Zn-MnO2 Batteries Research Articles

Synergistic enhanced Zinc-ion battery performance achieving by atomic layer deposition of TiO2 on three-dimensional carbon nanotube network decorated Zn anode

Herein, we report a unique synergistic effect between carbon nanotube (CNT) network and atomic layer deposition (ALD) of TiO2, which not only enhances the ability to capture zinc ions but also suppresses Zn dendrite growth, resulting in uniform deposition of zinc ions during repeated cycles. The CNTs with luxuriant three-dimensional skeleton structure can provide plentiful deposition sites on Zn metal anode, which significantly reduces the nucleation overpotential and improves the reaction kinetics. Meanwhile, the TiO2 can repeatedly guide the uniform deposition of Zn owing to the excellent zincophilic. The deposition mechanism of zinc in the modified anode (TiO2CNT@Zn anode) is fully explained by comparing different carbon materials. The TiO2CNT@Zn anode shows a high Zn plating/stripping reversibility with an ultralow nucleation overpotential and achieves an ultralong lifespan over 2000 h with a voltage hysteresis of 22.5 mV compared to bare zinc (BZ) anode (63.7 mV) at a high current density of 5 mA cm−2. Moreover, the TiO2CNT@Zn anode maintains a highly stable Coulombic efficiency of 98.9% for more than 500 h. Moreover, the Zn-MnO2 battery with the TiO2CNT@Zn anode shows remarkably enhanced cycling stability.

Evaluation of photocatalytic properties of zinc and cobalt mixed oxide recycled from spent Li-ion and Zn–MnO2 batteries in photo-Fenton-like process

In this study, ZnCo2O4–ZnO–Li(Mn0.75Ni0.25)2O4 mixed oxide was synthesized by green recycling of spent Li-ion and Zn–MnO2 batteries. The cathode of Li-ion batteries and the anode of Zn–MnO2 batteries were leached separately with citric acid. Then, both leachates were mixed, and oxalic acid was added, yielding an oxalate precursor material. The precursor was calcined at 450 °C for 3 h to afford a mixed oxide. Oxalate precursor and oxide structure, composition, and morphology were determined by X-ray diffraction, inductively coupled plasma optical emission spectroscopy, Fourier-transform infrared spectroscopy, Raman spectroscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and transmission electron microscopy. The photocatalytic properties of the mixed oxide were evaluated in the decolorization of methylene blue dye in aqueous solution under UVC radiation. The system composed of UVC radiation + H2O2 + catalyst reached a decolorization efficiency of 93% after 90 min of reaction.

Towards storable and durable Zn-MnO2 batteries with hydrous tetraglyme electrolyte

Aqueous rechargeable zinc-based batteries have attracted increasing interest and been considered potential alternatives for state-of-the-art lithium-ion batteries because of the low cost and high safety. Many cathode materials have been gradually developed and demonstrated excellent electrochemical performances. However, the complex electrochemistry, inevitable hydrogen release, and zinc corrosion severely hinder the practical application. The most concerned Zn-MnO2 batteries still suffer from the Mn dissolution and formation of byproducts. By adding organic solvents to inhibit the activity of water molecules, the hydrous organic electrolytes provide a sound solution for eliminating the unfavorable factors. Here we report a tetraethylene glycol dimethyl ether-based hydrous organic electrolyte consisting of LiClO4·3H2O and Zn(ClO4)2·6H2O, and a birnessite-type MnO2 cathode material for Zn-MnO2 batteries. The Li+/Zn2+ ions co-(de)insertion mechanism is ascertained by the structural and morphological analyses. The electrostatic interaction between inserted ions and crystal structure is reduced effectively by employment of monovalent Li+ ions, which ensures structural stability of cathode materials. Hydrous tetraglyme electrolyte inhibits the activity of water molecules and thus avoids the formation of byproduct Zn4ClO4(OH)7. Meanwhile, highly stable Zn plating/stripping for over 1500 h, an average coulombic efficiency of >99% in long-term cycling, and ultralong storage life (the cells can work well after stored over 1 year) are simultaneously realized in the novel electrolyte. Benefitting from these aspects, the Zn-MnO2 batteries manifest high specific capacity of 132 mA h g−1, an operating voltage of 1.25 V, and a capacity retention of >98% after 1000 cycles at a current density of 200 mA g−1.

