Synthesis and characterization of LAGP-glass-ceramics-based composite solid polymer electrolyte for solid-state Li-ion battery application

Solid‐state lithium batteries (SSLBs) with composite solid electrolytes (CSEs) offer enhanced energy density and high safety. However, their performance is hindered by large thickness and limited Li⁺ conductivity of CSEs, and large electrode/electrolyte interface resistance. This study develops an 18 µm‐thick CSE using a polyethylene scaffold, which incorporates garnet‐type Li6.25La3Zr2Ga0.25O12 (LLZGO) oxide and an ionic liquid (IL) additive in a poly(vinylidene fluoride‐co‐hexafluoropropylene)/polypropylene carbonate matrix, achieving a high ionic conductivity of 8.6 × 10−4 S cm−1 at 30 °C. The IL increases Li+ conduction of the CSE and reduces the interfacial resistance. The constructed LiNi0.8Co0.1Mn0.1O2 (NCM‐811)||CSE||Li cell shows remarkable charge–discharge performance. This study also integrates LLZGO and N‐propyl‐N‐methylpyrrolidinium bis(trifluorosulfonyl)imide (PMP‐TFSI) IL into a thick NCM‐811 cathode. The synergy between LLZGO and PMP‐TFSI within the cathode is examined. A high‐mass‐loading cathode with ≈20 mg cm−2 NCM‐811 is developed. The resulting composite cathode||CSE||Li cell achieves an areal capacity of ≈4 mAh cm−2. With the proposed scaffold‐supported CSE and thick NCM/LLZGO/IL composite cathode, the projected energy density of the resulting anode‐free pouch cell is ≈420 Wh kg−1. This study demonstrates a scalable and effective strategy for fabricating an oxide‐based SSLB with a high energy density and enhanced Li+ transport properties.

Solid polymer electrolytes (SPEs) are regarded as promising candidates for next-generation solid-state lithium metal batteries (SSLMBs) due to their high flexibility and excellent processability, whereas their practical application remains a challenge to simultaneously achieve high ionic conductivity, superior inherent stability, and desirable interfacial compatibility with the Li metal anode. Here, we report a composite solid electrolyte (CSE) incorporating a three-dimensional zeolite network (3D Zeo) into a poly(ethylene oxide) (PEO) matrix containing lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) salt (3D Zeo/PEO). The interconnected 3D Zeo provides continuous Li+-conduction pathways and promotes the amorphization of the polymer and the dissociation of the Li salt via Lewis acid–base interactions. The resulting 3D Zeo/PEO CSE exhibits an ionic conductivity of 1.62 × 10−4 S cm−1 at room temperature and an electrochemical stability window up to 5.7 V vs. Li+/Li, significantly surpassing those of LiTFSI–PEO SPE (3.23 × 10−6 S cm−1, 4.9 V). Leveraging the regulatory effect of the 3D Zeo/PEO CSE on Li+ deposition and solid electrolyte interphase formation, the symmetric cell demonstrates stable cycling over 2300 h with an overpotential of 0.13 V, and the full cells also deliver superior high-rate capability and long-term stability with a capacity retention of 92% after 500 cycles at room temperature, far exceeding the performance of batteries using LiTFSI–PEO SPE and CSE with zeolite-based particle fillers. This work provides a promising approach for the design of CSEs to achieve high interfacial compatibility and uniform Li+ deposition for next-generation SSLMBs.

Sodium-ion batteries (SIBs) are emerging as a promising alternative to lithium-ion batteries, primarily due to their plentiful raw materials and cost-effectiveness. However, the use of traditional organic liquid electrolytes in sodium battery applications presents significant safety risks, prompting the investigation of solid electrolytes as a more viable solution. Despite their advantages, single solid electrolytes encounter challenges, including low conductivity of sodium ions at room temperature and incompatibility with electrode materials. To overcome these limitations, the researchers develop composite polymer solid electrolytes (CPSEs), which merge the strengths of high ionic conductivity of inorganic solid electrolytes and the flexibility of polymer solid electrolytes. CPSEs are usually composed of inorganic materials dispersed in the polymer matrix. The final performance of CPSEs can be further improved by optimizing the particle size, relative content, and form of inorganic fillers. CPSEs show great advantages in improving ionic conductivity and interface compatibility, making them an important direction for future solid-state sodium battery research. Therefore, this paper summarizes recent advancements in composite solid electrolytes, discusses the impact of their preparation processes on performance, and outlines potential future developments in sodium-ion solid-state batteries.

