Analysis of electrochemical energy storage devices

Abstract

The present disclosure relates to an electronic circuit (101) comprising: first (103A) and second (103B) connection elements intended to be connected respectively to first (105A) and second (105B) conduction terminals of an electrochemical energy storage device (107); third (113A) and fourth (113B) connection elements intended to be coupled to a nuclear magnetic resonance spectrometer (305); and a radio frequency matching and tuning circuit (119) coupling the third (113A) and fourth (113B) connection elements to the first (103A) and second (103B) connection elements.

Description

DESCRIPTIONAnalysis of electrochemical energy storage devicesTechnical field

[0001] The present disclosure relates generally to the analysis of electrochemical energy storage devices such as, for example, commercial electrochemical battery cells, for example, flat pouch cells, cylindrical cells, multi-cell battery packs, and cells incorporated in operational portable devices (for example, smartphones and tablets) .Background art

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

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

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

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

[0006] Most common battery cells used in portable electronics and electric vehicles are based on the so-called "jelly roll" (cylindrical or flat-wound) and "plain stacked electrode" architectures encapsulated in metal (aluminum or steel) casings. Electrochemical materials (cathode, anode and electrolyte) are confined between conductive layers of current collectors, e.g., copper and aluminum foils. The metal casing and current collectors are the major obstacle to in situ battery analyses using NMR and magnetic resonance imaging (MRI) , as RF field penetration 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 types of RF structures) and irradiated with a pulsed RFfield to produce a temporal evolution of a transverse nuclear magnetization, termed free induction decay (FID) . At the end of the RF excitation pulse, the resonator is switched into an acquisition mode, and the 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. In battery cells, however, the electrochemical materials of interest are shielded by the external conductive casing and layers of current collectors, making the RF excitation with NMR resonators impossible.

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

[0009] The article by E. G. Sorte et al. entitled "In Situ Stripline Electrochemical NMR for Batteries", ChemElectroChem, vol. 5, issue 17, 2018, pp . 2336-2340 describes the introduction of a stripline NMR probe inside a commercial pouch cell in order to partially circumvent the RF screening challenge. However, this approach requires impractical destructive manipulation of the cell's casing, followed by cumbersome electrolyte refilling 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 excitation and detection of7Li NMR signals inside a pouch cell using capacitive coupling between the conductive cell's casing and external copper pads. However, the SNR of such a contactless approach is too low for routine applications .

[0011] The article by B. J. 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 skimming effect to show that the RF field can reach electrochemical layers of interest inside a commercial coin cell when the cell's metal enclosure is incomplete. However, this approach is not applicable to pouch, prismatic and cylindrical cells as these cells are fully enclosed in conductive casings. In addition, coin cells are a miniaturized, impractical, low capacity and low current rating approximation of real 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 inside-out MRI concept. The method measures the magnetic field perturbations induced by the cell placed in a uniform magnetic field. The patterns of magnetic field perturbation measurable outside the cell contain information about the distribution of magnetic susceptibility and charge transfer processes inside the cell. However, although surface-scan MRI is sensitive to variations in magnetism, current densities and different types of defects in cells, it does not provide direct information about the local chemical environment of charge carriers and the structure of charge storage sites.

[0013] In academic research settings, in situ and operando NMR spectroscopy analysis is performed on miniaturized prototypes of battery cells, e.g., "coin" cells, which are not suitable for practical applications. These NMR-compatible cells have charge capacities and current ratings several orders of magnitude lower than commercial cells. Other methodssuitable for in situ analysis of battery cells ( e . g . XRD) do not provide the same level of statistical detail as NMR and MRI .Summary of 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 access to methods and devices suitable for the fundamental analysis of structure and molecular dynamics in materials of commercial electrochemical battery cells in situ

[0015] To this end, one 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 ; third and fourth connection elements intended to be coupled to a nuclear magnetic resonance spectrometer ; and a radio frequency matching and tuning circuit coupling the third and fourth connection elements to the first and second connection elements .

[0016] According to one embodiment , the radio frequency matching and tuning circuit comprises : a first inductive element having a first terminal coupled, preferably connected, to the first connection element ; a second inductive element having a first terminal coupled, preferably connected, to the second connection element ; a first capacitive element having a first terminal coupled, preferably connected, to a second terminal of the first inductive element and a second terminal coupled, preferably connected, to the third connection element ; a second capacitive element having a first terminal coupled, preferably connected, to a second terminal of the second inductive element and a second terminal coupled, preferablyconnected, to the fourth connection element; and a third capacitive element coupling 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 element have a same inductance and the first and second capacitive elements have a 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 about a Larmor frequency of an atomic nucleus having a non-zero spin number, for example selected among:7Li,23Na,31P,63Cu,65Cu,59Co,2H,19F,27A1, 55Mn,6Li and39K.

[0020] One embodiment provides a system comprising: the circuit as previously described; and a nuclear magnetic resonance spectrometer equipped with: an RF transmit / receive channel connected to the third and fourth connection elements of the circuit; and a magnet provided with a cavity compatible with 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 either2H proton or19F fluorine isotopes.

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

[0024] According to one embodiment, the battery cell is a lithium pouch battery cell.

[0025] According to one embodiment, the battery cell is a lithium nickel manganese cobalt oxides pouch battery cell.

[0026] According to one embodiment, the battery cell is a lithium cobalt oxide pouch battery cell.

[0027] According to one embodiment, the battery cell is an electrochemical pouch cell.

[0028] According to one embodiment, the battery cell is an electrochemical cylindrical cell.

[0029] According to one embodiment, the battery cell forms part of a consumer electronic device battery or of an electric vehicle battery.

[0030] One embodiment provides a method of operating the system as previously described, the method comprising the following successive steps: a) apply 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 AC voltage pulse intended to produce an oscillating magnetic field in the battery cell; and c) acquire, using the nuclear magnetic resonance spectrometer, an NMR spectrum representative of electrochemical materials in the cell.

[0031] According to one embodiment, the method further comprises, at step c) , an acquisition of MRI data representative of spatial distributions of SoC-dependent magnetic susceptibility and / or current density in the battery cell .

[0032] According to one embodiment, the method further comprises, after step c) , a step d) of determination of a state of charge of the battery cell according to the spectrum acquired at step c) .

