纳米碳/聚甲基丙烯酸甲酯复合材料的研究

采用脉冲激光轰击浸于流动液相中固体靶的方法,直接连续制备了纳米碳/PMMA的乙酸乙酯溶液,经浇膜法得到了纳米碳/聚甲基丙烯酸甲酯复合材料.光谱分析表明复合体系中存在某种作用,导致该复合材料的玻璃化转变温度明显下降.透射电镜结果表明纳米碳可与聚甲基丙烯酸甲酯形成核/壳结构,使得纳米碳均匀分散于聚合物基体中.热分析结果表明纳米碳的加入对聚甲基丙烯酸甲酯的热分解性能没有显著影响.     

机械化学法原位合成硅/锡二元储锂母体复合负极材料的研究

以高活性、低熔点金属锂为还原剂,在惰性气氛保护下分别将一氧化硅和氧化亚锡还原为单质硅和锡。通过调节球磨参数并加入适量助磨剂有效抑制因金属锂熔化导致的物料结块现象,得到将纳米硅、锡颗粒均匀分散在含锂化合物基体中的二元储锂母体复合材料。通过该方法得到的复合材料中硅、锡颗粒粒径明显小于商品化的纳米硅和纳米锡,不仅能最大限度降低硅、锡颗粒的体积效应,避免纳米粉体的分散工序,且能大大降低材料的制备成本。交流阻抗和充放电循环测试显示,金属锡作为另一种储锂母体既能为复合材料提供部分可逆容量,也能有效降低活性物质颗粒之间     

乳液分散法制备高分散纳米锡/介孔碳复合材料及其电化学性能

以间苯二酚和糠醛聚合而成的可溶性树脂为碳源,SnCl2为锡源,表面活性剂F127为模板剂,通过乳液分散法将锡源原位复合嵌入于介孔碳材料中,制备了纳米锡基材料高度分散于介孔碳中的复合材料。利用X射线衍射(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)、N2吸脱附(BET)、循环伏安(CV)等对材料的微观结构和电化学性能进行了表征。结果显示锡基材料在介孔碳中较为密集,分布均匀,粒径小于5 nm。介孔碳丰富的孔道结构有效限制和缓解了锡基材料的生长、团聚和体积膨胀,同时高比表面积增加了电解液与锡基活性材料的接触,提供了更多的反应活性点,从而获得了更高的电化学活性。充放电测试结果显示,700℃热处理后,锡/介孔碳纳米复合材料经过50次循环后实际放电比容量达203.4 mAh.g-1,表现出良好的电化学性能。     

碳热还原原位合成锂离子电池硅/碳复合负极材料研究

以一氧化硅和蔗糖为原料,通过高能球磨和后续热解原位制备硅/碳复合材料。采用X射线衍射仪(XRD)和高分辨透射电子显微镜(HRTEM)对其进行了表征,得到的纳米(小于50 nm)硅颗粒均匀地分散于无定形碳基体中。复合材料电极电化学测试显示,循环50次其可逆容量仍保持在650 mAh·g-1以上,平均每次容量衰减率仅为0.27%。优异的电化学性能主要归因于原位生成的纳米硅颗粒处于无定形碳基体中对其体积变化具有良好的缓冲作用及纳米硅颗粒周围的石墨相对于导电性的改善。     

Ag负载KTa1-xNbxO3-BaTiO3颗粒掺杂P(VDF-TrFE-CTFE)复合材料的制备及介电性能

通过光照还原法制备了银颗粒负载的铌钽酸钾-钛酸钡复合粉体（Ag/KTN-BT）,并将其与聚偏氟乙烯-三氟乙烯-三氟氯乙烯（P（VDF-TrFE-CTFE））聚合物复合,获得Ag/KTN-BT聚合物基复合材料。研究发现,Ag/KTN-BT填料颗粒在聚合物基体中分散均匀,复合材料结构致密,无明显气孔和裂纹,且具有较好的柔韧性。银纳米颗粒的负载,一方面在复合材料中引入了额外的界面,导致界面极化作用增强,明显提高复合材料的介电常数;另一方面银纳米颗粒的量子尺寸效应和库伦阻塞效应使得复合材料保持较低的介电损耗。当填充体积分数为20%的Ag/KTN-BT颗粒时,聚合物基复合材料的介电常数大幅提升,从聚合物的37提升到125（100 Hz）,介电损耗仅为0.12。与KTN-BT基复合材料对比,Ag/KTN-BT基复合材料也显示出较好的介电性能。     

