Rate-Induced Solubility and Suppression of the First-Order Phase Transition in Olivine LiFePO₄

Abstract

The impact of ultrahigh (dis)charge rates on the phase transition mechanism in LiFePO4 Li-ion electrodes is revealed by in situ synchrotron diffraction. At high rates the solubility limits in both phases increase dramatically, causing a fraction of the electrode to bypass the first-order phase transition. The small transforming fraction demonstrates that nucleation rates are consequently not limiting the transformation rate. In combination with the small fraction of the electrode that transforms at high rates, this indicates that higher performances may be achieved by further optimizing the ionic/electronic transport in LiFePO4 electrodes.

Mesoscopic Modeling of a LiFePO4Electrode: Experimental Validation under Continuous and Intermittent Operating Conditions

“…The proposed mesoscopic model is supported by the experimental observation of collective lithiation/delithiation of nanoparticles in an LFP electrode; [29][30][31][36][37][38][39] in this situation, LFP nanoparticles can be considered as the elementary units. Our mesoscopic physical representation is also in line with high-resolution transmission-electronmicroscopy observations of chemically delithiated LFP particles where a large amount of microstructural defects partition the pristine particles (millimeter-sized to submicron-sized) into small meso-scale domains.…”

“…Unlike chemical delithiation studies, in-situ [36][37][38][39] and ex-situ [29][30][31] chemical phase mapping of electrochemically delithiated LFP electrodes made of nanoparticles have ubiquitously reported a discrete * Electrochemical Society Member. z E-mail: mfowler@uwaterloo.ca pattern for the lithiation/delithiation of particles in the electrodes.…”

“…34,35 Cabana et al 33 also reported biphasic nanoparticles with very few cracks indicating that the smaller particles could successfully withstand coherency stress and remain mechanically stable during chemical delithiation. 33 Unlike chemical delithiation studies, in-situ [36][37][38][39] and ex-situ [29][30][31] chemical phase mapping of electrochemically delithiated LFP electrodes made of nanoparticles have ubiquitously reported a discrete * Electrochemical Society Member. z E-mail: mfowler@uwaterloo.ca pattern for the lithiation/delithiation of particles in the electrodes.…”

Operando Neutron Depth Profiling to Determine the Spatial Distribution of Li in Li-ion Batteries

“…The set-up consists of an aluminum vacuum chamber where a Canberra PIPS detector is used to measure the energy of the emitted 3 H particles, as illustrated in Figure 1. All results are based on measurements on pouch cells (Gustafsson et al, 1992;Yu et al, 2006;Mohanty et al, 2013;Lv et al, 2018), also known as coffee bag cells (Singh et al, 2015), their flexible design allows the straightforward sealing of current collector window (Villevieille, 2015), as is also described in Zhang et al (2014). Also pouch cell type constructions are common practice in industrial applications (Trask et al, 2014).…”

“…Being a light element, lithium is difficult to detect with X-rays, for which reason most photon techniques typically use the change in oxidation state of the heavier ions to observe lithium intercalation (Nonaka et al, 2006;Katayama et al, 2014) or changes in interatomic spacing upon lithium insertion or extraction (Ganapathy et al, 2014;Zhang et al, 2014). Neutrons probe atom cores and therefore favor detection of the lighter elements compared to X-rays (Itkis et al, 2015).…”