CN110890506B - Heat-conducting composite diaphragm for battery and application thereof - Google Patents

Heat-conducting composite diaphragm for battery and application thereof Download PDF

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CN110890506B
CN110890506B CN201911094539.7A CN201911094539A CN110890506B CN 110890506 B CN110890506 B CN 110890506B CN 201911094539 A CN201911094539 A CN 201911094539A CN 110890506 B CN110890506 B CN 110890506B
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battery
aluminum salt
polymer
alumina
diaphragm
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CN110890506A (en
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解孝林
常晨
叶昀昇
周兴平
石清璇
裴会杰
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Huazhong University of Science and Technology
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Huazhong University of Science and Technology
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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
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/44—Fibrous material
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/431—Inorganic material
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/60—Heating or cooling; Temperature control
    • H01M10/65—Means for temperature control structurally associated with the cells
    • H01M10/653—Means for temperature control structurally associated with the cells characterised by electrically insulating or thermally conductive materials
    • 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
    • H01M10/60—Heating or cooling; Temperature control
    • H01M10/65—Means for temperature control structurally associated with the cells
    • H01M10/654—Means for temperature control structurally associated with the cells located inside the innermost case of the cells, e.g. mandrels, electrodes or electrolytes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/449—Separators, membranes or diaphragms characterised by the material having a layered structure
    • 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 invention belongs to the technical field of composite materials, and particularly relates to a heat-conducting composite diaphragm for a battery and application thereof. The invention provides a heat-conducting composite diaphragm for a battery, which comprises a polyolefin porous diaphragm and aluminum oxide/carbon hybrid fiber layers attached to two sides or one side of the polyolefin porous diaphragm. According to the polyolefin porous diaphragm/alumina/carbon hybrid fiber layer composite material provided by the invention, as the alumina with high thermal conductivity exists in the alumina/carbon hybrid fiber layer in a continuous fiber form, and meanwhile, the fibers are connected in a melting way in the high-temperature carbonization process, the contact interface is reduced, the interface thermal resistance is reduced, the construction of a thermal conduction path is realized, the thermal conductivity of the composite material is improved, and the diffusion of heat in the battery is realized. The heat-conducting composite diaphragm for the battery is applied to the lithium-sulfur battery, and the purpose of improving the performance of the battery can be achieved. Compared with the prior art, the battery performance can be effectively improved, and the problem of poor heat conductivity of the polyolefin porous diaphragm is solved.

Description

Heat-conducting composite diaphragm for battery and application thereof
Technical Field
The invention belongs to the technical field of composite materials, and particularly relates to a heat-conducting composite diaphragm for a battery and application thereof.
Background
With the population growth and economic development, the demand of people for energy is increasing. However, the existing fossil energy is increasingly exhausted and seriously polluted, and a new green, environment-friendly and renewable energy is urgently needed to solve the current energy crisis. The secondary battery is expected to be a breakthrough for future energy development as an environmentally-friendly and renewable new energy source. Wherein, the theoretical specific volume of the lithium-sulfur battery is up to 1675mAh g-1Theoretical energy density of 2600Wh kg-1The sulfur simple substance as the anode material is environment-friendly and cheap, and has abundant reserves, thereby having a plurality of advantages.
In the discharging process of the lithium-sulfur battery, lithium metal of the negative electrode loses electrons and becomes lithium ions, the lithium ions are diffused to the positive electrode through the porous battery diaphragm in the battery, meanwhile, the electrons reach the positive electrode through an external circuit, sulfur simple substances of the positive electrode obtain electrons, the electrons and the lithium ions react to generate lithium sulfide, and chemical energy is converted into electric energy to be applied. In the charging process of the lithium-sulfur battery, lithium sulfide at the positive electrode loses electrons to generate elemental sulfur and lithium ions, the lithium ions are diffused to the negative electrode of the battery through the porous battery diaphragm in the battery, the electrons are obtained at the negative electrode to generate the elemental lithium, and electric energy is converted into chemical energy to be stored. In the process of charging and discharging, because the aperture of the current commercial battery diaphragm is larger, lithium polysulfide which is an intermediate product soluble in electrolyte in electrochemical reaction penetrates through the porous battery diaphragm to diffuse to a negative electrode, and reacts with lithium metal to generate insoluble and insulated Li2S2Or Li2S, thereby causing the loss of sulfur and the passivation of lithium metal, and greatly reducing the specific capacitance and the cycling stability of the battery.
The battery separator that is currently commercially more mature is a polyolefin porous separator such as: polypropylene microporous membrane, polyethylene microporous membrane or polypropylene/polyethylene/polypropylene three-layer composite membrane. Aiming at the problem that the barrier effect of the polyolefin porous membrane on polysulfide is limited, the polyolefin porous membrane is traditionally used forThe battery separator is modified by coating a polysulfide barrier layer on the surface of the separator, such as porous carbon material layer, organic coating (perfluorosulfonic acid polymer, etc.), and transition metal oxide coating (MnO)2、Fe2O3、La2O3Etc.) to reduce the loss of sulfur, increase the specific capacitance and cycle stability of the battery by blocking or promoting the conversion of polysulfides. For example, patent CN107546355A discloses a modification method of sulfonated polyol to form a polymer barrier layer on the surface of a separator by interfacial reaction polymerization; patent CN103490027A discloses a modification method for loading a microporous barrier layer on the surface of a separator.
These battery separator modification methods are effective in blocking polysulfide shuttling. However, the polyolefin porous diaphragm is a high-molecular porous material, and the modified coating is mostly a high-molecular material, a porous material or a metal oxide and other materials with poor heat conductivity, so that the battery composite diaphragm material has poor heat conductivity. Heat generated in the charging and discharging processes of the battery is gathered on the surface of the composite diaphragm, so that the internal temperature of the battery is uneven, and the surface temperature of the composite diaphragm is overhigh. High temperature causes diaphragm deformation, aggravates diffusion and migration speed of polysulfide in the battery, reduces specific capacitance and cycling stability of the battery, and causes performance reduction of the battery. Therefore, a heat-conducting composite diaphragm for a battery is needed to solve the problem that the existing battery composite diaphragm is poor in heat-conducting property.
Disclosure of Invention
Aiming at the defects or improvement requirements in the prior art, the invention provides a heat-conducting composite diaphragm for a battery and application thereof.
In order to achieve the above objects, according to one aspect of the present invention, there is provided a thermally conductive composite separator for a battery, including a polyolefin porous separator and alumina/carbon hybrid fiber layers attached to both sides or one side of the polyolefin porous separator.
Preferably, the polyolefin porous membrane is a polypropylene microporous membrane, a polyethylene microporous membrane or a polypropylene/polyethylene/polypropylene three-layer composite membrane.
Preferably, the thickness of the alumina/carbon hybrid fiber layer is 5 to 100 μm.
