Optimizing the Void Size of Yolk–Shell Bi@Void@C Nanospheres for High-Power-Density Sodium-Ion Batteries

Abstract

Bismuth (Bi) has been demonstrated as a promising anode for Na-ion batteries (NIBs) because it has high gravimetry (386 mA h g–1) and volumetric capacity (3800 mA h cm–3). However, Bi suffers from large volume expansion during sodiation, leading to poor electrochemical performance. The construction of a nanostructure with sufficient void space to accommodate the volume change has been proven effective for achieving prolonged cycling stability. However the excessive void space will definitely decrease the volumetric energy density of the battery. Herein, we design optimized Bi@Void@C nanospheres (Bi@Void@C-2) with yolk–shell structure that exhibit the best cycling performance and enhanced volumetric energy density. The optimized void space not only could buffer the volume change of the Bi nanosphere but also could keep the high volumetric energy density of the battery. The Bi@Void@C-2 shows an excellent rate capacity of 173 mA h g–1 at ultrahigh current density of 100 A g–1 and long-cycle life (198 mA h g–1 at 20 A g–1 over 10 000 cycles). The origin of the superior performance is achieved through in-depth fundamental studies during battery operation using in situ X-ray diffraction (XRD) and in situ transmission electron microscope (TEM), complemented by theoretical calculations and ex situ TEM observation. Our rational design provides insights for anode materials with large volume variation, especially for conversion type and alloying type mechanism materials for batteries (i.e., Li-ion batteries, Na-ion batteries).

Revealing the Magnesium‐Storage Mechanism in Mesoporous Bismuth via Spectroscopy and Ab‐Initio Simulations

“…However,p oor kinetics associated with the high diffusion barrier of metal ions,a nd the severe volume variations originated from alloying/de-alloying process,a re two key obstacles that prevent wide application of this alloy anode. [21] Delicate structures,s uch as yolk-shell nanospheres for Na + storage, [22] colloidal nanocrystals for Mg-ion battery [13a] and dual-shell boxes for K-ion storage [23] can significantly enhance electrochemical performance by shortening the ion diffusion length. Here,f or the first time,m esoporous Bi nanosheets were loaded onto flexible substrate forming af ree-standing Mg 2+ storage anode.A si si llustrated in Figure S3 and S4, bismuth oxyiodide nanosheet was grown on carbon matrix via afacile hydrothermal approach.…”

Yolk–Shell Fe3O4@Void@N‐Carbon Nanostructures Based on One‐Step Deposition of SiO2 and Resorcinol‐3‐Aminophenol‐Formaldehyde (R‐APF) Cocondensed Resin Dual Layers onto Fe3O4 Nanoclusters

“…Up to date, typical yolk–shell nanostructures, defined as inner core@outer shell, integrating diverse functional components, such as Fe 3 O 4 @Carbon, [ 18 ] Fe 3 O 4 @SiO 2 , [ 19 ] Fe 3 O 4 @PMMA, [ 20 ] Au@PANI, [ 21 ] Au@Carbon, [ 22 ] Au@PNIPM, [ 23 ] Au@TiO 2 , [ 24 ] SiOx/Carbon, [ 25 ] Bi@Carbon, [ 26 ] and so on, have been developed. Among them, inner magnetic core, such as Fe 3 O 4 nanoparticles with strong magnetic responsivity and outer carbon shell with outstanding chemical stability, further functionalization and tunable pore structure were integrated to be one kind of most promising yolk–shell materials for facile drug targeting delivery, [ 27 ] rapid recovery of heterogenous catalysts in liquid phase, [ 28 ] rapid removal of metal ion and organic pollutants, [ 29,30 ] and rapid screening of biomolecules.…”

Bi‐Based Electrode Materials for Alkali Metal‐Ion Batteries

“…Notwithstanding, most Bi-based materials suffer from pulverization and fracture of the electrodes caused by dramatic volume variation, consequently diminishing the cycle stability. [29][30][31][32][33][34][35][36] To solve these problems, variety of strategies have been adopted, such as fabricating nanoscale materials to simultaneously alleviate mechanical stress and enhance the reaction kinetics, compounding with carbonaceous matrix to improve electrical conductivity, engineering alloys to strengthen the stability of active materials and optimizing electrolyte to build a stable solid electrolyte interface (SEI) film. [37][38][39][40][41][42][43][44][45][46][47] In this review, recent research progress on Bi-based electrode materials (e.g., metallic Bi and its oxides, sulfides, alloys and other compounds) for AIBs is summarized, mainly including the following three parts: 1) Thoroughly understand the relationship between the structure and performance of Bi-based materials and interface stability, focusing on the superior electrochemical performance of electrode materials.…”