Unlocking high-potential non-persistent radical chemistry for semi-aqueous redox batteries

Tian, Yuheng; Wu, Kuang‐Hsu; Cao, Liuyue; Saputera, Wibawa Hendra; Amal, Rose; Wang, Da‐Wei

doi:10.1039/c8cc09304k

Cited by 21 publications

(26 citation statements)

References 19 publications

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“…PINO tends to self-decompose rapidly in pure aqueous acid solution [150], so the NHPI redox couple is not reversible in this condition. A reversible NHPI positive electrode compound with the potential of +1.30 V (vs. SHE) was achieved in a semi-aqueous redox cell by Tian and coworkers [151]. A polymeric additive is required in such a system for stabilizing the formed micro-heterogenous electrolyte.…”

Section: N-o• Radicalsmentioning

confidence: 99%

Family Tree for Aqueous Organic Redox Couples for Redox Flow Battery Electrolytes: A Conceptual Review

2022

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Redox flow batteries (RFBs) are an increasingly attractive option for renewable energy storage, thus providing flexibility for the supply of electrical energy. In recent years, research in this type of battery storage has been shifted from metal-ion based electrolytes to soluble organic redox-active compounds. Aqueous-based organic electrolytes are considered as more promising electrolytes to achieve “green”, safe, and low-cost energy storage. Many organic compounds and their derivatives have recently been intensively examined for application to redox flow batteries. This work presents an up-to-date overview of the redox organic compound groups tested for application in aqueous RFB. In the initial part, the most relevant requirements for technical electrolytes are described and discussed. The importance of supporting electrolytes selection, the limits for the aqueous system, and potential synthetic strategies for redox molecules are highlighted. The different organic redox couples described in the literature are grouped in a “family tree” for organic redox couples. This article is designed to be an introduction to the field of organic redox flow batteries and aims to provide an overview of current achievements as well as helping synthetic chemists to understand the basic concepts of the technical requirements for next-generation energy storage materials.

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Section: N-o• Radicalsmentioning

confidence: 99%

Family Tree for Aqueous Organic Redox Couples for Redox Flow Battery Electrolytes: A Conceptual Review

2022

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“…Potential N-Oxyl Compounds Beyond TEMPO: Other classes of N-oxyl radicals, such as imidoxyl species (e.g., phthalimide N-oxyl, 3.2l, PINO), are also promising candidates for high potential catholytes for RFBs. PINO was first reported by Tian et al [121] in a semi-aqueous RFB based on an acidic wateracetonitrile (ACN) binary electrolyte. The redox potential of PINO was as high as 1.3 V SHE (500 mV higher than TEMPO) thanks to the higher OH bond strength of N-hydroxyimides (≈88 kcal mol −1 for N-hydroxyphthalimide (NHPI)) relative to hydroxylamines (≈69-71 kcal mol −1 for TEMPO).…”

Section: Challenges and Mitigation Strategiesmentioning

confidence: 99%

“…PINO was first reported by Tian et al. [ 121 ] in a semi‐aqueous RFB based on an acidic water–acetonitrile (ACN) binary electrolyte. The redox potential of PINO was as high as 1.3 V SHE (500 mV higher than TEMPO) thanks to the higher OH bond strength of N ‐hydroxyimides (≈88 kcal mol −1 for N ‐hydroxyphthalimide (NHPI)) relative to hydroxylamines (≈69–71 kcal mol −1 for TEMPO).…”

Section: Aqueous Organic Redox Flow Batteries (Aorfbs)mentioning

confidence: 99%

Material Design of Aqueous Redox Flow Batteries: Fundamental Challenges and Mitigation Strategies

