Conventional quasi-solid-state electrolytes (QSEs), while offering some advantages in terms of safety and mechanical integrity compared to liquid electrolytes, are significantly hindered by two primary bottlenecks. First, the transport of sodium ions (Na⁺) through the bulk electrolyte is inhibited due to the dominant movement of anions, resulting in reduced Na⁺ transference numbers typically ranging between 0.4 to 0.7. This imbalance precipitates concentration polarization, reducing the effective ionic mobility at high current densities and limiting ultrafast charging capabilities. Second, ionic diffusion at the interfaces between electrolyte and electrodes—the bilateral interphases—is often sluggish, fostering dendrite formation on the anode and accelerating electrolyte degradation, thereby compromising both longevity and safety of SMBs.

Shattering these limitations, a research consortium from Southeast University, in partnership with HiNa Battery Technology Co., Ltd. and Yangzhou University, has introduced an innovative dual interlocked mediator electrolyte system. This novel quasi-solid-state electrolyte, designated as Sn-FB QSE, achieves near-unity Na⁺ transference numbers alongside exceptional ionic conductivity without resorting to complex polymer functionalizations typically required in single-ion conducting strategies. The secret lies in the synergistic engineering of two mediators—cationic Sn²⁺ ions and anionic difluoro(oxalato)borate (DFOB⁻)—that simultaneously modulate the bulk electrolyte structure and interfacial chemistry, delivering unprecedented electrochemical performance tailored for ultrafast charging and extended battery life.

The dual interlocked mediator mechanism operates on two intertwined fronts. During the synthesis phase, Sn²⁺ initiates a controlled in situ cationic polymerization of 1,3-dioxolane (PDOL), constructing a uniformly cross-linked amorphous polymer network that imparts mechanical strength while facilitating ion transport. Simultaneously, DFOB⁻ acts as a polymerization retarder, preventing excessive cross-linking and maintaining an optimal network polydispersity index around 1.6—a value significantly lower than single-mediator systems—thus balancing mechanical robustness with ion mobility. This finely tuned polymer matrix strengthens puncture resistance to 8.5 kPa, crucial for preventing dendrite penetration while supporting flexible form factors.

At the molecular level, sophisticated simulations reveal that DFOB⁻ preferentially coordinates with Na⁺ ions, effectively attenuating the strong Na⁺-polymer oxygen interactions that traditionally bind salts tightly within polymer matrices. This chemical modulation reduces the average coordination number from 4.87 to 2.81, liberating a substantial fraction of free Na⁺ ions that are free to migrate swiftly through the electrolyte. The resulting diffusion coefficient, calculated at 16.8 Ų/ns, marks a sixfold enhancement over conventional liquid electrolytes, thereby enabling rapid Na⁺ conduction even under aggressive charging regimes.

Upon cell operation, an elegant interfacial transformation ensues shaped by the distinct frontier orbital energies of the two mediators. Sn²⁺$, possessing a low LUMO energy level of −4.87 eV, is preferentially reduced at the sodium metal anode surface, forming a hybrid solid-electrolyte interphase (SEI) composed of nano-scale NaSn alloys embedded within inorganic-rich matrices. This SEI effectively homogenizes local electric fields, dramatically reducing nucleation overpotentials to approximately 50 mV and creating a mechanically stable protective barrier that mitigates dendrite initiation and growth. Concurrently, the DFOB⁻ anion, with its higher HOMO energy of −8.12 eV, undergoes sacrificial oxidation at the cathode to establish a thin yet resilient cathode–electrolyte interphase (CEI) approximately 14 nm thick. This CEI exhibits an extraordinary Young’s modulus near 8.9 GPa, an order of magnitude greater than single-mediator counterparts, mitigating mechanical degradation during repeated cycling.

Electrochemical testing validates the transformative impact of this dual mediator approach. Symmetric Na|Na cells sustain stable cycling over an unprecedented 6000 hours at 0.1 mA cm⁻² with minimal polarization (~0.1 V) and no dendritic short-circuit events, comparable to nearly continuous operation for over eight months. The critical current density surges to 3.0 mA cm⁻², while the exchange current density rises to 10 μA cm⁻², reflecting enhanced interfacial kinetics. When paired with Na₃V₂(PO₄)₃ (NVP) cathodes, full cells demonstrate retention of 90% capacity after 2000 cycles at a rapid 3C charge-discharge rate, retaining 80.1 mAh g⁻¹ at an extraordinary 15C, and maintaining 53.4 mAh g⁻¹ after 800 cycles even at 5C. The electrochemical stability window is also broadly expanded to 4.7 V vs. Na⁺/Na, paving the way for compatibility with high-voltage cathode materials.

