Nanofiber-Based Composite Solid Electrolytes for Solid-State Batteries: From Fundamentals to Applications

Nanoscience Energy Chemistry Chemistry Materials Science Engineering Energy Engineering Materials Chemistry
nanofibers solid-state batteries composite solid electrolytes ionic conductivity high performance

Academic Background

With the rapid development of portable electronic devices and electric vehicles, the demand for high-performance energy storage technologies is growing. Lithium-ion batteries (LIBs), as the mainstream energy storage technology, still face challenges in terms of energy density and safety. In particular, the growth of lithium dendrites and the flammability of liquid organic electrolytes pose serious safety risks. To address these issues, solid-state batteries (SSBs) have emerged. SSBs replace liquid electrolytes with solid-state electrolytes (SSEs), offering higher safety and potential improvements in energy density. However, traditional solid-state electrolytes have limitations in ionic conductivity and mechanical properties, hindering their practical application.

Composite solid electrolytes (CSEs), which disperse fillers and salts in a polymer matrix, combine the advantages of polymer and inorganic electrolytes, becoming a research hotspot in the field of solid-state batteries. However, traditional CSEs still face issues such as uneven distribution and agglomeration of fillers, which may impede ion transport. Nanofibers (NFs), due to their long-range structure, high surface area-to-volume ratio, and high aspect ratio, are believed to significantly enhance the performance of CSEs. This article reviews the latest research progress on nanofiber-based composite solid electrolytes and explores their potential applications in solid-state batteries.

Paper Source

This article is co-authored by An-Giang Nguyen, Trang Thi Vu, Hang T. T. Le, Rakesh Verma, Phi Long Nguyen, Viet Bac T. Phung, and Chan-Jin Park. The authors are from multiple research institutions, including Chonnam National University (South Korea), VinUniversity (Vietnam), Hanoi University of Science and Technology (Vietnam), and University of Allahabad (India). The article was accepted on December 22, 2024, and published in the journal Advanced Fiber Materials, with the DOI: 10.1007/s42765-024-00508-3.

Main Content of the Paper

1. Fundamentals of Composite Solid Electrolytes

Composite solid electrolytes (CSEs) consist of a polymer matrix, fillers, and lithium salts. Fillers can be inorganic materials (e.g., oxides, sulfides) or polymers (e.g., polyethylene oxide, PEO). The design of CSEs aims to combine the flexibility of polymer electrolytes with the high ionic conductivity of inorganic electrolytes. However, the uneven distribution and agglomeration of fillers in traditional CSEs limit their performance. Nanofibers, as a new type of filler, can provide continuous ion transport pathways due to their high surface area-to-volume ratio and aspect ratio, significantly enhancing the performance of CSEs.

2. Design and Synthesis of Nanofibers

The synthesis methods for nanofibers include electrospinning, template methods, deposition methods, centrifugal spinning, and solution blow spinning. Electrospinning is the most commonly used technique for nanofiber preparation, where polymer solutions are stretched into fibers under a high-voltage electric field. The template method uses sacrificial templates to prepare inorganic fibers, suitable for large-scale production. Deposition methods (e.g., chemical vapor deposition, CVD) allow precise control over fiber size and morphology. Centrifugal spinning and solution blow spinning offer higher production efficiency and flexibility.

3. Preparation of Nanofiber-Based Composite Solid Electrolytes

The preparation methods for nanofiber-based composite solid electrolytes mainly include infiltration and in-situ polymerization. The infiltration method involves permeating polymer or inorganic electrolyte solutions into the nanofiber network to form a dense electrolyte membrane. In-situ polymerization involves infiltrating monomers into nanofibers, followed by thermal or photo-induced polymerization to form solid electrolytes. These methods preserve the unique structure of nanofibers while enhancing the ionic conductivity and mechanical properties of the electrolyte.

4. Applications of Nanofiber-Based Composite Solid Electrolytes

The applications of nanofiber-based composite solid electrolytes in solid-state batteries are mainly reflected in the following aspects: - Polymer Nanofiber-Based CSEs: Polymer nanofibers (e.g., polyacrylonitrile, PAN) as reinforcing materials can enhance the mechanical strength and ionic conductivity of electrolytes. For example, PAN-PEO/LiTFSI electrolytes exhibit good cycling performance at 60°C. - Inorganic Nanofiber-Based CSEs: Inorganic nanofibers (e.g., LLTO, LLZO) as active fillers can provide additional ion transport pathways. For example, LLTO-PEO electrolytes exhibit high ionic conductivity and good electrochemical stability at room temperature. - Composite Nanofiber-Based CSEs: Composite nanofibers combine the advantages of polymer and inorganic materials, further improving the overall performance of electrolytes. For example, PAN/LLZTO-PEO electrolytes exhibit excellent cycling stability and high discharge capacity at 60°C.

5. Interface Between Nanofiber-Based Composite Solid Electrolytes and Electrodes

The interfacial contact between the electrolyte and electrodes in solid-state batteries is a key factor affecting battery performance. Nanofiber-based composite solid electrolytes, with their unique network structure, can improve the contact between the electrolyte and electrodes, reducing interfacial resistance. For example, methods such as hot pressing or in-situ polymerization can achieve tight contact between the electrolyte and electrodes, enhancing the cycling performance and stability of the battery.

Significance and Value of the Paper

This article systematically reviews the research progress on nanofiber-based composite solid electrolytes, detailing their design, synthesis, preparation, and applications. Nanofibers, as a new type of filler, can significantly enhance the ionic conductivity and mechanical properties of composite solid electrolytes, providing new insights for addressing key issues in solid-state batteries. The research in this article offers theoretical guidance and technical support for the development of high-performance solid-state batteries, holding significant scientific and application value.

Research Highlights

  • Application of Nanofibers: Nanofibers, due to their high surface area-to-volume ratio and aspect ratio, can provide continuous ion transport pathways, significantly enhancing the performance of composite solid electrolytes.
  • Multiple Preparation Methods: Various nanofiber preparation methods, such as electrospinning, template methods, and deposition methods, offer flexible options for the development of composite solid electrolytes.
  • Interface Optimization: Infiltration and in-situ polymerization methods can achieve tight contact between the electrolyte and electrodes, reducing interfacial resistance and improving battery performance.

Conclusion

Through a comprehensive review of nanofiber-based composite solid electrolytes, this article demonstrates their immense potential in solid-state batteries. Future research can further explore the structural design and interface optimization of nanofibers to achieve higher-performance solid-state batteries.