A.C. Conductivity and Electric Modulus Studies of LiNi1/3Mn1/3Co1/3O2 Cathode Thin Films Grown by Pulsed Laser Deposition Technique

K.H. Prasad, R. Arumugam, E.S. Srinadhu, N. Satyanarayana
Pondicherry University,
India

Keywords: pulsed laser deposition, nanocrystalline LiNi1/3Mn1/3Co1/3O2 thin films, XRD, Raman, AFM, DC & AC conductivities, electric modulus

Summary:

Cathode, anode, and electrolyte materials are the major parts of the lithium batteries, of which, cathode material plays an important role in lithium battery technology. Recently, LiNi1/3Co1/3Mn1/3O2, which is composed of divalent Ni, tetravalent Mn, and trivalent Co, has received considerable attention due to the high capacity associated with the Ni2+/4+ and Co3+/4+ redox couples and its thermal and structural properties supported by tetravalent Mn, which are superior to those of conventional LiCoO2. The LiNi1/3Mn1/3Co1/3O2 (LNMCO) is the most widely used cathode materials in lithium-ion battery technology, due to its advantages of exhibiting high energy density, high discharge capacity, good reversibility during the oxidation and reduction process, etc. Thin film lithium-ion micro-batteries have gained so much importance as micro-power sources to the most of the portable electronic gadgets, implantable medical devices, smart cards, micro-robot, bio-chips, nano-electro-mechanical systems (NEMS), and micro-electro-mechanical systems (MEMS) etc., devices. In the present paper, lithium-rich layer-structured LiNi1/3Co1/3Mn1/3O2 (LNMCO) cathode thin films grown on the silicon (Si) (100) substrate by pulsed laser deposition technique at a substrate temperature of 500 oC under different oxygen partial pressures from 50 mTorr to 300 mTorr. Crystalline phase, structure and surface morphology of all the grown LNMCO thin films were investigated by using X-ray diffraction (XRD), Raman spectroscopy (RS) and atomic force microscopy (AFM) respectively. DC & AC conductivities and electric modulus properties were studied by analyzing the measured impedance data. Fig.1. shows the AC conductivity versus frequency plots obtained at 298 K of LNMCO thin films grown under various oxygen partial pressures from 50 mTorr to 300 mTorr and substrate temperature kept at 500 oC. Fig.2. shows the imaginary part of the electric modulus (M'') versus log(ω) plots obtained at 298 K of LNMCO thin films grown under various oxygen partial pressures from 50 mTorr to 300 mTorr and substrate temperature kept at 500 oC. From the analysis of the measured impedance data, the electrical conductivities of the LNMCO thin film samples grown at 298 K under different oxygen partial pressures 50 mTorr, 200 mTorr and 300 mTorr were respectively found to be 5.40 x 10-7 S cm-1, 3.28 x 10-6 S cm-1and 7.28 x 10-7 S cm-1. Detailed results will be presented and discussed.