Organic Batteries Research Articles

Boosting anion-cation coordination by anti-solvents towards durable hydrous organic zinc batteries

Hydrated fluoroborates offer excellent nonflammability and their spontaneous hydrolysis can generate a ZnF2-based solid electrolyte interphase (SEI) on Zn anodes in hydrous organic Zn batteries. However, uncontrolled hydrolysis can lead to thick and uneven SEI, as well as cathode collapse. Here, we propose using anti-solvents to regulate the hydrolysis of fluoroborate anions via facilitating anion-cation coordination, resulting in a thin but compact ZnF2 SEI. Consequently, Zn anodes maintain stable cycling for over 1400 h at 1 mA cm−2, a high Coulombic efficiency (CE) of 99.4 % and high-rate capability up to 15 mA cm−2. Even at a challenging temperature of 60 °C, the Zn anode demonstrates over 1000 h of stable cycling with a CE of 98.0 %. Furthermore, the modified electrolyte alleviates V2O5 cathode dissolution, enabling extended cycling lifespan with a high CE close to 100 % in Zn||V2O5 full cells at room and high temperatures. Our findings suggest an avenue toward electrolyte design for developing high-performance Zn batteries and beyond.

Advanced rigid carbazole-based membranes assembled with flexible piperidine alkyl chains for neutral aqueous organic redox flow battery

Neutral aqueous organic redox flow battery (NAORFB) represents a highly promising energy storage device. However, one of its challenges is the need for high Cl− conductivity, highly stable ion-selective membranes. In this work, N-methylpiperidine-modified carbazole-based long side chain anion exchange membranes (QPCEP-x) were designed and prepared. The rigidity and hydrophobicity provided by the carbazole on the main chain, in conjunction with the flexibility and hydrophilicity provided by the alkyl-piperidine groups on the side chains, resulted in the observed excellent microphase separation properties of the prepared membranes. The prepared membranes exhibited excellent overall performance, with QPCEP-1 achieving a Cl− conductivity of 20.33 mS cm−1 at 25 °C. In NAORFB, the energy efficiency of QPCEP-1 ranges from 91.7 % to 62.4 % at 20–160 mA cm−2, far exceeding the 89.1 %–38.4 % of commercial AMVN. Furthermore, long-term cell cycling tests demonstrate that the energy efficiency of QPCEP-1 remains unchanged at 82.7 % at 60 mA cm−2 after 10,000 complete charge and discharge cycles, exceeding the majority of cycles reported in literatures. These findings suggest that QPCEP-x has significant potential for use in NAORFB.

Constructing Microporous Ion Exchange Membranes via Simple Hypercrosslinking for pH‐Neutral Aqueous Organic Redox Flow Batteries

AbstractIon exchange membranes (IEMs) play a critical role in aqueous organic redox flow batteries (AORFBs). Traditional IEMs that feature microphase‐separated microstructures are well‐developed and easily available but suffer from the conductivity/selectivity tradeoff. The emerging charged microporous polymer membranes show the potential to overcome this tradeoff, yet their commercialization is still hindered by tedious syntheses and demanding conditions. We herein combine the advantages of these two types of membrane materials via simple in situ hypercrosslinking of conventional IEMs into microporous ones. Such a concept is exemplified by the very cheap commercial quaternized polyphenylene oxide membrane. The hypercrosslinking treatment turns poor‐performance membranes into high‐performance ones, as demonstrated by the above 10‐fold selectivity enhancement and much‐improved conductivities that more than doubled. This turn is also confirmed by the effective and stable pH‐neutral AORFB with decreased membrane resistance and at least an order of magnitude lower capacity loss rate. This battery shows advantages over other reported AORFBs in terms of a low capacity loss rate (0.0017 % per cycle) at high current density. This work provides an economically feasible method for designing AORFB‐oriented membranes with microporosity.

Constructing Microporous Ion Exchange Membranes via Simple Hypercrosslinking for pH-Neutral Aqueous Organic Redox Flow Batteries.

