Solvothermal alcoholysis synthesis of hierarchically porous TiO2-carbon tubular composites as high-performance anodes for lithium-ion batteries

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.

TiO2 quantum dots confined in 3D carbon framework for outstanding surface lithium storage with improved kinetics

Pseudocapacitive lithium storage is an effective way to promote the improvement of electrochemical performance for lithium ion batteries. However, the intrinsically sluggish lithium ionic diffusion and the low electronic conductivity of TiO₂ limit its capability of pseudocapacitive behavior with fast surface redox reaction. In this work, TiO₂ quantum dots confined in 3-dimensional carbon framework have been synthesized by a facile process of reverse microemulsion method combined with heat treatment. The obtained composites effectively combine electrochemical redox with surface pseudocapacitive, showing excellent electrochemical properties. An ultra-high discharge capacity of 370.5 mAh/g can be retained after 200 cycles at a current density of 0.1 A/g. Ultra-long life extends to 10,000 cycles with an average capacity loss of as low as 0.00314% per cycle can be obtained at a high current density of 5.0 A/g, due to the high pesudocapacitance contribution of fast surface redox reaction. Furthermore, the practice application of the obtained electrode is also investigated in a full cell with LiCoO₂ as the cathode and a high capacity retention of 93.5% is maintained after 100 cycles at the current density of 0.1 A/g.