Thorium(IV) and zirconium(IV) complexes of oxygen donor ligands,Part 6. thorium(IV) complexes of 2,6-lutidine-N-oxide and tetramethylene sulphoxide

Summary The synthesis and physical properties of crystalline thorium(IV) complexes, Th(ClO₄)₄ · 6 LNO, ThX₄ · 2 LNO (X = Br or SCN), ThX₄ · 4 LNO (X = NO₃ or I) andTh(ClO₄)₄ · 10 TMSO, Th(NO₃)₄ · 6 TMSO, ThX₄ · 4 TMSO (X = Cl or Br), ThI₄ · 6 TMSO and Th(NCS)₄ · 2 TMSO (where LNO = 2,6-lutidine-N-oxide and TMSO = tetramethylene sulphoxide) are reported together with their i.r. spectra, molar conductivities, molecular weights, t. g. a. and d. t. a. data. In all the complexes, LNO and TMSO are bonded to thorium(IV) through oxygen. The coordination number of thorium(IV) in these complexes varies from six to ten depending upon the nature of the anions.Presented at the XVI Annual Convention of Chemists, Andhra University, Waltair, A. P. India, December 27–31, 1978.     

Combustion-synthesized sodium manganese (cobalt) oxides as cathodes for sodium ion batteries

We report on the electrochemical properties of layered manganese oxides, with and without cobalt substituents, as cathodes in sodium ion batteries. We fabricated sub-micrometre-sized particles of Na_0.7MnO_2?+?z and Na_0.7Co_0.11Mn_0.89O_2?+?z via combustion synthesis. X-ray diffraction revealed the same layered hexagonal P2-type bronze structure with high crystallinity for both materials. Potentiostatic and galvanostatic charge/discharge cycles in the range 1.5–3.8 V vs. Na | Na⁺ were performed to identify potential-dependent phase transitions, capacity, and capacity retention. After charging to 3.8 V, both materials had an initial discharge capacity of 138 mA?h?g^?1 at a rate of 0.3 C. For the 20th cycle, those values reduced to 75 and 92 mA?h?g^?1 for Co-free and Co-doped samples, respectively. Our findings indicate that earlier works probably underestimated the potential of (doped) P2-type Na_0.7MnO_2?+?z as cathode material for sodium ion batteries in terms of capacity and cycle stability. Apart from doping, a simple optimization parameter seems to be the particle size of the active material.     

Photosensitive sol–gel preparation and micro-patterning of (100)-oriented (Ba0.7Sr0.3)TiO3 film on LaNiO3 electrode

Using La(NO₃)₃·nH₂O and Ni(CH₃COO)₂·4H₂O as starting materials, the LaNiO₃ sol was prepared with 2-methoxyethanol as solvent. Using this sol, (001)-oriented LNO films with high conductivity were prepared on LaAlO₃ single crystal substrate by sol–gel method. Using barium acetate, strontium acetate, and Ti(OC₄H₉)₄ as starting materials, acetylacetone and lactic acid as chemical modifiers, photosensitive BST sol was obtained. Using the BST sol, a-oriented BST films were prepared on (001)LNO/LAO. Due to the photosensitivity of the BST sol, the coated BST gel film itself can be used as photoresist. Thus, micro-patterned a-oriented BST films are obtained by exposing, leaching, and annealing the BST gel film. The a-oriented BST film capacitor on LNO/LAO has a high dielectric constant, a low dielectric loss and a low leakage current.     

Diffusion coefficients of ions through ion excange membrane in Donnan dialysis using ions of different valence

Donnan dialysis with an ion exchange membrane was investigated for ions of different valence. The effective diffusion coefficients (D_e) of various kinds of ions in the membrane were obtained by fitting of the equation derived from the Nernst–Planck equation to three or more sets of experimental data for Donnan dialysis. It became apparent that the value of D_e/D_s of monovalent ions (e.g., K⁺ or Na⁺ ions) at z_A=1 and z_B=2 (feed ions are monovalent ones and driving ions are bivalent ones) remained constant at ca. 1/210 and that of bivalent ions (e.g., Ca²⁺, Cu²⁺, or Mg²⁺ ions) remained constant at ca. 1/526 where D_s denotes the diffusion coefficient of ions at infinite dilution in water calculated from the Nernst–Einstein equation, and z_A and z_B represent the valences of the feed and driving ions, respectively. D_e/D_s of monovalent ions (e.g., H⁺, K⁺, or Na⁺ ions) at z_A=2 and z_B=1 (feed ions are bivalent ones and driving ions are monovalent ones) was constant at ca. 1/23.3 and that of bivalent ions remained constant at ca. 1/58.4. It was proved that D_e/D using D_e at z_A=1 and z_B=2 was constant at 1/3.0 and that at z_A=2 and z_B=1 remained constant at 3.0 where D represents the diffusion coefficient of ions in the membrane at z_A=z_B (the valences of both feed and driving ions are equal). Therefore, it was found that a large flux of ions could be obtained using the monovalent driving ions in Donnan dialysis. On the other hand, the small flux can be obtained using bi- or higher-valent driving ions.     

