Porous sulfur ceramics, its preparation process and its uses

Abstract

The present invention relates to a porous sulfur ceramic, its preparation process and its uses.

Description

Title of the invention: POROUS SULFUR CERAMIC, ITS PREPARATION PROCESS AND ITS USES

[0001] The present invention relates to a porous sulfur ceramic, its preparation process and its uses.

[0002] In the field of batteries, conventional electrolytes are composed of organic solvents in which alkali metal salts (Li, Na, K, ...) are dissolved. The use of these electrolytes severely limits the energy density of batteries, particularly due to the instability of these electrolytes on metallic Li, and presents a significant safety risk, as the solvents used are generally flammable and toxic.

[0003] The use of solid electrolytes is intended to improve the safety and electrochemical performance of new generation batteries.

[0004] Indeed, solid electrolytes are more chemically stable, do not present a risk of leakage, and are thus more durable and safer to use than conventional electrolytes.

[0005] Three main families of solid electrolytes are described in the literature: polymeric solid electrolytes, oxides, and sulfides. In the latter two families, solid electrolytes are typically in the form of ceramics, particularly glass-ceramics.

[0006] Solid oxide electrolytes exhibit attractive ionic conductivities and high thermal stability, but are limited by their high cost and difficult shaping. Solid sulfide electrolytes have ionic conductivities of the same order of magnitude as liquid electrolytes, but their electrochemical stabilities are very limited. Solid polymer electrolytes possess good properties at the electrode interfaces and are advantageous in terms of manufacturing cost and weight, but their ionic conductivity at room temperature is very low, necessitating use at high temperatures.

[0007] In order to improve the ionic conductivity of polymer electrolytes, many studies focus on the production of composite electrolytes. These electrolytes are composed of a conductive polymer matrix (a solid polymer electrolyte) and a conductive (or non-conductive) inorganic matrix.

[0008] However, in the context of these composite electrolytes, the use of inorganic matrices of the ceramic oxide or sulfide type does not give, without structuring, a suitable ionic conductivity.

[0009] In addition, sulfide ceramics (also known as sulfur ceramics) They are extremely sensitive to humidity and air, and are incompatible with many chemicals. This makes any attempt at structuring them extremely difficult.

[0010] In this context, a study reported the production of composite electrolytes using a continuous 3D porous matrix of argyrodite, synthesized by sublimation of SeS2 during a sintering step at 550°C for 5 hours. However, the conductivity of the argyrodite obtained after sublimation is low compared to the starting argyrodite (0.22 mS.cm1 versus 2.04 mS.cm1 for argyrodite alone). Furthermore, selenium disulfide is a compound with acute toxicity, making its handling very challenging. Finally, the temperature required to obtain the porous matrix is ​​very high, which makes the corresponding process disadvantageous from an economic and environmental point of view.

[0011] An objective of the invention is thus to provide a sulfur ceramic having pores, without degradation, pollution or alteration of its atomic structure, nor of its functional properties, in particular its ionic conductivity.

[0012] Another objective of the invention is to provide such a material using a process that does not require high temperatures for its implementation. This is therefore a process for which the energy consumption related to the production of the porous matrix is ​​reduced, which is advantageous from an economic and environmental point of view.

[0013] Another objective of the invention is to provide such a material using a process that does not require toxic compounds for its implementation.

[0014] Thus, the invention relates to a porous sulfur ceramic, which has a conductivity greater than or equal to 5.10 4 S.cm '.

[0015] The invention also relates to a porous sulfur ceramic, which has a conductivity greater than or equal to 5.105 S.cm'.

[0016] The conductivity of the ceramic can be measured, in particular, by complex impedance spectroscopy. This technique, well known to those skilled in the art, is based on characterizing the response of a sample to a sinusoidal alternating voltage of varying frequency. Typically, 10 mV has been applied for frequencies ranging from 1 kHz to 7 MHz.

[0017] According to a particular embodiment, the present invention relates to a ceramic as defined above, which is chosen from among lithia-coated argyrodites, Li-PS type glasses and glass-ceramics, thio-LISICON (Lithium Superionic Conductor), in particular compounds of type Li4_xGei_xPxS4_x or Lin_xM2_xPi+xS 12 with M=Ge, Sn and / or Si, x being between 0 and 1, and their composites.

