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Germanium (Ge) has a high specific capacity when used as an alloying anode in lithium-ion batteries. However, a large volume of expansion that occurs during charging and discharging hampers its practical applications. In order to improve the stability of the alloying anode, a three-dimensional (3D) germanium/carbon porous composite was produced. In situ X-ray diffraction and electrochemical dilatometry are used to study the alloying electrode's structural evolution during cycling, revealing that the carbon matrix and the linked porosity structure provide a high reversible lithiation and delithiation, resulting in limited electrode volume expansion and high stability. Moreover, combined with a high nickel content cathode, i.e., LiNi0.8Co0.1Mn0.1O2, the composite achieved a specific energy density of 396 W h kg−1 and stable cycling performance, which show potential for its application in lithium-ion full cells. [ABSTRACT FROM AUTHOR]

In this work, we successfully designed and synthesized Ge nanoparticles encapsulated in a carbon matrix and supported by three-dimensional interconnected porous N-doped carbon foam (3D Ge/C-NCF) nanoarchitecture. When applied as an anode material for lithium ion batteries, the obtained composite electrode exhibits high capacity of 878.1 mAh g −1 at a current density of 0.5 A g −1 after 150 cycles. Additionally, it also achieves excellent rate capability and cycling stability. The significant improved electrochemical performance of Ge/C-NCF can be attributed to the synergetic effects of the carbon matrix and the N-doped carbon framework: including a highly conductive carbon network and a structure with large porous for mitigates volume changes of Ge nanoparticles. This study of the composite electrode may provide an interesting method to creating efficient and practical electrodes for those that suffer from huge volume expansion for energy storage applications. [ABSTRACT FROM AUTHOR]

Three-dimensional (3D) titanium dioxide@germanium (TiO2@Ge) core-shell nanorod arrays on carbon textiles are fabricated by a facile two-step method and further investigated as flexible electrode for Li-ion batteries (LIBs). The synthesis of TiO2@Ge composite involves the hydrothermal growth of TiO2 nanorod arrays on carbon textiles and a subsequent coat with a thin layer of germanium with radio frequency (RF) magnetron sputtering. The TiO2 nanorod arrays can effectively not only increase the unit mass loading as a role of skeleton but also remarkably enhance the electrical conductivity via control the lithiation/delithiation voltage in the range of 0.01-1.0 V, where TiO2 can be in situ lithiated to LixTiO2 after the first discharge cycle. Moreover, each TiO2@Ge nanorod has enough space to accommodate the large volume expansion of Ge during charge and discharge cycles. Benefiting from unique electrode architectures, this additive free, self-supported electrode exhibits the high reversible capacity, outstanding rate capability, and the extremely long cycling stability even at a high rate (700.3 mAh g−1 is still retained at 5 A g−1 after 600 cycles). [ABSTRACT FROM AUTHOR]

Here, germanium (Ge) nanofilm as the high-capacity electrode was deposited on the three-dimensional porous nickel foam substrate by radio frequency sputtering. Then, cyclized-polyacrylonitrile (PAN) was coated on the surface of Ge nanofilm to get the excellent rate capability and cycle stability owing to the poor cycle life of the as-prepared Ge nanofilm. X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and energy-dispersive X-ray spectroscopy were employed to analyze the microstructure and morphology of the Ge/cyclized-PAN electrodes. The Ge/cyclized-PAN manifests excellent electrochemical performance with high specific capacity and good cycling stability due to the unique structural features. At the charge-discharge rate of 0.1, 0.2, 0.5, 1, 2, and 5 C over a voltage window of 0.01-1.0 V, the discharge capacities of the composite are 731, 722, 701, 676, 621, and 566 mAh g, respectively. The specific capacity retention is up to 98 % with less capacity fading after 100 cycles at 1 C. [ABSTRACT FROM AUTHOR]