WO2016127501A1 - 硫酸钡复合隔膜及其制备方法，以及锂离子电池 - Google Patents

硫酸钡复合隔膜及其制备方法，以及锂离子电池 Download PDF

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WO2016127501A1
WO2016127501A1 PCT/CN2015/077798 CN2015077798W WO2016127501A1 WO 2016127501 A1 WO2016127501 A1 WO 2016127501A1 CN 2015077798 W CN2015077798 W CN 2015077798W WO 2016127501 A1 WO2016127501 A1 WO 2016127501A1
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barium sulfate
lithium
nano
solution
composite separator
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PCT/CN2015/077798
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English (en)
French (fr)
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尚玉明
丁小磊
何向明
王莉
李建军
刘榛
许志新
王要武
高剑
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江苏华东锂电技术研究院有限公司
清华大学
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Publication of WO2016127501A1 publication Critical patent/WO2016127501A1/zh
Priority to US15/674,531 priority Critical patent/US20170338457A1/en

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • 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
    • H01M50/403—Manufacturing processes of separators, membranes or diaphragms
    • 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
    • H01M50/411—Organic material
    • H01M50/414—Synthetic resins, e.g. thermoplastics or thermosetting resins
    • H01M50/417—Polyolefins
    • 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
    • H01M50/411—Organic material
    • H01M50/414—Synthetic resins, e.g. thermoplastics or thermosetting resins
    • H01M50/42—Acrylic resins
    • 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
    • H01M50/411—Organic material
    • H01M50/414—Synthetic resins, e.g. thermoplastics or thermosetting resins
    • H01M50/426—Fluorocarbon polymers
    • 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
    • H01M50/451—Separators, membranes or diaphragms characterised by the material having a layered structure comprising layers of only organic material and layers containing inorganic 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
    • H01M50/489—Separators, membranes, diaphragms or spacing elements inside the cells, characterised by their physical properties, e.g. swelling degree, hydrophilicity or shut down properties
    • H01M50/491—Porosity
    • 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

Definitions

  • the present invention relates to a barium sulfate composite separator for a lithium ion battery, a method for preparing the same, and a lithium ion battery using the barium sulfate composite separator.
  • the lithium ion battery mainly includes a positive electrode, a negative electrode, a separator, and an electrolyte.
  • Lithium-ion battery separators although not involved in the electrochemical reaction in batteries, are important components of lithium-ion batteries.
  • the separator of the prior art is generally a microporous polyolefin separator, which causes heat shrinkage when the temperature is raised, thereby causing internal short circuit of the battery and affecting the safety of the battery; and the hydrophobicity of the surface of the microporous polyolefin membrane makes the separator wettability Poor, increase the internal resistance of the battery, affecting the cycle performance and charge and discharge performance of the battery. Therefore, the improvement of the performance of the separator plays an important role in improving the overall performance of the lithium battery.
  • nanometer barium sulfate has been applied to the surface of the separator to enhance the thermal dimensional stability of the separator, but the commercial nanometer barium sulfate is easy to agglomerate, after complicated and time-consuming grinding and dispersion. The process is still difficult to disperse evenly, the process is complicated and seriously affects the use effect of the modified separator.
  • a barium sulfate composite separator comprising: a base film and a coating applied to the surface of the base film, the coating comprising nano barium sulfate and a binder, the nano barium sulfate surface modified with a lithium carboxylate group .
  • a method for preparing a cerium sulfate composite separator comprising: adding a solution in which a lithium carboxylate is dissolved in an organic solvent, adding to a soluble cerium salt aqueous solution to form a first solution; and providing a soluble sulfate aqueous solution having a pH of 8-10. Adding the soluble sulfate aqueous solution to the first solution to form a precipitate; separating the precipitate, washing with water and drying to obtain nano-barium sulfate having a surface modified with a lithium carboxylate group; The binder is mixed to obtain a mixed slurry which is coated on the surface of a base film to form a barium sulfate composite separator.
  • a lithium ion battery includes a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode, the separator being the above-described barium sulfate composite separator, and a nonaqueous electrolyte penetrating into the barium sulfate composite separator.
  • the barium sulfate composite separator prepared by the invention has a surface modified with a lithium carboxylate group in the process of forming nano barium sulfate, and on the other hand, the nano barium sulfate is easily and uniformly dispersed, and the preparation is better.
  • the barium sulfate composite separator on the other hand, the application of nano-barium sulfate having a surface modified with a lithium carboxylate group to the composite membrane can promote the transport of lithium ions and improve the electrochemical performance of the lithium ion battery.
  • 1 is a scanning electron micrograph of nano barium sulfate according to an embodiment of the present invention.
  • FIG. 2 is a scanning electron micrograph of a barium sulfate composite separator according to an embodiment of the present invention.
  • Example 3 is a graph showing the change of heat shrinkage rate of the barium sulfate composite separator of Example 1 at different temperatures.
  • Example 4 is a cycle performance curve of the lithium ion battery of Example 1 and Comparative Example 2.
  • lithium ion battery barium sulfate composite separator provided by the present invention and a preparation method thereof will be further described in detail below with reference to the accompanying drawings and specific embodiments.
  • the embodiment of the invention provides a preparation method of a barium sulfate composite separator, which comprises the following steps:
  • a solution formed by dissolving lithium carboxylate in an organic solvent is added to a soluble cerium salt aqueous solution, and mixed to form a first solution;
  • the nanometer barium sulfate and the binder are mixed to obtain a mixed slurry, which is coated on the surface of a base film to form a barium sulfate composite separator.
  • the lithium carboxylate forms a stable ruthenium-carboxylate complex with Ba 2+ of the soluble sulfonium salt, and the complex slowly releases Ba 2 during the subsequent precipitation of barium sulfate.
  • the effect of + is such that the barium sulfate particles do not grow too large to form nano barium sulfate.
