Zinc Dendrites Research Articles

Mullite Mineral-Derived Robust Solid Electrolyte Enables Polyiodide Shuttle-Free Zinc-Iodine Batteries.

Zinc dendrite, active iodine dissolution, and polyiodide shuttle caused by the strong interaction between liquid electrolyte and solid electrode are the chief culprits for the capacity attenuation of aqueous zinc-iodine batteries (ZIBs). Herein, mullite is adopted as raw material to prepare Zn-based solid-state electrolyte (Zn-ML) for ZIBs through zinc ion exchange strategy. Owing to the merits of low electronic conductivity, low zinc diffusion energy barrier, and strong polyiodide adsorption capability, Zn-ML electrolyte can effectively isolate the redox reactions of zinc anode and AC@I2 cathode, guide the reversible zinc deposition behavior, and inhibit the active iodine dissolution as well as polyiodide shuttle during cycling process. As expected, wide operating voltage window of 2.7V (vs Zn2+/Zn), high Zn2+ transference number of 0.51, and low activation energy barrier of 29.7kJ mol-1 can be achieved for the solid-state Zn//Zn cells. Meanwhile, high reversible capacity of 127.4 and 107.6 mAh g-1 can be maintained at 0.5 and 1 A g-1 after 3000 and 2100 cycles for the solid-state Zn//AC@I2 batteries, corresponding to high-capacity retention ratio of 85.2% and 80.7%, respectively. This study will inspire the development of mineral-derived solid electrolyte, and facilitate its application in Zn-based secondary batteries.

Construction of an n-Type Fluorinated ZnO Interfacial Phase for a Stable Anode of Aqueous Zinc-Ion Batteries.

Aqueous rechargeable zinc-ion batteries have become an ideal solution for the next generation of energy storage systems due to their low cost and high safety. However, the uncontrollable zinc dendrites and harmful side reactions of metal zinc anodes hinder the further development of aqueous zinc-ion batteries. In this work, the artificial fluoride zinc oxide (F-ZnO) interface phase is integrated in situ on the surface of zinc foil. The F-ZnO interface phase significantly inhibits the side reactions on the surface of the zinc electrode by reducing the direct contact between the electrolyte and the surface of the zinc foil. In addition, F-ZnO modified by a small amount of F doping shows enhanced conductivity and electron transport capacity, avoiding the accumulation of high concentration Zn2+ on the anode surface, and ultimately promoting the efficient nucleation and orderly deposition of a zinc anode. The cycle life of the symmetrical cell based on F-ZnO is as high as 2600 cycles at an area current density of 4 mA cm-2, which is much better than that of a commercial pure Zn electrode. The modified F-ZnO@Zn anode truly achieves the purpose of prolonging the anode's life.

Improving Zn2+ migration via designing multiple zincophilic polymer electrolyte for advanced aqueous zinc ion batteries

Aqueous zinc ion batteries (AZIBs)-based on Zn metal anode face serious issues of hydrogen evolution, corrosion, and zinc dendrite growth, limiting their practical applications. Polymer-based electrolytes can effectively inhibit the above issue, but usually bring additional interfacial resistance, resulting in slow reaction kinetics. Herein, we report a poly(4-acryloylmorpholine) electrolyte with multiple zincophilic primitives for fast zinc ion transport at bulk and interface of Zn metal anode (zinc ion transfer number of 0.77) via a facile one-pot polymerization. The special electrolyte structure with multiple zincophilic primitives can adhere tightly to the Zn metal anode and induce uniform Zn deposition, resulting in low interface resistance and enhanced cycling life of batteries. Therefore, the symmetric Zn||Zn batteries assembled based on the designed and synthesized polymer electrolyte can be stably cycled for 1400 with low overpotential (∼220 mV) at 0.5 mA cm−2 with a capacity of 0.5 mAh cm−2, and the corresponding V2O5||Zn full batteries exhibit attractive reversibility, rate performance, and cycling stability. The electrolyte engineering in this work paves a new path for the construction of polymer-based electrolytes for safe and stable AZIBs.

