A solid composite electrolyte based on three-dimensional structured zeolite networks for high-performance solid-state lithium metal batteries

<p indent="0mm">Since the commercialization of lithium-ion batteries in the 1990s, lithium-ion batteries have been successfully applied in portable electronics, electric vehicles, and grid energy storage. Although current organic liquid electrolytes have high ionic conductivities, they are inherently flammable, volatile, and prone to leakage. Moreover, severe side reactions and dendrite growth on the surface of the lithium anode during the charge-discharge process can cause safety hazards, which greatly impede their applications in lithium metal batteries. Solid electrolytes, including inorganic solid electrolytes and polymer electrolytes, are regarded as effective alternatives to organic liquid electrolytes for the construction of lithium metal batteries with high energy density and safety. Among them, solid polymer electrolytes offer excellent flexibility, processability, and interfacial compatibility over inorganic solid electrolytes, and they are extraordinarily promising for lithium metal batteries with high energy density and safety. Ideal solid polymer electrolytes should have following features: (1) High ionic conductivity (&gt; <sc>10 ^–4 S cm ^–1) </sc> at room temperature; (2) high lithium ion transference number (~1) to reduce the concentration polarization and improve the rate performance of batteries; (3) intimate contact at the electrode/electrolyte interfaces; (4) wide electrochemical window <sc>(&gt;4.5 V</sc> vs. Li/Li ⁺) to match high-voltage cathodes and improve the energy density of batteries; (5) good mechanical stability to resist processing, buffer electrode volume change and inhibit dendrite growth; (6) good thermal stability to withstand environmental changes. Generally, the ionic conductivity of pure solid polymer electrolytes at room temperature is low <sc>(~10 ^–6 S cm ^–1). </sc> Researchers have tried to improve the ionic conductivities by adjusting the lithium salt concentration, such as developing “polymer-in-salt” solid electrolytes. However, increasing the concentration of lithium salt leads to the deterioration of the mechanical strength. Strategies such as developing novel lithium salts, modifying polymer matrix, and incorporating inorganic fillers into solid polymer electrolytes are proposed to promote ionic conductivities of solid polymer electrolytes. In particular, composite polymer electrolytes, fabricated by dispersing a certain amount of inorganic fillers into solid polymer electrolytes, have improved ionic conductivities without sacrificing their mechanical performances. Poor interfacial property between electrodes and electrolytes is also a critical issue for solid polymer electrolytes. On one hand, poor and uneven solid/solid contacts at the electrode/electrolyte interfaces lead to high resistance and sluggish ionic transport kinetics. Furthermore, the volume change of the positive and negative electrodes in the charge/discharge process deteriorates the interfacial contacts, blocks the ion and electron transport through the interfaces, and greatly reduces the electrochemical reaction kinetics. On the other hand, the electrochemical windows of solid polymer electrolytes are usually narrow <sc>(＜4.5 V).</sc> During cycling, redox reactions are prone to occur at the electrode/electrolyte interfaces, causing battery failure. Solid polymer electrolytes have also poor thermal and mechanical stabilities. Therefore, design and synthesis of polymer-based solid electrolytes with excellent comprehensive performances and construction of fast and stable ion transport channels at the electrolyte/electrode interfaces are of great significance for the successful development of solid-state lithium metal batteries. This paper presents a brief review of the research progress in solid polymer electrolytes from two aspects: Improving the ionic conductivities of solid polymer electrolytes and enhancing the interfacial performance at electrolyte/electrode interfaces. First, targeted optimization strategies on ionic conductivities of solid polymer electrolytes, including constructing continuously aligned ionic transport paths and shortening the ionic transport distance, are summarized. Second, interface optimization strategies, including constructing wetting interfaces and synthesizing asymmetric electrolytes, are presented to reduce the interface resistance and improve the interfacial contact. Finally, perspectives on the development of solid polymer electrolytes and high-performance solid-state lithium metal batteries are discussed, and key research directions and advanced test methods are proposed. This review may provide a comprehensive understanding and further guidance for not only the material design of solid polymer electrolytes, but also the structural design of lithium metal batteries with favorable electrochemical and interfacial performances.

