New insights into the pre-lithiation kinetics of single-crystalline Ni-rich cathodes for long-life Li-ion batteries

Developing single-crystalline Ni-rich cathodes is an effective strategy to improve the safety and cycle life of Li-ion batteries(LIBs).However,the easy-to-loss of Li and O in high-temperature lithiation results in unsatisfactory ordered layered structure and stoichiometry.Herein,we demonstrate the synthesis of highly-ordered and fully-stoichiometric single-crystalline LiNi_(0.83)Co_(0.12)Mn_(0.05)O_(2)(SC-NCM83)cathodes by the regulation of pre-lithiation kinetics.The well-balanced pre-lithiation kinetics have been proved to greatly improve the proportion of layered phase in the intermediate by inhibiting the formation of metastable spinel phase,which promoted the rapid transformation of the intermediate into highly-ordered layered SC-NCM83 in the subsequent lithiation process.After coating a layer of Li_(2)O–B_(2)O_(3),the resultant cathodes deliver superior cycling stability with 90.9%capacity retention at 1C after 300 cycles in pouch-type full batteries.The enhancement mechanism has also been clarified.These findings exhibit fundamental insights into the pre-lithiation kinetics process for guiding the synthesis of high-quality singlecrystalline Ni-rich cathodes.

Mesoscale interplay among composition heterogeneity,lattice deformation,and redox stratification in single-crystalline layered oxide cathode

Single-crystalline layered oxide materials for lithium-ion batteries are featured by their excellent capacity retention over their polycrystalline counterparts,making them sought-after cathode candidates.Their capacity degradation,however,becomes more severe under high-voltage cycling,hindering many high-energy applications.It has long been speculated that the interplay among composition heterogeneity,lattice deformation,and redox stratification could be a driving force for the performance decay.The underlying mechanism,however,is not well-understood.In this study,we use X-ray microscopy to systematically examine single-crystalline NMC particles at the mesoscale.This technique allows us to capture detailed signals of diffraction,spectroscopy,and fluorescence,offering spatially resolved multimodal insights.Focusing on early high-voltage charging cycles,we uncover heterogeneities in valence states and lattice structures that are inherent rather than caused by electrochemical abuse.These heterogeneities are closely associated with compositional variations within individual particles.Our findings provide useful insights for refining material synthesis and processing for enhanced battery longevity and efficiency.

Surfactant-aided hydrothermal preparation of La(2-x)Sr_xCuO_4 single crystallites and their catalytic performance on methane combustion

Perovskite-like oxide La2-xSrxCuO4 （x = 0, 1） single crystallites with microrod-like morphologies and tetragonal crystal structures were prepared hydrothermally at 240 ℃ with poly（ethylene glycol） （PEG） or hexadecyltrimethyl ammonium bromide （CTAB） as a surfactant and after calcination at 850 ℃. The physicochemical properties of the materials were characterized by means of XRD, BET, SEM, TEM/SAED （selected-area electron diffraction）, XPS and H2-TPR techniques. It is found that doping Sr2＋ to La2CuO4 lattice enhanced the catalytic activity for methane combustion and the LaSrCuO4 catalyst derived from PEG is the best among the tested ones. It is concluded that factors, such as adsorbed oxygen species concentration, reducibility and surface area, determined the catalytic performance of such single-crystalline materials.

A comparative investigation of NdSrCu_(1-x) Co_x O_(4-δ) and Sm_(1.8) Ce_(0.2) Cu_(1-x) Co_x O_(4-δ) (x:0–0.4) for NO decomposition

