Structural and conductivity studies of LiNi_0.5Mn_0.5O₂cathode materials for lithium-ion batteries

Abstract

Layered oxide LiMO 2 (Ni, Co, Mn) have been proposed as cathode materials for lithium-ion batteries. Mainly LiNiO 2 is accepted as an attractive cathode material because of its various advantages such as low cost, high discharge capacity, good reversibility. The LiNi 0.5 Mn 0.5 O 2 powders are synthesized by a sol-gel method using citric acid as a chelating agent. The structure of the synthesized material is analyzed by using XRD, FT-IR and the microstructures of the samples are observed by using FESEM. The intensities and positions of the peaks are in a good agreement with the previous results. The morphological changes are clearly observed as a result of manganese substitution. The Fourier transform infrared (FT-IR) spectra obtained with KBr pellet data reveal the structure of the oxide lattice constituted by LiO 6 and NiO 6 octahedra. The conductivity studies are characterized by (EIS) in the frequency range of 42 Hz to 1 MHz at room temperature to 120°C. The dielectric properties are analyzed in the framework of complex dielectric permittivity and complex electric modulus formalisms. It indicates that the conductivity increases with increasing temperature. The fitting data of EIS plots replicate the non-Debye relaxation process with negative temperature coefficient of resistance (NTCR) behavior.

The double phosphates MIMIIPO4 (MI – Na, K; MII – Mg, Mn, Co, Ni, Zn) – synthesis from chloride melts and characterization

“…Modes at 900 and 720 cm −1 correspond to symmetric and asymmetric stretching vibrations (ν as (POP) and ν s (POP)) of P 2 O 7 ‐groups, respectively. The peaks observed in the range 630–400 cm −1 can be assigned to corresponding deformation vibrations, and also to the stretching vibrations of NiO 6 units .…”

Structural and Morphological Characterization of Mg Doped LiNiO2 Cathode Materials for Lithium-Ion Batteries

“…All the synthesized compounds have the smallest particles and exhibit the small difference in particle size between the large particles and the small particles. The LiNi 0.92 Mg 0.08 O 2 has the small particles and LiNi 0.98 Mg 0.02 O 2 has the largest particles 12,13 .…”

SYNTHESIS, DIELECTRIC AND IMPEDANCE STUDIES OF LiNi1-X-0.02Mg0.02ZnXO2 (X = 0.0 and 0.02) CATHODE MATERIALS FOR LITHIUM-ION BATTERIES.

“…The recommended cathode materials for Li-ion batteries should have a low dielectric constant and high resistance. We observe that the dielectric constant of the synthesized cathode materials is 5.0 x10 3 and 5.0x10 5 for LiNi 1-x-0.02 Mg 0.02 Zn x O 2 (x = 0.0 and 0.02) respectively and they are found to be very small [20][21].…”

“…The discharge capacity of LiNiO 2 measured experimentally is certified to have about 140-150 mAhg -1 due to the synthesis of non-stoichiometric LiNiO 2 . It is difficult to synthesize stoichiometric LiNiO 2 because of the loss of lithium from the host structure during high temperature calcination due to the high vapor pressure of lithium [4][5]. Another typical problem is its capacity fade is observed even for stoichiometrically synthesized LiNiO 2 due to the formation of the NiO 2 phase of the phase transition of the LiNiO 2 structure when charging up to a high voltage (4.0 V vs. Li + /Li) during deintercalation of Li-ions [6][7].…”