TiO2 Anode Materials Research Articles

Graphite from Dead Li‐Ion Batteries: A “Powerful” Additive for Fabrication of High‐Performance Li‐Ion Capacitors

AbstractLithium‐ion capacitors (LICs) are considered a promising next‐generation energy storage system with high energy density and power capability. The conductive additive is a passive and indispensable material in deciding the electrochemical performance of an energy storage device during high current charging and discharging processes. The incorporation of a suitable conductive additive into the layers of an electrode improves electronic conductivity. It reduces the internal resistance and polarization of the electrode resulting in the enhanced performance of the charge‐storage system. Herein, recovered graphite (RG) is reported from dead Li‐ion batteries as an excellent conductive additive that can improve the electronic conductivity of the electrode material. Compared with commercial conductive additive acetylene black (AB), the TiO2 anode material with 5% RG delivered a high discharge capacity of 163 mAh g−1 at a current rate of 0.15 A g−1 with a coulombic efficiency of ≈99% after 500 cycles in half‐cell assembly. The fabricated AC/TiO2@5%RG LIC displays an excellent electrochemical performance with a maximum energy density of ≈50 Wh kg−1 at a current density of 0.15 A g−1. Notably, the LIC rendered promising performance at different temperature conditions (0, 10, 25, and 50 °C).

TiO2 recovered from spent selective catalytic reduction catalysts as anode material for lithium-ion batteries

Environmental protection and sustainable development are among the most severe problems in the world today. Spent selective catalytic reduction (SCR) catalysts are recognized as hazardous waste. Here, the TiO2, which accounts for nearly 80% of spent SCR catalysts, is recovered by the alkaline leaching method, and performed higher electrochemical performances than commercial TiO2 products for anode materials of Lithium-ion batteries. W, V, Si, and Al leaching rates are 40.04%, 89.59%, 61.64%, and 11.57%, respectively. A combination of density functional theory (DFT)--based calculations and experiments revealed that trace doping of Al is beneficial to the electrochemical performance of the cell, which helps us tune the Al content in the obtained materials. On this basis, the regenerated TiO2 anode materials with graphene (GR) materials are synthesized to improve the electrochemical performance, and the specific capacity of the recycled TiO2 is 188.5 mAh·g−1 after 500 cycles, and that of the regenerated TiO2/GR is the highest at 275.2 mAh·g−1. Finally, an environmental assessment of this recycling process is also carried out, human toxicity potential, CO2 gas emissions, NMVOC gas emissions, and SO2 gas emissions in this work are reduced by nearly 86.9%, 87.0%, 92.5%, and 87.0% compared with commercial sol-gel synthetic method. This work highlights the significance of recovery for preparing new energy storage materials from secondary resources.

The Influence of TiO2 Nanoparticles Morphologies on the Performance of Lithium-Ion Batteries.

Anode materials based on the TiO2 nanoparticles of different morphologies were prepared using the hydrothermal method and characterized by various techniques, such as X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), and N2 absorption. The TiO2 nanoparticles prepared were used as anode materials for lithium-ion batteries (LIBs), and their electrochemical properties were tested using discharging/charging measurements. The results showed that the initial morphology of the nanoparticles plays a minor role in battery performance after the first few cycles and that better capacity was achieved for TiO2 nanobelt morphology. The sharp drop in the specific capacity of LIB during their first cycles is examined by considering changes in the morphology of TiO2 particles and their porosity properties in terms of size and connectivity. The performance of TiO2 anode materials has also been assessed by considering their phase.

Improved Lithium Storage Performance of a TiO2 Anode Material Doped by Co

TiO2 is a promising anode material for lithium-ion batteries (LIBs) due to its low cost, suitable operating voltage, and excellent structural stability. The inherent poor electron conductivity and low ion diffusion coefficient, however, severely limit its application in lithium storage. Here, Co-doped TiO2 is synthesized by a hydrothermal method as an anode material since Co@TiO2 possesses a large specific surface area and high electronic conductivity. Thanks to the Co dopants, the ion diffusion and electron transport are both greatly improved, which is very beneficial for cycle stability, coulombic efficiency (CE), reversible capacity, and rate performance. As a result, Co@TiO2 shows a high reversible capacity of 227 mAh g-1 at 3 C, excellent rate performance, and cycling stability with a capacity of about 125 mAh g-1 at 10C after 600 cycles (1 C = 170 mA g-1).

