High‐Energy and Stable Subfreezing Aqueous Zn–MnO2 Batteries with Selective and Pseudocapacitive Zn‐Ion Insertion in MnO2. Issue 21 (28th April 2022)

• Record Type: Journal Article
• Authors: Gao, Siyuan; Li, Bomin; Tan, Haiyan; Xia, Fan; Dahunsi, Olusola; Xu, Wenqian; Liu, Yuzi; Wang, Rongyue; Cheng, Yingwen
• Is Part Of: Advanced materials. Volume 34:Issue 21(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-04-28
• Subjects: pseudocapacitive -- selective Zn 2+ insertion -- subfreezing aqueous batteries -- Zn–MnO 2 batteries; Materials -- Periodicals; Chemical vapor deposition -- Periodicals; 620.11
• DOI: 10.1002/adma.202201510
• Languages: English
• ISSNs: 0935-9648

Abstract

Abstract: One major challenge of aqueous Zn–MnO2 batteries for practical applications is their unacceptable performance below freezing temperatures. Here the use of simple Zn(ClO4 )2 aqueous electrolytes is described for all‐weather Zn–MnO2 batteries even down to −60 °C. The symmetric, bulky ClO4 − anion effectively disrupts hydrogen bonds between water molecules and provides intrinsic ion diffusion even while frozen, and enables ≈260 mAh g −1 on MnO2 cathodes at −30 °C . It is identified that subfreezing cycling shifts the reaction mechanism on the MnO2 cathode from unstable H + insertion to predominantly pseudocapacitive Zn 2+ insertion, which converts MnO2 nanofibers into complicated zincated MnO x that are largely disordered and appeared as crumpled paper sheets. The Zn 2+ insertion at −30 °C is faster and much more stable than at 20 °C, and delivers ≈80% capacity retention for 1000 cycles without Mn 2+ additives. In addition, simple Zn(ClO4 )2 electrolyte also enables a nearly fully reversible and dendrite‐free Zn anode at −30 °C with ≈98% Coulombic efficiency. Zn–MnO2 prototypes with an experimentally verified unit energy density of 148 Wh kg −1 at a negative‐to‐positive ratio of 1.5 and an electrolyte‐to‐capacity ratio of 2.0 are further demonstrated. Abstract : Stable cycling of experimentally verified unit level 148 Wh kg −1 aqueous Zn–MnO2 batteries is reported at −30 °C. This battery utilizes antifreezing aqueous Zn(ClO4 )2 electrolyte, and has selective Zn‐ion insertion instead of the problematic proton insertion at subfreezing temperatures. The selective Zn‐ion insertion is primarily pseudocapacitive, and delivers outstanding rate performance with 80% capacity retention for 1000 cycles.