Pulsed power capacitor development and outlook

Pulsed power capacitors are one of the key components the pulsed power systems for applications in mobile platforms including vehicles, ships and airplanes. The advances of capacitor technology have evolved slowly but steadily in the past 25 years. The energy density of large format millisecond discharge capacitors in >50 kJ sizes has been increased from 0.7 J/cc in the early 1990s to >2.4 J/cc in the 2010s with lifetimes over 10,000 shots. The energy density of microsecond discharge capacitors has been increased from 0.7 J/cc with a DC life less than 100 hours in early 1990s to 1.3 J/cc with a DC life of 2000 hours. The self-healing electrode has been the key to achieving higher energy density capacitors. The fault tolerance provided by these electrodes enables reliable operation near intrinsic breakdown strengths. In addition, the availability of higher quality and thinner biaxially oriented polypropylene (BOPP) film starting 2000s has contributed significantly by increasing the intrinsic breakdown strength of the films themselves. Coupled with design improvements, capacitors based on BOPP film have had significant, order-of-magnitude scale improvements in peak energy densities and peak power densities. The unfortunate consequence of this development is that these technologies have reached a point of diminishing returns, leading to significant efforts to develop new films to replace BOPP. We take this opportunity to review the advances and reflect what works so far to think about the future path.