Rechargeable Aqueous Zinc Batteries Research Articles

A zinc battery with ultra-flat discharge plateau through phase transition mechanism

Rechargeable aqueous zinc batteries have attracted enormous attention due to the distinctively economic and environmental advantages. However, the present zinc batteries delivered sloping voltage profiles based on the dominant mechanism of Zn ion intercalation. Typically, a Zn–V2O5 battery exhibits a discharge slope of ~4.3 V/(Ah g−1) and a slope of ~1.5 V/(Ah g−1) is observed for MnO2 cathodes. Furthermore, the rate capacity based on intercalation is limited. Here we report a highly flat voltage profile for a reversible alkaline zinc battery with α-Bi2O3 as the cathode. Different from the conventional zinc batteries, zinc-α-Bi2O3 batteries possess a first-order phase transition process that is the responsible cause of their outstanding performance, such as an ultra-flat output voltage [slope: ~0.1 V/(Ah g−1)], a high discharge capacity of 323 mAh g−1 at 0.1 A g−1 and excellent rate capacity with a 155 mAh g−1 capacity even at 20A g−1 (61C). In addition, a high areal energy density of 1.5 mWh cm−2 is achieved at power density of 4.4 mW cm−2. Moreover, the quasi-solid-state Zn-α-Bi2O3 battery is also fabricated using a sodium polyacrylate (PANa) as the hydrogel electrolyte, exhibiting promising application as power source for flexible devices.

Electrochemical intercalation of anions in graphite for high-voltage aqueous zinc battery

Rechargeable aqueous zinc batteries are ideal for large-scale energy storage due to their low cost and high safety. Here we demonstrate the reversible anion intercalation chemistry in graphite cathode for aqueous zinc battery, thus operating as a high-voltage dual-ion battery system. The use of a hybrid “water-in-salt” electrolyte with zinc and lithium bi-salts can maximize the ionic content, expand the anodic stability, promote dendrite-free zinc plating/stripping, and bring the reversible anion intercalation in graphite cathode. This cell configuration offers a high operating voltage and unprecedented cycling stability with comparable Coulombic efficiency to the organic dual-ion battery, opening new opportunities for the development of high-voltage rechargeable aqueous batteries.

Mechanistic Investigation of a Hybrid Zn/V2 O5 Rechargeable Battery with a Binary Li+ /Zn2+ Aqueous Electrolyte.

Low-cost, easily processable, and environmentally friendly rechargeable aqueous zinc batteries have great potential for large-scale energy storage, which justifies their receiving extensive attention in recent years. An original concept based on the use of a binary Li+ /Zn2+ aqueous electrolyte is described herein for the case of the Zn/V2 O5 system. In this hybrid, the positive side involves mainly the Li+ insertion/deinsertion reaction of V2 O5 , whereas the negative electrode operates according to zinc dissolution-deposition cycles. The Zn//3 mol L-1 Li2 SO4 -4 mol L-1 ZnSO4/ //V2 O5 cell worked in the narrow voltage range of 1.6-0.8 V with capacities of approximately 136-125 mA h g-1 at rates of C/20-C/5, respectively. At 1 C, the capacity of 80 mA h g-1 was outstandingly stable for more than 300 cycles with a capacity retention of 100 %. A detailed structural study by XRD and Raman spectroscopy allowed the peculiar response of the V2 O5 layered host lattice on discharge-charge and cycling to be unraveled. Strong similarities with the well-known structural changes reported in nonaqueous lithiated electrolytes were highlighted, although the emergence of the usual distorted δ-LiV2 O5 phase was not detected on discharge to 0.8 V. The pristine host structure was restored and maintained during cycling with mitigated structural changes leading to high capacity retention. The present electrochemical and structural findings reveal a reaction mechanism mainly based on Li+ intercalation, but co-intercalation of a few Zn2+ ions between the oxide layers cannot be completely dismissed. The presence of zinc cations between the oxide layers is thought to relieve the structural stress induced in V2 O5 under operation, and this resulted in a limited volume expansion of 4 %. This fundamental investigation of a reaction mechanism operating in an environmentally friendly aqueous medium has not been reported before.

