Lithium-ion cell for an energy storage device of a motor vehicle, method for producing

Abstract

Lithium-ion cell (1) for an energy storage device of a motor vehicle, with at least one anode (3), at least one cathode (4), an electrolyte and a separator (7) arranged between the cathode (4) and the anode (3) in the electrolyte, and with a reference electrode (8) made of lithium titanate for determining a voltage potential of the lithium-ion cell (1), wherein the reference electrode (8) is pressed from lithium titanate powder, characterized in that the reference electrode (8) is pressed directly onto the separator (7).

Description

[0001] The invention relates to a lithium-ion cell for an energy storage device of a motor vehicle, in particular a traction storage device, having at least one anode, at least one cathode, an electrolyte and a separator arranged between the cathode and the anode in the electrolyte, and having a reference electrode for determining a voltage potential of the lithium-ion cell.

[0002] Furthermore, the invention relates to a method for producing such a lithium-ion cell for an energy storage device of a motor vehicle, wherein an anode, a cathode, an electrolyte and a separator between the anode and the cathode are provided in the electrolyte.

[0003] Lithium-ion cells and manufacturing processes of the type mentioned above are known from the prior art. In conventional lithium-ion cells, the anode and cathode are usually electrically connected to each other by an electrolyte, which is usually a non-aqueous electrolyte solution. The separator arranged between the anode and cathode allows lithium ions to migrate freely through the electrolyte between the two electrodes, i.e., the anode and cathode. By adding a reference electrode as a third electrode, it is possible to determine the half-cell potential of the anode and cathode separately, allowing a detailed statement to be made about the state of charge and aging of the cell. Such reference electrodes are usually made of lithium metal, which, however, has poor long-term stability and is less suitable for impedance spectroscopy measurements. It is also known from "F. La Mantia, CD Wessells, HDDeshazer, Yi Cui: "Reliable reference electrodes for lithium-ion batteries. Electrochemistry Communications 31 (2013) 141-144", it is known to produce reference electrodes from lithium iron phosphate and lithium titanium oxide, wherein the reference electrodes are applied in a point-like manner. From "J. Costard, M. Ender, M. Weiss, E. Ivers-Tiffée: Three-Electrode Setups for Lithium-Ion Batteries. Journal of The Electrochemical Society, 164 (2) A80-A87 (2017)", it is also known to provide a reference electrode by coating a metal grid. The published patent application DE 102017 119 602 A1 discloses a lithium-ion cell with a reference electrode made of lithium titanate, wherein the reference electrode is manufactured using a screen printing process or a spray coating process. Such a reference electrode is also disclosed in the published patent application US 2013 / 0323542 A1.German Patent Application DE 10 2014 001 260 A1 discloses a reference electrode made of gold, platinum, carbon, or conductive organic polymers using a printing process. German Patent Application DE 10 2014 206 990 A1 discloses an electrochemical energy storage cell with a reference electrode element made of lithium titanate, which is pressed onto a plastic film winding core.

[0004] The invention is based on the object of creating an improved lithium-ion cell which can be used for impedance spectroscopic purposes and which also exhibits little aging.

[0005] The object underlying the invention is achieved by a lithium-ion cell having the features of claim 1. This has the advantage that the lithium-ion cell has a long service life overall, particularly with respect to the reference electrode used, and that impedance spectroscopic measurements, particularly for determining the aging state of the lithium-ion cell, can be carried out reliably and over a long period of time. According to the invention, this is achieved by making the reference electrode from lithium titanate. This results in advantageous suitability for impedance spectroscopic measurements and a robust reference electrode, which ensures a long service life.

[0006] According to the invention, the reference electrode is pressed from lithium titanate powder. This allows for simple and cost-effective production of the reference electrode, which then leads to the aforementioned advantages.

[0007] According to the invention, the reference electrode is pressed directly onto the separator. This ensures easy integration of the reference electrode into the lithium-ion cell.

[0008] The method according to the invention with the features of claim 2 is characterized in that the reference electrode is made of lithium titanate. This results in the advantages already mentioned.

[0009] According to the invention, the reference electrode is produced by compressing lithium titanate powder. Particularly preferably, the reference electrode is produced by longitudinally displacing a pressing die or pin.

[0010] Furthermore, the invention provides that the reference electrode is pressed directly onto the separator.