A series of single-phase T-structured NdSrCu 1-x Co x O 4-δ with oxygen vacancies and T -structured Sm 1.8 Ce 0.2 Cu 1-x Co x O 4-δ （x： 0–0.4） with oxygen excess were prepared using ultrasound-assisted citric acid complexing method, and characterized by means of techniques such as thermogravimetric analysis and NO temperature-programmed desorption （NO-TPD）. The catalytic activities of these materials were evaluated for the decomposition of NO. It was found that the NdSrCu 1-x Co x O 4-δ catalysts were of oxygen vacancies whereas the Sm 1.8 Ce 0.2 Cu 1？x Co x O 4-δ ones possessed excessive oxygen （i.e., over-stoichiometric oxygen）; with a rise in Co doping level, the oxygen vacancy density of NdSrCu 1-x Co x O 4-δ decreased while the over-stoichiometric oxygen amount of Sm 1.8 Ce 0.2 Cu 1-x Co x O 4-δ increased. The NO-TPD results revealed that NO could be activated much easier over the oxygen-deficient perovskite-like oxides than over the oxygen-excessive perovskite-like oxides, with the NdSrCuO 3.702 catalyst showing the best efficiency in activating NO molecules. Under the conditions of 1.0% NO/helium, 2800 hr -1 , and 600–900°C, the catalytic activity of NO decomposition followed the order of NdSrCuO 3.702 〉 NdSrCu 0.8 Co 0.2 O 3.736 〉 NdSrCu 0.6 Co 0.4 O 3.789 〉 Sm 1.8 Ce 0.2 Cu 0.6 Co 0.4 O 4.187 〉 Sm 1.8 Ce 0.2 Cu 0.8 Co 0.2 O 4.104 〉 Sm 1.8 Ce 0.2 CuO 4.045 , in concord with the sequence of decreasing oxygen vacancy or oxygen excess density. Based on the results, we concluded that the higher oxygen vacancy density and the stronger Cu 3＋ /Cu 2＋ redox ability of NdSrCu 1-x Co x O 4-δ account for the easier activation of NO and consequently improve the catalytic activity of NO decomposition over the catalysts.

The complex oxides with octahedral structures:Existence areas and phase transitions

The experimental and calculated data on the existence of complex oxides in solid state with the octahedral structures of four families,namely perovskites,Bi-containing layered perovskite-like ones,tetragonal tungsten bronzes and pyrochlores,and about their phase transitions are systematized and summarized on the basis of the quasi-elastic or geometric models of these structures.It has been established that similar existence areas and similar correlations between the interatomic bond strains in their structures,on the one hand,and the temperatures of their ferroelectric or antiferroelectric phase transitions,on the other hand,are observed for all of them,despite the differences in the compositions and structures of these oxides,but taking into account their similar parameters.

Catalytic combustion of soot particulates over La_(2-x)K_xNiMnO_6 catalysts

Nanosized La2-xKxNiMnO6 catalysts with ABO3 type perovskite-like structure were prepared by auto-combustion method using citric acid as a ligand to control particle size and morphology.The structures and properties of these perovskite-like oxides were investigated by X-ray powder diffraction（XRD）and temperature-programmed reduction（TPR）.The catalytic activities for soot combustion were evaluated by temperature- programmed oxidation（TPO）with pure O2 and O2/NOx as oxidant,respectively.In the La2-xKxNiMnO6 catalysts,the partial substitution of K at A-site leads to an increase of the concentrations of high valence cation and oxygen vacancy,which enhance the catalytic activity for soot combustion.The optimal substitution amount of K was equal to x=0.4 among these samples.Tp（peak temperature）in O2-TPO profile was 420-C and Tp in O2/NOx-TPO profile was 370-C over La1.6K0.4NiMnO6 catalyst for soot particulates combustion under loose contact conditions between catalyst and soot.

Transport and Magnetic Properties of Perovskite-Type Manganite (La_(0.8-x)Ce_x Sr_ (0.2))_ (0.97)MnO_3

Phase structures, the transport ana magnetic properties of the Perovskite-type manganite （La0.8-x CexSr0.2）0.97 MnO3（x = 0 - 0. 26） prepared by La2O3 containing CeO2 with different contents were studied. Experiments show that the compounds consist of a magnetic perovskite phase and non-magnetic CeO2 and Mn3O4. The resistivity and magnetoresistance ratio （MR） of the samples vary with changing x. Their room-temperature MR reaches -3% - - 14% at the magnetic field of 1 T. For x =0; x =0.037 and x = 0.26 samples, the conductance keeps unchanged basically in a relatively wide temperature range above 600 K, and the result shows that it is feasible for producing SOFC cathode materials with these samples.