Newly Developed Analysis Method Measures Charge States at Particle Level

Even microscopically small changes at particle level influence the performance of the battery cell macrosystem. In order to measure the charge states of single particles of lithium transition-metal oxides in the cathode, a team of scientists at MEET Battery Research Center led by Till-Niklas Kröger has developed a new characterisation technique. The application of single-particle inductively coupled plasma-optical emission spectroscopy enables the direct investigation of even complex, microscopically small changes in the charge states.

Changed Charge States Directly Measurable

“Investigations at particle level were previously only possible with very complex analytical methods such as synchrotron-based techniques,” says MEET researcher Till-Niklas Kröger. These are only available in a few research institutes. Additionally, the oxidation state distribution of the transition-metal oxides, especially of nickel, are primarily measured. “However, changes in the nickel oxidation states do not always indicate changes in the lithium content,” explains Kröger.

With the newly developed method at MEET Battery Research Center, the lithium amount on particle level can be measured directly. The charge states can then be determined. Local structural changes are a potential source of altered charge states at particle level. They are caused, for example, by high C-rates, i.e. high charge and discharge rates, at which particles can break. By influencing the diffusion paths of the lithium, different charge states occur. “Even smallest local differences in electrochemical processes can deteriorate the performance of the entire battery cell,” explains Kröger. The new characterisation technique now enables insights to address this.

Original Publication Online Available

The MEET scientists Till-Niklas Kröger, Dr Simon Wiemers-Meyer, Patrick Harte, Prof. Dr Martin Winter and Dr Sascha Nowak have published the detailed research results in the journal “Analytical Chemistry”. The publication is online available with corresponding access.