A type of polyaniline with H+ reservoirs for dual-mechanism NH4+ and I3−/I2 storage

The construction of aqueous rechargeable ammonium-iodine batteries (AIBs) must be eye-catching by combining the unique properties of ammonium ion (NH₄⁺) and the special redox mechanism of iodine. Polyaniline (PANI) as a conductive polymer is a potential cathode material for aqueous NH₄⁺ batteries. However, the proton (H⁺) escape of amino group (─NH─) in the oxidation process of PANI cannot realize the reversible reduction reaction from full-oxidized imine (─N═) to ─NH─. In this work, polyaniline with H⁺ reservoirs (PANI-H⁺) was successfully prepared by electrodeposition for the NH₄⁺ and I₃⁻/I₂ storage. Interestingly, ─SO₃⁻H⁺ groups as H⁺ reservoirs in 1, 5-Naphthalenedisulfonic acid (1, 5-NDSA) can provide H⁺ for the reduction of ═N─ to ─NH─, thus achieving the reversible redox process of PANI-H⁺. Therefore, PANI-H⁺ electrode exhibited excellent discharge capacity (299.3 mAh/g and 126.7mAh/g at the current density of 1 A/g and 10 A/g, respectively), and good stability of long-term cycles (≈100 % capacity retention after 1000 cycles at the current density of 10 A/g) in (NH₄)₂SO₄ + I₃⁻ electrolyte. A series of spectroscopy analyses indicated the dual storage mechanism of NH₄⁺ (de)intercalation and interfacial redox of I₃⁻/I₂. Finally, aqueous ammonium-iodine full cell (PTCDA|(NH₄)₂SO₄ + I₃⁻|PANI-H⁺) was constructed and presented satisfactory electrochemical performances. This work provides guidance to construct promising AIBs.