[0018] According to a particular embodiment, the present invention relates to a ceramic selected from 60Li2S.40P2S5 glass, 67Li2S.33P2S5 glass, 70Li2S.30P2S glass 5, glass 75Li2S.25P2S5, glass 80Li2S.20P2S5, glass 55(66Li2S.33P2S5).45LiI, glass 95(60Li2S.40SiS2).5Li3B03(Li3A103), glass 77(75Li2S.25P2S5).33LiBH4, glass 40Li2S.28SiS2.30LiI, glass 30Li2S.26B2S3.33LiI, Li7P3Sn, analogue Li7P3Sn de type Li7P29S 10.85M00.01, analogue Li7P3Sn de type Li7P2.QMno.iSio.7Io.3, argyrodite Li6PS5Cl, argyrodite Li6PS5Br argyrodite Li6PS5I, argyrodite Li7PS6, argyrodite Li7Ge3PSi2, argyrodite Li635 Po.65Sio.35S5Br, argyrodite Li6.6Po.4Geo.6S5l5.4, thio-LiSICON de type Li3.25Geo.25Po.75S4, analogue thio-LiSICON de type Li4SnS4, analogue thio LiSICON de type LinAlP2Si2, analogue thio-LiSICON de type Li3.833Sno.833Aso.i66S4, Li10GeP2S12, analogue LGPS de type Li10SnP2Si2, analogue LGPS de type Li10SiP2Si2, analogue LGPS de type Li9.54Si1.-74 Pi.44Sn.7Clo.3, 70Li2S.30P2S5-l,4-butanediol, 75Li2S.25P2S5-PFPE, 77.5Li2S.22.5P2S5 -methly-imine, (PEO18-LiTFSI)-LGPS, (PEO18-LiTFSI)-LGPS, [3-Li3PS4 -LZNO, [3-Li 3PS4-A12O3, [3-Li3PS4-SiO2, and [3-Li3PS4-LLZO, and their composites. .

[0019] According to a particular embodiment, the present invention relates to a ceramic selected from argyrodite Li6PS5Cl, argyrodite Li6PS5Br, argyrodite Li6PS5I, argyrodite Li7PS6, argyrodite Li7Ge3PSi2, argyrodite Lie.^Po.esSio.ssSsBr, argyrodite Li6 6 Po.4Geo.6S5I5.4, and their composites.

[0020] According to a particular embodiment, the ceramic as defined above comprises or is made up of a compound of formula Li6PS5X, where X is Cl, Br or I, the compound in particular having the formula Li6PS5Cl.

[0021] According to a particular embodiment, the ceramic as defined above has a conductivity less than or equal to 102 S / cm.

[0022] According to a particular embodiment, the ceramic as defined above has a conductivity of 5.105 to 102 S / cm.

[0023] According to a particular embodiment, the ceramic as defined above has a conductivity of 10⁴ to 10² S / cm.

[0024] According to a particular embodiment, the ceramic as defined above has a conductivity of 5.10 4 to 102 S / cm.

[0025] According to a particular embodiment, the ceramic as defined above has a conductivity of 6.10 4, 7.10 4, 8.10 4, 9.10 4, 103, 2.103, 3.10 3, 4.103, or 5.103 to 102 S / cm.

[0026] According to a particular embodiment, the total volume of the pores is from 30 to 70%, in particular from 40 to 60% of the total volume of said ceramic.

[0027] According to a particular embodiment, the largest dimension of the pores is from 0.1 to 500 pm, for example 50 pm.

[0028] According to a particular embodiment, the ceramic as defined above is a solid electrolyte.

[0029] According to a particular embodiment, the ceramic as defined above is devoid of selenium or of a compound comprising selenium.

[0030] By "free from", we mean in particular less than 0.1, 0.01, or even 0.001% by mass relative to the total mass of ceramic, or even "totally free from", that is to say "without any trace of".

[0031] According to another aspect, the invention also relates to the use of cyclododecane to make a sulfur ceramic porous. In particular, this porous sulfur ceramic thus obtained is as defined above.

[0032] According to a particular embodiment, the present invention relates to a ceramic as defined above, comprising in addition, in particular in all or part of the pores, cyclododecane.

[0033] According to another aspect, the invention also relates to a process for preparing a ceramic as defined above, which includes a step (i) of heating, in particular to a temperature greater than or equal to 40°C, a mixture comprising the sulfur ceramic and cyclododecane.

[0034] According to a particular embodiment, step (i) is carried out at a temperature of 40 to 150°C, in particular from 40 to 100°C, for example at approximately 40, 60, 80 or 100°C.

[0035] The duration of step (i) can be determined in a way well known to a person skilled in the art, in particular as a function of temperature.

[0036] The ceramic can in particular be weighed before and after step (i), in order to confirm where appropriate the sublimation of the cyclododecane and determine its progress.

