Co$lt;sub$gt;2$lt;/sub$gt;SnO$lt;sub$gt;4$lt;/sub$gt;/Graphene复合材料的制备与电化学性能研究

实验首先采用改进的Hummers法制备氧化石墨,然后以氧化石墨烯为前驱体,通过水热法将锡酸钴纳米颗粒均匀镶嵌在石墨烯薄膜基片上,最终获得Co₂SnO₄/Graphene镶嵌复合材料. 采用X射线衍射（XRD）、扫描电子显微镜（SEM）对材料的结构和形貌进行表征,通过恒电流充放电（CC）、循环伏安法（CV）与交流阻抗法（EIS）测试了材料的电化学性能. 实验结果表明,石墨烯良好的分散性及较高的电子导电率,可以提高锡酸钴材料的电化学性能,材料首次可逆容量达到1415.2 mA·h/g,50次循环后仍能保持469.7 mA·h/g的放电比容量. 关键词： 2SnO₄')" href="#">Co₂SnO₄ 石墨烯 电化学性能 锂离子电池     

碳热还原法制备V2O3-C双层包覆磷酸铁锂及其电化学性能

通过V₂O₅的碳热还原反应制备了具有优异倍率性能和循环稳定性的V₂O₃-C双层包覆的磷酸铁锂正极材料. 粉末X射线衍射、元素分析、高分辨投射电镜和拉曼光谱研究表明V2O3相与碳层共包覆于磷酸铁锂颗粒表面. 在V₂O₅的碳热还原反应后,碳含量明显降低,但石墨化程度未发生明显改变. 电化学测试结果表明少量V₂O₃显著改善了磷酸铁锂正极材料的倍率性能和高温循环性能,包含1%氧化钒的复合正极材料在0.2 C放电容量为167 mAh/g,5 C时放电容量为129 mAh/g,并且循环稳定性优异;在55 oC和1 C时放电容量为151 mAh/g,循环100次后无明显容量衰减.     

锂离子电池Sn-Ti合金负极材料的制备及性能研究

采用磁控溅射沉积技术制备了纳米级Sn-Ti合金负极材料,并用X射线衍射和扫描电子显微镜进行表征,用高精度电池测试系统进行充放电和循环伏安测试.结果表明先镀Sn后镀Ti（Sn/Ti复合膜）和先镀Ti后镀Sn（Ti/Sn复合膜）具有很大的性能差异,其中Sn/Ti复合膜具有优异的循环稳定性和较高的可逆容量.首次放电容量和充电容量分别为9275 mAh/g和6954 mAh/g,首次库仑效率为75％,经30次循环后,该电极的放电容量保持为4152 mAh/g,这主要归因于活性物质Sn与电解液界面之间存在非活 关键词： 锂离子电池 磁控溅射 Sn-Ti合金 电化学性能     

锂离子电池Sn-Al薄膜电极的制备及电化学性能研究

采用磁控溅射沉积技术制备了纳米级Sn-Al合金薄膜电极材料,并用X射线衍射和扫描电子显微镜进行表征,用高精度电池测试系统进行充放电和循环伏安测试.结果表明直流DC与射频RF两种不同的溅射方法制备的Sn-Al薄膜电极具有很大的性能差异,前者DC法制备的材料颗粒细小,表现出稳定的循环性能,其首次放电容量为1060 mAh/g,首次效率为71.7％,电极经过50次循环后比容量保持在700 mAh/g以上.后者RF法制备的材料颗粒较大,放电比容量开始上升,第五次循环后接着逐渐衰减,表现出较差的循环性能. 关键词： 锂离子电池 磁控溅射 Sn-Al合金 电化学性能     

锂离子电池LiMn1-xFexPO4(0<x<1)正极材料的制备及性能研究

本文采用固相法制备了纯相LiMn_1-xFe_xPO₄/C (x=0.2,0.4,0.6)正极材料,并用X射线衍射(XRD)和扫描电镜(SEM)进行表征,用高精度电池测试系统进行充放电和循环伏安测试.结果表明不同Mn和Fe原子比的电极材料具有很大的性能差异,其中当x=0.4时,材料具有优异的循环稳定性和较高的可逆容量.首次充电容量和放电容量分别达到141.5 mAh/g和125.7 mAh 关键词： 锂离子电池 固相法 1-xFe_xPO₄')" href="#">LiMn_1-xFe_xPO₄ 正极材料     

Co_2SnO_4/Graphene复合材料的制备与电化学性能研究

实验首先采用改进的Hummers法制备氧化石墨,然后以氧化石墨烯为前驱体,通过水热法将锡酸钴纳米颗粒均匀镶嵌在石墨烯薄膜基片上,最终获得Co2SnO4/Graphene镶嵌复合材料.采用X射线衍射(XRD)、扫描电子显微镜(SEM)对材料的结构和形貌进行表征,通过恒电流充放电(CC)、循环伏安法(CV)与交流阻抗法(EIS)测试了材料的电化学性能.实验结果表明,石墨烯良好的分散性及较高的电子导电率,可以提高锡酸钴材料的电化学性能,材料首次可逆容量达到1415.2 mA·h/g,50次循环后仍能保持469.7 mA·h/g的放电比容量.     

