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

Wang, Chunhui; Xian, Keyi; Zhao, Shuangshuang; Yang, Lishan; Zhou, Junjian; Yang, Yahui; Chen, Xiangping; Yin, Jiang et al. · Nano Lett · 2024

basic_science · Level V

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Abstract

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