Multiscale electronic transport in Li1+xNi1/3−uCo1/3−vMn1/3−wO2: a broadband dielectric study from 40 Hz to 10 GHz

• Published in: Physical chemistry chemical physics : PCCP Vol. 15; no. 45; pp. 1979 - 19798
• Main Authors: Seid, K. A, Badot, J. C, Dubrunfaut, O, Caldes, M. T, Stephant, N, Gautier, L, Guyomard, D, Lestriez, B
• Format: Journal Article
• Language: English
• Published: Cambridge Royal Society of Chemistry 01.01.2013
• Subjects: Applied sciences; Chemistry; Direct energy conversion and energy accumulation; Electrical engineering. Electrical power engineering; Electrical power engineering; Electrochemical conversion: primary and secondary batteries, fuel cells; Exact sciences and technology; General and physical chemistry; Surface physical chemistry; Lithium battery; Electrodes; Brownian motion; Particle; Polarization; Particle size; Conductivity; Low frequency; Interface; Powder; Drop; Dielectric relaxation
• ISSN: 1463-9076; 1463-9084
• DOI: 10.1039/c3cp52384e

This work is the first detailed study concerning the multiscale electronic transport and its temperature dependence in the LiNi 1/3 Co 1/3 Mn 1/3 O 2 (NMC) family, high-capacity electrode materials for lithium ion batteries. Powders with two different mean cluster sizes (3 μm and 10 μm) but the same particle sizes (0.4 to 1.3 m) were measured. The detailed formula of the studied compound is Li 1.04 Ni 2+ 0.235 Ni 3+ 0.09 Mn 4+ 0.315 Co 3+ 0.32 O 2 . Different electrical relaxations are evidenced, resulting from the polarizations at the different scales of the powder architecture. When the frequency increases, three dielectric relaxations are detected in the following order due to: (a) space-charge polarization (low-frequency range) owing to the interface between the sample and the conductive metallic layer deposited on it; (b) polarization of NMC clusters (micronic scale) induced by the existence of resistive junctions between them; and (c) polarization of NMC particles (at sub-micronic scale) induced by resistive junctions between them. High interatomic level conductivity of about 20 S m 1 was evidenced and attributed to the contribution of the extended states and to a Brownian motion of the charge carriers with mean free path similar to the lattice constant. The ratio between sample and local conductivity is more than 10 5 . The large conductivity drop of 3 to 4 orders of magnitude is observed from the particle to the cluster scale. A very large number of charge carriers are blocked by the interparticle junctions within the clusters. The conductivity drop from the cluster to the sample scale is comparatively very small, owing to the dense architecture of the NMC sample in which the spherical clusters are very piled up on each other. Broadband dielectric spectroscopy (40 Hz-10 GHz) on Li 1.04 Ni 2+ 0.235 Ni 3+ 0.09 Mn 4+ 0.315 Co 3+ 0.32 O 2 reveals polarizations from interatomic to macroscopic scale.