Andersson, E.K.W.; Sangeland, C.; Berggren, E.; Johansson, F.O.L.; Kühn, D.; Lindblad, A.; Mindemark, J.; Hahlin, M.: Early-stage decomposition of solid polymer electrolytes in Li-metal batteries. Journal of Materials Chemistry A 9 (2021), p. 22462-22471
10.1039/d1ta05015j
Open Access Version
Abstract:
Development of functional and stable solid polymer electrolytes (SPEs) for battery applications is an important step towards both safer batteries and for the realization of lithium-based or anode-less batteries. The interface between the lithium and the solid polymer electrolyte is one of the bottlenecks, where severe degradation is expected. Here, the stability of three different SPEs – poly(ethylene oxide) (PEO), poly(ε-caprolactone) (PCL) and poly(trimethylene carbonate) (PTMC) – together with lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) salt, is investigated after they have been exposed to lithium metal under UHV conditions. Degradation compounds, e.g. Li–O–R, LiF and LixSyOz, are identified for all SPEs using soft X-ray photoelectron spectroscopy. A competing degradation between polymer and salt is identified in the outermost surface region (<7 nm), and is dependent on the polymer host. PTMC:LiTFSI shows the most severe decomposition of both polymer and salt followed by PCL:LiTFSI and PEO:LiTFSI. In addition, the movement of lithium species through the decomposed interface shows large variation depending on the polymer electrolyte system.