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

Polyaniline was polymerized and deposited on the surface of Cu nanowire@carbon (C) nanocore-shells, and utilizing phytic acid as phosphorus source, a unique Cu₃P/Cu@C composite spherical structure with with N,P-codoped graphitic carbon nanotubes entwined has been fabricated through a simple high-temperature annealing. Such porous and doped Cu₃P-carbon anodes show excellent rate capability with ultra-long service life at current density up to 2000 mA/g.

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.

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