CN108550859B - Porous current collector, preparation method thereof and lithium battery - Google Patents

Porous current collector, preparation method thereof and lithium battery Download PDF

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CN108550859B
CN108550859B CN201810491391.XA CN201810491391A CN108550859B CN 108550859 B CN108550859 B CN 108550859B CN 201810491391 A CN201810491391 A CN 201810491391A CN 108550859 B CN108550859 B CN 108550859B
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current collector
lithium
solid electrolyte
oxide
mass
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CN108550859A (en
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王昊鹏
徐延铭
李俊义
李素丽
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Zhuhai Cosmx Battery Co Ltd
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Zhuhai Cosmx Battery Co Ltd
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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
    • H01M4/64—Carriers or collectors
    • H01M4/66—Selection of materials
    • 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
    • H01M4/64—Carriers or collectors
    • H01M4/70—Carriers or collectors characterised by shape or form
    • 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
    • H01M4/64—Carriers or collectors
    • H01M4/70—Carriers or collectors characterised by shape or form
    • H01M4/80—Porous plates, e.g. sintered carriers
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Abstract

The porous current collector comprises a current collector matrix with a hole structure, wherein solid electrolyte layers are attached to the surface of the current collector matrix and the inner surface of the hole, and at least one solid electrolyte layer is arranged. The porous current collector is used as a negative pole piece of the lithium battery, electrode active substances do not need to be filled on the negative pole piece, the three-dimensional porous current collector is adopted, the solid electrolyte layer is attached to the surface and the hole of the current collector substrate, a large amount of space is arranged in the current collector substrate and can accommodate lithium deposited during charging of the lithium battery, the volume of the current collector is kept unchanged during repeated deposition and separation of the lithium, the adverse effect caused by repeated change of the volume of lithium metal during the circulation process is reduced, meanwhile, the solid electrolyte layer can inhibit the formation of lithium dendrites, and the circulation performance of the lithium battery is improved. The invention does not directly use lithium metal during the manufacturing of the battery, does not need strict environmental control and reduces the manufacturing cost of the lithium battery.

Description

Porous current collector, preparation method thereof and lithium battery
Technical Field
The invention belongs to the technical field of lithium batteries, and particularly relates to a current collector with a porous structure, a preparation method of the current collector and a lithium battery.
Background
In recent years, with the rapid development of portable electronic devices, electric vehicles and power grid energy storage technologies, the demand of batteries and energy storage systems with high energy density and high safety is more and more urgent. Among the commercialized electrochemical energy storage devices, lithium ion batteries are the best choice for people due to their advantages of high energy density, long cycle life, and the like. However, due to the limitation of electrode materials, research on how to further improve the energy density of lithium ion batteries is slow.
Graphite is the most widely used lithium ion battery cathode material at present, but the theoretical capacity of the graphite is only 372mAh/g, and the demand of people on high-energy density batteries is more and more difficult to meet. Compared with a graphite cathode, the theoretical capacity of the lithium metal cathode is obviously higher and reaches 3860 mAh/g; and the lithium metal electrode has the most negative potential, up to-3.040V (vs. standard hydrogen electrode). Therefore, a battery using a lithium metal negative electrode is expected to be applied in a large scale in the future. However, lithium batteries using lithium metal negative electrodes also have some inherent drawbacks. Currently, the biggest impediment to the application of lithium metal negative electrodes to batteries is the cycling stability and safety of lithium metal. In the circulation process of the lithium battery, lithium ions are repeatedly deposited and separated on the surface of the lithium metal, so that the surface flatness of the lithium metal is easily reduced, the current density distribution is uneven, lithium dendrites are further formed, and potential safety hazards are brought. In addition, in the process of deposition and desorption of lithium ions, the volume of lithium metal repeatedly expands and contracts, so that the original SEI film on the surface of the lithium metal is damaged, and meanwhile, a new SEI film is continuously formed, so that the electrolyte and active lithium are seriously consumed, and the cycle performance of the lithium battery is rapidly attenuated. The cycling performance of the battery is further degraded if the deposited lithium detaches from the lithium metal surface to form "dead lithium". In addition, since lithium metal is very active in chemical properties, if lithium metal is directly used as a negative electrode, environmental temperature and humidity must be strictly controlled during the battery manufacturing process, which undoubtedly increases the manufacturing cost.
If the lithium metal negative electrode is not directly used during the manufacturing of the lithium battery, lithium ions which are extracted from the positive electrode can be reversibly deposited and extracted on the negative electrode current collector during the working of the battery, the manufacturing process of the battery does not need strict environmental control any more, the manufacturing difficulty can be obviously reduced, and the manufacturing cost can be reduced. In this regard, scientists have made some quest, such as developing LiFePO4Non-negative lithium battery (Advanced Functional Materials,2016,26, 7094) 7102) with positive electrode material, copper as negative electrode current collector and electrolyte containing high-concentration lithium salt]However, the cycle performance of the battery is not ideal. In order to reduce adverse effects caused by repeated volume change of lithium metal in a circulation process, inhibit formation of lithium dendrites, improve the circulation performance of a lithium battery and reduce the manufacturing cost of the lithium battery, development of a novel current collector is an important research direction.
