Synthesis and electrochemical characterization of carbon spheres as anode material for lithium-ion battery

Carbon spheres were synthesized by the thermal decomposition of RF precursor which was synthesized by surfactant-assisted polycondensation of resorcinol with formaldehyde. The morphology of precursor was preserved during the decomposition process. EDS, TG, SEM, CV and galvanostatic charge-discharge methods are used to characterize the composition, morphology, and electrochemical performance of carbon spheres. The results revealed that these carbon spheres had a spherical morphology, smooth surface and probable size of about 400 nm. When the carbon spheres were used as anode materials for lithium-ion battery, they exhibited a high lithium storage capacity and good cycle performance. In addition, the possible progress for the preparation of carbon spheres was proposed.     

高性能自支撑不锈钢网@MoS2锂离子电池负极材料

为了提高MoS₂作为Li离子电池负极材料整体的导电性和稳定性,将纳米化的MoS₂与其它导电性好的材料进行复合,通过水热法在导电基底不锈钢网(Stainless steel net, SS)上原位合成了一层MoS₂纳米花,制备了无粘结剂的自支撑结构的SS@MoS₂负极材料。纳米花状的MoS₂和导电性优异的SS提高了电子和Li离子的扩散速率,同时改善了电极的反应动力学。当作为Li离子电池负极材料时,SS@MoS₂电极表现出优异的储Li性能,特别是具有显著的大倍率充放电性能,即在1 000 mA/g的大电流密度下循环600次,比容量仍保持在862.1 mA·h/g。      

新型锡/碳复合材料的制备及其用于锂离子电池负极材料的研究

以煤焦油和SnCl2为原料,采用液相分散和碳热还原的方法制备了一种新型的锡/碳(Sn/C)复合材料.采用XRD、SEM及TEM手段对复合材料进行了结构表征,并对材料的电化学性能进行了检测.结果表明,金属锡以200nm大小的颗粒分散在碳材料中,复合材料的首次放电容量在371mAh·g-1,循环50次后比容量维持在305mAh·g-1以上,具有优异的循环性能.     

Structure and electrochemical performance of ZnO/CNT composite as anode material for lithium-ion batteries

Metal oxides are well-known potential alternatives to graphite as anode materials of lithium-ion batteries, and they can deliver much higher reversible capacities than graphite even at high current densities. In this study, hexagonal disk-shaped ZnO are synthesized by a facile solution reaction of ZnCl₂ and its composite is prepared in the presence of carbon nanotubes (CNTs). The as prepared ZnO/CNT composite has been characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, fourier transform-infrared spectroscopy and Rutherford backscattering spectroscopy. Electrochemical characterization by cyclic voltammetry, electrochemical impedance spectroscopy, and galvanostatic discharge/charge tests demonstrate that the conversion reactions in ZnO and ZnO/CNT electrodes enable reversible capacity of 478 and 602 mAh g^?1, respectively for up to 50 cycles. Our investigation highlights the importance of anchoring of small ZnO particles on CNTs for maximum utilization of electrochemically active ZnO and CNTs for energy storage application in lithium-ion batteries.     

优化碳质涂层以消除高性能硅阳极的电化学界面极化

有序碳和无序碳都普遍被用作硅(Si)的复合材料。但是具有不同结晶度和孔结构的碳对硅基负极电化学性能的影响仍存在争议。本工作在严格控制碳含量和表面官能团的基础上,选择沥青(Pitch)和酚醛树脂(PR)作为有序碳和无序碳的前驱体,制备了硅碳复合材料(Si@C)并系统地研究了其电化学行为。有序的晶体结构有利于复合物中的电子传输,中孔和大孔有利于锂离子的扩散。具有有序结构和小孔容的碳质涂层为Si的膨胀提供了很好的缓冲,电极在50次循环后仍保持结构完整性。然而,无序和多孔的结构降低了结构的稳定性并产生了很大的极化,这使得循环过程中体积不断膨胀,导致电化学性能较差。Si@C-Pitch在5 A g^?1下的容量是Si@C-PR的8倍,在0.5 A g^?1下100次循环后的容量保持率是Si@C-PR的1.9倍。该研究可为Si@C负极中炭材料的选择提供了理论指导。     

Facile synthesis and electrochemical properties of porous SnO2 micro-tubes as anode material for lithium-ion battery

