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Solid-state lithium batteries exhibit high-energy density and exceptional safety performance, thereby enabling an extended driving range for electric vehicles in the future. Solid-state electrolytes (SSEs) are the key materials in solid-state batteries that guarantee the safety performance of the battery. This review assesses the research progress on solid-state electrolytes, including polymers, inorganic compounds (oxides, sulfides, halides), and organic–inorganic composites, the challenges related to solid-state batteries in terms of their interfaces, and the status of industrialization research on solid-state electrolytes. For each kind of solid-state electrolytes, details on the preparation, properties, composition, ionic conductivity, ionic migration mechanism, and structure–activity relationship, are collected. For the challenges faced by solid-state batteries, the high interfacial resistance, the side reactions between solid-state electrolytes and electrodes, and interface instability, are mainly discussed. The current industrialization research status of various solid electrolytes is analyzed in regard to relevant enterprises from different countries. Finally, the potential development directions and prospects of high-energy density solid-state batteries are discussed. This review provides a comprehensive reference for SSE researchers and paves the way for innovative advancements in regard to solid-state lithium batteries. [ABSTRACT FROM AUTHOR]

To address the challenges posed by the narrow oxidation decomposition potential window and the characteristic of low ionic conductivity at room temperature of solid polymer electrolytes (SPEs), carbon dioxide (CO2), epichlorohydrin (PO), caprolactone (CL), and phthalic anhydride (PA) were employed in synthesizing di-block copolymer PCL-b-PPC and PCL-b-PPCP. The carbonate and ester bonds in PPC and PCL provide high electrochemical stability, while the polyether segments in PPC contribute to the high ion conductivity. To further improve the ion conductivity, we added succinonitrile as a plasticizer to the copolymer and used the copolymer to assemble lithium metal batteries (LMBs) with LiFePO4 as the cathode. The LiFePO4/SPE/Li battery assembled with PCL-b-PPC electrolyte exhibited an initial discharge-specific capacity of 155.5 mAh·g−1 at 0.5 C and 60 °C. After 270 cycles, the discharge-specific capacity was 140.8 mAh·g−1, with a capacity retention of 90.5% and an average coulombic efficiency of 99%, exhibiting excellent electrochemical performance. The study establishes the design strategies of di-block polymer electrolytes and provides a new strategy for the application of LMBs. [ABSTRACT FROM AUTHOR]

Practical high‐voltage lithium metal batteries hold promise for high energy density applications, but face stability challenges in electrolytes for both 4 V‐class cathodes and lithium anode. To address this, we delve into the positive impacts of two crucial moieties in electrolyte chemistry: fluorine atom (‐F) and cyano group (‐CN) on the electrochemical performance of polyether electrolytes and lithium metal batteries. Cyano‐bearing polyether electrolytes possess strong solvation, accelerating Li+ desolvation with minimal SEI impact. Fluorinated polyether electrolytes possess weak solvation, and stabilize the lithium anode via preferential decomposition of F‐segment, exhibiting nearly 6000‐h stable cycling of lithium symmetric cell. Furthermore, the electron‐withdrawing properties of ‐F and ‐CN groups significantly bolster the high‐voltage tolerance of copolymer electrolyte, extending its operational range up to 5 V. This advancement enables the development of 4 V‐class lithium metal batteries compatible with various cathodes, including 4.45 V LiCoO2, 4.5 V LiNi0.8Co0.1Mn0.1O2, and 4.2 V LiNi0.5Co0.2Mn0.3O2. These findings provide insights into design principles centered around polymer components for high‐performance polymer electrolytes. [ABSTRACT FROM AUTHOR]

