Phytic Acid Assisted Preparation of Cu3P/Cu@C Composites as High Performance Anodes for Lithium Storage.

Abstract

Phosphorus-based anodes show new perspectives in high-performance lithium-ion batteries, but harsh synthesis and severe capacity attenuation seriously preclude their practical application. Here, Cu nanowire@carbon (C) nanocore-shells are designed to utilize as sacrificial templates for polyaniline loading, and with the assistance of phytic acid (PA), a novel Cu₃P/Cu@C microsphere composite structure is successfully constructed via direct thermal annealing, in which heteroatom-doped graphitic carbon nanotubes are wounded with each other and firmly entangled on spheres. The polyaniline polymerization by (NH₄)₂S₂O₈ and the addition of PA are indispensable for the unique Cu₃P sphere formation. Both the spherical Cu₃P structure and its doped carbon encapsulating could largely alleviate volume expansion during lithium storage, while the intertwined carbon nanotubes provide fast transport channels for Li⁺. Therefore, as anode, it exhibits relatively stable cyclic performance, and after 10,000 cycles at an ultra-high rate of 2000 mA/g, it still maintain a capacity of 278.57 mAh/g with capacity retention of 73.12%. Through analysis, large specific surface area and multi-level pore distribution of the optimized Cu₃P-carbon anode, and the extended interlayer spacing of doped carbon are conducive to the reversible intercalation and adsorption of Li⁺. Electrochemical mechanism analysis also confirms its dramatic surface pseudo-capacitance contribution and excellent reaction kinetics.