In Situ Investigations of Simultaneous Two-Layer Slot Die Coating of Component-Graded Anodes for Improved High-Energy Li-Ion Batteries

The use of thicker electrodes can contribute to a reduction in cell costs. However, the properties of the electrode must be kept in view to be able to meet the performance requirements. Herein, the possibility of simultaneous multilayer slot die coating is investigated to improve the electrode properties of medium- and high-capacity anodes. The stable coating window of the two-layer slot die coating process is investigated to produce property-graded multilayer electrodes. Electrodes with different styrene–butadiene rubber (SBR) gradients are investigated with regard to adhesive force and electrochemical performance. An increase in the adhesive force of up to 43.5% and an increase in the discharge capacity is observed

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

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

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