Lithium metal batteries (LMBs) are anticipated to meet the demand for high energy density, but the growth of lithium dendrites seriously hinders its practical application. Herein, we constructed a kind of composite separator (ZIF-90@PP) consisting of zeolite imidazole framework-90 (ZIF-90) and polypropylene (PP) to promote the uniform deposition of Li+ and inhibit the growth of lithium dendrites. The aldehyde groups interacting with TFSI− and the nitrogen-containing negative groups attracting Li+ of ZIF-90 can facilitate the dissociation of LiTFSI to release more Li+, thus alleviating the influence of space charge near the electrode surface and accelerating the transfer of Li+. Not only does the excellent electrolyte wettability of ZIF-90 enhance the electrolyte retention capacity of the separator, but the orderly nano-channels in ZIF-90 also restrict the free migration of anions and homogenize the distribution of Li+. Consequently, the functional separator achieves a long-term stable Li plating/stripping cycling for over 780 h at 2 mA cm−2. Moreover, an impressive average coulombic efficiency of 98.67% at 0.5 C after 300 cycles is realized by Li || LFP full cells based on ZIF-90@PP with a capacity retention rate of 71.22%. The high-rate and long cycling performance of the modified Li || LFP cells further demonstrates the advantages of the ZIF-90@PP composite separator. [ABSTRACT FROM AUTHOR]

High ionic conductivity, outstanding mechanical stability, and a wide electrochemical window are the keys to the application of solid-state lithium metal batteries (LMBs). Due to their regular channels for ion transport and tailored functional groups, covalent organic frameworks (COFs) have been applied to solid electrolytes to improve their performance. Herein, we report a flexible polyethylene oxide-COF-LZU1 (abbreviated as PEO-COF) electrolyte membrane with a high lithium ion transference number and satisfactory mechanical strength, allowing for dendrite-free and long-time cycling for LMBs. Benefiting from the interaction between bis(triflfluoromethanesulonyl)imide anions (TFSI−) and aldehyde groups in COF-LZU1, the Li+ transference number of the PEO-5% COF-LZU1 electrolyte reached up to 0.43, much higher than that of neat PEO electrolyte (0.18). Orderly channels are conducive to the homogenous Li-+ deposition, thereby inhibiting the lithium dendrites. The assembled LiFePO4|PEO-5% COF-LZU1/Li cells delivered a discharge specific capacity of 146 mAh g−1 and displayed a capacity retention of 80% after 200 cycles at 0.1 C (60 °C). The Li/Li symmetrical cells of the PEO-5% COF-LZU1 electrolyte presented a longer working stability at different current densities compared to that of the PEO electrolyte. Therefore, the enhanced comprehensive performance of the solid electrolyte shows potential application prospects for use in LMBs. [ABSTRACT FROM AUTHOR]

Solid‐state lithium metal batteries (SSLMBs) are highly desirable for energy storage because of the urgent need for higher energy density and safer batteries. However, it remains a critical challenge for stable cycling of SSLMBs at low temperature. Here, a highly viscoelastic polyether‐b‐amide (PEO‐b‐PA) based composite solid‐state electrolyte is proposed through a one‐pot melt processing without solvent to address this key process. By adjusting the molar ratio of PEO‐b‐PA to lithium bis(trifluoromethanesulphonyl)imide (ethylene oxide:Li = 6:1) and adding 20 wt.% succinonitrile, fast Li+ transport channel is conducted within the homogeneous polymer electrolyte, which enables its application at ultra‐low temperature (−20 to 25 °C). The composite solid‐state electrolyte utilizes dynamic hydrogen‐bonding domains and ion‐conducting domains to achieve a low interfacial charge transfer resistance (<600 Ω) at −20 °C and high ionic conductivity (25 °C, 3.7 × 10−4 S cm−1). As a result, the LiFePO4|Li battery based on composite electrolyte exhibits outstanding electrochemical performance with 81.5% capacity retention after 1200 cycles at −20 °C and high discharge specific capacities of 141.1 mAh g−1 with high loading (16.1 mg cm−2) at 25 °C. Moreover, the solid‐state SNCM811|Li cell achieves excellent safety performance under nail penetration test, showing great promise for practical application. [ABSTRACT FROM AUTHOR]

