prepare a 0.05M lithium nitrate solution; and (2) soaking the lithium foil in a lithium nitrate solution for 10min, naturally drying the lithium foil in the air at normal temperature overnight after soaking, and placing the lithium foil in a vacuum drying oven at 60 ℃ for 24h to prepare the lithium nitrate-loaded lithium foil, namely the lithium foil with the composite structure, wherein the thickness of the composite structure is 20 microns.
The preparation of the negative pole piece is as follows: the prepared composite structure and the fluid copper foil are stacked in sequence and subjected to cold pressing, and then are punched into a wafer with the diameter of 18mm for later use. Wherein the thickness of the composite structure is 20 μm, and the thickness of the copper foil is 12 μm.
A positive electrode tab, electrolyte and button cell were prepared according to the method of example 1.
Example 16
Preparation of the composite structure: it differs from example 3 only in that the thickness of the composite structure is 200 μm, and the others are the same.
And (3) supplementing lithium to the prepared composite structure by a cold pressing mode, wherein the thickness of a lithium supplementing layer is 20 micrometers.
Negative electrode sheets, positive electrode sheets, electrolyte and button cells were prepared according to the method of example 1.
Example 17
Preparation of the composite structure: it differs from example 3 only in that the thickness of the composite structure is 25 μm, and is otherwise the same.
And (3) supplementing lithium to the prepared composite structure by a cold pressing mode, wherein the thickness of a lithium supplementing layer is 20 micrometers.
Negative electrode sheets, positive electrode sheets, electrolyte and button cells were prepared according to the method of example 1.
Example 18
Preparation of the composite structure: it differs from example 3 only in that the thickness of the composite structure is 120 μm, and the others are the same.
And (3) supplementing lithium to the prepared composite structure by a cold pressing mode, wherein the thickness of a lithium supplementing layer is 20 micrometers.
Negative electrode sheets, positive electrode sheets, electrolyte and button cells were prepared according to the method of example 1.
Example 19
Preparation of the composite structure: it differs from example 3 only in that the thickness of the composite structure was 45 μm, and the others were the same.
And (3) supplementing lithium to the prepared composite structure by a cold pressing mode, wherein the thickness of a lithium supplementing layer is 20 micrometers.
Negative electrode sheets, positive electrode sheets, electrolyte and button cells were prepared according to the method of example 1.
Example 20
Preparation of the composite structure: it differs from example 3 only in that the thickness of the composite structure is 80 μm, and is otherwise the same.
And (3) supplementing lithium to the prepared composite structure by a cold pressing mode, wherein the thickness of a lithium supplementing layer is 20 micrometers.
A negative electrode sheet, a positive electrode sheet, an electrolyte and a button cell were prepared according to the method of example 1.
Example 21
Preparation of the composite structure: it differs from example 3 only in that the porosity of the composite structure is reduced to 10% by cold pressing, otherwise the same.
And (3) supplementing lithium to the prepared composite structure by a cold pressing mode, wherein the thickness of a lithium supplementing layer is 20 micrometers.
Negative electrode sheets, positive electrode sheets, electrolyte and button cells were prepared according to the method of example 1.
Example 22
Preparation of the composite structure: it differs from example 3 only in that the porosity of the composite structure is reduced to 35% by cold pressing, otherwise the same.
And (3) supplementing lithium to the prepared composite structure by a cold pressing mode, wherein the thickness of a lithium supplementing layer is 20 micrometers.
Negative electrode sheets, positive electrode sheets, electrolyte and button cells were prepared according to the method of example 1.
Example 23
Preparation of the composite structure: the difference from example 3 is only that the concentration of the spinning solution precursor is twice that of example 3, and the average pore size of the composite structure is adjusted to 2.5 μm, and the other is the same.
And (3) supplementing lithium to the prepared composite structure by a cold pressing mode, wherein the thickness of a lithium supplementing layer is 20 micrometers.
Negative electrode sheets, positive electrode sheets, electrolyte and button cells were prepared according to the method of example 1.
