Lithium-ion battery energy storage device and associated manufacturing methods

Abstract

The invention relates to a lithium-ion battery energy storage device (1), and to the associated manufacturing method (2), the device (1) comprising active materials, the active materials comprising: an electrolyte (12), a negative electrode (11), and a positive electrode (13), the device (1) being characterized in that the device (1) has a total isotopic enrichment in 6Li greater than or equal to 8%, the total enrichment being determined with respect to all of the lithium atoms in the active materials. A better trade-off between power and energy density can be achieved, and therefore a better compromise between the range of the object powered by the battery and charging speed. Drawing_references_to_be_translated:

Description

[0001] "Lithium-ion battery-type energy storage devices and associated manufacturing processes"

[0002] TECHNICAL FIELD OF THE INVENTION

[0003] The present invention relates to the field of lithium-ion batteries. More particularly, the invention relates to the design, manufacture, and optimization of energy storage devices based on the migration, or equivalently the diffusion, of lithium ions between electrodes. Its applications are particularly advantageous in the fields of electric transportation, powering drones or connected portable devices (such as smartphones and tablets), and energy storage.

[0004] STATE OF THE ART

[0005] Lithium-ion batteries are widely used in the transportation sector, particularly for electric vehicles, due to their high energy density and fast charging.

[0006] However, managing fast charging in these batteries presents a major challenge. Indeed, while fast charging is advantageous for the convenience of electric vehicle users, it can pose several technical challenges.

[0007] Indeed, while fast charging improves convenience, it often comes at the cost of reduced battery range. To enable faster charging, which requires high power, manufacturers often have to sacrifice some of the battery's energy density, potentially impacting the range of electric vehicles. Therefore, a trade-off exists between energy density (and thus the range of the device powered by the battery) and power, inherent in the use of lithium in batteries.

[0008] Current research focuses on improving electrode design to increase power output, at the cost of reduced battery energy density. An electrode, according to existing solutions, typically comprises: a host material for energy storage, a carbon-based agent that enhances power, and a polymer material that ensures mechanical stability. To increase power output, existing solutions aim to reduce electrode thickness and increase the amount of carbon-based agent. This improves charging speed but simultaneously decreases the battery's energy density.

[0009] Therefore, there is a need to better reconcile fast charging with battery performance.

[0010] One objective of the present invention is therefore to provide a solution that improves lithium-ion batteries, and more specifically to increase the power of a lithium-ion battery. Another objective of the invention is to provide a fast-charging lithium-ion battery with a better balance between its energy density and its performance.

[0011] SUMMARY OF THE INVENTION

[0012] To achieve this objective, according to a first aspect, an energy storage device of the lithium-ion battery type is planned, comprising active materials, the active materials comprising an electrolyte, a positive electrode and a negative electrode.

[0013] Advantageously, the device includes a total enrichment rate in the 6Li isotope greater than or equal to 8%, the total enrichment rate being taken with respect to all the lithium atoms in the active materials.

[0014] The active materials in conventional lithium-ion batteries are based on natural lithium, which typically contains approximately 7.5% of the 6Li isotope and 92.5% of the 7Li isotope. Furthermore, the 6Li isotope alone weighs nearly 15% less than natural lithium, for the same number of atoms. These properties give 6Li increased speed and mobility, in terms of kinetics, compared to natural lithium. The 6Li enrichment, relative to the proportion of 6Li present in natural lithium, allows for increased kinetics and therefore faster diffusion of lithium within the battery, including the electrolyte and active materials. Thus, the battery's power output is increased at the same electrode. Therefore, at the same cycling rate, batteries enriched with 6Li perform better than their natural lithium equivalents.This power increase is not achieved at the expense of reduced energy density, unlike existing solutions. A better compromise between power and energy density can be found, thus achieving a better balance between the battery life of the device and charging speed. In particular, charging time can be reduced.

[0015] A second aspect of the invention relates to a method for manufacturing the lithium-ion battery type energy storage device comprising a supply of active materials, the active materials comprising a positive electrode and a negative electrode, an electrolyte, and an assembly of the positive electrode and the negative electrode and the electrolyte to form the storage device.

[0016] Advantageously, the active materials have a total enrichment rate in the 6Li isotope greater than or equal to 8%, the total enrichment rate being taken with respect to all the lithium atoms in the active materials.

[0017] BRIEF DESCRIPTION OF THE FIGURES

[0018] The aims, objects, features and advantages of the invention will be more apparent from the detailed description of an embodiment thereof, which is illustrated by the following accompanying drawings.

[0019] Figure 1 schematically represents a lithium-ion battery type energy storage device, the device having a total enrichment rate in 6Li isotope greater than or equal to 8%, according to an example of an embodiment.

[0020] Figure 2 schematically represents a lithium-ion battery type energy storage device, the device having a total enrichment rate in 6Li isotope of 70%, according to an example of an embodiment.

[0021] Figure 3 schematically represents a manufacturing process, according to an example of an embodiment, of a lithium-ion battery type energy storage device, the device having a total enrichment rate in 6Li isotope greater than or equal to 8% as illustrated in figure 1.

[0022] Figure 4 schematically represents an example of the manufacturing process, including a step of impregnating the positive and negative electrodes with the liquid electrolyte during the battery assembly step.

[0023] Figure 5 schematically represents an example of the manufacturing process, including a step of enrichment in 6Li isotope by at least partial substitution of natural lithium by the 6Li isotope of a positive electrode and / or a negative electrode using at least one bath comprising the 6Li isotope.

[0024] Figure 6 shows galvanostatic curves of a lithium-ion battery type energy storage device comprising a negative graphite electrode, cycled with respect to metallic lithium, and as a function of the isotope or isotope mixture used, according to an example embodiment.

[0025] Figure 7 graphically represents the specific capacity of a cell of a lithium-ion battery type energy storage device comprising a negative graphite electrode, cycled with respect to metallic lithium, and as a function of the isotope or isotope mixture used and the number of cycles applied, according to an example embodiment.

[0026] Figure 8 shows galvanostatic curves of a lithium-ion battery-type energy storage device comprising an NMC (Li₂O₅₂₂₂Co₂) positive electrode c )i-xO2 with (a+b+c=1)), cycled with respect to metallic lithium, and depending on the isotope or mixture of isotopes used, according to an example of an embodiment.

