Rechargeable zinc-aqueous batteries (RAZBs) are intrinsically safe, cost-effective and environmentally friendly, making them promising in energy storage systems. However, undesirable dendrite and corrosion side reactions are exacerbated during cycling, which limits the reversibility and scalable application of RAZB. This problem stems from the adverse side reaction of zinc corrosion in conventional aqueous electrolytes, which leads to the formation of by-products, uneven zinc nucleation, and eventually the formation of dendrites. To address these issues, researchers have employed a variety of methods, such as artificial electrode/electrolyte interface design, electrolyte engineering, external magnetic field conditioning, and structural design of zinc anodes or current collectors. Despite various successful reports, a versatile additive that not only reduces zinc corrosion and inhibits dendrites, but also reduces polarization has yet to be developed to complement previous research.
In order to solve the above problems, the team of Wan Jiayu of Southern University of Science and Technology and Han Jiajia of Xiamen University recently introduced the method of using nitritrinetriacetic acid (NTA) as an effective electrolyte additive, and conducted experimental and computational studies on its effect and mechanism. NTA is widely used in the metal contamination treatment and corrosion protection industries due to its ability to form strong coordination bonds with metals (ions) and its biodegradable properties. The authors demonstrated that only trace amounts of NTA (0.15 wt%) as an electrolyte additive can efficiently form the anode/electrolyte interface, resulting in excellent electrochemical performance. In the aqueous electrolyte with NTA added, the corrosion reaction rate of the zinc anode was reduced by 93.9%, while the polarization voltage of the zinc deposits was unexpectedly significantly reduced. This symmetrical cell exhibits stable electrochemical performance for 2100 hours in deposition/peel cycles at high current density (5 mA cm-2), much longer than Zn||| using common ZnSO4 electrolytesZn symmetrical battery (46 hours). The authors' study provides a simple and effective method for improving the reversibility and stability of zinc metal anodes by introducing a stable interfacial chemical reaction between NTA and zinc anodes. The authors hope that the understanding of this mechanism can become one of the guiding principles for future rechargeable battery electrolyte innovation.
【Points】
This work reports a highly effective functional additive, nitritriacetic acid (NTA), which can be preferentially adsorbed on the surface of zinc, avoid direct contact between zinc and water molecules, and significantly reduce corrosion. This clean, protected zinc surface promotes uniform zinc deposition/peeling. In addition, the adsorbed NTA molecules can also attract water molecules, promote the desolvation of Zn2+, and promote the rapid transport of Zn2+, which has been verified in experiments and calculations. Notably, the authors found that only a trace amount of NTA (0.15 wt%) was sufficient to form a stable electrode/electrolyte interface, reducing the corrosion rate from 3.63 mA cm-2 to only 0.22 mA cm-2. This stable interface enables symmetrical cells to undergo highly reversible zinc peeling/deposition at 5 mA cm-2 and 0.5 mAh cm-2 for approximately 2100 hours. In addition, an excellent average coulomb efficiency of 99.40% was achieved in 800 cycles. This research provides new insights into the realization of highly reversible zinc anodes for RAZB by adding highly efficient, multifunctional electrolyte additives, the design principles of which can be generalized to many rechargeable battery systems.
Figure 1.Schematic diagram and experimental results of NTA on zinc anode. Schematic of electrochemical galvanizing on a zinc electrode in (a) a typical ZnSO4 electrolyte (NTA-free) and (b) a ZnSO4 electrolyte with NTA added. (c) pH plot of 2M ZnSO4 electrolyte and 2M ZnSO4 + 0.01M NTA electrolyte. SEM image after three days immersion of Zn foil surface in (c) 2M ZnSO4 electrolyte and (e) 2M ZnSO4 + 0.01M NTA electrolyte. (f) XRD results after three days of immersion of Zn foil in an aqueous electrolyte without NTA and with NTA added. EDS plot of Zn surface after electrolyte immersion with NTA: (g) whole, (h) C, (i) N, and (j) O element distribution results.
Figure 2.Adsorption characteristics of NTA on Zn and its mechanism. (a) Raman spectra of raw Zn electrodes, NTA powder, and Zn electrode after rapid treatment in NTA-added electrolyte. (b) Zn||Electrochemical impedance spectroscopy (EIS) results of Zn symmetrical cells after 90 min in 2M ZnSO4 or 2M ZnSO4 + 0.01M NTA electrolyte. (c) Zn||Linear polarization curves of Zn symmetrical cells in 2M ZnSO4 and 2M ZnSO4 + 0.01M NTA electrolytes. (c) The adsorption energy of NTA on the surface of Zn has two configurations, namely L-Zn-NTA and S-Zn-NTA. (e) Adsorption energy of H2O on L-Zn-NTA, S-Zn-NTA and Zn, respectively. (f) High-resolution XPS spectra of C1s plated with Zn with NTA's electrolyte. (g) High-resolution XPS spectra of (g) Zn 2p3/2 and (h) O1s after deposition of Zn from the electrolyte added with NTA.
