WO2017185479A1 - 核壳结构的材料、其制备方法及应用 - Google Patents

核壳结构的材料、其制备方法及应用 Download PDF

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WO2017185479A1
WO2017185479A1 PCT/CN2016/084707 CN2016084707W WO2017185479A1 WO 2017185479 A1 WO2017185479 A1 WO 2017185479A1 CN 2016084707 W CN2016084707 W CN 2016084707W WO 2017185479 A1 WO2017185479 A1 WO 2017185479A1
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sulfur
core
shell structure
lithium
containing organic
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PCT/CN2016/084707
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English (en)
French (fr)
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胡晨吉
陈宏伟
卢威
吴晓东
陈立桅
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中国科学院苏州纳米技术与纳米仿生研究所
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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
    • H01M4/628—Inhibitors, e.g. gassing inhibitors, corrosion inhibitors
    • 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
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • 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
    • 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 particularly relates to a core-shell structure organic sulfur-coated elemental sulfur composite material, a preparation method thereof and application in a lithium-sulfur battery, and belongs to the technical field of electrochemistry.
  • lithium-sulfur batteries are high-energy density secondary batteries with great development potential and application prospects. It uses sulfur as the main positive active material, has a high specific capacity (1675mAh / g) and high energy density (2600Wh / kg), the actual energy density has also reached 400Wh / kg, while sulfur is cheap and non-toxic characteristics, so Lithium-sulfur batteries are receiving increasing attention.
  • the industry generally coats the surface of the positive electrode material, and the presence of the coating layer can reduce the dissolution rate of the polysulfide ions, thereby slowing down the shuttle effect.
  • the successful implementation of the case includes: Yang Yuan and other ultrasonically coated PEDOT: PSS wrapped carbon-sulfur cathode material, the method is to disperse the carbon-sulfur material in the polymer-containing solution, ultrasonic for a long time, and then remove Solvent, the carbon sulfur material with about 10nm polymer coating on the surface is obtained.
  • the method is simple and effective, the purity of the finished product is high, but the cost is high and the repeatability is poor.
  • Huang Yunhui and the like use hydrothermal method to grow microporous level on the surface of mesoporous carbon sulfur material.
  • the carbon coating further limits the dissolution of polysulfide ions.
  • the method is harsh and the process is complicated; other coating methods are similar.
  • various coating strategies have been successfully applied to the preparation of lithium-sulfur battery cathode materials, there is a logical contradiction in these pre-coating strategies, namely the contradiction between electrolyte entry and polysulfide ion dissolution.
  • the electrolyte needs to have pores to penetrate into the positive electrode material, and these channels provide a way for the dissolution of polysulfide ions during the cycle of the battery, so how to be reasonably effective
  • the surface coating of sulfur-containing materials to prevent polysulfide dissolution is a key task in the research and production of lithium-sulfur batteries.
  • the main object of the present invention is to provide a core-shell structure material, a preparation method thereof and an application thereof to overcome the deficiencies in the prior art.
  • the technical solution adopted by the present invention includes:
  • Embodiments of the present invention provide a core-shell structure material, comprising: a core of elemental sulfur, and a shell layer covering the core; the shell layer comprises a sulfur-containing organic substance, and the sulfur-containing organic substance can be selected The substance reacts to form an in situ coating on the shell layer, the selected material being selected from materials capable of nucleophilic or electrophilic reaction with the sulfur-containing organic material.
  • the core-shell structure material has a porous structure having a pore volume of 0.8 to 1.0 cm 3 /g and a pore diameter of 2 to 50 nm.
  • the selected material is selected from the group consisting of organic compounds containing phosphorus and/or fluorine.
  • the embodiment of the invention further provides a method for preparing the material of the core-shell structure, comprising: uniformly mixing the polymer-coated core with elemental sulfur, and then calcining at 300-450 ° C for 3-6 hours under an inert gas atmosphere. Obtaining a material of the core-shell structure; wherein the core comprises elemental sulfur.
  • Embodiments of the present invention also provide the use of the material of the foregoing core-shell structure for preparing a lithium-sulfur battery.
  • the embodiment of the invention further provides a cathode material of a lithium sulfur battery, comprising the material of the core shell structure.
  • the embodiment of the invention further provides a lithium-sulfur battery comprising a positive electrode, a negative electrode and an electrolyte, the positive electrode comprising the lithium-sulfur battery cathode material, the electrolyte comprising a selected substance, the selected substance being capable of
  • the sulfur-containing organic matter in the material of the core-shell structure undergoes a nucleophilic or electrophilic reaction to form an in-situ coating on the shell layer of the material of the core-shell structure.
