Recent Progress on the Alloy-Based Anode for Sodium-Ion Batteries and Potassium-Ion Batteries

Pb nanospheres encapsulated in metal-organic frameworks-derived porous carbon as anode for high-performance sodium-ion batteries

Alloying-type anode materials are considered promising candidates for sodium-ion batteries (SIBs) due to their high theoretical capacities. However, their application is limited by the severe capacity decay stemming from dramatic volume changes during Na+ insertion/extraction processes. Here, Pb nanospheres encapsulated in a carbon skeleton (Pb@C) were successfully synthesized via a facile metal-organic frameworks (MOFs)-derived method and used as anodes for SIBs. The nanosized Pb particles are uniformly incorporated into the porous carbon framework, effectively mitigating volume changes and enhancing Na+ ion transport during discharging/charging. Benefiting from this unique architecture, a reversible capacity of 334.2 mAh g-1 at 2 A g-1 is achieved after 6000 cycles corresponding to an impressive 88.2 % capacity retention and a minimal capacity loss of 0.00748 % per cycle. Furthermore, a high-performance full sodium-ion battery of Pb@C//NVPF was constructed, demonstrating a high energy density of 291 Wh kg-1 and power density of 175 W kg-1. This facile MOFs-derived method offers insights into the design of high-capacity alloy-type anode materials using Pb sources, opening up new possibilities for innovative approaches to Pb recycling and pollution prevention.

Unleashing the Power of Sn2S3 Quantum Dots: Advancing Ultrafast and Ultrastable Sodium/Potassium-Ion Batteries with N, S Co-Doped Carbon Fiber Network

Tin sulfide (Sn2S3) has been recognized as a potential anode material for sodium-ion batteries (SIBs) and potassium-ion batteries (PIBs) due to its high theoretical capacities. However, the sluggish ion diffusion kinetics, low conductivity, and severe volume changes during cycling have limited its practical application. In this study, Sn2S3 quantum dots (QDs) (≈1.6 nm) homogeneously embedded in an N, S co-doped carbon fiber network (Sn2S3-CFN) are successfully fabricated by sequential freeze-drying, carbonization, and sulfidation strategies. As anode materials, the Sn2S3-CFN delivers high reversible capacities and excellent rate capability (300.0 mAh g-1 at 10 A g-1 and 250.0 mAh g-1 at 20 A g-1 for SIBs; 165.3 mAh g-1 at 5 A g-1 and 100.0 mAh g-1 at 10 A g-1 for PIBs) and superior long-life cycling capability (279.6 mAh g-1 after 10 000 cycles at 5 A g-1 for SIBs; 166.3 mAh g-1 after 5 000 cycles at 2 A g-1 for PIBs). According to experimental analysis and theoretical calculations, the exceptional performance of the Sn2S3-CFN composite can be attributed to the synergistic effect of the conductive carbon fiber network and the Sn2S3 quantum dots, which contribute to the structural stability, reversible electrochemical reactions, and superior electron transportation and ions diffusion.

Cobalt-Mediated Defect Engineering Endows High Reversible Amorphous VS4 Anode for Advanced Sodium-Ion Storage

Metal sulfides are promising anode materials for sodium-ion batteries (SIBs) due to their structural diversity and high theoretical capacity, but the severe capacity decay and inferior rate capability caused by poor structural stability and sluggish kinetics impede their practical applications. Herein, a cobalt-doped amorphous VS4 wrapped by reduced graphene oxide (i.e., Co0.5-VS4/rGO) is developed through a Co-induced defect engineering strategy to boost the kinetics performances. The as-prepared Co0.5-VS4/rGO demonstrates excellent rate capacities over 10 A g-1 and superior cycling stability at 5 A g-1 over 1600 cycles, which is attributed to the defects formed by Co doping, the formed amorphous structure and the robust rGO substrate. The great features of Co0.5-VS4/rGO anode are further confirmed in sodium-ion capacitors when the active carbon cathode is used. Additionally, the relationships between metal doping, the derived defects, the amorphous structure, and the sodium storage of VS4 are uncovered. This work provides deep insights into preparing amorphous functional materials and also probes the potential applications of metal sulfide-based electrode materials for advanced batteries.

Construction of High-Performance Anode of Potassium-Ion Batteries by Stripping Covalent Triazine Frameworks with Molten Salt

Covalent triazine frameworks (CTFs) are promising battery electrodes owing to their designable functional groups, tunable pore sizes, and exceptional stability. However, their practical use is limited because of the difficulty in establishing stable ion adsorption/desorption sites. In this study, a melt-salt-stripping process utilizing molten trichloro iron (FeCl3) is used to delaminate the layer-stacked structure of fluorinated covalent triazine framework (FCTF) and generate iron-based ion storage active sites. This process increases the interlayer spacing and uniformly deposits iron-containing materials, enhancing electron and ion transport. The resultant melt-FeCl3-stripped FCTF (Fe@FCTF) shows excellent performance as a potassium ion battery with a high capacity of 447 mAh g-1 at 0.1 A g-1 and 257 mAh g-1 at 1.6 A g-1 and good cycling stability. Notably, molten-salt stripping is also effective in improving the CTF's Na+ and Li+ storage properties. A stepwise reaction mechanism of K/Na/Li chelation with C═N functional groups is proposed and verified by in situ X-ray diffraction testing (XRD), ex-situ X-ray photoelectron spectroscopy (XPS), and theoretical calculations, illustrating that pyrazines and iron coordination groups play the main roles in reacting with K+/Na+/Li+ cations. These results conclude that the Fe@FCTF is a suitable anode material for potassium-ion batteries (PIBs), sodium-ion batteries (SIBs), and lithium-ion batteries (LIBs).