  • the nanometer barium sulfate surface is modified with a lithium carboxylate group, so that the nano barium sulfate particles are not easily agglomerated, and is favorable for secondary dispersion in subsequent applications;
  • the lithium carboxylate group can increase the concentration of ions on the surface of the nano-barium sulfate particles and promote the transport of lithium ions in the separator.
  • the lithium carboxylate has at least 8 carbon atoms.
  • the lithium carboxylate may be lithium oleate, lithium stearate, lithium lauryl benzoate, lithium cetyl benzoate or lithium polyacrylate.
  • the mass of the lithium carboxylate is preferably from 1% to 5% by mass of the subsequently theoretically formed nanometer barium sulfate.
  • the organic solvent is capable of dissolving lithium carboxylate and forming mesopores inside the barium sulfate particles during subsequent formation of barium sulfate.
  • the organic solvent is a polar water-soluble organic solvent, and may be methanol, ethanol, isopropanol, acetone, N,N-dimethylformamide, N,N-dimethylacetamide or N-methylpyrrolidone.
  • the water-soluble organic solvent is preferably an alcoholic organic solvent such as ethanol, methanol or isopropanol.
  • the volume ratio of the organic solvent to the soluble hydrazine salt aqueous solution is from 1:1 to 2:1, preferably 1:1.
  • the concentration of the soluble cerium salt aqueous solution is in the range of 0.1 mol/L to 0.5 mol/L, and the soluble cerium salt is a commonly used soluble cerium salt such as cerium chloride, cerium nitrate or strontium sulfide.
  • the soluble sulfate is slowly added to the first solution, and the soluble sulfate SO 4 2- forms a nano-sized barium sulfate with the slowly released Ba 2+ in the first solution, and the nano-barium sulfate surface modification It has a lithium carboxylate group and contains mesopores inside.
  • the soluble sulfate may be a commonly used soluble sulfate such as sodium sulfate, potassium sulfate, ammonium sulfate or aluminum sulfate.
  • the concentration of the aqueous solution of the soluble sulfate is in the range of 0.1 mol/L to 0.5 mol/L.
  • the molar ratio of the soluble sulfate to the soluble cerium salt is 1:1.
  • the aqueous solution of the soluble sulfate is adjusted by an alkaline solution such as ammonia water, sodium hydroxide or potassium hydroxide to have a pH of preferably 8 to 10.
  • the precipitate is centrifugally separated from the solution, washed with water for 3 to 4 times and vacuum dried to obtain nano-barium sulfate having a surface modified with a lithium carboxylate group, and the particle diameter ranges from 30 nm to 500 nm.
  • the specific surface area is from 5 m 2 /g to 20 m 2 /g.
  • Each nanometer barium sulfate particle contains mesopores, and the pore diameter of the mesopores ranges from 6 nm to 10 nm.
  • the reaction temperature of the entire process is preferably from 15 ° C to 45 ° C.
  • the binder may be polyacrylonitrile, polyvinyl acetate, polyvinylpyrrolidone, polyvinylidene fluoride or polyimide.
  • the binder is used to enable a better binding of the nanobarium sulfate having a lithium carboxylate group on the surface to the base film.
  • the base film is a polyolefin porous film, and the polyolefin porous film may be a polypropylene porous film, a polyethylene porous film, a polypropylene porous film, a polypropylene-polyethylene-polypropylene composite porous film, or a nonwoven fabric film.
  • the base film is used to insulate electrons and pass lithium ions through the pores of the porous membrane.
  • the base film can be a commercially available lithium ion battery separator, such as a separator manufactured by Asahi, Tosei, Tobe, Ube, and Celgard. This embodiment employs a Celgard-2325 type separator manufactured by Celgard.
  • the step S4 may further include:
  • the nano-barium sulfate surface is modified with a lithium carboxylate group, and the lithium carboxylate group acts as a surfactant to contribute to uniform dispersion of the nano-barium sulfate in a polar solvent.
  • the polar solvent is selected from the group consisting of a common polar solvent such as N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone and acetone.
  • the mass percentage of each substance in the mixed slurry is preferably: the mass ratio of the binder to the nano barium sulfate is 5:100 to 15:100, and the mass ratio of the binder and the nano barium sulfate to the polar solvent is 5:100. ⁇ 20:100.
  • the coating layer is disposed on the surface of the base film and may be disposed on both sides or one side of the base film.
  • the coated base film is vacuum dried at 60 ° C to 80 ° C for 12 hours to 24 hours to remove the solvent in the coating layer, and the thickness of the coating layer after drying is preferably 2 ⁇ m to 10 ⁇ m.
  • An embodiment of the present invention provides a barium sulfate composite separator, comprising: a base film and a coating applied to the surface of the base film, the coating comprising nano barium sulfate and a binder, and the nano sulfuric acid in the coating
  • the crucible is evenly dispersed, and the coating acts as a support to prevent heat shrinkage of the separator.
  • the surface of the nanometer barium sulfate is modified with a lithium carboxylate group, the nanometer barium sulfate is not easy to agglomerate, and is easy to be uniformly dispersed, and can be uniformly applied to the surface of the base film in the process of preparing the barium sulfate composite separator, and the coating process does not Segregation affects the performance of the membrane.
  • the nanometer barium sulfate surface group contains lithium ions, which further facilitates the transport of lithium ions in the separator.
  • the nanometer barium sulfate contains mesopores inside, and a certain gap is formed between the barium sulfate particles and the particles, so that the porosity of the barium sulfate composite separator is increased, which facilitates the penetration of the electrolyte and further improves the wettability of the separator.
  • the barium sulfate particles have a small particle size of about 30 nm to 500 nm, and the nano barium sulfate particles form a certain gap with the particles, and each nanometer barium sulfate particle contains a mesopores therein.
  • the mesopore pore size is 6 nm to 10 nm.
  • the barium sulfate composite separator has a base film surface uniformly covered by a coating, and the nano-barium sulfate in the coating is uniformly dispersed.
