A multi-layered composite assembly of Bi nanospheres anchored on nitrogen-doped carbon nanosheets for ultrastable sodium storage

Enable the Domino-Like Structural Recovering in Bismuth Anode to Achieve Fast and Durable Na/K Storages

Alloying-type anodes show capacity and density advantages for sodium/potassium-ion batteries (SIBs/PIBs), but they encounter serious structural degradation upon cycling, which cannot be resolved through conventional nanostructuring techniques. Herein, we present an in-depth study to reveal the intrinsic reason for the pulverization of bismuth (Bi) materials upon (de)alloying, and report a novel particle-in-bulk architecture with Bi nanospheres inlaid in the bulk carbon (BiNC) to achieve durable Na/K storage. We simulate the volume-expansion-resistant mechanism of Bi during the (de)alloying reaction, and unveil that the irreversible phase transition upon (de)alloying underlies the fundamental origin for the structural degradation of Bi anode, while a proper compressive stress (~10 %) raised by the bulk carbon can trigger a "domino-like" Bi crystal recovering. Consequently, the as obtained BiNC exhibits a record high volumetric capacity (823.1 mAh cm-3 for SIBs, 848.1 mAh cm-3 for PIBs) and initial coulombic efficiency (95.3 % for SIBs, 96.4 % for PIBs), and unprecedented cycling stability (15000 cycles for SIBs with only 0.0015 % degradation per cycle), outperforming the state-of-the-art literature. This work provides new insights on the undesirable structural evolution, and proposes basic guidelines for design of the anti-degradation structure for alloy-type electrode materials.

Bi Nanospheres Embedded in N-Doped Carbon Nanowires Facilitate Ultrafast and Ultrastable Sodium Storage

Sodium ion batteries (SIBs) are considered as the ideal candidates for the next generation of electrochemical energy storage devices. The major challenges of anode lie in poor cycling stability and the sluggish kinetics attributed to the inherent large Na+ size. In this work, Bi nanosphere encapsulated in N-doped carbon nanowires (Bi@N-C) is assembled by facile electrospinning and carbonization. N-doped carbon mitigates the structure stress/strain during alloying/dealloying, optimizes the ionic/electronic diffusion, and provides fast electron transfer and structural stability. Due to the excellent structure, Bi@N-C shows excellent Na storage performance in SIBs in terms of good cycling stability and rate capacity in half cells and full cells. The fundamental mechanism of the outstanding electrochemical performance of Bi@N-C has been demonstrated through synchrotron in-situ XRD, atomic force microscopy, ex-situ scanning electron microscopy (SEM) and density functional theory (DFT) calculation. Importantly, a deeper understanding of the underlying reasons of the performance improvement is elucidated, which is vital for providing the theoretical basis for application of SIBs.

2D-Layer-Structure Bi to Quasi-1D-Structure NiBi3 : Structural Dimensionality Reduction to Superior Sodium and Potassium Ion Storage

Layer-structured bismuth (Bi) is an attractive anode for Na-ion and K-ion batteries due to its large volumetric capacity and suitable redox potentials. However, the cycling stability and rate capability of the Bi anode are restricted by the large volume expansion and sluggish Na/K-storage kinetics. Herein, a structural dimensionality reduction strategy is proposed and developed by converting 2D-layer-structured Bi into a quasi-1D structured NiBi3 with enhanced reaction kinetics and reversibility to realize high-rate and stable cycling performance for Na/K-ion storage. As a proof of concept, the quasi-1D intermetallic NiBi3 with low formation energy, metallic conductivity, and 3D Na/K-ion diffusion pathways delivers outstanding capacity retention of 94.1% (332 mAh g-1 ) after 15 000 cycles for Na-ion storage, and high initial coulombic efficiency of 93.4% with improved capacity retention for K-ion storage. Moreover, investigations on the highly reversible Na/K-storage reaction mechanisms and cycling-driven morphology reconstruction further reveal the origins of the high reversibility and the accommodation to volume expansion. The finding of this work provides a new strategy for high-performance anode design by structural dimensionality manipulation and cycling-driven morphology reconstruction.

