Spinel materials for Li-ion batteries: new insights obtained by operando neutron and synchrotron X-ray diffraction (original) (raw)
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The Journal of Physical Chemistry C, 2014
In-situ neutron diffraction (ND) during battery operation is becoming a promising technique for the study of electrode materials in Li-ion batteries. We recently designed an electrochemical cell for operando ND studies and demonstrated that it can deliver powder patterns of good quality for Rietveld structural refinements. Herein we used such a cell to study the deintercalation process occurring in manganese spinels of general formula Li 1+x Mn 2-x O 4. Three samples with increasing Li/Mn ratio (x = 0, x = 0.05 and x = 0.10) were synthesized and measured on the D20 high-flux powder diffractometer at ILL. We found fundamental differences between the phase diagrams of the three samples, intimately related to their electrochemical features. Upon charge, the study revealed a sequence of two biphasic reactions for LiMn 2 O 4 (with an intermediate phase of composition close to Li 0.6 Mn 2 O 4), a solid solution followed by a biphasic reaction for Li 1.05 Mn 1.95 O 4 and a full solid solution for Li 1.10 Mn 1.90 O 4. Moreover Rietveld refinement led key parameters such as cell parameters, oxygen's fractional atomic coordinates and, more importantly, lithium's site occupancy factors, whose rate of variation is found to be related to the state of charge of the electrode.
Symmetry, 2021
Among lithium battery cathode materials, Li1.2Ni0.13Mn0.54Co0.13O2 (LR-NMC) has a high theoretical capacity, but suffers from voltage and capacity fade during cycling. This is partially ascribed to transition metal cation migration, which involves the local transformation of the honeycomb layered structure to spinel-like nano-domains. Determination of the honeycomb layered/spinel phase ratio from powder X-ray diffraction data is hindered by the nanoscale of the functional material and the domains, diverse types of twinning, stacking faults, and the possible presence of the rock salt phase. Determining the phase ratio from transmission electron microscopy imaging can only be done for thin regions near the surfaces of the crystals, and the intense beam that is needed for imaging induces the same transformation to spinel as cycling does. In this article, it is demonstrated that the low electron dose sufficient for electron diffraction allows the collection of data without inducing a ph...
Journal of The Electrochemical Society, 1998
We describe synchroton based X‐ray diffraction techniques and issues related to in situ studies of intercalation processes in battery electrodes. We then demonstrate the utility of this technique, through a study of two batches of Formula cathode materials. The structural evolution of these spinel materials was monitored in situ during the initial charge of these electrodes in actual battery cells. Significant differences were observed in the two batches, particularly in the intercalation range of x= 0.45 to 0.20. The first‐order structural ...
Applications of In Situ Neutron-Based Techniques in Solid-State Lithium Batteries
Batteries
Solid-state lithium batteries (SSLBs) have made significant progress in recent decades in response to increasing demands for improved safety and higher energy density. Nonetheless, the current state SSLBs are not suitable for wide commercial applications. The low ionic conductivity, lithium dendrites growth, and unstable interfaces between solid electrodes and electrolytes are some of the challenges that need to be overcome. Therefore, it is critical to fully comprehend the structural information of SSLBs at a nanometer scale. Neutron-based techniques (NBTs) are sensitive to light elements (H, Li, B, N, O, etc.) and can distinguish heavy metals (e.g., Mn, Fe, Co, Ni, etc.) containing close atomic numbers or even isotopes (e.g., 1H and 2H). Therefore, NBTs are important and powerful structural and analytical tools for SSLB research and have substantially improved our understanding of these processes. To provide real-time monitoring, researchers have explored many sophisticated in sit...
Journal of Power Sources, 2010
The structural response to electrochemical cycling of the components within a commercial Li-ion battery (LiCoO 2 cathode, graphite anode) is shown through in situ neutron diffraction. Lithuim insertion and extraction is observed in both the cathode and anode. In particular, reversible Li incorporation into both layered and spinel-type LiCoO 2 phases that comprise the cathode is shown and each of these components features several phase transitions attributed to Li content and correlated with the state-of-charge of the battery. At the anode, a constant cell voltage correlates with a stable lithiated graphite phase. Transformation to de-lithiated graphite at the discharged state is characterised by a sharp decrease in both structural cell parameters and cell voltage. In the charged state, a two-phase region exists and is composed of the lithiated graphite phase and about 64% LiC 6. It is postulated that trapping Li in the solid|electrolyte interface layer results in minimal structural changes to the lithiated graphite anode across the constant cell voltage regions of the electrochemical cycle.
