Corrélation entre dégradation des composants internes et sécurité de fonctionnement des batteries Li-ion

Abstract : Lithium-ion batteries have undeniable assets to meet several of the requirements for embedded applications. They provide high energy density and long cycle life. Nevertheless, they can face irreversible damage during their lives which could cause safety issues like the thermal runaway of the battery and its explosion. It is then essential to understand the degradation mechanisms of all the internal components of an accumulator (i.e. electrode materials, collectors, separator and electrolyte) and the progress of events in abusive conditions that can lead to an accident scenario. The aim of this thesis is to work on the security aspects of Lithium-ion batteries in order to understand these degradation mechanisms and to help to prevent future incidents.Even if the degradation mechanisms of all the internal components are studied in this work, a special attention is given to the separator. This component is indeed one of the most important safety devices of a battery and have to be electrochemically, mechanically and thermally characterized after ageing. Different washing methods have been study in order to characterize the separator without any degradation product of the electrolyte which could interfere. Porosity and tortuosity associated with the ionic conductivity of the separator have been tested.The results show that even if the separator is electrochemically inactive, its porosity can decrease because of the degradation of the negative graphite electrode. Indeed, SEI components obstruct the surface porosity of the separator. This porosity change do not cause any mechanical degradation but decrease separator performances at high current rate and promote lithium dendrite growth.
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Xavier Fleury. Corrélation entre dégradation des composants internes et sécurité de fonctionnement des batteries Li-ion. Energie électrique. Université Grenoble Alpes, 2018. Français. ⟨NNT : 2018GREAI060⟩. ⟨tel-01943829⟩

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