A comparative study of the reduction of TiS2 in diverse electrolyte formulations involving Ca(BF4)2 and Ca(TFSI)2 salts was carried out at different temperatures (from 25 °C to 100 °C). While for the former salt intercalation of calcium is only observed at high temperatures, calcium intercalated phases are also observed for the latter even at room temperature. The nature of the electrolyte does also have an impact on the relative amounts of the phases formed. Since Ca(TFSI)2 based electrolytes do not enable calcium plating, cycling was attempted using activated carbon as counterelectrode, and the reversibility of the process was ascertained. Even if corrosion of stainless steel current collectors and side reactions do still prevent proper cyclability, the results achieved should contribute to the establishment of reliable and viable cell set-up and methodology for the unambiguous study of the intercalation process in multivalent battery systems.

Batteries based on naturally abundant, light metal anodes (such as Ca and Mg) and multivalent ion host cathodes can potentially achieve very high energy densities at relatively low cost and environmental impact, thus representing a compelling alternative to currently available Li-ion systems. While reversible Ca metal plating and stripping in conventional alkyl carbonate based electrolytes has been accomplished [1,2], unraveling cathode materials with fast and reversible ion mobility at high operating voltages remains a major open challenge, mainly hampered by the slow diffusion kinetics in the solid state of multivalent ions. Thus, besides the exploration of new materials, revisiting traditional layered intercalation hosts appears as a very useful tool to gain further insight into the fundamentals of divalent ion intercalation. In this context, a thorough study of the electrochemical intercalation of Ca2+ in layered TiS2, in alkyl carbonate based electrolytes, is herein presented [3]. Fundamental insights on the insertion process are acquired through X-ray diffraction. Ca2+ insertion is unambiguously proved by using both X-ray diffraction and differential absorption X-ray tomography at the Ca L2 edge and the reversibility of the process is demonstrated at moderate temperature. Different phases can be formed upon reduction of pristine TiS2, whose amount and composition dependon the experimental conditions employed. A comparative study with Mg2+ containing electrolytes and other conventional intercalation hosts, such as V2O5, was also carried out. Careful examination of results highlights the potential relevance of side reactions in these system and the need to use several complementary characterization techniques to unambiguously assess divalent ion intercalation. [1]A. Ponrouch, C. Frontera, F. Bardé and M. R. Palacín, Nat. Mater. (2016), 15, 169. [2] A. Ponrouch, M. R. Palacín, Curr. Opin. Electrochem. (2018), 1. [3] Tchitchekova D.S., Ponrouch A., Verrelli R., Broux T., Frontera C., Sorrentino A., Biskup N., Arroyo-de Dompablo M.E., Bardé F., Palacín M.R., Chem. Mat. (2018), 30, 847.

Layered CaTaN2 and MgTa2N3 and cubic Mg2Ta2N4 were prepared by direct solid state reaction from the binary nitrides Ta3N5 and A3N2 (A: Mg, Ca). CaTaN2 showed a slight Ca deficiency (0.11 moles per formula), and a monoclinic distortion from previously reported R3̅m symmetry, with space group C2/m and cell parameters a = 5.4011(2), b = 3.1434(1), c = 5.9464(2) Å and β = 107.91(3)°. Ca2+ and Mg2+ deintercalation was investigated in the three compounds both chemically and electrochemically. No significant Mg2+ extraction could be inferred for MgTa2N3 and Mg2Ta2N4, neither after reaction with NO2BF4 nor after electrochemical oxidation at 100 °C in alkyl carbonate electrolytes. Rietveld refinement of the X-ray powder diffraction pattern of chemically oxidized Ca0.89TaN2 indicates a decrease of the Ca content to 0.34 concomitant to the disappearance of the monoclinic distortion and expansion of the interlayer space from 5.658 to 5.762 Å, space group R3̅m and cell parameters a = 3.1103(1) and c = 17.287(1) Å. Deintercalation in this compound was also achieved electrochemically at 100 °C. Results of density functional theory calculations seem to indicate that reaction mechanisms for CaTaN2 oxidation additional and/or alternative to deintercalation are taking place, which is likely related to the loss of crystallinity observed upon oxidation and the irreversibility of the process.

