Executive Summary : | Currently, K-ion batteries (KIBs) have attracted much attention due to their higher-voltage operation than that of Li/Na-ion batteries and faster K+-ion diffusion in electrolytes than that of Li/Na-ions. Recently, dual-ion batteries (DIBs) where both cation and anion participate in the energy-storage process are emerging storage devices due to their high discharge voltage (≥ 4.5 V). The electrode materials and polymer electrolytes (PEs) are crucial in achieving the best performance of KIBs/DIBs. The understanding of ion dynamics in K-ion conducting PEs is a challenging problem from both fundamental and application points of view and remains unexplored. Recently, ionogels (IGs), solidification of liquid electrolyte (mixture of ionic salt in ionic liquids, ILs) are considered to be interesting PEs for energy-storage devices due to their high ionic conductivity, high transference number, good thermal and electrochemical stability. Among several polymer matrices, P(VdF-HFP) has been widely used in the IGs and exists as micro-phase in IGs due to poor miscibility with IL. Alternatively, poly(ionic liquid)s (PILs) have received significant attention as new polymer matrices containing an IL species in each of monomer unit and exhibit good compatibility with IL that constitute the polymer backbone. However, the novel PILs based IGs with high content of ILs offer some problems such as risk of leakage, less film-forming property, low thermal and mechanical properties, while a low content of the ILs in the IGs is unsuitable for applications for their low ionic conductivity. The phase separation also occurs due to the formation of IL-salt enriched domains which inhibit ionic conductivity. Hence, novel PIL based IGs with high ionic conductivity and simultaneously good film-forming properties are urgently needed at present.
The introduction of covalent organic frameworks (COFs) forms 2D/3D periodic structure through small molecules linked covalently arises our great interest because of their high porosity, low density, high regular channel, and stable. Moreover, 2D COFs with a regular 1D channel usually provide short and fast ion conduction paths, which makes themselves potential candidates for the ideal ionic conductors by absorbing ILs in PIL-IL-salt based IGs and also play a crucial role in the ion migration of electrolytes. Due to larger ionic radius of K+, the exploring of novel anode materials for K-ion storage is urgently needed for KIBs. The COFs are becoming an appealing option as anode materials due to diversity of building blocks; adjustability; well-defined covalent frameworks offer a uniform chemical environment, etc. and have been rarely investigated.
The main goal of the proposal is to synthesize COFs and COFs doped PIL-IGs for applications in KIBs/DIBs as a novel anode material and self separator respectively. The detailed insight into the structure and ion dynamics behaviors of the COFs and COFs based PIL-IGs are another significant goal. |