[0037] According to a particular embodiment, step (i) is carried out for a period of 12 hours to 96 hours, for example for about 48 hours, in particular at 40°C, or for about 24 hours, in particular at a temperature of about 60 to about 80°C.

[0038] According to a particular embodiment, step (i) is carried out under vacuum, in particular in a vacuum oven, for example at a pressure of 5x102 mbar to 1 mbar.

[0039] According to a particular embodiment, the mixture of step (i) is obtained at the end of a step (o) of mixing and possibly grinding, of sulfur ceramic, optionally previously in powder form, and of cyclododecane.

[0040] According to a particular embodiment, step (o) is carried out using a mixer, for example a planetary mixer, a mortar or a grinder, for example a planetary grinder.

[0041] According to a particular embodiment, step (i) is followed by a sintering step (ii), in particular at a temperature of 100 to 550°C, for example at 550°C.

[0042] This sintering step is likely to allow, if necessary, the improvement of the mechanical properties of the porous ceramic.

[0043] According to a particular embodiment, step (i) is preceded by a step (o') of shaping of the mixture, particularly under pressure.

[0044] Said step (o') follows step (o), when it exists.

[0045] This step (o') can be carried out according to procedures well known to those skilled in the art. The resulting shape can, for example, be a pellet, a block, or a plate.

[0046] By way of illustration, the mixture can be formed into a pellet, in particular at a pressure of about 130MPa, for example for 3 minutes.

[0047] According to a particular embodiment, step (i) is followed by a step (ii') of shaping the porous sulfur ceramic.

[0048] This step may precede or follow step (ii) where it exists.

[0049] This shaping of step (ii') can, for example, be carried out by cookie cutter- piecing.

[0050] According to a particular embodiment, step (o') is carried out, the mixture being in particular in the form of a block or slab, as well as step (ii'), in particular by cutting. In this case, step (ii) may also be carried out, in particular before step (ii).

[0051] According to another aspect, the invention also relates to the use of a porous sulfur ceramic as defined above for the preparation of a composite ceramic, in particular a composite solid electrolyte.

[0052] According to a particular embodiment, the invention relates to a porous sulfur ceramic as defined above, further comprising, in particular in all or part of the pores, a polymer.

[0053] Such polymers, well known to those skilled in the art, are for example described by Liu et al. (Adv. Energy Mater. 2023,13, 2300798) or Mindemark et al. (Progress in Polymer Science 2018, 81, 114-143).

[0054] According to another aspect, the invention also relates to a method for preparing a composite ceramic as defined above, which includes a step (a) of in situ polymerization.

[0055] This step (a) may include the following substeps:

[0056] (al) Injection of a polymerizable formulation into the porous conductive ceramic matrix;

[0057] (a2) Polymerization, in particular by heat treatment, to obtain the electrolyte composite.

[0058] According to a particular embodiment, the process according to the invention comprises the following steps:

[0059] (o') a step of shaping a mixture comprising sulfur ceramic and cy- clododecane, in particular under pressure, in particular to obtain a mixture comprising sulfur ceramic and cyclododecane in block or plate form;

[0060] (i) a heating step, in particular to a temperature greater than or equal to 40°C, of the mixture obtained at the end of step (o');

[0061] (a) an in situ polymerization step to obtain a porous sulfur ceramic composite;

[0062] (b) a step of shaping the composite porous sulfur ceramic, by example by cookie cutter.

[0063] According to a particular embodiment, step (i) is followed by a sintering step (ii), in particular at a temperature of 100 to 550°C, for example at 550°C.

[0064] According to a particular embodiment, the process according to the invention comprises the following steps:

[0065] (o') a shaping step of a mixture comprising sulfur ceramic and cy- clododecane, in particular under pressure, in particular to obtain a mixture comprising sulfur ceramic and cyclododecane in block or plate form;

[0066] (i) a heating step, in particular to a temperature greater than or equal to 40°C, of the mixture obtained at the end of step (o');

[0067] (ii) a sintering step, in particular at a temperature of 100 to 550°C, for example at 550°C;

[0068] (a) an in situ polymerization step to obtain a porous sulfur ceramic composite;

[0069] (b) a step of shaping the composite porous sulfur ceramic, by example by cookie cutter.