Ice crystal sublimation for easily producing MnO2 cathodes with hierarchically porous structure and enhanced cyclic reversibility.

The charge/discharge performance of rechargeable aqueous zinc ion batteries (RAZIBs) at high currents is often unsatisfactory due to the cathode preparation process and the use of hydrophobic binders. By adding freeze-drying treatment to the preparation process of the cathodes, MnO2 cathodes with hierarchically porous structures are obtained, which provide additional channels for ion transfer, thus greatly enhancing the charge/discharge performance in aqueous Zn-MnO2 batteries.

A zinc-ion battery-type self-powered strain sensing system by using a high-performance ionic hydrogel.

Flexible strain sensors based on conductive hydrogels have profound implications for wearable electronics and health-monitoring systems. However, such sensors still need to integrate with energy providing devices to drive their functions. Herein, we develop a soaking-free polyacrylamide/carboxymethyl cellulose/tannic acid (PAAM/CMC/TA) hydrogel containing 2 M ZnSO4 + 0.1 M MnSO4 electrolyte for a novel zinc-ion battery-type self-powered strain sensing system. The synthesized hydrogel possesses desirable stretchability (tensile strain/stress of 622%/132 kPa), self-healing and self-adhesive properties, as well as good ionic conductivity (0.76 ± 0.04 S m-1). A mechanically durable Zn-MnO2 battery is developed using the PAAM/CMC/TA hydrogel and it can deliver a high specific capacity (223.0 mA h g-1) and maintain stable energy outputs under severe mechanical deformations. The electrochemical behavior of the battery can recover even after several self-healing cycles. Due to the excellent strain and pressure sensing properties of the PAAM/CMC/TA hydrogel, the battery combined with a fixed resistor served as a self-powered wearable sensing device, which could translate different human movements into distinguishable electrical signals without an external power supply. Our work provides guidance for the development of next-generation self-powered sensors.

High-Energy and Long-Lived Zn–MnO2 Battery Enabled by a Hydrophobic-Ion-Conducting Membrane

Alkaline Zn-MnO2 batteries feature high security, low cost, and environmental friendliness while suffering from severe electrochemical irreversibility for both the Zn anode and MnO2 cathode. Although neutral electrolytes are supposed to improve the reversibility of the Zn anode, the MnO2 cathode indeed experiences a capacity degradation caused by the Jahn-Teller effect of the Mn3+ ion, thus shortening the lifespan of the neutral Zn-MnO2 batteries. Theoretically, the MnO2 cathode undergoes a highly reversible two-electron redox reaction of the MnO2/Mn2+ couple in strongly acidic electrolytes. However, acidic electrolytes would inevitably accelerate the corrosion of the Zn anode, making long-lived acidic Zn-MnO2 batteries impossible. Herein, to overcome the challenges faced by Zn-MnO2 batteries, we propose a hybrid Zn-MnO2 battery (HZMB) by coupling the neutral Zn anode with the acidic MnO2 cathode, wherein the neutral anode and acidic cathode are separated by a proton-shuttle-shielding and hydrophobic-ion-conducting membrane. Benefiting from the optimized reaction conditions for both the MnO2 cathode and Zn anode as well as the well-designed membrane, the HZMB exhibits a high working voltage of 2.05 V and a long lifespan of 2275 h (2000 cycles), breaking through the limitations of Zn-MnO2 batteries in terms of voltage and cycle life.

