Alkaline Secondary Batteries Research Articles

Optimization of Bi2O3 Content in CuO-Bi2O3 Cathodes for Secondary Zn Alkaline Batteries Leads to Improved Capacity and Cycling

Secondary alkaline batteries pairing Zn anodes with metal oxide cathodes (MnO2, CuO, etc.) are a promising route to energy-dense, inexpensive batteries for use in grid-scale energy storage. However, the low cycle life and material stability of secondary alkaline batteries, especially when compared to competing chemistries like Li-ion batteries, must be addressed in order to further develop these technologies. In recent years, studies have shown that the addition of chemical additives like Bi2O3 to the metal oxide cathodes can significantly improve their cyclability. Further work is needed, however, to better understand the mechanism of this improvement and further optimize cathode composition and performance.In this presentation, we will present our efforts to optimize the Bi2O3 composition of a CuO-Bi2O3 cathode for use in secondary Zn-CuO alkaline batteries. Earlier reports showed that relatively large quantities of Bi2O3 additive (10 wt.%) allowed for improved cathode conductivity and promoted the electroreduction of CuOx to Cu0. However, the use of such large quantities of a heavy additive also reduced the effective capacity of the resulting cathode by up to 15%, relative to a CuO cathode without any Bi2O3. Here, we show that the use of as little as 1 wt.% Bi2O3 is sufficient to affect a similar improvement in CuO cycling performance, and that even a Bi2O3-saturated KOH electrolyte solution is sufficient to impact the cyclability of a CuO cathode. Using a variety of physical and (electro)chemical techniques, we show that at these low Bi concentrations the Bi likely cycles between a sparingly soluble BiOx/Bi(OH)4 2- reservoir contained in both the cathode and electrolyte in the charged state, and solid Bi0 that is uniformly distributed on the surface of the CuOx/Cu0 cathode in the discharged state. Various electron microscopy techniques (SEM and STEM) show that this has a notable impact on the physical morphology of the active material in the cathodes after cycling, while electrochemical impedance spectroscopy (EIS) shows how electron transfer resistance varies based on Bi2O3 concentration. On a fundamental level, our results show that changes in Bi2O3 concentration notably impact the charge-discharge behavior of the CuO cathodes and results in the suppression of metal hydroxide-related redox peaks on charge. The absence of these peaks is thus correlated with improved cyclability, suggesting that the addition of Bi and the suppression of these recharge pathways may lead to higher capacity, more stable CuO cathodes in the future.This work was supported by the U.S. Department of Energy, Office of Electricity and Sandia National Laboratories, a multi-mission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC., a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-NA-0003525. This work was performed, in part, at the Center for Integrated Nanotechnologies, an Office of Science User Facility operated for the U.S. Department of Energy (DOE) Office of Science. Dr. Imre Gyuk, Director of Energy Storage Research, Office of Electricity is thanked for his financial support. The views expressed herein do not necessarily represent the views of the U.S. Department of Energy or the United States Government.

Enhancing Secondary Alkaline Battery Performance: Synthesis and Electrochemical Characterization of Zn Anodes, Based on ZnO@C Core‐Shell Nanoparticles

AbstractWhile alkaline Zn batteries, like traditional rechargeable aqueous batteries, boast an advantage in terms of energy density, their progress has been hampered by concerns related to the anode. These concerns include issues like Zn dendrites, self‐corrosion, passivation, shape change, and the hydrogen evolution reaction (HER). To tackle these challenges, we have introduced a nanostructuring approach for the anode, employing carbon‐coated ZnO nanoparticles (ZnO@C) as the active material. In this study, we synthesized ZnO@C nanoparticles in an environmentally sustainable and scalable manner to address passivation and dissolution issues jointly. Nanoscale ZnO particles effectively prevent passivation, while carbon shell slows down the dissolution of zincate. The Zn anode exhibits a significant performance boost when compared to Zn foil and bare ZnO nanoparticles, even when subjected to demanding conditions (without the use of ZnO‐saturated electrolyte). This rechargeable Zn anode marks a significant step toward the realization of practical, high‐energy rechargeable aqueous batteries, such as Zn‐air batteries.

