WO2013010346A1 - 锂离子电池负极用硅碳复合材料及其制备方法 - Google Patents

锂离子电池负极用硅碳复合材料及其制备方法 Download PDF

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WO2013010346A1
WO2013010346A1 PCT/CN2011/079008 CN2011079008W WO2013010346A1 WO 2013010346 A1 WO2013010346 A1 WO 2013010346A1 CN 2011079008 W CN2011079008 W CN 2011079008W WO 2013010346 A1 WO2013010346 A1 WO 2013010346A1
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composite material
pedot
pss
ion battery
negative electrode
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PCT/CN2011/079008
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English (en)
French (fr)
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张灵志
岳鹿
王素清
赵欣悦
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中国科学院广州能源研究所
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Priority to US14/131,385 priority Critical patent/US9437870B2/en
Publication of WO2013010346A1 publication Critical patent/WO2013010346A1/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
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B33/00—Silicon; Compounds thereof
    • C01B33/113—Silicon oxides; Hydrates thereof
    • C01B33/12—Silica; Hydrates thereof, e.g. lepidoic silicic acid
    • C01B33/18—Preparation of finely divided silica neither in sol nor in gel form; After-treatment thereof
    • 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
    • H01M4/1395—Processes of manufacture of electrodes based on metals, Si or alloys
    • 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
    • H01M4/386—Silicon or alloys based on silicon
    • 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
    • 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
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/60—Other road transportation technologies with climate change mitigation effect
    • Y02T10/70—Energy storage systems for electromobility, e.g. batteries

Definitions

  • the invention relates to the technical field of lithium ion battery anode materials, in particular to a novel silicon composite material used as a negative electrode of a lithium ion battery and a preparation method thereof.
  • Lithium-ion batteries have the advantages of high open circuit voltage, high energy density, long service life, no memory effect, less pollution, and low self-discharge rate. They are superior to other traditional secondary batteries in overall performance, and are consistently considered as various portable devices.
  • the cathode material of the conventional lithium ion battery anode material has good cycle stability and high cost performance, it has no advantage in volumetric specific capacity due to its low charge-discharge specific capacity, and it is difficult to meet the high power of the power system, especially the electric vehicle and the hybrid electric vehicle. Capacity requirements. Therefore, it is extremely urgent to develop a new lithium ion battery anode material having high specific capacity, high charge and discharge efficiency, and long cycle life.
  • Si-based materials have attracted more and more attention due to their highest theoretical lithium-insertion capacity (4200 mAh/g, which is much higher than all other anode materials currently available). If the Si-based anode can be put into practical use, the application range of the lithium-ion battery will be greatly expanded. However, the Si-based material has a severe volume effect under a high degree of deintercalation of lithium, resulting in a significant decrease in the cycle stability of the electrode. For the volumetric efficiency of silicon, the combination of silicon and a carrier with elasticity and stability, the volume change of buffered silicon will be an effective way to maintain high capacity of silicon while improving its cycle stability.
  • Carbon is widely used in Si composite materials due to its light weight, good electrical conductivity, low lithium insertion potential, small volume change during deintercalation, and low cost.
  • conductive polymers such as polyaniline, polypyrrole, etc.
  • As an organic polymer material a conductive polymer can also be used as a carbon source to prepare a carbon material. Wang et al. prepared carbon spheres with a diameter of less than 100 nm doped with N atoms by carbonized polypyrrole nanospheres, and applied them to the negative electrode of lithium ion batteries.
  • the battery can maintain a reversible capacity of 400 mAlrg- 1 for 60 cycles.
  • Conductive polymer polydioxyethylthiophene due to its wide application prospects, has caused People are highly concerned. Among them, the doped state has excellent electrical conductivity, high stability in air structure and electrical conductivity, and thus becomes a new research hotspot of conductive polymers.
  • the eigenstate PEDOT has poor conductivity and is insoluble and insoluble.
  • the poly(p-styrenesulfonic acid (PSS) anion doping can be dispersed and dissolved in an aqueous solution, and it is very stable in air and high in coating. The electrical conductivity, and its aqueous solution can be further processed, thus greatly promoting the application of PEDOT.
