Microporous Organic Ladder Polymer with Vertically Aligned Quinones for Sodium-Ion Battery

Sodium-ion battery is emerging as a promising technology in the post-lithium-ion battery era to meet the high demand for portable energy storage devices. Custom-designed organic materials have been pursued as sustainable alternative electrodes for sodium-ion batteries, offering a solution that bypasses the need for traditional high-temperature synthesis. However, the challenge lies in achieving the desired electrochemical properties through precise structural modulation and the incorporation of redox-active functional groups. In this study, a triptycene-based microporous organic ladder polymer is developed featuring redox-active quinone moieties, designed as an anode material for high-performance sodium-ion batteries. The vertically aligned quinone moieties in the porous ladder polymer prevent the eclipsed stacking of layers, thereby enhancing the exposure of electroactive sites to electrolyte ions. Additionally, the ladder polymer exhibits almost unimodal pores due to its structural rigidity, facilitating fast Na⁺ ion diffusion. The redox-active quinone moieties host Na⁺ ions, and the microporosity supports capacitive ion storage. Consequently, a high reversible specific capacity of 316 mAh g^-1 has been achieved. This study introduces a novel design strategy to develop redox-active microporous ladder polymers by carefully selecting organic building units for efficient Na⁺ ion storage.