ZnMn 2 (PO 4 ) 2 · n H 2 O: An H 2 O-Imbedding-Activated Cathode for Robust Aqueous Zinc-Ion Batteries.

Component modulation endows Mn-based electrodes with prominent energy storage properties due to their adjustable crystal structure characteristics. Herein, ZnMn 2 (PO 4 ) 2 · n H 2 O (ZMP· n H 2 O) was obtained by a hydration reaction from ZnMn 2 (PO 4 ) 2 (ZMP) during an electrode-aging evolution. Benefiting from the introduction of lattice H 2 O molecules into the ZMP structure, the ion transmission path has been expanded along with the extended d-spacing, which will further facilitate the ZMP → ZMP· n H 2 O phase evolution and electrochemical reaction kinetics. Meanwhile, the hydrogen bond can be generated between H 2 O and O in PO 4 3- , which strengthens the structure stability of ZMP· n H 2 O and lowers the conversion barrier from ZMP to ZMP·4H 2 O during the Zn 2+ uptake/removal process. Thereof, ZMP· n H 2 O delivers enhanced electrochemical reaction kinetics with robust structure tolerance (106.52 mA h g -1 at 100 mA g -1 over 620 cycles). This high-energy aqueous Zn||ZMP· n H 2 O battery provides a facile strategy for engineering and exploration of high-performance ZIBs to realize the practical application of Mn-based cathodes.