In recent years, a current collector having a three-dimensional porous structure has attracted relatively wide attention. Such a current collector has interconnected pores, and an electrode is manufactured by filling an electrode active material in the pores of the current collector. The ionic conduction and the electronic conduction of the electrode form a three-dimensional path, which is superior to the traditional coating electrode, theoretically, the utilization rate of the electrode active material can be improved, and the volume expansion of the electrode in the circulation process can be inhibited. For example, chinese invention patent No. 201210158278.2, chinese invention patent No. 201210433799.4, chinese invention patent No. 201210081945.1, chinese invention patent No. 201210433237.X, chinese invention patent application No. 201210082241.6, chinese invention patent application No. 201210413033.X, chinese invention patent application No. 201510117274.3, and the like all disclose electrodes using three-dimensional current collectors, and the common point of these electrodes is that porous current collectors are used and electrode active materials are filled into current collector pores, so as to achieve the purposes of forming a sufficient conductive network, efficiently utilizing active materials, and inhibiting volume expansion during active material circulation. However, the method of filling the active material in the current collector hole increases the contact area of the active material and the electrolyte, and brings more electrode-electrolyte interface side reactions; the inhibition of volume expansion during cycling of the active material is simply to reserve sufficient expandable space for the active material prior to cycling of the battery. More importantly, although the active material can be added according to the preset amount in the electrode manufacturing process, the actual filling amount of the active material in the current collector hole is difficult to control, a large amount of space is not effectively filled by the active material in the current collector hole, namely, the space reserved for the expansion of the active material in the current collector hole is far larger than the space required by the actual expansion of the active material, the actual space utilization rate of the current collector is low, and the consistency of electrodes manufactured in different batches is difficult to guarantee. These drawbacks have resulted in the inability of the simple combination of three-dimensional current collectors with active materials to improve battery energy density and cycle life in a desirable manner.
Disclosure of Invention
The invention aims to provide a porous current collector which is low in cost and can inhibit the formation of lithium dendrite and improve the cycle performance of a battery, a preparation method thereof and a lithium battery.
In order to achieve the purpose, the invention adopts the following technical solutions:
porous mass flow body, including the mass flow body that has the pore structure, mass flow body surface and downthehole surface are adhered to and are had the solid electrolyte layer, the solid electrolyte layer is the one deck at least.
Further, the solid electrolyte layer contains a polymer and a lithium salt.
Further, the polymer is at least one of polyvinyl alcohol, polyethylene oxide, polyvinylidene fluoride-hexafluoropropylene copolymer, alkylated polyethylene oxide, polyvinylpyrrolidone, polyvinyl butyral, hydroxyethyl cellulose, methyl hydroxyethyl cellulose, sodium carboxymethyl cellulose, cellulose acetate propionate, polyacrylamide, polymethyl methacrylate, polybutyl methacrylate, polyethyl acrylate, polyvinyl alcohol, ethylene-vinyl acetate copolymer, polyvinyl acetate, polyurethane, melamine formaldehyde, urea formaldehyde, maleic anhydride and its derivatives and esters copolymer, polyacrylonitrile, polycarbonate, polysiloxane, gelatin, starch; or the polymer is a copolymer containing at least two of polyvinyl alcohol, polyethylene oxide, polyvinylidene fluoride-hexafluoropropylene copolymer, alkylated polyethylene oxide, polyvinylpyrrolidone, polyvinyl butyral, hydroxyethyl cellulose, methyl hydroxyethyl cellulose, sodium carboxymethyl cellulose, cellulose acetate propionate, polyacrylamide, polymethyl methacrylate, polybutyl methacrylate, polyethyl acrylate, polyvinyl alcohol, ethylene-vinyl acetate copolymer, polyvinyl acetate, polyurethane, melamine formaldehyde, urea formaldehyde, copolymer of maleic anhydride and its derivatives and esters, polyacrylonitrile, polycarbonate, and polysiloxane.
Further, the lithium salt is LiClO4、LiPF6Or Rf for the moiety F-，LiBF4Or Rf for the moiety F-、LiAsF6Or Rf for the moiety F-、LiSbF6Or Rf for the moiety F-、LiB(C2O4)2、LiCF3SO3、LiCnF2n+1SO3(n≥2)、LiC(CF3SO2)3、LiC(CnF2n+1SO2)3、LiCF3CO2、LiCnF2n+1CO2(n≥2)、LiC2F4(SO3)2、LiN(FSO2)2、LiN(CF3SO2)2、LiN(C2F5SO2)2、LiN(CnF2n+1SO2)2、LiN(RfOSO2)2At least one of (1).
Further, the solid electrolyte layer contains an inorganic filler, and the mass of the inorganic filler accounts for 0-80% of the total mass of the solid electrolyte layer.
