title: Direct evidence of concurrent solid-solution and two-phase reactions and the nonequilibrium structural evolution of LiFePO4.
abstract: Lithium-ion batteries power many portable devices and in the future are likely to play a significant role in sustainable-energy systems for transportation and the electrical grid. LiFePO(4) is a candidate cathode material for second-generation lithium-ion batteries, bringing a high rate capability to this technology. LiFePO(4) functions as a cathode where delithiation occurs via either a solid-solution or a two-phase mechanism, the pathway taken being influenced by sample preparation and electrochemical conditions. The details of the delithiation pathway and the relationship between the two-phase and solid-solution reactions remain controversial. Here we report, using real-time in situ neutron powder diffraction, the simultaneous occurrence of solid-solution and two-phase reactions after deep discharge in nonequilibrium conditions. This work is an example of the experimental investigation of nonequilibrium states in a commercially available LiFePO(4) cathode and reveals the concurrent occurrence of and transition between the solid-solution and two-phase reactions.
authors.affiliation: The Bragg Institute, Australian Nuclear Science and Technology Organisation, Locked Bag 2001, Kirrawee DC, New South Wales 2232, Australia. n.sharma@ansto.gov.au
authors.forename: Neeraj
authors.initials: N
authors.lastname: Sharma
authors.forename: Xianwei
authors.initials: X
authors.lastname: Guo
authors.forename: Guodong
authors.initials: G
authors.lastname: Du
authors.forename: Zaiping
authors.initials: Z
authors.lastname: Guo
authors.forename: Jiazhou
authors.initials: J
authors.lastname: Wang
authors.forename: Zhaoxiang
authors.initials: Z
authors.lastname: Wang
authors.forename: Vanessa K
authors.initials: VK
authors.lastname: Peterson