Molecular carbon skeleton with self-regulating ion-transport channels for long-life potassium ion batteries

Developing anode materials with multiple-dimensional ion transport channels, especially to overcome huge volume expansion and sluggish ion diffusion kinetics caused by large radius of potassium ion (K+), is critical to improve the potassium storage performance. Herein, we propose a self-reversible conversion of chemical bonds with different bond lengths based on graphdiyne (GDY) to self-regulating the ion transport channels. Density functional theory (DFT) calculations and ex/in situ electrochemical tests proof the in-plane triangular-like pores (5.46 angstrom) of the GDY framework offer a transport channel for K+ (1.38 angstrom) diffusion in the direction perpendicular to the GDY plane, which differs it from carbonaceous materials whose ion diffusion is mostly governed by in-plane migration. Furthermore, the reversible alkyne-alkene bonds linking/breaking of GDY stimulated by K+ to realize self-regulating ion channels are demonstrated by in situ Raman and electro-kinetic analysis. Moreover, compared to graphite, the GDY anode with 2 orders of magnitude diffusion coefficient delivered a high reversible capacity of 202 mAh g- 1 at 100 mA g- 1 exhibited extraordinary durability corresponding to cycle time over 380 days. This work opens a new avenue of designing intelligent, efficient ion transport channels from molecular carbon skeleton perspective to enhance diffusion kinetic for high-performance KIBs.

Automated summary

In this study, an approach for designing anode materials based on two-dimensional ion transport channels is proposed, which achieves self-regulating ion channels through self-reversible conversion. The results show that the material based on graphdiyne exhibits a large diffusion coefficient and high reversible capacity, demonstrating excellent durability.