WO2017012500A1 - 正极材料及锂硫电池 - Google Patents

正极材料及锂硫电池 Download PDF

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WO2017012500A1
WO2017012500A1 PCT/CN2016/090020 CN2016090020W WO2017012500A1 WO 2017012500 A1 WO2017012500 A1 WO 2017012500A1 CN 2016090020 W CN2016090020 W CN 2016090020W WO 2017012500 A1 WO2017012500 A1 WO 2017012500A1
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positive electrode
sulfurized
monomer
sulfur
formula
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PCT/CN2016/090020
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English (en)
French (fr)
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何向明
钱冠男
王莉
尚玉明
李建军
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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 WO2017012500A1 publication Critical patent/WO2017012500A1/zh
Priority to US15/871,079 priority Critical patent/US10270103B2/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
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/621—Binders
    • H01M4/622—Binders being polymers
    • H01M4/623—Binders being polymers fluorinated polymers
    • 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
    • H01M10/05—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
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0565—Polymeric materials, e.g. gel-type or solid-type
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/04—Processes of manufacture in general
    • H01M4/0471—Processes of manufacture in general involving thermal treatment, e.g. firing, sintering, backing particulate active material, thermal decomposition, pyrolysis
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/137—Electrodes based on electro-active polymers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • H01M4/1399—Processes of manufacture of electrodes based on electro-active polymers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/621—Binders
    • H01M4/622—Binders being polymers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/028—Positive electrodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/364—Composites as mixtures
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/60—Selection of substances as active materials, active masses, active liquids of organic compounds
    • H01M4/602—Polymers
    • 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 invention relates to a positive electrode material and a lithium sulfur battery using the same.
  • lithium-sulfur secondary batteries are considered to be the most attractive battery system.
  • Sulfur has the highest theoretical specific energy (2800 Wh/kg) and theoretical specific capacity (1675 Ah/kg) in known cathode materials compared to other battery systems.
  • sulfur as a positive electrode of a lithium ion battery has good overcharge safety, large storage capacity in the natural world, low price, and environmentally friendly characteristics (please refer to the feasibility study of lithium-sulfur polymer secondary battery, Wan Chunrong, etc. , Battery Industry, Vol. 11, No. 5, p. 291-295 (2006)).
  • lithium-sulfur batteries generate polysulfides during the charge-discharge cycle, and polysulfides can be dissolved in the organic electrolyte, resulting in irreversible loss and capacity decay of the active materials.
  • the lithium ion is inserted into and removed from the sulfur positive electrode to cause volume expansion and contraction. As the number of cycles increases, the positive electrode structure collapses and the positive electrode material peels off, so that the battery capacity is rapidly attenuated. In order to solve the above problems, it is important to choose a suitable binder.
  • oil-based binders such as polyvinylidene fluoride (PVDF) are often used in conventional lithium-ion batteries for problems such as poor cycle performance of lithium-sulfur batteries.
  • PVDF polyvinylidene fluoride
  • aqueous binders typified by polyacrylic acid or polyacrylates are preferred in the prior art, such as Chinese patent application CN102569730A.
  • a positive electrode active material such as sulfur, a conductive agent, and a binder are mixed by adding a solvent to form an electrode slurry, which is applied to the surface of the current collector, and then dried to remove the solvent.
  • a volatile organic solvent can be used to make the electrode slurry easier to dry.
  • the drying process temperature cannot be too high, it takes a long time for the aqueous binder to completely dry the water as a solvent, and the active material in the battery pole piece is often oxidized during the drying process, which adversely affects the battery performance. .
  • a cathode material comprising a sulfur-containing cathode active material, a conductive agent and a cathode binder, wherein the cathode binder is a polymer obtained by polymerization of a diamine monomer and a dianhydride monomer, and the dianhydride
  • the monomer includes the formula (1), (2) at least one of the monomers represented by the formula (3), the diamine monomer comprising at least a monomer represented by the formula (4), and R in the formula (3) is a divalent organic substituent,
  • a lithium-sulfur battery comprising a positive electrode, a negative electrode and an electrolyte, the positive electrode comprising the above positive electrode material.
