Cathode Material For Rechargeable Li-ion Batteries Research Articles

Synthesis of 1D/2D VO2 (B) nanowire/g-C3N4 hybrid architectures as cathode materials for high-performance Li-ion batteries

Owing to energy density, powder density, and eco-friendliness, Li-ion batteries (LIBs) are increasingly used in transportable electronic devices and electric vehicles. Monoclinic VO2 (B) has been broadly used as a cathode owing to its abundance, affordability, high capacity, and multiple oxidation states, but it's low repeatability and slow kinetics have restricted its practical applications. To mitigate these shortcomings, novel 1D/2D VO2 (B) nanowire/g-C3N4 hybrid architecture cathode materials were synthesized via hydrothermal method, and its electrochemical activity (i.e., repeatability constancy and rate capability) for LIBs was investigated. X-ray diffraction experiments confirmed that VO2 (B) exhibited a monoclinic crystal phase. SEM images revealed that the g-C3N4 and VO2 (B) presented sheet-like morphologies and comprised nanowires of uniform thickness, respectively. Electrochemical experiments revealed that the hybrid architectures showed a capacity of 779 mAh/g, and VO2 (601.4 mAh/g) and g-C3N4 (340.6 mAh/g) at 0.1 C current density. The remarkable electrochemical activity of the materials was attributed to their distinctive structures, excellent electronic conductivity associated with g-C3N4 sheets, small transport distances for Li+ ions, and fast charge transmission owing to the presence of VO2 (B) nanowires attached to g-C3N4 sheets. Consequently, distinct VO2 (B) nanowire/g-C3N4 hybrid architectures delivered suitable electrode performance to facilitate the design of high-power LIBs and these hybrid composites can serve as suitable cathode materials for rechargeable LIBs.

Insights into the Electrochemical Reaction Mechanism of a Novel Cathode Material CuNi2(PO4)2/C for Li-Ion Batteries.

In this work, we first report the composite of CuNi2(PO4)2/C (CNP/C) can be employed as the high-capacity conversion-type cathode material for rechargeable Li-ion batteries (LIBs), delivering a reversible capacity as high as 306 mA h g-1 at a current density of 20 mA g-1. Furthermore, CNP/C also presents good rate performance and reasonable cycling stability based on a nontraditional conversion reaction mode. X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM) characterizations show that CNP is reduced to form Cu/Ni and Li3PO4 during the discharging process, which is reversed in the following charging process, demonstrating that a reversible conversion reaction mechanism occurs. X-ray absorption spectroscopy (XAS) discloses that Ni2+/Ni0 exhibits a better reversibility compared to Cu2+/Cu during the conversion reaction process, while Cu0 is more difficult to be reoxidized during the recharge process, leading to capacity loss as a consequence. The fundamental understanding obtained in this work provides some important clues to explore the high-capacity conversion-type cathode materials for rechargeable LIBs.