A large electrochemical setup for the anodization of aluminum towards highly ordered arrays of cylindrical nanopores

A new electrochemical setup and the associated procedures for growing ordered anodic aluminum oxide pore arrays on large surfaces are presented. The typical size of the samples is 14 × 14 cm2. The most crucial experimental parameters that allow for the stabilization of the high-field procedures are a very efficient cooling of sample and electrolyte, as well as the initial ramping up of the voltage at an accurately defined rate. The morphology of the cylindrical, parallel alumina pores is similar to those obtained on smaller scales with standard setups. Our setup facilitates the availability of porous anodic alumina as a template system for a number of applications

An electrochemically functional layer of hydrogenase extract on an electrode of large and tunable specific surface area

Electrode supports are generated by electrospinning of polyacrylonitrile fibers and subsequent coating of a thin electrically conductive TiO2 layer by atomic layer deposition. The supports are then functionalized with a [NiFe]-hydrogenase-containing membrane fraction from Escherichia coli and are characterized structurally and electrochemically. The hydrogenase suspension generates a micron-thick organic film around the fiber mat, which exhibits electrocatalytic activity for hydrogen evolution. Furthermore, the electrode geometric surface area is varied systematically via the electrospinning procedure, which reduces the charge transfer resistance and increases the hydrogen evolution current density to >500 μA cm−2 at 0.3 V overpotential

Combining a Fatigue Model and an Incremental Capacity Analysis on a Commercial NMC/Graphite Cell under Constant Current Cycling with and without Calendar Aging

Reliable development of LIBs requires that they be correlated with accurate aging studies. The present project focuses on the implementation of a weighted ampere-hour throughput model, taking into account the operating parameters, and modulating the impact of an exchanged ampere-hour by the well-established three major stress factors: temperature, current intensity (rated), and state of charge (SoC). This model can drift with time due to repeated solicitation, so its parameters need to be updated by on-field measurements, in order to remain accurate. These on-field measurements are submitted to the so-called Incremental Capacity Analysis method (ICA), consisting in the analysis of dQ/dV as a function of V. It is a direct indicator of the state of health of the cell, as the experimental peaks are related to the active material chemical/structural evolution, such as phase transitions and recorded potential plateaus during charging/discharging. It is here applied to NMC/graphite based commercial cells. These peaks’ evolution can be correlated with the here-defined Ah-kinetic and t -kinetic aging, which are chemistry-dependent, and therefore, has to be adjusted to the different types of cells

Influence of solid-electrolyte interfaces on electronic and ionic dynamics in porous electrodes

International audienc

Influence of a Liquid Electrolyte on Electronic and Ionic Transfers in a LiNi 0.5 Mn 0.3 Co 0.2 O 2 /Poly(vinylidene Fluoride- co -hexafluoropropylene)-Based Composite Material

International audienceThe permittivity and conductivity of a porous composite consisting of a mixture of a lithium-ion battery electrode material, LiNi0.5Mn0.3Co0.2O2 (NMC532), and a polymeric binder, poly(vinylidene fluoride-co-hexafluoropropylene) (PVdF-HFP), were simultaneously measured by broadband dielectric spectroscopy (BDS). The composite was either dry or wetted with a conventional battery electrolyte [LP30, LiPF6 in ethylene carbonate/dimethylcarbonate (EC/DMC)] or a mixture of electrolytic solvents (EC/DMC). The experimental results show that the electronic conductivity of NMC532 was much higher than that obtained with LiNi0.33Mn0.33Co0.33O2 (NMC333). In addition, a strong influence of liquids was evidenced. Dipolar species (in particular, EC dipoles) and ions (in particular, PF6– in LP30) considerably increased the surface conductivity of NMC532 clusters, leading to a facilitated electronic transfer from one cluster to another. The effective ionic conductivity was measured and compared to the ionic conductivity of the electrolyte to express the tortuosity factor of this composite electrode

Antimony sulfide as a light absorber in highly ordered, coaxial nanocylindrical arrays: preparation and integration into a photovoltaic device

We demonstrate the preparation of functional 'extremely thin absorber' solar cells consisting of massively parallel arrays of nanocylindrical, coaxial n-TiO2/i-Sb2S3/p-CuSCN junctions. Anodic alumina is used as an inert template that provides ordered pores of 80 nm diameter and 1-50 mu m length. Atomic layer deposition (ALD) then coats pores of up to 20 mm with thin layers of the electron conductor and the intrinsic light absorber. The crystallization of the initially amorphous Sb2S3 upon annealing is strongly promoted by an underlying crystalline TiO2 layer. After the remaining pore volume is filled with the hole conductor by solution evaporation, the resulting coaxial p-i-n junctions display stable diode and photodiode electrical characteristics. A recombination timescale of 40 ms is extracted from impedance spectroscopy in open circuit conditions, whereas transient absorption spectroscopy indicates that holes are extracted from Sb2S3 with a lifetime of 1 ns