Toward zero-excess lithium sulfur batteries: a systematic coin cell parameter study

Zero-excess lithium (ZEL) or "anode-free" batteries aim to minimise negative electrode material while addressing the challenges associated with handling thin Li metal foils during fabrication. To date, most studies have focused on Li-ion chemistry, with considerably fewer systematic investigations into ZEL-sulfur (ZELiS) cell fabrication and optimization. Here we develop a ZELiS battery, comprising a Li2S-based composite positive electrode on carbon paper paired with a Ni foil current collector and evaluate the effects of various current collector materials, electrolyte volume to Li2S mass ratio and C-rate. The developed cells reproducibly achieve an average Coulombic efficiency of 99% from cycles 2 to 200, and a final capacity of 272 mAh g-1Li2S at a C/10 rate. Furthermore, we employ X-ray computed tomography to elucidate the morphological changes and degradation processes occurring within the positive electrode composite, revealing the irreversible loss of Li2S/S8 during cycling, which is exacerbated at high rates. These results should be useful in the development of commercially viable ZEL energy storage devices.