Zinc-nickel Single Flow Battery Research Articles

Transient Mechanism Analysis of Three-Dimensional Zinc-Nickel Single Flow Battery Based on Different Negative Electrode Structures

On the basis of the mass, momentum, charge conservation equations, in addition to coupled with the global reaction kinetic equations, a transient three-dimensional mechanistic analytical model of zinc-nickel single flow batteries (ZNBs), which comprehensively takes into account the hydrogen and oxygen evolution side reactions, the polarization distribution, as well as the structural effects of the pole lugs, is developed in this paper. After grid independence validation and experimental verification, the polarization distribution, side-reaction current density, and battery efficiency of ZNBs at high current density and multiple cycles of charging and discharging were comparatively analyzed based on this model with different anode materials of nickel sheet (NS) and porous nickel foam (NF). Subsequently, the effects of changes in negative electrode porous nickel foam thickness and porosity on battery polarization, side-reaction current density and battery efficiency were further investigated. Finally, the performance of the battery under the optimal battery state was studied. The results showed that the NF negative electrode effectively reduced the battery polarization, suppressed the battery side reactions as well as improved the battery efficiency under high current density and multiple cycles of charging and discharging, which improved the efficiency and stability of the battery.

Numerical simulation of factors in charge of dendrite growth in zinc-nickel single flow batteries

There is a potential danger of battery internal short-circuiting and shortened life span in zinc-nickel single flow batteries which is usually caused by the formation of dendritic crystals as a result of non-uniform electrodeposition. For the purpose of restraining dendrite growth and prolonging the battery service life, it is necessary to investigate the mechanism of dendrite growth that occurs on the surface of zinc anode. Here, a model for two-dimensional zinc dendrite growth is established by the phase field-lattice Boltzmann method (PF-LBM) to simulate how the morphology of zinc dendrites evolves as well as the corresponding distribution of the concentration field, potential field and flow field, and to analyze the influences of the applied voltage, electrolyte flow rate, anisotropy strength and exchange current density on dendrite growth. As the results show, higher exchange current density and applied voltage can promote dendrite growth. By choosing a suitable anisotropic strength, it is possible to change the morphology of the dendrites and decrease the formation of dendrites. Enlarging the electrolyte flow rate may make the distribution of ion concentration more uniform, which can inhibit the dendrite growth as well as affect the morphology of dendrites.

Polarization analysis and optimization of negative electrode nickel foam structure of zinc-nickel single-flow battery

The polarization of zinc‑nickel single-flow battery (ZNB) seriously affects the power density of the battery. In this paper, the polarization of ZNB is studied by establishing a three-dimensional polarization model and using the numerical simulation method. Nickel foam (NF) is used to replace conventional nickel-plated steel strip (NS) as the anode, and the polarization of the battery with nickel foam as the negative electrode is studied by the response surface method for the first time. The reliability of the numerical model is proved by experimental comparison, and the effectiveness of the response surface method is also proved by analysis of variance. In this paper, the influence of multiple parameters (thickness of nickel foam, porosity, and flow rate of inlet electrolyte) on the negative polarization degree of the battery is discussed. The coupling function of the negative polarization to each parameter is fitted, and the optimal structure is given. The results show that the optimal nickel foam structure is compared with the traditional nickel-plated steel strip structure, negative activation polarization overpotential and concentration polarization overpotential decrease by 90.28 % and 88.12 % respectively when a state of charge is 0.5. In addition, the negative polarization of the optimal nickel foam structure is discussed with time and space.

Joint Estimation of SOC and SOH for Single-Flow Zinc–Nickel Batteries

The single-flow zinc–nickel battery (ZNB) is a new type of flow battery with a simple structure, large-scale energy storage, and low cost, and thus has attracted much attention in the battery field recently. The state of charge (SOC) and state of health (SOH) are key indicators of the battery, and their inaccurate estimation can damage the battery. However, little has been done so far to study how to jointly estimate SOC and SOH for the ZNB. In this paper, the method of adaptive IDUKF is proposed. A second-order equivalent circuit model is applied to improve the accuracy. At the same time, the double unscented Kalman filter (DUKF), which is optimized by the improved Harris hawk optimization (IHHO) algorithm, is used to estimate the SOC and parameters online. Then, the capacity update model is introduced to simulate the change in SOH. Finally, the proposed method is applied to a 16 Ah ZNB, and the experimental results confirm the validity of the proposed method.

