A critical review and assessment of 3D columnar silicon electrode architectures and their performance as negative electrodes in Li-ion cells

A critical review and assessment of 3D columnar Si electrode architectures, as negative electrodes for Li-ion cells, has been undertaken to provide insight on the structure parameters that enable high specific and total Li-storage capacities and high cycling performance. The selected set represents a sufficiently wide variety of columnar architectures, covering most of the possible routes of fabrication, including etching, patterning, photolithography and micromachining. The outcome of this evaluation identifies the structural factors that determine the best performing 3D electrode architecture. Specifically, electrodes with a high mass loading have been shown to correlate very well with high total capacities for Li-storage. Thus, the preferred 3D electrode structures are identified as those with columns of Si with an optimum porosity giving high enough mass loading, but with a balanced column depth and spacing providing effective volume accommodation during cell cycling. The review also provides details of experimental validations of the optimum electrode architecture, which effectively accommodates the volume change, and enables cycling for a larger number of cycles.