Electrical measuring device for alkaline solid electrolyte secondary batteries

Abstract

The present invention relates to a measuring device for secondary alkaline solid electrolyte batteries, the measuring device comprising: two half-cell bodies each having at least one feedthrough, one half-cell body having at least three perforations, each half-cell body having a receiving space for receiving a solid electrolyte battery cell having at least an anode, a cathode, and a solid electrolyte; a conductive retaining element for each feedthrough; an electrical contact element provided on each retaining element, the electrical contact element adapted to change its length in response to a force applied to the retaining element; and two planar current conductors having conductive and non-conductive regions, at least one of the current conductors adapted to form at least three separate conductive connections between the contact element and an electrode of the solid electrolyte battery cell. The present invention further relates to the use of the measuring device for determining the electrical characteristics of secondary alkaline solid electrolyte battery cells.

Description

[Technical field]

[0001] The present invention relates to a measuring device for secondary alkaline solid electrolyte batteries, two electrically non-conductive cell body halves, each of which has at least one feedthrough and one of which has at least three feedthroughs, each of which has a receiving space formed therein for receiving a solid electrolyte battery cell including at least an anode, a cathode, and a solid electrolyte; an electrically conductive retaining element provided on each feedthrough; an electrical contact element provided on each retaining element, the electrical contact element adapted to change its length in response to a force applied thereto; two planar current conductors with electrically conductive and electrically non-conductive regions, at least one of the current conductors adapted to form at least three separate electrically conductive connections between the contact element and electrodes of the solid electrolyte battery cell. Furthermore, the invention relates to the use of the measurement arrangement for determining the electrical properties of secondary alkaline solid electrolyte battery cells. [Background technology]

[0002] Increasing user demands for sustainability and mobility have significantly changed the landscape of distributed energy storage in recent decades. Traditionally, the size, weight and very limited electrical capacity of batteries rather limited the technical availability of batteries, but since the use of alkali metal-based energy storage systems, for example in the form of rechargeable lithium batteries, the possible applications have increased significantly. Since their market introduction in the early 1990s, lithium-ion batteries have made mobile applications such as smartphones and laptops suitable for mass use.

[0003] Furthermore, continuous developments are also increasing the energy density and the reliability of the applications. These optimization steps have contributed, for example, to the fact that lithium-ion batteries are now being considered as stationary energy storage devices for decentrally generated electricity in private and industrial applications. Furthermore, these innovative energy storage systems are the basis for new climate-smart transport concepts in the field of electromobility.

[0004] One of the most important foundations in the pursuit of battery optimization is the ability to determine the electrical properties of a battery quickly and reproducibly. In the field of liquid electrolyte research, two-electrode setups in the form of pouch bags or button cells are commonly used. These have a crucial drawback in that they lack a third electrode, the reference electrode, which is necessary for fundamental research but cannot be fitted, to identify the various degradation processes in the cell. For electrochemical analysis with a reference electrode, such as lithium metal, T-cells with appropriate inserts (e.g. from Swagelok) are often used. However, due to their shape, they are only valid for cells using liquid electrolytes. A cell assembly with a reference electrode consists of many individual parts, which must be cleaned separately and assembled appropriately through several steps. In a glove box, for example, this involves a greater consumption of time and an increased difficulty. The pressure in the cell is usually distributed by individual pressure springs, which transmit the pressure to the plunger of the press. Swagelok T-cells have a reference at right angles to the electrolyte layer, resulting in a large distance between the reference and the working and reaction electrodes. In cells using liquid electrolytes, such an arrangement is also acceptable due to the low absolute resistance of the liquid electrolyte. However, in solid electrolytes, the resistance increases due to the longer path, resulting in a measurable voltage difference. In addition, thermal deformation of the sample (e.g. melting of the polymer solid electrolyte) can lead to loss of contact between the electrodes and failure of the cell test. These drawbacks are crucial for the fact that simple, reliable and reproducible measurements with reference electrodes in solid electrolyte batteries are difficult with these devices.