Metal Phosphide Anodes in Sodium-Ion Batteries: Latest Applications and Progress

Sodium-ion batteries (SIBs), as the next-generation high-performance electrochemical energy storage devices, have attracted widespread attention due to their cost-effectiveness and wide geographical distribution of sodium. As a crucial component of the structure of SIBs, the anode material plays a crucial role in determining its electrochemical performance. Significantly, metal phosphide exhibits remarkable application prospects as an anode material for SIBs because of its low redox potential and high theoretical capacity. However, due to volume expansion limitations and other factors, the rate and cycling performance of metal phosphides have gradually declined. To address these challenges, various viable solutions have been explored. In this paper, the recent research progress of metal phosphide materials for SIBs is systematically reviewed, including the synthesis strategy of metal phosphide, the storage mechanism of sodium ions, and the application of metal phosphide in electrochemical aspects. In addition, future challenges and opportunities based on current developments are presented.

Facile synthesis of NiCoSe2@carbon anode for high-performance sodium-ion batteries

Sodium-ion batteries offer significant advantages in terms of low-temperature performance and safety. In this study, we present a straightforward synthetic approach to produce bimetallic selenide NiCoSe2 nanoparticles grown on a three-dimensional porous carbon framework for application as anode materials in sodium-ion batteries. This unique architecture enhances reaction kinetics and structural stability. The three-dimensional interconnected porous carbon network establishes a continuous pathway of electronic conductive, while increasing specific surface area and mitigating volume expansion. Consequently, these features expedite ion transfer and enhance electrolyte interaction. Notably, compared to CoSe, NiCoSe2 exhibits reduced ion transport distances and lower sodium diffusion barriers. Leveraging these attributes, NiCoSe2/N, Se co-doped carbon composite materials (NiCoSe2/NSC) demonstrate a high specific capacity of 320.8 mAh/g, even after 1000 cycles at 5.0 A/g, with a capacity retention rate of 85.1%. The study further delves into the revelation of the reaction mechanism and ion transport pathway through in-situ X-ray diffraction (XRD) analysis and theoretical calculations. The development of these anode materials is poised to pave the way for advancements in sodium-ion battery technology.

Heterostructured CoS2/SnS2 encapsulated in sulfur-doped carbon exhibiting high potassium ion storage capacity

Metallic sulfides are currently considered as ideal anode materials for potassium-ion batteries by virtue of their high specific capacities. However, their low intrinsic electronic conductivity, large volume variation and dissolution of polysulfides in electrochemical reactions hinder their further development toward practical applications. Here, we propose an effective structural design strategy by encapsulating CoS2/SnS2 in sulfur-doped carbon layers, in which internal voids are created to relieve the strain in the CoS2/SnS2 core, while the sulfur-doped carbon layer serves to improve the electron transport and inhibit the dissolution of polysulfides. These features enable the as-designed anode to deliver a high specific capacity (520 mAh/g at 0.1 A/g), a high rate capability (185 mA h g-1 at 10 A/g) and lifespan (0.016 % capacity loss per cycle up to 1500 cycles). Our comprehensive electrochemical characterization reveals that the heterostructure of CoS2/SnS2 not only promotes charge transfer at its interfaces, but also enhances the rate of K+ diffusion. Additionally, potassium-ion capacitors based on this novel anode are able to attain an energy density up to 162 Wh kg-1 and ∼ 96 % capacity retention after 3000 cycles at 10 A/g.The demonstrated design rule combining morphological and structural engineering strategies sheds light on the development of advanced electrodes for high performance potassium-based energy storage devices.

Exploring Carbonization Temperature to Create Closed Pores for Hard Carbon as High-Performance Sodium-Ion Battery Anodes

Biomass-derived porous carbon materials are meaningful to employ as a hard carbon precursor for anode materials of sodium-ion batteries (SIBs) from a sustainability perspective. Here, a straightforward approach is proposed to develop rich closed pores in pinenut-derived carbon, with the aim of improving Na+ plateau storage by adjusting the pyrolysis temperature. The optimized sample, namely the pinenut-derived carbon at 1300 °C, demonstrates remarkable reversible specific capacity of 278 mAh g-1, along with a high initial Coulomb efficiency of 85% and robust cycling stability (with a capacity retention of 89% after 800 cycles at 0.2 A g-1). In situ and ex situ analyses unveil that the developed closed pores play a significant role in enhancing the plateau capacity, providing compelling evidence for the "adsorption-filling" mechanism. Moreover, the corresponding full-cell achieves a high energy density of 245.7 Wh kg-1 (based on the total weight of both electrode active materials) and exhibits outstanding rate capability (191.4 mAh g-1 at 3 A g-1).

New Emerging Fast Charging Microscale Electrode Materials

Fast charging lithium (Li)-ion batteries are intensively pursued for next-generation energy storage devices, whose electrochemical performance is largely determined by their constituent electrode materials. While nanosizing of electrode materials enhances high-rate capability in academic research, it presents practical limitations like volumetric packing density and high synthetic cost. As an alternative to nanosizing, microscale electrode materials cannot only effectively overcome the limitations of the nanosizing strategy but also satisfy the requirement of fast-charging batteries. Therefore, this review summarizes the new emerging microscale electrode materials for fast charging from the commercialization perspective. First, the fundamental theory of electronic/ionic motion in both individual active particles and the whole electrode is proposed. Then, based on these theories, the corresponding optimization strategies are summarized toward fast-charging microscale electrode materials. In addition, advanced functional design to tackle the mechanical degradation problems related to next generation high capacity alloy- and conversion-type electrode materials (Li, S, Si et al.) for achieving fast charging and stable cycling batteries. Finally, general conclusions and the future perspective on the potential research directions of microscale electrode materials are proposed. It is anticipated that this review will provide the basic guidelines for both fundamental research and practical applications of fast-charging batteries.

Architectural design of anode materials for superior alkali-ion (Li/Na/K) batteries storage

Developing high-performance anode materials remains a significant challenge for clean energy storage systems. Herein, we investigated the (MXene/MoSe2@C) heterostructure hybrid nanostructure as a superior anode material for application in lithium, sodium, and potassium ion batteries (LIBs, SIBs, and PIBs). Moreover, the anode structure's stability was examined via the open-source Large-scale atomic/molecular massively Parallel Simulator code. Our results indicated that the migration of SIBs toward the anode material is significantly greater than other ions during charge and discharge cycles. Therefore, SIBs systems can be competitive with PIBs and LIBs systems. In addition, the average values of the potential energies for the anode materials/ions complexes are about ~ - 713.65, ~  - 2030.41, and ~ - 912.36 kcal mol-1 in systems LIBs, SIBs, and PIBs, respectively. This study provides a rational design strategy to develop high-performance anode materials in SIBs/PIBs/LIBs systems, which can be developed for other transition metal chalcogenide-based composites as a superior anode of alkali metal ion battery storage systems.

