Ag/Al2O3(Li2O)/g-C3N4光催化乙醇制取环氧乙烷

本文制备了一系列Ag/Al₂O₃(Li₂O)/g-C₃N₄复合催化剂,考察了其可见光催化乙醇制取环氧乙烷的性能。Li₂O可调变Al₂O₃表面的酸性,从而降低了主要副产物乙醛的选择性。Ag/Al₂O₃(Li₂O) 在g-C₃N₄上的负载量对产物环氧乙烷的选择性有较大影响,当Ag/Al₂O₃(Li₂O) 负载量为5wt%时,乙醇具有较高的转换率,且环氧乙烷的选择性高达100%。     

3D-functionalized carbon nanotube microsphere networks modified by 1-aminopyrene promote silicon anode with an enhanced cyclic performance for Li-ion batteries

Although silicon has higher theoretical specific capacity to meet the demand for higher energy density, its large volume expansion and low conductivity make the practical application of silicon anode difficult in the field of lithium-ion batteries. In this work, Si@(AP-AOCNTs) composites with uniform conductive network and pore structure are prepared by spray drying method. In the composite microspheres, silicon particles are embedded into the 3D interwoven network of 1-aminopyrene modified oxidized carbon nanotubes, which can not only buffer the volume expansion of silicon, but also ensure the effective transport of electrons and ions. This is demonstrated by the remarkable cycle life, and the electrode still has a reversible specific capacity of 939.3mAh/g after 975 cycles at 0.5A/g. Moreover, 97.3% of the initial capacity (at 0.5A/g) is still retained after the rate cycling, when the current density returns to 0.5A/g.     

铜基底上无黏结剂Co3V2O8多孔纳米片阵列的制备以及锂离子电池性能研究

直接在铜基底上生长具有不同金属离子的多孔过渡金属氧化物,成为有前途的锂离子电池电极材料的候选。本文提出了一种简便可行的低温水热沉积方法在铜基底上制备前驱物阵列。前驱物经过煅烧处理得到具有多孔特性Co₃V₂O₈纳米片阵列,多孔纳米片阵列用作锂离子电池负极材料显示出了长期循环稳定性和高倍率性能。在1.0 A/g电流密度下,电池经过240次循环后显示出1 010 mA∙h/g的容量;在3.0 A/g的电流密度下,电池循环600次后显示出552 mA∙h/g的可逆容量。     

Fabrication of layered structure VS4 anchor in 3D graphene aerogels as a new cathode material for lithium ion batteries

VS₄ has gained more and more attention for its high theoretical capacity (449 mAh/g with 3e⁻ transfer) in lithium ion batteries (LIBs). Herein, a layered structure VS₄ anchored in graphene aerogels is prepared and first reported as cathode material for LIBs. VS₄@GAs composite exhibits an exceptional high initial reversible capacity (511 mAh/g), an excellent high-rate capability (191 mAh/g at the 5 C), and an excellent cyclic stability (239 mAh/g after 15 cycles).     

A novel carbon-silicon composite nanofiber prepared via electrospinning as anode material for high energy-density lithium ion batteries

Electrospun carbon-silicon composite nanofiber is employed as anode material for lithium ion batteries. The morphology of composite nanofiber is optimized on the C/Si ratio to make sure well distribution of silicon particles in carbon matrix. The C/Si (77/23, w/w) nanofiber exhibits large reversible capacity up to 1240 mAh g⁻¹ and excellent capacity retention. Ex situ scanning electron microscopy is also conducted to study the morphology change during discharge/charge cycle, and the result reveals that fibrous morphology can effectively prevent the electrode from mechanical failure due to the large volume expansion during lithium insertion in silicon. AC impedance spectroscopy reveals the possible reason of unsatisfactory rate capability of the nanofiber. These results indicate that this novel C/Si composite nanofiber may has some limitations on high power lithium ion batteries, but it can be a very attractive potential anode material for high energy-density lithium-ion batteries.     

