Yolk-Shell-Structured Bismuth@N-Doped Carbon Anode for Lithium-Ion Battery with High Volumetric Capacity

Interfacial SbOC bond and structural confinement synergistically boosting the reaction kinetics and reversibility of Sb2Se3/NC nanorods anode for sodium storage

Antimony selenide (Sb2Se3) has been considered as a prospective material for sodium-ion batteries (SIBs) because of its large theoretical capacity. Whereas, grievous volume expansion caused by the conversion-alloying reaction leads to fast capacity decay and inferior cycle stability. Herein, the confined Sb2Se3 nanorods in nitrogen-doped carbon (Sb2Se3/NC) with interfacial chemical bond is designed to further enhance sodium storage properties of Sb2Se3. The robust enhancing effect of interfacial SbOC bonds can significantly promote electron transfer, Na+ ions diffusion kinetics and alloying reaction reversibility, combining the synergistic effect of the unique confinement structure of N-doped carbon shells can efficiently alleviate the volume change to ensure the structural integrity. Moreover, in-situ X-ray diffraction reveals intercalation/de-intercalation, conversion/reversed conversion reaction and alloying/de-alloying reaction mechanisms, and the kinetics analysis demonstrates the diffusion-controlled to contribute high capacity. As a result, Sb2Se3/NC anode delivers a high reversible capacity of 612.6 mAh/g at 0.1 A/g with a retentive specific capacity of 471.4 mAh/g after 1000 cycles, and long-cycle durability of over 2000 cycle with the reversible capacities of 371.1 and 297.3 mAh/g at 1 and 2 A/g are achieved, respectively, and an good rate capability. This distinctive interfacial chemical bonds and confinement effect design shows potential applications in the improved conversion/alloying-type materials for SIBs.

Scale Construction of "Breathing" Bi/N-CNSs Quasi-Array Structure with Hierarchical Bi Distribution for Sodium-Ion Battery

Sodium ion batteries (SIBs) are promising postlithium battery technologies with high safety and low cost. However, their development is hampered by complicated electrode material preparation and unsatisfactory sodium storage performance. Here, a bismuth/N-doped carbon nanosheets (Bi/N-CNSs) composite featuring a quasi-array structure (alternated porous Bi layers and N-CNSs) with hierarchical Bi distribution (large particles of ∼35 nm in Bi layers and ultrafine Bi of ∼8 nm on N-CNSs) is prepared. Bi/N-CNSs delivers an ultralong-lifespan of 26000 cycles at 5 A g-1 and prominent rate capability of 91.5% capacity retention at 100 A g-1. Even at -40 °C, it exhibits a high rate capability of 161 mAh g-1 at 5 A g-1. Notably, the involved preparation method is characterized by a high yield of 14.53 g in a single laboratory batch, which can be further scaled up, and such a method can also be extended to synthesize other metallic-based materials.

Engineering sulfur defective Bi2S3@C with remarkably enhanced electrochemical kinetics of lithium-ion batteries

Introducing the appropriate vacancies to augment the active sites and improve the electrochemical kinetics while maintaining high cyclability is a major challenge for its widespread application in electrochemical energy storage. Here, core-shell structured Bi2S3@C with sulfur vacancies was prepared by hydrothermal method and one-step carbonization/sulfuration process, which significantly improves the intrinsic electrical conductivity and ion transport efficiency of Bi2S3. Additionally, the uniform protective carbon layer around surface of composite maintains structural stability and effectively alleviates volume expansion during alloying/dealloying. As a result, the BSC-500 anode exhibits a brilliant reversible capacity of 636 mAh/g at 0.2 A/g and a long-term stable capacity of 524 mAh/g for 500 cycles at a high current density of 3 A/g in lithium-ion batteries. In addition, the assembled Bi2S3@C//LiCoO2 full cell delivered a capacity of 184 mAh/g at 1 A/g and excellent cyclability (125 mAh/g after 1000 cycles). The proposed strategy of combining sulfur vacancies with a core-shell structure to improve the electrochemical kinetics of Bi2S3 in lithium-ion batteries off the prospect for practical applications of transition metal sulfide anodes.

3D Dense Encapsulated Architecture of 2D Bi Nanosheets Enabling Potassium-Ion Storage with Superior Volumetric and Areal Capacities

2D alloy-based anodes show promise in potassium-ion batteries (PIBs). Nevertheless, their low tap density and huge volume expansion cause insufficient volumetric capacity and cycling stability. Herein, a 3D highly dense encapsulated architecture of 2D-Bi nanosheets (HD-Bi@G) with conducive elastic networks and 3D compact encapsulation structure of 2D nano-sheets are developed. As expected, HD-Bi@G anode exhibits a considerable volumetric capacity of 1032.2 mAh cm-3, stable long-life span with 75% retention after 2000 cycles, superior rate capability of 271.0 mAh g-1 at 104 C, and high areal capacity of 7.94 mAh cm-2 (loading: 24.2 mg cm-2) in PIBs. The superior volumetric and areal performance mechanisms are revealed through systematic kinetic investigations, ex situ characterization techniques, and theorical calculation. The 3D high-conductivity elastic network with dense encapsulated 2D-Bi architecture effectively relieves the volume expansion and pulverization of Bi nanosheets, maintains internal 2D structure with fast kinetics, and overcome sluggish ionic/electronic diffusion obstacle of ultra-thick, dense electrodes. The uniquely encapsulated 2D-nanosheet structure greatly reduces K+ diffusion energy barrier and accelerates K+ diffusion kinetics. These findings validate a feasible approach to fabricate 3D dense encapsulated architectures of 2D-alloy nanosheets with conductive elastic networks, enabling the design of ultra-thick, dense electrodes for high-volumetric-energy-density energy storage.

