Graphene-Boosted, High-Performance Aqueous Zn-Ion Battery - ACS

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Graphene-Boosted, High-Performance Aqueous Zn-ion Battery Chao Shen, Xin Li, Nan Li, Keyu Xie, Jian-Gan Wang, Xing-Rui Liu, and Bingqing Wei ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.8b07781 • Publication Date (Web): 06 Jul 2018 Downloaded from http://pubs.acs.org on July 9, 2018

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ACS Applied Materials & Interfaces

Graphene-Boosted, High-Performance Aqueous Zn-ion Battery

Chao Shen,† Xin Li,† Nan Li,† Keyu Xie,*,† Jian-gan Wang,† Xingrui Liu,† and Bingqing Wei *,†,‡

†

State Key Laboratory of Solidification Processing, Center for Nano Energy Materials,

School of Materials Science and Engineering, Northwestern Polytechnical University and Shaanxi Joint Laboratory of Graphene (NPU), Xi’an 710072, China. ‡

Department of Mechanical Engineering, University of Delaware, Newark, DE19716,

USA.

ACS Paragon Plus Environment

ACS Applied Materials & Interfaces 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: Given their low cost and eco-friendliness, rechargeable Zn-ion batteries (ZIBs) have received increasing attention as a device with great potential for large-scale energy storage. However, the development of ZIBs with high capacities and long lifespans is challenging due to the dendritic growth of Zn and absence of suitable cathode materials. Herein, we report a novel rechargeable aqueous Zn-ion battery (AZIB) that consist of Zn coated with reduced graphene oxide as the anode and V3O7·H2O/rGO composite as the cathode. The new AZIB exhibits excellent cycle stability with a high capacity retention of 79% after 1000 cycles. Moreover, it can deliver a high power density of 8400 W kg-1 at 77 Wh kg-1 and a high energy density of 186 Wh kg-1 at 216 W kg-1, and the former is higher than those of previously reported AZIBs. Our work provides a new perspective in developing rechargeable ZIBs and would greatly accelerate the practical applications of rechargeable ZIBs.

KEYWORDS: Zn/rGO, V3O7·H2O/rGO, dendrite-free, graphene, Zn-ion battery


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1. INTRODUCTION The pursuit of large-scale energy storage technologies that are high performing, low cost, safe, and eco-friendly has become increasingly urgent in recent years.1-3 However, today’s commercial batteries, including traditional lead-acid batteries and Li-ion batteries (LIBs), are unable to satisfy the large-scale and long-term energy storage requirements for the future. The lead-acid battery is a low-cost aqueous-based energy storage system, but it has low energy density and a short lifetime (usually < 500 cycles).4 Moreover, the use of lead usually causes significant environmental concerns.5,6 Meanwhile, LIBs have a high energy density but are expensive.7-9 Thus, an alternative high-performance and low-cost energy storage system is highly desired.10 In recent years, rechargeable batteries, especially aqueous rechargeable batteries based on multivalent metal anodes, such as Zn, Mg, and Al, have received much attention. Among them, the Zn anode is the most suitable for practical application in an aqueous system for the following three merits.11,12 First, compared with other multivalent metals as an anode in aqueous battery systems, Zn has a relatively low redox potential (–0.76 V versus standard hydrogen electrode) and a high capacity (5,854 mAh cm-3 and 820 mAh g-1).13-16 Second, due to the relatively high overpotential for hydrogen evolution, Zn exhibits excellent stability in water, indicating a large voltage window (∼2 V) for aqueous Zn-ion batteries (AZIBs).17,18 Finally, Zn is chemically stable in air and non-flammable compared with other high-energy density metals, such as Li and Mg.19 Considering its large capacity, high stability in aqueous electrolytes, low cost, eco-friendliness, and easy processing, AZIBs are a promising alternative for large-scale energy storage applications. However, the extensive researches of AZIBs suffer from dendritic Zn growth and



