Porous doped silicon nanowires for lithium ion battery anode with long cycle life

Porous silicon nanowires have been well studied for various applications; however, there are only very limited reports on porous silicon nanowires used for energy storage. Here, we report both experimental and theoretical studies of porous doped silicon nanowires synthesized by direct etching of boron-doped silicon wafers. When using alginate as a binder, porous silicon nanowires exhibited superior electrochemical performance and long cycle life as anode material in a lithium ion battery. Even after 250 cycles, the capacity remains stable above 2000, 1600, and 1100 mAh/g at current rates of 2, 4, and 18 A/g, respectively, demonstrating high structure stability due to the high porosity and electron conductivity of the porous silicon nanowires. A mathematic model coupling the lithium ion diffusion and the strain induced by lithium intercalation was employed to study the effect of porosity and pore size on the structure stability. Simulation shows silicon with high porosity and large pore size help to stabilize the structure during charge/discharge cycles.     

Hierarchical SnO2 hollow nanotubes as anodes for high performance lithium-ion battery

Nanostructured transition metal oxides are promising anode materials for lithium-ion batteries. Nevertheless, the problem of high volume expansion rate limits its further application. In this paper, we present a 3D hierarchical SnO₂ hollow nanotubes material by calcining C@SnS₂ materials in the air. This structure combines the advantages of both the hollow nanotubes and the outer staggered nanosheets structure, in which the hollow nanotube can provide more lithium ion transport channels, the space between the tubes can buffer the volume change, and the staggering nanosheets structure can effectively improve the relative specific surface area of the material and improve the storage capacity. As a result, the SnO₂ hollow nanotubes anode exhibits the highly reversible capacity of 1079 mAh g^?1 at a current density of 100 mA g^?1, while the reversible specific capacity of 770 mAh g^?1 was obtained after 100 cycles. The research results obtained in this work provide a feasible strategy for synthetic nanoscale transition metal oxide as high-performance lithium anode material.

     

Comparative life cycle assessment of lithium-ion batteries with lithium metal,silicon nanowire,and graphite anodes

Clean Technologies and Environmental Policy - Lithium metal and silicon nanowires, with higher specific capacity than graphite, are the most promising alternative advanced anode materials for use...     

SnO2纳米空心球的合成及在锂离子电池正极方面的应用

采用锡盐溶液浸渍-煅烧锯末法,制备了SnO2纳米空心球.分别用X射线衍射(XRD)、透射电子显微镜(TEM)、高分辨透射电子显微镜(HRTEM)及恒流充放电技术对产品的结构形态和电化学性质进行了表征.结果表明,SnO2空心球的尺寸在50～120nm之间,壳层厚度约为5nm.在作为锂离子电池正极使用时,初始放电容量为607.7 mAh g-1.     

Water-soluble-template-derived nanoscale silicon nanoflake and nano-rod morphologies: Stable architectures for lithium-ion battery anodes

Earth abundant and economical rock salt (NaCl) particles of different sizes (<3 μm and 5–20 μm) prepared by high energy mechanical milling were used as water-soluble templates for generation of Si with novel nanoscale architectures via low pressure chemical vapor deposition (LPCVD). Si nanoflakes (Si_NF) comprising largely amorphous Si (a-Si) with a small volume fraction of nanocrystalline Si (nc-Si), and Si nanorods (Si_NR) composed of a larger volume fraction of crystalline Si (c-Si) and a small volume fraction of a-Si resulted from modification of the NaCl crystals. Si_NF yielded first-cycle discharge and charge capacities of ～2,830 and 2,175 mAh·g^?1, respectively, at a current rate of 50 mA·g^?1 with a first-cycle irreversible loss (FIR loss) of ～15%–20%. Si_NR displayed first-cycle discharge and charge capacities of ～2,980 and ～2,500 mAh·g^?1, respectively, at a current rate of 50 mA·g^?1 with an FIR loss of ～12%–15%. However, at a current rate of 1 A·g^?1, Si_NF exhibited a stable discharge capacity of ～810 mAh·g^?1 at the end of 250 cycles with a fade rate of ～0.11% loss per cycle, while Si_NR showed a stable specific discharge capacity of ～740 mAh·g^?1 with a fade rate of ～0.23% loss per cycle. The morphology of the nanostructures and compositions of the different phases/phase of Si influence the performance of Si_NF and Si_NR, making them attractive anodes for lithium-ion batteries.