In Situ Formed Amorphous Bismuth Sulfide Cathodes with a Self-Controlled Conversion Storage Mechanism for High Performance Hybrid Ion Batteries

Conversion-type electrodes offer a promising multielectron transfer alternative to intercalation hosts with potentially high-capacity release in batteries. However, the poor cycle stability severely hinders their application, especially in aqueous multivalence-ion systems, which can fundamentally impute to anisotropic ion diffusion channel collapse in pristine crystals and irreversible bond fracture during repeated conversion. Here, an amorphous bismuth sulfide (a-BS) formed in situ with unprecedentedly self-controlled moderate conversion Cu2+ storage is proposed to comprehensively regulate the isotropic ion diffusion channels and highly reversible bond evolution. Operando synchrotron X-ray diffraction and substantive verification tests reveal that the total destruction of the Bi─S bond and unsustainable deep alloying are fully restrained. The amorphous structure with robust ion diffusion channels, unique self-controlled moderate conversion, and high electrical conductivity discharge products synergistically boosts the capacity (326.7 mAh g-1 at 1 A g-1 ), rate performance (194.5 mAh g-1 at 10 A g-1 ), and long-lifespan stability (over 8000 cycles with a decay rate of only 0.02 ‰ per cycle). Moreover, the a-BS Cu2+ ‖Zn2+ hybrid ion battery can well supply a stable energy density of 238.6 Wh kg-1 at 9760 W kg-1 . The intrinsically high-stability conversion mechanism explored on amorphous electrodes provides a new opportunity for advanced aqueous storage.

Advances in Electrochemical Energy Storage over Metallic Bismuth-Based Materials

Bismuth (Bi) has been prompted many investigations into the development of next-generation energy storage systems on account of its unique physicochemical properties. Although there are still some challenges, the application of metallic Bi-based materials in the field of energy storage still has good prospects. Herein, we systematically review the application and development of metallic Bi-based anode in lithium ion batteries and beyond-lithium ion batteries. The reaction mechanism, modification methodologies and their relationship with electrochemical performance are discussed in detail. Additionally, owing to the unique physicochemical properties of Bi and Bi-based alloys, some innovative investigations of metallic Bi-based materials in alkali metal anode modification and sulfur cathodes are systematically summarized for the first time. Following the obtained insights, the main unsolved challenges and research directions are pointed out on the research trend and potential applications of the Bi-based materials in various energy storage fields in the future.

Novel Bismuth Nanoflowers Encapsulated in N-Doped Carbon Frameworks as Superb Composite Anodes for High-Performance Sodium-Ion Batteries

Bismuth (Bi) has attracted attention as a promising anode for sodium-ion batteries (SIBs) owing to its suitable potential and high theoretical capacity. However, the large volumetric changes during cycling leads to severe degradation of electrochemical performance and limits its practical application. Herein, Bi nanoflowers are encapsulated in N-doped carbon frameworks to construct a novel Bi@NC composite via a facile solvothermal method and carbonization strategy. The well-designed composite structure endows the Bi@NC with uniformly dispersed Bi nanoflowers to alleviate the attenuation while the N-doped carbon frameworks improve the conductivity and ion transport of the whole electrode. As for sodium-ion half-cell, the electrode exhibits a high specific capacity (384.8 mAh g-1 at 0.1 A g-1 ) and excellent rate performance (341.5 mAh g-1 at 10 A g-1 ), and the capacity retention rate still remains at 94.9% after 5000 cycles at 10 A g-1 . Furthermore, the assembled full-cell with Na3 V2 (PO4 )3 cathode and Bi@NC anode can deliver a high capacity of 251.5 mAh g-1 at 0.1 A g-1 , and its capacity attenuates only 0.009% in each cycle after 2000 times at 5.0 A g-1 . This work offers a convenient, low-cost, and eco-friendliness approach for high-performance electrodes in the field of sodium ion electrochemical storage technology.

Bismuth-Nanoparticles-Embedded Porous Carbon Derived from Seed Husks as High-Performance for Anode Energy Electrode

In energy application technology, the anode part of the electrode is typically composed of carbon-coated materials that exhibit excellent electrochemical performance. The carbon-coated electrodes facilitate electrochemical reactions involving the fuel and the oxidant. Energy electrodes are used in stationary power plants to generate electricity for the grid. These large-scale installations are known as distributed generation systems and contribute to grid stability and reliability. Understanding the practical applications of energy materials remains a significant hurdle in the way of commercialization. An anode electrode has one key limitation, specifically with alloy-type candidates, as they tend to exhibit rapid capacity degradation during cycling due to volume expansion. Herein, biomass-derived carbon from sunflowers (seeds husks) via pyrolysis and then bismuth nanoparticles are treated with carbon via a simple wet-chemical method. The electrode Bi@C offers several structural advantages, such as high capacity, good cycling stability, and exceptional capability at the current rate of 500 mA g-1, delivering a capacity of 731.8 mAh g-1 for 200 cycles. The biomass-derived carbon coating protects the bismuth nanoparticles and contributes to enhanced electronic conductivity. Additionally, we anticipate the use of low-cost biomass with hybrid composition has the potential to foster environment-friendly practices in the development of next-generation advanced fuel cell technology.

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.

