Suppressing Rampant and Vertical Deposition of Cathode Intermediate Product via PH Regulation Toward Large‐Capacity and High‐Durability Zn//MnO2 Batteries

• Published in: Advanced materials (Weinheim) Vol. 36; no. 4; pp. e2304997 - n/a
• Main Authors: Chen, Minfeng, Yang, Ming, Han, Xiang, Chen, Jizhang, Zhang, Peixin, Wong, Ching‐Ping
• Format: Journal Article
• Language: English
• Published: Weinheim Wiley Subscription Services, Inc 01.01.2024
• Subjects: aqueous zinc‐ion batteries; Buffers; Cathodes; Deposition; Dissolution; Electrochemical analysis; Electrodissolution; Electrolytes; functional electrolyte additives; hydrogel electrolytes; Manganese dioxide; pH buffering capability; Solid electrolytes; Zinc; zinc sulfate hydroxides
• ISSN: 0935-9648; 1521-4095
• DOI: 10.1002/adma.202304997

Despite great prospects, Zn//MnO2 batteries suffer from rampant and vertical deposition of zinc sulfate hydroxide (ZSH) at the cathode surface, which leads to a significant impact on their electrochemical performance. This phenomenon is primarily due to the drastic increase in the electrolyte pH value upon discharging, which is closely associated with the electrodissolution of Mn‐based active materials. Herein, the pH value change is effectively inhibited by employing an electrolyte additive with excellent pH buffering capability. As such, the formation of ZSH at the cathode is postponed, resulting in the deposition of ZSH in a horizontal arrangement. This strategy can significantly enhance the utilization efficiency of cathode active material, while also enabling a solid electrolyte interphase layer at the Zn anode to address low Zn stripping/plating reversibility. With the optimal electrolyte, the Zn//MnO2 battery realizes a 25.6% increase in the specific capacity at 0.2 A g−1 compared to that with the baseline electrolyte, great rate capability (161.6 mAh g−1 at 5 A g−1), and superior capacity retention (90.2% over 5,000 cycles). In addition, the pH buffering strategy is highly applicable in hydrogel electrolytes. This work underscores the importance of pH regulation for Zn//MnO2 batteries and provides enlightening insights. In order to mitigate the detrimental effects of dramatic pH increases in Zn//MnO2 batteries upon discharging due to the electrodissolution of MnO2, an electrolyte additive with exceptional pH buffering capability has been introduced. This can effectively suppress rampant and vertical deposition of zinc hydroxide sulfate intermediate product at the cathode, thereby significantly improving the electrochemical performance of Zn//MnO2 batteries.