Redox-Active Phenanthrenequinone Triangles in Aqueous Rechargeable Zinc Batteries.

Aqueous rechargeable zinc batteries (ZBs) have received considerable attention recently for large-scale energy storage systems in terms of rate performance, cost, and safety. Nevertheless, these ZBs still remain a subject for investigation, as researchers search for cathode materials enabling high performance. Among the various candidate cathode materials for ZBs, quinone compounds stand out as candidates because of their high specific capacity, sustainability, and low cost. Quinone-based cathodes, however, suffer from the critical limitation of undergoing dissolution during battery cycling, leading to a deterioration in battery life. To address this problem, we have introduced a redox-active triangular phenanthrenequinone-based macrocycle (PQ-Δ) with a rigid geometry and layered superstructure. Notably, we have confirmed that Zn2+ ions, together with H2O molecules, can be inserted into the PQ-Δ organic cathode, and, as a consequence, the interfacial resistance between the cathode and electrolytes is decreased effectively. Density functional theory calculations have revealed that the low interfacial resistance can be attributed mainly to decreasing the desolvation energy penalty as a result of the insertion of hydrated Zn2+ ions in the PQ-Δ cathode. The combined effects of the insertion of hydrated Zn2+ ions and the robust triangular structure of PQ-Δ serve to achieve a large reversible capacity of 210 mAh g-1 at a high current density of 150 mA g-1, along with an excellent cycle-life, that is, 99.9% retention after 500 cycles. These findings suggest that the utilization of electron-active organic macrocycles, combined with the low interfacial resistance associated with the solvation of divalent carrier ions, is essential for the overall performance of divalent battery systems.

Understanding the mechanism of byproduct formation with in operando synchrotron techniques and its effects on the electrochemical performance of VO2(B) nanoflakes in aqueous rechargeable zinc batteries

The byproduct protects the vanadium-based positive electrode of ARZBs and facilitates Zn2+ insertion into the electrode.

Ultrathin δ-MnO2 nanoflakes with Na+ intercalation as a high-capacity cathode for aqueous zinc-ion batteries.

Pristine δ-MnO2 as the typical cathode for rechargeable zinc-ion batteries (ZIBs) suffers from sluggish reaction kinetics, which is the key issue to prepare high-performance manganese-based materials. In this work, Na+ incorporated into layered δ-MnO2 (NMO) was prepared for ZIB cathodes with high capacity, high energy density, and excellent durable stability. By an effective fabricated strategy of hydrothermal synthesis, a three-dimensional interconnected δ-MnO2 nanoflake network with Na+ intercalation showed a uniform array arrangement and high conductivity. Also, the H+ insertion contribution in the NMO cathode to the discharge capacity confirmed the fast electrochemical charge transfer kinetics due to the enhanced ion conductivity from the insertion of Na+ into the interlayers of the host material. Consequently, a neutral aqueous NMO-based ZIB revealed a superior reversible capacity of 335 mA h g−1, and an impressive durability over 1000 cycles, and a peak gravimetric energy output of 459 W h kg−1. As a proof of concept, the as-fabricated quasi-solid-state ZIB exhibited a remarkable capacity of 284 mA h g−1 at a current density of 0.5 A g−1, and good practicability. This research demonstrated a significant enhancement of the electrochemical performance of MnO2-based ZIBs by the intercalation of Na+ to regulate the microstructure and boost the electrochemical kinetics of the δ-MnO2 cathode, thus providing a new insight for high-performance aqueous ZIBs.

Conductive 2D metal-organic framework for high-performance cathodes in aqueous rechargeable zinc batteries

Currently, there is considerable interest in developing advanced rechargeable batteries that boast efficient distribution of electricity and economic feasibility for use in large-scale energy storage systems. Rechargeable aqueous zinc batteries are promising alternatives to lithium-ion batteries in terms of rate performance, cost, and safety. In this investigation, we employ Cu3(HHTP)2, a two-dimensional (2D) conductive metal-organic framework (MOF) with large one-dimensional channels, as a zinc battery cathode. Owing to its unique structure, hydrated Zn2+ ions which are inserted directly into the host structure, Cu3(HHTP)2, allow high diffusion rate and low interfacial resistance which enable the Cu3(HHTP)2 cathode to follow the intercalation pseudocapacitance mechanism. Cu3(HHTP)2 exhibits a high reversible capacity of 228 mAh g−1 at 50 mA g−1. At a high current density of 4000 mA g−1 (~18 C), 75.0% of the initial capacity is maintained after 500 cycles. These results provide key insights into high-performance, 2D conductive MOF designs for battery electrodes.