Estimation of Discharge Capacities Using Generalized Peukert’s Equation for Saft Industrial Standby Batteries

Saft Industrial Standby (ISD) battery utilizes robust nickel-cadmium alkaline electrochemistry that delivers reliable performance and long life of at least 15 years over a wide range of temperature (-20 °C to 50 °C). The battery is designed with nickel based positive electrode and plastic bonded cadmium electrode in a vented prismatic cell. Typically, telecom applications used to require long duration backup power sources. With the advent of 4G/5G, the duration for backup power has been reduced to 1 hour or less. Therefore, new ISD battery was designed for power applications like 174 W/cell discharge for 1 hour and at the same time it can deliver high energy density up to 100 Wh/l. Additionally, low water consumption due to the high charge efficiency makes this battery ideal for the maintenance free remote installations. All these features render the battery aptly suitable for providing back-up power in telecom networks (4G and 5G) including remote cabinets at the lowest total cost of ownership.The ISD battery (Tel.X-Plus) is compliant to the Telecordia GR (Generic Requirement)-3020 CORE standard, which is recommended for the secondary alkaline batteries used in the telecom back-up application. This standard requires declaration of minimum 28 discharge currents entailing different durations and end voltages for a specific battery capacity. Hence, correct estimation of deliverable capacities for any definite duration and end voltage can reduce significant number of test trials. In addition, it helps sizing the battery for different power and energy installations. There are a few analytical techniques, such as Peukert’s and Shepherd’s equations that can be used to model the discharge characteristics of batteries. There are three different forms of generalized Peukert’s equations: algebraic, hyperbolic tangent and complementary error functions. In this study, to evaluate the discharge capacities we investigated the complementary error function of the generalized Peukert’s equations described in the equation 1: C= (Cm/erfc(-1/n)) * efrc(((i/ik)-1)/n) ... (1)where, C is the capacity of the battery during discharge, Cm is the highest discharge capacity, i is the discharge current, ik and n are statistical parameters. We know that phase transition is key to the discharge of a battery. Therefore, we selected the equation which also defines the phase transition process. The discharge capacities were calculated between 24-hour and 0.20-hour discharge durations for 1 V/cell, 1.05 V/cell, 1.10 V/cell and 1.14 V/cell end points using the equation 1. Here, the discharge capacity that was experimentally determined at the nominal C/24 rate was used as the maximum discharge capacity, Cm. The value of the statistical parameter n is within 0 and 1 to satisfy the capacity limits when discharge current tends to infinite and zero. For example, n equals to 0.6 is used for the calculations pertaining to the 180 Ah rated battery. The other statistical parameter ik was empirically selected for each end point voltage e.g., 250 A for 1.1 V/cell. Figure 1 shows the results for the calculated discharge capacities along with the experimental values at the 1.1 V/cell cut-off. The calculated numbers closely match with the experimentally obtained values with the r2 of 0.998 (Figure 1)Results for the other cut-off voltages (1.0 V/cell, 1.05 V/cell and 1.14 V/cell) were also obtained using the equation 1 and closely match the experimental values. Thus, the phase transition form of generalized Peukert’s equation (complementary error function) can be used for evaluating the capacities between 24-hour and 0.20-hour of discharge durations. Consequently, it enhances the test efficiency remarkably and sets the stage for battery sizing. Future studies include but not limited to the significance of n and ik, algebraic form of Peukert’s equation and Shepherd’s equation to understand the effectivity of each model with a focus on the discharge durations below 0.20-hour. Figure 1

In situ growth of ZnO nanosheets on Ti3C2Tx MXene for Superior-Performance Zinc-Nickel secondary battery

