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A layered germanium telluride (GeTe) and its C-modified nanocomposite (GeTe–C) are synthesized by a simple solid-state synthesis technique, and their electrochemical behaviors for rechargeable lithium-ion batteries (LIBs) are evaluated. Various ex situ analytical tools are employed to demonstrate the electrochemical Li-insertion/-extraction mechanisms of the electrodes. GeTe during Li-insertion exhibits two-step conversion/alloying reactions, and does not recombine after Li-extraction. Interestingly, although GeTe–C shows the same two-step conversion/alloying reactions during Li-insertion, Ge and Te fully recombine after Li-extraction. Owing to the full recombination reactions by the ongoing Li-cycling, GeTe–C shows excellent electrochemical Li-ion storage performances, such as highly reversible capacities (1st Li-insertion/-extraction capacity: 841/691 mA h g−1 or 1767/1450 mA h cm−3), extremely rigid cycling durability (capacity retention: 97.8% after 100 cycling), and rapid rate-capabilities (940 mA h cm−3 at 3C-rate). Therefore, the GeTe–C modified with layered GeTe and amorphous C is a promising anode material with a high energy density for high-performance LIBs.

Puckered-layer-structured germanium monosulfide (GeS) and corresponding amorphous-carbon-decorated nanocomposites (GeS–C) were synthesized and used to fabricate Li-ion battery anodes which displayed remarkable reversible capacity above 1050 mA h g−1after 100 cycles.

A layered GeS2 material was assessed as an electrode material in the fabrication of superior rechargeable Li-ion batteries. The electrochemical Li insertion/extraction behavior of the GeS2 electrode was investigated from extended X-ray absorption measurements as well as by cyclic voltammetry and differential capacity plots to better understand its Li insertion/extraction behavior. Using the Li insertion/extraction reaction mechanism of the GeS2 electrode, an interesting amorphous GeS2-based composite was developed and tested for use as a high-performance electrode. Interestingly, the amorphous GeS2-based composite electrode exhibited highly reversible discharging and charging reactions, which were attributed to a conversion/recombination reaction. The amorphous GeS2-based composite electrode exhibited highly reversible and outstanding electrochemical performances, a highly reversible capacity (first charge capacity: 1298 mAh g–1) with a high first Coulombic efficiency (83.3%), rapid rate capability (ca. 8...

The electrochemical reaction mechanism of ZnO is investigated to understand its Li insertion/extraction behavior using ex situ X-ray diffraction, extended X-ray absorption fine structure, and high-resolution transmission electron microscopy. Based on these analyses, an interesting partial recombination reaction of ZnO is discovered, which demonstrates that Li2O formed during Li insertion is partially reversible. Additionally, we discover that the control of the partial recombination reaction of the metal oxide is very important for improving reversibility in the first cycle, which is a key finding for realization of highly reversible oxide-based electrode materials. In addition, to enhance the electrochemical performance of the ZnO electrode, a nanostructured ZnO/C composite is prepared by a simple high-energy mechanical milling process. This process allows the electrochemical performance of the ZnO electrode to be evaluated as an anode for rechargeable Li-ion batteries. Electrochemical tests show that the nanocomposite electrode exhibits a high initial charge capacity of 682 mAh g−1, fast rate capability of 371 mAh g−1 at 2 C, and excellent cyclability over 200 cycles.

Germanium telluride (GeTe) with a layered structure and a GeTe nanocomposite modified by amorphous carbon (GeTe/C) are prepared via a simple solid-state synthesis, and their electrochemical performance for sodium-ion batteries is evaluated. To determine the electrochemical sodiation/desodiation mechanism of the GeTe and GeTe/C, various ex situ analytical methods are employed. During sodiation, GeTe in both electrodes is converted into NaGe and Na2Te phases. By contrast, during desodiation, the converted NaGe and Na2Te phases in the only GeTe/C are completely recombined into the original GeTe phase. Because of the repeated conversion/recombination reactions during sodiation/desodiation, GeTe/C displays outstanding Na-ion storage characteristics, such as a high reversible first volumetric capacity of 662 mAh cm−3, a stable capacity retention of 98.5% up to after 100 cycles, and rapid rate capabilities of 704 mAh cm−3 at 1C and 630 mAh cm−3 at 3C. Therefore, the GeTe/C is expected to perform well as a high–capacity anode in rechargeable sodium-ion batteries.

A layered GeS