Fast and Durable Lithium Storage Enabled by Tuning Entropy in Wadsley–Roth Phase Titanium Niobium Oxides

Abstract

Wadsley–Roth phase titanium niobium oxides have received considerable interest as anodes for lithium ion batteries. However, the volume expansion and sluggish ion/electron transport kinetics retard its application in grid scale. Here, fast and durable lithium storage in entropy‐stabilized Fe0.4Ti1.6Nb10O28.8 (FTNO) is enabled by tuning entropy via Fe substitution. By increasing the entropy, a reduction of the calcination temperature to form a phase pure material is achieved, leading to a reduced grain size and, therefore, a shortening of Li+ pathway along the diffusion channels. Furthermore, in situ X‐ray diffraction reveals that the increased entropy leads to the decreased expansion along a–axis, which stabilizes the lithium intercalation channel. Density functional theory modeling indicates the origin to be the more stable FeO bond as compared to TiO bond. As a result, the rate performance is significantly enhanced exhibiting a reversible capacity of 73.7 mAh g−1 at 50 C for FTNO as compared to 37.9 mAh g−1 for its TNO counterpart. Besides, durable cycling is achieved by FTNO, which delivers a discharge capacity of 130.0 mAh g−1 after 6000 cycles at 10 C. Finally, the potential impact for practical application of FTNO anodes has been demonstrated by successfully constructing fast charging and stable LiFePO4‖FTNO full cells.

Fast-charging anodes for lithium ion batteries: progress and challenges

“…144–148 Among them, Ti x Nb y O z usually exhibits the highest theoretical capacity, the fastest ion diffusion and the longest cycle life. 149,150 In the following, the structural features and lithium storage mechanism of Wadsley–Roth shear structure NBMOs are introduced, taking the most classical TiNb 2 O 7 as an example. TiNb 2 O 7 belongs to the monoclinic crystal system with a space group of C 2/ m , consisting of shared prismatic TiO 6 and NbO 6 octahedra.…”

“…Moreover, the lattice parameter of FTNO along the a -axis was increased compared to that of the pristine TNO, which can well accommodate the lattice expansion caused by lithium ion insertion, resulting in excellent structural stability in electrochemical cycling. 150 Li et al synthesized micron-sized H-Nb 2 O 5 (d-H-Nb 2 O 5 ) with abundant Wadsley planar defects at 900 °C for fast lithium storage. Compared with H-Nb 2 O 5 with a perfect crystal structure synthesized at 1300 °C, the Wadsley planar defects in d-H-Nb 2 O 5 not only alleviated the strain induced by lithium ion insertion and enhanced the structural stability, but also accelerated the lithium ion insertion kinetics due to its strong adsorption capacity (Fig.…”

Simultaneous Enhancement of Lithium Transfer Kinetics and Structural Stability in Dual-Phase TiO2 Electrodes by Ruthenium Doping

“…Sufficiently high volumetric densities require the use of dual-phase TiO 2 with microsized domains. To enhance the ion/electron transfer within those domains, cation/anion substitution/doping is one of the most popular methods because it can effectively change the local electronic configuration, widen the diffusion channels, as well as tune the system entropy. − To date, most studies that optimize the lithium storage performance of dual-phase TiO 2 by cation substitution and doping are still focusing on nanomaterials. For example, Opra et al reported the effect of multivalent vanadium doping to improve the rate and cycling performance of bronze/anatase TiO 2 nanotubes.…”

Ultrafast Carbothermal Shock Synthesis of Wadsley–Roth Phase Niobium‐Based Oxides for Fast‐Charging Lithium‐Ion Batteries

“…To date, a variety of synthesis techniques, such as solid‐state reactions, [ 16–18 ] sol‐gel processes, [ 19 ] spray drying, [ 20 ] electrospinning, [ 21 ] and hydrothermal methods, [ 22 ] have been effectively employed to fabricate these materials. Nevertheless, these approaches almost invariably necessitate a prolonged annealing process—lasting from several hours to days—to yield well‐crystallized particles.…”