2D Bismuth@N-Doped Carbon Sheets for Ultrahigh Rate and Stable Potassium Storage

Metallic Bi, as an alloying-type anode material, has demonstrated tremendous potential for practical application of potassium-ion batteries. However, the giant volume expansion, severe structure pulverization, and sluggish dynamics of Bi-based materials result in unsatisfied rate performance and unstable cycling stability. Here, 2D bismuth@N-doped carbon sheets with BiOC bond and internal void space (2D Bi@NOC) are successfully fabricated via a self-template strategy to address these issues, which own ultrafast electrochemical kinetics and impressive long-term cycling stability for delivering an admirable capacity of 341.7 mAh g^-1 after 1000 cycles at 10 A g^-1 and impressive rate capability of 220.6 mAh g^-1 at 50 A g^-1 . Particularly, the in situ transmission electron microscopy observations visualize the real-time alloying/dealloying process and reveal that plastic carbon shell and void space can availably relieve dramatic volume stress and powerfully maintain structural integrity. Density functional theory calculation and ultraviolet photoelectron spectroscopy test certify that the robust BiOC bond is thermodynamically and kinetically beneficial for adsorption/diffusion of K⁺ . This work will light on designing advanced high-performance energy materials and provide important evidence for understanding the energy storage mechanism of alloy-based materials.

Engineering hierarchically ZnS/NiS/NiS2 hollow porous urchin-like composite towards exceptional lithium storage

Complex hollow structure nanostructure is regarded as the desired approach to alleviating the volume change of lithium-ion batteries (LIBs). In this work, ZnS/NiS/NiS₂ composite with a distinctive hierarchical hollow porous urchin-like structure was prepared through pyrolysis of bimetal-organic frameworks obtained by one-step solvothermal and firstly used as anodes for LIBs. Varying the metal molar ratios allows the control of the surface area and pore size distribution of ZnS/NiS/NiS₂. The obtained composite with a hollow porous urchin-like structure exhibits high porosity, large specific surface area, and strong synergetic interaction between ZnS and NiS/NiS₂ can greatly buffer the volume expansion to keep the mechanical stability, ensure sufficient contact region between electrolyte and electrodes and shorten the Li⁺ transfer distance, meanwhile, the carbon derived from organic ligand of bimetal-organic frameworks also constructs the conductive matrix to accelerate electrons transfer. Based on the above outstanding properties, the obtained material delivers excellent rate capacity, superior reversible capacity, and long-cycle stability, especially disclosing a capacity of 615 mAh·g^-1 after 300 cycles at 2 A·g^-1. This work proposes a feasible strategy to obtain a unique hollow porous urchin-like structure through pyrolysis of bimetal organic frameworks, it can be extended to fabricate other mixed metal sulfides nanostructures with excellent electrochemical performances.

Porous engineering of CoS2/N-doped carbon polyhedra anode for durable lithium-ion battery

In this work, the porous CoS₂/N-doped carbon polyhedra (P-CoS₂/CP) has been developed by employing ZIF-67 as the template for durable lithium-ion battery anode. The as-prepared P-CoS₂/CP exhibits the novel dodecahedron structure filling with nanopores and CoS₂nanoparticles. As compared to CoS₂/CP (122 m²g^-1), the P-CoS₂/CP possesses the higher specific surface area of 367 m²g^-1, which benefits to enlarge the electrode-electrolyte contact area and promote the Li⁺diffusion dynamics at high current density. On the other hand, the CoS₂nanoparticles are firmly wrapped by the carbon skeleton which can effectively suppresses the volume expansion of CoS₂during the charging/discharging process. Besides, the N-doping enable to improve the conductivity of CP. As a result, the initial discharge capacity of P-CoS₂/CP at 0.1 A g^-1is 1484.7 mAh g^-1with the coulombic efficiency of 48.9%. After 100 cycles, the reversible capacity stabilized at 726.2 mAh g^-1. Even the current density increases to 2.0 A g^-1, a high reversible capacity of 353.7 mAh g^-1can still be achieved, realizing the good rate capability. The superior Li⁺performance of P-CoS₂/CP is attributed to the synergistic effect of the unique multi-space structure and the high chemical activity of CoS₂. Moreover, the Li⁺diffusion coefficient of P-CoS₂/CP is 4.52 × 10^-6 to 1.98 × 10^-11cm²s^-1, which is higher than that of CoS₂/CP (1.45 × 10^-9 to 5.23 × 10^-11cm²s^-1), highlighting the significance of porous engineering.

Highly Dispersed Antimony-Bismuth Alloy Encapsulated in Carbon Nanofibers for Ultrastable K-Ion Batteries

Antimony-based alloys have appealed to an ever-increasing interest for potassium ion storage due to their high theoretical capacity and safe voltage. However, sluggish kinetics and the large radius of K⁺ lead to limited rate performance and severe capacity fading. In this Letter, highly dispersed antimony-bismuth alloy nanoparticles confined in carbon fibers are fabricated through an electrospinning technology followed by heat treatment. The BiSb nanoparticles are uniformly confined into the carbon fibers, which facilitate rapid electron transport and inhibit the volume change during cycling owing to the synergistic effect of the BiSb alloy and carbon confinement engineering. Furthermore, the effect of a potassium bis(fluorosulfonyl)imide (KFSI) electrolyte with different concentrations has been investigated. Theoretical calculation demonstrates that the incorporation of Bi metal is favorable for potassium adsorption. The combination of delicate nanofiber morphology and electrolyte chemistry endows the fiber composite with an improved reversible capacity of 274.4 mAh g^-1, promising rate capability, and cycling stability upon 500 cycles.

