Electrode Engineering: Impact of Processing and Design Towards Performance of Nano-Silicon Anodes

Silicon based materials show highest capacity among state-of-the art anode materials for LIBs and next generation batteries. Silicon anodes attract wide attention due to high specific capacity of Si, i.e. 3590mAh/g for Li₁₅Si₄ phase at room temperature.

As known, large volume changes and subsequent pulverization of brittle Si during cycling can be alleviated by using nano-sized Si particles [1]. However, the surrounding binder matrix still has to compensate large stress and strain induced by accumulated volume changes of the single particles.

The works presented here focus on the challenges on the electrode level. Choice of binder is crucial to create a matrix that can accommodate mechanical stress and strain during prolonged charge/discharge cycles. For reliable comparison of the impact of active material/binder ensembles, equal properties of electrodes (loading, porosity) are very important and hence receive special attention.

To investigate the impact of processing and electrode matrix in more detail, electrodes with high Si contents (60 to 80wt.%) and controlled, application-related loadings are produced. Characterization is carried out in laboratory sized pouch bag cells. Crucial parameters such as binder, processing, loading and voltage regime on available capacity and cycle life are discussed. Remaining reversible capacity of more than 1500mAh/g_coating (1875mAh/g_Si) after 100 cycles at 0.5C is reported. Remaining electrode capacity is approx. 1.5mAh/cm² at this point.

[1]: H. Wu, Y. Cui, Nano Today (2012)