absence of suitable cathode materials. Similar to the dendrite growth problem in Li-metal batteries, the suppression of dendrite growth on Zn metal anodes is also a great challenge in creating AZIBs. During the repeated charge and discharge processes, metal Zn dissolves into the electrolyte at discharge and deposits on the anode at a charge, resulting in the redistribution of Zn.20 The unavoidable growth of Zn dendrites is mainly formed on the Zn anode during these processes, shortening the cycle life as well as causing internal short circuits and safety concerns. To conquer this challenge, two major strategies have been proposed. One is developing new battery structures, such as the backside-plating configuration.21 By changing the dendrite-growth location from the “frontside” to the “backside” of the Zn anode, the internal shorting is avoided.21 The other method is to design novel structured anodes, such as a 3D Zn oxide or a porous Zn sponge, to confine the dendrites within their internal porous structure.22-24 Despite all this progress, dendrite growth still exists during the electrochemical process and hinders the long lifetime of ZIBs. Therefore, further exploring dendrite-free Zn anodes for practical application is of great importance. Furthermore, the development of AZIB technology has also lagged far behind other multivalent metal-based batteries due to the lack of suitable cathode materials, although the uses of MnO2, Prussian blue, Na3V2(PO4)3, and LiV3O8 have been explored.25-28 MnO2, which is the most common cathode material for ZIB, owns excellent properties in theory but poor cycle stability in practice.25 Prussian blue possesses preferable rate performance due to its large internal space, but its application is limited by its small specific capacity (about 50 mAh g-1).26 By contrast, the intrinsic low electronic conductivity of Na3V2(PO4)3 and LiV3O8 limits their rate performance.27,28 Hence, searching other suitable cathode materials is still critical for


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the realization of AZIBs. Unavoidable dendrite growth in the anode and the lack of suitable cathode materials are two of the major obstacles that seriously hinder the development of AZIBs at the current stage.29,30 Herein, we propose a novel AZIB in which Zn coated with reduced graphene oxide (Zn/rGO) and V3O7·H2O/rGO composites (V3O7·H2O/rGO) are used as the anode and the cathode, respectively, to conquer these two challenges (Figure 1). In this new system, the rGO can restrain the dendrite growth of Zn, while V3O7·H2O offers high specific capacity and rGO enhances rate capability. The growth of Zn dendrites is efficiently controlled and thus, a dendrite-free Zn anode can be obtained even at a high current density. This new AZIB shows a high specific power density of 8400 W kg-1 at 77 Wh kg-1 and an energy density of 186 Wh kg-1 at 216 W kg-1, which are higher than those of previously reported AZIBs.25-28,31-36 Meanwhile, the battery also shows long-term cycle stability (> 79% within the initial 1000 cycles). This novel Zn/rGO||V3O7·H2O/rGO battery system outperforms existing rechargeable batteries and shows great potential for large-scale energy storage applications.

Figure 1. Schematic of the Zn/rGO||V3O7·H2O/rGO battery system in ZnSO4 aqueous solution. The right illustration shows the basic structural unit of VxOy and the crystal



water of V3O7·H2O.

2. EXPERIMENTAL 2.1. Materials Highly uniform V3O7·H2O/rGO nanobelts were prepared using a hydrothermal method. In this procedure, 280 mg of V2O5 and 70 mg of GO were added to 35 mL of deionized water and magnetically stirred at room temperature for 12 h. The mixture was ultrasonically treated until a symmetrical solution was obtained. The solution was transferred to a polytetrafluoroethylene equipment liner and then heated at 190 ℃ for 12 h. After cooling to room temperature, the as-synthesized material was washed with distilled water three times and then dried via a vacuum drying method at room temperature. 2.2. Preparation of the Zn/rGO composite The Zn/rGO composite was synthesized as previously described.40 A 2 mg mL-1 GO aqueous solution was confected, and then Zn foil was soaked in the as-prepared solution for 10 min, followed by cleansing with deionized water three times and drying at room temperature. 2.3. Material Characterization X-ray diffraction (XRD) measurement was performed using a Bruker D8 advance diffractometer with Cu-Kα radiation (λ=1.5418 Å) from 10° to 70° (2θ). Scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS) mappings were recorded with a field-emission scanning electron microscope (FE-SEM, LEO 1530) equipped with an Oxford INCA x-sight EDS Si(Zn) detector at an acceleration


