  Battery degradation, which is the reduction of performance over time, is one
of the main roadblocks to the wide deployment of lithium-ion batteries.
Physics-based models, such as those based on the Doyle-Fuller-Newman model, are
invaluable tools to understand and predict such phenomena. However, these
models are often too complex for practical applications, so reduced models are
needed. In this article we introduce the Single Particle Model with electrolyte
and Side Reactions, a reduced model with electrochemical degradation which has
been formally derived from the Doyle-Fuller-Newman model with Side Reactions
using asymptotic methods. The reduced model has been validated against the full
model for three scenarios (solid-electrolyte interphase growth, lithium
plating, and both effects combined) showing similar accuracy at a much lower
computational cost. The implications of the results are twofold: the reduced
model is simple and accurate enough to be used in most real practical
applications, and the reduction framework used is robust so it can be extended
to account for further degradation effects.
