Résumé
Developing batteries based on Earth abundant elements such as sodium, magnesium or more recently potassium has become a mandatory challenge in the context of renewable energy growth that requires large-scale storage systems for which cost is the dominant factor and lithium supply a possible issue. Due to the beneficial potassium abundance (2.09 wt.% of the Earth’s crust), low standard potential of K
+
/K,
1
weaker K
+
Lewis acidity,
2
K-ion batteries (KIBs) are expected to greatly favor both the energy and power density compared to NIB. Numerous new materials for KIBs have thus rapidly been proposed
3
but their performance evaluation still remains greatly limited by the lack of efficient electrolytes and the high reactivity of K metal in half cells.
4
Indeed, the use of KN(SO
2
F)
2
(KFSI) instead of KPF
6
have been reported to be beneficial to most of the anode materials
5
while detrimental to some cathode materials,
6
probably due to the corrosion of Al current collector by KFSI at high potential.
In this presentation, the impact of KPF
6
and KFSI salts in carbonate- and glyme-based electrolytes is investigated. The reactivity of K metal is first evaluated by its immersion in the different electrolytes. The soluble/gaseous and solid electrolyte degradation species are analyzed using GC/MS and XPS, respectively. A comparison with the reactivity of Li metal in the equivalent Li salts based electrolyte is also performed. Moreover, K//graphite and K//KVPO
4
F half-cells have also been prepared and stored (no cycling) to investigate interactions between electrodes (
i.e.
migration of electrolyte degradation species from the K metal to the working electrode) and their impact in solid electrolyte interphases formation and resulting electrochemical performance.
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