Although Zn-Ni battery is a potential energy storage system, the anode zinc electrode often faces dendrite, passivation and deformation problems, which tend to be exacerbated at high current densities particularly, and severely hamper its practical applications. Zinc oxide was modified with 2D transition metal carbides/nitride (ZnO@MXene) firstly for the purpose of broadening the application scenarios of zinc alkaline secondary batteries. A variety of characterizations and density functional theory (DFT) calculations certify that highly conductive MXene matrix provides a high-speed electron transfer channel and its low ionic diffusion barrier and excellent ionic diffusion mobility of MXene can quickly reduce the ion concentration gradient at the solid–liquid interface, which weakens the concentration polarization. Also, MXene can tune the diffusion behavior to induce homogeneous deposition of zinc via the zinc-oriented-O groups, forming well-dispersed “seed points” to realize uniform nucleation and inhibiting dendrite growth. Therefore, ZnO@MXene as the anode of a Zn-Ni battery can keep its capacity of 594mAh·g−1 after 1500 cycles at 10C. That reaches 90% of its initial capacity (596mAh·g−1), suggesting superb specific capacity, rate performance, and cycle life span.

Approaches Towards Improving Zinc-Nickel Batteries Performance

The zinc/nickel electrochemical system has long been proposed as a good candidate of secondary alkaline batteries due to its excellent performance versus other aqueous batteries, such as high practical specific energy, excellent specific power, high open circuit voltage, low cost and low toxicity [1,2]. These advantages make it suitable for replacing lead-acid and nickel-cadmium batteries [3]. However, the high solubility of zinc in concentrated alkaline electrolytes is still a significant problem that induces two main failure mechanisms: a shape-change of the zinc electrode and a redistribution of the zinc active material due to its dissolution/redeposition during cycling. Dendritic growth can occur as a consequence of zinc dissolution/redeposition, and if severe, may lead to separators’ perforation and internal electrical short-circuits [4]. These drawbacks reduce the cell's capacity and lifetime, especially compared to traditional competing systems [5]. In addition, since the hydrogen evolution reaction (HER) is thermodynamically possible (especially during charging), the coulombic efficiency of the zinc electrode can be lowered by this parasite reaction [6]. The undesirable HER consumes water and some of the active material, yielding zinc hydroxide which in turn can generate a passivation layer that lowers the usability of the zinc anode materials [7]. There are different approaches to overcome these problems, such as the integration of additives in the active material formulation and/or in the electrolyte.In this contribution, we will show how regeneration of the active material can be obtained via appropriate steps of rest submitted to the active material and without the need for additional energy input. The so-called “self-healing” of the active material allows to recover a substantial part of the electrochemical performance. The concept was deeply studied and monitored by scanning electron microscopy coupled with elemental mapping by X-ray energy dispersive spectrometry, and operando tomography. An increase in the coulombic efficiency has been demonstrated making this discovery very promising for the future of zinc-based alkaline batteries. Keywords: Zinc-nickel batteries, additives, self-healing

Fe3S4@reduced graphene oxide composites as novel anode materials for high performance alkaline secondary batteries

High-performance Fe3S4@reduced graphene oxide (rGO) as a novel anode material for alkaline rechargeable battery is successfully achieved via a facile hydrothermal method. The structural and electrochemical properties of the Fe3S4@rGO composites are evaluated systematically. It is interestingly found that increasing GO content effectively decreases the particle size of Fe3S4 in the composites. As expected, the Fe3S4@rGO composite with 10% rGO shows better high-rate capability and excellent cycling stability than the pure Fe3S4. At the rates of 0.2 C, 1.0 C, 2.0 C, 5.0 C, 10 C and 20 C, the Fe3S4@(10%)rGO can present specific discharge capacities of ～343.6, ～299.6, ～273.5, ～247.4, ～220.5, and ～164.6 mAh g−1, respectively. After 400 cycles at 1 C, the capacity loss is just approximately 3.2%. The improved performance is attributable to the addition of rGO and its high S content, eventually leading to more rapid charge transportation, enhanced reversibility, and a helpful porous anode structure. According to the outstanding electrochemical performance, it is believed that the Fe3S4@(10%)rGO is a competitive anode material to satisfy the requirements of rapid charge-discharge and long service life. Consequently, the present work offers a facile strategy to synthesize promising Fe3S4@rGO composite anode materials for alkaline secondary batteries.

