WO2017143549A1 - 硫碳复合物及其制备方法、含有该硫碳复合物的电极材料和锂硫电池 - Google Patents

硫碳复合物及其制备方法、含有该硫碳复合物的电极材料和锂硫电池 Download PDF

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WO2017143549A1
WO2017143549A1 PCT/CN2016/074517 CN2016074517W WO2017143549A1 WO 2017143549 A1 WO2017143549 A1 WO 2017143549A1 CN 2016074517 W CN2016074517 W CN 2016074517W WO 2017143549 A1 WO2017143549 A1 WO 2017143549A1
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sulfur
carbon
carbon composite
lithium
carbon nanoparticles
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PCT/CN2016/074517
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English (en)
French (fr)
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崔彦辉
武俊伟
常嵩
郑新宇
张新河
李中延
屈德扬
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东莞市迈科科技有限公司
哈尔滨工业大学深圳研究生院
东莞市迈科新能源有限公司
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Priority to PCT/CN2016/074517 priority Critical patent/WO2017143549A1/zh
Publication of WO2017143549A1 publication Critical patent/WO2017143549A1/zh

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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
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • 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
    • 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 the technical field of lithium ion batteries, in particular to a sulfur-carbon composite for a lithium-sulfur battery, a preparation method thereof, an electrode material prepared by using the sulfur-carbon composite, and a lithium-sulfur battery.
  • Lithium-sulfur battery is a kind of lithium battery, which is a secondary battery with lithium metal as the negative electrode and sulfur as the positive electrode.
  • the negative electrode reacts to lose lithium and become lithium ion
  • the positive electrode reacts with sulfur and lithium.
  • the ions and electrons react to form sulfides, and the potential difference between the positive and negative electrodes is the discharge voltage provided by the lithium-sulfur battery.
  • the specific energy of lithium-sulfur battery can theoretically reach 2600Wh/kg, which is much larger than any commercial secondary battery used at this stage.
  • the elemental sulfur used in its positive electrode material is environmentally friendly.
  • lithium-sulfur batteries also have the advantages of low environmental pollution, good safety performance and low cost; therefore, they have broad application prospects in the field of new energy: on the one hand, they can be widely used as power batteries.
  • power batteries For plug-in hybrid vehicles, electric vehicles, space vehicles and underwater submersibles; on the other hand, it can also be used as an energy storage battery for backup power supply, wind energy and solar energy storage of communication base stations, and far away from the mains area. Regional power supply, etc.
  • the lithium-sulfur battery intermediate discharge product lithium polysulfide will dissolve into the organic electrolyte In the process, the viscosity of the electrolyte is increased to reduce the ionic conductivity; and the lithium polysulfide can migrate between the positive and negative electrodes, resulting in loss of active material and waste of electrical energy; and the dissolved lithium polysulfide diffuses across the separator to the negative electrode. Reacts with the negative electrode to destroy the solid electrolyte interface film (SEI film) of the negative electrode; 3.
  • SEI film solid electrolyte interface film
  • the surface of the lithium sulfide is separated from the conductive skeleton and cannot be converted into sulfur or a high-order polysulfide by a reversible charging process, resulting in a great attenuation of the capacity; 4.
  • the density of sulfur and lithium sulfide is 2.07 g, respectively.
  • c m -3 and 1.66g ⁇ cm -3 which have a volume expansion/contraction of up to 79% during charge and discharge.
  • the main solution at present is to solve the problem from the two aspects of the electrolyte and the positive electrode material; in terms of electrolyte, the main purpose is to replace the existing electrolyte with an ether electrolyte, or in the existing electrolyte.
  • Some additives are added, which can effectively alleviate the problem of dissolution of lithium polysulfide compounds; in terms of cathode materials, the combination of sulfur and carbon materials, or the combination of sulfur and organic matter can solve the problem of non-conductivity and volume expansion of sulfur.
  • the sulfur-carbon composite synthesized in the prior art can always avoid the problem that the polysulfide is dissolved into the electrolyte, and the lithium sulfur battery fabricated by using the sulfur-carbon composite has poor cycle stability and cannot meet the actual needs.
  • one of the objects of the present invention is to provide a sulfur-carbon composite for a lithium-sulfur battery to solve the above problems;
  • a second object of the present invention is to provide a method for preparing the above sulfur-carbon composite
  • a third object of the present invention is to provide an electrode material for a lithium sulfur battery, which comprises the above sulfur carbon composite;
  • a fourth object of the present invention is to provide a lithium sulfur battery comprising the above sulfur carbon composite.
  • a sulfur-carbon composite for a lithium-sulfur battery comprising carbon nanoparticles, a silica template agent dispersed in the carbon nanoparticles, and sulfur loaded in the carbon nanoparticles; wherein the carbon nanoparticles In the porous structure, the silica template agent is dispersed in the carbon nanoparticles, and 90% by weight or more of the sulfur is filled in the pores of the carbon nanoparticles, and the rest is dispersed on the surface of the carbon nanoparticles.
  • the silica template agent in the sulfur-carbon composite of the present invention is dispersed in the carbon nanoparticles to reduce the pore diameter of the carbon nanoparticles, so that when used, the carbon nanoparticles having a small pore diameter have an electrochemical reaction intermediate lithium sulfide. Stronger capture capacity, while the residual silica templating agent can effectively prevent the "shuttle effect" of lithium polysulfide.
  • the sulfur content is 40% to 70% by mass of the sulfur-carbon composite, and the silica template agent accounts for the sulfur-carbon composite. 0.3% to 3%.
  • the carbon nanoparticles have a diameter of 1 to 20 nm, a specific surface area of 20 to 3000 m 2 /g, and an average pore size of 2 to 50 nm.
  • the preparation method of the sulfur-carbon composite includes the following steps:
  • the sulfur-carbon composite of the invention is prepared by using carbon nanoparticles containing a silica template agent, wherein the silica template agent can reduce the pore diameter of the carbon nanoparticles, so that the carbon nanoparticles are stronger to the electrochemical intermediate lithium sulfide.
  • the ability to capture, and the silica templating agent can also effectively prevent the "flying effect" of lithium polysulfide; in addition, the preparation method of the present invention is simple and easy, and is suitable for large-scale production.
  • the method for preparing the carbon nanoparticle comprises the following steps:
  • nano-sized Na-X zeolite in the preparation of carbon nanoparticles is mainly due to the decomposition of nano-sized Na-X zeolite under the action of strong acid to produce aluminum ions, silica particles, silicates and other ions;
  • aluminum ions in the process of preparing carbon nanoparticles will generate aluminum hydroxide in situ, which acts as a template, and then removes aluminum hydroxide to obtain several pores of nanometer pores on carbon nanoparticles;
  • the ions are several molecules in size and are also used as templating agents here.
  • the silicates also obtain silica particles in the subsequent carbonization process. They are also used as templating agents.
