Electrochemical Characterization of Li_1.07V_0.83Fe_0.1O₂ ANODE Material for Li-ION Batteries

Abstract

INTRODUCTION Recently a novel compounds based on layered LiV 1-y M y O 2 (M = Li, Fe, Cr) were found to be promising anode materials for Li-ion technology [1-3], as they exhibit long low-voltage plateau vs. metallic lithium, and higher volumetric capacity than commonly used graphite-based anode materials. This work presents synthesis and evaluation of electrochemical properties of Li 1.07 V 0.83 Fe 0.1 O 2 , in particular open circuit voltage (OCV) and XRD analysis at different discharge (lithium content) stages. EXPERIMENTAL Li 1.07 V 0.83 Fe 0.1 O 2 was synthesized using a high-temperature solid-state reaction method with Li 2 CO 3 , V 2 O 3 and Fe 2 O 3 taken as substrates. Stoichiometric amounts of reactants were milled in a high efficiency mill. Obtained powder was pressed into pellets and sintered in two steps: 1) at 800 °C for 10 h in Ar and 2) at 1050 °C for 12 h in 5 vol.% of H 2 in Ar, followed by quenching. Structural studies were performed in 10-110° range with CuKα radiation using Panalytical Empyrean diffractometer, followed by Rietveld refinement of identified structures. Electrical conductivity was measured using 4-probe AC technique in -60°C to 70°C temperature range. Electrochemical studies were done in Li/Li + / Li 1.07 V 0.83 Fe 0.1 O 2 cells constructed using CR2032-type containers. 1M solution of LiPF 6 in EC/DEC (in 1:1 ratio) was used as the electrolyte. For the positive electrode powder of active material was used (mass ≈ 50mg). OCV values were assumed as voltages of batteries after discharging to designated compositions followed by at least 24 h of relaxation. RESULTS AND DISCUSSION XRD analysis shown that the material is single phase and exhibits layered R-3m α-NaFeO 2 type structure. Electrical conductivity values are almost two order of magnitude higher than for materials with no iron substitution. Discharge characteristics upon load shown step-like character, distinctly different than in Li 1.07 V 0.93 O 2 with shorter and right-shifted low voltage plateau. ACKNOWLEDGMENT This work was supported by NCN grant no. NCN 2011/02/A/ST5/00447. REFERENCES [1] A. R. Armstrong, C. Lyness, P. M. Panchmatia, M. S. Islam, P. G. Bruce, Nature Mater. 10 (2011) 223-229 [2] W.-T. Kim, Y. U. Jeong, H. C. Choi, Y. J. Lee, Y. J. Kim, J. H. Song, J. Power Sources 221 (2013) 366-371. [3] X. Ma, G. Hautier, A. Jain, R. Doe, G. Ceder, J. Electrochem. Soc., 160 (2013) A279-A284.