[0027] Figure 9 shows specific capacity curves of a lithium-ion battery type energy storage device comprising an NMC type positive electrode, cycled with respect to metallic lithium, as a function of the isotope or isotope mixture used and the number of cycles applied, according to an example embodiment.

[0028] Figure 10 schematically represents possible techniques for measuring the enrichment rate of at least one active material in a lithium-ion battery type energy storage device, according to an example of an embodiment.

[0029] Figure 11 schematically represents possible techniques for measuring the total enrichment rate of a lithium-ion battery type energy storage device, according to an example of an embodiment.

[0030] Figures 12A, 12B and 12C represent scanning electron microscopy (SEM) images of a lithium-ion battery type energy storage device comprising a positive electrode based on lithium-nickel-manganese-cobalt (8-1-1) oxide, commonly referred to as NMC811, with 100% natural lithium (Figure 12A), after 2 hours of chemical depletion delithiation (Figure 12B), after 6 hours of chemical depletion delithiation (Figure 12C), according to exemplary embodiments of the invention.

[0031] Figures 13A and 13B illustrate the extraction of a tip from a particle of an NMC811-based positive electrode, the extraction being performed by focused ion beam during SEM analysis, according to two embodiments of the invention. The drawings are given by way of example and are not limiting to the invention. They constitute schematic representations of the principle intended to facilitate understanding of the invention and are not necessarily to scale with practical applications. In particular, the dimensions of the active materials of the storage device, such as the positive electrode, negative electrode, or electrolyte, are not representative of reality. Furthermore, the fraction of 6Li and 7Li isotopes and their proportions relative to all the lithium atoms in the device are not representative of reality.

[0032] DETAILED DESCRIPTION OF THE INVENTION

[0033] Before beginning a detailed review of embodiments of the invention, optional features that may be used in combination or alternatively are stated below.

[0034] In one example, at least one of the negative and positive electrodes exhibits an altered surface morphology. This altered surface morphology can be characterized by pores, i.e., holes on the exposed surface of the agglomerated particles forming the electrode. This hole formation can, for example, be linked to corrosion of the exposed surface of the agglomerated particles forming the electrode. This porous surface morphology can also be characterized by more pronounced grain boundaries. These more pronounced grain boundaries are visible, for example, by transmission electron microscopy (TEM). This analytical technique can notably reveal a larger dimension of the grain boundaries, for example, their diameters.Automatic crystal orientation-phase mapping (MET-ASTAR) can be used to quantify the local chemistry of a grain boundary, its dimensions, and its crystallographic orientation. The crystallographic orientation of a grain boundary can, for example, have changed as a result of depletion by chemical delihiation.

[0035] As an example, the total enrichment in the 6Li isotope is greater than or equal to 30%, preferably greater than or equal to 50%. The higher the total enrichment in the 6Li isotope, the more the electrochemical performance of the storage device is improved due to the properties of 6Li.

[0036] As an example, the total enrichment in the 6Li isotope is strictly greater than 50%, preferably greater than or equal to 70%. A mixture of the two isotopes can induce intrinsic defects in the active materials due to the mass difference between them. These isotopes can follow different diffusion pathways in the active materials, which can lead to local fatigue. A higher prevalence of 6Li, and in particular a proportion of 6Li greater than or equal to 50%, and preferably strictly greater than 50%, therefore improves the mobility and diffusion, or equivalently the migration, of lithium ions (Li⁻). + and reduces intrinsic defects. A battery with better electrochemical performance and a longer lifespan can be obtained.

[0037] For example, the positive electrode may consist of a lithium metal oxide and / or a spinel-based material and / or a phosphate-based material. Lithium metal oxide positive electrodes are chosen for lithium-ion batteries primarily because of their stability, high energy density, ease of manufacture, and electrochemical behavior.

[0038] For example, the positive electrode has a 6Li isotope enrichment level of 8% or higher. Increasing the 6Li isotope enrichment level of the positive electrode further improves the battery's electrochemical performance.

[0039] In one example, the electrolyte is in liquid form; preferably, it is an organic liquid electrolyte comprising a lithium salt, preferably with a solvent mixture including carbonates. The use of a liquid electrolyte is preferable because a commercially available electrolyte can be used. This electrolyte can, for example, be enriched with 6Li during the manufacturing process, preferably by replacing the unenriched salt of the commercial liquid electrolyte with an enriched salt.

[0040] For example, the electrolyte is in solid form, preferably a solid polymer electrolyte. Solid polymers are preferred among solid-state electrolytes for batteries due to their advantages in terms of safety, thermal stability, and chemical stability. They thus represent a promising option for next-generation batteries, such as solid-state batteries. The solid electrolyte can be inorganic, organic, or a mixture of both.

[0041] For example, the electrolyte has a 6Li isotope enrichment level of 8% or higher. Increasing the 6Li isotope enrichment level of the electrolyte helps improve electrochemical performance and battery life.

[0042] For example, the negative electrode may consist of lithium metal or a lithium metal oxide. Using lithium metal for the negative electrode can be particularly advantageous. Indeed, in lithium-metal batteries, lithium metal can be used as the negative electrode. This allows for greater energy capacity because lithium metal has a higher energy density than graphite.

[0043] For example, the negative electrode has a 6Li isotope enrichment level of 8% or higher. Increasing the 6Li isotope enrichment level has a particularly beneficial effect on the negative electrode, which is generally the limiting factor for optimizing lithium-ion batteries. Therefore, increasing the 6Li isotope enrichment level within the battery significantly improves its electrochemical performance.

[0044] In one example, the active materials each have an enrichment level in the 6Li isotope greater than or equal to 8%. Through synergy, this makes it possible to achieve a high total enrichment level.

[0045] In one example, the negative electrode comprises lithium metal, the positive electrode comprises a lithium metal oxide, and the electrolyte is in solid form. The electrolyte is preferably inorganic, organic, or a mixture of both. The active materials can each have a 6Li isotope enrichment of 8% or higher. The use of 6Li is thus particularly advantageous due to the synergy between the enriched positive electrode, the lithium metal-based negative electrode, and the electrolyte. This results in higher energy density and improved energy conversion efficiency.

[0046] According to one example, the negative electrode comprises lithium metal, the positive electrode comprises a lithia metal oxide and the electrolyte is in liquid form, preferably organic, the active materials each having an enrichment rate in the 6Li isotope greater than or equal to 8%.

