Long term plan for electro chemistry

[jiweiqi]

Inspired by Cantera, which has recently made a lot of progress in modeling electrodes, e.g., https://cantera.org/examples/jupyter/electrochemistry/lithium_ion_battery.ipynb.html

It is good to have some high-level discussions and plans for the long-term futures. Those discussions can be kept in mind when design data structures and functions, as did for the RealGasThermo.