FLUORIDE COMPOUNDS, THEIR PREPARATION PROCESSES, AND THEIR USES, PARTICULARLY FOR THE PREPARATION OF FLUORIDE BATTERY ANODES

Abstract

The present invention relates to novel fluorinated compounds and their preparation methods. The invention also relates to the use of said compounds for the preparation of active materials for fluorine batteries, in particular for fluorine battery anodes, for the preparation of fluorine batteries themselves, as well as said active materials and said batteries per se. The compounds have the following formula (I): AxNiF2(I), in which: A is at least one metal selected from Na, K, Li, Rb, Cs, Mg, Ca, Sr, or Ba; and x is such that 0 < x ≤ 1. (no figure)

Description

Title of the invention: FLUORIDE COMPOUNDS, THEIR PREPARATION METHODS, AND THEIR USES, PARTICULARLY FOR THE PREPARATION OF BATTERY ANODES FLUORINE

[0001] The present invention relates to novel fluorinated compounds and their preparation methods. The invention also relates to the use of said compounds for the preparation of active materials for fluorine batteries, in particular for fluorine battery anodes, for the preparation of fluorine batteries themselves, as well as said active materials and said batteries per se.

[0002] Fluorine batteries have been proposed as a promising alternative to lithium-ion batteries currently used in many electronic devices, electric vehicles and energy storage systems.

[0003] Indeed, fluorine battery technology is based on the use of fluorinated electrolytes that have high ionic conductivity, thus allowing for a higher energy density than lithium-ion batteries. And one of the advantages of fluorine batteries is the possibility of using solid electrolytes, made possible by this high mobility of fluorine.

[0004] Furthermore, fluorine batteries are more stable than lithium-ion batteries, which reduces the risk of fires and explosions. Indeed, fluorinated electrolytes have greater chemical and thermal stability, allowing them to operate at higher temperatures without risk of decomposition.

[0005] In this context, batteries comprising a cathode or anode containing a conversion-type active material have been proposed. However, in a typical conversion reaction, the electrode material undergoes a redox reaction during fluorination / defluorination, which is accompanied by a change in the crystal structure leading to the breaking and recombination of chemical bonds and often a significant change in the volume of the active electrode material. This significant volume change results in a loss of physical contact between the active electrode material, the conductive particles, and the electrolyte, which can lead to a significant deterioration in the electrochemical performance of the electrode.

[0006] One objective of the invention is thus to provide a fluorinated compound enabling the obtaining of an active intercalation material for a negative electrode of a fluorine battery.

[0007] One advantage of the compounds of the invention lies in the fact that fluorine ions can be inserted into or removed from the host network reversibly, with very small volume changes during the redox reaction.

[0008] Thus, the compounds of the invention allow for improved performance during cycling, with, in particular, less degradation of the anode and therefore of the battery. In addition, these compounds make it possible to achieve higher volumetric and gravimetric energy densities than with other conceivable insertion materials.

[0009] Also, the invention relates to a compound of the following formula (I):

[0010] AxNiF2 (I),

[0011] in which:

[0012] A is at least one metal selected from Na, K, Li, Rb, Cs, Mg, Ca, Sr, or Ba;

[0013] and x is such that 0 < x < 1.

[0014] According to a particular embodiment, the compound of the invention has the following formula:

[0015] DxlEx2NiF2 (la),

[0016] in which:

[0017] D is at least one metal selected from Na, K, Li, Rb, Cs, Mg, Ca, Sr, or Ba;

[0018] E is another metal selected from at least Na, K, Li, Rb, Cs, Mg, Ca, Sr, or Ba;

[0019] xl is such that 0 < xl < 1;

[0020] x2 is such that 0 < x2 < 1;

[0021] with 0 < xl + x2 < 1.

[0022] Thus, E is different from D.

[0023] According to a particular embodiment, xl and x2 are not harmed.

[0024] According to a particular embodiment, xl is such that 0 < xl < 0.5, more particularly lirelatedly xl being for example 0.5; and / or x2 is such that 0.5 < x2 < 1, more particularly x2 being for example 0.5.

[0025] According to a particular embodiment, the compound of the invention has the following formula (Ib):

[0026] NaxlKx2Lix3Mgx4Cax5NiF2 (Ib),

[0027] in which:

[0028] xl is such that 0 < xl < 1;

[0029] x2 is such that 0 < x2 < 1;

[0030] x3 is such that 0 < x3 < 1;

[0031] x4 is such that 0 < x4 < 1;

[0032] x5 is such that 0 < x5 < 1;

[0033] with 0 < xl + x2 + x3 + x4 + x5 < 1.

