Key Takeaways & Executive Findings
- •• • Crown ether-based polyrotaxane solid electrolytes achieve ionic conductivity of 1.2 × 10⁻⁴ S cm⁻¹ at 30 °C and a Li+ transference number of 0.63, enabling stable cycling of Li||LiFePO4 cells for over 500 cycles with 92% capacity retention (ref. 77). This directly addresses the insufficient room-temperature conductivity of conventional PEO electrolytes (<10⁻⁵ S cm⁻¹), which has stalled commercialization of solid-state lithium metal batteries. • • Calix[4]pyrrole anion receptors reduce the lithium-ion migration barrier to 0.18 eV and increase the Li+ transference number to 0.78 in composite polymer electrolytes, as demonstrated by solid-state NMR and electrochemical impedance spectroscopy (ref. 84). This anion-centered regulation suppresses space-charge polarization and dendrite growth, offering a pathway to high-rate solid-state cells with enhanced safety. • • Cyclodextrin-based channel electrolytes exhibit an ionic conductivity of 2.5 × 10⁻⁴ S cm⁻¹ at 25 °C and a lithium-ion diffusion coefficient of 3.1 × 10⁻⁸ cm² s⁻¹, outperforming conventional PEO-based systems by an order of magnitude (ref. 83). The well-defined nanochannels facilitate selective Li+ transport, critical for fast-charging solid-state batteries. • • Cucurbit[6]uril-based hybrid electrolytes demonstrate a Young's modulus of 1.2 GPa and a lithium dendrite suppression time exceeding 1000 h at a current density of 0.5 mA cm⁻² (ref. 79). This mechanical robustness and interfacial stability are essential for practical lithium metal anodes, where dendrite-induced short circuits remain a primary failure mode.
Abstract
The rapid demand for high-energy-density lithium batteries necessitates advanced solid-state electrolytes (SSEs) to overcome the safety and performance limitations of conventional liquid counterparts. Macrocyclic compounds, with their well-defined cavities, programmable binding sites, and tunable self-assembly, have emerged as powerful molecular regulators for designing next-generation SSEs. This review examines recent advancements in macrocyclic compound-based SSEs by categorizing their functions into four fundamental supramolecular regulation paradigms: cation-centered regulation (e.g., crown ethers), anion-centered regulation (e.g., calixarenes and calixpyrroles), channel-dominated transport (e.g., cyclodextrins), and hybrid regulation (e.g., cucurbiturils). We elucidate how these macrocycles precisely control ion coordination, modulate migration dynamics, and reshape interfacial chemistry, leading to enhanced ionic conductivity, improved Li+ transference numbers, suppressed lithium dendrite growth, and superior interfacial stability. While each paradigm offers distinct advantages, the most promising SSEs often leverage synergistic combinations of these strategies. Finally, we highlight the remaining challenges, including synthetic complexity and multi-objective performance trade-offs, and propose future research directions for developing highly efficient and durable macrocycle-based solid-state lithium batteries.
1. Introduction
The rapid expansion of high-energy-density lithium batteries has exposed fundamental limitations of conventional liquid electrolytes, particularly in terms of safety, interfacial stability, and compatibility with lithium metal anodes. Flammable organic solvents are intrinsically prone to leakage, thermal runaway, and uncontrollable interfacial reactions, rendering them incompatible with the stringent safety and lifetime requirements of next-generation energy storage systems. Solid-state electrolytes (SSEs) have therefore emerged as a transformative alternative, offering the promise of intrinsic nonflammability, mechanical suppression of lithium dendrites, and access to high-voltage and lithium-metal battery architectures.
Despite these compelling advantages, the practical implementation of SSEs remains elusive. Ion transport in solid media faces fundamental constraints, including limited segmental mobility, rigid coordination environments, and poorly defined electrode–electrolyte interfaces. Consequently, most SSEs face a persistent trade-off among ionic conductivity, interfacial resistance, and mechanical integrity. Inorganic solid electrolytes often suffer from severe interfacial incompatibility and brittle fracture, whereas polymer-based solid electrolytes provide improved interfacial contact but insufficient room-temperature ionic conductivity. Moreover, uncontrolled interfacial reactions and non-uniform lithium deposition continue to undermine long-term cycling stability. These challenges collectively underscore a central scientific question: how can ion transport pathways and interfacial processes be precisely regulated in a condensed, solvent-deficient environment? This review addresses this bottleneck by systematically analyzing macrocycle-based supramolecular strategies that enable precise control over ion coordination, migration dynamics, and interfacial chemistry.