Porous SnO₂ micro-tubes were synthesized by the thermal decomposition of SnC₂O₄ precursor. The morphology of SnC₂O₄ could be preserved after the controlled heat treatment and a lot of mesopores left due to the release of gases. The mesoporous nature with a range of 3-50 nm was characterized by BET method. SEM images showed that the obtained SnO₂ samples were rhombic tube-like with swallow-tailed nozzles. When the porous SnO₂ micro-tubes were used as anode materials for lithium-ion battery, they exhibited high lithium storage capacity and coulomb efficiency. In addition, CV results demonstrated that the formation of Li₂O at high voltage was partially reversible reactions.     

Graphene and cobalt phosphide nanowire composite as an anode material for high performance lithium-ion batteries

The synthesis of a composite of cobalt phosphide nanowires and reduced graphene oxide (denoted CoP/RGO) via a facile hydrothermal method combined with a subsequent annealing step is reported. The resulting composite presents large specific surface area and enhanced conductivity, which can effectively facilitate charge transport and accommodates variations in volume during the lithiation/de-lithiation processes. As a result, the CoP/RGO nanocomposite manifests a high reversible specific capacity of 960 mA·h·g^–1 over 200 cycles at a current density of 0.2 A·g^–1 (297 mA·h·g^–1 over 10,000 cycles at a current density of 20 A·g^–1) and excellent rate capability (424 mA·h·g^–1 at a current density of 10 A·g^–1).

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Silicon lithium-ion battery anode with enhanced performance: Multiple effects of silver nanoparticles

Silicon has been regarded as one of the most promising next generation lithium-ion battery anode. However, the poor cyclic stability of the Si based anode has severely limited its practical applications, which is even worse with high mass loading density (>1?mg?cm^?2). A new concept has been developed to enhance the electrochemical performance of the Si nanoparticle anode. Silver nanoparticles are composited with the silicon nanoparticles in a facile way for the first time. It is found that the mechanical properties of the Si electrode have been significantly improved by the incorporation of the silver nanoparticles, leading to enhanced cyclic performance. With the Si/Ag mass ratio of 4:1, the reversible specific discharge capacity is retained as 1156?mA?h?g^?1 after 100 cycles at 200?mA?g^?1, which is more than three times higher than that of the bare silicon (318?mA?h?g^?1). The rate performance has been effectively improved as well due to excellent electron conductivity of the silver nanoparticles.     

机械合金化法制备锂离子电池Si基负极材料及其电化学性能研究

Si具有高的储锂容量,但是其循环性能很差。采用机械合金化方法,对纯Si进行处理。同时以石墨、炭黑对纯Si进行掺杂以改善Si的循环特性。对于纯Si,随着球磨时间的延长,材料的非晶化程度增加;经过球磨后材料的平均粒径由原来的29μm变成0.2μm;由大的块状变为小的圆形颗粒。充放电结果表明未经球磨处理的纯Si的首次放电比容量较高,但放电比容量损失较大,循环性能差,而经过球磨的纯Si能增加首次放电比容量,循环性能变化不大;对纯Si采用石墨、炭黑掺杂后材料的首次放电比容量下降,循环性能有所提高;球磨和掺杂没有改变Si储锂的电位。经过阻抗分析发现,球磨后纯Si材料中Li的扩散系数增大。     

Two-dimensional metallic BP as anode material for lithium-ion and sodium-ion batteries with unprecedented performance

Improving the storage capacities of electrode materials is one of the most critical points for ion batteries. Two-dimensional (2D) topological semimetals with high carrier mobility are naturally suitable as electrode materials. Herein, using the first-principle calculations, 2D BP monolayer with Dirac-type band structure is predicted to be a superior anode material with ultrahigh capacity for both Li/Na-ion batteries. The BP monolayer remains metallic after the adsorption of Li/Na ions, ensuring a good conductivity. Furthermore, BP owns low diffusion barriers (0.35 eV for Li ions and 0.16 eV for Na ions) and a moderate lattice change (3%) during the process of charging and discharging. Remarkably, the storage capacity of monolayer BP is enhanced to 1924 mAh/g by multilayer adsorption of both Li/Na ions, much higher than those of most previous 2D anode materials. All these characteristics strongly suggest that BP has great potential as a superior anode material in Li/Na-ion batteries.