  • the invention passes through an polymerization reaction of an organic diamine compound and a dianhydride monomer, and the polymer not only has a good viscosity, but also can be used for a lithium sulfur battery to improve the cycle performance of the lithium sulfur battery. It is a kind of lithium-sulfur battery oil binder with potential application.
  • Example 1 is a cycle performance curve of a lithium-sulfur battery according to Example 2 of the present invention and Comparative Example 1.
  • Embodiments of the present invention provide a positive electrode binder for a sulfur-containing cathode material of a lithium sulfur battery, which is a polymer obtained by polymerization of a diamine monomer and a dianhydride monomer.
  • the molecular formula of the dianhydride monomer is represented by the formula (1), the formula (2) or the formula (3).
  • R in the formula (3) is a divalent organic substituent, and specifically may be a bisphenol A group, -O-, -S-, -CH 2 -.
  • the dianhydride monomers include, but are not limited to, bisphenol A type diether dianhydride, diphenyl ether tetracarboxylic dianhydride, pyromellitic anhydride, and 3,3',4,4'-biphenyltetracarboxylic dianhydride. One or more of them.
  • the diamine monomer includes at least a monomer represented by the formula (4).
  • the diamine monomer may further include a monomer represented by the formula (5).
  • R 4 is a divalent organic substituent, specifically -(CH 2 ) n -, -O-, -S-, -CH 2 -O-CH 2 -, -CH(NH)-(CH 2 ) n - or
  • the molar ratio of the monomer of the formula (4) to the monomer of the formula (5) may be from 1:2 to 10:1, preferably from 1:1 to 3:1.
  • the total molar ratio of the dianhydride monomer to the diamine monomer may be from 1:10 to 10:1, preferably from 1:2 to 4:1.
  • the positive electrode binder may have a molecular weight of from 1,000 to 50,000.
  • the present application further provides a method for preparing the above positive electrode binder, comprising the steps of polymerizing a dianhydride monomer and the diamine monomer, in particular, the above diamine monomer and dianhydride monomer are organic Mix, heat and stir in the solvent to make the opposite It should be sufficiently carried out to obtain the positive electrode binder.
  • the above diamine monomer can be dissolved in an organic solvent to form a diamine solution.
  • the mass ratio of the diamine monomer to the organic solvent in the diamine solution may be from 1:100 to 1:1, preferably from 1:10 to 1:2.
  • the above dianhydride monomer can be dissolved in an organic solvent to form a dianhydride solution.
  • the mass ratio of the dianhydride monomer to the organic solvent in the dianhydride solution may be from 1:100 to 1:1, preferably from 1:10 to 1:2.
  • the organic solvent is an organic solvent capable of dissolving the dianhydride monomer and the diamine monomer, such as N,N-dimethylformamide, N,N-dimethylacetamide, propylene carbonate, and N- Methyl pyrrolidone (NMP).
  • One of the dianhydride solution and the diamine solution can be transported to the other by a transfer pump at a certain rate, and the stirring is continued for a certain period of time after the completion of the transfer, so that the reaction proceeds sufficiently.
  • the mixing and stirring time may be from 2 hours to 72 hours, preferably from 12 hours to 24 hours.
  • the reaction temperature of the polymerization reaction may be from 160 ° C to 200 ° C.
  • a catalyst may be further added, and the catalyst may be one or more of benzoic acid, benzenesulfonic acid, phenylacetic acid, pyridine, quinoline, pyrrole, imidazole, and the catalyst is added in an amount of dianhydride. 0.5-5 wt% of the total mass of the body and diamine monomer.
  • the dianhydride monomer and the diamine monomer may be completely dissolved in an organic solvent; then the temperature is raised to 30 ° C to 60 ° C, and the stirring reaction is continued for 1 hour to 10 hours, preferably 2 hours to 4 hours. Finally, the catalyst is added and the temperature is raised to 160 ° C to 200 ° C, and the reaction is continuously stirred for 6 hours to 48 hours, preferably 12 hours to 24 hours, to obtain the polymer.
  • the positive electrode binder may be further purified. Specifically, the produced polymer solution is washed and dried by a washing reagent to obtain a positive electrode binder.
  • the catalyst and the reaction solvent are dissolved in the washing reagent, and the positive electrode binder is insoluble in the washing reagent to form a precipitate.