  • the coating has a thickness of about 2 ⁇ m to 10 ⁇ m.
  • Embodiments of the present invention provide a lithium ion battery including a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode, the separator including the barium sulfate composite separator, and a nonaqueous electrolyte penetrating the barium sulfate composite separator .
  • the non-aqueous electrolyte solution comprises a solvent and a lithium salt solute dissolved in a solvent
  • the solvent may be selected from the group consisting of a cyclic carbonate, a chain carbonate, a cyclic ether, a chain ether, a nitrile, and an amide.
  • the lithium salt solute may be selected from lithium chloride (LiCl), lithium hexafluorophosphate (LiPF 6 ), lithium tetrafluoroborate (LiBF 4 ), lithium methanesulfonate (LiCH 3 SO 3 ), lithium trifluoromethanesulfonate (LiCF 3 SO) 3 ) one or more of lithium hexafluoroarsenate (LiAsF 6 ), lithium perchlorate (LiClO 4 ), and lithium bis(oxalate) borate (LiBOB).
  • LiCl lithium chloride
  • LiPF 6 lithium hexafluorophosphate
  • LiBF 4 lithium tetrafluoroborate
  • LiCH 3 SO 3 lithium methanesulfonate
  • LiCF 3 SO lithium trifluoromethanesulfonate
  • LiAsF 6 lithium hexafluoroarsenate
  • LiClO 4 lithium perchlorate
  • LiBOB lithium bis
  • the positive electrode may include a positive electrode current collector and a positive electrode material layer for supporting the positive electrode material layer and conducting current, and may be in the form of a foil or a mesh.
  • the material of the cathode current collector may be selected from aluminum, titanium or stainless steel.
  • the positive electrode material layer is disposed on at least one surface of the positive electrode current collector.
  • the positive electrode material layer includes a positive electrode active material, and further optionally includes a conductive agent and a binder. A conductive agent and a binder may be uniformly mixed with the positive electrode active material.
  • the positive electrode active material may be, for example, lithium iron phosphate, lithium spinel lithium manganate, lithium cobaltate, lithium nickelate or a nickel cobalt manganese ternary material.
  • the negative electrode may include a negative electrode current collector and a negative electrode material layer for supporting the negative electrode material layer and conducting current, and the shape may be a foil or a mesh.
  • the material of the anode current collector may be selected from copper, nickel or stainless steel.
  • the anode material layer is disposed on at least one surface of the anode current collector.
  • the negative material layer includes a negative active material, and further optionally includes a conductive agent and a binder. A conductive agent and a binder may be uniformly mixed with the anode active material.
  • the negative active material may be graphite, acetylene black, microbead carbon, carbon fiber, carbon nanotube or cracked carbon or the like.
  • a solution prepared by dissolving 0.01 g of lithium oleate in 50 ml of anhydrous methanol is added to 50 ml of a 0.5 mol/L barium chloride solution, and uniformly mixed for 20 minutes to 30 minutes to form a mixed solution; 50 ml, 0.5 mol/
  • the sodium sulfate solution of L is adjusted to a pH of 8 to 9 by aqueous ammonia, and is slowly added to the above mixed solution, and a precipitate is obtained by centrifugation.
  • the precipitate was washed 3 times in deionized water, and finally vacuum dried in a drying oven at 80 ° C to obtain nano barium sulfate having a surface modified with a lithium carboxylate group.
  • the nanometer barium sulfate has a particle diameter of 30 nm to 50 nm and a specific surface area of 19.9 m 2 /g.
  • a solution of 1 g of nano barium sulfate added to 20 ml of N-methylpyrrolidone solvent was stirred vigorously for 3 hours until the nano-barium sulfate was uniformly dispersed.
  • 0.05 g of the soluble polyimide was added to the above solution and stirred for 4 hours to form a mixed slurry.
  • the mixed slurry was uniformly applied to the upper and lower sides of a Celgard-2325 type separator having a thickness of 25 ⁇ m, and vacuum-dried in a 60 ° C dry box for 24 hours to obtain a barium sulfate composite separator.
  • a solution formed by dissolving 0.02 g of lithium stearate in 100 ml of N,N-dimethylformamide is added to 100 ml of a 0.5 mol/L lanthanum nitrate solution, and uniformly mixed for 20 minutes to 30 minutes to form a mixed solution; 100 ml of a 0.5 mol/L potassium sulfate solution was adjusted to a pH of 8 to 9 with a dilute sodium hydroxide solution, and slowly added to the above mixed solution, and a precipitate was obtained by centrifugation.
  • the precipitate was washed 3 to 4 times in deionized water, and finally dried in a vacuum oven at 80 ° C to obtain nano-barium sulfate having a surface modified with a lithium carboxylate group.
  • the nanometer barium sulfate has a particle diameter of 50 nm to 80 nm.
  • a solution of 1 g of nano barium sulfate added to 10 ml of N-methylpyrrolidone solvent was stirred for 3 hours until the nano barium sulfate was uniformly dispersed.
  • 0.116 g of polyvinylidene fluoride was added to the above solution, and after stirring for 6 hours, a mixed slurry was formed.
  • the mixed slurry was uniformly applied to the upper and lower sides of a Celgard-2325 type separator having a thickness of 25 ⁇ m, and vacuum-dried in a 60 ° C dry box for 24 hours to obtain a barium sulfate composite separator.
  • a solution prepared by dissolving 0.03 g of lithium polyacrylate in 150 ml of acetone was added to 150 ml of a 0.5 mol/L barium chloride solution, and uniformly mixed for 20 minutes to 30 minutes to form a mixed solution; 150 ml, 0.5 mol/L.
  • the ammonium sulfate solution was adjusted to a pH of 8 to 9 with a dilute potassium hydroxide solution, and slowly added to the above mixed solution, and a precipitate was obtained by centrifugation.
  • the precipitate was washed 3 times in deionized water, and finally vacuum dried in a drying oven at 80 ° C to obtain nano barium sulfate having a surface modified with a lithium carboxylate group.