A Zn(ClO4)2 Electrolyte Enabling Long-Life Zinc Metal Electrodes for Rechargeable Aqueous Zinc Batteries.

The degradation or dendrite formation of zinc metal electrodes has shown to limit the cycle life of rechargeable aqueous zinc batteries, and a few anode protection methods are proposed. We herein demonstrate that, except for external protections, a simple design of an electrolyte can effectively promote stable and facile Zn stripping/plating from/on zinc electrodes. By using Zn(ClO4)2 in the aqueous electrolyte, reversible Zn stripping/plating is achieved for over 3000 h at 1 mA cm-2 current density and 1 mA h cm-2 capacity, superior to the conventional ZnSO4 electrolyte. The overpotential is constant within each cycle and only increases slightly with the increase of current densities. The excellent performance is guaranteed by the controlled formation of a Cl- containing layer, which limits continuous side reactions. The Zn(ClO4)2 electrolyte shows anodic stability up to 2.4 V, and excellent electrochemical performance is achieved for an example cell with the VO2 cathode, confirming the applicability of the electrolyte for Zn batteries.

Artificial solid electrolyte interphase for thermally stable rechargeable aqueous zinc batteries

Rechargeable aqueous zinc battery (RAZB) represents a promising energy storage system for its high energy density, high safety and low-cost. Among available cathode materials for RAZBs, vanadium oxide (V2O5) is being considered thanks to its high specific discharge capacity, and the ease of Zn intake/extraction due to layered crystalline structure. However, V2O5 is unstable during charge and discharge processes in aqueous batteries. To address this issue, we introduce a surface modification method to form artificial solid electrolyte interphase (SEI) on the V2O5 particles before used in the battery. The artificial SEI layer, which is composed of conductive heterocyclic aromatic chains, protects the active material from direct contact with the aqueous electrolyte. Surprisingly, the ultrathin artificial-SEI benefits V2O5 to display a high capacity of 195.7 mAh·g−1 (at current density of 1 A g−1) with just 9.5% capacity decay at room temperature after 200 cycles. Under elevated temperature (60 °C), the RAZB still shows an outstanding 80.1% capacity retention after 150 cycles (at current density of 1 A g−1) vs. 25% retention of the bare V2O5 material. Overall, the use of artificial-SEI offers a new approach to realize a thermal stable energy storage system, which is considered an alternative to lithium-ion batteries.

Ultralong cycle stability of aqueous zinc-ion batteries with zinc vanadium oxide cathodes.

Rechargeable aqueous zinc-ion batteries are promising candidates for large-scale energy storage but are plagued by the lack of cathode materials with both excellent rate capability and adequate cycle life span. We overcome this barrier by designing a novel hierarchically porous structure of Zn-vanadium oxide material. This Zn0.3V2O5·1.5H2O cathode delivers a high specific capacity of 426 mA·h g-1 at 0.2 A g-1 and exhibits an unprecedented superlong-term cyclic stability with a capacity retention of 96% over 20,000 cycles at 10 A g-1. Its electrochemical mechanism is elucidated. The lattice contraction induced by zinc intercalation and the expansion caused by hydronium intercalation cancel each other and allow the lattice to remain constant during charge/discharge, favoring cyclic stability. The hierarchically porous structure provides abundant contact with electrolyte, shortens ion diffusion path, and provides cushion for relieving strain generated during electrochemical processes, facilitating both fast kinetics and long-term stability.

Inhibiting VOPO4 ⋅x H2 O Decomposition and Dissolution in Rechargeable Aqueous Zinc Batteries to Promote Voltage and Capacity Stabilities.