[0033] According to one embodiment, the method further comprises, after step c) , a step e) of determination of an overcharge of the battery cell according to the spectrum acquired at step c) .Brief description of drawings

[0034] The foregoing features and advantages, as well as others, will be described in detail in the following description of specific embodiments given by way of illustration and not limitation with reference to the accompanying drawings, in which:

[0035] Figure 1 is a partial and schematic two-dimensional projection view of a system comprising an electronic circuit according to one embodiment;

[0036] Figure 2 is an electrical diagram equivalent to the system of Figure 1;

[0037] Figure 3 is a partial and schematic perspective view of the system of Figure 1 placed inside a horizontal magnet;

[0038] Figure 4 is an example of a distribution of a7Li magnetic resonance imaging signal magnitude in a flat pouch cell based on lithium cobalt oxide (LCO) and graphite;

[0039] Figure 5 is a diagram comprising examples of7Li nuclear magnetic resonance spectra of different rechargeable pouch cells based on LCO and graphite;

[0040] Figure 6 is a diagram comprising examples of7Li nuclear magnetic resonance spectra of a rechargeable pouch cell based on LCO and graphite over a full galvanostatic cycle ;

[0041] Figure 7 is a diagram comprising examples of nuclear magnetic resonance spectra of an LCO / graphite battery cell subj ected to overcharge followed by discharge ;

[0042] Figure 8 is a diagram comprising examples of nuclear magnetic resonance spectra of a lithium nickel manganese cobalt oxide (NMC ) battery cell at several stages of a galvanostatic charging;

[0043] Figure 9 is a diagram comprising examples of nuclear magnetic resonance spectra of an NMC battery cell subj ected to overcharge followed by discharge ;

[0044] Figure 10 is a partial and schematic top view of a system comprising an electronic circuit according to one embodiment ;

[0045] Figure 11 is an electrical diagram equivalent to a bi- modal probe ; and

[0046] Figure 12 is an electrical diagram equivalent to a two- frequency variant of the electronic circuit of Figure 1 and Figure 12B represents6Li and7Li NMR spectra of a pouch cell subj ected to overcharging .Description of embodiments

[0047] Like features have been designated by like references in the various f igures . In particular, the structural and / or functional features that are common among the various embodiments may have the same references and may dispose identical structural , dimensional and material properties .

[0048] For the sake of clarity, only the operations and elements that are useful for an understanding of the embodiments described herein have been illustrated and described in detail . In particular, the various applications of the electrochemical energy storage devices have not been detailed, the embodiments described being compatible with all or most of the applications of electrochemical energy storagedevices, with possible adaptations within the capabilities of those skilled in the art based on the present description.

[0049] Unless indicated otherwise, when reference is made to two elements connected together, this signifies a direct connection without any intermediate elements other than conductors, and when reference is made to two elements coupled together, this signifies that these two elements can be connected or they can be coupled via one or more other elements .

[0050] In the following disclosure, unless indicated otherwise, when reference is made to absolute positional qualifiers, such as the terms "front", "back", "top", "bottom", "left", "right", etc., or to relative positional qualifiers, such as the terms "above", "below", "higher", "lower", etc., or to qualifiers of orientation, such as "horizontal", "vertical", etc., reference is made to the orientation shown in the figures.

[0051] Unless specified otherwise, the expressions "around", "approximately", "substantially" and "in the order of" signify within 10% or 10°, and preferably within 5% or 5°.

[0052] In the following description, "insulating" and "conductive" respectively mean electrically insulating and electrically conductive, unless specified otherwise.

[0053] Unless specified otherwise, "in contact with" means "in mechanical contact with".

[0054] Figure 1 is a partial and 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.

[0055] According to one embodiment, the circuit 101 comprises connection elements 103A and 103B intended to be connected to conduction terminals of an electrochemical energy storagedevice . In the example shown, the connection elements 103A and 103B are respectively connected 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 respectively positive ( + ) and negative ( - ) conduction terminals of the cell 107 . As an example , the connection elements 103A and 103B are solder- free connectors .

[0056] In the illustrated example , the connection element 103A is connected to a terminal of an inductive element 109A. In a similar way, the connection element 103B is connected to a terminal of another inductive element 109B . The inductive elements 109A and 109B, for example , present a same inductance L to within manufacturing dispersions . By way of example , the inductive elements 109A and 109B are inductors each comprising, for example , a coil .

[0057] Furthermore , in the example shown, another terminal of the inductive element 109A is connected to a terminal of a capacitive element 111A. In a similar way, another terminal of the inductive element 109B is connected to a terminal of another capacitive element 111B . The capacitive elements 111A and 111B, for example , present a same capacitance CM to within manufacturing dispersions . By way of example , the capacitive elements 111A and 111B are capacitors each comprising an insulating region interposed between conducting regions .

[0058] In the example illustrated in Figure 1 , another terminal of the capacitive element 111A is connected to a connection element 113A. In a similar way, another terminal of the capacitive element 111B is connected to another connection element 113B . By way of example , the connection elements 113A and 113B form part of a same connector 115 , for example , a BNC connector . In this example , the connection element 113A corresponds to an outer conductive region of theBNC connector 115, intended to be connected to a concentric conducting shield of a coaxial cable (not shown in Figure 1) , and the connection element 113B corresponds to an inner conductive region of the BNC connector 115, intended to be connected to a conductive core of a coaxial cable. However, this example is not limitative and the connector 115 can, alternatively, be of a different type, for example, a SMA or SMB connector.

[0059] According to one embodiment, the connection elements 113A and 113B are intended to be coupled to a nuclear magnetic resonance (NMR) spectrometer, not illustrated in Figure 1, for example, using a coaxial cable connected to the connector 115. As an example, the connection elements 113A and 113B are intended to be connected, more specifically, to a preamplifier of the NMR spectrometer.

[0060] In the example shown, the terminals of the inductive elements 109A and 109B connected to the capacitive elements 111A and 111B are coupled together by another capacitive element 117. The capacitive element 117, for example, presents a capacitance C . AS an example, the capacitive element 117 is a capacitor.

[0061] In the example illustrated, the connection elements 103A and 103B, the inductive elements 109A and 109B, and the capacitive elements 111A, 111B and 117 form part of a radio frequency (RF) matching and tuning circuit 119, also called radio frequency adaptation and adjustment circuit 119, coupling the connection elements 113A and 113B to the connection elements 103A and 103B. As an example, the RF matching and tuning circuit 119 is formed on a printed circuit board (RGB) . In this example, the connection 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 tracks 121.

