Structural and dielectric studies of LiNiPO₄and LiNi_0.5Co_0.5PO₄cathode materials for lithium-ion batteries

Abstract

Olivine-type LiNiPO 4 has been considered as a most competitive positive electrode active material for lithium-ion batteries. In the present paper, the LiNiPO 4 and Co-doped LiNi 0.5 Co 0.5 PO 4 are synthesized by solid-state reaction method under air atmosphere. All the X-ray diffraction peaks of both the compounds are indexed and it is found that the samples are well crystallized in orthorhombic olivine structure belonging to the space group Pnma. The crystallite size is calculated from the Scherrer formula and it is found to be 6.918 and 4.818 nm for pure and doped samples, respectively. The surface morphology and grain sizes of the materials are investigated through scanning electron microscope. Presence of preferred local cation environment is understood from Fourier transform infrared spectroscopy (FTIR) studies. The conductivity and dielectric analysis of the samples are carried out at different temperatures and frequencies using the complex impedance spectroscopy technique. The electrical conductivity of LiNi 0.5 Co 0.5 PO 4 is higher than that of pure LiNiPO 4 .

Mechanism of Na-Ion Conduction in the Highly Efficient Layered Battery Material Na2Mn3O7

“…The linear behaviour of the Arrhenius plot (Figure 3d) reveals a thermally activated conduction process. With increasing temperature, the dc conductivity value increases from ~ 10 -5 Sm -1 at 353 K to ~ 10 -1 Sm -1 at 713 K. The linear fitting to the curve reveals two different slopes corresponding to activation energies 0.161 (7) eV and 0.377 (6) eV for the temperature regions 383-518 K and 518-713 K, respectively. The derived activation energy Ea = 0.161 eV is in good agreement with the value of 0.18 eV predicted by the earlier reported DFT calculation.…”

“…The Arrhenius plots of the peak frequencies ν α and ν m of the imaginary parts of polarizability (α″) and modulus (M″) overlap with each other for the entire temperature range (Figure 8b), suggesting a thermally activated conduction process. The activation energies are found to be 0.162(5) and 0.347 (6) eV for the temperature ranges 383−518 and 518−713 K, respectively. The activation energies are the same as the values obtained from the dc conductivity and the electric modulus studies.…”

“…[17][18] The inset of Figure 1a highlights the broad peaks of the measured pattern (points) and compare with the pattern (black line) of the stacking fault free ideal structure of Na2Mn3O7 (ICSD_collcode5665). The Bragg peaks (1-10) and (2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20) are sharp whereas, the Bragg peaks (-1-21), (012), (-2-11), (0-23), (-203), (-122), (3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20), (-301), (1-33), (1-41), , (3)(4)(5)(6)(7)(8)(9)(10)(11)…”

“…Various approaches via structure modification, introduction of defects, selective doping with transition metal ions, etc., have been put forward to improve the ionic conductivity. 6 The electrical response is dictated by the microstructural network. The understanding of the microscopic conduction mechanism is a key requirement for the design of high-performance battery materials and the advancement of battery technology.…”

Electrical, dielectric properties and study of AC electrical conduction mechanism of Li 0.9 □ 0.1 NiV 0.5 P 0.5 O 4

“…Olivine-type LiNiPO 4 [5,6] has been considered as a most competitive positive electrode active material for lithium-ion batteries. The previously studied oxide LiNiV 0.5 P 0.5 O 4 [7], which belongs to the olivine-type family, is also a promising cathode material for application in lithium-ion batteries.…”