Polymer‐based solid electrolytes (PSEs) have attracted tremendous interests for the next‐generation lithium batteries in terms of high safety and energy density along with good flexibility. Remarkable performances have been demonstrated in PSEs, which endowed PSEs with the potential to replace liquid electrolytes to meet the market demands. In this review, polymer matrices, different polymer architectures, and functional filler materials used in PSEs are discussed to explore the design concepts, methodologies, working mechanisms, and pros and cons of various PSEs. In addition, their recent notable applications in all‐solid‐state lithium ion batteries, lithium–sulfur batteries, suppression of lithium dendrites, and flexible lithium batteries are also introduced. Finally, the challenges and future prospects are sketched to provide strategies to explore novel PSEs for high‐performance all‐solid‐state lithium batteries. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel rigid-flexible multiblock copolymer PBC-mb-PBS was successfully synthesized. • Microphase separation structure was modulated by block molar ratio to regulate ionic conductivity. • This rational multiblock copolymer design for QSPEs offers superior overall performance. The growth of lithium dendrites and associated safety issues hinder the further development of liquid lithium metal batteries. A novel rigid-flexible multiblock copolymer PBC-mb-PBS was successfully synthesized based on molecular design. Incorporating crystalline rigid phase polybutylene succinate (PBS) into PBC-mb-PBS significantly enhances its tensile strength and low-temperature toughness through physical crosslinking. The flexible polydibutyl 2-(2-cyanoethyl)malonate (PBC) phase with side-chain cyano groups facilitate ionic conduction, forming a LiN-rich stabilized interfacial layer, thereby improving oxidative stability and high-voltage cathode compatibility. A series of multiblock copolymers with varying segment lengths were synthesized to balance mechanical properties and ionic conductivity by adjusting microphase separation. The quasi-solid-state polymer electrolyte (QSPE), derived from PBC-mb-PBS with the molar block ratio of 0.42, exhibits optimal electrochemical performance with ionic conductivity of 6.20 × 10−5 S cm−1 at 30°C and 4.22 × 10−4 S cm−1 at 60°C. Due to its bicontinuous microphase structure, it also shows excellent mechanical strength and promotes uniform lithium deposition at high current densities. Li//LiFePO 4 and Li//LiNi 0.83 Co 0.05 Mn 0.12 O 2 cells demonstrate high capacity retention, confirming the potential of this polymer electrolyte in high-voltage applications. This design strategy offers insights for developing quasi-solid-state lithium metal batteries with superior overall performance. [ABSTRACT FROM AUTHOR]

The mechanically hard phase and ionically conductive phase endow suitably designed block copolymer electrolytes (BCPEs) with the "Janus" property, thus providing the opportunity to decouple the trade-off between mechanical strength and ionic conductivity by controlling the phase-separated structures. The conductivity of BCPEs is predominantly determined by the molecular structure of block copolymers and the type and concentration of additives, while the manipulation of phase-separated structures helps strengthen their mechanical support and ion transport. This review article presents an overview of BCPEs and focuses on the "molecular structure-phase structure-property" relationship. Ideally, BCPE membranes should have high-throughput and aligned ion transport channels perpendicular to electrodes. First, given the desired attributes of polymer electrolytes, i.e., high ionic conductivity, high strength, low thickness, and high limiting current density, we summarize the research status and optimization strategies for BCPEs. Second, we present a summary of methods that control the phase behavior of BCPEs based on the phase separation mechanism. Third, BCPEs are classified into dual-ion conductor and single-ion conductor, whose advantages and disadvantages are analyzed. Furthermore, we propose a design rationale for high-performance quasi-solid-state BCPEs. We elaborate polymerization methods for the regulation of molecular and phase structure. These aspects are believed to collectively contribute to BCPE membranes with both high ion-conductivity and high mechanical strength, further boosting the development of safe and high-energy solid-state lithium metal batteries. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • Self-healing polymer electrolytes IBshPE were based on synergetic dynamic bonds. • IBshPE possesses high ionic conductivity of 5.08 × 10−3 S cm−1 at 30 °C. • IBshPE can self-heal within 4 h at room temperature. • IBshPE can effectively suppress dendrite growth on Li metal anodes. • LiFePO 4 cells assembled with IBshPE exhibit excellent performance. Self-healing polymer electrolytes can improve the safety, reliability and cycle life of the batteries. Herein, we developed a self-healing polymer electrolyte (IBshPE) with high ionic conductivity and excellent self-healing property. IBshPE cross-linked by synergetic dynamic imine bond and boroxine bond was prepared via the reaction of 2-formylphenylboronic acid and poly(ethylene glycol) diamine. In IBshPE, boroxine bonds with B-N coordination and imine bonds can synchronously undergo fast bond exchange reactions, enabling rapid self-healing of IBshPE. IBshPE shows high self-healing efficiency of 97% within 4 h. The healed IBshPE has nearly the same mechanical property and ionic conductivity as the original IBshPE. IBshPE exhibits the highest ionic conductivity (5.08 × 10−3 S cm−1 at 30 °C) among the reported self-healing polymer electrolytes. IBshPE facilitates the construction of robust LiF-rich SEI and efficiently inhibits dendrite growth. LiFePO 4 /Li cells with IBshPE exhibits excellent cycle performance (capacity retention of 98.6% after 80 cycles) and good rate capability (specific capacity of 130.5 mAh g−1 at 2C rate). More importantly, IBshPE is capable of self-repairing damage in the LiFePO 4 /Li cells and restoring the performance of the cells, thus effectively enhancing the reliability and safety of the battery. [ABSTRACT FROM AUTHOR]

