Lithium-ion storage mechanism in closed pore-rich hard carbon with ultrahigh extra plateau capacity

A closed pore-rich hard carbon is fabricated from mildly cured phenolic-formaldehyde resin. It can deliver a high capacity of 550 mAh g −1 , including a low-voltage plateau capacity of 230 mAh g −1 from lithium-ion insertion in closed ultramicropores.