Further, the inorganic filler is at least one of lithium silicate, lithium borate, lithium phosphate, lithium carbonate, lithium alumina, lithium titanium oxide, lithium lanthanum oxide, lithium aluminum phosphate, lithium titanium aluminum phosphate, lithium germanium aluminum phosphate, lithium lanthanum zirconate, silicon oxide, magnesium oxide, aluminum oxide, calcium oxide, strontium oxide, barium oxide, titanium oxide, zirconium oxide, gallium oxide, tin oxide, calcium sulfate, strontium sulfate, barium sulfate, calcium carbonate, strontium carbonate, barium carbonate, and aluminum hydroxide.
Furthermore, the thickness of the current collector substrate is 1-2000 μm.
Further, the thickness of the solid electrolyte layer is 0.01 to 30 μm.
The preparation method of the porous current collector comprises the following steps:
adding a polymer and a lithium salt into a solvent for mixing, and uniformly stirring to prepare a solution;
coating the prepared solution on a current collector substrate, or putting the current collector substrate into the prepared solution for soaking and taking out;
and drying the current collector matrix to obtain the porous current collector with the solid electrolyte layer attached to the surface and the inner surface of the hole of the current collector matrix.
The preparation method of the porous current collector comprises the following steps:
adding a polymer and a lithium salt into a solvent, mixing to prepare a solution, adding an inorganic filler into the solution, and uniformly stirring to prepare a suspension;
coating the prepared suspension liquid on a current collector substrate, or soaking the current collector substrate in the prepared suspension liquid and then taking out;
and drying the current collector matrix to obtain the porous current collector with the solid electrolyte layer attached to the surface and the inner surface of the hole of the current collector matrix.
Further, the mass of the polymer accounts for 4-6% of the total mass of the solution, and the mass of the lithium salt accounts for 1.5-2.5% of the total mass of the solution.
Furthermore, the mass of the polymer accounts for 4-6% of the total mass of the solution, the mass of the lithium salt accounts for 1.5-2.5% of the total mass of the solution, and the mass of the inorganic filler accounts for 0.9-11% of the total mass of the suspension.
Further, when the solid electrolyte layers on the surface of the current collector substrate and on the inner surface of the hole have two or more layers, the composition of the solid electrolyte layers of two adjacent layers is not completely the same, and the solid electrolyte layer which is not in direct contact with the current collector substrate contains a polymer, or contains a polymer and a lithium salt and/or an inorganic filler.
The lithium battery comprises a positive pole piece, a negative pole piece and a diaphragm, wherein the negative pole piece is a porous current collector prepared by the preparation method of the porous current collector, and the negative pole piece is not filled with an electrode active material.
According to the technical scheme, the three-dimensional porous current collector is different from the traditional two-dimensional foil current collector, the three-dimensional porous current collector is applied to the negative electrode of the lithium battery, the inner wall of the hole has certain curvature, and when lithium separated from the positive electrode is deposited in the hole of the three-dimensional porous current collector, lithium dendrites can grow in all directions in a three-dimensional space, so that the growth perpendicular to the direction of the current collector is reduced to a great extent, the probability of puncturing a diaphragm is reduced, and in addition, the solid electrolyte layer has good mechanical strength, the formation of the lithium dendrites can be inhibited, and the safety risk is further reduced; and different from the scheme that the existing porous current collector only uses a polymer as a binder or a coating layer, the invention forms a solid electrolyte layer without an electrode active substance on the surface and the inner surface of the hole of the three-dimensional porous current collector matrix, and the solid electrolyte layer contains lithium salt, so that the current collector matrix and the solid electrolyte layer can form a complete electrode, and lithium ions in the lithium salt are deposited between the current collector matrix and the solid electrolyte layer in a metal form, thereby improving the conductivity of lithium ions, ensuring that the lithium ions are smoothly deposited and extracted on the surface and the inner surface of the hole of the matrix of the three-dimensional porous current collector, and improving the cycle performance of the lithium battery. Because lithium metal is not directly used in the manufacturing process of the battery, strict environmental control is not needed, and the manufacturing cost of the lithium battery can be reduced.
Detailed Description
In order to make the aforementioned and other objects, features and advantages of the invention more apparent, embodiments of the invention are described in detail below.
The invention adopts a current collector with a through hole structure, such as foamed nickel, foamed copper and the like, as a current collector matrix, and solid electrolyte layers are attached to the surface of the current collector matrix and the inner surface of the hole. The thickness of the current collector substrate may be 1 μm to 2000 μm, and the thickness of the solid electrolyte layer may be 0.01 μm to 30 μm. The solid electrolyte layer attached to the surface of the current collector substrate and the inner surface of the hole is at least one or more than one layer.
