A conjugated plier-linked nano-spacing graphite network for sodium-ion battery

A sodium-ion battery to use natural graphite is challenging due to the hard accessibility of sodium ions into graphite. Here, we report a plier-linked graphite network (PGN) with plier-like, conjugated active-molecule for sodium-ion battery anode. The newly designed PGN with conjugated linkers provides additional sodium-ion storage sites and sufficient nano-meter level wide two-dimensional spaces for sodium-ion access. The plier-linked graphite network (PDA-PGN) with 9,9-dihexylfluorene-2,7-diboronic acid (PDA) among variable linkers delivers the highest sodiation/desodiation capacity (298/245 mAh g⁻¹), at approximately 10 times the level of graphite, while maintaining acceptable rate capability and stability, realizing 1.52 mAh cm⁻² areal capacity with high electrode thickness (282 µm) and mass loading (7.8 mg cm⁻²). We revealed the knowledge of a major synergistic phenomenon between the conjugated PDA molecules and the nano-sized interlayer distance. Our PDA-PGN design added the new understanding to the alkali-metal ion storage and offers the production potential for low-cost and versatile electrodes.