Ion exchange membranes (IEMs) play a critical role in aqueous organic redox flow batteries (AORFBs). Traditional IEMs that feature microphase-separated microstructures are well-developed and easily available but suffer from the conductivity/selectivity tradeoff. The emerging charged microporous polymer membranes show the potential to overcome this tradeoff, yet their commercialization is still hindered by tedious syntheses and demanding conditions. We herein combine the advantages of these two types of membrane materials via simple in situ hypercrosslinking of conventional IEMs into microporous ones. Such a concept is exemplified by the very cheap commercial quaternized polyphenylene oxide membrane. The hypercrosslinking treatment turns poor-performance membranes into high-performance ones, as demonstrated by the above 10-fold selectivity enhancement and much-improved conductivities that more than doubled. This turn is also confirmed by the effective and stable pH-neutral AORFB with decreased membrane resistance and at least an order of magnitude lower capacity loss rate. This battery shows advantages over other reported AORFBs in terms of a low capacity loss rate (0.0017 % per cycle) at high current density. This work provides an economically feasible method for designing AORFB-oriented membranes with microporosity.

Multi-redox covalent organic frameworks for aluminium organic batteries

Aluminium ion batteries utilizing advanced organic electrode materials have attracted increasing attention in achieving the energy transition to net zero carbon emissions. Nevertheless, extensive studies have focused on structural innovations to enhance electrochemical performance while overlooking inherent constraints, such as frustrating aggregation and stacking, stemming from organic materials. These constraints result in compromised conductivity, sluggish charge storage kinetics, and suboptimal stabilities. Therefore, this study demonstrates a controlled nuclear-growth strategy for the landscaping of redox-active covalent organic frameworks (COFs) featuring multiple C=O and C=N groups. Theoretical simulation and ex-situ analysis were applied to uncover the pivotal roles of the C=O and C=N as active sites for the reversible storage of AlCl2+ ions. Employing an interfacial crystallization strategy, we further orchestrate the vertical stacked growth of COF on multiwall carbon nanotubes, which yields significant improvements in battery performance, including a high capacity of 150 mAh g−1 at 200 mA g−1, excellent rate capability, and an exceptional cycling lifespan of 140 mAh g−1 over 2400 cycles at 1 A g−1, along with 10,000 cycles exhibiting ∼100 % Coulombic efficiency at 2 A g−1. This study paves the way for a new avenue in achieving precise structural engineering of COF materials, promising considerable potential for energy storage applications.

Reactive strontium nitride Additive: Constructing ion/electronic conductive paths for garnet-based solid-state lithium metal batteries

Solid-state lithium metal batteries (SSLMBs) using the garnet electrolyte Li6.4La3Zr1.4Ta0.6O12 (LLZTO) offer high safety and energy density compared to liquid organic electrolyte lithium-ion batteries. However, the interfacial electrochemical stabilization of Li metal anode with LLZTO leads to problems such as high interfacial resistance and Li dendrite growth, which hinders the wide application of SSLMBs. In this work, a multifunctional Li-Sr-N composite anode by mixing molten Li with Sr3N2 is constructed, in which the reactive wetting of in situ-formed Li3N achieves intimate interfacial contact, and the ionic/electronic conductive paths created by Li-Sr alloys and Li3N effectively homogenise Li deposition and suppress Li dendrites. The interfacial resistance is reduced to 40.42 Ω cm2, and the symmetric cell is stably cycled for 5500 h and 600 h at current densities of 0.1mA cm−2 and 0.4 mA cm−2, respectively, and the full cell of Li-Sr-N|LLZTO|LiFePO4 could be stably cycled for 200 cycles at 0.5C. The preparation of composite anodes using Sr3N2 as an additive may be a new strategy for producing of garnet-based SSLMBs with outstanding energy density and safety performance.