Vanadium pentoxide has been investigated for multivalent ion battery technologies but the structural characterization of inserted phases is poor, and conflicting reports exist in the literature. This study presents a critical overview of controversial aspects related to Mg and Ca insertion in alpha-V2O5 under diverse conditions by combined electrochemical and ex-situ XRD experiments. Galvanostatic tests are carried out in dry and wet alkyl carbonate-based electrolytes at RT and 100 degrees C. The formation of protonated phases with negligible divalent ion content if any is evidenced by Rietveld refinements of the XRD data, unambiguously dismissing the presence of AV(2)O(5) (A: Mg, Ca) as electrochemical reduction products. Furthermore, thermal instability of V2O5 at 100 degrees C in alkyl carbonate solvents is demonstrated by XRD and TEM analysis and the formation of an orthorhombic phase with increased a parameter, most likely due to degradation favored by both water and temperature, is observed for both Mg and Ca. In order to assess the feasibility of the reverse reaction, fully intercalated AV(2)O(5) (A = Ca, Mg) phases were also prepared by solid state reaction and oxidation attempted both electrochemically and chemically without evidence of any significant amount of Mg2+ or Ca2+ extraction, further corroborating the sluggish diffusion kinetics of divalent cations in alpha-V2O5.

Ternary CuO-Fe2O3-MCMB conversion anode is herein characterized and combined with highvoltage Li1.35Ni0.48Fe0.1Mn1.72O4 spinel cathode in a lithium-ion battery of relevant performances in terms of cycling stability and rate capability. The CuO-Fe2O3-MCMB composite is prepared using high-energy milling, i.e., a low-cost pathway which leads to a crystalline structure, and homogeneous submicrometrical morphology revealed by X-ray diffraction and electronic microscopy. The anode reversibly exchanges lithium ions by conversion reactions of CuO and Fe2O3, as well as by insertion into MCMB carbon. Electrochemical tests, including impedance spectroscopy, reveal a conductive electrode/electrolyte interface, which enables the anode to achieve a reversible capacity value higher than 500 mAh g when cycled at a current of 120 mA g. The remarkable stability of the CuO-Fe2O3-MCMB electrode, and its suitable characteristics in terms of delivered capacity and voltage profile retention, allow its combination in an efficient full lithium-ion cell using high voltage Li1.35Ni0.48Fe0.1Mn1.72O4 cathode. The cell has a working voltage of 3.6 V and delivers a capacity of 110 mAh gcathode −1 with coulombic efficiency above 99% upon 100 cycles at 148 mA gcathode . This relevant performance, rarely 2 achieved by lithium-ion systems using conversion reaction, is due to an excellent cell balance in terms of negative-to-positive ratio, favored by the anode composition and electrochemical features.

A comparative study of the electrochemical intercalation of Ca2+ and Mg2+ in layered TiS2 using alkylcarbonate-based electrolytes is reported, and for the first time, reversible electrochemical Ca2+ insertion is proved in this compound using both X-ray diffraction and differential absorption X-ray tomography at the Ca L-2 edge. Different new phases are formed upon M2+ insertion that are structurally characterized, their amount and composition being dependent on M2+ and the experimental conditions. The first phase formed upon reduction is found to be the result of an ion-solvated intercalation mechanism, with solvent molecule(s) being cointercalated with the M2+ cation. Upon further reduction, new non-cointercalated calcium-containing phases seem to form at the expense of unreacted TiS2. The calculated activation energy barriers for Ca2+ migration in TiS2 (0.75 eV) are lower than those previously reported for Mg (1.14 eV) at the dilute limit and within the CdI2 structural type. DFT results indicate that the expansion of the interlayer space lowers the energy barrier and favors a different pathway for Ca2+ migration.