3D CNTs networks enable core-shell structured Si@Ni nanoparticle anodes with enhanced reversible capacity and cyclic performance for lithium ion batteries

Silicon, to be a potential anode material of LIBs, possesses a pretty high lithium storage capacity. However, the structural integrity can be destructed by its huge volume expansion through cycles, which results in a large capacity attenuation. Meanwhile, the poor electrochemical performance of silicon-based anodes can be attributed to its poor conductance which reduces the reaction kinetics. According to the above challenges, core-shell structured silicon-nickel nanoparticles have been dispersed on 3D intertwined carbon nanotube networks (Si@Ni-NP/CNTs) via nitric acid pre-treatment and amino functionalization. The nickel-plated shell outside silicon core nanoparticles (Si@Ni-NP) can play a certain supporting role to prevent the volume expansion of silicon, which finally brings down the degree of powdering. Especially, the 3D framework composed of intertwined carbon nanotubes can efficiently provide not only an ample buffer space during intercalation/deintercalation but also a more stable conductive network to increase ion/electron transfer rate. Due to the above improvements in structural stability and reaction kinetics, Si@Ni-NP/CNTs reveal a reversible capacity of 1008 mAh g^?1 with a 98% capacity retention over 100 cycles at a current density of 100 mA g^?1. Under different current densities in rate test, the specific capacity recovery rate can reach 92%. The novel structure enables Si@Ni-NP/CNTs excellent stability under cycles and various rates, as a promising anode material of LIBs.     

Electrochemical characteristics and cycle performance of LiMn2O4/a-Si microbattery

A LiMn₂O₄ thin film and an amorphous Si (a-Si) thin film were prepared by radio-frequency (rf) magnetron sputtering. Each thin film was electrochemically evaluated by cyclic voltammetry (CV) and galvanostatic cycling. The rate of capacity fade on cycling was monitored as a function of the voltage window and current density. This was compared with the cycle performance of cathode and anode using two kinds of electrolyte, 1 M LiPF₆ in EC/DMC and PC, for 100 cycles. It was found that the discharge capacity of optimized LiMn₂O₄/a-Si full-cell reached 24 μAh/(cm²-μm) in the first cycle, and a reversible capacity of about 16 μAh/(cm² μm) was still maintained after 100 cycles. In a voltage window of 3.0–4.2 V, LiMn₂O₄/a-Si full-cell exhibits relatively stable cycle performance compared to a voltage window of 2.75–4.2 V.     

Rb掺杂Li4Ti5O12作为锂离子电池负极材料的合成及电化学性能

合成了不同Rb掺杂量的钛酸锂（Li_4-xRb_xTi₅O₁₂; x = 0.010, 0.015, 0.020）作为锂离子电池的负极材料。测试结果显示,Rb离子掺杂有效增强了钛酸锂的电子电导率。相同的测试条件下,相比于未掺杂样品和高Rb含量掺杂样品（x = 0.015, 0.020）,适量的Rb掺杂钛酸锂（Li_3.99Rb_0.01Ti₅O₁₂; x = 0.010）表现出最优的电化学性能。Li_3.99Rb_0.01Ti₅O₁₂材料表现出161.2 mA∙h/g的初始容量,且在1 C下经过1000次循环后容量保持率可达90.9%。此外,全电池Li_3.99Rb_0.01Ti₅O₁₂ // LiFePO₄在0.5 C条件下首次放电容量为144 mA∙h/g,经过150次循环后,容量保持率为78.8%。     

石墨烯包封Na3V2(PO4)3用作钠离子电池负极材料的电化学性能探究

具有三维网络结构的NASICON型Na₃V₂(PO₄)₃材料,由于其稳定的电压平台,较高的理论容量(117 mA·h/g),被视为一种具有良好应用前景的钠离子电池负极材料。采用溶剂热和进一步热处理的方式,获得石墨烯包封Na₃V₂(PO₄)₃的复合材料[Na₃V₂(PO₄)₃/G],有效提高了Na₃V₂(PO₄)₃的电子导电性。在0.01～3.00 V电压区间,0.2 C倍率进行测试时,Na₃V₂(PO₄)₃/G复合材料在230圈循环后,其放电比容量保持在100.9 mA·h/g,容量保持率高达68.4%,即使在5 C倍率,其放电比容量仍可达65.2 mA...     

State-of-the-art progress in overall water splitting of carbon nitride based photocatalysts

Converting solar energy into hydrogen (H₂) by photocatalytic water splitting is a promising approach to simultaneously address the increasing energy demand and environmental issues. Half decade has passed since the discovery of photo-induced water splitting phenomenon on TiO₂ photoanode, while the solar to H₂ efficiency is still around 1%, far below the least industrial requirement. Therefore, developing efficient photocatalyst with a high energy conversion efficiency is still one of the main tasks to be overcome. Graphitic carbon nitride (g-C₃N₄) is just such an emerging and potential semiconductor. Therefore, in this review, the state-of-the-art advances in g-C₃N₄ based photocatalysts for overall water splitting were summarized in three sections according to the strategies used, and future challenges and new directions were discussed.     

