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X-ray photoelectron spectroscopy (XPS) was used to investigate the surface chemistry of high voltage spinel, LiNi0.5Mn1.5O4 (LNMO) positive electrodes cycled 5 and 10 times in Li-cells with 1 M LiPF6 in (3:7) EC:DMC. The XPS spectra were collected using conventional Mg X-rays with energy of 1253.6 eV as well as synchrotron X-rays with energies of 2493.6 and 3498.4 eV in order to examine the depth distribution of various surface chemical species induced during cycling. The XPS spectra revealed a 5 – 10 nm surface layer of organic and LixPFyOz-type species formed as result of electrolyte decomposition, and a comparatively thinner layer composed of transition metal fluorides and LiF. These results suggest that electrolyte decomposition is a major contributor to parasitic reactions in LNMO battery electrochemistry. Limiting electrolyte decomposition with the use of solvents with wide electrochemical stability windows thus comprises a promising strategy for ensuring the practical feasibility of high voltage spinel materials in future Li-ion systems., National Science Foundation (U.S.). Materials Research Science and Engineering Centers (Program) (award number DMR-0819762), United States. Dept. of Energy. Office of FreedomCAR and Vehicle Technologies(contract number DE-AC03-76SF00098), Lawrence Berkeley National Laboratory, United States. Dept. of Energy. Office of Basic Energy Sciences (contract number DE-AC02-98CH10886)

The “AlPO[subscript4]” coating has been shown to improve the electrochemical performance of LiCoO2 batteries. We previously showed that the “AlPO[subscript4]” coating promotes the formation of metal fluorides, which could act as a stable surface film and protect LiCoO[subscript2] from continuous degradation upon cycling. In this work, we removed the fluorine source in the LiPF[subscript6] salt by using the LiClO[subscript4] salt and investigated the effectiveness of the “AlPO[subscript4]” coating. Interestingly, the “AlPO[subscript4]” coating was found to improve the voltage efficiency and capacity retention when cycling in the LiPF[subscript6] electrolyte, but was detrimental when cycling in the LiClO[subscript4] electrolyte. XPS revealed that the “AlPO[subscript4]” coating promotes the formation of metal fluoride in both electrolytes, with the surface film formed in LiClO4 being more electrically resistive compared to that formed in LiPF[subscript6]. The source of fluorine in the coated electrode cycled in LiPF[subscript6] is largely attributed to the LiPF[subscript6] salt whereas the source of fluorine in the coated electrode cycled in LiClO[subscript4] is the binder PVDF. We believe that the coating could react with HF impurity in the LiPF[subscript6] electrolyte or from the binder PVDF and form stable metal fluoride films on the surface., National Science Foundation (U.S.). Materials Research Science and Engineering Centers (Program) (award number DMR-0819762), United States. Department of Energy. Office of FreedomCAR and Vehicle Technologies (contract no. DE-AC03-76SF00098), United States. Department of Energy. Office of Basic Energy Sciences (contract no. DE-AC02-98CH10886)

