Analysis of electrochemical energy storage devices

Abstract

Analysis of Electrochemical Energy Storage Devices This description relates to an electronic circuit (101) comprising: first (103A) and second (103B) connecting elements for connection, respectively, to first (105A) and second (105B) conduction terminals of an electrochemical energy storage device (107); third (113A) and fourth (113B) connecting elements for connection to a nuclear magnetic resonance spectrometer (305); and a radio frequency matching and tuning circuit (119) connecting the third (113A) and fourth (113B) connecting elements to the first (103A) and second (103B) connecting elements. Figure for the abstract: Fig. 1

Description

Title of the invention: Analysis of electrochemical energy storage devices. Technical field

[0001] The present description relates generally to the analysis of electrochemical energy storage devices such as, for example, commercially available electrochemical battery cells. Previous technique

[0002] The development of high-performance electrochemical energy storage technologies depends on an understanding of the molecular energy storage mechanisms occurring in commercial devices. Furthermore, the accurate assessment of the state of charge (SoC) and state of health (SoH) of commercial batteries is a problem that has not yet been satisfactorily solved.

[0003] More specifically, in industrial and scientific devices, battery cell analysis is performed using electrochemical and physical processes based on measurements of charge capacity, voltage, internal resistance, state of charge, self-discharge rate, temperature, and several other more complex parameters. Among these processes, potentiometry, voltammetry, amperometry, impedance spectroscopy, electrogravimetry, and electrochemical noise analysis are the most commonly used electrochemical techniques. Due to various limitations of these processes, the reliability of state of charge and health assessments is often unsatisfactory. Furthermore, some of these techniques are time-consuming or involve destructive procedures and are therefore not suitable for high-throughput analysis of commercially available cells.

[0004] Furthermore, the risk of battery malfunction is often due to the presence of degraded or poor-quality electrochemical materials in individual battery cells. In the case of lithium-ion (Li-ion) batteries, flammable or heat-generating components of the cells cause risks of thermal runaway due to metallic lithium (Li) dendrites induced by violations of operating conditions, such as overcharging, and mechanical defects. Although the presence of metallic lithium in commercially available pouch batteries can be reliably detected by ex situ, or "post-mortem," measurements, rapid and non-destructive solutions to this problem are scarce and have not yet been developed for industrial applications.

[0005] Nuclear magnetic resonance (NMR) spectroscopy is very sensitive to local environments and the dynamics of many electro- elements Chemically relevant, thus providing useful insights into electrochemical phenomena occurring in battery cells. NMR techniques have been used extensively in studies of energetic materials and model electrochemical devices. NMR uses radio-frequency (RF) fields to induce transitions between Zeeman energy levels of atomic nuclei. In response, the nuclei emit an RF radiation spectrum that can be detected by a probe of an NMR spectrometer.

[0006] The most common battery cells used in portable electronic devices and electric vehicles are based on so-called "jelly roll" (cylindrical or flat winding) and "single stacked electrode" architectures encapsulated in metallic (aluminum or steel) casings. Electrochemical materials (cathode, anode, and electrolyte) are confined between conductive layers of current collectors, for example, copper and aluminum foils. The metallic casing and current collectors are the main obstacle to in-situ battery analysis using NMR and magnetic resonance imaging (MRI), because the penetration of an RF field through these metallic structures is negligible.

[0007] In a conventional NMR experiment, a sample is placed inside an RF resonator (e.g., birdcage, solenoid, saddle, or other RF structures) and irradiated with a pulsed RF field to produce a time evolution of a transverse nuclear magnetization, called a free precession (FID) signal. At the end of the RF excitation pulse, the resonator is switched to an acquisition mode, and detection of the FID signal begins, followed by a magnetization recovery period. The signal-to-noise ratio (SNR) of the NMR data can be improved by repeated accumulation of FID signals. However, in battery cells, the electrochemical materials of interest are screened by the external conductive casing and current collector layers, making RF excitation with NMR resonators impossible.

[0008] As a result, NMR analysis of electrochemical materials in commercial cells is commonly performed ex situ, which involves various destructive procedures (e.g., cutting to open external casings and scraping materials from current collectors).

[0009] The article by EG Sorte et al. entitled “In Situ Stripline Electrochemical RMN for Batteries” ChemElectroChem, vol. 5, issue 17, 2018, pp. 2336-2340 describes the introduction of a stripline electrochemical RMN probe into a commercially available pocket battery to partially circumvent the RF screening problem. However, this approach requires inconvenient destructive handling of the cell casing, followed by complex electrolyte filling and sealing procedures.

[0010] The article by S. Benders et al. entitled “Nuclear magnetic resonance spectroscopy of rechargeable pouch cell batteries: beating the skin depth by excitation and detection via the casing,” Sci. Rep. 10, 2020, art. 13781, describes the possibility of exciting and detecting 7Li NMR signals in a pouch cell using capacitive coupling between the conductive cell casing and external copper pads. However, the signal-to-noise ratio (SNR) of such a contactless approach is too low for routine applications.

[0011] The article by BJ Walder et al. entitled “NMR spectroscopy of coin cell batteries with metal casings”, Sci. Adv. 7, 2021, vol. 7, issue 37, describes the use of an RF clipping effect to show that the RF field can reach interesting electrochemical layers inside a commercial coin cell battery when the metal casing of the cell is incomplete. However, this approach is not applicable to prismatic and cylindrical coin cell batteries because these cells are completely contained within conductive casings. Moreover, coin cell batteries are a miniaturized, impractical, low-capacity, and low-current approximation of actual battery cells.

[0012] The article by K. Romanenko and N. Avdievich entitled “Unilateral RF sensors based on parallel-plate architecture for improved surface-scan MRI analysis of commercial pouch cells,” J. Magn. Reson. Open 18, 2024, vol. 18, 100141, describes a surface-scan MRI technique, which is an approach based on the so-called reverse MRI concept. The method measures the magnetic field perturbations induced by the cell placed in a uniform magnetic field. The magnetic field perturbation patterns measurable outside the cell contain information about the magnetic susceptibility distribution and charge transfer processes within the cell.However, although surface scanning MRI is sensitive to variations in magnetism, current density, and other types of defects in cells, it does not provide direct information regarding the local chemical environment of charge carriers and the structure of charge storage sites.

