Sodium ion batteries are attractive for the rapidly emerging large‐scale energy storage market for intermittent renewable resources. Currently a viable cathode material does not exist for practical non‐aqueous sodium ion battery applications. Here we disclose a high performance, durable electrode material based on the 3D NASICON framework. Porous Na3V2(PO4)3/C was synthesized using a novel solution‐based approach. This material, as a cathode, is capable of delivering an energy storage capacity of ∼400 mWh/g vs. sodium metal. Furthermore, at high current rates (10, 20 and 40 C), it displayed remarkable capacity retention. Equally impressive is the long term cycle life. Nearly 50% of the initial capacity was retained after 30,000 charge/discharge cycles at 40 C (4.7 A/g). Notably, coulombic efficiency was 99.68% (average) over the course of cycling. To the best of our knowledge, the combination of high energy density, high power density and ultra long cycle life demonstrated here has never been reported before for sodium ion batteries. We believe our findings will have profound implications for developing large‐scale energy storage systems for renewable energy sources.

Sodium-ion batteries are an alternative to lithium-ion batteries for large-scale applications. However, low capacity and poor rate capability of existing anodes are the main bottlenecks to future developments. Here we report a uniform coating of antimony sulphide (stibnite) on graphene, fabricated by a solution-based synthesis technique, as the anode material for sodium-ion batteries. It gives a high capacity of 730 mAh g À 1 at 50 mA g À 1 , an excellent rate capability up to 6C and a good cycle performance. The promising performance is attributed to fast sodium ion diffusion from the small nanoparticles, and good electrical transport from the intimate contact between the active material and graphene, which also provides a template for anchoring the nanoparticles. We also demonstrate a battery with the stibnite-graphene composite that is free from sodium metal, having energy density up to 80 Wh kg À 1 . The energy density could exceed that of some lithium-ion batteries with further optimization.

We report here the electrochemical properties of Na 2 Ti 3 O 7 , a potential non-carbon based, low-voltage anode material for room temperature sodium ion battery applications. A solid-state route was used to prepare Na 2 Ti 3 O 7 . Further, XRD, SEM, TEM, HRTEM, SAED, XPS and EDX techniques were used to characterize the material. The Na/Na 2 Ti 3 O 7 cell displayed a charge capacity of 177 mA h g À1 at 0.1 C rate. High rate and long term cyclic performance at different rates showed relatively stable storage capacities. Surprisingly, if the lower cut-off voltage is altered, the appearance of a new charge plateau is seen, with no apparent change in the discharge behaviour. The kinetics of sodium insertion and extraction are discussed utilizing CV and EIS techniques. We also report the sodium chemical diffusion coefficient of the Na 2 Ti 3 O 7 /CB electrode estimated using GITT.

Na 3 V 2 (PO 4 ) 3 is a popular sodium-ion intercalating cathode material. It degrades in aqueous electrolytes, though. By substitution of half of the vanadium with titanium, the related compound, Na 2 VTi(PO 4 ) 3 , was obtained. Three distinct sets of experiments were employed to qualify the potential utility of this material in various aqueous ion battery applications, including sodium and zinc ion. High levels of cycle stability were observed in neutral sodium-containing electrolyte, but less-so in zinc-containing electrolyte. At the end, pouch cells were built with both activated carbon and NaTi 2 (PO 4 ) 3 anode materials, demonstrating practical capabilities of systems utilizing these materials.A wide variety of new battery technologies are currently under development for large scale energy storage applications. Utility, residential, and commercial energy storage is becoming an important industry due to frequency regulation requirements, mitigation of peak energy demand, and the proliferation of intermittent renewable energy sources. Battery technology can target these market opportunities, but significant work remains to develop products to meet the requirements at better costs.Aqueous ion batteries (AIBs) have received renewed interest from the research community recently as a means to fill a niche requiring low cost, high efficiency, and high power density, with competitive energy densities. 1-3 The basic concept has been to apply advances realized over the past two decades with lithium ion batteries to the aqueous battery technologies that have existed for well over a century. Utilizing highly facile alkali ion intercalation in a low cost, waterbased electrolyte is the goal.AIBs must be engineered carefully to ensure anode, cathode, and electrolyte operate in harmony. Spinel LiMn 2 O 4 is the most attractive cathode material thus far studied, but requires conditions that are not excessively alkaline to achieve full capacity. Early work by the Dahn group demonstrated the initial approach to AIBs, utilizing LiMn 2 O 4 cathode and VO 2 -B anode material. 4,5 Capacity fade was an issue due to the rapid degradation of the anode material. Recently, Aquion Energy has successfully coupled LiMn 2 O 4 cathode with an activated carbon/NaTi 2 (PO 4 ) 3 composite anode in a hybrid ion electrolyte, and is working toward commercialization. 6,7 Layered oxides also have been extensively studied, but the use of expensive cobalt is not synergistic with a low cost water-based electrolyte. 1,2 LiFePO 4 is another attractive cathode material, but has low voltage and degrades in alkaline conditions -once again limiting potential anode partners. 8 Cyanometallates are under heavy development for very high power applications, but also require significant optimization. 9 Many configurations are also being evaluated to utilize a zinc anode in a hybrid ion or fully zinc ion systems. [10][11][12][13] On the anode side, NASICON LiTi 2 (PO 4 ) 3 and the aforementioned NaTi 2 (PO 4 ) 3 have undoubtedly been proven to be good intercala...

