Ag-Modified Cu Foams as Three-Dimensional Anodes for

Subscriber access provided by ALBRIGHT COLLEGE

Article

Ag-Modified Cu Foams as Three-Dimensional Anodes for Rechargeable Zinc-Air Batteries Jiayuan Yu, Fuyi Chen, Quan Tang, Tesfaye Tadesse Gebremariam, Jiali Wang, Xiaofang Gong, and Xiaolu Wang ACS Appl. Nano Mater., Just Accepted Manuscript • DOI: 10.1021/acsanm.9b00156 • Publication Date (Web): 29 Apr 2019 Downloaded from http://pubs.acs.org on April 30, 2019

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 34 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Applied Nano Materials

Ag-Modified Cu Foams as Three-Dimensional Anodes for Rechargeable Zinc-Air Batteries Jiayuan Yua,b, Fuyi Chen*,a,b, Quan Tanga,b, Tesfaye Tadesse Gebremariama,b, Jiali Wanga,b, Xiaofang Gonga,b, Xiaolu Wanga,b a. State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xian, 710072, China. b. School of Materials Science and Engineering, Northwestern Polytechnical University, Xi’an, 710072, China. *Corresponding author: [email protected] (Fuyi Chen)

ACS Paragon Plus Environment

ACS Applied Nano Materials 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Abstract Rechargeable zinc-air batteries are typical environment-friendly energy storage devices with high energy density and low cost. Nevertheless, dendrite formation and self-corrosion of zinc anode directly reduce battery performance. Herein, we report a novel Cu foam substrate with uniform Ag nanoparticles deposited on the surface as three-dimensional (3D) anode in rechargeable zinc-air battery and battery stacks for the first time. Tafel and linear scanning voltammetry measurements exhibit the Ag deposited on Cu foam suppresses hydrogen evolution reaction and reduces corrosion current density on the anode. Ag-modified three-dimensional anode is used in a primary zinc-air battery with 200 mAh anode capacity and Ag-Cu catalyzed cathode, which demonstrates a high specific capacity of 676 mAh gZn-1, an energy density of 786 Wh kgZn-1 and a high zinc utilization of 87%. Afterwards, Ag-modified three-dimensional anode is used in a rechargeable zinc-air battery, which presents a coulombic efficiency of 94% after 80 cycles with 2 h cycle period. Besides, Ag-modified three-dimensional anode is free of Zn dendrites at different depth of discharge from 5% to 20%. By connecting two rechargeable zinc-air batteries in both series and parallel, these batteries show a high energy efficiency of 55% and 60%, respectively, and deliver stable cycling over 40 cycles. The stable cycling performance can be attributed to Ag nanoparticles on the substrate surface which regulate the Zn deposition uniformly in the voids between Cu foam skeleton and prevent dendrite formation by providing continuous uniform electronic transmission channels. Keywords: Rechargeable zinc-air battery; Ag nanoparticles; copper foam anode; Zn dendrites

Introduction As the indispensable need for cost-effective and sustainable energy storage devices in our daily life, more than ever before, it is paramount to develop new energy technologies. Zinc-air battery is a typical high-performance environmentally benign


Page 2 of 34

Page 3 of 34 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


energy storage system in addition to lithium-ion battery, which has been widely used in energy storage1, consumer electronics2 and other conversion devices due to its low cost, non-toxicity, relatively high specific capacity, high energy density3-4, competitive power density and cycling stability. Rechargeable zinc-air battery is a promising technology due to its high theoretical energy density and the abundant and environmentally benign materials. Alkaline zinc-air batteries (ZABs) discharge via the oxidation of metal Zn coupled with the reduction of O2 according to the anodic (Eqs.1 to 3; Zn) and cathodic (Eq.4; O2) reactions5： Electrooxidation: Zn ⇌ Zn2+ + 2e–

(1)

Complexation: Zn2+ + 4OH– ⇌ Zn(OH)42–

(2)

Dehydration: Zn(OH)42– ⇌ ZnO + H2O + 2OH–

(3)

Electroreduction: O2 + 2H2O + 4e– ⇌ 4OH–

(4)

However, the corrosion, dendrite growth and shape change are the most detrimental effects for ZABs， resulting in decreasing the effective surface area and utilization of Zn electrode, which seriously cause capacity loss and limited cycle life or lead to catastrophic failure of the battery directly6. For ZABs, Zn anodes suffer from self-corrosion caused by hydrogen evolution reaction (HER) as Zn has a more negative reduction potential than H2, resulting in capacity decay. Specifically, this reaction consumes Zn and H2O, producing Zn(OH)2 and H2 on the surface of Zn anodes simultaneously: Zn + 2H2O → Zn(OH)2 + H2

(5)

Theoretically, the electrochemical potentials of the anode and cathode should be



between the lowest unoccupied molecular orbital (LUMO) and the highest occupied molecular orbital (HOMO) of the electrolyte so that the electrolyte will not decompose. However, the electrochemical potential of Zn is above LUMO of the electrolyte, resulting in Zn-electrolyte corrosion reaction7. As a matter of fact, broader application of ZABs is hindered by limited rechargeability and low Zn utilization (typically < 60% of theoretical discharge capacity). Specifically, due to the large electric field intensity near the protuberances and uneven electron distribution resulting from the ZnO layer on electrode surface, current density will increase and great amount of free zincate ions are intensively adsorbed on the tips, commonly known as the“tip effect”, forming Zn dendrites8. Thus, various metal substrates have been studied to provide uniform electron transmission channels and large active surface area to reduce zincate concentration polarization, as well as improve the efficiency of Zn deposition by increasing the overvoltage of HER, which attribute to accelerate Zn deposition kinetics or alter the crystal habit of deposited Zn9. Recent researches on self-supporting 3D porous Zn electrodes provide Zn-based secondary batteries excellent electrical conductivity and unimpeded mass transport. This strategy has also been used by other researchers for lithium-ion battery10-11 or for zinc-air cell designs, reaching a high power density and long cycle life12-14. Furthermore, 3D porous architecture with large surface areas is effective to decrease concentration polarization of zincate, effectively reducing Zn dendrites growth15. Besides, it is glaring that 3D porous structure is beneficial to sufficient penetration of OH- ions to achieve reversibility. Parker et al.16-17 designed a 3D self-supporting Zn