Ni@C/HDPE复合材料的制备及其正温度系数性能研究

采用还原气氛喷雾燃烧法制备了具有核壳结构Ni@C纳米复合颗粒,并与HDPE共混挤出制备了聚合物基PTC导电复合材料,并且对其结构和性能进行了表征.结果表明,所制备的Ni@C复合纳米颗粒具有典型的核壳结构,其中,金属镍的核的粒径为30~50 nm,碳包覆壳层的厚度约为2.9 nm,热重分析结果表明Ni@C复合纳米颗粒的含碳量为3.4%,碳包覆层的存在阻止了金属镍颗粒的团聚;对Ni@C/HDPE复合材料的断面SEM和切片TEM分析结果表明复合颗粒在HDPE基体中分散性良好,复合材料的渗流阈值为10wt%,PTC强度为8个数量级.     

等离子体辅助球磨Si-C复合负极材料及其电化学性能研究

首次采用介质阻挡放电等离子体辅助高能两次球磨制得Si-C复合材料,其结构为微纳尺度硅颗粒均匀分散于微米级碳基体上. Si-C复合电极首周期循环放电容量为1259 mAh·g^-1,20和100周期循环的容量分别为474和396 mAh·g^-1. 该电极充放电曲线和交流阻抗测试的结果表明,复合材料中的硅和碳均参与锂离子嵌/脱反应,且其电荷传导阻抗明显低于纯Si.     

聚丙烯/锡氟磷酸盐玻璃复合材料的结构与性能

锡氟磷酸盐玻璃(Pglass)具有较低的玻璃化转变温度,在常规聚合物加工温度窗口内具有熔融流动性,是一种新型的无机类聚合物玻璃。本文采用双螺杆挤出机制备了聚丙烯(PP)/Pglass有机聚合物/无机玻璃复合材料,并对其相形貌、界面性能、流动性能、结晶性能、力学性能和热稳定性能进行了研究。结果表明:Pglass以微米级颗粒分散在PP基体中,且两相之间界面明显、相容性较差。Pglass的添加使复合材料的熔体剪切粘度降低。Pglass的存在促进了基体PP的结晶。复合材料的弹性模量随着Pglass含量的增加而增加。Pglass提高了复合材料的热稳定性。     

PMMA/PS纳米复合材料的制备及分散相稳定性研究

纳米复合材料具有许多优异的性能,但是由于纳米粒子常常很难以纳米尺寸均匀地分散在基体中,有时即使实现了纳米级分散,在后加工或应用过程中又会发生二次团聚,使得纳米材料的特性不能充分发挥．因此,要获得性能优异的纳米复合材料首先必须解决纳米材料在基体中的均匀、稳定分散问题．     

聚酰亚胺/纳米MgO复合材料的制备与性能研究

采用直接分散法将纳米MgO颗粒均匀分散在聚酰胺酸溶液中,经旋涂、热亚胺化制得聚酰亚胺/纳米MgO复合材料.利用傅里叶变换红外光谱(FTIR)、X射线衍射(XRD)、扫描电子显微镜(SEM)、紫外可见光谱(UV-Vis)、热重分析(TGA)和纳米划痕等测试技术对复合材料的结构和性能进行了表征.结果表明,平均粒径约为20 nm的纳米MgO颗粒均匀地分散在聚酰亚胺基体中,有机无机两组分相容性良好;复合材料在可见光区具有优良的光学透明性,在近紫外光区随着纳米MgO含量的增加呈现出了显著的紫外屏蔽性能;纳米MgO的加入能大幅提高复合薄膜的抗划伤性能,在100μN的划痕力下,划痕深度由纯聚酰亚胺的57.4 nm降至10 nm左右,且划痕的宽度也明显减小;尽管复合材料的热稳定性能较纯聚酰亚胺略有下降,但在300℃以下仍具有较好的热稳定性.     