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SiO_2@C hollow sphere anodes for lithium-ion batteries

As anode materials for lithium-ion batteries, SiO_2 is of great interest because of its high capacity, low cost and environmental affinity. A facile approach has been developed to fabricate SiO_2@C hollow spheres by hydrolysis of tetraethyl orthosilicate(TEOS) to form SiO_2 shells on organic sphere templates followed by calcinations in air to remove the templates, and then the SiO_2 shells are covered by carbon layers.Electron microscopy investigations confirm hollow structure of the SiO_2@C. The SiO_2@C hollow spheres with different SiO_2 contents display gradual increase in specific capacity with discharge/charge cycling,among which the SiO_2@C with SiO_2 content of 67 wt% exhibits discharge/charge capacities of 653.4/649.6 mAh g~(-1) over 160 cycles at current density of 0.11 mA cm~(-2). The impedance fitting of the electrochemical impedance spectroscopy shows that the SiO_2@C with SiO_2 content of 67 wt% has the lowest charge transfer resistance, which indicates that the SiO_2@C hollow spheres is promising anode candidate for lithium-ion batteries.     

Practical considerations of Si-based anodes for lithium-ion battery applications

Using Si-based anodes in Li-ion batteries is one of the most feasible approaches to achieve high energy densities despite their disadvantages, such as low conductivity and massive volume expansion, which cause unstable solid electrolyte interphase layers with mechanical failure. The forefront in research and development to address the above challenges suggests the possibility of fully commercially viable cells using various structural and interfacial modifications. In particular, we present a discussion of each dimension of Si-based anodes in multiple controlled systems, including plain, hollow, porous, and uniquely engineered structures, which are further evaluated based on their anode performances, such as initial reversibility, capacity retention for extended cycles with its efficiency, degree of volume expansion tolerance, and rate capabilities, by several practical standards in half cells. With these practical considerations, multi-dimensional structures with uniform size distributions (micrometers, on average) are strongly desired to satisfy the rigorous requirements for widespread applications. Furthermore, we closely examined several full cells composed of Si-based multicomponent anodes coupled with suitable cathodes based on practical standards to propose future research directions for Si-based anodes to keep pace with the rapidly changing market demands for diverse energy storage systems.

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Solvothermal synthesis of solid and hollow CoO nanospheres and their electrochemical properties in lithium-ion battery

Solid and hollow CoO nanospheres were synthesized by solvothermal method with oleic acid as reactant and SiO₂ as template. Each sample of high-purity CoO was characterized by X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy and X-ray photoelectron energy spectroscopy, respectively. Both solid and hollow CoO nanospheres as anode for lithium-ion battery were tested by galvanostatic discharge–charge experiments. The first discharge capacity of 1598 and 1640 mAh g^?1 was obtained at 0.1C for solid and hollow CoO nanospheres, respectively. Hollow CoO nanospheres showed better cycle performance.     

Engineering empty space between Si nanoparticles for lithium-ion battery anodes

Silicon is a promising high-capacity anode material for lithium-ion batteries yet attaining long cycle life remains a significant challenge due to pulverization of the silicon and unstable solid-electrolyte interphase (SEI) formation during the electrochemical cycles. Despite significant advances in nanostructured Si electrodes, challenges including short cycle life and scalability hinder its widespread implementation. To address these challenges, we engineered an empty space between Si nanoparticles by encapsulating them in hollow carbon tubes. The synthesis process used low-cost Si nanoparticles and electrospinning methods, both of which can be easily scaled. The empty space around the Si nanoparticles allowed the electrode to successfully overcome these problems Our anode demonstrated a high gravimetric capacity (~1000 mAh/g based on the total mass) and long cycle life (200 cycles with 90% capacity retention).     