To bridge the gap between laboratory innovation and practical application, the research team scaled their Sn-FB QSE technology into high-mass-loading full cells containing 5 mg cm⁻² NVP cathodes, achieving 75% capacity retention after 500 cycles at 1C. Pouch cells without applied pressure, measuring 4 × 5 cm², demonstrated impressive mechanical resilience by retaining 84% capacity after 19 cycles and powering smartphones continuously even through repeated full folding. Additionally, compatibility with advanced sodium nickel iron manganese oxide (NaNi₁/₃Fe₁/₃Mn₁/₃O₂, NFM) cathodes with high mass loading (17.54 mg cm⁻²) was confirmed, showcasing initial capacities of 129.9 mAh g⁻¹ and stable cycling performance over multiple cycles, indicating versatility across diverse cathode chemistries.

This pioneering dual interlocked mediator electrolyte paradigm overturns the long-standing trade-offs in electrolyte design—simultaneously achieving single-ion conduction, high mechanical strength, and adaptive bilateral interphases, properties traditionally viewed as mutually exclusive. By harnessing the complementary chemical and electronic properties of the Sn²⁺ and DFOB⁻ mediators, the approach delivers holistic control over ion transport and interfacial stability, unlocking performance metrics previously deemed unattainable for quasi-solid-state sodium electrolytes. Moreover, its intrinsic scalability via in situ polymerization and compatibility with existing battery manufacturing infrastructures spotlight this innovation as a viable candidate for commercial deployment.

Looking forward, this versatile mediator strategy harbors significant potential beyond sodium systems. Its principles may be extended to lithium and potassium metal batteries, where similar challenges in ion selectivity and interface stability prevail. Moreover, integrating this dual mediator system into fully solid-state configurations could yield safer, denser energy storage solutions with ultrafast charging capabilities. Concurrently, advancing mechanistic understanding through AI-guided frontier orbital screening may expedite the discovery of new mediator pairs optimized for specific chemistries, ushering an era of rational electrolyte design tailored to next-generation battery demands.

In essence, the dual interlocked mediator engineering approach pioneers a transformative paradigm for battery electrolytes that bridges performance, safety, and manufacturability. By breaking free from the restrictions imposed by traditional electrolyte designs, sodium metal batteries can now realistically aspire to meet the rigorous demands of ultrafast charging, long cycle life, and intrinsic safety at scale. This breakthrough marks a critical milestone propelling sodium batteries from a niche laboratory curiosity to a formidable contender in the mainstream energy storage landscape, drawing us closer to a sustainable energy future predicated on earth-abundant and cost-effective materials.

Subject of Research:
Article Title: Dual Interlocked Mediators Enable Single‑Ion‑Conducting Quasi‑Solid‑State Electrolytes for Ultrafast‑Charging Long‑Life Sodium Metal Batteries
News Publication Date: 21-May-2026
Web References: http://dx.doi.org/10.1007/s40820-026-02236-2
Image Credits: Yuan Zhang, Long Pan, Cheong Wa Leong, Xing-Guo Qi, Xiaozhong Huang, Xinyi Cai, Mufan Cao, Min Gao, Haoyu Zhang, Dawei Sha, Yang Zhou, ZhengMing Sun*

Keywords

Sodium Metal Batteries, Quasi-Solid-State Electrolytes, Single-Ion Conduction, Dual Interlocked Mediators, Sn-FB QSE, Polymer Electrolytes, Solid-Electrolyte Interphase, Cathode-Electrolyte Interphase, Ultrafast Charging, Electrochemical Stability, Ion Transport, Battery Cycle Life

With the global shift towards sustainable energy sources, the demand for more efficient battery systems becomes increasingly urgent. Current lithium-ion batteries, while widely adopted, face significant challenges, including resource scarcity and limited energy density. These factors drive the need for viable alternatives, such as calcium-ion batteries, which offer a promising solution. CIBs leverage abundant materials on Earth and possess an electrochemical window that could potentially rival that of traditional lithium-ion batteries. However, to date, they have struggled with issues related to efficient cation transport and consistent performance over extended use.

Led by Professor Yoonseob Kim, Associate Professor of the Department of Chemical and Biological Engineering at HKUST, the research team embarked on a mission to address these pressing challenges by developing redox covalent organic frameworks. These materials serve as QSSEs, enhancing the ionic conductivity of the battery system. Remarkably, the QSSEs exhibited an ionic conductivity of 0.46 mS cm⁻¹ and a Ca²⁺ transport capability exceeding 0.53 at room temperature. This breakthrough in material science opens new avenues for achieving stable, high-performance CIB technology.

