Abstract
Solid-state sodium metal batteries hold promise for next-generation energy storage but face interfacial challenges at the anode/solid electrolyte, including poor contact, polarization fluctuations, and dendrite formation. Herein, we demonstrate a ferroelectric interlayer strategy by coating Na
3
Zr
2
Si
2
PO
12
solid electrolyte with Bi
4
Ti
3
O
12
nanoplates rendering ferroelectric features to homogenize interfacial charge distribution and suppress dendrite-like Na propagation. Homogeneous Na
+
flux distribution induced by the ferroelectric interlayer is confirmed by finite element analysis, and flat sodium plating around the Bi
4
Ti
3
O
12
nanoplates is observed by focus-ion-beam scanning electron microscopy. Besides, distribution of relaxation time analysis on the electrochemical impedance reveals a small interfacial resistance of 6.5 Ω·cm
2
for the symmetrical Na|Bi
4
Ti
3
O
12
-Na
3
Zr
2
Si
2
PO
12
|Na cells at 30 °C. Long-term Na plating/stripping cycles are achieved for 8,770 h at 0.2 mA/cm
2
, further indicating the excellence of the ferroelectric interlayer design. Additionally, full cells using Na
3
V
2
(PO
4
)
3
cathodes with an active mass loading around 15 mg/cm
2
demonstrate a reversible capacity of 1.42 mAh/cm
2
with 96.49% retention after the 90th cycle at a 1 C rate and 30 °C. This work provides fundamental insights into ferroelectric-electrochemical interactions and will promote the development of high-capacity solid-state sodium metal batteries working at ambient temperature.