Electrochemical Properties of Tin Oxide Flake/Reduced Graphene Oxide/Carbon Composite Powders as Anode Materials for Lithium‐Ion Batteries

Hierarchically structured tin oxide/reduced graphene oxide (RGO)/carbon composite powders are prepared through a one‐pot spray pyrolysis process. SnO nanoflakes of several hundred nanometers in diameter and a few nanometers in thickness are uniformly distributed over the micrometer‐sized spherical powder particles. The initial discharge and charge capacities of the tin oxide/RGO/carbon composite powders at a current density of 1000 mA g^?1 are 1543 and 1060 mA h g^?1, respectively. The discharge capacity of the tin oxide/RGO/carbon composite powders after 175 cycles is 844 mA h g^?1, and the capacity retention measured from the second cycle is 80 %. The transformation during cycling of SnO nanoflakes, uniformly dispersed in the tin oxide/RGO/carbon composite powder, into ultrafine nanocrystals results in hollow nanovoids that act as buffers for the large volume changes that occur during cycling, thereby improving the cycling and rate performances of the tin oxide/RGO/carbon composite powders.     

Fabrication of Sn–C composite electrodes by electrodeposition and their cycle performance for Li-ion batteries

To improve the cycle performance of the thick Sn electrode of 10 μm thickness, the Sn–C composite electrodes were fabricated by co-electrodeposition with two kinds of carbon particles which were the graphite and the acetylene black. The acetylene black particles were well dispersed in the Sn matrix more than the graphite particles. The carbon content in the Sn–C composite electrodes was measured about 12% of the graphite and 16% of the acetylene black particles. Even though carbon content of the Sn–acetylene black electrode was not significantly higher than that of the Sn–graphite electrode, the cycle performance of the Sn–acetylene black electrode was much higher than that of the Sn–graphite electrode. This demonstrates that the ‘buffering effects’ of well dispersed acetylene black particles was larger than that of the graphite particles. The cycle performance of the Sn–acetylene black electrode was significantly improved by the aging treatment.     

Sn–Co–C composites obtained from resorcinol-formaldehyde gel as anodes in lithium-ion batteries

Sn–Co–C composites have been prepared by using the resorcinol/formaldehyde polymerization method combined with the carbothermal reduction of metal oxides during carbonization. Homogeneously dispersed metal/carbon composites were identified by electron microscopy. Scanning electron microscopy images revealed the presence of carbonaceous particles with inclusions of metal agglomerates, and the X-ray diffraction patterns revealed the presence of tin and cobalt–tin phases. The introduction of small amounts of cobalt led to higher capacities as compared to coke and cobalt-free samples. The sample with a Sn/Co molar ratio of 85:15 and a higher, initial metal oxide-to-resorcinol ratio was able to maintain capacity values near 380 mAh/g after 30 cycles. The instability of cobalt–tin phases on cycling was not a hindrance for the electrochemical behavior. Charge transfer resistance values were kept low during cycling for cobalt-containing composites.     

纳米锡/硬碳复合材料作为嵌锂负极的研究

利用金属铁和钴纳米颗粒的催化活化作用,制备了多孔硬碳球.应用聚焦离子束切割技术,观察到扩孔后的硬碳球中充满彼此连通的发达中孔.在此多孔硬碳球中填入纳米锡(Sn)颗粒,对复合材料的电化学性能进行了测试.     

Electrospun Cu/Sn/C Nanocomposite Fiber Anodes with Superior Usable Lifetime for Lithium‐ and Sodium‐Ion Batteries

Cu/Sn/C composite nanofibers were synthesized by using dual‐nozzle electrospinning and subsequent carbonization. The composite nanofibers are a homogeneous amorphous matrix comprised of Cu, Sn, and C with a trace of crystalline Sn. The Li‐ and Na‐ion storage performance of the Cu/Sn/C fiber electrodes were investigated by using cyclic voltammetry, galvanostatic cycling, and electrochemical impedance spectroscopy. Excellent, stable cycling performance indicates capacities of 490 and 220 mA h g^?1 for Li‐ion (600 cycles) and Na‐ion (200 cycles) batteries, respectively. This is a significant improvement over other reported Sn/C nanocomposite devices. These superior electrochemical properties could be attributed to the advantages of incorporating one‐dimensional nanostructures into the electrodes, such as short electron diffusion lengths, large specific surface areas, ideal homogeneous structures for buffering volume changes, and better electronic conductivity that results from the amorphous copper and carbon matrix.     

