DFT Study on Gas Phase Decomposition of Ethylene Carbonate in the Presence of LiPF6, LiBF4, PF6-, and BF4-
Farrel Dzaudan Naufal, Elbert Timothy Lasiman, Az Zahrah Fitriana Syafira, Muhammad Fadhlan Anshor, Dicky Setianto, Achmad Ubaidillah, Bernardus Rendy, Ganes Shukri, Adhitya Gandaryus Saputro

Teknik Fisika ITB

Abstract

Battery degradation by electrolyte decomposition has been a well-known problem that attracts much attention, especially on its mechanism. The most common electrolyte on lithium-ion batteries is ethylene carbonate (EC) which acts as a solvent for lithium salts. In this work, we investigate the decomposition mechanism of EC in the presence of LiPF6, LiBF4, and their delithiated counterpart by means of first-principles density functional theory (DFT) calculations. We found that the energy barrier on BF4- anion presence is lower than PF6- anion presence about 0.42 eV (with Li+) and 0.22 eV (without Li+), suggesting that BF4- anion presence reduces EC stability more than PF6- anion. In both salt anion cases, the presence of Li+ ion increases the activation energy (0.79 eV on PF6-, 0.59 eV on BF4-) but decreases enthalpy change significantly (1.58 eV on PF6-, 1.43 eV on BF4-). While Li+ ion causes forward reaction rate to be slower, the relative forward-reverse rate increases drastically. This suggests that Li+ presence destabilizes the EC thus making it easier to decompose.

Keywords: lithium-ion battery- electrolyte decomposition- ethylene carbonate- Li-salt -density functional theory

Topic: Nanomaterial and Nanotechnology