Realizing High‐Performance Li–Polysulfide Full Cells by using a Lithium Bis(trifluoromethanesulfonyl)imide Salt Electrolyte for Stable Cyclability

Since concentrated electrolytes have attracted great attention for the stabilization of lithium‐metal anodes for lithium‐ion batteries, the demonstration of a full cell with an electrolyte concentration study has become a research topic of interest. Herein, we have demonstrated a proof of concept, a lithium–polysulfide full cell battery using various lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) electrolyte concentrations with glass‐fiber‐based composite and hard carbon as the cathode and anode, respectively. The initial capacity of the lithium‐polysulfide full cell is found to be 970 mA h g<jats:sup/>−1 at 0.1 C. The capacity is stabilized at 870 mA h g<jats:sup/>−1 after 100 cycles with a capacity retention of 88.6 %. An excellent capacity retention of ≈80 % is achieved after long 800 cycles at 0.5 C by using full cell technology. Further, our post‐mortem analysis sheds light on the difference in SEI layer formation on hard carbon anodes with changing electrolyte concentration, thereby indicating reasons for the obtainment of a high cyclic performance with 1 m LiTFSI salt electrolyte. The successful demonstration of the long cyclic performance of Li–polysulfide full cells is indeed a step towards producing high performance Li–polysulfide full cell batteries with long cycling using conventional LiTFSI salt electrolyte and commercial anode materials.