  • PEDOT or PEDOT:PSS has been mainly used as a positive electrode material for lithium ion batteries (Electrochim. Acta, 53 (2008): 8319-8323), or as a composite material for positive electrodes for related research (Electrochem. Commun) ., 4 (2002): 545-549).
  • Both the PEDOT and PSS structural units contain an S atom, and the carbonized material may have a small amount of doping of the hetero atom S. Yu et al. believe that the formation of -CSC-bonds in carbon materials will be more conducive to the insertion of lithium ions (J. Power Sources, 108 (2002): 245-249). Therefore, a Si/PEDOT composite material containing a small amount of S atoms can be prepared by preparing a Si/PEDOT:PSS composite material and then carbonizing it. Summary of the invention
  • the object of the present invention is to provide a lithium ion battery negative electrode new silicon composite material with excellent performance by using conductive polymer PEDOT and its aqueous solution dispersant PSS as a coating layer and carbon source of nano Si powder.
  • Another object of the present invention is to provide a method for producing the above silicon carbon composite material.
  • the active material in the silicon carbon composite material is nano silicon powder
  • the dispersion medium is carbon of high temperature cracking of conductive polymer poly 3,4-ethylenedioxythiophene (PEDOT), by adjusting EDOT monomer (3,4- The ratio of ethylene dioxythiophene to nano silicon powder can be controlled to be 60 to 90% by weight.
  • the precursor of the dispersion medium is a conductive polymer poly 3,4-ethylenedioxythiophene (PEDOT).
  • PEDOT conductive polymer poly 3,4-ethylenedioxythiophene
  • PSS polystyrene sulfonic acid
  • the carbon coated by the Si/PEDOT:PSS composite of the present invention is a small amount of S-doped carbon.
  • the silicon-carbon composite material is composed of a nano-Si-containing lithium-containing material as a main active material, and the PEDOT:PSS is first polymerized on the surface of the nano-Si particles by in-situ polymerization, and then the prepared Si/PEDOT:PSS composite is in an inert atmosphere.
  • the Si/C composite material is obtained by high temperature carbonization. Since the preparation is first subjected to a chemical process, the Si and carbon in the subsequently prepared composite material are in better contact, and the electrochemical properties of the composite material are greatly improved due to the doping of the S element (the S source is contained in the carbon source).
  • the Si/C composite material of the invention is prepared by using water as a dispersion medium and using Fe 2 (S0 4 ) 3 /(NH 4 )S 2 0 8 as a catalyst to prepare Si/PEDOT by in-situ polymerization under magnetic stirring:
  • the PSS composite is then carbonized by high temperature. The specific steps are:
  • step (4) The mixed solution of step (4) is firstly dried in an ice bath for 6 h, then filtered at room temperature for 18 h to obtain a Si/PEDOT:PSS complex, and the mixture is heated to 800-1000 ° C under a protective gas. , thermal insulation carbonization
  • the preparation of the raw material of the invention is cheap, and the coating of the nano Si in the conductive polymer is carried out in an aqueous solution, and the process is simple and environmentally friendly, and the yield is high.
  • the Si/C composite prepared by the invention has extremely low initial irreversible capacity loss (2.8%), and has excellent charge and discharge performance, is convenient for industrial production, and has potential application prospects in power sources such as electric vehicles.
  • Figure 1 is an infrared spectrum of Si/C, Si/PEDOT:PSS, EDOT, PSS and Si according to an embodiment of the present invention.
  • 2 is a SEM and TEM photograph of a sample prepared and an associated sample according to an embodiment of the present invention.
  • (a) and (b) are SEM and TEM images of Si
  • (c) and (d) are SEM and TEM images of Si/PEDOT:PSS
  • (e) and (f) are SEM images of Si/C.
  • Fig. 3 is an X-ray energy dispersive spectrum (EDS) of a Si/C composite material according to an embodiment of the present invention.
  • FIG. 4 is an XRD pattern of a sample and related samples prepared in accordance with an embodiment of the present invention.
  • (a) is Si
  • (b) is Si/PEDOT:PSS
  • (c) is Si/C.