  • silica particles After removing the silica particles, they will be A smaller pore size pore is formed on the carbon nanoparticle; other ions can also be used as a template in the subsequent process, which generates an ammonium salt in situ during the preparation of the carbon nanoparticle, acts as a template, and then removes the ammonium salt.
  • In-situ generation of a large number of molecular-scale pores in carbon nanoparticles can be used to load sulfur below S4 molecules, so that the prepared sulfur-carbon composite can eliminate some electrochemical intermediate reactions during charging and discharging, and improve the production of lithium. Cycle performance of sulfur batteries.
  • the nano-sized Na-X zeolite is in a molar ratio (7-12) NaOH: 2NaAlO 2 : (3 ⁇ 5) Si (OC 2 H 5 ) 4 : (180 ⁇ 200) H 2 O will be aluminoic acid
  • the sodium solution, the ethyl orthosilicate solution, sodium hydroxide and water are mixed and reacted; the obtained nano-sized Na-X zeolite has a size of 10 to 100 nm, preferably 20 to 50 nm.
  • the strong acid is one of hydrochloric acid, sulfuric acid or nitric acid, and the concentration of the strong acid is ⁇ 0.06M (specifically, mol/L, the same below); under the action of strong acid, nanometer
  • the grade Na-X zeolite is decomposed into a molecular-scale templating agent.
  • the nano-sized Na-X zeolite forms an aluminum salt, a silica and a silicate under the action of a strong acid, and is in the process of preparing the carbon nano particles in the subsequent process.
  • aluminum hydroxide is formed by the action of a strong alkali, and the silica and the subsequently formed aluminum hydroxide are used as a template for preparing the carbon nanoparticles, and both can function as a template.
  • the content of the phenolic resin in the ethanol solution of the phenolic resin is 1% to 5% by mass.
  • the concentrated ammonia water is added to mix the concentrated ammonia water with the ethanol, and then added dropwise to the mixed liquid mixture, and stirred at 40 to 60 ° C for 2 to 10 hours until the reaction is completed.
  • the concentrated ammonia water is added, on the one hand, the aluminum ions in the templating agent can be converted into aluminum hydroxide in situ to serve as a template; on the other hand, an excessive amount of strong acid is added in the neutralization step 11) to generate
  • the ammonium salt acts as a template for the molecular level; more importantly, it also promotes the polymerization of the phenolic resin.
  • the carbonization temperature is 800-1500 ° C, and the temperature rising rate during the carbonization is 1 to 10 ° C / min; the carbonized phenolic resin to be polymerized is converted into carbon nanoparticles.
  • the pickling in the step 14) is to sequentially wash the primary carbon nanoparticles with hydrochloric acid and hydrofluoric acid, and the aluminum hydroxide used as a template is easily reacted with hydrofluoric acid to easily form fluorine with less solubility.
  • Aluminum is difficult to remove. Therefore, the aluminum hydroxide is removed first, and then the other template is removed by hydrofluoric acid. When cleaning, the order of use cannot be reversed.
  • the templating agent such as aluminum hydroxide or silica is removed, and minute pores are obtained in the carbon nanoparticle in situ; when removed, the hydrofluoride used in the pickling is controlled.
  • the "flying effect" of the intermediate lithium polysulfide can be effectively prevented; while the templating agent such as ammonium salt is removed, a large number of molecular-scale pores are also generated in situ in the carbon nanoparticle, which can be used for loading below the S4 molecule.
  • the sulfur so that the prepared sulfur-carbon composite can eliminate some electrochemical intermediate reactions during charging and discharging, and improve the cycle performance of the fabricated lithium-sulfur battery.
  • the loading of the sulfur to the carbon nano particles is specifically: mixing the sulfur source with the carbon nanoparticles, and then co-heating at 120 to 190 ° C for 10 to 30 hours under a protective atmosphere, that is, The sulfur-carbon composite is obtained.
  • the sulfur source is melted upon heating, and the specific form thereof is variable.
  • the bulk sulfur may also be selected from powdered sulfur, preferably powdered sulfur.
  • An electrode material for a lithium-sulfur battery which comprises the sulfur-carbon composite as described above, which has good electrical conductivity.
  • a lithium sulfur battery comprising a sulfur-carbon composite as described above.
  • the lithium-sulfur battery of the invention adopts the above-mentioned sulfur-carbon composite, on the one hand, the sulfur-carbon composite has good conductivity, and the obtained lithium-sulfur battery has good high-rate performance; on the other hand, the sulfur-carbon composite It has many internal pores, which can effectively inhibit the dissolution of lithium polysulfide, thereby preventing the phenomenon that the active material of the electrode is gradually reduced, and preventing the dissolved lithium polysulfide from passing through the separator to the negative electrode of the battery due to the shuttle principle.
  • the phenomenon of negative electrode corrosion and increase of internal resistance of the battery caused by the lithium sheet occurs, thereby improving the cycle performance of the battery and reducing the speed of battery capacity decay, that is, the sulfur-carbon composite obtained by the method of the invention has higher sulfur. Utilization, the lithium-sulfur battery containing the carbon-sulfur composite has good cycle stability.
  • FIG. 1 Schematic diagram of the cycle life of the sulfur-carbon composite prepared in the present invention and the sulfur-carbon composite prepared by super P.
  • the sulfur-carbon composite for a lithium-sulfur battery of the present invention comprising carbon nanoparticles, sulfur loaded in the carbon nanoparticles, and a silica template agent dispersed in the carbon nanoparticles; wherein the carbon nanoparticles a porous structure, the silica template agent is dispersed in pores of the carbon nanoparticles, the sulfur is mostly filled in pores of the carbon nanoparticles, and the rest is dispersed on a surface of the carbon nanoparticles; 1 and 2, wherein the sulfur-carbon composite has a sulfur content of 40% to 70% by mass of the sulfur-carbon composite, and the silica template agent accounts for the sulfur. 0.3% to 3% of the carbon composite; the carbon nanoparticle has a diameter of 1 to 20 nm, a specific surface area of 20 to 3000 m 2 /g, and an average pore diameter of 2 to 50 nm.
  • silica template agent in the sulfur-carbon composite of the invention is dispersed in the inner pores of the carbon nanoparticles to reduce the pore diameter of the carbon nanoparticles, so that when used, the carbon nanoparticles have more electrochemical reaction intermediate lithium polysulfide. Strong capture capacity, while silica templating agent can also effectively prevent the "shuttle effect" of lithium polysulfide.
  • the specific process of the step 2) is: mixing the sulfur source with the carbon nano particles by mass ratio (0.8-1.5):1, and then co-heating at 120-190 ° C for 10-30 h under a protective atmosphere, that is, Said sulfur a carbon composite; wherein the silica template agent accounts for 0.3% to 3% of the sulfur-carbon composite by mass percentage.