[0013] Under scientific research conditions, in situ and operating NMR spectroscopy analysis is performed on miniaturized prototype battery cells, for example, "flat" batteries, which are not suitable for practical applications. These NMR-compatible cells have charge capacities and current levels several times lower than those of commercially available cells. Other methods suitable for in situ analysis of battery cells (for example, X-ray diffraction, XRD) do not provide the same level of statistical detail as NMR and MRI. Summary of the invention

[0014] There is a need for non-destructive (in situ) analytical tools enabling rapid analysis of electrochemical energy storage devices. In particular, it would be desirable to have processes and devices suitable for the fundamental in situ analysis of structural and molecular dynamics in commercially available electrochemical battery cell materials.

[0015] For this purpose, an embodiment provides an electronic circuit comprising: first and second connection elements intended to be connected respectively to first and second conduction terminals of an electrochemical energy storage device; the third and fourth connecting elements intended to be linked to a nuclear magnetic resonance spectrometer; and a radio frequency 'adaptation and adjustment' circuit linking the third and fourth connection elements to the first and second connection elements.

[0016] According to one embodiment, the radio frequency adaptation and adjustment circuit comprises: a first inductive element having a first terminal connected, preferably connected, to the first connection element; a second inductive element having a first terminal connected, preferably connected, to the second connection element; a first capacitive element having a first terminal connected, preferably connected, to a second terminal of the first inductive element and a second terminal connected, preferably connected, to the third connection element; a second capacitive element having a first terminal connected, preferably connected, to a second terminal of the second inductive element and a second terminal connected, preferably connected, to the fourth connection element; a third capacitive element connecting the second terminals of the first and second inductive elements.

[0017] According to one embodiment, the first and second inductive elements are inductors and the first, second and third capacitive elements are capacitors.

[0018] According to one embodiment, the first and second inductive elements have the same inductance and the first and second capacitive elements have the same first capacitance different from a second capacitance of the third capacitive element.

[0019] According to one embodiment, the circuit has a resonance frequency equal to approximately a Larmor frequency of an atomic nucleus chosen from: Li, Na, P, Cu, Cu, 59Co, 'H, 19F, 27Al, 55Mn, 6Li and 39K.

[0020] One embodiment provides a system comprising: the circuit as described previously; and a nuclear magnetic resonance spectrometer comprising: an RF transmit / receive channel connected to the third and fourth connection elements of the circuit; and a magnet 'presenting a cavity compatible with the dimensions of the system.

[0021] According to one embodiment, the magnet has a hollow cylindrical or rectangular cavity arranged vertically or horizontally.

[0022] According to one embodiment, the system further comprises a radio frequency sensor intended to operate at a Larmor frequency of either the proton 'H, or isotopes of fluorine 19F.

[0023] According to one embodiment, the system further comprises a battery cell having first and second conduction terminals connected respectively to the first and second connection elements of the circuit.

[0024] According to one embodiment, the battery cell is a lithium iron phosphate pocket battery cell.

[0025] According to one embodiment, the battery cell is a lithium cobalt oxide pocket battery cell.

[0026] According to one embodiment, the battery cell is part of a battery of a consumer electronic device or of a battery of an electric vehicle.

[0027] One embodiment provides for a method of operating the system as described above, the method comprising the following successive steps: a) applying to the battery cell, using the magnet, a polarizing magnetic field; b) 'apply to the third and fourth connection elements of the circuit, using the nuclear magnetic resonance spectrometer, 'an alternating voltage pulse intended to produce an oscillating magnetic field in the battery cell; and c) ' to acquire, using the nuclear magnetic resonance spectrometer, a representative NMR spectrum of electrochemical materials present in the cell.

[0028] According to one embodiment, the method further comprises, in step c), an acquisition of MRI data representative of spatial distributions of a magnetic susceptibility and / or a current density in the battery cell which depend on the state of charge.

[0029] According to one embodiment, the method further comprises, after step c), a step d) of determining a state of charge of the battery cell as a function of the spectrum acquired in step c).

[0030] According to one embodiment, the method further comprises, after step c), a step e) of determining an overload of the battery cell as a function of the spectrum acquired in step c). Brief description of the drawings

[0031] These features and advantages, as well as others, will be described in detail in the following description of particular embodiments, given by way of non-limiting example, in relation to the accompanying figures, among which:

[0032] [Fig.1] is a partial and schematic two-dimensional projection view of a system comprising an electronic circuit according to an embodiment;

[0033] [Fig.2] is an electrical diagram equivalent to the system of [Fig.1];

[0034] [Fig.3] is a partial and schematic perspective view of the system of [Fig.1] placed inside a magnet;

[0035] [Fig.4] is a density image illustrating an example of a nuclear magnetic resonance signal intensity distribution in a battery;

[0036] [Fig.5] is a diagram including examples of nuclear magnetic resonance spectra of different battery cells;

[0037] [Fig.6] is a diagram comprising examples of nuclear magnetic resonance spectra of a battery cell over a complete galvanostatic cycle;

[0038] [Fig.7] is a diagram including examples of nuclear magnetic resonance spectra of a battery cell subjected to overcharge followed by discharge;

[0039] [Fig.8] is a diagram including examples of nuclear magnetic resonance spectra of a battery cell at several stages of a galvanostatic charge;

[0040] [Fig. 9] is a diagram comprising examples of nuclear magnetic resonance spectra of a battery cell subjected to overcharging followed by discharging; and

[0041] [Fig.10] is a partial and schematic top view of a system comprising an electronic circuit according to one embodiment. Description of the implementation methods

[0042] The same elements have been designated by the same reference numerals in the different figures. In particular, the structural and / or functional elements common to the different embodiments may have the same reference numerals and may have identical structural, dimensional and material properties.

[0043] For the sake of clarity, only the steps and elements useful for understanding the described embodiments have been shown and detailed. In particular, the various applications of electrochemical energy storage devices have not been described. In detail, the embodiments described are compatible with all or most applications of electrochemical energy storage devices, with possible adaptations that are within the reach of a person skilled in the art on the basis of this description.

[0044] Unless otherwise specified, when referring to two elements connected between them, this means directly connected without intermediate elements other than conductors, and when referring to two elements connected (in English "coupled") to each other, this means that these two elements can be connected or linked via one or more other elements.

