Enhanced Electrochemical Performances of Cu/Cu_xO‑Composite-Decorated LiFePO₄ through a Facile Magnetron Sputtering

Through a facile magnetron sputtering technique, Cu/Cu_xO composite nanoparticles were dispersed uniformly on the surface of the LiFePO₄ electrode. Confirmed by X-ray photoelectron spectra, Raman spectroscopy, and high-resolution transmission electron microscopy, the Cu/Cu_xO composite particle possesses an eccentric core–shell structure with metallic copper as the core, whose partial superficies are surrounded by an oxidation composite consisting of cuprous oxide and cupric oxide. The deposition time of the Cu/Cu_xO composite on the pole piece is varied in the range from 20 to 120 s. The best results are attained for the sample prepared at sputtering time of 60 s. The electrochemical measured results indicate that LiFePO₄ with appropriate composite decoration displays excellent rate performances and cycling stability under high current density. The enhanced performances are considered to be induced by the existence of metallic copper on the surface of the electrode, which contributes to the strengthening ion diffusivity and conductivity with moderate copper additive. The LiFePO₄ with appropriate composite modification has a lower surface work function, which can verify this point well. Furthermore, it is observed that the LiFePO₄ electrode modified by a moderate composite remains an intact lattice structure after many cycles at high C-rate, implying that homogeneous composite surface modification can effectively suppress the degeneration of the material crystal structure. This is attributed to the oxidation composite wrapping around the metallic copper surface which acts as a significant role in buffering the undesirable reaction between active material and electrolyte. Therefore, the surface modification of the electrode based on the facile magnetron sputtering technique has a great advantage for simplifying the preparation process while evidently enhancing the electrochemical performances of materials.