Integrating Bi@C Nanospheres in Porous Hard Carbon Frameworks for Ultrafast Sodium Storage

Sodium-ion batteries (SIBs) have emerged as an alternative technology because of their merits in abundance and cost. Realizing their real applications, however, remains a formidable challenge. One is that among the limitations of anode materials, the alloy-type candidates tolerate fast capacity fading during cycling. Here, a 3D framework superstructure assembled with carbon nanobelt arrays decorated with a metallic bismuth (Bi) nanospheres coated carbon layer by thermolysis of Bi-based metal-organic framework nanorods is synthesized as an anode material for SIBs. Due to the unique structural superiority, the anode design promotes excellent sodium-storage performance in terms of high capacity, excellent cycling stability, and ultrahigh rate capability up to 80 A g^-1 with a capacity of 308.8 mAh g^-1 . The unprecedented sodium-storage ability is not only attributed to the unique hybrid architecture, but also to the production of a homogeneous and thin solid electrolyte interface layer and the formation of uniform porous nanostructures during cycling in the ether-based electrolyte. Importantly, deeper understanding of the underlying cause of the performance improvement is illuminated, which is vital to provide the theoretical basis for application of SIBs.

Carbon Dots-Regulated Pomegranate-Like Metal Oxide Composites: From Growth Mechanism to Lithium Storage

Carbon dots (CDs) are considered as excellent structural regulator for metal oxides (MOs) due to their abundant functional groups, superior dispersibility, and ultrasmall size (<10 nm). Herein, a new approach is proposed to construct porous pomegranate-like MOs/CDs composite based on the CDs-induced in situ growth mechanism of ion adsorption-multipoint surface nucleation-crosslinking agglomeration. The proposed methodology is successfully applied to prepare SnO₂ /CDs, Cu₂ O/CDs, and Fe₂ O₃ /CDs composites, respectively, demonstrating its universality to metal oxides. Taking SnO₂ /CDs composite as a case study for anode material in lithium-ion batteries, it exhibits high lithium storage capacity, excellent cycling stability, and a special feature of capacity increase upon cycling. This study provides a new idea for the design of metal oxides materials tuned by CDs and broadens the application of CDs in the field of material synthesis.

Recent progress on Sb- and Bi-based chalcogenide anodes for potassium ion batteries

Potassium ion batteries (PIBs) are potential alternative energy storage systems to lithium ion batteries (LIBs), due to elemental abundance of potassium, low cost and similar working principle to LIBs. Recently, metal chalcogenides (MCs) have gained enormous interests, especially antimony (Sb)-, bismuth (Bi) -based chalcogenides because they were able to undergo alloying/conversion dual mechanism, which can provide higher specific capacity and energy density (K 3 Sb~660 mA h g -1 , K 3 Bi~385 mA h g -1 ). However, several challenges hinder the development of Sb-, Bi-based chalcogenide anode materials for PIBs , such as huge volume expansion during potassiation, unstable solid-electrolyte interface (SEI), slow reaction kinetics, and polychalcogenide-induced shuttle effect . In this review, the current state-of-the-art Sb-, Bi-based chalcogenides are comprehensively summarized, including the reaction mechanism, electrochemical performance, ingenious nanostructures, electrolyte systems, and prospects for future development. This review contributes to understanding the K + storage mechanism and the interaction between active materials and electrolytes, providing guidance and foundation for the design of next-generation high-performance PIBs.

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

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, Bi@C@GR-2 presents a superior reversible capacity for sodium storage (300 mAh g^-1 over 80 cycles) and potassium storage (200 mAh g^-1 over 70 cycles) at 0.1 A g^-1. Furthermore, in situ electrochemical impedance spectroscopy and ex situ transmission electron microscopy are carried out to analyze and reflect the kinetic reaction mechanism and the phase change of the Bi@C@GR-2 electrode during the charge/discharge processes.

Azo-dye derived oxidized-nitrogen rich carbon sheets with high adsorption capability for dye effluent under both batch and continuous conditions

The removal of methyl blue (MB) from wastewater using graphene and its derivative is very successful due to their high aromaticity which drives adsorption via π-π and electron-donor-acceptor (EDA) interactions; however, graphene is expensive and difficult to synthesize, which limit its practical application. Meanwhile, low aromatic carbon materials (LACM) derived from farm-water and other materials are cheaper and easier to synthesize but have limited π-π and EDA interactions and low adsorption capacity. Herein, we demonstrate that LACM with oxidized-nitrogen (N-O^-) functionality overcomes this limitation via chemisorption of MB through a combination of hydrophobic-hydrophobic interactions and EDA interactions. This is confirmed using XPS analysis of LACM/N-O^- post MB adsorption. Consequently, a remarkable adsorption capacity of 3904 mg g^-1 is achieved under batch condition which is the highest ever reported for any MB adsorbent. Furthermore, LACM/N-O^- works equally well under continuous-flow adsorption conditions which shows its practicability. Amongst several LACM precursors tested, only Azo-dyes are able to generate LACM/N-O^- implying that the NN moiety is key to N-O^- formation. A carbonization temperature of 700 °C generates the highest N-O^- sites hence the highest adsorption capacity. Characterization of LACM/N-O^- is done mainly using BET, XPS, Raman, TGA, and FTIR analysis.

