Integrated Bifunctional Oxygen Electrodes for Flexible Zinc–Air Batteries: From Electrode Designing to Wearable Energy Storage

Abstract

The global market of flexible/printed and organic electronics is about 41 billion dollars in 2020, which is expected to reach over 74 billion dollars in 2030 according to the relevant reports by IDTechEx. [3] As for the development and expansion toward practical application, flexible/wearable electronics urgently request for flexible energy sources and power devices with high specific energy density and long lifetime. During the past decade, a variety of flexible energy harvesting/conversion (e.g., solar cells, nanogenerators) and energy storage devices (e.g., batteries, supercapacitors, hybrid batteries) have dedicatedly progressed and gained ongoing recognition for future wearable applications. [4][5][6] Among those promising renewable energy technologies, rechargeable lithium-ion batteries (LIBs) have received widespread adoptions for power supplies ranging from mobile/portable electronics to plug-in/ hybrid electric vehicles because of their high working voltage, appreciable energy density, easy use, and ecofriendliness. [7] Flexible LIBs became one of the potential options for powering flexible electronics. With further advance, flexible LIBs are plagued by their limited energy density, deficient safety, and relatively high cost of electrode materials (e.g., lithium, cobalt). In this case, alternative battery technologies, especially metal-air batteries gain immense attention (Table 1). [8,9] Metal-air batteries (MABs) own 2-10 times higher specific energy than current LIBs (200-250 Wh kg −1 ) due to the direct utilization of oxygen from the atmosphere within a halfopen device system. Alongside, rechargeable MABs have more freedom in metallic anodes such as lithium, sodium, potassium, zinc, aluminum and magnesium, etc., where the latter three-based MABs are compatible with aqueous alkaline electrolytes and also intrigued numerous interest. [10][11][12] Given the high theoretical specific energy (1218 Wh kg −1 , 6136 Wh L −1 ), low fabrication cost, high operational safety and environmental benignancy, aqueous zinc-air batteries (ZABs) show far more practical prospect for new-generation energy storage sources. [11] Figure 1 illustrates the brief chronology of the development of ZABs. Dating back to 1878, the first The strong propulsion stem from flexible/wearable electronics has greatly stimulated the development of miniaturized and high-performance rechargeable batteries with adaptable shape. Flexible zinc-air batteries (FZABs), which exhibit high theoretical energy density (1218 Wh kg −1 ), low cost, environmental benignancy, and admirable operational safety, have been widely recognized as one of the promising portable powers to serve future wearable electronics for ubiquitous application. During the past five years, the energy/ power density and cycling stability of FZABs have gained significant improvement largely due to the rational construction of high-efficiency bifunctional air electrodes. Herein, the recent progress of integrated binder-free bifunctional oxygen electrodes is overviewed via elaborate ...

3D Binder‐free Integrated Electrodes Prepared by Phase Separation and Laser Induction (PSLI) Method for Oxygen Electrocatalysis and Zinc–Air Battery

“…On the contrary, these shortcomings can be easily mitigated through constructing integrated electrodes (IEs) which assemble catalysts with substrates directly without the use of binder. [12,13] Methods including electrospinning, hydrothermal synthesis and templating have been reported to fabricate IEs. [2,14,15] However, considerable time period and extra procedures are needed, leading to a cost-prohibitive process.…”

Synergistic Bimetallic CoCu‐Codecorated Carbon Nanosheet Arrays as Integrated Bifunctional Cathodes for High‐Performance Rechargeable/Flexible Zinc‐Air Batteries

“…The degradation of the flexible battery may be due to the inherent deficient water retention capacity and inferior mass transfer efficiency of the gel electrolyte, resulting in deteriorated ionic conductivity that seriously limits the long‐term cyclic performance of flexible ZABs. [ 61–63 ] Figure 5f shows the voltage curves of the flexible ZABs at various discharge currents from 2 to 50 mA cm −2 , where the voltage plateau of CoCu/N‐CNS‐2‐based flexible battery gradually drops from 1.34 to 1.13 V, respectively, manifesting excellent rate capabilities and high‐rate performance.…”

“…The degradation of the flexible battery may be due to the inherent deficient water retention capacity and inferior mass transfer efficiency of the gel electrolyte, resulting in deteriorated ionic conductivity that seriously limits the long-term cyclic performance of flexible ZABs. [61][62][63] Figure 5f shows the voltage curves of the flexible ZABs at various discharge currents from Furthermore, it is particularly noteworthy that flexible ZAB can steadily operate with stable discharge performance upon 90° bending and repeated bent cycling. Based on Figure 6d, the discharge voltage only attenuated by 72 mV compared to the initial voltage even after 1000 repetitions, which implies the long-term mechanical stability and prominent versatility of the flexible ZABs under a realistic deformation environment.…”

Advanced and Stable Metal-Free Electrocatalyst for Energy Storage and Conversion: The Structure–Effect Relationship of Heteroatoms in Carbon

“…29−32 (ii) G u o e t a l . 3 phosphazene (HCCP) has been favored by researchers because of its rich N and P elements. 34,35 In the past, HCCP was mostly used in antitumor drugs and flame-retardant cotton.…”

“…Rechargeable zinc–air batteries (ZABs) are a promising portable energy device due to their high energy density, high safety, and environmental friendliness, and the high theoretical specific energy of ZABs up to 1218 Wh kg –1 is far more than that of lithium–sulfur batteries. − However, it seriously hinders its overall performance due to the slow kinetic reaction of the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) that occurs at the cathode of ZABs; − therefore, the development of highly efficient ORR and OER catalysts is urgent. At present, precious metals (Pt, RuO 2 , etc.)…”