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Following the prevalence of the Li-ion battery for electrical energy storage systems (EESs), the world is looking toward alternative, cost-effective, electrical EESs for portable electronics, electric vehicles, and grid storage from renewable sources. Na-based batteries are the most promising candidates and show similar chemistry as Li-based batteries. All-solid-state sodium batteries (AS3Bs) have attracted great attention due to safe operation, high energy density, and wide operational temperature. Herein, current development of solid-state crystalline borate- and chalcogenide-based Na-ion conductors is discussed together with historically important Na-β-alumina and Na superionic conductors (NASICONs). Furthermore, we report on engineering a ceramic Na-ion electrolyte and electrode interface, which is considered a bottleneck for practical applications of solid-state electrolytes in AS3Bs. A soft Na-ion conducting interlayer is critical to suppress the interfacial Na-ion charge transfer resistance between the solid electrolyte and electrode. Several Na-ion conducting ionic liquids, polymers, gels, crystalline plastics interlayers, and other interfacial modification strategies have been effectively employed in advanced AS3Bs.

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Polymer-based solid-state electrolytes (SSEs) are promising candidates to enhance the performances of current lithium-ion batteries (LiBs), as they possess advantages of facile processing and flexibility over ceramic SSEs. However, polymer SSEs such as poly(ethylene oxide) (PEO) suffer from low ionic conductivity, a limited voltage stability window, and thermal stability. Poly(vinylidene fluoride) (PVDF)-based polymer electrolytes (PPEs) with lean solvent confinement provide improved ionic conductivity and outstanding chemical/electrochemical stability. In this study, we report the effects of different solvents on the morphological structure and ionic conductivity of PPEs. We demonstrate that solvents with relatively high boiling points (dimethylformamide (DMF), dimethyl sulfoxide (DMSO), N-Methyl-2-pyrrolidone (NMP), and dimethylacetamide (DMA)) can be trapped in PPEs, and they all have positive effects on the ionic conductivity. The ionic conductivity is related to the quantity of the trapped solvent; for a PPE with DMF retention of ∼20%, the ionic conductivity is about 0.1 mS cm−1. Increasing the amount of lithium salt was found to improve the solvent retention but at the cost of membranes’ mechanical property. It is also possible to introduce a low boiling point co-solvent in order to reduce the production cost and drying duration for manufacturing PPEs.

An economical and simple technique to mitigate the solid electrolyte–lithium metal anode interfacial charge transfer resistance.