Reassembled graphene-platelets encapsulated silicon nanoparticles for Li-ion battery anodes

Among lithium alloy metals, silicon is an attractive candidate to replace commercial graphite anode because silicon possesses about ten times higher theoretical energy density than graphite. However, electrically nonconducting silicon undergoes a large volume changes during lithiation/delithiation reactions, which causes fast loss of storage capacity upon cycling due to electrode pulverization. To alleviate these problems, electrodes comprising Si nanoparticles (20 nm) and graphene platelets, denoted as SiGP-1 (Si = 35.5 wt%) and SiGP-2 (Si = 57.6 wt%), have been prepared with low cost materials and using easily scalable solution-dispersion methods. X-ray diffraction (XRD), scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HR-TEM) analyses indicated that Si nanoparticles were highly dispersed and encapsulated between graphene sheets that stacked into platelets in which portions of graphite phases were reconstituted. From the galvanostatic cycling test, SiGP-1 exhibited a reversible lithiation capacity of approximately 802 mAh/g with excellent capacity retention up to 30 cycles at 100 mA/g. Further cycling with a step-increase of current density (100-1,000 mA/g) up to 120 cycles revealed that it has an appreciable power capability as well, showing 520 mAh/g at 1,000 mA/g with capacity loss of 0.2-0.3% per cycle. The improved electrochemical performance is attributed to the robust electrical integrity provided by flexible graphene sheets that encapsulated dispersed Si nanopraticles and stacked into platelets with portions of reconstituted graphite phases in their structure.     

Carbon-supported and nanosheet-assembled vanadium oxide microspheres for stable lithium-ion battery anodes

Naturally abundant transition metal oxides with high theoretical capacity have attracted more attention than commercial graphite for use as anodes in lithium-ion batteries. Lithium-ion battery electrodes that exhibit excellent electrochemical performance can be efficiently achieved via three-dimensional (3D) architectures decorated with conductive polymers and carbon. As such, we developed 3D carbon-supported amorphous vanadium oxide microspheres and crystalline V₂O₃ microspheres via a facile solvothermal method. Both samples were assembled with ultrathin nanosheets, which consisted of uniformly distributed vanadium oxides and carbon. The formation processes were clearly revealed through a series of time-dependent experiments. These microspheres have numerous active reaction sites, high electronic conductivity, and excellent structural stability, which are all far superior to those of other lithium-ion battery anodes. More importantly, 95% of the second-cycle discharge capacity was retained after the amorphous microspheres were subjected to 7,000 cycles at a high rate of 2,000 mA/g. The crystalline microspheres also exhibited a high-rate and long-life performance, as evidenced by a 98% retention of the second-cycle discharge capacity after 9,000 cycles at a rate of 2,000 mA/g. Therefore, this facile solvothermal method as well as unique carbon-supported and nanosheet-assembled microspheres have significant potential for the synthesis of and use in, respectively, lithium-ion batteries.

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High-performance lithium battery anodes using silicon nanowires

There is great interest in developing rechargeable lithium batteries with higher energy capacity and longer cycle life for applications in portable electronic devices, electric vehicles and implantable medical devices. Silicon is an attractive anode material for lithium batteries because it has a low discharge potential and the highest known theoretical charge capacity (4,200 mAh g(-1); ref. 2). Although this is more than ten times higher than existing graphite anodes and much larger than various nitride and oxide materials, silicon anodes have limited applications because silicon's volume changes by 400% upon insertion and extraction of lithium which results in pulverization and capacity fading. Here, we show that silicon nanowire battery electrodes circumvent these issues as they can accommodate large strain without pulverization, provide good electronic contact and conduction, and display short lithium insertion distances. We achieved the theoretical charge capacity for silicon anodes and maintained a discharge capacity close to 75% of this maximum, with little fading during cycling.     

Facile co-precipitated synthesis of NdFeO3 perovskite nanoparticles for lithium-ion battery anodes

In this report, NdFeO₃ perovskite nanoparticles were facilely prepared by co-precipitation of Nd³⁺ and Fe³⁺ cations in hot water, followed with the pyrolysis process in atmospheric conditions. Morphology and crystal structure of NdFeO₃ perovskite were determined with appropriate methods, revealing orthorhombic lattice with size distribution from 40 to 180 nm. Functioning as anode lithium-ion batteries (LIBs), NdFeO₃ exhibited great electrochemical performance such as high retention capacity, excellent cyclability, and high current rate. Such enhanced electrochemical efficiency was evidently ascribed to the perovskite structure of NdFeO₃ due to short lithium-ion diffusion pathway and volume expansion control of working material during lithiation/delithiation operation. By demonstrating a capacity value of 475 mAh g^?1 even through 450 cycles at 0.1 A g^?1, NdFeO₃ perovskite nanoparticles proved itself a competitive anode material for the coming generations of LIBs. In addition, this novel synthesis method is suitable for mass production of perovskite materials for long-life lithium-storage facilities.

