Process for treating a solid electrolyte selected from sulfides

Abstract

The present invention relates to a process for treating a solid electrolyte selected from among the sulfides comprising the following steps: a) adding said solid electrolyte selected from among the sulfides into acetonitrile; b) stirring the solution obtained at the end of step a) for a time D1 less than or equal to 4 hours; c) vacuuming said solution to remove the acetonitrile; d) recovering the solid electrolyte selected from among the sulfides obtained.

Description

Title of the invention: Process for treating a solid electrolyte selected from sulfides technical field

[0001] The present invention relates to the field of solid electrolytes. More particularly, the present invention relates to a process for treating a solid electrolyte selected from among sulfides. Previous techniques

[0002] In a conventional manner, all-solid-state batteries comprise one or more positive electrodes, one or more negative electrodes, a solid electrolyte forming a separator, an anodic current collector and a cathodic current collector.

[0003] The performance of a battery depends on its ionic and electronic transport properties. In the case of an all-solid-state battery, ionic transport at the electrode scale occurs through the network formed by the solid electrolyte. For such a battery to be operational, this network is percolated, forming ionic conduction pathways throughout the entire volume of the electrode, to ensure the transport of ions to and from all the particles of active material.

[0004] All-solid-state batteries use different types of materials as solid electrolytes, for example polymers, such as poly(ethylene oxide) (PEO), ..., Oxides such as Garnet, perovskites, Nasicon, ... or those chosen from among the sulfides (LGPS, LPS, LPSCL, ...).

[0005] The manufacture of all-solid-state batteries is a major challenge for all players in this field, but many problems remain to be solved before this technology can be developed on an industrial scale. Players in the field are indeed encountering various technological barriers.

[0006] The preservation of solid electrolytes selected from among sulfides is one of the issues. Indeed, it has been observed that the ionic conductivity of these electrolytes decreases with storage time, even when they are stored under optimized conditions, for example in a glove box under an argon atmosphere. This observation implies the use of these electrolytes immediately after their synthesis.

[0007] To combat this problem, various avenues have been explored.

[0008] One of the methods studied consists of treating the solid electrolyte selected from among the sulfides by a process involving vacuum drying. As described in documents JP 2013 / 239296 and JP 2015 / 018726, the control of this vacuum drying This is necessary because of the production of hydrogen sulfide resulting from a secondary reaction between the chosen solid electrolyte (from among the sulfides) and water. Hydrogen sulfide is an irritating gaseous compound that disperses easily into the atmosphere. Thus, in specific drying techniques such as heat drying or low-humidity drying, hydrogen sulfide is released into the atmosphere instead of being absorbed by the treated solid electrolyte. Consequently, this method requires strict control of temperature and humidity conditions during the drying process.

[0009] There is therefore a need to find other treatment processes that are easy to implement in order to combat the problem described above. Description of the invention

[0010] The invention therefore relates to a process for treating a solid electrolyte selected from sulfides, comprising the following steps:

[0011] a) add said solid electrolyte selected from among the sulfides into acetonitrile;

[0012] b) stir the solution obtained at the end of step a) for a duration DI less than or equal to 4 hours;

[0013] c) to vacuum-seal said solution to eliminate acetonitrile;

[0014] d) recover the solid electrolyte chosen from the sulfides obtained.

[0015] The treatment process according to the invention allows for the regeneration of the ionic conductivity of the solid electrolyte selected from among the sulfides, with a material that is ready for use immediately after the process according to the invention. The process according to the invention also allows for easy implementation without the need for strict control of the operating conditions.

[0016] Other advantages and features of the invention will become more apparent upon examination of the detailed description and the accompanying drawing, in which:

[0017] [Fig-1] is a graph representing the evolution of the ionic conductivity of a solid electrolyte chosen from among the sulfides before the implementation of a process according to the invention and that of a solid electrolyte chosen from among the sulfides after the implementation of a process according to the invention.

[0018] It is specified that the expression "from... to..." used in the present description of the invention should be understood as including each of the limits mentioned.

[0019] As indicated above, the process for treating a solid electrolyte selected from sulfides comprises:

[0020] a) add said solid electrolyte selected from among the sulfides in acetonitrile.

[0021] The solid electrolyte selected from among the sulfides added to acetonitrile can be any solid electrolyte selected from among the sulfides and may have been subjected to any type of pretreatment. For example, it may have been previously stored in any conditions, in particular it may have been stored in a glove box under an inert gas atmosphere, for example under an argon atmosphere.

[0022] Advantageously, the solid electrolyte chosen from among the sulfides is chosen from materials of formula:

[0023] Am+12_n_xBn+S\xX„ in which:

[0024] - A designates Cu, Ag or Li, B designates Ge, Si, Al or P, and X designates Cl, Br or I;

[0025] - m is equal to 1;

[0026] - n is equal to 3, 4 or 5;

[0027] - x varies from 0 to 2.