  • the advantages of the present invention are at least:
  • the core-shell structure material of the present invention is a core-shell structure material in which organic sulfur is coated with elemental sulfur, and the elemental sulfur/carbon material of the core layer ensures the ionic conductivity and electronic conductivity of the entire electrode material, and the pre-coating layer
  • the porous sulfur-containing organic matter can further limit the dissolution of polysulfide ions.
  • the cathode material of the sulfur-containing organic substance coated with elemental sulfur is applied to a lithium-sulfur battery, and the lithium-sulfur battery has high discharge capacity and excellent cycle stability performance, and still has about 83 after 500 cycles. % capacity retention rate.
  • the material of the core-shell structure of the invention and the preparation method of the cathode material do not require complicated chemical reaction design, the process is simple, the efficiency is high, the condition is mild, the equipment is simple to operate, and is suitable for large-scale industrial application.
  • 1a-1b are transmission electron micrographs of a sulfur-containing organic-coated carbon-sulfur composite material prepared in Example 1 of the present invention
  • 2a-2b are transmission electron micrographs of a sulfur-containing organic-coated carbon-sulfur composite material in an electrolyte containing an electrolyte additive according to Embodiment 1 of the present invention
  • FIG. 3 is a cycle performance diagram of a button cell (CR2025) assembled by using a sulfur-containing organic-coated carbon-sulfur composite material prepared in Example 1 of the present invention as a positive electrode, metallic lithium as a negative electrode, and an electrolyte containing an electrolyte additive.
  • a core-shell structure material of organic sulfur-encapsulated elemental sulfur is provided, followed by a corresponding preparation method and its application as a positive electrode material in a lithium-sulfur battery.
  • a new cladding layer is formed in situ on the surface of the organic sulfur to form a core-shell-shell structure, and the electrolyte is confined to the positive electrode material at the same time, thereby maximizing It inhibits the dissolution and shuttle of polysulfide ions.
  • An aspect of an embodiment of the present invention provides a core-shell structure material comprising a core of elemental sulfur, and a shell layer covering the core, the shell layer comprising a sulfur-containing organic substance, the sulfur-containing organic substance capable of The selected material reacts to form an in situ coating on the shell layer, the selected material being selected from materials capable of nucleophilic or electrophilic reaction with the sulfur-containing organic material.
  • the shell layer has a thickness of 10 to 20 nm.
  • the mass ratio of the sulfur-containing organic matter to elemental sulfur is from 1:10 to 1:20.
  • the core-shell structure material has a porous structure having a pore volume of 0.8 to 1.0 cm 3 /g and a pore diameter of 2 to 50 nm.
  • the core comprises a composite of elemental sulfur and a conductive agent.
  • the core comprises a carbon-sulfur composite material, wherein the content of elemental sulfur in the carbon-sulfur composite material is 70% by weight or more and less than 100%.
  • the carbon-sulfur composite material has a mesoporous structure having a pore volume of 0.8 to 1.0 cm 3 /g and a pore diameter of 2 to 50 nm.
  • the shell layer is comprised of a sulfur-containing organic compound.
  • the sulfur in the sulfur-containing organic compound exists in the form of a carbon-sulfur chemical bond and/or a sulfur-sulfur chemical bond.
  • the sulfur-containing organic substance includes one or a combination of two or more of sulfurized polyacrylonitrile, sulfurized polyvinyl chloride, and sulfurized glucose, but is not limited thereto.
  • the selected material is selected from the group consisting of organic compounds containing phosphorus and/or fluorine.
  • the phosphorus- and/or fluorine-containing organic compound includes triphenylphosphine and tris(2,2,2-trifluoroethyl)phosphoric acid. Any one or a combination of two or more of an ester and lithium oxalate borate, but is not limited thereto.
  • Another aspect of the present invention provides a method for preparing a material of the core-shell structure, comprising: uniformly mixing a polymer-coated core with elemental sulfur, and then 300 to 450 ° C under an inert gas atmosphere. Calcined for 3-6 hours to obtain a material of the core-shell structure; wherein the core comprises elemental sulfur.
  • the preparation method comprises: uniformly mixing the mesoporous carbon material and the elemental sulfur powder, heating at 100 to 200 ° C for 12 to 24 hours to form a carbon-sulfur composite material, and then reacting with the polymer monomer and capable of promoting polymerization.
