Pseudocapacitive Contributions to Electrochemical Energy Storage in TiO 2 (Anatase) Nanoparticles

作者：John Wang, Julien Polleux, James Lim, Bruce Dunn · 发表于：The Journal of Physical Chemistry C · 年份：2007 · DOI：10.1021/jp074464w · 被引用次数：5287 · 研究领域：Advancements in Battery Materials、Supercapacitor Materials and Fabrication、Advanced battery technologies research

The advantages in using nanostructured materials for electrochemical energy storage have largely focused on the benefits associated with short path lengths. In this paper, we consider another contribution, that of the capacitive effects, which become increasingly important at nanoscale dimensions. Nanocrystalline TiO 2 (anatase) was studied over a dimensional regime where both capacitive and lithium intercalation processes contribute to the total stored charge. An analysis of the voltammetric sweep data was used to distinguish between the amount of charge stored by these two processes. At particle sizes below 10 nm, capacitive contributions became increasingly important, leading to greater amounts of total stored charge (gravimetrically normalized) with decreasing TiO 2 particle size. The area normalized capacitance was determined to be well above 100 μF/cm 2, confirming that the capacitive contribution was pseudocapacitive in nature. Moreover, reducing the particle size to the nanoscale regime led to faster charge/discharge rates because the diffusion-controlled lithium ion intercalation process was replaced by faradaic reactions which occur at the surface of the material. The charge storage and kinetics benefits derived from using nanoscale metal oxides provide an interesting direction for the design of materials that offer both power density and energy density.