No abstract

Lithium-ion batteries are essential for portable technology and are now poised to disrupt a century of combustion-based transportation. The electrification revolution could eliminate our reliance on fossil fuels and enable a clean energy future; advanced batteries would facilitate this transition. However, owing to the demanding performance, cost, and safety requirements, it is challenging to translate new materials from laboratory prototypes to industrial-scale products. This Perspective describes that journey for a new lithium-ion battery anode material, TiNb2O7 (TNO). TNO is intended as an alternative to graphite or Li4Ti5O12 with better rate and safety characteristics than the former and higher energy density than the latter. The high capacity of TNO stems from the multielectron redox of Nb5+ to Nb3+, its operating voltage window well above the Li+/Li reduction potential prevents lithium dendrite formation, and its open crystal structure leads to high-power performance. Nevertheless, the creation of a practical TNO anode was nonlinear and nontrivial. Its history is built on 30 years of fundamental science that preceded its application as a battery anode, and its battery development included a nearly 30-year gap. The insights and lessons contained in this Perspective, many of them acquired firsthand, serve two purposes: (i) to unite the disparate studies of TiNb2O7 into a coherent modern understanding relevant to its application as a battery material and (ii) to highlight briefly some of the challenges faced when scaling up a new material that affect TiNb2O7 as well as new electrode candidates more generally.

No abstract

The junction characteristics of metal/organic (M/Org) and organic/organic (Org/Org) interfaces, composing an organic electroluminescent (EL) device, M/Alq3/Diamine/ITO, were studied by measuring the displacement current characteristics of M/Org/Org/ SiO2/Si structures. The M/Alq3 junction was found to be both electron and hole injective, depending on the metal electrode. As for the Alq3/Diamine interface, it was found that two band offsets (Φ VB and Φ CB) existed for respective valence and conduction bands. Φ VB was not very large, and holes in Diamine were able to pass through into the adjacent Alq3 layer by applying a forward-bias, but Φ CB was so large that the electrons in Alq3 were blocked. Based on the standpoint that characteristics of the organic thin-film devices are governed by those junctions, we discussed carrier-injection mechanism, and explain the efficient EL emission.

No abstract