In Situ Atomic‐Scale Observation of Reversible Potassium Storage in Sb₂S₃@Carbon Nanowire Anodes

Abstract

Antimony trisulfide-based materials have drawn growing attention as promising anode candidates for potassium-ion batteries (PIBs) because of their high capacity and good working potential. Despite the extensive investigations on their electrochemical properties, the fundamental reaction mechanisms of Sb 2 S 3 anodes, especially the reaction kinetics, structural changes, and phase evolutions, remain controversial or even largely unknown. Here, using in situ transmission electron microscopy, the entire potassiationdepotassiation cycles of carbon-coated Sb 2 S 3 single-crystal nanowires are tracked in real time at the atomic scale. The potassiation of Sb 2 S 3 involves multistep reactions including intercalation, conversion, and two-step alloying, and the final products are identified as cubic K 2 S and hexagonal K 3 Sb. These findings are confirmed by density functional theory calculations. Interestingly, a rocket-launching-like nanoparticle growth behavior is observed during alloying reactions, which is driven by the K + concentration gradient and release of stress. More impressively, the potassiated products (i.e., K 3 Sb and K 2 S) can transform into the original Sb 2 S 3 phase during depotassiation, indicating a reversible phase transformation process, as distinct from other metal chalcogenide based electrodes. This work reveals the detailed potassiation/depotassiation mechanisms of Sb 2 S 3-based anodes and can facilitate the analysis of the mechanisms of other metal chalcogenide anodes in PIBs.

Stimulating the Reversibility of Sb2S3 Anode for High‐Performance Potassium‐Ion Batteries

“…Obviously, comparable initial CES (≈70%) are delivered by these electrodes. Their irreversible capacities in the first cycle are associated with the formation of SEI layers and other irreversible reaction, [3,27] which is common in KIBs anodes. In the 2nd cycle, the CEs of the Sb 2 S 3 -C@ Nb 2 O 5 -C and Sb 2 S 3 -C@C NFs electrodes ramp to 98.1% and 98.9%, respectively, while the CEs of Sb 2 S 3 -C and Nb 2 O 5 -C NFs electrode are only 97.3% and 97.7%.…”

Unveiling Intrinsic Potassium Storage Behaviors of Hierarchical Nano Bi@N‐Doped Carbon Nanocages Framework via In Situ Characterizations

“…After the first charge-discharge cycle,t he 850-Bi@N-CNCs almost restores their original state (Supporting Information, Movie S2). Moreover,a fter 20 potassiation/ depotassiation cycles,t he well-defined 850-Bi@N-CNCs still can maintains its structural integrity without noticeable structure rupture (Supporting Information, Movie S3), which authenticates that the internal void space and elastic shell of N-CNCs can effectively relieve the volume expansion of Bi NPs.B yc ontrast, the bismuth NPs in the 550-Bi@N-CNCs (Supporting Information, Figure S22;M ovie S4) and 700-Bi@N-CNCs (Supporting Information, Figure S23;Movie S5) are both broken and seriously agglomerated after the depotassiation process.T he comparative real-time observations here visualize the superior structural reversibility of the 850-Bi@N-CNCs,which ensures the formation of astable yet thin Angewandte Chemie Forschungsartikel SEI layer on the outer robust N-CNCs, [31][32][33][34] and ac lose electronic contact between the continuous carbon network and Bi NPs meantime. [35][36][37] While for the 550-Bi@N-CNCs or 700-Bi@N-CNCs,the repetitive rupturing and reformation of the passivating SEI film occur, and always convert the cyclable Ks pecies in electrode sur-/interfaces to dead Ki n the SEI, eventually leading to the death of the batteries due to the Ke xhaustion.…”

“…Ty pical SAED pattern of the fresh 850-Bi@N-CNCs show astrong diffraction ring, corresponding to the (012) plane of the wellcrystallized Bi NPs (Figure 5a). In the early stage of potassiation reaction, the diffraction rings related to the (400)/(511) planes of cubic KBi 2 with aspace group of Fd3 m (227) appear, which evidences that bismuth NPs are partially alloyed to form KBi 2 due to insufficient potassium supply, [31] as shown in Figure 5b.After full potassiation, all the diffraction signals are well indexed into the hexagonal K 3 Bi with as pace group of P63/mmc (194) (Figure 5c). Therefore,t he phase transition of electroactive bismuth in the first potassium process of the 850-Bi@N-CNCs is as follows:B i-KBi 2 -K 3 Bi, indicating the two-step alloying reaction for our case here.C orresponding ex situ TEM and SA-ED observations (Supporting Information, Figure S24) further corroborate that the final potassiation product of metal Bi is the K 3 Bi phase indeed.…”

A Self‐Healing Volume Variation Three‐Dimensional Continuous Bulk Porous Bismuth for Ultrafast Sodium Storage

“…To directly reveal the excellent structure stability of the 3DPBi electrode, the in situ TEM observation was performed in real time through the nanobattery shown in Figure 5a. [30,[50][51][52][53][54] The 3DPBi is attached to the gold (Au) probe, and Na/Na 2 O is sticked to the tungsten (W) probe tip, where the as-formed Na 2 O on Na acts as a solid electrolyte. [30] The 3DPBi is sodiated when a negative bias (−7 V) is applied to the W probe.…”