Page 4 of 34

Page 5 of 34 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


sponges based on Zn powder without dendritic morphology after 45 charge-discharge (C-D) cycles ascribed to the excellent inter-particle conductivity of the monolithic 3D structure electrode. However, the depth of discharge (DOD) of such a 3D Zn sponge is limited, because the 3D structure would collapse while reaching a deep DOD, which limits the cycle stability of Zn-based batteries. To resolve the issue of anodes collapse, Cheng et al.18 proposed a 3D porous anode by depositing Zn on nickel foam for a single flow Zn/Ni battery, as a result, the cycling stability and power density were both improved. However, the low hydrogen evolution overpotential of nickel foam leads severe hydrogen evolution and self-corrosion between Zn and nickel galvanic cell, reducing the capacity of batteries and Zn utilization. To overcome the hydrogen evolution, Yan et al.13 introduced a Zn/Cu foam anode by pulse electro-deposition of Zn on copper foam substrate for Zn/Ni battery. The capacity of 3D Zn/Cu foam electrode remains 59% after ten days storage while the Zn/Ni foam electrode drops to only 5% of the theoretical capacity in contrast. Methods mentioned above make it a promising prospect of preparing a 3D Zn anode against dendrite problems and corrosion problems to apply for rechargeable alkaline ZABs, which exhibit higher specific capacity and energy density. Herein, we demonstrate an Ag-modified 3D Zn anode for ZABs by depositing Ag nanoparticles (Ag NPs) layer uniformly on Cu foam skeleton followed by electrodeposition of Zn on this Ag-modified 3D host material, which effectively impeded Zn dendrite formation and corrosion problems, and improved cycling performance compared to unmodified 3D electrode. Highly conductive Ag NPs



provide continuous and smooth electron transfer channels and provide low nuclear overpotential deposition sites for Zn deposition, which constrain Zn deposition process effectively19. Heterogeneous Ag NPs dispersed on 3D skeleton are expected to guide Zn deposition into the 3D host uniformly during C-D process, which effectively constrain the growth of Zn dendrites. Meanwhile, the interconnected 3D skeleton ensures the mechanical strength and toughness of the entire electrode structure, avoiding anode collapse during C-D process. Moreover, the porous structure can relieve the concentration of Zincate in the solution and reduce ZnO layer formation, thus inhibiting Zn dendrite growth. Briefly, Ag-modified 3D host structure improves the kinetics and mass transfer of electrochemical reactions, and efficiently minimizes the energy loss of ZABs20. In this work, the mechanism of dendrite growth and hydrogen evolution corrosion suppression was further investigated based on theoretical and experimental analysis. 1. Material and methods 2.1 Materials All commercial reagents were of analytical grade and serviced as received. The water for all solutions was deionized. The copper foam (110 ppi, thickness: 1.5 mm, Kunshan Jiayisheng Electronics Co.Ltd.), nickel foam (120 ppi, average pore size: 500mm, thickness: 1.7 mm, Lizhiyuan Battery Material Co. Ltd.) and zinc plates (Nantong Xinxiang Zinc Co, 1mm) were used in this study. All experiments were conducted at room temperature. 2.2 Preparation of Ag-modified 3D Zn anode


Page 6 of 34

Page 7 of 34 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


The Ag-modified 3D host was prepared by galvanostatic electrodeposition to form Ag nanoparticles on the Cu foam. The commercial Cu foam was cut into applicable pieces (10*30mm) and soaked in acetone and alcohol and cleaned in an ultrasonic cleaner for 30 min, respectively, removing organic impurities. Subsequently, as-prepared diluted hydrochloric acid was used to remove the oxide of copper foam and then rinsed by deionized water for three times followed by drying under flowing N2. A three-electrode system was set up for the electrodeposition process. The pretreated Cu foam, Pt electrode and SCE electrode served as work electrode (WE), counter electrode (CE) and reference electrode (RE), respectively. The proportional ratio of Ag+ precursor solution contained 0.01M Ag2SO4 and 2M KSCN in this procedure. The deposition current density of -1.5 A cm-2 is applied to the device for 20s. The prepared Ag-modified Cu foam was rinsed with deionized water followed by drying under flowing N2. The two-electrode sulfate plating system was selected for Zn electrodeposition on as-prepared Ag-modified 3D host to make Zn anode. The 3D host and a carbon rod were used as WE and CE. 1M ZnSO4 and 1M KCl were used as electrolyte. KCl is conductive salt, which is used to enhance the ionic conductivity in the solution and improve the dispersing ability, forming more detailed Zn coating. The electrodeposition of Zn was carried out by depositing at current density of 0.05 A cm-2 and deposition area is 2 cm2. The loading capacity 200 mAh and the mass loading is about 130 mg cm−2. An unmodified anode is carried out by depositing Zn on bare Cu foam directly in same preparation condition for further comparison.