Manipulation of Linked Phosphorus Chemistry to Enhance the Battery Performance of Phenazine‐Based Porous Polymers

AbstractOrganic p‐type cathodes have captured increasing attention for lithium‐organic batteries due to their high voltage output. However, because of the low electronic and ionic conductivity, the p‐type organic electrode materials often show sluggish reaction kinetics and hence low capacities and poor cyclability. In this work, three conjugated polymers (Pz‐TPPO, Pz‐TPPS, and Pz‐TPP) based on p‐type phenazine linked with triphenyl phosphine are reported with different chemical modifications of phosphorus atom. Through oxidation and sulfuration of phosphorus atoms, the electron‐accepting property strength is increased, resulting in higher electronic conductivity of Pz‐TPPO and Pz‐TPPS. It is also found that the P═O unit in Pz‐TPPO exhibits stronger Li+ coordination, which can bring anions into close proximity to the redox centers, further improving the anion shuttling during charge and discharge. All these lead to the best lithium‐organic battery performance of Pz‐TPPO, such as high voltage output (3.1–3.9 V), high reversible specific capacity (149 mAh g−1 at 0.2 A g−1) and excellent cycle stability. The potential application has also been demonstrated in Pz‐TPPO//graphite full battery. This work provides a novel strategy for designing donor–acceptor (D–A) conjugated polymer by simple phosphorus modification toward high‐performance organic batteries.

Assembling-induced redox property adjustment of Fe(III)/Fe(IV) electroredox couple-based commercial dye catholyte via bio-inspired multicoordination sphere construction strategy for stable aqueous redox flow batteries

Redox flow batteries (RFBs) are capable of storing and integrating indirect clean energy. This is due to their scalability, safety, and reliability, as well as their independent decoupling of power and energy. Aqueous organic redox flow batteries (AORFBs) have redox-active materials that are composed of abundant elements, have tunable redox potential, greater solubility, and lower cost. Here We propose the use of an inexpensive commercial dye, naphthol green B (NGB), as a catholyte material for AORFBs. This is the first time that NGB has been utilized in the Fe(III)/Fe(IV) electroredox couple, demonstrating a high redox potential of 0.73 V vs. NHE under neutral conditions. Experimental characterizations and theoretical simulations indicate that hydroxypropyl-β-cyclodextrin (HP-β-CD) can serve as the secondary and outer coordination sphere of NGB, enhancing its electrochemical performance and stability, while also preventing transmembrane crossover. In the NGB/K3Fe(CN)6 test with HP-β-CD symmetric battery, NGB demonstrated excellent electrochemical stability. When used as anolyte with 1,1′-bis(3-sulfonatopropyl)-4,4′-bipyridinium (Spr)2V, the NGB/(Spr)2V AORFB with HP-β-CD demonstrated exceptional cycling performance at current rates ranging from 5 to 30 mA cm−2. It is worth noting that the NGB/(Spr)2V AORFB maintained over 99 % of its total capacity or experienced less than 0.00125 % capacity decay per cycle, with an average Coulombic efficiency of almost 100 % over 800 cycles at 10 mA cm−2. NGB is a novel and superior catholyte that offers multiple options for studying AORFBs and the potential for large-scale energy storage applications.

High-efficiency metal-free CO2 mineralization battery using organic redox catalysts

CO2 batteries offer a promising avenue for mitigating CO2 emissions and conversion, but encounter challenges such as high costs, dendrite, corrosion, flooding and slow kinetics stemming from the use of metal electrodes. CO2 mineralization is thermodynamically favorable (ΔGCO2), presenting an opportunity for processing solid waste and reducing CO2 emissions while potentially producing energy. However, the lack of direct electron transfer in the CO2 mineralization reaction hinders the direct generation of electrical energy. Here, we propose an organic CO2 mineralization battery (OCMB) without using metal, which efficiently harnesses CO2 to mineralize solid waste carbide slag, maximizing the recovery of mineralization reaction energy to generate electricity and produce carbonate products, without requiring renewable electricity charging. We employ a high-solubility, stable under strong alkaline conditions, and fast kinetics organic phenazine derivative—DSPZ as the electron and proton carrier, which facilitates the conversion of ΔpH between electrodes by interacting with alkaline wastes and CO2 into electricity. Simultaneously, the OCMB undergoes regeneration cycles through mineralization reactions. The theoretical model predicted the open circuit voltage (OCV) and discharge behavior of OCMB, offering insights for improved battery engineering. We demonstrate an impressive peak power density exceeding 227.5 W/m2 for the OCMB, with an estimated electricity production of ∼ 178.03 kWh per ton of CO2 mineralization. This research underscores the potential integration of OCMBs into CO2 energy systems, waste treatment processes, and chemical production, offering both economic and environmental benefits.

