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^–2) showed stable charge capacity of 686 mA h g^–1 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^–1 when the current density was brought back to 50 mA g^–1 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 (Si­(B)­CN) ceramic and Si­(B)­CN coated-multiwalled carbon nanotube (CNT) composite as a lithium-ion battery anode. Reversible capacity of Si­(B)­CN 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 Si­(B)­CN-CNT composite showed further enhancement demonstrating 412 mA h/g after 30 cycles. Improved performance of Si­(B)­CN 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 (Si­(B)­CN) functionalized multiwall carbon nanotube (MWCNT) composite spray coatings on copper substrate. We report a damage threshold value of 15 kWcm^‑2 and an optical absorbance of 0.97 after irradiation. This is an order of magnitude improvement over MWCNT (1.4 kWcm^‑2, 0.76), SWCNT (0.8 kWcm^–2, 0.65) and carbon paint (0.1 kWcm^–2, 0.87) coatings previously tested at 10.6 μm (2.5 kW CO₂ laser) exposure. Electron microscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy suggests partial oxidation of Si­(B)­CN forming a stable protective SiO₂ 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 (Si­(B)­CN) functionalized multiwall carbon nanotube (MWCNT) composite spray coatings on copper substrate. We report a damage threshold value of 15 kWcm^‑2 and an optical absorbance of 0.97 after irradiation. This is an order of magnitude improvement over MWCNT (1.4 kWcm^‑2, 0.76), SWCNT (0.8 kWcm^–2, 0.65) and carbon paint (0.1 kWcm^–2, 0.87) coatings previously tested at 10.6 μm (2.5 kW CO₂ laser) exposure. Electron microscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy suggests partial oxidation of Si­(B)­CN forming a stable protective SiO₂ phase upon irradiation