  • the sulfur-carbon composite of the invention is prepared by using carbon nanoparticles containing a silica template agent, wherein the silica template agent can reduce the pore diameter of the carbon nanoparticles, so that the carbon nanoparticles are stronger to the electrochemical intermediate lithium sulfide.
  • the trapping ability, and the residue of the silica template agent can also effectively prevent the "flying effect" of the lithium polysulfide; in addition, the preparation method of the invention is simple and easy, and is suitable for large-scale production.
  • the key is the carbon nano-particles therein, and the preparation method thereof comprises the following steps:
  • Nanoscale Na-X zeolite is used in the preparation of carbon nanoparticles, and is used as a source of the template to make the prepared carbon nanoparticles form a porous structure to increase the specific surface area of the carbon material, so that the electrolyte is in full contact with the active material.
  • nano-sized Na-X zeolite decomposes under the action of strong acid to produce aluminum ions, silica particles, silicates and other ions; among them, aluminum ions in the process of preparing carbon nanoparticles In situ formation of aluminum hydroxide, which acts as a template, and then removes aluminum hydroxide, which can obtain several pores of nanometer pores on carbon nanoparticles; silica ions are several molecular sizes, which are also used as templates here.
  • the silicate will also obtain silica particles in the subsequent carbonization process, and as a templating agent, after removing the silica particles, a pore having a smaller pore diameter will be formed on the carbon nanoparticles; other ions It can also be used as a template in the subsequent process, which will form an ammonium salt in situ during the preparation of carbon nanoparticles, function as a template, and then remove the above ammonium salt in the carbon nano A large number of particles generated in situ molecular level pores, the following molecules can be used to load S4 sulfur, sulfur-carbon formed such that During the charging and discharging process, the composite can eliminate some electrochemical intermediate reactions and improve the cycle performance of the fabricated lithium-sulfur battery.
  • the strong acid is one of hydrochloric acid, sulfuric acid or nitric acid, and the concentration of the strong acid is ⁇ 0.06 M; under the action of strong acid, the nano-sized Na-X zeolite is decomposed into molecular grade.
  • the templating agent specifically, the nano-sized Na-X zeolite forms aluminum salt, silica and silicate under the action of strong acid, and in the process of preparing carbon nano particles in the subsequent process, the aluminum salt is in situ under the action of strong alkali
  • the formation of aluminum hydroxide, silica and the subsequently formed aluminum hydroxide used as a template for the preparation of carbon nanoparticles can serve as a template.
  • the content of the phenolic resin in the ethanol solution of the phenolic resin is from 1% to 5% by mass.
  • the concentrated ammonia water is added to mix the concentrated ammonia water with the ethanol, and then added dropwise to the mixed liquid mixture, and stirred at 40 to 60 ° C for 2 to 10 hours until the reaction is completed.
  • the concentrated ammonia water is added, on the one hand, the aluminum ions in the templating agent can be converted into aluminum hydroxide in situ to serve as a template; on the other hand, an excessive amount of strong acid is added in the neutralization step 11) to generate
  • the ammonium salt acts as a template for the molecular level; more importantly, it also promotes the polymerization of the phenolic resin.
  • the carbonization temperature is 800 to 1500 ° C, and the temperature increase rate during the carbonization is 1 to 10 ° C / min; the carbonized phenolic resin to be polymerized is converted into carbon nanoparticles.
  • the pickling in the step 14) is to sequentially wash the primary carbon nanoparticles with hydrochloric acid and hydrofluoric acid, and the aluminum hydroxide used as a template is easily reacted with hydrofluoric acid to easily form fluorine with less solubility.
  • Aluminum is difficult to remove. Therefore, the aluminum hydroxide is removed first, and then the other template is removed with hydrofluoric acid.
  • the templating agent is removed by a strong acid, and during the removal process, a templating agent such as aluminum hydroxide or silicon dioxide is removed, and minute pores are obtained in the carbon nanoparticles in situ; in the removal, the control is used in pickling.
  • the silicon reacts electrochemically, it can effectively prevent the "flying effect" of the intermediate lithium polysulfide; while removing the template agent such as ammonium salt, a large number of molecular-level pores are generated in situ in the carbon nanoparticle, which can be used for loading S4. Sulfur below the molecule, so that the prepared sulfur-carbon composite can be exempted during charge and discharge In addition to some electrochemical intermediate reactions, the cycle performance of the fabricated lithium-sulfur battery is improved.
  • the present invention also relates to a nano-sized Na-X type zeolite and a preparation method thereof, wherein the nano-sized Na-X type zeolite adopts hydrothermal synthesis method, using tetraethyl orthosilicate as a silicon source and sodium metasilicate as an aluminum source. It is prepared by mixing with sodium hydroxide and water according to the formula amount; the specific synthesis process is as follows:
  • the prepared sodium metaaluminate solution is transferred to the reactor, and stirred in an ice water bath for 0.5 to 3 hours, preferably 1 hour; then the ethyl orthosilicate treated with the ice water bath is slowly added dropwise to the partial In a sodium aluminate solution, the mixture is stirred for 5 to 10 hours, preferably for 6 hours, and then reacted at room temperature for 10 to 72 hours, preferably 24 hours; the mixture after completion of the reaction is transferred to a Teflon-lined cup, and the liner is lined.
  • the cup is placed in a stainless steel reaction vessel, and then the reaction vessel is placed in a heating oven at 50-80 ° C for 1 to 5 days; finally, the nano-sized Na-X zeolite formed by crystallization is taken out, centrifuged, and washed to pH ⁇ 10, drying to obtain nano-sized Na-X zeolite.
  • the molar ratio of sodium metaaluminate, ethyl orthosilicate, sodium hydroxide and water in the reaction is 2:(3 ⁇ 5):(7-12):(180-200), preferably the molar ratio is 2NaAlO 2 4Si(OC 2 H 5 ) 4 : 9 NaOH : 190H 2 O; and the nano-sized Na-X type zeolite prepared by the method has a size of 10 to 100 nm, preferably 20 to 50 nm.
  • a sulfur carbon composite the preparation method thereof comprises the following steps:
  • the nano-Na-X zeolite having a size of 40 nm prepared by the above method is dispersed in 20 mL of deionized water, 6 M concentrated hydrochloric acid is added dropwise, and stirred while stirring until a clear and translucent aqueous solution is obtained;
  • the second step is to prepare carbon nano particles: the above aqueous solution is mixed with 70 ml of an ethanol solution containing 3 wt% of phenolic resin at 50 ° C to obtain a mixed solution; 30 mL of concentrated aqueous ammonia is mixed with 100 mL of ethanol, and then the above mixed solution is added, and stirred at 50 ° C. 3h, followed by evaporation and evaporation at 60 ° C, removing the solvent (ethanol and water) to obtain a mixture of carbon nano precursor and templating agent;
  • the mixture of the carbon nano precursor and the templating agent is carbonized at 850 ° C or higher in a protective atmosphere, and then the template is removed by hydrochloric acid and hydrofluoric acid, and the remaining 1 wt% of the templating agent is controlled to obtain carbon nanoparticles;
  • the prepared carbon nanoparticles and the sulfur source are mixed at a mass ratio of 1:1, and the mixture is heated at 155 ° C for more than 10 hours under a protective atmosphere to obtain a sulfur-carbon composite.