[0011] This results in the aforementioned advantages. Further advantages and preferred features and combinations of features emerge in particular from the above description and from the claims. The invention will be explained in more detail below with reference to the drawings. These show: Fig. 1A and B a lithium-ion cell in a side view and in a top view, Fig. 2 a device for producing the lithium-ion cell and Fig. 3 a method for producing the lithium-ion cell.

[0012] Fig. 1A and Fig. 1B show a lithium-ion cell 1 for an energy storage device of a motor vehicle, which is used in particular as a traction battery for the motor vehicle. The lithium-ion cell 1 is in Fig. 1A in a side view and in Fig. 1B shows a plan view of the terminals. The lithium-ion cell 1 has a housing 2 in which an anode 3 and a cathode 4 are arranged, of which external terminals 5 and 6 protrude from the housing 2 for electrical contact. Also present in the housing 2 is an electrolyte, preferably a non-aqueous electrolyte solution, as well as a separator 7, indicated by a dashed line, which lies between the anode 3 and the cathode 4.

[0013] The lithium-ion cell 1 also has a reference electrode 8, which has a terminal 9 protruding from the housing 2 for electrical contact. The reference electrode 8 is made of lithium titanate powder.

[0014] Fig. Figure 2 shows a device 10 for producing the reference electrode 8 of the lithium-ion cell 1. The device 10 has a press die 11, which has a plastic sleeve 12 and a metal bolt 13 connected thereto. The metal bolt 13 has a thread 14 at one free end and is inserted into the plastic sleeve 12 at its other end. The plastic sleeve 12 has, at its end facing away from the thread 14, a closed bottom 15 that serves as a press die. The metal bolt 13 acts like a spindle of a spindle drive and is accordingly coupled at its free end to the thread 14 with a spindle nut 16. By rotating the spindle nut 16, the press die 11 is displaceable in its longitudinal direction, as indicated by an arrow 17 in Fig. 2 is displayed.

[0015] Lithium titanate powder 18 is arranged between the press die 11 and the separator 7, in particular before the separator 7 is introduced into the housing 2, preferably in a depression or recess 19 of a mask 20 placed on the separator 7, and is then pressed against the separator 7 by the press die 11, so that the reference electrode 8 made of lithium titanate is obtained.

[0016] Fig. Figure 3 summarizes the manufacturing process again in a flowchart. In a first step S1, the lithium-ion cell 1 is prepared with cathode 4, anode 3, and electrolyte. Optionally, the anode 3 and cathode are provided on an electrode coil, which has, as a base element, a strip forming the separator 7, on which the cathode 4 and anode 3 are arranged. Before this coil is introduced into the housing 2, it is fed to the device 10 in a step S2, and the reference electrode 8 is produced.

[0017] Subsequently, in a step S3, the coil is introduced together with the reference electrode 8 into the housing 2 in such a way that the reference electrode 8 is exposed from the outside, as in Fig.1A and described accordingly. Thus, in step S4, the lithium-ion cell 1 is finally obtained with an advantageous reference electrode 8 made of lithium titanate, which ensures a long service life and advantageous properties in an impedance spectroscopic measurement. List of reference symbols 1 lithium-ion cell 2 housings 3 Anode 4 Cathode 5 Connection 6 Connection 7 Separator 8 Reference electrode 9 Connection 10 Device 11 press stamps 12 plastic sleeve 13 metal bolts 14 threads 15 Floor 16 spindle nut 17 Arrow 18 Lithium titanate powder 18 recess 20 Mask

Claims

[1] Lithium-ion cell (1) for an energy storage device of a motor vehicle, with at least one anode (3), at least one cathode (4), an electrolyte and a separator (7) arranged between the cathode (4) and the anode (3) in the electrolyte, and with a reference electrode (8) made of lithium titanate for determining a voltage potential of the lithium-ion cell (1), wherein the reference electrode (8) is pressed from lithium titanate powder, characterized by that the reference electrode (8) is pressed directly onto the separator (7). [2] Method for producing a lithium-ion cell (1) for an energy storage device of a motor vehicle, comprising the following steps: - providing an anode (3), a cathode (4), an electrolyte and a separator (7) arranged / to be arranged between the anode (3) and the cathode (4), - providing a reference electrode (8) made of lithium titanate, wherein the reference electrode (8) is produced by pressing lithium titanate powder, characterized by that the reference electrode (8) is pressed directly onto the separator (7).

Images