SBIR-STTR Award

EMI vulnerability is a broad topic.This proposal focuses on one key element common to all advanced military devices - the energy storage element.While there has been extensive study on electronic devices, there has been little study of the effect of EMI on batteries or super-capacitors.If the battery destructs, it does not matter if the electronics survive.This study will determine the vulnerability of COTS cells, and develop a model to determine if cell design can affect vulnerability to EMP. The approach is to start with the simplest element (of a cell), model its response to various pulses, compare the model to laboratory test results, revise and then go to the next level of complexity.Two approaches will be tried: A 3D electrode pair model, where the elements would then be stacked or rolled into a cell, and a 2D end-view model of a stack or spiral, which would then be extruded in the third dimension.Next, the compound elements packaged in foil or a can will be modeled and tested. And finally the finished cell with connecting wires.Themodeling will be validated experimentally at each stage. Various EMPs will be characterized to apply to the model.Modeling,EMI,EMP,vulnerability,Batteries,Super-capacitors,Power

Phase I work included an extensive literature review, modeling an energy storage device, experimentation with a new carbon nanotube (CNT) coated graphite for EMI coatings and development of a new testing procedure and equipment for determining permittivity. After developing a multiphysics model of a simple electrode pair lithium cell, COMSOL was used to implement the model. After verifying normal cell performance, a magnetic field was imposed on the 2D model perpendicular to the plane. The model projected a very unusual phenomenon when subjected to a magnetic field – the behavior of a simple electrode pair cell could be affected by a static magnetic field. Depending on the orientation of the field, the cell could be made to [apparently] charge faster or slower as indicated by a faster or slower voltage rise time. These simulations were the subject of limited validation testing at the very end of the program and the cells showed a greater response than projected. Such a response offers the potential of improving the performance or possibly damaging the cell and the verification and characterisation is the objective of continuing research and development. Exposure of munitions and its components to high levels of electromagnetic interference (EMI) and electromagnetic pulse (EMP) is one of the threats that can result in catastrophic consequences. Graphene has been receiving a lot of attention for the development of conformal EMI coatings for electronics. NTeC from Chasm Technologies, a novel material was encountered in one of LBE’s other lithium ion battery SBIRs. It is a graphite particle with carbon nanotubes (CNTs) grown on the surface which offers the potential of developing an easier coating process than graphene with equivalent results. (CNTs are simply rolled up graphene sheets) Graphene is notoriously difficult to disperse in a coating as it gels around 5% solids and the resultant coating dries to an aerogel which is very fragile and has large holes and poor conductivity. The new CNT/graphite results in particles that range in appearance from a sea urchin (with spiny protrusions) to a sheep (covered with wool) or a particle covered with steel wool. The benefit of this material is that it can be processed normally in coatings at 30-40% solids and still have superior conductivity. Chasm also makes a silver coated version - AgeNT – which has even higher conductivity and is used to make clear membrane switches. These CNT/graphites, blended with high dielectric fillers offer the potential of improved conformal EMI coatings. After working with many test procedures, a new simple concept was developed for testing magnetic permittivity of thin films – basically simply using an air gap transformer or inductor and placing the film in the gap. The objective in pursuing this approach is to develop a new easier, faster, cheaper test to characterize materials.