The solid electrolyte layer of the present invention contains a polymer and a lithium salt. The polymer has higher viscosity after being dissolved in solvents such as nitrile and the like, and the hardness is not large after the solid electrolyte layer is dried, the polymer can be at least one of polyvinyl alcohol, polyethylene oxide, polyvinylidene fluoride-hexafluoropropylene copolymer, alkylated polyethylene oxide, polyvinylpyrrolidone, polyvinyl butyral, hydroxyethyl cellulose, methyl hydroxyethyl cellulose, sodium carboxymethyl cellulose, cellulose acetate propionate, polyacrylamide, polymethyl methacrylate, polybutyl methacrylate, polyethyl acrylate, polyvinyl alcohol, ethylene-vinyl acetate copolymer, polyvinyl acetate, polyurethane, melamine formaldehyde, urea formaldehyde, maleic anhydride and copolymer of derivative and ester thereof, polyacrylonitrile, polycarbonate, polysiloxane, gelatin and starch; or the polymer is a copolymer containing at least two of polyvinyl alcohol, polyethylene oxide, polyvinylidene fluoride-hexafluoropropylene copolymer, alkylated polyethylene oxide, polyvinylpyrrolidone, polyvinyl butyral, hydroxyethyl cellulose, methyl hydroxyethyl cellulose, sodium carboxymethyl cellulose, cellulose acetate propionate, polyacrylamide, polymethyl methacrylate, polybutyl methacrylate, polyethyl acrylate, polyvinyl alcohol, ethylene-vinyl acetate copolymer, polyvinyl acetate, polyurethane, melamine formaldehyde, urea formaldehyde, copolymer of maleic anhydride and its derivatives and esters, polyacrylonitrile, polycarbonate, and polysiloxane.
The lithium salt of the present invention may be LiClO4、LiPF6Or Rf (polyfluoroalkyl) substituted for the moiety F-，LiBF4Or Rf for the moiety F-、LiAsF6Or Rf for the moiety F-、LiSbF6Or Rf for the moiety F-、LiB(C2O4)2、LiCF3SO3、LiCnF2n+1SO3(n≥2)、LiC(CF3SO2)3、LiC(CnF2n+1SO2)3、LiCF3CO2、LiCnF2n+1CO2(n≥2)、LiC2F4(SO3)2、LiN(FSO2)2、LiN(CF3SO2)2、LiN(C2F5SO2)2、LiN(CnF2n+1SO2)2、LiN(RfOSO2)2At least one of (1).
The solid electrolyte layer may further contain an inorganic filler such as at least one of lithium silicate, lithium borate, lithium phosphate, lithium carbonate, lithium alumina, lithium titanium oxide, lithium lanthanum oxide, lithium aluminum phosphate, lithium titanium aluminum phosphate, lithium germanium aluminum phosphate, lithium lanthanum zirconate, silicon oxide, magnesium oxide, aluminum oxide, calcium oxide, strontium oxide, barium oxide, titanium oxide, zirconium oxide, gallium oxide, tin oxide, calcium sulfate, strontium sulfate, barium sulfate, calcium carbonate, strontium carbonate, barium carbonate, and aluminum hydroxide. The mass of the inorganic filler accounts for 0-80% of the total mass of the solid electrolyte layer. The inorganic filler can improve the mechanical strength of the solid electrolyte layer, and can improve the conductivity to some extent since the inorganic filler can reduce the crystallinity of the polymer.
The preparation method of the negative current collector comprises the following steps:
adding a polymer, a lithium salt and an inorganic filler (when the inorganic filler is contained) into a solvent for mixing, and uniformly stirring to prepare a solution or a suspension;
the method comprises the following steps of (1) coating a prepared solution or suspension on a current collector substrate by using a porous current collector as the current collector substrate, or immersing the current collector substrate in the prepared solution or suspension to attach the solution or suspension to the current collector substrate and then taking out the solution or suspension;
and drying the current collector matrix to obtain the porous current collector with the solid electrolyte layer attached to the surface and the inner surface of the hole of the current collector matrix.
When the solid electrolyte layers on the surface of the current collector substrate and the inner surface of the hole have two or more layers, the composition of the solid electrolyte layers of adjacent two layers may not be completely the same. And when the solid electrolyte layer has two or more layers, repeating the second step and the third step to obtain the negative electrode current collector with the multiple solid electrolyte layers. When the porous current collector has a plurality of solid electrolyte layers, the solid electrolyte layer not in direct contact with the porous current collector contains a polymer, and may or may not contain a lithium salt, an inorganic filler, or an inorganic filler.
When the porous current collector is used as a negative pole piece for preparing a lithium battery, the porous current collector is assembled with a conventional positive pole piece and a diaphragm into the battery, and the negative pole piece does not need to be filled with any electrode active material.
The present invention will be further illustrated by the following specific examples. The reagents, materials and instruments used in the following description are all conventional reagents, conventional materials and conventional instruments, which are commercially available, and the reagents may be synthesized by a conventional synthesis method, if not specifically described.
Example 1
Mixing polyethylene oxide and LiN (CF)3SO2)2Dissolving in acetonitrile, and stirring to obtain solution, wherein the mass of polyoxyethylene accounts for the total mass of the solution4% of the amount LiN (CF)3SO2)2The mass of (a) accounts for 1.5% of the total mass of the solution;
coating the obtained solution on a copper foam with the thickness of 1 mm;
and drying the porous current collector for 24 hours at normal temperature to obtain the porous current collector with the solid electrolyte layer.