Occurrence of shape change in rechargeable alkaline zinc electrodes observed by operando confocal optics and X-ray diffraction

Alkaline secondary batteries with zinc negative electrodes are attractive power sources for large-scale energy storage systems. However, low cyclabilities of zinc electrodes prevent their wide applications. While shape change has been known as one of the predominant degradation modes, its origin has not been clarified yet. In this study, we analyze the initial charge-discharge behavior of ZnO composite electrodes using a unique “laboratory” operando observation method combining confocal optics and X-ray diffraction to capture the occurrence of shape change and elucidate the mechanisms. It is shown that the ZnO composite electrodes in 4.0 mol dm −3 KOH solution, which show relatively short cycle life, suffers from uneven reactions caused by spatially concentrated metallic zinc depositions on charging and significant ZnO dissolutions on discharging, whereas those in 1.0 mol dm −3 KOH solution and the ionomer-modified electrodes in 4.0 mol dm −3 KOH with improved durability exhibit uniform formation of metallic zinc and ZnO precipitation during charge-discharge cycles. We thus conclude that the occurrence of the shape change processes limiting the cycle life is essentially ascribed to the spatially uneven reactions in the zinc electrodes. • Initial charge-discharge behaviors of ZnO composite electrodes are analyzed. • Operando confocal optics and operando X-ray diffraction are combined. • The occurrence of the shape change is ascribed to the spatially uneven reactions.

The Trade-Offs in the Design of Reversible Zinc Anodes for Secondary Alkaline Batteries

The Trade-Offs in the Design of Reversible Zinc Anodes for Secondary Alkaline Batteries

Operando Observation of Zinc Negative Electrode Using Confocal Optical System and X-Ray Diffraction

Alkaline secondary batteries using zinc negative electrodes are attractive candidates for large-scale energy storage systems since they potentially satisfy low cost, high safety standard and high energy density. However, the short cycle life of the zinc electrodes hinders their practical applications. To overcome this problem, it is necessary to understand the degradation mechanism. In this work, we applied the combination of operando confocal optical system and operando x-ray diffraction (XRD) to alkaline zinc electrode systems to investigate the mechanism of the degradation from the physical and the chemical points of view. Operando confocal optical system is a confocal-optics-based microscopy system that enables acquisition of all-in-focus high definition color image on uneven surface by vertical scanning of observation surface. It also enables time-resolved observation of morphological and color change of electrodes during charge-discharge cycle by periodical scanning. We previously applied this to lithium-ion battery systems and successfully visualized local reaction distribution.[1] Since the morphological change and the local reaction distribution mainly cause the degradation of zinc electrode[2], the operando confocal optical system possibly supplies important information about the degradation mechanism. On the other hand, it is difficult to analyze the chemical properties with the optical system. To compensate the chemical aspect, we also carried out operando XRD. Nakata et al. applied operando synchrotron XRD to zinc electrode systems and successfully quantified ZnO and Zn phases.[2] In this work, we expanded synchrotron XRD into laboratory XRD, which has higher versatility and higher availability.The optical measurements and the XRD were separately employed with a confocal optical system (ECCS, Lasertec) and XRD system (SmartLab, Rigaku), respectively, but the same electrochemical cell and operating conditions were applied. The electrochemical cell consists of ZnO composite electrode filled in Cu foam (working electrode), Hg|HgO electrode (reference electrode), Zn wire (counter electrode), poly(propylene) film (observation window) and 1.0 and 4.0 mol dm–3 KOH solutions saturated (sat’d) with ZnO (electrolyte solution).Figure (a), (b) shows parts of operando confocal optical images and operando XRD patterns of the cross-section of the ZnO composite electrodes in 1.0 and 4.0 mol dm–3 KOH solutions sat’d with ZnO. Zn deposited to form clusters at around the Cu current collectors at the charge in 4.0 mol dm–3 KOH sat’d with ZnO while relatively uniform Zn deposition was observed at the charge in 1.0 mol dm–3 KOH sat’d with ZnO. The diffraction pattern of ZnO was hardly observed after the discharge in 4.0 mol dm–3 KOH sat’d with ZnO. In contrast, ZnO110 peak was clearly observed and bluish blacked deposition was uniformly observed in the optical image after the discharge in 1.0 mol dm–3 KOH sat’d with ZnO. Charge-discharge measurements using three-electrode full-cells with Ni(OH)2 counter electrodes showed that the ZnO composite electrode in 1.0 mol dm–3 KOH exhibited about 4 times longer cycle life than that in 4.0 mol dm–3 KOH. These results indicated that higher solubility of [Zn(OH)4]2– in 4.0 mol dm–3 KOH caused local deposition of Zn and ZnO followed by the degradation due to the shape change.