[0045] In the following description, when reference is made to absolute position qualifiers, such as the terms "front", "back", "top", "bottom", "left", "right", etc., or relative position qualifiers, such as the terms "above", "below", "superior", "lower", etc., or to orientation qualifiers, such as the terms "horizontal", "vertical", etc., reference is made, unless otherwise specified, to the orientation of the figures.

[0046] Unless otherwise specified, the expressions "approximately", "about", " "Significantly" and "of the order of" mean to within 10% or 10°, preferably to within 5% or 5°.

[0047] In the following description, "insulator" and "conductor" mean respectively electrically insulating and electrically conductive, unless otherwise specified.

[0048] Unless otherwise specified, "in contact with" means "in mechanical contact with".

[0049] Figure 1 is a partial, schematic, two-dimensional projection view of a system 100 comprising an electronic circuit 101 according to one embodiment. The electronic circuit 101 is, for example, a radio frequency (RF) circuit.

[0050] According to one embodiment, the circuit 101 comprises connecting elements 103A and 103B for connection to conduction terminals of an electrochemical energy storage device. In the example shown, the connecting elements 103A and 103B are connected respectively to conduction terminals 105A and 105B of an electrochemical battery cell 107. In this example, the conduction terminals 105A and 105B of the electrochemical battery cell 107 are the positive (+) and negative (-) conduction terminals of the cell 107, respectively. By way of example, the connecting elements 103A and 103B are solderless connectors.

[0051] In the example shown, the connecting element 103A is connected to one terminal of an inductive element 109A. Similarly, the connecting element 103B is connected to one terminal of another inductive element 109B. The inductive elements 109A and 109B, for example, have the same inductance LT, within manufacturing variations. By way of example, the inductive elements 109A and 109B are inductors, each comprising, for example, a coil.

[0052] Furthermore, in the illustrated example, another terminal of the inductive element 109A is connected to a terminal of a capacitive element 11IA. Similarly, another terminal of the inductive element 109B is connected to a terminal of a capacitive element 11IB. The capacitive elements 11IA and 11IB, for example, have the same capacitance CN, within manufacturing variations. By way of example, the capacitive elements 11A and 11IB are capacitors, each comprising an insulating region interposed between conductive regions.

[0053] In the example shown in [Fig. 1], another terminal of the capacitive element 11 IA is connected to a connecting element 113A. Similarly, another terminal of the capacitive element 11 IB is connected to a connecting element 113B. By way of example, the connecting elements 113A and 113B are part of the same connector 115, for example, a BNC connector. In this example, the connecting element 113A corresponds to an external conductive region of the BNC connector 115, intended to be connected to a concentric conductive screen of a coaxial cable (not shown in [Fig. 1]), and the connecting element 113B corresponds to an internal conductive region of the BNC connector 115, intended to be connected to a conductive core of a coaxial cable. However, this example is not exhaustive and connector 115 may, depending on the variant, be of a different type, for example an SMA or SMB connector.

[0054] According to one embodiment, the connecting elements 113A and 113B are intended to be connected to a nuclear magnetic resonance (NMR) spectrometer, not shown in [Fig.1], for example, using a coaxial cable connected to connector 115. By way of example, the connecting elements 113A and 113B are intended to be connected, more specifically, to a preamplifier of the NMR spectrometer.

[0055] In the example shown, the terminals of the inductive elements 109A and 109B connected to the capacitive elements 111A and 111B are connected together by another capacitive element 117. The capacitive element 117 has, for example, a capacitance CT. By way of example, the capacitive element 117 is a capacitor.

[0056] In the example shown, the connecting elements 103A and 103B, the inductive elements 109A and 109B, and the capacitive elements 11IA, 11IB, and 117 are part of a radio frequency (RF) matching and tuning circuit 119 that connects the connecting elements 113A and 113B to the connecting elements 103A and 103B. By way of example, the RF matching and tuning circuit 119 is formed on a printed circuit board (PCB). In this example, the connecting elements 103A, 103B, 113A, and 113B, the inductive elements 109A and 109B, and the capacitive elements 111A, 111B, and 117 are, for example, connected by conductive traces 121.

[0057] In the example shown, the inductive element 109A and the capacitive element 11IA are connected in series between the connecting elements 103A and 113A. In this example, The inductive element 109B and the capacitive element 11 IB are connected in series between the connecting elements 103B and 113B.

[0058] The battery cell 107 can be of any type (e.g., commercially available or custom-made pocket-sized, prismatic, cylindrical, and "flat") or of any capacity. The process is not limited by the cell's capacity: typical commercial cells have capacities in the range of approximately one to several hundred ampere-hours (Ah). In the example shown, the battery cell 107 has a capacitance CB, an inductance LB, and a resistance R. For example, the battery cell 107 is fully encapsulated in a conductive housing (e.g., aluminum). The battery cell 107 can be used in a portable consumer electronic device or in an electric vehicle.

[0059] In the orientation of [Fig.1], the system 100 comprises, for example, a section 100-1 providing rigid alignment and mechanical support to the battery cell 107 and a section 100-2 containing the RF circuit 101. For example, the two sections 100-1 and 100-2 of the system 100 may be mechanically connected or separate parts provided with compatible electrical connectors at the terminals of the cell 105A and 105B.

[0060] As will be described in detail later, the electronic circuit 101 and the battery cell 107 are intended to be placed inside a magnet of an NMR spectrometer (not shown in [Fig. 1]). The magnet is intended to apply a polarizing magnetic field B0 to the battery cell 107.

[0061] The electronic circuit 101 enables in-situ analysis of the battery cell 107 by NMR spectroscopy. More specifically, the electronic circuit 101 is designed to resonate at a selected Larmor frequency so that the battery cell 107 becomes part of a resonant structure. By connecting the RF circuit 101 directly to terminals 105A and 105B of the cell 107, an alternating current (AC) can be supplied by the current collectors of the cell 107, which is intended to produce an oscillating magnetic field (Bi) in an area occupied by layers of electrochemical materials such as a cathode, an anode, and an electrolyte. Supplying RF waves to the cell 107 allows for the excitation and detection of NMR signals without the need for NMR probes, since the cell itself acts as an RF probe.The RF in situ NMR circuit 101 is advantageously tunable over a wide Larmor frequency band, which can be used for in situ multinuclear NMR analyses of the battery cell 107.

