Fast formation of anode-free Li-metal batteries by pulsed current.

Anode-free Li-metal batteries offer high energy density but are prone to dendrite formation during charging which can cause catastrophic failures. Ensuring dendrite-free smooth Li deposits during charging is therefore necessary. Suppressing dendrite growth can be achieved by pulsed current charging, especially during the formation cycle that largely determines the corrosion trajectory of a cell. As opposed to the constant-current technique, pulsed current techniques apply intermittently stopped current flows. This work investigates the electroplating of metallic Li onto a Cu foil current collector under constant-current and pulsed current formation protocols. In addition to smoother, less resistive electroplated metallic Li deposits and increased Coulombic efficiency, we show that by employing an optimized pulsed current formation protocol, the formation process is accelerated by a factor of 2 and the Coulombic efficiency was increased by 10% compared to a C/20 protocol. Finally, by employing a simple regression coupled to experimentation, we propose the pseudo-IR-drop to be used for live adjustment of pulsed current protocols i.e., individually approach each cell at all SOC during formation.

Film before aggregates: an operando GISAXS study on electrochemically assisted surfactant assembly.

The process of electrochemically assisted surfactant assembly was followed in real time by grazing incidence small angle X-ray scattering with the aim to deconvolute the formation of mesoporous silica film and unwanted porous particles. The X-ray technique proved to be useful for the characterisation of this process, as it takes place at a very dynamic, solid/liquid interface. This paper shows the electrochemically driven onset and evolution of silica/surfactant structures. Additional control experiments indicate the formation of vertically aligned structures without the use of an electric field, although it seems to be beneficial for increased pore ordering.

Thermoelectric Properties of Bismuth Telluride Thin Films Electrodeposited from a Nonaqueous Solution.

We report the thermoelectric properties of Bi2Te3 thin films electrodeposited from the weakly coordinating solvent dichloromethane (CH2Cl2). It was found that the oxidation of porous films is significant, causing the degradation of its thermoelectric properties. We show that the morphology of the film can be improved drastically by applying a short initial nucleation pulse, which generates a large number of nuclei, and then growing the nuclei by pulsed electrodeposition at a much lower overpotential. This significantly reduces the oxidation of the films as smooth films have a smaller surface-to-volume ratio and are less prone to oxidation. X-ray photoelectron spectroscopy (XPS) shows that those films with Te(O) termination show a complete absence of oxygen below the surface layer. A thin film transfer process was developed using polystyrene as a carrier polymer to transfer the films from the conductive TiN to an insulating layer for thermoelectrical characterization. Temperature-dependent Seebeck measurements revealed a room-temperature coefficient of -51.7 µV/K growing to nearly -100 µV/K at 520 °C. The corresponding power factor reaches a value of 88.2 µW/mK2 at that temperature.

Towards a 3D GeSbTe phase change memory with integrated selector by non-aqueous electrodeposition.

We have recently reported a new method for the electrodeposition of thin film and nanostructured phase change memory (PCM) devices from a single, highly tuneable, non-aqueous electrolyte. The quality of the material was confirmed by phase cycling via electrical pulsed switching of both 100 nm nano-cells and thin film devices. This method potentially allows deposition into extremely small confined cells down to less than 5 nm, 3D lay-outs that require non-line-of-sight techniques, and seamless integration of selector devices. As electrodeposition requires a conducting substrate, the key condition for electronic applications based on this method is the use of patterned metal lines as the working electrode during the electrodeposition process. In this paper, we show the design and fabrication of a 2D passive memory matrix in which the word lines act as the working electrode and nucleation site for the growth of confined cells of Ge-Sb-Te. We will discuss the precursor requirement for deposition from non-aqueous, weakly coordinating solvents, show the transmission electron microscopy analysis of the electrodeposition growth process and elemental distribution in the deposits, and show the fabrication and characterisation of the Ge-Sb-Te memory matrix.