Lithium sulfide

Methyl-2-pyrrolidone (NMP, 99.5 wt%), polyvinylidene fluoride (PVDF, 99.5 wt%), elemental sulfur (99.5 wt%), lithium sulfide (Li₂S, 99.98 wt%), 1,3-dioxolane (DOL, 99.8 wt%), 1,2-dimethoxyethane (DME, 99.5 wt%), tetraglyme (99 wt%), lithium bis (trifluoromethanesulfonyl) imide (LiTFSI, 99.95 wt%), lithium nitrate (LiNO₃, 99.99 wt%), cobalt chloride hexahydrate (CoCl₂·6H₂O), potassium permanganate (KMnO₄, 99.5 wt%), graphite powder, ammonium tetrathiomolybdate ((NH₄)₂MoS₄, 99.95 wt%), reduced graphene oxide (rGO, chemically reduced) were purchased from Sigma-Aldrich. Graphene oxide (GO, >99 wt%) was purchased from Aladdin reagent. Hydrochloric acid (HCl, 37 wt%), sodium nitrate (NaNO₃, 99 wt%), hydrogen peroxide (H₂O₂, 30 wt%) were purchased from Chuandong Reagent. Super P carbon (99.5 wt%) from Timcal were used as received. The carbon paper (HCP120, thickness ∼0.21 mm) was purchased from Shanghai HESEN Co., Ltd.

The preparation of lithium polysulfide electrolyte blends followed
a procedure previously reported within the group.^{22 (link)} In an argon-filled glovebox, lithium sulfide (99.98%, Sigma-Aldrich)
and sulfur (S₈, 100 mesh, sublimed, Sigma-Aldrich, dried
at room temperature under vacuum over 72 h) were added into a vial
in ratios to give the desired Li₂S₆ composition,
followed by adding the electrolyte solution 1 M LiTFSI in DOL/DME
(1:1 by vol). The solution was stirred at 60 °C for 10 days to
ensure full dissolution. After 10 days of stirring, a clear ruby-red
polysulfide solution is obtained with an average chain length of Li₂S₆.

All chemicals were used as received. Cobalt nitrate hexahydrate (Co(NO₃)₂·6H₂O, 99.99%), thiourea (H₂NCSNH₂, 99%), sodium dodecyl sulfate (CH₃(CH₂)₁₁OSO₃Na, 99%), sodium hydrosulfide hydrate (NaHS·xH₂O, NaHS ≥ 60%), sodium hydroxide (NaOH, 98%), 1,3-dioxolane (DOL, 99.8 wt%), 1,2-dimethoxyethane (DME, 99.5 wt%), lithium bis(trifluoromethanesulfonyl) imide (LiTFSI, 99.95 wt%), lithium nitrate (LiNO₃, 99.99%), lithium sulfide (Li₂S, 99.98%) and sulfur (S, flakes, 99.99%) were purchased from Sigma-Aldrich. Ultrapure water (UPW) filtered by a Millipore Milli-Q Integral Water Purification System (Millipore Corp.) was used as the common solvent.