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This review aims to address the status of transition metal‐based cathode materials for Mg2+ and Ca2+‐based multivalent‐ion batteries on a critical standpoint, providing a comprehensive overview. Multivalent‐based ions battery (MIB) technologies are among the most promising post‐lithium electrochemical energy storage devices currently studied, but they still fall short in several aspects due to their early stage of research. In addition, difficult experimental conditions related to the electrolyte systems and the cathode materials require an additional quote of care when performing experiments. In this review, a global approach is undertaken, from an introduction to electrolytes to the studied insertion parameters that allow a fast (de)insertion of multivalent ions. Then, the currently studied structural classes of cathode materials and a critical comment on data reporting, which are among the focal points of the actual state‐of‐the‐art research, are thoroughly discussed.

In this research, twenty-four high capacity (1360 mAh) NMC622/Si-alloy Li-ion full pouch cells with high silicon-alloy content (55%) are cycle aged under seven different cycling conditions to study the effect of different stressors on the cycle life of Si-anode full cells, among which are the effect of ambient temperature, Depth of Discharge (DoD) and the discharge current. The cells are volumetrically constrained at an optimal initial pressure to improve their cycle life, energy and power capabilities. Furthermore, the innovative test setup allows measuring the developed pressure as a result of repeated (de-)lithiation during battery cycling. This uniquely vast testing campaign on Si-anode full cells allows us to study and quantify independently the influence of different stress factors on their cycle life for the first time, as well as to develop a new capacity fade model based on an observed linear relationship between capacity retention and total discharge capacity throughput.

In lithium-ion batteries, Si-based materials such as silicon alloys are regarded as a promising alternative to graphite negative electrode to achieve higher energy. Unfortunately, they often suffer from a large volume change that can result in poor cycle life. We monitored the electrode expansion/contraction that occurs during lithiation/delithiation in real time by electrochemical dilatometry. Volume changes of Si alloy-based electrode with three different polymer binders have been compared. Electrode manufactured with lithiated polyacrylic acid (LiPAA) exhibited the greatest expansion but also demonstrated the highest reversibility as well as the best cycling performance. Ex situ SEM imaging along with dilatometer measurements revealed that electrode porosity after contraction (delithiation) increases compared to that after precedent expansion (lithiation), which can buffer volume expansion at the subsequent cycle. Proof-of-concept in situ optical microscopy (IOM) experiments were carried out with the best performing LiPAA electrode. The results demonstrated that LiPAA electrode in the IOM cell expanded much less than the same electrode in the dilatometer cell. This implies that internal pressure existing in a lithium-ion cell has a great impact on total electrode expansion.

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