Battery & Hydrogen

C rate

Formulas

secondary batteries

Li, Zi-MH, Lead acid

energy density= li>Zi-MH>Lead acid

cell volt= Li>Lead>Zi-MH

Li battery

Charge : External charge give graphite negative charges and Li+ ion are extracted at the same time through the ionic conducting Electrolyte.

Discharge: Li+ ion pass through the porous separator but electrons cannot so they take the external route to reach Li (cathode)

Three problems with Li battery :

1) Charging/discharging causes volume expansion and structural stress due to continuous lithium addition to the anode, this reduces the structural integrity

2) Battery degradation due to some lithium ions remain stuck in the graphite (anode) this reduces the battery capacity

3) there is staging phenomena as the lithium deposition is not uniform, this causes uneven strain fields

Other alternative is silicon but it also suffers big volume expansion. To mitigate this composite of graphite and silicon matrix is used

PEM vs SOEC