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voltage of 200 kV. Furthermore, a JEM 2100F (field emission) scanning transmission electron microscope was employed for transmission electron microscopy (TEM). 2.4. Fabrication of Electrodes The V3O7·H2O/rGO nanobelts electrode was prepared by mixing the as-synthesized nanobelts, nanocarbon Super P, and polyvinylidene fluoride at a weight ratio of 7:2:1 in N-methyl pyrrolidone solvent to form a homogeneous slurry. The slurry was coated onto aluminum foil with a thickness of 150 µm. After being dried at 120 ℃ for 24 h in a vacuum oven, the electrode was then punched into circular discs with a diameter of 12 mm. After drying, the cathode was 160 µm thick (Al foil is about 10 µm), and the average weight of the active material was 5.8 mg. The Zn or Zn/rGO anodes were punched into circular discs with a diameter of 16 mm and a thickness of about 110 µm. The SEM and elemental mapping images of both negative electrodes are shown in Figure S1. 2.5. Electrochemical Measurements Two ZIBs were assembled using V3O7·H2O/rGO nanobelts electrode as the cathode, glass fiber as the separator, Zn/rGO or Zn electrode as the anode, and 1 M ZnSO4 aqueous solution (pH 4–7) as the electrolyte in CR2032 coin cells in an air environment. Meanwhile, two symmetric batteries were prepared using Zn/rGO or Zn as both the cathode and anode respectively, and other conditions were the same as those for the ZIBs. All batteries were tested on a CT2001A cell test instrument (LAND Electronic Co, BT2013A, China) for electrochemical testing at the voltage range of 0.3 V to 1.5 V versus Zn2+/Zn. For electrochemical property measurements, 300 mA g-1 was defined as 1C rate after theoretical calculation, and for symmetry battery testings, the Zn deposition capacity was set at 2.0 mAh cm-2. Cyclic



voltammetry (CV) was performed in a three-electrode cell using polished Zn wire as the reference and the counter electrodes, and a V3O7·H2O/rGO disk as the working electrode. A Solartron electrochemical workstation (1260+1287) was employed for electrochemical impedance spectrometry in the frequency range of 100 kHz to 10 mHz.

Figure 2. Comparison of the cycling stability of Zn/rGO||Zn/rGO and Zn||Zn symmetric cells at a current density of (a) 1 mA cm-2, (b) 2 mA cm-2, (c) 5 mA cm-2,


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and (d) 10 mA cm-2. (e-h) Top-view SEM images of Zn/rGO and bare Zn electrodes after cycles at different current densities. Voltage profile of (i) bare Zn and (j) Zn/rGO symmetric cells at different current densities. (k) Nyquist plots of the impedance spectra of Zn/rGO||Zn/rGO and Zn||Zn symmetric cells after cycles at a current density of 1 mA cm-2. 3. RESULTS AND DISCUSSION Graphene with excellent mechanical properties was expected to suppress dendrite growth in Zn anodes. Hence, the Zn/rGO electrodes were first prepared (See Experimental Section and Figure S1). Symmetric 2032 cells were assembled to compare

the

stripping/plating

processes

of

Zn/rGO

and

Zn

electrodes.

Electrochemical performances of the two symmetric cells at different current densities are shown in Figure 2. The rGO layer on top of Zn significantly decreased the overpotential between plating and stripping curves (Figure 2i, j). The voltage variations are shown in Figure 2a–d. At a low current density, such as 1 mA cm-2 or 2 mA cm-2, both cells exhibited relatively good cycling stability within 200 cycles. However, when cycled at a high current density of 10 mA cm-2, the Zn/rGO cell held less change (∼140 mV in the several initial cycles and ∼170 mV for the 200th cycle) than the Zn cell (∼330 mV in the initial cycles and ∼480 mV for the 200th cycle). The formation of dendrites after cycles is displayed in the SEM images (Figure 2e–h). Obvious dendrite growth was observed on the bare Zn electrode after cycles, and the dendrites grew sharper with increasing current density. By contrast, dendrite growth was not observed for the Zn/rGO electrode even at a high current density of 10 mA cm-2. To further prove the conclusion, the ex-situ SEM observations were conducted after certain stripping and plating cycles of Zn2+ at 2 mA cm-2. Here, the state of the



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initial charging state is set to state I, the state of discharging for 30 minutes as state II, the state of discharging over as state III, the state of charging for 30 minutes as state IV, and the state of charging over as state V. The SEM images of Zn or Zn/rGO at different state also describe the dendrite-growth/dissolution and dendrite-free phenomenon, respectively (Figure S4). For the Zn/rGO electrode, the rGO layer is always close to the Zn metal surface during the charging/discharging process, restraining

the

dendrite

formation.