[0005] Furthermore, various proposals regarding measuring devices using reference electrodes are published in the patent literature. For example, EP1924849B1 discloses a measurement system for the thermodynamic evaluation of an electrochemical cell having electrodes, said system comprising: means for measuring an open circuit voltage of said electrochemical cell as a function of time; a composition controller electrically connected to the electrochemical cell for determining a selected electrochemical cell composition, the composition controller capable of determining a plurality of the selected compositions; a temperature controller in thermal contact with the electrochemical cell for determining a plurality of the electrochemical cell temperatures at each of the selected compositions, thereby determining a plurality of the electrochemical cell temperature and composition combinations; and an open circuit voltage analyzer for receiving open circuit voltage measurements as a function of time from said open circuit voltage measurement means and for identifying a thermochemically stable open circuit voltage of said electrochemical cell at said electrochemical cell temperature and composition combination, said open circuit voltage analyzer being capable of executing an algorithm using the open circuit voltage measurements as a function of time received from said open circuit voltage measurement means to calculate an observed rate of change of open circuit voltage per unit time at a selected electrochemical cell temperature and composition combination, means that the open circuit voltage analyzer is a processor having an algorithm executed to calculate an observed change in open circuit voltage at a combination of electrochemical cell temperature and composition as a function of time for receiving measurements of open circuit voltage at a combination of electrochemical cell temperature and composition at which the electrochemical cell is in a thermochemically stable state; The algorithm compares an absolute value of the rate of change of the observed open circuit voltage per unit time at the selected electrochemical cell temperature and composition combination to a threshold rate of change of the open circuit voltage per unit time, and when the absolute value of the rate of change of the open circuit voltage per unit time is equal to or less than the threshold rate of change of the open circuit voltage per unit time, the algorithm identifies an open circuit voltage that is the same as the open circuit voltage of the electrode plate under thermally stable conditions at the selected electrochemical cell temperature and composition combination, wherein the threshold rate of change of the open circuit voltage as a function of time is equal to or less than 1 mVh. -1 is equal to or less than.

[0006] Furthermore, EP 3108224 B1 discloses a reference electrode insert for testing electrochemical test cells, in particular lithium-ion batteries, comprising a reference electrode and a sleeve for holding the reference electrode, characterised in that the sleeve and the annular reference electrode form a structural unit, the reference electrode being tightly and captivatingly enclosed and held in the sleeve. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] European Patent No. 1924849 [Patent Document 2] European Patent No. 3108224 Summary of the Invention [Problem to be solved by the invention]

[0008] Such solutions known from the prior art could be further improved, especially with regard to the flexibility and simplicity of the measurement setup and the reproducibility of the parameters that can be collected. The object of the present invention is to at least partially overcome the drawbacks known from the prior art, in particular to provide a solution which allows a large number of reproducible measurements within short set-up times under reproducible sample conditions. This problem is solved by the features of the respective independent claims directed to a measurement set-up according to the invention and to the use according to the invention. Preferred embodiments of the invention are set out in the dependent claims, in the description or in the drawings, whereby further features set out or shown in the dependent claims or in the description or drawings can, individually or in any combination, constitute the object of the invention, unless the context explicitly dictates otherwise. [Means for solving the problem]

[0009] According to the invention, this problem is solved by an electrical measurement arrangement for a secondary alkaline solid electrolyte battery, which comprises at least the following features: two electrically non-conductive cell body halves, both of which have at least one feedthrough and one of which has at least three feedthroughs, each of which has a recess on its inner side, the recess forming a receiving space for receiving a solid electrolyte battery cell including at least an anode, a cathode and a solid electrolyte, each of the feedthroughs extending from an outer side of the cell body halves into the receiving space; a conductive retaining element for each feedthrough, the retaining element being equipped to be mechanically connectable to a respective cell body half; an electrical contact element for each retaining element, the electrical contact element being attachable to the retaining member toward the receiving space and adapted to change its length in response to a force acting on the element; and Two flat current conductors consisting of conductive and non-conductive regions, at least one of the current conductors being arranged to form at least three separate conductive connections between the contact element and the electrodes of the solid electrolyte battery cell, and the mechanical force of the contact element being exerted on the solid electrolyte battery cell via the current conductor.

[0010] Surprisingly, it turned out that the above-mentioned multi-electrode measuring device allows very reproducible determination of the electrical properties of solid electrolyte battery cells. The device is simple in the sense that it consists of only a few parts, and as a result can be disassembled and assembled quickly even under "unfavorable" glove box conditions. It is also easy to clean. Furthermore, large-area metal current collectors can be used as holding elements, which allows for a fast and uniform temperature control inside the cell at the same time. The device generally applies a very uniform and controllable force to the solid electrolyte battery cell to be measured. Therefore, the risk of mechanically damaging the cell and, as a result, inevitably erroneous measurements or interruptions to the measurement is small. Furthermore, the design ensures that the usually uneven sample surface of the solid electrolyte battery can be leveled and contacted reliably. Moreover, due to the small number of moving parts, a reliable seal can be achieved with a small number of seals. In particular, the selection of the holding elements and their materials allows the heating period of the entire cell assembly to be controlled, so that fast temperature profiles can be performed in the measurement arrangement.