2.3 Preparation of air electrode Ag-Cu bifunctional catalyst and the gas diffusion layer (GDL) were prepared by the procedures as described in our previous work21. Briefly, the commercial nickel foam was rinsed with absolute ethanol and deionized water respectively, and was then placed into as-prepared 0.3M CuSO4 solution for 3 hours and 0.01M AgNO3 solution for 3 minutes, consecutively. GDL was prepared by combining acetylene black and 60% PTFE with a mass ratio of 0.5:2.5, and was then pressed to piece with thickness of 0.5mm by the roll machine (Kejing CO. Ltd Hefei). Finally, as-prepared catalyst layer was placed next to the GDL to obtain the air electrode, and the nickel foam served as current collector. 2.4 Physical and electrochemical characterization XRD (X-Pert-PRO, Cu-Kα) with Cu Ka radiation was used to characterize the phase and crystal structures of the Ag-modified electrode. The working potential and current employed were 40 kV and 40 mA, respectively. SEM (ZEISS SUPRA 55, JSM-6390) equipped with an energy dispersive spectrometer (EDS) was used to study the morphologies of the Ag-modified electrodes. Electrochemical tests for 3D Zn electrode were conducted in three-electrode system, while Pt electrode and Hg/HgO (1.0 M KOH, 0.098 V vs SHE) were used as counter electrode and reference electrode, respectively. The area of working electrode was 1 cm2. Tafel plots, linear sweep voltammograms (LSV), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) tests were carried out by an electrochemical workstation CHI660C (Chenhua Instrument, Shanghai). Tafel plots


Page 8 of 34

Page 9 of 34 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


and LSV were tested in N2 saturated 6 mol L-1 KOH with scan rate of 10 mV s-1. CV was tested in 6M KOH with a voltage window from -1.8 V to -0.6 V (vs.Hg/HgO). EIS was tested with the frequency range of 105Hz to 10-2Hz. All the samples were rinsed by deionized water and dried by N2, and then cut into 1cm*1cm before measurement. 2.5 Cycling performance measurements for ZABs As-prepared Ag-modified 3D Zn anodes were assembled with air electrode to rechargeable ZABs, and tested by galvanostatic charge-discharge (GCD) cycling technique. The battery performance was characterized in primary ZABs, rechargeable ZABs and battery stacks both in series and parallel. Tests were examined by battery test system BTS-4000 (Neware Electronic Ltd. Shenzhen) in an air atmosphere, and all the capacity values were calculated based on the weight of Zn in 3D anode. Energy efficiency was calculated using Equation (6) as follows:

Energy efficiency (%) =

(6)

u(t), J and t represent the cell voltage, current density and time, respectively22. 3. Results and discussion 3.1. Physical characterization Ag-modified Cu foam structure was synthesized by a facile electrodeposition method, as shown in Scheme. 1. Figure 1 shows scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis of the Ag-modified substrate. In Figure 1a, uneven pores on bare Cu foam can depress electrochemical performance of Zn anodes



by disorganizing electron transport. Furthermore, as shown in Figure S1a, the detachment of some Zn protrusions from the substrate could lead to “dead Zn” with widening polarization during C-D process23. Figure 1b demonstrates an aggregated morphology of densely and uniformly deposited flat Ag nanoparticles anchored on Cu foam substrate. As a result, large dendritic Zn is effectively prevented by Ag-modified Cu foam in Zn anode preparation During the Zn plating/stripping process, these results highlight the importance of utilizing uniform Ag particles on 3D host materials for Zn anode preparation. EDS spectra in Figure 1c and XRD patterns in Figure 1d illuminate pure Ag particles anchored on Cu foam without being oxidized. 3.2. Electrochemical analysis Figure 2 exhibits the Tafel plots and LSV curves of Ag-modified 3D substrates in N2 saturated 6 mol L-1 KOH solution. As shown in Figure 2a, the corrosion potentials of Cu foam, Ag-modified Cu foam, Ni foam and Ag-modified Ni foam and pure Zn plate are -0.487 V, -0.513 V, -0.06 V, -0.412 V and -1.552V, respectively. It provides a direct evidence that both the Cu foam and Ni foam are stable at the broad potential range during Zn plating/stripping process (-1 V to -2 V vs. Hg/HgO). Crucially, Ag-modified Cu foam has lowest corrosion current density, which illustrates lowest corrosion ability. Figure 2b clearly indicates that Ag-modified Cu foam exhibits large hydrogen evolution overpotential of -1.47V, which is larger than unmodified Cu foam of -1.39V, as well as shows smallest hydrogen evolution current density, which contribute to less self-corrosion of Zn in alkaline electrolyte. These results support that Ag-modified Cu foam substrate is suitable for 3D Zn electrode


Page 10 of 34

Page 11 of 34 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


than previous reports9, 13-14, 18. Figure 3 shows the electrochemical performance of the Ag-modified 3D Zn anodes. The cyclic voltammetry curves were conducted to estimate the reversibility of the oxidation and reduction reaction within the voltage window from -1.8V to -0.6V (vs. Hg/HgO). As shown in Figure 3a-b, it clearly shows the one couple redox peaks in CV curves, and the reduction peak means Zn(OH)42-+2e−Zn. Compared to unmodified electrode, the modified one contains a highly conductive layer of Ag nanoparticles which provides more nucleation sites for Zn deposition, thus, we can confirm that the reversibility of the Zn electrode was improved by the Ag particles anchored on 3D host. For Ag-modified 3D electrode, a linear relationship between the Ip of the redox peaks and v1/2 at different scanning rates is calculated in Figure S2, which indicates a standard linear relationship. According to diffusion control calculation: i=Av1/2

