Gas-phase Kirkendall effect inducing built-in bifunctional ultrafine Cu nanocrystalline integrated 3D hollow nanoporous Cu_xO anode towards excellent lithium storage performance

Traditional Cu_xO (x = 1, 2) electrodes exhibit excellent specific capacity, but the poor stress-buffering performance and inferior conductivity hinder its further application. To solve these issues, herein, we develop a built-in bifunctional ultrafine Cu nanocrystalline networks hybridized 3D hollow nanoporous Cu_xO (BUCN@3D-HN Cu_xO) integrated anode by a facile gas-phase Kirkendall effect. The 3D hollow nanoporous (3D-HN) structure can bidirectionally retard the change of stress, while the built-in ultrafine Cu nanocrystalline networks (BUCN) own the effect of providing rapid internal electron transport across the active/inert Cu/Cu_xO system. Benefiting from the synergistic effect of the excellent stress-buffering ability and improved electronic conductivity, the designed BUCN@3D-HN Cu_xO electrode delivers a high initial reversible capacity of 1.67 mAh cm⁻² under the current density of 1 mA cm⁻². Besides, a high capacity retention of 0.96 mAh cm⁻² with a high capacity retention ratio of 85.7 % is achieved even after 800 cycles at a high rate of 4 mA cm⁻². This work provides a facile yet effective method to prepare hollow nanoporous electrodes and emphasizes the significance of active/inert system, which may shed light on the design of other high-performance electrodes beyond Lithium-ion batteries.