Electrophoretic Deposition of Thin-Film Coatings of Solid Electrolyte Based on Microsize BaCeO<Subscript>3</Subscript> Powders

Results are presented of an electrophoretic deposition of thin-film coatings based on doped barium cerate BaCeO₃ on a cathode substrate La₂NiO₄ (LNO), which are of interest for the technology of medium-temperature solid-oxide fuel cells. Suspensions for electrophoretic deposition in a mixed dispersion medium isopropanol/acetylacetone = 70/30 vol %, prepared from microsized powders BaCe_0.8Sm_0.2O_3–δ (BCSO) and BaCe_0.89Gd_0.1Cu_0.01O_3–δ (BCGCuO) synthesized by the citrate-nitrate method, demonstrated a high positive ζ-potential (+25 mV) suitable for deposition. A combination of the ultrasonic treatment and centrifugation made it possible to diminish the hydrodynamic diameter of BCSO and BCGCuO particles to 880 and 294 nm, respectively. It was shown that the BCGCuO film deposited onto an LNO cathode substrate has a higher density as compared with the BCSO film, which is due to the properties of the suspensions obtained. Upon a cyclic electrophoretic deposition in six stages, the total mass and thickness of the BCGCuO coating were 3.2 mg cm^–2 and 5 μm, which is sufficient for a unit solid-oxide cell to be formed. According to SEM data, the BCGCuO film is dense and has fully formed grains with sizes of 1 to 7 μm. Methods are discussed for eliminating the loss of Ba in sintering of a thin film based on BaCeO₃.     

Exact electronic properties in the classically forbidden region of a metal surface

We derive exact properties of the inhomogeneous electron gas in the asymptotic classically forbidden region at a metal–vacuum interface within the framework of local effective potential energy theory. We derive a new expression for the asymptotic structure of the Kohn–Sham density functional theory (KS‐DFT) exchange‐correlation potential energy v_xc(r) in terms of the irreducible electron self‐energy. We also derive the exact asymptotic structure of the orbitals, density, the Dirac density matrix, the kinetic energy density, and KS exchange energy density. We further obtain the exact expression for the Fermi hole and demonstrate its structure in this asymptotic limit. The exchange‐correlation potential energy is derived to be v_xc(z → ∞) = ?α_KS,xc/z, and its exchange and correlation components to be v_x(z → ∞) = ?α_KS,x/z and v_c(z → ∞) = ?α_KS,c/z, respectively. The analytical expressions for the coefficients α_KS,xc and α_KS,x show them to be dependent on the bulk‐metal Wigner–Seitz radius and the barrier height at the surface. The coefficient α_KS,c = 1/4 is determined in the plasmon‐pole approximation and is independent of these metal parameters. Thus, the asymptotic structure of v_xc(z) in the vacuum region is image‐potential‐like but not the commonly accepted one of ?1/4z. Furthermore, this structure depends on the properties of the metal. Additionally, an analysis of these results via quantal density functional theory (Q‐DFT) shows that both the Pauli W_x(z → ∞) and lowest‐order correlation‐kinetic W(z → ∞) components of the exchange potential energy v_x(z → ∞), and the Coulomb W_c(z → ∞) and higher‐order correlation‐kinetic components of the correlation potential energy v_c(z → ∞), all contribute terms of O(1/z) to the structure. Hence correlations attributable to the Pauli exclusion principle, Coulomb repulsion, and correlation‐kinetic effects all contribute to the asymptotic structure of the effective potential energy at a metal surface. The relevance of the results derived to the theory of image states and to KS‐DFT is also discussed. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005     

NMR evidence of LiF coating rather than fluorine substitution in Li(Ni0.425Mn0.425Co0.15)O2

