In operando tracking phase transformation evolution of lithium iron phosphate with hard X-ray microscopy

Abstract

The delithiation reaction in lithium ion batteries is often accompanied by an electrochemically driven phase transformation process. Tracking the phase transformation process at nanoscale resolution during battery operation provides invaluable information for tailoring the kinetic barrier to optimize the physical and electrochemical properties of battery materials. Here, using hard X-ray microscopy-which offers nanoscale resolution and deep penetration of the material, and takes advantage of the elemental and chemical sensitivity-we develop an in operando approach to track the dynamic phase transformation process in olivine-type lithium iron phosphate at two size scales: a multiple-particle scale to reveal a rate-dependent intercalation pathway through the entire electrode and a single-particle scale to disclose the intraparticle two-phase coexistence mechanism. These findings uncover the underlying twophase mechanism on the intraparticle scale and the inhomogeneous charge distribution on the multiple-particle scale. This in operando approach opens up unique opportunities for advancing high-performance energy materials.

In operando quantitation of Li concentration for a commercial Li-ion rechargeable battery using high-energy X-ray Compton scattering

“…It is important to monitor Li ion distributions in the electrodes in order to understand where the overvoltage state is made. Although development of experimental technique to visualize Li distribution have attracted much attention, these experimental methods are mainly adopted to only positive electrode (Liu et al, 2010;Mima et al, 2012;Wang et al, 2014;Jensen et al, 2015;He et al, 2015). The reactions in whole of the battery have been observed by using neutron source.…”

Phase evolution in single-crystalline LiFePO4 followed by in situ scanning X-ray microscopy of a micrometre-sized battery

“…For a sufficiently large single particle clearly the formation of an interface is favoured. Shrinking core but also the inverse scenario (size-dependent), as well as delithiation from only one side of the particle have been detected 2,16 . Chen et al 1 identified stripe patterns with a period typical for spinodal decomposition or decomposition heavily influenced by elastic effects.…”

Rate Dependent Multi-Mechanism Discharge of Ag0.50VOPO4·1.8H2O: Insights from In Situ Energy Dispersive X-ray Diffraction

“…A few studies imaged the reduction process of LiFePO 4 electrodes with similarities to the initial discharge of SVOP. 21,[44][45][46][47][48][49] A recent study of the spatial lithiation and delithiation of LiFePO 4 using in-operando transmission hard X-ray microscopy showed that a faster rate provokes heterogeneous particle deliathion or lithiation while a sample charged or discharged 50 times slower exhibited more homogeneous distribution of particle delithiation or lithiation. 44 At a faster rate some particles fully delithiate before other particles even begin to delithiate and at a slower rate most particles simultaneously delithiate.…”