SAXS unveils porous anodes for potassium-ion batteries: dynamic evolution of pore structures in Fe@Fe2O3/PCNFs composite nanofibers

The porous structure of composite nanofibers plays a key role in improving their electrochemical performance. However, the dynamic evolution of pore structures and their action during ion intercalation/extraction processes for negative electrodes are not clear. Herein, porous carbon composite nanofibers (Fe@Fe2O3/PCNFs) were prepared as negative electrode materials for potassium-ion batteries. Electrochemical test findings revealed that the composites had good electrochemical characteristics, and the porous structure endowed composite electrodes with pseudo-capacitive behaviors. After 1500 discharge/charge cycles at a current density of 1000 mA g-1, the specific capacity of the potassium-ion batteries was 144.8 mAh g-1. We innovatively used synchrotron small-angle X-ray scattering (SAXS) technique to systematically investigate the kinetic process of potassium formation in composites and showed that the kinetic process of potassium reaction in composites can be divided into four stages, and the pores with smaller average diameter distribution are more sensitive to changes in the reaction process. This work paves a new way to study the deposition kinetics of potassium in porous materials, which facilitates the design of porous structures and realizes the development of alkali metal ion-anode materials with high energies.

Preparation of MoP-based quasi-two-dimensional belt-like composite fibers and its performance modulation for sodium/potassium ion storage

Beyond round nanofibers, electrospinning method is able to fabricate thin fibers with various cross-sectional shapes. In this work, using phosphomolybdic acid to trigger the polymerization reaction of pyrrole with addition of tin salt for the filler of carbon fibers, we prepared quasi-two-dimensional thick belt-like fibers through single spinneret electrospinning. The side-by-side welding nanofiber bundles with dog-bone-shaped cross-section improved the connection between fibers, endowing the fiber films with some flexibility and enabling it to be used as freestanding electrode. Employed as anode for sodium/potassium ion storage, the carbon fiber encapsulated MoP/SnO2 material exhibited promising electrochemical performance. Controlling the collection process of electrospinning, the electrode mass loading can be increased to 10 mg cm-2. Combined with surface selenizing modification, the performance of as-prepared MoP/SnO2/MoSe2 was further improved, which exhibited areal capacity about 1.5 mAh cm-2 as anode for sodium/potassium ion storage with mass loading of 8-9 mg cm-2.

Enhanced Sodium Ion Batteries' Performance: Optimal Strategies on Electrolytes for Different Carbon-based Anodes

Carbon-based materials have emerged as promising anodes for sodium-ion batteries (SIBs) due to the merits of cost-effectiveness and renewability. However, the unsatisfactory performance has hindered the commercialization of SIBs. During the past decades, tremendous attention has been put into enhancing the electrochemical performance of carbon-based anodes from the perspective of improving the compatibility of electrolytes and electrodes. Hence, a systematic summary of strategies for optimizing electrolytes between hard carbon, graphite, and other structural carbon anodes of SIBs is provided. The formulations and properties of electrolytes with solvents, salts, and additives added are comprehensively presented, which are closely related to the formation of solid electrolyte interface (SEI) and crucial to the sodium ion storage performance. Cost analysis of commonly used electrolytes has been provided as well. This review is anticipated to provide guidance in future rational tailoring of electrolytes with carbon-based anodes for sodium-ion batteries.

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 Ultra-Stable 2D SbBi Alloy Structure with Precise Regulation Ratio Enables Long-Stable Potassium/Lithium-Ion Storage

The inferior cycling stabilities or low capacities of 2D Sb or Bi limit their applications in high-capacity and long-stability potassium/lithium-ion batteries (PIBs/LIBs). Therefore, integrating the synergy of high-capacity Sb and high-stability Bi to fabricate 2D binary alloys is an intriguing and challenging endeavor. Herein, a series of novel 2D binary SbBi alloys with different atomic ratios are fabricated using a simple one-step co-replacement method. Among these fabricated alloys, the 2D-Sb0.6 Bi0.4 anode exhibits high-capacity and ultra-stable potassium and lithium storage performance. Particularly, the 2D-Sb0.6 Bi0.4 anode has a high-stability capacity of 381.1 mAh g-1 after 500 cycles at 0.2 A g-1 (≈87.8% retention) and an ultra-long-cycling stability of 1000 cycles (0.037% decay per cycle) at 1.0 A g-1 in PIBs. Besides, the superior lithium and potassium storage mechanism is revealed by kinetic analysis, in-situ/ex-situ characterization techniques, and theoretical calculations. This mainly originates from the ultra-stable structure and synergistic interaction within the 2D-binary alloy, which significantly alleviates the volume expansion, enhances K+ adsorption energy, and decreases the K+ diffusion energy barrier compared to individual 2D-Bi or 2D-Sb. This study verifies a new scalable design strategy for creating 2D binary (even ternary) alloys, offering valuable insights into their fundamental mechanisms in rechargeable batteries.

Bismuth Telluride Nanoplates Hierarchically Confined by Graphene and N-Doped C as Conversion-Alloying Anode Materials for Potassium-Ion Batteries

Potassium-ion batteries (PIBs) have broad application prospects in the field of electric energy storage systems because of its abundant K reserves, and similar "rocking chair" operating principle as lithium-ion batteries (LIBs). Aiming to the large volume expansion and sluggish dynamic behavior of anode materials for storing large sized K-ion, bismuth telluride (Bi2 Te3 ) nanoplates hierarchically encapsulated by reduced graphene oxide (rGO), and nitrogen-doped carbon (NC) are constructed as anodes for PIBs. The resultant Bi2 Te3 @rGO@NC architecture features robust chemical bond of Bi─O─C, tightly physicochemical confinement effect, typical conductor property, and enhanced K-ion adsorption ability, thereby producing superior electrochemical kinetics and outstanding morphological and structural stability. It is visually elucidated via high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) that conversion-alloying dual-mechanism plays a significant role in K-ion storage, allowing 12 K-ion transport per formular unit employing Bi as redox site. Thus, the high first reversible specific capacity of 322.70 mAh g-1 at 50 mA g-1 , great rate capability and cyclic stability can be achieved for Bi2 Te3 @rGO@NC. This work lays the foundation for an in-depth understanding of conversion-alloying mechanism in potassium-ion storage.