  • the nanometer barium sulfate has a particle diameter of 80 nm to 120 nm.
  • a solution of 1 g of nano barium sulfate added to 10 ml of N-methylpyrrolidone solvent was stirred for 2 hours until the nano barium sulfate was uniformly dispersed.
  • 0.15 g of polyacrylonitrile was added to the above solution, and after stirring for 5 hours, a mixed slurry was formed.
  • the mixed slurry was uniformly applied to the upper and lower sides of a Celgard-2325 type separator having a thickness of 25 ⁇ m, and vacuum-dried in a 60 ° C dry box for 24 hours to obtain a barium sulfate composite separator.
  • Example 1 The difference from Example 1 was that the prepared barium sulfate composite separator was replaced with the commercially available nano barium sulfate to replace the nano barium sulfate prepared in Example 1.
  • Example 2 The difference from Example 1 is that the separator is a Celgard-2325 type separator which is not coated with any slurry.
  • Example 1 The same volume of the same electrolyte solution was dropped on the separators prepared in the same area of Example 1, Comparative Example 1 and Comparative Example 2, and after 5 minutes, the surface electrolyte of the barium sulfate composite separator in Example 1 was found to have spread over a large area.
  • the surface area of the barium sulfate composite separator in Comparative Example 1 was smaller than that of Example 1, and the electrolyte on the surface of the Celgard-2325 separator in Comparative Example 2 spread slowly, and the spread area was smaller than that of Comparative Example 1.
  • the separators of the same size of Example 1, Comparative Example 1 and Comparative Example 2 were placed in a high-temperature heat oven, respectively, and baked at 120 ° C, 130 ° C, 140 ° C, and 150 ° C for 0.5 h, respectively. Cool to room temperature.
  • the heat shrinkage rate is calculated, where ⁇ is the heat shrinkage ratio, L 0 is the original length of the separator, and L is the length after high temperature baking.
  • the heat shrinkage ratio of the barium sulfate composite separator of Example 1 was maintained at 1% to 3% at 120 ° C to 150 ° C.
  • the heat shrinkage rates of the separators of Example 1, Comparative Example 1, and Comparative Example 2 were tested, and the test results are shown in Table 2.
  • Example 1 1.00% 1.25% 1.30% 3.00% Comparative example 1 2.00% 3.00% 4.00% 6.00% Comparative example 2 7.10% 14.80% 24.36% 30.10%
  • the liquid absorption rate of the electrolyte solution of the first embodiment of the barium sulfate composite separator reaches 3.56 mg/cm 2 , and the heat shrinkage rate is only 3% at a high temperature of 150 ° C, which is visible, compared with the commercialization.
  • the barium sulfate composite separator prepared by the nanometer barium sulfate, the barium sulfate composite separator prepared by the embodiment of the invention has improved heat shrinkage resistance and wettability.
  • Example 1 The separators of Example 1, Comparative Example 1, and Comparative Example 2 were assembled into a lithium ion battery, and the other components of the lithium ion battery were the same. Put three lithium-ion batteries in 0.1C, 0.5C, 1C, 2C, 4C,
  • Example 1 142.5mAh/g 138mAh/g 135mAh/g 129.5mAh/g 124mAh/g 120mAh/g Comparative example 1 141 mAh/g 138 mAh/g 134 mAh/g 128 mAh/g 115 mAh/g 112 mAh/g Comparative example 2 144mAh/g 138mAh/g 134mAh/g 129mAh/g 125mAh/g 121mAh/g
  • the lithium ion battery of Example 1 and the lithium ion battery of Comparative Example 2 were substantially equivalent in performance as the current rate was increased, and were superior to the performance of the lithium ion battery of Comparative Example 1.
  • the lithium ion batteries to which the separators of Example 1, Comparative Example 1, and Comparative Example 2 were applied were discharged five times before the 0.1 C charge and discharge cycle, and then discharged at 0.5 C for 1 C until 100 cycles were performed. It can be seen that the cycle performance of the lithium ion battery of Example 1 was significantly better than that of the lithium ion batteries of Comparative Example 1 and Comparative Example 2 as the number of cycles increased.
  • the nanometer barium sulfate surface modified with a lithium carboxylate group is obtained by the preparation method of the barium sulfate composite separator of the invention, and the nanometer barium sulfate is coated on the surface of the base film by a binder to form a coating layer, thereby obtaining a barium sulfate composite. Diaphragm.
  • the coating acts as a rigid support to prevent heat shrinkage of the separator;
  • the nano-barium sulfate surface is modified with a lithium carboxylate group, and on the one hand, the lithium carboxylate group makes nano-barium sulfate during the precipitation of barium sulfate It is not easy to agglomerate, and the nano-barium sulfate can be uniformly dispersed in subsequent applications; on the other hand, the lithium carboxylate group increases the concentration of ions on the surface of the nano-barium sulfate particles, and can promote the transport of lithium ions in the separator, thereby improving the application. Charge, discharge and cycle performance of lithium ion batteries with barium sulfate composite separator.