Figure 3.Characteristics and testing of zinc surfaces after galvanizing with two different electrolytes. (a). Zn||, with/without NTAThe Cu cell measures a representative voltage curve of CE at 1mAcm-2. The inset is an enlarged image of the voltage curve showing the overpotential difference of the test electrolyte. (b) CE and nucleation overpotential averages for ZnSO4, ZnSO4 + NTA. (c) Photo of Zn electrode after deposition of 10 mAh cm-2 Zn metal in 2M ZnSO4 electrolyte and 2M ZnSO4 +0.01M NTA electrolyte. (c) XRD analysis after deposition of fresh zinc metal and zinc anode in 2M ZnSO4 electrolyte and 2M ZnSO4 + 0.01M NTA electrolyte. Scanning electron microscopy image of Zn electrode after deposition of 10 mAh cm-2 Zn metal in 2M ZnSO4 electrolyte (e) and 2M ZnSO4 +0.01M NTA electrolyte (f).
Figure 4.Zinc||Zinc symmetrical batteries and zinc ||Performance of copper half-cell. (a) Zn|| with 2M ZnSO4 electrolyte or 2M ZnSO4 +0.01M NTA electrolyteCycling performance of Zn symmetrical cells at 5 mA cm-2 and 0.5 mAh cm-2; (b) Cycling performance at 10 mA cm-2 and 2 mAh cm-2. (c) Rate performance at 1/2/5/10/20/1 mA cm-2. (c) Zn|| with 2M ZnSO4 electrolyte or 2M ZnSO4 +0.01M NTA electrolyteCE of Cu batteries at 1 mA cm-2 and 1 mAh cm-2. (e) Zn||| with 2M ZnSO4 electrolyte or 2M ZnSO4 +0.01M NTA electrolyte at 2 mA cm-2 and 2 mAh cm-2CE for Cu batteries. (f) Zn|| using two different electrolytesAverage CE of a Cu cell after deposition once and standing for 0/24/48/72 hours. (g) Comparison chart of cycle reversibility of this study with previously reported.
Figure 5.DFT calculation of Zn diffusion and deposition process on metal Zn surface (a) The diffusion energy barrier of a single deposited Zn on the L-NTA-Zn, S-NTA-Zn, and Zn surfaces, where the x-axis represents the diffusion of Zn in the direction of the green arrow. b-d) In the three cases of L-NTA-Zn, S-NTA-Zn and Zn surfaces, when Zn ions gradually accumulate from 1 to 4, the atomic configuration of Zn ions and the corresponding adsorption energy. The dotted box shows the spontaneous transition of the four Zn ions from the dendrite structure to a monolayer tiled configuration.
Figure 6.Full battery performance. (a). Rate performance and (b) corresponding capacity retention of Zn-MnO2 cells using two different electrolytes. Cycling performance of Zn-MnO2 cells at (c) 5 mA cm-2 and (c) 10 mA cm-2. (e) NTA-Zn||Photo of MnO2 pouch battery at different bending angles.
【Conclusion】
In conclusion, the authors investigated NTA, a multifunctional electrolyte additive, which has a very limited amount (0.15 wt%) added to the aqueous electrolyte, but can bring excellent reversibility and stability to zinc metal batteries. This NTA additive has the following advantages: (1) NTA molecules can be firmly adsorbed on the surface of metal Zn, inhibiting the direct contact between Zn and water molecules, thereby significantly reducing the adverse corrosion of Zn to water; (2) The NTA-rich Zn surface can accelerate the migration of Zn2+ by attracting water molecules to preferentially desolvate Zn2+ ions when they shuttle through the NTA adsorption layer; (3) The NTA coated Zn surface can adjust Zn deposition, and Zn2+ tends to be deposited on the Zn surface, so that the free energy of the system is minimized, so that the Zn deposition is more uniform and the formation of dendrites is inhibited. Both experiments and DFT calculations confirm these advantages. Symmetrical cell polarization with NTA as an additive is relatively low (approximately 49 mV) compared to the control group, with an ultra-long lifetime of more than 2100 hours at 5 mA cm-2. After up to 810 cycles, zinc||The CE of copper batteries (with NTA added) is still as high as 99.61%. The assembled NTA-Zn || MnO2 batteries exhibit better cycling stability at 5mA cm-2 cycles 900 times. This study proposes a scalable, low-cost, and easy-to-use method to achieve high-performance zinc metal anodes, which will help develop long-cycle, practical RAZBs.
https://doi.org/10.1016/j.ensm.2023.102980
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