Vapor-phase derived ultra-fine Bismuth nanoparticles embedded in carbon nanotube networks as anodes for sodium and potassium ion batteries

Bismuth (Bi) is a promising material as the anode for sodium-ion batteries (SIBs) and potassium-ion batteries (PIBs) due to its characteristics such as reasonable price and high theoretical volumetric capacity (3800 mAh cm^-3). Nevertheless, considerable drawbacks have hindered the practical applications of Bi, including its relatively low electrical conductivity and inevitable volumetric change during the alloying/dealloying processes. To solve these problems, we proposed a novel design:Bi nanoparticles were synthesized via a single-step low-pressure vapor-phase reaction and embedded onto the surfaces of multi-walled carbon nanotubes (MWCNTs). After being vaporized at 650℃ and 10^-5 Pa, Bi nanoparticles less than 10 nm were uniformly distributed in the three-dimensional (3D) MWCNT networks to form a Bi/MWNTs composite. In this unique design, the nanostructured Bi can reduce the risk of structural rupture during cycling, and the structure of the MWCMT network is beneficial in shortening the electron/ion transport path. In addition, MWCNTs can improve the overall conductivity of the Bi/MWCNTs composite and prevent particle aggregation, thus improving the cycling stability and rate performance. As an anode material for SIB, the Bi/MWCNTs composite has demonstrated excellent fast charging performance with a reversible capacity of 254 mAh/g at 20 A/g. A capacity of 221mAhg^-1 after cycling at 10 A/g for 8000 cycles has also been achieved for SIB. As an anode material for PIB, the Bi/MWCNTs composite has delivered excellent rate performances with a reversible capacity of 251 mAh/g at 20 A/g. A specific capacity of 270mAhg^-1 after cycling at 1Ag^-1 for 5000 cycles has also been achieved for PIB.

Synergistically Achieving Superior Sodium Storage of Metal Selenides by Constructing N-Doped Carbon Foams and Utilizing Cu-Driven Replacement Reaction

Metal selenides are considered as one of the most promising anode materials for Na-ion batteries owing to high specific capacity and relatively higher electronic conductivity compared with metal sulfides or oxides. However, such anodes still suffer from huge volume change upon repeated Na⁺ insertion/extraction processes and simultaneously undergo severe shuttle effect of polyselenides, thus leading to poor electrochemical performance. Herein, a facile chemical-blowing and selenization strategy to fabricate 3D interconnected hybrids built from metal selenides (MSe, M = Mn, Co, Cr, Fe, In, Ni, Zn) nanoparticles encapsulated in in situ formed N-doped carbon foams (NCFs) is reported. Such hybrids not only provide ultrasmall active nanobuilding blocks (≈15 nm), but also efficiently anchor them inside the conductive NCFs, thus enabling both high-efficiency utilization of active components and high structural stability. On the other hand, Cu-driven replacement reaction is utilized for efficiently inhibiting the shuttle effect of polyselenides in ether-based electrolyte. Benefiting from the combined merits of the unique MSe@NCFs and the utilization of the conversion of metal selenides to copper selenides, the as-obtained hybrids (MnSe as an example) exhibit superior rate capability (386.6 mAh g^-1 up to 8 A g^-1 ) and excellent cycling stability (347.7 mAh g^-1 at 4.0 A g^-1 after 1200 cycles).

Bismuth-Antimony Alloy Embedded in Carbon Matrix for Ultra-Stable Sodium Storage

Alloy-type anodes are the most promising candidates for sodium-ion batteries (SIBs) due to their impressive Na storage capacity and suitable voltage platform. However, the implementation of alloy-type anodes is significantly hindered by their huge volume expansion during the alloying/dealloying processes, which leads to their pulverization and detachment from current collectors for active materials and the unsatisfactory cycling performance. In this work, bimetallic Bi-Sb solid solutions in a porous carbon matrix are synthesized by a pyrolysis method as anode material for SIBs. Adjustable alloy composition, the introduction of porous carbon matrix, and nanosized bimetallic particles effectively suppress the volume change during cycling and accelerate the electrons/ions transport kinetics. The optimized Bi₁Sb₁@C electrode exhibits an excellent electrochemical performance with an ultralong cycle life (167.2 mAh g^-1 at 1 A g^-1 over 8000 cycles). In situ X-ray diffraction investigation is conducted to reveal the reversible and synchronous sodium storage pathway of the Bi₁Sb₁@C electrode: (Bi,Sb) Na(Bi,Sb) Na₃(Bi,Sb). Furthermore, online electrochemical mass spectrometry unveils the evolution of gas products of the Bi₁Sb₁@C electrode during the cell operation.