Sustainable energy storage may be achieved by using advanced lithium-ion battery configurations with high energy, low cost and environmental compatibility.

A ternary CuO-Fe2O3-mesocarbon microbeads (MCMB) conversion anode was characterized and combined with a high-voltage Li1.35Ni0.48Fe0.1Mn1.72O4 spinel cathode in a lithium-ion battery of relevant performance in terms of cycling stability and rate capability. The CuO-Fe2O3-MCMB composite was prepared by using high-energy milling, a low-cost pathway that leads to a crystalline structure and homogeneous submicrometrical morphology as revealed by XRD and electron microscopy. The anode reversibly exchanges lithium ions through the conversion reactions of CuO and Fe2O3 and by insertion into the MCMB carbon. Electrochemical tests, including impedance spectroscopy, revealed a conductive electrode/electrolyte interface that enabled the anode to achieve a reversible capacity value higher than 500mAhg(-1) when cycled at a current of 120mAg(-1). The remarkable stability of the CuO-Fe2O3-MCMB electrode and the suitable characteristics in terms of delivered capacity and voltage-profile retention allowed its use in an efficient full lithium-ion cell with a high-voltage Li1.35Ni0.48Fe0.1Mn1.72O4 cathode. The cell had a working voltage of 3.6V and delivered a capacity of 110mAhg(cathode)(-1) with a Coulombic efficiency above 99% after 100 cycles at 148mAg(cathode)(-1). This relevant performances, rarely achieved by lithium-ion systems that use the conversion reaction, are the result of an excellent cell balance in terms of negative-to-positive ratio, favored by the anode composition and electrochemical features.

Layered MgMoN2 was prepared by solid state reaction at high temperature between Mo and Mg3N2 in N-2 which represents a simple synthetic pathway compared to the previously reported method that used NaN3 as the nitrogen source. The crystal structure of MgMoN2 was studied by synchrotron X-ray and neutron powder diffraction. The feasibility of oxidizing this compound and concomitantly extracting magnesium from the structure was assessed by both chemical and electrochemical approaches, using different protocols. The X-ray diffraction patterns of the oxidized samples do not exhibit any relevant difference with respect to that of the as prepared MgMoN2 and no differences in the cell parameters are deduced from Rietveld refinements. No hints pointing at the presence of any amorphous phase are observed either. These results are rationalized through DFT calculated energy barriers for Mg2+ ion migration in MgMoN2.

New Li-ion cells are formed by combining a LiFe0.25Mn0.5Co0.25PO4 olivine cathode either with Sn-Fe2O3-C or with Sn-C composite anodes. These active materials exhibit electrochemical properties very attractive in view of practical use, including the higher working voltage of the LiFe0.25Mn0.5Co0.25PO4 cathode with respect to conventional LiFePO4, as well as the remarkable capacity and rate capability of Sn-Fe2O3-C and Sn-C anodes. The stable electrode/electrolyte interfaces, demonstrated by electrochemical impedance spectroscopy, along with proper mass balancing and anode pre-lithiation, allow stable galvanostatic cycling of the full cells. The two batteries, namely Sn-Fe2O3-C/LiFe0.25Mn0.5Co0.25PO4 and Sn-C/LiFe0.25Mn0.5Co0.25PO4, reversibly operate revealing promising electrochemical features in terms of delivered capacity, working voltage and stability, thus suggesting these electrodes combinations as suitable alternatives for an efficient energy storage. (C) 2016 Elsevier Ltd. All rights reserved.