[0047] The electrolyte has an enrichment level in the 6Li isotope greater than or equal to 8%. The use of an enriched liquid electrolyte allows the manufacture of the simplest enriched battery for an industrial manufacturer because the impregnation of the negative and positive electrodes by the liquid electrolyte at the time of battery assembly minimizes modification of the manufacturing line, in particular by not involving any modifications with regard to the electrodes.

[0048] For example, the negative electrode contains graphite. Using graphite negative electrodes in Li-ion batteries offers advantages, particularly in terms of stability, cost, electrochemical performance, and longevity. This is why graphite remains one of the most commonly used materials in battery manufacturing. Using graphite for the negative electrode avoids the need to modify existing production lines. Furthermore, using graphite leads to a reduction in fluorine levels and persistent pollutants such as PFAs (perfluoroalkoxylated per ...

[0049] As an example, substitutional enrichment involves depletion of the 7Li isotope using a depletion bath. The depletion is configured to deplete at least one of the negative and positive electrodes of natural lithium, and therefore also of the 7Li isotope. The conditions of the depletion bath, and in particular its concentration, influence the extent of visible surface defects on at least one of the negative and positive electrodes.

[0050] As an example, depletion-induced delithiation can cause pitting of the primary particles of at least one of the negative and positive electrodes. This pitting is characterized, for example, by increased porosity of the agglomerated particles (also called primary particles or grains) at the nanometer scale. The pore size can be assessed using a specific surface area measurement technique, such as BET analysis, named after its inventors Brunauer-Emmett-Teller. Thus, the electrode(s) subjected to depletion-induced delithiation will have a BET that increases by at least 5%.

[0051] As an example, substitution enrichment involves enrichment using an enrichment bath configured to increase the 6Li isotope enrichment level of at least one of the negative and positive electrodes. Electrochemical cycling can, for instance, be used to restore the 6Li isotope level. Furthermore, inductively coupled plasma (ICP) measurements can also be used to achieve this level. An atom probe can be used to observe the 6Li isotope distribution in a localized manner on an exposed surface of the electrode(s). X-ray diffraction can also reveal the relithiation of one or more electrodes via substitution enrichment.

[0052] As an example, the depletion bath includes an oxidizing agent. Preferably, the depletion bath includes NOBF4.

[0053] As an example, the enrichment bath includes a lithium salt. Preferably, the enrichment bath includes 6U2CO3 or 6Lil.

[0054] For example, during the electrolyte supply stage, the electrolyte has a 6Li isotope enrichment level of 8% or higher. The electrolyte may be commercially supplied already enriched, or the battery manufacturing process may include an electrolyte enrichment step.

[0055] Preferably, the electrolyte enrichment step, whether solid or liquid, is carried out by cation complexing agents and / or by ion exchange resins and / or by fractional crystallization and / or by thermal diffusion and / or by electrolytic separation and / or by laser separation and / or by distillation and / or by micro-algae enrichment.

[0056] For example, the electrolyte is in liquid form, and during the battery assembly stage, the electrolyte is impregnated into the negative and positive electrodes to form the storage device. Adding a step to impregnate the negative and positive electrodes with the liquid electrolyte minimizes the modification to the manufacturing line for the manufacturer.

[0057] In one example, the electrolyte is in solid form, preferably a solid polymer electrolyte. The use of a solid electrolyte, preferably enriched, can be an advantageous solution for manufacturing solid-state batteries.

[0058] For example, at least one of the negative and positive electrodes has a 6Li isotope enrichment level of 8% or higher. Using an enriched positive and / or negative electrode, preferably with an enriched electrolyte, allows for the highest levels of total enrichment, further increasing electrochemical performance and battery life. Specifically, it is possible to ensure that the positive electrode is enriched while the negative electrode is not.

[0059] According to one example, the process includes, for at least one of the positive and negative electrodes, an enrichment in the 6Li isotope.

[0060] As an example, enriching at least one of the negative and positive electrodes involves at least partial substitution of natural lithium with the 6Li isotope using at least one bath, preferably two baths, containing the 6Li isotope, such that at least one of the negative and positive electrodes has a 6Li isotope enrichment level greater than or equal to 8%. It is therefore conceivable for manufacturers to include in their battery manufacturing process a substep of at least partial substitution of natural lithium with the 6Li isotope using a substitution bath to obtain the enriched storage device.

[0061] As an example, at least partial substitution of natural lithium with the 6Li isotope yields better electrochemical performance results for the enriched storage device than other 6Li enrichment methods. Furthermore, no active material is lost during the substitution, particularly when using a substitution bath. This makes it possible to recover the 7Li that has been substituted.

[0062] Furthermore, it becomes possible to use active materials optimized for battery applications, unlike enrichment by synthesis, for example. This also allows for simpler and better control over the enrichment rate and the resulting percentage compared to other enrichment methods, particularly for lithium-6. In addition, this alternative method overcomes the constraints related to the embargo on lithium-6 in the nuclear sector.

[0063] For example, the negative electrode contains lithium metal, with a 6Li isotope enrichment level of 8% or higher. This allows for synergy, enabling higher total enrichment levels and further enhancing electrochemical performance and battery life.

[0064] As an example, the process includes measuring the total lithium enrichment level using neutron imaging, nuclear magnetic resonance, mass spectrometry, and / or inductively coupled plasma analysis. Preferably, neutron imaging is considered because it allows the amount of 6Li in a sample, whether liquid or solid, to be determined without having to dismantle the electrochemical cell. Indeed, this technique allows manipulation of the 6Li and 7Li cross-sections; since 6Li is visible and 7Li is transparent, it is then possible, using Beer-Lambert's law, to determine the amount of 6Li in a sample.

[0065] According to one example, the process includes, preferably before the first cycling of the storage device, a measurement of the enrichment rate in 6Li isotope of at least one active material taken in isolation by neutron imaging, nuclear magnetic resonance, mass spectrometry and / or inductively coupled plasma analysis.

[0066] In one example, the process further includes a measurement of the spatial distribution of the 6Li isotope on a surface of at least one of the negative and positive electrodes, the measurement being performed by atom probe tomography. In another example, the process further includes characterizing the morphology of a surface of at least one of the negative and positive electrodes, the characterization being performed by scanning electron microscopy. In particular, the at least one of the negative and positive electrodes exhibits an altered morphology at the primary grain level. These two techniques can confirm that the enriched at least one of the negative and positive electrodes was indeed obtained by enrichment via substitution.