  • the washing reagent may be water, methanol, ethanol, a mixed solution of methanol and water or a mixed solution of ethanol and water (concentration of methanol or ethanol is 5 to 99% by weight).
  • An embodiment of the present invention provides a cathode material comprising a sulfur-containing cathode active material, a conductive agent, and a cathode binder, wherein the cathode binder is a polymerization obtained by polymerization of a diamine monomer and a dianhydride monomer. Things.
  • the positive electrode binder can be uniformly mixed with the sulfur-containing positive electrode active material and the conductive agent.
  • the positive electrode binder may have a mass percentage in the positive electrode material of 0.01% to 50%, preferably 5% to 20%.
  • the sulfur-containing positive electrode active material is at least one of elemental sulfur and a sulfur-based conductive polymer.
  • the sulfur-based conductive polymer may be a product obtained by mixing a conductive polymer with elemental sulfur and performing a pyrolysis reaction, a dehydrocarbonization reaction, a dehydration reaction, a dehydrochlorination reaction or a deamination reaction.
  • the sulfur-based conductive polymer may, but not limited to, sulfurized polypyridyl, sulfurized polystyrene, sulfurized polyethylene oxide, sulfurized polyvinyl alcohol, sulfurized polyvinylidene chloride, sulfurized polyvinylidene fluoride, sulfurized polyvinyl chloride, One or more of vulcanized polyvinyl fluoride, sulfurized poly(1,2-dichloroethylene), sulfurized poly(1,2-difluoroethylene), sulfurized polymethyl methacrylate, and sulfurized phenolic resin.
  • the conductive agent may be one or more of a carbon material such as carbon black, a conductive polymer, acetylene black, carbon fiber, carbon nanotubes, and graphite.
  • the positive electrode binder is oily and soluble in an oily solvent, it can be combined with an oily organic solvent commonly used in the preparation of an existing lithium ion battery electrode slurry, such as N-methylpyrrolidone, in the process of preparing the positive electrode slurry.
  • the oily organic solvent can be quickly and effectively removed during the drying process of the electrode slurry, thereby avoiding the adverse effect of the drying process on the battery pole piece and the battery performance.
  • the embodiment of the invention further provides a lithium-sulfur battery, comprising a positive electrode, a negative electrode and an electrolyte disposed between the positive electrode and the negative electrode.
  • the positive electrode includes the above positive electrode material, and may further include a positive electrode current collector disposed on the surface of the positive electrode current collector.
  • the negative electrode includes a negative electrode material, and may further include a negative electrode current collector disposed on a surface of the negative electrode current collector.
  • the negative electrode material may be metallic lithium.
  • the electrolyte can be an electrolyte or a solid electrolyte.
  • the lithium-sulfur battery may further include a separator opposite to the cathode material and disposed through the separator, the electrolyte impregnating the cathode, the anode and the separator.
  • the electrolyte is a solid electrolyte
  • the solid electrolyte may be in the form of a film which is opposed to the positive electrode material and disposed at intervals by the solid electrolyte membrane.
  • the separator may be a polyolefin porous film, a modified polypropylene felt, a polyethylene felt, a glass fiber felt, an ultrafine glass fiber paper vinylon felt or a nylon felt and a wettable polyolefin microporous film welded or bonded. Composite film.
  • the electrolyte solution includes a lithium salt and a non-aqueous solvent.
  • the nonaqueous solvent may include one or more of a cyclic carbonate, a chain carbonate, a cyclic ether, a chain ether, a nitrile, and an amide, such as ethylene carbonate (EC), diethyl carbonate.
  • EC ethylene carbonate
  • the lithium salt may include lithium chloride (LiCl), lithium hexafluorophosphate (LiPF 6 ), lithium tetrafluoroborate (LiBF 4 ), lithium methanesulfonate (LiCH 3 SO 3 ), lithium trifluoromethanesulfonate (LiCF 3 SO 3 ) Lithium hexafluoroarsenate (LiAsF 6 ), lithium hexafluoroantimonate (LiSbF 6 ), lithium perchlorate (LiClO 4 ), Li[BF 2 (C 2 O 4 )], Li[PF 2 (C2O 4 ) 2 ], Li[N(CF 3 SO 2 ) 2 ], Li[C(CF 3 SO 2 ) 3 ], lithium bis(oxalate)borate (LiBOB) and lithium bis(trifluoromethyl)sulfonimide (LiTFSI) One or more of them.