  • Si/PEDOT: PSS Si/C in an air atmosphere (10 ° C / min) and Si / PEDOT: PSS in an Ar atmosphere according to an embodiment of the present invention (the temperature rise setting is the same as the experimental process, and 800 ° C Thermogravimetric plot of constant temperature 3 h).
  • (a) is Si in an air atmosphere
  • (b) Si/PEDOT: PSS is in an Ar atmosphere
  • (c) is Si/PEDOT: PSS in an air atmosphere
  • PEDOT: PSS in an air atmosphere is PEDOT: PSS in an air atmosphere.
  • 6 is a cycle performance test curve of an electrode prepared from Si, Si/PEDOT: PSS, and Si/C materials at a charge and discharge current density of 100 mA-g 1 according to an embodiment of the present invention.
  • Figure 7 is a Nyquist diagram of an AC impedance test of electrodes prepared from Si, Si/PEDOT:PSS and Si/C materials in accordance with an embodiment of the present invention. detailed description
  • the Si is added in an amount of 1 to 2 times the mass of the EDOT monomer.
  • the amount of (NH 4 )S 2 0 8 added is 1.5 to 3 times the mass of the EDOT monomer.
  • the amount of FeCl 3 added is 0.01 to 0.05 times the mass of the EDOT monomer.
  • the amount of PSS added is 1.5 to 4 times the mass of the EDOT monomer.
  • the shielding gas is a mixture of Ar, N 2 or Ar/H 2 .
  • the rate of temperature rise of the reaction is 1 to 5 ° C / min.
  • EDOT monomer 0.28 g was slowly added to an aqueous solution (90 mL) containing 0.82 g of PSS, and ultrasonically dispersed.
  • the structure and morphology of the Si/C composite and the precursor Si/PEDOT:PSS composite prepared by the present invention were tested and characterized by infrared spectrum, SEM and TEM photographs, XRD patterns and TG spectra.
  • Figure 2 is a SEM or TEM photograph of a sample prepared according to the present invention and related samples.
  • Figures 2(a) and (b) show SEM and TEM images of nano-silicon particles. It can be seen that Si has a particle size ranging from 30 to 50 nm and exhibits a spherical shape.
  • Fig. 2 (c) and (d) are SEM and TEM photographs of Si/PEDOT:PSS. It can be seen that Si/PEDOT:PSS forms a large agglomerate, and the nano Si particles are uniformly dispersed in the crystal of PEDOT:PSS. In the grid.
  • FIGS. 2 (e) and (f) are SEM photographs of the Si/C composite, and it can be seen that the Si particles are completely coated in the crystal lattice of C.
  • Figure 3 is an EDS analysis chart of the SEM, which shows that there is a little S doping in the Si/C composite, and the content is about U wt%.
  • Figure 4 is an XRD pattern of Si, Si/PEDOT: PSS and Si/C.
  • Figure 4 (a) is an XRD pattern of Si at 28.4°, 47.4°, 56.2.
  • the diffraction peaks at 69.2° and 76.5° represent the (111), (220), (311), (400) and (331) crystal faces of Si, respectively.
  • These diffraction peaks all appear in the diffraction spectrum of Si/PEDOT in Fig. 3 (b) and the diffraction spectrum of Si/C in Fig. 4 (c).
  • Si/PEDOT On the diffraction spectrum of Si/PEDOT, it was found that a diffraction peak appeared near 26.0°, which is a characteristic diffraction peak of the polymer PEDOT (020) crystal plane.
  • Fig. 5 is a thermogravimetric graph of Si, Si/PEDOT: PSS and Si/C in an air atmosphere and Si/PEDOT:PSS in an Ar atmosphere. Based on the weight loss of different samples under air or inert atmosphere at 800 ° C, it can be inferred that Si is about 51.6% in Si/PEDOT:PSS composite, and Si is about 85.7wt in Si/C composite. %.
  • the electrochemical properties of the Si/C composite prepared by the present invention were tested and characterized by cycle performance testing and AC impedance spectroscopy.