A series of “Li_1+z/2(Ni_0.425Mn_0.425Co_0.15)_1−z/2O_2−zF_z” materials was prepared by a coprecipitation route and their structure was characterized using X-ray diffraction (XRD), as well as ⁷Li and ¹⁹F Magic Angle Spinning (MAS) NMR spectroscopy. Two hypotheses were considered: (i) formation of layered oxyfluoride materials and (ii) formation of a mixture between the layered material and LiF. Structural parameters were refined by the Rietveld method, using XRD diffraction data. The refinement results did not allow us to choose between these two hypotheses: no significant change in crystallinity and structural parameters was observed irrespective of the fluorine ratio. ⁷Li and ¹⁹F MAS NMR analyses showed signals with isotropic positions characteristic of LiF, but envelopes characteristic of very strong dipolar interactions with the electron spins of the material, demonstrating that LiF was not incorporated into the layered oxide structure but was instead present as a coating.     

Nanoscale battery cathode materials induce DNA damage in bacteria

The increasing use of nanoscale lithium nickel manganese cobalt oxide (Li_xNi_yMn_zCo_1−y−zO₂, NMC) as a cathode material in lithium-ion batteries poses risk to the environment. Learning toxicity mechanisms on molecular levels is critical to promote proactive risk assessment of these complex nanomaterials and inform their sustainable development. We focused on DNA damage as a toxicity mechanism and profiled in depth chemical and biological changes linked to DNA damage in two environmentally relevant bacteria upon nano-NMC exposure. DNA damage occurred in both bacteria, characterized by double-strand breakage and increased levels of many putative chemical modifications on bacterial DNA bases related to direct oxidative stress and lipid peroxidation, measured by cutting-edge DNA adductomic techniques. Chemical probes indicated elevated intracellular reactive oxygen species and transition metal ions, in agreement with DNA adductomics and gene expression analysis. By integrating multi-dimensional datasets from chemical and biological measurements, we present rich mechanistic insights on nano-NMC-induced DNA damage in bacteria, providing targets for biomarkers in the risk assessment of reactive materials that may be extrapolated to other nano–bio interactions.

The increasing use of nanoscale lithium nickel manganese cobalt oxide (Li_xNi_yMn_zCo_1−y−zO₂, NMC) as a cathode material in lithium-ion batteries poses risk to the environment. We report DNA damage that occurs in bacteria after nano-NMC exposure with rich chemical details.     

Mechanism of Formation of the Major Estradiol Product Ions Following Collisional Activation of the Molecular Anion in a Tandem Quadrupole Mass Spectrometer

The importance of the mass spectral product ion structure is highlighted in quantitative assays, which typically use multiple reaction monitoring (MRM), and in the discovery of novel metabolites. Estradiol is an important sex steroid whose quantitation and metabolite identification using tandem mass spectrometry has been widely employed in numerous clinical studies. Negative electrospray ionization tandem mass spectrometry of estradiol (E2) results in several product ions, including the abundant m/z 183 and 169. Although m/z 183 is one of the most abundant product ions used in many quantitative assays, the structure of m/z 183 has not been rigorously examined. We suggest a structure for m/z 183 and a mechanism of formation consistent with collision induced dissociation (CID) of E2 and several stable isotopes ([D₄]-E2, [¹³C₆]-E2, and [D₁]-E2). An additional product ion from E2, namely m/z 169, has also been examined. MS³ experiments indicated that both m/z 183 and m/z 169 originate from only E2 [M – H]^– m/z 271. These ions, m/z 183 and m/z 169, were also present in the collision induced decomposition mass spectra of other prominent estrogens, estrone (E1) and estriol (E3), indicating that these two product ions could be used to elucidate the estrogenic origin of novel metabolites. We propose two fragmentation schemes to explain the CID data and suggest a structure of m/z 183 and m/z 169 consistent with several isotopic variants and high resolution mass spectrometric measurements.      

Mechanochemical Synthesis of Nanoparticles by a Dilution Method: Determination of the Particle Mixing Coefficient in a Ball Mill

Experimental study of the kinetics of mechanosynthesis of TlCl nanoparticles in the reaction 2NaCl + Tl₂SO₄ + zNa₂SO₄ = = (z + 1)Na₂SO₄ + 2TlCl with z = z^*₁ = z^* = 11.25 and comparison of kinetic parameters for this reaction with those determined theoretically for the model reaction KBr + TlCl + zKCl = (z + 1)KCl + TlBr with z = z^*₁ = 13.5 made it possible to estimate the mass transfer (mixing of particles) coefficient in a mechanochemical reactor by the mobile milling tools.     