  • the initiator and/or polymer are thoroughly mixed in a solvent to produce the polymer-coated core.
  • a typical polymer may be selected from the group consisting of polyacrylonitrile, polyvinyl chloride, polystyrene, and the like which can be dehydrogenated with elemental sulfur.
  • a typical initiator may be selected from a free radical initiator such as azobisisobutyronitrile (AIBN) or potassium persulfate.
  • Another aspect of an embodiment of the present invention also provides the use of the material of the foregoing core-shell structure for preparing a lithium-sulfur battery.
  • Another aspect of an embodiment of the present invention also provides a lithium sulfur battery positive electrode material, including the material of the foregoing core-shell structure.
  • Another aspect of the present invention further provides a lithium-sulfur battery comprising a positive electrode, a negative electrode and an electrolyte, the positive electrode comprising the lithium-sulfur battery cathode material, the electrolyte comprising a selected substance, the selected substance
  • An nucleophilic or electrophilic reaction can occur with the sulfur-containing organic material in the material of the core-shell structure to form an in-situ coating on the shell layer of the material of the core-shell structure.
  • the selected material is selected from the group consisting of organic compounds containing phosphorus and/or fluorine.
  • the phosphorus-and/or fluorine-containing organic compound includes triphenylphosphine, tris(2,2,2-trifluoroethyl)phosphite, and lithium or potassium oxalate borate. Combination, but not limited to.
  • the electrolyte comprises from 1 wt% to 10 wt% of the selected material.
  • the core-shell structure material of the present invention can be used as a cathode material containing sulfur-containing organic substances to coat elemental sulfur.
  • a cathode material containing sulfur-containing organic substances to coat elemental sulfur.
  • the coating layer can be formed in situ on the surface of the sulfur-containing organic substance, thereby effectively suppressing the dissolution of the polysulfide ions and suppressing the shuttle, and greatly improving the working performance of the lithium-sulfur battery.
  • an in-situ coating is produced by a chemical reaction between a sulfur-containing organic substance in a pre-coating layer (ie, a shell layer) in a material of an electrolyte additive and a core-shell structure, the in-situ coating
  • the layer is formed while confining the electrolyte to the positive electrode material, thereby suppressing the dissolution of polysulfide ions.
  • the elemental sulfur/carbon material in the core layer of the core-shell structure material ensures the ionic conductivity and electronic conductivity of the entire electrode material, and the pre-coated porous sulfur-containing organic substance can further It limits the dissolution of polysulfide ions, and more importantly, it forms a coating layer in situ as an inducing layer and an electrolyte additive, thereby maximally inhibiting the dissolution and shuttling of polysulfide ions.
  • the material for preparing the core-shell structure in the present invention is a nucleophilic reaction between the electrolyte additive and the sulfur-containing organic compound to form a core-shell-shell structure; for this system, the polymer reaction is easy to carry out, and the degree of reaction is easily controlled. The property can realize uniform polymerization coating of the polymer on the surface of the carbon sulfur material.
  • the method of the present invention is universal and can be applied to the preparation of almost all carbon-sulfur cathode materials.
  • the organic sulfur-coated carbon-sulfur composite material synthesized above is mixed with a binder and a conductive agent and then coated on an aluminum foil.
  • the binder may be selected from lithium sulfur such as polyvinylidene fluoride (PVDF).
  • PVDF polyvinylidene fluoride
  • a commonly used binder for batteries; a lithium metal, a lithium alloy, a lithium powder, or the like can be used as the negative electrode.
  • the electrolyte was allowed to stand for 6 h in a LiTFSI+DOL/DME (1:1, by volume) electrolyte containing 2% by mass of triphenylphosphine, followed by a charge and discharge test.
  • the transmission electron micrograph of the sulfur-containing organic-coated carbon-sulfur composite material prepared in the present embodiment in an electrolyte containing an electrolyte additive forms an in-situ coating layer.
  • FIG. 3 is a cycle performance diagram of a button cell (CR2025) assembled by using a sulfur-containing organic-coated carbon-sulfur composite material prepared in the present embodiment as a positive electrode, metallic lithium as a negative electrode, and an electrolyte containing an electrolyte additive.
  • the prepared positive electrode material is applied to a lithium-sulfur battery, and the obtained lithium-sulfur battery has high discharge capacity and excellent cycle stability performance, and the battery still has about 83% capacity retention after 500 cycles. rate.
  • the organic sulfur-coated carbon-sulfur composite material synthesized above is mixed with a binder and a conductive agent and then applied to an aluminum foil.
