Nickel oxide nanotubes: synthesis and electrochemical performance for use in lithium ion batteries

Uniform and aligned Nickel Oxide (NiO) nanotube bundles have been synthesized by a template process. Individual nanotubes are 60 microm long with a 200 nm outer diameter and wall thickness of 20-30 nm. The synthesis involved forming Ni(OH)2 nanotubes that were subsequently heated to 350 degrees C in order to fully convert the product to NiO nanotubes. NiO nanotube powder was used in lithium-ion cells for assessment of lithium storage ability and electrochemical performance. Discharge capacity of the NiO nanotube electrode was in excess of 30% higher than that of the standard NiO nanocrystalline powder electrode after 20 cycles. Impedance data suggests the NiO nanotube electrode provides more controlled and sustainable Li diffusion when compared to the NiO reference powder electrode system.     

Hollow iron oxide nanoparticles for application in lithium ion batteries

Material design in terms of their morphologies other than solid nanoparticles can lead to more advanced properties. At the example of iron oxide, we explored the electrochemical properties of hollow nanoparticles with an application as a cathode and anode. Such nanoparticles contain very high concentration of cation vacancies that can be efficiently utilized for reversible Li ion intercalation without structural change. Cycling in high voltage range results in high capacity (～132 mAh/g at 2.5 V), 99.7% Coulombic efficiency, superior rate performance (133 mAh/g at 3000 mA/g) and excellent stability (no fading at fast rate during more than 500 cycles). Cation vacancies in hollow iron oxide nanoparticles are also found to be responsible for the enhanced capacity in the conversion reactions. We monitored in situ structural transformation of hollow iron oxide nanoparticles by synchrotron X-ray absorption and diffraction techniques that provided us clear understanding of the lithium intercalation processes during electrochemical cycling.     

Electrospun carbon-tin oxide composite nanofibers for use as lithium ion battery anodes

Composite carbon-tin oxide (C-SnO(2)) nanofibers are prepared by two methods and evaluated as anodes in lithium-ion battery half cells. Such an approach complements the long cycle life of carbon with the high lithium storage capacity of tin oxide. In addition, the high surface-to-volume ratio of the nanofibers improves the accessibility for lithium intercalation as compared to graphite-based anodes, while eliminating the need for binders or conductive additives. The composite nanofibrous anodes have first discharge capacities of 788 mAh g(-1) at 50 mA g(-1) current density, which are greater than pure carbon nanofiber anodes, as well as the theoretical capacity of graphite (372 mAh g(-1)), the traditional anode material. In the first protocol to fabricate the C-SnO(2) composites, tin sulfate is directly incorporated within polyacrylonitrile (PAN) nanofibers by electrospinning. During a thermal treatment the tin salt is converted to tin oxide and the polymer is carbonized, yielding carbon-SnO(2) nanofibers. In the second approach, we soak the nanofiber mats in tin sulfate solutions prior to the final thermal treatment, thereby loading the outer surfaces with SnO(2) nanoparticles and raising the tin content from 1.9 to 8.6 wt %. Energy-dispersive spectroscopy and X-ray diffraction analyses confirm the formation of conversion of tin sulfate to tin oxide. Furthermore, analysis with Raman spectroscopy reveals that the additional salt soak treatment from the second fabrication approach increases in the disorder of the carbon structure, as compared to the first approach. We also discuss the performance of our C-SnO(2) compared with its theoretical capacity and other nanofiber electrode composites previously reported in the literature.     

Electrochemical performance of modified synthetic graphite for lithium ion batteries

The carbon-coated composite has been manufactured and investigated as the negative electrode for Li-ion batteries. The carbon-coated composite powders are prepared by a simple mixing of two types of synthetic graphite particles (SFG6 and SFG44) with polyvinylchloride powders and heating to a temperature between 800 and 1100°C under an argon gas flow.As a result of the carbon-coating treatment, the flake particles of the original graphites changed into a bulky shape of carbon-coated composite with a largely increased particle size due to aggregation through the treatment. It is shown that carbon-coated composite electrodes for the two types of graphite have much lower irreversible loss than the original graphites and coulombic efficiency of 91% in the first cycle in a PC-based electrolyte. The carbon coating treatment improves the cycling performance. Despite their coarse morphology due to aggregation, carbon-coated composite electrodes show the enhanced high rate capabilities.     