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Abstract

本发明涉及一种硫酸钡复合隔膜的制备方法，其包括：将羧酸锂溶解于有机溶剂形成的溶液加入到可溶性钡盐水溶液中混合形成第一溶液；提供一pH值为8~10的可溶性硫酸盐水溶液，将该可溶性硫酸盐水溶液加入到该第一溶液中，反应生成沉淀物；将该沉淀物分离、水洗并干燥，得到表面修饰有羧酸锂基团的纳米硫酸钡；将该纳米硫酸钡和粘结剂混合得到一混合浆料，涂覆于一基膜表面形成硫酸钡复合隔膜。

Description

硫酸钡复合隔膜及其制备方法，以及锂离子电池 技术领域
本发明涉及一种用于锂离子电池的硫酸钡复合隔膜及其制备方法，以及应用该硫酸钡复合隔膜的锂离子电池。
背景技术
锂离子电池主要包括正极、负极、隔膜和电解液。锂离子电池的隔膜尽管并不参与电池中的电化学反应，但却是锂离子电池的重要组件。现有技术的隔膜一般为微孔聚烯烃隔膜，在温度升高时会发生热收缩，从而引起电池内部短路，影响电池的安全性；并且微孔聚烯烃隔膜表面的疏水性使得隔膜浸润性较差，增大电池内阻，影响电池的循环性能和充放电性能，因此，隔膜性能的改善对提高锂电池的综合性能起着重要作用。
近几年，为了改善锂离子电池隔膜性能，人们将纳米硫酸钡涂覆在隔膜表面，以便增强隔膜的热尺寸稳定性，但是商品化的纳米硫酸钡易于团聚，经过复杂耗时的研磨和分散工序仍难以分散均匀，工艺复杂且严重影响改性隔膜的使用效果。
发明内容
有鉴于此，确有必要提供一种能够使纳米硫酸钡分散均匀的复合隔膜及其制备方法，以及锂离子电池。
一种硫酸钡复合隔膜，包括：一基膜和一涂覆于该基膜表面的涂层，该涂层包括纳米硫酸钡和粘结剂，所述纳米硫酸钡表面修饰有羧酸锂基团。
一种硫酸钡复合隔膜的制备方法，其包括：将羧酸锂溶解于有机溶剂形成的溶液加入到可溶性钡盐水溶液中混合形成第一溶液；提供一pH值为8~10的可溶性硫酸盐水溶液，将该可溶性硫酸盐水溶液加入到该第一溶液中，反应生成沉淀物；将该沉淀物分离、水洗并干燥，得到表面修饰有羧酸锂基团的纳米硫酸钡；将该纳米硫酸钡和粘结剂混合得到一混合浆料，涂覆于一基膜表面形成硫酸钡复合隔膜。
一种锂离子电池，包括正极、负极以及设置在该正极与负极之间的隔膜，该隔膜为上述硫酸钡复合隔膜，以及渗透于该硫酸钡复合隔膜中的非水电解液。
与现有技术比较，本发明制备的硫酸钡复合隔膜通过在形成纳米硫酸钡的过程中使其表面修饰有羧酸锂基团，一方面使纳米硫酸钡易于均匀分散，方便制备出较好性能的硫酸钡复合隔膜，另一方面将表面修饰有羧酸锂基团的纳米硫酸钡应用于复合隔膜能够促进锂离子的传输，提高锂离子电池的电化学性能。
 附图说明
图1为本发明实施例的纳米硫酸钡的扫描电镜照片。
图2为本发明实施例的硫酸钡复合隔膜的扫描电镜照片。
图3为实施例1的硫酸钡复合隔膜在不同温度下热收缩率的变化曲
线。
图4为实施例1及对比例2的锂离子电池的循环性能曲线。
具体实施方式
下面将结合附图及具体实施例对本发明提供的锂离子电池硫酸钡复合隔膜及其制备方法作进一步的详细说明。
本发明实施例提供一种硫酸钡复合隔膜的制备方法，其包括以下步骤：
S1，将羧酸锂溶解于有机溶剂形成的溶液加入到可溶性钡盐水溶液中，混合形成第一溶液；
S2，提供一pH值为8~10的可溶性硫酸盐水溶液，将该可溶性硫酸盐水溶液加入到该第一溶液中，反应生成沉淀物；
S3，将该沉淀物分离、水洗并干燥，得到表面修饰有羧酸锂基团的纳米硫酸钡；
S4，将该纳米硫酸钡和粘结剂混合得到一混合浆料，涂覆于一基膜表面形成硫酸钡复合隔膜。
在该步骤S1中，该羧酸锂与可溶性钡盐的Ba2+形成一种稳定的钡~羧酸锂络合物，该络合物在后续沉淀硫酸钡的过程中起到缓慢释放Ba2+的作用，使该硫酸钡颗粒不会生长过大，从而形成纳米硫酸钡。另外，在沉淀硫酸钡的过程中该纳米硫酸钡表面修饰有羧酸锂基团，从而使该纳米硫酸钡颗粒不易团聚，并有利于后续应用时的二次分散；在后续制备的硫酸钡复合隔膜中，该羧酸锂基团可以增加纳米硫酸钡颗粒表面载离子的浓度，促进锂离子在隔膜中传输。
该羧酸锂中含碳原子数至少为8个。该羧酸锂可以为油酸锂、硬脂酸锂、十二烷基苯甲酸锂、十六烷基苯甲酸锂或聚丙烯酸锂。该羧酸锂的质量优选为后续理论上形成的纳米硫酸钡质量的1%~5%。
该有机溶剂能够溶解羧酸锂，且在后续形成硫酸钡过程中使硫酸钡颗粒内部形成介孔。该有机溶剂为极性水溶性有机溶剂，可以为甲醇、乙醇、异丙醇、丙酮、N,N-二甲基甲酰胺、N,N-二甲基乙酰胺或N-甲基吡咯烷酮等极性水溶性有机溶剂，优选为醇类有机溶剂，如乙醇、甲醇或异丙醇。该有机溶剂与可溶性钡盐水溶液体积比为1：1至2：1，优选为1：1。
该可溶性钡盐水溶液浓度范围为0.1mol/L~0.5mol/L，该可溶性钡盐为氯化钡、硝酸钡或硫化钡等常用可溶性钡盐。