  • the binder may be a commonly used binder for a lithium-sulfur battery such as PVDF;
  • the negative electrode is made of lithium metal, lithium alloy, lithium powder or the like.
  • the electrolyte was allowed to stand for 6 h in a LiTFSI+DOL/DME (1:1, by volume) electrolyte containing 5% by weight of triphenylphosphine, followed by a charge and discharge test.
  • mesoporous carbon material 0.5 g was added to 50 ml of a mixed solvent of dimethyl sulfoxide and water and stirred to obtain a mixed solution. Under vigorous stirring, 10 ml of acrylonitrile monomer, 75 mg of AIBN was sequentially added to the above mixed solution, sealed, and polymerized at 65 ° C for 2 h under a nitrogen atmosphere. The obtained product is sequentially centrifuged, washed, and dried to obtain a polyacrylonitrile-coated carbon sulfur material.
  • 100 mg of the obtained polyacrylonitrile-coated carbon sulfur material was mixed with 100 mg of elemental sulfur, and calcined at 300 ° C for 6 h under argon gas protection to form an organic sulfur-coated mesoporous carbon material.
  • the above-mentioned organic sulfur-coated mesoporous carbon material and commercially available sulfur powder are calcined at 155 ° C for 12 hours under the protection of argon gas to form an organic sulfur-coated carbon-sulfur composite material (ie, Core-shell structure material).
  • the organic sulfur-coated carbon-sulfur composite material synthesized above is mixed with a binder and a conductive agent and then applied to an aluminum foil as a positive electrode material of a lithium-sulfur battery, and a binder commonly used for a lithium-sulfur battery such as PVDF may be selected as a binder.
  • the negative electrode is made of metal lithium, lithium alloy, lithium powder or the like.
  • the electrolyte was allowed to stand for 6 h in a LiTFSI+DOL/DME (1:1, by volume) electrolyte containing 5% by weight of triphenylphosphine, followed by a charge and discharge test.

