Abstract

Aqueous ammonium ion batteries are currently advancing rapidly due to their high safety and sustainability. However, they still face significant challenges. Firstly, the selection of host materials with both high storage capacity and high-rate performance remains quite limited. This limitation stems from the sluggish diffusion kinetics of NH₄⁺ ions, which are relatively large in size and often incompatible with many electrode materials. Secondly, the weakly acidic nature of electrolytes, caused by NH₄⁺ ion hydrolysis, results in severe side reactions such as water decomposition and dissolution of host materials.

In this thesis, we propose effective solutions to address these challenges by leveraging hydrogen bond chemistry between electrodes and electrolytes. Specifically, our approach focuses on optimizing battery performance through unique strategies: designing electrode materials using hydrogen bond coordination chemistry; modulating electrolytes to suppress side reactions via hydrogen bond interactions; and co-optimization of electrodes and electrolytes by hydrogen bond chemistry.

In our study, we initially designed aza-based covalent organic frameworks as host materials for NH₄⁺ ion storage. Combining theoretical simulations with spectrum analysis, we elucidated a universal mechanism involving nitrogen and oxygen bridged by hydrogen bonds. This mechanism enabled fast solid-state diffusion kinetics of NH₄⁺ ions, resulting in a high capacity of 220.4 mAh g⁻¹ at a current density of 0.5 A g⁻¹. This capacity surpasses that most reported NH₄⁺ ion host materials.

Furthermore, we extended our exploration of hydrogen bond chemistry to electrolyte design. We proposed a sustainable strategy to modulate the water hydrogen bond network by incorporating sucrose into the electrolyte. Sucrose forms hydrogen bond networks with water molecules, disrupting the continuous hydrogen bond network of water and significantly inhibiting water decomposition. Additionally, the weak hydrogen bond interaction between ammonium and sucrose promotes rapid ion migration, enhancing ionic conductivity.

Finally, by integrating covalent organic frameworks as electrode materials with sucrose-modulated electrolytes, we developed a super-long-life aqueous ammonium ion battery capable of 20,000 stable cycles. This achievement highlights the transformative potential of harnessing unique hydrogen bond chemistry for advanced battery technologies.