[0062] In the example shown, the inductive elements 109A and 109B are variable inductive adjustment elements, the capacitive elements 111A and 111B are variable capacitive matching elements, and the capacitive element 117 is a variable capacitive adjustment element. The inductive elements 109A and 109B and the capacitive elements 111A and 11 IB and 117 are, for example, intended to set a resonance frequency v0 of the electronic circuit 101.

[0063] The resonance frequency v0 of the electronic circuit 101 is defined by the following equation:

[0064] [Math.l] 1 vo ——

[0065] In the preceding equation [Math 1], L is an inductance related to the inductance LT of each of the inductive elements 109A and 109B, to an inductance Lo of a loop 123 represented as a dashed rectangle in [Fig. 1], and to the inductance Lb of the battery cell 107. The loop 123 comprises the battery cell 107, the inductive elements 109A and 109B, the capacitive element 117, and conductive elements, such as connecting elements and conductive tracks, for connecting these elements. The total inductance L is defined by the following equation:

[0066] [Math.2] l = l b +l e

[0067] In the preceding equation [Math 2], LE is a total external inductance given by Le = Lo + 2Lt.

[0068] Furthermore, in the preceding equation [Math 1], C is a total capacity related to the capacitance CT of the capacitive element 117 and the capacitance CB of the battery cell 107. The total capacity C is given by the following equation:

[0069] [Math.3] _ cBcT CB+CT

[0070] The capacitance CB of the battery cell 107 is, for example, several times greater in amplitude than the capacitance CT of the capacitive element 117, for example, at least 10 times greater. Furthermore, the inductance LB of the battery cell 107 is, for example, several times smaller in amplitude than the total external inductance Le, for example, at least 100 times smaller. Consequently, the reactive elements (inductive and capacitive) of the circuit 101 make it easy to control the resonant frequency v0 over a wide range. As an example, the resonance frequency v0 can be set over a wide range of Larmor frequencies of nuclear isotopes that can be included within the 107 battery cell such as, for example, 7Li, 23Na, 31P, 63Cu, 65Cu, 59Co, 'H, 19F, 27Al, 55Mn, 6Li, 39K, etc.

[0071] By way of example, the CM capacitance of each of the capacitive elements 11 IA and 11 IB is set for an impedance match of 50 Q.

[0072] The position of the capacitive element 117 along the vertical axis, in the orientation of [Fig.1], determines an area of ​​the loop 123 and consequently controls the value of the inductance Lo. For example, the inductance Lo is adjusted by changing the length of the conductive tracks 121 connecting the inductive elements 109A and 109B to the connecting elements 103A and 103B and / or the length of the conductive tracks 121 connecting the capacitive element 117 to the inductive elements 109A and 109B.

[0073] In the example shown, the resonant frequency v0 of the electronic circuit 101 can be tuned to the Larmor frequency of the nucleus of interest by adjusting either the capacitance CT of the capacitive element 117, or the inductance LT of the inductive elements 109A and 109B, or the area of ​​the loop 123 by adjusting the vertical position of the capacitive element 117. The RF circuit 101 can be optimized by using magnetic inductors and capacitors with a high (i.e., low) quality factor Q. Depending on its resonant frequency v0, the electronic circuit 101 can have Q factors in the range of 40 to 120.

[0074] By way of example, at approximately 117 MHz, which corresponds to the Larmor frequency of the 7Li isotope at 7T, Q factors between 50 and 100 can be obtained. In this example, the values ​​of the reactive elements are approximately equal to: 25 nH for the total external inductance LE; 80 pF for the CT capacitance of the capacitive element 117; 3 nF for the CB capacitance of battery cell 107; 10 nH for the LB inductance of battery cell 107; 15 pF for the capacitance CM of each of the capacitive elements 11 IA and 11 IB; and 15 nH for the inductance Lo of loop 123.

[0075] In the battery cell 107, interesting electrochemical materials are, for example, screened by the external conductive casing and current collector layers, thus making external RF detection and excitation impossible. The RF circuit 101, which is connected to the conduction terminals 105A and 105B of the battery cell 107, is intended to resonate at the Larmor frequency of one of the nuclear isotopes in the battery cell 107. This advantageously allows the battery cell 107 to be used as part of a resonant structure, with the connecting elements 103A and 103B of the RF circuit 101 being connected to the conduction terminals 105A and 105B of the battery cell 107. RF waves thus propagate, for example, inside the cell 107 by means of folded sheets of the current collectors, and deflect the nuclear spin magnetizations of the anode, cathode and electrolyte materials from thermal equilibrium.

[0076] In order to perform an in situ analysis by NMR, a circuit of an external battery management system (BMS) (if initially provided) of cell 107 may be deactivated in order to improve NMR sensitivity.

[0077] The [Fig.2] is an equivalent electrical diagram of system 100 of the [Fig.1].

[0078] In the example shown, the circuit 101 includes the capacitive element 117 which connects two nodes 201A and 201B of the circuit 101. More specifically, the capacitive element 117 of capacitance CT has one terminal connected, preferably connected, to the node 201A and another terminal connected, preferably connected, to the node 201B. In the example shown, the circuit 101 further includes the capacitive elements 11 IA and 11 IB, each of capacitance CM, connecting nodes 201A and 201B respectively to two other nodes 203A and 203B of the circuit 101. In this example, the capacitive element 11 IA has one terminal connected, preferably connected, to node 201A and another terminal connected, preferably connected, to node 203A, and the capacitive element 11 IB has one terminal connected, preferably connected, to node 201B and another terminal connected, preferably connected, to node 203B.

[0079] In the example shown, the circuit 101 further comprises inductive elements 205A and 205B, each having an inductance equal to LE / 2. The inductive elements 205A and 205B connect nodes 201A and 201B respectively to the other nodes 207A and 207B of the circuit 101. The nodes 207A and 207B are, for example, equivalent to the connecting elements 103A and 103B of the circuit 101. In this example, the inductive element 205A has one terminal connected, preferably connected, to node 201A and another terminal connected, preferably connected, to node 207A, and the inductive element 205B has one terminal connected, preferably connected, to node 201B and another terminal connected, preferably connected, to node 207B.