Solid Solution of Bi and Sb for Robust Lithium Storage Enabled by Consecutive Alloying Reaction

Materials with alloying reactions have significant potential as electrodes for lithium-ion batteries (LIBs) due to its high theoretical capacity and appropriate lithiation potentials. Nonetheless, their cycling performance is inferior due to violent volume expansion and severe pulverization of active materials. Herein, solid solution of Bi_0.5 Sb_0.5 encapsulated with carbon is discovered to enable consecutive alloying reactions with manageable volume change, suitable for developing LIBs with high capacity and robust cyclability. A Sb-rich shell and Bi-rich core structure is formed in cycling since the alloying reaction between Sb and Li occurs first, followed by the alloying reaction between Bi and Li. Such a consecutive alloying reaction obeying the thermodynamic path is experimentally realized by the carbon capsulation, which acts as a protecting solid layer to avoid polarized reactions occurred when exposed directly to liquid electrolyte. The LIBs using Bi_0.5 Sb_0.5 @carbon run on the consecutive alloying reactions exhibits high capacity, prolonged lifespan (489.4 mAh g^-1 after 2000 cycles at 1 A g^-1 ) and fast kinetic, while those using bare Bi_0.5 Sb_0.5 suffer from worsened kinetic and thus a poor cycling performance owning to the polarized reactions. The work paves a way of developing alloy electrodes for alkaline-ion rechargeable batteries with potential industry applications.

Restraining polysulfide shuttling by designing a dual adsorption structure of bismuth encapsulated into carbon nanotube cavity

The shuttle effect derived from the dissolution of lithium polysulfides (LIPs) seriously hinders commercialization of lithium-sulfur (Li-S) batteries. Hence, we skillfully designed 1D cowpea-like CNTs@Bi composites with a double adsorption structure, where the bismuth nanoparticles/nanorods are encapsulated in the cavities of CNTs, avoiding the aggregation of bismuth nanoparticles during cycling and improving the conductivity of the electrode. Meanwhile, the sulfur was evenly distributed on the surface of bismuth nanoparticles/nanorods, ensuring effective catalytic activity and displaying high sulfur loading. Under the synergetic effects of the physical detention of abundant pores and chemical adsorption of bismuth, LIPs can be minimised, effectively curbing the shuttle effect. Benefiting from the above advantages, the CNTs@Bi/S cathodes exhibit a high capacity of 1352 mA h g-1, long cycling lifespan (708 mA h g-1 after 200 cycles at 1 C) and excellent coulombic efficiency. As the anodes of lithium-ion batteries (LIBs), the CNTs@Bi composites also show excellent performance due to the encapsulated structure to accommodate the serious volume change. This work offers an innovative strategy for improving the performances of the Li-S batteries and LIBs.

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

Bismuth (Bi) is a promising anode candidate for sodium ion batteries (SIBs) with a high volumetric capacity (3765 mA h cm-3) and moderate working potential but suffers from large volume change (ca. 250%) during the sodiation/desodiation process, resulting in pulverization of the electrode, electrical contact loss, excessive accumulation of solid electrolyte interfaces, etc., devastating the cycling stability of the electrode seriously. Addressing this issue significantly relies on rational micro- and nano-structuring. Herein, we prepared a 3D multi-layered composite assembly of Bi/carbon heterojunctions with 0D bismuth nanospheres distributed and anchored on 2D nitrogen-doped carbon nanosheets (NCSs), using a preorganization strategy by taking full advantage of the strong complexation ability of Bi3+. The multi-layered composite assembly is periodic and close-packed, with Bi nanospheres <25 nm, carbon nanosheets ∼30 nm, and an average interlayer space of ∼75 nm. Such a specific architecture provides abundant electrochemically active surfaces and ion migration channels as the Bi nanospheres are attached to the 2D nitrogen-doped carbon nanosheets via a point-to-surface pattern. Moreover, the mono-layer Bi nanospheres oriented along the 2D-surface of NCSs are kinetically favorable for the recognition of Na+ by the active sites of Bi nanospheres as well as for avoiding the long distance migration of Na+ (external diffusion of Na+). Furthermore, thermodynamically, the small size and high surface energy of ultrasmall Bi nanospheres could contribute to high ion mobility (internal diffusion of Na+) and promote electrochemical reactions as well. The multi-layered composite assembly of Bi@NCSs (ML-Bi@NCSs) not only provides a robust 3D framework guaranteeing the whole structural stability but also ensures direct and full contact of each active nano-building block with electrolyte, thereby forming a high-throughput electron/ion transport system. When evaluated as the anode for SIBs, ML-Bi@NCSs deliver superior high-rate capability up to 30 A g-1 (specific capacity: 288 mA h g-1) and long-term cycling stability (capacity retention: 95.8% after 5000 cycles at 10 A g-1 and 90.6% after 10 000 cycles at 20 A g-1, respectively).

On-Site Fluorination for Enhancing Utilization of Lithium in a Lithium-Sulfur Full Battery

The rechargeability of the lithium anode in lithium-sulfur (Li-S) batteries is an issue for this type of battery. In this work, we demonstrate a Li-S full battery comprising a protected anode scaffold and a Li₂S cathode. The stabilized performance is attained by an on-site fluorination strategy, using BiF₃ for the interfacial coating of the anode. Unlike previously reported LiF protective coating derived from the vapor/solution depositions, BiF₃ nanocrystals would be lithiated on-site to the anode surface and server as the protective layer. The chemically inertial Li₃Bi alloy can provide additional ion-conductive paths and stitch the LiF to form a seamless protective layer, thereby suppressing the dendrite propagation and parasitic reactions effectively. With the designed anode structures and compositions, the high-loading full battery (8.05 mg cm^-2) can achieve an exceptional utilization of both sulfur (898 mAh g_S^-1) and lithium (1533 mAh g_Li^-1) over 200 cycles, marking a step toward cyclable Li metal batteries at a high capacity.

