Study of the Composite Modified Positive Electrode between NCM811 and V2O5 Materials in Li-Ion Cells

Abstract

The possibility of combining the promising cathode material LiNi[Formula: see text]Co[Formula: see text]Mn[Formula: see text]O2 (NCM811) with V2O5 material with excellent conductivity as a composite cathode material for lithium-ion batteries was discussed. The fact that the mechanical and physical mixing process did not change the original structure of both NCM811 and V2O5 was confirmed by XRD. SEM and TEM show that the V2O5 particles were attached to the surface of NCM811 and filled the gaps between NCM811 particles. Furthermore, TEM image after cycling reveals that the gathering of Nano-plates V2O5 on the surface of spherical-like NCM811 particles transformed to coating layers ([Formula: see text][Formula: see text]nm) after reacting with lithium, which leads to the increase of impedance, while the stable coating layer would protect the active material from being corroded by the decomposition products of the electrolyte and prevent the collapse of the microstructure to maintain the stability of Li[Formula: see text] mobility channels. The sample exhibited an attractive first discharge capacity of 214[Formula: see text]mAh[Formula: see text]g[Formula: see text] with the 94.7% initial columbic efficiency and a higher capacity retention when the mass ratio of V2O5 is 15[Formula: see text]wt.%. Thus, the reversibility of reaction at low voltage 2.0[Formula: see text]V and high temperature have been enhanced after the modification. This is undoubtedly the necessary condition to improve the security of electrolyte thermal decomposition. Our work will provide some guidance for the future development of high temperature Li-ion batteries.