[0028] Preferably, the solid electrolyte chosen from among the sulfides is chosen from the material of formula:

[0029] Li7 LSg iX. in which:

[0030] X denotes Cl, Br or I, and t varies from 0 to 2,

[0031] more preferably Li6PS5X, in which X denotes Cl, Br or I,

[0032] even more preferentially Li6PS5Cl.

[0033] The method according to the invention also comprises:

[0034] b) agitate the solution obtained at the end of step a) for a duration DI less than or equal to 4 hours.

[0035] During step b), the solution obtained at the end of step a) is stirred for a duration DI less than or equal to 4 hours such that the exposure time of the solid electrolyte chosen from among the sulfides with the acetonitrile is less than or equal to 4 hours.

[0036] This limited DI duration helps to avoid the formation of polysulfides (Sn).

[0037] Advantageously, the duration DI is less than or equal to 2 hours, preferably from 10 seconds to 60 minutes, more preferably from 30 seconds to 30 minutes, even more preferably from 1 minute to 15 minutes.

[0038] Thus, advantageously, the exposure time of the solid electrolyte chosen from among the sulfides with acetonitrile is less than or equal to 2 hours, preferably from 10 seconds to 60 minutes, more preferably from 30 seconds to 30 minutes, even more preferably from 1 minute to 15 minutes.

[0039] As previously stated, the treatment process according to the invention also comprises:

[0040] c) put said solution under vacuum to eliminate acetonitrile.

[0041] Vacuum packing can be carried out according to any method known to a person skilled in the art.

[0042] This vacuuming step thus makes it possible to eliminate the acetonitrile and consequently to separate the solid electrolyte chosen from among the sulfides and the acetonitrile.

[0043] Acetonitrile can thus be recovered in a separate bottle, which can be fitted with a cold trap, cooled by liquid nitrogen.

[0044] Advantageously, the vacuum sealing is carried out at a temperature ranging from 15°C to 60°C.

[0045] Thus, vacuum sealing can be carried out at various temperatures, which represents an advantage over prior art methods requiring strict control of temperature conditions, among other things.

[0046] According to a preferred embodiment, the vacuum sealing is carried out for a duration D2 of at least 5 minutes, preferably from 15 minutes to 48 hours, more preferably from 30 minutes to 36 hours, even more preferably from 1 hour to 24 hours.

[0047] As previously stated, the treatment process according to the invention also comprises:

[0048] d) recover the solid electrolyte chosen from the sulfides obtained.

[0049] At the end of step c), the solid electrolyte among the sulfides is recovered after removal of the acetonitrile.

[0050] Advantageously, all the steps of the treatment process according to the invention are carried out under an inert gas atmosphere, such as an argon atmosphere. All the steps of the treatment process according to the invention can be carried out in a glove box under an inert gas atmosphere, such as an argon atmosphere.

[0051] Another object of the invention is a battery cell comprising at least one solid electrolyte selected from the sulfides obtained by the treatment process according to the invention.

[0052] Another object of the present invention is a battery comprising at least one battery cell as defined above.

[0053] The present invention also relates to a device comprising at least one battery as defined above.

[0054] Said device may be any system incorporating a battery, such as for example an electric or electrified rolling vehicle, in particular a bus, a scooter, a motorcycle, an electronic device, a portable device.

[0055] The present invention is illustrated in a non-limiting manner by the following examples. Example Measurement of ionic conductivity

[0056] The ionic conductivities of the samples were determined by alternating current impedance spectroscopy. The samples were placed in a controlled environment sample holder (CESH, Biology) in order to maintain a argon atmosphere. The temperature of the sample holder was regulated using an intermediate temperature system (ITS, BioLogic).

[0057] The AC impedance spectrum was recorded by an MTZ-35 frequency response analyzer (BioLogic) over a temperature range of -10°C to 25°C. The samples were kept at 25°C for one hour before the start of measurements. The temperature was then gradually increased at a rate of 1 K per minute until it reached the predetermined temperature. It was then held at this temperature for 30 minutes before the impedance measurement. For the impedance measurement, a sinusoidal voltage perturbation of 50 mV was introduced in the frequency range of 10⁻⁷ to 0.05 Hz.

[0058] Materials of formula Li6PS5Cl in granular form were prepared using a 10 mm diameter cold granulator in order to measure ionic conductivity.

[0059] Li6PS5Cl powders were placed between two flexible graphite sheets (PAPYEX®, Mersen) to serve as blocking electrodes. The assembly was then subjected to a pressure of 1.25 MPa for five minutes. Materials preparation

[0060] Two materials were used.

[0061] The first material is a material with the formula Li6PS5Cl that was stored in a glove box under an inert gas atmosphere for 3 months. This material was not subjected to any treatment process. This material is referred to hereafter as material A. Then, the ionic conductivity of this material A was measured.

[0062] The second material is a material of formula Li6PS5Cl which was kept in a glove box under an inert gas atmosphere for 3 months and was then subjected to a treatment process according to the invention.