在该步骤S2中，所述可溶性硫酸盐缓慢加入第一溶液，该可溶性硫酸盐的SO4 2-与第一溶液中缓慢释放的Ba2+形成纳米尺寸的硫酸钡，该纳米硫酸钡表面修饰有羧酸锂基团，内部含有介孔。所述可溶性硫酸盐可以为硫酸钠、硫酸钾、硫酸铵或硫酸铝等常用可溶性硫酸盐。所述可溶性硫酸盐水溶液浓度范围为0.1mol/L ~0.5mol/L。该可溶性硫酸盐与该可溶性钡盐的摩尔比为1：1。所述可溶性硫酸盐水溶液通过氨水、氢氧化钠或氢氧化钾等碱性溶液进行调节，使pH值优选为8~10。
在该S3步骤中，将沉淀物从溶液中离心分离，并经过水洗3~4次和真空干燥后，即得到表面修饰有羧酸锂基团的纳米硫酸钡，粒径范围为30nm~500nm，比表面积为5m2/g ~20m2/g。每一纳米硫酸钡颗粒中均含有介孔，介孔的孔径范围为6nm~10nm。
在上述S1~S3步骤中，优选的，整个过程反应温度优选为15℃~45℃。
在该S4步骤中，所述粘结剂可以为聚丙烯腈、聚乙酸乙烯酯、聚乙烯吡咯烷酮、聚偏氟乙烯或聚酰亚胺。该粘结剂用于使表面含有羧酸锂基团的纳米硫酸钡能够与基膜更好的结合。
所述基膜为聚烯烃多孔膜，该聚烯烃多孔膜可以为聚丙烯多孔膜、聚乙烯多孔膜、聚丙烯多孔膜、聚丙烯-聚乙烯-聚丙烯复合多孔膜或无纺布薄膜。该基膜用于隔绝电子并使锂离子从多孔膜的微孔中通过。该基膜可以采用市售的锂离子电池隔膜，如日本旭化成Asahi、东燃化学Tonen、宇部Ube、美国Celgard等公司生产的隔膜产品。本实施例采用Celgard公司生产的Celgard-2325型隔膜。
该步骤S4进一步可包括：
S41，将该纳米硫酸钡和极性溶剂混合搅拌，直至所述纳米硫酸钡均匀分散，得到一混合溶液；
S42，将粘结剂加入到该混合溶液中搅拌直至该粘结剂溶解，形成一混合浆料；以及
S43，将该混合浆料涂覆于一基膜的表面形成一涂层，并干燥形成硫酸钡复合隔膜。
该纳米硫酸钡表面修饰有羧酸锂基团，该羧酸锂基团起到表面活性剂的作用，有助于纳米硫酸钡在极性溶剂中分散均匀。所述极性溶剂选自N,N-二甲基甲酰胺、N,N-二甲基乙酰胺、N-甲基吡咯烷酮及丙酮等常用的极性溶剂。
该混合浆料中各物质的质量百分比优选为：粘结剂与纳米硫酸钡质量比为5：100~15：100，粘结剂及纳米硫酸钡质量总和与极性溶剂质量比为5：100~20：100。
该涂层设置于所述基膜的表面，可以设置于基膜的两侧或单侧。在60℃~80℃下真空干燥涂覆后的基膜12小时~24小时以去除涂层中的溶剂，干燥后所述涂层厚度范围优选为2μm~10μm。
本发明实施例提供一种硫酸钡复合隔膜，包括：一基膜和一涂覆于该基膜表面的涂层，该涂层包括纳米硫酸钡和粘结剂，所述涂层中的纳米硫酸钡均匀分散，该涂层起到一支撑作用，可以阻止隔膜的热收缩。所述纳米硫酸钡表面修饰有羧酸锂基团，该纳米硫酸钡不易团聚，易于均匀分散，在制备硫酸钡复合隔膜的过程中能够均匀地涂覆于基膜表面，涂覆过程中不会偏析从而影响隔膜的性能。所述纳米硫酸钡表面基团含有锂离子，进一步有利于锂离子在隔膜中传输。该纳米硫酸钡内部含有介孔，且该硫酸钡微粒与微粒之间形成一定的空隙，使该硫酸钡复合隔膜孔隙率增大，利于电解液的渗透，使隔膜的浸润性进一步得到改善。
请参阅图1，所述硫酸钡颗粒的粒径较小，约为30nm ~500nm，所述纳米硫酸钡颗粒与颗粒之间形成一定的空隙，并且每一纳米硫酸钡颗粒内部含有介孔，该介孔孔径为6nm~10nm。
请参阅图2，该硫酸钡复合隔膜为一基膜表面被一涂层均匀覆盖，该涂层中的纳米硫酸钡均匀分散。该涂层厚度约为2μm~10μm。
本发明实施例提供一种锂离子电池，包括正极、负极以及设置在该正极与负极之间的隔膜，该隔膜包括该硫酸钡复合隔膜，以及渗透于该硫酸钡复合隔膜中的非水电解液。
该非水电解液包括溶剂及溶于溶剂的锂盐溶质，该溶剂可选自环状碳酸酯、链状碳酸酯、环状醚类、链状醚类、腈类及酰胺类中的一种或多种，如碳酸乙烯酯、碳酸丙烯酯、碳酸二乙酯、碳酸二甲酯、碳酸甲乙酯、乙酸甲酯、乙酸乙酯、乙酸丙酯、丙酸甲酯、丙酸乙酯、二乙醚、乙腈、丙腈、苯甲醚、丁酸酯、戊二腈、已二腈、γ-丁内酯、γ-戊内酯、四氢呋喃、1,2-二甲氧基乙烷及乙腈及二甲基甲酰胺中的一种或多种。该锂盐溶质可选自氯化锂（LiCl）、六氟磷酸锂（LiPF6）、四氟硼酸锂（LiBF4）、甲磺酸锂（LiCH3SO3）、三氟甲磺酸锂（LiCF3SO3）、六氟砷酸锂（LiAsF6）、高氯酸锂（LiClO4）及双草酸硼酸锂（LiBOB）中的一种或多种。
该正极可包括正极集流体及正极材料层，该正极集流体用于担载该正极材料层并传导电流，形状可以为箔片或网状。该正极集流体的材料可以选自铝、钛或不锈钢。该正极材料层设置在该正极集流体至少一表面。该正极材料层包括正极活性材料，进一步可选择的包括导电剂以及粘结剂。导电剂以及粘结剂可以与所述正极活性材料均匀混合。该正极活性材料可以为如磷酸铁锂、尖晶石锰酸锂、钴酸锂、镍酸锂或镍钴锰三元材料等。