Cutting a porous current collector into rectangular pieces with the length of 79mm and the width of 45mm to be used as negative electrode pieces, cutting an aluminum foil into rectangular pieces with the length of 95mm and the width of 40mm, coating lithium cobaltate on one surface of the aluminum foil, wherein the area of the coated lithium cobaltate is smaller than that of the negative electrode pieces, and manufacturing positive electrode pieces; and stacking the negative pole piece, the diaphragm and the positive pole piece in sequence, packaging by using an aluminum plastic film, injecting electrolyte and sealing to prepare the single-chip battery. The electrolyte of the present example was 1mol/L LiPF6The EC/DEC/EMC solution of (1), wherein the EC/DEC/EMC mass ratio is 1:1: 1.
Example 2
This example differs from example 1 in that: mixing polyethylene oxide and LiN (CF)3SO2)2Dissolving in acetonitrile, stirring to obtain solution (polyoxyethylene accounts for 4 wt% of the total solution), and LiN (CF)3SO2)2The mass of the solution accounts for 1.5 percent of the total mass of the solution), adding lanthanum lithium zirconate into the solution, and stirring to form a turbid liquid, wherein the mass of the lanthanum lithium zirconate accounts for 5 percent of the total mass of the turbid liquid;
coating the obtained suspension on foam copper with the thickness of 1 mm;
and drying the porous current collector for 24 hours at normal temperature to obtain the porous current collector with the solid electrolyte layer.
And cutting the porous current collector into rectangular pieces with the length of 79mm and the width of 45mm, using the rectangular pieces as negative pole pieces, stacking the rectangular pieces with a diaphragm and a positive pole piece in sequence, packaging the rectangular pieces with an aluminum plastic film, injecting electrolyte, and sealing the opening to obtain the single-piece battery. The positive electrode sheet, separator, and electrolyte in this example were the same as in example 1.
Example 3
Polyacrylonitrile and LiN (CF)3SO2)2、LiB(C2O4)2Dissolving in acetonitrile, stirringHomogenizing to obtain solution containing polyacrylonitrile 5 wt% and LiN (CF)3SO2)2The mass of (a) is 1% of the total mass of the solution, and LiB (C)2O4)2Adding lithium carbonate, lanthanum lithium oxide and barium sulfate into the solution, and stirring to form a suspension, wherein the mass of the lithium carbonate accounts for 0.5 percent of the total mass of the suspension, the mass of the lanthanum lithium oxide accounts for 0.5 percent of the total mass of the suspension, and the mass of the barium sulfate accounts for 0.2 percent of the total mass of the suspension;
coating the obtained suspension on foam copper with the thickness of 1 mm;
and drying the porous current collector for 24 hours at normal temperature to obtain the porous current collector with the solid electrolyte layer.
And cutting the porous current collector into rectangular pieces with the length of 79mm and the width of 45mm, using the rectangular pieces as negative pole pieces, stacking the rectangular pieces with a diaphragm and a positive pole piece in sequence, packaging the rectangular pieces with an aluminum plastic film, injecting electrolyte, and sealing the opening to obtain the single-piece battery. The positive electrode sheet, separator, and electrolyte in this example were the same as in example 1.
Example 4
Polyacrylonitrile, polyvinylidene fluoride and LiN (FSO)2)2Dissolving in NMP, stirring to obtain solution containing polyacrylonitrile 5 wt%, polyvinylidene fluoride 0.8 wt%, and LiN (FSO)2)2Adding lithium aluminum titanium phosphate, aluminum oxide and silicon oxide into the solution, and stirring to form a suspension, wherein the mass of the lithium aluminum titanium phosphate accounts for 5% of the total mass of the suspension, the mass of the aluminum oxide accounts for 0.2% of the total mass of the suspension, and the mass of the silicon oxide accounts for 0.1% of the total mass of the suspension;
coating the obtained suspension on foam copper with the thickness of 1 mm;
and drying at normal temperature for 48 hours to obtain the porous current collector with the solid electrolyte layer.
And cutting the porous current collector into rectangular pieces with the length of 79mm and the width of 45mm, using the rectangular pieces as negative pole pieces, stacking the rectangular pieces with a diaphragm and a positive pole piece in sequence, packaging the rectangular pieces with an aluminum plastic film, injecting electrolyte, and sealing the opening to obtain the single-piece battery. The positive electrode sheet, separator, and electrolyte in this example were the same as in example 1.
Example 5
Polyacrylonitrile, polyvinylidene fluoride-hexafluoropropylene copolymer, LiN (FSO)2)2Dissolving in NMP, stirring to obtain solution containing polyacrylonitrile 5 wt%, polyvinylidene fluoride-hexafluoropropylene copolymer 0.5 wt%, and LiN (FSO)2)2The mass of the solution is 2.5 percent of the total mass of the solution, then lanthanum lithium zirconate and silicon oxide are added into the solution, and the solution is stirred to form a suspension, wherein the mass of the lanthanum lithium zirconate accounts for 10 percent of the total mass of the suspension, and the mass of the silicon oxide accounts for 0.1 percent of the total mass of the suspension;
coating the obtained suspension on foam copper with the thickness of 1 mm;
and drying at normal temperature for 48 hours to obtain the porous current collector with the solid electrolyte layer.
