Self-supported SnO2 nanowire electrodes for high-power lithium-ion batteries

High-Resolution Nanoanalytical Insights into Particle Formation in SnO2/ZnO Core/Shell Nanowire Lithium-Ion Battery Anodes

Tin oxide (SnO₂)/zinc oxide (ZnO) core/shell nanowires as anode materials in lithium-ion batteries (LIBs) were investigated using a combination of classical electrochemical analysis and high-resolution electron microscopy to correlate structural changes and battery performance. The combination of the conversion materials SnO₂ and ZnO is known to have higher storage capacities than the individual materials. We report the expected electrochemical signals of SnO₂ and ZnO for SnO₂/ZnO core/shell nanowires as well as unexpected structural changes in the heterostructure after cycling. Electrochemical measurements based on charge/discharge, rate capability, and electrochemical impedance spectroscopy showed electrochemical signals for SnO₂ and ZnO and partial reversibility of lithiation and delithiation. We find an initially 30% higher capacity for the SnO₂/ZnO core/shell NW heterostructure compared to the ZnO-coated substrate without the SnO₂ NWs. However, electron microscopy characterization revealed pronounced structural changes upon cycling, including redistribution of Sn and Zn, formation of ∼30 nm particles composed of metallic Sn, and a loss of mechanical integrity. We discuss these changes in terms of the different reversibilities of the charge reactions of both SnO₂ and ZnO. The results show stability limitations of SnO₂/ZnO heterostructure LIB anodes and offer guidelines on material design for advanced next-generation anode materials for LIBs.

Highly Ordered SnO2 Nanopillar Array as Binder-Free Anodes for Long-Life and High-Rate Li-Ion Batteries

SnO₂, a typical transition metal oxide, is a promising conversion-type electrode material with an ultrahigh theoretical specific capacity of 1494 mAh g⁻¹. Nevertheless, the electrochemical performance of SnO₂ electrode is limited by large volumetric changes (~300%) during the charge/discharge process, leading to rapid capacity decay, poor cyclic performance, and inferior rate capability. In order to overcome these bottlenecks, we develop highly ordered SnO₂ nanopillar array as binder-free anodes for LIBs, which are realized by anodic aluminum oxide-assisted pulsed laser deposition. The as-synthesized SnO₂ nanopillar exhibit an ultrahigh initial specific capacity of 1082 mAh g⁻¹ and maintain a high specific capacity of 524/313 mAh g⁻¹ after 1100/6500 cycles, outperforming SnO₂ thin film-based anodes and other reported binder-free SnO₂ anodes. Moreover, SnO₂ nanopillar demonstrate excellent rate performance under high current density of 64 C (1 C = 782 mA g⁻¹), delivering a specific capacity of 278 mAh g⁻¹, which can be restored to 670 mAh g⁻¹ after high-rate cycling. The superior electrochemical performance of SnO₂ nanoarray can be attributed to the unique architecture of SnO₂, where highly ordered SnO₂ nanopillar array provided adequate room for volumetric expansion and ensured structural integrity during the lithiation/delithiation process. The current study presents an effective approach to mitigate the inferior cyclic performance of SnO₂-based electrodes, offering a realistic prospect for its applications as next-generation energy storage devices.

Regulating the interface defect of TiO2/Ag2O nanoheterojunction and its effect on photogenerated carrier dynamics

In this paper, the defects of TiO₂/Ag₂O nanoheterojunctions are regulated to evaluate the effect of the interface defects on carrier trapping and recombination dynamics by time-resolved photoluminescence spectroscopy (TRPL) and time-resolved terahertz (THZ) spectroscopy. TRPL spectra reveal that interface defects can act as a recombination center and have an accelerative effect on the recombination process of photogenerated carriers under ultraviolet light. Moreover, THZ spectroscopy results demonstrate that interface defects can effectively trap electrons and expedite the Auger recombination. Furthermore, the influence of interface defects on the photocarrier dynamics of TiO₂/Ag₂O nanoheterojunctions was comprehensively analyzed, providing a valuable experimental reference for the regulation and application of interface defect-fabricated nanoheterojunctions.

