Journal Article LLZO grain boundary Li2CO3 Lithium penetration mechanism Review all‐solid‐state batteries capacitive storage carbon coated Li1.4Al0.4Ti1.6(PO4)3 composite solid-state electrolyte dielectric materials electron and ion co-conductive catalysts high rate high‐rate performance high‐voltage polymer electrolytes in situ NMR ion transport ion/electron transport lithium metal lithium-ion batteries lithium-sulfur batteries porous carbon salt segregation sieving effects sodium-ion batteries sodium‐ion storage solid electrolyte interfaces solid polymer electrolytes solid-state NMR solid‐state lithium batteries space charge layer