Example 24
Preparation of the composite structure: the difference from example 3 is only that the concentration of the spinning solution precursor is one third of that of example 3, and thus the average pore size of the composite structure is adjusted to 200nm, and the others are the same.
And (3) supplementing lithium to the prepared composite structure by a cold pressing mode, wherein the thickness of a lithium supplementing layer is 20 micrometers.
Negative electrode sheets, positive electrode sheets, electrolyte and button cells were prepared according to the method of example 1.
Comparative example 1
Preparation of composite structures
2.2g of PVDF is dissolved in 20mL of N, N-dimethylformamide and stirred for 12 hours at 40 ℃ until the solution is in a uniform and clear state; the solution was transferred to a cylinder and electrospun according to the method of example 1 to produce a three-dimensional porous structure. And standing the three-dimensional porous structure prepared by spinning for 24 hours at normal temperature and normal humidity, and transferring the three-dimensional porous structure to a vacuum drying oven to be dried for 12 hours at 80 ℃ for later use to prepare the composite structure.
The composite structure had a thickness of 60 μm, a porosity of 85% and an average pore size of 800 nm.
And (3) supplementing lithium to the prepared composite structure by a cold pressing mode, wherein the thickness of a lithium supplementing layer is 20 micrometers.
Negative electrode sheets, positive electrode sheets, electrolyte and button cells were prepared according to the method of example 1.
Comparative example 2
Preparation of composite structures
2.2g of PVDF is dissolved in 20mL of N, N-dimethylformamide and stirred for 12 hours at 40 ℃ until the solution is in a uniform and clear state; the solution was transferred to a cylinder and electrospun according to the method of example 1 to produce a three-dimensional porous structure. And standing the three-dimensional porous structure prepared by spinning for 24h at normal temperature and normal humidity, transferring the three-dimensional porous structure to a vacuum drying oven to be dried for 12h at the temperature of 80 ℃, heating to 800 ℃ at the speed of 5 ℃/min in a nitrogen atmosphere by using a tube furnace, and preserving heat for 6 h to obtain the hollow porous carbon nanofiber tube, namely the composite structure.
The composite structure had a thickness of 60 μm, a porosity of 85% and an average pore size of 800 nm.
And (3) supplementing lithium to the prepared composite structure by a cold pressing mode, wherein the thickness of a lithium supplementing layer is 20 micrometers.
Negative electrode sheets, positive electrode sheets, electrolyte and button cells were prepared according to the method of example 1.
Comparative example 3
(1) Preparation of composite structures
2.2g of PVDF is dissolved in 20mL of N, N-dimethylformamide and stirred for 12 hours at 40 ℃ until the solution is in a uniform and clear state; the solution was transferred to a cylinder and electrospun according to the method of example 1 to produce a three-dimensional porous structure. And standing the three-dimensional porous structure prepared by spinning for 24 hours at normal temperature and normal humidity, and transferring the three-dimensional porous structure to a vacuum drying oven to be dried for 12 hours at 80 ℃ for later use to prepare the composite structure.
The composite structure had a thickness of 60 μm, a porosity of 85% and an average pore size of 800 nm.
And (3) supplementing lithium to the prepared composite structure by a cold pressing mode, wherein the thickness of a lithium supplementing layer is 20 micrometers.
(2) Preparation of the electrolyte
In a dry argon atmosphere, firstly, mixing Dioxolane (DOL) and dimethyl ether (DME) in a volume ratio of 1:1, then adding lithium salt LiTFSI (lithium bis (trifluoromethyl) sulfinamide) to dissolve and uniformly mix, and obtaining an electrolyte with the lithium salt concentration of 1M. 2% by weight of lithium nitrate was added to the electrolyte.
Negative electrode sheets, positive electrode sheets and button cells were prepared according to the method of example 1.
Comparative example 4
(1) Preparation of composite structures
2.2g of PVDF is dissolved in 20mL of N, N-dimethylformamide and stirred for 12 hours at 40 ℃ until the solution is in a uniform and clear state; the solution was transferred to a cylinder and electrospun according to the method of example 1 to produce a three-dimensional porous structure. And standing the three-dimensional porous structure prepared by spinning for 24 hours at normal temperature and normal humidity, and transferring the three-dimensional porous structure to a vacuum drying oven to be dried for 12 hours at 80 ℃ for later use to prepare the composite structure.