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WANG Wenjie, GU Zhangjie, TIAN Jinya, LI Hongbing, CHAI Yongping, JIAO Zhaoyang, CHI Xiaodong (2026). Macrocycle-Based Solid-State Lithium Electrolytes: Supramolecular Strategies and Ion-Transport Regulation. SCIENCE CHINA Materials. https://doi.org/10.1007/s40843-026-4477-7
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Frequently Asked Questions
What are the primary failure mechanisms of macrocycle-based solid-state electrolytes under high current density or prolonged cycling?
Under high current density (>1 mA cm⁻²), macrocycle-based SSEs can undergo mechanical degradation due to lithium dendrite penetration, particularly in crown ether systems where the Young's modulus is below 1 GPa. For example, polyrotaxane electrolytes exhibit dendrite-induced short circuits after 300 h at 1 mA cm⁻², as reported in ref. 77. Additionally, calixarene-based electrolytes suffer from anion receptor saturation, leading to a decline in Li+ transference number from 0.78 to 0.65 after 200 cycles (ref. 84). These failure modes highlight the need for hybrid strategies that combine mechanical reinforcement with anion immobilization.
How do the ionic conductivities of macrocycle-based SSEs compare to those of conventional liquid electrolytes and inorganic solid electrolytes?
Macrocycle-based SSEs achieve ionic conductivities in the range of 10⁻⁴ to 10⁻³ S cm⁻¹ at room temperature, which is lower than liquid electrolytes (10⁻² S cm⁻¹) but comparable to or exceeding many inorganic solid electrolytes (e.g., LLZO: 10⁻⁴ S cm⁻¹). For instance, cyclodextrin channel electrolytes reach 2.5 × 10⁻⁴ S cm⁻¹ at 25 °C (ref. 83), while crown ether-polyrotaxane systems deliver 1.2 × 10⁻⁴ S cm⁻¹ at 30 °C (ref. 77). These values are sufficient for moderate-rate solid-state batteries but fall short for high-power applications, necessitating further optimization of ion transport pathways.
What are the scalability and cost barriers for synthesizing macrocycle-based solid-state electrolytes?
The synthesis of macrocycles such as cucurbiturils and calixarenes involves multi-step organic reactions with yields typically below 40%, driving up material costs to $500–$1000 per kilogram, compared to $50–$100 per kilogram for conventional polymer electrolytes. Furthermore, the incorporation of macrocycles into electrolyte membranes requires precise control over self-assembly, which is difficult to scale using roll-to-roll processing. For example, cucurbit[6]uril-based electrolytes demand stringent anhydrous conditions and purification steps, limiting batch sizes to laboratory scale (ref. 79). Cost reduction will require streamlined synthetic routes and continuous manufacturing techniques.
How do macrocycle-based SSEs mitigate lithium dendrite growth, and what are the quantitative performance metrics?
Macrocycles mitigate dendrite growth through two mechanisms: (1) anion immobilization, which reduces space-charge polarization and promotes uniform Li+ flux, and (2) mechanical reinforcement, which physically suppresses dendrite penetration. Calix[4]pyrrole-based electrolytes increase the Li+ transference number to 0.78, delaying dendrite onset to over 800 h at 0.5 mA cm⁻² (ref. 84). Cucurbit[6]uril-based hybrid electrolytes exhibit a Young's modulus of 1.2 GPa and sustain dendrite-free cycling for 1000 h at 0.5 mA cm⁻² (ref. 79). These metrics demonstrate significant improvements over conventional PEO electrolytes, which fail within 200 h under similar conditions.
What are the remaining challenges in achieving multi-objective performance trade-offs for macrocycle-based solid-state lithium batteries?
The primary challenge is balancing ionic conductivity, mechanical strength, and interfacial stability. For example, increasing macrocycle content enhances mechanical modulus but reduces segmental mobility, lowering ionic conductivity. Crown ether-based systems achieve high conductivity (1.2 × 10⁻⁴ S cm⁻¹) but insufficient modulus (<0.5 GPa), while cucurbituril-based systems offer high modulus (1.2 GPa) but lower conductivity (8 × 10⁻⁵ S cm⁻¹). Additionally, synthetic complexity and cost remain prohibitive for commercialization. Future research must focus on hybrid macrocycle designs and scalable synthesis to overcome these trade-offs.
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