Electrochemical Studies of the Nickel‐based Hydroxide Electrode for the Oxygen Evolution Reaction and Coulombic Efficiency of the Electrode

AbstractNickel hydroxide, Ni(OH)2 electrode material has been used as a positive electrode in commercial alkaline secondary batteries for more than 100 years. This is because Ni(OH)2 has a good high rate discharge ability performance, wide operation and storage temperature range and relatively low. However, the Ni(OH)2 positive electrode exhibits poor performance which results from (i) competitive reactions of the oxidation of the active material and evolution of oxygen. (ii) The reduced charge acceptance of Ni(OH)2 positive electrode is suspected to be related to a relatively long distance between Ni(OH)2 particles and the nearest portion of the substrate. In this study, electrodes are prepared using β‐Ni(OH)2 powder as the active electrode material, hot‐pressed onto a nickel mesh current collector. The Ni2+ in the compound β‐Ni(OH)2 material is partially substituted with Co2+ and Al3+ metals and the performance of as‐prepared materials are optimized and examined. XRD, FTIR, TG‐DTA, SEM/EDS, and ICP confirms the formation of the expected compositions. The samples with 5 wt.% Co2+, and 10 wt.% Al3+ metals are found to be the optimal compositions with promising electrochemical activities. The modification of Ni(OH)2 by the partial substitution of Co2+ and Al3+ metals for Ni2+ shows some effect on the redox peaks of Ni(OH)2 and the oxygen evolution reaction (OER). E.g. the onset for oxidation of the active material is significantly improved with partial substitution of Ni2+ by Co2+. On the other hand partial substitution of Ni2+ with Al3+ moves the onset of electrode oxidation to higher potential. In addition, the partial substitution of 10 wt.% Al3+ metal improves both discharge capacity (from 128 mAh/g to 170 mAh/g), and the coulombic efficiency (from 87 % to 93 %) of the β‐Ni(OH)2 electrode.

The influence of copper and carbon black on electrochemical behavior of nickel positive electrode

Nickel hydroxide is used as an active material in positive electrodes of secondary alkaline batteries. In alkaline batteries, the capacity of the negative electrode is greater than that of the positive electrode, hence the cell capacity is limited by the positive electrode. The practical capacity of the Ni(OH) 2 positive electrode depends on the efficiency of the conductive network connecting the Ni(OH) 2 particles with the current collector. In this study, hot-pressed-type electrodes were prepared using fiber-like β-Ni(OH) 2 powder as the active material on a nickel mesh as a current collector. The effect of carbon black as a conductive network for Ni(OH) 2 active material and the partial substitution of Cu(OH) 2 for β-Ni(OH) 2 material on the electrode performance, are examined. The carbon black powder addition improves the utilization of the active material; however it lead to a decrease in stability of the electrode. The partial substitution of Cu(OH) 2 for β-Ni(OH) 2 significantly improves the coulombic efficiency of the β-Ni(OH) 2 active material and it also increases the specific discharge capacity and enhance the stability of the electrode. These findings showed that the copper modified β-Ni(OH) 2 electrodes possessed an improved specific capacity and stability and thus may be recognized as a promising hybrid material for battery electrode applications. • The β-phase Ni(OH) 2 is formed when hydrothermal treatment is applied. • Carbon black improves specific discharge capacity but not stability. • Cu 2+ substitution improves both capacity and stability.

