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 TiO2 (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 TiO2 particle size. The area normalized capacitance was determined to be well above 100 μF/cm2, 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.

The advantages in using nanoscale materials for electrochemical energy storage are generally attributed to short diffusion path lengths for both electronic and lithium ion transport. Here, we consider another contribution, namely the charge storage from faradaic processes occurring at the surface, referred to as pseudocapacitive effect. This paper describes the synthesis and pseudocapacitive characteristics of block copolymer templated anatase TiO(2) thin films synthesized using either sol-gel reagents or preformed nanocrystals as building blocks. Both materials are highly crystalline and have large surface areas; however, the structure of the porosity is not identical. The different titania systems are characterized by a combination of small- and wide-angle X-ray diffraction/scattering, combined with SEM imaging and physisorption measurements. Following our previously reported approach, we are able to use the voltammetric sweep rate dependence to determine quantitatively the capacitive contribution to the current response. Considerable enhancement of the electrochemical properties results when the films are both made from nanocrystals and mesoporous. Such materials show high levels of capacitive charge storage and high insertion capacities. By contrast, when mesoscale porosity is created in a material with dense walls (rather than porous walls derived from the aggregation of nanocrystals), insertion capacities comparable to templated nanocrystal films can be achieved, but the capacitance is much lower. The results presented here illustrate the importance of pseudocapacitive behavior that develops in high surface area mesoporous oxide films. Such systems provide a new class of pseudocapacitive materials, which offer increased charge storage without compromising charge storage kinetics.

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Interleukin 17 (IL-17) is a cytokine associated with inflammation, autoimmunity and defense against some bacteria. Here we show that IL-17 can promote autoimmune disease through a mechanism distinct from its proinflammatory effects. As compared with wild-type mice, autoimmune BXD2 mice express more IL-17 and show spontaneous development of germinal centers (GCs) before they increase production of pathogenic autoantibodies. We show that blocking IL-17 signaling disrupts CD4 + T cell and B cell interactions required for the formation of GCs and that mice lacking the IL-17 receptor have reduced GC B cell development and humoral responses. Production of IL-17 correlates with upregulated expression of the genes Rgs13 and Rgs16, which encode regulators of G-protein signaling, and results in suppression of the B cell chemotactic response to the chemokine CXCL12. These findings suggest a mechanism by which IL-17 drives autoimmune responses by promoting the formation of spontaneous GCs.