[0011] The measurement arrangement according to the invention is an electrical measurement arrangement for alkaline solid electrolyte secondary batteries. Solid electrolytes are also called solid-state electrolytes, solid bulk electrolytes or solid ionic conductors. A solid electrolyte has a coherent polymeric support structure with embedded alkali metal ions that are mobile within the polymeric matrix of the solid electrolyte. Electric current flows via the movement of ions in the solid electrolyte. Solid electrolytes are electrically conductive, but have a much lower electronic conductivity than metals. An alkali metal solid-state battery has at least two electrodes and a solid electrolyte (particularly a non-flowing electrolyte) disposed between the electrodes. In addition to these components, a solid-state battery may have other layers or sheets. For example, a solid-state battery may have other layers between the solid electrolyte and the electrodes. The electrical properties of an alkali metal solid-state battery are based on the redox reactions of alkali metals, i.e., metals of the first main group of the periodic table. In particular, lithium, sodium, and potassium can be used as alkali metals.

[0012] The structure according to the invention comprises two electrically non-conductive cell body halves, both cell body halves having at least one feedthrough and one cell body half having at least three feedthroughs, each of which extends from the outside of the cell body half towards the receiving space. The electrically non-conductive cell body halves may be made of PP, PE, PTFE, PEEK or POM or other non-conductive plastics. PEEK may be suitable for combination with conductive parts made of stainless steel, since the thermal expansion coefficients of both materials are approximately the same in the temperature range used here. The cell body halves may have a symmetrical structure, in the sense that they are constructed in the same way. The feedthroughs extend for each from the top to the bottom, the feedthroughs penetrating the entire cell body half in each case. For each cell half, the feedthroughs allow contact with the receiving space of the battery cell to be measured, for example in the form of one or more concentric holes. The number of possible feedthroughs is in principle limited only by the area of ​​the feedthroughs and the area of ​​the cell body. Advantageously, each cell body half may have 1, 2, 3, 4, 5 or 6 feedthroughs, with at least one cell body half having at least 3 feedthroughs. The two cell body halves may further comprise means for mechanically holding the two cell body halves together. The latter is for example in the form of a clamp or a hand screw. However, it is also possible that the two cell parts are held together by a mechanical press that is not part of the actual measurement setup. In the further description, reference is made to "upper" and "lower" cell body halves. These names are arbitrary and can be replaced by "right" and "left".

[0013] Each of the two half cell bodies has a recess on the inside, which together form a receiving space for receiving a solid electrolyte battery cell consisting of at least an anode, a cathode and a solid electrolyte. Thus, both half cell bodies have an "upper" part and a "lower" part, and when the half cell bodies are joined together, the lower parts come into contact with each other. The lower parts of the half cell bodies also have a recess, which together form the receiving space of the battery cell. In addition to the battery cell, the receiving space can also at least partially receive other components of the cell structure, such as current collectors or contact elements. The recesses for the receiving space on the two half cell bodies can be the same size, approximately the same size or different sizes. Preferably, both half cell bodies have recesses of approximately the same size, which results in a symmetrical receiving space of the battery cell. One or both half cell bodies can also include a device for temperature control of the cell or further sensors, such as a temperature sensor.

[0014] An electrically conductive retaining element can be inserted into each feed-through, which retaining element is equipped with the respective cell body half so as to be mechanically connectable. An electrically conductive retaining element can be or has been introduced into each feed-through in order to contact the battery cell in the receiving space. The retaining element can be designed, for example, as a metal pin or a metal screw which is driven or screwed into the cell body half. By driving or screwing, a mechanical connection is formed between the retaining element and the cell body half. The retaining element can be made of stainless steel, steel, copper, platinum or other electrically conductive metals. Stainless steel screws are preferred. The distance of the retaining element from the beginning of the receiving space can be in the range of 0.1-35 mm, preferably 0.25-5 mm. This allows a fast thermal response of the battery cell.

[0015] Each holding element is connected to an electric contact element, which can be attached to the holding element towards the receiving space and is adapted to change its length depending on the forces acting on it. The electric contact elements, which are attached or can be attached to the holding element, are used to make electrical contact with the battery in the receiving space. This can be done, for example, by threading the contact element through the hollow holding element and emerging from the tip of the holding element. However, it is also possible for the contact element to be attached to the tip of the holding element. In this case, the contact elements can be made of different metals or metal alloys. The contact element is adapted to change its length depending on the forces acting on it. The contact element does not have a rigid mechanical structure and can adapt to mechanically acting forces. For example, a spring effect in the contact can ensure that the length of the element is not rigid but is a function of the currently present mechanical load. For example, it is also possible to use contacts with gas springs or gas spring elements.