During the experimental phase, the researchers conducted a comprehensive analysis combining both experimental data and simulation studies. The investigation revealed that Ca²⁺ ions move rapidly along the aligned carbonyl groups embedded within the ordered covalent organic framework’s pores. This understanding is crucial for optimizing the performance of calcium-ion batteries and illustrates the unique advantages presented by the new materials in comparison to traditional electrolytes.

The innovative work culminated in the successful fabrication of a complete calcium-ion cell which demonstrated a reversible specific capacity of 155.9 mAh g⁻¹ at a current density of 0.15 A g⁻¹. Additionally, after enduring 1,000 cycles at 1 A g⁻¹, the battery retained over 74.6% of its capacity, showcasing the potential longevity and reliability of this new battery design. This performance marks a pivotal step towards making CIBs a competitive alternative to existing lithium-ion systems, potentially transforming the energy storage landscape.

“By harnessing the unique characteristics of redox covalent organic frameworks, our research illustrates the transformative potential of calcium-ion batteries as a sustainable counterpart to lithium-ion technology,” remarks Prof. Kim. This statement encapsulates the team’s vision of not just creating a functioning battery but contributing to a more sustainable energy future, capable of supporting the global transition towards greener alternatives.

The implications of this research extend far beyond laboratory confines. The enhanced performance and sustainability of calcium-ion batteries present opportunities for integration in various applications, from renewable energy storage systems to electric vehicles. As the world increasingly prioritizes reductions in carbon emissions and the adoption of clean energy sources, the role of efficient and economically viable energy storage systems becomes indispensable.

While the road to widespread adoption of calcium-ion batteries may still involve overcoming regulatory hurdles and market acceptance, the research undertaken at HKUST showcases the foundational innovations required to inspire confidence in alternative energy storage solutions. The collaboration between HKUST and Shanghai Jiao Tong University highlights the importance of international partnerships in tackling complex challenges facing global energy needs.

In conclusion, this groundbreaking research on quasi-solid-state calcium-ion batteries signifies a potential shift in energy storage paradigms. By leveraging new materials and innovative designs, researchers are paving the way for a future where sustainable energy solutions can effectively meet the growing demands of modern society. As developments continue, the excitement around CIB technology is palpable, and its eventual commercialization could herald a new era in energy storage.

Strong collaborations in academia and industry will be vital to the successful transition from research findings to practical applications. More research will undoubtedly follow, with teams around the world looking to capitalize on the discoveries made by Prof. Kim and his colleagues. The trajectory set by this research promises not just improvements in functionality, but also a broader impact on global energy sustainability.

The findings discussed pave the way for further investigations into the scalability of this technology and its integration into commercial products. With continued advancement in battery technology, we stand on the edge of a transformative era where energy storage systems can become more efficient, sustainable, and accessible for everyone.

As interest grows in this critical area of research, the implications extend to policy-makers, industry leaders, and consumers alike, all of whom stand to benefit from a global shift towards more sustainable and reliable energy solutions. The role of innovative research as a catalyst for change cannot be overstated, and the breakthroughs occurring at institutions like HKUST reinforce the necessity of continued investment in energy research and development.

The research team’s achievements not only contribute to academic literature but also underscore the importance of applied science in addressing the most pressing challenges of our time. Through their exploration of calcium-ion technology, they offer a glimpse into the future of energy storage that aligns with our collective aspirations for a cleaner, more sustainable planet.

Subject of Research: Calcium-ion battery technology
Article Title: High-Performance Quasi-Solid-State Calcium-Ion Batteries from Redox-Active Covalent Organic Framework Electrolytes
News Publication Date: 16-Nov-2025
Web References: Advanced Science
References: 10.1002/advs.202512328
Image Credits: Credit: HKUST

Keywords

Alternative energy, Energy resources, Applied sciences, Engineering

Magnesium-ion batteries present several advantages over their lithium-ion counterparts, including higher theoretical energy density, lower cost, and improved safety features. Despite these benefits, the development of effective electrolyte materials remains a challenge. Conventional liquid electrolytes can pose safety hazards and lead to performance degradation. Hence, researchers have shifted their focus toward more stable solid-state or quasi-solid-state electrolytes that minimize these risks while maintaining desirable ionic conductivity.

In the study, the researchers synthesized a Mg⁺⁺ ion-conducting quasi-solid-state electrolyte utilizing polyethylene oxide blended with magnesium triflate. Polyethylene oxide, a polymer with excellent film-forming capabilities, serves as an ideal matrix for the incorporation of ionic salts. By combining polyethylene oxide with magnesium triflate, which is known for its high ionic conductivity, the researchers aimed to create a stable electrolyte with significant ion transport characteristics.

