TORONTO and AUSTIN, Texas, March 12, 2018 (GLOBE NEWSWIRE) -- EEStor Corporation (TSXV:ESU), developers of high energy density, solid-state capacitors, today announced completion of its Phase 8 independent third-party testing to characterize layers of dielectric materials (electric insulator) made from its Composition Modified Barium Titanate (CMBT) ceramic powder using specialized glass as the binder. CMBT-glass sintered part 344 was sliced into several layers and each layer was sent for separate testing by Intertek (344-2B), Radiant Technologies (344-1) and MRA Laboratories (344-3).
The results of Intertek’s testing found that EEStor’s CMBT-glass dielectric sample 344-2B, which was thinned down to 32 microns, had an energy density of 1.4 watt-hours per liter and a leakage current of 1.8 nano-amperes at 85.94 volts per micron, which is 92% of the breakdown strength. From these measured results, Intertek calculated an insulation resistance of 1.5 tera-ohms and a relative permittivity (k) of 154 at 2750 volts (a field of 85.94 volt per micron). X7R dielectrics are the most commonly used type of commercial Multi Layer Ceramic Capacitors (MLCC). Layer 344-2B demonstrates energy density slightly higher both at the 35 volts per micron operating voltage, and at 80 v per micron, near breakdown voltages of 90 volts/micron for the X7R and 93.75 for 344-2B.1 In addition EEStor capacitors have all the advantages of being a cubic paraelectric lead-free relaxor as discussed in the phase 7 white paper.
At this high field, a self-discharging time constant of 453 seconds was calculated, which is a 492 times the time constant of EEStor’s published Phase 6 results at a comparable energy density. Sample 344-2B ultimately broke down at 3000 volts, exhibiting a breakdown strength of 93.75 volts per micron.
The energy that can be stored in an EEStor capacitor grows proportionally to the k (permittivity) and to the square of the field voltage. The ultimate objective is to continue to push the limits of the technology by reaching higher field voltages without breaking down the sample and by maintaining a high relative permittivity (k) at high field voltages. The relationship between these factors and the ongoing improvement of both is necessary for increased energy storage. It must be noted that higher breakdown strength values have systematically been measured by EEStor as its layer thicknesses are reduced to sub 100-micron thicknesses.
Efficiency and breakdown strength
Layer 344-1 tested by Radiant Technologies was 460 microns thick. The thin Polarization to Electric Field (P-E) hysteresis loop plots were fundamentally characteristic of relaxor dielectrics. Radiant Technologies also calculated the efficiency of the dielectric on charge/discharge to be 83% at both 4800 volts (10.4 volts per micron) and at 5300 volts (11.5 volts per micron), while the breakdown voltage was 5800 volts (12.6 volts per micron). At these values, the sample tested by Radiant Technologies exhibited 83% efficiency at an electrical field equal to 91% of the breakdown strength and 2 nano-amperes of leakage. With the findings of the breakdown strength of layer 344-2B tested by Intertek, efficiency is expected to be in the same 80% range at 1.4 watt-hours/per/liter.
Thermal stability and life expectancy
The testing of layer 344-3 by MRA Laboratories further confirmed relaxor dielectric behavior. Specifically, when the frequency of AC voltage was increased from test to test, the maximum permittivity was recorded at higher temperatures. Temperature Coefficient of Capacitance (TCC) testing demonstrated CMBT-glass layers have good thermal stability and Highly Accelerated Life Testing (HALT) revealed a long-expected lifetime of the dielectric.
Together, these tests show that EEStor’s proprietary CMBT-glass features good energy density, high efficiency, low leakage, low dissipation factor, good thermal stability and a robust life expectancy. The third-party testing reports and a further discussion of the tested parameters and their significance can be found in the white paper.
About EEStor Corporation
EEStor Corporation's mission is to be the provider of leading edge electrical energy storage and related technologies. EEStor operates on the principle and belief that a fundamental breakthrough in energy storage will be the catalyst for positive environmental and economic change globally. EEStor’s current business strategy is focused on licensing opportunities across a broad spectrum of industries and applications building on its recent technology achievements related to solid-state, high energy density capacitors.
The Company’s success depends on the commercialization of its technology. There is no assurance that EEStor will be successful in the completion of the various enhancement phases underway to warrant the anticipated licensing opportunities in the technology. Readers are directed to the "Risk Factors" disclosed in the Company’s public filings.
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1 J. Am. Ceram. Soc., 92  1719–1724 (2009) DOI: 10.1111/j.1551-2916.2009.03104.x