  • Fig. 6 is a cycle performance test curve of an electrode prepared by Si/C and Si and Si/PEDOT:PSS materials at a charge and discharge current density of 100 mA_g- 1 . It can be seen that the capacity decay rate of Si is the largest, which is rapidly attenuated from the initial 2710 mAlrg- 1 after 80 cycles to 128 mAlrg-Si/PEDOT: PSS composite electrode. The attenuation rate of the Si electrode is slower than that of the Si electrode, but the irreversible capacity The losses are still large. The cycle performance of the Si/C composite electrode was significantly improved. The first irreversible capacity loss was only 2.8%, and the capacity of 768 mAlrg- 1 was maintained after 80 cycles.
  • Figure 7 shows the AC impedance test of electrodes prepared from Si/C and Si and Si/PEDOT:PSS materials. After fitting, it was found that the charge transfer resistance of the Si/C electrode was reduced by 5 times compared with the Si electrode, and the electric double layer capacitance was increased by 4 times, which enabled the Si/C electrode to operate at a lower polarization. Therefore, the performance has been greatly improved.
  • the nano Si is successfully coated in the carbon matrix carbonized by the conductive polymer PEDOT:PSS, so that the Si particles have a great volume during charging and discharging.
  • the expansion is effectively suppressed, thereby greatly improving the cycle performance of the material.

Abstract

提供一种锂离子电池负极用硅碳复合材料及其制备方法。该锂离子电池负极用硅碳复合材料是以纳米硅粉为活性物质，纳米硅外包覆由导电聚合物聚（3，4-乙撑二氧噻吩）高温热解后的碳。该制备方法包括如下歩骤：（1）将单体3，4-乙撑二氧噻吩缓慢加入到聚苯乙烯磺酸的水溶液中，均匀分散；（2）将纳米硅粉加入到歩骤（1）中，超声分散，搅拌均匀；（3）用稀盐酸调节歩骤（2）溶液的pH值；（4）在冰浴下，向歩骤（3）的溶液中滴加（NKH4）S2O8/FeCl3的水溶液作为催化剂；（5）将歩骤（4）的混合溶液先在冰浴下6小时，然后在室温下反应18小时，过滤，得到Si/PEDOT：PSS复合物；（6）将歩骤（5）的Si/PEDOT：PSS复合物在保护气下升温至800〜1000°C，保温碳化3小时，反应结束后，降温。

