Understanding the electrochemical lithiation/delithiation process in the anode material for lithium ion batteries NiFeOPO4/C using ex-situ X-ray absorption near edge spectroscopy and in-situ synchrotron X-ray (original) (raw)
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The Journal of Physical Chemistry C, 2013
Iron oxide (mostly α-Fe 2 O 3) model thin-film electrodes were prepared by thermal oxidation of pure metal iron substrates at 300 ± 5°C in air and used for comprehensive investigation of the lithiation/delithiation mechanisms of anode material undergoing an electrochemical conversion reaction with lithium ions. Surface (X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS)) and electrochemical (cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS)) analytical techniques were combined. The results show that intercalation of Li in the Fe 2 O 3 matrix and solid electrolyte interphase (SEI) layer formation both precede conversion to metallic iron and Li 2 O upon lithiation. Depth profile analysis evidences stratification of the converted thin-film electrode into fully and partially lithiated outer and inner parts, respectively, due to mass transport limitation. The SEI layer has a stable composition (Li 2 CO 3 with minor ROCO 2 Li) but dynamically increases/decreases in thickness upon lithiation/delithiation. Conversion, proceeding mostly in the outer part of the electrode, causes material swelling accompanied by SEI layer thickening. Upon delithiation, lithium is trapped in the deconverted electrode subjected to shrinking, and the SEI layer mostly decomposes and reduces in thickness after deconversion. The nonreversibility of both conversion and surface passivation mechanisms is demonstrated.
The Journal of Physical Chemistry C, 2018
A cobalt iron oxyphosphate CoFeOPO 4 @C (abbreviated as CFP@C) anode was prepared via a solid-state route, and its electrochemical performance was investigated vs. Li + /Li over a wide voltage range of 0.01-3.0 V at different current rates C/n (n= 20, 10, 5, 2 and 1). This anode material is able to intercalate more than six lithium ions into the structure at the C/10 current rate, delivering a specific capacity of 748.23 mAh g-1 , which is much higher than the theoretical capacity (593.7 mAh g-1) calculated when the insertion of a single lithium ion is considered. A reversible capacity of 200 mAhg-1 was maintained after 30 cycles. Raman spectroscopy confirmed the incorporation of carbon layers into the CoFeOPO 4 @C composite. Scanning electronic microscopy revealed that CFP@C particles have an angular-flake shape with particle sizes ranging between 1 and 5 µm. In situ X-ray absorption spectroscopy of Fe and Co at the K-edge showed that both transition metals are active during the whole discharge and charge. In operando high energy X-ray diffraction revealed that this material undergoes a gradual evolution of the structure with lower crystallinity after the first discharge. Correlating electrochemical performance to the structural and electronic features indicated that the cycling mechanism of the CFP@C anode material exhibits a combination of intercalation and conversion processes.
Analysis of Chemical and Electrochemical Lithiation/Delithiation of a Lithium-Ion Cathode Material
Journal of The Electrochemical Society, 2020
Redox targeting reactions between lithium-ion battery materials and redox shuttles have been proposed to design high energy density redox flow batteries. Designing these batteries would require a deeper understanding of the kinetics of redox targeting reactions and the phase transformation of the materials involved. In this study, the oxidation and reduction of lithium iron phosphate, LiFePO4, via chemical and electrochemical routes will be compared. Ultraviolet-visible spectroscopy was used as a technique to characterize the extent of chemical lithiation/delithiation during chemical redox of LiFePO4, while the electrochemical redox was characterized using battery coin cells. The kinetic parameters extracted using the Johnson–Mehl–Avrami–Erofeyev–Kolomogorov model suggested that chemical redox was slower than electrochemical redox within the experimental regimes. Calculated apparent activation energies suggested the limitations in the chemical redox rate were due to different proces...
Intercalation and conversion reactions in Ni0.5TiOPO4 Li-ion battery anode materials
Journal of Power Sources, 2013
h i g h l i g h t s < Ni 0.5 TiOPO 4 anode material was synthesized by solegel method directly from H 3 PO 4 acid. < The small particle size and the carbon coating of Ni 0.5 TiOPO 4 lead to enhanced electrochemical performance. < Ex-situ XRD analysis during the first discharge shows an amorphization of this anode material. < A model explaining the anomalous 1st discharge capacity and the amorphization of this phosphate was proposed.
Nickel ferrite (NiFe 2 O 4) has been previously shown to have a promising electrochemical performance for lithium-ion batteries (LIBs) as an anode material. However, associated electrochemical processes, along with structural changes, during conversion reactions are hardly studied. Nanocrystalline NiFe 2 O 4 was synthesized with the aid of a simple citric acid assisted sol−gel method and tested as a negative electrode for LIBs. After 100 cycles at a constant current density of 0.5 A g −1 (about a 0.5 Crate), the synthesized NiFe 2 O 4 electrode provided a stable reversible capacity of 786 mAh g −1 with a capacity retention greater than 85%. The NiFe 2 O 4 electrode achieved a specific capacity of 365 mAh g −1 when cycled at a current density of 10 A g −1 (about a 10 Crate). At such a high current density, this is an outstanding capacity for NiFe 2 O 4 nanoparticles as an anode. Ex-situ X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS) were employed at different potential states during the cell operation to elucidate the conversion process of a NiFe 2 O 4 anode and the capacity contribution from either Ni or Fe. Investigation reveals that the lithium extraction reaction does not fully agree with the previously reported one and is found to be a hindered oxidation of metallic nickel to nickel oxide in the applied potential window. Our findings suggest that iron is participating in an electrochemical reaction with full reversibility and forms iron oxide in the fully charged state, while nickel is found to be the cause of partial irreversible capacity where it exists in both metallic nickel and nickel oxide phases.