[0070] According to a particular embodiment, the process according to the invention comprises the following steps:

[0071] (o) a mixing and optionally grinding step of sulfur ceramic, op- technically previously in powder form, and cyclododecane;

[0072] (o') a step of shaping the mixture obtained at the end of step (o), particularly under pressure, in particular to obtain a mixture comprising sulfur ceramic and cyclododecane in block or plate form;

[0073] (i) a heating step, in particular to a temperature greater than or equal to 40°C, of the mixture obtained at the end of step (o');

[0074] (a) an in situ polymerization step to obtain a porous sulfur ceramic composite;

[0075] (b) a step of shaping the composite porous sulfur ceramic, by example by cookie cutter.

[0076] According to a particular embodiment, the process according to the invention comprises the following steps:

[0077] (o) a mixing and optionally grinding step of sulfur ceramic, op- technically previously in powder form, and cyclododecane;

[0078] (o') a step of shaping the mixture obtained at the end of step (o), particularly under pressure, in particular to obtain a mixture comprising sulfur ceramic and cyclododecane in block or plate form;

[0079] (i) a heating step, in particular to a temperature greater than or equal to 40°C, of the mixture obtained at the end of step (o');

[0080] (ii) a sintering step, in particular at a temperature of 100 to 550°C, for example at 550°C;

[0081] (a) an in situ polymerization step to obtain a porous sulfur ceramic composite;

[0082] (b) a step of shaping the composite porous sulfur ceramic, by example by cookie cutter.

[0083] The composite solid electrolyte formed can be used in new generation batteries (Li metal).

[0084] The fabrication of the composite electrolyte by in situ polymerization can be carried out during the assembly of the cell (all-solid-state battery). This can, if necessary, allow for an improvement in ionic conductivity (compared to that of the polymer) as well as better capacity retention during cycling (by allowing for better electrolyte / electrode interfaces). DEFINITIONS

[0085] As understood here, value ranges in the form of "xy" or "from x to y" or "between x and y" include the bounds x and y, the integers between these bounds, and all other real numbers between these bounds. For example, "1-5", or "from 1 to 5", or "between 1 and 5" refers to the integers 1, 2, 3, 4, and 5, as well as all other real numbers between 1 and 5. Preferred embodiments include each individual integer within the value range, as well as any subcombination of these integers and any set of real numbers between these integers. As an example, preferred values ​​for "1-5" may include the integers 1, 2, 3, 4, 5, 1-2, 1-3, 1-4, 1-5, 2-3, 2-4, 2-5, etc.

[0086] 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. EXAMPLES

[0087] Example 1: Synthesis of a porous sulfur matrix according to the invention

[0088] The experimental protocol for producing the porous sulfur ceramic matrix can be divided into 3 stages:

[0089] 1. A 50 / 50 volume mixture (= 67.5 / 32.5 mass) of commercial argyrodite, Li6PS5Cl (supplier: NEI) and cyclododecane is prepared in a glove box. The mixture is made manually in a mortar.

[0090] 2. The mixture is then formed into a pellet by applying a pressure of 130 MPa for 3 minutes at room temperature. Pellets of varying diameters and thicknesses can be produced depending on the mold used. The pellet is placed in a quartz crucible, then in a hermetically sealed Buchi ball furnace tube inside the glove box.

[0091] 3. The tube is placed under vacuum and then heated to 60°C. After 24 hours, it is returned to the box at Gloves are worn to collect the porous argyrodite that forms. The mass of the pellet is measured to confirm the total or partial sublimation of the cyclododecane.

[0092] A 50 / 50 volume mixture of cyclododecane and LPSC1 yielded a ceramic with a porosity of 50%. This porosity percentage can be modified by increasing or decreasing the volume ratio between cyclododecane and LPSC1, for example to obtain values ​​of 40%, 50% or 60%.

[0093] The sublimation temperature can be modified. Experiments have been successfully conducted at 40°C, 80°C and 100°C. The sublimation temperature does not typically influence the formation of porosity in the ceramic (quantity, morphology) but does have an impact on the sublimation kinetics (2 days required at 40°C versus 24 hours at 60 and 80°C).

[0094] This process makes it possible to reduce the toxicity of the porous agent, to form porosities in the ceramic matrix without pollution or alteration thereof at a lower temperature than that of the state of the art.

[0095] Several pellets of different sizes were produced during the study. Table 1 shows two cases, one presenting the results on a pellet 7 mm in diameter and the other 13 mm in diameter. In both cases, a mass loss of approximately 31.5% was obtained, confirming the almost complete sublimation of the cyclododecane. Pellet diameter (mm) Mass before sublimation (mg) Mass after sublimation (mg) Mass loss (mg) Percentage mass loss (%) 7 34.1 23.3 10.8 31.7 13 440.7 301.7 139 31.5

[0096] Table 1: Evidence of cyclododecane sublimation by the mass loss of the pellet after heat treatment

[0097] Example 2: Analyses relating to a porous sulfur matrix according to the invention

[0098] The pellets obtained in Example 1 were analyzed by Electron Microscopy A scanning technique was used to observe the pores formed after sublimation of cyclododecane. Pores are visible after sublimation, confirming the formation of a porous argyrodite. The pores are approximately 50 pm in length.