Advances in Alkaline Secondary Batteries for Grid Storage Applications

Rechargeable Zn/MnO2 batteries have recently become a strong candidate for electrical grid storage applications due to their established materials supply chain, high energy density, and low cost. Such cells could rival Li-ion systems in terms of theoretical specific energy and, when produced at scale, could cost as little as $50/kWh (S. Banerjee et al.). Yadav and coworkers have developed a MnO2 cathode stabilized by Bi and Cu, which can reversibly access the full 2e– capacity of MnO2, but pairing this electrode with Zn is still met with a number of issues, deeming the long cycle lives (e.g. ≥ 5000 cycles) necessary for grid storage currently unobtainable.Over repeated charge–discharge cycles in alkaline conditions, Zn anodes undergo numerous dissolution/re-precipitation reactions, resulting in irreversible shape change, redistribution of active material, and eventual electrode passivation, limiting the achievable capacity and lifetime. Recently, our group examined pre-saturation of the electrolyte with zincate (Zn(OH)4 2 –), which forms when ZnO is dissolved in strong base, as a potential solution to this problem, showing a 110-235% improvement in cycle life of Zn/Ni cells at increased Zn depth-of-discharge (DOD) (14-35% DOD) (M. Lim et al.). Unfortunately, these benefits are nullified when a MnO2 cathode is used, because the cell shorts and (Zn(OH)4 2 –) further reacts with soluble Mn(III) species, causing the formation of insoluble and/or electrochemically inactive side products, such as ZnMn2O4. Thus, the development of a zincate-blocking, yet hydroxide and/or cation-conducting separator, which could isolate the zincate-saturated electrolyte within only the anode was undertaken in order to enable longer cycle lives of higher DOD Zn/MnO2 cells.As a result, we have now developed several permselective polymeric separators for use in higher depth-of-discharge Zn/MnO2 batteries at enhanced rates (Kolesnichenko et al.). After synthesis and characterization, the functionalized separators were screened for hydroxide and zincate crossover, using pH measurements and our newly-developed anodic stripping voltammetry assay (Duay et al.), respectively. Several separators showed a strong selectivity for hydroxide over zincate, while ionic conductivity measurements were comparable to those of commercial CelgardTM 3501 and Cellophane 350P00 separators.This presentation will discuss various aspects of improving Zn anode performance at higher depths-of-discharge and implementation of functionalized polymeric separators into Zn/MnO2 batteries to isolate the cathode from zincate.This work was supported by the U.S. Department of Energy, Office of Electricity, and the Laboratory Directed Research and Development program at Sandia National Laboratories. Sandia National Laboratories is a multi-program laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC., a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-NA-0003525. Dr. Imre Gyuk, Director of Energy Storage Research at the U.S. Department of Energy Office of Electricity, is thanked for his financial support of this project. The views expressed herein do not necessarily represent the views of the U.S. Department of Energy or the United States Government.

The dodecahedral Nitrogen-doped carbon coated ZnO composite derived from zeolitic inidazolate framework-8 with excellent cycling performance for zinc based rechargeable batteries

A novel Nitrogen-doped carbon coated ZnO(NC@ZnO) composite derived from zeolitic inidazolate framework-8(ZIF-8) precursor is successfully synthesized through a simple hydrothermal reaction followed by calcination treatment. The as-prepared NC@ZnO composite is characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and Nitrogen adsorption-desorption analysis, and its formation mechanism is proposed. When evaluated as anode material for Ni–Zn alkaline secondary batteries, the NC@ZnO composite exhibits outstanding electrochemical performance compared with that of the commercial ZnO, delivering a discharge specific capacity of 531 mAh g−1 with the capacity retention ratio about 83.5% after 945 cycles. The outstanding electrochemical performance is ascribed to the Nitrogen-doped carbon layer and the unique dodecahedral porous architectures with a larger specific surface area, which can facilitate the electrons transfer and restrain the formation of zinc dendrites during repeated charge-discharge process.