Preferably, the preparation method of the alumina/carbon hybrid fiber layer comprises the following steps:
(1) dissolving a polymer in an aluminum salt dispersion liquid to obtain an aluminum salt-polymer mixed liquid; the aluminum salt dispersion is obtained by dispersing aluminum salt in a solvent;
(2) spinning the aluminum salt-polymer mixed solution obtained in the step (1) into an aluminum salt-polymer fiber membrane by adopting an electrostatic spinning process;
(3) and (3) heating and carbonizing the aluminum salt-polymer fiber membrane obtained in the step (2) in a protective atmosphere to obtain the alumina/carbon hybrid fiber layer.
Preferably, the solvent in step (1) is one or more of water, ethanol and N, N-dimethylformamide; the aluminum salt is an inorganic aluminum salt or an organic aluminum salt which can be decomposed into aluminum oxide under the heating condition; preferably, the aluminum salt is any one of aluminum nitrate, aluminum tert-butoxide, and aluminum hydroxide.
Preferably, the total mass fraction of the aluminum salt and the polymer in the aluminum salt-polymer mixed solution in the step (1) is 10-50%, wherein the mass ratio of the aluminum salt to the polymer is 1: 1-1: 10; the polymer is a polymer which can be carbonized under heating condition.
Preferably, the polymer is any one of polyvinylpyrrolidone, polyacrylonitrile and polyvinyl butyral.
Preferably, in the step (2), the operating voltage of the electrostatic spinning process is 10kV to 30kV, and the feeding rate is 0.5mL/h to 5 mL/h; the thickness of the aluminum salt-polymer fiber membrane is 5-100 mu m.
Preferably, in the step (3), the heating carbonization comprises sequentially performing low-temperature pre-carbonization and high-temperature carbonization; the treatment temperature of the low-temperature pre-carbonization is 200-400 ℃, and the treatment time is 0.5-2 h; the high-temperature carbonization treatment temperature is 600-800 ℃, and the treatment time is 1-4 h.
According to another aspect of the present invention, there is provided a use of the thermally conductive composite separator for a battery as a thermally conductive composite separator for a secondary battery.
According to another aspect of the present invention, a secondary battery is provided, wherein the battery is assembled by using the heat-conducting composite membrane, and the battery is assembled by using a positive electrode shell, a pole piece, the heat-conducting composite membrane for the battery (with electrolyte dropwise added), a lithium piece, a steel sheet, an elastic sheet and a negative electrode shell in this order. In the heat-conducting composite diaphragm for the battery, the alumina/carbon hybrid fiber layer is attached to one side or two sides of the polyolefin porous diaphragm; when the aluminum oxide/carbon hybrid fiber layer is attached to one side of the polyolefin porous diaphragm, the aluminum oxide/carbon hybrid fiber layer is attached to one side of the polyolefin porous diaphragm facing the pole piece.
Compared with the prior art, the technical scheme of the invention has the advantages that the high-heat-conductivity material alumina in the alumina/carbon hybrid fiber layer exists in the form of continuous fibers, so that the construction of a heat-conducting path is realized, and the heat is rapidly transferred transversely and longitudinally through the alumina fibers. The carbon material on the surface of the fiber effectively adsorbs polysulfide, so that the barrier effect of the polysulfide is realized, and meanwhile, the conductivity of lithium ions is promoted due to the conductivity of the carbon material, so that the performance of the battery is improved. The invention simultaneously achieves the purposes of improving the heat-conducting property of the composite diaphragm and improving the specific capacitance and the cycle stability of the battery.
Compared with the existing preparation method of the heat conduction material, the preparation method has obvious advantages in preparation and performance. In the prior art, the thermal conductivity of the composite material is improved by filling a matrix with a thermally conductive filler. The filling type heat conduction material increases the content of the filling particles as much as possible on the basis of ensuring other properties of the matrix material, so that effective heat transmission channels are formed among the filling particles, and finally the heat conduction property of the composite material is improved. The problems faced by such methods are that under the condition of low filling amount, an effective heat conducting network is difficult to form, and high interface thermal resistance is generated; at high loadings, however, the filler interacts weakly with the polymer substrate and tends to agglomerate. In the invention, the mixed solution of the precursor aluminum salt of the heat-conducting filler alumina and the polymer is spun into the fiber by adopting an electrostatic spinning process, aluminum salt molecules are uniformly dispersed in the fiber, and the filling amount in the fiber is improved. And further carrying out high-temperature carbonization treatment in a protective atmosphere, pyrolyzing aluminum salt to obtain aluminum oxide, and carbonizing the polymer to form an aluminum oxide/carbon hybrid fiber layer. Because aluminum salt molecules are uniformly and continuously dispersed in the fibers, alumina which is a high-thermal-conductivity material exists in the alumina/carbon hybrid fiber layer as continuous fibers, the length-diameter ratio of the alumina fibers is high, the fibers are fused and combined in the high-temperature carbonization process, and the fibers are combined together through fused intersection points, so that the construction of a thermal-conductivity path is realized, and the interface thermal resistance is greatly reduced.
Specifically, the present invention can achieve the following advantageous effects:
(1) the invention provides a heat-conducting composite diaphragm for a battery, which comprises a polyolefin porous diaphragm and aluminum oxide/carbon hybrid fiber layers attached to two sides or one side of the polyolefin porous diaphragm. According to the polyolefin porous diaphragm/alumina/carbon hybrid fiber layer composite material provided by the invention, as the alumina which is a high-thermal-conductivity material in the alumina/carbon hybrid fiber layer is a continuous fiber, and meanwhile, the fibers are connected in a melting way in the high-temperature carbonization process, the contact interface is reduced, the interface thermal resistance is reduced, the construction of a thermal conduction path is realized, the thermal conductivity of the composite material is improved, and the diffusion of heat in the battery is realized.
(2) According to the polyolefin porous diaphragm/alumina/carbon hybrid fiber layer composite material provided by the invention, alumina fibers in the alumina/carbon hybrid fiber layer conduct heat, carbon conducts electricity, and the construction of a heat conduction path and a conductive path dual network is realized.
(3) According to the polyolefin porous diaphragm/alumina/carbon hybrid fiber layer composite material provided by the invention, polysulfide is effectively adsorbed by the carbon material on the surface of the fiber, so that the barrier effect of the polysulfide is realized, and meanwhile, the conduction of lithium ions is promoted due to the conductivity of the carbon material, so that the battery performance is improved.
(4) According to the preparation method of the heat-conducting composite diaphragm for the battery, provided by the invention, in the preparation process of the aluminum oxide/carbon hybrid fiber layer, the fiber is spun by adopting an electrostatic spinning process on the mixed solution of the precursor aluminum salt of the heat-conducting filler aluminum oxide and the polymer, so that the dispersibility of the micromolecule aluminum salt in the fiber is improved, and the micromolecule aluminum salt is uniformly and continuously dispersed.