电泳法制备三维纳米硅/石墨烯锂离子电池负极材料

采用直流电泳技术制备了具有多孔结构的纳米硅/石墨烯三维复合材料,并探究了其作为锂离子电池负极的电化学特性.结果表明:通过控制电泳工艺可以获得硅纳米粒子分散较为均匀的三维复合材料.作为锂离子电池负极,在放电电流密度为100mA/g时,该类复合材料的面容量可达到5.5mAh/cm~2.     

不同气氛下裂解含苯环聚硅氧烷制备锂离子电池Si-O-C复合负极材料的电池性能研究

在惰性气氛Ar和还原性气氛H₂中通过高温裂解含苯环的聚硅氧烷分别制备了硅氧碳化物Si-O-C复合负极材料,并且采用了元素分析element analysis、广角粉末X射线衍射XRD、傅里叶激光拉曼光谱Raman等手段表征了二者组成和结构的差别.实验发现,在H₂气氛中裂解制备的Si-O-C复合负极含有较高的可逆、较低的不可逆容量,而且可逆容量随温度的增加而增长.其中H₂气氛中1000 ℃情况下制备的Si-O-C复合负极的可逆容量622 mAh/g,首次库仑效率59%.Si-O-C复合负极的不可逆容量与氧的含量相关,可逆容量可能与碳含量及碳结构,以及SiOC中硅的结构相关.在H₂气氛中制备的Si-O-C负极材料是一种潜在的锂离子电池的负极材料. 关键词： 硅氧碳化物 负极材料 锂离子电池     

氮掺杂石墨烯纳米片的制备及其电化学性能

以石墨片为原料,在氮气气氛下,通过机械针磨法制备了氮掺杂石墨烯纳米片.扫描电子显微镜和比表面积分析表明机械针磨过程可以有效地将大尺寸石墨片破碎成石墨烯纳米片.在石墨片的破碎过程中,会引起C—C键的破坏.因此,在破坏的边缘位置能够产生碳活性点.这些碳活性点可以与氮反应实现氮元素的掺杂.X射线光电子能谱分析表明碳活性点与氮反应使氮元素掺入石墨烯结构边缘,形成吡咯型氮和吡啶型氮.电化学阻抗谱分析表明所制备的氮掺杂石墨烯纳米片对I_3~-还原反应具有较高的电催化活性,循环伏安与恒流充放电测试表明氮掺杂石墨烯纳米片具有较好的电容性能.较高的比表面积和边缘氮掺杂结构是氮掺杂石墨烯纳米片具有优异电化学性能的主要原因.因此,氮掺杂石墨烯纳米片可以应用于染料敏化太阳能电池对电极和超级电容器电极.     

离子束辅助沉积硅薄膜负极材料的研究

采用离子束辅助沉积法制备了锂离子电池硅薄膜负极材料,研究了硅薄膜的晶体结构、表面形貌和电化学性能.研究结果表明：硅薄膜是非晶态的结构;非晶态硅薄膜发生嵌脱锂反应的电位分别为0.03 V与0.34 V和0.16 V与0.49 V;硅薄膜表现出很高比容量和充放电效率,其可逆比容量和库仑效率分别为3134.4 mAh/g和87.1％;硅薄膜具有优异的循环性能,在0.5C倍率下200次循环后容量保持率为92.2%. 关键词： 硅薄膜 离子束辅助沉积 锂离子电池 负极材料     

Density functional theory prediction for oxidation and exfoliation of graphite to graphene

A density functional theory (DFT) study of graphene synthesis from graphite oxidation and exfoliation is presented. The calculated DFT results for O adsorption predict CO as a most stable bond on the graphene oxide (GO) sheet. The obtained exfoliation energy for the graphene and the GO are 143 and ∼70 mJ/m² that verify easier exfoliation of the graphite oxide compared with the graphite. Furthermore, the DFT results show that for decreasing the exfoliation energy of the GO at least two layers of the graphite should be oxidized during the oxidation process.     