Construction of an anti-anionic-depletion layer to mitigate the tip deposition effect for dendrite-free zinc anode

Rechargeable aqueous zinc-ion batteries have been plagued by the well-known problem of zinc dendrite formation. This issue mainly arises from the inherent depletion of anions in the vicinity of the zinc anode during deposition process, leading to a strong spatial electric field that influences Zn2+ cations deposition and triggers dendrite growth. Herein, the anti-anionic-depletion strategy is proposed that involves anions anchored in the surface region of zinc anode to mitigate the adverse effects of the spatial electric field and inhibit dendrite growth. By theoretical calculations and experimental verification, layered double hydroxides (LDHs) materials were selected to immobilize SO42- anions and construct a protective coating layer against anion depletion (anti-anionic-depletion layer). Furthermore, the deposition flux of Zn2+ cations was also regulated by in-situ growing LDH nanosheets. Benefiting from these modifications, the in-situ grown ZnAl-LDH modified electrode (Zn@ZnAl) exhibits outstanding stability (5500 cycles at 40 mA cm−2), and shows negligible capacity degradation in both Zn-Mn full cells and zinc hybrid capacitors.

Hydrous Molybdenum Oxide Coating of Zinc Metal Anode via the Facile Electrodeposition Strategy and Its Performance Improvement Mechanisms for Aqueous Zinc-Ion Batteries.

Aqueous zinc-ion batteries (ZIBs) are widely recognized as highly promising energy storage devices because of their inherent characteristics, including superior safety, affordability, eco-friendliness, and various other benefits. However, the significant corrosion of the zinc metal anode, side reactions occurring between the anode and electrolyte, and the formation of zinc dendrites significantly hinder the practical utilization of ZIBs. Herein, we utilized an electrodeposition method to apply a unique hydrous molybdenum oxide (HMoOx) layer onto the surface of the zinc metal anode, aiming to mitigate its corrosion and side reactions during the process of zinc deposition and stripping. In addition, the HMoOx layer not only improved the hydrophilicity of the zinc anode, but also adjusted the migration of Zn2+, thus facilitating the uniform deposition of Zn2+ to reduce dendrite formation. A symmetrical cell with the HMoOx-Zn anode displayed reduced-voltage hysteresis (80 mV at 2.5 mA/cm2) and outstanding cycle stability after 3000 cycles, surpassing the performance of the uncoated Zn anode. Moreover, the HMoOx-Zn anode coupled with a γ-MnO2 cathode created a considerably more stable rechargeable full battery compared to the bare Zn anode. The HMoOx-Zn||γ-MnO2 full cell also displayed excellent cycling stability with a charge/discharge-specific capacity of 129/133 mAh g-1 after 300 cycles. In summary, this research offers a straightforward and advantageous approach that can significantly contribute to the future advancements in rechargeable ZIBs.

Functional cellulose interfacial layer on zinc metal for enhanced reversibility in aqueous zinc ion batteries

Aqueous zinc ion batteries have emerged as promising energy storage devices due to their high safety, cost-effectiveness, and environmental friendliness. However, the practical implementation of zinc ion batteries faces significant challenges associated with the poor surface stability of Zn metal anode, including dendrite growth, side reactions, and poor cycling stability. Herein, an eco-friendly cellulose layer is applied to the Zn metal anode by a scalable coating method for Zn/electrolyte interfacial engineering. The cellulose coating has multiple functions: physical passivation, reducing the resistive native oxide, enhancing wettability between the Zn metal and electrolyte, and facilitating the insertion and extraction of zinc ions during charge–discharge cycles at both room temperature and low temperature (−10 ℃). The cellulose-coated Zn metal anode (ZCL) also inhibits the formation of zinc dendrites, thereby reducing the risk of short circuits and capacity loss. As a result, the ZCL||ZCL symmetric cell achieved 1000 electrochemical cycles at 2 mA cm−2, which is more than eight times longer compared to that of a bare Zn symmetric cell. The electrochemical performance of the ZCL||MnO2 full cell was also found to be superior to that using the bare Zn anode electrode.

