Combining electrochemistry and metallurgy for new electrode designs in Li-ion batteries

To benefit from the large electrochemical capacity advantages offered by Li-driven conversion reactions and to overcome poor kinetics, a new electrode configuration concept is reported. The originality of this electrode design is nested in metallurgical aspects of stainless steel, namely, the appearance of temperature-driven surface microstructures that enable the growth of a nanostructured, electrochemically active, chromium-rich oxide surface layer in close contact with a current collector. The thickness of the oxide layer can reach hundreds of nanometers and is shown to be rooted in the preferential migration of Cr toward the sample surface. We further show that chemical etching of the stainless steel surface, prior to high-temperature annealing, enables reversible capacities as high as 750 mAh/g of chromium-rich oxide for at least 800 cycles. On the basis of modeling, several scenarios involving stainless steel/chromium-based oxides current collectors of various porosities show how this new electrode configuration could boost the electrode capacity beyond that of today's carbon negative electrodes used in Li-ion cells by a factor of 2 or 3.