And cutting the porous current collector into rectangular pieces with the length of 79mm and the width of 45mm, using the rectangular pieces as negative pole pieces, stacking the rectangular pieces with a diaphragm and a positive pole piece in sequence, packaging the rectangular pieces with an aluminum plastic film, injecting electrolyte, and sealing the opening to obtain the single-piece battery. The positive electrode sheet, separator, and electrolyte in this example were the same as in example 1.
Example 6
Mixing polyethylene oxide, polyacrylonitrile, sodium carboxymethylcellulose, LiN (FSO)2)2Dissolving in NMP, stirring to obtain solution, wherein the mass of polyoxyethylene accounts for 3% of the total mass of the solution, the mass of polyacrylonitrile accounts for 2% of the total mass of the solution, the mass of sodium carboxymethylcellulose accounts for 1% of the total mass of the solution, and LiN (FSO)2)2The mass of the solution is 2.5 percent of the total mass of the solution, then lithium aluminum titanium phosphate, magnesium oxide and barium oxide are added into the solution, and the solution is stirred to form a suspension, wherein the mass of the lithium aluminum titanium phosphate accounts for 10 percent of the total mass of the suspension, the mass of the magnesium oxide accounts for 0.5 percent of the total mass of the suspension, and the mass of the barium oxide accounts for 0.5 percent of the total mass of the suspension;
coating the obtained suspension on foam copper with the thickness of 1 mm;
and drying at normal temperature for 48 hours to obtain the porous current collector with the solid electrolyte layer.
And cutting the porous current collector into rectangular pieces with the length of 79mm and the width of 45mm, using the rectangular pieces as negative pole pieces, stacking the rectangular pieces with a diaphragm and a positive pole piece in sequence, packaging the rectangular pieces with an aluminum plastic film, injecting electrolyte, and sealing the opening to obtain the single-piece battery. The positive electrode sheet, separator, and electrolyte in this example were the same as in example 1.
Example 7
Polyacrylonitrile and LiN (FSO)2)2Dissolving in NMP, stirring to obtain solution, wherein polyacrylonitrile accounts for 5% of total mass of the solution, and LiN (FSO)2)2Adding lithium aluminum titanium phosphate and aluminum oxide into the solution, and stirring to form a suspension, wherein the mass of the lithium aluminum titanium phosphate accounts for 8% of the total mass of the suspension, and the mass of the aluminum oxide accounts for 0.5% of the total mass of the suspension;
coating the obtained suspension on foam copper with the thickness of 1 mm;
drying for 48 hours at normal temperature to obtain the foamy copper with the solid electrolyte layer;
mixing polyethylene oxide and LiN (CF)3SO2)2Dissolving in acetonitrile, stirring to obtain solution, wherein the mass of polyoxyethylene accounts for 5% of the total mass of the solution, and LiN (FSO)2)2The weight of the porous current collector is 2 percent of the total weight of the solution, the porous current collector is coated on the dried foamy copper with the solid electrolyte layer, and the porous current collector with two solid electrolyte layers is obtained after drying for 24 hours at normal temperature.
And cutting the porous current collector into rectangular pieces with the length of 79mm and the width of 45mm, using the rectangular pieces as negative pole pieces, stacking the rectangular pieces with a diaphragm and a positive pole piece in sequence, packaging the rectangular pieces with an aluminum plastic film, injecting electrolyte, and sealing the opening to obtain the single-piece battery. The positive electrode sheet, separator, and electrolyte in this example were the same as in example 1.
Example 8
Mixing polyethylene oxide and LiN (CF)3SO2)2Dissolving in acetonitrile, and stirring to obtain solution, wherein the mass of polyoxyethylene accounts for 5% of the total mass of the solution, and LiN(CF3SO2)2Adding lanthanum lithium zirconate, magnesium oxide and strontium oxide into the solution, and stirring to form a suspension, wherein the mass of the lanthanum lithium zirconate accounts for 8% of the total mass of the suspension, the mass of the magnesium oxide accounts for 0.2% of the total mass of the suspension, and the mass of the magnesium oxide accounts for 0.1% of the total mass of the suspension;
coating the obtained suspension on foam copper with the thickness of 1 mm;
drying for 24 hours at normal temperature to obtain the foamy copper with the solid electrolyte layer;
dissolving polyacrylonitrile and polyvinylidene fluoride in NMP, uniformly stirring to form a solution, wherein the mass of the polyacrylonitrile accounts for 3% of the total mass of the solution, the mass of the polyvinylidene fluoride accounts for 3% of the total mass of the solution, coating the solution on dried copper foam with a solid electrolyte layer, and drying the solution at normal temperature for 48 hours to obtain the porous current collector with two solid electrolyte layers.