(5) According to the preparation method of the heat-conducting composite diaphragm for the battery, provided by the invention, in the high-temperature carbonization process, aluminum salt is pyrolyzed to generate aluminum oxide, and meanwhile, a polymer is carbonized to form an aluminum oxide/carbon hybrid fiber layer. Because the small-molecular aluminum salt is uniformly dispersed and continuous, the alumina fiber in the generated alumina/carbon hybrid fiber layer is continuous and complete.
(6) The preparation method of the composite material provided by the invention has the advantages of controllable mass ratio of the alumina/carbon hybrid fiber layer, controllable thickness of the alumina/carbon hybrid fiber layer and simple preparation process, and is more suitable for large-scale industrial production
Drawings
FIG. 1 is a scanning electron microscope image of aluminum nitrate/polyacrylonitrile fiber.
Fig. 2 is a scanning electron microscope image of the alumina/carbon hybrid fiber layer.
Fig. 3 is a scanning electron microscope image of the alumina fiber after carbon on the surface of the alumina/carbon hybrid fiber layer is decomposed by oxidation.
FIG. 4 is a diagram showing the unmodified polyethylene microporous membrane (PE) in comparative example 2, the polyethylene microporous membrane/carbon Fiber composite membrane (PE/C-Fiber) in comparative example 1, and the polyethylene microporous membrane/alumina/carbon hybrid Fiber layer composite membrane (PE/Al)2O3@ C-Fiber) assembled cell, the EIS curves of fig. 4(a) before three battery charge-discharge cycles and fig. 4(b) after 50 cycles. In FIG. 4(a) and FIG. 4(b), three curves are sequentially a polyethylene microporous membrane (PE), a polyethylene microporous membrane/carbon Fiber composite membrane (PE/C-Fiber), and a polyethylene microporous membrane/alumina/carbon hybrid Fiber layer composite membrane (PE/Al) from top to bottom2O3@C-Fiber)。
FIG. 5 is a diagram showing the unmodified polyethylene microporous membrane (PE) in comparative example 2, the polyethylene microporous membrane/carbon Fiber composite membrane (PE/C-Fiber) in comparative example 1, and the polyethylene microporous membrane/alumina/carbon hybrid Fiber layer composite membrane(PE/Al2O3@ C-Fiber) assembled cell, three sets of cells cycled at 0.5C. In FIG. 5, the three curves are sequentially a polyethylene microporous membrane/alumina/carbon hybrid fiber layer composite membrane (PE/Al) from top to bottom2O3@ C-Fiber), polyethylene microporous membrane/carbon Fiber composite membrane (PE/C-Fiber), and polyethylene microporous membrane (PE).
FIG. 6 shows a polyethylene microporous membrane/alumina/carbon hybrid fiber layer composite membrane (PE/Al)2O3@ C-Fiber) assembled cell charge and discharge curves at 0.5C.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.
The invention provides a heat-conducting composite diaphragm for a battery, which comprises a polyolefin porous diaphragm and aluminum oxide/carbon hybrid fiber layers attached to two sides or one side of the polyolefin porous diaphragm.
The slash "/" in the alumina/carbon hybrid fiber layer according to the present invention represents a composite hybrid of alumina and carbon.
The polyolefin porous membrane of the invention has the same type and size as the polyolefin porous membrane commercially available on the market, can be obtained commercially, and can be prepared by itself according to the method of the prior art. In some embodiments, the polyolefin porous membrane is a polypropylene microporous membrane, a polyethylene microporous membrane, or a polypropylene/polyethylene/polypropylene three-layer composite membrane.
In some embodiments, the alumina/carbon hybrid fiber layer has a thickness of 5 μm to 100 μm.
In some embodiments, the alumina/carbon hybrid fiber layer is prepared as follows:
(1) dissolving a polymer in an aluminum salt dispersion liquid to obtain a uniformly dispersed aluminum salt-polymer mixed liquid; the aluminum salt dispersion is obtained by dispersing aluminum salt in a solvent;
(2) spinning the aluminum salt-polymer mixed solution obtained in the step (1) into an aluminum salt-polymer fiber membrane by adopting an electrostatic spinning process;
(3) and (3) heating and carbonizing the aluminum salt-polymer fiber membrane obtained in the step (2) in a protective atmosphere to obtain the alumina/carbon hybrid fiber layer.
After the aluminum oxide/carbon hybrid fiber layer is prepared, the aluminum oxide/carbon hybrid fiber layer obtained in the step (3) is attached to two sides or one side of the polyolefin porous diaphragm, and the heat-conducting composite diaphragm for the battery is obtained.
In some embodiments, the solvent of step (1) is one or more of water, ethanol, and N, N-dimethylformamide; the aluminum salt is an inorganic aluminum salt or an organic aluminum salt which can be decomposed into aluminum oxide under the heating condition; in a preferred embodiment, the aluminum salt is any one of aluminum nitrate, aluminum tert-butoxide, and aluminum hydroxide.
In some embodiments, the total mass fraction of the aluminum salt and the polymer in the aluminum salt-polymer mixed solution in the step (1) is 10% to 50%, wherein the mass ratio of the aluminum salt to the polymer is 1:1 to 1: 10; the polymer is a polymer which can be carbonized under the heating condition; in a preferred embodiment, the polymer is any one of polyvinylpyrrolidone, polyacrylonitrile and polyvinyl butyral.
In some embodiments, in step (2), the operating voltage of the electrospinning process is 10kV to 30kV, and the feeding rate is 0.5mL/h to 5 mL/h; the thickness of the aluminum salt-polymer fiber membrane is 5-100 mu m.
In the step (2), the aluminum salt-polymer fiber membrane is prepared by adopting an electrostatic spinning process, and the aluminum salt-polymer fiber membrane which is mutually interwoven and stacked layer by layer can be obtained by regulating and controlling the rotating speed of a rotating disc collector and enabling an electrostatic spinning nozzle to circularly and repeatedly move at a constant speed in the horizontal direction. By controlling the acceptance time of the rotating disc collector, the thickness of the aluminum salt-polymer fiber film can be controlled.
In some embodiments, the thickness of the alumina/carbon hybrid fiber layer in the step (3) is 5 μm to 100 μm. The thickness of the aluminum salt-polymer fiber membrane and the alumina/carbon hybrid fiber membrane is not greatly changed before and after carbonization.
In some embodiments, the protective atmosphere in step (3) is nitrogen or an inert atmosphere, such as an argon atmosphere.
In some embodiments, in the step (3), the heating carbonization includes a low-temperature pre-carbonization and a high-temperature carbonization which are sequentially performed; the treatment temperature of the low-temperature pre-carbonization is 200-400 ℃, and the treatment time is 0.5-2 h; the high-temperature carbonization treatment temperature is 600-800 ℃, and the treatment time is 1-4 h.