Structural investigation of the Cu2Se-In2Se3-Ga2Se3 phase diagram, X-ray photoemission and optical properties of the Cu1−z(In0.5Ga0.5)1+z/3Se2 compounds

Structures of compounds in the Cu₂Se-In₂Se₃-Ga₂Se₃ system have been investigated through X-ray diffraction. Single crystal structure studies for the so-called stoichiometric compounds Cu(In,Ga)Se₂ (CIGSe) confirm that the chalcopyrite structure (space group I4¯2d) is very flexible and can adapt itself to the substitution of Ga for In. On the other hand a structure modification is evidenced in the Cu_1−z(In_0.5Ga_0.5)_1+z/3Se₂ series when the copper vacancy ratio (z) increases; the chalcopyrite structure turns to a modified-stannite structure (I4¯2m) when z≥0.26. There is a continuous evolution of the structure from Cu_0.74(In_0.5Ga_0.5)_1.09Se₂ to Cu_0.25(In_0.5Ga_0.5)_1.25Se₂ ((i.e. Cu(In_0.5Ga_0.5)₅Se₈), including Cu_0.4(In_0.5Ga_0.5)_1.2Se₂ (i.e. Cu(In_0.5Ga_0.5)₃Se₅). From this single crystal structural investigation, it is definitively clear that no ordered vacancy compound exists in that series. X-ray photoemission spectroscopy study shows for the first time that the surface of powdered Cu_1−z(In_0.5Ga_0.5)_1+z/3Se₂ compounds (z≠0) is more copper-poor than the bulk. The same result has often been observed on CIGSe thin films material for photovoltaic applications. In addition, optical band gaps of these non-stoichiometric compounds increase from 1.2 to 1.4 eV when z varies from 0 to 0.75.     

Simulated ion trajectory and induced signal in ion cyclotron resonance ion traps. Effect of ion initial axial position on ion coherence,induced signal,and radial or z ejection in a cubic trap

The effects of ion initial axial position on coherence of ion motion, induced ion cyclotron resonance (ICR) signal. and radial and z ejection have been evaluated by numerical simulation for a cubic Fourier transform-ion cyclotron resonance ion trap. For a given initial ion cyclotron phase and radius, ions of different initial z position are shown to be excited to significantly different ion cyclotron radii (and ultimately radially ejected at significantly different excitation amplitude-duration products). Ion initial z displacement from the trap midplane affects observed ICR signal magnitude in two ways: (1) for the same postexcitation cyclotron radius, an ion with larger initial z displacement induces a smaller ICR signal and (2) an ion with larger initial z displacement is excited to a smaller cyclotron radius. We also evaluate the induced ICR signal as a function of excitation amplitude-duration product for spatially uniform or Gaussian ion initial z distributions. In general, if the excitation waveform contains components at frequency, 2 ω_z or (ω₊ + 2 ω_z, in which ω_z is the axial C“trapping”) oscillation frequency, then ejection occurs axially. However, the resulting excitation amplitude-duration product for such axial ejection is significantly higher (factor of, ～ 4) than that required for radial ejection (at ω₊) for ions of small initial radius. The present results offer the first explanation of how, even if the ion is initially at rest on the z axis (i.e., zero excitation electric field amplitude on the z axis), z ejection (axial ejection) may nevertheless occur if the excitation waveform contains frequency components at ω₊ + 2ω_z and/or 2_{w z} Namely, our simulations reveal that off-resonant excitation pushes ions away from the z axis, after which the ions are exposed to z excitation and eventual z ejection.     

Al,B, and F doped LiNi<Subscript>1/3</Subscript>Co<Subscript>1/3</Subscript>Mn<Subscript>1/3</Subscript>O<Subscript>2</Subscript> as cathode material of lithium-ion batteries

A series of the mixed transition metal compounds, Li[(Ni_1/3Co_1/3Mn_1/3)_1–x-y Al _x B _y ]O_2-z F _z (x = 0, 0.02, y = 0, 0.02, z = 0, 0.02), were synthesized via coprecipitation followed by a high-temperature heat-treatment. XRD patterns revealed that this material has a typical α-NaFeO₂ type layered structure with R3^- m space group. Rietveld refinement explained that cation mixing within the Li(Ni_1/3Co_1/3Mn_1/3)O₂ could be absolutely diminished by Al-doping. Al, B and F doped compounds showed both improved physical and electrochemical properties, high tap-density, and delivered a reversible capacity of 190 mAh/g with excellent capacity retention even when the electrodes were cycled between 3.0 and 4.7 V.     

