Article

Synthesis and crystal chemistry of the NaMSO4F family (M = Mg, Fe, Co, Cu, Zn)

ChemInform 01/2012; 14(1):15-20. DOI: 10.1016/j.solidstatesciences.2011.09.004

ABSTRACT Our work in metal fluorosulphate chemistry, which was triggered by the discovery of the tavorite-phase of LiFeSO4F, has unveiled many novel Li- and Na-based phases with desirable electrochemical and/or transport properties. Further exploring this rich crystal chemistry, we have synthesized the Na-based magnesium, copper and zinc fluorosulphates, which crystallise in the maxwellite (tavorite-like framework) structure just as their Fe and Co counterparts, which were previously reported. These phases show ionic conductivities in the range of ∼10−7 S cm−1 or ∼10−11 S cm−1 depending upon their synthesis process and no reversible electrochemical activity versus Na.

1 Follower
 · 
281 Views
  • [Show abstract] [Hide abstract]
    ABSTRACT: The ever-increasing demand for high-performing, economical, and safe power storage for portable electronics and electric vehicles stimulates R&D in the field of chemical power sources. In the past two decades, lithium-ion technology has proven itself a most robust technology, which delivers high energy and power capabilities. At the same time, current technology requires that the energy and power capabilities of Li-ion batteries be ‘beefed up’ beyond the existing state of the art. Increasing the battery voltage is one of the ways to improve battery energy density; in Li-ion cells, the objective of current research is to develop a 5-volt cell, and at the same time to maintain high specific charge capacity, excellent cycling, and safety. Since current anode materials possess working potentials fairly close to the potential of a lithium metal, the focus is on the development of cathode materials. This work reviews and analyzes the current state of the art, achievements, and challenges in the field of high-voltage cathode materials for Li-ion cells. Some suggestions regarding possible approaches for future development in the field are also presented.
    Advanced Energy Materials 08/2012; 2(8-8):922–939. DOI:10.1002/aenm.201200068 · 14.39 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Vying for newer sodium-ion chemistry for rechargeable batteries, Na2FeP2O7 pyrophosphate has been recently unveiled as a 3 V high-rate cathode. In addition to its low cost and promising electrochemical performance, here we demonstrate Na2FeP2O7 as a safe cathode with high thermal stability. Chemical/electrochemical desodiation of this insertion compound has led to the discovery of a new polymorph of NaFeP2O7. High-temperature analyses of the desodiated state NaFeP2O7 show an irreversible phase transition from triclinic (P1̅) to the ground state monoclinic (P21/c) polymorph above 560 °C. It demonstrates high thermal stability, with no thermal decomposition and/or oxygen evolution until 600 °C, the upper limit of the present investigation. This high operational stability is rooted in the stable pyrophosphate (P2O7)4– anion, which offers better safety than other phosphate-based cathodes. It establishes Na2FeP2O7 as a safe cathode candidate for large-scale economic sodium-ion battery applications.
    ChemInform 08/2013; 25(17):3480–3487. DOI:10.1021/cm401657c
  • [Show abstract] [Hide abstract]
    ABSTRACT: Compounds within the solid solution (Co1–xNix)3Sb4O6F6 were prepared by the hydrothermal method. The compounds crystallize in the noncentrosymmetric cubic space group I 4̅3m with unit cell parameters a = 8.176(1) Å for M = Co and a = 8.0778(1) Å for M = Ni. The crystal structure is made up by corner sharing [MO2F4] octahedra via the fluorine atoms. [Sb4O6E4] supertetrahedra (T2) consisting of four [SbO3E] groups (E being the stereochemically active lone-pair on Sb) that share O atoms with the [MO2F2]n network. Magnetic ordering phenomena are observed with two characteristic temperatures, TN and T*, in the range from 67 to 170 K, that evolve gradually with composition and collapse for M = Co (x = 0) to one transition. TN is assigned to a transition into a long-range ordered antiferromagnetic phase, and T* marks a temperature in the range of 45 to 65 K where field cooled (FC) and zero field cooled (ZFC) susceptibility splits. The latter is tentatively attributed to a canting of the spin moments.
    Chemistry of Materials 05/2014; 26(12). DOI:10.1021/cm500339z · 8.54 Impact Factor