Potential vs Capacity of various compounds

I was reading some literature when i came across the following figure and was wondering if someone could help explain it to me. I see on the vertical axis it is potential vs Li/Li+ and see that Oxides are at ~1.2V since the potential of lithium ion batteries are ~4V and it is a transition metal oxide are they talking about other oxides? I am assuming by potential they mean Reduction potential? Graphite is at ~0.2V Silicon at~0.3V and TiO2~1.5V but they are all used as anodes in lithium ion batteries why are they not reduced as $$ \Delta G = -zFE $$ and E is positive so dG is negative?

  • $\begingroup$ I understand that the cathode material is probably at an even higher potential and is thus preferentially reduced but is TiO2 also reduced? $\endgroup$
    – ChemEng
    Oct 16 '19 at 0:30
  • $\begingroup$ I think the y- axis is oxidation potential rather than reduction potential, the way they are writing Li/Li+ suggests that. You have to check the context very well. $\endgroup$
    – M. Farooq
    Oct 16 '19 at 3:04
  • $\begingroup$ The standard reduction potential of Lithium is approx -3V and the standard reduction potential of TiO is approx -1.3V thats +1.7V like on the diagram en.wikipedia.org/wiki/Standard_electrode_potential_(data_page) $\endgroup$
    – ChemEng
    Oct 16 '19 at 3:15
  • $\begingroup$ The symbolism of Li/Li+ as a half cell is wrong since electrochemical convention is to always show the half cell as reduction e.g., Li+/Li rather. $\endgroup$
    – M. Farooq
    Oct 16 '19 at 3:26
  • $\begingroup$ @M. Farooq It rather follows the usual electrode description schema like <electrode>[/<coating>][/<electrolyte significant ion>]. The measured electrode potential obviously does not depend on notation. $\endgroup$
    – Poutnik
    Oct 16 '19 at 5:29

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