| 초록 |
The biggest drawbacks of olivine-type LiFePO4 (LFP) is its poor electronic conductivity which will retard their electrochemical performance. The most efficient way to deal with this drawback is to add carbon coating. Here we develop a simple liquid CO2 (l-CO2) based carbon coating method to achieve ultra-thin, uniform, and conformal carbon layer on the surface of mesoporous LFP. The low surface tension and viscosity of l-CO2 ensure thorough penetration of carbon precursor into the mesoporous LFP structure. The resulting carbon layer has a thickness of 1.9 nm on the whole primary nanosized particles (20-240 nm diameter). This unique carbon coated LFP structure provides facile penetration of liquid electrolytes, rapid electron transfer and Li ion transport. Hence, carbon coated LFP can deliver high reversible capacity, gravimetric energy density and power density with an excellent long-term cyclability. In addition, the ultrathin and uniform carbon coating on the primary particles that consist of mesoporous microspheres lead to high tap density, resulting in a high volumetric energy density which is an important factor for next generation electric vehicle and hybrid electric vehicle. |
