56 research outputs found
Silicon oxycarbide glass-graphene composite paper electrode for long-cycle lithium-ion batteries
Citation: David, L., Bhandavat, R., Barrera, U., & Singh, G. (2016). Silicon oxycarbide glass-graphene composite paper electrode for long-cycle lithium-ion batteries. Nature Communications, 7, 10. doi:10.1038/ncomms10998Silicon and graphene are promising anode materials for lithium-ion batteries because of their high theoretical capacity; however, low volumetric energy density, poor efficiency and instability in high loading electrodes limit their practical application. Here we report a large area (approximately 15 cm x 2.5 cm) self-standing anode material consisting of molecular precursor-derived silicon oxycarbide glass particles embedded in a chemically-modified reduced graphene oxide matrix. The porous reduced graphene oxide matrix serves as an effective electron conductor and current collector with a stable mechanical structure, and the amorphous silicon oxycarbide particles cycle lithium-ions with high Coulombic efficiency. The paper electrode (mass loading of 2mg cm(-2)) delivers a charge capacity of similar to 588mAhg(-1) (electrode) (similar to 393mAhcm(-3) (electrode)) at 1,020th cycle and shows no evidence of mechanical failure. Elimination of inactive ingredients such as metal current collector and polymeric binder reduces the total electrode weight and may provide the means to produce efficient lightweight batteries
Polymer-Derived Ceramic Functionalized MoS2 Composite Paper as a Stable Lithium-Ion Battery Electrode
Citation: David, L., Bhandavat, R., Barrera, U., & Singh, G. (2015). Polymer-Derived Ceramic Functionalized MoS2 Composite Paper as a Stable Lithium-Ion Battery Electrode. Scientific Reports, 5, 7. doi:10.1038/srep09792A facile process is demonstrated for the synthesis of layered SiCN-MoS2 structure via pyrolysis of polysilazane functionalized MoS2 flakes. The layered morphology and polymer to ceramic transformation on MoS2 surfaces was confirmed by use of electron microscopy and spectroscopic techniques. Tested as thick film electrode in a Li-ion battery half-cell, SiCN-MoS2 showed the classical three-stage reaction with improved cycling stability and capacity retention than neat MoS2. Contribution of conversion reaction of Li/MoS2 system on overall capacity was marginally affected by the presence of SiCN while Li-irreversibility arising from electrolyte decomposition was greatly suppressed. This is understood as one of the reasons for decreased first cycle loss and increased capacity retention. SiCN-MoS2 in the form of self-supporting paper electrode (at 6 mg.cm(-2)) exhibited even better performance, regaining initial charge capacity of approximately 530 mAh.g(-1) when the current density returned to 100 mA.g(-1) after continuous cycling at 2400 mA.g(-1) (192 mAh.g(-1)). MoS2 cycled electrode showed mud-cracks and film delamination whereas SiCN-MoS2 electrodes were intact and covered with a uniform solid electrolyte interphase coating. Taken together, our results suggest that molecular level interfacing with precursor-derived SiCN is an effective strategy for suppressing the metal-sulfide/electrolyte degradation reaction at low discharge potentials
Stable and efficient Li-ion battery anodes prepared from polymer-derived silicon oxycarbide-carbon nanotube shell/core composites
We demonstrate synthesis and electrochemical performance of polymer-derived silicon oxycarbide-carbon nanotube (SiOC-CNT) composites as a stable lithium intercalation material for secondary battery applications. Composite synthesis was achieved through controlled thermal decomposition of 1,3,5,7-tetramethyl 1,3,5,7-tetravinyl cyclotetrasiloxane (TTCS) precursor on carbon nanotubes surfaces that resulted in formation of shell/core type ceramic SiOC-CNT architecture. Li-ion battery anode (prepared at a loading of~ 1.0 mg cmˉ²) showed stable charge capacity of 686 mAh gˉ¹ even after 40 cycles. The average coulombic efficiency (excluding the first cycle loss) was 99.6 %. Further, the post electrochemical imaging of the dissembled cells showed no apparent damage to the anode surface, highlighting improved chemical and mechanical stability of these composites. Similar trend was observed in the rate capability tests, where the SiOC-CNT anode (with 5 wt.% loading in TTCS) again showed stable performance, completely recovering the first cycle capacity of ~ 750 mAh gˉ¹ when the current density was brought back to 50 mA gˉ¹ after cycling at higher current densities
Stable and Efficient Li-Ion Battery Anodes Prepared from Polymer-Derived Silicon Oxycarbide–Carbon Nanotube Shell/Core Composites
We
demonstrate the synthesis and electrochemical performance of
polymer-derived silicon oxycarbide–carbon nanotube (SiOC–CNT)