Recent developments in advanced anode materials for lithium-ion batteries
Energy Materials, 2021
The rapid expansion of electric vehicles and mobile electronic devices is the main driver for the improvement of advanced high-performance lithium-ion batteries (LIBs). The electrochemical performance of LIBs depends on the specific capacity, rate performance and cycle stability of the electrode materials. In terms of the enhancement of LIB performance, the improvement of the anode material is significant compared with the cathode material. There are still some challenges in producing an industrial anode material that is superior to commercial graphite. Based on the different electrochemical reaction mechanisms of anode materials for LIBs during charge and discharge, the advantages/disadvantages and electrochemical reaction mechanisms of intercalation-, conversion- and alloying-type anode materials are summarized in detail here. The methods and strategies for improving the electrochemical performance of different types of anode materials are described in detail. Finally, challenges ...
2011
The complex structural transformations of Li 0.5 Ni 0.25 TiOPO 4 during electrochemical lithiation have been examined by in situ X-ray diffraction. During the first lithiation two structural changes take place: first a transition to a second monoclinic phase (a = 9.085(4), b =8.414(5), c =6.886(5), β = 99.85(4)) and secondly a transition to a third phase with limited long-range order. The third phase is held together by a network of corner sharing Ti-O octahedra and phosphate ions with disordered Ni-Li channels. During delithiation the third phase is partially transformed back to a slightly disordered original phase, Li 0.5 Ni 0.25 TiOPO 4 without formation of the second intermediate phase. These phase transitions correspond well to the different voltage plateaus that this material shows during electrochemical cycling.
Journal of Solid State Chemistry, 2001
Chemical states and structural changes accompanying the electrochemical Li deintercalation of Li 1؊x (Mn, M) 2 O 4 (M ؍ Cr, Co, Ni) were studied by the in situ X-ray absorption 5ne structure (XAFS) technique. The X-ray absorption near-edge structures (XANES) of Mn and M as a function of x showed that the high voltage (&5 V) in the cathode materials of an Li secondary battery is due to the oxidation of M 3؉ to M 4؉ (M ؍ Cr, Co) and M 2؉ to M 4؉ (in the case of M ؍ Ni), while the origin of the low voltage (3.9+4.3 V) can be ascribed to the oxidation of Mn 3؉ to Mn 4؉. The extended X-ray absorption 5ne structure (EXAFS) analysis of Li 1؊x (Mn, Ni) 2 O 4 revealed that Ni 2؉ is oxidized to Ni 4؉ via the Ni 3؉ state with a Jahn+Teller distorted Ni 3؉ +O octahedron.
mESC-IS 2019 : The Fourth International Symposium on Materials for Energy Storage and Conversion, 2019
This is the fourth activity in a series of symposia initiated back in 2015. The first symposium organized at METU comprised topics; solid state hydrogen storage, fuel cell-electrolysers and batteries-supercapacitors. This was followed by the second symposium in Cappadocia in Ortahisar 2017. The third symposium took place in Belgrade in September of 2018. In this series emphasis varied from one topic to the other. The current symposium comprises again three activity areas; namely, batteries-supercapacitors, fuel cells-electrolysers and hydrides for energy storage and conversion. The symposium, as before, has a fair balance of plenary sessions covering cross-cutting issues and the state of the art reviews and in-depth parallel sessions with contributed papers and poster presentation. Summer school is an integral part of this symposium. This has preceded the symposium and span over a four day period from September 7 th to 10 th , taken place at Mugla Sıtkı Koçman University. It comprised overviews on selected topics in energy storage and conversion with the view of acquainting the newcomers with the essentials of the topic plus portraying an outlook for possible future direction of research in the respective fields. Following recommendations made in mESC-School 2017 Cappadocia, we have introduced hands-on sessions into the program on selected techniques in material and electrochemical characterization. A substantial number of trainees from a variety of institutions in different disciplines, some new or early in their graduate study, some quite experienced have benefited greatly from this experience. This event was made possible with generous support of several institutions as well as of sponsors. We would like to acknowledge TUBITAK for the support both for summer school through the program 2237-A and symposium through 2223-B. ENDAM workshop was made possible by funds from Ministry of Development which we also gratefully acknowledge. We also acknowledge the support of our respective universities in a number of ways. Tayfur Öztürk. on behalf of mESC-IS2019 Organizing Committee mESC-IS 2019, 4th Int. Symposium on Materials for Energy Storage and Conversion Akyaka, Mugla Summer School on Materials for Energy Storage and Conversion,mESC-School 2019 took place from 7 th to 11 th September 2019. A total of 48 participants have taken part in the summer school. The program comprised material/electrochemical Characterization techniques;