Hybrid design of bulk-Na metal anode to minimize cycle-induced interface deterioration of solid Na metal battery

The pursuit for high-energy and intrinsically safe energy storage is significantly driving the development of solid-state alkali metal batteries. The interfacial contact between the metal anode and the solid electrolyte plays a key role in enabling stable cycling of solid batteries. However, the sluggish alkali atom replenishment rate during stripping unavoidably leads to the interface deterioration that destroys the initial physical contact by forming interfacial voids and triggering the dendrite growth. Herein, a hybrid bulk Na anode approach is proposed by incorporating an ion-conducting phase into a metallic Na matrix, constructing an abundant interfacial electrochemical reaction area and enabling a balanced Na replenishment and consumption to minimize cycle-induced interface deterioration. Specific attention is paid to the effects of the second phase on the wettability and creep ability of hybrid Na metal. A high critical current density (3.1 mA cm-2) and long cycling life (6000 h in 0.5 mA cm-2) are achieved for the symmetric cells. Full cells coupling the hybrid anode with the Na3V2(PO4)3/C cathode deliver excellent cyclability over 7300 cycles at a high rate of 5 C. The viewpoint of balancing the consumption and replenishment rate of metal atoms paves a new way for designing cycle-stable anode/electrolyte interface in solid-state batteries.