Rational design of double-shelled Cu₂MoS₄@N-doped carbon hierarchical nanoboxes toward fast and stable sodium-ion batteries

Abstract

Bimetal and/or mixed-metal sulfides have received significant attention for efficient sodium storage due to their high capacity and decent redox activity. However, the poor-rate capability and fast capacity decay dramatically...

Aliovalent doping engineering enables multiple modulations of FeS2anodes to achieve fast and durable sodium storage

“…Generally, EIS patterns consist of a semicircle in the high-frequency region and a straight line at low frequency, which are associated with the charge transfer resistance and Warburg diffusion process, respectively. 36,49,50 As shown in Fig. 4e, the P–FeS 2 @C electrode exhibits a smaller semicircle than that of the undoped FeS 2 @C, which demonstrates that it possesses a smaller charge transfer resistance.…”

Spatially Confined Fe7S8 Nanoparticles Anchored on a Porous Nitrogen-Doped Carbon Nanosheet Skeleton for High-Rate and Durable Sodium Storage

“…Upon discharging to 0.7 V, two minimized semicircles appear in the EIS curve, which are related to the interfacial resistance (R sei ) originating from the generation of a thin SEI layer at the highfrequency region and charge transfer resistance (R ct ) at the medium-frequency region, respectively. 68 When further discharged to 0.01 V, the two semicircles continue to exist and the total resistance (R tot ) as the sum of R sei and R ct is progressively decreased, which is attributed to the further conversion reaction to generate metallic Fe particles with improved electrical conductivity. During the charging process, R tot shows a continuous increasing trend with the gradual increase of the semicircle diameter due to the structural stress caused by the volume contraction and reverse conversion reaction of metallic Fe to form less electrically conductive species.…”

“…When discharged from open circuit voltage (OCV) to 1.2 V, the diameter of the semicircle decreases obviously, which is possibly attributed to the volume expansion induced by the intercalation of Na + into Fe 7 S 8 with structural stress. Upon discharging to 0.7 V, two minimized semicircles appear in the EIS curve, which are related to the interfacial resistance ( R sei ) originating from the generation of a thin SEI layer at the high-frequency region and charge transfer resistance ( R ct ) at the medium-frequency region, respectively . When further discharged to 0.01 V, the two semicircles continue to exist and the total resistance ( R tot ) as the sum of R sei and R ct is progressively decreased, which is attributed to the further conversion reaction to generate metallic Fe particles with improved electrical conductivity.…”

Interface Engineering of Fe7S8/FeS2 Heterostructure in situ Encapsulated into Nitrogen-Doped Carbon Nanotubes for High Power Sodium-Ion Batteries

“…Transition metal sulfides (TMSs) are considered as promising electrode candidates due to their high theoretical capacities [ 11 – 15 ]. The weak M-S bond is favorable for electrochemical conversion reaction, resulting in active redox kinetics and reversibility.…”