Towards storable and durable Zn-MnO2 batteries with hydrous tetraglyme electrolyte

Aqueous rechargeable zinc-based batteries have attracted increasing interest and been considered poten-tial alternatives for state-of-the-art lithium-ion batteries because of the low cost and high safety. Many cathode materials have been gradually developed and demonstrated excellent electrochemical perfor-mances. However, the complex electrochemistry, inevitable hydrogen release, and zinc corrosion severely hinder the practical application. The most concerned Zn-MnO2 batteries still suffer from the Mn dissolution and formation of byproducts. By adding organic solvents to inhibit the activity of water molecules, the hydrous organic electrolytes provide a sound solution for eliminating the unfavorable fac-tors. Here we report a tetraethylene glycol dimethyl ether-based hydrous organic electrolyte consisting of LiClO4.3H2O and Zn(ClO4)2.6H2O, and a birnessite-type MnO2 cathode material for Zn-MnO2 batteries. The Li+/Zn2+ ions co-(de)insertion mechanism is ascertained by the structural and morphological analy-ses. The electrostatic interaction between inserted ions and crystal structure is reduced effectively by employment of monovalent Li+ ions, which ensures structural stability of cathode materials. Hydrous tet-raglyme electrolyte inhibits the activity of water molecules and thus avoids the formation of byproduct Zn4ClO4(OH)7. Meanwhile, highly stable Zn plating/stripping for over 1500 h, an average coulombic effi-ciency of >99% in long-term cycling, and ultralong storage life (the cells can work well after stored over 1 year) are simultaneously realized in the novel electrolyte. Benefitting from these aspects, the Zn-MnO2 batteries manifest high specific capacity of 132 mA h g-1, an operating voltage of 1.25 V, and a capacity retention of >98% after 1000 cycles at a current density of 200 mA g-1.(c) 2023 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences Published by Elsevier B.V. All rights reserved.