Evaporated C60 as fast anode for thin-film solid-state batteries

Thin-film solid-state batteries require anode materials that combine fast lithium storage, cycling stability, and compatibility with scalable vacuum processing to enable novel applications. Here, we demonstrate thermally evaporated C60 based films as high-rate anodes in planar LiPON-based thin-film solid-state half-cells. Structural characterization by X-ray diffraction and transmission electron microscopy shows that the as-deposited films lack long-range fullerite crystallinity and are best described as structurally disordered C60-derived layers. Electrochemically, the 200 nm films deliver reversible multistep lithiation with capacities up to ~560 mAh g−1, exceeding the nominal Li12C60 composition, and retain substantial capacity at extreme C-rates. The cells provide ~410 mAh g−1 at 1 mA cm−2 and ~220 mAh g−1 at 12 mA cm−2, corresponding to real rates of approximately 75 C and 1600 C, respectively. Long-term cycling is highly stable, with capacities above 400 mAh g−1 at 75 C maintained over more than 7000 cycles and only minor impedance growth. Impedance analysis indicates that, at the highest current densities, the cell polarization is heavily influenced by the LiPON electrolyte with C60 not limiting the cell performance. These results identify evaporated C60 as a promising Li-host anode for thin-film solid-state batteries.