  • LiCl lithium chloride
  • LiPF 6 lithium
  • BAPP 2,2'-bis(4-aminophenoxyphenyl)propane
  • 4'-diaminodiphenylmethane 1,3-bis(4-aminophenoxyphenyl)propane
  • organic solvent m-cresol 1,3-bis(4-aminophenoxyphenyl)propane
  • the test conditions were: a constant current charge and discharge cycle at a current rate of 0.1 C in the range of 1 V to 3 V. 1 and Table 1, the cycle performance of the lithium-sulfur battery of Example 2 and Comparative Example 1 is shown in FIG. 1, and the first discharge specific capacity and the 30th discharge specific capacity of Examples 2, 3, and 5 and Comparative Example 1. And the 30th capacity retention rate is shown in Table 1. It can be seen that the lithium-sulfur battery cycle performance using the polyimide binder is greatly improved compared to the lithium-sulfur battery using the PVDF binder.
  • the positive electrode tabs of Examples 2, 3, and 5 and Comparative Example 1 were subjected to adhesion test. Use a tape width of 20mm ⁇ 1mm, first remove the outer 3 to 5 layers of adhesive tape, and then take more than 150mm of adhesive tape (adhesive tape bonding surface can not contact hands or other substances). One end is bonded to the surface of the positive electrode piece, the length is 100mm, and the other end is connected to the holder, and then rolled back and forth three times on the positive electrode piece with a pressure roller at a speed of about 300 mm/min under the own weight, and parked for 20 minutes under the test environment ⁇ The test was carried out after 40 minutes.
  • the free end of the positive electrode tab was folded in half by 180°, and the adhesive face was peeled off from the positive electrode tab by 15 mm.
  • the free end of the positive electrode tab and the test plate are respectively clamped on the upper and lower holders. Make the peeling surface consistent with the test machine line.