Bi-Based Electrode Materials for Alkali Metal-Ion Batteries

Alkali metal (Li, Na, K) ion batteries with high energy density are urgently required for large-scale energy storage applications while the lack of advanced anode materials restricts their development. Recently, Bi-based materials have been recognized as promising electrode candidates for alkali metal-ion batteries due to their high volumetric capacity and suitable operating potential. Herein, the latest progress of Bi-based electrode materials for alkali metal-ion batteries is summarized, mainly focusing on synthesis strategies, structural features, storage mechanisms, and the corresponding electrochemical performance. Particularly, the optimization of electrode-electrolyte interphase is also discussed. In addition, the remaining challenges and further perspectives of Bi-based electrode materials are outlined. This review aims to provide comprehensive knowledge of Bi-based materials and offer a guideline toward more applications in high-performance batteries.

Scalable One-Pot Synthesis of Hierarchical Bi@C Bulk with Superior Lithium-Ion Storage Performances

Lithium-ion batteries (LIBs), the most successful commercial energy storage devices, are now widespread in our daily life. However, the lack of appropriate electrode materials with long lifespan and superior rate capability is the urgent bottleneck for the development of high-performance LIBs. Herein, a hierarchical Bi@C bulk is developed via a scalable pyrolysis method. Due to the ultrafine size of Bi nanoparticles and in situ generated porous carbon framework, this Bi@C anode evidently facilitates the diffusion of Li⁺/electron, availably inhibits the agglomeration of active nano-Bi, and effectively mitigates the volume fluctuation. This hierarchical Bi@C bulk exhibits stable cycling performance for both LIBs (256 mAh g^-1 at 1.0 A g^-1 over 1400 cycles) and potassium-ion batteries (271 mAh g^-1 at 0.1 A g^-1 for 200 cycles). More importantly, when coupled with a commercial LiCoO₂ cathode, the assembled LiCoO₂//Bi@C cells provide an output voltage of 2.9 V and retain a capacity of 202 mAh g^-1 at 0.15 A g^-1. Moreover, kinetic analysis and in situ X-ray diffraction characterization reveal that the Bi@C anode displays a dominated pseudocapacitance behavior and a typical alloying storage mechanism during the cycling process.

A novel sulfur@void@hydrogel yolk-shell particle with a high sulfur content for volume-accommodable and polysulfide-adsorptive lithium-sulfur battery cathodes

High-energy-density secondary batteries are required for many applications such as electric vehicles. Lithium-sulfur (Li-S) batteries are receiving broad attention because of their high theoretical energy density. However, the large volume change of sulfur during cycling, poor conductivity, and the shuttle effect of sulfides severely restrict the Li-storage performance of Li-S batteries. Herein, we present a novel core-shell nanocomposite consisting of a sulfur core and a hydrogel polypyrrole (PPy) shell, enabling an ultra-high sulfur content of about 98.4% within the composite, which greatly exceeds many other conventional composites obtained by coating sulfur onto some hosts. In addition, the void inside the core-shell structure effectively accommodates the volume change; the conductive PPy shell improves the conductivity of the composite; and PPy is able to adsorb polysulfides, suppressing the shuttle effect. After cycling for 200 cycles, the prepared S@void@PPy composite retains a stable capacity of 650 mAh g^-1, which is higher than the bare sulfur particles. The composite also exhibits a fast Li ion diffusion coefficient. Furthermore, the density functional theory calculations show the PPy shell is able to adsorb polysulfides efficiently, with a large adsorption energy and charge density transfer.

MnSe embedded in carbon nanofibers as advanced anode material for sodium ion batteries

MnSe with high theoretical capacity and reversibility is considered as a promising material for the anode of sodium ion batteries. In this study, MnSe nanoparticles embedded in 1D carbon nanofibers (MnSe-NC) are successfully prepared via facile electrospinning and subsequent selenization. A carbon framework can effectively protect MnSe dispersed in it from agglomeration and can accommodate volume variation in the conversion reaction between MnSe and Na⁺ to guarantee cycling stability. The 1D fiber structure can increase the area of contact between electrode and electrolyte to shorten the diffusion path of Na⁺ and facilitate its transfer. According to the kinetic analysis, the storage process of sodium by MnSe-NC is a surface pseudocapacitive-controlled process with promising rate capability. Impressively, An MnSe-NC anode in sodium ion full cells is investigated by pairing with an Na₃V₂(PO₄)₂@rGO cathode, which exhibits a reversible capacity of 195 mA h g^-1 at 0.1 A g^-1.

