Modified MnO2-Based Cathode for Zinc-Ion Batteries Using Facile Processing and Easily Available Materials

Aqueous zinc-ion batteries (AZIBs) have been investigated intensively as effective energy storage devices that are environmentally friendly, safe, and have a lower cost than current Li-ion batteries.[1-5] Being outstandingly safe due to usage of non-organic electrolyte, AZIBs could also be used as power supply for wearable electronics. This also put high standard requirements in terms of flexibility, stability and electrochemical performance to AZIBs. On the other hand, the general challenges, such as the formation of the dendrites on the Zn anodes, hydrogen evolution and side reactions, have been obstructing the practical application of AZIBs. In this presentation, a simple method to assemble quasi-solid-state Zn ion pouch cell with excellent mechanical performance, flexibility and electrochemical performance was developed, combining in-situ electrodeposition of MnO2 cathode and aramid nano fiber-based hydrogel with Zn plate as anode. In-situ and cycling measurements of the electrodeposition of MnO2 on carbon nanotube mat shows excellent capacitance and superior cycling stability. In addition, Kevlar derivatized aramid nanofiber-based hydrogel shows extremely strong strength when combined with polyvinyl alcohol, which prolonged the lifetime of the cell by preventing Zn dendrite growth largely.[5,6] Moreover, the method to assemble the AZIBs pouch cell enables us to optimize the process, decrease the steps, and save time effectively by taking advantage of hydrogel formation stage and avoiding conventional verbose slurry-casting-drying steps. This work paves an efficient path to assemble flexible and stable AZIBs pouch cells with high capacity and cycling stability.[1] Tang, Boya, et al. "Issues and opportunities facing aqueous zinc-ion batteries." Energy & Environmental Science 12.11 (2019): 3288-3304.[2] Li, Chang, et al. "Toward practical aqueous zinc-ion batteries for electrochemical energy storage." Joule 6.8 (2022): 1733-1738.[3] Yu, Feng, et al. "An aqueous rechargeable zinc-ion battery on basis of an organic pigment." Rare Metals 41.7 (2022): 2230-2236.[4] Lin, Yuexing, et al. "Dendrite-free Zn anode enabled by anionic surfactant-induced horizontal growth for highly-stable aqueous Zn-ion pouch cells." Energy & Environmental Science 16.2 (2023): 687-697.[5] Wang, Peng, and Petru Andrei. "High Performance Separator and Hydrogel Based on Aramid Fibers for Zn Ion Batteries." Electrochemical Society Meeting s 242. No. 4. The Electrochemical Society, Inc., 2022.[6] Xu, Lizhi, et al. "Water‐rich biomimetic composites with abiotic self‐organizing nanofiber network." Advanced Materials 30.1 (2018): 1703343.

Flexible electronics have been limited by inadequate energy storage solutions. Despite extensive research, the energy efficiency and lifespan of current flexible storage devices fall short of commercial standards. Additionally, the high cost of these solutions hampers the scalability of flexible electronics. Flexible batteries offer a promising energy storage solution, leveraging the success of commercial batteries. While flexible lithium-ion batteries have been investigated, their intrinsic safety hazards limit their broader adoption, particularly in wearable and medical electronics. Flexible zinc-ion batteries have recently garnered attention for their safety, high capacity, and low cost. However, challenges such as shuttling effects, zinc dendrites, and low energy efficiency remain. Although advancements have been made in electrodes, electrolytes, and separators for flexible zinc-ion batteries, further research is needed before they can achieve commercial viability. This thesis investigates the materials and structural design of flexible aqueous zinc-ion batteries, focusing on methodologies to enhance reaction kinetics and lifespan for potential industrial applications. We first introduce a hydrogel cellulose paper-based separator that integrates seamlessly with electrode materials, facilitating the rapid and straightforward fabrication of large-area flexible zinc-ion batteries, thus supporting scalable production. The hydrogel-reinforced cellulose paper also provides excellent mechanical durability, addressing the issue of repeated bending and enhancing the overall robustness of paper batteries. In the next chapter, we introduce a layer-expanding strategy to enhance electrodes for aqueous zinc-ion batteries by increasing active sites and facilitating smooth hydrated zinc ion transport. The insertion of n-butylamine expands the interlayer spacing of Zr(HPO4)2•H2O (α-ZrP), creating expanded-interlayer ZrP (EI-ZrP). EI-ZrP is also proved to facilitate electron transport. By combining hydrogel cellulose paper (HCP) as the separator, a paper battery with EI-ZrP in the cathode material is fabricated and proved to be efficiently relieved from shuttling effects. Furthermore, zinc-air batteries, which use atmospheric oxygen at the cathode, reduce material costs and show immense potential for flexible energy storage applications due to their high capacity and low production cost. This thesis introduces an innovative double-layer electrolyte design that leverages the distinct kosmotropism of different anions to induce phase separation, eliminating the need for a separator. This design enhances zinc utilization and battery lifespan by mitigating side reactions and provides a framework for further advancements in zinc-air batteries and their cost-effective, scalable production. All proposed solutions for cellulose-based zinc-ion batteries have been demonstrated through integration with practical electronic devices, validating their capability for prolonged use. These experiments offer valuable insights into industrial applications of flexible cellulose-based batteries in wearables, medical devices, and other flexible electronics.

