Tunneling Interpenetrative Lithium Ion Conduction Channels in Polymer-in-Ceramic Composite Solid Electrolytes

Abstract

Polymer-in-ceramic composite solid electrolytes (PIC−CSEs) provide important advantages over individual organic or inorganic solid electrolytes. In conventional PIC− CSEs, the ion conduction pathway is primarily confined to the ceramics, while the faster routes associated with the ceramic− polymer interface remain blocked. This challenge is associated with two key factors: (i) the difficulty in establishing extensive and uninterrupted ceramic−polymer interfaces due to ceramic aggregation; (ii) the ceramic−polymer interfaces are unresponsive to conducting ions because of their inherent incompatibility. Here, we propose a strategy by introducing polymer-compatible ionic liquids (PCILs) to mediate between ceramics and the polymer matrix. This mediation involves the polar groups of PCILs interacting with Li + ions on the ceramic surfaces as well as the interactions between the polar components of PCILs and the polymer chains. This strategy addresses the ceramic aggregation issue, resulting in uniform PIC−CSEs. Simultaneously, it activates the ceramic−polymer interfaces by establishing interpenetrating channels that promote the efficient transport of Li + ions across the ceramic phase, the ceramic−polymer interfaces, and the intervening pathways. Consequently, the obtained PIC−CSEs exhibit high ionic conductivity, exceptional flexibility, and robust mechanical strength. A PIC−CSE comprising poly(vinylidene fluoride) (PVDF) and 60 wt % PCIL-coated Li 3 Zr 2 Si 2 PO 12 (LZSP) fillers showcasing an ionic conductivity of 0.83 mS cm −1 , a superior Li + ion transference number of 0.81, and an elongation of ∼300% at 25 °C could be produced on meter-scale. Its lithium metal pouch cells show high energy densities of 424.9 Wh kg −1 (excluding packing films) and puncture safety. This work paves the way for designing PIC−CSEs with commercial viability.

Improving the Ionic Conductivity and Anode Interface Compatibility of LLZO/PVDF Composite Polymer Electrolytes by Compositional Tuning

“…Their extensive electrochemical stability window and superior mechanical properties effectively prevent lithium dendrite formation, facilitating the use of lithium metal anodes with high-voltage cathodes . However, challenges persist with certain solid-state materials: ceramic electrolytes suffer from brittleness and complex processing, whereas polymer electrolytes struggle with dendrite suppression due to inadequate mechanical strength. , Composite polymer electrolytes (CPEs) emerge as a leading solution by integrating the benefits of both polymer matrices and ceramic fillers, offering improved ion conductivity, mechanical strength, and dendrite mitigation. − Among various CPEs, poly­(ethylene oxide) (PEO) systems have been extensively researched and utilized in commercial 3 V Li|PEO|LiFePO 4 batteries. − CPEs featuring PEO and active fillers like garnet-type Li 7 La 3 Zr 2 O 12 (LLZO) showcase enhanced mechanical robustness and dendrite resistance, improving the stability of the PEO/Li metal interface. , Nonetheless, PEO’s susceptibility to oxidation above 4 V leads to challenges in accommodating high-voltage cathode materials, such as LCO and nickel-rich ternary compounds, thereby limiting the potential energy density of solid-state batteries …”

Across Interfacial Li+ Conduction Accelerated by a Single-Ion Conducting Polymer in Ceramic-Rich Composite Electrolytes for Solid-State Batteries

“…However, the Li + conduction across the polymer–ceramic interface was interrupted on the surface of ceramic particles owing to the lack of Li + vacancies. Moreover, the huge grain boundary impedance in ceramic-rich composite electrolytes and the inferior interface conduction in asymmetric hierarchical composite electrolytes constrain the development of composite electrolytes.…”