# Synthesis of C/SiC Mixtures for Composite Anodes of Lithium-Ion Power Sources
## 1 Introduction  
Graphite is traditionally used as an anode material of lithium-ion batteries (LIBS) due to its relatively low cost, low volume expansion (up to 10%), high electrical conductivity, charge rate. On the other hand, this material capacity (up to 372 mAh g\({}^{-1}\)) [1, 2, 3] no longer meets the requirements of modern devices and machines for an increased energy density.  
Promising anode materials with a higher specific capacity for LIBS are transition metal oxides [4, 5, 6, 7, 8, 9], silicon [10, 11, 12, 13, 14], germanium [15, 16, 17], SiC [18, 19], as well as various composite mixtures of the above materials with carbon [20, 21, 22, 23, 24, 25, 26, 27]. Transition metal oxides seem to be cheap, easy to synthesize. They provide a relatively high capacity (theoretical up to 718 mAh g\({}^{-1}\)[4]; experimental up to 1150 mAh g\({}^{-1}\)[4]) and charge rate, but suffer from high volume expansion (about 96% [8]). Silicon also seems to be a suitable material that provides maximum capacity (theoretical up to 4200 mAh g\({}^{-1}\)[9, 10, 11, 12], experimentally achieved--3900 mAh g\({}^{-1}\)[13]) and a sufficiently high charge rate, but drastic volume expansion (up to 300% [10, 11, 12]) still presents the biggest challenge to the realization of Si anodes. Germanium is a less accessible material with a lower capacity (theoretical, up to 1624 mAh g\({}^{-1}\); experimental, up to 1248 mAh g\({}^{-1}\)[16]) compared to silicon, but it provides advantages such as higher electronic conductivity. Moreover, the diffusion coefficient of lithium ions in germanium is 400 times higher than in silicon [17].  
Silicon carbide is a perspective easily available anode material with high mechanical, chemical and thermal stability [18; 19]. However, for lithiation, pure SiC must have a certain structure and size. Therefore, it is considered more as a matrix or substrate that allows to compensate the volume expansion of silicon. Nevertheless, several works have reported on the LIBs with SiC anode. In [28; 29], a decrease in the thickness of SiC films or particles leads to an increase in their capacity from 300 to 1370 mAh g\({}^{-1}\) with a Coulombic efficiency of about 90%. This also explains the significant scatter of the SiC anode capacity in the available papers. Finally, recently a significant number of articles have been devoted to the development of LIBs with composite anode materials represented by silicon, graphite, SiC, SiO\({}_{x}\), etc., including various sizes and structures: core-shell wires, tubes, needles, fibers, multilayer films of graphene and silicene [30; 31; 32; 33; 34]. Calculations showed improved electrochemical parameters of such structures during lithiation/delithiation [35]. Despite the advantages of such composite anodes, their relatively complex production should be noted. Often, single samples are presented in the existing works and nothing is reported about the large-scale production of the materials. At present, the hydrothermal method is mainly used for the large-scale production of silicon carbide [36; 37]. At the same time, many works are devoted to the metallothermic preparation of SiC [38; 39], although these methods require further purification of carbide from intermediate synthesis products.  
Previously, we showed the possibility of synthesizing ultrafine SiC fibers from cheap materials using carbothermal synthesis [40; 41]. The feature of our method is the use of natural samples of pure quartz and graphite with a certain morphology and particle size. In this work, in addition to the obtaining of SiC, this approach was also used for obtaining of C/SiC mixtures suitable for use as composite anodes of lithium-ion power sources.