Synthesis of Low-Cost and High-Performance Dual-Atom Doped Carbon-Based Materials with a Simple Green Route as Anodes for Sodium-Ion Batteries

Sodium-ion batteries (SIBs) are promising alternatives to replace lithium-ion batteries as future energy storage batteries because of their abundant sodium resources, low cost, and high charging efficiency. In order to match the high energy capacity and density, designing an atomically doped carbonous material as the anode is presently one of the important strategies to commercialize SIBs. In this work, we report the preparation of high-performance dual-atom-doped carbon (C) materials using low-cost corn starch and thiourea (CH4N2S) as the precursors. The electronegativity and radii of the doped atoms and C are different, which can vary the embedding properties of sodium ions (Na+) into/on C. As sulfur (S) can effectively expand the layer spacing, it provides more channels for embedding and de-embedding Na+. The synergistic effect of N and S co-doping can remarkably boost the performance of SIBs. The capacity is preserved at 400 mAh g -1 after 200 cycles at 500 mA g-1; more notably, the initial Coulombic efficiency is 81%. Even at a high rate of high current of 10 A g-1, the cell capacity can still reach 170 mAh g-1. More importantly, after 3000 cycles at 1 A g-1, the capacity decay is less than 0.003% per cycle, which demonstrates its excellent electrochemical performance. These results indicate that high-performance carbon materials can be prepared using low-cost corn starch and thiourea.

Relaxation of Stress Propagation in Alloying-Type Sn Anodes for K-Ion Batteries

Alloying-type metallic tin is perceived as a potential anode material for K-ion batteries owing to its high theoretical capacity and reasonable working potential. However, pure Sn still face intractable issues of inferior K+ storage capability owing to the mechanical degradation of electrode against large volume changes and formation of intermediary insulating phases K4 Sn9 and KSn during alloying reaction. Herein, the TiC/C-carbon nanotubes (CNTs) is prepared as an effective buffer matrix and composited with Sn particles (Sn-TiC/C-CNTs) through the high-energy ball-milling method. Owing to the conductive and rigid properties, the TiC/C-CNTs matrix enhances the electrical conductivity as well as mechanical integrity of Sn in the composite material and thus ultimately contributes to performance supremacy in terms of electrochemical K+ storage properties. During potassiation process, the TiC/C-CNTs matrix not only dissipates the internal stress toward random radial orientations within the Sn particle but also provides electrical pathways for the intermediate insulating phases; this tends to reduce microcracking and prevent considerable electrode degradation.

A TiSe monolayer as a superior anode for applications of Li/Na/K-ion batteries

Using density functional theory (DFT), we investigated the energy-storage capabilities of a two-dimensional TiSe monolayer for applications of the anode material of Li/Na/K-ion batteries. The TiSe monolayer showed high thermodynamic stability at 800 K according to ab initio molecular dynamics (AIMD) simulation. The ion-diffusion barrier was estimated to be 0.29/0.36/0.33 eV for Li/Na/K, respectively, indicating the high-rate capacity of this material. The theoretical specific capacity was 422.63 mA h g-1 for Li/Na/K, with an energy density of 1000.19, 802.30, and 802.41 mW h g-1, respectively. Fully charged TiSe was mechanically stable according to the calculated elastic constants. Our results show that the TiSe monolayer could be used as an excellent anode material for Li/Na/K-ion batteries.

Recent Advances and Challenges in Ti-Based Oxide Anodes for Superior Potassium Storage

Developing high-performance anodes is one of the most effective ways to improve the energy storage performances of potassium-ion batteries (PIBs). Among them, Ti-based oxides, including TiO2, K2Ti6O13, K2Ti4O9, K2Ti8O17, Li4Ti5O12, etc., as the intrinsic structural advantages, are of great interest for applications in PIBs. Despite numerous merits of Ti-based oxide anodes, such as fantastic chemical and thermal stability, a rich reserve of raw materials, non-toxic and environmentally friendly properties, etc., their poor electrical conductivity limits the energy storage applications in PIBs, which is the key challenge for these anodes. Although various modification projects are effectively used to improve their energy storage performances, there are still some related issues and problems that need to be addressed and solved. This review provides a comprehensive summary on the latest research progress of Ti-based oxide anodes for the application in PIBs. Besides the major impactful work and various performance improvement strategies, such as structural regulation, carbon modification, element doping, etc., some promising research directions, including effects of electrolytes and binders, MXene-derived TiO2-based anodes and application as a modifier, are outlined in this review. In addition, noteworthy research perspectives and future development challenges for Ti-based oxide anodes in PIBs are also proposed.

Bi nanoparticles confined in N,S co-doped carbon nanoribbons with excellent rate performance for sodium-ion batteries

Bismuth (Bi) has emerged as a promising candidate for sodium-ion battery anodes because of its unique layered crystal structure, superior volumetric capacity, and high theoretical gravimetric capacity. However, the large volume expansion and severe aggregation of Bi during the alloying/dealloying reactions are extremely detrimental to cycling stability, which seriously hinders its practical application. To overcome these issues, we propose an effective synthesis of composite materials, encapsulating Bi nanoparticles in N,S co-doped carbon nanoribbons and composites with carbon nanotubes (N,S-C@Bi/CNT), using Bi₂S₃ nanobelts as templates. The uniform distribution of Bi nanoparticles and the structure of carbon nanoribbons can reduce the diffusion path of ions/electrons, efficiently buffer the large volume change and prevent Bi from aggregating during cycles. As expected, the N,S-C@Bi/CNT electrode shows superior sodium storage performance in half cells, including a high specific capacity (345.3 mA h g^-1 at 1.0 A g^-1), long cycling stability (1000 cycles), and superior rate capability (336.0 mA h g^-1 at 10.0 A g^-1).