[0034] According to a particular embodiment: - At least two of the xl-x5 are not harmful; or - At least three of the xl-x5 are not harmful; or - At least four of the xl-x5 are not harmful; or - xl-x5 are not harmful.

[0035] According to a particular embodiment, the compound of the invention has the following formula:

[0036] NaxlKx2NiF2 (the),

[0037] in which:

[0038] xl is such that 0 < xl < 1;

[0039] x2 is such that 0 < x2 < 1;

[0040] with 0 < xl + x2 < 1.

[0041] According to a particular embodiment, the compound of the invention has an infinite layer type structure, and in particular a crystalline form of the type P4 / mmm, I4 / mcm, C2 / c, or Pbnm.

[0042] The crystalline form can for example be determined by X-ray diffraction, in particular according to one of the protocols well known to those skilled in the art.

[0043] According to another aspect, the invention also relates to a process for preparing a compound as defined above, comprising a defluorination step of a compound of the following formula (II):

[0044] AxNiF3 (II),

[0045] in which A and x are such as defined above.

[0046] All embodiments mentioned with regard to the compound of the invention also apply here, alone or in combination.

[0047] According to a particular embodiment, the compound of formula (II) as defined above, is of one of the following formulas:

[0048] DxlEx2NiF3 (lia),

[0049] NaxlKx2Lix3Mgx4Cax5NiF3(IIb), or

[0050] NaxlKx2NiF3 (Ile),

[0051] in which D, E, xl, x2, x3, x4, and x5 are as defined above.

[0052] According to a particular embodiment, the defluorination step is carried out under hydrogen, in particular under a flow of hydrogen.

[0053] According to another particular embodiment, the defluorination step is carried out in the presence of a reducing agent such as NaH and / or CaH2.

[0054] According to another particular embodiment, the defluorination step is carried out by electrochemical means.

[0055] According to another aspect, the invention also relates to a method for preparing a compound as defined above, comprising a thin film growth step by epitaxy.

[0056] All embodiments mentioned in relation to the compound of the invention also apply here, alone or in combination.

[0057] According to a particular embodiment, the thin film growth step is carried out on a substrate of the type SrTiO3, KTaO3, or EuScO3.

[0058] According to another aspect, the invention also relates to the use of a compound as defined above for the preparation of an active material, in particular an intercalation material, for a negative electrode.

[0059] All embodiments mentioned in relation to the compound of the invention also apply here, alone or in combination.

[0060] According to another aspect, the invention also relates to an active material, in particular an intercalation material, for a negative electrode, in particular a fluorine battery, made up of or comprising a compound as defined above.

[0061] All embodiments mentioned in relation to the compound of the invention also apply here, alone or in combination.

[0062] According to a particular embodiment, the present invention relates to an active material as defined above, the compound of which as defined above forms a redox couple with a compound of the following formula (II):

[0063] AxNiF2+y (II),

[0064] in which A and x are such as defined above and 0 < y < 1.

[0065] According to a particular embodiment, the compound of formula (II) as defined previously, is one of the following formulas:

[0066] DxlEx2NiF2+y (lia),

[0067] NaxlKx2Lix3Mgx4Cax5NiF2+y(IIb), or

[0068] NaxlKx2NiF2+y (Ile),

[0069] in which D, E, xl, x2, and y are such as defined previously.

[0070] According to a particular embodiment, the compound of formula (I) has an infinite layer type structure, and in particular a crystalline form of type P4 / mmm, I4 / mcm, C2 / c, or Pbnm.

[0071] According to another aspect, the invention also relates to the use of a compound as defined above, or of an active material as defined above, for the preparation of a battery, in particular an intercalation battery, with fluorine.

[0072] All embodiments mentioned in relation to the compound of the invention also apply here, alone or in combination.

[0073] According to another aspect, the invention also relates to a fluorine battery, in particular an intercalation battery, comprising: - a negative electrode comprising or made of an active material as defined above; - a positive electrode; - an electrolyte, having in particular a conductivity in fluoride ions.

[0074] All embodiments mentioned with regard to the compound of the invention also apply here, alone or in combination.

[0075] In addition to the active material, the electrode may contain electrolyte and a carbon additive, as illustrated in Example 2.

