Electrode/Electrolyte Strategies toward Better Rechargeable Zinc Metal Batteries
Creators: Deng, Wenjing
Publisher: name: University of Alberta Library
Year: 2024

<p>The pollution from traditional foil fuel and development of electric vehicle have driven new research regarding utilizing renewable energy storage technology. Lithium-ion batteries have become the market standard in battery realm due to the ability to store large quantities of renewable energy. However, raw materials such as lithium, cobalt and nickel are expensive and scarce. Meanwhile, flammable liquid electrolytes used in lithium-ion batteries induce safety issues and other fire or explosion risks. Rechargeable zinc-based batteries are believed to be a highly potent technology among the “beyond-lithium-ion” chemistries, owing to the abundance of zinc, low cost and safety with water-based electrolytes. Designing high-performance anode, electrolyte and cathode is crucial, considering the low plating/stripping reversibility, unstable zinc surface, dissolution of cathode and poor energy density of zinc-based energy storage systems. In this case, this thesis aims to achieve practical and long-life Zn batteries through electrode/electrolyte engineering, including i) making multifunctional artificial protection layer to enhance Zn reversibility; ii) construction of high-donor-number solvent additive for efficient zinc plating/stripping; iii) design of in situ electrochemical self-transformation strategy for vanadium-based cathode; and iv) utilizing organic solvent and iodide source in electrolyte to realize stable iodine conversion reaction.The first work described in the thesis focuses on mitigating degradation of zinc surface toward high-performance zinc-ion batteries. A new-formed ZnO/C hybrid serving as a multifunctional artificial protection layer is designed. The as-synthesized inorganic/carbon hybrid interlayer is utilized as a robust physical barrier to remit corrosion of electrolytes and avoid drastic evolution of dendrite, which can contribute to uniform interfacial zinc ion flux. Even under high currentiiidensity of 10 mA cm-2, the coated electrode can still stably operate for over 300 h. Moreover, the feasibility of artificial layer is also investigated by full cells with MnO2- and V2O5-based cathodes.To further achieve high Zn reversibility, high-donor-number organic solvent N, N-dimethyl acetamide (DMA) as electrolyte additive is introduced. Based on multiscale theoretical and experimental investigations, it is demonstrated that high-donor DMA additive with strong electron-donating ability can confine free water activity, replace the water in Zn2+ solvation sheath, and reshape hydrogen-bonding network of water. The DMA-modified electrolyte enables remarkable suppression of water-involved hydrogen evolution and severe corrosion, which contributes to preferentially uniform deposition and ultralong cycling life. Coupling with VO2-based cathodes, the full battery can deliver high specific capacity of 261 mAh g-1 at -18 oC and long operation stability of 500 cycles.It is still challenging to achieve high rates and ultra-long cycles for cathode materials in zinc ion batteries. An in situ self-transformation approach is reported to electrochemically boost the activity of high-temperature, argon-treated VO2 (AVO) microsphere for effective Zn ion storage. The pre-synthesized AVO with hierarchical structure and high crystallinity allows efficient electrochemical oxidation and water insertion to induce self-phase transformation into V2O5·nH2O within the first charging process, which leads to rich active sites and fast electrochemical kinetics. Using AVO cathode, the outstanding discharge capacity of 446 mAh g-1 at 0.1 A g-1, high rate capability of 323 mAh g-1 at 10 A g-1 are demonstrated. Such zinc-ion batteries with phase self-transition can also perform well at high-loading, sub-zero temperature or pouch cell conditions for practical application.ivTo overcome sluggish redox kinetics, uncontrolled side reactions, superhalide structure and iodide-proof solid electrolyte interphase are designed in rechargeable zinc-iodine batteries. The optimization synergy by using methanol (MeOH) as organic solvent, tetrabutylammonium iodide (TI) as organic iodide source in electrolyte is illustrated. The dissociative electron-donating I- anion enables participation in zinc solvation sheath and form superhalide ZnI(MeOH)5+, which increase electron transfer to Zn2+ and the reduction stability of electrolyte. Meanwhile, MeOH as hydroxyl solvent coupling with TI cations can induce iodide-proof, inorganic/organic solid electrolyte interphase (SEI) to suppress corrosion and facilitate dendrite-free zinc deposition. Noticeably, the zinc-iodine batteries achieve superior specific capacity of 127 mAh g-1 at 5 A g-1, ultralong working life of 45000 cycles with high capacity retention and satisfactory cyclability in small N/P ratio and low-temperature condition.</p>