A Two‐Dimensional Zirconium Carbide by Selective Etching of Al3C3 from Nanolaminated Zr3Al3C5

The room‐temperature synthesis of a new two‐dimensional (2D) zirconium‐containing carbide, Zr₃C₂T_z MXene is presented. In contrast to traditional preparation of MXene, the layered ternary Zr₃Al₃C₅ material instead of MAX phases is used as source under hydrofluoric acid treatment. The structural, mechanical, and electronic properties of the synthesized 2D carbide are investigated, combined with first‐principles density functional calculations. A comparative study on the structrual stability of our obtained 2D Zr₃C₂T_z and Ti₃C₂T_z MXenes at elevated temperatures is performed. The obtained 2D Zr₃C₂T_z exhibits relatively better ability to maintain 2D nature and strucural integrity compared to Ti‐based Mxene. The difference in structural stability under high temperature condition is explained by a theoretical investigation on binding energy.     

Hybrid Polyoxotungstates as Functional Comonomers in New Cross‐Linked Catalytic Polymers for Sustainable Oxidation with Hydrogen Peroxide

Anchoring terminal octenyl tails on molecular polyoxotungstates yield polymerizable organic–inorganic monomers with formula [{CH₂?CH(CH₂)₆Si}_xO_ySiW_wO_z]^4? [x=2, w=11, y=1, z=39 ( 1 ); x=2, w=10, y=1, z=36 ( 2 ); and x=4, w=9, y=3, z=34 ( 3 )]. These molecular hybrids can use aqueous hydrogen peroxide to catalyze the selective oxidation of organic sulfides in CH₃CN. Copolymerization of 1 – 3 with methyl methacrylate and ethylene glycol dimethacrylate leads to porous materials with a homogeneous distribution of the functional monomers, as indicated by converging evidence from FTIR spectroscopy and electronic microscopy. The catalytic polymers activate hydrogen peroxide for oxygen transfer, as demonstrated by the quantitative and selective oxidation of methyl p‐tolyl sulfide, which was screened as model substrate. The hybrid material containing monomer 2 was also tested in n‐octane to evaluate its potential for the oxidation and removal of dibenzothiophene, a well‐known gasoline contaminant.     

Mass spectra of some α-substituted phenyl-α,α′-dimethoxyl ketones and their derivatives

The mass spectra of some α-substituted phenyl-α,α′-dimethoxyl ketones (compounds 1) and their 2,4-dinitrophenylhydrazones (compounds 2) and semicarbazones (compounds 3) have been studied. The characteristic fragments at m/z (M ? 73) from compounds 1, m/z (M ? 253) from compounds 2 and m/z (M ? 130) from compounds 3 are abundant and proposed to be [ArCROCH₃]⁺. Fragmentations yielding [M⁺ ? 49] from compounds 2 are abnormal and probably involve the methoxyl and nitro groups. The intense peak at m/z 130 due to [CH₃OCH₂CNNHCONH₂]⁺ from compounds 3 corresponds to α-cleavage of the molecular ion. Some other fragments from these new compounds are interpreted in this paper.     

Synthesis of LiNi1/3Co1/3Mn1/3O2−zFz cathode material from oxalate precursors for lithium ion battery

The layered LiNi_1/3Co_1/3Mn_1/3O_2−zF_z (0 ≤ z ≤ 0.12) cathode materials were synthesized from oxalate precursors by a simple self-propagating solid-state metathesis method with the help of the ball milling and the following calcination. Li(Ac)·2H₂O, Ni(Ac)₂·4H₂O, Co(Ac)₂·4H₂O, Mn(Ac)₂·4H₂O(Ac = acetate), LiF and excess H₂C₂O₄·2H₂O were used as starting materials without any solvent. The structural and electrochemical properties of the prepared LiNi_1/3Co_1/3Mn_1/3O_2−zF_z were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and electrochemical measurements, respectively. The XRD patterns indicate that all samples have a typical hexagonal structure with a space group of . The FESEM images show that the primary particle size of LiNi_1/3Co_1/3Mn_1/3O_2−zF_z gradually increases with increasing fluorine content. Though the fluorine-substituted LiNi_1/3Co_1/3Mn_1/3O_2−zF_z have lower initial discharge capacities, a small amount of fluorine-substituted LiNi_1/3Co_1/3Mn_1/3O_2−zF_z (z = 0.04 and 0.08) exhibit excellent cycling stability and rate capability compared to fluorine-free LiNi_1/3Co_1/3Mn_1/3O₂.     