  • the test machine was continuously peeled off at a descending speed of 300 mm/min ⁇ 10 mm/min, and an automatic recorder was used to draw a peeling curve. As can be seen from Table 2, Examples 2, 3, and 5 all had better adhesion than Comparative Example 1.

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Abstract

本发明涉及一种正极材料，包括含硫正极活性材料、导电剂及正极粘结剂，该正极粘结剂是由二胺类单体与二酐类单体通过聚合反应得到的聚合物。该含硫正极活性材料为单质硫或硫基导电聚合物。本发明还涉及一种锂硫电池，包括正极、负极及电解质。该正极包括上述正极材料。

Description

正极材料及锂硫电池
相关申请
本发明申请要求2015年07月17日申请的，申请号为201510422483.9，名称为“正极材料及锂硫电池”的中国专利申请的优先权，在此将其全文引入作为参考。
技术领域
本发明涉及一种正极材料及应用该正极材料的锂硫电池。
背景技术
长久以来，人们一直致力于新型储能系统的研究和开发。其中，锂-硫二次电池被认为是最为吸引人的电池体系。与其他电池体系相比，硫在已知正极材料中具有最高的理论比能量(2800Wh/kg)及理论比容量(1675Ah/kg)。并且，硫作为锂离子电池的正极具有耐过充安全性好，在自然界存储量大，价格便宜，以及对环境友好的特点(请参阅锂硫聚合物二次电池可行性研究，万春荣等,《电池工业》，Vol.11,No.5,p291-295(2006))。
然而，锂硫电池在充放电循环过程中会产生多硫化物，多硫化物能溶解于有机电解液中，导致活性物质的不可逆损失和容量衰减。并且，充放电循环过程中随着锂离子的插入与脱出硫正极产生体积膨胀和收缩，随着循环次数的增加，正极结构发生坍塌、正极材料出现剥落，使电池容量较快衰减。为解决上述问题，选择合适的粘结剂至关重要。
实验证明，在传统的锂离子电池中常用油性粘结剂如聚偏氟乙烯(PVDF)对于锂硫电池存在循环性能变差等问题。对于锂硫电池体系，现有技术中倾向于使用以聚丙烯酸或聚丙烯酸盐为代表的水性粘结剂，如中国专利申请CN102569730A。然而，在电池极片制作过程中，正极活性物质，如硫，与导电剂、粘结剂通过加入溶剂进行混合形成电极浆料涂覆于集流体表面，然后进行烘干以去除溶剂。对于油性粘结剂，可以使用易挥发的有机溶剂，从而使电极浆料更容易干燥。由于烘干过程温度不能过高，对于水性粘结剂，彻底烘干作为溶剂的水则需要较长时间，常常会在干燥过程中导致电池极片中活性物质被氧化，对电池性能造成不利影响。
发明内容
有鉴于此，确有必要开发适合锂硫电池的油性粘结剂，用于含硫正极材料以及锂硫电池。
一种正极材料，包括含硫正极活性材料、导电剂及正极粘结剂，该正极粘结剂是由二胺类单体与二酐类单体通过聚合反应得到的聚合物，该二酐类单体包括由分子通式由式(1)、式 (2)及式(3)表示的单体中的至少一种，该二胺类单体至少包括由式(4)表示的单体，式(3)中R为二价有机取代基，
Figure PCTCN2016090020-appb-000001
一种锂硫电池，包括正极、负极及电解质，该正极包括上述正极材料。
本发明通过有机二胺类化合物与二酐类单体通过聚合反应一种聚合物，该聚合物不但具有较好的粘度，在锂硫电池中用于含硫正极还能够提高锂硫电池循环性能，是一种具有应用潜力的锂硫电池油性粘结剂。
说明书附图
图1为本发明实施例2及比较例1的锂硫电池的循环性能曲线。
下面结合附图对本发明作进一步描述。
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正极材料及应用该正极材料的锂硫电池作进一步的详细说明。
本发明实施方式提供一种用于锂硫电池含硫正极材料的正极粘结剂，是由二胺类单体与二酐类单体通过聚合反应得到的聚合物。
该二酐类单体的分子通式由式(1)、式(2)或式(3)表示。