LiNi[subscript 0.5]Mn[subscript 0.5]O[subscript 2] samples were prepared from NiMnO[subscript 3] and Li[subscript 2]CO[subscript 3] in a range of temperatures from 900 to1050°C . Synchrotron X-ray diffraction analysis combined with X-ray absorption spectroscopy showed that LiNi[subscript 0.5]Mn[subscript 0.5]O[subscript 2]segregated into one major Ni[superscript 2+]O -enriched phase and one minor Li[subscript 2]Mn[superscript 4+]O[subscript 3] -enriched phase, where the extent of segregation decreased with increasing synthesis temperature from 900 to1050°C . Scanning and transmission electron microscopy combined with energy dispersive X-ray spectroscopy revealed that the segregated domains exist in individual particles. Although all of the LiNi[subscript 0.5]Mn[subscript 0.5]O[subscript 2] samples showed comparable specific capacity (∼200mAh/g) and capacity retention at low current densities, the rate capability of LiNi[subscript 0.5]Mn[subscript 0.5]O[subscript 2] of 900°C is lower than that of LiNi[subscript 0.5]Mn[subscript 0.5]O[subscript 2] of 1000°C . As X-ray photoelectron spectroscopy analysis showed that all of the LiNi[subscript 0.5]Mn[subscript 0.5]O[subscript 2] samples had comparable surface chemistry, the higher rate capability of LiNi[subscript 0.5]Mn[subscript 0.5]O[subscript 2] of 1000°C can be attributed to reduced cation segregation of Ni[superscript 2+]O -enriched domains in the layered structure of the major phase, having potentially faster lithium diffusion than that of LiNi[subscript 0.5]Mn[subscript 0.5]O[subscript 2] of 900°C ., United States. Dept. of Energy (Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Freedom CAR and Vehicle Technologies, DOE DE-AC03-76SF00098), Japan. Ministry of Education, Culture, Sports, Science and Technology (Nanotechnology Support Project Proposal no. 2009A1074/BL02B2 with the approval of Japan Synchrotron Radiation Research Institute (JASRI))

Subsequent annealing at Formula enhances the rate capability of LiNi[subscript 0.5]Mn[subscript 0.5]O[subscript 2], delivering 180 mAh/g at 55[degrees]C and 8C rate compared to 50 mAh/g of LiNi[subscript 0.5]Mn[subscript 0.5]O[subscript 2] quenched from 1000[degrees]C . Although Rietvled refinement analyses of X-ray diffraction (XRD) data showed that there were no significant changes in the lattice parameters and cation distributions of the layered structure before and after annealing, XRD and X-ray photoelectron spectroscopy revealed that annealing significantly reduced surface impurity phases such as lithium carbonate and Mn[superscript +3]-containing species. The influence of surface chemistry changes on the rate capability of LiNi[subscript 0.5]Mn[subscript 0.5]O[subscript 2] was discussed., United States. Dept. of Energy (Assistant Secretary for Energy Efficiency and Renewable Energy, Office of FreedomCAR and Vehicle Technologies of the DOE DE-AC03-76SF00098)

Recent advances in nanomanufacturing have made it possible for large amounts ( 6 wt.%) of carbon to be incorporated as nanoscale carbon during a reaction process in molten aluminum, copper, silver, and other metals. These materials developed by Third Millennium Metals, LLC are called covetics. The carbon is highly stable despite its form not being predicted in phase diagrams, and remains dispersed after remelting and resolidification. The carbon incorporates into the metal matrix and has an effect on several of the properties of the material. We have performed a detailed investigation of the structure and composition of several covetics using a variety of microscopy and spectroscopy techniques and found that the carbon forms nanoparticles of 5-200 nm diameter that are embedded in the host matrix. EELS spectra obtained from these regions show characteristic shape of carbon nanotubes (CNT). Raman data obtained from these samples also show the G-mode and D-mode characteristic of CNT., Presented at Tech Connect World held in Santa Clara, CA on 18-12 June 2012. The original document contains color images.

We characterized the chemical, thermophysical, and mechanical properties of nanomaterials with up to 5 wt% nanocarbon (aka covetics) in aluminum and copper metals. The nanocarbon is detectable by EDS and XPS but not by analytical methods such as LECO and GDMS. Nanocarbon raises the melting point and significantly alters surface tension, and thus porosity, during solidification. Open questions remain about the observation of higher density than would be predicted by the rule of mixtures. In aluminum alloys, we observed an increase in as-rolled strength and hardness with increasing amounts of nanocarbon. In copper, thermal conductivity was anisotropic: up to 50% higher in the extrusion direction and at least 25% lower in the transverse direction,and was different between transient and steady state test conditions. In aluminum, we observed a significant increase in electrical conductivity with nanocarbon, from 47 to 67% IACS. These materials are commercially promising because they are produced by conversion of inexpensive carbon powder to nanocarbon in the melt?paving the way for the production of nanomaterials in pyrometallurgical operations with economies of scale., The original document contains color images.