In

comparison,

an

obvious

dendrite-growth/dissolution process is shown for the Zn electrode. The rGO layer was still close to the Zn electrode after numerous cycles (Figure 2h). The surface composition of Zn/rGO after numerous cycles is also displayed in the elemental mapping (Figure S2), and element Zn mostly existed in the form of ZnSO4 residue in the electrolyte. Compared with the Zn||Zn symmetric cells, the Zn/rGO||Zn/rGO symmetric cells hold smaller impedance after different cycles, and it appears the less increase of impedance with cycles for the Zn/rGO||Zn/rGO symmetric cells (Figure S3 and Figure 2k). The introduction of the rGO layer decreased the interface resistance as shown in the Nyquist plots of the symmetric cells, due to that the Zn/rGO can effectively inhibit the Zn dendrite formation and avoid low conductive “dead-Zinc” by enabling a uniform charge distribution and providing fast and effective electron transfer channels.29 As for the cathode material, highly uniform V3O7·H2O/rGO composites were prepared via a hydrothermal method. The XRD pattern reveals that all characteristic peaks of the as-prepared samples can be readily indexed to the standard card of V3O7·H2O (JPCDS No. 01-085-2401) (Figure 3a), indicating that the as-synthesized material is crystalline. The morphology and microstructures of the as-prepared V3O7·H2O/rGO were investigated by SEM coupled with EDS and TEM. A unique


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nanobelt morphology is shown in Figure 3b, being tens of micrometers in length and 100–200 nm in width. TEM and corresponding high-resolution TEM (HRTEM) images in Figure 3c–e show the V3O7·H2O/rGO nanobelts with a d-spacing of ≈0.370 nm, which corresponds to the (310) plane of V3O7·H2O. The EDS elemental mappings indicate that vanadium, oxygen, and carbon are distributed along with the nanobelts (Figure 3f–i). Moreover, the HRTEM images and the elemental mappings also demonstrated that the V3O7·H2O nanobelts were well combined with rGO.

Figure 3. (a) X-ray diffraction data of V3O7·H2O/rGO. (b) SEM image of V3O7·H2O/rGO nanobelts. (c) Typical diffraction pattern and (d) the representative TEM image of a single nanoribbon, revealing a width of 100–200 nm. (e) Lattice-resolved HRTEM image (from the region highlighted in (d)). (f) SEM image and corresponding elemental mapping of (g) carbon, (h) oxygen, and (i) vanadium. Both Zn/rGO||V3O7·H2O/rGO and Zn||V3O7·H2O/rGO coin batteries were prepared and tested. In consideration of the water decomposition reaction, a voltage window of 0.3~1.5 V versus Zn was chosen for all the tests. The Zn/rGO||V3O7·H2O/rGO battery



can conduct a reversible and durable reaction, which can be proven from the CV curve (Figure S5a). The electrochemical performance of the Zn/rGO||V3O7·H2O/rGO battery is shown in Figure 4, illustrating its great advantages over the control Zn||V3O7·H2O/rGO battery. The cyclic performance of the Zn/rGO||V3O7·H2O/rGO battery was tested at a current density of 1500 mA g-1, and it showed a high initial discharge specific capacity of 245 mAh g-1 (Figure 4a). After 1000 cycles, the discharge specific capacity reduced to 202 mAh g-1 (∼79% of the value in the first cycle). Meanwhile, the Coulombic efficiency maintained over 95% in all cycles. For the control Zn||V3O7·H2O/rGO battery, the discharge specific capacity was 240 mAh g-1 in the initial cycle but decreased to only 141 mAh g-1 (∼59% of the value in the first cycle) in the 1000th cycle (Figure S6a). The charge and discharge curves at different cycles for the Zn/rGO||V3O7·H2O/rGO battery are shown in Figure 4b. Notably, multiple cycles had a very small effect on the discharge plateaus, benefiting long-term energy storage. The Zn||V3O7·H2O/rGO battery only offered capacities of 267 mAh g-1 under 1 C, 240 mAh g-1 under 2 C, 218 mAh g-1 under 5 C, 185 mAh g-1 under 10 C, 161 mAh g-1 under 20 C, and 85 mAh g-1 under 40 C (Figure S6b). In comparison, the Zn/rGO||V3O7·H2O/rGO battery provided capacities of 271 mAh g-1 under 1 C, 253 mAh g-1 under 2 C, 229 mAh g-1 under 5 C, 209 mAh g-1 under 10 C, 186 mAh g-1 under 20 C, and 157 mAh g-1 under 40 C (Figure 4c). And a standard three-electrode system experiment was also tested at -0.25~1.0 V, with the V3O7·H2O/rGO acted as working electrode, Pt plate acted as a counter electrode, and the calomel electrode acted as a reference electrode. A remarkable rate performance of the V3O7·H2O/rGO was obtained with 263 mAh g-1, 224 mAh g-1, 197 mAh g-1, 178 mAh g-1 and 141


