Neeraj completed his Ph.D. at the University of Sydney then moved to the Bragg Institute at Australian Nuclear Science and Technology Organisation (ANSTO) for a post-doc. He started at the School of Chemistry, UNSW on a Australian Institute of Nuclear Science and Engineering (AINSE) Research Fellowship followed by an Australian Research Council (ARC) Discovery Early Career Research Award (DECRA). He is currently an Associate Professor and ARC Future Fellow. Neeraj has been the Royal Australian Chemical Institute (RACI) Nyholm Youth Lecturer (2013/2014) and has won the NSW Premiers Prize for Science and Engineering (Early Career Researcher in Physical Sciences, 2019), Australian Synchrotron Research Award (2018), RACI Rennie Memorial Medal for Chemical Science (2018), UNSW Postgraduate Supervisor Award (2017) and a NSW Young Tall Poppy Award (2014). Neeraj has over 150 publications and has been invited to present his work at over 30 conferences. Neeraj’s research interests are based on solid state chemistry, designing new materials and investigating their structure-property relationships. He loves to undertake in situ or operando experiments of materials inside full devices, especially batteries, in order to elucidate the structural subtleties that lead to superior performance parameters. Neeraj’s projects are typically highly collaborative working with colleagues from all over the world with a range of skillsets.
We chemically tune the atomic arrangement (crystal structure) of solid state materials to enhance their physical properties such as energy storage capacity, ionic conductivity or thermal expansion.
We use a combination of techniques to characterise our materials, including but not limited to X-ray and neutron diffraction (at the Australian Synchrotron and ANSTO), solid state NMR, electrochemical and impedance analysis, and electron microscopy.
Our goal is to fully characterise materials, place them into real-world devices such as batteries and solid oxide fuel cells, and then characterise how they work in these devices.
Solid state and Materials Chemistry
Energy-related devices such as batteries and fuel cells are essential in our lives. In order to develop the next generation of technologies we need more power, or better performance, at a lower environmental cost. Research into understanding the interplay between the crystal structure of new materials and their physical properties will allow us to revolutionise how we obtain and store energy.
My research approach encompasses exploratory synthesis, structural determination, physical property measurements and in situ structure and property characterisation of batteries and other devices.
Towards the next generation of batteries: Sodium-ion batteries
Lithium-ion batteries are ubiquitous in our daily lives, e.g. mobile phones and laptop computers, but their limitations have restricted wide-scale use in applications requiring higher power, e.g. electric vehicles and energy storage of renewable energy. This project will target new battery chemistries, in particular sodium-ion batteries, by developing and characterizing new electrode and electrolyte materials. We will work to develop a reliable and affordable room-temperature sodium-ion battery to provide sufficient power for large-scale energy storage from intermittent renewable power sources. Students will work on one of the following parts of a battery and test their component in idealized batteries.
- Positive electrode materials
These electrodes provide the source of the sodium-ions and represent the largest cost and energy limitations for lithium-ion batteries. Here, new sodium-containing transition metal oxides, phosphates or sulfates are be synthesized and characterized to determine the relationship between crystal structure and battery performance.
Sodium-ion conducting ceramics or glassy-ceramics are known to be excellent electrolytes at high temperatures (>300°C). We work towards making materials with sufficient sodium-ion conduction at room temperature.
- Negative electrode materials
Negative electrodes are the least investigated component in a sodium-ion battery and the compounds used for lithium-ion batteries show poor performance in sodium-ion batteries. By developing new negative electrodes and understanding their limitations towards reversible sodium insertion/extraction we will be enable the next generation of devices. The focus of these projects are carbon based materials and the use of solid state 23Na NMR to characterise the insertion/extraction processes.
Tuning negative thermal expansion to produce zero thermal expansion materials
The majority of materials expand during heating via thermal expansion and this process is responsible for billions of dollars per year in maintenance, re-manufacture and replacement costs due to wear and tear on both moving parts (e.g. in aircraft gas turbines), and components that are designed to be static (e.g. in optics, coatings, electronics). If a zero thermal expansion (ZTE) material can be made, a material that neither expands nor contracts upon heating, this could dramatically reduce industrial costs. In order to achieve this, the opposite extreme of materials are considered in this project - negative thermal expansion (NTE) is a property exhibited by a small group of materials predominantly due to transverse vibrations of atom groups or cooperative rotations of units (e.g. –CN- or WO4). These materials typically feature large crystallographic voids and cations with variable oxidation states. So why not use a battery as a synthesis tool? In this project we will controllably insert Li and Na into the voids of the NTE materials, via a battery, in order to tune the cooperative rotations to produce ZTE materials.
In situ studies of materials
Investigating materials functioning in actual devices, i.e. in situ, allows the direct comparison of device performance to the atomic-level changes in the material. By manipulating the atomic-scale crystal structure of components, using a variety of synthetic techniques, improvements in device performance can be achieved, e.g. better lithium-ion batteries can be made.
In a lithium-ion battery, the charge process is characterised by the removal of lithium from the cathode, while on discharge lithium is inserted into the cathode. The cathode above features relatively small crystal-structure changes with the lithium insertion/extraction (top) making it an attractive material for commercial applications. The information on crystal-structure evolution is derived from in situ neutron powder diffraction data (bottom left) during charge/discharge cycling of the battery. The battery (bottom right) was fabricated by collaborators in Fudan University, China.
Development of new ionic conductors
Full solid-state devices are more advantageous than liquid-containing devices as they are generally safer and more robust under harsh conditions however limitations arise particularly due to the lower ionic conductivity in solids. Exploring the mechanism of ionic conduction in solids, and its relationship to factors such as temperature and dopant concentration is a method to significantly improve solid-state devices.
An example of ‘watching’ a synthesis reaction using neutron powder diffraction. Starting materials are placed on the diffractometer and the synthesis procedures are initiated while neutron powder diffraction patterns are continuously collected. For Li6PS5Cl the synthesis temperature is found to have a significant influence on the ionic conduction properties.
Structural investigations using neutron and X-ray scattering
Single crystal, solid-state and electrochemical synthetic techniques can be used to tailor-make new materials for specific applications, but critical to this process is the characterisation tools employed to elucidate the arrangement of atoms. Our use of the Australian Synchrotron and the neutron scattering facilities at ANSTO provide unparalleled insight into these materials.