[0016] The structure also has two flat current collectors with electrically conductive and electrically non-conductive areas, at least one of the current collectors being configured to form at least three separate electrically conductive connections between the contact elements and the electrodes of the solid electrolyte battery cell. The flat current conductors can be, for example, in the form of more or less thin disks or cylinders, and preferably cover at least the electrode surfaces of the battery, measured by surface area. Preferably, the area of ​​the current collectors may be somewhat smaller (e.g., 0.1 mm) than the area of ​​the recesses in the assembled cell body halves, so that the current collectors can be easily slid in the assembled cell body halves. In this regard, for the assembly of at least two electrodes, the current collectors are made of at least two different conductive and non-conductive materials. The different materials can provide current dissipation paths through the current collectors so that different conductive connections can be made to the different contact elements. Furthermore, contacts can be made to different locations on the battery electrodes. Furthermore, the current collectors can also accommodate a portion of the battery cell, so that, for example, the electrodes of the measurement array can be present embedded in the current collector. This can contribute to a more homogeneous pressure distribution and a reduced risk of short circuits due to penetration of the softer polymer membrane. For example, the current collector may be in the form of a ring electrode. In this case, the distance between one inner current collector surface and the outer current collector surface may be in the range of 0.1-5 mm, preferably the distance may be in the range of 0.5-2 mm, more preferably in the range of 1-1.5 mm.

[0017] In the setup according to the invention, the mechanical force of the contact element is applied to the solid electrolyte battery via the current collector. This results in a setup in which the battery cell to be measured is in the center of the receiving space formed by the recesses of the cell body halves, whereby the battery cell is surrounded by at least two current collectors and is in electrical contact with the contact element via the current collectors. An electrical signal can then be conducted out of the measurement arrangement via the holding element. The contact element provides an electrical contact to the current collectors, and as the length of the contact element is variable, it is also possible to define the range of forces that can be applied via the contact element to the current collectors and thus to the battery cell.

[0018] Within the preferred embodiment of the measurement arrangement, the measurement arrangement can be rotationally symmetric. Rotationally symmetric measurement cells have proven to be particularly suitable for obtaining a mechanical and thermal structure that is as symmetrical as possible. This setup allows to reduce the number of cell errors during the measurement. Furthermore, the measurements obtained are particularly meaningful, since differences due to different temperature gradients or different mechanical loads on the cell can be almost eliminated. This is a particular advantage compared to prior art setups, which are often based on asymmetric cell designs. For example, Swagelok T-cells have a large distance between the reference and working / counter electrodes, due to the reference being placed at right angles to the electrolyte layer.

[0019] In a preferred embodiment of the measurement arrangement, the different contact elements of each cell body half may be made of different metals. Thus, the contact elements of the cell body halves may be made of different metals or metal alloys. Due to the fact that the contact elements can be independently connected to the holding element, each individual contact element can be selected independently from the other contact elements based on its desired electrical properties. Furthermore, the choice of metals for the contact elements can also be selected differently for the two halves of the cell body. For example, in a structure with four holes and four contact elements, one contact element can be designed as a copper, platinum, nickel and iron contact, respectively. This results in a design that is flexible in adapting to the measurement tasks by selecting a specific material for each contact.

[0020] Within the scope of the preferred features of the measurement arrangement, the electrical contact elements can be spring contacts and the arrangement of the contact elements can be rotationally symmetric towards the receiving space. Symmetrical contacting of the battery cells via spring contacts has proven to be particularly mechanically reproducible. Thus, the proportion of measurement errors due to physical failures of the solid-state setup during the measurement can be reduced. Furthermore, the properties of the mechanical spring elements allow a flexible adaptation to different solid-state battery cells. The rotationally symmetrical design of the contact elements ensures that the mechanical and thermal loads on the battery cells are as uniform as possible, and different measured values ​​can be attributed purely to the battery properties. The spring contacts may be made of copper or gold or gold-plated, in order to allow an ideal electrical contact. At the same time, these materials are inert to chemical reactions with the substances to be tested in the battery. In principle, however, all electrically conductive spring contacts are possible. Gold is preferred, especially for use with sulfur-based electrolytes and sulfur-based materials, in order to prevent reactions and degradation with the common copper contacts. The ratio of the spring contact area to the current collector area may preferably be in the range of 1:1500-1500:1, ideally in the range of 1:200-200:1, more preferably in the range of 150:1-50:1. The maximum deflection of the spring contact in the grounded state is preferably at least the depth of the light receiving space. The ratio of the height above the receiving space to the height of the contact element may be in the range of 100:1-1:1, preferably 1.5:1.

