Preparation of CFx@C Microcapsules as a High-rate Capability Cathode of Lithium Primary Battery

The Core-shell structure carbon-coated graphite fluoride (CFx@C) microcapsules were prepared by microencapsulation and carbonization. The CFx@C has a spherical shape and the carbon coating is constructed of thousands of carbon micro-shperes. With the exterior conductivity provided by the carbon coating, CFx@C cathode achieves a higher energy density and a higher power density than the pristin CFx. The energy density is increased from 505 Wh Kg-1 by CFx to 1171 Wh Kg-1 by CFx@C at 0.5 C and the maximun discharge rate is improved from 0.5 C by CFx to 5 C by CFx@C. Both fully discharged (at 0.1 C) pristin CFx and CFx@C cathodes are studied to reveal the effect mechanism. The high power density is attributed to: 1) the enhanced combination of CFx@C and acetylene black by plyurea guarantees the electrons transferring from Al collector to the surface of CFx@C; 2) the carbon coating of CFx@C with a good electronic conductivity accelerates the shift of electrons to the GIC interface; 3) the carbon coating which shows an porous surface enlarges the contact area and can store much electrolyte and allows more channels for the Li+ ion transferring.