(7)

where A, i and v represents constant, peak current and scanning rates, respectively. The linear relationship shows that the electrochemical reaction of the Zn anode during the cycle is mainly controlled by Zn(OH)42- diffusion，due to the large surface area of 3D porous structure provide large ion transport channels. Furthermore, in order to evaluate the effect of Ag-modified 3D skeleton on electrode polarization, C-D polarization curves at different current densities are shown in Figure S3. It clearly indicates that the Ag-modified 3D Zn anode exhibits a lower C-D overpotential, which is is beneficial to improve the cycle stability and higher energy efficiency of



the battery, especially when the current density is greater than 40 mA cm-2. The Ag-modified 3D skeleton provides an excellent uniform electronic conductor which has deposition site with a lower overpotential, therefore, the energy efficiency will be enhanced. It proves that the Ag-modified 3D Zn anode can maintain good cycle performance at a large current density. 3.3. Performance of zinc-air battery and battery stacks Figure 4 shows the performance of a homemade primary zinc-air battery with Ag-modified 3D Zn electrode. In Figure 4a, the battery with Ag-modified 3D Zn electrode shows a Zn utilization of 87% while the unmodified one is 68.6%, both of which are much higher than a similar work by Schmid et al.24. Besides, the battery with Ag-modified 3D Zn electrode shows a specific capacity of 676 mAh gZn−1 while the unmodified one shows 505 mAh gZn−1. In addition, discharge specific capacity and power density are calculated in Figure 4c and Figure 4d. The highest specific capacity achieved is 676 mAh gZn−1 at 10 mA cm−2, while the energy density is approach to 786 Wh kg−1, much higher than that of the reported Zn-Co3O4 battery (241 Wh kg−1)25 and Zn-MnO2 battery with powder-based Zn foam anode (405 mAh g−1and 500 Wh kg−1)26 In addition, the polarization curve of this zinc-air battery after the first charging activation shows a high power density of 75 mW cm−2 at 100 mA cm−2, which is much greater than that of Zn-Co3O4 battery(41 mW cm−2 at 24 mA cm−2)27. The obvious smooth and flat voltage plateau at about 1.2 V indicates the ORR process of a typical zinc-air battery, which reflects the reaction kinetics ability of the as-prepared electrocatalyst.


Page 12 of 34

Page 13 of 34 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure 5 shows the stability tests for Ag-modified 3D Zn anode and unmodified 3D Zn anode performed by GCD cycling at 25 mA cm−2. It obviously shows the cycling behavior of ZABs in different DOD. As displayed in Figure 5a-c, representative C-D curves were cycled at 5% DOD, 10% DOD and 20% DOD, respectively. Apparently, ZABs with Ag-modified 3D anode exhibit stable voltage profiles with negligible fluctuations whereas ZABs with unmodified anode show a gradual obvious decay over 30h cycling process, and it was impossible for the electrode to undergo further reversibility due to the dendrite formation at its surface. Surprisingly, upon the Ag-modified electrode, we discovered that no dendrite was formed and thus reversibility was possible up to 40 cycles. Briefly, the cycling lives of the ZABs based on 3D Ag-modified anodes could be prolonged beyond 2 times by the Ag-modified 3D substrate. Figure 5d shows the long-term cycling of zinc-air battery with Ag-modified 3D anode in 2h cycle period at 25 mA cm−2, which exhibits small C-D polarization after 130h cycling. C-D polarization curves in different current densities are shown in Figure S3. The high conductive silver nanoparticle layer provides a fast and continuous electron transport channel and provides a lower overpotential deposition site for Zn deposition, which reduces the nucleation resistance during Zn deposition, thus, it effectively constrains the Zn deposition process. The 3D metal foam skeleton provides better mechanical strength and toughness, supporting large amount of Zn deposition. Furthermore, it buffers the internal pressure caused by the deposition and dissolution of Zn during the long cycle, effectively alleviating the electrode deformation28-29. A large number of pore



structures can balance the ion concentration of Zincate in the solution, reduce Zincate concentration polarization and inhibit the growth of Zn dendrite. In addition, when Ag-modified 3D host used as the anode substrate can reduce the charging polarization of the battery, existing lower charging overpotential. Also, the reciprocating cycle efficiency is improved, thereby improving the power efficiency of ZABs. Figure 5e shows the long-term cycling performance of zinc-air battery at 2h cycle period. Coulombic efficiency (CE) of the battery with Ag-modified 3D Zn anode maintained 100% over 70 cycles and still remained 94.2% over 80 cycles, meanwhile, specific capacity remained beyond 650 mAh/g. Conversely, the capacity and CE of the battery with unmodified 3D Zn anode had a sharp decline approaching to battery failure due to the detachment of Zn dendrites from the electrode surface, which reduces cycle stability of the unmodified ZABs. This result is prior than a similar work of Ni foam-based Zn anode, whose CE and specific capacity remains only 87.7% and 282.3mAh g-1 after cycling tests30. Figure 6 shows the surface morphologies of unmodified 3D Zn anode (a-c) and Ag-modified 3D Zn anode (d-f) after 40 cycles at different DOD, which clearly verifies the efficiency of Zn dendrite suppression of Ag particles on skeleton during the cycling of Zn C-D reactions. As a result, the Ag-modified 3D electrode exhibits a longer cyclic life than unmodified 3D electrode, which shows dense and uniform morphological features without dendritic growth. This means Ag particles suppressed the dendrite formation in Zn reduction process, because there are uniform distribution of electrons transferring on 3D substrate material and the porous structure reduces


