Electrolyte material for an all-solid-state battery

Abstract

The invention relates to a solid inorganic material for use as an electrolyte material comprising an oxide of formula Ax(MgM1M2CuyZn)1-xO, M1 and M2 being independently selected from among the metals of block d of the periodic table, with the exception of Co, and A being an alkali metal. The oxide is a high-entropy oxide.

Description

Description Title of the invention: Electrolytic material for all-solid-state battery

[0001] The present invention relates to the field of materials used in batteries and more particularly concerns a layer of electrolytic material and a stack of material for producing an all-solid-state battery.

[0002] Bibliographic references in the following text are noted in the description text as follows: [] ; and listed in the reference table. State of the art

[0003] Autonomous and portable applications often require a large amount of energy. Most of these devices rely on rechargeable batteries, provided they can provide higher volumetric and gravimetric energy densities. State-of-the-art Li-ion batteries are the most widely used for high energy density applications. These Li-ion batteries use liquid organic electrolytes and specific polymers. Therefore, these batteries require hermetic and resistant packaging, which increases the weight of the batteries and reduces their energy density. In addition, several problems related to the use of an organic liquid electrolyte are known, such as leakage, accelerated aging, flammability, etc.

[0004] The Li-ion batteries known from the state of the art have a maximum energy storage capacity which remains too limited with regard to the intended applications (< 300 Wh / kg). In addition, these Li-ion batteries use expensive materials and / or the mining of which poses environmental problems, as is the case with cobalt. Such Li-ion batteries use a liquid electrolyte, which, in addition to the technical problems mentioned above, complicates their recycling at the end of their life due to the presence of toxic compounds they contain, which are difficult to separate and eliminate.

[0005] Higher-performance batteries are needed, particularly for reuse in electrified transport such as electric cars or in aviation, with an energy density greater than 500 Wh / kg, which must be safer and therefore without thermal runaway or flammability; and more environmentally friendly thanks to the use of less toxic materials, with a smaller environmental footprint and more easily recyclable.

[0006] Batteries incorporating solid electrolytes are known from the prior art: [1-5], However, such batteries have the disadvantages of using solid electrolytes: - not very chemically stable in air or humidity; - electrically unstable at the operating potentials of the electrode materials; - which use materials that are difficult to access in sufficient quantities, such as lanthanum and germanium, and generally require the implementation of complex production processes; and - not very resistant to the propagation of lithium dendrites during cycling.

[0007] The present invention aims to provide alternative solid-state electrolytes based on the family of high-entropy oxides, by replacing critical metals such as cobalt and nickel used until now, with compositions containing iron and / or manganese. Such materials demonstrate ionic conduction properties allowing their use as solid electrolyte for all-solid-state batteries. Such new-generation batteries must be able to provide a high level of performance by integrating a high-energy density metal such as lithium and / or sodium in the negative electrode and by using an insertion material typically comprising alkali ions, in the positive electrode. Description of the invention

[0008] To overcome the drawbacks of the aforementioned state of the art, the present invention relates to a solid inorganic material for use as an electrolyte material comprising an oxide of formula A x (MgMiM2Cu y Zn)i-xO, Mi and M2 being independently chosen from the metals of the d block of the periodic table, except Co, and A is a metal alkali, x is taken between 0.15 and 0.35 and y is selected from the two integer values ​​0 and 1, preferably the oxide is a high entropy oxide. Such high entropy oxides are referred to as "HEOx", and are defined as a class of materials discovered in 2015 by an American team according to the publication in the journal Nature communication [6], Such alkali metal doping of these high entropy oxides gives the inorganic material excellent thermal conductivity.

[0009] Advantageously, Mi and M2 are independently selected from Fe, Ni and Mn.

[0010] Advantageously, the oxide of the solid inorganic material according to the invention is chosen from A x (MgFeNiCuZn)i- x O ; A x (MgMnNiCuZn)i- x O and A x (MgFeMnCuZn)i- x O, and A is chosen from Na and Li. These electrolytes offer the advantage of being perfect ionic conductors at room temperature, and avoid having to reach an operating temperature, typically heating, to benefit from the full potential of the material.

[0011] Advantageously, the oxide is chosen from (MgFeNiCuZn)o.7oLio.3oO; (MgMnNiCuZn)o.75Lio.2sO; (MgFeNiCuZn)o.7oNao.3oO and (MgFeNiCuZn)o.75Nao.2sO.

[0012] Advantageously, the oxide does not include one of the elements selected from Ni and Cu, or the material does not contain either of the two elements Ni and Cu. The inventors have shown that it is possible to avoid the presence of Co, but also of Ni and / or Cu, which opens up access to a greater variety of materials for new applications.