The application of the heat-conducting composite diaphragm provided by the invention can be used as the heat-conducting composite diaphragm of a secondary battery. The aluminum oxide/carbon hybrid fiber layer is attached to one side or two sides of the polyolefin porous diaphragm, and when the aluminum oxide/carbon hybrid fiber layer is attached to one side of the polyolefin porous diaphragm facing the pole piece, the aluminum oxide/carbon hybrid fiber layer is attached to one side of the polyolefin porous diaphragm facing the pole piece.
The invention also provides a secondary battery which comprises the heat-conducting composite diaphragm for the battery, and at least one layer of the aluminum oxide/carbon hybrid fiber layer in the diaphragm is attached to the side, facing the pole piece, of the polyolefin porous diaphragm.
In some embodiments, the secondary battery is a lithium sulfur battery.
When in use, the assembly method of the battery is the same as that of the battery in the prior art, except that the conventional polyolefin porous diaphragm is replaced by the composite diaphragm provided by the invention. Generally, the electrolyte is required to be dripped between the pole piece and the composite diaphragm during the operation of the battery, so that the electrolyte can be dripped on the pole piece and also can be dripped on the diaphragm during the assembly of the battery. Specifically, if the battery is assembled by adopting the heat-conducting composite diaphragm jointed at two sides, the battery is assembled according to the sequence of a positive electrode shell, a pole piece, an alumina/carbon hybrid fiber layer (dropwise added with electrolyte), a polyolefin porous diaphragm, an alumina/carbon hybrid fiber layer, a lithium sheet, a steel sheet, an elastic sheet and a negative electrode shell; if the battery is assembled by adopting the heat-conducting composite diaphragm which is attached on one side, the battery is assembled according to the sequence of the positive electrode shell, the pole piece, the alumina/carbon hybrid fiber layer (which is dropwise added with the electrolyte), the polyolefin porous diaphragm, the lithium piece, the steel sheet, the elastic sheet and the negative electrode shell. In the process of assembling the battery, due to the infiltration effect of the electrolyte, the effective bonding of the alumina/carbon hybrid fiber layer and the polyolefin porous diaphragm can be realized. Because the aluminum oxide/carbon hybrid fiber layer is tightly attached to the polyolefin porous diaphragm, the heat on the surface of the polyolefin porous diaphragm can be effectively transferred to the pole piece, the lithium piece or the battery shell through the aluminum oxide/carbon hybrid fiber layer with high heat conductivity, and then transferred to the external environment, so that the heat transfer is realized.
The invention provides a heat-conducting composite diaphragm for a battery, which comprises a polyolefin porous diaphragm and an alumina/carbon hybrid fiber layer attached to two sides or one side of the polyolefin porous diaphragm, wherein an aluminum salt-polymer mixed solution is spun into fibers by adopting an electrostatic spinning process, the fibers are carbonized at high temperature under a protective atmosphere to form the alumina/carbon hybrid fiber layer, and the alumina/carbon hybrid fiber layer is attached to one side or two sides of the polyolefin porous diaphragm to prepare the heat-conducting composite diaphragm for the battery with high heat conductivity. The polyolefin porous diaphragm used in the invention is a polypropylene microporous diaphragm, a polyethylene microporous diaphragm or a polypropylene/polyethylene/polypropylene composite film. According to the invention, by improving the proportion of key components in the heat-conducting composite diaphragm for the battery, the whole process flow of the corresponding preparation method, the reaction conditions of each step and the like, compared with the prior art, the battery performance can be effectively improved, and the problem of poor heat-conducting property of the polyolefin porous diaphragm can be solved.
The following are examples:
example 1
A thermally conductive composite separator for a battery. The heat-conducting composite diaphragm for the battery comprises a polyolefin porous diaphragm and an alumina/carbon hybrid fiber layer. The aluminum salt-polymer mixed solution is spun into fiber by adopting an electrostatic spinning process, and is carbonized at high temperature under protective atmosphere to form an alumina/carbon hybrid fiber layer which is attached to one side of the polyolefin porous diaphragm facing to the pole piece. The polyolefin porous diaphragm is a polyethylene microporous diaphragm; the aluminum salt is aluminum nitrate; the polymer is polyacrylonitrile; the solution is N, N-dimethylformamide; the total mass fraction of aluminum salt and polymer in the aluminum salt-polymer mixed solution is 10%, wherein the mass ratio of the aluminum salt to the polymer is 1: 1; the thickness of the aluminum salt-polymer fiber film obtained was 10 μm.
The preparation method of the heat-conducting composite diaphragm for the battery comprises the following steps:
(1) dispersing 0.5g of aluminum nitrate in 9g N, N-dimethylformamide, and magnetically stirring for 1 hour to obtain a uniform dispersion liquid;
(2) dissolving 0.5g of polyacrylonitrile in the aluminum nitrate dispersion liquid obtained in the step (1), and continuing to stir for 1 hour by magnetic force to obtain uniformly dispersed aluminum nitrate-polyacrylonitrile mixed liquid;
(3) and (3) spinning the aluminum nitrate-polyacrylonitrile mixed solution obtained in the step (2) into an aluminum nitrate-polypropylene fiber membrane by adopting an electrostatic spinning process, wherein the operating voltage is 10kV, and the feeding rate is 0.5 mL/h.
(4) Carbonizing the aluminum nitrate-polypropylene fiber membrane obtained in the step (3) at a high temperature under nitrogen, wherein the low-temperature pre-carbonization treatment temperature is 200 ℃, the treatment time is 0.5h, the high-temperature carbonization treatment temperature is 600 ℃, and the treatment time is 1h, so as to obtain an aluminum oxide/carbon hybrid fiber layer;
(5) and (3) attaching the alumina/carbon hybrid fiber layer obtained in the step (4) to one side of the polyethylene microporous diaphragm facing the pole piece to obtain the heat-conducting composite diaphragm for the battery.
(6) And (4) applying the heat-conducting composite diaphragm for the battery obtained in the step (5) to a lithium-sulfur battery.
Example 2
A thermally conductive composite separator for a battery. The heat-conducting composite diaphragm for the battery comprises a polyolefin porous diaphragm and an alumina/carbon hybrid fiber layer. The aluminum salt-polymer mixed solution is spun into fiber by adopting an electrostatic spinning process, and is carbonized at high temperature under protective atmosphere to form an alumina/carbon hybrid fiber layer which is attached to one side of the polyolefin porous diaphragm facing to the pole piece. The polyolefin porous diaphragm is a polyethylene microporous diaphragm; the aluminum salt is tert-butyl aluminum; the polymer is polyvinylpyrrolidone; the solution is water; the total mass fraction of the aluminum salt and the polymer in the aluminum salt-polymer mixed solution is 25%, wherein the mass ratio of the aluminum salt to the polymer is 1:4, and the thickness of the prepared aluminum salt-polymer fiber film is 20 mu m.