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mAh g-1 at 1C, 5 C, 10C, 20C and 40 C, respectively (Figure S7), which is similar to the value of the nanobelts measured in the Zn/rGO|| V3O7·H2O/rGO battery. Moreover, the discharge plateaus of the Zn/rGO||V3O7·H2O/rGO battery demonstrated only a slight decrease from 0.74 V to 0.70 V as the current density was increased (Figure S5b). Figure 4d shows that the new Zn/rGO||V3O7·H2O/rGO battery possessed a high specific power density of 8400 W kg-1 at 77 Wh kg-1 and energy density of 186 Wh kg-1 at 216 W kg-1 based on the cathode material, which are higher than those of previously reported AZIBs.25-28,31-36 In the present study, considering that all voltage profiles were slanted, we calculated the energy density by integrating the X-axis on the charge/discharge curve.

Figure 4. (a) Cycle capability and Coulombic efficiency for Zn/rGO||V3O7·H2O/rGO battery at a rate of 5 C (1 C=300 mA g-1) for 1000 cycles. (b) Corresponding charge and discharge plateaus change within 1000 cycles. (c) Rate capability at varying C rates and Coulombic efficiency for the Zn/rGO||V3O7·H2O/rGO battery. (d) Comparison of specific power and energy density with other AZIBs. Ex-situ XRD, ex-situ Raman, and X-ray photoelectron spectroscopy (XPS) were



applied to explore the storage mechanism of the Zn/rGO||V3O7·H2O/rGO systems. Figure 5b and c display the XRD patterns and Raman spectra of the V3O7·H2O/rGO electrode at different charge/discharge states of the second cycle. As shown in Figure 5a, reversible water intercalation into V3O7·H2O/rGO immersed when the material was in electrolyte/H2O,31,34,37,38 which resulted in differences in the XRD patterns and the Raman spectra with the original active material at state ℃ (Figure 3a and Figure S8). In detail, a reversible change for the plane (310) and the peak of 10.5° was observed in the XRD pattern during charge/discharge progress. Meanwhile, obvious changes in the main peaks at 138.9, 282.6, 403.5, 513.2 and 990.4 cm-1 occurred during the electrochemical processes. Moreover, when charged to 1.5 V, the peaks, whether in the XRD pattern or the Raman spectrum, returned to their original states, indicating a completely reversible structure evolution. The Zn 2p, V 2p, and O 1s core level spectra of the cathode in pristine, discharged, and charged states are shown in Figure 5d–i. The pristine electrode showed no Zn 2p, only V4+ (2p3/2: 516.8 eV) and V5+ (2p3/2: 517.8 eV).31,39 Upon discharge, a Zn 2p component (2p3/2: 1,022.82 eV)31 appeared due to the active Zn2+ site in V3O7·H2O/rGO, and a new V3+ (2p3/2: 515.8 eV)31,39 feature arose. During the charging process, V5+ increased and V3+ decreased. However, Zn 2p and V3+ components still existed even when charged to 1.5 V, indicating that some Zn remained in the cathode, as shown in Figure 5a. The mechanism of the Zn/rGO||V3O7·H2O/rGO system is illustrated in Figure 5a. A reversible water intercalation into V3O7·H2O/rGO immersed firstly, and then during the first discharge progress, Zn2+ ions were intercalated into the layers of V3O7·H2O/rGO. In the following electrochemical processes, some Zn remained in the cathode, and the others can proceed to the reversible reaction.