Solid composite polymer electrolytes are the optimal candidate for all solid-state lithium batteries, because of their enhanced ionic conductivities, long-life cycle ability and compatibility to lithium anode. Herein, we reported a kind of solid composite polymer electrolyte comprised of poly(ethylene oxide), graphitic-like carbon nitride and lithium perchlorate, which was prepared by a facile solution blending method. Microstructure of the solid composite polymer electrolyte was regulated by thermal annealing and interaction among components and was characterized by XRD, DSC, FTIR-ATR, and ROM. The obtained solid composite polymer electrolyte achieved an ionic conductivity as high as 1.76 × 10−5 S cm−1 at 25°C. And the electrochemical stable window and the lithium ion transference number, t+, were also obviously enhanced. LiFePO4/Li solid-state batteries with the annealed PEO-LiClO4-g-C3N4 solid polymer electrolyte presented a high initial discharge capacity of 161.2 mAh g−1 and superior cycle stability with a capacity retention ratio of 81% after 200 cycles at 1C at 80°C. The above results indicates that the thermal annealing treatment and g-C3N4 as a novel structure modifier is crucial for obtaining the high-performance solid composite polymer electrolytes used in the all solid-state lithium battery.

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

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.

Copolymers comprising poly(ethylene glycol) acrylate soft unit and sulfobetaine methacrylate zwitterionic unit and its application in solid-state lithium metal battery at ambient temperature

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

Poly(ethylene oxide) (PEO)-based solid polymer electrolytes (SPEs) incorporating lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) offer excellent potential for solid-state lithium metal batteries (SSLMBs) due to their wide electrochemical stability window and high lithium salt solubility. LiTFSI supplies Li+ ions and also acts as a plasticizer, promoting the formation of the amorphous phase, which is vital for ionic conduction. Reduced ionic conductivity can result from very high crystallinity, spherulitic morphology, and secondary crystallization disrupting the ion pathways. The [EO:Li] molar ratio critically governs crystallization behavior and ionic transport; a ratio of 10:1, close to the stable amorphous eutectic composition (9:1), promotes amorphous phase formation and high ionic conductivity while limiting excessive crystallization. However, high salt content at this ratio leads to membrane stickiness, low mechanical strength, and handling difficulties. Here, we present a parafilm-assisted peeling technique that enables the fabrication of freestanding PEO/LiTFSI membranes while preserving their structural integrity. SEM analysis shows that conventional Teflon-mold peeling yields cracked, stretched surfaces, whereas parafilm-assisted films are smooth and defect-free. FTIR confirms Li+–PEO coordination with no parafilm–electrolyte interaction. Both methods deliver similar electrochemical performance: ∼4.30 V stability window, ionic conductivity 3.96 × 10−3 S cm−1 at 50 ° C (E a ∼ 0.898 eV), and Li+ transference number ∼0.14–0.15. Symmetric Li|SPE|Li cells cycle stably for 300 h at 50 ° C , while LiFePO4 full cells retain ∼161 mAh g−1 and >98% Coulombic efficiency over 30 cycles, confirming parafilm-assisted peeling as an effective fabrication method. This approach presents an effective means to address processing difficulties, thereby extending the viability of PEO based SPEs in next-generation energy storage devices.

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).

Solid polymer electrolytes offer a promising pathway toward safe, high-energy solid-state lithium metal batteries. However, their practical deployment remains limited by insufficient ionic conductivity, narrow oxidative stability windows, and poor interfacial compatibility with metal anodes. In particular, conventional polymer systems such as PEO typically operate below ∼3.8 V and cannot sustain high-voltage cathode chemistry. In this work, a solid polymer electrolyte based on a proprietary carbonate–fluorinated methacrylate copolymer PIRION-F (denoted as PCFMA) is developed and systematically evaluated. Comprehensive FTIR, X-ray diffraction, differential scanning calorimetry, TGA, and scanning electron microscopy analyses confirm the amorphous nature of the polymer, its robust thermal stability, and the dense microstructure of the solid electrolyte membrane. The PCFMA exhibits outstanding LiTFSI solubility, high ionic conductivity (0.1 mS cm–1 at room temperature and 1.2 mS cm–1 at 70 °C), and a wide oxidative stability window up to ∼4.8 V vs Li+/Li, enabling operation with high-voltage cathodes. Li symmetric cells display ultrastable cycling for over 4500 h with low polarization. All-solid-state Li//NCM622 and high-voltage Ni-rich cells further show reversible charge/discharge behavior and strong capacity retention during extended cycling at room temperature. To contextualize broader manufacturability, an independent multilayer pouch-cell prototype fabricated by a technology startup collaborator delivers a cell-level energy density of 523 Wh kg–1. Collectively, these results demonstrate the strong potential of PCFMA-based solid electrolytes for next-generation high-voltage solid-state lithium metal batteries.