Tin dioxide-based nanomaterials as anodes for lithium-ion batteries

The development of new electrode materials for lithium-ion batteries (LIBs) has attracted significant attention because commercial anode materials in LIBs, like graphite, may not be able to meet the increasing energy demand of new electronic devices. Tin dioxide (SnO2) is considered as a promising alternative to graphite due to its high specific capacity. However, the large volume changes of SnO2 during the lithiation/delithiation process lead to capacity fading and poor cycling performance. In this review, we have summarized the synthesis of SnO2-based nanomaterials with various structures and chemical compositions, and their electrochemical performance as LIB anodes. This review addresses pure SnO2 nanomaterials, the composites of SnO2 and carbonaceous materials, the composites of SnO2 and transition metal oxides, and other hybrid SnO2-based materials. By providing a discussion on the synthesis methods and electrochemistry of some representative SnO2-based nanomaterials, we aim to demonstrate that electrochemical properties can be significantly improved by modifying chemical composition and morphology. By analyzing and summarizing the recent progress in SnO2 anode materials, we hope to show that there is still a long way to go for SnO2 to become a commercial LIB electrode and more research has to be focused on how to enhance the cycling stability.

Solution-gated transistors of two-dimensional materials for chemical and biological sensors: status and challenges

Two-dimensional (2D) materials have been the focus of materials research for many years due to their unique fascinating properties and large specific surface area (SSA). They are very sensitive to the analytes (ions, glucose, DNA, protein, etc.), resulting in their wide-spread development in the field of sensing. New 2D materials, as the basis of applications, are constantly being fabricated and comprehensively studied. In a variety of sensing applications, the solution-gated transistor (SGT) is a promising biochemical sensing platform because it can work at low voltage in different electrolytes, which is ideal for monitoring body fluids in wearable electronics, e-skin, or implantable devices. However, there are still some key challenges, such as device stability and reproducibility, that must be faced in order to pave the way for the development of cost-effective, flexible, and transparent SGTs with 2D materials. In this review, the device preparation, device physics, and the latest application prospects of 2D materials-based SGTs are systematically presented. Besides, a bold perspective is also provided for the future development of these devices.

Spray-Drying-Induced Assembly of Skeleton-Structured SnO2/Graphene Composite Spheres as Superior Anode Materials for High-Performance Lithium-Ion Batteries

Three-dimensional skeleton-structured assemblies of graphene sheets decorated with SnO₂ nanocrystals are fabricated via a facile and large-scalable spray-drying-induced assembly process with commercial graphene oxide and SnO₂ sol as precursors. The influences of different parameters on the morphology, composition, structure, and electrochemical performances of the skeleton-structured SnO₂/graphene composite spheres are studied by XRD, TGA, SEM, TEM, Raman spectroscopy, and N₂ adsorption-desorption techniques. Electrochemical properties of the composite spheres as the anode electrode for lithium-ion batteries are evaluated. After 120 cycles under a current density of 100 mA g^-1, the skeleton-structured SnO₂/graphene spheres still display a specific discharge capacity of 1140 mAh g^-1. It is roughly 9.5 times larger than that of bare SnO₂ clusters. It could still retain a stable specific capacity of 775 mAh g^-1 after 50 cycles under a high current density of 2000 mA g^-1, exhibiting extraordinary rate ability. The superconductivity of the graphene skeleton provides the pathway for electron transportation. The large pore volume deduced from the skeleton structure of the SnO₂/graphene composite spheres increases the penetration of electrolyte and the diffusion of lithium ions and also significantly enhances the structural integrity by acting as a mechanical buffer.

