A facile synthesis of mesoporous graphene-tin composites as high-performance anodes for lithium-ion batteries

Graphene-based metals and their oxides usually exhibit enhanced electrochemical behavior in lithium-ion batteries due to the outstanding properties of graphene. Moreover, the structure and morphology of electrodes can also take an important role in their electrochemical properties. Herein we describe a facile synthesis of graphene–Sn composites containing ca. 3–6 nm diameter mesopores formed by aggregation of Sn nanoparticles on the graphene surface. These mesoporous composites with large surface area deliver higher capacity and better cycle performance in comparison with pristine Sn particles. Furthermore, the mesoporous composites treated under hydrothermal treatment exhibit higher rechargeable capacities and cycle performances.     

用于锂离子电池的石墨烯材料——储能特性及前景展望

石墨烯具有独特的二维结构、优异的性能和各种潜在的应用价值,是当前材料科学领域研究的热点.通过简要评述石墨烯作为锂离子电池负极材料的结构与性能的关系,讨论了作为电极材料的石墨烯结构与功能调控的重要性,指出石墨烯基纳米材料是一种很有吸引力的锂离子电池电极材料,尤其针对高能量密度与高功率密度电池.     

Composites of graphene and encapsulated silicon for practically viable high-performance lithium-ion batteries

A facile and scalable approach to synthesize silicon composite anodes has been developed by encapsulating Si particles via in situ polymerization and carbonization of phloroglucinol-formaldehyde gel, followed by incorporation of graphene nanoplatelets. As a result of its structural integrity, high packing density and an intimate electrical contact consolidated by the conductive networks, the composite anode yielded excellent electrochemical performance in terms of charge storage capability, cycling life and coulombic efficiency. A half cell achieved reversible capacities of 1,600 mAh·g^?1 and 1,000 mAh·g^?1 at 0.5 A·g^?1 and 2.1 A·g^?1, respectively, while retaining more than 70% of the initial capacities over 1,000 cycles. Complete lithium-ion pouch cells coupling the anode with a lithium metal oxide cathode demonstrated excellent cycling performance and energy output, representing significant advance in developing Si-based electrode for practical application in high-performance lithium-ion batteries.      

Nanosized-bismuth-embedded 1D carbon nanofibers as high-performance anodes for lithium-ion and sodium-ion batteries

Bi is a promising candidate for energy storage materials because of its high volumetric capacity,stability in moisture/air,and facile preparation.In this study,the electrochemical performance of nanosized-Bi-embedded one-dimensional (1D) carbon nanofibers (Bi/C nanofibers) as anodes for Li-ion batteries (LIBs) and Na-ion batteries (NIBs) was systematically investigated.The Bi/C nanofibers were prepared using a single-nozzle electrospinning method with a specified Bi source followed by carbothermal reduction.Abundant Bi nanoparticles with diameters of approximately 20 nm were homogeneously dispersed and embedded in the 1D carbon nanofibers,as confirmed by structural and morphological characterization.Electrochemical measurements indicate that the Bi/C nanofiber anodes could deliver a long cycle life for LIBs and a preferable rate performance for NIBs.The superior electrochemical performances of the Bi/C nanofiber anodes are attributed to the 1D carbon nanofiber structure and uniform distribution of Bi nanoparticles embedded in the carbon matrix.This unique embedded structure provides a favorable electron carrier and buffering matrix for the effective release of mechanical stress caused by volume change and prevents the aggregation of Bi nanoparticles.     

Spin-coated silicon nanoparticle/graphene electrode as a binder-free anode for high-performance lithium-ion batteries

Si has been considered as a promising anode material but its practical application has been severely hindered due to poor cyclability caused by the large volume change during charge/discharge. A new and effective protocol has been developed to construct Si nanoparticle/graphene electrodes with a favorable structure to alleviate this problem. Starting from a stable suspension of Si nanoparticles and graphene oxide in ethanol, spin-coating can be used as a facile method to cast a spin-coated Si nanoparticle/graphene (SC-Si/G) film, in which graphene can act as both an efficient electronic conductor and effective binder with no need for other binders such as polyvinylidenefluoride (PVDF) or polytetrafluoroethylene (PTFE). The prepared SC-Si/G electrode can achieve a high-performance as an anode for lithium-ion batteries benefiting from the following advantages: i) the graphene enhances the electronic conductivity of Si nanoparticles and the void spaces between Si nanoparticles facilitate the lithium ion diffusion, ii) the flexible graphene and the void spaces can effectively cushion the volume expansion of Si nanoparticles. As a result, the binder-free electrode shows a high capacity of 1611 mA·h·g^?1 at 1 A·g^?1 after 200 cycles, a superior rate capability of 648 mA·h·g^?1 at 10 A·g^?1, and an excellent cycle life of 200 cycles with 74% capacity retention.      