Oxygen Vacancies‐Rich TiO2/C Nanofibers with Boron, Nitrogen Dual‐Doping for Ultrafast Sodium Storage

AbstractTiO2 is an intercalation pseudocapacitive material with low potential and minor structural changes during the sodium storage process. However, the intrinsic electronic conductivity and ionic diffusion kinetics are not unsatisfactory for ultrafast sodium storage. Defect engineering plays a pivotal part in improving the sodium storage kinetics of TiO2 anode materials. Now the common defect regulation methods are complicated. Herein, a simple NaBH4 reduction method is proposed to produce rich oxygen vacancies and boron doping in nitrogen‐doped TiO2/C mesoporous nanofibers, and the finally obtained oxygen vacancies (OVs)‐rich TiO2/C nanofibers (TC‐OVs) also build internal vertical channels. This particular structure of TC‐OVs favors fast transport for electrons and ions, resulting in ultrafast rate capability (156 mAh g−1, 2 A g−1) and long lifespan (139 mAh g−1, 1000 cycles, 1.0 A g−1). The inspiring sodium storage performance of TC‐OVs benefits from the high pseudocapacitance contribution (94%, 5.0 mV s−1). This work provides a method to adjust defects and structures of TiO2 electrode materials for ultrafast chemical energy storage.

Synthesis of Porous Hollow Spheres Co@TiO2−x-Carbon Composites for Highly Efficient Lithium-Ion Batteries

The hollow TiO2 anode material has received great attention for next-generation LIBs because of its excellent stability, environmental friendly, and low volume change during lithiation/delithiation. However, there are some problems associated with the current anatase TiO2 anode materials in practical application owing to low lithium-ion diffusivity and poor reversible theoretical capacities. The introduction of defects has been turned out to be a significant and effective method to improve electronic conductivity, especially oxygen vacancies. In this paper, a facile hydrothermal reaction and subsequent chemical vapor deposition method were successfully used to fabricate Co@TiO2−x-carbon hollow nanospheres. These results suggest that the synthesized product exhibits good rate performance and superior cycling stability.

Influences of calcination temperature on the shape and electrochemical performance of TiO2 anode materials prepared through normal-pressure hydrolysis-ion exchange of potassium salt

Influences of calcination temperature on the shape and electrochemical performance of TiO2 anode materials prepared through normal-pressure hydrolysis-ion exchange of potassium salt

Characterization of Sn@TiO2 Anode Material for Li-Ion Battery Application

In this work, various phases of nanorod TiO2 were fabricated by hydrothermal process. Different crystalline phases of TiO2 nanowires will be analyzed by electrochemical analysis (CV, LSV, C-rate, charge and discharge, and EIS test) to investigate the influence of Li+ diffusion rate on specific capacitance. The in-situ XRD structure for charging and discharging will be carried out to explore the diffusion and structural behavior of Li+ in TiO2 was explored its fast charging, high capacitance and high safety characteristics, which will be a fundamental research of Sn modified on TiO2 nanowire. Transmission electron microscope image showed a range of 20 to 80 nm length TiO2 nanorods was success synthesized, and the XRD indicated the phase were rutile, anatase and rutile/anatase mixed by controlling the chelating agents (citric acid). The specific capacity of TiO2 nanorod was 120 mAh/g which the Columbic efficiency was ~ 99% under 0.1 C. A morphology of Sn@TiO2 was investigated as nano-capsule. The results are supposed to clarify the key factors of the fast charge, high specific capacitance and safety. It is expected that the Li+ ion influence on structure changes during the charge and discharge process by implementing this research. The fast charging, high specific capacity and high safety mechanism will be established as an index for material application and commercial products.Keywords: TiO2 anode materials, Sn@TiO2 anode materials, Li-ion battery, In-operando XRD

Comparative study of the morphological and optical properties of RE3+ (=ND3+, DY3+) doped TiO2: A pursuit for suitable anode material for DSSCs

Nano scaled trivalent Rare-earth Elements (RE3+ = Nd3+ and Dy3+) doped TiO2 anode materials were synthesized by hydrothermal method and characterized to analyze the morphological and optical properties. Having N719 as the dye and Platinum as counter electrode, the solar cells were fabricated to harness the solar energy. The reduction in bandgap and the enhanced efficiency of DSSCs in the TiO2-dye-electrolyte system were analyzed. Nd3+ doped TiO2 exhibits the desired results and superior efficiency than the pure and Dy3+ doped TiO2. Thus comparing the materials’ morphological and optical properties as well as the solar cell efficiency, Nd3+ doped TiO2 proved to be an improved anode material for the fabrication of DSSCs.

Graphether: a reversible and high-capacity anode material for sodium-ion batteries with ultrafast directional Na-ion diffusion.

