Analysis on discharge behavior and performance of As- and B-doped silicon anodes in non-aqueous Si–air batteries under pulsed discharge operation

Abstract: Very high theoretical specific energies and abundant resource availability have emerged interest in primary Si–air batteries during the last decade. When operated with highly doped Si anodes and EMIm(HF)_2.3F ionic liquid electrolyte, specific energies up to 1660 Wh kg_Si ⁻¹ can be realized. Owing to their high-discharge voltage, the most investigated anode materials are ⟨ 100 ⟩ oriented highly As-doped Si wafers. As there is substantial OCV corrosion for these anodes, the most favorable mode of operation is continuous discharge. The objective of the present work is, therefore, to investigate the discharge behavior of cells with ⟨ 100 ⟩ As-doped Si anodes and to compare their performance to cells with ⟨ 100 ⟩ B-doped Si anodes under pulsed discharge conditions with current densities of 0.1 and 0.3 mA cm⁻². Nine cells for both anode materials were operated for 200 h each, whereby current pulse time related to total operating time ranging from zero (OCV) to one (continuous discharge), are considered. The corrosion and discharge behavior of the cells were analyzed and anode surface morphologies after discharge were characterized. The performance is evaluated in terms of specific energy, specific capacity, and anode mass conversion efficiency. While for high-current pulse time fractions, the specific energies are higher for cells with As-doped Si anodes, along with low-current pulse fractions the cells with B-doped Si anodes are more favorable. It is demonstrated, that calculations for the specific energy under pulsed discharge conditions based on only two measurements—the OCV and the continuous discharge—match very well with the experimental data. Graphic abstract: [Figure not available: see fulltext.].