Description

锂离子电池负极用硅碳复合材料及其制备方法 技术领域
本发明涉及锂离子电池负极材料技术领域，具体涉及一种用作锂离子电池负 极的新型硅复合材料及其制备方法。 技术背景
锂离子电池具有开路电压高、 能量密度大、 使用寿命长、 无记忆效果、 少污 染以及自放电率小等优点， 它在总体性能上优于其它传统二次电池， 一致被认为 是各种便携式电子设备及电动汽车用最为理想的电源。传统锂离子电池负极材料 石墨虽然循环稳定性好以及性价比较高，但是由于其充放电比容量较低， 体积比 容量更是没有优势，难以满足动力***特别是电动车及混合电动车对电池高容量 化的要求。 因此开发具有高比容量、 高充放电效率、 长循环寿命的新型锂离子电 池负极材料极具迫切性。
在新型非碳负极材料的研究中， Si基材料因具有最高的理论嵌锂容量（4200 mAh/g, 远高于目前其它所有的负极材料） 而越来越受瞩目。 Si基负极若能达到 实用化程度， 必将使锂离子电池的应用范围大大拓宽。 但是， Si基材料在高程度 脱嵌锂条件下， 存在严重的体积效应， 造成电极的循环稳定性大幅度下降。针对 硅的体积效率， 将硅与具有弹性且性能稳定的载体复合， 缓冲硅的体积变化， 将 是保持硅高容量的同时提高其循环稳定性的有效途径。 碳由于拥有较轻的质量， 较好的导电性，较低的嵌锂电位， 脱嵌过程中体积变化小及价格低廉等诸多优点 等被广泛运用在 Si的复合材料中。 近些年导电聚合物如聚苯胺、 聚吡咯等， 由于 其自身电导率高、 晶格弹性好等， 也被尝试作为 Si的复合材料对象。 导电聚合物 作为一种有机高分子材料， 本身也可用作为碳源用以制备碳材料。 Wang等人通 过碳化聚吡咯纳米球制备出含 N原子掺杂的直径小于 100 nm的碳球， 把其运用于 锂离子电池负极， 电池运行 60个循环还能保持 400 mAlrg—1的可逆容量 （Ind. Eng. Chem. Res., 47(2008): 2294-2300) o 但是直到目前为止， 只有 Zhang等人把导电聚 合物中的聚对苯 (Polyparaphenylene)作为制备 Si/C 复合材料的碳源用于锂离子 电池的负极研究 （J. Power Sources, 125(2004): 206-213.)°
导电聚合物聚二氧乙基噻吩 （PEDOT) ， 由于其广泛的应用前景， 已经引起 了人们的高度关注。其中的掺杂态具有电导率高、在空气中结构和电导率高度稳 定等卓越性能因而成为导电高分子新的研究热点。 本征态的 PEDOT导电性很差， 而且不熔不溶， 聚对苯乙烯磺酸 （PSS) 根阴离子掺杂的可以分散溶解在水溶液 中， 涂布成膜后在空气中非常稳定， 同时具有高电导率， 且其水溶液可以进一步 加工处理， 因而大大地促进了 PEDOT的应用。 直到目前为止， PEDOT或 PEDOT:PSS主要被用来作为锂离子电池的正极材料 （Electrochim. Acta, 53(2008): 8319-8323) ， 或是作为正极的复合材料进行相关的研究 （Electrochem. Commun., 4(2002): 545-549) 。 PEDOT和 PSS的结构单元中都包含了一个 S原子， 其碳化材 料可能会有少量杂原子 S的掺杂。 而 Yu等人认为碳材料中 -C-S-C-键的形成将更 有利于锂离子的*** （J. Power Sources, 108(2002): 245-249) 。因此， 可以通过制 备 Si/PEDOT:PSS复合材料， 然后将其进行碳化处理， 从而制备出新型的含少量 S 原子掺杂的 Si/C复合材料。 发明内容
本发明的目的是利用导电聚合物 PEDOT及其水溶液分散剂 PSS作为纳米 Si 粉的包覆层以及碳源， 提供一种性能优异的锂离子电池负极新硅复合材料。
本发明的另一个目的是提供上述硅碳复合材料的制备方法。