  • the lithium-sulfur battery is charged and discharged at a current of 2.6 to 1.7 V 1 C, and the capacity is maintained at 750 mAh g -1 after 100 cycles, as shown in FIG. Shown.
  • a sulfur carbon composite the preparation method thereof comprises the following steps:
  • the second step is to prepare carbon nano particles: the above aqueous solution is mixed with 80 ml of an ethanol solution containing 3 wt% of phenolic resin at 50 ° C to obtain a mixed solution; 30 mL of concentrated aqueous ammonia is mixed with 100 mL of ethanol, and then the above mixed solution is added, and stirred at 50 ° C. 3h, followed by evaporation and evaporation at 60 ° C, removing the solvent (ethanol and water) to obtain a mixture of carbon nano precursor and templating agent;
  • the mixture of the carbon nano precursor and the templating agent is carbonized at 850 ° C or higher in a protective atmosphere, and then the template is removed by hydrochloric acid and hydrofluoric acid, and the remaining 5 wt% of the templating agent is controlled to obtain carbon nanoparticles;
  • the prepared carbon nanoparticles and the sulfur source are mixed at a mass ratio of 1:0.8, and the mixture is heated at 185 ° C for 24 hours under a protective atmosphere to obtain a sulfur-carbon composite.
  • the sulfur-carbon composite prepared in this case was used as an electrode material to prepare a lithium-sulfur battery to be charged and discharged at a current of 2.6 to 1.7 V1 C, and the capacity was maintained at 700 mAh g -1 after 100 cycles.
  • a sulfur carbon composite the preparation method thereof comprises the following steps:
  • the carbon nanoparticle is provided, and the specific preparation method is substantially the same as that in the first embodiment, except that the mass percentage of the template agent in the obtained carbon nanoparticle is 3 wt%; the carbon nanoparticle and the sulfur source are in a mass ratio of 1:1.3.
  • the mixture was heated and heated at 130 ° C for 48 h under a protective atmosphere to obtain a sulfur-carbon composite.
  • the sulfur-carbon composite prepared in this case was used as an electrode material to prepare a lithium-sulfur battery to be charged and discharged at a current of 2.6 to 1.7 V1 C, and the capacity was maintained at 600 mAh g -1 after 100 cycles.
  • a super P-sulfur composite prepared by mixing conventional super P and sulfur with the same ratio of carbon nanomaterials and sulfur in the first embodiment, and then heating at 155 ° C for 24 hours under a protective atmosphere.
  • the super P-sulfur composite is obtained;
  • the super P-sulfur composite is used as an electrode material to prepare a lithium-sulfur battery for charging and discharging at a current of 2.6 to 1.7 V 1 C , and the capacity is reduced to 430 mAh g -1 after 50 cycles;
  • Figure 3 shows.
  • the lithium-sulfur battery containing the sulfur-carbon composite has a capacity of 750 mAh/g after being charged and discharged 100 times in a voltage range of 2.6 V-1.7 V at 1 C, and is super P-sulfur composited under the same conditions.
