Dual interface design of Ga‐doped Li ₇ La ₃ Zr ₂ O ₁₂ /polymer composite electrolyte for solid‐state lithium batteries

Abstract

Summary Solid‐state lithium‐metal batteries (SSLMBs) with a Li7La3Zr2O12‐based composite solid electrolyte (CSE) show great potential for overcoming the safety and specific energy concerns of conventional liquid‐electrolyte Li‐ion batteries. Nevertheless, achieving a satisfactory connection between a solid electrolyte and the cathode and anode materials is a major challenge. A dual interface modification strategy is proposed here to address this problem. CSEs with various fractions of Ga‐doped Li7La3Zr2O12 (LGLZO), polyethylene oxide (PEO), and lithium bis(trifluorosulfonyl)imide (LiTFSI) are spin‐coated directly onto a lithium iron phosphate (LFP) cathode to improve the cathode/CSE interfacial contact and establish a Li+ conducting network within the cathode. The effects of the Ga concentration in LGLZO on CSE conductivity and battery performance are investigated. The LGLZO:PEO:LiTFSI fraction and the number of spin‐coated layers are adjusted to optimize battery performance. The advantage of a spin‐coated CSE over a freestanding CSE in terms of reducing the migration barrier is demonstrated. In addition, an ionic liquid (IL) interconnection layer is incorporated at the Li/CSE junction to improve wettability. The effects of two IL anions, namely bis(fluorosulfonyl)imide (FSI−) and bis(trifluorosulfonyl)imide (TFSI−), on interfacial modification are systematically investigated. The optimal ionic conductivity of the CSE is ~1.0 × 10−3 S cm−1 at 60 °C. With this SSLMB configuration, the specific LFP capacities are 150 and 141 mAh g−1 at 0.1 and 1 C, respectively. Capacity retention of ~96% after 300 cycles is demonstrated.

A review on “Growth mechanisms and optimization strategies for the interface state of solid‐state lithium‐ion batteries”

“…[76][77][78][79][80][81] For low-molecular-weight polymers and polymers, the mode of ion conduction is similar to that of carbonate-based liquid electrolytes, which mainly occurs through diffusion in the form of solvation. 70,[82][83][84][85][86] It has been reported that the ionic conductivity in crystalline domain of polymer electrolytes is also higher than that in amorphous phase. In crystalline domains, polymer 281 Reprinted (adapted) with permission from Ref.…”

“…Therefore, the main form of ion conduction is interstage hopping 76–81 . For low‐molecular‐weight polymers and polymers, the mode of ion conduction is similar to that of carbonate‐based liquid electrolytes, which mainly occurs through diffusion in the form of solvation 70,82–86 …”

Suppression of Dehydrofluorination Reactions of a Li0.33La0.557TiO3-Nanofiber-Dispersed Poly(vinylidene fluoride-co-hexafluoropropylene) Electrolyte for Quasi-Solid-State Lithium-Metal Batteries by a Fluorine-Rich Succinonitrile Interlayer

“…PEO-based SPEs have been widely studied owing to their superior stability toward the Li metal anode and their good interface contact with the electrodes due to their soft texture. , A bilayer-SPE consisting of a cross-linked PEO layer and a linear PEO layer has been proposed to inhibit Li dendrite penetration and increase the cell charge–discharge Coulombic efficiency at the same time . However, low thermal stability and low ionic conductivity at room temperature restrict the applications of PEO-based electrolytes in SSLMBs. ,, PVDF-HFP-based SPEs have attracted much attention because of their good mechanical strength, great thermal stability, and wide electrochemical stability window. − Importantly, the HFP moiety in PVDF-HFP significantly reduces polymer crystallinity. , The strong electron-withdrawing effect of the C–F groups results in a high dielectric constant. − As a result, a satisfactory Li + conductivity can be achieved at ambient temperature. ,− To further improve the properties, various ISE fillers have been introduced into PVDF-HFP to fabricate composite solid electrolytes (CSEs). ,, The ISE fillers provide high Li + conductivity and enhance the mechanical properties of the CSE to suppress Li dendrite propagation. , A CSE thus combines the merits of SPEs and ISEs, showing desirable characteristics that have aroused great research interest in the SSLMB field. Nevertheless, the optimal ISE chemical composition and morphology have not been completely understood.…”

“…18 However, low thermal stability and low ionic conductivity at room temperature restrict the applications of PEO-based electrolytes in SSLMBs. 15,19,20 PVDF-HFP-based SPEs have attracted much attention because of their good mechanical strength, great thermal stability, and wide electrochemical stability window. 21−23 Importantly, the HFP moiety in PVDF-HFP significantly reduces polymer crystallinity.…”