该负极可包括负极集流体及负极材料层，该负极集流体用于担载该负极材料层并传导电流，形状可以为箔片或网状。该负极集流体的材料可以选自铜、镍或不锈钢。该负极材料层设置在该负极集流体至少一表面。该负极材料层包括负极活性材料，进一步可选择的包括导电剂以及粘结剂。导电剂以及粘结剂可以与所述负极活性材料均匀混合。该负极活性材料可以为石墨、乙炔黑、微珠碳、碳纤维、碳纳米管或裂解碳等。
实施例1
将0.01g的油酸锂溶解于50ml的无水甲醇中形成的溶液加入到50ml，0.5mol/L的氯化钡溶液中，均匀混合20分钟~30分钟形成混合溶液；将50ml，0.5mol/L的硫酸钠溶液通过氨水调节至pH值为8~9，并缓慢加入到上述混合溶液中，经过离心处理分离得到沉淀物。将该沉淀物在去离子水中洗涤3次，最后在80°C干燥箱中真空干燥，得到表面修饰有羧酸锂基团的纳米硫酸钡。该纳米硫酸钡粒径为30nm~50nm，比表面积为19.9m2/g。
将1g纳米硫酸钡加入到20ml的N-甲基吡咯烷酮溶剂中形成的溶液，剧烈搅拌3小时，直至均匀分散该纳米硫酸钡。将0.05g的可溶性聚酰亚胺加入到上述溶液中，搅拌4小时，形成一混合浆料。将该混合浆料均匀涂覆于厚度为25μm的Celgard-2325型隔膜的上下两侧，并在60°C干燥箱中真空干燥24小时，得到硫酸钡复合隔膜。
实施例2
将0.02g的硬脂酸锂溶解于100ml的N,N-二甲基甲酰胺中形成的溶液加入到100ml，0.5mol/L的硝酸钡溶液中，均匀混合20分钟~30分钟形成混合溶液；将100ml，0.5mol/L的硫酸钾溶液用稀氢氧化钠溶液调节至pH值为8~9，并缓慢加入到上述混合溶液中，经过离心处理分离得到沉淀物。将该沉淀物在去离子水中洗涤3~4次，最后在80°C干燥箱中真空干燥，得到表面修饰有羧酸锂基团的纳米硫酸钡。该纳米硫酸钡粒径为50nm~80nm。
将1g纳米硫酸钡加入到10ml的N-甲基吡咯烷酮溶剂中形成的溶液搅拌3小时直至均匀分散该纳米硫酸钡。将0.116g的聚偏氟乙烯加入到上述溶液中，搅拌6小时后形成一混合浆料。将该混合浆料均匀涂覆于厚度为25μm的Celgard-2325型隔膜的上下两侧，并在60°C干燥箱中真空干燥24小时，得到硫酸钡复合隔膜。
实施例3
将0.03g的聚丙烯酸锂溶解于150ml的丙酮中形成的溶液加入到150ml，0.5mol/L的氯化钡溶液中，均匀混合20分钟~30分钟形成混合溶液；将150ml，0.5mol/L的硫酸铵溶液用稀氢氧化钾溶液调节至pH值为8~9，并缓慢加入到上述混合溶液中，经过离心处理分离得到沉淀物。将该沉淀物在去离子水中洗涤3次，最后在80°C干燥箱中真空干燥，得到表面修饰有羧酸锂基团的纳米硫酸钡。该纳米硫酸钡粒径为80nm~120nm。
将1g纳米硫酸钡加入到10ml的N-甲基吡咯烷酮溶剂中形成的溶液搅拌2小时直至均匀分散该纳米硫酸钡。将0.15g的聚丙烯腈加入到上述溶液中，搅拌5小时后形成一混合浆料。将该混合浆料均匀涂覆于厚度为25μm的Celgard-2325型隔膜的上下两侧，并在60°C干燥箱中真空干燥24小时，得到硫酸钡复合隔膜。
对比例1
与实施例1的区别为制备的硫酸钡复合隔膜是应用商品化的纳米硫酸钡替换实施例1制备的纳米硫酸钡。
对比例2
与实施例1的区别是该隔膜为未涂覆任何浆料的Celgard-2325型隔膜。
将同样体积的同一电解液分别滴在同样面积的实施例1、对比例1和对比例2制备的隔膜上，5min后会发现实施例1中的硫酸钡复合隔膜表面电解液已经大面积铺展，对比例1中的硫酸钡复合隔膜表面电解液铺展面积相比实施例1较小，对比例2中Celgard-2325隔膜表面的电解液铺展缓慢，相比对比例1铺展面积更小。通过公式
Figure WO256-appb-I000001
（A为吸液率，m为吸收电解液后隔膜的总质量，m0为吸收电解液前隔膜的质量，S为隔膜的面积）分别计算实施例1、对比例1、对比例2隔膜的吸液率，测试结果如表1所示。
表1
吸液率
实施例1 3.56mg/cm2
对比例1 2.46mg/cm2
对比例2 0.91mg/cm2
将相同尺寸的实施例1、对比例1及对比例2的隔膜分别放置于高温热烘箱中，在120°C、130°C、140°C、150°C下分别烘烤0.5h后，自然冷却至室温。根据公式
Figure WO256-appb-I000002
计算热收缩率，其中η为热收缩率，L0为隔膜的原始长度，L为高温烘烤后的长度。如图3所示，实施例1的硫酸钡复合隔膜在120°C~150°C时热收缩率维持在1%~3%。分别测试实施例1、对比例1及对比例2的隔膜的热收缩率，测试结果如表2所示。
表2
120°C 130°C 140°C 150°C
实施例1 1.00% 1.25% 1.30% 3.00%
对比例1 2.00% 3.00% 4.00% 6.00%
对比例2 7.10% 14.80% 24.36% 30.10%
