Nitrogen-doped carbon coated LiFePO4/carbon nanotube interconnected nanocomposites for high performance lithium ion batteries

摘要

Nitrogen-doped carbon layer coated LiFePO4/carbon nanotube (LFP/CNT) interconnected nanocomposites, which are characteristic of a hybrid structure by incorporating the merits of CNTs and nitrogen-doped carbon, have been prepared via a facile method for large scale industrial production in the presence of polyvinylpyrrolidone (PVP). Scanning electron microscopy (SEM) demonstrated that CNT networks connect the LFP nanoparticles and form three dimensional (3D) CNT-LFP interconnected composites. X-ray photoelectron spectrometry (XPS) confirmed the existence of nitrogen-doped carbon formed by the carbonization of PVP. These hybrid conductive networks could clearly reduce the electrochemical impedance, and thus markedly improve the electrochemical performance. The galvanostatic charge-discharge tests indicated that the LFP/CNT composites present outstanding cycling stability and high rate capability. A specific discharge capacity retention of up to 95.7% (similar to 140 mA h g(-1)) over 900 cycles at 5C and a high rate capability of up to 98 mA h g(-1) at 25C are achieved for the sample sintered at 750 degrees C for 5 h.