Synthesis and optimization of nanoparticle Ge confined in a carbon matrix for lithium battery anode material

Ge nanoparticles with different particle sizes confined in a carbon matrix were prepared by annealing Ge nanoparticles terminated with butyl groups at 400, 600, and 800°C. X-ray diffraction and transmission electron microscopy results showed that the Ge nanoparticles' size increased from 8 to 100 nm as the annealing temperature of the as-prepared samples increased from 400 to 800°C. Raman spectra confirmed that the parts of the Ge nanoparticles were not covered by the carbon starting at 600°C after annealing for 9 h. Moreover, the graphitization degree of the carbon increases with increasing temperature, and the sample, annealed at 800°C for 3 h, showed the graphitization degree. Electrochemical cycling results revealed that the 10 nm Ge nanoparticles, confined in a carbon matrix obtained after annealing the as-prepared sample at 600°C for 3 h, showed the best charge capacity of 1067 mAhg with 12% capacity loss after 30 cycles. On the other hand, Ge nanoparticles that had not been covered with the carbon matrix showed a rapid capacity decrease, along with pulverization of Ge nanoparticles to a size of about 5-10 nm after cycling.close515

Multiscale Engineered Si/SiO x Nanocomposite Electrodes for Lithium-Ion Batteries Using Layer-by-Layer Spray Deposition

Si-based high-capacity materials have gained much attention as an alternative to graphite in Li-ion battery anodes. Although Si additions to graphite anodes are now commercialized, the fraction of Si that can be usefully exploited is restricted due to its poor cyclability arising from the large volume changes during charge/discharge. Si/SiO x nanocomposites have also shown promising behavior, such as better capacity retention than Si alone because the amorphous SiO x helps to accommodate the volume changes of the Si. Here, we demonstrate a new electrode architecture for further advancing the performance of Si/SiO x nanocomposite anodes using a scalable layer-by-layer atomization spray deposition technique. We show that particulate C interlayers between the current collector and the Si/SiO x layer and between the separator and the Si/SiO x layer improved electrical contact and reduced irreversible pulverization of the Si/SiO x significantly. Overall, the multiscale approach based on microstructuring at the electrode level combined with nanoengineering at the material level improved the capacity, rate capability, and cycling stability compared to that of an anode comprising a random mixture of the same materials

Sn0.9Si0.1/carbon core-shell nanoparticles for high-density lithium storage materials

Sn0.9Si0.1 core/carbon shell nanoparticles, with the sizes of 16 and 10 nm, were prepared by annealing as-prepared butyl-capped Sn0.9Si0.1 particles with an average particle size of 1 ??m. Even though as-prepared samples were severely encapsulated by butyl terminators, annealing led to pulverization of the bulky particles into core - shell nanoparticles with a shell thickness dependent on the annealing temperature. The core Sn0.9Si0.1 size was estimated to be constant at 6 nm, and the carbon shell thickness decreased from 10 to 4 nm with increasing annealing temperature from 600 to 700??C, respectively. In addition, the carbon shell was found to be more ordered at 700??C than at 600??C. Sn0.9Si0.1 core/carbon shell nanoparticles exhibited excellent lithium storage ability at a high current rate, resulting in a value of 964 mA??h/g at a rate of 0.3 C (1 C = 1200 mA/g), and demonstrated good capacity retention after 50 cycles.close363

Observation of reversible pore change in mesoporous tin phosphate anode material during Li alloying/dealloying

We observed the pore expansion and contraction of mesoporous tin phosphate during Li alloying/dealloying using small-angle X-ray scattering and transmission electron microscopy. As-prepared mesoporous tin phosphate showed pore and porewall sizes of 3 and 2 nm, respectively. During lithium alloying (discharging), pore size was slightly contracted, but porewall size was slightly expanded within the range of 1 nm. However, during lithium dealloying (charging), pore and porewall sizes recovered to their original sizes before cycling. The charged sample had a nanoscale pore (∼3 nm) array with a more or less uniformly sized open-porewall structure of amorphous lithium phosphates with metallic α-Sn face-centered-cubic nanocrystals ∼2 nm in diameter.close101

Development of Harmonic Drive Combining Four Arcs for Conventional Kinematic Application

This paper proposes a modified harmonic cam, which is used to design a harmonic drive. Conventional harmonic drives using a sinusoidal cam type pertain to an elastic body concept and are thus difficult to design and evaluate. Unlike the conventional sinusoidal cam, the proposed harmonic cam involves a combination of four arcs. Such cams can be designed based on a rigid body concept, and thus, the tooth profile can be designed and analyzed using the established gear theory. The novel harmonic cam is designed by exploiting four-arc combinations, and guides for designing harmonic drives with involute and cycloid angular teeth are presented. A harmonic drive with a difference of two teeth between the circular spline and flex spline is designed. The operation, tooth engagement, and interference are validated through a mock-up production using a 3D printer and gear simulation program. The findings can facilitate the facile design and manufacturing of harmonic drives