所述的硅碳复合材料中活性物质为纳米硅粉， 分散介质为导电聚合物聚 3，4- 乙撑二氧噻吩 （PEDOT) 高温裂解后的碳， 通过调节 EDOT单体 (3,4-乙撑二氧噻 吩)和纳米硅粉的比例， 硅的含量可控制为 60-90wt%。 所述的分散介质的前驱体 为导电聚合物聚 3，4-乙撑二氧噻吩 （PEDOT), 为使复合材料易于制备， 使用聚 苯乙烯磺酸（PSS)水溶液为 PEDOT的分散剂。 由于 PEDOT和 PSS的结构单元中 都包含了一个 S原子， 本发明的 Si/PEDOT:PSS复合材料碳化后， 纳米 Si颗粒外所 包覆的碳为少量 S掺杂碳。
所述硅碳复合材料由含纳米 Si类储锂材料作为主要活性物质，先通过原位聚 合反应在纳米 Si颗粒的表面聚合 PEDOT:PSS， 然后把制备的 Si/PEDOT:PSS复合 物在惰性气氛下经由高温碳化处理， 制得 Si/C复合材料。 由于制备先经过化学过 程，使得随后所制备复合材料中 Si和碳有更好的接触，另外由于 S元素的掺杂（碳 源中含有 S原子）， 使得复合材料的电化学性能得到大大改善。 本发明 Si/C复合材料的制备， 是以水为分散介质， 以 Fe2(S04)3/(NH4)S208 为催化剂， 在磁力搅拌下原位聚合先制备 Si/PEDOT:PSS复合材料， 然后经由高 温碳化而成。 具体步骤为：
(1) 前驱体的单体 EDOT缓慢加入到 PSS的水溶液中， 进行均匀分散处理； (2) 将纳米硅粉加入步骤 （1) 中， 超声分散， 搅拌均匀；
(3) 用稀盐酸调节步骤 （2)溶液的 pH值为 2左右；
(4) 在冰浴条件下，往步骤 （3) 的溶液里滴加 (NH4)S208/FeCl3的水溶液为催 化剂；
(5) 将步骤 （4) 的混合溶液先在冰浴下 6 h， 然后室温下反应 18 h过滤得到 Si/PEDOT:PSS复合物， 将此复合物在保护气体下升温至 800~1000°C， 保温碳化
3 h。
(6) 反应结束后降温。
本发明制备原料便宜， 纳米 Si在导电聚合物中的包覆在水溶液中进行， 工 艺简单环保， 收率高。 本发明制备的 Si/C复合材料具有极低的初始不可逆容量 损失 （2.8%)， 材料的充放电性能优异， 便于工业化生产， 在电动汽车等动力电 源上有潜在的应用前景。 附图说明
图 1为本发明实施例 Si/C、 Si/PEDOT:PSS、 EDOT、 PSS以及 Si的红外光谱图。 图 2为本发明实施例所制备样品及相关样品的 SEM及 TEM照片。（a)及 (b)为 Si 的 SEM和 TEM图， （c)及 (d) 为 Si/PEDOT:PSS的 SEM及 TEM图， （e)和 (f )为 Si/C的 SEM图。
图 3为本发明实施例 Si/C复合材料的 X射线能量色散谱 (EDS)。
图 4为本发明实施例所制备样品及相关样品的的 XRD图谱。 （a)为 Si， （b)为 Si/PEDOT:PSS， （c)为 Si/C。
图 5为本发明实施例 Si、 Si/PEDOT:PSS及 Si/C在空气气氛 （ 10°C/Min) 及 Si/PEDOT:PSS在 Ar气氛下（升温设置与实验过程相同， 且 800°C恒温 3 h)的热重 曲线图。（a)为 Si在空气气氛下，（b) Si/PEDOT:PSS在 Ar气氛下，（c)为 Si/PEDOT:PSS 在空气气氛下， （d)为 PEDOT:PSS在空气气氛下。 图 6为本发明实施例 Si、 Si/PEDOT:PSS及 Si/C材料所制备电极在 100 mA-g 1 的充放电电流密度下的循环性能测试曲线。
图 7为本发明实施例 Si、 Si/PEDOT:PSS及 Si/C材料所制备电极的交流阻抗测 试的 Nyquist图。 具体实施方式
本发明 Si/C复合材料的具体制备步骤为：
将 EDOT单体缓慢加入到 PSS的水溶液中， 超声分散 30~60 min, 于 0~5°C剧 烈搅拌 l~2 h; 将纳米硅粉加入上述溶液， 超声分散 60 min; 用 2 M稀盐酸调节上 述混合液的 pH值为 2~3；在 0~5°C条件下，往上述的混合液里滴加 (NH4)S208/FeCl3 水溶液催化剂， 超声分散 30~60 min， 搅拌情况下反应 6 h后， 撤去冰浴， 室温下 继续搅拌 18 h; 聚合产物经过过滤， 洗涤， 干燥， 得到 Si/PEDOT:PSS复合物； 将 此复合物在保护气体下升温至 800~900°C， 保温碳化 3 h， 得到 Si/C复合材料。
