  Computational modeling is vital for the fundamental understanding of
processes in Li-ion batteries. However, capturing nanoscopic to mesoscopic
phase thermodynamics and kinetics in the solid electrode particles embedded in
realistic electrode morphologies is challenging. In particular for electrode
materials displaying a first order phase transition, such as LiFePO$_4$,
graphite and spinel Li$_4$Ti$_5$O$_{12}$ (LTO), predicting the macroscopic
electrochemical behavior requires an accurate physical model. Herein, we
present a thermodynamic phase field model for Li-ion insertion in LTO which
captures the performance limitations presented in literature as a function of
all relevant electrode parameters. The phase stability in the model is based on
ab-initio DFT calculations and the Li-ion diffusion parameters on nanoscopic
NMR measurements of Li-ion mobility, resulting in a parameter free model. The
direct comparison with prepared electrodes shows good agreement over three
orders of magnitude in the discharge current. Overpotentials associated with
the various charge transport processes, as well as the active particle fraction
relevant for local hotspots in batteries, are analyzed. It is demonstrated
which process limits the electrode performance under a variety of realistic
conditions, providing comprehensive understanding of the nanoscopic to
microscopic properties. These results provide concrete directions towards the
design of optimally performing LTO electrodes.
