Rechargeable sodium-air batteries have been the focus in recent years, owing to the low cost and natural abundance of sodium and high energy density. The discovered different electrochemical mechanism from other metal-air batteries bring unique advantages and challenges to the development of sodium-air batteries. This review comprehensively conclude the key problems and development of different electrochemical mechanism. In the last, remarks are made on the further developments of sodium-air batteries.

Because of the natural abundance, low cost and environmental friendliness of sodium, sodium-ion battery has been considered as the most likely alternative of lithium-ion battery for large-scale energy storage applications. The electrochemical performance of a sodium-ion battery depends mainly on its positive and negative sodium storage materials, and the negative one is even a more important component. Among the negative materials currently studied, carbon-based ones have been considered as the most promising candidates because of their advantages of abundant resources, low sodium embedded platform and good cycle stability. This paper reviews the Na-storage behavior and research progress of graphite, graphene, soft carbon and hard carbon, and investigates the correlation between Na-storage performance and micro-structure, and reveals the application advantages of the hard carbon as the most promising carbon anodes for sodium-ion batteries. This paper also discusses two controversial Na-storage mechanisms of hard carbon, which are intercalation-absorption and absorption-intercalation respectively, and prospects the future development of hard carbon for sodium ion storage.

Abstract: With the rapid development of renewable energy of wind and solar power, the large-scale energy storage system has become more and more important. Lithium-ion batteries have been widely used in portable electronic devices, and are the best choice for the electric vehicles due to their high energy density, long cycle life, high voltage. However, the limited, non-uniform distribution of lithium resources and the high cost would hinder the applications in the field of grid-scale energy storage. Sodium has similar physical and chemical properties with lithium, while sodium resources distribute everywhere around the world. In recent years, room temperature sodium ion battery has attracted widespread attention, particularly for the grid energy storage. Although a large number of sodium-ion battery electrode materials were reported, most of them are still not suitable for practical application. In this review, we will introduce some electrode materials for sodium-ion batteries and point out that in order to realize the commercialization of sodium-ion batteries, we need to explore new cathode and anode materials with high stability in air, high safety, high capacity, high rate capability, superior cycling stability and low cost.

As a novel generation of energy storage battery system, sodium-ion batteries have rapidly captured much attention due to its abundant resources, low cost, high energy density. Electrolyte plays an important role in making sodium-ion batteries with high energy density, long cycling life and high security. The research of organic electrolyte, aqueous electrolyte, ionic liquid electrolyte, polymer gel electrolyte, polymer solid electrolyte and inorganic solid composite electrolyte was reviewed and the ionic conductivity, electrochemical window and thermal stability of these electrolytes were discussed. So far, organic electrolyte is widely used in sodium-ion batteries, exhibiting good electrochemical performances, whose safety still needs improvement. For ionic liquid electrolyte, solid electrolyte and gel electrolyte with better safety, there are still many fundamental issues to be understood; and some problems, such as cost, ionic conductivity and mechanical strength, are to be optimized. Furthermore, prospective of the development of sodium-ion battery electrolyte is put forward.

 Titanium-based materials have attracted increasing attention in recent years as anode materials for sodium ion batteries due to their properties of environmentally friendly, safe, and good stability. However, titanium-based materials show wide band gap, poor electronic conductivity, and low specific capacity, which limit their development and application in sodium ion batteries. This review focuses on the electrochemical properties, modification, and sodium storage mechanism of three titanium-based materials, which are TiO2, Na2TinO2n+1, and NaTi2(PO4)3. The problems and prospect are also pointed out for these materials. Future researches could be focused on the following aspects: ① investigating the electrochemical mechanism of titanium-based materials deeply and systematically; ② the anions/cations doping effects on the structural, electronic and electrochemical  properties of titanium-based materials; ③ the synergistic effect of titanium-based materials and anode materials with high specific capacity; ④ the design of hierarchically structure and three-dimensional structure for titanium-based materials;⑤ exploring titanium-based materials with novel structures.

null

Na-beta alumina batteries are one of the most promising technologies for renewable energy storage and grid applications. Na-beta alumina batteries can be constructed in either tubular or planar designs, depending on the shape of the beta-alumina solid electrolyte. The tubular designs have been widely studied and developed since the 1960s primarily because of their ease of sealing. However, planar designs are considered superior to tubular designs in terms of power output, cell packing, ease of assembly, thermal management, and other characteristics. Recently, Pacific Northwest National Laboratory has begun to develop high-performance planar Na-beta alumina batteries. In this paper, we provide an overview on the basic battery electrochemistry, solid electrolyte synthesis and fabrication, and our recent progress in developing planar batteries. Future trends for further technology improvement will also be presented.

Aqueous sodium ion battery (ASIB) shows good potential for stationary energy storage applications because it offers benefits in safety, environmental impact, cost, and durability. The development and commercialization of ASIB are getting more and more active worldwide as one of the key technologies towards adoption of renewable energy (solar and wind) and smart grid. This review summarizes the R&D history, theory, current technologies, and commercialization status of ASIB. Meanwhile, some cases of demonstrations and commercial applications are also introduced briefly. In addition, the strategies on further developments of key technologies are proposed. After years of rapid development, a series of electrode materials with high capacity and cycle stability has been developed. Through the design and optimization of the battery system, increase of energy density and decrease of manufacturing cost have also been achieved, therefore, commercialization has taken shape. Although ASIB is not a mature technology yet, recent achievements by the academia and industry show great potential for future application.

