Carbon‐Microcuboid‐Supported Phosphorus‐Coordinated Single Atomic Copper with Ultrahigh Content and Its Abnormal Modification to Na Storage Behaviors

Abstract Carbon‐supported single atomic metals (SAMs) have aroused great interest in energy conversion and storage fields. However, metal content has to date, been far below expectation. Additionally, theoretical calculations show that SAMs are superb anchoring sites for alkali metal‐ion storage, but the experimental research remains untouched. Herein, a metal–organophosphine framework derived strategy is proposed to prepare carbon microcuboids‐supported single atomic Cu with a high content of 26.3 wt%. Atomic Cu is stabilized mainly by P moieties, exhibiting robust stability even in concentrated HCl and HNO 3 . Interestingly, experimental investigations and first‐principle calculations indicate that Cu atoms can alter the Na storage behavior and enable Na to maintain an ionic state at a fully discharging state for sodium‐ion batteries, which may be a new pathway to mitigate safety concerns of dendrite formation. The Cu atoms also enhance electron transfer and diffusion kinetics. As a result, the carbon cuboids can deliver a high capacity of 107.7 mAh g −1 at 5 A g −1 and show a long life of 1000 cycles for Na storage. This strategy offers a new possibility for fabricating high‐content P‐coordinated atomic metals for energy conversion and storage.