Page 14 of 34

Page 15 of 34 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


concentration polarization of Zincate around the electrode surface. Considering the standpoint previously reported by Zhang et al., general Zn nuclear formation needs to overcome a higher energy barrier than steady growth of pre-existing nuclear on Ag-modified 3D host31. The polarization of ZABs with Ag-modified 3D host is smaller, especially during the Zn plating process, which is attributed to the uniform deposition of Zn enabled by the Ag particles on substrate. Large overpotential and random voltage vibrations are observed for unmodified 3D Zn anode after 30h C-D curves, which can be ascribed to the irregular generation of Zn dendritic seeds in Figure 6a-c. In comparison, Ag-modified 3D Zn anode exhibit more stable voltage curves during C-D process with uniform non-dendrite morphologies in Figure 6d-f. Continuous electron transfer passage built by the 3D porous skeleton of Ag-modified Cu foam provides excellent electrical conductivity even after few ZnO formed on the surface of Zn which always hinders electron transfer between Zn particles in traditional Zn paste electrodes. Moreover, diffusion of reactants and products in high concentration of KOH electrolyte through the interconnected macro-pores encounters less resistance than that in water-containing polymer binders which are widely used in Zn paste electrodes. Therefore, ZABs based on this Ag-modified 3D Zn anode are able to achieve stable cycling curves at different DOD. Furthermore, the amount of Ag particles in 3D anode before and after cycling tests in ZABs is further confirmed by Energy Dispersive Spectrometer (EDS) and X-ray photoelectron spectroscopy (XPS) as shown in Figure S4. The spectrum of as



obtained sample indicates the existence of Ag elements on the Cu foam. The proportions of the ingredients calculated inside indicate that the content of Ag remained nearly the same, which proves the stability of Ag content on the substrate. The Ag 3d XPS spectrum is given in Figure S4c. The binding energies at 368.30 eV and 374.27 eV present Ag 3d5/2 and Ag 3d3/2, respectively. A spin energy separation of 5.97 eV between Ag 3d5/2 and Ag 3d3/2 is attributed to formation of the zero valence metallic state. Moreover, it clearly shows that the peaks are completely consistent, indicating that the energy level of Ag has not shifted even after 40 cycles, which strongly proves that the structure and characteristics of Ag without oxidation change. Besides, Figure S4d and Figure S4e also show the stability of Ag particles on 3D skeleton. Figure 7 shows electrochemical impedance spectroscopy (EIS) performed on unmodified 3D Zn anodes and Ag-modified 3D Zn anodes after 10, 40, and 75 cycles. EIS reflects the kinetic phenomena and interfacial reactions of the battery reaction. Among two arcs, the high-frequency capacitive anti-arc is related to the formation of the electric double layer caused by surface ZnO passivation film, and the low-frequency capacitive anti-arc is related to the interface electric double layer of the electrochemical reaction. The slope of the oblique line in the low frequency region represents the impedance caused by the diffusion of Zn(OH)42- ions at the electrode interface, and the larger slope reflects smaller impedance value of Zn(OH)42- ion diffusion at the interface. Figure 7a shows the internal resistance of unmodified 3D Zn anode increases 2.2Ω to 13Ω significantly with the increase of the number of cycles,


Page 16 of 34

Page 17 of 34 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


resulting from the continuous occurrence of surface ZnO layer during the circulation of the electrode, because in the later stage of the battery cycle, the deposited Zn particles are relatively coarse and dense, which greatly reduces the reaction area of the electrode and increases the polarization of the electrode, causing active Zn to passivate. This result is accordance with the XRD patterns shown in Figure S5. A large amount of ZnO appears on unmodified Zn anode during discharging while ZnO hardly presents on Ag-modified 3D Zn anode. The ZnO layer on the surface of the anode directly decreases Zn utilization and reduces the reversibility of Zn redox during C-D period32. Conversely, the Ag-modified 3D Zn anode shows small change in internal impedance from 1.5 Ω to 2.5 Ω during cycling as shown in Figure 7b.

Interestingly, two arcs appear in the high-frequency region, which is different from unmodified electrode. Considering the high-frequency arc impedance represents the interface impedance33,34, we consider the reason relates to the interface of the Ag-modified electrode after cycling, which exists various interfaces, such as Zn layer, deposited Ag particles and Cu foam skeleton. Different charge transport processes are implemented and result in two arcs in the high-frequency region. In terms of the low frequency region, the slope of Ag-modified Zn anode is significantly higher than that of unmodified Zn anode under same cycle number, indicating that Ag-modified substrate shows smaller interface diffusion impedance. Results above indicate that the Ag-modified substrate suppress the formation of ZnO layer, thereby, it achieves the plate and strip process of Zn efficiently and improves the cycle performance of ZABs.



