Fast and Long‐Lasting Potassium‐Ion Storage Enabled by Rationally Engineering Strain‐Relaxation Bi/Bi₂O₃ Nanodots Embedded in Carbon Sheets

Abstract

Bismuth (Bi)‐based materials merit high theoretical volumetric specific capacity (3800 mAh mL⁻1) but suffer from huge volume variations and sluggish reaction kinetics during cycling. Herein, the optimal framework of Bi/Bi2O3 nanodots enriched in suitable outer amorphous carbon sheets (Bi/Bi2O3 NDs@CSs) is first proposed to alleviate volume variations and accelerate stable charge transport to boost K+ storage performance. The introduction of proper Bi2O3 not only provides an efficient K+ adsorption path, but also effectively buffers volume changes via conversion reaction. Accordingly, the as‐prepared anode exhibits a remarkable rate capability (149.3 mAh g−1 at 60 A g−1, 42% capacity retention with a 120‐fold current‐density increase) and extraordinary durability (1800 cycles at 5.0 A g−1, 95% capacity retention), among the best rate and cycling performance to date in potassium ion batteries (PIBs) anodes. Theoretical calculations reveal the feasible structures of Bi/Bi2O3 NDs@CSs with double protection of carbon sheets and Bi2O3 are conducive to enhance charge transfer and efficiency of electrochemical reaction. Substantial in situ/ex situ characterizations and finite element simulation further unveil high reversibility and robust mechanical behavior of Bi/Bi2O3 NDs@CSs, favorable for the reinforcement of structural stability. This study provides new insights into developing high‐performance and durable Bi‐based anodes for PIBs.

Unveiling the Synergy of Architecture and Anion Vacancy on Bi2Te3–x@NPCNFs for Fast and Stable Potassium Ion Storage

“…The presence of the Bi−O−C bond implies a robust interaction between Bi 2 Te 3 and the carbon nanofibers, which is beneficial for accelerating electron transport and facilitating structural stability. 2 The potassium storage behaviors of Bi 2 Te 3−x @NPCNFs electrodes were evaluated by using coin-type half-cells with K metal as the counter electrode. As shown in Figure S7, the cyclic voltammetry (CV) curves of the first three cycles of the Bi 2 Te 3−x @NPCNFs, Bi 2 Te 3−x @NCNFs, and Bi 2 Te 3 @NCNFs electrodes exhibit remarkable similarity, indicating a shared redox reaction process.…”

“…Importantly, the peaks associated with the Bi–O bond, Bi–O–C bond, and C–O bond in the O 1s spectrum are positioned at 529.5, 531.1, and 532.6 eV, respectively (Figure S6b). The presence of the Bi–O–C bond implies a robust interaction between Bi 2 Te 3 and the carbon nanofibers, which is beneficial for accelerating electron transport and facilitating structural stability …”

“…Potassium-ion batteries (PIBs) have been considered for the application in the next generation of large-scale energy storage systems owing to their similar operating mechanism to lithium-ion batteries as well as the low cost and abundant resources of K. − However, the large radius of K + (K + : 1.38 Å vs Li + : 0.76 Å) often leads to slow diffusion kinetics and collapse of the electrode structure during the potassiation/depotassiation processes, which is impeding the development of PIBs for practical applications. − Therefore, exploring structurally stable electrode materials with fast kinetics is important to accelerating the commercialization of high-performance PIBs.…”

Recent advances in rational design for high-performance potassium-ion batteries

“…In general, alloy-type anodes are very promising PIB electrode materials because their theoretical capacity is several times higher than that of graphite and they have a lower average voltage relative to conversion materials. 370,413,581–587 However, alloy-type anodes face the following challenges: (1) the alloy-type anode needs to form an alloy compound K x M y with K + ions. Due to significant differences in the crystal structures of different elements, this process is often accompanied by huge volume expansion.…”

“…Liu et al 581 constructed a strain-relaxation structure by embedding Bi/Bi 2 O 3 nanodots into amorphous carbon sheets (Bi/Bi 2 O 3 NDs@CSs). This structure can effectively buffer the stress and strain caused by volume expansion, and the introduction of Bi 2 O 3 not only protects and buffers metal Bi, but also contributes greatly to the adsorption capacity of K + .…”