Synergistic effect of holey graphene and CoSe2-NiSe2 heterostructure to enhance fast Na-ion transport

Abstract

Inspired by the “Barrel principle” and based on the working principle of the “rocking chair”. We propose two shortboards that “bulk diffusion rate” and “ion reaction rate”, which affect the fast charging of sodium ion batteries (SIBs). The holey reduced graphene oxide (HrGO) with abundant nanopores provides longitudinal diffusion channels, enabling rapid Na+ diffusion along this direction, which solves the shortboard of bulk diffusion rate. Additionally, heterojunctions are considered a viable approach for enhancing fast Na+ storage performance by providing more storage sites and accelerating the kinetics of Na+ reaction, which solve the shortboard of ion reaction rate. Herein, we construct HrGO combined with CoSe2-NiSe2 heterojunctions has been rationally fabricated to synergistically enhance the ionic and electronic diffusion kinetics. As expected, the CoSe2-NiSe2/HrGO anode in SIBs shows an excellent fast-charging performance (392.4mAh/g at 15 A/g), surpassing most Co/Ni-based selenide anodes. Additionally, the assembled CoSe2-NiSe2/HrGO||NVP full cell delivers a high specific capacity of 116.1 and 95.4mAh/g at 0.1 and 20C, respectively, coupled with 97.8 % capacity retention rate for 100 cycles. Furthermore, we elucidate the mechanism of Na+ storage and fast transport through electrochemical kinetic analysis, in situ and ex situ characterizations, density functional theory (DFT) calculations, and distribution of relaxation times (DRT). Importantly, this study provides theoretical insights into accelerating rapid Na+ transfer.