Solid polymer electrolytes (SPEs) are critical for advancing the safety and performance of solid-state batteries (SSBs). However, challenges such as low ionic conductivity, limited mechanical strength, and narrow electrochemical stability windows hinder their widespread adoption. This study investigates the role of lithium salt formulation, specifically lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), and a binary mixture of the two, on the molecular structure and charge density of poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP)-based SPEs. Through comprehensive characterization, we demonstrate that the choice of lithium salt profoundly affects the crystallinity, dehydrofluorination degree, and ionic conductivity of SPEs. Notably, the binary salt mixture provides a balanced improvement in ionic conductivity (4.93 × 10-4 S/cm at 20°C) and mechanical strength (127MPa), alongside a broad electrochemical stability window. These findings suggest that strategic lithium salt formulation can significantly enhance the overall performance of SPEs, paving the way for their effective use in next-generation SSBs.

Anti-corrosion lithium anode interface by Li6.4La3Zr1.4Ta0.6O12 modified buffer layer for stable cycling of room-temperature solid-state lithium metal batteries.

Chemically bonding inorganic fillers with polymer to achieve ultra-stable solid-state sodium batteries

Practical implementations of solid polymer electrolytes (SPEs) in solid‐state lithium‐metal batteries (SSLMBs) are inhibited by the limited lithium‐ion (Li+) transport and poor‐quality interface between SPEs and both electrodes. SPEs exhibit lower ionic conductivity than other electrolytes and are oxidized and decomposed by oxide‐based cathode materials in high‐voltage windows. SSLMBs are also long‐term destabilized by parasitic side reactions at the electrode–electrolyte interfaces and Li dendrite formations. This study proposes a selectively designed Janus‐structured polymer electrolyte (JPE), which is more physically and chemically compatible with the electrodes than other SPEs. The proposed JPE includes a cathode‐facing composite polymer electrolyte (C‐CPE) containing succinonitrile and Li7La3Zr2O12, and an anode‐facing composite polymer electrolyte (A‐CPE) incorporating fluoroethylene carbonate (FEC). The C‐CPE layer provides additional Li+ paths and increases the antioxidant properties, improving the high‐voltage tolerance of the SSLMB, while the A‐CPE layer alleviates side reactions with the Li metal anode and improves the stability against protruding dendrites. Full cells of Li|JPE|Ni0.8Co0.15Al0.05O2 and Li|JPE|LiCoO2 remain stable over 1600 cycles at 1 C, demonstrating the potential of the JPE structures for SSLMBs. Moreover, symmetric Li||Li cells assembled with the JPE cycle over 2500 h at 0.1 mA cm−2 and 1000 h at 0.5 mA cm−2.