Identifying interfacial mechanisms limitations within aqueous Zn-MnO2 batteries and means to cure them with additives

Li-ion batteries are playing a key role within the field of electrical mobility, grid applications and related objects owing to their high energy densities and long lifetime, but their sustainability remains to be improved. Pushing in this direction, there is a rising interest towards rechargeable aqueous batteries. Great efforts are devoted to turn the primary alkaline zinc-manganese dioxide batteries that have dominated the primary battery applications into rechargeable systems. This turns out to be a colossal task owing to the complexity of the Zn-MnO 2 chemistry that is not yet fully rationalized, thus causing delay in practical deployment. In this work we revisit this chemistry by combining fundamental solution chemistry considerations and complementary analytical techniques (TEM, Raman spectroscopy and EQCM) together with the assembly of cells using either MnO 2 or MnO 2 -free initial positive electrodes. We confirm the key role of the electrolyte together with the inseparable link between its pH and the system's electrochemical response. Moreover, during discharge and charge, we provide experimental evidence for the occurrence of MnO 2 electrodissolution and back electrodeposition conjointly with the formation of soluble zinc hydroxides up to chemical precipitation and back dissolution of a Zn 4 SO 4 (OH) 6 .xH 2 O phase. We show that this phase is essential in the buffering of the system's pH and demonstrate the beneficial role of its initial presence in the positive electrode composite. Further pushing the idea of buffering the pH of the electrolyte, we propose the use of additives such as ZnO, Mg(OH) 2 or La(OH) 3 that enhance the capacity retention upon cycling, while slightly penalize the cell capacity. These insights provide missing links regarding the interplay between the conjoint electrochemical-chemical reactions ruling the functioning of rechargeable Zn-MnO 2 batteries, hence providing a step forward towards their development.

Development of MnO2 Based Cathodes for Alkaline Batteries via Combinatorial Approach

A combinatorial study is carried out to develop new cathode compositions in alkaline Zn-MnO2 secondary batteries. MnO2 is modified with ternary additions using Bi2O3, Na0.7MnO2, and NiO. A library of thick film cathodes over a wide compositional range is synthesized via sputter deposition. Thick film cathodes are investigated both electrochemically and structurally. Structural studies show that thick film cathodes are largely amorphous in the as-deposited state but upon charge-discharge cycling, are crystallized into δ-MnO2, i.e. layered polymorph of MnO2. The thick film cathodes are evaluated with cyclic voltammetry and charge-discharge cycling. Two compositional regions are noted as significant in terms of useful cathodes for rechargeable batteries. Compositions rich in NiO yield quite a reliable cell performance which might be considered as cathode material for Zn-NiO batteries. More importantly, there was also a region where Mn and Na had similar proportions doped by Bi and Ni, e.g. Bi0.08Na0.39Ni0.09Mn0.44Ox, which might be made the basis for improved cathode for Zn-MnO2 batteries.

Revealing the Real Charge Carrier in Aqueous Zinc Batteries Based on Polythiophene/Manganese Dioxide Cathode

The rechargeable aqueous zinc–manganese dioxide (Zn–MnO2) batteries are promising candidates for grid‐scale energy storage because of their high energy density and safety, low cost, and environmental friendliness. Unfortunately, capacity fading and ambiguous energy storage mechanisms are obstacles to the commercial application of Zn–MnO2 batteries. Herein, the polythiophene (PTh)‐MnO2 (PTM) nanocomposites are synthesized through a simple and low‐energy consumption interfacial polymerization method. Benefiting from the flexibility and high conductivity of PTh, the PTM electrodes exhibit high reversible specific capacity, acceptable rate performance, and impressive cycle life. Furthermore, ex situ characterizations of the PTM electrodes reveal that the real charge carriers are protons (H+) and hydrated alkaline zinc sulfate (ZSH) is the main product during the discharge state of Zn‐PTM batteries. Consequently, the reversible H+ insertion/extraction accompanying the formation/dissolution mechanism of the Zn‐PTM battery is proposed. In addition, the Zn‐PTM pouch battery as a power source can drive 3C commodities even under striking and piercing conditions. This study not only offers a promising strategy to scale synthesize cathode materials but also promotes insight into energy storage mechanisms and practical applications for aqueous zinc batteries.