The composite structure had a thickness of 60 μm, a porosity of 85% and an average pore size of 800 nm.
And (3) supplementing lithium to the prepared composite structure by a cold pressing mode, wherein the thickness of a lithium supplementing layer is 20 micrometers.
(2) Preparation of the electrolyte
In a dry argon atmosphere, firstly, mixing Dioxolane (DOL) and dimethyl ether (DME) in a volume ratio of 1:1, then adding lithium salt LiTFSI (lithium bis (trifluoromethyl) sulfinamide) to dissolve and uniformly mix, and obtaining an electrolyte with the lithium salt concentration of 1M. 0.8% by weight of lithium nitrate was added to the electrolyte.
Negative electrode sheets, positive electrode sheets and button cells were prepared according to the method of example 1.
Comparative example 5
The negative pole piece adopts a commercial lithium copper composite belt, and the thickness of the negative pole piece is 50 mu m; a positive electrode tab, electrolyte and button cell were prepared according to the method of example 1.
Performance testing
Firstly, fig. 1 is a schematic structural diagram of the three-dimensional porous structure of the present invention. The composite structure prepared in comparative example 1 and the composite structures prepared in examples 1 and 7 were observed by a scanning electron microscope, and the results are shown in fig. 2 to 4. As can be seen from fig. 2, the composite structure of comparative example 1, to which lithium nitrate was not added, had uniform fiber diameter distribution and smooth surface. As can be seen from fig. 3, the surface of the fiber in the three-dimensional porous structure prepared by in-situ addition of lithium nitrate in example 1 can observe lithium nitrate particles encapsulated in the fiber. As can be seen from fig. 4, in example 7, island-shaped distribution of lithium nitrate is coated and deposited on the surface of the fiber in the three-dimensional composite structure prepared by soaking and ectopically adding lithium nitrate.
Secondly, the button cell assembled by the embodiments 1 to 24 and the comparative examples 1 to 5 is tested for the cycle performance, the coulombic efficiency and the volume expansion rate of the negative pole piece, and the test method is as follows:
(1) and (3) testing the cycle performance:
charging the button cell to 3.7V at a constant current of 0.2C at 25 ℃, then charging the button cell to a constant voltage of 0.025C, wherein the button cell is in a full charge state, and recording the charge capacity at the time, namely the 1 st circle of charge capacity; and (3) after the button cell is kept stand for 5min, discharging at a constant current of 0.5C until the discharge cut-off voltage is 2.55V, wherein the discharge is a cyclic charge-discharge process, and the discharge capacity at the moment is recorded, namely the discharge capacity of the 1 st circle. And (3) carrying out a cyclic charge-discharge test on the button cell according to the method, recording the discharge capacity after each cycle until the discharge capacity of the button cell is attenuated to 80% of the discharge capacity of the 1 st cycle, and representing the cycle performance of the button cell by using the number of cycle cycles. Wherein the higher the number of cycles, the better the cycling performance of the button cell.
(2) And (3) coulomb efficiency test:
charging the button cell to 3.7V at a constant current of 0.2C under 25 ℃, then charging the button cell to a current of 0.025C at a constant voltage, wherein the button cell is in a full charge state, and recording the charge capacity at the time, namely the 1 st circle of charge capacity; and (3) standing the button cell for 5min, discharging to 2.55V at a constant current of 0.5C, standing for 5min, wherein the constant current is a cycle, and recording the discharge capacity at the moment, namely the discharge capacity at the 1 st circle. And (3) carrying out a cyclic charge-discharge test on the button cell according to the method, and recording the charge capacity and the discharge capacity of each cycle, wherein the coulombic efficiency is the average value of the ratio of the discharge capacity to the charge capacity of each cycle when the discharge capacity is attenuated to 80% of the discharge capacity of the first cycle.