Nanomaterials for lithium-ion rechargeable batteries

In lithium-ion batteries, nanocrystalline intermetallic alloys, nanosized composite materials, carbon nanotubes, and nanosized transition-metal oxides are all promising new anode materials, while nanosized LiCoO2, LiFePO4, LiMn2O4, and LiMn2O4 show higher capacity and better cycle life as cathode materials than their usual larger-particle equivalents. The addition of nanosized metal-oxide powders to polymer electrolyte improves the performance of the polymer electrolyte for all solid-state lithium rechargeable batteries. To meet the challenge of global warming, a new generation of lithium rechargeable batteries with excellent safety, reliability, and cycling life is needed, i.e., not only for applications in consumer electronics, but especially for clean energy storage and for use in hybrid electric vehicles and aerospace. Nanomaterials and nanotechnologies can lead to a new generation of lithium secondary batteries. The aim of this paper is to review the recent developments on nanomaterials and nanotechniques used for anode, cathode, and electrolyte materials, the impact of nanomaterials on the performance of lithium batteries, and the modes of action of the nanomaterials in lithium rechargeable batteries.     

Polymer electrolytes for lithium-ion batteries

The motivation for lithium battery development and a discussion of ion conducting polymers as separators begin this review, which includes a short history of polymer electrolyte research, a summary of the major parameters that determine lithium ion transport in polymer matrices, and consequences for solid polymer electrolyte development. Two major strategies for the application of ion conducting polymers as separators in lithium batteries are identified: One is the development of highly conductive materials via the crosslinking of mobile chains to form networks, which are then swollen by lithium salt solutions ("gel electrolytes"). The other is the construction of solid polymer electrolytes (SPEs) with supramolecular architectures, which intrinsically give rise to much enhanced mechanical strength. These materials as yet exhibit relatively common conductivity levels but may be applied as very thin films. Molecular composites based on poly(p-phenylene)- (PPP)-reinforced SPEs are a striking example of this direction. Neither strategy has as yet led to a "breakthrough" with respect to technical application, at least not for electrically powered vehicles. Before being used as separators, the gel electrolytes must be strengthened, while the molecularly reinforced solid polymer electrolytes must demonstrate improved conductivity.     

Metal hydrides for lithium-ion batteries

Classical electrodes for Li-ion technology operate via an insertion/de-insertion process. Recently, conversion electrodes have shown the capability of greater capacity, but have so far suffered from a marked hysteresis in voltage between charge and discharge, leading to poor energy efficiency and voltages. Here, we present the electrochemical reactivity of MgH(2) with Li that constitutes the first use of a metal-hydride electrode for Li-ion batteries. The MgH(2) electrode shows a large, reversible capacity of 1,480 mAh g(-1) at an average voltage of 0.5 V versus Li(+)/Li(o) which is suitable for the negative electrode. In addition, it shows the lowest polarization for conversion electrodes. The electrochemical reaction results in formation of a composite containing Mg embedded in a LiH matrix, which on charging converts back to MgH(2). Furthermore, the reaction is not specific to MgH(2), as other metal or intermetallic hydrides show similar reactivity towards Li. Equally promising, the reaction produces nanosized Mg and MgH(2), which show enhanced hydrogen sorption/desorption kinetics. We hope that such findings can pave the way for designing nanoscale active metal elements with applications in hydrogen storage and lithium-ion batteries.     

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).