[0080] In the example shown in [Fig.2], a source 209 of an alternating voltage V connects the nodes 203A and 203B of the RF circuit 101. The source 209 is, for example, part of an NMR spectrometer which is not described in detail in [Fig.2].

[0081] In this example, the battery cell 107 is equivalent to a capacitive element 211 of capacitance CB, an inductive element 213 of inductance LB and a resistive element 215 of resistance R associated in series between nodes 207A and 207B.

[0082] Fig. 3 is a partial and schematic perspective view of system 100 of Fig. 1 placed inside a magnet 301.

[0083] In the example shown, the magnet 301 is a horizontal bore magnet. More precisely, in this example, the magnet 301 has a hollow cylindrical shape extending laterally along a horizontal axis Ox. In the illustrated example, the magnet 301 produces the polarizing magnetic field Bo along the Ox axis. The magnet 301 can have any suitable structure, for example, with a horizontal or vertical bore, provided that it has a cavity that is either rectangular or cylindrical. The cavity of magnet 301 is compatible with the dimensions of system 100. For example, the magnet cavity has dimensions strictly larger than those of system 100, so that system 100 can be inserted inside the cavity.

[0084] By way of example, the magnet 301 is either a permanent magnet or a superconducting magnet, the magnetic fields produced by superconducting magnets being typically stronger than those produced by permanent magnets. Depending on the magnetism of the materials in the battery cell 107, permanent magnets may be preferred. For example, cylindrical cells containing highly magnetic parts such as steel casings and tabs cannot be used safely with high magnetic fields, typically exceeding 1 T, produced by superconducting magnets because they would be subjected to extreme attractive forces. In this case, permanent magnets are more suitable. On the other hand, prismatic and polymer pocket cells can be analyzed using high magnetic fields, typically exceeding 3 T, such as those produced by superconducting magnets.

[0085] In the example shown, connector 115 of circuit 101 is connected, for example, using cable 303, to an NMR spectrometer 305. In this example, connector 115 is more precisely connected to the RF voltage source 209, which is part of the NMR spectrometer 305. For example, cable 303 is a coaxial cable, for example, having an impedance of 50 Ω. For example, the NMR spectrometer 305 is equipped with an RF transmit / receive channel connected to the connecting elements 113A and 113B of circuit 101. In the example shown, the oscillating magnetic field Bi is supplied by the source 209 to the current collectors of cell 107 (not shown in detail in [Fig. 3]). The magnetic field Bi oscillates along a horizontal direction O y orthogonal to the direction Ox of the polarization magnetic field Bo.In this example, the circuit 101, for example the PCB on top of which the circuit 101 is formed, and the battery cell 107 are in a plane substantially parallel to the horizontal Oxy plane. In the orientation of [Fig. 3], the Oxy plane is orthogonal to a vertical Oz axis. The NMR spectrometer 305 is, for example, a pulsed-field NMR spectrometer.

[0086] Figure 3 illustrates, by way of example, a horizontal bore arrangement. This corresponds, for example, to a case in which the system 100 is intended for use in industrial installations, for example, for screening and recycling operations. In such a case, other battery cells similar or identical to battery cell 107 are, for example, successively introduced along the horizontal axis Ox, for example, using a conveyor, into the magnet 301 so that these cells can be analyzed by in-situ NMR spectroscopy. In situ NMR applications of system 100 are not limited to the configuration shown in [Fig. 3]. It is possible to use, for example, a vertically bored magnet. In such a case, magnet 301 produces the polarizing magnetic field Bo along the vertical axis Oz, while circuit 100 can be located in any arbitrary vertical plane (e.g., Oxz) and source 209 produces the oscillating magnetic field Bi (e.g., along the Ox axis).

[0087] The magnet 301 is, for example, controlled by the NMR spectrometer 305. In such a case, the magnet 301 is, for example, connected to the NMR spectrometer 305. For example, the magnet 301 is part of the NMR spectrometer 305.

[0088] According to one embodiment, the system of [Fig.3] is made to operate by implementing a process comprising the following successive steps: a) apply to the battery cell 107, using the magnet 301, the polarization magnetic field Bo; b) apply to the connecting elements 113A and 113B of circuit 101, using the NMR spectrometer 305, an alternating voltage (RF pulse) intended to produce the oscillating magnetic field Bi in the battery cell 107; and c) Acquire, using the pulsed-field NMR spectrometer 305, a time evolution of the alternating voltage between terminals 105A and 105B of cell 107 induced in the current collectors by oscillating transverse nuclear magnetization (free precession signal - FID) in the battery materials. The Fourier transform of the FID signal provides an NMR spectrum, which is the Larmor frequency distribution of a particular nuclear isotope.

[0089] Figure 4 is an example of a density image 400 illustrating an intensity distribution I of a 7Li NMR signal, expressed as Log(I / Imax), in the battery cell 107. The image 400 is, for example, obtained by magnetic resonance imaging (MRI) using the circuit 101 described previously in relation to Figures 1 and 2. In this example, the battery cell 107 is, for example, a pocket Li-ion battery cell, for example, intended for use in a mobile phone or smartphone.

[0090] Figure 400 represents a superposition of 7Li NMR signals (T2*-weighted Bb-modulated) from Li-containing elements in cell 107, i.e., the anode, the cathode, and various interface structures. The imaging plane of [Fig. 4] is perpendicular to the smallest dimension of cell 107, in the case where cell 107 is a pocket cell. In the example shown, the imaging plane is perpendicular to the Oz axis and parallel to the Oxy plane. This implies that the signal is averaged along the Oz direction.

[0091] In the example shown in [Fig. 4], the most efficient signal excitation occurs in regions 401A and 401B of cell 107 above conduction terminals 105A and 105B, respectively. The Bi amplitude distribution has two local maxima located a few millimeters from the cell terminals 105A and 105B. This indicates that the current collectors of battery cell 107 do not behave like a parallel flat resonator in terms of Bi field homogeneity. However, the local NMR signal excitation is sufficient to analyze the materials present inside cell 107.

[0092] Figure 5 is a schematic diagram showing examples of 7Li NMR spectra of commercially available pocket smartphone cells varying in size and charge capacity. The cells are based on lithium cobalt oxide (LiCoO2 - LCO) cathode and graphite anode chemical compositions. Each NMR spectrum measurement (Fig. 5) performed with the RF circuit takes approximately 12 minutes. In the example shown, the battery cells are in a fully charged state, meaning they have a state of charge (SoC) of approximately 100%.