Energetic aqueous zinc-sulfur battery achieved via co-solvent and redox mediator synergistic regulation

Aqueous Zn–S batteries (AZSBs) have received significant attention due to the outstanding energy density, low cost, and high safety. However, the slow kinetics and poor reversibility of the sulfur conversion reaction, coupled with the formation of dendrites in zinc anode and hydrogen evolution reaction (HER), hinder the practical applications of AZSBs. In this paper, we developed a novel co-solvent electrolyte that utilizes N-methylpyridine (NMP) and KI as additives to regulate the cathode reversibility and anode stability synergistically. Firstly, the electrophilic group of NMP (–CO–NR2-) effectively activates the oxidation of I− to form I3−. The resulting I3−/I− redox mediator participates in the sulfur conversion reaction and lowers its energy barrier, thus enhancing the reaction kinetics of ZnS ↔ S and inhibiting the formation of irreversible by-products. Secondly, NMP alters the solvation structure of Zn(H2O)62+, achieving uniform deposition of Zn2+ and inhibiting the growth of zinc dendrites. Thirdly, NMP forms a dense solid-electrolyte-interphase layer between the zinc metal and H2O during cycling, inhibiting HER. Under the synergistic effect from solvent and redox mediator, AZSBs exhibit an impressive capacity of 775 mAh g−1 at 5 A g−1 (10 C) with 77.5 % capacity retention after 300 cycles.

A functional MXene/cellulose nanofibers separator for high-performance dendrite-free zinc anode under harsh conditions

Aqueous zinc-ion batteries (AZIBs) show great potential for mass energy storage because of their intrinsic plentifulness and security. Nevertheless, the development of zinc dendrites is still a major challenge for the practical industrialisation of AZIB, especially under the demanding conditions of elevated current density and high temperatures. To combat this situation, we developed an ultrathin separator composed of cellulose nanofibers and MXene (noted as CM-15 separator) with a thickness of only 27 μm. The strong zincophilic characteristics and outstanding electrical/thermal conductivity of MXene make them suitable for use as an ion pump to expedite the transmission of Zn2+ through the electrolyte, which significantly increases the zinc ion transfer number and results in the deposition of homogeneous Zn nuclei and dendritic-free Zn. As a result, the symmetric battery equipped with a CM-15 separator enabled excellent dendrite free plating/stripping behavior, high coulomb efficiency (97.7 %) and cumulative plated capacity of 4.8 Ah/cm2 at 80 mA/cm2 at room temperature and as well as sustained operation for at least 300 h under 60 °C. More impressively, the Zn-MnO2/CNT battery equipped with a CM-15 separator achieved 72.6 % capacity retention after 10,000 cycles at 2 A/g under room temperature and 92.1 % capacity retention after 200 cycles at 1 A/g under 60 °C. Our research confirms the potential of functional separators to promote the application of AZIBs, especially under demanding conditions.

In situ preparation of MOF-74 for compact zincophilic surfaces enhancing the stability of aqueous zinc-ion battery anodes

Zinc-ion batteries (ZIBs), while celebrated for their environmental friendliness, abundant material availability, and inherent safety, face significant challenges that curtail their performance and lifecycle. These challenges include the formation of zinc dendrites, susceptibility to electrolyte corrosion, and the propensity for hydrogen evolution reactions. Addressing these critical issues, our research introduces an innovative surface modification strategy for zinc anode of ZIB with mild electrolyte, by the in-situ synthesis of Metal-Organic Framework (MOF-74) facilitated by the mild acidity of a 2,5-dihydroxyterephthalic acid (DHTA) methanol solution. The zincophilic sites and pore structure introduced by MOF-74 to substantially enhance the surface properties of zinc anodes and accelerate the solvation process, enabling uniform zinc deposition, inhibiting dendrite growth, and significantly bolstering corrosion resistance and electrochemical stability. Combination of physical and electrochemical characterization techniques are employed to validate the successful implementation of MOF-74 on the zinc anode surface and its resultant benefits. When tested in full cell setups with α-MnO2 as the cathode, the MOF-74 modified zinc anodes displayed exceptional cyclic stability and rate performance, surpassing those of unmodified counterparts. This investigation highlights the potential of MOF materials to address the electrochemical challenges facing zinc anodes, offering a straightforward yet efficacious strategy to enhance the performance and longevity of ZIBs.