A Robust and Conductive Black Tin Oxide Nanostructure Makes Efficient Lithium-Ion Batteries Possible

SnO₂ -based lithium-ion batteries have low cost and high energy density, but their capacity fades rapidly during lithiation/delithiation due to phase aggregation and cracking. These problems can be mitigated by using highly conducting black SnO_2-x , which homogenizes the redox reactions and stabilizes fine, fracture-resistant Sn precipitates in the Li₂ O matrix. Such fine Sn precipitates and their ample contact with Li₂ O proliferate the reversible Sn → Li _x Sn → Sn → SnO₂ /SnO_2-x cycle during charging/discharging. SnO_2-x electrode has a reversible capacity of 1340 mAh g^-1 and retains 590 mAh g^-1 after 100 cycles. The addition of highly conductive, well-dispersed reduced graphene oxide further stabilizes and improves its performance, allowing 950 mAh g^-1 remaining after 100 cycles at 0.2 A g^-1 with 700 mAh g^-1 at 2.0 A g^-1 . Conductivity-directed microstructure development may offer a new approach to form advanced electrodes.

Recent Progress in Self-Supported Metal Oxide Nanoarray Electrodes for Advanced Lithium-Ion Batteries

The rational design and fabrication of electrode materials with desirable architectures and optimized properties has been demonstrated to be an effective approach towards high-performance lithium-ion batteries (LIBs). Although nanostructured metal oxide electrodes with high specific capacity have been regarded as the most promising alternatives for replacing commercial electrodes in LIBs, their further developments are still faced with several challenges such as poor cycling stability and unsatisfying rate performance. As a new class of binder-free electrodes for LIBs, self-supported metal oxide nanoarray electrodes have many advantageous features in terms of high specific surface area, fast electron transport, improved charge transfer efficiency, and free space for alleviating volume expansion and preventing severe aggregation, holding great potential to solve the mentioned problems. This review highlights the recent progress in the utilization of self-supported metal oxide nanoarrays grown on 2D planar and 3D porous substrates, such as 1D and 2D nanostructure arrays, hierarchical nanostructure arrays, and heterostructured nanoarrays, as anodes and cathodes for advanced LIBs. Furthermore, the potential applications of these binder-free nanoarray electrodes for practical LIBs in full-cell configuration are outlined. Finally, the future prospects of these self-supported nanoarray electrodes are discussed.

Rational design of Sn-based multicomponent anodes for high performance lithium-ion batteries: SnO2@TiO2@reduced graphene oxide nanotubes

Reduced graphene oxide (rGO)-wrapped SnO₂@TiO₂ nanotubes (NTs) anodes exhibit superior rate capability and cycle retention due to stable solid electrolyte interphase (SEI) layer and enhanced electrical conductivity through TiO₂ and rGO-coated layer.

Hollow Core-Shell SnO2/C Fibers as Highly Stable Anodes for Lithium-Ion Batteries

Given their competitive prospects for energy storage, lithium-ion batteries (LIBs) have attracted ever-intensive research interest. However, the large volume changes during cycling and structural pulverization significantly hinder the cycling stability and high capacity for lithium-alloy electrodes. Herein, novel one-dimensional (1D) hollow core-shell SnO2/C fibers were synthesized by facile coaxial electrospinning. The as-prepared fibers that possess sufficient hollow voids and nanosized SnO2 particles on the inner shell are able to serve as an anode in LIBs. The results suggest a reversible capacity of 1002 mAh g(-1) (for the initial cycle at 100 mA g(-1)), excellent rate capability, and a highly stable cycling performance with a discharge capacity of 833 mAh g(-1) after 500 cycles at 600 mA g(-1). The superior electrochemical performance is attributed to the unique hollow core-shell structure, which offers sufficient voids for alleviating the volume changes of SnO2 nanoparticles during lithiation/delithiation processes. The promising strategies and associated opportunities here demonstrate great potential in the fabrication of advanced anode materials for long-life LIBs.

