Each day brings a new technical innovation and the demand for smaller, portable and increasingly functionality in consumer electronics intensifies. This trend is putting increasing pressure on battery power systems to be light and small, yet run for long periods.

Overview

Energy storage devices may be broadly characterized by their energy density (energy stored per unit volume or mass) and by their power (how fast that energy can be delivered from the device).

Batteries have been the preferred storage device for most applications because of their superior capability to store energy (i.e. high energy density). But batteries are limited in their ability to deliver power — they can store lots of energy but take a long time to discharge or recharge. Where the application has demanded high power, batteries have been over engineered and the lifetime of the battery compromised.

New battery technology such as lithium ion has been developed to increase power and energy storage. Fundamentally, however, they are energy storage devices.

As such batteries will always be a poor solution where high power is required. Because of this, mature battery and capacitor technologies are unlikely to be able to meet the needs of today's wireless, power-hungry technologies. Supercapacitors, however, offer a unique combination of high power and high energy performance parameters with commercial relevance.

Supercapacitors

Supercapacitors are unique in that they are able to combine the energy storage properties of batteries with the power discharge characteristics of capacitors. They are very high surface area activated carbon capacitors that use a molecule-thin layer of electrolyte, rather than a manufactured sheet of material, as the dielectric to separate charge. As the energy stored is proportional to the charge surface area and inversely proportional to the thickness of the dielectric, these capacitors have an extremely high energy density. They are ableto hold a very high charge which can be released in a controlled manner.

Engineering Characteristics

Charge/Discharge Time	Milliseconds to seconds
Operating Temperature	C -40 ° to +75 °
Operating Voltage Aqueous	1.1 V; Organic 2.5 V
Capacitance	100 mF to > 1000 F
Life	3,000 to 50,000 hrs
Power Density	0.01 to 10 3 kW/kg
Energy Density	0.05 to 10 Wh/kg
Pulse Load	0.1 to 100 A
Pollution Potential	Aqueous electrolyte is highly corrosive

 

Advantages

• Extends battery run time
• Provides backup power
• Enables design to meet current specifications
• Cuts pulse current noise
• Lessens RF noise by eliminating DC/DC
• Allows low/high temperature operation
• Minimizes space requirements
• Reduces battery size
• Enhances load balancing when used in parallel with a battery
• Meets environmental standards

As the information revolution unfolds, there is a strong trend towards making consumer equipment smaller, portable and more highly functional. This, in turn, is greatly increasing demands for battery power systems to be light and small but still provide long run times. Battery and capacitor technologies are mature and seem unlikely to meet these increased demands. CAP-XX believes that supercapacitors will increasingly become the critical enabling technology which allows OEMs to meet all these objectives at a competitive cost.