所述 Si加入量为 EDOT单体的质量的 1~2倍。
(NH4)S208的加入量为 EDOT单体的质量的 1.5~3倍。
FeCl3的加入量为 EDOT单体的质量的 0.01~0.05倍。
PSS的加入量为 EDOT单体的质量的 1.5~4倍。
所述的保护气体为 Ar、 N2或 Ar/H2混合气。 反应的升温速率为 l~5°C/min。 实施例 1
将 0.28 g EDOT单体缓慢加入到含 0.82 g PSS的水溶液 （90 mL) 中， 超声分散
60 min, 于冰浴下剧烈搅拌 1~2 h; 将 0.4 g纳米硅粉加入上述溶液， 超声分散 60 min; 用 2 M稀盐酸调节上述混合液的 pH值为 2; 在冰浴条件下， 往上述的混合液 里滴加 (NH4)S208 (0.70 g)/FeCl3 (6 mg) 的水溶液， 超声分散 60 min， 搅拌情况下 反应 6 h后， 撤去冰浴， 室温下继续搅拌 18 h; 聚合产物经过过滤后， 用乙醇洗三 次 （用于除去没有反应完全的有机物） ， 再用去离子水清洗三次 （除去一些离子 及过量的 PSS) ，然后 60°C真空干燥 24 h。将干燥后的复合物在 Ar保护以 3°C /min 的速率升温至 800°C， 保温碳化 3 h， 自然冷却后得到 Si/C复合材料。 将制备的材 料充分研磨后，和炭黑及羧甲基纤维素按照 62:30:8的比例，混合均匀，涂膜后 60°C 真空干燥 24 h， 制备得到 Si/C电极。 将电极在 2025电池壳内， 以锂片为对电极， 以聚乙烯膜为隔膜， 以 1 M LiPF6 EC/DEC (v/v=l/l) 为电解液组装电池进行恒电 流充放电测试。
下面通过红外光谱图、 SEM及 TEM照片、 XRD图谱及 TG图谱及对本发明制 备的 Si/C复合材料及其前躯体 Si/PEDOT:PSS复合材料的结构和形貌等进行测试 和表征。
1、 红外光谱分析
图 1为 Si/C、 Si/PEDOT:PSS、 EDOT、 PSS以及 Si的红外光谱图。 从 Si/PEDOT:PSS的光谱图上可以看到， 清晰出现 -C-S-峰 （980 cm-1), -C-0-C-伸 縮振动峰（1090 cm-1) ， 以及代表噻吩环上 C-C及 C=C的醌基结构的伸縮振动峰 (1338 cm-1) 。 另外， 代表单体 EDOT的特征峰=〔-11振动峰 （891 cm-1) 在 Si/PEDOT:PSS的光谱图上消失。 以上这些结果表明 EDOT成功实现了聚合。而在 Si/C复合物的光谱图上发现， 代表噻吩环上 C-C及 C=C的醌基结构的伸縮振动峰 (1338 cm-1) 完全消失，这表明 PEDOT:PSS结构经过 800°C碳化后已经完全转化为 碳结构。
2、 电镜分析
图 2为本发明所制备样品及相关样品的 SEM或 TEM照片。 图 2 (a) 及 （b) 为纳 米硅颗粒的 SEM和 TEM照片，可以看出 Si的颗粒尺寸范围为 30~50 nm，且呈现球 形状。 图 2 (c) 及 （d) 为 Si/PEDOT:PSS的 SEM和 TEM照片， 可以看出 Si/PEDOT:PSS形成了较大的团聚物， 纳米 Si颗粒被均匀度分散在 PEDOT:PSS的 晶格中。 图 2 (e) 及 （f) 为 Si/C复合物的 SEM照片， 可以看出 Si颗粒被完全的包覆 在 C的晶格中。 图 3为 SEM自带的 EDS分析图， 其表明在 Si/C复合物中有少许 S掺 杂， 含量大约为 U wt%。
3、 XRD分析
