Potential and Limitations of Research Battery Cell Types for Electrochemical Data Acquisition

Developing new electrode materials and/or electrolytes for lithium-ion batteries requires reliable electrochemical testing thereof. For this purpose, in academic research typically handmade coin-type cells are assembled. Their advantage is a rather cheap and facile assembly, and possibility to prepare full-cells as well as half-cells, meaning cathode-anode or electrode-elemental lithium configurations. Critical parameters for testing data quality and the potential and limitations of cell tests in half-cell configuration are discussed. Further, on the basis of a round robin test, using highly homogenous commercial electrodes, where graphite is used as anode and LiNi0.33Mn0.33Co0.33O2 (NMC111) as the cathode material, it is shown that data acquired is highly influenced by assembling parameters. Besides known variables such as the amount of electrolyte or electrode positioning, the proper height of the cell stack and the steel grade of the housing material are identified as decisive variables. Finally, it is demonstrated that under proper conditions coin cells can show a great cycle stability of > 2200 cycles using 1 C as dis-/charge rate while retaining a capacity of 80%. This performance is close to pouch-type cells containing the same electrodes and electrolyte, which were used as a benchmark system and showed > 3500 cycles of lifetime.