Sorption-based atmospheric water harvesting (SAWH) is a promising technology to alleviate freshwater scarcity. Recently, hygroscopic salt-hydrogel composites (HSHCs) have emerged as attractive candidates with their high water uptake, versatile designability, and scale-up fabrication. However, achieving high-performance SAWH applications for HSHCs has been challenging because of their sluggish kinetics, attributed to their limited mass transport properties. Herein, a universal network engineering of hydrogels using a cryogelation method is presented, significantly improving the SAWH kinetics of HSHCs. As a result of the entangled mesh confinements formed during cryogelation, a stable macroporous topology is attained and maintained within the obtained entangled-mesh hydrogels (EMHs), leading to significantly enhanced mass transport properties compared to conventional dense hydrogels (CDHs). With it, corresponding hygroscopic EMHs (HEMHs) simultaneously exhibit faster moisture sorption and solar-driven water desorption. Consequently, a rapid-cycling HEMHs-based harvester delivers a practical freshwater production of 2.85 L water kg sorbents −1 day −1 via continuous eight sorption/desorption cycles, outperforming other state-of-the-art hydrogel-based sorbents. Significantly, the generalizability of this strategy is validated by extending it to other hydrogels used in HSHCs. Overall, this work offers a new approach to efficiently address long-standing challenges of sluggish kinetics in current HSHCs, promoting them toward the next-generation SAWH applications.
Jingteng Zhao,Shaobo Ma,Zhongqiang Wang,Qixin Gao,Huang Xiao,Jian Gao,Fang Li,Guoxing Li
The structures and properties of the electric double layer (EDL) on zinc (Zn) anodes significantly influence the cycling and rate performance of aqueous Zn batteries (ZBs). Here, a strategy is reported to regulate the EDL structure through work function ( W f ) engineering to effectively enhance the electrochemical performance of ZBs, which is enabled by electrolyte-tailored growth of heterogenous metal with a large W f on the Zn anode. The metal-to-metal charge transfer in heterostructured Zn metal induced by the disparity of W f increases the surface charge density, which enriches the Zn ions and shortens the thickness of EDL. The compressed EDL weakens the repulsive force of Zn deposits to achieve a tightly stacked and dendrite-free Zn deposition. Besides, the formed H 2 O-deficient EDL structure enables the inorganic-rich solid electrolyte interphase (SEI) with high Zn-ion conductivity to inhibit the notorious parasitic reactions and improve the electrode reaction kinetics. Consequently, the Zn||Zn symmetric cells demonstrate an ultra-long cycling life over 2700 cycles (the cumulative capacity reaches 5400 mA h cm −2 ) at a high current density of 50 mA cm −2 . The Zn anodes show a high average Coulombic efficiency of 99.70% over 3650 cycles. The Zn||MnO 2 full cells exhibit excellent practical-level performance under cyclic continuous mode (3000-cycle life at high rates) and cyclic intermittent mode (1170-cycle life with 83.05% capacity retention). Practical pouch cells are also demonstrated with outstanding cycling performance.
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