Cathode For Aqueous Zinc-ion Batteries Research Articles

Long‐Life Pillar[5]quinone Cathode for Aqueous Zinc‐Ion Batteries

AbstractAqueous zinc ion batteries (ZIBs) are currently gaining a significant amount of attention as a low‐cost and high safety energy storage option. While mostly inorganic structures are used as cathode materials in aqueous zinc batteries, these materials undergo structural degradation, therefore, alternative organic cathodes are expected to be developed to replace inorganic materials in aqueous zinc ion batteries (AZIBs). In this work, pillar[5]quinone (P5Q) is used as a cathode in AZIBs for the first time. Besides investigating the charge storage mechanism and interfacial property evolution of P5Q by various ex situ analyses, electrochemical quartz crystal microbalance (EQCM) and density functional theory (DFT) demonstrates both Zn2+ and H+ incorporation. The P5Q exhibits >99 % Coulombic efficiency through 10000 cycles at ultra‐fast (500 °C) current density, yielding a capacity value of approximately 120 mAh g−1 at the end of the cycle. When the current density is changed from 500 °C to 120 °C, an initial discharge capacity of approximately 182 mAh g−1 is achieved, demonstrating outstanding performance with over 80 % capacity retention for the subsequent 7000 cycles.

Tailored crystal planes of VO2 cathode power fast Zn2+ storage

Vanadium dioxide (VO2) cathode with specific tunnel structure and favorable specific capacity is critical for developing aqueous zinc-ion batteries (AZIBs) with excellent electrochemical performance. However, sluggish electrochemical kinetics hampered its development in burgeoning energy storage devices. Herein, we tailored VO2 material with different exposed crystal planes and employed as cathodes for AZIBs. The comprehensive analyses indicate the exposed (201) and (001) crystal planes are favorable for fast electrochemical kinetics, high capacitance storage, and the smallest diffusion energy barrier, which guarantee electrodes with high discharge capacity (367 mA h/g at 0.1 A/g), excellent rate capability (281 mA h/g at 4 A/g) and cycling stability over 800 cycles. Besides, Ex-situ characterizations manifest VO2 cathode with specific exposed crystal planes easily transformed to Zn3+x(OH)2V2O7·2H2O in the first discharge process, hence allowing continuous embedding of Zn2+ in this layered structure, and the ex-situ scanning electron microscopy (SEM) analysis confirms the morphology change matched well with the structural transformation. This study may enlighten and promote the role of exposed crystal plane to develop high-performance rechargeable batteries.

Exploring Zinc-Doped Manganese Hexacyanoferrate as Cathode for Aqueous Zinc-Ion Batteries.

Aqueous zinc-ion batteries (AZiBs) have emerged as a promising alternative to lithium-ion batteries as energy storage systems from renewable sources. Manganese hexacyanoferrate (MnHCF) is a Prussian Blue analogue that exhibits the ability to insert divalent ions such as Zn2+. However, in an aqueous environment, MnHCF presents weak structural stability and suffers from manganese dissolution. In this work, zinc doping is explored as a strategy to provide the structure with higher stability. Thus, through a simple and easy-to-implement approach, it has been possible to improve the stability and capacity retention of the cathode, although at the expense of reducing the specific capacity of the system. By correctly balancing the amount of zinc introduced into the MnHCF it is possible to reach a compromise in which the loss of capacity is not critical, while better cycling stability is obtained.

A Cu/MnOx Composite with Copper-Doping-Induced Oxygen Vacancies as a Cathode for Aqueous Zinc-Ion Batteries.

Aqueous zinc-ion batteries are anticipated to be the next generation of important energy storage devices to replace lithium-ion batteries due to the ongoing use of lithium resources and the safety hazards associated with organic electrolytes in lithium-ion batteries. Manganese-based compounds, including MnOx materials, have prominent places among the many zinc-ion battery cathode materials. Additionally, Cu doping can cause the creation of an oxygen vacancy, which increases the material's internal electric field and enhances cycle stability. MnOx also has great cyclic stability and promotes ion transport. At a current density of 0.2 A g-1, the Cu/MnOx nanocomposite obtained a high specific capacitance of 304.4 mAh g-1. In addition, Cu/MnOx nanocomposites showed A high specific capacity of 198.9 mAh g-1 after 1000 cycles at a current density of 0.5 A g-1. Therefore, Cu/MnOx nanocomposites are expected to be a strong contender for the next generation of zinc-ion battery cathode materials in high energy density storage systems.