通过上述实验可以看到，实施例1硫酸钡复合隔膜对电解液的吸液率达到3.56mg/cm2，在高温150°C时，热收缩率仅为3%，可见，相对于商品化的纳米硫酸钡制备的硫酸钡复合隔膜，本发明实施例制备的硫酸钡复合隔膜提高了其抗热收缩性能和浸润性能。
分别将实施例1、对比例1及对比例2的隔膜组装锂离子电池，该锂离子电池的其他组件均相同。将三种锂离子电池在0.1C、0.5C、1C、2C、4C、
8C倍率下进行倍率性能测试，测试结果如表3所示。
表3
0.1C放电容量（mAh/g） 0.5C放电容量（mAh/g） 1C放电容量（mAh/g） 2C放电容量（mAh/g） 4C放电容量（mAh/g） 8C放电容量（mAh/g）
实施例1 142.5mAh/g 138mAh/g 135mAh/g 129.5mAh/g 124mAh/g 120mAh/g
对比例1 141 mAh/g 138 mAh/g 134 mAh/g 128 mAh/g 115 mAh/g 112 mAh/g
对比例2 144mAh/g 138mAh/g 134mAh/g 129mAh/g 125mAh/g 121mAh/g
从表中可以看到，随着电流倍率的升高，实施例1的锂离子电池与对比例2的锂离子电池的性能基本相当，且优于对比例1锂离子电池的性能。
请参阅图4及表4，将应用实施例1、对比例1及对比例2隔膜的锂离子电池以0.1C充放电循环前5次，再以0.5C充电1C放电，直至循环100次。可以看到，随着循环次数的增加，实施例1的锂离子电池的循环性能明显优于对比例1及对比例2的锂离子电池。
表4
第1次循环放电比容量（mAh/g） 第50次循环放电比容量（mAh/g） 第100次循环放电比容量（mAh/g） 第100次循环容量保持率
实施例1 142 mAh/g 129mAh/g 127 mAh/g 89%
对比例1 142mAh/g 130mAh/g 124mAh/g 87%
对比例2 142 mAh/g 127 mAh/g 122 mAh/g 86%
通过本发明硫酸钡复合隔膜的制备方法得到表面修饰有羧酸锂基团的纳米硫酸钡，并通过粘结剂将该纳米硫酸钡涂覆于基膜表面形成一涂层，从而得到硫酸钡复合隔膜。该涂层起到一刚性支撑作用，能够阻止隔膜的热收缩；该纳米硫酸钡表面修饰有羧酸锂基团，一方面，在沉淀硫酸钡的过程中该羧酸锂基团使纳米硫酸钡不易团聚，并且使纳米硫酸钡在后续应用中能够分散均匀；另一方面该羧酸锂基团增加了纳米硫酸钡颗粒表面载离子的浓度，能够促进锂离子在隔膜中传输，从而提高应用该硫酸钡复合隔膜的锂离子电池的充放电及循环性能。
另外，本领域技术人员还可在本发明精神内做其他变化，当然，这些依据本发明精神所做的变化，都应包含在本发明所要求保护的范围之内。

Claims (10)

  1. 一种硫酸钡复合隔膜，包括：一基膜和一涂覆于该基膜表面的涂层，该涂层包括纳米硫酸钡和粘结剂，其特征在于，所述纳米硫酸钡表面修饰有羧酸锂基团。
  2. 如权利要求1所述的硫酸钡复合隔膜，其特征在于，所述羧酸锂基团中碳原子数至少为8个。
  3. 如权利要求1所述的硫酸钡复合隔膜，其特征在于，所述纳米硫酸钡内部含有介孔。
  4. 如权利要求1所述的硫酸钡复合隔膜，其特征在于，所述涂层的厚度为2μm~10μm。
  5. 一种硫酸钡复合隔膜的制备方法，包括：
    将羧酸锂溶解于有机溶剂形成的溶液加入到可溶性钡盐水溶液中，混合形成第一溶液；
    提供一pH值为8~10的可溶性硫酸盐水溶液，将该可溶性硫酸盐水溶液加入到该第一溶液中，反应生成沉淀物；
    将该沉淀物分离、水洗并干燥，得到表面修饰有羧酸锂基团的纳米硫酸钡；
    将该纳米硫酸钡和粘结剂混合得到一混合浆料，涂覆于一基膜表面形成硫酸钡复合隔膜。
  6. 如权利要求5所述的硫酸钡复合隔膜的制备方法，其特征在于，所述有机溶剂与可溶性钡盐水溶液体积比为1：1至2：1，所述有机溶剂为极性水溶性有机溶剂。
  7. 如权利要求5所述的硫酸钡复合隔膜的制备方法，其特征在于，所述羧酸锂为油酸锂、硬脂酸锂、聚丙烯酸锂、十二烷基苯甲酸锂及十六烷基苯甲酸锂中的一种或多种的混合物，所述羧酸锂质量为理论上纳米硫酸钡质量的1%~5%。
  8. 如权利要求5所述的复合隔膜的制备方法，其特征在于，该混合浆料的制
    备步骤包括：
    将该纳米硫酸钡和极性溶剂混合搅拌，直至所述纳米硫酸钡均匀分散，得到一混合溶液；
    将粘结剂加入到该混合溶液中搅拌直至该粘结剂溶解，形成一混合浆料。
  9. 如权利要求8所述的硫酸钡复合隔膜的制备方法，其特征在于，所述混合
    浆料中各物质所占的质量百分比: 粘结剂与纳米硫酸钡质量比为5：100~
  10. 一种锂离子电池，包括正极、负极以及设置在该正极与负极之间的隔膜，其特征在于，该隔膜为如权利要求1~4所述的硫酸钡复合隔膜，以及渗透于该硫酸钡复合隔膜中的非水电解液。
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