# Intercalating Sn/Fe Nanoparticles in Compact Carbon Monolith for Enhanced Lithium Ion Storage
## 3 Results and Discussion
These may mainly result from reconstruction of Sn and Li\({}_{x}\)Sn crystals within the lithiated SnO\({}_{2}\) layer, because Sn coarsening and Li\({}_{x}\)Sn agglomeration can dwinddle the reaction dynamics during (de-)lithiation. By sharp contrast, as the cycle number increases, all DCC peaks of SFO ascribed to the de-conversion reactions quickly decay and utterly vanish in the 10\({}^{\text{th}}\) cycle, indicating that the electroactivity of the de-conversion reaction drops fiercely; meanwhile the DCC peaks indexed to the dealloying reactions experience an appreciable attenuation in the fiftieth cycle (Figure 5b), further interpreting the poor cyclability. Considering that the dealloying reaction of Li\({}_{x}\)Sn to Sn occurs in the range of 0.005-1.0 V and the reversion of Sn to SnO\({}_{2}\) takes place at between 1.0 and 2.5 V, the segmentalized charge capacities (Figure 5c,d) in the regions of 0.005-1.0 V and 1.0-2.5 V in each cycle are further calculated based upon the charge curves to quantify the individual contribution and evolution of dealloying and de-conversion reactions between Sn and Li phases. In the case of SFO (Figure 5c), the segmental reversible capacity delivered at potential ranges of 0.005-1.0 V and 1.0-2.5 V is only 3.119 and 32 mAh/g with capacity retention of 0.6% and 11% after 100 consecutive cycles, respectively, indicating a drastic and complete degradation of the reversible capacity. What is worse, the segmentalized reversible capacity in the range of 1.0-2.5 V slumps by 40% in the second cycle. This evolution hints that the generation of the Li\({}_{x}\)Sn and SnO\({}_{2}\) components has been seriously impeded by the increased impedance, which may ensue from the SEI thickening or formation of the isolated/separated granules. Apparently, both the structural stability of electrode and reversibility of conversion reaction for the SFO electrode are very unsatisfactory. Conversely, the segmentalized reversible capacity in the range of 1.0-2.5 V on the SFO@C-400 does not suffer from a dramatical decrement upon cycling. In spite of a gradual fading of the segmentalized reversible capacity during the subsequent cycles, a segmentalized reversible capacity up to 358 mAh/g in the potential range of 1.0-2.5 V is still preserved after 100 cycles (about 76% retention of the first cycle segmentalized charge capacity), which sets forth the persistent reversibility of de-conversion reactions during cycling. Besides, an exceedingly stable segmentalized charge capacity in the range of 0.005-1.0 V of 310 mAh/g (which is about 95.6% of the initial segmentalized charge capacity at 0.005-1.0 V) can be well maintained, even over 100 cycles. The variations in the segmentalized charge capacity at these two potential regions reveal that the capacity deterioration of the SFO@C-400 electrode takes place primarily in the potential range of 1-3 V because of the reversible decay of de-conversion of Li\({}_{2}\)O/Sn to SnO\({}_{2}\). These can pertain to the stepwise coarsening of the Sn particles amidst the Li\({}_{2}\)O matrix. The Sn nanoparticle coarsening can notably decline proportions of the Sn-Li\({}_{2}\)O interphases, abating the interphase diffusion between Sn and LiO\({}_{2}\) and eventually a segmentalized reversible capacity produced from the re-conversion reactions (1-3 V vs. Li/Li\({}^{+}\)). This slight decay of SFO@C-400 in contrast to SFO demonstrates that the Sn coarsening is inhibited to great extent by the metal-in-carbon structure. Nevertheless, as to (de-)alloying events, the electroactive Li\({}_{x}\)Sn/Sn districts get well encircled by the Li\({}_{2}\)O matrix. While the particle size of Sn nanocrystals may grow from several nanometers up to several ten nanometers, such Li\({}_{2}\)O phases in combination with the carbon matrix function as the cushion substrate for the volume fluctuation of Li\({}_{x}\)Sn/Sn, imparting the superior structural stability and integrity of the electroactive substances in the potential region of 0.005-1 V vs. Li/Li\({}^{+}\).