Unveiling the Nature of Ultrastable Potassium Storage in Bi0.48Sb1.52Se3 Composite

The conversion and alloying-type anodes for potassium-ion batteries (PIBs) have drawn attention. However, it is still a challenge to relieve the huge volume expansion/electrode pulverization. Herein, we synthesized a composite material comprising Bi_0.48Sb_1.52Se₃ nanoparticles uniformly dispersed in carbon nanofibers (Bi_0.48Sb_1.52Se₃@C). Benefiting from the synergistic effects of the high electronic conductivity of Bi_0.48Sb_1.52Se₃ and the mechanical confinement of the carbon fiber that buffers the large chemomechanical stress, the Bi_0.48Sb_1.52Se₃@C//K half cells deliver a high reversible capacity (491.4 mAh g^-1, 100 cycles at 100 mA g^-1) and an extraordinary cyclability (80% capacity retention, 1000 cycles at 1000 mA g^-1). Furthermore, the Bi_0.48Sb_1.52Se₃@C-based PIB full cells achieve a high energy density of 230 Wh kg^-1. In situ transmission electron microscopy (TEM) reveals an intercalation, conversion, and alloying three-step reaction mechanism and a reversible amorphous transient phase. More impressively, the nanofiber electrode can almost return to its original diameter after the potassiation and depotassiation reaction, indicating a highly reversible volume change process, which is distinct from the other conversion type electrodes. This work reveals the stable potassium storage mechanisms of Bi_0.48Sb_1.52Se₃@C composite material, which provides an effective strategy to enable conversion/alloying-type anodes for high performance PIBs for energy storage applications.

Stress-Dispersed Superstructure of Sn3 (PO4 )2 @PC Derived from Programmable Assembly of Metal-Organic Framework as Long-Life Potassium/Sodium-Ion Batteries Anodes

The structures of anode materials significantly affect their properties in rechargeable batteries. Material nanosizing and electrode integrity are both beneficial for performance enhancement of batteries, but it is challenging to guarantee optimized nanosizing particles and high structural integrity simultaneously. Herein, a programmable assembly strategy of metal-organic frameworks (MOFs) is used to construct a Sn-based MOF superstructure precursor. After calcination under inert atmosphere, the as-fabricated Sn₃ (PO₄ )₂ @phosphorus doped carbon (Sn₃ (PO₄ )₂ @PC-48) well inherited the morphology of Sn-MOF superstructure precursor. The resultant new material exhibits appreciable reversible capacity and low capacity degradation for K⁺ storage (144.0 mAh g^-1 at 5 A g^-1 with 90.1% capacity retained after 10000 cycles) and Na⁺ storage (202.5 mAh g^-1 at 5 A g^-1 with 96.0% capacity retained after 8000 cycles). Detailed characterizations, density functional theory calculations, and finite element analysis simulations reveal that the optimized electronic structure and the stress-dispersed superstructure morphology of Sn₃ (PO₄ )₂ @PC promote the electronic conductivity, enhance K⁺ / Na⁺ binding ability and improve the structure stabilization efficiently. This strategy to optimize the structure of anode materials by controlling the MOF growth process offer new dimension to regulate the materials precisely in the energy field.

Graphene supported FeS2 nanoparticles with sandwich structure as a promising anode for High-Rate Potassium-Ion batteries

Pyrite FeS₂ now emerges as a promising anode for potassium-ion batteries (PIBs) due to its low cost and high theoretical capacity. However, the significant volume expansion, low electrical conductivity, and the ambiguous mechanism related to potassium storage severely hinder its development for PIBs anodes. Herein, FeS₂ nanostructures are skillfully dispersed on the graphene surface layer by layer (FeS₂@C-rGO) to form a sandwich structure by using Fe-based metal organic framework (Fe-MOF) as precursors. The unique structural design can improve the transfer kinetics of K⁺ and effectively buffer the volume expansion during cycling, thereby enhancing the potassium storage performance. As a result, the FeS₂@C-rGO delivers a high capacity of 550 mAh/g at a current density of 0.1 A/g. At a high rate of 2 A/g, the capacity can maintain 171 mAh/g even after 500 cycles. Moreover, the electrochemical reaction mechanism and potassium storage behavior are revealed by in-situ X-ray diffractionand density functional theory calculations. This work not only provides a novel insight into the structural design of electrode materials for high-performance PIBs, but also proposes a valuable understanding of the potassium storage mechanism of the FeS₂-based anode.

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.

Electrostatic Shielding Boosts Electrochemical Performance of Alloy-Type Anode Materials of Sodium-Ion Batteries

The applications of alloy-type anode materials for Na-ion batteries are always obstructed by enormous volume variation upon cycles. Here, K⁺ ions are introduced as an electrolyte additive to improve the electrochemical performance via electrostatic shielding, using Sn microparticles (μ-Sn) as a model. Theoretical calculations and experimental results indicate that K⁺ ions are not incorporated in the electrode, but accumulate on some sites. This accumulation slows down the local sodiation at the "hot spots", promotes the uniform sodiation and enhances the electrode stability. Therefore, the electrode maintains a high specific capacity of 565 mAh g^-1 after 3000 cycles at 2 A g^-1 , much better than the case without K⁺ . The electrode also remains an areal capacity of ≈3.5 mAh cm^-2 after 100 cycles. This method does not involve time-consuming preparation, sophisticated instruments and expensive reagents, exhibiting the promising potential for other anode materials.

