The rapid market expansion for LIBs8 is driving down cost, but making LIBs last longer is just as important. This improves the lifetime economics, enables longer warranties4 and dilutes the environmental impacts associated with raw material extraction and manufacturing.9,10 Understanding battery degradation is key to increasing operational lifetime. Between degradation mechanisms and observable effects lie the degradation modes: a method of grouping degradation mechanisms, based on their overall impact on the cell's thermodynamic and kinetic behaviour. We would like to highlight four modes, all of which impact the thermodynamic behaviour of the cell, i.e. the shape of the open-circuit voltage. Many variations of galvanostatic and potentiostatic methods exist, each providing different key insights. Electrochemical impedance spectroscopy (EIS), for instance, is a core technique for decoupling resistance contributions in battery electrodes. Other electrochemical techniques involving the OCV of the cell, such as analysing the curve itself,14. By predicting the key performance parameters of a battery, such as capacity and lifetime, models can also be useful tools for designing electrodes, cells and packs, enabling the vast design space of batteries to be explored, where the constituent materials, electrode structure, thermal management and many more aspects can be varied and combined, wi. Multiple interactions between degradation mechanisms have been identified and discussed, which in many cases require further study to properly understand. Multiple explanations to explain the transition between linear and non-linear degradation were found, also known as the knee point, cell drop-off, sudden failure, etc.Two examples of coupling fou.
