Verwendung einer Drei-Elektroden-Zelle bei Batterietests

Batterien haben in der Regel zwei Elektroden: Anode und Kathode. Während der Lade- und Entladezyklen wandern die Ionen durch den Separator zu einer der beiden Elektroden und setzen dabei Energie frei. 

Batterieprüfzellen können so gebaut werden, dass sie eine dritte Elektrode enthalten. Diese wird als Referenzelektrode (RE) bezeichnet. Die RE ermöglicht eine bessere Analyse der Batterieleistung, da sie die Testergebnisse zwischen Anode und Kathode entkoppelt.

Bei der Erforschung von Batteriematerialien ermöglicht die Verwendung einer Referenzelektrode (RE) den Forschern, den Beitrag der einzelnen Komponenten der Zelle zu ihrer Gesamtleistung zu messen und zu differenzieren. Mit Hilfe von Drei-Elektroden-Experimenten lässt sich feststellen, welche Elektrode (Anode oder Kathode) die Leistung der Zelle bei Langzeittests begrenzt. Es ist wichtig zu ermitteln, wie jede einzelne Elektrode unter verschiedenen Testbedingungen zur Zelldegradation beiträgt, anstatt blind mit einer oder beiden zu experimentieren.

Warum ist das wichtig?

Die meisten alle electrochemical experiments and battery tests provide greater understanding of the cell when the anode and cathode results can be decoupled through use of a reference electrode.  This extends to what are traditionally considered “industrial” applications as well.  The dynamic charge-discharge profiles and fast charge simulations associated with commercial devices and electric vehicles can draw unique performance from a battery compared to low-rate constant current cycling.

Three-electrode testing is also beneficial for evaluating battery safety.  Minter and Juarez-Robles highlight how fast-charging, which is a highly sought characteristic for electric vehicles, creates a great need to detect and monitor lithium plating occurring on a cell anode.  [Minter RD, Juarez-Robles D, et al 2018 J Vis Exp., (135):57735.]  This can best be achieved using a three-electrode cell during testing.

One fundamental goal of battery research is to develop cells that are long-lasting.  This is especially important for electric vehicle and grid storage applications where the commercial cells and battery packs must last thousands of cycles and up to 10 years.  Three-electrode testing allows researchers to identify the limiting factor in their cell to focus attention where improvement is needed most.

Wie die Referenzelektrode in verschiedenen Testsituationen verwendet wird

• During HPPC test, which are common for Elektrofahrzeug-AnwendungenDie Verwendung einer Referenzelektrode zeigt die Polarisierung der Elektrode.

• Performing EIS shows the decoupled impedance from anode and cathode individually when a three-electrode cell is utilized.

• The individual contribution of anode and cathode is revealed when demonstrating lithium loss due to SEI growth as a dominant aging mechanism.

• Die Differenzkapazitätsanalyse kann Veränderungen im Spannungsprofil von Anode und Kathode aufdecken und aufzeigen, wie sie einzeln zur Zelldegradation beitragen.

Die Hindernisse bei der Entwicklung einer stabilen und zuverlässigen Drei-Elektroden-Zelle

Comparing results from a new three-electrode experiment to other published results needs to keep as many variables consistent as possible, such as electrode size, material amount, cell uniformity, etc., or else attempt to normalize results.  This is a principal reason why traditional cell types are modified to incorporate a reference electrode as “homemade” cell, so results are easier to compare with minimal normalization.  Researchers wish to demonstrate and compare their results to existing two-electrode data of the same cell type (cylindrical, pouch, coin).  However, since most battery material work is conducted using coincells, this is the natural choice for three-electrode experiments to compare the new results with the vast amount of tradition two-electrode data in publication.  The new experimental data will decouple the anode and cathode and provide new insights.

Suggestion

A wide range of three-electrode cell configurations—such as Swagelok-style cells, split-cell designs, and PAT cells—are available and commonly used for electrochemical studies. However, it is important to recognize that these systems also have limitations. They can be expensive, complex to assemble, and challenging to scale for practical applications. Additionally, data obtained from such specialized cells must be carefully normalized when compared with conventional battery formats (e.g., coin, cylindrical, or pouch cells). Therefore, these considerations should be thoroughly evaluated when selecting an appropriate testing configuration for your specific research or development objectives.