Thermal processes in the systems with Li-battery cathode materials and LiPF6 -based organic solutions

Ortal Haik, Francis Susai Amalraj, Daniel Hirshberg, Luba Burlaka, Michael Talianker, Boris Markovsky, Ella Zinigrad, Doron Aurbach, Jordan K. Lampert, Ji Yong Shin, Martin Schulz-Dobrick, Arnd Garsuch

Research output: Contribution to journalArticlepeer-review

12 Scopus citations

Abstract

Thermodynamic instability of positive electrodes (cathodes) in Li-ion batteries in humid air and battery solutions results in capacity fading and batteries degradation, especially at elevated temperatures. In this work, we studied thermal interactions between cathode materials Li2MnO 3, xLi2MnO3 .(1∈-∈x) Li(MnNiCo)O2,LiNi0.33Mn0.33Co 0.33O2, LiNi0.4Mn0.4Co 0.2O2, LiNi0.8Co0.15Al 0.05O2 LiMn1.5Ni0.5O4, LiMn(or Fe)PO4, and battery solutions containing ethylene carbonate (EC) or propylene carbonate (PC), dimethyl carbonate (DMC) or ethylmethyl carbonate (EMC) and LiPF6 salt in the temperature range of 40-400 °C. It was found that these materials are stable chemically and well performing in LiPF6-based solutions up to 60 °C. The thermal decomposition of the electrolyte solutions starts >180 °C. The macro-structural transformations of cathode materials upon exothermic reactions were studied by transmission electron microscopy (TEM), X-ray difraction (XRD) and Raman spectroscopy. Differential scanning calorimetry (DSC) studies have shown that the exothermic reactions in the temperature range of 60-140 °C lead to partial decomposition of both the cathode material and electrolyte solution. The systems thus formed consisted of partially decomposed solutions and partially chemically delithiated cathode materials covered by reactions products. Thermal reactions terminate and this system reaches equilibrium at about 120 °C. It remains stable up to the beginning of the solution decomposition at about 180 °C. The increased content of surface Li 2CO3 is found to significantly affect the thermal processes at high temperature range due to extensive exothermic decomposition at low temperatures.

Original languageEnglish
Pages (from-to)2333-2342
Number of pages10
JournalJournal of Solid State Electrochemistry
Volume18
Issue number8
DOIs
StatePublished - 1 Jan 2014

Keywords

  • Cathodes
  • Chemical reactions
  • DSC
  • Li-ion batteries
  • Thermal decomposition

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