Flexible High‐Energy Polymer‐Electrolyte‐Based Rechargeable Zinc–Air Batteries

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electronic insulator with abundant oxygen-containing groups (epoxy, hydroxyl, and carboxyl groups), which can be easily functionalized to improve its ionic conductivity. [12,16] Owing to the wide range of oxygen functional groups on its basal planes and edges, GO is also readily exfoliated to yield well-dispersed solution of individual GO sheets in both water and organic solvents, and then flow-directed assembled into a free-standing paper-like material by vacuum filtration. [12,17] However, despite all the progress of the development of a free-standing GO electrolyte membrane, its advantages are diminished with the difficulty to form a mechanically robust membrane. [17,18] Consequently, that makes the free-standing GO membranes less attractive for being used as practical solid-state electrolytes in energy storage systems. To enhance the mechanical strength, several fillers can be incorporated into GO matrix. Among the multifarious materials, cellulose-the most abundant renewable material-is recognized as a good binder and surface modifier thanks to its low cost, high hygroscopicity, flexibility, ad porous substrate that allows strong binding of other materials. Particularly, considerable interest has been directed to nanocellulose fiber because of its low thermal expansion, high surface area, high surface area-to-volume ratio, strengthening effect, good mechanical and optical properties which may find many applications in nanocomposites. [19] Meanwhile, due to its highly reactive area rich in hydroxyl groups, cellulose can be easily refashioned through a surface-functionalization to conduct ions and be utilized in advanced batteries. [7] Herein, for the first time, we report on a laminate-structured nanocellulose/GO membrane functionalized with highly hydroxide-conductive quaternary ammonium (QA) groups to be applied as a robust solid-state electrolyte in flexible, rechargeable zinc-air batteries. The QA-functionalized nanocellulose/GO (QAFCGO) membrane is fabricated through chemical functionalization, layer-by-layer filtration, cross-linking, and ion-exchange processes (Figure 1a). For the functionalization process, dimethyloctadecyl [3-(trimethoxysilyl)-propyl] ammonium chloride (DMAOP) has been selected as the functional precursor containing QA moieties. The hydroxide conductivity and the alkaline stability in the highly surface-active DMAOP are provided by quaternary ammonium groups which are already attached to this organic compound. Thus, the hydroxide conducting characteristic of the electrolyte membrane can be achieved directly through the precursor DMAOP without complex organic synthesis. First, the trimethoxy groups of trimethoxysilyl are hydrolyzed to form the corresponding silanols, and the hydrolyzed silanols undergo self-condensation to yield silanol oligomers intermediates ( Figure S1, step 1, Supporting Information). Then, these intermediates are adsorbed onto nanocellulose/GO surface rich in oxygen-containing groups through hydrogen bonding ( Figure S1,

Section: Doi: 101002/aenm201600476mentioning

confidence: 99%

Section: Doi: 101002/aenm201600476mentioning

confidence: 99%

Laminated Cross‐Linked Nanocellulose/Graphene Oxide Electrolyte for Flexible Rechargeable Zinc–Air Batteries

Zhang

Song

et al. 2016

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“…[1][2][3][4][5] In addition, the process of assembling zinc-air battery does not require water-free and/or oxygenfree environment, which is in favor of scaling up at low cost. [2,[13][14][15][16][17] However, the PVA-based electrolyte possesses very poor stretchability (even worse when alkaline electrolyte infiltrated), and meanwhile it shows limited ion-transport capability, resulting in poorly electrochemical performance and mechanical flexibility. [11,12] On the other hand, most super-stretchable hydrogels that are considered as an essential component of a stretchable energy storage device will lose their stretchability under such strong alkaline environment.…”

mentioning

confidence: 99%

Super‐Stretchable Zinc–Air Batteries Based on an Alkaline‐Tolerant Dual‐Network Hydrogel Electrolyte

