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Cobalt substitution for manganese sites in Na0.44MnO2 initiates a dynamic structural evolution process, yielding a composite cathode material comprising intergrown P2 and P3 phases. The novel P2/P3 composite cathode exhibits a reversible phase transition process during Na+ extraction/insertion, showcasing its attractive battery performance in sodium-ion batteries. [ABSTRACT FROM AUTHOR]

Sodium-ion batteries (SIBs) are experiencing a large-scale renaissance to supplement or replace expensive lithium-ion batteries (LIBs) and low energy density lead-acid batteries in electrical energy storage systems and other applications. In this case, layered oxide materials have become one of the most popular cathode candidates for SIBs because of their low cost and comparatively facile synthesis method. However, the intrinsic shortcomings of layered oxide cathodes, which severely limit their commercialization process, urgently need to be addressed. In this review, inherent challenges associated with layered oxide cathodes for SIBs, such as their irreversible multiphase transition, poor air stability, and low energy density, are systematically summarized and discussed, together with strategies to overcome these dilemmas through bulk phase modulation, surface/interface modification, functional structure manipulation, and cationic and anionic redox optimization. Emphasis is placed on investigating variations in the chemical composition and structural configuration of layered oxide cathodes and how they affect the electrochemical behavior of the cathodes to illustrate how these issues can be addressed. The summary of failure mechanisms and corresponding modification strategies of layered oxide cathodes presented herein provides a valuable reference for scientific and practical issues related to the development of SIBs. [ABSTRACT FROM AUTHOR]

As a class of promising cathodes in the field of large-scale power storage systems especially for alkali-metal-ion batteries (MIBs), Prussian blue (PB) and its analogues (PBAs) have received wide research attention due to their open framework, high theoretical specific capacity, and simple synthesis method. For large-scale applications, cathode materials with low-cost and long cycle life are preferred. However, only a few of the review papers have concentrated on the detailed analysis of low-cost PBAs, including Fe-based and Mn-based PBAs, which also show excellent electrochemical performance. This review aims to first provide an all-sided understanding of low-cost PBAs in terms of their application and recent progress in MIBs. Then, the major challenges such as inferior electrochemical properties of low-cost PBAs are discussed. Meanwhile, we provide feasible strategies to prepare PBA electrodes with advanced electrochemical performance. Finally, we present some personal perspectives and guidance for future research, aiming to narrow the gap between laboratory investigation and practical application. [ABSTRACT FROM AUTHOR]

Carbon nanospheres (CNSs) have attracted great interest in energy conversion and storage technologies due to their excellent chemical and thermal stability, high electrical conductivity and controllable size structure characteristics. In order to further improve the energy storage properties, many efforts have been made to design suitable nanocarbon spherical materials to improve electrochemical performance. In this overview, we summarize the recent research progress on CNSs, mainly focusing on the synthesis methods and their application as high-performance electrode materials in rechargeable batteries. As for the synthesis methods, hard template methods, soft template methods, the extension of the Stöber method, hydrothermal carbonization, aerosol-assisted synthesis are described in detail. In addition, the use of CNSs as electrodes in energy storage devices (mainly concentrated on lithium-ion batteries (LIBs)), sodium-ion batteries (SIBs) and potassium-ion batteries (PIBs) are also discussed in detail in this article. Finally, some perspectives on the future research and development of CNSs are provided. [ABSTRACT FROM AUTHOR]

Aqueous zinc-ion batteries (AZIBs) based on high-safety zinc metal anodes have advantages of low cost and high theoretical capacity and are considered as a promising large-scale energy storage system. Their practical application, however, is hampered by slow transport kinetics, low energy density, and poor cycling performance. In this work, we design and successfully synthesize ultrastable lattice water-rich VO2·xH2O materials by considering the fact that abundant crystallized water can act as "water lubrication", and a charge shielding medium to weaken the electrostatic effect. As a result, VO2·xH2O as a cathode for AZIBs can provide a specific capacity of 376 mA h g−1 after 200 cycles at 1 A g−1 and no apparent capacity decay after 8000 cycles at 15 A g−1. The excellent zinc storage performance can be ascribed to the efficient kinetics and abundant reaction sites of the VO2·xH2O electrode. A series of in situ and ex situ characterizations indicate that it is the H+/Zn2+ co-intercalation mechanism to store zinc in the VO2·xH2O electrode. In short, the abundant crystallized water vanadium-based materials may be excellent candidates for advanced cathode materials of AZIBs. [ABSTRACT FROM AUTHOR]