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Abstract

一种核壳结构的材料、其制备方法及应用。所述核壳结构的材料包括包含单质硫的核以及包覆所述核的壳层，所述壳层包含含硫有机物，所述含硫有机物能够与选定物质反应而在所述壳层上形成原位包覆层，所述选定物质选自能够与所述含硫有机物发生亲核或者亲电反应的物质。该核壳结构的材料可以用作锂硫电池正极材料，且其制备工艺简便，效率高，条件温和，设备简单，适合大规模工业化应用。该核壳结构的材料中含硫有机物能与锂硫电解液添加剂发生化学反应，并生成原位包覆层，从而抑制多硫离子的溶出和穿梭。基于该核壳结构材料的锂硫电池具有较高的放电容量以及优异的循环稳定性能。

Description

核壳结构的材料、其制备方法及应用 技术领域
本发明具体涉及一种核壳结构的有机硫包覆单质硫的复合材料、其制备方法以及在锂硫电池中的应用，属于电化学技术领域。
背景技术
随着传统资源和能源日益紧缺、环境问题日趋严重，开发新的能源储存及转换技术已经成为各国的能源战略重点。其中，锂硫电池是极具发展潜力和应用前景的高能量密度二次电池。它以硫作为主要正极活性物质，具有高比容量(1675mAh/g)和高能量密度(2600Wh/kg)，实际能量密度也已经能达到400Wh/kg，同时硫具有廉价而无毒的特点，因此锂硫电池正日益受到关注。
但是由于单质硫的放电行为是固-液-固的过程，其中间态的多硫离子是可溶于电解液的，在循环的过程中会溶出正极材料，继而由于浓度差的存在其会到达负极去得电子并生成固体产物，而这些固体产物在后续的充电过程中又会回到正极，如此来回形成穿梭效应，会造成电池循环性能差、库伦效率低等不良影响。因而，如何抑制多硫离子的溶出和穿梭效应就成为了问题。
目前，业界一般都是在正极材料表面进行包覆，由于包覆层的存在可以降低多硫离子的溶出速率，从而减缓穿梭效应。比如，已成功实施的案例包括：杨源等采用超声包覆制备出PEDOT:PSS包裹的碳硫正极材料，该方法是将碳硫材料分散在含有聚合物的溶液中，长时间超声，然后去除溶剂，得到表面有大约10nm聚合物包覆的碳硫材料，方法简单有效，成品纯度很高，但成本高，重复性差；黄云辉等利用水热法在介孔碳硫材料表面生长微孔级别的碳包覆层，进一步限制多硫离子的溶出。但是此方法的条件苛刻，工艺复杂；其它的包覆方法也都类似。然而，虽然各样五花八门的包覆策略被成功应用到锂硫电池正极材料制备上，但是这些预先包覆的策略都存在一个逻辑上的矛盾，即电解液进入和多硫离子溶出的矛盾。具体来说，无论采用哪种预先包覆手段，电解液都需要有孔道渗透到正极材料当中，而这些孔道在电池循环的过程中又会为多硫离子溶出提供途径，因此，如何合理的有效的对含硫材料进行表面包覆以防止多硫化物溶出是锂硫电池研究生产中一个关键的工作。
发明内容
本发明的主要目的在于提供一种核壳结构的材料、其制备方法及应用，以克服现有技术中的不足。
为实现前述发明目的，本发明采用的技术方案包括：
本发明实施例提供了一种核壳结构的材料，包含：单质硫的核，以及，包覆所述核的壳层；所述壳层包含含硫有机物，所述含硫有机物能够与选定物质反应而在所述壳层上形成原位包覆层，所述选定物质选自能够与所述含硫有机物发生亲核或者亲电反应的物质。
在一些优选实施方案中，所述核壳结构的材料具有多孔结构，其孔容为0.8～1.0cm3/g，孔径为2～50nm。
在一些优选实施方案中，所述选定物质选自含磷和/或氟的有机化合物。
本发明实施例还提供了一种制备所述核壳结构的材料的方法，包括：将聚合物包覆的核与单质硫混合均匀，再在惰性气体氛围下于300～450℃煅烧3～6h，获得所述核壳结构的材料；其中所述的核包括单质硫。
本发明实施例还提供了前述核壳结构的材料于制备锂硫电池中的用途。
本发明实施例还提供了一种锂硫电池正极材料，包括前述核壳结构的材料。
本发明实施例还提供了一种锂硫电池，包含正极、负极及电解液，所述正极包含前述锂硫电池正极材料，所述电解液包含选定物质，所述选定物质能够与所述核壳结构的材料内的含硫有机物发生亲核或者亲电反应，从而在所述核壳结构的材料的壳层上生成原位包覆层。
与现有技术相比，本发明的优点至少在于：