Recent advances and perspectives in MXene-based cathodes for aqueous zinc-ion batteries

Recent advances and perspectives in MXene-based cathodes for aqueous zinc-ion batteries

Anchored VN Quantum Dots Boosting High Capacity and Cycle Durability of Na3V2(PO4)3@NC Cathode for Aqueous Zinc-Ion Battery and Organic Sodium-Ion Battery.

Na3V2(PO4)3 is a promising high-voltage cathode for aqueous zinc-ion batteries (ZIBs) and organic sodium-ion batteries (SIBs). However, the poor rate capability, specific capacity, and cycling stability severely hamper it from further development. In this work, Na3V2(PO4)3 (NVP) with vanadium nitride (VN) quantum dots encapsulated by nitrogen-doped carbon (NC) nanoflowers (NVP/VN@NC) are manufactured as cathode using in situ nitridation, carbon coating, and structural adjustment. The outer NC layer increases the higher electronic conductivity of NVP. Furthermore, VN quantum dots with high theoretical capacity not only improve the specific capacity of pristine NVP, but also serve as abundant "pins" between NVP and NC to strengthen the stability of NVP/VN@NC heterostructure. For Zn-ion storage, these essential characteristics allow NVP/VN@NC to attain a high reversible capacity of 135.4mAhg-1 at 0.1Ag-1, and a capacity retention of 91% after 2000 cycles at 5Ag-1. Meanwhile, NVP/VN@NC also demonstrates to be a stable cathode material for SIBs, which can reach a high reversible capacity of 124.5mAhg-1 at 0.1Ag-1, and maintain 92% of initial capacity after 11000 cycles at 5Ag-1. This work presents a feasible path to create innovative high-voltage cathodes with excellent reaction kinetics and structural stability.

Shielding unfavorable interaction by oxygen-mediated interlayer chemical bonding enables high-capacity and stable MoS2 cathode

Molybdenum disulfide (MoS2) as cathodes for aqueous zinc-ion batteries (AZIBs) typically undergoes sluggish kinetics and irreversible structure distortion because of the strong interaction between intensely electronegative sulfur and intercalated Zn2+, especially for thick electrodes. Herein, we propose a new oxygen-mediated interlayer chemical bonding strategy to achieve high-performance MoS2 cathode in thick electrode (5–15 mg cm−2). The oxygen-mediated interlayer chemical bonding is facilely formed by intercalating oxygen-rich β-cyclodextrin into MoS2 nanosheets (denoted as MoS2-β-CD), which not only expands the interlayer spacing (from 6.4 to 9.6 Å) but also effectively weakens the electrostatic interaction between Zn2+ and host frameworks, endowing it with fast electron/ion transport and robust structural stability. Consequently, even with 10 mg cm−2 loading, the MoS2-β-CD cathode delivers an impressive specific capacity of 228.0 mA h g−1 (2.3 mA h cm−2) at 4 mA cm−2, superior to most advanced MoS2-based electrodes. Additionally, the MoS2-β-CD electrode also possesses significantly enhanced durability (85.3 % vs. 28.6 % capacity retention after 5000 cycles). This work provides unique inspiration for rational design of AZIB cathodes for practical applications.

Supramolecular channels via crown ether functionalized polyaniline for proton-self-doped cathode in aqueous zinc-ion battery

Polyaniline (PANI) has been widely used as a cathode in aqueous zinc-ion batteries (AZIBs) because of its attractive conductivity and energy storage capability. However, the extensive application of PANI is limited by spontaneous deprotonation and slow diffusion kinetics. Herein, an 18-crown-6-functionalised PANI pseudorotaxane (18C6@PANI) cathode is successfully developed through a facile template-directed polymerisation reaction. The 18C6@PANI cathode exhibits a high specific capacity of 256 mAh g−1 at 0.2 A/g, excellent rate performance of 134 mAh g−1 at 6 A/g and outstanding cycle stability at a high current density of 3 A/g over 10,000 cycles. Experimental and theoretical analyses demonstrate the formation of the –N–Zn–O– structure. The abundant supramolecular channels in pseudorotaxane, induced by crown ether functional groups, are beneficial for achieving superior cyclability and rate capability. These encouraging results highlight the potential for designing more efficient PANI-based cathodes for high-performance AZIBs.

