Influence of pyrolysis atmosphere on the lithium storage properties of carbon-rich polymer derived SiOC ceramic anodes

Polymer derived carbon-rich SiOC ceramics are prepared from polysiloxane precursors through a pyrolysis process at 1000 degrees C using pure argon and argon/hydrogen mixture as pyrolysis atmosphere. The precursor is synthesized from a linear (Si-H)-containing polysiloxane cross-linked with divinylbenzene using hydrosilylation reaction in the presence of a platinum catalyst Pyrolysis in Ar/H-2 mixtures, compared to the treatment under pure Ar, results into a decrease of the concentration of C dangling bonds as revealed by electron spin resonance (ESR) measurements. The amount of free carbon phase is 10 wt.% lower in the sample pyrolysed in a Ar/H-2 mixture, while the ratio of hydrogen to free carbon remains constant for both, in Ar and in Ar/H-2 PYrolysed samples. The sample prepared under Ar/H-2 mixture shows an excellent cycling stability with an increase in the specific capacity of about 150 mAhg(-1) compared to its analogues pyrolysed in pure argon atmosphere.