[0063] Then, this material was placed in a bottle and dispersed in acetonitrile at a ratio of 2.5 mL of acetonitrile to 1 g of Li6PS5Cl. The solution turned transparent blue upon contact. This blue color originates from the radical pennant S. The solution was shaken for varying durations, specifically for 1 minute, 5 minutes, 10 minutes, and 15 minutes, respectively.

[0064] The solution was then placed under vacuum to remove the acetonitrile. This step corresponds to a drying step. One test was carried out at room temperature, and another test was carried out at a temperature of 60°C.

[0065] Then, after 1 hour of vacuum, it was observed that the acetonitrile was eliminated. The vacuum was maintained for a total of 24 hours to ensure complete removal of the acetonitrile residues from the surface of the Li6PS5Cl.

[0066] During this vacuum sealing, the acetonitrile was recovered in a separate vial, equipped with a cold trap, cooled by liquid nitrogen.

[0067] The Li6PS5Cl material was thus recovered.

[0068] This Li6PS5Cl material obtained at the end of the treatment process according to the invention is referred to hereafter as material B. Then, the ionic conductivity of this material B was measured.

[0069] Other materials were also tested. Instead of being dispersed in acetonitrile, they were dispersed in methanol, ethanol, and toluene, respectively. The protocol followed remained the same as for the test with acetonitrile. These materials are designated materials C, D, and E, respectively. Results

[0070] The evolution of the ionic conductivity of materials A (curve A) and B (curve B) can be observed on the graph in [Fig. 1].

[0071] It is clear that the ionic conductivity of material B is significantly higher than that of material A.

[0072] It was also noted that the exposure time of the selected solid electrolyte from among the sulfides with acetonitrile of 1 minute, 5 minutes, 10 minutes, and 15 minutes, respectively, had no impact on the ionic conductivity. The ionic conductivity measurements of the material were identical for these different exposure times.

[0073] It was also noted that the temperature used during vacuum sealing had no impact on the ionic conductivity. The ionic conductivity measurements of the material were identical for these different temperatures.

[0074] At room temperature, the ionic conductivity of material A is approximately 0.27 mS / cm while that of material B is approximately 1.36 mS / cm.

[0075] Thus, the ionic conductivity of material B was improved by a factor of about 5 compared to that of material A, thanks to the treatment process according to the invention.

[0076] This value of 1.36 mS / cm is also entirely satisfactory insofar as it is within the range of ionic conductivity values ​​of solid electrolytes chosen from among the commercial sulfides mentioned in the academic literature or by suppliers in their product sheets (from 1 to 3 mS / cm).

[0077] Furthermore, it was observed that the ionic conductivities of materials C, D and E were low, significantly lower than that of material B.

[0078] This demonstrates the critical nature of acetonitrile.

[0079] Thus, the treatment process according to the invention allows for a particularly efficient regeneration of the ionic conductivity of the solid electrolyte selected from sulfides. The process according to the invention also allows for easy implementation without the need for strict control of the conditions of execution.

Claims

Demands

1. A process for treating a solid electrolyte selected from sulfides comprising the following steps: a) adding said solid electrolyte selected from sulfides to acetonitrile; b) stirring the solution obtained at the end of step a) for a time DI less than or equal to 4 hours; c) vacuuming said solution to remove the acetonitrile; d) recovering the solid electrolyte selected from sulfides obtained.

2. A method according to claim 1, characterized in that the solid electrolyte chosen from among the sulfides is chosen from the materials of formula: Am+i2 ri xB"+S2 6 xX x, in which: - A denotes Cu, Ag or Li, B denotes Ge, Si, Al or P, and X denotes Cl, Br or I; - m is equal to 1; - n is equal to 3, 4 or 5; - x varies from 0 to 2.

3. A method according to claim 1 or 2, characterized in that the solid electrolyte chosen from among the sulfides is chosen from the material of formula: Li7 tPS6 tX, in which: X denotes Cl, Br or I, and t varies from 0 to 2, more preferably Li6PS5X, in which X denotes Cl, Br or I, even more preferably Li6PS5Cl.

4. A method according to any one of the preceding claims, characterized in that the duration DI is less than or equal to 2 hours, preferably from 10 seconds to 60 minutes, more preferably from 30 seconds to 30 minutes, even more preferably from 1 minute to 15 minutes.

5. A method according to any one of the preceding claims, characterized in that the vacuuming is carried out at a temperature ranging from 15°C to 60°C.

6. A method according to any one of the preceding claims, characterized in that the vacuum is applied for a duration D2 of at least 5 minutes, preferably from 15 minutes to

7.

8.

9. 48 hours, more preferably from 30 minutes to 36 hours, even more preferably from 1 hour to 24 hours. Battery cell comprising at least one solid electrolyte selected from the sulfides obtained by the treatment process as defined in any one of the preceding claims. Battery comprising at least one battery cell as defined in the preceding claim. Device comprising at least one battery as defined in the preceding claim.

Images