8 research outputs found
Endothermic Dehydrogenation-Driven Preventive Magnesiation of SiO for High-Performance Lithium Storage Materials
Silicon monoxide (SiO)-based materials have gained much
attention
as high-capacity lithium storage materials based on their high capacity
and stable capacity retention. However, low initial Coulombic efficiency
associated with the irreversible electrochemical reaction of the amorphous
SiO2 phase in SiO inhibits the wide usage of SiO-based
anode materials for lithium-ion batteries. Magnesiation of SiO is
one of the most promising solutions to improve the initial efficiency
of SiO-based anode materials. Herein, we demonstrate that endothermic
dehydrogenation-driven magnesiation of SiO employing MgH2 enhanced the initial Coulombic efficiency of 89.5% with much improved
long-term cycle performance over 300 cycles compared to the homologue
prepared by magnesiation of SiO with Mg and pristine SiO. High-resolution
transmission electron microscopy with thermogravimetry–differential
scanning calorimetry revealed that the endothermic dehydrogenation
of MgH2 suppressed the sudden temperature rise during magnesiation
of SiO, thereby inhibiting the coarsening of the active Si phase in
the resulting Si/Mg2SiO4 nanocomposite
Dendrite-Free Polygonal Sodium Deposition with Excellent Interfacial Stability in a NaAlCl<sub>4</sub>–2SO<sub>2</sub> Inorganic Electrolyte
Room-temperature
Na-metal-based rechargeable batteries, including Na–O<sub>2</sub> and Na–S systems, have attracted attention due to their high
energy density and the abundance of sodium resources. Although these
systems show considerable promise, concerns regarding the use of Na
metal should be addressed for their success. Here, we report dendrite-free
Na-metal electrode for a Na rechargeable battery, engineered by employing
nonflammable and highly Na<sup>+</sup>-conductive NaAlCl<sub>4</sub>·2SO<sub>2</sub> inorganic electrolyte, as a result, showing
superior electrochemical performances to those in conventional organic
electrolytes. We have achieved a hard-to-acquire combination of nondendritic
Na electrodeposition and highly stable solid electrolyte interphase
at the Na-metal electrode, enabled by inducing polygonal growth of
Na deposit using a highly concentrated Na<sup>+</sup>-conducting inorganic
electrolyte and also creating highly dense passivation film mainly
composed of NaCl on the surface of Na-metal electrode. These results
are highly encouraging in the development of room-temperature Na rechargeable
battery and provide another strategy for highly reliable Na-metal-based
rechargeable batteries
Dual-Size Silicon Nanocrystal-Embedded SiO<sub><i>x</i></sub> Nanocomposite as a High-Capacity Lithium Storage Material
SiO<sub><i>x</i></sub>-based materials attracted a great deal of attention as high-capacity Li<sup>+</sup> storage materials for lithium-ion batteries due to their high reversible capacity and good cycle performance. However, these materials still suffer from low initial Coulombic efficiency as well as high production cost, which are associated with the complicated synthesis process. Here, we propose a dual-size Si nanocrystal-embedded SiO<sub><i>x</i></sub> nanocomposite as a high-capacity Li<sup>+</sup> storage material prepared <i>via</i> cost-effective sol–gel reaction of triethoxysilane with commercially available Si nanoparticles. In the proposed nanocomposite, dual-size Si nanocrystals are incorporated into the amorphous SiO<sub><i>x</i></sub> matrix, providing a high capacity (1914 mAh g<sup>–1</sup>) with a notably improved initial efficiency (73.6%) and stable cycle performance over 100 cycles. The highly robust electrochemical and mechanical properties of the dual-size Si nanocrystal-embedded SiO<sub><i>x</i></sub> nanocomposite presented here are mainly attributed to its peculiar nanoarchitecture. This study represents one of the most promising routes for advancing SiO<sub><i>x</i></sub>-based Li<sup>+</sup> storage materials for practical use
Hydrogen Silsequioxane-Derived Si/SiO<sub><i>x</i></sub> Nanospheres for High-Capacity Lithium Storage Materials
Si/SiO<sub><i>x</i></sub> composite materials have been explored for
their commercial possibility as high-performance anode materials for
lithium ion batteries, but suffer from the complexity of and limited
synthetic routes for their preparation. In this study, Si/SiO<sub><i>x</i></sub> nanospheres were developed using a nontoxic
and precious-metal-free preparation method based on hydrogen silsesquioxane
obtained from sol–gel reaction of triethoxysilane. The resulting
Si/SiO<sub><i>x</i></sub> nanospheres with a uniform carbon
coating layer show excellent cycle performance and rate capability
with high-dimensional stability. This approach based on a scalable
sol–gel reaction enables not only the development of Si/SiO<sub><i>x</i></sub> with various nanostructured forms, but also
reduced production cost for mass production of nanostructured Si/SiO<sub><i>x</i></sub>
