Nanostructured materials are advantageous in offering huge surface to volume ratios, favorable transport properties, altered physical properties, and confinement effects resulting from the nanoscale dimensions, and have been extensively studied for energy-related applications such as solar cells, catalysts, thermoelectrics, lithium ion batteries, supercapacitors, and hydrogen storage systems. This review focuses on a few select aspects regarding these topics, demonstrating that nanostructured materials benefit these applications by (1) providing a large surface area to boost the electrochemical reaction or molecular adsorption occurring at the solid-liquid or solid-gas interface, (2) generating optical effects to improve optical absorption in solar cells, and (3) giving rise to high crystallinity and/or porous structure to facilitate the electron or ion transport and electrolyte diffusion, so as to ensure the electrochemical process occurs with high efficiency. It is emphasized that, to further enhance the capability of nanostructured materials for energy conversion and storage, new mechanisms and structures are anticipated. In addition to highlighting the obvious advantages of nanostructured materials, the limitations and challenges of nanostructured materials while being used for solar cells, lithium ion batteries, supercapacitors, and hydrogen storage systems have also been addressed in this review.

Self-supported Li(4) Ti(5) O(12) nanowire arrays with high conductivity architectures are designed and fabricated for application in a Li-ion battery. The Li(4) Ti(5) O(12) nanowire arrays grow directly on Ti foil by a facile solution-based method, further enhancing Li-ion storage properties by creating Ti(3+) sites through hydrogenation. This configuration ensures that every Li(4) Ti(5) O(12) nanowire participates in the fast electrochemical reaction, enabling remarkable rate performance and a long cycle life.

A mesoporous Li 4 Ti 5 O 12 /C nanocomposite is synthesized by a nanocasting technique using the porous carbon material CMK-3 as a hard template. Modifi ed CMK-3 template is impregnated with Li 4 Ti 5 O 12 precursor, followed by heat treatment at 750 ° C for 6 h under N 2 . Li 4 Ti 5 O 12 nanocrystals of up to several tens of nanometers are successfully synthesized in micrometer-sized porous carbon foam to form a highly conductive network, as confi rmed by fi eld emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Raman spectroscopy, and nitrogen sorption isotherms. The composite is then evaluated as an anode material for lithium ion batteries. It exhibits greatly improved electrochemical performance compared with bulk Li 4 Ti 5 O 12 , and shows an excellent rate capability (73.4 mA h g − 1 at 80 C) with signifi cantly enhanced cycling performance (only 5.6% capacity loss after 1000 cycles at a high rate of 20 C). The greatly enhanced lithium storage properties of the mesoporous Li 4 Ti 5 O 12 /C nanocomposite may be attributed to the interpenetrating conductive carbon network, ordered mesoporous structure, and the small Li 4 Ti 5 O 12 nanocrystallites that increase the ionic and electronic conduction throughout the electrode.

Amorphous and nanocrystalline vanadium pentoxide (V 2 O 5 ) were prepared through a combination of sol-gel processing paired with electrochemical deposition and investigated as cathodes for sodiumion batteries. Amorphous V 2 O 5 demonstrated superior electrochemical properties upon sodiation as compared to its crystalline counterpart. More specifically, amorphous vanadium pentoxide had a measured capacity of 241 mA h g À1 , twice the capacity of its crystalline contemporary at 120 mA h g À1 . In addition, the amorphous vanadium pentoxide demonstrated a much higher discharge potential, energy density, and cycle stability. The development of amorphous materials could enable the usage and design of previously unexplored electrode materials; herein, the possible relationship between the improved sodiation properties and the amorphous structure is discussed.

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to develop and install renewable energy harvesting technologies [3]. However, their successful implementation will be dependent on reliable and robust storage devices since harvesting solar and wind energy is inherently intermittent and the majority of consumption targets cannot be readily tethered to the grid.As energy storage devices, batteries possess high portability, high energy density, high Coulombic efficiency, and long cycle life. They are ideal power sources for portable devices, automobiles, and backup power supplies; accordingly, batteries power nearly all of our mobile electronics and are used to improve the efficiency of hybrid electric vehicles [4,5]. Unfortunately, considerable improvements in performance are still required in order to meet the demands of advanced portable devices and achieve energy sustainability (e.g., through smart grid and electric vehicle technologies) [6]. These enduring needs have driven intensive research investments. While efforts have been successful, there is still significant room for improvement regarding the development and understanding of electrode materials [7]. The overall capacity and potential cycling window of many electrode materials are limited to prevent degradation over long term cycling. In addition to exploring new electrode materials, there have been strong efforts to improve those that are already utilized. Expense reduction is a priority as approximately 23% and 8% of the overall battery pack costs stem from the respective cathode and anode active materials alone [8].An alkali-ion battery consists of several electrochemical cells connected in parallel and/or in series to provide a designated current or voltage. Each electrochemical cell has two electrodes separated by an electrolyte that is electrically insulating but ionically conductive. During discharge, when the alkali-ion battery operates as a galvanic cell, alkali ions exit the negative electrode (typically carbon) and insert themselves into the positive electrode while electronsThe need for economical and sustainable energy storage drives battery research today. While Li-ion batteries are the most mature technology, scalable electrochemical energy storage applications benefit from reductions in cost and improved safety. Sodium-and magnesium-ion batteries are two technologies that may prove to be viable alternatives. Both metals are cheaper and more abundant than Li, and have better safety characteristics, while divalent magnesium has the added bonus of passing twice as much charge per atom. On the other hand, both are still emerging fields of research with challenges to overcome. For example, electrodes incorporating Na + are often pulverized under the repeated strain of shuttling the relatively large ion, while insertion and transport of Mg 2+ is often kinetically slow, which stems from larger electrostatic forces. This review provides an overview of cathode and anode materials for sodium-ion batteries, and a comprehensive summary of research on cathodes for magnesium-ion batteries. In additi...