[0062] In the example shown, the inductive element 109A and the capacitive element 111A are associated in series between the connection elements 103A and 113A. In this example, the inductive element 109B and the capacitive element 111B are associated in series between the connection elements 103B and 113B.

[0063] The battery cell 107 can be of any type (e.g., commercial or custom made pouch, prismatic, cylindrical and "coin") or capacity. The method is not limited by the cell capacity: typical commercial cells have capacities in the range from around one to several hundreds of ampere-hours (Ah) . In the example shown, the battery cell 107 presents a capacitance CB, an inductance LB and a resistance R. For example, the battery cell 107 is fully encapsulated in a conductive (e.g. aluminum) casing. The battery cell 107 can be used in a consumer portable electronic device or in an electric vehicle.

[0064] In the orientation of Figure 1, the system 100, for example, comprises 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 can be mechanically connected or separated parts provided with compatible electric connectors at the cell's terminals 105A and 105B.

[0065] As will be detailed 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 Figure 1) . The magnet is intended to apply a polarizing magnetic field Bo to the battery cell 107.

[0066] The electronic circuit 101 enables in situ NMR spectroscopy analysis of the battery cell 107. More specifically, the electronic circuit 101 is designed in order to be able to resonate at a selected Larmor frequency so thatthe battery cell 107 forms part of a resonating structure. By connecting the RF circuit 101 directly to the terminals 105A and 105B of the cell 107, alternating current (AC) can be supplied through 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. Feeding RF waves into the cell 107 enables excitation and detection of NMR signals without the need for NMR probes, as the cell itself acts as an RF probe. The in situ NMR RF circuit 101 is advantageously tunable over a broad range of Larmor frequencies, which can be used for multi-nuclear in situ NMR analysis of the battery cell 107.

[0067] In the example shown, the inductive elements 109A and 109B are variable inductive tuning elements, the capacitive elements 111A and 111B are variable capacitive matching elements, and the capacitive element 117 is a variable capacitive tuning element. The inductive elements 109A and 109B and the capacitive elements 111A, 111B and 117 are, for example, intended to adjust a resonance frequency vo of the electronic circuit 101.

[0068] The resonance frequency vo of the electronic circuit 101 is defined by the following equation:

[0069] [Math 1]

[0070] In the equation [Math 1] above, L is a total inductance related to the inductance L of each of the inductive elements 109A and 109B, to an inductance Lo of a loop 123 shown as a dotted rectangle in Figure 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 the conductive elements, such as connection elementsand conductive tracks, enabling to connect these elements. The total inductance L is defined by the following relation:

[0071] [Math 2]L = LB+ LE

[0072] In the equation [Math 2] above, LE is a total external inductance given by LE = Lo + 2LT.

[0073] Furthermore, in the equation [Math 1] above, C is a total capacitance related to the capacitance CT of the capacitive element 117 and to the capacitance CB of the battery cell 107. The total capacitance C is given by the following equation :

[0074] [Math 3] _CBCT CB + CT

[0075] The capacitance CB of the battery cell 107 is, for example, several orders of magnitude higher than the capacitance CT of the capacitive element 117, for example, at least 10 times higher. Furthermore, the inductance LB of the battery cell 107 is, for example, several orders of magnitude lower than the total external inductance LE, for example, at least 100 times lower. Therefore, the reactive (capacitive and inductive) elements of the circuit 101 allow easy control of the resonance frequency Vo over a wide range. By way of example, the resonance frequency vo can be tuned to a broad range of Larmor frequencies of nuclear isotopes that may be comprised inside the battery cell 107 such as, for example, any atomic nucleus having a non-zero spin number I (for example I = 1 / 2, 1, 3 / 2, 2, 5 / 2, etc.) , for example:7Li,23Na, 31P,63Cu,65Cu,59Co,2H,19F,27A1,55Mn,6Li,39K, etc.

[0076] As an example, the capacitance CM of each of the capacitive elements 111A and 111B is adjusted for 50 Q impedance matching.

[0077] The position of the capacitive element 117 along the vertical axis, in the orientation of Figure 1, determines an area of the loop 123 and therefore controls the value of the inductance Lo. For example, the inductance Lo is tuned by varying the length of the conductive tracks 121 connecting the inductive elements 109A and 109B to the connection 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.

[0078] In the illustrated example, the resonance frequency vo of the electronic circuit 101 can be tuned to the Larmor frequency of the nucleus of interest by adjusting either the capacitance C of the capacitive element 117, or the inductance L 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 nonmagnetic inductors and high Q (i.e. low value) capacitors. Depending on its resonance frequency o, the electronic circuit 101 can have Q factors in the range from 40 to 120.

[0079] As an example, at around 117 MHz, which corresponds to the Larmor frequency of the7Li isotope at 7 T, Q factors ranging from 50 to 100 can be achieved. 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 capacitance CT of the capacitive element 117;3 nF, for the capacitance CB of the battery cell 107;10 nH, for the inductance LB of the battery cell 107;15 pF, for the capacitance CM of each of the capacitive elements 111A and 111B; and15 nH, for the inductance Lo of the loop 123.

[0080] In the battery cell 107 , electrochemical materials of interest are , for example , shielded by the external conductive casing and layers of current collectors , thus making external RF excitation and detection 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 enables to use the battery cell 107 as a part of a resonating structure , the connection 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 for example propagate into the cell 107 through folded sheets of current collectors , and deviate the nuclear spin magneti zations of the anode , cathode and electrolyte materials from the thermal equilibrium .

[0081] For the purpose of in situ NMR analysis , an external battery management system (BMS ) circuit ( i f initially provided) of the cell 107 can be disabled in order to improve the NMR sensitivity .

[0082] Figure 2 is an equivalent electrical diagram of the system 100 of Figure 1 .

