3D Coral-like LLZO/PVDF Composite Electrolytes with Enhanced Ionic Conductivity and Mechanical Flexibility for Solid-State Lithium Batteries

Abstract

Composite polymer electrolytes (CPEs) are very promising for high-energy lithium-metal batteries as they combine the advantages of polymeric and ceramic electrolytes. The dimensions and morphologies of active ceramic fillers play critical roles in determining the electrochemical and mechanical performances of CPEs. Herein, a coral-like LLZO (Li6.4La3Zr2Al0.2O12) is designed and used as a 3D active nanofiller in a poly­(vinylidene difluoride) polymer matrix. Building 3D interconnected frameworks endows the as-made CPE membranes with an enhanced ionic conductivity (1.51 × 10–4 S cm–1) at room temperature and an enlarged tensile strength up to 5.9 MPa. As a consequence, the flexible 3D-architectured CPE enables a steady lithium plating/stripping cycling over 200 h without a short circuit. Moreover, the assembled solid-state Li|LiFePO4 cells using the electrolyte exhibit decent cycling performance (95.2% capacity retention after 200 cycles at 1 C) and excellent rate capability (120 mA h g–1 at 3 C). These results demonstrate the superiority of 3D interconnected garnet frameworks in developing CPEs with excellent electrochemical and mechanical properties.

Excellent Performances of Composite Polymer Electrolytes with Porous Vinyl-Functionalized SiO2 Nanoparticles for Lithium Metal Batteries

“…The excellent flexibility of the CPE membranes could also be proved by Figure 5a, which depicted ultrahigh 650% maximum elongation. This value was much higher than that reported in other studies in the literature [25,27,34,39]. The TGA data and FT-IR spectra (see Figures S1 and S2 in the Supporting Information) could confirm the complete removal of CTAB, successful grafting of vinyl, and full polymerization of monomers.…”

“…The excellent flexibility of the CPE membranes could also be proved by Figure 5a, which depicted ultrahigh 650% maximum elongation. This value was much higher than that reported in other studies in the literature [25,27,34,39]. The safety and availability of LMBs operating under long-term and extreme conditions are largely dependent on the thermal stability and mechanical strength of the electrolytes.…”

“…In the FT-IR spectra, the absorption peaks at 3467 cm −1 , 2900 cm −1 , 1750 cm −1 , and 1215 cm −1 represented the associating O-H of SiO 2 nanoparticles as well as stretching vibration of C-H, C=O, and C-O bonds, respectively. Moreover, the peak at 1660 cm −1 was related to the C=C, and 1120 cm −1 and 880 cm −1 were assigned to the symmetrical and asymmetrical stretching vibration of Si-O-Si [25,34,42,45].…”

“…SPEs are usually prepared by dissolving lithium salts in polymers (e.g., PEO, PVDF, PAN, PMMA), in which Li + are transported across polymer segments [22]. Unfortunately, they are suffering from low Li + conductivity at room temperature and are far from commercialization [23][24][25]. CPEs combine the advantages of ISEs and SPEs, which are constructed by introducing ceramic materials into polymer matrixes to obtain remarkably ionic conductivity (≈10 −4 S cm −1 ) to enhance the flexibility and good interfacial contact [26,27].…”

Improved Performance of All‐Solid‐State Lithium Metal Batteries via Physical and Chemical Interfacial Control

“…Before hot pressing, the SCE surface morphology showed many voids (Figure S1b, Supporting Information). The PVDF‐HFP/LLZO (1:1 wt%) SCE had a thickness of 30 µm (Figure 2h), which is thinner than that of recently reported SCEs, [ 33,34,50–52 ] and contained fewer voids.…”