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Iron(iii) sulfate, a rhombohedral NASICON compound, has been demonstrated as a sodium intercalation host. This cost-effective material is attractive, as it can be slurry processed in bulk with ball-milling, while utilizing the iron 2(+)/3(+) redox couple, offering stable 3.2 V performance for over 400 cycles.

N THE manufacture of commercial trisodium phosphate, the caking of the product due to the formation of a mat by the needlelike crystals of the dodecahydrate is a serious problem (42). A small admixture of fluoride has been used to give a product consisting mainly of octahedral crystals, the granular character of which improves the physical properties of the product. The nature of these crystals has been in question, and they have been considered to be either a double salt of sodium phosphate and sodium fluoride, or else sodium phosphate decahydrate.It seemed questionable whether the latter hydrate actually existed or whether a double salt containing sodium fluoride (a persistent impurity in phosphate) had been repeatedly mistaken for it even in supposedly pure materials. It was also possible that here was a case of the stabilization of a metastable phase by adsorption of some impurity (possibly fluoride ion) which would prevent the crystallization of the stable hydrate. It can be stated a t the outset that, although fluoride is apparently strongly adsorbed by trisodium phosphate dodecahydrate, no stabilization of any lower hydrate has been observed. Trisodium phosphate decahydrate was first described by Rammelsberg (34) in 1865. He prepared it in the form of colorless, transparent, regular octahedra by recrystallizing small red and yellow crystals which were sometimes obtained as an impurity in the manufacture of soda. Later (36) he reported that this compound contained fluorine. In 1885 Baker (3) prepared and analyzed trisodium vanadate decahydrate, isometric octahedra and dodecahedra; he stated that, although they had not been prepared in any quantity, the isomorphous arsenate and phosphate could be demonstrated microscopically. Continuing Baker's work, Hall (20) gave details of a method for preparing trisodium arsenate decahydrate but did not succeed in obtaining the corresponding phosphate.More recently Salkowski (39) claimed to have prepared a trisodium phosphate decahydrate by treating a 10 per cent solution of potassium, sodium, or ammonium dihydrogen phosphate with 0.3 to 0.4 volume of sodium hydroxide solution of density 1.34 and recrystallizing the product from water. Westbrook (4) patented a process for the preparation of the decahydrate in which a solution with the composition 1NaaPO4: lOHzO is held above its crystallization temperature and seeded with the decahydrate, and the crystals formed of the latter are removed. Mason (8, 49)

INDUSTRIAL AND ENGINEERING CHEMISTRY 935 have a controlling effect on refinery practice. This is well illustrated in the case of the two gas oils. Oil 5 of 1926 was described as an asphalt-base gas oil, and (Figure 2) contained practically nothing of the lubricating oil fraction. Oil 12 of 1926 was described as a paraffin-base gas oil, but it contained a large amount of material ordinarily considered lubricating oil. As a consequence, though similarly named, oil 12 made an effective spray and oil 5 did not. Conclusions