Synthesis and Electrochemical Properties Investigation of MnO₂ Materials Derived from Manganese Salts for Cathode Applications in Zinc-Ion Batteries via the Hydrothermal Method

Manganese dioxide (MnO<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>) has recently attracted significant attention as a cathode material for zinc-ion batteries (ZIBs) due to its outstanding advantages, including environmental friendliness, non-toxicity, and high specific capacity. However, commercially available Mn O<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> typically exhibits large and irregular particle sizes, which adversely affect its electrochemical performance. In this study, Mn O<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> was synthesized from manganese precursors, including MnCl<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>, Mn(CH<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf>COO)<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>, and MnSO<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</inf>, via a hydrothermal method to optimize the synthesis process and obtain Mn O<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> with uniform, nanoscale particle size suitable for aqueous pouch-type Zn-ion batteries. Among the synthesized materials, Mn O<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> derived from MnCl<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> exhibited superior electrochemical properties, achieving a charge/discharge efficiency of over 95% and a high specific capacity of approximately 200 mAh/g at a current rate of 0.6C.