Functionalization: An Effective Approach to Open and Close Channels for Electron Transfer in Nitrogenated Holey Graphene C2N Anodes in Sodium-Ion Batteries.

Electron transfer plays a crucial role in energy storage materials, such as metal-ion batteries (MIBs). Numerous approaches have been developed to facilitate the electron transfer for MIBs, and most of them extend the special surface areas, which promotes the contact between metal ions and the electrodes. Herein, we report the formation of intramolecular channels for electron transfer to open and close intermolecular channels in sodium-ion batteries (SIBs) through functionalization, modulating the cell performance of two-dimensional (2D) nitrogenated holey graphene C2N anodes. This also activates the inactive metal ions in the anodes, reducing their production costs. Upon increasing the concentration of hydrogen atoms, the intramolecular electron transfer increases, lowering the intermolecular electron transfer between C2N and metal ions and thus weakening their interaction and reducing the capacities of the anodes. A high concentration of hydrogen atoms introduced in C2N would further promote the intramolecular electron transfer and block the channels for intermolecular electron transfer. For functionalized C2N monolayers that can be used as anodes in SIBs, they possess high specific capacities, high conductivities, and low open-circuit voltages. This work proposes the fabrication of 2D energy storage materials with tunable macroscale behaviors (e.g., performance) through the relationships between the macroscale and microscale levels and between intramolecular and intermolecular electron transfer.