Rechargeable aqueous zinc-ion batteries (ZIBs) have attracted much attention recently due to the high abundance, low cost, high theoretical capacity up to 820 mAh g-1 with multi-valent charge carrier, and compatibility with aqueous electrolyte of the zinc anode.[1] Especially, the introduction of neutral or mild acidic electrolyte greatly improves the reversibility of zinc anode compared to conventional alkaline ZIBs.[2] Among all the cathode candidates, MnO2 is most attractive due to its relatively high energy density, low toxicity and low cost.[3] However, MnO2 electrode suffers from capacity fading during cycling mainly due to Mn dissolution and structural change. The addition of Mn2+ into the mild acidic electrolyte is a common method to suppress Mn dissolution.[4] Other strategies like structural design and surface coatings are also developed to suppress Mn dissolution.[5, 6] Though the cycle performance still cannot meet the demand of application, as the irreversible formation of inactive ZnMn2O4 during cycles still requires to be tackled.Here, we proposed Bi2O3 as a facile electrode additive in the electrode to suppress ZnMn2O4 formation and improve the cyclability of commercial electrolytic manganese dioxide (EMD). XRD, in-situ pH measurements and ICP tests suggest that inactive ZnMn2O4 is formed upon cycling due to the interaction between MnO2 and zincate ions in the electrolyte from localized increase in pH, and Bi2O3 dissolves into the electrolyte in the presence of zincate ions and forms a complex with the zincate ions to suppress the reaction pathway. A high capacity of 269 mAh g-1 is maintained at 100 mA g-1 after 50 cycles with a capacity retention of 91.5% when EMD with 10 wt% of Bi2O3 is tested in ZnSO4 electrolyte without Mn2+ additive. Combining both Bi2O3 electrode additive and Mn2+ electrolyte additive, EMD can maintain a stable capacity of 190 mAh g-1 for 1000 cycles at 1000 mA g-1 (about 3.3C). More characterizations are underway to further understand the role of Bi2O3 and the results will be shown during the meeting.Reference:[1] B. Tang, L. Shan, S. Liang, J. Zhou, Issues and opportunities facing aqueous zinc-ion batteries, Energy & Environmental Science, 12 (2019) 3288-3304.[2] J. Hao, X. Li, X. Zeng, D. Li, J. Mao, Z. Guo, Deeply understanding the Zn anode behaviour and corresponding improvement strategies in different aqueous Zn-based batteries, Energy & Environmental Science, 13 (2020) 3917-3949.[3] N. Zhang, X. Chen, M. Yu, Z. Niu, F. Cheng, J. Chen, Materials chemistry for rechargeable zinc-ion batteries, Chemical Society Reviews, 49 (2020) 4203-4219.[4] H. Pan, Y. Shao, P. Yan, Y. Cheng, K.S. Han, Z. Nie, C. Wang, J. Yang, X. Li, P. Bhattacharya, Reversible aqueous zinc/manganese oxide energy storage from conversion reactions, Nature Energy, 1 (2016) 1-7.[5] J. Huang, Z. Wang, M. Hou, X. Dong, Y. Liu, Y. Wang, Y. Xia, Polyaniline-intercalated manganese dioxide nanolayers as a high-performance cathode material for an aqueous zinc-ion battery, Nature communications, 9 (2018) 1-8.[6] B. Wu, G. Zhang, M. Yan, T. Xiong, P. He, L. He, X. Xu, L. Mai, Graphene scroll‐coated α‐MnO2 nanowires as high‐performance cathode materials for aqueous Zn‐ion battery, Small, 14 (2018) 1703850. Figure 1

V-MOF@graphene derived two-dimensional hierarchical V2O5@graphene as high-performance cathode for aqueous zinc-ion batteries

Mechanically robust and conductive Ti5Te4/P@C composite materials as promising lithium-ion battery anodes