A novel, low cost and environmentally sustainable lithium sulfide-carbon composite cathode, suitably prepared by combining polyethylene oxide (PEO), LiCF3SO3 and Li2S-C powders is here presented. The cathode is characterized in lithium-metal cell employing a solution of LiCF3SO3 salt in dioxolane-dimethylether (DOL-DME) as the electrolyte. Detailed NMR investigation of the diffusion properties of the electrolyte is reported in order to determine its suitability for the proposed cell. The addition of LiNO3 to the electrolyte solution allows practical application in a lithium sulfur cell using the Li2S-C-based cathode characterized by a specific capacity of about 500 mAh g-1 (as referenced to the Li2S mass). The cell holds its optimal performances for over 70 cycles at C/5 rate, with a steady state efficiency approaching 99%. X-ray diffraction patterns of the cell upon operation suggest the reversibility of the Li2S electrochemical process, while repeated electrochemical impedance spectroscopy (EIS) measurements indicate the suitability of the electrode-electrolyte interface in terms of low and stable cell impedance. Furthermore, the EIS study clarifies the activation process occurring at the Li2S cathode during the first charge process, leading to the decrease of the cell polarization during the following cycles. The data here reported shed light on important aspects to be considered for the efficient application of the Li2S cathode in lithium battery.

A CuO-Carbon anode storing lithium through a conversion mechanism is electrochemically studied in cells employing Pyr(14)TFSI-LiTFSI electrolyte [Pyr(14): N-butyl-N-methylpyrrolidinium], [TFSI: bis(trifluoromethanesulfonyl) imide]. The electrode delivers a specific capacity as high as 580 mAhg(-1) with a coulombic efficiency exceeding 98%. The combination of CuO-carbon with a high-voltage LiNi0.5Mn1.5O4 cathode in the ionic liquid electrolyte produces a Li-ion battery with an average operating voltage of 3 V and specific capacity of approximately 120 mAhg(-1). The cell, employing easily-prepared electrodes and a safe ionic liquid electrolyte, represents a good candidate for use in sustainable power sources.

Batteries based on alkali-ions, such as lithium, sodium and potassium are considered the energy storage systems of choice for the next generation applications, such as electrified mobility and supply for renewable energy storage [1]. These systems are, in principle, light, efficient and potentially capable to meet several of the targets characterizing the emerging markets [2]. However, the use of the alkali-metal anode is definitely hindered by severe safety issues, including extreme reactivity with the electrolyte, eventual dendrite formation and cell short-circuit, leading to possible heating, thermal runway and fire [3,4]. Therefore, the severe requirements of the modern society triggered the replacement of the metallic anode by alternative materials characterized by higher safety content, in particular based on carbon [5], alloys [6] and metal oxides [7]. This radical change, partially succeeding in particular for lithium [6], is however still limited to few examples of efficient systems, employed for practical energy storage [1,3], such as Graphite/LCO, Graphite/LFP and Graphite/LNMC. Within this paper we developed a series of lithium-ion and sodium-ion batteries, including metal alloying [8], conversion [9] and graphene [10] anodes, high voltage spinel [11], olivine [12], sulfur [13,14] and oxygen [15] cathodes, and ionic liquid electrolyte [10,16] considered of interest for practical employment as alternative, safe and high energy storage systems for next generation applications. Figure: examples of various sodium and lithium ion cells in which the metal anode has been replaced by alternative materials References [1] D. Larcher, J-M. Tarascon, Nature Chemistry, 2015, 7, 19. [2] J. B. Goodenough, K.-S. Park, JACS, 2013, 135, 116. [3] J.-M. Tarascon, M. Armand, Nature, 2001, 414, 359. [4] V. L. Chevrier, G. Ceder, J. Electrochem. Soc., 2011, 158, 9, A1011. [5] M. Winter, J. O. Besenhard, M. E. Spahr, P. Novak, Adv. Mater., 1998, 10, 725. [6] J. Hassoun, P. Reale, B. Scrosati, J. Mater. Chem, 2007, 17, 3668. [7] J. Cabana, L. Monconduit, D. Larcher, M. R. Palacìn, Adv. Energy Mater., 2010, 22, E170. [8] J. Hassoun, S. Panero, P. Reale, and B. Scrosati, Adv. Mater., 2009, 21, 4808 [9] R. Verrelli, J. Hassoun, A. Farkas, T. Jacob, B. Scrosati, J. Mater. Chem. A, 2013, 1, 15329 [10] J. Hassoun, F. Bonaccorso, M. Agostini, M. Angelucci, M.G. Betti, R. Cingolani, M. Gemmi, C. Mariani, S. Panero, V. Pellegrini, B. Scrosati, Nano Letters, 2014, 14, 4901 [11] R. Verrelli, B. Scrosati, Y.-K. Sun, J. Hassoun, ACS Appl. Mater. Interfaces, 2014, 6, 5206 [12] I. Hasa, J. Hassoun, Y.-K. Sun, B. Scrosati, ChemPhysChem, 2014, 15, 2152 [13] M. Agostini, J. Hassoun, Scientific Reports, 20155, 7591 [14] D.-J. Lee, J.-W. Park, I. Hasa, Y.-K. Sun, B. Scrosati, J. Hassoun, J. Mater. Chem. A, 2013, 1, 5256 [15] G.A. Elia, R. Bernhard, J. Hassoun, RSC Advances, DOI: 10.1039/c4ra17277a [16] D. Di Lecce, S. Brutti, S. Panero, J. Hassoun, Materials Letters, 2015, 139, 329 Figure 1