A facile route to unlock the high capacity of molecular organic cathode for aqueous zinc-ion battery

The small-molecule organic materials have become promising candidates for aqueous zinc-ion batteries (AZIBs). However, the capacity output of these molecular organic cathodes still remains far from their theoretical values. Herein, we present a facile route by integrating a small amount of porous carbon (ketjen black, KB) into phenazine (PNZ) organic cathode by a facile route, which significantly improves the specific capacity for aqueous zinc-ion storage. Specifically, the PNZ/KB based battery delivers a high specific capacity of 179 mAh g−1 at 50 mA g−1 and still remains a high-rate capacity of 81 mAh g−1 at 1000 mA g−1. Additionally, the battery demonstrates stable cycling performance, retaining 70.6% of the initial capacity after 1000 charge-discharge cycles at 500 mA g−1. The spectroscopic analyses show that the zinc-ion coordination process of PNZ/KB cathode is highly reversible. The good performance of PNZ/KB cathode is ascribed to the unique branched chain shape of KB, which can give full access to active material of PNZ and generate more conductive paths for zinc-ion. The theoretical computation demonstrates that the intermolecular coordination between zinc-ion and PNZ molecule is more stable than that through the intramolecular interaction. This work provides a facile and effective strategy to boost the high capacity of organic cathode materials for aqueous zinc-ion batteries.

Hydrated Calcium Vanadate Nanoribbons with a Stable Structure and Fast Ion Diffusion as a Cathode for Quasi-Solid-State Zinc-Ion Batteries.

We demonstrated the use of hydrated calcium vanadate (CaV6O16·3H2O, denoted as CaVO-2) as a cathode for aqueous zinc-ion batteries (AZIBs). Nanoribbons of hydrated calcium vanadate facilitated shortening of the Zn2+ transport distance and accelerated zinc-ion insertion. The introduction of interlayer structure water increased the interlayer spacing of calcium vanadate and as a "lubricant". Ca2+ insertion also expanded the interlayer spacing and further stabilized the interlayer structure of vanadium-based oxide. The density functional theory results showed that the introduction of Ca2+ and structured water could effectively improve the diffusion kinetics, resulting in the rapid transport of zinc ions. As a result, AZIBs based on the CaVO-2 cathode offered high specific capacity (329.6 mAh g-1 at 200 mA g-1) and fast charge/discharge capability (147 mAh g-1 at 10 A g-1). Impressively, quasi-solid-state zinc-ion batteries based on the CaVO-2 cathode and polyacrylamide-cellulose nanofiber hydrogel electrolytes maintained an outstanding specific capacity and long cycle life (162 mAh g-1 over 10 000 cycles at 5 A g-1). This study provided a reliable strategy for metal-ion insertion and the structural water introduction of oxides to produce a high-quality cathode for ZIBs. Meanwhile, it provides ideas for the combination of vanadium-based materials and gel electrolytes to construct solid-state zinc-ion batteries.

Facile fabrication of mesoporous Ag-doped γ-MnO2 nanowires with rich oxygen defects for boosting performance of aqueous Zn-ion batteries

In recent years, the aqueous zinc-ion batteries (AZIBs) have attracted a remarkable attention due to their low cost, abundance, low toxicity and high safety. MnO2 is considered a potential electrode for AZIBs owing to its high theoretical capacity and abundance. However, MnO2 suffers a challenging issue of poor cyclability. Herein, mesoporous Ag-doped γ-MnO2 nanowires were fabricated for the first time by a facile room temperature co-precipitation method under the assistance of Ag+ and investigated electrochemically as cathode for AZIBs. The as-obtained sample electrode delivers a remarkable discharge specific capacity of 978 mAh g-1 at the 65th cycle at a current rate of 0.1 C to be steady at 804 mAh g-1 after 150 cycles and exhibits an excellent rate capability at high C-rate due to the surface-controlled capacitive process of the electrochemical reaction, which is attributed to the unique structure of Ag-doped γ-MnO2 nanowires with rich oxygen defects and crystal water for more active sites and stable structure. This work offers aspiration for the future cathode material engineering as AZIBs.

The Construction of Nanoflower‐like MoO2@C Composites via Crystal Engineering for Ultrastable Aqueous Zinc‐Ion Batteries

Aqueous zinc‐ion batteries (AZIBs) offer advantages such as low cost, high safety, and environmental friendliness. However, the crystal structure design of cathode materials such as molybdenum oxide is of vital importance for AZIBs. Herein, a novel nanoflower‐structured molybdenum dioxide (MoO2@C) is synthesized by using MnMoO4 nanoflower‐like precursor. The presence of manganese and reduction process play a crucial role in the formation of nanoflower structure, which enhances the electrochemical performance when it is used as cathode for AZIBs. As a result, the MoO2@C cathode exhibits high initial coulombic efficiency, excellent cycling stability, and outstanding rate capability. Moreover, in situ/ex situ analysis (ex situ X‐Ray diffraction/in situ Raman spectroscopy) is used to reveal Zn‐ion storage mechanism of reversible intercalation and ultrastable structural framework.