Synthesis, characterization and photocatalytic applications of N-, S-, and C-doped SnO2 nanoparticles under ultraviolet (UV) light illumination

N-, S-, and C-doped SnO2 nanoparticles were synthesized via a precipitation method and were characterized by X-ray diffractometer (XRD), X-ray photoelectron spectra (XPS), scanning electron microscopy (SEM), Transmission Electron Microscope (TEM), UV-vis diffuse reflectance spectral (UV-vis DRS) and Brunauer-Emmett-Teller (BET) techniques. The photocatalytic activities of these SnO2 samples were investigated with methyl orange as the organic pollutant under UV light illumination. UV-vis spectroscopy demonstrated that dopants N,S,C-species can shift the absorption edge to the near UV and visible light region. N,S,C-SnO2 nanoparticles achieved the best photocatalytic efficiency and the most optimal doping ratio was 3 (T/S). The degradation of methyl orange by N,S,C-SnO2 nanoparticles fitted well with the Langmuir-Hinshelwood kinetics model. The results of subsequent experiments indicate that enhanced adsorption ability of light and high separation rate of photo induced charge carriers all play an major role in promotion of photocatalytic activity of N,S,C-SnO2 nanoparticles.

Incorporation of PEDOT:PSS into SnO2/reduced graphene oxide nanocomposite anodes for lithium-ion batteries to achieve ultra-high capacity and cyclic stability

A conducting polymer matrix of PEDOT:PSS is incorporated into SnO₂/reduced graphene oxide composite for increasing the stability of lithium-ion battery anodes.

SnO2 nanocrystals anchored on N-doped graphene for high-performance lithium storage

A SnO₂–N-doped graphene composite with high-performance lithium storage properties is synthesized by a fast, facile and one-pot microwave-assisted solvothermal method.

Germanium microflower-on-nanostem as a high-performance lithium ion battery electrode

We demonstrate a new design of Ge-based electrodes comprising three-dimensional (3-D) spherical microflowers containing crystalline nanorod networks on sturdy 1-D nanostems directly grown on a metallic current collector by facile thermal evaporation. The Ge nanorod networks were observed to self-replicate their tetrahedron structures and form a diamond cubic lattice-like inner network. After etching and subsequent carbon coating, the treated Ge nanostructures provide good electrical conductivity and are resistant to gradual deterioration, resulting in superior electrochemical performance as anode materials for LIBs, with a charge capacity retention of 96% after 100 cycles and a high specific capacity of 1360 mA h g(-1) at 1 C and a high-rate capability with reversible capacities of 1080 and 850 mA h g(-1) at the rates of 5 and 10 C, respectively. The improved electrochemical performance can be attributed to the fast electron transport and good strain accommodation of the carbon-filled Ge microflower-on-nanostem hybrid electrode.

Highly stable and reversible lithium storage in SnO2 nanowires surface coated with a uniform hollow shell by atomic layer deposition

SnO2 nanowires directly grown on flexible substrates can be a good electrode for a lithium ion battery. However, Sn-based (metal Sn or SnO2) anode materials always suffer from poor stability due to a large volume expansion during cycling. In this work, we utilize atomic layer deposition (ALD) to surface engineer SnO2 nanowires, resulting in a new type of hollowed SnO2-in-TiO2 wire-in-tube nanostructure. This structure has radically improved rate capability and cycling stability compared to both bare SnO2 nanowires and solid SnO2@TiO2 core-shell nanowire electrodes. Typically a relatively stable capacity of 393.3 mAh/g has been achieved after 1000 charge-discharge cycles at a current density of 400 mA/g, and 241.2 mAh/g at 3200 mA/g. It is believed that the uniform hollow TiO2 shell provides stable surface protection and the appropriate-sized gap effectively accommodates the expansion of the interior SnO2 nanowire. This ALD-enabled method should be general to many other battery anode and cathode materials, providing a new and highly reproducible and controllable technique for improving battery performance.