Iodine-Ion-Assisted Galvanic Replacement Synthesis of Bismuth Nanotubes for Ultrafast and Ultrastable Sodium Storage

Bismuth (Bi) has emerged as a promising anode material for fast-charging and long-cycling sodium-ion batteries (SIBs). However, its dramatically volumetric variations during cycling will undesirably cause the pulverization of active materials, severely limiting the electrochemical performance of Bi-based electrodes. Constructing hollow nanostructures is recognized as an effective way to resolve the volume expansion issues of alloy-type anodes but remains a great challenge for metallic bismuth. Here, we report a facile iodine-ion-assisted galvanic replacement approach for the synthesis of Bi nanotubes (NTs) for high-rate, long-term and high-capacity sodium storage. The hollow tubular structure effectively alleviates the structural strain during sodiation/desodiation processes, resulting in excellent structural stability; the thin wall and large surface area enable ultrafast sodium ion transport. Benefiting from the structural merits, the Bi NT electrode exhibits extraordinary rate capability (84% capacity retention at 150 A g^-1) and outstanding cycling stability (74% capacity retention for 65,000 cycles at 50 A g^-1), which represent the best rate performance and longest cycle life among all reported anodes for SIBs. Moreover, when coupled with the Na₃(VOPO₄)₂F cathode in full cells, this electrode also demonstrates excellent cycling performance, showing the great promise of Bi NTs for practical application. A combination of advanced research techniques reveals that the excellent performance originates from the structural robustness of the Bi NTs and the fast electrochemical kinetics during cycling.

Metal-organic framework-derived nitrogen-doped carbon-confined CoSe2 anchored on multiwalled carbon nanotube networks as an anode for high-rate sodium-ion batteries

Metal selenides, as potential alternative candidates for sodium storage, have promising applicability due to their high theoretical specific capacity. However, their huge volume change and sluggish electrode kinetics during sodium ion uptake and release processes can result in insufficient cycling life and inferior rate performance, hindering their practical application. Herein, nitrogen (N)-doped carbon-confined cobalt selenide anchored on multiwalled carbon nanotube networks (denoted as CoSe₂@NC/MWCNTs) was designed and successfully built through a selenization process with ZIF-67 MOF as the template. The existence of the interconnected MWCNT network plays a crucial role in not only enhancing the electronic conductivity and ion/electron-transfer efficiency but also ensuring structural stability. Consequently, the optimized CoSe₂@NC/MWCNTs composite delivers a high reversible capacity of 479.6 mA h g^-1 at a current rate of 0.2 A g^-1, accompanied by a 92.0% capacity retention over 100 cycles and a predominant rate performance of 227.4 mA h g^-1 even under 20 A g^-1 when examined as the anode in Na-ion batteries. Moreover, the kinetic behaviors were confirmed using CV profiles at various rates, as well as the galvanostatic intermittent titration technique (GITT) and electrochemical impedance spectroscopy (EIS). Besides, the HRTEM images clearly reveal the sodium-ion storage mechanism of the CoSe₂ hybrid. These results make CoSe₂@NC/MWCNTs a prospective anode material in advanced sodium-ion batteries.

3D Carbon Networks: Design and Applications in Sodium Ion Batteries

As the key component of a new generation for low-cost energy storage systems, sodium-ion batteries (SIBs) have attracted enormous attention and research due to its promising potentiality in large-scale electrochemical energy storage. For practical application of SIBs, carbonaceous materials have been considered to be one of the best choices for electrodes in virtue of their abundant reserves, low cost, easy availability, and environmental friendliness. 3D carbon network (3D-carbon) is of particular interests, which has displayed outstanding features, including abundant active sites, interconnected multi-level pore structures, high electronic conductivity, and excellent mechanical stability. Herein, we review the structural advantages of 3D-carbon and its preparation methods, and then discuss recent progress in 3D carbon materials and their composites for SIBs. The superior functionalities of 3D-carbon are emphasized as support templates or encapsulation shell membranes. Finally, we summarize and outline the challenges and future prospects of 3D-carbon in SIBs.

Self-assembled peptide and protein nanostructures for anti-cancer therapy: Targeted delivery, stimuli-responsive devices and immunotherapy

Self-assembled peptides and proteins possess tremendous potential as targeted drug delivery systems and key applications of these well-defined nanostructures reside in anti-cancer therapy. Peptides and proteins can self-assemble into nanostructures of diverse sizes and shapes in response to changing environmental conditions such as pH, temperature, ionic strength, as well as host and guest molecular interactions; their countless benefits include good biocompatibility and high loading capacity for hydrophobic and hydrophilic drugs. These self-assembled nanomaterials can be adorned with functional moieties to specifically target tumor cells. Stimuli-responsive features can also be incorporated with respect to the tumor microenvironment. This review sheds light on the growing interest in self-assembled peptides and proteins and their burgeoning applications in cancer treatment and immunotherapy.