[0013] Advantageously, the value of x is greater than or equal to 0.20. The inventors have shown, completely unexpectedly, that such doping of high-entropy oxides with alkali metals taken in these proportions makes it possible to considerably improve the ionic conductivity. Preferably, the value of x is greater than or equal to 0.25.

[0014] The present invention also relates to a solid electrolytic material, and more particularly to a solid electrolyte comprising the solid inorganic material described above within the scope of the invention. Such a solid electrolyte is advantageously integrated into an energy storage and / or restitution system, such as a cell, a battery or an accumulator. The inventors have shown, quite unexpectedly, that such a system storage system according to the invention was particularly efficient thanks to energy densities greater than 500 Wh / kg, while being safer than known systems regarding the health, safety and environmental criteria, known as HES. Such a solid electrolyte also serves as a separation layer between the cathode and anode electrodes of an energy storage system such as a battery. Such a battery does not form an unstable passivation layer (SEI), which results in very low self-discharge rates. It can store energy for several years with the least loss and is expected to operate 50 to 100 times longer than conventional liquid electrolyte batteries.

[0015] The present invention also relates to a method for manufacturing a solid inorganic material as described previously in the context of the invention, obtained from a ground and compacted mixture of metal oxides and alkali carbonate. The alkali carbonates are preferably selected from lithium carbonate Li2CC>3 and sodium carbonate Na2CC>3. The inventors have shown that it is possible to compact the powders to reduce the porosity without altering the conduction properties.

[0016] Preferably, the ground mixture of metal oxides and alkali carbonate is subjected to a compression step of 10 7 at 2.10 8Pa at a temperature between 25 and 250°C. Such a compaction step makes it possible to make the powder mixture dense so that the chemical reactions in the solid state and high temperature take place efficiently and homogeneously throughout the sample. Preferably, the pressure applied to the sample is carried out using a uniaxial press by applying a conversion pressure of 1 ton / cm 2 or 100 Mpa. Preferably, the pressure is applied with a hydraulic press marketed by the company Eurolab®. The pressure gauge of the device gives the applied pressure in tons. The diameters of the pellets are 13mm in diameter, the pressure in pascals is obtained by performing the conversion.

[0017] Preferably, the method according to the invention comprises two additional steps: 1- carry out a heat treatment, at a temperature T > 900°C, under an air atmosphere; and 2- carry out a quench, immediately after step 1-, under pressure partial oxygen Pox, with: 0 Pa < Pox < 2.104 Pa. The press used and the methods for obtaining the pressure are as described previously and use a hydraulic press marketed by the company Eurolab®.

[0018] The present invention also relates to a solid-state battery comprising the following three layers of materials: - a negative electrode layer; - a positive electrode layer; and - a solid electrolyte as described previously in the context of the invention, placed between the negative and positive electrode layers.

[0019] Preferably, the negative electrode layer comprises at least one metal selected from Li and Na, and the positive electrode layer comprises a ceramic and graphite, the ceramic preferably being a ceramic having a content of more than 50% of an active material comprising an alkali ion, the content expressed as a percentage being a mass percentage relative to the total mass of the ceramic. Preferably, said active material is selected from at least one of the materials selected from the following oxides: LiNi x Co y Mn z O2, LiFcPCL / C. LiMr^CL. LiCoCh. Nao.yMnCh and NaCoO2.

[0020] The present invention also relates to a thin film comprising the solid-state battery described above within the scope of the invention, for its integrated use in an electronic device, said electronic device preferably being chosen from a smart card, a biotechnology device and a graphic calculator.

[0021] The present invention also relates to a use of a solid-state battery as previously described within the scope of the invention, chosen between integration into an electric vehicle, large-scale stationary transport and storage, integration into aerospace aircraft, medical sectors and robotics.

[0022] The present invention is also described in the detailed description which follows, using the experimental part which details certain embodiments using examples, given solely for illustrative purposes and which should not be considered as limiting, and the figures briefly described in the part which follows. Brief description of the figures

[0023] [Fig. l] - Figure 1 represents the ionic conductivities of (MgFeNiCuZn)o.7oLi0.3oO at 20°C and 100°C;

[0024] [Fig.2] - Figure 2 represents the ionic conductivities of (MgMnNiCuZn)o.75Lio.250 at 20°C and 100°C;

[0025] [Fig.3] - Figure 3 represents the demonstration of the stability of (MgFeNiCuZn)o.7oNao.3oO air and comparison with the same Heox stored under vacuum;

[0026] [Fig.4] - Figure 4 shows the assembly of a positive electrode (composite) / electrolyte according to the invention (cold pressed);

[0027] [Fig.5] - Figure 5 represents cyclic voltammetry of (MgFeNiCuZn)o.75Nao.2sO ; and

[0028] [Fig.6] - Figure 6 represents the charge curve of an all-solid-state battery with (MgFeNiCuZn)o.75Nao.2sO;

[0029] [Fig.7] Figure 7 shows the EDX chemical analysis of the compound (MgMnNiCuZn)o.7oLio.3oO in accordance with the expected stoichiometry.

