Flexible Quasi‐Solid‐State Aqueous Zinc‐Ion Batteries: Design Principles, Functionalization Strategies, and Applications

Abstract

The commercial traditional energy storage devices such as lithium-ion batteries and sodium-ion batteries are bulk and stiff, which hardly meet the requirements of flexible and wearable electronics. [2] Thus, seeking the power sources with high safety, reliability, and flexibility is highly urgent. [3] Aqueous zinc-ion batteries (AZIBs) have attracted a lot of interests with the features of inherent safety, plentiful reserves, low standard redox potential of Zn/Zn 2+ of −0.76 V versus the standard hydrogen electrode (SHE), and facile fabrication process. [4] Besides, the mild or weak acid aqueous electrolytes deliver higher conductivity and safety than organic electrolytes, implying the favorable power density of AZIBs. [5] These virtues endow the AZIBs present marvelous potential application in flexible electronic devices, under a condition that the AZIBs possess excellent flexibility via adopting flexible current collector and flexible packaging materials. [6] However, when the flexible AZIBs based on liquid electrolyte undergo various mechanical deformations, the occurrence of electrolyte leakage may jeopardize the cyclic performance of the batteries. [7] Moreover, the aqueous liquid Aqueous zinc-ion batteries (AZIBs) may have applications in macroscale energy storage on account of their advantages of high-safety, cost-effectiveness, and ecofriendliness. As a promising application, flexible quasi-solidstate AZIBs (FQAZIBs) can withstand mechanical deformation, and can act as favorable power supply devices for wearable electronics. As FQAZIBs are one of the most exciting and rapidly ongoing topics among aqueous batteries, it is critical yet timely to summarize the latest development in this field, providing the much-needed guidance for the fabrication of FQAZIBs. In this review, the recent progress and rational design strategies for FQAZIBs from mechanisms, design principles, and applications are systematically presented. First, the energy storage and flexible mechanisms of FQAZIBs are illuminated in detail. Subsequently, the design philosophies of FQAZIBs are also systematically elucidated. Moreover, the latest progress and practical applications of FQAZIBs in wearable electronics are reviewed in detail according to various functions such as compressibility, stretchability, electrochromic ability, anti-freezing ability, self-healing ability, self-charging properties, photodetecting function, shape memory, biodegradability, and actuated function. Finally, some applications and promising prospects in the research area of FQAZIBs are demonstrated to supply guidelines on the exploitation of their practical applications.

Recent progress in structural modification of polymer gel electrolytes for use in solid-state zinc-ion batteries

“…36–38 Among the solid-state electrolytes, solid polymer electrolytes (SPEs) and gel polymer electrolytes (GPEs) have been recognized as promising electrolytes. 39 SPEs can effectively achieve dense and uniform Zn deposition because they dissolve zinc salts directly into polymer chains, which helps in inhibiting zinc dendrite formation. 40–43 However, there is a serious problem with SPEs, which is their high crystallinity that causes low ionic conductivity at room temperature, and the poor contact with the electrodes limits the application of SPEs.…”

Crystal water intercalated interlayer expanded MoS2 nanosheets as a cathode for efficient zinc-ion storage

“…Moreover, the poor ionic/electronic conductivity and low hydrophilicity of MoS 2 have also been a severe hindrance to its performance. 6,7 To surmount the abovementioned problems, researchers have adopted various modification strategies such as interlayer engineering for expanding lattices of MoS 2 , defect engineering by introducing S and Mo vacancies, phase engineering by controlling the 1T/2H content of MoS 2 and hybridization with other conductive materials. 4 By expanding the interlayer spacing of MoS 2 , one can facilitate the effective insertion of Zn 2+ ions and reduce ion diffusion resistance without lattice breathing.…”

“…Moreover, the poor ionic/electronic conductivity and low hydrophilicity of MoS 2 have also been a severe hindrance to its performance. 6,7…”

Low-Cost “Water-in-Salt” Hydrogel Electrolyte Enabled Flexible Supercapacitors with 2.7 V Voltage and −40 °C Adaptability

“…With the widespread use of portable and wearable energy storage devices, various aqueous energy storage devices have emerged. − Correspondingly, the development of electrolytes with stable electrochemical properties and mechanical safety is highly desired. Among various electrolytes, hydrogel electrolyte is one of the best choices for the characteristics of good safety, low cost, and environmental friendliness in the technical field of large-scale energy storage in the future.…”