[0021] In a preferred embodiment of the measurement arrangement, each measurement body half has four feedthroughs, four holding elements and four contact elements, one of the electrical contact elements being arranged in the center, the other three contact elements being arranged on a circular path around the central contact element and the other three contact elements being offset on the circular path by 120° each. Such an arrangement of the contact elements on the current collector leads to a particularly uniform mechanical load on the battery cell. As a result, a flat structure of the battery cell is obtained with close contact between the solid electrolyte and the electrodes. Furthermore, this thermal structure allows the temperature gradient in the battery cell to be as small as possible. Such a design of the electrode inserts allows the measurement of up to four different electrical signals of a four-electrode cell. For example, lithium metal serves as counter and reference electrode, and at the same time the potential can be measured against a freely selectable reference electrode, such as gold.

[0022] In a further preferred embodiment of the measurement arrangement, the electrical contact elements of the lower and upper halves of the cell body can be positioned offset from each other by 60° during the measurement. In the assembled state, a cell design in which the electrical contacts of the lower and upper halves of the cell body are offset from each other has proven effective. This increases the contact area for heat transfer and allows the sample to heat up faster. It also helps to distribute the pressure on the sample.

[0023] In a preferred embodiment of the measurement arrangement, the current collector can have a recess at the point where the current collector is electrically contacted by the contact element. The recess is filled by the contact element towards the measurement. This design results in a flat alignment of the battery cell assembly with as uniform a mechanical load as possible during the measurement. Furthermore, this design allows to improve the hermeticity of the assembly, which contributes to reducing measurement failures due to leakage.

[0024] In a preferred embodiment of the measuring arrangement, one current collector may have a cylindrical shape and the other current collector may have a cylindrical shape with rounded edges. Preferably, at least one of the electrode inserts may have rounded edges to allow a more flexible contact of the current collector with the inserted electrode. The latter is particularly relevant for ceramic electrodes, where the creation of a flat surface for this type of electrode is technically difficult.

[0025] In a preferred feature of the measurement arrangement, each of the current collectors may have a recess towards the inside of the receiving space, the recess being adapted to receive an electrode of a solid electrolyte battery. By integrating one or more electrodes of the battery cell into the current collector, a particularly flat arrangement of the solid electrolyte and a particularly efficient and uniform contact of the solid electrolyte by the current collector may be provided. This setup is mechanically balanced and also provides a symmetrical temperature behavior. This design makes it possible to reduce the number of measurement interruptions due to poor contact of the solid electrolyte or leakage in the cell.

[0026] The spring constant should be greater than or equal to 0.05 N and less than or equal to 50 N. These ranges of spring constants have proven particularly suitable for providing a sufficient mechanical connection of the current collector to the contact element. The spring constant is not too high to prevent breakage of the current collector, and is not too low to ensure sufficient mechanical contact even if the battery cell expands or contracts due to heat.

[0027] The use of the measurement arrangement according to the invention for determining the electrical properties of secondary alkaline solid electrolyte battery cells is also according to the invention. The setup according to the invention can be used to flexibly and reliably measure a wide variety of solid electrolyte battery cells, for example with a three-electrode structure. The proportion of measurement artefacts resulting from mechanical damage of the battery cell or from insufficient contact between the solid electrolyte and the current collector can be significantly reduced by this setup. Moreover, it can be easily assembled without additional consumables such as polymer membranes. Furthermore, the above-mentioned advantages of the measurement setup according to the invention are explicitly mentioned: Further advantages and advantageous embodiments of the subject matter according to the invention are shown by the drawings and explained in the following description, it being noted that the drawings are illustrative and do not limit the invention in any way. [Brief description of the drawings]