VOPO4 ⋅x H2 O has been proposed as a cathode for rechargeable aqueous zinc batteries. However, it undergoes significant voltage decay in conventional Zn(OTf)2 electrolyte. Investigations show the decomposition of VOPO4 ⋅x H2 O into VOx in the electrolyte and voltage drops after losing the inductive effect from polyanions.PO4 3- was thus added to shift the decomposition equilibrium. A high concentration of cheap, highly soluble ZnCl2 salt in the electrolyte further prevents VOPO4 ⋅x H2 O dissolution. The cathode shows stable capacity and voltage retentions in 13 m ZnCl2 /0.8 m H3 PO4 aqueous electrolyte, in direct contrast to that in Zn(OTf)2 where the decomposition product VOx provides most electrochemical activity over cycling. Sequential H+ and Zn2+ intercalations into the structure are revealed, delivering a high capacity (170 mAh g-1 ). This work shows the potential issue with polyanion cathodes in zinc batteries and proposes an effective solution using fundamental chemical principles.

Inhibiting VOPO4⋅x H2O Decomposition and Dissolution in Rechargeable Aqueous Zinc Batteries to Promote Voltage and Capacity Stabilities

AbstractVOPO4⋅x H2O has been proposed as a cathode for rechargeable aqueous zinc batteries. However, it undergoes significant voltage decay in conventional Zn(OTf)2 electrolyte. Investigations show the decomposition of VOPO4⋅x H2O into VOx in the electrolyte and voltage drops after losing the inductive effect from polyanions.PO43− was thus added to shift the decomposition equilibrium. A high concentration of cheap, highly soluble ZnCl2 salt in the electrolyte further prevents VOPO4⋅x H2O dissolution. The cathode shows stable capacity and voltage retentions in 13 m ZnCl2/0.8 m H3PO4 aqueous electrolyte, in direct contrast to that in Zn(OTf)2 where the decomposition product VOx provides most electrochemical activity over cycling. Sequential H+ and Zn2+ intercalations into the structure are revealed, delivering a high capacity (170 mAh g−1). This work shows the potential issue with polyanion cathodes in zinc batteries and proposes an effective solution using fundamental chemical principles.

A Self-Doped Polyaniline Cathode for Rechargeable Aqueous Zinc Batteries

Rechargeable batteries offer promising solutions to the energy shortage issue.[1] In comparison to non-aqueous Li-ion batteries, aqueous rechargeable batteries possess the merits of using low-cost and high-safety water-based electrolytes. Aqueous electrolytes also provide higher ionic conductivities than non-aqueous ones, which promotes better rate performance of the cell.[2] These superiorities make the system suitable for stationary grid-level energy storages. The zinc metal is a convenient anode for aqueous batteries due to its low redox potential (-0.76 V vs. standard hydrogen electrode), high theoretical capacity (5845 mAh cm-3, 819 mAh g-1) and good compatibility with water.[3]-[5] Its abundant earth storage, non-toxicity and stability in air furthermore benefits large-scale productions. Using neutral or slightly acidic solutions to replace the alkaline electrolytes can suppress the dendritic growth of Zn anode.[4] One urgent requirement of zinc battery research is to find a suitable cathode. Benefiting from the long π-electron conjugated systems, conducting polymers hold higher conductivities compared to metal oxides and organic materials.[6] The highly conductive polyaniline (PANI) is a potential cathode, but it tends to deactivate in low acidic electrolytes (i.e. pH > 1) due to the de-protonation of the polymer. Herein, we synthesized a sulfo self-doped PANI electrode by a facile electrochemical copolymerization process. The -SO3 - self-dopant functions as an internal proton reservoir to ensure locally high acidic environment and facilitate the redox process in the weak acidic ZnSO4 electrolyte. In a full zinc cell, the self-doped PANI cathode delivers a high capacity of 180 mAh g-1, excellent rate performance of 70% capacity retention at 50 times current density increase, and long cycle life of over 2000 cycles with coulombic efficiency close to 100%. The detailed charge storage processes were investigated by X-ray photoelectron spectroscopy and X-ray diffraction. They suggest partial proton insertion into self-doped PANI during discharge, which leads to the internal protonation of -N= units and facilitates further reduction. This helps the polymer to maintain high electrochemical activity and stable capacity retention over cycling, in direct contrast to the fast capacity decay with the non-self-doped PANI cathode. Overall, our work utilizes the smart pH adjustment ability of self-dopants to overcome the discrepancy of active conditions between PANI cathode and Zn anode. More importantly, it demonstrates the potential applications of conducting polymers as cathode materials for rechargeable zinc batteries, with the specific energy storage behavior tunable thanks to the rich chemistry of their family.