To meet high energy and power needs for practical applications, we had constructed ZABs integrated in series and in parallel to enlarge the output voltage or current of the battery systems. Figure 8 shows GCD curves of those battery stacks. All tests were conducted at a current density of 10 mA cm−2. As shown in Figure 8a, two batteries connected in series can achieve an output voltage of 2.4 V with a similar discharge time to a single ZAB, which shows an operating voltage of 1.2 V. The initial C-D voltage gap of the battery stack is about 2.03 V, and that of a single one is about 1.02 V, which is little bit higher than that of the average of the battery stack due to a small C-D voltage polarization. Due to the doubling circuit resistance, the average voltage polarization of battery stack is only 0.05V higher than the single one. In Figure 8c, by connecting two batteries in parallel, the discharge time of the assembly was found to be about two times that of a single device when discharged at the same current density. Similarly, the charging voltage shows 0.85V while a single ZAB shows 0.97V, which results from the battery's resistance decrease in the case of parallel connection. The initial C-D voltage gap of the battery stack is about 0.85 V, which is 0.12 V lower than that of the single one, in other words, the C-D voltage polarization is greatly reduced by 12.4%. The experimental results findings are in accord with that of theoretical findings confirming the home-made ZABs can work normally in series and parallel conditions. Furthermore, Figure 8b and Figure 8d show the long-time cycling tests of battery stacks. As evidenced by the figures, even after 40 cycles, the average battery voltage gap of batteries in series is about 2.15V, which is only 0.06V higher than that of initial. The average battery voltage gap of batteries


Page 18 of 34

Page 19 of 34 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


in parallel is about 0.96V, and is about 0.11V higher than that of initial. Successive GCD curves of two batteries connected in series and in parallel are shown in Figure S6, indicating excellent stability of battery stacks beyond 40 cycles without significant overpotential increase. Coulombic efficiency and energy efficiency of battery stacks are shown in Figure 8e and Figure 8f. Battery stacks in parallel exhibit higher energy efficiency of 60% than that of the battery stacks in series (55%), but the stability of the battery in parallel is not as good as the battery in series. Therefore, large further work still need to be done for zinc-air battery stacks. 4. Conclusions In conclusion, the Ag-modified 3D Zn anode shows excellent performance in rechargeable zinc-air batteries and in rechargeable zinc-air battery stacks. On the one hand, Ag-modified substrate increases HER overpotential to reduce self-corrosion of Zn anode. On the other hand, the high conductivity of Ag particles on 3D substrate ensures uniform electron transport, and the high specific surface area of the overall framework also contributes to the reduction of local current density and zincate concentration polarization, inhibiting Zn dendrite growth. Besides, high mechanical strength attributes to alleviate electrode deformation. As a result, a primary zinc-air battery with Ag-modified 3D anode achieves a high specific capacity of 676 mAh gZn-1, specific energy of 786 Wh kgZn-1, power density of 75 mW cm-2 and Zn utilization of 87%. Moreover, the batteries present superior cycling stability in different DOD without Zn dendrite growth, and coulombic efficiency remained 94.2% beyond 80 cycles while specific capacity remained 640 mAh gZn-1. Surprisingly,



rechargeable zinc-air battery stacks connected in both series and in parallel present a cycling stability in 40 cycles with stable energy efficiency of 55% and 60%, respectively. Therefore, we have been able to improve cycling performance of batteries with the Ag-modified 3D Zn anode. Our work provides a novel idea for the development of 3D non-dendrite anode for other high-performance Zn-based batteries, showing promising prospect in flexible energy storage systems.

Acknowledgements This work was supported by the National Natural Science Foundation of China (grant nos. 51874243, 51271148 and 50971100), the Research Fund of State Key Laboratory of Solidification Processing in China (grant no. 150-ZH-2016), the Aeronautic Science Foundation Program of China (grant no.2012ZF53073), the Project of Transformation of Scientific and Technological Achievements of NWPU (grant no. 19-2017), and the Open Fund of State Key Laboratory of Advanced Technology for Materials Synthesis and Processing (Wuhan University of Technology grant no. 2018-KF-18). We would like to thank the Analytical & Testing Center of Northwestern Polytechnical University for SEM characterizations.


Page 20 of 34

Page 21 of 34 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


References 1.

Rugolo, J.; Aziz, M. J. Electricity Storage for Intermittent Renewable Sources. Energy Environ.

Sci. 2012, 5, 7151-7160. 2.

Goldstein, J.; Brown, I.; Koretz, B. New Developments in the Electric Fuel Ltd. Zinc/Air System.

J. Power Sources 1999, 80, 171-179. 3.

Li, Y.; Dai, H., Recent Advances in Zinc-Air Batteries. Chem. Soc. Rev. 2014, 43, 5257-5275.

4.

Pei, P.; Ma, Z.; Wang, K.; Wang, X.; Song, M.; Xu, H., High Performance Zinc Air Fuel Cell

Stack. J. Power Sources 2014, 249, 13-20. 5.

Parker, J. F.; Chervin, C. N.; Vila, M.; Rolison, D. R.; Long, J. W. In Rechargeable Zn-Air

Batteries Enabled by Zn Sponge Anodes and Bi (Tri?) Functional Cathodes, Meeting Abstracts, The Electrochemical Society 2017, 5, 562-562. 6.

Mainar Aroa, R.; Colmenares Luis, C.; Blázquez, J. A.; Urdampilleta, I. A Brief Overview of

Secondary Zinc Anode Development: The Key of Improving Zinc-Based Energy Storage Systems. Int. J. Energ. Res. 2017, 42, 903-918. 7.

Wongrujipairoj, K.; Poolnapol, L.; Arpornwichanop, A.; Suren, S.; Kheawhom, S. Suppression of

Zinc Anode Corrosion for Printed Flexible Zinc-Air Battery. Phys. Status Solidi (B) 2016, 254, 1600442. 8.

Enze, L., The Distribution Function of Surface Charge Density with Respect to Surface

Curvature. J. Phys. D-Appl. Phys. 1989, 19, 1-6. 9.