[0067] As an example, the tomographic atom probe is made on a conical tip extracted from at least one of the negative and positive electrodes. Extraction can, for example, be performed by focused ion beam scanning electron microscopy (FIB-SEM).

[0068] According to one example, the characterization of a surface morphology of at least one of the negative and positive electrodes includes an observation of the distribution of the 6Li isotope on the surface of the electrode.

[0069] In one example, the process further includes a measurement of the spatial distribution of the 6Li isotope on a surface of at least one of the negative and positive electrodes, the measurement being performed by time-of-flight secondary ion mass spectrometry (TOF-SIMS). This measurement is, for example, a quantification of the proportions of 6Li and 7Li isotopes on the electrode surface and / or a 6Li isotope substitution rate.

[0070] According to one example, the process further includes a measurement relating to a spatial localization in 6Li isotope of at least one among the negative electrode and the positive electrode, the measurement being by atom probe tomography.

[0071] According to one example, at least one of the negative electrode and the enriched positive electrode exhibits a spatial distribution gradient in 6Li isotope along a direction substantially oblique or perpendicular to its exposed surface, for example to the exposed surface of the agglomerated particles forming said electrode.

[0072] Preferably, the technique of inductively coupled plasma mass spectrometry is considered because it is easy to implement in the laboratory and allows for the quantification of 6Li and 7Li with highly high precision.

[0073] Preferably, the nuclear magnetic resonance technique can also be considered because it allows the 6Li to be separated from the 7Li and thus the enrichment rate of the active materials in the battery to be determined.

[0074] For the purposes of this disclosure, "A and / or B" means (A), (B), or (A and B). For the purposes of this disclosure, "A, B and / or C" means (A), (B), (C), (A and B), (A and C), (B and C), or (A, B and C).

[0075] Several embodiments of the invention implementing successive steps of the manufacturing process are described below. Unless explicitly stated, the adjective "successive" does not necessarily imply, although this is generally preferred, that the steps follow each other immediately; intermediate steps may separate them.

[0076] Furthermore, the term "step" refers to the completion of a part of the process, and can designate a set of sub-steps.

[0077] Furthermore, the term "step" does not necessarily imply that the actions carried out during a step are simultaneous or immediately successive. Some actions in a first step may be followed by actions related to a different step, and other actions from the first step may be repeated later. Thus, the term "step" does not necessarily refer to unitary actions that are inseparable in time and in the sequence of phases of the process.

[0078] It is generally known that isotopes of a chemical element have the same number of protons but a different number of neutrons in their nucleus. Natural lithium, in particular, comprises two isotopes: lithium-6 (6Li) and lithium-7 (7Li). The numbers 6 and 7 refer to the number of protons (3) and neutrons (3 for 6Li and 4 for 7Li) in the nucleus of these lithium isotopes.

[0079] Enrichment rate refers to the proportion, expressed as a percentage, of 6Li atoms relative to all lithium atoms in a given material, for example, in the negative electrode, the electrolyte and / or the positive electrode.

[0080] The total enrichment rate refers to the percentage of 6Li atoms relative to all lithium atoms in all active materials. The term "total enrichment rate" should be distinguished from the enrichment rate of an individual active material in battery 1, such as that of the negative electrode 11, the electrolyte 12, or the positive electrode 13. The total lithium atoms may specifically include atoms of the 7Li isotope and atoms of the 6Li isotope.

[0081] A material "based" on a species A is understood to be a material comprising only that species A or that species A and possibly other species.

[0082] Generally speaking, a lithium-ion battery-type energy storage device is also referred to as a battery. In the following, the term "battery" is used interchangeably, without limitation, to refer to a lithium-ion battery-type energy storage device.

[0083] Batteries are used in various fields, notably in transportation to power electric vehicles, thus offering greater safety and energy density. They are also used to power drones, enabling longer and safer flights thanks to their thermal stability. Batteries also equip portable devices such as smartphones and tablets, where they help extend battery life while improving the safety and durability of the devices. These examples are not exhaustive; batteries can be used in other areas not mentioned, such as energy storage.

[0084] One problem with existing lithium-ion batteries is that increasing power leads to a decrease in energy density, thus reducing range.

[0085] To optimize the balance between power and energy density in batteries, enrichment with the 6Li isotope is being considered. Specifically, this enrichment reduces battery charging time while maintaining energy density.

[0086] The invention can also be applied to the marking of batteries, with a 6Li / 7Li ratio controlled by the manufacturer allowing him to certify the origin of manufacture of the battery or of one of its materials.

[0087] Battery 1 and its manufacturing process 2 are now described on a non-limiting basis according to particular embodiment examples and with reference to the figures.

[0088] The components that battery 1 may include are detailed below. Thus, as illustrated by Figure 1, battery 1 may include a negative electrode 11, an electrolyte 12, and a positive electrode 13. According to this example, battery 1 has a total enrichment rate approximately equal to 8%.

[0089] For example, the negative electrode 11 may comprise a lithium host insertion material or an alloy or conversion material comprising lithium, lithium metal, or graphite. As an example, the negative electrode 11 comprises a lithium metal oxide such as lithium titanium oxide (LTO). Preferably, the negative electrode 11 is graphite-based.

[0090] The positive electrode 13 may include a lithium metal oxide or a lithium phosphate.

[0091] Electrolyte 12 can be present in liquid or solid form.

[0092] As shown in Figure 1, the set of lithium atoms in the battery1 may more specifically include atoms of the 7Li 14 isotope and atoms of the 6Li 15 isotope.

[0093] Battery 1 functions through the migration / diffusion of lithium ions (Li16). + between the negative electrode 11 and the positive electrode 13. During charging, lithium ions 16 migrate from the positive electrode 13 to the negative electrode 11 through the electrolyte 12, where they are stored. During discharge, the lithium ions 16 travel back, releasing energy in the form of electrons that flow in an external electrical circuit. This migration of lithium ions 16 is essential for energy transfer and allows the battery 1 to store and supply energy reversibly with each cycle.

[0094] In a battery 1, an electrochemical cell (also referred to as a "cell") is a functional unit comprising a positive electrode 13, a negative electrode 11 and an electrolyte 12. A battery 1 can typically comprise several electrochemical cells.

[0095] Preferred thresholds for the total enrichment rate in 6Li 15 of battery 1 are announced below.

