Reunderstanding the Reaction Mechanism of Aqueous Zn–Mn Batteries with Sulfate Electrolytes: Role of the Zinc Sulfate Hydroxide

Abstract

Rechargeable aqueousZn-Mn batteries have garnered extensive attention for next-generation high-safety energy storage. However, the charge-storage chemistry of Zn-Mn batteries remains controversial. Prevailing mechanisms include conversion reaction and cation (de)intercalation in mild acid or neutral electrolytes, and a MnO 2 /Mn 2+ dissolution−deposition reaction in strong acidic electrolytes. Herein, a Zn 4 SO 4 •(OH) 6 •xH 2 O (ZSH)-assisted deposition−dissolution model is proposed to elucidate the reaction mechanism and capacity origin in Zn-Mn batteries based on mild acidic sulfate electrolytes. In this new model, the reversible capacity originates from a reversible conversion reaction between ZSH and Zn x MnO(OH) 2 nanosheets in which the MnO 2 initiates the formation of ZSH but contributes negligibly to the apparent capacity. The role of ZSH in this new model is confirmed by a series of operando characterizations and by constructing Zn batteries using other cathode materials (including ZSH, ZnO, MgO, and CaO). This research may refresh the understanding of the most promising Zn-Mn batteries and guide the design of high-capacity aqueous Zn batteries.

Methods for Rational Design of Advanced Zn‐Based Batteries

“…Interestingly, the cointercalated 4d). [12] This mechanism is also applicable to other systems, such as ZnO, MgO, and CaO.…”

“…d) Schematic diagram of the ZSH-assisted deposition-dissolution reaction model. Reproduced with permission [12]. Copyright 2022, Wiley-VCH.…”

Suppressed Dissolution and Enhanced Desolvation in Core–Shell MoO3@TiO2 Nanorods as a High‐Rate and Long‐Life Anode Material for Proton Batteries

“…[1][2][3][4] Aqueous batteries stand out from many types of batteries, due to their intrinsic safe, low material costs, and facile manufacturing as well. [5][6][7] One of the typical examples is lead-acid batteries that have been commercialized and adopted in many fields. [8][9][10] However, the strong corrosion on cell components caused by highly concentrated acid, the unsatisfactory cycle life, and the high toxicity of Pb to organisms greatly limit the applications of lead-acid batteries.…”

Bi3+ Induced Crystal Growth of a Symbiotic Heterojunction Enables Long‐Lifespan Zn‐Ion Batteries

“…Meanwhile, two discharge plateaus (1.2 and 1.4 V, respectively) can be distinguished in the galvanostatic charge‐discharge (GCD) curve at 300 mAg −1 (Figure 5b), in accordance with two pairs of reduction/oxidation peaks in CV. In particular, in the first cycle of charge and discharge, the capacity is only 150.6 mAh g −1 , and then after the 50 th and 100 th cycles, the capacity reaches 234.7 mAh g −1 and 267.1 mAh g −1 respectively, indicating a gradual electrochemical activation process [46,47] . The MnO 2 /Mn 2 O 3 electrode also experienced such an activation process (Figure S10), but the discharge platform had gradually shortened and the capacity decreased when cycle numbers to 300.…”

“…In particular, in the first cycle of charge and discharge, the capacity is only 150.6 mAh g À 1 , and then after the 50 th and 100 th cycles, the capacity reaches 234.7 mAh g À 1 and 267.1 mAh g À 1 respectively, indicating a gradual electrochemical activation process. [46,47] The MnO 2 /Mn 2 O 3 electrode also experienced such an activation process (Figure S10), but the discharge platform had gradually shortened and the capacity decreased when cycle numbers to 300. Rate performance measurements were evaluated by varying the current density from 0.1 to 3 A g À 1 every ten cycles in Figure 5c.…”