Wei, X.; Desai, D.; Yadav, G. G.; Turney, D. E.; Couzis, A.; Banerjee, S. Impact of Anode

Substrates on Electrodeposited Zinc over Cycling in Zinc-Anode Rechargeable Alkaline Batteries. Electrochimi. Acta 2016, 212, 603-613. 10. Barchasz, C.; Mesguich, F.; Dijon, J.; Leprêtre, J.-C.; Patoux, S.; Alloin, F. Novel Positive Electrode Architecture for Rechargeable Lithium/Sulfur Batteries. J. Power Sources 2012, 211, 19-26. 11. Etiemble, A.; Adrien, J.; Maire, E.; Idrissi, H.; Reyter, D.; Roué, L. 3D Morphological Analysis of Copper Foams as Current Collectors for Li-ion Batteries by Means of X-ray Tomography. Mater. Sci. Eng. B 2014, 187, 1-8. 12. Masri, M. N.; Nazeri, M. F. M.; Ng, C. Y.; Mohamad, A. A. Tapioca Binder for Porous Zinc Anodes Electrode in Zinc-Air Batteries. Journal of King Saud University-Engineering Sciences 2015, 27, 217-224. 13. Yan, Z.; Wang, E.; Jiang, L.; Sun, G. Superior Cycling Stability and High Rate Capability of Three-Dimensional Zn/Cu Foam Electrodes for Zinc-Based Alkaline Batteries. RSC Adv. 2015, 5, 83781-83787. 14. Titscher, P.; Riede, J.-C.; Wiedemann, J.; Kunz, U.; Kwade, A. Multiscale Structured Particle-Based Zinc Anodes in Non-Stirred Alkaline Systems for Zinc-Air Batteries. Energy Technol. 2018, 6, 773-780. 15. Fu, J.; Liang, R.; Liu, G.; Yu, A.; Bai, Z.; Yang, L.; Chen, Z. Recent Progress in Electrically Rechargeable Zinc-Air Batteries. Adv. Mater. 2018, 1805230. 16. Parker, J. F.; Chervin, C. N.; Pala, I. R.; Machler, M.; Burz, M. F.; Long, J. W.; Rolison, D. R. Rechargeable Nickel-3D Zinc Batteries: An Energy-Dense, Safer Alternative to Lithium-Ion. Science 2017, 356, 415-418. 17. Parker, J. F.; Chervin, C. N.; Nelson, E. S.; Rolison, D. R.; Long, J. W. Wiring Zinc in Three Dimensions Re-writes Battery Performance-Dendrite-Free Cycling. Energy. Environ. Sci. 2014, 7,



1117-1124. 18. Cheng, Y.; Zhang, H.; Lai, Q.; Li, X.; Shi, D.; Zhang, L. A High Power Density Single Flow Zinc-Nickel Battery with Three-Dimensional Porous Negative Electrode. J. Power Sources 2013, 241, 196-202. 19

Lu, L.-L.; Ge, J.; Yang, J.-N.; Chen, S.-M.; Yao, H.-B.; Zhou, F.; Yu, S.-H. Free-Standing Copper

Nanowire Network Current Collector for Improving Lithium Anode Performance. Nano Lett. 2016, 16, 4431-4437. 20. Newman, J.; Tiedemann, W. Porous-Electrode Theory with Battery Applications. AIChE Journal 1975, 21, 25-41. 21. Jin, Y.; Chen, F. Facile Preparation of Ag-Cu Bifunctional Electrocatalysts for Zinc-Air Batteries. Electrochimi. Acta 2015, 158, 437-445. 22. Ma, H.; Wang, B.; Fan, Y.; Hong, W. Development and Characterization of an Electrically Rechargeable Zinc-Air Battery Stack. Energies 2014, 7, 6549-6557. 23. Wood, K. N.; Kazyak, E.; Chadwick, A. F.; Chen, K.-H.; Zhang, J.-G.; Thornton, K.; Dasgupta, N. P. Dendrites and Pits: Untangling the Complex Behavior of Lithium Metal Anodes through Operando Video Microscopy. ACS Central Sci. 2016, 2, 790-801. 24. Schmid, M.; Willert-Porada, M. Electrochemical Behavior of Zinc Particles with Silica Based Coatings as Anode Material for Zinc Air Batteries with Improved Discharge Capacity. J. Power Sources 2017, 351, 115-122. 25. Wang, X.; Wang, F.; Wang, L.; Li, M.; Wang, Y.; Chen, B.; Zhu, Y.; Fu, L.; Zha, L.; Zhang, L.; Wu, Y.; Huang, W. An Aqueous Rechargeable Zn//Co3O4 Battery with High Energy Density and Good Cycling Behavior. Adv. Mater. 2016, 28, 4904-4911. 26. Drillet, J.-F.; Adam, M.; Barg, S.; Herter, A.; Koch, D.; Schmidt, V.; Wilhelm, M. Development of a Novel Zinc/Air Fuel Cell with a Zn Foam Anode, a PVA/KOH Membrane and a MnO2/SiOC-Based Air Cathode. ECS Transactions 2010, 28, 13-24. 27. Tan, P.; Chen, B.; Xu, H.; Cai, W.; He, W.; Liu, M.; Shao, Z.; Ni, M. Co3O4 Nanosheets as Active Material for Hybrid Zn Batteries. Small 2018, 14, 1800225. 28. Xue, P.; Liu, S.; Shi, X.; Sun, C.; Lai, C.; Zhou, Y.; Sui, D.; Chen, Y.; Liang, J. A Hierarchical Silver-Nanowire-Graphene Host Enabling Ultrahigh Rates and Superior Long-Term Cycling of Lithium-Metal Composite Anodes. Adv. Mater. 2018, 30, 1804165. 29. Zhang, R.; Chen, X.-R.; Chen, X.; Cheng, X.-B.; Zhang, X.-Q.; Yan, C.; Zhang, Q. Lithiophilic Sites in Doped Graphene Guide Uniform Lithium Nucleation for Dendrite-Free Lithium Metal Anodes. Angew. Chem. Int. Edit. 2017, 129, 7872-7876. 30. Chamoun, M.; Hertzberg, B. J.; Gupta, T.; Davies, D.; Bhadra, S.; Tassell, B. V.; Erdonmez, C.; Steingart, D. A. Hyper-Dendritic Nanoporous Zinc Foam Anodes. NPG Asia Mater. 2015, 7, e178. 31. Zhang, Y.; Wang, C.; Pastel, G.; Kuang, Y.; Xie, H.; Li, Y.; Liu, B.; Luo, W.; Chen, C.; Hu, L. 3D Wettable Framework for Dendrite-Free Alkali Metal Anodes. Adv. Energy Mater. 2018, 8, 1800635. 32. Thomas, S.; Cole, I. S.; Sridhar, M.; Birbilis, N. Revisiting Zinc Passivation in Alkaline Solutions. Electrochim. Acta 2013, 97, 192-201. 33. Zhang, S.; Xu, K.; Jow, TR. EIS study on the formation of solid electrolyte interface in Li-ion battery. Electrochim. Acta 2006, 51, 1636-1640. 34. Gan, L.; Guo, H.; Wang, Z.; Li, X.; Peng, W.; Wang, J.; Huang, S.; Su, M. A facile synthesis of graphite/silicon/graphene spherical composite anode for lithium-ion batteries. Electrochim. Acta 2013,