The Li-metal interphases formed in contact with solid-state (polymer) electrolytes (SSE) during electrochemical plating and stripping influences remarkably the lifespan and safety of solid-state batteries (SSBs). Effective interphases play a crucial role in impeding the continuous decomposition of electrolytes, the growth of dendrites, and consequently, enhancing the overall battery performance. However, the investigation of interphases of solid electrolytes remains a challenge, necessitating development of advanced techniques and methodologies. Moreover, highly sensitive instruments are demanded to detect the extremely thin interphases. Furthermore, real-time monitoring experimentations are needed to capture the interfacial dynamics. Addressing the interphase in solid-state battery under real working conditions is another major complication regarding the signal acquisition of the buried interfacial products between non-transparent electrodes. As a result, there are very limited studies of such a kind, which make our state-of-the-art understanding of interfacial process in SSBs very poor.Towards addressing this, we have developed and operando spectroscopy technique based-on Attenuated Total Reflection Fourier-Transform Infrared (ATR-FTIR) for real time monitoring of interphase composition between Li-metal and solid polymer electrolytes. ATR-FTIR spectroscopy is a powerful analytical technique that offers several significant advantages, including rapid data acquisition, applicability for various sample forms, and high sensitivity to trace even small amounts of substances non-destructively. The preservation of the original interphase composition is crucial for the characterization under real working conditions. Moreover, it is rather straightforward to combine the ATR-FTIR measurements with the electrochemical system by utilizing specifically designed spectro-electrochemical cells.Our team has been developing the advanced ATR-FTIR set-up for operando interphase analysis, which has already worked successfully for characterizing the interphases of liquid electrolyte system on Si and Li-metal electrode1. Based on the successful implementation of this technique, we further developed the setup for the analysis the interphases on solid-state electrolytes with lithium metal in anode-free configuration. In our investigation, a well-known system comprising polyethylene oxide (PEO) polymer, lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), and benzophenone as photoinitiated crosslinker, was chosen for use as a proof of concept. PEO is one of the most extensively used polymer for SSE, its conductivity at room temperature is however relatively low, as its optimated usage temperature is above 60oC. To ensure that our experimental setup remains comparable to contemporary research on PEO electrolytes, a temperature control system was implemented in the design of our spectro-electrochemical cell, besides, pressure controlling is also incorporated to enhance internal material adhesion. Furthermore, the ATR-FTIR instrument is equipped with adjustable incident angles for the IR beam, enabling the characterization of the interphases at different penetration depths. In terms of cell internal configuration, an anode-free setup was opted, which not only facilitates penetration of infrared beam, but is also regarded as a promising configuration for next-generation SSBs.Following the acquisition of IR spectrum during the Li plating-stripping process, it was observed that certain bands exhibited intensity variations, as a result of dynamicity in interfacial composition. Notably, some prominent variations were observed in the IR spectrum around 1500-1750 cm-1, primarily originated from bands associated with benzophenone. The reactions of the crosslinker may undergo within the electrolyte system during electrochemical process are often overlooked, which is due to the lack of techniques with the ability to monitor these reactions. The presented study outlines the need for advanced operando methods to increase the understanding of interphases formed by solid-electrolytes.In future perspectives, efforts will be directed towards further optimizing the cell setups and with the aim of applying this technique to investigate interphases and aging mechanisms in various solid electrolyte systems.Reference: Weiling, Matthias, et al. "Mechanistic Understanding of Additive Reductive Degradation and SEI Formation in High‐Voltage NMC811|| SiOx‐Containing Cells via Operando ATR‐FTIR Spectroscopy." Advanced Energy Materials5 (2024): 2303568.

Lithium metal is considered one of the most promising anode materials for lithium batteries due to its high theoretical specific capacity (3860 mA h g-1) and low redox potential (-3.04 V). However, uncontrolled lithium dendrite growth and severe interfacial side reactions during cycling result in poor performance and safety risks, significantly limiting its practical applications. Replacing liquid electrolytes with solid polymer electrolytes (SPEs) offers a solution, as SPEs provide flexibility and good electrode compatibility, effectively inhibiting dendrite growth and reducing interfacial reactions. Among SPEs, poly(vinylidene fluoride) (PVDF)-based solid electrolytes offer excellent thermal stability and mechanical strength, making them highly suitable for high-energy-density flexible batteries. This review presents recent advances in PVDF-based solid-state electrolytes (SSEs) for stable, high-performance lithium metal batteries (LMBs). We focus on modification strategies that enhance the performance of PVDF-based SSEs in solid-state LMBs and highlight how synthesis methods, nano/microstructural design, and electrochemical properties are interrelated. Lastly, we discuss the challenges and prospects for PVDF-based SSEs in next-generation high-performance LMBs.