Energy storage and conversion

High energy density supercapacitors

Diagram of a supercapacitor

Supercapacitors (also known as ultracapacitors, electrochemical capacitors, or double-layer capacitors) are electrochemical devices that store and release charge and deliver high power densities over short periods of time. Their ability to store electrical energy efficiently and release electrical energy very quickly makes them ideally suited for applications where short-time backup power and peak power needs are critical.

Using special nanomaterials researchers at UCLA’s California NanoSystems Institute have prepared ”LSG-manganese capacitors” that ”store as much electrical charge as a lead acid battery” and that ”yet can be recharged in seconds and store about six times the capacity of state-of-the-art commercially available supercapacitors”.

> Read more about LSG-manganese capacitors here

And the electrochemical instrumentation for analyzing them

PGSTAT101 system with cell and laptop computer

The development of supercapacitors such as this requires stringent electrochemical analysis. Metrohm Autolab offers the appropriate instrumentation for such analyses.

> Read more about electrochemical analysis with Metrohm Autolab

Anions and cations using ion chromatography

Chromatogram for anions and cations in energy storage

Lithium-ion (Li-ion) batteries are the most important storage technology in portable and mobile applications. They excel not only by their high cell voltage levels and their flexible discharge time, but also by their high gravimetric energy density. In the development and optimization of Li-ion batteries, one of the aspects of special interest is the content of ions such as lithium, fluoride, and hexafluorophosphate in the electrolyte or in eluates of different components.

940 Professional IC Vario, open

With ion chromatography, it is possible to determine various inorganic and organic anions and cations in parallel and over a wide concentration range. Any sample preparation steps that might be required (elution, dilution, filtration) can be automated with the Metrohm Inline Sample Preparation (“MISP”) techniques. The following ions can be determined:

  • fluoride, hexafluorophosphate, tetrafluoroborate, and lithium in eluates of individual components such as anodes, cathodes, and separator foils
  • fluoride, hexafluorophosphate, and lithium in electrolyte liquids


Water in Li-ion batteries

Li-ion battery pack

Battery electrolyte consists of mixtures of anhydrous aprotic solvents and lithium salts. Lithium ion batteries must be completely free of water (< 20 mg/L), because water reacts with the conducting salt, e.g., LiPF6, to form hydrofluoric acid.

The water content in the electrolyte is determined using Karl Fischer coulometry and the oven method. Alternatively, manual or automated injection with dosing units can be applied. Besides the electrolyte, water can be determined in all Li-ion battery parts – from the raw materials and electrolytes used to the coated anode and cathode foils and the electrode coating preparations.

> Read more about Karl Fischer titration

Electrochemical characterization of …

… batteries, electrode materials, and electrolytes

Various batteries

A large number of secondary-battery types exist today. This group includes, for instance, the world’s most widely used battery type, lead-acid, or NiCd/NiMH, lithium-ion, metal-air, sodium-sulfur, and sodium-nickel batteries, in addition to a number of technologies under development. The total power output of batteries is determined by the properties of the electrolytes used and of the anode and cathode materials. Electrochemical methods are suitable for, e.g.:

  • determining current/voltage characteristics
  • tests for polarity reversal (charging) of batteries
  • characterizing ageing effects using electrochemical impedance spectroscopy (EIS)
  • recording discharge and charge cycles
  • determining battery capacity
  • measuring the electrolyte resistance and charge transfer resistance (electrode reaction)
  • determining pulse power rating / high-current capability
Metrohm Autolab instruments are ideal for the characterization and development of battery materials, e.g., anode and cathode materials, separations, electrolytes, boundary layers as well as the determination of Fe(II) und Fe(III) in lithium iron phosphate.


… supercapacitors

PGSTAT204 potentiostat setup
The performance of a supercapacitor is determined by measuring its capacitance (which can vary with the applied potential) and equivalent series resistance (ESR). These parameters can be measured by charging the supercapacitor at constant current and monitoring the potential response (chronopotentiometry), applying a potential pulse and monitoring the current response (chronoamperometry), or with electrochemical impedance spectroscopy (EIS). Whatever you want to measure, Metrohm Autolab has the appropriate instrument.


… fuel cells

Diagram of a fuel cell

Fuel cells are considered chemical energy storage systems that produce electricity by oxidizing hydrogen or methane. They perform at a higher efficiency than heat engines and produce no carbon dioxide. Fuel cells are different from batteries in that they require a continuous fuel source to sustain the chemical reaction. As long as fuels are provided, fuel cells produce electricity.

There are different types of fuel cells, such as alkaline (AFC), polymer electrolyte membrane (PEMFC), direct methanol (DMFC), phosphoric acid (PAFC), molten carbonate (MCFC), or solid oxide (SOFC) fuel cells.

Characterization of the fuel cells includes electrochemical impedance spectroscopy (EIS) as well as polarization and power density curves of the cell pointing to the optimal operating conditions.



"We have been using the Metrohm instruments for the last ten years ... without any problem."

Prof. S. Basu, Dept. of Chemical Engineering, Indian Institute of Technology, Delhi