Figure PCTCN2016090020-appb-000002
式(3)中R为二价有机取代基，具体可以是双酚A基,-O-,-S-,-CH2-。该二酐类单体包括但不局限于双酚A型二醚二酐、二苯醚四甲酸二酐、均苯四甲酸酐及3,3',4,4'-联苯四甲酸二酐中的一种或多种。
该二胺类单体至少包括由式(4)表示的单体。
Figure PCTCN2016090020-appb-000003
另外，该二胺类单体还可进一步包括由式(5)表示的单体。
Figure PCTCN2016090020-appb-000004
其中R4为二价有机取代基，具体可以是-(CH2)n-，-O-，-S-，-CH2-O-CH2-，-CH(NH)-(CH2)n-
Figure PCTCN2016090020-appb-000005
或
Figure PCTCN2016090020-appb-000006
其中，式(4)的单体和式(5)的单体的摩尔比可以为1:2～10:1，优选为1:1～3:1。
该二酐类单体与该二胺类单体的总的摩尔比可以为1:10～10:1，优选为1:2～4:1。
该正极粘结剂的分子量可以为1000～50000。
本申请进一步提供一种上述正极粘结剂的制备方法，包括将二酐类单体与该二胺类单体聚合的步骤，具体是将上述二胺类单体与二酐类单体在有机溶剂中混合、加热并搅拌，使反 应充分进行，得到该正极粘结剂。
可以将上述二胺类单体在有机溶剂中溶解形成二胺溶液。该二胺溶液中二胺类单体与有机溶剂的质量比可以为1:100～1:1，优选为1:10～1:2。
可以将上述二酐类单体在有机溶剂中溶解形成二酐溶液。该二酐溶液中二酐类单体与有机溶剂的质量比可以为1:100～1:1，优选为1:10～1:2。
该有机溶剂为能够溶解该二酐类单体与该二胺类单体的有机溶剂，例如N,N-二甲基甲酰胺、N,N-二甲基乙酰胺、碳酸丙烯酯及N-甲基吡咯烷酮(NMP)。
可以通过输送泵以一定速率将二酐溶液与二胺溶液中的一种输送至另一种中，输送完毕后持续搅拌一定时间，使反应充分进行。该混合搅拌的时间可以为2小时～72小时，优选为12小时～24小时。该聚合反应的反应温度可以为160℃～200℃。
在上述聚合反应的过程中可进一步加入催化剂，该催化剂可以为苯甲酸、苯磺酸、苯乙酸、吡啶、喹啉、吡咯、咪唑中的一种或多种，催化剂的加入量为二酐单体与二胺单体总质量的0.5-5wt％。
具体地，可先将二酐类单体与该二胺类单体在有机溶剂中完全溶解；随后升温至30℃～60℃，持续搅拌反应1小时～10小时，优选为2小时～4小时；最后加入催化剂并升温至160℃～200℃，持续搅拌反应6小时～48小时，优选为12小时～24小时，得到所述聚合物。
在反应完毕后可进一步将该正极粘结剂提纯，具体为将生成的聚合物溶液通过一洗涤试剂进行洗涤并烘干，得到正极粘结剂。该催化剂及反应溶剂溶于该洗涤试剂，而该正极粘结剂在该洗涤试剂中不溶，从而形成沉淀。该洗涤试剂可以为水、甲醇、乙醇、甲醇与水的混合溶液或乙醇与水的混合溶液(甲醇或乙醇的浓度为5-99wt％)。
本发明实施方式提供一种正极材料，包括含硫正极活性材料、导电剂及正极粘结剂，该正极粘结剂为上述由二胺类单体与二酐类单体通过聚合反应得到的聚合物。该正极粘结剂可以与该含硫正极活性材料及导电剂均匀混合。该正极粘结剂在该正极材料中的质量百分含量可以为0.01％～50％，优选为5％～20％。
该含硫正极活性材料为单质硫及硫基导电聚合物中的至少一种。该硫基导电聚合物可以为将导电聚合物与单质硫进行混合并进行热解反应、脱氢碳化反应、脱水反应、脱氯化氢反应或脱胺反应后的产物。该硫基导电聚合物可以列举但不限于硫化聚并吡啶、硫化聚苯乙烯、硫化聚氧化乙烯、硫化聚乙烯醇、硫化聚偏二氯乙烯、硫化聚偏二氟乙烯、硫化聚氯乙烯、硫化聚氟乙烯、硫化聚1，2-二氯乙烯、硫化聚1，2-二氟乙烯、硫化聚甲基丙烯酸甲酯及硫化酚醛树脂中的一种或多种。
该导电剂可以为碳素材料，如碳黑、导电聚合物、乙炔黑、碳纤维、碳纳米管及石墨中的一种或多种。
由于该正极粘结剂为油性，易溶于油性溶剂，在制备正极浆料的过程中可以与现有的锂离子电池电极浆料制备过程中常用的油性有机溶剂，如N-甲基吡咯烷酮配合使用，油性有机溶剂在电极浆料的烘干过程中可以迅速有效的去除，避免烘干过程对电池极片及电池性能造成不利影响。