Engineering a High-Energy-Density and Long Lifespan Aqueous Zinc Battery via Ammonium Vanadium Bronze.

Aqueous rechargeable zinc batteries (ARZBs) are desirable for energy storage devices owing to their low cost and abundance of the Zn anode, but their further development is limited by a dearth of ideal cathode materials that can simultaneously possess high capacity and stability. Herein, we employ a layered structure of ammonium vanadium bronze (NH4)0.5V2O5 as the cathode material for ARZBs. The large interlayer distance supported by the NH4+ insertion not only facilitates the Zn2+-ion intercalation/deintercalation but also improves the electrochemical stability in ARZBs. As a result, the layered structural (NH4)0.5V2O5 cathode delivers a high capacity up to 418.4 mA h g-1 at a current density of 0.1 A g-1. A reversible capacity of 248.8 mA h g-1 is still retained after 2000 cycles and a capacity retention of 91.4% was maintained at 5 A g-1. Furthermore, in comparison with previously reported Zn-ion batteries, the Zn/(NH4)0.5V2O5 battery achieves a prominent high energy density of 418.4 W h kg-1 while delivering a high power density of 100 W kg-1. The results would enlighten and push the ammonium vanadium compounds to a brand new stage for the application of aqueous batteries.

Manganese oxides/N-doped carbon particles with high capacity retention for aqueous rechargeable zinc battery

Manganese dioxide as the electrode for aqueous zinc-ion batteries (AZIBs) is influenced by the material dissolution. Herein, β-MnO2/N-doped carbon matrix (NCm) or Mn5O8/NCm composites were fabricated by effective synthesis process using polyaniline (PANI) as carbon/nitrogen sources. The conductive N-doped carbon layer was tied to β-MnO2, which increased the electrical conductivity of the β-MnO2 nanorod. At current densities of 200 mA g−1, the β-MnO2/NCm electrode delivered a higher discharge capacity of 331 mAh g−1 comparing with 185 mAh g−1 for the pure β-MnO2 electrode. Besides, the Mn5O8/NCm electrode could provide a discharge capacity of 266 mAh g−1. Therefore, the approach in this study may pave the way on preparing manganese oxides/NCm materials for AZIBs.

Hydrated Layered Vanadium Oxide as a Highly Reversible Cathode for Rechargeable Aqueous Zinc Batteries

AbstractRechargeable aqueous zinc batteries have gained considerable attention for large‐scale energy storage systems because of their low cost and high safety, but they suffer from limitations in cycling stability and energy density with advanced cathode materials. Here, a high‐performance V5O12·6H2O (VOH) nanobelt cathode uniformly located on a stainless‐steel substrate via a facile electrodeposition technique is reported. We show that the hydrated layered VOH cathode enables highly reversible and ultrafast Zn2+ cation (de)intercalation processes, as confirmed by various electrochemical, X‐ray diffraction, X‐ray photoelectron spectroscopy, and transmission electron microscopy analyses. It is demonstrated that the binder‐free VOH cathode can deliver a discharge capacity of 354.8 mAh g−1 at 0.5 A g−1 with a high initial Coulombic efficiency of 99.5%, a high energy density of 194 Wh kg−1 at 2100 W kg−1, and a long cycle life with a capacity retention of 94% over 1000 cycles. In addition, a flexible quasi‐solid‐state Zn–VOH battery is constructed, achieving a reversible capacity of ≈300 mAh g−1 with a capacity retention of 96% after 50 cycles and displaying excellent electrochemical behaviors under different bending states. This work sheds light on the development of rechargeable aqueous zinc batteries for stationary grid storage applications or flexible energy storage devices.