Sodium-ion batteries have attracted widespread attentions due to the abundant sodium resources and their potential low cost. It is crucial to develop low-cost and excellent performance cathode materials for SIBs. Herein, O3-NaCu1/9Ni2/9Fe1/3Mn1/3O2, a novel cathode material without Mn3+ has been synthesized by a simple solid-state reaction. Galvanostatic charge/discharge measurement for the O3-NaCu1/9Ni2/9Fe1/3Mn1/3O2 electrode between 2.0 V and 4.0 V provides a reversible capacity of 127 mA•h/g and the average discharge voltage of 3.1 V. The full cell using it as the cathode and hard carbon as the anode delivers an energy density of 248 W•h/kg, an energy conversion efficiency of 93% and an excellent cycling performance.

NGK has developed a sodium sulfur battery (NAS® battery) for load leveling applications, allowing the grid to deal with increasing peak. The recent growth in environmentally friendly renewable energies causes network instability. A secondary battery based energy storage system is seen as one of the strongest solutions to stabilize the network while improving the efficiency and usability of these renewable energy technologies. The NAS battery features long duration discharge, compactness, and a long lifespan of 15 years. The capacity for long duration discharge is one of the most notable features of this technology, a feature which becomes more important as renewable energy generation increases. In this paper, recent design of the NAS® battery system is detailed, and a few applications are described.

Hard carbon anode materials have attracted wide attention for the development of practical sodium ion batteries. However, the effect of the structure of pyrolytic precursor on sodium storage performance of the hard carbon was rarely reported. In this article three different carbohydrate precursors are chosen to investigate the influence of their molecular weight on the microstructure and sodium storage property of the final pyrolyzed hard carbons. Results of X-ray powder diffraction (XRD), transmission electron microscopy (TEM) and Raman spectroscopy (Raman) showed that the graphitization degree of the hard carbon materials increases with molecular weight of their precursors. The reversible specific capacity of the hard carbons with glucose, sucrose and starch as precursors reached 242, 275 and 310 mA·h/g respectively, indicating its proportional relationship with the molecular weight of the precursors, and a precursor with high molecular weight is easier to form a more regular graphite-sheet structure, thereby providing more fitted and more sodium reaction sites. This work provides a reference for selecting the precursor of hard carbon as anode material of sodium-ion batteries.

Sodium-nickel chloride cells with different contents of sulfur were prepared. Electrochemical test results of the cells showed that the addition of sulfur in the cathode significantly improve cycling performance of the cells, among which 5% (weight ratio) additive performed the best. According to the phase and morphological characterizations for the cathode, a mechanism based on the Ni₃S₂ layer modification resulted from the reaction between the added sulfur and nickel particles during the cell cycling was supposed. The Ni₃S₂ modification layer was proved effective to prevent the growth of nickel particle in the electrode and therefore improve the cycling performance of the cell. Growth of NaCl particles was ascribed to capacity degradation of the cell at the late cycling stage.

This bimonthly review paper highlights 100 recent published papers on lithium batteries. We searched the Web of Science and found 2241 papers online from Feb. 1, 2016 to Mar. 31, 2016. 89 of them were selected to be highlighted. Layered oxide and high voltage spinel cathode materials are still under extensive investigations for influences of doping, coating and interface modifications on their cycling performances. Large efforts were devoted to Si based composite anode materials for analyzing the SEI and making nano structures. There are a few papers related to electrolyte additives, solid state lithium batteries, Li/S batteries, Li-air batteries, and modeling, and more papers for the charcterzations and calculations of doping to cathode materials, SEI and solid state electrolytes and batteries.
lithium batteries; cathode material; anode material; electrolyte; battery technology

This four months review paper highlights 100 recent published papers on supercapacitors. We searched the Web of Science and found 830 papers online from November 1, 2015 to February 29, 2016. 100 of them were selected to be highlighted. The researches of electrical double-layer capacitor (EDLC) are mainly focused on new carbon material designed preparation, such as porous carbon materials, graphene, and their effect on supercapacitor performance. The published papers of pseudocapacitor include four aspects, such as metal oxide composites, conductive polymer composite, heteroatom doping carbon materials and new type of pseudocapactive materials. Hybrid supercapacitor includes aqueous hybrid supercapacitor and organic hybrid supercapacitor.

 

It is a goal for all-electric vehicles that the requirement of the energy density for Li-ion batteries must be over 400 W·h/kg in demand. In this review, the recent progresses of Li-rich layered oxide cathode materials in our group are briefly introduced. After many years’ research, their initial coulombic efficiency, the rate capability and cycling performance were improved significantly. Moreover, the voltage decay was suppressed effectively. Based on these processes we also manufactured a 24 A·h-class cell using a Li-rich layered cathode and a Nano Si/C anode. The cell is confirmed to have the mass energy density of 374 W·h/kg and the volumetric energy density of 577 W·h/L.