[0096] Thus, battery 1 preferably has a total enrichment rate in 6Li 15 isotope greater than or equal to 30%, and for example strictly less than 50%.

[0097] Preferably, the device has a total enrichment rate in 6Li 15 isotope strictly greater than 50%, and less than 100%.

[0098] As an example, a battery 1 with a total enrichment rate in 6Li 15 isotope approximately equal to 70% is illustrated by Figure 2.

[0099] Note that the term "total enrichment rate" is used to account for the possibility that, due to lithium ion migration, ions of the 6Li isotope can become dispersed within the battery after cycling. Furthermore, lithium can passivate around the active materials. Lithium can thus be found in various forms (U2CO3, LiF, for example) within what is called a passivation layer. This passivation layer is included in the calculation of the total enrichment rate of the 6Li isotope.

[0100] A cycling stage refers to the process of charging and discharging battery 1, which is typically repeated during its use. The cycling of battery 1 may include a testing phase, where battery 1 is subjected to controlled charging and discharging processes to evaluate its performance and durability.

[0101] Several possibilities are conceivable to achieve a total enrichment rate in 6Li isotope greater than or equal to 8%.

[0102] Thus, each of the active materials taken in isolation can be enriched to obtain a battery 1 according to the invention. That is to say, the negative electrode 11 and / or the electrolyte 12 and / or the positive electrode 13 can be enriched in order to obtain a total enrichment rate greater than or equal to 8% of the battery 1.

[0103] Other examples are possible besides the specific examples described below, which are not exhaustive.

[0104] For example, all the active materials in battery 1 can be enriched to achieve together a total enrichment rate greater than or equal to 8% for battery 1. When all the active materials are enriched, a higher total enrichment rate in the 6Li isotope can be achieved.

[0105] The process 2 for obtaining a battery 1 is described according to an example embodiment and with reference to Figure 3. The process 2 for obtaining a battery 1 may include a step of supplying the active materials 21 and the assembly 22 of the active materials to form the battery 1.

[0106] In the following, particular embodiments of battery 1 and process 2 are presented by way of non-limiting agreement.

[0107] In one example, electrolyte 12 is in liquid form. In this example, electrolyte 12 may be commercially supplied already enriched, or process 2 may include, after the supply 21 of active materials, a step of enriching electrolyte 12 in liquid form.

[0108] Preferably, the enrichment step of electrolyte 12, whether solid or liquid, is carried out by cation complexing agents and / or by ion exchange resins and / or by fractional crystallization and / or by thermal diffusion and / or by electrolytic separation and / or by laser separation and / or by distillation and / or by micro-algae enrichment.

[0109] As illustrated by Figure 4, in this example, process 2 may include a substep 31 of impregnating the negative electrode 11 and the positive electrode 13 with the liquid electrolyte 12, to form the battery 1. For example, the liquid electrolyte 12 may be injected into an assembly comprising the negative electrode 11 and the positive electrode 13.

[0110] Preferably, the liquid electrolyte 12 comprises a lithium salt such as lithium hexafluorophosphate (LiPFe). Indeed, this lithium salt is the most commonly used, due to its balance between electrochemical performance, safety, and stability.

[0111] This example offers the possibility of achieving total 6Li 15 enrichment levels of 8% or higher and less than 100%. Typically, a total 6Li 15 enrichment level greater than 8% can be obtained in this way.

[0112] In one example, electrolyte 12 is in solid form. Preferably, electrolyte 12 is a solid polymer. This solid polymer is generally preferred in next-generation batteries for its safety, thermal stability, flexibility, and ability to improve battery life. This example yields a battery 1 particularly well-suited to future developments, especially with the growth of all-solid-state batteries.

[0113] This example offers the possibility of achieving total 6Li 15 enrichment levels of 8% or higher and less than 100%. Typically, a total 6Li 15 enrichment level greater than 8% can be obtained in this way.

[0114] It should be mentioned that for these two examples of embodiment, the negative electrode 11 and the positive electrode 13 can be unenriched, which simplifies the modification of the assembly line for industrialists.

[0115] However, in order to increase the total enrichment rate in 6Li 15 of battery 1, enrichment of the negative electrode 11 and / or the positive electrode 13 is preferred.

[0116] Preferably, the negative electrode 11 and / or the positive electrode 13, as well as the electrolyte 12, are enriched. However, it is also possible to provide that the electrolyte 12 is unenriched and that the negative electrode 11 and the positive electrode 13 are enriched.

[0117] For this purpose, according to an example, process 2 may include a substep 32 of at least partial substitution of natural lithium by the isotope 6Li 15 of at least one of the negative electrode 11 and the positive electrode 13.

[0118] Substep 32 of natural lithium to 6Li 15 using bath means a process in which the negative electrode 11 and / or the positive electrode 13 of the battery 1 are immersed in different solutions successively in order to deplete their natural lithium content and then enrich their 6Li 15 content.

[0119] For this substep, a substitution bath may be used. Preferably, the substitution bath comprises two baths. The first bath is a depletion bath 321 of the positive electrode 13 and / or the negative electrode 11 in natural lithium. The second bath is an enrichment bath 322 of the positive electrode 13 and / or the negative electrode 11 in 6Li 15. The first depletion bath 321 may contain NOBF4. The second enrichment bath 322 may contain 6U2CO3 or 6Li.

[0120] Furthermore, the various phases of the substitution step 32 preferably include a depletion phase of the positive electrode 13 and / or the negative electrode 11 with natural lithium and an enrichment phase of the positive electrode 13 and / or the negative electrode 11 with 6Li 15. Preferably, during the depletion phase, the electrode powder is placed in an oxidizing bath with, for example, a NOBF4-type oxidizing agent, for a specified period of time at room temperature in order to deplete the electrode material of natural lithium. Preferably, in order to avoid morphologically damaging the electrode material, the agitation during the depletion phase is carried out under vortexing. Furthermore, the enrichment phase of the positive electrode 13 and / or the negative electrode 11 in 6Li 15 is preferably carried out using a bath containing a lithia salt such as 6U2CO3 or 6Li.Preferably, this enrichment phase aims to enrich the electrode material depleted in natural lithium following the previously mentioned depletion phase with 6Li 15.

