In-operando neutron reflectometry studies on lithium insertion into silicon electrodes of Li-ion batteries

Lithium ion incorporation into amorphous silicon electrodes was monitored via in-op-erando neutron reflectometry in real-time during battery cell operation. Recent results of cyclic voltammetry experiments are presented. These experiments enable us to mon-itor the enormous volume expansion, the formation and evolution of the SEI (solid elec-trolyte interphase), the determination of irreversible capacity losses and voltage hyste-resis effects during cycling

Lithium insertion into silicon electrodes studied by cyclic voltammetry and operando neutron reflectometry

Operando neutron reflectometry measurements were carried out to study the insertion of lithium into amorphous silicon film electrodes during cyclic voltammetry CV experiments at a scan rate of 0.01 mV s amp; 8722;1. The experiments allow mapping of regions where significant amounts of Li are incorporated released from the electrode and correlation of the results to modifications of characteristic peaks in the CV curve. High volume changes up to 390 accompanied by corresponding modifications of the neutron scattering length density which is a measure of the average Li fraction present in the electrode are observed during electrochemical cycling for potentials below 0.3 V lithiation and above 0.2 V delithiation , leading to a hysteretic behaviour. This is attributed to result from mechanical stress as suggested in the literature. Formation and modification of a surface layer associated with the solid electrolyte interphase SEI were observed during cycling. Within the first lithiation cycle the SEI grows to 120 for potentials below 0.5 V. Afterwards a reversible and stable modification of the SEI between 70 delithiated state and 120 lithiated state takes plac

Electrochemical lithiation of silicon electrodes neutron reflectometry and secondary ion mass spectrometry investigations

In situ neutron reflectometry and ex situ secondary ion mass spectrometry in combination with electrochemical methods were used to study the lithiation of amorphous silicon electrodes. For that purpose specially designed closed three electrode electrochemical cells with thin silicon films as the working electrode and lithium as counter and reference electrodes were used. The neutron reflectometry results obtained in situ during galvanostatic cycling show that the incorporation, redistribution and removal of Li in amorphous silicon during a lithiation cycle can be monitored. It was possible to measure the volume modification during lithiation, which is found to be rather independent of cycle number, current density and film thickness and in good agreement with first principles calculations as given in literature. Indications for an inhomogeneous lithiation mechanism were found by secondary ion mass spectrometry measurements. Lithium tracer diffusion experiments indicate that the diffusivities inside the lithiated region D gt; 10 amp; 8722;15 m2 s amp; 8722;1 are considerably higher than in pure amorphous silicon as known from literature. This suggests a kinetics based explanation for the occurrence of an inhomogeneous lithiation mechanis

Health literacy, self-perceived health and self-reported chronic morbidity among older people in Kosovo

The aim was to describe health literacy among the older population of Kosovo, an Albanian speaking post-war country in the Western Balkans, in the context of self-perceived health status and self-reported chronic morbidity. A cross-sectional study was conducted in Kosovo in 2011 including 1753 individuals aged a parts per thousand yen65 years (886 men, 867 women; mean age 73.4 +/- 6.3 years; response rate: 77%). Participants were asked to assess, on a scale from 1 to 5, their level of difficulty with regard to access, understanding, appraisal and application of health information. Sub-scale scores and an overall health literacy score were calculated for each participant. Information on self-perceived health status, presence and number of chronic diseases and socioeconomic characteristics was also collected. Mean values of the overall health literacy score and all sub-scale scores (access, understanding, appraisal and application) were lower among older people who reported a poorer health status or at least one chronic condition compared with individuals who perceived their health status as good or had no chronic conditions (p <0.001 for all). Our findings provide valuable evidence on the independent and inverse association between health literacy levels and self-perceived health and chronic morbidity in this post-war European population. The putative link with chronic morbidity and lower adherence to health services is hard to establish through this cross-sectional study. Prospective population-based studies should be conducted in Kosovo and other transitional settings to replicate these findings and properly address the causal relationship between health literacy and health status

Neutron reflectometry studies on the lithiation of amorphous silicon electrodes in lithium ion batteries

Neutron reflectometry is used to study in situ the intercalation of lithium into amorphous silicon electrodes. The experiments are done using a closed three electrode electrochemical cell setup. As a working electrode, an about 40 nm thick amorphous silicon layer is used that is deposited on a 1 cm thick quartz substrate coated with palladium as a current collector. The counter electrode and the reference electrode are made of lithium metal. Propylene carbonate with 1 M LiClO4 is used as an electrolyte. The utility of the cell is demonstrated during neutron reflectometry measurements where Li is intercalated at a constant current of 100 [small mu ]A 7.8 [small mu ]A cm 2 for different time steps. The results show a that the change in Li content in amorphous silicon and the corresponding volume expansion can be monitored, b that the formation of the solid electrolyte interphase becomes visible and c that an irreversible capacity loss is presen