Electrochemical Study of Polymorphic MnO2 in Rechargeable Aqueous Zinc Batteries

Manganese dioxide is regarded as a promising energy functional material due to its open tunnel structure with enormous applications in energy storage and catalysis. In this paper, α-MnO2 with a 2 × 2 tunnel structure and β-MnO2 with a 1 × 1 tunnel structure were hydrothermally synthesized, which possess characteristic tunnel structures formed by the interconnected unit structure of [MnO6] octahedrons. With regards to their different tunnel dimensions, the specific mechanism of ion intercalation in these two phases and the effect on their performance as aqueous Zn-MnO2 battery cathodes are explored and compared. Comprehensive analyses illustrate that both α-MnO2 and β-MnO2 provide decent capacity in the aqueous battery system, but their intrinsic stability is poor due to the structural instability upon cycling. At the same time, experiments show that α-MnO2 has a better rate performance than β-MnO2 under larger currents, thus implying that the former has a broader application in this aqueous battery system.

Enhancing the Kinetics of Zinc Ion Deposition by Catalytic Ion in Polymer Electrolytes for Advanced Zn–MnO2 Batteries

AbstractThe practicality of zinc‐ion batteries (ZIBs) is compromise seriously because of the mutual restrictions of hydrogen evolution, by‐product formation and zincdendrite growth. Herein, anhydrous gel polymer electrolytes (GPEs) with catalytic ions and in situdomain‐constrained zinc ions are designed. Innovatively, copper ions are confined in the network structure of the gel for accelerating the deposition and migration kinetics of zinc ions. Not only does this anhydrous GPEs exhibit strong mechanicaland thermal properties, but it also presents a high ionic conductivity (24.32 mS cm−1) and a high zinc ion transference number (0.42). Consequently, the anhydrous GPEs is capable of stable cycling of symmetrical Zn cells at 1 mA cm−2 with acumulative capacity of 1000 mAh cm−2 and maintaines a high discharge specific capacity of 124.6 mAh g−1 after 1000 long‐term cycles of the Zn‐MnO2 battery (ZMB) at 1 C. The synergistic catalytic strategy of composite gel opens new opportunities for a promising pathway to facilitate the large‐scale application of ZIBs with hydrogel electrolytes.

Elucidating MnO2 Reaction Mechanism By Multi-Modal Characterization in Aqueous Zn-MnO2 Batteries

Aqueous Zn-ion batteries has attracted great attention in recent years, as a promising candidate for grid energy storage applications. An aqueous system offers intrinsic safety, high ionic conductivity contributing improved power capability and raw materials that are more earth abundant and environment friendly. Numerous promising reports haven been focusing on the Zn/MnO2 system owing to its low cost, moderate discharge potentials and with improved reversibility in the mild aqueous electrolyte. However, many questions remain unanswered regarding its reaction mechanism. The different reaction mechanisms including Zn+2 insertion, H+ insertion, chemical conversion reaction including the combined intercalation and conversion reaction mechanism, and the dissolution-deposition of the manganese oxide.In this work, we aim to unravel the reaction mechanism by a systematic multimodal synchrotron characterization. This work discusses the galvano-static charge-discharge process of aqueous Zn-MnO2 batteries using operando measurements, which provides us with a direct insight into the phenomenon and can be directly correlated to the battery's electrochemical response. The multimodal techniques include operando X-ray diffraction to study the structural phase change of the cathode active material, operando X-ray absorption spectroscopy to probe the local structure changes and transmission X-ray microscopy studies to observe the key morphological events. Overall, this multimodal approach gives us an insight into the reaction mechanism enabling us to better design Zn-MnO2 batteries for practical applications.