Preparation, characterization and ionic conductivity studies of composite sulfide solid electrolyte

Lithium-ion solid-state batteries with spinel Li4Ti5O12 (LTO) electrodes have significant advantages, such as stability, long life, and good multiplication performance. In this work, the LTO electrode was obtained by the atmospheric plasma spraying method, and a composite solid electrolyte was prepared by in situ ultraviolet (UV) curing on the LTO electrode. The composite solid electrolyte was designed using a soft-hard combination strategy, and the electrolyte was prepared into a composite of a poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) flexible structure and high-conductivity Li1.3Al0.3Ti1.7(PO4)3 (LATP) hard particles. The composite electrolyte exhibited a good ionic conductivity up to 0.35 mS cm-1 at 30 °C and an electrochemical window above 4.0 V. In situ and ex situ electrolytes were assembled into LTO//electrolyte//Li solid-state batteries to investigate their impact on the electrochemical performance of the batteries. As a result, the assembled Li4Ti5O12//in situ electrolytes//Li batteries exhibited excellent rate of performance, and their capacity retention rate was 90% at 0.2 mA/cm2 after 300 cycles. This work provides a new method for the fabrication of novel advanced solid-state electrolytes and electrodes for applications in solid-state batteries.

Ambient temperature solid-state Li-battery based on high-salt-concentrated solid polymeric electrolyte

The sulfide-type solid electrolyte (SE) is a promising candidate for realizing all-solid-state batteries (ASSBs) due to its good mechanical properties and high ionic conductivity. However, challenges such as limited electrochemical stability, inadequate solid-solid contact with the electrode, and reactivity with lithium often lead to dendrite growth and electrolyte reduction. A simple, solvent-free method was developed to form a robust artificial interphase between lithium metal and the solid electrolyte to address these issues. This was achieved by incorporating a composite electrolyte composed of Li6PS5Cl, polyethylene glycol (PEG), and lithium bis(fluorosulfonyl)imide (LiFSI), leading to the in-situ formation of a LiF-rich interfacial layer. This interphase effectively suppresses electrolyte reduction and enhances lithium-ion diffusion. Notably, the PEG additive improves the mechanical strength of the electrolyte by enhancing adhesion between sulfide particles. It also increases the flexibility of the Li6PS5Cl solid electrolyte, improving physical contact with the lithium anode and acting as a protective barrier to prevent direct SE-Li interaction, thus reducing electrolyte decomposition. As a result, Li/Li symmetric cells exhibited excellent cycling stability, maintaining performance for over 3000 hours at a current density of 0.1 mA cm-2, while the composite solid electrolyte achieved a critical current density of 4.75 mA cm-2. This study underscores the synergistic benefits of combining an artificial solid electrolyte interphase (SEI) with composite solid electrolytes, paving the way for high-performance all-solid-state lithium metal batteries (ASSLBs).

Battery safety is increasingly at the forefront of consumer concerns, especially regarding electric vehicles. Current lithium ion battery technology utilizes liquid electrolytes, which have very high ionic conductivities but are extremely flammable. To improve safety, researchers are investigating replacing liquid electrolytes in lithium ion batteries with solid electrolytes. A promising approach is the use of solid polymer composite electrolytes where lithium conductive ceramic powders are dispersed into polymer electrolyte matrix. These materials are intended to improve lithium conductivities and mechanical properties relative to pure polymer electrolyte, lower manufacturing and battery cell construction costs relative to using pure ceramic electrolytes, and eliminate volatile and flammable electrolyte solvents. Currently, the archetypal polymer matrix used in composite electrolytes is polyethylene oxide (PEO). When mixed with lithium salts, such as lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), and ceramics, such as Li7La3Zr2O12 (LLZO), PEO based composites have conductivities (~10-7 S/cm at room temperature) that are still insufficient for today’s applications. In addition, PEO tends to crystallize and has poor oxidative stability (decomposition ca. 4V). We are exploring poly(polyethylene glycol methyl ether methacrylate) (PEGMA) and polyethylene carbonate (PEC) as alternatives to PEO to address issues with crystallization and oxidative stability, respectively. Composite electrolytes are fabricated by blending bulk polymer with LiTFSI and LLZO powders. We have formed rubbery PEGMA-based composites with comparable conductivities (~10-7 S/cm at room temperature, 70 vol% polymer, 10:1 ethylene oxide:lithium). Lithium symmetric cycling was observed to be stable over 250 hours at 1C. We have also recently formed stand-alone PEC based composites with high conductivities (~10-6 S/cm at room temperature, 60 vol% polymer, 10:1 ethylene carbonate:lithium). Investigations into the origin of this high conductivity and measurements of electrochemical stability are currently underway.