Because of its extreme safety and outstanding cycle life, Li 4 Ti 5 O 12 has been regarded as one of the most promising anode materials for next-generation high-power lithium-ion batteries. Nevertheless, Li 4 Ti 5 O 12 suffers from poor electronic conductivity. Here, we develop a novel strategy for the fabrication of Li 4 Ti 5 O 12 /carbon core−shell electrodes using metal oxyacetyl acetonate as titania and single-source carbon. Importantly, this novel approach is simple and general, with which we have successfully produce nanosized particles of an olivine-type LiMPO 4 (M = Fe, Mn, and Co) core with a uniform carbon shell, one of the leading cathode materials for lithium-ion batteries. Metal acetylacetonates first decompose with carbon coating the particles, which is followed by a solid state reaction in the limited reaction area inside the carbon shell to produce the LTO/C (LMPO 4 /C) core−shell nanostructure. The optimum design of the core−shell nanostructures permits fast kinetics for both transported Li + ions and electrons, enabling high-power performance. KEYWORDS: Lithium ion batteries, Li 4 Ti 5 O 12 , lithium metal phosphates, core−shell structures, anode, cathode L ithium-ion batteries (LIBs), dominating the portable power market, have attracted enormous attention in the last several years for large-scale battery applications, such as electric vehicles (EV) and hybrid electric vehicles (HEV). 1,2 However, further improvements in terms of power densities, safety, and lifetime require new materials or new structures with a higher storage capacity and faster charge and discharge rate and desired potentials. 3−6 Graphitic carbon is commonly used as an anode in commercial LIBs but exhibits poor rate performance due to its low Li diffusion coefficient and presents serious safety issues because of potential solid electrolyte interphase (SEI) film formation. 7−10 As for cathode materials, lithium transition metal oxides suffer from the intrinsic disadvantage of poor thermal stability due to the release of oxygen from the highly delithiated oxide materials. 11 Advanced materials with better safety and excellent rate capability are critical components for the next generation of LIBs.Compared to graphite, spinel Li 4 Ti 5 O 12 (LTO) exhibits a relatively high lithium insertion/extraction voltage of approximately 1.55 V (vs Li/Li + ), which circumvents the formation of the SEI and suppress lithium dendrite deposition on the surface of the anode. 12−14 As a zero-strain insertion material, LTO possesses excellent reversibility and excellent Li-ion mobility in the charge−discharge process. 15−17 As a cathode material, olivine-type LiMPO 4 (M = Fe, Mn, Co, and Ni) compounds which display high Li-ion mobility, superior safety properties, and high electrochemical and thermal stability. 18−23 Therefore, a LiMPO 4 /LTO cell system possessing unique properties would enable a promising rechargeable batteries for large-scale application.However, both materials suffer from poor electronic conductivity (for example: ...

Loosely packed MoS 2 nanosheets with thin carbon coating were synthesized via a facile, one-pot hydrothermal growth method. In the resulting optimally-designed nanoarchitecture, the ultrathin nanosheets, with a wall-thickness of approximately 5-10 nm, provide a large electrode-electrolyte interface so as to facilitate faster lithium-ion intercalation and diffusion. The flexible and conductive carbon overcoats stabilize the disordered structure of flower-like MoS 2 nanosheets to accommodate more lithium-ions intercalation and thus maintain the structural and electrical integrity during cycling processes. In favor of the synergy and interplay of the carbon effect and intrinsic structural advantages, C@MoS 2 (2 : 1) composites synthesized with a D-glucose precursor: MoO 3 molar ratio of 2 : 1 exhibit high reversible specific capacity of 1419 mA h g À1 at 0.1 A g À1 , retain 80% of the capacity after 50 cycles, and excellent rate capability as high as 672 mA h g À1 at 10 A g À1 with nearly 100% coulombic efficiency.The good electrochemical performance suggests that these C@MoS 2 composites with unique flowerlike morphology could be a promising candidate as an anode material for lithium-ion batteries.