[0093] Scheme 500 comprises six spectra 501-1, 501-2, 501-3, 501-4, 501-5, and 501-6 exhibiting similar 7Li NMR line shapes and similar peak positions. In the example shown, each spectrum includes a cathode peak Pc at a chemical shift δ of approximately 135 ppm, the integral intensity of which is correlated with the amount of lithium intercalated within the cell's cathode material. Each spectrum further includes an anode peak PA at a chemical shift δ of approximately 40 ppm, the integral intensity of which is correlated with the amount of lithium intercalated within the cell's anode material and with the SoC. The ratio of the cathode-to-anode 7Li NMR signals is correlated with the SoC. In the fully charged state (SoC = 100%), the integral intensity of the peak at 40 ppm approaches its maximum value in the interval 0% < SoC < 100%.In general, the chemical shifts of the anode and cathode 7Li NMR lines are unique characteristics specific to the corresponding materials, for example, graphite and LCO, respectively. Similarly, any intercalated ion (e.g., Li, Na, K, Mg, Al) will exhibit variations in line shape and chemical shift with SoC.

[0094] Figure 6 is a diagram 600 comprising examples of NMR spectra of an LCO battery cell, for example, cell 107, acquired over a complete galvanostatic cycle. The diagram 600 comprises thirteen spectra 601-1, 601-2, 601-3, 601-4, 601-5, 601-6, 601-7, 601-8, 601-9, 601-10, 601-11, 601-12 and 601-13 corresponding respectively to states of charge (SoC) of approximately 100%, 87.5%, 75%, 63%, 50%, 38%, 25%, 12.5%, 0%, 25%, 50%, 75% and 100%.

[0095] During discharge (spectra 601-1 to 601-9), the cathode peak Pc, with a chemical shift δ initially of approximately 135 ppm when the battery cell is charged (spectrum 601-1), increases in intensity while shifting to a lower chemical shift δ. Simultaneously, the anode peak PA decreases in intensity with a very small change in chemical shift δ (a change of approximately 1 ppm) of about 40 ppm.

[0096] When the SoC is approximately 0% (spectrum 601-9), a peak at approximately 57 ppm appears, corresponding to a high degree of cathode lithiation. A group of peaks between approximately -30 and approximately -60 ppm, which decrease during discharge, are associated with lithium in electrolyte-filled pores of the carbon anode material, electrolyte-anode interfaces, and local susceptibility variations. Furthermore, a low-intensity peak at approximately 0 ppm is attributable to mobile ions of the electrolyte.

[0097] Over the complete galvanostatic cycle, the total spectral integral varies by 20%. This is due to the fact that the transverse relaxation rates in the cathode and anode environments are substantially different, as evidenced by their 7Li NMR linewidths. Spectra 601-10 to 601-13 show that the in situ 7Li NMR lineforms are reversible during one cycle. Furthermore, spectra 601-1 to 601-13 are reproducible over several galvanostatic cycles.

[0098] 7Li NMR intensities and chemical line shifts associated with charge carriers intercalated in the cell cathode and anode (as previously described for LCO and LFP cells) provide reliable SoC measurements. Such a method is superior to conventional voltage-based SoC measurements. For low SoC values, typically below 40%, the 7Li NMR chemical shift of the LCO Pc cathode peak is an additional sensitive SoC indicator, as it varies with SoC between approximately 135 ppm (SoC = 100%) and approximately 57 ppm (SoC = 0%).

[0099] Figure 7 is a diagram 700 comprising examples of nuclear magnetic resonance spectra of an LCO battery cell, for example cell 107, subjected to overcharge followed by discharge. Diagram 700 comprises eleven spectra 701-1, 701-2, 701-3, 701-4, 701-5, 701-6, 701-7, 701-8, 701-9, 701-10 and 701-11 corresponding respectively to a SoC of approximately 113%, 125%, 138%, 150%, 163%, 131%, 125%, 113%, 100%, 49% and 25%.

[0100] Overcharging a battery is known to cause metallic microstructures associated with capacity loss, internal short circuits, and dangerous phenomena, such as thermal runaway, can occur. Therefore, detecting lithium coatings in commercially available batteries would reduce the risks associated with thermal runaway and facilitate the development of fast battery charging protocols.

[0101] Orientation-dependent magnetic susceptibility effects in lithium metal lead to a very distinctive range of 7Li shifts (Knight shifts) from about 230 ppm to about 290 ppm. Indeed, as illustrated in [Fig. 7], in situ NMR of cells overcharged to varying degrees reveals signals at about 265 ppm that gradually increase with the measurement range. About 30% of these signals drop off at the time of discharge (spectra 701-5 to 701-11), indicating that some of the material has redissolved in the electrolyte. The remaining signal appears to result from the presence of "dead" lithium, a performance degradation mechanism that leads to a decrease in cell capacity. The presence of "dead" lithium signals in LCO cells is observed after several charge-discharge cycles.

[0102] The use of the circuit 101 and the implementation of the method described above advantageously allows non-destructive, in situ detection of the lithium coating in individual cells of a battery case, which can facilitate the development of fast battery charging protocols and optimized case structures with reduced risks of thermal runaway.

[0103] Cobalt-free cathode materials such as lithium iron phosphate (LiFePO4, LFP) are more environmentally friendly, cost-effective, and safer alternatives to their LCO counterparts. For battery cells implementing such materials, in situ NMR analysis of 7Li and 31P provides a valuable source of structural information and allows for a rapid and reliable evaluation of the SoC and SoH as described below.

[0104] Figure 8 is a scheme 800 comprising examples of NMR spectra of a multi-stage LFP battery cell with galvanostatic charging. Scheme 800 comprises eight spectra 801-1, 801-2, 801-3, 801-4, 801-5, 801-6, 801-7 and 801-8 corresponding respectively to states of charge (SoC) of approximately 0%, 14%, 27%, 41%, 54%, 68%, 80% and 100%.

[0105] In the fully charged cell (spectrum 801-8), there are three main groups of signals at approximately -10, -77, and 61 ppm. The spectral component at -10 ppm has a high-field shoulder that appears during charging, thus identifying the main anode species. Near full discharge (spectrum 801-1), a broad signal at approximately -77 ppm originates from residual lithium at the anode. A group of relatively narrow lines at approximately 149 ppm (spectrum 801-1) which shift towards high fields at the time of charging originates from mobile lithium ions or their complexes in the paramagnetic environment.

