Oxycarbide glass

Silicon oxycarbide features a high Li‐ion storage capacity ranging from 600 to 700 mAh g⁻¹,[7] low volume expansion upon lithiation of about 7%[8] [9] [10] and high electronic conductivity.

To maximize the anodic charge storage capacity of Li-ion batteries, alloying-type anode materials such as Sn and Sb have attracted considerable interest because of their high theoretical capacity of 992 and 660 mAh g⁻¹ and a suitable lithiation/delithiation voltage window of 0.01–1.5 V vs. Li⁺/Li. Recent advances in nanostructuring of the alloying-type anodes provide an effective way of mitigating the challenges of their volume expansion upon lithiation that severely hinder the cycling stability. [11] Besides, one of the prevailing approaches toward stabilization of such electrodes is the embedding of Sn or Sb in the form of nanoparticles in a matrix. The matrix helps to buffer the volume changes, impart better electronic connectivity, and prevent particle aggregation upon lithiation/delithiation. In this context, silicon oxycarbide is an appealing candidate for stabilizing Sn and Sb inclusions.

A facile synthesis of Sn nanoparticles embedded in a SiOC matrix via the pyrolysis of a preceramic polymer as a single‐source precursor has been reported. This polymer contains Sn 2‐ethyl‐hexanoate (Sn(Oct)₂) and poly(methylhydrosiloxane) as sources of Sn and Si, respectively. Upon functionalization with apolar divinyl benzene sidechains, the polymer is rendered compatible with Sn(Oct)₂. This approach yields a homogeneous dispersion of Sn nanoparticles in a SiOC matrix with sizes on the order of 5–30 nm. Anodes of the SiOC/Sn nanocomposite demonstrate high capacities of 644 and 553 mAh g⁻¹ at current densities of 74.4 and 2232 mA g⁻¹ (C/5 and 6C rates for graphite), respectively, and show superior rate capability with only 14% capacity decay at high currents. [12]

A similar approach has been reported for the stabilization of Sb nanoparticles; homogeneously embedded Sb nanoparticles in a SiOC matrix with the size of 5–40 nm have been obtained via the pyrolysis of a preceramic polymer. The latter is obtained through the Pt-catalyzed gelation reaction of Sb 2-ethylhexanoate and a poly(methylhydrosiloxane)/divinylbenzene mixture. The complete miscibility of these precursors was achieved by the functionalization of poly(methylhydrosiloxane) with apolar divinyl benzene side-chains. It has been shown that anodes composed of SiOC/Sb exhibit a high rate capability, delivering charge storage capacity in the range of 703–549 mA h g⁻¹ at a current density of 74.4–2232 mA g⁻¹. [13]