[0030] [Fig.8(a)]-[Fig.8(c)] Figures 8(a), 8(b) and 8(c) show the X-ray diffractograms of the compositions (MgFeNiCuZn)o.8oLio.2oO, (MgMnNiCuZn)o.8oLio.2oO and (MgMnNiCuZn)o.75Nao.2sO ; and

[0031] [Fig.9] Figure 9 shows the complex impedance, at two different temperatures, of the compound (MgFeNiCuZn)o.8oNao.2oO. Experimental Part

[0032] Materials and methods In the context of the invention, the diffractometer used for X-ray diffraction is a Philips Panalytical® X-Pert Pro MPD diffractometer.

[0033] All high entropy solid electrolyte samples are prepared from oxides such as magnesium(II) oxide (MgO - Alfa Aesar® 99.95%), iron(III) oxide (FC2O3 - Alfa Aesar®), manganese(II) oxide (Mn2CC>3 - Alfa Aesar®), copper(II) oxide (CuO - Alfa Aesar® 99.7%), nickel(II) oxide (NiO), zinc(II) oxide (ZnO - Alfa Aesar® 4N), and carbonates such as lithium carbonate (Li2COs - Alfa Aesar® 99.998%), sodium carbonate (Na2COs). The composition (formula) The chemical properties of the obtained materials are determined by energy dispersive X-ray spectroscopic analysis, also known as EDX, using a Philips Panalytical® X-Pert Pro MPD diffractometer. Results and discussion

[0034] Preparation of oxides

[0035] The starting powders in stoichiometric quantities of the precursors are mixed in equimolar ratios of all the cations Mg, Fe or Mn or both, Ni, Cu and Zn, for a total mass of 4 g, by adding the ingredients in a mortar, or agate bowls, with a capacity of 20 ml followed by the use of a Fritsch® planetary micro-mill, under the reference Pulverisette 7 Premium Line, with 5 agate grinding balls of 1 cm in diameter for a period of one hour at 350 rpm with a one-minute break after each five-minute cycle.

[0036] The resulting mixture is then pressed evenly into a rectangular die measuring 12x3x3 mm 3 or cylindrical 13x13 mm 2 under a hydraulic pressure of 10 7 at 2. 10 8Pa, while the applied temperature varies between 25 and 250 °C; then, the pellets obtained are placed and maintained in an alumina crucible, and heated to a temperature chosen according to the composition of the sample and between 850 °C and 1100 °C for 12 hours in air with a heating rate of 2 °C / minute (120 °C / h) continuously (a total of 20 hours of sintering). Then a quenching step is carried out in liquid nitrogen or directly on a metal plate under vacuum (partial pressure of oxygen Pox, with: 0 Pa < Pox < 2. 104 Pa). Solid mixtures prepared with a large amount of lithium / sodium (x > 0.25) must be kept in a glove box to avoid their hydration (hygroscopic compounds).

[0037] The geometric density of all samples, after heat treatment, is calculated to be between 75 and 80% of the theoretical density. Since the reaction is complete, the chemical formula obtained is the same as that expected from the molar ratios of the compounds introduced.

[0038] The solid materials obtained have the following general formulas: (MgF eNiCuZn) i- x Li x O (MgMnNiCuZn) i- x Li x O (MgFeNiCuZn)i. x N / A x O (MgMnNiCuZn) i. x N / A x O (MgF eMnCuZn) i- x Li x O (MgFeMnCuZn)i- x N / A x O; and are more particularly of the following formula: (MgFeNiCuZn)o.7oLio.3oO; (MgMnNiCuZn)o.75Lio.2sO; (MgFeNiCuZn)o.7oNao.3oO; (MgFeNiCuZn)o.75Nao.2sO; (MgFeNiCuZn)o.8oLio.2oO; (MgMnNiCuZn)o.soLio.2oO and (MgFeNiCuZn)o.75Nao.2sO.

[0039] Results The high entropy oxides obtained as described above exhibit good ionic conductivity at room temperature, making them good candidates as solid electrolytes, as shown for the compounds (MgFeNiCuZn)o.7oLio.3oO and (MgMnNiCuZn)o.75Lio.2sO in Figure 1 and Figure 2.