The methodology employed in this research involved systematic experimentation, varying concentrations of magnesium triflate within the polyethylene oxide matrix. Through precise control of the polymer to salt ratio, the team was able to optimize the ionic conductivity of the resulting electrolyte. The performance of the electrolyte was meticulously evaluated under various ambient conditions to ascertain its stability and effectiveness in a battery setup.

One of the standout findings of this research was the substantial enhancement in ionic conductivity observed at specific concentrations of magnesium triflate. The study revealed that a finely-tuned ratio of polyethylene oxide to magnesium triflate yielded an electrolyte with exceptional ion transport properties, making it a promising candidate for use in rechargeable magnesium-ion batteries. This breakthrough marks a significant stride toward developing safer and more efficient energy storage systems.

In addition to enhancing ionic conductivity, the researchers conducted a series of electrochemical tests to evaluate the performance of this quasi-solid-state electrolyte within a battery configuration. The charge-discharge cycles displayed remarkable stability, indicating that the electrolyte effectively facilitated ion movement between the electrodes during operation. Such performance metrics are vital for assessing the viability of magnesium-ion batteries in practical applications.

Another critical aspect addressed in the study was the thermal stability of the synthesized electrolyte. Unlike traditional liquid electrolytes that can evaporate or decompose at elevated temperatures, the quasi-solid-state configuration exhibited remarkable thermal stability. This characteristic is particularly valuable in battery applications where heat dissipation could pose a risk to safety and performance, making this technology suitable for a wide range of operating conditions.

The researchers also investigated the compatibility of the quasi-solid-state electrolyte with typical anode and cathode materials used in magnesium-ion batteries. By employing a series of material characterization techniques, the team assessed the interface behavior, which is pivotal for ensuring the efficiency of the electrochemical reactions driving the battery performance. Their findings indicated that the synthesized electrolyte maintained good interfacial stability, further validating its potential for commercial applications.

Despite the promising results, the study acknowledged the existing challenges in scaling up the production of such electrolytes. The researchers emphasized the importance of developing cost-effective manufacturing processes as a critical step in facilitating broader adoption of magnesium-ion battery technology. As the demand for energy storage solutions continues to grow, addressing these economic aspects will be crucial for the commercialization of these innovative battery systems.

Looking ahead, the implications of this research extend beyond magnesium-ion batteries. The materials and methodologies explored can serve as foundational building blocks for future electrolyte developments across various battery chemistries. The quest for more efficient, safer, and environmentally friendly energy storage solutions remains a priority for researchers and industry stakeholders alike.

In conclusion, the pioneering work of Sarangika, Dissanayake, and Senadeera marks a significant advancement in the exploration of magnesium-ion battery technology. By developing a novel quasi-solid-state electrolyte based on polyethylene oxide and magnesium triflate, the researchers have opened new avenues for enhancing battery performance. As the field of energy storage continues to evolve, such innovations hold the potential to redefine our approaches to sustainable energy technologies, bringing us closer to a future powered by efficient, reliable, and environmentally friendly battery systems.

As we delve deeper into the implications of this research, it becomes apparent that the energy landscape is on the brink of transformative changes. With ongoing efforts to optimize these new materials and adapt them for various applications, the potential impact on energy storage solutions globally is immense. The quest for efficient and safer battery technologies warrants continuing investment in research and development, ensuring that we harness the full capabilities of emerging materials science.

This study serves as a catalyst for further investigations into magnesium-ion batteries, encouraging a collaborative approach among researchers dedicated to overcoming existing hurdles in battery technology. By working together, the scientific community can accelerate the development and commercialization of next-generation energy storage systems that meet the growing demands of a sustainable future.

Subject of Research: Quasi-solid-state electrolytes for magnesium-ion batteries.

Article Title: Mg⁺⁺ ion conducting polyethylene oxide/magnesium triflate quasi-solid state electrolyte for rechargeable Mg⁺⁺ battery application.

Article References:

Sarangika, H.N.M., Dissanayake, M.A.K.L. & Senadeera, G.K.R. Mg⁺⁺ ion conducting polyethylene oxide/magnesium triflate quasi-solid state electrolyte for rechargeable Mg⁺⁺ battery application.
Ionics (2025). https://doi.org/10.1007/s11581-025-06536-2

Image Credits: AI Generated

DOI: https://doi.org/10.1007/s11581-025-06536-2

Keywords: Magnesium-ion batteries, quasi-solid-state electrolyte, polyethylene oxide, magnesium triflate, ion conductivity, energy storage systems.