# Prospects for the Development of High Energy Density Dielectric Capacitors
## 5 Evaluation/Testing of Dielectric Cells  
This paper is concerned with the development of dielectric materials and cells for batteries for vehicles, industrial, and electric utility applications. These applications require the storage of many kWh of energy and power levels of many kWs and system response times of fractions of seconds. In other words, the dielectric devices would be used much like lithium batteries are currently used. Hence testing of dielectric materials and cells should be done using procedures and data interpretation consistent with those applications. Nearly all the testing of dielectric materials and devices in the literature is for power electronics applications and most of the data available were taken over wide ranges of AC frequencies (10\({}^{2}\)-10\({}^{6}\)). Hence the responses of the dielectric devices were measured for response times of ms and shorter.  
There has been experience testing electrochemical supercapacitors (EDLCs) that has relevance to testing the dielectric devices (DLCDs) of interest in this paper. The voltage change of both types of devices in charging and discharging is dominated by their capacitance (\(\Delta\)V = \(\Delta\)Q/C). The energy stored in both types of devices is 1/2 CV\({}^{2}\) for ideal, no loss devices. Test procedures and typical data for testing electrochemical supercapacitors are given in [49; 50]. That testing is directed to measuring C, R, Wh/L, W/L, and energy efficiencies for ranges of currents and powers. Similar testing will be required of DLCDs.  
There are, of course, major differences between EDLCs and DLCDs. First and foremost, the charge in the DLCDs is bound to the layered dielectric material and in the EDLCs, it is free to move through the device. Hence EDLCs have a resistance in the classic sense and DLCDs do not. Most of the losses in the DLDCs are associated with rapid changes in the polarization of the molecules in the dielectric layer as the device is charged and discharged. In addition, EDLCs are low voltage devices with rated (maximum) voltage fixed by the electrolyte. DLCD are high voltage devices with their maximum operating voltage determined by the breakdown strength (MV/m) of the layered dielectric material and its thickness. These differences will influence significantly how DDLCs are tested compared to EDLCs.  
There seems to be little discussion of DC testing of DLCDs in the literature. One source is a chapter in [9], which discusses both DC and high frequency testing of DLCDs. The testing should determine the characteristics of both the dielectric layer and the device as a function of current, power, SOC, temperature, and voltage (MV/m). The key parameters to be determined are the dielectric constant of the dielectric layer and the Wh/L, W/L, charge-discharge efficiency, effective parallel resistance, leakage current, and thermal stability of the devices. Varying the thickness of dielectric layer will permit investigation of the effects of high MV/m. Special test equipment will be needed to measure the very low currents expected to be encountered in testing small DLDC cells.