Simultaneous Carbon Coating and Lithiation of Oxides by Contact Reaction

摘要

Chemical lithiation and carbon coating of cathode materials can lead to strongly improved electrochemical properties, especially if the active materials have low electronic conductivity. This behavior is quite often the case for new high-capacity materials. A novel synthesis method is presented in which the two processes are performed simultaneously by employing Li_2C_2 as both the carbon and the lithium source. In this contact reaction, the acetylide anion C_2~(2-) is oxidized to carbon and deposited directly on the surface of the active material, while lithium is reductively inserted into the oxidant. Two different synthesis routes are demonstrated: a tribochemical approach at room temperature and heat treatments between 150 and 600 °C. The applicability of these new carbon-coating methods are demonstrated on various crystalline and amorphous Li_xV_2O_5 phases. The composites obtained were characterized by powder X-ray diffraction, transmission electron microscopy, and Raman spectroscopy. In addition, electrochemical data confirm the chemical lithiation and show that lithiated Li_xV_2O_5 with specific phases can be prepared selectively.