High Rate and Long Cycle Life of a CNT/rGO/Si Nanoparticle Composite Anode for Lithium‐Ion Batteries

Si nanoparticle (Si‐NP) composite anode with high rate and long cycle life is an attractive anode material for lithium‐ion battery (LIB) in hybrid electric vehicle (HEV)/pure electric vehicle (PEV). In this work, a carbon nanotube (CNT)/reduced graphene oxide (rGO)/Si nanoparticle composite with alternated structure as Li‐ion battery anode is prepared. In this structure, rGO completely wraps the entire Si/CNT networks by different layers and CNT networks provide fast electron transport pathways with reduced solid‐state diffusion, so that the stable solid‐electrolyte interphase layer can form on the whole surface of the matrix instead of on single Si nanoparticle, which ensure the high cycle stability to achieve the excellent cycle performance. As a result, the CNT/rGO/Si‐NP anode exhibits high performances with long cycle life (≈455 mAh g^?1 at 15 A g^?1 after 2000 cycles), high specific charge capacity (≈2250 mAh g^?1 at 0.2 A g^?1, ≈650 mAh g^?1 at 15 A g^?1), and fast charge/discharge rates (up to 16 A g^?1). This nanostructure anode with facile and low‐cost synthesis method, as well as excellent electrochemical performances, makes it attractive for the long life cycles at high rate of the next generation LIB applications in HEV/PEV.     

Effect of nickel coating on electrochemical performance of graphite anodes for lithium ion batteries

Among the different materials often studied and proposed as negative electrodes for lithium-ion batteries, graphite anodes are the most used in commercial batteries. For this study, synthetic graphite was tested. During the first discharge 0.2 Li ions were consumed for the formation of the SEI film and the capacity reaches about 387 mAh/g. But at the end of the first charge only 72% of the initial charge was recovered (the reversible capacity is about 279 mAh/g). In order to improve this performance we have deposited metallic nickel on graphite with the intention to obtain a homogeneous thin layer able to modify the nature of the SEI film, to allow the diffusion of lithium ions through the protective layer, and also to increase the performance of graphite electrodes. The results show a decrease of the irreversible capacity loss (16% instead of 28% for pure graphite electrodes) as well as better cycleability for a nickel-deposited graphite electrode with only 11% weight ratio of nickel. On the other hand, an increase of the nickel content decreases this performance.     

Structural and optical properties of thermally reduced graphene oxide for energy devices

Natural intercalation of the graphite oxide, obtained as a product of Hummer's method, via ultra-sonication of water dispersed graphite oxide has been carried out to obtain graphene oxide(GO) and thermally reduced graphene oxide(RGO).Here we report the effect of metallic nitrate on the oxidation properties of graphite and then formation of metallic oxide(MO) composites with GO and RGO for the first time. We observed a change in the efficiency of the oxidation process as we replaced the conventionally used sodium nitrate with that of nickel nitrate Ni(NO_3)_2, cadmium nitrate Cd(NO_3)_2,and zinc nitrate Zn(NO_3)_2. The structural properties were investigated by x-ray diffraction and observed the successful formation of composite of MO–GO and MO–RGO(M = Zn, Cd, Ni). We sought to study the effect on the oxidation process through optical characterization via UV-Vis spectroscopy and Fourier Transform Infrared(FTIR) spectroscopy.Moreover, Thermo Gravimetric Analysis(TGA) was carried out to confirm 90% weight loss in each process thus proving the reliability of the oxidation cycles. We have found that the nature of the oxidation process of graphite powder and its optical and electrochemical characteristics can be tuned by replacing the sodium nitrate(NaNO_3) by other metallic nitrates as Cd(NO_3)_2, Ni(NO_3)_2, and Zn(NO_3)_2. On the basis of obtained results, the synthesized GO and RGO may be expected as a promising material in antibacterial activity and in electrodes fabrication for energy devices such as solar cell, fuel cell,and super capacitors.     