Prussian Blue Analogue-Derived Fe-Doped CoS2 Nanoparticles Confined in Bayberry-like N-Doped Carbon Spheres as Anodes for Sodium-Ion Batteries

Obvious volume change and the dissolution of polysulfide as well as sluggish kinetics are serious issues for the development of high performance metal sulfide anodes for sodium-ion batteries (SIBs), which usually result in fast capacity fading during continuous sodiation and desodiation processes. In this work, by utilizing a Prussian blue analogue as functional precursors, small Fe-doped CoS2 nanoparticles spatially confined in N-doped carbon spheres with rich porosity were synthesized through facile successive precipitation, carbonization, and sulfurization processes, leading to the formation of bayberry-like Fe-doped CoS2/N-doped carbon spheres (Fe-CoS2/NC). By introducing a suitable amount of FeCl3 in the starting materials, the optimal Fe-CoS2/NC hybrid spheres with the designed composition and pore structure exhibited superior cycling stability (621 mA h g−1 after 400 cycles at 1 A g−1) and improved the rate capability (493 mA h g−1 at 5 A g−1). This work provides a new avenue for the rational design and synthesis of high performance metal sulfide-based anode materials toward SIBs.

Nanostructured Conducting Polymers and Their Applications in Energy Storage Devices

Due to the energy requirements for various human activities, and the need for a substantial change in the energy matrix, it is important to research and design new materials that allow the availability of appropriate technologies. In this sense, together with proposals that advocate a reduction in the conversion, storage, and feeding of clean energies, such as fuel cells and electrochemical capacitors energy consumption, there is an approach that is based on the development of better applications for and batteries. An alternative to commonly used inorganic materials is conducting polymers (CP). Strategies based on the formation of composite materials and nanostructures allow outstanding performances in electrochemical energy storage devices such as those mentioned. Particularly, the nanostructuring of CP stands out because, in the last two decades, there has been an important evolution in the design of various types of nanostructures, with a strong focus on their synergistic combination with other types of materials. This bibliographic compilation reviews state of the art in this area, with a special focus on how nanostructured CP would contribute to the search for new materials for the development of energy storage devices, based mainly on the morphology they present and on their versatility to be combined with other materials, which allows notable improvements in aspects such as reduction in ionic diffusion trajectories and electronic transport, optimization of spaces for ion penetration, a greater number of electrochemically active sites and better stability in charge/discharge cycles.

Precise Construction of Sn/C Composite Membrane with Graphene-Like Sn-in-Carbon Structural Units toward Hyperstable Anode for Lithium Storage

A new-type binder-free Sn/C composite membrane with densely stacked Sn-in-carbon nanosheets was prepared by vacuum-induced self-assembly of graphene-like Sn alkoxide and following in situ thermal conversion. The successful implementation of this rational strategy is based on the controllable synthesis of graphene-like Sn alkoxide by using Na-citrate with the critical inhibitory effect on polycondensation of Sn alkoxide along the a and b directions. Density functional theory calculations reveal that graphene-like Sn alkoxide can be formed under the joint action of oriented densification along the c axis and continuous growth along the a and b directions. The Sn/C composite membrane constructed by graphene-like Sn-in-carbon nanosheets can effectively buffer volume fluctuation of inlaid Sn during cycling and much enhance the kinetics of Li⁺ diffusion and charge transfer with the developed ion/electron transmission paths. After temperature-controlled structure optimization, Sn/C composite membrane displays extraordinary Li storage behaviors, including reversible half-cell capacities up to 972.5 mAh g^-1 at a density of 1 A g^-1 for 200 cycles, 885.5/729.3 mAh g^-1 over 1000 cycles at large current densities of 2/4 A g^-1, and terrific practicability with reliable full-cell capacities of 789.9/582.9 mAh g^-1 up to 200 cycles under 1/4 A g^-1. It is worthy of noting that this strategy may open up new opportunities to fabricate advanced membrane materials and construct hyperstable self-supporting anodes in lithium ion batteries.

Nickel sulfide/nickel phosphide heterostructures anchored on porous carbon nanosheets with rapid electron/ion transport dynamics for sodium-ion half/full batteries

Nickel-based materials have been extensively deemed as promising anodes for sodium-ion batteries (SIBs) owing to their superior capacity. Unfortunately, the rational design of electrodes as well as long-term cycling performance remains a thorny challenge due to the huge irreversible volume change during the charge/discharge process. Herein, the heterostructured ultrafine nickel sulfide/nickel phosphide (NiS/Ni₂P) nanoparticles closely attached to the interconnected porous carbon sheets (NiS/Ni₂P@C) are designed by facile hydrothermal and annealing methods. The NiS/Ni₂P heterostructure promotes ion/electron transport, thus accelerating the electrochemical reaction kinetics benefited from the built-in electric field effect. Moreover, the interconnected porous carbon sheets offer rapid electron migration and excellent electronic conductivity, while releasing the volume variance during Na⁺ intercalation and deintercalation, guaranteeing superior structural stability. As expected, the NiS/Ni₂P@C electrode exhibits a high reversible specific capacity of 344 mAh g^-1 at 0.1 A g^-1 and great rate stability. Significantly, the implementation of NiS/Ni₂P@C//Na₃(VPO₄)₂F₃ SIB full cell configuration exhibits relatively satisfactory cycle performance, which suggests its widely practical application. This research will develop an effective method for constructing heterostructured hybrids for electrochemical energy storage.

Air-stabilized pore structure engineering of antimony-based anode by electrospinning for potassium ion batteries

Due to the large ionic radius and associated slow reaction kinetics of potassium ions, it is a major challenge to find suitable anode materials for potassium-ion batteries. Herein, we design porous antimony-based nanofibres via a simple, low-cost and large scalable method to promote the electrochemical performance of potassium-ion batteries. Unlike those traditionally treated in inert atmospheres, using the different decomposition processes of polyacrylonitrile and polyvinylpyrrolidone in air, we obtain antimony trioxide embedded in porous carbon nanofibres (Sb₂O₃@PCN). The porous structure can promote the permeation of electrolyte into electrode materials and increase the active sites of the redox reaction. The porous carbonaceous fibre skeleton structure establishes a fast ion transport channel and enhances the kinetic performance. In a concentrated 5 M potassium bis(fluorosulfonyl)-imide/dimethyl carbonate electrolyte, Sb₂O₃@PCN exhibits a stable discharge specific capacity of 437.3 mAh g^-1 at a current density of 100 mA g^-1 after 50 cycles, which is much higher than that treated in a N₂ atmosphere (247.5 mAh g^-1). This method provides a new approach for the preparation of efficient potassium-ion battery electrode materials.