图 4为 Si、 Si/PEDOT:PSS及 Si/C的 XRD图谱。图 4 (a) 为 Si的 XRD图，在 28.4°、 47.4°、 56.2。、 69.2°及 76.5°的衍射峰分别代表 Si的 (111) 、 (220) 、 (311) 、 (400) 和 (331)晶面。 这些衍射峰全部出现在图 3 (b) Si/PEDOT的衍射谱及图 4 (c) Si/C的 衍射谱上。 在 Si/PEDOT的衍射谱上发现， 在 26.0°附近出现了一个衍射峰， 这是 聚合物 PEDOT (020)晶面的特征衍射峰。另外在 Si/C的衍射谱上只是在 20.0°和 25° 之间出现一个弱的宽峰， 没有出现明显的代表石墨碳的衍射尖峰， 表明 PEDOT:PSS经过高温碳化后形成的碳是无定形结构。 4、 TG分析
图 5为 Si、 Si/PEDOT:PSS及 Si/C在空气气氛及 Si/PEDOT:PSS在 Ar气氛下的热 重曲线图。 基于 800°C时在空气或惰性气氛下不同样品的失重量， 大约可以推测 出 Si在 Si/PEDOT:PSS复合物中含量大约为 51.6%， Si在 Si/C复合物中含量大约为 85.7wt%。
下面通过循环性能测试及交流阻抗图谱对本发明制备的 Si/C复合材料的电 化学性能进行测试和表征。
5、 循环性能测试
图 6为 Si/C及 Si和 Si/PEDOT:PSS材料所制备电极在 100 mA_g- 1的充放电电流密 度下的循环性能测试曲线。 图上可以看出 Si的容量衰减速率最大， 由初始的 2710 mAlrg-1经过 80个循环后快速衰减至 128 mAlrg- Si/PEDOT:PSS复合材料电极相 比 Si电极衰减速率变缓， 但不可逆容量损失仍然较大。 而 Si/C复合材料电极的循 环性能得到明显的改善，首次不可逆容量损失仅为 2.8%，经过 80个循环后仍能保 持 768 mAlrg- 1的容量。
6、 交流阻抗测试
图 7为 Si/C及 Si和 Si/PEDOT:PSS材料所制备电极的交流阻抗测试。 经过拟合 后的结果发现， Si/C电极的电荷转移电阻相比 Si电极减小 5倍，而双电层电容增大 4倍， 这使得 Si/C电极能在较低的极化下运行， 因此性能得到大幅改善。
综上所述， 本发明制备的 Si/C复合材料中， 纳米 Si被成功的包覆在由导电聚 合物 PEDOT:PSS碳化后的碳基体中，使得 Si颗粒在充放电过程中极大的体积膨胀 得到有效的抑制， 从而极大的改善了材料的循环性能。

Claims

权 利 要 求
1、 一种锂离子电池负极用硅碳复合材料， 其特征在于所述的硅碳复合材料 中活性物质为纳米硅粉， 分散介质为导电聚合物聚 (3,4-乙撑二氧噻吩)及其高温 裂解后的碳。
2、 按照权利要求 1所述的锂离子电池负极用硅碳复合材料， 其特征在于所 述的分散介质的前驱体为导电聚合物聚 (3,4-乙撑二氧噻吩)， 使用聚苯乙烯磺酸 水溶液为聚 (3,4-乙撑二氧噻吩)的分散剂。
3、 按照权利要求 1所述的锂离子电池负极用硅碳复合材料， 其特征在于： 纳米硅颗粒外所包覆的碳为 S掺杂碳。
4、 权利要求 1所述的锂离子电池负极用硅碳复合材料的制备方法， 其特征 包括如下步骤：
(1) 前驱体的单体 3,4-乙撑二氧噻吩缓慢加入到聚苯乙烯磺酸的水溶液中， 进行 均匀分散处理；
(2) 将纳米硅粉加入步骤 （1) 中， 超声分散， 搅拌均匀；
(3) 用稀盐酸调节步骤 （2) 溶液的 pH值；
(4) 在冰浴条件下， 往步骤 （3) 的溶液里滴加 (NH4)S208/FeCl3的水溶液为催化 剂；
(5) 将步骤 （4) 的混合溶液先在冰浴下 6 h， 然后室温下反应 18 h 过滤得到 Si/PEDOT:PSS复合物；
(6) 将 Si/PEDOT:PSS复合物在保护气下升温至 800~1000°C， 保温碳化 3 h反应 结束后降温。
5、 如权利要求 4所述的锂离子电池负极用硅碳复合材料的制备方法， 其特 征在于： 所述 Si加入量为 EDOT单体的质量的 1~2 倍； （NH4)S208的加入量为 EDOT单体的质量的 1.5~3 倍； FeCl3的加入量为 EDOT单体的质量的 0.01~0.05 倍； PSS的加入量为 EDOT单体的质量的 1.5~4倍。
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