[0121] This example offers the possibility of achieving total 6Li 15 enrichment levels between 9% and 100%. Typically, a total 6Li 15 enrichment level exceeding 80% can thus be obtained, particularly in synergy with a 6Li-enriched electrolyte.

[0122] As an example, the substitution of natural lithium to 6Li15 can be achieved through chemical substitution. For instance, a commercially available lithium-containing material can be immersed in a chemical depletion oxidizing bath to enable its delithiation. The immersion time, the concentration of the depletion bath, and the stirring characteristics are parameters that can be considered for this step. Oxidizers such as nitrosonium tetrafluoroborate (NOBF4) or nitronium tetrafluoroborate (NO2BF4), in an anhydrous solvent such as acetonitrile, can be used to perform substitution by chemical delithiation. This approach allows the degree of lithium substitution within the particles of the active material to be controlled by the time or concentration of the depletion bath applied.In a second step, it may be envisaged to relithify the material using for example an enrichment bath 322 enriched in 6Li 15. Several types of enrichment baths 322 are conceivable for carrying out the enrichment in 6Li 15, such as, by way of non-limiting examples, a bath comprising lithium-6 iodide (. 6 Lil) and / or a bath containing lithium-6 chloride ( 6 LiCl) and / or a bath comprising lithium-6 nitrate ( 6 LiNC>3).

[0123] The following example provides an even more efficient battery 1 in terms of the trade-off between energy density and power. Thus, according to this example, battery 1 comprises a negative electrode 11 made of lithium metal, a positive electrode 13 made of lithium metal oxide, and a solid electrolyte 12.

[0124] Enrichment with 6Li 15 has particularly beneficial effects in this configuration. This is because the use of lithium metal for the negative electrode 11 already allows for a higher energy density and better efficiency in energy conversion.

[0125] Increasing the total enrichment rate of 6Li 15 isotope in battery 1 can then further improve the electrochemical performance and lifespan of battery 1.

[0126] Specific examples of batteries are now described to illustrate the effects of enrichment with 6Li 15.

[0127] According to one example, the negative electrode 11 includes graphite and is cycled in a half-cell with respect to metallic lithium.

[0128] Figure 6 shows galvanostatic curves of a half-cell comprising electrolyte 12 with negative electrode 11, as a function of the isotope used: 6Li 61 or 7Li 62 or natural lithium Li 63 in the LP30 type electrolyte (1 M LiPFe in a mixture of ethylene carbonate (EC) and dimethyl carbonate DMC (50 / 50)). The electrolyte is enriched in 6Li or 7Li with a purity of 95%.

[0129] The galvanostatic curves in Figure 6 show the specific charge 64 in milliampere-hours per gram on the x-axis and the potential vs Li on the y-axis + / Li 65 in volts. This potential vs Li + / Li 65 refers to the electrochemical potential of a battery or material relative to a specific 0 V reference: the Li system + / Li (that is, the lithium ion 16Li + and metallic lithium (Li).

[0130] In addition, Figure 7 graphically represents the specific capacity of a half-cell with a positive electrode 11 made of cycled graphite with respect to metallic lithium as a function of the isotope used, the number of cycles 66 applied and the coulombic efficiency 67. In this way, the measurement points correspond to the use of the isotope 6Li 61, the isotope 7Li 62 and natural lithium 63 in the electrolyte.

[0131] Figure 7 shows on the x-axis the number of cycles 66 applied to the cell, on the first ordinate the specific charge 64 in milliampere-hours per gram and on the second ordinate the coulombic efficiency 67 in percentage.

[0132] As can be seen in Figures 6 and 7, preliminary laboratory tests with 6Li 61, 7Li 62 and natural Li 63 show a specific charge gain 64 of a positive graphite electrode 11 cycling in a half-cell (with respect to metallic lithium) for an electrolyte enriched in 6Li 61 at an enrichment rate of 100%, depending on the charging rate.

[0133] Note that in Figure 6, during low-regime cycling, there is little difference between the different isotopes because we are close to thermodynamic equilibrium.

[0134] On the other hand, when we increase the battery cycle rate, we clearly see that the 6Li 61 surpasses the 7Li 62 and the natural Li 63. Moreover, as can be seen in figure 7, at the same cycle rate of around 1-C (a charge in 1 h), we can see that the 6Li 61 delivers almost the theoretical capacity of graphite (around 372 mAh / g), while the natural lithium 63 only reaches 300 mAh / g and finally the 7Li 62 does not deliver more than 275 mAh / g, or 30% less than the 6Li 61.

[0135] The underlying reason for this difference stems from the diffusion limit of lithium within the graphite sheets on the lithium-rich plateaus, namely the LiC12 and LiC6 transition. These LiC12 and LiC6 compounds are formed during the intercalation of lithium into the graphite sheets.

[0136] In another example, the positive electrode 13 is of the NMC type for Li₂ + x(Ni, Mn, Co)₁xO₂, thus combining nickel, manganese, cobalt, and lithium. This NMC-type positive electrode 13 is cycled as a half-cell with respect to metallic lithium. The electrolyte is of the LC₃O type (1 M U₂CO₄ in a mixture of ethylene carbonate (EC) and dimethyl carbonate (DMC) (50 / 50). The electrolyte is enriched in ⁶Li or ⁷Li with a purity of 90%.

[0137] Figure 8 shows the galvanostatic curves of a battery with a 13 NMC positive electrode cycled with respect to metallic lithium as a function of the isotope used. The curves correspond to the use of two references of natural lithium (68 and 69), two references of the 6Li isotope (70 and 71), and two references of the 7Li isotope (72 and 73). The exact electrolyte composition is provided in the example above.

[0138] In addition, Figure 9 graphically represents specific capacity curves of a cell with the positive electrode 13 NMC cycled with respect to metallic lithium as a function of the isotope used and the number of cycles 66 applied.

[0139] As is generally known, positive electrode materials are less subject to mass transport limitations, so this study focused on the impact of lithium isotopes on the cycling of NMC-type materials. Thus, as can be seen in Figure 8, the impact of the 6Li isotope is less readily apparent, even though, at high cycling rates, 6Li 70 and 71 is still superior to 7Li 72 and 73 and natural lithium 68 and 69, despite its lower salt purity.

[0140] The results of the two preceding examples confirm the relevance of the 6Li 15 enrichment approach for improving the rapid charging of batteries 1. Indeed, the most noticeable effect is on the negative electrode 11, which is generally the bottleneck in conventional batteries. Furthermore, the use of 6Li 15 also slightly improves the cycling of the positive electrode 13.

