An Electrochemically Anodic Study of Anatase TiO2 Tuned through Carbon-Coating for High-performance Lithium-ion Battery

Biomass-derived hierarchical N, P codoped porous 3D-carbon framework@TiO2 hybrids as advanced anode for lithium ion batteries

Advanced anode materials with high theoretical capacity and rate capability are urgently required for next generation lithium ion batteries (LIBs). In this study, hierarchical N, P codoped porous 3D-carbon framework@TiO₂ nanoparticle hybrid (N, PC@TiO₂) is synthesized by using pollen as biomass precursor through a facile template assisted sol-gel methode and exhibits hierarchical porous hollow structure with plenty of redox active sites and enhanced specific surface area. Compared with N, P codoped porous micro-carbon sphere framework and TiO₂ porous hollow microspheres anodes, the N, PC@TiO₂ anode shows superior reversible capacity of 687.3 mAh g^-1 at 0.1 A g^-1 after 200 cycles and 440.5 mAh g^-1 after 1000 cycles at 1 A g^-1. The excellent performance can be attributed to the rational hierarchical porous hollow structure and the synergetic contributions from the N, P codoped-carbon and TiO₂ components, which enhance Li⁺ storage capability, accelerate the reaction kinetics and stabilize the electrode structure and interface during charge/discharge process. This study suggests a practical strategy to prepare novel anode material with abundant natural resource and facile synthetic route, and the optimized hybrid anode with outstanding Li⁺ storage properties provides hopeful application prospect in advanced LIBs and other energy storage devices.

Size-Tunable Olive-Like Anatase TiO2 Coated with Carbon as Superior Anode for Sodium-Ion Batteries

Olive-shaped anatase TiO₂ with tunable sizes in nanoscale are designed employing polyvinyl alcohol (PVA) as structure directing agents to exert dramatic impacts on structure shaping and size manipulation. Notably, the introduced PVA simultaneously serves as carbon sources, bringing about a homogenous carbon layer with intimate coupling interfaces for boosted electronic conductivity. Constructed from tiny crystalline grains, the uniformly dispersed carbon-coated TiO₂ nano-olives (TOC) possess subtle loose structure internally for prompt Na⁺ transportations. When utilized for sodium-ion storage, the size effects are increasingly significant at high charge-discharge rates, leading to the much superior rate performances of TOC with the smallest size. Bestowed by the improved Na⁺ adsorption and diffusion kinetics together with the promoted electron transfer, it delivers a high specific capacity of 267 mAh g^-1 at 0.1 C (33.6 mA g^-1 ) and sustains 110 mAh g^-1 at a rather high rate of 20 C. Even after cycled at 10 C over 1000 cycles, a considerable capacity of 125 mAh g^-1 with a retention of 94.6% is still obtained, highlighting its marvelous long-term cyclability and high-rate capabilities.

Black Anatase Titania with Ultrafast Sodium-Storage Performances Stimulated by Oxygen Vacancies

Nanostructured black anatase titania with oxygen vacancies (OVs) is efficiently obtained and employed as an anode in sodium-ion batteries (SIBs) for the first time. The incorporation of OVs into TiO2 is demonstrated to render considerably enhanced-rate performances, higher initial capacities, and an accelerated electrochemical activation process during cycling, derived from the boosted intrinsic electric conductivity and improved kinetics of Na uptake. Bestowed with the integrated merits of OVs and shortened Na ion diffusion length in the nanostructure, black titania delivers a reversible specific capacity of 207.6 mAh g(-1) at 0.2 C, retains 99.1% over 500 cycles at 1 C stably, and still maintains 91.2 mAh g(-1) even at the high rate of 20 C. Density functional theory (DFT) calculations suggest that the lower sodiation energy barrier of anatase with OVs enables a more favorable Na intercalation into black anatase. Thus, it is of great significance to introduce OVs into TiO2 to stimulate ultrafast and durable sodium-storage properties, which also offers a potential strategy to project more superior electrodes, utilizing internal defects.