Single Particle Measurement to Determine the Intrinsic Properties of Cathode Active Material in Li-Ion Batteries

Kurzfassung

Conventional methods of electrochemical analysis of novel or optimized active materials involve the study of composite electrodes which contain a mixture of active material, binder, and conductive additive on a metallic current collector (CC) foil. The resulting electrochemical response is convoluted and is a function of various factors such as electrode thickness, porosity and composition, making it difficult to assess the intrinsic nature of the active material [1]. To measure intrinsic material properties, the aforementioned matrix effect needs to be removed. This can be achieved by the development of localized electrochemical probes with which single particle measurements (SPMs) can be performed. Thereby, SPM facilitates the determination of the impact of particle size, shape etc. on electrochemical behavior of the material. Here, we employ a pipette-based technique called scanning micropipette contact method (SMCM) [2] to study the kinetic and transport properties of active materials through various electrochemical measurement techniques. As a first step, for validation of the experimental set-up, cyclic voltammetry (CV) measurements with different active materials were performed. Figure 1-B shows exemplary CV data for Li(Ni1/3Mn1/3Co1/3)O2 (NMC) and LiFePO4 (LFP) micro-particles, where the redox peaks represent typical potential values for the respective material. Subsequently, lithium nickel manganese oxide (LNMO) with varying particle properties will be characterized to derive the relationship between synthesis parameters, material properties and electrochemical behavior. The measurements will serve as input for single particle simulations at a later stage providing insights into the underlying phenomena. References: [1] C. Heubner, U. Langklotz, C. Lämmel, M. Schneider, and A. Michaelis, Electrochimica Acta, vol. 330, p. 135160, 2020. [2] M. E. Snowden, M. Dayeh, N. A. Payne, S. Gervais, J. Mauzeroll, and S. B. Schougaard, Journal of Power Sources, vol. 325, pp. 682–689, 2016.