“…To solve tough issues aforementioned, the semiconducting pyrite (FeS 2 ; band gap: 0.95 eV), a vital member in the FeS x family, has attracted tremendous attention as a compelling anode candidate attributed to its unique intrinsic advantages. − Primarily, the good mechanical stability and inherent electrical conductivity of FeS 2 allow for more rapid/efficient electron transfer in ESDs. , For example, Venkateshalu et al once proved that FeS 2 can exhibit remarkable specific capacity/energy when applied for high-rate power sources . Second, the incorporation of sulfur-contained substances covering on ferruginous reaction sites as the depassivation/protective agent can suppress the undesired HER phenomenon/side reactions and HER -induced low charging efficiency. , Nevertheless, pure FeS 2 is yet incompetent for commercial utilizations since it still suffers from formidable kinetic challenges including inevitable phase changes, large volumetric expansions, and actives dissolution, enabling the actual electrode performances far from satisfactory to fulfill practical criterions. , In an attempt to overcome these constraints, a great deal of work has been devoted to one rational/proper strategy; that is, delicate design of FeS 2 into expectative micro-/nanoparticles for preferred reaction kinetics and meantime construction of robust/functionalized “armor” on each dispersed FeS 2 unit for mechanical protections. , Though worldwide scientists are rationally committed to making state-of-the-art FeS 2 electrodes and accordingly achieving acquired significant improvements, nearly all of them elaborate the success roughly based on an ambiguous mechanism assumption of “FeS 2 + OH – ↔ FeS 2 OH + e – ”; in other words, detailed pyrite phase conversions/intrinsic working dynamics in deep cyclic period are rarely uncovered . In this regard, in-depth probes into optimal electrodes of FeS 2 @protective matrix via real-time monitoring detection/analysis on a structural/constituent level are highly deserved to gain insights into more inherent properties and critical information.…”