Electrolyte safety

  • Thermal stability of solvents w/LiPF\(_6\): DMC>EMC>EC>DEC

  • DEC found to be particularly unstable, with the most flammable products.

  • Typical stability window of organic electrolytes:

    • \(E_g \approx 3V\)
    • HOMO \(4.3V\) below Li ref electrode.
      • Meaning Graphite anode is outside stability window(higher \(\mu_A\) than LUMO of e-lyte)
      • Degrades e-lyte on anode. Mitigated by SEI.

When pure electrolyte:

  • EMC and DMC only evaporates, no combustion upto 400\(^\circ C\)
  • DEC and EC starts decomposing at 300\(\^circ\)C and 180\(^\circ\)C

When 1.2M LiPF\(_6\):

  • DMC only evaporates, no combustion upto 400\(^\circ C\)
  • EMC has small decomp at 180\(^\circ\)C
  • DEC and EC starts decomposing at 1600\(\^circ\)C and 200\(^\circ\)C

DEC:

  • Produces the lowest amount of CO\(_2\), and the highest amount of H\(_2\), ethane and propane. DMC:
  • Highest CO\(_2\) production: Lowest flammable gas production.
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