     

A carbon nanofiber network for stable lithium metal anodes with high Coulombic efficiency and long cycle life

Li metal is considered one of the most promising candidates for the anode material in high-energy-density Li-ion batteries. However, the dendritic growth of Li metal during the plating/stripping process can severely reduce Coulombic efficiency and cause safety problems, which is a key issue limiting the application of Li metal anodes. Herein, we present a novel strategy for dendrite-free deposition of Li by modifying the Cu current collector with a three-dimensional carbon nanofiber (CNF) network. Owing to the large surface area and high conductivity of the CNF network, Li metal is inserted into and deposited onto the CNF directly, and no dendritic Li metal is observed, leaving a flat Li metal surface. With Li metal as the counter electrode for Li deposition, an average Coulombic efficiency of 99.9% was achieved for more than 300 cycles, at large current densities of 1.0 and 2.0 mA·cm^?2, and with a high Li loading of 1 mAh·cm^?2. The scalability of the preparation method and the impressive results achieved here demonstrate the potential for the application of our design to the future development of dendrite-free Li metal anodes.

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Three-dimensional metal scaffold supported bicontinuous silicon battery anodes

Silicon-based lithium ion battery anodes are attracting significant attention because of silicon's exceptionally high lithium capacity. However, silicon's large volume change during cycling generally leads to anode pulverization unless the silicon is dispersed throughout a matrix in nanoparticulate form. Because pulverization results in a loss of electric connectivity, the reversible capacity of most silicon anodes dramatically decays within a few cycles. Here we report a three-dimensional (3D) bicontinuous silicon anode formed by depositing a layer of silicon on the surface of a colloidal crystal templated porous nickel metal scaffold, which maintains electrical connectivity during cycling due to the scaffold. The porous metal framework serves to both impart electrical conductivity to the anode and accommodate the large volume change of silicon upon lithiation and delithiation. The initial capacity of the bicontinuous silicon anode is 3568 (silicon basis) and 1450 mAh g(-1) (including the metal framework) at 0.05C. After 100 cycles at 0.3C, 85% of the capacity remains. Compared to a foil-supported silicon film, the 3D bicontinuous silicon anode exhibits significantly improved mechanical stability and cycleability.     

CoP nanoparticles enwrapped in N-doped carbon nanotubes for high performance lithium-ion battery anodes

CoP is a candidate lithium storage material for its high theoretical capacity. However, large volume variations during the cycling processes haunted its application. In this work, a four-step strategy was developed to synthesize N-doped carbon nanotubes wrapping CoP nanoparticles (CoP@N-CNTs). Integration of nanosized particles and hollow-doped CNTs render the as-prepared CoP@N-CNTs excellent cycling stability with a reversible charge capacity of 648 mA·h·g⁻¹ at 0.2 C after 100 cycles. The present strategy has potential application in the synthesis of phosphide enwrapped in carbon nanotube composites which have potential application in lithium-ion storage and energy conversion.     

Electrospun core-shell fibers for robust silicon nanoparticle-based lithium ion battery anodes

Because of its unprecedented theoretical capacity near 4000 mAh/g, which is approximately 10-fold larger compared to those of the current commercial graphite anodes, silicon has been the most promising anode for lithium ion batteries, particularly targeting large-scale energy storage applications including electrical vehicles and utility grids. Nevertheless, Si suffers from its short cycle life as well as the limitation for scalable electrode fabrication. Herein, we develop an electrospinning process to produce core-shell fiber electrodes using a dual nozzle in a scalable manner. In the core-shell fibers, commercially available nanoparticles in the core are wrapped by the carbon shell. The unique core-shell structure resolves various issues of Si anode operations, such as pulverization, vulnerable contacts between Si and carbon conductors, and an unstable sold-electrolyte interphase, thereby exhibiting outstanding cell performance: a gravimetric capacity as high as 1384 mAh/g, a 5 min discharging rate capability while retaining 721 mAh/g, and cycle life of 300 cycles with almost no capacity loss. The electrospun core-shell one-dimensional fibers suggest a new design principle for robust and scalable lithium battery electrodes suffering from volume expansion.