Simultaneous Regulation on Solvation Shell and Electrode Interface for Dendrite‐Free Zn Ion Batteries Achieved by a Low‐Cost Glucose Additive

Abstract

Dendrite growth and by‐products in Zn metal aqueous batteries have impeded their development as promising energy storage devices. We utilize a low‐cost additive, glucose, to modulate the typical ZnSO4 electrolyte system for improving reversible plating/stripping on Zn anode for high‐performance Zn ion batteries (ZIBs). Combing experimental characterizations and theoretical calculations, we show that the glucose in ZnSO4 aqueous environment can simultaneously modulate solvation structure of Zn2+ and Zn anode‐electrolyte interface. The electrolyte engineering can alternate one H2O molecule from the primary Zn2+‐6H2O solvation shell and restraining side reactions due to the decomposition of active water. Concomitantly, glucose molecules are inclined to absorb on the surface of Zn anode, suppressing the random growth of Zn dendrite. As a proof of concept, a symmetric cell and Zn‐MnO2 full cell with glucose electrolyte achieve boosted stability than that with pure ZnSO4 electrolyte.

Manipulating Interfacial Stability Via Absorption-Competition Mechanism for Long-Lifespan Zn Anode

“…In pure ZnSO 4 electrolyte, under the testing condition of 1 mA cm −2 /1 mAh cm −2 and 2 mA cm −2 /2 mAh cm −2 , the symmetric cells encountered short circuit induced by developed Zn dendrite all at around 150 h. After the addition of the veratraldehyde additive, Zn–Zn cells can achieve a super-long cycling life of over 3200 h, 900 h under 1 mA cm −2 /1 mAh cm −2 , 2 mA cm −2 /2 mAh cm −2 , respectively, and great stability (over 800 h) even at a high current density/capacity of 5 mAcm −2 /5 mAh cm −2 , much better than that with pure ZnSO 4 electrolyte (54 h) and most of the previous work (Fig. 4 d) [ 12 , 14 , 20 , 23 , 32 , 33 , 35 , 50 , 51 ]. Moreover, the veratraldehyde also can ensure stable rate cycling performance in Zn–Zn cells (Fig.…”

“…MnO 2 was prepared on carbon cloth through electrodeposition method following our previous work [ 33 , 41 ]. Firstly, carbon cloth was washed with acetone, ethanol and deionized water each for 10 min under ultrasonic bath before the electrodeposition process.…”

“…The in-situ microscope images for Zn deposition process were obtained by commercial high-resolution camera (Mshot, MS60) equipped a magnifying glass holder, the same as our previous work [ 33 ]. The morphology of Zn foil before and after deposition or cycles were characterized by field-emission scanning electron microscopy (SEM, ZEISS ULTRA 55).…”

“…For instance, strategies like decorating protective layers/solid electrolyte interphase [ 10 – 19 ], selecting proper separators, constructing three-dimensional alloy structure or regulating crystal orientation could effectively control the Zn ion diffusion and deposition rate [ 18 , 20 – 27 ], while cut off the pathway of hydrogen evolution reaction (HER), random corrosion and by-products formation to some extent. Besides, another type of important methods focused mainly on designing the composition or state of the electrolyte to change the primary solvation shell constitution or the environment in Zn anode/electrolyte interface, achieving similar functions mentioned before, including introducing different solvent into pure water or small amount of additives [ 28 – 33 ], constructing highly concentrated “water in salt” structure and utilizing ionic liquid, eutectic liquid, hydrogels or solid-state electrolyte [ 34 – 38 ].…”

Strategies of regulating Zn2+solvation structures for dendrite-free and side reaction-suppressed zinc-ion batteries

“…53,54 It is well-known that there are two kinds of water molecules, namely, free water molecules and solvated water molecules in the aqueous electrolyte, 55–57 and the ratio of Zn 2+ to water is 1 : 56 in the commonly used ZnSO 4 electrolyte (2 mol L −1 ). Furthermore, Zn 2+ ions tend to form a close ion pair ([Zn(H 2 O) 6 ] 2+ ) with six free water molecules during the electrodeposition process, 58 which produces a great deal of active H 2 O molecules in the anode/electrolyte interface, thus leading to various side reactions. Generally, the active H 2 O molecules derived from solvated Zn 2+ are easy to be decomposed into H + and OH − , 3,59 and the accumulated H + ions tend to be reduced into H 2 by obtaining electrons from Zn and then escape from electrolytes, resulting in a serious HER effect and anode corrosion.…”