3D structure through planting core-shell Si@TiN into an amorphous carbon slag: improved capacity of lithium-ion...

A 3D-structured anode material, planting core-shell Si@TiN into an amorphous carbon slag (3D STC), was synthesized via a facile pyrolyzing process in assistance with the low-temperature reduction route in a liquid Na-NH3 system. The as-prepared samples were characterized by X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, cyclic voltammetry and galvanostatic discharge-charge tests. From morphological analysis, TiN nanoparticles were homogeneously dispersed on the surface of Si to form the Si@TiN core-shell structure, subsequently plating into an amorphous C slag to form the 3D STC composite. The electrochemical capacity of the 3D STC anode was measured at a higher rate of 1 C with the cut-off voltages of 0.01 V and 1.5 V. It was found that the initial charge capacity reached up to 1604.6 mA h g(-1). In particular, the reversible charge capacity was as high as 588.7 mA h g(-1) over 100 cycles, with a small capacity loss of about 0.63% per cycle, exhibiting the excellent cycle stability of the 3D STC anode at the higher rate of 1 C. Furthermore, the reversible capacity of the 3D STC anode decreased from 2048.8 mA h g(-1) to 624.0 mA h g(-1) with increasing the current rate from 0.1 C to 2 C, while it was still maintained at 1419.7 mA h g(-1) as the current rate returned to 0.1 C. Consequentially, the 3D structure with a continuous conductive path could provide facile lithium insertion/extraction and fast electron transfer, making for the high rate capacity and good cycle stability.