Capturing metastable structures during high-rate cycling of LiFePO 4 nanoparticle electrodes

• DOI: 10.1126/science.1252817
• Publication Date: 2014-06-26T18:15:49Z
• Authors: Hao Liu; Fiona C. Strobridge; Olaf J. Borkiewicz; Kamila M. Wiaderek; Karena W. Chapman; Peter J. Chupas; Clare P. Grey
• Keywords: Metastability

The absence of a phase transformation involving substantial structural rearrangements and large volume changes is generally considered to be key characteristic underpinning the high-rate capability any battery electrode material. In apparent contradiction, nanoparticulate LiFePO4, commercially important cathode material, displays exceptionally high rates, whereas its lithium-composition diagram indicates that it should react via kinetically limited, two-phase nucleation growth process. Knowledge concerning equilibrium phases therefore insufficient, direct investigation dynamic process required. Using time-resolved in situ x-ray powder diffraction, we reveal existence continuous metastable solid solution during rapid lithium extraction insertion. This nonequilibrium facile route provides mechanism for realizing materials operate reactions.