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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.

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The stability of CuO nanoparticles (NPs) is expected to play a key role in the environmental risk assessment of nanotoxicity in aquatic systems. In this study, the effect of alginate (model polysaccharides) on the stability of CuO NPs in various environmentally relevant ionic strength conditions was investigated by using time-resolved dynamic light scattering. Significant aggregation of CuO NPs was observed in the presence of both monovalent and divalent cations. The critical coagulation concentrations (CCC) were 54.5 and 2.9 mM for NaNO3 and Ca(NO3)2, respectively. The presence of alginate slowed nano-CuO aggregation rates over the entire NaNO3 concentration range due to the combined electrostatic and steric effect. High concentrations of Ca(2+) (>6 mM) resulted in stronger adsorption of alginate onto CuO NPs; however, enhanced aggregation of CuO NPs occurred simultaneously under the same conditions. Spectroscopic analysis revealed that the bridging interaction of alginate with Ca(2+) might be an important mechanism for the enhanced aggregation. Furthermore, significant coagulation of the alginate molecules was observed in solutions of high Ca(2+) concentrations, indicating a hetero-aggregation mechanism between the alginate-covered CuO NPs and the unabsorbed alginate. These results suggested a different aggregation mechanism of NPs might co-exist in aqueous systems enriched with natural organic matter, which should be taken into consideration in future studies. Graphical abstract Hetero-aggregation mechanism of CuO nanoparticles and alginate under high concentration of Ca(2.)

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