Self-transforming stainless-steel into the next generation anode material for lithium ion batteries

Abstract

Here, an extremely cost-effective and simple method is proposed in order to morphologically self-transform stainless steel from a completely inactive material to a fully operational, nanowire-structured, 3D anode material for lithium ion batteries. The reagentless process of a single heating step of the plain stainless steel in a partially reducing atmosphere, converts the stainless steel into an active anode via metal-selective oxidation, creating vast spinel-structured nanowires directly from the electrochemically inactive surface. The simple process allows the complete utilization of the 3D mesh structure as the electrochemically-active spinel nanowires greatly enhance the active surface area. The novel material and architecture exhibits high capacities (~1000 mAh/g after ~400 cycles), long cycle life (>1100 cycles) and fast rate performance (>2C). Simple modulation of the substrate can result in very high areal and volumetric capacities. Thus, areal capacities greater than 10 mAh/cm2 and volumetric capacities greater than 1400 mAh/cm3 can be achieved. Using the proposed method, the potential reduction in cost from the use of battery-grade graphite is at least an order of magnitude, with considerable better results achieved in terms of capacity and intrinsic structural benefits of the substrate, which include direct contact of the active material with the current collector, lack of delamination and binder-free performance. This work provides a new paradigm and a key step in the long route to replace the commercial graphite anode as the next-generation anode material.