Boosting Zn2+ intercalation in manganese oxides for aqueous zinc ion batteries via delocalizing the d-electrons spin states of Mn site

Rechargeable aqueous zinc-ion batteries (AZIBs) have received increasing attention on account of their eco-friendliness and low cost. However, the limited capacity and poor rate properties of cathodes remain a major challenge due to the low electrochemical reactivity of cathode materials and sluggish Zn2+ transport kinetics. Herein, we design a 1,5-naphthalenediamine (NAPD) pre-intercalate potassium manganese dioxide (KMO-NAPD) with high capacity and rate capability for AZIBs. The introduction of NAPD can delocalize the d-electrons spin states of the Mn site and activate the reactivity of KMO-NAPD for Zn2+ intercalation. Moreover, the interaction between intercalated Zn2+ and KMO-NAPD is weakened due to the decreased electrostatic interaction force, which promotes the diffusion of Zn2+. Consequently, the KMO-NAPD cathode exhibits high specific capacity (237 mAh g−1 at 1 A g−1) satisfying rate capability (129 mAh g−1 at 4 A g−1), and excellent cycling stability (85% capacity retention after 1000 cycles). Furthermore, the fabricated AZIBs based on the KMO-NAPD exhibit a high energy density of 294.3 Wh kg−1 and a peak power density of 8.6 kW kg−1. This study opens up a new path for the development of high-energy organic-inorganic hybrid cathode materials with modulated electronic structures for advanced AZIBs.