The development of novel cell configurations represents a key step towards a lithium ion batteries technology able to meet the increasing global energy demand. The search for sustainable and low cost electrode materials exhibiting high specific capacity, efficiency and stability is a longstanding goal of electrochemistry(1). In this respect, the replacement of conventional intercalation anodes with transition metal oxides reacting by conversion mechanisms is a promising, cheap approach to increase the cell specific capacity(2). Furthermore, the exploitation of cobalt-free, manganese spinel-structure materials at the cathode side is expected to overcome the problems deriving from the high cost and relatively low operating voltage of the presently most used LiCoO2 electrodes. Here we propose an alternative lithium ion battery combining an easily prepared, eco-compatible CuO-MCMB (Meso Carbon Micro Beads) conversion anode(3) (Theoretical capacity: 520 mAh g-1) with a high voltage, Li0.85Ni0.46Cu0.1Mn1.49O4 spinel-structure cathode(4) (Theoretical capacity: 146 mAh g-1), using propylene carbonate (PC), LiPF6 electrolyte solution. Both the anode, prepared by high energy ball milling, and the cathode, obtained by co-precipitation and solid state reaction, exhibit optimized morphologies that lead to good electrochemical responses in terms of stability, efficiency and rate-capability. The electrodes structures and morphologies are analyzed by X-ray diffraction and scanning electron microscopy, respectively, while their electrochemical behaviors in cell are investigated by means of potentiodinamic cycling with galvanostatic acceleration (PCGA) and galvanostatic cycling tests at different C-rates. The novel electrode combination here disclosed results in a full lithium ion battery characterized by an operating voltage of 3.4 V, a stable capacity of 90 mA h g-1 and a coulombic efficiency higher than 95% (see Figure below), with estimated gravimetric and volumetric energy densities of about 100 Wh/kg and 220 Wh/l, respectively. The rationale of this cell configuration lies in the employment of sustainable, low-cost and easily prepared electrode materials that make the battery particularly suitable for practical exploitation. (1) D. Larcher, J-M. Tarascon, Nature Chemistry, 2015, 7, 19. (2) J. Cabana, L. Monconduit, D. Larcher and M. Palacìn, Advanced Materials, 2001, 22, E170. (3) R. Verrelli, J. Hassoun, A. Farkas, T. Jacob, B.Scrosati, Journal of Material Chemistry A, 2013,1, 15329. (4) R. Verrelli, B. Scrosati, Y.-K. Sun, J. Hassoun, ACS Applied Materials & Interfaces, 2014, 6, 5206. Figure 1

