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 electro-chemically 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 mate-rial 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 rnAh/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 con-tact 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.