Open image in new window

     

Crystal engineering of TMPOx-coated LiNi0.5Mn1.5O4 cathodes for high-performance lithium-ion batteries

The use of cobalt-free LiNi_0.5Mn_1.5O₄ (LNMO) would provide a great leap forward towards the realization of sustainable lithium-ion batteries. However, the high operating voltage remains to be a great challenge for the cathode/electrolyte stability. Herein, we report a rational material design to address these challenges by carefully tuning the synthesis parameters in order to engineer LNMO crystals with tailored surface facets, providing an exceptional rate capability and improved interfacial stability. The additional introduction of protective TMPO_x coatings further enhances the long-term cycling stability, in particular, at elevated cut-off potentials up to 4.95 V, increased temperature of 40 °C, and high dis-/charge rates. As a result of the careful design of the LNMO active material particles, lithium-ion cells employing this material together with Li₄Ti₅O₁₂ anodes provide an excellent rate capability with 80% of the low-rate capacity at fast dis-/charge rates of 10C combined with highly stable cycling at such high rate, as highlighted by a capacity fading of less than 5% after 1000 cycles.     

LiFePO4 mesocrystals for lithium-ion batteries

Olivine LiFePO₄ is considered one of the most promising cathode materials for Li‐ion batteries. A simple one‐step, template‐free, low‐temperature solvothermal method is developed for the synthesis of urchinlike hierarchical mesocrystals of pristine LiFePO₄ as well as carbon‐coated LiFePO₄ composites. Each urchinlike mesocrystal consists of LiFePO₄ sheets self‐assembled via a dipolar field in spheres during a solvothermal process under the influence of Cl^? anions. The obtained primary sheets of LiFePO₄ are single crystalline in nature and can be coated in situ with an amorphous nitrogen‐doped carbonaceous layer several nanometers in thickness. To increase the conductivity of the carbon coating, the materials are subjected to further temperature treatment (700 °C) under an inert atmosphere. The lithium storage performance of the pure LiFePO₄ is compared with that of its carbon‐coated counterparts.     

简易制备中空微球锰酸锂的方法及性能研究

通过多层核壳结构的γ-MnO2成功制备了一种由尖晶石单晶组合而成的空心球形尖晶石锰酸锂正极材料,所制备的样品采用X射线衍射、扫描电镜进行了表征,并进一步通过循环伏安、交流阻抗以及恒电流充放电对其电化学性能进行了研究。结果表明,所合成的空心球形锰酸锂颗粒大小均匀,平均直径在8μm左右,由结晶良好的尖晶石八面体单晶组成。电性能测试结果表明,空心球形尖晶石锰酸锂具有高比容量、高倍率以及优异的循环性能。在3.3～4.3V电压范围、0.2C下的首次放电比容量高达145.9mAh/g,50次循环后的容量保持率为95.9%,10C时的首次放电比容量仍为113.3mAh/g,100次循环后的容量保持率达95.5%。     

Ultralong-life and high-rate web-like Li4Ti5O12 anode for high-performance flexible lithium-ion batteries

Flexible lithium ion batteries （LIBs） have recently attracted increasing attention as they show unique promising advantages, such as flexibility, shape diversity, and light weight. Similar to conventional LIBs, flexible LIBs with long cycle life and high-rate performance are very important for applications of high performance flexible electronics. Herein, we report a three-dimensional （3D） web-like binderfree Li4Ti5O12 （LTO） anode assembled from numerous 1D nanowires exhibiting excellent cycling performance with high capacities of 153 and 115 mA·h·g^-1 after 5,000 cycles at 2 C and 20 C, respectively, and excellent rate property with a capacity of 103 mA·h·g^-1 even at a very high current rate of 80 C. Surprisingly, a flexible full battery assembled from the web-like LTO nanostructure and LiMn2O4 （LMO） nanorods exhibited a high capacity of 125 mA·h·g^-1 at high current rate of 20 C, and showed excellent flexibility with little performance degradation even in seriously bent states.     

Electrosprayed porous Fe3O4/carbon microspheres as anode materials for high-performance lithium-ion batteries

Nano Research - Porous Fe3O4/carbon microspheres (PFCMs) were successfully fabricated via a facile electrospray method and subsequent heat treatment, using ferrous acetylacetonate, carbon nanotubes...     