[0083] In the example illustrated, the circuit 101 comprises the capacitive element 117 coupling two nodes 201A and 201B of the circuit 101 . More speci fically, the capacitive element 117 of capacitance C has a terminal coupled, preferably connected, to the node 201A and another terminal coupled, preferably connected, to the node 201B . In the example shown, the circuit 101 further comprises the capacitive elements 111A and 111B, each of capacitance CM, coupling respectively the nodes 201A and 201B to two other nodes 203A and 203B of the circuit 101 . In this example , the capacitive element 111A has a terminal coupled, preferably connected, to the node 201A and another terminal coupled, preferably connected, tothe node 203A, and the capacitive element 111B has a terminal coupled, preferably connected, to the node 201B and another terminal coupled, preferably connected, to the node 203B .

[0084] 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 respectively couple the nodes 201A and 201B to other nodes 207A and 207B of the circuit 101 . The nodes 207A and 207B are , for example , equivalent to the connection elements 103A and 103B of the circuit 101 . In this example , the inductive element 205A has a terminal coupled, preferably connected, to the node 201A and another terminal coupled, preferably connected, to the node 207A, and the inductive element 205B has a terminal coupled, preferably connected, to the node 201B and another terminal coupled, preferably connected, to the node 207B .

[0085] In the example illustrated in Figure 2 , a source 209 of an AC voltage V couples the nodes 203A and 203B of the RF circuit 101 . The source 209 , for example , forms part of an NMR spectrometer, not detailed in Figure 2 .

[0086] 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 the nodes 207A and 207B .

[0087] Figure 3 is a partial and schematic perspective view of the system 100 of Figure 1 placed inside a magnet 301 .

[0088] In the example shown, the magnet 301 is a hori zontal bore magnet . In this example , the magnet 301 more precisely has a hollow cylindrical shape extending laterally along a hori zontal axis Ox . In the example illustrated, the magnet 301 produces the polari zing magnetic field Bo along the axis Ox . The magnet 301 can have any suitable design, for example ,vertical or hori zontal bore , while provided with either rectangular or cylindrical cavity . The cavity of the magnet 301 is compatible with the dimensions of the system 100 . For example , the cavity of the magnet has dimensions strictly larger to those of the system 100 , so that the system 100 can be inserted inside the cavity .

[0089] As an example , the magnet 301 is either a permanent magnet or a superconductive magnet , the magnetic fields produced by superconductive magnets being typically higher than those produced by permanent magnets . Depending on the magnetism of materials in the battery cell 107 , permanent magnets can be preferred . For example , cylindrical cells containing strongly magnetic parts such as steel casings and tabs are not safe for use with high magnetic fields , typically higher than 1 T , produced by superconductive magnets as they would undergo extreme attractive forces . In this case , permanent magnets are more suitable . On the other hand, polymer pouch and prismatic cells can be analyzed using high magnetic fields , typically higher than 3 T , such as those produced by superconductive magnets .

[0090] In the example shown, the connector 115 of the circuit 101 is connected, for example , using a cable 303 , to an NMR spectrometer 305 . In this example , the connector 115 is more precisely coupled to the RF voltage source 209 , which forms part of the NMR spectrometer 305 . For example , the cable 303 is a coaxial cable , for example , having an impedance of 50 Q . For example , the NMR spectrometer 305 is equipped with an RF transmit / receive channel connected to the connection elements 113A and 113B of the circuit 101 . In the example illustrated, the oscillating magnetic field Bi is provided by the source 209 to the current collectors of the cell 107 (not detailed in Figure 3 ) . The magnetic field Bi oscillates along a hori zontal direction Oy orthogonal to the direction Ox of thepolarizing magnetic field Bo. In this example, the circuit 101, for example, the PCB on top of which is formed the circuit 101, and the battery cell 107 lie in a plane substantially parallel to the horizontal plane Oxy. In the orientation of Figure 3, the plane Oxy is orthogonal to a vertical axis Oz . The NMR spectrometer 305 is, for example, a pulsed-field NMR spectrometer .

[0091] Figure 3 illustrates, as an example, a horizontal bore arrangement. This corresponds, for example, to a case where the system 100 is intended to be used in industrial facilities, for example, for screening and recycling operations. In such a case, other battery cells similar or identical to the battery cell 107 are, for example, successively fed 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 the system 100 are not limited to the configuration shown in Figure 3. It is possible to use, for example, a vertical bore magnet. In such a case, the magnet 301 produces the polarizing magnetic field Bo along the vertical axis Oz, while the circuit 100 can lie in any arbitrary vertical plane (e.g., Oxz) , and the source 209 produces the horizontal oscillating magnetic field Bi (e.g., along the axis Ox) .

[0092] 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 forms part of the NMR spectrometer 305.

[0093] According to one embodiment, the system of Figure 3 is operated by implementing a method comprising the following successive steps: a) applying to the battery cell 107, using the magnet 301, the polarizing magnetic field Bo; b) apply to the connection elements 113A and 113B of thecircuit 101, using the pulsed-field NMR spectrometer 305, an AC 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 temporal evolution of the AC voltage between the cell's 107 terminals 105A and 105B induced in the current collectors by the oscillating transverse nuclear magnetization (free- induction decay - FID) in the battery materials. Fourier transformation of the FID signal provides an NMR spectrum, that is the distribution of Larmor frequencies of a specific nuclear isotope.

[0094] Figure 4 is an example of a density image 400 showing a distribution of a7Li NMR signal intensity I, expressed as Log(I / Imax) , in the battery cell 107, the battery cell 107 being for example a flat pouch cell based on lithium cobalt oxide (LCO) and graphite. The image 400 is, for example, obtained by magnetic resonance imaging (MRI) using the circuit 101 previously described in relation with Figures 1 and 2. In this example, the battery cell 107 is, for example, a Li-ion battery pouch cell, for example, intended to be implemented in a mobile phone or smartphone.

[0095] The image 400 illustrates a superposition of7Li NMR signals (Bi-modulated, T2*-weighted) from Li-containing species in the cell 107, i.e. anode, cathode, electrolyte and various inter-facial structures. The imaging plane of Figure 4 is perpendicular to the shortest dimension of the cell 107, in the case where the cell 107 is a pouch cell. In the shown example, the imaging plane is perpendicular to the Oz axis and parallel to the Oxy plane. This implies signal averaging along direction Oz .

[0096] In the example shown in Figure 4, the most efficient signal excitation occurs in regions 401A and 401B of the cell 107 above the conduction terminals 105A and 105B, respectivelyThe Bi magnitude distribution has two local maxima located within a few millimeters from the cell's terminals 105A and 105B. This indicates that the current collectors of the battery cell 107 do not behave like a parallel plate resonator in terms of Bi-field homogeneity. However, the local NMR signal excitation is sufficient to analyze the materials present inside the cell 107.