[0076] According to a particular embodiment, the battery of the invention comprises: - a negative electrode layer comprising or consisting of an active material as defined above; - a layer of positive electrode; and - between said negative electrode layer and said negative electrode layer, in contact with them, a layer of electrolyte, in particular solid.

[0077] According to a particular embodiment, the electrolyte has the following formula:

[0078] La0j9Ba0jiF2j9.

[0079] According to a particular embodiment, the positive electrode is made of or comprises a material of the following formula:

[0080] La2NiO(4+ô)Fx, with ô varying from -1.5 to 0.25, ô being for example 1.3; and x varying from 1 to 3.

[0081] In addition to this material, the electrode may contain electrolyte and a carbon additive, as illustrated in Example 2.

[0082] Examples of cathode and / or electrolyte that may also be suitable within the framework of the present invention are described in particular by Nowroozi et al., J. Mater. Chem. A, 2021, 9, 5980 (2020). DEFINITIONS

[0083] As understood here, and unless otherwise indicated, ranges of values ​​in the form of "xy" or "from x to y" or "between x and y" include the bounds x and y, all numbers to one decimal place between these bounds, and, where appropriate, the integers between these bounds.

[0084] By way of example, "0-1", or "from 0 to 1" or "between 0 and 1" refers in particular, and unless otherwise indicated, to the integers 0 and 1, as well as the decimal numbers 0.1; 0.2; 0.3; 0.4; 0.5; 0.6; 0.7; 0.8 and 0.9.

[0085] As used in this description, the term "approximately" refers to a range of values ​​within ±10% of a specific value. For example, the expression "approximately 20" includes values ​​within 20 ±10%, that is, values ​​from 18 to 22.

[0086] For the purposes of this description, percentages refer to percentages by mass relative to the total mass of the formulation, unless otherwise stated.

[0087] By layer, we mean in particular a stratum of superimposed elements. FIGURES

[0088] Fig. 1 shows the phonon spectra of KNiF2 (A) and NaNiF2 (B) in P4 / mmm structure at 300K, according to example 1. EXAMPLES

[0089] Example 1: Preparation of compounds of the invention

[0090] The AxNiF2 compounds of the invention can be obtained from Ax NiF3 precursors by topochemical reduction.

[0091] For example, NaNiF3 can be obtained from an equimolar mixture of crude NaF and NiF2 materials.

[0092] NaF (Wako Pure Chemical Industries, 99.0%) and NiF2 (Alfa Aesar, 99%) were mixed in a 1:1 molar ratio in an agate mortar, and the mixture was shaped into a pellet. This sample handling was carried out in an argon-filled glove box. The pellet was heated at 500 °C for 12 hours under a flow of argon gas (see, in particular, Journal of Solid State Chemistry 2012, 191, 167-174).

[0093] AxNiF3 can also generally be obtained by mild hydrothermal or solvothermal processes, where the reactions are carried out at 140-250 °C. The precursors are again the crude materials AXF and NiF2, and the solvent can be ethylene glycol (Chemistry Letters 2002, 31(5), 538-539).

[0094] The subsequent reduction can be carried out by topochemistry using reducing agents such as CaH2 or NaH according to the following reactions:

[0095] AxNiF3 + NaH -> AxNiF2 + NaF + 0.5 H2

[0096] AxNiF3 + 0.5 CaH2 -> AxNiF2 + 0.5 CaF2 + 0.5 H2

[0097] The reaction temperature can be below 300 °C. In practice, to reduce the precursor and obtain AxNiF2, the precursor can be mixed with the reducing agent using a mortar and pestle in an argon-filled glove box. The mixture is then placed in a corundum crucible, sealed in vacuum-tight stainless steel reactors, and heated for several hours. After the reaction, the reactor is opened inside an argon-filled glove box to remove the samples.

[0098] The following compounds: NaNiF2 and KNiF2 can thus be obtained.

[0099] These are of P4 / mmm structure, as demonstrated by X-ray diffraction.

[0100] The room-temperature phonon spectra of these compounds are illustrated in [Fig. 1]. This shows that these structures are dynamically stable, particularly at 300 K.

[0101] The average potentials of the corresponding couples, as calculated by density functional theory, are as follows:

[0102] NaNiF2 + L2 ZnF2 -> L2 Zn + NaNiF3: AE = 0.14 eV.

[0103] KNiF2 + ½ ZnF2 -> L2 Zn + KNiF3: AE = -0.23 eV.