Enhanced cycle performance of SiO-C composite anode for lithium-ion batteries

A silicon monoxide (SiO)-carbon composite prepared by ball-milling and pyrolysis is evaluated as an anode material for lithium-ion batteries. Electrochemical tests demonstrated that the first charge and discharge capacities of the material are about 1050 and 800 mAh g⁻¹, respectively, with a first-cycle efficiency of 76%. The disproportionation reaction of pure SiO into Si and SiO₂ during pyrolysis is confirmed by means of XRD and ²⁹Si MAS NMR. The cycle performance of this material shows an excellent reversible capacity retention of 710 mAh g⁻¹ over 100 cycles without any potential or capacity restrictions. This improved cycle performance is attributed to the stable microstructure, enhanced electrical contact afforded by the pyrolyzed carbon, and the amorphous phase transformation of the active material during cycling.     

A novel flower-like metal-based oxides with cross-linked networks for rapid lithium-ion storage

A cross-linked MnO₂ coated ZnFe₂O₄ hollow nanosphere composite is synthesized and controlled via a facial and handy route. The connected MnO₂ nanoplates form a cross-linked network, which is conducive to the rapid transfer of Li ions. The composite with unique architecture can not only release the strain and stress caused by the insertion and desertion of lithium ions but also greatly improve the electrical conductivity and lithium ion diffusivity. Consequently, when used as a lithium-ion battery anode material, the electrode shows an excellent initial reversible capacity of 933.5 mAh/g with an initial coulombic efficiency of 62.5%. After 100 cycles, the reversible capacity stabilized at 605.6 mAh/g with a high capacity retention of 91% from the 20th cycle to the 100th cycle. At a high current density of 3 A/g, an excellent capacity of 390.6 mAh/g can be retained. In this case, the electrode shows broad application prospects for novel power storage systems.     

一种分散在多孔碳上的碳包覆硅负极的制备及应用

硅负极具有高比容量的显著优势,其理论比容量（4 200 mA∙h/g）达到传统石墨负极的10倍以上,被认为是锂离子电池最有潜力的负极之一。然而,硅负极存在导电性较差、充放电过程中体积膨胀巨大等诸多问题,导致其循环性能较差,限制了大规模实际应用。本文提供了一种高性能硅负极的制备方法及应用,通过将硅负极分散在多级孔碳中,连同黏结剂聚丙烯腈涂覆在集流体上,再对极片进行热处理实现聚丙烯腈碳包覆,有效提高电极的整体导电性并能为巨大的体积变化提供空间,从而提升硅负极的大倍率性能和循环稳定性。     

Facile controlled synthesis of hierarchically structured mesoporous Li4Ti5O12/C/rGO composites as high-performance anode of lithium-ion batteries

In this paper, a facile strategy is proposed to controllably synthesize mesoporous Li₄Ti₅O₁₂/C nanocomposite embedded in graphene matrix as lithium-ion battery anode via the co-assembly of Li₄Ti₅O₁₂ (LTO) precursor, GO, and phenolic resin. The obtained composites, which consists of a LTO core, a phenolic-resin-based carbon shell, and a porous frame constructed by rGO, can be denoted as LTO/C/rGO and presents a hierarchical structure. Owing to the advantages of the hierarchical structure, including a high surface area and a high electric conductivity, the mesoporous LTO/C/rGO composite exhibits a greatly improved rate capability as the anode material in contrast to the conventional LTO electrode.     

有机溶剂浸泡法回收再利用锂离子电池钛酸锂负极材料

利用有机溶剂法回收了废旧锂离子电池中的钛酸锂负极材料,并对回收的钛酸锂材料的结构、形貌和电化学性能进行了测试。XRD结果表明,材料除炭后添加适量锂源进一步合成得到的产物具有尖晶石结构,且不含其他的杂质。SEM图像显示,其颗粒分布均匀、无团聚现象。EIS结果表明,最终回收的钛酸锂电极材料比未添加锂源进行煅烧处理的材料具有较小的电荷转移阻抗和较高的锂离子扩散系数。在0.1 C倍率下,经过100次循环后其容量保持率为92.4%,具有优异的循环稳定性和可逆性,可以实现循环利用。     

