Silicon nanowires (Si NWs) have been identified as an excellent candidate material for the replacement of graphite in anodes, allowing for a significant boost in the capacity of lithium‐ion batteries (LIBs). Herein, high‐density Si NWs are grown on a novel 3D interconnected network of binary‐phase Cu‐silicide nanofoam (3D CuxSiy NF) substrate. The nanofoam facilitates the uniform distribution of well‐segregated and small‐sized catalyst seeds, leading to high‐density/single‐phase Si NW growth with an areal‐loading in excess of 1.0 mg cm−2 and a stable areal capacity of ≈2.0 mAh cm−2 after 550 cycles. The use of the 3D CuxSiy NF as a substrate is further extended for Al, Bi, Cu, In, Mn, Ni, Sb, Sn, and Zn mediated Si NW growth, demonstrating the general applicability of the anode architecture.
A scalable and cost‐effective process is used to electroplate metallic Zn seeds on stainless steel substrates. Si and Ge nanowires (NWs) are subsequently grown by placing the electroplated substrates in the solution phase of a refluxing organic solvent at temperatures >430 °C and injecting the respective liquid precursors. The native oxide layer formed on reactive metals such as Zn can obstruct NW growth and is removed in situ by injecting the reducing agent LiBH4. The findings show that the use of Zn as a catalyst produces defect‐rich Si NWs that can be extended to the synthesis of Si–Ge axial heterostructure NWs with an atomically abrupt Si–Ge interface. As an anode material, the as grown Zn seeded Si NWs yield an initial discharge capacity of 1772 mAh g−1 and a high capacity retention of 85% after 100 cycles with the active participation of both Si and Zn during cycling. Notably, the Zn seeds actively participate in the Li‐cycling activities by incorporating into the Si NWs body via a Li‐assisted welding process, resulting in restructuring the NWs into a highly porous network structure that maintains a stable cycling performance.
Direct colloidal
synthesis of multinary metal chalcogenide nanocrystals
typically develops dynamically from the binary metal chalcogenide
nanocrystals with the subsequent incorporation of additional metal
cations from solution during the growth process. Metal seeding of
binary and multinary chalcogenides is also established, although the
seed is solely a catalyst for nanocrystal nucleation and the metal
from the seed has never been exploited as active alloying nuclei.
Here we form colloidal Cu–Bi–Zn–S nanorods (NRs)
from Bi-seeded Cu
2–
x
S heterostructures.
The evolution of these homogeneously alloyed NRs is driven by the
dissolution of the Bi-rich seed and recrystallization of the Cu-rich
stem into a transitional segment, followed by the incorporation of
Zn
2+
to form the quaternary Cu–Bi–Zn–S
composition. The present study also reveals that the variation of
Zn concentration in the NRs modulates the aspect ratio and affects
the nature of the majority charge carriers. The NRs exhibit promising
thermoelectric properties with very low thermal conductivity values
of 0.45 and 0.65 W/mK at 775 and 605 K, respectively, for Zn-poor
and Zn-rich NRs. This study highlights the potential of metal seed
alloying as a direct growth route to achieving homogeneously alloyed
NRs compositions that are not possible by conventional direct methods
or by postsynthetic transformations.
Despite significant efforts to fabricate high energy density (ED) lithium (Li) metal anodes, problems such as dendrite formation and the need for excess Li (leading to low N/P ratios) have hampered Li metal battery (LMB) development. Here, the use of germanium (Ge) nanowires (NWs) directly grown on copper (Cu) substrates (Cu‐Ge) to induce lithiophilicity and subsequently guide Li ions for uniform Li metal deposition/stripping during electrochemical cycling is reported. The NW morphology along with the formation of the Li15Ge4 phase promotes uniform Li‐ion flux and fast charge kinetic, resulting in the Cu‐Ge substrate demonstrating low nucleation overpotentials of 10 mV (four times lower than planar Cu) and high Columbic efficiency (CE) efficiency during Li plating/stripping. Within a full‐cell configuration, the Cu‐Ge@Li – NMC cell delivered a 63.6% weight reduction at the anode level compared to a standard graphite‐based anode, with impressive capacity retention and average CE of over 86.5% and 99.2% respectively. The Cu‐Ge anodes are also paired with high specific capacity sulfur (S) cathodes, further demonstrating the benefits of developing surface‐modified lithiophilic Cu current collectors, which can easily be integrated at the industrial scale.
In this paper, we have developed a "phosphine-free" method for synthesising copper telluride nanocrystals using diphenyl ditelluride as an air-stable tellurium source. The diphenyl ditelluride is shown to have optimal reactivity for the colloidal synthesis of Cu2Te, allowing optimal control over the phase and morphology. Using this unexplored Te precursor for copper telluride synthesis, 1-D nanorods of hexagonal phase (Cu2Te) were synthesised at a moderate temperature of 180 °C. The precise control over key parameters for this system results in Cu2-XTe nanocrystals forming with varied shapes (1-D nanorods and 2-D nanoplates), sizes, and crystal phases (hexagonal Cu2Te and orthorhombic Cu1.43Te).
A solution-based synthesis of well-ordered Cu-rich silicide nanoarchitectures, consisting of a pair of layered cups and stems (ρ-Cu 15 Si 4 ), is demonstrated. The as-grown ρ-Cu 15 Si 4 typically exhibits distinct interconnected 1D stems consisting of a stack of nanorods (∼300 nm in length) terminated with concave hexagonal 3D cups that evolve through a self-regulated layer-by-layer growth mechanism. Discrete-time ex situ experimental observations reveal that the ρ-Cu 15 Si 4 evolution is driven by interatomic diffusion, initially triggering the formation of binary-phase silicide islands (spheres) followed by the formation of hexagonal discs, stem growth, and lateral elongation in exactly opposite directions. It is further shown that electrochemically pregrown Cu crystals can facilitate the direct growth of ρ-Cu 15 Si 4 in high yield with an enhanced substrate coverage.
The
growth mechanism and synthetic controls for colloidal multinary
metal chalcogenide nanocrystals (NCs) involving alkali metals and
the pnictogen metals Sb and Bi are unknown. Sb and Bi are prone to
form metallic nanocrystals that stay as impurities in the final product.
Herein, we synthesize colloidal NaBi1–x
Sb
x
Se2–y
S
y
NCs using amine–thiol–Se
chemistry. We find that ternary NaBiSe2 NCs initiate with
Bi0 nuclei and an amorphous intermediate nanoparticle formation
that gradually transforms into NaBiSe2 upon Se addition.
Furthermore, we extend our methods to substitute Sb in place of Bi
and S in place of Se. Our findings show the initial quasi-cubic morphology
transforms into a spherical shape upon increased Sb substitution,
and the S incorporation promotes elongation along the <111>
direction.
We further investigate the thermoelectric transport properties of
the Sb-substituted material displaying very low thermal conductivity
and n-type transport behavior. Notably, the NaBi0.75Sb0.25Se2 material exhibits an ultralow thermal conductivity
of 0.25 W·m–1·K–1 at
596 K with an average thermal conductivity of 0.35 W·m–1·K–1 between 358 and 596 K and a ZT
max of 0.24.
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