Composite solid electrolytes (CSEs), which are composed of inorganic fillers and organic polymers, show improved safety and suppressed lithium dendrite growth in Li-metal batteries, as compared to flammable liquid electrolytes. However, the performance of current CSEs is limited by the agglomeration effect, with low content of inorganic Li+-conducting fillers and ineffective Li+ transport between the inorganic fillers and the polymer matrix. We therefore set out to design a CSE toward high-performance, solid-state Li-metal batteries based mainly on inorganic Li-conductors, with supplementary polymer content for improving interfacial contact. A new type of CSE with enriched inorganic Li-conductors and well-percolated network was introduced utilizing one dimensional Li6.28La3Al0.24Zr2O12 (LLAZO) nanofibers to provide long-range and fast Li+ conduction. Additionally, acrylate functional groups (CH2=CHCOO-) were covalently bonded on the surface of LLAZO nanofibers, which enabled the chemical grafting of functional monomers directly from the nanofiber surfaces. In the resultant composite electrolytes, silane-decorated LLAZO nanofibers (s@LLAZO nanofibers) were cross-linked along with polymerization of monomers. This controlled fabrication of composite structures led to a well-percolated network, forming continuous, 3-dimensional, and fast Li+ conductive pathways within the CSE. The silane coupling agent significantly prevented the inhomogeneous distribution of inorganic Li+ conductors and enhanced the interaction between the LLAZO nanofibers and the polymer matrix, which improved the mechanical strength of CSE, favored the amorphization of polymer, and reduced the activation energy of Li+ conduction between the filler and polymer. Consequently, the silane coupling agent successfully eliminated the agglomeration effect, and the introduced CSEs (LLAZO nanofibers &gt; 60 wt.%) exhibited higher ionic conductivity, larger lithium transference number, and wider electrochemical stability window. Excellent cycling stability and extraordinarily high rate capability (up to 10C) was demonstrated in the all-solid-state Li-metal batteries with LiFePO4 and high-voltage Li[Ni1/3Mn1/3Co1/3]O2 cathodes at ambient temperature. This novel design of CSEs with s@LLAZO nanofibers paves the way for a new generation of improved functioning all-solid-state Li-metal batteries.

Garnet-rich composite solid electrolytes for dendrite-free, high-rate, solid-state lithium-metal batteries

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.