Sodium-ion batteries (SIBs) have been attracting great attention as the most promising alternative to lithium-ion batteries (LIBs) for large-scale energy storage. However, the absence of suitable anode materials is the main bottleneck for the commercial application of SIBs. Herein, the adsorption and diffusion behaviors of Na on graphether are predicted by first-principles density functional calculations. Our results show that Na atoms can be adsorbed on graphether forming a uniform and stable coverage on both sides. Even at low intercalated Na concentrations, the semiconducting graphether can be changed to a metallic state, ensuring good electrical conductivity. Due to the structural anisotropy of graphether, the Na+ ions show a remarkable one-dimensional diffusion with an ultralow energy barrier of 0.04 eV, suggesting ultrafast charge/discharge characteristics. The graphether monolayer has a high theoretical specific capacity of 670 mA h g-1, which is much higher than commercial graphite anode materials. Furthermore, the average voltage is 1.58 V, comparable with that of commercial TiO2 anode materials for LIBs (1.5 V). During the charge/discharge process, graphether could mostly preserve the structural integrity upon the adsorption of Na even at the maximum concentration, suggesting its good reversibility. All these results show that graphether is a promising anode material for high-performance SIBs.

A coordinated regulation strategy to improve electronic conductivity and Li-ion transport for TiO2 lithium battery anode materials

Titanium dioxide (TiO2) is considered as one of the most promising anode materials for lithium-ion batteries. However, improving the poor electronic conductivity and slow Li-ion diffusion of TiO2 anode materials are urgently required. In this study, we design a Cu-doped TiO2 hollow nanosphere structure based on the coordinated regulation strategy of size, nanostructure and doping. The results revealed the cause of the oxygen vacancy generation and its mechanism of action in the battery electrode reaction process. Moreover, the electrochemical results showed that Cu-doped hollow nanosphere structure significantly improves the low conductivity and the slow Li-ion diffusion rate of TiO2. These findings show that our work provides a new modification idea to improve the electrochemical performance of TiO2 anode materials for LIBs.

Hierarchical TiO2 microspheres with enlarged lattice spacing for rapid and ultrastable sodium storage

Intercalation-type TiO2 anode materials have garnered extensive interest for use in Na-ion batteries owing to their low cost and excellent stability. However, such materials are limited by their unsatisfactory specific capacity, particularly at high rates. Herein, we demonstrated the synthesis of hierarchical anatase TiO2 microspheres with enlarged lattice spacings using a simple salt template-assisted spray pyrolysis technique. The broad lattice distance can not only promote ionic transfer but also reduce the band gap with locally enhanced differential charge density, according to density functional theory calculations. Consequently, the resultant sample exhibited reversible specific capacities as high as 362 and 141.8 mA h g−1 at 50 and 5 A g−1, respectively. Impressively, the sample retained specific capacities of 154 mA h g−1 at 1.0 A g−1 after 1600 cycles and of 93.4 mA h g−1 at 5 A g−1 after 7700 cycles. To the best of our knowledge, the Na storage performance of the prepared sample is one of the best among that of TiO2-dominated anode materials. These findings provide new insight into the preparation of novel anode materials for Na-ion batteries with high ionic and electronic conductivities.

Preparation of nanoporous Sn-doped TiO2 anode material for lithium-ion batteries by a simple dealloying method

Nanoporous Sn-doped TiO2 (NP-TiO2/Sn) composite is successfully fabricated by etching AlTiSn ternary alloy ribbons in NaOH solution at room temperature. The NP-TiO2/Sn composite exhibits a 3D nanosponge structure accompanied with nanowires on it. Besides, Sn nanoparticles embed into the ligaments of amorphous TiO2. Owing to the unique hierarchical structure and the introduction of Sn, the NP-TiO2/Sn composite exhibits enhanced rate capacities and long cycling life compared with non-added Sn composition. Moreover, it also performs good cycling life and coulombic efficiency at both low and high current densities. When atomic ratio of Ti and Sn is 9:1, the best discharge capacity and cycling performance are exhibited. After circulating 300 cycles at 1 A g−1, the NP-TiO2/Sn composite shows a high capacity, which doubles pure NP-TiO2. The good electrochemical performance and facile process favor the practical utilization as the anode material of lithium-ion batteries.

