Facile synthesis of hollow Ti2Nb10O29 microspheres for high-rate anode of Li-ion batteries

Li+ Diffusion in LinCoNb2O6 (0 < n ≤ 6) Anode with High Capacity Density: Fast Kinetics and Mechanistic Insights

The potential of high power/capacity density and Li+ solid diffusion mechanisms of niobium-based binary metal oxide (CoNb2O6) anode material are investigated by combining high-rate Nb2O5 with the redox-active 3d transition metal Co. CoNb2O6 exhibited exceptional rate capability and cycling stability, which is attributed to anisotropic expansion during cycling and dual diffusion mechanisms at high and low lithium concentrations. The anisotropic expansion of crystals ensures structural stability, whereas the organic combination of a direct-hopping diffusion mechanism in LinCoNb2O6 (0 ≤ n ≤ 3) and a knock-off diffusion mechanism in LinCoNb2O6 (3 < n ≤ 6) based on the nudged elastic band (NEB) calculations reveals rapid Li+ solid diffusion and excellent rate performance during lithiation/delithiation. The electrochemical performance of CoNb2O6 also depends on its morphology, where different structures modulate synergistic Nb and Co interactions, influencing Li+ diffusion in the Nb layers. Specifically, the micron-scale structure formed by secondary particle attachment (CoNb2O6-MP) provides space for anisotropic expansion, fully utilizing the dual ion diffusion mechanism, enhancing diffusion efficiency, and delivering both high-capacity density and excellent rate performance. This work not only introduces CoNb2O6 with superior electrochemical properties but also provides insights into the solid diffusion mechanisms under various lithium concentrations, offering a foundation for designing electrode materials with enhanced ion diffusion pathways.

Rational design of hollow Ti2Nb10O29 nanospheres towards High-Performance pseudocapacitive Lithium-Ion storage

Ti2Nb10O29, as one of the most promising anode materials for lithium-ion batteries (LIBs), possesses excellent structural stability during lithiation/delithiation cycling and higher theoretical capacity. However, Ti2Nb10O29 faces some challenges, such as insufficient ion diffusion coefficient and poor electronic conductivity. To overcome these problems, this study investigates the effect of applying nanostructure engineering on Ti2Nb10O29 and the lithium storage behaviors. We successfully synthesized hollow Ti2Nb10O29 nanospheres (h-TNO NSs) via solvothermal method using phenolic resin nanospheres as the template. The effects of using a template or not and the annealing atmospheres on the microstructures of the as-prepared Ti2Nb10O29 are investigated. Different nanostructures (porous Ti2Nb10O29 nanoaggregates (p-TNO NAs) without a template and core-shelled Ti2Nb10O29@C nanospheres (cs-TNO@C NSs)) were formed through annealing in Ar. When examined as anodes for LIBs, the h-TNO NSs electrode with hollow spherical structure displayed a better lithium storage performance. Compared to its counterparts, p-TNO NAs and cs-TNO@C NSs, h-TNO NSs electrode exhibited a higher reversible capacity of 282.5 mAh g-1 at 1C, capacity retention of 79.5% (i.e., 224.6 mAh g-1) after 200 cycles, and a higher rate capacity of 173.1 mAh g-1 at 10C after 600 cycles. The excellent electrochemical performance of h-TNO NSs is attributed to the novel structure. The hollow nanospheres with cavities and thin shells not only exposed more active sites and improved ion diffusion, but also buffered the volume variation upon cycling and facilitated electrolyte penetration. This consequently enhanced the lithium storage performance of the electrode and its high pseudocapacitive contribution (90% at 1.0 mV s-1).

Mesoscopic Ti2Nb10O29 cages comprised of nanorod units as high-rate lithium-ion battery anode

Benefiting from large tunnel structure, zero strain feature, and excellent pseudocapacitive performance, Ti₂Nb₁₀O₂₉ was considered as a potential anode material for lithium-ion batteries (LIBs). Herein, Ti₂Nb₁₀O₂₉ cages comprised of nanorod units were elaborately designed. The mesoscopic structure could effectively shorten the ion diffusion pathway, and the big central electrolyte reservoir relieves the concentration polarization of electrolyte. Moreover, the perforated pore feature guarantees competent contact between electrolyte and framework. As the anode of LIBs, the mesoscopic Ti₂Nb₁₀O₂₉ cages deliver high reversible capacity (302.5 mAh/g) and rate capability (134.3 mAh/g at 30 A/g). This unique mesoscopic structure holds excellent potential for the electrode design of high-rate and long-life LIBs.

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.

A General Synthesis Strategy for Hollow Metal Oxide Microspheres Enabled by Gel-Assisted Precipitation

Hollow metal oxide microspheres (HMMs) have drawn enormous attention in different research fields. Reliable and scalable synthetic protocols applicable for a large variety of metal oxides are in emergent demand. Here we demonstrated that polymer hydrogel, such as the resorcinol formaldehyde (RF) one, existed as an efficient synthetic platform to build HMMs. Specifically, the RF gel forms stacked RF microspheres enlaced with its aqueous phase, where the following evaporation of the highly dispersed water leads to a gel-assisted precipitation (GAP) of the dissolved metal precursor onto the embedded polymeric solids suited for the creation of HMMs. By taking advantage of the structural features of hydrogel, this synthesis design avoids the delicate control on the usually necessitated coating process and provides a simple and effective synthetic process versatile for functional HMMs, particularly Nb₂ O₅ as a high-performance electrode material in Li-ion intercalation pseudocapacitor.

Titanium Niobium Oxide Ti2 Nb10 O29 /Carbon Hybrid Electrodes Derived by Mechanochemically Synthesized Carbide for High-Performance Lithium-Ion Batteries

This work introduces the facile and scalable two-step synthesis of Ti₂ Nb₁₀ O₂₉ (TNO)/carbon hybrid material as a promising anode for lithium-ion batteries (LIBs). The first step consisted of a mechanically induced self-sustaining reaction via ball-milling at room temperature to produce titanium niobium carbide with a Ti and Nb stoichiometric ratio of 1 to 5. The second step involved the oxidation of as-synthesized titanium niobium carbide to produce TNO. Synthetic air yielded fully oxidized TNO, while annealing in CO₂ resulted in TNO/carbon hybrids. The electrochemical performance for the hybrid and non-hybrid electrodes was surveyed in a narrow potential window (1.0-2.5 V vs. Li/Li⁺ ) and a large potential window (0.05-2.5 V vs. Li/Li⁺ ). The best hybrid material displayed a specific capacity of 350 mAh g^-1 at a rate of 0.01 A g^-1 (144 mAh g^-1 at 1 A g^-1 ) in the large potential window regime. The electrochemical performance of hybrid materials was superior compared to non-hybrid materials for operation within the large potential window. Due to the advantage of carbon in hybrid material, the rate handling was faster than that of the non-hybrid one. The hybrid materials displayed robust cycling stability and maintained ca. 70 % of their initial capacities after 500 cycles. In contrast, only ca. 26 % of the initial capacity was maintained after the first 40 cycles for non-hybrid materials. We also applied our hybrid material as an anode in a full-cell lithium-ion battery by coupling it with commercial LiMn₂ O₄ .