Nowadays, aqueous rechargeable batteries (ARBs) are emerging as highly promising energy storage alternatives to current Li-ion batteries for stationary applications. This is attributed to their significant advantages in terms of safety and cost-effectiveness, in addition to high performance. Especially, acid-based ARBs stand out as a compelling substitute due to the accelerated proton kinetics resulting from their minimal ionic mass and diminutive radius,^[1] distinguishing them from their neutral^[2] and alkaline^[3][4] counterparts. Moreover, of paramount importance is the proton's ability to achieve exceptionally rapid ionic conduction in aqueous electrolytes, due to its advantageous utilization of the Grotthuss mechanism.^[5]

Conventional acid-based ARBs are based on inorganic electrode materials and face significant drawbacks, including high costs of both anode and cathode material (based on rare elements) and severe active-material corrosion and/or dissolution. Moreover, using a metal anode (e.g., Pb) results in dendrite formation caused by uneven and irregular metal plating on the anode side, in addition to the formation of a thick lead (II) sulphate (PbSO₄) passivation layer.^[2] As a consequence, battery cycle stability is seriously impeded, possibly with short-circuit risks and safety compromises.

Recently, organic electrode materials (OEMs) are re-emerging as green and sustainable alternatives over traditional inorganic materials as they offer distinct advantages. First, they are composed of readily available and cost-effective elements (C, O, N, H). Moreover, by their distinctive ion-coordination mechanism, they can interact with different charge carriers (Li⁺, Na⁺, H⁺, Zn²⁺, etc), finding application in different battery technologies.^[2] Furthermore, under acidic conditions these materials are less prone to the dendrites formation, corrosion, and/or dissolution, common issues faced by their inorganic counterparts.

Recently, we demonstrated the rapid kinetics, good electrochemical performance and excellent robustness of a new conjugated microporous polymer based on phenazine (named IEP-27-SR) in 1 M H₂SO₄ electrolyte.^[6] Here, I will present our recent results on the use of this anode (IEP-27-SR) in combination with an electrodeposited MnO₂-based cathode in a full acid battery. The full battery not only reached an impressive number of cycles (20000 at 30 C with 83% retention) but also could withstand high current densities (100 C, yet achieving 40 mAh g^-1) using 2 mg cm^-2 polymer mass loading anode. Moreover, in this study we could increase the polymer mass loading up to 30 mg cm^-2, while keeping its content high (80 wt%) in the electrode. This enhancement contributed to a significant increase in the areal capacity of the aqueous battery up to 2.8 mAh cm^–2, while maintaining a noteworthy value of 1 mAh cm^{- 2} even under the extreme high current of 79.6 mA cm^-2. This porous polymer//MnO₂ battery offers a sustainable and cost-effective alternative to the conventional acidic battery (e.g., PbO₂ / / Pb), without compromising its performance, paving the way toward practical and sustainable energy storage solutions.