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thesis and Electrochemical Analysis of Li3Ti0.75(MoO4)3 Phase with Lyonsite Structure D. Saritha* Department of Chemistry, Chaitanya Bharathi Institute of Technology, Hyderabad, 500075 India *e-mail: [email protected] Received July 19, 2019; revised October 10, 2019; accepted December 10, 2019

Abstract—Li3Ti0.75(MoO4)3 compound crystallizes in lyonsite type structure. The structure was prepared by the solid state reaction method. Electrochemical lithium insertion was performed into sample for the first time. Preliminary studies were carried out to analyze the sample as electrode material for Li-ion batteries. The electrochemical charge discharge curves shows insertion of 4.8Li is obtained in sample when discharged to 1.5 V and extraction of 3.3Li is observed during charge. A reversible capacity of 112 mA h/g is observed after 25 cycles. Keywords: electrochemical studies, electrode material, Li3Ti0.75(MoO4)3, XRD, lithium insertion, capacity, charge–discharge studies DOI: 10.1134/S1023193520080054

INTRODUCTION LiCoO2 and LiMn2O4 are the familiar cathode materials for Lithium ion batteries [1, 2]. Low price, better electrochemical results inspire the scientists to explore the poly anionic compounds as option to the positive electrode materials. Olivine LiFePO4, nasicon Li3Fe2(PO4)3, Li2Ni2(MoO4)3 and Li2Co2(MoO4)3, Fe2(MoO4)3 are the familiar examples of ploy anionic compounds which considered as electrode materials [3–6]. The benefit of using the molybdates and vanadates groups in polyanionic compounds is thanks to the redox couples of Mo6+/Mo4+ and V5+/V4+ as well to the structural stabilizers through cycling while compared to Sulphates and phosphates groups. Consequently molybdates and vanadates groups are able to offer capacity [7–9]. This leads to high theoretical specific capacity. A variety of Titanium based electrode materials are considered as worthy negative electrode material for Li-ion batteries owing to the good reversibility of the Ti4+/3+ redox couple [10, 11]. Based on all above considerations, Titanium and Molybdenum based oxides are considered as effective positive electrodes [7–11]. Li3Ti0.75(MoO4)3 crystallizes in lyonsite type structure with orthorhombic system. It has four atoms per unit cell. Lyonsite structure belongs to the latest category of oxides. The calculated lattice parameters of this compound matches fine with the literature. The crystal structure of Li3Ti0.75(MoO4)3 is shown in Fig. 1. The structure consists of one LiO6 trigonal prismatic site enclosed by two dissimilar isolated MoO4 tetrahedra [12, 13]. Pseudo hexagonal

tunnels are produced by connecting edge—sharing LiO6 trigonal prisms and (Li/Ti)O6 octahedra along the a-axis. In recent times, polyanion compounds like Li3V(MoO4)3 [14], Li3Fe(MoO4)3 [15] and Li2Ni2(MoO4)3 [16] have been reported as electrode materials for Li ion batteries. Li insertion behavior into Li3Ti0.75(MoO4)3, a new type lyonsite compound will be discussed in this manuscript for the first time. Structure of Li3Ti0.75(MoO4)3 and redox couples of Ti4+/Ti3