Binders as a bridge in electrodes can bring various components together thus guaranteeing the integrity of electrodes and electronic contact during battery cycling. In this review, we summarize the recent progress of traditional binders and novel binders in the different electrodes of SIBs. The challenges faced by binders in terms of bond strength, wettability, thermal stability, conductivity, cost, and environment are also discussed in details. Correspondingly, the designing principle and advanced strategies of future research on SIB binders are also provided. Moreover, a general conclusion and perspective on the development of binder design for SIBs in the future are presented. [ABSTRACT FROM AUTHOR]

A novel sulfiphilic host is reported with single Co atoms (Co1) and ZnS quantum dots (ZnS-QDs) (∼10 nm) grown in N-doped carbon microparticles. The introduction of Co cations into the precursor is crucial, because it leads to the dispersion of single-atom Co on the carbon matrix, decreasing the size and improving the dispersion of the resultant ZnS-QDs as well. Benefitting from the resilient and stable carbon framework, the single-atom Co and small ZnS-QDs synergically electro-catalyze the S redox process, which can greatly enhance sodium polysulfide conversion and reduction of non-conductive Na2S. The refined S cathode achieves remarkable cycling capability (640 mA h g−1 after 500 cycles at 0.1 A g−1), enhanced capacity retention, and outstanding energy density (541 W h kg−1), giving it great promise for scientific research and practical applications. [ABSTRACT FROM AUTHOR]

Potassium ion batteries (PIBs) as promising energy storage candidates have attracted increasing attention due to the low-cost and abundant potassium resources. Despite numerous emerging electrode materials, the development of PIBs has consecutively encountered major challenges compared with lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs), such as low reversible specific capacities, inferior cycling stabilities, and unsatisfactory energy densities. In light of this, we provide a state-of-the-art review on the development of emerging classes of cathode materials, especially for polyanionic composites and organic compounds, with the aim of achieving high energy density for non-aqueous PIBs. First of all, we highlight the recent development of electrode materials towards non-aqueous PIBs with the discussion on their existing problems and the potential solutions. Then, the recent advancements in polyanionic and organic compounds towards achieving high energy density of PIBs are provided. We focus on their structure–performance relationships with a comparison of their electrochemical properties, and further promising investigations of these types of cathode materials are identified and discussed as well. Finally, personal perspectives on future optimization on cathode materials towards realizing the real applications in PIBs are constructively discussed. [ABSTRACT FROM AUTHOR]

Electrocatalysis for cathodic oxygen is of great significance for achieving high-performance lithium–oxygen batteries. Herein, we report a facile and green method to prepare an interconnected nanoporous three-dimensional (3D) architecture, which is composed of RuO2 nanogranulates coated with few layers of carbon. The as-prepared 3D nanoporous RuO2@C nanostructure can demonstrate a high initial specific discharge capacity of 4000 mA h g−1 with high round-trip efficiency of 95%. Meanwhile, the nanoporous RuO2@C could achieve stable cycling performance with a fixed capacity of 1500 mA h g−1 over 100 cycles. The terminal discharge and charge potentials of nanoporous RuO2@C are well maintained with minor potential variation of 0.14 and 0.13 V at the 100th cycle, respectively. In addition, the formation of discharge products is monitored by using in situ high-energy synchrotron X-ray diffraction (XRD). [ABSTRACT FROM AUTHOR]

Triclinic (t-) Ba2V2O7 helical-like meso/nanosquares assembled from self-spiraling nanosheets have been controllably synthesized by a high-efficiency microwave irradiation-assisted surfactant process. The microstructure and morphology of the as-prepared t-Ba2V2O7 products were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The results show that the spirals of stacked nanosheets grow along the z-axis of microsquares, leading to the formation of a helical shape. Based on parallel experiments and theoretical analysis of t-Ba2V2O7 helical mesosquares at different reaction stages, the formation mechanism has been proposed to be a “self-assembly–dissolution–recrystallization–Ostwald-ripening” mechanism. The helical structures with uniform morphology and size may find promising applications in a variety of fields. The SDBS-assisted microwave irradiation method offers an easy path to the controllable fabrication of helical Ba2V2O7meso/nanomaterials, which can be readily extended to the development of functional structures of other alkaline earth vanadates. Moreover, it is found that the helical-like materials exhibit unique magnetic properties, corresponding to shape evolutions with different particle sizes at continuous reaction time. [ABSTRACT FROM AUTHOR]

