Ageing mechanisms have a great impact into batteries calendar life and performance. A better understanding of these complex processes is critical to improve the lifetime of the battery. Additional capacity from layered transition metal oxides, can be accessed at higher potentials, in some systems this is associated with oxidation of N2+ to N4+ and partial oxidation of O2-. The extra capacity associated with O-redox cannot be fully exploited in practical battery systems due to oxygen loss and side reactions with the electrolyte, as well as transition metal dissolution reactions. Raman microscopy is a powerful technique to follow intercalation and redox mechanisms under operando conditions, as well as monitoring state of charge and distribution of materials within the composite electrode. Raman can also identify the nature of "O-O" bonding in the next generation positive electrode materials [JACS 2019 141, 7333]. Shell Isolated Nanoparticles for Enhanced Raman Spectroscopy (SHNERS) is a technique that allows the surface enhanced Raman spectroscopy (SERS) effect to be applied to any surface, including battery electrodes. A SERS active gold core is coated with an inert shell which prevents the gold core from taking part in reactions. SHN can be placed onto a surface to greatly enhance their otherwise weak Raman signal and permit the observation of species which cannot otherwise be detected [Chem Sci. 2019 10 2956].

Research teamwork record WUT Team has many years of experience in testing electrode and electrolyte materials for lithiumion cells and ther successors (>200 articles). Prof Marcinek (WUT) ULV team has many years of experience in advanced spectroscopic measurements of battery electrodes (>50 articles). Prof Hardwick (ULV) are partners on existing (BIG-MAP) previous (SIRBATT) EU project and worked together during their postdoctoral period in the group of R.Kostecki at LEN, USA on Raman characterisation of battery materials (2007-2008).

The project involves in-depth in operando Raman analysis of the positive electrode via the study of intercalation process on the active materials, nature of anion redox, surface components, charges on the carbon additive and distribution of electrode components. The state of charge accross the range of transition metal oxides will be monitored via high resolution (10m2) Raman mapping. This will allow the monitoring of inconsistent kinetic behaviour of indiviual oxide particles, which can be attributed to degradation of the electronically conducting carbon matrix in the composite positive electrode upon testing. Materials that will be investigated are higher nickel containing layered oxides with the formula LiNxMnyOozO2. In particlar, the effect adding a dopant, such as Y3+ or Al3+, and surface coatings have on electrochemical properties state of charge and surface evolution on this classs of material will be examined.

Additionally, experiments will be carried out using modern electrolytes which WUT pionnered the development of, based on weakly coordinating salts, based on anions followinf the Hückel rule, such as lithium 4,5-dicyano-2-(trifluoromethyl)imidazole (LiTDI) and lithium4.5-dicyano-2-(pentafluoroethly)imidazolide (LiPDI). The impact of these salts on the chemical nature of surface films and cyclability of electrode materials will be analysed. The work will be carried out via operando Raman microscopy (WUT) and complementary by SHNERS studies as ULV.

Mobility scheme: Y1: 2 months at Liverpool (learning basics of in operando Raman Technique. Y2:  3 months at Liverpool perfoming SHNERS on with GEN materials. Y3: 3 months at Liverpool perfoming SHNERS in operando (if needed) of with GEN2 materials.

Supervisor(s) contact: Marek MARCINEK, marek.marcinek@pw.edu.pl (WUT)