No abstract

A casting process for composite Nafion®/STA membranes was achieved. The membrane casting was based on the evaporation of 5% Nafion® solution in N,N′‐dimethylformamide (DMF) with and without silicotungstic acid (STA) as an additive. Optimized parameters for the casting process were determined. The water uptake and the ionic conductivity of the cast membranes were measured. The variation of the volume of Nafion® and the STA concentrations on the water uptake and conductivity of the cast membranes were investigated under various conditions. The sulphuric acid uptake was also determined. The effect of the membrane soaking conditions, on water uptake and conductivity, were determined. The contribution of the (‐SO3H) groups, the STA species, and/or the sulphuric acid to the membrane properties was discussed. The performance of hydrogen/oxygen (H2/O2) PEM Fuel Cells based on the membranes cast with STA was compared to those based on membranes cast without STA. It was shown that the water uptake of the cast membrane increased from 18% to 50% when the STA concentration used in the casting bath increased from 0 to 5 × 10–3�M. For the membrane fabricated without STA, the water uptake and the conductivity do not change with membrane thickness, whereas for the membranes cast with STA, the water uptake and the conductivity increase with membrane thickness. A performance improvement of 0.3 A cm–2 at 0.6 V was obtained with the H2/O2 PEM fuel cell based on membranes cast with STA, compared to the performance of the cell based on membranes cast without STA. On the other hand, this performance improvement, for the cells based on the membranes cast in DMF (0.3 A cm–2 at 0.6 V), is higher than that for the cells based on membranes cast in aqueous electrolyte (0.15 A cm–2 at 0.6 V).It was anticipated that soaking the membranes in sulphuric acid might improve their performance for H2/O2 PEMFC applications.

Solid-state sodium ion batteries have attracted widely attentions due to its high energy density, low cost and high security. However, the poor contact and high interfacial resistance between sodium and...

Solid sodium-ion batteries (SSIBs) with high safety and high energy density have broad application prospects. Unfortunately, the poor contact and dendrite growth between sodium and the solid electrolyte severely hinder their development. Herein, an in-situforming electron-blocking interlayer (EBI) has been designed on the surface of Na 3.2 Hf 1.9 Ca 0.1 Si 2 PO 12 (NHSP). The EBI could effectively improve the interface wetting and block the transmission of electrons, so as to ensure the long-term stability between sodium and the NHSP electrolyte. The batteries with the EBI@NHSP electrolyte could cycle stably for more than 700 h at 0.2 mA cm −2 . Even with the increase of the current density to 2.3 mA cm −2 , the batteries could still work normally. The full cell with the Na 3 V 2 (PO 4 ) 3 cathode also exhibited a good long-term cycling stability, which could cycle stably for more than 300 cycles at 0.5 C while maintaining a high Coulombic efficiency of 99.76%. This work provides a new feasible strategy to prevent sodium dendrite growth and promote the development of SSIBs.

Solid-state sodium-ion batteries are attracting great attention due to their high energy density and high safety. However, the Na dendrite growth and poor wettability between sodium and electrolytes seriously limit its application. Herein, we designed a stable and dendrite-suppressed quasi-liquid alloy interface (C@Na–K) for solid sodium-ion batteries (SSIBs). The batteries exhibit excellent electrochemical performance thanks to better wettability and accelerated charge transfer and nucleation mode shifts. The thickness of the liquid phase alloy interface fluctuates along with the exotherm of the cell cycling process, which leads to better rate performance. The symmetrical cell can cycle steadily over 3500 h at 0.1 mA/cm2 at room temperature, and the critical current density can reach 2.6 mA/cm2 at 40 °C. The full cells with the quasi-liquid alloy interface also show outstanding performance; the capacity retention can reach 97.1%, and the average Coulombic efficiency can reach 99.6% of the battery at 0.5 C even after 300 cycles. These results proved the feasibility of using a liquid alloy interface of the anode for high-energy SSIBs, and this innovative approach to stabilizing the interface performance could serve as a basis for the development of next-generation high-energy SSIBs.