Low-temperature carbonization of p-Phenylenediamine guided by an iron alginate template for lithium-ion capacitors

Porous carbon has attracted great interest as an anode for lithium-ion capacitors (LICs) due to its high lithium-ion storage capacity. However, its low electrical conductivity and tap density are major challenges facing its commercialization. In this study, a low-cost Fe3C@N-doped C material has been synthesized via the polymerization and carbonization of the natural biomass material sodium alginate (SA) and commercial p-Phenylenediamine (PPD). FeCl3 is used as both a crosslinking agent and catalyst to promote the PPD oxidation reaction and the degree of carbonization. The as-obtained graphite-like Fe3C@N-doped C with a carbonization treatment at 700 °C exhibits both high Fe and N contents of 3.93 wt% and 5.34 wt%, respectively, and a high electrical conductivity equivalent to graphite, which would be favorable for lithium-ion storage due to the synergistic effect of the high electrical conductivity and pseudocapacitive characteristics. Moreover, the Fe3C@N-doped C exhibits a superior lithium-ion storage capacity of 566.0 mA h g−1, higher than that of commercial graphite, and a high tap density of 0.59 g cm−3. As the negative electrode for an LIC, the capacitor delivers a high specific energy of 86.6 W h kg−1 at a current density of 0.1 A g−1. Meanwhile, good cyclability has also been achieved for the cell. The superior electrochemical properties of the LICs could be attributed to the high lithium-ion storage capacity and good cycling stability of the Fe3C@N-doped C material.