[0097] Figure 5 is a diagram 500 comprising examples of in situ7Li NMR spectra of commercial smartphone rechargeable pouch cells varying in dimensions and charge capacity. The cells are based on lithium cobalt oxide (LiCoCt - LCO) cathode and graphite anode chemistries. The measurement of each NMR spectrum (Figure 5) performed with the RF circuit 101 takes approximately 12 min. In the example shown, the battery cells are in the fully charged state, meaning they present a state of charge (SoC) equal to approximately 100%.

[0098] The diagram 500 comprises six spectra 501-1, 501-2501-3, 501-4, 501-5 and 501-6 exhibiting similar7Li NMR line shapes and peak positions. In the example shown, each spectrum comprises a cathode peak Pc at a chemical shift 5 equal to about 135 ppm, the integral intensity of which correlates with an amount of lithium intercalated into the cathode material of the cell. Each spectrum further comprises an anode peak PA at a chemical shift 5 of about 40 ppm, the integral intensity of which correlates with the amount of lithium intercalated into the anode material of the cell, and with SoC. The ratio of the cathode and anode7Li NMR signals correlates with SoC. In the fully charged state (SoC = 100%) , the integral intensity of the 40 ppm peak approaches its maximum value in the interval 0% < SoC < 100%. In general, the chemical shifts of anode and cathode7Li NMR lines are unique characteristics specific to the corresponding materials, for example, graphite and LCO, respectively. In asimilar manner, any intercalant ion (e.g., Li, Na, K, Mg, Al) will exhibit line-shape and chemical shift variations with SoC.

[0099] Figure 6 is a diagram 600 comprising examples of7Li NMR spectra of an LCO rechargeable pouch cell based on LCO and graphite, for example, the cell 107, acquired over a full 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% .

[0100] Upon discharging (spectra 601-1 to 601-9) , the cathode peak Pc at the chemical shift 5 initially equal to about 135 ppm when the battery cell is charged (spectrum 601-1) increases in intensity while shifting to lower chemical shift 5. Meanwhile, the anode peak PA decreases in intensity with a relatively small variation in the chemical shift 5 (variation roughly equal to 1 ppm) around 40 ppm.

[0101] When the SoC is equal to about 0% (spectrum 601-9) , a peak at around 57 ppm emerges, which corresponds to a high degree of cathode lithiation. A group of peaks between around -30 and around -60 ppm receding upon discharging are associated with lithium in electrolyte-filled pores of the carbonaceous anode material, electrolyte-anode interfaces, and local susceptibility variations. Furthermore, a low- intensity spike at around 0 ppm is attributable to mobile ions of the electrolyte.

[0102] Over the complete galvanostatic cycle, the total spectral integral varies within 20%. This is due to the fact that the transverse relaxation rates in the cathode and anode environments are noticeably different, as apparent from their respective7Li NMR linewidths. The spectra 601-10 to 601-13show that the in situ7Li NMR line shapes are reversible upon cycling. Furthermore, the spectra 601-1 to 601-13 are reproducible over several galvanostatic cycles.

[0103] Intensities and chemical shifts of in situ NMR lines associated with charge carriers intercalated in the cathode and anode of the cell (as described above for LCO and LFP cells) provide accurate SoC measurements. Such method is superior to conventional voltage-based SoC measurements. For low SoC values, typically lower than 40%, the7Li NMR chemical shift of the LCO cathode peak Pc is an additional sensitive SoC indicator, as it varies with SoC between about 135 ppm (SoC = 100%) and about 57 ppm (SoC = 0%) .

[0104] Figure 7 is a diagram 700 comprising examples of nuclear magnetic resonance spectra of an LCO / graphite battery cell, for example the cell 107, subjected to overcharge followed by discharge. The 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 SoC of approximately 113%, 125%, 138%, 150%, 163%, 131%, 125%, 113%, 100%, 49% and 25%.

[0105] Battery overcharging is known to bring about metallic micro-structures associated with the capacity loss, internal shorts, and hazardous phenomena such as thermal runaway. Hence, the detection of lithium plating in commercial batteries would reduce risks associated with thermal runaway and facilitate the development of rapid battery charging protocols.

[0106] Orientation-dependent magnetic susceptibility effects in lithium metal result in a very distinctive range of7Li shifts (Knight shifts) from about 230 ppm to about 290 ppm. Indeed, as shown in Figure 7, in situ NMR of cells overcharged to different degrees reveal signals at about 265 ppm that increases gradually with the extent of overcharge. Around 30% of these signals receded upon discharging (spectra 701-5 to701-11) , indicating that part of the metal re-dissolved in the electrolyte. The remaining signal seems to result from the presence of the "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 multiple charge-discharge cycles.

[0107] The use of the circuit 101 and the implementation of the method described above advantageously enables an in situ, non-destructive detection of lithium plating in individual cells of a battery pack, which can facilitate the development of rapid battery charging protocols and optimal pack designs with reduced risks of thermal runaway.

[0108] Cobalt-free cathode materials such as lithium iron phosphate (LiFePCt, LFP) are more environmentally-f riendly, cost-effective and safer alternatives to their LCO counterparts. For battery cells implementing such materials, in situ7Li and31P NMR analysis provides a valuable source of structural information and allows for rapid and accurate assessment of SoC and SoH as shown below.

[0109] Figure 8 is a diagram 800 comprising examples of NMR spectra of an NMC (lithium nickel manganese cobalt oxides) battery cell at several stages of a galvanostatic charging. The diagram 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%.

[0110] In the fully charged cell (spectrum 801-8) , there are three major groups of signals at about -10, -77 and 61 ppm. The spectral component at -10 ppm has a high-field shoulder that emerges upon charging, thus identifying the main anode species. Near complete discharge (spectrum 801-1) , a broad signal at about -77 ppm comes from residual lithium at the anode. A group of relatively narrow lines around 149 ppm(spectrum 801-1) shifting to high field upon charging comes from mobile lithium ions or their complexes in the paramagnetic environment.

