Help understanding Electrochemistry diagram

[![Potential vs Capacity of various compounds](https://i.stack.imgur.com/4856o.jpg)](https://i.stack.imgur.com/4856o.jpg)


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?


