Aqueous “rocking-chair” Mn-ion battery based on an industrial pigment anode

Aqueous divalent manganese (Mn)-ion batteries are beginning to get more attention because of the abundant resources, low costs, environmental friendliness, and low reactivity of manganese in aqueous solution. Yet, the huge polarization of the Mn anode still exists, which is undesirable for practical applications. Thus, developing high-performance anode has remained a challenge. Herein, we explore the use of industrial pigment red 224, Perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA) as an anode host for Mn²⁺ with high-rate capacity. Additionally, the concentration of the electrolyte is observed to affect the cycling stability due to the co-insertion of hydronium ion, and PTCDA has a best lifespan in a low-concentration electrolyte of 0.1 M MnSO₄. A reversible contraction/expansion phenomenon in main crystallographic directions during Mn²⁺ into/out PTCDA crystal structures is demonstrated by experimental and theoretical results. Moreover, a “rocking-chair” Mn-ion battery is fabricated based on PTCDA anode and high-entropy Mn-based hexacyanoferrate (Mn-HEPBA) cathode. The Mn-HEPBA||PTCDA full cell delivers a high energy density of 98.8 Wh kg⁻¹. This work will promote the further investigation of Mn-based aqueous rechargeable batteries.