Insight into the effects of dislocations in nanoscale titanium niobium oxide (Ti2Nb14O39) anode for boosting lithium-ion storage

Defect engineering through induction of dislocations is an efficient strategy to design and develop an electrode material with enhanced electrochemical performance in energy storage technology. Yet, synthesis, comprehension, identification, and effect of dislocation in electrode materials for lithium-ion batteries (LIBs) are still elusive. Herein, we propose an ethanol-thermal method mediated with surfactant-template and subsequent annealing under air atmosphere to induce dislocation into titanium niobium oxide (Ti₂Nb₁₄O₃₉), resultant nanoscale-dislocated-Ti₂Nb₁₄O₃₉ (Nano-dl-TNO). High-resolution transmission electron microscope (HRTEM), fast Fourier transform (FFT), and Geometrical phase analysis (GPA) denote that the high dislocation density engraved with stacking faults forms into the Ti₂Nb₁₄O₃₉ lattice. The presence of dislocation could offer an additional active site for lithium-ion storage and tune the electrical and ionic properties of the Ti₂Nb₁₄O₃₉. The resultant Nano-dl-TNO delivers superior rate capability, high specific capacity, better cycling stability, and making Ti₂Nb₁₄O₃₉ a suitable candidate among fast-charging anode materials for lithium-ion batteries. Moreover, In-situ High-resolution transmission electron microscope (HRTEM) and Geometrical phase analysis (GPA) evinces that the removal of the dislocated area in the Nano-dl-TNO leads to the contraction of the lattice, alleviation of the total volume expansion, causing the symmetrization and preserves structural stability. The present findings and designed approach reveal the rose-colored perspective of dislocation engineering into mixed transition metal oxides as next-generation anodes for advanced lithium-ion batteries and all-solid-state lithium-ion batteries.

Effects of Transition Metal Substituents on Interfacial and Electronic Structure of CH3NH3PbI3/TiO2 Interface: A First-Principles Comparative Study

To evaluate the influence of transition metal substituents on the characteristics of CH3NH3PbI3/TiO2, we investigated the geometrical and electronic properties of transition metal-substituted CH3NH3PbI3/TiO2 by first-principles calculations. The results suggested that the substitution of Ti4+ at the five-fold coordinated (Ti5c) sites by transition metals is energetically favored. The substituted interface has enhanced visible light sensitivity and photoelectrocatalytic activity by reducing the transition energies. The transition metal substitution can effectively tune the band gap of the interface, which significantly improves the photo-reactivity. The substituted systems are expected to be more efficient in separating the photo-generated electrons-holes and active in the visible spectrum.

Stability of Halide Perovskite Solar Cell Devices: In Situ Observation of Oxygen Diffusion under Biasing

Using in situ electrical biasing transmission electron microscopy, structural and chemical modification to n-i-p-type MAPbI₃ solar cells are examined with a TiO₂ electron-transporting layer caused by bias in the absence of other stimuli known to affect the physical integrity of MAPbI₃ such as moisture, oxygen, light, and thermal stress. Electron energy loss spectroscopy (EELS) measurements reveal that oxygen ions are released from the TiO₂ and migrate into the MAPbI₃ under a forward bias. The injection of oxygen is accompanied by significant structural transformation; a single-crystalline MAPbI₃ grain becomes amorphous with the appearance of PbI₂ . Withdrawal of oxygen back to the TiO₂ , and some restoration of the crystallinity of the MAPbI₃ , is observed after the storage in dark under no bias. A subsequent application of a reverse bias further removes more oxygen ions from the MAPbI₃ . Light current-voltage measurements of perovskite solar cells exhibit poorer performance after elongated forward biasing; recovery of the performance, though not complete, is achieved by subsequently applying a negative bias. The results indicate negative impacts on the device performance caused by the oxygen migration to the MAPbI₃ under a forward bias. This study identifies a new degradation mechanism intrinsic to n-i-p MAPbI₃ devices with TiO₂ .

Influence of charged defects on the interfacial bonding strength of tantalum- and silver-doped nanograined TiO2

The negatively charged defects and accumulated electrons at the interfacial layer of tantalum- and silver-doped nanograined TiO₂ increase its bonding strength.