| Author: | Liu, Qun |
| Title: | Designing polymer-derived interfaces for advanced zinc metal anodes |
| Advisors: | Zhang, Biao (AP) |
| Degree: | Ph.D. |
| Year: | 2024 |
| Subject: | Zinc ion batteries Anodes Electrodes Hong Kong Polytechnic University -- Dissertations |
| Department: | Department of Applied Physics |
| Pages: | xxiii, 180 pages : color illustrations |
| Language: | English |
| Abstract: | Zn-ion batteries (ZIBs) have gathered increasing interest due to their intrinsic safety, affordability and environmental benignity. Nevertheless, spontaneous corrosion and uncontrolled dendrites accumulation would rapidly degrade Zn metal anode. Remarkably, polymers with inherent properties of low density, high processability, structural flexibility and superior stability, demonstrate great potential in tackling these challenges. In this thesis, various polymer-derived strategies were exploited to optimize the interface of Zn metal anode for improved performance. Firstly, we adopt Zn powder as the raw material and mixed it with conductive carbon, thickening agent (poly(ethylene glycol, PEG) and Zn salt to prepare a semi-liquid electrode with rheological properties. The electrode demonstrates a stress-release mechanism that can address the dendrite growth on the root. In addition, the dual conductive network in the electrode promotes redox kinetics and facilitates Zn ion flux, achieving uniform deposition inside the electrode. The hydrogen bond interaction between PEG and water reduces the activity of water, achieving anti-corrosion capability. These advantages promote the potential application of Zn powder anode. Considering the limited mechanical properties of the Zn powder, we turn to Zn foil metal anodes. An elastomer-alginate interface is introduced on the surface of Zn foil as a physical barrier to inhibit the corrosion of Zn metal and adapt to the volume change during Zn plating/stripping. Impressively, the constraining effect of the elastomer and the ionic conductivity of Zn alginate concurrently realize a high-capacity Zn anode under high current rates. Along this direction, we note that the volume change of the Zn metal anode demonstrates a compressive fatigue effect on the electrolyte, especially for polymer electrolytes. We systematically analyze the compressive fatigue-resistance properties of the hydrogel electrolyte, revealing the critical roles of the salts and copolymer matrix on crack initiation and propagation. We reveal that on the premise of homogeneous Zn deposition, an improved anti-fatigue property is essential to achieve high-capacity Zn metal anodes. The optimal Zn(ClO4)2-polyacrylamide/chitosan hydrogel electrolyte (C-PAMCS) exhibits an unprecedented lifespan of 1500 h for Zn//Zn cells at a current density of 10 mA cm-2 and a high areal capacity of 10 mAh cm-2. Finally, considering the inconsistent requirements of the Zn anode and various cathodes, an asymmetric hydrogel electrolyte (AHE) with varying compositions and chemical structures on each electrolyte-electrode interface is designed, aiming to simultaneously address the distinct issues encountered by cathode and anode. Taking the Zn-I2 battery as an example, the elaborate AHE alleviates the shuttle effect of polyiodide and sluggish I2/I- kinetics associated with I2 cathode, and resolves dendrite growth and the parasitic reaction of Zn anode. The optimized Zn-I2 cell exhibits superior Coulombic efficiency of 99.84 % with minimal capacity degradation at 0.1 A g-1, and an enhanced stability of over 10000 cycles. This work offers inspiration to address multiple challenges through a holistic approach. |
| Rights: | All rights reserved |
| Access: | open access |
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