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Effect of titanium substitution in P2-Na2/3Co0.95Ti0.05O2 cathode material on the structural and electrochemical properties Noha Sabi, Angelina Sarapulova, Sylvio Indris, Helmut Ehrenberg, Jones Alami, and Ismael Saadoune ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.7b11636 • Publication Date (Web): 03 Oct 2017 Downloaded from http://pubs.acs.org on October 5, 2017
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ACS Applied Materials & Interfaces
Effect of Titanium Substitution in P2-Na2/3Co0.95Ti0.05O2 Cathode Material on the Structural and Electrochemical Properties Noha Sabi1,2, Angelina Sarapulova3, Sylvio Indris3, Helmut Ehrenberg3, Jones Alami 2 and Ismael Saadoune1,2* 1
LCME, FST Marrakesh, University Cadi Ayyad, Av. A. Khattabi, BP 549, 40000, Marrakech, Morocco
2
Materials Science and Nano-engineering Department, Mohammed VI Polytechnic University, 43150,
Ben Guerir, Morocco 3
Institute for Applied Materials (IAM), Karlsruhe Institute of Technology (KIT), P.O. Box 3640, 76021
Karlsruhe, Germany
ABSTRACT: The worry about lithium supply has supported the development of research on sodium batteries. Sodium ion batteries are regarded to be the next generation energy storage devices thanks to the generous resources of Na. In spite of that, structural changes in the electrode materials remain the main challenge of this storage technology. NaCoO2 was widely investigated as the competitive candidate for LiCoO2. It has been found that the electrochemical cycling curves of this material present numerous potential steps as a result of electronic transitions and/or structural ordering. From this stand point, this paper reports a novel cathode material, Na2/3Co0.95Ti0.05O2 where 5% of cobalt was replaced by Ti, prepared via a facile solid-state route. The sodiation/desodiation mechanism of this layered material was investigated. The Na//Na2/3Co0.95Ti0.05O2 exhibits a first initial capacity of 119 mAh/g in the potential window 2-4.2V with less potential jumps in the potential vs capacity curve compared to NaCoO2. Genuinely, the electrochemistry of this material demonstrated a reversibility upon insertion/desinertion process with a low polarization. In-situ synchrotron investigations on Na2/3Co0.95Ti0.05O2 reveal the occurrence of reversible ordered phases. Ex-situ MAS-NMR disclosed different environment around sodium starting from the pristine state to the end of charge. KEYWORDS: Na-ion batteries, Na0.66Co0.95Ti0.05O2, In-situ synchrotron XRD, NMR, P2 structure
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Introduction The interest for renewable and cleaner energy such as solar and wind power has attracted a significant attention in recent years, as the incremental depletion of fossil fuels is foreseen and notably their hostile impact on the environment is recognized1. For this purpose, the necessity for efficient, cost effective, energy storage devices have become crucial2. World-wide technology is based on lithium ion batteries. They are powering the majority of mobile devices such as laptops, mobile phones, tablets, hybrid and plug in hybrid vehicles thanks to their high gravimetric and volumetric energy3 It turns out that lithium, the main component of this technology is regarded to be non-abundant and unevenly distributed in the earth crust which will drive up the prices in the future. However, the demand for this technology is exponentially increasing which has disclosed a huge challenge to the electrochemical research community to find a solution to face this lack4. Sodium has attracted a wide attention, owing to its safety, unlimited and inexhaustible resources everywhere and therefore its low cost (4th most abundant element in the earth crust)5. However, even if sodium has a large ionic radius (1.02) in comparison to lithium (0.76), it displays similar characteristics and compatibilities as lithium, as they are located in the same group in the periodic table, such as the electropositive nature6. Beside this, sodium has the tendency to form in layered oxides7 and offers the advantage of non-alloying reaction towards aluminum which contributes to the minimization of the technology cost8. Since 2010 many novel compounds regarding sodium electrode materials have been explored in order to come up with the suitable one to be the next generation in sodium-ion batteries (SIBs)4,9. Layered oxides with the general formula NaxMO2, have attracted significant attention thanks to their high capacity and rate capability, the open path for sodium ion diffusion and the ability to prevent cation mixing4. The polymorphs of layered oxides can be classified into P2, stable when the sodium stoichiometry is typically 0.6