[0104] This indicates that these compounds can be used as a negative electrode for Fluorine batteries.

[0105] The theoretical capacity for the NaNiF2 / NaNiF3 couple is approximately 193 mAh / g, and for KNiF2 / KNiF3 is 173 mAh / g. Example 2: Preparing a fluorine battery

[0106] A fluorine intercalation battery of the type La2NiO3F2 / Lao.gBao.iF2.g / NaNiF2 can be prepared as follows.

[0107] La0.gBa0.iF2 g is prepared from BaF2 and LaF3 by mechanosynthesis under argon, then pressed, as for example described by Mohammad Ali Nowroozi on page 31 of his thesis manuscript (On the Development of Intercalation-Based Cathode Materials for All-Solid-State Fluoride Ion Batteries, Darmstadt 2020).

[0108] La2NiO3F2 is for example prepared as described in paragraph 2.1 of Wissel et al. (Inorg. Chem. 2018, 57(11), 6549-6560): first La2NiO(4+d) is synthesized by sintering La2O3 and NiO, then mixed with PVDF and heated to 370 degrees Celsius under air for 24 hours.

[0109] The compound has been shown to be usable as a positive electrode in a fluorine battery in Wissel et al. (Chem. Mater. 2021, 33(2), 499-512).

[0110] NaNiF2 is prepared as described above.

[0111] The positive and negative electrodes are first formed by mixing each of the active materials with electrolyte and a carbon additive (in proportion 50:40:10) and then by pressing them. The electrodes and electrolyte are assembled by layering and then pressure in an argon atmosphere, and then transferred into a Swagelok-type cell with stainless steel current collectors. The process is described by Mohammad Ali Nowroozi, for example, in section 4.3 of his thesis manuscript (ibid.).

Claims

Claims

1. Compound of the following formula (I): AxNiF2 (I), in which: A is at least one metal chosen from Na, K, Li, Rb, Cs, Mg, Ca, Sr, Ba; and x is such that 0 < x < 1.

2. Compound according to claim 1, of the following formula (la): DxiEx2NiF2 (la), in which: D is at least one metal chosen from Na, K, Li, Rb, Cs, Mg, Ca, Sr, Ba; E is another metal chosen from at least Na, K, Rb, Cs, Mg, Ca, Sr, Ba; xl is such that 0 < xl < 1; x2 is such that 0 < x2 < 1; with 0 < xl + x2 < 1;

3. A compound according to any preceding claim, which has an infinite layer type structure, and in particular a crystalline form of the P4 / mmm, I4 / mcm, C2 / c, or Pbnm type.

4. A process for preparing a compound according to any one of claims 1 to 3, comprising a step of defluorination of a compound of the following formula (II): AxNiF3 (II), in which A and x are as defined in claim 1.

5. Method according to claim 4, in which the defluorination step is carried out: - under hydrogen, in particular under a flow of hydrogen; - in the presence of a reducing agent such as NaH and / or CaH2; or - electrochemically.

6. Process for preparing a compound according to any one of claims 1 to 3, comprising a step of growing a thin layer by epitaxy, in particular on a substrate of the SrTiO3, KTaO3, or EuScO3 type.

7. Active material, in particular intercalation material, for negative electrode, in particular fluorine battery, consisting of or comprising a compound according to any one of claims 1 to 3.

8. Active material according to claim 7, the compound of formula (I) of which forms a redox couple with a compound of the following formula (II): AxNiF2+y (II), in which A and x are as defined in claim 1 and 0 < y 1

9. S 1. Active material according to claim 8, the compound of formula (I) of which has an infinite layer type structure, and in particular a crystalline form of type P4 / mmm, I4 / mcm, C2 / c, or Pbnm.

10. Battery, in particular intercalation battery, with fluorine, comprising: - a negative electrode comprising or consisting of an active material according to any one of claims 7 to 9; - a positive electrode; - an electrolyte, having in particular a conductivity in fluoride ions; which comprises in particular: - a negative electrode layer comprising or consisting of an active material according to any one of claims 7 to 9; - a positive electrode layer; and - between said negative electrode layer and said negative electrode layer, in contact with them, a layer of electrolyte, in particular solid.

11. Battery according to claim 10, in which: - the electrolyte is of the following formula: Lao^BaojF^; and / or - the positive electrode is made of or comprises a material of the following formula: La2NiO(4+ô)Fx ; with ô varying from -1.5 to 0.25, ô being for example 1.3; and x varying from 1 to 3.

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