碳包覆纳米SnSb合金作为高性能钠离子电池负极材料

采用喷雾热解法合成了碳包覆的SnSb/C合金复合材料,利用X射线粉末衍射仪(XRD)、场发射扫描电子显微镜(FESEM)、透射电子显微镜(TEM)等方法对产物的物相和形貌进行了表征,其中SnSb/C颗粒为10 nm左右的复合材料(10-SnSb/C)作为钠离子电池负极时,表现出优异的循环和倍率性能。首圈放电达到722.1m Ah·g~(-1),首圈库仑效率86.3%,在100、1000、3000 m A·g~(-1)下比容量分别为607.7、645.4、452.2 m Ah·g~(-1),在1000 m A·g~(-1)电流下循环200周后可逆容量达到623 m Ah·g~(-1),容量保持率为95%。SnSb/C复合材料出色的储钠性能源于其完全被碳包裹的纳米结构,该结构可以有效提高活性物质的利用率,促进电子、离子的传导,并且抑制纳米粒子在长循环过程中的粉化和团聚。     

Effects of carbon sources and carbon contents on the electrochemical properties of LiFePO4/C cathode material

LiFePO₄/C composites are prepared by using two types of carbon source: one using polymer (PAALi) and the other using sucrose. The physical characteristics of LiFePO₄/C composites are investigated by X-ray diffraction), scanning electron microscopy, BET, laser particle analyzer, and Raman spectroscopy. Their electrochemical properties are characterized by cyclic voltammograms, constant current charge–discharge, and electrochemical impedance spectra. These analyses indicate that the carbon source and carbon content have a great effect on the physical and electrochemical performances of LiFePO₄/C composites. An ideal carbon source and appropriate carbon content can effectively increase the lithium-ion diffusion coefficient and exchange current density, decrease the charge transfer resistance (R _ct), and enhance the electrochemical performances of LiFePO₄/C composite. The results show that PAALi is a better carbon source for the synthesis of LiFePO₄/C composites. When the carbon content is 4.11 wt.% (the molar ratio of PAALi/Li₂C₂O₄ was 2:1), as-prepared LiFePO₄/C composite shows the best combination between electrochemical performances and tap density.     

Unfolding Tin–Cobalt Interactions in Oxide‐Based Composite Electrodes for Li‐Ion Batteries by Mössbauer Spectroscopy

With a view to the development of new composite electrodes for lithium-ion batteries with electroactive tin and cobalt, Co-doped tin dioxide samples are studied. The role played by oxygen and cobalt atoms in the electrochemical behavior of tin-based electrodes for Li-ion batteries is examined by the powerful and selective (119)Sn M?ssbauer spectroscopy. For the discharged electrodes, the oxygen atoms in the lithia matrix tend to destabilize the Sn(0) atoms. In contrast, the presence of cobalt atoms helps to form a matrix that stabilizes the reduced tin atoms. Cobalt-tin interactions in electrochemical reduced Co(x)Sn(1-x)O(2) electrodes are deduced from the electrochemical and M?ssbauer results.     

Leak testing of carbon–tin nanocomposites by thermal analysis methods

Electrode materials consisted of tin nanograins encapsulated in different origin carbon buffer matrix (starch or water soluble polymer) were obtained in a simple and inexpensive process. The tin precursor was synthesized using modified reverse nanoemulsion technique (w/o) and then coated by a source of carbon. The composites precursors were pyrolysed, affording formation of C/Sn anode materials. The resulting samples were investigated by powder X-ray diffraction studies in order to verify the structure and calculate crystallites sizes. The morphology of the nanocomposites was characterized by low-temperature nitrogen adsorption method (N₂-BET). Thermal analysis measurements (EGA-TG/DTG/DTA and DSC) allowed determining optimal conditions of preparation process and estimating carbon content in the obtained anode materials. Thermogravimetric studies also proved to be highly useful in establishing the leak behaviour of C/Sn nanocomposites. The electrochemical performance of the nanopowders was examined by charge–discharge tests in R2032-type coin cell. The thermal analysis results as well as low-temperature nitrogen adsorption data indicated that the origin of carbon precursor has major impact on morphology and leak behaviour of the obtained carbon buffer matrix. The electrochemical tests showed that better tightness of carbon–tin nanocomposites resulted in higher gravimetric capacity and better cell performance.