  • the lithium-sulfur battery as the electrode material has an obvious advantage; thus, it can be seen that the lithium-sulfur battery including the sulfur-carbon composite of the present invention has excellent cycle performance.
  • the sulfur-carbon composite prepared by the above method can be used to prepare an electrode material of a lithium-sulfur battery, and the lithium-sulfur battery has good conductivity; and the electrode material is used for preparing a lithium-sulfur battery, and the preparation thereof is Lithium-sulfur battery, due to the use of the above-mentioned sulfur-carbon composite, on the one hand, the sulfur-carbon composite has good electrical conductivity, and the obtained lithium-sulfur battery has good high-rate performance; on the other hand, the sulfur-carbon composite has More internal pores can effectively inhibit the dissolution of lithium polysulfide, thereby preventing the phenomenon that the active material of the electrode is gradually reduced, and preventing dissolved lithium polysulfide due to the shuttle principle from passing through the separator to the negative lithium sheet of the battery.
  • the phenomenon of negative electrode corrosion and increase of internal resistance of the battery occurs, thereby improving the cycle performance of the battery and reducing the speed of battery capacity decay, that is, the sulfur-carbon composite obtained by the method of the invention has high sulfur utilization rate.
  • the lithium-sulfur battery containing the carbon-sulfur composite has good cycle stability.

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Abstract

提供一种用于锂硫电池的硫碳复合物及其制备方法、以及包含该硫碳复合物的电极材料和锂硫电池。该复合物包括碳纳米颗粒、加载于碳纳米颗粒中的硫和残留于碳纳米颗粒中的二氧化硅模板剂，其中按照质量百分数计，硫含量为40%-70%，二氧化硅模板剂含量为0.3%-3%，残留的二氧化硅模板剂分散于碳纳米颗粒中，以减小碳纳米颗粒的孔径。

Description

硫碳复合物及其制备方法、含有该硫碳复合物的电极材料和锂硫电池 技术领域
本发明涉及锂离子电池技术领域，尤其涉及一种锂硫电池用的硫碳复合物及其制备方法、采用该硫碳复合物制备的电极材料和锂硫电池。
背景技术
锂硫电池是锂电池的一种，其为以金属锂为负极、硫元素为正极的二次电池；锂硫电池放电时，负极反应为锂失去电子变为锂离子，正极反应为硫与锂离子及电子反应生成硫化物，正极和负极反应的电势差即为锂硫电池所提供的放电电压。锂硫电池的比能量理论上可达到2600Wh/kg，远大于现阶段所使用的任何商业化二次电池；除了具有能量密度高的优点，由于其正极材料所采用的单质硫具有对环境友好、且来源丰富和价格低廉等优点，锂硫电池还具有环境污染小、安全性能好和成本低廉等优点；因此，在新能源领域中具有广阔的应用前景：一方面可作为动力电池可广泛地应用于插电式混合动力车、电动汽车、空间飞行器以及水下潜器等；另一方面也可以作为储能电池可应用于通讯基站的备用电源、风能和太阳能储能、远离市电区域的边远地区供电电源等。
但是，目前锂硫电池尚存在一些阻碍其实际应用的问题，具体存在以下问题：1.单质硫的电子导电性和离子导电性差，硫材料在室温下的电导率极低(5.0×10-30S·cm-1)，反应的最终产物Li2S2和Li2S也是电子绝缘体，不利于电池的高倍率性能；2.锂硫电池的中间放电产物锂多硫化物会溶解到有机电解液中，增加电解液的黏度，降低离子导电性；且锂多硫化物能在正负极之间迁移，导致活性物质损失和电能的浪费；而溶解的锂多硫化物会跨越隔膜扩散到负极，与负极反应，破坏负极的固体电解质界面膜(SEI膜)；3.锂硫电池的最终放电产物Li2Sn(n＝1～2)电子绝缘且不溶于有机电解液，将沉积在导电骨架的表面；部分硫 化锂脱离导电骨架，无法通过可逆的充电过程反应变成硫或者是高阶的多硫化物，造成了容量的极大衰减；4.硫和硫化锂的密度分别为2.07g·cm-3和1.66g·cm-3，在充放电过程中有高达79％的体积膨胀/收缩，这种膨胀会导致正极形貌和结构的改变，进而导致硫与导电骨架的脱离，从而造成容量的衰减；而这种体积效应在纽扣电池下不显著，但在大型电池中体积效应会放大，会产生显著的容量衰减，甚至有可能导致电池的损坏，巨大的体积变化会破坏电极结构。
针对以上问题，目前主要的解决方法是从电解液和正极材料两个方面入手来解决；电解液方面，主要是改用醚类电解液来替代现有的电解液，或在现有的电解液中加入一些添加剂，如此可以非常有效的缓解锂多硫化合物的溶解问题；正极材料方面，主要是把硫和碳材料复合，或者把硫和有机物复合，可以解决硫的不导电和体积膨胀问题。然而，现有技术中合成的硫-碳复合物总是无法避免多硫化物溶解进入电解质的问题，导致采用该硫碳复合物制作的锂硫电池循环稳定性不好，不能满足实际的需要。