Acetamide-based deep eutectic solvents as efficient electrolytes for K–MnHCFe//Zn dual-ion batteries

In this study, a cost-effective, eco-friendly deep eutectic solvent (DES), comprising acetamide, sodium perchlorate, and zinc chloride serves as an innovative electrolyte for dual ion batteries. Notably, the DES exhibits a broad electrochemical stability window, self-extinguishing behavior, and great resilience in low temperatures. The interplay between the electrolyte components is being thoroughly scrutinized, with a particular focus on the benefits of adding a co-solvent to the DES. This addition prevents unwanted reactions and zinc dendrite growth through the formation of a solid electrolyte interphase (SEI) layer, ultimately leading to enhanced coulombic efficiency and cyclic stability. The electrochemical performance of zinc ion batteries (ZIBs) using a Prussian blue analog (K–MnHCFe) as cathode is being examined in the dual-ion DES electrolyte. The device displays a discharge capacity of 76.4 mAh g−1 at 0.3 A g−1 and a maximum energy density of 111.7 Wh kg−1 at a power density of 437.5 W kg−1. Furthermore, it retains 65 % of its initial specific capacity even after 3000 cycles at 0.5 A g−1. It is noteworthy that the ZIB device with dual-ion DES operates normally in temperatures as low as −20 °C, outperforming traditional cells with aqueous electrolytes.

High-performance zinc-ion hydrogel electrolytes based on molecular-level hybridization of PVA with polymer quantum dots

Aqueous zinc ion batteries have received widespread attention. However, the growth of zinc dendrites and hydrogen evolution reaction generation seriously hinder the practical application of zinc ion batteries. Herein, it is reported that a multifunctional dendrites-free low-temperature PVA-based gel electrolyte by introducing negatively charged polymer carbon quantum dots (QDs) and the organic antifreeze dimethyl sulfoxide (DMSO) into it. The QDs carrying a large number of functional groups on the surface can effectively adsorb Zn2+, eliminating the “tip effect”, and inducing the uniform deposition of Zn2+ and the formation of a dendrites-free structure. Meanwhile, the solvation structure of adsorbed Zn2+ can be controlled by charged groups to reduce the generation of side reactions, thus obtaining high-performance zinc ion batteries. The Zn/polyaniline (PANi) full battery can be stably cycled more than 1000 times at –20 °C, and the design of this gel electrolyte can provide good feasibility for safe, stable, and flexible energy storage devices.

Dynamic Covalent Bonds Regulate Zinc Plating/Stripping Behaviors for High-Performance Zinc Ion Batteries.

Artificial interfaces provide a comprehensive approach to controlling zinc dendrite and surface corrosion in zinc-based aqueous batteries (ZABs). However, due to consistent volume changes during zinc plating/stripping, traditional interfacial layers cannot consistently adapt to the dendrite surface, resulting in uncontrolled dendrite growth and hydrogen evolution. Herein, dynamic covalent bonds exhibit the Janus effect towards zinc deposition at different current densities, presenting a holistic strategy for stabilizing zinc anode. The PBSC intelligent artificial interface consisting of dynamic B-O covalent bonds is developed on zinc anode to mitigate hydrogen evolution and restrict dendrite expansion. Owing to the reversible dynamic bonds, PBSC exhibits shape self-adaptive characteristics at low current rates, which rearranges the network to accommodate volume changes during zinc plating/stripping, resisting hydrogen evolution. Moreover, the rapid association of B-O dynamic bonds enhances mechanical strength at dendrite tips, presenting a shear-thickening effect and suppressing further dendrite growth at high current rates. Therefore, the assembled symmetrical battery with PBSC maintains a stable cycle of 4500 hours without significant performance degradation and the PBSC@Zn||V2O5 pouch cell demonstrates a specific capacity exceeding 170 mAh g-1. Overall, the intelligent interface with dynamic covalent bonds provides innovative approaches for zinc anode interfacial engineering and enhances cycling performance.

Dynamic Covalent Bonds Regulate Zinc Plating/Stripping Behaviors for High‐Performance Zinc Ion Batteries