Transition-metal-doped perovskite oxide LaNi0.9M0.1O3 (M = Cu, Co) nanosheets were grown on nickel foam to serve as a complete carbon- and binder-free three-dimensional (3D) porous air electrode for lithium–oxygen batteries. The design of this porous air electrode can facilitate rapid gas and electrolyte diffusion, as well as form a continuous electronic conductive network throughout the whole energy conversion process. Because of a combination of abundant lattice strain and the oxygen vacancy effect caused by substitution of an element with a different valence state in Ni sites, LaNi0.9Cu0.1O3 exhibits a significant oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), showing improvement in both aqueous and non-aqueous systems compared with pure LaNiO3 and LaNi0.9Co0.1O3. Especially with the redox mediator additive tetrathiafulvalene (TTF) in the electrolyte, this LaNi0.9Cu0.1O3 perovskite oxide nanosheet catalyst grown on 3D microporous nickel foam exhibits excellent bifunctional catalytic activities in the lithium–oxygen battery, showing the same highly active catalytic kinetics and high round-trip efficiency as those of reported precious metal catalysts. The overpotential remains at 0.72 V, and the round-trip efficiency is up to 80% under a current density of 0.1 mA cm−2, with capacity limited to 1000 mA h g−1. [ABSTRACT FROM AUTHOR]

Organic electroactive materials are promising candidates for next generation sodium ion batteries (SIBs) due to their low cost, sustainability and environmental benignity. It is of great interest to develop organic compounds with multifunctional groups to be used as electrode materials for SIBs owing to their light weight, multi-electron reactions, redox stability and structural diversity. The organic compound 4,8-dihydrobenzo[1,2-b:4,5-b′] dithiophene-4,8-dione (BDT) was prepared by a facile solution method, and its graphene composite (BDT–G) was synthesized by a simple dispersion–deposition process. BDT–G as a cathode material demonstrated much enhanced electrochemical performance, including higher reversible capacity (217 mA h g−1vs. 145 mA h g−1), better cycling performance (∼175 mA h g−1vs.∼100 mA h g−1 after 70 cycles at 0.2C), and higher rate capabilities (1.7 times better than BDT at 2C) compared with BDT. It is revealed that these improved electrochemical properties should be mainly attributed to the excellent electronic conductivity and ionic transport efficiency promoted by graphene. Furthermore, the fast electrode reaction of BDT with the help of unlimited electron transport via the two-dimensional graphene network results in enhanced usage of materials, and BDT in the composite with graphene could be inhibited from dissolution in the organic electrolyte. [ABSTRACT FROM AUTHOR]

Among anode materials for sodium ion batteries, red phosphorus is a very promising one due to its abundant reserves, low-cost and high theoretical capacity of 2600 mA h g−1. However, its huge volume expansion on sodiation (∼490%) and poor conductivity leads to dramatic capacity decay, restraining its practical application. To improve the electrochemical performance, here, we prepared a red phosphorus and graphene nanoplate composite using cheap red P and natural graphite as the starting materials via a simple and scalable ball-milling method. The phosphorus–carbon bond formed during the milling process improves the electrical connectivity between P particles and graphene nanoplates, consequently stabilizing the structure of the composite to achieve high cycling performance and rate capability. As a result, the red phosphorus and graphene nanoplate composite delivered a high reversible capacity of 1146 mA h g−1 (calculated on the basis of the composite mass) at a current density of 100 mA g−1 and an excellent cycling stability of 200 cycles with 92.5% capacity retention. [ABSTRACT FROM AUTHOR]

A B4C nanowire as a novel bifunctional electrocatalyst was synthesized using carbon nanotubes as the template. Because of the highly efficient catalytic activity, together with the abundant catalytic sites in the B4C nanowire and carbon nanotube composite, this material exhibits great catalytic activity as an efficient bifunctional catalyst for the oxygen reduction and evolution reactions in lithium oxygen batteries. Excellent cycling performance under capacity limited mode is demonstrated, in which the terminal discharge voltage is higher than 2.2 V after 120 cycles at a current density of 0.4 mA cm−2. This novel electrocatalyst is a promising bifunctional electrocatalyst for lithium oxygen batteries, with high energy density, favorable rechargeability, and high round-trip efficiency (76%). [ABSTRACT FROM AUTHOR]

A hybrid gel–solid-state polymer electrolyte has been used as the separator and an electrolyte for lithium oxygen batteries. It can not only avoid electrolyte evaporation but also protect the lithium metal anode during reactions over long-term cycling. Due to its high ionic conductivity and low activation energy, excellent cycling performance is demonstrated, in which the terminal voltage is higher than 2.2 V after 140 cycles at 0.4 mA cm−2, with a capacity of 1000 mA h g(composite)−1. [ABSTRACT FROM AUTHOR]