[0141] Two alternative or combinable examples are described, concerning measurements 41 of the enrichment rate in 6Li 15 of at least one active material or 42 of the total enrichment rate in 6Li 15.

[0142] Measurement 41 of the 6Li enrichment rate of at least one active material is preferably carried out before battery cycling. This makes it possible to obtain the enrichment rate for a given active material before the 6Li is distributed in the battery 1 as a result of cycling.

[0143] According to one example, the measurement 41 of the 6Li enrichment rate of at least one active material 15 of the battery 1 can be carried out by neutron imaging 411, by nuclear magnetic resonance 412 by mass spectrometry 413, and / or by inductively coupled plasma analysis 414.

[0144] This measurement step 41 of the 6Li15 enrichment level of at least one active material can be illustrated by Figure 10, the arrows in Figure 10 indicating the elements that precede or follow them, individually or in combination. Thus, the measurement 41 of the 6Li15 enrichment level of at least one active material can be carried out with the negative electrode 11, with the electrolyte 12, or with the positive electrode 13, separately or with several of these elements combined. Furthermore, several techniques can be considered in combination with these different combinations of active materials.

[0145] The 413 mass spectrometry technique can, for example, include time-of-flight secondary ion mass spectrometry, more commonly known by the acronym TOF-SIMS. This analytical technique allows for the quantification of 6Li and 7Li present on the surface of the active material.

[0146] Preferably, the use of inductively coupled plasma analysis 414 and / or nuclear magnetic resonance 412 is considered, as these techniques are easy to implement in the laboratory. The use of nuclear magnetic resonance 412, however, requires the use of a calibrator to compare peak intensity ratios. The measurement step 42 of the total 6Li-15 enrichment rate is illustrated in Figure 11, with the arrows in Figure 11 indicating the elements that follow it, individually or in combination. Thus, the measurement of the total 6Li-15 enrichment rate 42 of battery 1 can be carried out using several of the techniques described above, either in combination or separately.

[0147] According to one example, the measurement 42 of the total enrichment rate in 6Li 15 of battery 1 can be carried out by neutron imaging 411, by nuclear magnetic resonance 412 by mass spectrometry 413 and / or by inductively coupled plasma analysis 414.

[0148] Preferably, the use of neutron imaging technique 411 is envisaged, as it allows the quantity of 6Li 15 to be determined in a sample, whether liquid or solid, without having to dismantle battery 1.

[0149] Figures 12A, 12B, and 12C show scanning electron microscopy (SEM) images of a battery 1 comprising a positive electrode 13 made of a polycrystalline material, namely NMC811. NMC811 is composed of lithium oxide, nickel, manganese, and cobalt, in proportions of approximately 80% nickel, 10% manganese, and 10% cobalt. An unenriched electrode typically comprises agglomerated particles or grains of active material. As can be seen in these figures, after immersion in a chemical depletion bath 321 allowing partial or total delithiation of the active material, the positive electrode 13 exhibits an altered morphology at the level of the grains, also referred to as primary particles.

[0150] Figure 12A shows a SEM image of the intact positive electrode material 13 with 100% natural lithium. This material has a polycrystalline structure corresponding to an agglomeration of primary particles of nanometer size, typically with a diameter between 200 and 400 nm. Figure 12B shows the same positive electrode material 13 after two hours of immersion in a chemical depletion bath 321. This sample shows the first visible signs of corrosion, typically the presence of holes or pores on the surface of the primary particles, as well as more pronounced grain boundaries. These phenomena become even more pronounced after 6 or 24 hours of depletion by chemical delithiation, for example. Indeed, in these cases, the corrosion is more pronounced. Only some of the grains may exhibit this surface porosity, or all of them, depending on the degree of delithiation.These signs are characteristic of a chemical substitution 32, generating locally defects whose importance varies according to the conditions of the depletion bath 321.

[0151] Experiments have shown that relithiation in a 322 enrichment bath of 6Li 15 does not cause further damage or morphological changes. Therefore, the alterations induced during relithiation are permanent.

[0152] Figures 13A and 13B illustrate the characterization of a battery 1 comprising at least one of the substitutionally enriched active materials 32. The characterization is carried out by measurement methods such as scanning electron microscopy (SEM) and / or atom probe tomography.

[0153] As an example, after a substitution 32, surface defects may be visible on the enriched active materials, particularly on the positive electrode 13, as shown in the SEM images in Figures 12B and 12C. However, if no visible changes are detected, more advanced techniques may be considered to confirm that the enriched active material in question was indeed obtained through enrichment via a substitution 32.

[0154] One method that can be considered is atom probe tomography. Indeed, this method allows a three-dimensional reconstruction of a tip extracted from a material, for example, a tip extracted from a particle of the positive electrode 13. In particular, this method can allow observation of the distribution of the 6Li 15 isotope on one of the enriched active materials of a battery 1, going back to the angstrom scale.

[0155] As an example, a tip can be extracted from a particle of an active material to be analyzed by focused ion beam during a SEM analysis (FIB-SEM, from the English Focused Ion Beam - Scanning Electron Microscopy) to obtain a conical shape.

[0156] Figures 13A and 13B illustrate the extraction of a tip by FIB-SEM from a particle of an NMC811-based positive electrode 13. In these two examples, the dimensions used for the cone enabling tip extraction from an NMC811 particle of the positive electrode 13 are, for example, approximately 100 nm for the minimum diameter of the cone tip, with a maximum diameter reaching up to 625 nm, these values ​​being given with a tolerance of 5%. These cone dimensions allow for the extraction of a tip for atom probe analysis, yielding several NMC811 grains from the positive electrode 13. The polycrystalline grains are, for example, identifiable in the SEM image of Figure 13B.

[0157] The atom probe tomography offers atomic-scale resolution, including the isotopes 6Li-15 and 7Li-14, and reveals the spatial location of the elements, highlighting a spatial gradient occurring during enrichment by delithiation and depletion by chemical relithiation. Furthermore, Time-of-Flight Secondary Ion Mass Spectrometry (TOF-SIMS) can also be used to quantify the proportions of the 6Li-15 and 7Li-14 isotopes in the active material of a battery, in order to determine, in particular, the chemical substitution rate.

