RESUMO
Free-standing, binder-free, and conductive additive-free mesoporous titanium dioxide/carbon hybrid electrodes were prepared from co-assembly of a poly(isoprene)-block-poly(styrene)-block-poly(ethyleneâ oxide) block copolymer and a titanium alkoxide. By tailoring an optimized morphology, we prepared macroscopic mechanically stable 300â µm thick monoliths that were directly employed as lithium-ion battery electrodes. High areal mass loading of up to 26.4â mg cm-2 and a high bulk density of 0.88â g cm-3 were obtained. This resulted in a highly increased volumetric capacity of 155â mAh cm-3 , compared to cast thin film electrodes. Further, the areal capacity of 4.5â mAh cm-2 represented a 9-fold increase compared to conventionally cast electrodes. These attractive performance metrics are related to the superior electrolyte transport and shortened diffusion lengths provided by the interconnected mesoporous nature of the monolith material, assuring superior rate handling, even at high cycling rates.
RESUMO
Free-standing, binder-free, titanium-niobium oxide/carbon hybrid nanofibers are prepared for Li-ion battery applications. A one-pot synthesis offers a significant reduction of processing steps and avoids the use of environmentally unfriendly binder materials, making the approach highly sustainable. Tetragonal Nb2 O5 /C and monoclinic Ti2 Nb10 O29 /C hybrid nanofibers synthesized at 1000 °C displayed the highest electrochemical performance, with capacity values of 243 and 267â mAh g-1 , respectively, normalized to the electrode mass. At 5â A g-1 , the Nb2 O5 /C and Ti2 Nb10 O29 /C hybrid fibers maintained 78 % and 53 % of the initial capacity, respectively. The higher rate performance and stability of tetragonal Nb2 O5 compared to that of monoclinic Ti2 Nb10 O29 is related to the low energy barriers for Li+ transport in its crystal structure, with no phase transformation. The improved rate performance resulted from the excellent charge propagation in the continuous nanofiber network.
Assuntos
Carbono/química , Fontes de Energia Elétrica , Eletrodos , Lítio/química , Nanofibras/química , Nióbio/química , Titânio/química , Técnicas Eletroquímicas , Transporte de Íons , Microscopia Eletrônica de Varredura , Estrutura Molecular , Óxidos/química , Espectroscopia Fotoeletrônica , Espectrometria por Raios X , Difração de Raios XRESUMO
Symmetric and asymmetric diffusers with a directional diffusion property were both fabricated based on a photopolymerizable hologram material using an ionic liquid as an additive. The diffusion property can be regulated by changing the concentration of the ionic liquid. The fiber structure, the surface-relief structure, and the formation of nanoparticles led to the directional diffusion property of the diffuser.