A novel nanostructured Sn–Fe2O3–C anode material, prepared by high-energy ball milling, is here originally presented. The anode benefits from a unique morphology consisting in Fe2O3 and Sn active nanoparticles embedded in a conductive buffer carbon matrix of micrometric size. Furthermore, the Sn metal particles, revealed as amorphous according to X-ray diffraction measurement, show a size lower than 10 nm by transmission electron microscopy. The optimal combination of nano-scale active materials and micrometric electrode configuration of the Sn–Fe2O3–C anode reflects into remarkable electrochemical performances in lithium cell, with specific capacity content higher than 900 mAh g−1 at 1C rate (810 mA g−1) and coulombic efficiency approaching 100% for 100 cycles. The anode, based on a combination of lithium conversion, alloying and intercalation reactions, exhibits exceptional rate-capability, stably delivering more than 400 mAh g−1 at the very high current density of 4 A g−1. In order to fully confirm the suitability of the developed Sn–Fe2O3–C material as anode for lithium ion battery, the electrode is preliminarily studied in combination with a high voltage LiNi0.5Mn1.5O4 cathode in a full cell stably and efficiently operating with a 3.7 V working voltage and a capacity exceeding 100 mAh g−1.

A conversion-type, NiO-MCMB (mesocarbon microbeads) composite anode prepared by high-energy ball milling is here characterized and tested in lithium half and full cells. An optimized and submicrometric morphology allows the NiO-MCMB electrode to achieve high cell performance and excellent rate capability, that is, delivering specific capacities of 515 and 450mAhg(-1) when cycled at current densities as high as 545 and 1090mAg(-1), respectively. The NiO-MCMB composite anode is studied in a full lithium-ion battery using a high-voltage LiNi0.5Mn1.5O4 electrode that is considered a suitable cathode in combination with conversion-type electrodes. The battery delivers a specific capacity of 90mAhg(-1) with high coulombic efficiency and an average working voltage of 4.1V. The electrochemical results suggest the viability of the alternative cell configuration here adopted for the development of low-cost, high-energy-density lithium-ion batteries.

Herein, we characterize various metal oxide-carbon composites, i.e. CuO-MCMB (mesocarbon microbeads), Fe2O3–MCMB and NiO-MCMB, as anode materials for application in sodium-ion battery. The electrodes, supposed to react through a conversion mechanism, are studied in terms of structure, morphology and electrochemical behavior in sodium cell. The results demonstrate a specific capacity of the order of 100 mAh g−1 for Fe2O3–MCMB and NiO-MCMB, and of about 300 mAh g−1 for CuO-MCMB. The remarkable performance of the latter suggests the copper oxide-based electrode as the preferred anode material for battery application. Indeed, further study aimed to clarify the Na/CuO-MCMB reaction mechanism is performed by ex-situ X-ray diffraction on electrode material cast onto aluminum support. The study suggests a partial conversion reaction for CuO-based anode that is considered suitable candidate in replacement of sodium metal, in efficient and safe Na-ion battery.

In this paper we report a new lithium ion battery (LIB) consisting of a conversion-type, high capacity Fe2O3–Meso Carbon Micro Beads (MCMB) composite anode and a high voltage, Li1.35Ni0.48Fe0.1Mn1.72O4 cathode, prepared by using facile, low cost synthetic pathways. These electrodes have been characterized by a series of techniques including scanning and transmission electron microscopy, X-ray diffraction analysis, potentiodynamic cycling with galvanostatic acceleration (PCGA) and galvanostatic cycling tests in lithium cells at different C-rates. The results show that the Fe2O3–MCMB anode benefits by a composite, sub micrometric morphology and by a stable specific capacity ranging from 800 to 600 mA h g−1, evolving around 0.9 V, while the Li1.35Ni0.48Fe0.1Mn1.72O4 cathode is formed by an agglomeration of micrometric crystals delivering a reversible capacity of about 115 mA h g−1 at a 4.7 V high voltage. The combination of the Fe2O3–MCMB anode with the Li1.35Ni0.48Fe0.1Mn1.72O4 cathode leads to a complete lithium ion battery having an operating voltage of about 3 V, a high coulombic efficiency and a stable capacity of about 100 mA h g−1, which translates into in a theoretical energy density of about 300 Wh kg−1.