有鉴于此，有必要提供一种新的硫碳复合物以制备出具有良好的电化学性能的高能量密度的锂硫电池，以解决上述问题。
发明内容
针对上述现有技术的不足，本发明的目的之一在于提供一种用于锂硫电池的硫碳复合物，以解决上述问题；
本发明的目的之二在于提供上述硫碳复合物的制备方法；
本发明的目的之三在于提供锂硫电池的电极材料，其包括上述硫碳复合物；
本发明的目的之四在于提供锂硫电池，其包括上述硫碳复合物。
为了实现上述目的，本发明的技术方案如下：
一种用于锂硫电池的硫碳复合物，包括碳纳米颗粒、分散于所述碳纳米颗粒中的二氧化硅模板剂和加载于所述碳纳米颗粒中的硫；其中所述碳纳米颗粒为多孔结构，所述二氧化硅模板剂分散于所述碳纳米颗粒中，90wt％以上的所述硫填充于所述碳纳米颗粒的孔中，其余分散于所述碳纳米颗粒的表面。
本发明硫碳复合物中二氧化硅模板剂分散于碳纳米颗粒中，以减小碳纳米颗粒的孔径，这样在使用时，具有小孔径的碳纳米颗粒对电化学反应中间产物多硫化锂具有更强的捕获能力，同时二氧化硅模板剂的残留还可以有效阻止多硫化锂的“飞梭效应”。
较佳地，所述硫碳复合物中，按质量百分数计，所述硫含量为所述硫碳复合物的40％～70％，所述二氧化硅模板剂占所述硫碳复合物的0.3％～3％。
具体地，所述碳纳米颗粒的直径为1～20nm，比表面积为20～3000m2/g，平均孔径大小为2～50nm。
所述硫碳复合物的制备方法，包括如下步骤：
1)提供碳纳米颗粒，且所述碳纳米颗粒中分散有二氧化硅模板剂；
2)加载硫至所述酸洗后的碳纳米颗粒，即得所述硫碳复合物；其中，按质量百分数计，所述二氧化硅模板剂占所述硫碳复合物的0.3％～3％。
本发明硫碳复合物采用含有二氧化硅模板剂的碳纳米颗粒来制备，其中二氧化硅模板剂可以减小碳纳米颗粒的孔径，使碳纳米颗粒对电化学中间产物多硫化锂具有更强的捕获能力，且二氧化硅模板剂还可以有效阻止多硫化锂的“飞梭效应”；此外本发明的制备方法简单易行，适宜大规模的生产。
其中，所述碳纳米颗粒的制备方法，包括如下步骤：
11)提供纳米级Na-X沸石的水悬浮液，向其中滴加强酸直至所述水悬浮液变澄清，得水溶液；
12)将所述水溶液与酚醛树脂的乙醇溶液混匀后，再与浓氨水反应，反应完全后蒸干溶剂(主要为水和乙醇)，得到碳纳米前驱体和模板剂的混合物；
13)将所述碳纳米前驱体和模板剂的混合物在保护气氛中碳化，得到初级碳纳米颗粒；
14)对所述初级碳纳米颗粒进行酸洗，至其中残留有占所述模板剂总量1wt％～5wt％的二氧化硅模板剂，即得所述碳纳米颗粒。
在制备碳纳米颗粒中采用纳米级Na-X沸石，主要是因为纳米级Na-X沸石在强酸的作用下，分解产生铝离子、二氧化硅微粒、硅酸盐以及其他离子等； 其中，铝离子在制备碳纳米颗粒的过程中会原位生成氢氧化铝，起到模板作用，随后将氢氧化铝去除，即可在碳纳米颗粒上得到几个纳米孔径的孔；二氧化硅离子为几个分子大小，在此也用作模板剂，此外硅酸盐在后续的碳化过程中也会得到二氧化硅微粒，一样用作模板剂，在去除上述二氧化硅微粒后，将在碳纳米颗粒上形成更小孔径的孔；其他离子在后续过程中也可以用作模板，其在制备碳纳米颗粒的过程中与会原位生成铵盐，起到模板作用，随后将上述铵盐去除，在碳纳米颗粒中原位生成大量分子级的孔，可用于装载S4分子以下的硫，这样使得制成的硫碳复合物在充放电过程中，能免除一些电化学中间反应，提高制作的锂硫电池的循环性能。
其中，所述纳米级Na-X沸石为按摩尔比例(7～12)NaOH∶2NaAlO2∶(3～5)Si(OC2H5)4∶(180～200)H2O将偏铝酸钠溶液、正硅酸乙酯溶液、氢氧化钠和水混合后反应制得；所得纳米级Na-X沸石的尺寸为10～100nm，优选20～50nm。
具体地，所述步骤11)中，所述强酸为盐酸、硫酸或硝酸中的一种，且所述强酸的浓度≥0.06M(具体为mol/L，下同)；在强酸作用下，纳米级Na-X沸石被分解成为分子级的模板剂，具体为，纳米级Na-X沸石在强酸作用下，生成铝盐、二氧化硅和硅酸盐等，在后续制备碳纳米颗粒的过程中，在强碱作用下铝盐原位生成氢氧化铝，二氧化硅和后续生成的氢氧化铝用作制备碳纳米颗粒的模板剂，均能起到模板作用。
较佳地，所述步骤12)中，所述酚醛树脂的乙醇溶液中酚醛树脂的含量，按质量百分数计为1％～5％。
具体地，所述步骤12)中，所述添加浓氨水反应为将浓氨水与乙醇混合后，滴加到前述混匀后的混合液中，在40～60℃下搅拌2～10h至反应完成；其中，添加浓氨水，一方面可以使模板剂中的铝离子原位转化为氢氧化铝，起到模板作用；另一方面，用于中和步骤11)中添加过量的强酸，使之生成铵盐，起到分子级的模板作用；此外，最重要的是其还可以促进酚醛树脂的聚合。
具体地，所述步骤13)中，所述碳化温度为800-1500℃，所述碳化时的升温速率为1～10℃/min；碳化即将聚合的酚醛树脂转化为碳纳米颗粒。
具体地，所述步骤14)中所述酸洗是依次用盐酸和氢氟酸清洗所述初级碳纳米颗粒，由于用作模板的氢氧化铝与氢氟酸反应后容易生成溶解度较小的氟化铝，较难去除，因此，选用盐酸先将氢氧化铝去除，后再用氢氟酸去除其他模板剂，在清洗时，其使用顺序不能颠倒。
此外，用强酸去除模板剂的过程中，将氢氧化铝、二氧化硅等模板剂去除的同时，原位在碳纳米颗粒中得到微小的孔隙；在去除时，控制酸洗中使用的氢氟酸的量，用以控制二氧化硅模板剂的残留量，以减小碳纳米颗粒中的孔径，增强碳纳米颗粒材料对多硫化锂的捕获能力，同时碳纳米颗粒中的二氧化硅在电化学反应时，可有效阻止中间产物多硫化锂的“飞梭效应”；而在去除铵盐等模板剂的同时，同样在碳纳米颗粒中原位生成大量分子级的孔，可用于装载S4分子以下的硫，这样使得制成的硫碳复合物在充放电过程中，能免除一些电化学中间反应，提高制作的锂硫电池的循环性能。
具体地，所述步骤2)中，所述加载硫至所述碳纳米颗粒具体为将硫源与所述碳纳米颗粒混合后，在保护气氛下于120～190℃共热10～30h，即得所述硫碳复合物。其中，所述硫源在加热时熔化，其具体形式不定，可选用块状硫也可选用粉末状硫，优选粉末状硫。
一种锂硫电池的电极材料，其包括如上所述的硫碳复合物，其具有良好的导电性。
一种锂硫电池，其包括如上所述的硫碳复合物。
本发明锂硫电池，由于采用了上述硫碳复合物，一方面，硫碳复合物具有良好的导电性，制得的锂硫电池具有较好的高倍率性能；另一方面，硫碳复合物中具有较多的内孔，能够有效地抑制多硫化锂的溶解，从而防止电极的活性物质逐渐减少的现象的发生，并防止由于穿梭原理导致的溶解的多硫化锂穿过隔膜到达电池的负极锂片上引起的负极腐蚀和电池内阻的增加的现象发生，进而提高电池的循环性能，降低电池容量衰减的速度，也就是说，采用本发明的方法获得的硫碳复合物具有较高的硫利用率，包含该碳-硫复合物的锂硫电池具有良好的循环稳定性。
附图说明
图1、本发明硫碳复合物的扫描电镜图片；
图2、本发明硫碳复合物中硫的元素分布图；
