基于聚合反应制备的钛离子掺杂LiFePO4/C复合材料

首先基于聚合反应合成FePO4/PANI前驱体,再以为LiOH·H2O,FePO4/PANI 和 PVA原料制备了LiFePO4正极材料,此外再对其进行碳包覆以及Ti4+掺杂,三种试样分别标记为LiFePO4,LiFePO4/C及LiFe0.96Ti0.02PO4/C.通过XRD、EDS及充放电测试等手段表征了材料的微观结构与电化学性能.实验结果证明:试样的XRD图谱均与标准LiFePO4图谱一致,不存在无定形碳衍射峰.与未掺杂试样LiFePO4/C相比,LiFe0.96Ti0.02PO4/C的电子电导率与其相近,但离子扩散系数有所改善,Ti4+在晶格中均匀分布,因此与其他两试样相比,其电化学性能更好.试样在C/10、C/2、1C、3C及5C倍率下的放电比容量为158.7 mAh·g-1、153.3 mAh·g-1、147.6 mAh·g-1、136.4 mAh·g-1及123.5 mAh·g-1,具有良好的倍率性能与电位稳定性.     

磁性碳包铁纳米粒子在重金属元素检测分离富集中的应用

以氩电弧等离子体法制备的碳包铁纳米粒子为固相萃取材料,采用等离子体原子发射光谱法(ICP-AES)系统研究了该材料对Cr、Ni、Cd、Pb离子的吸附性能,并确定了最佳吸附和洗脱条件。实验结果表明:当pH值为8.0～9.0时,分析物均可被碳包铁纳米粒子定量吸附;采用酸性溶液(pH=1.0～2.0)可将吸附在碳包铁纳米粒子上的金属离子完全脱附。该法对Cr、Ni、Cd、Pb的检出限分别为3.6、4.1、1.1、9.8μg/L,Cr、Ni、Cd的线性范围为1～500μg.L-1,Pb的线性范围为10～1 000μg.L-1,线性相关系数均大于0.999。方法用于自来水中Cr、Ni、Cd、Pb离子的测定,回收率可达到93%～105%;碳包铁纳米粒子对Cr、Ni、Cd、Pb离子的吸附量分别为3.6、4.8、6.3、2.1 mg/g。     

碳包覆改性制备高倍率性能的锂离子电池正极材料LiNi1/3Co1/3Mn1/3O2

采用碳酸盐共沉淀-高温固相法制备了一系列表面碳包覆改性（w=1.0%,2.0%,3.0%）的LiNi_1/3Co_1/3Mn_1/3O₂正极材料,借助X射线衍射（XRD）分析、扫描电镜（SEM）、透射电镜（TEM）、电化学阻抗谱（EIS）和恒电流充放电测试等表征手段对材料的晶体结构、微观形貌和电化学性能进行了较系统的研究。结果表明,碳成功地包覆在了材料颗粒的表面,碳包覆改性后的材料具有良好的α-NaFeO₂结构（空间群为R3m）,且随着包碳量的增加,一次颗粒平均尺寸逐渐增大（从177 nm增至209 nm）。表面的无定形碳层可以提高材料的电子导电率,减少电极材料与电解液的副反应,故而碳包覆材料的电化学性能都有了一定程度提升。包覆碳量为2.0%的样品高倍率和长循环性能最好,在2.7~4.3 V,1C下循环100次后,容量保持率为93%;在0.1C、0.2C、0.5C、1C、3C、5C、10C和20C时的放电比容量分别为：155、148、145、138、127、116、104和96 mAh·g^-1。在超高倍率50C（9 A·g^-1）时,其放电比容量还能达到62 mAh·g^-1（原始LiNi_1/3Co_1/3Mn_1/3O₂材料仅为30 mAh·g^-1）,倍率性能十分优异。     

碳涂覆光纤的最新进展

本文首先介绍了气密性光纤的发展过程，接着重点分析了碳涂覆光纤的两个重要参数：长期可靠性和抗氢渗透性。引入了新的衡量碳涂覆光纤抗氢渗参量－缺氢渗因子，最后介绍了西安应用光学研究所碳涂覆光纤“八．五”末的进展情况，以及国内外现状比较。     

碳包覆Li3V2(PO4)3:溶胶-凝胶法合成及性能

利用V₂O₅、LiOH·H₂O、H₂O₂、NH₄H₂PO₄与柠檬酸为原料,通过溶胶-凝胶法合成了碳包覆的Li₃V₂(PO₄)₃复合正极材料。采用XPS、XRD、SEM、TEM、拉曼光谱和电化学方法对材料的性能进行了研究。还研究了其结构与焙烧温度、样品电导率和电化学性能的关系。研究表明复合材料具有空间群为P2₁/n的单斜结构,表面包覆粗糙多孔的碳层。在800 ℃下制备的碳包覆样品的电子导电率高达9.81×10^-5 S·cm^-1,约为高温固相氢气还原法制备的未包覆碳Li₃V₂(PO₄)₃的10000倍。测试结果表明碳包覆Li₃V₂(PO₄)₃的电化学性能远优于未包覆碳的样品。在3.0～4.3 V电压范围内,以0.1C和2C倍率充放电时,碳包覆的Li₃V₂(PO₄)₃具有高比容量(分别为128和109 mAh·g^-1)和优异的循环性能。     

Facile Synthesis of Sponge-Like Porous Nano Carbon-Coated Silicon Anode with Tunable Pore Structure for High-Stability Lithium-Ion Batteries

