Beyond the Lithium-ion battery! A Look at Supercapacitors And Other Batteries

Supercapacitors

A supercapacitor (also electric double-layer capacitor (EDLC), also called supercar, ultra capacitor or Goldcap) is a high-capacity capacitor with capacitance values much higher than other capacitors (but lower voltage limits) that bridge the gap between electrolytic capacitors and rechargeable batteries.

	SuperCapacitor	Lithium-ion
Charge Time	1-20 seconds	10-60 minutes
Cycle life	1 million	>500
Cell Voltage	2.3 -2.7V	3.6V (nominal)
Specific energy	5 Wh/kg	1000-3000 Wh/kg
Service life	10-15 years	5-10years
Cost	10,000 USD	250-1000

Fig: Voltage behavior of lithium ion battery and supercapacitor

Advantages:

Virtually unlimited cycle life

High specific power

Low resistance

Enables high load currents

Charges in seconds

no end-of-charge termination required

Simple charging, draws only what it needs, not subject to overcharge

Safer

Excellent low-temperature charge and discharge performance

Disadvantages:

Linear discharge voltage prevents using the full energy spectrum

High self-discharge; higher than most batteries

Low cell voltage; requires series connections with voltage balancing

High cost per watt

Fact: As of 2013 commercially available lithium-ion supercapacitors offered the highest gravimetric specific energy to date, reaching 15 Wh/kg (54 kJ/kg)

Lithium-Air

Anode-Cathode: Lithium- Porous carbon (Oxygen)

Advantages: 10x greater energy density than Li-ion

Disadvantages: Air is not pure enough and would need to be filtered. Lithium and oxygen form peroxide films that produce a barrier, ultimately killing storage capacity. Cycle life is only 50 cycles in lab tests.

Variations: Scientists also trying aluminum-air and sodium-air batteries as well.

Lithium-Sulphur

Anode- Cathode: Lithium- Sulphur, Carbon

Advantages: Lighter, cheaper, and more powerful than li-ion

Disadvantages: Volume expansion of up to 80%, causing mechanical stress. Unwanted reactions with electrolytes. Poor conductivity and poor stability at higher temperatures.

Variations: Many different variations exist, including using graphite/graphene, and silicon in the chemistry.

Vanadium Flow Batteries

Anolyte - Catholyte: Vanadium -Vanadium

Advantages: Using vanadium ions in different oxidation states to store chemical potential energy at scale. Can be expanded simply by using larger electrolyte tanks.

Disadvantages: Poor energy-to-volume ratio. Very heavy; must be used in stationary applications.

Variations: Scientists are experimenting with other flow battery chemistries as well, such as zinc-bromine.

Fig: Battery test methods for common battery chemistries

Courtesy: Batteryuniverity.com

TIP: Charge Li-ion battery at a moderate rate. Ultra-fast charging works only to 70 percent state-of-charge (SoC) and causes stress; topping charge takes longer (NiCad is the only battery that can accept ultra-fast charge with minimal stress.)