composites as a stable lithium intercalation material for secondary
battery applications. Composite synthesis was achieved through controlled
thermal decomposition of 1,3,5,7-tetramethyl 1,3,5,7-tetravinyl cyclotetrasiloxane
(TTCS) precursor on carbon nanotubes surfaces that resulted in formation
of shell/core type ceramic SiOC–CNT architecture. Li-ion battery
anode (prepared at a loading of ∼1.0 mg cm<sup>–2</sup>) showed stable charge capacity of 686 mA h g<sup>–1</sup> even after 40 cycles. The average Coulombic efficiency (excluding
the first cycle loss) was 99.6%. Further, the post electrochemical
imaging of the dissembled cells showed no apparent damage to the anode
surface, highlighting improved chemical and mechanical stability of
these composites. A similar trend was observed in the rate capability
tests, where the SiOC–CNT anode (with 5 wt % loading in TTCS)
again showed stable performance, completely recovering the first cycle
capacity of ∼750 mA h g<sup>–1</sup> when the current
density was brought back to 50 mA g<sup>–1</sup> after cycling
at higher current densities
Improved Electrochemical Capacity of Precursor-Derived Si(B)CN-Carbon Nanotube Composite as Li-Ion Battery Anode
We study the electrochemical behavior of precursor-derived
siliconboron
carbonitride (SiÂ(B)ÂCN) ceramic and SiÂ(B)ÂCN coated-multiwalled carbon
nanotube (CNT) composite as a lithium-ion battery anode. Reversible
capacity of SiÂ(B)ÂCN was observed to be 138 mA h/g after 30 cycles,
which is four times that of SiCN (∼25 mA h/g) processed under
similar conditions, while the SiÂ(B)ÂCN-CNT composite showed further
enhancement demonstrating 412 mA h/g after 30 cycles. Improved performance
of SiÂ(B)ÂCN is attributed to the presence of boron that is known to
modify SiCN’s nanodomain structure resulting in improved chemical
stability and electronic conductivity. Post-cycling microscopy and
chemical analysis of the anode revealed formation of a stable passivating
layer, which resulted in stable cycling
Very High Laser-Damage Threshold of Polymer-derived Si(B)CN- Carbon Nanotube Composite Coatings
We study the laser irradiance behavior
and resulting structural evolution of polymer-derived silicon–boron–carbonitride
(SiÂ(B)ÂCN) functionalized multiwall carbon nanotube (MWCNT) composite
spray coatings on copper substrate. We report a damage threshold value
of 15 kWcm<sup>‑2</sup> and an optical absorbance of 0.97 after
irradiation. This is an order of magnitude improvement over MWCNT
(1.4 kWcm<sup>‑2</sup>, 0.76), SWCNT (0.8 kWcm<sup>–2</sup>, 0.65) and carbon paint (0.1 kWcm<sup>–2</sup>, 0.87) coatings
previously tested at 10.6 μm (2.5 kW CO<sub>2</sub> laser) exposure.
Electron microscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy
suggests partial oxidation of SiÂ(B)ÂCN forming a stable protective
SiO<sub>2</sub> phase upon irradiation
Synthesis of Polymer-Derived Ceramic Si(B)CN-Carbon Nanotube Composite by Microwave-Induced Interfacial Polarization
We demonstrate synthesis of a polymer-derived ceramic
(PDC)-multiwall
carbon nanotube (MWCNT) composite using microwave irradiation at 2.45
GHz. The process takes about 10 min of microwave irradiation for the
polymer-to-ceramic conversion. The successful conversion of polymer
coated carbon nanotubes to ceramic composite is chemically ascertained
by Fourier transform-infrared and X-ray photoelectron spectroscopy
and physically by thermogravimetric analysis and transmission electron
microscopy characterization. Frequency dependent dielectric measurements
in the S-Band (300 MHz to 3 GHz) were studied to quantify the extent
of microwave–CNT interaction and the degree of selective heating
available at the MWCNT-polymer interface. Experimentally obtained
return loss of the incident microwaves in the specimen explains the
reason for heat generation. The temperature-dependent permittivity
of polar molecules further strengthens the argument of internal heat
generation
Very High Laser-Damage Threshold of Polymer-derived Si(B)CN- Carbon Nanotube Composite Coatings
We study the laser irradiance behavior
and resulting structural evolution of polymer-derived silicon–boron–carbonitride
(SiÂ(B)ÂCN) functionalized multiwall carbon nanotube (MWCNT) composite
spray coatings on copper substrate. We report a damage threshold value
of 15 kWcm<sup>‑2</sup> and an optical absorbance of 0.97 after
irradiation. This is an order of magnitude improvement over MWCNT
(1.4 kWcm<sup>‑2</sup>, 0.76), SWCNT (0.8 kWcm<sup>–2</sup>, 0.65) and carbon paint (0.1 kWcm<sup>–2</sup>, 0.87) coatings
previously tested at 10.6 μm (2.5 kW CO<sub>2</sub> laser) exposure.
Electron microscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy
suggests partial oxidation of SiÂ(B)ÂCN forming a stable protective
SiO<sub>2</sub> phase upon irradiation
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