Li2CO3 effects: New insights into polymer/garnet electrolytes for dendrite-free solid lithium batteries

Garnet particles are usually introduced into polymer matrices as fillers to fabricate polymer/garnet composite electrolytes (PGEs), which can not only improve the ionic conductivity but also enhance the mechanical strength to suppress Li dendrites. However, the surface Li 2 CO 3 contamination of garnet particles through air exposure has long been overlooked when fabricating the PGEs. Considering the ultralow ionic conductivity and low oxidation voltage of Li 2 CO 3 , the effects of Li 2 CO 3 should be taken into consideration. Herein, the PGEs with Li 2 CO 3 -containing and Li 2 CO 3 -free garnet particles are fabricated from “garnet-in-polymer” (GIP) to “polymer-in-garnet” (PIG) electrolyte compositions. The results indicate that Li + can be transported faster along the polymer/garnet interface in the Li 2 CO 3 -free GIP electrolytes, while Li + migration through the garnet bulk can be improved in the Li 2 CO 3 -free PIG electrolytes. The Lewis acid-base interactions between garnet and polymer are enhanced due to the Li 2 CO 3 removal, thus increasing the Li + transference number. Furthermore, cathode-supported solid-state batteries with vertically aligned LiFePO 4 cathodes and Li 2 CO 3 -free PIG electrolytes are constructed, which show excellent rate and cycle performance. This work provides new insights into PGEs and the effects of Li 2 CO 3 , which can guide the improved design of PGEs for dendrite-free solid garnet batteries.