Setup for measuring electrode potentials

Abstract

The invention relates to a setup for measuring the electrode potentials of an electrochemical cell (1), comprising two electrodes (2, 3), a separator (4) arranged between them, and an electrolyte (10) surrounding them, relative to a reference electrode (9). The setup according to the invention is characterized in that the reference electrode (9) is arranged in a passive region of the electrolyte (10) with an electrolyte potential equivalent to that of the electrolyte (10) of the electrode (2) to be measured.

Description

[0001] The invention relates to a structure for measuring electrode potentials of an electrochemical cell according to the type defined in more detail in the preamble of claim 1.

[0002] Measuring electrode potentials is, in principle, well-known from the state of the art. Conventional measurement methods rely on a reference electrode placed in the active region of the electrolyte or at an equivalent potential level to it. This leads to overvoltages during operation on the ionic path between the reference electrode and the electrode being measured, also known as the working electrode. These are harmful and distort the measurement.

[0003] One such common measurement method is described, for example, in the article "Three-Electrode Setups for Lithium-ion Batteries" by M. Ender et al., Journal of The Electrochemical Society, 164(2)A71-A79(2017). In this article, various electrode shapes are measured, such as a point-shaped, a wire-shaped, or a mesh-shaped or grid-shaped electrode, which is inserted halfway between the working electrode to be measured and the corresponding counter electrode. Here, too, the aforementioned disadvantage of overvoltages that exist during operation cannot be avoided with this type of electrode arrangement, so the measurements are distorted to a certain extent.

[0004] The object of the present invention is to provide an improved structure which enables improved measurement of electrode potentials.

[0005] According to the invention, this object is achieved by the structure having the features in claim 1, and in particular in the characterizing part of claim 1. An advantageous further development results from the dependent claim.

[0006] In the inventive setup, the reference electrode is arranged in a passive region of the electrolyte with an equivalent electrolyte potential to the electrolyte of the electrode to be measured. Such a passive region is a region that lies outside the current flow or potential gradient between the working electrode to be measured and its counter electrode. This special arrangement of the reference electrode in the aforementioned passive region allows a real electrode potential to be recorded. The half-cell can therefore be measured in its actual setup without disruptive influences, as is the case with prior art setups. This allows, for example, optimized charging maps to be determined, half-cell models to be parameterized, or improved charging and aging states to be measured and estimated accordingly under load. Furthermore, the charging current can also be regulated in this way.The complete measurements are efficient and extremely precise, since the values ​​that distort the measurement in the setups described at the beginning do not occur here due to the principle.

[0007] According to an extremely advantageous development, it can further be provided that the reference electrode is arranged on the side of the electrode to be measured facing away from the separator. Thus, the reference electrode can in particular not be located between the working electrode and its counter electrode, as in the prior art, but rather on the side of the working electrode facing away from the separator and thus also from the counter electrode, for which this area is also surrounded by the electrolyte. This results in an extremely simple and efficient structure in which a cell is positioned within the electrolyte at a distance from the reference electrode arranged on the side of the electrode to be measured, in order to measure the working electrode and thus the half-cell accordingly.Various measurement methods are conceivable, all of which can measure the electrode potentials without the interference of the electrolyte or other side effects. In particular, the impedance of the half-cells can also be determined in this way without distortion or interference caused by the influence of the electrolyte.

[0008] Further advantageous embodiments of the structure according to the invention also emerge from the exemplary embodiment which is described in more detail below with reference to the single attached figure.

[0009] This Fig. 1 shows a cross section through a part of the structure according to the invention in a schematic representation.

[0010] The schematic representation shows an electrochemical cell, for example a lithium-ion cell 1. It consists of a first electrode 2, referred to as the working electrode, and a second electrode 3, referred to here as the counter electrode. A separator 4 is arranged between these. Each of the two electrodes 2, 3 itself consists of an electrical conductor material, for example an aluminum foil for one and a copper foil for the other of the two electrodes 2, 3. This foil is provided with the reference numeral 5 for the working electrode 2 and with the reference numeral 6 for the counter electrode 3. Between this metal foil 5, 6 and the separator 4 there is active material, which is designated 7 for the working electrode 2 and 8 for the counter electrode 3. The current flow or the potential gradient between the electrodes 2, 3 and their metal foils 5, 6 is shown via a double arrow.The entire area shown is filled with the liquid electrolyte 10.

[0011] A reference electrode 9 is used to measure the working electrode 2. This reference electrode is located on the side of the working electrode 2 facing away from the separator 4 and the counter electrode 6, i.e., behind the latter. The distance, designated here as A, is selected such that the reference electrode 9 is located in a passive region of the electrolyte 10 with an equivalent electrolyte potential to the electrolyte 10 in the working electrode 2 to be measured.

[0012] Using this reference electrode 9, which is arranged behind the working electrode 2 from the perspective of the counter electrode 6, i.e. its arrangement outside the battery cell 1 to be measured, the electrode potential can be determined reliably, efficiently and easily without the disturbing influence of the electrolyte 10 or other side effects. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited non-patent literature

[0000] Three-Electrode Setups for Lithium-lon Batteries” by M. Ender et al., Journal of The Electrochemical Society, 164(2)A71-A79(2017

[0003]

Claims

[1] Structure for measuring electrode potentials of an electrochemical cell (1), with two electrodes (2, 3), with a separator (4) arranged between them and with an electrolyte (10) surrounding them, opposite a reference electrode (9), characterized by that the reference electrode (9) is arranged in a passive region of the electrolyte (10) with an equivalent electrolyte potential to the electrolyte (10) of the electrode (2) to be measured. [2] Structure according to claim 1, characterized by that the reference electrode (9) is arranged on the side of the electrode (2) to be measured facing away from the separator (4).

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