Edge-Nitrogen Enriched Porous Carbon Nanosheets Anodes with Enlarged Interlayer Distance for Fast Charging Sodium-Ion Batteries

The application of nitrogen-doped porous carbon for sodium-ion batteries (SIBs) has attracted tremendous attention. Herein, a series of edge-nitrogen enriched porous carbon nanosheets (ENPCNs) are synthesized by annealing g-C₃ N₄ and glucose in a sealed graphite crucible at different temperatures (T = 700, 800, and 900 °C). Surprisingly, under the closed thermal treatment condition, the ENPCNs-T possess a high N-doping level (>12.62 at%) and different carbon interlayer distance ranging from 0.429 to 0.487 nm. By correlating the carbon interlayer distance with the N configurations of ENPCNs-T materials, a reasonable perception of the important influence of pyrrolic N on the increase of carbon interlayer distance is proposed. When applied as anode materials for SIBs, the ENPCNs-800 exhibits a remarkable capacity (294.1 mAh g^-1 at 0.1 A g^-1 ), excellent rate performance (132.8 mAh g^-1 at 10 A g^-1 ), and outstanding cycle life (180.6 mAh g^-1 at 1 A g^-1 after 1000 cycles with a capacity retention of 104.7%). Meanwhile, the characterizations of cyclic voltammetry, galvanostatic intermittent titration technique, and electrochemical impedance spectroscopy demonstrate that the edge-nitrogen doping and enlarged carbon interlayer distance improve the capacity and fast charging performance of ENPCNs-800. Considering the detailed investigation of the Na⁺ storage mechanism and excellent electrochemical performance of ENPCNs-800, this work can pave a new avenue for the research of SIBs.

Unique Spindle-Like Bismuth-Based Composite toward Ultrafast Potassium Storage

Bismuth (Bi)-based materials have attracted great attention as anodes in potassium ion batteries (PIBs) for their high theoretical capacity and suitable voltage range. Herein, the authors report a unique spindle-like structured Bi@N-doped carbon composite (SPB@NC) consisting of interconnected nano-Bi coated heteroatom-doped hard carbon layer via an interesting in situ carbon thermal reduction method. The special interconnected Bi nanoparticles gradually form porous structure with ample inner voids for accommodating volume variations while the N-doped carbon layer not only keeps the electrode stable, but also contributes to rapid electron/ion transfer. As a result, such a robust framework endows SPB@NC fast potassium storage with outstanding capacity of 276.5 mAh g^-1  at 30 A g^-1 (i.e., 1 min for discharge/charge) and durable cycling performance of 299.3 mAh g^-1  at 5 A g^-1  after 2000 cycles. Notably, a full cell assembled with potassium vanadate cathode is promising for practical applications. A series of ex situ techniques reveals the in-depth potassium storage mechanism and kinetics reactions. This work illuminates helpful insights into Bi-based anodes for PIBs.

Rechargeable Batteries for Grid Scale Energy Storage

Ever-increasing global energy consumption has driven the development of renewable energy technologies to reduce greenhouse gas emissions and air pollution. Battery energy storage systems (BESS) with high electrochemical performance are critical for enabling renewable yet intermittent sources of energy such as solar and wind. In recent years, numerous new battery technologies have been achieved and showed great potential for grid scale energy storage (GSES) applications. However, their practical applications have been greatly impeded due to the gap between the breakthroughs achieved in research laboratories and the industrial applications. In addition, various complex applications call for different battery performances. Matching of diverse batteries to various applications is required to promote practical energy storage research achievement. This review provides in-depth discussion and comprehensive consideration in the battery research field for GSES. The overall requirements of battery technologies for practical applications with key parameters are systematically analyzed by generating standards and measures for GSES. We also discuss recent progress and existing challenges for some representative battery technologies with great promise for GSES, including metal-ion batteries, lead-acid batteries, molten-salt batteries, alkaline batteries, redox-flow batteries, metal-air batteries, and hydrogen-gas batteries. Moreover, we emphasize the importance of bringing emerging battery technologies from academia to industry. Our perspectives on the future development of batteries for GSES applications are provided.

Radical Covalent Organic Frameworks Associated with Liquid Na-K toward Dendrite-Free Alkali Metal Anodes

Liquid sodium-potassium (Na-K) alloy has the characteristics of high abundance, low redox potential, high capacity, and no dendrites, which has become an ideal alternative material for potassium/sodium metal anodes. However, the high surface tension of liquid sodium potassium alloy at room temperature makes it inconvenient in practical use. Here, the Na-K as reducing agent treats with hydrazone linkages of covalent organic frameworks (COFs) and obtain the carbon-oxygen radical COFs (COR-Tf-DHzDM-COFs). The preparation method solves the problems that the preparation process of the traditional Na-K composite anode is complex and has high cost. The structures of the COR-Tf-DHzDM-COFs are characterized by X-ray diffraction （XRD), fourier transform infrared (FT-IR), electron paramagnetic resonance (EPR), and solid-state NMR measurements. It is the first time that carbon-oxygen radical COFs from bulk COFs are constructed by one-step method and the operation is flexible, convenient, and high rate of quality, which is suitable for big production and widely used. The cycle stability of the composite Na-K anode is improved, which provides a new idea for the design of high-performance liquid metal anode.

Alloy-Type Anodes for High-Performance Rechargeable Batteries

Alloy-type anodes are one of the most promising classes of next-generation anode materials due to their ultrahigh theoretical capacity (2-10 times that of graphite). However, current alloy-type anodes have several limitations: huge volume expansion, high tendency to fracture and disintegrate, an unstable solid-electrolyte interphase (SEI) layer, and low Coulombic efficiency. Efforts to overcome these challenges are ongoing. This Review details recent progress in the research of batteries based on alloy-type anodes and discusses the direction of their future development. We conclude that improvements in structural design, the introduction of a protective interface, and the selection of suitable electrolytes are the most effective ways to improve the performance of alloy-type anodes. Furthermore, future studies should direct more attention toward analyzing their synergistic promoting effect.

