Multicore–Shell Bi@N‐doped Carbon Nanospheres for High Power Density and Long Cycle Life Sodium‐ and Potassium‐Ion Anodes

Abstract

Bismuth (Bi) is an attractive material as anodes for both sodium-ion batteries (NIBs) and potassium-ion batteries (KIBs), because it has a high theoretical gravimetric capacity (386 mAh g −1 ) and high volumetric capacity (3800 mAh L −1 ). The main challenges associated with Bi anodes are structural degradation and instability of the solid electrolyte interphase (SEI) resulting from the huge volume change during charge/discharge. Here, a multicore-shell structured Bi@N-doped carbon (Bi@N-C) anode is designed that addresses these issues. The nanosized Bi spheres are encapsulated by a conductive porous N-doped carbon shell that not only prevents the volume expansion during charge/discharge but also constructs a stable SEI during cycling. The Bi@N-C exhibits unprecedented rate capability and long cycle life for both NIBs (235 mAh g −1 after 2000 cycles at 10 A g −1 ) and KIBs (152 mAh g −1 at 100 A g −1 ). The kinetic analysis reveals the outstanding electrochemical performance can be attributed to significant pseudocapacitance behavior upon cycling.

Controlled Design of Well‐Dispersed Ultrathin MoS2 Nanosheets inside Hollow Carbon Skeleton: Toward Fast Potassium Storage by Constructing Spacious “Houses” for K Ions

“…Hollow architectures including yolk–shell, egg‐like, capsule‐like, tube‐like nanostructures have been extensively studied in the fields of drug‐controlled release, catalysis, and energy conversion . Particularly for electrode materials, loading active materials in such enclosed or half‐enclosed structures would not only avoid the exfoliation of active materials from the electrodes, but also provide enough space to alleviate the volume expansion . Thereby, loading MoS 2 inside such hollow architectures is anticipated to construct the stable MoS 2 @C electrode materials with the weak capacity fading in the potassiation/depotassiation process.…”

N-Doped Modified Graphene/Fe2O3 Nanocomposites as High-Performance Anode Material for Sodium Ion Storage

“…However, there are still some obstacles hindering the practical application of sodium ion energy storage devices, such as poor rate performance, low coulombic efficiency, and undesirable Nanomaterials 2019, 9, 1770 2 of 13 cycle stability. The foremost reason is the bigger radius of Na + (0.102 nm) compared to Li + (0.076 nm), which leads to low reaction kinetics for Na + insertion/extraction from the anode materials [4][5][6]. Meanwhile, excellent anode materials should have suitable microscopic internal structures that can accommodate the lager Na + and enable reversible insertion/extraction electrochemical behavior, and should also be compatible with electrolytes, cost-efficient, and easy to prepare.…”

Recent Developments in Alloying‐type Anode Materials for Potassium‐Ion Batteries

“…Bismuth is a promising alloying type anode material due to its nontoxic, high abundance on earth, and low melting point for the cost saving synthesis. Importantly, the layered structure of bismuth has large lattice space along the c ‐axis with a value of 3.95 Å, indicating the facile transportation of K + . Like other alloying type elements, volume swelling/shrinking is the most severe issue to hinder bismuth to achieve high capacity and good cyclic stability.…”

“…Yu's group reported two bismuth‐carbon composites, multicore‐shell structured Bi@N‐doped carbon (Bi@N−C) and bismuth nanoparticles embedded in 3D macroporous graphene frameworks (Bi@3DGFs), which presented superb electrochemical properties, especially the rate capability. The carbon layers, N‐doped carbon and hierarchical graphene frameworks, uniformly and tightly covered on the bismuth nanoparticles, which could effectively prevent the volume expansion of bismuth during electrochemical reactions and enhance the electrical conductivity of the whole composites.…”

“… (a) Long‐term cycling performance of Bi@N−C, (b) galvanostatic charge/discharge curves at different current densities corresponding (c), (c) rate capability of Bi@N−C, (d) comparison of rate capability of Bi@N−C with the reported anode materials for PIBs, (e) rate capability and (f) cycling performance of Bi@3DGFs …”