本发明实施例进一步提供一种锂硫电池，包括正极、负极及设置在该正极与负极之间的电解质。该正极包括上述正极材料，并可进一步包括正极集流体，该正极材料设置在该正极集流体表面。该负极包括负极材料，并可进一步包括负极集流体，该负极材料设置在该负极集流体表面。该负极材料可以为金属锂。该电解质可以为电解液或固态电解质。当该电解质为电解液时，该锂硫电池可进一步包括一隔膜，该负极材料与正极材料相对且通过所述隔膜间隔设置，该电解液浸润该正极、负极及隔膜。当该电解质为固态电解质时，该固态电解质可以为膜状，该负极材料与正极材料相对且通过固态电解质膜间隔设置。
该隔膜可以为聚烯烃多孔膜、改性聚丙烯毡、聚乙烯毡、玻璃纤维毡、超细玻璃纤维纸维尼纶毡或尼龙毡与可湿性聚烯烃微孔膜经焊接或粘接而成的复合膜。
该电解质溶液包括锂盐及非水溶剂。该非水溶剂可包括环状碳酸酯、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(EC)、碳酸二乙酯(DEC)、碳酸丙烯酯(PC)、碳酸二甲酯(DMC)、碳酸甲乙酯(EMC)、乙二醇二甲醚(DME)、碳酸丁烯酯、γ-丁内酯、γ-戊内酯、碳酸二丙酯、N-甲基吡咯烷酮(NMP)、N-甲基甲酰胺、N-甲基乙酰胺、二甲基甲酰胺、二乙基甲酰胺、二乙醚、乙腈、丙腈、苯甲醚、丁二腈、己二腈、戊二腈、二甲亚砜、亚硫酸二甲酯、碳酸亚乙烯酯、碳酸甲乙酯、碳酸二甲酯、碳酸二乙酯、氟代碳酸乙烯酯、氯代碳酸丙烯酯、酸酐、环丁砜、甲氧基甲基砜、四氢呋喃、2-甲基四氢呋喃、环氧丙烷、乙酸甲酯、乙酸乙酯、乙酸丙酯、丁酸甲酯、丙酸乙酯、丙酸甲酯、二甲基甲酰胺、1,3-二氧戊环(DOL)、1,2-二乙氧基乙烷、1,2-二甲氧基乙烷、或1,2-二丁氧基中的一种或几种的组合。
该锂盐可包括氯化锂(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)、六氟锑酸锂(LiSbF6)、高氯酸锂(LiClO4)、Li[BF2(C2O4)]、Li[PF2(C2O4)2]、Li[N(CF3SO2)2]、Li[C(CF3SO2)3]、双草酸硼酸锂(LiBOB)及双(三氟甲基)磺酰亚胺锂(LiTFSI)中的一种或多种。
实施例1
按摩尔比，在三口烧瓶中加入0.4份2,2'-双(4-氨基苯氧基苯基)丙烷(BAPP)，0.6份4,4’-二氨基二苯醚(ODA)，有机溶剂间甲酚(溶液固含量约10％)，室温搅拌，待完全溶解后，加入1份二苯醚四甲酸二酐，完全溶解后，升温至50℃，反应4小时，加入催化剂苯甲酸1.5ml，升温至180℃，反应24小时，终止反应，在甲醇中沉淀，得到正极粘结剂，为一种纤维状高 分子聚合物，由式(6)表示
Figure PCTCN2016090020-appb-000007
实施例2
按质量百分比，将70％的硫碳正极材料、10％的实施例1中的正极粘结剂和20％的导电石墨混合，用NMP分散，将此浆料涂布于铝箔上，于60℃真空干燥24小时，制成正极极片。以锂片作为对电极，电解液为1M LiTFSI溶于组成为DOL/DME＝1/1(v/v)的溶剂中，组装成2032扣式电池。
实施例3
按质量百分比，将75％的硫碳正极材料、5％的实施例1中的正极粘结剂和20％的导电石墨混合，用NMP分散，将此浆料涂布于铝箔上，于60℃真空干燥24小时，制成正极极片。以锂片作为对电极，电解液为1M LiTFSI溶于组成为DOL/DME＝1/1(v/v)的溶剂中，组装成2032扣式电池。
实施例4
按摩尔比，在三口烧瓶中加入0.4份2,2'-双(4-氨基苯氧基苯基)丙烷(BAPP)，0.6份4,4’-二氨基二苯甲烷，有机溶剂间甲酚(溶液固含量约10％)，室温搅拌，待完全溶解后，加入1份二苯醚四甲酸二酐，完全溶解后，升温至50℃，反应4小时，加入催化剂苯甲酸1.5ml，升温至180℃，反应24小时，终止反应，在甲醇中沉淀，得到正极粘结剂，为一种纤维状高分子聚合物，由式(7)表示
Figure PCTCN2016090020-appb-000008
实施例5
按质量百分比，将70％的硫碳正极材料、10％的实施例4中的正极粘结剂和20％的导电石墨混合，用NMP分散，将此浆料涂布于铝箔上，于60℃真空干燥24小时，制成正极极片。以锂片作为对电极，电解液为1M LiTFSI溶于组成为DOL/DME＝1/1(v/v)的溶剂中，组装成2032扣式电池。
比较例1
