title: Spinel materials for Li-ion batteries: new insights obtained by operando neutron and synchrotron X-ray diffraction.
abstract: In the last few decades Li-ion batteries changed the way we store energy, becoming a key element of our everyday life. Their continuous improvement is tightly bound to the understanding of lithium (de)intercalation phenomena in electrode materials. Here we address the use of operando diffraction techniques to understand these mechanisms. We focus on powerful probes such as neutrons and synchrotron X-ray radiation, which have become increasingly familiar to the electrochemical community. After discussing the general benefits (and drawbacks) of these characterization techniques and the work of customization required to adapt standard electrochemical cells to an operando diffraction experiment, we highlight several very recent results. We concentrate on important electrode materials such as the spinels Li1 + xMn2 - xO4 (0 ≤ x ≤ 0.10) and LiNi0.4Mn1.6O4. Thorough investigations led by operando neutron powder diffraction demonstrated that neutrons are highly sensitive to structural parameters that cannot be captured by other means (for example, atomic Debye-Waller factors and lithium site occupancy). Synchrotron radiation X-ray powder diffraction reveals how LiMn2O4 is subject to irreversibility upon the first electrochemical cycle, resulting in severe Bragg peak broadening. Even more interestingly, we show for the first time an ordering scheme of the elusive composition Li0.5Mn2O4, through the coexistence of Mn(3+):Mn(4+) 1:3 cation ordering and lithium/vacancy ordering. More accurately written as Li0.5Mn(3+)0.5Mn(4+)1.5O4, this intermediate phase loses the Fd\overline 3m symmetry, to be correctly described in the P213 space group.
authors.affiliation: Laboratoire de Réactivité et de Chimie des Solides, CNRS-UMR#7314, Université de Picardie Jules Verne, F-80039 Amiens CEDEX 1, France.
authors.forename: Matteo
authors.initials: M
authors.lastname: Bianchini
authors.affiliation: CELLS - ALBA synchrotron, Cerdanyola del Vallès, E-08290 Barcelona, Spain.
authors.forename: François
authors.initials: F
authors.lastname: Fauth
authors.affiliation: Institut Laue-Langevin, 71 Avenue des Martyrs, F-38000 Grenoble, France.
authors.forename: Emmanuelle
authors.initials: E
authors.lastname: Suard
authors.affiliation: Laboratoire de Réactivité et de Chimie des Solides, CNRS-UMR#7314, Université de Picardie Jules Verne, F-80039 Amiens CEDEX 1, France.
authors.forename: Jean Bernard
authors.initials: JB
authors.lastname: Leriche
authors.affiliation: Laboratoire de Réactivité et de Chimie des Solides, CNRS-UMR#7314, Université de Picardie Jules Verne, F-80039 Amiens CEDEX 1, France.
authors.forename: Christian
authors.initials: C
authors.lastname: Masquelier
authors.affiliation: CNRS, Université de Bordeaux, Bordeaux INP, ICMCB UPR 9048, F-33600 Pessac, France.
authors.forename: Laurence
authors.initials: L
authors.lastname: Croguennec
keywords: batteries; neutron diffraction; operando; spinel; synchrotron X-ray diffraction