Tsinghua’s Zhou Guangmin Team Breaks Through the Bottleneck of Aqueous Zn//MnO₂ Batteries: Trace M4 Enables 3000 Cycles, Achievement Published in AngewDescription: Aqueous Zn//MnO₂ batteries have become a popular direction for large-scale energy storage due to their high safety and low cost, but they are plagued by acidic corrosion of the Zn anode and hydrogen evolution reaction (HER). The team led by Zhou Guangmin from Tsinghua University only added a trace amount of p-Hydroxybenzaldehyde (M4) to the electrolyte. Through a dual mechanism of "reconstructing the solvation shell + interface protection", the Zn//MnO₂ batteries achieved over 3000 cycles, and the pouch batteries operated stably for more than 100 cycles. The related achievements were published in the top journal Angewandte Chemie International Edition.  I. Industry Background: Aqueous Zn//MnO₂ Batteries with Both Potential and Pain Points   In the field of large-scale energy storage, rechargeable aqueous Zn//MnO₂ batteries have become a research hotspot due to two core advantages:   - High safety: They use aqueous electrolytes, which completely avoid the fire and explosion risks of organic electrolytes, making them suitable for scenarios with high safety requirements such as home energy storage and grid energy storage;   - High cost-effectiveness: The raw materials Zn (zinc) and MnO₂ (manganese dioxide) are abundant in reserves and low in price, without relying on rare metals, laying a foundation for large-scale mass production.   However, their commercialization process is hindered by a key issue—insufficient stability of the Zn anode. In acidic electrolytes, the Zn anode undergoes both "acidic corrosion" and "hydrogen evolution reaction (HER)": the former consumes electrode materials, while the latter produces hydrogen that clogs the electrode pores. Under the combined effect, the battery life is significantly shortened, becoming a core bottleneck restricting its practical application.  II. Core Solution: "Dual Protection" of Trace M4 Solves the Anode Dilemma   To address the above pain points, the team led by Zhou Guangmin from the Shenzhen International Graduate School of Tsinghua University proposed a "simple yet efficient" solution—introducing a trace amount of p-Hydroxybenzaldehyde (coded as M4) into the electrolyte, which achieves stable protection of the Zn anode only through molecular-level regulation.   The role of p-Hydroxybenzaldehyde is not a single mechanism but solves the problem through "dual synergy", whose core logic stems from its strong affinity for Zn²⁺ and H₂O:   1. First layer of protection: Reconstructing the Zn²⁺ solvation shell P-Hydroxybenzaldehyde molecules replace one water molecule in [Zn(H₂O)₆]²⁺ (zinc ion hydration structure) to form a new solvation structure. This reconstruction reduces the contact between free water molecules and the Zn anode, fundamentally lowering the probability of acidic corrosion and HER;   2. Second layer of protection: Adsorption to form an interface barrier P-Hydroxybenzaldehyde molecules actively adsorb on the surface of the Zn anode to form a dense "protective film". This film can directly block the direct reaction between H⁺ (hydrogen ions) and Zn, while changing the hydrogen bond network of the electrolyte and reducing the activity of water molecules, further enhancing interface stability.  III. Mechanism Analysis: How Does M4 Optimize the Battery Environment at the Molecular Level?   Through theoretical calculations and experimental verification, the team clarified the molecular mechanism by which M4 improves battery performance, whose core can be summarized in two points:   - Binding energy regulation: Data shows that the binding energy between Zn²⁺ and M4, as well as between H₂O and M4, is stronger than the interactions in the traditional solvation structure. This allows M4 to stably "occupy" the solvation shell and electrode interface, compressing the space for harmful reactions;   - Hydrogen bond network optimization: The addition of M4 changes the hydrogen bond network of water molecules in the electrolyte and reduces the number of "free water molecules"—these water molecules are precisely the "accomplices" of acidic corrosion and HER. After their activity is reduced, the overall stability of the electrolyte is significantly improved.  IV. Experimental Data: Four Sets of Figures Verify Leapfrog Improvements in Performance   The team verified the effect of M4 through four core experiments (corresponding to Figures 1–4), covering the entire chain from "electrolyte properties → anode protection → electrochemical stability → battery performance". The key data are as follows:   Figure 1: Characterization of Electrolyte Properties – Proving the Molecular-Level Regulation Effect of M4   This set of figures focuses on "how M4 changes the electrolyte environment", with core conclusions including:   - (a) Clearly demonstrates the battery energy storage mechanism, side reactions (corrosion/HER), and M4 optimization strategy, intuitively presenting the solution;   - (c) Compares the Zn²⁺ solvation structure before and after adding M4, confirming that M4 successfully replaces water molecules and reconstructs the solvation shell;   - (d)(e)(f) Verifies that M4 changes the hydrogen bond network of the electrolyte and reduces the activity of free water molecules through characterizations such as infrared spectroscopy and nuclear magnetic resonance.   