The preparation method of the heat-conducting composite diaphragm for the battery comprises the following steps:
(1) 0.5g of aluminum tert-butoxide was dispersed in 7.5g of water to give a homogeneous dispersion;
(2) dissolving 2g of polyvinylpyrrolidone in the aluminum tert-butoxide solution obtained in the step (1) to obtain a uniformly dispersed aluminum tert-butoxide-polyvinylpyrrolidone mixed solution;
(3) spinning the mixed solution of aluminum tert-butoxide and polyvinylpyrrolidone obtained in the step (2) into an aluminum tert-butoxide and polyvinylpyrrolidone fibrous membrane by adopting an electrostatic spinning process, wherein the operating voltage is 20kV, and the feeding rate is 1 mL/h;
(4) carbonizing the aluminum tert-butoxide-polyvinylpyrrolidone fiber membrane obtained in the step (3) at a high temperature under argon, wherein the low-temperature pre-carbonization treatment temperature is 300 ℃, the treatment time is 1h, the high-temperature carbonization treatment temperature is 700 ℃, and the treatment time is 2h, so as to obtain an alumina/carbon hybrid fiber layer;
(5) and (3) attaching the alumina/carbon hybrid fiber layer obtained in the step (4) to one side of the polyethylene microporous diaphragm facing the pole piece to obtain the heat-conducting composite diaphragm for the battery.
(6) And (4) applying the heat-conducting composite diaphragm for the battery obtained in the step (5) to a lithium-sulfur battery.
Example 3
A thermally conductive composite separator for a battery. The heat-conducting composite diaphragm for the battery comprises a polyolefin porous diaphragm and an alumina/carbon hybrid fiber layer. The aluminum salt-polymer mixed solution is spun into fibers by adopting an electrostatic spinning process, and is carbonized at high temperature under a protective atmosphere to form an alumina/carbon hybrid fiber layer which is attached to two sides of the polyolefin porous diaphragm. The polyolefin porous diaphragm is a polypropylene/polyethylene/polypropylene composite film; the aluminum salt is aluminum hydroxide; the polymer is polyvinyl butyral; the solution is ethanol; the total mass fraction of the aluminum salt and the polymer in the aluminum salt-polymer mixed solution is 50%, wherein the mass ratio of the aluminum salt to the polymer is 1:10, and the thickness of the prepared aluminum salt-polymer fiber film is 30 mu m.
The preparation method of the heat-conducting composite diaphragm for the battery comprises the following steps:
(1) dispersing 0.5g of aluminum hydroxide in 5.5g of ethanol to obtain a uniform dispersion liquid;
(2) dissolving 5g of polyvinyl butyral in the aluminum hydroxide solution obtained in the step (1) to obtain a uniformly dispersed aluminum hydroxide-polyvinyl butyral mixed solution;
(3) spinning the aluminum hydroxide-polyvinyl butyral mixed solution obtained in the step (2) into an aluminum hydroxide-polyvinyl butyral fiber membrane by adopting an electrostatic spinning process, wherein the operating voltage is 30kV, and the feeding speed is 1.5 mL/h;
(4) carbonizing the aluminum hydroxide-polyvinyl butyral fiber film obtained in the step (3) at a high temperature under nitrogen, wherein the low-temperature pre-carbonization treatment temperature is 400 ℃, the treatment time is 2 hours, the high-temperature carbonization treatment temperature is 800 ℃, and the treatment time is 4 hours, so as to obtain an aluminum oxide/carbon hybrid fiber layer;
(5) and (3) attaching the alumina/carbon hybrid fiber layer obtained in the step (4) to two sides of a polypropylene/polyethylene/polypropylene composite membrane to obtain the heat-conducting composite membrane for the battery.
(6) And (4) applying the heat-conducting composite diaphragm for the battery obtained in the step (5) to a lithium-sulfur battery.
Example 4
A thermally conductive composite separator for a battery. The heat-conducting composite diaphragm for the battery comprises a polyolefin porous diaphragm and an alumina/carbon hybrid fiber layer. The aluminum salt-polymer mixed solution is spun into fiber by adopting an electrostatic spinning process, and is carbonized at high temperature under protective atmosphere to form an alumina/carbon hybrid fiber layer which is attached to one side of the polyolefin porous diaphragm facing to the pole piece. The polyolefin porous diaphragm is a polypropylene microporous diaphragm; the aluminum salt is tert-butyl aluminum; the polymer is polyvinylpyrrolidone; the solution is water; the total mass fraction of the aluminum salt and the polymer in the aluminum salt-polymer mixed solution is 30%, wherein the mass ratio of the aluminum salt to the polymer is 1: 5; the thickness of the aluminum salt-polymer fiber film obtained was 5 μm.
The preparation method of the heat-conducting composite diaphragm for the battery comprises the following steps:
(1) 0.5g of aluminum tert-butoxide is dispersed in 7g of water to obtain a homogeneous dispersion;
(2) dissolving 2.5g of polyvinylpyrrolidone in the aluminum tert-butoxide solution obtained in the step (1) to obtain a uniformly dispersed aluminum tert-butoxide-polyvinylpyrrolidone mixed solution;
(3) spinning the mixed solution of aluminum tert-butoxide and polyvinylpyrrolidone obtained in the step (2) into an aluminum tert-butoxide and polyvinylpyrrolidone fibrous membrane by adopting an electrostatic spinning process, wherein the operating voltage is 15kV, and the feeding rate is 2 mL/h;
(4) carbonizing the aluminum tert-butoxide-polyvinylpyrrolidone fiber membrane obtained in the step (3) at a high temperature under argon, wherein the low-temperature pre-carbonization treatment temperature is 250 ℃, the treatment time is 1.5h, the high-temperature carbonization treatment temperature is 650 ℃, and the treatment time is 1.5h, so as to obtain an alumina/carbon hybrid fiber layer;
(5) and (3) attaching the alumina/carbon hybrid fiber layer obtained in the step (4) to one side of the polypropylene microporous diaphragm facing the pole piece to obtain the heat-conducting composite diaphragm for the battery.
(6) And (4) applying the heat-conducting composite diaphragm for the battery obtained in the step (5) to a lithium-sulfur battery.
Example 5
A thermally conductive composite separator for a battery. The heat-conducting composite diaphragm for the battery comprises a polyolefin porous diaphragm and an alumina/carbon hybrid fiber layer. The aluminum salt-polymer mixed solution is spun into fiber by adopting an electrostatic spinning process, and is carbonized at high temperature under protective atmosphere to form an alumina/carbon hybrid fiber layer which is attached to one side of the polyolefin porous diaphragm facing to the pole piece. The polyolefin porous diaphragm is a polyethylene microporous diaphragm; the aluminum salt is aluminum hydroxide; the polymer is polyvinyl butyral; the solution is ethanol; the total mass fraction of aluminum salt and polymer in the aluminum salt-polymer mixed solution is 40%, wherein the mass ratio of the aluminum salt to the polymer is 1: 7; the thickness of the aluminum salt-polymer fiber film obtained was 100. mu.m.