Scientific Reports, 2016
Among the energy storage devices for applications in electric vehicles and stationary uses, lithium batteries typically deliver high performance. However, there is still a missing link between the engineering developments for large-scale batteries and the fundamental science of each battery component. Elucidating reaction mechanisms under practical operation is crucial for future battery technology. Here, we report an operando diffraction technique that uses high-intensity neutrons to detect reactions in non-equilibrium states driven by high-current operation in commercial 18650 cells. The experimental system comprising a time-of-flight diffractometer with automated Rietveld analysis was developed to collect and analyse diffraction data produced by sequential charge and discharge processes. Furthermore, observations under high current drain revealed inhomogeneous reactions, a structural relaxation after discharge, and a shift in the lithium concentration ranges with cycling in the electrode matrix. The technique provides valuable information required for the development of advanced batteries. Since the commercialization of secondary lithium batteries in 1991 1 , this excellent system of electrochemical energy storage has been assiduously developed, and its uses have expanded from small batteries to a much wider range of large-scale applications 2,3 in which high reliability, safety, and long-term stability are required 4. To improve these characteristics, battery reactions under practical usage conditions must be better understood 5. In commercial batteries, the most common configuration is the 18650 cylindrical cell, with an 18 mm diameter and 65 mm height; these are used for laptop computers and even for electric vehicle (EV) applications. Reactions in these practical batteries proceed in a non-equilibrium state within an electrode matrix composed of conducting agents, adhesive additives, and electrode materials. In addition, the extremely high current caused by the pulsed operational conditions, for example, makes the battery reactions non-equilibrium and non-homogeneous; this may induce a lithium concentration gradient in the electrode matrix which will lead to relaxation processes after the current passes through the cell 6-8. Non-equilibrium conditions may also change the lithium concentration ranges used for the reactions in the electrodes, which is a key factor for balancing the lithium between the cathode and anode, and thus, for designing batteries 8,9. The development of experimental tools to detect and analyse these reactions under practical conditions is urgently necessary for improved battery design.
Journal of The Electrochemical Society, 2013
In-situ techniques proved to be exceptionally useful tools to understand electrode materials for Li-ion batteries. In-situ neutron diffraction (ND) knew a slow development, due to the intrinsic difficulties it held. We have designed a new electrochemical cell, manufactured with a completely neutron-transparent (Ti,Zr) alloy. Such a cell is able to combine, for the first time, good electrochemical properties and the ability to collect neutron diffraction patterns operando, with good statistics and no other Bragg peaks than those of the electrode material of interest. This allows detailed structural determinations of electrode materials by Rietveld refinement during operation. First case studies hereby reported are the olivine LiFePO 4 and the overstoichiometric spinel Li 1.1 Mn 1.9 O 4 , investigated at the D20 diffractometer of ILL (Grenoble), and compared to pure powder patterns obtained from the high-resolution D2B diffractometer. These studies demonstrate the feasibility and reliability of such experiments and open the field to a wide range of investigations on battery electrode materials.
A reinvestigation of the structures of lithium-cobalt-oxides with neutron-diffraction data
Materials Research Bulletin, 1993
The structures of LT-LiCoO 2 (synthesised by reaction of LizCO a and CoCO a at 40(Y'C) and its delithiated product LT-Lio.4CoO 2 have been reinvestigated by neutron powder diffraction. Despite an unusually close similarity between diffraction profiles that makes it difficult to determine whether the structures are layered or spinel-like, the data confirm that the preferred structure of the LT-LiCoO 2 sample made for this study is one that has a cobalt distribution which is intermediate between an ideal layered and an ideal lithiated spinel structure. On the other hand, refinement of the data of LT-Li0.4CoO 2 prepared by reacting LT-LiCoO 2 with acid shows, unequivocally, that a spineltype structure is formed. These structures are discussed in relation to previously reported electrochemical data obtained from Li/LT-LiCoO 2 cells.