图3、本发明中制备的硫碳复合物和super P制备的硫碳复合物的循环寿命示意图。
具体实施方式
下面将结合附图和上述发明内容对本发明的具体实施方式作进一步的详细说明。
本发明用于锂硫电池的硫碳复合物，包括碳纳米颗粒、加载于所述碳纳米颗粒中的硫和分散于所述碳纳米颗粒中的二氧化硅模板剂；其中所述碳纳米颗粒为多孔结构，所述二氧化硅模板剂分散于所述碳纳米颗粒的孔中，所述硫大部分填充于所述碳纳米颗粒的孔中，其余分散于所述碳纳米颗粒的表面；如图1和2所示，其中所述硫碳复合物中，按质量百分数计，所述硫含量为所述硫碳复合物的40％～70％，所述二氧化硅模板剂占所述硫碳复合物的0.3％～3％；所述碳纳米颗粒的直径为1～20nm，比表面积为20～3000m2/g，平均孔径大小为2～50nm。
本发明硫碳复合物中二氧化硅模板剂分散于碳纳米颗粒的内孔中，以减小碳纳米颗粒的孔径，这样在使用时，碳纳米颗粒对电化学反应中间产物多硫化锂具有更强的捕获能力，同时二氧化硅模板剂还可以有效阻止多硫化锂的“飞梭效应”。
本发明在制备硫碳复合物时，采用如下步骤：
1)提供碳纳米颗粒，且所述碳纳米颗粒中分散有二氧化硅模板剂；
2)加载硫至所述酸洗后的碳纳米颗粒，即得所述硫碳复合物。
其中，所述步骤2)的具体工艺为，将硫源与所述碳纳米颗粒按质量比(0.8-1.5)∶1混合后，在保护气氛下于120～190℃共热10～30h，即得所述硫 碳复合物；其中，按质量百分数计，所述二氧化硅模板剂占所述硫碳复合物的0.3％～3％。
本发明硫碳复合物采用含有二氧化硅模板剂的碳纳米颗粒来制备，其中二氧化硅模板剂可以减小碳纳米颗粒的孔径，使碳纳米颗粒对电化学中间产物多硫化锂具有更强的捕获能力，且二氧化硅模板剂的残留还可以有效阻止多硫化锂的“飞梭效应”；此外本发明的制备方法简单易行，适宜大规模的生产。
而上述硫碳复合物在制备时，其关键在于其中碳纳米颗粒，其制备方法包括如下步骤：
11)提供纳米级Na-X沸石的水悬浮液，向其中滴加强酸直至所述水悬浮液变澄清，得水溶液；
12)将所述水溶液与酚醛树脂的乙醇溶液混匀后，再与浓氨水反应，反应完全后蒸干溶剂(水和乙醇)，得到碳纳米前驱体和模板剂的混合物；
13)将所述碳纳米前驱体和模板剂的混合物在保护气氛中碳化，得到初级碳纳米颗粒，
14)对所述初级碳纳米颗粒进行酸洗，至其中二氧化硅模板剂含量为1wt％～5wt％，即得所述碳纳米颗粒。
在制备碳纳米颗粒中采用纳米级Na-X沸石，用作模板剂的来源，以使制备的碳纳米颗粒形成多孔结构，以增大碳材料的比表面积，使电解液与活性物质充分接触，提高电池性能；具体地，纳米级Na-X沸石在强酸的作用下，分解产生铝离子、二氧化硅微粒、硅酸盐以及其他离子等；其中，铝离子在制备碳纳米颗粒的过程中会原位生成氢氧化铝，起到模板作用，随后将氢氧化铝去除，即可在碳纳米颗粒上得到几个纳米孔径的孔；二氧化硅离子为几个分子大小，在此也用作模板剂，此外硅酸盐在后续的碳化过程中也会得到二氧化硅微粒，一样用作模板剂，在去除上述二氧化硅微粒后，将在碳纳米颗粒上形成更小孔径的孔；其他离子在后续过程中也可以用作模板，其在制备碳纳米颗粒的过程中与会原位生成铵盐，起到模板作用，随后将上述铵盐去除，在碳纳米颗粒中原位生成大量分子级的孔，可用于装载S4分子以下的硫，这样使得制成的硫碳 复合物在充放电过程中，能免除一些电化学中间反应，提高制作的锂硫电池的循环性能。
具体地，所述步骤11)中，所述强酸为盐酸、硫酸或硝酸中的一种，且所述强酸的浓度≥0.06M；在强酸作用下，纳米级Na-X沸石被分解成为分子级的模板剂，具体为，纳米级Na-X沸石在强酸作用下，生成铝盐、二氧化硅和硅酸盐等，在后续制备碳纳米颗粒的过程中，在强碱作用下铝盐原位生成氢氧化铝，二氧化硅和后续生成的氢氧化铝用作制备碳纳米颗粒的模板剂，均能起到模板作用。
优选地，所述步骤12)中，所述酚醛树脂的乙醇溶液中酚醛树脂的含量，按质量百分数计为1％～5％。
具体地，所述步骤12)中，所述添加浓氨水反应为将浓氨水与乙醇混合后，滴加到前述混匀后的混合液中，在40～60℃下搅拌2～10h至反应完成；其中，添加浓氨水，一方面可以使模板剂中的铝离子原位转化为氢氧化铝，起到模板作用；另一方面，用于中和步骤11)中添加过量的强酸，使之生成铵盐，起到分子级的模板作用；此外，最重要的是其还可以促进酚醛树脂的聚合。
具体地，所述步骤13)中，所述碳化温度为800～1500℃，所述碳化时的升温速率为1～10℃/min；碳化即将聚合的酚醛树脂转化为碳纳米颗粒。
具体地，所述步骤14)中所述酸洗是依次用盐酸和氢氟酸清洗所述初级碳纳米颗粒，由于用作模板的氢氧化铝与氢氟酸反应后容易生成溶解度较小的氟化铝，较难去除，因此，选用盐酸先将氢氧化铝去除，后再用氢氟酸去除其他模板剂。此外，用强酸去除模板剂，其在去除过程中，将氢氧化铝、二氧化硅等模板剂去除的同时，原位在碳纳米颗粒中得到微小的孔隙；在去除时，控制酸洗中使用的氢氟酸的量，用以控制二氧化硅模板剂的残留量，以减小碳纳米颗粒中的孔径，增强碳纳米颗粒材料对多硫化锂的捕获能力，同时碳纳米颗粒中的二氧化硅在电化学反应时，可有效阻止中间产物多硫化锂的“飞梭效应”；而在去除铵盐等模板剂的同时，在碳纳米颗粒中原位生成大量分子级的孔，可用于装载S4分子以下的硫，这样使得制成的硫碳复合物在充放电过程中，能免 除一些电化学中间反应，提高制作的锂硫电池的循环性能。
此外本发明还涉及纳米级Na-X型沸石及其制备方法，该纳米级Na-X型沸石采用水热合成法，以正硅酸乙酯作为硅源，以偏铝酸钠作为铝源，与氢氧化钠和水按配方量混合后反应制得；其具体合成工艺如下：
首先将刚制备好的偏铝酸钠溶液转移到反应器中，并在冰水浴中搅拌0.5～3小时，优选1小时；接着将用冰水浴处理后的正硅酸乙酯缓慢滴加到偏铝酸钠溶液中，混合搅拌5～10小时，优选6小时，随后在室温下反应10～72小时，优选24小时；将反应完成后的混合物转入特氟龙内衬杯中，将内衬杯放入不锈钢反应釜中，接着把反应釜放入50～80℃的加热箱中结晶1～5天；最后将结晶生成的纳米级Na-X型沸石取出，离心沉淀，洗涤至pH值≤10，干燥即得纳米级Na-X型沸石。
其中，反应中偏铝酸钠、正硅酸乙酯、氢氧化钠和水的摩尔比为2∶(3～5)∶(7～12)∶(180～200)，优选摩尔比为2NaAlO2∶4Si(OC2H5)4∶9NaOH∶190H2O；且采用该方法制备的纳米级Na-X型沸石的尺寸为10～100nm，优选20～50nm。
下面将列出本发明的优选实施例，以更详细地说明本发明。
实施例1
一种硫碳复合物，其制备方法包括如下步骤：
第一步，取4g的上述方法制备的尺寸为40nm的纳米Na-X沸石分散于20mL去离子水中，滴加6M的浓盐酸，边加边搅拌，直至得到澄清半透明的水溶液；
第二步，制备碳纳米颗粒：将上述水溶液与70ml含有3wt％酚醛树脂的乙醇溶液中，在50℃搅拌均匀得到混合溶液；将30mL浓氨水与100mL乙醇混合后加入上述混合溶液，50℃搅拌3h，接着在60℃搅拌蒸干，除去溶剂(乙醇和水)，得到碳纳米前驱体和模板剂的混合物；
