Cost-effective scalable synthesis of mesoporous germanium particles via a redox-transmetalation reaction for high-performance energy storage devices

Nanostructured germanium is a promising material for high-performance energy storage devices. However, synthesizing it in a cost-effective and simple manner on a large scale remains a significant challenge. Herein, we report a redox-transmetalation reaction-based route for the large-scale synthesis of mesoporous germanium particles from germanium oxide at temperatures of 420-600 °C. We could confirm that a unique redox-transmetalation reaction occurs between Zn(0) and Ge(4+) at approximately 420 °C using temperature-dependent in situ X-ray absorption fine structure analysis. This reaction has several advantages, which include (i) the successful synthesis of germanium particles at a low temperature (∼450 °C), (ii) the accommodation of large volume changes, owing to the mesoporous structure of the germanium particles, and (iii) the ability to synthesize the particles in a cost-effective and scalable manner, as inexpensive metal oxides are used as the starting materials. The optimized mesoporous germanium anode exhibits a reversible capacity of ∼1400 mA h g(-1) after 300 cycles at a rate of 0.5 C (corresponding to the capacity retention of 99.5%), as well as stable cycling in a full cell containing a LiCoO2 cathode with a high energy density (charge capacity = 286.62 mA h cm(-3)).

In situ SEM study of lithium intercalation in individual V2O5 nanowires

Progress in rational engineering of Li-ion batteries requires better understanding of the electrochemical processes and accompanying transformations in the electrode materials on multiple length scales. In spite of recent progress in utilizing transmission electron microscopy (TEM) to analyze these materials, in situ scanning electron microscopy (SEM) was mostly overlooked as a powerful tool that allows probing these phenomena on the nano and mesoscale. Here we report on in situ SEM study of lithiation in a V2O5-based single-nanobelt battery with ionic liquid electrolyte. Coupled with cyclic voltammetry measurements, in situ SEM revealed the peculiarities of subsurface intercalation, formation of a solid-electrolyte interface (SEI) and electromigration of liquid. We observed that single-crystalline vanadia nanobelts do not undergo large-scale amorphization or fracture during electrochemical cycling, but rather transform topochemically with only a slight shape distortion. The SEI layer seems to have significant influence on the lithium ion diffusion and overall capacity of the single-nanobelt battery.

Hierarchical NiCo2 O4 nanosheets grown on Ni nanofoam as high-performance electrodes for supercapacitors

A high-performance electrode for supercapacitors is designed and synthesized by growing electroactive NiCo2 O4 nanosheets on conductive Ni nanofoam. Because of the structural advantages, the as-prepared Ni@NiCo2 O4 hybrid nanostructure exhibits significantly improved electrochemical performance with high capacitance, excellent rate capability, and good cycling stability.

Hierarchical micron-sized mesoporous/macroporous graphene with well-tuned surface oxygen chemistry for high capacity and cycling stability Li-O2 battery

Nonaqueous Li-O2 battery is recognized as one of the most promising energy storage devices for electric vehicles due to its super-high energy density. At present, carbon or catalyst-supporting carbon materials are widely used for cathode materials of Li-O2 battery. However, the unique electrode reaction and complex side reactions lead to numerous hurdles that have to be overcome. The pore blocking caused by the solid products and the byproducts generated from the side reactions severely limit the capacity performance and cycling stability. Thus, there is a great need to develop carbon materials with optimized pore structure and tunable surface chemistry to meet the special requirement of Li-O2 battery. Here, we propose a strategy of vacuum-promoted thermal expansion to fabricate one micron-sized graphene matrix with a hierarchical meso-/macroporous structure, combining with a following deoxygenation treatment to adjust the surface chemistry by reducing the amount of oxygen and selectively removing partial unstable groups. The as-made graphene demonstrates dramatically tailored pore characteristics and a well-tuned surface chemical environment. When applied in Li-O2 battery as cathode, it exhibits an outstanding capacity up to 19 800 mA h g(-1) and is capable of enduring over 50 cycles with a curtaining capacity of 1000 mA h g(-1) at a current density of 1000 mA g(-1). This will provide a novel pathway for the design of cathodes for Li-O2 battery.

The lithium/air battery: still an emerging system or a practical reality?