The preparation method of the heat-conducting composite diaphragm for the battery comprises the following steps:
(1) dispersing 0.5g of aluminum hydroxide in 6g of ethanol to obtain a uniform dispersion liquid;
(2) 3.5g of polyvinyl butyral is dissolved in the aluminum hydroxide solution obtained in the step (1) to obtain a uniformly dispersed aluminum hydroxide-polyvinyl butyral mixed solution;
(3) spinning the aluminum hydroxide-polyvinyl butyral mixed solution obtained in the step (2) into an aluminum hydroxide-polyvinyl butyral fiber membrane by adopting an electrostatic spinning process, wherein the operating voltage is 25kV, and the feeding rate is 2.5 mL/h; the thickness of the aluminum hydroxide-polyvinyl butyral fiber film was 100. mu.m.
(4) Carbonizing the aluminum hydroxide-polyvinyl butyral fiber membrane obtained in the step (3) at a high temperature under nitrogen, wherein the low-temperature pre-carbonization treatment temperature is 350 ℃, the treatment time is 0.5h, the high-temperature carbonization treatment temperature is 750 ℃, and the treatment time is 2.5h, so as to obtain an aluminum oxide/carbon hybrid fiber layer;
(5) and (3) attaching the alumina/carbon hybrid fiber layer obtained in the step (4) to one side of the polyethylene microporous diaphragm facing the pole piece to obtain the heat-conducting composite diaphragm for the battery.
(6) And (4) applying the heat-conducting composite diaphragm for the battery obtained in the step (5) to a lithium-sulfur battery.
Example 6
A thermally conductive composite separator for a battery. The heat-conducting composite diaphragm for the battery comprises a polyolefin porous diaphragm and an alumina/carbon hybrid fiber layer. The aluminum salt-polymer mixed solution is spun into fibers by adopting an electrostatic spinning process, and is carbonized at high temperature under a protective atmosphere to form an alumina/carbon hybrid fiber layer which is attached to two sides of the polyolefin porous diaphragm. The polyolefin porous diaphragm is a polypropylene/polyethylene/polypropylene composite film; the aluminum salt is aluminum nitrate; the polymer is polyacrylonitrile; the solution is N, N-dimethylformamide; the total mass fraction of aluminum salt and polymer in the aluminum salt-polymer mixed solution is 35%, wherein the mass ratio of the aluminum salt to the polymer is 1: 6; the thickness of the aluminum salt-polymer fiber film obtained was 20 μm.
The preparation method of the heat-conducting composite diaphragm for the battery comprises the following steps:
(1) 0.5g of aluminum nitrate was dispersed in 6.5g of water to obtain a uniform dispersion;
(2) dissolving 3g of polyacrylonitrile in the aluminum nitrate solution obtained in the step (1) to obtain uniformly dispersed aluminum nitrate-polyacrylonitrile mixed solution;
(3) spinning the aluminum nitrate-polyacrylonitrile mixed solution obtained in the step (2) into an aluminum nitrate-polyacrylonitrile fiber membrane by adopting an electrostatic spinning process, wherein the operating voltage is 25kV, and the feeding rate is 3 mL/h;
(4) carbonizing the aluminum nitrate-polyacrylonitrile fiber membrane obtained in the step (3) at a high temperature under argon, wherein the treatment temperature of low-temperature pre-carbonization is 200 ℃, the treatment time is 2 hours, the treatment temperature of high-temperature carbonization is 600 ℃, and the treatment time is 2 hours, so as to obtain an aluminum oxide/carbon hybrid fiber layer;
(5) and (3) attaching the alumina/carbon hybrid fiber layer obtained in the step (4) to two sides of a polypropylene/polyethylene/polypropylene composite membrane to obtain the heat-conducting composite membrane for the battery.
(6) And (4) applying the heat-conducting composite diaphragm for the battery obtained in the step (5) to a lithium-sulfur battery.
Example 7
A thermally conductive composite separator for a battery. The heat-conducting composite diaphragm for the battery comprises a polyolefin porous diaphragm and an alumina/carbon hybrid fiber layer. The aluminum salt-polymer mixed solution is spun into fibers by adopting an electrostatic spinning process, and is carbonized at high temperature under a protective atmosphere to form an alumina/carbon hybrid fiber layer which is attached to two sides of the polyolefin porous diaphragm. The polyolefin porous diaphragm is a polypropylene microporous diaphragm; the aluminum salt is tert-butyl aluminum; the polymer is polyvinyl butyral; the solution is water; the total mass fraction of the aluminum salt and the polymer in the aluminum salt-polymer mixed solution is 15%, wherein the mass ratio of the aluminum salt to the polymer is 1: 2; the thickness of the aluminum salt-polymer fiber film obtained was 15 μm.
The preparation method of the heat-conducting composite diaphragm for the battery comprises the following steps:
(1) 0.5g of aluminum tert-butoxide is dispersed in 8.5g of water to obtain a homogeneous dispersion;
(2) dissolving 1g of polyvinyl butyral in the aluminum tert-butoxide solution obtained in the step (1) to obtain a uniformly dispersed aluminum tert-butoxide-polyvinyl butyral mixed solution;
(3) spinning the aluminum tert-butoxide-polyvinyl butyral mixed solution obtained in the step (2) into an aluminum tert-butoxide-polyvinyl butyral fiber membrane by adopting an electrostatic spinning process, wherein the operating voltage is 25kV, and the feeding rate is 3.5 mL/h;
(4) carbonizing the aluminum tert-butoxide-polyvinyl butyral fiber film obtained in the step (3) at high temperature under nitrogen, wherein the low-temperature pre-carbonization treatment temperature is 400 ℃, the treatment time is 1.5h, the high-temperature carbonization treatment temperature is 650 ℃, and the treatment time is 1.5h, so as to obtain an aluminum oxide/carbon hybrid fiber layer;
(5) and (5) attaching the alumina/carbon hybrid fiber layer obtained in the step (4) to two sides of a polypropylene microporous diaphragm to obtain the heat-conducting composite diaphragm for the battery.
(6) And (4) applying the heat-conducting composite diaphragm for the battery obtained in the step (5) to a lithium-sulfur battery.
Example 8
A thermally conductive composite separator for a battery. The heat-conducting composite diaphragm for the battery comprises a polyolefin porous diaphragm and an alumina/carbon hybrid fiber layer. The aluminum salt-polymer mixed solution is spun into fiber by adopting an electrostatic spinning process, and is carbonized at high temperature under protective atmosphere to form an alumina/carbon hybrid fiber layer which is attached to one side of the polyolefin porous diaphragm facing to the pole piece. The polyolefin porous diaphragm is a polyethylene microporous diaphragm; the aluminum salt is aluminum hydroxide; the polymer is polyacrylonitrile; the solution is N, N-dimethylformamide; the total mass fraction of aluminum salt and polymer in the aluminum salt-polymer mixed solution is 20%, wherein the mass ratio of the aluminum salt to the polymer is 1: 3; the thickness of the aluminum salt-polymer fiber film obtained was 25. mu.m.