第三步，将碳纳米前驱体和模板剂的混合物在保护气氛下850℃以上碳化，后依次用盐酸和氢氟酸去除模板剂，控制剩余1wt％的模板剂，即可得到碳纳米颗粒；
第四步，将制备好的碳纳米颗粒与硫源按质量比1∶1混合，在保护气氛下155℃共热10h以上，即可得到硫碳复合物。
采用该方法制备的硫碳复合物用作电极材料制作出锂硫电池后，该锂硫电池在2.6～1.7V 1C电流下进行充放电，循环100次后容量保持750mAh g-1，如图3所示。
实施例2
一种硫碳复合物，其制备方法包括如下步骤：
第一步，取4g的上述方法制备的尺寸为20nm的纳米Na-X沸石分散于20mL去离子水中，滴加8M的浓盐酸，边加边搅拌，直至得到澄清半透明的水溶液；
第二步，制备碳纳米颗粒：将上述水溶液与80ml含有3wt％酚醛树脂的乙醇溶液中，在50℃搅拌均匀得到混合溶液；将30mL浓氨水与100mL乙醇混合后加入上述混合溶液，50℃搅拌3h，接着在60℃搅拌蒸干，除去溶剂(乙醇和水)，得到碳纳米前驱体和模板剂的混合物；
第三步，将碳纳米前驱体和模板剂的混合物在保护气氛下850℃以上碳化，后依次用盐酸和氢氟酸去除模板剂，控制剩余5wt％的模板剂，即可得到碳纳米颗粒；
第四步，将制备好的碳纳米颗粒与硫源按质量比1∶0.8混合，在保护气氛下185℃共热24h，即可得到硫碳复合物。
此种情况下制备的硫碳复合物用作电极材料制作出锂硫电池在2.6～1.7V1C电流下进行充放电，循环100次后容量保持700mAh g-1。
实施例3
一种硫碳复合物，其制备方法包括如下步骤：
提供碳纳米颗粒，其具体制备方法与实施例1大致相同，区别在于其得到的碳纳米颗粒中模板剂的质量百分含量为3wt％；将该碳纳米颗粒与硫源按质量比1∶1.3混合，在保护气氛下130℃共热48h，即可得到硫碳复合物。
此种情况下制备的硫碳复合物用作电极材料制作出锂硫电池在2.6～1.7V1C电流下进行充放电，循环100次后容量保持600mAh g-1。
对比例1
一种super P-硫复合物，采用如下方法制备：将常规的super P与硫按与实施例1中碳纳米材料与硫的相同比例混合后，在保护气氛下155℃共热24h，即可得到super P-硫复合物；将该super P-硫复合物用作电极材料制作出锂硫电池在2.6～1.7V 1C电流下进行充放电，循环50次后容量降至430mAh g-1，如图3所示。
如图3所示，包含硫碳复合物的锂硫电池在1C下在2.6V-1.7V的电压范围内充放电100次后容量稳定在750mAh/g，比相同条件下采用super P-硫复合物作为电极材料的锂硫电池优势明显；由此可见，包含本发明的硫碳复合物的锂硫电池具有优异的循环性能。
综上所述，采用上述方法制备出来的硫碳复合物可用来制备锂硫电池的电极材料，该锂硫电池具有良好的导电性；再将该电极材料用于制备锂硫电池，其制备的锂硫电池，由于采用了上述硫碳复合物，一方面，硫碳复合物具有良好的导电性，制得的锂硫电池具有较好的高倍率性能；另一方面，硫碳复合物中具有较多的内孔，能够有效地抑制多硫化锂的溶解，从而防止电极的活性物质逐渐减少的现象的发生，并防止由于穿梭原理导致的溶解的多硫化锂穿过隔膜到达电池的负极锂片上引起的负极腐蚀和电池内阻的增加的现象发生，进而提高电池的循环性能，降低电池容量衰减的速度，也就是说，采用本发明的方法获得的硫碳复合物具有较高的硫利用率，包含该碳-硫复合物的锂硫电池具有良好的循环稳定性。
上述实施例，只是本发明的较佳实施例，并非用来限制本发明实施范围，故凡以本发明权利要求所述的构造、特征及原理所做的等效变化或修饰，均应包括在本发明权利要求范围之内。

Claims (14)

  1. 一种用于锂硫电池的硫碳复合物，其特征在于：包括碳纳米颗粒、加载于所述碳纳米颗粒中的硫和分散于所述碳纳米颗粒中的二氧化硅模板剂，其中所述碳纳米颗粒为多孔结构，所述二氧化硅模板剂分散于所述碳纳米颗粒中，所述硫部分填充于所述碳纳米颗粒的孔中，其余分散于所述碳纳米颗粒的表面。
  2. 根据权利要求1所述的硫碳复合物，其特征在于：按质量百分数计，所述硫含量为所述硫碳复合物的40％～70％，所述二氧化硅模板剂占所述硫碳复合物的0.3％～3％。
  3. 根据权利要求1所述的硫碳复合物，其特征在于：所述碳纳米颗粒的直径为1～20nm，比表面积为20～3000m2/g，平均孔径大小为2～50nm。
  4. 一种用于锂硫电池的硫碳复合物的制备方法，其特征在于，包括如下步骤：
    1)提供碳纳米颗粒，且所述碳纳米颗粒中分散有二氧化硅模板剂；
    2)加载硫至所述碳纳米颗粒，即得所述硫碳复合物，其中，按质量百分数计，所述二氧化硅模板剂占所述硫碳复合物的0.3％～3％。
  5. 根据权利要求4所述的制备方法，其特征在于，所述碳纳米颗粒的制备方法如下：11)提供纳米Na-X沸石的水悬浮液，向其中滴加强酸直至所述水悬浮液变澄清，得水溶液；
    12)将所述水溶液与酚醛树脂的乙醇溶液混合后，再与浓氨水反应，反应完成后蒸干溶剂，得到碳纳米前驱体和模板剂的混合物；
    13)将所述碳纳米前驱体和模板剂的混合物在保护气氛中碳化，得到初级碳纳米颗粒；
    14)对所述初级碳纳米颗粒进行酸洗，至其中残留有占所述模板剂总量 1wt％～5wt％的所述二氧化硅模板剂，即得所述碳纳米颗粒。
  6. 根据权利要求4或5所述的制备方法，其特征在于：所述步骤2)中，所述加载硫至所述碳纳米颗粒具体为将硫源与所述碳纳米颗粒混合后，在保护气氛下于120～190℃共热10～30h，即得所述硫碳复合物。
  7. 根据权利要求5所述的制备方法，其特征在于：所述步骤13)中，所述碳化温度为800～1500℃，所述碳化时的升温速率为1～10℃/min。
  8. 根据权利要求5所述的制备方法，其特征在于：所述步骤14)中，所述酸洗为依次用盐酸和氢氟酸清洗所述碳纳米颗粒，以除去碳纳米颗粒中的模板剂。
  9. 根据权利要求5所述的制备方法，其特征在于：所述步骤12)中，所述酚醛树脂的乙醇溶液中酚醛树脂的含量，按质量百分数计为1％～5％。
  10. 根据权利要求5所述的制备方法，其特征在于：所述步骤11)中，所述强酸为盐酸、硫酸或硝酸中的一种，且所述强酸的浓度≥0.06M。
  11. 根据权利要求5所述的制备方法，其特征在于：所述纳米级Na-X沸石的尺寸为10～100nm。
  12. 根据权利要求5所述的制备方法，其特征在于：所述纳米级Na-X沸石为按摩尔比例(7～12)NaOH∶2NaAlO2∶(3～5)Si(OC2H5)4∶(180～200)H2O将偏铝酸钠溶液、正硅酸乙酯溶液、氢氧化钠和水混合后反应制得。
  13. 一种锂硫电池的电极材料，其包括如权利要求1～3任一项所述的硫碳复 合物或权利要求4～12任一项所述制备方法制备的硫碳复合物。
  14. 一种锂硫电池，其包括如权利要求1～3任一项所述的硫碳复合物或权利要求4～12任一项所述制备方法制备的硫碳复合物。
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