Prediction Clue on the Fading Capacity of Multi-Walled Carbon Nanotube-Decorated Li_2(Fe_(1-x)Ti_x)SiO_4/C High-Performance Cathode Materials

摘要

The key challenges of Li2FeSiO4 are poor conductivity, low Li-ion diffusion, and extreme capacity fading during the charge-discharge process. In this research, a new attempt has been made to combine three key strategies: carbon coating, cation (Ti4+) doping, and the incorporation of multi-walled carbon nanotubes (MWCNTs) to address major electrochemical impediments in the Li2FeSiO4 cathode material. The field emission-scanning electron microscopy and high-resolution transmission electron microscopy analyses demonstrated the homogeneous distribution of spherical Li2Fe0.94Ti0.06SiO4/C nanoparticles entangled in the MWCNT framework. The 5 wt % MWCNT-integrated Li2Fe0.94Ti0.06SiO4/C composite cathode offers an excellent initial specific charge capacity of 240 mA h g(-1) and the discharge capacity of 238 mA h g(-1), which are higher than those of the bare Li2FeSiO4/C. The sample exhibits an excellent rate capability (124 mA h g(-1)@15 C) and a good long-term cycle life up to 1000 cycles. The Ti doping at the Fe site of Li2FeSiO4/C prohibits the structural distortion during the charge and discharge processes. The surface charge-transfer performance has improved via carbon coating and incorporation of MWCNTs into the Ti-doped Li2FeSiO4/C nanoparticles. To date, the results of the research have been very enlightening, especially in terms of the rate capability and stability of cycling.