[0040] The chemical stability of the high-entropy oxides is tested with air (oxygen) and humidity (water) which are found to be very stable under both conditions. The obtained high-entropy oxides also exhibit chemical stability with respect to the negative and positive electrodes when implemented in a battery, which eliminates the problems of protecting the solid-solid interface and allows for a reduction in the ohmic drop within the battery itself, as shown by X-ray diffraction for (MgFeNiCuZn)o.7oNao.3oO in Figure 3.

[0041] Figure 4 shows the assembly of a positive electrode (composite) / electrolyte according to the invention using the solid organic material according to the invention (cold pressed). More particularly, Figure 4 represents the positive electrode (at the bottom of the figure) comprising a mixture of inorganic material according to the invention and solid electrolyte, the positive electrode is therefore a composite. Above in Figure 4 is the solid electrolyte alone. The white line materializes the interface between the solid electrolyte alone (above) and the positive electrode (below).

[0042] Figure 5 and Figure 6 show the characterized electrical properties for the material (MgFeNiCuZn)o.75Nao.2sO.

[0043] Figure 7 shows the EDX chemical analysis of the compound (MgMnNiCuZn)o.7oLio.3oO in accordance with the expected stoichiometry.

[0044] Figures 8(a) to 8(c) show the variety of possible compositions with three X-ray diffractograms corresponding to stoichiometries different from those of the previous figures 1 to 7

[0045] Figure 9 shows the complex impedance of the compound (MgFeNiCuZn)o.8oNao.2oO at a temperature of 25°C (corresponding to an ionic conductivity of 2.3.10' 6 S / cm) and at a temperature of 50°C (corresponding to an ionic conductivity of 3.2.10' 6 S / cm). References

[0046] The following Table 1 lists the references cited previously in the text: [Table 1]

Claims

Claims

1. Solid inorganic material for use as an electrolyte material comprising an oxide of formula A x (MgMiM2Cu y Zn)i-xO, Mi and M2 being independently chosen from the metals of the d block of the periodic table, except Co, and A is an alkali metal, x is taken between 0.15 and 0.35 and y is selected from the two integer values ​​0 and 1, preferably the oxide is a high entropy oxide.

2. The material of claim 1, wherein Mi and M2 are independently selected from Fe, Ni and Mn.

3. Material according to one of claims 1 or 2, in which the oxide is chosen from A x (MgFeNiCuZn)i- x O ; A x (MgMnNiCuZn)i- x O and A x (MgFeMnCuZn)i- x O, and A is chosen from Na and Li.

4. Material according to one of claims 1 to 3, wherein the oxide is chosen from (MgFeNiCuZn)o.7oLio.3oO; (MgMnNiCuZn)o.75Lio.2sO; (MgFeNiCuZn)o.7oNao.3oO and (MgFeNiCuZn)o.75Nao.2sO.

5. A material according to either of claims 1 or 2, wherein the oxide does not comprise one of the elements selected from Ni and Cu, or the material does not contain either of the elements Ni and Cu.

6. Material according to one of claims 1 to 5, in which the value of x is greater than or equal to 0.

20.

7. A solid electrolyte comprising the solid inorganic material according to one of claims 1 to 6.

8. A method of manufacturing a solid inorganic material according to one of claims 1 to 6, obtained from a ground mixture of metal oxides and alkali carbonate, comprising a compression step of 10 7 at 2.10 8 Pa at a temperature between 25 and 250°C, to obtain a ground and compacted mixture.

9. A method of manufacturing a solid inorganic material according to claim 8, obtained from said ground and compacted mixture of metal oxides and alkali carbonate, comprising the following two steps: 1- carry out a heat treatment of the crushed and compacted mixture, at a temperature T > 900°C, under an air atmosphere; and 2- carry out a quench, immediately after step 1-, under the partial pressure of oxygen Pox, with: 0 Pa < Pox < 2.104 Pa.

10. A solid state battery comprising the following three layers of materials: - a negative electrode layer; - a positive electrode layer; and - a solid electrolyte according to claim 7, placed between the negative and positive electrode layers.

11. The battery of claim 10, wherein the negative electrode layer comprises at least one metal selected from Li and Na, and the positive electrode layer comprises a ceramic and graphite.

12. Thin film comprising the solid-state battery according to one of claims 10 or 11, intended to be integrated into an electronic device, preferably chosen from a smart card, a biotechnology device and a graphic calculator.

13. Use of a solid-state battery according to one of claims 10 or 11, selected from integration into an electric vehicle, large-scale stationary transport and storage, integration into aerospace aircraft, medical sectors and robotics.

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