[0028] [Figure 1] FIG. 1 is a schematic perspective view showing one embodiment of a cell body half (lower part) according to the present invention. [Diagram 2] FIG. 2 is a schematic plan view showing one embodiment of a cell body half (lower part) according to the present invention. [Diagram 3] FIG. 3 is a schematic bottom view showing one embodiment of a cell body half (lower part) according to the present invention. [Figure 4] FIG. 4 is a schematic perspective view showing one embodiment of a cell body half (upper part) according to the present invention. [Diagram 5] FIG. 5 is a schematic plan view showing one embodiment of a cell body half (upper part) according to the present invention. [Figure 6] FIG. 6 is a schematic bottom view showing one embodiment of a cell body half (upper part) according to the present invention. [Figure 7] FIG. 7 is a schematic cross-sectional view showing one embodiment of a cell body half (lower part) according to the present invention. [Figure 8] FIG. 8 is a schematic cross-sectional view showing one embodiment of a cell body half (upper part) according to the present invention. [Figure 9] FIG. 9 is a schematic plan view of one embodiment of a cell body half having four different contact elements according to the present invention. [Figure 10] FIG. 10 is a schematic plan view (lower part) showing one embodiment of a current collecting device according to the present invention. [Figure 11] FIG. 11 is a schematic plan view (lower part) showing one embodiment of a current collector according to the present invention in which an electrode layer is embedded. [Figure 12] FIG. 12 is a schematic plan view (upper part) showing one embodiment of a current collecting device according to the present invention. [Figure 13] FIG. 13 is a schematic cross-sectional view (top) of a current collector according to the present invention. [Figure 14] FIG. 14 is a schematic cross-sectional view of a current collector according to the present invention (lower part). [Figure 15] FIG. 15 is a schematic cross-sectional view of a current collector according to the present invention with embedded electrode layers (bottom). [Figure 16] FIG. 16 is a schematic cross-sectional view of a current collector according to the invention for a four electrode insert. [Figure 17] FIG. 17 shows the voltage as a function of specific capacitance measured on an NMC622 / Li half cell. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0029] FIG. 1 is a schematic perspective view of a cell body half 1. The depicted cell body half 1 may for example be referred to as the lower cell body half 1. The actual cell body 2 may be made of plastic, such as PEEK. The cell body half 1 is designed to be combined with another cell body half 1. For this purpose, the cell body half 1 has a bore 5 by which both cell body halves 1 can be connected to each other. For example, a screw can be guided through the hole 5, through which both cell body halves 1 can be screwed together. The depicted cell body half 1 also has an optional groove 6, which can accommodate an O-ring. Furthermore, the figure shows contact elements 4 and a receiving space 3 in which a battery cell can be placed for the actual measurement.

[0030] 2 is a plan view of a half cell body 1 according to the invention. The actual cell body 2 with the holes 5, the optional recesses for O-rings 6, the individual contact elements 4, in this example four individual contact elements 4, and the receiving space 3 for the actual battery cells are shown.

[0031] FIG. 3 shows a bottom view of a half cell body 1 according to the invention. In this view, the actual cell body 2, three holes for connecting the two half cell bodies 1 and a holding element 7 are shown. The holding element 7 may be a mechanical connection to the actual cell body 2, for example in the form of a screw. The holding element 7 may be, for example, a stainless steel screw leading from the underside of the half cell body 1 into the receiving space. At its end inside the cell, the stainless steel screw has a recess for a spring contact (not shown). This allows for a simple and flexible replacement of damaged spring contacts when unscrewing or for the spring contacts to be used with other spring constants to change the contact pressure in the cell.

[0032] The retaining element 7 is held gas-tight towards the outside by an O-seal ring (located in a sealing ring groove) which is pressed against the body by the screw head. At the same time, a hole with a diameter of 4 mm can lead to the screw head. The retaining element 7 can be electrically contacted from below with a conventional 4 mm laboratory plug. The head of the retaining member can have any shape, but may also be provided with a groove for a screwdriver. Due to the small number of parts, it can be assembled very easily both under normal conditions and in a glove box with limited space for movement.

[0033] FIG. 4 shows a further embodiment of a cell body half 1 according to the invention. This cell body half 1 can be regarded as, for example, the upper cell body half 1 of an arrangement of two cell body half 1. Like the lower cell body half 1, the upper cell body half 1 has a hole 5, which is used to connect the two cell body half 1. The cell body 2 itself is made of a plastic material. The individual contact elements 4 are shown at the tips of the holding elements (not shown). Also in this embodiment, the upper cell body half 1 is shown with four contact elements 4 by way of example. However, different cell body halves 1 can have a different number of contact elements 4 and thus holding elements 7. It is also possible, for example, that the upper cell body half 1 has only one contact element 4. Like the lower cell body half 1, the upper cell body half 1 has a recess 3 in which the actual measuring cell is placed during the measurement.