Study on Ion Transport Mechanism of Zinc-Nickel Single-Flow Battery with Different Porous Electrode Structures based on Lattice Boltzmann Method

Since the microstructure of porous electrode is very important to the performance of zinc-nickel single-flow battery, this paper reconstructed the microstructure of porous nickel oxide electrode by quartet structure generation set (QSGS) method. The flow mass transfer and electrochemical reaction in porous electrode were simulated by lattice Boltzmann method (LBM). The effects of different porous electrode structures (porosity, particle size and electrode thickness) on local ion concentration distribution and charging performance are studied from the perspective of seepage and mass transfer in pores. It is found that the ion concentration in the electrode presents an uneven distribution due to the randomness of the particle size and distribution of active substances. The uneven distribution of OH − concentration caused the difference of charging depth in the direction of electrode thickness, and the uneven distribution of H + concentration caused the difference of charging depth in the radial direction of particles. Under different pore structures, the decrease of porosity and particle size can increase the diffusion rates of OH − and H +, and then promote the electrochemical reaction rate, improve the charging speed of the battery, and improve the performance of the battery. The larger electrode thickness will increase the OH − diffusion resistance in the electrode, which is not conducive to the diffusion of OH − and reduce the electrochemical reaction rate, thus affecting the diffusion of H +, increasing the concentration polarization and affecting the charging efficiency of the battery. The uneven distribution of OH − concentration caused the difference of charging depth in the direction of electrode thickness, while the uneven distribution of H + concentration caused the difference of charging depth in the radial direction of particles. Under different pore structures, the decrease of porosity and particle size can increase the diffusion rate of OH − and solid phase H +, and then promote the electrochemical reaction rate and accelerate the charging speed. The larger electrode thickness increases the OH − diffusion resistance in the electrode, which is not conducive to OH − diffusion, and then affects H + diffusion and increases concentration polarization.

Study on the effect of hydrogen evolution reaction in the zinc-nickel single flow battery

Considering the conservation laws of mass, momentum, and charge, and further coupling the global reaction kinetics equation and bubble kinetics equation, a two-dimensional transient two-phase flow model of zinc-nickel single flow battery considering hydrogen evolution parasitic reaction is established, which is used to investigate the influence of bubble flow formed by hydrogen bubbles and electrolyte on the battery performance. The accuracy of the model is verified by experimental data, and then the changes of hydrogen volume fraction, hydrogen evolution reaction current density, and negative electrode main reaction current density in the battery with time and space are investigated. Based on further analyzing the influence mechanism of bubble flow on ion transfer at the negative electrode interface, the effects of electrolyte flow rate, applied current density, hydroxide ion concentration, and bubble diameter on hydrogen volume fraction and polarization loss are also studied. The results show that the extra disturbance caused by bubble flow can effectively promote the ion transfer at the negative electrode interface and reduce the concentration polarization and activation polarization loss; On the other hand, it also causes the uneven distribution of ion concentration at the negative electrode interface, which leads to the uneven distribution of current density of hydrogen evolution reaction and negative electrode main reaction at the negative electrode interface. In addition, decreasing electrolyte flow rate, increasing applied current density, increasing hydroxide ion concentration, and increasing bubble diameter can enhance the disturbance effect of bubble flow. For the zinc-nickel single flow battery, this work provides a mechanistic explanation for the influence of the two-phase flow phenomenon caused by hydrogen evolution reaction on battery performance for the first time and lays a theoretical foundation for improving battery cycle life through side reaction management.

A Robust Algorithm for State-of-Charge Estimation under Model Uncertainty and Voltage Sensor Bias

Accurate estimation of the state of charge (SOC) of zinc–nickel single-flow batteries (ZNBs) is an important problem in battery management systems (BMSs). A nonideal electromagnetic environment will usually cause the measured signal to contain nonnegligible noise and bias. At the same time, due to the influence of battery ageing, environmental temperature changes, and a complex reaction mechanism, it is difficult to establish a very accurate system model that can be applied to various complex working conditions. The unscented Kalman filter (UKF) is a widely used SOC estimation algorithm, but the UKF will reduce the estimation accuracy and divergence under the influence of inaccurate model and sensor errors. To improve the performance of the UKF, a robust desensitized unscented Kalman filter (RDUKF) is proposed to realize an accurate SOC estimation of batteries in the context of different disturbances. Then, the proposed method is applied to cases of error interference, such as Gaussian noise, voltage sensor drift, an unknown initial state, and inaccurate model parameters. The simulation and experimental results show that compared with the standard UKF algorithm, the proposed estimation algorithm can effectively suppress the influence of various errors and disturbances and achieve higher accuracy and robustness.