Template-assisted loading of Fe3O4 nanoparticles inside hollow carbon "rooms" to achieve high volumetric lithium storage

The design of electrodes with simultaneously high compaction density, developed porosity, and structural stability has always been a challenge so as to meet the demand of high volumetric performance lithium ion storage devices. In this paper, we demonstrate a new compositing method for hollow carbon "room" loading of Fe₃O₄ nanoparticles (HCR@Fe₃O₄) with the assistance of Na₂CO₃ salt crystal templates. The as-obtained HCR@Fe₃O₄ composites have a massive compaction density (1.79 g cm^-3), abundant multimodal pores (1.26 cm³ g^-1), and a large content of Fe₃O₄ (64.2 wt%), which leads to excellent volumetric capacitive performance. More importantly, the unique compositing model not only provides a fast transmission channel for Li⁺ but also alleviates the mechanical strain efficiently through the cavity between the Fe₃O₄ nanoparticles and the carbon wall. When evaluated as an anode of lithium ion batteries, the resultant HCR@Fe₃O₄ electrode exhibits a remarkable volumetric capacity of 2044 mA h cm^-3 at 0.2 A g^-1 and a stable cycle life of 828 mA h cm^-3 after 1000 cycles at 5 A g^-1. The assembled HCR@Fe₃O₄//AC lithium ion hybrid capacitor device exhibits a high energy density of 173 W h L^-1 at a power density of 190 W L^-1, demonstrating its high-level integrated volumetric density/power density.

Bipolar Electrochemistry Exfoliation of Layered Metal Chalcogenides Sb2 S3 and Bi2 S3 and their Hydrogen Evolution Applications

Efficient exfoliation and downsizing of Sb₂ S₃ and Bi₂ S₃ layered compounds by using scalable bipolar electrochemistry on their suspensions in aqueous media are here demonstrated. The resulting samples were characterized in detail by transmission electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy; their electrochemistry toward hydrogen evolution was also investigated. Hydrogen evolution ability of exfoliated Sb₂ S₃ and Bi₂ S₃ was investigated and compared to the bulk counterparts.

Facile synthesis of novel tungsten-based hierarchical core-shell composite for ultrahigh volumetric lithium storage

The development of novel high volumetric capacity electrode materials is crucial to the application of lithium-ion batteries (LIBs) in miniaturized consumer electronics. In this work, a novel tungsten-based octahedron (CoWO₄/Co₃O₄) with unique hierarchical core-shell structure is successfully fabricated by simply calcinating a cyanide-metal framework precursor. Benefitting from the heavy element W, the CoWO₄/Co₃O₄ octahedrons show a high mass density of 5.18 g cm^-3. When applied as anode materials for LIBs, the CoWO₄/Co₃O₄ octahedrons exhibit an ultrahigh volumetric capacity (6226 mAh cm^-3 after 350 cycles at 0.4 A g^-1), superior rate capability (3165 mAh cm^-3 at 3.0 A g^-1) and outstanding long-term cycling performance (4703 mAh cm^-3 at 1.0 A g^-1 after 800 cycles). The extraordinary lithium storage performance can be ascribed to the unique hierarchical core-shell structure and the possible synergistic effect between W and Co, which provide more Li⁺ insertion sites and effectively buffer the volume variation during cycling. This work not only provides an ultrahigh volumetric lithium storage anode, but also gives a simple and general strategy for the synthesis of novel anode materials for high volumetric energy density LIBs.

Co3V2O8 Nanoparticles Supported on Reduced Graphene Oxide for Efficient Lithium Storage

Co₃V₂O₈ (CVO) with high theoretical specific capacity derived from the multiple oxidation states of V and Co is regarded as a potential electrode material for lithium-ion batteries (LIBs). Herein, reduced graphene oxide (rGO)-supported ultrafine CVO (rGO@CVO) nanoparticles are successfully prepared via the hydrothermal and subsequent annealing processes. The CVO supported on 2D rGO nanosheets possess excellent structural compatibility for the accommodation of volume variation to maintain the structural integrity of an electrode during the repeated lithiation/delithiation process. On the other hand, the rGO, as a highly-conductive network in the rGO@CVO composite, facilitates rapid charge transfer to ensure fast reaction kinetics. Moreover, the CV kinetic analysis indicates that the capacity of rGO@CVO is mainly dominated by a pseudocapacitive process with favorable rate capability. As a result, the rGO@CVO composite exhibits improved specific capacity (1132 mAh g⁻¹, 0.1 A g⁻¹) and promising rate capability (482 mAh g⁻¹, 10 A g⁻¹).

Monolayer Mo2C as anodes for magnesium-ion batteries

The adsorption and diffusion behaviors of magnesium (Mg) on monolayer Mo₂C have been investigated by the first principles method based on density functional theory (DFT). The structural stability and theoretical capacity of monolayer Mo₂C as anodes for magnesium-ion batteries (MIBs) have also been investigated. The results show that Mg prefer to occupy the H and T_C sites with the adsorption energies of - 1.439 and - 1.430, respectively, followed by B and T_Mo sites on Mo₂C monolayer. The Mg prefers to diffuse along the H-T_C-H path, furthermore, the other two possible paths (along H-B-H and H-T_Mo-H) also possess quite low energy barrier with the value of about 0.039 eV. The present results demonstrate that the adsorption energy per Mg atom and the volume expansion change mildly. The volume expansions change slightly from 0.7 to 7.08% with the variety of x, ranging from 0.167 to 2.0. The theoretical gravimetric capacity reaches to 469.791 mAhg^-1 with relatively small deformation and expansion as x = 2.0. The results mentioned above suggest that Mo₂C monolayer is one of the promising candidates for anode material of MIBs.

N-Doped carbon coated bismuth nanorods with a hollow structure as an anode for superior-performance potassium-ion batteries

Bismuth (Bi) is a promising anode material for potassium-ion batteries due to its high energy density. However, the large volume change limits its applications. Herein, N-doped carbon coated Bi nanorods with a hollow structure are fabricated and they exhibit excellent long-term cycling performance (88% capacity retention over 1000 cycles) and high-rate ability (297 mA h g-1 at 20C, 94% capacity of that at 1C). Furthermore, the mechanism was expounded by in situ XRD, indicating a multi-phase reaction for the initial discharge process and three two-phase reactions for the subsequent charge/discharge processes.