[0106] During discharge, lithium ions undergo a transfer from a weakly magnetic anode environment, where linewidths are less than 50 ppm, to a strongly paramagnetic LFP material, where linewidths exceed 2,000 ppm. Thus, in the cathode, the magnetization lifetime is short compared to the pre-acquisition delay (equal to approximately 6.5 ps), and about 70% of the lithium becomes "invisible" when the battery discharges. The evolution of the line shape shown in [Fig. 8] is completely reversible when the cycle is performed in the range 0 < SoC < 100%.

[0107] Figure 9 is a 900 diagram comprising examples of nuclear magnetic resonance spectra of an LFP battery cell subjected to overcharge followed by discharge. The 900 diagram includes six spectra 901-1, 901-2, 901-3, 901-4, 901-5 and 901-6 corresponding respectively to a SoC of approximately 112%, 122%, 133%, 143%, 154% and 100%.

[0108] In the example shown, an overcharge of the cell causes the formation of quasi-metallic lithium, which is identified by a signal at approximately 220 ppm (spectra 901-1 to 901-5). At the time of discharge from 154% to 100% (spectra 901-1 and 901-6), a significant portion of the metallic lithium redissolves. A remaining signal at approximately 210 ppm (spectrum 901-6) indicates the presence of "dead" lithium in the cell.

[0109] Schemes 500, 600, 700, 800 and 900 are, for example, acquired using RF circuit 101, for example, in system 100. System 100 is, for example, placed in the structure described previously in relation to [Fig.3].

[0110] Figure 10 is a partial, schematic top view of a system 1000 comprising the electronic circuit 101 according to one embodiment. The system 1000 shown in Figure 10 has elements in common with the system 100 shown in Figure 1. These common elements will not be described in detail again here. [YES] System 1000 of [Fig. 10] differs from system 100 of [Fig. 1] in that system 1000 additionally includes a one-sided RF sensor 1001 specifically designed for battery cell analysis (pocket and prismatic). The one-sided RF sensor 1001 is, for example, an RF resonator similar to a parallel flat transmission line. In the example shown, the RF sensor 1001 consists of two parallel metal plates separated by a 1 mm thick layer of a proton-containing polymer material (e.g., silicon). The working surface of the RF sensor 1001 is in contact with one side of the flat battery cell 107.

[0112] The RF sensor 1001 is, for example, controlled by the NMR spectrometer 305 described previously in relation to [Fig. 3]. In such a case, the RF sensor 1001 is, for example, connected to a 'H' channel of the NMR spectrometer 305, and an 'X' channel (where X is, for example, 7Li) of the NMR spectrometer 305 is connected to the in situ NMR circuit 101.

[0113] The 1001 sensor enables surface scanning NMR analysis, a methodology based on magnetic susceptibility sensitive to mechanical defects, spatial distributions of the SoC, magnetic phases, and current density distribution in battery cells, particularly in flat cells (e.g., pocket and prismatic). The 1001 RF sensor is designed to operate at a proton Larmor frequency ('H'), producing a BiH magnetic field, while the 101 in situ NMR RF circuit operates at a nucleus frequency 'X', for example, of 7Li, 23Na, etc., producing a BiX magnetic field. According to an alternative, the 1001 RF sensor is designed to operate at a 19F Larmor frequency if the sensor's detection medium is made of a fluorine-based polymer. Compared to system 100 of [Fig.1], system 1000 of [Fig.10] allows for an additional and / or complementary analysis of battery cell 107.

[0114] By way of example, the RF 1001 sensor is implemented as described in the previously mentioned article by K. Romanenko and N. Avdievich entitled “Unilateral RF sensors based on parallel-plate architecture for improved surface-scan IRM analysis of commercial pouch cells”, J. Magn. Reson. Open 18, 2024, vol. 18, 100141.

[0115] The 1000 system constitutes, for example, a composite device which allows multimodal in situ analysis of pocket cells, in particular by spectroscopy and by magnetic-based MRI contrast of these cells.

[0116] One advantage of the 1000 system is that it eliminates the problem caused by the conductive metal casing and conductive metal current collectors of commercial battery cells and provides detailed spectroscopic and spatially resolved (SMR) information concerning the composition of the battery cells, the chemical environment of the electrochemically active elements, mechanical defects, electrochemical degradation, susceptibility distribution, magnetic phase composition of the cathode material, and current density distribution within the cell. This "in situ" information represents a series of statistical measurements describing the cell chemistry, the SoC, the SoH, the lifetime, the life cycle history, etc.

[0117] Another advantage of the 100 and 1000 systems is that they do not require destructive handling of the sealed cell and terminal housings.

[0118] The process described above is, for example, intended to be implemented: in scientific laboratories as part of basic research activities; in industrial environments, near battery production lines, to perform analysis and detection of electrochemical and mechanical defects, dendrites, and other poor-quality conditions; and in battery recycling facilities to perform non-destructive chemical analysis and identification of battery materials.

[0119] The RF 101 circuit and the 100 and 1000 systems improve various aspects of battery cell analysis. In particular, they enable the following functions: 1. non-destructive in situ analysis, by NMR and MRI, multi-nuclear electrochemical materials in commercial battery cells of various configurations (e.g., pocket, prismatic and cylindrical cells), these measurements providing fundamental structural information and new measurements to determine the SoC and SoH; 2. the accurate and rapid measurement of the SoC by a) quantifying the charge carrier populations intercalated in the cathode and anode instead of relying on classical SoC measurements such as voltage measurements between battery terminals, and b) by means of magnetic field contrast-based MRI measurements using the 1000 system which provide the spatial distribution of the SoC; 3. Improved SoH characterization, as the RF 101 circuit and the 100 and 1000 systems allow obtaining magnetic resonance data that are correlated with a battery cell state such as charge capacity, internal resistance, presence of dendrites, self-discharge rate, total service life, etc.; 4. the detection of hazardous metallic lithium in order to reduce the risks associated with thermal runaway, thereby preventing fire incidents, for example, in battery-powered domestic and transport environments; 5. Accurate detection and quantification of lithium coating, which facilitates the development of fast, dendrite-free charging protocols; 6. Improved analysis and design of battery packs, in particular with regard to synchronization and consistency between the various cells within the same pack; and 7. Aiding the recycling of battery materials, for example, by classifying cells by their cathode chemistry.