Efficient in Situ One-Pot Synthesis of Water-Soluble Hydroxynaphthoquinones for Redox Flow Batteries.

Given the importance of energy storage and its hybridization with renewable technologies for the energy transition, the development of redox flow batteries (RFB) is receiving particular attention. Among the various emerging technologies, aqueous organic redox flow batteries (AORFBs) are of particular interest, as the objectives in terms of durability, cost, and safety can be achieved thanks to the possibilities offered by molecular engineering. While anthraquinones have been widely explored as negolytes, few works report the use of naphthoquinones. This work aims to exploit an innovative in situ and cost-effective method for the one-pot synthesis of water-soluble naphthoquinones for application as a negolyte in redox flow batteries. As exemplified with alizarin, the energy of the naphthoquinone synthetic reaction in fuel cell mode can be recovered and the electrolyte solution used directly in redox flow batteries without purification. A 0.3 M naphthoquinone solution paired with 0.6 M ferrocyanide demonstrated good stability compared with other naphthoquinones, with a capacity fade rate of 0.017%/cycle (0.84%/day) over 320 cycles. Additionally, the system exhibited one of the highest energy efficiencies (82%) and a power density of 80-105 mW cm-2 at 50% SOC. These first results are promising for further exploration of new water-soluble naphthoquinones efficiently synthesized from hydroxyanthraquinones for application in AORFBs.

Flexible Hydrogel Electrolytes for Organic Batteries with High Cyclability

Flexible Hydrogel Electrolytes for Organic Batteries with High Cyclability

Characteristics of all organic redox flow battery (AORFB) active species TEMPO-methyl viologen at different electrolyte solution

Characteristics of all organic redox flow battery (AORFB) active species TEMPO-methyl viologen at different electrolyte solution

Aqueous Redox Flow Cells Utilizing Verdazyl Cations enabled by Polybenzimidazole Membranes.

Non-aqueous organic redox flow batteries (RFB) utilizing verdazyl radicals are increasingly explored as energy storage technology. Verdazyl cations in RFBs with acidic aqueous electrolytes, however, have not been investigated yet. To advance the application in aqueous RFBs it is crucial to examine the interaction with the utilized membranes. Herein, the interactions between the 1,3,5-triphenylverdazyl cation and commercial Nafion 211 and self-casted polybenzimidazole (PBI) membranes are systematically investigated to improve the performance in RFBs. The impact of polymer backbones is studied by using mPBI and OPBI as well as different pre-treatments with KOH and H3PO4. Nafion 211 shows substantial absorption of the 1,3,5-triphenylverdazylium cation resulting in loss of conductivity. In contrast, mPBI and OPBI are chemically stable against the verdazylium cation without noticeable absorption. Pre-treatment with KOH leads to a significant increase in ionic conductivity as well as low absorption and permeation of the verdazylium cation. Symmetrical RFB cell tests on lab-scale highlight the beneficial impact of PBI membranes in terms of capacity retention and I-V curves over Nafion 211. With only 2 % d-1 capacity fading 1,3,5-triphenylverdazyl cations in acidic electrolytes with low-cost PBI based membranes exhibit a higher cycling stability compared to state-of-the-art batteries using verdazyl derivatives in non-aqueous electrolytes.

Development of Modular Nitrenium Bipolar Electrolytes for Possible Applications in Symmetric Redox Flow Batteries.

