(10) At this voltage, electroplating is prevented, and a safer device operation is enabled. (9) The operating redox potential of Nb 2O 5 is above 1 V vs. Niobium pentoxide (Nb 2O 5) is an alternative insertion-type anode to LIBs due to its various superior features. While there is the benefit of a low volume change for TiO 2 (4%) and LTO (<1%), these two materials provide only a limited theoretical capacity of about 170 mAh/g. (6) As an alternative, researchers have explored TiO 2 and Li 4Ti 5O 12 (LTO), which have a high operating voltage of 1.7 and 1.5 V vs. (1) However, graphite suffers from large stress during Li insertion/desertion, resulting in reduced cycling stability. Li/Li +, which translates to a high energy and power density. (4,5) Graphite, for example, provides a high specific capacity of 372 mAh/g and a low insertion potential of +0.2 V vs. standard hydrogen electrode (SHE) but is plagued by dendrite formation and safety concerns therefore, lithium insertion compounds are preferred for rechargeable LIBs. Metallic lithium offers a high theoretical capacity of 3860 mAh/g with a low redox potential of −3.04 V vs. (4) To meet the growing demands in energy and power ratings, there is a constant need for the development of improved and optimized LIB electrode materials. (1,2) The most advanced and widespread type of EES is the lithium-ion battery (LIB) (3) because of its long cycle life, high energy density, and efficiency. Carbide-derived Nb 2O 5 materials also show robust cycling stability over 500 cycles with capacity fading only 24% for the sample m-Nb 2O 5/CDC and 28% for o-Nb 2O 5/CDC, suggesting low degree of expansion/compaction during lithiation and delithiation.Įlectrochemical energy storage (EES) with high specific energy and power is essential for the successful transition of combustion engine vehicles to electric cars, advanced mobile communication devices, and energy harvesting technologies. The charge storage capacities of the resulting m-Nb 2O 5/CDC and o-Nb 2O 5/CDC are, in both cases, around 300 mAh/g at a specific current of 10 mA/g, thereby, the values are significantly higher than that of the state-of-the-art for Nb 2O 5 as a LIB anode. This defect engineering allows access to a very high specific capacity exceeding the two-electron transfer process of conventional Nb 2O 5. Our combined diffraction and spectroscopic data confirm that carbide-derived Nb 2O 5 materials show disordering of the crystallographic planes caused by oxygen deficiency in the structural units and, in the case of m-Nb 2O 5/CDC, severe stacking faults. The two-step process yielded a mixed-phase tetragonal and monoclinic Nb 2O 5 with CDC (m-Nb 2O 5/CDC). In situ formation of chlorine gas from metal chloride salt under vacuum conditions yields CDC covering the remaining carbide core, which can be transformed into metal oxides covered by a carbon shell upon thermal treatment in CO 2 gas.

By in situ production of chlorine gas from metal chloride salt at ambient pressure, we obtain in just one step directly orthorhombic Nb 2O 5 alongside carbide-derived carbon (o-Nb 2O 5/CDC). Our work introduces coarse-grained carbide-derived Nb 2O 5 phases obtained either by a one-step or a two-step bulk conversion process. For the first time, we present coarse-grained Nb 2O 5 materials that significantly overcome this capacity limitation with the promise of enabling high power applications. Nb 2O 5 has been explored as a promising anode material for use as lithium-ion batteries (LIBs), but depending on the crystal structure, the specific capacity was always reported to be usually around or below 200 mAh/g.

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