To address the challenge of the huge volume expansion of silicon anode, carbon-coated silicon has been developed as an effective design strategy due to the improved conductivity and stable electrochemical interface. However, although carbon-coated silicon anodes exhibit improved cycling stability, the complex synthesis methods and uncontrollable structure adjustment still make the carbon-coated silicon anodes hard to popularize in practical application. Herein, we propose a facile method to fabricate sponge-like porous nano carbon-coated silicon (sCCSi) with a tunable pore structure. Through the strategy of adding water into precursor solution combined with a slow heating rate of pre-oxidation, a sponge-like porous structure can be formed. Furthermore, the porous structure can be controlled through stirring temperature and oscillation methods. Owing to the inherent material properties and the sponge-like porous structure, sCCSi shows high conductivity, high specific surface area, and stable chemical bonding. As a result, the sCCSi with normal and excessive silicon-to-carbon ratios all exhibit excellent cycling stability, with 70.6% and 70.2% capacity retentions after 300 cycles at 500 mA g⁻¹, respectively. Furthermore, the enhanced buffering effect on pressure between silicon nanoparticles and carbon material due to the sponge-like porous structure in sCCSi is further revealed through mechanical simulation. Considering the facile synthesis method, flexible regulation of porous structure, and high cycling stability, the design of the sCCSi paves a way for the synthesis of high-stability carbon-coated silicon anodes.     

碳包覆改性制备高倍率性能的锂离子电池正极材料LiNi_(1/3)Co_(1/3)Mn_(1/3)O_2

采用碳酸盐共沉淀-高温固相法制备了一系列表面碳包覆改性(w=1.0%,2.0%,3.0%)的LiNi_(1/3)Co_(1/3)Mn_(1/3)O_2正极材料,借助X射线衍射(XRD)分析、扫描电镜(SEM)、透射电镜(TEM)、电化学阻抗谱(EIS)和恒电流充放电测试等表征手段对材料的晶体结构、微观形貌和电化学性能进行了较系统的研究。结果表明,碳成功地包覆在了材料颗粒的表面,碳包覆改性后的材料具有良好的α-Na Fe O2结构(空间群:R3m),且随着包碳量的增加,一次颗粒平均尺寸逐渐增大(从177 nm增至209 nm)。表面的无定形碳层可以提高材料的电子导电率,减少电极材料与电解液的副反应,故而碳包覆材料的电化学性能都有了一定程度提升。包覆碳量为2.0%的样品高倍率和长循环性能最好,在2.7~4.3 V,1C下循环100次后,容量保持率为93%;在0.1C、0.2C、0.5C、1C、3C、5C、10C和20C时的放电比容量分别为:155、148、145、138、127、116、104和96 m Ah·g-1。在超高倍率50C(9 A·g-1)时,其放电比容量还能达到62 m Ah·g-1(原始LiNi_(1/3)Co_(1/3)Mn_(1/3)O_2材料仅为30 m Ah·g-1),倍率性能十分优异。     

碳包覆Na2Ti6O13纳米管的电化学性能研究

以金红石型TiO2和NaOH为原料,由水热反应制备Na2Ti6O13纳米管.然后,在含有0.1 mol.L-1NaOH的葡萄糖水溶液中反应4 h制得碳包覆的Na2Ti6O13纳米管.X射线衍射(XRD)、扫描电子显微镜(SEM)和透射电子显微镜(TEM)等分析表明,该碳包覆Na2Ti6O13纳米管外径约14～19 nm,内径约2～5 nm,长度为数百纳米,有一层厚度约为2 nm的碳层包覆在纳米管外壁.以其作为锂离子电池负极材料,恒电流充放电测试表明,在50 mA.g-1电流密度下首周可逆容量达到161 mAh.g-1,循环100周后容量保持在147 mAh.g-1.相比于Na2Ti6O13纳米管,提高了20%以上.电流密度升至1600 mA.g-1充放电,碳包覆Na2Ti6O13纳米管可逆容量仍有70 mAh.g-1左右,远高于Na2Ti6O13纳米管,表现出良好的倍率性能.     

Theoretical calculation and experiment of microwave electromagnetic property of Ni(C) nanocapsules

With the combination of the dielectric loss of the carbon layer with the magnetic loss of the ferromagnetic metal core,carbon-coated nickel Ni(C) nanoparticles are expected to be the promising microwave absorbers. Microwave electromagnetic parameters and reflection loss in a frequency range of 2 GHz–18 GHz for paraffin-Ni(C) composites are investigated.The values of relative complex permittivity and permeability, the dielectric and magnetic loss tangent of paraffin-Ni(C) composites are measured, respectively, when the weight ratios of Ni(C) nanoparticles are equal to 10 wt%, 40 wt%, 50 wt%,70 wt%, and 80 wt% in paraffin-Ni(C) composites. The results reveal that Ni(C) nanoparticles exhibit a peak of magnetic loss at about 13 GHz, suggesting that magnetic loss and a natural resonance could be found at that frequency. Based on the measured complex permittivity and permeability, the reflection losses of paraffin-Ni(C) composites with different weight ratios of Ni(C) nanoparticles and coating thickness values are simulated according to the transmission line theory. An excellent microwave absorption is obtained. To be proved by the experimental results, the reflection loss of composite with a coating thickness of 2 mm is measured by the Arch method. The results indicate that the maximum reflection loss reaches-26.73 d B at 12.7 GHz, and below-10 d B, the bandwidth is about 4 GHz. The fact that the measured absorption position is consistent with the calculated results suggests that a good electromagnetic match and a strong microwave absorption can be established in Ni(C) nanoparticles. The excellent Ni(C) microwave absorber is prepared by choosing an optimum layer number and the weight ratio of Ni(C) nanoparticles in paraffin-Ni(C) composites.