Supercapacitors vs. batteries | element14 Singapore

Supercapacitors vs. Batteries

Evaluating energy storage solutions

Figure 1: Power density vs energy density graph (Source)

Energy is essential for the survival of the human civilization, powering everything from electric vehicles (EVs) and grid systems to consumer electronics.

Efficient energy storage is thus a fundamental pillar of energy transition. However, it can be tough to choose the right technology, as each application has specific power output, charge times, and cycle life. As of today, Supercapacitors and storage batteries remain the two most popular options, each serving different purposes based on power and energy requirements. This article will provide a comparative analysis of supercapacitors and batteries based on their performance, characteristics, and capacity.

Supercapacitors

These energy storage devices are also called ultracapacitors or electrochemical capacitors. Unlike traditional capacitors that store energy through electrostatically, supercapacitors store energy through the electrostatic field and electrochemical reactions. They have significantly higher capacitance values (ranging from tens to thousands of Farads) than regular capacitors, allowing them to store and discharge much more energy quickly. They consist of two electrodes, usually made from activated carbon immersed in an electrolyte solution, where energy is stored either electrostatically or through pseudo-capacitance via reversible redox reactions. The below chart describes the different types and variations of supercapacitors, along with their specific applications, advantages, and disadvantages.

Variations	Applications	Advantages	Disadvantages
Electric Double Layer Capacitor (EDLC)	Backup power, regenerative braking systems	High power density, long cycle life	Low energy density and expensive
Pseudo capacitor	Energy storage in renewable energy systems, high power applications	Higher energy density than EDLC, fast charge/discharge	Complex design and not cost-effective.
Hybrid Capacitor	Grid stabilization, electric vehicles	Combines benefits of batteries and capacitors with good energy storage	Limited energy storage and expensive

Batteries

These electrochemical devices store energy through chemical reactions within their cells. Most battery chemistries include lithium-ion, nickel-metal hydride (NiMH), and lead-acid. Lithium-ion batteries are the most widely used due to their high energy density, long cycle life, and low self-discharge. The below chart describes the different types and variations of batteries, along with their specific applications, advantages, and disadvantages.

Variations	Applications	Advantages	Disadvantages
Lithium-ion	Consumer electronics, electric vehicles, grid storage etc.	High energy density, lightweight, long cycle life	Safety concerns like thermal runaway
Lead-acid	Uninterruptible power supply (UPS), automotive applications	Low cost, reliable for large scale applications	Heavy in weight and low energy density
Nickel-Metal Hydride (NiMH)	Portable electronics, hybrid vehicles	Effective power output, longer life than alkaline batteries	Lower energy density than lithium-ion

Significant distinctions between supercapacitors and batteries

Batteries and supercapacitors are two popular energy storage options that are used extensively in many different sectors. How the two store and distribute energy is where they are different. In this section, we will explore the significant distinctions between supercapacitors and batteries, focusing on their operational principles, performance characteristics, and best applications.

Power density and charge-discharge time: Power density is a measure of how much power is generated per unit of volume, area, or mass. It is directly related to the charge rate and discharge times of the energy storage technology. Supercapacitors have a high-power density of up to 10000 watts per liter, compared to batteries like Lithium-ion, which is 10 to 100 times higher. They can charge and discharge within seconds, whereas batteries typically take hours due to slower electrochemical reactions. This makes supercapacitors ideal for applications requiring rapid energy delivery, such as backup systems, electric vehicles, and camera flashes. However, supercapacitors also experience higher self-discharge rates than batteries.
Energy density: Energy density indicates the energy a device can hold relative to its mass or volume. Batteries have much higher energy densities than supercapacitors, making them appropriate for applications that require long-lasting energy storage, such as electric vehicles and renewable energy systems. Li-ion batteries can achieve energy densities up to 650 watt-hours per liter (Wh/L), while even the most advanced supercapacitors offer only around 10 Wh/L or 1.5% of a battery’s energy density. Compared to supercapacitors, batteries can store and deliver more energy over extended periods, enabling applications like grid storage and EVs to function efficiently for longer durations between charging intervals. While supercapacitors excel in quick power delivery, their lower energy density limits their use in applications that need large amounts of stored energy. In contrast, batteries give continual energy output, important for powering devices over longer cycles.

Figure 2: Comparing cycling capabilities of Lead acid, Nickel Cadmium, Lithium-ion, and supercapacitor storage technologies (Source)

Figure 1: Power density vs energy density graph (Source)

Calendar and cycle life/ recycle ability: Cycle life refers to how many charges and discharge cycles a device can undergo before significant degradation occurs. Among batteries, Lithium-ion batteries in particular deteriorate over time due to chemical reactions and mechanical strain while charging. Although the solid-electrolyte interphase (SEI) layer created by these techniques contributes to longer battery life, it eventually results in lower capacity and power density. Li-ion batteries normally have a 2,000–3,000 cycle life before they begin to lose efficiency. Supercapacitors have an exceptionally long cycle life, often exceeding 1 million cycles as they don't suffer the same degradation as batteries. This happens because there are no chemical changes or material wear as store energy through the electrostatic field. They are thus ideal for applications that need frequent charging and discharging, offering a better and longer lifespan with minimal loss of performance over a time period.

Figure 2: Comparing cycling capabilities of Lead acid, Nickel Cadmium, Lithium-ion, and supercapacitor storage technologies (Source)

Operating temperature: Batteries normally run between -20°C and 40°C, which is a minimal temperature range. Lower temperatures cause chemical reactions to slow down, which lowers the output of power and energy. On the other hand, high temperatures have the potential to trigger dangerous thermal runaway, which could result in explosions or overheating. As a result, temperature monitoring is essential for safety. Supercapacitors, however, function effectively across a much broader range, from -40°C to 85°C. They do not experience self-accelerating reactions and produce less heat during use because they store energy through electrostatic means, eliminating the risk of thermal runaway. This characteristic makes supercapacitors more resilient in extreme temperature environments.
Cost: Supercapacitors are costly compared to batteries. This is the reason batteries are chosen for many applications. However, due to their longer lifespan, supercapacitors appear to be cost-effective in the long term. Although they cost more per watt, their ability to bear millions of charge-discharge cycles can offset the initial investment over time.

Feature	Supercapacitors	Batteries
Voltage	48-62V	12-24V
Energy density (Wh/L)	1-10	100-650
Power density (W/L)	1000-10000	100-3000
Charge rate (C/x)	>1500	1-40
Discharge time	Seconds to minutes	1-3 hours
Cycle life	>1000000	300-10000
Efficiency	>98%	80-90%
Temperature range	-40°C to 70°C	-20°C to 45°C
Lifespan	5-20 years	0.5-10 years
Size and weight	Typically larger and heavier for same energy	Compact and lightweight for energy stored
Cost	Higher cost per Wh	Lower cost per Wh
Applications	High power, short duration (backup power, regenerative braking)	Energy storage, longer duration (EVs, portable devices)

Table 1: Comparison chart of the features of supercapacitors and batteries (Source)

Conclusion

A majority of supercapacitors, except the sophisticated ones like hybrid and pseudo-supercapacitors, suffer from lower energy densities vis-a-vis batteries. Their superior power density and quick charge-discharge cycles come with a compromise of power efficiency. Batteries, especially the lithium-ion ones, can store energy in large amounts, making them perfect for longer duration use. The choice between batteries and supercapacitors ultimately boils down to a particular application's specific energy and power needs. As a worldwide distributor, Farnell provides a large selection of batteries and supercapacitors to meet various needs and guarantee excellent performance in a variety of sectors.