Lithium/air is a fascinating energy storage system. The effective exploitation of air as a battery electrode has been the long-time dream of the battery community. Air is, in principle, a no-cost material characterized by a very high specific capacity value. In the particular case of the lithium/air system, energy levels approaching that of gasoline have been postulated. It is then not surprising that, in the course of the last decade, great attention has been devoted to this battery by various top academic and industrial laboratories worldwide. This intense investigation, however, has soon highlighted a series of issues that prevent a rapid development of the Li/air electrochemical system. Although several breakthroughs have been achieved recently, the question on whether this battery will have an effective economic and societal impact remains. In this review, a critical evaluation of the progress achieved so far is made, together with an attempt to propose future R&D trends. A forecast on whether Li/air may have a role in the next years' battery technology is also postulated.

Co3O4@MWCNT nanocable as cathode with superior electrochemical performance for supercapacitors

Using a simple hydrothermal procedure, cobalt oxide (Co3O4) with preferred orientation along (220) planes is in situ prepared and coated on MWCNT. The prepared Co3O4@MWCNT nanocable shows superior electrochemical performance as cathode material for aqueous supercapacitors in 0.5 M KOH solution. Its redox peaks retain the well-defined shapes even when the scan rate increases to 200 mV/s. Its specific capacitance is high, 590 F/g at 15 A/g and 510 F/g even at 100 A/g within the potential range from -0.2 to 0.58 V (vs SCE). There is no capacitance fading after 2000 full cycles. This excellent performance is superior to the pristine and the reported Co3O4, which is ascribed to the unique nanocable structure with orientation.

Te/C nanocomposites for Li-Te Secondary Batteries

New battery systems having high energy density are actively being researched in order to satisfy the rapidly developing market for longer-lasting mobile electronics and hybrid electric vehicles. Here, we report a new Li-Te secondary battery system with a redox potential of ~1.7 V (vs. Li⁺/Li) adapted on a Li metal anode and an advanced Te/C nanocomposite cathode. Using a simple concept of transforming TeO₂ into nanocrystalline Te by mechanical reduction, we designed an advanced, mechanically reduced Te/C nanocomposite electrode material with high energy density (initial discharge/charge: 1088/740 mA h cm⁻³), excellent cyclability (ca. 705 mA h cm⁻³ over 100 cycles), and fast rate capability (ca. 550 mA h cm⁻³ at 5C rate). The mechanically reduced Te/C nanocomposite electrodes were found to be suitable for use as either the cathode in Li-Te secondary batteries or a high-potential anode in rechargeable Li-ion batteries. We firmly believe that the mechanically reduced Te/C nanocomposite constitutes a breakthrough for the realization and mass production of excellent energy storage systems.

Interfacial oxygen stabilizes composite silicon anodes

Silicon can store Li(+) at a capacity 10 times that of graphite anodes. However, to harness this remarkable potential for electrical energy storage, one has to address the multifaceted challenge of volume change inherent to high capacity electrode materials. Here, we show that, solely by chemical tailoring of Si-carbon interface with atomic oxygen, the cycle life of Si/carbon matrix-composite electrodes can be substantially improved, by 300%, even at high mass loadings. The interface tailored electrodes simultaneously attain high areal capacity (3.86 mAh/cm(2)), high specific capacity (922 mAh/g based on the mass of the entire electrode), and excellent cyclability (80% retention of capacity after 160 cycles), which are among the highest reported. Even at a high rate of 1C, the areal capacity approaches 1.61 mAh/cm(2) at the 500th cycle. This remarkable electrochemical performance is directly correlated with significantly improved structural and electrical interconnections throughout the entire electrode due to chemical tailoring of the Si-carbon interface with atomic oxygen. Our results demonstrate that interfacial bonding, a new dimension that has yet to be explored, can play an unexpectedly important role in addressing the multifaceted challenge of Si anodes.

Graphene quantum dots coated VO2 arrays for highly durable electrodes for Li and Na ion batteries

Nanoscale surface engineering is playing important role in enhancing the performance of battery electrode. VO2 is one of high-capacity but less-stable materials and has been used mostly in the form of powders for Li-ion battery cathode with mediocre performance. In this work, we design a new type of binder-free cathode by bottom-up growth of biface VO2 arrays directly on a graphene network for both high-performance Li-ion and Na-ion battery cathodes. More importantly, graphene quantum dots (GQDs) are coated onto the VO2 surfaces as a highly efficient surface "sensitizer" and protection to further boost the electrochemical properties. The integrated electrodes deliver a Na storage capacity of 306 mAh/g at 100 mA/g, and a capacity of more than 110 mAh/g after 1500 cycles at 18 A/g. Our result on Na-ion battery may pave the way to next generation postlithium batteries.

