Among the many challenges to enable large scale commercialization of lithium ion batteries in plug-in hybrid electric vehicles (PHEVs) and full electric vehicles (EVs), stabilizing the electrolyte/electrode interface for long term battery durability and safety remains one critical issue. In this talk, our recent efforts on probing and stabilizing the electrolyte and negative electrode interface will be discussed. We will start with the characterization of SEI on various electrodes (Cu, graphite, etc.) with novel techniques, highlighting time-of-flight secondary ion mass spectrometry (TOF SIMS) and isotope tracer as effective methods to probe SEI chemistry and lithium transport.Next, SEI evolution during battery operation is studied with these techniques. A Cu model system is selected to show SEI formation on a non-insertion electrode, and a graphite/LMO full cell system is used to elucidate SEI evolution in the presence of Mn contamination. SEI formation and change through battery operation will be demonstrated, and its chemistry is correlated with the electrochemical properties.Finally, we will demonstrate surface coating and modification as effective approaches to stabilize the interface. On atomic layer deposition (ALD) modified negative electrodes, SEI formation (both chemistry and thickness) is changed and results in better columbic efficiency. We will also show reducing the graphite/LMO full cell impedance by removal of SEI with a simple surface treatment method. Figure 1. TOF SIMS images showing surface film composition on graphite electrode from a LMO/graphite full cell.

Probing and stabilizing the electrolyte and negative electrode interface in lithium ion batteries: A surface chemistry perspective

247th National Meeting (2014)

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