An in-situ generated Bi-based sodiophilic substrate with high structural stability for high-performance sodium metal batteries

Sodium (Na) metal anode exhibits a potential candidate in next-generation rechargeable batteries owing to its advantages of high earth abundance and low cost. Unfortunately, the practical development of sodium metal batteries is inherently plagued by challenges such as the side reactions and the growth of Na dendrites. Herein we report a highly stable Bi-based “sodiophilic” substrate to stabilize Na anode, which is created by in-situ electrochemical reactions of 3D hierarchical porous Bi2MoO6 (BMO) microspheres. BMO is initially transformed into the Bi “nanoseeds” embedded in the Na-Mo-O matrix. Subsequently, the Bi nanoseeds working as preferential nucleation sites through the formation of Bi-Na alloy enable the non-dendritic Na deposition. The asymmetric cells based on such BMO-based substrate can deliver a long-term cycling for 600 cycles at a large capacity of 4 mAh cm−2and for 800 cycles at a high current density of 10 mA cm−2. Even at a high depth of discharge (66.67%), the Na-predeposited BMO (Na@BMO) electrodes can cycle for more than 1600 h. The limited Na@BMO anodes coupled with the Na3V2(PO4)3 cathodes (N/P ratio of 3) in full cells also show excellent electrochemical performance with a capacity retention of about 97.4% after 1100 cycles at 2 C.