Improving Ionic Conductivity with Bimodal-Sized Li₇La₃Zr₂O₁₂ Fillers for Composite Polymer Electrolytes

Abstract

Ceramic–polymer composite electrolytes (CPEs) are being explored to achieve both high ionic conductivity and mechanical flexibility. Here, we show that, by incorporating 10 wt % (3 vol %) mixed-sized fillers of Li7La3Zr2O12 (LLZO) doped with Nb/Al, the room-temperature ionic conductivity of a polyvinylidene fluoride (PVDF)–LiClO4-based composite can be as high as 2.6 × 10–4 S/cm, which is 1 order of magnitude higher than that with nano- or micrometer-sized LLZO particles as fillers. The CPE also shows a high lithium-ion transference number of 0.682, a stable and low Li/CPE interfacial resistance, and good mechanical properties favorable for all-solid-state lithium-ion battery applications. X-ray photoelectron spectroscopy and Raman analysis demonstrate that the LLZO fillers of all sizes interact with PVDF and LiClO4. High packing density (i.e., lower porosity) and long conducting pathways are believed responsible for the excellent performance of the composite electrolyte filled with mixed-sized ionically conducting ceramic particles.

Garnet‐Polymer Composite Electrolytes with High Li+ Conductivity and Transference Number via Well‐Fused Grain Boundaries in Microporous Frameworks

“…These well‐fused grain boundaries effectively eliminate the transfer barriers between the grain interfaces. Moreover, the activation energy of the presented PIC‐typed CPCE is estimated to be 0.42 eV from the Arrhenius plot (Figure c), which is based on the typical Nyquist plots of EIS measured at different temperatures (Figure S6).The activation energy of the presented PIC‐typed CPCE is comparable to the reported value of LLZTO electrolytes, which suggests that the ion conduction in the presented CPCE is dominated by the microporous LLZTO framework by providing continuous and conductive pathways for Li + transport. Besides, the Li + transference number ( ) of the presented CPCE is calculated to be as high as ∼0.71 (Figure d), which is a cutting‐edge value reported for solid‐state composite electrolytes (Table S3).…”

“…Forth, the CSEs framework in PIC configuration should induce a high Li + transference number, since CSEs are generally single‐ion conductors, while anions contribute significantly to the ion conduction in CIP configuration . A high Li + transference number is in favor of preventing side reactions at electrolyte‐electrode interfaces, which benefits the cycle life of batteries …”

Building Better Batteries in the Solid State: A Review

“…Following the same strategy, a membrane composed of LLZO particles and PVDF–HFP polymer matrix was proposed by Zhang et al [285]. Sun et al proposed a new composite based on LLZO and PVDF:LiClO 4 observing a high ionic conductivity at room temperature (2.6 × 10 −4 S cm −1 at 20 °C) [286]. The results are in agreement with the work proposed by Zhang et al in 2017 [287].…”

Toward safer solid-state lithium metal batteries: a review

“…It is accepted that composite electrolytes, including inorganic-polymer composite electrolytes and polymer-polymer composite electrolytes, can be a promising way to tackle the problem of the low shear modulus of SPEs. [20][21][22] In inorganicpolymer composite electrolytes, commonly used inorganic llers are classied into inert llers such as SiO 2 , TiO 2 , and Al 2 O 3 , and active llers which are mainly Li + conductors such as LLZO and LGPS. Both kinds of inorganic llers can improve the mechanical strength of SPEs and impose a certain inhibitory effect on lithium dendrites.…”