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Figure 5. (a) Mechanism of the Zn/rGO||V3O7·H2O/rGO system, where x > y, n > k > m. (b) Ex-situ XRD and (c) ex-situ Raman measurements of the positive electrode during the second cycle. (d, f, h) Zn 2p region of the XPS spectra, (e, g, i) V 2p and O 1s regions of the XPS spectra. (d, e) pristine material, (f, g) discharged electrode, (h, i), and charged electrode. In the fitted XPS spectra: black dot, experimental data; black line, overall fitted data; other color lines, fitted individual components (in the V 2p region, V3+ is blue, V4+ is red, and V5+ is olive green).



Figure 6. (a) Schematic of the Zn/rGO||V3O7·H2O/rGO battery with the perforated separator. (b) Cycle performance of the Zn/rGO||V3O7·H2O/rGO battery and Zn||V3O7·H2O/rGO battery with a perforated separator at a rate of 5 C (1 C=300 mA g-1). SEM images of (c) the bare Zn and (d) Zn/rGO electrodes before and after cycles. The scale of the embedded picture is 10 µm.


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To accelerate dendrite growth progress, we assembled two specially designed 2032 coin batteries with perforated separators, as shown in Figure 6a. The batteries used the same electrodes and electrolyte as the Zn/rGO||V3O7·H2O/rGO battery discussed above, except separators were holed in the center. The performance comparison of the two “special” batteries is illustrated in Figure 6b. The new Zn/rGO||V3O7·H2O/rGO battery with the perforated separator can be charged/discharged for more than 1000 cycles at a rate of 5 C, whereas the Zn/rGO||V3O7·H2O/rGO battery with no separators suffered short circuit at the 155th cycle due to dendrite growth. After cycles, both batteries were dissembled, and the negative electrodes were rechecked by SEM (Figure 6c, d). The Zn/rGO surface was still dense and smooth without discernible dendrite growth, whereas the Zn metal surface was rough with obvious dendrites. The SEM images at the right side of Figure 6d illustrate that the graphene layer on the Zn/rGO surface was still uniform even after numerous cycles, which can explain why the new battery achieved a longer cycle lifetime and better electrochemical performance compared with the original battery.

4. Conclusion To conquer the two major challenges of ZIBs (the unavoidable dendrite growth of the Zn anode and the lack of suitable intercalation in cathode materials) for their commercialization, we designed and developed an aqueous Zn/rGO||V3O7·H2O/rGO battery for the first time. Remarkably, unlike the traditional bare Zn electrode, the new Zn/rGO electrode can work steadily and efficiently within 1000 cycles. As a result,



compared with the Zn||V3O7·H2O/rGO battery, the Zn/rGO||V3O7·H2O/rGO battery realized longer-term cyclic stability (capacity retention ratio was 79% after 1000 cycles) and better rate performance. Moreover, a power density of 8400 W kg-1 at 77 Wh kg-1 was achieved, which is higher than those of previously reported ZIBs. This novel battery system has promising practical applications in the future.

ASSOCIATED CONTENT Supporting Information The Supporting Information is available free of charge on the ACS Publications website at DOI: xxxxxxx. SEM images of Zn and Zn/rGO electrode before test and the corresponding elemental mapping of Zn/rGO electrode; the top-view SEM images and corresponding elemental mappings of Zn/rGO anode after cycles; electrochemical performances of Zn/rGO ||V3O7·H2O/rGO battery and Zn||V3O7·H2O/rGO battery; Raman spectra of V3O7·H2O/rGO.

AUTHOR INFORMATION Corresponding Authors *Email: [email protected] *Email: [email protected]


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Author Contributions †C. S. and X. L. contributed equally. The manuscript was written through contributions of all authors. All authors have approved the final version of the manuscript. Notes The authors declare no competing financial interest.

Acknowledgments The authors acknowledge the financial support from the National Natural Science Foundation of China (51674202, 51402236, and 51521061), the Fundamental Research Funds for the Central Universities (3102017HQZZ007), and the Key R&D Program of Shaanxi (2017ZDCXL-GY-08-03).

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Graphene-Boosted, High-Performance Aqueous Zn-Ion Battery - ACS

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