AbstractArtificial interfaces provide a comprehensive approach to controlling zinc dendrite and surface corrosion in zinc‐based aqueous batteries (ZABs). However, due to consistent volume changes during zinc plating/stripping, traditional interfacial layers cannot consistently adapt to the dendrite surface, resulting in uncontrolled dendrite growth and hydrogen evolution. Herein, dynamic covalent bonds exhibit the Janus effect towards zinc deposition at different current densities, presenting a holistic strategy for stabilizing zinc anode. The PBSC intelligent artificial interface consisting of dynamic B−O covalent bonds is developed on zinc anode to mitigate hydrogen evolution and restrict dendrite expansion. Owing to the reversible dynamic bonds, PBSC exhibits shape self‐adaptive characteristics at low current rates, which rearranges the network to accommodate volume changes during zinc plating/stripping, resisting hydrogen evolution. Moreover, the rapid association of B−O dynamic bonds enhances mechanical strength at dendrite tips, presenting a shear‐thickening effect and suppressing further dendrite growth at high current rates. Therefore, the assembled symmetrical battery with PBSC maintains a stable cycle of 4500 hours without significant performance degradation and the PBSC@Zn||V2O5 pouch cell demonstrates a specific capacity exceeding 170 mAh g−1. Overall, the intelligent interface with dynamic covalent bonds provides innovative approaches for zinc anode interfacial engineering and enhances cycling performance.

3D MXene/PVA Aerogel Enabling a Dendrite-Free Zn Metal Anode.

Aqueous zinc-ion batteries have attracted widespread attention due to their low cost and high safety. Unfortunately, their commercial applications are greatly inhibited by the negative effects of zinc dendrites and side reactions. A solution that utilizes a 3D host can help mitigate these issues. In this paper, we present a 3D host that is composed of an aerogel scaffold with a poly(vinyl alcohol) and MXene structure. The embedded Zn can be densely packed inside the host due to its zincophilic properties. During cycling, the fluorine-based functional groups on the surface of MXene were able to react with the electrolyte to form the ZnF2 solid electrolyte interphase, which can effectively protect the composite anode. As a result, the symmetrical battery was capable of stable cycling for >300 h at a high current density of 10 mA cm-2. More impressively, the assembled full cell retained 93.86% after 800 cycles at a current density of 5 A g-1. This work provides an effective idea for improving the cycling performance of aqueous zinc-ion batteries.

Quantifying Asymmetric Zinc Deposition: A Guide Factor for Designing Durable Zinc Anodes.

Zinc metal is recognized as the most promising anode for aqueous energy storage but suffers from severe dendrite growth and poor reversibility. However, the coulombic efficiency lacks specificity for zinc dendrite growth, particularly in Zn||Zn symmetric cells. Herein, a novel indicator (fD) based on the characteristic crystallization peaks is proposed to evaluate the growth and distribution of zinc dendrites. As a proof of concept, triethylenetetramine (TETA) is adopted as an electrolyte additive to manipulate the zinc flux for uniform deposition, with a corroborating low fD value. A highly durable zinc symmetric cell is achieved, lasting over 2500h at 10mAcm-2 and 400h at a large discharge of depth (10mAcm-2, 10mAhcm-2). Supported by the low fD value, the Zn||TETA-ZnSO4||MnO2 batteries overcome the sudden short circuit and fast capacity fading. The study provides a feasible method to evaluate zinc dendrites and sheds light on the design of highly reversible zinc anodes.

Improving Aqueous Zinc Ion Batteries with Alkali Metal Ions.

Aqueous zinc (Zn) ion batteries have received broad attention recently. However, their practical application is limited by severe Zn dendrite growth and the hydrogen evolution reaction. In this study, three alkali metal ions (Li+, Na+, and K+) are added in ZnSO4 electrolytes, which are subjected to electrochemical measurements and molecular dynamics simulations. The studies show that since K+ has the highest mobility and self-diffusion coefficient among the four ions (Li+, Na+, K+, and Zn2+), it enables K+ to preferentially approach a zinc dendrite at an earlier time, driven by a negative electric field during a cathodic process. The electric double layer, with K+ around the negatively charged Zn dendrite, inhibits dendrite growth and mitigates the hydrogen evolution reaction on the Zn anode. Under this kinetic effect, the Zn-Zn symmetric cell with K+ exhibits a long cycling stability of 1000 h at 1 mA·cm-2 of 1 mAh·cm-2 and 190 h at 30 mA·cm-2 of 2 mAh·cm-2. Such a kinetic effect is also observed with additives Na+ and Li+, though less profound than that of K+.

Pre-Corrosion of Zinc Metal Anodes for Enhanced Stability and Kinetics.