Metal-ion batteries based on aqueous electrolyte are attracting widespread attention in the field of large-scale energy storage due to the low cost, high safety and environmental friendliness. However, the development of the most studied aqueous Li+ and Na+ batteries are plagued by the low energy density, which mainly derived from the low capacity of electrode materials (<150 mAh g-1) and the limited voltage window of aqueous electrolyte (<1.8 V). The latter could be conquered by the water-in-salt electrolyte, and the operating voltage > 3V could be obtained1. But the capacity of electrode materials still needs to be enhanced. Due to the high capacity of metal zinc anode (820 mAh g-1), aqueous Zinc-ion battery based on Zn2+ storage cathode and metal Zn anode holds immense potential to achieve high capacity. But the capacity of cathode still has much room for improvement. As the most used cathode materials for zinc-ion battery, manganese oxides exhibit high theoretical capacity (308 mAh g-1), low cost and low toxicity. Various manganese dioxides, including the α-MnO2, β-MnO2, γ-MnO2, δ-MnO2, etc. have been reported as host materials for Zn2+/H+ insertion in the mild aqueous electrolyte. However, all the crystalline form of manganese oxides undergo structure transformation to layered structure with interlaminar water molecules during zinc-ion insertion, leading to capacity fading of the cell. And the cycling stability of manganese oxides decreases dramatically when cycled at high depth of discharge2. In this work, we proposed novel polyaniline-intercalated MnO2 nanolayers as a high performance cathode material for zinc-ion battery, which is prepared by a simple one-step inorganic/organic interface reaction3. With the typical nano-size (approximately 10 nm), expanded interlayer space, uniform meso-structure and polymer-reinforced layered structure, the polyaniline-intercalated MnO2 nanolayers show a high rate performance and excellent cycle stability at high charge/discharge depth (200 stable cycles with capacity of 280 mAh g-1, corresponding 90.9% utilization of theoretical capacity of 308 mAh g-1), which is much superior to previous reports. The polyaniline-reinforced layered structure efficiently eliminate the hydrated H+/Zn2+-insertion-induced phase transformation and the subsequent structure collapse, which is important to achieve long cycle life and high utilization simultaneously. In addition, a H+/Zn2+ co-insertion process in the layered MnO2 was proposed, and a self-regulating mechanism of electrolyte involving generation/dissolution of flake-like zinc hydroxide sulfate was clarified. Reference: 1 C. Yang, J. Chen, T. Qing, X. Fan, W. Sun, A. von Cresce, M.S. Ding, O. Borodin, J. Vatamanu, M.A. Schroeder, N. Eidson, C. Wang, and K. Xu, Joule, 1, 122 (2017). 2 J. Huang, Z. Guo, Y. Ma, D. Bin, Y. Wang, and Y. Xia, Small methods, 1800272 (2018). 3 J. Huang, Z. Wang, M. Hou, X. Dong, Y. Liu, Y. Wang, and Y. Xia, Nature Communications, 9, 2906 (2018).

Industrial VN@reduced graphene oxide cathode for aqueous zinc ion batteries with high rate capability and long cycle stability

Manipulating intercalation-extraction mechanisms in structurally modulated δ-MnO2 nanowires for high-performance aqueous zinc-ion batteries

The rapid development of large-scale energy storage systems urgently demands safe, efficient, and green battery technologies. Aqueous zinc-ion batteries (ZIBs) have emerged as promising candidates owing to their environmental friendliness, low cost, and high theoretical capacity. However, challenges such as dendrite growth, hydrogen evolution, and poor cycling stability severely hinder their practical application. Here, we report a novel PVA/CMC/PEG-SiO2 (PCPSiO2) gel electrolyte that achieves exceptional ionic conductivity (46.24 mS cm–1) and zinc ion transference number (0.89). The abundant functional groups in the gel matrix induced the uniform deposition of Zn during the plating/stripping process, which effectively inhibited the dendrite growth. The results demonstrate that the Zn∥Zn symmetric cell can cycle for over 3500 h at 0.5 mA cm–2 and over 8500 h at 0.1 mA cm–2. Additionally, it maintains stable cycling for over 1100 h even under high capacity (6 mAh). Furthermore, the full cell using V2O5/CNT cathodes exhibits excellent rate performance (193 mAh g–1 at 9 A g–1) and superior cycling stability (87% capacity retention after 1000 cycles at 3 A g–1). This study provides new insights and technical support for improving the performance of zinc-ion batteries, holds great promise for advancing their commercial applications, and is expected to make a significant contribution to the development of more environmentally friendly and efficient energy storage solutions.

