Electronic structure, x-ray spectra, and magnetic properties of the LiCoO2−δ and NaxCoO2 nonstoichiometric oxides

Galakhov, V. R.; Karelina, V. V.; Келлерман, Д. Г.; Gorshkov, V. S.; Ovechkina, N. A.; Neumann, M.

doi:10.1134/1.1451011

Cited by 53 publications

(49 citation statements)

References 16 publications

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“…[120][121][122][123]). This section focuses on the in situ PES and XAS studies of the electronic properties of thin film cathode materials and their interfaces to elucidate the stability vs. potential.…”

Section: Electronic Processes: Electronic Structure Of Bulk Materialsmentioning

confidence: 97%

Fundamental degradation mechanisms of layered oxide Li-ion battery cathode materials: Methodology, insights and novel approaches

Hausbrand

Cherkashinin

Ehrenberg

et al. 2015

Materials Science and Engineering: B

410

280

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Available online xxx a b s t r a c tThis overview addresses the atomistic aspects of degradation of layered LiMO 2 oxide Li-ion cell cathode materials, aiming to shed light on the fundamental degradation mechanisms especially inside active cathode materials and at their interfaces. It includes recent results obtained by novel in situ/in operando diffraction methods, modelling, and quasi in situ surface science analysis. Degradation of the active cathode material occurs upon overcharge, resulting from a positive potential shift of the anode. Oxygen loss and eventual phase transformation resulting in dead regions are ascribed to changes in electronic structure and defect formation. The anode potential shift results from loss of free lithium due to side reactions occurring at electrode/electrolyte interfaces. Such side reactions are caused by electron transfer, and depend on the electron energy level alignment at the interface. Side reactions at electrode/electrolyte interfaces and capacity fade may be overcome by the use of suitable solid-state electrolytes and Licontaining anodes.

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Section: Electronic Processes: Electronic Structure Of Bulk Materialsmentioning

confidence: 97%

Fundamental degradation mechanisms of layered oxide Li-ion battery cathode materials: Methodology, insights and novel approaches

Hausbrand

Cherkashinin

Ehrenberg

et al. 2015

Materials Science and Engineering: B

410

280

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“…7(a), spectrum (iii)) and the DE(Co3s) m,s* energy distance fits well to the energy distance characteristic of the Co 2+ , HS-configuration. 44 Fig. 7(b) shows the difference between the Co3s emissions of the LCO cathodes cycled to the different end-of-charge voltages.…”

Section: Cycled Cathodesmentioning

confidence: 99%

The stability of the SEI layer, surface composition and the oxidation state of transition metals at the electrolyte–cathode interface impacted by the electrochemical cycling: X-ray photoelectron spectroscopy investigation

Cherkashinin

Nikolowski

Ehrenberg

et al. 2012

Phys. Chem. Chem. Phys.

117

112

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The stability of the valence state of the 3d transition metal ions and the stoichiometry of LiMO(2) (M = Co, Ni, Mn) layered oxides at the surface-electrolyte interface plays a crucial role in energy storage applications. The surface oxidation/reduction of the cations caused by the contact of the solids to air or to the electrolyte results in the blocking of the Li-transport through the interface that leads to the fast batteries deterioration. The influence of the end-of-charge voltage on the chemical composition and the oxidation state of 3d transition metal ions, as well as the stability of the solid-electrolyte interface formed during the electrochemical Li-deintercalation/intercalation of the LiCoO(2) and Li(Ni,Mn,Co)O(2), have been investigated by X-ray photoelectron spectroscopy. While the chemical composition of the solid-electrolyte interface is similar for both layered oxide surfaces, the electrochemical cycling to some critical voltage values leads to the disappearance of the interface. By the analysis of the shape of the 2p and 3s photoelectron emissions we show that the formation of the solid-electrolyte interface layer correlates with the partial reduction of the trivalent Co ions at the electrolyte-LiCoO(2) interface and the amount of the Co(2+) ions is increased as the solid-electrolyte interface vanishes. In contrast, the Mn(4+), Co(3+) and Ni(2+) ions of the Li(Ni,Mn,Co)O(2) are stable at the interface under the electrochemical cycling to higher end-of-charge voltage. A correlation between deterioration of the LiCoO(2) and Li(Ni,Mn,Co)O(2) batteries and the change of electronic structure at the surface/interface after the electrochemical cycling has been found. The dissolution of the solid-electrolyte interface layer might be the reason for the fast deterioration of the Li-ion batteries.

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“…This view is consistent with spectroscopy data 27,28 showing that holes induced by delithiation reside on O rather than on Co. ͑One should also recognize an analogy to the CuO 2 planes in high-T c superconductors.͒ It is most likely that a similar explanation applies to the Na x CoO 2−␦ system. Indeed, a recent x-ray photoelectron and emission spectroscopy study 29 revealed that the holes created upon Na deintercalation are mostly induced in the O 2p band. That is, upon doping the A x CoO 2−␦ ͑A =Li or Na͒ system with holes, the Co cation becomes more electronegative ͑i.e., less attractive͒ than oxygen for the doped holes ͑in chemistry terminology͒.…”

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confidence: 99%

Oxygen nonstoichiometry and actual Co valence inNaxCoO2−δ

et al. 2005

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The Na x CoO 2−␦ system-a host lattice for superb thermoelectrics and parent of the watery CoO 2 -layer superconductor-is found to be oxygen nonstoichiometric for x ഛ 0.7, such that with decreasing x, the concentration of oxygen vacancies increases. Accordingly, upon Na deintercalation, the Co valence first increases but does not exceed the value of 3.5. To reveal this, the actual valence of Co was systematically determined by means of wet-chemical redox analysis for a series of Na x CoO 2−␦ samples with the Na content x ranging from 0.78 down to 0.12. The low-Na-content samples were obtained from Na-rich ones ͑0.70ഛ x ഛ 0.78͒ through chimie douce extraction of Na utilizing I 2 , Br 2 , or NO 2 BF 4 as an oxidizing agent. For the lowest-Na-content sample of x = 0.12, the oxygen nonstoichiometry parameter ␦ was 0.23. The ␦-x relation presently established for a wide x range of Na x CoO 2−␦ is indispensable for proper interpretations of physical properties of this system.

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Electronic structure, x-ray spectra, and magnetic properties of the LiCoO2−δ and NaxCoO2 nonstoichiometric oxides

Cited by 53 publications

References 16 publications

Fundamental degradation mechanisms of layered oxide Li-ion battery cathode materials: Methodology, insights and novel approaches

Fundamental degradation mechanisms of layered oxide Li-ion battery cathode materials: Methodology, insights and novel approaches

The stability of the SEI layer, surface composition and the oxidation state of transition metals at the electrolyte–cathode interface impacted by the electrochemical cycling: X-ray photoelectron spectroscopy investigation

Oxygen nonstoichiometry and actual Co valence inNaxCoO2−δ

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