A novel and low-cost FeP anode with a high capacity of 764.7 mA h g−1 synthesized by a ball-milling method is reported for sodium ion batteries. Ex situ X-ray diffraction and transmission electron microscopy have been used to explore the sodium storage mechanism of FeP. [ABSTRACT FROM AUTHOR]

We here describe the extraordinary performance of NASICON Na3V2(PO4)3-carbon nanofiber (NVP -- CNF) composites with ultra-high power and excellent cycling performance. NVP -- CNFs are composed of CNFs at the center part and partly embedded NVP nanoparticles in the shell. We first report this unique morphology of NVP -- CNFs for the electrode material of secondary batteries as well as for general energy conversion materials. Our NVP -- CNFs show not only a high discharge capacity of ~88.9 mA h g-1 even at a high current density of 50 C but also ~93% cyclic retention property after 300 cycles at 1 C. The superb kinetics and excellent cycling performance of the NVP -- CNFs are attributed to the facile migration of Na ions through the partly exposed regions of NVP nanoparticles that are directly in contact with an electrolyte as well as the fast electron transfer along the conducting CNF pathways. [ABSTRACT FROM AUTHOR]

Conductive polypyrrole (PPy)-coated LiNi0.5Mn1.5O4 (LNMO) composites are applied as cathode materials in Li-ion batteries, and their electrochemical properties are explored at both room and elevated temperature. The morphology, phase evolution, and chemical properties of the as-prepared samples are analyzed by means of X-ray powder diffraction, thermogravimetric analysis, Raman spectroscopy, X-ray photoelectron spectroscopy and scanning and transmission electron microscopy techniques. The composite with 5 wt% polypyrrole coating shows a discharge capacity retention of 92% after 300 cycles and better rate capability than the bare LNMO electrode in the potential range of 3.5-4.9 V vs. Li/Li+ at room temperature. At the elevated temperature, the cycling performance of the electrode made from LNMO-5 wt% PPy is also remarkably stable (~91% capacity retention after 100 cycles). It is revealed that the polypyrrole coating can suppress the dissolution of manganese in the electrolyte which occurs during cycling. The charge transfer resistance of the composite electrode is much lower than that of the bare LNMO electrode after cycling, indicating that the polypyrrole coating significantly increases the electrical conductivity of the LNMO electrode. Polypyrrole can also work as an effective protective layer to suppress the electrolyte decomposition arising from undesirable reactions between the cathode electrode and electrolyte on the surface of the active material at elevated temperature, leading to high coulombic efficiency. [ABSTRACT FROM AUTHOR]

Li and Na batteries are very important as energy storage devices for electric vehicles and smart grids. It is well known that, when an electrode is analysed in detail, each of the components (the active material, the conductive carbon, the current collector and the binder) makes a portion of contribution to the battery performance in terms of specific capacity, rate capability, cycle life, etc. However, there has not yet been a review on the binder, though there are already many review papers on the active materials. Binders make up only a small part of the electrode composition, but in some cases, they play an important role in affecting the cycling stability and rate capability for Li-ion and Na-ion batteries. Poly(vinylidene difluoride) (PVDF) has been the mainstream binder, but there have been discoveries that aqueous binders can sometimes make a battery perform better, not to mention they are cheaper, greener, and easier to use for electrode fabrication. In this review, we focus on several kinds of promising electrode materials, to show how their battery performance can be affected significantly by binder materials: anode materials such as Si, Sn and transitional metal oxides; cathode materials such as LiFePO4, LiNi1/3Co1/3Mn1/3O2, LiCoO2 and sulphur. [ABSTRACT FROM AUTHOR]

Copper telluride nanocubes, nanosheets, and nanoparticles were prepared byasolvothermal method under the protection of an inert atmosphere. The influence of reaction parameters, including precursor concentration, precursor ratio, precursor type, reaction time, reaction temperature, solvent, and organic ligands, on the size, morphology, crystalline structure, and composition of the resultant copper telluride nanostructures was comprehensively investigated. The results showed that the crystal structure and composition of the resultant nanostructures varied case by case, demonstrating the complexity of copper tellurides, despite their simple molecular formula. The obtained copper telluride nanostructures were tested as anodes in lithium ion batteries. The assembled Li/LiPF6/CuxTe cells exhibit extremely high cycling stability (up to 5000 cycles) and their highest specific capacity is 280 mA h g[sup -1]. The results also showed better performance of the Cu2-xTe nanosheet electrodes than those of electrodes made from nanoparticles and nanocubes, demonstrating the importance of controlling the morphology of copper telluride during preparation. [ABSTRACT FROM AUTHOR]