Flexible poly(ethylene carbonate)/garnet composite solid electrolyte reinforced by poly(vinylidene fluoride-hexafluoropropylene) for lithium metal batteries

This review focuses on the application of silicon-based materials in high-energy-density solid state batteries (SSBs), systematically organizing major research progress in SSBs centered on silicon-based anodes. The article reviews the technological development pathways in this field, analyzes the electrochemical processes, structural evolution behavior, and failure mechanisms of silicon-based anodes in solid-state batteries, and summarizes the research status of polymer solid electrolytes (PSEs), oxide solid state electrolytes (OSSEs), sulfide solid state electrolytes (SSSEs), halide solid state electrolytes (HSSEs), and composite solid electrolytes (CSEs) in silicon-based anode systems. It also proposes targeted potential future research directions. Finally, the commercial prospects of silicon-based anode solid-state batteries are discussed, aiming to provide insights for the strategic design of advanced silicon-based solid-state batteries and to offer clear theoretical and practical guidance for the development of high-performance lithium-ion batteries (LiBs).

Polyethylene oxide (PEO) based-solid polymer electrolytes were prepared with low weight polymers bearing carboxylic acid groups added onto the polymer backbone, and the variation of the conductivity and performance of the resulting Li ion battery system was examined. The composite solid polymer electrolytes (CSPEs) were composed of PEO, LiClO4, PAA (polyacrylic acid), PMAA (polymethacrylic acid), and Al2O3. The addition of additives to the PEO matrix enhanced the ionic conductivities of the electrolyte. The composite electrolyte composed of PEO:LiClO4:PAA/PMAA/Li0.3 exhibited a low polarization resistance of 881.5 ohms in its impedance spectra, while the PEO:LiClO4 film showed a high value of 4,592 ohms. The highest ionic conductivity of 9.87 × 10−4 S cm−1 was attained for the electrolyte composed of PEO:LiClO4:PAA/PMAA/Li0.3 at 20 °C. The cyclic voltammogram of Li+ recorded for the cell consisting of the PEO:LiClO4:PAA/PMAA/Li0.3:Al2O3 composite electrolyte exhibited the same diffusion process as that obtained with an ultra-microelectrode. Based on this electrolyte, the applicability of the solid polymer electrolytes to lithium batteries was examined for an Li/SPE/LiNi0.5Co0.5O2 cell.

Composite solid electrolyte with improved ionic conductivity and high lithium transference number through reduced PVDF-HFP crystallinity

Garnet‐type oxide Li6.4La3Zr1.4Ta0.6O12 (LLZTO) features superior ionic conductivity and good stability toward lithium (Li) metal, but requires high‐temperature sintering (≈1200 °C) that induces high fabrication cost, poor mechanical processability, and high interface resistance. Here, a novel high‐performance tricomponent composite solid electrolyte (CSE) comprising LLZTO−4LiBH4/xLi3BN2H8 is reported, which is prepared by ball milling the LLZTO−4LiBH4 mixture followed by hand milling with Li3BN2H8. Green pellets fabricated by heating the cold‐pressed CSE powders at 120 °C offer ultrafast room‐temperature ionic conductivity (≈1.73 × 10−3 S cm−1 at 30 °C) and ultrahigh Li‐ion transference number (≈0.9999), which enable the Li|Li symmetrical cells to cycle over 1600 h at 30 °C with only 30 mV of overpotential. Moreover, the Li|CSE|TiS2 full cells deliver 201 mAh g−1 of capacity with long cyclability. These outstanding performances are due to the low open porosity in the electrolyte pellets as well as the high intrinsic ionic conductivity and easy deformability of Li3BN2H8.

Synergistic design of 3D Na3.2Zr1.9Ca0.1Si2PO12-based composite solid electrolyte via in-situ polymerization for solid-state sodium batteries.

The development of solid-state electrolytes (SSEs) effectively solves the safety problem derived from dendrite growth and volume change of lithium during cycling. In the meantime, the SSEs possess non-flammability compared to conventional organic liquid electrolytes. Replacing liquid electrolytes with SSEs to assemble all-solid-state lithium metal batteries (ASSLMBs) has garnered significant attention as a promising energy storage/conversion technology for the future. Herein, a composite solid electrolyte containing two inorganic components (Li6.25Al0.25La3Zr2O12, Al2O3) and an organic polyvinylidene difluoride matrix is designed rationally. X-ray photoelectron spectroscopy and density functional theory calculation results demonstrate the synergistic effect among the components, which results in enhanced ionic conductivity, high lithium-ion transference number, extended electrochemical window, and outstanding dual interface compatibility. As a result, Li||Li symmetric battery maintains a stable cycle for over 2500h. Moreover, all-solid-state lithium metal battery assembled with LiNi0.6Co0.2Mn0.2O2 cathode delivers a high discharge capacity of 168mAhg-1 after 360 cycles at 0.1C at 25°C, and all-solid-state lithium-sulfur battery also exhibits a high initial discharge capacity of 912mAhg-1 at 0.1C. This work demonstrates a long-life flexible composite solid electrolyte with excellent interface compatibility, providing an innovative way for the rational construction of next-generation high-energy-density ASSLMBs.