[Display omitted] • A self-healing polymer electrolyte based on dynamic imine bonds was developed. • PBPE can completely self-heal within 1 h at room temperature. • PBPE possesses high ionic conductivity of 4.79 × 10−3 S cm−1 at 30 °C. • PBPE can effectively suppress dendrite growth on Li metal anodes. • LiFePO 4 cells assembled with PBPE exhibit excellent performance. High-performance polymer electrolytes with the capability to self-heal mechanical damage can effectively enhance reliability, safety and service life of the batteries. Herein, a novel polymer electrolyte (PBPE) with excellent self-healing capacity and high ionic conductivity was developed. PBPE with polymer networks cross-linked by highly reversible imine bonds was fabricated by the Schiff-base reaction between poly(ethylene glycol) diamine and benzene-1,3,5-tricarbaldehyde. PBPE can quickly repair the cut damage spontaneously within 1 h at room temperature and recover its mechanical strength and electrochemical properties. The healed PBPE exhibits almost the same ionic conductivities and mechanical properties as the original PBPE shows. PBPE possesses the highest ionic conductivity (4.79 × 10−3 S cm−1 at 30 °C) among the self-healing polymer electrolytes. PBPE can promote the generation of LiF-rich SEI and effectively suppress dendrite growth on Li metal anodes. LiFePO 4 (LFP) cells assembled with PBPE exhibit excellent rate capability (discharge capacity of 118.2 mAh g−1 at 5 C rate) and good cycling performance (capacity retention of 97.8% over 125 cycles). More importantly, the healed PBPE can completely recover its properties from damage in LFP cells and enable the cells to possess cycle performance identical to original PBPE. [ABSTRACT FROM AUTHOR]

Conventional liquid electrolytes applied in lithium-ion batteries suffer from high flammability, lithium dendrites and leakage. Gel polymer electrolytes (GPEs) are promising alternative electrolytes owing to their high ionic conductivities and enhanced safeties. Nevertheless, the flammable plasticizers of GPEs still bring safety hazards for the batteries. To address these issues, nonflammable highly-fluorinated quasi-solid-state polymer electrolytes (ED@PVDF) with ultrahigh ionic conductivities, excellent flame-retardant properties and superior cycling stability are developed. ED@PVDF possesses three-dimensional polymeric network within the framework of electrospun PVDF fibers, which is fabricated by thiol-ene click reaction. Highly-fluorinated carbonates (fluoroethylene carbonate and methyl 2,2,2-trifluoroethyl carbonate) are employed as plasticizers for ED@PVDF to improve flame-retardant property and enhance compatibility with anodes. Nonflammable ED@PVDF exhibits remarkable flame resistance, the highest ionic conductivity (4.41 mS cm−1 at 30 °C) among the nonflammable polymer electrolytes and wide electrochemical windows (5.6 V). ED@PVDF can promote the generation of LiF-rich solid electrolyte interphase and effectively restrain dendrite growth on Li metal anodes. ED@PVDF endows LiFePO 4 cells with outstanding rate capability (specific capacity of 123.8 mAh g−1 at 5C rate) and superior cycling stability (capacity retention of 81.4% over 1000 cycles). [Display omitted] • A nonflammable quasi-solid-state polymer electrolytes ED@PVDF was developed. • ED@PVDF exhibits remarkable flame resistance. • ED@PVDF possesses high ionic conductivity of 4.41 mS cm−1 at 30 °C. • ED@PVDF can effectively suppress dendrite growth on Li metal anodes. • LiFePO 4 cells assembled with ED@PVDF exhibit excellent performance. [ABSTRACT FROM AUTHOR]