Improving zinc porous electrode for secondary alkaline batteries: Toward a simple design of optimized 3D conductive network current collector

The internal migration of zinc within the thickness of porous composite negative electrodes for rechargeable zinc batteries causes detrimental shape change of the zinc electrode. It depends on various parameters linked to the electron conduction in the electrode: electronic percolation, conductive additives, primary current collector. This study highlights a simple solution, that drastically enhances the electrochemical performance of thick and porous zinc electrodes, by rethinking their architecture. Using a multiplicity of thin current collectors enables to create a 3D network of electronic percolation and a better repartition of the current lines within the electrode; as a result, the formation of multiple active zinc cores in the electrode volume is better controlled. This strategy allows to improve the management of zinc migration within the electrode structure, leading to minimal densification of each zinc core, and overall enables higher reversibility of zinc oxidation/reduction upon discharge/charge. It finally mitigates the initial drastic capacity fading observed on standard type calcium zincate negative electrode.

Effects of the Low Coulombic Efficiency of Zinc Anode on the Cycle Performance of Zn–Ni Battery

Zn–Ni battery is an attractive aqueous alkaline secondary battery due to its low cost, safety, and environmental friendliness. However, the problems of hydrogen evolution reaction, zinc dendrites growth and deformation of zinc anodes hampering the commercial application of Zn–Ni battery. In this work, the dynamic imbalance behavior of capacity of the Zn–Ni battery which caused by low coulombic efficiency of the anode is studied. Results reveal that due to the hydrogen evolution effect of the anode, the sintered Ni(OH)2 cathode which commonly used in the research of anode of Zn–Ni batteries cannot be fully discharged. Residual capacity will increase the potential of the cathode continuously, shorten the constant current charging time, and cause the battery cycle capacity decay rapidly. This phenomenon is confirmed by adding nano Bi powders to suppresse the hydrogen evolution of the zinc anode. This work reveals that the decline in the cycle life of Zn–Ni batteries is not only due to irreversible changes in the electrode structure but also due to the coulombic efficiency mismatch of the cathode and anode.

Shape-controlled growth of three-dimensional flower-like ZnO@Ag composite and its outstanding electrochemical performance for Ni-Zn secondary batteries

A novel three-dimensional (3D) flower-like ZnO@Ag composite is successfully synthesized through a simple and facile process, which is characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS).When evaluated as an anodic material for nickel-zinc alkaline secondary batteries, the 3D flower-like ZnO@Ag composite exhibits the high discharge capacity (627 mAh g−1) and long cycle life (830 cycles). The outstanding electrochemical performance is ascribed to the Ag nanoparticles enhancing electron conductivity and the uniform flower-like structure providing enough electrochemical reaction sites, so as to reduce electrode polarization and improve cell efficiency. Furthermore, the possible growth mechanism of 3D flower-like ZnO@Ag composite has been proposed. The effect of silver content on formation of ZnO@Ag composites was also investigated in detail, indicating the appropriate silver content plays a key role in forming a defined 3 D flower-like structure for the ZnO@Ag composite.

Facile preparation of sulfur/nitrogen co-doped graphene coupled with Ni(OH)2 for battery-type electrode with superior electrochemical performance

A novel hybrid material composed of Ni(OH)2 nanoplates and sulfur/nitrogen co-doped reduced graphene oxide frameworks (SN-RGO) was successfully prepared by a hydrothermal method. The co-doping of S and N provides a large number of structural defects on the graphene surface, which makes the C atoms more active and increases the number of active sites. The as-obtained SN-RGO/Ni(OH)2 electrode delivers an excellent discharge capacity (363.4 mAh/g at 0.2C), which is better than those of the Ni(OH)2 hybrid with un-doped or N-doped graphene. This superior performance can be attributed to the increased number of defects and active sites of SN-RGO, and the loose sandwich-like structure. The SN-RGO/Ni(OH)2 composites are promising candidates for battery-type electrode materials for alkaline secondary batteries.