Figure 2: Evaluation of Zn Anode’s Acidic Corrosion Resistance and HER Inhibition   This set of figures directly tests the protective effect of M4 on the Zn anode, with key results including:   - (a) Immersion experiments show that the Zn foil with M4 added has a higher mass retention rate and more stable electrolyte pH, proving that corrosion is inhibited;   - (g) In-situ optical microscopy observations show that hydrogen bubbles in the M4 group are significantly reduced, and HER is effectively blocked;   - (d)(f) Tafel curves and linear sweep voltammetry (LSV) curves confirm that M4 reduces the kinetic rate of corrosion reactions and HER.   Figure 3: Electrochemical Stability and Reversibility of Zn Metal Anode   This set of figures focuses on the cycle reversibility of the Zn anode, with core data including:   - (h)(i) The Zn symmetric battery in the M4 electrolyte has a cycle stability of over 2000 hours (5 mA cm⁻², 1 mAh cm⁻²), which is 5 times the lifespan of batteries with traditional electrolytes;   - (e) The Coulombic efficiency of the Zn//Cu battery is stable, proving that the reversibility of the Zn deposition/stripping process is significantly improved;   - (b)(c)(d) SEM (Scanning Electron Microscopy) and CLSM (Confocal Laser Scanning Microscopy) images of the Zn anode after cycling show that the electrode surface of the M4 group is smoother, with no obvious corrosion traces.   Figure 4: Electrochemical Performance of Zn//MnO₂ Batteries – Breakthrough from Coin Cells to Pouch Cells   This set of figures verifies the performance improvement of M4 on complete batteries, with highlights including:   - (e) The Zn//MnO₂ coin battery in the M4 electrolyte achieves stable cycling for over 3000 times, with an average Coulombic efficiency of 97.3%;   - (g) The Zn//MnO₂ pouch battery with a capacity of 1.68 Ah (size: 12.2×15 cm²) operates stably for more than 100 times at 0.1 A g⁻¹, verifying its practical application potential;   - (h) Performance comparison shows that this achievement far exceeds the level of aqueous Zn//MnO₂ batteries reported previously.   V. Research Significance and Conclusions: Opening a New Path for Aqueous Energy Storage   The core value of this research lies in providing a "simple, low-cost, and scalable" optimization strategy for aqueous batteries—without complex electrode structure design, only through a trace amount of molecular additive (M4), the fundamental problem of the Zn anode can be solved at the molecular level.   Its key conclusions can be summarized in three points:   1. P-Hydroxybenzaldehyde (M4) simultaneously inhibits the acidic corrosion and HER of the Zn anode through the dual mechanism of "reconstructing the solvation shell + interface adsorption";   2. This strategy achieves a leapfrog improvement in battery performance: the symmetric battery cycles for over 2000 hours, and the Zn//MnO₂ battery cycles for over 3000 times;   3. The stable performance of the pouch battery proves that this solution has practical application potential, providing a new direction for the development of large-scale aqueous energy storage systems.  

Yongjin Group’s Vision: P-Hydroxybenzaldehyde Empowers the Next Generation of Energy Storage   Yongjin Group believes that the successful application of p-Hydroxybenzaldehyde in Zn//MnO₂ batteries is not only a breakthrough in the energy storage field but also a model of cross-field integration between fine chemical materials and new energy. In the future, Yongjin Group will promote the innovative application of p-Hydroxybenzaldehyde in two key directions:   First, it will optimize the production process of p-Hydroxybenzaldehyde to reduce costs, while developing high-purity, low-impurity "energy storage-grade" products to meet the needs of new energy technologies; second, it will strengthen cooperation with research institutions and battery enterprises to explore the application of p-Hydroxybenzaldehyde in other aqueous batteries (e.g., Zn//V₂O₅ batteries, Zn//Prussian blue analog batteries), helping more energy storage technologies break through performance bottlenecks.   As a professional enterprise in the field of p-Hydroxybenzaldehyde production, Yongjin Group will rely on technological innovation and high-quality products to drive the high-quality development of the industry and inject impetus into the progress of energy storage, pharmaceuticals, chemical engineering, and other fields.   Source of Paper Information：Liu, Y., Liu, Z., Xiao, Z., Lao, Z., Liu, J., Xiao, X., Fu, Q., Zheng, F., & Zhou, G. (2025). Suppressing spontaneous acidic corrosion and hydrogen evolution for stable Zn//MnO₂ batteries. Angewandte Chemie International Edition.