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Lecture

Thermochemistry of selected compositions in the LiNiO2-LiCoO2-LiMnO2 system as promising lithium ion battery cathode materials

Tuesday (27.09.2016)
15:15 - 15:30
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In recent years, rechargeable lithium ion batteries have become significant power sources ‎for portable electronics, electric vehicles and large-scale grid storage as a response to an ‎increasing worldwide demand for high energy density batteries. As one of the most ‎important components in a battery, cathode materials have been highly investigated in ‎recent years. ‎

The layered lithium mixed transition metal oxides with the general formula of ‎LiNixMnyCozO2 (x+y+z=1) are promising intercalation type active materials for lithium ion ‎batteries, with a theoretical capacity of approximately 280 mAh/g. These so-called NMC ‎materials offer higher capacities, lower cost, and improved safety compared to LiCoO2 ‎and are particularly attractive for applications in electric vehicles and grid storage.‎

Although the electrochemical behavior of many promising compositions in the NMC ‎system is to some extent investigated, there are not many studies devoted to the ‎measurement of their thermochemical properties. The enthalpies of formation of ‎LiNi1−xCoxO2 compounds were determined by Wang et al. [1] using high temperature ‎oxide solution calorimetry and the enthalpy of formation of LixNi1/3Mn1/3Co1/3O2 and its ‎delithiated phases were measured by Idemoto et al. [2] using acid solution calorimetry. ‎The aim of the present study is therefore to determine the enthalpy of formation of ‎selected compositions in the NMC system, including the technologically relevant NMC111 ‎and NMC442 compositions, by high temperature oxide drop solution calorimetry. ‎

High temperature oxide melt drop solution calorimetry was performed on samples ‎synthesized by the sol-gel method. In addition, the thermal stabilities of different ‎compositions were studied using simultaneous differential thermal analysis/ ‎thermogravimetric analysis to investigate possible decomposition reactions. The chemical ‎compositions of the NMC samples were measured by ICP-OES (inductively coupled ‎optical emission spectroscopy). Powder X-ray diffraction (XRD) was also performed to ‎determine phase impurities and lattice parameters of the respective compounds.‎

The thermochemical data obtained in this work could be used as valuable input data for ‎the development of CALPHAD-based thermodynamic descriptions of the Li–Ni-Mn-Co–‎O system, which can then be used to calculate open circuit voltages and coulometric ‎titration curves based on the Gibbs free energy descriptions of the assessed phases in the ‎multi-component systems.‎

Speaker:
Maryam Masoumi
Karlsruhe Institute of Technology (KIT)
Additional Authors:
  • Dr. Damian Cupid
    Karlsruhe Institute of Technology
  • Dr. Thomas Reichmann
    Karlsruhe Institute of Technology
  • Prof. Hans Jürgen Seifert
    Karlsruhe Institute of Technology