A surface chemistry assistant strategy to high power/energy density and cost-effective cathode for sodium ion battery

In this work, high power/energy density (6750 W kg−1/364.2 Wh kg−1) Na2.4Fe1.8(SO4)3 (NFS) composite has been achieved by surface chemistry assistant effective carbon coating at 350 °C with highly improved electrochemical performance as cathode materials for sodium ion batteries (SIBs). The prepared NFS/C composite shows superb electrochemical performance of high capacity (100.2 mAh g−1 at 1C), great cyclability (95.0 mAh g−1 after 100 cycles at 1 C) and excellent rate performance (95.1 mAh g−1 at 5 C, 91.3 mAh g−1 at 10 C). The full battery of NFS/C coupled with TiO2 anode material also exhibits high reversible capacity of 87.0 mAh g−1 at 10 C with an average discharge voltage over 3.0 V. The outstanding performance of this NFS/C composite originates from highly improved electron conductivity by surface chemistry enhanced effective carbon coating and restricted particle size. This NFS/C composite has fully demonstrated the high-voltage and low cost advantages of polyanion type sulfate materials. It can be one of the most pragmatic candidates for large scale energy storage cathode material in SIBs. This synthesis method for low temperature carbon coating can also be useful for other electrode materials especially those may decompose or reduce at high temperature.

Annealing temperature-dependent electrochemical properties of Aeroxide P25 TiO2 nanoparticles as anode material for lithium storage

TiO2 has been widely studied as an important electrode material for electrochemical energy storage. Understanding its relationship between textural properties and electrochemical characteristics is essential to boosting its practical performances. Herein, Aeroxide P25 TiO2 nanoparticles annealing at different temperatures (400–600 °C) were investigated as an anode material of lithium ion battery. Their evolution in crystal phase and microstructural characteristics were characterized by XRD and BET surface analysis, and their lithium storage properties in half-cells were evaluated by various electrochemical analyses, including cyclic voltammetry, cycling testing, and electrochemical impedance spectroscopy. It was found that the lithium storage properties were critically dependent on the size of TiO2 anode materials. Pristine P25 initially exhibited the highest initial discharge specific capacity due to its smallest particle size; however, rapid capacity loss occurred during extended cycling. The annealing process was found to effectively enhance the cycling stability of TiO2 although possessing a large particle size and smaller surface area. Typically, P400 showed the best performances in cycling stability, capacity retention ratio, and rate capability, which is mainly attributed to the synergistic effect of high crystallinity, reasonable particle size, and less internal resistance. This study provides an instance of optimizing the textural properties of metal oxides for advanced LIB anode material applications.

Preparation and lithium storage properties of C@TiO2/3D carbon hollow sphere skeleton composites

Rational design and facile synthesis of hybrid TiO2 anode materials with high electrical conductivity and ionic accessibility are urgently desired to construct high performance litium-ion batteries. In this work, We first utilize conductive hollow porous pollen carbon microsphere as skeleton to load C@TiO2 nanoparticles. The C@TiO2/3D pollen carbon (CTPC) composite with hollow porous structure has been successfully developed via a simple method. As a result, CTPC-700 (calcination temperature of 700 °C) electrode material exhibits superior electrochemical performance for lithium ion batteries, delivering an outstanding specific capacity of 148 mA h g−1 up to 1000 cycles at 5.0C and a superior high-rate performance of 112 mA h g−1 at 10.0C. Therefore, the special structure of the as-prepared composites can improve the stability of the electrode and enhance its electrochemical performance, which is promising for the next-generation of lithium-ion batteries.

TiO2/NiO/reduced graphene oxide nanocomposites as anode materials for high-performance lithium ion batteries

In this study, NiO was synthesized via a facile method and coated on the surface of a TiO2 anode material doped with rGO (reduced graphene oxide). TiO2/NiO/rGO nanocomposite structures were synthesized by a two-step solid-state method, and their lithium storage capacity was investigated and compared with that of both as-prepared TiO2/NiO and pure TiO2. The coating over the TiO2 surface helped to attain a higher capacity and cycle stability than that without it, even at high current rates. The TiO2/NiO/rGO nanocomposites show excellent performance with an initial discharge capacity of up to 324 mAh/g between 0 and 3 V vs Li at 20 mA/g. Furthermore, at a high current density of 100 mA/g, the TiO2/NiO/rGO nanocomposite still achieved a capacity of 245 mAh/g after 200 cycles. This excellent performance could be attributed to the stable framework and high electronic conductivity within the TiO2/NiO/rGO nanocomposite.