Co-insertion of K+ and Ca2+ in vanadium oxide as high-performance aqueous zinc-ion battery cathode material

Inserting metal ions into vanadium oxides can effectively improve their electrochemical properties, and the insertion of different single metal ions into vanadium-based compounds can enhance their electrochemical performance in different ways. Moreover, the insertion of multiple metal ions into vanadium-based compounds may provide a synergistic effect. Therefore, in this work a K0.02Ca0.18V2O5·0.7H2O (KCaVOH) cathode material was obtained by co-inserting the monovalent metal ion K+ and the divalent metal ion Ca2+ into vanadium oxide through a one-step hydrothermal method. The insertion of K+ enhances the structural stability of the cathode material, while the insertion of Ca2+ increases the layer spacing between the V-O layers and improves the specific capacity of the cathode material. The co-insertion of K+ and Ca2+ effectively enhances the electrochemical performance of V2O5·1.6H2O, and the KCaVOH cathode provides a high specific capacity of 410 mAh·g−1 at 0.3 A·g−1. Moreover, the capacity still reaches 265 mAh·g−1 after 1800 cycles at 5 A·g−1. This method provides a strategy for significantly enhancing the electrochemical performance of vanadium-based cathode materials.

Enhancing the electrochemical activation kinetics of V2O3 for high-performance aqueous zinc-ion battery cathode materials

The discharge capacity and lifespan of zinc ion batteries currently remain impractical due to limitations in the cathode. Low-valence vanadium oxides are promising cathode material precursors that can be electrochemically converted into highly active hydrated amorphous oxides. However, the activation process itself suffers from structural instability or high local strain, due to the low electronic conductivity and the limited ion diffusion kinetics. To tackle this issue, herein, we synthesize porous carbon-coated nitrogen-doped V2O3 (p-NVO@C) microparticles utilizing a nitrogen-containing vanadium-based metal–organic framework (MOF) as the precursor. The uniform N doping and carbon coating improve the electronic conductivity of the active material particles. The carbon coating also traps the active material to reduce its dissolution loss; the high porosity of the p-NVO@C alleviates the stress from Zn2+-intercalation-induced expansion and shortens the ion transport paths. Moreover, first-principles calculations indicate that the doped N atoms in vanadium oxides generate a locally enhanced electric field, which accelerates the diffusion of Zn2+. Given the above advantages, the p-NVO@C particles demonstrate an outstanding specific capacity of 501 mAh/g at a current density of 0.2 A/g and a remarkable rate performance after the initial activation. The capacity retention rate remains as high as 95.7 % after 2000 cycles at a current density of 10 A/g. Ex-situ characterizations confirm the robust structural stability during phase transition cycles. This work provides an excellent solution to developing cathode materials for high-performance aqueous zinc ion batteries.

Vanadium-based compound with large lattice spacing as stable cathode for aqueous zinc-ion battery

Vanadium oxide (VO) cathode with large theoretical capacity has attracted much attention for aqueous zinc-ion batteries (ZIBs). However, VO cathode suffers from poor zinc-ion (Zn2+) diffusion kinetics, hindering the development of ZIBs for practical application. Herein, large lattice spacing vanadium-based compound (L-VO) was designed by the pillar between the V-O layers, in which the lattice spacing has increased from 1.15 nm (VO) to 1.64 nm (L-VO). Owing to the large lattice spacing, the L-VO cathode shows rapid Zn2+ diffusion kinetics, delivering high capacity of 399 mAh/g and stable cycle performance (retention rate of 95 % after 2000 cycles).

Fabricating composites of multicomponent active substances embedded in carbon matrix for enhancing structural stability and redox kinetics of cathode in aqueous zinc-ion batteries

Rechargeable aqueous zinc-ion batteries (ZIBs) are recognized as a potential candidate for large-scale energy storage due to its high-security and low-expense aspects. However, the poor structural stability and sluggish redox kinetics of cathode material lead to the serious capacity fading and bad rate performances, which hinders its practical applications. Herein, a novel one-step pyrolysis strategy is conducted for fabricating the composites of multicomponent active substances (including WO3, Bi and Bi2O3) embedded in amorphous N-doped carbon matrix (BWO@C) using polydopamine-coated Bi2WO6 micro-flowers as the precursors. The amorphous nitrogen-doped carbon endows BWO@C composite to possess more active-sites and higher electrical conductivity for rapid electrons/ions transport, and meanwhile the active substances could be effectively utilized even undergoing thousands of charge/discharge cycles. Therefore, the resulting BWO@C as cathode for aqueous ZIBs exhibits satisfying rate performances as well as outstanding cycling stability. This work provides a simple and efficient pathway for designing the cathode materials with high conductivity and high structural stability to achieve remarkable performances and long life-span of aqueous ZIBs.

