ABSTRACT
Ultrathin separators are indispensable to high-energy-density zinc-ion batteries (ZIBs), but their easy failure caused by zinc dendrites poses a great challenge. Herein, 23 µm-thick functional ultrathin separators (FUSs), realizing superb electrochemical stability of zinc anodes and outstanding long-term durability of ultrathin separators, are reported. In the FUSs, an ultrathin but mechanically strong nanoporous membrane substrate benefits fast and flux-homogenized Zn2+ transport, while a metal-organic framework (MOF)-derived C/Cu nanocomposite decoration layer provides rich low-barrier zinc nucleation sites, thereby synergistically stabilizing zinc anodes to inhibit zinc dendrites and dendrite-caused separator failure. Investigation of the zinc affinity of the MOF-derived C/Cu nanocomposites unravels the high zincophilicity of heteroatom-containing C/Cu interfaces. Zinc anodes coupled with the FUSs present superior electrochemical stability, whose operation lifetime exceeds 2000 h at 1 mA cm-2 and 600 h at 10 mA cm-2 , 40-50 times longer than that of the zinc anodes using glass-fiber separators. The reliability of the FUSs in ZIBs and zinc-ion hybrid supercapacitors is also validated. This work proposes a new strategy to stabilize zinc anodes and provides theoretical guidance in developing ultrathin separators for high-energy-density zinc-based energy storage.
ABSTRACT
Zn-based electrochemical energy storage (EES) systems are plagued by the uncontrollable generation of dendritic zinc and side reactions on zinc anodes. Herein, we report a ZnO porous sheets-assembled sieve-like interface to stabilize zinc anodes. Specifically, ZnO porous sheets are synthesized through the thermal decomposition of basic zinc sulfate nanoflakes and then served as an artificial zinc anode-electrolyte interface. Benefiting from the sieve-like interface formed by the ZnO porous sheets, Zn2+ flux is effectively homogenized during the zinc plating process and thus zinc dendrite growth is restricted. Meanwhile, the corrosion behavior of zinc anodes is alleviated thanks to the hydrophobic feature of the ZnO porous sheets. As a result, the electrochemical properties of zinc anodes are notably optimized under the protection of such a sieve-like interface. Cycling life evaluated at 1 mA cm-2 of the zinc anodes is prolonged from less than 100 h for bare zinc anodes to 2800 h for the protected zinc anodes (Zn@ZnO), and even at 5 mA cm-2, the latter ones can operate normally for 400 h. As expected, the cycling life of VO2//Zn@ZnO zinc-ion batteries is greatly increased, achieving 90% capacity retention after 1000 cycles at 5 A g-1 and activated carbon fiber//Zn@ZnO zinc-ion hybrid supercapacitors possess 96% capacity retention after 10,000 cycles at 1 A g-1. This work provides a promising approach for improving the electrochemical stability of the Zn-based EES system.
ABSTRACT
Mn-based cathodes have been widely explored for aqueous zinc-ion batteries (ZIBs), by virtue of their high theoretical capacity and low cost. However, Mn-based cathodes suffer from poor rate capability and cycling performance. Researchers have presented various approaches to address these issues. Therefore, these endeavors scattered in various directions (e. g., designing electrode structures, defect engineering and optimizing electrolytes) are necessary to be connected through a systematic review. Hence, we comprehensively overview Mn-based cathode materials for ZIBs from the aspects of phase compositions, electrochemical behaviors and energy storage mechanisms, and try to build internal relations between these factors. Modification strategies of Mn-based cathodes are then introduced. Furthermore, this review also provides some new perspectives on future efforts toward high-energy and long-life Mn-based cathodes for ZIBs.
ABSTRACT
Zn-based electrochemical energy storage (EES) systems have received tremendous attention in recent years, but their zinc anodes are seriously plagued by the issues of zinc dendrite and side reactions (e.g., corrosion and hydrogen evolution). Herein, we report a novel strategy of employing zincophilic Cu nanowire networks to stabilize zinc anodes from multiple aspects. According to experimental results, COMSOL simulation and density functional theory calculations, the Cu nanowire networks covering on zinc anode surface not only homogenize the surface electric field and Zn2+ concentration field, but also inhibit side reactions through their hydrophobic feature. Meanwhile, facets and edge sites of the Cu nanowires, especially the latter ones, are revealed to be highly zincophilic to induce uniform zinc nucleation/deposition. Consequently, the Cu nanowire networks-protected zinc anodes exhibit an ultralong cycle life of over 2800 h and also can continuously operate for hundreds of hours even at very large charge/discharge currents and areal capacities (e.g., 10 mA cm-2 and 5 mAh cm-2), remarkably superior to bare zinc anodes and most of currently reported zinc anodes, thereby enabling Zn-based EES devices to possess high capacity, 16,000-cycle lifespan and rapid charge/discharge ability. This work provides new thoughts to realize long-life and high-rate zinc anodes.