The preparation method of the heat-conducting composite diaphragm for the battery comprises the following steps:
(1) 0.5g of aluminum hydroxide was dispersed in 8g of water to obtain a uniform dispersion;
(2) dissolving 1.5g of polyacrylonitrile in the aluminum hydroxide solution obtained in the step (1) to obtain uniformly dispersed aluminum hydroxide-polyacrylonitrile mixed solution;
(3) spinning the aluminum hydroxide-polyacrylonitrile mixed solution obtained in the step (2) into an aluminum hydroxide-polyacrylonitrile fiber membrane by adopting an electrostatic spinning process, wherein the operating voltage is 30kV, and the feeding rate is 4 mL/h;
(4) carbonizing the aluminum hydroxide-polyacrylonitrile fiber membrane obtained in the step (3) at a high temperature under nitrogen, wherein the low-temperature pre-carbonization treatment temperature is 250 ℃, the treatment time is 0.5h, the high-temperature carbonization treatment temperature is 800 ℃, and the treatment time is 2.5h, so as to obtain an aluminum oxide/carbon hybrid fiber layer;
(5) and (3) attaching the alumina/carbon hybrid fiber layer obtained in the step (4) to one side of the polyethylene microporous diaphragm facing the pole piece to obtain the heat-conducting composite diaphragm for the battery.
(6) And (4) applying the heat-conducting composite diaphragm for the battery obtained in the step (5) to a lithium-sulfur battery.
Example 9
A thermally conductive composite separator for a battery. The heat-conducting composite diaphragm for the battery comprises a polyolefin porous diaphragm and an alumina/carbon hybrid fiber layer. The aluminum salt-polymer mixed solution is spun into fiber by adopting an electrostatic spinning process, and is carbonized at high temperature under protective atmosphere to form an alumina/carbon hybrid fiber layer which is attached to one side of the polyolefin porous diaphragm facing to the pole piece. The polyolefin porous diaphragm is a polypropylene/polyethylene/polypropylene composite film; the aluminum salt is aluminum hydroxide; the polymer is polyvinyl butyral; the solution is water; the total mass fraction of the aluminum salt and the polymer in the aluminum salt-polymer mixed solution is 45%, wherein the mass ratio of the aluminum salt to the polymer is 1: 8; the thickness of the aluminum salt-polymer fiber film obtained was 15 μm.
The preparation method of the heat-conducting composite diaphragm for the battery comprises the following steps:
(1) 0.5g of aluminum hydroxide was dispersed in 5.5g of water to obtain a uniform dispersion;
(2) dissolving 4g of polyvinyl butyral in the aluminum hydroxide solution obtained in the step (1) to obtain a uniformly dispersed aluminum hydroxide-polyvinyl butyral mixed solution;
(3) spinning the aluminum hydroxide-polyvinyl butyral mixed solution obtained in the step (2) into an aluminum hydroxide-polyvinyl butyral fiber membrane by adopting an electrostatic spinning process, wherein the operating voltage is 25kV, and the feeding rate is 5 mL/h;
(4) carbonizing the aluminum hydroxide-polyvinyl butyral fiber film obtained in the step (3) at a high temperature under nitrogen, wherein the treatment temperature of low-temperature pre-carbonization is 300 ℃, the treatment time is 1h, the treatment temperature of high-temperature carbonization is 700 ℃, and the treatment time is 2h, so as to obtain an aluminum oxide/carbon hybrid fiber layer;
(5) and (3) attaching the alumina/carbon hybrid fiber layer obtained in the step (4) to one side of the polypropylene/polyethylene/polypropylene composite membrane facing the pole piece to obtain the heat-conducting composite diaphragm for the battery.
(6) And (4) applying the heat-conducting composite diaphragm for the battery obtained in the step (5) to a lithium-sulfur battery.
Comparative example 1
The solution of the polymer is spun into fiber by adopting an electrostatic spinning process, and is carbonized at high temperature under protective atmosphere to form a carbon fiber layer which is attached to one side of the polyolefin porous diaphragm facing to the pole piece. The polyolefin porous diaphragm is a polyethylene microporous diaphragm; the polymer is polyacrylonitrile; the solution is N, N-dimethylformamide; the mass fraction of the polymer in the polymer dispersion liquid is 10 percent; the thickness of the obtained polymer fiber film was 10 μm.
The preparation method of the heat-conducting composite diaphragm for the battery comprises the following steps:
(1) dispersing 1g of polyacrylonitrile in 9g N, N-dimethylformamide, and magnetically stirring for 1h to obtain a uniform dispersion liquid;
(2) spinning the polyacrylonitrile mixed solution obtained in the step (1) into a polyacrylonitrile fiber membrane by adopting an electrostatic spinning process, wherein the operating voltage is 10kV, and the feeding rate is 0.5 mL/h;
(3) carbonizing the polyacrylonitrile fiber membrane obtained in the step (2) at a high temperature under nitrogen, wherein the treatment temperature of low-temperature pre-carbonization is 200 ℃, the treatment time is 0.5h, the treatment temperature of high-temperature carbonization is 600 ℃, and the treatment time is 1h, so as to obtain a carbon fiber layer;
(4) and (4) attaching the carbon fiber layer obtained in the step (3) to one side of the polyethylene microporous diaphragm facing the pole piece.
(5) And (3) applying the composite diaphragm obtained in the step (4) to a lithium-sulfur battery.
Comparative example 2
Unmodified polyethylene microporous membranes. The unmodified polyethylene microporous separator was applied to a lithium sulfur battery.
The composites provided in example 1 and comparative examples 1 and 2, and the performance of the assembled cells were tested in relation thereto, and the results are shown in table 1.
TABLE 1 comparison of the Performance indices of the materials of the invention with those of the prior art
Figure BDA0002267902650000181
Note: comparative example 1 in the table is an unmodified polyethylene microporous separator (PE).
Comparative example 2 is a carbon Fiber layer composite separator (C-Fiber).
Example 1 composite separator of alumina/carbon hybrid fiber layer (Al)2O3@C-Fiber)。
By analyzing the scanning images of the aluminum nitrate/polyacrylonitrile fiber (figure 1), the alumina/carbon hybrid fiber layer (figure 2) and the alumina fiber (figure 3) left after the carbon on the surface of the alumina/carbon hybrid fiber layer is thermally decomposed, it is shown that the remaining alumina fiber exists in the form of complete and continuous fiber after the carbon on the surface of the alumina/carbon hybrid fiber layer is thermally decomposed, which shows that the alumina in the alumina/carbon hybrid fiber layer exists in the form of complete and mutually cross-linked fiber, thus not only realizing the construction of a heat conduction path, but also greatly reducing the interface thermal resistance and improving the thermal conductivity of the composite material. The data in table 1 show that the thermal conductivity of the alumina/carbon hybrid fiber layer is the highest compared with that of the unmodified polyethylene microporous diaphragm and carbon fiber composite membrane.
