Aging of Electrode/Electrolyte Interfaces in LiFePO4/Graphite Cells Cycled with and without PMS Additive

作者：Hogstrom Katarzyna Ciosek; Hahlin Maria; Malmgren Sara; Gorgoi Mihaela; Rensmo Hakan; Edstrom Kristina^*

来源：Journal of Physical Chemistry C, 2014, 118(24): 12649-12660.

DOI：10.1021/jp502732j

LiFePO4/graphite cells are studied with hard X-ray photoelectron spectroscopy (HAXPES) in order to evaluate the influence of aging on the electrode/electrolyte interfaces. Cells cycled with the standard electrolyte, LiPF6 in ethylene carbonate/diethyl carbonate, are compared to cells cycled with addition of the film-forming additive propargyl methanesulfonate (PMS). Cycling is performed to accelerate aging at both 21 and 60 degrees C. The results show that PMS cells have better capacity retention at both temperatures. The thorough HAXPES analysis of the samples reveals that the PMS additive affects the interfaces on both negative and positive electrodes. The effects on the negative electrode show important variations in thicknesses and surface chemistry. Lower loss of cyclable lithium in the SEI and interface thicknesses that are stable during cycling are some reasons for the better capacity retention at 21 degrees C. The cycling fades quickly at 60 degrees C for both electrolytes, but the PMS electrolyte gives still a more stable cycling with thinner formed interface layers as probed by depth profiling characterization. PMS give a better long-term interface protection for Li-ion batteries, but capacity fading still cannot be fully prevented.

• 出版日期2014-6-19