[0034] 5 is a plan view of a cell body half 1 according to the invention, in this case the upper cell body half 1. In this plan view one can see the actual cell body 2, the hole 5, the receiving space 3 and the contact elements 4. In this embodiment there are four individual contact elements 4 in the receiving space 3. It can also be seen that each cell body half 1 does not necessarily have to have a sealing ring groove.

[0035] 6 shows a view from below of a possible design of an upper half cell body 1 according to the invention. The actual cell body 2 is visible, in which four holding elements 7 are embedded. Furthermore, the view also shows the holes 5 through which the two half cell bodies 1 are connected to each other by means of screws.

[0036] FIG. 7 is a cross-sectional view of one embodiment of a lower cell body half 1 according to the invention. It can be seen that a retaining element 7 extends through the cell body 2. The retaining element 7 is hollow and can accommodate, for example, a plug for electrical contact. At each tip of the retaining element 7 a contact element (not shown) can be attached. Together with the contact element, the retaining element 7 connects one side of the cell body to the receiving space 3. Furthermore, the actual cell body 2 is provided with a recess 6, which serves to receive a sealant. Furthermore, a hole 5 is shown, through which a screw can connect the two halves of the cell body.

[0037] FIG. 8 is a cross-sectional view of one embodiment of an upper cell body half 1 according to the invention. Retaining elements 7 extending through the cell body 2 can be seen. The retaining elements 7 are hollow and can accommodate, for example, plugs for making electrical contacts. At each tip of the retaining elements 7 a contact element (not shown) can be attached. The retaining elements 7 together with the contact elements connect one side of the cell body to the receiving space 3. Furthermore, the actual cell body 2 is provided with a recess 6, which can serve to receive a seal. Furthermore, holes 5 are shown through which a screw can connect the two halves of the cell body.

[0038] 9 shows a plan view of an embodiment of a receptacle 3 of a cell body half 1 according to the invention with four different contact elements 4, e.g. made of copper, platinum, nickel or iron, which serve as measuring points during assembly of the cells one by one or simultaneously. Compared to microcontacts, which use a spring to press against the sample over a small area, the pressure on the sample is distributed more evenly, which reduces the risk of short circuits.

[0039] Figures 10 and 11 are schematic diagrams of a current collector 8 (bottom) according to the invention. The current collector 8 is annular and has a minimum size (e.g. 0.1 mm) smaller than the diameter of the receiving space 3 so that it can slide easily in the receiving space 3. This represents a major advantage of this design. It allows a defined cell design so that any current collector 8 of different structures can be used. Figure 10 shows that the current collector 8 can have a recess 9 on its surface, which recess 9 can be filled with the electrode material of the battery cell to be measured. In Figure 10, the current collector 8 is shown without further filling with electrode material. In Figure 11, the same embodiment is shown with the recess of the current collector 8 filled with, for example, lithium metal 10. This results in two concentric regions on the current collector, separated by a non-conductive central region.

[0040] 12 is a plan view (top) of a further embodiment of a current collector 8 according to the present invention. This current collector 8 does not have any recesses on its surface. The inner circle of the current collector 8 indicates that this current collector is made of two different materials. For example, the inner area may be made of stainless steel and the outer area of ​​a non-conductive plastic material.

[0041] 13 and 14 show possible designs of the current collector 8 according to the invention in cross-section. FIG. 13 shows an embodiment for the upper current collector 8, for example. This current collector 8 does not have any recesses on its surface and is not designed to receive the electrode material of the battery cell to be measured. The inner part 11 is made of stainless steel, while the two outer parts 12 may be made of a plastic material. The upper current collector 8 has a cylindrical shape, the corners of which are rounded. FIG. 14 shows a cross-section of a possible lower current collector 8. Here, the lower current collector 8 may be a cylinder with straight edges. This serves to ensure that the lower current collector 8 is pressed on one axis by the spring contact, while the upper current collector 8 has more flexibility in the housing due to the rounded edges and can be pressed more uniformly against any sample surface, for example by the four contact elements 4. This is important, for example, in the case of brittle ceramic solid electrolyte disks or pressed sulfide tablets, to allow the advantage of reproducible internal pressure that is not dependent on an external screw connection. This is the case, for example, with Swagelok's T-cells. In this context, it is possible to swap these current collectors 8 up or down, or to combine two rounded or two non-rounded current collectors 8.

