Density-Functional Theoretical Study on the Intercalation Properties of Layered LiMO 2 (M = Zr, Nb, Rh, Mo, and Ru)
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Density-Functional Theoretical Study on the Intercalation Properties of Layered LiMO2 ( M = Zr, Nb, Rh, Mo, and Ru) S. P. Singh, M. Tomar, Yasuyuki Ishikawa*, S. B. Majumder**, and R. S. Katiyar** Department of Physics, University of Puerto Rico, Mayagüez, PR - 00681-9016., **Department of Physics, University of Puerto Rico, San Juan, PR - PR – 00931-3343, *Department of Chemistry, University of Puerto Rico, San Juan, PR – 00931-3346,
Abstract: Average Li intercalation potentials were calculated for lithium-4d-transition-metaloxides. The effect on the intercalation voltage of metal substitution was systematically studied by altering the 4d transitional metals M (M= Mo, Nb, Rh, Zr, Ru) in LiMO2 in the α-NaFeO2 structure. Lattice parameters in the layered α-NaFeO2 structure computed in the GGA approximation are in reasonable agreement with experiment. The intercalation potentials and relative formation energies of the fully lithiated LiNi1/3Mn1/3Mo1/3O2, fully delithiated and the intermediate phases, Li1/3Ni1/3Mn1/3Mo1/3O2 and Ni1/3Mn1/3Mo1/3O2 Li2/3Ni1/3Mn1/3Mo1/3O2, were computed by employing a generalized alloy theory. A minute substitution of cationic Mo in LiNiMnO2 was experimentally investigated to examine the effect of the Mo substitution on the electrochemical properties. Introduction: Since the discovery of LiCoO2 [1], a number of theoretical and experimental studies [2-7] have been undertaken in search of economic and environment-friendly cathode materials for lithium ion batteries. LiCoO2, widely used as a commercial cathode material, suffers from drawbacks like high cost and toxicity. LiMnO2 in layered α-NaFeO2 structure is touted to be a promising material due to its low cost, nontoxic nature and high theoretical capacity. Despite its all promises, this material is hard to synthesize and undergoes a phase transformation from layered to spinel upon delithiation as shown by Ceder and coworkers [8]. LiNiO2 is another layered cathode material that has high intercalation voltage and theoretical capacity of 200mAh/g. But it also suffers from thermal instability due to the formation of nickel dioxide [9]. These lithiated transition metal oxides possess α-NaFeO2 layered structure with alternate layer of Li and metal ions occupying the octahedral sites of cubic close-packed oxygen atoms. Various molybdenum oxide phases have also been identified as alkali metal insertion host for use in rechargeable batteries [10, 11]. LiMoO2 in the layered structure has emerged as a promising candidate with a theoretical capacity of 200 mhA/g [6]. Recently a great deal of effort has been expended to synthesize the isostructural mixed-metal cathode materials, such as the LiNi1/3Co1/3Mn1/3O2, for advanced lithium ion batteries [12-16]. Density-functional theoretical calculations have played a dominant role in predicting the structural and electrochemical behavior of cathode materials in recent years [2,12,14]. A major advantage of the computational study is that it provides full control over a number of experimental variabl
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