(Invited) Nanostructured Electrochemical Devices and Self-Powered Systems for Biosensing

Self-powered systems for biosensing have attracted tremendous research interest in recent years, mainly due to the rapidly expanding market of wearable and portable devices for applications in clinical diagnosis and physiological monitoring. In our work, novel and unique hierarchical nanostructures were designed and synthesized to realize electrochemical devices with high performance, especially the sensor stability and energy storage capability. Meanwhile, scalable and printable approach was developed to integrate these electrochemical devices into monolithically integrated self-powered systems. The as-developed nanostructured electrochemical devices in conjunction with printable approach show great potency in fabrication of various wearable integrated self-powered devices for personalized healthcare monitoring applications. Our research highlights are as follow: Development of nanoporous membranes for electrochemical sensor applications. It eliminates enzymes escaping and provides sufficient surface area for molecular/ion diffusion and interactions, so as to ensure the sustainable catalytic activities of the sensors and generate reliable measurable signals during noninvasive monitoring. The highly improved stability of sensors is extremely desirable for investigation of metabolic activities in physiological systems.A fully integrated and self-powered system in a smartwatch fashion for continuous monitoring of sweat glucose levels during both equilibrium status and dynamic activities. The smartwatch can be self-powered by flexible photovoltaic cells, without external charging, the harvested energy can also be stored in the flexible Zn-MnO2 batteries as backup power source. It is also capable for real-time and in situ data analysis/display with integrated circuit board and E-ink screen.A monolithically integrated self-powered smart sensor system with energy supplied by fully printable planar supercapacitors and embedded solar cells, was fabricated on plastic substrate with inkjet printing technique as a proof-of-concept. The as-developed printable nanostructured electrochemical devices in conjunction with printable approach for system integration show great potency in fabrication of various wearable integrated self-powered devices for personalized healthcare monitoring applications.

Regulating proton distribution by ion exchange resin to achieve long lifespan aqueous Zn-MnO2 battery

Despite progress in aqueous rechargeable Zn/MnO 2 batteries, mechanism of the complicated cathode reactions is not fully understood. Therefore, the battery system still suffers from some operation issues, such as unsatisfactory cyclability, especially at small current densities (<1C). In this work, we report that the side product from pH fluctuation, Zn 4 (OH) 6 SO 4 ∙xH 2 O (ZHS), can react with Mn 2+ during charge process at over 1.55 V (vs. Zn/Zn 2+ ) to form a lowly crystallized Woodruffite ((Zn,Mn) 2 Mn 5 O 12 ∙4H 2 O, or ZMO), which severely hinders the electrochemical performance of MnO 2 cathode and causes rapid capacity fading. To tackle this issue, we demonstrate that the introduction of ion exchange resin (IER) can regulate proton distribution in the electrolyte and eliminate the ZHS at 1.55 V during charge process, thus effectively inhibit the generation of ZMO. In Mn 2+ -additive free electrolyte, the proposed battery with IER provides a reversible specific capacity of 170 mAhg −1 over 200 cycles (>1450 h continuous discharging/charging) at 50 mAg −1 . When Mn 2+ is pre-added in the electrolyte, a specific capacity of 384 mAhg −1 and a capacity retention of 77.7% after 900 cycles can be obtained at 100 mAg −1 and 5 Ag −1 , respectively. This study shows a general approach to the design of long lifespan aqueous Zn/MnO 2 batteries.

How to increase the potential of aqueous Zn-MnO2 batteries: The effect of pH gradient electrolyte

Non-rechargeable alkaline Zn-MnO2 batteries are dominating the primary battery market and are a promising candidate for secondary battery storage systems as well. However, these batteries suffer from low potential and poor rechargeability. Here, we report a rechargeable membrane-less amphoteric aqueous Zn-MnO2 battery with a 2.4 V open circuit potential. We have employed alkaline (KOH), acidic (H2SO4) and neutral (K2SO4) Pluronic F-127 hydrogels as electrolytes. By placing the anode in an alkaline environment but the cathode in an acidic environment, we have successfully widened the potential window in an aqueous medium avoiding hydrogen and oxygen evolution reactions. The obtained open circuit potential of as prepared amphoteric battery is stable for more than 25 h and 200 charge-discharge cycles.