Inducing Mn defects within MnTiO3 cathode for aqueous zinc-ion batteries

Layered manganese-based cathode materials are considered as one of the promising cathodes benefit from inherent low manufacturing cost, non-toxic and high safety in aqueous zinc-ion batteries (AZIBs). However, the sluggish reaction kinetics within layered cathodes is inevitable due to the poor electrical/ionic conductivity. Herein, MnTiO3 is reported as a new cathode material for AZIBs and in-situ induced Mn-defect within MnTiO3 during the first charging is desirable to improve the reaction kinetics to a great extent. Additionally, DFT calculations further demonstrate that MnTiO3 with manganese defects exhibits a uniform charge distribution at the defect sites, enhancing the attraction towards H+ and Zn2+ ions. Furthermore, it performs good cycling stability which can obtain 115 mA h g−1 even at 400 mA g−1 after 450 cycles and the discharge capacity reaches up to 233.8 mAh/g at 100 mA g−1 when Mn-defect MnTiO3 was employed as the cathode. This research could provide a new method for the development and mechanism research of cathode materials for AZIBs.

Self-supporting oxygen vacancy-rich α-MnO2 nanowire/few-layer graphite/SWNT bundle composite film for high-performance flexible aqueous zinc-ion battery cathode

The increasing demand for flexible and wearable electronic devices has led to widespread interest in flexible electrochemical energy storage devices. However, the transformation of the battery structure from conventional to flexible presents a great challenge to the battery design. Herein, we developed a facile method for the preparation of a self-supporting composite film consisting of oxygen-vacancy rich MnO2 nanowires (NWs), few-layer graphite nanosheets (FLGs), and single-walled carbon nanotube (SWNT) bundles as the cathode of flexible zinc-ion batteries. This ternary interwoven interconnection 3D structure enhances the electrochemical performance of the battery and realizes fast charge transfer; oxygen vacancies in the MnO2 NWs caused by heat treatment (300 °C in Ar) allow for rapid intercalation and diffusion of Zn2+. The interwoven FLGs and SWNT bundles improve the electrical conductivity, and the robust interactions between the two carbon nanomaterials and the MnO2 NWs effectively make the composite film with excellent mechanical properties. This self-supporting flexible electrode exhibits a high specific capacity of 374 mAh/g at 0.4 A/g, maintains a Coulombic efficiency of ∼ 100 % after 1600 cycles at 2 A/g, and has a high energy density of 651.5 Wh kg−1 at 65.2 W kg−1. Moreover, the flexible zinc ion batteries assembled with the electrode demonstrate good mechanical properties and a high reversible specific capacity of 343 mAh/g after 75 bending cycles. Based on these findings, we believe that this composite film holds great promise as a cathode material in flexible energy storage applications.

Hollow VO2 microspheres anchored on graphene as advanced cathodes for aqueous zinc-ion batteries

Vanadium dioxide-based materials have been proved to be promising cathodes for aqueous zinc ion batteries (AZIBs) due to their cost-effectiveness and high theoretical specific capacity; nevertheless, the low electronic conductivity and poor cycle stability restrict their application. Herein, hollow VO2 microspheres anchored on graphene oxide (H-VO2@GO) are synthesized via a facile simple hydrothermal reaction as high-performance cathodes for AZIBs. The hollow micromorphology of the material provides a large specific surface area and effectively alleviates the volume changes during cycling, while the anchoring of VO2 on graphene oxide greatly improves the electronic conductivity and inhibits the agglomeration and pulverization of the material. Resulting from the combination of unique micromorphology and graphene oxide anchoring, the as-prepared H-VO2@GO exhibits the impressive specific capacity of 400.1 mAh/g at 0.5 A/g and excellent cycling performance with 96.1 % of capacity retention after 1500 cycles at 10 A/g. This investigation provides a use reference for designing high-performance cathodes materials for AZIBs by optimizing the microstructure of electrode materials.

Defect engineering and morphology adjustment assist NH4V4O10 to be a high-performance aqueous zinc ion battery cathode

The ultrathin size of SNVO with oxygen vacancies and more active sites improved the diffusion ability of Zn2+ ions. SNVO exhibits excellent cycle stability, retaining 94.6% of its capacity after 1000 cycles at 10 A g−1.