Real-time observation of the solid-liquid-vapor dissolution of individual tin(IV) oxide nanowires

The well-known vapor-liquid-solid (VLS) mechanism results in high-purity, single-crystalline wires with few defects and controllable diameters, and is the method of choice for the growth of nanowires for a vast array of nanoelectronic devices. It is of utmost importance, therefore, to understand how such wires interact with metallic interconnects-an understanding which relies on comprehensive knowledge of the initial growth process, in which a crystalline wire is ejected from a metallic particle. Though ubiquitous, even in the case of single elemental nanowires the VLS mechanism is complicated by competing processes at multiple heterogeneous interfaces, and despite decades of study, there are still aspects of the mechanism which are not well understood. Recent breakthroughs in studying the mechanism and kinetics of VLS growth have been strongly aided by the use of in situ techniques, and would have been impossible through other means. As well as several systematic studies of nanowire growth, reports which focus on the role and the nature of the catalyst tip reveal that the stability of the droplet is a crucial factor in determining nanowire morphology and crystallinity. Additionally, a reverse of the VLS process dubbed solid-liquid-vapor (SLV) has been found to result in the formation of cavities, or "negative nanowires". Here, we present a series of heating studies conducted in situ in the transmission electron microscope (TEM), in which we observe the complete dissolution of metal oxide nanowires into the metal catalyst particles at their tips. We are able to consistently explain our observations using a solid-liquid-vapor (SLV) type mechanism in which both evaporation at the liquid-vapor interface and adhesion of the catalyst droplet to the substrate surface contribute to the overall rate.

A novel method to enhance the conductance of transitional metal oxide electrodes

Transitional metal oxides hold great potential for high capacity anodes. However, the low electron conductivity of such materials leads to poor cycling stability and inferior rate capability. We reported herein the use of a novel hydrogen plasma technology to improve the conductance of metal oxides, which leads great success in improving the rate performance of CuO nanotube based anodes. This method has the potential to be widely adopted in the field of lithium ion batteries and supercapacitors.

Self-supported single crystalline H2Ti8O17 nanoarrays as integrated three-dimensional anodes for lithium-ion microbatteries

Well-ordered, one-dimensional H2Ti2O5, H2Ti8O17, TiO2-B, and anatase TiO2/TiO2-B nanowire arrays were innovatively designed and directly grown on current collectors as high performance three dimensional (3D) anodes for binder and carbon free lithium ion batteries (LIBs). The prepared thin nanowires exhibited a single crystalline phase with highly uniform morphologies, diameters ranging from 70-80 nm, and lengths of around 15 μm. Specifically, reversible Li insertion and extraction reactions around 1.6-1.8 V with initial intercalation capacities of 326 and 271 mA h g(-1) at a cycling rate of 0.1 C (where 1 C = 335 mA g(-1)) were observed for H2Ti8O17 and TiO2-B nanowire arrays, respectively. Among the four compounds investigated, the H2Ti8O17 nanowire electrode demonstrated optimal cycling stability, delivering a high specific discharge capacity of 157.8 mA h g(-1) with a coulombic efficiency of 100%, even after the 500th cycle at a current rate of 1 C. Furthermore, the H2Ti8O17 nanowire electrode displayed superior rate performance with rechargeable discharge capacities of 127.2, 111.4, 87.2, and 73.5 mA h g(-1) at 5 C, 10 C, 20 C, and 30 C, respectively. These results present the potential opportunity for the development of high-performance LIBs based on nanostructured Ti-based anode materials in terms of high stability and high rate capability.

