Bifunctional Sn/NaF Interlayer Enables Stable Solid State Sodium Batteries

Tinghu Liu

doi:10.1002/aenm.71103

Bifunctional Sn/NaF Interlayer Enables Stable Solid State Sodium Batteries

2026-05-21

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DOI：10.1002/aenm.71103

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The practical application of sodium superionic conductor (NASICON) electrolytes in solid-state sodium batteries is restricted by poor interfacial compatibility between the solid electrolyte and Na anode, as well as continuous dendrite growth. Herein, a bifunctional Sn/NaF interlayer is introduced at the Na/Na3.4Zn0.1Zr1.9Si2.2P0.8O12 (NZZP) interface to improve wettability and suppress dendrite formation. Experimental and computational results confirm that NaF with a band gap of 6.1 eV can significantly enhance the electron transport barrier to prevent Na nucleation on the side of NZZP. Moreover, the in situ formed NaxSn alloys at Na/NaF@NZZP interface possess excellent electronic conductivity, fast Na+ migration kinetics, and low interfacial energy of 14.05 meV Å−2 with Na, effectively improving interfacial contact and facilitating uniform Na plating. Benefiting from the NaxSn/NaF interphase, the critical current density of NZZP increased from 2.7 to 11.6 mA cm−2 under 60°C. The assembled Na3V2(PO4)3@PEG/NZZP@NaF@Sn/Na solid state batteries show a high initial reversible discharge capacity of 92.0 mAh g−1 with a capacity retention of 88.9% at 0.5C after 1000 cycles. Even at 1C and 3C, the batteries still maintain stable cycling for 10 000 cycles with capacity retention of 68.8% and 67.6%, respectively.

Keywords:

bifunctional interphase

dendrite suppression

metallic sodium anode

NASICON solid electrolyte

solid state sodium batteries

Bifunctional Sn/NaF Interlayer Enables Stable Solid State Sodium Batteries

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