Polymer Electrolyte Glue: A Universal Interfacial Modification Strategy for All-Solid-State Li Batteries.

In recent years solid Li+ conductors with competitive ionic conductivity to those of liquid electrolytes have been reported. However, the incorporation of highly conductive solid electrolytes into the lithium-ion batteries is still very challenging mainly due to the high resistance existing at the solid-solid interfaces throughout the battery structure. Here, we demonstrated a universal interfacial modification strategy through coating a curable polymer-based glue electrolyte between the electrolyte and electrodes, aiming to address the poor solid-solid contact and thus decrease high interfacial resistance. The liquid glue exhibits both great wettability as well as chemical/electrochemical stability to most of the electrodes, and it can be easily solidified into a polymer electrolyte layer through a "post-curing" treatment. As a result, symmetric Li batteries with the glue modification exhibit much smaller impedance and enhanced stability upon plating/stripping cycles compared to the batteries without glue modification. The all-solid-state Li-S batteries with glue modification show significantly enhanced performances. The strategy of developing glue electrolytes to improve the electrode-electrolyte interface contact provides an alternative option for improving many other solid-state batteries.

Cationic Covalent Organic Framework Nanosheets for Fast Li-Ion Conduction.

Covalent organic frameworks (COFs) with their porous structures that are accommodative of Li salts are considered to be potential candidates for solid-state fast Li+ conductors. However, Li salts simply infiltrated in the pores of solid-state COFs tend to be present in closely associate ion pairs, resulting in slow ionic diffusion dynamics. Here we incorporate cationic skeleton into the COF structure to split the Li salt ion pair through stronger dielectric screening. It is observed that the concentration of free Li+ ions in the resulting material is drastically increased, leading to a significantly improved Li+ conductivity in the absence of any solvent (up to 2.09 × 10-4 S cm-1 at 70 °C).

Porous covalent organic frameworks for high transference number polymer-based electrolytes.

While solid polymer electrolytes are poised to be the key component of next-generation solid-state batteries, the low Li+ transference number of the polymer electrolytes limits their practical applications. Here, porous boron-containing covalent organic frameworks with different surface areas were synthesized and employed as functional additives for enhancing the Li+ transference number of the polymer electrolytes. The boron-containing frameworks enable strong adsorption of the anions of the lithium salt, leading to a significantly enhanced Li+ transference number of the polymer electrolyte containing COF additives. It is observed that solid-state cells assembled with the COF-containing polymer electrolytes exhibited remarkably decreased overpotentials and enhanced rate performances, which opens up new ways to apply porous organics in next-generation solid-state batteries.