     

纳米Li2MnSiO4正极材料的高压水热法制备及其电化学特性

采用高压水热法制备锂离子电池正极材料Li 2MnSiO 4,研究压强、反应温度和前驱体浓度对合成Li 2MnSiO 4的影响,并进一步研究碳包覆前后Li 2MnSiO 4的电化学性能。通过X射线衍射、扫描电镜、透射电镜、充放电测试和交流阻抗等方法对样品的结构、形貌和电化学性能进行表征分析。结果表明:采用水热法在高压高温条件下可以合成高纯度的Li 2MnSiO 4材料,提高前驱体浓度有助于形成粒径较小的Li 2MnSiO 4纳米颗粒。电化学性能测试显示碳包覆后的 Li 2MnSiO 4/C比Li 2MnSiO 4具有更高的比容量,在0.1C (电流密度为33.3mA·g -1 )下首次放电比容量可达178.6mAh·g -1 ,循环50次后放电比容量为97.1mAh·g -1 ,容量保持率为54.4%。同时,Li 2MnSiO 4/C还具有比Li 2MnSiO 4更小的电荷转移阻抗和更高的锂离子扩散系数。     

Ag-Sb composite prepared by chemical reduction method as new anode materials for lithium-ion batteries

Ag-Sb composite anode was prepared by chemical reductive method. The structure, morphology, chemical composition and electrochemical properties of synthesized Ag-Sb composite anode were evaluated by XRD, FE-SEM, EDS and galvanostatical charge-discharge tests. The results indicated that the changes of structure and volume were alleviated effectively by using metal phase instead of intermetallic phase and restraining the lithiation reaction of Ag at high current density (0.2 mA cm⁻²). The electrochemical reactions took place in a stable and highly conductive Ag framework, which ensured the good cyclability of the Ag-Sb composite electrode.     

Double diamond structured bicontinuous mesoporous titania templated by a block copolymer for anode material of lithium-ion battery

Titania has received considerable attention as a promising anode material of Li-ion battery(LIB).Controlling the structure and morphology of titania nanostructures is crucial to govern their performance.Herein,we report a mesoporous titania scaffold with a bicontinuous shifted double diamond(SDD)structure for anode material of LIB.The titania scaffold was synthesized by the cooperative self-assembly of a block copolymer poly(ethylene oxide)-block-polystyrene template and titanium diisopropoxide bis(acetylacetonate)as the inorganic precursor in a mixture solvent of tetrahydrofuran and HCl/water.The structure shows tetragonal symmetry(space group I4₁/amd)comprising two sets of diamond networks adjoining each other with the unit cell parameter of a=90 nm and c=127 nm,which affords the porous titania a specific surface area(SSA)of 42 m²·g^-1with a mean pore diameter of 38 nm.Serving as an anode material of LIB,the bicontinuous titania scaffold exhibits a high specific capacity of 254 mAh·g^-1at the current density of 1 A·g^-1and an alluring self-improving feature upon charge/discharge over 1,000 cycles.This study overcomes the difficulty in building up ordered bicontinuous functional materials and demonstrates their potential in energy storage application.     

Nano-sized SnSbAgx alloy anodes prepared by reductive co-precipitation method used as lithium-ion battery materials

Nano-sized SnSbAgx alloy anode materials are prepared by reductive co-precipitation method combining with the aging treatment in water bath at 80 degrees C. The microstructure, morphology and electrochemical properties of synthesized SnSbAgx alloy powders are evaluated by X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), galvanostatical cycling tests and electrochemical impedance spectroscopy (EIS). The XRD results indicate that the phases are composed of beta-Sn, Sb, Ag3Sb, Ag3Sn and SnSb in the SnSbAgx alloy. The existence of inactive element Ag and the complex multi-step reaction mechanism in SnSbAgx alloy anodes are propitious to improve the structure stability and thus improve the cycling performance. When cycled at a constant current density of 0.1 mA cm(-2) between 0.1 and 1.50 V, SnSbAg alloy shows better performance that the first discharge capacity is 794 mAh g(-1) and the reversible capacity of 20th cycle attains to 327 mAh g(-1). EIS results show that the semicircle relates to the passivation on the surface in the higher frequency zone and the bias relates to the diffusion in the lower frequency zone.     

