Lithiation Behavior of Coaxial Hollow Nanocables of Carbon-Silicon Composite

A design of coaxial hollow nanocables of carbon nanotubes and silicon composite (CNTs@Silicon) was presented, and the lithiation/delithiation behavior was investigated. The FIB-SEM studies demonstrated hollow structured silicon tends to expand inward and shrink outward during lithiation/delithiation, which reveal the mechanism of inhibitive effect of the excessive growth of solid-electrolyte interface by hollow structured silicon. The as-prepared coaxial hollow nanocables demonstrate an impressive reversible specific capacity of 1150 mAh g^-1 over 500 cycles, giving an average Coulombic efficiency of >99.9%. The electrochemical impedance spectroscopy and differential scanning calorimetry confirmed the SEI film excessive growth is prevented.

Three-Dimensional Porous Si and SiO2 with In Situ Decorated Carbon Nanotubes As Anode Materials for Li-ion Batteries

A high-capacity Si anode is always accompanied by very large volume expansion and structural collapse during the lithium-ion insertion/extraction process. To stabilize the structure of the Si anode, magnesium vapor thermal reduction has been used to synthesize porous Si and SiO₂ (pSS) particles, followed by in situ growth of carbon nanotubes (CNTs) in pSS pores through a chemical vapor deposition (CVD) process. Field-emission scanning electron microscopy and high-resolution transmission electron microscopy have shown that the final product (pSS/CNTs) possesses adequate void space intertwined by uniformly distributed CNTs and inactive silica in particle form. pSS/CNTs with such an elaborate structural design deliver improved electrochemical performance, with better coulombic efficiency (70% at the first cycle), cycling capability (1200 mAh g^-1 at 0.5 A g^-1 after 200 cycles), and rate capability (1984, 1654, 1385, 1072, and 800 mAh g^-1 at current densities of 0.1, 0.2, 0.5, 1, and 2 A g^-1, respectively), compared to pSS and porous Si/CNTs. These merits of pSS/CNTs are attributed to the capability of void space to absorb the volume changes and that of the silica to confine the excessive lithiation expansion of the Si anode. In addition, CNTs have interwound the particles, leading to significant enhancement of electronic conductivity before and after Si-anode pulverization. This simple and scalable strategy makes it easy to expand the application to manufacturing other alloy anode materials.

First-principles calculation of lithium insertion into homogeneous a-SiC2/5O6/5as high performance anode

Amorphous silicon oxycarbide is considered as a promising anode material for new generation of lithium-ion batteries, and figuring out the lithiation mechanism is crucial for its application.

Silicon-Reduced Graphene Oxide Self-Standing Composites Suitable as Binder-Free Anodes for Lithium-Ion Batteries

Silicon-reduced graphene oxide (Si-rGO) composites processed as self-standing aerogels (0.2 g cm^-3) and films (1.5 g cm^-3) have been prepared by the thermal reduction of composites formed between silicon nanoparticles and a suspension of graphene oxide (GO) in ethanol. The characterization of the samples by different techniques (X-ray diffraction, Raman, thermogravimetric analysis, and scanning electron microscopy) show that in both cases the composites are formed by rGO sheets homogeneously decorated with 50 nm silicon nanoparticles with silicon contents of ∼40% wt. The performances of these self-standing materials were tested as binder-free anodes in lithium-ion batteries (LIBs) in a half cell configuration under two different galvanostatic charge-discharge cutoff voltages (75 and 50 mV). The results show that the formation of a solid electrolyte interphase (SEI) is favored in composites processed as aerogels due to its large exposed surface, which prevents the activation of silicon when they are cycled within the 2 to 0.075 V voltage windows. It is also found that the composites processed in the form of self-standing films exhibit good stability over the first 100 cycles, high reversible specific capacity per mass of electrode (∼750 mAh g^-1), areal capacities that reach 0.7 mAh cm^-2, and high Coulombic efficiencies (80% for the first charge-discharge cycle and over 99% in the subsequent cycles).

Graphite–silicon alloy composite anodes employing cross-linked poly(vinyl alcohol) binders for high-energy density lithium-ion batteries

Graphite–silicon alloy composite anodes employing cross-linked poly(vinyl alcohol) binders exhibited high discharge capacities and good cycling stabilities.