Amid the escalating integration of renewable energy sources, the demand for grid energy storage solutions, including non-aqueous organic redox flow batteries (oRFBs), has become ever more pronounced. oRFBs face a primary challenge of irreversible capacity loss attributed to the crossover of redox-active materials between half-cells. A possible solution for the crossover challenge involves utilization of bipolar electrolytes that act as both the catholyte and anolyte. Identifying such molecules poses several challenges as it requires a delicate balance between the stability of both oxidation states and energy density, which is influenced by the separation between the two redox events. We report the development of a diaminotriazolium redox-active core capable of producing two electronically distinct persistent radical species with typically extreme reduction potentials (E1/2red < -2 V, E1/2ox > +1 V, vs Fc0/+) and up to 3.55 V separation between the two redox events. Structure-property optimization studies allowed us to identify factors responsible for fine-tuning of potentials for both redox events, as well as separation between them. Mechanistic studies revealed two primary decomposition pathways for the neutral radical charged species and one for the radical biscation. Additionally, statistical modeling provided evidence for the molecular descriptors to allow identification of the structural features responsible for stability of radical species and to propose more stable analogues.

Structural engineering on indole derivative for rechargeable organic lithium-ion battery

Structural engineering on indole derivative for rechargeable organic lithium-ion battery

Fast-Charging Carbon Fiber Structural Battery Electrodes Using an Organic Polymer Active Material

Structural batteries require electrodes with integrated energy storage and load-bearing properties. Adoption of structural batteries can lead to mass and volume savings in electrified transportation and aerospace applications by storing energy within the object’s structural elements. However, to date, active materials investigated in structural batteries exhibit poor rate capabilities at higher C-rates and even worse performance at lower temperatures due to diffusion limitations. Organic radical polymers are promising alternatives because they possess fast-charging properties and good cycling stability. In this work, we integrate an organic radical polymer with carbon fiber (CF) fabric, in which the polymer acts as the active cathode material and the CF fabric possesses excellent tensile strength, modulus and electronic conductivity. At 20 °C, the structural cathodes exhibited a reversible capacity of 67 mAh g−1 at 1C-rate and an 88% capacity retention at 25C-rate. Further, these structural electrodes retained more than 50% of their performance at −10 °C (vs 20 °C). These electrodes were further examined in a full cell containing a graphite-based anode, demonstrating a pathway for utilizing redox-active polymer-based active materials in structural and fast-charging organic batteries.

Highly soluble and crossover-free all-organic redox pair using N-heterocycle-linked TEMPO and two-electron-capable bipyridinium towards high performance aqueous flow batteries

Aqueous organic redox flow batteries (AORFBs) are the brilliant technologies for safe and sustainable stationary energy storage. However, the cross-contamination, limited cell voltage, and inferior cycling stability remain challenges. Herein, the N-heterocycle-substituted TEMPO (TMP-TEMPO) and pyrrolidinium-/ammonium-grafted bipyridinium ([PyrTMAV]Cl4) redox pair with multiple charges are designed for high-performance AORFBs. The whole material preparation is relatively simple and only needs two or three synthetic steps. The TMP-TEMPO and [PyrTMAV]Cl4 show high aqueous solubility of 2.4 M and 1.71 M, respectively, excellent electrochemical reversibility, and fast redox kinetics. Notably, the introduction of multiple charges into the active materials can produce a strong Gibbs-Donnan effect with ion exchange membranes, thus preventing the permeability of molecules through the membrane and avoiding the cross-contamination of active molecules. By using the crossover-free TMP-TEMPO and two-electron [PyrTMAV]Cl4 redox pair, the assembled two-electron AORFBs at an electron concentration of 0.2 M exhibit stable battery performancein environments with O2 contents of both 10 ppm and 100 ppm with a capacity retention of over 99 % per day for hundreds of cycles (268 and 310 cycles), and a high energy efficiency of ∼89 % and Coulombic efficiency of ∼100 %. Furthermore, the AORFB achieves a high capacity of ∼37.4 Ah L−1 at an ultra-high electron concentration of 1.5 M, while maintaining a capacity retention rate of ∼99.7 % over 138 cycles and a theoretical capacity utilization rate of 93 %. The versatile molecular design for TMP-TEMPO and [PyrTMAV]Cl4 can be easily extended to the synthesis of various amino-functionalized TEMPO and asymmetric bipyridinium derivatives.