Structural Modification of Negative Electrode for Zinc–Nickel Single–Flow Battery Based on Polarization Analysis

In order to improve the power density of zinc-nickel single-flow battery (ZNB), the polarization distribution characteristics and influence mechanism of the battery are investigated. In this paper, polarization of the positive and negative electrodes and the overall polarization of the battery are analyzed for the first time based on the three-dimensional transient model of ZNB. The accuracy of the simulation model is verified by experiments, and then the polarization distribution in a zinc-nickel single-flow battery with nickel-plated steel strip (NS) as the negative electrode is systematically investigated. Due to the serious polarization phenomenon of NS as negative electrode, in order to reduce the polarization and improve the performance of zinc anode, porous nickel foam (NFs) is used as negative electrode. The optimized thickness and porosity of NF under different application current density and electrolyte flow rate are screened out, and the influence rules of current density and electrolyte flow rate on the optimum NF parameters are summarized. When the electrode thickness reaches a certain level, increasing the electrode thickness will lead to the increase of over-potential on the contrary.

Three-dimensional transient model of zinc-nickel single flow battery considering side reactions

Based on a comprehensive description of the conservation of momentum, mass and charge, as well as the global dynamics involving ion and proton reactions, a three-dimensional transient model for zincnickel single flow battery considering side reactions of hydrogen evolution and oxygen evolution was established. The accuracy of the model is verified by experiments. The effects of current density, electrolyte flow rate, initial ion concentration, temperature and electrode porosity on the side reactions of hydrogen evolution and oxygen evolution were investigated. The effects of side reactions on the activation polarization and concentration polarization of the battery were studied by comparing the two cases of whether side reactions were considered or not. The results show that the reaction rate of hydrogen evolution and oxygen evolution can be effectively reduced by reducing the applied current density, ambient temperature or increasing the flow rate of electrolyte. Increasing the initial concentration of hydroxyl ions inhibited the occurrence of hydrogen evolution side reaction, but also promoted the occurrence of oxygen evolution side reaction. As the porosity of the positive electrode increases, the reaction rate of the side reaction of oxygen evolution and the oxygen concentration in the positive electrode area gradually decrease. In the later stage of charging, when the shielding effect of oxygen bubbles on the positive reaction interface is not considered, compared with the case without considering the side reactions, the positive electrode activation polarization is larger when considering the side reaction.

Analysis of transient characteristics for zinc-nickel single flow battery considering side reactions

Analysis of transient characteristics for zinc-nickel single flow battery considering side reactions

Tab Design Based on the Internal Distributed Properties in a Zinc–Nickel Single-Flow Battery

The distribution of physicochemical properties inside the battery, which is difficult to measure using experimental methods, has a significant impact on the performance of the battery. Therefore, based on the numerical simulation method, this paper established a three-dimensional transient model of a zinc–nickel single-flow battery considering the tabs for the first time. The model is based on universal conservation laws (mass, momentum, and charge) coupled with global reaction dynamics. On this basis, the influence of tabs on the physicochemical property distribution in the battery was studied, including the change of ion concentration, current density, overpotential, and local state of charge distribution with time and space. Based on overpotential distribution and ion concentration distribution, the effects of tab size, position, and number on voltage loss and ion concentration distribution were investigated. The results show that the extreme values of various physicochemical properties always appear in the region near the tabs, and the chemical reaction rate in the region near the positive electrode tab decreases significantly in the later period of discharge. The voltage loss of the positive electrode is greater than that of the negative electrode during discharge, especially in the later period of discharge. Also, at the end of discharge, the maximum value of the local charge state of the negative electrode appears in the region near the positive electrode tab. In addition, increasing the length and number of tabs can effectively reduce the voltage loss and improve the uneven distribution of ion concentration; however, when the number of tabs is larger than two sets, this effect is obviously weakened. However, changing the position and width of the tab has little effect on voltage loss and ion concentration distribution.

Simulation of dendritic growth of a zinc anode in a zinc–nickel single flow battery using the phase field-lattice Boltzmann method

The mechanism of zinc dendrite formation was explored to obtain high-safety zinc nickel single liquid batteries.

Study on electrolyte supply strategy for energy storage system of multi zinc nickel single flow battery stack loaded with single pump

Zinc nickel single flow battery (ZNB) has the advantages of low cost, low toxicity and long life, which is considered as one of the ideal choices for large-scale fixed energy storage. The efficient operation of ZNB is a necessary condition for maximizing system efficiency and safe operation. In this paper, a dynamic model of ZNB of single pump loaded with multi stack considering electrochemical reaction, mass transfer and hydraulic loss is constructed. Based on the principle of minimizing charging energy and maximizing discharge energy, the effects of electrolyte flow rate and current density on potential window and morphology of zinc deposition are considered, an adaptively adjusted electrolyte flow supply scheme is proposed. By considering the effect of flow rate on zinc deposition, the optimized electrolyte supply strategy can not only improve the system efficiency, but also effectively extend the service life of ZNB.