Electronic structure calculation of cohesive properties of some Si6−zAlzOzN8−z spinels

The structures of a spinel form of Si_6−zAl_zO_zN_8−z are investigated using techniques of ab initio density functional plane wave electronic structure theory with soft pseudopotentials. Four spinel configurations are considered corresponding to z=0, 1, 2, and 4. In the case of z=2 (Si₂AlON₃ spinels), that has now been synthesized, a normal or inversed configuration is considered. Very small energy differences are found suggesting that a mixed random atomic structure is very likely for the Si₂AlON₃ spinels. Results across the other range of spinels show that incompressible structures are associated with larger concentrations of N. These structures also have the larger cohesive energies. All spinels have direct energy band gaps varying between 3 and in the spinel 56-atom unit cell depending upon oxygen concentration.     

Endogenous high‐performance liquid chromatography/tandem mass spectrometry interferences and the case of perfluorohexane sulfonate (PFHxS) in human serum; are we overestimating exposure?

Perfluorinated acids have received increasing scientific attention due to their widespread global distribution, environmental persistence and bioaccumulation in wildlife and humans. For perfluorohexane sulfonate (PFHxS, C₆F₁₃SO, m/z 399), all existing human data have been generated using high‐performance liquid chromatography (HPLC) and its most sensitive tandem mass spectrometric (MS/MS) transitions (m/z 399/80 [SO₃]^? or m/z 399/99 [SO₃F]^?), but this may be problematic because of co‐eluting endogenous steroid sulfates that share common fragmentation pathways. We examined the magnitude of over‐reporting for PFHxS in pregnant women (n = 29), and in pooled serum of males, non‐pregnant and pregnant females (n = 3, 100 samples per pool), by comparing m/z 399/80 and 399/99 data with an interference‐free transition, m/z 399/119. PFHxS concentrations in pregnant women determined using m/z 399/80 and 399/99 (p < 0.05), but not m/z 399/119, were positively correlated to the response of the steroid sulfates. This led to an average overestimation of PFHxS by 1.5‐ and 4.7‐fold, using m/z 399/80 and 399/99, respectively, and validated the use of m/z 399/119 for the first time. The interferences were a problem in all human serum samples, and analysis of pooled serum revealed statistically significant over‐reporting by m/z 399/80 and 399/99 for pregnant women > non‐pregnant women > men. The magnitude of over‐reporting here represents a worst‐case scenario, but the extent to which the published literature values are biased is unknown due to limited details of methods in existing reports. Instead of using the less sensitive m/z 399/119 transition, we showed that an alternative selection of column and mobile phase can allow for sufficient chromatographic separation of the interferences. In conclusion, it was shown that routine analytical methods are prone to systematically overestimating PFHxS concentrations in serum of men or women, but that this can be avoided by alternative chromatographic steps or MS/MS transitions. Copyright © 2009 John Wiley & Sons, Ltd.     

Quantifying Degradation Parameters of Single-Crystalline Ni-Rich Cathodes in Lithium-Ion Batteries

Single-crystal LiNi_xCo_yMn_zO₂ (SC-NCM, x+y+z=1) cathodes are renowned for their high structural stability and reduced accumulation of adverse side products during long-term cycling. While advances have been made using SC-NCM cathode materials, careful studies of cathode degradation mechanisms are scarce. Herein, we employed quasi single-crystalline LiNi_0.65Co_0.15Mn_0.20O₂ (SC-NCM65) to test the relationship between cycling performance and material degradation for different charge cutoff potentials. The Li/SC-NCM65 cells showed >77 % capacity retention below 4.6 V vs. Li⁺/Li after 400 cycles and revealed a significant decay to 56 % for 4.7 V cutoff. We demonstrate that the SC-NCM65 degradation is due to accumulation of rock-salt (NiO) species at the particle surface rather than intragranular cracking or side reactions with the electrolyte. The NiO-type layer formation is also responsible for the strongly increased impedance and transition-metal dissolution. Notably, the capacity loss is found to have a linear relationship with the thickness of the rock-salt surface layer. Density functional theory and COMSOL Multiphysics modeling analysis further indicate that the charge-transfer kinetics is decisive, as the lower lithium diffusivity of the NiO phase hinders charge transport from the surface to the bulk.