Effect of reaction temperature on carbon films prepared by a hydrothermal electrochemical method

Carbon films were synthesized under hydrothermal electrochemical conditions using sugar as the carbon source at temperature ranging from 170 °C to 180 °C. The reaction temperature affects the degree of sugar decomposition, the concentration of carbon ions, supersaturation and overpotential of the solution, thereby affecting the morphology, orientation, and crystallinity of the films. The graphitic content (sp²) increases with increasing the processing temperature and vice versa. The higher the synthesizing temperature the less the amount of amorphous carbon (sp³). The graphite in thin films prepared at 170 °C and 175 °C shows a (101) preferred orientation, whereas those prepared at 180 °C show a fairly random orientation. The mechanism of this synthesizing process seems to consist of three stages.     

二氧化锡中空球的制备及其电化学性能研究

用碳球做模板,SnCl_4·5H_2O和尿素为前驱体制备了二氧化锡(SnO_2)中空球.X射线衍射(XRD)、扫描电镜(SEM)和高分辨透射电镜(HRTEM)结果表明:制备出来的SnO_2中空球为四方相结构,其直径和壁厚分别约为250nm和40nm.恒电流充放电测试结果显示:在电流密度为160mAh·g~(-1)(0.20时,该SnO_2中空球的首次放电容量为1720mAh·g~(-1),第15周期放电容量保持到615mAh·g~(-1);从第4周期开始,库仑效率均保持在90%以上.电流密度为320mAh·g~1(0.4C)时,第15周期放电容量保持到588mAh·g~(-1).以上结果表明,这种材料具有较高的储锂容量和较好的可逆性能,是一种有前景的锂离子电池负极材料.     

A carbon-covered silicon material modified by phytic acid with 3D conductive network as anode for lithium-ion batteries

The requirement for silicon-based anode material is growing and has received attentions. Silicon is a promising anode material for lithium-ion batteries due to the high theoretical capacity. However, the high volumetric variability of silicon has led to severe chalking and rapid capacity degradation. To ameliorate these problems, a carbon-covered silicon material with a 3D conductive network structure was prepared employing glucose and phytic acid as carbon sources. When acted as the anode for Lithium-ion batteries, the prepared composite material delivered 1612 mAh/g in the first cycle and approximately 600 mAh/g at 0.1 A/g after 200 cycles. In addition, even at 5 A/g, a high capacity of 503 mAh/g was reached, and when recovered to 0.1 A/g, the capacity of 878 mAh/g was maintained.     

One-step preparation of six-armed Fe3O4 dendrites with carbon coating applicable for anode material of lithium-ion battery

Six-armed Fe₃O₄ dendrites with carbon coating were synthesized by a simple one-step reaction between ferrocene and urea at 550 °C. Electron microscopy examinations indicate the formation of large numbers of Fe₃O₄ dendrites with mutually vertical arms and uniform carbon shells. Electrochemical measurement demonstrates that the dendrites using as anode materials for lithium-ion battery exhibit an initial capacity of 658 mAh g^? 1 and a reversible capacity of 473 mAh g^? 1 after 100 cycles at a rate of C/10, as well as a high cycling efficiency of 97% after the forth cycle. The formation mechanism of the six-armed dendrites was also discussed.     

Synthesis of anode active material particles for lithium-ion batteries by surface modification via chemical vapor deposition and their electrochemical characteristics

The high capacity and optimal cycle characteristics of silicon render it essential in lithium-ion batteries. We have attempted to realize a composite material by coating individual silicon (Si) particles of μm-order diameter with a silicon oxide film to serve as an active material in the anode of a lithium-ion battery and thus improve its charge-discharge characteristics. The particles were coated using an inductively coupled plasma-chemical vapor deposition (ICP-CVD) process that realized a homogeneously coated silicon oxide film on each Si particle. The film was synthesized using tetraethyl orthosilicate (TEOS) with hydrogen (H₂) gas used as a reducing agent to deoxidize the silicon dioxide. This enabled the control of the silicon oxidation number in the layers produced by adjusting the H₂ flow during the silicon oxide deposition by ICP-CVD. The silicon oxide covering the Si particles included both silicon monoxide and suboxide, which served to improve the charge-discharge characteristics. We succeeded in realizing an active material using Si, which is abundant in nature, for the anode of a lithium-ion battery with highly charged, improved cycle properties.