Si–SiC nanocomposite anodes synthesized using high-energy mechanical milling

The Si–SiC nanocomposites were synthesized by high-energy mechanical milling (HEMM) using two different starting mixtures, Si:SiC=1:2 and Si:C=3:2. Both mixtures result in amorphous silicon and nanocrystalline silicon carbide as confirmed by XRD results. The Si–SiC nanocomposite corresponding to Si:SiC=1:2 obtained after milling for 30 h shows a capacity as high as 370 mAh/g. The nanocomposite synthesized using HEMM for 24 h from a mixture corresponding to Si:C=3:2 also exhibits a stable capacity of 370 mAh/g. Transmission electron microscopy (TEM) analysis shows that SiC nanocrystallites 10 nm in size are distributed homogeneously within the nanocomposite. Electron energy-loss spectroscopy (EELS) maps of C suggests that SiC is uniformly present within the particles.     

锂离子电池硅基负极黏结剂研究进展

硅在自然界中储量丰富,其理论比容量高达4 200 mA∙h/g,已成为高能量密度锂离子电池负极材料的研究热点。但是Si作为负极材料也存在许多不足,最大的问题是电池充放电过程中,硅体积膨胀（高达300%）,导致Si基负极材料粉化脱落、电池容量迅速衰减,其循环性能尚难以满足实际需求。通过研究开发硅基负极专用黏结剂材料,可以有效抑制循环过程中硅的体积变化,维持硅负极结构稳定,提升电池循环性能。本文综述了近年来硅基负极黏结剂材料的研究进展,主要从合成高分子聚合物黏结剂、天然高分子聚合物黏结剂、导电高分子聚合物黏结剂三个方面进行详细归纳总结,并介绍了本课题组在硅基负极黏结剂方面的部分研究成果,期望能为将来的硅基负极专用黏结剂的研究和应用提供一些思路。     

Gamma-ray radiation on P-doped Si nanoparticles towards the Li+-storage performances

The high theoretical capacity of Si makes it a promising anode material for lithium ion batteries. However, the poor electrical conductivity and large volume expansion during lithiation/delithiation hinders its electrochemical performances. Herein, we report a γ irradiation treatment method to prepare P-doped Si nanoparticles. The sample exhibits a capacity of 1698 mAh/g at 0.1 C rate after 100 cycles, which is about 3 times larger than that of undoped Si. The rate performance of γ irradiated P-doped Si is also highly improved when compared to P-doped Si without γ irradiation treatment. The enhanced performance can be attributed that γ irradiation can facilitate the phosphorus doping into Si lattice, which can enhance the electrical conductivity of Si.     

A mini-review of ferrites-based photocatalyst on application of hydrogen production

Photocatalytic water splitting for hydrogen production is a promising strategy to produce renewable energy and decrease production cost. Spinel-ferrites are potential photocatalysts in photocatalytic reaction system due to their room temperature magnetization, the high thermal and chemical stability, narrow bandgap with broader visible light absorption, and proper conduction band energy level with strong oxidation activity for water or organic compounds. However, the fast recombination of the photoexcited electrons and holes is a critical drawback of ferrites. Therefore, the features of crystallinity, particle size, specific surface area, morphology, and band energy structure have been summarized and investigated to solve this issue. Moreover, composites construction with ferrites and the popular support of TiO₂ or g-C₃N₄ are also summarized to illustrate the advanced improvement in photocatalytic hydrogen production. It has been shown that ferrites could induce the formation of metal ions impurity energy levels in TiO₂, and the strong oxidation activity of ferrites could accelerate the oxidation reaction kinetics in both TiO₂/ferrites and g-C₃N₄/ferrites systems. Furthermore, two representative reports of CaFe₂O₄/MgFe₂O₄ composite and ZnFe₂O₄/CdS composite are used to show the efficient heterojunction in a ferrite/ferrite composite and the ability of resistance to photo-corrosion, respectively.     

Research progress on Si/C composites as anode for lithium ion batteries

硅基负极材料具有比容量高、电压平台低、环境友好、资源丰富等优点,有望替代石墨负极应用于下一代高比能锂离子电池。但是硅的导电性较差,且在充放电过程中存在巨大的体积效应,极易导致电极极化、材料粉化、SEI膜重构、库仑效率低和容量持续衰减。硅和碳复合能很好地综合两者的优势,形成结构稳定、循环性好及容量高的负极材料。本文从不同维度的硅（SiNPs、SiNTs/SiNWs、SiNFs、Bulk Si）与碳复合这一角度,综述了硅碳复合材料在结构设计、制备工艺、电化学性能等方面的最新研究进展,并对未来的硅碳复合材料的研究工作进行了展望。