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The formation of the solid electrolyte interphase (SEI) during the formation and conditioning steps, is a very time consuming and expensive process. We present an active formation method for reducing the formation time in LIBs whilst maintaining the cycling performance of the cells. LiNi0.3Mn0.3Co0.3O2 (NMC-111) vs Graphite coin cells were assembled using 1 M LiPF6 in organic solvents as the electrolyte to evaluate 10 different active formation protocols. The cells were evaluated using electrochemical impedance spectroscopy (EIS) and cycling performance for 500 charge/discharge cycles. X-ray photoelectron spectroscopy was used to analyse the surface of the cells to compare the active formation sample with the standard and fresh electrodes in order to study the SEI layer formed on the anode. Cycling performance and resistance measurements from the EIS results confirm the effect of different formation protocols in the life-time and performance of the cells. We show that the interface formation is optimised through the transport of lithium ions through the initial organic decomposition layer on the graphite at higher cell voltages (g3.65V). These higher voltage cycling formation protocols give an interface with greater stability and enhanced cycling is observed in the cells. The composition of the graphite interface on the cells formed between 3.65 and 4V shows fewer organic decomposition compounds and less additionally fluorinated PVDF compared to the cells formed between 2.7 and 4.2V (no formation). From XPS the chemical composition of the interface is dominated by carbon and oxygen (C-O) from the decomposition of the ethylene carbonate with some LiF content. In addition less graphitic contribution is observed from the carbon XPS indicating a smoother and more even surface coating on the graphite and NMC cathode. Surface coatings were observed on both the anode and the cathode.

Active formation of Li-ion batteries and its effect on cycle life