Intermediate-motivated charge transfer via alternate dipoles accelerating the deep redox of iodine/sulfur/molybdenum for high-performance multiple ion batteries

Abstract

Sodium-sulfur and sodium-iodine batteries are attractive due to their low cost and high capacities. However, they suffer from polysulfide/polyiodide dissolution and fast capacity decay. To solve these issues, herein, an organic species-intercalated layered MoS₂ with oxygen-dopant (Org-MoS₂) was designed for the iodine encapsulation. The chemically-bonded S²⁻ from the S–Mo–S layer can not only stabilize the in situ generated I⁺ intermediate to boost the redox kinetics and deep transformations of 2I⁻ ↔ I₂ ↔ 2I⁺, but also undergo the conversion of S²⁻ ↔ S^δ− in the high voltage range of 1.5–3.4 V without structural collapse and shuttle effect. That is owning to the I⁺-induced local charge and the electron reservoir of multi-valent Mo, which facilitate effective charge transfer via alternate dipoles of I^δ+−^δ−S^δ+/^δ−O^δ+−^δ−Mo^δ+−^δ−S^δ+ and promote the redox of I/S/Mo. Meanwhile, the incorporated organic species are transformed into an aromatic carbonaceous material with improved electron conductivity and thinner thickness in the cycling test accompanied by the exposure of more Mo–O–Mo linkages, resulting in an increasing ultrahigh capacity and outstanding long-term durability of Org-MoS₂@I₂.