| Author: | Zhang, Jing |
| Title: | Study on novel composite structural supercapacitors with excellent mechanical and electrochemical performance |
| Advisors: | Huang, Haitao (AP) Zhou, Limin (ME) |
| Degree: | Ph.D. |
| Year: | 2026 |
| Department: | Department of Applied Physics |
| Pages: | xxvii, 161 pages : color illustrations |
| Language: | English |
| Abstract: | Composite structural supercapacitors (CSSs) are essential and promising multifunctional materials in a wide range of weight- and volume-reduced electric vehicles and aircraft, as they exhibit both good mechanical and electrochemical properties in a single unit. However, the study of CSSs is predominantly hindered by maintaining good mechanical and electrochemical performance simultaneously under extensive and extreme application conditions. Research on the effect of electrochemical cycling on structural failure, particularly under applied loads, remains limited for CSSs. The electrochemical cycling-induced fatigue (electro-fatigue) failure and mechano-electrochemical coupling performance were investigated in a Zn-ion-based hybrid composite structural supercapacitor. Zn ion concentration gradient during the charge and discharge process induces alternating stress, which can be equivalent to a mechanical fatigue stress. The electro-fatigue stress gives rise to structural failure and a reduction in electrochemical performance. Moreover, for CSSs, coupling electro-fatigue stress with constant external stress results in an increased fatigue stress, significantly accelerating structural failure. These findings offer valuable insights and strategies to concurrently preserve superior electrochemical and mechanical integrity. To enhance the electrochemical capacitance and mechanical strength of CSS, a special structure of the electrode and electrolyte interface was designed. The energy unit with the snap-on buckle structure of electrode and hydrogel electrolyte interface is integrated into a complex matrix to enhance the interlock effect. Strong bonding between the electrode and electrolyte is crucial for maintaining excellent electrochemical performance under mechanical bending by minimizing shear movement between layers. Practical applications also indicate that the unique structure enables a new design of composite structural devices. Under external forces, the deformation of CSSs results in an uneven distribution of electric field intensity, potentially compromising both electrochemical performance and mechanical performance. An MXene-based electrolyte for Zn-ion-based hybrid CSS was fabricated to effectively modulate the electric field distribution through a polarized electric field formed by hydrogen bonds between MXene and polymer chains. Integrating MXene into the electrolyte potentially paves the way for the design of high-performance structural power sources capable of functioning under deformation. Low-temperature applications pose significant challenges due to electrolyte freezing and external force-induced deformation. To overcome these limitations, composite structural hybrid supercapacitors (CSSs) with enhanced mechanical strength and electrochemical performance at low temperatures were fabricated using a robust, freezing-resistant solid electrolyte. An unconventional Hofmeister effect of chaotropic ClO₄⁻ anions was observed in anti-freezing ethylene glycol (EG)-polymer, leading to simultaneous enhancements in the stiffness and toughness of the polymer composite. The formation of strong and long hydrogen bonding (SHB) among ClO₄⁻, EG, and the polymer matrix makes the material stiff and tough. Benefiting from the superior freeze resistance and mechanical strength, the fabricated CSS demonstrates exceptional electrochemical stability. Furthermore, this investigation deepens our understanding of CSS operation under both mechanical impact and subzero conditions, establishing design principles for CSS applications. Overall, this thesis focuses on the balance of electrochemical and mechanical performance of CSSs under practical and extreme application conditions. Through structural design or modification, satisfactory results are obtained, paving the way for the design and development of CSSs. |
| Rights: | All rights reserved |
| Access: | open access |
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