Non-uniform zinc plating/stripping in aqueous zinc-ion batteries (ZIBs) often leads to dendrites formation and low Coulombic efficiency (CE), limiting their large-scale application. In this study, a pre-corroded Zn (PC-Zn) anode with 3D ridge-like structure is constructed by a facile solution etching in sodium hypophosphite (NaH2PO2) solution. The surface preparation process can significantly remove impurities from the passivation layer of bare Zn anode, thus exposing a great quantity of active sites for easy plating/stripping. Moreover, the pre-corroded structure enables a uniform-distributed electric field to promote the 3D Zn2+ diffusion process and accelerate the transfer kinetics, thereby suppressing the zinc dendrites and interfacial side reactions. Consequently, symmetric cells with PC-Zn electrodes demonstrate remarkable stability, maintaining cycles for over 3200h under 1mA cm-2. The PC-Zn/VO2 full cell maintains a specific capacity of 361 mAh g-1 at 0.1 A g-1, and a capacity retention rate of ≈80% over 1000 cycles at 4 A g-1. Notably, no obvious dendrites and side reactions are detected after extended cycling. Leveraging the cost-effectiveness, environmentally friendly nature, and easy fabrication of the PC-Zn electrode, this Zn protection strategy holds promise for advancing the industrial application of ZIBs.

Unlocking zinc storage in silver vanadate structures for high-performance aqueous zinc batteries

Zinc-ion batteries (ZIBs) are being increasingly recognized as promising candidates for large-scale energy-storage systems owing to their stability in air, abundance of elemental zinc, low cost, and ease of handling. Although various cathode materials have been explored for ZIBs, silver vanadate stands out for its highly stable structure. However, the presence of silver in silver vanadate may hinder its electrochemical performance, necessitating activation over several cycles. In this study, we introduce an ion-exchange reaction to directly activate silver vanadate. The resulting ion-exchanged zinc vanadate demonstrates superior performance compared with silver vanadate, showcasing stable cycling behavior and high-rate capability. Remarkably, it maintains a capacity retention of 71 % even after 400 cycles. Analysis of the zinc intercalation mechanism reveals a combination of capacitive and diffusion-based processes contributing to energy storage in ZIBs. Post-cycling examinations reveal the presence of dendritic zinc anodes and confirm the stability and safety of the framework, with no silver migration to the anode side. These findings highlight the potential of ZIBs as next-generation energy-storage solutions and underscore the need for continued research in optimizing electrode materials and electrolytes for practical applications.

2D Tungsten Borides Induced Interfacial Modulation Engineering Toward High-Rate Performance Zinc-Iodine Battery.

Aqueous zinc-iodine batteries are promising candidates for large-scale energy storage due to their high energy density and low cost. However, their development is hindered by several drawbacks, including zinc dendrites, anode corrosion, and the shuttle of polyiodides. Here, the design of 2D-shaped tungsten boride nanosheets with abundant borophene subunits-based active sites is reported to guide the (002) plane-dominated deposition of zinc while suppressing side reactions, which facilitates interfacial nucleation and uniform growth of zinc. Meanwhile, the interfacial d-band orbits of tungsten sites can further enhance the anchoring of polyiodides on the surface, to promote the electrocatalytic redox conversion of iodine. The resulting tungsten boride-based I2 cathodes in zinc-iodine cells exhibit impressive cyclic stability after 5000 cycles at 50 C, which accelerates the practical applications of zinc-iodine batteries.

Tuning Vertical Electrodeposition for Dendrites-Free Zinc-Ion Batteries.

Manipulating the crystallographic orientation of zinc deposition is recognized as an effective approach to address zinc dendrites and side reactions for aqueous zinc-ion batteries (ZIBs). We introduce 2-methylimidazole (Mlz) additive in zinc sulfate (ZSO) electrolyte to achieve vertical electrodeposition with preferential orientation of the (100) and (110) crystal planes. Significantly, the zinc anode exhibited long lifespan with 1500 h endurance at 1 mA cm-2 and an excellent 400 h capability at a depth of discharge (DOD) of 34% in Zn||Zn battery configurations, while in Zn||MnO2 battery assemblies, a capacity retention of 68.8% over 800 cycles is attained. Theoretical calculation reveals that the strong interactions between Mlz and (002) plane impeding its growth, while Zn atoms exhibit lower migration energy barrier and superior mobility on (100) and (110) crystal planes guaranteed the heightened mobility of zinc atoms on the (100) and (110) crystal planes, thus ensuring their superior ZIB performance than that with only ZSO electrolyte, which offers a route for designing next-generation high energy density ZIB devices.