Multifunctional TiO2-C/MnO2 core-double-shell nanowire arrays as high-performance 3D electrodes for lithium ion batteries

The unique TiO2-C/MnO2 core-double-shell nanowires are synthesized for the first time using as anode materials for lithium ion batteries (LIBs). They combine both advantages from TiO2 such as excellent cycle stability and MnO2 with high capacity (1230 mA h g(-1)). The additional C interlayer intends to improve the electrical conductivity. The self-supported nanowire arrays grown directly on current-collecting substrates greatly simplify the fabrication processing of electrodes without applying binder and conductive additives. Each nanowire is anchored to the current collector, leading to fast charge transfer. The unique one-dimensional core-double-shell nanowires exhibit enhanced electrochemical performance with a higher discharge/charge capacity, superior rate capability, and longer cycling lifetime.

Small quantities of cobalt deposited on tin oxide as anode material to improve performance of lithium-ion batteries

In this report, we present a hybrid structure involving a small quantity of Co element uniformly deposited on porous SnO(2) spheres as stable and high capacity anode materials for lithium-ion batteries. Specifically, Co element deposited on SnO(2) nanomaterials exhibited an exceptional reversible capacity of 810 mA h g(-1) after 50 cycles which is higher than the pure SnO(2) electrode. Based on the experiments results, a possible mechanism for the change of this structure during lithium ion insertion/extraction was proposed. The minute quantity of Co element uniformly deposited on SnO(2) spherical structure could prevent Sn aggregation during charging-discharging, and high porosity of the spherical structure allowed the volume expansion during lithium ion alloying/dealloying. The SnO(2) deposited with small quantities of Co element as electrode facilitated improved performance of lithium ion batteries with higher energy densities.

Treatment of nanowaste via fast crystal growth: with recycling of nano-SnO2 from electroplating sludge as a study case

The treatment of industrial sludge containing amorphous/nanophase metal oxides or hydroxides is one of the vital issues in hazardous waste disposal. In this work, we developed a strategy to recycle nano-SnO(2) from tinplate electroplating sludge. It revealed that the major components of this sludge were acid soluble Sn and Fe amorphous phases. By introducing NaOH as a mineralizer, a fast growth of amorphous Sn compound into acid-insoluble SnO(2) nanowires was achieved selectively. Thus, the as-formed nano-SnO(2) could be recycled via dissolving other solid compositions in the sludge by using acid. The role of NaOH on accelerating both the Oriented Attachment (OA) and Ostwald Ripening (OR) growth of SnO(2) was discussed, which was regarded as a critical factor for treating the sludge. A pilot-scale experiment was conducted to treat 2.3 kg original sludge and the recycling of about 90 g nano-SnO(2) was achieved. We anticipate this work can provide a good example for the recycling of valuable metals from industrial sludge containing fine metal oxides or hydroxides.

One-Dimensional SnO2Nanostructures: Synthesis and Applications

Nanoscale semiconducting materials such as quantum dots (0-dimensional) and one-dimensional (1D) structures, like nanowires, nanobelts, and nanotubes, have gained tremendous attention within the past decade. Among the variety of 1D nanostructures, tin oxide (SnO2) semiconducting nanostructures are particularly interesting because of their promising applications in optoelectronic and electronic devices due to both good conductivity and transparence in the visible region. This article provides a comprehensive review of the recent research activities that focus on the rational synthesis and unique applications of 1D SnO2nanostructures and their optical and electrical properties. We begin with the rational design and synthesis of 1D SnO2nanostructures, such as nanotubes, nanowires, nanobelts, and some heterogeneous nanostructures, and then highlight a range of applications (e.g., gas sensor, lithium-ion batteries, and nanophotonics) associated with them. Finally, the review is concluded with some perspectives with respect to future research on 1D SnO2nanostructures.