In-depth structural understanding of zinc oxide addition to alkaline electrolytes to protect aluminum against corrosion and gassing

Several approaches have been tried to reduce Al corrosion in primary and secondary alkaline batteries. The most successful to date has been the addition of ZnO to the electrolyte, which results in the spontaneous deposition of a protective metallic Zn film on the Al surface. However, there is a limited understanding in the literature of the structure of this Zn film and how that structure (i) influences the protection of Al, and (ii) is influenced by the electrolyte composition. This work aims to develop a fundamental understanding of the protection mechanism against Al corrosion when zincate is added to KOH electrolytes. This was accomplished through morphological studies of the resulting Zn film using SEM, XRD, N2 adsorption, and measurements of H2 gas evolution as well as electrochemical characterization during discharge. It was found that adding saturated ZnO to KOH electrolytes provides the most protective Zn film with good adherence and high density, which can lower the Al corrosion rate by 2 orders of magnitude. Moreover, configurations with a capacity near the Al theoretical capacity were achieved.

Facile preparation of α-Ni(OH)2/graphene nanosheet composite as a cathode material for alkaline secondary batteries

α-Ni(OH)2 has attracted great attention as a cathode material for alkaline secondary batteries (ASBs) because of its high theoretical capacity and small volume change during charge/discharge cycles. However, poor cycling stability and low electronic conductivity of α-Ni(OH)2 severely hinder its development and practical applications in ASBs. In this work, α-Ni(OH)2/graphene nanosheet composite was successfully fabricated by a facile homogeneous precipitation method. The nanocomposite is composed of α-Ni(OH)2 nanoflowers decorated homogeneously on the surfaces of graphene nanosheets. When evaluated as cathode material for ASBs, this α-Ni(OH)2/graphene nanocomposite exhibits much enhanced high-rate capability and cycling stability compared to the pure α-Ni(OH)2 due to the improved electrochemical reaction kinetic, enhanced electronic conductivity, and hierarchical nanostructure. For example, the α-Ni(OH)2/graphene nanocomposite presents a rate retention of 74.8% as the current density increasing from 250 to 5000 mA g−1, much higher than that (49.0%) of pure α-Ni(OH)2; moreover, at a current density of 2000 mA g−1, the α-Ni(OH)2/graphene nanocomposite still maintains a reversible capacity of 177 mA h g−1 after 200 cycles, which is four times higher than that (41 mA h g−1) of the pure α-Ni(OH)2. The attractive electrochemical performances and facile synthesis route made the prepared α-Ni(OH)2/graphene nanocomposite become a promising electrode material for ASBs.

Understanding How Structure Influences Electrochemical Behavior When ZnO Is Used to Suppress Aluminum Corrosion in Alkaline Electrolytes

The severe corrosion rate of aluminum (Al), coupled with hydrogen evolution (H2 gassing), is the major roadblock preventing the widespread deployment of Al as the anode material in primary and secondary alkaline batteries. One of the most successful approaches to reduce this corrosion has been the addition of ZnO to the alkaline KOH electrolyte, which results in the spontaneous electroless deposition of a protective metallic Zn film on the Al surface. However, the fundamental structural and electrochemical characterization of Zn on Al as well as the influence of ZnO/KOH composition need to be investigated. This study aims to develop a novel fundamental understanding of the protection mechanism against Al corrosion when zincate (from dissolved ZnO) is added to KOH electrolytes. The effects of both ZnO concentration and KOH concentration are probed. Morphological studies of the spontaneous Zn film were realized using SEM, XRD, N2 adsorption and measurements of real time H2 gas evolution. These were coupled with discharge experiments to create a new structure-function understanding for ZnO protection of Al. It should be noted that electrolytes enabling protective Zn films with good adherence and density were found, and capacities near the Al theoretical capacity were achieved.