The carbon layer material on the surface of the alumina/carbon hybrid fiber layer has strong adsorption capacity to electrolyte and is beneficial to the transfer of lithium ions. The data in table 1 show that the contact angle of the electrolyte of the alumina/carbon hybrid fiber layer is reduced compared with that of the unmodified polyethylene microporous diaphragm and the unmodified polyethylene carbon fiber composite membrane, and the soaking effect on the electrolyte is good; and meanwhile, the conductivity of the alumina/carbon hybrid fiber layer and the carbon fiber composite membrane is increased, which shows that the carbon layer is favorable for the conduction of lithium ions. In conclusion, the aluminum oxide/carbon hybrid fiber layer has good wettability to electrolyte, is beneficial to lithium ion conduction, can promote lithium ions to participate in charge-discharge electrochemical reaction in the battery, and improves the battery performance.
And assembling the unmodified polyethylene microporous diaphragm, the polyethylene microporous diaphragm/carbon fiber layer composite diaphragm and the polyethylene microporous diaphragm/alumina/carbon hybrid fiber layer composite diaphragm into a battery. Unmodified polyethylene microporous membrane (PE) in comparative example 2, polyethylene microporous membrane/carbon Fiber composite membrane (PE/C-Fiber) in comparative example 1, and polyethylene microporous membrane/alumina/carbon hybrid Fiber layer composite membrane (PE/Al)2O3@ C-Fiber), and the EIS curves of fig. 4(a) before three battery charge-discharge cycles and fig. 4(b) after 50 cycles of the cycle, found that the impedance of the battery assembled with the polyethylene microporous membrane/alumina/carbon hybrid Fiber layer composite membrane was the smallest before and after 50 cycles of the charge-discharge cycle.
FIG. 5 is a diagram showing the unmodified polyethylene microporous membrane (PE) in comparative example 2, the polyethylene microporous membrane/carbon Fiber composite membrane (PE/C-Fiber) in comparative example 1, and the polyethylene microporous membrane/alumina/carbon hybrid Fiber layer composite membrane (PE/Al)2O3@ C-Fiber) assembled cells, three groups of cells at 0.5C cycling performance. The coulombic efficiency of 100 charge-discharge cycles (fig. 5) at 0.5C was maintained above 98.5% higher than that of the other two groups of cells. The discharge specific capacity is reduced by 42 percent and is lower than that of other two groups of batteries.
FIG. 6 shows a polyethylene microporous membrane/alumina/carbon hybrid fiber layer composite membrane (PE/Al)2O3@ C-Fiber) assembled cell charge and discharge curves at 0.5C. In the late stage of charge and discharge (fig. 6), the specific capacity decreased slowly. These data demonstrate that polyethylene microporous membranes/alumina/carbon hybrid fibersThe battery performance of the battery assembled by the heat-conducting composite diaphragm for the layer battery is higher than that of the other two groups.
It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims (10)

1. A heat-conducting composite diaphragm for a battery is characterized by comprising a polyolefin porous diaphragm and aluminum oxide/carbon hybrid fiber layers attached to two sides or one side of the polyolefin porous diaphragm;
the aluminum oxide/carbon hybrid fiber layer is prepared by dissolving a polymer in an aluminum salt dispersion liquid to obtain an aluminum salt-polymer mixed liquid, spinning the aluminum salt-polymer mixed liquid into an aluminum salt-polymer fiber membrane by adopting an electrostatic spinning process, and finally heating and carbonizing the aluminum salt-polymer fiber membrane in a protective atmosphere; wherein the polymer is any one of polyvinylpyrrolidone and polyvinyl butyral; also, alumina exists in the state of intact fibers in the alumina/carbon hybrid fiber layer.
2. The thermally conductive composite separator according to claim 1, wherein the polyolefin porous separator is a polypropylene microporous separator, a polyethylene microporous separator, or a polypropylene/polyethylene/polypropylene three-layer composite separator.
3. The thermally conductive composite separator according to claim 1 or 2, wherein the thickness of the alumina/carbon hybrid fiber layer is 5 μm to 100 μm.
4. The method for preparing a thermally conductive composite separator for a battery as set forth in any one of claims 1 to 3, comprising a process for preparing an alumina/carbon hybrid fiber layer, the process for preparing the alumina/carbon hybrid fiber layer comprising the steps of:
(1) dissolving a polymer in an aluminum salt dispersion liquid to obtain an aluminum salt-polymer mixed liquid; the aluminum salt dispersion is obtained by dispersing aluminum salt in a solvent; wherein the polymer is any one of polyvinylpyrrolidone and polyvinyl butyral;
(2) spinning the aluminum salt-polymer mixed solution obtained in the step (1) into an aluminum salt-polymer fiber membrane by adopting an electrostatic spinning process;
(3) and (3) heating and carbonizing the aluminum salt-polymer fiber membrane obtained in the step (2) in a protective atmosphere to obtain the alumina/carbon hybrid fiber layer.
5. The method according to claim 4, wherein the solvent in the step (1) is one or more of water, ethanol and N, N-dimethylformamide; the aluminum salt is an inorganic aluminum salt or an organic aluminum salt which can be decomposed into alumina under heating.
6. The method according to claim 4, wherein the total mass fraction of the aluminum salt and the polymer in the aluminum salt-polymer mixture in the step (1) is 10 to 50%, and the mass ratio of the aluminum salt to the polymer is 1:1 to 1: 10.
7. The method according to claim 4, wherein in the step (2), the electrospinning process is operated at a voltage of 10kV to 30kV and at a feed rate of 0.5mL/h to 5 mL/h; the thickness of the aluminum salt-polymer fiber membrane is 5-100 mu m.
8. The production method according to claim 4, wherein in the step (3), the heating carbonization comprises sequentially performing low-temperature pre-carbonization and high-temperature carbonization; the treatment temperature of the low-temperature pre-carbonization is 200-400 ℃, and the treatment time is 0.5-2 h; the high-temperature carbonization treatment temperature is 600-800 ℃, and the treatment time is 1-4 h.
9. Use of the thermally conductive composite separator for batteries according to any one of claims 1 to 3, as a thermally conductive composite separator for secondary batteries.
10. A secondary battery comprising the thermally conductive composite separator for a battery according to any one of claims 1 to 3, wherein an alumina/carbon hybrid fiber layer is attached to one side or both sides of a polyolefin porous separator; when the aluminum oxide/carbon hybrid fiber layer is attached to one side of the polyolefin porous diaphragm, the aluminum oxide/carbon hybrid fiber layer is attached to one side of the polyolefin porous diaphragm facing the pole piece.
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