Silicon is a key enabler of future high-energy-density lithium-ion batteries (LIBs). E-magy’s nanoporous, micron-sized silicon offers a silane-free route to LIB anodes with strongly reduced expansion [1], potentially greatly simplifying battery cell engineering. However, even in the absence of intrinsic material degradation by fracture, cycle lifetime of a full cell is limited by progressive electrolyte decomposition, which immobilizes an ever-greater part of the active lithium.

The initial lithium inventory of a battery can be increased by prelithiation of the anode, providing a greater Li reservoir to mitigate the effects of Li consumption by electrolyte decomposition [2]. Another mechanism of action of the prelithiation step is reducing the reactivity between Si and the electrolyte by pre-forming a solid electrolyte interphase (SEI). Furthermore, Si is most reactive at low Li-content, above 0.75 V vs. Li [3], and a sufficient extent of prelithiation will keep the anode voltage below this value even in the fully discharged state of the battery.

Prelithiation of anode sheets produced with E-magy’s porous Silicon has been conducted on a small-scale commercial pilot line. Three prelithiation depths have been tested: 370, 540 and 610 mAh/gSi. A cycle life extension of more than a factor 2 was achieved for a LixSiNMC622 cell, where ‘x’ corresponds to a prelithiation degree of 540 mAh/gSi.

Prelithiation in an industrially relevant setup has thus been successfully demonstrated for our micron-sized porous silicon material. Further improvements are expected from electrolyte optimization, both in the prelithiation bath and during cycling.