GeO2/Ge/C anode material synthesized using a simple method involving simultaneous carbon coating and reduction by acetylene gas is composed of nanosized GeO2/Ge particles coated by a thin layer of carbon, which is also interconnected between neighboring particles to form clusters of up to 30 μm. The GeO2/Ge/C composite shows a high capacity of up to 1860 mAh/g and 1680 mAh/g at 1 C (2.1 A/g) and 10 C rates, respectively. This good electrochemical performance is related to the fact that the elemental germanium nanoparticles present in the composite increases the reversibility of the conversion reaction of GeO2. These factors have been found through investigating and comparing GeO2/Ge/C, GeO2/C, nanosized GeO2, and bulk GeO2.

The automobile industry is currently shifting towards hybrid and electric vehicles which are powered by electrochemical energy storage systems. However, these "greener" alternatives still suffer from low mileage when compared to a full tank of gasoline. Therefore, it is important to develop batteries that have a high energy density, high power density, and long cycle life. Lithium-ion batteries (LIBs) have been widely used in the consumer market for portable electronic devices since their introduction in the 1990s. This battery system is a more suitable candidate for hybrid/electric vehicles compared to nickel metal hydride, alkaline, and lead-acid batteries because of its higher volumetric and gravimetric energy density. However, there is still room for improvement in the case of the energy and power densities of LIBs. One strategy to increase the performance of LIBs is to find alternative anode materials that satisfy both requirements.Germanium is an excellent candidate as anode material for LIBs when compared to other metallic anode materials that undergo lithium alloying reactions, such as tin [1] and silicon. [2] This is because of its high theoretical capacity (1600 mA h g À1 , 4.4 Li + ions per Ge atom), good lithium diffusivity (400 times faster than in silicon), and high electrical conductivity (104 times higher than silicon). Nevertheless, the price of germanium is the major drawback for the commercialization of this anode material. Furthermore, similar to silicon and tin, germanium suffers large volume changes during lithium alloying/de-alloying reactions. With prolonged cycling, the mechanical stress causes electrode pulverization from the current collector, and this leads to capacity fading.Various approaches have been reported to enhance the cycling stability of germanium. These include using morphologies that have better structural stability for accommodating volume changes (nanoparticles, [3] nanowires, [4] nanotubes, [5] and porous [6] and mesoporous [7] structures), germaniumbased composites (tin-germanium, [8] germanium/carbon nanotubes [9] ), germanium oxides, [10] and carbon coating of germanium. However, rate capabilities of germanium anodes that have been reported need more improvement to satisfy the requirements of electric vehicles with high energy consumption.Herein, we report a facile synthesis method to produce germanium/carbon nanostructures by carbon coating and reduction of the oxide precursor. When the particle size of the germanium oxide precursor was varied, two different selfassembled germanium/carbon nanostructures could be obtained, namely, a cluster (C) nanostructure and a nonclustered (NC) structure. Hereafter, they are denoted as "C-Ge/C" and "NC-Ge/C". Both germanium/carbon nanostructures displayed good cycling stability at the 0.2 C rate (0.32 A g À1 ) for over 50 cycles and at the 1 C rate (1.6 A g À1 ) for over 120 cycles. Surprisingly, the C-Ge/C structure shows an exceptionally high rate capability up to the 40 C rate (64 A g À1 ). The NC-Ge/C structure, however, sh...

Sodium-ion batteries can be the best alternative to lithium-ion batteries, because of their similar electrochemistry, nontoxicity, and elemental abundance and the low cost of sodium. They still stand in need of better cathodes in terms of their structural and electrochemical aspects. Accordingly, the present study reports the first example of the preparation of Na2/3(Fe1/2Mn1/2)­O2 hierarchical nanofibers by electrospinning. The nanofibers with aggregated nanocrystallites along the fiber direction have been characterized structurally and electrochemically, resulting in enhanced cyclability when compared to nanoparticles, with initial discharge capacity of ∼195 mAh g–1. This is attributed to the good interconnection among the fibers, with well-guided charge transfers and better electrolyte contacts.

An exfoliated MoS2-C composite (E-MoS2-C) was prepared via simple chemical exfoliation and a hydrothermal method. The obtained E-MoS2-C was tested as an anode material for sodium ion batteries. High capacity (~400 mA h g(-1)) at 0.25 C (100 mA g(-1)) was maintained over prolonged cycling life (100 cycles). Outstanding rate capability was also achieved with a capacity of 290 mA h g(-1) at 5 C.

A novel hierarchical star-like Co3O4 was successfully synthesized from self-assembled hierarchical Co(OH)F precursors via a facile hydrothermal method and subsequent annealing in air. The morphological evolution process of the Co(OH)F precursors was investigated by examining the different reaction times during synthesis. First, hexagonal plates are formed, and then nanodiscs grow on the surface of the plates. Subsequently, dissolution and regrowth of Co(OH)F occur to form the star-like hierarchical structures. Co3O4 obtained from thermal decomposition of the Co(OH)F precursor in air at 350 °C exhibited high reversible capacity as an anode material in lithium ion batteries. The specific charge capacity of 1036 mA h g−1 was obtained in the first cycle at a current density of 50 mA g−1, and after 100 cycles, the capacity retention was nearly 100%. When the current density was increased to 500 mA g−1 and 2 A g−1, the capacities were 995 and 641 mA h g−1, respectively, after 100 cycles. In addition, a capacity of 460 mA h g−1 was recorded at a current density of 10 A g−1 in the rate capability test. The excellent electrochemical performance of the Co3O4 electrodes can be attributed to the porous interconnected hierarchical nanostructures, which protect the small particles from agglomeration and buffer the volume change during the discharge-charge process. mA/g, and after 100 cycles, the capacity retention was nearly 100%. When the current density was increased to 500 mA/g and 2 A/g, the capacities were 995 and 641 mAh/g, respectively, 2 after 100 cycles. In addition, a capacity of 460 mAh/g was recorded at current density of 10 A/g in the rate capability test. The excellent electrochemical performance of the Co 3 O 4 electrodes can be attributed to the porous interconnected hierarchical nanostructures, which protect the small particles from agglomeration and buffer the volume change during the discharge/charge process.