Sulfur nanodots electrodeposited on ni foam as high-performance cathode for Li-S batteries

In this Letter, we report the preparation of sulfur nanodots (2 nm average) electrodeposited on flexible nickel foam and their application as high-performance cathode of Li-S batteries. An electrodepostion method was applied to prepare the cathode at room temperature and the sulfur mass was controllable from 0.21 to 4.79 mg/cm(2) in a large area of over 100 cm(2). The optimized cathode with 0.45 mg/cm(2) S on Ni foam displayed high initial discharge capacity (1458 mAh/g at 0.1 C), high rate capability (521 mAh/g at 10 C), and long cycling stability (895 mAh/g after 300 cycles at 0.5 C and 528 mAh/g after 1400 cycles at 5 C). Moreover, in situ Raman and transmission electron microscopy analysis demonstrated the fundamentals of reversible electrochemical reaction between S and Li2S nanodots. This fast, facile, and one-step cathode preparation method with excellent electrochemical performance will lead to technological advances of S cathode in Li-S batteries.

Ultrathin sandwich-like MoS2@N-doped carbon nanosheets for anodes of lithium ion batteries

In this work, we report on a simple and scalable process to synthesize the core-shell nanostructure of MoS2@N-doped carbon nanosheets (MoS2@C), in which polydopamine is coated on the MoS2 surface and is then carbonized. An intensive investigation using transmission electron microscopy and Raman spectroscopy reveals that the as-synthesized MoS2@C possesses a nanoscopic and ultrathin layer of MoS2 sheets with a thin and conformal coating of carbon layers (∼ 3 nm). The MoS2@C demonstrates a superior electrochemical performances as an anode material for lithium ion batteries compared to exfoliated MoS2 and bulk MoS2 samples. This unique core-shell structure is capable of delivering an excellent Li(+) ion charging-discharging process as follows: a specific capacity as high as 1239 mA h g(-1), a high rate capability even at a high current rate of 10 A g(-1) while retaining 597 mA h g(-1), and a good cycle stability over 200 cycles at a high current rate of 2 A g(-1).

A rechargeable sodium-ion battery using a nanostructured Sb–C anode and P2-type layered Na0.6Ni0.22Fe0.11Mn0.66O2 cathode

A promising example of a low cost, rechargeable sodium-ion battery efficiently combines a nanostructured Sb–C anode and P2-type layered Na_0.6Ni_0.22Fe_0.11Mn_0.66O₂ cathode.

Template-assisted synthesis of multi-shelled carbon hollow spheres with an ultralarge pore volume as anode materials in Li-ion batteries

Double/quadruple shells carbon hollow spheres can be obtained under the assistance of permeably mesoporous silica hollow spheres, which exhibit superior electrochemical performance.

CO2 and ambient air in metal–oxygen batteries: steps towards reality

Studies on involving CO₂ and ambient air in cathode gas bring the potential of a real rechargeable high-energy metal–air battery.

Solution processible hyperbranched inverse-vulcanized polymers as new cathode materials in Li–S batteries

Highly soluble inverse-vulcanized hyperbranched polymers were synthesized as cathode-active materials in Li–S batteries.

Electrospun nanofibers: A prospective electro-active material for constructing high performance Li-ion batteries

The present review outlines high performance Li-ion cells fabricated with all one-dimensional materials as the cathode and anode, as well as a separator-cum-electrolyte prepared by an electrospinning technique.

Microwave-assisted optimization of the manganese redox states for enhanced capacity and capacity retention of LiAlxMn2−xO4 (x = 0 and 0.3) spinel materials

Microwave can shrink particle size and lattice parameters for improved crystallinity, and tune the manganese average valence for enhanced electrochemistry.

Design and synthesis of hierarchical NiCo2S4@NiMoO4core/shell nanospheres for high-performance supercapacitors

A novel electrode material of three-dimensional hierarchical NiCo₂S₄@NiMoO₄core/shell nanospheres was synthesized by a facile two-step hydrothermal method. These hierarchical NiCo₂S₄@NiMoO₄core/shell nanospheres exhibit a high specific capacitance of 1714 F g⁻¹at a current density of 1 A g⁻¹, which indicated the excellent electrochemistry performance.

Mechanistic investigation of ion migration in Na3V2(PO4)2F3 hybrid-ion batteries

The ion-migration mechanism of Na₃V₂(PO₄)₂F₃ is investigated in Na₃V₂(PO₄)₂F₃–Li hybrid-ion batteries through a combined computational and experimental study.