Multidimensional antimony nanomaterials tailored by electrochemical engineering for advanced sodium-ion and potassium-ion batteries

Downsizing the dimensions of materials holds great importance for promoting the alkali-ion storage properties, which is considered to be one of the most efficient methods for improving the cycling stability and rate capability of alloy anodes. Nevertheless, efficient, affordable, and scalable methods to prepare low-dimensional electrode materials are lacking. In this study, we developed a tunable electrochemical strategy for synthesizing multidimensional antimony (Sb) nanomaterials. Depending on different reaction mechanisms in different electrolytes, we fabricated zero-dimensional Sb nanoparticles, two-dimensional (2D) antimonene nanosheets, and a three-dimensional porous Sb network through the electrochemical delamination of bulk Sb in lithium hexafluorophosphate in propylene carbonate, tetraethylammonium hydroxide aqueous solution, and tetraethylammonium hexafluorophosphate in N, N-dimethylformamide, respectively. In the preferred electrolyte, 2D antimonene nanosheets deliver a large sodium storage capacity of 572.5 mAh g^-1 after 200 cycles at 0.2 A g^-1 and an excellent rate capability of 553.6 mAh g^-1 at 5 A g^-1. When used as anode materials for potassium-ion batteries, we obtained a high capacity of 550.3 mAh g^-1 after 300 cycles, and observed a high rate capability of 302.3 mAh g^-1 at 4 A g^-1. These results provide an easy and tunable strategy for designing high-performance low-dimensional materials for next-generation batteries.

Multi-heterostructured SnO2/SnSx embedded in carbon framework for high-performance sodium-ion storage

Heterostructure materials, as newborn electrode materials for rechargeable batteries, are attracting increasing attention due to their robust architectures and superior electrochemical performances. It is widely believed that the inner electric field induced at the interface can improve the electric conductivity and ion diffusion kinetics, thus enhancing the long-term stability and high-rate performance of the batteries. Although much progress is made on heterostructure construction, the performance of the batteries is still far from satisfying the commercial applications. In this work, a new type of SnO₂/SnS_x (x = 1, 1.5) heterostructure embedded in carbon framework (C@SnO₂/SnS_x) is constructed via a facile sulfidation process. Compared to a single heterojunction, the multi-heterojunctions generated at SnO₂/SnS_x interface can induce an intensified built-in electric field, which promotes charge transportation and reaction kinetics of the electrode for Na-ions storage. Upon the sodiation process, the induced intensified electric field drives Na ions from Sn₂S₃ or SnO₂ to SnS, while an inverse transportation of Na ions are accelerated upon the desodation process. As a result, C@SnO₂/SnS_x exhibits an outstanding reversible capacity of 510 mA h g^-1 after 300 cycles at 200 mA g^-1.

Engineering monodispersed 2 nm Sb2S3 particles embedded in a porphyrin-based MOF-derived mesoporous carbon network via an adsorption method to construct a high-performance sodium-ion battery anode

Sodium ion batteries (SIBs) are expected to replace lithium ion batteries (LIBs) as the next generation of large-scale energy storage applications because of their superior cost performance. However, the larger ionic radius of Na⁺ causes a remarkable volume expansion than that of Li⁺ during charge and discharge, which reduces the performance of the battery. In this work, we engineered a composite material in that monodispersed 2 nm Sb₂S₃ particles are uniformly loaded into a carbon matrix (Sb₂S₃/CZM), which is obtained by carbonization of a zirconium-based MOF with adsorption of Sb. The obtained composite material has a high specific surface area in favor of mass transfer, and the porous structure can resist many volume changes in the circulation process. Moreover, the ultrafine Sb₂S₃ particles are well-distributed in the composite material, which increases the utilization of the active substance and is promising for the storage of Na⁺. Based on its unique structure, the Sb₂S₃/CZM composite shows a specific capacity of 550 mA h g^-1 at 100 mA g^-1 and an excellent cycling stability of 88.9% retention after 1000 cycles at 3 A g^-1. The excellent electrochemical performance provides enlightenment for the rational design of hierarchical heterostructures for energy storage applications.

Vanadium Tetrasulfide for Next-Generation Rechargeable Batteries: Advances and Challenges

Alkali metal-ion batteries (SIBs and PIBs) and multivalent metal-ion batteries (ZIBs, MIBs, and AIBs), among the next-generation rechargeable batteries, are deemed appealing alternatives to lithium-ion batteries (LIBs) because of their cost competitiveness. Improving the electrochemical properties of electrode materials can greatly accelerate the pace of development in battery systems to cover the increasing demands of realistic applications. Vanadium tetrasulfide (VS₄ ) is known as a prospective electrode material due to its unique one-dimensional atomic chain structure with a large chain spacing, weak interactions between adjacent chains, and high sulfur content. This review summarizes the synthetic strategies and recent advances of VS₄ as cathodes/anodes for rechargeable batteries. Meanwhile, we describe the structural characteristics and electrochemical properties of VS₄ . And we describe in detail its specific applications in batteries such as SIBs, PIBs, ZIBs, MIBs, and AIBs as well as modification strategies. Finally, the opportunities and challenges of VS₄ in the domain of energy research are described.

Sn-, Sb- and Bi-Based Anodes for Potassium Ion Battery

Owing to the abundant resources of potassium resources, potassium ion batteries (PIBs) hold great potential in various energy storage devices. However, the poor lifespan of PIBs anodes limit their merchant applications. The exploitation of anode materials with high performance is one of the critical factors to the development of PIBs. Metallic Sn-, Sb-, and Bi-based materials, show promising future thanks to their high theoretical capacities and safe working voltage. However, the rapid capacity decay caused by the large K⁺ is still a pivotal challenge. In this review, recent progresses on alloying anodes were summarized. Schemes, such as ultra-small nanoparticles, hetero-element doping, and electrolyte optimization are effective strategies to improve their electrochemical properties. This review provides an outlook on the nanostructures and their synthesis methods for the alloying-type materials, and will stimulate their intensive study for practical application in the near future.