Rational Design of a ZIF‐67/Cobalt‐Glycolate Heterostructure with Improved Conductivity for High Cycling Stability and High‐Capacity Lithium Storage

Abstract

AbstractCobalt‐glycolate (Co‐glycolate) is a kind of layered coordination polymer with abundant electrochemically active sites but low conductivity. The fabrication of heterostructures is a novel strategy to enhance the electrical conductivity. Herein, Co‐glycolate serves as a host substrate for the in situ growth of guest ZIF‐67 to build MOFs‐on‐CPs heterostructures (named Co‐glycolate /ZIF‐67) via a simple ligand‐exchange method as an anode for lithium‐ion batteries. A heterojunction interface with distorted lattice between the Co‐glycolate phase and the ZIF‐67 phase can be observed. Theoretical calculations and experimental results simultaneously prove that the formed heterojunction reduces the band gap and enhances the conductivity. Compared with both single components, optimized Co‐glycolate/ZIF‐67 shows a higher capacity and better cycling and rate performances due to the improved charge‐transfer rate of the heterostructure. Its specific capacity remains at 652 mAh g−1 after 800 cycles at 1 A g−1. These excellent electrochemical properties can be due to the smaller size, rough surface, and strong combination of a unique heterostructure as well as to the greatly reduced band gap of the individual components. A lithium‐storage mechanism for Co‐glycolate/ZIF‐67 was proposed. This work provides a new strategy for building MOFs‐on‐CPs heterostructures to improve the electrochemical performance of metal‐glycolate‐based electrode materials for energy‐storage and conversion systems.