An Automatized Rebalancing System to Address Faradaic Imbalance and Prolong Cycle Life in Alkaline Ferrocyanide – Anthraquinone Redox Flow Batteries

AbstractAqueous Organic Redox Flow Batteries are a family of promising energy storage systems. However, they face various challenges related to their lifetime, such as the Faradaic imbalance due to the occurrence of parasitic reaction leading to the fading of its energy storage capacity. Herein, automatization of a rebalancing system to reverse the detrimental effects of Faradaic imbalance due to the unavoidable presence of small quantities of oxygen in the negative reservoir or hydrogen evolution reaction is developed and implemented in an alkaline flow battery. A membrane‐free rebalancing cell is proposed to promote the oxygen evolution reaction and reverse the accumulated charge in the catholyte showing a 100 % coulombic efficiency. The programmable logic controller monitors the open circuit voltage to calculate the charge stored in each charge/discharge step and closes a circuit so a fixed voltage is applied to the rebalancing cell when the battery needs to be rebalanced. The system is tested using an alkaline flow battery consisting of ferrocyanide and 2,6‐dihydroxyanthraquinone, improving the energy capacity retention from 0.27 % cycle‐1 and 0.47 % h‐1 without rebalancing system to 100 % retention after &gt;850 cycles and &gt;24 days (without Ar‐filled glovebox), demonstrating the feasibility of this proposed system to address the Faradaic imbalance.

Steric hindrance shielding viologen against alkali attack in realizing ultrastable aqueous flow batteries

Viologens known as a kind of promising negolyte materials for aqueous organic redox flow batteries, face a critical stability challenge due to the SN2 nucleophilic attack by hydroxide ions (OH–) during the battery cycling. In this work, a N-cyclic quaternary ammonium-grafted viologen molecule, viz. 1,1′-bis(4,4′-dimethylpiperidiniumyl)-4,4′-bipyridinium tetrachloride ((DBPPy)Cl4), is developed by the molecular engineering strategy. The obtained (DBPPy)Cl4 molecule shows a decent solubility of 1.84 M and a redox potential of −0.52 V vs. Ag/AgCl. Experimental and theoretical results reveal that the grafted N-cyclic quaternary ammonium groups act as the steric hindrance to prevent nucleophilic attack by OH–, increasing the alkali resistance of the electroactive molecule. The symmetrical battery with 0.50 M (DBPPy)Cl4 shows negligible decay during the 13-day cycling test. As demonstration, the flow battery utilizing 1.0 M (DBPPy)Cl4 as the negolyte and 1-(1-oxyl-2,2′,6,6′-tetramethylpiperidin-4-yl)-1′-(3-(trimethylammonio)propyl)-4,4′-bipyridinium trichloride as the posolyte exhibits a high capacity retention rate of 99.99% per cycle at 60 mA cm−2.

Recyclable Organic Radical Electrodes for Metal-Free Batteries.

Organic batteries are one of the possible routes for transitioning to sustainable energy storage solutions. However, the recycling of organic batteries, which is a key step toward circularity, is not easily achieved. This work shows the direct recycling of poly(2,2,6,6-tetramethylpiperidinyloxy-4-yl) (PTMA) and poly(2,2,6,6-tetramethylpiperidinyloxy-4-yl acrylamide) (PTAm) based composite electrodes. After charge-discharge cycling, the electrodes are deconstructed using a solubilizing-solvent and then reconstructed using a casting-solvent. The electrochemical properties of the original and recycled electrodes are compared using cyclic voltammetry (CV) and galvanostatic charge-discharge (GCD) cycling, from which it is discovered using time-of-flight secondary ion mass spectrometry (ToF-SIMS) that recycling can be challenged by the formation of a cathode electrolyte interphase (CEI). In turn, an additive is proposed to modify the CEI layer and improve the properties after recycling. Last, an anionic rocking chair battery consisting of PTAm electrodes as both positive and negative electrodes is demonstrated, in which the electrodes are recycled to form a new battery. This work demonstrates the recycling of composite electrodes for organic batteries and provides insights into the challenges and possible solutions for recycling the next-generation electrochemical energy storage devices.