Hydrogenated vanadium oxides as an advanced anode material in lithium ion batteries

Current research on vanadium oxides in lithium ion batteries (LIBs) considers them as cathode materials, whereas they are rarely studied for use as anodes in LIBs because of their low electrical conductivity and rapid capacity fading. In this work, hydrogenated vanadium oxide nanoneedles were prepared and incorporated into freeze-dried graphene foam. The hydrogenated vanadium oxides show greatly improved charge-transfer kinetics, which lead to excellent electrochemical properties. When tested as anode materials (0.005–3.0 V vs. Li/Li⁺) in LIBs, the sample activated at 600 °C exhibits high specific capacity (～941 mA·h·g^?1 at 100 mA·g^?1) and high-rate capability (～504 mA·h·g^?1 at 5 A·g^?1), as well as excellent cycling performance (～285 mA·h·g^?1 in the 1,000^th cycle at 5 A·g^?1). These results demonstrate the promising application of vanadium oxides as anodes in LIBs.

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Hierarchical 3D mesoporous silicon@graphene nanoarchitectures for lithium ion batteries with superior performance

Silicon has been recognized as the most promising anode material for high capacity lithium ion batteries. However, large volume variations during charge and discharge result in pulverization of Si electrodes and fast capacity loss on cycling. This drawback of Si electrodes can be overcome by combination with well-organized graphene foam. In this work, hierarchical three-dimensional carbon-coated mesoporous Si nanospheres@graphene foam （C@Si@GF） nanoarchitectures were successfully synthesized by a thermal bubble ejection assisted chemical-vapor-deposition and magnesiothermic reduction method. The morphology and structure of the as-prepared nanocomposites were characterized by field emission scanning electron microscopy, transmission electron microscopy and Raman spectroscopy. When employed as anode materials in lithium ion batteries, C@Si@GF nanocomposites exhibited superior electrochemical per- formance including a high specific capacity of 1,200 mAh/g at the current density of 1A/g, excellent high rate capabilities and an outstanding cyclability. Post-mortem analyses identified that the morphology of 3D C@Si@GF electrodes after 200 cycles was well maintained. The synergistic effects arising from the combination of mesoporous Si nanospheres and graphene foam nanoarchitectures may address the intractable pulverization problem of Si electrode.     

High performance of LiFePO4 with nitrogen-doped carbon layers for lithium ion batteries

Herein, we demonstrate a facile approach to fabricate a cathode material of LiFePO₄ with nitrogen-doped carbon layers by applying egg white as both carbon source and nitrogen sources. The nitrogen doped carbon layers are in situ coated on the LiFePO₄ particles, which effectively improves the electrical conductivity of rapid Li-ion diffusion. When evaluated as a cathode material for lithium ion batteries (LIBs), LiFePO₄ material with nitrogen doped carbon shows high capacities of 164 mA h g⁻¹ at 0.1 C, 144 mA h g⁻¹ at 1 C and 120 mA h g⁻¹ at 5 C. The result implies that such novel LiFePO₄ material is a potential cathode material for LIBs.     

Improved electrochemical performance of LiCoPO4 nanoparticles for lithium ion batteries

Single phase LiCoPO4 nanoparticles were synthesized by solid-state reaction. LiCoPO4/Li batteries were fabricated in an argon-filled glove box, and their electrochemical properties were analyzed by cyclic voltammetry (CV) and charge-discharge tests. The structural performance of LiCoPO4 nanoparticles was investigated by X-ray diffraction (XRD) and scanning electron microscope (SEM). The XRD result demonstrated that LiCoPO4 nanoparticles had an orthorhombic olivine-type structure with a space group of Pmnb. The charge-discharge tests indicated that the initial discharge capacity and coulombic efficiency of LiCoPO4/Li batteries were 110 mA h/g and 48% in cut-off voltage range of 3.0-5.3 V, 90 mA h/g and 54% in cut-off voltage range of 3.0-5.1 V, 70 mA h/g and 60% in cut-off voltage range of 3.0-5.0 V, respectively. After 30 cycles, the coulombic efficiency was 78% for 3.0-5.3 V, 88% for 3.0-5.1 V, 91% for 3.0-5.0 V, respectively. These results indicated that the coulombic efficiency of LiCoPO4/Li battery increased upon cycling and upon decreasing in charge upper limit voltage, respectively.     