And cutting the porous current collector into rectangular pieces with the length of 79mm and the width of 45mm, using the rectangular pieces as negative pole pieces, stacking the rectangular pieces with a diaphragm and a positive pole piece in sequence, packaging the rectangular pieces with an aluminum plastic film, injecting electrolyte, and sealing the opening to obtain the single-piece battery. The positive electrode sheet, separator, and electrolyte in this example were the same as in example 1.
Comparative example
The negative electrode plate of the comparative example was a foamy copper without any treatment, and the foamy copper was cut into a rectangular sheet having a length of 79mm and a width of 45mm, stacked in order with a separator and a positive electrode plate, and after being packaged with an aluminum plastic film, an electrolyte was injected and sealed to produce a single-piece battery. The positive electrode sheet, separator and electrolyte of the comparative example were the same as those of example 1.
The batteries prepared in examples 1 to 8 and comparative example were subjected to cycle performance tests, the test methods were according to the industry standards, and the batteries were subjected to charge and discharge cycle tests at a current density of 0.2mA/cm2, and the test results are shown in the following table.
Figure BDA0001667946540000101
Figure BDA0001667946540000111
The test results in the table show that the cycle performance of the lithium battery is obviously improved by using the porous current collector as a negative pole piece. The invention adopts the three-dimensional porous current collector, and the solid electrolyte layer is adhered on the surface and in the hole of the current collector matrix, because a large amount of space is arranged in the current collector matrix and can accommodate lithium deposited during the charging of the lithium battery, the volume of the current collector is kept unchanged in the process of repeated deposition and separation of the lithium, the adverse effect caused by repeated change of the volume of lithium metal in the circulating process is reduced, meanwhile, the formation of lithium dendrite can be inhibited due to the existence of the solid electrolyte layer, and the circulating performance of the lithium battery is improved. And because lithium metal is not directly used in the manufacturing process of the battery, strict environmental control is not needed, and the manufacturing cost of the lithium battery is reduced.
The three-dimensional porous current collector is directly used as the negative electrode of the lithium battery, the volume of lithium metal deposited on the negative electrode can be estimated according to the lithium removal amount of the positive electrode material, and the three-dimensional porous current collector with proper porosity and proper pore size is selected; or calculating the space capable of accommodating lithium metal deposition in the current collector according to the volume and the porosity of the current collector, further determining the usage amount of the positive active material, and ensuring that the space in the three-dimensional porous current collector is fully utilized while reserving enough lithium metal deposition space.
For example: when copper foam having a thickness t (cm), a porosity α, and an average pore diameter r (μm) is used as the porous current collector substrate, the copper foam per unit area has a total pore volume of about t × α (cm)3) (ii) a When a solid electrolyte layer having a thickness of delta (mu m) is attached to the surface and the pore surfaces of the copper foam, the porous current collector has a total pore volume per unit area of about t x alpha x (1-delta/r)3(cm3). And the density of lithium metal was 0.534 (g/cm)3) And a molar mass of 6.94(g/mol), the amount of lithium metal that can be theoretically deposited per unit area of the porous current collector is 0.534 Xt. times.alpha. × (1-delta/r)3(g) I.e. theoretical surface of lithium metal depositionThe upper limit of the density is 0.534 Xt. times.alpha. × (1-. delta./r)3(g/cm2). If the positive electrode active material is LiCoO2The molar mass is 97.87(g/mol), the upper limit of lithium removal is calculated according to 50%, and for a single-chip battery, one porous current collector corresponds to one positive plate, so that LiCoO in the positive plate2The upper limit of the theoretical areal density of (C) should be 15.06 Xt. times.alpha. × (1-. delta./r)3(g/cm2) (ii) a For a laminated cell, a porous current collector is shared by both positive electrodes, and the theoretical upper limit of areal density for each positive electrode sheet should be 7.53 XT × (1- δ/r)3(g/cm2) Therefore, the using amount of the positive active material can be determined according to the volume and the porosity of the current collector, so that the pore space of the porous current collector is fully utilized.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims (12)

1. The lithium battery comprises a positive pole piece, a negative pole piece and a diaphragm, wherein the positive pole piece, the diaphragm and the negative pole piece are stacked in sequence and packaged, and then electrolyte is filled to prepare the battery, and the lithium battery is characterized in that: the negative pole piece is porous mass flow body, porous mass flow body is including the mass flow body base member that has the pore structure, mass flow body base member surface and downthehole surface are adhered to and are had solid electrolyte layer, solid electrolyte layer contains polymer and lithium salt, solid electrolyte layer is the one deck at least, do not fill electrode active material on the negative pole piece.