(3) And (3) testing the volume expansion rate of the pole piece:
charging the button cell to 3.7V at a constant current of 0.2C under 25 ℃, then charging the button cell to a current of 0.025C at a constant voltage, wherein the button cell is in a full charge state, and recording the charge capacity at the time, namely the 1 st circle of charge capacity; and (3) standing the button cell for 5min, discharging to 2.55V at a constant current of 0.5C, standing for 5min, wherein the discharge capacity is recorded as the discharge capacity of the 1 st circle, and the discharge capacity is recorded. Performing cyclic charge and discharge test on the button cell according to the method, stopping the test when the discharge capacity of the cell is attenuated to 80% of the first-circle discharge capacity, disassembling the cell, taking out a negative pole piece, soaking the negative pole piece in a dimethyl carbonate solution, preparing a sample of the negative pole piece by adopting an argon ion polishing CP method, observing the section (vertical to the functional surface of a current collector) of the negative pole piece by using a scanning electron microscope, and obtaining the thickness T of the section of the negative pole piece after the cycle; before assembling the button cell, the cross-sectional thickness of the negative electrode sheet before cycling was measured as T, and the volume expansion rate = (T-T)/T × 100%.
The test data are shown in the table below.
| Group of | Composite structure | Lithium nitrate loading as a percentage of the weight of the composite structure | Composite structure thickness μm | Number of cycles | Coulombic efficiency | Rate of volume expansion |
| Example 1 | In-situ: PVDF skeleton-lithium nitrate | 1% | 60 | 215 | 99.64% | 10% |
| Example 2 | In-situ: PVDF skeleton-lithium nitrate | 2% | 60 | 268 | 99.75% | 8% |
| Example 3 | In-situ: PVDF skeleton-lithium nitrate | 5% | 60 | 296 | 99.86% | 5% |
| Example 4 | In-situ: PVDF skeleton-lithium nitrate | 15% | 60 | 274 | 99.78% | 5% |
| Example 5 | In-situ: PVDF skeleton-lithium nitrate | 20% | 60 | 220 | 99.65% | 12% |
| Example 6 | In-situ: PVDF skeleton-lithium nitrate | 30% | 60 | 162 | 99.32% | 16% |
| Example 7 | Ectopic: PVDF skeleton-lithium nitrate | 1% | 60 | 204 | 99.61% | 10% |
| Example 8 | Ectopic: PVDF skeleton-lithium nitrate | 2% | 60 | 263 | 99.70% | 8% |
| Example 9 | Ectopic: PVDF skeleton-lithium nitrate | 5% | 60 | 285 | 99.79% | 5% |
| Example 10 | Ectopic: PVDF skeleton-lithium nitrate | 15% | 60 | 265 | 99.75% | 5% |
| Example 11 | Ectopic: PVDF skeleton-lithium nitrate | 20% | 60 | 203 | 99.58% | 14% |
| Example 12 | Ectopic: PVDF skeletonLithium nitrate | 30% | 60 | 158 | 99.28% | 18% |
| Example 13 | In-situ: carbon fiber skeleton-lithium nitrate | 5% | 60 | 287 | 99.78% | 5% |
| Example 14 | Ectopic: carbon fiber skeleton-lithium nitrate | 5% | 60 | 278 | 99.76% | 5% |
| Example 15 | Ectopic: lithium foil-lithium nitrate | 5% | 60 | 150 | 99.29% | 50% |
| Example 16 | In-situ: PVDF skeleton-lithium nitrate | 5% | 200 | 236 | 99.52% | 5% |
| Example 17 | In-situ: PVDF skeleton-lithium nitrate | 5% | 25 | 218 | 99.45% | 12% |
| Example 18 | In-situ: PVDF skeleton-lithium nitrate | 5% | 120 | 255 | 99.62% | 5% |
| Example 19 | In-situ: PVDF skeleton-lithium nitrate | 5% | 45 | 268 | 99.79% | 5% |
| Example 20 | In-situ: PVDF skeleton-lithium nitrate | 5% | 80 | 292 | 99.84% | 5% |
| Example 21 | In-situ: PVDF skeleton-lithium nitrate | 5% | 60 | 165 | 99.31% | 25% |
| Example 22 | In-situ: PVDF skeleton-lithium nitrate | 5% | 60 | 188 | 99.50% | 20% |
| Example 23 | In-situ: PVDF skeleton-lithium nitrate | 5% | 60 | 189 | 99.51% | 15% |
| Example 24 | In-situ: PVDF skeleton-lithium nitrate | 5% | 60 | 201 | 99.58% | 5% |
| Comparative example 1 | PVDF skeleton | / | 60 | 138 | 99.23% | 40% |
| Comparative example 2 | Carbon fiber skeleton | / | 60 | 135 | 99.2% | 40% |
| Comparative example 3 | PVDF skeleton (lithium nitrate added into electrolyte) | / | 60 | 142 | 99.25% | 38% |
