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

Abstract

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.