Solvent-Free Process for Blended PVDF-HFP/PEO and LLZTO Composite Solid Electrolytes with Enhanced Mechanical and Electrochemical Properties for Lithium Metal Batteries

Abstract

All solid-state lithium metal batteries are viewed as a potential next-generation energy storage technology due to their high energy density and better safety performance. The study on solid-state electrolytes (SSE) is of crucial importance for the development of technology in this field. Here, we develop a solvent-free preparation and matrix modification process for allsolid-state composite electrolytes (CSEs) based on the blended PVDF-HFP/PEO polymer matrix, and systematically study the effects of the solvent-free process on their properties. The results show that the solvent-free PVDF-HFP/PEO/10 wt % LLZTO solid-state electrolytes (1:1 mass ratio blended polymer matrix) combine the electrochemical and mechanical advantages of both polymers, thus-prepared electrolytes perform excellent tensile strength and ductility (over 500% strain for polymer matrix as well as 170% strain and 4.78 MPa strength for CSEs), and the ionic conductivity can reach ∼6.2 × 10 −4 S•cm −1 at 80 °C. At the same time, the electrochemical stability and cycle stability of the electrolytes are enhanced due to the optimized process. The discoloration reaction of PVDF-HFP in composite electrolytes is further studied in this work as well. In addition to excellent performance, the simple process based on the solvent-free method also lays the foundation for scale-up production.

An Ultrathin, Flexible Solid Electrolyte with High Ionic Conductivity Enhanced by a Mutual Promotion Mechanism

“…As shown in Figure 4d, the discharge capacity of the LLZTO@SN/PAN cell first increases and then decreases, which is a common phenomenon in lithium-ion batteries considered as a battery activation process. 40 In the LLZTO@ SN/PAN cell, the coulomb efficiency is maintained above 99% after the second cycle. After 500 cycles, the capacity remains 87%, which is advanced in the research of USE-based cells (Table S1).…”

Polypropylene separator-reinforced polymer-in-salt solid composite electrolytes for high-performance lithium ion batteries at room temperature

“…S10 †), both indicating the outstanding electrochemical stability of the electrolytes under high current density conditions. 11 It is noteworthy that, whether at the beginning or aer 200 h cycling at 0.3 mA cm −2 , the PVDF-Li-LZ SSCEs always exhibit a good structural stability with the PVDF-Li-LZ layers tightly adhered on both sides of the PP separator (Fig. S11 and S12 †), which could strongly guarantee continues pathways inside the electrolyte for ion transfer.…”

“…[6][7][8] Unfortunately, their practical applications are always seriously hindered owing to the quite low ionic conductivity and unsatisfactory lithium-ion transference number (t Li +) at room temperature, which are derived from the insufficient amorphous regions for chain segment motion-based ion conduction and the weakly restricted anion migration in the polymer matrix, respectively. [9][10][11] To solve this issue, several primary approaches such as introducing diversied inorganic nanollers, [12][13][14] synthesizing copolymers and constructing cross-linked or interpenetrated networks [15][16][17] have been adopted to reduce the crystallinity of polymer chains along with enhancing the cation dissociation from lithium salt. However, for these strategies, the concentration of lithium salt in SPEs closely related to the ion conduction behavior is oen ignored.…”

Understanding Lithium Dendrite Suppression by Hybrid Composite Separators: Indentation Measurements Informed by Operando X-ray Computed Tomography

“…One strategy is to leverage the high ionic conductivity and strong modulus of inorganic fillers within an organic matrix . Several works simply disperse particles in gel separators and coatings, while others utilize covalent bonds and interactions between organic and inorganic phases to maximize spatial uniformity. ,− A prevalent duo in the hybrid inorganic–organic literature is filling poly­(vinylidene fluoride- co -hexafluoropropylene) (PVDF-HFP) with active (e.g., lithium-containing) inorganic particles, which together comprise an ionically conductive separator, coating, or electrolyte. ,− Several studies show that an optimal inorganic content exists to maximize the ionic conductivity of the material and the performance of the lithium metal battery. − Improvement of mechanics is also cited as a reason to incorporate the particles. However, mechanical experiments are often underappreciated in these works.…”