In Situ Generation of Iron Nitride Nanoparticles to Modulate Microcrystalline Structure of Hard Carbon for “Fast-Charging” Metal-Ion Batteries

Hard carbon anodes exhibit superior storage capacity and rate performance due to their special structure, when applied in various alkali metal ion batteries. The ability to store Li+ and Na+ is related to the proportion of pseudographite domains and the distribution of the pore structure. This work uses a one-step carbonization strategy to generate uniformly sized Fe2N nanoparticles to be embedded into hard carbon, the former could catalyze the microcrystalline structure of the latter. The as-prepared hard carbon exhibits up to 54% occupation of microcrystalline domains, while its specific surface area (867.1 m2 g–1) and the maximum probable aperture (6.220 Å) are larger than that of pure hard carbon (519.2 m2 g–1 and 4.680 Å). The composites show a capacity of 581.8 mAh g–1 in LIBs and 334.1 mAh g–1 in SIBs at 0.05 A g–1. It can stably cycle for 2000 times with capacity retention of 97.92% in LIBs and cycles for 1500 cycles (98.64%) in SIBs at 2.0 A g–1. This work provides a simple preparation strategy and enriches the regulation mechanism of microcrystal structure for hard carbon anodes, which would be references for the regulation of “fast-charging” carbon-based anode materials.