Quinone/ester-based oxygen functional group-incorporated full carbon Li-ion capacitor for enhanced performance

Lithium ion capacitors (LICs) are regarded as one of the most promising energy storage devices since they can bridge the gap between lithium ion batteries and supercapacitors. However, the mismatches in specific capacity, high-rate behavior, and cycling stability between the two electrodes are the most critical issues that need to be addressed, severely limiting the large energy density and long cycling life of LICs while delivering high-power density output. Herein, quinone and ester-type oxygen-modified carbon has been successfully obtained by chemical activation with alkali, which is beneficial to the absorption of PF₆^- together with lithium ions, which would largely improve the electrode kinetics. In particular, the cathode capacity is considerably enhanced with the increase in the amount of oxygen functional groups. Moreover, for the full carbon LIC device, an energy density of 144 W h kg^-1 is exhibited at the power density of 200 W kg^-1. Surprisingly, even after 10 000 cycles at 20 000 W kg^-1, a capacity retention of 70.8% is successfully achieved. These remarkable results could be ascribed to the enhancement of cathode capacity and the acceleration of anode kinetics. Furthermore, the density functional theory (DFT) calculations prove that the oxygen functional groups can deliver enhanced electrochemical activity for lithium storage through surface-induced redox reactions. This elaborate study may open an avenue for resolving the issues with the electrode materials of LICs and deepen the understanding on the surface engineering strategies for incorporating oxygen-functional groups.

Bismuth-Antimony Alloy Nanoparticle@Porous Carbon Nanosheet Composite Anode for High-Performance Potassium-Ion Batteries

Antimony (Sb)-based anode materials have recently aroused great attention in potassium-ion batteries (KIBs), because of their high theoretical capacities and suitable potassium inserting potentials. Nevertheless, because of large volumetric expansion and severe pulverization during potassiation/depotassiation, the performance of Sb-based anode materials is poor in KIBs. Herein, a composite nanosheet with bismuth-antimony alloy nanoparticles embedded in a porous carbon matrix (BiSb@C) is fabricated by a facile freeze-drying and pyrolysis method. The introduction of carbon and bismuth effectively suppress the stress/strain originated from the volume change during charge/discharge process. Excellent electrochemical performance is achieved as a KIB anode, which delivers a high reversible capacity of 320 mA h g^-1 after 600 cycles at 500 mA g^-1. In addition, full KIBs by coupling with Prussian Blue cathode deliver a high capacity of 396 mA h g^-1 and maintain 360 mA h g^-1 after 70 cycles. Importantly, the operando X-ray diffraction investigation reveals a reversible potassiation/depotassiation reaction mechanism of (Bi,Sb) ↔ K(Bi,Sb) ↔ K₃(Bi,Sb) for the BiSb@C composite. Our findings not only propose a reasonable design of high-performance alloy-based anodes in KIBs but also promote the practical use of KIBs in large-scale energy storage.

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

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).

Bismuth dots imbedded in ultralong nitrogen-doped carbon tubes for highly efficient lithium ion storage

A hollow tube-shaped Bi/carbon hybrid is constructed for lithium ion storage, which is made up of ultrafine Bi nanodots homogeneously space-confined in the inner wall of ultralong nitrogen-doped carbon tubes.

Multi-yolk–shell bismuth@porous carbon as a highly efficient electrocatalyst for artificial N2 fixation under ambient conditions

Multi-yolk–shell bismuth@porous carbon catalyst was fabricated by facile synthetic processes. The MB@PC catalyst displays deliver a NH₃ yield of 28.63 μg h⁻¹ mg⁻¹_cat., a Faraday efficiency of 10.58 % at −0.5 V versus RHE under ambient conditions.

Investigation of Binary Metal (Ni, Co) Selenite as Li-Ion Battery Anode Materials and Their Conversion Reaction Mechanism with Li Ions

Highly efficient anode materials with novel compositions for Li-ion batteries are actively being researched. Multicomponent metal selenite is a promising candidate, capable of improving their electrochemical performance through the formation of metal oxide and selenide heterostructure nanocrystals during the first cycle. Here, the binary nickel-cobalt selenite derived from Ni-Co Prussian blue analogs (PBA) is chosen as the first target material: the Ni-Co PBA are selenized and partially oxidized in sequence, yielding (NiCo)SeO₃ phase with a small amount of metal selenate. The conversion mechanism of (NiCo)SeO₃ for Li-ion storage is studied by cyclic voltammetry, in situ X-ray diffraction, ex situ X-ray photoelectron spectroscopy, in situ electrochemical impedance spectroscopy, and ex situ transmission electron microscopy. The reversible reaction mechanism of (NiCo)SeO₃ with the Li ions is described by the reaction: NiO + CoO + xSeO₂ + (1 - x)Se + (4x + 6)Li⁺ + (4x + 6)e^- ↔ Ni + Co + (2x + 2)Li₂ O + Li₂ Se. To enhance electrochemical properties, polydopamine-derived carbon is uniformly coated on (NiCo)SeO₃ , resulting in excellent cycling and rate performances for Li-ion storage. The discharge capacity of C-coated (NiCo)SeO₃ is 680 mAh g^-1 for the 1500th cycle when cycled at a current density of 5 A g^-1 .