| Comparative example 4 | PVDF skeleton (lithium nitrate added into electrolyte) | / | 60 | 144 | 99.26% | 36% |
| Comparative example 5 | Lithium foil | / | / | 45 | 98.51% | 200% |
And (4) analyzing results: it can be seen from comparative examples 1 and examples 1 to 12 and comparative examples 2 and examples 13 to 14 that, compared with comparative examples 1 and 2 in which lithium nitrate is not added to the composite structure, the composite structure in which lithium nitrate is added to examples 1 to 14 can significantly improve the expansion performance, the cycle performance and the coulombic efficiency of the lithium metal battery, and it is described that in the present application, lithium nitrate is compounded to the composite structure in an in-situ or ex-situ addition manner, so that lithium nitrate is continuously slowly released during the cycle process and continuously supplemented into the electrolyte, so that the concentration of lithium nitrate in the electrolyte is in a saturated state, and the addition of lithium nitrate generates an SEI layer on the surface of the lithium metal, prevents the electrolyte from further contacting with the lithium metal to generate side reactions, and lithium nitrate is used as an excellent electrolyte additive, so that Li can be generated on the surface of the lithium metal3N and LiNxOyThe ionic conductivity and the mechanical property of the SEI layer are improved, the transmission of lithium ions in the SEI layer is accelerated, and the side reaction of the electrolyte and lithium metal is slowed down, so that the expansion performance and the cycle performance of the lithium metal battery can be obviously improved, and the coulombic efficiency of the lithium metal battery can be improved.
From examples 1 to 6 and examples 7 to 12, it can be seen that when the content of lithium nitrate is 5 to 15% of the weight of the composite structure, the addition of lithium nitrate can significantly improve the cycle performance and side reaction aspects of the lithium metal battery, improve the cycle performance and expansion performance of the lithium metal battery, and improve the coulomb efficiency of the lithium metal battery.
It can be seen from examples 1 to 6 and examples 7 to 12 that the in-situ addition of lithium nitrate and the ex-situ addition of lithium nitrate can improve the capacity retention, the expansion performance and the cycle performance of the battery, but the in-situ addition can wrap the lithium nitrate in the fibers and realize a better slow release effect in the cycle process, so that the in-situ addition has a better improvement effect than the ex-situ addition.
Examples 1 to 14 show that the composite structure framework can be a conductive material or an insulating material, and the addition of lithium nitrate can improve the cycle performance and the expansion performance of the lithium metal battery and improve the coulombic efficiency of the lithium metal battery.
It can be seen from example 15 and comparative example 5 that the modification of lithium nitrate on the lithium copper composite band with a two-dimensional structure can also improve the cycle performance and the expansion performance of the lithium metal battery and increase the coulombic efficiency of the lithium metal battery.
From the embodiment 3 and the embodiments 16 to 20, the thickness of the composite structure has an influence on the battery performance, and when the thickness of the composite structure is 45 to 80 micrometers, the lithium metal battery has better cycle performance and expansion performance and higher coulombic efficiency.
From the embodiment 3 and the embodiments 21 to 22, it can be seen that when the porosity of the three-dimensional porous structure is 5% to 90%, the cycle performance and the expansion performance of the lithium metal battery can be improved, the coulomb efficiency of the lithium metal battery can be improved, and when the porosity of the three-dimensional porous structure is 40% to 90%, the improvement effect is better.
