Electrospun poly(lithium 2-acrylamido-2-methylpropanesulfonic acid) fiber-based polymer electrolytes for lithium-ion batteries

Spiroborate-Linked Ionic Covalent Adaptable Networks with Rapid Reprocessability and Closed-Loop Recyclability

Covalent adaptable networks (CANs) represent a novel class of polymeric materials crosslinked by dynamic covalent bonds. Since their first discovery, CANs have attracted great attention due to their high mechanical strength and stability like conventional thermosets under service conditions and easy reprocessability like thermoplastics under certain external stimuli. Here, we report the first example of ionic covalent adaptable networks (ICANs), a type of crosslinked ionomers, consisting of negatively charged backbone structures. More specifically, two ICANs with different backbone compositions were prepared through spiroborate chemistry. Given the dynamic nature of the spiroborate linkages, the resulting ionomer thermosets display rapid reprocessability and closed-loop recyclability under mild conditions. The materials mechanically broken into smaller pieces can be reprocessed into coherent solids at 120 °C within only 1 min with nearly 100% recovery of the mechanical properties. Upon treating the ICANs with dilute hydrochloric acid at room temperature, the valuable monomers can be easily chemically recycled in almost quantitative yield. This work demonstrates the great potential of spiroborate bonds as a novel dynamic ionic linkage for development of new reprocessable and recyclable ionomer thermosets.

Enhancement of the electrochemical performance of lithium-ion batteries by SiO2@poly(2-acrylamido-2-methylpropanesulfonic acid) nanosphere addition into a polypropylene membrane

Employing electrostatic self-assembly and free radical polymerization, the surface of SiO₂ nanospheres was coated with poly(2-acrylamido-2-methylpropanesulfonic acid) (SiO₂@PAMPS) bearing strong electron withdrawing sulfonic and amide groups, enhancing the dissociation ability of the lithium salt of the liquid electrolyte and absorbing anions via hydrogen bonds. After SiO₂@PAMPS nanospheres were introduced into the polypropylene (PP) membrane (SiO₂@PAMPS/PP), the electrolyte affinity and electrolyte uptake of the composite separators were significantly improved. The ionic conductivity of SiO₂@PAMPS/PP-18% (where 18% represents the concentration of the solution used for coating) soaked in liquid electrolyte was even 0.728 mS cm^-1 at 30 °C, much higher than that of the pristine PP membrane. The LiFePO₄/Li half-cell with SiO₂@PAMPS/PP-18% had a discharge capacity of 148.10 mA h g^-1 and retained 98.67% of the original capacity even after 120 cycles at 0.5C. Even at a rate of 1.0C, the cell capacity could be maintained above 120 mA h g^-1. Therefore, a coating formula was developed that could considerably improve the cycling ability and high rate charge-discharge performance of lithium ion batteries.