Chen

Wang

et al. 2019

311

296

remains a challenge. Meanwhile, zincair battery provides a theoretical energy density up to 1086 Wh•kg −1 , even much higher than commercial lithium-ion batteries, promising to next-generation longlasting power system. [1][2][3][4][5] In addition, the process of assembling zinc-air battery does not require water-free and/or oxygenfree environment, which is in favor of scaling up at low cost. [6][7][8][9][10] Therefore, developing stretchable zinc-air batteries with stretchability and weavability will be highly attractive as a power unit for various flexible/wearable devices.The difficulty to develop super-stretchable zinc-air battery is that it must use strong alkaline electrolyte (always 6 m KOH) to achieve decent power density considering all zinc-air batteries with neutral electrolyte possess unacceptable low power output. [11,12] On the other hand, most super-stretchable hydrogels that are considered as an essential component of a stretchable energy storage device will lose their stretchability under such strong alkaline environment. Currently, a zincair battery is typically assembled using polyvinyl alcohol (PVA)-based electrolyte. [2,[13][14][15][16][17] However, the PVA-based electrolyte possesses very poor stretchability (even worse when alkaline electrolyte infiltrated), and meanwhile it shows limited ion-transport capability, resulting in poorly electrochemical performance and mechanical flexibility. [18][19][20][21] Although other hydrogels, such as polyacrylic acid (PAA), polyacrylamide (PAM), show strong water-retention capability and high stretchability, [22,23] unfortunately, they will lose their mechanical robustness, especially the stretchability, when they are incorporated with strong alkaline electrolyte. [24][25][26] Therefore, the absence of alkaline-tolerant hydrogel electrolyte with high stretchability and excellent ion transport capability is the key challenge to fabricate super-stretchable zinc-air battery and enhance its weavability. An alternative way to fabricate stretchable zinc-air battery (very limited stretchability with a maximum strain less than 10%) has been proposed, that is to use electron/ion-inactive stretchable substrate (e.g., rubber elastomer) or strain-accommodating engineering of device structure (e.g., fiber-shaped planar structure). [27][28][29] The problem is that the stretchable components are additional, and they are not involved in any chemical reactions. In some cases, Stretchable devices need elastic hydrogel electrolyte as an essential component, while most hydrogels will lose their stretchability after being incorporated with strong alkaline solution. This is why highly stretchable zinc-air batteries have never been reported so far. Herein, super-stretchable, flat-(800% stretchable) and fiber-shaped (500% stretchable) zinc-air batteries are first developed by designing an alkaline-tolerant dual-network hydrogel electrolyte. In the dualnetwork hydrogel electrolyte, sodium polyacrylate (PANa) chains contribute to the formation of soft domains and the carboxyl gr...

“…Such batteries are freed from the constraints of rigidity and weight that characterize current portable batteries. [9][10][11][12][13][14][15] Companies working in rechargeable, polymer Zn-MnO 2 batteries have demonstrated that this new zinc secondary battery chemistry is well suited to a broad range of features for flexible electronics at reduced cost. To provide a power source for these applications, flexible batteries delivering a high volumetric energy density are particularly desirable because there is often a limited volume for integrating the batteries into these applications.…”

Section: Introductionmentioning

confidence: 99%

Recent Advances in Flexible Zinc‐Based Rechargeable Batteries

Zhong

et al. 2018

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date, there have been commercial efforts to manufacture lithium thin film batteries (<1 mm in thickness) being flexible and suitable for use in card-type and wearable devices. [3] However, these thin and flexible lithium-ion batteries have typically exhibited far less volumetric energy densities (<200 Wh L −1 ) than those of conventional lithium-ion batteries (<650 Wh L −1 ). [4] This performance roll-off is largely due to the fact that high barrier encapsulation of air and moisture sensitive lithium battery materials can severely impact the effective volumetric efficiency as the batteries are miniaturized. Therefore, high volumetric energy density lithium batteries with thickness <1 mm will be critical to enabling flexible electronics. [5] To this end, notable advancements have been made in the design of flexible lithium-sulfur and lithium-air batteries-those cathode chemistries enable high theoretical energy densities of 2800 and 6940 Wh L −1 , respectively-yet there remains substantial room for improvement. [6][7][8] The potential to yield high volumetric capacities by using less environmentally sensitive materials in the batteries sees zinc as an attractive anode alternative to lithium. In addition to the stability, zinc is likely to experience less cost pressure on raw material availability compared to lithium. In all cases, zinc secondary batteries represent a highly promising area of technology for Flexible Zn-based batteries are regarded as promising alternatives to flexible lithium-ion batteries for wearable electronics owing to the natural advantages of zinc, such as environmental friendliness and low cost. In the past few years, flexible Zn-based batteries have been studied intensively and exciting achievements have been obtained in this field. However, the development of flexible Zn-based batteries is still at an early stage. The challenges of developing flexible lithium-ion batteries are presented here. Then, a brief overview of recent progress in flexible zinc secondary batteries from the perspective of advanced materials and some issues that remain to be addressed are discussed.