High-Performance Si/SiO<sub><i>x</i></sub> Nanosphere Anode Material by Multipurpose Interfacial Engineering with Black TiO<sub>2–<i>x</i></sub>
Silicon oxides (SiO<sub><i>x</i></sub>) have attracted recent attention for their great potential
as promising anode materials for lithium ion batteries as a result
of their high energy density and excellent cycle performance. Despite
these advantages, the commercial use of these materials is still impeded
by low initial Coulombic efficiency and high production cost associated
with a complicated synthesis process. Here, we demonstrate that Si/SiO<sub><i>x</i></sub> nanosphere anode materials show much improved
performance enabled by electroconductive black TiO<sub>2–<i>x</i></sub> coating in terms of reversible capacity, Coulombic
efficiency, and thermal reliability. The resulting anode material
exhibits a high reversible capacity of 1200 mAh g<sup>–1</sup> with an excellent cycle performance of up to 100 cycles. The introduction
of a TiO<sub>2–<i>x</i></sub> layer induces further
reduction of the Si species in the SiO<sub><i>x</i></sub> matrix phase, thereby increasing the reversible capacity and initial
Coulombic efficiency. Besides the improved electrochemical performance,
the TiO<sub>2–<i>x</i></sub> coating layer plays
a key role in improving the thermal reliability of the Si/SiO<sub><i>x</i></sub> nanosphere anode material at the same time.
We believe that this multipurpose interfacial engineering approach
provides another route toward high-performance Si-based anode materials
on a commercial scale
<i>In Operando</i> Monitoring of the Pore Dynamics in Ordered Mesoporous Electrode Materials by Small Angle X‑ray Scattering
To monitor dynamic volume changes of electrode materials during electrochemical lithium storage and removal process is of utmost importance for developing high performance lithium storage materials. We herein report an <i>in operando</i> probing of mesoscopic structural changes in ordered mesoporous electrode materials during cycling with synchrotron-based small angel X-ray scattering (SAXS) technique. <i>In operando</i> SAXS studies combined with electrochemical and other physical characterizations straightforwardly show how porous electrode materials underwent volume changes during the whole process of charge and discharge, with respect to their own reaction mechanism with lithium. This comprehensive information on the pore dynamics as well as volume changes of the electrode materials will not only be critical in further understanding of lithium ion storage reaction mechanism of materials, but also enable the innovative design of high performance nanostructured materials for next generation batteries
Highly Cyclable Lithium–Sulfur Batteries with a Dual-Type Sulfur Cathode and a Lithiated Si/SiO<sub><i>x</i></sub> Nanosphere Anode
Lithium–sulfur batteries could
become an excellent alternative to replace the currently used lithium-ion
batteries due to their higher energy density and lower production
cost; however, commercialization of lithium–sulfur batteries
has so far been limited due to the cyclability problems associated
with both the sulfur cathode and the lithium–metal anode. Herein,
we demonstrate a highly reliable lithium–sulfur battery showing
cycle performance comparable to that of lithium-ion batteries; our
design uses a highly reversible dual-type sulfur cathode (solid sulfur
electrode and polysulfide catholyte) and a lithiated Si/SiO<sub><i>x</i></sub> nanosphere anode. Our lithium–sulfur cell
shows superior battery performance in terms of high specific capacity,
excellent charge–discharge efficiency, and remarkable cycle
life, delivering a specific capacity of ∼750 mAh g<sup>–1</sup> over 500 cycles (85% of the initial capacity). These promising behaviors
may arise from a synergistic effect of the enhanced electrochemical
performance of the newly designed anode and the optimized layout of
the cathode
Si/Ge Double-Layered Nanotube Array as a Lithium Ion Battery Anode
Problems related to tremendous volume changes associated with cycling and the low electron conductivity and ion diffusivity of Si represent major obstacles to its use in high-capacity anodes for lithium ion batteries. We have developed a group IVA based nanotube heterostructure array, consisting of a high-capacity Si inner layer and a highly conductive Ge outer layer, to yield both favorable mechanics and kinetics in battery applications. This type of Si/Ge double-layered nanotube array electrode exhibits improved electrochemical performances over the analogous homogeneous Si system, including stable capacity retention (85% after 50 cycles) and doubled capacity at a 3<i>C</i> rate. These results stem from reduced maximum hoop strain in the nanotubes, supported by theoretical mechanics modeling, and lowered activation energy barrier for Li diffusion. This electrode technology creates opportunities in the development of group IVA nanotube heterostructures for next generation lithium ion batteries