Electrochemical sensor prepared with materials from spent Zn-MnO2 batteries for copper(II) determination in alcoholic beverages

Electrochemical sensor prepared with materials from spent Zn-MnO2 batteries for copper(II) determination in alcoholic beverages

Understanding intercalation chemistry for sustainable aqueous zinc–manganese dioxide batteries

Rechargeable aqueous Zn–MnO2 technology combines one of the oldest battery chemistries with favourable sustainability characteristics, including safety, cost and environmental compatibility. However, the ambiguous charge storage mechanism presents a challenge to fulfil the great potential of this energy technology. Here we leverage on advanced electron microscopy, electrochemical analysis and theoretical calculations to look into the intercalation chemistry within the cathode material, or α-MnO2 more specifically. We show that Zn2+ insertion into the cathode is unlikely in the aqueous system; rather, the charge storage process is dominated by proton intercalation to form α-HxMnO2. We further reveal anisotropic lattice change as a result of entering protons proceeding from the surface into the bulk of α-MnO2, which accounts for the structural failure and capacity decay of the electrode upon cycling. Our work not only advances the fundamental understanding of rechargeable zinc batteries but also suggests the possibility to optimize proton intercalation kinetics for better-performing cell designs. A rechargeable aqueous Zn–MnO2 battery features a combination of favourable sustainability characteristics from safety to cost. The authors deploy advanced characterizations and theoretical calculations to provide fresh insight into the charge storage mechanism, which not only closes an ongoing debate but suggests ways forward.

Decoupling the Dynamics of Zinc Hydroxide Sulfate Precipitation/Dissolution in Aqueous Zn–MnO2 Batteries by Operando Optical Microscopy: A Missing Piece of the Mechanistic Puzzle (Adv. Energy Mater. 30/2022)

Zn–MnO2 Batteries With a high theoretical gravimetric capacity, intrinsic safety, and low cost, aqueous Zn–MnO2 batteries are promising candidates for grid-scale energy storage. However, the charge storage at the MnO2 electrode remains a mystery, delaying real-life applications. In article number 2200722, Frédéric Kanoufi and co-workers shine light on its mechanism using optical microscopy.

Insights into complexing effects in acetate-based Zn-MnO2 batteries and performance enhancement by all-round strategies

Aqueous Zn-MnO2 batteries with Mn2+/MnO2 conversion reaction have attracted enormous attentions in these years, in which the proposal of acetate-based electrolyte further boosts the redox chemistry and achieves the two-electron reaction with mitigated anode corrosion. However, the lower redox potential, the generation of dead MnO2, and MnO2 suspension in acetate-based Zn-MnO2 batteries inhibit their commercialization. Herein, the acetate-based electrolyte is optimized by introducing electrolyte modification and manageable Cr2+/Cr3+ reaction, contributing to higher cathodic potential and longer lifetime. Additionally, the dead MnO2 with incompact morphology is found to facilitate the further deposition in the initial stage. Based on the above discussions, we proposed the all-round optimizations, which additionally include a pre-cycling process and a simple ultrasonic treatment, achieving a triple lifetime and the record-large accumulated capacity of 10 Ah cm−2 with the power density higher than 75 mW cm−2. Moreover, the sources of the above issues and their relations to complexing effects are elaborated. This work may be instructive and pioneering for the future development of complexes-based Zn-MnO2 batteries.

Robust, Conductive, and High Loading Fiber-Shaped Electrodes Fabricated by 3D Active Coating for Flexible Energy Storage Devices.

Flexible power sources are critical to achieve the wide adoption of portable and wearable electronics. Herein, a facile and general strategy of fabricating a fibrous electrode was developed by 3D active coating technology, in which a stepping syringe with electrode paste was synchronously injected onto a rotating conductive wire, distinguished from the conventional direct-write 3D printing without a current collector. A series of such electrodes with different coating weight can be fabricated accurately and efficiently by adjusting critical process parameters following a set of derived equations. The demonstrated fibrous Zn-MnO2 battery with a high commercial ε-MnO2 loading of 14.9 mg cm-2 onto a stainless steel wire shows a reasonable energy density of 108 mWh cm-3, while the fiber-shaped supercapacitor with commercial porous graphene exhibits a high capacitance of 142.9 F g-1 and good durability for bending 10,000 cycles. This work constructs a bridge between materials and fiber-shaped electrodes for flexible energy storage devices.