[0111] During discharge, lithium ions undergo a transfer from a weakly magnetic anode environment, where the linewidths are less than 50 ppm, into a strongly paramagnetic NMC material, where linewidths exceed 2,000 ppm. Thus, in the cathode, the magnetization lifetime is short as compared to a preacquisition delay (equal to about 6,5 ps) , and around 70% of lithium become "invisible" as the battery discharges. The line shape evolution shown in Figure 8 is completely reversible when cycling is performed within the range 0 < SoC < 100%.

[0112] Figure 9 is a diagram 900 comprising examples of nuclear magnetic resonance spectra of an NMC battery cell subjected to overcharge followed by discharge. The diagram 900 comprises six spectra 901-1, 901-2, 901-3, 901-4, 901-5 and 901-6 corresponding respectively to SoC of approximately 112%, 122%, 133%, 143%, 154% and 100%.

[0113] In the example shown, overcharging the cell results in a formation of quasi-metallic lithium, which is identified by a signal at about 220 ppm (spectra 901-1 to 901-5) . Upon discharging from 154% to 100% (spectra 901-5 and 901-6) , a large part of the metallic lithium re-dissolves. A remaining signal at about 210 ppm (spectrum 901-6) indicates the presence of "dead" lithium in the cell.

[0114] The diagrams 500, 600, 700, 800 and 900 are, for example, acquired using the RF circuit 101, for example, in the system 100. The system 100 is, for example, placed in the arrangement previously described with reference to Figure 3.

[0115] Figure 10 is a partial and schematic top view of a system 1000 comprising the electronic circuit 101 according to one embodiment. Figure 10 more particularly illustrates aT1 multi-modal probe comprising NMR and surface-scan MRI RF subcircuits. 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 detailed again below.

[0116] The system 1000 of Figure 10 differs from the system 100 of Figure 1 in that the system 1000 further comprises a unilateral RF sensor 1001 specifically designed for studies of flat battery cells (pouch and prismatic) . The unilateral RF sensor 1001 is, for example, an RF resonator similar to a parallel-plate transmission line. In the example shown, the RF sensor 1001 has a shape of two parallel metal plates separated by a 1 mm thick layer of proton-containing polymer material (e.g., silicone) . The working surface of the RF sensor 1001 is placed in contact with one side of the flat battery cell 107. In particular, the battery cell 107 is placed in contact with the working surface of the surfacescan MRI sensor 1001.

[0117] The RF sensor 1001 is, for example, controlled by the NMR spectrometer 305 previously described with reference to Figure 3. In such a case, the RF sensor 1001 is, for example, connected to an7H channel of the NMR spectrometer 305, and a "X" channel (where X is e.g.7Li) of the NMR spectrometer 305 is connected to the in situ NMR circuit 101.

[0118] The sensor 1001 enables to perform surface-scan MRI analysis, which is a magnetic susceptibility-based methodology sensitive to mechanical defects, spatial distributions of SoC, magnetic phases, and current density distribution in battery cells, more specifically in flat cells (e.g., pouch and prismatic) . The RF sensor 1001 is intended to operate at a Larmor frequency of protons (7H) , producing a magnetic field BiH, while the in situ NMR RF circuit 101 operates at a frequency of a "X" nuclei, for example,7Li, 23Na, etc., producing a magnetic field Bix. The RF sensor 1001is alternatively intended to operate at a Larmor frequency of 19F if the detection medium of the sensor 1001 is made of a fluorine-based polymer. With respect to the system 100 of Figure 1, the system 1000 of Figure 10 enables to perform a further and / or a complementary analysis of the battery cell 107. The surface-scan MRI sensor design is based on the parallel-plate architecture. One plate is the working surface places in contact with the pouch cell. The backside comprises variable tuning and matching capacitors C -mri and CM-mri . Two arrays of fixed capacitors (top and bottom) connect two copper sheets separated by a thin layer of the proton-rich polymer (for example, silicone) . The cell's terminals are connected to the plug-and-play NMR sub-circuit.

[0119] By way of example, the RF sensor 1001 is implemented as described in the above-mentioned 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.

[0120] The system 1000, for example, forms a composite device that allows multi-modal in situ analysis of pouch cells, in particular by spectroscopy and magnetism-based MRI contrast of those cells.

[0121] An advantage of the system 1000 is that it eliminates the RF shielding problem caused by the conductive metal casing and current collectors of commercial battery cells, and provides detailed spectroscopic and spatially resolved (MRI) information about the composition of the battery cells, chemical environment of the electrochemically active elements, mechanical defects, electrochemical degradation, susceptibility distribution, magnetic phase composition of the cathode material, and current density distribution in the cell. This "in situ" information represents a series ofstatistical metrics describing the cell's chemistry, SoC, SoH, lifetime, life-cycle history, etc.

[0122] Another advantage of the systems 100 and 1000 is that they do not require destructive manipulations with sealed casings of cells and terminals.

[0123] The method described above is, for example, intended to be implemented: in academic laboratories as part of fundamental research activities ; within industrial environments, close to battery production lines, for performance analysis and detection of electrochemical and mechanical defects, dendrites and other substandard conditions; and on battery recycling lines for non-destructive chemical analysis and identification of battery materials.

[0124] The RF circuit 101 and the systems 100 and 1000 improve various aspects of battery cell analysis. More specifically, they enable the following capabilities:1. non-destructive multi-nuclear in situ NMR and MRI analysis of electrochemical materials in commercial battery cells of various configurations (e.g. pouch, prismatic and cylindrical cells) , these measurements providing fundamental structural information and new metrics for the determination of SoC and SoH;2. accurate and rapid SoC measurement by a) quantifying the populations of intercalated charge carriers in the cathode and anode instead of relying on conventional SoC metrics such as voltage measurements between battery terminals and b) via magnetic field contrast-based MRI measurements using the system 1000, which provides the spatial distribution of SoC;3. improved SoH characterization, because the RF circuit 101 and the systems 100 and 1000 enable to obtain magnetic resonance data correlating with the battery cell conditionsuch as charge capacity, internal resistance , presence of dendrites , sel f-discharge rate , overall period in service , etc . ;4 . detection of hazardous metallic lithium in order to reduce risks associated with thermal runaway, which enables to prevent fire incidents , for example , on battery-powered transport and household environments ;5 . accurate detection and quanti fication of lithium plating, which facilitates the development of rapid, dendrite- free charging protocols ;6 . improved analysis and design of battery packs , in particular regarding synchroni zation and consistency between the various cells of a same pack; and7 . assistance to battery materials recycling, for example , by sorting cells by their cathode chemistry .