1.本发明的核壳结构的材料，为有机硫包裹单质硫的核壳结构材料，最核心层的单质硫/碳材料保证了整个电极材料的离子电导率和电子电导率，预包覆层的多孔含硫有机物可以进一步限制多硫离子的溶出。
2.本发明的含硫有机物包覆单质硫的正极材料，在含有功能添加剂的锂硫电解液中，由于化学反应的存在可以在含硫有机物表面原位生成包覆层，从而抑制多硫离子的溶出。
3.本发明的含硫有机物包覆单质硫的正极材料，应用于锂硫电池中，所制得锂硫电池具有较高的放电容量以及优异的循环稳定性能，500次循环之后仍有约83％的容量保留率。
4.本发明的核壳结构的材料及正极材料的制备方法不需要复杂的化学反应设计，工艺简便，效率高，条件温和，设备简单操作易掌握，适合大规模工业化应用。
附图说明
图1a-图1b为本发明实施例1中制备的含硫有机物包覆的碳硫复合材料的透射电镜图；
图2a-图2b为本发明实施例1中含硫有机物包覆的碳硫复合材料在含有电解液添加剂的电解液中的透射电镜图；
图3为应用本发明实施例1制备的含硫有机物包覆的碳硫复合材料作为正极，金属锂为负极，采用含有电解液添加剂的电解液组装的扣式电池(CR2025)的循环性能图。
具体实施方式
鉴于现有技术中的不足，本案发明人经长期研究和大量实践，得以提出本发明的技术方案。首先提供了一种有机硫包裹单质硫的核壳结构的材料，随后提出相应的制备方法，及其在锂硫电池中作为正极材料的应用。利用其在锂硫电池电解液中由于化学反应使得在有机硫表面原位生成新的包覆层，从而形成核-壳-壳结构，生成的同时把电解液限制在正极材料当中，从而最大程度上抑制多硫离子的溶出和穿梭。
如下将对该技术方案、其实施过程及原理等作进一步的解释说明。
本发明实施例的一个方面提供的一种核壳结构的材料，包含单质硫的核，以及，包覆所述核的壳层，所述壳层包含含硫有机物，所述含硫有机物能够与选定物质反应而在所述壳层上形成原位包覆层，所述选定物质选自能够与所述含硫有机物发生亲核或者亲电反应的物质。
在一些优选实施方案中，所述壳层的厚度为10～20nm。
在一些优选实施方案中，所述含硫有机物与单质硫的质量比为1：10～1：20。
在一些优选实施方案中，所述核壳结构的材料具有多孔结构，其孔容为0.8～1.0cm3/g，所含孔洞的孔径为2～50nm。
在一些优选实施方案中，所述的核包括单质硫与导电剂的复合材料。
进一步的，所述的核包括碳硫复合材料，其中所述碳硫复合材料中单质硫的含量在70wt％以上而小于100％。
更进一步的，所述碳硫复合材料具有介孔结构，其孔容为0.8～1.0cm3/g，所含孔洞的孔径为2～50nm。
在一些优选实施方案中，所述壳层由含硫有机物组成。
进一步的，所述含硫有机物中的硫以碳-硫化学键和/或硫-硫化学键形式存在。
更进一步的，所述含硫有机物包括硫化聚丙烯腈、硫化聚氯乙烯和硫化葡萄糖中的一种或两种以上的组合，但不限于此。
在一些优选实施方案中，所述选定物质选自含磷和/或氟的有机化合物。
进一步的，所述含磷和/或氟的有机化合物包括三苯基膦、三(2,2,2-三氟乙基)亚磷酸 酯，二草酸硼酸锂中的任意一种或两种以上的组合，但不限于此。
本发明实施例的另一方面还提供了一种制备所述核壳结构的材料的方法，包括：将聚合物包覆的核与单质硫混合均匀，再在惰性气体氛围下于300～450℃煅烧3～6h，从而获得所述核壳结构的材料；其中所述的核包括单质硫。
进一步的，所述制备方法包括：将介孔碳材料与单质硫粉体均匀混合后，于100～200℃加热12～24h，形成碳硫复合材料，之后与聚合物单体及能够促成聚合反应的引发剂和/或聚合物于溶剂中充分混合，从而制得所述聚合物包覆的核。
其中，典型的聚合物可以选自聚丙烯腈、聚氯乙烯、聚苯乙烯等可以和单质硫发生脱氢反应的物质。而相应的，典型的引发剂可以选自偶氮二异丁腈(AIBN)、过硫酸钾等自由基引发剂。
本发明实施例的另一方面还提供了前述核壳结构的材料于制备锂硫电池中的用途。
本发明实施例的另一方面还提供了一种锂硫电池正极材料，包括前述核壳结构的材料。
本发明实施例的另一方面还提供了一种锂硫电池，包含正极、负极及电解液，所述正极包含前述锂硫电池正极材料，所述电解液包含选定物质，所述选定物质能够与所述核壳结构的材料内的含硫有机物发生亲核或者亲电反应，从而在所述核壳结构的材料的壳层上生成原位包覆层。
在一些优选实施方案中，所述选定物质选自含磷和/或氟的有机化合物。
优选的，所述含磷和/或氟的有机化合物包括三苯基膦，三(2,2,2-三氟乙基)亚磷酸酯，二草酸硼酸锂中的任意一种或两种以上的组合，但不限于此。
