Abstract
Rechargeable magnesium-metal batteries (RMMBs) are promising next-generation secondary batteries; however, their development is inhibited by the low capacity and short cycle lifespan of cathodes. Although various strategies have been devised to enhance the Mg(2+) migration kinetics and structural stability of cathodes, they fail to improve electronic conductivity, rendering the cathodes incompatible with magnesium-metal anodes. Herein, we propose a dual-defect engineering strategy, namely, the incorporation of Mg(2+) pre-intercalation defect (P-Mg(d)) and oxygen defect (O(d)), to simultaneously improve the Mg(2+) migration kinetics, structural stability, and electronic conductivity of the cathodes of RMMBs. Using lamellar V(2)O(5)·nH(2)O as a demo cathode material, we prepare a cathode comprising Mg(0.07)V(2)O(5)·1.4H(2)O nanobelts composited with reduced graphene oxide (MVOH/rGO) with P-Mg(d) and O(d). The O(d) enlarges interlayer spacing, accelerates Mg(2+) migration kinetics, and prevents structural collapse, while the P-Mg(d) stabilizes the lamellar structure and increases electronic conductivity. Consequently, the MVOH/rGO cathode exhibits a high capacity of 197 mAh g(-1), and the developed Mg foil//MVOH/rGO full cell demonstrates an incredible lifespan of 850 cycles at 0.1 A g(-1), capable of powering a light-emitting diode. The proposed dual-defect engineering strategy provides new insights into developing high-durability, high-capacity cathodes, advancing the practical application of RMMBs, and other new secondary batteries.