Cost-competitive manufacture of porous-silicon anodes via the magnesiothermic reduction: A techno-economic analysis

Abstract

Lithium-ion batteries play a central role in the electrification of our energy systems, however this technology still suffers from low energy density. Porous silicon (p-Si) has been recognised as a promising, high-energy density anode material as a replacement for the currently used graphite. The demand for p-Si is therefore expected to increase in the coming decades and the magnesiothermic reduction (MgTR) has shown great promise as a scalable process that can be used to meet this demand. However, without a preliminary or detailed economic analysis, it is not possible to determine whether this process is economically feasible at larger scales, under conditions that have thus been reported in the literature. Herein, as a first of a kind study, the total cost of production (TCOP) at scales between 300 and 1500kg/batch are calculated using experimentally verified data. Fixed costs make up the greatest proportion of TCOP, at 58 % of the TCOP at the largest scale, with a payback time of 10 years. Total variable costs (feedstock and energy) was 42 % of the TCOP. When recently reported modifications to MgTR – a two-step and ultra-low temperature methods – were considered, the variable costs reduced by ∼40 % and ∼32 % respectively, and reducing the TCOP for the two-step and low-temperature methods by 45 % and 37 % respectively. When the cost of producing p-Si through the MgTR process was compared to that of graphite on a “capacity cost” basis ($/Ah), it was clear that p-Si produced via MgTR process rivals the market price of graphite. These results provide the first evidence that the MgTR is a highly competitive and scalable process for producing anode grade porous silicon. The variable costs can be lowered in the future by changing the conditions, and the most effective ways to do this are presented in this study.