Bi@C Nanospheres with the Unique Petaloid Core–Shell Structure Anchored on Porous Graphene Nanosheets as an Anode for Stable Sodium- and Potassium-Ion Batteries

Abstract

Bismuth (Bi) has emerged as a prospective candidate as Na-ion and potassium-ion battery anodes because of its unique advantages of low cost, high theoretical gravimetric capacity (386 mAh g −1 ), and superior volumetric capacity (3800 mAh cm −3 ). However, the low electronic conductivity and the huge volume expansion of Bi during the alloying/dealloying reactions are extremely detrimental to cycling stability, which seriously hinder its practical application. To overcome these issues, we propose a rational design: Bi@C nanospheres with the unique petaloid core−shell structure are synthesized in one step for the first time and then combined with different contents of graphene (GR) nanosheets to form the composites Bi@C@GR. The Bi@C nanospheres with a core−shell structure are beneficial to shortening the transmission path of electrons/ions and reducing the risk from structural rupture of the particles during cycling. In addition, the combination of Bi@C nanospheres and porous GR could greatly improve the conductivity and prevent the aggregation of particles, which is conducive to better cycling stability and rate performance. Consequently,

Facile Construction of Nano-Dimensional Bi Encapsulated in N-Doped Porous Carbon Frameworks for High-Performance Sodium-Ion Hybrid Capacitors

“…Meanwhile, it can also be observed that bismuth NPs are coated by the amorphous carbon layer, which can improve their structural stability and inhibit the agglomeration during the electrochemical test. 18,31 The energy dispersive X-ray elemental mapping images (Figure 2h−l) further prove that the clear elements (C, Bi, and N) are uniformly distributed in the hybrid architecture. The crystal structures of the Bi-based materials were determined by X-ray diffraction.…”

“…The HRTEM image of Bi@NPC-850-U shows the clear lattice fringes (interplanar distance: 0.329 nm) corresponding to the (012) plane of the hexagonal bismuth (Figure g). Meanwhile, it can also be observed that bismuth NPs are coated by the amorphous carbon layer, which can improve their structural stability and inhibit the agglomeration during the electrochemical test. , The energy dispersive X-ray elemental mapping images (Figure h–l) further prove that the clear elements (C, Bi, and N) are uniformly distributed in the hybrid architecture.…”

“…The pore size distribution of Bi@NPC-850-U further confirms the co-existence of micropores, mesopores, and macropores (Figure h). Such a unique hierarchical porous structure is advantageous for the fast diffusion of electrons and ions, contributing to the exposure of great many active sites for efficient Na + storage. , The thermogravimetric (TG) test was conducted in an oxygen atmosphere to confirm the content of Bi in the composites. As shown in Figure i, the weight change of samples corresponds to combustion of the carbon matrix and the oxidation of metallic bismuth at 300–500 °C.…”

Anion‐Vacancy Modified WSSe Nanosheets on 3D Cross‐Networked Porous Carbon Skeleton for Non‐Aqueous Sodium‐Based Dual‐Ion Storage

“…To further investigate the diffusion behavior, ex/in situ electrochemical impedance spectroscopy (EIS) was then performed. [42] In situ EIS measurements after ten cycles of full activation of WSSe@CPCS, WSe 2 @CPCS, and bare WSe 2 electrodes were tested (Figure S17e-g, Supporting Information). The total R ct of the three electrodes is shown in Figure S17h, Supporting Information.…”

Multilayered Architecture Assembled from Sn(HPO4)2 Nanosheets and Reduced Graphene Oxide As Superior Cyclability Anodes for Sodium-Ion Batteries

“…For three-dimensional lattice-embedded sodium anode materials, electrochemical properties of sodium storage are highly dependent on the structure and chemistry of their surface and near surface. Therefore, decreasing the size/dimension of metal oxides/carbide/phosphide, − metallic sulfide/selenides, − and alloy-based − anode materials to expose more active sites for sodium storage to the surface and regulating the pore structure , and doping , of carbon-based anode materials to shorten the diffusion distance of sodium ions inside the electrode and enhance the surface charge accumulation ability can all greatly enhance the rate capability. However, the volume change of the electrode structure still hinders the stability of long-term charge/discharge cycles.…”