Page 22 of 34

Page 23 of 34 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


104, 117-123.




Page 24 of 34

Page 25 of 34 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Scheme. 1 Schematic of the synthesis process for Ag-modified 3D Zn anode. The 3D anode is synthesized by two-step deposition method, and the precursor solution was mixed Ag2SO4 with KSCN and ZnSO4 with KCl, respectively.



Fig. 1 SEM images of (a) bare Cu foam and (b) Ag-modified Cu foam. (c) EDS spectra of Ag-modified Cu foam. (d) XRD patterns of bare Cu foam (black) and Ag-modified Cu foam (red).


Page 26 of 34

Page 27 of 34 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Fig. 2 The electrochemical performances of Ag-modified 3D substrate. (a) Tafel plots of different 3D metal foam substrates (electrolyte: N2 saturated 6 mol L-1 KOH, scan rate: 10 mV s-1). The corrosion current density reflects corrosion degree when applied for zinc electrode. (b) Linear sweep voltammograms of different metal substrates (electrolyte: N2 saturated 6 mol L-1 KOH, scan rate: 10 mV s-1). Large hydrogen evolution overpotential and low current density reflects less hydrogen evolution reactions when applied for zinc anode.



Fig.3 Cyclic voltammetry curves of Ag-modified zinc anode (a) at scan rates of 10, 20, 30, 40, 50 mV s-1 respectively and (b) in different cycles at scan rate of 20 mV s-1. The corresponding anodic and cathodic peak areas indicate the reversibility of Ag-modified zinc anode. (c) Cyclic voltammetry curves of unmodified zinc anode in different cycles at scan rate of 20 mV s-1. Cathodic peaks disappear at 5th cycle reflects poor reversibility of the unmodified zinc anode. (d) Cyclic voltammetry curves comparison of the two zinc anodes. Ag-modified zinc anode exhibits more positive anodic peak and cathodic peak.


Page 28 of 34

Page 29 of 34 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Fig.4 (a) Zinc utilization and (b) discharge specific capacities of primary zinc-air batteries with Ag-modified zinc anode (red) and unmodified zinc anode (blue), respectively. (c) Discharge specific capacities of zinc-air batteries with Ag-modified zinc anodes at different current densities. (d) The cell voltage and power density polarization curves of a primary zinc-air battery with unmodified zinc anode (black) and Ag-modified zinc anode (red) in 6 M KOH solution.



Fig. 5 The C-D polarization curves of the rechargeable zinc-air batteries with unmodified zinc anodes (black) and Ag-modified zinc anodes (red) in 6 M KOH with 0.2 M zinc acetate solution at (a) 5% DOD, (b) 10% DOD and (c) 20% DOD. (d) The C-D cycling performance for the rechargeable zinc-air battery with Ag-modified zinc anode at 2h cycle period. (e) Coulombic efficiency and discharge capacity of the rechargeable zinc-air battery with Ag-modified zinc anode at 2h cycle period. GCD current density is 25 mA cm−2.


Page 30 of 34

Page 31 of 34 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Fig. 6 SEM morphologies of the (a-c) unmodified zinc anode and (d-f) Ag-modified zinc anode in rechargeable zinc-air batteries after 40 cycles at different DOD under a current density of 25 mA cm−2.



Fig. 7 Electrochemical impedance spectra (EIS) of the (a) unmodified zinc anodes and (b) Ag-modified zinc anodes after different C-D cycles in rechargeable zinc-air batteries.


Page 32 of 34

Page 33 of 34 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Fig.8 GCD curves of two zinc-air batteries with Ag-modified zinc anodes connected in series (a) compared with a single battery and (b) at different cycles. Current density is 10mA cm-2. GCD curves of two zinc-air batteries connected in parallel (c) compared with a single battery and (d) at different cycles. Current density is 10mA cm-2. Coulombic efficiency and energy efficiency of two batteries connected (e) in series and (f) in parallel. Battery stacks both in series and parallel can achieve stable cycling performance over 40 cycles.



For Table of Contents Only


Page 34 of 34

Ag-Modified Cu Foams as Three-Dimensional Anodes for

Recommend Documents