NASICON- (Na superionic conductor-) based solid-state electrolytes (SSEs) are believed to be attracting candidates for solid-state sodium batteries due to their high ionic conductivity and prospectively reliable stability. However, the poor interface compatibility and the formation of Na dendrites inhibit their practical application. Herein, we directly observed the propagation of Na dendrites through NASICON-based Na3.1Zr2Si2.1P0.9O12 SSE for the first time. Moreover, a fluorinated amorphous carbon (FAC) interfacial layer on the ceramic surface was simply developed by in situ carbonization of PVDF to improve the compatibility between Na metal and SSEs. Surprisingly, Na dendrites were effectively suppressed due to the formation of NaF in the interface when molten Na metal contacts with the FAC layer. Benefiting from the optimized interface, both the Na||Na symmetric cells and Na3V2(PO4)3||Na solid-state sodium batteries deliver remarkably electrochemical stability. These results offer benign reference to the maturation of NASICON-based solid-state sodium batteries.

A porous polyimide (PI) membrane is successfully prepared via nonsolvent-induced phase separation with two porogens: dibutyl phthalate and glycerin. The as-prepared uniform porous PI membrane shows excellent separator properties for lithium-ion batteries (LIBs). Compared with the commercial polyethylene (PE) separator, the PI separator exhibits significant thermal stability, better ionic conductivity, and wettability both in carbonate and ether electrolytes for LIBs. The battery coin-cells assembled with the PI separator is more robust and still works even after heating at 140 °C for 1 h, while the cells with the commercial PE separator could not charge any more due to the shrinkage of the PE under the same condition.

Garnet-type Li7La3Zr2O12 (LLZO) is among the most attractive candidates for achieving solid-state lithium batteries. LLZO pellets with high density are preferred because of their potential to prevent dendritic Li growth and penetration. However, the presence of pores inside the LLZO electrolyte is inevitable if it is prepared by a traditional solid-state reaction. Large numbers of pores have an adverse influence on both the ionic conductivity and density of the LLZO pellets. In this work, we studied the origin of pore formation in Li6.4La3Zr1.4Ta0.6O12 (LLZTO) and introduced a fast oxygen-assisted sintering method to eliminate the pores. All of the basic physical properties of the LLZTO sintered in oxygen for only 1 h are better than those of the LLZTO sintered in air. The conductivity and Vickers hardness of the LLZTO increased to 6.13 × 10–4 S cm–1 and 9.82 GPa, corresponding to 12.3% and 62.8% enhancement, respectively, even at a low precalcined temperature of 600 °C. A Li||Li symmetric cell with the LLZTO sintered in oxygen also showed more stable and longer cycling at a higher current density (0.4 mA cm–2).

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