Lithium-ion batteries (LIBs) since their launch in 1991 has always drawn a great interest due to their outstanding potential and performances. Nowadays is possible to find them everywhere from portable electronics to power tools and the demand is increasing for electric vehicles and stationary storage systems. Therefore, LIBs are still a current topic, as improved performances are necessary to meet the automotive demand. Therefore, towards the years, both the cell systems and the materials of composition have been largely studied and improved to boost the efficiency and the safety of the LIBs. In the present work, the properties of a novel binder B for the cathode, developed by Solvay Specialty Polymers SPA, are studied in relation to the standard binder A to highlight its advantages. Moreover, the work is focused on the correlation between the polymer properties and the slurry, electrode and cell characteristics to underline the effect of the intrinsic binder characteristics and the processing on the battery performance. The novel binder B exhibits a significantly increased average molecular weight of about the 33% with respect to A. On the other hand, the bulk density, the particle size distribution, the mechanical properties and thermal properties are analogous to A. The higher molecular weight of polymer B may determine some processing issue as it leads to a higher viscosity of the binder solution and a significant higher time to complete dissolution in NMP. At constant formulation and TSC, the slurries prepared with B, NMC622, carbon black and NMP, exhibit higher viscosity of the 12% at 10 s-1 than A, due to the binder molecular weight. Moreover, the TSC of slurries B must be lowered to 73,3% to obtain the same behavior during coating step. The characterization of the electrode, prepared with A and B through coating of the collector and drying, results in: higher adhesion of electrodes based on B compared to A, as the peeling strength is increased of the 33,86%, while the pull-off one present a boost of 18,5%, and the electrical properties are unaffected by the binder choice. Finally, the cell galvanic cycling at room temperature and 45°C results in similar performances. As consequence, considering the use of binder B the advantage is the possibility to reduce the binder content obtaining equivalent adhesion to A and improved cell performances.
Le batterie agli ioni di litio, sin dal loro lancio sul mercato nel 1991, hanno sempre suscitato un crescente interesse a causa del loro eccezionale potenziale e delle loro prestazioni. Ai giorni nostri è possibile trovarle ovunque dall'elettronica portatile agli utensili elettrici e la domanda è in aumento per i veicoli elettrici e i sistemi di stoccaggio fissi. Pertanto, le batterie agli ioni di litio sono ancora un tema attuale, poiché sono necessarie prestazioni migliori per soddisfare in particolare le richieste dell’automotive. Perciò, durante gli ultimi anni, sia i sistemi delle celle che tutti i materiali di composizione sono stati ampiamente studiati e migliorati per incrementare sempre di più l'efficienza e la sicurezza delle batterie. Nel presente lavoro, le proprietà di un nuovo legante B per il catodo, sviluppato da Solvay Specialty Polymers SPA, sono studiate in correlazione al legante polimerico standard A per evidenziarne i vantaggi. Inoltre, il lavoro si concentra sull'interrelazione tra le proprietà di base del polimero e le caratteristiche della slurry, dell’elettrodo e della cella per sottolineare l'effetto delle proprietà intrinseche del legante e del processing sulle prestazioni finali della batteria. Il nuovo legante B mostra un peso molecolare medio significativamente aumentato circa del 33% rispetto ad A. D'altra parte, la densità apparente, la distribuzione granulometrica, le proprietà meccaniche e le proprietà termiche sono analoghe ad A. Il peso molecolare più elevato del polimero B può determinare alcune criticità di processing in quanto porta ad un valore di viscosità più elevato della soluzione legante e un tempo significativamente più lungo per completare la dissoluzione del legante. Considerando fissi la formulazione e il TSC, le slurries preparate con B, NMC622, carbon black e NMP, presentano una viscosità più elevata del 12% rispetto ad A a 10 s-1, a causa del maggiore peso molecolare del binder. Inoltre, il TSC delle slurries B deve essere abbassato al 73,3% per ottenere lo stesso comportamento di A durante la fase di rivestimento. La caratterizzazione dell’elettrodo, preparato attraverso il rivestimento del collettore con la slurry e l’essicazione, risulta in: maggiore adesione negli elettrodi realizzati con B rispetto ad A, poiché la resistenza al peeling è aumentata del 33,86%, mentre la resistenza a strappo presenta un incremento di 18,5%, e le proprietà elettriche non sono influenzate dalla scelta del legante. Infine, le performance delle celle a temperatura ambiente e a 45°C risultano simili. Di conseguenza, considerando l'impiego del legante B, il vantaggio è la possibilità di ridurre il contenuto del legante ottenendo così un'adesione equivalente ad A e migliorando le prestazioni delle celle.
Performance of advanced cathode binders for lithium ion batteries : a comparative study
CAODURO, BEATRICE
2018/2019
Abstract
Lithium-ion batteries (LIBs) since their launch in 1991 has always drawn a great interest due to their outstanding potential and performances. Nowadays is possible to find them everywhere from portable electronics to power tools and the demand is increasing for electric vehicles and stationary storage systems. Therefore, LIBs are still a current topic, as improved performances are necessary to meet the automotive demand. Therefore, towards the years, both the cell systems and the materials of composition have been largely studied and improved to boost the efficiency and the safety of the LIBs. In the present work, the properties of a novel binder B for the cathode, developed by Solvay Specialty Polymers SPA, are studied in relation to the standard binder A to highlight its advantages. Moreover, the work is focused on the correlation between the polymer properties and the slurry, electrode and cell characteristics to underline the effect of the intrinsic binder characteristics and the processing on the battery performance. The novel binder B exhibits a significantly increased average molecular weight of about the 33% with respect to A. On the other hand, the bulk density, the particle size distribution, the mechanical properties and thermal properties are analogous to A. The higher molecular weight of polymer B may determine some processing issue as it leads to a higher viscosity of the binder solution and a significant higher time to complete dissolution in NMP. At constant formulation and TSC, the slurries prepared with B, NMC622, carbon black and NMP, exhibit higher viscosity of the 12% at 10 s-1 than A, due to the binder molecular weight. Moreover, the TSC of slurries B must be lowered to 73,3% to obtain the same behavior during coating step. The characterization of the electrode, prepared with A and B through coating of the collector and drying, results in: higher adhesion of electrodes based on B compared to A, as the peeling strength is increased of the 33,86%, while the pull-off one present a boost of 18,5%, and the electrical properties are unaffected by the binder choice. Finally, the cell galvanic cycling at room temperature and 45°C results in similar performances. As consequence, considering the use of binder B the advantage is the possibility to reduce the binder content obtaining equivalent adhesion to A and improved cell performances.| File | Dimensione | Formato | |
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https://hdl.handle.net/10589/164691