Sn-Doped Rutile TiO2 Hollow Nanocrystals with Enhanced Lithium-Ion Batteries Performance

Highly Reversible Ti/Sn Oxide Nanocomposite Electrodes for Lithium Ion Batteries Obtained by Oxidation of Ti3 Al(1-x) Snx C2 Phases

Among the materials for the negative electrodes in Li-ion batteries, oxides capable of reacting with Li+ via intercalation/conversion/alloying are extremely interesting due to their high specific capacities but suffer from poor mechanical stability. A new way to design nanocomposites based on the (Ti/Sn)O2 system is the partial oxidation of the tin-containing MAX phase of Ti3 Al(1-x) Snx O2 composition. Exploiting this strategy, this work develops composite electrodes of (Ti/Sn)O2 and MAX phase capable of withstanding over 600 cycles in half cells with charge efficiencies higher than 99.5% and specific capacities comparable to those of graphite and higher than lithium titanate (Li4 Ti5 O12 ) or MXenes electrodes. These unprecedented electrochemical performances are also demonstrated at full cell level in the presence of a low cobalt content layered oxide and explained through an accurate chemical, morphological, and structural investigation which reveals the intimate contact between the MAX phase and the oxide particles. During the oxidation process, electroactive nanoparticles of TiO2 and Ti(1-y) Sny O2 nucleate on the surface of the unreacted MAX phase which therefore acts both as a conductive agent and as a buffer to preserve the mechanical integrity of the oxide during the lithiation and delithiation cycles.

Europium modified TiO2 as a high-rate long-cycle life anode material for lithium-ion batteries

Oxygen vacancies and Ti3+ were produced by Eu3+/Eu2+ doped TiO2, which features excellent rate performance and long-term stability.

Ultrafast and Stable Lithium Storage Enabled by the Electric Field Effect in Layer-Structured Tablet-Like NH4TiOF3 Mesocrystals

Design and synthesis of advanced electrode materials with fast and stable ion storage are of importance for energy storage applications. Herein, we propose that introducing the heterogeneous interface in layer-structured mesocrystals is an efficient way to greatly improve the rate capability and cycle stability of lithium-ion battery (LIB) devices. NH₄TiOF₃ mesocrystals were employed as a typical model system to demonstrate the idea. The NH₄TiOF₃ mesocrystals were obtained via the hydrothermal reaction, and the NH₄TiOF₃/TiO₂ interfaces were generated through calcining at different temperatures under an argon atmosphere. Phase composition, microstructure, and chemical analyses show that the as-prepared NH₄TiOF₃ mesocrystals possess "tablet-like" morphology, and the formation of the NH₄TiOF₃/TiO₂ interface can be controlled by the calcination temperature. When evaluated as the anode for LIBs, the optimized sample (NH₄TiOF₃ calcined at 250 °C, NTF-250) shows excellent, fast, and stable lithium storage properties. Specifically, the NTF-250 electrode holds a reversible capacity of 159.5 mA h g^-1 after 200 cycles at 0.2 A g^-1. At a high current density of 20 A g^-1, the electrode still maintains a reversible capacity of 89.6 mA h g^-1 and reaches a reversible capacity of 128.6 mA h g^-1 at a current density of 1 A g^-1 after 2000 cycles. Theoretical and experimental studies show that the synergistic effects of the heterogeneous NH₄TiOF₃/anatase TiO₂ interface in the layer-structured NH₄TiOF₃ mesocrystals lead to the upgraded electrochemical properties. Especially, the local build-in electric field induced by the nonuniform distribution of charge across the NH₄TiOF₃/anatase TiO₂ interface facilitates the charge transport during the charging and discharging cycling. The current electrode design strategy paves a new way in boosting stable ion storage and thus is of great interest in energy storage and conversion.

Biomass-Mediated Synthesis of Cu-Doped TiO2 Nanoparticles for Improved-Performance Lithium-Ion Batteries

Pure TiO₂ and Cu-doped TiO₂ nanoparticles are synthesized by the biomediated green approach using the Bengal gram bean extract. The extract containing biomolecules acts as capping agent, which helps to control the size of nanoparticles and inhibit the agglomeration of particles. Copper is doped in TiO₂ to enhance the electronic conductivity of TiO₂ and its electrochemical performance. The Cu-doped TiO₂ nanoparticle-based anode shows high specific capacitance, good cycling stability, and rate capability performance for its envisaged application in lithium-ion battery. Among pure TiO₂, 3% Cu-doped TiO₂, and 7% Cu-doped TiO₂ anode, the latter shows the highest capacity of 250 mAh g^-1 (97.6% capacity retention) after 100 cycles and more than 99% of coulombic efficiency at 0.5 A g^-1 current density. The improved electrochemical performance in the 7% Cu-doped TiO₂ is attributed to the synergetic effect between copper and titania. The results reveal that Cu-doped TiO₂ nanoparticles might be contributing to the enhanced electronic conductivity, providing an efficient pathway for fast electron transfer.