优选的，所述电解液包含1wt％～10wt％所述选定物质。
本发明的核壳结构的材料可以作为一种含硫有机物包覆单质硫的正极材料，当这类材料被置入含有功能添加剂的锂硫电解液中形成电化学体系时，由于化学反应的存在可以在含硫有机物表面原位生成包覆层，从而可以有效抑制多硫离子的溶出及抑制穿梭，大幅提升锂硫电池的工作性能。
具体而言，本发明中利用由电解液添加剂和核壳结构的材料中预包覆层(即壳层)内的含硫有机物之间的化学反应产生原位包覆层，该原位包覆层在生成的同时把电解液限制在正极材料当中，进而抑制多硫离子的溶出。进一步的，对于此电化学体系，所述核壳结构的材料内最核心层的单质硫/碳材料保证了整个电极材料的离子电导率和电子电导率，预先包覆的多孔含硫有机物可以进一步限制多硫离子的溶出，而更为重要的是其作为诱导层和电解液添加剂原位生成包覆层，从而最大程度上抑制多硫离子的溶出和穿梭。本发明中的制备核壳结构的材料是利用电解液添加剂和含硫有机物之间的亲核反应从而形成核-壳-壳结构；对于此体系，利用高分子反应容易进行，反应程度容易控制的 特性，可以实现聚合物在碳硫材料表面均匀聚合包覆。
需要说明的是，在本发明的电化学体系中，对于所述核壳结构的材料的中心核层的碳硫材料没有选择性。因此，本发明此方法是普适性的，可以应用到几乎所有碳硫正极材料的制备上。
以下通过若干实施例并结合附图进一步详细说明本发明的技术方案。然而，所选的实施例仅用于说明本发明，而不限制本发明的范围。
实施例1
将3g市售的硫粉末和7g介孔碳材料(商用介孔碳材料，其孔径分布在2～5nm，孔容约1.0cm3/g)混合均匀，于100～200℃下加热12～24h，得到碳硫复合材料。然后将0.5g碳硫复合材料加入到50ml乙醇中，并搅拌分散得到混合溶液。在强力搅拌作用下，向前述混合溶液中依次加入10ml丙烯腈单体、75mg偶氮二异丁腈(AIBN)，密封，在氮气保护氛围下于65℃聚合3h。得到的产物依次经离心、洗涤、干燥，制得聚丙烯腈包覆的碳硫材料。将100mg所制得聚丙烯腈包覆的碳硫材料和300mg单质硫混合，在氩气保护下，于300℃煅烧6h，形成有机硫包覆的碳硫复合材料(亦即核壳结构的材料)。如图1a～图1b所示，为本实施例制备的含硫有机物包覆的碳硫复合材料的透射电镜图。
将上述合成的有机硫包覆的碳硫复合材料与粘结剂、导电剂混合后涂覆于铝箔，作为锂硫电池的正极材料，粘结剂可选用聚偏氟乙烯(PVDF)等锂硫电池常用的粘结剂；负极可采用金属锂、锂合金、锂粉等。电解液为含有质量百分比为2％三苯基膦的(LiTFSI+DOL/DME(1:1，体积比)电解液中静置6h，随后进行充放电测试。
如图2a～图2b所示，为本实施例制备的含硫有机物包覆的碳硫复合材料在含有电解液添加剂的电解液中的透射电镜图，即形成了原位包覆层。
图3为应用本实施例制备的含硫有机物包覆的碳硫复合材料作为正极，金属锂为负极，采用含有电解液添加剂的电解液组装的扣式电池(CR2025)的循环性能图。
由图可知，将制备的正极材料，应用于锂硫电池中，所制得锂硫电池具有较高的放电容量以及优异的循环稳定性能，电池经过500次循环之后仍有约83％的容量保留率。
实施例2
将3g市售的硫粉末和7g介孔碳材料(商用介孔碳材料，其孔径分布在2～5nm，孔容约1.0cm3/g)混合均匀，于100～200℃下加热12～24h，得到碳硫复合材料。然后将上述碳硫复合材料在强力搅拌作用下，加入到含有聚丙烯腈的二甲基亚砜溶液中，超声1小时，随后加热挥发溶剂二甲基亚砜，从而制得聚丙烯腈包覆的碳硫材料。将100mg所制得聚丙烯腈包覆的碳硫材料和100mg单质硫混合，在氩气保护下，于300℃煅烧6h，形成有机硫包覆的碳硫复合材料(亦即核壳结构的材料)。
将上述合成的有机硫包覆的碳硫复合材料与粘结剂、导电剂混合后涂覆于铝箔，作 为锂硫电池的正极材料，粘结剂可选用PVDF等锂硫电池常用的粘结剂；负极采用金属锂、锂合金、锂粉等。电解液为含有质量百分比为5％三苯基膦的(LiTFSI+DOL/DME(1:1，体积比)电解液中静置6h，随后进行充放电测试。
实施例3
将0.5g介孔碳材料加入到50ml二甲基亚砜和水的混合溶剂中并搅拌分散得到混合溶液。在强力搅拌作用下，向前述混合溶液中依次加入10ml丙烯腈单体，75mg AIBN，密封，在氮气保护下于65℃聚合2h。得到的产物依次经离心、洗涤、干燥，制得聚丙烯腈包覆的碳硫材料。将100mg所制得聚丙烯腈包覆的碳硫材料和100mg单质硫混合，在氩气保护下，于300℃煅烧6h，形成有机硫包覆的介孔碳材料。将上述的有机硫包覆的介孔碳材料和市售的硫粉按照3：7的比例在氩气保护下、于155℃煅烧12小时，形成有机硫包覆的碳硫复合材料(亦即核壳结构的材料)。