2020

Advanced Materials

172

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redox flow systems to date. [7] However, their high chemical cost (V 2 O 5 , $24 kg −1) and low energy density (E d < 50 Wh L −1 , normalized based on both side of the electrolytes, unless specified otherwise) limit their wide implementation for large-scale grid storage. To boost the energy density of RFBs, nonaqueous RFBs with a wider potential window were developed. However, nonaqueous RFBs face intrinsic challenges such as high cost, flammability, and low ionic conductivity of organic electrolytes. [8] Here, we review recent developments of advanced materials for electrolyte design in ARFBs. We further classified ARFBs based on the type of active material: inorganic ARFBs (i.e., AIRFBs, including vanadium-, zinc-, iron-, polysulfide-based, and two other emerging systems); and organic ARFBs (i.e., AORFBs, including viologen-, 2,2,6,6-tetramethylpiperidine-N-oxyl (TEMPO)-, quinone-, and N-centered heteroaromatic-mole culebased systems). We first summarize the fundamental physicochemical properties of redox couples in each ARFB system and then discuss critical challenges and mitigation design strategies to shed light on the design guidelines for future RFBs. Finally, assessment methodologies and metrics for evaluating battery stability among different ARFBs are discussed. 2. Aqueous Inorganic Redox Flow Batteries (AIRFBs) 2.1. Vanadium-Based AIRFBs 2.1.1. Fundamental Physicochemical Properties All-vanadium redox flow batteries (VRFBs, Figure 1a) are the most developed and widely used RFB system to date. Applying a vanadium element with diverse valence states (i.e., +2, +3, +4, and +5) effectively minimizes cross contamination, facilitates electrolyte regeneration, and provides long-term durability (Figure 1b-e). For example, a 200 MW/800 MWh system has been under construction by Dalian Rongke Power since 2016. [9] The reversible cell voltage of a VRFB is 1.26 V. The nominal cell voltage of VRFBs ranges from 1.15 to 1.55 V in acidic electrolytes, since the catholyte potential is pH-dependent. [10] The redox reactions on both sides are shown in the cyclic voltammetry (CV) analysis in Figure 1f. [11] Redox flow batteries (RFBs) are critical enablers for next-generation grid-scale energy-storage systems, due to their scalability and flexibility in decoupling power and energy. Aqueous RFBs (ARFBs) using nonflammable electrolytes are intrinsically safe. However, their development has been limited by their low energy density and high cost. Developing ARFBs with higher energy density, lower cost, and longer lifespan than the current standard is of significant interest to academic and industrial research communities. Here, a critical review of the latest progress on advanced electrolyte material designs of ARFBs is presented, including a fundamental overview of their physicochemical properties, major challenges, and design strategies. Assessment methodologies and metrics for the evaluation of RFB stability are discussed. Finally, future directions for material design to realize practical applications and achieve the comme...

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“…Initially, deprotonation of N-hydroxyphthalimide 2 under the action of pyridine gives anion A, the anodic oxidation of which leads to the formation of phthalimide-N-oxyl radical (PINO). [36,38] Subsequently, PINO adds to the terminal carbon atom of double C=C bond of vinyl azide 1 a with the elimination of N 2 molecule and formation of iminyl radical B. [20] At the last stage recombination of B and PINO radicals occurs giving final product 3 a.…”

Section: Full Papermentioning

confidence: 99%

Electrochemical Synthesis of O‐Phthalimide Oximes from α‐Azido Styrenes via Radical Sequence: Generation, Addition and Recombination of Imide‐N‐Oxyl and Iminyl Radicals with C−O/N−O Bonds Formation

et al. 2020

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Electrochemically induced radical‐initiated reaction of vinyl azides with N‐hydroxyphthalimide resulting O‐phthalimide oximes with challenging for organic chemistry N−O‐N fragment has been discovered. The developed approach introduces in synthesis electrochemically generated O‐centered imide‐N‐oxyl radicals as the coupling components. Sequential formation of C−O and N−O bonds was achieved via generation and selective addition of imide‐N‐oxyl radicals, followed by recombination with iminyl radicals. A wide range of O‐phthalimide oximes was obtained with the yields up to 84%.

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Unlocking high-potential non-persistent radical chemistry for semi-aqueous redox batteries

Abstract: Stabilizing non-persistent radical opens the gate to low-cost high-potential cathode for all-organic aqueous redox batteries with fast reversible rate capability.

Cited by 21 publications

References 19 publications

Family Tree for Aqueous Organic Redox Couples for Redox Flow Battery Electrolytes: A Conceptual Review

Family Tree for Aqueous Organic Redox Couples for Redox Flow Battery Electrolytes: A Conceptual Review

Material Design of Aqueous Redox Flow Batteries: Fundamental Challenges and Mitigation Strategies

Electrochemical Synthesis of O‐Phthalimide Oximes from α‐Azido Styrenes via Radical Sequence: Generation, Addition and Recombination of Imide‐N‐Oxyl and Iminyl Radicals with C−O/N−O Bonds Formation

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