Leapfrog cracking and nanoamorphization of ZnO nanowires during in situ electrochemical lithiation

The lithiation reaction of single ZnO nanowire (NW) electrode in a Li-ion nanobattery configuration was observed by in situ transmission electron microscopy. Upon first charge, the single-crystalline NW was transformed into a nanoglass with multiple glassy nanodomains (Gleiter, H. MRS Bulletin2009, 34, 456) by an intriguing reaction mechanism. First, partial lithiation of crystalline NW induced multiple nanocracks ∼70 nm ahead of the main lithiation front, which traversed the NW cross-section and divided the NW into multiple segments. This was followed by rapid surface diffusion of Li(+) and solid-state amorphization along the open crack surfaces. Finally the crack surfaces merged, leaving behind a glass-glass interface (GGI). Such reaction front instability also repeated in the interior of each divided segment, further subdividing the NW into different nanoglass domains (nanoamorphization). Instead of the profuse dislocation plasticity seen in SnO(2) NWs (Science2010, 330, 1515), no dislocation was seen and the aforementioned nanocracking was the main precursor to the electrochemically driven solid-state amorphization in ZnO. Ab initio tensile decohesion calculations verified dramatic lithium embrittlement effect in ZnO, but not in SnO(2). This is attributed to the aliovalency of Sn cation (Sn(IV), Sn(II)) in contrast to the electronically more rigid Zn(II) cation.

Sn-induced low-temperature growth of Ge nanowire electrodes with a large lithium storage capacity

We herein present the synthesis of germanium (Ge) nanowires on Au-catalyzed low-temperature substrates using a simple thermal Ge/Sn co-evaporation method. Incorporation of a low-melting point metal (Sn) enables the efficient delivery of Ge vapor to the substrate, even at a source temperature below 600 °C. The as-synthesized nanowires were found to be a core/shell heterostructure, exhibiting a uniform single crystalline Ge sheathed within a thin amorphous germanium suboxide (GeO(x)) layer. Furthermore, these high-density Ge nanowires grown directly on metal current collectors can offer good electrical connection and easy strain relaxation due to huge volume expansion during Li ion insertion/extraction. Therefore, the self-supported Ge nanowire electrodes provided excellent large capacity with little fading upon cycling (a capacity of ∼900 mA h g(-1) at 1C rate).

Building one-dimensional oxide nanostructure arrays on conductive metal substrates for lithium-ion battery anodes

Lithium ion battery (LIB) is potentially one of the most attractive energy storage devices. To meet the demands of future high-power and high-energy density requirements in both thin-film microbatteries and conventional batteries, it is challenging to explore novel nanostructured anode materials instead of conventional graphite. Compared to traditional electrodes based on nanostructure powder paste, directly grown ordered nanostructure array electrodes not only simplify the electrode processing, but also offer remarkable advantages such as fast electron transport/collection and ion diffusion, sufficient electrochemical reaction of individual nanostructures, enhanced material-electrolyte contact area and facile accommodation of the strains caused by lithium intercalation and de-intercalation. This article provides a brief overview of the present status in the area of LIB anodes based on one-dimensional nanostructure arrays growing directly on conductive inert metal substrates, with particular attention to metal oxides synthesized by an anodized alumina membrane (AAM)-free solution-based or hydrothermal methods. Both the scientific developments and the techniques and challenges are critically analyzed.

In Situ Observation of the Electrochemical Lithiation of a Single SnO2 Nanowire Electrode

We report the creation of a nanoscale electrochemical device inside a transmission electron microscope—consisting of a single tin dioxide (SnO2) nanowire anode, an ionic liquid electrolyte, and a bulk lithium cobalt dioxide (LiCoO2) cathode—and the in situ observation of the lithiation of the SnO2 nanowire during electrochemical charging. Upon charging, a reaction front propagated progressively along the nanowire, causing the nanowire to swell, elongate, and spiral. The reaction front is a “Medusa zone” containing a high density of mobile dislocations, which are continuously nucleated and absorbed at the moving front. This dislocation cloud indicates large in-plane misfit stresses and is a structural precursor to electrochemically driven solid-state amorphization. Because lithiation-induced volume expansion, plasticity, and pulverization of electrode materials are the major mechanical effects that plague the performance and lifetime of high-capacity anodes in lithium-ion batteries, our observations provide important mechanistic insight for the design of advanced batteries.