A transmission electron microscopy study of crack formation and propagation in electrochemically cycled graphite electrode in lithium-ion cells

摘要: Abstract Subsurface defects and local compositional changes that occurred in graphite anodes subjected to cyclic voltammetry tests (vs. Li/Li + , using an electrolyte consisting of 1 M LiClO 4 a 1:1 volumetric mixture ethylene carbonate 1,2-dimethoxy ethane) were investigated high-resolution transmission electron microscopy (HR-TEM). Cross-sections prepared by focused ion beam (FIB) milling indicated layers adjacent solid (SEI)/graphite interface exhibited partial delamination due the formation interlayer cracks. The SEI layer formed on surface consisted Li 2 CO 3 was identified {1 1 0} {0 0 2} crystallographic planes. Lithium compounds, LiC 6 O, observed surfaces separated layers. Deposition these co-intercalation compounds near crack tip caused closure propagating cracks during electrochemical cycling, possibly reduced growth rate. Graphite fibres bridge faces likely provided additional mechanism for retardation propagation.