Vanadium oxide nanospheres encapsulated in N-doped carbon nanofibers with morphology and defect dual-engineering toward advanced aqueous zinc-ion batteries

MOF-derived Zn/Co co-doped MnO/C microspheres as cathode and Ti3C2@Zn as anode for aqueous zinc-ion full battery

Graphite nanosheets with highly oriented conductive coatings have been developed to guide uniform zinc deposition in aqueous zinc-ion batteries (ZIBs). By leveraging mechanical ball milling and chemical functionalization, hydroxyl and carboxyl groups are grafted onto graphite nanosheets. The graphite nanosheets’ slurry is coated on copper foil using shear force, ensuring the coating thickness is smaller than the graphite nanosheet diameter to promote horizontal alignment, which contributes to the formation of the (002)-oriented structure of the conductive coating. The resulting Cu@C current collector exhibits enhanced hydrophilicity and abundant zincophilic sites from rich oxygen-containing groups, promoting uniform Zn2+ distribution around the anode and guiding Zn2+ uniform transport along the (002) plane and zinc epitaxial growth. Structural characterization confirms the formation of two-dimensional, highly oriented graphite nanosheets on the copper substrate. Electrochemical tests reveal that Zn||Cu@C asymmetric cells achieve outstanding cycling stability and high Coulombic efficiency over thousands of cycles at various current densities, while Zn||Cu cells suffer from dendrite formation and rapid performance decay. Full cells with MnO2 cathodes further demonstrate improved capacity, rate performance, and charge-transfer kinetics when paired with Cu@C anodes. This work provides a practical strategy for crystal-plane-guided zinc deposition, offering insights into the design of long-life and high-performance zinc-ion batteries.

Owing to high safety and low cost, aqueous rechargeable zinc-ion batteries (ZIBs) is currently a major research topic. In this study, we propose the microwave-assisted hydrothermal synthesis of polypyrrole (PPy)-coated Na1.1V3O7.9 (P-NVO) nanorods for the first time as a highenergy and high-power cathode material for ZIBs. The highly conductive PPy surface-coating layer is significant to enhance the electronic conductivity and Zn2+ diffusion kinetics, leading to utilize the V3+/V4+/V5+ multiple redox reactions of the NVO cathode in ZIBs. Compared to the NVO cathode, therefore, the P-NVO cathode offers higher discharge capacity, power capability and cycling stability; in particular, PPy coating triggers the full theoretical capacity of the NVO cathode (527 mAh g- 1 with ~ 3 mol Zn insertion per formula unit) and directly reflects a superior energy density of 408 Wh kg-1. Even at a high current density of 6000 mA g- 1, the P-NVO cathode sustains 1000 cycles with almost 100% capacity retention. Galvanostatic intermittent titration technique, cyclic voltammetry, in situ X-ray diffraction, and ex situ X-ray absorption near edge structure analyses are combined to verify the superior Zn2+ storage mechanism of the P-NVO cathode.

Aqueous zinc-ion batteries (ZIBs) are gaining significant attention for their numerous advantages, including high safety, high energy density, affordability, and environmental friendliness. However, the development of ZIBs has been hampered by the lack of suitable cathode materials that can store Zn2+ with high capacity and reversibility. Currently, vanadium-based materials with tunnel or layered structures are widely researched owing to their high theoretical capacity and diversified structures. However, their long-term cycling stability is unsatisfactory because of material dissolution, phase transformation, and restrictive kinetics in aqueous electrolytes, which limits their practical applications. Different from previous reviews on ZIBs, this review specifically addresses the critical issues faced by vanadium-based cathodes for practical aqueous ZIBs and proposes potential solutions. Focusing on vanadium-based cathodes, their ion storage mechanisms, the critical parameters affecting their performance, and the progress made in addressing the aforementioned problems are also summarized. Finally, future directions for the development of practical aqueous ZIB are suggested.

Aqueous zinc-ion batteries (AZIBs) are promising energy storage systems due to their low cost, high safety, and considerable theoretical energy density. However, the use of zinc anodes could lead to dendrite growth, low Zn stripping/plating efficiency, and side reactions, hindering rate performance and cycling stability. To address these issues, a hollow Cu2O@CuSe core-shell structure was synthesized via a simple and eco-friendly solution method. Benefiting from its unique core-shell structure, the material exhibits high specific capacity (430mAhg-1 at 0.1Ag-1), good rate performance (248mAhg-1 at 5.0Ag-1), and better cycling stability (74.4% retention after 4000 cycles at 1.0Ag-1). A series of tests and characterizations, including in situ electrochemical impedance spectroscopy (EIS), distribution of relaxation times (DRT) analysis and density functional theory (DFT) calculation, confirmed that the CuSe shell not only enhanced the redox activity at the electrode/electrolyte interface, but also provided structural stability for the Cu2O core. A rocking-chair battery using Cu2O@CuSe as the anode and ZnMn2O4 as the cathode achieves long-term stable cycling (95.7% retention after 500 cycles at 0.1Ag-1, 84% retention after 20000 cycles at 2.0Ag-1), demonstrating a promising strategy for high-performance AZIBs anodes.