[0125] Figure 11 is an electrical diagram equivalent to a bi- modal NMR / MRI probe 1100 . The bi-modal probe 1100 comprises the circuit 101 previously described in relation to Figure 1 and a circuit forming part of the RF sensor 1001 .

[0126] In the example shown, the battery cell 107 is placed in contact with a working surface of the surface-scan MRI sensor 1001 . The working surface for example comprises a first conductive plate 1101 , for example a copper sheet . The terminals of the cell 107 are connected to the NMR circuit at positions 105A and 105B, corresponding respectively to the nodes 207A and 207B of the circuit 101 . In the example shown, the surface-scan MRI sensor 1001 comprises a second conductive plate 1103 , for example another copper sheet , parallel to the first conductive plate 1101 . The second conductive plate is for example separated from the first conductive plate by a thin layer of proton-rich polymer . In the example illustrated in Figure 11 , the battery cell 107 is interposed between the conductive plates 1101 and 1103 .

[0127] In the shown example , two arrays 1105A, 1105B of fixed capacitors 1107 having a capacitance Cp, interconnect the two conductive plates 1101 and 1103 . The capacitors 1107 are adapted to control a distribution of the Bi field in the volume of the resonator . The conductive plates 1101 and 1103 are for example further interconnected by a variable capacitor 1109 having a capacitance Cp-mri .

[0128] In the example shown in Figure 11 , the circuit of the RF sensor 1001 comprises a capacitor 1111 interconnecting the conductive plates 1101 and 1103 . The capacitor 1111 has a capacitance Co . The circuit further comprises a capacitor 1113A coupling the conductive plate 1101 to a first terminal of a source 1115 of an AC voltage V2 and another capacitor 1113B coupling the conductive plate 1103 to a second terminal of the source 1115 . The capacitors 1113A and 1113B for example each have a capacitance CM-mri .

[0129] The RF sub-circuits of the surface-scan MRI sensor 1001 and the circuit 101 are for example located respectively on opposite sides of a double-sided electronic circuit board . Although this design is optimal for flat pouch and prismatic cells , a similar architecture can be applied to cylindrical cells and battery packs .

[0130] Figure 12A is an electrical diagram equivalent to a system 1200 comprising an electronic circuit 1201 according to one embodiment . The electronic circuit 1201 is , for example , a radio frequency (RF) circuit . The circuit 1201 is , for example , a two- frequency variant of the electronic circuit 101 of Figure 1 .

[0131] In the example illustrated, the circuit 1201 comprises a capacitive element 1203 coupling the nodes 201A and 201B of the circuit 1201 , the node 201A being for example connected to the node 207A . More speci fically, the capacitive element 1203 of capacitance C1has a terminal coupled, preferablyconnected, to the node 201A and another terminal coupled, preferably connected, to the node 201B . In the example shown, the circuit 1201 further comprises capacitive elements 1205A and 1205B, each of capacitance CM1, coupling respectively the nodes 201A and 201B to first terminals of LC circuits 1207A and 1207B, respectively . In this example , the LC circuit 1207A has a second terminal connected to a node 1209 of the circuit 1201 . The node 1209 is for example a node of application of a reference potential , for example the ground . In the shown example , the LC circuit 1207B has a second terminal connected to a first terminal of a source 1211 of an AC voltage RF1 . In this example , the second terminal of the source 1211 is connected to the node 1209 .

[0132] In the shown example , the circuit 1201 further comprises a capacitive element 1223 coupling the nodes 207B and 201B of the circuit 1201 . More speci fically, the capacitive element 1223 o f capacitance C2has a terminal coupled, preferably connected, to the node 207B and another terminal coupled, preferably connected, to the node 201B . In the example shown, the circuit 1201 further comprises capacitive elements 1225A and 1225B, each of capacitance CM2. The capacitive element 1225A couples the node 201B to a first terminal of a source 1231 of an AC voltage RF2 . The capacitive element 1225B couples a second terminal of the source 1231 to a first terminal of an LC circuit 1227B . The second terminal of the LC circuit 1227B is connected to the node 207B . In the shown example , the circuit 1201 further comprises another LC circuit 1227A coupling the nodes 201B and 207B .

[0133] The LC circuits 1207A, 1207B, 1227A and 1227B for example each comprise at least one inductive element and at least one capacitive element . The LC circuits 1207A, 1207B, 1227A and 1227B are for example LC-trap circuits .

[0134] In the shown example, the circuit 1201, corresponding to a two-frequency version of the circuit 101 previously described, is provided with tuning and matching capacitors C and CM and with LC-traps for each sub-resonator. Based on the same principles as the circuit 101, the two-frequency circuit 1201 is designed as a two-channel probe enabling complex 2-NMR experiments and allowing improved spectral analysis for battery diagnostics.

[0135] Figure 12B represents6Li and7Li NMR spectra of a pouch cell subjected to overcharging. The spectra of Figure 12B are for example obtained using the system 1200 comprising the circuit 1201.

[0136] The quadrupolar NMR lineshape effects in spin systems (I > 1 / 2) are a powerful approach to study the material structure on both local and macroscopic levels. Quadrupolar splitting (indicated by star symbols in Figure 12B) arises from the interaction between the nuclear quadrupole moment and the electric field gradient (EFG) at the nucleus. This interaction depends on the nuclear quadrupole moment and EFG tensor-related parameters (determined by the local structure) Distinct quadrupolar splitting of7Li NMR lines of the graphite anode in commercial pouch cells, as shown in Figure 12B, is sensitive to macroscopic mechanical deformations affecting the average EFG tensor. This is of particular importance for understanding volumetric deformations in electrodes due to solid-state chemical reactions. The6Li spectrum allows improved differentiating of signals in the 7Li spectrum at different states of charges.

[0137] Figure 12A illustrates a two-frequency variant of the circuit 101. However, those skilled in the art are able, based on the present description, to adapt this variant to more than two frequencies, the circuit 101 thus having a first resonance frequency equal to about a Larmor frequency of afirst atomic nucleus having a non-zero spin number and at least one second resonance frequency equal to about a Larmor frequency of a second atomic nucleus having a non-zero spin number different from the Larmor frequency of the first atomic nucleus .

