  Predicting lithium-ion battery lifetime is one of the greatest unsolved
problems in battery research right now. Recent years have witnessed a surge in
lifetime prediction papers using physics-based, empirical, or data-driven
models, most of which have been validated against the remaining capacity
(capacity fade) and sometimes resistance (power fade). However, there are many
different combinations of degradation mechanisms in lithium-ion batteries that
can result in the same patterns of capacity and power fade, making it
impossible to find a unique validated solution. Experimentally, degradation
mode analysis involving measuring the loss of lithium inventory, loss of active
material at both electrodes, and electrode drift/slippage has emerged as a
state-of-the-art requirement for cell degradation studies. In this paper we
coupled five degradation mechanisms together for the first time. We also showed
how three models with different levels of complexity can all fit the remaining
capacity and resistance well, but only the model with five coupled degradation
mechanisms could also fit the degradation modes at all temperatures. This work
proves that validating only against capacity and power fade is no longer
sufficient, and state-of-the-art experimental and modelling degradation studies
should include degradation mode analysis for validation in the future.