[0042] 14 and 15 show possible embodiments of the lower current collector 8, which has a recess on its surface. In the recess of the current collector 8, a part of the electrode of the battery cell can be embedded. Such an electrode part results in a flat surface on the current collector 8. Furthermore, it can be seen from the figures that the current collector 8 has a cylindrical shape and is made of different materials. In this respect, the current collector 8 can consist of areas made of stainless steel 11 or areas made of plastic material 12. By the selection of the conductive areas, contact to the contact elements 4 (not shown) is established. This design of the current collector 8 is so flexible that in principle it can also be used as a current collector for other types of cells, such as Swagelok T-cells. These are an improvement on the basic principle of these T-cells, since the reference electrode no longer needs to be mounted at a right angle. Moreover, the same advantages in principle as the structure according to the invention arise, such as an improved pressure distribution.

[0043] 16 shows a further embodiment of a current collector 8 according to the invention, which is suitable for example for measuring battery cells with a structure having four contact elements 4 (not shown).

[0044] FIG. 17 shows the measurement curves obtained using the cell design according to the present invention. It shows the voltage behavior of a lithium secondary battery cell as a function of the specific capacitance in a cycling experiment. The battery cell has the following structure: The cell body parts of FIG. 1 and FIG. 3 were used, with an O-seal ring and a gold-plated copper spring contact with a spring constant of 1.5 N. The reference electrode and the negative electrode were used as a function of the specific capacitance in a cycling experiment. The reference electrode and the negative electrode were made of lithium and embedded in a current collector as shown in FIG. 11. The active material of the positive electrode was NMC622, which was in electrical contact with the current collector as shown in FIG. 12. The separator and the solid electrolyte were PEO-LiTFSI. The cell had a current of 15 mAg -1 The measurement was performed electrostatically with a charge and discharge current of 1000 mA. The measurements were highly reproducible and the rate of measurement failure was extremely low.

Claims

1. A measuring device for a secondary alkaline solid electrolyte battery, comprising: The measuring device includes at least two electrically non-conductive cell body halves (1), both cell body halves (1) having at least one feedthrough and one cell body half (1) having at least three feedthroughs, each of both cell body halves (1) having a recess on its inside, the recess forming a receiving space (3) for receiving a solid electrolyte battery cell comprising at least an anode, a cathode and a solid electrolyte, each of said feedthroughs extending from the outside of said cell body halves (1) towards the receiving space (3); an electrically conductive retaining element (7) for each feed-through, said retaining element (7) being equipped so as to be mechanically connectable to the respective cell body half (1); an electrical contact element (4) provided on each holding element (7), the electrical contact element (4) being attachable to the holding element (7) towards the receiving space (3) and adapted to change its length depending on the force acting on the electrical contact element (4); two flat current conductors (8) having conductive areas (11) and non-conductive areas (12), at least one of said current conductors (8) being equipped to form at least three separate conductive connections between at least three of said electrical contact elements (4) and one electrode of said solid electrolyte battery cell, The mechanical force of the electrical contact element (4) acts on the solid electrolyte battery cell via the current conductor (8).

2. 2. Measuring device according to claim 1, characterized in that the receiving space (3) is rotationally symmetrical.

3. 3. Measuring device according to claim 1 or 2, characterized in that the different electrical contact elements (4) of each cell body half (1) consist of different metals.

4. 4. The measuring device according to claim 1, wherein the electrical contact elements (4) are spring contacts and the arrangement of the electrical contact elements (4) is rotationally symmetric towards the receiving space.

5. 5. The measuring device according to claim 4, characterized in that each cell body half (1) has four of the feedthroughs, four of the retaining elements (7) and four of the electrical contact elements (4), one of the four electrical contact elements (4) being centrally arranged and the remaining three of the electrical contact elements (4) being arranged on a circular path around the central electrical contact element (4), the remaining three of the electrical contact elements (4) being offset by 120° on the circular path.

6. 6. The measuring device according to claim 5, characterized in that the electrical contact elements (4) of the lower and upper cell body halves (1) are arranged offset by 60° to each other during measurement.

7. 7. Measuring device according to any one of the preceding claims, characterized in that the current conductor (8) has a recess at the point where the current conductor (8) electrically contacts the electrical contact element (4).

8. 8. Measuring device according to any one of the preceding claims, characterized in that one of the current conductors (8) has a cylindrical shape and the other current conductor (8) has a cylindrical shape with rounded edges.

9. 9. The measuring device according to claim 1, wherein each of the current conductors (8) has a recess facing inwardly into the receiving space (3), the recess being adjusted to receive the one electrode of the solid electrolyte battery cell.

10. 7. A measuring device according to claim 4, wherein the spring contact has a spring constant of 0.05N to 50N.

11. Use of a measuring device according to any one of claims 1 to 10 for determining the electrical properties of a secondary alkaline solid electrolyte battery cell.

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