Magnetic Properties of Li3V2(PO4)3/Li3PO4 Composite

Abstract

Here, we present the investigation of the magnetic properties of Li3V2(PO4)3/Li3PO4 composites, which can be potentially used as a cathode material in lithium-ion batteries. Li3V2(PO4)3/Li3PO4 was synthesized by the thermal hydrolysis method and has a granular mesoporous structure. Magnetic properties of the composite were investigated using magnetometry and electron spin resonance methods. Based on magnetization measurements, the simultaneous existence of the paramagnetic phase with antiferromagnetic interactions between spins of V3+ ions and magnetically correlated regions was suggested. Most probably, magnetically correlated regions were formed due to anti-site defects and the presence of V4+ ions that was directly confirmed by electron spin resonance measurements.

Li3V2(PO4)3 Cathode Material: Synthesis Method, High Lithium Diffusion Coefficient and Magnetic Inhomogeneity

“…The unit cell contains Z = 4 formula units. The obtained lattice parameters are very close to those that were previously reported and can slightly differ depending on the synthesis process and monoclinic axis selection [ 13 , 32 , 33 , 37 , 38 , 39 , 40 , 41 , 42 ]. The structure of LVPO consists of a three-dimensional framework of slightly distorted VO 6 octahedra and PO 4 tetrahedra.…”

“…The second condition for ESR detection from the exited (S = 1) state in the conventional perpendicular state is that the energy of the microwave field should be sufficient for the transition between these sublevels. Based on a set of experimental data given in the literature [ 31 , 45 , 46 ] and our previous works [ 13 , 32 , 33 ], no signal is expected from trivalent vanadium in perpendicular mode for the above reasons, which may exist separately or together. The direct probe of V 3+ via the ESR test was presented in [ 31 ].…”

“…The higher absolute value of the Curie–Weiss temperature in LVPO compared to LVPO/C composite [ 32 ] indicates stronger magnetic interactions in pure LVPO. However, when comparing with Li 3 V 2 (PO 4 ) 3 (92.5 wt.%)/Li 3 PO 4 (7.5 wt.%) composite, one can see close values of the Curie–Weiss temperature: θ CW = −68 K for composite [ 33 ] and θ CW = −59.5 K for LVPO, and therefore, close values of AFM interactions for both samples. The comparison of Curie–Weiss temperature and Curie constant values with the same values for Li 3 V 2 (PO 4 ) 3 (86 wt.%)/Li 3 PO 4 (14 wt.%) composite seems difficult due to the small linear range in the temperature dependence of the inverse magnetic susceptibility to approximate by the Curie–Weiss law ( Figure S5 ).…”

“…In [ 39 ], cyclic voltammograms for carbon composites were provided, and similar measurements for LVP@M-101 composites at different scanning rates of 0.05–0.25 mVs −1 were presented in [ 45 ]. The SEM images reveal that the samples exhibit a more pronounced granular structure with smaller granule sizes compared to LVPO/LPO composites [ 13 , 33 ], synthesized using similar technology. It appears that the presence of salt does not significantly influence the absolute values of specific capacitance, even slightly enhancing it.…”

“…Electron spin resonance (ESR) detects the qualitative and quantitative information of unpaired electrons contained in local atoms or molecules of matter and the structural characteristics of its surrounding environment. NMR is commonly used in the study of light elements such as Li, Na, O and F, while ESR is suitable for the evaluation of transition metals (Fe, Co, Mn, V) and oxygen vacancies and for the characterization of redox processes [ 13 , 31 , 32 , 33 ]. Owing to the ultrahigh sensitivity to magnetization, magnetometry can accurately monitor the magnetic changes caused by electron transfer during electrochemical processes, and it is a powerful tool for investigating conversion or alloy-type alkali metal ion batteries (AMIBs), spin-based devices [ 34 , 35 ] or solid electrolyte interphase characterization by operando magnetometry [ 36 ].…”