A 12V automotive lead-acid battery. Each anode/cathode pair in this schematic cutaway produces a voltage of about 2V. Six pairs of electrodes are connected in series, producing12V .
It's built of:
lead grid filled with spongy lead (anode)
H2SO4 electrolyte
lead grid filled with PbO2 (Cathode).
What is the oxidation state of lead in the cathode of this battery?