Guo, Xiaoxia; (2023) Construction of better zinc ion batteries via electrolyte design. Doctoral thesis (Ph.D), UCL (University College London).

Text Construction of better zinc ion batteries via electrolyte design.pdf - Accepted Version Access restricted to UCL open access staff until 1 November 2024. Download (10MB)

Abstract

The potential of the aqueous zinc ion storage system as a substitute for lithium-ion batteries has garnered significant interest owing to its remarkable attributes, including a high capacity for zinc metal anode, cost-effectiveness, and robust safety features. In recent times, notable strides have been made towards the development of high-performing aqueous zinc batteries (AZBs), resulting in substantial advancements. However, despite these achievements, a number of challenges persist, necessitating further optimization. This thesis suggests multiple approaches to tackle these challenges and ultimately enhance the battery's overall performance, with a primary focus on electrolyte engineering. The first study investigates the formation of a Li2O/Li2CO3 layer on the Zn metal anode by using LiCl as a simple electrolyte additive. Through the analysis of electrolytes containing different anions, it was found that Cl− ions in the electrolyte can reduce polarization and increase ion transport. As a result, the symmetric and full cells displayed enhanced electrochemical performance and stability. Additionally, a non-flammable hybrid electrolyte was developed to achieve a highly stable and reversible Zn ion battery. The involvement of propylene carbonate (PC) in the Zn2+ solvation sheath structure was found to result in a unique solvation structure that reduces PC and forms a hydrophobic solid electrolyte interphase. Both Zn anodes and cathodes in the hybrid electrolyte exhibited excellent stability and reversibility. This study identified that most of the parasitic side reactions were associated with the aqueous electrolyte. Consequently, a hybrid electrolyte was devised to decrease the water's reactivity in Zn metal batteries. After adding DME, the H-bonding between H2O and the ether oxygen of DME can lower the reactivity of free water in an aqueous electrolyte. The HER and other corrosive reactions caused by free water can be mitigated. When the appropriate concentration of 20 vol% DME was added to the Zn(BF4)2/PC electrolyte, the Zn anode's cyclic stability was enhanced.

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