Lithium diffusivity in antimony-based intermetallic and FeSb–TiC composite anodes as measured by GITT
The diffusion coefficient of lithium is an important parameter in determining the rate capability of an electrode and its ability to deliver high power output. Galvanostatic intermittent titration technique (GITT) is a quick electrochemical method to determine diffusion coefficients in electrode materials and is applied here to antimony-based anodes for lithium-ion batteries. Like other alloy anodes, antimony suffers from large volume change and a short cycle life, so GITT is also applied to determine the effects on lithium diffusivity of antimony intermetallics and composite electrodes designed to mitigate these issues. Pure antimony is measured to have a diffusion coefficient of 4.0 × 10−9 cm2 s−1, in agreement with previously measured values. The intermetallics NiSb, FeSb, and FeSb2 all demonstrate diffusivity values within an order of magnitude of antimony, while Cu2Sb shows roughly an order of magnitude improvement due to the persistence of the Cu2Sb phase during cycling. The composite electrode FeSb–TiC is shown to offer significant enhancement of the diffusion coefficient positively correlated with higher concentrations of TiC in the composite up to a maximum value of 1.9 × 10−7 cm2 s−1 at 60 wt% TiC, nearly two full orders of magnitude greater than that of pure antimony.