按质量百分比，将70％的硫碳正极材料、10％的PVDF和20％的导电石墨混合，用NMP分散，将此浆料涂布于铝箔上，于120℃真空干燥24小时，制成正极极片。以锂片作为对电极，电解液为1M LiTFSI溶于组成为DOL/DME＝1/1(v/v)的溶剂中，组装成2032扣式电池。
上述实施例及比较例均采用相同的硫碳正极材料，具体为硫单质与导电碳均匀混合得到。
电池循环性能测试
测试条件为：在1V～3V范围内，以0.1C的电流倍率恒流充放电循环。请参阅图1及表1，实施例2及比较例1的锂硫电池的循环性能如图1所示，实施例2、3、5和比较例1首次放电比容量、第30次放电比容量及第30次容量保持率如表1所示。可以看到采用聚酰亚胺粘结剂的锂硫电池循环性能相对于采用PVDF粘结剂的锂硫电池具有较大提高。
表1
Figure PCTCN2016090020-appb-000009
粘结力测试
分别对实施例2、3、5和比较例1的正极极片进行粘结力测试。使用的胶粘带宽度为20mm±1mm，先撕去外面的3～5层的胶粘带，然后再取150mm以上的胶粘带(胶粘带粘合面不能接触手或其他物质)。一端与正极极片表面粘结，长度100mm，另一端接夹持器，然后用压辊在自重下以约300mm/min的速度在正极极片上来回滚压三次，在试验环境下停放20min～40min后进行试验。将正极极片自由端对折180°，并从正极极片上剥开粘合面15mm。把正极极片自由端和试验板分别夹在上、下夹持器上。使剥离面与试验机力线保持一致。试验机以300mm/min±10mm/min下降速度连续剥离，并有自动记录仪绘出剥离曲线。从表2中可以看出，实施例2、3、5与比较例1相比均具有较好的粘结力。
表2
正极极片 试样厚度μm 试样宽度mm 最大负荷N
实施例2 58±2 20 3.6
实施例3 58±2 20 3.2
实施例5 58±2 20 3.7
比较例1 58±2 20 1.6
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. 一种正极材料，包括含硫正极活性材料、导电剂及正极粘结剂，其特征在于，该正极粘结剂是由二胺类单体与二酐类单体通过聚合反应得到的聚合物，该二酐类单体包括由分子通式由式(1)、式(2)及式(3)表示的单体中的至少一种，该二胺类单体至少包括由式(4)表示的单体，式(3)中R为二价有机取代基，
    Figure PCTCN2016090020-appb-100001
  2. 如权利要求1所述的正极材料，其特征在于，R是双酚A基,-O-,-S-,或-CH2-。
  3. 如权利要求1所述的正极材料，其特征在于，该二酐类单体包括双酚A型二醚二酐、二苯醚四甲酸二酐、均苯四甲酸酐及3,3',4,4'-联苯四甲酸二酐中的一种或多种。
  4. 如权利要求1所述的正极材料，其特征在于，该二胺类单体进一步包括由式(5)表示的单体，其中R4为二价有机取代基，
    Figure PCTCN2016090020-appb-100002
  5. 如权利要求4所述的正极材料，其特征在于，R4是-(CH2)n-，-O-，-S-，-CH2-O-CH2-，-CH(NH)-(CH2)n-
    Figure PCTCN2016090020-appb-100003
    Figure PCTCN2016090020-appb-100004
  6. 如权利要求4所述的正极材料，其特征在于，所述式(4)的单体和式(5)的单体的摩尔比为1:2～10:1。
  7. 如权利要求1所述的正极材料，其特征在于，该二酐类单体与该二胺类单体的摩尔比为1:2～4:1。
  8. 如权利要求1所述的正极材料，其特征在于，该聚合物的分子量为1000～50000。
  9. 如权利要求1所述的正极材料，其特征在于，该含硫正极活性材料为单质硫及硫基导电聚合物中的至少一种，该硫基导电聚合物为硫化聚并吡啶、硫化聚苯乙烯、硫化聚氧化乙烯、硫化聚乙烯醇、硫化聚偏二氯乙烯、硫化聚偏二氟乙烯、硫化聚氯乙烯、硫化聚氟乙烯、硫化聚1，2-二氯乙烯、硫化聚1，2-二氟乙烯、硫化聚甲基丙烯酸甲酯及硫化酚醛树脂中的一种或多种。
  10. 一种锂硫电池，包括正极、负极及电解质，该正极包括如权利要求1-9中任意一项所述的正极材料。
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