For the past 2 years, CEE has been involved in studying the cause of failure of SVO (silver vanadium oxide primary batteries), Nickel-Metal Hydride and Lithium-ion batteries. This program has been funded by both private and government funds. The National Reconnaissance Office and the Office of Basic Research, Department of Energy have been supporting this effort. To perform extensive cycle life studies we have 3 Arbin cyclers with more than 100 channels and 4 Bitrode cyclers with more than 150 channels. Using these cyclers it is possible to study the rate capabilities and the cycle life characteristics of the batteries under various charging protocols. The Arbin BT2000 Charger shown on right has the capability to perform both cycle life and 3 electrode characterization studies. With Potentiostatic and Galvanostatic capability, the channels in the charger can be coupled to achieve higher currents if needed. Further, the charger can be used for doing GSM and CDMA discharge and pulse charging for very small durations (milliseconds) to the battery.

Characterization of the electrode materials is carried out using a three-electrode setup. The function of a potentiostat is both to control the potential of an electrode immersed in a solution and to measure the current at that electrode. Using this it is possible to measure the rate of the reaction at the interface of the catalyst/ionomer in different MEAs. The center has 10 Potentiostats (PAR Model with Impedance Analyzers) with the capability to test both the reaction rate and electrochemical behavior of various metals and alloys. Apart from EG&G Potentiostats, we also have a portable electrochemical test station from Gamry Instruments. This test station is mobile and can be carried anywhere to perform electrochemical studies. The kinetics of the processes occurring at the electrode-electrolyte interface can be determined by using slow scan voltammetry.

The virtual test bed developed by Professor Roger Dougal at the CEE, is a multi-language computational environment for modeling, simulation, analysis, design and optimization of complex engineering systems that can generally be described by a system of algebraic-differential equations representing coupled multidisciplinary engineering and physical processes.

One focus of the VTB modeling is to study the performance of electrochemical power sources (batteries, fuel cells, double layer capacitors, and hydrogen storage element) as well as their hybrids under fully defined and configurable load environment. The VTB facilitates models with different levels of detail, from averaged to behavioral, physics-based, and even finite-element model. It co-simulates with MatLab/Simulink, ACSL, FE solver, and even hardware in the loop. This provides a full capability to reveal the dynamic behavior, power capability, energy efficiency and life cycle of power sources, and to perform design and optimization.

The oxygen reduction activity is directly dependent on the surface area available for reaction and hence on the particle size. Increase in particle size results in the decrease of activity and utilization of platinum. Hence, the Pt/C ratio cannot be increased beyond 40 wt% by the traditional method without losing catalytic activity. Further, this limitation of Pt/carbon in carbon also imposes a limitation on decreasing the catalyst layer thickness. Since the ion exchange membrane used in PEM fuel cell is a solid type, the contact between membrane and Pt becomes a critical factor in order to obtain high performance. For this reason, the Pt should be placed closer to the surface of the electrode. Our present research is aimed at developing high Pt/C ratio catalysts with 3-4 nm particle size and an effective catalyst layer thickness of 1-2 microns. This has been accomplished by selective coating of Pt on the GDL using pulse electrodeposition. Our current research is aimed at developing Pt-X (X=transition metal) alloys using this technique. MEA studies show that the activity of our electrodes is superior to commercial E-TEK electrodes with lesser amount of catalyst.

This is also confirmed from the concentration profile of Pt measured across a typical portion of the cross section of MEA by line scan using EPMA. It is useful here to distinguish between the two different approaches used to prepare the anode and cathode. The E-TEK anode was prepared using the conventional powder type approach where Pt/C mixture is dispersed and then loaded on the membrane by spraying or coating. The cathode has been prepared by the pulse electrodeposition approach by plating Pt on the carbon support and subsequently attaching it to the Nafion membrane. In general, the pulse electrodeposited cathode exhibits much higher intensity of Pt peak in the limited area near the membrane while Pt line scan across the E-TEK anode electrode shows a relatively uniform intensity with a thickness of 50 mm of thickness. It is also seen that the anode thickness is much more than that of the cathode.By placing smaller particles of platinum on the surface of the electrode, the MEA prepared by our technique shows higher performance with smaller amounts of Pt than conventional electrodes. Pulse plating allows a higher current to be applied through control of the duty cycle (on-time/total pulse width). Electrodes fabricated under pulse conditions display better performance.

Porosity and pore size distribution (PSD) are physical characteristics that are crucial to the understanding of porous materials. This knowledge is also essential in the development of porous catalysts and gas diffusion layers used for PEM fuel cells. CEE is equipped with a mercury porosimeter (Micromeritics AutoPore IV) which can analyze any porous media with a pore size range between 3 nm and 360 m. The pore distribution is a more important parameter than the total porosity since the water and gas transport are controlled by the specific volume of small and large pores. The water transport is expected to occur simultaneously through micro and macro transport. The role of the micro-pores is to transfer the condensed water from the electrode interface. The macro-pores serve to reduce the mass transport limitations due to water flooding. They provide, when the micropores are completely closed by water, a gas diffusion path toward the catalytic region.