[0158] The invention is not limited to the embodiments described above and extends to all embodiments covered by the invention. The present invention is not limited to the examples described above. Many other embodiments are possible, for example, by combining features described above, without departing from the scope of the invention. Furthermore, the features described with respect to one aspect of the invention can be combined with another aspect of the invention. It should also be noted that for the positive and negative electrode materials, materials other than NMC and graphite are conceivable. NMC and graphite are specific examples, but there are applications with other materials.

Claims

24 DEMANDS 1. Lithium-ion battery-type energy storage device (1) comprising: • A negative electrode (11), • An electrolyte (12), • A positive electrode (13), the device (1) having a total enrichment rate in 6Li isotope (15) greater than or equal to 8%, the total enrichment rate being taken with respect to all the lithium atoms of the negative electrode (11), the electrolyte (12) and the positive electrode (13), Characterized in that at least one of the negative electrode (11) and the positive electrode (13) is enriched in the 6Li isotope (15) by at least partial substitution (32) of natural lithium by the 6Li isotope (15) using at least one bath (321, 322) comprising the 6Li isotope (15), such that at least one of the negative electrode (11) and the positive electrode (13) has an enrichment level in the 6Li isotope (15) greater than or equal to 8%.

2. Device (1) according to the preceding claim, wherein at least one of the negative electrode (11) and the positive electrode (13) comprises agglomerated particles including an exposed surface, the exposed surface of at least a portion of the agglomerated particles having a porous morphology.

3. Device (1) according to any one of the preceding claims, wherein the total enrichment rate in 6Li isotope (15) is greater than or equal to 30%.

4. Device (1) according to any one of the preceding claims, wherein the total enrichment rate in 6Li isotope (15) is strictly greater than 50%, preferably greater than or equal to 70%.

5. Device (1) according to any one of the preceding claims, wherein the positive electrode (13) comprises a lithium metal oxide and / or a spinel-based material and / or a phosphate-based material, the positive electrode (13) having an enrichment in the 6Li isotope (15) greater than or equal to 8%.

6. Device (1) according to any one of the preceding claims, wherein the negative electrode (11) comprises graphite.

7. Device (1) according to any one of claims 1 to 5, wherein the negative electrode (11) comprises lithium metal or a lithium metal oxide, the negative electrode (11) having an enrichment in the 6Li isotope (15) greater than or equal to 8%.

8. Device (1) according to any one of the preceding claims, wherein the electrolyte (12) is in liquid form, the electrolyte (12) having an enrichment in the 6Li isotope (15) greater than or equal to 8%.

9. Device (1) according to any one of claims 1 to 7, wherein the electrolyte (12) is in solid form, preferably the electrolyte (12) is a solid polymer electrolyte (12), the electrolyte (12) having an enrichment level in 6Li isotope (15) greater than or equal to 8%.

10. Device (1) according to any one of claims 1 to 5, 7 or 9, wherein the negative electrode (11) comprises lithium metal, the positive electrode (13) comprises a lithia metal oxide and the electrolyte (12) is in solid form, the negative electrode (11), the electrolyte (12) and the positive electrode (13) each having an enrichment of 6Li isotope (15) greater than or equal to 8%.

11. Method (2) for manufacturing a lithium-ion battery-type energy storage device (1) comprising: • A supply (21) of a negative electrode (11), a positive electrode (13) and an electrolyte (12), • An assembly (22) of the negative electrode (11), the positive electrode (13) and the electrolyte (12) to form the storage device (1), the storage device (1) having a total enrichment rate in the 6Li isotope (15) greater than or equal to 8%, the total enrichment rate being taken with respect to all the lithium atoms of the negative electrode (11), the electrolyte (12) and the positive electrode (13), the process (2) further comprising at least one of the negative electrode (11) and the positive electrode (13): • An enrichment in 6Li isotope (15) by substitution (32) at least partial of natural lithium by the 6Li isotope (15) using a bath (321, 322) comprising the 6Li isotope (15), such that at least one of the negative electrode (11) and the positive electrode (13) has an enrichment rate in 6Li isotope (15) greater than or equal to 8%.

12. A method (2) according to the preceding claim, wherein the substitution enrichment (32) comprises a depletion in 7Li isotope (14) of at least one of the negative electrode (11) and the positive electrode (13), carried out using a depletion bath (321) and an enrichment in 6Li isotope of at least one of the negative electrode (11) and the depleted positive electrode (13), carried out using an enrichment bath (322) configured to increase the enrichment rate in 6Li isotope (15) of at least one of the negative electrode (11) and the positive electrode (13) to form an enriched electrode.

13. Method (2) according to the preceding claim, wherein the depletion bath (321) comprises an oxidizing agent and the enrichment bath (322) comprises a lithiated salt.

14. Method (2) according to any one of the three preceding claims, wherein the electrolyte (12) is in liquid form, and, during the assembly step (22) of the battery (1), the electrolyte (12) is impregnated (31) in the negative electrode (11) and in the positive electrode (12) to form the storage device (1).

15. Method (2) according to any one of claims 11 to 13, wherein the electrolyte (12) is in solid form, preferably the electrolyte (12) is a solid polymer electrolyte (12).

16. A method (2) according to any one of claims 11 to 15, wherein the negative electrode (11) comprises lithium metal, the negative electrode (11) having an enrichment in the 6Li isotope (15) greater than or equal to 8%.

17. A method (2) according to any one of the six preceding claims, further comprising a measurement of the total enrichment (42) in lithium by neutron imaging (411), nuclear magnetic resonance (412), mass spectrometry (413) and / or inductively coupled plasma analysis (414).

18. Method (2) according to any one of the seven preceding claims further comprising, before the first cycling of the storage device (1), a measurement of the enrichment rate in 6Li isotope (41) of at least one of the negative electrode (11), the electrolyte (12) and the positive electrode (13) taken separately by neutron imaging (411), by nuclear magnetic resonance (412), by mass spectrometry (413) and / or by inductively coupled plasma analysis (414).

19. A method (2) according to any one of the eight preceding claims, further comprising: • a measurement relating to a spatial distribution of the 6Li isotope (15) on a surface of at least one of the negative electrode (11) and the positive electrode (13), the measurement being carried out by atom probe tomography and / or by time-of-flight secondary ion mass spectrometry, and / or • a characterization of a porous morphology of an exposed surface of at least one of the negative electrode (11) and the positive electrode (13), the characterization being carried out by scanning electron microscopy.

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