Existing electrochemical activation mechanisms and related cathode materials for aqueous Zn ion batteries

Different from conventional material synthesis, such as, microstructure control, heteroatom doping and hybridization tactic, electrochemical activation and electrochemical conversion/oxidation strategy have been reported to reconstruct the microstructure and composition of electrode materials by electrochemical intervention, further boosting the energy storage capability. Up to now, lots of works have been published about electro-chemical activation in aqueous Zn ion batteries. However, there is no special review about electrochemical activation strategy for boosting the electrochemical performance of aqueous Zn ion batteries. Herein, this review summarizes the reaction mechanism and electrochemical activation mechanism of aqueous Zn ion batteries, and highlights the recent advances of related cathode materials. When activated in alkaline electrolyte, the activation mechanism is divided into redox reaction, anion exchange, redox reaction and anion exchange, and related cathode materials include Ni, Cu foil, Co3O4, Ni(OH)2, Ni4Co1-(NO3)2(OH)4, transition metal phosphides and selenides. While in neutral/weak acid electrolytes, the activation mechanisms are classified into three categories, phase transformation, oxidation intercalation and substance transition. Corresponding cathode hosts involve Mn-based and V-based materials. Finally, current problems, practical solutions and future prospects in aqueous Zn ion batteries are proposed. It is anticipated that this review provide a novel idea of electrochemical activation for constructing high performance aqueous Zn ion batteries.