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DE-102025001415-B3 - Device for measuring the surface potential of a working electrode and method for controlling a charging current of a battery

DE102025001415B3DE 102025001415 B3DE102025001415 B3DE 102025001415B3DE-102025001415-B3

Abstract

The invention relates to a device for measuring the surface potential of a working electrode (3) of an electrode/separator arrangement of a single battery cell (1) by means of at least one reference electrode (8), wherein the reference electrode (8) is connected to an electrolyte-containing layer (7). The device according to the invention is characterized in that the layer (7) is arranged in the contact area between the working electrode (3) and a separator (5), wherein the layer (7) is extended outside the contact area at a distance from the working electrode (3) to the at least one reference electrode (8), which, from the perspective of the separator (5), is arranged in a plane behind the working electrode (3).

Inventors

  • Gerrit Karl Mertin
  • Johannes Sieg
  • Dominik Wycisk

Assignees

  • Mercedes-Benz Group AG

Dates

Publication Date
20260513
Application Date
20250428

Claims (6)

  1. Device for measuring the surface potential of a working electrode (3) of an electrode/separator arrangement of a single battery cell (1), by means of at least one reference electrode (8), wherein the reference electrode (8) is connected to an electrolyte-containing layer (7), characterized in that the layer (7) is arranged in the contact area between the working electrode (3) and a separator (5), wherein the layer (7) is led outside the contact area at a distance from the working electrode (3) to the at least one reference electrode (8), which is arranged in a plane behind the working electrode (3) from the viewpoint of the separator (5).
  2. Device according to Claim 1 , characterized in that the layer (7) consists of a separator material.
  3. Device according to Claim 2 , characterized in that the separator (5) and the layer (7) are made of the same material.
  4. Device according to Claim 1 , 2 or 3 characterized in that at least a reference electrode (8) is laminated into the layer (7).
  5. device according to one of the Claims 1 until 4 , characterized in that the at least one reference electrode (8) is designed as a ring electrode.
  6. Method for controlling the charging current of a single battery cell (1), wherein the charging current is regulated such that the highest potential of a working electrode (3) is smaller than a critical limit potential, characterized in that , by means of the device according to one of the Claims 1 until 5 the potential of the reference electrode (8) is detected and adjusted to a value which is smaller than the critical limit potential.

Description

The invention relates to a device for measuring the surface potential of a working electrode using a reference electrode of the type defined in more detail in the preamble of claim 1. The invention also relates to a method for controlling a charging current of a battery. Reference electrodes in individual battery cells or half-cells are fundamentally known from the prior art. For example, one can refer to the... JP 2006 179 329 A be referred to. A suitable one specifically for lead-acid batteries is described in the JP 2018 045 898 A describe. Furthermore, for example, the WO 2018 / 141 723 A1 an energy storage device with a reference electrode and a charging method in which the charging current is regulated depending on this reference electrode. A similar method is also described by the EP 4 345 988 A1 . The aforementioned WO publication describes various locations where the reference electrode can be positioned. The reference electrode itself is coated with a porous insulating layer that is permeable only to the electrolyte, i.e., it conducts only ions. Even though this electrolyte-containing insulation of the reference electrode is generally useful, in the various arrangements of the reference electrode described in the aforementioned WO publication, it is, for example, mounted on the current collector, thus always measuring the potential of the working electrode as well. In another embodiment, the reference electrode is arranged in the area of the active electrolyte, in which case the working electrode, due to its planar design, extends beyond the counter electrode. Here, too, different potentials and fields are measured in this area due to the different sizes of the electrodes. In another embodiment, the reference electrode is arranged laterally on the combined structure of two electrodes and an intermediate current collector. Here, too, the electrode measures a potential drop across the thickness of the porous electrode and the electrolyte layer. Ideally, the surface potential of the working electrode should be measured as precisely as possible. However, if the reference electrode is positioned as described in the WO document, this can only ever be estimated, since the potential drop of the electrode or other interfering voltage influences are always included in the measurement. These must then be estimated and subtracted from the measured value. Due to the necessary safety margins, the surface potential of the working electrode is generally assumed to be too low, resulting in a charging current for the battery that is lower than it could be without risking battery damage. This represents a significant disadvantage, particularly for the fast-charging capability that is crucial in automotive applications for quickly restoring the vehicle's maximum range. The object of the present invention is to provide an improved device and an improved charging method using this device, which improves the aforementioned disadvantages. According to the invention, this problem is solved by a device with the features of claim 1 and a method with the features of claim 6. Advantageous embodiments and further developments of the device according to the invention are set forth in the dependent claims of claim 1. The device according to the invention, unlike the setups in the prior art mentioned above, is now able to directly measure the surface potential of the working electrode, that is, the potential at the interface between the electrolyte-impregnated separator on the one hand and the surface of the working electrode on the other. In the device according to the invention, the reference electrode, whereby several reference electrodes are also conceivable in principle, is connected to an electrolyte-containing layer which is arranged between the working electrode and the separator. The layer is positioned at a distance from the working electrode to the at least one reference electrode, which, viewed from the separator's perspective, is arranged in a plane behind the working electrode. The reference electrode is thus connected to a region behind the working electrode via the electrolyte-containing layer, which is not directly electrically conductive but allows ionic conduction. This setup ensures that the region between the interface of the electrode and the separator and the reference electrode exhibits a near-equipotential level, since the reference electrode is located downstream of the working electrode being measured, and the shortest ionic path to the separator region runs through the layer that contacts the surface of the working electrode facing the separator. The reference electrode is therefore not located in the actively energized region of the electrolyte, so there are no direct interactions with the current flow. The potential of the layer is directly adjacent to the surface of the working electrode being measured and thus has the same or at least approximately the same potential as the surface of the working e