[0120] Various embodiments and variations have been described. Those skilled in the art will understand that certain features of these various embodiments and variations could be combined, and other variations will become apparent to those skilled in the art. In particular, the implementations of circuit 101 and systems 100 and 1000 may vary depending on the types of NMR instruments used, which are categorized, for example, by the amplitude of their polarization field Bo, their magnet bore diameter, and their spatial orientation. These various implementations are within the grasp of those skilled in the art based on this description.

[0121] Moreover, what has been described more particularly in relation to an example of application to mobile phone or smartphone battery cells applies more generally to any type of commercial battery cell which may be found, for example, in portable electronic devices, such as laptops, touch tablets, smartwatches, connected activity trackers, etc., and in electric vehicles, such as electric cars, motorcycles, trucks, etc.

[0122] Moreover, what has been described more specifically in relation to examples where the battery cell 107 has an LCO or LFP chemistry applies more generally to any type of transition metal oxide chemistry and to intercalated ions of Li, Na, K, Cu, Mg, Ca, Al and Zn, for example, a cobalt and lithium or sodium oxide, an iron and lithium or sodium phosphate, a lithium manganese oxide, vanadium oxides, NaNixFeyMnzO2, etc. The observed NMR data will be similar in any transition metal oxide-based cell, although having different characteristic chemical shifts.

[0123] Finally, the practical implementation of the described embodiments and variants is within the reach of a person skilled in the art, based on the functional specifications given above. In particular, the dimensions of the RF circuit 101 can vary depending on the type of battery cell 107 to be analyzed. Specifically, depending on the application, the distance between the connection elements 103A and 103B can be specific to a cell or universal, i.e., adjustable for many cell sizes and geometries.

Claims

Demands

1. Electronic circuit (101) comprising: first (103A) and second (103B) connecting elements for connection, respectively, to first (105A) and second (105B) conduction terminals of an electrochemical energy storage device (107); third (113A) and fourth (113B) connecting elements for connection to a nuclear magnetic resonance spectrometer (305); and a radio frequency matching and tuning circuit (119) connecting the third (113A) and fourth (113B) connecting elements to the first (103A) and second (103B) connecting elements.

2. Circuit (101) according to claim 1, wherein the radio frequency adaptation and adjustment circuit (119) comprises: a first inductive element (109A) having a first terminal connected, preferably connected, to the first connecting element (103A); a second inductive element (109B) having a first terminal connected, preferably connected, to the second connecting element (103B); a first capacitive element (11IA) having a first terminal connected, preferably connected, to a second terminal of the first inductive element (109A) and a second terminal connected, preferably connected, to the third connecting element (113A); a second capacitive element (11IB) having a first terminal connected, preferably connected, to a second terminal of the second inductive element (109B) and a second terminal connected, preferably connected, to the fourth connecting element (113B);and a third capacitive element (117) connecting the second terminals of the first (109A) and second (109B) inductive elements.;

3. Circuit (101) according to claim 2, wherein the first (109A) and second (109B) inductive elements are inductors and wherein the first (11IA), second (11IB), and third (117) capacitive elements are capacitors.

4. Circuit (101) according to claim 2 or 3, wherein the first (109A) and second (109B) inductive elements have the same inductance (LT) and wherein the first (11IA) and second (11IB) capacitive elements have the same first capacitance (CM) ) different from a second capacity (CT) of the third capacitive element (117).

5. Circuit (101) according to any one of claims 1 to 4, wherein the circuit has a resonance frequency equal to about a Larmor frequency of an atomic nucleus selected from: Li, Na, P, 63Cu, 65Cu, 59Co, 'H, 19F, 27Al, 55Mn, 6Li and 39K.

6. System (100; 1000) comprising: the circuit (101) according to any one of claims 1 to 5; and a nuclear magnetic resonance spectrometer (305) comprising: an RF transmit / receive channel connected to the third (113A) and fourth (113B) connection elements of the circuit; and a magnet (301) having a cavity compatible with dimensions of the system (100; 1000).

7. System (100; 1000) according to claim 6, wherein the magnet (301) has a cylindrical or rectangular hollow cavity arranged vertically or horizontally.

8. System (1000) according to claim 6 or 7, further comprising a radio frequency sensor (1001) intended to operate at a Larmor frequency of either the proton 'H, or isotopes of fluorine 19F.

9. System (100; 1000) according to any one of claims 6 to 8, further comprising a battery cell (107) having first (105A) and second (105B) conduction terminals connected respectively to first (103A) and second (103B) connection elements of the circuit (101).

10. System (100; 1000) according to claim 9, wherein the battery cell (107) is a lithium iron phosphate pocket battery cell.

11. System (100; 1000) according to claim 9, wherein the battery cell (107) is a lithium cobalt oxide pocket battery cell.

12. System (100; 1000) according to any one of claims 9 to 11, wherein the battery cell (107) is part of a battery of a consumer electronic device or of a battery of an electric vehicle.

13. A method of operating the system (100; 1000) according to any one of claims 9 to 12, the method comprising the following successive steps: a) applying to the battery cell (107), using the magnet (301), a polarizing magnetic field (Bo); b) applying to the third (113A) and fourth (113B) connection elements of the circuit (101), using the nuclear magnetic resonance spectrometer (305), an alternating voltage pulse intended to produce in the battery cell an oscillating magnetic field (BiX); and c) acquiring, using the nuclear magnetic resonance spectrometer, an NMR spectrum representative of electrochemical materials present in the cell.

14. A method according to claim 13, in its dependence on any one of claims 9 to 12 in combination with claim 8, further comprising, in step c), an acquisition of MRI data representative of spatial distributions of magnetic susceptibility and / or current density in the battery cell (107) which depend on the state of charge.

15. A method according to claim 13 or 14, further comprising, after step c), a step d) of determining a state of charge of the battery cell (107) as a function of the spectrum acquired in step c).

16. A method according to any one of claims 13 to 15, further comprising, after step c), a step e) of determining an overload of the battery cell (107) as a function of the spectrum acquired in step c).

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