Aqueous Solution‐Processable Small Molecular Metal‐Chelate Complex Electrolyte for Flexible All‐Solid State Energy Storage Devices

Abstract

solar cells (OSCs), organic thin fi lm transistors (OTFTs), organic memory devices (OMDs), etc. [4][5][6][7][8] Interestingly, liquid or gel-type electrolytes have been still used for sophisticated energy storage devices including batteries and capacitors, [9][10][11][12][13][14] even though a couple of inorganic solid-state electrolytes such as thio-LISICON (Li 3.25 Ge 0.25 P 0.75 S 4 ), Li 2 NaPO 4 (nalipoite structure), and a-60Li 2 S·40SiS 2 have been developed. [15][16][17] Here we note that such inorganic electrolytes cannot be used for fl exible devices because of their intrinsic brittleness. In the case of liquid electrolytes such as aqueous solutions, [ 18,19 ] organic solutions, [ 20,21 ] and ionic liquids, [ 22,23 ] there are essential limitations for miniaturizing devices because of tricky sealing processes to avoid leakage of electrolyte solutions that are normally toxic and corrosive.Compared to the liquid electrolytes, gel-type electrolytes deliver improved processability but they do still contain liquid components so that they bear potential disadvantages as liquid electrolytes do. To date, most reports claiming "solid-state electrolytes" have employed gel-type electrolytes such as proton conducting polymer gel electrolytes, [24][25][26] lithium ion gel polymer electrolytes, [27][28][29] and alkaline gel polymer electrolytes. [30][31][32] Hence a perfect solid-state electrolyte without including any liquid components should be developed to achieve real ultrathin/ fl exible devices in the coming fl exible electronics era. In addition, the perfect solid-state electrolyte is required to have solution processability using water as a solvent in consideration of environmental issue for using toxic solvents in the conventional fabrication processes. In particular, a well-defi ned small molecular electrolyte, which is of course highly reproducible in the large scale synthesis, is practically desirable for device miniaturization toward a nanoscale energy storage device that needs only few molecules in the thickness direction of the electrolyte nanolayers.In this work, we attempted to design a small molecular metal-chelate complex that has three sulfonic acid groups per molecule in order to maximize solubility in water and secure proton ions for energy storage. Taking into account easy synthesis for possible mass production, one-step synthesis protocol was adopted on the basis of condensation reaction between aluminum triisopropoxide (AltiP) and 8-hydroxyquinoline-5-sulfonic acid (HQSA). The resulting metal-chelate A small molecular metal-chelate complex, tris(8-hydroxyquinoline-5-sulfonic acid) aluminum (AlQSA 3 ), that has three sulfonic acid groups per molecule leading to an excellent solubility in water is reported as a liquid-free perfect solid-state electrolyte for fl exible fi lm-type all-solid-state energy storage devices. The AlQSA 3 material is synthesized by one-step reaction of aluminum triisopropoxide and 8-hydroxyquinoline-5-sulfonic acid. The aqueous solutions of AlQSA 3 are applied to fabric...

Strong Photo-Amplification Effects in Flexible Organic Capacitors with Small Molecular Solid-State Electrolyte Layers Sandwiched between Photo-Sensitive Conjugated Polymer Nanolayers

“…The solid-state electrolyte material, tris(8-hydroxyquinoline-5-sulfonic acid) aluminum (ALQSA 3 ), was synthesized with higher yield (>90%) by improving the previously reported method 28 . In brief, aluminum triisopropoxide (AltiP, 0.61 g, Sigma-Aldrich) and 8-hydroxyquinoline-5-sulfonic acid (HQSA, 2.03 g, Sigma-Aldrich) were mixed and dissolved in solvent (N,N-dimethylacetamide, 10 ml, Sigma-Aldrich).…”

“…Very recently, all-solid-state organic capacitors have been reported by introducing a sold-state electrolyte of organic-metal chelate complex, tris(8-hydroxyquinoline-5-sulfonic acid) aluminum (ALQSA 3 ), which can be coated from aqueous solutions 28 . In particular, the transparent conducting oxide (TCO)-coated plastic film substrates with high optical transparency could be used for the fabrication of such all-solid-state organic capacitors.…”

Bulk‐Heterojunction Organic Solar Cells: Five Core Technologies for Their Commercialization

“…In the following sections, we will introduce various IFL materials and their impact and working mechanisms within OSCs. Although many studies have found a variety of promising IFL materials, including metal carbonates, self‐assembled monolayers, conjugated molecules, organic electrolytes, metal oxides, and combinations thereof, we will focus on some selected IFL materials that are cost‐effective and that can be simply deposited via solution processing at low temperature, so that they are highly applicable to roll‐to‐roll processing on flexible plastic substrates. Meanwhile, the effects of the IFLs on the device stability will be discussed in detail in Section .…”

Layer Structured Materials for Advanced Energy Storage and Conversion

“…Therefore, it is of great importance to develop high performance conformable electrolytes with fast ionic transportation, superior mechanical properties, and more importantly, excellent adhesion properties bonding strongly to the electrodes . In addition, liquid‐free perfect solid‐state electrolytes should also be introduced to meet the specific requirements in the coming flexible devices' era …”