Advanced materials for lithium-ion batteries

Lead Research Organisation: University of Oxford
Department Name: Materials

Abstract

The need for better batteries has never been greater. Many automotive manufacturers now believe that limitations in the performance of current lithium-ion batteries represent the greatest barrier to the electrification of transport. The energy density of lithium batteries is currently restricted by the cathode material, delivering ~ 160-180 mAh g-1. New high-energy-density cathode materials are much sought after to meet the increasing requirements of consumer electronics, electric vehicles and grid energy storage. The so called lithium-rich layered oxide materials (e.g. Li1-x[Li0.2Mn0.6Ni0.2]O2), exceed the conventional limit of charge storage as far more lithium (x approximately 1, corresponding to ~310 mAh g-1) can be extracted than can be accounted for through transition metal oxidation (x approximately 0.4 for Ni2+/4+). The source of this "extra capacity" has been explained previously by a number of models including oxygen loss, electrolyte decomposition and anion redox. With anion redox now identified as the predominate effect. Further understanding of the underlying mechanism and also the discovery of new compounds exhibiting similar behavior is key.

This project will focus on understanding the fundamental science behind anion redox using advanced characterisation methods such X-ray Absorption Spectroscopy with both hard and soft X-rays (XAS), Resonant Inelastic X-Scattering (RIXS), X-ray photo electron spectroscopy, X-ray diffraction, Nuclear Magnetic Resonance, Raman Spectroscopy and Electrochemistry. The project will involve the preparation of several different composition materials through inorganic synthesis routes such as Solid State, Sol-Gel and hydrothermal methods to produce materials such as Li[Li0.2Mn0.6Ni0.2]O2 where oxygen redox is known to occur. These materials will be constructed into electrochemical cells and will be charged until specific points where the materials will be removed and then examined using the range of different techniques. The student will need to engage broadly with scientists working at Diamond and ISIS and the techniques available at these world leading X-ray and Neutron facilities. Neutrons are of particular importance to the study of battery materials since the scattering cross section of Lithium is significant. This allows us to better understand the position of Lithium ions at various states of charge. In addition to the students ex situ work a significant effort to the development of in situ cells will be made. This will allow us to better understand the phenomena of oxygen redox and hopefully design new materials utilizing the same effect. These new materials could potentially increase capacity stored beyond 400 mAhg-1.

The Themes are:
Energy
Engineering
Manufacturing the future
Physical sciences

Publications

10 25 50

Studentship Projects

Project Reference Relationship Related To Start End Student Name
EP/N509711/1 01/10/2016 30/09/2021
1801766 Studentship EP/N509711/1 01/10/2016 31/03/2020 Dominic Forstermann
 
Description Developed an operands cell to accurately measure battery materials in operation using synchrotron and x-ray radiation. Combining realistic battery performance and radiation transparency is hard, and especially difficult for so-called "lithium-rich" materials such as Li1-x[Li0.2Mn0.6Ni0.2]O2. The cell accomplished this task and is currently being used to investigate a range of compounds from this class using hard-Xray spectroscopy and diffraction experiments, to understand charge compensation in these materials.
Exploitation Route The cell will allow various researchers to accurately measure battery materials in real time, and should greatly support their research.
Sectors Chemicals,Energy