Crystal water for high performance layered manganese oxide cathodes in aqueous rechargeable zinc batteries

Crystal water improves electrochemical performance of the layered manganese oxide for aqueous rechargeable zinc batteries.

A Long-Cycle-Life Self-Doped Polyaniline Cathode for Rechargeable Aqueous Zinc Batteries.

Rechargeable aqueous zinc batteries are promising energy-storage systems for grid applications. Highly conductive polyaniline (PANI) is a potential cathode, but it tends to deactivate in electrolytes with low acidity (i.e. pH >1) owing to deprotonation of the polymer. In this study, we synthesized a sulfo-self-doped PANI electrode by a facile electrochemical copolymerization process. The -SO3 - self-dopant functions as an internal proton reservoir to ensure a highly acidic local environment and facilitate the redox process in the weakly acidic ZnSO4 electrolyte. In a full zinc cell, the self-doped PANI cathode provided a high capacity of 180 mAh g-1 , excellent rate performance of 70 % capacity retention with a 50-fold current-density increase, and a long cycle life of over 2000 cycles with coulombic efficiency close to 100 %. Our study opens a door for the use of conducting polymers as cathode materials for high-performance rechargeable zinc batteries.

A Long‐Cycle‐Life Self‐Doped Polyaniline Cathode for Rechargeable Aqueous Zinc Batteries

AbstractRechargeable aqueous zinc batteries are promising energy‐storage systems for grid applications. Highly conductive polyaniline (PANI) is a potential cathode, but it tends to deactivate in electrolytes with low acidity (i.e. pH >1) owing to deprotonation of the polymer. In this study, we synthesized a sulfo‐self‐doped PANI electrode by a facile electrochemical copolymerization process. The −SO3− self‐dopant functions as an internal proton reservoir to ensure a highly acidic local environment and facilitate the redox process in the weakly acidic ZnSO4 electrolyte. In a full zinc cell, the self‐doped PANI cathode provided a high capacity of 180 mAh g−1, excellent rate performance of 70 % capacity retention with a 50‐fold current‐density increase, and a long cycle life of over 2000 cycles with coulombic efficiency close to 100 %. Our study opens a door for the use of conducting polymers as cathode materials for high‐performance rechargeable zinc batteries.

Water-Lubricated Intercalation in V2O5·nH2o for High-Capacity and High-Rate Aqueous Rechargeable Zinc Batteries

Low cost, environmentally friendly aqueous Zn batteries have great potential for large-scale energy storage. In our previous work, we found that the intercalation of zinc ions in the cathode materials is challenging and complex [1, 2]. In this talk, we will try to clarify it by showing the critical role of structural H2O on Zn2+ intercalation into the V2O5 framework [3]. Our latest results demonstrate that the H2O solvation of Zn2+ largely reduces its effective charge and thus its electrostatic interactions with the V2O5 framework, effectively promoting the diffusion of solvated Zn2+. Benefited from the ‘lubricating’ effect, the aqueous Zn battery shows a specific energy of ~ 144 Wh kg-1 at 0.3 A g-1. Meanwhile, it can maintain an energy density of 90 Wh kg-1 at a high power density of 6.4 kW kg-1 (based on the cathode and 200% Zn anode), making it a promising candidate for high-performance, low-cost, safe, and environmentally friendly energy storage device. Such a ‘lubricating’ effect in Zn batteries could be applicable to other multivalent metal ion-based batteries for further improving the energy storage performance, and could also shed light on discovering new battery materials. Reference [1] H. Pan, Y. Shao, P. Yan, Y. Cheng, K. S. Han, Z. Nie, C. Wang, J. Yang, X. Li, P. Bhattacharya, Nature Energy 2016, 1, 16039. [2] P. He, M. Yan, G. Zhang, R. Sun, L. Chen, Q. An, L. Mai, Advanced Energy Materials 2017, 7. [3] M. Yan, P. He, Y. Chen, S. Wang, Q. Wei, K. Zhao, X. Xu, Q. An, Y. Shuang, Y. Shao, K. T. Mueller, L. Mai, J. Liu, J. Yang, Advanced Materials, 1703725, doi: 10.1002/adma.201703725.