A structured SnO2–reduced graphene oxide (RGO) nanocomposite has been synthesized with SnO2 nanoparticles (∼5 nm) anchored on a RGO framework. It has been successfully applied as an anode material in sodium-ion batteries. The electrode delivers a reversible Na-storage capacity of 330 mA h g−1 with an outstanding capacity retention of 81.3% over 150 cycles. Moreover, it possesses a relatively good rate capability, exhibiting a capacity retention of 25.8% at high rate (1000 mA h g−1). With its combined advantages of low cost and environmental benignity, the SnO2–RGO nanocomposite would be a promising anode for Na-ion batteries. [ABSTRACT FROM AUTHOR]

Correction for ‘A new, cheap, and productive FeP anode material for sodium-ion batteries’ by Wei-Jie Li et al., Chem. Commun., 2015, DOI: URL10.1039/c4cc09604e/URL. [ABSTRACT FROM AUTHOR]

Na 2 Fe 2 (SO 4 ) 3 (NFS), as a promising cathode for sodium-ion batteries, is still plagued by its poor intrinsic conductivity. In general, hybridization with carbon materials is an effective strategy to improve the sodium storage performance of NFS. However, the role of carbon materials in the electrochemical performance of NFS cathode materials has not been thoroughly investigated. Herein, the effect of carbon materials was revealed by employing various conductive carbon materials as carbon sources. Among these, the NFS coated with Ketjen Black (NFS@KB) shows the largest specific surface area, which is beneficial for electrolyte penetration and rapid ionic/electronic migration, leading to improved electrochemical performance. Therefore, NFS@KB shows a long cycle life (74.6 mA h g -1 after 1000 cycles), superior rate performance (61.5 mA h g -1 at a 5.0 A g -1 ), and good temperature tolerance (-10 °C to 60 °C). Besides, the practicality of the NFS@KB cathode was further demonstrated by assembling a NFS@KB//hard carbon full cell. Therefore, this research indicates that a suitable carbon material for the NFS cathode can greatly activate the sodium storage performance., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Electrocatalysis for cathodic oxygen is of great significance for achieving high-performance lithium-oxygen batteries. Herein, we report a facile and green method to prepare an interconnected nanoporous three-dimensional (3D) architecture, which is composed of RuO2 nanogranulates coated with few layers of carbon. The as-prepared 3D nanoporous RuO2@C nanostructure can demonstrate a high initial specific discharge capacity of 4000 mA h g-1 with high round-trip efficiency of 95%. Meanwhile, the nanoporous RuO2@C could achieve stable cycling performance with a fixed capacity of 1500 mA h g-1 over 100 cycles. The terminal discharge and charge potentials of nanoporous RuO2@C are well maintained with minor potential variation of 0.14 and 0.13 V at the 100th cycle, respectively. In addition, the formation of discharge products is monitored by using in situ high-energy synchrotron X-ray diffraction (XRD).

An exfoliated MoS2-C composite (E-MoS2-C) was prepared via simple chemical exfoliation and a hydrothermal method. The obtained E-MoS2-C was tested as an anode material for sodium ion batteries. High capacity (~400 mA h g(-1)) at 0.25 C (100 mA g(-1)) was maintained over prolonged cycling life (100 cycles). Outstanding rate capability was also achieved with a capacity of 290 mA h g(-1) at 5 C.

A tin nanoparticle/polypyrrole (nano-Sn/PPy) composite was prepared by chemically reducing and coating Sn nanoparticles onto the PPy surface. The composite shows a much higher surface area than the pure nano-Sn reference sample, due to the porous higher surface area of PPy and the much smaller size of Sn in the nano-Sn/PPy composite than in the pure tin nanoparticle sample. Poly(vinylidene fluoride) (PVDF) and sodium carboxymethyl cellulose (CMC) were also used as binders, and the electrochemical performance was investigated. The electrochemical results show that both the capacity retention and the rate capability are in the same order of nano-Sn/PPy-CMC > nano-Sn/PPy-PVDF > nano-Sn-CMC > nano-Sn-PVDF. Scanning electronic microscopy (SEM) and electrochemical impedance spectroscopy (EIS) results show that CMC can prevent the formation of cracks in electrodes caused by the big volume changes during the charge-discharge process, and the PPy in the composite can provide a conducting matrix and alleviate the agglomeration of Sn nanoparticles. The present results indicate that the nano-Sn/PPy composite could be suitable for the next generation of anode materials with relatively good capacity retention and rate capability., (This journal is © The Royal Society of Chemistry 2011)