Janina Molenda

Abstract:

The author of this work basing on her own investigations of Li_xMO₂ cathode materials ( M=Ni, Co, Mn, Cu) has demonstrated that the chemical disorder influenced on electronic structure of these materials plays an important role in the electrochemical intercalation process [1].
The paper reveals correlation between chemical disorder, crystal and electronic structure, transport and electrochemical properties of layered Li_xCoO₂, Li_xNi_1-y-zCo_yCu_zMn_0.1O₂ and Na_xCoO_2-y [2] cathode materials and explains of apparently different character of the discharge/charge curve in those systems. Comprehensive experimental studies of physicochemical properties of Li_xNi_1-y-zCo_yCu_zMn_0.1O₂ and Na_xCoO_2-y cathode materials (XRD, electrical conductivity, thermoelectric power) are supported by electronic structure calculations performed using the Korringa-Kohn-Rostoker method [3] with the coherent potential approximation (KKR-CPA) to account for chemical disorder. It is found that even small O defects (~1%) may significantly modify DOS characteristics via formation of extra broad peaks inside the former gap leading to its substantial reduction. Moreover, these DOS peaks of “defects” strongly evolve with Li and Na contents, actually leading to the overall reducing of the gap and to even the pseudogap.
The battery on the base on the developed LiNi_0.9-y-zCo_yMn_0.1Cu_zO₂ cathode materials are characterized by high potential, high capacity and high rate capability guaranteeing high energy and power densities.
This work was funded by the National Science Centre Poland (NCN) under the “OPUS 12 programme on the basis of the decision number UMO- 2016/23/B/ST8/00199.

REFERENCES:
[1] J.Molenda, A.Milewska, W. Zajac, M.Rybski, J. Tobola, Phys. Chem. Phys. Chem. 19, (2017)25697.
[2] J. Molenda, D. Baster,M. Molenda, K.Świerczek, J. Tobola, Anomaly in the electronic structure of the NaxCoO2-y cathode as a source of its steplike discharge curve, Physical Chemistry Chemical Physics,16 (2014)14845-14857.
[3] A. Bansil, S. Kaprzyk, P. E. Mijnarends and J. Tobola, Phys., Rev. B: Condens. Matter Mater. Phys., 60 (1999) 13396.