Ditty Dixon

Sodium vanadium titanium phosphate electrode for symmetric sodium-ion batteries with high power and long lifespan

Sodium-ion batteries operating at ambient temperature hold great promise for use in grid energy storage owing to their significant cost advantages. However, challenges remain in the development of suitable electrode materials to enable long lifespan and high rate capability. Here we report a sodium super-ionic conductor structured electrode, sodium vanadium titanium phosphate, which delivers a high specific capacity of 147 mA h g−1 at a rate of 0.1 C and excellent capacity retentions at high rates. A symmetric sodium-ion full cell demonstrates a superior rate capability with a specific capacity of about 49 mA h g−1 at 20 C rate and ultralong lifetime over 10,000 cycles. Furthermore, in situ synchrotron diffraction and X-ray absorption spectroscopy measurement are carried out to unravel the underlying sodium storage mechanism and charge compensation behaviour. Our results suggest the potential application of symmetric batteries for electrochemical energy storage given the superior rate capability and long cycle life.

Design of in-situ experimentation for the study of fuel cells with X-rays and neutrons

Abstract In situ neutron and X-ray measurements are of essential importance for the rational design of tailor-made catalysts and cell components, in particular when they can be performed with spatial resolution. Neutron radiography allows the investigation of the local fluid distribution in direct methanol fuel cells (DMFCs) under operating conditions with spatial resolutions in the order of some tens of micrometers. In the through-plane mode, an overview of the local water and gas distribution in the flow field channels is obtained, while the in-plane mode provides information on spatially and time resolved fluid distribution across the cell, hydration/dehydration processes and water distribution across the walls of flow field channels. Combined studies of high resolution neutron radiography and segmented cell measurements are especially valuable, because they enable a correlation of the local fluid distribution and local performance. This knowledge is essential in order to optimise water management and performance and to establish a homogeneous fluid, current and temperature distribution in order to achieve high performance and durability of DMFCs. While the neutron studies focus on the cell components, additional information about the catalyst performance and stability is obtained by in situ X-ray absorption spectroscopy (XAS), thus nicely complementing the neutron measurements. Particle size and particle composition as well as degradation processes by oxidation, de-alloying, and particle growth can be probed with spatial resolution during operation. However, both for neutron and X-ray investigations dedicated cell and experiment design are crucial for the success of the measurements.