Electrochemical Failure Mechanism of δ‐MnO<sub>2</sub> in Zinc Ion Batteries Induced by Irreversible Layered to Spinel Phase Transition
Chunyu Zhao, Mengqi Wu, Wencheng Lu, Yingjie Cheng, Xiaoya Zhang, Ismae͏̈l Saadoune, Ruqian Lian, Yizhan Wang, Yingjin Wei
Abstract
Abstract Phase transitions of Mn‐based cathode materials associated with the charge and discharge process play a crucial role on the rate capability and cycle life of zinc ion batteries. Herein, a microscopic electrochemical failure mechanism of Zn‐MnO 2 batteries during the phase transitions from δ‐MnO 2 to λ‐ZnMn 2 O 4 is presented via systematic first‐principle investigation. The initial insertion of Zn 2+ intensifies the rearrangement of Mn. This is completed by the electrostatic repulsion and co‐migration between guest and host ions, leading to the formation of λ‐ZnMn 2 O 4 . The Mn relocation barrier for the λ‐ZnMn 2 O 4 formation path with 1.09 eV is significantly lower than the δ‐MnO 2 re‐formation path with 2.14 eV, indicating the irreversibility of the layered‐to‐spinel transition. Together with the phase transition, the rearrangement of Mn elevates the Zn 2+ migration barrier from 0.31 to 2.28 eV, resulting in poor rate performance. With the increase of charge–discharge cycles, irreversible and inactive λ‐ZnMn 2 O 4 products accumulate on the electrode, causing continuous capacity decay of the Zn‐MnO 2 battery.