| 1. |
- Yucel, Yasemin Duygu, et al.
(author)
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Enhancing Structural Battery Performance : Investigating the Role of Conductive Carbon Additives in LiFePO4-Impregnated Carbon Fiber Electrodes
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Other publication (other academic/artistic)abstract
- This study centers on investigating the influence of conductive additives, carbon black (Super P) and graphene, within the context of LiFePO4 (LFP)-impregnated carbon fibers (CFs) produced using the powder impregnation method. The performance of these additives was subject to an electrochemical evaluation. The findings reveal that there are no substantial disparities between the two additives at lower cycling rates, highlighting their adaptability in conventional energy storage scenarios. However, as cycling rates increase, graphene emerges as the better performer. At a rate of 1.5C in a half-cell versus lithium, electrodes containing graphene exhibited a discharge capacity of 83 mAh g-1LFP ; those with Super P and without any additional conductive additive showed a capacity of 65 mAh g-1LFP and 48 mAh g-1LFP , respectively. This distinction is attributed to the structural and conductivity advantages inherent to graphene, showing its potential to enhance the electrochemical performance of structural batteries. Furthermore, LFP-impregnated CFs were evaluated in full cells versus pristine CFs, yielding relatively similar results, though with a slightly improved outcome observed with the graphene additive. These results provide valuable insights into the role of conductive additives in structural batteries and their responsiveness to varying operational conditions, underlining the potential for versatile energy storage solutions.
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| 2. |
- Yucel, Yasemin Duygu, et al.
(author)
-
Enhancing structural battery performance: Investigating the role of conductive carbon additives in LiFePO4-Impregnated carbon fiber electrodes
- 2024
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In: Composites Science And Technology. - : Elsevier BV. - 0266-3538 .- 1879-1050. ; 251
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Journal article (peer-reviewed)abstract
- This study centers on investigating the influence of conductive additives, carbon black (Super P) and graphene, within the context of LiFePO4 (LFP)-impregnated carbon fibers (CFs) produced using the powder impregnation method. The performance of these additives was subject to an electrochemical evaluation. The findings reveal that there are no substantial disparities between the two additives at lower cycling rates, highlighting their adaptability in conventional energy storage scenarios. However, as cycling rates increase, graphene emerges as the better performer. At a rate of 1.5C in a half-cell versus lithium, electrodes containing graphene exhibited a discharge capacity of 83 mAhgLFP−1; those with Super P and without any additional conductive additive showed a capacity of 65 mAhgLFP−1 and 48 mAhgLFP−1, respectively. This distinction is attributed to the structural and conductivity advantages inherent to graphene, showing its potential to enhance the electrochemical performance of structural batteries. Furthermore, LFP-impregnated CFs were evaluated in full cells versus pristine CFs, yielding relatively similar results, though with a slightly improved outcome observed with the graphene additive. These results provide valuable insights into the role of conductive additives in structural batteries and their responsiveness to varying operational conditions, underlining the potential for versatile energy storage solutions.
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| 3. |
- Yucel, Yasemin Duygu
(author)
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LiFePO4-coated carbon fiber electrodes for structural batteries
- 2024
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Doctoral thesis (other academic/artistic)abstract
- Lithium-ion batteries (LIBs) have a central role in products, from portable devices to large-scale energy storage for the electric grid and continue to undergo rapid development. The surge in electric vehicles has intensified the focus on technological advancements and new-generation technologies. Structural batteries have received considerable attention for their multifunctionality and lightweight properties. These batteries utilize carbon fibers to combine their mechanical strength with battery functionalities in a single structure, consequently reducing overall weight and increasing energy density. Similar to traditional LIBs, structural batteries comprise negative and positive electrodes, reinforced within a structural battery electrolyte (SBE). While extensive research has been conducted on carbon fibers as negative electrodes, there has been a relative scarcity in the development of positive electrodes that align with the structural battery concept. This thesis explores coating methodologies on polyacrylonitrile (PAN)-based carbon fibers (CF) with positive electrode active material, specifically focusing on the utilization of lithium iron phosphate (LFP). Electron microscopy and electrochemical tests were conducted to evaluate the relation between structure with long-term and rate performances of these electrodes in half-cells. Spray coating and siphon impregnation (later referred to as ‘powder impregnation’ in this thesis) techniques were employed to coat the carbon fibers, which serve as current collectors instead of conventional aluminum foil. The spray coating method utilized a standard electrode slurry based on an organic solvent, with efforts made to optimize parameters such as the height of the spray gun and plate temperature. The sprayed coating was quite thin, resulting in excellent rate capability. In the powder impregnation method, a water-based slurry was utilized with polyethylene glycol (PEG) as a binder. Efforts were made to obtain good fiber distribution within a homogeneous matrix of coating in the electrode. The parameters, including slurry viscosity, binder effect, electrode design, cell design, electrode preparation, and drying temperatures, were regulated for the best electrochemical performance and cell life. It was found that a binder is necessary for ensuring robust electrodes. Elevated drying temperatures are essential to eliminate moisture from the water-based process and components. Additionally, conductive carbon additives such as carbon black and graphene were incorporated, and their impact was assessed. A small amount of carbon additive (< 1 wt.%) improved performance at higher cycling rates. The electrodes produced via powder impregnation were finally integrated into double-sided full cells versus uncoated PAN-derived CFs serving as negative electrodes in commercial liquid electrolyte or SBE, respectively. The LFP-coated CF electrodes exhibited good performance in full cells, indicating promising performance for the structural battery. The main limitation was observed in the power losses in the CF negative electrodes and in the ionic conductivity of the SBE. Overall, the thesis shows that the encapsulation of individual PAN-derived carbon fiber filaments using the applied coating methodologies was successful and that the use of carbon fibers as current collectors proved to be effective.
