# The Progress of Cobalt-Based Anode Materials for Lithium Ion Batteries and Sodium Ion Batteries
## 3 Preparation Methods of Synthesizing Cobalt-based Active Materials
### Other Methods  
With the exception of these methods, many other practical approaches, such as electrospinning, magnetron sputtering, chemical vapor deposition (CVD) and electric arc melting, have been applied to synthesize cobalt-based electrode materials with novel nanostructures [19; 44; 50; 90; 91; 92; 93; 94; 95; 96]. Electrospinning is a method to synthesize 1D nanomaterials by the breakdown of a high-polymer solution by a high-voltage electrostatic field [97; 24; 93]. [PERSON]'s group distributed CoSe\({}_{2}\) nanoparticles uniformly into nitrogen-doped carbon nanofibers through two steps, including the electrospinning approach and subsequent selenization process (Figure 8a) [24]. TEM image, HRTEM image and corresponding elements mapping clearly reveal that CoSe\({}_{2}\) particles were well-wrapped in the N-doped nanofibers without aggregation, as shown in Figure 8b-d, respectively. Co-Sn/CNF composites were fabricated by [PERSON]'s group through electrospinning, followed with heat treatments [90]. SEM image of the Co-Sn/CNF surface shows that the average diameter of the fibers was 180 nm (Figure 8e). [PERSON] et al. prepared carbon-encapsulated wire-in-tube Co\({}_{3}\)O\({}_{4}\)/MnO\({}_{2}\) heterostructure nanofibers through electrospinning, followed by calcination [91]. The TEM image in Figure 8f shows a tubular structure with three layers, including an MnO\({}_{2}\) wire, Co\({}_{3}\)O\({}_{4}\) tube and carbon layer, subsequently. X-ray EDS in Figure 8g clearly indicates the presence of Mn, Co, O, N and C elements. [PERSON]'s group prepared 1D carbon nanofibers embedded with uniformly SnCo nanoparticles via electrospinning, followed by calcination [92]. SEM image in Figure 8h shows that SnCo alloys with size distributions of 5-10 nm were homogeneously encapsulated in carbon nanofibers. [PERSON]'s group successfully synthesized a novel urchin-like sample composed of CoSe\({}_{2}\) nanofibers rooted into the carbon nanofibers (CoSe\({}_{2}\)@CNFs) [93]. In the preparation process, [PERSON]'s group firstly synthesized the precursor (Co@CNF) via electrospinning, followed by calcination, and subsequently prepared CoSe\({}_{2}\)@CNFs through a hydrothermal selenation. TEM image and corresponding HRTEM image (inset) in Figure 8i obviously show that urchin-like CoSe\({}_{2}\) nanorods with lengths of 50-100 nm and diameters of 20-30 nm are rooted into the electrospun CNFs. [PERSON] et al. employed the electrospinning method to synthesize Co/Co\({}_{3}\)O\({}_{4}\)-carbon nanofibers with porous structures [94]. The Co/Co\({}_{3}\)O\({}_{4}\) nanoparticles were distributed throughout the carbon nanofiber, as shown in Figure 8j. Chemical vapor deposition (CVD) processes have also been applied to synthesize cobalt-based electrode materials with multifarious structures [44; 98; 99; 100]. He's group successfully prepared a novel structure via the CVD process [44]. The TEM image in Figure 8k clearly indicates a typical 0D-1D-3D hierarchical structure. The magnetron sputtering method is also developed to prepare cobalt-based materials on substrates [19; 101]. [PERSON] et al. synthesized a Co\({}_{3}\)O\({}_{4}\)-C core-shell nanowire array via hydrothermal and magnetron sputtering. SEM image in Figure 8l shows that the Co\({}_{3}\)O\({}_{4}\) nanowires were well-coated by carbon layers with a thickness of 18 nm. Furthermore, [PERSON]'s group reported an electric arc-melting method to produce a Co\({}_{2}\)MnSi ingot [96]. Figure 8m indicates that the synthesized materials exhibited a certain degree of aggregation. Various strategies for the preparation of cobalt-based electrode materials are summarized in Table 2. Obviously, hydrothermal/solvothermal, heat treatment, galvanic replacement and HEMM can be used to prepare different types of cobalt-based materials due to their economy and simplicity naturally. Other methods like electrospinning, electrodeposition and magnetron sputtering are more likely to synthesize cobalt-based materials with specific morphologies and structures, such as nanofibers and films.