[0099] Further analysis by EDX showed that the proportions of P, S, and Cl did not change on the surface of the argyrodite before and after sublimation, suggesting that no chemical reaction occurred at the interfaces between the argyrodite and the cyclododecane. It should be noted that Li cannot be detected by EDX. Elements Atomic proportions of argyrodite alone (%) Atomic proportions of porous argyrodite (%) P 15.7 15.4 S 71.2 71.2 Cl 13.1 13.4

[0100] Table 2: Evolution of the proportions of the elements composing ar-gyrodites (P,S and Cl) before and after sublimation of cyclododecane.

[0101] Since the pellet could not be analyzed directly by XRD, a one-gram porous argyrodite pellet was synthesized to obtain sufficient powder to fill the dedicated sealed sample holder. A mass loss of 32.3% was measured after sublimation of the cyclododecane. The porous argyrodite pellet was then ground to fill the sample holder with powder. The aim was to verify that there was no alteration of the argyrodite during the production of the porous ceramic by sublimation (formation of secondary phases, change in the structure of the argyrodite, etc.). Comparison of the data between the argyrodite before and after sublimation of the cyclododecane showed that no atomic-scale structural modification was observed, suggesting that there was no chemical reaction between the two precursors used under our synthesis conditions. Note that after refining the two diffractograms, the lattice parameter is equal to 9.85 Â for both compounds. .

[0102] Finally, regarding ionic conductivity, impedance spectroscopy measurements were performed on a pellet of argyrodite alone, on a pellet of a 50 / 50 volume mixture of argyrodite and cyclododecane, and on the same pellet after sublimation of the pore-forming agent. A pressure of 50 MPa was applied for the measurements. Table 3 summarizes the ionic conductivity values ​​obtained for the three samples. Samples Ionic conductivity (S / cm) Argyrodite alone 2.3xL03 50 / 50 volume mixture of argyrodite / cyclododecane 0.79 x 0.3 Porous argyrodite l.2 x 0.3

[0103] Table 3: Ionic conductivities of argyrodite alone, of the argyrodite / cyclododecane mixture and of porous argyrodite under a pressure of 50 MPa

[0104] An expected decrease in ionic conductivity is measured after mixing with cyclododecane, which is not ionically conductive. In contrast, the porous argyrodite synthesized according to the invention exhibits a conductivity of 1.2 mS / cm, considerably higher than that of sulfur-containing ceramics of the prior art.

Claims

Claims

1. Porous sulfur ceramic, which has a conductivity greater than or equal to 5.10 4 S.cm '.

2. Ceramic according to claim 1, which is chosen from lithiated ar-gyrodites, Li-PS type glasses and glass-ceramics, thio-LISICON, and their composites, said ceramic comprising in particular or being in particular constituted by a compound of formula Li6PS5X, where X is Cl, Br or I, the compound being in particular of formula Li6PS5Cl.

3. Ceramic according to any one of the preceding claims, in which the total volume of the pores is from 30 to 70%, in particular from 40 to 60% of the total volume of said ceramic.

4. Use of cyclododecane to make a sulfur ceramic porous.

5. Process for preparing a ceramic according to any one of claims 1 to 4, which comprises a step (i) of heating, in particular at a temperature greater than or equal to 40°C, a mixture comprising the sulfur ceramic and cyclododecane.

6. Method according to claim 5, in which the mixture of step (i) is obtained at the end of a step (o) of mixing and optionally grinding, sulfur ceramic, optionally previously in powder form, and cyclododecane.

7. A method according to any one of claims 5 to 6, wherein step (i) is followed by a sintering step (ii), in particular at a temperature of from 100 to 550°C, for example at 550°C.

8. Method according to any one of claims 5 to 7, in which step (i) is preceded by a step (o') of shaping the mixture, in particular under pressure.

9. Use of a porous sulfur ceramic according to any one of claims 1 to 3 for the preparation of a composite ceramic, in particular a composite solid electrolyte.

10. Porous sulfur ceramic according to any one of claims 1 to 3, further comprising, in particular in all or part of the pores, a polymer.

11. A method of preparing a composite ceramic according to claim 10, which comprises a step (a) of in situ polymerization.