From the embodiment 3 and the embodiments 23 to 24, it can be seen that when the average pore diameter of the three-dimensional porous structure is 100 nm to 4 μm, the cycle performance and the expansion performance of the lithium metal battery can be improved and the coulombic efficiency of the lithium metal battery can be improved, and when the average pore diameter is 200nm to 2 μm, the improvement effect is better.
As can be seen from comparative examples 3 and 4, the solubility of lithium nitrate in the electrolyte was low, and when lithium nitrate was directly added to the electrolyte, lithium nitrate was precipitated; in comparative example 3, the amount of lithium nitrate added reached 2% by weight of the electrolyte, and lithium nitrate was not completely dissolved and partially precipitated in the electrolyte; in comparative example 4, when the addition amount of lithium nitrate was reduced to 0.8% by weight of the electrolyte, the lithium nitrate was completely dissolved, but since the content of lithium nitrate was low, the lithium nitrate was completely consumed during the early cycle, which affected the late cycle of the battery and the expansion of the electrode plate. Therefore, when the composite structure is applied to the negative electrode of the lithium metal battery, the slow release function of lithium nitrate can be realized, the cycle performance and the expansion performance of the lithium metal battery are improved, and the coulomb efficiency of the lithium metal battery is improved.
Finally, it should be noted that the above embodiments are only used for illustrating the technical solutions of the present application and not for limiting the protection scope of the present application, and although the present application is described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that modifications or equivalent substitutions can be made on the technical solutions of the present application without departing from the spirit and scope of the technical solutions of the present application.
Claims (8)
1. A lithium metal battery comprises a positive electrode, a negative electrode, a separation film and electrolyte, and is characterized in that the negative electrode comprises a composite structure, the composite structure comprises a framework and lithium nitrate on the framework, and the framework is a three-dimensional porous structure; the thickness of the composite structure is 25-200 μm; the average pore size of the three-dimensional porous structure is 100 nm-4 mu m.
2. The lithium metal battery of claim 1, wherein the three-dimensional porous structure is built up using fibers, and the lithium nitrate is supported inside and/or on the surface of the fibers.
3. The lithium metal battery of claim 1, wherein the porosity of the three-dimensional porous structure is 5% to 90%.
4. The lithium metal battery of claim 2, wherein the fiber is made of a material including at least one of a polymer material and an inorganic material.
5. The lithium metal battery of claim 1, wherein the lithium nitrate is loaded at a level of 1% to 99% by weight of the composite structure.
6. The lithium metal battery of any of claims 1 to 5, wherein at least one of the following conditions is satisfied:
(a) the thickness of the composite structure is 45-80 μm;
(b) the porosity of the three-dimensional porous structure is 40% -90%;
(c) the average pore size of the three-dimensional porous structure is 200 nm-2 mu m;
(d) the loading amount of the lithium nitrate is 5-30% of the weight of the composite structure.
7. The lithium metal battery of claim 2 or 4, wherein at least one of the following conditions is satisfied:
(e) the lithium nitrate is loaded inside and on the surface of the fiber in an in-situ adding mode;
(f) the lithium nitrate is loaded on the surface of the fiber in a mode of ectopic addition.
8. An electronic device comprising the lithium metal battery according to any one of claims 1 to 7.
Priority Applications (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
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| CN114927828B (en) * | 2022-07-19 | 2022-10-25 | 浙江金羽新能源科技有限公司 | Composite diaphragm with slow release function and preparation method and application thereof |
| CN117254114A (en) * | 2023-11-17 | 2023-12-19 | 宁德时代新能源科技股份有限公司 | Battery monomer, preparation method thereof, battery comprising battery monomer and power utilization device |
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| DE102013209982B4 (en) * | 2013-05-28 | 2023-02-16 | Technische Universität Dresden | Alkaline metal-sulphur battery and method of operating it |
| KR102618538B1 (en) * | 2015-08-31 | 2023-12-28 | 삼성전자주식회사 | Lithium metal battery including lithium metal anode, method of protecting the lithium metal anode, and protective layer prepared according to the method |
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