Composite Mesh Electrodes with Immobilized Bacteria for Bio-Batteries

An anode was constructed using a novel technique and subsequently tested in a bio-battery. The anode comprised of a composite electrode coated with immobilized bacteria. The immobilized bacteria used in this study were Escherichia coli K-12. The composite electrode contained three layers: a 304 L stainless steel mesh base, an electro-polymerized layer of pyrrole, and an electro-polymerized layer of methylene blue. The bacteria were immobilized utilizing a technique incorporating a carbon nanoparticle and TeflonTM emulsion. The composite electrode combined with immobilized bacteria was examined whilst incorporated into the anodic chamber of a bio-battery. Different tests were conducted, including Electrochemical Impedance Spectroscopy. Results from these tests were compared with data obtained from alternate configurations and values from the open literature. The maximum power density generated by the composite electrode with immobilized bacteria whilst incorporated into the anodic chamber of a bio-battery was 378 mW/m2. Results demonstrate this composite anode configuration with immobilized bacteria produced approximately 69% more power density and 53% more current density than alternate electrode configurations with bacteria suspended in solution. Also, it was found that a significant portion of the bio-battery’s resistance to charge transfer occurred at the surface of the anode and this resistance was lowered by 51% through bacteria immobilization.

Two-Dimensional Lithium-Ion Battery Modeling with Electrolyte and Cathode Extensions

A two-dimensional model for transport and the coupled electric field is applied to simulate a charging lithium-ion cell and investigate the effects of lithium concentration gradients within electrodes on cell performance. The lithium concentration gradients within electrodes are affected by the cell geometry. Two different geometries are investigated: extending the length of the electrolyte past the edges of the electrodes and extending the length of the cathode past the edge of the anode. It is found that the electrolyte extension has little impact on the behavior of the electrodes, although it does increase the effective conductivity of the electrolyte in the edge region. However, the extension of the cathode past the edge of the anode, and the possibility for electrochemical reactions on the flooded electrode edges, are both found to impact the concentration gradients of lithium in electrodes and the current distribution within the electrolyte during charging. It is found that concentration gradients of lithium within electrodes may have stronger impacts on electrolytic current distributions, depending on the level of completeness of cell charge. This is because very different gradients of electric potential are expected from similar electrode gradients of lithium concentrations at different levels of cell charge, especially for the LixC6 cathode investigated in this study. This leads to the prediction of significant electric potential gradients along the electrolyte length during early cell charging, and a reduced risk of lithium deposition on the cathode edge during later cell charging, as seen experimentally by others.