Bottom-up Synthesis of Copper Fluoride Nanocomposites and Their Application to Rechargeable Li Batteries

Copper fluoride (CuF₂) is one of the attractive cathode candidates for rechargeable Li batteries that have high theoretical operation potential (3.55 V vs. Li/Li⁺) and large specific capacity (528 mAh/g). However, synthesizing nanostructured CuF₂, as well as harnessing its potential rechargeability, has been a challenge because of it inherent chemical and electrochemical properties. Only top-down approaches have been reported for down-sizing CuF₂, and there are no reports on reversible electrochemical performance of CuF₂ even at the first several cycles. Herein, we report a facile and versatile synthetic method for CuF₂/mesoporous carbon nanocomposites and their application to the cathodes of rechargeable Li batteries. Through heat treatment with NH₄F in a solventless system, CuF₂ was easily synthesized from various copper precursors. CuF₂ nanoparticles confined in mesoporous carbon exhibited not only superior specific capacity and rate capability at the first discharge in the normal coin-type cell, but also promising cycle performance in the solid-electrolyte-incorporated cell. To the best of our knowledge, this is the first report in which nanostructured CuF₂ is synthesized using a bottom-up approach and successfully applied to rechargeable Li batteries.