Low-temperature magnetic properties and high-temperature diffusive behavior ofLiNiO2investigated by muon-spin spectroscopy

Abstract

In order to elucidate the effect of Ni ions in the Li layer on magnetism and Li diffusion of LiNiO 2 , we have measured muon-spin rotation and muon-spin relaxation ͑ + SR͒ spectra for the polycrystalline Li 1−x Ni 1+x O 2 samples with x = 0.02, 0.03, and 0.15. Weak transverse-field-+ SR measurements demonstrated the existence of a bulk ferromagnetic transition at T m =48͑6͒ K for the x = 0.03 sample and 161͑7͒ K for x = 0.15 while the x = 0.02 sample exhibited an antiferromagnetic transition at 18͑4͒ K. Zero-magnetic-field-͑ZF͒ + SR measurements below T m clarified the formation of static ferromagnetic ͑FM͒ order for the x = 0.03 and 0.15 samples but only a highly disordered antiferromagnetic ͑AF͒ order for the x = 0.02 sample. Therefore, the variation in the low-T magnetism with x is most unlikely due to the change in the concentration of an AF NiO-type domain or an FM Ni-rich cluster but likely due to a homogeneous change in the whole system. In the paramagnetic state, ZF-and longitudinal-field-+ SR spectra exhibited a dynamic nuclear field relaxation. From the temperature dependence of the field fluctuation rate, a diffusion coefficient of Li + ions ͑D Li ͒ at 300 K was estimated about 0.39͑3͒ ϫ 10 −11 cm 2 / s for the x = 0.02 sample and 0.12͑7͒ ϫ 10 −11 cm 2 / s for x = 0.15. On the other hand, the related compound, LiCrO 2 , did not show any diffusive behavior even at the highest temperature measured ͑=475 K͒. Considering the hindrance of diffusion by Ni in the Li + diffusion plane and the fact that LiCrO 2 is electrochemically inactive, the estimated D Li is thought to be very reasonable for the positive electrode material of Li-ion batteries. Furthermore, at low temperatures where the Li + ions are static, the internal magnetic field was still found to be fluctuating, due to a dynamic local Jahn-Teller distortion of the Ni 3+ ions in a low-spin state with S =1/ 2͑t 2g 6 e g 1 ͒.

Probing magnetic order in LiMPO4(M=Ni, Co, Fe) and lithium diffusion in LiBaker1, Franke2, Pratt3 et al. 2011Phys. Rev. B446300View full textAdd to dashboardCite

“…In studies of lithium-containing battery materials it has been usual to multiply the dynamic Gaussian Kubo-Toyabe function by an exponential relaxation to eliminate any magnetic contribution to the relaxation. 27,28,31,33 This does not lead to reliable fits to our raw data either. A consistently better quality of fit was obtained by applying Keren's analytic generalization of the Abragam function appropriate for µSR, 47 multiplied by a temperature-independent relaxation rate fixed for each sam-ple:…”

“…6 (a) show the trend observed in the vast majority of lithium-containing battery materials investigated to date for x = 0.9, where a low-temperature plateau is followed by a smooth decrease to a high-temperature plateau. 27,28,31,33 In the x = 0.8 and 1 samples there is a peak at around the temperature where the low-temperature plateau ends in the x = 0.9 sample. The values of ∆ ∼ 0.…”

“…27 Lithium diffusion is a process that provides such a perturbation and µSR has now been applied to studying it in a wide range of battery cathode materials: Li 30 Li 3−x−y Ni x N, 31 , Li x CoO 2 , 27,32 and LiNiO 2 . 33 Of these, the studies on Li x CoO 2 have been the most extensive and found that the lithium diffusion rate in this compound is well suited to the timescale probed by µSR. Similar studies on a different timescale can be carried out using NMR.…”

Charge disproportionation and Jahn-Teller distortion in LiNiO2and NaNiO2: A density functional theory study

“…Both the data of ref [11] and the more recent μSR data 42 suggest that the ferromagnetic and antiferromagnetic states are close in energy. The ESR data suggests that the dominant interactions are ferromagnetic, but that strong antiferromagnetic fluctuations exist between 13 K and 50 K. However, the saturation of the linewidth suggests that the antiferromagnetic correlations do not propagate below 10 K. The detailed interpretation of the behaviour in terms of orbital frustration is not consistent with later neutron 5 and electron diffraction 12 work.…”

Ion Diffusion in Solids Probed by Muon-Spin Spectroscopy

“…This is a highly unsatisfactory situation, since D Li is one of the primary parameters that govern the charge and discharge rate of a Li-ion battery, particularly in the case of future solid state batteries. We have, therefore, attempted to measure D Li for layered lithium-transition-metal-oxides with µ + SR since 2005 [14][15][16][17][18][19][20]. Muons do not feel fluctuating magnetic moments at high T , but instead sense the change in nuclear dipole field due to Li diffusion.…”