Rechargeable sodium-ion batteries are becoming a viable alternative to lithium-based technology in energy storage strategies, due to the wide abundance of sodium raw material. In the past decade, this has generated a boom of research interest in such systems. Notwithstanding the large number of research papers concerning sodium-ion battery electrodes, the development of a low-cost, well-performing anode material remains the largest obstacle to overcome. Although the well-known anatase, one of the allotropic forms of natural TiO, was recently proposed for such applications, the material generally suffers from reduced cyclability and limited power, due to kinetic drawbacks and to its poor charge transport properties. A systematic approach in the morphological tuning of the anatase nanocrystals is needed, to optimize its structural features toward the electrochemical properties and to promote the material interaction with the conductive network and the electrolyte. Aiming to face with these issues, we were able to obtain a fine tuning of the nanoparticle morphology and to expose the most favorable nanocrystal facets to the electrolyte and to the conductive wrapping agent (graphene), thus overcoming the intrinsic limits of anatase transport properties. The result is a TiO-based composite electrode able to deliver an outstandingly stability over cycles (150 mA h g for more than 600 cycles in the 1.5-0.1 V potential range) never achieved with such a low content of carbonaceous substrate (5%). Moreover, it has been demonstrated for the first time than these outstanding performances are not simply related to the overall surface area of the different morphologies but have to be directly related to the peculiar surface characteristics of the crystals.

IntroductionAs renewable energy sources are taking a wider share of worldwide energy production, [1] grids reliability and utilization efficiency are plummeting. [2,3] This is mainly due to intermittency and discontinuity of power sources, such as wind and solar, which determine uncertainties in energy production capability and in fulfilling the instantaneous energy demand. This aspect, in turn, sensibly increases the unpredictability of energy prices spikes and marginal and maintenance costs of traditional fossil fuel plants, which are demanded Since the breakthrough achieved in the research around material intercalating lithium, almost a decade has passed before the commercialization of the first lithium-ion battery (LIB). On the brink of an energy voracious future, convergence of scientific efforts over efficient and low-cost energy production and storage would be advantageous and beneficial. The research hovering around sodium-ion rechargeable batteries (SIBs), a more sustainable alternative to LIBs, has been observing a positive momentum for ten years now, and chemically stable and electrochemically performing anode and cathode materials represent important milestones on the path toward a commercial full-cell. Material science breakthroughs achieved in carbon and graphite based matrices, layered and open framework structures, and sodium storing alloys, disclose new full-cell set up opportunities going beyond traditional "rocking chair" configuration. In this contribution an in-depth analysis of chemical and physical principles lying beyond the energy storage provided by SIBs most recently investigated active materials is given. In the second half of the review, challenges, opportunities, and state-of-the art description of full-cell SIBs lab scale prototypes are discussed. The latter, indeed, stands for a technological validation of a low-cost alternative to lithium-ion batteries guaranteeing energy densities close to 150 Wh kg −1 . Sodium-Ion Batteriesdiscontinuously to provide for power unbalances between demand and supply. In general, resilience to these drawbacks would be higher providing an incremented flexibility from demand response resources, interregional energy transmission, and energy storage. Plenty of energy storage systems (ESS) are being utilized to curb renewable energy sources intermittency. Among them, worth to be listed are hydroelectric (pumped hydro), mechanical (flywheels and compressed air), and electrochemical (lead-acid, Na-S, Na-NiCl 2 , and Li-ion batteries). [4] Nevertheless not all the previously cited energy storage technologies are comparable one with another in terms of scalability, environmental impact, investment costs, maintenance, and moreover, responsivity to energy needs. Batteries energy storage, directly suppling electric energy without requiring any mechanical-to-electrical energy transducer, surely represents the most versatile appliance. In particular, intrinsic flexibility of modern Li-ion batteries coupled to renewable power plants, ensures the proper response not...

A novel WS 2 −graphite dual-ion battery (DIB) is developed by combining a conventional graphite cathode and a high-capacity few-layer WS 2flake anode. The WS 2 flakes are produced by exploiting wet-jet milling (WJM) exfoliation, which allows large-scale and free-material loss production (i.e., volume up to 8 L h −1 at concentration of 10 g L −1 and exfoliation yield of 100%) of fewlayer WS 2 flakes in dispersion. The WS 2 anodes enable DIBs, based on hexafluorophosphate (PF 6 − ) and lithium (Li + ) ions, to achieve charge-specific capacities of 457, 438, 421, 403, 295, and 169 mAh g −1 at current rates of 0.1, 0.2, 0.3, 0.4, 0.8, and 1.0 A g −1 , respectively, outperforming conventional DIBs. The WS 2 -based DIBs operate in the 0 to 4 V cell voltage range, thus extending the operating voltage window of conventional WS 2 -based Li-ion batteries (LIBs). These results demonstrate a new route toward the exploitation of WS 2 , and possibly other transition-metal dichalcogenides, for the development of next-generation energy-storage devices.

No abstract

No abstract