# Intercalating Sn/Fe Nanoparticles in Compact Carbon Monolith for Enhanced Lithium Ion Storage
## 4 Discussion  
In general, the electrochemical performance of our optimal SFO@C composite outperforms both carbon-free SFO counterpart and multifarious SnO\({}_{2}\)-based anode substances recorded in the literature so far, signifying the preponderant structural design and multicomponent synergy in ameliorating the energy storage. The distinguished Li\({}^{+}\) storage properties supra between a series of SFO@C and SFO composites can be associated with its distinct nanoscale complex configurations, as demonstrated by a unique scheme in Figure 7. Firstly, the ultrasmall-sized sub-10 nm SnO\({}_{2}\)/Fe\({}_{2}\)O\({}_{3}\)-based nanoclusters furnish a myriad of electroactive centers for Li to access without incurring any serious degeneration of electrodes due to the nanoscale size effects, namely the low structural strains/stresses in the course of (de-)lithiation events and substantially dwindled solid-state migration/transport distance for Li\({}^{+}\). At the same time, such nanometer granules firmly implanted in the carbon substrates do conduce to thwarting the Sn' locomotion/interdiffusion and accordingly frustrating their coarsening into bulk Sn crystals in the process of (de-)alloying reactions, if any, they still get \"trapped or sequestrated\" within continuous protecting carbon matrix and keep the active materials in close contact with carbon matrix during cycling, thus preserving its outstanding electrical contact/connection to facilitate the charge transfer to active materials. Secondly, the robust and conducting carbon skeleton not only guarantees the rapid/efficient electron mobility, but also contributes to sustaining the mechanical integrity of the hybrid electrode throughout a long-term cyclic ion insertion/extraction. Besides, the compact nature of the hybrids can prevent the morphological issues of highly hierarchical porous architectures and provide a continuous pathway for Li+/e\({}^{-}\) transfer across the whole electrode and, more significantly, is able to powerfully buffer the volume change of the SnO\({}_{2}\)-based nanocrystals to restrict the electrode fractures. Thirdly, both decomposition of Li\({}_{2}\)O triggered by Fe reduced from Fe\({}_{2}\)O\({}_{3}\) and enhancement of electric conductivity and Li\({}^{+}\) ions diffusion synergistically cause the conversion reaction of SnO\({}_{2}\) to occur and maintain the high reversibility during the repeated cycling. Fourthly, the carbon coating or encapsulation around the SnO\({}_{2}\) or Fe\({}_{2}\)O\({}_{3}\) nanoparticles can also avert the direct touch between electrolyte and active materials, which greatly benefits the production of stable and thin SEI films over cycling. Lastly, the in situ generated SnO\({}_{2}\)/Fe\({}_{2}\)O\({}_{3}\) heterostructures offer the additional charge transfer driving force as a result of the built-in internal electric (potential) field, and stabilize the intercalation compact structure over cycling due to the collaborative interaction within this binary system [41; 42; 43; 44; 45; 46; 47; 48]. In short, due to the striking integration of the elastic carbon matrix, metal-in-carbon construction, and multicomponent effect, the inevitable stress-induced volume variation is robustly accommodated, accompanied by the much-facilitated reaction kinetics.