Our current research interests are fully focused in rechargeable battery materials covering a wide spectrum from commercial traditional systems, such as Ni based, to promising alternatives such as Na-ion to fully new concepts as Ca metal. Specific emphasis is set in tailoring structure and microstructure of electrode materials to maximise electrochemical performance and in the development of new materials.
Some of the recent achievements involve elucidating the crystal structure of the nickel battery positive electrode material in the fully charged state, which consists of metastable β-NiOOH. This has been possible through a joint approach involving NMR and FTIR spectroscopies, powder neutron diffraction and DFT calculations. The results confirm that structural changes occur during the β-Ni(OH)2/β-NiOOH transformation in each electrochemical cycle. 
In the field of Na-ion batteries, hard carbons were prepared from different precursors (phenolic resin and commercially available cellulose and lignin) under different pyrolysis and processing conditions using industrially adapted syntheses protocols. The study of their microstructural features enabled to assess that the nature of the precursor and the temperature of pyrolysis are the major factors determining the carbon yield and the surface area, the latter one having a major effect on the useful electrochemical capacity. 
Last but not least, a comparative study of the electrochemical intercalation of Ca2+ and Mg2+ in layered TiS2 using alkylcarbonate based electrolytes was carried out. Reversible electrochemical Ca2+ insertion was assessed both using X-ray diffraction and differential absorption X-ray tomography at the Ca L2 edge. Different new phases are formed upon M2+ insertion, their amount and composition being dependent on M2+ and the experimental conditions. 
Overall, crystal chemistry is a very useful tool in battery research, enabling tailoring structure and microstructure of electrode materials to maximise electrochemical performance for traditional technologies and development of new materials for emerging technologies.
 The nickel battery positive electrode revisited: stability and structure of the beta-NiOOH phase
Journal of Materials Chemistry A 6, 19256-19265 (2018)
 Optimization of Large Scale Produced Hard Carbon Performance in Na-Ion Batteries: Effect of Precursor, Temperature and Processing Conditions,
Journal of the Electrochemical Society 165 (16), A4058-A4066 (2018)
 Electrochemical Intercalation of Calcium and Magnesium in TiS2: Fundamental Studies Related to Multivalent Battery Applications
Chemistry of Materials 30 (3), 847-856 (2018)
Top: Electrochemical profile corresponding to a Ca//TiS2 cell at 100 °C and synchrotron X-ray diffraction patterns XRD collected at different stages of TiS2 reduction and after full reoxidation, with peaks corresponding to new phases formed labelled as 1, 2 and 3. Bottom: Three dimensional Ca distribution representation obtained by differential absorption tomography at the Ca L2 edge. Three Ca regions were identified: “high absorption external Ca” (red) with ∆μ=3.2±0.9 μm-1, “low absorption external Ca” (orange) with ∆μ=1.0±0.3 μm-1 and “intercalated Ca” (pink) inside the TiS2 particle with ∆μ=0.4±0.1 μm-1.
Authors: Deyana Tchitchekova, Alexandre Ponrouch, Roberta Verrelli, Thibault Broux, Carlos Frontera, Andrea Sorrentino, Fanny Barde, Neven Biskup, M. Elena Arroyo-de Dompablo and M. Rosa Palacín.