Enhancement of electrochemical performance in lithium-ion battery via tantalum oxide coated nickel-rich cathode materials

Nickel-rich cathode materials are increasingly being applied in commercial lithium-ion batteries to realize higher specific capacity as well as improved energy density. However, low structural stability and rapid capacity decay at high voltage and temperature hinder their rapid large-scale application. Herein, a wet chemical method followed by a post-annealing process is utilized to realize the surface coating of tantalum oxide on LiNi_0.88Mn_0.03Co_0.09O₂, and the electrochemical performance is improved. The modified LiNi_0.88Mn_0.03Co_0.09O₂ displays an initial discharge capacity of ～ 233 mAh/g at 0.1 C and 174 mAh/g at 1 C after 150 cycles in the voltage range of 3.0 V-4.4 V at 45℃, and it also exhibits an enhanced rate capability with 118 mAh/g at 5 C. The excellent performance is due to the introduction of tantalum oxide as a stable and functional layer to protect the surface of LiNi_0.88Mn_0.03Co_0.09O₂, and the surface side reactions and cation mixing are suppressed at the same time without hampering the charge transfer kinetics.     

还原温度对氧化石墨烯结构及室温下H_2敏感性能的影响

以氧化石墨凝胶制备的氧化石墨烯(GO)溶胶为前驱体,在100—350℃温度下还原获得不同还原程度的还原氧化石墨烯(rGO)样品,并采用旋涂工艺制备还原氧化石墨烯气敏薄膜元件.采用X射线衍射、拉曼光谱、傅里叶变换红外光谱和气敏测试等手段研究还原温度对样品结构、官能团和气敏性能的影响.结果表明:经热还原处理的氧化石墨烯结构向较为有序的类石墨结构转变,还原温度为200℃时,样品处于GO向rGO转变的过渡阶段,还原温度达到250℃时,则表现出还原氧化石墨烯特性;无序程度随还原温度的升高先由0.85增大至1.59,随后减小至1.41,总体呈现增加趋势;氧化石墨烯表面含氧官能团随还原温度的升高逐渐热解失去,不同含氧官能团的失去温度范围不同;热还原氧化石墨烯具有优异的室温H_2敏感性能,随着还原温度的升高,元件灵敏度逐渐减小,响应-恢复时间逐渐增大,最佳灵敏度为88.56%,响应时间为30 s.     

Graphene‐Based Phosphorus‐Doped Carbon as Anode Material for High‐Performance Sodium‐Ion Batteries

Graphene‐based phosphorus‐doped carbon (GPC) is prepared through a facile and scalable thermal annealing method by triphenylphosphine and graphite oxide as precursor. The P atoms are successfully doped into few layer graphene with two forms of P–O and P–C bands. The GPC used as anode material for Na‐ion batteries delivers a high charge capacity 284.8 mAh g^?1 at a current density of 50 mA g^?1 after 60 cycles. Superior cycling performance is also shown at high charge?discharge rate: a stable charge capacity 145.6 mAh g^?1 can be achieved at the current density of 500 mA g^?1 after 600 cycles. The result demonstrates that the GPC electrode exhibits good electrochemical performance (higher reversible charge capacity, super rate capability, and long‐term cycling stability). The excellent electrochemical performance originated from the large interlayer distance, large amount of defects, vacancies, and active site caused by P atoms doping. The relationship of P atoms doping amount with the Na storage properties is also discussed. This superior sodium storage performance of GPC makes it as a promising alternative anode material for sodium‐ion batteries.     

Influence of graphite size on the synthesis and reduction of graphite oxides

We investigated the influence of the precursor, graphite, size on the synthesis and reduction of graphite oxide. Three precursors of graphite with different size were used to synthesize the graphite oxide which was consecutively reduced by hydrazine of different concentration ratios. Size dependent effect on the reduction of the graphite oxide was found, and the graphite oxide of the smallest size provided the best reduction result. Electrochemical properties of the reduced graphene oxide were investigated in both of the base and acid electrolytes, finding the reduced graphene oxide of the smallest size gives the best electrochemical performance due to the high reduction. Therefore, the precursor size is a very important factor in the synthesis and reduction of graphite oxide, affecting the electrochemical performance considerably for the energy storage applications.     

Study on the electrochemical performance of LiNi0.5Mn1.5O4 with different precursor

LiNi_0.5Mn_1.5O₄ cathodes were synthesized by three different raw materials at high temperature. The samples were characterized by X-ray diffraction and scanning electron microscopy tests, respectively. The results indicate that the synthesized samples show pure spinel structure, and the samples synthesized by nickel?Cmanganese hydrate and nickel?Cmanganese oxide show regular geometrical shape. The electrochemical performance of sample synthesized by nickel?Cmanganese oxide is best. The first discharge capacity is 141 mAh/g, and the capacity retention is 98.6% after 50 cycles at 0.5?C rate. The discharge capacity at 5?C rate is still 120 mAh/g. Better crystallization, smaller specific surface area, and lower polarization may be responsible for the excellent electrochemical performance of the LiNi_0.5Mn_1.5O₄.