Enhanced electrochemical performance of Li2NiTiO4 with micro-structural rearrangement via urea treatment

After urea-treatment, the voltage platform differences (ΔV) are decreased in the first cycle (0.1 C) and fiftieth cycle (2 C), respectively. Moreover, the rate capability is improved remarkably.

3-Methylpiperidinium ionic liquids

Ionic liquids based on the 3-methylpiperidinium cation core exhibit little or no tendency to crystallise upon cooling and high electrochemical stabilities.

Role of organic solvent addition to ionic liquid electrolytes for lithium–sulphur batteries

A mixed organic solvent/ionic liquid electrolyte combined the beneficial properties of both worlds, high capacity and high safety, through the local arrangement around the Li-ion.

A layered porous ZrO2/RGO composite as sulfur host for lithium–sulfur batteries

The novel structure of ZrO₂@RGO composite provide a layered porous framework for sulfur cathode.

A chemistry and material perspective on lithium redox flow batteries towards high-density electrical energy storage

This review summarizes the latest advances and challenges from a chemistry and material perspective on Li-redox flow batteries that combine the synergistic features of Li-ion batteries and redox flow batteries towards large-scale high-density energy storage systems.

Electrospun porous CuCo2O4 nanowire network electrode for asymmetric supercapacitors

A porous network CuCo₂O₄ nanostructure has been fabricated by a simple spinning method, which shows excellent electrochemical performance for asymmetric supercapacitor.

Recent advances in the electrolytes for interfacial stability of high-voltage cathodes in lithium-ion batteries

We present the useful processes in the research of functional electrolytes for interfacial stability of high-voltage cathodes in Li-ion batteries.

Preparation of high performance lithium-ion batteries with a separator–cathode assembly

Comparison of the lithium-ion batteries with conventional separator (A) and separator–cathode assembly (B).

Crumpled graphene: preparation and applications

This paper reviews the newest form of graphene (crumpled graphene) for energy storage applications.

One-step synthesis of the nickel foam supported network-like ZnO nanoarchitectures assembled with ultrathin mesoporous nanosheets with improved lithium storage performance

Novel network-like ZnO nanoarchitectures are supported on nickel foam as binder-free anodes for high-performance lithium-ion batteries.

Research progress on design strategies, synthesis and performance of LiMn2O4-based cathodes

In this work, we review recent progress in structural design, designing composites with graphene/carbon nanotubes, crystalline doping, and coatings for improving the electrochemical performance of LiMn₂O₄-based cathode materials.

Interconnected mesoporous NiO sheets deposited onto TiO2nanosheet arrays as binder-free anode materials with enhanced performance for lithium ion batteries

TiO₂nanosheet arrays were synthesized by a hydrothermal method as a stable backbone for subsequent chemical bath deposition of interconnected NiO sheets.

Ion conduction behaviour in chemically crosslinked hybrid ionogels: effect of free-dangling oligoethyleneoxides

Ion conduction studies of chemically crosslinked hybrid ionogels fabricated with newly synthesized PEO-functionalized ladder-like polysilsesquioxanes revealed insight into the design of electrolytes for next generation lithium ion batteries.

SnSe alloy as a promising anode material for Na-ion batteries

SnSe alloy is examined for the first time as an anode for Na-ion batteries, and shows excellent electrochemical performance.

A separator modified by high efficiency oxygen plasma for lithium ion batteries with superior performance

The separator modified by high efficiency oxygen plasma is used for the Li/LiMn₂O₄ batteries, which show excellent electrochemical performance in terms of capacity and cycling performance, especially at the elevated temperature of Li-ion batteries.

Preparation and electrochemical characteristics of electrospun water-soluble resorcinol/phenol-formaldehyde resin-based carbon nanofibers

Porous carbon nanofibers prepared by combining electrospinning and one-step activation exhibit remarkable capacitance performances due to the synergistic effect of the optimized pore size distribution, specific surface area and surface properties.

Improved supercapacitive charge storage in electrospun niobium doped titania nanowires

Niobium doped titania nanowires showed an order of magnitude higher capacitance than the parent material.

A facile approach to prepare biomimetic composite separators toward safety-enhanced lithium secondary batteries

A mussel-inspired polydopamine (PDA) coating makes radio-frequency Al₂O₃ sputtering a damage-free, reliable, and cost-efficient process for polyethylene (PE) surface modification for lithium secondary batteries (LIBs).