将上述合成的有机硫包覆的碳硫复合材料与粘结剂、导电剂混合后涂覆于铝箔，作为锂硫电池的正极材料，粘结剂可选用PVDF等锂硫电池常用的粘结剂；负极采用金属锂、锂合金、锂粉等。电解液为含有质量百分比为5％三苯基膦的(LiTFSI+DOL/DME(1:1，体积比)电解液中静置6h，随后进行充放电测试。
需要指出的是，上述实施例仅为说明本发明的技术构思及特点，其目的在于让熟悉此项技术的人士能够了解本发明的内容并据以实施，并不能以此限制本发明的保护范围。凡根据本发明精神实质所作的等效变化或修饰，都应涵盖在本发明的保护范围之内。

Claims (18)

  1. 一种核壳结构的材料，其特征在于包括：包含单质硫的核，以及，包覆所述核的壳层，所述壳层包含含硫有机物，所述含硫有机物能够与选定物质反应而在所述壳层上形成原位包覆层，所述选定物质选自能够与所述含硫有机物发生亲核或者亲电反应的物质。
  2. 根据权利要求1所述的核壳结构的材料，其特征在于：所述核壳结构的材料具有多孔结构，其孔容为0.8～1.0cm3/g，所含孔洞的孔径为2～50nm；和/或，所述壳层的厚度为10～20nm，含硫有机物与单质硫的质量比为1：10～1：20。
  3. 根据权利要求1所述的核壳结构的材料，其特征在于：所述的核包括单质硫与导电剂的复合材料。
  4. 根据权利要求2所述的核壳结构的材料，其特征在于：所述的核包括碳硫复合材料，其中所述碳硫复合材料中单质硫的含量在70wt％以上而小于100％。
  5. 根据权利要求4所述的核壳结构的材料，其特征在于：所述碳硫复合材料具有介孔结构，其孔容为0.8～1.0cm3/g，所含孔洞的孔径为2～50nm。
  6. 根据权利要求1所述的核壳结构的材料，其特征在于：所述壳层由含硫有机物组成。
  7. 根据权利要求6所述的核壳结构的材料，其特征在于：所述含硫有机物中的硫以碳-硫化学键和/或硫-硫化学键形式存在。
  8. 根据权利要求7所述的核壳结构的材料，其特征在于：所述含硫有机物包括硫化聚丙烯腈、硫化聚氯乙烯和硫化葡萄糖中的任意一种或两种以上的组合。
  9. 根据权利要求1所述的核壳结构的材料，其特征在于：所述选定物质选自含磷和/或氟的有机化合物。
  10. 根据权利要求9所述的核壳结构的材料，其特征在于：所述含磷和/或氟的有机化合物包括三苯基膦，三(2,2,2-三氟乙基)亚磷酸酯，二草酸硼酸锂中的任意一种或两种以上的组合。
  11. 根据权利要求1-10中任一项所述的核壳结构的材料的制备方法，其特征在于包括：将聚合物包覆的核与单质硫混合均匀，再在惰性气体氛围下于300～450℃煅烧3～6h，获得所述核壳结构的材料；其中所述的核包括单质硫。
  12. 根据权利要求11所述的制备方法，其特征在于包括：将介孔碳材料与单质硫粉体均匀混合后，于100～200℃加热12～24h，形成碳硫复合材料，之后将所述硫碳复合材料与聚合物单体及能够促成聚合反应的引发剂和/或聚合物于溶剂中充分混合，从而制 得所述聚合物包覆的核。
  13. 如权利要求1-10中任意一项所述的核壳结构的材料于制备锂硫电池中的用途。
  14. 一种锂硫电池正极材料，其特征在于包括权利要求1-10中任意一项所述的核壳结构的材料。
  15. 一种锂硫电池，包含正极、负极及电解液，其特征在于：所述正极包含权利要求14所述的锂硫电池正极材料，所述电解液包含选定物质，所述选定物质能够与所述核壳结构的材料内的含硫有机物发生亲核或者亲电反应，从而在所述核壳结构的材料的壳层上生成原位包覆层。
  16. 根据权利要求15所述的锂硫电池，其特征在于：所述选定物质选自含磷和/或氟的有机化合物。
  17. 根据权利要求16所述的锂硫电池，其特征在于：所述含磷和/或氟的有机化合物包括三苯基膦，三(2,2,2-三氟乙基)亚磷酸酯，二草酸硼酸锂中的任意一种或两种以上的组合。
  18. 根据权利要求15-17中任一项所述的锂硫电池，其特征在于：所述电解液包含1wt％-10wt％所述选定物质。
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