2. A lithium battery as claimed in claim 1, characterized in that: the polymer is at least one of polyvinyl alcohol, polyethylene oxide, polyvinylidene fluoride-hexafluoropropylene copolymer, alkylated polyethylene oxide, polyvinylpyrrolidone, polyvinyl butyral, hydroxyethyl cellulose, methyl hydroxyethyl cellulose, sodium carboxymethyl cellulose, cellulose acetate propionate, polyacrylamide, polymethyl methacrylate, polybutyl methacrylate, polyethyl acrylate, polyvinyl alcohol, ethylene-vinyl acetate copolymer, polyvinyl acetate, polyurethane, melamine formaldehyde, urea formaldehyde, copolymers of maleic anhydride and derivatives and esters thereof, polyacrylonitrile, polycarbonate, polysiloxane, gelatin and starch; or the polymer is a copolymer containing at least two of polyvinyl alcohol, polyethylene oxide, polyvinylidene fluoride-hexafluoropropylene copolymer, alkylated polyethylene oxide, polyvinylpyrrolidone, polyvinyl butyral, hydroxyethyl cellulose, methyl hydroxyethyl cellulose, sodium carboxymethyl cellulose, cellulose acetate propionate, polyacrylamide, polymethyl methacrylate, polybutyl methacrylate, polyethyl acrylate, polyvinyl alcohol, ethylene-vinyl acetate copolymer, polyvinyl acetate, polyurethane, melamine formaldehyde, urea formaldehyde, copolymer of maleic anhydride and its derivatives and esters, polyacrylonitrile, polycarbonate, and polysiloxane.
3. A lithium battery as claimed in claim 1, characterized in that: the lithium salt is LiClO4、LiPF6Or Rf for the moiety F-，LiBF4Or Rf for the moiety F-、LiAsF6Or Rf for the moiety F-、LiSbF6Or Rf for the moiety F-、LiB(C2O4)2、LiCF3SO3、LiCnF2n+1SO3(n≥2)、LiC(CF3SO2)3、LiC(CnF2n+1SO2)3、LiCF3CO2、LiCnF2n+1CO2(n≥2)、LiC2F4(SO3)2、LiN(FSO2)2、LiN(CF3SO2)2、LiN(C2F5SO2)2、LiN(CnF2n+1SO2)2、LiN(RfOSO2)2At least one of (1).
4. A lithium battery as claimed in claim 1, characterized in that: the solid electrolyte layer contains an inorganic filler, and the mass of the inorganic filler accounts for 0-80% of the total mass of the solid electrolyte layer.
5. A lithium battery as claimed in claim 4, characterized in that: the inorganic filler is at least one of lithium silicate, lithium borate, lithium phosphate, lithium carbonate, lithium aluminum oxide, lithium titanium oxide, lithium lanthanum oxide, lithium aluminum phosphate, lithium titanium aluminum phosphate, lithium germanium aluminum phosphate, lithium lanthanum zirconate, silicon oxide, magnesium oxide, aluminum oxide, calcium oxide, strontium oxide, barium oxide, titanium oxide, zirconium oxide, gallium oxide, tin oxide, calcium sulfate, strontium sulfate, barium sulfate, calcium carbonate, strontium carbonate, barium carbonate and aluminum hydroxide.
6. A lithium battery as claimed in claim 1, characterized in that: the thickness of the current collector matrix is 1-2000 mu m.
7. A lithium battery as claimed in claim 1, characterized in that: the thickness of the solid electrolyte layer is 0.01-30 μm.
8. A lithium battery as claimed in claim 1, characterized in that: the preparation method of the porous current collector comprises the following steps:
adding a polymer and a lithium salt into a solvent for mixing, and uniformly stirring to prepare a solution;
coating the prepared solution on a current collector substrate, or soaking the current collector substrate in the prepared solution and then taking out;
and drying the current collector matrix to obtain the porous current collector with the solid electrolyte layer attached to the surface and the inner surface of the hole of the current collector matrix.
9. A lithium battery as claimed in claim 4, characterized in that: the preparation method of the porous current collector comprises the following steps:
adding a polymer and a lithium salt into a solvent, mixing to prepare a solution, adding an inorganic filler into the solution, and uniformly stirring to prepare a suspension;
coating the prepared suspension liquid on a current collector substrate, or soaking the current collector substrate in the prepared suspension liquid and then taking out;
and drying the current collector matrix to obtain the porous current collector with the solid electrolyte layer attached to the surface and the inner surface of the hole of the current collector matrix.
10. A lithium battery as claimed in claim 8, characterized in that: the mass of the polymer accounts for 4-6% of the total mass of the solution, and the mass of the lithium salt accounts for 1.5-2.5% of the total mass of the solution.
11. A lithium battery as claimed in claim 9, characterized in that: the mass of the polymer accounts for 4-6% of the total mass of the solution, the mass of the lithium salt accounts for 1.5-2.5% of the total mass of the solution, and the mass of the inorganic filler accounts for 0.9-11% of the total mass of the suspension.
12. A lithium battery as claimed in claim 8 or 9, characterized in that: when the solid electrolyte layers on the surface of the current collector matrix and the inner surface of the hole are provided with two or more layers, the composition of the solid electrolyte layers of the two adjacent layers is not completely the same, and the solid electrolyte layer which is not in direct contact with the current collector matrix contains a polymer or contains a polymer and lithium salt and/or inorganic filler.
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