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| 4. |
- Yucel, Yasemin Duygu, et al.
(author)
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LiFePO4-coated carbon fibers as positive electrodes in structural batteries : Insights from spray coating technique
- 2024
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In: Electrochemistry communications. - : Elsevier BV. - 1388-2481 .- 1873-1902. ; 160, s. 107670-
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Journal article (peer-reviewed)abstract
- This study presents the fabrication of LiFePO4 (LFP)-coated carbon fibers (CFs) as a positive electrode component for structural batteries, utilizing a spray coating technique. The successful coating of CFs through this method demonstrated their usefulness as efficient current collectors. The electrodes obtained using this method underwent electrochemical evaluations. Throughout the extended cycling tests at C/7, the maximum specific discharge capacity reached 146 mAh/g, maintaining a 77% capacity retention after 100 cycles. In rate performance assessments at the faster C-rate of 1.5C, the capacity measured 123 mAh/g, with a retention of 96%. The application of spray coating emerges as a promising technique for electrode production in structural batteries, showcasing its potential for optimizing performance in multifunctional energy storage systems.
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| 5. |
- Yucel, Yasemin Duygu, et al.
(author)
-
Powder-impregnated carbon fibers with lithium iron phosphate as positive electrodes in structural batteries
- 2023
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In: Composites Science And Technology. - : Elsevier Ltd. - 0266-3538 .- 1879-1050. ; 241
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Journal article (peer-reviewed)abstract
- A structural battery is a multifunctional battery that can carry a load while storing energy. Structural batteries have been a cutting-edge research focus in the last decade and are mainly based on polyacrylonitrile (PAN)-carbon fibers (CFs). In this work, positive electrodes based on PAN-carbon fibers were manufactured with powder impregnation (siphon impregnation) technique using a water-based slurry containing lithium iron phosphate (LFP) as the active electrode material and the water-soluble binder polyethylene glycol (PEG). Different coating compositions, electrode-drying temperatures, and coating parameters were investigated to optimize the coating uniformity and the electrochemical performances. Scanning electron microscopy results showed that the electrode materials coat the CFs uniformly, conformably, and individually. Electrochemical characterization of pouch cells shows that the electrodes containing 6 wt% PEG dried at 140 °C have the best battery performance, delivering a first discharge capacity of 151 mAh g−1 and capacity retention higher than 80% after 100 cycles. Moreover, excellent capacity reversibility was achieved when the electrodes were cycled at multiple C-rates attesting to their stability. The results demonstrate that CFs perform excellently as current collectors in positive electrodes.
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| 6. |
- Yucel, Yasemin Duygu, et al.
(author)
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Structural Batteries with LiFePO4-Impregnated Carbon Fibers
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Other publication (other academic/artistic)abstract
- This study focuses on the fabrication and evaluation of structural batteries, emphasizing their electrochemical performance. LiFePO4 (LFP)-impregnated carbon fibers (CFs), produced via the powder impregnation method, were employed as positive electrodes. These electrodes underwent infusion with structural battery electrolyte (SBE) and curing to yield positive structural battery electrodes. A structural battery fully based on CFs was constructed and subjected to electrochemical testing, with positive electrodes assembled versus pristine CF of T800S as negative electrodes. The results revealed specific discharge capacities of 123 mAh g-1LFP for the structural positive electrode and 178 mAh g-1T800S for the structural battery, both at similar current densities. Both the half and full structural cells maintained capacities of 94% and 96%, respectively, during rate capability tests when reverting to their initial current densities. The electrochemical impedance spectroscopy (EIS) results revealed that, the structural battery demonstrated a relatively improved surface impedance, with the values ranging between 186 Ω cm² and 2000 Ω cm². Additionally, similar comparative studies were conducted on full cells in a commercial liquid electrolyte consisting of 1M LiPF6 in EC: DEC (1:1 vol.%). The research introduces a prototype of laminated composite batteries, showing their potential, especially when utilizing fully carbon fiber-based electrodes.
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