[0138] . More generally, multiple frequencies can be placed on the same PCB board. It is, for example, possible to arrange an in situ RF adapter that contains simultaneously subcircuits operating at Larmor frequencies ofXH,7Li,59Co, and other NMR sensitive nuclei represented in the battery cell.

[0139] Various embodiments and variants have been described. Those skilled in the art will understand that certain features of these embodiments can be combined and other variants will readily occur to those skilled in the art. In particular, the implementations of the circuit 101 and of the systems 100 and 1000 may vary depending on NMR instrument types used, which are categorized, for example, by the magnitude of their polarizing field Bo, their magnet bore diameter, and their spatial orientation. These various implementations are within the reach of those skilled in the art based on the present description .

[0140] Furthermore, what is described more specifically in relation to an example of application to mobile phone or smartphone battery cells applies more generally to any type of commercial battery cell that can be found, for example, in portable electronic devices, such as laptop computers, touch tablets, smart watches, smart activity trackers, etc., and in electric vehicles, such as electric cars, motorcycles, trucks, etc .

[0141] Furthermore, what is described more specifically in relation to examples where the battery cell 107 has an LCO or an NMC chemistry applies more generally to any type of transition metal oxide chemistry and Li, Na, K, Cu, Mg, Ca,Al and Zn ions as intercalants , for example, lithium or sodium cobalt oxide, lithium or sodium iron phosphate, lithium manganese oxide, vanadium oxides, NaNixFeyMnz02, etc. NMR data characterize a specific transition metal oxide material in a cell, as described by specific characteristic chemical shifts and NMR line-shapes.

[0142] Finally, the practical implementation of the embodiments and variants described herein is within the capabilities of those skilled in the art based on the functional description provided herein above. In particular, the dimensions of the RF circuit 101 may vary depending on the type of the battery cell 107 to be analyzed. In particular, depending on the application, the distance between the connection elements 103A and 103B may be cell-specific or universal, that is adjustable to multiple cell dimensions and geometries .

Claims

36CLAIMS1. An electronic circuit (101) comprising: first (103A) and second (103B) connection elements intended to be connected respectively to first (105A) and second (105B) conduction terminals of an electrochemical energy storage device (107) ; third (113A) and fourth (113B) connection elements intended to be coupled to a nuclear magnetic resonance spectrometer (305) ; and a radio frequency matching and tuning circuit (119) coupling the third (113A) and fourth (113B) connection elements to the first (103A) and second (103B) connection elements, wherein the radio frequency matching and tuning circuit (119) comprises: a first inductive element (109A) having a first terminal coupled, preferably connected, to the first connection element (103A) ; a second inductive element (109B) having a first terminal coupled, preferably connected, to the second connection element (103B) ; a first capacitive element (111A) having a first terminal coupled, preferably connected, to a second terminal of the first inductive element (109A) and a second terminal coupled, preferably connected, to the third connection element (113A) ; a second capacitive element (111B) having a first terminal coupled, preferably connected, to a second terminal of the second inductive element (109B) and a second terminal coupled, preferably connected, to the fourth connection element (113B) ; and a third capacitive element (117) coupling the second terminals of the first (109A) and second (109B) inductive elements .

372. The circuit (101) of claim 1, wherein the first (109A) and second (109B) inductive elements are inductors and wherein the first (111A) , second (111B) and third (117) capacitive elements are capacitors.

3. The circuit (101) of claim 1 or 2, wherein the first (109A) and second (109B) inductive element have a same inductance (L ) and wherein the first (111A) and second (111B) capacitive elements have a same first capacitance (CM) different from a second capacitance (C ) of the third capacitive element (117) .

4. The circuit (101) of any one of claims 1 to 3, wherein the circuit has a first resonance frequency equal to about a Larmor frequency of a first atomic nucleus having a nonzero spin number, for example selected among:7Li,23Na,31P, 63Cu,65Cu,59Co,2H,19F,27A1,55Mn,6Li and39K.

5. The circuit (101) of any one of claims 1 to 4, wherein the circuit has at least one second resonance frequency equal to about a Larmor frequency of a second atomic nucleus having a non-zero spin number different from the Larmor frequency of the first atomic nucleus.

6. A system (100; 1000; 1100; 1200) comprising: the circuit (101) according to any one of claims 1 to 5 ; and a nuclear magnetic resonance spectrometer (305) equipped with: an RF transmit / receive channel connected to the third (113A) and fourth (113B) connection elements of the circuit; and a magnet (301) provided with a cavity compatible with dimensions of the system (100; 1000) .

7. The system (100; 1000; 1100; 1200) of claim 6, wherein the magnet (301) has a hollow cylindrical or rectangular cavity arranged vertically or horizontally.

8. The system (1000; 1100; 1200) of claim 6 or 7, further comprising a radio frequency sensor (1001) intended to operate at a Larmor frequencies of either9H proton or19F fluorine isotopes.

9. The system (100; 1000; 1100; 1200) of any one of claims 6 to 8, further comprising a battery cell (107) having first (105A) and second (105B) conduction terminals respectively connected to the first (103A) and second (103B) connection elements of the circuit (101) .

10. The system (100; 1000; 1100; 1200) of claim 9, wherein the battery cell (107) is an electrochemical pouch cell.

11. The system (100; 1000; 1100; 1200) of claim 9, wherein the battery cell (107) is an electrochemical cylindrical cell .

12. The system (100; 1000; 1100; 1200) of any one of claims 8 to 10, wherein the battery cell (107) forms part of a consumer electronic device battery or of an electric vehicle battery.

13. The system (1100) of any one of claims 9 to 12, further comprising a magnetic resonance imaging probe comprising first (1105A) and second (1105B) conductive plates, wherein the battery cell (107) is interposed between the first (1105A) and second (1105B) conductive plates.

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

15. The method of claim 14, in its dependence on claim 9, further comprising, at step c) , an acquisition of MRI data representative of spatial distributions of SoC-dependent magnetic susceptibility and / or current density in the battery cell (107) .

16. The method of claim 14 or 15, further comprising, after step c) , a step d) of determination of a state of charge of the battery cell (107) according to the spectrum acquired at step c) .

17. The method of any one of claims 14 to 16, further comprising, after step c) , a step e) of determination of an overcharge of the battery cell (107) according to the spectrum acquired at step c) .

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