Lithium-enhanced functionalized carbon nanofibers as a mixed electronic/ionic conductor for sulfide all solid-state batteries

Despite the recent advancement of sulfide all-solid-state lithium batteries, the choice of their respective components yet requires further comprehensive investigations into their functionality and compatibility. While the development of cathode materials and sulfide electrolytes appears to be greatly advanced, there seems a lack of attention on carbon conductive additives. As sulfide electrolytes are unstable with conventional carbon conductive additives, it is necessary to develop conductive additives with a satisfactory electronic conductivity and good chemical/electrochemical stability with sulfide electrolytes. This study proposes a new mixed conductor based on carbon nanofiber (CNF), namely lithium-enhanced functionalized carbon nanofiber (LF-CNF), exhibiting a greatly enhanced Li-ion conductivity with a little compensation of their electronic conductivity. By utilizing LF-CNF, a discharge capacity of ca. 198 mAh g−1 at 0.05C and ca. 148mAh g−1 after 50 cycles at 0.1C were achieved from the cathode composite of LiNi0.8Co0.1Mn0.1O2, argyrodite solid electrolyte and LF-CNF (70:30:5 in mass). Furthermore, LF-CNF appears to reduce detrimental cation mixing after storage in Ar-atmosphere over one month and at high voltage cycling of 4.5 V. Our work highlights that the conductivity tuning of conductive additives offers a great performance enhancement for high-energy sulfide electrolyte based solid-state batteries.