A highly stabilized Ni-rich NCA cathode for high-energy lithium-ion batteries

In this study, we have demonstrated that boron doping of Ni-rich Li[Ni_xCo_yAl_1−x−y]O₂ dramatically alters the microstructure of the material. Li[Ni_0.885Co_0.1Al_0.015]O₂ is composed of large equiaxed primary particles, whereas a boron-doped Li[Ni_0.878Co_0.097Al_0.015B_0.01]O₂ cathode consists of elongated particles that are highly oriented to produce a strong, crystallographic texture. Boron reduces the surface energy of the (0 0 3) planes, resulting in a preferential growth mode that maximizes the (0 0 3) facet. This microstructure modification greatly improves the cycling stability; the Li[Ni_0.878Co_0.097Al_0.015B_0.01]O₂ cathode maintains a remarkable 83% of the initial capacity after 1000 cycles even when it is cycled at 100% depth of discharge. By contrast, the Li[Ni_0.885Co_0.1Al_0.015]O₂ cathode retains only 49% of its initial capacity. The superior cycling stability clearly indicates the importance of the particle microstructure (i.e., particle size, particle shape, and crystallographic orientation) in mitigating the abrupt internal strain caused by phase transitions in the deeply charged state, which occurs in all Ni-rich layered cathodes. Microstructure engineering by surface energy modification, when combined with protective coatings and composition modification, may provide a long-sought method of harnessing the high capacity of Ni-rich layered cathodes without sacrificing the cycling stability.     

Ferrodispersion: a promising candidate for an optical capacitor

A ferrodispersion, which comprises micrometer-sized magnetizable spheres dispersed in a ferrofluid, is shown to store retrievable optical energy. It is observed that when such dispersion is subjected to a transverse magnetic field and a linearly polarized monochromatic light with its electric vector perpendicular to the applied field is incident on it, then for a critical static magnetic field of moderate intensity the emerging light disappears. Upon removing the light and then switching off the field, again light of the same frequency and same state of polarization reappears. A time delay between emission of the light and switching off the field is observed. The statistical distribution of this delay is reported. Intensity of the retrieval signal is found to depend on the storage time. This effect is investigated. Storing and retrieval of optical energy will be useful for developing a magnetically tunable optical capacitor.     

锂离子电池聚氨酯型凝胶态聚合物电解质的研究

采用一种自制新型超支化聚醚(PHEMO)与甲苯2,4-二异氰酸酯(MDI)在电解液中进行缩合反应,制备了一种具有交联网状结构的聚氨酯(PEU)型凝胶态聚合物电解质.利用傅立叶红外光谱(FTIR)、示差扫描量热分析(DSC)、热重分析(TGA)、交流阻抗谱等测试方法对聚合物电解质的结构、热稳定性能、离子电导率进行了研究.研究发现:上述制备的PM-1M-Z4聚合物电解质体系室温电导率可达2.53×10-3S/cm,电化学稳定窗口为2.3～4.0V,并且具有较好的热稳定性和优良的机械性能.此外,在这种新型的电解质中,电解液小分子被聚合物大分子包裹在其中,可有效防止凝胶聚合物电解质的漏液问题,从而可提高锂离子电池的安全性能.     

Recent progress of NiCo2O4-based anodes for high-performance lithium-ion batteries

Lithium-ion batteries (LIBs) are deemed as the most promising energy storage devices due to their high power density, excellent safety performance and superior cyclability. However, traditional carbon-based anodes are incapable of satisfying the ever-growing demand for high energy density owing to their low intrinsic theoretical capacity. Therefore, the research of post-carbon anodes (such as transition metal) for LIBs has exponentially increased. Among them, NiCo₂O₄ together with its composites have been widely studied by academic workers due to their high theoretical capacity and excellent electronic conductivity. In this review, the electrochemical reaction mechanism and recent progress including the synthetic method, various nanostructures and the strategies for improving performance of NiCo₂O₄ are summarized and discussed here. Specially, the hollow porous nanostructured NiCo₂O₄-based materials composed of 2D structures usually exhibit excellent capacity and stable cyclability. This review also offers some rational understandings and new thinking of the relationship between the synthetic method, morphologies, blending, current collector and electrochemical performance of NiCo₂O₄-based anodes. We have reason to believe that the integration of NiCo₂O₄ materials in these clean energy devices provides important chances to address challenges driven by increasing world energy demand.