Status and development of the zinc-nickel single flow battery

Status and development of the zinc-nickel single flow battery

Effect of Composite Additives on the Zinc Anode of Zinc-Nickel Single-Flow Batteries

Effect of Composite Additives on the Zinc Anode of Zinc-Nickel Single-Flow Batteries

Transient simulation of porous cathodes of zinc-nickel single-flow batteries based on lattice Boltzmann method

The charging of positive electrode of zinc-nickel single-flow battery involves processes of hydroxide ion transport in pores, proton diffusion in matrixes and electrochemical reaction on matrix/solution interfaces. A lattice Boltzmann model is developed to study the dynamics of charging processes of positive electrodes at the pore-scale level by considering complex structures of porous electrodes. The concentration evolutions of hydroxide ions and proton during the charging process are revealed, and effects of charging current density, porosity and thickness of the porous electrode on the dynamic processes are investigated. Simulation results show that the diffusion resistance of proton in the small-size particle is low, which is conducive to a quick charging process. Under the same operation condition, the charging rate is limited by the particle size instead of the particle position in the electrode. Increasing the charging current density can reduce the charging time, but the effect gradually weakens. The high charging current density tends to cause the excessive concentration polarization. A large electrode thickness is not conducive to the diffusion of hydroxide ions, and too small porosity may even hinder the diffusion of hydroxide ions. Both cases cause a large concentration polarization in the porous electrode.

Pore-scale simulation of internal reaction mechanism of positive electrode for zinc-nickel single-flow battery

According to the structure and working characteristics of zinc-nickel single-flow battery stack cell, this paper proposes a pore-size analysis model for internal mass transfer and chemical reaction of positive electrode to describe liquid-phase mass transfer, solid-phase mass transfer, and electrochemical reaction. The lattice Boltzmann method was used to simulate the steady-state reaction under constant current charging. The distribution of the concentration of liquid-phase reaction ions, the proton concentration of the solid phase, and the reaction current density were determined. The influence of electrolyte flow velocity and constant current charge-current density on the electrode reaction was further explored.

Simulation Modeling and Charge–Discharge Characteristics of a Zinc–Nickel Single-Flow Battery Stack

Simulation Modeling and Charge–Discharge Characteristics of a Zinc–Nickel Single-Flow Battery Stack

Joint SoC and SoH Estimation for Zinc–Nickel Single-Flow Batteries

The zinc–nickel single-flow battery is a new and special type of flow battery with a number of promising features, such as membrane free and high scalability, and thus has attracted substantial interests in recent years. However, the cyclability of alkaline zinc cells is rather poor, with sharpened capacity degradation resulted from undesirable zinc deposition formation. Yet, little has been done so far to investigate how to effectively and reliably manage this new type of battery. In this article, an open-circuit-voltage estimator based online joint estimation of both the state of charge (SoC) and the state of health (SoH) is proposed. A second-order equivalent circuit model is applied to improve the accuracy. Meanwhile, an extended Kalman filter with reduced state dimension is formulated to estimate the SoC assisted with the proposed estimator, which solves the increased complexity issue in a higher order model. An SoH indicator is then derived from capacity estimate and employed to determine the time for reconditioning maintenance, which is a key stage to update capacity and prolong service life. The method is finally applied to a bench-scale cell demonstrator, and the experimental results confirm the efficacy of the proposed method.

Real-time peak power prediction for zinc nickel single flow batteries

The Zinc Nickel single flow batteries (ZNBs) have gained increasing attention recently. Due to the high variability of the intermittent renewable energy sources, load demands, and the operating conditions, the state of charge (SoC) is not an ideal indicator to gauge the potential cycling abilities. Alternatively, the peak power is more closely related to the instantaneous power acceptance and deliverance, and its real-time estimation plays a key role in grid-based energy storage systems. However, little has been done to comprehensively examine the peak power delivery capability of Zinc Nickel single flow batteries (ZNBs). To fill this gap, the recursive least square (RLS) method is first employed to achieve online battery model identification and represent the impact of varying working conditions. The state of charge (SoC) is then estimated by the extended Kalman filter (EKF). With these preliminaries, a novel peak power prediction method is developed based on the rolling prediction horizon. Four indices are proposed to capture the characteristics of the peak power capability over length-varying prediction windows. Finally, the consequent impacts of the electrode material and applied flow rate on peak power deliverability are analysed qualitatively.