Hierarchically ordered mesoporous TiO2 nanofiber bundles derived from natural collagen fibers for lithium and sodium storage

To date, most of reported high performance TiO2 anode materials for both lithium and sodium ion batteries rely on employing tedious, high cost, and complex preparation procedures, which impede its scalable production and practical uses. Here, we demonstrate a facile synthetic strategy to engineer a one-dimensional (1D) hierarchically ordered mesoporous TiO2 nanofiber bundles (TBs) by using low-cost natural collagen fibers as the biotemplate. The as-prepared TBs are mainly constructed by hierarchical organization of ordered nanofibers (∼50–100 nm in diameter) each of which composed of well-crystallized TiO2 nanoparticles with a particle size of ∼10–20 nm, endowing a well-defined mesoporous structrue of the TBs along with a large specific surface area of 100.89 m2 g−1. This 1D hierarchical mesoporous structure is not only able to offer shortened ion diffusion paths, but also to ensure efficient electrolyte penetration for ion access and keep the structure integrity. As a result, the TBs-based anode materials show excellent electrochemical lithium and sodium storage prorperties. When evaluated in a lithium ion cell, TBs delivery a high discharge capacity of 120 mAh g−1 under 5C rate, and exhibits long-term cycling stability with an extremely low capacity decay of 0.03% over 500 cycles. Even for sodium ion cell tests, a remarkable capacity of nearly 130 mAh g−1 is also achieved at a current density of 200 mA g−1, suggesting the reversible sodium storage capability of the TBs. This synthetic approach is promising for developing low cost, high efficient and practical TiO2 anode materials available for lithium and sodium ion batteries.

The Impact of Crystallinity on Mesoporous TiO2 Nanoparticle Electrode for Li- and Na- Ion Batteries

Demands for rechargeable batteries have been significantly increasing not only in portable electronics (e.g. cell phones and laptops), but also in large-scale energy storage systems (e.g. grids).1-3 TiO2 as anode materials is electrochemically active in both lithium and sodium ion batteries. It has drawn significant attentions due to its nontoxicity, stability, low production cost and high capacity. Indeed, many works have been conducted to study the impact of morphology, particle size, facet control and electronic structure manipulation on the electrochemical performance of TiO2 materials in either lithium or sodium ion batteries.4-9 In addition, in terms of crystalline structures, TiO2 materials with various polymorphs, for example, anatase (tetragonal, I41/amd), rutile (tetragonal, P42/mnm), TiO2-B (monoclinic, C2/m), brookite (orthorhombic, Pbcv) and amorphous TiO2 have been extensively investigated.10-14 Previously, Xiong et al. observed a phase transformation from amorphous to face-centered cubic phase when the amorphous TiO2 nanotube electrode first discharged under 1 V vs. Li/Li+, significantly self-improving the long-term reversibility and specific capacity.15 Xiong et al. also investigated the electrochemical performance of amorphous TiO2 nanotubes as anode materials in sodium cell.14Though capacity increased gradually with charge-discharge cycling, the phase transition from amorphous to cubic phase was not observed. Herein, we demonstrate the impact of various degree of crystallinity on pure TiO2 anode materials for both Li and Na ion batteries. XRD, Raman, selected area electron diffraction (SAED) and high resolution transmission electron microscopy (HRTEM) were conducted to confirm the gradually crystalized TiO2 nanoparticles. Electrochemical performance of TiO2 nanoparticles was tested by voltage profile, rate capability, cycle life, cyclic voltammetry (CV) and galvanostatic intermittent titration technique (GITT). Structure evolution during cycling was tested by ex situRaman spectroscopy and soft XAS.

Defect-rich TiO2-δ nanocrystals confined in a mooncake-shaped porous carbon matrix as an advanced Na ion battery anode

Abstract Inferior electronic conductivity and sluggish sodium ion diffusion are still two big challenges for TiO2 anode material for Na ion batteries (SIBs). Herein, we synthesize TiO2/C composites by the pyrolysis of MIL-125(Ti) precursor and successfully introduce defects to TiO2/C composite by a simple magnesium reduction. The as-prepared defect-rich TiO2-δ/C composite shows mooncake-shaped morphology consisting of TiO2-δ nanocrystals with an average particle size of 5 nm well dispersed in the carbon matrix. When used as a SIBs anode, the defect-rich TiO2-δ/C composite exhibits a high reversible capacity of 330.2 mAh g−1 at 50 mA g−1 at the voltage range of 0.001–3.0 V and long-term cycling stability with negligible decay after 5000 cycles. Compared with other four TiO2/C samples, the electrochemical performance of defect-rich TiO2-δ/C is highly improved, which may benefit from the enhanced electronic/ionic conductivities owing to the defect-rich features, high surface area rendering shortened electronic and ionic diffusion path, and the suppress of the TiO2 crystal aggregation during sodiation and desodiation process by the carbon matrix.