Layered iron orthovanadate microrods as cathode for lithium ion batteries with enhanced cycle performance

Iron orthovanadate microrods with layered structure have been synthesized by a simple hydrothermal method. The composition and structure of the microrods were investigated by X-ray powder diffraction, thermogravimetric analysis, X-ray photoelectron spectroscopy, scanning electron microscopy and transmission electron microscopy. Electrochemical measurements indicated that the microrods maintained high capacity when used as lithium ion battery cathode. As-obtained iron orthovanadate microrods electrode exhibits a stable and reversible capacity of over 250 mAh g⁻¹ at 16 mA g⁻¹ between 1.6 V and 4.7 V after 15 cycles. Detailed investigations reveal that the layered structure may reduce the lithium ion diffusion path and be helpful for stable capacity.     

Rationally designed carbon-coated Fe304 coaxial nanotubes with hierarchical porosity as high-rate anodes for lithium ion batteries

Fe3O4 is a promising high-capacity anode material for lithium ion batteries, but challenges including short cycle life and low rate capability hinder its widespread implementation. In this work, a well-defined tubular structure constructed by carbon-coated Fe3O4 has been successfully fabricated with hierarchically porous structure, high surface area, and suitable thickness of carbon layer. Such purposely designed hybrid nanostructures have an enhanced electronic/ionic conductivity, stable electrode/electrolyte interface, and physical buffering effect arising from the nanoscale combination of carbon with Fe3O4, as well as the hollow, aligned and hierarchically porous architectures. When used as an anode material for a lithium-ion half cell, the carbon-coated hierarchical Fe3O4 nanotubes showed excellent cycling performance with a specific capacity of 1,020 mAh.g^-1 at 200 mA.g^-1 after 150 cycles, a capacity retention of ca. 103%. Even at a higher current density of 1,000 mA·g^-1, a capacity of 840 mAh·g^-1 is retained after 300 cycles with no capacity loss. In particular, a superior rate capability can be obtained with a stable capacity of 355 mAh.g^-1 at 8,000 mA·g^-1. The encouraging results indicate that hierarchically tubular hybrid nanostructures can have important implications for the development of high-rate electrodes for future rechargeable lithium ion batteries （LIBs）.     

Mesoporous SnO2@carbon core-shell nanostructures with superior electrochemical performance for lithium ion batteries

SnO2@carbon nanostructure composites are prepared by a simple hydrothermal method. The composite exhibits unique structure, which consists of a mesoporous SnO2 core assembled of very small nanoparticles and a carbon shell with 10 nm thickness. The mesoporous SnO2@carbon core-shell nanostructures manifest superior electrochemical performance as an anode material for lithium ion batteries. The reversible specific capacity of the composite is about 908 mAh g(-1) for the first cycle and it can retain about 680 mAh g(-1) after 40 charge/discharge cycles at a current density of 0.3 C. Moreover, it shows excellent rate capability even at the high rate of 4.5 C. The enhanced performance was attributed to the mesoporous structure and a suitable carbon coating.     

锂离子电池电解质用含硼锂盐研究进展

电解质材料是锂离子电池的关键材料之一。LiBF4、双草酸硼酸锂(LiBOB)及草酸二氟硼酸锂(LiODFB)是极具应用前景的3种含硼锂盐。介绍了3种锂盐各自的优缺点及研究近况,重点综述了它们的离子传导特性及与电极材料的相容性能。     

SnO2-reduced graphene oxide nanoribbons as anodes for lithium ion batteries with enhanced cycling stability

A nanocomposite material of SnO2-reduced graphene oxide nanoribbons has been developed. In this composite, the reduced graphene oxide nanoribbons are uniformly coated by nanosized SnO2 that formed a thin layer of SnO2 on the surface. When used as anodes in lithium ion batteries, the composite shows outstanding electrochemical performance with the high reversible discharge capacity of 1,027 mAh/g at 0.1 A/g after 165 cycles and 640 mAh/g at 3.0 A/g after 160 cycles with current rates varying from 0.1 to 3.0 A/g and no capacity decay after 600 cycles compared to the second cycle at a current density of 1.0 A/g. The high reversible capacity, good rate performance and excellent cycling stability of the composite are due to the synergistic combination of electrically conductive reduced graphene oxide nanoribbons and SnO2, The method developed here is practical for the large-scale development of anode materials for lithium ion batteries.     

Polycrystalline SnO2 nanowires coated with amorphous carbon nanotube as anode material for lithium ion batteries

One-dimensional (1D) SnO₂ nanowires, coated by in situ formed amorphous carbon nanotubes (a-CNTs) with a mean diameter of ca. 60 nm, were synthesized by annealing the anodic alumina oxide (AAO) filled with a sol of SnO₂. X-ray diffraction (XRD) and selected area electron diffraction (SAED) patterns revealed that the prepared SnO₂ nanowires exist in polycrystalline rutile structure. The coating of carbon nanotubes has some defects on the wall after the internal SnO₂ nanoparticles were removed. The 1D SnO₂ nanowires present a reversible capacity of 441 mAh/g and an excellent cycling performance as an anode material for lithium ion batteries. This suggests that 1D nanostructured materials have great promise for practical application.     

二次锂电池NiS正极材料的制备及性能研究

以NiCl2.6H2O和硫代乙酰胺(TAA)为反应物,通过化学合成法成功制备了NiS正极材料。采用XRD和SEM对材料进行了表征。结果显示,合成的材料颗粒均匀,分散度高。通过充放电测试及循环伏安测试表征其电化学性能。在电流密度为0.1mA.cm-2,充放电区间1.0~3.5V时,该材料首次放电比容量为554mAh.g-1。     

Recent breakthroughs and perspectives of high-energy layered oxide cathode materials for lithium ion batteries

Ni-rich layered oxides (NRLOs) and Li-rich layered oxides (LRLOs) have been considered as promising next-generation cathode materials for lithium ion batteries (LIBs) due to their high energy density, low cost, and environmental friendliness. However, these two layered oxides suffer from similar problems like capacity fading and different obstacles such as thermal runaway for NRLOs and voltage decay for LRLOs. Understanding the similarities and differences of their challenges and strategies at multiple scales plays a paramount role in the cathode development of advanced LIBs. Herein, we provide a comprehensive review of state-of-the-art progress made in NRLOs and LRLOs based on multi-scale insights into electrons/ions, crystals, particles, electrodes and cells. For NRLOs, issues like structure disorder, cracks, interfacial degradation and thermal runaway are elaborately discussed. Superexchange interaction and magnetic frustration are blamed for structure disorder while strains induced by universal structural collapse result in issues like cracks. For LRLOs, we present an overview of the origin of high capacity followed by local crystal structure, and the root of voltage hysteresis/decay, which are ascribed to reduced valence of transition metal ions, phase transformation, strains, and microstructure degradation. We then discuss failure mechanism in full cells with NRLO cathode and commercial challenges of LRLOs. Moreover, strategies to improve the performance of NRLOs and LRLOs from different scales such as ion-doping, microstructure designs, particle modifications, and electrode/electrolyte interface engineering are summarized. Dopants like Na, Mg and Zr, delicate gradient concentration design, coatings like spinel LiNi_0.5Mn_1.5O₄ or Li₃PO₄ and novel electrolyte formulas are highly desired. Developing single crystals for NRLOs and new crystallographic structure or heterostructure for LRLOs are also emphasized. Finally, remaining challenges and perspectives are outlined for the development of NRLOs and LRLOs. This review offers fundamental understanding and future perspectives towards high-performance cathodes for next-generation LIBs.     

锂离子二次电池负极材料的研究综述

总结了在碳材料、合金材料和复合材料等3个锂离子电池负极材料研发的主导方向上的开发情况和它们各自特点,描述了目前的研究所面临难题,给出了锂离子电池负极材料研发取得重大突破的可能途径和建议.